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51.
Sparse Modeling of Textures 总被引:3,自引:0,他引:3
Gabriel Peyré 《Journal of Mathematical Imaging and Vision》2009,34(1):17-31
52.
Juan Gabriel Brida David Matesanz Gómez Wiston Adrián Risso 《Expert systems with applications》2009,36(4):7721-7728
In this paper we introduce a new method to describe dynamical patterns of the real exchange rate co-movements time series and to analyze contagion in currency crisis. The method combines the tools of symbolic time series analysis with the nearest neighbor single linkage clustering algorithm. Data symbolization allows us obtaining a metric distance between two different time series that is used to construct an ultrametric distance. By analyzing the data of various countries, we derive a hierarchical organization, constructing minimal-spanning and hierarchical trees. From these trees we detect different clusters of countries according to their proximity. We show that this methodology permits us to construct a structural and dynamic topology that is useful to study interdependence and contagion effects among financial time series. 相似文献
53.
Flavio J. Reyes-Díaz Gabriel Hernández-Sierra José R. Calvo de Lara 《International Journal of Speech Technology》2017,20(3):475-485
The performance of state-of-the-art speaker verification in uncontrolled environment is affected by different variabilities. Short duration variability is very common in these scenarios and causes the speaker verification performance to decrease quickly while the duration of verification utterances decreases. Linear discriminant analysis (LDA) is the most common session variability compensation algorithm, nevertheless it presents some shortcomings when trained with insufficient data. In this paper we introduce two methods for session variability compensation to deal with short-length utterances on i-vector space. The first method proposes to incorporate the short duration variability information in the within-class variance estimation process. The second proposes to compensate the session and short duration variabilities in two different spaces with LDA algorithms (2S-LDA). First, we analyzed the behavior of the within and between class scatters in the first proposed method. Then, both proposed methods are evaluated on telephone session from NIST SRE-08 for different duration of the evaluation utterances: full (average 2.5 min), 20, 15, 10 and 5 s. The 2S-LDA method obtains good results on different short-length utterances conditions in the evaluations, with a EER relative average improvement of 1.58%, compared to the best baseline (WCCN[LDA]). Finally, we applied the 2S-LDA method in speaker verification under reverberant environment, using different reverberant conditions from Reverb challenge 2013, obtaining an improvement of 8.96 and 23% under matched and mismatched reverberant conditions, respectively. 相似文献
54.
In this paper, we investigate control strategies for a scalar, one-step delay system in discrete-time, i.e., the state of the system is the input delayed by one time unit. In contrast with classical approaches, here the control action must be a memoryless function of the output of the plant, which comprises the current state corrupted by measurement noise. We adopt a first order state-space representation for the delay system, where the initial state is a Gaussian random variable. In addition, we assume that the measurement noise is drawn from a white and Gaussian process with zero mean and constant variance. Performance evaluation is carried out via a finite-time quadratic cost that combines the second moment of the control signal, and the second moment of the difference between the initial state and the state at the final time. We show that if the time-horizon is one or two then the optimal control is a linear function of the plant’s output, while for a sufficiently large horizon a control taking on only two values will outperform the optimal affine solution. This paper complements the well-known counterexample by Hans Witsenhausen, which showed that the solution to a linear, quadratic and Gaussian optimal control paradigm might be nonlinear. Witsenhausen’s counterexample considered an optimization horizon with two time-steps (two stage control). In contrast with Witsenhausen’s work, the solution to our counterexample is linear for one and two stages but it becomes nonlinear as the number of stages is increased. The fact that our paradigm leads to nonlinear solutions, in the multi-stage case, could not be predicted from prior results. In contrast to prior work, the validity of our counterexample is based on analytical proof methods. Our proof technique rests on a simple nonlinear strategy that is useful in its own right, since it outperforms any affine solution. 相似文献
55.
Transforming smoothers are known as a successful approach to the multigrid treatment of saddlepoint problems resulting from variational problems. In this paper we analyze similar multigrid methods in the context of the practically important class of optimization problems with partial differential equation constraint, which lead to a different kind of saddle point problems. We prove level independent convergence properties for the resulting multigrid methods and demonstrate this also in numerical investigations for a relevant model problem. 相似文献
56.
Roman Krepki Benjamin Blankertz Gabriel Curio Klaus-Robert Müller 《Multimedia Tools and Applications》2007,33(1):73-90
The investigation of innovative Human-Computer Interfaces (HCI) provides a challenge for future multimedia research and development.
Brain-Computer Interfaces (BCI) exploit the ability of human communication and control bypassing the classical neuromuscular
communication channels. In general, BCIs offer a possibility of communication for people with severe neuromuscular disorders,
such as Amyotrophic Lateral Sclerosis (ALS) or spinal cord injury. Beyond medical applications, a BCI conjunction with exciting
multimedia applications, e.g., a dexterity game, could define a new level of control possibilities also for healthy customers
decoding information directly from the user’s brain, as reflected in electroencephalographic (EEG) signals which are recorded
non-invasively from user’s scalp. This contribution introduces the Berlin Brain–Computer Interface (BBCI) and presents setups
where the user is provided with intuitive control strategies in plausible gaming applications that use biofeedback. Yet at
its beginning, BBCI thus adds a new dimension in multimedia research by offering the user an additional and independent communication
channel based on brain activity only. First successful experiments already yielded inspiring proofs-of-concept. A diversity
of multimedia application models, say computer games, and their specific intuitive control strategies, as well as various
Virtual Reality (VR) scenarios are now open for BCI research aiming at a further speed up of user adaptation and increase
of learning success and transfer bit rates.
相似文献
Klaus-Robert MüllerEmail: |
57.
Starting from the idea of determinism in membrane systems, we introduce a language generating device consisting of morphisms
placed in the nodes of a tree. Initial strings are given in the leaves; by iteratively applying the morphisms to them, we
produce new strings, which are collected in the root of the tree. Such a device is called a tree-system of morphisms (in short, a T system). We investigate here the power of T systems, both in the extended (a terminal alphabet is considered
and only strings over it are accepted) and non-extended case, mainly in comparison with classes of languages in Lindenmayer
hierarchy.
Received: 8 February 2001 / 18 September 2001 相似文献
58.
Ayub V. Ofulla Samson O. Adoka Douglas N. Anyona Paul O. Abuom Diana Karanja John M. Vulule Tom Okurut Ally‐Said Matano Gabriel O. Dida Tsuma Jembe John Gichuki 《Lakes & Reservoirs: Research and Management》2013,18(2):197-215
Intermediate host snails of schistosomiasis were surveyed in this study to determine their abundance and distribution in the lake and land aquatic habitats of Lake Victoria basin of Kenya. Several sites were sampled at eight locations, both in the lake and on the land. The habitat and/or vegetation type (i.e. open water, hippo grass, hyacinth, ambatch trees, other vegetation, stream, swamp, pond, dam) of the sampled aquatic sites within the locations were also differentiated, water physicochemical parameters were determined, and the abundance of different species or taxa of phytoplankton and zooplankton were enumerated and correlated with the abundance of schistosomiasis snails in the sites. The results indicated significantly more Biomphalaria sudanica snails than Bulinus africanus snails in different physical habitats on land (Student's t‐test, P < 0.05), as well as in different locations on land (Student's t‐test, P = 0.026). Regression analyses revealed that several physicochemical parameters, including dissolved oxygen (R2 = ?0.659; n = 8; P = 0.014), pH (R2 = 0.728; n = 8; P = 0.007) and turbulence (R2 = ?0.616; n = 8; P = 0.02), were predictive of Biomphalaria spp. abundance, while pH (R2 = 0.610; n = 8; P = 0.02) and turbulence (R2 = ?0.578; n = 8; P = 0.028) were predictive of Bulinus spp. abundance in different locations in the lake. Cyanobacteria (R2 = 0.638; n = 8; P = 0.02) and chlorophyceae (R2 = ?0.50; n = 8; P = 0.05) were shown to be predictive of both Biomphalaria spp. and Bulinus spp. abundance in different locations in the lake. Zooplankton abundance varied significantly between different locations in the lake (One‐way anova , P < 0.001). Bosmina spp. were found to be predictive of both Biomphalaria spp. (R2 = ?0.627; n = 8; P = 0.01) and Bulinus spp. (R2 = ?0.50; n = 8; P = 0.05) in different locations in the lake. The results from this study will help inform policy regarding control measures for schistosomias and intermediate snail hosts in Lake Victoria waters, as well as in adjacent terrestrial aquatic habitats and even beyond. 相似文献
59.
In this paper, we introduce two algorithms to address the two-echelon capacitated location-routing problem (2E-CLRP). We introduce a branch-and-cut algorithm based on the solution of a new two-index vehicle-flow formulation, which is strengthened with several families of valid inequalities. We also propose an adaptive large-neighbourhood search (ALNS) meta-heuristic with the objective of finding good-quality solutions quickly. The computational results on a large set of instances from the literature show that the ALNS outperforms existing heuristics. Furthermore, the branch-and-cut method provides tight lower bounds and is able to solve small- and medium-size instances to optimality within reasonable computing times. 相似文献
60.
Berger Andrea; Sadeh Michelle; Tzur Gabriel; Shuper Avinoam; Kornreich Liora; Inbar Dov; Cohen Ian J.; Michowiz Shalom; Yaniv Isaac; Constantini Shlomi; Kessler Yoav; Merian Nachshon 《Canadian Metallurgical Quarterly》2005,19(3):362
The authors of this study investigated task switching following cerebellar damage. The study group consisted of 7 children and adolescents (M age = 13.8 years) who underwent surgical removal of a benign posterior fossa tumor. They were tested at a sufficient interval after surgery (M lag = 6.13 years) for restoration of normal cognitive skills and intelligence. Although all showed normal learning of the task compared with control participants, when rapid behavioral changes were required (short preparation time), they exhibited behavioral rigidity manifested by enhanced switching cost. These results are in line with another study on serial reaction time with the same patients (A. Berger et al., in press). They have important implications for our understanding of the cognitive sequelae of early cerebellar damage as well as the involvement of the cerebellum in task switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献