ICA based algorithms for computing optimal 1-D linear block transforms in variable high-rate source coding

International audienceThe Karhunen-Loève Transform (KLT) is optimal for transform coding of Gaussian sources, however, it is not optimal, in general, for non-Gaussian sources. Furthermore, under the high-resolution quantization hypothesis, nearly everything is known about the performance of a transform coding system with entropy constrained scalar quantization and mean-square distortion. It is then straightforward to find a criterion that, when minimized, gives the optimal linear transform under the abovementioned conditions. However, the optimal transform computation is generally considered as a difficult task and the Gaussian assumption is then used in order to simplify the calculus. In this paper, we present the abovementioned criterion as a contrast of independent component analysis modified by an additional term which is a penalty to non-orthogonality. Then we adapt the icainf algorithm by Pham in order to compute the transform minimizing the criterion either with no constraint or with the orthogonality constraint. Finally, experimental results show that the transforms we introduced can (1) outperform the KLT on synthetic signals, (2) achieve slightly better PSNR for high-rates and better visual quality (preservation of lines and contours) for medium-to-low rates than the KLT and 2-D DCT on grayscale natural images

Planning d'affectation des marchandises: problème de transport à quatre indices

International audienc

Production of xylanases by Bacillus polymyxa using lignocellulosic wastes

Production of xylanolytic enzymes with no detectable cellulase activity was investigated using two strains of Bacillus polymyxa. The optimum pH and temperature for activities of the two xylanases ranged from 6.0 to 7.0 and from 45 to 50°C, respectively. The highest titres of xylanase, up to 24 nKat ml^-1 were produced within 36 and 42 h, respectively in shake flask cultures at 30°C. Enzyme production showed a cell growth associated profile. One of two strains, B. polymyxa CECT 153 was chosen for further detailed study. Numerous carbohydrates were examined for their ability to induce xylanase. It was found that xylan or xylan containing substrates, such as wheat straw, induced maximum and comparable levels of xylanase, while pure cellulose (avicel, a-cellulose) and the easily metabolisable sugars (glucose, sucrose) did not improve xylanase synthesis. Low levels of constitutive enzyme were produced as evidence from the culture medium without carbon source addition. Among various nitrogen sources tested, yeast extract was optimal for the production of xylanase

Optimization of a culture medium for xylanase production by Bacillus sp. using statistical experimental designs

The concentrations of oat spelt xylan, casein hydrolysate and NH4Cl in the culture medium for production of xylanase from Bacillus sp. I-1018 were optimized by means of response surface methods. The path of steepest ascent was used to approach the optimal region of the medium composition. The optimum composition of the nutrient medium was then easily determined by using a central composite design and was found to be 3.16g/l of xylan, 1.94g/l casein hydrolysate, 0.8g/l of NH4Cl. The xylanase production was increased by 135% when the strain was grown in the optimized medium compared to initial medium

Etiology, distribution, treatment modalities and complications of maxillofacial fractures

Purpose: This study evaluated the trends and factors associated with maxillofacial fractures treated from 1997 to 2007 in the Oral and Maxillofacial Surgery Department of the Clermont-Ferrand University Hospital. Material and Methods: This study included 364 patients of which 82% were men and 45%, 20-29-years old. The etio- logy, anatomical distribution, treatment modality and complications of maxillofacial fractures were examined. Results: Overall, interpersonal violence, traffic accidents and falls were the most common mechanisms of injury. There was a decreasing trend in traffic accidents and increasing one in falls as a cause of fracture over the 11-years period of this study. Young male patients were preferentially victim of interpersonal violence and traffic accidents, while middle-aged ones were of falls and work-related accidents. Middle-aged female patients were preferentially victim of traffic accidents and interpersonal violence, while older ones were of falls. And the number of fractures per patient varied according to the mechanism of injury: low after work-related accidents and high after traffic accidents. About two-third of fractures involved the mandible. Most of these mandibular fractures were treated by osteosynthesis with or without intermaxillary fixation, with the proportion of the latter increasing over time. There were very few postoperative infections and only in mandible. Conclusions: Maxillofacial fractures predominantly occur in young men, due to interpersonal violence. There is nevertheless an increasing trend in falls as a cause of fracture, especially in female patients, consistent with the increasing trend in presentation of older people. Most maxillofacial fractures involve the mandible and there is an increasing trend in treating these fractures by osteosynthesis without intermaxillary fixation. Antibiotic prophy - laxis associated with dental hygiene care can be indicated to prevent postoperative infections

Affect as a Decision-Making System of the Present

article is based on the first author’s doctoral dissertation completed under the second author’s direction at Columbia University. The authors thank the other members of the dissertation committee—Eric Johnson, Leonard Lee, Tom Meyvis, and Elke Weber—for their very useful input at various stages of this project. They also thank Jiewen Hong, Seshan Ramaswami, and Anne-Laure Sellier for their helpful comments, and the various members of the Research o

Recurrence phenomenon for Vlasov-Poisson simulations on regular finite element mesh

In this paper, we focus on one difficulty arising in the numerical simulationof the Vlasov-Poisson system: when using a regular grid-based solver with periodicboundary conditions, perturbations present at the initial time artificially reappear at alater time. For regular finite-element mesh in velocity, we show that this recurrence timeis actually linked to the spectral accuracy of the velocity quadrature when computingthe charge density. In particular, choosing trigonometric quadrature weights optimallydefers the occurence of the recurrence phenomenon. Numerical results using the Semi-Lagrangian Discontinuous Galerkin and the Finite Element / Semi-Lagrangian methodconfirm the analysis