Search results for "GRADIENTS"
showing 10 items of 48 documents
Attēlu aprakstīšana ar konvolūciju un rekurentajiem neironu tīkliem
2017
Automātiskā attēlu aprakstīšana ir fundamentāla mākslīgās inteliģences problēma, ku- ra apvieno kompjūter-redzes un naturālās valodas apstrādes algoritmus. Šajā darbā tiks apskatīta šī nozare, pielietots apbalvojumus izcīnījis modelis un pētītas šī modeļa variāci- jas. Attēlus aprakstošais modelis ir mākslīgais neironu tīkls, kurš sevī apvieno konvolūciju un rekurento neironu tīklu arhitektūras. Darbā vispirms abas arhitektūras ir apskatītas atsevišķi, kā arī teorija, uz kuru balstās modelis. Apskatītais modelis un tā variācijas tiek salīdzinātas, izmantojot klasiskos mašīnmācīšanās rādītājus un mašīntulkošanā izman- totas metrikas. Pēc dažiem rādītājiem oriģinālā modeļa uzlabojumi izrādījā…
Evidence for the Existence of an Effective Interfacial Tension between Miscible Fluids: Isobutyric Acid-Water and 1-Butanol-Water in a Spinning-Drop …
2006
We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-)(3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more…
Chemical, biochemical and microbial diversity through a Pachic Humudept profile in a temperate upland grassland
2013
There is great interest in understanding the factors that drive soil microbial activity and community composition in upland grassland ecosystems. We investigated the role of vertical gradients of chemical properties and various soluble C and N pools on soil microbial community structure by using a combination of chemical and biochemical methods coupled with PCR-denaturing gradient gel electrophoresis (DGGE) community fingerprinting and phospholipid fatty acid (PLFA) profiling. Soil samples were collected at increasing depth from a temperate upland grassland. Soil organic matter-related pools (total organic C and total Kjeldahl N) and functionally related active pools (microbial biomass C an…
Al-27 and Si-29 Solid-State NMR Characterization of Calcium-Aluminosilicate-Hydrate
2012
International audience; Calcium silicate hydrate (C-S-H) is the main constituent of hydrated cement paste and determines its cohesive properties. Because of the environmental impact of cement industry, it is more and more common to replace a part of the clinker in cement by secondary cementitious materials (SCMs). These SCMs are generally alumina-rich and as a consequence some aluminum is incorporated into the C-S-H. This may have consequences on the cohesion and durability of the material, and it is thus of importance to know the amount and the location of Al in C-S-H and what the parameters are that control these features. The present paper reports the Si-29 and Al-27 MAS NMR analyses of …
Classification of SD-OCT volumes with multi pyramids, LBP and HOG descriptors: application to DME detections.
2016
This paper deals with the automated detection of Diabetic Macular Edema (DME) on Optical Coherence Tomography (OCT) volumes. Our method considers a generic classification pipeline with preprocessing for noise removal and flattening of each B-Scan. Features such as Histogram of Oriented Gradients (HOG) and Local Binary Patterns (LBP) are extracted and combined to create a set of different feature vectors which are fed to a linear-Support Vector Machines (SVM) Classifier. Experimental results show a promising sensitivity/specificity of 0.75/0.87 on a challenging dataset.
An Image Segmentation Algorithm based on Community Detection
2016
International audience; With the recent advances in complex networks, image segmentation becomes one of the most appropriate application areas. In this context, we propose in this paper a new perspective of image segmentation by applying two efficient community detection algorithms. By considering regions as communities, these methods can give an over-segmented image that has many small regions. So, the proposed algorithms are improved to automatically merge those neighboring regions agglomerative to achieve the highest modularity/stability. To produce sizable regions and detect homogeneous communities, we use the combination of a feature based on the Histogram of Oriented Gradients of the …
Definition of a mutual reference shape based on information theory and active contours
2013
In this paper, we propose to consider the estimation of a reference shape from a set of different segmentation results using both active contours and information theory. The reference shape is then defined as the minimum of a criterion that benefits from both the mutual information and the joint entropy of the input segmentations. This energy criterion is here justified using similarities between information theory quantities and area measures, and presented in a continuous variational framework. This framework brings out some interesting evaluation measures such as the specificity and sensitivity. In order to solve this shape optimization problem, shape derivatives are computed for each te…
Mapping spatial patterns of denitrifiers for bridging community ecology and microbial processes along environmental gradients
2009
International audience; While there is ample evidence that microbial processes can exhibit large variations at a field scale, very little is known about the spatial distribution of the communities mediating these processes. The objective of this study was to explore spatial patterns of size and activity of the denitrifying community, a functional guild involved in N-cycling, in a grassland field subjected to different cattle grazing regimes. We used geostatistical modeling to map the distribution of size and activity of the denitrifier community in the pasture. Size of the denitrifier community was estimated by PCR quantification of the denitrification gene copy numbers while its activity w…
Genome‐phenotype‐environment associations identify signatures of selection in a panmictic population of threespine stickleback
2023
Adaptive genetic divergence occurs when selection imposed by the environment causes the genomic component of the phenotype to differentiate. However, genomic signatures of natural selection are usually identified without information on which trait is responding to selection by which selective agent(s). Here we integrate whole-genome-sequencing with phenomics and measures of putative selective agents to assess the extent of adaptive divergence in threespine stickleback occupying the highly heterogeneous lake Mývatn, NE Iceland. We find negligible genome wide divergence, yet multiple traits (body size, gill raker structure and defence traits) were divergent along known ecological gradients (t…
Temporal species turnover and plant community changes across different habitats in the Lake Engure Nature Park, Latvia
2014
Veģetācijas dinamikas izpētē reti ir gadījumi, kad monitoringu vienlaicīgi veic vairākās atšķirīgās ekosistēmās. Tomēr šāda veida pētījumi ļauj padziļināti izprast veģetācijas struktūras un pazīmju izmaiņu mehānismus. Šajā pētījumā aplūkotas lakstaugu stāva izmaiņas, sugu aprite un sugu skaita-laika attiecība dažādu biotopu griezumā 12 gadu periodā ILTER monitoringa stacijā Engures ezera dabas parkā. Sugu aprite laikā definēta kā atšķirība sugu sastāvā starp diviem laika periodiem. Sugu skaita-laika attiecība tika novērtēta, izmantojot slīdošo logu pieeju. Detrendētā korespondentanalīze izmantota, lai noskaidrotu ikgadējās izmaiņas sugu sastāvā. Sugu skaits un kumulatīvais skaits, kā arī da…