83 research outputs found
Automatic Detection of Calibration Grids in Time-of-Flight Images
It is convenient to calibrate time-of-flight cameras by established methods,
using images of a chequerboard pattern. The low resolution of the amplitude
image, however, makes it difficult to detect the board reliably. Heuristic
detection methods, based on connected image-components, perform very poorly on
this data. An alternative, geometrically-principled method is introduced here,
based on the Hough transform. The projection of a chequerboard is represented
by two pencils of lines, which are identified as oriented clusters in the
gradient-data of the image. A projective Hough transform is applied to each of
the two clusters, in axis-aligned coordinates. The range of each transform is
properly bounded, because the corresponding gradient vectors are approximately
parallel. Each of the two transforms contains a series of collinear peaks; one
for every line in the given pencil. This pattern is easily detected, by
sweeping a dual line through the transform. The proposed Hough-based method is
compared to the standard OpenCV detection routine, by application to several
hundred time-of-flight images. It is shown that the new method detects
significantly more calibration boards, over a greater variety of poses, without
any overall loss of accuracy. This conclusion is based on an analysis of both
geometric and photometric error.Comment: 11 pages, 11 figures, 1 tabl
Synthesis of fluvirucins and their aglycons, the fluvirucinins
Fluvirucins are bioactive macrolactam glycosides isolated from actinomycetes. This review gives an overview of this family of natural products, covering isolation, biological activities, biosynthesis, and total synthesis. The synthesis of fluvirucins and their aglycons, the fluvirucinins, is presented, paying special attention to the synthetic strategy and stereochemical aspects. 1 Introduction 2 Isolation, Biological Activity, and Biosynthesis 3 Synthetic Approaches 3.1 Closure of the 14-Membered Ring by Ring-Closing Metathesis 3.2 Closure of the 14-Membered Ring by Macrolactamization 3.3 Construction of the 14-Membered Ring by Aza-Claisen Ring Expansion 4 Conclusio
Access to enantiopure 4-substituted 1,5-aminoalcohols from phenylglycinol-derived δ-lactams: synthesis of Haliclona alkaloiods
LiNH2BH3-promoted reductive opening of 8-substituted phenylglycinol-derived oxazolopiperidone lactams leads to enantiopure 4-substituted-5-aminopentanols, which are used as starting building blocks in the synthesis of the Haliclona alkaloids haliclorensin C, haliclorensin, and halitulin (formal). The starting lactams are easily accessible by a cyclocondensation reaction of (R)-phenylglycinol with racemic γ-subtituted δ-oxoesters, in a process that involves a dynamic kinetic resolution
Enantioselective synthesis of the ethyl analog of the marine alkaloid haliclorensin C
The enantioselective synthesis (3.7% overall yield in nine steps from 2) and biological screening of the ethyl analog of the macrocyclic marine alkaloid haliclorensin C (compound 5) are reported. Amino alcohol 3, generated by a LiNH2BH3-promoted reductive ring-opening/debenzylation sequence from phenylglycinol-derived lactam 2, was used as the starting chiral linear building block. Incorporation of the undecene chain via the nosyl derivative 12, methylenation of the pentanol moiety, and a ring-closing metathesis are the key steps of the synthesis
Enantioselective total synthesis of fluvirucinin B1
A convergent synthesis of fluvirucinin B1 from acid ent-6a and nitrile ent-9, involving an organocopper coupling, a stereoselective allylation, a ring-closing metathesis reaction, and a stereoselective hydrogenation as the key steps, is reported. The starting building blocks have been prepared in a straightforward manner from a common phenylglycinol-derived lactam 1. An unprecedented regioselective oxidation of phenylglycinol-derived secondary amines 5 to carboxylic acids 6 has been developed
Image analysis applied to quality control in transparent packaging: a case study of table olives in plastic pouches
[EN] Consumers consider food products sold in transparent packaging to be trustworthy and of higher quality, but only if the contained product is visually attractive. However, at points of sale, the appearance of food products can change, which affects their perceived quality and purchase intention. Image analysis could mimic the visual evaluations made by humans, and data processing allows to establish models to predict changes in food quality. This study aimed to evaluate the feasibility of the image analysis to monitor the perceived quality of table olives during storage as a system model. For this purpose, the brine colour, sensory acceptance and image analysis of table olives packed in transparent pouches were evaluated at two different temperatures. The proposed system was able to predict brine browning and to assess product sensory perception. Therefore, image analysis proved a non-destructive and fast tool to predict consumer acceptance of table olives packed in transparent pouches.This study was funded by "Ministerio de Economia y Competitividad" within the State Program for I+D+i, aimed at the challenges of society (Retos-Colaboracion RTC-2015-3586-2).Fuentes López, A.; Verdú Amat, S.; Fuentes López, C.; Ginzel, M.; Barat Baviera, JM.; Grau Meló, R. (2022). Image analysis applied to quality control in transparent packaging: a case study of table olives in plastic pouches. European Food Research and Technology. 248(7):1859-1867. https://doi.org/10.1007/s00217-022-04011-018591867248
Las inferencias lógicas: una vÃa para desarrollar el aprendizaje del escolar de secundaria básica
Las investigaciones en la enseñanza y el aprendizaje de la Matemática abarcan muchos elementos que intervienen en el proceso mediante el cual maestros y profesores tratan de desarrollar habilidades, actitudes y conocimientos matemáticos en sus alumnos. Durante el proceso de inferencia que se realiza en todo razonamiento se efectúa sobre la base de la estructura lógica de las premisas y conclusiones, de esta forma hemos podido determinar como aprenden los estudiantes de la enseñanza media las reglas de inferencia y asà poder potenciar la transformación de su aprendizaje a través de la ejecución de estrategias que activen el proceso formativo. En el trabajo se muestran una serie de inferencias lógicas que de trabajarse de esa forma podrÃan obtenerse resultados superiores, pues contribuyen al desarrollo del pensamiento lógico del estudiante, de manera que puedan enfrentar exitosamente los contenidos con mayores dificultades en la secundaria básica, tal es el caso de la GeometrÃa Plana, quedando explicadas en detalles y con ejemplos que ilustran lo que hemos planteado.Eje: Educación secundaria y profesional. Experiencias educativasRed de Universidades con Carreras en Informática (RedUNCI
Las inferencias lógicas: una vÃa para desarrollar el aprendizaje del escolar de secundaria básica
Las investigaciones en la enseñanza y el aprendizaje de la Matemática abarcan muchos elementos que intervienen en el proceso mediante el cual maestros y profesores tratan de desarrollar habilidades, actitudes y conocimientos matemáticos en sus alumnos. Durante el proceso de inferencia que se realiza en todo razonamiento se efectúa sobre la base de la estructura lógica de las premisas y conclusiones, de esta forma hemos podido determinar como aprenden los estudiantes de la enseñanza media las reglas de inferencia y asà poder potenciar la transformación de su aprendizaje a través de la ejecución de estrategias que activen el proceso formativo. En el trabajo se muestran una serie de inferencias lógicas que de trabajarse de esa forma podrÃan obtenerse resultados superiores, pues contribuyen al desarrollo del pensamiento lógico del estudiante, de manera que puedan enfrentar exitosamente los contenidos con mayores dificultades en la secundaria básica, tal es el caso de la GeometrÃa Plana, quedando explicadas en detalles y con ejemplos que ilustran lo que hemos planteado.Eje: Educación secundaria y profesional. Experiencias educativasRed de Universidades con Carreras en Informática (RedUNCI
La búsqueda de relaciones: una vÃa para resolver problemas matemáticos en la educación primaria
El hombre desde que nace empieza a aprender. Algunos conocimientos se adquieren sin percatarnos de ellos, otros necesitan esfuerzos y dedicación, algunos son estrictamente necesarios, otros no lo son tanto. El proceso de búsqueda de relaciones es un modo de actuación de extraordinaria utilidad a la hora de resolver problemas y en particular problemas matemáticos, pues si no se logra encontrar las relaciones que ofrecen los datos, figuras, fórmulas. ... y su relación con la o las preguntas que formula el problema, entonces será difÃcil concebir un plan que conduzca al éxito en la resolución de problemas. En nuestro trabajo pretendemos dar algunas ideas de cómo desarrollar el pensamiento relacional de los estudiantes, evitar el impulso a la ejecución inmediata, influir en la forma de captar la información, interpretar el contenido y exponer sus ideas lo que le permite desarrollar su comunicación y la lengua materna en general.The time man is born he begins to learn. Some knowledge are acquired without his noticing it, others call for effort and dedication, some are strictly necessary, others are not. The process of searching for relations is an extraordinarily useful way of acting at the time of solving problems, particularly those related to mathematics, because if the relations offered by the data, the figures, the formula … and their relations with the question or questions from the problem are not found, it will be hard to conceive a plan that may lead to success in problem solving. In our work we intend to offer some ideas about how to develop the students relational thinking, avoid the tendency to immediate execution, influence upon the way of processing the information, interpret the content and express ideas, so that communication may be developed as well as mother tongue in general.Eje: Educación primaria: experiencias educativasRed de Universidades con Carreras en Informática (RedUNCI
Histoire des forêts du versant nord des Pyrénées au cours des 30000 dernières années
Les recherches playnologiques réalisées dans le versant nord des Pyrénées ainsi que les données anthracologiques disponibles et les études de macrorestes végétaux permettent de décrire les étapes de la mise en place des principales essences forestières au cours des 30000 dernières années. Dans les Pyrénées centrales, avant 30000 BP, l'épicéa était bien développé. Les données anthracologiques permettent de penser qu'il a disparu des Pyrénées vers 18000-17000 BP. Entre 11000 BP et 10000 BP, l'ultime phase de dégradation climatique de la fin du dernier épisode glaciaire, le Dryas récent, a davantage affecté la couverture végétale des Pyrénées méditerranéennes que celle de la moitié nord occidentale. Au Postglaciaire, le sapin se développe précocement dans la partie orientale de la chaîne et beaucoup plus tard dans la partie occidentale. L'homme agit très tôt sur le milieu montagnard, dès 6200 BP dans les Pyrénées méditerranéennes. Son ection s'accentue particulièrement vers 4000 BP, au Moyen Age, puis au 16è-17è et 18 è siècles lors du développement des forges, déterminant d'importantes modifications phytogéographiques, notamment une extension du hêtre aux dépens du sapin
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