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Experimental Evaluation of Four Intermediate Filters to Improve the Motion Field Estimation
No full textFor the last 40 years, optical flow (OF) estimation has been challenging the computer vision community. OF is the apparent motion of the pixels in two consecutive images. Variational models are the most used technique to estimate OF, stating an OF estimation error energy model. The minimization of this energy performs an iterative coarse-to-fine approach. In each iteration, the OF is processed with an intermediate filter to eliminate outliers. In the literature, there are studies related to the number of warpings, the number of considered scales, and their effect on the optical flow estimation. However, in the literature, there is no work that studies in depth the effect of different intermediate filters on the optical flow estimation performance. That fact motivates us to compare the effect of different filters in optical flow estimation. Taking an OF model, which is robust to large displacements and illumination changes, we tested it with four different filters: Bilateral filter (BF), Median filter (MF), Weighted median filter (WMF), and a new filter called a Balanced median filter (BMF). This BMF is a weighted sum of the Median filter and the Bilateral filter (BF) using an adaptive weight map that balances the optical flow estimation error due to the median filter or the Bilateral median filter. We assessed these three filters in the state-of-the-art MPI-Sintel training set. That contains realistic synthetic scenes presenting blur, fog, illumination changes, and sequences with significant displacement. Our experimental evaluation shows that the Balanced median filter performs better than the other two filters. When we validated our results on the MPI-Sintel benchmark webpage, we observed that our model performs better than classical methods such as Horn-Schunck, TVL1, and LDOF. Besides, it performs similar to current optical flow estimation methods such as GeoFlow, CPNFlow, and FLOW_UFO
Rasgos-CL: A functional trait database of Chilean woody plants
No full textMotivation: Due to language and networking barriers, global initiatives to compile trait data often fail to integrate data from sources in non-English languages or scientists that largely speak and write in non-English languages. To illustrate the potential for regional databases to fill gaps in trait data, and how such databases may fill critical gaps in global biodiversity databases, we built the Rasgos-CL Database. Rasgos-CL provides a comprehensive set of plant traits for the woody flora of Chile by mobilizing and standardizing unstructured data largely from the Spanish-language literature. We quantified the gains in trait coverage compared to global trait databases and identified phylogenetic and geographic biases of trait data gaps.Main Types of Variables Contained: Rasgos-CL contains 25,174 trait records, including 2 continuous and 21 categorical traits for 662 woody species.Spatial Location and Grain: National coverage, with species that occur across all ecosystems in continental Chile.Time Period and Grain: Data were extracted from sources published between 1833 and 2023.Major Taxa and Level of Measurement: Rasgos-CL includes trait data aggregated at the species level for 662 tree and shrub species, and also provides trait records from individual data sources.Software Format: Rasgos-CL includes four csv files. A GitHub repository contains the csv files.Our research was funded by the Agencia Nacional de Investigacion y Desarrollo (Chile; FONDECYT Regular 1201347) and the Data Observatory Foundation. RS was supported by FONDECYT Iniciacion 1120096 and ANID Basal FB210006
Neighbourhood landscape context shapes local species richness patterns across continents
No full textAim: Recent studies highlight the importance of linking landscape ecology and macroecology for a better understanding of broad-scale biodiversity patterns. The "landscape context effect" denotes that species responses and biodiversity in a focal area are shaped by neighbouring landscape composition and structure outside the focal area. Here, we test whether the landscape context effect could be pronounced at macroecological scales.Location: Sub-Saharan Africa and continental China.Time period: Late 20th to early 21st centuries.Taxa studied: Terrestrial mammals (>= 2 kg).Methods: We calculated species richness on the basis of grid cells of 50 km x 50 km and 100 km x 100 km. We used ordinary least square and random forest models to examine the relationships between species richness within grid cells and landscape context (defined as composition and structure of the neighbouring landscape outside the grid cells, with distances of 10-400 km to the boundary of a given grid cell). We used variation partitioning to quantify the independent and shared explanatory power of the landscape context variables, grouping species by body size and diet.Results: Landscape context alone explained <= 20% of the variation in species richness, even when controlling for correlations with macroenvironmental variables (climate, productivity and topography) and correlations with landscape attributes within the grid cells. Importantly, the explanatory power of landscape context at the scales of 100-400 km ofen outweighed grid-cell landscape attributes or macro-environmental variables. The independent explanatory power of landscape context was lowest for small-sized omnivores. Furthermore, we found higher independent explanatory power for large herbivores in sub-Saharan Africa than in continental China.Main conclusions: Landscape context plays a substantial role in shaping local biodiversity patterns at regional and continental scales, with its strength varying with organism diet and movement needs and possibilities. These findings support that conservation efforts should include effective management of landscape structure, with attention to differing space requirements among organism groups. Our work also illustrates the scope for testing landscape ecological hypotheses at macroecological scales.ACKNOWLEDGEMENTS We thank Dr Petr Keil and two anonymous reviewers for their valuable suggestions on earlier versions of this paper. This study was supported by the National Natural Science Foundation of China (grant numbers 32061143014 and 42001044), the Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB31000000), and the Open Fund for Key Lab. of Land Degradation and Ecological Restoration in northwestern China of Ningxia University (grant number). S.A. and C.X. acknowledge the support by FONDECYT 1170995. J.S. was funded by Fundo Europeu de Desenvolvimento Regional through the Operational Competitiveness Factors Program "COMPETE" and by National Funds through the Foundation for Science and Technology (FCT) through the project ALIENTRADE (PTDC/BIA-ECO/30931/2017-POCI-01-0145-FEDER-030931). L.R. was supported through FCT, IP, under the programme of "Stimulus of Scientific Employment-Individual Support" with the contract "CEECIND/00445/2017". J.-C.S. considers this work a contribution to his VILLUM Investigator project "Biodiversity Dynamics in a Changing World", funded by VILLUM FONDEN (grant 16549), and Center for Ecological Dynamics in a Novel Biosphere (ECONOVO), funded by Danish National Research Foundation (grant DNRF173)
Loss of native herbivores triggers diversity decline of ephemeral plant communities
No full textAim: Evaluate the temporal changes in species diversity, composition, and structure of ephemeral plant communities and the seed bank in response to long-term herbivore exclusion over 11 years in plots with and without herbivores.LocationNorth-central Chile.Methods: We obtained information on ephemeral vegetation cover in August and September using the intercept point method and recorded seed abundance in April. The Bosque Fray Jorge National Park Long-Term Socio-Ecological Research (LTSER) provided these records covering 11 years (2009-2019). From the original experiment of 20 plots, we used eight plots divided into two treatments: four plots allowed free access to all herbivores (with herbivores), while the other four plots excluded herbivores (without herbivores).Results: We found that Hill-Shannon diversity increased in plant communities with herbivores and a temporal increase in the cover of the dominant species, Plantago hispidula, under herbivore exclusion. In wet years, species richness and temporal turnover of plant communities increased independently of treatment. Although seed abundance differed among treatments and years, population structure remained constant over time and among treatments, suggesting that the seed bank acts as a buffer against shocks that modify plant community dynamics. Structural equation modeling revealed that precipitation, via its positive effects on Plantago hispidula, increases native plant richness to a greater extent than herbivores. However, in the absence of herbivores, precipitation directly affects native species richness. Moreover, we found that precipitation also influences the native species richness of the seed bank, both directly and indirectly, although its impacts exhibit a time lag.Conclusions: Our study demonstrates that the temporal dynamics of ephemeral plant communities and seed banks in semi-arid ecosystems are strongly coupled to climate variability, highlighting the vulnerability of these communities to biodiversity loss and climate change.FONDECYT 1220358, 1201347, 10302225, and 1160026 and NSF LTREB- DEB2025816, ACE210006, and PIA/BASAL FB210006
Tipologia funcional para áreas naturais protegidas: ruralização e urbanização na zona central do Chile
No full textLas principales transformaciones territoriales en el valle central de Chile están asociadas a los procesos de urbanización, dejando susceptible las áreas de importancia ambiental. Este trabajo tiene como objetivo determinar los tipos de cambios en relación con las áreas naturales protegidas (ANP) de la zona central, determinando las principales y ofreciendo una explicación para cada una de ellas. La metodologÃa empleada se basa en los cambios de cobertura de usos de suelo entre 2002 y 2015 a partir de la fotointerpretación. Para establecer las tipológicas se elaboró una matriz de confusión, caracterizando cada una de las unidades de estudio. A partir de lo anterior, se estableció la relación existente entre las infraestructuras urbanas a las ANP. Entre las conclusiones principales se destaca que el mayor impacto sobre las ANP se da por la tipologÃa urbana, ejerciendo mayor presión con el avance del tiempo. Existe una permeabilidad en los espacios urbanos-rurales-naturales, lo que obliga a pensar en nuevas tipologÃas funcionales que den cuenta de estos nuevos espacios. En definitiva, estos espacios dinámicos cumplen un rol dentro de un contexto que también va evolucionado
Impact of internal structure on aggregate collisions
No full textGranular-mechanics simulations are used to study collisions between granular aggregates. We compare the collision outcomes for three different types of aggregate: (i) aggregates constructed by a ballistic particle–cluster aggregation (BPCA) process, and two homogeneous spherical aggregates which differ by their grain coordination. All aggregates contain the same number of grains and (central) filling factor. We find that BPCA aggregates have a slightly decreased growth velocity for central impacts. After scaling the collision velocities to the growth velocity for central impact and the impact parameter to the gyration radius, our collision results show a remarkable degree of agreement for the aggregates studied. Also, the collision-induced compaction as well as the size of fluctuations during the collision process are identical for all aggregate types. Even at glancing collisions, the larger extension and rough surface of BPCA aggregates do not cause major changes as compared to homogeneous aggregates with a well-defined and smooth surface. However, monomer ejection during the collision is enhanced for BPCA aggregates. This study thus shows that details of the internal aggregate structure are of little importance in collisions of granular aggregates, except for grain ejection.Simulations were performed at the High Performance Cluster Elwetritsch (Regionales Hochschulrechenzentrum, TU Kaiserslautern, Germany). BP and EMB thank support from PICTO2019-UM-00048 (Proyectos de Investigación CientÃfica y Tecnológica Orientados, Universidad de Mendoza) and SIIP 06/M008-T1 (SecretarÃa de Investigación, Internacionales y Posgrado, Universidad Nacional de Cuyo)
Nonlinear optomechanical resonance entering a self-organized energy transfer pattern
No full textThe energy transfer between different subsystems or different vibration modes is always one of the most interested problems in the study of the resonance phenomena in coupled nonlinear dynamical systems. With an optomechanical system operating in the regime of unresolved sideband, where its mechanical frequency is lower than the cavity field damping rate, we illustrate the existence of a special nonlinear resonance phenomenon. This type of previously unknown resonance manifests an organized pattern of the coupled cavity field and mechanical oscillation, so that the cavity field precisely pushes the mechanical oscillator within an appropriate small time window in each mechanical oscillation period and the mechanical energy will increase by a jump of almost fixed amount after each oscillation cycle. The scenario is realized at a resonance point where the frequency difference of two driving fields matches the mechanical frequency of the system, and this condition of drive-frequency match is found to trigger a mechanism to lock the two subsystems of an unresolved-sideband optomechanical system into a highly ordered energy transfer as the above mentioned. Due to a significantly enhanced nonlinearity in the vicinity of the resonance point, optical frequency combs can be generated under pump powers of thousand times lower, as compared to the use of a single-tone driving field for the purpose. An unresolved sideband system under the drives without satisfying the resonance condition also demonstrates other interesting dynamical behaviors. Most of all, by providing a realistic picture for the nonlinear optomechanical dynamics in unresolved sideband regime, our study points to a direction to observe novel dynamical phenomena and realize other applications with the systems of less technical restrictions.We thank Dr. Zhen Shen, Dr. Yan-Lei Zhang, Dr. Ming Li, and Dr. Luis MartÃnez for the helpful discussions on the relevant experimental issues. This work was supported by National Natural Science Foundation of China (11574093), Natural Science Foundation of Fujian Province, China (2020J01061), ANID Fondecyt Regular, Chile (1221250), and Fondo de Iniciación de Universidad Mayor, Chile (PEP I-2019021)
Niveles de Burnout y factores asociados en trabajadores de la unidad de cuidados intensivos en la primera ola de la pandemia COVID-19 en Chile: estudio transversal
No full textIntroduction: The COVID-19 pandemic resulted in an unpredictable healthcare crisis with a high psychological burden on healthcare workers. Objective: To evaluate burnout levels and their associated demographics and occupational factors among intensive care unit healthcare workers during the COVID-19 pandemic in a single hospital in the city of Temuco, Chile. Methods: A cross-sectional design in which a sociodemographic questionnaire and the Maslach Burnout Inventory for Human Services were sent to health care workers in a single Chilean Intensive Care Unit during the pandemic COVID-19. Burnout levels, demographic, and occupational factors are reported using descriptive statistics; correlations between burnout levels and demographic-occupational factors were analyzed using Spearman's and rank-biserial correlation coefficients; and multiple linear stepwise regression was used to assess the contribution of demographic and occupational factors to participants' burnout levels. Results: A total of 84 participants (46 women and 38 men) were included in the analysis. Depersonalization and low personal accomplishment were evidenced in 95.2% and 98.8% of the intensive care unit healthcare workers, respectively. Emotional exhaustion was positively correlated with having children ( = 0.72; < 0.01). Age ( = 0.79; < 0.05), sex ( = 0.30; < 0.05), and prior experience in intensive care unit facilities ( = 0.71; < 0.05) were correlated with depersonalization. Feeling of personal accomplishment was positively correlated with with sex ( = 0.70; < 0.05) and type of work shift ( = 0.29; < 0.01). Conclusions: The intensive care unit healthcare workers in this study reported high levels of depersonalization and low feelings of personal accomplishment during an advanced stage of the COVID-19 pandemic. Older age, being female, having children, having intensive care unit experience, and working at 4th shift were factors related to burnout dimensions
The thinking of Chilean Teachers about Pedagogical Knowledge: Evidence from the Last Decade
No full textEl trabajo revisa la evidencia cientÃfica producida durante el periodo 2011-2019 sobre el pensamiento del profesorado chileno y los saberes pedagógicos y disciplinarios, en el contexto del sistema escolar. El periodo 2011-2019 se caracterizó por la implementación de nuevas polÃticas educativas, esencialmente centradas en la carrera docente, asà como por la emergencia de aulas diversas, gatilladas por el fenómeno migratorio y nuevas polÃticas inclusivas. El trabajo se desarrolló bajo una metodologÃa cualitativa, con un diseño tipo revisión sistemática, propio de un estudio secundario. De acuerdo con los criterios establecidos, se seleccionaron 29 fuentes de información (estudios), cuyos datos fueron organizados en ocho categorÃas. Los resultados demostraron que en el pensamiento del profesorado chileno cohabitan perspectivas contrapuestas; no obstante, se revela en general una preponderancia de referencias asociadas al constructivismo. Del mismo modo, se apreció una alta valoración del profesorado sobre su propio desempeño, que no necesariamente se podrÃa armonizar con la evidencia de aprendizajes escolares
CURRENT STATE AND TRANSFORMATIONS OF RURAL EMPLOYMENT IN LATIN AMERICA: AN ANALYSIS OF THE CASE OF CHILE
No full textEl empleo rural de América Latina se ha mantenido históricamente en una situación desfavorable respecto de las áreas urbanas. Mientras los ingresos de los habitantes rurales son inferiores, el trabajo por cuenta propia, el trabajo agrÃcola y la pluriactividad, tÃpicamente asociados a alta vulnerabilidad, son mayores en áreas rurales. Pese a lo anterior, en las últimas décadas los paÃses de la región han observado modificaciones en sus estructuras de empleo rural. El objetivo del estudio es plasmar el estado actual y las transformaciones del empleo rural en América Latina, analizando los cambios recientes producidos en Chile. Se utilizan diversas encuestas de hogares para describir la situación del empleo rural para cuatro paÃses de América Latina: Chile, Colombia, Guatemala y Nicaragua, y se analizan los cambios recientes producidos en Chile. Los resultados indican que, si bien las áreas rurales de América Latina se encuentran en condiciones desfavorable, en el Chile rural se observa una caÃda en el empleo agrÃcola y en el trabajo por cuenta propia, y una mayor participación femenina, lo que se condice con una mejora en las condiciones de vida de los habitantes rurales y una potencial convergencia económica hacia las áreas urbanas