Virtual Reality Volumetric Rendering Using Ray Marching with WebGL

This work is concerned with virtual reality web applications that implement volumetric visualizations based on Ray Marching, combined with traditional triangle-based rendering. The use case selected was an interactive tool to navigate through a 3D model of sedimentary basins and natural reservoirs of oil and gas. The surfaces are described by signed distance functions computed in the GPU within a pixel shader. A procedural 3D texture defines the distribution of sedimentary strata inside the volume and provides visual clues of the internal structures. In VR mode, the user can navigate the scene by moving his body. He can subtract portions of the 3D volume in real time through a set of Boolean operators (plane, cylinder or sphere) using VR hand controllers. A virtual control panel, dynamically generated from a JSON file, allows parameters to be adjusted within VR. The application can also be used in desktop mode.Workshop: WCGIV - Computación Gráfica, Imágenes y VisualizaciónRed de Universidades con Carreras en Informátic

Estimation of RF PA Non-Linearities After Cross-Correlating Current and Output Voltage

The estimation of 1 dB compression and third-order intercept points can be obtained after the cross-correlation between dynamic current and output voltage of radio frequency power amplifiers. This estimation is performed using actual power measures and not power inferred from voltage measurements. The underlining theory and a correlator that allows implementing this measurement on-chip are presented. The trade-off between measuring voltage and the actual power is also discussed and it is shown that different information concerning the output load is obtained when observing the PA's output voltage and power. Simulation results, obtained with the model of a prototype demonstration chip, show that good accuracy can be obtained with relatively simple measurement conditions. These results include the analysis of optimum stimuli amplitudes and the effect of noise in estimation accuracy

Aspectos da determinação da área basal em função da média aritmética dos diâmetros: II - vícios na determinação da área basal retirada

As shown by PIMENTEL GOMES (1965), the theory proves that the use of the arithmetic mean of diameters to estimate basal areas in forestry leads to a bias. This paper evaluates this bias in the computation of cut out basal area in forestry thinnings, by means of theoretical study, samples generated in a computer, and also through the study of actual populations of trees in groves of Araucaria angustifolia (Bert.) O. Ktze, Pinus elliottii Eng., P. taeda L. and P. caribaea var. hondurensis Mor. The study thus carried out showed that the bias indicated can be rather serious.Em estudos teóricos, em amostras geradas em computador, e em desbastes conduzidos em povoamentos florestais, foram determinados os vícios cometidos no cálculo da área basal retirada a partir da média aritmética dos diâmetros. Os resultados contra-indicam êsse tipo de cálculo para a determinação da área basal retirada, devendo ser utilizada a determinação a partir da soma dos quadrados dos diâmetros

Aspectos da determinação da área basal em função da média aritmética dos diametros III: vícios na determinação da área basal remanescente

As shown by PIMENTEL GOMES (1965), the theory proves that the use of the arithmetic mean of diameters to estimate basal areas in forestry leads to a bias. This paper evaluates this bias in the computation of remaining basal area in forestry thinnings, by means of theoretical study, samples generated in a computer, and also through the study of actual populations of trees in groves of Araucaria angustifolia (Bert.) O. Ktze, Pinus elliottii Eng., P. taeda L. and P. caribaea var. hondurensis Mor. The study thus carried out showed that the bias indicated can be rather serious.São determinados vícios no cálculo da área basal remanescente a partir da média aritmética dos diâmetros, em comparação com o método de cálculo a partir da soma dos quadrados dos diâmetros. Os estudos são conduzidos tanto teòricamente como em amostras geradas em computador, com confirmações com dados coletados em desbastes de povoamentos florestais. Os resultados mostram-se desfavoráveis ao uso da média aritmética para determinações da área basal remanescente

Phenotyping GABA transaminase deficiency: a case description and literature review

Gamma-aminobutyric acid transaminase (GABA-T) deficiency is an autosomal recessive disorder reported in only three unrelated families. It is caused by mutations in the ABAT gene, which encodes 4-aminobutyrate transaminase, an enzyme of GABA catabolism and mitochondrial nucleoside salvage. We report the case of a boy, deceased at 12 months of age, with early-onset epileptic encephalopathy, severe psychomotor retardation, hypotonia, lower-limb hyporeflexia, central hypoventilation, and rapid increase in weight and, to a lesser rate, length and head circumference. He presented signs of premature pubarche, thermal instability, and water-electrolyte imbalance. Serum total testosterone was elevated (43.3 ng/dl; normal range  T (p.Gln296His),not previously described. In vitro analysis concluded that this variant is pathogenic. The clinical features of this patient are similar to those reported so far in GABA-T deficiency. However, distinct mutations may have a different effect on enzymatic activity, which potentially could lead to a variable clinical outcome. Clinical investigation aiming for a diagnosis should not end with the patient's death, as it may allow a more precise genetic counselling for the family.info:eu-repo/semantics/publishedVersio

Visualización de cuencas hidrocarburíferas con realidad virtual

Se presenta una aplicación web de realidad virtual, orientada a la industria de Gas y Petróleo, capaz de construir una representación interactiva y tridimensional de una cuenca sedimentaria con potencial hidrocarburífero. Esta herramienta didáctica permite navegar un modelo 3D utilizando un casco de realidad virtual. Las vistas 3D se generan mediante la combinación de las técnicas de rendering tradicional con la técnica de Raymarching. Las superficies se describen a partir de funciones SDF (Signed Distance Functions) y son computadas mediante un píxel shader en la GPU. Esto permite alterar en tiempo real, la forma de las superficies sin utilizar triángulos. El usuario puede controlar con sus manos, un conjunto de operadores que permiten sustraer partes del volumen. La visualización del terreno permite analizar sus propiedades en distintas direcciones, facilitando la comprensión de los componentes de la cuenca y la identificación de reservorios de hidrocarburos.Sociedad Argentina de Informática e Investigación Operativ

Risks to carbon storage from land-use change revealed by peat thickness maps of Peru

This work was funded by NERC (grant ref. NE/R000751/1) to I.T.L., A.H., K.H.R., E.T.A.M., C.M.A., T.R.B., G.D. and E.C.D.G.; Leverhulme Trust (grant ref. RPG-2018-306) to K.H.R., L.E.S.C. and C.E.W.; Gordon and Betty Moore Foundation (grant no. 5439, MonANPeru network) to T.R.B., E.N.H.C. and G.F.; Wildlife Conservation Society to E.N.H.C.; Concytec/British Council/Embajada Británica Lima/Newton Fund (grant ref. 220–2018) to E.N.H.C. and J.D.; Concytec/NERC/Embajada Británica Lima/Newton Fund (grant ref. 001–2019) to E.N.H.C. and N.D.; the governments of the United States (grant no. MTO-069018) and Norway (grant agreement no. QZA-12/0882) to K.H.; and NERC Knowledge Exchange Fellowship (grant ref no. NE/V018760/1) to E.N.H.C.Tropical peatlands are among the most carbon-dense ecosystems but land-use change has led to the loss of large peatland areas, associated with substantial greenhouse gas emissions. To design effective conservation and restoration policies, maps of the location and carbon storage of tropical peatlands are vital. This is especially so in countries such as Peru where the distribution of its large, hydrologically intact peatlands is poorly known. Here field and remote sensing data support the model development of peatland extent and thickness for lowland Peruvian Amazonia. We estimate a peatland area of 62,714 km2 (5th and 95th confidence interval percentiles of 58,325 and 67,102 km2, respectively) and carbon stock of 5.4 (2.6–10.6) PgC, a value approaching the entire above-ground carbon stock of Peru but contained within just 5% of its land area. Combining the map of peatland extent with national land-cover data we reveal small but growing areas of deforestation and associated CO2 emissions from peat decomposition due to conversion to mining, urban areas and agriculture. The emissions from peatland areas classified as forest in 2000 represent 1–4% of Peruvian CO2 forest emissions between 2000 and 2016. We suggest that bespoke monitoring, protection and sustainable management of tropical peatlands are required to avoid further degradation and CO2 emissions.PostprintPeer reviewe