Paleoflood events recorded by speleothems in caves

Speleothems are usually composed of thin layers of calcite (or aragonite). However, cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves. Flowstones comprising discontinuous carbonate layers form due to flowing water films, while flood events introduce fluviokarstic sediments in caves that, on occasion, are recorded as clayey layers inside flowstones and stalagmites. This record provides a potential means of understanding the frequency of palaeofloods using cave records. In this work, we investigate the origin of this type of detrital deposit in El Soplao Cave (Northern Spain). The age of the lowest aragonite layer of a flowstone reveals that the earliest flood period occurred before 500 ka, though most of the flowstone formed between 422 +69/‐43 ka and 400 +66/‐42 ka. This suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events, especially at around 400 ka. The mineralogical data enable an evolutionary model for this flowstone to be generated based on the alternation of flood events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found. Copyright © 2014 John Wiley & Sons, Ltd.     

Quadruplet orientation of aerial photographs

Summary A new procedure of the relative orientation of pencils of light reconstructed from aerial photographs having 60% end and side overlaps is suggested. The basic unit for the procedure is a quadruplet of photographs forming a square. The geometrical characteristics of a block of photographs with 60% overlaps are exploited fully, and, the present author believes, that way an optimum relative orientation of all photographs within the block can be achieved.     

Evaluation of the removal of heavy metals in a natural wetland impacted by mining activities in Mexico

This research is focused on evaluating heavy metals (Cd, Cu, Fe, Mn, Pb, and Zn) uptake and removal by Eleocharis ovata, Cyperus manimae, Typha dominguensis, and Pteridium aquilinum in a natural wetland impacted by mining activities. We analyzed heavy metals content and distribution in native plants, soils, and water of a semipermanent natural wetland in Taxco de Alarcón, Guerrero, and we also determined the physicochemical characteristics of the water. Translocation factor (TF) and bioconcentration factor (BCF) were evaluated. Results showed that physical and chemical conditions are favorable for plants development. Correlation analysis showed a good and positive relation (0.95) between Cu and Pb in soils and plants. In the analyzed matrices: Zn (0.62–2.20 mg/L) exceeded the permissible limits in water, high concentrations of Pb and Zn (26.57–525.67 and 266.67–983.33 mg/kg, respectively) were detected in the studied soils, and Pb exceeded the normal range for E. ovata and P. aquilinum in the analyzed plants. Uptake of heavy metals in the tissues of different species was found in the following order: root > leaf. Data of TF and BCF showed that E. ovata is a tolerant plant with respect to heavy metals exposure since TF value was greater than 1. This study showed that E. ovata could be considered as a bioaccumulator of heavy metals in contaminated soils.     

The Beach Crowding Index: A Tool for Assessing Social Carrying Capacity of Vulnerable Beaches

The aim of this article is to introduce the Beach Crowding Index (BCI), a procedure to assess the social carrying capacity of vulnerable beaches. The study uses the people at one time (PAOT) approach and data gathered weekly throughout the bathing season regarding the number of beachgoers in 100 m² cells of the beach to assess how many beachgoers it can comfortably hold. The procedure is based on fieldwork, interviews with beachgoers, and geographic information system (GIS) analysis and has been tested on four beaches in protected areas on the Spanish Mediterranean coast. On a scale from 0 to 4, minimum scores throughout the bathing season are 0.7 and maximum 3.7, although results showed wide variation between the beaches, the section of the beach, and the time of day. This study suggests that determining the location of beachgoers and collecting a long-term series of data is fundamental to assessing social carrying capacity and that the BCI procedure can be used for a large number of applications.     

利用遥感技术建立墨西哥热带地上生物量模型(英文)

Spatially-explicit estimation of aboveground biomass(AGB) plays an important role to generate action policies focused in climate change mitigation,since carbon(C) retained in the biomass is vital for regulating Earth’s temperature.This work estimates AGB using both chlorophyll(red,near infrared) and moisture(middle infrared) based normalized vegetation indices constructed with MCD43A4 MODerate-resolution Imaging Spectroradiometer(MODIS) and MOD44B vegetation continuous fields(VCF) data.The study area is located in San Luis Potosí,Mexico,a region that comprises a part of the upper limit of the intertropical zone.AGB estimations were made using both individual tree data from the National Forest Inventory of Mexico and allometric equations reported in scientific literature.Linear and nonlinear(expo-nential) models were fitted to find their predictive potential when using satellite spectral data as explanatory variables.Highly-significant correlations(p = 0.01) were found between all the explaining variables tested.NDVI62,linked to chlorophyll content and moisture stress,showed the highest correlation.The best model(nonlinear) showed an index of fit(Pseudo-r2) equal to 0.77 and a root mean square error equal to 26.00 Mg/ha using NDVI62 and VCF as explanatory variables.Validation correlation coefficients were similar for both models:lin-ear(r = 0.87**) and nonlinear(r = 0.86**).     

An OLS regression model for context-aware tile prefetching in a web map cache

The increasing popularity of web map services has motivated the development of more scalable services in the spatial data infrastructures. Tiled map services have emerged as a scalable alternative to traditional map services. Instead of rendering map images on the fly, a collection of pre-generated image tiles can be served very fast from a server-side cache. However, during the start-up of the service, the cache is initially empty and users experience a poor quality of service. Tile prefetching attempts to improve hit rates by proactively fetching map images without waiting for client requests.

While most popular prefetching policies in traditional web caching consider only the previous access history to make predictions, significant improvements could be achieved in web mapping by taking into account the background geographic information.

This work proposes a regressive model to predict which areas are likely to be requested in the future based on spatial cross-correlation between an unconstrained catalog of geographic features and a record of past cache requests. Tiles that are anticipated to be most frequently requested can be pre-generated and cached for faster retrieval. Trace-driven simulations with several million cache requests from two different nation-wide public web map services in Spain demonstrate that accurate predictions and performance gains can be obtained with the proposed model.     

Modelling the wave-current interactions in an offshore basin using the SWAN model

The theoretical background of the wave-current interactions, including the transformation of the wave spectrum and breaking waves due to currents, are first presented in this work. In the next part of the work, experimental data resulted from studies performed in an offshore wave basin of the Danish Hydraulic Institute concerning the wave-current interactions were presented in parallel with some wave model simulations performed in similar conditions. SWAN, which is presently the state-of-the-art spectral model for the wave transformations, was adopted for performing numerical simulations. In general, a good agreement was encountered between the experimental data and the simulation results.