Importancia del conocimiento empírico en obras civiles

This article is presented on the importance of empirical knowledge in order to make known the need, incidence and application of such knowledge in civil works. In addition, it is made with the purpose of documenting the subject that involves masters of work, engineers, workers and other participants of work, but that does not count with diffusion. The article was mostly written at the Universidad Distrital Francisco José de Caldas, Facultad Tecnológica, with the support of workers from the area, master builders, civil engineers and other participants in the work at the university and in the surrounding areas. It established the need for empirical thinking and made it clear that it is not the only thing necessary for good performance in civil works, reaching the conclusion that empirical knowledge and academic knowledge are necessary to perform in the best way in civil works because both knowledge are important for certain moments of working life.Se presenta este artículo sobre la importancia del conocimiento empírico con el fin de dar a conocer la necesidad, incidencia y aplicación de dicho conocimiento en obras civiles. Además, se realiza con el fin de documentar sobre el tema que involucra a maestros de obra, ingenieros, obreros y demás participantes de obra, pero que no cuanta con difusión. El artículo se realizó mayormente en la Universidad Distrital Francisco José de Caldas, Facultad Tecnológica con el apoyo de obreros de la zona, maestros de obra, ingenieros civiles y demás participantes de obras en la universidad y en zonas aledañas. Se establecieron necesidades del pensamiento empírico y se dejó claro que no es lo único necesario para un buen desempeño en obra civiles, llegando a la conclusión de que el conocimiento empírico y el conocimiento académico son necesarios para desempeñarse de la mejor manera en obras civiles pues ambos conocimientos son importantes para ciertos momentos de la vida laboral

Evolution and assessment of a nitrate vulnerable zone over 20 years: Gallocanta groundwater body (Spain)

Nitrate pollution from agricultural sources is one of the biggest issues facing groundwater management in the European Union (EU). During the last three decades, tens of nitrate vulnerable zones (NVZ) have been designated across the EU, aiming to make the problem more manageable. The Gallocanta Groundwater Body in NE Spain was declared as an NVZ in 1997, and after more than 20 years, significant improvements in water quality were expected to be observed. In the present study, the spatiotemporal trend of nitrate concentration within the Gallocanta NVZ in the last 38 years was assessed, and the effectiveness of the NVZ implementation was tested. Data from the official Ebro Basin Confederation monitoring network from 1980 to 2018 were used, and the results showed an increasing but fluctuating trend in nitrate concentration since 1980. Although a slight improvement was detected after the NVZ designation in 1997, the low rate of improvement would take decades to reach desirable levels in most of the area. The lack of update and control of action programmes, the inappropriate NVZ delimitation, and the influence of natural factors seem to be the reasons for the failure of the nitrate reduction measures. Currently, nitrate pollution and groundwater management are a matter of concern for the EU, so given the recurring problems in water supply in the area and the nonfulfillment of the goal of good quality status, more demanding measures are needed to be implemented in the short term

Evaluation of alternatives for flood irrigation and water usage in Spain under Mediterranean climate

Evaluation of water management has been progressively more necessary to determine the availability of water resources, especially in the Mediterranean environment where competition for these resources is maximum. This work evaluates the irrigation management and evolution of hydric needs for the main crops implemented in the Ebro basin (Spain), through the monitoring of a pilot experimental basin between 1998 and 2012. This 15-year period comprehends changes in irrigation implemented by the Irrigation District as well as climate and agronomic variabilities of the region. Changes in water management (implementation of an on-demand irrigation system with annual water allowances and payment per surface and consumption, in opposition to an irrigation system in shifts) and crops contributed to reduce irrigation by 40% and drainage by 72%. This occurred due to better adjustments between the water volumes applied and the hydric needs of the crops, achieving flood irrigation efficiencies of 80%. However, small negative trends were detected in the water deficit evolution of corn and sunflower, which should be addressed and improved. Improvements in water management by farmers have enabled the increase of irrigation efficiency up to values found in pressurized irrigation systems, especially in initial stages of the irrigation campaigns. However, specific water deficit episodes were detected that should be remediated

Galaxy groups in the 2dF galaxy redshift survey: Large Scale Structure with Groups

We use the 2dF Galaxy Group Catalogue constructed by Merch\'an & Zandivarez to study the large scale structure of the Universe traced by galaxy groups. We concentrate on the computation of the power spectrum and the two point correlation function. The resulting group power spectrum shows a similar shape to the galaxy power spectrum obtained from the 2dF Galaxy Redshift Survey by Percival et al., but with a higher amplitude quantified by a relative bias in redshift space of $b_s(k) \sim 1.5$ . The group two point correlation function for the total sample is well described by a power law with correlation length s_0=8.9 \pm 0.3 \mpc and slope $\gamma=-1.6 \pm 0.1$ on scales s < 20 \mpc. In order to study the dependence of the clustering properties on group mass we split the catalogue in four subsamples defined by different ranges of group virial masses. These computations allow a fair estimate of the relation described by the correlation length $s_0$ and the mean intergroup separation $d_c$ for galaxy systems of low mass. We also extend our study to the redshift space distortions of galaxy groups, where we find that the anisotropies in the clustering pattern of the 2dF group catalogue are consistent with gravitational instability, with a flattening of the redshift-space correlation function contours in the direction of the line of sight.Comment: 11 pages, 9 figures, resubmitted to MNRAS after revisio

Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland

A surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3 -) pollution from agricultural runoff water. The water flow rate and NO3 - concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3 - attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (e) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3 - attenuation between two weeks and one month (a reduction in NO3 - between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3 - reduction between 0.1 and 1.5 mM). The e15NNO3/N2 and e18ONO3/N2 values obtained from the laboratory experiments allowed to estimate the induced denitrification percentage. At an approximate average flow rate of 16 L/s, at least 60% of NO3 - attenuation was achieved in the CW. The field samples exhibited a slope of 1.0 for d18O-NO3 - versus d15N-NO3 -, similar to those of the laboratory experiments (0.9–1.2). Plant uptake seemed to play a minor role in NO3 - attenuation in the CW. Hence, the application of stubble in the CW allowed the removal of large amounts of NO3 - from the Lerma gully, especially when applied during the warm months, but its efficacy was limited to a short time period (up to three months). © 2019 Elsevier B.V

The galaxy size - halo mass scaling relations and clustering properties of central and satellite galaxies

In this work, we combine size and stellar mass measurements from the Sloan Digital Sky Server (SDSS) with the group finder algorithm of Rodriguez \& Merch\'an in order to determine the stellar and halo mass -- size relations of central and satellite galaxies separately. We show that, while central and satellite galaxies display similar stellar mass -- size relations, their halo mass -- size relations differ significantly. As expected, more massive haloes tend to host larger central galaxies. However, the size of satellite galaxies depends only slightly on halo virial mass. We show that these results are compatible with a remarkably simple model in which the size of central and satellite galaxies scales as the cubic root of their host halo mass, with the normalization for satellites being $\sim$ 30 \% smaller than that for central galaxies, which can be attributed to tidal stripping. We further check that our measurements are in excellent agreement with predictions from the IllustrisTNG hydrodynamical simulation. In the second part of this paper, we analyse how the clustering properties of central and satellite galaxies depend on their size. We demonstrate that, independently of the stellar mass threshold adopted, smaller galaxies are more tightly clustered than larger galaxies when either the entire sample or only satellites are considered. The opposite trend is observed on large scales when the size split is performed for the central galaxies alone. Our results place significant constraints for halo-galaxy connection models that link galaxy size with the properties of their hosting haloes.Comment: 15 pages, 12 figures. Accepted for publication in MNRA

Occupational Traffic Accidents among Teachers in Spain

Occupational traffic accidents are a leading cause of injuries or deaths among workers. Teachers in Spain are especially concerned about the problem of commuting due to their particular labor conditions. Multiple work-related factors are associated with the risk and severity of occupational traffic-related motor vehicle crashes. The objective of this research is to analyze the influence of the variables associated with the severity of occupational traffic accidents among teachers in Spain. A logistic regression model was used for the current study. The odds ratio (OR) and confidence interval (CI) were calculated for the injured worker on a sample of 20,190 occupational traffic accidents suffered by teachers. The results showed that women, Spanish nationality, younger than 55 years, and those driving a car were more likely to suffer a light crash. In contrast, men, foreign nationalities, older than 55 years, and those riding a motorbike were more likely to suffer a serious crash. Based on these findings, motor vehicle safety training could be designed and adapted to the riskiest profiles. Additionally, effective mobility plans for commuting could help reduce work-related traffic accidents.This research received funding from the project referenced as “UMA20-FEDERJA-078” and titled Diseño de un sistema smart carpooling para la mejora de la movilidad, y la reducción de la siniestralidad laboral and from “Plan Propio-Universidad de Málaga”. Partial funding for open access charge: Universidad de Málag