Montaña Rufo

New contributions to granite characterization by ultrasonic testing

Ultrasound evaluation permits the state of rocks to be determined quickly and cheaply, satisfying the demands faced by todays producers of ornamental stone, such as environmental sustainability, durability and safety of use. The basic objective of the present work is to analyse and develop the usefulness of ultrasound testing in estimating the physico-mechanical properties of granite. Various parameters related to Fast Fourier Transform (FFTs) and attenuation have been extracted from some of the studies conducted (parameters which have not previously been considered in work on this topic, unlike the ultrasonic pulse velocity). The experimental study was carried out on cubic specimens of 30 cm edges using longitudinal and shear wave transducers and equipment which extended the normally used natural resonance frequency range up to 500 kHz. Additionally, a validation study of the laboratory data has been conducted and some methodological improvements have been implemented. The main contribution of the work is the analysis of linear statistical correlations between the aforementioned new ultrasound parameters and physico-mechanical properties of the granites that had not previously been studied, i.e., resistance to salt crystallization and breaking load for anchors. Being properties that directly affect the durability and safety of use of granites, these correlations consolidate ultrasonics as a nondestructive method well suited to this type of material.

Electrical stimulation vs thermal effects in a complex electromagnetic environment

Studies linking exposure to low levels of radiofrequencies with adverse health effects, notwithstanding their present apparent inconsistency, have contributed to a steady improvement in the quality of evaluating that exposure. In complex electromagnetic environments, with a multitude of emissions of different frequencies acting simultaneously, knowledge of the spectral content is fundamental to evaluating human exposure to non-ionizing radiation. In the present work, we quantify the most significant spectral components in the frequency band 0.5-2200 MHz in an urban area. The measurements were made with a spectrum analyzer and monopole, biconical, and log-periodic antennas. Power density levels were calculated separately for the medium wave, short wave, and frequency modulation radio broadcasting bands, and for the television and GSM, DCS, and UMTS mobile telephony bands. The measured levels were compared with the ICNIRP reference levels for exposure to multiple frequency sources for thermal effects and electrical stimulation. The results showed the criterion limiting exposure on the basis of preventing electrical stimulation of peripheral nerves and muscles to be stricter (exposure quotient 24.7 10(-4)) than that based on thermal considerations (exposure quotient 0.16 10(-4)). The bands that contribute most to the latter are short wave, with 46.2%, and mobile telephony with 32.6% of the total exposure. In a complex electromagnetic environment, knowledge of the radiofrequency spectrum is essential in order to quantify the contribution of each type of emission to the publics exposure. It is also necessary to evaluate the electrical effects as well as the thermal effects because the criterion to limit exposure on the basis of the effect of the electrical stimulation of tissues is stricter than that based on thermal effects.

Estimation of Uncertainties in Electric Field Exposure From Medium-Frequency AM Broadcast Transmitters

International guidelines for limiting exposure to electromagnetic fields set out basic restrictions and reference levels to protect human health. To ensure compliance with these guidelines, standard measurement procedures must be used, and assessments of the uncertainties in the measurements must be reported. Nevertheless, neither the exposure restrictions nor the technical assessment standards specify how the measurement and computation of the uncertainties should be considered. This paper analyzes the following two sources of uncertainties that are not often considered in the assessment of exposure to electromagnetic fields: 1) repeatability and 2) spatial interpolation. For this purpose, electric field measurements were made in an area in which three medium-wave radio broadcasting transmitters are located. Systematic random sampling was performed with a spectrum analyzer and a monopole-type antenna, and geostatistical techniques were used to construct contour maps of the electromagnetic radiation and its associated uncertainties. The results suggest that, in handling uncertainties in assessments of human exposure to electromagnetic fields based on spatial interpolation from point measurements, based on medium-frequency amplitude modulation broadcast transmitters, the additive approach (i.e., the uncertainty is added to the results of the assessment before the exposure level is compared to the relevant limit) is the most appropriate.

Exposure to high-frequency electromagnetic fields (100 kHz-2 GHz) in Extremadura (Spain).

The last decade has seen a rapid increase in peoples exposure to electromagnetic fields. This paper reports the measurements of radiofrequency (RF) total power densities and power density spectra in 35 towns of the region of Extremadura, Spain. The spectra were taken with three antennas covering frequencies from 100 kHz to 2.2 GHz. This frequency range includes AM/FM radio broadcasting, television, and cellular telephone signals. The power density data and transmitting antenna locations were stored in a geographic information system (GIS) as an aid in analyzing and interpreting the results. The results showed the power density levels to be below the reference level guidelines for human exposure and that the power densities are different for different frequency ranges and different size categories of towns.

Exposure estimates based on broadband ELF magnetic field measurements versus the ICNIRP multiple frequency rule

The evaluation of exposure to extremely low-frequency (ELF) magnetic fields using broadband measurement techniques gives satisfactory results when the field has essentially a single frequency. Nevertheless, magnetic fields are in most cases distorted by harmonic components. This work analyses the harmonic components of the ELF magnetic field in an outdoor urban context and compares the evaluation of the exposure based on broadband measurements with that based on spectral analysis. The multiple frequency rule of the International Commission on Non-ionizing Radiation Protection (ICNIRP) regulatory guidelines was applied. With the 1998 ICNIRP guideline, harmonics dominated the exposure with a 55% contribution. With the 2010 ICNIRP guideline, however, the primary frequency dominated the exposure with a 78% contribution. Values of the exposure based on spectral analysis were significantly higher than those based on broadband measurements. Hence, it is clearly necessary to determine the harmonic components of the ELF magnetic field to assess exposure in urban contexts.

Medium wave exposure characterisation using exposure quotients

One of the aspects considered in the International Commission on Non-Ionizing Radiation Protection guidelines is that, in situations of simultaneous exposure to fields of different frequencies, exposure quotients for thermal and electrical stimulation effects should be examined. The aim of the present work was to analyse the electromagnetic radiation levels and exposure quotients for exposure to multiple-frequency sources in the vicinity of medium wave radio broadcasting antennas. The measurements were made with a spectrum analyser and a monopole antenna. Kriging interpolation was used to prepare contour maps and to estimate the levels in the towns and villages of the zone. The results showed that the exposure quotient criterion based on electrical stimulation effects to be more stringent than those based on thermal effects or power density levels. Improvement of dosimetry evaluations requires the spectral components of the radiation to be quantified, followed by application of the criteria for exposure to multiple-frequency sources.

Temporal evolution of the3H levels in the surface waters around the Almaraz Nuclear Power Plant

We have quantified the evolution during 1994 of the impact on the Tagus river of liquid releases of3H (51.3 TBq in the cited year), originating from the functioning of the Almaraz Nuclear Power Plant, and conditioned by the management of the cooling reservoir water. Taking into account, on the one hand, that tritiated water is hydrodynamically indistinguishable from untritiated water when both form part of the same mass of liquid, and, on the other, the practically null stratification and forced circulation of the water in the cited cooling reservoir, together with the hydrological fluxes interchanged between the said reservoir and the Tagus river (which is entirely regulated in the section under study and, because of prolonged drought, had a relatively small flow during the study period), we were able to model satisfactorily the temporal evolution of the3H activity in the cooling reservoir.

Spectral Analysis and Measurements of Exposure to Magnetic Fields (up to 32 kHz) in Private and Public Transport

Abstract During recent years there has been a recognition of the growing public as well as scientific interest in the biological effects of electric and magnetic fields. Transport, for instance, is not free from electric and magnetic fields because electricity is used both as the power source and as a control mechanism generating oscillating magnetic fields with a wide range of frequencies. We here present the results of a study of people’s levels of exposure to the magnetic fields that exist in different modes of private and public transport. The study included the determination of the intensity and frequency of the fields, and a comparison with the ICNIRP reference levels.

Optimization and comparison of three spatial interpolation methods for electromagnetic levels in the AM band within an urban area

Abstract A comparative study was made of three methods of interpolation – inverse distance weighting (IDW), spline and ordinary kriging – after optimization of their characteristic parameters. These interpolation methods were used to represent the electric field levels for three emission frequencies (774 kHz, 900 kHz, and 1107 kHz) and for the electrical stimulation quotient, QE, characteristic of complex electromagnetic environments. Measurements were made with a spectrum analyser in a village in the vicinity of medium‐wave radio broadcasting antennas. The accuracy of the models was quantified by comparing their predictions with levels measured at the control points not used to generate the models. The results showed that optimizing the characteristic parameters of each interpolation method allows any of them to be used. However, the best results in terms of the regression coefficient between each models predictions and the actual control point field measurements were for the IDW method. HighlightsInterpolation methods were used to represent the electric field levels in a village.Temporal variation values were less than spatial variations detected in the area.Inverse distance weighting, spline, and ordinary kriging were compared.The accuracy was quantified comparing the predictions with levels at control points.The best fits between predicted and measured values corresponded to the IDW model.

Contributions to ultrasound monitoring of the process of milk curdling

HighlightsEwe’s milk coagulation process has been monitored in a dairy industry environment.New ultrasonic parameters provided by the Fast Fourier transform (FFT) are studied.Significant correlations were found between various ultrasound parameters.Ultrasound parameters of the raw milk influence those measured during curdling.FFT and attenuation are strongly correlated with protein content. Abstract Ultrasound evaluation permits the state of milk being curdled to be determined quickly and cheaply, thus satisfying the demands faced by today’s dairy product producers. This paper describes the non‐invasive ultrasonic method of in situ monitoring the changing physical properties of milk during the renneting process. The basic objectives of the study were, on the one hand, to confirm the usefulness of conventional non‐destructive ultrasonic testing (time‐of‐flight and attenuation of the ultrasound waves) in monitoring the process in the case of ewe’s milk, and, on the other, to include other ultrasound parameters which have not previously been considered in studies on this topic, in particular, parameters provided by the Fast Fourier Transform technique. The experimental study was carried out in a dairy industry environment on four 52‐l samples of raw milk in which were immersed 500 kHz ultrasound transducers. Other physicochemical parameters of the raw milk (pH, dry matter, protein, Gerber fat test, and lactose) were measured, as also were the pH and temperature of the curdled samples simultaneously with the ultrasound tests. Another contribution of this study is the linear correlation analysis of the aforementioned ultrasound parameters and the physicochemical properties of the curdled milk.