Age and growth of four spot megrim (Lepidorhombus boscii) in northern Iberian waters corroborated by cohort tracking

Age and growth are key biological aspects for the age-structured assessment of exploited fish populations. Confirming the consistency of fish age interpretation by validation/corroboration studies is essential for providing accurate age estimates to the stock assessment process. The Atlantic Iberian stock of four-spot-megrim (Lepidorhombus boscii), an important exploited demersal fish, is annually assessed by age-structured models in ICES, and specimens are routinely aged by IEO expert readers for this purpose. A total of 11,741 otoliths of this stock were aged from 23 annual groundfish surveys carried out in Cantabrian Sea and Galician waters (ICES Div. VIIIc, IXa) and following internationally standardized protocols. Annual age-length-keys were built using the respective age estimates and applied to the length distribution of each survey, thus obtaining a matrix of abundance indices by age and year. Similar mean lengths are obtained for each age group along most of the time-series. The von Bertalanffy growth parameters for the time-series are estimated (L∞: 49.0; k: 0.13; t0: 1.13) and the results are compared with previous studies. The annual growth pattern estimated for L. boscii is here corroborated by tracking cohort abundance indices in the surveys. The current otolith age estimation criterion used and the resulting age estimates obtained by the age readers can be considered valid. Strong and weak cohorts are well tracked along most of their age classes, and the correlations between age abundance indices are statistically significant up to the age 6, which represent around 95% of the total number of this species caught in the surveys. The findings here presented on the age of L. boscii and its corroboration can help to reduce the uncertainty in the estimation of its demographic structure and hence, ultimately, it will be important for a better understanding of its relevance in the functioning of the benthic community of the shelf.Versión del edito

Propuesta de un modelo de simulación de líneas de espera para optimizar el tiempo y el número de camiones de transporte de material y palas de la mina de Fosfato Bayovar a la planta concentradora

La presente investigación en la Mina de Sechura, que explota la Empresa MiskiMayo, se realizó para determinar el numero optimo de camiones mineros y palas necesarias para transportar el mineral a la zona de acopio evitando desabastecimiento en la planta concentradora. En este trabajo de simulación se empleó como herramienta de soporte el software Arena versión 12 tipo estudiantil. En este sentido, después de realizar los escenarios, a partir de los parámetros reales de producción de la empresa MiskiMayo, se obtuvo que actualmente la empresa opera con 7 palas y 20 camiones mineros trasladando 10’099,249.78 toneladas por año, cuya cifra es aproximada en un 3.9% respecto a la producción publicada por la empresa MiskiMayo el año 2016, asi como 916,000 tm en el mes de mayo del año 2021 y el modelo realizado nos dio como resultado 918,000 mensuales, siendo un aproximado de 0.02% de diferencia, lo cual valida el trabajo de simulación realizado. Luego se realizan los escenarios con parámetros aproximados de 18 y 22 camiones con 6 y 8 palas y se obtiene un valor optimo recomendado de 22 camiones con 8 palas que incrementan el traslado de mineral en un 5% aproximadamente. En cuanto a los costos de operación, por referencia a lo que menciona Cabezas Oruna(2011) que la inversión minera fue de 566 millones de dólares y por otro lado la Empresa Caterpillar, con su experiencia de liderazgo mundial, indica en tabla 3, que más del 40% del costo es por excavación y transporte lo que equivale aproximadamente a 226.4 millones de dólares.The present investigation in the Sechura Mine, operated by the MiskiMayo Company, was carried out to determine the optimal number of mining trucks and shovels necessary to transport the mineral to the storage area, avoiding shortages in the concentrator plant. In this simulation work, the Arena software version 12 student type was used as a support tool. In this sense, after carrying out the scenarios, based on the real production parameters of the MiskiMayo company, it was obtained that the company currently operates with 7 shovels and 20 mining trucks moving 10'099,249.78 tons per year, which figure is approximate in 3.9% compared to the production published by the company MiskiMayo in 2016, as well as 916,000 mt in the month of May 2021 and the model carried out gave us 918,000 monthly results, with an approximate difference of 0.02%, which validates the simulation work performed. Then the scenarios are carried out with approximate parameters of 18 and 22 trucks with 6 and 8 shovels and an optimum recommended value of 22 trucks with 8 shovels is obtained, which increases the transfer of ore by approximately 5%. Regarding the operating costs, by reference to what Cabezas Oruna (2011) mentions that the mining investment was 566 million dollars and on the other hand the Caterpillar Company, with its world leadership experience, indicates in table 3, that more than 40% of the cost is for excavation and transportation, which is equivalent to approximately 226.4 million dollars.Tesi

Double-difference waveform inversion: Feasibility and robustness study with pressure data

Time-lapse seismic data are widely used to monitor reservoir changes. Qualitative comparisons between baseline and monitor data sets or image volumes provide information about fluid and pressure effects within the reservoir during production. However, to perform real quantitative analysis of such reservoir changes, quantitative estimates of the elastic parameters are required as input parameters to rock-physics-based reservoir models. Full-waveform inversion has been proposed as a potential tool for retrieving subsurface properties, such as P- and S-wave velocities and density by fitting simulated waveforms to seismic data. An extension of this method to time-lapse applications seems straightforward, but, in fact, it requires more tailored processes such as double-difference waveform inversion (DDWI). We used realistic 2D synthetic pressure data examples to compare the performance of DDWI with that of two other inversion schemes: one using the same starting model for both inversions and the other starting the monitor inversion with the final baseline inversion model. The data simulation and inversion were based on acoustic theory. Although P-wave velocity changes were reliably recovered by each inversion method, DDWI was found to deliver the best results when perfectly repeated surveys were used. However, differencing the baseline and monitor data sets, as required by DDWI, could be found to be sensitive to the presence of survey nonrepeatability. To investigate the feasibility of using DDWI in practice, the dependence of DDWI on the quality of the baseline models and its robustness to survey nonrepeatability were studied with numerical tests. Various types of nonrepeatability were considered separately in the synthetic tests, including random noise, acquisition geometry mismatch, source wavelet discrepancy, and overburden velocity changes. A study of the correlation between the levels and types of nonrepeatability and the resulting contamination of the inversion results found that, for pressure data, DDWI was capable of inverting reliably for P-wave velocity changes under realistic survey nonrepeatability conditions