Multilevel Monte Carlo simulation for Levy processes based on the Wiener-Hopf factorisation

In Kuznetsov et al. (2011) a new Monte Carlo simulation technique was introduced for a large family of Levy processes that is based on the Wiener-Hopf decomposition. We pursue this idea further by combining their technique with the recently introduced multilevel Monte Carlo methodology. Moreover, we provide here for the first time a theoretical analysis of the new Monte Carlo simulation technique in Kuznetsov et al. (2011) and of its multilevel variant for computing expectations of functions depending on the historical trajectory of a Levy process. We derive rates of convergence for both methods and show that they are uniform with respect to the "jump activity" (e.g. characterised by the Blumenthal-Getoor index). We also present a modified version of the algorithm in Kuznetsov et al. (2011) which combined with the multilevel methodology obtains the optimal rate of convergence for general Levy processes and Lipschitz functionals. This final result is only a theoretical one at present, since it requires independent sampling from a triple of distributions which is currently only possible for a limited number of processes

A local and global tour on MOMoT

Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time, transformation problems often span a very large search space with respect to possible transformation results. Recently, different proposals for finding good transformation results without enumerating the complete search space have been proposed by using meta-heuristic search algorithms. However, determining the impact of the different kinds of search algorithms, such as local search or global search, on the transformation results is still an open research topic. In this paper, we present an extension to MOMoT, which is a search-based model transformation tool, for supporting not only global searchers for model transformation orchestrations, but also local ones. This leads to a model transformation framework that allows as the first of its kind multi-objective local and global search. By this, the advantages and disadvantages of global and local search for model transformation orchestration can be evaluated. This is done in a case-study-based evaluation, which compares different performance aspects of the local- and global-search algorithms available in MOMoT. Several interesting conclusions have been drawn from the evaluation: (1) local-search algorithms perform reasonable well with respect to both the search exploration and the execution time for small input models, (2) for bigger input models, their execution time can be similar to those of global-search algorithms, but global-search algorithms tend to outperform local-search algorithms in terms of search exploration, (3) evolutionary algorithms show limitations in situations where single changes of the solution can have a significant impact on the solution’s fitness.Ministerio de Economia y Competitividad TIN2015-70560-RJunta de Andalucía P12-TIC-186

Propuesta de diseño de ambientes simulados para capacitación y entrenamiento en seguridad industrial para la empresa avícola San Fernando

La oportunidad de modificar la realidad gracias a la llegada de nuevas tecnologías, nos permite adaptar nuevos contextos educativos, sociales, capacitación y de entretenimiento a estos nuevos cambios. En el último semestre San Fernando presento un incremento significativo de eventos (accidentes de trabajo) registrados en sus plantas industriales, esto debido a actos subestándar ocasionados por los colaboradores dentro de sus zonas de trabajo, por lo que se viene generando días de descanso médico por incapacidad parcial temporal y esto se refleja en la reducción de productividad de las operaciones dentro de sus plantas industriales, causal del decrecimiento de mano de obra y más aun poniendo en riesgo la integridad de los mismos colaboradores. La capacitación en prevención de los riesgos laborales es clave para que los colaboradores de las distintas áreas puedan adherirse a conductas alineadas con la cultura de la seguridad que hoy es la tendencia para afrontar los nuevos desafíos del mercado actual. Es por esto que, en este proyecto de investigación se planteará un nuevo modelo de capacitación y entrenamiento en temas de Seguridad y Salud en el Trabajo (SST) para sus colaboradores basado en el uso de la realidad virtual ligada a las plantas industriales en San Fernando. Del mismo modo, se ha realizado una investigación sobre la aplicación que tiene actualmente la realidad virtual dentro de la Educación y Capacitación, brindándonos la posibilidad de crear escenarios reales donde los usuarios puedan comprender como reaccionar física y psicológicamente ante una situación similar en la vida real. En conclusión, en el presente proyecto se llegará a diseñar los prototipos y escenarios de simulación que tendrá el software.Trabajo de investigaciónCampus Lima Centr

Estimation of wall shear stress using 4D flow cardiovascular MRI and computational fluid dynamics

Company In the last few years, wall shear stress (WSS) has arisen as a new diagnostic indicator in patients with arterial disease. There is a substantial evidence that the WSS plays a significant role, together with hemodynamic indicators, in initiation and progression of the vascular diseases. Estimation of WSS values, therefore, may be of clinical significance and the methods employed for its measurement are crucial for clinical community. Recently, four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has been widely used in a number of applications for visualization and quantification of blood flow, and although the sensitivity to blood flow measurement has increased, it is not yet able to provide an accurate three-dimensional (3D) WSS distribution. The aim of this work is to evaluate the aortic blood flow features and the associated WSS by the combination of 4D flow cardiovascular magnetic resonance (4D CMR) and computational fluid dynamics technique. In particular, in this work, we used the 4D CMR to obtain the spatial domain and the boundary conditions needed to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. Similar WSS distributions were found for cases simulated. A sensitivity analysis was done to check the accuracy of the method. 4D CMR begins to be a reliable tool to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. The combination of both techniques may provide the ideal tool to help tackle these and other problems related to wall shear estimatio

Quantile effects of prenatal care utilization on birth weight in Argentina

The effects of prenatal care utilization on birth weight (BW) may vary by unobserved fetal health endowments. This heterogeneity will be masked by estimating the effects at BW mean but can be evaluated by estimating the effects at BW quantiles as fetal health endowment is a strong correlate with the BW quantile order. We estimated the effects of prenatal care visits and delay before prenatal care initiation, on BW mean and quantiles using a sample of infants from Argentina. Self-selection into prenatal care was modeled using 2SLS and instrumental variable quantile regression. Results suggest that the 'mean' effect of prenatal care utilization largely underestimates the effects at lower BW quantiles. About 35 and 77 g increase in BW mean and 0.1 quantile respectively, per visit and about 30 and 139 g decrease in BW mean and 0.1 quantile respectively, per week delayed, were estimated. Ignoring self-selection into prenatal care resulted in underestimation of mean and quantile effects. Results highlight the limitation of analyses focused on 'mean effects' in the presence of treatment heterogeneity and emphasize the importance of identifying women at risk for having infants at lower BW quantiles as they may benefit most from earlier and more intensive prenatal care.Instituto Multidisciplinario de Biología Celula

Prenatal care effectiveness and utilization in Brazil

The impact of prenatal care use on birth outcomes has been understudied in South American countries. This study assessed the effects of various measures of prenatal care use on birth weight (BW) and gestational age outcomes using samples of infants born without and with common birth defects from Brazil, and evaluated the demand for prenatal care. Prenatal visits improved BW in the group without birth defects through increasing both fetal growth rate and gestational age, but prenatal care visits had an insignificant effect on BW in the group with birth defects when adjusting for gestational age. Prenatal care delay had no effects on BW in both infant groups but increased preterm birth risk in the group without birth defects. Inadequate care versus intermediate care also increased LBW risk in the group without birth effects. Quantile regression analyses revealed that prenatal care visits had larger effects at low compared with high BW quantiles. Several other prenatal factors and covariates such as multivitamin use and number of previous live births had significant effects on the studied outcomes. The number of prenatal care visits was significantly affected by several maternal health and fertility indicators. Significant geographic differences in utilization were observed as well. The study suggests that more frequent use of prenatal care can increase BW significantly in Brazil, especially among pregnancies that are uncomplicated with birth defects but that are at high risk for low birth weight. Further research is needed to understand the effects of prenatal care use for pregnancies that are complicated with birth defects.Instituto Multidisciplinario de Biología Celula

Análisis de factores operacionales para el incremento de la productividad en el sistema de carguío y acarreo en minera Chinalco Perú S. A. - 2021

La presente tesis permite realizar el análisis de los factores operacionales para el incremento de la productividad en el sistema de carguío y acarreo, considerando el tonelaje cargado y acarreado, el grado de fragmentación, el dig rate (tasa de excavación), tiempo de carguío, tiempo de acarreo, disponibilidad y utilización para la mejora del rendimiento de los equipos de carguío y acarreo en minera Chinalco Perú S. A. Se aplicó el método analítico porque se define la investigación bajo un alcance descriptivo - explicativo. La tesis es de un nivel preexperimental, donde se analiza e interpreta las diferentes variables operacionales relacionadas a los equipos de carguío y acarreo, con la finalidad de la mejora del rendimiento de los equipos. Se analizó e interpretó la información durante dos periodos comparativos: de octubre a diciembre del 2020 y de enero a marzo del 2021. El tonelaje transportado durante el periodo octubre a diciembre del 2020 fue de 220,555.50 toneladas y durante el periodo enero a marzo del 2021 fue de 367,106.90. El incremento de toneladas transportadas fue de 146,551.40 toneladas, producto de un mejor control de la granulometría (P80) y el dig rate (tasa de excavación). El tiempo de carguío se incrementó durante el periodo de estudio octubre a diciembre 2020 de 5.57 minutos a 6.05 minutos; mientras que, en el periodo enero a marzo 20201 se tuvo un incremento de 0.47 minutos. Este mayor tiempo de carguío está relacionado a un mayor dig rate (tasa de excavación) con un incremento de 10,341.78 t/h durante el periodo octubre a diciembre 2020 a 11,394.86 t/h durante el periodo enero a marzo 2021. El tiempo de acarreo se incrementó durante el periodo de estudio octubre a diciembre 2020 de 33.00 minutos a 35.69 minutos; mientras que, en el periodo de enero a marzo 20201 se tuvo un incremento de 2,69 minutos. Este mayor tiempo XI de acarreo está relacionado a un mayor dig rate (tasa de excavación) con un incremento de 10,341.78 t/h durante el periodo octubre a diciembre 2020 a 11,394.86 t/h durante el periodo enero a marzo 2021. La disponibilidad en equipos de carguío durante la primera etapa de estudio fue del 79.57 %; mientras que, en el segundo periodo de estudio se tuvo una mejora en 85.86 % con un incremento del 6.29 %. La utilización fue del 85.94 % durante la primera etapa y de 85.05 % en la segunda etapa. La disponibilidad en equipos de acarreo durante la primera etapa de estudio fue de 80.47 %; mientras que, en el segundo periodo de estudio se tuvo una mejora en 88.14 % con un incremento del 7.67 %. Palabras clave: tonelaje, tiempo de carguío, tiempo de acarreo, dig rate, granulometría, horas efectivas, etc

Surgical management of skull base tumors

AimTo present a review of the contemporary surgical management of skull base tumors.BackgroundOver the last two decades, the treatment of skull base tumors has evolved from observation, to partial resection combined with other therapy modalities, to gross total resection and no adjuvant treatment with good surgical results and excellent clinical outcomes.Materials and methodsThe literature review of current surgical strategies and management of skull base tumors was performed and complemented with the experience of Barrow Neurological Institute.ResultsSkull base tumors include meningiomas, pituitary tumors, sellar/parasellar tumors, vestibular and trigeminal schwannomas, esthesioneuroblastomas, chordomas, chondrosarcomas, and metastases. Surgical approaches include the modified orbitozygomatic, pterional, middle fossa, retrosigmoid, far lateral craniotomy, midline suboccipital craniotomy, and a combination of these approaches. The selection of an appropriate surgical approach depends on the characteristics of the patient and the tumor, as well as the experience of the neurosurgeon.ConclusionModern microsurgical techniques, diagnostic imaging, intraoperative neuronavigation, and endoscopic technology have remarkably changed the concept of skull base surgery. These refinements have extended the boundaries of tumor resection with minimal morbidity