Debates—Stochastic subsurface hydrology from theory to practice: why stochastic modeling has not yet permeated into practitioners?

This is the peer reviewed version of the following article: [Sanchez-Vila, X., and D. Fernàndez-Garcia (2016), Debates—Stochastic subsurface hydrology from theory to practice: Why stochastic modeling has not yet permeated into practitioners?, Water Resour. Res., 52, 9246–9258, doi:10.1002/2016WR019302], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/2016WR019302/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingWe address modern topics of stochastic hydrogeology from their potential relevance to real modeling efforts at the field scale. While the topics of stochastic hydrogeology and numerical modeling have become routine in hydrogeological studies, nondeterministic models have not yet permeated into practitioners. We point out a number of limitations of stochastic modeling when applied to real applications and comment on the reasons why stochastic models fail to become an attractive alternative for practitioners. We specifically separate issues corresponding to flow, conservative transport, and reactive transport. The different topics addressed are emphasis on process modeling, need for upscaling parameters and governing equations, relevance of properly accounting for detailed geological architecture in hydrogeological modeling, and specific challenges of reactive transport. We end up by concluding that the main responsible for nondeterministic models having not yet permeated in industry can be fully attributed to researchers in stochastic hydrogeology.Peer ReviewedPostprint (author's final draft

Stochastic estimation of hydraulic transmissivity fields using flow connectivity indicator data

This is the peer reviewed version of the following article: [Freixas, G., D. Fernàndez-Garcia, and X. Sanchez-Vila (2017), Stochastic estimation of hydraulic transmissivity fields using flow connectivity indicator data, Water Resour. Res., 53, 602–618, doi:10.1002/2015WR018507], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/2015WR018507/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Most methods for hydraulic test interpretation rely on a number of simplified assumptions regarding the homogeneity and isotropy of the underlying porous media. This way, the actual heterogeneity of any natural parameter, such as transmissivity ( math formula), is transferred to the corresponding estimates in a way heavily dependent on the interpretation method used. An example is a long-term pumping test interpreted by means of the Cooper-Jacob method, which implicitly assumes a homogeneous isotropic confined aquifer. The estimates obtained from this method are not local values, but still have a clear physical meaning; the estimated math formula represents a regional-scale effective value, while the log-ratio of the normalized estimated storage coefficient, indicated by math formula, is an indicator of flow connectivity, representative of the scale given by the distance between the pumping and the observation wells. In this work we propose a methodology to use math formula, together with sampled local measurements of transmissivity at selected points, to map the expected value of local math formula values using a technique based on cokriging. Since the interpolation involves two variables measured at different support scales, a critical point is the estimation of the covariance and crosscovariance matrices. The method is applied to a synthetic field displaying statistical anisotropy, showing that the inclusion of connectivity indicators in the estimation method provide maps that effectively display preferential flow pathways, with direct consequences in solute transport.Peer ReviewedPostprint (published version

Avaluació de riscos ambientals mitjançant modelació geoquímica

L'interés sobre la recàrrega artificial d'aqüífers s'ha incrementat en els últims anys. La recerca del Grup d'Hidrologia Subterrània (GHS) de l'ETSECCPB vol donar una visió integrada i multidisciplinar sobre el risc (enginyeril i sanitari) associat a les pràctiques de recàrrega en basses d'infiltració. Per això és necessari avançar en paral·lel tant en l'estudi de la reducció en l'infiltració amb el temps, com en diferents aspectes relacionats amb les variacions hidrogeoquímiques durant el procés d'infiltració de l'aigua pel sòl i un cop a l'aqüífer. La incertesa lligada al desconeixement del medi natural implica haver de tractar amb el concepte risc des d'un punt de vista probabilístic. Els estudis realitzats o en marxa integren aspectes teòrics i numèrics amb assajos de laboratori i treball de camp en una zona pilot ja parcialment instrumentada

Static partitioning and mapping of kernel-based applications over modern heterogeneous architectures

Heterogeneous Architectures Are Being Used Extensively To Improve System Processing Capabilities. Critical Functions Of Each Application (Kernels) Can Be Mapped To Different Computing Devices (I.E. Cpus, Gpgpus, Accelerators) To Maximize Performance. However, Best Performance Can Only Be Achieved If Kernels Are Accurately Mapped To The Right Device. Moreover, In Some Cases Those Kernels Could Be Split And Executed Over Several Devices At The Same Time To Maximize The Use Of Compute Resources On Heterogeneous Parallel Architectures. In This Paper, We Define A Static Partitioning Model Based On Profiling Information From Previous Executions. This Model Follows A Quantitative Model Approach Which Computes The Optimal Match According To User-Defined Constraints. We Test Different Scenarios To Evaluate Our Model: Single Kernel And Multi-Kernel Applications. Experimental Results Show That Our Static Partitioning Model Could Increase Performance Of Parallel Applications By Deploying Not Only Different Kernels Over Different Devices But A Single Kernel Over Multiple Devices. This Allows To Avoid Having Idle Compute Resources On Heterogeneous Platforms, As Well As Enhancing The Overall Performance. (C) 2015 Elsevier B.V. All Rights Reserved.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement n. 609666 [24]

Application Partitioning and Mapping Techniques for Heterogeneous Parallel Platforms

Proceedings of the First PhD Symposium on Sustainable Ultrascale Computing Systems (NESUS PhD 2016) Timisoara, Romania. February 8-11, 2016.Parallelism has become one of the most extended paradigms used to improve performance. Legacy source code needs to be re-written so that it can take advantage of multi-core and many-core computing devices, such as GPGPU, FPGA, DSP or specific accelerators. However, it forces software developers to adapt applications and coding mechanisms in order to exploit the available computing devices. It is a time consuming and error prone task that usually results in expensive and sub-optimal parallel software. In this work, we describe a parallel programming model, a set of annotating techniques and a static scheduling algorithm for parallel applications. Their purpose is to simplify the task of transforming sequential legacy code into parallel code capable of making full use of several different computing devices with the objetive of increasing performance, lowering energy consumption and increase the productivity of the developer.European Cooperation in Science and Technology. COSTThe work presented in this paper has been partially supported by EU under the COST programme Action IC1305, ’Network for Sustainable Ultrascale Computing (NESUS)’ The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n. 609666 and by the Spanish Ministry of Economics and Competitiveness under the grant TIN2013-41350-P

The effects of fiscal shocks on the exchange rate in the EMU and differences with the US

We analyse the impact of government spending shocks on the real effective exchange rate and net exports in the Euro Area within a standard structural VAR framework. We employ a new database that contains quarterly fiscal variables for the Euro Area as a whole. We show that higher government spending leads to real exchange rate appreciation and to a fall in net exports, jointly with lower primary budgetary surpluses, which turns out to be fully consistent with the “twin deficits” hypothesis. The different components of public spending, namely wage and non-wage consumption expenditure, overall public consumption expenditure and public investment, bring about real appreciations. Our results are therefore also consistent both with the home-bias hypothesis of public expenditure and with public investment contributing to generating relative productivity gains in the traded goods sector. Contrary to what is observed in the Euro Area, the real effective exchange rate depreciates in the US in response to higher government spending. This discrepancy can ultimately be explained by the reaction of nominal interest rate spreads and the uncovered interest parity condition. The dissimilar reaction of short-term nominal interest rate spreads is attributed to two factors, namely the role of the US dollar as a "safe haven" currency and the countercyclical behaviour of discretionary government spending in the USEn este trabajo se analiza el efecto de las variaciones de gasto público sobre el tipo de cambio efectivo real y sobre las exportaciones netas en el conjunto del área del euro con un VAR estructural estándar. Con este fin se utiliza una nueva base de datos fiscal trimestral para el área del euro. Nuestros resultados muestran que los aumentos de gasto público directo provocan una apreciación del tipo de cambio efectivo real y un deterioro del saldo por cuenta corriente, así como un empeoramiento del saldo primario de las Administraciones Públicas, resultado que está en consonancia con la hipótesis de «déficits gemelos». Los principales componentes del gasto público directo, (a saber, gastos de personal y consumo público en compras de bienes y servicios, el consumo público total y la inversión pública) generan apreciaciones reales. Así pues, nuestros resultados están también en consonancia con la hipótesis de existencia de un sesgo nacional en el gasto público y con la hipótesis de que la inversión pública da lugar a ganancias de productividad relativa en el sector de bienes comerciables. Contrariamente a lo que se observa en el área del euro, el tipo de cambio efectivo real en Estados Unidos se deprecia como respuesta a incrementos del gasto público. Tal discrepancia puede explicarse por la reacción del diferencial del tipo de interés con respecto al resto del mundo y la condición de la paridad no cubierta del tipo de interés. La diferente respuesta del diferencial de tipos de interés a corto plazo entre ambas áreas geográficas puede atribuirse a la conjunción de dos elementos de distinta naturaleza: el papel de moneda refugio del dólar y el comportamiento contracíclico del gasto público discrecional en Estados Unido

Managing occupational doses with smartphones in interventional radiology

Purpose: This study presents a prototype smartphone application for occupational dosimetry in interventional practices based on electronic personal dosimeters to assist in dose monitoring. Methods: The prototype receives and records information from the occupational dose report containing the cumulative dose of electronic personal dosimeters worn over the apron at chest level and electronic area dosimeters located on Carms (reference dosimeters), for each fluoroscopy- guided procedure. Using their smartphones, personnel involved in interventional practices can review and compare their occupational records with an investigation level, the dose limits, and their department colleagues (anonymously). The ratio between Hp(10) measured by the personal and the reference dosimeters at the C- arm is presented as an indicator of consistent use of suspended operator shield. Some general results extracted from the first months of use are presented. Results: The reference dosimeter located at the C- arm (without lead protection and acting as an ambient dosimeter) recorded in one of the laboratories 217 mSv during 308 procedures over 5 months, showing an indication of the radiation risk present in an interventional laboratory. The ratio between the personal cumulative dose and the dose at a reference C- arm dosimeter ranged from 0.2% to 1.67% (a factor of 8.5) for different interventionalists. These differences suggest different protection habits among interventional operators, as well as a target for dose reduction. Conclusions: With this system, professionals have easy access to their occupational dosimetry records (including information on the workload) in the setting of their interventional departments, to thereby actively engage in the protection process.post-print1248 K

Improved max-value entropy search for multi-objective bayesian optimization with constraints

We present MESMOC+, an improved version of Max-value Entropy search for Multi-Objective Bayesian optimization with Constraints (MESMOC). MESMOC+ can be used to solve constrained multi-objective problems when the objectives and the constraints are expensive to evaluate. It is based on minimizing the entropy of the solution of the optimization problem in function space (i.e., the Pareto front) to guide the search for the optimum. The cost of MESMOC+ is linear in the number of objectives and constraints. Furthermore, it is often significantly smaller than the cost of alternative methods based on minimizing the entropy of the Pareto set. The reason for this is that it is easier to approximate the required computations in MESMOC+. Moreover, MESMOC+’s acquisition function is expressed as the sum of one acquisition per each black-box (objective or constraint). Therefore, it can be used in a decoupled evaluation setting in which it is chosen not only the next input location to evaluate, but also which black-box to evaluate there. We compare MESMOC+ with related methods in synthetic, benchmark and real optimization problems. These experiments show that MESMOC+ has similar performance to that of state-of-the-art acquisitions based on entropy search, but it is faster to execute and simpler to implement. Moreover, our experiments also show that MESMOC+ is more robust with respect to the number of samples of the Pareto frontThe authors acknowledge financial support from Spanish Plan Nacional I + D+i, grant PID2019-106827 GB-I00/ AEI/ 10.13039/50110001103