Correct Simulation Research Articles

Development of functionalities extension approach and implementation of address routing for IFogSim based simulators

The object of research is an approach of functionality extension for simulation toolkits based on iFogSim. It is assumed by the native approach that enhancement of functionalities should be achieved by inheriting the fog device class and defining new features in its body. However, this approach makes it impossible to use inherited simulators together and significantly decreases flexibility even when utilizing a single simulator. Another problem related exclusively to iFogSim is a specific communication scheme between application modules, which results in data routing limitations in fog architectures and odd data streams taken into account. This paper introduces an alternative extension approach incorporating a peculiar inheritance scheme which tries to reconsider the standard approach from a behavioral design patterns point of view. The key feature of the suggested approach is an extraction of fog device features from the native class into separate behavioral classes. Meanwhile, the designed inheritance scheme allows to flexibly override and combine behaviors. According to the approach principles the developed simulator extends iFogSim with application modules addressing capabilities solving limitations, along with implementing users’ mobility and dynamic wireless connectivity as it is done in MobFogSim. With the aim to check its correctness, the designed toolkit was validated with the standard for iFogSim case study of «EEG Tractor Beam game» application. The validation included four scenarios. In the first two scenarios the features of users’ mobility and dynamic base station connectivity were validated. And in the next scenarios that utilized address routing the obtained delay and network usage values were compared with theoretically calculated ones. The validation results indicated the correct simulator behavior, and introduced functionalities extension approach, being more complex in comparison with the inative one, can significantly improve flexibility of the simulator

Iterative Soft-Input Soft-Output Bit-Level Reed-Solomon Decoder Based on Information Set Decoding

In this paper, a bit-level decoder is presented for soft-input soft-output iterative decoding of Reed-Solomon (RS) codes. The main aim for the development of the proposed algorithm is to reduce the complexity of the decoding process, while yielding a relatively good error correction performance, for the efficient use of RS codes. The decoder utilises information set decoding techniques to reduce the computational complexity cost by lowering the iterative convergence rate during the decoding process. As opposed to most iterative bit-level soft-decision decoders for RS codes, the proposed algorithm is also able to avoid the use of belief propagation in the iterative decoding of the soft bit information, which also contributes to the reduction in the computational complexity cost of the decoding process. The performance of the proposed decoder is investigated when applied to short RS codes. The error correction simulations show the proposed algorithm is able to yield a similar performance to that of the Adaptive Belief Propagation (ABP) algorithm, while being a less complex decoder.

Study of temperature and stresses using finite element analysis in turning of C45 material

Parts machined by high cutting speeds can often exhibit high fatigue strength, increased micro-hardness in the surface layers and plastic deformations, due to the tool cutting edge radius associated with the induced stresses. The changing of rake and clearance angles has an important influence on the chip formation, cutting forces, residual stresses, temperatures in both the workpiece and the tool. International research on the influence of geometric parameters of the tool on the entire cutting process, are of particular importance to understand this process development. The approach of this study, considers the parametric realization of the cutting tool profile - a coated TiC turning chisel, which will be used in the finite element simulation of the orthogonal turning process. Deform 2D application, which is a powerful simulation engine was chosen and allows the correct simulation of the cutting process in real machining conditions. Deform 2D enables the automatically meshing and remeshing generation and also the optimization whenever needed and wherever is required a high accuracy, thereby reducing the overall difficulty of the problem and the computational requirements. Using Lagrangian discretization, the machining process was simulated and made possible to observe and present a series of conclusions and own points of view regarding the temperature distribution at the tool tip and in the workpiece, the effective stresses distribution and the cutting force variation under the rake and clearance angles influences.

Automated assessment of a kinetic database for fcc Co–Cr–Fe–Mn–Ni high entropy alloys

The development of accurate kinetic databases by parametrizing the composition and temperature dependence of elemental atomic mobilities, is essential for correct multicomponent calculations and simulations. In this work the automated assessment procedure for the establishment of CALPHAD-type kinetic databases is proposed, including the storage of raw data and assessment results, automatic weighting of data, parameter selection and automated reassessments. This allows the establishment of reproducible up-to-date databases. The proposed software, written in python, is applied to the assessment of a kinetic database for the fcc Co–Cr–Fe–Mn–Ni high entropy alloy using only tracer diffusion data for a sharp separation of thermodynamic and kinetic data. The established database is valid for the whole composition range of the five-component high entropy alloy.

Discrete element method models of elastic and elastoplastic fiber assemblies

AbstractGeometry‐dependency and plasticity are considered in the contact force models for the discrete element method simulations of elastic and elastoplastic fiber assemblies subject to uniaxial compression. It is observed that the contact force models have a significant impact on compressive loads. A simplified normal contact force model leads to smaller loads at large solid volume fractions compared to the experimental results, while the present geometry‐dependent models give better predictions. Simulations with a simple Coulombic tangential contact force model (considering sliding friction only) significantly underestimate the loads, while a Mindlin tangential force model that considers static friction improves the predictions. For the modeling of the fibers that undergo large plastic deformations, plasticity should be considered for both the fiber bending and fiber–fiber normal contact in order to obtain correct simulation results. Elastic models for fiber–fiber contact and fiber bending deformation remarkably overpredict the loads for the plastic fibers.

Implementation of Improved Parameterization of Terrestrial Flux in WRF‐VPRM Improves the Simulation of Nighttime CO2 Peaks and a Daytime CO2 Band Ahead of a Cold Front

AbstractEnhanced CO2 mole fraction bands were often observed immediately ahead of cold front during the Atmospheric Carbon and Transport (ACT)‐America mission and their formation mechanism is undetermined. Improved understanding and correct simulation of these CO2 bands are needed for unbiased inverse CO2 flux estimation. Such CO2 bands are hypothesized to be related to nighttime CO2 respiration and investigated in this study using WRF‐VPRM, a weather‐biosphere‐online‐coupled model, in which the biogenic fluxes are handled by the Vegetation Photosynthesis and Respiration Model (VPRM). While the default VPRM satisfactorily parameterizes gross ecosystem exchange, its treatment of terrestrial respiration as a linear function of temperature was inadequate as respiration is a nonlinear function of temperature and also depends on the amount of biomass and soil wetness. An improved ecosystem respiration parameterization including enhanced vegetation index, a water stress factor, and a quadratic temperature dependence is incorporated into WRF‐VPRM and evaluated in a year‐long simulation before applied to the investigation of the frontal CO2 band on August 4, 2016. The evaluation shows that the modified WRF‐VPRM increases ecosystem respiration during the growing season, and improves model skill in reproducing nighttime near‐surface CO2 peaks. A nested‐domain WRF‐VPRM simulation is able to capture the main characteristics of the August 4 CO2 band and informs its formation mechanism. Nighttime terrestrial respiration leads to accumulation of near‐surface CO2 in the region. As the cold front carrying low‐CO2 air moves southeastward, and strong photosynthesis depletes CO2 further southeast of the front, a CO2 band develops immediately ahead of the front.

Optimization of synthetic jet actuation by analytical modeling

PurposeThe purpose of this paper is to analyze and optimize synthetic jet actuators (SJAs) by means of a literature-known one-dimensional analytical model.Design/methodology/approachThe model was fit to a wide range of experimental data from in-house built SJAs with different dimensions. A comprehensive parameter study was performed to identify coupling between parameters of the model and to find optimal dimensions of SJAs.FindingsThe coupling of two important parameters, the diaphragm resonance frequency and the cavity volume, can be described by a power law. Optimal orifice length and diameter can be calculated from cavity height in good agreement with literature. A transient oscillation correction is required to get correct simulation outcomes.Originality/valueBased on these findings, SJA devices can be optimized for maximum jet velocity and, therefore, high performance.

Применение численного и блочного геомеханического моделирования для определения параметров крепления камерных выработок большого сечения

The study is exemplified by complex workings of a main ore pass that include a variety of underground structures, usually with unique dimensions which depend on the function and size of the equipment placed. The technical solutions for the underground crushing plant and associated structures envisage construction of chambers with the height of up to 35 m and the width of up to 20 m at the depths exceeding 800-1000 m. Such conditions call for a closer attention to be paid to the mine support parameters, especially the bolting depth. A block geomechanical model was designed in the Micromine Mining Software for the rock mass of the new main ore pass. Geotechnical boreholes logs and results of physical and mechanical rock tests were used as the input data for the model. Four domains were identified in the block geomechanical model for subsequent numerical modelling. A 3D model of the stress-and-strain state of the rock mass was made using the CAE Fidesys software based on the Micromine wire-frame model of the main ore pass. The history of the rock mass incremental loading was reconstructed for correct simulation of its stress-and-strain state. Prior to the excavation, the rock mass is pre-stressed by the weight of the rock strata. The excavation phase was then simulated in the stepwise manner. An array of points with the values of maximum principal stresses was downloaded from the numerical model post-processing program and interpolated into the block geomechanical model to refine the SRF parameter of the Barton's Q rating. Based on the obtained Q values, the mine support parameters for chambers were determined using the Barton, Hutchinson and Potvin empirical methods.

Intraseasonal oscillation of the southwest monsoon over Sri Lanka and evaluation of its subseasonal forecast skill

Sri Lanka, a small island country located near the southernmost end of the Indian subcontinent, is controlled by the southwest monsoon (SWM) during May to September, when it suffers the most accumulated rainfall in a year. Compared with extensive studies on the intraseasonal oscillation (ISO) of the Indian monsoon, less attention has been paid to the ISO of the SWM over Sri Lanka. Based on observational data, this study reveals that the leading mode of SWM rainfall shows a significant variability on a 10–35-day time scale, and it accounts for 66% of the fractional variance. The development of the intraseasonal rainfall anomaly is associated with a westward propagating anomalous cyclonic circulation. Furthermore, the skill of current dynamic models in simulating the SWM on the subseasonal time scale was evaluated by using the ECMWF (European center for Medium-Range Weather Forecasts) reforecast data from S2S (the Subseasonal to Seasonal Prediction project). In general, the model is more skillful in predicting the monsoonal wind index than the monsoonal rainfall index, with the skill for the former being beyond 30 days and the latter about two weeks. The forecast skills exhibit prominent interannual differences for both indices. It is suggested that a correct simulation of the large-scale circulation response to tropical convection is crucial for the subseasonal prediction of monsoonal rainfall over Sri Lanka.摘要斯里兰卡的雨季发生于5–9月间, 主要受西南季风的控制. 本文发现该地区的西南季风降水存在很强的次季节变率, 主导周期为10–35天. 降水的季节内变化与西传的异常气旋有关. 进一步, 利用S2S比较计划中欧洲中心的数值预报模式 (ECMWF) 提供的回报试验数据, 评估了当今动力模式对斯里兰卡西南季风次季节变化的预报技巧. 结果显示, 对季风指数的预测技巧超过30天, 而对降水指数的预测技巧大约两周, 且模式的预报技巧具有明显的年际差异. 分析表明, 能否正确模拟出大尺度环流对热带对流的响应是影响斯里兰卡降水预测的重要因子.

Review of Mobility Scenarios Generators for Vehicular Ad-Hoc Networks Simulators

The most used technology for ITS (Intelligent Transportation System) is VANET (Vehicular Ad-hoc NETworks) which is a subclass of MANET (Mobile Ad-hoc NETworks).VANET enables wireless communication between vehicles as well as RSU (Road Side Units), by using the standard 802.11p channels bandwidth to transmit all sort of information to each vehicle, within the range of the communication, providing passengers with plethora of safety, comfort and traffic monitoring applications. These networks are characterized by the predictable motion nature of vehicles which allows to predict the future locations of the nodes. They are also known for their varying topology through time, due to the changing number of nodes and the lane-constrained mobility patterns and their reduced power consumption requirements. However, the implementation, deployment and testing of VANET implies significant cost and requires a huge experimental platform. Therefore, computer simulation seems to be one of the best alternatives to test VANET communication protocols, before their deployment. However, the correct simulation of these networks requires to have access to a large number of heterogeneous mobility and traffic scenarios. Several research works try to solve these issues by creating mobility models that tend to accurately generate trace-files, that reflect the true nature of road traffic motion. This paper reviews these existing solutions and the need to develop them into intelligent tools, capable of faithfully reflecting human driving behavior in computer simulation scenarios designed to accurately test VANETs.

Random intercept and linear mixed models including heteroscedasticity in a logarithmic scale: Correction terms and prediction in the original scale.

Random intercept models are linear mixed models (LMM) including error and intercept random effects. Sometimes heteroscedasticity is included and the response variable is transformed into a logarithmic scale, while inference is required in the original scale; thus, the response variable has a log-normal distribution. Hence, correction terms should be included to predict the response in the original scale. These terms multiply the exponentiated predicted response variable, which subestimates the real values. We derive the correction terms, simulations and real data about the income of elderly are presented to show the importance of using them to obtain more accurate predictions. Generalizations for any LMM are also presented.

A finite element assessment of chip formation mechanisms in the machining of CFRP laminates with different fibre orientations

The virtual assessment of a composite machining process using finite element (FE) models constitutes a cost-effective solution to study the surface quality of machined parts. Thus, the correct simulation of the chip fracture becomes essential to obtain consistent numerical results. This work develops an original FE approach to emulate the chip formation in the machining of carbon fibre reinforced polymer (CFRP) laminates. Composite damage initiation modes are evaluated via hybrid Puck-Hashin composite failure criteria. Subsequently, mechanical properties of the damaged elements are linearly degraded. Finally, a novel strain-based element deletion criterion is applied to reliably simulate the chip release process. Five different cutting configurations are successfully modelled. The influence of relevant fibre orientations and cutter rake angles on chip formation are analysed in detail. The shape of the simulated chips reaches a high similarity with the chips obtained in relevant experimental trials presented in the literature. Useful insights about the modelling of sub-surface damage in composite machining are also produced in this investigation. For instance, the modelling of the fibre bending damage which take place in the machining of 90° laminates is modelled with great precision.

СРАВНЕНИЕ МОДЕЛЕЙ ДВИЖЕНИЯ ИЗМЕЛЬЧАЕМОГО МАТЕРИАЛА В КОРПУСЕ ЦЕНТРОБЕЖНОЙ МЕЛЬНИЦЫ ВЕРТИКАЛЬНОГО ТИПА

Introduction. Improving the performance, increasing productivity, reducing the metal consumption of grinding equipment and other mining machines is usually a very expensive process. It requires a large amount of development work, the production of prototype machines, and a large amount of experimental research. In this regard, one of the most important tasks is to simulate the movement of bulk material in operations for processing minerals in various equipment. In such modeling, the discrete element method (DEM) is widely used. The purpose of the research is to compare the models of the movement of the crushed material in the body of a vertical centrifugal mill. Research methodology The motion of the bulk medium in a vertical centrifugal mill was modeled using two models. In the first model, the cylindrical body of the centrifugal mill was assumed to be stationary, and on its surface and on the entire surface of the rotor, conditions were set for the absence of a relative speed of movement of the crushed material. In the second model, a hydrodynamic model was used to describe the motion of a granular material as a viscous incompressible liquid with a compression ratio that depends on the pres-sure. In this model, the viscosity coefficient is represented as consisting of two terms: a constant (analogous to dynamic viscosity) and an excess pressure over hydrostatic pressure. Research results It is established that both models give the same character of the movement of the material in the mill body. It is determined that the absolute velocity of the material movement near the walls and near the mill rotor is approximately the same for both models, but in the data obtained using the hydrodynamic model, as the material moves away from the walls and the rotor, it slows down more than for the model using the discrete element method. It is revealed that the absolute velocity of the material movement near the walls and at the axis of the mill rotor is approximately the same for both models, but in the data obtained using the hydrodynamic model, as it moves away from the walls and the rotor, the material slows down significantly more than for the model using the discrete element method. Based on the simulation results, it can be concluded that for a more accurate simulation of the processes occurring during the rapid movement of bulk material in the grinding equipment, it is preferable to use a model using the discrete element method. It is advisable to use the hydrodynamic model for conducting a large number of search dawns or as a predicate model that will allow you to quickly set the initial velocity values for particles in a model using the discrete element method. Conclusions 1. A hydrodynamic model of the motion of a bulk medium in a vertical centrifugal mill, represented as a viscous incompressible liquid with a compression coefficient depending on the pressure has been developed. 2. It is established that for a more correct simulation of the processes occurring during the rapid movement of bulk material in the grinding equipment, it is preferable to use a model using the discrete element method. At the same time, it is advisable to use the hydrodynamic model for conducting a large number of search calculations or as a predicate model that will allow you to quickly set the initial velocity values for particles in a model using the discrete element method.

A four-qubit germanium quantum processor.

The prospect of building quantum circuits1,2 using advanced semiconductor manufacturing makes quantum dots an attractive platform for quantum information processing3,4. Extensive studies of various materials have led to demonstrations of two-qubit logic in gallium arsenide5, silicon6-12 and germanium13. However, interconnecting larger numbers of qubits in semiconductor devices has remained a challenge. Here we demonstrate a four-qubit quantum processor based on hole spins in germanium quantum dots. Furthermore, we define the quantum dots in a two-by-two array and obtain controllable coupling along both directions. Qubit logic is implemented all-electrically and the exchange interaction can be pulsed to freely program one-qubit, two-qubit, three-qubit and four-qubit operations, resulting in a compact and highly connected circuit. We execute a quantum logic circuit that generates a four-qubit Greenberger-Horne-Zeilinger state and we obtain coherent evolution by incorporating dynamical decoupling. These results are a step towards quantum error correction and quantum simulation using quantum dots.

Fractional operators for the magnetic dynamic behavior of ferromagnetic specimens: An overview

This paper reviews the use of the fractional derivative operators for the dynamic magnetization of ferromagnetic specimens. Magnetic behaviors in ferromagnetic specimens are strongly nonlinear and frequency dependent. Magnetism has an atomic origin but the magnetic behavior as observed at the human scale is highly affected by phenomena occurring at larger scales. Under the influence of an external magnetic field, the homogeneity of a ferromagnetic sample magnetization is linked to the excitation dynamics. Models and simulations in this domain are strongly needed, as they provide theoretical explanations and allow us to anticipate complex phenomena, difficult to observe in a practical way. On the one hand, such multi-scale dynamical behaviors can hardly be taken into account with the usual mathematical operators. On the other hand, correct simulation results on large frequency bandwidths can be obtained using fractional derivative operators. The use of fractional derivatives can be envisaged through different approaches: Lump models based on time fractional differential equations is one option, and fractional anomalous diffusion equations is another. In this manuscript, these two methods are detailed and compared. Theoretical results are compared to experimental ones, and conclusions and perspectives are drawn such as possible improvements.

Channel Geometry Scaling Effect in Printed Inorganic Electrolyte-Gated Transistors

Unlike nanoscale silicon transistors, printed thin-film transistors usually rely on micrometer size channel lengths. The device dimensions, the morphology of the channel material, and the interface properties strongly influence important device parameters such as the threshold voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\text th</sub> ) and the transconductance parameter ( k). In this article, we analyze and model the dependence of critical electrical device properties of printed, electrolyte-gated transistors, based on crystalline indium oxide channel, for various device geometries. It is shown that the threshold voltage scales with the charge density at the electrolyte channel interface and is hence linearly dependent on the channel length ( L). Furthermore, nonlinear scaling effects in the transconductance parameter and in the ON-current are studied, which turn out to be dependent on both, channel width and length. Finally, we present a scaling model capturing the width/length dependencies of the studied transistor technology which enables the correct simulation of logic gates.

Evaluation of Weather Research and Forecast (WRF) microphysics schemes in simulating zenith total delay for InSAR atmospheric correction

ABSTRACT Many researches have demonstrated the potential of Interferometric Synthetic Aperture Radar (InSAR) atmospheric correction method based on the Weather Research and Forecast (WRF) model. However, there remain some doubts about its robustness and accuracy over complex topographical areas. For meteorology, microphysics schemes play a significant role on the simulation of atmospheric parameters. But no studies have focused specifically on the impact of the microphysics schemes (MPs) on the atmospheric zenith total delay (ZTD) simulation for InSAR atmospheric correction. Therefore, we test four sophisticated MPs in WRF version 3.9.1 to simulate ZTD during the SAR signal propagation over Haiyuan in China in summer. And the ZTD values from WRF are validated by comparing to those obtained from four global position system (GPS) stations. The results show that all of the MPs can effectively reconstruct the major absolute ZTD, but regarding differential ZTD values, the Morrison double moment (M2M) and WRF Double moment 6 classes Model (WDM6) predict more accurate differential ZTD data. Moreover, WRF-based InSAR atmospheric correction utilizing the M2M obtains the most accurate deformation map results. A proper choice of MP schemes can enhance the WRF model to simulate more precise ZTD and contribute to reach a conclusion on the robustness of WRF-based InSAR atmospheric correction, especially in the complex mountain area in summer.

Using radar observations to evaluate 3-D radar echo structure simulated by the Energy Exascale Earth System Model (E3SM) version 1

Abstract. The Energy Exascale Earth System Model (E3SM) developed by the Department of Energy has a goal of addressing challenges in understanding the global water cycle. Success depends on correct simulation of cloud and precipitation elements. However, lack of appropriate evaluation metrics has hindered the accurate representation of these elements in general circulation models. We derive metrics from the three-dimensional data of the ground-based Next-Generation Radar (NEXRAD) network over the US to evaluate both horizontal and vertical structures of precipitation elements. We coarsened the resolution of the radar observations to be consistent with the model resolution and improved the coupling of the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) and E3SM Atmospheric Model Version 1 (EAMv1) to obtain the best possible model output for comparison with the observations. Three warm seasons (2014–2016) of EAMv1 simulations of 3-D radar reflectivity features at an hourly scale are evaluated. A general agreement in domain-mean radar reflectivity intensity is found between EAMv1 and NEXRAD below 4 km altitude; however, the model underestimates reflectivity over the central US, which suggests that the model does not capture the mesoscale convective systems that produce much of the precipitation in that region. The shape of the model-estimated histogram of subgrid-scale reflectivity is improved by correcting the microphysical assumptions in COSP. Different from previous studies that evaluated modeled cloud top height, we find the model severely underestimates radar reflectivity at upper levels – the simulated echo top height is about 5 km lower than in observations – and this result is not changed by tuning any single physics parameter. For more accurate model evaluation, a higher-order consistency between the COSP and the host model is warranted in future studies.

Adequacy of Near Real-Time Satellite Precipitation Products in Driving Flood Discharge Simulation in the Fuji River Basin, Japan

Flood management is an important topic worldwide. Precipitation is the most crucial factor in reducing flood-related risks and damages. However, its adequate quality and sufficient quantity are not met in many parts of the world. Currently, near real-time satellite precipitation products (NRT SPPs) have great potential to supplement the gauge rainfall. However, NRT SPPs have several biases that require corrections before application. As a result, this study investigated two statistical bias correction methods with different parameters for the NRT SPPs and evaluated the adequacy of its application in the Fuji River basin. We employed Global Satellite Mapping of Precipitation (GSMaP)-NRT and Integrated Multi-satellitE Retrievals for GPM (IMERG)-Early for NRT SPPs as well as BTOP model (Block-wise use of the TOPMODEL (Topographic-based hydrologic model)) for flood runoff simulation. The results showed that the corrected SPPs by the 10-day ratio based bias correction method are consistent with the gauge data at the watershed scale. Compared with the original SPPs, the corrected SPPs improved the flood discharge simulation considerably. GSMaP-NRT and IMERG-Early have the potential for hourly river-flow simulation on a basin or large scale after bias correction. These findings can provide references for the applications of NRT SPPs in other basins for flood monitoring and early warning applications. It is necessary to investigate the impact of number of ground observation and their distribution patterns on bias correction and hydrological simulation efficiency, which is the future direction of this study.

Climate models capture key features of extreme precipitation probabilities across regions

Quantitative simulation of precipitation in current climate has been an ongoing challenge for global climate models. Despite serious biases in correctly simulating probabilities of extreme rainfall events, model simulations under global warming scenarios are routinely used to provide estimates of future changes in these probabilities. To minimize the impact of model biases, past literature tends to evaluate fractional (instead of absolute) changes in probabilities of precipitation extremes under the assumption that fractional changes would be more reliable. However, formal tests for the validity of this assumption have been lacking. Here we evaluate two measures that address properties important to the correct simulation of future fractional probability changes of precipitation extremes, and that can be assessed with current climate data. The first measure tests climate model performance in simulating the characteristic shape of the probability of occurrence of daily precipitation extremes and the second measure tests whether the key parameter governing the scaling of this shape is well reproduced across regions and seasons in current climate. Contrary to concerns regarding the reliability of global models for extreme precipitation assessment, our results show most models lying within the current range of observational uncertainty in these measures. Thus, most models in the Coupled Model Intercomparison Project Phase 6 ensemble pass two key tests in current climate that support the usefulness of fractional measures to evaluate future changes in the probability of precipitation extremes.