Benchmark For Calibration Research Articles

Post-earthquake safety assessment of schools after the 2016 Ecuador M7.8 earthquake

The 2016 Muisne earthquake generated significant structural damage especially along the coast of Ecuador. Tests of concrete and reinforcing bars taken from collapsed buildings aided at assessing the impact of materials properties on the behavior of buildings. The paper describes the statistics of damage sustained by schools following the ATC-20 scheme. A set of statistics are developed describing the scaling of damage with distance and PGA. The analyses showed that 30% of the buildings surrounding schools performed “Better” than them, and approximately 33% performed “Worse” than them. For those schools tagged under RESTRICTED USE and with UNSAFE placards, 44% of the surrounding buildings behave “Better” than them, and only 16% behaved “Worse”, indicating the need for a strong public policy to reduce vulnerability of school in Ecuador. Georeferenced data allow a spatial cross-correlation of different levels of damage observed with the ground motion intensity. This information may serve as benchmark for calibration of seismic risk models, and for post-earthquake risk comparison. Furthermore, regional seismic risk assessment may be calibrated with the results of the spatial cross-correlation analyses presented.

Comparative Analysis of Fire and Explosion Properties of Lycopodium Powder

Lycopodium (L.) clavatum powder, due to its uniform particle size distribution and low equilibrium moisture content, is often used as a reference material and a calibration benchmark for dust combustion and dust explosion studies. The aim of the study was to determine its fire and explosion parameters, compare them to values obtained in the previous literature findings, and assess the appropriateness of using lycopodium powder as a reference material. The research included the determination of minimum ignition temperatures of dust layer and dust clouds, spontaneous ignition behavior, and explosion characteristics of dust clouds including maximum explosion pressure, maximum rate of explosion pressure rise, and the lower explosion limit of the air/dust mixture. The results reveal that the maximum equipment temperature used with lycopodium dust should not exceed 215 °C for dust thickness up to 5 mm. In order to eliminate the risk of lycopodium dust ignition, the temperature of the equipment surfaces that can come into contact with the dust cloud should not exceed 300 °C. In order to prevent explosions, the concentration of lycopodium dust in air should not be greater than 15 g/m3. Based on the obtained results, it can be seen that lycopodium fire and explosion parameters vary slightly, and its usage as a benchmark is considered legitimate.

Unravelling and improving the potential of global discharge reanalysis dataset in streamflow estimation in ungauged basins

Mastery in forecasting the streamflow is of great importance in environmental and sustainability research. Although many global-scale reanalysis products provide a new way to overcome the lack of streamflow records in ungauged basins, streamflow estimation through hydrological models remains a great challenge mostly due to inevitable biases. In this study, we developed a novel bias-correction system equipped with the proposed Piecewise Random Forest (P-RF) model to improve the potential of GloFAS-ERA5 (GloFAS), a global-scale river discharge reanalysis product, as a calibration benchmark for building hydrological models in ungauged basins. Considering three ungauged scenarios, several cases of temporal, spatial, and spatiotemporal bias-corrections were implemented with a total of 13 river gauges located in the Min River Basin in China, and the Fuji River Basin and the Shinano River Basin in Japan. Then, the well-improved GloFAS discharge was applied for the calibration of the Block-wise use of the TOPMODEL (BTOP) model to evaluate its performance in substituting the discharge observations. The results show that: (1) the bias-correction system performs better on the temporal scale, which applies to ungauged basins lacking long-term continuous observations; (2) the integrity and adequacy of the samples used for training the P-RF model have a significant impact on the spatial and spatiotemporal bias-corrections, and they can be reliably estimated by the proposed metric, Ratio of the Valid samples' Proportion; and (3) the statistical metric differences between the simulated discharges obtained by the calibrated BTOP model using observations and GloFAS discharge, are reduced by 25%–50% through the bias-correction.

A novel positioning method for Hall magnetic field measurement of heavy ion accelerator

In the magnetic field measurement of accelerator magnets, the precise positioning of the magnetic field measurement system and the magnet is a basic and very important part. By analyzing the mechanical structure and working principle of Hall magnetic field measurement system, a novel positioning method is proposed in this research for the high-precision and fast positioning of magnet and Hall magnetic field measurement system. By measuring the geometric elements of the magnetic field measurement system and the calibration benchmark of the magnet, the geometric relationship between the magnetic field measurement system and the magnet is established, so as to quickly locate the magnet to the position and attitude required by the magnetic field measurement. The mechanical structure of the Hall probe of the magnetic field measurement system is optimized. Two special ceramic reflectors are installed on the vertical and horizontal axes corresponding to the center of the Hall sensor, and the two ceramic reflectors installed on the Hall probe is monitored with a laser tracker. In this way the Hall sensor can be intuitively positioned at the geometric center of the magnet with an accuracy better than 0.05 mm. In the measurement process, the magnetic field measurement trajectory of Hall sensor in the magnet can also be detected by monitoring the coordinates of ceramic reflector in real time. The practical application in Space Environment Simulation and Research Infrastructure (SESRI) magnet magnetic field measurement show that, compared with the traditional positioning method, the proposed positioning method not only improves the repeatability of Hall magnetic field measurement integral field by nearly 10 times, but also improves the positioning efficiency of magnetic field measurement. These results have verified the practicability and effectiveness of the proposed positioning method.

Subsidising Formal Childcare Versus Grandmothers' Time: Which Policy is More Effective?

Abstract This article quantifies the relative effectiveness of childcare subsidies and subsidies on grandmothers’ time on married mothers’ employment and fertility rates, paying special attention to heterogeneous effects. A heterogeneous agent model, populated by married households who make decisions related to labour supply and fertility, and the Spanish economy are used as a benchmark for calibration. The results indicate that childcare subsidies conditional on employment are more effective than subsidies on grandmothers’ time to foster the participation of married mothers in the labour force. However, they induce women to work fewer hours, unless after-school hours are also subsidised. This overtime subsidy is also necessary for the fertility rate to increase, but it implies a significant adjustment in tax rates to maintain the same fiscal balance. If the aim is simply to raise the employment rate of mothers of children aged 2 years or younger, then subsidising childcare costs only is more effective because the fiscal effort is lower. Regarding the heterogeneous effects, in all the policies studied, the growth in female employment is mainly accounted for by the behaviour of women without tertiary education while that of fertility is accounted for by women with tertiary education. Considerations related to inequality and distributional effects of these policies would also seem to favour childcare subsidies versus subsidies on grandmothers’ time.

A semi-analytical solution to steady-state groundwater inflow into a circular tunnel considering anisotropic permeability

The groundwater inflow into the tunnel will cause various adverse effects on the tunnel and a proper estimation of the groundwater inflow is of great significance for tunnel drainage system design. In this paper, a semi-analytical solution, which considers the anisotropic permeability of the soil mass, is developed to assess the steady-state groundwater inflow into the tunnel. The solution is developed based on the coordinate transformation and conformal mapping technique. The present solution only requires once conformal mapping and has the advantage of effectively avoiding the distortion of the ground surface during conformal mapping. Two typical boundary conditions on the tunnel surface, the zero water pressure and the constant total water head, both of which are commonly encountered in tunneling engineering, are considered in the present solution. The proposed solution is validated by comparing with the results extracted from a finite element model, which shows that the present solution is capable of predicting the total water head and the pressure head around the tunnel, and the inflow rate along the tunnel surface with sufficient accuracy. Extensive parametric studies are conducted to investigate the effects of permeability ratio, depth of the tunnel centre from the ground surface, and water depths above the ground on the groundwater inflow. The results show that the anisotropy of the permeability has a significant effect on the inflow rate along the tunnel surface under the two boundary conditions. The proposed solution not only provides an efficient approach for assessing the groundwater into the tunnel, but also can serve as a benchmark for calibration of numerical simulations.

Calibrating 3D Scanner in the Coordinate System of Optical Tracker for Image-To-Patient Registration.

Three-dimensional scanners have been widely applied in image-guided surgery (IGS) given its potential to solve the image-to-patient registration problem. How to perform a reliable calibration between a 3D scanner and an external tracker is especially important for these applications. This study proposes a novel method for calibrating the extrinsic parameters of a 3D scanner in the coordinate system of an optical tracker. We bound an optical marker to a 3D scanner and designed a specified 3D benchmark for calibration. We then proposed a two-step calibration method based on the pointset registration technique and nonlinear optimization algorithm to obtain the extrinsic matrix of the 3D scanner. We applied repeat scan registration error (RSRE) as the cost function in the optimization process. Subsequently, we evaluated the performance of the proposed method on a recaptured verification dataset through RSRE and Chamfer distance (CD). In comparison with the calibration method based on 2D checkerboard, the proposed method achieved a lower RSRE (1.73 mm vs. 2.10, 1.94, and 1.83 mm) and CD (2.83 mm vs. 3.98, 3.46, and 3.17 mm). We also constructed a surgical navigation system to further explore the application of the tracked 3D scanner in image-to-patient registration. We conducted a phantom study to verify the accuracy of the proposed method and analyze the relationship between the calibration accuracy and the target registration error (TRE). The proposed scanner-based image-to-patient registration method was also compared with the fiducial-based method, and TRE and operation time (OT) were used to evaluate the registration results. The proposed registration method achieved an improved registration efficiency (50.72 ± 6.04 vs. 212.97 ± 15.91 s in the head phantom study). Although the TRE of the proposed registration method met the clinical requirements, its accuracy was lower than that of the fiducial-based registration method (1.79 ± 0.17 mm vs. 0.92 ± 0.16 mm in the head phantom study). We summarized and analyzed the limitations of the scanner-based image-to-patient registration method and discussed its possible development.

The Black Hole Mass of the z = 2.805 Multiply Imaged Quasar SDSS J2222+2745 from Velocity-resolved Time Lags of the C iv Emission Line

Abstract We present the first results of a 4.5 yr monitoring campaign of the three bright images of multiply imaged z = 2.805 quasar SDSS J2222+2745 using the Gemini North Multi-Object Spectrograph and the Nordic Optical Telescope. We take advantage of gravitational time delays to construct light curves surpassing 6 yr in duration in the observed frame and achieve an average spectroscopic cadence of 10 days during the 8 months of visibility per season. Using multiple secondary calibrators and advanced reduction techniques, we achieve percent-level spectrophotometric precision and carry out an unprecedented reverberation mapping analysis, measuring both integrated and velocity-resolved time lags for the C iv emission line. The full line lags the continuum by τ cen = 36.5 − 3.9 + 2.9 rest-frame days. We combine our measurement with published C iv emission line lags and derive the r BLR − L relationship log 10 ​ ( τ / d a y ) = ( 0.99 ± 0.07 ) + ( 0.48 ± 0.03 ) log 10 ​ [ λ L λ ( 1350 A A ) / 10 44 e r g s − 1 ] with 0.30 ± 0.06 dex intrinsic scatter. The velocity-resolved lags are consistent with circular Keplerian orbits, with τ cen = 86.2 − 5.0 + 4.5 , 25 − 15 + 11 , and 7.5 − 3.5 + 4.2 rest-frame days for the core, blue wing, and red wing, respectively. Using σ line with the mean spectrum and assuming log 10 ( f mean , σ ) = 0.52 ± 0.26 , we derive log 10 ( M BH / M ⊙ ) = 8.63 ± 0.27 . Given the quality of the data, this system represents a unique benchmark for calibration of M BH estimators at high redshift. Future work will present dynamical modeling of the data to constrain the virial factor f and M BH.

Simulation of the fragmentation and propagation of jointed rock masses in rockslides: DEM modeling and physical experimental verification

Rockslides are among the most dangerous geohazards. The discrete element method (DEM) has been increasingly used to simulate the emplacement process of rockslides. However, few studies have modeled the fragmentation of jointed rock masses during movement via DEM simulations and verified the reliability of the results through comparison with the results of laboratory experiments and field events. In this paper, a series of DEM simulations based on PFC3D5.0 was conducted to replicate laboratory experiments in which breakable blocks with different structural forms impact and slide on a horizontal plane and experience fragmentation. The results show that the DEM model provides first-order estimates that are comparable with the results of experiments in terms of the kinetic features and depositional characteristics of rockslides, including crack propagation, velocity distribution, preservation of source stratigraphy, progressive fragmentation, and spreading of fragments. Conversely, the normalized horizontal runout and degree of fragmentation are poorly represented in the DEM model. A theoretical analysis is further conducted to discuss the causes of travel distance discrepancy between the DEM model and experiments. It is found that the inconsistency of fragment interactions caused by the defect of the fragmentation process in DEM simulation may take primary responsibility. An alterable restitution coefficient method based on the rock mass fragmentation process is proposed for application to the fragmenting rock mass movement in DEM simulation, with the utilization of additional laboratory experimentation as the calibration benchmark. Further verification of our method needs to be performed in the future.

Lateral Buckling of Cantilevered Circular Arches Under Various End Moments

Lateral buckling of cantilevered circular arches under various end moments is studied using an analytical approach. Three types of conservative moments are considered, i.e. the quasi-tangential moments of the 1st and 2nd kinds, and the semi-tangential moment. The induced moments associated with each of the moment mechanisms undergoing three-dimensional rotations are included in the Newman boundary conditions. Using the differential equations available for the out-of-plane buckling of curved beams, the analytical solutions are derived for a cantilevered circular arch, which can be used as the benchmarks for calibration of other methods of analysis.

Evidence of a Substellar Companion to AB Dor C

Abstract Studies of fundamental parameters of very low-mass objects are indispensable to provide tests of stellar evolution models that are used to derive theoretical masses of brown dwarfs and planets. However, only objects with dynamically determined masses and precise photometry can effectively evaluate the predictions of stellar models. AB Dor C (0.090 M ⊙) has become a prime benchmark for calibration of theoretical evolutionary models of low-mass young stars. One of the ambiguities remaining in AB Dor C is the possible binary nature of this star. We observed AB Dor C with the VLTI/AMBER instrument in low-resolution mode at the J, H, and K bands. The interferometric observables at the K band are compatible with a binary brown dwarf system with tentative components AB Dor Ca/Cb with a K-band flux ratio of 5% ± 1% and a separation of 38 ± 1 mas. This implies theoretical masses of 0.072 ± 0.013 M ⊙ and 0.013 ± 0.001 M ⊙ for each component, near the hydrogen-burning limit for AB Dor Ca, and near the deuterium-burning limit, straddling the boundary between brown dwarfs and giant planets, for AB Dor Cb. The possible binarity of AB Dor C alleviates the disagreement between observed magnitudes and theoretical mass–luminosity relationships.

Rupture Energetics in Crustal Rock From Laboratory‐Scale Seismic Tomography

AbstractThe energy released during earthquake rupture is partly radiated as seismic waves and mostly dissipated by frictional heating on the fault interface and by off‐fault fracturing of surrounding host rock. Quantification of these individual components is crucial to understand the physics of rupture. We use a quasi‐static rock fracture experiment combined with a novel seismic tomography method to quantify the contribution of off‐fault fracturing to the energy budget of a rupture and find that this contribution is around 3% of the total energy budget and 10% of the fracture energy Gc. The off‐fault dissipated energy changes the physical properties of the rock at the early stages of rupture, illustrated by the 50% drop in elastic moduli of the rock near the fault, and thus is expected to greatly influence later stages of rupture and slip. These constraints are a unique benchmark for calibration of dynamic rupture models.

Concept and benchmarks for assessing narrow-sense validity of genetic risk score values.

While higher genetic risk score (GRS) has been statistically associated with increased disease risk (broad-sense validity), the concept and tools for assessing the validity of reported GRS values from tests (narrow-sense validity) are underdeveloped. We propose two benchmarks for assessing the narrow-sense validity of GRS. The baseline benchmark requires that the mean GRS value in a general population approximates 1.0. The calibration benchmark assesses the agreement between observed risks and estimated risks (GRS values). We assessed benchmark performance for three prostate cancer (PCa) GRS tests, derived from three SNP panels with increasing stringency of selection criteria, in a PCa chemoprevention trial where 714 of 3225 men were diagnosed with PCa during the 4-year follow-up. GRS from Panels 1, 2, and 3 were all statistically associated with PCa risk; P = 5.58 × 10-3 , P = 1 × 10-3 , and P = 1.5 × 10-13 , respectively (broad-sense validity). For narrow-sense validity, the mean GRS value among men without PCa was 1.33, 1.09, and 0.98 for Panels 1, 2, and 3, respectively (baseline benchmark). For assessing the calibration benchmark, observed risks were calculated for seven groups of men with GRS values <0.3, 0.3-0.79, 0.8-1.19, 1.2-1.49, 1.5-1.99, 2-2.99, and ≥3. The calibration slope (higher is better) was 0.15, 0.12, and 0.60, and the bias score (lower is better) between the observed risks and GRS values was 0.08, 0.08, and 0.02 for Panels 1, 2, and 3, respectively. Performance differed considerably among GRS tests. We recommend that all GRS tests be evaluated using the two benchmarks before clinical implementation for individual risk assessment.

Uncertainty quantification in the analyses of operational wind power plant performance

In the present work, we examine the variation introduced in the evaluation of an operating plant’s wind power production as a result of the choices analysts make in the processing of the operational data. For this study, an idealized power production for individual turbines over an operational period was predicted by fitting power curves to the turbine production data collected during expected operation (that is, without curtailment or availability losses). A set of 240 possible methods were developed for (a) defining what data represented expected operation and (b) modeling the power curve. The spread in the idealized power production as predicted by the different methods was on average almost 3% for the 100 turbines considered. Such significant variation places a lower bound on the precision with which analysts may employ such data as benchmarks for calibration of their energy estimation processes and limits the potential for identification of refinements to the energy estimation models for improved accuracy.

An Automated Calibration Method of Ultrasonic Probe Based on Coherent Point Drift Algorithm

Ultrasound-based navigation, as a non-invasive and non-radiation image guiding system, is becoming a research focus in minimally invasive navigation surgery, and calibration between an ultrasonic probe and a 3D vision device is one of the key technologies for ultrasonic registration-based navigation. In this paper, a phantom model was designed as a benchmark for calibration. Both iterative closet point (ICP) and coherent point drift (CPD) algorithms are chosen as point cloud registration methods to implement calibration between ultrasonic scanned points and original phantom points to set up the relationship between the ultrasonic probe and the 3D vision device. Because of large topological difference between the ultrasound scanned points and the points from model, ICP algorithm cannot complete the registration, but the CPD algorithm could implement the registration automatically. The average errors of the center point position for each cavity were 1.50, 1.31, and 1.19 mm, respectively, and the average errors of the axis for each cavity were 0.85°, 0.61°, and 0.99°, respectively. Experiment results showed that the average error of calibration by this method satisfies acquirements of most orthopedic surgeries, and the fully automatic implementation of ultrasonic image processing and subsequent calculation is suitable for on-line calibration and verification in surgery.

Size dependent surface energy of nanoplates: Molecular dynamics and nanoscale continuum theory correlations

A nanoscale gradient continuum theory along with molecular dynamics simulations are employed to investigate the size-dependent surface energy of nanoplates. Molecular dynamics simulations reveal that upon nanoplate thickness reduction, the redistribution of surface energy density along thickness direction causes the decrease of the surface energy of nanoplate free surfaces. Via introducing a calibration benchmark, the length scale model parameter of the gradient continuum theory is methodically determined. The calibrated continuum theory is shown to well predict the size-dependent surface energy and the associated redistribution of surface energy density within nanoplates.

THE K2 M67 STUDY: REVISITING OLD FRIENDS WITH K2 REVEALS OSCILLATING RED GIANTS IN THE OPEN CLUSTER M67

ABSTRACT Observations of stellar clusters have had a tremendous impact in forming our understanding of stellar evolution. The open cluster M67 has a particularly important role as a calibration benchmark for stellar evolution theory due to its near-solar composition and age. As a result, it has been observed extensively, including attempts to detect solar-like oscillations in its main sequence and red giant stars. However, any asteroseismic inference has so far remained elusive due to the difficulty in measuring these extremely low-amplitude oscillations. Here we report the first unambiguous detection of solar-like oscillations in the red giants of M67. We use data from the Kepler ecliptic mission, K2, to measure the global asteroseismic properties. We find a model-independent seismic-informed distance of 816 ± 11 pc, or mag, an average red giant mass of , in agreement with the dynamical mass from an eclipsing binary near the cluster turn-off, and ages of individual stars compatible with isochrone fitting. We see no evidence of strong mass loss on the red giant branch. We also determine seismic of all the cluster giants with a typical precision of dex. Our results generally show good agreement with independent methods and support the use of seismic scaling relations to determine global properties of red giant stars with near-solar metallicity. We further illustrate that the data are of such high quality that future work on individual mode frequencies should be possible, which would extend the scope of seismic analysis of this cluster.

Reproducing CO2 exchange rates of a crop rotation at contrasting terrain positions using two different modelling approaches

In undulating landscapes erosion is largely responsible for the spatial distribution of C stocks in agricultural soils. Whether these stocks contribute to global atmospheric CO2 concentrations as source or sink of CO2 is under constant debate. Periodic CO2 measurements were carried out at a hummocky ground moraine site grown with maize, fodder rye and sorghum using dynamic non-steady-state transparent and opaque chambers. Flux calculation for CO2 was conducted using the empirical gap-filling model of Hoffmann et al. (2015b), which uses temperature and radiation to simulate ecosystem respiration (Reco) and gross primary production (GPP) and to calculate net ecosystem CO2 exchange (NEE). This model was compared with a process-based agro-ecosystem simulation model, MONICA, which was tested for its ability to simulate Reco, GPP and NEE, using the empirical model as benchmark. Both models simulated GPP and Reco in the same order of magnitude, with MONICA simulating a considerably higher amount of CO2 produced by photosynthesis for maize and less deviating CO2 produced by photosynthesis for the other crops and CO2 consumed by respiration for all crops as compared to the empirical model. Both models largely agree in CO2 flux patterns, but show considerable differences directly after harvest and during bare soil periods. Strengths and weaknesses of both approaches were discussed and synergies of applying both approaches in conjunction were identified in a way that (i) MONICA may act as an independent method to identify significant deviations from the optimum crop growth pattern and thus point at times during which assumptions of the empirical model for simulating NEE may be violated and that (ii) the empirical model may act as a calibration benchmark for MONICA flux simulations.

Structural Transformation Under Trade Imbalances: The Case of the Postwar U.S.

A striking feature of the structural change literature is that, even though the U.S. economy is often used as a benchmark for calibration, the traditional models cannot account for the steep decline in manufacturing and rise in services in the United States since the late 1970s (Buera et al., 2009). In order to solve this puzzle, this paper develops a three-sector model to evaluate various factors that could have contributed to the structural transformation process from 1950 to 2005. The results show that, in addition to traditional explanations, such as non-homothetic preference and sector-biased productivity progress, international trade is another major source of structural change and is able to explain about 35.5% of the overall labor share decrease in American manufacturing. The quantitative calibration estimates that the inter-sector trade makes a moderate contribution, while trade imbalances dominate the recent contraction of manufacturing employment share. This paper quantitatively explores the role of trade imbalances in the structural change literature, and it supports the argument that persistent trade deficits have a substantial impact on labor markets.

Site-site direct correlation functions for three popular molecular models of liquid water

Direct correlation functions (DCFs) play a pivotal role in the applications of classical density functional theory (DFT) to addressing the thermodynamic properties of inhomogeneous systems beyond the local-density or mean-field approximations. Whereas numerous studies have been dedicated to the radial distribution functions of liquid water--the most important solvent on earth, relatively little attention has been given to the site-site DCFs. The water DCFs are long-ranged and difficult to calculate directly by simulation, and the predictions from conventional liquid-state theories have been rarely calibrated. Here we report a computational procedure for accurate evaluation of the site-site DCFs of liquid water based on three popular molecular models (viz., SPC, SPC∕E, and TIP3P). The numerical results provide a benchmark for calibration of conventional liquid-state theories and fresh insights into development of new DFT methods. We show that: (1) the long-range behavior of the site-site DCFs depends on both the molecular model and the thermodynamic condition; (2) the asymptotic limit of DCFs at large distance does not follow the mean-spherical approximation (MSA); (3) individual site-site DCFs are long ranged (~40 nm) but a summation of all DCF pairs exhibits only short-range behavior (~1 nm or a few water diameters); (4) the site-site bridge correlation functions behave as the DCFs, i.e., they are also long-ranged while the summation of all bridge correlation functions is short ranged. Our analytical and numerical analyses of the DCFs provide some simple strategies for possible improvement of the numerical performance of conventional liquid-state theories.