Empirical Correction Factors Research Articles

Influence of lateral flow contraction on bed shear stress estimation by using measured turbulent kinetic energy

Sedimentation, including erosion, transport, and deposition of river-bed material, is a complex process influenced by several parameters related to flow, materials, and geometries. Evaluation of the bed shear stress under a wide range of flow conditions is the primary step in understanding the sedimentation process. In this study, the bed shear stress is analyzed experimentally near an obstruction where maximum erosion occurs. The local flow conditions near the obstruction are varied by modeling several typical lateral flow contractions in the flume. Through analysis of the results, we discuss the effects of local turbulence on the bed shear stress in terms of Reynolds stress and turbulent kinetic energy that are measured for various ranges of water depth, velocity, and flow contractions. From the findings, we suggest an empirical correction factor that accounts for the local turbulence in calculation of bed shear stress using turbulent kinetic energy. It is concluded from experiments that the empirical correction factor is a function of the flow contraction ratio.

Current Approaches for Predicting Human PK for Small Molecule Development Candidates: Findings from the IQ Human PK Prediction Working Group Survey.

Accurate prediction of human clearance (CL) and volume of distribution at steady state (Vd,ss) for small molecule drug candidates is an essential component of assessing likely efficacious dose and clinical safety margins. In 2021, the IQ Consortium Human PK Prediction Working Group undertook a survey of IQ member companies to understand the current PK prediction methods being used to estimate these parameters across the pharmaceutical industry. The survey revealed a heterogeneity in approaches being used across the industry (e.g., the use of allometric approaches, differing incorporation of binding terms, and inconsistent use of empirical correction factors for in vitro-in vivo extrapolation, IVIVE), which could lead to different PK predictions with the same input data. Member companies expressed an interest in improving human PK predictions by identifying the most appropriate compound-class specific methods, as determined by physiochemical properties and knowledge of CL pathways. Furthermore, there was consensus that increased understanding of the uncertainty inherent to the compound class-dependent prediction would be invaluable in aiding communication of human PK and dose uncertainty at the time of candidate nomination for development. The human PK Prediction Working Group is utilizing these survey findings to help interrogate clinical IV datasets from across the IQ consortium member companies to understand PK prediction accuracy and uncertainty from preclinical datasets.

Synchronized high-speed scintillation imaging of proton beams, generated by a gantry-mounted synchrocyclotron, on a pulse-by-pulse basis.

With the emergence of more complex and novel proton delivery techniques, there is a need for quality assurance tools with high spatiotemporal resolution to conveniently measure the spatial and temporal properties of the beam. In this context, scintillation-based dosimeters, if synchronized with the radiation beam and corrected for ionization quenching, are appealing. To develop a synchronized high-speed scintillation imaging system for characterization and verification of the proton therapy beams on a pulse-by-pulse basis. A 30cm×30cm×5cm block of BC-408 plastic scintillator placed in a light-tight housing was irradiated by proton beams generated by a Mevion S250 proton therapy synchrocyclotron. A high-speed camera system, placed perpendicular to the beam direction and facing the scintillator, was synchronized to the accelerator's pulses to capture images. Opening and closing of the camera's shutter was controlled by setting a proper time delay and exposure time, respectively. The scintillation signal was recorded as a set of two-dimensional (2D) images. Empirical correction factors were applied to the images to correct for the nonuniformity of the pixel sensitivity and quenching of the scintillator. Proton range and modulation were obtained from the corrected images. The camera system was able to capture all data on a pulse-by-pulse basis at a rate of ∼504 frames per second. The applied empirical correction method for ionization quenching was effective and the corrected composite image provided a 2D map of dose distribution. The measured range (depth of distal 90%) through scintillation imaging agreed within 1.2mm with that obtained from ionization chamber measurement. A high-speed camera system capable of capturing scintillation signals from individual proton pulses was developed. The scintillation imaging system is promising for rapid proton beam characterization and verification.

Implementation of empirical modified generalized Harvey–Shack scatter model on smooth surface

We propose a modified generalized Harvey–Shack model by adding the empirical correction factor related to the scattering angle on the basis of the original theory. The result shows that the modified model reduces the root mean square error (RMSE) from less than 2% to less than 1%, and the relative peak error from less than 50% to less than 20%, which significantly improves the accuracy of scattering prediction. The prediction of the Rayleigh–Rice model is not as good as the Harvey–Shack model. The RMSE of the Rayleigh–Rice model is within 2.5%, and the relative peak error is within 60%.

Characterisation of intravenous pharmacokinetics in Göttingen minipig and clearance prediction using established in vitro to in vivo extrapolation methodologies

The use of the Göttingen minipig as an animal model for drug safety testing and prediction of human pharmacokinetics (PK) continues to gain momentum in pharmaceutical research and development. The aim of this study was to evaluate in vitro to in vivo extrapolation (IVIVE) methodologies for prediction of hepatic, metabolic clearance (CLhep,met) in Göttingen minipig, using a comprehensive set of compounds. In vivo clearance was determined in Göttingen minipig by intravenous cassette dosing and hepatocyte intrinsic clearance, plasma protein binding and non-specific incubation binding were determined in vitro. Prediction of CLhep,met was performed by IVIVE using conventional and adapted formats of the well-stirred liver model. The best prediction of in vivo CLhep,met from scaled in vitro kinetic data was achieved using an empirical correction factor based on a ‘regression offset’ of the IVIV relationship. In summary, these results expand the in vitro and in vivo PK knowledge in Göttingen minipig. We show regression corrected IVIVE provides superior prediction of in vivo CLhep,met in minipig offering a practical, unified scaling approach to address systematic under-predictions. Finally, we propose a reference set for researchers to establish their own ‘lab-specific’ regression correction for IVIVE in minipig.

Correlating R-ratio effects on FCG behavior using ΔKd function

This paper provides correlations of R-ratio effects on fatigue crack growth (FCG) behavior under constant amplitude at lab air. The proposed crack driving force ΔKd is analogous to the Smith-Watson-Topper’s (SWT) parameter, which is based on the energy consideration and its role in FCG process. Proposed correlation doesn’t invoke any fitting parameters for R < 0.6. For a high R > 0.6 an empirical correction factor is used, which accounts for the effect of the excessive forward plastic zone. Key practical implication of the proposed ΔKd function is its ability to account for load ratio effects in threshold and the Paris region for both positive and negative R. Correlations are compared with experimental data taken from the literature for a wide variety of different alloys.

Continuous electric field modeling of Macro-Fiber Composites for actuation and energy harvesting

This paper presents a new low-order electric field model for Macro-Fiber Composite devices with interdigitated electrodes. Specifically, the paper proposes a continuous electric field model, where the differential form of Gauss's law is used to obtain spatial terms of the electric field, and the integral form of Gauss's law is used to obtain temporal term of the electric field. By neglecting three-dimensional effects, the method of matched asymptotic expansion is employed to obtain the electric field between two pairs of interdigitated electrodes under quasi-electrostatic conditions. By averaging the solution along with the thickness of piezoceramic fibers and expanding it to the device's entire geometry by Fourier series, the low-order model of the electric field between the interdigitated electrodes is obtained. The matched asymptotic expansion and the low-order model agree well with finite element results. Generalized Hamilton's principle is employed to obtain the coupled electromechanical equations of motion for a beam with the Macro-Fiber Composite device. The Euler-Bernoulli assumptions are used to approximate strain distribution. Under current assumptions, equivalent capacitance and electromechanical coupling terms are obtained without using discontinuous functions (e.g., Heaviside or piecewise functions) for electric field terms. The equivalent capacitance is within 2% of the values reported by the manufacturer. Frequency response functions are obtained for the output voltage, tip displacement, and optimum working load of the energy harvester, and the current and the tip displacement for the actuator by assumed modes solution for a cantilever beam. It is shown that the actuator's current is related to the optimum working load of the energy harvester by Ohm's law. In the limited case, the proposed continuous electric field model reduces to the constant electric field model. When the constant electric field model is compared to the continuous electric field model, it is shown that the constant electric field model overpredicts the equivalent capacitance and electromechanical coupling. The relative difference between the two models for equivalent capacitance is around 41%, and for electromechanical coupling is around 22%. These relative differences are in agreement with the empirical correction factors defined in the earlier constant field models.

NESS2.0: An Updated Version of the Worldwide Dataset for Calibrating and Adjusting Ground-Motion Models in Near Source

ABSTRACT We present an extended and updated version of the worldwide NEar-Source Strong-motion (NESS) flat file, which includes an increased number of moderate-to-strong earthquakes recorded in epicentral area, new source metadata and intensity measures, comprising spectral displacements and fling-step amplitudes retrieved from the extended baseline correction processing of velocity time series. The resulting dataset consists of 81 events with moment magnitude≥5.5 and hypocentral depth shallower than 40 km, corresponding to 1189 three-component waveforms, which are selected to have a maximum source-to-site distance within one fault length. Details on the flat files, metadata, and ground-motion parameters, processing scheme, and statistical findings are presented and discussed. The analysis of these data allows recognizing the presence of distinctive features (such as pulse-like waveforms, large vertical components, and hanging-wall effects) that can be exploited to assess their impact on near-source seismic motion. As an example, we use the NESS2.0 dataset for calibrating an empirical correction factor of a regional ground-motion model (GMM) mainly based on far-field records. In this way, we can adjust the median predictions to account for near-source effects not fully captured by the reference model. The final goal of this work is to promote the use of the NESS2 flat file as a tool to disseminate qualified and referenced near-source data and metadata in the light of improving the constraints of GMMs (both empirical and physics-based) close to the source.

Spatial Patterns in Actual Evapotranspiration Climatologies for Europe

Spatial patterns in long-term average evapotranspiration (ET) represent a unique source of information for evaluating the spatial pattern performance of distributed hydrological models on a river basin to continental scale. This kind of model evaluation is getting increased attention, acknowledging the shortcomings of traditional aggregated or timeseries-based evaluations. A variety of satellite remote sensing (RS)-based ET estimates exist, covering a range of methods and resolutions. There is, therefore, a need to evaluate these estimates, not only in terms of temporal performance and similarity, but also in terms of long-term spatial patterns. The current study evaluates four RS-ET estimates at moderate resolution with respect to spatial patterns in comparison to two alternative continental-scale gridded ET estimates (water-balance ET and Budyko). To increase comparability, an empirical correction factor between clear sky and all-weather ET, based on eddy covariance data, is derived, which could be suitable for simple corrections of clear sky estimates. Three RS-ET estimates (MODIS16, TSEB and PT-JPL) and the Budyko method generally display similar spatial patterns both across the European domain (mean SPAEF = 0.41, range 0.25–0.61) and within river basins (mean SPAEF range 0.19–0.38), although the pattern similarity within river basins varies significantly across basins. In contrast, the WB-ET and PML_V2 produced very different spatial patterns. The similarity between different methods ranging over different combinations of water, energy, vegetation and land surface temperature constraints suggests that robust spatial patterns of ET can be achieved by combining several methods.

The Effects of Spacecraft Potential on Ionospheric Ion Measurements

The energetic electrostatic analyzer has been developed to act as a miniaturized, rugged, and low-cost instrument capable of providing in situ measurements of ion or electron energy and subsequent derived density, temperature, and spacecraft potential. We present laboratory calibration results using a magnetically filtered low-Earth-orbit plasma simulator to quantify the effects of spacecraft charge on laminated analyzer ion energy distribution measurements and the resulting impact on the derived temperature and density values. The calibration results are then applied as an empirical correction method to Space Test Program Satellite-3 integrated miniaturized electrostatic analyzer data to present corrected temperature and density values. Application of the empirical correction factor improved the agreement between in situ measurements and the international reference ionosphere model in terms of ion temperature by 0.01 eV and in terms of density to within 20%.

Unveiling the existing condition and energy use in Hellenic school buildings

This work exploits available data from energy audits of about 350 Hellenic school buildings from the national electronic repository that have been performed for issuing energy performance certificates The average construction characteristics of the building’s envelope and technical characteristics of the electromechanical installations are defined in order to gain a better understanding of the existing condition of school buildings. The resulting final and primary energy use intensities are calculated, as well as the respective energy ratings. Building envelopes are not thermally insulated or partly insulated, and the prevailing central heating systems are oil-fired boilers. Schools are commonly ranked at energy class-D, with average energy use intensity 98.8 kWh/m2 for final and 158.9 kWh/m2 for primary energy. Generally, space heating is the most significant service, followed by lighting and space cooling. In addition, available data on actual energy use of the buildings is analysed and used to generate empirical correction factors that relate the calculated energy consumption with the actual energy use. On average, actual thermal energy use is about twenty percent higher than calculated, while the actual electricity consumption is about half of the calculated value.

A model-based framework for correcting inhomogeneity effects in magnetization transfer saturation and inhomogeneous magnetization transfer saturation maps.

In this work, we propose that Δ -induced errors in magnetization transfer (MT) saturation (MTsat ) maps can be corrected with use of an R1 and map and through numerical simulations of the sequence. One healthy subject was scanned at 3.0T using a partial quantitative MT protocol to estimate the relationship between observed R1 (R1,obs ) and apparent bound pool size ( ) in the brain. MTsat values were simulated for a range of , R1,obs , and . An equation was fit to the simulated MTsat , then a linear relationship between R1,obs and was generated. These results were used to generate correction factor maps for the MTsat acquired from single-point data. The proposed correction was compared to an empirical correction factor with different MT-preparation schemes. was highly correlated with R1,obs (r > 0.96), permitting the use of R1,obs to estimate for correction. All corrected MTsat maps displayed a decreased correlation with compared to uncorrected MTsat and MTsat corrected with an empirical factor in the corpus callosum. There was good agreement between the proposed approach and the empirical correction with radiofrequency saturation at 2 kHz, with larger deviations seen when using saturation pulses further off-resonance and in inhomogeneous (ih) MTsat maps. The proposed correction decreases the dependence of MTsat on inhomogeneities. Furthermore, this flexible framework permits the use of different saturation protocols, making it useful for correcting inhomogeneities in ihMT.

Nuclear temperature and its dependence on the source neutron-proton asymmetry deduced using the Albergo thermometer

Albergo thermometers with double isotope, isotone, and isobar yield ratio pairs with one proton and/or neutron difference are investigated. Without any extra sequential decay correction, a real temperature value of $4.9\ifmmode\pm\else\textpm\fi{}0.5$ MeV is deduced from the yields of the experimentally reconstructed primary hot intermediate mass fragments (IMFs) from $^{64}\mathrm{Zn}+^{112}\mathrm{Sn}$ collisions at 40 MeV/nucleon using the Albergo thermometer for the first time. An experimental sequential decay correction from the apparent temperatures to the real ones for 12 other reaction systems with different neutron-proton ($N/Z$) asymmetries in the same experiment, $^{70}\mathrm{Zn}$, $^{64}\mathrm{Ni}$ on $^{112,124}\mathrm{Sn}$, $^{58,64}\mathrm{Ni}$, $^{197}\mathrm{Au}$, and $^{232}\mathrm{Th}$ at 40 MeV/nucleon, is performed using an empirical correction factor approach of Tsang et al. [Phys. Rev. Lett. 78, 3836 (1997)] with the deduced 4.9-MeV temperature value. The dependence of nuclear temperature on the source $N/Z$ asymmetry is further investigated using these deduced real source temperature values from the present 13 systems. It is found that the deduced real source temperatures at the present source $N/Z$ range show a rather weak dependence on the source $N/Z$ asymmetry. By comparison between our previous results and those from other independent experiments, a consistent description for the $N/Z$ asymmetry dependence of nuclear temperature is addressed.

Direct Current Electrokinetic Particle Trapping in Insulator-Based Microfluidics: Theory and Experiments

The classic theory of direct-current (DC) insulator-based dielectrophoresis (iDEP) considers that, in order to elicit particle trapping, dielectrophoretic (DEP) velocity counterbalances electrokinetic (EK) motion, that is, electrophoresis (EP) and electro-osmotic flow (EOF). However, the particle velocity DEP component requires empirical correction factors (sometimes as high as 600) to account for experimental observations, suggesting the need for a refined model. Here, we show that, when applied to particle suspensions, a high-magnitude DC uniform electric field induces nonlinear particle velocities, leading to particle flow reversal beyond a critical field magnitude, referred to as the EK equilibrium condition. We further demonstrate that this particle motion can be described through an exploratory induced-charge EP nonlinear model. The model predictions were validated under an insulator-based microfluidic platform demonstrating predictive particle trapping for three different particle sizes (with an estimation error < 10%, not using correction factors). Our findings suggest that particle motion and trapping in "DC-iDEP" devices are dominated by EP and EOF, rather than by DEP effects.

Simulation-Based Generation of Representative and Valid Training Data for Acoustic Resonance Testing

Analyzing eigenfrequencies of serial parts by acoustic resonance testing enables an efficient nondestructive assessment of component quality or structural state. Usually, each application is based on experimentally acquired training data, which represent the typical natural vibration behavior of the component type to be inspected. From the training data, suitable test characteristics are identified according to the inspection objective. The experimental collection of training data, which involves selecting and characterizing numerous representing parts, is often associated with a great amount of effort. Instead, this work focuses on a simulation-based generation of synthetic training data. Within an application example, the eigenfrequencies of a set of virtual parts were calculated with FEM as a function of geometry. The resulting simulation values were adapted using empirical correction factors, which were derived from both calculated and measured eigenfrequencies of machine-made reference parts. The simulation-based data were finally used to form linear regression models within a training procedure. These models enabled the precise estimation of geometric dimensions of further machine-made parts using their measured eigenfrequencies as input data. The novel approach, which requires the experimental characterization of only a few real parts, can thus significantly reduce the effort associated with efficient and reliable acoustic resonance testing.

Adaptation of mathematical model of heat and energy characteristics of medium pressure boilers to real operating conditions

The object of this research is the thermal and energy characteristics of medium-pressure boilers at the thermal power plant of a metallurgical plant operating on a common steam header. The fuel used is a mixture of blast furnace and natural gases. The volume fraction of blast furnace gas is 80–95 %. The characteristics of blast-furnace gas are not constant: the elementary composition, humidity and dust content change significantly.The mathematical model developed for the purpose of comprehensive optimization of the modes of joint operation of boilers requires adaptation of the energy characteristics obtained by calculation to real operating conditions. Adaptation of the calculated energy characteristics was carried out individually on the basis of thermal balance tests of boilers and taking into account the design and operational features of each boiler. During the tests, the fraction of the convective component of heat transfer in the furnace for the considered boiler units was determined using a non-stationary heat meter. The absolute value of the heat flux density was determined according to the theory of non-stationary regular heating of the sensitive element (SE). It was found that as the fuel burns out, the level of heat fluxes decreases, and with an increase in the thermal fraction of blast furnace gas, the absolute value of local falling fluxes decreases. The average share of the convective component is 15–20 %. It is proposed to adapt to the real operating conditions of the superheater and tail heating surfaces using empirical correction factors obtained during processing of the results of balance tests.Taking into account the proportion of convective heat flux in the furnace makes it possible to more accurately determine the parameters of the heat carriers along the steam-gas path of the boiler, and, therefore, it is possible to obtain adapted energy characteristics of the boilers. In comparison with analytical calculated dependences, the proposed method provides an individual approach to the operating modes of boilers. Thanks to this, it is possible to reduce the error in determining the optimal solutions to less than 1 %.

Energy absorption mechanisms and capabilities for magnesium extrusions under impact

There is significant interest in replacing conventional materials with novel, lightweight alternatives. Magnesium alloys are favorable candidates since magnesium is the lightest structural metal available. The impetus of this investigation was to examine the mechanical performance for AM30 magnesium extrusions subjected to quasi-static and dynamic progressive crushing and axial cutting with impact velocities up to 18 m/s investigated. These magnitudes replicated high speed, transportation-related impacts in a range where experimental data is crucial but absent from the literature. The collected data was compared in terms of total energy absorption, force efficiency and overall deformation stability to assess the feasibility of this novel material as a potential substitute for vehicular safety systems which are traditionally composed of steel. Axial cutting was generally outperformed in terms of energy absorption capacity when compared to crushing, except for the case of 10-bladed cutting. However, the degree of fracture observed and corresponding lack of stability under crushing was unacceptable for a safety system while every cutting test proceeded with a highly repeatable, near-constant force response which successfully mitigated fracture. The average cutting force efficiency was approximately 85%, compared to 30% for the progressively crushed specimens. A fully analytical model to predict the complete force-displacement response under a cutting deformation mode was derived and validated, based upon experimental observations, with an average error of 4% for a series of geometries, alloys, loading rates and cutting tools. Additionally, this revised model possesses a stronger theoretical basis than the original by considering the influence of strain energy release rate per unit area (J-integral) and a brittle cutting membrane rather than empirical correction factors. The influence of mechanical leverage on the axial cutting force, by radial clamping of the flared sidewalls, was also considered in the revised analytical model and validated for an expanded parametric scope.

Sparse Sampling of Intermittent Turbulence Generated by Breaking Surface Waves

AbstractWe examine how Eulerian statistics of wave breaking and associated turbulence dissipation rates in a field of intermittent events compare with those obtained from sparse Lagrangian sampling by surface following drifters. We use a polydisperse two-fluid model with large-eddy simulation (LES) resolution and volume-of-fluid surface reconstruction (VOF) to simulate the generation and evolution of turbulence and bubbles beneath short-crested wave breaking events in deep water. Bubble contributions to dissipation and momentum transfer between the water and air phases are considered. Eulerian statistics are obtained from the numerical results, which are available on a fixed grid. Next, we sample the LES/VOF model results with a large number of virtual surface-following drifters that are initially distributed in the numerical domain, regularly or irregularly, before each breaking event. Time-averaged Lagrangian statistics are obtained using the time series sampled by the virtual drifters. We show that convergence of statistics occurs for signals that have minimum length of approximately 1000–3000 wave periods with randomly spaced observations in time and space relative to three-dimensional breaking events. We further show important effects of (i) extent of measurements over depth and (ii) obscuration of velocity measurements due to entrained bubbles, which are the two typical challenges in most of the available in situ observations of upper ocean wave breaking turbulence. An empirical correction factor is developed and applied to the previous observations of Thomson et al. Applying the new correction factor to the observations noticeably improves the inferred energy balance of wind input rates and turbulence dissipation rates. Finally, both our simulation results and the corrected observations suggested that the total wave breaking dissipation rates have a nearly linear relation with active whitecap coverage.

On the calculation of wavenumber from measured time traces

When characterising local geometry for unsteady water waves, the accurate determination of spatial quantities such as the wavenumber from measured time traces is non-trivial. The present study investigates different methods in order to highlight the discrepancies that arise when estimating the wavenumber from fully nonlinear numerical time traces of the free surface profile. To this extent, the open research topic relating to the accuracy of the Hilbert transform in analysing broad-banded signals is addressed. The accuracy of local wavenumber estimates from the Hilbert transform are shown to have a strong dependency on the bandwidth of the underlying spectrum. For broad-banded sea-states there is a significant departure of the Hilbert transform predictions from actual wavenumber values. In contrast, the Double Fourier numerical model of Baldock and Swan (1994) [1] is shown to obtain accurate estimates of local wave geometry from just a single measured time trace, regardless of spectral characteristics; it is thus the recommended method. In addition, an empirical correction factor is proposed that can be applied to the linear dispersion equation in order to obtain an improved wavenumber estimate. The correction is tested for unidirectional deep water, nonlinear random sea-states and shown to offer considerable improvements in the local wavenumber estimates.

Validation of coupled fission matrix – TRACE methods for thermal-hydraulic and control feedback on the Penn State Breazeale Reactor

A new method for calculating power shape and critical control rod position is described and validated in view of increasing the fidelity of the Penn State Breazeale Reactor's (PSBR) fuel management code. Currently, the PSBR fuel management code is biased against experimental results and requires the use of empirical correction factors. This is likely due to a combination of assumptions, such as the control rods being fixed in the all-out position and the use of a uniform fuel temperature. The proposed method supplies this data using fission-matrix-based neutronics coupled with TRACE thermal-hydraulics. The fission-matrix-based neutronics relies on Serpent for precalculation of fission matrices. Steady-state fuel temperature distributions, power shapes, and control rod positions are calculated through iteration between TRACE and fission matrix calculations. Validation is performed on the coupled TRACE-fission matrix model for powers ranging from 50 kW to 1 MW. For these cases, the RMS average error with experimental data is 12.7 K for instrumented element fuel temperature and $0.07 for reactivity change. Agreement is generally within estimated experimental uncertainty. The effect of various modeling parameters, such as the fuel-cladding gap heat transfer coefficient and the exact radial location of the instrumented element thermocouple, are shown. Finally, the impact of this increased modeling fidelity on the depletion calculation is estimated. In the future, this validation should be repeated on later core loadings of the PSBR where more detailed experimental data is available. Comparison between the current PSBR fuel management code and the proposed model should also be made.