Relative Parameter Sensitivity Research Articles

Dynamical Analysis of Hybrid-Scale Bifurcation in One-Cycle Controlled Single-Inductor Dual-Output Buck DC–DC Converters

In this paper, the hybrid-scale bifurcation evolutionary phenomena in one-cycle controlled (OCC) single-inductor dual-output (SIDO) Buck DC–DC converter are investigated thoroughly. First, the single-cycle and crossing-cycle iterative mapping models of the OCC SIDO converter in four operation modes are derived to describe the dynamical information under different topology switching sequences. Second, the evolutionary trend of hybrid-scale bifurcation behaviors is identified by numerical simulation. Third, bifurcation analysis based on the proposed models is performed by the trajectories of the eigenvalues, and significantly, the occurrence mechanism of hybrid-scale bifurcations in the evolutionary phenomena is explained in detail. And then, the participation factor is used to analyze the relationship between the variables and the eigenvalues. Especially, the relative parameter sensitivity of the iterative mapping model is proposed to evaluate the influence of such key parameters as load resistors on the eigenvalues so that plenty of design-oriented information will be provided to avoid the hybrid-scale bifurcation behaviors. Finally, PSpice circuit simulation and hardware experiments are carried out to verify the analysis results.

Wear Analysis of Support Spring of Sprag Clutch during State of Overrunning

This paper analyzes the wear of the support spring of sprag clutches for different structural parameters during overrunning state. Specifically, the stiffness model of the support spring is established based on the characteristics of the variable helix angle, and also the supporting force model is established according to the energy conservation law during the working process of the sprag clutch. Meanwhile, the relative rotation speed between the support spring and the wedge is analyzed by dynamic simulation method. Furthermore, the wear model of the support spring in process of overrunning is established based on Archard wear theory. The results show that there is a linear relationship between supporting force and spring radial displacement compression. In addition, increasing free length and wire diameter of springs will aggravate the wear of springs, whereas enlarging pitch diameter of springs will reduce it. When free length is increased from 270 to 290 mm, the wear time is reduced by 20.88%; when wire diameter is increased from 0.5 to 0.7 mm, the wear time is reduced by 42.75%; when pitch diameter is increased from 2 to 2.4 mm, the wear time is increased by 3.35%. The degree of influence of the structural parameters on the spring wear from large to small is free length, wire diameter, and pitch diameter. Exactly speaking, when wear time is 100 hr, the relative sensitivity of structural parameters affecting the wear of the support spring is in order of free length (2.2), wire diameter (0.97), and pitch diameter (0.08). The research provides a reference for the design and optimization of the support spring for highly reliable sprag clutches.

Regional Photometric Modeling of Asteroid (101955) Bennu

Abstract We present a regional photometric analysis of asteroid (101955) Bennu, using image data from the MapCam color imager of the OSIRIS-REx Camera Suite (OCAMS). This analysis follows the previously reported global photometric analysis of Bennu, which found that Bennu’s roughness was difficult to photometrically model owing to unresolved surface variation. Here we find that, even with a high-resolution shape model (20 cm per facet) and automatic image registration (<1 pixel error), Bennu remains a challenging surface to photometrically model: neither a suite of empirical photometric models nor the physically motivated Hapke model were able to eliminate the scatter in the data due to pixel-scale variations. Nonetheless, the models improved on the global analysis by identifying regional variations in Bennu’s photometric response. A linear empirical model, when compared with independent measures of surface roughness and albedo, revealed correlations between those characteristics and phase slope. A regional Hapke analysis showed the same structure in its single-scattering albedo and asymmetry factors; although the Hapke parameters were loosely constrained, complicating interpretation of their spatial variation, the regional variation in relative parameter sensitivity also correlated with shallower phase slope, higher albedo, and less macroscopic roughness.

Semi-analytical atomic-level uncertainty quantification for the elastic properties of 2D materials

Inherent stochasticity in the nanostructural geometry and molecular mechanics properties of lattice-like two-dimensional (2D) materials can significantly deviate the predicted elastic properties that are widely reported in a deterministic framework. Such uncertainties can be attributed to inevitable fabrication uncertainties and random error in parameterizing the atomic-level constants depending on the accuracy of highly complicated nanoscale experiments. Generalized high-fidelity analytical models are developed in this article to quantify the influence of these source-uncertainties on the basis of first- and second-order perturbation theories coupled with nanoscale continuum mechanics. The proposed stochastic mechanics–based analytical framework is further validated using the baseline Monte Carlo simulation–assisted probabilistic approach. To provide comprehensive numerical insights, four different 2D materials with uniform and non-uniform atomic distributions are considered covering the monoplanar as well as multiplanar nanostructural configurations (graphene, hexagonal boron nitride, stanene and molybdenum disulfide). The perturbation-based approach is further extended to quantify the relative sensitivity of different nanostructural and molecular mechanics parameters on the elastic moduli of 2D materials. The proposed analytical approach leads to a significant level of computational efficiency by alleviating the necessity of carrying out thousands of molecular dynamics simulations to obtain deep computational insights concerning uncertainty quantification and sensitivity analysis, which would assume a crucial role to ensure robust analysis and design of technologically demanding multifunctional devices and systems across the length-scales.

Energy performance of mixed-mode office buildings: Assessing typical construction design practices

Studies have demonstrated the energy savings potential of mixed-mode ventilated office buildings. Yet, it is important to widen the knowledge about how those buildings have been designed and built in practice, and which design parameters have greater influence on its energy performance. The aim of this paper was to evaluate how building envelope design parameters influence the energy performance of cellular mixed-mode office buildings, in order to identify key design variables. The analysis presents a comparison among literature research studies and typical construction practices from a sample of buildings located in the city of Sao Paulo, Brazil. According to a base case model, established based on the real buildings sample, three sensitivity analysis techniques were performed to obtain relative parameter sensitivity to thermal loads: OFAT, Morris and Monte Carlo. Results showed the importance of the window opening effective area and the reduced impact of the window-to-wall ratio on the energy performance of mixed-mode office buildings. By applying a multivariate regression model, it showed significant in predicting 78.1% of the variance in annual thermal loads. The accurate determination of annual thermal loads into mixed-mode office buildings can be used to optimize the envelope characteristics based on a combination of input data and the building geometry. Findings from this study could also be applied to other locations, provided that similar climatic environment and urban context are taken into account.

Sensitivity analysis of the parameter‐efficient distributed (PED) model for discharge and sediment concentration estimation in degraded humid landscapes

AbstractSustainable development in degraded landscapes in the humid tropics requires effective soil and water management practices. Coupled hydrological‐erosion models have been used to understand and predict the underlying processes at watershed scale and the effect of human interventions. One prominent tool is the parameter‐efficient distributed (PED) model, which improves on other models by considering a saturation‐excess runoff generation driving erosion and sediment transport in humid climates. This model has been widely applied at different scales for the humid monsoonal climate of the Ethiopian Highlands, with good success in estimating discharge and sediment concentrations. However, previous studies performed manual calibration of the involved parameters without reporting sensitivity analyses or assessing equifinality. The aim of this article is to provide a multiobjective global sensitivity analysis of the PED model using automatic random sampling implemented in the SAFE Toolbox. We find that relative parameter sensitivity depends greatly on the purpose of model application and the outcomes used for its evaluation. Five of the 13 PED model parameters are insensitive for improving model performance. Additionally, associating behavioural parameter values with a clear physical meaning provides slightly better results and helps interpretation. Lastly, good performance in one module does not translate directly into good performance in the other module. We interpret these results in terms of the represented hydrological and erosion processes and recommend field data to inform model calibration and validation, potentially improving land degradation understanding and prediction and supporting decision‐making for soil and water conservation strategies in degraded humid landscapes.

Stability parameter analysis of a composite foundation of an oil storage tank in a loess area treated with compaction piles

The research takes the composite foundation of the Lintao oil depot belonging to the Gansu branch of PetroChina treated with compaction piles in the collapsible loess region as the research background. A large number of compaction piles dispersed in the composite foundation are simplified using the equivalent continuum method. Discrete piles arranged in a triangular shape are simplified in the model, where the annular piles and compacted soil are arranged alternately, which can provide new ideas for the three-dimensional calculation mode of composite foundation and greatly improve the convergence and computational efficiency of the finite element model. To more realistically reflect the actual situation, the soil-structure and fluid–structure interactions, the material and the contact nonlinearities are considered, and a large-scale three-dimensional calculation model, which includes the composite foundation, concrete foundation, tank and liquid, is established. A sensitivity analysis is used to analyze the sensitivity of the elastic modulus, internal friction angle and cohesion of the composite foundation. The sensitivity of a single factor is evaluated based on the absolute value of the slope of the result-parameter curve; the relative sensitivity of various parameters is discussed according to the dimensionless sensitivity. The results show that for composite foundation, an increase in the friction angle or the cohesion of the foundation will significantly increase the safety factor. The sensitivity of the friction angle is greater than that of cohesion, and the sensibility of the elasticity modulus on the stability is very small. The results suggest that the accuracy of the mechanical parameter selection should be considered in the research on the stability of composite foundations. Measures to increase the angle of internal friction should be preferentially taken and increasing the cohesion should be considered secondary to improve the stability and safety reserve of composite foundation.

Optimization of Parameter Ranges for Composite Tape Winding Process Based on Sensitivity Analysis

This study is focus on the parameters sensitivity of winding process for composite prepreg tape. The methods of multi-parameter relative sensitivity analysis and single-parameter sensitivity analysis are proposed. The polynomial empirical model of interlaminar shear strength is established by response surface experimental method. Using this model, the relative sensitivity of key process parameters including temperature, tension, pressure and velocity is calculated, while the single-parameter sensitivity curves are obtained. According to the analysis of sensitivity curves, the stability and instability range of each parameter are recognized. Finally, the optimization method of winding process parameters is developed. The analysis results show that the optimized ranges of the process parameters for interlaminar shear strength are: temperature within [100 °C, 150 °C], tension within [275 N, 387 N], pressure within [800 N, 1500 N], and velocity within [0.2 m/s, 0.4 m/s], respectively.

Catchment‐scale sensitivity and uncertainty in water quality modelling

AbstractIn this paper, we assess the performance of the catchment model SIMulated CATchment model (SIMCAT), to predict nitrate and soluble reactive phosphorus concentrations against four monitoring regimes with different spatial and temporal sampling frequencies. The Generalised Likelihood Uncertainty Estimation (GLUE) uncertainty framework is used, along with a general sensitivity analysis to understand relative parameter sensitivity. Improvements to model calibration are explored by introducing more detailed process representation using the Integrated Catchments model (INCA) water quality model, driven by the European hydrological predictions for the environment model. The results show how targeted sampling of headwater watercourses upstream of point discharges is essential for calibrating diffuse loads and can exert a strong influence on the whole‐catchment model performance. Further downstream, if the point discharges and loads are accurately represented, then the improvement in the catchment‐scale model performance is relatively small as more calibration points are added or frequency is increased.The higher‐order, dynamic model integrated catchments model of phosphorus dynamics, which incorporates sediment and biotic interaction, resulted in improved whole‐catchment performance over SIMCAT, although there are still large epistemic uncertainties from land‐phase export coefficients and runoff. However, the very large sampling errors in routine monitoring make it difficult to invest confidence in the modelling, especially because we know phosphorous transport to be very episodic and driven by high flow conditions for which there are few samples. The environmental modelling community seems to have been stuck in this position for some time, and whilst it is useful to use an uncertainty framework to highlight these issues, it has not widely been adopted, perhaps because there is no clear mechanism to allow uncertainties to influence investment decisions. This raises the question as to whether it might better place a cost on uncertainty and use this to drive more data collection or improved models, before making investment decisions concerning, for example, mitigation strategies. Copyright © 2016 John Wiley & Sons, Ltd.

Multi-objective calibration of a hydrologic model using spatially distributed remotely sensed/in-situ soil moisture

Summary The objective of this study is to evaluate the relative potential of spatially distributed surface and root zone soil moisture estimates in calibration of Soil and Water Assessment Tool (SWAT) toward improving its hydrologic predictability with reduced equifinality. The Upper Wabash and Cedar Creek, two agriculture-dominated watersheds in Indiana, USA are considered as test beds to implement this multi-objective SWAT calibration. The proposed calibration approach is performed using remotely sensed Advanced Microwave Scanning Radiometer-Earth Observing System surface soil moisture (∼1 cm top soil) estimates (NASA’s Aqua daily level-3 gridded land surface product-version 2) in sub-basin/HRU level together with observed streamflow data at the watershed’s outlet. Although application of remote sensing data in calibration improves surface soil moisture simulation, other hydrologic components such as streamflow, evapotranspiration (ET) and deeper layer moisture content in SWAT remain less affected. An extension of this approach to apply root zone soil moisture estimates from limited field sensor data showed considerable improvement in the simulation of root zone moisture content and streamflow with corresponding observed data. Difference in relative sensitivity of parameters and reduced extent of uncertainty are also evident from the proposed method, especially for parameters related to the subsurface hydrologic processes. Regardless, precise representation of vertical soil moisture stratification at different layers is difficult with current SWAT ET depletion mechanism. While the results from this study show that root zone soil moisture can play a major role in SWAT calibration, more studies including various soil moisture data products are necessary to validate the proposed approach.

Quantitative Sensitivity Analysis of Physical Parameterizations for Cases of Deep Convection in the NASA GEOS-5

Abstract Parameterization of processes that occur on length scales too small to resolve on a computational grid is a major source of uncertainty in global climate models. This study investigates the relative importance of a number of parameters used in the Goddard Earth Observing System Model, version 5 (GEOS-5), atmospheric general circulation model, focusing on cloud, convection, and boundary layer parameterizations. Latin hypercube sampling is used to generate a few hundred sets of 19 candidate physics parameters, which are subsequently used to generate ensembles of single-column model realizations of cloud content, precipitation, and radiative fluxes for four different field campaigns. A Gaussian process model is then used to create a computationally inexpensive emulator for the simulation code that can be used to determine a measure of relative parameter sensitivity by sampling the response surface for a very large number of input parameter sets. Parameter sensitivities are computed for different geographic locations and seasons to determine whether the intrinsic sensitivity of the model parameterizations changes with season and location. The results indicate the same subset of parameters collectively control the model output across all experiments, independent of changes in the environment. These are the threshold relative humidity for cloud formation, the ice fall speeds, convective and large-scale autoconversion, deep convection relaxation time scale, maximum convective updraft diameter, and minimum ice effective radius. However, there are differences in the degree of parameter sensitivity between continental and tropical convective cases, as well as systematic changes in the degree of parameter influence and parameter–parameter interaction.

Sensitivity of chloride ingress modelling in concrete to input parameter variability

The Rosenblueth point estimator method is used to propagate uncertainty on stochastic parameters in a multi-ionic reactive transport model for concrete degradation. The degradation mechanism that was analysed is the ingress of chlorides into concrete. This point estimator method is used because it requires a minimum number of simulations to compute means, standard deviations and skewness for the solution of the transport model. Two exposure cases are considered in this article: the first is a saturated case, and the second is an unsaturated case with wetting (4 days) and drying (3 days at 50 % relative humidity) cycles. The sodium chloride exposure during the wetting cycle of both cases was 500 mmol/L. In both cases, predictions from the model were compared to experimental results. The Rosenblueth approach yielded results comparable to Monte Carlo simulations for both saturated and unsaturated cases. The relative sensitivity of model parameters on prediction results are investigated through a sensitivity analysis. The sensitivity results show the high importance of ionic diffusion parameters and of exposure conditions, while the calculated initial mineral phases in the hydrated paste have lower importance.

Developmental immunotoxicity of ethanol in an extended one-generation reproductive toxicity study

The susceptibility of developing immune system to chemical disruption warrants the assessment of immune parameters in reproductive and developmental testing protocols. In this study, a wide range of immune endpoints was included in an extended one-generation reproduction toxicity study (EOGRTS) design to determine the relative sensitivity of immune and developmental parameters to ethanol (EtOH), a well-known developmental toxicant with immunomodulatory properties. Adult Wistar rats were exposed to EtOH via drinking water (0, 1.5, 4, 6.5, 9, 11.5 and 14% (w/v EtOH)) during premating, mating, gestation and lactation and continuation of exposure of the F(1) from weaning until killed. Immune assessments were performed at postnatal days (PNDs) 21, 42 and 70. Keyhole limpet hemocyanin (KLH)-specific immune responses were evaluated following subcutaneous immunizations on PNDs 21 and 35. EtOH exposure affected innate as well as adaptive immune responses. The most sensitive immune parameters included white blood cell subpopulations, ConA-stimulated splenocyte proliferation, LPS-induced NO and TNF-α production by adherent splenocytes and KLH-specific immune responses. Most parameters showed recovery after cessation of EtOH exposure after weaning in the 14% exposure group. However, effects on LPS-induced NO and TNF-α production by adherent splenocytes and KLH-specific parameters persisted until PND 70. The results demonstrate the relative sensitivity to EtOH of especially functional immune parameters and confirm the added value of immune parameters in the EOGRTS. Furthermore, this study identified an expanded KLH-specific parameter set and LPS-induced NO and TNF-α production by adherent splenocytes as valuable parameters that can provide additional information on functional immune effects.

Relative parameter sensitivity in prenatal toxicity studies with substances classified as developmental toxicants

Developmental toxicity testing according to the globally standardized OECD 414 protocol is an important basis for decisions on classification and labeling of developmental toxicants in the European Union (EU). This test requires relatively large animal numbers, given that parental and offspring generations are involved. In vitro assay designs and systems biology paradigms are being developed to reduce animal use and to improve prediction of human hazard. Such approaches could benefit from the long-term experience with animal protocols and more specifically from information on the relevance of effects observed in these tests for developmental toxicity. Therefore, we have analyzed relative parameter sensitivity in 22 publicly available developmental toxicity studies, representing about one third of all classified developmental toxicants under European legislation. Maternal and fetal weight effects and fetal survival were most often affected parameters at the developmental Lowest Observed Adverse Effect Level (dLOAEL), followed by skeletal malformations. Specific end points such as cleft palate were observed in fewer studies at dLOAEL, but if observed may have been crucial in classification and labeling decisions. These results are similar to earlier studies using different selections of chemicals, indicating that in general classified developmental toxicants have a similar pattern of effects at the dLOAEL as chemicals in general. These findings are discussed within the perspective of the development of innovative alternative approaches to developmental hazard assessment.

Viscosity dependent dual‐permeability modeling of liquid manure movement in layered, macroporous, tile drained soil

A scarcity of information exists on how physical processes govern the movement of liquid manure, or other viscous fluids, through layered macroporous soils. To elucidate these complex flow and transport phenomena, a viscosity dependent, two‐dimensional dual‐permeability model that considers macropore anisotropy is employed to simulate field experiments where liquid swine manure (LSM) was applied to silt loam with both a soil crust and plowpan layer present. Using data from the field experiment as a benchmark, the model was used to predict nutrient (NH4‐N and total P) breakthrough to tile drains; and to assess the influence of reduced permeability crust and plowpan layers, and fluid viscosity, on solute movement within 48 h of LSM application. Results demonstrate the importance of viscosity on flow and transport in macroporous soils. By increasing LSM viscosity, nutrient breakthrough to tile drains can be greatly reduced, and near surface nutrient retention can increase. The presence of a nonmacroporous soil crust layer can also lead to reduced nutrient concentrations in tile discharge by reducing pressure heads in the underlying A‐horizon soil matrix, resulting in reduced macropore flow; whereas a low permeability plowpan layer at the base of the A horizon can increase pressure heads in the A‐horizon soil matrix and lead to increased macropore flow. Multiple target point parameter sensitivity analysis revealed that relative parameter sensitivity can be a transient characteristic, and that hydraulic properties of the A and B horizon tend to exhibit their greatest influence over the respective early and late time solute breakthrough characteristics.

Relative sensitivity of developmental and immune parameters in juvenile versus adult male rats after exposure to di(2-ethylhexyl) phthalate

The developing immune system displays a relatively high sensitivity as compared to both general toxicity parameters and to the adult immune system. In this study we have performed such comparisons using di(2-ethylhexyl) phthalate (DEHP) as a model compound. DEHP is the most abundant phthalate in the environment and perinatal exposure to DEHP has been shown to disrupt male sexual differentiation. In addition, phthalate exposure has been associated with immune dysfunction as evidenced by effects on the expression of allergy. Male wistar rats were dosed with corn oil or DEHP by gavage from postnatal day (PND) 10–50 or PND 50–90 at doses between 1 and 1000mg/kg/day. Androgen-dependent organ weights showed effects at lower dose levels in juvenile versus adult animals. Immune parameters affected included TDAR parameters in both age groups, NK activity in juvenile animals and TNF-α production by adherent splenocytes in adult animals. Immune parameters were affected at lower dose levels compared to developmental parameters. Overall, more immune parameters were affected in juvenile animals compared to adult animals and effects were observed at lower dose levels.The results of this study show a relatively higher sensitivity of juvenile versus adult rats. Furthermore, they illustrate the relative sensitivity of the developing immune system in juvenile animals as compared to general toxicity and developmental parameters. This study therefore provides further argumentation for performing dedicated developmental immune toxicity testing as a default in regulatory toxicology.

Utilising temperature differences as constraints for estimating parameters in a simple climate model

Simple climate models can be used to estimate the global temperature response to increasing greenhouse gases. Changes in the energy balance of the global climate system are represented by equations that necessitate the use of uncertain parameters. The values of these parameters can be estimated from historical observations, model testing, and tuning to more complex models. Efforts have been made at estimating the possible ranges for these parameters. This study continues this process, but demonstrates two new constraints. Previous studies have shown that land-ocean temperature differences are only weakly correlated with global mean temperature for natural internal climate variations. Hence, these temperature differences provide additional information that can be used to help constrain model parameters. In addition, an ocean heat content ratio can also provide a further constraint. A pulse response technique was used to identify relative parameter sensitivity which confirmed the importance of climate sensitivity and ocean vertical diffusivity, but the land-ocean warming ratio and the land-ocean heat exchange coefficient were also found to be important. Experiments demonstrate the utility of the land-ocean temperature difference and ocean heat content ratio for setting parameter values. This work is based on investigations with MAGICC (Model for the Assessment of Greenhouse-gas Induced Climate Change) as the simple climate model.

Developmental Immunotoxicity of Methylmercury: The Relative Sensitivity of Developmental and Immune Parameters

Current developmental and reproductive toxicity protocols include only a limited set of parameters for effects on the developing immune system. In this study, a wide range of immunological parameters were included in a pre- and postnatal developmental toxicity study. Dose-response data were compared to determine the relative sensitivity of different immune and developmental parameters. Mated female Wistar rats were dosed daily by gavage with methylmercury (0, 0.1, 0.4, 0.7, 1.0, 1.5, and 2.0 mg/kg BW/day) from gestational day 6 to postnatal day (PND) 10. In addition to general, reproductive, and developmental parameters, a wide range of immunological parameters were assessed in male offspring at PNDs 21, 42, and 70. The T cell-dependent antibody response to keyhole limpet hemocyanin (KLH) was assessed following sc immunizations on PNDs 21 and 35. Dose-response data were analyzed using the benchmark dose (BMD) approach by fitting dose-response models to the various endpoints. Methylmercury induced effects on developmental parameters, such as growth parameters and pup mortality. Effects on the immune system were found at doses without observed developmental toxicity. Immune effects differed at the three time points and consisted mainly of effects on functional parameters. The parameter with the lowest 5% lower confidence bound of the BMD (BMDL) was the primary KLH-specific IgG antibody response, which showed a dose-dependent decrease with a BMD of 0.039 mg/kg BW/day (CI 0.010-0.12). These data show the relatively high sensitivity of the developing immune system and thereby illustrate the relevance of testing immune parameters in reproductive and developmental toxicity testing protocols.

Developmental immunotoxicity of methylmercury: The relative sensitivity of developmental and immune parameters

Developmental immunotoxicity of methylmercury: The relative sensitivity of developmental and immune parameters

Retrospective analysis of relative parameter sensitivity in multi-generation reproductive toxicity studies

Current suggestions towards amending the OECD two-generation protocol include omission of the second generation and inclusion of additional parameters. This study analysed the relative parameter sensitivity in 18 individually published multi-generation studies with substances toxic to fertility. Among parameters that most often determined the reproductive LOAEL were weight of testis, dam and pup as well as litter size. Several other parameters were found to be unaffected in all studies evaluated. Some substances affected a specific set of parameters, indicating that rarely affected parameters may prove crucial in individual situations. This argues for the inclusion of a wide spectrum of parameters to cover all possible effects. Less sensitive parameters, mechanistically related to more sensitive ones, may be omitted as they will unlikely contribute to the overall LOAEL. This study gives first insights and needs follow-up by more extensive analyses before firm conclusions on the design of the two-generation study protocol can be drawn.