Elaborate Models Research Articles

Coupled effects of pressure and frequency on velocities of tight sandstones saturated with fluids: measurements and rock physics modelling

SUMMARY Elastic moduli and velocities of tight sandstones are strongly influenced by rock-frame heterogeneity, pore microstructure and fluid in addition to pressure and probing-wave frequency. The effects of pressure and frequency on the elastic moduli and velocities are different from those of conventional sandstones with high porosity and high permeability due to complexity of pore microstructure. To investigate these effects, we measured two tight sandstone samples for their velocities in the dry and fluid saturation conditions using the ultrasonic transmission technique and the low-frequency stress–strain method. The variations in the ultrasonic velocities with pressure see a transition from non-linear to linear increase for the dry samples, in contrast to a gradual increase for the fluid-saturated samples. The low frequency velocities of the saturated sample T1 and T2 directly show significant dispersion in a wide range of frequencies (1–100 Hz), and the magnitudes of the dispersion are suppressed by the pressure. The low-frequency velocities also increase with pressure, showing increasing trends bounded by the ultrasonic velocity–pressure curves for the dry and fluid saturation conditions. An elaborate rock physics model, considering a discrete aspect ratio spectrum and the simple squirt flow model, was constructed to account for the pressure and frequency dependence of the velocities. The predictions from the modified squirt flow model can fit well the measured velocities at varying pressures, both in the low-frequency range and the ultrasonic frequency range. The real measurements and the modelling results suggest that the pressure- and frequency-dependence cannot be modelled without considering such aspect ratio spectra. The effects of pressure and frequency are coupled in that they are interconnected by the microstructure of the pores. Changes in the pressure and fluid saturation (and thus wave frequency) both contribute to stiffening of the rock frame, and they both strongly depend on the presence of microcracks in the rock. Therefore, this rock physics model could be applied in extraction of pore microstructure and fluid properties provided elastic moduli or velocities can be estimated accurately.

Benchmark for the Coupled Magneto-Mechanical Boundary Value Problem in Magneto-Active Elastomers.

Within this contribution, a novel benchmark problem for the coupled magneto-mechanical boundary value problem in magneto-active elastomers is presented. Being derived from an experimental analysis of magnetically induced interactions in these materials, the problem under investigation allows us to validate different modeling strategies by means of a simple setup with only a few influencing factors. Here, results of a sharp-interface Lagrangian finite element framework and a diffuse-interface Eulerian approach based on the application of a spectral solver on a fixed grid are compared for the simplified two-dimensional as well as the general three-dimensional case. After influences of different boundary conditions and the sample size are analyzed, the results of both strategies are examined: for the material models under consideration, a good agreement of them is found, while all discrepancies can be ascribed to well-known effects described in the literature. Thus, the benchmark problem can be seen as a basis for future comparisons with both other modeling strategies and more elaborate material models.

Which image-based phenotypes are most promising for using AI to understand cellular functions and why?

Which image-based phenotypes are most promising for using AI to understand cellular functions and why?

Mimicry of a Conceptual Hydrological Model (HBV): What's in a Name?

AbstractModels that mimic an original model might have a different model structure than the original model, that affects model output. This study assesses model structure differences and their impact on output by comparing 7 model implementations that carry the name HBV. We explain and quantify output differences with individual model structure components at both the numerical (e.g., explicit/implicit scheme) and mathematical level (e.g., lineair/power outflow). It was found that none of the numerical and mathematical formulations of the mimicking models were (originally) the same as the benchmark, HBV‐light. This led to small but distinct output differences in simulated streamflow for different numerical implementations (KGE difference up to 0.15), and major output differences due to mathematical differences (KGE median loss of 0.27). These differences decreased after calibrating the individual models to the simulated streamflow of the benchmark model. We argue that the lack of systematic model naming has led to a diverging concept of the HBV‐model, diminishing the concept of model mimicry. Development of a systematic model naming framework, open accessible model code and more elaborate model descriptions are suggested to enhance model mimicry and model development.

Deployment of electric vehicles in China to meet the carbon neutral target by 2060: Provincial disparities in energy systems, CO2 emissions, and cost effectiveness

Switching to electricity in the ground transport sector is considered a promising way to achieve the energy transition and CO2 emission reductions required to meet China's carbon neutral target by 2060. In this study, a transport energy model containing an elaborate transport demand model and a technology bottom-up model for detailed behavioral and technological representations was developed to investigate how electric vehicles (EVs) will penetrate the markets in the long-term and what impacts on energy consumption and emissions would emerge following EV adoption in China at the provincial level. A set of scenarios was created based on different policy interventions for the promotion of electric mobility. The results showed that subsidies for EV adoption would significantly boost the market share and foster a rapid transition away from fossil fuels, while the business-as-usual scenario would only generate a moderate influence on EV penetration. The regional differences in the emission reduction potential due to EV subsidies across the 31 provinces indicated that policy instruments for EV promotion would have significant positive effects in the developed provinces in both the capital metropolitan area and southeastern China. An economic cost analysis revealed a relatively low economic feasibility in northeastern and northwestern regions where the emission reduction potential is also lower than the national average, implying that the developing provinces in northeastern and northwestern China require greater financial assistance and the establishment of supportive policies for EV promotion.

Hypertension due to loss of water

In the current issue of Acta Physiologica, two papers are published investigating the development of arterial hypertension under conditions of pathological loss of free water in two disease models. Kovaric et al 1 studied rats with chronic renal failure, shedding excessive free water via their remnant kidney due to a hypostenuric concentrating defect. Wild et al. 2 investigated a transgenic mouse model for psoriasis, losing free water via the psoriatic skin lesions. In both cases the animals displayed hypertension, cutaneous vasoconstriction, and metabolic adaptations towards enhanced production of urea and organic osmolytes typical for a phylogenetically ancient water conservation response termed aestivation 3 . The international consortia of investigators spearheaded by Titze, Karbach, and Kitada therefore conclude that in both cases the hypertension was due to cutaneous vasoconstriction in an attempt to limit epidermal water loss. Because in either case the hypertension was associated with loss of water, and thus with hypo- rather than hypervolemia, the authors argue, that this concept of pathogenesis of hypertension is antipodal to the classic view that relies on hypervolemia due to sodium retention.

The Hydraulically Controlled Oscillating Piston Converter

One way to realize inertia in energy saving hydraulic switching converters is a mechanical oscillator connected to a piston. Its two basic advantages over the use of fluid in an inductance pipe are higher compactness and a better decoupling of inductance and capacitance; these are opposed by a more complex valve system, which raises costs if electric control is applied. This paper presents and studies an oscillating mass converter with pure hydraulic control. It features a pressure control function and constitutes a step-up converter. A simple model is established to elucidate the basic properties of the function principle under idealized conditions. The complete system with the hydraulic control concept is studied by an elaborate dynamical model. It is shown that the converter is able to operate in the intended way under the conditions of the mathematical model. A potential application for a load sensing type meter out control of a cylinder drive is sketched.

Numerical investigation of characteristics of fluidic oscillator operating in quiescent air and a crossflow

We present a detailed numerical study of characteristics of fluidic oscillator operating in originally quiescent air and in a crossflow. Our study is focused on the visualization of flow field evolution associated with fluidic oscillator in an attempt to shed some light into the elucidation of mechanism of jet oscillation and interaction of jet flow with crossflow and into the revelation of flow control mechanism of fluidic oscillator. Reynolds-averaged two-dimensional computation with elaborate Reynolds stress turbulence model allows us to reproduce the experimentally observed salient flow features like recirculation bubbles in actuator and oscillating jet. The excellent agreement between simulation and experiment in both qualitative flow structures and quantitative jet oscillation frequency gives credibility to a number of new observations made from simulation, which, however, are not apparent in experimental data. For example, it is found from our simulation that the scaling of a specific actuator does not significantly influence the characteristics of the scaled actuator and mechanism of associated flow oscillation. In addition, the interaction of oscillating jet with external crossflow leads to the generation of spanwise vortices, which, in the presence of flow separation, is believed to be able to entrain high momentum external flow towards body surface and play a dominant role in flow separation control. Moreover, when the intensity of crossflow increases, the frequency of jet oscillation decreases. Thus, our work presents an updated description of working principles and mechanisms of fluidic oscillator.

Match Analysis of Soccer Refereeing Using Spatiotemporal Data: A Case Study.

This case study explored how spatiotemporal data can develop key metrics to evaluate and understand elite soccer referees’ performance during one elite soccer match. The dynamic position of players from both teams, the ball and three elite referees allowed to capture the following performance metrics: (i) assistant referees: alignment with the second last defender; (ii) referee: referee diagonal movement—a position density was computed and a principal component analysis was carried to identify the directions of greatest variability; and (iii) referee: assessing the distance from the referee to the ball. All computations were processed when the ball was in-play and separated by 1st and 2nd halves. The first metric showed an alignment lower than 1 m between the assistant referee and the second last defender. The second metric showed that in the 1st half, the referee position ellipsis area was 548 m2, which increased during the 2nd half (671 m2). The third metric showed an increase in the distance from the referee to the ball and >80% of the distance between 5–30 m during the 2nd half. The findings may be used as a starting point to elaborate normative behavior models from the referee’s movement performance in soccer.

Shift in representation and symbolisation of affective experience: A paradoxical outcome in therapy

Shift in representation and symbolisation of affective experience: A paradoxical outcome in therapy: Defining outcome represents a key challenge for psychotherapy theory, research and practice. The present paper uses a case study of a client with anorexia nervosa to contribute to the development of conceptual understanding of the nature of paradoxical outcome. In this case, different sources of outcome data offered different answers to the question of whether or not the therapy had been successful. Qualitative thematic analysis of therapy transcriptions was carried out, using Interpretative Phenomenological Analysis (IPA). Both the process of change that occurred in this case, and the conflicting outcome indicators, could be explained in terms of a model of affect elaboration. These findings are discussed in terms of the need for caution when interpreting results from outcome measures in psychotherapy research and practice.

Autonomous UAV Trajectory for Localizing Ground Objects: A Reinforcement Learning Approach

Disaster management, search and rescue missions, and health monitoring are examples of critical applications that require object localization with high precision and sometimes in a timely manner. In the absence of the global positioning system (GPS), the radio received signal strength index (RSSI) can be used for localization purposes due to its simplicity and cost-effectiveness. However, due to the low accuracy of RSSI, unmanned aerial vehicles (UAVs) or drones may be used as an efficient solution for improved localization accuracy due to their agility and higher probability of line-of-sight (LoS). Hence, in this context, we propose a novel framework based on reinforcement learning (RL) to enable a UAV (agent) to autonomously find its trajectory that results in improving the localization accuracy of multiple objects in shortest time and path length, fewer signal-strength measurements (waypoints), and/or lower UAV energy consumption. In particular, we first control the agent through initial scan trajectory on the whole region to 1) know the number of nodes and estimate their initial locations, and 2) train the agent online during operation. Then, the agent forms its trajectory by using RL to choose the next waypoints in order to minimize the average location errors of all objects. Our framework includes detailed UAV to ground channel characteristics with an empirical path loss and log-normal shadowing model, and also with an elaborate energy consumption model. We investigate and compare the localization precision of our approach with existing methods from the literature by varying the UAV's trajectory length, energy, number of waypoints, and time. Furthermore, we study the impact of the UAV's velocity, altitude, hovering time, communication range, number of maximum RSSI measurements, and number of objects. The results show the superiority of our method over the state-of-art and demonstrates its fast reduction of the localization error.

Onset of runaway fragmentation of salt marshes

Summary Salt marshes are valuable but vulnerable coastal ecosystems that adapt to relative sea level rise (RSLR) by accumulating organic matter and inorganic sediment. The natural limit of these processes defines a threshold rate of RSLR beyond which marshes drown, resulting in ponding and conversion to open waters. We develop a simplified formulation for sediment transport across marshes to show that pond formation leads to runaway marsh fragmentation, a process characterized by a self-similar hierarchy of pond sizes with power-law distributions. We find the threshold for marsh fragmentation scales primarily with tidal range and that sediment supply is only relevant where tides are sufficient to transport sediment to the marsh interior. Thus the RSLR threshold is controlled by organic accretion in microtidal marshes regardless of the suspended sediment concentration at the marsh edge. This explains the observed fragmentation of microtidal marshes and suggests a tipping point for widespread marsh loss.

Sustainable Business Models for Informal Charcoal Producers in Kenya

The sustainable business model (SBM) concept requires enterprises to integrate sustainability aspects in their planning and operations. Although 60% of the global working population make their living in the informal sector mostly in low-and middle income countries, the potential for SBMs has rarely been analyzed for this category. This study explores the SBMs of informal charcoal-producing enterprises in coastal Kenya. It describes key business-model components: value proposition, value creation and delivery, and economic value capture. Impact and dependency on sustainability-related indicators were also studied. Data were obtained through individual interviews, focus-group discussions, and workshops for charcoal producers and other relevant stakeholders. Findings demonstrated that charcoal enterprises, despite their informal status, adopt elaborate business models. The incomes positively affect several Sustainable Development Goals (SDGs) by reducing, if not eradicating, poverty and supporting basic livelihood needs. Examples of negative impacts on some SDG include the activity’s contribution to forest degradation. Feedback impacts, where SDG status influence the informal enterprises’ opportunities were also identified. The SBM model contributes to the development of a balanced sustainability transition of the charcoal sector. We suggest further analyses of the role of informal enterprises in the bioenergy sector for sustainable development and how their SBMs could be improved.

Application of a new X-ray reflection model to V1223 Sagittarii

ABSTRACT In intermediate polars (IPs), the intrinsic thermal emissions from white dwarfs (WDs) have typically been studied. Few reports have analysed X-ray reflections from WDs. We recently developed an elaborate IP-reflection spectral model. Herein, we report the first application of a reflection model with an IP thermal model to the spectra of the brightest typical IP V1223 Sagittarii observed by the Suzaku and Nuclear Spectroscopic Telescope Array satellites. The model reasonably reproduces the spectra within the range of 5–78 keV and estimates the WD mass as 0.92 ± 0.02 M⊙. The WD mass estimated by the proposed model is consistent with that measured using an active galactic nucleus reflection model and a partial covering absorption model. However, the choice of incorrect parameter values, such as an unsuitable fitting energy band and an incorrect metal abundance, was found to introduce systematic errors (e.g. ≲0.2 M⊙ in the WD mass) in the WD mass measurement. Our spin-phase-resolved analysis resulted in discoveries regarding the modulations of the equivalent width of the fluorescent iron K α line and the angle between the post-shock accretion column and the line of sight (viewing angle). The viewing angle anticorrelates approximately with the X-ray flux and has average and semi-amplitude values of 55° and 7°, respectively, which points towards two WD spin axis angles from the line of sight of 55° and 7°, respectively. Both estimated spin axis angles are different from the reported system inclination of 24°.

Numerical Investigation of Wellbore Stability in Deepwater Shallow Sediments

An elaborate poro-elastoplastic numerical model has been developed in this paper to explore the stability characteristics of wellbore in shallow sediments of deepwater oil/gas wells. The combined Drucker-Prager/cap plasticity model is employed to characterize the mechanical behavior of the weakly consolidated or unconsolidated shallow sediments, by which both plastic compaction deformation and plastic shear deformation can be considered. Possible penetration of drilling fluid into the formation and its coupling to deformation have also been accounted for in the model. Using this model, deformation, stress evolution, and failure characteristics of the formation around the wellbore are analyzed in detail. Results presented in this paper demonstrate the necessity of considering the plastic compaction capability of the formation during the wellbore stability analysis of shallow sediments in deepwater. For mud pressures lower than the in situ horizontal stress, excessive wellbore shrinkage may occur if the mud pressure is too low, which, however, can be effectively mitigated through properly increasing the mud pressure even fluid penetration into the near-wellbore region may occur. It is also evidenced that, if penetration of drilling fluid into the formation is prevented, fracturing of the wellbore will not occur even the mud pressure is very high. Instead, the wellbore will expand substantially due to plastic compaction, and the deformed wellbore radius could be several times larger than the original value. However, if drilling fluid can penetrate into the formation, high pore pressure will develop within the near-wellbore region, resulting in tensile hoop stress at the wellbore and thus fracturing of the wellbore along the radial direction. The numerical results and implications in this paper are anticipated to be beneficial for the drilling operation in the shallow portion of deepwater oil/gas wells.

Awe, wonder, and the human mind.

The human mind is unique in its ability to form, store, and manipulate elaborate conceptual models of the world; yet these models have vast, inevitable gaps. Where the models end, the potential for wonder and awe begins. Psychology research has begun to uncover distinctive implications of awe for how we perceive our environment and ourselves. More science investigating basic features of awe is needed to fulfill its promise for improving the human experience. Awe, accessible in everyday life, can be a valuable tool for enhancing well-being.

Ground Deformation After a Caldera Collapse: Contributions of Magma Inflow and Viscoelastic Response to the 2015–2018 Deformation Field Around Bárðarbunga, Iceland

AbstractImprovement of our understanding of the role of ground deformation due to viscoelastic relaxation following eruptions is important, as the generated signals can resemble renewed magma inflow. We study post‐eruptive unrest at the subglacial Bárðarbunga volcano, Iceland, after a caldera collapse and major magma drainage in 2014–2015. Elevated seismicity began about 6 months after the eruption ended, including nine Mlw > 4.5 earthquakes. Global Navigation Satellite System and Sentinel‐1 Interferometric Synthetic Aperture Radar geodesy are applied to evaluate post‐eruptive ground deformation from 2015 to 2018. Horizontal velocities locally exceed 10 cm/year and rapidly decay with distance away from the caldera. We explore two end‐member models and their combination to explain the post‐eruptive deformation field: 1) viscoelastic relaxation caused by the co‐eruptive caldera collapse and magma withdrawal, and 2) renewed magma inflow. We find parameter combinations for each model that explain the observed ground deformation. The purely viscoelastic relaxation model, consisting of a half‐space composed of a 7‐km thick elastic layer on top of a viscoelastic layer with a viscosity of 3.0 × 1018 Pa s reproduces broadly the observations. A simple magma inflow model consisting of a single point source with an inflow rate of 1 × 107 m3/year at 0.7 km depth broadly fits the observations, but may be unrealistic. A more elaborate model of magma inflow into a 10‐km deep sill combined with slip on the caldera ring fault explains the observations well. Our results suggest that the co‐eruptive deformation field is likely influenced by viscoelastic relaxation, renewed magma inflow, or a combination of both processes.

Definition of Reference Models for Power, Mass, Working Width, and Price for Tillage Implements

Farm machinery selection, operation and management directly impact crop cultivation processes and outputs. A priori quantification of technical and financial needs allows definition of proportionate distribution and management of available resources and simplification of selection process. Appropriate planning, association and adjustment of the power unit and implement are required for soil cultivation. Consideration of functional parameters of the implement, their proper estimation and operation directly impact the soil structure, productivity and return on investment. Thus, a modelling approach was implemented for the definition of possible parameter-price relations for tillage equipment. The performed analysis allowed us to investigate the main relevant parameters, quantify their impact, and elaborate forecasting models for price, power, mass and working width. The significant relevance of the technical parameters and adjustment issues were outlined for each tillage implement group. For harrows and cultivators, the dependencies between studied parameters expressed better predictive qualities, especially for price-mass relation (R² > 0.8). While for ploughs power and mass relation had a primary output (R² = 0.7). The prediction features of the models provided reliable results for the estimation of the indicative values of the price and parameters of the implements.

Seizing the benefits of age diversity: could empowering leadership be the answer?

PurposeAcknowledging that only examining the main effects of diversity may be limiting, the authors explore integrating van Knippenberg et al.'s (2004) categorization–elaboration model (CEM) of workgroup diversity as a linchpin in the relationship between empowering leadership and performance in age-diverse work groups. While prior research has focused almost exclusively on the impact of transformational leadership in diverse contexts, few studies have found the positive effects of transformational leadership to be diminished in certain age-diverse contexts. Consequently, the authors investigate whether empowering leadership may be a better approach in this context due to its emphasis on accommodating and participative behaviors.Design/methodology/approachUsing survey data gathered from work group members across a wide array of industries (N = 214), the authors test for the moderating effects of empowering leadership on the relationship between age diversity and work group performance and its indirect relationship via information elaboration (while controlling for transformational leadership).FindingsEmpowering leadership positively moderated the direct relationship between age diversity and work group performance and the indirect relationship via information elaboration, whereas transformational leadership had the opposite effect. “Coaching” and “showing concern/interacting with the team” drove the positive effects of empowering leadership, and “personal recognition” and “intellectual stimulation” predicted the negative effects of transformational leadership.Practical implicationsThis research offers insights into how managers can lead age-diverse work groups more effectively (i.e. by utilizing an empowering as opposed to a transformational leadership approach, with a particular emphasis on “coaching” and “showing concern/interacting with the team” behaviors).Originality/valueThe study identifies an “alternative” moderating contingency to the age diversity–performance relationship (empowering leadership).

Climbing down Charney's ladder: machine learning and the post-Dennard era of computational climate science.

The advent of digital computing in the 1950s sparked a revolution in the science of weather and climate. Meteorology, long based on extrapolating patterns in space and time, gave way to computational methods in a decade of advances in numerical weather forecasting. Those same methods also gave rise to computational climate science, studying the behaviour of those same numerical equations over intervals much longer than weather events, and changes in external boundary conditions. Several subsequent decades of exponential growth in computational power have brought us to the present day, where models ever grow in resolution and complexity, capable of mastery of many small-scale phenomena with global repercussions, and ever more intricate feedbacks in the Earth system. The current juncture in computing, seven decades later, heralds an end to what is called Dennard scaling, the physics behind ever smaller computational units and ever faster arithmetic. This is prompting a fundamental change in our approach to the simulation of weather and climate, potentially as revolutionary as that wrought by John von Neumann in the 1950s. One approach could return us to an earlier era of pattern recognition and extrapolation, this time aided by computational power. Another approach could lead us to insights that continue to be expressed in mathematical equations. In either approach, or any synthesis of those, it is clearly no longer the steady march of the last few decades, continuing to add detail to ever more elaborate models. In this prospectus, we attempt to show the outlines of how this may unfold in the coming decades, a new harnessing of physical knowledge, computation and data.This article is part of the theme issue ‘Machine learning for weather and climate modelling’.