Distribution Of Coefficients Research Articles

Nanodomains and Their Temperature Dependence in a Phosphonium-Based Ionic Liquid: A Single-Molecule Tracking Study.

Ionic liquids (ILs) exhibit a unique nanoscale structure (i.e., nanodomains) characterized by their organization into distinct domains. We present evidence of nanodomains in trihexyl(tetradecyl)phosphonium chloride, [P66614][Cl], using single-molecule tracking (SMT) and the maximum entropy method (MEM) to analyze single-molecule trajectories. The diffusion properties of ATTO 647N were assessed as the temperature of [P66614][Cl] increased from 20 °C (4020 cP), 35 °C (1239 cP), 45 °C (599 cP) to 50 °C (439 cP). The MEM analysis revealed a distinct two-population distribution of diffusion coefficients representing nanodomains in [P66614][Cl] at 20 °C (4020 cP). The slow population accounts for 16%, with a diffusion coefficient of 0.104 μm2/s, while the fast population constitutes 84% with a diffusion coefficient of 0.634 μm2/s. Two diffusing populations were also measured for the chemically different probes ATTO 647N, DiD, and Nile Blue chloride in [P66614][Cl] at 20 °C. In contrast, only a single fast population was measured in [P66614][Cl] at 50 °C. At a similar viscosity (640 cP) but a lower temperature of 20 °C, trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)-sulfonyl]imide, [P66614][NTf2], also showed only a single diffusing population. The elimination of the slow population and the presence of a single diffusing population in [P66614][Cl] as the temperature increases and the viscosity decreases is consistent with liquid-liquid phase separation (LLPS) as a mechanism of nanodomain formation. In addition, the measurement of two diffusing populations for three fluorophores with different chemical structures is also consistent with a physical mechanism, and not a chemical mechanism, for nanodomain formation.

3D CFD analysis of pressure, boundary layer and shear stresses on a gudgeon (Gobio gobio)

The fish’s mechanosensory lateral line system detects non-acoustic hydrodynamic stimuli required for feeding, schooling, predator avoidance and underwater object detection. Biological investigations have established that flow stimuli are detected through the boundary layer as pressure gradients by canal neuromasts and as shear stresses acting on the superficial neuromasts. Previous works have also shown that the spatial distribution of neuromasts is strongly correlated with the pressure coefficient. Despite these fundamental insights, substantial knowledge gaps persist in understanding how fish body geometry influences the boundary layer, the pressure distribution and shear stresses. To address these gaps, we provide a set of numerical models based on the open-source CFD toolkit OpenFOAM which are experimentally validated using velocity measurements obtained in a laboratory fish swim tunnel. Specifically, we investigate the mid dorsal-ventral planar flow fields around a 3D fish-shaped body of gudgeon (Gobio gobio), a common freshwater bottom-dwelling fish. The contributions of this work are two-fold: First, we provide a comparison of the boundary layer thicknesses and velocity profiles at flow velocities ranging from 0.25 to 1.25 m/s. Second, we qualitatively compare the spatial distributions of the pressure coefficient, dynamic pressure and shear stresses to biological observations of the neuromast locations of adult gudgeon.

Evaluation of reduced-order models for the rapid aerodynamic analysis of supersonic and hypersonic bodies

Abstract This paper presents a comprehensive evaluation of reduced-order models (ROMs) for the determination of pressure coefficient distributions on supersonic and hypersonic bodies. The study investigates the limitations, aerodynamic precision and computational performance associated with various methodologies, ranging from simplistic Newtonian theory-based approaches to more advanced first and second-order shock-expansion theories. Validation is performed by comparing computed results with experimental and computational data for pressure distributions, drag and lift coefficients and centres of pressure for fundamental geometries and authentic vehicle design over a wide range of freestream conditions. The study also includes a comprehensive computational complexity analysis, demonstrating the superiority of finite-element ROM approaches over traditional finite-volume computational fluid dynamics (CFD) simulations. The primary objective of this paper is to scrutinise the extension of these methodological classes to the low supersonic regime. Hence, thermo-chemical reactions within the flow are disregarded, and the ideal gas law is adopted. A value of $\gamma = 1.4$ is chosen for consistency and comparability across the analyses. The proposed ROMs show remarkable potential for reducing high-speed simulation execution times by four orders of magnitude, maintaining accuracy within 20 per cent and as low as 1 per cent. The study unveils three key findings: first, the accuracy degradation of Newtonian-based theories for inclined elements, particularly around 45 degrees, and their reduced dependency on Mach number at large inclination. Secondly, the study presents novel insights into the impact of shock-wave-Mach-wave interactions on pressure distribution calculations, emphasising the Mach number as a crucial metric governing recompression effects. Lastly, the study demonstrates the exceptional accuracy of DeJarnette’s method, providing ${C_P}$ results within 2 per cent for a wide range of conditions, offering an attractive alternative to the Taylor-Maccoll equation.

State analysis of a biobased hydrogel subjected to freeze and thaw processes by X ray absorption spectroscopy using synchrotron radiation

Freezing hydrogels can compromise their network structures and modify their properties as a result of ice crystal formation. Therefore, understanding the internal structure, including ice crystals and the state of chemical components within hydrogels, is essential. In this study, we evaluated the elemental distribution in bio-based hydrogels subjected to freezing-thaw process using X-ray absorption spectroscopy with synchrotron radiation. A bio-based hydrogel, prepared from Alaska pollock, underwent both slow and rapid freezing processes. Tomographic images and linear X-ray absorption coefficient distributions of the rapidly frozen hydrogel displayed a uniform image with a mean absorption coefficient of 2.81 cm−1. Conversely, the slowly frozen sample exhibited distinct contrasts with peaks at 2.516 cm−1 (dark) and 3.691 cm−1 (bright), occupying 28% and 72% of the image, respectively. The mean absorption coefficient of the slowly frozen sample was comparable to that of the rapidly frozen sample, indicating no elemental loss. The elements within the hydrogel were categorized into organic elements, macrominerals, and trace elements. The bright areas in the images were attributed to the concentration of macrominerals. Notably, Cl and Na were the primary contributors to the absorption coefficients among the elements present, signifying salt migration during freezing. These findings suggest that the contrast observed in X-ray computed tomography images after freezing reflects the elemental distribution within the hydrogel and successfully demonstrates element localization due to cryoconcentration.

Evidence for Nanostructures of at Least 20 nm in a Phosphonium Ionic Liquid at Room Temperature Using Fluorescence Correlation Spectroscopy.

Fluorescence correlation spectroscopy (FCS) measurements are performed on the ionic liquid (IL), tetradecyl(trihexyl) phosphonium chloride, [P66614+][Cl-], using fluorescent probes of varying sizes: ATTO 532, ∼2 nm; and 20- and 40 nm fluorescent beads. The fluorescence correlation function, G(t), is analyzed in terms of a distribution of diffusion coefficients using a maximum entropy method (MEM). For ATTO 532 and the 20 nm beads, the fit to G(t) yields two well-defined distributions; for the 40 nm beads, however, only one is obtained. These results are consistent with the existence of two nanodomains whose size is greater than or equal to 20 nm and less than 40 nm. The origin of such nanodomains is attributed to a liquid-liquid phase transition. Other groups have observed liquid-liquid phase transitions experimentally in a number of systems, including [P66614+][Cl-]. We suggest that because large regions (i.e., greater than 1-2 nm) resulting from the liquid-liquid phase transition would be expected to have different properties, such as viscosity, and because their presence would necessarily increase the number of interfaces in the IL, these regions may provide an explanation for the exceptional behavior of ILs in various separation systems.

Drag Reduction of Truck and Trailer Combination with Different Passive Flow Control Methods

In this study, drag force and surface pressure measurements were conducted on a 1/32 scaled truck-trailer combination model. The experimental tests were carried out between the ranges of 312×103- 844×103 Reynolds Numbers in a suction type wind tunnel. The aerodynamic drag coefficient (CD) and distribution of pressure coefficient (CP) were experimentally determined on the truck and trailer combination. The regions where has big pressure coefficients were determined on the truck-trailer by using flow visualizations. The aerodynamic structure of truck-trailer combination models was improved by passive flow control methods on 4 different models. By using newly designed spoiler on the model 1, drag coefficient was reduced 10.01 %. On the model 2, adding trailer rear extension with a spoiler, the reduction was obtained as 11.35 %. For the model 3 which is obtained adding side skirt to model 2, the improvement reached 18.85 %. The model 4 was composed of model 2 and a bellow between the truck and trailer. The drag force improvement was obtained as 22.80 % for model 4.

Aerodynamic and codification study of low-rise buildings: Part II – Partially elevated structures

This study constitutes part II of an extensive study where the aerodynamics of elevated buildings is investigated using large-scale wind tunnel testing. Part II focuses on the case of elevated buildings with partially enclosed spaces beneath the elevated floor. For this purpose, four 1:10 scaled models of elevated single-story gable-roof buildings were selected, three of which were partially elevated with enclosed regions covering areas ranging from 19% to 54% of the model footprint. The tests aimed to examine the effect of the enclosed regions below the floor on the distribution of the localized peak pressure coefficients on the walls, floor, and roof surfaces of the models. Furthermore, the study evaluates the ASCE 7–22 provisions and the proposed provisions, presented by the authors in Part I, for estimating external wind pressure coefficients acting on the floor, roof, and walls of elevated buildings. The results indicate that enclosed regions below the floor significantly alter the aerodynamics of elevated low-rise buildings and could increase the wind-induced loads on the roof and walls of such structures, with the increase in some cases exceeding 80%. Furthermore, the results align well with the proposed modifications by the authors in Part I to the ASCE 7 provisions for estimating the external pressure coefficients for the various zones of low-rise buildings, addressing the underestimation issues previously identified within the current ASCE standard.

Hypersonic Flow past LD-Haack Series, Parabolic Series, Power Series Nose Cone: A Comparative Study

This research paper presents a detailed aerodynamic analysis of three rocket nose cone designs—LD-Haack, Parabolic, and Power Series—under hypersonic conditions ranging from Mach 5 to Mach 12. Using advanced Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent, the study focuses on key aerodynamic parameters, including drag force, drag coefficient, velocity, pressure, and temperature distributions. The results indicate that the Parabolic Nose Cone offers the most favorable aerodynamic performance, with the lowest drag force and drag coefficient across all Mach numbers. This superior performance can be attributed to its ability to streamline airflow and minimize boundary layer separation, effectively reducing pressure drag and limiting the onset of turbulent wake regions. In contrast, the LD-Haack Series Nose Cone, though designed to minimize wave drag at supersonic speeds, shows moderate drag at hypersonic velocities due to its less optimal control of boundary layer behavior. The Power Series Nose Cone, despite its highly tapered shape, experiences the highest drag. This is largely caused by increased flow separation and turbulent wake generation, which exacerbate pressure drag, particularly at higher Mach numbers. These findings highlight the critical influence of nose cone geometry on aerodynamic efficiency and emphasize the importance of optimizing designs for hypersonic applications. This study provides valuable insights for aerospace engineers seeking to reduce drag and improve performance in high-speed flight scenarios.

Analysis of methods for reducing the signal PAPR under the influence of the Doppler effect in hybrid communication networks

Background. For further development of communication networks, it is planned to use hybrid satellite networks for traffic transmission. However, satellite communication channels have features such as distortion caused by the Doppler effect and increased energy efficiency requirements. Aim of this study is to analyze variants of orthogonal frequency multiplexing methods and modulation methods in order to choose the most stable technology, taking into account destabilizing factors. Method. Comparing different signal processing technologies and studying their resistance to bit errors is the imitation modeling of the communication channel in the Matlab environment. This approach allows creating a model of the communication network, taking into account the main parameters of communication channels, such as the Doppler effect, energy deficiency and destabilizing factors. Results. The distribution of the bit error coefficient for various signal processing technologies, depending on the signal-to-noise ratio, is compared. The method of frequency multiplexing is defined, providing the minimum peak factor and the most resistant to bit error. It is also noted that the effectiveness of all the studied technologies depends on the spacing and modulation constellations, and that it is necessary to adjust the characteristics of the system for each case. Conclusion. The results of this study can be used to improve the quality of communication in difficult interference conditions of hybrid mobile networks of 5 and 6 generations using the satellite segment.

Ion-exchange of copper into mordenite and clinoptilolite zeolites by molecular dynamics simulations and experimental investigations

Copper-exchanged zeolites have been subjected to several investigations because of their application as selective redox-active catalysts, and sensors. However, the ability of different types of zeolites to exchange Cu ions remains a matter of debate. All-atom molecular dynamics (MD) simulations, energy dispersive X-ray spectroscopy (EDS), and X-ray Fluorescence (XRF) methods have been used to evaluate the exchange of Cu(II) in mordenite and clinoptilolite zeolites using an aqueous method in the current study. Several parameters of copper ions have been measured for both types of zeolites, such as ion exchange ratio, mean square displacement (MSD), diffusion coefficient, and radial distribution function (RDF). These parameters were calculated for each zeolite system at different Cu ion concentrations in the feed solution. Copper exchange ratio and RDF analyses revealed a higher exchange ratio of copper ions in the mordenite framework. Analysis of the potential energy indicates the major adsorption sites for mordenite and clinoptilolite, which are located in the largest cavities of the zeolites. The adsorption energy of the mordenite sites (1.52 eV) was larger than that of clinoptilolite (1.28 eV). The stronger attraction between the copper ions and mordenite sites is consistent with the lower diffusion coefficients of the ions in this zeolite. The ion-exchange abilities of the zeolites were examined using EDS analysis. According to the EDS results, the mordenite zeolite exchanged more copper ions than the clinoptilolite, which is in agreement with the computational results.

Multiboundary wormholes and OPE statistics

We derive higher moments in the statistical distribution of OPE coefficients in holographic 2D CFTs, and show that such moments correspond to multiboundary Euclidean wormholes in pure 3D gravity. The nth cyclic non-Gaussian contraction of heavy-heavy-light OPE coefficients follows from crossing symmetry of the thermal n-point function. We derive universal expressions for the cubic and quartic moments and demonstrate that their scaling with the microcanonical entropy agrees with a generalization of the Eigenstate Thermalization Hypothesis. Motivated by this result, we conjecture that the full statistical ensemble of OPE data is fixed by three premises: typicality, crossing symmetry and modular invariance. Together, these properties give predictions for non-factorizing observables, such as the generalized spectral form factor. Using the Virasoro TQFT, we match these connected averages to new on-shell wormhole topologies with multiple boundary components. Lastly, we study and clarify examples where the statistics of heavy operators are not universal and depend on the light operator spectrum. We give a gravitational interpretation to these corrections in terms of Wilson loops winding around non-trivial cycles in the bulk.

Determining the prior mean in Bayesian logistic regression with sparse data: a nonarbitrary approach

Abstract Logistic regression models lead to a bias of the odds ratio (OR) as estimated using the maximum-likelihood (ML) method, when there are few study participants at the binary outcome and factor levels. Although Bayesian methods are frequently applied to reduce this sparse data bias, the specification of the prior distribution for regression coefficients is the most controversial feature. We propose a nonarbitrary and empirical method to determine the prior mean for regression coefficients in Bayesian logistic regression analysis for sparse data. The proposed prior mean is calculated as the difference between the observed log OR and the quasi-expectation of log OR, and is interpreted as a shrinkage statistic of the ML estimate. Further, for easy and fast inference, the proposed method applies to Bayesian logistic regression with the normal prior and the log-F prior via data augmentation. Simulation results indicate that the OR bias based on the proposed method is consistently smaller than that based on the ML method. The OR bias estimated using the proposed method is generally smaller than that based on the mean prior of zero for the regression coefficient. We apply the proposed methods to 2 real data sets.

Light attenuation parameterization in a highly turbid mega estuary and its impact on the coastal planktonic ecosystem

Light is essential for phytoplankton photosynthesis and many other biogeochemical processes in the aquatic system. However, light regimes vary greatly in the estuaries and coasts due to the optical complexity of the Case-2 waters. In this study, observed vertical profiles of photosynthetically active radiation (PAR; 400-700 nm) in a highly turbid mega estuary, the Changjiang (Yangtze River) Estuary, are used to quantify the effects of sedimentary and biogeochemical components on PAR attenuation in the water column and associated ecological impacts. The in-situ data suggest suspended sediment plays the most crucial role in light diffuse attenuation coefficient (Kd) distribution, followed by salinity (i.e., an index for colored dissolved organic matter) and phytoplankton chlorophyll-a. A new parameterization of Kd, based on suspended sediment, chlorophyll-a concentration, and salinity, is fitted using multiple linear regression. The previous and new Kd parameterizations are further applied to a coupled hydrodynamics-sediment-ecosystem model to simulate spring phytoplankton blooms. Comparative model runs reveal that the new Kd parameterization resulted in a better representation of the spring bloom patterns in magnitude, horizontal distribution, and vertical thickness of the high chlorophyll-a band offshore the turbidity maximum zone during the spring bloom. In summary, accurate representations of underwater light fields in the optically complex Case-2 water are critical in understanding biophysical processes that control planktonic ecosystem dynamics in the estuaries and coastal seas.

Experimental and numerical study of wind effect on an ultra‐thin concrete triangular plan shell structure

AbstractSelf‐supporting concrete shell structures are highly efficient in distributing loads, which can result in very reduced thicknesses (ultra‐thin), giving them remarkable slenderness. Due to their geometric complexity, it is difficult to predict how they interact with wind action. The main aim of the present study is to assess the mean surface pressure coefficient distribution in a shell with a triangular plan shape and three supports for different angles of wind incidence. To determine the distribution of surface pressure coefficients and lift and drag force coefficients, an experimental study was carried out in a wind tunnel, and a numerical simulation study was performed through computational fluid dynamics. The experimental and numerical results were analyzed and compared, and making it possible to identify the most critical surface zones and wind incidences when the shell is under the wind action.

Numerical Study of the Combustion Process in the Vertical Heating Flue of Air Staging Coke Oven

To investigate the combustion process and reduce Nitric Oxide (NO) emissions in the vertical heating flue of air-staged coke ovens, a three-dimensional computational fluid dynamics method was applied to simulate the combustion process. The model integrates the k-ε turbulence model with a multi-component transport combustion model. The impact of air staging on the flow field and NO emissions in the vertical fire chamber was assessed through comparative validation with experimental data. The impact of air staging on the flow field and NO emissions in the vertical fire chamber was assessed through comparative validation with experimental data. Based on this research, the effects of the excess air coefficient and air inlet distribution ratio on NO emission levels at the flue gas outlet were further investigated. Analysis of the flow field structure, temperature at the center cross-section, component concentration, and NO emission levels indicates that as the excess air coefficient increases, the NO emission levels at the flue gas outlet initially decrease and then increase, accompanied by corresponding changes in outlet temperature. At an air excess factor of 1.3 and an air inlet distribution ratio of 7:3, NO emission levels are at their lowest—53% lower than those in a conventional coke oven—and the temperature distribution in the riser channel is more uniform. These results provide a theoretical foundation for designing the air-staged coke oven standing fire channel structure.

Improving turbulence modeling for gas turbine blades: A novel approach to address flow transition and stagnation point anomalies

Accurate prediction of temperature and Heat Transfer Coefficient (HTC) distributions over gas turbine blades is crucial for the design process and life assessment of these components. Numerical studies of flow over gas turbine blades face significant challenges in accurately simulating two complex phenomena: (1) the transition of flow from laminar to turbulent, and (2) stagnation point flow at the leading edge. Many turbulence models tend to overpredict the temperature on turbine blades, leading to incorrect identification of hot-spot regions and, consequently, erroneous estimations of blade life. This paper investigates the performance of various turbulence models in simulating flow and heat transfer over gas turbine vanes. The study includes three full turbulence models, i.e., Spalart-Allmaras (SA), Shear Stress Transport k−ω (SST-kw), and v2−f (V2F), as well as two transitional models, i.e., Transition SST (Trans-SST) and k−kL−ω (k-kl-w). Simulation results indicate that the v2−f, Trans-SST, and k−kL−ω models can detect flow transition. However, the transition length and onset location predicted by the Trans-SST and k−kL−ω models do not align with experimental data. Conversely, the v2−f model suffers from over-predictions at the leading edge due to stagnation point anomaly. To address these issues and due to capacities of the V2F model, this study proposes two modifications to enhance the performance of the V2F model. First, the production term of turbulent kinetic energy is redefined to mitigate the stagnation point anomaly. Second, the model is recalibrated to improve the prediction of flow transition. The new model, named the Production Modified V2F (PMV2F) model, shows promising results in predicting temperature and heat transfer coefficients.

Automatic structuring of radiology reports with on-premise open-source large language models.

Structured reporting enhances comparability, readability, and content detail. Large language models (LLMs) could convert free text into structured data without disrupting radiologists' reporting workflow. This study evaluated an on-premise, privacy-preserving LLM for automatically structuring free-text radiology reports. We developed an approach to controlling the LLM output, ensuring the validity and completeness of structured reports produced by a locally hosted Llama-2-70B-chat model. A dataset with de-identified narrative chest radiograph (CXR) reports was compiled retrospectively. It included 202 English reports from a publicly available MIMIC-CXR dataset and 197 German reports from our university hospital. Senior radiologist prepared a detailed, fully structured reporting template with 48 question-answer pairs. All reports were independently structured by the LLM and two human readers. Bayesian inference (Markov chain Monte Carlo sampling) was used to estimate the distributions of Matthews correlation coefficient (MCC), with [-0.05, 0.05] as the region of practical equivalence (ROPE). The LLM generated valid structured reports in all cases, achieving an average MCC of 0.75 (94% HDI: 0.70-0.80) and F1 score of 0.70 (0.70-0.80) for English, and 0.66 (0.62-0.70) and 0.68 (0.64-0.72) for German reports, respectively. The MCC differences between LLM and humans were within ROPE for both languages: 0.01 (-0.05 to 0.07), 0.01 (-0.05 to 0.07) for English, and -0.01 (-0.07 to 0.05), 0.00 (-0.06 to 0.06) for German, indicating approximately comparable performance. Locally hosted, open-source LLMs can automatically structure free-text radiology reports with approximately human accuracy. However, the understanding of semantics varied across languages and imaging findings. Question Why has structured reporting not been widely adopted in radiology despite clear benefits and how can we improve this? Findings A locally hosted large language model successfully structured narrative reports, showing variation between languages and findings. Critical relevance Structured reporting provides many benefits, but its integration into the clinical routine is limited. Automating the extraction of structured information from radiology reports enables the capture of structured data while allowing the radiologist to maintain their reporting workflow.

A subchannel analysis code for advanced liquid metal fast reactor cores and study on heat transfer characteristics of core geometry parameters

The liquid metal fast reactor represents an important reactor type for the future development of nuclear energy. Accurately modeling and predicting the subchannel flow and heat transfer phenomenon in the rod bundles plays a key role in ensuring core safety. Consequently, a subchannel code suitable for the liquid metal fast reactor is analyzed based on the subchannel analysis code of the Pressurized Water Reactor (PWR). The modified code incorporates various types of liquid metals, such as lead, lead-bismuth eutectic (LBE), and sodium, along with their constitutive models, enhancing the applicability of the liquid metal reactor systems. This code has been verified and validated at several levels, including comparing the code simulation results with other similar subchannel codes results, high-dimensional Computational Fluid Dynamics (CFD) simulations, and experiment data. The sensitivity analysis of core geometric parameters and turbulent mixing coefficients is performed based on the modified version code. The influence of the core geometry, including the rod Pitch to Diameter ratio (P/D), Rod to Wall gap (RTW) and the wire wrap pitch (H) on the sensitivity of outlet temperature has been investigated. The results show that the new subchannel analysis code suitable for liquid metal cooled reactor shows reasonable agreement with the verified and validated results. The geometric parameters, such as P/D, RTW and H have noticeable effects on the outlet temperature difference of the subchannels. Additionally, the outlet temperature distribution in the subchannel is significantly affected by different turbulent mixing coefficients and the distribution of the turbulent mixing coefficient also influenced by the reactor core sizes. Overall, this study could support the rod bundles design and safety analysis in the liquid metal reactors.

Enhancing older care services: a comprehensive internet + community home indicator system

ObjectiveConstructing a demand-oriented Internet + community home care service indicator system, starting from the actual needs of the elderly, and quantifying the demand into specific service contents that can be provided, so as to realize the effective supply of services. It aims to provide a theoretical basis for the government to formulate relevant aging policies and provide a reference basis for promoting the innovation and development of the Internet + elderly care model.MethodsBased on existence needs, relationship needs and growth needs abbreviated as “Existence, Relatedness, Growth (ERG)” demand theory, through the discussion in the group meeting, form the expert consultation questionnaire of the demand-oriented Internet + community home care service indicator system, select experts in related fields to conduct two rounds of Delphi expert consultation, summarize the experts’ opinions to determine the indicator system items, and use the Analytic Hierarchy Process (AHP) method to construct the judgment matrix to derive the weighting coefficients of the indicators, and establish the ultimate demand-oriented Internet + community home care service indicator system.ResultsThe effective recovery rates for the two rounds of expert consoulation questionnaires were 100%, with expert authority coefficients of 0.852 and 0.868, respectively. The Kendall coefficients for the second round of expert views varied from 0.226 to 0.431, with coefficients of variation for all indexes less than 0.25.The finalized demand-oriented Internet + community home care service indicator system includes 3 first-level indicators, 10 s-level indicators, and 46 third-level indicators. The consistency ratios of indicator judgment matrices at all levels are less than 0.10, suggesting that the hierarchical analysis findings are consistent, implying that the weight coefficient distribution is appropriate.ConclusionThe demand-oriented Internet + community home care service Indicator System, which was created through expert consultation and AHP method, has reasonable content and is more dependable as an evaluation tool for reliably assessing demand for elderly servic.

Generalized field inversion strategies for data-driven turbulence closure modeling

Most data-driven turbulence closures are based on the general structure of nonlinear eddy viscosity models. Although this structure can be embedded into the machine learning algorithm and the Reynolds stress tensor itself can be fit as a function of scalar- and tensor-valued inputs, there exists an alternative two-step approach. First, the spatial distributions of the optimal closure coefficients are computed by solving an inverse problem. Subsequently, these are expressed as functions of solely scalar-valued invariants of the flow field by virtue of an arbitrary regression algorithm. In this paper, we present two general inversion strategies that overcome the limitation of being applicable only when all closure tensors are linearly independent. We propose to either cast the inversion into a constrained and regularized optimization problem or project the anisotropy tensor onto a set of previously orthogonalized closure tensors. Using the two-step approach together with either of these strategies then enables us to quantify the model-form error associated with the closure structure independent of a particular regression algorithm. Eventually, this allows for the selection of the a priori optimal set of closure tensors for a given, arbitrary complex test case.