One-sided Model Research Articles

Model order reduction of time-domain acoustic finite element simulations with perfectly matched layers

This paper presents a stability-preserving model reduction method for an acoustic finite element model with perfectly matched layers (PMLs). PMLs are often introduced into an unbounded domain to simulate the Sommerfeld radiation condition. These layers act as anisotropic damping materials to absorb the scattered field, of which the material properties are frequency- and coordinate-dependent. The corresponding time-domain model size is often very large due to this frequency-dependent property and the number of elements needed per wavelength. Therefore, to enable efficient transient simulations, this paper proposes a two-step method to generate stable reduced order models (ROMs) of such systems. Firstly, the modified and stable version of PMLs is projected by a one-sided split basis, which gives a stable intermediate ROM. Secondly, the intermediate ROM is modified to satisfy the stability-preserving condition by applying the modal transformation. Applying any one-sided model order reduction method on this modified model leads to a stable and small ROM. This two-step method is further extended to account for the locally-conformal PML model by reformulating it in curvilinear coordinates, which works for arbitrary convex truncated domains. The proposed method is successfully verified by several numerical simulations.

Condensation dynamics on inclined heterogeneous substrates

This study presents numerical simulations of dropwise condensation on inclined chemically heterogeneous substrates in pure vapor atmosphere. To capture the dynamics of this process, a one-sided condensation model with a disjoining pressure is employed that incorporates the effects of gravity and chemical heterogeneities. We consider surfaces decorated with an array of square patches which are more hydrophilic compared to the rest of the surface, which act as nucleation, inception regions over which droplets form and grow and ultimately depin once their size becomes sufficiently large. The impact of the size and of the inception regions and the angle of inclination on the dynamics is considered, revealing significant qualitative and quantitative differences between the cases. For cases with purely structured substrates, it is observed that, as the number of inception regions increases, the condensation process transitions from steady to unsteady, with the critical number of inception regions increasing with the inclination angle increases. Further insight is provided by analyzing the snapshots of the liquid phase on the substrate, revealing the formation of liquid streaks or films, which influence both the dynamics of the flow and the total liquid volume on the substrate. The inclusion of random impurities on the structured substrate dramatically impacts the condensation dynamics, which is found to hinder the formation of liquid film, leading to a decrease in the total liquid volume generated on the substrate.

HITLinQ: Improving path capacity through hybrid information-theoretic link scheduling in multi-hop wireless networks

By taking advantage of full-duplex radios, a one-sided interference channel model in the case of co-directional transmission on two links having a common node is introduced. Analysis of this model shows that asymmetric increase of transmitter power or decrease of distance will change the path capacity. When the signal noise ratio is high in this channel, using full-duplex radios for simultaneous co-directional transmission will worsen the path capacity, while direct transmission is better. On this basis, a scheduling strategy, called the hybrid information-theoretic link scheduling (HITLinQ) algorithm, which combines self-interference and inter-link interference management with link reconstruction, is proposed. The simulation results show that HITLinQ can provide capacity of not less than several baseline algorithms on a long multi-hop path under given setting.

Алгоритм широковещательной рассылки на основе биномиального дерева в модели удаленного доступа к памяти

This article introduces a broadcast (one-to-all scheme) algorithm, designed to enhance the efficiency of utilizing Remote Memory Access (RMA), a one-sided communication model within the MPI standard, for parallel programming in distributed computing systems. The algorithm leverages a binomial tree structure to organize interprocess interactions, a scheme widely employed for classic collective operations within the MPI standard. With logarithmic complexity, this algorithm proves to be more efficient than linear counterparts. The article also provides analytical complexity estimates within the LogP and LogGP models. Experimental results confirm the algorithm's advantages, although the ultimate efficiency depends on several factors, including the number of processes in the communicator, data transmission size, and the performance of the interconnect.

Financial Performance of Accountable Care Organizations: A 5-Year National Empirical Analysis.

Of 513 accountable care organizations (ACOs) participating in the Medicare Shared Savings Program (MSSP) in 2020, 67% generated a positive shared savings of approximately $2.3 billion. This research aimed to examine their financial performance trends and drivers over time. The unit of analysis was the ACO in each year of the study period from 2016 to 2020. The dependent variable was the ACOs' total shared savings earned annually per beneficiary. The independent variables included ACO age, risk model, clinician staffing type, and provider type (hybrid, hospital-led, or physician-led). Covariates were the average risk score among beneficiaries, payer type, and calendar year. The Centers for Medicare & Medicaid Services (CMS) public use files (PUFs) and a commercial healthcare data aggregator were the data sources. ACOs' earned shared savings grew annually by 35%, while the proportions of ACOs with positive shared savings grew by 21%. For 1-year increase in ACO age, an additional $0.57 of shared savings per beneficiary was observed. ACOs with two-sided risk contracting were associated with an average marginal increase of $109 in shared savings per beneficiary compared to ACOs with one-sided risk contracting. Primary care physicians were associated with the greatest increase in earned shared savings per beneficiary. In contrast, nurse practitioners/physician assistants/clinical nurse specialists were associated with a reduction in earned shared savings. Under a one-sided risk model, hospital-led ACOs were associated with $18 higher average shared savings earning per beneficiary compared to hybrid ACOs, while physician-led ACOs were associated with lower average saved shared earnings per beneficiary at -$2 compared to hybrid ACOs. Provider-type results were not statistically significant at the 5% nominal level. No statistically significant differences were observed between provider types under a two-sided risk model. For all ACO provider types, building broader primary care provider networks was correlated with positive financial results. Future research should examine whether ACOs are conducting specific preventive screenings for cancer or monitoring conditions such as diabetes, hypertension, heart disease, obesity, mental disorders, and joint disorders. Such studies may answer health policy and strategy questions about the effects of incentives for improved ACO performance in serving a healthier population.

Fractional and tempered fractional models for Reynolds-averaged Navier–Stokes equations

Turbulence is a non-local phenomenon and has multiple-scales. Non-locality can be addressed either implicitly or explicitly. Implicitly, by subsequent resolution of all spatio-temporal scales. However, if directly solved for the temporal or spatially averaged fields, a closure problem arises on account of missing information between two points. To solve the closure problem in Reynolds-averaged Navier–Stokes equations (RANS), an eddy-viscosity hypotheses has been a popular modelling choice, where it follows either a linear or nonlinear stress–strain relationship. Here, a non-constant diffusivity is introduced. Such a non-constant diffusivity is also characteristic of non-Fickian diffusion equation addressing anomalous diffusion process. An alternative approach, is a fractional derivative-based diffusion equations. Thus, in the paper, we formulate a fractional stress–strain relationship using variable-order Caputo fractional derivative. This provides new opportunities for future modelling effort. We pedagogically study of our model construction, starting from one-sided model and followed by two-sided model applied to channel, couette and pipe flow. Non-locality at a point is the amalgamation of all the effects, thus we find the two-sided model is physically consistent. Further, our construction can also addresses viscous effects, which is a local process. Thus, our fractional model addresses the amalgamation of local and non-local process. We also show its validity at infinite Reynolds number limit. An expression for the fractional order is also found, thereby solving the closure problem for the considered cases. This study is further extended to tempered fractional calculus, where tempering ensures finite jump lengths, this is an important remark for unbounded flows. Within the context of this paper, we limit ourselves to wall bounded flow. Two tempered definitions are introduced with a smooth and sharp cutoff, by the exponential term and Heaviside function, respectively and we also define the horizon of non-local interactions. We further study the equivalence between the two definitions, as truncating the domain has computational advantages. For the above investigations, we carefully designed algorithms, notably, the pointwise version of fractional physics-informed neural network to find the fractional order as an inverse problem.

Temperature dependence of avalanche breakdown in 4H-SiC devices

We report new data on the temperature coefficient of the avalanche breakdown voltage (BV) in 4H-SiC devices. We compare avalanche in different device types (MOSFETs/Schottky diodes), different measurement types [Id(Vd)-sweeps and unclamped inductive switching stress], and avalanche directions (vertical and lateral) for a wide range of avalanche voltages. We fit the measured BV(T)-curves to the one-sided abrupt junction model and extract values for the temperature coefficients of impact ionization coefficients in their Chynoweth and Thornber forms for both holes and electrons.

Orderly arrangement of agricultural biomass particles in designed gas–solid fluidized beds using CFD-DEM and image experiment

A CFD-DEM model is developed to reproduce the orderly arrangement process of agricultural biomass particles in designed fluidized beds, and ordered biomass bundles are obtained. Moreover, the high-speed fluidization image experiment platform is established, and a biomass angle recognition method is proposed. Result shows that the biomass is gradually adjusted from random to vertical attitude and entanglement is eliminated in the adjustment zone. The biomass trajectory is acceleration, collision, deceleration and adsorption. Limited by the height of the fluidized bed, the pressurization holes and deflector optimization designs are proposed to accelerate biomass adjustment. The double-side pressurization model reduces tangles and collisions and has symmetrical airflow distribution; thus, orientation control performance is better than the one-sided pressurization model. For the optimum design of deflectors, large deflector hinders the fluidization of biomass particles. The small deflector with a radian of 38° controls the particle orientation in the adjustment zone and prevents the relative slip between the particles and circulating adsorption belt. Therefore, the average particle longitudinal and cross-sectional orderliness in biomass bundles improved by 31% and 17%, respectively. The predictions on biomass velocity and orientation distribution agree well with the experimental findings. This research solves the shortcomings of biomass disorder, which provides new insights for the industrial application of particle filling and packaging.

Numerical model for sessile drop evaporation on heated substrate under microgravity

• One-sided numerical model is developed for sessile drop evaporation on heated substrate under microgravity. • Flow motion is analyzed by 3D resolved computations of evaporating sessile drop. • Transition from primary to secondary instability occurs at critical aspect ratio. • First time fine effects of secondary instabilities on evaporation rate are captured. Although sessile drops have simple geometries, the physics involved in their evaporation process is complex owing to their numerous intricate interactions and their fluid nature. An accurate quantitative model of the evaporation process will enable increased understanding and control over the process. In this study, a numerical model is developed for sessile drop evaporation on a heated substrate under microgravity based on the results of rocket and parabolic experiments to understand the ’internal dynamics of a sessile drop. The model is quantitatively validated through experiments. Subsequently, a correlation between substrate temperature and evaporation rate is suggested for an ethanol sessile drop. The flow motion is analyzed by conducting three-dimensional resolved computations of an evaporating sessile drop. This provides insights into the Marangoni effect in the dynamics of the evaporation process and the occurrence of secondary instabilities. For the first time, the fine effects of secondary instabilities on the evaporation rate are captured. Our numerical model is valid in the absence of convection in the vapor phase, producing an interface of an evaporating drop in a fully saturated vapor, which typically exists under microgravity conditions.

Two Candidate KH 15D–like Systems from the Zwicky Transient Facility

KH 15D contains a circumbinary disk that is tilted relative to the orbital plane of the central binary. The precession of the disk and the orbital motion of the binary together produce rich phenomena in the photometric light curve. In this work, we present the discovery and preliminary analysis of two objects that resemble the key features of KH 15D from the Zwicky Transient Facility. These new objects, Bernhard-1 and Bernhard-2, show large-amplitude ( >1.5 mag), long-duration (more than tens of days), and periodic dimming events. A one-sided screen model is developed to model the photometric behavior of these objects, the physical interpretation of which is a tilted, warped circumbinary disk occulting the inner binary. Changes in the object light curves suggest potential precession periods over timescales longer than 10 yr. Additional photometric and spectroscopic observations are encouraged to better understand the nature of these interesting systems.

Subspace method for the estimation of large-scale structured real stability radius

We consider the autonomous dynamical system \(x^{\prime } = Ax,\) with \(A\in {\mathbb {R}}^{n\times n}.\) This linear dynamical system is asymptotically stable if all of the eigenvalues of A lie in the open left-half of the complex plane. In this case, the matrix A is said to be Hurwitz stable or shortly a stable matrix. In practice, the stability of a system can be violated because of perturbations such as modeling errors. In such cases, one deals with the robust stability of the system rather than its stability. The system above is said to be robustly stable if the system, as well as all of its perturbations from a certain perturbation class, are stable. To measure the robustness of the system subject to perturbations, a quantity of interest is the stability radius or in other words the distance to instability. In this paper, we focus on the estimation of the structured real stability radius for large-scale systems. We propose a subspace framework to estimate the structured real stability radius and prove that our new method converges at a quadratic rate in theory. Our method benefits from a one-sided interpolatory model order reduction technique, in the sense that the left and the right subspaces are the same. The quadratic convergence of the method is due to the certain Hermite interpolation properties between the full and reduced problems. The proposed framework estimates the structured real stability radius for large-scale systems efficiently. The efficiency of the method is demonstrated on several numerical experiments.

Design and Simulation of Highly Efficient One-Sided Short PIN Diode Silicon Heterojunction Solar Cell

Performance of highly efficient one-sided short PIN diode heterojunction solar cell model is studied using AFORS-HET simulation software. Here, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -type crystalline silicon is used as an absorber layer, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -type amorphous silicon as emitter layer, and a thin intrinsic amorphous silicon (i-a-Si:H) layer is sandwiched in between, which acts as a passivation layer. The diode model concept has been introduced mainly to lower the reverse saturation current by appropriate selection of the cell parameters. Short diode reduces recombination phenomenon in the short quasi-neutral region (n-a-Si:H in this article), and one-sided junction allows the maximum amount of light absorption in the absorber layer (p-c-Si in this article). The one-sided junction nature has been confirmed by capacitance–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C–V</i> ) analysis. Further thickness variation of layers and role of the carrier concentration of n-a-Si layer on various parameters, such as short-circuit current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> ), open-circuit voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> ), and fill factor (FF) have also been studied. The structure has exhibited an open circuit voltage of 0.714 V, fill factor 0.80, and maximum efficiency of 24.2%. Further, experimental validation is also established by comparing the theoretical results with the fabricated NIP structure.

Debiased learning and forecasting of first derivative

In the era of big data, there are many data sets recorded in equal intervals of time. To model the change rate of such data, one often constructs a nonparametric regression model and then estimates the first derivative of the mean function. Along this direction, we propose a symmetric two-sided local constant regression for interior points, an asymmetric two-sided local polynomial regression for boundary points, and a one-sided local linear forecasting model for outside points. Specifically, under the framework of locally weighted least squares regression, we derive the asymptotic bias and variance of the proposed estimators, as well as establish their asymptotic normality. Moreover, to reduce the estimation bias for highly-oscillatory functions, we propose debiased estimators based on high-order polynomials and derive their corresponding kernel functions. A data-driven two-step procedure for simultaneous selection of the model and tuning parameters is also proposed. Finally, the usefulness of our proposed estimators is demonstrated by simulation studies and two real data examples.

Variable-Order Fractional Models for Wall-Bounded Turbulent Flows.

Modeling of wall-bounded turbulent flows is still an open problem in classical physics, with relatively slow progress in the last few decades beyond the log law, which only describes the intermediate region in wall-bounded turbulence, i.e., 30–50 y+ to 0.1–0.2 R+ in a pipe of radius R. Here, we propose a fundamentally new approach based on fractional calculus to model the entire mean velocity profile from the wall to the centerline of the pipe. Specifically, we represent the Reynolds stresses with a non-local fractional derivative of variable-order that decays with the distance from the wall. Surprisingly, we find that this variable fractional order has a universal form for all Reynolds numbers and for three different flow types, i.e., channel flow, Couette flow, and pipe flow. We first use existing databases from direct numerical simulations (DNSs) to lean the variable-order function and subsequently we test it against other DNS data and experimental measurements, including the Princeton superpipe experiments. Taken together, our findings reveal the continuous change in rate of turbulent diffusion from the wall as well as the strong nonlocality of turbulent interactions that intensify away from the wall. Moreover, we propose alternative formulations, including a divergence variable fractional (two-sided) model for turbulent flows. The total shear stress is represented by a two-sided symmetric variable fractional derivative. The numerical results show that this formulation can lead to smooth fractional-order profiles in the whole domain. This new model improves the one-sided model, which is considered in the half domain (wall to centerline) only. We use a finite difference method for solving the inverse problem, but we also introduce the fractional physics-informed neural network (fPINN) for solving the inverse and forward problems much more efficiently. In addition to the aforementioned fully-developed flows, we model turbulent boundary layers and discuss how the streamwise variation affects the universal curve.

The nascent coffee ring: how solute diffusion counters advection

We study the initial evolution of the coffee ring that is formed by the evaporation of a thin, axisymmetric, surface-tension-dominated droplet containing a dilute solute. When the solutal Péclet number is large, we show that diffusion close to the droplet contact line controls the coffee-ring structure in the initial stages of evaporation. We perform a systematic matched asymptotic analysis for two evaporation models – a simple, non-equilibrium, one-sided model (in which the evaporative flux is taken to be constant across the droplet surface) and a vapour-diffusion limited model (in which the evaporative flux is singular at the contact line) – valid during the early stages in which the solute remains dilute. We call this the ‘nascent coffee ring’ and describe the evolution of its features, including the size and location of the peak concentration and a measure of the width of the ring. Moreover, we use the asymptotic results to investigate when the assumption of a dilute solute breaks down and the effects of finite particle size and jamming are expected to become important. In particular, we illustrate the limited validity of this model in the diffusive evaporative flux regime.

Spreading and retraction dynamics of sessile evaporating droplets comprising volatile binary mixtures

Abstract

Rayleigh–Taylor unstable condensing liquid layers with nonlinear effects of interfacial convection and diffusion of vapour

Abstract

Bayesian One-Sided Variable Selection

This paper presents a novel Bayesian variable selection approach that accounts for the sign of the regression coefficients based on multivariate one-sided tests. We propose a truncated g prior to specify a prior distribution of coefficients with anticipated signs in a given model. Informative priors for the direction of the effects can be incorporated into prior model probabilities. The best subset of variables is selected by comparing the posterior probabilities of the possible models. The new Bayesian one-sided variable selection procedure has higher chance to include relevant variables and therefore select the best model, if the anticipated direction is accurate. For a large number of candidate variables, we present an adaptation of a Bayesian model search method for the one-sided variable selection problem to ensure fast computation. In addition, a fully Bayesian approach is used to adjust the prior inclusion probability of each one-sided model to correct for multiplicity. The performance of the proposed method is investigated using several simulation studies and two real data examples.

A One-Sided Competition Mathematical Model for the Sterile Insect Technique

We study a simple mathematical model describing the dynamics of a wild-type pest insects population experiencing competition from sterile insects (one-sided competition). This model can be used for conceiving control strategies based on the Sterile Insect Technique (SIT) or the Incompatible Insect Technique (IIT), aiming to reduce or eradicate Red Palm Weevil (RPW) populations in some target regions. We show that suppression may occur for continuous and periodic release strategies for various intraspecific and interspecific submodels except in the case of a single release strategy where a strong Allee effect is required.

A two-sided lateral gap continuum model and its numerical simulation for non-lane based heterogeneous traffic environment

The objective of this study is to model the complex behavior of non-lane based heterogeneous traffic which is predominantly occupied by vehicles with varying physical and dynamical characteristics and their staggered car following behavior. This study proposes a new continuum model by considering the properties of two-sided lateral gap in a non-lane based heterogeneous traffic stream. The model is built on a strong empirical background and modified car following theory. In particular, the model consists of density dependent disturbance propagation speed, viscosity term and a frictional clearance term to describe the complex vehicular interactions in a traffic stream. Viscosity term in the model represents the driver’s reaction to a sudden change in density and further, it helps in smoothening out the shock fronts. Frictional clearance term in the model considers the effect of slow moving vehicles on the dynamics of fast moving vehicles. The results of mathematical and numerical analysis show that the proposed model satisfies all the qualitative and physical properties of the real world system. Moreover, two sided lateral gap in the model improves the stability region of traffic flow and increases the capacity and density of traffic stream. In addition, it is able to dissipate the traffic perturbation rapidly when compared to one-sided lateral gap model. It is anticipated that the new model provides the basis for evaluating alternative transport policy measures and helps in analyzing the system performance in the future.