Intermediate-scale Model Research Articles

Modelación multi-escala para la comprensión de los sistemas de flujo en un acuífero multicapa, Urabá-Colombia

Numerical modelling is a valuable tool which allows the characterisation of groundwater flow behaviour, its interactions, and the representation of different flow systems that occur in an aquifer. A regional-scale model requires general information to describe the flow trends. In contrast, local and intermediate-scale models require a more detailed knowledge of the flow boundaries, and more field information. In order to understand the groundwater flow in the aquifer system of the Eje Bananero del Urabá Antioqueño-Colombia, a multi-scale numerical model was implemented using MODFLOW®. This was performed following modelling protocols on three spatial scales in which the regional model provided the boundary conditions for the intermediate pattern, and the intermediate pattern for the local model. Finally, we represented some details that relate local and intermediate flows to regional flows, in which surface-groundwater interactions involving both shallow and deep ascending flows became evident. The results obtained in this work show the potential of multi-scale modelling as a tool to recognise and understand the groundwater flows in a layered aquifer system, which provide grounds for decision-making and proper management of hydrogeological systems.

Modeling microbial cross-feeding at intermediate scale portrays communitydynamics and species coexistence.

Social interaction between microbes can be described at many levels of details: from the biochemistry of cell-cell interactions to the ecological dynamics of populations. Choosing an appropriate level to model microbial communities without losing generality remains a challenge. Here we show that modeling cross-feeding interactions at an intermediate level between genome-scale metabolic models of individual species and consumer-resource models of ecosystems is suitable to experimental data. We applied our modeling framework to three published examples of multi-strain Escherichia coli communities with increasing complexity: uni-, bi-, and multi-directional cross-feeding of either substitutable metabolic byproducts or essential nutrients. The intermediate-scale model accurately fit empirical data and quantified metabolic exchange rates that are hard to measure experimentally, even for a complex community of 14 amino acid auxotrophies. By studying the conditions of species coexistence, the ecological outcomes of cross-feeding interactions, and each community's robustness to perturbations, we extracted new quantitative insights from these three published experimental datasets. Our analysis provides a foundation to quantify cross-feeding interactions from experimental data, and highlights the importance of metabolic exchanges in the dynamics and stability of microbial communities.

Rytov-approximation-based wave-equation traveltime tomography

Most finite-frequency traveltime tomography methods are based on the Born approximation, which requires that the scale of the velocity heterogeneity and the magnitude of the velocity perturbation should be small enough to satisfy the Born approximation. On the contrary, the Rytov approximation works well for large-scale velocity heterogeneity. Typically, the Rytov-approximation-based finite-frequency traveltime sensitivity kernel (Rytov-FFTSK) can be obtained by integrating the phase-delay sensitivity kernels with a normalized weighting function, in which the calculation of sensitivity kernels requires the numerical solution of Green’s function. However, solving the Green’s function explicitly is quite computationally demanding, especially for 3D problems. To avoid explicit calculation of the Green’s function, we show that the Rytov-FFTSK can be obtained by crosscorrelating a forward-propagated incident wavefield and reverse-propagated adjoint wavefield in the time domain. In addition, we find that the action of the Rytov-FFTSK on a model-space vector, e.g., the product of the sensitivity kernel and a vector, can be computed by calculating the inner product of two time-domain fields. Consequently, the Hessian-vector product can be computed in a matrix-free fashion (i.e., first calculate the product of the sensitivity kernel and a model-space vector and then calculate the product of the transposed sensitivity kernel and a data-space vector), without forming the Hessian matrix or the sensitivity kernels explicitly. We solve the traveltime inverse problem with the Gauss-Newton method, in which the Gauss-Newton equation is approximately solved by the conjugate gradient using our matrix-free Hessian-vector product method. An example with a perfect acquisition geometry found that our Rytov-approximation-based traveltime inversion method can produce a high-quality inversion result with a very fast convergence rate. An overthrust synthetic data test demonstrates that large- to intermediate-scale model perturbations can be recovered by diving waves if long-offset acquisition is available.

An intermediate-scale model for thermal hydrology in low-relief permafrost-affected landscapes

Integrated surface/subsurface models for simulating the thermal hydrology of permafrost-affected regions in a warming climate have recently become available, but computational demands of those new process-rich simu- lation tools have thus far limited their applications to one-dimensional or small two-dimensional simulations. We present a mixed-dimensional model structure for efficiently simulating surface/subsurface thermal hydrology in low-relief permafrost regions at watershed scales. The approach replaces a full three-dimensional system with a two-dimensional overland thermal hydrology system and a family of one-dimensional vertical columns, where each column represents a fully coupled surface/subsurface thermal hydrology system without lateral flow. The system is then operator split, sequentially updating the overland flow system without sources and the one-dimensional columns without lateral flows. We show that the app- roach is highly scalable, supports subcycling of different processes, and compares well with the corresponding fully three-dimensional representation at significantly less computational cost. Those advances enable recently developed representations of freezing soil physics to be coupled with thermal overland flow and surface energy balance at scales of 100s of meters. Although developed and demonstrated for permafrost thermal hydrology, the mixed-dimensional model structure is applicable to integrated surface/subsurface thermal hydrology in general.

Generic hierarchy of sandstone facies quality and static connectivity: an example from the Middle-Late Miocene Miri Formation, Sarawak Basin, Borneo

A significant percentage of the world’s hydrocarbon reserves are found in shallow marine sandstone rocks. Understanding reservoir connectivity and quality of shallow-marine sandstones from outcrop analysis and facies characteristics is a challenging task. Here, we analyze well-exposed outcrops of the Miri Formation, Sarawak Basin, Borneo, to characterize reservoir properties (grain-size, petrography, pore-perm, and static connectivity) of different sandstone facies and to construct a 2D intermediate-scale model of sandstone distribution and connectivity. The outcrops, with lateral extent of ∼200–500 m, consist of mostly sandstone with mud-rich deposits including some isolated sand bodies. Field description in terms of facies distribution and dimensions of sand bodies and rock sampling for grain-size (Folk and Ward methods), petrographic (point count method for porosity, sorting, grain-size, and sand-mud %), and poro-perm (for porosity and permeability) analyses were performed to quantify and examine seven different types of sandstones facies, i.e., (i) hummocky cross-stratified sandstones (HCSS, ∼0.5–4 m thick), (ii) herringbone cross-bedded (HBCBS, ∼0.5–3 m thick), (iii) trough cross-bedded sandstones (TCBS, ∼0.5–2 m thick), (iv) wavy- to flaser-bedded (W-FBS, ∼1–3 m thick), (v) cross-bedded sandstone (CS), ∼0.5–3 m thick), (vi) bioturbated sandstone (BS, ∼1–5 m thick), and (vii) massive sandstone (MS, ∼0.5–2 m thick). Our results show that compared to other sandstone facies, sandstones of HCSS and HBCBS are better sorted, have minimal mud content, and display increasing vertical and lateral connectivity due to depositional patterns even in bioturbated rich sand. Sandstones of BS and CB are of poor quality in terms of grain sorting and poro-perm, while TCB and MS sandstone facies are of less lateral and vertical extent. On the basis of these results, a 2-D outcrop-based model is constructed that provide additional insights into the significance of small-scale heterogeneity and static connectivity of shallow marine sandstone deposits which can be an analogue for subsurface reservoir quality analysis.

Hydrodynamic modeling of Singapore's coastal waters: Nesting and model accuracy

The tidal variation in Singapore's coastal waters is influenced by large-scale, complex tidal dynamics (by interaction of the Indian Ocean and the South China Sea) as well as monsoon-driven low frequency variations, requiring a model with large spatial coverage. Close to the shores, the complex topography, influenced by headlands and small islands, requires a high resolution model to simulate tidal dynamics. This can be achieved through direct nesting or multi-scale nesting, involving multiple model grids. In this paper, we investigate the effect of grid resolution and multi-scale nesting on the tidal dynamics in Singapore's coastal waters, by comparing model results with observations using different statistical techniques. The results reveal that the intermediate-scale model is generally sufficiently accurate (equal to or better than the most refined model), but also that the most refined model is only more accurate when nested in the intermediate scale model (requiring multi-scale nesting). This latter is the result of the complex tidal dynamics around Singapore, where the dominantly diurnal tidal currents are decoupled from the semi-diurnal water level variations. Furthermore, different techniques to quantify model accuracy (harmonic analysis, basic statistics and more complex statistics) are inconsistent in determining which model is more accurate.

Postcards from oases in the desert: phenomenology of SUSY with intermediate scales

The presence of new matter fields charged under the Standard Model gauge group at intermediate scales below the Grand Unification scale modifies the renormalization group evolution of the gauge couplings. This can in turn significantly change the running of the Minimal Supersymmetric Standard Model parameters, in particular the gaugino and the scalar masses. In the absence of new large Yukawa couplings we can parameterise all the intermediate scale models in terms of only two parameters controlling the size of the unified gauge coupling. As a consequence of the modified running, the low energy spectrum can be strongly affected with interesting phenomenological consequences. In particular, we show that scalar over gaugino mass ratios tend to increase and the regions of the parameter space with neutralino Dark Matter compatible with cosmological observations get drastically modified. Moreover, we discuss some observables that can be used to test the intermediate scale physics at the LHC in a wide class of models.

A Mechanochemical Model of Actin Filaments

In eukaryotic cells, actin filaments are involved in important processes such as motility, division, cell shape regulation, contractility, and mechanosensation. Actin filaments are polymerized chains of monomers, which themselves undergo a range of chemical events such as ATP hydrolysis, polymerization, and depolymerization. When forces are applied to F-actin, in addition to filament mechanical deformations, the applied force must also influence chemical events in the filament. We develop an intermediate-scale model of actin filaments that combines actin chemistry with filament-level deformations. The model is able to compute mechanical responses of F-actin during bending and stretching. The model also describes the interplay between ATP hydrolysis and filament deformations, including possible force-induced chemical state changes of actin monomers in the filament. The model can also be used to model the action of several actin-associated proteins, and for large-scale simulation of F-actin networks. All together, our model shows that mechanics and chemistry must be considered together to understand cytoskeletal dynamics in living cells.

The Effects of Selective Logging Behaviors on Forest Fragmentation and Recovery

To study the impacts of selective logging behaviors on a forest landscape, we developed an intermediate-scale spatial model to link cross-scale interactions of timber harvesting, a fine-scale human activity, with coarse-scale landscape impacts. We used the Lotka-Volterra predator-prey model with Holling’s functional response II to simulate selective logging, coupled with a cellular automaton model to simulate logger mobility and forest fragmentation. Three logging scenarios were simulated, each varying in timber harvesting preference and logger mobility. We quantified forest resilience by evaluating (1) the spatial patterns of forest fragmentation, (2) the time until the system crossed a threshold into a deforested state, and (3) recovery time. Our simulations showed that logging behaviors involving decisions made about harvesting timber and mobility can lead to different spatial patterns of forest fragmentation. They can, together with forest management practices, significantly delay or accelerate the transition of a forest landscape to a deforested state and its return to a recovered state. Intermediate-scale models emerge as useful tools for understanding cross-scale interactions between human activities and the spatial patterns that are created by anthropogenic land use.

Modeling multiscale effects on transients during chemical vapor deposition

Several important manufacturing processes for integrated circuits (ICs) involve the flow of gaseous reactants over the wafer(s) on which the ICs are being made. We discuss a model in which reactive components of the gas phase do not collide; either because there is a dominant carrier species, or the pressure is low enough. The kinetic transport and reaction model consists of a system of transient linear Boltzmann equations for the reactive species in the flow. This model applies to a wide range of transport regimes, characterized by a wide range of Knudsen numbers as a function of pressure and length scale of interest. A numerical simulator based on a spectral Galerkin method in velocity space approximates each linear Boltzmann equation by a system of transient conservation laws in space and time with diagonal coefficient matrices, which are solved using the discontinuous Galerkin method. This deterministic solver gives direct access to the kinetic density that is the solution to the Boltzmann equation, as a function of position, velocity, and time. The availability of the kinetic density as a function of velocity is useful to analyze the underlying kinetic causes of macroscopic observables. Using chemical vapor deposition as an important application example, the influence of process parameters is studied in transient two-dimensional and three-dimensional features that represent structures seen during integrated circuit fabrication for a wide range of Knudsen numbers. The results highlight the capabilities of the KTRM and its implementation, and indicate that kinetic solvers may be needed for models characterized by Knudsen numbers on the order of unity. This regime applies both to feature scale simulators at certain operating conditions and to intermediate scale models used as part of multiscale simulators.

Selecting Supersymmetric String Scenarios From Sparticle Spectra

We approach the following question: if supersymmetry is discovered, how can we select among different supersymmetric extensions of the Standard Model? In particular, we perform an analysis of the sparticle spectrum in low-energy string effective theories, asking which observables best distinguish various scenarios. We examine scenarios differing by the fundamental string scale and concentrate on GUT and intermediate scale models. We scan over all parameters (two goldstino angles, tan beta and the gravitino mass) in each scenario, finding ratios of sparticle masses that provide the maximum discrimination between them. The necessary accuracy for discrimination is determined in each case. We find that the required accuracy on various sparticle mass ratios is at the few percent level, a precision that may be achieved in future linear colliders. We also map out phenomenologically viable regions of parameter space.

Effect of extra dimensions on gauge coupling unification

The effects of extra dimensions on gauge coupling unification is studied. We start with a comparison between power law running of the gauge couplings in models with extra dimensions and logarithmic running that happens in many realistic cases. We then discuss the effect of extra dimensions on various classes of unification models. We identify products of evolution coefficients that dictate the profile of unification in different models. We use them to study under what conditions unification of couplings can occur in both one and two step unification models. We find that Kaluza-Klein modes can help generate interesting intermediate scale models with gauge coupling unification such as the minimal left-right models with the seesaw mechanism with a M W R ∼ 10 13 GeV intermediate scale, useful in understanding neutrino oscillations. We also obtain several examples where the presence of non-canonical normalization of couplings enables us to obtain unification scales around 10 11 GeV. This fits very well into a class of models proposed recently where the string scale is advocated to be at this value from physical arguments.

The Combination of Equipment Scale and Feature ScaleModels for Chemical Vapor Deposition Via aHomogenization Technique

In the context of semiconductor manufacturing, chemical vapor deposition (CVD) denotes the deposition of a solid from gaseous species via chemical reactions on the wafer surface. In order to obtain a realistic process model, this paper proposes the introduction of an intermediate scale model on the scale of a die. Its mathematical model is a reaction‐diffusion equation with associated boundary conditions including a flux condition at the micro structured surface. The surface is given in general parameterized form. A homoganization technique from asymptotic analysis is used to replace this boundary condition by a condition on the flat surface to make a numerical solution feasible. Results from a mathematical test problem are included.

On the light spinless particle in superstring models

We describe the properties of an additional light boson with both scalar and pseudoscalar interactions in superstring inspired intermediate-scale models.

模擬石炭層の無炎燃焼に対する窒素ガスの抑制効果 石炭の自然発火の不活性化消火に関する研究

To obtain the fundamental data on suppressive effect of nitrogen injection against spontanious combustion in coal mines, some extinguishing experiments were carried out by using intermediate scale model coal seams in a test gallery. The results obtained through experiments and discussion are summerized as follows:(1) The upper limit of oxygen concentration in sealing area to suppress smoldering combustion of coal was about 5% in case of the early heating stage, and under 1% in case of its growing stage.(2) Temperatures in model coal seams during the nitrogen injection dropped rapidly according with the decrease rate of oxygen concentration, and so early extinguishment can be expected in case of lower oxygen concentration in sealing area.(3) Gas composition in sealing area has some relation with temperatures in coal seams under suppression process of combustion.

Comments on intermediate-scale models

Some superstring-inspired models employ intermediate scales m 1 of gauge symmetry breaking. Such scales should exceed 10 16 GeV in order to avoid prima facie problems with baryon decay through heavy particles and non-perturbative behaviour of the gauge couplings above m I . However, the intermediate-scale phase transition does not occur until the temperature of the Universe falls below O( m w), after which an enormous excess of entropy is generated. Moreover, gauge symmetry breaking by renormalization group-improved radiative corrections is inapplicable because the symmetry-breaking field has no renormalizable interactions at scales below m I . We also comment on the danger of baryon and lepton number violation in the effective low-energy theory.

Observations of the Stability of a Normal Mode Sound Field in an Intermediate Scale Model

Spectra of sound pressure amplitude versus frequency in the range 1.1–2.4 kc have been obtained at regular intervals in shallow (10 ft) water during two periods of extended observation. The acoustical data have been presented in the form of contour diagrams of sound pressure amplitude versus frequency and time as coordinates and compared with water conditions. The form of the contour diagrams permits differentiation between field structure variation and variation in attenuation, although differentiation between the associated processes has not been possible. Temporal variation in the vertical sound velocity profile produced only small changes in the gross features of the field structure—as inferred from the contour diagram—for up to the first three modes of propagation. For frequencies above 1.6 kc (i.e., when three or four modes were stimulated) the variations in field structure were prominent. Attempts have been made, with little success, to explain periods when the received signal was strongly attenuated in terms of vertical sound velocity structure.

Observations of the Stability of a Normal Mode Sound Field in an Intermediate Scale Model

Spectra of sound-pressure amplitude versus frequency in the range 1.1 to 2.4 kc have been obtained at regular intervals in shallow (10 ft) water during two periods of extended observation. The acoustical data have been presented in the form of contour diagrams of sound-pressure amplitude versus frequency and time as coordinates and compared with water conditions. The form of the contour diagrams permits differentiation between field-structure variation and variation in attenuation although differentiation between the associated processes has not been possible. Temporal variation in the vertical sound-velocity profile produced only small changes in the gross features of the field structure, as inferred from the contour diagram, for up to the first three modes of propagation. For frequencies above 1.6 kc (i.e., when three or four modes were stimulated) the variations in field structure were prominent. Attempts have been made, with little success, to explain periods when the received signal was strongly attenuated in terms of vertical sound-velocity structure.

Shallow Water Sound Propagation Studies in an Intermediate Scale Model

A one-half square mile of constant water depth of about 10 ft is situated close to Pacific Naval Laboratory in the Esquimalt Lagoon and forms a natural intermediate scale model tank for shallow water propagation studies. Bottom velocities and layering depths have been obtained from a seismic survey. The dependence of sound level of a cw signal on transmitter depth at range to depth ratios of 30, 45, 60, 75, 90, 105 has been obtained for the first three modes of propagation. The received sound level from a transducer moved at constant depth towards the receiver has been recorded with acoustic wavelength and transducer depth as parameters. Instrumentation to (a) permit rapid measurement of vertical temperature profiles from a remote position, and (b) to record surface wave amplitude at the Tx and Rx position has been installed. Fluctuations in level of received cw signals appear well-correlated in frequency with surface waves. The dependence of the percentage of fluctuations on (a) surface wave amplitude, and (b) acoustical wavelength has been determined. A wave packet experiment, using the bow wave from a boat to produce the sound fluctuations, throws some light on the mechanism involved.