Simple Coarse Research Articles

Dynamic Surrogate Trip-Level Energy Model for Electric Bus Transit System Optimization

The introduction of electric mobility solutions mitigates transportion-related greenhouse gas emissions. Transit buses are considered a promising candidate for electrification. This study contributes to the growing literature on battery-electric buses (BEBs) and aims to quantify the optimal allocation of BEB infrastructure and charging schedules. A generic model for the charging capacity and scheduling of the BEB network is developed. The proposed model proposes an algorithm for the calculation of trip-level BEB energy consumption based on a surrogate model-based space mapping algorithm. Instead of using vehicle simulators or constant values for the energy consumption rate for each trip, the input space mapping has been applied to a simple coarse model to build an accurate surrogate model. The proposed algorithm is tested on the bus transit network in Belleville City in Canada considering BEBs using both Flash and Opportunity charging. The results show the efficiency of the proposed model and highlight the impact on the optimization results of calculating the trip-level energy consumption compared with the traditional methods.

Coupling Parareal with Optimized Schwarz Waveform Relaxation for Parabolic Problems

We propose and analyse a parallel method, both in the time and space directions, that couples the Parareal algorithm with the Optimized Schwarz waveform relaxation (OSWR) method, with only few OSWR iterations in the fine propagator and with a simple coarse propagator deduced from the Backward Euler method. The analysis of this coupled method is presented for a one-dimensional advection-reaction-diffusion equation. We prove a general convergence result for this method via energy estimates. Numerical results for two-dimensional advection-diffusion problems and for a diffusion equation with strong heterogeneities are presented, to illustrate the performance of the coupled Parareal-OSWR algorithm.

A Comprehensive Review on Self-Nano Emulsifying Drug Delivery Systems: Advancements and Applications

Lipid-based drug delivery systems are extensively reported in literature for enhancing the drug solubility, permeability and bioavailability. These systems include simple oil solutions, coarse, multiple and dry emulsions, complex self-emulsifying, microemulsifying or nanoemulsifying drug delivery systems. Self-emulsifying systems are further classified as self-microemulsifying drug delivery systems (SMEDDS) and self-nanoemulsifying drug delivery systems (SNEDDS) are most prevailing and commercially viable oil based approach for drugs that exhibit low dissolution rate and inadequate absorption. Ever since the progress of SNEDDS, they drew the interest of researchers in order to deal with the challenges of poorly water-soluble drugs. SNEDDS is a proven method for enhancing solubility and bioavailability of lipophilic compounds. Considering the ease of large-scale production and the robustness of SNEDDS, several formulations techniques are commercially available. The stability of SNEDDS can be further enhanced by solidifying liquid SNEDDS. Controlled release and supersaturated SNEDDS received patient compliance with larger drug loading. Presence of biodegradable ingredients and ‘drug-targeting opportunities’ facilitate SNEDDS a clear merit and distinction amongst available solubility enhancement techniques. In this article attempt was made to present an overview of SNEDDS, their mechanism, formulation excipients and potentials of SNEDDS, recent advancements, advantages and disadvantages of SNEDDS formulations. The article also focuses on reviewing the application of SNEDDS in enhancing bioavailability of antihypertensive drugs.

Defect-Assisted Permeation Through a Phospholipid Membrane: Experimental and Computational Study of the Peptide WKW.

We investigate membrane permeation by the peptide WKW that is amidated at its C-terminus and therefore carries a positive charge of +2. To facilitate an efficient calculation, we introduce a novel set of simple coarse variables that measure permeation depth and membrane distortion. The phospholipid head groups shift toward the center of the membrane, following the permeating peptide, and create a defect that assists permeation. The Milestoning algorithm was used in the new coarse space to compute the free-energy profile and the mean first passage time. The barrier was lower than expected from a simple continuum estimate. This behavior is consistent with the known behavior of positively charged cell-penetrating peptides, and is explained by a detailed mechanism of defect formation and propagation revealed by the simulations.

Improvement of semi-resolved CFD-DEM model for seepage-induced fine-particle migration: Eliminate limitation on mesh refinement

The semi-resolved CFD-DEM model, proposed in our previous paper (Cheng et al., 2018) for the modelling of seepage-induced fine-particle migration through coarse skeleton in gap-graded soils, is improved through using Gaussian-based weighting function for fine particle-fluid coupling based on locally averaging theory. By doing so, it eliminates the limitation on fine particle-fluid mesh size ratio and thereby facilitates capturing detailed flow pattern through the coarse skeleton by refining fluid meshes. The improved semi-resolved CFD-DEM model is validated by Particle Image Velocimetry results of velocity field of fine glass beads migration through a simple coarse skeleton.

Numerical simulation for multi-phase fluids considering different densities with continuous finite element method

In this paper, we compute a phase field model of Cahn-Hilliard type for multi-component mixture fluids considering surface tension and buoyancy effects. We discretize Navier-Stokes and Cahn-Hilliard coupled equations with a continuous finite element scheme in space and the finite difference in time. Also, we apply a penalty formulation to the continuity equation which may increase the stability in solving the continuity condition and momentum equation. The dynamic of a rising lighter drop due to different densities between other two immiscible fluids is studied as the numerical example with a relatively coarse grid. Numerical results show that this model can be solved with a relative simple scheme and coarse grid which leads to the higher efficiency.

Principal component analysis acceleration of rovibrational coarse-grain models for internal energy excitation and dissociation.

The present work introduces a novel approach for obtaining reduced chemistry representations of large kinetic mechanisms in strong non-equilibrium conditions. The need for accurate reduced-order models arises from compression of large ab initio quantum chemistry databases for their use in fluid codes. The method presented in this paper builds on existing physics-based strategies and proposes a new approach based on the combination of a simple coarse grain model with Principal Component Analysis (PCA). The internal energy levels of the chemical species are regrouped in distinct energy groups with a uniform lumping technique. Following the philosophy of machine learning, PCA is applied on the training data provided by the coarse grain model to find an optimally reduced representation of the full kinetic mechanism. Compared to recently published complex lumping strategies, no expert judgment is required before the application of PCA. In this work, we will demonstrate the benefits of the combined approach, stressing its simplicity, reliability, and accuracy. The technique is demonstrated by reducing the complex quantum N2(Σg+1)-N(Su4) database for studying molecular dissociation and excitation in strong non-equilibrium. Starting from detailed kinetics, an accurate reduced model is developed and used to study non-equilibrium properties of the N2(Σg+1)-N(Su4) system in shock relaxation simulations.

Coarse-grained molecular dynamics simulations of fibrin polymerization: effects of thrombin concentration on fibrin clot structure.

Studies suggest that patients with deep vein thrombosis and diabetes often have hypercoagulable blood plasma, leading to a higher risk of thromboembolism formation through the rupture of blood clots, which may lead to stroke and death. Despite many advances in the field of blood clot formation and thrombosis, the influence of mechanical properties of fibrin in the formation of thromboembolisms in platelet-poor plasma is poorly understood. In this paper, we combine the concepts of reactive molecular dynamics and coarse-grained molecular modeling to predict the complex network formation of fibrin clots and the branching of fibrin monomers. The 340-kDa fibrinogen molecule was converted into a coarse-grained molecule with nine beads, and using our customized reactive potentials, we simulated the formation and polymerization process of a fibrin clot. The results show that higher concentrations of thrombin result in higher branch-point formation in the fibrin clot structure. Our results also highlight many interesting properties, such as the formation of thicker or thinner fibers depending on the thrombin concentration. To the best of our knowledge, this is the first successful molecular polymerization study of fibrin clots to focus on thrombin concentration.

Substructuring Preconditioners with a Simple Coarse Space for 2-D 3-T Radiation Diffusion Equations

Substructuring Preconditioners with a Simple Coarse Space for 2-D 3-T Radiation Diffusion Equations

Coarse graining ofNNinelastic interactions up to 3 GeV: Repulsive versus structural core

The repulsive short distance core is one of the main paradigms of nuclear physics which even seems confirmed by QCD lattice calculations. On the other hand nuclear potentials at short distances are motivated by high energy behavior where inelasticities play an important role. We analyze NN interactions up to 3 GeV in terms of simple coarse grained complex and energy dependent interactions. We discuss two possible and conflicting scenarios which share the common feature of a vanishing wave function at the core location in the particular case of S- waves. We find that the optical potential with a repulsive core exhibits a strong energy dependence whereas the optical potential with the structural core is characterized by a rather adiabatic energy dependence which allows to treat inelasticity perturbatively. We discuss the possible implications for nuclear structure calculations of both alternatives.

An efficient multiscale computational formulation for geometric nonlinear analysis of heterogeneous piezoelectric composite

In this contribution, an efficient multiscale computational formulation is developed for the geometric nonlinear analysis of heterogeneous piezoelectric materials. In this formulation, the relations between the microscopic heterogeneous properties and macroscopic behaviors of the piezoelectric composite are established by the numerically constructed displacement and electric potential base functions. The heterogeneous and complex microstructure can be equivalent to a simple macroscopic piezoelectric coarse element through those constructed multiscale base functions. Then the equivalent tangent stiffness matrix and internal force vector of the macroscopic coarse element are deduced based on the co-rotational approach, which can describe the motion of macroscopic coarse element clearly and efficiently. Thus the original electro-mechanical coupling geometric nonlinear problem could be solved iteratively on the macroscopic scale, which will save a tremendous amount of computing time and cost. After all the macroscopic calculations, the microscopic mechanical and electrical responses could be retrieved and calculated from the macroscopic solutions by using the above-mentioned multiscale shape functions. To verify the validation and high-efficiency of the proposed multiscale computation formulation, several typical numerical examples are carried out. All the computation results indicate that the developed multiscale formulation not only could provide high precision solutions but also has high efficiency.

Simple coarse sensing to achieve high precision From attractive region in environment to constrained region in environment

ABSTRACTAs a fundamental yet urgent issue, achieving high-precision robotic manipulation is becoming an active research area. Unfortunately, it is practically impossible to obtain an unlimited increase in sensor accuracy. In contrast, sensor-less manipulation approaches have attracted considerable attention. In particular, the concept of attractive region in environment has achieved encouraging results. Moreover, note that certain information cannot be captured directly from the sensors. With the above observations and inspired by the behaviour mechanism of human beings when accomplishing complex operations, this article proposed a novel bio-inspired co-sensing framework, which aims to solve the high-precision sensing problem by simple coarse sensors. One of the distinguishing features of the established framework is the constrained region in environment, the key idea of which is the integration of the relaxed constraint and the coarse sensor information. An illustrative example is provided to demonstrate the effectiveness and benefits of our theoretical findings.

The Effect of Attractive Interactions and Macromolecular Crowding on Crystallins Association.

In living systems proteins are typically found in crowded environments where their effective interactions strongly depend on the surrounding medium. Yet, their association and dissociation needs to be robustly controlled in order to enable biological function. Uncontrolled protein aggregation often causes disease. For instance, cataract is caused by the clustering of lens proteins, i.e., crystallins, resulting in enhanced light scattering and impaired vision or blindness. To investigate the molecular origins of cataract formation and to design efficient treatments, a better understanding of crystallin association in macromolecular crowded environment is needed. Here we present a theoretical study of simple coarse grained colloidal models to characterize the general features of how the association equilibrium of proteins depends on the magnitude of intermolecular attraction. By comparing the analytic results to the available experimental data on the osmotic pressure in crystallin solutions, we identify the effective parameters regimes applicable to crystallins. Moreover, the combination of two models allows us to predict that the number of binding sites on crystallin is small, i.e. one to three per protein, which is different from previous estimates. We further observe that the crowding factor is sensitive to the size asymmetry between the reactants and crowding agents, the shape of the protein clusters, and to small variations of intermolecular attraction. Our work may provide general guidelines on how to steer the protein interactions in order to control their association.

Trigger sequence can influence final morphology in the self-assembly of asymmetric telechelic polymers.

We report on a numerical study of polymer network formation of asymmetric biomimetic telechelic polymers with two reactive ends based on a self-assembling collagen, elastin or silk-like polypeptide sequence. The two reactive ends of the polymer can be activated independently using physicochemical triggers such as temperature and pH. We show, using a simple coarse grained model that the order in which this triggering occurs influences the final morphology. For both of collagen-silk and elastin-silk topologies we find that for relatively short connector chains the morphology of the assembly is greatly influenced by the order of the trigger, whereas for longer chains the equilibrium situation is more easily achieved. Moreover, self-assembly is greatly enhanced at moderate collagen interaction strength, due to facilitated binding and unbinding of the peptides. This finding indicates that both the trigger sequence and strength can be used to steer self-assembly in these biomimetic polymer systems.

Transferability of a coarse-grained atactic polystyrene model: the non-bonded potential effect.

In this paper, we construct an efficient and simple coarse grained (CG) model for atactic polystyrene (PS) by using a 1 : 1 mapping scheme at 463 K and 1 atm pressure and derive the corresponding bonded and non-bonded potentials in the CG force field (FF) via a direct Boltzmann inversion approach and a combined structure-based and thermodynamic quantities-based CG method, respectively. For computational considerations, the non-bonded interaction between CG particles is described by Lennard-Jones (LJ) type potentials, and both the radial distribution function (RDF) and the bulk density of the atomistic simulations are taken as target properties in the parameterization of the two LJ parameters. To shed light on the choice of LJ forms of CG non-bonded potentials when designing the CG models, a series of CG models with different LJ potentials are constructed and compared in order to understand how the quality of a CG model in reproducing the structure and thermodynamic properties of chemically realistic systems is affected by the choice of non-bonded potentials. We find that with our structural and thermodynamics combined CG method to construct the CG FF at a single thermodynamic state point without any temperature dependent LJ potential correction and/or pressure optimization, the resulting CG models possess good temperature transferability in a wide range of temperatures 300-600 K, where both the target properties and several other static properties (such as thermal expansion coefficient and mean-square radius of gyration) are generally reproduced. Furthermore, the non-bonded LJ potential influences the density response of CG models to the temperature change, i.e., CG models with harder LJ potentials show better temperature transferability than the softer ones. Meanwhile, the derived Tg increases with increasing LJ repulsion strength while thermal expansion coefficients in both melt and glass states are lowered as the LJ potential hardens. With regard to the local conformation and local packing distribution functions, varying non-bonded LJ potential hardness influences only the magnitude of the peak height but does not affect the peak position, in particular the magnitude of the non-bonded potential effect on local distribution functions becomes stronger at lower temperatures. More specifically, this effect on the local chain conformation statistics at the CG level is different for the distribution of bond-lengths, bond angles and dihedrals. As a result, the size of the CG chains is fairly insensitive to the non-bonded LJ potentials within 300-600 K. In short, the CG model with the harder LJ-type non-bonded CG potential is a more realistic representation of excluded volume interactions of the underlying atomistic PS monomer and thus has the potential to generate a higher Tg to match with the atomistic systems.

Kinetics of aggregation of an anisotropic model of self-assembling molecules.

We study the kinetics of aggregation of a two site model of interacting spherical molecules. A given site on one molecule can interact with one or more sites on other neighboring molecules. The sites represent the result of a simple coarse graining of putative amino acid residues or two specifically designed sites on a colloidal particle. We study the kinetics and equilibrium morphology for a fixed angle between the two sites, for several angles between 30° and 150°. In the model, the sites interact via an attractive Asakura-Oosawa potential and the molecules have the usual hard sphere repulsion interaction. We find a transition from a micelle-like morphology at small angles to a rod-like morphology at intermediate angles and to a gel-like structure at values of the angle greater than about ninety degrees. However, at 150 degrees, after a long induction time during which there is no aggregation, we observe a nucleation and growth process that leads to a final spherical-like aggregate. Our results show that this angle is a control parameter for the kinetics and equilibrium properties of the system.

Material Effect in the Nuclear Fuel–Coolant Interaction: Analyses of Prototypic Melt Fragmentation and Solidification in the KROTOS Facility

During a severe accident sequence in a pressurized light water reactor, the hot (~3000 K) molten materials (corium) coming from the degraded reactor core may generate a violent interaction if they come in contact with water. This melt-water interaction, called fuel-coolant interaction (FCI), may damage the structures and threaten the reactor integrity if there is a steam explosion. FCI occurs generally in two phases: a premixing phase, during which the molten corium jet is fragmented into large droplets and mixed with the water, and the explosion phase, during which the vapor film that has developed around the fuel droplets is destabilized and the droplets are finely fragmented. The presented work covers a set of experimental studies describing the morphology and nature of the solidified materials after interaction with water. Debris from experiments performed in the KROTOS (Commissariat à l’Énergie Atomique, Cadarache, France); PREMIX, ECO (Karlsruhe Institute of Technology, Karlsruhe, Germany); and MISTEE (Royal Institute of Technology, Stockholm, Sweden) facilities have been characterized by metallographic, analytical, and microscopic techniques. These post-test analyses are able to provide important information on the solidification path and other main phenomena involved during FCI. It was found that the behavior of metallic and oxide melts differs significantly from the standpoint of debris morphology. Oxide melts that underwent simple coarse fragmentation showed spherical or angular rocklike shape, unlike metallic melts. A statistical analysis was performed on the debris from the KROTOS tests; a data set of particles was described by the circularity, solidity, and porosity. The mechanism of water ingression (Kim and Corradini) inside the melt droplet was observed to be the key mechanism of fine (secondary) fragmentation. The particles participating in fine “thermal” fragmentation have significantly higher porosity, up to ~30% for prototypic corium in the KROTOS facility. It was calculated that only a part of the premixed melt participates in fine fragmentation, i.e., about one-third of the melt mass for the KROTOS tests using UO2-ZrO2 mixture.

A Low-Cost Photodiode Sun Sensor for CubeSat and Planetary Microrover

This paper presents the development of low-cost methodologies to determine the attitude of a small, CubeSat-class satellite and a microrover relative to the sun's direction. The use of commercial hardware and simple embedded designs has become an effective path for university programs to put experimental payloads in space for minimal cost, and the development of sensors for attitude and heading determination is often a critical part. The development of two compact and efficient but simple coarse sun sensor methodologies is presented in this research. A direct measurement of the solar angle uses a photodiode array sensor and slit mask. Another estimation of the solar angle uses current measurements from orthogonal arrays of solar cells. The two methodologies are tested and compared on ground hardware. Testing results show that coarse sun sensing is efficient even with minimal processing and complexity of design for satellite attitude determination systems and rover navigation systems.

Coarse correlated equilibria in linear duopoly games

For duopoly models, we analyse the concept of coarse correlated equilibrium using simple symmetric devices that the players choose to commit to in equilibrium. In a linear duopoly game, we prove that Nash-centric devices, involving a sunspot structure, are simple symmetric coarse correlated equilibria. Any small unilateral perturbation from such a structure fails to be an equilibrium.

A new multiscale methodology for modeling of single and multi-body solid structures

Fixed Interfacial Multiscale Method (FIMM), a concurrent multiscale model is developed for mechanical analysis of solid nanostructures at the finite temperatures. A direct link between the nano field atoms and macro field nodes using the local atomic volume displacements associated with every macro field node in their common zone has been replaced with the previous methods. FIMM leaves negligible relative motion of atoms in every atomic volume by moving the interface into the macro part. A nano plate in extension and a nanorobotic manipulator have been simulated for comparison. The responses have been compared with the results of semi continuum approach, Molecular Dynamics (MDs), a developed simple Coarse Grained MD (CGMD) and two recently developed multiscale methods. Comparisons show that FIMM is at least 450% better than other methods in numerical cost, and it is also more accurate than other multiscale methods.