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Results for “Mathematical Model”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

The Decarburization Kinetics of Metal Droplets in Emulsion Zone

Abstract:: A mathematical model has been developed to predict the decarburization rate within individual droplets in the emulsion zone. All the chronological events pertaining to the life cycle of a metal droplet in the emulsion zone like oxygen supply (from slag), external and internal decarburization have been modeled dynamically and validated against experimental data available in open literature. The bloating behavior of metal droplets in the emulsion was represented theoretically by incorporating an escape function dependent on internal CO gas generation. The model is able to predict the onset of bloating and the residence time of metal droplets in the emulsion zone. The residence time of droplet containing 2.6 wt pct C and 0.007 wt pct S is in the range of 10 to 13 seconds. The contribution of decarburization rate in the emulsion zone to the overall decarburization rate is studied using the industrial data reported by Cicutti et al. The model predicts 5 to 75 pct of total decarburization takes place in the emulsion zone. It is found that the extent of decarburization of a metal droplet depends on its initial carbon content rather than its oxygen content for slag containing FeO greater than 10 wt pct.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Dynamics of Synchronous Hydromechanical Drive in Mobile Machine

A mathematical model of the synchronous hydromechanical drive in a mobile machine with a flux divider of choke type is developed on the basis of the theory of the stiffness of a hydraulic system. To obtain the best dynamic characteristics of the system, the properties of the flow divider must be strictly consistent with the dynamic properties of the system.

42 ENGINEERING↗
DOE OSTI2019

Three-Layer Cylindrical Shell with Nonlinear Deformation

A mathematical model is proposed for the stress–strain state of a three-layer (sandwich) structure, taking account of nonlinear deformation of the supporting layers. Nonlinear deformation of a symmetric three-layer cylindrical shell under the action of transverse loads is considered, for different boundary conditions.

42 ENGINEERING↗
DOE OSTI2021

The role of memory in non-genetic inheritance and its impact on cancer treatment resistance

Intra-tumour heterogeneity is a leading cause of treatment failure and disease progression in cancer. While genetic mutations have long been accepted as a primary mechanism of generating this heterogeneity, the role of phenotypic plasticity is becoming increasingly apparent as a driver of intra-tumour heterogeneity. Consequently, understanding the role of this plasticity in treatment resistance and failure is a key component of improving cancer therapy. We develop a mathematical model of stochastic phenotype switching that tracks the evolution of drug-sensitive and drug-tolerant subpopulations to clarify the role of phenotype switching on population growth rates and tumour persistence. By including cytotoxic therapy in the model, we show that, depending on the strategy of the drug-tolerant subpopulation, stochastic phenotype switching can lead to either transient or permanent drug resistance. We study the role of phenotypic heterogeneity in a drug-resistant, genetically homogeneous population of non-small cell lung cancer cells to derive a rational treatment schedule that drives population extinction and avoids competitive release of the drug-tolerant sub-population. This model-informed therapeutic schedule results in increased treatment efficacy when compared against periodic therapy, and, most importantly, sustained tumour decay without the development of resistance.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Drawing of Hardening Materials with Radial-Matrix Clamping

A mathematical model is developed for the drawing of an anisotropic hardening material without wall thinning, in the case of radial-matrix clamping. For sheets of various materials, the forces required and the associated damage are investigated as a function of the drawing coefficient, the rounding radius of the matrix, the frictional conditions at tool–workpiece contact, and the clamping materials.

42 ENGINEERING↗
DOE OSTI2018

Nanoindentation of ZrN Coatings on Silicon and Copper Substrates

An effective mathematical model is proposed to describe experiments on the indentation of samples with layered or functionally graded coatings. The model is based on the elastic contact problem corresponding to the penetration of a punch in a coated elastic half-space. A Berkovich indenter is considered. The results of the simulation and the experiments are compared for the indentation of two zirconium nitride (ZrN) coatings on substrates of monocrystalline (100) silicon and annealed copper. The agreement of the results is good.

42 ENGINEERING↗
DOE OSTI2017

Some estimation problems in epidemic modeling

In the field of computer virus, a growing number of mathematical models have been published during the last decade. In this paper, we consider several estimation methods under two parametric models, the random constant scanning model and the nonhomogeneous random scanning model, to propose a comparison of the estimators’ performances based on the simulation of random populations. We conclude our work with an application of the different estimation methods to a real data set of worm propagation.

Mathematics↗
DOE OSTI2021

Daily Forecasting of Regional Epidemics of Coronavirus Disease with Bayesian Uncertainty Quantification, United States

To increase situational awareness and support evidence-based policymaking, we formulated a mathematical model for coronavirus disease transmission within a regional population. This compartmental model accounts for quarantine, self-isolation, social distancing, a nonexponentially distributed incubation period, asymptomatic persons, and mild and severe forms of symptomatic disease. We used Bayesian inference to calibrate region-specific models for consistency with daily reports of confirmed cases in the 15 most populous metropolitan statistical areas in the United States. We also quantified uncertainty in parameter estimates and forecasts. This online learning approach enables early identification of new trends despite considerable variability in case reporting.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

The combined approach to obtain approximate analytical solution of instability phenomenon arising in secondary oil recovery process

Instability phenomenon mainly occurs in secondary oil recovery process due to viscosity difference of water and oil. Mathematical modeling of this phenomenon yields the non-linear partial differential equation. The homotopy perturbation new integral transform method has been proposed to solve this non-linear partial differential equation subject to appropriate initial and boundary conditions. It is concluded that the saturation of injected water S{sub w}(X,T) is increasing during instability phenomenon, when length of fingers(perturbance) and time increases.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

The Study of Magnetic Fluid Flows in a Laterally Heated Vertical Channel

Convection of a stratified magnetic fluid in a laterally heated vertical channel is investigated experimentally and theoretically. The dynamics of the behavior of convective rolls, their velocity and deformation, are investigated. It is shown that the complex inhomogeneous structure of the flow is attributed to the stratification of nanoparticles in the gravitational field. On the basis of a mathematical model of convection in the Boussinesq approximation, a large series of computational experiments are carried out for various parameters of the problem: the initial distribution of nanopartciles, the Boltzmann number, the Soret parameter, and the sedimentation length. A range of parameters is found in which the numerical and experimental results are qualitatively similar.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Superinfection and cure of infected cells as mechanisms for hepatitis C virus adaptation and persistence

Significance Viral populations exhibit an extraordinary ability to survive abrupt changes in host environment by rapidly generating adaptive mutations. However, our understanding of how viral populations respond to selection pressure and the underlying molecular mechanisms supporting viral adaptation in vivo is limited. Here, we report a set of clinical data sampled from subjects chronically infected by hepatitis C virus (HCV). The data show rapid expansion and turnover of drug-resistant viruses following treatment with an HCV protease inhibitor. By fitting mathematical models to the data, we propose that superinfection and cure of infected cells play critical roles in facilitating the rapid expansion and turnover of viral populations. Our results highlight the importance of considering intracellular viral competition in understanding rapid viral adaptation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Design and performance analysis of all-optical 1:4 and 1:8 high speed demultiplexer using InGaAsP–InP optical microring resonator in Z-domain

All-optical 1:4 and 1:8 demultiplexers are designed and demonstrated using the process of photon absorption that is induced using an external optical pumping of wavelength 532 nm in InGaAsP–InP add-drop microring resonators. The 1:4 demultiplexer is designed with two cascaded optical microring resonators (OMRRs) and 1:8 demultiplexer is designed with four OMRRs. The mathematical modeling is pursued in Z-domain. The delay has been reduced by implementing a three level parallel circuit for 1:8 demultiplexer. The nonlinearity that occurs as a resonance frequency shift in OMRR due to photon energized electron–hole pairs is used to realize the optical switching operation of OMRR. The simulation is carried using MATLAB. The circuit has less propagation delay, fast switching time and can be integrated on CMOS photonic chips.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Change in Limiting Channel Dimensions during Pneumatic Shaping of Multilayer Structures

A mathematical model is developed for determining the inert-gas pressure within rectangular channels in multilayer structures. The model permits calculation of the pressure, stress, and damage in the shaping of materials with different properties. The influence of the relative channel height on the relative limiting rounding radius of a corner element and the membrane thickness and also on the failure time for titanium (VT6S) and aluminum (AMg6) alloys is investigated. The deformation processes are described by the energetic and kinetic theories of creep and damage for viscous flow.

42 ENGINEERING↗
DOE OSTI2017

Influence of the Length of a Torch Tongue on Heat Flow in a Burner Device

Results of mathematical modeling of the burner torch of the furnaces of steam boilers with radiating cylindrical gas volumes are presented. As a result of modeling it is established that with a short torch tongue, the heat flows to the burner device can be significant and the service life of the burners reduced. By means of calculations it is established that with a 1.5 – 2-fold increase in the length of the torch tongue at constant power, heat flow decreases 2 – 3-fold in the burner device and the useful life of the latter increases to 10 years and more.

42 ENGINEERING↗
DOE OSTI2018

Phase Portraits of Dynamical Equations of Motion of a Rigid Body in a Resistive Medium

We consider a mathematical model of the influence of a medium on a rigid body with a specific shape of its surface. In this model, we take into account the additional dependence of the moment of the interaction force on the angular velocity of the body. We present a complete system of equations of motion under the quasi-stationarity conditions. The dynamical part of equations of motion forms an independent third-order system, which contains, in its turn, an independent secondorder subsystem. We ovtain a new family of phase portraits on the phase cylinder of quasi-velocities, which differs from families obtained earlier.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Selective detection of polarisation components of a coherent population trapping signal in hot alkali metal atoms

A mathematical model of the interaction of bichromatic laser radiation with alkali metal atoms in an optically dense gas cell at above room temperature is constructed. Within the framework of the model, complete hyperfine and Zeeman structures of alkali metal atom levels are considered, which allows the propagation of radiation polarisation along the cell and the effect of a constant magnetic field to be correctly taken into account. It is found that the selective detection of polarisation radiation components carries additional information in comparison with a signal of total intensity. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Scalable synthesis of supported catalysts using fluidized bed atomic layer deposition

Overcoating layers deposited on the surface of heterogeneous catalysts using atomic layer deposition (ALD) have been shown to increase catalyst activity, lifetime, and selectivity. In this study, we performed Al 2 O 3 ALD and Pd ALD in a commercial fluidized bed reactor on high surface area mesoporous powder supports to create overcoated catalysts with high precursor utilization. We investigated the reaction mechanism for both Al 2 O 3 ALD and Pd ALD using in situ mass spectrometry and developed a mathematical model to understand the precursor saturation behaviors. We characterized the catalyst samples using a variety of techniques to measure the surface area, porosity, composition, and surface chemistry of the overcoated catalysts. Finally, we used propane dehydrogenation as a probe reaction to evaluate the performance of the catalysts prepared by fluidized bed ALD.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Experimental and Theoretical Research into Dynamic Loading of Tungsten Porous Alloy with Reinforcing Agent

The paper studies the behavior of ceramic porous tungsten alloy with reinforcing agents under the shock-wave loading conditions. Penetrating capacity of tungsten kinetic energy projectiles is calculated and experimentally investigated during their high-speed impacts on steel plates. It is shown that the increased penetration depth of tungsten projectiles exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron cast alloy. A mathematical model is developed together with the design technique of the behavior of tungstennickel-iron-cobalt metal foams alloyed with boron carbide, tungsten titanium carbide and tungsten carbide during the high-speed impact interaction. The composite ceramic material is described here as a porous medium. The matrix of this medium is a homogeneous two-phase mixture of the tungsten-nickel-iron-cobalt system and reinforcing agents added in the required proportions.

36 MATERIALS SCIENCE↗