Rahatgaonkar, P. S.; Datta, D.; Malhotra, P. K.; Ghadge, S. G.
2012-07-01
Prediction of groundwater movement and contaminant transport in soil is an important problem in many branches of science and engineering. This includes groundwater hydrology, environmental engineering, soil science, agricultural engineering and also nuclear engineering. Specifically, in nuclear engineering it is applicable in the design of spent fuel storage pools and waste management sites in the nuclear power plants. Ground water modeling involves the simulation of flow and contaminant transport by groundwater flow. In the context of contaminated soil and groundwater system, numerical simulations are typically used to demonstrate compliance with regulatory standard. A one-dimensional Computational Fluid Dynamics code GFLOW had been developed based on the Finite Difference Method for simulating groundwater flow and contaminant transport through saturated and unsaturated soil. The code is validated with the analytical model and the benchmarking cases available in the literature. (authors)
1995-07-07
DUST solves for release and transport of contaminants from containerized wastes. Each container may have unique properties (i.e., time to failure or localized failure, e.g., pitting) and each waste form may have unique release properties. Release from the waste form is limited by one of four physical or chemical restraints: solubility, diffusion, dissolution, and surface wash-off with partitioning. The release from the waste form acts as a source for transport in the advection/dispersion equation. Transportmore » is modeled in one-dimension through the groundwater pathway from subsurface disposal. RNUCL.DAT, database of half-lives, solubility limits, and atomic mass for selected radionuclides, is included in this package.« less
Varank, Gamze; Demir, Ahmet; Yetilmezsoy, Kaan; Bilgili, M. Sinan; Top, Selin; Sekman, Elif
2011-11-15
Highlights: > We conduct 1D advection-dispersion modeling to estimate transport parameters. > We examine fourteen phenolic compounds and three inorganic contaminants. > 2-MP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,3,4,6-TeCP have the highest coefficients. > Dispersion coefficients of Cu are determined to be higher than Zn and Fe. > Transport of phenolics can be prevented by zeolite and bentonite in landfill liners. - Abstract: One-dimensional (1D) advection-dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m{sup 3}) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L{sub e} = 0.20 m, k{sub e} = 1 x 10{sup -8} m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L{sub e} = 0.20 m, k{sub e} = 1 x 10{sup -8} m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L{sub e} = 0.22 m, k{sub e} = 1 x 10{sup -8} m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L{sub e} = 0.22 m, k{sub e} = 4.24 x 10{sup -7} m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 x 10{sup -10} to 10.67 x 10{sup -10} m{sup 2}/s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors
Transport in a one-dimensional hyperconductor
NASA Astrophysics Data System (ADS)
Plamadeala, Eugeniu; Mulligan, Michael; Nayak, Chetan
2016-03-01
We define a "hyperconductor" to be a material whose electrical and thermal dc conductivities are infinite at zero temperature and finite at any nonzero temperature. The low-temperature behavior of a hyperconductor is controlled by a quantum critical phase of interacting electrons that is stable to all potentially gap-generating interactions and potentially localizing disorder. In this paper, we compute the low-temperature dc and ac electrical and thermal conductivities in a one-dimensional hyperconductor, studied previously by the present authors, in the presence of both disorder and umklapp scattering. We identify the conditions under which the transport coefficients are finite, which allows us to exhibit examples of violations of the Wiedemann-Franz law. The temperature dependence of the electrical conductivity, which is characterized by the parameter ΔX, is a power law, σ ∝1 /T1 -2 (2 -ΔX) when ΔX≥2 , down to zero temperature when the Fermi surface is commensurate with the lattice. There is a surface in parameter space along which ΔX=2 and ΔX≈2 for small deviations from this surface. In the generic (incommensurate) case with weak disorder, such scaling is seen at high temperatures, followed by an exponential increase of the conductivity lnσ ˜1 /T at intermediate temperatures and, finally, σ ∝1 /T2 -2 (2 -ΔX) at the lowest temperatures. In both cases, the thermal conductivity diverges at low temperatures.
Electron transport in one-dimensional plasmas
Wienke, B.R.
1983-11-01
A one-dimensional, multigroup, discrete ordinates technique for computing electron energy deposition in plasmas is detailed. The Fokker-Planck collision operator is employed in the continuous approximation and electric fields (considered external) are included in the equation. Bremsstrahlung processes are not treated. Comparisons with analytic and Monte Carlo results are given. Fits to deposition profiles and energy scaling are proposed and discussed for monoenergetic and Maxwellian sources in the range, 0 to 150 keV, with and without uniform fields. The techniques employed to track electrons are generally useful in situations where the background plasma temperature is an order of magnitude smaller than the electron energy and collective plasma effects are negligible. We have used the approach successfully in laser pellet implosion applications.
A. S. Rood
2010-10-01
This report describes the Mixing Cell Model code, a one-dimensional model for water flow and solute transport in the unsaturated zone under steady-state or transient flow conditions. The model is based on the principles and assumptions underlying mixing cell model formulations. The unsaturated zone is discretized into a series of independent mixing cells. Each cell may have unique hydrologic, lithologic, and sorptive properties. Ordinary differential equations describe the material (water and solute) balance within each cell. Water flow equations are derived from the continuity equation assuming that unit-gradient conditions exist at all times in each cell. Pressure gradients are considered implicitly through model discretization. Unsaturated hydraulic conductivity and moisture contents are determined by the material-specific moisture characteristic curves. Solute transport processes include explicit treatment of advective processes, first-order chain decay, and linear sorption reactions. Dispersion is addressed through implicit and explicit dispersion. Implicit dispersion is an inherent feature of all mixing cell models and originates from the formulation of the problem in terms of mass balance around fully mixed volume elements. Expressions are provided that relate implicit dispersion to the physical dispersion of the system. Two FORTRAN codes were developed to solve the water flow and solute transport equations: (1) the Mixing-Cell Model for Flow (MCMF) solves transient water flow problems and (2) the Mixing Cell Model for Transport (MCMT) solves the solute transport problem. The transient water flow problem is typically solved first by estimating the water flux through each cell in the model domain as a function of time using the MCMF code. These data are stored in either ASCII or binary files that are later read by the solute transport code (MCMT). Code output includes solute pore water concentrations, water and solute inventories in each cell and at each
A. S. Rood
2009-04-01
This report describes the Mixing Cell Model code, a one-dimensional model for water flow and solute transport in the unsaturated zone under steady-state or transient flow conditions. The model is based on the principles and assumptions underlying mixing cell model formulations. The unsaturated zone is discretized into a series of independent mixing cells. Each cell may have unique hydrologic, lithologic, and sorptive properties. Ordinary differential equations describe the material (water and solute) balance within each cell. Water flow equations are derived from the continuity equation assuming that unit-gradient conditions exist at all times in each cell. Pressure gradients are considered implicitly through model discretization. Unsaturated hydraulic conductivity and moisture contents are determined by the material-specific moisture characteristic curves. Solute transport processes include explicit treatment of advective processes, first-order chain decay, and linear sorption reactions. Dispersion is addressed through implicit and explicit dispersion. Implicit dispersion is an inherent feature of all mixing cell models and originates from the formulation of the problem in terms of mass balance around fully mixed volume elements. Expressions are provided that relate implicit dispersion to the physical dispersion of the system. Two FORTRAN codes were developed to solve the water flow and solute transport equations: (1) the Mixing-Cell Model for Flow (MCMF) solves transient water flow problems and (2) the Mixing Cell Model for Transport (MCMT) solves the solute transport problem. The transient water flow problem is typically solved first by estimating the water flux through each cell in the model domain as a function of time using the MCMF code. These data are stored in either ASCII or binary files that are later read by the solute transport code (MCMT). Code output includes solute pore water concentrations, water and solute inventories in each cell and at each
Algorithms and a short description of the D1_Flow program for numerical modeling of one-dimensional steady-state flow in horizontally heterogeneous aquifers with uneven sloping bases are presented. The algorithms are based on the Dupuit-Forchheimer approximations. The program per...
Technology Transfer Automated Retrieval System (TEKTRAN)
Mathematical models describing contaminant transport in heterogeneous porous media are often formulated as an advection-dispersion transport equation with distance-dependent transport coefficients. In this work, a general analytical solution is presented for the linear, one-dimensional advection-di...
Programmers manual for a one-dimensional Lagrangian transport model
Schoellhamer, D.H.; Jobson, H.E.
1986-01-01
A one-dimensional Lagrangian transport model for simulating water-quality constituents such as temperature, dissolved oxygen , and suspended sediment in rivers is presented in this Programmers Manual. Lagrangian transport modeling techniques, the model 's subroutines, and the user-written decay-coefficient subroutine are discussed in detail. Appendices list the program codes. The Programmers Manual is intended for the model user who needs to modify code either to adapt the model to a particular need or to use reaction kinetics not provided with the model. (Author 's abstract)
Spin transport in a one-dimensional anisotropic Heisenberg model.
Znidarič, Marko
2011-06-01
We analytically and numerically study spin transport in a one-dimensional Heisenberg model in linear-response regime at infinite temperature. It is shown that as the anisotropy parameter Δ is varied spin transport changes from ballistic for Δ<1 to anomalous at the isotropic point Δ=1, to diffusive for finite Δ>1, ending up as a perfect isolator in the Ising limit of infinite Δ. Using perturbation theory for large Δ a quantitative prediction is made for the dependence of diffusion constant on Δ. PMID:21702588
Users manual for a one-dimensional Lagrangian transport model
Schoellhamer, D.H.; Jobson, H.E.
1986-01-01
A Users Manual for the Lagrangian Transport Model (LTM) is presented. The LTM uses Lagrangian calculations that are based on a reference frame moving with the river flow. The Lagrangian reference frame eliminates the need to numerically solve the convective term of the convection-diffusion equation and provides significant numerical advantages over the more commonly used Eulerian reference frame. When properly applied, the LTM can simulate riverine transport and decay processes within the accuracy required by most water quality studies. The LTM is applicable to steady or unsteady one-dimensional unidirectional flows in fixed channels with tributary and lateral inflows. Application of the LTM is relatively simple and optional capabilities improve the model 's convenience. Appendices give file formats and three example LTM applications that include the incorporation of the QUAL II water quality model 's reaction kinetics into the LTM. (Author 's abstract)
Quasi one dimensional transport in individual electrospun composite nanofibers
Avnon, A. Datsyuk, V.; Trotsenko, S.; Wang, B.; Zhou, S.
2014-01-15
We present results of transport measurements of individual suspended electrospun nanofibers Poly(methyl methacrylate)-multiwalled carbon nanotubes. The nanofiber is comprised of highly aligned consecutive multiwalled carbon nanotubes. We have confirmed that at the range temperature from room temperature down to ∼60 K, the conductance behaves as power-law of temperature with an exponent of α ∼ 2.9−10.2. The current also behaves as power law of voltage with an exponent of β ∼ 2.3−8.6. The power-law behavior is a footprint for one dimensional transport. The possible models of this confined system are discussed. Using the model of Luttinger liquid states in series, we calculated the exponent for tunneling into the bulk of a single multiwalled carbon nanotube α{sub bulk} ∼ 0.06 which agrees with theoretical predictions.
Diffusion and ballistic transport in one-dimensional quantum systems.
Sirker, J; Pereira, R G; Affleck, I
2009-11-20
It has been conjectured that transport in integrable one-dimensional systems is necessarily ballistic. The large diffusive response seen experimentally in nearly ideal realizations of the S=1/2 1D Heisenberg model is therefore puzzling and has not been explained so far. Here, we show that, contrary to common belief, diffusion is universally present in interacting 1D systems subject to a periodic lattice potential. We present a parameter-free formula for the spin-lattice relaxation rate which is in excellent agreement with experiment. Furthermore, we calculate the current decay directly in the thermodynamic limit using a time-dependent density matrix renormalization group algorithm and show that an anomalously large time scale exists even at high temperatures. PMID:20366058
Bioinspired one-dimensional materials for directional liquid transport.
Ju, Jie; Zheng, Yongmei; Jiang, Lei
2014-08-19
One-dimensional materials (1D) capable of transporting liquid droplets directionally, such as spider silks and cactus spines, have recently been gathering scientists' attention due to their potential applications in microfluidics, textile dyeing, filtration, and smog removal. This remarkable property comes from the arrangement of the micro- and nanostructures on these organisms' surfaces, which have inspired chemists to develop methods to prepare surfaces with similar directional liquid transport ability. In this Account, we report our recent progress in understanding how this directional transport works, as well our advances in the design and fabrication of bioinspired 1D materials capable of transporting liquid droplets directionally. To begin, we first discuss some basic theories on droplet directional movement. Then, we discuss the mechanism of directional transport of water droplets on natural spider silks. Upon contact with water droplets, the spider silk undergoes what is known as a wet-rebuilt, which forms periodic spindle-knots and joints. We found that the resulting gradient of Laplace pressure and surface free energy between the spindle-knots and joints account for the cooperative driving forces to transport water droplets directionally. Next, we discuss the directional transport of water droplets on desert cactus. The integration of multilevel structures of the cactus and the resulting integration of multiple functions together allow the cactus spine to transport water droplets continuously from tip to base. Based on our studies of natural spider silks and cactus spines, we have prepared a series of artificial spider silks (A-SSs) and artificial cactus spines (A-CSs) with various methods. By changing the surface roughness and chemical compositions of the artificial spider silks' spindle-knots, or by introducing stimulus-responsive molecules, such as thermal-responsive and photoresponsive molecules, onto the spindle-knots, we can reversibly manipulate
Charge transport through one-dimensional Moiré crystals.
Bonnet, Roméo; Lherbier, Aurélien; Barraud, Clément; Della Rocca, Maria Luisa; Lafarge, Philippe; Charlier, Jean-Christophe
2016-01-01
Moiré superlattices were generated in two-dimensional (2D) van der Waals heterostructures and have revealed intriguing electronic structures. The appearance of mini-Dirac cones within the conduction and valence bands of graphene is one of the most striking among the new quantum features. A Moiré superstructure emerges when at least two periodic sub-structures superimpose. 2D Moiré patterns have been particularly investigated in stacked hexagonal 2D atomic lattices like twisted graphene layers and graphene deposited on hexagonal boron-nitride. In this letter, we report both experimentally and theoretically evidence of superlattices physics in transport properties of one-dimensional (1D) Moiré crystals. Rolling-up few layers of graphene to form a multiwall carbon nanotube adds boundaries conditions that can be translated into interference fringes-like Moiré patterns along the circumference of the cylinder. Such a 1D Moiré crystal exhibits a complex 1D multiple bands structure with clear and robust interband quantum transitions due to the presence of mini-Dirac points and pseudo-gaps. Our devices consist in a very large diameter (>80 nm) multiwall carbon nanotubes of high quality, electrically connected by metallic electrodes acting as charge reservoirs. Conductance measurements reveal the presence of van Hove singularities assigned to 1D Moiré superlattice effect and illustrated by electronic structure calculations. PMID:26786067
Charge transport through one-dimensional Moiré crystals
NASA Astrophysics Data System (ADS)
Bonnet, Roméo; Lherbier, Aurélien; Barraud, Clément; Rocca, Maria Luisa Della; Lafarge, Philippe; Charlier, Jean-Christophe
2016-01-01
Moiré superlattices were generated in two-dimensional (2D) van der Waals heterostructures and have revealed intriguing electronic structures. The appearance of mini-Dirac cones within the conduction and valence bands of graphene is one of the most striking among the new quantum features. A Moiré superstructure emerges when at least two periodic sub-structures superimpose. 2D Moiré patterns have been particularly investigated in stacked hexagonal 2D atomic lattices like twisted graphene layers and graphene deposited on hexagonal boron-nitride. In this letter, we report both experimentally and theoretically evidence of superlattices physics in transport properties of one-dimensional (1D) Moiré crystals. Rolling-up few layers of graphene to form a multiwall carbon nanotube adds boundaries conditions that can be translated into interference fringes-like Moiré patterns along the circumference of the cylinder. Such a 1D Moiré crystal exhibits a complex 1D multiple bands structure with clear and robust interband quantum transitions due to the presence of mini-Dirac points and pseudo-gaps. Our devices consist in a very large diameter (>80 nm) multiwall carbon nanotubes of high quality, electrically connected by metallic electrodes acting as charge reservoirs. Conductance measurements reveal the presence of van Hove singularities assigned to 1D Moiré superlattice effect and illustrated by electronic structure calculations.
Charge transport through one-dimensional Moiré crystals.
Bonnet, Roméo; Lherbier, Aurélien; Barraud, Clément; Della Rocca, Maria Luisa; Lafarge, Philippe; Charlier, Jean-Christophe
2016-01-20
Moiré superlattices were generated in two-dimensional (2D) van der Waals heterostructures and have revealed intriguing electronic structures. The appearance of mini-Dirac cones within the conduction and valence bands of graphene is one of the most striking among the new quantum features. A Moiré superstructure emerges when at least two periodic sub-structures superimpose. 2D Moiré patterns have been particularly investigated in stacked hexagonal 2D atomic lattices like twisted graphene layers and graphene deposited on hexagonal boron-nitride. In this letter, we report both experimentally and theoretically evidence of superlattices physics in transport properties of one-dimensional (1D) Moiré crystals. Rolling-up few layers of graphene to form a multiwall carbon nanotube adds boundaries conditions that can be translated into interference fringes-like Moiré patterns along the circumference of the cylinder. Such a 1D Moiré crystal exhibits a complex 1D multiple bands structure with clear and robust interband quantum transitions due to the presence of mini-Dirac points and pseudo-gaps. Our devices consist in a very large diameter (>80 nm) multiwall carbon nanotubes of high quality, electrically connected by metallic electrodes acting as charge reservoirs. Conductance measurements reveal the presence of van Hove singularities assigned to 1D Moiré superlattice effect and illustrated by electronic structure calculations.
Charge transport through one-dimensional Moiré crystals
Bonnet, Roméo; Lherbier, Aurélien; Barraud, Clément; Rocca, Maria Luisa Della; Lafarge, Philippe; Charlier, Jean-Christophe
2016-01-01
Moiré superlattices were generated in two-dimensional (2D) van der Waals heterostructures and have revealed intriguing electronic structures. The appearance of mini-Dirac cones within the conduction and valence bands of graphene is one of the most striking among the new quantum features. A Moiré superstructure emerges when at least two periodic sub-structures superimpose. 2D Moiré patterns have been particularly investigated in stacked hexagonal 2D atomic lattices like twisted graphene layers and graphene deposited on hexagonal boron-nitride. In this letter, we report both experimentally and theoretically evidence of superlattices physics in transport properties of one-dimensional (1D) Moiré crystals. Rolling-up few layers of graphene to form a multiwall carbon nanotube adds boundaries conditions that can be translated into interference fringes-like Moiré patterns along the circumference of the cylinder. Such a 1D Moiré crystal exhibits a complex 1D multiple bands structure with clear and robust interband quantum transitions due to the presence of mini-Dirac points and pseudo-gaps. Our devices consist in a very large diameter (>80 nm) multiwall carbon nanotubes of high quality, electrically connected by metallic electrodes acting as charge reservoirs. Conductance measurements reveal the presence of van Hove singularities assigned to 1D Moiré superlattice effect and illustrated by electronic structure calculations. PMID:26786067
Thermal transport in disordered one-dimensional spin chains
NASA Astrophysics Data System (ADS)
Poboiko, Igor; Feigel'man, Mikhail
2015-12-01
We study a one-dimensional anisotropic XXZ Heisenberg spin-1/2 chain with weak random fields hizSiz by means of Jordan-Wigner transformation to spinless Luttinger liquid with disorder and bosonization technique. First, we reinvestigate the phase diagram of the system in terms of dimensionless disorder γ =
Characterization of Thermal Transport in One-dimensional Solid Materials.
Liu, Guoqing; Lin, Huan; Tang, Xiaoduan; Bergler, Kevin; Wang, Xinwei
2014-01-01
The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (ρcp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses. PMID:24514072
Characterization of Thermal Transport in One-dimensional Solid Materials
Liu, Guoqing; Lin, Huan; Tang, Xiaoduan; Bergler, Kevin; Wang, Xinwei
2014-01-01
The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (ρcp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses. PMID:24514072
McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P
2015-02-01
In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors. PMID:25621878
McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P
2015-02-01
In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors.
Half-range acceleration for one-dimensional transport problems
Zika, M.R.; Larsen, E.W.
1998-12-31
Researchers have devoted considerable effort to developing acceleration techniques for transport iterations in highly diffusive problems. The advantages and disadvantages of source iteration, rebalance, diffusion synthetic acceleration (DSA), transport synthetic acceleration (TSA), and projection acceleration methods are documented in the literature and will not be discussed here except to note that no single method has proven to be applicable to all situations. Here, the authors describe a new acceleration method that is based solely on transport sweeps, is algebraically linear (and is therefore amenable to a Fourier analysis), and yields a theoretical spectral radius bounded by one-third for all cases. This method does not introduce spatial differencing difficulties (as is the case for DSA) nor does its theoretical performance degrade as a function of mesh and material properties (as is the case for TSA). Practical simulations of the new method agree with the theoretical predictions, except for scattering ratios very close to unity. At this time, they believe that the discrepancy is due to the effect of boundary conditions. This is discussed further.
A one-dimensional heat-transport model for conduit flow in karst aquifers
Long, A.J.; Gilcrease, P.C.
2009-01-01
A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d.
NASA Astrophysics Data System (ADS)
Li, Lei; Liang, Lizhi; Wu, Heng; Zhu, Xinhua
2016-03-01
One-dimensional nanostructures, including nanowires, nanorods, nanotubes, nanofibers, and nanobelts, have promising applications in mesoscopic physics and nanoscale devices. In contrast to other nanostructures, one-dimensional nanostructures can provide unique advantages in investigating the size and dimensionality dependence of the materials' physical properties, such as electrical, thermal, and mechanical performances, and in constructing nanoscale electronic and optoelectronic devices. Among the one-dimensional nanostructures, one-dimensional perovskite manganite nanostructures have been received much attention due to their unusual electron transport and magnetic properties, which are indispensable for the applications in microelectronic, magnetic, and spintronic devices. In the past two decades, much effort has been made to synthesize and characterize one-dimensional perovskite manganite nanostructures in the forms of nanorods, nanowires, nanotubes, and nanobelts. Various physical and chemical deposition techniques and growth mechanisms are explored and developed to control the morphology, identical shape, uniform size, crystalline structure, defects, and homogenous stoichiometry of the one-dimensional perovskite manganite nanostructures. This article provides a comprehensive review of the state-of-the-art research activities that focus on the rational synthesis, structural characterization, fundamental properties, and unique applications of one-dimensional perovskite manganite nanostructures in nanotechnology. It begins with the rational synthesis of one-dimensional perovskite manganite nanostructures and then summarizes their structural characterizations. Fundamental physical properties of one-dimensional perovskite manganite nanostructures are also highlighted, and a range of unique applications in information storages, field-effect transistors, and spintronic devices are discussed. Finally, we conclude this review with some perspectives/outlook and future
ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT
This technical report describes a new sediment transport model and the supporting post-processor, and sampling procedures for sediments in streams. Specifically, the following items are described herein:
EFDC1D - This is a new one-dimensional hydrodynamic and sediment tr...
NASA Astrophysics Data System (ADS)
Sykes, J. F.; Scott, M. E.; Jyrkama, M. I.
2005-05-01
Wilmot Township is located in southwestern Ontario within the Grand River Watershed. The township is approximately 266 square kilometers, of which 80 percent is classified as farmland. A majority of the region relies on groundwater as the source of drinking water and it is therefore important to determine the effect of crop fertilization on the groundwater quality. The purpose of this study is to determine the one-dimensional transport of nitrate through the vadose zone to the water table with attenuation due to biodegradation. The model is simulated over a 30-year period to investigate the impact of seasonal applications of nitrate fertilizers on the concentration at the water table. Based on land use/land class maps, ArcView GIS is used to spatially define the location of fertilizer applications. Fertilizer sources are determined from Statistics Canada's Agricultural Census and include livestock manure and popular commercial fertilizers for the past 30 years. A physically based and readily implemented methodology for estimating recharge, as developed by Jyrkama (2003), is used to approximate the advective velocity through the soil column. This research methodology can be applied at the watershed scale. Future large-scale modeling will be performed on the Grand River Watershed, which is approximately 7000 square kilometers. Municipalities can utilize this model as a management tool to determine the extent of contamination and delineate site sensitive locations, such as well-head protection zones. This research is a first step in developing agricultural contaminant loadings for a regional scale surface water and groundwater model.
NASA Astrophysics Data System (ADS)
Brasiello, Antonio; Crescitelli, Silvestro; Giona, Massimiliano
2016-05-01
We consider the one-dimensional Cattaneo equation for transport of scalar fields such as solute concentration and temperature in mass and heat transport problems, respectively. Although the Cattaneo equation admits a stochastic interpretation-at least in the one-dimensional case-negative concentration values can occur in boundary-value problems on a finite interval. This phenomenon stems from the probabilistic nature of this model: the stochastic interpretation provides constraints on the admissible boundary conditions, as can be deduced from the wave formulation here presented. Moreover, as here shown, energetic inequalities and the dissipative nature of the equation provide an alternative way to derive the same constraints on the boundary conditions derived by enforcing positivity. The analysis reported is also extended to transport problems in the presence of a biasing velocity field. Several general conclusions are drawn from this analysis that could be extended to the higher-dimensional case.
Transport properties of coupled one-dimensional interacting electron systems with impurities
NASA Astrophysics Data System (ADS)
Kimura, Takashi; Kuroki, Kazuhiko; Aoki, Hideo
1995-05-01
We consider two one-dimensional interacting electron systems that are coupled via interchain tunneling to calculate transport properties in the presence of impurities or a single barrier by using the bosonization formalisms for the non-Luttinger-liquid phases on the phase diagram obtained by Fabrizio [Phys. Rev. B 48, 15 838 (1993)]. We find for the weak- and strong-interaction phases, where the superconducting correlation dominates in the ground state, that the interchain transfer enhances the conductivity and the Anderson localization is suppressed. This shows that multichain systems can have unique transport properties.
One-dimensional transport code modeling of the divertor-limiter region in tokamaks
Ogden, J.M.; Singer, C.E.; Post, D.E.; Jensen, R.V.; Seidl, F.G.P.
1981-12-01
A model of the diverter-limiter scrapeoff region has been incorporated into the BALDUR one-dimensional tokamak transport code. Simulations of the proposed Toroidal Fusion Test Reactor (TFTR), and Poloidal Diverter (PDX) experiments and existing Alcator-A tokamak experiments have been carried out for ohmic and neutral beam heated cases. In particular it is studied how the edge conditions and energy-loss mechanisms in PDX depend upon plasma density, and results are compared with analytic estimates. The sensitivity of the results to changes in the transport coefficients and scrapeoff model is discussed with particular reference to the power loading on the TFTR limiter. 13 refs.
One-dimensional transport code modelling of the limiter-divertor region in tokamaks
Ogden, J.M.; Post, D.E.; Jensen, R.V.; Seidl, F.G.P.
1980-02-01
A model of the limiter-divertor scrape-off region has been incorporated into the BALDUR one-dimensional tokamak transport code. Simulations of PDX and ALCATOR have been carried out for ohmic and neutral beam heated cases. In particular, we have studied how the edge conditions and energy loss mechanisms of PDX depend upon plasma density, and compared our results with analytic estimates. The sensitivity of the results to changes in the transport coefficients and scrape-off model is also discussed.
An exact solution of solute transport by one-dimensional random velocity fields
Cvetkovic, V.D.; Dagan, G.; Shapiro, A.M.
1991-01-01
The problem of one-dimensional transport of passive solute by a random steady velocity field is investigated. This problem is representative of solute movement in porous media, for example, in vertical flow through a horizontally stratified formation of variable porosity with a constant flux at the soil surface. Relating moments of particle travel time and displacement, exact expressions for the advection and dispersion coefficients in the Focker-Planck equation are compared with the perturbation results for large distances. The first- and second-order approximations for the dispersion coefficient are robust for a lognormal velocity field. The mean Lagrangian velocity is the harmonic mean of the Eulerian velocity for large distances. This is an artifact of one-dimensional flow where the continuity equation provides for a divergence free fluid flux, rather than a divergence free fluid velocity. ?? 1991 Springer-Verlag.
Wuebbles, D.J.
1981-09-01
Since the LLNL one-dimensional coupled transport and chemical kinetics model of the troposphere and stratosphere was originally developed in 1972 (Chang et al., 1974), there have been many changes to the model's representation of atmospheric physical and chemical processes. A brief description is given of the current LLNL one-dimensional coupled transport and chemical kinetics model of the troposphere and stratosphere.
NASA Astrophysics Data System (ADS)
Wang, Jianjin; He, Dahai; Zhang, Yong; Wang, Jiao; Zhao, Hong
2015-09-01
We study effects of interaction symmetry in one-dimensional, momentum-conserving disordered lattices. It is found that asymmetric and symmetric interparticle interactions may result in significant difference: localized modes can be delocalized by very weak asymmetric interactions but survive much stronger symmetric interactions. Moreover, in the delocalization regime, asymmetric and symmetric interactions also have qualitatively different effects on transport: the former (the latter) may lead to a fast decaying (slow power-law decaying) heat current correlation function and in turn a convergent (divergent) heat conductivity. A method for detecting delocalization in systems at a nonzero temperature is proposed as well.
Photon transport in a one-dimensional nanophotonic waveguide QED system
NASA Astrophysics Data System (ADS)
Liao, Zeyang; Zeng, Xiaodong; Nha, Hyunchul; Zubairy, M. Suhail
2016-06-01
The waveguide quantum electrodynamics (QED) system may have important applications in quantum device and quantum information technology. In this article we review the methods being proposed to calculate photon transport in a one-dimensional (1D) waveguide coupled to quantum emitters. We first introduce the Bethe ansatz approach and the input–output formalism to calculate the stationary results of a single photon transport. Then we present a dynamical time-dependent theory to calculate the real-time evolution of the waveguide QED system. In the longtime limit, both the stationary theory and the dynamical calculation give the same results. Finally, we also briefly discuss the calculations of the multiphoton transport problems.
Photon transport in a one-dimensional nanophotonic waveguide QED system
NASA Astrophysics Data System (ADS)
Liao, Zeyang; Zeng, Xiaodong; Nha, Hyunchul; Zubairy, M. Suhail
2016-06-01
The waveguide quantum electrodynamics (QED) system may have important applications in quantum device and quantum information technology. In this article we review the methods being proposed to calculate photon transport in a one-dimensional (1D) waveguide coupled to quantum emitters. We first introduce the Bethe ansatz approach and the input-output formalism to calculate the stationary results of a single photon transport. Then we present a dynamical time-dependent theory to calculate the real-time evolution of the waveguide QED system. In the longtime limit, both the stationary theory and the dynamical calculation give the same results. Finally, we also briefly discuss the calculations of the multiphoton transport problems.
Proceedings of the Advanced Seminar on one-dimensional, open-channel Flow and transport modeling
Schaffranek, Raymond W.
1989-01-01
In view of the increased use of mathematical/numerical simulation models, of the diversity of both model investigations and informational project objectives, and of the technical demands of complex model applications by U.S. Geological Survey personnel, an advanced seminar on one-dimensional open-channel flow and transport modeling was organized and held on June 15-18, 1987, at the National Space Technology Laboratory, Bay St. Louis, Mississippi. Principal emphasis in the Seminar was on one-dimensional flow and transport model-implementation techniques, operational practices, and application considerations. The purposes of the Seminar were to provide a forum for the exchange of information, knowledge, and experience among model users, as well as to identify immediate and future needs with respect to model development and enhancement, user support, training requirements, and technology transfer. The Seminar program consisted of a mix of topical and project presentations by Geological Survey personnel. This report is a compilation of short papers that summarize the presentations made at the Seminar.
Oxygen isotopic transport and exchange during fluid flow: One-dimensional models and applications
Bowman, J.R. ); Willett, S.D. ); Cook, S.J. Environ Corp., Houston, TX )
1994-01-01
In this work the authors investigate the consequences of fluid flow and fluid-rock interaction to the isotopic evolution of fluids and rock with one-dimensional transport models of fluid flow and oxygen isotope exchange. Transport models dealing with stable isotopes are well established in recent geochemical literature. The authors extend previous treatments by presenting the derivation of both analytical and numerical solutions to the transport equations incorporating simultaneously advection, diffusion and hydrodynamic dispersion, and kinetics of isotopic exchange. The increased generality of numerical solutions allows the incorporation of other effects which control the spatial patterns of [delta][sup 18]O values developed in rocks and fluids including multiple reactive species and temperature gradients. The authors discuss the effects of flow parameters, conditions of isotopic exchange, and temperature gradients on the spatial patterns of isotopic shifts produced in rock sequences subjected to fluid flow, and on conventionally calculated W/R ratios for these rock sequences. Finally, the authors examine the implications of oxygen isotope transport for two natural systems where isotopic shifts or gradients could be interpreted in terms of unidirectional fluid infiltration. Solutions of one-dimensional transport equations including the mechanisms of advection, diffusion, hydrodynamic dispersion, and non-equilibrium exchange between water and rock indicate that the time-space evolution of oxygen isotopic compositions of rock and infiltrating fluid is dependent on (1) the rate of fluid infiltration, (2) the diffusive and dispersive properties of the rock matrix, (3) the rate of isotopic exchange, and (4) the rock-water mass oxygen ratio in a unit volume of water-saturated, porous rock. 56 refs., 18 figs., 2 tabs.
Eigen decomposition solution to the one-dimensional time-dependent photon transport equation.
Handapangoda, Chintha C; Pathirana, Pubudu N; Premaratne, Malin
2011-02-14
The time-dependent one-dimensional photon transport (radiative transfer) equation is widely used to model light propagation through turbid media with a slab geometry, in a vast number of disciplines. Several numerical and semi-analytical techniques are available to accurately solve this equation. In this work we propose a novel efficient solution technique based on eigen decomposition of the vectorized version of the photon transport equation. Using clever transformations, the four variable integro-differential equation is reduced to a set of first order ordinary differential equations using a combination of a spectral method and the discrete ordinates method. An eigen decomposition approach is then utilized to obtain the closed-form solution of this reduced set of ordinary differential equations. PMID:21369115
NASA Astrophysics Data System (ADS)
Kopelevich, Dmitry I.
2013-10-01
Transport of a fullerene-like nanoparticle across a lipid bilayer is investigated by coarse-grained molecular dynamics (MD) simulations. Potentials of mean force (PMF) acting on the nanoparticle in a flexible bilayer suspended in water and a bilayer restrained to a flat surface are computed by constrained MD simulations. The rate of the nanoparticle transport into the bilayer interior is predicted using one-dimensional Langevin models based on these PMFs. The predictions are compared with the transport rates obtained from a series of direct (unconstrained) MD simulations of the solute transport into the flexible bilayer. It is observed that the PMF acting on the solute in the flexible membrane underestimates the transport rate by more than an order of magnitude while the PMF acting on the solute in the restrained membrane yields an accurate estimate of the activation energy for transport into the flexible membrane. This paradox is explained by a coexistence of metastable membrane configurations for a range of the solute positions inside and near the flexible membrane. This leads to a significant reduction of the contribution of the transition state to the mean force acting on the solute. Restraining the membrane shape ensures that there is only one stable membrane configuration corresponding to each solute position and thus the transition state is adequately represented in the PMF. This mechanism is quite general and thus this phenomenon is expected to occur in a wide range of interfacial systems. A simple model for the free energy landscape of the coupled solute-membrane system is proposed and validated. This model explicitly accounts for effects of the membrane deformations on the solute transport and yields an accurate prediction of the activation energy for the solute transport.
Lee, Sang Uck; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki
2010-12-01
We present a systematic analysis of electron transport characteristics for one-dimensional heterojunctions with two multi-nitrogen-doped (multi-N-doped) capped carbon nanotubes (CNTs) facing one another at different numbers of nitrogen atoms and conformations. Our results show that the modification of the molecular orbitals by the nitrogen dopants generates conducting channels in the designed heterojunctions inducing multi-switching behavior with sequential negative differential resistance (NDR). The NDR behavior significantly depends on the doping site and conformation of doped nitrogen atoms. Furthermore, we provide a clear interpretation for the NDR behavior by a rigid shift model of the HOMO- and LUMO-filtered energy levels in the left and right electrodes under the applied biases. We believe that our results will give an insight into the design and implementation of various electronic logic functions based on CNTs for applications in the field of nanoelectronics.
Analytically-derived sensitivities in one-dimensional models of solute transport in porous media
Knopman, D.S.
1987-01-01
Analytically-derived sensitivities are presented for parameters in one-dimensional models of solute transport in porous media. Sensitivities were derived by direct differentiation of closed form solutions for each of the odel, and by a time integral method for two of the models. Models are based on the advection-dispersion equation and include adsorption and first-order chemical decay. Boundary conditions considered are: a constant step input of solute, constant flux input of solute, and exponentially decaying input of solute at the upstream boundary. A zero flux is assumed at the downstream boundary. Initial conditions include a constant and spatially varying distribution of solute. One model simulates the mixing of solute in an observation well from individual layers in a multilayer aquifer system. Computer programs produce output files compatible with graphics software in which sensitivities are plotted as a function of either time or space. (USGS)
1985-02-01
Version 00 TP1 is a transport theory code, developed to determine reactivity effects and kinetic parameters such as effective delayed neutron fractions and mean generation time by applying the usual perturbation formalism for one-dimensional geometry.
Code System Calculate One-Dimensional Vertical Transport Unsaturated Soil Zone
1989-03-01
SESOIL, as an integrated screening-level soil compartment model, is designed to simultaneously model water transport, sediment transport, and pollutant fate. SESOIL is a one-dimensional vertical transport model for the unsaturated soil zone. Only one compound at a time can be considered. The model is based on mass balance and equilibrium partitioning of the chemical between different phases (dissolved, sorbed, vapor, and pure). The SESOIL model was designed to perform long-term simulations of chemical transport andmore » transformations in the soil and uses theoretically derived equations to represent water transport, sediment transport on the land surface, pollutant transformation, and migration of the pollutant to the atmosphere and groundwater. Climatic data, compartment geometry, and soil and chemical property data are the major components used in the equations. SESOIL was developed as a screening-level model, utilizing less soil, chemical, and meteorological values as input than most other similar models. Output of SESOIL includes time-varying pollutant concentrations at various soil depths and pollutant loss from the unsaturated zone in terms of surface runoff, percolation to the groundwater, volatilization, and degradation. The February 1995 release corrects an error that caused the code to fail when average monthly air temperature was -10C and includes an improved iteration procedure for the mass balance equations in the model. PLEASE NOTE: The RISKPRO information management software (see OTHER PROG/OPER SYS INFO) was used by the developers of the New SESOIL User''s Guide in their study and revisions of SESOIL. Using RISKPRO in conjunction with SESOIL is an option, and it may provide the easiest way to use SESOIL. The other option, use of SESOIL in stand-alone mode, has been tested and used. The stand-alone option is covered in ''Instructions for Running Stand-Alone SESOIL Code'', and in ''A Seasonal Soil Compartment Model''.« less
One-Dimensional Solute Transport in Variably Saturated Soil Using a Geocentrifuge Apparatus
NASA Astrophysics Data System (ADS)
Mattson, E. D.; Baker, K. E.; Palmer, C. D.; Smith, R. W.; Simunek, J.
2003-12-01
Solute transport data in variably saturated porous media have been difficult to obtain due to long experimental times required to conduct such experiments. Larger length scales of tens of cm require months of experimental time. These long experimental times increase the likelihood of undesirable secondary effects, such as biofouling and instrumentation failure compromising the experimental results. The geocentrifuge offers a potential experimental technique to shorten experimental time scales and thereby overcome these limitations. One-dimensional solute transport experiments (10-cm diameter by 30-cm in length) were conducted using the INEEL 2-m geocentrifuge. Potassium bromide was used as a tracer through Ottawa quartz sand to develop geocentrifuge experimental methodologies and to test a modified numerical tool to design and analyze the results from these experiments. Breakthrough curves were determined through in-flight monitoring of the electrical conductivity of the outflow at 10- and 20-``g''s. Solute transport velocity is proportional to the applied centrifugal acceleration. Breakthrough curves presented in this paper were obtained in less than 2 hours. The time it took to obtain these experimental results is inversely proportional to the applied centrifugal acceleration and is a fraction of the time that it would have taken in using traditional laboratory methods. A modified version of HYDRUS-1D was used to evaluate the solute breakthrough curves. The success of these geocentrifuge experiments suggests that the geocentrifuge technique is a practical and faster experimental methodology to complete tracer experiments in variable saturated media.
Degenerate Bogdanov-Takens bifurcations in a one-dimensional transport model of a fusion plasma
NASA Astrophysics Data System (ADS)
de Blank, H. J.; Kuznetsov, Yu. A.; Pekkér, M. J.; Veldman, D. W. M.
2016-09-01
Experiments in tokamaks (nuclear fusion reactors) have shown two modes of operation: L-mode and H-mode. Transitions between these two modes have been observed in three types: sharp, smooth and oscillatory. The same modes of operation and transitions between them have been observed in simplified transport models of the fusion plasma in one spatial dimension. We study the dynamics in such a one-dimensional transport model by numerical continuation techniques. To this end the MATLAB package CL_MATCONTL was extended with the continuation of (codimension-2) Bogdanov-Takens bifurcations in three parameters using subspace reduction techniques. During the continuation of (codimension-2) Bogdanov-Takens bifurcations in 3 parameters, generically degenerate Bogdanov-Takens bifurcations of codimension-3 are detected. However, when these techniques are applied to the transport model, we detect a degenerate Bogdanov-Takens bifurcation of codimension 4. The nearby 1- and 2-parameter slices are in agreement with the presence of this codimension-4 degenerate Bogdanov-Takens bifurcation, and all three types of L-H transitions can be recognized in these slices. The same codimension-4 situation is observed under variation of the additional parameters in the model, and under some modifications of the model.
Generalization of one-dimensional solute transport: A stochastic-convective flow conceptualization
NASA Astrophysics Data System (ADS)
Simmons, C. S.
1986-04-01
A stochastic-convective representation of one-dimensional solute transport is derived. It is shown to conceptually encompass solutions of the conventional convection-dispersion equation. This stochastic approach, however, does not rely on the assumption that dispersive flux satisfies Fick's diffusion law. Observable values of solute concentration and flux, which together satisfy a conservation equation, are expressed as expectations over a flow velocity ensemble, representing the inherent random processess that govern dispersion. Solute concentration is determined by a Lagrangian pdf for random spatial displacements, while flux is determined by an equivalent Eulerian pdf for random travel times. A condition for such equivalence is derived for steady nonuniform flow, and it is proven that both Lagrangian and Eulerian pdfs are required to account for specified initial and boundary conditions on a global scale. Furthermore, simplified modeling of transport is justified by proving that an ensemble of effectively constant velocities always exists that constitutes an equivalent representation. An example of how a two-dimensional transport problem can be reduced to a single-dimensional stochastic viewpoint is also presented to further clarify concepts.
A transport based one-dimensional perturbation code for reactivity calculations in metal systems
Wenz, T.R.
1995-02-01
A one-dimensional reactivity calculation code is developed using first order perturbation theory. The reactivity equation is based on the multi-group transport equation using the discrete ordinates method for angular dependence. In addition to the first order perturbation approximations, the reactivity code uses only the isotropic scattering data, but cross section libraries with higher order scattering data can still be used with this code. The reactivity code obtains all the flux, cross section, and geometry data from the standard interface files created by ONEDANT, a discrete ordinates transport code. Comparisons between calculated and experimental reactivities were done with the central reactivity worth data for Lady Godiva, a bare uranium metal assembly. Good agreement is found for isotopes that do not violate the assumptions in the first order approximation. In general for cases where there are large discrepancies, the discretized cross section data is not accurately representing certain resonance regions that coincide with dominant flux groups in the Godiva assembly. Comparing reactivities calculated with first order perturbation theory and a straight {Delta}k/k calculation shows agreement within 10% indicating the perturbation of the calculated fluxes is small enough for first order perturbation theory to be applicable in the modeled system. Computation time comparisons between reactivities calculated with first order perturbation theory and straight {Delta}k/k calculations indicate considerable time can be saved performing a calculation with a perturbation code particularly as the complexity of the modeled problems increase.
Uncertainty estimation in one-dimensional heat transport model for heterogeneous porous medium.
Chang, Ching-Min; Yeh, Hund-Der
2014-01-01
In many practical applications, the rates for ground water recharge and discharge are determined based on the analytical solution developed by Bredehoeft and Papadopulos (1965) to the one-dimensional steady-state heat transport equation. Groundwater flow processes are affected by the heterogeneity of subsurface systems; yet, the details of which cannot be anticipated precisely. There exists a great deal of uncertainty (variability) associated with the application of Bredehoeft and Papadopulos' solution (1965) to the field-scale heat transport problems. However, the quantification of uncertainty involved in such application has so far not been addressed, which is the objective of this wok. In addition, the influence of the statistical properties of log hydraulic conductivity field on the variability in temperature field in a heterogeneous aquifer is also investigated. The results of the analysis demonstrate that the variability (or uncertainty) in the temperature field increases with the correlation scale of the log hydraulic conductivity covariance function and the variability of temperature field also depends positively on the position.
NASA Astrophysics Data System (ADS)
Paradiso, Daniele; Perelli Cippo, Enrico; Gorini, Giuseppe; Rossi, Giorgio; Larese, John Z.
The development of new materials for use in energy and environmental applications is of great interest, in particular in the areas of gas separation and carbon capture, where molecular transport plays a significant role. The dipeptides are organic molecules that offer an attractive possibility in such areas, because they form open hexagonal crystalline structures (space group P61) with quasi one-dimensional channels of tunable pore diameters in the range 3-6 Å. These molecular crystals exhibit selective adsorption, as well as, water and gas transport properties: these are believed to result from collective vibrations of the crystal structure that are coupled to the motions of the guest molecules within the channels. Current studies focus on characterizing the system methane and L-Isoleucyl-L-Valine (IV): this was initially done with high-resolution adsorption isotherms; then, high-resolution Inelastic Neutron Scattering measurements at the Spallation Neutron Source (BASIS spectrometer) revealed clear rotational tunneling peaks, offering details to unravel the potential energy surface of the system, as well as, evidences that channels flexibility and dynamical motion of the molecules have influence on the dipeptides adsorption properties.
Runkel, Robert L.
2010-01-01
OTEQ is a mathematical simulation model used to characterize the fate and transport of waterborne solutes in streams and rivers. The model is formed by coupling a solute transport model with a chemical equilibrium submodel. The solute transport model is based on OTIS, a model that considers the physical processes of advection, dispersion, lateral inflow, and transient storage. The equilibrium submodel is based on MINTEQ, a model that considers the speciation and complexation of aqueous species, acid-base reactions, precipitation/dissolution, and sorption. Within OTEQ, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (waterborne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach. The model's ability to simulate pH, precipitation/dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between instream chemistry and hydrologic transport at the field scale. This report details the development and application of OTEQ. Sections of the report describe model theory, input/output specifications, model applications, and installation instructions. OTEQ may be obtained over the Internet at http://water.usgs.gov/software/OTEQ.
2013-01-01
Single crystalline one-dimensional (1D) nanostructures of silver telluride (Ag2Te) with well-controlled shapes and sizes were synthesized via the hydrothermal reduction of sodium tellurite (Na2TeO3) in a mixed solution. The morphological evolution of various 1D nanostructures was mainly determined by properly controlling the nucleation and growth process of Ag2Te in different reaction times. Based on the transmission electron microscopy and scanning electron microscopy studies, the formation mechanism for these 1D nanostructures was rationally interpreted. In addition, the current–voltage (I-V) characteristics as a function of magnetic field of the highly single crystal Ag2Te nanowires were systematically measured. From the investigation of I-V characteristics, we have observed a rapid change of the current in low magnetic field, which can be used as the magnetic field sensor. The magneto-resistance behavior of the Ag2Te nanowires with monoclinic structure was also investigated. Comparing to the bulk and thin film materials, we found that there is generally a larger change in R (T) as the sample size is reduced, which indicates that the size of the sample has a certain impact on magneto-transport properties. Simultaneously, some possible reasons resulting in the observed large positive magneto-resistance behavior are discussed. PMID:23958372
Single-photon transport through an atomic chain coupled to a one-dimensional nanophotonic waveguide
NASA Astrophysics Data System (ADS)
Liao, Zeyang; Zeng, Xiaodong; Zhu, Shi-Yao; Zubairy, M. Suhail
2015-08-01
We study the dynamics of a single-photon pulse traveling through a linear atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide. We derive a time-dependent dynamical theory for this collective many-body system which allows us to study the real time evolution of the photon transport and the atomic excitations. Our analytical result is consistent with previous numerical calculations when there is only one atom. For an atomic chain, the collective interaction between the atoms mediated by the waveguide mode can significantly change the dynamics of the system. The reflectivity of a photon can be tuned by changing the ratio of coupling strength and the photon linewidth or by changing the number of atoms in the chain. The reflectivity of a single-photon pulse with finite bandwidth can even approach 100 % . The spectrum of the reflected and transmitted photon can also be significantly different from the single-atom case. Many interesting physical phenomena can occur in this system such as the photonic band-gap effects, quantum entanglement generation, Fano-like interference, and superradiant effects. For engineering, this system may serve as a single-photon frequency filter, single-photon modulation, and may find important applications in quantum information.
Single Photon Transport through an Atomic Chain Coupled to a One-dimensional Photonic Waveguide
NASA Astrophysics Data System (ADS)
Liao, Zeyang; Zeng, Xiaodong; Zubairy, M. Suhail
2015-03-01
We study the dynamics of a single photon pulse travels through a linear atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide. We derive a time-dependent dynamical theory for this collective many-body system which allows us to study the real time evolution of the photon transport and the atomic excitations. Our result is consistent with previous calculations when there is only one atom. For an atomic chain, the collective interaction between the atoms mediated by the waveguide mode can significantly change the dynamics of the system. The reflectivity can be tuned by changing the ratio of coupling strength and the photon linewidth or by changing the number of atoms in the chain. The reflectivity of a single photon pulse with finite bandwidth can even approach 100%. The spectrum of the reflected and transmitted photon can also be significantly different from the single atom case. Many interesting physics can occur in this system such as the photonic bandgap effects, quantum entanglement generation, Fano-type interference, superradiant effects and nonlinear frequency conversion. For engineering, this system may be used as a single photon frequency filter, single photon modulation and photon storage.
One-dimensional edge state transport in a topological Kondo insulator
NASA Astrophysics Data System (ADS)
Nakajima, Yasuyuki; Syers, Paul; Wang, Xiangfeng; Wang, Renxiong; Paglione, Johnpierre
2016-03-01
Topological insulators, with metallic boundary states protected against time-reversal-invariant perturbations, are a promising avenue for realizing exotic quantum states of matter, including various excitations of collective modes predicted in particle physics, such as Majorana fermions and axions. According to theoretical predictions, a topological insulating state can emerge from not only a weakly interacting system with strong spin-orbit coupling, but also in insulators driven by strong electron correlations. The Kondo insulator compound SmB6 is an ideal candidate for realizing this exotic state of matter, with hybridization between itinerant conduction electrons and localized f-electrons driving an insulating gap and metallic surface states at low temperatures. Here we exploit the existence of surface ferromagnetism in SmB6 to investigate the topological nature of metallic surface states by studying magnetotransport properties at very low temperatures. We find evidence of one-dimensional surface transport with a quantized conductance value of e2/h originating from the chiral edge channels of ferromagnetic domain walls, providing strong evidence that topologically non-trivial surface states exist in SmB6.
Self-consistent mode-coupling approach to one-dimensional heat transport.
Delfini, Luca; Lepri, Stefano; Livi, Roberto; Politi, Antonio
2006-06-01
In the present Rapid Communication we present an analytical and numerical solution of the self-consistent mode-coupling equations for the problem of heat conductivity in one-dimensional systems. Such a solution leads us to propose a different scenario to accommodate the known results obtained so far for this problem. More precisely, we conjecture that the universality class is determined by the leading order of the nonlinear interaction potential. Moreover, our analysis allows us to determine the memory kernel, whose expression puts on a more firm basis the previously conjectured connection between anomalous heat conductivity and anomalous diffusion.
Proceedings of the Advanced Seminar on one-dimensional, open-channel Flow and transport modeling
Schaffranek, R. W.
1989-01-01
If several limiting assumptions are valid, flow in a waterbody can be represented by one-dimensional equations of unsteady open-channel flow. The equations can be expressed in a number of forms of varying complexity, depending upon the choice of dependent variables used in their formulation and on possible additional limiting assumptions which allow various terms to be excluded. The assumptions are related to the physical characteristics of water and water flow, characteristics of the flow channel, and the effects of boundary friction and turbulence. With the assumptions, unsteady open-channel flow can be described by two dependent variables, either flow discharge and water surface elevation or flow velocity and cross-sectional area. These variables are expressed as a function of distance and time at a given cross section. The equations are derived from the principles of conservation of mass and momentum. Additional variables may be included to account for wind effects , the Coriolis effect, overbank storage, and other influences. Equations are formulated for unsteady gradually varied flow, steady gradually varied flow, steady uniform flow (the Manning equation), and other variations. More rudimentary continuity-based equations, such as the kinematic wave equation and storage-routing equations, are inherently more empirical and considerable caution must be exercised in their use. Models employing the full dynamic equations for simulating unsteady open-channel flow should be used whenever possible. (See also W90-10652) (Tappert-PTT)
NASA Astrophysics Data System (ADS)
Liu, Jingyi; Zhang, Wenzhao; Li, Xun; Yan, Weibin; Zhou, Ling
2016-10-01
We investigate the two-photon transport properties inside one-dimensional waveguide side coupled to an atom-optomechanical system, aiming to control the two-photon transport by using the nonlinearity. By generalizing the scheme of Phys. Rev. A 90, 033832, we show that Kerr nonlinearity induced by the four-level atoms is remarkable and can make the photons antibunching, while the nonlinear interaction of optomechanical coupling participates in both the single photon and the two photon processes so that it can make the two photons exhibiting bunching and antibunching.
Heat and particle transport in a one-dimensional hard-point gas model with on-site potential
Wang, Lei
2015-05-15
Heat and particle transport in a one-dimensional hard-point gas of elastically colliding particles are studied. In the nonequal mass case, due to the presence of on-site potential, the heat conduction of the model obeys the Fourier law and all the transport coefficients asymptotically approach constants in the thermodynamic limit. The thermoelectric figure of merit ZT increases slowly with the system length L and is proportional to the height of the potential barriers H in high H regime. These findings may serve as a guide for future theoretical and experimental studies.
A One-group, One-dimensional Transport Benchmark in Cylindrical Geometry
Barry Ganapol; Abderrafi M. Ougouag
2006-06-01
A 1-D, 1-group computational benchmark in cylndrical geometry is described. This neutron transport benchmark is useful for evaluating reactor concepts that possess azimuthal symmetry such as a pebble-bed reactor.
Electronic transport properties of one dimensional lithium nanowire using density functional theory
Thakur, Anil; Kumar, Arun; Chandel, Surjeet; Ahluwalia, P. K.
2015-05-15
Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.
Deterministic proton transport solving a one dimensional Fokker-Planck equation
Marr, D.; Prael, R.; Adams, K.; Alcouffe, R.
1997-10-01
The transport of protons through matter is characterized by many interactions which cause small deflections and slight energy losses. The few which are catastrophic or cause large angle scattering can be viewed as extinction for many applications. The transport of protons at this level of approximation can be described by a Fokker Planck Equation. This equation is solved using a deterministic multigroup differencing scheme with a highly resolved set of discrete ordinates centered around the beam direction which is adequate to properly account for deflections and energy losses due to multiple Coulomb scattering. Comparisons with LAHET for a large variety of problems ranging from 800 MeV protons on a copper step wedge to 10 GeV protons on a sandwich of material are presented. The good agreement with the Monte Carlo code shows that the solution method is robust and useful for approximate solutions of selected proton transport problems.
One dimensional heavy ion beam transport: Energy independent model. M.S. Thesis
NASA Technical Reports Server (NTRS)
Farhat, Hamidullah
1990-01-01
Attempts are made to model the transport problem for heavy ion beams in various targets, employing the current level of understanding of the physics of high-charge and energy (HZE) particle interaction with matter are made. An energy independent transport model, with the most simplified assumptions and proper parameters is presented. The first and essential assumption in this case (energy independent transport) is the high energy characterization of the incident beam. The energy independent equation is solved and application is made to high energy neon (NE-20) and iron (FE-56) beams in water. The numerical solutions is given and compared to a numerical solution to determine the accuracy of the model. The lower limit energy for neon and iron to be high energy beams is calculated due to Barkas and Burger theory by LBLFRG computer program. The calculated values in the density range of interest (50 g/sq cm) of water are: 833.43 MeV/nuc for neon and 1597.68 MeV/nuc for iron. The analytical solutions of the energy independent transport equation gives the flux of different collision terms. The fluxes of individual collision terms are given and the total fluxes are shown in graphs relative to different thicknesses of water. The values for fluxes are calculated by the ANASTP computer code.
NASA Astrophysics Data System (ADS)
Soldano, Caterina
The investigation of the electronic and magnetotransport properties at low temperature in individual MWNT with embedded clusters are here presented. The majority of studies of transport in MWNT reported in literature has been carried out on arc-discharge grown tubes, generally considered "clean" and defect-free. In this project, individual MWNT grown in alumina template are used; these tubes are highly disordered compared for example to arc-discharge ones, conditions that dramatically will impact the charge transport. As-fabricated devices are in general highly resistive. A large decrease in the value of the device resistance can be achieved through a controlled and fast high-bias sweep method (HBT) across the sample. Scanning electron microscopy analysis shows that this method induces a metal (platinum) decoration of the MWNT surface as a consequence of the large amount of Joule heating developed during the sweep. Temperature dependence study (5
One-dimensional transport in hybrid metal-semiconductor nanotube systems
NASA Astrophysics Data System (ADS)
Gelin, M. F.; Bondarev, I. V.
2016-03-01
We develop an electron transport theory for the hybrid system of a semiconducting carbon nanotube that encapsulates a one-atom-thick metallic wire. The theory predicts Fano resonances in electron transport through the system, whereby the interaction of electrons on the wire with nanotube plasmon generated near fields blocks some of the wire transmission channels to open up the new coherent plasmon-mediated channel in the nanotube forbidden gap outside the wire transmission band. Such a channel makes the entire hybrid system transparent in the energy domain where neither wire nor nanotube is individually transparent. This effect can be used to control and optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems.
Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials
Lotz, Mikkel R.; Boll, Mads; Bøggild, Peter; Petersen, Dirch H.; Hansen, Ole; Kjær, Daniel
2014-08-04
The presence of defects in graphene have for a long time been recognized as a bottleneck for its utilization in electronic and mechanical devices. We recently showed that micro four-point probes may be used to evaluate if a graphene film is truly 2D or if defects in proximity of the probe will lead to a non-uniform current flow characteristic of lower dimensionality. In this work, simulations based on a finite element method together with a Monte Carlo approach are used to establish the transition from 2D to quasi-1D current transport, when applying a micro four-point probe to measure on 2D conductors with an increasing amount of line-shaped defects. Clear 2D and 1D signatures are observed at low and high defect densities, respectively, and current density plots reveal the presence of current channels or branches in defect configurations yielding 1D current transport. A strong correlation is found between the density filling factor and the simulation yield, the fraction of cases with 1D transport and the mean sheet conductance. The upper transition limit is shown to agree with the percolation threshold for sticks. Finally, the conductance of a square sample evaluated with macroscopic edge contacts is compared to the micro four-point probe conductance measurements and we find that the micro four-point probe tends to measure a slightly higher conductance in samples containing defects.
NASA Astrophysics Data System (ADS)
Kosevich, Yuriy A.; Savin, Alexander V.
2016-10-01
We provide molecular dynamics simulation of heat transport and energy diffusion in one-dimensional molecular chains with different interparticle pair potentials at zero and non-zero temperature. We model the thermal conductivity (TC) and energy diffusion (ED) in the chain of coupled rotators and in the Lennard-Jones chain either without or with the confining parabolic interparticle potential. The considered chains without the confining potential have normal TC and ED at non-zero temperature, while the corresponding chains with the confining potential are characterized by anomalous (diverging with the system length) TC and superdiffusion of energy. Similar effect is produced by the anharmonic quartic confining pair potential. We confirm in such a way that, surprisingly, the confining pair potential makes both heat transport and energy diffusion anomalous in one-dimensional phononic systems. We show that the normal TC is always accompanied by the normal ED in the thermalized anharmonic chains, while the superdiffusion of energy occurs in the thermalized chains with only anomalous heat transport.
Theory of nonlinear ballistic transport in quasi-one-dimensional constrictions
NASA Astrophysics Data System (ADS)
Xu, Hongqi
1993-06-01
We report on quantum-mechanical calculations of the differential conductance G of a ballistic and uniform constriction in the nonlinear-response regime of transport. The constriction has been connected to two semi-infinite two-dimensional electron gases, which serve as emitter and collector when a source-drain voltage Vsd is applied. In accordance with the fact that there should not be any electron backscatterings in the idealized constriction, it is assumed, in the calculations, that the electrostatic potential is flat in the constriction along the transport direction and the voltage drops of the applied source-drain voltage occur only at the ends of the constriction. Our calculations show that in addition to the conductance plateaus, which are quantized at multiples of 2e2/h in the linear-response regime of transport, new plateau structure develops as the source-drain voltage is increased. We predict that the edges of the conductance plateaus are shifted linearly with the applied source-drain voltage. Based on this prediction we discuss a method proposed for measuring the energy spacings of the sublevels of the constriction. Under the assumption that the transmission of an electron depends only on the difference between the energy of the electron incident on the constriction and the bottom of the electrostatic confining potential, a simple analytical form is derived for the nonlinear differential conductance of the constriction. This form complements our exact calculational results and shows that at zero temperature the differential conductance at a given finite Vsd and a given Fermi energy EF is a weighted average of two zero-Vsd conductances at Fermi energies of EF+(1-α)eVsd and EF-αeVsd, where α describes the fraction of the source-drain voltage that drops on the connection between the constriction and the drain reservoir.
O'Dell, R.D.; Brinkley, F.W. Jr.; Marr, D.R.
1982-02-01
ONEDANT is designed for the CDC-7600, but the program has been implemented and run on the IBM-370/190 and CRAY-I computers. ONEDANT solves the one-dimensional multigroup transport equation in plane, cylindrical, spherical, and two-angle plane geometries. Both regular and adjoint, inhomogeneous and homogeneous (k/sub eff/ and eigenvalue search) problems subject to vacuum, reflective, periodic, white, albedo, or inhomogeneous boundary flux conditions are solved. General anisotropic scattering is allowed and anisotropic inhomogeneous sources are permitted. ONEDANT numerically solves the one-dimensional, multigroup form of the neutral-particle, steady-state form of the Boltzmann transport equation. The discrete-ordinates approximation is used for treating the angular variation of the particle distribution and the diamond-difference scheme is used for phase space discretization. Negative fluxes are eliminated by a local set-to-zero-and-correct algorithm. A standard inner (within-group) iteration, outer (energy-group-dependent source) iteration technique is used. Both inner and outer iterations are accelerated using the diffusion synthetic acceleration method. (WHK)
Quantum ballistic transport by interacting two-electron states in quasi-one-dimensional channels
Huang, Danhong; Gumbs, Godfrey; Abranyos, Yonatan; Pepper, Michael; Kumar, Sanjeev
2015-11-15
For quantum ballistic transport of electrons through a short conduction channel, the role of Coulomb interaction may significantly modify the energy levels of two-electron states at low temperatures as the channel becomes wide. In this regime, the Coulomb effect on the two-electron states is calculated and found to lead to four split energy levels, including two anticrossing-level and two crossing-level states. Moreover, due to the interplay of anticrossing and crossing effects, our calculations reveal that the ground two-electron state will switch from one anticrossing state (strong confinement) to a crossing state (intermediate confinement) as the channel width gradually increases and then back to the original anticrossing state (weak confinement) as the channel width becomes larger than a threshold value. This switching behavior leaves a footprint in the ballistic conductance as well as in the diffusion thermoelectric power of electrons. Such a switching is related to the triple spin degeneracy as well as to the Coulomb repulsion in the central region of the channel, which separates two electrons away and pushes them to different channel edges. The conductance reoccurrence region expands from the weak to the intermediate confinement regime with increasing electron density.
Yoo-Kong, Sikarin; Liewrian, Watchara
2015-12-01
We report on a theoretical investigation concerning the polaronic effect on the transport properties of a charge carrier in a one-dimensional molecular chain. Our technique is based on the Feynman's path integral approach. Analytical expressions for the frequency-dependent mobility and effective mass of the carrier are obtained as functions of electron-phonon coupling. The result exhibits the crossover from a nearly free particle to a heavily trapped particle. We find that the mobility depends on temperature and decreases exponentially with increasing temperature at low temperature. It exhibits large polaronic-like behaviour in the case of weak electron-phonon coupling. These results agree with the phase transition (A.S. Mishchenko et al., Phys. Rev. Lett. 114, 146401 (2015)) of transport phenomena related to polaron motion in the molecular chain. PMID:26701710
Kavitha, L; Priya, R; Ayyappan, N; Gopi, D; Jayanthi, S
2016-01-01
The dynamics of protons in a one-dimensional hydrogen-bonded (HB) polypeptide chain (PC) is investigated theoretically. A new Hamiltonian is formulated with the inclusion of higher-order molecular interactions between peptide groups (PGs). The wave function of the excitation state of a single particle is replaced by a new wave function of a two-quanta quasi-coherent state. The dynamics is governed by a higher-order nonlinear Schrödinger equation and the energy transport is performed by the proton soliton. A nonlinear multiple-scale perturbation analysis has been performed and the evolution of soliton parameters such as velocity and amplitude is explored numerically. The proton soliton is thermally stable and very robust against these perturbations. The energy transport by the proton soliton is more appropriate to understand the mechanism of energy transfer in biological processes such as muscle contraction, DNA replication, and neuro-electric pulse transfer on biomembranes.
NASA Astrophysics Data System (ADS)
Xiong, Daxing
2016-04-01
Previous studies have suggested a crossover from superdiffusive to normal heat transport in one-dimensional (1D) anharmonic oscillator systems with a double-well type interatomic interaction like V(ξ )=-{ξ2}/2+{ξ4}/4 , when the system temperature is varied. In order to better understand this unusual manner of thermal transport, here we perform a direct dynamics simulation to examine how the spreading processes of the three physical quantities, i.e. the heat, the total energy and the momentum, would depend on temperature. We find three main points that are worth noting. (i) The crossover from superdiffusive to normal heat transport is well verified from a new perspective of heat spread. (ii) The spreading of the total energy is found to be very distinct from heat diffusion, especially under some temperature regimes, energy is strongly localized, while heat can be superdiffusive. So one should take care to derive a general connection between the heat conduction and energy diffusion. (iii) In a narrow range of temperatures, the spreading of momentum implies clear unusual non-ballistic behaviors; however, such unusual transport of momentum cannot be directly related to the normal transport of heat. An analysis of phonon spectra suggests that one should also take the effects of phonon softening into account. All of these results may provide insights into establishing the connection between the macroscopic heat transport and the underlying dynamics in 1D systems.
Nonlinear transport in quasi-one-dimensional Nb{sub 2}PdS{sub 5} nanowires
Ning, Wei; Yu, Hongyan; Wang, Ning; Han, Yuyan; Yang, Jiyong; Du, Haifeng; Zhang, Changjin; Liu, Yequn; Yang, Kun; Tian, Mingliang Zhang, Yuheng
2014-10-27
Nb{sub 2}PdS{sub 5} is a newly discovered quasi-one-dimensional (quasi-1D) superconductor with a high upper critical field along the chain direction. Here, we report the size-dependent electronic properties of Nb{sub 2}PdS{sub 5} nanowires obtained by ultrasonically cleaving the bulk crystals. The nanowires exhibit a superconductor to insulator transition as the cross-sectional area decreases. Moreover, for the thinner nanowires with insulating state, the transport properties exhibit a power-law dependence on both temperature and bias voltage at an intermediate temperature (<30 K), followed by a conduction saturation below 10 K. We found that such an apparent power-law behavior can be described by the extended variable range hopping theory developed recently for the multichannel quasi-1D systems, where the localization of electrons is expected to be dominant instead of the Luttinger liquid nature.
Length-dependent thermal transport in one-dimensional self-assembly of planar π-conjugated molecules
NASA Astrophysics Data System (ADS)
Tang, Hao; Xiong, Yucheng; Zu, Fengshuo; Zhao, Yang; Wang, Xiaomeng; Fu, Qiang; Jie, Jiansheng; Yang, Juekuan; Xu, Dongyan
2016-06-01
This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become `amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the `amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport.This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport
Tang, Hao; Xiong, Yucheng; Zu, Fengshuo; Zhao, Yang; Wang, Xiaomeng; Fu, Qiang; Jie, Jiansheng; Yang, Juekuan; Xu, Dongyan
2016-06-01
This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become 'amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the 'amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport.
Tang, Hao; Xiong, Yucheng; Zu, Fengshuo; Zhao, Yang; Wang, Xiaomeng; Fu, Qiang; Jie, Jiansheng; Yang, Juekuan; Xu, Dongyan
2016-06-01
This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become 'amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the 'amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport. PMID:27240641
NASA Astrophysics Data System (ADS)
Bobik, P.; Boschini, M. J.; Della Torre, S.; Gervasi, M.; Grandi, D.; La Vacca, G.; Pensotti, S.; Putis, M.; Rancoita, P. G.; Rozza, D.; Tacconi, M.; Zannoni, M.
2016-05-01
The cosmic rays propagation inside the heliosphere is well described by a transport equation introduced by Parker in 1965. To solve this equation, several approaches were followed in the past. Recently, a Monte Carlo approach became widely used in force of its advantages with respect to other numerical methods. In this approach the transport equation is associated to a fully equivalent set of stochastic differential equations (SDE). This set is used to describe the stochastic path of quasi-particle from a source, e.g., the interstellar space, to a specific target, e.g., a detector at Earth. We present a comparison of forward-in-time and backward-in-time methods to solve the cosmic rays transport equation in the heliosphere. The Parker equation and the related set of SDE in the several formulations are treated in this paper. For the sake of clarity, this work is focused on the one-dimensional solutions. Results were compared with an alternative numerical solution, namely, Crank-Nicolson method, specifically developed for the case under study. The methods presented are fully consistent each others for energy greater than 400 MeV. The comparison between stochastic integrations and Crank-Nicolson allows us to estimate the systematic uncertainties of Monte Carlo methods. The forward-in-time stochastic integrations method showed a systematic uncertainty <5%, while backward-in-time stochastic integrations method showed a systematic uncertainty <1% in the studied energy range.
NASA Astrophysics Data System (ADS)
Vettchinkina, V.; Kartsev, A.; Karlsson, D.; Verdozzi, C.
2013-03-01
We investigate the static and dynamical behavior of one-dimensional interacting fermions in disordered Hubbard chains contacted to semi-infinite leads. The chains are described via the repulsive Anderson-Hubbard Hamiltonian, using static and time-dependent lattice density-functional theory. The dynamical behavior of our quantum transport system is studied using an integration scheme available in the literature, which we modify via the recursive Lanczos method to increase its efficiency. To quantify the degree of localization due to disorder and interactions, we adapt the definition of the inverse participation ratio to obtain an indicator which is suitable for quantum transport geometries and can be obtained within density-functional theory. Lattice density-functional theories are reviewed and, for contacted chains, we analyze the merits and limits of the coherent-potential approximation in describing the spectral properties, with interactions included via lattice density-functional theory. Our approach appears to be able to capture complex features due to the competition between disorder and interactions. Specifically, we find a dynamical enhancement of delocalization in the presence of a finite bias and an increase of the steady-state current induced by interparticle interactions. This behavior is corroborated by results for the time-dependent densities and for the inverse participation ratio. Using short isolated chains with interaction and disorder, a brief comparative analysis between time-dependent density-functional theory and exact results is then given, followed by general concluding remarks.
User's Guide for Mixed-Size Sediment Transport Model for Networks of One-Dimensional Open Channels
Bennett, James P.
2001-01-01
This user's guide describes a mathematical model for predicting the transport of mixed sizes of sediment by flow in networks of one-dimensional open channels. The simulation package is useful for general sediment routing problems, prediction of erosion and deposition following dam removal, and scour in channels at road embankment crossings or other artificial structures. The model treats input hydrographs as stepwise steady-state, and the flow computation algorithm automatically switches between sub- and supercritical flow as dictated by channel geometry and discharge. A variety of boundary conditions including weirs and rating curves may be applied both external and internal to the flow network. The model may be used to compute flow around islands and through multiple openings in embankments, but the network must be 'simple' in the sense that the flow directions in all channels can be specified before simulation commences. The location and shape of channel banks are user specified, and all bedelevation changes take place between these banks and above a user-specified bedrock elevation. Computation of sediment-transport emphasizes the sand-size range (0.0625-2.0 millimeter) but the user may select any desired range of particle diameters including silt and finer (<0.0625 millimeter). As part of data input, the user may set the original bed-sediment composition of any number of layers of known thickness. The model computes the time evolution of total transport and the size composition of bed- and suspended-load sand through any cross section of interest. It also tracks bed -surface elevation and size composition. The model is written in the FORTRAN programming language for implementation on personal computers using the WINDOWS operating system and, along with certain graphical output display capability, is accessed from a graphical user interface (GUI). The GUI provides a framework for selecting input files and parameters of a number of components of the sediment-transport
Nonlinear Transport of the Wigner Crystal on Superfluid 4He in a Quasi-One-Dimensional Channel
NASA Astrophysics Data System (ADS)
Vasylenko, Anna A.; Misko, Vyacheslav R.
2014-07-01
We study transport properties of a Wigner crystal driven by an external force on the surface of superfluid 4He, in the "quantum wire" regime, i.e. in the quasi-one-dimensional (quasi-1D) case when a typical width of the channel is comparable to the inter-electron separation. Utilizing molecular dynamics simulations, we investigate the electronic transport through the channels with different constrictions: (i) geometrical constrictions with varying shape and size, and (ii) a saddle-point potential with varying gate voltage. The average particle velocity has been calculated as a function of the driving force or gate voltage. We have revealed a significant difference in the dynamical behavior for long and short constrictions. In particular, we found that the oscillations of the average particle velocity in channels with short constrictions exhibit a clear correlation with the transitions between the states with different numbers of rows of particles in the constriction, while for channels with longer constrictions these oscillations are suppressed. The obtained results are in agreement with the recent experimental observations,1 and thus bring new important insights into the dynamics of electrons floating on the surface of superfluid 4He in channels with constrictions. Special Issue Comments: This article presents results on the dynamics of electrons moving on the surface of liquid helium in narrow channels with constrictions, with a focus on the "quantum wire", i.e. single file, regime. This article is connected to the Special Issue articles about advanced statistical properties in single file dynamics39 and the experiments on liquid helium.40
Runkel, Robert L.
1998-01-01
OTIS is a mathematical simulation model used to characterize the fate and transport of water-borne solutes in streams and rivers. The governing equation underlying the model is the advection-dispersion equation with additional terms to account for transient storage, lateral inflow, first-order decay, and sorption. This equation and the associated equations describing transient storage and sorption are solved using a Crank-Nicolson finite-difference solution. OTIS may be used in conjunction with data from field-scale tracer experiments to quantify the hydrologic parameters affecting solute transport. This application typically involves a trial-and-error approach wherein parameter estimates are adjusted to obtain an acceptable match between simulated and observed tracer concentrations. Additional applications include analyses of nonconservative solutes that are subject to sorption processes or first-order decay. OTIS-P, a modified version of OTIS, couples the solution of the governing equation with a nonlinear regression package. OTIS-P determines an optimal set of parameter estimates that minimize the squared differences between the simulated and observed concentrations, thereby automating the parameter estimation process. This report details the development and application of OTIS and OTIS-P. Sections of the report describe model theory, input/output specifications, sample applications, and installation instructions.
This technical report describes the new one-dimensional (1D) hydrodynamic and sediment transport model EFDC1D. This model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. EFDC1D can simulate bi-directional unstea...
Technology Transfer Automated Retrieval System (TEKTRAN)
Analytical solutions of the advection-dispersion solute transport equation remain useful for a large number of applications in science and engineering. In this paper we extend the Duhamel theorem, originally established for diffusion type problems, to the case of advective-dispersive transport subj...
NASA Astrophysics Data System (ADS)
Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath
2014-07-01
The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2-300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80-300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.
Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath
2014-07-14
The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2–300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80–300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.
NASA Astrophysics Data System (ADS)
Dujardin, Julien; Engl, Thomas; Schlagheck, Peter
2016-01-01
We study the transport of an interacting Bose-Einstein condensate through a 1D correlated disorder potential. We use for this purpose the truncated Wigner method, which is, as we show, corresponding to the diagonal approximation of a semiclassical van Vleck-Gutzwiller representation of this many-body transport process. We also argue that semiclassical corrections beyond this diagonal approximation are vanishing under disorder average, thus confirming the validity of the truncated Wigner method in this context. Numerical calculations show that, while for weak atom-atom interaction strengths Anderson localization is preserved with a slight modification of the localization length, for larger interaction strengths a crossover to a delocalized regime exists due to inelastic scattering. In this case, the transport is fully incoherent.
Dupree, S. A.
1980-06-01
The use of adjoint techniques to determine the interaction of externally incident collimated beams of particles with cylindrical targets is a convenient means of examining a class of problems important in radiation transport studies. The theory relevant to such applications is derived, and a simple example involving a fissioning target is discussed. Results from both discrete ordinates and Monte Carlo transport-code calculations are presented, and comparisons are made with results obtained from forward calculations. The accuracy of the discrete ordinates adjoint results depends on the order of angular quadrature used in the calculation. Reasonable accuracy by using EQN quadratures can be expected from order S/sub 16/ or higher.
Fan Shanhui; Kocabas, Suekrue Ekin; Shen, Jung-Tsung
2010-12-15
We extend the input-output formalism of quantum optics to analyze few-photon transport in waveguides with an embedded qubit. We provide explicit analytical derivations for one- and two-photon scattering matrix elements based on operator equations in the Heisenberg picture.
NASA Astrophysics Data System (ADS)
Zheleznyak, Anatoley T.
The problem of the ground states of the high-Tsb{c} superconductors is approached by considering the electron system with flat regions on the opposite sides of the Fermi surface. The possible instabilities are classified in the framework of the parquet approximation and corresponding renormalization-group equations, that determine the evolution of susceptibilities with decreasing temperature, are solved numerically. Solutions of the parquet equations are found to be in qualitative agreement with a ladder approximation. For the repulsive Hubbard interaction, the antiferromagnetic (spin-density-wave) instability dominates, but when the Fermi surface is not perfectly flat, the d-wave superconducting instability takes over. The phenomenology of the high-Tsb{c} superconductors is studied on the basis of ac and dc magnetotransport data in the normal state of YBasb2Cusb3Osb7 within the Fermi-liquid and non-Fermi-liquid models. In the Fermi-liquid analysis we use the Fermi surface deduced from the band structure calculations and assume that the electron relaxation rate varies over the Fermi surface. Introducing two characteristic scattering times, an additive two-tau model is formulated, and corresponding phenomenological parameters are determined. The non-Fermi-liquid models are the two-dimensional Luttinger liquid model and the charge-conjugation-symmetry model. The existing experimental data can be adequately fitted by any of these models, not allowing to discriminate among these concepts. The second part of the dissertation is devoted to the umklapp resistivity of the quasi-one-dimensional organic conductors in the magnetic field. The magnetoresistance in the classical magnetic field is considered due to the nonhomogeneous distribution of the electron scattering rate on the Fermi surface. Microscopical calculations show that in certain regions on the Fermi surface the scattering rate is indeed anomalously high. The reason for the existence of these "hot spots" is
Knopman, D.S.; Voss, C.I.
1988-01-01
Sensitivities of solute concentration to parameters associated with first-order chemical decay, boundary conditions, initial conditions, and multilayer transport are examined. A sensitivity is a change in solute concentration resulting from a change in a model parameter. Minimum information required in regression on chemical data for the estimation of model parameters by regression is expressed in terms of sensitivities. Nonlinear regression models were tested on sets of noiseless observations from known models that exceeded the minimum sensitivity information requirements. Results demonstrate that the regression models consistently converged to the correct parameters when the initial sets of parameter values substantially deviated from the correct parameters. -from Authors
Kerstein, A.R.
1996-12-31
One-Dimensional Turbulence is a new turbulence modeling strategy involving an unsteady simulation implemented in one spatial dimension. In one dimension, fine scale viscous and molecular-diffusive processes can be resolved affordably in simulations at high turbulence intensity. The mechanistic distinction between advective and molecular processes is thereby preserved, in contrast to turbulence models presently employed. A stochastic process consisting of mapping {open_quote}events{close_quote} applied to a one-dimensional velocity profile represents turbulent advection. The local event rate for given eddy size is proportional to the velocity difference across the eddy. These properties cause an imposed shear to induce an eddy cascade analogous in many respects to the eddy cascade in turbulent flow. Many scaling and fluctuation properties of self-preserving flows, and of passive scalars introduced into these flows, are reproduced.
Mieles, John; Zhan, Hongbin
2012-06-01
The permeable reactive barrier (PRB) remediation technology has proven to be more cost-effective than conventional pump-and-treat systems, and has demonstrated the ability to rapidly reduce the concentrations of specific chemicals of concern (COCs) by up to several orders of magnitude in some scenarios. This study derives new steady-state analytical solutions to multispecies reactive transport in a PRB-aquifer (dual domain) system. The advantage of the dual domain model is that it can account for the potential existence of natural degradation in the aquifer, when designing the required PRB thickness. The study focuses primarily on the steady-state analytical solutions of the tetrachloroethene (PCE) serial degradation pathway and secondly on the analytical solutions of the parallel degradation pathway. The solutions in this study can also be applied to other types of dual domain systems with distinct flow and transport properties. The steady-state analytical solutions are shown to be accurate and the numerical program RT3D is selected for comparison. The results of this study are novel in that the solutions provide improved modeling flexibility including: 1) every species can have unique first-order reaction rates and unique retardation factors, and 2) daughter species can be modeled with their individual input concentrations or solely as byproducts of the parent species. The steady-state analytical solutions exhibit a limitation that occurs when interspecies reaction rate factors equal each other, which result in undefined solutions. Excel spreadsheet programs were created to facilitate prompt application of the steady-state analytical solutions, for both the serial and parallel degradation pathways.
NASA Technical Reports Server (NTRS)
Ghorai, S. K.
1983-01-01
The purpose of this project was to use a one-dimensional discrete coordinates transport code called ANISN in order to determine the energy-angle-spatial distribution of neutrons in a 6-feet cube rock box which houses a D-T neutron generator at its center. The project was two-fold. The first phase of the project involved adaptation of the ANISN code written for an IBM 360/75/91 computer to the UNIVAC system at JSC. The second phase of the project was to use the code with proper geometry, source function and rock material composition in order to determine the neutron flux distribution around the rock box when a 14.1 MeV neutron generator placed at its center is activated.
NASA Astrophysics Data System (ADS)
Suzuki, Yohichi; Singh, Rupashree Balia; Matsuzaki, Hiroyuki; Furube, Akihiro; Ma, Guijun; Hisatomi, Takashi; Domen, Kazunari; Seki, Kazuhiko
2016-09-01
The semiconductor La5Ti2CuS5O7 (LTC) is a potential photocatalyst capable of operating under visible light irradiation and behaves both as a photocathode and anode when embedded onto metal layers. Time-resolved diffuse reflectance (TRDR) measurements were carried out on LTC powder and LTC deposited on Au as the back contact using the particle-transfer method. Results of TRDR measurements of powdered LTC indicated the existence of long-lived photo-excited carriers, and suggested the existence of a mechanism for preventing carrier loss in LTC. Prior research has reported that LTC has a rod-shaped crystal structure and that electrons and holes are transported through different, spatially separated channels. Based on this, we introduced a one-dimensional carrier transport model. By analyzing TRDR data, we extracted material parameters such as the diffusion coefficient of LTC. Theoretical results indicated that a micron-sized LTC particle would be preferable if carriers trapped at the top-surface do contribute to photocatalytic gas generation.
NASA Astrophysics Data System (ADS)
Katzourakis, Vasileios; Chrysikopoulos, Constantinos
2016-04-01
The present work re-introduces ColloidFit, which is an autonomous, modular, multipurpose fitting software for dense colloid and biocolloid transport phenomena in porous media. The initial version of ColloidFit, introduced by Sim and Chrysikopoulos (1995), was substantially improved and combined with a relatively intuitive and easy to use graphical user interface. The re-introduced ColloidFit can simulate the migration of suspended colloid or biocolloid particles in one-dimensional, water saturated, homogeneous porous media with uniform flow, accounting for non-equilibrium attachment onto the solid matrix, as well as gravitational effects. Furthermore, the improved ColloidFit software employs a variety of non-equilibrium, linear and nonlinear models for the simulation of colloid attachment onto a solid matrix under batch experimental conditions. The re-introduced ColloidFit uses the state of the art fitting software "Pest" to estimate unknown model parameter values, together with their 95% confidence intervals. Pest is a model-independent parameter estimation software capable of adjusting model parameters, so that discrepancies between model-generated data and the corresponding experimental measurements are reduced to a user preselected minimum. The fitting process is graphed and displayed in real time. The user is allowed to overview every step of the fitting progress, and if needed to change the initial parameter values. The re-introduced ColloidFit software is expected to make the fitting process of colloid and biocolloid transport data, just a simple task.
One-Dimensionality and Whiteness
ERIC Educational Resources Information Center
Calderon, Dolores
2006-01-01
This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…
Parkhurst, David L.; Appelo, C.A.J.
1999-01-01
PHREEQC version 2 is a computer program written in the C programming language that is designed to perform a wide variety of low-temperature aqueous geochemical calculations. PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations involving reversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and irreversible reactions, which include specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters, within specified compositional uncertainty limits.New features in PHREEQC version 2 relative to version 1 include capabilities to simulate dispersion (or diffusion) and stagnant zones in 1D-transport calculations, to model kinetic reactions with user-defined rate expressions, to model the formation or dissolution of ideal, multicomponent or nonideal, binary solid solutions, to model fixed-volume gas phases in addition to fixed-pressure gas phases, to allow the number of surface or exchange sites to vary with the dissolution or precipitation of minerals or kinetic reactants, to include isotope mole balances in inverse modeling calculations, to automatically use multiple sets of convergence parameters, to print user-defined quantities to the primary output file and (or) to a file suitable for importation into a spreadsheet, and to define solution compositions in a format more compatible with spreadsheet programs. This report presents the equations that are the basis for chemical equilibrium, kinetic, transport, and inverse-modeling calculations in PHREEQC; describes the input for the program; and presents examples that demonstrate most of the program's capabilities.
NASA Astrophysics Data System (ADS)
Hemme, C.; van Berk, W.
2015-12-01
In carbon capture and storage (CCS) systems supercritical CO2 is injected into a reservoir and dissolves in the reservoir brine. Subsequently, CO2(aq) diffuses into the cap rock to regions of lower total pressure and temperature and triggers CO2-water-rock interactions that are coupled with mass transport and result in precipitation and/or dissolution of minerals along the CO2 migration path. Such hydrogeochemical interactions change porosities and are responsible for the improvement or deterioration of the long term integrity of the system. This study presents a semi-generic hydrogeochemical model based on chemical equilibrium thermodynamics, data from several CO2 storage systems, and plausible assumptions regarding non-available data. One-dimensional reactive transport modeling is performed by using the U.S.G.S. PHREEQC code (3.1.4-8929; phreeqc.dat database) to identify and quantify the loss or gain of total porosity affected by hydrogeochemical reactions driven by diffusive mass transport exposed to pressure and temperature gradients. A fine spatial and temporal discretization, the use of non-reactive tracers, and a broad variety of modeling scenarios enable the calculation of the relevant timescale for simulations of long-term storage of CO2 and the consideration of the pressure dependent mass action law constants along the CO2 migration path. Modeling results show that the relevant timescale for simulations of long-term storage of CO2 is in the range of 106 years, and that pressure/temperature conditions, heterogeneities (veins and fractures) and the mineralogical composition of the cap rock have the strongest influence on the increase in cap rock porosity (maximum increase from initial 5 % to 7.5 %). Critical parameter combinations - total pressure effects are crucial - could put long-term integrity at risks. Nevertheless, a wide range of conditions and parameter combinations for safe CO2 storage is identified by other modeling scenarios.
Parkhurst, David L.; Appelo, C.A.J.
2013-01-01
PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model. Using any of these aqueous models, PHREEQC has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations with reversible and irreversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and pressure and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters within specified compositional uncertainty limits. Many new modeling features were added to PHREEQC version 3 relative to version 2. The Pitzer aqueous model (pitzer.dat database, with keyword PITZER) can be used for high-salinity waters that are beyond the range of application for the Debye-Hückel theory. The Peng-Robinson equation of state has been implemented for calculating the solubility of gases at high pressure. Specific volumes of aqueous species are calculated as a function of the dielectric properties of water and the ionic strength of the solution, which allows calculation of pressure effects on chemical reactions and the density of a solution. The specific conductance and the density of a solution are calculated and printed in the output file. In addition to Runge-Kutta integration, a stiff ordinary differential equation solver (CVODE) has been included for kinetic calculations with multiple rates that occur at widely different time scales
de Vries, M. Peter; Weiss, L.A.
2001-01-01
The Hudson River is being considered for use as a supplemental source of water supply for New York City during droughts. One proposal entails withdrawal of Hudson River water from locations near Newburgh, Chelsea, or Kingston, but the extent to which this could cause the salt front to advance upstream to points where it could adversely affect community water supplies is unknown. The U.S. Geological Survey (USGS) one-dimensional Branch-Network Dynamic Flow model (BRANCH) was used in conjunction with the USGS one-dimensional Branched Lagrangian Solute-Transport Model (BLTM) to simulate the effect of five water-withdrawal scenarios on the salt-front location. The modeled reach contains 132 miles of the lower Hudson River between the Federal Dam at Troy and Hastings-on-Hudson (near New York City). The BRANCH model was calibrated and verified to 19 tidal-cycle discharge measurements made at 11 locations by conventional and acoustic Doppler current-profiler methods. Maximum measured instantaneous tidal flow ranged from 20,000 ft3/s (cubic feet per second) at Albany to 368,000 ft3/s at Tellers Point; daily-mean flow at Green Island near Troy ranged from 3,030 ft3/s to 45,000 ft3/s during the flow measurements. Successive ebb- and flood-flow volumes were measured and compared with computed volumes; daily-mean bias was -1.6 percent (range from -21.0 to +23.7 percent; 13.5 percent mean absolute error). Daily-mean deviation between simulated and measured stage at eight locations (from Bowline Point to Albany) over the 19 tidal-cycle measurements averaged +0.06 ft (range from -0.31 to +0.40 ft; 0.21 ft root mean square error, RMSE). These results indicate that the model can accurately simulate flow in the Hudson River under a wide range of flow, tide, and meteorological conditions. The BLTM was used to simulate chloride transport in the 61-mi reach from Turkey Point to Bowline Point under two seasonal conditions in 1990.one representing spring conditions of high inflow and low
NASA Astrophysics Data System (ADS)
Dewaide, Lorraine; Bonniver, Isabelle; Rochez, Gaëtan; Hallet, Vincent
2016-03-01
This paper presents the modelling results of several tracer-tests performed in the cave system of Han-sur-Lesse (South Belgium). In Han-sur-Lesse, solute flows along accessible underground river stretches and through flooded areas that are rather unknown in terms of geometry. This paper focus on the impact of those flooded areas on solute transport and their dimensioning. The program used (One-dimensional Transport with Inflow and Storage: OTIS) is based on the two-region non equilibrium model that supposes the existence of an immobile water zone along the main flow zone in which solute can be caught. The simulations aim to replicate experimental breakthrough curves (BTCs) by adapting the main transport and geometric parameters that govern solute transport in karst conduits. Furthermore, OTIS allows a discretization of the investigated system, which is particularly interesting in systems presenting heterogeneous geometries. Simulation results show that transient storage is a major process in flooded areas and that the crossing of these has a major effect on the BTCs shape. This influence is however rather complex and very dependent of the flooded areas geometry and transport parameters. Sensibility tests performed in this paper aim to validate the model and show the impact of the parametrization on the BTCs shape. Those tests demonstrate that transient storage is not necessarily transformed in retardation. Indeed, significant tailing effect is only observed in specific conditions (depending on the system geometry and/or the flow) that allow residence time in the storage area to be longer than restitution time. This study ends with a comparison of solute transport in river stretches and in flooded areas.
Parkhurst, David L.; Appelo, C.A.J.
2013-01-01
PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model. Using any of these aqueous models, PHREEQC has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations with reversible and irreversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and pressure and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters within specified compositional uncertainty limits. Many new modeling features were added to PHREEQC version 3 relative to version 2. The Pitzer aqueous model (pitzer.dat database, with keyword PITZER) can be used for high-salinity waters that are beyond the range of application for the Debye-Hückel theory. The Peng-Robinson equation of state has been implemented for calculating the solubility of gases at high pressure. Specific volumes of aqueous species are calculated as a function of the dielectric properties of water and the ionic strength of the solution, which allows calculation of pressure effects on chemical reactions and the density of a solution. The specific conductance and the density of a solution are calculated and printed in the output file. In addition to Runge-Kutta integration, a stiff ordinary differential equation solver (CVODE) has been included for kinetic calculations with multiple rates that occur at widely different time scales
Wang, Yuwen; Zhang, Yongyou; Zhang, Qingyun; Zou, Bingsuo; Schwingenschlogl, Udo
2016-01-01
We study the dynamics of an ultrafast single photon pulse in a one-dimensional waveguide two-point coupled with a Jaynes-Cummings system. We find that for any single photon input the transmissivity depends periodically on the separation between the two coupling points. For a pulse containing many plane wave components it is almost impossible to suppress transmission, especially when the width of the pulse is less than 20 times the period. In contrast to plane wave input, the waveform of the pulse can be modified by controlling the coupling between the waveguide and Jaynes-Cummings system. Tailoring of the waveform is important for single photon manipulation in quantum informatics. PMID:27653770
NASA Astrophysics Data System (ADS)
Cohn, Joshua L.; Dos Santos, Carlos A. M.; Neumeier, John J.
We present resistivity, Hall, Seebeck, and Nernst coefficient measurements in the range 0 . 4 K <= T <= 20 K on single crystals of the quasi-one-dimensional (Q1D) metal, Li0.9Mo6O17 with current along the Q1D metallic chains. At temperatures below the nominal superconducting transition temperature (Tc = 2 K), a transition from hole-like (μ0 H < 1 T) to electron-like (μ0 H >= 2 T) behavior is evidenced in the magnetotransport coefficients. Possible insights from these results into the nature of the mysterious density-wave ordera,b responsible for the upturn in resistivity below ~ 25 K will be discussed. a. Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences (DE-FG02-12ER46888, Univ. Miami), the National Science Foundation (DMR-0907036, Mont. St. Univ.), and in Lorena by the CNPq (308162/2013-7) and FAPESP (2009/54001-2).
Technology Transfer Automated Retrieval System (TEKTRAN)
Transport equations governing the movement of multiple solutes undergoing sequential first-order decay reactions have relevance in analyzing a variety of subsurface contaminant transport problems. In this study, a one-dimensional analytical solution for multi-species transport is obtained for finite...
One-Dimensional Heat Conduction
Sutton, Steven B.
1992-03-09
ICARUS-LLNL was developed to solve one-dimensional planar, cylindrical, or spherical conduction heat transfer problems. The IBM PC version is a family of programs including ICARUSB, an interactive BASIC heat conduction program; ICARUSF, a FORTRAN heat conduction program; PREICAR, a BASIC preprocessor for ICARUSF; and PLOTIC and CPLOTIC, interpretive BASIC and compiler BASIC plot postprocessor programs. Both ICARUSB and ICARUSF account for multiple material regions and complex boundary conditions, such as convection or radiation. In addition, ICARUSF accounts for temperature-dependent material properties and time or temperature-dependent boundary conditions. PREICAR is a user-friendly preprocessor used to generate or modify ICARUSF input data. PLOTIC and CPLOTIC generate plots of the temperature or heat flux profile at specified times, plots of the variation of temperature or heat flux with time at selected nodes, or plots of the solution grid. First developed in 1974 to allow easy modeling of complex one-dimensional systems, its original application was in the nuclear explosive testing program. Since then it has undergone extensive revision and been applied to problems dealing with laser fusion target fabrication, heat loads on underground tests, magnetic fusion switching tube anodes, and nuclear waste isolation canisters.
One-Dimensional Heat Conduction
1992-03-09
ICARUS-LLNL was developed to solve one-dimensional planar, cylindrical, or spherical conduction heat transfer problems. The IBM PC version is a family of programs including ICARUSB, an interactive BASIC heat conduction program; ICARUSF, a FORTRAN heat conduction program; PREICAR, a BASIC preprocessor for ICARUSF; and PLOTIC and CPLOTIC, interpretive BASIC and compiler BASIC plot postprocessor programs. Both ICARUSB and ICARUSF account for multiple material regions and complex boundary conditions, such as convection or radiation. In addition,more » ICARUSF accounts for temperature-dependent material properties and time or temperature-dependent boundary conditions. PREICAR is a user-friendly preprocessor used to generate or modify ICARUSF input data. PLOTIC and CPLOTIC generate plots of the temperature or heat flux profile at specified times, plots of the variation of temperature or heat flux with time at selected nodes, or plots of the solution grid. First developed in 1974 to allow easy modeling of complex one-dimensional systems, its original application was in the nuclear explosive testing program. Since then it has undergone extensive revision and been applied to problems dealing with laser fusion target fabrication, heat loads on underground tests, magnetic fusion switching tube anodes, and nuclear waste isolation canisters.« less
Kurylyk, Barret L.; McKenzie, Jeffrey M; MacQuarrie, Kerry T. B.; Voss, Clifford I.
2014-01-01
Numerous cold regions water flow and energy transport models have emerged in recent years. Dissimilarities often exist in their mathematical formulations and/or numerical solution techniques, but few analytical solutions exist for benchmarking flow and energy transport models that include pore water phase change. This paper presents a detailed derivation of the Lunardini solution, an approximate analytical solution for predicting soil thawing subject to conduction, advection, and phase change. Fifteen thawing scenarios are examined by considering differences in porosity, surface temperature, Darcy velocity, and initial temperature. The accuracy of the Lunardini solution is shown to be proportional to the Stefan number. The analytical solution results obtained for soil thawing scenarios with water flow and advection are compared to those obtained from the finite element model SUTRA. Three problems, two involving the Lunardini solution and one involving the classic Neumann solution, are recommended as standard benchmarks for future model development and testing.
One-dimensional Cooper pairing
NASA Astrophysics Data System (ADS)
Mendoza, R.; Fortes, M.; de Llano, M.; Solís, M. A.
2011-09-01
We study electron pairing in a one-dimensional (1D) fermion gas at zero temperature under zero- and finite-range, attractive, two-body interactions. The binding energy of Cooper pairs (CPs) with zero total or center-of-mass momentum (CMM) increases with attraction strength and decreases with interaction range for fixed strength. The excitation energy of 1D CPs with nonzero CMM display novel, unique properties. It satisfies a dispersion relation with two branches: a phonon-like linear excitation for small CP CMM; this is followed by roton-like quadratic excitation minimum for CMM greater than twice the Fermi wavenumber, but only above a minimum threshold attraction strength. The expected quadratic-in-CMM dispersion in vacuo when the Fermi wavenumber is set to zero is recovered for any coupling. This paper completes a three-part exploration initiated in 2D and continued in 3D.
Liu, Xiao-Yong; Zou, Zhi-Qiang
2015-05-15
We demonstrate the formation of contact barriers at the interfaces between MnSi1.7 nanowires (NWs) and Si substrates by the current-voltage (I-V) curves measured by scanning tunneling microscope with the tip contacting the NWs. The NWs on Si(110) exhibit linear reverse bias I-V curves, which suggests a parallel Ohmic surface state conductance of the Si(110) surface. The NWs on Si(111) exhibit nonlinear reverse bias I-V behavior, which indicates a considerable amount of minority carrier recombination-generation current. The NW length-dependence study of the forward bias current clearly shows that the quantitative change in NW length leads to a qualitative change in electrical transport properties. We derive a characteristic length LC ≈ 200 nm and the corresponding aspect ratio of ∼12-18 for MnSi1.7 NWs according to the variation of current density with the NW length.
NASA Astrophysics Data System (ADS)
Liu, Xiao-Yong; Zou, Zhi-Qiang
2015-05-01
We demonstrate the formation of contact barriers at the interfaces between MnSi1.7 nanowires (NWs) and Si substrates by the current-voltage (I-V) curves measured by scanning tunneling microscope with the tip contacting the NWs. The NWs on Si(110) exhibit linear reverse bias I-V curves, which suggests a parallel Ohmic surface state conductance of the Si(110) surface. The NWs on Si(111) exhibit nonlinear reverse bias I-V behavior, which indicates a considerable amount of minority carrier recombination-generation current. The NW length-dependence study of the forward bias current clearly shows that the quantitative change in NW length leads to a qualitative change in electrical transport properties. We derive a characteristic length LC ≈ 200 nm and the corresponding aspect ratio of ˜12-18 for MnSi1.7 NWs according to the variation of current density with the NW length.
NASA Astrophysics Data System (ADS)
Prasai, Narayan; Cohn, Joshua; Rebello, Alwyn; Smith, Michael; Neumeier, John J.
2014-03-01
We report thermal conductivity (κ) measurements on single crystals of the S = 1 / 2 antiferromagnetic spin-chain compound CuSb2O6 over the temperature range 5 K <= T <= 300 K . Similar measurements on the non-magnetic analog compound, ZnSb2O6, allow for a comparison of the lattice thermal conductivities. The role of spin-phonon coupling and twinning on the anisotropic thermal transport of CuSb2O6 will be discussed. This material is based upon work supported by the U.S. Department of Energy Office of Basic Energy Sciences grant DE-FG02-12ER46888 (Univ. Miami) and the National Science Foundation under grant DMR-0907036 (Mont. St. Univ.).
NASA Astrophysics Data System (ADS)
Vasylenko, Anna A.; Misko, Vyacheslav R.
2015-04-01
When floating on a two-dimensional surface of superfluid 4He, electrons arrange themselves in two-dimensional crystalline structure known as Wigner crystal. In channels, the boundaries interfere the crystalline order and in case of very narrow channels one observes a quasi-one-dimensional (quasi-1D) Wigner crystal formed by just a few rows of electrons and, ultimately, one row in the "quantum wire" regime. Recently, the "quantum wire" regime was accessed experimentally [D.G. Rees, H. Totsuji, K. Kono, Phys. Rev. Lett. 108, 176801 (2012)] resulting in unusual transport phenomena such as, e.g., oscillations in the electron conductance. Using molecular dynamics simulations, we study the nonlinear transport of electrons in channels with various types of constrictions: single and multiple symmetric and asymmetric geometrical constrictions with varying width and length, and saddle-point-type potentials with varying gate voltage. In particular, we analyze the average particle velocity of the particles and the corresponding electron current versus the driving force or the gate voltage. We have revealed a significant difference in the dynamics for long and short constrictions: The oscillations of the average velocity of the particles for the systems with short constrictions exhibit a clear correlation with the transitions between the states with different numbers of rows of particles; on the other hand, for the systems with longer constrictions these oscillations are suppressed. The obtained results qualitatively agree with the experimental observations. Next, we propose a FET-like structure that consists of a channel with asymmetric constrictions. We show that applying a transverse bias results either in increase of the average particle velocity or in its suppression thus allowing a flexible control tool over the electron transport. The advantage of the asymmetric FET is that it does not have a gate and it allows an easy control of relatively large electron flow
Modelling contaminant transport for pumping wells in riverbank filtration systems.
Mustafa, Shaymaa; Bahar, Arifah; Aziz, Zainal Abdul; Suratman, Saim
2016-01-01
Analytical study of the influence of both the pumping well discharge rate and pumping time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both pumping time and travelling time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the pumping time and pumping rate, which control the travelling time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the pumping rate or simulation pumping time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
Concentration distribution of contaminant transport in wetland flows
NASA Astrophysics Data System (ADS)
Wu, Zi; Fu, Xudong; Wang, Guangqian
2015-06-01
Study on contaminant transport in wetland flows is of fundamental importance. Recent investigation on scalar transport in laminar tube flows (Wu and Chen, 2014. J. Fluid Mech., 740: 196-213.) indicates that the vertical concentration difference in wetland flows may be remarkable for a very long time, which cannot be captured by the extensively applied one-dimensional Taylor dispersion model. To understand detailed information for the vertical distribution of contaminant in wetland flows, for the first time, the present paper deduces an analytical solution for the multi-dimensional concentration distribution by the method of mean concentration expansion. The solution is verified by both our analytical and numerical results. Representing the effects of vegetation in wetlands, the unique dimensionless parameter α can cause the longitudinal contraction of the contaminant cloud and the change of the shape of the concentration contours. By these complicated effects, it is shown unexpectedly that the maximum vertical concentration difference remains nearly unaffected, although its longitudinal position may change. Thus the slow-decaying transient effect (Wu and Chen, 2014. J. Hydrol., 519: 1974-1984.) is shown also apply to the process of contaminant transport in wetland flows.
MODELING CONTAMINANT TRANSPORT THROUGH SUBSURFACE SYSTEMS
Modeling of contaminant transport through soil to groundwater to a receptor requires that consideration be given to the many processes which control the transport and fate of chemical constituents in the subsurface environment. These processes include volatilization, degradation,...
Bäßler, Svenja Hamdou, Bacel; Sergelius, Philip; Michel, Ann-Kathrin; Zierold, Robert; Gooth, Johannes; Reith, Heiko; Nielsch, Kornelius
2015-11-02
The geometry of topological insulators (TIs) has a major impact on the magnetoelectric band structure of their surface states. Here, we investigate the surface states of cylindrical TI bismuth telluride selenide nanowires with three different diameters, by parallel and transverse magnetoresistance (MR) measurements. In parallel configuration, we observe Aharonov-Bohm oscillations as well as weak antilocalization, indicating two-dimensional TI surface states. In transverse magnetic fields, we observed MR oscillations that are non-linear against the reciprocal of the magnetic field and thus cannot be explained by two- or three-dimensional states. Instead, our transport data analysis reveals that these MR oscillations are the consequence of one-dimensional edge channels at the nanowire surface that form due to the projection of the external magnetic field on the cylindrically curved surface plane in high magnetic fields. Our observation provides an exotic class of surface states that might be used for electronic and spintronic devices.
Verification tests for contaminant transport codes
Rowe, R.K.; Nadarajah, P.
1996-12-31
The importance of verifying contaminant transport codes and the techniques that may be used in this verification process are discussed. Commonly used contaminant transport codes are characterized as belonging to one of several types or classes of solution, such as analytic, finite layer, boundary element, finite difference and finite element. Both the level of approximation and the solution methodology should be verified for each contaminant transport code. One powerful method that may be used in contaminant transport code verification is cross-checking (benchmarking) with other codes. This technique is used to check the results of codes from one solution class with the results of codes from another solution class. In this paper cross-checking is performed for three classes of solution; these are, analytic, finite layer, and finite element.
One-Dimensional Czedli-Type Islands
ERIC Educational Resources Information Center
Horvath, Eszter K.; Mader, Attila; Tepavcevic, Andreja
2011-01-01
The notion of an island has surfaced in recent algebra and coding theory research. Discrete versions provide interesting combinatorial problems. This paper presents the one-dimensional case with finitely many heights, a topic convenient for student research.
Subsurface Flow and Contaminant Transport
2000-09-19
FACT is a transient three-dimensional, finite element code for simulating isothermal groundwater flow, moisture movement, and solute transport in variably and/or fully saturated subsurface porous media. Both single and dual-domain transport formulations are available. Transport mechanisms considered include advection, hydrodynamic dispersion, linear adsorption, mobile/immobile mass transfer and first-order degradation. A wide range of acquifier conditions and remediation systems commonly encountered in the field can be simulated. Notable boundary condition (BC) options include, a combined rechargemore » and drain BC for simulating recirculation wells, and a head dependent well BC that computes flow based on specified drawdown. The code is designed to handle highly heterogenous, multi-layer, acquifer systems in a numerically efficient manner. Subsurface structure is represented with vertically distorted rectangular brick elements in a Cartesian system. The groundwater flow equation is approximated using the Bubnov-Galerkin finite element method in conjunction with an efficient symmetric Preconditioned Conjugate Gradient (PCG) ICCG matrix solver. The solute transport equation is approximated using an upstream weighted residual finite element method designed to alleviate numerical oscillation. An efficient asymmetric PCG (ORTHOMIN) matrix solver is employed for transport. For both the flow and transport equations, element matrices are computed from either influence coefficient formulas for speed, or two point Gauss-Legendre quadrature for accuracy. Non-linear flow problems can be solved using either Newton-Ralphson linearization or Picard iteration, with under-relaxation formulas to further enhance convergence. Dynamic memory allocation is implemented using Fortran 90 constructs. FACT coding is clean and modular.« less
Anomalous heat conduction in a one-dimensional ideal gas.
Casati, Giulio; Prosen, Tomaz
2003-01-01
We provide firm convincing evidence that the energy transport in a one-dimensional gas of elastically colliding free particles of unequal masses is anomalous, i.e., the Fourier law does not hold. Our conclusions are confirmed by a theoretical and numerical analysis based on a Green-Kubo-type approach specialized to momentum-conserving lattices. PMID:12636549
Enforced one-dimensional photoconductivity in core-cladding hexabenzocoronenes.
Cohen, Yaron S; Xiao, Shengxiong; Steigerwald, Michael L; Nuckolls, Colin; Kagan, Cherie R
2006-12-01
Photoconductivity in contorted hexabenzocoronene liquid crystals is found to be exclusively one-dimensional. Spectroscopic measurements and density functional theory support the existence of two pi-systems attributed to a low-energy radialene-core and higher energy out-of-plane alkoxyphenyl rings. Persistent photocurrents, measured as a function of field, channel length, and intensity, fit a stretched exponential characteristic of intracolumnar transport, restricted through the radialene-core by the alkoxyphenyl-cladding. Bimolecular recombination is enhanced with increasing carrier concentration by the system's one-dimensionality.
Arctic seabirds transport marine-derived contaminants.
Blais, Jules M; Kimpe, Lynda E; McMahon, Dominique; Keatley, Bronwyn E; Mallory, Mark L; Douglas, Marianne S V; Smol, John P
2005-07-15
Long-range atmospheric transport of pollutants is generally assumed to be the main vector for arctic contamination, because local pollution sources are rare. We show that arctic seabirds, which occupy high trophic levels in marine food webs, are the dominant vectors for the transport of marine-derived contaminants to coastal ponds. The sediments of ponds most affected by seabirds had 60 times higher DDT, 25 times higher mercury, and 10 times higher hexachlorobenzene concentrations than nearby control sites. Bird guano greatly stimulates biological productivity in these extreme environments but also serves as a major source of industrial and agricultural pollutants in these remote ecosystems.
Contaminant transport in organophilic waste deposit liners
Stockmeyer, M.R.; Madsen, F.T.; Kahr, G.
1995-12-31
The advective transport and diffusive transport of phenol through a soil liner material improve with organophilic bentonites was studied. The results were compared with the transport of phenol through the unimproved soil, a silty sand with a natural clay minerals content of approximately 5%, and through samples which were blended with a common calcium bentonite. With an increasing amount of added organophilic bentonite the adsorption capacity of the liner material and the contaminant retention increase. The diffusive transport of phenol is significantly retarded in the presence of organophilic bentonites, whereas the addition of a common hydrophilic calcium bentonite to the liner material only reduces the hydraulic permeability. There is little contaminant retention due to a low adsorption capacity for phenol of the hydrophilic bentonite. The diffusion is independent on the permeability of a liner material. In the appendix, the significance and the velocity of the hydraulic and diffusive contaminant transport of phenol as an organic test compound in a mineral sealing layer were studied. In a natural, hydrophilic, 1 m-thick liner, diffusion was calculated to be the faster transport mechanism. In the presence of organophilic bentonites the diffusive transport of phenol was found to be considerably hindered. 17 refs., 8 figs., 5 tabs.
Stationary one-dimensional dispersive shock waves.
Kartashov, Yaroslav V; Kamchatnov, Anatoly M
2012-02-01
We address shock waves generated upon the interaction of tilted plane waves with negative refractive index defects in defocusing media with linear gain and two-photon absorption. We found that, in contrast to conservative media where one-dimensional dispersive shock waves usually exist only as nonstationary objects expanding away from a defect or generating beam, the competition between gain and two-photon absorption in a dissipative medium results in the formation of localized stationary dispersive shock waves, whose transverse extent may considerably exceed that of the refractive index defect. One-dimensional dispersive shock waves are stable if the defect strength does not exceed a certain critical value.
One-Dimensional Wavefront Sensor Analysis
1996-04-25
This software analyzes one-dimensional wavefront sensor data acquired with any of several data acquisition systems. It analyzes the data to determine centroids, wavefront slopes and overall wavefront error. The data can be displayed in many formats, with plots of various parameters vs time and position, including computer generated movies. Data can also be exported for use by other programs.
One-Dimensional Oscillator in a Box
ERIC Educational Resources Information Center
Amore, Paolo; Fernandez, Francisco M.
2010-01-01
We discuss a quantum-mechanical model of two particles that interact by means of a harmonic potential and are confined to a one-dimensional box with impenetrable walls. We apply perturbation theory to the cases of different and equal masses and analyse the symmetry of the states in the latter case. We compare the approximate perturbation results…
One-dimensional quantum pump simulated by cold atoms
NASA Astrophysics Data System (ADS)
Xiao, Yun-Chang; Zhu, Ming-Han; Liu, Zheng-Qin
2015-05-01
Quantum pump set up in one-dimensional (1D) channel was proposed by the cold atom simulation. The target pumping system is driven by the double time-dependent potentials. We investigated that the system can be achieved via the study of the cold atoms simulation. And by using the Floquet scattering method and the related transport theories in the mesoscopic systems, simulations of the pumping processes were presented in detail.
Transient One-dimensional Pipe Flow Analyzer
1986-04-08
TOPAZ-SNLL, the Transient One- dimensional Pipe flow AnalyZer code, is a user-friendly computer program for modeling the heat transfer, fluid mechanics, and thermodynamics of multi-species gas transfer in arbitrary arrangements of pipes, valves, vessels, and flow branches. Although the flow conservation equations are assumed to be one-dimensional and transient, multidimensional features of internal fluid flow and heat transfer may be accounted for using the available quasi-steady flow correlations (e.g., Moody friction factor correlation and variousmore » form loss and heat transfer correlations). Users may also model the effects of moving system boundaries such as pistons, diaphragms, and bladders. The features of fully compressible flow are modeled, including the propagation of shocks and rarefaction waves, as well as the establishment of multiple choke points along the flow path.« less
Transient One-dimensional Pipe Flow Analyzer
1986-04-08
TOPAZ-SNLL, the Transient One- dimensional Pipe flow AnalyZer code, is a user-friendly computer program for modeling the heat transfer, fluid mechanics, and thermodynamics of multi-species gas transfer in arbitrary arrangements of pipes, valves, vessels, and flow branches. Although the flow conservation equations are assumed to be one-dimensional and transient, multidimensional features of internal fluid flow and heat transfer may be accounted for using the available quasi-steady flow correlations (e.g., Moody friction factor correlation and various form loss and heat transfer correlations). Users may also model the effects of moving system boundaries such as pistons, diaphragms, and bladders. The features of fully compressible flow are modeled, including the propagation of shocks and rarefaction waves, as well as the establishment of multiple choke points along the flow path.
One-dimensional nano-interconnection formation.
Ji, Jianlong; Zhou, Zhaoying; Yang, Xing; Zhang, Wendong; Sang, Shengbo; Li, Pengwei
2013-09-23
Interconnection of one-dimensional nanomaterials such as nanowires and carbon nanotubes with other parts or components is crucial for nanodevices to realize electrical contacts and mechanical fixings. Interconnection has been being gradually paid great attention since it is as significant as nanomaterials properties, and determines nanodevices performance in some cases. This paper provides an overview of recent progress on techniques that are commonly used for one-dimensional interconnection formation. In this review, these techniques could be categorized into two different types: two-step and one-step methods according to their established process. The two-step method is constituted by assembly and pinning processes, while the one-step method is a direct formation process of nano-interconnections. In both methods, the electrodeposition approach is illustrated in detail, and its potential mechanism is emphasized.
NASA Astrophysics Data System (ADS)
Ntsime, Basetsana P.; Moitsheki, Raseelo J.
2016-06-01
In this paper we consider a nonlinear convection-dispersion equation arising in contaminant transport. The water flow velocity is considered to be spatially-dependent and dispersion coefficient depends on concentration. A direct group classification resulted in a number of cases for which the governing equation admits Lie point symmetries. In each case the one dimensional optimal system of subalgebras is constructed. Reductions are performed. The reduced ordinary differential equations (ODEs) are nonlinear and difficult to solve exactly. On the other hand we consider the steady state problem and applied the method of canonical coordinates to determine exact solutions.
NASA Astrophysics Data System (ADS)
Ostrowski, J.; Shlomi, S.; Michalak, A.
2007-12-01
The process of estimating the release history of a contaminant in groundwater relies on coupling a limited number of concentration measurements with a groundwater flow and transport model in an inverse modeling framework. The information provided by available measurements is generally not sufficient to fully characterize the unknown release history; therefore, an accurate assessment of the estimation uncertainty is required. The modeler's level of confidence in the transport parameters, expressed as pdfs, can be incorporated into the inverse model to improve the accuracy of the release estimates. In this work, geostatistical inverse modeling is used in conjunction with Monte Carlo sampling of transport parameters to estimate groundwater contaminant release histories. Concentration non-negativity is enforced using a Gibbs sampling algorithm based on a truncated normal distribution. The method is applied to two one-dimensional test cases: a hypothetical dataset commonly used in validating contaminant source identification methods, and data collected from a tetrachloroethylene and trichloroethylene plume at the Dover Air Force Base in Delaware. The estimated release histories and associated uncertainties are compared to results from a geostatistical inverse model where uncertainty in transport parameters is ignored. Results show that the a posteriori uncertainty associated with the model that accounts for parameter uncertainty is higher, but that this model provides a more realistic representation of the release history based on available data. This modified inverse modeling technique has many applications, including assignment of liability in groundwater contamination cases, characterization of groundwater contamination, and model calibration.
TNT transport and fate in contaminated soil
Comfort, S.D.; Shea, P.J.; Hundal, L.S.
1995-11-01
Past disposal practices at munitions production plants have contaminated terrestrial and aquatk ecosystems with 2,4,6-trinitrotoluene (TNT). We determined TNT transport, degradation, and long-term sorption characteristics in soil. Transport experiments were conducted with repacked, unsaturated soil columns containing uncontaminated soil or layers of contaminated and uncontaminated soil. Uncontaminated soil columns received multiple pore volumes (22-50) of a TNT-{sup 3}H{sub 2}O pulse, containing 70 or 6.3 mg TNT L{sup -1} at a constant pore water velocity. TNT breakthrough curves (BTCs) never reached initial solute pulse concentrations. Apex concentrations (C/C{sub o}) were between 0.6 and 0.8 for an initial pulse of 70 mg TNT L{sup -1} and 0.2 to 0.3 for the 6.3 mg TNT L{sup -1} pulse. Earlier TNT breakthrough was observed at the higher pulse concentration. This mobility difference was predicted from the nonlinear adsorption isotherm determined for TNT sorption. In all experiments, a significant fraction of added TNT was recovered as amino degradates of TNT. Mass balance estimates indicated 81% of the added TNT was recovered (as TNT and amino degradates) from columns receiving the 70 mg TNT L{sup -1} pulse compared to 35% from columns receiving the 6.3 mg TNT L{sup -1} pulse. Most of the unaccountable TNT was hypothesized to be unextractable. This was supported by a 168-d sorption experiment, which found that within 14d, 80% of {sup 14}C activity (added as {sup 14}C-TNT) was adsorbed and roughly 40% unextractable. Our observations illustrate that TNT sorption and degradation are concentration-dependent and the assumptions of linear adsorption and adsorption-desorption singularity commonly used in transport modeling, may not be valid for predicting TNT transport in munitions-contaminated soils. 29 refs., 6 figs., 7 tabs.
Computer model of one-dimensional equilibrium controlled sorption processes
Grove, D.B.; Stollenwerk, K.G.
1984-01-01
A numerical solution to the one-dimensional solute-transport equation with equilibrium-controlled sorption and a first-order irreversible-rate reaction is presented. The computer code is written in FORTRAN language, with a variety of options for input and output for user ease. Sorption reactions include Langmuir, Freundlich, and ion-exchange, with or without equal valance. General equations describing transport and reaction processes are solved by finite-difference methods, with nonlinearities accounted for by iteration. Complete documentation of the code, with examples, is included. (USGS)
One-dimensional hypersonic phononic crystals.
Gomopoulos, N; Maschke, D; Koh, C Y; Thomas, E L; Tremel, W; Butt, H-J; Fytas, G
2010-03-10
We report experimental observation of a normal incidence phononic band gap in one-dimensional periodic (SiO(2)/poly(methyl methacrylate)) multilayer film at gigahertz frequencies using Brillouin spectroscopy. The band gap to midgap ratio of 0.30 occurs for elastic wave propagation along the periodicity direction, whereas for inplane propagation the system displays an effective medium behavior. The phononic properties are well captured by numerical simulations. The porosity in the silica layers presents a structural scaffold for the introduction of secondary active media for potential coupling between phonons and other excitations, such as photons and electrons.
Enhancing one dimensional sensitivity with plasmonic coupling.
O'Mullane, Samuel; Peterson, Brennan; Race, Joseph; Keller, Nick; Diebold, Alain C
2014-10-20
In this paper, we propose a cross-grating structure to enhance the critical dimension sensitivity of one dimensional nanometer scale metal gratings. Making use of the interaction between slight changes in refractive index and localized plasmons, we demonstrate sub-angstrom scale sensitivity in this structure. Compared to unaltered infinite metal gratings and truncated finite gratings, this cross-grating structure shows robust spectra dependent mostly on the dimension of the smaller line width and pitch. While typical scatterometry simulations show angstrom resolution at best, this structure has demonstrated picometer resolution. Due to the wide range of acceptable specifications, we expect experimental confirmation of such structures to soon follow. PMID:25401657
The one-dimensional hydrogen atom revisited
NASA Astrophysics Data System (ADS)
Palma, G.; Raff, U.
2006-09-01
The one-dimensional Schrodinger hydrogen atom is an interesting mathematical and physical problem for the study of bound states, eigenfunctions, and quantum-degeneracy issues. This one-dimensional physical system has given rise to some intriguing controversy for more than four decades. Presently, still no definite consensus seems to have been reached. We reanalyzed this apparently controversial problem, approaching it from a Fourier-transform representation method combined with some fundamental (basic) ideas found in self-adjoint extensions of symmetric operators. In disagreement with some previous claims, we found that the complete Balmer energy spectrum is obtained together with an odd-parity set of eigenfunctions. Closed-form solutions in both coordinate and momentum spaces were obtained. No twofold degeneracy was observed as predicted by the degeneracy theorem in one dimension, though it does not necessarily have to hold for potentials with singularities. No ground state with infinite energy exists since the corresponding eigenfunction does not satisfy the Schrodinger equation at the origin.
NASA Astrophysics Data System (ADS)
Kipka, H.; Pfennig, B.; Fink, M.; Kralisch, S.; Krause, P.; Flügel, W.
2010-12-01
Fully spatially distributed hydrological modeling requires a topological linkage of single modeling entities (e.g. Hydrological Response Units - HRU) in order to reproduce relevant attenuation and translation processes within the stream but also during the transport of water in form of lateral surface or subsurface flow. Most often such linkage is considered by a one dimensional (1D) approach which links one modeling entity to only one receiver that follows in flow direction. The comparison with actual lateral water movement in catchments show that such a 1D routing scheme is often too simple which can lead to an overestimation of the runoff concentration along the 1D flow paths. On the other hand an underestimation of runoff in flow cascades that do not reside next to the main 1D flow paths can occur as the affected HRUs don’t receive realistic inflow from their source entities above. As a catchment-wide consequence the 1D routing scheme can result in a significant over- or underestimation of the contributing area for specific parts of a catchment which can have important implications on the spatial distribution of accompanying processes such as spatial variation of soil moisture, soil erosion or nutrient/contaminant transport. To address the problems outlined above a new approach has been developed that allows a multi-dimensional linkage of model entities in such a way that each entity can have various receivers to which the water is passed. This extended routing scheme was implemented in the hydrological, nutrient transport and erosion modeling system J2000-S-E and was used for the simulation of the hydrological processes of a number of meso-scaled catchments in Thuringia, Germany. This work will present the most important facts of the extended routing scheme, the simulation results along with the comparison of those obtained with the 1D linkage and will highlight the impacts on the hydrological process dynamics as well as on the HRU-based mass transport and
Three one-dimensional structural heating programs
NASA Technical Reports Server (NTRS)
Wing, L. D.
1978-01-01
Two computer programs for calculating profiles in a ten-element structure consisting of up to ten materials are presented, along with a third program for calculating the mean temperature for a payload container placed in an orbiting vehicle cargo bay. The three programs are related by the sharing of a common analytical technique; the energy balance is based upon one-dimensional heat transfer. The first program, NQLDW112, assumes a non-ablating surface. NQLDW117 is very similar but allows the outermost element to ablate. NQLDW040 calculates an average temperature profile through an idealized model of the real payload cannister and contents in the cargo bay of an orbiting vehicle.
One-dimensional spin-orbit interferometer
NASA Astrophysics Data System (ADS)
Li, Tommy; Sushkov, Oleg P.
2013-04-01
We demonstrate that the combination of an external magnetic field and the intrinsic spin-orbit interaction results in nonadiabatic precession of the electron spin after transmission through a quantum point contact (QPC). We suggest that this precession may be observed in a device consisting of two QPCs situated in series. The pattern of resonant peaks in the transmission is strongly influenced by the non-Abelian phase resulting from this precession. Moreover, an unusual type of resonance which is associated with suppressed, rather than enhanced, transmission (i.e., antiresonance) emerges in the strongly nonadiabatic regime. The shift in the resonant transmission peaks is dependent on the spin-orbit interaction and therefore offers a way to directly measure these interactions in a ballistic one-dimensional system.
Can contaminant transport models predict breakthrough?
Peng, Wei-Shyuan; Hampton, Duane R.; Konikow, Leonard F.; Kambham, Kiran; Benegar, Jeffery J.
2000-01-01
A solute breakthrough curve measured during a two-well tracer test was successfully predicted in 1986 using specialized contaminant transport models. Water was injected into a confined, unconsolidated sand aquifer and pumped out 125 feet (38.3 m) away at the same steady rate. The injected water was spiked with bromide for over three days; the outflow concentration was monitored for a month. Based on previous tests, the horizontal hydraulic conductivity of the thick aquifer varied by a factor of seven among 12 layers. Assuming stratified flow with small dispersivities, two research groups accurately predicted breakthrough with three-dimensional (12-layer) models using curvilinear elements following the arc-shaped flowlines in this test. Can contaminant transport models commonly used in industry, that use rectangular blocks, also reproduce this breakthrough curve? The two-well test was simulated with four MODFLOW-based models, MT3D (FD and HMOC options), MODFLOWT, MOC3D, and MODFLOW-SURFACT. Using the same 12 layers and small dispersivity used in the successful 1986 simulations, these models fit almost as accurately as the models using curvilinear blocks. Subtle variations in the curves illustrate differences among the codes. Sensitivities of the results to number and size of grid blocks, number of layers, boundary conditions, and values of dispersivity and porosity are briefly presented. The fit between calculated and measured breakthrough curves degenerated as the number of layers and/or grid blocks decreased, reflecting a loss of model predictive power as the level of characterization lessened. Therefore, the breakthrough curve for most field sites can be predicted only qualitatively due to limited characterization of the hydrogeology and contaminant source strength.
Unitary equivalent classes of one-dimensional quantum walks
NASA Astrophysics Data System (ADS)
Ohno, Hiromichi
2016-09-01
This study investigates unitary equivalent classes of one-dimensional quantum walks. We prove that one-dimensional quantum walks are unitary equivalent to quantum walks of Ambainis type and that translation-invariant one-dimensional quantum walks are Szegedy walks. We also present a necessary and sufficient condition for a one-dimensional quantum walk to be a Szegedy walk.
Packaging and transportation of radioactively contaminated lead
Gleason, Eugene; Holden, Gerard
2007-07-01
Under the management of the Nuclear Decommissioning Authority (NDA) the government of the United Kingdom has launched an ambitious program to remediate the nation's nuclear waste legacy. Over a twenty-five year period NDA plans to decommission several first generation nuclear power plants and other radioactive facilities. The use innovative, safe 'fit for purpose' technologies will be a major part of this complex program. This paper will present a case study of a recently completed project undertaken in support of the nuclear decommissioning activities at the Sellafield site in the United Kingdom. The focus is on an innovative application of new packaging technology developed for the safe transportation of radioactively contaminated lead objects. Several companies collaborated on the project and contributed to its safe and successful conclusion. These companies include British Nuclear Group, Gravatom Engineering, W. F. Bowker Transport, Atlantic Container Lines, MHF Logistical Solutions and Energy Solutions. New containers and a new innovative inter-modal packaging system to transport the radioactive lead were developed and demonstrated during the project. The project also demonstrated the potential contribution of international nuclear recycling activities as a safe, economic and feasible technical option for nuclear decommissioning in the United Kingdom. (authors)
Biologically mediated transport of contaminants to aquatic systems.
Blais, Jules M; Macdonald, Robie W; Mackay, Donald; Webster, Eva; Harvey, Colin; Smol, John P
2007-02-15
The prevailing view is that long-range transport of semivolatile contaminants is primarily conducted by the physical system (e.g., winds, currents), and biological transport is typically ignored. Although this view may be correct in terms of bulk budgets and fluxes, it neglects the potential of animals to focus contaminants into foodwebs due to their behaviors and lifecycles. In particular, gregarious animals that biomagnify and bioaccumulate certain contaminants and then migrate and congregate can become the predominant pathway for contaminants in many circumstances. Fish and birds provide prominent examples for such behavior. This review examines the potential for biovector transport to expose populations to contaminants. In addition, we apply a modeling approach to compare the potential of biovector transport to other physical transport pathways for a hypothetical lake receiving large numbers of fish. We conclude that biovector transport should not be neglected when considering environmental risks of biomagnifying contaminants.
High-Level Waste Tanks Multi-Dimensional Contaminant Transport Model Development
Collard, L.B.
1999-11-15
A suite of multi-dimensional computer models was developed to analyze the transport of residual contamination from high-level waste tanks through the subsurface to seeplines. Cases analyzed ranged from all the tanks in the F- and H-tank farms for an overall look; to the Tank 17-20 4-pack to study plume interaction; to individual tanks, such as Tank 17 and 20 for comparison with one-dimensional and modeling. The main purpose of this work was to develop and test the models, so only two relatively conservative contaminants were examined, Tc-99 and I-129. More complex analyses, such as solubility-limited species and radionuclides that head a decay chain were not addressed in this study.
Exciton quasicondensation in one-dimensional systems
NASA Astrophysics Data System (ADS)
Werman, Yochai; Berg, Erez
2015-06-01
Two Luttinger liquids, with an equal density and opposite sign of charge carriers, may exhibit enhanced excitonic correlations. We term such a system an exciton quasicondensate, with a possible realization being two parallel oppositely doped quantum wires, coupled by repulsive Coulomb interactions. We show that this quasiexciton condensate can be stabilized in an extended range of parameters, in both spinless and spinful systems. We calculate the interwire tunneling current-voltage characteristic, and find that a negative differential conductance is a signature of excitonic correlations. For spinful electrons, the excitonic regime is shown to be distinct from the usual quasi-long-range ordered Wigner crystal phase characterized by power-law density wave correlations. The two phases can be clearly distinguished through their interwire tunneling current-voltage characteristics. In the quasiexciton condensate regime the tunneling conductivity diverges at low temperatures and voltages, whereas in the Wigner crystal it is strongly suppressed. Both the Wigner crystal and the excitonic regime are characterized by a divergent Coulomb drag at low temperature. Finally, metallic carbon nanotubes are considered as a special case of such a one-dimensional setup, and it is shown that exciton condensation is favorable due to the additional valley degree of freedom.
One-dimensional model of inertial pumping.
Kornilovitch, Pavel E; Govyadinov, Alexander N; Markel, David P; Torniainen, Erik D
2013-02-01
A one-dimensional model of inertial pumping is introduced and solved. The pump is driven by a high-pressure vapor bubble generated by a microheater positioned asymmetrically in a microchannel. The bubble is approximated as a short-term impulse delivered to the two fluidic columns inside the channel. Fluid dynamics is described by a Newton-like equation with a variable mass, but without the mass derivative term. Because of smaller inertia, the short column refills the channel faster and accumulates a larger mechanical momentum. After bubble collapse the total fluid momentum is nonzero, resulting in a net flow. Two different versions of the model are analyzed in detail, analytically and numerically. In the symmetrical model, the pressure at the channel-reservoir connection plane is assumed constant, whereas in the asymmetrical model it is reduced by a Bernoulli term. For low and intermediate vapor bubble pressures, both models predict the existence of an optimal microheater location. The predicted net flow in the asymmetrical model is smaller by a factor of about 2. For unphysically large vapor pressures, the asymmetrical model predicts saturation of the effect, while in the symmetrical model net flow increases indefinitely. Pumping is reduced by nonzero viscosity, but to a different degree depending on the microheater location. PMID:23496615
A one dimensional model of population growth
NASA Astrophysics Data System (ADS)
Ribeiro, Fabiano L.; Ribeiro, Kayo N.
2015-09-01
In this work, a one dimensional population growth model is proposed. The model, based on the cooperative and competitive individual-individual distance-dependent interaction, allows us to get a full analytical solution. With this analytical approach, it was possible to investigate the dynamics of the population according to some parameters, as intrinsic growth rate, strength of the interaction between individuals, and the distance-dependent interaction. As a consequence of the individuals' interaction, a rich phase diagram to which the population has access was observed. The phases observed are: convergence to carrying capacity, exponential growth, divergence at finite time, and extinction. Moreover, it was also observed that some phases are strictly dependent on the initial condition. For instance, in the cooperative regime with negative intrinsic growth rate, the population can diverge or become extinct according to the initial population size. The phases accessible to the population can be seen as a macroscopic behavior which emerges from the interaction among the individuals (the microscopic level).
One-dimensional model of inertial pumping.
Kornilovitch, Pavel E; Govyadinov, Alexander N; Markel, David P; Torniainen, Erik D
2013-02-01
A one-dimensional model of inertial pumping is introduced and solved. The pump is driven by a high-pressure vapor bubble generated by a microheater positioned asymmetrically in a microchannel. The bubble is approximated as a short-term impulse delivered to the two fluidic columns inside the channel. Fluid dynamics is described by a Newton-like equation with a variable mass, but without the mass derivative term. Because of smaller inertia, the short column refills the channel faster and accumulates a larger mechanical momentum. After bubble collapse the total fluid momentum is nonzero, resulting in a net flow. Two different versions of the model are analyzed in detail, analytically and numerically. In the symmetrical model, the pressure at the channel-reservoir connection plane is assumed constant, whereas in the asymmetrical model it is reduced by a Bernoulli term. For low and intermediate vapor bubble pressures, both models predict the existence of an optimal microheater location. The predicted net flow in the asymmetrical model is smaller by a factor of about 2. For unphysically large vapor pressures, the asymmetrical model predicts saturation of the effect, while in the symmetrical model net flow increases indefinitely. Pumping is reduced by nonzero viscosity, but to a different degree depending on the microheater location.
Parafermion braid statistics in quasi-one-dimensional networks
NASA Astrophysics Data System (ADS)
Clarke, David; Alicea, Jason; Shtengel, Kirill
2012-02-01
One dimensional systems with Majorana zero modes at phase boundaries may be thought of as physical realizations of a discrete quantum wire model first put forth by Kitaev [1]. Proposed methods for braiding such Majorana fermions in one-dimensional wire networks [2] have greatly expanded the set of plausible avenues toward topological quantum computation. Recently, a generalization of the Kitaev model to parafermion modes has been developed.[3] Here, we describe the transport of such parafermion modes along the chain by the adiabatic transformation of the Hamiltonian, analogous to the transport of Majorana fermion modes. We determine the (braid) transformations of the ground state sector allowed by the adiabatic exchange of the parafermion modes in wire networks. We show that, as with Majorana fermions, none of the parafermion braid sets are universal for quantum computation. Certain parafermion chain models, unlike Majorana fermion systems, become universal with the addition of measurement operations. We discuss possible physical realizations of the parafermion models. [4pt] [1] J Alicea et al., Nature Physics 7, 412-417 (2011) [0pt] [2] A. Kitaev, arXiv:cond-mat/0010440v2 [0pt] [3] P. Fendley, unpublished
Shielding analysis of the long length contaminated equipment transportation package
Nelson, J.V., Westinghouse Hanford
1996-05-10
A shielding analysis of a potential long length contaminated equipment transportation package was completed. The analysis was performed to support the design of the transportation package and external shielding.
Perched-Water Analysis Related to Deep Vadose Zone Contaminant Transport and Impact to Groundwater
Oostrom, Martinus; Truex, Michael J.; Carroll, KC; Chronister, Glen B.
2013-11-15
Perched-water conditions have been observed in the vadose zone above a fine-grained zone that is located just a few meters above the water table beneath the B-complex at the Hanford Site. The perched water, containing elevated concentrations of uranium and technetium-99, is important to consider in evaluating the future flux of contaminated water into the groundwater. A study was conducted to examine the perched-water conditions and quantitatively evaluate 1) factors that control perching behavior, 2) contaminant flux toward groundwater, and, 3) associated groundwater impact. Based on the current vertical transport pathways and large areal extent of the perched system, the evaluation was conducted using a one-dimensional (1-D) analysis. Steady-state scoping calculations showed that the perching-layer hydraulic conductivity is likely to be up to two orders of magnitude less than the base case value obtained from Hanford site literature. Numerical flow and transport simulations provided both steady-state and transient system estimates of water and contaminant behavior and were used to further refine the range of conditions consistent with current observations of perched water height and to provide estimates of future water and contaminant flux to groundwater. With a recharge rate of 6 cm/yr, representative of current disturbed surface conditions, contaminant flux from the perched water occurs over a time interval of tens of years. However, if the recharge rate is 0.35 cm/yr, representative of returning recharge to pre-Hanford Site levels, the contaminant flux into the groundwater is spread over hundreds of years. It was also demonstrated that removal of perched water by pumping would reduce the flux of water (and associated contaminants) to the groundwater, thereby impacting the long-term rate of contaminant movement to the groundwater.
One-dimensional quantum spin heterojunction as a thermal switch
NASA Astrophysics Data System (ADS)
Yang, Chuan-Jing; Jin, Li-Hui; Gong, Wei-Jiang
2016-03-01
We study the thermal transport through a quantum spin-1 2 heterojunction, which consists of a finite-size chain with two-site anisotropic XY interaction and three-site XZX+YZY interaction coupled at its ends to two semi-infinite isotropic XY chains. By performing the Jordan-Wigner transformation, the original spin Hamiltonian is mapped onto a fermionic Hamiltonian. Then, the fermionic structure is discussed, and the heat current as a function of structural parameters is evaluated. It is found that the magnetic fields applied at respective chains play different roles in adjusting the heat current in this heterojunction. Moreover, the interplay between the anisotropy of the XY interaction and the three-site spin interaction assists to further control the thermal transport. In view of the numerical results, we propose this heterojunction to be an alternate candidate for manipulating the heat current in one-dimensional (1D) systems.
Feed gas contaminant removal in ion transport membrane systems
Underwood, Richard Paul; Makitka, III, Alexander; Carolan, Michael Francis
2012-04-03
An oxygen ion transport membrane process wherein a heated oxygen-containing gas having one or more contaminants is contacted with a reactive solid material to remove the one or more contaminants. The reactive solid material is provided as a deposit on a support. The one or more contaminant compounds in the heated oxygen-containing gas react with the reactive solid material. The contaminant-depleted oxygen-containing gas is contacted with a membrane, and oxygen is transported through the membrane to provide transported oxygen.
Transmission resonances anomaly in one-dimensional disordered quantum systems
NASA Astrophysics Data System (ADS)
Eisenbach, A.; Bliokh, Y.; Freilkher, V.; Kaveh, M.; Berkovits, R.
2016-07-01
Connections between the electronic eigenstates and conductivity of one-dimensional (1D) disordered systems is studied in the framework of the tight-binding model. We show that for weak disorder only part of the states exhibit resonant transmission and contribute to the conductivity. The rest of the eigenvalues are not associated with peaks in transmission and the amplitudes of their wave functions do not exhibit a significant maxima within the sample. Moreover, unlike ordinary states, the lifetimes of these "hidden" modes either remain constant or even decrease (depending on the coupling with the leads) as the disorder becomes stronger. In a wide range of the disorder strengths, the averaged ratio of the number of transmission peaks to the total number of the eigenstates is independent of the degree of disorder and is close to the value √{2 /5 }, which was derived analytically in the weak-scattering approximation. These results are in perfect analogy to the spectral and transport properties of light in one-dimensional randomly inhomogeneous media [Y. P. Bliokh et al., New J. Phys. 17, 113009 (2015), 10.1088/1367-2630/17/11/113009], which provides strong grounds to believe that the existence of hidden, nonconducting modes is a general phenomenon inherent to 1D open random systems, and their fraction of the total density of states is the same for quantum particles and classical waves.
Simulating higher-dimensional geometries in GADRAS using approximate one-dimensional solutions.
Thoreson, Gregory G.; Mitchell, Dean J; Harding, Lee T.
2013-02-01
The Gamma Detector Response and Analysis Software (GADRAS) software package is capable of simulating the radiation transport physics for one-dimensional models. Spherical shells are naturally one-dimensional, and have been the focus of development and benchmarking. However, some objects are not spherical in shape, such as cylinders and boxes. These are not one-dimensional. Simulating the radiation transport in two or three dimensions is unattractive because of the extra computation time required. To maintain computational efficiency, higher-dimensional geometries require approximations to simulate them in one-dimension. This report summarizes the theory behind these approximations, tests the theory against other simulations, and compares the results to experimental data. Based on the results, it is recommended that GADRAS users always attempt to approximate reality using spherical shells. However, if fissile material is present, it is imperative that the shape of the one-dimensional model matches the fissile material, including the use of slab and cylinder geometry.
Reprint of : Absorbing/Emitting Phonons with one dimensional MOSFETs
NASA Astrophysics Data System (ADS)
Bosisio, Riccardo; Gorini, Cosimo; Fleury, Geneviève; Pichard, Jean-Louis
2016-08-01
We consider nanowires in the field effect transistor device configuration. Modeling each nanowire as a one dimensional lattice with random site potentials, we study the heat exchanges between the nanowire electrons and the substrate phonons, when electron transport is due to phonon-assisted hops between localized states. Shifting the nanowire conduction band with a metallic gate induces different behaviors. When the Fermi potential is located near the band center, a bias voltage gives rise to small local heat exchanges which fluctuate randomly along the nanowire. When it is located near one of the band edges, the bias voltage yields heat currents which flow mainly from the substrate towards the nanowire near one boundary of the nanowire, and in the opposite direction near the other boundary. This opens interesting perspectives for heat management at submicron scales: arrays of parallel gated nanowires could be used for a field control of phonon emission/absorption.
Entanglement dynamics in one-dimensional quantum cellular automata
Brennen, Gavin K.; Williams, Jamie E.
2003-10-01
Several proposed schemes for the physical realization of a quantum computer consist of qubits arranged in a cellular array. In the quantum circuit model of quantum computation, an often complex series of two-qubit gate operations is required between arbitrarily distant pairs of lattice qubits. An alternative model of quantum computation based on quantum cellular automata (QCA) requires only homogeneous local interactions that can be implemented in parallel. This would be a huge simplification in an actual experiment. We find some minimal physical requirements for the construction of unitary QCA in a one-dimensional Ising spin chain and demonstrate optimal pulse sequences for information transport and entanglement distribution. We also introduce the theory of nonunitary QCA and show by example that nonunitary rules can generate environment assisted entanglement.
FACILITATED TRANSPORT OF INORGANIC CONTAMINANTS IN GROUNDWATER: PART II. COLLOIDAL TRANSPORT
This project consisted of both field and laboratory components. Field studies evaluated routine sampling procedures for determination of aqueous inorganicgeochemistry and assessment of contaminant transport by colloidal mobility. Research at three different metal-contaminated sit...
NASA Astrophysics Data System (ADS)
Sanders, J. E.; Miller, G. R.
2015-12-01
Magnetic shell crosslinked knedel-like nanoparticles (MSCKs) were originally engineered to aid in the cleanup of oil spills. These polymeric particles are spherical and approximately 70 nm in diameter. MSCKs have a hydrophobic shell and hydrophilic core which encapsulates suspended iron oxide nanoparticles, rendering them magnetic. MSCKs operate like discrete surfactant packets: increasing the mobility and apparent solubility of hydrophobic species, but do so within the confines of discrete particles which can then be recovered by filtration or magnetic removal. MSCKs accomplish this via sequestration of hydrophobic species from through the hydrophilic shell and into the hydrophobic core where hydrocarbon contaminants are entropically stabilized. In batch reactor testing, MSCKs have been shown to sequester crude oil up to ten times their mass (1000 mg of oil per 100 mg of MSCKs). This study examines the transport characteristics and contaminant sequestration capabilities of MSCKs in saturated porous media, in order to establish their potential for use in groundwater remediation. Baseline MSCK transport parameters were determined via one dimensional impulse column experiments. MSCKs were readily transported in saturated sand, with an average recovery rate of 99%. In the presence of 10% clay particles, recovery was reduced to 68%. MSCKs were able to completely sequester an aqueous phase pollutant (8.7 mg/L m-xylene), although it further reduced their recovery rate to 61% in sand and 53% in clay. The presence of a free phase contaminant (5% of pore space occupied by mineral oil) reduced MSCKs recovery in sand to 53%. The MSCKs recovered in the effluent had sequestered the mineral at ratios far below their capability (3-10 mg of oil per 100 mg of MSCKs). Overall, this study indicated that MSCKs show a number of promising attributes for use in remediation. However, further manipulation of their chemical and morphological properties is needed, with the objective of
Preliminary study of niobium alloy contamination by transport through helium
NASA Technical Reports Server (NTRS)
Scheuermann, C. M.; Moore, T. J.; Wheeler, D. R.
1987-01-01
Transport of gaseous contaminants through the working fluid to or from sensitive refractory alloys is theoretically possible during long time operation of Brayton and Stirling space power generation systems which use a gas as the working fluid. A test was designed which could give an answer to whether transport of contaminants through the working fluid was a potential major problem. The findings of that preliminary study are summarized.
A reactive transport model for mercury fate in contaminated soil--sensitivity analysis.
Leterme, Bertrand; Jacques, Diederik
2015-11-01
We present a sensitivity analysis of a reactive transport model of mercury (Hg) fate in contaminated soil systems. The one-dimensional model, presented in Leterme et al. (2014), couples water flow in variably saturated conditions with Hg physico-chemical reactions. The sensitivity of Hg leaching and volatilisation to parameter uncertainty is examined using the elementary effect method. A test case is built using a hypothetical 1-m depth sandy soil and a 50-year time series of daily precipitation and evapotranspiration. Hg anthropogenic contamination is simulated in the topsoil by separately considering three different sources: cinnabar, non-aqueous phase liquid and aqueous mercuric chloride. The model sensitivity to a set of 13 input parameters is assessed, using three different model outputs (volatilized Hg, leached Hg, Hg still present in the contaminated soil horizon). Results show that dissolved organic matter (DOM) concentration in soil solution and the binding constant to DOM thiol groups are critical parameters, as well as parameters related to Hg sorption to humic and fulvic acids in solid organic matter. Initial Hg concentration is also identified as a sensitive parameter. The sensitivity analysis also brings out non-monotonic model behaviour for certain parameters.
Simulation of phosphate transport in sewage-contaminated groundwater, Cape Cod, Massachusetts
Stollenwerk, K.G.
1996-01-01
Sewage-contaminated groundwater currently discharges to Ashumet Pond, located on Cape Cod, Massachusetts Phosphate concentrations as high as 60 ??mol l-1 have been measured in groundwater entering Ashumet Pond, and there is concern that the rate of eutrophication could increase. Phosphate in the sewage plume is sorbed by aquifer sediment; the amount is a function of phosphate concentration and pH. A nonelectrostatic surface-complexation model coupled with a one-dimensional solute-transport code was used to simulate sorption and desorption of phosphate in laboratory column experiments. The model simulated sorption of phosphate reasonably well, although the slow rate of approach to complete breakthrough indicated a nonequilibrium process that was not accounted for in the solute-transport model The rate of phosphate desorption in the column experiments was relatively slow Phosphate could still be measured in effluent after 160 pore volumes of uncontaminated groundwater had been flushed through the columns. Desorption was partly a function of the slowly decreasing pH in the columns and could be modeled quantitatively. Disposal of sewage at this site is scheduled to stop in 1995; however, a large reservoir of sorbed phosphate exists on aquifer sediment upgradient from Ashumet Pond. Computer simulations predict that desorption of phosphate could result in contamination of Ashumet Pond for decades.
The new potential for understanding groundwater contaminant transport.
Hadley, Paul W; Newell, Charles
2014-01-01
The groundwater remediation field has been changing constantly since it first emerged in the 1970s. The remediation field has evolved from a dissolved-phase centric conceptual model to a DNAPL-dominated one, which is now being questioned due to a renewed appreciation of matrix diffusion effects on remediation. Detailed observations about contaminant transport have emerged from the remediation field, and challenge the validity of one of the mainstays of the groundwater solute transport modeling world: the concept of mechanical dispersion (Payne et al. 2008). We review and discuss how a new conceptual model of contaminant transport based on diffusion (the usurper) may topple the well-established position of mechanical dispersion (the status quo) that is commonly used in almost every groundwater contaminant transport model, and evaluate the status of existing models and modeling studies that were conducted using advection-dispersion models.
Reentrant phase coherence in a quasi-one-dimensional superconductor
NASA Astrophysics Data System (ADS)
Ansermet, Diane; Petrovic, Alexander P.; He, Shikun; Chernyshov, Dmitri; Hoesch, Moritz; Salloum, Diala; Gougeon, Patrick; Potel, Michel; Boeri, Lilia; Andersen, Ole K.; Panagopoulos, Christos
Short coherence lengths characteristic of low-dimensional superconductors are related to high critical fields or temperatures. Fatally, such materials are often sensitive to disorder and suffer from phase fluctuations in the order parameter which diverge with temperature T, magnetic field H or current I. To solve synthesis and fluctuation problems, we propose to build superconductors from inhomogeneous composites of nanofilaments. Single crystals of quasi-one-dimensional Na2-δMo6Se6 featuring Na vacancy disorder (δ ~ 0 . 2) behave as percolative networks of superconducting nanowires. Long range order is established via transverse coupling between individual filaments, yet phase coherence is unstable to fluctuations and localization in the zero-(T, H, I) limit. A region of reentrant phase coherence develops upon raising (T, H, I) and is attributed to an enhancement of the transverse coupling due to electron delocalization. The observed reentrance in the electronic transport coincides with a peak in the Josephson energy EJ at non-zero (T, H, I). Na2-δMo6Se6 is a blueprint for a new generation of low dimensional superconductors with resilience to phase fluctuations at high (T, H, I). This work was supported by the National Research Foundation, Singapore, through Grant NRF-CRP4-2008-04.
Transport of trace contaminants through porous media
NASA Technical Reports Server (NTRS)
Madey, R.
1975-01-01
Research accomplishments in the following areas are discussed: (1) the calibration of the gas chromatograph for acetaldehyde and ethanol; (2) the development of data reduction and analysis methods; (3) the generation and analysis of experimental data for the transport of 100 ppm acetaldehyde through a cylindrical bed packed with activated carbon granules; (4) the generation and analysis of experimental data for the transport of 100 ppm ethanol through a cylindrical bed packed with activated carbon granules; and (5) a comparison of the volume adsorption capacity of activated carbon for 100 ppm concentrations of acetaldehyde, ethanol, and acetone. Activities in progress and planned activities are reviewed.
Preliminary study of niobium alloy contamination by transport through helium
NASA Technical Reports Server (NTRS)
Scheuermann, Coulson M.; Moore, Thomas J.; Wheeler, Donald R.
1987-01-01
Preliminary tests were conducted to determine if interstitial element transport through a circulating helium working fluid was a potential problem in Brayton and Stirling space power systems. Test specimens exposed to a thermal gradient for up to 3000-hr included Nb-1%Zr, a Sm-Co alloy (referred to as SmCo in this paper), Hiperco 50 steel, and alumina to simulate various engine components of the Brayton and Stirling systems. Results indicate that helium transport of interstitial contaminants can be minimized over a 7-yr life with a monometallic Nb-1%Zr design. Exposure with other materials indicated a potential for interstitial contaminant transport. Determination of contamination kinetics and the effects on structural integrity will require additional testing.
Contaminant transport from Elliott and Commencement Bays. Technical memo
Curl, H.C.; Baker, E.T.; Bates, T.S.; Cannon, G.A.; Feely, R.A.
1988-04-01
Contaminant transport from Elliott and Commencement Bays to the main basin of the Puget Sound was investigated by the Pacific Marine Environmental Laboratory during the spring and summer of 1985 and January of 1986. Distributions of water properties (salinity, suspended particulate matter, and toxic trace metals and organics) were mapped during periods of high river runoff and during combined sewer outflow after heavy rainfall. Results indicate that: (1) dissolved contaminants remain in the very thin, fresh-water plume and are transported through the bays into the main basin quite rapidly; (2) PCB and DDT isomers were undetectable in either bay; and (3) there was no evidence that resuspension and transport of contaminated bottom sediments was taking place in Elliot Bay. These results must be qualified due to the short periods during which measurements were taken.
Tomasko, D.
1990-04-01
One-dimensional analytical expressions are developed to simulate two processes in a homogeneous porous medium: contaminant transport through a porous medium that has a zero-concentration sink located at a finite distance from a step-function source; and contaminant transport through a porous medium that has an initial steady-state distribution corresponding to a constant strength source and zero-concentration sink separated by a finite distance. The governing equations are cast in dimensionless form, making use of the flow system's Peclet number. Evaluation of the analytical expressions is accomplished by numerical inversion of Laplace-space concentrations using either a full Fourier series approach with acceleration, or the Stehfest algorithm. The analytical expressions are used to evaluate possible contaminant conditions at the Weldon Spring quarry near Weldon Spring, Missouri. The following results have been found: contaminant concentrations should be at or near steady-state conditions; the spatial distribution of contaminants should be a function of the flow system's Peclet number; contaminant concentrations near the Femme Osage Slough should approach zero; contaminant concentrations near the quarry during dewatering and bulk-waste removal should monotonically decrease with time; and the spatial distribution of contaminants during remedial activities should be relatively flat, especially near the dewatering pumps. Future work will entail evaluating existing radionuclide or chemical concentration data to determine the applicability of the proposed contaminant transport model and to improve the hydrogeological conceptualization of the quarry area and vicinity. 20 refs., 27 figs.
One-dimensional reacting gas nonequilibrium performance program
NASA Technical Reports Server (NTRS)
Frey, H. M.; Kliegel, J. R.
1968-01-01
Computer program calculates the inviscid one-dimensional equilibrium, frozen, and nonequilibrium nozzle expansion of gaseous propellant exhaust mixtures containing the elements - carbon, hydrogen, oxygen, nitrogen, fluorine and chlorine. The program performs calculations for conical nozzles only.
Extending the Analysis of One-Dimensional Motion.
ERIC Educational Resources Information Center
Canderle, Luis H.
1999-01-01
Proposes that introductory physics courses extend the analysis of one-dimensional motion to a more sophisticated level. Gives four experimental setups and graphical analysis of the distance, velocity, and acceleration in the vertical and horizontal directions. (WRM)
Asymptotic formula for eigenvalues of one dimensional Dirac system
NASA Astrophysics Data System (ADS)
Ulusoy, Ismail; Penahlı, Etibar
2016-06-01
In this paper, we study the spectral problem for one dimensional Dirac system with Dirichlet boundary conditions. By using Counting lemma, we give an asymptotic formulas of eigenvalues of Dirac system.
Wagner, B.J.
1992-01-01
Parameter estimation and contaminant source characterization are key steps in the development of a coupled groundwater flow and contaminant transport simulation model. Here a methodologyfor simultaneous model parameter estimation and source characterization is presented. The parameter estimation/source characterization inverse model combines groundwater flow and contaminant transport simulation with non-linear maximum likelihood estimation to determine optimal estimates of the unknown model parameters and source characteristics based on measurements of hydraulic head and contaminant concentration. First-order uncertainty analysis provides a means for assessing the reliability of the maximum likelihood estimates and evaluating the accuracy and reliability of the flow and transport model predictions. A series of hypothetical examples is presented to demonstrate the ability of the inverse model to solve the combined parameter estimation/source characterization inverse problem. Hydraulic conductivities, effective porosity, longitudinal and transverse dispersivities, boundary flux, and contaminant flux at the source are estimated for a two-dimensional groundwater system. In addition, characterization of the history of contaminant disposal or location of the contaminant source is demonstrated. Finally, the problem of estimating the statistical parameters that describe the errors associated with the head and concentration data is addressed. A stage-wise estimation procedure is used to jointly estimate these statistical parameters along with the unknown model parameters and source characteristics. ?? 1992.
One-dimensional simulation of temperature and moisture in atmospheric and soil boundary layers
NASA Technical Reports Server (NTRS)
Bornstein, R. D.; Santhanam, K.
1981-01-01
Meteorologists are interested in modeling the vertical flow of heat and moisture through the soil in order to better simulate the vertical and temporal variations of the atmospheric boundary layer. The one dimensional planetary boundary layer model of is modified by the addition of transport equations to be solved by a finite difference technique to predict soil moisture.
The effects of a perturbed source on contaminant transport near the Weldon Spring quarry
Tomasko, D.
1989-03-01
The effects of a perturbed contamination source at the Weldon Spring quarry in St. Charles County, Missouri, on downstream solute concentrations were investigated using one-dimensional analytical solutions to an advection-dispersion equation developed for both constant-strength and multiple-stepped source functions. A sensitivity study using parameter base-case values and ranges consistent with the geologic conceptualization of the quarry area indicates that the parameters having the greatest effect on predicted concentrations are the distance from the quarry to the point of interest, the average linear groundwater velocity, the contaminant retardation coefficient, and the amplitude and duration of the source perturbation caused by response action activities. Use of base-case parameter value and realistic values for the amplitude and duration of the source perturbation produced a small effect on solute concentrations near the western extremity of the nearby municipal well field, as well as small uncertainties in the predicted results for the assumed model. The effect of simplifying assumptions made in deriving the analytic solution is unknown: use of a multidimensional flow and transport model and additional field work are needed to validate the model. 13 refs., 18 figs.
NASA Astrophysics Data System (ADS)
Li, Nianbei; Li, Baowen
2012-12-01
Heat transport in low-dimensional systems has attracted enormous attention from both theoretical and experimental aspects due to its significance to the perception of fundamental energy transport theory and its potential applications in the emerging field of phononics: manipulating heat flow with electronic anologs. We consider the heat conduction of one-dimensional nonlinear lattice models. The energy carriers responsible for the heat transport have been identified as the renormalized phonons. Within the framework of renormalized phonons, a phenomenological theory, effective phonon theory, has been developed to explain the heat transport in general one-dimensional nonlinear lattices. With the help of numerical simulations, it has been verified that this effective phonon theory is able to predict the scaling exponents of temperature-dependent thermal conductivities quantitatively and consistently.
Heterolayered, one-dimensional nanobuilding block mat batteries.
Choi, Keun-Ho; Cho, Sung-Ju; Chun, Sang-Jin; Yoo, Jong Tae; Lee, Chang Kee; Kim, Woong; Wu, Qinglin; Park, Sang-Bum; Choi, Don-Ha; Lee, Sun-Young; Lee, Sang-Young
2014-10-01
The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.
One dimensional time-to-explode (ODTX) in HMX spheres
Breshears, D.
1997-06-02
In a series of papers researchers at Lawrence Livermore National Laboratory (LLNL) have reported measurements of the time to explosion in spheres of various high explosives following a rapid, uniform increase in the surface temperature of the sphere. Due to the spherical symmetry, the time-dependent properties of the explosive (temperature, chemical composition, etc.) are functions of the radial spatial coordinate only; thus the name one-dimensional time-to-explosion (ODTX). The LLNL researchers also report an evolving series of computational modeling results for the ODTX experiments, culminating in those obtained using a sophisticated heat transfer code incorporating accurate descriptions of chemical reaction. Although the chemical reaction mechanism used to describe HMX decomposition is quite simple, the computational results agree very well with the experimental data. In addition to reproducing the magnitude and temperature dependence of the measured times to explosion, the computational results also agree with the results of post reaction visual inspection. The ODTX experiments offer a near-ideal example of a transport process (heat transfer in this case) tightly coupled with chemical reaction. The LLNL computational model clearly captures the important features of the ODTX experiments. An obvious question of interest is to what extent the model and/or its individual components (specifically the chemical reaction mechanism) are applicable to other experimental scenarios. Valid exploration of this question requires accurate understanding of (1) the experimental scenario addressed by the LLNL model and (2) details of the application of the model. The author reports here recent work addressing points (1) and (2).
Reductive dissolution and reactive solute transport in a sewage-contaminated glacial outwash aquifer
Lee, R.W.; Bennett, P.C.
1998-01-01
Contamination of shallow ground water by sewage effluent typically contains reduced chemical species that consume dissolved oxygen, developing either a low oxygen geochemical environment or an anaerobic geochemical environment. Based on the load of reduced chemical species discharged to shallow ground water and the amounts of reactants in the aquifer matrix, it should be possible to determine chemical processes in the aquifer and compare observed results to predicted ones. At the Otis Air Base research site (Cape Cod, Massachusetts) where sewage effluent has infiltrated the shallow aquifer since 1936, bacterially mediated processes such as nitrification, denitrification, manganese reduction, and iron reduction have been observed in the contaminant plume. In specific areas of the plume, dissolved manganese and iron have increased significantly where local geochemical conditions are favorable for reduction and transport of these constituents from the aquifer matrix. Dissolved manganese and iron concentrations ranged from 0.02 to 7.3 mg/L, and 0.001 to 13.0 mg/L, respectively, for 21 samples collected from 1988 to 1989. Reduction of manganese and iron is linked to microbial oxidation of sewage carbon, producing bicarbonate and the dissolved metal ions as by-products. Calculated production and flux of CO2 through the unsaturated zone from manganese reduction in the aquifer was 0.035 g/m2/d (12% of measured CO2 flux during winter). Manganese is limited in the aquifer, however. A one-dimensional, reaction-coupled transport model developed for the mildly reducing conditions in the sewage plume nearest the source beds showed that reduction, transport, and removal of manganese from the aquifer sediments should result in iron reduction where manganese has been depleted.
CONTAMINANT TRANSPORT IN PARALLEL FRACTURED MEDIA: SUDICKY AND FRIND REVISITED
This paper is concerned with a modified, nondimensional form of the parallel fracture, contaminant transport model of Sudicky and Frind (1982). The modifications include the boundary condition at the fracture wall, expressed by a parameter , and the power-law relationship betwe...
CONTAMINANT TRANSPORT IN PARALLEL FRACTURED MEDIA: SUDICKY AND FRIND REVISITED
This paper is concerned with a modified, nondimensional form of the parallel fracture, contaminant transport model of Sudicky and Frind (1982). The modifications include the boundary condition at the fracture wall, expressed by a parameter, and the power-law relationship between...
One-dimensional rainbow technique using Fourier domain filtering.
Wu, Yingchun; Promvongsa, Jantarat; Wu, Xuecheng; Cen, Kefa; Grehan, Gerard; Saengkaew, Sawitree
2015-11-16
Rainbow refractometry can measure the refractive index and the size of a droplet simultaneously. The refractive index measurement is extracted from the absolute rainbow scattering angle. Accordingly, the angular calibration is vital for accurate measurements. A new optical design of the one-dimensional rainbow technique is proposed by using a one-dimensional spatial filter in the Fourier domain. The relationship between the scattering angle and the CCD pixel of a recorded rainbow image can be accurately determined by a simple calibration. Moreover, only the light perpendicularly incident on the lens in the angle (φ) direction is selected, which exactly matches the classical inversion algorithm used in rainbow refractometry. Both standard and global one-dimensional rainbow techniques are implemented with the proposed optical design, and are successfully applied to measure the refractive index and the size of a line of n-heptane droplets.
Some topological states in one-dimensional cold atomic systems
Mei, Feng; Zhang, Dan-Wei; Zhu, Shi-Liang
2015-07-15
Ultracold atoms trapped in optical lattices nowadays have been widely used to mimic various models from condensed-matter physics. Recently, many great experimental progresses have been achieved for producing artificial magnetic field and spin–orbit coupling in cold atomic systems, which turn these systems into a new platform for simulating topological states. In this paper, we give a review focusing on quantum simulation of topologically protected soliton modes and topological insulators in one-dimensional cold atomic system. Firstly, the recent achievements towards quantum simulation of one-dimensional models with topological non-trivial states are reviewed, including the celebrated Jackiw–Rebbi model and Su–Schrieffer–Heeger model. Then, we will introduce a dimensional reduction method for systematically constructing high dimensional topological states in lower dimensional models and review its applications on simulating two-dimensional topological insulators in one-dimensional optical superlattices.
One-dimensional rainbow technique using Fourier domain filtering.
Wu, Yingchun; Promvongsa, Jantarat; Wu, Xuecheng; Cen, Kefa; Grehan, Gerard; Saengkaew, Sawitree
2015-11-16
Rainbow refractometry can measure the refractive index and the size of a droplet simultaneously. The refractive index measurement is extracted from the absolute rainbow scattering angle. Accordingly, the angular calibration is vital for accurate measurements. A new optical design of the one-dimensional rainbow technique is proposed by using a one-dimensional spatial filter in the Fourier domain. The relationship between the scattering angle and the CCD pixel of a recorded rainbow image can be accurately determined by a simple calibration. Moreover, only the light perpendicularly incident on the lens in the angle (φ) direction is selected, which exactly matches the classical inversion algorithm used in rainbow refractometry. Both standard and global one-dimensional rainbow techniques are implemented with the proposed optical design, and are successfully applied to measure the refractive index and the size of a line of n-heptane droplets. PMID:26698532
Pose estimation for one-dimensional object with general motion
NASA Astrophysics Data System (ADS)
Liu, Jinbo; Song, Ge; Zhang, Xiaohu
2014-11-01
Our primary interest is in real-time one-dimensional object's pose estimation. In this paper, a method to estimate general motion one-dimensional object's pose, that is, the position and attitude parameters, using a single camera is proposed. Centroid-movement is necessarily continuous and orderly in temporal space, which means it follows at least approximately certain motion law in a short period of time. Therefore, the centroid trajectory in camera frame can be described as a combination of temporal polynomials. Two endpoints on one-dimensional object, A and B, at each time are projected on the corresponding image plane. With the relationship between A, B and centroid C, we can obtain a linear equation system related to the temporal polynomials' coefficients, in which the camera has been calibrated and the image coordinates of A and B are known. Then in the cases that object moves continuous in natural temporal space within the view of a stationary camera, the position of endpoints on the one-dimensional object can be located and also the attitude can be estimated using two end points. Moreover the position of any other point aligned on one-dimensional object can also be solved. Scene information is not needed in the proposed method. If the distance between the endpoints is not known, a scale factor between the object's real positions and the estimated results will exist. In order to improve the algorithm's performance from accuracy and robustness, we derive a pain of linear and optimal algorithms. Simulations' and experiments' results show that the method is valid and robust with respect to various Gaussian noise levels. The paper's work contributes to making self-calibration algorithms using one-dimensional objects applicable to practice. Furthermore, the method can also be used to estimate the pose and shape parameters of parallelogram, prism or cylinder objects.
Explicit solutions of one-dimensional total variation problem
NASA Astrophysics Data System (ADS)
Makovetskii, Artyom; Voronin, Sergei; Kober, Vitaly
2015-09-01
This work deals with denosing of a one-dimensional signal corrupted by additive white Gaussian noise. A common way to solve the problem is to utilize the total variation (TV) method. Basically, the TV regularization minimizes a functional consisting of the sum of fidelity and regularization terms. We derive explicit solutions of the one-dimensional TV regularization problem that help us to restore noisy signals with a direct, non-iterative algorithm. Computer simulation results are provided to illustrate the performance of the proposed algorithm for restoration of noisy signals.
Hybrid surface-relief/volume one dimensional holographic gratings
NASA Astrophysics Data System (ADS)
Lucchetta, D. E.; Spegni, P.; Di Donato, A.; Simoni, F.; Castagna, R.
2015-04-01
Many one dimensional optically patterned photopolymers exist as surface relief or volume phase gratings. However, as far as we know, holographically recorded acrylate-based gratings in which both configurations are present are not described in literature. In this work we report a two steps fabrication process in which a large-area high-resolution hybrid volume/surface relief grating phase gratings is created in a thin film of multiacrylate material spinned on a proper designed substrate. Optical and morphological investigations, made on the optically patterned area, confirm the presence of a one dimensional double (surface relief and Bragg volume phase) periodic structure.
Lateral electronic screening in quasi-one-dimensional plasmons
NASA Astrophysics Data System (ADS)
Lichtenstein, T.; Tegenkamp, C.; Pfnür, H.
2016-09-01
The properties of one-dimensional (1D) plasmons are rather unexplored. We investigated the plasmonic collective excitations, measured as one-dimensional plasmon dispersions with electron energy loss spectroscopy, highly resolved both in energy and lateral momentum, for both phases of Au induced chains on stepped Si(553) substrates. We observe 1D dispersions that are strongly influenced by the lateral chain width and by the interchain coupling. Indications for the existence of two different plasmons originating from two surface bands of the systems are given for the low coverage phase.
Thermal Conductivity of the One-Dimensional Fermi-Hubbard Model.
Karrasch, C; Kennes, D M; Heidrich-Meisner, F
2016-09-01
We study the thermal conductivity of the one-dimensional Fermi-Hubbard model at a finite temperature using a density matrix renormalization group approach. The integrability of this model gives rise to ballistic thermal transport. We calculate the temperature dependence of the thermal Drude weight at half filling for various interaction strengths. The finite-frequency contributions originating from the fact that the energy current is not a conserved quantity are investigated as well. We report evidence that breaking the integrability through a nearest-neighbor interaction leads to vanishing Drude weights and diffusive energy transport. Moreover, we demonstrate that energy spreads ballistically in local quenches with initially inhomogeneous energy density profiles in the integrable case. We discuss the relevance of our results for thermalization in ultracold quantum-gas experiments and for transport measurements with quasi-one-dimensional materials. PMID:27661705
THE IMPACT OF GROUND WATER-SURFACE WATER INTERACTIONS ON CONTAMINANT TRANSPORT AT CONTAMINATED SITES
The purpose of this document is to provide an overview of the dynamics of chemical processes that govern contaminant transport and speciation during water exchange across the GW/SW transition zone. A conceptual model of the GW/SW transition zone is defined to serve as a starting...
Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels
Miller, Julianne J.; Mizell, Steve A.; Nikolich, George; Campbell, Scott A.
2012-02-01
The U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA), Nevada Site Office (NSO), Environmental Restoration Soils Activity has authorized the Desert Research Institute (DRI) to conduct field assessments of potential sediment transport of contaminated soil from Corrective Action Unit (CAU) 550, Area 8 Smoky Contamination Area (CA), during precipitation runoff events. CAU 550 includes Corrective Action Sites (CASs) 08-23-03, 08-23-04, 08-23-06, and 08-23-07; these CASs are associated with tests designated Ceres, Smoky, Oberon, and Titania, respectively.
Mass transfer model of nanoparticle-facilitated contaminant transport in saturated porous media.
Johari, Wan Lutfi Wan; Diamessis, Peter J; Lion, Leonard W
2010-02-01
A one-dimensional model has been evaluated for transport of hydrophobic contaminants, such as polycyclic aromatic hydrocarbon (PAH) compounds, facilitated by synthetic amphiphilic polyurethane (APU) nanoparticles in porous media. APU particles synthesized from poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains have been shown to enhance the desorption rate and mobility of phenanthrene (PHEN) in soil. A reversible process governed by attachment and detachment rates was considered to describe the PMUA binding in soil in addition to PMUA transport through advection and dispersion. Ultimately, an irreversible second-order PMUA attachment rate in which the fractional soil saturation capacity with PMUA was a rate control was found to be adequate to describe the retention of PMUA particles. A gamma-distributed site model (GS) was used to describe the spectrum of physical/chemical constraints for PHEN transfer from solid to aqueous phases. Instantaneous equilibrium was assumed for PMUA-PHEN interactions. The coupled model for PMUA and PHEN behavior successfully described the enhanced elution profile of PHEN by PMUA. Sensitivity analysis was performed to analyze the significance of model parameters on model predictions. The adjustable parameter alpha in the gamma-distribution shapes the contaminant desorption distribution profile as well as elution and breakthrough curves. Model simulations show the use of PMUA can be also expected to improve the release rate of PHEN in soils with higher organic carbon content. The percentage removal of PHEN mass over time is shown to be influenced by the concentration of PMUA added and this information can be used to optimize cost and time require to accomplish a desired remediation goal. PMID:19406449
Mass transfer model of nanoparticle-facilitated contaminant transport in saturated porous media.
Johari, Wan Lutfi Wan; Diamessis, Peter J; Lion, Leonard W
2010-02-01
A one-dimensional model has been evaluated for transport of hydrophobic contaminants, such as polycyclic aromatic hydrocarbon (PAH) compounds, facilitated by synthetic amphiphilic polyurethane (APU) nanoparticles in porous media. APU particles synthesized from poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains have been shown to enhance the desorption rate and mobility of phenanthrene (PHEN) in soil. A reversible process governed by attachment and detachment rates was considered to describe the PMUA binding in soil in addition to PMUA transport through advection and dispersion. Ultimately, an irreversible second-order PMUA attachment rate in which the fractional soil saturation capacity with PMUA was a rate control was found to be adequate to describe the retention of PMUA particles. A gamma-distributed site model (GS) was used to describe the spectrum of physical/chemical constraints for PHEN transfer from solid to aqueous phases. Instantaneous equilibrium was assumed for PMUA-PHEN interactions. The coupled model for PMUA and PHEN behavior successfully described the enhanced elution profile of PHEN by PMUA. Sensitivity analysis was performed to analyze the significance of model parameters on model predictions. The adjustable parameter alpha in the gamma-distribution shapes the contaminant desorption distribution profile as well as elution and breakthrough curves. Model simulations show the use of PMUA can be also expected to improve the release rate of PHEN in soils with higher organic carbon content. The percentage removal of PHEN mass over time is shown to be influenced by the concentration of PMUA added and this information can be used to optimize cost and time require to accomplish a desired remediation goal.
Teaching Module for One-Dimensional, Transient Conduction.
ERIC Educational Resources Information Center
Ribando, Robert J.; O'Leary, Gerald W.
1998-01-01
Describes a PC-based teaching module designed to instruct engineering students in transient one-dimensional conduction heat transfer analysis. The discussion considers problem formulation, nondimensionalization, discretization, numerical stability and the time-step restriction, program operation, and program verification. (MES)
Exact Results for One Dimensional Fluids Through Functional Integration
NASA Astrophysics Data System (ADS)
Fantoni, Riccardo
2016-06-01
We review some of the exactly solvable one dimensional continuum fluid models of equilibrium classical statistical mechanics under the unified setting of functional integration in one dimension. We make some further developments and remarks concerning fluids with penetrable particles. We then apply our developments to the study of the Gaussian core model for which we are unable to find a well defined thermodynamics.
Approximate Approaches to the One-Dimensional Finite Potential Well
ERIC Educational Resources Information Center
Singh, Shilpi; Pathak, Praveen; Singh, Vijay A.
2011-01-01
The one-dimensional finite well is a textbook problem. We propose approximate approaches to obtain the energy levels of the well. The finite well is also encountered in semiconductor heterostructures where the carrier mass inside the well (m[subscript i]) is taken to be distinct from mass outside (m[subscript o]). A relevant parameter is the mass…
Underwater striling engine design with modified one-dimensional model
NASA Astrophysics Data System (ADS)
Li, Daijin; Qin, Kan; Luo, Kai
2015-05-01
Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs) is discussed. And a one-dimensional model incorporated with empirical equations of mechanical loss and auxiliary power obtained from experiments is derived while referring to the Stirling engine computer model of National Aeronautics and Space Administration (NASA). The P-40 Stirling engine with sufficient testing results from NASA is utilized to validate the accuracy of this one-dimensional model. It shows that the maximum error of output power of theoretical analysis results is less than 18% over testing results, and the maximum error of input power is no more than 9%. Finally, a Stirling engine for UUVs is designed with Schmidt analysis method and the modified one-dimensional model, and the results indicate this designed engine is capable of showing desired output power.
Underwater striling engine design with modified one-dimensional model
NASA Astrophysics Data System (ADS)
Li, Daijin; Qin, Kan; Luo, Kai
2015-09-01
Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs) is discussed. And a one-dimensional model incorporated with empirical equations of mechanical loss and auxiliary power obtained from experiments is derived while referring to the Stirling engine computer model of National Aeronautics and Space Administration (NASA). The P-40 Stirling engine with sufficient testing results from NASA is utilized to validate the accuracy of this one-dimensional model. It shows that the maximum error of output power of theoretical analysis results is less than 18% over testing results, and the maximum error of input power is no more than 9%. Finally, a Stirling engine for UUVs is designed with Schmidt analysis method and the modified one-dimensional model, and the results indicate this designed engine is capable of showing desired output power.
Transition density of one-dimensional diffusion with discontinuous drift
NASA Technical Reports Server (NTRS)
Zhang, Weijian
1990-01-01
The transition density of a one-dimensional diffusion process with a discontinuous drift coefficient is studied. A probabilistic representation of the transition density is given, illustrating the close connections between discontinuities of the drift and Brownian local times. In addition, some explicit results are obtained based on the trivariate density of Brownian motion, its occupation, and local times.
One-Dimensional SO2 Predictions for Duct Injection
1993-10-05
DIAN1D is a one-dimensional model that predicts SO2 absorption by slurry droplets injected into a flue gas stream with two-fluid atomizers. DIANUI is an interactive user interface for DIAN1D. It prepares the input file for DIAN1D from plant design specifications and process requirements.
One-Dimensional Ising Model with "k"-Spin Interactions
ERIC Educational Resources Information Center
Fan, Yale
2011-01-01
We examine a generalization of the one-dimensional Ising model involving interactions among neighbourhoods of "k" adjacent spins. The model is solved by exploiting a connection to an interesting computational problem that we call ""k"-SAT on a ring", and is shown to be equivalent to the nearest-neighbour Ising model in the absence of an external…
The Long Decay Model of One-Dimensional Projectile Motion
ERIC Educational Resources Information Center
Lattery, Mark Joseph
2008-01-01
This article introduces a research study on student model formation and development in introductory mechanics. As a point of entry, I present a detailed analysis of the Long Decay Model of one-dimensional projectile motion. This model has been articulated by Galileo ("in De Motu") and by contemporary students. Implications for instruction are…
Sandia One-Dimensional Direct and Inverse Thermal Code
1995-02-27
SODDIT is a reliable tool for solving a wide variety of one-dimensional transient heat conduction problems. Originally developed in 1972 to predict the ablation of graphite/carbon bodies reentering the earth''s atmosphere, it has since been modified by the authors to extend its capabilities well beyond its original scope.
IMPACT OF REDOX DISEQUILIBRIA ON CONTAMINANT TRANSPORT AND REMEDIATION IN SUBSURFACE SYSTEMS
Partitioning to mineral surfaces exerts significant control on inorganic contaminant transport in subsurface systems. Remedial technologies for in-situ treatment of subsurface contamination are frequently designed to optimize the efficiency of contaminant partitioning to solid s...
One-dimensional fast migration of vacancy clusters in metals
Matsukawa, Yoshitaka; Zinkle, Steven J
2007-01-01
The migration of point defects, e.g. crystal lattice vacancies and self-interstitial atoms (SIAs), typically occurs through three-dimensional (3-D) random walk. However, when vacancies and SIAs agglomerate with like defects forming clusters, the migration mode may change. Recently, atomic-scale computer simulations using molecular dynamics (MD) codes have reported that nanometer-sized two-dimensional (2-D) clusters of SIAs exhibit one-dimensional (1-D) fast migration1-7. The 1-D migration mode transports the entire cluster containing several tens of SIAs with a mobility comparable to single SIAs3. This anisotropic migration of SIA clusters can have a significant impact on the evolution of a material fs neutron-irradiation damage microstructure, which dominates the material fs lifetime in nuclear reactor environments8-9. This is also proposed to be a key physical mechanism for the self-organization of nanometer-sized sessile vacancy cluster arrays10-13. Given these findings for SIA clusters, a fundamental question is whether the 1-D migration mode is also possible for 2-D clusters of vacancies. Preceding MD results predicted that 1-D migration of vacancy clusters is possible in body-centered cubic (bcc) iron, but not in face-centered cubic (fcc) copper2. Previous experimental studies have reported 1-D migration of SIA clusters14, but there have been no observations of 1-D vacancy cluster migration. Here we present the first experimental transmission electron microscopy (TEM) dynamic observation demonstrating the 1-D migration of vacancy clusters in fcc gold. It was found that the mobility of the vacancy clusters via the 1-D migration is much higher than single vacancies via 3-D random walk and comparable to single SIAs via 3-D random walk. Hence, the mobility of the glissile clusters is not associated with the character of their constituent point defects. Dynamic conversion of a planar vacancy loop into a 3-D stacking fault tetrahedron geometry was also observed.
Simulation of contaminated sediment transport in White Oak Creek basin
Bao, Y.; Clapp, R.B.; Brenkert, A.L.; Moore, T.D.; Fontaine, T.A.
1995-12-31
This paper presents a systematic approach to management of the contaminated sediments in the White Oak Creek watershed at Oak Ridge National Laboratory near Oak Ridge, Tennessee. The primary contaminant of concern is radioactive cesium-137 ({sup 137}Cs), which binds to soil and sediment particles. The key components in the approach include an intensive sampling and monitoring system for flood events; modeling of hydrological processes, sediment transport, and contaminant flux movement; and a decision framework with a detailed human health risk analysis. Emphasis is placed on modeling of watershed rainfall-runoff and contaminated sediment transport during flooding periods using the Hydrologic Simulation Program- Fortran (HSPF) model. Because a large number of parameters are required in HSPF modeling, the major effort in the modeling process is the calibration of model parameters to make simulation results and measured values agree as closely as possible. An optimization model incorporating the concepts of an expert system was developed to improve calibration results and efficiency. Over a five-year simulation period, the simulated flows match the observed values well. Simulated total amount of sediment loads at various locations during storms match with the observed values within a factor of 1.5. Simulated annual releases of {sup 137}Cs off-site locations match the data within a factor of 2 for the five-year period. The comprehensive modeling approach can provide a valuable tool for decision makers to quantitatively analyze sediment erosion, deposition, and transport; exposure risk related to radionuclides in contaminated sediment; and various management strategies.
Prediction methodology for contaminant transport from rangeland watersheds
Devaurs, M.A.; Springer, E.P.; Lane, L.J.; Langhorst, G.J.
1988-01-01
Weather on arid and semiarid lands can be extremely variable. Runoff is generally emphermeral, and high intensity, short-duration rainfall events are the major stimulus for runoff events. Transport of sediment and associated contaminants occurs with these infrequent events. Incorporation of variability in weather into any prediction technology is essential to provide accurate representations of climate-induced uncertainty in predictions of hydrologic response. The objective of this study is to investigate a method for including short-term climatic variations in analyses for contaminant transport from rangeland watersheds in arid/semiarid regions. Short term is defined here as a twenty to fifty time frame and it is assumed that lone term climatic fluctuations are not observed during this time. Also, most weather records are available for this time period; predictions of greater length are extrapolations of existing records unless corroborative data for longer term trends are collected. Predictions are being made with condensable uncertainty in the weather inputs even if the models for water, sediment, and contaminant transport are perfectly unknown. This study will incorporate uncertainty in weather inputs into the prediction process and address the ramifications of this uncertainty. Uncertainty introduced by improper model or parameter specification is only briefly addressed.
Modeling of contaminant transport in underground coal gasification
Lanhe Yang; Xing Zhang
2009-01-15
In order to study and discuss the impact of contaminants produced from underground coal gasification on groundwater, a coupled seepage-thermodynamics-transport model for underground gasification was developed on the basis of mass and energy conservation and pollutant-transport mechanisms, the mathematical model was solved by the upstream weighted multisell balance method, and the model was calibrated and verified against the experimental site data. The experiment showed that because of the effects of temperature on the surrounding rock of the gasification panel the measured pore-water-pressure was higher than the simulated one; except for in the high temperature zone where the simulation errors of temperature, pore water pressure, and contaminant concentration were relatively high, the simulation values of the overall gasification panel were well fitted with the measured values. As the gasification experiment progressed, the influence range of temperature field expanded, the gradient of groundwater pressure decreased, and the migration velocity of pollutant increased. Eleven months and twenty months after the test, the differences between maximum and minimum water pressure were 2.4 and 1.8 MPa, respectively, and the migration velocities of contaminants were 0.24-0.38 m/d and 0.27-0.46 m/d, respectively. It was concluded that the numerical simulation of the transport process for pollutants from underground coal gasification was valid. 42 refs., 13 figs., 1 tab.
Isotopic Studies of Contaminant Transport at the Hanford Site, Washington.
Christensen, John N.; Conrad, Mark E.; DePaolo, Donald J.; Dresel, P. Evan
2007-11-01
Processes of fluid flow and chemical transport through the vadose zone can be characterized through the isotopic systematics of natural soils, minerals, pore fluids and groundwater. In this contribution, we first review our research using measured isotopic variations, due both to natural and site related processes, of the elements H, O, N, Sr and U, to study the interconnection between vadose zone and groundwater contamination at the Hanford Site in south-central Washington. We follow this brief review with a presentation of new data pertaining to vadose zone and groundwater contamination in the WMA T-TX-TY vicinity. Uranium (U) isotopic data for the C3832 core (WMA TX) indicates the involvement of processed natural U fuel, and links the observed U contamination to the nearby single shelled tank TX-104. The data also precludes contamination from an early 1970’s TX-107 leak. In the case of the C4104 core (WMA T), the U isotopic data indicates a mixture of processed natural and enriched U fuels consistent with the major leak from T-106 in 1973. Uranium and Strontium isotopic data for the cores also provides direct evidence for chemical interaction between high-pH waste fluid and sediment. Isotopic data for groundwater nitrate contamination in the vicinity of WMA-T strongly suggests high-level tank waste (most likely from T-106) as the source of very high 99Tc concentrations recently observed at the NE corner of WMAT.
Emergence of correlated optics in one-dimensional waveguides for classical and quantum atomic gases
NASA Astrophysics Data System (ADS)
Ruostekoski, Janne; Javanainen, Juha
2016-09-01
We analyze the emergence of correlated optical phenomena in the transmission of light through a waveguide that confines classical or ultracold quantum degenerate atomic ensembles. The conditions of the correlated collective response are identified in terms of atom density, thermal broadening, and photon losses by using stochastic Monte Carlo simulations and transfer matrix methods of transport theory. We also calculate the "cooperative Lamb shift" for the waveguide transmission resonance, and discuss line shifts that are specific to effectively one-dimensional waveguide systems.
Spatial coherence properties of one dimensional exciton-polariton condensates.
Fischer, J; Savenko, I G; Fraser, M D; Holzinger, S; Brodbeck, S; Kamp, M; Shelykh, I A; Schneider, C; Höfling, S
2014-11-14
In this work, we combine a systematic experimental investigation of the power- and temperature-dependent evolution of the spatial coherence function, g^{(1)}(r), in a one dimensional exciton-polariton channel with a modern microscopic numerical theory based on a stochastic master equation approach. The spatial coherence function g^{(1)}(r) is extracted via high-precision Michelson interferometry, which allows us to demonstrate that in the regime of nonresonant excitation, the dependence g^{(1)}(r) reaches a saturation value with a plateau, which is determined by the intensity of the pump and effective temperature of the crystal lattice. The theory, which was extended to allow for treating incoherent excitation in a stochastic frame, matches the experimental data with good qualitative and quantitative agreement. This allows us to verify the prediction that the decay of the off-diagonal long-range order can be almost fully suppressed in one dimensional condensate systems.
The one-dimensional Coulomb lattice fluid capacitor
NASA Astrophysics Data System (ADS)
Démery, Vincent; Dean, David S.; Hammant, Thomas C.; Horgan, Ronald R.; Podgornik, Rudolf
2012-08-01
The one-dimensional Coulomb lattice fluid in a capacitor configuration is studied. The model is formally exactly soluble via a transfer operator method within a field theoretic representation of the model. The only interactions present in the model are the one-dimensional Coulomb interaction between cations and anions and the steric interaction imposed by restricting the maximal occupancy at any lattice site to one particle. Despite the simplicity of the model, a wide range of intriguing physical phenomena arise, some of which are strongly reminiscent of those seen in experiments and numerical simulations of three-dimensional ionic liquid based capacitors. Notably, we find regimes where over-screening and density oscillations are seen near the capacitor plates. The capacitance is also shown to exhibit strong oscillations as a function of applied voltage. It is also shown that the corresponding mean-field theory misses most of these effects. The analytical results are confirmed by extensive numerical simulations.
Fate of classical solitons in one-dimensional quantum systems.
Pustilnik, M.; Matveev, K. A.
2015-11-23
We study one-dimensional quantum systems near the classical limit described by the Korteweg-de Vries (KdV) equation. The excitations near this limit are the well-known solitons and phonons. The classical description breaks down at long wavelengths, where quantum effects become dominant. Focusing on the spectra of the elementary excitations, we describe analytically the entire classical-to-quantum crossover. We show that the ultimate quantum fate of the classical KdV excitations is to become fermionic quasiparticles and quasiholes. We discuss in detail two exactly solvable models exhibiting such crossover, the Lieb-Liniger model of bosons with weak contact repulsion and the quantum Toda model, and argue that the results obtained for these models are universally applicable to all quantum one-dimensional systems with a well-defined classical limit described by the KdV equation.
Entanglement vs. gap for one-dimensional spin systems
Hastings, Matthew; Aharonov, Dorit; Gottesman, Daniel
2008-01-01
We study the relationship between entanglement and spectral gap for local Hamiltonians in one dimension. The area law for a one-dimensional system states that for the ground state, the entanglement of any interval is upper-bounded by a constant independent of the size of the interval. However, the possible dependence of the upper bound on the spectral gap {Delta} is not known, as the best known general upper bound is asymptotically much larger than the largest possible entropy of any model system previously constructed for small {Delta}. To help resolve this asymptotic behavior, we construct a family of one-dimensional local systems for which some intervals have entanglement entropy which is polynomial in 1/{Delta}, whereas previously studied systems had the entropy of all intervals bounded by a constant times log(1/{Delta}).
Excitonic condensation in spatially separated one-dimensional systems
Abergel, D. S. L.
2015-05-25
We show theoretically that excitons can form from spatially separated one-dimensional ground state populations of electrons and holes, and that the resulting excitons can form a quasicondensate. We describe a mean-field Bardeen-Cooper-Schrieffer theory in the low carrier density regime and then focus on the core-shell nanowire giving estimates of the size of the excitonic gap for InAs/GaSb wires and as a function of all the experimentally relevant parameters. We find that optimal conditions for pairing include small overlap of the electron and hole bands, large effective mass of the carriers, and low dielectric constant of the surrounding media. Therefore, one-dimensional systems provide an attractive platform for the experimental detection of excitonic quasicondensation in zero magnetic field.
One-dimensional Hubbard-Luttinger model for carbon nanotubes
NASA Astrophysics Data System (ADS)
Ishkhanyan, H. A.; Krainov, V. P.
2015-06-01
A Hubbard-Luttinger model is developed for qualitative description of one-dimensional motion of interacting Pi-conductivity-electrons in carbon single-wall nanotubes at low temperatures. The low-lying excitations in one-dimensional electron gas are described in terms of interacting bosons. The Bogolyubov transformation allows one to describe the system as an ensemble of non-interacting quasi-bosons. Operators of Fermi excitations and Green functions of fermions are introduced. The electric current is derived as a function of potential difference on the contact between a nanotube and a normal metal. Deviations from Ohm law produced by electron-electron short-range repulsion as well as by the transverse quantization in single-wall nanotubes are discussed. The results are compared with experimental data.
Scaling properties of one-dimensional driven-dissipative condensates
NASA Astrophysics Data System (ADS)
He, Liang; Sieberer, Lukas M.; Altman, Ehud; Diehl, Sebastian
2015-10-01
We numerically investigate the scaling properties of a one-dimensional driven-dissipative condensate described by a stochastic complex Ginzburg-Landau equation (SCGLE). We directly extract the static and dynamical scaling exponents from the dynamics of the condensate's phase field, and find that both coincide with the ones of the one-dimensional Kardar-Parisi-Zhang (KPZ) equation. We furthermore calculate the spatial and the temporal two-point correlation functions of the condensate field itself. The decay of the temporal two-point correlator assumes a stretched-exponential form, providing further quantitative evidence for an effective KPZ description. Moreover, we confirm the observability of this nonequilibrium scaling for typical current experimental setups with exciton-polariton systems, if cavities with a reduced Q factor are used.
Nonequilibrium statistical mechanics in one-dimensional bose gases
NASA Astrophysics Data System (ADS)
Baldovin, F.; Cappellaro, A.; Orlandini, E.; Salasnich, L.
2016-06-01
We study cold dilute gases made of bosonic atoms, showing that in the mean-field one-dimensional regime they support stable out-of-equilibrium states. Starting from the 3D Boltzmann-Vlasov equation with contact interaction, we derive an effective 1D Landau-Vlasov equation under the condition of a strong transverse harmonic confinement. We investigate the existence of out-of-equilibrium states, obtaining stability criteria similar to those of classical plasmas.
On numerical modeling of one-dimensional geothermal histories
Haugerud, R.A.
1989-01-01
Numerical models of one-dimensional geothermal histories are one way of understanding the relations between tectonics and transient thermal structure in the crust. Such models can be powerful tools for interpreting geochronologic and thermobarometric data. A flexible program to calculate these models on a microcomputer is available and examples of its use are presented. Potential problems with this approach include the simplifying assumptions that are made, limitations of the numerical techniques, and the neglect of convective heat transfer. ?? 1989.
Cooling of a One-Dimensional Bose Gas.
Rauer, B; Grišins, P; Mazets, I E; Schweigler, T; Rohringer, W; Geiger, R; Langen, T; Schmiedmayer, J
2016-01-22
We experimentally study the dynamics of a degenerate one-dimensional Bose gas that is subject to a continuous outcoupling of atoms. Although standard evaporative cooling is rendered ineffective by the absence of thermalizing collisions in this system, we observe substantial cooling. This cooling proceeds through homogeneous particle dissipation and many-body dephasing, enabling the preparation of otherwise unexpectedly low temperatures. Our observations establish a scaling relation between temperature and particle number, and provide insights into equilibration in the quantum world.
Beyond the Born approximation in one-dimensional profile reconstruction
NASA Astrophysics Data System (ADS)
Trantanella, Charles J.; Dudley, Donald G.; Nabulsi, Khalid A.
1995-07-01
A new method of one-dimensional profile reconstruction is presented. The method is based on an extension to the Born approximation and relates measurements of the scattered field to the Fourier transform of the slab profile. Since the Born and our new approximations are most valid at low frequency, we utilize superresolution to recover high-frequency information and then invert for the slab profile. Finally, we vary different parameters and examine the resulting reconstructions. approximation, profile reconstruction, superresolution.
Interaction of one-dimensional waves in media without dispersion
NASA Astrophysics Data System (ADS)
Vasileva, O. A.; Karabutov, A. A.; Lapshin, E. A.; Rudenko, O. V.
Numerical and analytical studies of the excitation and propagation of nondispersing waves of finite amplitude are examined; difference schemes for the calculation of generalized solutions are considered along with a third-order-accuracy scheme. Attention is given to one-dimensional regular and random perturbations: plane, cylindrical, and spherical convergent waves. A considerable amount of the material is given in the form of tables and figures, which makes it possible to use the work as a handbook.
Superlensing properties of one-dimensional dielectric photonic crystals
NASA Astrophysics Data System (ADS)
Savo, Salvatore; di Gennaro, Emiliano; Andreone, Antonello
2009-10-01
We present the experimental observation of the superlensing effect in a slab of a one-dimensional photonic crystal made of tilted dielectric elements. We show that this flat lens can achieve subwavelength resolution in different frequency bands. We also demonstrate that the introduction of a proper corrugation on the lens surface can dramatically improve both the transmission and the resolution of the imaged signal.
Defects in a nonlinear pseudo one-dimensional solid
NASA Astrophysics Data System (ADS)
Blanchet, Graciela B.; Fincher, C. R., Jr.
1985-03-01
These infrared studies of acetanilide together with the existence of two equivalent structures for the hydrogen-bonded chain suggest the possibility of a topological defect state rather than a Davydov soliton as suggested previously. Acetanilide is an example of a class of one-dimensional materials where solitons are a consequence of a twofold degenerate structure and the nonlinear dynamics of the hydrogen-bonded network.
Cryptography using multiple one-dimensional chaotic maps
NASA Astrophysics Data System (ADS)
Pareek, N. K.; Patidar, Vinod; Sud, K. K.
2005-10-01
Recently, Pareek et al. [Phys. Lett. A 309 (2003) 75] have developed a symmetric key block cipher algorithm using a one-dimensional chaotic map. In this paper, we propose a symmetric key block cipher algorithm in which multiple one-dimensional chaotic maps are used instead of a one-dimensional chaotic map. However, we also use an external secret key of variable length (maximum 128-bits) as used by Pareek et al. In the present cryptosystem, plaintext is divided into groups of variable length (i.e. number of blocks in each group is different) and these are encrypted sequentially by using randomly chosen chaotic map from a set of chaotic maps. For block-by-block encryption of variable length group, number of iterations and initial condition for the chaotic maps depend on the randomly chosen session key and encryption of previous block of plaintext, respectively. The whole process of encryption/decryption is governed by two dynamic tables, which are updated time to time during the encryption/decryption process. Simulation results show that the proposed cryptosystem requires less time to encrypt the plaintext as compared to the existing chaotic cryptosystems and further produces the ciphertext having flat distribution of same size as the plaintext.
Development of versatile molecular transport model for modeling spacecraft contamination
NASA Astrophysics Data System (ADS)
Chang, Chien W.; Kannenberg, Keith; Chidester, Michael H.
2010-08-01
This paper describes a MATLAB-based molecular transport model developed for modeling contamination of spacecraft and optical instruments in space. The model adopts the Gebhart inverse-matrix theory for thermal radiation to analyze mass (molecular) transfer due to direct and reflected flux processes by balancing the mass fluxes instead of heat fluxes among surfaces with prescribed boundary conditions (contamination sticking fractions). The model can easily input view factor results from current thermal tools as well as measured outgassing data from ASTM E 1559 tests or vacuum bake-outs of flight components. Application examples of a geosynchronous satellite and an optical telescope are given to demonstrate versatile applications of the developed model.
Attenuation of Selected Emerging Contaminants During River Transport
NASA Astrophysics Data System (ADS)
Reinhard, M.; Gross, B.; Hadeler, A.
2002-12-01
The ubiquitous occurrence of emerging (non-regulated) contaminants in the aquatic environment is of concern because some of these chemicals are biologically active at low concentrations and a potential threat to wildlife and human health.. Emerging contaminants include a diverse range of chemicals, including pharmaceuticals, natural and synthetic hormones and industrial surfactants, such as alkylphenol ethoxylates (APEO) and their metabolites. To address the ecotoxicological impact of these chemicals, it is necessary to know their sources, removal efficiencies during wastewater treatment, and their behavior in the environment. In this study, the fate of selected emerging contaminants in the Santa Ana River (SAR) in Southern California was investigated. The SAR originates in the San Bernardino Mountains and flows 80 miles into the Pacific Ocean. The SAR flow stems mainly from storm runoff, wastewater treatment effluents and several other minor sources. During the dry season, SAR flow is dominated by effluent from public wastewater treatment plants. Input into the SAR was studied by analyzing samples from four major treatment plants that employ different tertiary treatment processes. To assess the fate during river water transport and during wetland treatment, samples from six sites along the river were analyzed. Effluent samples were analyzed every two months, river water every four months. River samples were taken considering the flow velocity, which is approximately 1 mile per hour. The analytical method involves solid-phase extraction using C-18 cartridges and extraction of three fractions. Samples were analyzed with and without further derivatization using GC/MS and GC/MS/MS. Results indicate significant contaminant removal during river transport, presumably by photochemical oxidation. Within a distance of nine miles, pharmaceuticals, plasticizers, flame retardants, APEOs and metabolites were attenuated with removal rates ranging from 76% for a flame retardant
Modeling solute/contaminant transport in heterogeneous aquifers.
Kocabas, Ibrahim; Bulbul, Mahmut
2015-03-01
A fissured aquifer may be considered as a dense network of fissures separated by low permeability matrix blocks. A conceptual modeling of such a system consists of an infinite number of parallel fractures separated by constant width matrix slabs. While the fissures are assumed to be main flow conduits, the fluid in the porous matrix blocks are considered to be virtually immobile. The mathematical model of the transport of a solute and/or contaminant which assumes a purely convective flow in fissures and diffusion into the matrix blocks consists of two coupled differential equations. An analytical solution of this model for the case of solute entering into the system at a constant concentration has been presented by Skopp and Warrick in Soil Sci Soc Am Proc 38:545-550, 1974. Note however, Skopp and Warrick (Soil Sci Soc Am Proc 38:545-550, 1974) have not considered the additional processes of adsorption and radioactive decay. Unfortunately, their solution had computational limitations as it involved numerical integration of a quite complex expression. Therefore, one had to turn to employing numerical Laplace transform inverters to compute the solutions. This work presents simple real space analytical solutions for the contaminant transport model described above including the adsorption and radioactive decay. The real space solutions have been developed using the method of double Laplace transform and binomial series approximation. An accurate approximate solution has also been presented which converges to the exact solution only after computing three terms in the series full solution. The developed model has been used for 1) assessment of the efficiency of numerical Laplace transform algorithms and 2) investigation of the degree and scale of contamination, and 3) designing remediation schemes for the already contaminated aquifers.
Phononic heat transfer through a one dimensional system subject to two sources of nonequilibrium
NASA Astrophysics Data System (ADS)
Beraha, N.; Soba, A.; Barreto, R.; Carusela, M. F.
2015-09-01
We analyze the energy transport in a one dimensional chain composed by two Frenkel-Kontorova (FK) segments connected together by a time modulated coupling. The ends are immersed in two thermal reservoirs with oscillating temperatures. We observe a single and multiresonant heat transport depending on the regimes considered, with a crossover between a mechanical resonance and a thermodynamical resonance. The dynamical tuning between these two regimes requires the synergetic presence of both time dependent sources of nonequilibrium. In the single resonant regime we analyze a "red shifted" resonant frequency that is dependent on the size of the system.
NASA Astrophysics Data System (ADS)
Choi, SangKook; Park, Cheol-Hwan; Louie, Steven G.
2014-07-01
Electron supercollimation, in which a wave packet is guided to move undistorted along a selected direction, is a highly desirable property that has yet to be realized experimentally. Disorder in general is expected to inhibit supercollimation. Here we report a counterintuitive phenomenon of electron supercollimation by disorder in graphene and related Dirac fermion materials. We show that one can use one-dimensional disorder potentials to control electron wave packet transport. This is distinct from known systems where an electron wave packet would be further spread by disorder and hindered in the potential fluctuating direction. The predicted phenomenon has significant implications in the understanding and applications of electron transport in Dirac fermion materials.
Transport of contaminants in the planetary boundary layer
NASA Technical Reports Server (NTRS)
Lee, I. Y.; Swan, P. R.
1978-01-01
A planetary boundary layer model is described and used to simulate PBL phenomena including cloud formation and pollution transport in the San Francisco Bay Area. The effect of events in the PBL on air pollution is considered, and governing equations for the average momentum, potential temperature, water vapor mixing ratio, and air contaminants are presented. These equations are derived by integrating the basic equations vertically through the mixed layer. Characteristics of the day selected for simulation are reported, and the results suggest that the diurnally cyclic features of the mesoscale motion, including clouds and air pollution, can be simulated in a readily interpretable way with the model.
Dust resuspension as a contaminant source and transport pathway
Loosmore, G.A,; Hunt, J.R.
1999-07-01
Numerous environmental contaminants sorb to dust particles or exist as particles, including metals, hydrophobic organic compounds, asbestos, pollens, and microbial pathogens. Wind resuspension of dust and other particulate matter provides a dust source for the atmosphere and a contaminant transport pathway. Not only do these materials pose a risk to human health, but also, resuspended dust particles are believed to play a role in global climate change and chemical reactions in the atmosphere. The conditions under which contaminated sites are vulnerable to wind resuspension are not generally known, as the basic physics of the problem are poorly understood. Field data show tremendous variability. Conventional dust flux models assume that dust resuspension occurs only for high winds and then only temporarily, with a transient dust flux occurring only when the bed is first exposed to the high wind. The surface is then assumed to stabilize such that no further dust moves until the surface is disturbed or a higher wind occurs. Recent wind tunnel experiments demonstrate that surfaces yield continuous steady dust fluxes under steady wind conditions well beyond the initial high transient flux, even when no erosion is visible and the velocity is below the predicted threshold velocity for movement. This average steady-state dust flux increases with average wind speed. Ongoing work is investigating the influence of air relative humidity on these processes. Contaminant resuspension models capture trends only and fail to predict sporadic high flux events that may control doses. Successful modeling of contaminant resuspension will depend on development of better dust flux predictions. Risk analyses require better predictive modeling, necessitating a deeper understanding of the underlying phenomena.
Gao, Guangyao; Fu, Bojie; Zhan, Hongbin; Ma, Ying
2013-05-01
Predicting the fate and movement of contaminant in soils and groundwater is essential to assess and reduce the risk of soil contamination and groundwater pollution. Reaction processes of contaminant often decreased monotonously with depth. Time-dependent input sources usually occurred at the inlet of natural or human-made system such as radioactive waste disposal site. This study presented a one-dimensional convection-dispersion equation (CDE) for contaminant transport in soils with depth-dependent reaction coefficients and time-dependent inlet boundary conditions, and derived its analytical solution. The adsorption coefficient and degradation rate were represented as sigmoidal functions of soil depth. Solute breakthrough curves (BTCs) and concentration profiles obtained from CDE with depth-dependent and constant reaction coefficients were compared, and a constant effective reaction coefficient, which was calculated by arithmetically averaging the depth-dependent reaction coefficient, was proposed to reflect the lumped depth-dependent reaction effect. With the effective adsorption coefficient and degradation rate, CDE could produce similar BTCs and concentration profiles as those from CDE with depth-dependent reactions in soils with moderate chemical heterogeneity. In contrast, the predicted concentrations of CDE with fitted reaction coefficients at a certain depth departed significantly from those of CDE with depth-dependent reactions. Parametric analysis was performed to illustrate the effects of sinusoidally and exponentially decaying input functions on solute BTCs. The BTCs and concentration profiles obtained from the solutions for finite and semi-infinite domain were compared to investigate the effects of effluent boundary condition. The finite solution produced higher concentrations at the increasing limb of the BTCs and possessed a higher peak concentration than the semi-infinite solution which had a slightly long tail. Furthermore, the finite solution gave
Gao, Guangyao; Fu, Bojie; Zhan, Hongbin; Ma, Ying
2013-05-01
Predicting the fate and movement of contaminant in soils and groundwater is essential to assess and reduce the risk of soil contamination and groundwater pollution. Reaction processes of contaminant often decreased monotonously with depth. Time-dependent input sources usually occurred at the inlet of natural or human-made system such as radioactive waste disposal site. This study presented a one-dimensional convection-dispersion equation (CDE) for contaminant transport in soils with depth-dependent reaction coefficients and time-dependent inlet boundary conditions, and derived its analytical solution. The adsorption coefficient and degradation rate were represented as sigmoidal functions of soil depth. Solute breakthrough curves (BTCs) and concentration profiles obtained from CDE with depth-dependent and constant reaction coefficients were compared, and a constant effective reaction coefficient, which was calculated by arithmetically averaging the depth-dependent reaction coefficient, was proposed to reflect the lumped depth-dependent reaction effect. With the effective adsorption coefficient and degradation rate, CDE could produce similar BTCs and concentration profiles as those from CDE with depth-dependent reactions in soils with moderate chemical heterogeneity. In contrast, the predicted concentrations of CDE with fitted reaction coefficients at a certain depth departed significantly from those of CDE with depth-dependent reactions. Parametric analysis was performed to illustrate the effects of sinusoidally and exponentially decaying input functions on solute BTCs. The BTCs and concentration profiles obtained from the solutions for finite and semi-infinite domain were compared to investigate the effects of effluent boundary condition. The finite solution produced higher concentrations at the increasing limb of the BTCs and possessed a higher peak concentration than the semi-infinite solution which had a slightly long tail. Furthermore, the finite solution gave
One-dimensional behavior and high thermoelectric power factor in thin indium arsenide nanowires
Mensch, P.; Karg, S. Schmidt, V.; Gotsmann, B.; Schmid, H.; Riel, H.
2015-03-02
Electrical conductivity and Seebeck coefficient of quasi-one-dimensional indium arsenide (InAs) nanowires with 20 nm diameter are investigated. The carrier concentration of the passivated nanowires was modulated by a gate electrode. A thermoelectric power factor of 1.7 × 10{sup −3} W/m K{sup 2} was measured at room temperature. This value is at least as high as in bulk-InAs and exceeds by far typical values of thicker InAs nanowires with three-dimensional properties. The interpretation of the experimental results in terms of power-factor enhancement by one-dimensionality is supported by model calculations using the Boltzmann transport formalism.
NASA Astrophysics Data System (ADS)
Molins, S.; Mayer, K.
2007-05-01
The unsaturated zone acts as a buffer zone for contaminants on their way to the water table but can also attenuate the emission of contaminants leaving the subsurface environment through the gas phase. A reactive transport model that includes multicomponent gas transport has been developed to investigate the processes that contribute to the generation and attenuation of contaminants in the unsaturated zone. In particular, the model is suitable to study the feedback processes between advective-diffusive gas transport and geochemical reactions. The model is also able to estimate diffusive and advective contributions to gas transport in multicomponent systems. Two model applications are presented that investigate gas transport and reactions in mine tailings and at a site with organic contamination. In mine tailings, atmospheric oxygen transported into the sediment column is consumed in the oxidation of sulfide minerals. Gas volume loss caused by the consumption of atmospheric oxygen drives advective fluxes. In the absence of carbonate minerals, the advective component accounts for 16 % of the net oxygen flux into the column, while, in a carbonate-rich system, advection accounts for 10 % of the net oxygen flux. Dissolution of carbonate minerals has a moderating effect on advective gas transport since carbon dioxide can partially compensate for the depletion of oxygen. At an oil spill site, volatilization and degradation of organic contaminants cause advective and diffusive fluxes of organic vapors away from the source zone. At early stages, volatilization dominates and oxidation of these organic vapors attenuates the emission of contaminants to the atmosphere. The contribution of advection to organic vapor fluxes is significant initially but decreases with time. At later stages, the oil source becomes depleted of its most volatile fraction, and anaerobic degradation of aromatic compounds and heavier n-alkanes results in the production of methane. Up to 15 % of methane
One-Dimensional Scanning Approach to Shock Sensing
NASA Technical Reports Server (NTRS)
Tokars, Roger; Adamovsky, Girgory; Floyd, Bertram
2009-01-01
Measurement tools for high speed air flow are sought both in industry and academia. Particular interest is shown in air flows that exhibit aerodynamic shocks. Shocks are accompanied by sudden changes in density, pressure, and temperature. Optical detection and characterization of such shocks can be difficult because the medium is normally transparent air. A variety of techniques to analyze these flows are available, but they often require large windows and optical components as in the case of Schlieren measurements and/or large operating powers which precludes their use for in-flight monitoring and applications. The one-dimensional scanning approach in this work is a compact low power technique that can be used to non-intrusively detect shocks. The shock is detected by analyzing the optical pattern generated by a small diameter laser beam as it passes through the shock. The optical properties of a shock result in diffraction and spreading of the beam as well as interference fringes. To investigate the feasibility of this technique a shock is simulated by a 426 m diameter optical fiber. Analysis of results revealed a direct correlation between the optical fiber or shock location and the beam s diffraction pattern. A plot of the width of the diffraction pattern vs. optical fiber location reveals that the width of the diffraction pattern was maximized when the laser beam is directed at the center of the optical fiber. This work indicates that the one-dimensional scanning approach may be able to determine the location of an actual shock. Near and far field effects associated with a small diameter laser beam striking an optical fiber used as a simulated shock are investigated allowing a proper one-dimensional scanning beam technique.
The solving of one dimensional unsteady flow with difference methods
NASA Astrophysics Data System (ADS)
Shao, Guangri; Shang, Yu; Wang, Rongsheng
In this paper, one-dimensional unsteady gas flow equations are formulated with Riemann variables as the functions of time and space to be solved. By using the 'de Haller' test and a simple pipe flow with a temperature discontinuity, the equations are solved by difference methods of first-order accuracy and second-order accuracy for non-homentropic cases. As compared with the commonly used characteristic method, the results show the above-mentioned formulation and difference methods have the advantages of consuming less computer time and being easier to reach higher order accuracy. The application to turbocharged internal combustion engines is also discussed in this paper.
Bloch oscillations in a one-dimensional spinor gas.
Gangardt, D M; Kamenev, A
2009-02-20
A force applied to a spin-flipped particle in a one-dimensional spinor gas may lead to Bloch oscillations of the particle's position and velocity. The existence of Bloch oscillations crucially depends on the viscous friction force exerted by the rest of the gas on the spin excitation. We evaluate the friction in terms of the quantum fluid parameters. In particular, we show that the friction is absent for integrable cases, such as an SU(2) symmetric gas of bosons or fermions. For small deviations from the exact integrability the friction is very weak, opening the possibility to observe Bloch oscillations.
Quantum Simulations of One-Dimensional Nanostructures under Arbitrary Deformations
NASA Astrophysics Data System (ADS)
Koskinen, Pekka
2016-09-01
A powerful technique is introduced for simulating mechanical and electromechanical properties of one-dimensional nanostructures under arbitrary combinations of bending, twisting, and stretching. The technique is based on an unconventional control of periodic symmetry which eliminates artifacts due to deformation constraints and quantum finite-size effects and allows transparent electronic-structure analysis. Via density-functional tight-binding implementation, the technique demonstrates its utility by predicting nonlinear electromechanical properties in carbon nanotubes and abrupt behavior in the structural yielding of Au7 and Mo6 S6 nanowires. The technique drives simulations markedly closer to the realistic modeling of these slender nanostructures under experimental conditions.
Numerical computations on one-dimensional inverse scattering problems
NASA Technical Reports Server (NTRS)
Dunn, M. H.; Hariharan, S. I.
1983-01-01
An approximate method to determine the index of refraction of a dielectric obstacle is presented. For simplicity one dimensional models of electromagnetic scattering are treated. The governing equations yield a second order boundary value problem, in which the index of refraction appears as a functional parameter. The availability of reflection coefficients yield two additional boundary conditions. The index of refraction by a k-th order spline which can be written as a linear combination of B-splines is approximated. For N distinct reflection coefficients, the resulting N boundary value problems yield a system of N nonlinear equations in N unknowns which are the coefficients of the B-splines.
Coherent Backscattering of Light Off One-Dimensional Atomic Strings
NASA Astrophysics Data System (ADS)
Sørensen, H. L.; Béguin, J.-B.; Kluge, K. W.; Iakoupov, I.; Sørensen, A. S.; Müller, J. H.; Polzik, E. S.; Appel, J.
2016-09-01
We present the first experimental realization of coherent Bragg scattering off a one-dimensional system—two strings of atoms strongly coupled to a single photonic mode—realized by trapping atoms in the evanescent field of a tapered optical fiber, which also guides the probe light. We report nearly 12% power reflection from strings containing only about 1000 cesium atoms, an enhancement of 2 orders of magnitude compared to reflection from randomly positioned atoms. This result paves the road towards collective strong coupling in 1D atom-photon systems. Our approach also allows for a straightforward fiber connection between several distant 1D atomic crystals.
Superconductivity in a one-dimensional correlated quantum system
NASA Astrophysics Data System (ADS)
Ding, Hanqin; Zhang, Jun
2016-07-01
We construct a one-dimensional (1D) theoretical model to clarify the occurrence of superconductivity. The weak-coupling (WC) theory allows a determination of the phase diagram. The constrained hopping induces additional two-body and three-body interactions. At half-filling, the three-body interaction is responsible for the triplet superconducting (TS) correlation. Away from half-filling, the two-body interaction works, favoring the singlet superconducting (SS) correlation. The results are expected to provide an insignificant insight into the superconductivity mechanism.
Fourier's law for quasi-one-dimensional chaotic quantum systems
NASA Astrophysics Data System (ADS)
Seligman, Thomas H.; Weidenmüller, Hans A.
2011-05-01
We derive Fourier's law for a completely coherent quasi-one-dimensional chaotic quantum system coupled locally to two heat baths at different temperatures. We solve the master equation to first order in the temperature difference. We show that the heat conductance can be expressed as a thermodynamic equilibrium coefficient taken at some intermediate temperature. We use that expression to show that for temperatures large compared to the mean level spacing of the system, the heat conductance is inversely proportional to the level density and, thus, inversely proportional to the length of the system.
Quantum quench in an atomic one-dimensional Ising chain.
Meinert, F; Mark, M J; Kirilov, E; Lauber, K; Weinmann, P; Daley, A J; Nägerl, H-C
2013-08-01
We study nonequilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to antiferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response. PMID:23952393
One-dimensional hydrodynamic model generating a turbulent cascade.
Matsumoto, Takeshi; Sakajo, Takashi
2016-05-01
As a minimal mathematical model generating cascade analogous to that of the Navier-Stokes turbulence in the inertial range, we propose a one-dimensional partial-differential-equation model that conserves the integral of the squared vorticity analog (enstrophy) in the inviscid case. With a large-scale random forcing and small viscosity, we find numerically that the model exhibits the enstrophy cascade, the broad energy spectrum with a sizable correction to the dimensional-analysis prediction, peculiar intermittency, and self-similarity in the dynamical system structure. PMID:27300972
Dynamical Structure Factors of quasi-one-dimensional antiferromagnets
NASA Astrophysics Data System (ADS)
Hagemans, Rob; Caux, Jean-Sébastien; Maillet, Jean Michel
2007-03-01
For a long time it has been impossible to accurately calculate the dynamical structure factors (spin-spin correlators as a function of momentum and energy) of quasi-one-dimensional antiferromagnets. For integrable Heisenberg chains, the recently developed ABACUS method (a first-principles computational approach based on the Bethe Ansatz) now yields highly accurate (over 99% of the sum rule) results for the DSF for finite chains, allowing for a very precise description of neutron-scattering data over the full momentum and energy range. We show remarkable agreement between results obtained with ABACUS and experiment.
One-dimensional parabolic-beam photonic crystal laser.
Ahn, Byeong-Hyeon; Kang, Ju-Hyung; Kim, Myung-Ki; Song, Jung-Hwan; Min, Bumki; Kim, Ki-Soo; Lee, Yong-Hee
2010-03-15
We report one-dimensional (1-D) parabolic-beam photonic crystal (PhC) lasers in which the width of the PhC slab waveguide is parabolically tapered. A few high-Q resonant modes are confirmed in the vicinity of the tapered region where Gaussian-shaped photonic well is formed. These resonant modes originate from the dielectric PhC guided mode and overlap with the gain medium efficiently. It is also shown that the far-field radiation profile is closely associated with the symmetry of the structural perturbation.
Lattice-induced resonances in one-dimensional bosonic systems.
von Stecher, Javier; Gurarie, Victor; Radzihovsky, Leo; Rey, Ana Maria
2011-06-10
We study the resonant effects produced when a Feshbach dimer crosses a scattering continuum band of atoms in an optical lattice. We numerically obtain the exact spectrum of two particles in a one-dimensional lattice and develop an effective atom-dimer Hamiltonian that accurately captures resonant effects. The lattice-induced resonances lead to the formation of bound states simultaneously above and below the scattering continuum and significantly modify the curvature of the dimer dispersion relation. The nature of the atom-dimer coupling depends strongly on the parity of the dimer state leading to a novel coupling in the case of negative parity dimers. PMID:21770514
Lattice-Induced Resonances in One-Dimensional Bosonic Systems
NASA Astrophysics Data System (ADS)
von Stecher, Javier; Gurarie, Victor; Radzihovsky, Leo; Rey, Ana Maria
2011-06-01
We study the resonant effects produced when a Feshbach dimer crosses a scattering continuum band of atoms in an optical lattice. We numerically obtain the exact spectrum of two particles in a one-dimensional lattice and develop an effective atom-dimer Hamiltonian that accurately captures resonant effects. The lattice-induced resonances lead to the formation of bound states simultaneously above and below the scattering continuum and significantly modify the curvature of the dimer dispersion relation. The nature of the atom-dimer coupling depends strongly on the parity of the dimer state leading to a novel coupling in the case of negative parity dimers.
Functional One-Dimensional Lipid Bilayers on Carbon Nanotube Templates
Artyukhin, A; Shestakov, A; Harper, J; Bakajin, O; Stroeve, P; Noy, A
2004-07-23
We present one-dimensional (1-D) lipid bilayer structures that integrate carbon nanotubes with a key biological environment-phospholipid membrane. Our structures consist of lipid bilayers wrapped around carbon nanotubes modified with a hydrophilic polymer cushion layer. Despite high bilayer curvature, the lipid membrane maintains its fluidity and can sustain repeated damage-recovery cycles. We also present the first evidence of spontaneous insertion of pore-forming proteins into 1-D lipid bilayers. These structures could lead to the development of new classes of biosensors and bioelectronic devices.
Numerical Simulations of One-dimensional Microstructure Dynamics
Berezovski, M.; Berezovski, A.; Engelbrecht, J.
2010-05-21
Results of numerical simulations of one-dimensional wave propagation in microstructured solids are presented and compared with the corresponding results of wave propagation in given layered media. A linear microstructure model based on Mindlin theory is adopted and represented in the framework of the internal variable theory. Fully coupled systems of equations for macro-motion and microstructure evolution are rewritten in the form of conservation laws. A modification of wave propagation algorithm is used for numerical calculations. It is shown how the initial microstructure model can be improved in order to match the results obtained by both approaches.
Parallel solution of sparse one-dimensional dynamic programming problems
NASA Technical Reports Server (NTRS)
Nicol, David M.
1989-01-01
Parallel computation offers the potential for quickly solving large computational problems. However, it is often a non-trivial task to effectively use parallel computers. Solution methods must sometimes be reformulated to exploit parallelism; the reformulations are often more complex than their slower serial counterparts. We illustrate these points by studying the parallelization of sparse one-dimensional dynamic programming problems, those which do not obviously admit substantial parallelization. We propose a new method for parallelizing such problems, develop analytic models which help us to identify problems which parallelize well, and compare the performance of our algorithm with existing algorithms on a multiprocessor.
Accuracy of differential sensitivity for one-dimensional shock problems
Henninger, R.J.; Maudlin, P.J.; Rightley, M.L.
1998-07-01
The technique called Differential Sensitivity has been applied to the system of Eulerian continuum mechanics equations solved by a hydrocode. Differential Sensitivity uses forward and adjoint techniques to obtain output response sensitivity to input parameters. Previous papers have described application of the technique to two-dimensional, multi-component problems. Inaccuracies in the adjoint solutions have prompted us to examine our numerical techniques in more detail. Here we examine one-dimensional, one material shock problems. Solution accuracy is assessed by comparison to sensitivities obtained by automatic differentiation and a code-based adjoint differentiation technique. {copyright} {ital 1998 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Ngo-Cong, D.; Mohammed, F. J.; Strunin, D. V.; Skvortsov, A. T.; Mai-Duy, N.; Tran-Cong, T.
2015-06-01
The contaminant transport process governed by the advection-diffusion equation plays an important role in modelling industrial and environmental flows. In this article, our aim is to accurately reduce the 2-D advection-diffusion equation governing the dispersion of a contaminant in a turbulent open channel flow to its 1-D approximation. The 1-D model helps to quickly estimate the horizontal size of contaminant clouds based on the values of the model coefficients. We derive these coefficients analytically and investigate numerically the model convergence. The derivation is based on the centre manifold theory to obtain successively more accurate approximations in a consistent manner. Two types of the average velocity profile are considered: the classical logarithmic profile and the power profile. We further develop the one-dimensional integrated radial basis function network method as a numerical approach to obtain the numerical solutions to both the original 2-D equation and the approximate 1-D equations. We compare the solutions of the original models with their centre-manifold approximations at very large Reynolds numbers. The numerical results obtained from the approximate 1-D models are in good agreement with those of the original 2-D model for both the logarithmic and power velocity profiles.
Subsurface Flow and Contaminant Transport Documentation and User's Guide
Aleman, S.E.
1999-07-28
This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media. The code is designed specifically to handle complex multi-layer and/or heterogeneous aquifer systems in an efficient manner and accommodates a wide range of boundary conditions. Additionally, 1-D and 2-D (in Cartesian coordinates) problems are handled in FACT by simply limiting the number of elements in a particular direction(s) to one. The governing equations in FACT are formulated only in Cartesian coordinates.
Analysis of Contaminant Transport through the Vadose and Saturated Zones for Source Screening
NASA Astrophysics Data System (ADS)
Bedekar, V.; Neville, C. J.; Tonkin, M. J.
2010-12-01
At complex sites there may be many potential source areas. Screening level analyses are useful to identify which of the source areas should be the focus of detailed investigation and analysis. A screening tool has been developed to evaluate the threat posed by waste sites on groundwater quality. This tool implements analytical solutions to simulate contaminant transport through the vadose and saturated zones and predict time-varying concentrations at potential groundwater receptors. The screening tool is developed within a user friendly, Microsoft ExcelTM based interface; however, care has been taken to implement rigorous solutions. The screening tool considers the following mechanisms: (a) Partitioning of soil contamination in to an equivalent dissolved concentration. For a time-invariant source, the solution is generalized from [3] for sorption and decay. For a time-varying source, the solution represents a special, degenerate, case of a solution implemented in ATRANS [2]; (b) One-dimensional (1D) transport of the dissolved contamination through the vadose zone considering 1D dispersion, equilibrium sorption, and first order transformation reactions. Steady state infiltration and moisture content are assumed; (c) Blending (mixing) of ambient water quality in the saturated zone with the contaminated water leaching from the vadose zone; and (d) Three-dimensional (3D) transport through the saturated zone using the formulation provided in [2], considering advection, dispersion, sorption, and first-order transformation reactions. The solution is derived using integral transform methods, following approaches adopted in [1] and [4]. Independent verification showed that the analytical techniques implemented in this study generate solutions that closely approximate those obtained using sophisticated numerical approaches, with a systematic over-estimate of the likely impact to groundwater that (predictably) stems from the use of a 1D approximation in the vadose zone. As a
Generation of long-term record of contaminant transport
Solo-Gabriele, H.M.
1998-07-01
A long-term record (1900--1993) of streamflow, sediment, and metal transport was simulated for an urbanized watershed, the Aberjona River watershed, located near Boston, Mass. The approach is an innovative procedure that includes the use of a watershed-specific contaminant transport model. The input to the program is hourly precipitation; the output is hourly streamflow, sediment, and metal fluxes. Hourly precipitation was available for part of the record. For time periods for which only daily precipitation data were available, the data were disaggregated into hourly values. The effects of urbanization on streamflow were simulated by adjusting the timing of river flood routing and the area contributing to different flow components. Variations in industrial water withdrawals were also considered. Sediment core data were utilized to estimate changes in source metal concentrations in time. The long-term record that was generated confirms that urbanization can account for a flashier river response including larger peaks in streamflow and sediment transport. Metal transport was affected by changes in metal source characteristics as well as hydrologic factors.
Silicon-based one-dimensional photonic crystal microcavity
NASA Astrophysics Data System (ADS)
Chen, San; Qian, Bo; Chen, Kunji; Xu, Jun; Li, Wei; Huang, Xinfan
2004-12-01
The layer-by-layer method is employed to prepare a-SiNx:H microcavity structure in a Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber. Measurements of transmittance spectrum of as-grown samples show that the transmittance resonant peak of a cavity mode at 750 nm is introduced into the band gap of one-dimensional photonic crystal distributed Bragg reflectors based on hydrogenated amorphous silicon nitride. Also the PL measurements of a-SiNx:H microcavities are performed. There is a well agreement between the transmittance spectra and the PL of microcavity samples. In order to clarify the microcavity effects on the bulk a-SiNx:H, the PL of a λ/2-thick layer of bulk a-SiNx:H obtained under the same experimental conditions is presented. By comparison, a dramatic narrowing of emission linewidth and enhancement of PL intensity is observed. The wide emission band with 208 nm is strongly narrowed to 17 nm, and the resonant enhancement of the peak PL intensity is about two orders of magnitude with respect to the emission of the λ/2-thick layer of bulk a-SiNx:H. A linewidth of Δλ=17 nm and a quality factor of Q=50 are achieved in our one-dimensional a-SiNx photonic crystal microcavities.
Dislocation-mediated melting of one-dimensional Rydberg crystals
Sela, Eran; Garst, Markus; Punk, Matthias
2011-08-15
We consider cold Rydberg atoms in a one-dimensional optical lattice in the Mott regime with a single atom per site at zero temperature. An external laser drive with Rabi frequency {Omega} and laser detuning {Delta} creates Rydberg excitations whose dynamics is governed by an effective spin-chain model with (quasi) long-range interactions. This system possesses intrinsically a large degree of frustration resulting in a ground-state phase diagram in the ({Delta},{Omega}) plane with a rich topology. As a function of {Delta}, the Rydberg blockade effect gives rise to a series of crystalline phases commensurate with the optical lattice that form a so-called devil's staircase. The Rabi frequency {Omega}, on the other hand, creates quantum fluctuations that eventually lead to a quantum melting of the crystalline states. Upon increasing {Omega}, we find that generically a commensurate-incommensurate transition to a floating Rydberg crystal that supports gapless phonon excitations occurs first. For even larger {Omega}, dislocations within the floating Rydberg crystal start to proliferate and a second, Kosterlitz-Thouless-Nelson-Halperin-Young dislocation-mediated melting transition finally destroys the crystalline arrangement of Rydberg excitations. This latter melting transition is generic for one-dimensional Rydberg crystals and persists even in the absence of an optical lattice. The floating phase and the concomitant transitions can, in principle, be detected by Bragg scattering of light.
Lattice Boltzmann method for one-dimensional vector radiative transfer.
Zhang, Yong; Yi, Hongliang; Tan, Heping
2016-02-01
A one-dimensional vector radiative transfer (VRT) model based on lattice Boltzmann method (LBM) that considers polarization using four Stokes parameters is developed. The angular space is discretized by the discrete-ordinates approach, and the spatial discretization is conducted by LBM. LBM has such attractive properties as simple calculation procedure, straightforward and efficient handing of boundary conditions, and capability of stable and accurate simulation. To validate the performance of LBM for vector radiative transfer, four various test problems are examined. The first case investigates the non-scattering thermal-emitting atmosphere with no external collimated solar. For the other three cases, the external collimated solar and three different scattering types are considered. Particularly, the LBM is extended to solve VRT in the atmospheric aerosol system where the scattering function contains singularities and the hemisphere space distributions for the Stokes vector are presented and discussed. The accuracy and computational efficiency of this algorithm are discussed. Numerical results show that the LBM is accurate, flexible and effective to solve one-dimensional polarized radiative transfer problems. PMID:26906779
Generating arbitrary one-dimensional dose profiles using rotational therapy
NASA Astrophysics Data System (ADS)
Zhuang, Tingliang; Wu, Qiuwen
2010-10-01
Conformal radiation therapy can be delivered using several methods: intensity-modulated radiotherapy (IMRT) at fixed gantry angles, through the continuous gantry rotation of linac (rotational arc therapy), or by a dedicated treatment unit such as tomotherapy. The recently developed volumetric modulated arc therapy (VMAT), a form of rotational arc therapy, has attracted lots of attention from investigators to explore its capability of generating highly conformal dose to the target. The main advanced features of VMAT are the variable dose rate and gantry rotation speed. In this paper, we present a theoretical framework of generating arbitrary one-dimensional dose profiles using rotational arc therapy to further explore the new degree of freedom of the VMAT technique. This framework was applied to design a novel technique for total body irradiation (TBI) treatment, where the desired dose distribution can be simplified by a one-dimensional profile. The technique was validated using simulations and experimental measurements. The preliminary results demonstrated that the new TBI technique using either dynamic MLC only, variable dose rate only, or a combination of dynamic MLC and variable dose rate can achieve arbitrary dose distribution in one dimension, such as uniform dose to target and lower dose to critical organ. This technique does not require the use of customized compensators, nor large treatment rooms as in the conventional extended SSD technique.
One-Dimensional Electrical Contact to Molybdenum Disulfide
NASA Astrophysics Data System (ADS)
Yang, Zheng; Ra, Changho; Ahmed, Faisal; Lee, Daeyeong; Choi, Minsup; Liu, Xiaochi; Qu, Deshun; Yoo, Won Jong; Nano Device Processing Lab Team
Molybdenum disulfide (MoS2) is one of the promising two-dimensional materials for future application in nano electronics, which has high carrier mobility, very good stability under atmosphere, proper band gap, etc. However, its application to electronic switching devices is hindered by Fermi level pinning at metal-MoS2 interfaces. Here, we experimentally demonstrate one-dimensional electrical contact to MoS2 formed via controllable plasma etching. We fabricated Al/MoS2 FET (n-type), Mo/MoS2 FET (n-type), and Pd/MoS2 FET (ambipolar). For Mo/MoS2 FET (n-type), on/off current ratio is around 108 and mobility is around 104 cm2/(Vs). By contrast, for Pd/MoS2 FET (ambipolar), on/off current ratio is around 108, hole mobility is ranged from 350 to 650 cm2/(Vs), and the mean free path of holes at 9K is around 23 nm. All the measured mobilities are evaluated by using two-terminal field-effect configuration. We can also achieve complementary logic gates with intrinsic MoS2/metal one-dimensional electrical contact.
One dimensional wavefront sensor development for tomographic flow measurements
Neal, D.; Pierson, R.; Chen, E.
1995-08-01
Optical diagnostics are extremely useful in fluid mechanics because they generally have high inherent bandwidth, and are non-intrusive. However, since optical probe measurements inherently integrate all information along the optical path, it is often difficult to isolate out-of-plane components in 3-dimensional flow events. It is also hard to make independent measurements of internal flow structure. Using an arrangement of one-dimensional wavefront sensors, we have developed a system that uses tomographic reconstruction to make two-dimensional measurements in an arbitrary flow. These measurements provide complete information in a plane normal to the flow. We have applied this system to the subsonic free jet because of the wide range of flow scales available. These measurements rely on the development of a series of one-dimensional wavefront sensors that are used to measure line-integral density variations in the flow of interest. These sensors have been constructed using linear CCD cameras and binary optics lenslet arrays. In designing these arrays, we have considered the coherent coupling between adjacent lenses and have made comparisons between theory and experimental noise measurements. The paper will present examples of the wavefront sensor development, line-integral measurements as a function of various experimental parameters, and sample tomographic reconstructions.
A Sectored-One-Dimensional Model for Simulating Combustion Instabilities in Premix Combustors
NASA Technical Reports Server (NTRS)
Paxson, Daniel E.
1999-01-01
A one-dimensional, CFD based combustor simulation has been developed that exhibits self-excited, thermoacoustic oscillations in premixed combustor geometries that typically have large, abrupt changes in cross sectional area. The combustor geometry is approximated by dividing it into a finite number of one-dimensional sectors. Within each sector, the equations of motion are integrated numerically, along with a species transport and a reaction equation. Across the sectors, mass and energy are conserved, and momentum loss is prescribed using appropriately compatible boundary conditions that account for the area change. The resulting simulation and associated boundary conditions essentially represent a one-dimensional, multi-block technique. Details of the simulation code are presented herein. Results are then shown comparing experimentally observed and simulated operation of a particular combustor rig that exhibited different instabilities at different operating points. It will be shown that the simulation closely matched the rig data in oscillation amplitudes, frequencies, and operating points at which the instabilities occurred. Finally, advantages and limitations of the simulation technique are discussed.
Periodic transmission peak splitting in one dimensional disordered photonic structures
NASA Astrophysics Data System (ADS)
Kriegel, Ilka; Scotognella, Francesco
2016-08-01
In the present paper we present ways to modulate the periodic transmission peaks arising in disordered one dimensional photonic structures with hundreds of layers. Disordered structures in which the optical length nd (n is the refractive index and d the layer thickness) is the same for each layer show regular peaks in their transmission spectra. A proper variation of the optical length of the layers leads to a splitting of the transmission peaks. Notably, the variation of the occurrence of high and low refractive index layers, gives a tool to tune also the width of the peaks. These results are of highest interest for optical application, such as light filtering, where the manifold of parameters allows a precise design of the spectral transmission ranges.
One-Dimensional Time to Explosion (Thermal Sensitivity) of ANPZ
Hsu, P.; Hust, G.; McClelland, M.; Gresshoff, M.
2014-11-12
Incidents caused by fire and combat operations can heat energetic materials that may lead to thermal explosion and result in structural damage and casualty. Some explosives may thermally explode at fairly low temperatures (< 100 C) and the violence from thermal explosion may cause a significant damage. Thus it is important to understand the response of energetic materials to thermal insults. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory has been used for decades to measure times to explosion, threshold thermal explosion temperature, and determine kinetic parameters of energetic materials. Samples of different configurations (pressed part, powder, paste, and liquid) can be tested in the system. The ODTX testing can also provide useful data for assessing the thermal explosion violence of energetic materials. This report summarizes the recent ODTX experimental data and modeling results for 2,6-diamino-3,5-dintropyrazine (ANPZ).
Negative refraction characterization in one-dimensional photonic crystals
NASA Astrophysics Data System (ADS)
Doti, R.; Lugo, J. E.; Faubert, J.
2012-10-01
In this work we present two experiments as evidence of negative refraction in one dimensional photonics crystals (1D PC). Particularly the porous silicon (p-Si) multilayer structure is used as 1D PC since this structure presents periodic dielectric components with specific refraction indexes and under certain conditions it can abnormally refract the light. In the first experiment we show the negative refraction for two different wavelengths, one in the visible, and the other in the infrared regions of the spectrum. In this experiment we use a fixed incidence angle for a conditioned white light beam and we look for the emerging negative refracted beam. In the second experiment we characterize de negative refraction observed for the same material by varying the incidence angle in a wide range. The obtained results are compared with a theoretic prediction according a model proposed by the authors [1]. We present a brief description of the material production and its properties, as well.
Negative refraction in one-dimensional photonic crystals
NASA Astrophysics Data System (ADS)
Lugo, J. E.; Doti, Rafael; Faubert, J.
2012-10-01
Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here, we discuss recent theoretical and simulation results that showed that negative refraction could be present near the low frequency edge of at least the second, fourth and sixth bandgaps of a lossless one-dimensional photonic crystals (1DPC) structure. That is, negative refraction is a multiband phenomenon. We also discuss the negative refraction correctness condition that gives the angular region where negative refraction occurs. We compare two current negative refraction theoretical models with recent experimental results. In order to succeed, an output refraction correction is utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theoretical models in the negative refraction zone.
A Reduced Order, One Dimensional Model of Joint Response
DOHNER,JEFFREY L.
2000-11-06
As a joint is loaded, the tangent stiffness of the joint reduces due to slip at interfaces. This stiffness reduction continues until the direction of the applied load is reversed or the total interface slips. Total interface slippage in joints is called macro-slip. For joints not undergoing macro-slip, when load reversal occurs the tangent stiffness immediately rebounds to its maximum value. This occurs due to stiction effects at the interface. Thus, for periodic loads, a softening and rebound hardening cycle is produced which defines a hysteretic, energy absorbing trajectory. For many jointed sub-structures, this hysteretic trajectory can be approximated using simple polynomial representations. This allows for complex joint substructures to be represented using simple non-linear models. In this paper a simple one dimensional model is discussed.
One-dimensional Kondo lattice model at quarter filling
NASA Astrophysics Data System (ADS)
Xavier, J. C.; Miranda, E.
2008-10-01
We revisit the problem of the quarter-filled one-dimensional Kondo lattice model, for which the existence of a dimerized phase and a nonzero charge gap had been reported by Xavier [Phys. Rev. Lett. 90, 247204 (2003)]. Recently, some objections were raised claiming that the system is neither dimerized nor has a charge gap. In the interest of clarifying this important issue, we show that these objections are based on results obtained under conditions in which the dimer order is artificially suppressed. We use the incontrovertible dimerized phase of the Majumdar-Ghosh point of the J1-J2 Heisenberg model as a paradigm with which to illustrate this artificial suppression. Finally, by means of extremely accurate density-matrix renormalization-group calculations, we show that the charge gap is indeed nonzero in the dimerized phase.
Localization of wave packets in one-dimensional random potentials
NASA Astrophysics Data System (ADS)
Valdes, Juan Pablo Ramírez; Wellens, Thomas
2016-06-01
We study the expansion of an initially strongly confined wave packet in a one-dimensional weak random potential with short correlation length. At long times, the expansion of the wave packet comes to a halt due to destructive interferences leading to Anderson localization. We develop an analytical description for the disorder-averaged localized density profile. For this purpose, we employ the diagrammatic method of Berezinskii which we extend to the case of wave packets, present an analytical expression of the Lyapunov exponent which is valid for small as well as for high energies, and, finally, develop a self-consistent Born approximation in order to analytically calculate the energy distribution of our wave packet. By comparison with numerical simulations, we show that our theory describes well the complete localized density profile, not only in the tails but also in the center.
Novel superconducting phenomena in quasi-one-dimensional Bechgaard salts
NASA Astrophysics Data System (ADS)
Jerome, Denis; Yonezawa, Shingo
2016-03-01
It is the saturation of the transition temperature Tc in the range of 24 K for known materials in the late sixties that triggered the search for additional materials offering new coupling mechanisms leading in turn to higher Tc's. As a result of this stimulation, superconductivity in organic matter was discovered in tetramethyl-tetraselenafulvalene-hexafluorophosphate, (TMTSF)2PF6, in 1979, in the laboratory founded at Orsay by Professor Friedel and his colleagues in 1962. Although this conductor is a prototype example for low-dimensional physics, we mostly focus in this article on the superconducting phase of the ambient-pressure superconductor (TMTSF)2ClO4, which has been studied most intensively among the TMTSF salts. We shall present a series of experimental results supporting nodal d-wave symmetry for the superconducting gap in these prototypical quasi-one-dimensional conductors. xml:lang="fr"
Probing the excitations of a one dimensional topological Bose insulator
NASA Astrophysics Data System (ADS)
Dalla Torre, Emanuele G.; Berg, Erez; Altman, Ehud
2008-03-01
We investigate the dynamic response of a system of ultracold dipolar atoms or molecules in the one dimensional Haldane Bose insulator phase. This phase, which was recently predicted theoretically [1], is characterized by non-local string order and its elementary excitations are domain walls in this order. We compute experimentally relevant response functions and we derive asymptotically exact expressions near the quantum critical points separating the Haldane insulator from the conventional Mott and density wave insulators. In particular, we predict a narrow absorption peak in Bragg spectroscopy experiments, due to the excitation of a single domain wall in the string order. [1] E.G. Dalla Torre, E. Berg, E. Altman, Phys. Rev Lett. 97, 260401 (2006)
One-dimensional hybrid nanostructures for heterogeneous photocatalysis and photoelectrocatalysis.
Xiao, Fang-Xing; Miao, Jianwei; Tao, Hua Bing; Hung, Sung-Fu; Wang, Hsin-Yi; Yang, Hong Bin; Chen, Jiazang; Chen, Rong; Liu, Bin
2015-05-13
Semiconductor-based photocatalysis and photoelectrocatalysis have received considerable attention as alternative approaches for solar energy harvesting and storage. The photocatalytic or photoelectrocatalytic performance of a semiconductor is closely related to the design of the semiconductor at the nanoscale. Among various nanostructures, one-dimensional (1D) nanostructured photocatalysts and photoelectrodes have attracted increasing interest owing to their unique optical, structural, and electronic advantages. In this article, a comprehensive review of the current research efforts towards the development of 1D semiconductor nanomaterials for heterogeneous photocatalysis and photoelectrocatalysis is provided and, in particular, a discussion of how to overcome the challenges for achieving full potential of 1D nanostructures is presented. It is anticipated that this review will afford enriched information on the rational exploration of the structural and electronic properties of 1D semiconductor nanostructures for achieving more efficient 1D nanostructure-based photocatalysts and photoelectrodes for high-efficiency solar energy conversion.
Strongly-Refractive One-Dimensional Photonic Crystal Prisms
NASA Technical Reports Server (NTRS)
Ting, David Z. (Inventor)
2004-01-01
One-dimensional (1D) photonic crystal prisms can separate a beam of polychromatic electromagnetic waves into constituent wavelength components and can utilize unconventional refraction properties for wavelength dispersion over significant portions of an entire photonic band rather than just near the band edges outside the photonic band gaps. Using a ID photonic crystal simplifies the design and fabrication process and allows the use of larger feature sizes. The prism geometry broadens the useful wavelength range, enables better optical transmission, and exhibits angular dependence on wavelength with reduced non-linearity. The properties of the 1 D photonic crystal prism can be tuned by varying design parameters such as incidence angle, exit surface angle, and layer widths. The ID photonic crystal prism can be fabricated in a planar process, and can be used as optical integrated circuit elements.
Topological phase transition in quasi-one dimensional organic conductors.
Ye, Xiao-Shan; Liu, Yong-Jun; Zeng, Xiang-Hua; Wu, Guoqing
2015-01-01
We explore topological phase transition, which involves the energy spectra of field-induced spin-density-wave (FISDW) states in quasi-one dimensional (Q1D) organic conductors, using an extended Su-Schrieffer-Heeger (SSH) model. We show that, in presence of half magnetic-flux FISDW state, the system exhibits topologically nontrivial phases, which can be characterized by a nonzero Chern number. The nontrivial evolution of the bulk bands with chemical potential in a topological phase transition is discussed. We show that the system can have a similar phase diagram which is discussed in the Haldane's model. We suggest that the topological feature should be tested experimentally in this organic system. These studies enrich the theoretical research on topologically nontrivial phases in the Q1D lattice system as compared to the Haldane topological phase appearing in the two-dimensional lattices. PMID:26612317
Polaron and bipolaron of uniaxially strained one dimensional zigzag ladder
NASA Astrophysics Data System (ADS)
Yavidov, B. Ya.
2016-09-01
An influence of the uniaxial strains in one dimensional zigzag ladder (1DZL) on the properties of polarons and bipolarons is considered. It is shown that strain changes all the parameters of the system, in particular, spectrum, existing bands and the masses of charge carriers. Numerical results obtained by taking into an account the Poisson effect clearly indicate that the properties of the (bi)polaronic system can be tuned via strain. Mass of bipolaron can be manipulated by the strain too which in turn leads to the way of tuning Bose-Einstein condensation temperature TBEC of bipolarons. It is shown that TBEC of bipolarons in strained 1DZL reasonably correlates with the values of critical temperature of superconductivity of certain perovskites.
Loschmidt echo in one-dimensional interacting Bose gases
Lelas, K.; Seva, T.; Buljan, H.
2011-12-15
We explore Loschmidt echo in two regimes of one-dimensional interacting Bose gases: the strongly interacting Tonks-Girardeau (TG) regime, and the weakly interacting mean-field regime. We find that the Loschmidt echo of a TG gas decays as a Gaussian when small (random and time independent) perturbations are added to the Hamiltonian. The exponent is proportional to the number of particles and the magnitude of a small perturbation squared. In the mean-field regime the Loschmidt echo shows richer behavior: it decays faster for larger nonlinearity, and the decay becomes more abrupt as the nonlinearity increases; it can be very sensitive to the particular realization of the noise potential, especially for relatively small nonlinearities.
Nonlinear dynamics of one-dimensional supersonic Langmuir waves
Jungwirth, K. ); Breizman, B.N. )
1991-08-01
In this review specific features of dynamics of Langmuir waves in the supersonic regime are illustrated with several examples. It is shown that the limit of an adiabatic approximation considerably extends the range of analytically solvable problems. It permits one to formulate and rigorously analyze the modulational instability, as well as to explain many empirical laws deduced from numerical simulations. The formulation describes not only collapsing cavities in two and three dimensions, but predicts also the existence of compound'' solitons in a one-dimensional model. In the same model the transition from weak turbulence to the adiabatic approximation is analyzed, including phenomena of ion-sound emission by autolocalized and self-trapped plasmons. Further, the individual and collective processes of soliton formation, their mutual collisions, and their destruction by ion-sound pulses are discussed.
Quantum quench dynamics in analytically solvable one-dimensional models
NASA Astrophysics Data System (ADS)
Iucci, Anibal; Cazalilla, Miguel A.; Giamarchi, Thierry
2008-03-01
In connection with experiments in cold atomic systems, we consider the non-equilibrium dynamics of some analytically solvable one-dimensional systems which undergo a quantum quench. In this quench one or several of the parameters of the Hamiltonian of an interacting quantum system are changed over a very short time scale. In particular, we concentrate on the Luttinger model and the sine-Gordon model in the Luther-Emery point. For the latter, we show that the order parameter and the two-point correlation function relax in the long time limit to the values determined by a generalized Gibbs ensemble first discussed by J. T. Jaynes [Phys. Rev. 106, 620 (1957); 108, 171 (1957)], and recently conjectured by M. Rigol et.al. [Phys. Rev. Lett. 98, 050405 (2007)] to apply to the non-equilibrium dynamics of integrable systems.
Critical conductance of a one-dimensional doped Mott insulator
NASA Astrophysics Data System (ADS)
Garst, M.; Novikov, D. S.; Stern, Ady; Glazman, L. I.
2008-01-01
We consider the two-terminal conductance of a one-dimensional Mott insulator undergoing the commensurate-incommensurate quantum phase transition to a conducting state. We treat the leads as Luttinger liquids. At a specific value of compressibility of the leads, corresponding to the Luther-Emery point, the conductance can be described in terms of the free propagation of noninteracting fermions with charge e/2 . At that point, the temperature dependence of the conductance across the quantum phase transition is described by a Fermi function. The deviation from the Luther-Emery point in the leads changes the temperature dependence qualitatively. In the metallic state, the low-temperature conductance is determined by the properties of the leads, and is described by the conventional Luttinger-liquid theory. In the insulating state, conductance occurs via activation of e/2 charges, and is independent of the Luttinger-liquid compressibility.
Atom-Molecule Coherence in a One-Dimensional System
NASA Astrophysics Data System (ADS)
Citro, R.; Orignac, E.
2005-09-01
We study a model of one-dimensional fermionic atoms with a narrow Feshbach resonance that allows them to bind in pairs to form bosonic molecules. We show that at low energy, a coherence develops between the molecule and fermion Luttinger liquids. At the same time, a gap opens in the spin excitation spectrum. The coherence implies that the order parameters for the molecular Bose-Einstein condensation and the atomic BCS pairing become identical. Moreover, both bosonic and fermionic charge density wave correlations decay exponentially, in contrast with a usual Luttinger liquid. We exhibit a Luther-Emery point where the systems can be described in terms of noninteracting pseudofermions. At this point we discuss the threshold behavior of density-density response functions.
One-dimensional compression of sands at high pressures
Yamamuro, J.A.; Bopp, P.A.; Lade, P.V.
1996-02-01
A one-dimensional testing apparatus was developed to test soils to axial stresses up to 850 MPa. The apparatus was instrumented with strain gauges such that lateral soil stresses, and therefore K{sub 0}, could be inferred from measured circumferential strains. Three different initial densities of quartz, Cambria, and gypsum sands were tested and it was found that the effect of initial density was eliminated at high stress magnitudes. This stress magnitude was higher for mineralogically harder grains than for softer grains. The inferred values of K{sub 0} for the mineralogically harder Cambria sand was found to be constant at high pressures, but slightly below that indicates by Jaky`s equation. However, the softer gypsum sand indicated increasing values of K{sub 0} as the stress magnitude increased. This apparently was caused by inelastic, viscous flow during shearing.
Pseudo-one-dimensional nucleation in dilute polymer solutions
NASA Astrophysics Data System (ADS)
Zhang, Lingyun; Schmit, Jeremy D.
2016-06-01
Pathogenic protein fibrils have been shown in vitro to have nucleation-dependent kinetics despite the fact that one-dimensional structures do not have the size-dependent surface energy responsible for the lag time in classical theory. We present a theory showing that the conformational entropy of the peptide chains creates a free-energy barrier that is analogous to the translational entropy barrier in higher dimensions. We find that the dynamics of polymer rearrangement make it very unlikely for nucleation to succeed along the lowest free-energy trajectory, meaning that most of the nucleation flux avoids the free-energy saddle point. We use these results to construct a three-dimensional model for amyloid nucleation that accounts for conformational entropy, backbone H bonds, and side-chain interactions to compute nucleation rates as a function of concentration.
Topological phase transition in quasi-one dimensional organic conductors
NASA Astrophysics Data System (ADS)
Ye, Xiao-Shan; Liu, Yong-Jun; Zeng, Xiang-Hua; Wu, Guoqing
2015-11-01
We explore topological phase transition, which involves the energy spectra of field-induced spin-density-wave (FISDW) states in quasi-one dimensional (Q1D) organic conductors, using an extended Su-Schrieffer-Heeger (SSH) model. We show that, in presence of half magnetic-flux FISDW state, the system exhibits topologically nontrivial phases, which can be characterized by a nonzero Chern number. The nontrivial evolution of the bulk bands with chemical potential in a topological phase transition is discussed. We show that the system can have a similar phase diagram which is discussed in the Haldane’s model. We suggest that the topological feature should be tested experimentally in this organic system. These studies enrich the theoretical research on topologically nontrivial phases in the Q1D lattice system as compared to the Haldane topological phase appearing in the two-dimensional lattices.
NASA Astrophysics Data System (ADS)
Vidal, A. J.; Astrakharchik, G. E.; Vranješ Markić, L.; Boronat, J.
2016-05-01
The ground-state properties of one-dimensional electron-spin-polarized hydrogen 1H, deuterium 2H, and tritium 3H are obtained by means of quantum Monte Carlo methods. The equations of state of the three isotopes are calculated for a wide range of linear densities. The pair correlation function and the static structure factor are obtained and interpreted within the framework of the Luttinger liquid theory. We report the density dependence of the Luttinger parameter and use it to identify different physical regimes: Bogoliubov Bose gas, super-Tonks-Girardeau gas, and quasi-crystal regimes for bosons; repulsive, attractive Fermi gas, and quasi-crystal regimes for fermions. We find that the tritium isotope is the one with the richest behavior. Our results show unambiguously the relevant role of the isotope mass in the properties of this quantum system.
Topological phase transition in quasi-one dimensional organic conductors
Ye, Xiao-Shan; Liu, Yong-Jun; Zeng, Xiang-Hua; Wu, Guoqing
2015-01-01
We explore topological phase transition, which involves the energy spectra of field-induced spin-density-wave (FISDW) states in quasi-one dimensional (Q1D) organic conductors, using an extended Su-Schrieffer-Heeger (SSH) model. We show that, in presence of half magnetic-flux FISDW state, the system exhibits topologically nontrivial phases, which can be characterized by a nonzero Chern number. The nontrivial evolution of the bulk bands with chemical potential in a topological phase transition is discussed. We show that the system can have a similar phase diagram which is discussed in the Haldane’s model. We suggest that the topological feature should be tested experimentally in this organic system. These studies enrich the theoretical research on topologically nontrivial phases in the Q1D lattice system as compared to the Haldane topological phase appearing in the two-dimensional lattices. PMID:26612317
Sonic black holes in a one-dimensional relativistic flow
NASA Astrophysics Data System (ADS)
Carbonaro, P.
2015-09-01
The analogy between sound propagation in a fluid background and light propagation in a curved spacetime, discovered by Unruh in 1981, does not work in general when considering the motion of a fluid which is confined in one spatial dimension being unable in (1+1) dimensions to introduce in a coherent manner an effective acoustic metric, barring some exceptional cases. In this paper a relativistic fluid is considered and the general condition for the existence of an acoustic metric in strictly one-dimensional systems is found. Attention is also paid to the physical meaning of the equations of state characterizing such systems and to the remarkable symmetry of structure taken by the basic equations. Finally the Hawking temperature is calculated in an artificial de Laval nozzle.
One-dimensional optical lattices and impenetrable bosons
Cazalilla, M.A. |
2003-05-01
We study the limit of large on-site repulsion of the one-dimensional Bose-Hubbard model at low densities, and derive a strong-coupling effective Hamiltonian. By taking the lattice parameter to zero, the Hamiltonian becomes a continuum model of fermions with attractive interactions. The leading corrections to the internal energy of a hard-core-boson (Tonks) gas as well as the (finite temperature) pair correlations of a strongly interacting Bose gas are calculated. We explore the possibility of realizing, in an optical lattice, a Luttinger liquid with stronger density correlations than the Tonks gas. A quantum phase transition to a charge-density-wave Mott insulator is also discussed.
Asymmetrically doped one-dimensional trans-polymers
NASA Astrophysics Data System (ADS)
Caldas, Heron
2009-10-01
More than 30 years ago [H. Shirakawa, E.J. Louis, A.G. MacDiarmid, C.K. Chiang, A.J. Heeger, J. Chem. Soc. Chem. Comm. 578 (1977); S. Etemad, A.J. Heeger, Ann. Rev. Phys. Chem. 33 (1982) 443] it was discovered that doped trans-polyacetylene (CH)x, a one-dimensional (1D) conjugated polymer, exhibits electrical conductivity. In this work we show that an asymmetrically doped 1D trans-polymer has non-conventional properties, as compared to symmetrically doped systems. Depending on the level of asymmetry between the chemical potentials of the two involved fermionic species, the polymer can be in a partially or fully spin polarized state. Some possible experimental consequences of doped 1D trans-polymers used as 1D organic polarized conductors are discussed.
One-dimensional Ising model with multispin interactions
NASA Astrophysics Data System (ADS)
Turban, Loïc
2016-09-01
We study the spin-1/2 Ising chain with multispin interactions K involving the product of m successive spins, for general values of m. Using a change of spin variables the zero-field partition function of a finite chain is obtained for free and periodic boundary conditions and we calculate the two-spin correlation function. When placed in an external field H the system is shown to be self-dual. Using another change of spin variables the one-dimensional Ising model with multispin interactions in a field is mapped onto a zero-field rectangular Ising model with first-neighbour interactions K and H. The 2D system, with size m × N/m, has the topology of a cylinder with helical BC. In the thermodynamic limit N/m\\to ∞ , m\\to ∞ , a 2D critical singularity develops on the self-duality line, \\sinh 2K\\sinh 2H=1.
Growth of One-Dimensional MnO2 Nanostructure
NASA Astrophysics Data System (ADS)
Lu, Pai; Xue, Dongfeng
Large scale MnO2 nanorods were controllably synthesized from the inexpensive precursors (e.g., manganese acetate, ammonium persulfate) via a facile one-step low temperature hydrothermal strategy. The crystal phase and microscopic morphology of the as-prepared MnO2 nanorods were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Through investigating the morphology evolution of MnO2 products in the whole synthesis process, a novel growth mechanism of these MnO2 nanorods was proposed, which may be efficiently extended to other material systems as a general approach towards one-dimensional nanostructures. The obtained MnO2 nanorods may have potential applications in Li-ion batteries and supercapacitors.
Magnons in one-dimensional k-component Fibonacci structures
Costa, C. H.; Vasconcelos, M. S.
2014-05-07
We have studied the magnon transmission through of one-dimensional magnonic k-component Fibonacci structures, where k different materials are arranged in accordance with the following substitution rule: S{sub n}{sup (k)}=S{sub n−1}{sup (k)}S{sub n−k}{sup (k)} (n≥k=0,1,2,…), where S{sub n}{sup (k)} is the nth stage of the sequence. The calculations were carried out in exchange dominated regime within the framework of the Heisenberg model and taking into account the RPA approximation. We have considered multilayers composed of simple cubic spin-S Heisenberg ferromagnets, and, by using the powerful transfer-matrix method, the spin wave transmission is obtained. It is demonstrated that the transmission coefficient has a rich and interesting magnonic pass- and stop-bands structures, which depends on the frequency of magnons and the k values.
Quantum rectifier in a one-dimensional photonic channel
NASA Astrophysics Data System (ADS)
Mascarenhas, E.; Santos, M. F.; Auffèves, A.; Gerace, D.
2016-04-01
By using a fully quantum approach based on an input-output formulation of the stochastic Schrödinger equation, we show rectification of radiation fields in a one-dimensional waveguide doped with a pair of ideal two-level systems for three topical cases: classical driving, under the action of noise, and single-photon pulsed excitation. We show that even under the constant action of unwanted noise the device still operates effectively as an optical isolator, which is of critical importance for noise resistance. Finally, harnessing stimulated emission allows for nonreciprocal behavior for single-photon inputs, thus showing purely quantum rectification at the single-photon level. The latter is a considerable step towards the ultimate goal of devising an unconditional quantum rectifier for arbitrary quantum states.
Excitations of one-dimensional supersolids with optical lattices
NASA Astrophysics Data System (ADS)
Hsueh, C.-H.; Tsai, Y.-C.; Wu, W. C.
2016-06-01
Based on mean-field Gross-Pitaevskii and Bogoliubov-de Gennes approaches, we investigate excitations of a one-dimensional soft-core interacting ultracold Bose gas under the effect of an optical lattice. It is found that no matter how deep the lattice is, at q →0 the lowest mode corresponds to a gapless phonon, ω12=v12q2 , whereas the second lowest mode corresponds to a gapped optical phonon, ω22=Δ2±v22q2 . Determination of the velocities v1,v2 , the gap Δ , and the possible sign change in ω2 upon the change of lattice depth can give decisive measures to the transitions across various supersolid and solid states. The power law v1˜(fs) 1 /2 with fs the superfluid fraction is identified in the present system at the tight-binding regime.
Erosion by a one-dimensional random walk
NASA Astrophysics Data System (ADS)
Chisholm, Rebecca H.; Hughes, Barry D.; Landman, Kerry A.
2014-08-01
We consider a model introduced by Baker et al. [Phys. Rev. E 88, 042113 (2013), 10.1103/PhysRevE.88.042113] of a single lattice random walker moving on a domain of allowed sites, surrounded by blocked sites. The walker enlarges the allowed domain by eroding the boundary at its random encounters with blocked boundary sites: attempts to step onto blocked sites succeed with a given probability and convert these sites to allowed sites. The model interpolates continuously between the Pólya random walker on the one-dimensional lattice and a "blind" walker who attempts freely, but always aborts, moves to blocked sites. We obtain some exact results about the walker's location and the rate of erosion.
One dimensional modeling of blood flow in large networks
NASA Astrophysics Data System (ADS)
Wang, Xiaofei; Lagree, Pierre-Yves; Fullana, Jose-Maria; Lorthois, Sylvie; Institut de Mecanique des Fluides de Toulouse Collaboration
2014-11-01
A fast and valid simulation of blood flow in large networks of vessels can be achieved with a one-dimensional viscoelastic model. In this paper, we developed a parallel code with this model and computed several networks: a circle of arteries, a human systemic network with 55 arteries and a vascular network of mouse kidney with more than one thousand segments. The numerical results were verified and the speedup of parallel computing was tested on multi-core computers. The evolution of pressure distributions in all the networks were visualized and we can see clearly the propagation patterns of the waves. This provides us a convenient tool to simulate blood flow in networks.
Superconducting cosmic strings and one dimensional extended supersymmetric algebras
Oikonomou, V.K.
2014-11-15
In this article we study in detail the supersymmetric structures that underlie the system of fermionic zero modes around a superconducting cosmic string. Particularly, we extend the analysis existing in the literature on the one dimensional N=2 supersymmetry and we find multiple N=2, d=1 supersymmetries. In addition, compact perturbations of the Witten index of the system are performed and we find to which physical situations these perturbations correspond. More importantly, we demonstrate that there exists a much more rich supersymmetric structure underlying the system of fermions with N{sub f} flavors and these are N-extended supersymmetric structures with non-trivial topological charges, with “N” depending on the fermion flavors.
Experiment and simulation on one-dimensional plasma photonic crystals
Zhang, Lin; Ouyang, Ji-Ting
2014-10-15
The transmission characteristics of microwaves passing through one-dimensional plasma photonic crystals (PPCs) have been investigated by experiment and simulation. The PPCs were formed by a series of discharge tubes filled with argon at 5 Torr that the plasma density in tubes can be varied by adjusting the discharge current. The transmittance of X-band microwaves through the crystal structure was measured under different discharge currents and geometrical parameters. The finite-different time-domain method was employed to analyze the detailed properties of the microwaves propagation. The results show that there exist bandgaps when the plasma is turned on. The properties of bandgaps depend on the plasma density and the geometrical parameters of the PPCs structure. The PPCs can perform as dynamical band-stop filter to control the transmission of microwaves within a wide frequency range.
Properties of surface modes in one dimensional plasma photonic crystals
Shukla, S.; Prasad, S. Singh, V.
2015-02-15
Properties of surface modes supported at the interface of air and a semi-infinite one dimensional plasma photonic crystal are analyzed. The surface mode equation is obtained by using transfer matrix method and applying continuity conditions of electric fields and its derivatives at the interface. It is observed that with increase in the width of cap layer, frequencies of surface modes are shifted towards lower frequency side, whereas increase in tangential component of wave-vector increases the mode frequency and total energy carried by the surface modes. With increase in plasma frequency, surface modes are found to shift towards higher frequency side. The group velocity along interface is found to control by cap layer thickness.
Pseudo-one-dimensional nucleation in dilute polymer solutions.
Zhang, Lingyun; Schmit, Jeremy D
2016-06-01
Pathogenic protein fibrils have been shown in vitro to have nucleation-dependent kinetics despite the fact that one-dimensional structures do not have the size-dependent surface energy responsible for the lag time in classical theory. We present a theory showing that the conformational entropy of the peptide chains creates a free-energy barrier that is analogous to the translational entropy barrier in higher dimensions. We find that the dynamics of polymer rearrangement make it very unlikely for nucleation to succeed along the lowest free-energy trajectory, meaning that most of the nucleation flux avoids the free-energy saddle point. We use these results to construct a three-dimensional model for amyloid nucleation that accounts for conformational entropy, backbone H bonds, and side-chain interactions to compute nucleation rates as a function of concentration. PMID:27415194
Switching synchronization in one-dimensional memristive networks
NASA Astrophysics Data System (ADS)
Slipko, Valeriy A.; Shumovskyi, Mykola; Pershin, Yuriy V.
2015-11-01
We report on a switching synchronization phenomenon in one-dimensional memristive networks, which occurs when several memristive systems with different switching constants are switched from the high- to low-resistance state. Our numerical simulations show that such a collective behavior is especially pronounced when the applied voltage slightly exceeds the combined threshold voltage of memristive systems. Moreover, a finite increase in the network switching time is found compared to the average switching time of individual systems. An analytical model is presented to explain our observations. Using this model, we have derived asymptotic expressions for memory resistances at short and long times, which are in excellent agreement with results of our numerical simulations.
Equilibrium properties of a one-dimensional kinetic system.
NASA Technical Reports Server (NTRS)
Williams, J. H.; Joyce, G.
1973-01-01
One-dimensional systems of N = 500 and 250 particles in equilibrium are numerically simulated utilizing the method of molecular dynamics. Periodic boundary conditions are imposed. The classical two-body interaction potential is short range, repulsive and has a corresponding finite force. The equations of state are determined for densities both less and greater than one. Corresponding theoretical isochores are determined from models based on nearest-neighbor interactions and on a truncated virial expansion, and a comparison is made with the experimental isochores. Time independent radial distributions are constructed numerically and discussed. A change of state from a solidlike state to a fluid-gas state based on the penetrability of the particles is predicted. The transition temperatures are estimated from the radial distribution functions and the nearest-neighbor model. Self-diffusion is observed and the corresponding constants are determined from the velocity autocorrelation functions.
Efficient algorithm for approximating one-dimensional ground states
Aharonov, Dorit; Arad, Itai; Irani, Sandy
2010-07-15
The density-matrix renormalization-group method is very effective at finding ground states of one-dimensional (1D) quantum systems in practice, but it is a heuristic method, and there is no known proof for when it works. In this article we describe an efficient classical algorithm which provably finds a good approximation of the ground state of 1D systems under well-defined conditions. More precisely, our algorithm finds a matrix product state of bond dimension D whose energy approximates the minimal energy such states can achieve. The running time is exponential in D, and so the algorithm can be considered tractable even for D, which is logarithmic in the size of the chain. The result also implies trivially that the ground state of any local commuting Hamiltonian in 1D can be approximated efficiently; we improve this to an exact algorithm.
One-dimensional quantum walk with unitary noise
Shapira, Daniel; Biham, Ofer; Bracken, A.J.; Hackett, Michelle
2003-12-01
The effect of unitary noise on the discrete one-dimensional quantum walk is studied using computer simulations. For the noiseless quantum walk, starting at the origin (n=0) at time t=0, the position distribution P{sub t}(n) at time t is very different from the Gaussian distribution obtained for the classical random walk. Furthermore, its standard deviation, {sigma}(t) scales as {sigma}(t){approx}t, unlike the classical random walk for which {sigma}(t){approx}{radical}(t). It is shown that when the quantum walk is exposed to unitary noise, it exhibits a crossover from quantum behavior for short times to classical-like behavior for long times. The crossover time is found to be T{approx}{alpha}{sup -2}, where {alpha} is the standard deviation of the noise.
Majorana fermion exchange in strictly one-dimensional structures
NASA Astrophysics Data System (ADS)
Chiu, Ching-Kai; Vazifeh, M. M.; Franz, M.
2015-04-01
It is generally thought that the adiabatic exchange of two identical particles is impossible in one spatial dimension. Here we describe a simple protocol that permits the adiabatic exchange of two Majorana fermions in a one-dimensional topological superconductor wire. The exchange relies on the concept of “Majorana shuttle” whereby a π domain wall in the superconducting order parameter which hosts a pair of ancillary majoranas delivers one zero mode across the wire while the other one tunnels in the opposite direction. The method requires some tuning of parameters and does not, therefore, enjoy full topological protection. The resulting exchange statistics, however, remain non-Abelian for a wide range of parameters that characterize the exchange.
One-dimensional cloud fluid model for propagating star formation
NASA Technical Reports Server (NTRS)
Titus, Timothy N.; Struck-Marcell, Curtis
1990-01-01
The aim of this project was to study the propagation of star formation (SF) with a self-consistent deterministic model for the interstellar gas. The questions of under what conditions does star formation propagate in this model and what are the mechanisms of the propagation are explored. Here, researchers used the deterministic Oort-type cloud fluid model of Scalo and Struck-Marcell (1984, also see the review of Struck-Marcell, Scalo and Appleton 1987). This cloud fluid approach includes simple models for the effects of cloud collisional coalescence or disruption, collisional energy dissipation, and cloud disruption and acceleration as the result of young star winds, HII regions and supernovae. An extensive one-zone parameter study is presented in Struck-Marcell and Scalo (1987). To answer the questions above, researchers carried out one-dimensional calculations for an annulus within a galactic disk, like the so-called solar neighborhood of the galactic chemical evolution. In the calculations the left-hand boundary is set equal to the right hand boundary. The calculation is obviously idealized; however, it is computationally convenient to study the first order effects of propagating star formation. The annulus was treated as if it were at rest, i.e., in the local rotating frame. This assumption may remove some interesting effects of a supersonic gas flow, but was necessary to maintain a numerical stability in the annulus. The results on the one-dimensional propagation of SF in the Oort cloud fluid model follow: (1) SF is propagated by means of hydrodynamic waves, which can be generated by external forces or by the pressure generated by local bursts. SF is not effectively propagated via diffusion or variation in cloud interaction rates without corresponding density and velocity changes. (2) The propagation and long-range effects of SF depend on how close the gas density is to the critical threshold value, i.e., on the susceptibility of the medium.
Magnetic properties of manganese based one-dimensional spin chains.
Asha, K S; Ranjith, K M; Yogi, Arvind; Nath, R; Mandal, Sukhendu
2015-12-14
We have correlated the structure-property relationship of three manganese-based inorganic-organic hybrid structures. Compound 1, [Mn2(OH-BDC)2(DMF)3] (where BDC = 1,4-benzene dicarboxylic acid and DMF = N,N'-dimethylformamide), contains Mn2O11 dimers as secondary building units (SBUs), which are connected by carboxylate anions forming Mn-O-C-O-Mn chains. Compound 2, [Mn2(BDC)2(DMF)2], contains Mn4O20 clusters as SBUs, which also form Mn-O-C-O-Mn chains. In compound 3, [Mn3(BDC)3(DEF)2] (where DEF = N,N'-diethylformamide), the distorted MnO6 octahedra are linked to form a one-dimensional chain with Mn-O-Mn connectivity. The magnetic properties were investigated by means of magnetization and heat capacity measurements. The temperature dependent magnetic susceptibility of all the three compounds could be nicely fitted using a one-dimensional S = 5/2 Heisenberg antiferromagnetic chain model and the value of intra-chain exchange coupling (J/k(B)) between Mn(2+) ions was estimated to be ∼1.1 K, ∼0.7 K, and ∼0.46 K for compounds 1, 2, and 3, respectively. Compound 1 does not undergo any magnetic long-range-order down to 2 K while compounds 2 and 3 undergo long-range magnetic order at T(N) ≈ 4.2 K and ≈4.3 K, respectively, which are of spin-glass type. From the values of J/k(B) and T(N) the inter-chain coupling (J(⊥)/k(B)) was calculated to be about 0.1J/k(B) for both compounds 2 and 3, respectively.
Magnetic properties of manganese based one-dimensional spin chains.
Asha, K S; Ranjith, K M; Yogi, Arvind; Nath, R; Mandal, Sukhendu
2015-12-14
We have correlated the structure-property relationship of three manganese-based inorganic-organic hybrid structures. Compound 1, [Mn2(OH-BDC)2(DMF)3] (where BDC = 1,4-benzene dicarboxylic acid and DMF = N,N'-dimethylformamide), contains Mn2O11 dimers as secondary building units (SBUs), which are connected by carboxylate anions forming Mn-O-C-O-Mn chains. Compound 2, [Mn2(BDC)2(DMF)2], contains Mn4O20 clusters as SBUs, which also form Mn-O-C-O-Mn chains. In compound 3, [Mn3(BDC)3(DEF)2] (where DEF = N,N'-diethylformamide), the distorted MnO6 octahedra are linked to form a one-dimensional chain with Mn-O-Mn connectivity. The magnetic properties were investigated by means of magnetization and heat capacity measurements. The temperature dependent magnetic susceptibility of all the three compounds could be nicely fitted using a one-dimensional S = 5/2 Heisenberg antiferromagnetic chain model and the value of intra-chain exchange coupling (J/k(B)) between Mn(2+) ions was estimated to be ∼1.1 K, ∼0.7 K, and ∼0.46 K for compounds 1, 2, and 3, respectively. Compound 1 does not undergo any magnetic long-range-order down to 2 K while compounds 2 and 3 undergo long-range magnetic order at T(N) ≈ 4.2 K and ≈4.3 K, respectively, which are of spin-glass type. From the values of J/k(B) and T(N) the inter-chain coupling (J(⊥)/k(B)) was calculated to be about 0.1J/k(B) for both compounds 2 and 3, respectively. PMID:26455515
Bjorken flow in one-dimensional relativistic magnetohydrodynamics with magnetization
NASA Astrophysics Data System (ADS)
Pu, Shi; Roy, Victor; Rezzolla, Luciano; Rischke, Dirk H.
2016-04-01
We study the one-dimensional, longitudinally boost-invariant motion of an ideal fluid with infinite conductivity in the presence of a transverse magnetic field, i.e., in the ideal transverse magnetohydrodynamical limit. In an extension of our previous work Roy et al., [Phys. Lett. B 750, 45 (2015)], we consider the fluid to have a nonzero magnetization. First, we assume a constant magnetic susceptibility χm and consider an ultrarelativistic ideal gas equation of state. For a paramagnetic fluid (i.e., with χm>0 ), the decay of the energy density slows down since the fluid gains energy from the magnetic field. For a diamagnetic fluid (i.e., with χm<0 ), the energy density decays faster because it feeds energy into the magnetic field. Furthermore, when the magnetic field is taken to be external and to decay in proper time τ with a power law ˜τ-a, two distinct solutions can be found depending on the values of a and χm. Finally, we also solve the ideal magnetohydrodynamical equations for one-dimensional Bjorken flow with a temperature-dependent magnetic susceptibility and a realistic equation of state given by lattice-QCD data. We find that the temperature and energy density decay more slowly because of the nonvanishing magnetization. For values of the magnetic field typical for heavy-ion collisions, this effect is, however, rather small. It is only for magnetic fields about an order of magnitude larger than expected for heavy-ion collisions that the system is substantially reheated and the lifetime of the quark phase might be extended.
Coliform contamination of a coastal embayment: Sources and transport pathways
Weiskel, P.K.; Howes, B.L.; Heufelder, G.R.
1996-01-01
Fecal bacterial contamination of nearshore waters has direct economic impacts to coastal communities through the loss of shellfisheries and restrictions of recreational uses. We conducted seasonal measurements of fecal coliform (FC) sources and transport pathways contributing to FC contamination of Buttermilk Bay, a shallow embayment adjacent to Buzzards Bay, MA. Typical of most coastal embayments, there were no direct sewage discharges (i.e., outfalls), and fecal bacteria from human, domestic animal, and wildlife pools entered open waters primarily through direct deposition or after transport through surface waters or groundwaters. Direct fecal coliform inputs to bay waters occurred primarily in winter (December-March) from waterfowl, ~33 x 1012 FC yr-1 or ~67% of the total annual loading. Effects of waterfowl inputs on bay FC densities were mitigated by their seasonality, wide distribution across the bay surface, and the apparent limited dispersal from fecal pellets. On-site disposal of sewage by septic systems was the single largest FC source in the watershed-embayment system, 460 x 1012 FC yr-1, but due to attenuation during subsurface transport only a minute fraction, < 0.006 x 1012 FC yr-1, reached bay waters (<0.01% of annual input to bay). Instead, surface water flows, via storm drains and natural streams under both wet- and dry-weather conditions, contributed the major terrestrial input, 12 x 1012 FC yr-1 (24% of annual input), all from animal sources. Since most of the surface water FC inputs were associated with periodic, short-duration rain events with discharge concentrated in nearshore zones, wet-weather flows were found to have a disproportionately high impact on nearshore FC levels. Elution of FC from shoreline deposits of decaying vegetation (wrack) comprised an additional coliform source. Both laboratory and field experiments suggest significant elution of bacteria from wrack, ~3 x 1012 FC yr-1 on a bay-wide basis (6% of annual input), primarily
Dynamic modeling of contaminant transport with surface runoff and sediment
Ashraf, M.S.
1992-01-01
Non-point source pollution in surface runoff due to agricultural activities presents one of the principal problems in the U.S. Solution to the problem of delivering pollutants is crucial to a non-point abatement program. Mathematical models can serve as tools to relate hydrologic conditions and soil properties to the processes of pollutant transport, and can be used to evaluate the effectiveness of best management practices in reducing non-point source pollutant load in surface waters. In this study, a dynamic model component is developed to simulate transport of non-point source pollutants, mostly agricultural chemicals, with surface runoff and sediment in agricultural watersheds. Algorithms are developed to route chemicals and infiltrating water through different soil increments assuming complete mixing until time of ponding or initiation of runoff. Once runoff starts, the runoff interacts with a mixing soil layer in a non-uniform fashion and exchange of chemicals takes place between runoff and the mixing soil layer. When runoff storage builds up, it is assumed that a relatively stagnant depth of runoff interacts with the mixing soil layer. This stagnant depth is obtained by applying boundary layer theory. Mass balance equations are used to route chemicals associated with runoff and sediment along the slope lengths for overland and channel flow. Model algorithms are coupled with the hydrologic and sediment transport model RUNOFF to simulate transport of contaminants with surface runoff and sediments in agricultural watersheds. The model performance is evaluated with data ranging from controlled laboratory experiments to watershed scale. The concept of non-uniform mixing is tested with a laboratory data set found in the literature. A total of fifteen runs are made, five for each of the chemicals, nitrate, phosphate, and cyanazine. The model results show good agreements with the observed yields of runoff, sediment, orthophosphate, and ammonium.
A Linear Systems Approach to Segmented Watershed Contaminant Transport
NASA Astrophysics Data System (ADS)
Carleton, J. N.
2013-12-01
The U.S. Environmental Protection Agency (USEPA) employs simulation models to estimate concentrations of pesticide residues in surface waters for risk assessment. These models have historically been used to simulate runoff loadings from homogeneous landscapes to isolated, well-mixed lentic systems that generically represent vulnerable waters. Recent efforts to refine this approach in terms of realism and geographic specificity have focused on enhancing the level of detail of the landscape representation, rather than that of receiving water hydrology. Linear systems theory and transfer function based approaches have been applied by various investigators to the representation of contaminant leaching through soils, and to surface water hydrology (e.g., unit hydrographs), but rarely to contaminant transport either within surface waters, or through multi-compartment systems such as stream networks. This poster describes a straightforward approach to simulating watersheds as segmented into collections of linked water bodies. The approach employs convolution integrals, impulse response functions, and the Discrete Fourier Transform to propagate concentration time series from upstream to downstream locations. Given knowledge only of estimated mean stream residence times, with appropriately-scaled segmentations of catchments, realistic representations of concentration dynamics are shown to be achievable. These representations are based upon high-frequency atrazine monitoring data sets collected over common time periods from upstream and downstream locations within the same small watersheds. Simulated concentrations are shown to match measured concentrations well in both the temporal and spectral domains without the need for calibration, and despite inherent simplifying assumptions such as steady flow. The approach may have utility for enhancing surface water hydrologic representation in contaminant modeling used for regulatory purposes.
Noise and counting statistics of insulating phases in one-dimensional optical lattices
Lamacraft, Austen
2007-07-15
We discuss the correlation properties of current-carrying states of one-dimensional insulators, which could be realized by applying an impulse to atoms loaded onto an optical lattice. While the equilibrium noise has a gapped spectrum, the quantum uncertainty encoded in the amplitudes for the Zener process gives a zero-frequency contribution out of equilibrium. We derive a general expression for the generating function of the full counting statistics and find that the particle transport obeys binomial statistics with doubled charge, resulting in super-Poissonian noise that originates from the coherent creation of particle-hole pairs.
Numerical studies of variable-range hopping in one-dimensional systems
NASA Astrophysics Data System (ADS)
Rodin, A. S.; Fogler, M. M.
2010-03-01
We report on our recent numerical study [1] of hopping transport in disordered one-dimensional systems. A fast new algorithm, based on Dijkstra shortest-path algorithm, is devised to find the lowest-resistance path through the hopping network at arbitrary electric field. Probability distribution functions of individual resistances on the path and the net resistance are calculated and fitted to compact analytic formulas. Qualitative differences between statistics of resistance fluctuations in Ohmic and non-Ohmic regimes are elucidated. The results are compared with prior theoretical and experimental work on the subject.[6pt] [1] A. S. Rodin and M. M. Fogler, Phys. Rev. B 80, 155435 (2009).
Pseudo one-dimensional analysis of polymer electrolyte fuel cell cold-start
Mukherjee, Partha P; Mukundan, Rangachary; Borup, Rodney L; Wang, Yun; Mishlera, Jeff
2009-01-01
This paper investigates the electrochemical kinetics, oxygen transport, and solid water formation in polymer electrolyte fuel cell (PEFC) during cold start. Following [Yo Wang, J. Electrochem. Soc., 154 (2007) B1041-B1048], we develop a pseudo one-dimensional analysis, which enables the evaluation of the impact of ice volume fraction and temperature variations on cell performance during cold-start. The oxygen profile, starvation ice volume fraction, and relevant overpotentials are obtained. This study is valuable for studying the characteristics of PEFC cold-start.
Verification of a one-dimensional, unsteady-flow model for the Fox River in Illinois
Ishii, Audrey; Turner, Mary J.
1996-01-01
The previously-calibrated application of the Full EQuations (FEQ) model of one-dimensional, unsteady flow to a 30.7-mile reach of the Fox River in northeastern Illinois was verified with discharge, stage, and dye-transport data collected during a 12-day period in October-November 1990. The period included unsteady flow induced by the operation of a sluice gate dam located at the upstream end of the reach. The model flow field was input to the Branched Lagrangian Transport Model (BLTM) for the simulation of dye transport. The results of the FEQ and BLTM model simulations are compared with the measured data and sensitivity analyses of the model parameters for this application are presented.
Huang, Jinzhao; Fu, Ke; Yao, Nannan; Deng, Xiaolong; Ding, Meng; Shao, Minghui; Xu, Xijin; Wei, Mingzhi
2016-02-01
A new architecture of one dimensional ordered TiO2 nanorods modified by graphene oxide (GO) was assembled. The GO as the higher carrier mobility can reduce the recombination of carriers, which is more favourable for the methy orange (MO) degradation. Incorporating GO with the unblocked passageway for carrier transportation of the TiO2 nanorods can separate the transport pathway of electron and hole effectively. Furthermore, the large surface areas of TiO2 nanorods grown on the GO are beneficial to the enhancement of photocatalytic properties, and the reasonable band energy level can be obtained for the architecture, which is favorable for enhancing carrier separation and transportation. Finally, the higher transparency of the structure can enhance the light absorption. The photocatalyst grown on FTO substrates makes it easier to collect and recycle. PMID:27433607
Monitoring and modeling contaminated sediment transport in the White Oak Creek watershed
Fontaine, T.A.
1991-11-01
Over the past 47 years, operations and waste disposal activities at Oak Ridge National Laboratory have resulted in the contamination of the White Oak Creek drainage system. The containments presenting the highest risk to human health and the environment are particle reactive and are associated with the soils and sediments in White Oak Creek. During floods, the erosion of these sediments results in the transport of contaminants out of the catchment into the Clinch River. A long-term strategy is required to monitor the movement of contaminated sediments and to predict the transport of these sediments that could occur during major floods. A monitoring program will provide the information required to (1) evaluate the existing off-site transport of contaminated sediments, (2) evaluate the need for short-term control measures, (3) set priorities for remediation of contaminated areas in White Oak Creek (4) verify the success of completed remedial actions intended to control the movement of contaminated sediments, and (5) develop a computer model to simulate the transport of contaminated sediments in White Oak Creek. A contaminant-transport model will be developed to (1) evaluate the potential for the off-site transport of contaminated sediments during major floods, (2) develop long term control measures and remediation solutions, (3) predict the impact of future land-use changes in White Oak Creek on the transport of contaminated sediment. This report contains a plan for the monitoring and modeling activities required to accomplish these objectives.
Wang, Bin; Li, Xianglong; Luo, Bin; Jia, Yuying; Zhi, Linjie
2013-02-21
A unique silicon-based anode for lithium ion batteries is developed via the facile hybridization of one-dimensional silicon nanowires and two-dimensional graphene sheets. The resulting paper-like film holds advantages highly desirable for not only accommodating the volume change of silicon, but also facilitating the fast transport of electron and lithium ions.
An adaptive grid algorithm for one-dimensional nonlinear equations
NASA Technical Reports Server (NTRS)
Gutierrez, William E.; Hills, Richard G.
1990-01-01
Richards' equation, which models the flow of liquid through unsaturated porous media, is highly nonlinear and difficult to solve. Step gradients in the field variables require the use of fine grids and small time step sizes. The numerical instabilities caused by the nonlinearities often require the use of iterative methods such as Picard or Newton interation. These difficulties result in large CPU requirements in solving Richards equation. With this in mind, adaptive and multigrid methods are investigated for use with nonlinear equations such as Richards' equation. Attention is focused on one-dimensional transient problems. To investigate the use of multigrid and adaptive grid methods, a series of problems are studied. First, a multigrid program is developed and used to solve an ordinary differential equation, demonstrating the efficiency with which low and high frequency errors are smoothed out. The multigrid algorithm and an adaptive grid algorithm is used to solve one-dimensional transient partial differential equations, such as the diffusive and convective-diffusion equations. The performance of these programs are compared to that of the Gauss-Seidel and tridiagonal methods. The adaptive and multigrid schemes outperformed the Gauss-Seidel algorithm, but were not as fast as the tridiagonal method. The adaptive grid scheme solved the problems slightly faster than the multigrid method. To solve nonlinear problems, Picard iterations are introduced into the adaptive grid and tridiagonal methods. Burgers' equation is used as a test problem for the two algorithms. Both methods obtain solutions of comparable accuracy for similar time increments. For the Burgers' equation, the adaptive grid method finds the solution approximately three times faster than the tridiagonal method. Finally, both schemes are used to solve the water content formulation of the Richards' equation. For this problem, the adaptive grid method obtains a more accurate solution in fewer work units and
Hydrophobic organic contaminant transport property heterogeneity in the Borden Aquifer
NASA Astrophysics Data System (ADS)
Allen-King, Richelle M.; Kalinovich, Indra; Dominic, David F.; Wang, Guohui; Polmanteer, Reid; Divine, Dana
2015-03-01
We determined that the spatial heterogeneity in aquifer properties governing the reactive transport of volatile organic contaminants is defined by the arrangement of lithofacies. We measured permeability (k) and perchloroethene sorption distribution coefficient (Kd) for lithofacies that we delineated for samples from the Canadian Forces Base Borden Aquifer. We compiled existing data and collected 57 new cores to characterize a 30 m section of the aquifer near the test location of Mackay et al. (1986). The k and Kd were measured for samples taken at six elevations from all cores to create a data set consisting of nearly 400 colocated measurements. Through analysis of variance (corrected for multiple comparisons), we determined that the 12 originally mapped lithofacies could be grouped into five relatively distinct chemohydrofacies that capture the variability of both transport properties. The mean of ln k by lithofacies was related to the grain size and the variance was relatively consistent. In contrast, both the mean and variance of ln Kd were greater for more poorly sorted lithofacies, which were also typically more coarse-grained. Half of the aquifer sorption capacity occurred in the three highest-sorbing lithofacies but comprised only 20% of its volume. The model of the aquifer that emerged is that of discontinuous scour-fill deposits of medium sand, generally characterized by greater Kd and k, within laterally extensive fine-grained to very fine-grained sands of lower Kd and k. Our findings demonstrate the importance of considering source rock composition, transport, and deposition processes when constructing conceptual models of chemohydrofacies.
A Smart Colorful Supercapacitor with One Dimensional Photonic Crystals.
Liu, Cihui; Liu, Xing; Xuan, Hongyun; Ren, Jiaoyu; Ge, Liqin
2015-01-01
To meet the pressing demands for portable and flexible equipment in contemporary society, developing flexible, lightweight, and sustainable supercapacitor systems with large power densities, long cycle life, and ease of strongly required. However, estimating the state-of-charge of existing supercapacitors is difficult, and thus their service life is limited. In this study, we fabricate a flexible color indicative supercapacitor device with mesoporous polyaniline (mPANI)/Poly(N-Isopropyl acrylamide-Graphene Oxide-Acrylic Acid) (P(NiPPAm-GO-AA)) one dimensional photonic crystals (1DPCs) as the electrode material through a low-cost, eco-friendly, and scalable fabrication process. We found that the state-of-charge could be monitored by the structural color oscillation due to the change in the photonic band gap position of the 1DPCs. The flexible 1DPCs supercapacitor is thin at 3 mm and exhibits good specific capacitance of 22.6 F g(-1) with retention of 91.1% after 3,000 cycles. This study shows the application of the 1DPCs supercapacitor as a visual ultrathin power source. The technology may find many applications in future wearable electronics. PMID:26689375
Dynamic response of one-dimensional bosons in a trap
Golovach, Vitaly N.; Minguzzi, Anna; Glazman, Leonid I.
2009-10-15
We calculate the dynamic structure factor S(q,{omega}) of a one-dimensional (1D) interacting Bose gas confined in a harmonic trap. The effective interaction depends on the strength of the confinement enforcing the (1D) motion of atoms; interaction may be further enhanced by superimposing an optical lattice on the trap potential. In the compressible state, we find that the smooth variation in the gas density around the trap center leads to softening of the singular behavior of S(q,{omega}) at the first Lieb excitation mode compared to the behavior predicted for homogeneous 1D systems. Nevertheless, the density-averaged response S(q,{omega}) remains a nonanalytic function of q and {omega} at the first Lieb excitation mode in the limit of weak trap confinement. The exponent of the power-law nonanalyticity is modified due to the inhomogeneity in a universal way and thus bears unambiguously the information about the (homogeneous) Lieb-Liniger model. A strong optical lattice causes formation of Mott phases. Deep in the Mott regime, we predict a semicircular peak in S(q,{omega}) centered at the on-site repulsion energy, {omega}=U. Similar peaks of smaller amplitudes exist at multiples of U as well. We explain the suppression of the dynamic response with entering into the Mott regime, observed recently by Clement et al. [Phys. Rev. Lett. 102, 155301 (2009)], based on an f-sum rule for the Bose-Hubbard model.
Digital noise generators using one-dimensional chaotic maps
Martínez-Ñonthe, J. A; Palacios-Luengas, L.; Cruz-Irisson, M.; Vazquez Medina, R.; Díaz Méndez, J. A.
2014-05-15
This work shows how to improve the statistical distribution of signals produced by digital noise generators designed with one-dimensional (1-D) chaotic maps. It also shows that in a digital electronic design the piecewise linear chaotic maps (PWLCM) should be considered because they do not have stability islands in its chaotic behavior region, as it occurs in the case of the logistic map, which is commonly used to build noise generators. The design and implementation problems of the digital noise generators are analyzed and a solution is proposed. This solution relates the output of PWLCM, usually defined in the real numbers' domain, with a codebook of S elements, previously defined. The proposed solution scheme produces digital noise signals with a statistical distribution close to a uniform distribution. Finally, this work shows that it is possible to have control over the statistical distribution of the noise signal by selecting the control parameter of the PWLCM and using, as a design criterion, the bifurcation diagram.
Topological water wave states in a one-dimensional structure
NASA Astrophysics Data System (ADS)
Yang, Zhaoju; Gao, Fei; Zhang, Baile
2016-07-01
Topological concepts have been introduced into electronic, photonic, and phononic systems, but have not been studied in surface-water-wave systems. Here we study a one-dimensional periodic resonant surface-water-wave system and demonstrate its topological transition. By selecting three different water depths, we can construct different types of water waves - shallow, intermediate and deep water waves. The periodic surface-water-wave system consists of an array of cylindrical water tanks connected with narrow water channels. As the width of connecting channel varies, the band diagram undergoes a topological transition which can be further characterized by Zak phase. This topological transition holds true for shallow, intermediate and deep water waves. However, the interface state at the boundary separating two topologically distinct arrays of water tanks can exhibit different bands for shallow, intermediate and deep water waves. Our work studies for the first time topological properties of water wave systems, and paves the way to potential management of water waves.
Automated quantification of one-dimensional nanostructure alignment on surfaces
NASA Astrophysics Data System (ADS)
Dong, Jianjin; Goldthorpe, Irene A.; Mohieddin Abukhdeir, Nasser
2016-06-01
A method for automated quantification of the alignment of one-dimensional (1D) nanostructures from microscopy imaging is presented. Nanostructure alignment metrics are formulated and shown to be able to rigorously quantify the orientational order of nanostructures within a two-dimensional domain (surface). A complementary image processing method is also presented which enables robust processing of microscopy images where overlapping nanostructures might be present. Scanning electron microscopy (SEM) images of nanowire-covered surfaces are analyzed using the presented methods and it is shown that past single parameter alignment metrics are insufficient for highly aligned domains. Through the use of multiple parameter alignment metrics, automated quantitative analysis of SEM images is shown to be possible and the alignment characteristics of different samples are able to be quantitatively compared using a similarity metric. The results of this work provide researchers in nanoscience and nanotechnology with a rigorous method for the determination of structure/property relationships, where alignment of 1D nanostructures is significant.
Validation and Comparison of One-Dimensional Graound Motion Methodologies
B. Darragh; W. Silva; N. Gregor
2006-06-28
Both point- and finite-source stochastic one-dimensional ground motion models, coupled to vertically propagating equivalent-linear shear-wave site response models are validated using an extensive set of strong motion data as part of the Yucca Mountain Project. The validation and comparison exercises are presented entirely in terms of 5% damped pseudo absolute response spectra. The study consists of a quantitative analyses involving modeling nineteen well-recorded earthquakes, M 5.6 to 7.4 at over 600 sites. The sites range in distance from about 1 to about 200 km in the western US (460 km for central-eastern US). In general, this validation demonstrates that the stochastic point- and finite-source models produce accurate predictions of strong ground motions over the range of 0 to 100 km and for magnitudes M 5.0 to 7.4. The stochastic finite-source model appears to be broadband, producing near zero bias from about 0.3 Hz (low frequency limit of the analyses) to the high frequency limit of the data (100 and 25 Hz for response and Fourier amplitude spectra, respectively).
Solitary Wave in One-dimensional Buckyball System at Nanoscale
Xu, Jun; Zheng, Bowen; Liu, Yilun
2016-01-01
We have studied the stress wave propagation in one-dimensional (1-D) nanoscopic buckyball (C60) system by molecular dynamics (MD) simulation and quantitative modeling. Simulation results have shown that solitary waves are generated and propagating in the buckyball system through impacting one buckyball at one end of the buckyball chain. We have found the solitary wave behaviors are closely dependent on the initial temperature and impacting speed of the buckyball chain. There are almost no dispersion and dissipation of the solitary waves (stationary solitary wave) for relatively low temperature and high impacting speed. While for relatively high temperature and low impacting speed the profile of the solitary waves is highly distorted and dissipated after propagating several tens of buckyballs. A phase diagram is proposed to describe the effect of the temperature and impacting speed on the solitary wave behaviors in buckyball system. In order to quantitatively describe the wave behavior in buckyball system, a simple nonlinear-spring model is established, which can describe the MD simulation results at low temperature very well. The results presented in this work may lay a solid step towards the further understanding and manipulation of stress wave propagation and impact energy mitigation at nanoscale. PMID:26891624
Interspecies tunneling in one-dimensional Bose mixtures
Pflanzer, Anika C.; Zoellner, Sascha; Schmelcher, Peter
2010-02-15
We study the ground-state properties and quantum dynamics of few-boson mixtures with strong interspecies repulsion in one-dimensional traps. If one species localizes at the center, e.g., due to a very large mass compared to the other component, it represents an effective barrier for the latter, and the system can be mapped onto identical bosons in a double well. For weaker localization, the barrier atoms begin to respond to the light component, leading to an induced attraction between the mobile atoms that may even outweigh their bare intraspecies repulsion. To explain the resulting effects, we derive an effective Hubbard model for the lighter species accounting for the back action of the barrier in correction terms to the lattice parameters. Also the tunneling is drastically affected: by varying the degree of localization of the 'barrier' atoms, the dynamics of intrinsically noninteracting bosons can change from Rabi oscillations to effective pair tunneling. For identical fermions (or fermionized bosons), this leads to the tunneling of attractively bound pairs.
Dynamical spin structure factor of one-dimensional interacting fermions
NASA Astrophysics Data System (ADS)
Zyuzin, Vladimir A.; Maslov, Dmitrii L.
2015-02-01
We revisit the dynamic spin susceptibility χ (q ,ω ) of one-dimensional interacting fermions. To second order in the interaction, backscattering results in a logarithmic correction to χ (q ,ω ) at q ≪kF , even if the single-particle spectrum is linearized near the Fermi points. Consequently, the dynamic spin structure factor Im χ (q ,ω ) is nonzero at frequencies above the single-particle continuum. In the boson language, this effect results from the marginally irrelevant backscattering operator of the sine-Gordon model. Away from the threshold, the high-frequency tail of Im χ (q ,ω ) due to backscattering is larger than that due to finite mass by a factor of kF/q . We derive the renormalization group equations for the coupling constants of the g -ology model at finite ω and q and find the corresponding expression for χ (q ,ω ) , valid to all orders in the interaction but not in the immediate vicinity of the continuum boundary, where the finite-mass effects become dominant.
Weak lasing in one-dimensional polariton superlattices
Zhang, Long; Xie, Wei; Wang, Jian; Poddubny, Alexander; Lu, Jian; Wang, Yinglei; Gu, Jie; Liu, Wenhui; Xu, Dan; Shen, Xuechu; Rubo, Yuri G.; Altshuler, Boris L.; Kavokin, Alexey V.; Chen, Zhanghai
2015-01-01
Bosons with finite lifetime exhibit condensation and lasing when their influx exceeds the lasing threshold determined by the dissipative losses. In general, different one-particle states decay differently, and the bosons are usually assumed to condense in the state with the longest lifetime. Interaction between the bosons partially neglected by such an assumption can smear the lasing threshold into a threshold domain—a stable lasing many-body state exists within certain intervals of the bosonic influxes. This recently described weak lasing regime is formed by the spontaneously symmetry breaking and phase-locking self-organization of bosonic modes, which results in an essentially many-body state with a stable balance between gains and losses. Here we report, to our knowledge, the first observation of the weak lasing phase in a one-dimensional condensate of exciton–polaritons subject to a periodic potential. Real and reciprocal space photoluminescence images demonstrate that the spatial period of the condensate is twice as large as the period of the underlying periodic potential. These experiments are realized at room temperature in a ZnO microwire deposited on a silicon grating. The period doubling takes place at a critical pumping power, whereas at a lower power polariton emission images have the same periodicity as the grating. PMID:25787253
Weak lasing in one-dimensional polariton superlattices.
Zhang, Long; Xie, Wei; Wang, Jian; Poddubny, Alexander; Lu, Jian; Wang, Yinglei; Gu, Jie; Liu, Wenhui; Xu, Dan; Shen, Xuechu; Rubo, Yuri G; Altshuler, Boris L; Kavokin, Alexey V; Chen, Zhanghai
2015-03-31
Bosons with finite lifetime exhibit condensation and lasing when their influx exceeds the lasing threshold determined by the dissipative losses. In general, different one-particle states decay differently, and the bosons are usually assumed to condense in the state with the longest lifetime. Interaction between the bosons partially neglected by such an assumption can smear the lasing threshold into a threshold domain--a stable lasing many-body state exists within certain intervals of the bosonic influxes. This recently described weak lasing regime is formed by the spontaneously symmetry breaking and phase-locking self-organization of bosonic modes, which results in an essentially many-body state with a stable balance between gains and losses. Here we report, to our knowledge, the first observation of the weak lasing phase in a one-dimensional condensate of exciton-polaritons subject to a periodic potential. Real and reciprocal space photoluminescence images demonstrate that the spatial period of the condensate is twice as large as the period of the underlying periodic potential. These experiments are realized at room temperature in a ZnO microwire deposited on a silicon grating. The period doubling takes place at a critical pumping power, whereas at a lower power polariton emission images have the same periodicity as the grating.
Covering by random intervals and one-dimensional continuum percolation
Domb, C. )
1989-04-01
A brief historical introduction is given to the problem of covering a line by random overlapping intervals. The problem for equal intervals was first solved by Whitworth in the 1890s. A brief resume is given of his solution. The advantages of the present author's approach, which uses a Poisson process, are outlined, and a solution is derived by Laplace transforms. The asymptotic behavior as the line becomes long is calculated and is related to the one-dimensional continuum percolation problem. It is shown that as long as the mean interval size is finite, the probability of complete coverage decays exponentially, so that the critical percolation probability p{sub c} = 1. However, as soon as the mean interval size becomes infinite, the critical percolation probability p{sub c} switches to 0. This is in accord with previous results for a lattice model by Chinese workers, but differs from those of Schulman. A possible reason for the discrepancy is a difference in boundary conditions.
Fractal geometry in an expanding, one-dimensional, Newtonian universe.
Miller, Bruce N; Rouet, Jean-Louis; Le Guirriec, Emmanuel
2007-09-01
Observations of galaxies over large distances reveal the possibility of a fractal distribution of their positions. The source of fractal behavior is the lack of a length scale in the two body gravitational interaction. However, even with new, larger, sample sizes from recent surveys, it is difficult to extract information concerning fractal properties with confidence. Similarly, three-dimensional N-body simulations with a billion particles only provide a thousand particles per dimension, far too small for accurate conclusions. With one-dimensional models these limitations can be overcome by carrying out simulations with on the order of a quarter of a million particles without compromising the computation of the gravitational force. Here the multifractal properties of two of these models that incorporate different features of the dynamical equations governing the evolution of a matter dominated universe are compared. For each model at least two scaling regions are identified. By employing criteria from dynamical systems theory it is shown that only one of them can be geometrically significant. The results share important similarities with galaxy observations, such as hierarchical clustering and apparent bifractal geometry. They also provide insights concerning possible constraints on length and time scales for fractal structure. They clearly demonstrate that fractal geometry evolves in the mu (position, velocity) space. The observed patterns are simply a shadow (projection) of higher-dimensional structure.
One-dimensional nanoferroic rods; synthesis and characterization
NASA Astrophysics Data System (ADS)
Ahmed, M. A.; Seddik, U.; Okasha, N.; Imam, N. G.
2015-11-01
One-dimensional nanoferroic rods of BaTiO3 were synthesized by improved citrate auto-combustion technology using tetrabutyl titanate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize the prepared sample. The results indicated that the crystal structure of BaTiO3 is tetragonal phase with an average crystallite size of 47 nm. SEM image gives a cauliflower-like morphology of the agglomerated nanorods. The stoichiometry of the chemical composition of the BaTiO3 ceramic was confirmed by EDX. TEM micrograph exhibited that BaTiO3 nanoparticles have rod-like shape with an average length of 120 nm and width of 43 nm. AFM was used to investigate the surface topography and its roughness. The topography image in 3D showed that the BaTiO3 particles have a rod shape with an average particle size of 116 nm which in agreement with 3D TEM result.
A one-dimensional model of Nucleosome distribution in DNA
NASA Astrophysics Data System (ADS)
Osberg, Brendan; Moebius, Wolfram; Nguyen, Kien; Gerland, Ulrich
2012-02-01
Nucleosome positioning along DNA is neither random nor precisely regular. Genome-wide maps of nucleosome positions in various eukaryotes have revealed a common pattern around transcription start sites, involving a nucleosome-free region flanked by a periodic pattern in the average nucleosome density. We take a quantitative mathematical description of the nucleosome pattern, and incorporate specifically bound transcription factors. Our model assumes a dense, one-dimensional gas of particles, however, instead of previous work which assumes fixed-size particles interacting only by exclusion, our model explicitly accounts for transient unwrapping of short segments of nucleosomal DNA. Hence, such particles no longer have a fixed size, but interact by an effective repulsive potential. This model has been succesfully used, by us, to provide a unified description of 12 Hemiascomycota yeast species with a single unified set of model parameters. We incorporate into this model, specifically bound particles, or transcription factors (TF), which serve an important role in gene regulation. Nucleosome distribution patterns have an important influence on TF binding, and can even mediate interactions between transcription factors at a distance. This interaction can account for cooperative or competitive binding between these proteins, and we will discuss the implications this can have on gene regulation.
Topological water wave states in a one-dimensional structure.
Yang, Zhaoju; Gao, Fei; Zhang, Baile
2016-01-01
Topological concepts have been introduced into electronic, photonic, and phononic systems, but have not been studied in surface-water-wave systems. Here we study a one-dimensional periodic resonant surface-water-wave system and demonstrate its topological transition. By selecting three different water depths, we can construct different types of water waves - shallow, intermediate and deep water waves. The periodic surface-water-wave system consists of an array of cylindrical water tanks connected with narrow water channels. As the width of connecting channel varies, the band diagram undergoes a topological transition which can be further characterized by Zak phase. This topological transition holds true for shallow, intermediate and deep water waves. However, the interface state at the boundary separating two topologically distinct arrays of water tanks can exhibit different bands for shallow, intermediate and deep water waves. Our work studies for the first time topological properties of water wave systems, and paves the way to potential management of water waves. PMID:27373982
One-dimensional consolidation in unsaturated soils under cyclic loading
NASA Astrophysics Data System (ADS)
Lo, Wei-Cheng; Sposito, Garrison; Lee, Jhe-Wei; Chu, Hsiuhua
2016-05-01
The one-dimensional consolidation model of poroelasticity of Lo et al. (2014) for an unsaturated soil under constant loading is generalized to include an arbitrary time-dependent loading. A closed-form solution for the pore water and air pressures along with the total settlement is derived by employing a Fourier series representation in the spatial domain and a Laplace transformation in the time domain. This solution is illustrated for the important example of a fully-permeable soil cylinder with an undrained initial condition acted upon by a periodic stress. Our results indicate that, in terms of a dimensionless time scale, the transient solution decays to zero most slowly in a water-saturated soil, whereas for an unsaturated soil, the time for the transient solution to die out is inversely proportional to the initial water saturation. The generalization presented here shows that the diffusion time scale for pore water in an unsaturated soil is orders of magnitude greater than that in a water-saturated soil, mainly because of the much smaller hydraulic conductivity of the former.
Topological order in interacting one-dimensional Bose Systems
NASA Astrophysics Data System (ADS)
Grusdt, Fabian; Höning, Michael; Fleischhauer, Michael
2015-05-01
We discuss topological aspects of one-dimensional inversion-symmetric systems of interacting bosons, which can be implemented in current experiments with ultra cold atoms. We consider both integer and fractional fillings of a topologically non-trivial Bloch band. Our starting point is the chiral-symmetric Su-Schrieffer-Heeger (SSH) model of non-interacting fermions, which can be realized by hard-core bosons. When the hard-core constraint is removed, we obtain a bosonic system with inversion-symmetry protected topological order. Because the chiral symmetry is broken by finite interactions, the bulk-boundary correspondence of the SSH model is no longer valid. Nevertheless we show that the fractional part of the charge which is localized at the edge can distinguish topologically trivial- from non-trivial states. We generalize our analysis by including nearest neighbor interactions and present a topological classification of the resulting quarter-filling Mott insulating phase. In this case fractionally charged bulk excitations exist, which we identify in the grand-canonical phase diagram. F.G. acknowledges support from the Graduate School of Material Science MAINZ.
One dimensional coordination polymers: Synthesis, crystal structures and spectroscopic properties
NASA Astrophysics Data System (ADS)
Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Şahin, Onur
2016-11-01
Two new one dimensional (1D) cyanide complexes, namely [M(4-aepy)2(H2O)2][Pt(CN)4], (4-aepy = 4-(2-aminoethyl)pyridine M = Cu(II) (1) or Zn(II) (2)), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that 1 and 2 are isomorphous and isostructural, and crystallize in the monoclinic system and C2 space group. The Pt(II) ions are coordinated by four cyanide-carbon atoms in the square-planar geometry and the [Pt(CN)4]2- ions act as a counter ion. The M(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4-aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. The crystal structures of 1 and 2 are similar each other and linked via intermolecular hydrogen bonding, Pt⋯π interactions to form 3D supramolecular network. Vibration assignments of all the observed bands are given and the spectral features also supported to the crystal structures of the complexes.
Numerical method of characteristics for one-dimensional blood flow
NASA Astrophysics Data System (ADS)
Acosta, Sebastian; Puelz, Charles; Rivière, Béatrice; Penny, Daniel J.; Rusin, Craig G.
2015-08-01
Mathematical modeling at the level of the full cardiovascular system requires the numerical approximation of solutions to a one-dimensional nonlinear hyperbolic system describing flow in a single vessel. This model is often simulated by computationally intensive methods like finite elements and discontinuous Galerkin, while some recent applications require more efficient approaches (e.g. for real-time clinical decision support, phenomena occurring over multiple cardiac cycles, iterative solutions to optimization/inverse problems, and uncertainty quantification). Further, the high speed of pressure waves in blood vessels greatly restricts the time step needed for stability in explicit schemes. We address both cost and stability by presenting an efficient and unconditionally stable method for approximating solutions to diagonal nonlinear hyperbolic systems. Theoretical analysis of the algorithm is given along with a comparison of our method to a discontinuous Galerkin implementation. Lastly, we demonstrate the utility of the proposed method by implementing it on small and large arterial networks of vessels whose elastic and geometrical parameters are physiologically relevant.
Bulk-edge correspondence of one-dimensional quantum walks
NASA Astrophysics Data System (ADS)
Cedzich, C.; Grünbaum, F. A.; Stahl, C.; Velázquez, L.; Werner, A. H.; Werner, R. F.
2016-05-01
We outline a theory of symmetry protected topological phases of one-dimensional quantum walks. We assume spectral gaps around the symmetry-distinguished points +1 and ‑1, in which only discrete eigenvalues are allowed. The phase classification by integer or binary indices extends the classification known for translation invariant systems in terms of their band structure. However, our theory requires no translation invariance whatsoever, and the indices we define in this general setting are invariant under arbitrary symmetric local perturbations, even those that cannot be continuously contracted to the identity. More precisely we define two indices for every walk, characterizing the behavior far to the right and far to the left, respectively. Their sum is a lower bound on the number of eigenstates at +1 and ‑1. For a translation invariant system the indices add up to zero, so one of them already characterizes the phase. By joining two bulk phases with different indices we get a walk in which the right and left indices no longer cancel, so the theory predicts bound states at +1 or ‑1. This is a rigorous statement of bulk-edge correspondence. The results also apply to the Hamiltonian case with a single gap at zero.
Inelastic collapse in one-dimensional driven systems under gravity.
Wakou, Jun'ichi; Kitagishi, Hiroyuki; Sakaue, Takahiro; Nakanishi, Hiizu
2013-04-01
We study inelastic collapse in a one-dimensional N-particle system when the system is driven from below under gravity. We investigate the hard-sphere limit of inelastic soft-sphere systems by numerical simulations to find how the collision rate per particle n(coll) increases as a function of the elastic constant of the sphere k when the restitution coefficient e is kept constant. For systems with large enough N>/~20, we find three regimes in e depending on the behavior of n(coll) in the hard-sphere limit: (i) an uncollapsing regime for 1≥e>e(c1), where n(coll) converges to a finite value, (ii) a logarithmically collapsing regime for e(c1)>e>e(c2), where n(coll) diverges as n(coll)~logk, and (iii) a power-law collapsing regime for e(c2)>e>0, where n(coll) diverges as n(coll)~k(α) with an exponent α that depends on N. The power-law collapsing regime shrinks as N decreases and seems not to exist for the system with N=3, while, for large N, the size of the uncollapsing and the logarithmically collapsing regime decreases as e(c1)=/~1-2.6/N and e(c2)=/~1-3.0/N. We demonstrate that this difference between large and small systems exists already in the inelastic collapse without external drive and gravity.
Nucleation and growth of nanoscaled one-dimensional materials
NASA Astrophysics Data System (ADS)
Cui, Hongtao
Nanoscaled one-dimensional materials have attracted great interest due to their novel physical and chemical properties. The purpose of this dissertation is to study the nucleation and growth mechanisms of carbon nanotubes and silicon nitride nanowires with their field emission applications in mind. As a result of this research, a novel methodology has been developed to deposit aligned bamboo-like carbon nanotubes on substrates using a methane and ammonia mixture in microwave plasma enhanced chemical deposition. Study of growth kinetics suggests that the carbon diffusion through bulk catalyst particles controls growth in the initial deposition process. Microstructures of carbon nanotubes are affected by the growth temperature and carbon concentration in the gas phase. High-resolution transmission electron microscope confirms the existence of the bamboo-like structure. Electron diffraction reveals that the iron-based catalyst nucleates and sustains the growth of carbon nanotubes. A nucleation and growth model has been constructed based upon experimental data and observations. In the study of silicon nitride nanoneedles, a vapor-liquid-solid model is employed to explain the nucleation and growth processes. Ammonia plasma etching is proposed to reduce the size of the catalyst and subsequently produce the novel needle-like nanostructure. High-resolution transmission electron microscope shows the structure is well crystallized and composed of alpha-silicon nitride. Other observations in the structure are also explained.
SUSY-hierarchy of one-dimensional reflectionless potentials
Maydanyuk, Sergei P. . E-mail: maidan@kinr.kiev.ua
2005-04-01
A class of one-dimensional reflectionless potentials is studied. It is found that all possible types of the reflectionless potentials can be combined into one SUSY-hierarchy with a constant potential. An approach for determination of a general form of the reflectionless potential on the basis of construction of such a hierarchy by the recurrent method is proposed. A general integral form of interdependence between superpotentials with neighboring numbers of this hierarchy, opening a possibility to find new reflectionless potentials, is found and has a simple analytical view. It is supposed that any possible type of the reflectionless potential can be expressed through finite number of elementary functions (unlike some presentations of the reflectionless potentials, which are constructed on the basis of soliton solutions or are shape invariant in one or many steps with involving scaling of parameters, and are expressed through series). An analysis of absolute transparency existence for the potential which has the inverse power dependence on space coordinate (and here tunneling is possible), i.e., which has the form V (x) = {+-} {alpha}/ vertical bar x-x{sub 0} vertical bar{sup n} (where {alpha} and x{sub 0} are constants, n is natural number), is fulfilled. It is shown that such a potential can be reflectionless at n = 2 only. A SUSY-hierarchy of the inverse power reflectionless potentials is constructed. Isospectral expansions of this hierarchy are analyzed.
Topological water wave states in a one-dimensional structure
Yang, Zhaoju; Gao, Fei; Zhang, Baile
2016-01-01
Topological concepts have been introduced into electronic, photonic, and phononic systems, but have not been studied in surface-water-wave systems. Here we study a one-dimensional periodic resonant surface-water-wave system and demonstrate its topological transition. By selecting three different water depths, we can construct different types of water waves - shallow, intermediate and deep water waves. The periodic surface-water-wave system consists of an array of cylindrical water tanks connected with narrow water channels. As the width of connecting channel varies, the band diagram undergoes a topological transition which can be further characterized by Zak phase. This topological transition holds true for shallow, intermediate and deep water waves. However, the interface state at the boundary separating two topologically distinct arrays of water tanks can exhibit different bands for shallow, intermediate and deep water waves. Our work studies for the first time topological properties of water wave systems, and paves the way to potential management of water waves. PMID:27373982
Moving solitons in a one-dimensional fermionic superfluid
NASA Astrophysics Data System (ADS)
Efimkin, Dmitry K.; Galitski, Victor
2015-02-01
A fully analytical theory of a traveling soliton in a one-dimensional fermionic superfluid is developed within the framework of time-dependent self-consistent Bogoliubov-de Gennes equations, which are solved exactly in the Andreev approximation. The soliton manifests itself in a kinklike profile of the superconducting order parameter and hosts a pair of Andreev bound states in its core. They adjust to the soliton's motion and play an important role in its stabilization. A phase jump across the soliton and its energy decrease with the soliton's velocity and vanish at the critical velocity, corresponding to the Landau criterion, where the soliton starts emitting quasiparticles and becomes unstable. The "inertial" and "gravitational" masses of the soliton are calculated and the former is shown to be orders of magnitude larger than the latter. This results in a slow motion of the soliton in a harmonic trap, reminiscent of the observed behavior of a solitonlike texture in related experiments in cold fermion gases [T. Yefsah et al., Nature (London) 499, 426 (2013), 10.1038/nature12338]. Furthermore, we calculate the full nonlinear dispersion relation of the soliton and solve the classical equations of motion in a trap. The strong nonlinearity at high velocities gives rise to anharmonic oscillatory motion of the soliton. A careful analysis of this anharmonicity may provide a means to experimentally measure the nonlinear soliton spectrum in superfluids.
Carbyne with finite length: The one-dimensional sp carbon
Pan, Bitao; Xiao, Jun; Li, Jiling; Liu, Pu; Wang, Chengxin; Yang, Guowei
2015-01-01
Carbyne is the one-dimensional allotrope of carbon composed of sp-hybridized carbon atoms. Definitive evidence for carbyne has remained elusive despite its synthesis and preparation in the laboratory. Given the remarkable technological breakthroughs offered by other allotropes of carbon, including diamond, graphite, fullerenes, carbon nanotubes, and graphene, interest in carbyne and its unusual potential properties remains intense. We report the first synthesis of carbyne with finite length, which is clearly composed of alternating single bonds and triple bonds, using a novel process involving laser ablation in liquid. Spectroscopic analyses confirm that the product is the structure of sp hybridization with alternating carbon-carbon single bonds and triple bonds and capped by hydrogen. We observe purple-blue fluorescence emissions from the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of carbyne. Condensed-phase carbyne crystals have a hexagonal lattice and resemble the white crystalline powder produced by drying a carbyne solution. We also establish that the combination of gold and alcohol is crucial to carbyne formation because carbon-hydrogen bonds can be cleaved with the help of gold catalysts under the favorable thermodynamic environment provided by laser ablation in liquid and because the unique configuration of two carbon atoms in an alcohol molecule matches the elementary entity of carbyne. This laboratory synthesis of carbyne will enable the exploration of its properties and applications. PMID:26601318
Topological phase in one-dimensional Rashba wire
NASA Astrophysics Data System (ADS)
Sa-Ke, Wang; Jun, Wang; Jun-Feng, Liu
2016-07-01
We study the possible topological phase in a one-dimensional (1D) quantum wire with an oscillating Rashba spin-orbital coupling in real space. It is shown that there are a pair of particle-hole symmetric gaps forming in the bulk energy band and fractional boundary states residing in the gap when the system has an inversion symmetry. These states are topologically nontrivial and can be characterized by a quantized Berry phase ±π or nonzero Chern number through dimensional extension. When the Rashba spin-orbital coupling varies slowly with time, the system can pump out 2 charges in a pumping cycle because of the spin flip effect. This quantized pumping is protected by topology and is robust against moderate disorders as long as the disorder strength does not exceed the opened energy gap. Project supported by the National Natural Science Foundation of China (Grant Nos. 115074045 and 11204187) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20131284).
One-dimensional particle models for heat transfer analysis
NASA Astrophysics Data System (ADS)
Bufferand, H.; Ciraolo, G.; Ghendrih, Ph; Tamain, P.; Bagnoli, F.; Lepri, S.; Livi, R.
2010-11-01
For a better understanding of Spitzer-Härm closure restrictions and for estimating the relevancy of this expression when collisionnality decreases, an effort is done in developing simple models that aim at catching the physics of the transition from conductive to free-streaming heat flux. In that perspective, one-dimensional particle models are developed to study heat transfer properties in the direction parallel to the magnetic field in tokamaks. These models are based on particles that carry energy at a specific velocity and that can interact with each other or with heat sources. By adjusting the particle dynamics and particle interaction properties, it is possible to generate a broad range of models of growing complexity. The simplest models can be solved analytically and are used to link particle behavior to general macroscopic heat transfer properties. In particular, some configurations recover Fourier's law and make possible to investigate the dependance of thermal conductivity on temperature. Besides, some configurations where local balance is lost require defining non local expression for heat flux. These different classes of models could then be linked to different plasma configurations and used to study transition from collisional to non-collisional plasma.
Using the NASA GRC Sectored-One-Dimensional Combustor Simulation
NASA Technical Reports Server (NTRS)
Paxson, Daniel E.; Mehta, Vishal R.
2014-01-01
The document is a user manual for the NASA GRC Sectored-One-Dimensional (S-1-D) Combustor Simulation. It consists of three sections. The first is a very brief outline of the mathematical and numerical background of the code along with a description of the non-dimensional variables on which it operates. The second section describes how to run the code and includes an explanation of the input file. The input file contains the parameters necessary to establish an operating point as well as the associated boundary conditions (i.e. how it is fed and terminated) of a geometrically configured combustor. It also describes the code output. The third section describes the configuration process and utilizes a specific example combustor to do so. Configuration consists of geometrically describing the combustor (section lengths, axial locations, and cross sectional areas) and locating the fuel injection point and flame region. Configuration requires modifying the source code and recompiling. As such, an executable utility is included with the code which will guide the requisite modifications and insure that they are done correctly.
Reflectometry as a fluctuation diagnostic: A one-dimensional simulation
Chou, A.E.; Luhmann, N.C. Jr.; Peebles, W.A.; Rhodes, T.L. )
1992-10-01
Reflectometry is currently employed to characterize turbulence in fusion plasmas worldwide and is expected to be a major diagnostic on the next generation of machines (e.g., ITER). Until recently, little was known about the response of a reflectometer to fluctuations (degree of localization of the signal, sensitivity to fluctuation wave number, dependence on density scale length, etc.). To elucidate these properties, we have been modeling reflectometer behavior with a code based on solution of a one-dimensional full wave equation. The code models an infinite plane plasma with density gradient in the {ital x} direction and solves the full wave equation to find the electric field of the reflectometer's electromagnetic wave. It can simulate stationary and moving density perturbations with arbitrary waveforms and wave numbers in plasmas with arbitrary density profiles. We present results of test cases comparing computational results to known analytic solutions for linear and 1{minus}{alpha}{sup 2}/{ital x}{sup 2} plasma density profiles, which show very good agreement.
Topological phase in one-dimensional Rashba wire
NASA Astrophysics Data System (ADS)
Sa-Ke, Wang; Jun, Wang; Jun-Feng, Liu
2016-07-01
We study the possible topological phase in a one-dimensional (1D) quantum wire with an oscillating Rashba spin–orbital coupling in real space. It is shown that there are a pair of particle–hole symmetric gaps forming in the bulk energy band and fractional boundary states residing in the gap when the system has an inversion symmetry. These states are topologically nontrivial and can be characterized by a quantized Berry phase ±π or nonzero Chern number through dimensional extension. When the Rashba spin–orbital coupling varies slowly with time, the system can pump out 2 charges in a pumping cycle because of the spin flip effect. This quantized pumping is protected by topology and is robust against moderate disorders as long as the disorder strength does not exceed the opened energy gap. Project supported by the National Natural Science Foundation of China (Grant Nos. 115074045 and 11204187) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20131284).
Multi-symplectic, Lagrangian, one-dimensional gas dynamics
NASA Astrophysics Data System (ADS)
Webb, G. M.
2015-05-01
The equations of Lagrangian, ideal, one-dimensional, compressible gas dynamics are written in a multi-symplectic form using the Lagrangian mass coordinate m and time t as independent variables, and in which the Eulerian position of the fluid element x = x(m, t) is one of the dependent variables. This approach differs from the Eulerian, multi-symplectic approach using Clebsch variables. Lagrangian constraints are used to specify equations for xm, xt, and St consistent with the Lagrangian map, where S is the entropy of the gas. We require St = 0 corresponding to advection of the entropy S with the flow. We show that the Lagrangian Hamiltonian equations are related to the de Donder-Weyl multi-momentum formulation. The pullback conservation laws and the symplecticity conservation laws are discussed. The pullback conservation laws correspond to invariance of the action with respect to translations in time (energy conservation) and translations in m in Noether's theorem. The conservation law due to m-translation invariance gives rise to a novel nonlocal conservation law involving the Clebsch variable r used to impose ∂S(m, t)/∂t = 0. Translation invariance with respect to x in Noether's theorem is associated with momentum conservation. We obtain the Cartan-Poincaré form for the system, and use it to obtain a closed ideal of two-forms representing the equation system.
Transmission properties of one-dimensional ternary plasma photonic crystals
Shiveshwari, Laxmi; Awasthi, S. K.
2015-09-15
Omnidirectional photonic band gaps (PBGs) are found in one-dimensional ternary plasma photonic crystals (PPC) composed of single negative metamaterials. The band characteristics and transmission properties are investigated through the transfer matrix method. We show that the proposed structure can trap light in three-dimensional space due to the elimination of Brewster's angle transmission resonance allowing the existence of complete PBG. The results are discussed in terms of incident angle, layer thickness, dielectric constant of the dielectric material, and number of unit cells (N) for TE and TM polarizations. It is seen that PBG characteristics is apparent even in an N ≥ 2 system, which is weakly sensitive to the incident angle and completely insensitive to the polarization. Finite PPC could be used for multichannel transmission filter without introducing any defect in the geometry. We show that the locations of the multichannel transmission peaks are in the allowed band of the infinite structure. The structure can work as a single or multichannel filter by varying the number of unit cells. Binary PPC can also work as a polarization sensitive tunable filter.
Scattering by infinitely rising one-dimensional potentials
NASA Astrophysics Data System (ADS)
Ferreira, E. M.; Sesma, J.
2015-12-01
Infinitely rising one-dimensional potentials constitute impenetrable barriers which reflect totally any incident wave. However, the scattering by such kind of potentials is not structureless: resonances may occur for certain values of the energy. Here we consider the problem of scattering by the members of a family of potentials Va(x) = - sgn(x) | x | a, where sgn represents the sign function and a is a positive rational number. The scattering function and the phase shifts are obtained from global solutions of the Schrödinger equation. For the determination of the Gamow states, associated to resonances, we exploit their close relation with the eigenvalues of the PT-symmetric Hamiltonians with potentials VaPT(x) = - i sgn(x) | x | a. Calculation of the time delay in the scattering at real energies is used to characterize the resonances. As an additional result, the breakdown of the PT-symmetry of the family of potentials VaPT for a < 3 may be conjectured.
A disorder-enhanced quasi-one-dimensional superconductor
Petrović, A. P.; Ansermet, D.; Chernyshov, D.; Hoesch, M.; Salloum, D.; Gougeon, P.; Potel, M.; Boeri, L.; Panagopoulos, C.
2016-01-01
A powerful approach to analysing quantum systems with dimensionality d>1 involves adding a weak coupling to an array of one-dimensional (1D) chains. The resultant quasi-1D (q1D) systems can exhibit long-range order at low temperature, but are heavily influenced by interactions and disorder due to their large anisotropies. Real q1D materials are therefore ideal candidates not only to provoke, test and refine theories of strongly correlated matter, but also to search for unusual emergent electronic phases. Here we report the unprecedented enhancement of a superconducting instability by disorder in single crystals of Na2−δMo6Se6, a q1D superconductor comprising MoSe chains weakly coupled by Na atoms. We argue that disorder-enhanced Coulomb pair-breaking (which usually destroys superconductivity) may be averted due to a screened long-range Coulomb repulsion intrinsic to disordered q1D materials. Our results illustrate the capability of disorder to tune and induce new correlated electron physics in low-dimensional materials. PMID:27448209
A Smart Colorful Supercapacitor with One Dimensional Photonic Crystals
Liu, Cihui; Liu, Xing; Xuan, Hongyun; Ren, Jiaoyu; Ge, Liqin
2015-01-01
To meet the pressing demands for portable and flexible equipment in contemporary society, developing flexible, lightweight, and sustainable supercapacitor systems with large power densities, long cycle life, and ease of strongly required. However, estimating the state-of-charge of existing supercapacitors is difficult, and thus their service life is limited. In this study, we fabricate a flexible color indicative supercapacitor device with mesoporous polyaniline (mPANI)/Poly(N-Isopropyl acrylamide-Graphene Oxide-Acrylic Acid) (P(NiPPAm-GO-AA)) one dimensional photonic crystals (1DPCs) as the electrode material through a low-cost, eco-friendly, and scalable fabrication process. We found that the state-of-charge could be monitored by the structural color oscillation due to the change in the photonic band gap position of the 1DPCs. The flexible 1DPCs supercapacitor is thin at 3 mm and exhibits good specific capacitance of 22.6 F g−1 with retention of 91.1% after 3,000 cycles. This study shows the application of the 1DPCs supercapacitor as a visual ultrathin power source. The technology may find many applications in future wearable electronics. PMID:26689375
A disorder-enhanced quasi-one-dimensional superconductor.
Petrović, A P; Ansermet, D; Chernyshov, D; Hoesch, M; Salloum, D; Gougeon, P; Potel, M; Boeri, L; Panagopoulos, C
2016-01-01
A powerful approach to analysing quantum systems with dimensionality d>1 involves adding a weak coupling to an array of one-dimensional (1D) chains. The resultant quasi-1D (q1D) systems can exhibit long-range order at low temperature, but are heavily influenced by interactions and disorder due to their large anisotropies. Real q1D materials are therefore ideal candidates not only to provoke, test and refine theories of strongly correlated matter, but also to search for unusual emergent electronic phases. Here we report the unprecedented enhancement of a superconducting instability by disorder in single crystals of Na2-δMo6Se6, a q1D superconductor comprising MoSe chains weakly coupled by Na atoms. We argue that disorder-enhanced Coulomb pair-breaking (which usually destroys superconductivity) may be averted due to a screened long-range Coulomb repulsion intrinsic to disordered q1D materials. Our results illustrate the capability of disorder to tune and induce new correlated electron physics in low-dimensional materials. PMID:27448209
A disorder-enhanced quasi-one-dimensional superconductor.
Petrović, A P; Ansermet, D; Chernyshov, D; Hoesch, M; Salloum, D; Gougeon, P; Potel, M; Boeri, L; Panagopoulos, C
2016-01-01
A powerful approach to analysing quantum systems with dimensionality d>1 involves adding a weak coupling to an array of one-dimensional (1D) chains. The resultant quasi-1D (q1D) systems can exhibit long-range order at low temperature, but are heavily influenced by interactions and disorder due to their large anisotropies. Real q1D materials are therefore ideal candidates not only to provoke, test and refine theories of strongly correlated matter, but also to search for unusual emergent electronic phases. Here we report the unprecedented enhancement of a superconducting instability by disorder in single crystals of Na2-δMo6Se6, a q1D superconductor comprising MoSe chains weakly coupled by Na atoms. We argue that disorder-enhanced Coulomb pair-breaking (which usually destroys superconductivity) may be averted due to a screened long-range Coulomb repulsion intrinsic to disordered q1D materials. Our results illustrate the capability of disorder to tune and induce new correlated electron physics in low-dimensional materials.
Numerical investigation of one-dimensional heat-flux calculations
NASA Astrophysics Data System (ADS)
Boyd, C. F.; Howell, A.
1994-10-01
New computer codes to determine the heat transfer rate from wind tunnel model surface temperature measurements have been developed for use in the Navy's Hypervelocity Wind Tunnel No. 9 (Tunnel 9). The existing code, which assumes one-dimensional (1D) conduction in a Cartesian coordinate system, accurately predicts 1D heat-flux when applied to flat or nearly flat geometries. Heating rates are overpredicted when the code is applied to cylindrical, spherical, and conical geometries. The over-prediction increases with larger test times and smaller radius of curvature. Heating rates are also over-predicted when the code is applied under a two-dimensional (2D) heating load that varies linearly in space. This over-prediction increases with larger test times and larger spatial gradient of heat-flux but is small for typical Tunnel 9 applications. Two new computer codes, which assume 1D conduction in cylindrical and spherical coordinates, accurately predict 1D heat-flux applied to cylindrical, spherical, and conical geometries. These two codes are online for use as a tool in evaluating heat transfer from Tunnel 9 data.
Solitary Wave in One-dimensional Buckyball System at Nanoscale.
Xu, Jun; Zheng, Bowen; Liu, Yilun
2016-01-01
We have studied the stress wave propagation in one-dimensional (1-D) nanoscopic buckyball (C60) system by molecular dynamics (MD) simulation and quantitative modeling. Simulation results have shown that solitary waves are generated and propagating in the buckyball system through impacting one buckyball at one end of the buckyball chain. We have found the solitary wave behaviors are closely dependent on the initial temperature and impacting speed of the buckyball chain. There are almost no dispersion and dissipation of the solitary waves (stationary solitary wave) for relatively low temperature and high impacting speed. While for relatively high temperature and low impacting speed the profile of the solitary waves is highly distorted and dissipated after propagating several tens of buckyballs. A phase diagram is proposed to describe the effect of the temperature and impacting speed on the solitary wave behaviors in buckyball system. In order to quantitatively describe the wave behavior in buckyball system, a simple nonlinear-spring model is established, which can describe the MD simulation results at low temperature very well. The results presented in this work may lay a solid step towards the further understanding and manipulation of stress wave propagation and impact energy mitigation at nanoscale. PMID:26891624
Decay of Bogoliubov excitations in one-dimensional Bose gases
NASA Astrophysics Data System (ADS)
Ristivojevic, Zoran; Matveev, K. A.
2016-07-01
We study the decay of Bogoliubov quasiparticles in one-dimensional Bose gases. Starting from the hydrodynamic Hamiltonian, we develop a microscopic theory that enables one to systematically study both the excitations and their decay. At zero temperature, the leading mechanism of decay of a quasiparticle is disintegration into three others. We find that low-energy quasiparticles (phonons) decay with the rate that scales with the seventh power of momentum, whereas the rate of decay of the high-energy quasiparticles does not depend on momentum. In addition, our approach allows us to study analytically the quasiparticle decay in the whole crossover region between the two limiting cases. When applied to integrable models, including the Lieb-Liniger model of bosons with contact repulsion, our theory confirms the absence of the decay of quasiparticle excitations. We account for two types of integrability-breaking perturbations that enable finite decay: three-body interaction between the bosons and two-body interaction of finite range.
A Smart Colorful Supercapacitor with One Dimensional Photonic Crystals
NASA Astrophysics Data System (ADS)
Liu, Cihui; Liu, Xing; Xuan, Hongyun; Ren, Jiaoyu; Ge, Liqin
2015-12-01
To meet the pressing demands for portable and flexible equipment in contemporary society, developing flexible, lightweight, and sustainable supercapacitor systems with large power densities, long cycle life, and ease of strongly required. However, estimating the state-of-charge of existing supercapacitors is difficult, and thus their service life is limited. In this study, we fabricate a flexible color indicative supercapacitor device with mesoporous polyaniline (mPANI)/Poly(N-Isopropyl acrylamide-Graphene Oxide-Acrylic Acid) (P(NiPPAm-GO-AA)) one dimensional photonic crystals (1DPCs) as the electrode material through a low-cost, eco-friendly, and scalable fabrication process. We found that the state-of-charge could be monitored by the structural color oscillation due to the change in the photonic band gap position of the 1DPCs. The flexible 1DPCs supercapacitor is thin at 3 mm and exhibits good specific capacitance of 22.6 F g-1 with retention of 91.1% after 3,000 cycles. This study shows the application of the 1DPCs supercapacitor as a visual ultrathin power source. The technology may find many applications in future wearable electronics.
Isotopic Tracers for Biogeochemical Processes and Contaminant Transport: Hanford, Washington
Donald J. DePaolo; John N. Christensen; Mark E. Conrad; and P. Evan Dresel
2007-04-19
Our goal is to use isotopic measurements to understand how contaminants are introduced to and stored in the vadose zone, and what processes control migration from the vadose zone to groundwater and then to surface water. We have been using the Hanford Site in south-central Washington as our field laboratory, and our investigations are often stimulated by observations made as part of the groundwater monitoring program and vadose zone characterization activities. Understanding the transport of contaminants at Hanford is difficult due to the presence of multiple potential sources within small areas, the long history of activities, the range of disposal methods, and the continuing evolution of the hydrological system. Observations often do not conform to simple models, and cannot be adequately understood with standard characterization approaches, even though the characterization activities are quite extensive. One of our objectives is to test the value of adding isotopic techniques to the characterization program, which has the immediate potential benefit of addressing specific remediation issues, but more importantly, it allows us to study fundamental processes at the scale and in the medium where they need to be understood. Here we focus on two recent studies at the waste management area (WMA) T-TX-TY, which relate to the sources and transport histories of vadose zone and groundwater contamination and contaminant fluid-sediment interaction. The WMA-T and WMA-TX-TY tank farms are located within the 200 West Area in the central portion of the Hanford Site (Fig. 2). They present a complicated picture of mixed groundwater plumes of nitrate, {sup 99}Tc, Cr{sup 6+}, carbon tetrachloride, etc. and multiple potential vadose zone sources such as tank leaks and disposal cribs (Fig. 3). To access potential vadose zone sources, we analyzed samples from cores C3832 near tank TX-104 and from C4104 near tank T-106. Tank T-106 was involved in a major event in 1973 in which 435,000 L
EVALUATION OF THE STATE-OF-THE-ART CONTAMINATED SEDIMENT TRANSPORT AND FATE MODELING SYSTEM
Modeling approaches for evaluating the transport and fate of sediment and associated contaminants are briefly reviewed. The main emphasis is on: 1) the application of EFDC (Environmental Fluid Dynamics Code), the state-of-the-art contaminated sediment transport and fate public do...
Hardening transition in a one-dimensional model for ferrogels.
Annunziata, Mario Alberto; Menzel, Andreas M; Löwen, Hartmut
2013-05-28
We introduce and investigate a coarse-grained model for quasi one-dimensional ferrogels. In our description the magnetic particles are represented by hard spheres with a magnetic dipole moment in their centers. Harmonic springs connecting these spheres mimic the presence of a cross-linked polymer matrix. A special emphasis is put on the coupling of the dipolar orientations to the elastic deformations of the matrix, where a memory effect of the orientations is included. Although the particles are displaced along one spatial direction only, the system already shows rich behavior: as a function of the magnetic dipole moment, we find a phase transition between "soft-elastic" states with finite interparticle separation and finite compressive elastic modulus on the one hand, and "hardened" states with touching particles and therefore diverging compressive elastic modulus on the other hand. Corresponding phase diagrams are derived neglecting thermal fluctuations of the magnetic particles. In addition, we consider a situation in which a spatially homogeneous magnetization is initially imprinted into the material. Depending on the strength of the magneto-mechanical coupling between the dipole orientations and the elastic deformations, the system then relaxes to a uniaxially ferromagnetic, an antiferromagnetic, or a spiral state of magnetization to minimize its energy. One purpose of our work is to provide a largely analytically solvable approach that can provide a benchmark to test future descriptions of higher complexity. From an applied point of view, our results could be exploited, for example, for the construction of novel damping devices of tunable shock absorbance.
Tunneling dynamics of two interacting one-dimensional particles
NASA Astrophysics Data System (ADS)
Gharashi, Seyed Ebrahim; Blume, D.
2015-09-01
We present one-dimensional simulation results for the cold-atom tunneling experiments by the Heidelberg group [Zürn et al., Phys. Rev. Lett. 108, 075303 (2012), 10.1103/PhysRevLett.108.075303; Zürn et al., Phys. Rev. Lett. 111, 175302 (2013), 10.1103/PhysRevLett.111.175302] on one or two 6Li atoms confined by a potential that consists of an approximately harmonic optical trap plus a linear magnetic-field gradient. At the noninteracting particle level, we find that the Wentzel-Kramers-Brillouin approximation may not be used as a reliable tool to extract the trapping potential parameters from the experimentally measured tunneling data. We use our numerical calculations along with the experimental tunneling rates for the noninteracting system to reparametrize the trapping potential. The reparametrized trapping potentials serve as input for our simulations of two interacting particles. For two interacting (distinguishable) atoms on the upper branch, we reproduce the experimentally measured tunneling rates, which vary over several orders of magnitude, fairly well. For infinitely strong interaction strength, we compare the time dynamics with that of two identical fermions and discuss the implications of fermionization on the dynamics. For two attractively interacting atoms on the molecular branch, we find that single-particle tunneling dominates for weakly attractive interactions, while pair tunneling dominates for strongly attractive interactions. Our first set of calculations yields qualitative but not quantitative agreement with the experimentally measured tunneling rates. We obtain quantitative agreement with the experimentally measured tunneling rates if we allow for a weakened radial confinement.
Spectroscopy of one-dimensionally inhomogeneous media with quadratic nonlinearity
Golubkov, A A; Makarov, Vladimir A
2011-11-30
We present a brief review of the results of fifty years of development efforts in spectroscopy of one-dimensionally inhomogeneous media with quadratic nonlinearity. The recent original results obtained by the authors show the fundamental possibility of determining, from experimental data, the coordinate dependences of complex quadratic susceptibility tensor components of a onedimensionally inhomogeneous (along the z axis) medium with an arbitrary frequency dispersion, if the linear dielectric properties of the medium also vary along the z axis and are described by a diagonal tensor of the linear dielectric constant. It is assumed that the medium in question has the form of a plane-parallel plate, whose surfaces are perpendicular to the direction of the inhomogeneity. Using the example of several components of the tensors X{sup (2)}(z, {omega}{sub 1} {+-} {omega}{sub 2}; {omega}{sub 1}, {+-} {omega}{sub 2}), we describe two methods for finding their spatial profiles, which differ in the interaction geometry of plane monochromatic fundamental waves with frequencies {omega}{sub 1} and {omega}{sub 2}. The both methods are based on assessing the intensity of the waves propagating from the plate at the sum or difference frequency and require measurements over a range of angles of incidence of the fundamental waves. Such measurements include two series of additional estimates of the intensities of the waves generated under special conditions by using the test and additional reference plates, which eliminates the need for complicated phase measurements of the complex amplitudes of the waves at the sum (difference) frequency.
One dimensional blood flow in a planetocentric orbit
NASA Astrophysics Data System (ADS)
Haranas, Ioannis; Gkigkitzis, Ioannis
2012-05-01
All life on earth is accustomed to the presence of gravity. When gravity is altered, biological processes can go awry. It is of great importance to ensure safety during a spaceflight. Long term exposure to microgravity can trigger detrimental physiological responses in the human body. Fluid redistribution coupled with fluid loss is one of the effects. In particular, in microgravity blood volume is shifted towards the thorax and head. Sympathetic nervous system-induced vasoconstriction is needed to maintain arterial pressure, while venoconstriction limits venous pooling of blood prevents further reductions in venous return of blood to the heart. In this paper, we modify an existing one dimensional blood flow model with the inclusion of the hydrostatic pressure gradient that further depends on the gravitational field modified by the oblateness and rotation of the Earth. We find that the velocity of the blood flow VB is inversely proportional to the blood specific volume d, also proportional to the oblateness harmonic coefficient J2, the angular velocity of the Earth ωE, and finally proportional to an arbitrary constant c. For c = -0.39073 and ξH = -0.5 mmHg, all orbits result to less blood flow velocities than that calculated on the surface of the Earth. From all considered orbits, elliptical polar orbit of eccentricity e = 0.2 exhibit the largest flow velocity VB = 1.031 m/s, followed by the orbits of inclination i = 45°and 0°. The Earth's oblateness and its rotation contribute a 0.7% difference to the blood flow velocity.
Two dimensionality in quasi-one-dimensional cobalt oxides
NASA Astrophysics Data System (ADS)
Sugiyama, J.; Nozaki, H.; Brewer, J. H.; Ansaldo, E. J.; Morris, G. D.; Takami, T.; Ikuta, H.; Mizutani, U.
2006-03-01
Magnetism of quasi-one-dimensional (1D) cobalt oxides ACoO ( A=Ca, Sr and Ba, n=1-5 and ∞) was investigated by μ+SR using polycrystalline samples, at temperatures from 300 K down to 1.8 K. The wTF- μ+SR experiments showed the existence of a magnetic transition in all six samples investigated. The onset temperature of the transition (Tcon) was found to decrease with n; that is, 100±25, 90±10, 85±10, 65±10 50±10, and 15±1 K for n=1-5, and ∞, respectively. In particular, for the samples with n=2-5, Tcon was detected only by the present μ+SR measurements. A muon spin oscillation was clearly observed in both Ca 3Co 2O 6(n=1) and BaCoO 3(n=∞), whereas only a fast relaxation is apparent even at 1.8 K in the other four samples ( n=2-5). Taking together with the fact that the paramagnetic Curie temperature ranges from -150 to -200 K for the compound with n=2 and 3, the μ+SR result indicates that a two-dimensional (2D) short-range antiferromagnetic (AF) order, which has been thought to be unlikely to exist at high T due to a relatively strong 1D F interaction, appears below Tcon for all compounds with n=1-5; but quasi-static long-range AF order formed only in Ca 3Co 2O 6, below 25 K. For BaCoO 3(n=∞), as T decreased from 300 K, 1D F order appeared below 53 K, and a sharp 2D AF transition occurred at 15 K.
Electronic properties of one-dimensional conductors: A study of molybdenum selenide molecular wires
NASA Astrophysics Data System (ADS)
Venkataraman, Latha
Quantum wires, such as nanowires and nanotubes, are ideal systems for exploring fundamental physics concepts in one-dimension. In this thesis, we present a new system of metallic one-dimensional conductors---molybdenum selenide molecular wires---that is well suited for such a study, along with experimental evidence of its one-dimensional character. We describe the synthesis of molybdenum selenide (Mo6Se 6) molecular wires from the dissolution of quasi-one-dimensional Li 2Mo6Se6 crystals in polar solvents. We then present atomically-resolved scanning tunneling microscopy images of these nanowires, ranging from 8.5 A wide individual molecular chains to bundles of chains over 5 nm in diameter. The electronic properties of these molecular wires, characterized by spatially resolved tunneling spectroscopy, reveal sharp peaks in the conductance. These peaks suggest the existence of van Hove singularities, as expected for one-dimensional systems, and as also predicted by tight binding calculations. Low-temperature tunneling spectroscopy measurements show no evidence of a band gap down to 5 K, implying that at these temperatures the wires remain metallic, and they do not undergo a Peierls distortion. We also present electron transport studies on Mo6Se6 nanowires. The measured two-terminal tunneling conductance of these wires is shown to scale as a power of temperature and bias voltage, consistent with the Luttinger liquid theory of interacting electrons in one-dimension. In addition, the exponents governing the power-law dependence of the conductance with temperature are found to vary inversely with wire diameter. From these data, we determine the Luttinger liquid interaction parameter to be g = 0.06, implying a strongly repulsive electron-electron interaction in this system. This finding is in contrast with measurements on micron-sized Mo6Se6 wires, where the conductance increases linearly with decreasing temperature, showing typical three-dimensional metallic behavior
Moment-Preserving SN Discretizations for the One-Dimensional Fokker-Planck Equation
Warsa, James S.; Prinja, Anil K.
2012-06-14
The Fokker-Planck equation: (1) Describes the transport and interactions of charged particles, (2) Many small-angle scattering collisions, (3) Asymptotic limit of the Boltzmann equation (Pomraning, 1992), and (4) The Boltzmann collision operator becomes the angular Laplacian. SN angular discretization: (1) Angular flux is collocated at the SN quadrature points, (2) The second-order derivatives in the Laplacian term must be discretized, and (3) Weighted finite-difference method preserves zeroth and first moments (Morel, 1985). Moment-preserving methods: (1) Collocate the Fokker-Planck operator at the SN quadrature points, (2) Develop several related and/or equivalent methods, and (3) Motivated by discretizations for the angular derivative appearing in the transport equation in one-dimensional spherical coordinates.
Decoherence-induced conductivity in the one-dimensional Anderson model
Stegmann, Thomas; Wolf, Dietrich E.; Ujsághy, Orsolya
2014-08-20
We study the effect of decoherence on the electron transport in the one-dimensional Anderson model by means of a statistical model [1, 2, 3, 4, 5]. In this model decoherence bonds are randomly distributed within the system, at which the electron phase is randomized completely. Afterwards, the transport quantity of interest (e.g. resistance or conductance) is ensemble averaged over the decoherence configurations. Averaging the resistance of the sample, the calculation can be performed analytically. In the thermodynamic limit, we find a decoherence-driven transition from the quantum-coherent localized regime to the Ohmic regime at a critical decoherence density, which is determined by the second-order generalized Lyapunov exponent (GLE) [4].
MULTI-IFE-A one-dimensional computer code for Inertial Fusion Energy (IFE) target simulations
NASA Astrophysics Data System (ADS)
Ramis, R.; Meyer-ter-Vehn, J.
2016-06-01
The code MULTI-IFE is a numerical tool devoted to the study of Inertial Fusion Energy (IFE) microcapsules. It includes the relevant physics for the implosion and thermonuclear ignition and burning: hydrodynamics of two component plasmas (ions and electrons), three-dimensional laser light ray-tracing, thermal diffusion, multigroup radiation transport, deuterium-tritium burning, and alpha particle diffusion. The corresponding differential equations are discretized in spherical one-dimensional Lagrangian coordinates. Two typical application examples, a high gain laser driven capsule and a low gain radiation driven marginally igniting capsule are discussed. In addition to phenomena relevant for IFE, the code includes also components (planar and cylindrical geometries, transport coefficients at low temperature, explicit treatment of Maxwell's equations) that extend its range of applicability to laser-matter interaction at moderate intensities (<1016 W cm-2). The source code design has been kept simple and structured with the aim to encourage user's modifications for specialized purposes.
One-Dimensional Poole-Frenkel Conduction in the Single Defect Limit.
Pan, Deng; Fuller, Elliot J; Gül, O Tolga; Collins, Philip G
2015-08-12
A single point defect surrounded on either side by quasi-ballistic, semimetallic carbon nanotube is a nearly ideal system for investigating disorder in one-dimensional (1D) conductors and comparing experiment to theory. Here, individual single-walled nanotubes (SWNTs) are investigated before and after the incorporation of single point defects. Transport and local Kelvin Probe force microscopy independently demonstrate high-resistance depletion regions over 1.0 μm wide surrounding one point defect in semimetallic SWNTs. Transport measurements show that conductance through such wide depletion regions occurs via a modified, 1D version of Poole-Frenkel field-assisted emission. Given the breadth of theory dedicated to the possible effects of disorder in 1D systems, it is surprising that a Poole-Frenkel mechanism appears to describe defect scattering and resistance in this semimetallic system. PMID:26189911
Contaminant transport model validation: The Oak Ridge Reservation
Lee, R.R.; Ketelle, R.H.
1988-09-01
In the complex geologic setting on the Oak Ridge Reservation, hydraulic conductivity is anisotropic and flow is strongly influenced by an extensive and largely discontinuous fracture network. Difficulties in describing and modeling the aquifer system prompted a study to obtain aquifer property data to be used in a groundwater flow model validation experiment. Characterization studies included the performance of an extensive suite of aquifer test within a 600-square-meter area to obtain aquifer property values to describe the flow field in detail. Following aquifer test, a groundwater tracer test was performed under ambient conditions to verify the aquifer analysis. Tracer migration data in the near-field were used in model calibration to predict tracer arrival time and concentration in the far-field. Despite the extensive aquifer testing, initial modeling inaccurately predicted tracer migration direction. Initial tracer migration rates were consistent with those predicted by the model; however, changing environmental conditions resulted in an unanticipated decay in tracer movement. Evaluation of the predictive accuracy of groundwater flow and contaminant transport models on the Oak Ridge Reservation depends on defining the resolution required, followed by field testing and model grid definition at compatible scales. The use of tracer tests, both as a characterization method and to verify model results, provides the highest level of resolution of groundwater flow characteristics. 3 refs., 4 figs.
Modeling uranium transport in acidic contaminated groundwater with base addition
Zhang, Fan; Luo, Wensui; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip; Gu, Baohua
2011-01-01
This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.
Modeling uranium transport in acidic contaminated groundwater with base addition.
Zhang, Fan; Luo, Wensui; Parker, Jack C; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua
2011-06-15
This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO(3)(-), SO(4)(2-), U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.
Molecular Self-Assembly into One-Dimensional Nanostructures
PALMER, LIAM C.; STUPP, SAMUEL I.
2008-01-01
CONSPECTUS Self-assembly of small molecules into one-dimensional nanostructures offers many potential applications in electronically and biologically active materials. The recent advances discussed in this Account demonstrate how researchers can use the fundamental principles of supramolecular chemistry to craft the size, shape, and internal structure of nanoscale objects. In each system described here, we used atomic force microscopy (AFM) and transmission electron microscopy (TEM) to study the assembly morphology. Circular dichroism, nuclear magnetic resonance, infrared, and optical spectroscopy provided additional information about the self-assembly behavior in solution at the molecular level. Dendron rod–coil molecules self-assemble into flat or helical ribbons. They can incorporate electronically conductive groups and can be mineralized with inorganic semiconductors. To understand the relative importance of each segment in forming the supramolecular structure, we synthetically modified the dendron, rod, and coil portions. The self-assembly depended on the generation number of the dendron, the number of hydrogen-bonding functions, and the length of the rod and coil segments. We formed chiral helices using a dendron–rod–coil molecule prepared from an enantiomerically enriched coil. Because helical nanostructures are important targets for use in biomaterials, nonlinear optics, and stereoselective catalysis, researchers would like to precisely control their shape and size. Tripeptide-containing peptide lipid molecules assemble into straight or twisted nanofibers in organic solvents. As seen by AFM, the sterics of bulky end groups can tune the helical pitch of these peptide lipid nanofibers in organic solvents. Furthermore, we demonstrated the potential for pitch control using trans-to-cis photoisomerization of a terminal azobenzene group. Other molecules called peptide amphiphiles (PAs) are known to assemble in water into cylindrical nanostructures that
Quasi-One-Dimensional Modeling of Pulse Detonation Rocket Engines
NASA Technical Reports Server (NTRS)
Morris, Christopher I.
2002-01-01
. While such a nozzle is a considerable idealization, it is clear that nozzle design and optimization will play a critical role in whether the performance potential of PDREs can be effectively realized in practice. In order to study PDRE nozzle issues with greater accuracy, a quasi-one-dimensional, finite-rate chemistry CFD code has been developed by the author. Comparisons of the code with both the previous MOC model and experimental data from Stanford University are reported. The effect of constant-gamma and finite-rate chemistry assumptions on the flowfield and performance is examined. Parametric studies of the effect of nozzle throat size and expansion ratio, at various blowdown pressure ratios, are reported.
Xie, Haijian; Yan, Huaxiang; Feng, Shijin; Wang, Qiao; Chen, Peixiong
2016-10-01
One-dimensional mathematical model is developed to investigate the behavior of contaminant transport in landfill composite liner system considering coupled effect of consolidation, diffusion, and degradation. The first- and second-type bottom boundary conditions are used to derive the steady-state and quasi-steady-state analytical solutions. The concentration profiles obtained by the proposed analytical solution are in good agreement with those obtained by the laboratory tests. The bottom concentration and flux of the soil liners can be greatly reduced when the degradation effect and porosity changing are considered. For the case under steady-state, the bottom flux and concentration for the case with t 1/2 =10 years can be 2.8 and 5.5 times lower than those of the case with t 1/2 =100 years, respectively. The bottom concentration and flux of the soil liners can be greatly reduced when the coefficient of volume compressibility decreases. For quasi-steady-state and with t 1/2 = 10 years, the bottom flux and concentration for the case with m v = 0.02/MPa can be 17.4 and 21 times lower than the case with m v = 0.5/MPa. This may be due to the fact that the true fluid velocity induced by consolidation is greater for the case with high coefficient of volume compressibility. The bottom flux for the case with single compacted clay liner (CCL) can be 1.5 times larger than that for the case with GMB/CCL considering diffusion and consolidation for DCM. The proposed analytical model can be used for verification of more complicated numerical models and assessment of the coupled effect of diffusion, consolidation, and degradation on contaminant transport in landfill liner systems. PMID:27370538
Xie, Haijian; Yan, Huaxiang; Feng, Shijin; Wang, Qiao; Chen, Peixiong
2016-10-01
One-dimensional mathematical model is developed to investigate the behavior of contaminant transport in landfill composite liner system considering coupled effect of consolidation, diffusion, and degradation. The first- and second-type bottom boundary conditions are used to derive the steady-state and quasi-steady-state analytical solutions. The concentration profiles obtained by the proposed analytical solution are in good agreement with those obtained by the laboratory tests. The bottom concentration and flux of the soil liners can be greatly reduced when the degradation effect and porosity changing are considered. For the case under steady-state, the bottom flux and concentration for the case with t 1/2 =10 years can be 2.8 and 5.5 times lower than those of the case with t 1/2 =100 years, respectively. The bottom concentration and flux of the soil liners can be greatly reduced when the coefficient of volume compressibility decreases. For quasi-steady-state and with t 1/2 = 10 years, the bottom flux and concentration for the case with m v = 0.02/MPa can be 17.4 and 21 times lower than the case with m v = 0.5/MPa. This may be due to the fact that the true fluid velocity induced by consolidation is greater for the case with high coefficient of volume compressibility. The bottom flux for the case with single compacted clay liner (CCL) can be 1.5 times larger than that for the case with GMB/CCL considering diffusion and consolidation for DCM. The proposed analytical model can be used for verification of more complicated numerical models and assessment of the coupled effect of diffusion, consolidation, and degradation on contaminant transport in landfill liner systems.
Thermal conductivity of one-dimensional Fibonacci quasicrystals
NASA Astrophysics Data System (ADS)
Maciá, Enrique
2000-03-01
We consider a general Fibonacci quasicrystal (FQC) in which both the masses and the elastic constants are aperiodically arranged. Making use of a suitable decimation scheme, inspired by real-space renormalization-group concepts, we obtain closed analytical expressions for the global transfer matrix and transmission coefficient for several resonant critical normal modes. The fractal structure of the frequency spectrum significantly influences both the cumulative contribution of the different normal modes to the thermal transport and the dependence of the thermal conductivity with the temperature over a wide temperature range. The role of resonant effects in the heat transport through the FQC is numerically and analytically discussed.
Preface: The 0.7 feature and interactions in one-dimensional systems
NASA Astrophysics Data System (ADS)
Pepper, Michael; Bird, Jonathan
2008-04-01
For over 25 years, studies on one-dimensional transport phenomena in semiconductors have been carried out: first in silicon, then in gallium arsenide and presently in numerous other materials. These studies have provided an extremely effective means to investigate a broad variety of mesoscopic and nanoelectronic phenomena. In the ballistic (point contact) regime these structures show excellent examples of quantized conductance in integer units of the fundamental quantum of conductance, 2e2/h. For a long time this has been understood to arise from the almost perfect transmission of one-dimensional subbands. On the other hand, the origin of the 0.7 structure, an additional plateau-like feature that occurs ubiquitously at a conductance value close to 0.7 × 2e2/h remains undetermined. Interest in the 0.7 structure, which is now approaching its twelfth year, is helping to raise awareness of the interesting effects that can be observed in semiconductor nanostructures, and also the versatility of these devices. The 0.7 structure has been apparent from the earliest days of one-dimensionality and its remarkable persistence in both published and unpublished data has led to detailed investigations and the finding that it is clearly related to electron spin. It has now been observed in a variety of one-dimensional systems and investigations have widened to include spin effects and the consequences of electron interaction in general. The effect has also stimulated theorists with many explanations being proposed. This has taken the theory into new areas, which in turn has led to new experiments. When a special issue devoted to the 0.7 structure was first proposed, the level of interest that it would generate was unclear. However, the scientific community's enthusiasm for the idea, and significant interest from authors, were extremely gratifying. We must express our thanks to all of the authors for their cooperation and help in preparing their articles on time. It is hoped that
Applications of One-Dimensional Nanomaterials for Stretchable Electronics
NASA Astrophysics Data System (ADS)
Xu, Feng
Electronics that can be stretched and/or conformal to curvilinear surfaces has recently attracted broad attention. Success of stretchable electronics depends on the availability of electronic materials and structures that can be highly stretched, compressed, bent, and twisted. One-dimensional (1D) nanomaterials are expected to aid the development of the stretchable electronic systems by improving performance, expanding integration possibilities, and potentially lowering cost, due to their superior mechanical/electronic/optical properties, high aspect ratios, and compatibility with bulk synthesis. This dissertation is primarily focused on the application of 1D nanomaterials, including silicon nanowires (SiNWs), carbon nanotubes (CNTs) and silver nanowires (AgNWs) for stretchable electronics. The mechanical properties of SiNWs, grown by the vapor-liquid-solid process, were first studied with in situ tensile tests inside a scanning electron microscope (SEM). It was found that the fracture strain increased from 2.7% to about 12% when the NW diameter decreased from 60 to 15 nm. The Young's modulus decreased while the fracture strength increased up to 12.2 GPa, as the nanowire diameter decreased. The fracture strength also increased with the decrease of the side surface area. Repeated loading and unloading during tensile tests demonstrated that the nanowires are linear elastic until fracture without appreciable plasticity. Then, SiNW coils were fabricated on elastomeric substrates by a controlled buckling process. SiNWs were first transferred onto prestrained and ultraviolet/ozone (UVO)-treated poly(dimethylsiloxane) (PDMS) substrates and buckled upon release of the prestrain. Two buckling modes (the in-plane wavy mode and the three-dimensional coiled mode) were found; a transition between them was achieved by controlling the UVO treatment of PDMS. Structural characterization revealed that the NW coils were oval-shaped. The oval-shaped NW coils exhibited very large
Chen, Kuo-Fu
1996-11-01
The health risks for an individual exposed to contaminants released from SRS outfalls from 1989 to 1995 were estimated. The exposure pathways studied are ingestion of drinking water, ingestion of contaminated fish and dermal contact with contaminants in water while swimming. The estimated incremental risks for an individual developing cancer vary from 3.E-06 to 1.0E-05. The estimated total exposure chronic noncancer hazard indices vary from 6.E-02 to 1.E-01. The critical contaminants were ranked based on their cancer risks and chronic noncarcinogenic hazard quotients. For cancer risks, the critical contaminants released from SRS outfalls are arsenic, tetrachloroethylene, and benzene. For chronic noncarcinogenic risks, the critical contaminants released from srs outfalls are cadmium, arsenic, silver, chromium, mercury, selenium, nitrate, manganese, zinc, nickel, uranium, barium, copper, tetrachloroethylene, cyanide, and phenol. The critical pathways in decreasing risk order are ingestion of contaminated fish, ingestion of drinking water and dermal contact with contaminants in water while swimming.
Electron supercollimation in graphene using one-dimensional disorder potentials
NASA Astrophysics Data System (ADS)
Choi, Sangkook; Park, Cheol-Hwan; Louie, Steven G.
2014-03-01
Due to its unique electronic structure, electrons in graphene interact with external potential in a counter-intuitive way, manifesting various different interesting characteristics Here we present another surprising, counter-intuitive electron transport phenomenon in graphene. We discovered that electron supercollimation can be induced by 1D disorder potentials. An electron wave packet is guided to propagate undistorted along the fluctuating direction of the external disorder potential, independent of its initial motion. The more disorder, the better is the supercollimation. This robust novel phenomenon is expected to have significant implications in the fundamental understanding of transport in graphene, as well as other materials with Dirac cone physics, and the potential to be exploited in the design of devices based on these materials. This work was supported by NSF grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by NERSC.
Impurity induced current oscillations in one-dimensional conductors
NASA Astrophysics Data System (ADS)
Artemenko, S. N.; Shapiro, D. S.; Vakhitov, R. R.; Remizov, S. V.
2009-11-01
We study theoretically electronic transport through an isolated local defect in a 1D conductor described in terms of the Luttinger liquid, and show that the well-known tunneling regime of electronic transport leading to power-law I-V curves takes place only in the limit of small voltage. At voltages exceeding a threshold value a new dynamic regime of transport starts in which the DC current bar I induces AC oscillations of frequency f = bar I/e. In gated quantum wires where interaction between electrons is short-ranged, generation linewidth is small provided the inter-electronic repulsion is strong enough, otherwise a wide-band noise is generated. In case of long-range Coulomb interaction generation is coherent at any interaction strength. The effect is related to interaction of the current with Friedel oscillations of the electronic density around the impurity. Manifestations of the effect resemble the Coulomb blockade and the Josephson effect. Oscillations of the electric current are accompanied by spin current oscillations. The results are related to semiconducting quantum wires, metallic atomic chains, carbon nanotubes, graphene nanoribbons and others.
Fabrication and characterization of one dimensional zinc oxide nanostructures
NASA Astrophysics Data System (ADS)
Cheng, Chun
In this thesis, one dimensional (1D) ZnO nanostructures with controlled morphologies, defects and alignment have been fabricated by a simple vapor transfer method. The crystal structures, interfaces, growth mechanisms and optical properties of ZnO nanostructures have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Great efforts have been devoted to the patterned growth and assembly of ZnO nanostructures as well as the stability of ZnO nanowires (NWs). Using carbonized photoresists, a simple and very effective method has been developed for fabricating and patterning high-quality ZnO NW arrays. ZnO NWs from this method show excellent alignment, crystal quality, and optical properties that are independent of the substrates. The carbonized photoresists provide perfect nucleation sites for the growth of aligned ZnO NWs and also perfectly connect to the NWs to form ideal electrodes. This approach is further extended to realize large area growth of different forms of ZnO NW arrays (e.g., the horizontal growth and multilayered ZnO NW arrays) on other kinds of carbon-based materials. In addition, the as-synthesized vertically aligned ZnO NW arrays show a low weighted reflectance (Rw) and can be used as antireflection coatings. Moreover, non c-axis growth of 1D ZnO nanostructures (e.g., nanochains, nanobrushes and nanobelts) and defect related 1D ZnO nanostructures (e.g., Y-shaped twinned nanobelts and hierarchical nanostructures decorated by flowers induced by screw dislocations) is also present. Using direct oxidization of pure Zn at high temperatures in air, uniformed ZnO NWs and tetrapods have been fabricated. The spatially-resolved PL study on these two kinds of nanostructures suggests that the defects leading to the green luminescence (GL) should originate from the structural changes along the legs of the tetrapods. Surface defects in these ZnO nanostructures play an unimportant
Large Bragg Reflection from One-Dimensional Chains of Trapped Atoms Near a Nanoscale Waveguide
NASA Astrophysics Data System (ADS)
Corzo, Neil V.; Gouraud, Baptiste; Chandra, Aveek; Goban, Akihisa; Sheremet, Alexandra S.; Kupriyanov, Dmitriy V.; Laurat, Julien
2016-09-01
We report experimental observations of a large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period nearly commensurate with the resonant wavelength, we observe a reflectance of up to 75% for the guided mode. Each atom behaves as a partially reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum network capabilities and the study of many-body effects emerging from long-range interactions.
Quasi-One Dimensional Analogues of BiS2-Based Superconductors
NASA Astrophysics Data System (ADS)
Panella, Jessica; Chamorro, Juan; McQueen, Tyrel
Many recently-reported superconductors have layered structures consisting of superconducting planes separated by insulating charge reservoir layers. Studies linking the width of the blocking layer to the critical temperature of the superconductivity onset draw a direct connection from the superconducting properties to the structure. We report three new compounds (Sr2O2Bi2Se3, Ba2O2Bi2Se3, and Sr2O2Sb2Se3) which are quasi-one dimensional analogues of the bismuth sulfide and bismuth selenide superconductors, providing a unique opportunity to study the role of dimensionality on superconductivity. The physical properties of the compounds were studied via magnetic susceptibility, thermal transport, resistivity, and heat capacity. This work is supported by a Cottrell Research Scholar Fellowship.
Fermi surface study of quasi-one-dimensional metals using magneto-optical techniques
NASA Astrophysics Data System (ADS)
Oshima, Y.; Kimata, M.; Kishigi, K.; Ohta, H.; Koyama, K.; Motokawa, M.; Nishikawa, H.; Kikuchi, K.; Ikemoto, I.
2003-08-01
Magneto-optical measurements of a quasi-one-dimensional (q1D) organic superconductor (DMET)2I3 have been performed by using a cavity perturbation technique. Several resonant absorption lines, which can be attributed to the q1D periodic orbit resonance (q1D POR), were observed as well as quite unusual high order q1D PORs coming from its corrugated Fermi surface (FS) in the interlayer direction. Moreover, these resonances seem to disappear when the magnetic field is applied close to the conducting axis due to the FS topological effect, and the transfer integral ratio can be obtained from the angular dependence of q1D POR. The FS of (DMET)2I3 can be estimated from these analyses of q1D PORs, and we will show that it has a characteristic FS structure. The observed results also indicate that the interlayer transport of (DMET)2I3 is coherent.
Intra-molecular Carrier Pathway Analysis in One-Dimensional Fused Furan Polymer
NASA Astrophysics Data System (ADS)
Ohmori, Shigekazu; Kawabata, Hiroshi; Tokunaga, Ken; Tachikawa, Hiroto
2010-01-01
The electronic structure and density distribution in the poly-fused furans were investigated using density functional theory (DFT) calculations. Differential electron density (DED) distribution analysis of the neutral and charged states of oligomer species were calculated to visualize spatial charge modulation in the molecular. Polymers of fused furans [p-F(n)] were also investigated using one-dimensional periodic boundary conditions (PBC) for comparison. A difference in the electronic structure and density distribution of p-F(n) was found between electron and hole transport processes. The electronic states of F(n) and p-F(n) were discussed on the basis of the differential electron density distribution, density of states (DOS) around the frontier states, and crystal orbital overlap population (COOP) analysis.
Electron conduction through quasi-one-dimensional indium wires on silicon
NASA Astrophysics Data System (ADS)
Uchihashi, Takashi; Ramsperger, Urs
2002-06-01
Electron conduction through quasi-one-dimensional (1D) indium atomic wires on silicon (the Si(111)-4×1-In reconstruction) is clarified with the help of local structural analysis using scanning tunneling microscopy. The reconstruction has a conductance per square as high as 100 μS, with global conduction despite numerous surface steps. A complete growth of indium wires up to both the surface steps and the lithographically printed electrodes is essential for the macroscopic transport. The system exhibits a metal-insulator transition at 130 K, consistent with a recent ultraviolet photoemission study [H. W. Yeom, S. Takeda, E. Rotenberg, I. Matsuda, K. Horikoshi, J. Schaefer, C. M. Lee, S. D. Kevan, T. Ohta, T. Nagao, and S. Hasegawa, Phys. Rev. Lett. 82, 4898 (1999)].
Chemical contaminants in the Wadden Sea: Sources, transport, fate and effects
NASA Astrophysics Data System (ADS)
Laane, R. W. P. M.; Vethaak, A. D.; Gandrass, J.; Vorkamp, K.; Köhler, A.; Larsen, M. M.; Strand, J.
2013-09-01
The Wadden Sea receives contaminants from various sources and via various transport routes. The contaminants described in this overview are various metals (Cd, Cu, Hg, Pb and Zn) and various organic contaminants (polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and lindane (hexachlorocyclohexane, γ-HCH)). In addition, information is presented about other and emerging contaminants such as antifouling biocides (e.g. TBT and Irgarol), brominated flame retardants (BFRs), poly- and perfluorinated compounds (PFCs) and pharmaceutical and personal care products (PPCPs). Special attention is given to biogeochemical processes that contribute to the mobilization of contaminants in the surface sediments of the Wadden Sea. Finally, the effects on organisms of contaminants are reviewed and discussed. The main source of contaminants in the Wadden Sea are the rivers Rhine (via de Dutch coastal zone), Elbe and Weser. The Wadden Sea is not a sink for contaminants and adsorbed contaminants are transported from east to west. The surface sediments of the Wadden Sea are an important source for contaminants to the water above. The input and concentration of most contaminants have significantly decreased in water, sediments, organisms (e.g., mussel, flounder and bird eggs) in various parts of the Wadden Sea in the last three decades. Remarkably, the Cd concentration in mussels is increasing the last decades. In recent decades, the effects of contaminants on organisms (e.g., flounder, seal) have fallen markedly. Most of the affected populations have recovered, except for TBT induced effects in snails. Little is known about the concentration and effects of most emerging contaminants and the complex environmental mixtures of contaminants. It is recommended to install an international coordinated monitoring programme for contaminants and their effects in the whole Wadden Sea and to identify the chemical contaminants that really cause the effect.
NASA Astrophysics Data System (ADS)
Cullin, J. A.; Ward, A. S.; Cwiertny, D. M.; Barber, L. B.; Kolpin, D. W.; Bradley, P. M.; Keefe, S. H.; Hubbard, L. E.
2013-12-01
Contaminants of emerging concern (CECs) are an unregulated suite of constituents possessing the potential to cause a host of reproductive and developmental problems in humans and wildlife. CECs are frequently detected in environmental waters. Degradation pathways of several CECs are well-characterized in idealized laboratory settings, but CEC fate and transport in complex field settings is poorly understood. In the present study we used a multi-tracer solute injection study to quantify physical transport, photodegradation, and sorption in a wastewater effluent-impacted stream. Conservative tracers were used to quantify physical transport processes in the stream. Use of reactive fluorescent tracers allows for isolation of the relative contribution of photodegradation and sorption within the system. Field data was used to calibrate a one-dimensional transport model allowing us to use forward modeling to predict the transport of sulfamethoxazole, an antibiotic documented to be present in the wastewater effluent and in Fourmile Creek which is susceptible to both sorption and photolysis. Forward modeling will predict both temporal persistence and spatial extent of sulfamethoxazole in Fourmile Creek
Predicting subsurface contaminant transport and transformation requires mathematical models based on a variety of physical, chemical, and biological processes. The mathematical model is an attempt to quantitatively describe observed processes in order to permit systematic forecas...
Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers
DALE, R.N.
2000-05-01
Long Length Contaminated Equipment Removal System Receiver Trailer and Transport Trailer require a configuration management plan for design, requirements and operations baseline documents. This report serves as the plan for the Trailers.
Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers
DALE, R.N.
2000-12-18
Long Length Contaminated Equipment Removal System Receiver Trailers and Transport Trailers require identification and control for the design, requirements and operations baseline documents. This plan serves as those controls for the subject trailers.
Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I
2015-01-01
A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers. PMID:24909793
Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I
2015-01-01
A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers.
Bai, Chunmei; Li, Yusong
2014-08-01
Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed. PMID:24987973
NASA Astrophysics Data System (ADS)
Bai, Chunmei; Li, Yusong
2014-08-01
Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed.
BIOPLUME MODEL FOR CONTAMINANT TRANSPORT AFFECTED BY OXYGEN LIMITED BIODEGRADATION
Many of the organic pollutants entering ground water are potentially biodegradable in the subsurface. This potential has been demonstrated in aquifers contaminated by wood-creosoting process wastes. The persistence of many of these organic compounds in the subsurface indicated ...
Kanti Sen, Tushar; Khilar, Kartic C
2006-02-28
In this review article, the authors present up-to-date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment/plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here the authors first present the compilation on in situ colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role in inorganic and organic contaminants transport in porous media. The important aspects of this article are as follows: (i) it gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviews the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon also depends on various factors such as concentration of colloidal fines, superficial velocity and bead-to-particle size ratio. This plugging-based contaminant transport can be used to develop containment technique in soil and groundwater remediation. (ii) It also presents the importance of critical salt concentration (CSC), critical ionic strength for mixed salt, critical shear stressor critical particle concentration (CPC) on in situ colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) It also reviews another class of colloidal fines called biocolloids and their transport in porous media. Finally, the authors highlight the future research based on their critical review on colloid-associated contaminant transport in saturated porous media. PMID:16324681
Characterization of Contaminant Transport Using Naturally-Occurring U-Series Disequilibria
TEH-LUNG KU
2001-06-01
Study the migration of nuclear waste contaminants in subsurface fractured systems using naturally occurring uranium and thorium-series radionuclides as tracers under in-situ physico-chemical and hydrogeologic conditions. Radioactive disequilibria among members of these decay-series nuclides can provide information on the rates of adsorption-desorption and transport of contaminants as well as on fluid transport and rock dissolution in a natural setting.
Kanti Sen, Tushar; Khilar, Kartic C
2006-02-28
In this review article, the authors present up-to-date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment/plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here the authors first present the compilation on in situ colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role in inorganic and organic contaminants transport in porous media. The important aspects of this article are as follows: (i) it gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviews the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon also depends on various factors such as concentration of colloidal fines, superficial velocity and bead-to-particle size ratio. This plugging-based contaminant transport can be used to develop containment technique in soil and groundwater remediation. (ii) It also presents the importance of critical salt concentration (CSC), critical ionic strength for mixed salt, critical shear stressor critical particle concentration (CPC) on in situ colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) It also reviews another class of colloidal fines called biocolloids and their transport in porous media. Finally, the authors highlight the future research based on their critical review on colloid-associated contaminant transport in saturated porous media.
Truex, Michael J.; Oostrom, Martinus; Tartakovsky, Guzel D.
2015-09-01
An approach was developed for evaluating vadose zone transport and attenuation of aqueous wastes containing inorganic (non-volatile) contaminants that were disposed of at the land surface (i.e., directly to the ground in cribs, trenches, tile fields, etc.) and their effect on the underlying groundwater. The approach provides a structured method for estimating transport of contaminants through the vadose zone and the resulting temporal profile of groundwater contaminant concentrations. The intent of the approach is also to provide a means for presenting and explaining the results of the transport analysis in the context of the site-specific waste disposal conditions and site properties, including heterogeneities and other complexities. The document includes considerations related to identifying appropriate monitoring to verify the estimated contaminant transport and associated predictions of groundwater contaminant concentrations. While primarily intended for evaluating contaminant transport under natural attenuation conditions, the approach can also be applied to identify types of, and targets for, mitigation approaches in the vadose zone that would reduce the temporal profile of contaminant concentrations in groundwater, if needed.
Stochastic analysis of biodegradation fronts in one-dimensional heterogeneous porous media
NASA Astrophysics Data System (ADS)
Xin, Jack; Zhang, Dongxiao
We consider a one-dimensional model biodegradation system consisting of two reaction-advection equations for nutrient and pollutant concentrations and a rate equation for biomass. The hydrodynamic dispersion is ignored. Under an explicit condition on the decay and growth rates of biomass, the system can be approximated by two component models by setting biomass kinetics to equilibrium. We derive closed form solutions for constant speed traveling fronts for the reduced two component models and compare their profiles in homogeneous media. For a spatially random velocity field, we introduce travel time and study statistics of degradation fronts via representations in terms of the travel time probability density function ( pdf) and the traveling front profiles. The travel time pdf does not vary with the nutrient and pollutant concentrations and only depends on the random water velocity. The traveling front profiles are expressed analytically or semi-analytically as functions of the travel time. The problem of nonlinear transport by a random velocity reduces to two subproblems: one being nonlinear transport by a known (unit) velocity, and the other being linear (advective) transport by a random velocity. The approach is illustrated through some examples where the randomness in velocity stems from the spatial variability of porosity.
Natural circulation in a liquid metal one-dimensional loop
NASA Astrophysics Data System (ADS)
Tarantino, M.; De Grandis, S.; Benamati, G.; Oriolo, F.
2008-06-01
A wide use of pure lead, as well as its alloys (such as lead-bismuth, lead-lithium), is foreseen in several nuclear-related fields: it is studied as coolant in critical and sub-critical nuclear reactors, as spallation target for neutron generation in several applications and for tritium generation in fusion systems. In this framework, a new facility named NAtural CIrculation Experiment (NACIE), has been designed at ENEA-Brasimone Research Centre. NACIE is a rectangular loop, made by stainless steel pipes. It consists mainly of a cold and hot leg and an expansion tank installed on the top of the loop. A fuel bundle simulator, made by three electrical heaters placed in a triangular lattice, is located in the lower part of the cold leg, while a tube in tube heat exchanger is installed in the upper part of the hot leg. The adopted secondary fluid is THT oil, while the foreseen primary fluid for the tests is lead-bismuth in eutectic composition (LBE). The aim of the facility is to carry out experimental tests of natural circulation and collect data on the heat transfer coefficient (HTC) for heavy liquid metal flowing through rod bundles. The paper is focused on the preliminary estimation of the LBE flow rate along the loop. An analytical methodology has been applied, solving the continuity, momentum and energy transport equations under appropriate hypothesis. Moreover numerical simulations have been performed. The FLUENT 6.2 CFD code has been utilized for the numerical simulations. The main results carried out from the pre-tests simulations are illustrated in the paper, and a comparison with the theoretical estimations is done.
One dimensional modeling of anthropogenic beach berm erosion
NASA Astrophysics Data System (ADS)
Shakeri Majd, M.; Sanders, B. F.
2013-12-01
Anthropogenic beach berms (sometimes called artificial berms or artificial dunes) are in use internationally to guard against beach overtopping and consequent coastal flooding. Berms can be constructed on a seasonal basis or in anticipation of a hazardous event, e.g., when a storm is expected to arrive coincident with an astronomical high tide. In either case, a common approach is to scrape sand from the foreshore with heavy equipment and deposit it on the crest of the natural beach dune, thus providing added protection from the possibility of wave overtopping. Given the potential for higher sea levels globally and more extreme storm events, anthropogenic berms will surely be tested to their limits and will ultimately fail, causing flooding. A better understanding of the conditions under which these berms fail is therefore needed to support coastal flood risk management. An experimental campaign in Newport Beach, California was conducted to document the dynamic erosion of prototype beach berms under a rising tide and mild to moderate wave conditions. Terrestrial laser scanning (TLS) of the berm produced a digital model of how the berm shape evolved over time. Here, a numerical model of swash zone hydromorphodynamics based on shallow-water flow physics is presented to evaluate whether and to what extent the timing and degree of berm erosion and overtopping can be predicted from first principles. The model tightly couples flow and sediment transport within an approximate Riemann solver, and thus is of the Godunov-type variety of finite volume schemes. Additionally, the model includes an avalanching scheme to account for non-hydrodynamic slumping down the angle of repose. Results indicate that it is possible to calibrate the model for a particular event, and then successfully predict erosion for another event, but due to parameter sensitivities, it is unlikely that the model can be applied at a site without calibration (true prediction).
NASA Astrophysics Data System (ADS)
Srivastava, Shubham
The past few decades have seen a great amount of interest in the field of nanotechnology. As our world moves towards miniaturized devices nanotechnology is set to revolutionize the electronics, storage and sensing industry. Various methods for synthesis of different types of nanoparticles are being explored. A few of these processes that hold great promise for the future are the flame synthesis methods. These methods are highly efficient but at the same time it is difficult to control the morphology of the produced nanoparticles due to a high number of control parameters involved because of the complex flow processes. These issues demand a better understanding before these processes can be exploited to their maximum potential. Most numerical methods developed cater to the simulation of spherical nanoparticles. However, it is now being increasingly understood that the shape and structure of a nanoparticle plays critical role in determining its chemical, physical and electronic properties. Therefore a high level of control on the shape of nanoparticles is highly imperative. With this purpose in mind this work proposes a novel numerical scheme to simulate the synthesis of one-dimensional nanorods and further presents mathematical simulations based on it followed by validation with experimental results. The ability to predict the morphology of a nanoparticle formed by a synthesis process adds a distinct advantage. Therefore, intricate solutions have been found for the fluid flow and these have been coupled to each stage of nanoparticle development, namely monomer formation, nucleation, particle growth and particle transport. The numerical scheme takes into account all the details of the complex surface phenomena taking place on a nanorod. Later, factors are studied which transition the growth characteristics of a nanoparticle from one dimensional to a spherical structure, thus encompassing all the factors that influence the particle shape. Group characteristics of
Soil and biosolid nano- and macro-colloid properties and contaminant transport behavior
NASA Astrophysics Data System (ADS)
Ghezzi, Jessique L.
Despite indications that they are potential contaminant transport systems and threats to groundwater quality, very little effort has been invested in comparing contaminant transport behavior of natural environmental nanocolloids and their corresponding macrocolloid fractions in the presence of As, Se, Pb, and Cu contaminants. This study involved physico-chemical, mineralogical, stability and contaminant-transport characterizations of nano- (< 100 nm) and macro-colloids (100-2000 nm) fractionated from three Kentucky soils and one biosolid waste. Particle size was investigated with SEM/TEM and dynamic light scattering. Surface reactivity was estimated using CEC and zeta potential. Mineralogical composition was determined by XRD, FTIR, and thermogravimetric analyses. Sorption isotherms assessed affinities for Cu2+, Pb2+, AsO3-, and SeO4 -2 contaminants, while settling kinetics experiments of suspensions at 0, 2 and 10 mg/L contaminants determined stability and transportability potential. Undisturbed 18x30 cm KY Ashton Loam soil monoliths were also used for transport experiments, involving infusion of 50 mg L-1 colloid suspensions spiked with 2 mg L-1 mixed contaminant loads in unsaturated, steady state, unit gradient downward percolation experiments. Overall, nanocolloids exhibited greater stability over corresponding macrocolloids in the presence and absence of contaminants following specific mineralogy trends. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the nanocolloid fractions, in spite of some hindrance by nano-aggregation phenomena. In the transport experiments, nanocolloids eluted significantly higher concentrations of colloids, total, and colloid-bound metals than corresponding macrocolloids. Contaminant elutions varied by colloid type, mineralogy and contaminant, with the following sequences: soil-colloids>bio-colloids, smectitic
Two-dimensional optical processing using one-dimensional input devices
NASA Technical Reports Server (NTRS)
Psaltis, D.
1984-01-01
Two-dimensional optical processing architectures that are implemented with one-dimensional input spatial light modulators are reviewed. The advanced state of the art of available one-dimensional devices and the flexibility that exists in the design of two-dimensional architectures with one-dimensional transducers leads to the implementation of the most powerful and versatile optical processors. Signal and image processing architectures of this type are discussed.
Benthic processes affecting contaminant transport in Upper Klamath Lake, Oregon
Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Carlson, Rick A; Parchaso, Francis; Fend, Steven V.; Stauffer-Olsen, Natalie; Manning, Andrew J.; Land, Jennie M.
2016-09-30
Executive SummaryMultiple sampling trips during calendar years 2013 through 2015 were coordinated to provide measurements of interdependent benthic processes that potentially affect contaminant transport in Upper Klamath Lake (UKL), Oregon. The measurements were motivated by recognition that such internal processes (for example, solute benthic flux, bioturbation and solute efflux by benthic invertebrates, and physical groundwater-surface water interactions) were not integrated into existing management models for UKL. Up until 2013, all of the benthic-flux studies generally had been limited spatially to a number of sites in the northern part of UKL and limited temporally to 2–3 samplings per year. All of the benthic invertebrate studies also had been limited to the northern part of the lake; however, intensive temporal (weekly) studies had previously been completed independent of benthic-flux studies. Therefore, knowledge of both the spatial and temporal variability in benthic flux and benthic invertebrate distributions for the entire lake was lacking. To address these limitations, we completed a lakewide spatial study during 2013 and a coordinated temporal study with weekly sampling of benthic flux and benthic invertebrates during 2014. Field design of the spatially focused study in 2013 involved 21 sites sampled three times as the summer cyanobacterial bloom developed (that is, May 23, June 13, and July 3, 2013). Results of the 27-week, temporally focused study of one site in 2014 were summarized and partitioned into three periods (referred to herein as pre-bloom, bloom and post-bloom periods), each period involving 9 weeks of profiler deployments, water column and benthic sampling. Partitioning of the pre-bloom, bloom, and post-bloom periods were based on water-column chlorophyll concentrations and involved the following date intervals, respectively: April 15 through June 10, June 17 through August 13, and August 20 through October 16, 2014. To examine
Prediction of contaminant fate and transport in potable water systems using H2OFate
NASA Astrophysics Data System (ADS)
Devarakonda, Venkat; Manickavasagam, Sivakumar; VanBlaricum, Vicki; Ginsberg, Mark
2009-05-01
BlazeTech has recently developed a software called H2OFate to predict the fate and transport of chemical and biological contaminants in water distribution systems. This software includes models for the reactions of these contaminants with residual disinfectant in bulk water and at the pipe wall, and their adhesion/reactions with the pipe walls. This software can be interfaced with sensors through SCADA systems to monitor water distribution networks for contamination events and activate countermeasures, as needed. This paper presents results from parametric calculations carried out using H2OFate for a simulated contaminant release into a sample water distribution network.
The major hypothesis driving this research, that the transport of colloids in a contaminant plume is limited by the advance of the chemical agent causing colloid mobilization, was tested by (1) examining the dependence of colloid transport and mobilization on chemical perturbatio...
Interest in coupled biodegradation and transport of organic contaminants has expanded greatly in the past several years. In a system in which biodegradation is coupled with solute transport, the magnitude and rate of biodegradation is influenced not only by pr...
Technology Transfer Automated Retrieval System (TEKTRAN)
Contaminant transport processes in streams, rivers, and other surface water bodies can be analyzed or predicted using the advection-dispersion equation and related transport models. In part 1 of this two-part series we presented a large number of one- and multi-dimensional analytical solutions of t...
FACT (Version 2.0) - Subsurface Flow and Contaminant Transport Documentation and User's Guide
Aleman, S.E.
2000-05-05
This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media.
Binning, P.; Celia, M.A.; Johnson, J.C.
1995-05-01
A numerical model of multiphase air-water flow and contaminant transport in the unsaturated zone is presented. The multiphase flow equations are solved using the two-pressure, mixed form of the equations with a modified Picard linearization of the equations and a finite element spatial approximation. A volatile contaminant is assumed to be transported in either phase, or in both phases simultaneously. The contaminant partitions between phases with an equilibrium distribution given by Henry`s Law or via kinetic mass transfer. The transport equations are solved using a Galerkin finite element method with reduced integration to lump the resultant matrices. The numerical model is applied to published experimental studies to examine the behavior of the air phase and associated contaminant movement under water infiltration. The model is also used to evaluate a hypothetical design for a low-level radioactive waste disposal facility. The model has been developed in both one and two dimensions; documentation and computer codes are available for the one-dimensional flow and transport model.
Contaminant transport in two central Missouri karst recharge areas
Technology Transfer Automated Retrieval System (TEKTRAN)
Karst watersheds with significant losing streams represent a particularly vulnerable setting for ground water contamination because of the direct connection to surface water. Because of the existing agricultural land-use and future likelihood of urbanization, two losing stream karst basins were chos...
Synthesis, Characterization and Applications of One-Dimensional Metal Oxide Nanostructures
NASA Astrophysics Data System (ADS)
Santulli, Alexander
Nanomaterials have been of keen research interest, owing to their exciting and unique properties (e.g. optical, magnetic, electronic, and mechanical). These properties allow nanomaterials to have many applications in areas of medicine, alternative energy, catalysis, and information storage. In particular, one-dimensional (1D) nanomaterials are highly advantageous, owing to the inherent anisotropic nature, which allows for effective transport and study of properties on the nanoscale. More specifically, 1D metal oxide nanomaterials are of particular interest, owing to their high thermal and chemical stability, as well as their intriguing optical, electronic, and magnetic properties. Herein, we will investigate the synthesis and characterization of vanadium oxide, lithium niobate and chromium oxide. We will explore the methodologies utilized for the synthesis of these materials, as well as the overall properties of these unique nanomaterials. Furthermore, we will explore the application of titanium dioxide nanomaterials as the electron transport layer in dye sensitized solar cells (DSSCs), with an emphasis on the effect of the nanoscale morphology on the overall device efficiency.
A New One-dimensional Quantum Material - Ta2Pd3Se8 Atomic Chain
NASA Astrophysics Data System (ADS)
Liu, Xue; Liu, Jinyu; Hu, Jin; Yue, Chunlei; Mao, Zhiqiang; Wei, Jiang; Antipina, Liubov; Sorokin, Pavel; Sanchez, Ana
Since the discovery of carbon nanotube, there has been a persistent effort to search for other one dimensional (1D) quantum systems. However, only a few examples have been found. We report a new 1D example - semiconducting Ta2Pd3Se8. We demonstrate that the Ta2Pd3Se8 nanowire as thin as 1.3nm can be easily obtained by applying simple mechanical exfoliation from its bulk counterpart. High resolution TEM shows an intrinsic 1D chain-like crystalline morphology on these nano wires, indicating weak bonding between these atomic chains. Theoretical calculation shows a direct bandgap structure, which evolves from 0.53eV in the bulk to 1.04eV in single atomic chain. The field effect transistor based on Ta2Pd3Se8 nanowire achieved a promising performance with 104On/Off ratio and 80 cm2V-1s-1 mobility. Low temperature transport study reflects two different mechanisms, variable range hopping and thermal activation, which dominate the transport properties at different temperature regimes. Ta2Pd3Se8 nanowire provides an intrinsic 1D material system for the study low dimensional condensed matter physics.
One-dimensional carbon nanostructures for terahertz electron-beam radiation
NASA Astrophysics Data System (ADS)
Tantiwanichapan, Khwanchai; Swan, Anna K.; Paiella, Roberto
2016-06-01
One-dimensional carbon nanostructures such as nanotubes and nanoribbons can feature near-ballistic electronic transport over micron-scale distances even at room temperature. As a result, these materials provide a uniquely suited solid-state platform for radiation mechanisms that so far have been the exclusive domain of electron beams in vacuum. Here we consider the generation of terahertz light based on two such mechanisms, namely, the emission of cyclotronlike radiation in a sinusoidally corrugated nanowire (where periodic angular motion is produced by the mechanical corrugation rather than an externally applied magnetic field), and the Smith-Purcell effect in a rectilinear nanowire over a dielectric grating. In both cases, the radiation properties of the individual charge carriers are investigated via full-wave electrodynamic simulations, including dephasing effects caused by carrier collisions. The overall light output is then computed with a standard model of charge transport for two particularly suitable types of carbon nanostructures, i.e., zigzag graphene nanoribbons and armchair single-wall nanotubes. Relatively sharp emission peaks at geometrically tunable terahertz frequencies are obtained in each case. The corresponding output powers are experimentally accessible even with individual nanowires, and can be scaled to technologically significant levels using array configurations. These radiation mechanisms therefore represent a promising paradigm for light emission in condensed matter, which may find important applications in nanoelectronics and terahertz photonics.
Thompson, J.S.; Zeiler, R.M.
1995-04-01
A field investigation characterizing contamination at the Rocky Flats Plant (Rocky Flats Environmental Technology Site) near Golden, Colorado revealed unexpectedly high moisture contents in the unsaturated soil column (vadose zone) beneath several of the Plant`s Waste Water Treatment Plant (WWTP) sludge drying beds. Because these beds were seldom in use, researchers had hypothesized that the water required to maintain the saturated conditions observed beneath several of the sludge drying beds was coming from sources other than the beds themselves. In an effort to substantiate this hypothesis, a one-dimensional physically-based unsaturated flow model was utilized to simulate the vertical movement of moisture from the sludge drying beds into the unsaturated soil column below. The model was run to simulate vertical flow over a two-year period and results indicated that no significant changes from initial conditions were apparent. This evidence supports the hypothesis that the high moisture contents found beneath the sludge drying beds are being fed by sources other than infiltration of sludge applied to the beds themselves. This paper presents the details of the simulation and provides further evidence of the hypothesized flow regime.
Dynamic one-dimensional modeling of secondary settling tanks and design impacts of sizing decisions.
Li, Ben; Stenstrom, Michael K
2014-03-01
As one of the most significant components in the activated sludge process (ASP), secondary settling tanks (SSTs) can be investigated with mathematical models to optimize design and operation. This paper takes a new look at the one-dimensional (1-D) SST model by analyzing and considering the impacts of numerical problems, especially the process robustness. An improved SST model with Yee-Roe-Davis technique as the PDE solver is proposed and compared with the widely used Takács model to show its improvement in numerical solution quality. The improved and Takács models are coupled with a bioreactor model to reevaluate ASP design basis and several popular control strategies for economic plausibility, contaminant removal efficiency and system robustness. The time-to-failure due to rising sludge blanket during overloading, as a key robustness indicator, is analyzed to demonstrate the differences caused by numerical issues in SST models. The calculated results indicate that the Takács model significantly underestimates time to failure, thus leading to a conservative design.
Gent, David B.; Wani, Altaf; Alshawabkeh, Akram N.
2012-01-01
A combination of direct electrochemical reduction and in-situ alkaline hydrolysis has been proposed to decompose energetic contaminants such as 1,3,5-Trinitroperhydro- 1,3,5-triazine and 2,4,6-Trinitrotoluene (RDX) in deep aquifers. This process utilizes natural groundwater convection to carry hydroxide produced by an upstream cathode to remove the contaminant at the cathode as well as in the pore water downstream as it migrates toward the anode. Laboratory evaluation incorporated fundamental principles of column design coupled with reactive contaminant modeling including electrokinetics transport. Batch and horizontal sand-packed column experiments included both alkaline hydrolysis and electrochemical treatment to determine RDX decomposition reaction rate coefficients. The sand packed columns simulated flow through a contaminated aquifer with a seepage velocity of 30.5 cm/day. Techniques to monitor and record the transient electric potential, hydroxide transport and contaminant concentration within the column were developed. The average reaction rate coefficients for both the alkaline batch (0.0487 hr−1) and sand column (0.0466 hr−1) experiments estimated the distance between the cathode and anode required to decompose 0.5 mg/L RDX to the USEPA drinking water lifetime Health Advisory level of 0.002 mg/L to be 145 and 152 cm. PMID:23472044
Gent, David B; Wani, Altaf; Alshawabkeh, Akram N
2012-12-30
A combination of direct electrochemical reduction and in-situ alkaline hydrolysis has been proposed to decompose energetic contaminants such as 1,3,5-Trinitroperhydro- 1,3,5-triazine and 2,4,6-Trinitrotoluene (RDX) in deep aquifers. This process utilizes natural groundwater convection to carry hydroxide produced by an upstream cathode to remove the contaminant at the cathode as well as in the pore water downstream as it migrates toward the anode. Laboratory evaluation incorporated fundamental principles of column design coupled with reactive contaminant modeling including electrokinetics transport. Batch and horizontal sand-packed column experiments included both alkaline hydrolysis and electrochemical treatment to determine RDX decomposition reaction rate coefficients. The sand packed columns simulated flow through a contaminated aquifer with a seepage velocity of 30.5 cm/day. Techniques to monitor and record the transient electric potential, hydroxide transport and contaminant concentration within the column were developed. The average reaction rate coefficients for both the alkaline batch (0.0487 hr(-1)) and sand column (0.0466 hr(-1)) experiments estimated the distance between the cathode and anode required to decompose 0.5 mg/L RDX to the USEPA drinking water lifetime Health Advisory level of 0.002 mg/L to be 145 and 152 cm.
Influencing factors on particle-bound contaminant transport in the Elbe estuary
NASA Astrophysics Data System (ADS)
Kleisinger, Carmen; Haase, Holger; Schubert, Birgit
2016-04-01
Particulate matter, i.e. suspended particulate matter and sediments in rivers and estuaries, often are contaminated with trace metals and selected organic contaminants and are mainly associated with fine-grained fractions. Transport processes and fate of particles in estuaries are influenced by several factors, e.g. freshwater discharge, tide, flow velocity and dredging activities (Kappenberg et al., 2007). Understanding the transport processes in estuaries may help to achieve the objectives of the Water Framework Directive and the Marine Strategy Framework Directive. The German Federal Institute of Hydrology (BfG) operates for more than 20 years five monitoring sites in the Elbe estuary in order to monitor the development of particle-bound contaminant concentrations over time and to understand their transport mechanisms. Results of the monitoring revealed freshwater discharge as an important influencing factor on the transport of contaminated particulate matter (Ackermann et al., 2007). The bidirectional transport of marine and fluvial water and particulate matter in estuaries results in a turbidity zone where large amounts of particulate matter are temporarily retained and thus in a delayed transport of particulate matter towards the sea. The extent and the location of the turbidity zone as well as the ratio of highly contaminated fluvial and less contaminated marine sediments at a given location are mainly influenced by the freshwater discharge (Kowalewska et al., 2011). Furthermore, at high freshwater discharge conditions the highly contaminated particulate matter from fluvial origin are transported downstream the estuary, whereas at low freshwater discharges, upstream transport of less contaminated marine sediments prevails. Hence, residence times of particulate matter in the estuary are difficult to estimate. Furthermore, sedimentation areas with flow reduced conditions, e.g. wadden areas or branches of the Elbe estuary, may act as sinks for particle bound
Benthic processes affecting contaminant transport in Upper Klamath Lake, Oregon
Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Carlson, Rick A; Parchaso, Francis; Fend, Steven V.; Stauffer-Olsen, Natalie; Manning, Andrew J.; Land, Jennie M.
2016-09-30
Executive SummaryMultiple sampling trips during calendar years 2013 through 2015 were coordinated to provide measurements of interdependent benthic processes that potentially affect contaminant transport in Upper Klamath Lake (UKL), Oregon. The measurements were motivated by recognition that such internal processes (for example, solute benthic flux, bioturbation and solute efflux by benthic invertebrates, and physical groundwater-surface water interactions) were not integrated into existing management models for UKL. Up until 2013, all of the benthic-flux studies generally had been limited spatially to a number of sites in the northern part of UKL and limited temporally to 2–3 samplings per year. All of the benthic invertebrate studies also had been limited to the northern part of the lake; however, intensive temporal (weekly) studies had previously been completed independent of benthic-flux studies. Therefore, knowledge of both the spatial and temporal variability in benthic flux and benthic invertebrate distributions for the entire lake was lacking. To address these limitations, we completed a lakewide spatial study during 2013 and a coordinated temporal study with weekly sampling of benthic flux and benthic invertebrates during 2014. Field design of the spatially focused study in 2013 involved 21 sites sampled three times as the summer cyanobacterial bloom developed (that is, May 23, June 13, and July 3, 2013). Results of the 27-week, temporally focused study of one site in 2014 were summarized and partitioned into three periods (referred to herein as pre-bloom, bloom and post-bloom periods), each period involving 9 weeks of profiler deployments, water column and benthic sampling. Partitioning of the pre-bloom, bloom, and post-bloom periods were based on water-column chlorophyll concentrations and involved the following date intervals, respectively: April 15 through June 10, June 17 through August 13, and August 20 through October 16, 2014. To examine
NASA Astrophysics Data System (ADS)
Yin, Y.; Sykes, J. F.
2006-12-01
Transport parameter estimation and contaminant source identification are critical steps in the development of a physically based groundwater contaminant transport model. For most transient field scale problems, the high computational burden required by parameter identification algorithms combined with sparse data sets often limits calibration. However, when data are available, a high performance computing system and parallel computing may make the calibration process feasible. The selection of the optimization algorithm is also critical. In this paper, the contaminant transport and source parameters were estimated and compared using optimization with two heuristic search algorithms (a dynamically dimensioned search and a parallelized micro genetic algorithm) and a gradient based multi-start PEST algorithm which were implemented on the Shared Hierarchical Academic Research Computing Network (Sharcnet). The case study is located in New Jersey where improper waste disposal resulted in the contamination of down gradient public water supply wells. Using FRAC3DVS, a physically based transient three-dimensional groundwater flow model with spatially and temporally varying recharge was developed and calibrated using both approximately 9 years of head data from continuous well records and data over a period of approximately 30 years from traditional monitoring wells. For the contaminant system, the parameters that were estimated include source leaching rate, source concentration, dispersivities, and retardation coefficient. The groundwater domain was discretized using 214,520 elements. With highly changing pump rates at the 7 municipal wells, time increments over the approximately 30 year simulation period varied dynamically between several days and 3 months. On Sharcnet, one forward simulation on a single processor of both transient flow and contaminant transport takes approximately 3 to 4 hours. The contaminant transport model calibration results indicate that overall
NASA Astrophysics Data System (ADS)
Wierenga, P. J.; Hills, R. G.; Hudson, D. B.
1991-10-01
A comprehensive field trench study was conducted in a semiarid area of southern New Mexico to provide data to test deterministic and stochastic models of vadose zone flow and transport. A 4 m by 9 m area was irrigated with water containing a tracer using a carefully controlled drip irrigation system. The area was heavily instrumented with tensiometers and neutron probe access tubes to monitor water movement and with suction tubes to monitor solute transport. Approximately 600 disturbed and 600 core samples of soil were taken to support deterministic and stochastic characterization of the soil water hydraulic parameters. The core sample-based saturated hydraulic conductivities ranged from 1.4 to 6731 cm/d with a mean of 533 cm/d and a standard deviation of 647 cm/d, indicating significant spatial variability. However, visual observation of the wetting front on the trench wall shows no indication of preferential flow or water flow through visible root channels and cracks. The tensiometer readings and the neutron probe measurements also suggest that the wetting front moves in a fairly homogeneous fashion despite the significant spatial variability of the saturated hydraulic conductivity. In addition to the description of the experiment and the presentation of the experimental results, predictions of simple one-dimensional uniform and layered soil deterministic models for infiltration are presented and compared to field observations. These models are presented here to provide a base case against which more sophisticated deterministic and stochastic models can be compared in the future. The results indicate that the simple models give adequate predictions of the overall movement of the wetting front through the soil during infiltration. However, the models give poor predictions of point values for water content due to the spatial variability of the soil. Comparisons between the one-dimensional infiltration model predictions and field observations show that the use of
Wastewater contaminant transport and treatment in a nutrient limited ribbed fen
NASA Astrophysics Data System (ADS)
McCarter, C. P. R.; Price, J. S.; Branfireun, B. A.
2015-12-01
To minimize the discharge of wastewater contaminants from remote northern communities and mining operations, fen peatlands in sub-arctic regions are used for tertiary wastewater treatment to detain, transform, and remove these contaminants. However, there is a limited understanding of contaminant transport and treatment in fen peatlands, particularly in sub-arctic Canada. To better characterize wastewater contaminant transport and treatment in these systems, approximately 44 m3 day-1 of simulated wastewater, concentrated custom-blend fertilizer (NO3-, PO33-, and SO42-) and Cl- diluted with water, was pumped into a small 0.5 ha sub-arctic ribbed fen continuously for 47 days (July 15th -August 31st 2014). Contaminant concentration of 3 similar ribbed fens varied between 0.0-3.0 mg L-1 over the study period (May - September 2014). An exponential increase in transmissivity (2.4 to 16.8 m2 day-1) as the water table rose (~0.16 m) increased the average linear groundwater velocity (0.5 to 3.4 m day-1) and resulted in rapid SO42- (0.8 m day-1) and Cl- (1.9 m day-1) transport. Notwithstanding the rapid transport of Cl-, diffusion into inactive pores still retarded Cl- transport by a factor of 1.8. Contrary to the rapid transport of SO42- and Cl-, the other contaminants were rapidly removed from the pore water (likely through biological uptake or adsorption) and minimal transport was observed (0.29 and 0.04 m day-1 for PO33- and NO3-, respectively). Northern ribbed fens have a large capacity to detain certain wastewater contaminants (e.g., NO3- and PO33-), yet allow rapid transport of others (e.g., SO42- and Cl-). Thus, these peatlands have the potential to significantly decrease wastewater contamination in northern aquatic environment by both biogeochemical and physical processes but careful management of the hydrology is required to prevent the release of mobile contaminants.
POWELL, KIMBERLYR.
2004-05-25
Implementation of monitored natural attenuation (MNA) as a remediation method requires a mechanistic understanding of the natural attenuation processes occurring at a given site. For inorganic contaminants, natural attenuation typically involves a decrease in metal toxicity and/or mobility. These natural processes include dilution, dispersion, sorption (including adsorption, absorption, and precipitation), and redox processes. In order to better quantify these processes in terms of metal availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site. These laboratory scale studies provide mechanistic information regarding the solid phases in the soils associated with natural attenuation of the contaminant metals. This data provides input to be evaluated in the definition of the contaminant source term as well as transport of contaminants for site transport models.
Carrigan, C.R.; Hudson, G.B.
1998-06-01
'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities
A study for evaluation of contaminant transport characteristics through fine-grained soil.
Kumar, Sunil; Mukherjee, S N; Ghosh, S; Ray, R
2006-10-01
Transport of soluble toxic substances through porous media lead to some significant geoenvironmental problems, for example, leachate migration from municipal and industrial solid waste resulting from unregulated disposal. Advection, dispersion, diffusion, and decay are reported to be the principal mechanisms in such phenomena. Geotechnical properties of the soil also play a significant role in this deterioration. In the present study, laboratory tests were conducted to formulate an appropriate method for assessment of migration of metal ions, such as nickel, through the soil. Relevant kinetic and process parameters, such as aquifer data, surface area, dielectric constant, pH of zero point charge (pHzpc), and permeability were also studied. One-dimensional mathematical modeling was used to describe the dynamics of the process. The present investigation was carried out at an ash pond site of a thermal power plant situated in West Bengal, India.
[Solute transport modeling application in groundwater organic contaminant source identification].
Wang, Shu-Fang; Wang, Li-Ya; Wang, Xiao-Hong; Lin, Pei; Liu, Jiu-Rong; Xin, Bao-Dong; He, Guo-Ping
2012-03-01
Investigation and numerical simulation, based on RT3D (reactive transport in 3-dimensions)were used to identify the source of tetrachloroethylene (PCE) and trichloroethylene (TCE) in the groundwater of a city in the north of China and reverse the input intensity. Multiple regressions were applied to analyze the influenced factors of input intensity of PCE and TCE using Stepwise function in Matlab. The results indicate that the factories and industries are the source of the PCE and TCE in groundwater. Natural attenuation was identified and the natural attenuation rates are 93.15%, 61.70% and 61.00% for PCE, and 70.05%, 73.66% and 63.66% for TCE in 173 days. The 4 source points identified by the simulation have released 0.910 6 kg PCE and 95.693 8 kg TCE during the simulation period. The regression analysis results indicate that local precipitation and the thickness of vadose zone are the main factors influencing organic solution transporting from surface to groundwater. The PCE and TCE concentration are found to be 0 and 5 mg x kg(-1) from surface to 35 cm in vadose zone. All above results suggest that PCE and TCE in groundwater are from the source in the surface. Natural attenuation occurred when PCE and TCE transporting from the surface to groundwater, and the rest was transported to groundwater through vadose zone. Local precipitation was one of the critical factors influencing the transportation of PCE and TCE to aquifer through sand, pebble and gravel of the Quaternary.
Gorelick, S.M.; Voss, C.I.; Gill, P.E.; Murray, W.; Saunders, M.A.; Wright, M.H.
1984-01-01
A simulation-management methodology is demonstrated for the rehabilitation of aquifers that have been subjected to chemical contamination. Finite element groundwater flow and contaminant transport simulation are combined with nonlinear optimization. The model is capable of determining well locations plus pumping and injection rates for groundwater quality control. Examples demonstrate linear or nonlinear objective functions subject to linear and nonlinear simulation and water management constraints. -from Authors
Analysis of heat transfer and contaminant transport in fume hoods
Pathanjali, C.; Rahman, M.M.
1996-12-31
The paper presents the analysis of three-dimensional flow patterns and the associated heat and mass transfer mechanisms in a fume hood enclosure. The flow enters the hood through the front window opening (positive x-direction) and leaves the cupboard through an opening on the top of the hood (positive z-direction). The flow was assumed to be fully turbulent. The flow pattern for different sash openings were studied. The flow pattern around an object located at the bottom of the hood was studied for different locations of the object. It was found that air entering the hood proceeds directly to the back wall, impinges it and turns upward toward the top wall and exits through the outlet. The flow finds its way around any object forming a recirculating region at its training surface. With an increase in the sash opening, the velocity becomes higher and the fluid traces the path to the outlet more quickly. The volume occupied by recirculating flow decreases with increase in sash opening. Both temperature and concentration were found to be maximum near the source and gradually decreased as the heated air or gaseous contaminant entrained with incoming air. The local concentration decreased with increase in sash opening area. The results will be very useful to design experiments with optimum sash opening providing adequate disposal of contaminants with minimum use of conditioned air inside the room.
Modeling the transport behavior of 16 emerging organic contaminants during soil aquifer treatment.
Nham, Hang Thuy Thi; Greskowiak, Janek; Nödler, Karsten; Rahman, Mohammad Azizur; Spachos, Thomas; Rusteberg, Bernd; Massmann, Gudrun; Sauter, Martin; Licha, Tobias
2015-05-01
In this study, four one-dimensional flow and transport models based on the data of a field scale experiment in Greece were constructed to investigate the transport behavior of sixteen organic trace pollutants during soil aquifer treatment. At the site, tap water and treated wastewater were intermittently infiltrated into a porous aquifer via a small pilot pond. Electrical conductivity data was used to calibrate the non-reactive transport models. Transport and attenuation of the organic trace pollutants were simulated assuming 1st order degradation and linear adsorption. Sorption was found to be largely insignificant at this site for the compounds under investigation. In contrast, flow path averaged first order degradation rate constants were mostly higher compared to the literature and lay between 0.036 d(-1) for clofibric acid and 0.9 d(-1) for ibuprofen, presumably owing to the high temperatures and a well adapted microbial community originating from the wastewater treatment process. The study highlights the necessity to obtain intrinsic attenuation parameters at each site, as findings cannot easily be transferred from one site to another. PMID:25687671
Advances in Dynamic Transport of Organic Contaminants in Karst Groundwater Systems
NASA Astrophysics Data System (ADS)
Padilla, I. Y.; Vesper, D.; Alshawabkeh, A.; Hellweger, F.
2011-12-01
Karst groundwater systems develop in soluble rocks such as limestone, and are characterized by high permeability and well-developed conduit porosity. These systems provide important freshwater resources for human consumption and ecological integrity of streams, wetlands, and coastal zones. The same characteristics that make karst aquifers highly productive make them highly vulnerable to contamination. As a result, karst aquifers serve as an important route for contaminants exposure to humans and wildlife. Transport of organic contaminants in karst ground-water occurs in complex pathways influenced by the flow mechanism predominating in the aquifer: conduit-flow dominated systems tend to convey solutes rapidly through the system to a discharge point without much attenuation; diffuse-flow systems, on the other hand, can cause significant solute retardation and slow movement. These two mechanisms represent end members of a wide spectrum of conditions found in karst areas, and often a combination of conduit- and diffuse-flow mechanisms is encountered, where both flow mechanisms can control the fate and transport of contaminants. This is the case in the carbonate aquifers of northern Puerto Rico. This work addresses advances made on the characterization of fate and transport processes in karst ground-water systems characterized by variable conduit and/or diffusion dominated flow under high- and low-flow conditions. It involves laboratory-scale physical modeling and field-scale sampling and historical analysis of contaminant distribution. Statistical analysis of solute transport in Geo-Hydrobed physical models shows the heterogeneous character of transport dynamics in karstic units, and its variability under different flow regimes. Field-work analysis of chlorinated volatile organic compounds and phthalates indicates a large capacity of the karst systems to store and transmit contaminants. This work is part of the program "Puerto Rico Testsite for Exploring Contamination
NASA Astrophysics Data System (ADS)
Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean
2013-04-01
Certain contaminants may travel faster through soils when they are sorbed to subsurface colloidal particles. Indeed, subsurface colloids may act as carriers of some contaminants accelerating their translocation through the soil into the water table. This phenomenon is known as colloid-facilitated contaminant transport. It plays a significant role in contaminant transport in soils and has been recognized as a source of groundwater contamination. From a mechanistic point of view, the attachment/detachment of the colloidal particles from the soil matrix or from the air-water interface and the straining process may modify the hydraulic properties of the porous media. Šimůnek et al. (2006) developed a model that can simulate the colloid-facilitated contaminant transport in variably saturated porous media. The model is based on the solution of a modified advection-dispersion equation that accounts for several processes, namely: straining, exclusion and attachement/detachement kinetics of colloids through the soil matrix. The solutions of these governing, partial differential equations are obtained using a standard Galerkin-type, linear finite element scheme, implemented in the HYDRUS-2D/3D software (Šimůnek et al., 2012). Modeling colloid transport through the soil and the interaction of colloids with the soil matrix and other contaminants is complex and requires the characterization of many model parameters. In practice, it is very difficult to assess actual transport parameter values, so they are often calibrated. However, before calibration, one needs to know which parameters have the greatest impact on output variables. This kind of information can be obtained through a sensitivity analysis of the model. The main objective of this work is to perform local and global sensitivity analyses of the colloid-facilitated contaminant transport module of HYDRUS. Sensitivity analysis was performed in two steps: (i) we applied a screening method based on Morris' elementary
Color image analysis of contaminants and bacteria transport in porous media
Rashidi, M.; Dehmeshid, J.; Dacini, F.; Cole, L.; Dickenson, E.
1997-07-01
Transport of contaminants and bacteria in aqueous heterogeneous saturated porous systems have been studies experimentally using a novel fluorescent microscopic imaging (FMI) technique. The approach involves color visualization and quantification of bacterium and contaminant distributions within a transparent porous column. By introducing stained bacteria and an organic dye as a contaminant into the column and illuminating the porous regions with a planar sheet of laser beam, contaminant and bacterial transport processes through the porous medium can be observed and measured microscopically. A computer controlled CCD camera is used to record the fluorescent images as a function of time. These images are recorded by a frame accurate high resolution VCR and are then analyzed using a color image analysis code written in our laboratories. The color images are digitalized this way and simultaneously concentration and velocity distributions of both contaminant and bacterium are evaluated as a function of time and pore characteristics. The approach provides a unique dynamic probe to observe these transport processes microscopically. These results are extremely valuable in in-situ bioremediation problems since microscopic particle-contaminant-bacterium interactions are the key to understanding and optimization of these processes.
Modeling the emission, transport and deposition of contaminated dust from a mine tailing site.
Stovern, Michael; Betterton, Eric A; Sáez, A Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P; Russell, Mackenzie R; King, Matt
2014-01-01
Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.
Modeling the emission, transport and deposition of contaminated dust from a mine tailing site
Stovern, Michael; Betterton, Eric A.; Sáez, A. Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P.; Russell, MacKenzie R.; King, Matt
2014-01-01
Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations. PMID:24552963
Impact of scaling and body movement on contaminant transport in airliner cabins
NASA Astrophysics Data System (ADS)
Mazumdar, Sagnik; Poussou, Stephane B.; Lin, Chao-Hsin; Isukapalli, Sastry S.; Plesniak, Michael W.; Chen, Qingyan
2011-10-01
Studies of contaminant transport have been conducted using small-scale models. This investigation used validated Computational Fluid Dynamics (CFD) to examine if a small-scale water model could reveal the same contaminant transport characteristics as a full-scale airliner cabin. But due to similarity problems and the difficulty of scaling the geometry, a perfect scale up from a small water model to an actual air model was found to be impossible. The study also found that the seats and passengers tended to obstruct the lateral transport of the contaminants and confine their spread to the aisle of the cabin. The movement of a crew member or a passenger could carry a contaminant in its wake to as many rows as the crew member or passenger passed. This could be the reason why a SARS infected passenger could infect fellow passengers who were seated seven rows away. To accurately simulate the contaminant transport, the shape of the moving body should be a human-like model.
Bourigault, C; Daniel, L; Jourdain, S; Hardy, E; Heriaud, K; Virmaux, M; Eniafe-Eveillard, B; Lejeune, B
2007-03-01
From September to December 2004, contaminations were found in fifteen conservation and transport mediums of corneal grafts at the tissue bank of Brest, including seven by Sphingomonas paucimobilis. The pulsed-field gel electrophoresis made it possible to establish the genotypic profiles of each strain and to compare them. Similarities were found between certain strains of the contaminated mediums and those of the thermostated double boiler of the tissue bank. The link between the contamination and the defrosting of the mediums in the double boiler was thus established. Measures of prevention are currently proposed to defrost the bottles like the use of a dry bath to replace the current one.
Feed gas contaminant control in ion transport membrane systems
Carolan, Michael Francis; Minford, Eric; Waldron, William Emil
2009-07-07
Ion transport membrane oxidation system comprising an enclosure having an interior and an interior surface, inlet piping having an internal surface and adapted to introduce a heated feed gas into the interior of the enclosure, and outlet piping adapted to withdraw a product gas from the interior of the enclosure; one or more planar ion transport membrane modules disposed in the interior of the enclosure, each membrane module comprising mixed metal oxide material; and a preheater adapted to heat a feed gas to provide the heated feed gas to the inlet piping, wherein the preheater comprises an interior surface. Any of the interior surfaces of the enclosure, the inlet piping, and the preheater may be lined with a copper-containing metal lining. Alternatively, any of the interior surfaces of the inlet piping and the preheater may be lined with a copper-containing metal lining and the enclosure may comprise copper.
Lee, Jung Ah; Lim, Young Rok; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae
2016-10-21
To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes. PMID:27640642
Meidan, Dganit; Romito, Alessandro; Brouwer, Piet W
2014-08-01
We construct a scattering matrix formulation for the topological classification of one-dimensional superconductors with effective time-reversal symmetry in the presence of interactions. For an isolated system, Fidkowski and Kitaev have shown that such systems have a Z_{8} topological classification. We here show that these systems have a unitary scattering matrix at zero temperature when weakly coupled to a normal-metal lead, with a topological index given by the trace of the Andreev-reflection matrix, trr_{he}. With interactions, trr_{he} generically takes on the finite set of values 0, ±1, ±2, ±3, and ±4. We show that the two topologically equivalent phases with trr_{he}=±4 support emergent many-body end states, which we identify to be a topologically protected Kondo-like resonance. The path in phase space that connects these equivalent phases crosses a non-Fermi-liquid fixed point where a multiple-channel Kondo effect develops. Our results connect the topological index to transport properties, thereby highlighting the experimental signatures of interacting topological phases in one dimension. PMID:25126932
Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review
Arafat, M. M.; Dinan, B.; Akbar, Sheikh A.; Haseeb, A. S. M. A.
2012-01-01
Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research. PMID:22969344
Unified One-Dimensional Simulations of Gamma-Ray Line Emission from Type Ia Supernovae
NASA Astrophysics Data System (ADS)
Milne, P. A.; Hungerford, A. L.; Fryer, C. L.; Evans, T. M.; Urbatsch, T. J.; Boggs, S. E.; Isern, J.; Bravo, E.; Hirschmann, A.; Kumagai, S.; Pinto, P. A.; The, L.-S.
2004-10-01
The light curves of Type Ia supernovae (SNe Ia) are powered by gamma rays emitted by the decay of radioactive elements such as 56Ni and its decay products. These gamma rays are downscattered, absorbed, and eventually reprocessed into the optical emission that makes up the bulk of all SN observations. Detection of the gamma rays that escape the expanding star provide the only direct means to study this power source for SN Ia light curves. Unfortunately, disagreements between calculations for the gamma-ray lines have made it difficult to interpret any gamma-ray observations. Here we present a detailed comparison of the major gamma-ray line transport codes for a series of one-dimensional SN Ia models. Discrepancies in past results were due to errors in the codes, and the corrected versions of the seven different codes yield very similar results. This convergence of the simulation results allows us to infer more reliable information from the current set of gamma-ray observations of SNe Ia. The observations of SN 1986G, SN 1991T, and SN 1998bu are consistent with explosion models based on their classification: subluminous, superluminous, and normally luminous, respectively.
NASA Astrophysics Data System (ADS)
Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae
2016-10-01
To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.
Tran, T D; Simpson, R L; Maienschein, J; Tarver, C
2001-03-23
The thermal explosion of trinitrotoluene (TNT) is used as a basis for evaluating the performance of a new One-Dimensional-Time-to-Explosion (ODTX) apparatus. The ODTX experiment involves holding a 12.7 mm-diameter spherical explosive sample under confinement (150 MPa) at a constant elevated temperature until the confining pressure is exceeded by the evolution of gases during chemical decomposition. The resulting time to explosion as a function of temperature provides valuable decomposition kinetic information. A comparative analysis of the measurements obtained from the new unit and an older system is presented. Discussion on selected performance aspects of the new unit will also be presented. The thermal explosion of TNT is highly dependent on the material. Analysis of the time to explosion is complicated by historical and experimental factors such as material variability, sample preparation, temperature measurement and system errors. Many of these factors will be addressed. Finally, a kinetic model using a coupled thermal and heat transport code (chemical TOPAZ) was used to match the experimental data.
Lee, Jung Ah; Lim, Young Rok; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae
2016-10-21
To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.
Interfacial thermal conduction and negative temperature jump in one-dimensional lattices
NASA Astrophysics Data System (ADS)
Cao, Xiaodong; He, Dahai
2015-09-01
We study the thermal boundary conduction in one-dimensional harmonic and ϕ4 lattices, both of which consist of two segments coupled by a harmonic interaction. For the ballistic interfacial heat transport through the harmonic lattice, we use both theoretical calculation and molecular dynamics simulation to study the heat flux and temperature jump at the interface as to gain insights into the Kapitza resistance at the atomic scale. In the weak coupling regime, the heat current is proportional to the square of the coupling strength for the harmonic model as well as anharmonic models. Interestingly, there exists a negative temperature jump between the interfacial particles in particular parameter regimes. A nonlinear response of the boundary temperature jump to the externally applied temperature difference in the ϕ4 lattice is observed. To understand the anomalous result, we then extend our studies to a model in which the interface is represented by a relatively small segment with gradually changing spring constants and find that the negative temperature jump still exists. Finally, we show that the local velocity distribution at the interface is so close to the Gaussian distribution that the existence or absence of a local equilibrium state is unable to be determined by numerics in this way.
Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding
NASA Astrophysics Data System (ADS)
Essaid, Hedeff I.; Bekins, Barbara A.; Cozzarelli, Isabelle M.
2015-07-01
Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.
Organic contaminant transport and fate in the subsurface: evolution of knowledge and understanding
Essaid, Hedeff I.; Bekins, Barbara A.; Cozzarelli, Isabelle M.
2015-01-01
Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.
One-dimensional vibrational excitons in 1,2,4,5-tetrachlorobenzene
NASA Astrophysics Data System (ADS)
Abramson, E. H.; Jongenelis, A. P. J. M.; Schmidt, J.
1987-10-01
We have studied the line shapes of vibronic transitions in the phosphorescence spectrum of the one-dimensional triplet exciton of TCB between 4.2 and 0.4 K. It is shown that also the vibrational excitons are highly one dimensional. This finding is confirmed by time-resolved emission spectra. Observed vibron bandwidths vary up to 15 cm-1 with k=0 either at the top or at the bottom of the band. In contrast to the fundamental vibrations, no overtones or combination bands give evidence of a well-defined one-dimensional quasimomentum.
Comment on "Calculations for the one-dimensional soft Coulomb problem and the hard Coulomb limit"
NASA Astrophysics Data System (ADS)
Carrillo-Bernal, M. A.; Núñez-Yépez, H. N.; Salas-Brito, A. L.; Solis, Didier A.
2015-02-01
In the referred paper, the authors use a numerical method for solving ordinary differential equations and a softened Coulomb potential -1 /√{x2+β2 } to study the one-dimensional Coulomb problem by approaching the parameter β to zero. We note that even though their numerical findings in the soft potential scenario are correct, their conclusions do not extend to the one-dimensional Coulomb problem (β =0 ). Their claims regarding the possible existence of an even ground state with energy -∞ with a Dirac-δ eigenfunction and of well-defined parity eigenfunctions in the one-dimensional hydrogen atom are questioned.
Photocatalytic activity of silver vanadate with one-dimensional structure under fluorescent light.
Ren, Jia; Wang, Wenzhong; Shang, Meng; Sun, Songmei; Zhang, Ling; Chang, Jiang
2010-11-15
One-dimensional β-AgVO(3) nanobelts (SVN) were realized by a facile hydrothermal method. It indicates the anisotropic crystallographic characteristics through the characterization. With the additive PEG, the sample was restrained in the one-dimensional preferential orientation (SV-P) effectively. The photocatalytic activity studies reveal that the photocatalyst β-AgVO(3) exhibits excellent photocatalytic activity in the inactivation of Escherichia coli under fluorescent light. In addition, it is found that the morphology has effect on the photocatalytic activity. The β-AgVO(3) photocatalyst with one-dimensional structure has the potential and promising application in bacterial disinfection indoor using fluorescent light. PMID:20800352
NASA Astrophysics Data System (ADS)
Ng, Chiu-On
2000-01-01
In this paper, an analytical study on the advective-dispersive transport of a chemical contaminant resulting from the discharge of contaminated fine solid particles into a two-dimensional, steady and uniform turbulent open-channel flow is presented. Because of sorptive exchange, the transport of the chemical cloud is affected by that of the suspended particulates. Such a relationship has so far not been explicitly established by intuitive arguments. The effective transport equations are formally derived by an extended method of homogenization. It is found that over a long time scale the fall velocity will delay the sediment advection, and the advection velocity and dispersion coefficient for the chemical transport will change with space and time according to the local sediment concentration. Numerical results confirm that the centers of mass of the sediment and dissolved phase clouds are not advancing at the same speed, and the dispersion of the chemical is enhanced by the local retardation factor.
Transport of organic contaminants in geomembranes under stress
Xiao, S. ); Moresoli, C. . Dept. of Chemical Engineering); Burczyk, A. ); Pintauro, P.; De Kee, D. . Dept. of Chemical Engineering)
1999-07-01
The transport properties of aqueous solutions of benzene, dichloromethane, and trichloroethylene through extended polyvinyl chloride and high-density polyethylene geomembranes are investigated. It is found that extension enhances the permeation rates of the penetrants through polyvinyl chloride geomembranes, and the opposite effect is found in the case of high-density polyethylene. This difference in response is attributed to the type of structural change, which occurred as a result of the extension. The diffusivities of a mixture of the three organic solvents through the geomembranes are also determined.
Berman, D. H.; Khodas, M.; Flatté, M. E.
2014-10-15
We study the spin transport in a quasi-one-dimensional channel defined in a two-dimensional electron gas. The combined action of geometrical confinement and the spin precession is analyzed. We demonstrate that for certain orientations of the in-plane magnetic field and for specific range of its magnitude the spin polarization exhibits a strong decrease referred to as ballistic spin resonance (BSR). The phenomenon is due to the commensuration of the Zeeman and inter-subband energy splitting. We show that the BSR requires a finite spin-orbit (SO) interaction although the condition for the BSR onset is independent on SO coupling.
Effect of gate-driven spin resonance on the conductance through a one-dimensional quantum wire
NASA Astrophysics Data System (ADS)
Sadreev, Almas F.; Sherman, E. Ya.
2013-09-01
We consider quasiballistic electron transmission in a one-dimensional quantum wire subject to both time-independent and periodic potentials of a finger gate that results in a local time-dependent Rashba-type spin-orbit coupling. A spin-dependent conductance is calculated as a function of external constant magnetic field, the electric field frequency, and potential strength. The results demonstrate the effect of the gate-driven electric dipole spin resonance in a transport phenomenon such as spin-flip electron transmission.
NASA Astrophysics Data System (ADS)
Mosthaf, K.; Rosenberg, L.; Balbarini, N.; Broholm, M. M.; Bjerg, P. L.; Binning, P. J.
2014-12-01
It is important to understand the fate and transport of contaminants in limestone aquifers because they are a major drinking water resource. This is challenging because they are highly heterogeneous; with micro-porous grains, flint inclusions, and being heavily fractured. Several modeling approaches have been developed to describe contaminant transport in fractured media, such as the discrete fracture (with various fracture geometries), equivalent porous media (with and without anisotropy), and dual porosity models. However, these modeling concepts are not well tested for limestone geologies. Given available field data and model purpose, this paper therefore aims to develop, examine and compare modeling approaches for transport of contaminants in fractured limestone aquifers. The model comparison was conducted for a contaminated site in Denmark, where a plume of a dissolved contaminant (PCE) has migrated through a fractured limestone aquifer. Multilevel monitoring wells have been installed at the site and available data includes information on spill history, extent of contamination, geology and hydrogeology. To describe the geology and fracture network, data from borehole logs was combined with an analysis of heterogeneities and fractures from a nearby excavation (analog site). Methods for translating the geological information and fracture mapping into each of the model concepts were examined. Each model was compared with available field data, considering both model fit and measures of model suitability. An analysis of model parameter identifiability and sensitivity is presented. Results show that there is considerable difference between modeling approaches, and that it is important to identify the right one for the actual scale and model purpose. A challenge in the use of field data is the determination of relevant hydraulic properties and interpretation of aqueous and solid phase contaminant concentration sampling data. Traditional water sampling has a bias
Zinc-, cadmium-, and mercury-containing one-dimensional tetraphenylporphyrin arrays: a DFT study.
Castillo, Ulises Jiménez; Torres, Ana E; Fomine, Serguei
2014-04-01
Metal-free, Zn-, Cd-, and Hg-containing one-dimensional tetraphenylporphyrin arrays containing up to eight repeat units were modeled at the PBE/def2-SVP level of theory with D3 empirical dispersion correction. Two different configurations--face to face (F) and parallel displaced (P)--were detected, the latter being the most stable for all types of nanoarrays. According to the calculations, the binding that occurs in nanoarrays is mostly due to dispersion, with binding energies of 33-35 kcal/mol seen for the metal-free nanoarrays and energies of 37-40 kcal/mol for the metal-containing ones. The band gaps, estimated as the S0 → S1 excitation energies and extrapolated to the infinite chain limit using the TD-CAM-B3LYP/def2-SVP model, were close to 2 eV; the band gap size was barely dependent on the nature of the metal and the number of repeat units in the nanoarray. The ionization potentials and electron affinities were greatly influenced by the number of repeat units due to delocalization of polarons across each nanoarray. Polaron delocalization and the related reorganization energies were clearly dependent on the nature of the metal. For the metal-free and Zn-containing nanoarrays, the reorganization energies for hole and electron transport decreased linearly with 1/n, where n is the number of repeat units in the nanoaggregate. The reorganization energies therefore reach zero for an infinitely long chain. These energies for Cd- and Hg-containing nanoarrays were found to be one order of magnitude higher for both hole and electron transport due to the localization of polarons in these nanoarrays.
Javadi, A A; Al-Najjar, M M
2007-05-17
The movement of chemicals through soils to the groundwater is a major cause of degradation of water resources. In many cases, serious human and stock health implications are associated with this form of pollution. Recent studies have shown that the current models and methods are not able to adequately describe the leaching of nutrients through soils, often underestimating the risk of groundwater contamination by surface-applied chemicals, and overestimating the concentration of resident solutes. Furthermore, the effect of chemical reactions on the fate and transport of contaminants is not included in many of the existing numerical models for contaminant transport. In this paper a numerical model is presented for simulation of the flow of water and air and contaminant transport through unsaturated soils with the main focus being on the effects of chemical reactions. The governing equations of miscible contaminant transport including advection, dispersion-diffusion and adsorption effects together with the effect of chemical reactions are presented. The mathematical framework and the numerical implementation of the model are described in detail. The model is validated by application to a number of test cases from the literature and is then applied to the simulation of a physical model test involving transport of contaminants in a block of soil with particular reference to the effects of chemical reactions. Comparison of the results of the numerical model with the experimental results shows that the model is capable of predicting the effects of chemical reactions with very high accuracy. The importance of consideration of the effects of chemical reactions is highlighted.
It is well known that the fate and transport of contaminants in the subsurface are controlled by complex processes including advection, dispersion-diffusion, and chemical reactions. However, the interplay between the physical transport processes and chemical reactions, and their...
Properties governing the transport of trace organic contaminants through ion-exchange membranes.
Vanoppen, Marjolein; Bakelants, Annelise F A M; Gaublomme, Dorien; Schoutteten, Klaas V K M; Vanden Bussche, Julie; Vanhaecke, Lynn; Verliefde, Arne R D
2015-01-01
Ion exchange membranes could provide a solution to the selective separation of organic and inorganic components in industrial wastewater. The phenomena governing the transport of organics through the IEM however, are not yet fully understood. Therefore, the transport of trace organic contaminants (TOrCs) as a model for a wide variety of organic compounds was studied under different conditions. It was found that in the absence of salt and external potential, the chemical equilibrium is the main driver for TOrC-transport, resulting in the transport of mainly charged TOrCs. When salt is present, the transport of TOrCs is hampered in favor of the NaCl transport, which shows a preferential interaction with the membranes due to its small size, high mobility and concentration. It is hypothesized that electrostatic interactions and electron donor/acceptor interactions are the main drivers for TOrC transport and that transport is mainly diffusion driven. This was confirmed in the experiments with different current densities, where the external potential seemed to have only a minor influence on the transport of TOrCs. It is only when the salt becomes nearly completely depleted that the TOrCs are transported as charge carriers. This shows that it is very difficult to get preferential transport of organic compounds due to the diffusive nature of their transport.
Brownian-dynamics computer simulations of a one-dimensional polymer model. I. Simple potentials
Cook, R.; Livornese, L.L.
1982-11-01
Brownian Dynamics computer simulation results are presented on a simple one-dimensional polymer model which contains the essential features of rotational angle flexibility. Comparison is made with analytical treatments of the model.
NASA Astrophysics Data System (ADS)
Singhal, Naresh; Islam, Jahangir
2008-02-01
This paper uses the findings from a column study to develop a reactive model for exploring the interactions occurring in leachate-contaminated soils. The changes occurring in the concentrations of acetic acid, sulphate, suspended and attached biomass, Fe(II), Mn(II), calcium, carbonate ions, and pH in the column are assessed. The mathematical model considers geochemical equilibrium, kinetic biodegradation, precipitation-dissolution reactions, bacterial and substrate transport, and permeability reduction arising from bacterial growth and gas production. A two-step sequential operator splitting method is used to solve the coupled transport and biogeochemical reaction equations. The model gives satisfactory fits to experimental data and the simulations show that the transport of metals in soil is controlled by multiple competing biotic and abiotic reactions. These findings suggest that bioaccumulation and gas formation, compared to chemical precipitation, have a larger influence on hydraulic conductivity reduction.
Singhal, Naresh; Islam, Jahangir
2008-02-19
This paper uses the findings from a column study to develop a reactive model for exploring the interactions occurring in leachate-contaminated soils. The changes occurring in the concentrations of acetic acid, sulphate, suspended and attached biomass, Fe(II), Mn(II), calcium, carbonate ions, and pH in the column are assessed. The mathematical model considers geochemical equilibrium, kinetic biodegradation, precipitation-dissolution reactions, bacterial and substrate transport, and permeability reduction arising from bacterial growth and gas production. A two-step sequential operator splitting method is used to solve the coupled transport and biogeochemical reaction equations. The model gives satisfactory fits to experimental data and the simulations show that the transport of metals in soil is controlled by multiple competing biotic and abiotic reactions. These findings suggest that bioaccumulation and gas formation, compared to chemical precipitation, have a larger influence on hydraulic conductivity reduction.
GASPS: A time-dependent, one-dimensional, planar gas dynamics computer code
Pierce, R.E.; Sutton, S.B.; Comfort, W.J. III
1986-12-05
GASP is a transient, one-dimensional planar gas dynamic computer code that can be used to calculate the propagation of a shock wave. GASP, developed at LLNL, solves the one-dimensional planar equations governing momentum, mass and energy conservation. The equations are cast in an Eulerian formulation where the mesh is fixed in space, and material flows through it. Thus it is necessary to account for convection of material from one cell to its neighbor.
Demonstration of one-dimensional quantum random walks using orbital angular momentum of photons
Zhang, Pei; Ren, Xi-Feng; Zou, Xu-Bo; Liu, Bi-Heng; Huang, Yun-Feng; Guo, Guang-Can
2007-05-15
Quantum random walks have attracted special interest because they could lead to new quantum algorithms. Photons can carry orbital angular momentum (OAM) thereby offering a practical realization of a high-dimensional quantum information carrier. By employing OAM of photons, we experimentally realized the one-dimensional discrete-time quantum random walk. Three steps of a one-dimensional quantum random walk were implemented in our protocol showing the obvious difference between quantum and classical random walks.
NASA Astrophysics Data System (ADS)
Ooshida, Takeshi; Goto, Susumu; Matsumoto, Takeshi; Otsuki, Michio
2015-12-01
While the slow dynamics in glassy liquids are known to be accompanied by collective motions undetectable with static structure factor and requiring four-point space-time correlations for their detection, it is usually difficult to calculate such correlations analytically. In the present study, a system of Brownian particles in a (quasi-)one-dimensional passageway is taken as an example to demonstrate the usefulness of displacement correlation. In the purely one-dimensional case (known as the single-file diffusion) with overtaking forbidden, the diffusion slows down and collective motion is captured by displacement correlation both calculated here numerically and analytically. On the other hand, displacement correlation vanishes if overtaking is allowed, which leads to normal diffusion.
Zhu, C; Burden, D S
2001-10-01
Mineralogical compositions and their spatial distributions are important initial conditions for reactive transport modeling. However, popular Kd-based "reactive" transport models only require contaminant concentrations in the pore fluids as initial conditions, and minerals implicitly represent infinite sources and sinks in these models. That situation results in a general neglect of mineralogical characterization in site investigations. This study uses a coupled multi-component reactive mass transport model to predict the natural attenuation of a ground water plume at a uranium mill tailings site in western USA. Numerous ground water geochemistry data are available at this site, but mineralogical data are sketchy. Even given the well-defined pore fluid chemistry, variations of secondary mineral species and mineral abundances in the aquifer resulted in significantly different modeling outcomes. Results show that the amount of calcite in the aquifer determines the distances of plume migration. The possible presence of jurbanite, an aluminum sulfate phase, can store acidity temporarily but cause more severe contamination on a later date. The surfaces of iron oxyhydroxides can store significant amounts of sulfate and protons and serve as a second source for prolonged contamination. These simulations under field conditions illustrate that mineralogical compositions are an essential requirement for accurate prediction of contaminant fate and transport. PMID:11588823
Technology Transfer Automated Retrieval System (TEKTRAN)
Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-w...
Longshore transport modeling of the contaminated sediment in the Fukushima area
NASA Astrophysics Data System (ADS)
Kitamura, A.; Machida, M.; Itakura, M.; Yamada, S.
2015-12-01
The cesium-contaminated sediment in the Fukushima mountain area is expected to be transported by the river flow to the downstream region, and eventually to the ocean. The contaminated sediment discharged from the river to the ocean settles down to the seabed of the coastal area around the river mouth. Some part of the settled sediment is transported to the offshore region and the contamination of the coastal area is expected to decay gradually. Estimation of the environmental half-life of the contaminated sediment is important for the assessment of the safety of the edible fish in the Fukushima coastal area. Thus we need to calculate the sediment transport in the coastal area induced by various ocean phenomena, such as tidal current, river current, wave and wind-induced current. We have estimated the effect of several kinds of ocean phenomena on the coastal sediment transport, and found that the wind-induced current and the wave-induced suspension are the most dominant phenomena, while contributions from tidal current and the river flow is negligible.
Technology Transfer Automated Retrieval System (TEKTRAN)
The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, groundwater storage, and contaminant transport processes. The groundwater flow in agricultural karst areas, such as Kentucky’s Pennyroyal Plat...
Todd Arbogast; Steve Bryant; Clint N. Dawson; Mary F. Wheeler
1998-08-31
This report describes briefly the work of the Center for Subsurface Modeling (CSM) of the University of Texas at Austin (and Rice University prior to September 1995) on the Partnership in Computational Sciences Consortium (PICS) project entitled Grand Challenge Problems in Environmental Modeling and Remediation: Groundwater Contaminant Transport.
Investigation of the pathway of contaminated soil transported to plant surfaces by raindrop splash
Dreicer, M.; Hakonson, T.E.; Whicker, F.W.; White, G.C.
1983-10-21
The environmental transport pathway of soil-borne radioisotopes to vegetation surfaces via raindrop splash was studied. The data show that soil can significantly contribute to the contamination found on plants. Further detailed study is needed to calculate the rate constant for the raindrop splash and retention pathways. 8 references, 1 figure. (ACR)
Fraction of uninfected walkers in the one-dimensional Potts model.
O'Donoghue, S J; Bray, A J
2002-05-01
The dynamics of the one-dimensional q-state Potts model, in the zero-temperature limit, can be formulated through the motion of random walkers which either annihilate (A+A-->Phi) or coalesce (A+A-->A) with a q-dependent probability. We consider all of the walkers in this model to be mutually infectious. Whenever two walkers meet, they experience mutual contamination. Walkers which avoid an encounter with another random walker up to time t remain uninfected. The fraction of uninfected walkers is known to obey a power-law decay U(t) approximately t(-phi(q)), with a nontrivial exponent phi(q) [C. Monthus, Phys. Rev. E 54, 4844 (1996); S. N. Majumdar and S. J. Cornell, ibid. 57, 3757 (1998)]. We probe the numerical values of phi(q) to a higher degree of accuracy than previous simulations and relate the exponent phi(q) to the persistence exponent theta(q) [B. Derrida, V. Hakim, and V. Pasquier, Phys. Rev. Lett. 75, 751 (1995)], through the relation phi(q)=gamma(q)theta(q) where gamma is an exponent introduced in [S. J. O'Donoghue and A. J. Bray, preceding paper, Phys. Rev. E 65, 051113 (2002)]. Our study is extended to include the coupled diffusion-limited reaction A+A-->B, B+B-->A in one dimension with equal initial densities of A and B particles. We find that the density of walkers decays in this model as rho(t) approximately t(-1/2). The fraction of sites unvisited by either an A or a B particle is found to obey a power law, P(t) approximately t(-theta) with theta approximately 1.33. We discuss these exponents within the context of the q-state Potts model and present numerical evidence that the fraction of walkers which remain uninfected decays as U(t) approximately t(-phi), where phi approximately 1.13 when infection occurs between like particles only, and phi approximately 1.93 when we also include cross-species contamination. We find that the relation between phi and theta in this model can also be characterized by an exponent gamma, where similarly, phi
A cellular automaton simulation of contaminant transport in porous media
Freed, D.M.; Simonson, S.A.
1995-12-01
A simulation tool to investigate radionuclide transport in porous groundwater flow is described. The flow systems of interest are those important in determining the fate of radionuclides emplaced in an underground repository, such as saturated matrix flow, matrix and fracture flow in the unsaturated zone, and viscous fingering in porous fractures. The work discussed here is confined to consideration of saturated flow in porous media carrying a dilute, sorptive species. The simulation technique is based on a special class of cellular automata known as lattice gas automata (LGA) which are capable of predicting hydrodynamic behavior. The original two-dimensional scheme (that of Frisch et. al. known as the FHP model) used particles of unit mass traveling on a triangular lattice with unit velocity and undergoing simple collisions which conserve mass and momentum at each node. These microscopic rules go over to the incompressible Navier-Stokes equations in the macroscopic limit. One of the strengths of this technique is the natural way that heterogeneities, such as boundaries, are accommodated. Complex geometries such as those associated with porous microstructures can be modeled effectively. Several constructions based on the FHP model have been devised, including techniques to eliminate statistical noise, extension to three dimensions, and the addition of surface tension which leads to multiphase flow.
Code System to Solve for Release and Transport of Contaminants through Saturated/Unsaturated Media.
1996-03-07
The BLT code solves for release and transport of contaminants from containerized wastes. Each container may have unique properties (i.e., time to failure or localized failure, e.g. pitting) and each waste form may have unique release properties. Release from the waste form is limited by one of four physical or chemical constraints: solubility, diffusion, dissolution, and surface wash-off with partitioning. The release from the waste form acts as a source for transport in the advection/dispersionmore » equation. Transport is modeled in two-dimensions through the groundwater pathway from subsurface disposal.« less
Lan, Yann-Wen; Chang, Wen-Hao; Chang, Yuan-Chih; Chang, Chia-Seng; Chen, Chii-Dong
2015-02-01
Focused ion beam (FIB) deposition produces unwanted particle contamination beyond the deposition point. This is due to the FIB having a Gaussian distribution. This work investigates the spatial extent of this contamination and its influence on the electrical properties of nano-electronic devices. A correlation study is performed on carbon-nanotube (CNT) devices manufactured using FIB deposition. The devices are observed using transmission electron microscopy (TEM) and these images are correlated with device electrical characteristics. To discover how far Pt-nanoparticle contamination occurs along a CNT after FIB electrical contact deposition careful TEM inspections are performed. The results show FIB deposition efficiently improves electrical contact; however, the practice is accompanied by serious particle contamination near deposition points. These contaminants include metal particles and amorphous elements originating from precursor gases and residual water molecules in the vacuum chamber. Pt-contamination extends for approximately 2 μm from the point of FIB contact deposition. These contaminants cause current fluctuations and alter the transport characteristics of devices. It is recommended that nano-device fabrication occurs at a distance greater than 2 μm from the FIB deposition of an electrical contact.
One-dimensional quantum transport in hybrid metal-semiconductor nanotube systems
NASA Astrophysics Data System (ADS)
Gelin, Maxim; Bondarev, Igor
We study the inter-play between the intrinsic 1D conductance of metallic atomic wires (AWs) and plasmon mediated near-field effects for semiconducting single wall carbon nanotubes (CNs) that encapsulate AWs of finite length. We use the matrix Green's functions formalism to develop an electron transfer theory for such a hybrid quasi-1D metal-semiconductor nanotube system. The theory predicts Fano resonances in electron transmission through the system. That is the AW-CN near-field interaction blocks some of the pristine AW transmission band channels to open up new coherent channels in the CN forbidden gap outside the pristine AW transmission band. This makes the entire hybrid system transparent in the energy domain where neither of the individual pristine constituents, neither AW nor CN, are transparent. The effect can be used to control electron charge transfer in semiconducting CN based devices for nanoscale energy conversion, separation and storage. Nsf-ECCS-1306871 (M.G.), DOE-DE-SC0007117 (I.B.).
Knopman, Debra S.; Voss, Clifford I.
1987-01-01
The spatial and temporal variability of sensitivities has a significant impact on parameter estimation and sampling design for studies of solute transport in porous media. Physical insight into the behavior of sensitivities is offered through an analysis of analytically derived sensitivities for the one-dimensional form of the advection-dispersion equation. When parameters are estimated in regression models of one-dimensional transport, the spatial and temporal variability in sensitivities influences variance and covariance of parameter estimates. Several principles account for the observed influence of sensitivities on parameter uncertainty. (1) Information about a physical parameter may be most accurately gained at points in space and time. (2) As the distance of observation points from the upstream boundary increases, maximum sensitivity to velocity during passage of the solute front increases. (3) The frequency of sampling must be 'in phase' with the S shape of the dispersion sensitivity curve to yield the most information on dispersion. (4) The sensitivity to the dispersion coefficient is usually at least an order of magnitude less than the sensitivity to velocity. (5) The assumed probability distribution of random error in observations of solute concentration determines the form of the sensitivities. (6) If variance in random error in observations is large, trends in sensitivities of observation points may be obscured by noise. (7) Designs that minimize the variance of one parameter may not necessarily minimize the variance of other parameters.
NASA Astrophysics Data System (ADS)
Hamilton, P.; Strom, K.; Hoyal, D. C. J. D.
2015-12-01
Subaqueous fans are distributive channel systems that form in a variety of settings including offshore marine, sub-lacustrine, and reservoirs. These distributive systems create complex sedimentation patterns through repeated avulsion to fill in a basin. Here we ran a series of experiments to explore the intrinsic controls on avulsion cycles on subaqueous fans. Experiments are a convenient way to study these systems since the time-scale of fan development is dramatically shortened compared to natural settings, all boundary conditions can be controlled, and the experimental domain can be instrumented to monitor the pertinent hydraulic and morphologic variables. Experiments in this study used saline underflows and crushed plastic sediment fed down an imposed slope covered in the sediment. Avulsion cycles are a central feature in these experiments which are characterized by: (1) channel extension and stagnation; (2) bar aggradation and hydraulic jump initiation; (3) upstream retreat; and (4) flow avulsion. Looking at and analyzing these cycles yield the following conclusions: (1) distributive channels cease progradation due to a drop in sediment transport capacity in an expanded region ahead of the channel; (2) mouth bar aggradation leads to a large flow obstacle to cause the hydraulic jump feedback; (3) hydraulic jump regions are a significant locus of deposition; and (4) the upstream retreat rate is a function of sediment supply and the strength of the jump. We found that simple one-dimensional hydraulic principles such as the choked flow condition and the sequent depth ratio help to explain hydraulic jump initiation and emplaced lobe thickness respectively.
Annual loads of organic contaminants in Chesapeake Bay contributed through fluvial transport
Foster, G.D.; Lippa, K.A.
1994-12-31
Organic contaminants in fluvial transport, atmospheric deposition, urban runoff, and shoreline erosion are being quantified and compared in an effort to understand contaminant inputs and mass balances in Chesapeake Bay. Concentrations of nine organonitrogen and organophosphorus (organo-N/P) pesticides, eight organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and four polynuclear aromatic hydrocarbons in fluvial transport were determined at the Susquehanna, Potomac, and James River fall lines for the period of March 1992 through February 1993. Together these rivers account for ca. 75% of the freshwater inflow to the bay from fluvial sources. Sampling was conducted monthly during base flow conditions and during all major storm events. Analysis of nanogram and picogram per liter concentrations of the organic contaminants was performed for both the dissolved and particulate phases of the surface water samples. Daily fluvial loads were calculated using an iterative-increment method from concentration and discharge data, and the resulting daily load estimates were summed to provide annual loads. Loads contributed by the three tributaries from March 1992 through February 1993 were 6.9 metric tons for the organo-N/P pesticides, 0.73 metric tons for the OC compounds and PCBs, and 1.2 metric tons for the PAH. Preliminary comparisons show that loads from fluvial transport are generally greater than other sources for most contaminants except PAH, where atmospheric deposition and urban runoff contribute greater loads of some compounds.
NASA Astrophysics Data System (ADS)
Weber, Bent; Simmons, Michelle Y.
2016-08-01
Atomic-scale silicon wires, patterned by scanning tunneling microscopy (STM) and degenerately doped with phosphorus (P), have attracted significant interest owing to their exceptionally low resistivity and semiclassical Ohmic conduction at temperatures as low as T =4.2 K . Here, we investigate the transition from semiclassical diffusive to quantum-coherent conduction in a 4.6 nm wide wire as we decrease the measurement temperature. By analyzing the temperature dependence of universal conductance fluctuations (UCFs) and one-dimensional (1D) weak localization (WL)—fundamental manifestations of quantum-coherent transport in quasi-1D metals—we show that transport evolves from quantum coherent to semiclassical at T ˜4 K . Remarkably, our study confirms that universal concepts of mesoscopic physics such as UCF and 1D WL retain their validity in quasi-1D metallic conductors down to the atomic scale.
Cheng, Tao; Saiers, James E
2015-01-01
Colloid-facilitated transport of contaminants in the vadose zone has important implications to groundwater quality, and has received considerable attention. Natural organic matter (NOM) is ubiquitous in subsurface environments, and its influence on mineral colloids and solute transport has been well documented. However, research on the influence of NOM on colloid-facilitated transport is limited. The objective of this paper is to elucidate the effects of NOM on colloid-facilitated transport of a radioactive contaminant (Cs-137) within partially-saturated sediments. Measurements made with re-packed columns reveal that Cs-137 mobility was low when mineral colloids were absent and was unaffected by the presence of NOM. The addition of mineral colloids to influent increased Cs-137 mobility, and effluent Cs-137 was dominated by the colloid-associated form. When NOM was added to systems that contained mineral colloids and Cs-137, the mobility of Cs-137 further increased. A mathematical model simulating colloid-facilitated transport showed that NOM increases Cs-137 transport by increasing colloid mobility and reducing the rate of Cs-137 adsorption to the porous medium.