A Model of Solid State Gas Sensors

NASA Astrophysics Data System (ADS)

Woestman, J. T.; Brailsford, A. D.; Shane, M.; Logothetis, E. M.

1997-03-01

Solid state gas sensors are widely used to measure the concentrations of gases such as CO, CH_4, C_3H_6, H_2, C_3H8 and O2 The applications of these sensors range from air-to-fuel ratio control in combustion processes including those in automotive engines and industrial furnaces to leakage detection of inflammable and toxic gases in domestic and industrial environments. As the need increases to accurately measure smaller and smaller concentrations, problems such as poor selectivity, stability and response time limit the use of these sensors. In an effort to overcome some of these limitations, a theoretical model of the transient behavior of solid state gas sensors has been developed. In this presentation, a model for the transient response of an electrochemical gas sensor to gas mixtures containing O2 and one reducing species, such as CO, is discussed. This model accounts for the transport of the reactive species to the sampling electrode, the catalyzed oxidation/reduction reaction of these species and the generation of the resulting electrical signal. The model will be shown to reproduce the results of published steady state models and to agree with experimental steady state and transient data.

Mesoscopic entanglement induced by spontaneous emission in solid-state quantum optics.

PubMed

González-Tudela, Alejandro; Porras, Diego

2013-02-22

Implementations of solid-state quantum optics provide us with devices where qubits are placed at fixed positions in photonic or plasmonic one-dimensional waveguides. We show that solely by controlling the position of the qubits and with the help of a coherent driving, collective spontaneous decay may be engineered to yield an entangled mesoscopic steady state. Our scheme relies on the realization of pure superradiant Dicke models by a destructive interference that cancels dipole-dipole interactions in one dimension.

Primary and secondary creep in aluminum alloys as a solid state transformation

NASA Astrophysics Data System (ADS)

Fernández, R.; Bruno, G.; González-Doncel, G.

2016-08-01

Despite the massive literature and the efforts devoted to understand the creep behavior of aluminum alloys, a full description of this phenomenon on the basis of microstructural parameters and experimental conditions is, at present, still missing. The analysis of creep is typically carried out in terms of the so-called steady or secondary creep regime. The present work offers an alternative view of the creep behavior based on the Orowan dislocation dynamics. Our approach considers primary and secondary creep together as solid state isothermal transformations, similar to recrystallization or precipitation phenomena. In this frame, it is shown that the Johnson-Mehl-Avrami-Kolmogorov equation, typically used to analyze these transformations, can also be employed to explain creep deformation. The description is fully compatible with present (empirical) models of steady state creep. We used creep curves of commercially pure Al and ingot AA6061 alloy at different temperatures and stresses to validate the proposed model.

High performance Solid Rocket Motor (SRM) submerged nozzle/combustion cavity flowfield assessment

NASA Technical Reports Server (NTRS)

Freeman, J. A.; Chan, J. S.; Murph, J. E.; Xiques, K. E.

1987-01-01

Two and three dimensional internal flowfield solutions for critical points in the Space Shuttle solid rocket booster burn time were developed using the Lockheed Huntsville GIM/PAID Navier-Stokes solvers. These perfect gas, viscous solutions for the high performance motor characterize the flow in the aft segment and nozzle of the booster. Two dimensional axisymmetric solutions were developed at t = 20 and t = 85 sec motor burn times. The t = 85 sec solution indicates that the aft segment forward inhibitor stub produces vortices with are shed and convected downwards. A three dimensional 3.5 deg gimbaled nozzle flowfield solution was developed for the aft segment and nozzle at t = 9 sec motor burn time. This perfect gas, viscous analysis, provided a steady state solution for the core region and the flow through the nozzle, but indicated that unsteady flow exists in the region under the nozzle nose and near the flexible boot and nozzle/case joint. The flow in the nozzle/case joint region is characterized by low magnitude pressure waves which travel in the circumferential direction. From the two and three dimensional flowfield calculations presented it can be concluded that there is no evidence from these results that steady state gas dynamics is the primary mechanism resulting in the nozzle pocketing erosion experienced on SRM nozzles 8A or 17B. The steady state flowfield results indicate pocketing erosion is not directly initiated by a steady state gas dynamics phenomenon.

Virus transport during infiltration of a wetting front into initially unsaturated sand columns.

PubMed

Kenst, Andrew B; Perfect, Edmund; Wilhelm, Steven W; Zhuang, Jie; McCarthy, John F; McKay, Larry D

2008-02-15

We investigated the effect of different flow conditions on the transport of bacteriophage phiX174 in Memphis aquifer sand. Virus transport associated with a wetting front moving into an initially unsaturated horizontal sand column was experimentally compared with that observed under steady-state saturated vertical flow. Results obtained by sectioning the sand columns showthattotal (retained and free) resident virus concentrations decreased approximately exponentially with the travel distance. The rate of decline was similar under both transient unsaturated flow and steady-state saturated flow conditions. Total resident virus concentrations near the inlet were an order of magnitude greater than the virus concentration of the influent solution in both experiments, indicating continuous virus sorption during flow through this zone. Virus retardation was quantified using the ratio of the centroids of the relative saturation and virus concentration versus relative distance functions. The mean retardation factors were 6.43 (coefficient of variation, CV = 14.4%) and 8.22 (CV = 8.22%) for the transient unsaturated and steady-state saturated flow experiments, respectively. Attest indicated no significant difference between these values at P < 0.05. Air-water and air-water-solid interfaces are thought to enhance virus inactivation and sorption to solid particles. The similar retardation factors obtained may be attributable to the reduced presence of these interfaces in the two flow systems investigated as compared to steady-state unsaturated flow experiments in which these interfaces occur throughout the entire column.

Energy repartition in the nonequilibrium steady state

NASA Astrophysics Data System (ADS)

Yan, Peng; Bauer, Gerrit E. W.; Zhang, Huaiwu

2017-01-01

The concept of temperature in nonequilibrium thermodynamics is an outstanding theoretical issue. We propose an energy repartition principle that leads to a spectral (mode-dependent) temperature in steady-state nonequilibrium systems. The general concepts are illustrated by analytic solutions of the classical Heisenberg spin chain connected to Langevin heat reservoirs with arbitrary temperature profiles. Gradients of external magnetic fields are shown to localize spin waves in a Wannier-Zeemann fashion, while magnon interactions renormalize the spectral temperature. Our generic results are applicable to other thermodynamic systems such as Newtonian liquids, elastic solids, and Josephson junctions.

COMPUTATIONAL MODELING OF CIRCULATING FLUIDIZED BED REACTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, Essam A

2013-01-09

Details of numerical simulations of two-phase gas-solid turbulent flow in the riser section of Circulating Fluidized Bed Reactor (CFBR) using Computational Fluid Dynamics (CFD) technique are reported. Two CFBR riser configurations are considered and modeled. Each of these two riser models consist of inlet, exit, connecting elbows and a main pipe. Both riser configurations are cylindrical and have the same diameter but differ in their inlet lengths and main pipe height to enable investigation of riser geometrical scaling effects. In addition, two types of solid particles are exploited in the solid phase of the two-phase gas-solid riser flow simulations tomore » study the influence of solid loading ratio on flow patterns. The gaseous phase in the two-phase flow is represented by standard atmospheric air. The CFD-based FLUENT software is employed to obtain steady state and transient solutions for flow modulations in the riser. The physical dimensions, types and numbers of computation meshes, and solution methodology utilized in the present work are stated. Flow parameters, such as static and dynamic pressure, species velocity, and volume fractions are monitored and analyzed. The differences in the computational results between the two models, under steady and transient conditions, are compared, contrasted, and discussed.« less

Vibronic singlet and triplet steady-state interplay emissions in phenazine-based 1,2,3-triazole films

NASA Astrophysics Data System (ADS)

Costa, Bárbara B. A.; Souza, Paula D. C.; Gontijo, Rafael N.; Jardim, Guilherme A. M.; Moreira, Roberto L.; da Silva, Eufrânio N.; Cury, Luiz A.

2018-03-01

Photoluminescence and phosphorescence emissions of solid-state phenazine films were investigated in steady-state experimental conditions. Important discrepancies were observed for blended films where a host optically inert matrix was introduced to disperse the probe molecules. A vibronic spin-orbit phosphorescent emission clearly appeared, while for the films solely composed by the probe molecules, the phosphorescence broadened and presented a structureless shape, shifted to longer wavelengths. Further Arrhenius behavior analysis on the photoluminescent and phosphorescent emissions on temperature, corroborated the direct and reverse intersystem crossing interplay between singlet and triplet states. Molecular aggregation is responsible for the deterioration of non-blended triazole films phosphorescence.

The 17th JANNAF Combustion Meeting, Volume 1

NASA Technical Reports Server (NTRS)

Eggleston, D. S. (Editor)

1980-01-01

The combustion of solid rocket propellants and combustion in ramjets is addressed. Subjects discussed include metal burning, steady-state combustion of composite propellants, velocity coupling and nonlinear instability, vortex shedding and flow effects on combustion instability, combustion instability in solid rocket motors, combustion diagnostics, subsonic and supersonic ramjet combustion, characterization of ramburner flowfields, and injection and combustion of ramjet fuels.

Electrochemical disinfection of repeatedly recycled blackwater in a free-standing, additive-free toilet.

PubMed

Hawkins, Brian T; Sellgren, Katelyn L; Klem, Ethan J D; Piascik, Jeffrey R; Stoner, Brian R

2017-11-01

Decentralized, energy-efficient waste water treatment technologies enabling water reuse are needed to sustainably address sanitation needs in water- and energy-scarce environments. Here, we describe the effects of repeated recycling of disinfected blackwater (as flush liquid) on the energy required to achieve full disinfection with an electrochemical process in a prototype toilet system. The recycled liquid rapidly reached a steady state with total solids reliably ranging between 0.50 and 0.65% and conductivity between 20 and 23 mS/cm through many flush cycles over 15 weeks. The increase in accumulated solids was associated with increased energy demand and wide variation in the free chlorine contact time required to achieve complete disinfection. Further studies on the system at steady state revealed that running at higher voltage modestly improves energy efficiency, and established running parameters that reliably achieve disinfection at fixed run times. These results will guide prototype testing in the field.

Feasibility study of solid oxide fuel cell engines integrated with sprinter gas turbines: Modeling, design and control

NASA Astrophysics Data System (ADS)

Jia, Zhenzhong; Sun, Jing; Dobbs, Herb; King, Joel

2015-02-01

Conventional recuperating solid oxide fuel cell (SOFC)/gas turbine (GT) system suffers from its poor dynamic capability and load following performance. To meet the fast, safe and efficient load following requirements for mobile applications, a sprinter SOFC/GT system concept is proposed in this paper. In the proposed system, an SOFC stack operating at fairly constant temperature provides the baseline power with high efficiency while the fast dynamic capability of the GT-generator is fully explored for fast dynamic load following. System design and control studies have been conducted by using an SOFC/GT system model consisting of experimentally-verified component models. In particular, through analysis of the steady-state simulation results, an SOFC operation strategy is proposed to maintain fairly constant SOFC power (less than 2% power variation) and temperature (less than 2 K temperature variation) over the entire load range. A system design procedure well-suited to the proposed system has also been developed to help determining component sizes and the reference steady-state operation line. In addition, control analysis has been studied for both steady-state and transient operations. Simulation results suggest that the proposed system holds the promise to achieve fast and safe transient operations by taking full advantage of the fast dynamics of the GT-generator.

Retooling the ethanol industry: thermophilic anaerobic digestion of thin stillage for methane production and pollution prevention.

PubMed

Schaefer, Scott H; Sung, Shihwu

2008-02-01

Anaerobic digestion of corn ethanol thin stillage was tested at thermophilic temperature (55 degrees C) with two completely stirred tank reactors. The thin stillage wastestream was organically concentrated with 100 g/L total chemical oxygen demand and 60 g/L volatiles solids and a low pH of approximately 4.0. Steady-state was achieved at 30-, 20-, and 15-day hydraulic retention times (HRTs) and digester failure at a 12-day HRT. Significant reduction of volatile solids was achieved, with a maximum reduction (89.8%) at the 20-day HRT. Methane yield ranged from 0.6 to 0.7 L methane/g volatile solids removed during steady-state operation. Effluent volatile fatty acids below 200 mg/L as acetic acid were achieved at 20- and 30-day HRTs. Ultrasonic pretreatment was used for one digester, although no significant improvement was observed. Ethanol plant natural gas consumption could be reduced 43 to 59% with the methane produced, while saving an estimated $7 to $17 million ($10 million likely) for a facility producing 360 million L ethanol/y.

Properties of Poly- and Oligopentacenes Synthesized from Modular Building Blocks

DOE PAGES

Kumarasamy, Elango; Sanders, Samuel N.; Pun, Andrew B.; ...

2016-02-09

Here, we describe a facile route to well-defined, solution-processable pentacene oligomers (2 to 7) and homopolymer using Suzuki–Miyaura cross-coupling reactions. This synthetic strategy leads to regioisomers, regiopure syn- and anti-trimers were also synthesized, revealing minimal changes in solution properties but significant changes in the solid state arising from differing levels of crystallinity. The materials were characterized by steady state absorption spectroscopy and cyclic voltammetry to study their electronic structure. The steady state absorption spectra exhibit a new high-energy transition in the oligomers, which intensifies as a function of oligomer length, thus increasing the range of absorption to include the entiremore » visible spectrum. Density functional theory calculations indicate that the new peak results directly from the oligomerization. Solid state UV–vis suggests that while the monomer is amorphous, bricklayer packing in the higher oligomers significantly alters the solid state absorption relative to solution. The effect of oligomerization on packing was corroborated by GIWAXS analysis, which revealed crystalline domains in the oligomers. These domains, which are most evident in anti-trimer, become more pronounced upon thermal annealing. Photodegradation studies revealed considerable stability enhancement of oligomers toward oxygen and cycloaddition reactions relative to monomer. The synthesis and characterization of the first higher oligomers and homopolymer of pentacene should pave the way to applications in singlet fission, organic field-effect transistors, and organic photovoltaics.« less

Ionizing Shocks in Argon. Part 1: Collisional-Radiative Model and Steady-State Structure (Preprint)

DTIC Science & Technology

2010-09-09

absorption oscillator strength is given by fabsij = gj gi Aji 3γ . (43) Contributions to the parameter γ have been assumed to result from a combination of...discretization, the Saha temperatures of the higher states (green, red and blue solid curves) overshoot Te and relaxes with Th, indicating over

Transient Numerical Modeling of Catalytic Channels

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

2007-01-01

This paper presents a transient model of catalytic combustion suitable for isolated channels and monolith reactors. The model is a lumped two-phase (gas and solid) model where the gas phase is quasi-steady relative to the transient solid. Axial diffusion is neglected in the gas phase; lateral diffusion, however, is accounted for using transfer coefficients. The solid phase includes axial heat conduction and external heat loss due to convection and radiation. The combustion process utilizes detailed gas and surface reaction models. The gas-phase model becomes a system of stiff ordinary differential equations while the solid phase reduces, after discretization, into a system of stiff ordinary differential-algebraic equations. The time evolution of the system came from alternating integrations of the quasi-steady gas and transient solid. This work outlines the numerical model and presents some sensitivity studies on important parameters including internal transfer coefficients, catalytic surface site density, and external heat-loss (if applicable). The model is compared to two experiments using CO fuel: (1) steady-state conversion through an isothermal platinum (Pt) tube and (2) transient propagation of a catalytic reaction inside a small Pt tube. The model requires internal mass-transfer resistance to match the experiments at lower residence times. Under mass-transport limited conditions, the model reasonably predicted exit conversion using global mass-transfer coefficients. Near light-off, the model results did not match the experiment precisely even after adjustment of mass-transfer coefficients. Agreement improved for the first case after adjusting the surface kinetics such that the net rate of CO adsorption increased compared to O2. The CO / O2 surface mechanism came from a sub-set of reactions in a popular CH4 / O2 mechanism. For the second case, predictions improved for lean conditions with increased external heat loss or adjustment of the kinetics as in the first case. Finally, the results show that different initial surface-species distribution leads to different steady-states under certain conditions. These results demonstrate the utility of a lumped two-phase model of a transient catalytic combustor with detailed chemistry.

Hydrodynamic Attraction of Swimming Microorganisms by Surfaces

NASA Astrophysics Data System (ADS)

Berke, Allison P.; Turner, Linda; Berg, Howard C.; Lauga, Eric

2008-07-01

Cells swimming in confined environments are attracted by surfaces. We measure the steady-state distribution of smooth-swimming bacteria (Escherichia coli) between two glass plates. In agreement with earlier studies, we find a strong increase of the cell concentration at the boundaries. We demonstrate theoretically that hydrodynamic interactions of the swimming cells with solid surfaces lead to their reorientation in the direction parallel to the surfaces, as well as their attraction by the closest wall. A model is derived for the steady-state distribution of swimming cells, which compares favorably with our measurements. We exploit our data to estimate the flagellar propulsive force in swimming E. coli.

Semiconductor Crystal Growth in Static and Rotating Magnetic fields

NASA Technical Reports Server (NTRS)

Volz, Martin

2004-01-01

Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a critical magnetic field value. Growth conditions in which static magnetic fields rotational magnetic fields, and reduced gravitational levels can have a beneficial role will be described.

Kinetics of dissolution of UO2 in nitric acid solutions: A multiparametric study of the non-catalysed reaction

NASA Astrophysics Data System (ADS)

Cordara, T.; Szenknect, S.; Claparede, L.; Podor, R.; Mesbah, A.; Lavalette, C.; Dacheux, N.

2017-12-01

UO2 pellets were prepared by densification of oxides obtained from the conversion of the oxalate precursor. Then characterized in order to perform a multiparametric study of the dissolution in nitric acid medium. In this frame, for each sample, the densification rate, the grain size and the specific surface area of the prepared pellets were determined prior to the final dissolution experiments. By varying the concentration of the nitric acid solution and temperature, three different and successive steps were identified during the dissolution. Under the less aggressive conditions considered, a first transient step corresponding to the dissolution of the most reactive phases was observed at the solid/solution interface. Then, for all the tested conditions, a steady state step was established during which the normalised dissolution rate was found to be constant. It was followed by a third step characterized by a strong and continuous increase of the normalised dissolution rate. The duration of the steady state, also called "induction period", was found to vary drastically as a function of the HNO3 concentration and temperature. However, independently of the conditions, this steady state step stopped at almost similar dissolved material weight loss and dissolved uranium concentration. During the induction period, no important evolution of the topology of the solid/liquid interface was evidenced authorizing the use of the starting reactive specific surface area to evaluate the normalised dissolution rates thus the chemical durability of the sintered pellets. From the multiparametric study of UO2 dissolution proposed, oxidation of U(IV) to U(VI) by nitrate ions at the solid/liquid interface constitutes the limiting step in the overall dissolution mechanism associated to this induction period.

Ion Current Rectification, Limiting and Overlimiting Conductances in Nanopores

PubMed Central

van Oeffelen, Liesbeth; Van Roy, Willem; Idrissi, Hosni; Charlier, Daniel; Lagae, Liesbet; Borghs, Gustaaf

2015-01-01

Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dependent and steady state PNP simulations under less restrictive boundary conditions, including Neumann boundary conditions applied throughout the membrane relatively far away from the nanopore. We simulated ion currents through cylindrical and conical nanopores with several surface charge configurations, studying the spatial and temporal dependence of the currents contributed by each ion species. This revealed that, due to slow co-diffusion of oppositely charged ions, steady state is generally not reached in simulations or in practice. Furthermore, it is shown that ion concentration polarization is responsible for the observed limiting conductances and ion current rectification in nanopores with asymmetric surface charges or shapes. Hence, after more than a decade of collective research attempting to understand the nature of ion current rectification in solid-state nanopores, a relatively intuitive model is retrieved. Moreover, we measured and simulated current-voltage characteristics of rectifying silicon nitride nanopores presenting overlimiting conductances. The similarity between measurement and simulation shows that overlimiting conductances can result from the increased conductance of the electric double-layer at the membrane surface at the depletion side due to voltage-induced polarization charges. The MATLAB source code of the simulation software is available via the website http://micr.vub.ac.be. PMID:25978328

Coarsening in Solid-liquid Mixtures: Overview of Experiments on Shuttle and ISS

NASA Technical Reports Server (NTRS)

Duval, Walter M. B.; Hawersaat, Robert W.; Lorik, T.; Thompson, J.; Gulsoy, B.; Voorhees, P. W.

2013-01-01

The microgravity environment on the Shuttle and the International Space Station (ISS) provides the ideal condition to perform experiments on Coarsening in Solid-Liquid Mixtures (CSLM) as deleterious effects such as particle sedimentation and buoyancy-induced convection are suppressed. For an ideal system such as Lead-Tin in which all the thermophysical properties are known, the initial condition in microgravity of randomly dispersed particles with local clustering of solid Tin in eutectic liquid Lead-Tin matrix, permitted kinetic studies of competitive particle growth for a range of volume fractions. Verification that the quenching phase of the experiment had negligible effect of the spatial distribution of particles is shown through the computational solution of the dynamical equations of motion, thus insuring quench-free effects from the coarsened microstructure measurements. The low volume fraction experiments conducted on the Shuttle showed agreement with transient Ostwald ripening theory, and the steady-state requirement of LSW theory was not achieved. More recent experiments conducted on ISS with higher volume fractions have achieved steady-state condition and show that the kinetics follows the classical diffusion limited particle coarsening prediction and the measured 3D particle size distribution becomes broader as predicted from theory.

Interfacing a General Purpose Fluid Network Flow Program with the SINDA/G Thermal Analysis Program

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Popok, Daniel

1999-01-01

A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program Systems Improved Numerical Differencing Analyzer/Gaski (SINDA/G). The flow code, Generalized Fluid System Simulation Program (GFSSP), is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasi-steady (unsteady solid, steady fluid) conjugate heat transfer modeling.

Solid propellant grain design and internal ballistics

NASA Technical Reports Server (NTRS)

1972-01-01

The ballistic aspects of grain design were studied to outline the steps necessary to achieve a successful grain design. The relationships of the grain design to steady-state mass balance and erosive burning are considered. Grain design criteria is reviewed, and recommended design criteria are included.

Degradation of Leakage Currents in Solid Tantalum Capacitors Under Steady-State Bias Conditions

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2010-01-01

Degradation of leakage currents in various types of solid tantalum capacitors under steady-state bias conditions was investigated at temperatures from 105 oC to 170 oC and voltages up to two times the rated voltage. Variations of leakage currents with time under highly accelerated life testing (HALT) and annealing, thermally stimulated depolarization currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. During HALT the currents increase gradually up to three orders of magnitude in some cases, and then stabilize with time. This degradation is reversible and annealing can restore the initial levels of leakage currents. The results are attributed to migration of positively charged oxygen vacancies in tantalum pentoxide films that diminish the Schottky barrier at the MnO2/Ta2O5 interface and increase electron injection. A simple model allows for estimation of concentration and mobility of oxygen vacancies based on the level of current degradation.

Electrochemical disinfection of repeatedly recycled blackwater in a free‐standing, additive‐free toilet

PubMed Central

Sellgren, Katelyn L.; Klem, Ethan J. D.; Piascik, Jeffrey R.; Stoner, Brian R.

2017-01-01

Abstract Decentralized, energy‐efficient waste water treatment technologies enabling water reuse are needed to sustainably address sanitation needs in water‐ and energy‐scarce environments. Here, we describe the effects of repeated recycling of disinfected blackwater (as flush liquid) on the energy required to achieve full disinfection with an electrochemical process in a prototype toilet system. The recycled liquid rapidly reached a steady state with total solids reliably ranging between 0.50 and 0.65% and conductivity between 20 and 23 mS/cm through many flush cycles over 15 weeks. The increase in accumulated solids was associated with increased energy demand and wide variation in the free chlorine contact time required to achieve complete disinfection. Further studies on the system at steady state revealed that running at higher voltage modestly improves energy efficiency, and established running parameters that reliably achieve disinfection at fixed run times. These results will guide prototype testing in the field. PMID:29242713

Method and apparatus for adapting steady flow with cyclic thermodynamics

DOEpatents

Swift, Gregory W.; Reid, Robert S.; Ward, William C.

2000-01-01

Energy transfer apparatus has a resonator for supporting standing acoustic waves at a selected frequency with a steady flow process fluid thermodynamic medium and a solid medium having heat capacity. The fluid medium and the solid medium are disposed within the resonator for thermal contact therebetween and for relative motion therebetween. The relative motion is produced by a first means for producing a steady velocity component and second means for producing an oscillating velocity component at the selected frequency and concomitant wavelength of the standing acoustic wave. The oscillating velocity and associated oscillating pressure component provide energy transfer between the steady flow process fluid and the solid medium as the steady flow process fluid moves through the resonator.

High energy bursts from a solid state laser operated in the heat capacity limited regime

DOEpatents

Albrecht, G.; George, E.V.; Krupke, W.F.; Sooy, W.; Sutton, S.B.

1996-06-11

High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes. 5 figs.

High energy bursts from a solid state laser operated in the heat capacity limited regime

DOEpatents

Albrecht, Georg; George, E. Victor; Krupke, William F.; Sooy, Walter; Sutton, Steven B.

1996-01-01

High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes.

Coupled fluid and solid evolution in analogue volcanic vents

NASA Astrophysics Data System (ADS)

Solovitz, Stephen A.; Ogden, Darcy E.; Kim, Dave (Dae-Wook); Kim, Sang Young

2014-07-01

Volcanic eruptions emit rock particulates and gases at high speed and pressure, which change the shape of the surrounding rock. Simplified analytical solutions, field studies, and numerical models suggest that this process plays an important role in the behavior and hazards associated with explosive volcanic eruptions. Here we present results from a newly developed laboratory-scale apparatus designed to study this coupled process. The experiments used compressed air jets expanding into the laboratory through fabricated rock analogue material, which evolves through time during the experiment. The compressed air was injected at approximately 2.5 times atmospheric pressure. We fabricated rock analogues from sand and steel powder samples with a three-dimensional printing process. We studied the fluid development using phase-locked particle image velocimetry, while simultaneously observing the solid development via a video camera. We found that the fluid response was much more rapid than that of the solid, permitting a quasi-steady approximation. In most cases, the solid vent flared out rapidly, increasing its diameter by 20 to 100%. After the initial expansion, the vent and flow field achieved a near-steady condition for a long duration. The new expanded vent shapes permitted lower vent exit pressures and larger jet radii. In one experiment, after an initial vent shape development and establishment of steady flow behavior, rock failure occurred a second time, resulting in a new exit diameter and new steady state. This second failure was not precipitated by changes in the nozzle flow condition, and it radically changed the downstream flow dynamics. This experiment suggests that the brittle nature of volcanic host rock enables sudden vent expansion in the middle of an eruption without requiring a change in the conduit flow.

Incompressibility without tears - How to avoid restrictions of mixed formulation

NASA Technical Reports Server (NTRS)

Zienkiewicz, O. C.; Wu, J.

1991-01-01

Several time-stepping schemes for incompressibility problems are presented which can be solved directly for steady state or iteratively through the time domain. The difficulty of mixed interpolation is avoided by using these schemes. The schemes are applicable to problems of fluid and solid mechanics.

Steady State Transportation Cooling in Porous Media Under Local, Non-Thermal Equilibrium Fluid Flow

NASA Technical Reports Server (NTRS)

Rodriquez, Alvaro Che

2002-01-01

An analytical solution to the steady-state fluid temperature for 1-D (one dimensional) transpiration cooling has been derived. Transpiration cooling has potential use in the aerospace industry for protection against high heating environments for re-entry vehicles. Literature for analytical treatments of transpiration cooling has been largely confined to the assumption of thermal equilibrium between the porous matrix and fluid. In the present analysis, the fundamental fluid and matrix equations are coupled through a volumetric heat transfer coefficient and investigated in non-thermal equilibrium. The effects of varying the thermal conductivity of the solid matrix and the heat transfer coefficient are investigated. The results are also compared to existing experimental data.

Measuring the Thermodynamics of the Alloy/Scale Interface

NASA Technical Reports Server (NTRS)

Copland, Evan

2004-01-01

A method is proposed for the direct measurement of the thermodynamic properties of the alloy and oxide compound at the alloy/scale interface observed during steady-state oxidation. The thermodynamic properties of the alloy/scale interface define the driving force for solid-state transport in the alloy and oxide compound. Accurate knowledge of thermodynamic properties of the interface will advance our understanding of oxidation behavior. The method is based on the concept of local equilibrium and assumes that an alloy+scale equilibrium very closely approximates the alloy/scale interface observed during steady-state oxidation. The thermodynamics activities of this alloy+scale equilibrium are measured directly by Knudsen effusion-cell mass spectrometer (KEMS) using the vapor pressure technique. The theory and some practical considerations of this method are discussed in terms of beta-NiAl oxidation.

FLUSH: A tool for the design of slush hydrogen flow systems

NASA Technical Reports Server (NTRS)

Hardy, Terry L.

1990-01-01

As part of the National Aerospace Plane Project an analytical model was developed to perform calculations for in-line transfer of solid-liquid mixtures of hydrogen. This code, called FLUSH, calculates pressure drop and solid fraction loss for the flow of slush hydrogen through pipe systems. The model solves the steady-state, one-dimensional equation of energy to obtain slush loss estimates. A description of the code is provided as well as a guide for users of the program. Preliminary results are also presented showing the anticipated degradation of slush hydrogen solid content for various piping systems.

Mechanisms of heterogeneous crystal growth in atomic systems: insights from computer simulations.

PubMed

Gulam Razul, M S; Hendry, J G; Kusalik, P G

2005-11-22

In this paper we analyze the atomic-level structure of solid/liquid interfaces of Lennard-Jones fcc systems. The 001, 011, and 111 faces are examined during steady-state growth and melting of these crystals. The mechanisms of crystallization and melting are explored using averaged configurations generated during these steady-state runs, where subsequent tagging and labeling of particles at the interface provide many insights into the detailed atomic behavior at the freezing and melting interfaces. The interfaces are generally found to be rough and we observe the structure of freezing and melting interfaces to be very similar. Large structural fluctuations with solidlike and liquidlike characteristics are apparent in both the freezing and melting interfaces. The behavior at the interface observed under either growth or melting conditions reflects a competition between ordering and disordering processes. In addition, we observe atom hopping that imparts liquidlike characteristics to the solid side of the interfaces for all three crystal faces. Solid order is observed to extend as rough, three-dimensional protuberances through the interface, particularly for the 001 and 011 faces. We are also able to reconcile our different measures for the interfacial width and address the onset of asymmetry in the growth rates at high rates of crystal growth/melting.

FFT analysis of sensible-heat solar-dynamic receivers

NASA Astrophysics Data System (ADS)

Lund, Kurt O.

The use of solar dynamic receivers with sensible energy storage in single-phase materials is considered. The feasibility of single-phase designs with weight and thermal performance comparable to existing two-phase designs is addressed. Linearized heat transfer equations are formulated for the receiver heat storage, representing the periodic input solar flux as the sum of steady and oscillating distributions. The steady component is solved analytically to produce the desired receiver steady outlet gas temperature, and the FFT algorithm is applied to the oscillating components to obtain the amplitudes and mode shapes of the oscillating solid and gas temperatures. The results indicate that sensible-heat receiver designs with performance comparable to state-of-the-art two-phase receivers are available.

Chemically durable polymer electrolytes for solid-state alkaline water electrolysis

NASA Astrophysics Data System (ADS)

Park, Eun Joo; Capuano, Christopher B.; Ayers, Katherine E.; Bae, Chulsung

2018-01-01

Generation of high purity hydrogen using electrochemical splitting of water is one of the most promising methods for sustainable fuel production. The materials to be used as solid-state electrolytes for alkaline water electrolyzer require high thermochemical stability against hydroxide ion attack in alkaline environment during the operation of electrolysis. In this study, two quaternary ammonium-tethered aromatic polymers were synthesized and investigated for anion exchange membrane (AEM)-based alkaline water electrolyzer. The membranes properties including ion exchange capacity (IEC), water uptake, swelling degree, and anion conductivity were studied. The membranes composed of all C-C bond polymer backbones and flexible side chain terminated by cation head groups exhibited remarkably good chemical stability by maintaining structural integrity in 1 M NaOH solution at 95 °C for 60 days. Initial electrochemical performance and steady-state operation performance were evaluated, and both membranes showed a good stabilization of the cell voltage during the steady-state operation at the constant current density at 200 mA/cm2. Although both membranes in current form require improvement in mechanical stability to afford better durability in electrolysis operation, the next generation AEMs based on this report could lead to potentially viable AEM candidates which can provide high electrolysis performance under alkaline operating condition.

Dry-thermophilic anaerobic digestion of organic fraction of municipal solid waste: methane production modeling.

PubMed

Fdez-Güelfo, L A; Alvarez-Gallego, C; Sales, D; García, L I Romero

2012-03-01

The influence of particle size and organic matter content of organic fraction of municipal solid waste (OFMSW) in the overall kinetics of dry (30% total solids) thermophilic (55°C) anaerobic digestion have been studied in a semi-continuous stirred tank reactor (SSTR). Two types of wastes were used: synthetic OFMSW (average particle size of 1mm; 0.71 g Volatile Solids/g waste), and OFMSW coming from a composting full scale plant (average particle size of 30 mm; 0.16 g Volatile Solids/g waste). A modification of a widely-validated product-generation kinetic model has been proposed. Results obtained from the modified-model parameterization at steady-state (that include new kinetic parameters as K, Y(pMAX) and θ(MIN)) indicate that the features of the feedstock strongly influence the kinetics of the process. The overall specific growth rate of microorganisms (μ(max)) with synthetic OFMSW is 43% higher compared to OFMSW coming from a composting full scale plant: 0.238 d(-1) (K=1.391 d(-1); Y(pMAX)=1.167 L CH(4)/gDOC(c); θ(MIN)=7.924 days) vs. 0.135 d(-1) (K=1.282 d(-1); Y(pMAX)=1.150 L CH(4)/gDOC(c); θ(MIN)=9.997 days) respectively. Finally, it could be emphasized that the validation of proposed modified-model has been performed successfully by means of the simulation of non-steady state data for the different SRTs tested with each waste. Copyright © 2011 Elsevier Ltd. All rights reserved.

Steady state rheology from homogeneous and locally averaged simple shear simulations

NASA Astrophysics Data System (ADS)

Shi, Hao; Luding, Stefan; Magnanimo, Vanessa

2017-06-01

Granular materials and particulate matter are ubiquitous in our daily life and they display interesting bulk behaviors from static to dynamic, solid to fluid or gas like states, or even all these states together. To understand how the micro structure and inter-particle forces influence the macroscopic bulk behavior is still a great challenge today. This short paper presents stress controlled homogeneous simple shear results in a 3D cuboidal box using MercuryDPM software. An improved rheological model is proposed for macroscopic friction, volume fraction and coordination number as a function of inertial number and pressure. In addition, the results are compared with the locally averaged data from steady state shear bands in a split bottom ring shear cell and very good agreement is observed in low to intermediate inertia regime at various confining pressure but not for high inertia collisional granular flow.

On the local relaxation of solid neon upon Rydberg excitation of a NO impurity: the role of the NO(A)-Ne interaction potential and zero-point quantum delocalization.

PubMed

Pajón-Suárez, Pedro; Rojas-Lorenzo, Germán A; Rubayo-Soneira, Jesús; Hernández-Lamoneda, Ramón; Larrégaray, Pascal

2009-12-31

The local relaxation of solid neon subsequent to the impulsive excitation of the NO chromophore to its A(3s sigma) Ryberg state is investigated using molecular dynamics simulations. This study makes use of empirical NO(X,A)-Ne isotropic pair potentials as well as a recently developed ab initio triatomic potential energy surface for the excited state. The role of these interaction potentials is analyzed, including many-body effects. In particular, empirical potentials, designed to reproduce correctly both the NO X-A steady-state absorption and emission bands, are shown to lead to a good description of the subpicosecond relaxation dynamics. The 600 fs expansion of the electronic bubble fairly agrees with experimental data. This relatively long time scale with respect to solid Argon, which was previously attributed to the range of the NO(A)-Ne interaction, is presumably related to the quantum nature of the medium. The time-resolved local relaxation of the Ne solid is understandably intermediate between that of classical solids (e.g., Ar) and that of quantum solids (e.g., H(2)).

Prokaryotic diversity and dynamics in a full-scale municipal solid waste anaerobic reactor from start-up to steady-state conditions.

PubMed

Cardinali-Rezende, Juliana; Colturato, Luís F D B; Colturato, Thiago D B; Chartone-Souza, Edmar; Nascimento, Andréa M A; Sanz, José L

2012-09-01

The prokaryotic diversity of an anaerobic reactor for the treatment of municipal solid waste was investigated over the course of 2 years with the use of 16S rDNA-targeted molecular approaches. The fermentative Bacteroidetes and Firmicutes predominated, and Proteobacteria, Actinobacteria, Tenericutes and the candidate division WWE1 were also identified. Methane production was dominated by the hydrogenotrophic Methanomicrobiales (Methanoculleus sp.) and their syntrophic association with acetate-utilizing and propionate-oxidizing bacteria. qPCR demonstrated the predominance of the hydrogenotrophic over aceticlastic Methanosarcinaceae (Methanosarcina sp. and Methanimicrococcus sp.), and Methanosaetaceae (Methanosaeta sp.) were measured in low numbers in the reactor. According to the FISH and CARD-FISH analyses, Bacteria and Archaea accounted for 85% and 15% of the cells, respectively. Different cell counts for these domains were obtained by qPCR versus FISH analyses. The use of several molecular tools increases our knowledge of the prokaryotic community dynamics from start-up to steady-state conditions in a full-scale MSW reactor. Copyright © 2012 Elsevier Ltd. All rights reserved.

Precise non-steady-state characterization of solid active materials with no preliminary mechanistic assumptions

DOE PAGES

Constales, Denis; Yablonsky, Gregory S.; Wang, Lucun; ...

2017-04-25

This paper presents a straightforward and user-friendly procedure for extracting a reactivity characterization of catalytic reactions on solid materials under non-steady-state conditions, particularly in temporal analysis of products (TAP) experiments. The kinetic parameters derived by this procedure can help with the development of detailed mechanistic understanding. The procedure consists of the following two major steps: 1) Three “Laplace reactivities” are first determined based on the moments of the exit flow pulse response data; 2) Depending on a select kinetic model, kinetic constants of elementary reaction steps can then be expressed as a function of reactivities and determined accordingly. In particular,more » we distinguish two calculation methods based on the availability and reliability of reactant and product data. The theoretical results are illustrated using a reverse example with given parameters as well as an experimental example of CO oxidation over a supported Au/SiO 2 catalyst. The procedure presented here provides an efficient tool for kinetic characterization of many complex chemical reactions.« less

Evolution of microorganisms in thermophilic-dry anaerobic digestion.

PubMed

Montero, B; Garcia-Morales, J L; Sales, D; Solera, R

2008-05-01

Microbial population dynamics were studied during the start-up and stabilization periods in thermophilic-dry anaerobic digestion at lab-scale. The experimental protocol was defined to quantify Eubacteria and Archaea using Fluorescent in situ hybridization (FISH) in a continuously stirred tank reactor (CSTR), without recycling solids. The reactor was subjected to a programme of steady-state operation over a range of the retention times from 40 to 25 days, with an organic loading rate between 4.42 and 7.50 kg volatile solid/m3/day. Changes in microbial concentrations were linked to traditional performance parameters such as biogas production and VS removal. The relations of Eubacteria:Archaea and H2-utilising methanogens:acetate-utilising methanogens were 88:12 and 11:1, respectively, during start-up stage. Hydrogenotrophic methanogens, although important in the initial phase of the reactor start-up, were displaced by acetoclastic methanogens at steady-state, thus their relation were 7:32, respectively. The methane yield coefficient, the methane content in the biogas and VS removal were stabilized around 0.30 LCH4/gCOD, 50% and 80%, respectively. Methanogenic population correlated well with performance measurements.

A numerical study of the segregation phenomenon of lognormal particle size distributions in the rotating drum

NASA Astrophysics Data System (ADS)

Yang, Shiliang; Sun, Yuhao; Zhao, Ya; Chew, Jia Wei

2018-05-01

Granular materials are mostly polydisperse, which gives rise to phenomena such as segregation that has no monodisperse counterpart. The discrete element method is applied to simulate lognormal particle size distributions (PSDs) with the same arithmetic mean particle diameter but different PSD widths in a three-dimensional rotating drum operating in the rolling regime. Despite having the same mean particle diameter, as the PSD width of the lognormal PSDs increases, (i) the steady-state mixing index, the total kinetic energy, the ratio of the active region depth to the total bed depth, the mass fraction in the active region, the steady-state active-passive mass-based exchanging rate, and the mean solid residence time (SRT) of the particles in the active region increase, while (ii) the steady-state gyration radius, the streamwise velocity, and the SRT in the passive region decrease. Collectively, these highlight the need for more understanding of the effect of PSD width on the granular flow behavior in the rotating drum operating in the rolling flow regime.

Role of back stress in the creep behavior of particle strengthened alloys

NASA Technical Reports Server (NTRS)

Purushothaman, S.; Tien, J. K.

1978-01-01

Recent developments in the interpolation of high-temperature steady-state creep results have introduced the concept that the stress dependence of the creep rate should be in terms of the effective stress referred to as the applied stress minus a back stress. This paper reports on back stresses taken from data on a gamma-prime-strengthened wrought nickel-base superalloy, an oxide dispersion-strengthened ODS nickel-base solid solution alloy, and an ODS nickel-base superalloy. The effect of air versus vacuum environments and the effect of dynamic changes in the strengthening microstructures on the magnitude of the back stress are assessed. The role of modulus normalization and the back stress correction in determining the true creep activation energy are examined. It is shown that the high values of the apparent stress exponent 'n' of the steady-state creep equation can be easily explained through a relationship between n, the true stress exponent of steady-state creep, and the stress which when subtracted from the applied stress results in the effective driving stress acting on the mobile dislocations during creep.

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

PubMed Central

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-01-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η − γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment. PMID:27682811

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

NASA Astrophysics Data System (ADS)

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-09-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η - γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment.

Moving bed reactor setup to study complex gas-solid reactions.

PubMed

Gupta, Puneet; Velazquez-Vargas, Luis G; Valentine, Charles; Fan, Liang-Shih

2007-08-01

A moving bed scale reactor setup for studying complex gas-solid reactions has been designed in order to obtain kinetic data for scale-up purpose. In this bench scale reactor setup, gas and solid reactants can be contacted in a cocurrent and countercurrent manner at high temperatures. Gas and solid sampling can be performed through the reactor bed with their composition profiles determined at steady state. The reactor setup can be used to evaluate and corroborate model parameters accounting for intrinsic reaction rates in both simple and complex gas-solid reaction systems. The moving bed design allows experimentation over a variety of gas and solid compositions in a single experiment unlike differential bed reactors where the gas composition is usually fixed. The data obtained from the reactor can also be used for direct scale-up of designs for moving bed reactors.

Anaerobic digestion of municipal solid waste composed of food waste, wastepaper, and plastic in a single-stage system: performance and microbial community structure characterization.

PubMed

Wan, Shungang; Sun, Lei; Douieb, Yaniv; Sun, Jian; Luo, Wensui

2013-10-01

The performance of municipal organic solid waste anaerobic digestion was investigated using a single-stage bioreactor, and the microbial community structures were characterized during the digestion. The results showed that the biogas and methane production rates were 592.4 and 370.1L/kg with volatile solid added at the ratio of 2:1:1 for food waste, wastepaper, and plastic based on dry weight. The methane volume concentration fluctuated between 44.3% and 75.4% at steady stage. Acetic acid, propionic acid, and butyric acid were the major volatile fatty acids produced during the digestion process. The anaerobic process was not inhibited by the accumulation of ammonia and free ammonia. The bacterial community was found to consist of at least 21 bands of bacteria and 12 bands of archaea at the steady state. All of the results indicated that the mixture of food waste, wastepaper, and plastic could be efficiently co-digested using the anaerobic digestion system. Copyright © 2013 Elsevier Ltd. All rights reserved.

Chamber measurement of surface-atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties

NASA Astrophysics Data System (ADS)

Hutchinson, G. L.; Livingston, G. P.; Healy, R. W.; Striegl, R. G.

2000-04-01

We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere trace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulations showed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steady-state chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

Probing solid catalysts under operating conditions: electrons or X-rays?

PubMed

Thomas, John Meurig; Hernandez-Garrido, Juan-Carlos

2009-01-01

Seeing is believing: In light of recent advances, the pros and cons of using electrons and X-rays for in situ studies of catalysts are analyzed: by using X-rays the structure of bound reactants at steady state are obtained from extended X-ray adsorption fine structure spectroscopy (EXAFS) data (see graph), thereby affording mechanistic insights.

Nuclear electric propulsion technologies - Overview of the NASA/DoE/DoD Nuclear Electric Propulsion Workshop

NASA Technical Reports Server (NTRS)

Barnett, John W.

1991-01-01

Nuclear propulsion technology offers substantial benefits to the ambitious piloted and robotic solar system exploration missions of the Space Exploration Initiative (SEI). This paper summarizes a workshop jointly sponsored by NASA, DoE, and DoD to assess candidate nuclear electric propulsion technologies. Twenty-one power and propulsion concepts are reviewed. Nuclear power concepts include solid and gaseous fuel concepts, with static and dynamic power conversion. Propulsion concepts include steady state and pulsed electromagnetic engines, a pulsed electrothermal engine, and a steady state electrostatic engine. The technologies vary widely in maturity. The workshop review panels concluded that compelling benefits would accrue from the development of nuclear electric propulsion systems, and that a focused, well-funded program is required to prepare the technologies for SEI missions.

FLUSH - PREDICTION OF FLOW PARAMETERS OF SLUSH HYDROGEN

NASA Technical Reports Server (NTRS)

Hardy, T.

1994-01-01

Slush hydrogen, a mixture of the solid and liquid phases of hydrogen, is a possible source of fuel for the National Aerospace Plane (NASP) Project. Advantages of slush hydrogen over liquid hydrogen include greater heat capacity and greater density. However, practical use of slush hydrogen as a fuel requires systems of lines, valves, etc. which are designed to deliver the fuel in slush form with minimal solid loss as a result of pipe heating or flow friction. Engineers involved with the NASP Project developed FLUSH to calculate the pressure drop and slush hydrogen solid fraction loss for steady-state, one-dimensional flow. FLUSH solves the steady-state, one-dimensional energy equation and the Bernoulli equation for pipe flow. The program performs these calculations for each two-node element--straight pipe length, elbow, valve, fitting, or other part of the piping system--specified by the user. The user provides flow rate, upstream pressure, initial solid hydrogen fraction, element heat leak, and element parameters such as length and diameter. For each element, FLUSH first calculates the pressure drop, then figures the slush solid fraction exiting the element. The code employs GASPLUS routines to calculate thermodynamic properties for the slush hydrogen. FLUSH is written in FORTRAN IV for DEC VAX series computers running VMS. An executable is provided on the tape. The GASPLUS physical properties routines which are required for building the executable are included as one object library on the program media (full source code for GASPLUS is available separately as COSMIC Program Number LEW-15091). FLUSH is available in DEC VAX BACKUP format on a 9-track 1600 BPI magnetic tape (standard media) or on a TK50 tape cartridge. FLUSH was developed in 1989.

Long-term PAH monitoring results from the Anacostia River active capping demonstration using polydimethylsiloxane (PDMS) fibers.

PubMed

Lampert, David J; Lu, Xiaoxia; Reible, Danny D

2013-03-01

In this paper, the long-term monitoring results for hydrophobic organic compounds, specifically polycyclic aromatic hydrocarbons (PAHs), from a field demonstration of capping contaminated sediments at the Anacostia River in Washington DC are presented and analyzed. In situ pore water concentrations in field-contaminated sediments in the demonstration caps were quantified using a polydimethylsiloxane (PDMS)-based passive sampling device. High resolution vertical pore water concentration profiles were measured using the device and were used to infer fate and transport of polycyclic aromatics hydrocarbons (PAHs) at the site. The derived pore water concentrations were compared with observed bioaccumulation and solid-phase concentration profiles to infer contaminant migration rates and mechanisms. Observed pore water concentrations were found to be a better predictor of bioaccumulation than solid-phase concentrations. Solid-phase concentrations were low in cores which implied containment of contamination; however pore water profiles showed that contaminant migration had occurred in the first few years after cap placement. The discrepancy is the result of the low sorption capacity of the sand. Because of surface re-contamination, low sorption capacity in the demonstration caps and strong tidal pumping effects, steady state contaminant profiles were reached in the caps several years after placement. Despite re-contamination at the surface, steady state concentrations in the capped areas showed decreased contamination levels relative to the control area.

Anaerobic digestion of water hyacinth and sludge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biljetina, R.; Srivastava, V.J.; Chynoweth, D.P.

1986-01-01

The Institute of Gas Technology (IGT) has been operating an experimental test unit (ETU) at the Walt Disney World (WDW) wastewater treatment plant to demonstrate the conversion of water hyacinth and sludge to methane in a solids concentrating (SOLCON) digester. Results from 2 years to operation have confirmed earlier laboratory observations that this digester achieves higher methane yields and solids conversion than those observed in continuous stirred tank reactors. Methane yields as high as 0.49 m/sup 3/ kg/sup -1/ (7.9 SCF/lb) volatile solids added have been obtained during steady-state operation on a blend of water hyacinth and sludge. 9 refs.,more » 5 figs., 5 tabs.« less

Thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity

NASA Technical Reports Server (NTRS)

Lan, C. W.; Kou, Sindo

1990-01-01

Computer simulation of steady-state axisymmetrical heat transfer and fluid flow was conducted to study thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity. The effects of key variables on the extent of thermocapillary flow in the melt zone, the shapes of melt/solid interfaces and the length of the melt zone were discussed. These variables are: (1) the temperature coefficient of surface tension (or the Marangoni number), (2) the pulling speed (or the Peclet number), (3) the feed rod radius, (4) the ambient temperature distribution, (5) the heat transfer coefficient (or the Biot number), and (6) the thermal diffusivity of the material (or the Prandtl number).

Thermal treatment of stabilized air pollution control residues in a waste incinerator pilot plant. Part 2: Leaching characteristics of bottom ashes.

PubMed

Baun, Dorthe L; Christensen, Thomas H; Bergfeldt, Brita; Vehlow, Jürgen; Mogensen, Erhardt P B

2004-02-01

With the perspective of generating only one solid residue from waste incineration, co-feeding of municipal solid waste and air pollution control residues stabilized by the Ferrox process was investigated in the TAMARA pilot plant incinerator as described in Bergfeldt et al. (Waste Management Research, 22, 49-57, 2004). This paper reports on leaching from the combined bottom ashes. Batch leaching test, pH-static leaching tests, availability tests and column leaching tests were used to characterize the leaching properties. The leaching properties are key information in the context of reuse in construction or in landfilling of the combined residue. In general, the combined bottom ashes had leaching characteristics similar to the reference bottom ash, which contained no APC residue. However, As and Pb showed slightly elevated leaching from the combined bottom ashes, while Cr showed less leaching. The investigated combined bottom ashes had contents of metals comparable to what is expected at steady state after continuous co-feeding of APC residues. Only Cd and Pb were partly volatilized (30-40%) during the incineration process and thus the combined bottom ashes had lower contents of Cd and Pb than expected at steady state. Furthermore, a major loss of Hg was, not surprisingly, seen and co-feeding of Ferrox-products together with municipal solid waste will require dedicated removal of Hg in the flue gas to prevent a build up of Hg in the system. In spite of this, a combined single solid residue from waste incineration seems to be a significant environmental improvement to current technology.

Theoretical and experimental analysis of the contact between a solid-rubber tire and a chassis dynamometer

NASA Astrophysics Data System (ADS)

Belkin, A. E.; Semenov, V. K.

2016-05-01

We consider the problem of modeling the test where a solid-rubber tire runs on a chassis dynamometer for determining the tire rolling resistance characteristics.We state the problem of free steady-state rolling of the tire along the test drum with the energy scattering in the rubber in the course of cyclic deformation taken into account. The viscoelastic behavior of the rubber is described by the Bergströ m-Boyce model whose numerical parameters are experimentally determined from the results of compression tests with specimens. The finite element method is used to obtain the solution of the three-dimensional viscoelasticity problem. To estimate the adequacy of the constructed model, we compare the numerical results with the results obtained in the solid-rubber tire tests on the Hasbach stand from the values of the rolling resistance forces for various loads on the tire.

Accelerated transport and growth with symmetrized dynamics

NASA Astrophysics Data System (ADS)

Merikoski, Juha

2013-12-01

In this paper we consider a model of accelerated dynamics with the rules modified from those of the recently proposed [Dong et al., Phys. Rev. Lett. 109, 130602 (2012), 10.1103/PhysRevLett.109.130602] accelerated exclusion process (AEP) such that particle-vacancy symmetry is restored to facilitate a mapping to a solid-on-solid growth model in 1+1 dimensions. In addition to kicking a particle ahead of the moving particle, as in the AEP, in our model another particle from behind is drawn, provided it is within the "distance of interaction" denoted by ℓmax. We call our model the doubly accelerated exclusion process (DAEP). We observe accelerated transport and interface growth and widening of the cluster size distribution for cluster sizes above ℓmax, when compared with the ordinary totally asymmetric exclusion process (TASEP). We also characterize the difference between the TASEP, AEP, and DAEP by computing a "staggered" order parameter, which reveals the local order in the steady state. This order in part explains the behavior of the particle current as a function of density. The differences of the steady states are also reflected by the behavior of the temporal and spatial correlation functions in the interface picture.

Nano confinement effects on dynamic and viscoelastic properties of Selenium Films

NASA Astrophysics Data System (ADS)

Yoon, Heedong; McKenna, Gregory

2015-03-01

In current study, we use a novel nano bubble inflation technique to study nano confinement effects on the dynamic and viscoelastic properties of physical vapor deposited Selenium films. Film thicknesses ranged from 60 to 260 nm. Creep experiments were performed for the temperatures ranging from Tg,macroscopic-14 °C to Tg,\\ macroscopic + 19 °C. Time temperature superposition and time thickness superposition were applied to create reduced creep curves, and those were compared with macroscopic data [J. Non-Cryst. Solids. 2002, 307, 790-801]. The results showed that the time temperature superposition was applicable in the glassy relaxation regime to the steady-state plateau regime. However in the long time response of the creep compliance, time thickness superposition failed due to the thickness dependence on the steady-state plateau. It was observed that the steady state compliance increased with film thickness. The thickness dependence on the plateau stiffening followed a power law of DPlateau ~ h2.46, which is greater than observed in organic polymers where the exponents observed range from 0.83 to 2.0 [Macromolecules. 2012, 45 (5), 2453-2459]. National Science Foundation Grant No. CHE 1112416 and John R. Bradford Endowment at Texas Tech

Emission switching of 4,6-diphenylpyrimidones: solvent and solid state effects.

PubMed

Adjaye-Mensah, Edward; Gonzalez, Walter G; Bussé, David R; Captain, Burjor; Miksovska, Jaroslava; Wilson, James N

2012-08-30

The photophysics of 1-ethyl-4,6-bis(4-methoxyphenyl)-2(1H)-pyrimidone (1) and 1-ethyl-4,6-bis(4-(dimethylamino)phenyl)-2(1H)-pyrimidone (2) were investigated to determine the mechanisms of emission switching in response to protonation. UV-vis and steady state emission spectroscopy of the protonated and unprotonated forms across a range of solvents reveal the polarity dependence of the vertical excitation energies. Emission lifetimes and quantum yields show the solvent dependency of the excited states. Emission enhancements were observed in polyethylene glycol solutions and in the solid state (both thin film and single crystal), demonstrating the role of intramolecular rotation in thermal relaxation of the excited states. TD-DFT calculations provide insights into the excited state geometries and the role of intramolecular charge transfer. The collected data show that emission of diphenylpyrimidones can be modulated by four factors, including the identity of the electron-donating auxochrome, protonation state, solvent polarity, and viscosity.

Steady-state solidification of aqueous ammonium chloride

NASA Astrophysics Data System (ADS)

Peppin, S. S. L.; Huppert, Herbert E.; Worster, M. Grae

We report on a series of experiments in which a Hele-Shaw cell containing aqueous solutions of NH4Cl was translated at prescribed rates through a steady temperature gradient. The salt formed the primary solid phase of a mushy layer as the solution solidified, with the salt-depleted residual fluid driving buoyancy-driven convection and the development of chimneys in the mushy layer. Depending on the operating conditions, several morphological transitions occurred. A regime diagram is presented quantifying these transitions as a function of freezing rate and the initial concentration of the solution. In general, for a given concentration, increasing the freezing rate caused the steady-state system to change from a convecting mushy layer with chimneys to a non-convecting mushy layer below a relatively quiescent liquid, and then to a much thinner mushy layer separated from the liquid by a region of active secondary nucleation. At higher initial concentrations the second of these states did not occur. At lower concentrations, but still above the eutectic, the mushy layer disappeared. A simple mathematical model of the system is developed which compares well with the experimental measurements of the intermediate, non-convecting state and serves as a benchmark against which to understand some of the effects of convection. Movies are available with the online version of the paper.

The effect of volume phase changes, mass transport, sunlight penetration, and densification on the thermal regime of icy regoliths

NASA Technical Reports Server (NTRS)

Fanale, Fraser P.; Salvail, James R.; Matson, Dennis L.; Brown, Robert H.

1990-01-01

The present quantitative modeling of convective, condensational, and sublimational effects on porous ice crust volumes subjected to solar radiation encompasses the effect of such insolation's penetration of visible bandpass-translucent light, but opaque to the IR bandpass. Quasi-steady-state temperatures, H2O mass fluxes, and ice mass-density change rates are computed as functions of time of day and ice depth. When the effects of latent heat and mass transport are included in the model, the enhancement of near-surface temperature due to the 'solid-state greenhouse effect' is substantially diminished. When latent heat, mass transport, and densification effects are considered, however, a significant solid-state greenhouse effect is shown to be compatible with both morphological evidence for high crust strengths and icy shell decoupling from the lithosphere.

Holographic investigation of solid propellant particulates

NASA Astrophysics Data System (ADS)

Gillespie, T. R.

1981-12-01

The investigation completed the development process to establish a technique to obtain holographic recordings of particulate behavior during the combustion process of solid propellants in a two-dimensional rocket motor. Holographic and photographic recordings were taken in a crossflow environment using various compositions of metallized propellants. The reconstructed holograms are used to provide data on the behavior of aluminum/aluminum oxide particulates in a steady state combustion environment as a function of the initial aluminum size cast into the propellant. High speed, high resolution motion pictures were taken to compare the cinematic data with that available from the holograms.

Fuzzy Logic Based Controller for a Grid-Connected Solid Oxide Fuel Cell Power Plant.

PubMed

Chatterjee, Kalyan; Shankar, Ravi; Kumar, Amit

2014-10-01

This paper describes a mathematical model of a solid oxide fuel cell (SOFC) power plant integrated in a multimachine power system. The utilization factor of a fuel stack maintains steady state by tuning the fuel valve in the fuel processor at a rate proportional to a current drawn from the fuel stack. A suitable fuzzy logic control is used for the overall system, its objective being controlling the current drawn by the power conditioning unit and meet a desirable output power demand. The proposed control scheme is verified through computer simulations.

The solid surface combustion experiment aboard the USML-1 mission

NASA Technical Reports Server (NTRS)

Altenkirch, Robert A.; Sacksteder, Kurt; Bhattacharjee, Subrata; Ramachandra, Prashant A.; Tang, Lin; Wolverton, M. Katherine

1994-01-01

AA Experimental results from the five experiments indicate that flame spread rate increases with increasing ambient oxygen content and pressure. An experiment was conducted aboard STS-50/USML-1 in the solid Surface Combustion Experiment (SSCE) hardware for flame spread over a thin cellulosic fuel in a quiescent oxidizer of 35% oxygen/65% nitrogen at 1.0 atm. pressure in microgravity. The USML-1 test was the fourth of five planned experiments for thin fuels, one performed during each of five Space Shuttle Orbiter flights. Data that were gathered include gas- and solid-phase temperatures and motion picture flame images. Observations of the flame are described and compared to theoretical predictions from steady and unsteady models that include flame radiation from CO2 and H2O. Experimental results from the five esperiments indicate that flame spread rate increases with increasing ambient oxygen content and pressure. The brightness of the flame and the visible soot radiation also increase with increasing spread rate. Steady-state numerical predictions of temperature and spread rate and flame structure trends compare well with experimental results near the flame's leading edge while gradual flame evolution is captured through the unsteady model.

Evaluation of ground-water flow and solute transport in the Lompoc area, Santa Barbara County, California

USGS Publications Warehouse

Bright, Daniel J.; Nash, David B.; Martin, Peter

1997-01-01

Ground-water quality in the Lompoc area, especially in the Lompoc plain, is only marginally acceptable for most uses. Demand for ground water has increased for municipal use since the late 1950's and has continued to be high for irrigation on the Lompoc plain, the principal agricultural area in the Santa Ynez River basin. As use has increased, the quality of ground water has deteriorated in some areas of the Lompoc plain. The dissolved-solids concentration in the main zone of the upper aquifer beneath most of the central and western plains has increased from less than 1,000 milligrams per liter in the 1940's to greater than 2,000 milligrams per liter in the 1960's. Dissolved- solids concentration have remained relatively constant since the 1960's. A three-dimensional finite-difference model was used to simulate ground-water flow in the Lompoc area and a two-dimensional finite-element model was used to simulate solute transport to gain a better understanding of the ground-water system and to evaluate the effects of proposed management plans for the ground-water basin. The aquifer system was simulated in the flow model as four horizontal layers. In the area of the Lompoc plain, the layers represent the shallow, middle, and main zones of the upper aquifer, and the lower aquifer. For the Lompoc upland and Lompoc terrace, the four layers represent the lower aquifer. The solute transport model was used to simulate dissolved-solids transport in the main zone of the upper aquifer beneath the Lompoc plain. The flow and solute-transport models were calibrated to transient conditions for 1941-88. A steady-state simulation was made to provide initial conditions for the transient-state simulation by using long-term average (1941-88) recharge rates. Model- simulated hydraulic heads generally were within 5 feet of measured heads in the main zone for transient conditions. Model-simulated dissolved- solids concentrations for the main zone generally differed less than 200milligrams per liter from concentrations in 1988. During 1941-88 about 1,096,000 acre-feet of water was pumped from the aquifer system. Average pumpage for this period (22,830 acre-feet per year) exceeded pumpage for the steady-state simulation by 16,590 acre-feet per year. The results of the transient simulation indicate that about 60 percent of this increase in pumpage was contributed by increased recharge, 28 percent by decreased natural discharge from the system (primarily discharge to the Santa Ynez River and transpiration), and 13 percent was withdrawn from storage. Total simulated downward leakage from the middle zone to the main zone in the central plain and upward leakage from the consolidated rocks to the main zone significantly increased in response to increased pumpage, which increased from about 6,240 to 30,870 acre-feet per year from 1941 to 1988. Average dissolved-solid concentration in the middle zone in 1987-88 ranged from 2,000 to 3,000 milligrams per liter beneath the northeastern plain and the dissolved-solids concentration of two samples from the consolidated rocks beneath the western plain averaged 4,300 milligrams per liter. Because the dissolved-solids concentration for the middle zone and the consolidated rocks is higher than the simulated steady-state dissolved-solids concentration of the main zone, the increase in the leakage from these two sources resulted in increased dissolved-solids concentration in the main zone during the transient period. The model results indicate that the main source of increased dissolved- solids concentration in the northeastern and central plains was downward leakage from the middle zone; whereas, upward leakage from the consolidated rocks was the main source of the increased dissolved-solids concentrations in the northwestern and western plains. The models were used to estimate changes in hydraulic head and in dissolved-solids concentration resulting from three proposed management alternatives: (1) average recharge

Influence of forced internal air circulation on airflow distribution and heat transfer in a gas double-dynamic solid-state fermentation bioreactor.

PubMed

Chen, Hongzhang; Qin, Lanzhi; Li, Hongqiang

2014-02-01

Internal air circulation affects the temperature field distribution in a gas double-dynamic solid-state fermentation bioreactor (GDSFB). To enhance heat transfer through strengthening internal air circulation in a GDSFB, we put an air distribution plate (ADP) into the bioreactor and studied the effects of forced internal air circulation on airflow, heat transfer, and cellulase activity of Trichoderma viride L3. Results showed that ADP could help form a steady and uniform airflow distribution, and with gas-guide tubes, air reversal was formed inside the bioreactor, thus resulting in a smaller temperature difference between medium and air by enhancing convective heat transfer inside the bioreactor. Using an ADP of 5.35 % aperture ratio caused a 1 °C decrease in the average temperature difference during the solid-state fermentation process of T. viride L3. Meanwhile, the cellulase activity of T. viride L3 increased by 13.5 %. The best heat-transfer effect was attained when using an ADP of 5.35 % aperture ratio and setting the fan power to 125 V (4.81 W) in the gas double-dynamic solid-state fermentation (GDSF) process. An option of suitable aperture ratio and fan power may be conducive to ADPs' industrial amplification.

A simple differential steady-state method to measure the thermal conductivity of solid bulk materials with high accuracy.

PubMed

Kraemer, D; Chen, G

2014-02-01

Accurate measurements of thermal conductivity are of great importance for materials research and development. Steady-state methods determine thermal conductivity directly from the proportionality between heat flow and an applied temperature difference (Fourier Law). Although theoretically simple, in practice, achieving high accuracies with steady-state methods is challenging and requires rather complex experimental setups due to temperature sensor uncertainties and parasitic heat loss. We developed a simple differential steady-state method in which the sample is mounted between an electric heater and a temperature-controlled heat sink. Our method calibrates for parasitic heat losses from the electric heater during the measurement by maintaining a constant heater temperature close to the environmental temperature while varying the heat sink temperature. This enables a large signal-to-noise ratio which permits accurate measurements of samples with small thermal conductance values without an additional heater calibration measurement or sophisticated heater guards to eliminate parasitic heater losses. Additionally, the differential nature of the method largely eliminates the uncertainties of the temperature sensors, permitting measurements with small temperature differences, which is advantageous for samples with high thermal conductance values and/or with strongly temperature-dependent thermal conductivities. In order to accelerate measurements of more than one sample, the proposed method allows for measuring several samples consecutively at each temperature measurement point without adding significant error. We demonstrate the method by performing thermal conductivity measurements on commercial bulk thermoelectric Bi2Te3 samples in the temperature range of 30-150 °C with an error below 3%.

Programmable Analog Memory Resistors For Electronic Neural Networks

NASA Technical Reports Server (NTRS)

Ramesham, Rajeshuni; Thakoor, Sarita; Daud, Taher; Thakoor, Anilkumar P.

1990-01-01

Electrical resistance of new solid-state device altered repeatedly by suitable control signals, yet remains at steady value when control signal removed. Resistance set at low value ("on" state), high value ("off" state), or at any convenient intermediate value and left there until new value desired. Circuits of this type particularly useful in nonvolatile, associative electronic memories based on models of neural networks. Such programmable analog memory resistors ideally suited as synaptic interconnects in "self-learning" neural nets. Operation of device depends on electrochromic property of WO3, which when pure is insulator. Potential uses include nonvolatile, erasable, electronically programmable read-only memories.

Polymer translocation in solid-state nanopores: Dependence on hydrodynamic interactions and polymer configuration

NASA Astrophysics Data System (ADS)

Edmonds, Christopher M.; Hesketh, Peter J.; Nair, Sankar

2013-11-01

We present a Brownian dynamics investigation of 3-D Rouse and Zimm polymer translocation through solid-state nanopores. We obtain different scaling exponents α for both polymers using two initial configurations: minimum energy, and 'steady-state'. For forced translocation, Rouse polymers (no hydrodynamic interactions), shows a large dependence of α on initial configuration and voltage. Higher voltages result in crowding at the nanopore exit and reduced α. When the radius of gyration is in equilibrium at the beginning and end of translocation, α = 1 + υ where υ is the Flory exponent. For Zimm polymers (including hydrodynamic interactions), crowding is reduced and α = 2υ. Increased pore diameter does not affect α at moderate voltages that reduce diffusion effects. For unforced translocation using narrow pores, both polymers give α = 1 + 2υ. Due to increased polymer-pore interactions in the narrow pore, hydrodynamic drag effects are reduced, resulting in identical scaling.

Si nanowire growth on sapphire: Classical incubation, reverse reaction, and steady state supersaturation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shakthivel, Dhayalan; Rathkanthiwar, Shashwat; Raghavan, Srinivasan, E-mail: sraghavan@cense.iisc.ernet.in

2015-04-28

Si nanowire growth on sapphire substrates by the vapor-liquid-solid (VLS) method using Au catalyst particles has been studied. Sapphire was chosen as the substrate to ensure that the vapor phase is the only source of Si. Three hitherto unreported observations are described. First, an incubation period of 120–480 s, which is shown to be the incubation period as defined in classical nucleation theory, is reported. This incubation period permits the determination of a desolvation energy of Si from Au-Si alloys of 15 kT. Two, transmission electron microscopy studies of incubation, point to Si loss by reverse reaction as an important partmore » of the mechanism of Si nanowire growth by VLS. Three, calculations using these physico-chemical parameters determined from incubation and measured steady state growth rates of Si nanowires show that wire growth happens from a supersaturated catalyst droplet.« less

An Overview of Recent PISCES Program PMI Results

NASA Astrophysics Data System (ADS)

Tynan, George; Doerner, Russell; Abe, Shota; Baldwin, Matthew; Barton, Joseph; Chen, Renkun; Gosselin, Jordan; Hollmann, Eric; Nishijima, Daisuke; Simmonds, Michael; Wang, Yong; Yu, Jonathan

2015-11-01

The PISCES Program is focused on fundamental PMI studies of Be and W-based solid plasma facing components under steady-state and transient conditions. We will show results from studies in W, Be and mixed W-Be material systems. Topics of investigation include formation of near-surface nanobubbles from He plasma ion implantation, growth of W-fuzz from these bubbles in steady-state and transient conditions, D retention in Be and W and development of a D-retention model for both H/D isotope exchange and displacement damage experiments. Initial studies of PMI in displacement damaged W are also presented, showing the effect of damage and exposure temperature on D retention, D diffusion, W thermal conductivity. Be-based results include morphology evolution under high plasma flux exposure, Be erosion mechanisms, and retention in Be-based materials. Future plans and connections to fusion energy system requirements will be discussed. This work supported by grant DE-FG02-07ER54912.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gundlach-Graham, Alexander W.; Dennis, Elise; Ray, Steven J.

An inductively coupled plasma distance-of-flight mass spectrometer (ICP-DOFMS) has been coupled with laser-ablation (LA) sample introduction for the elemental analysis of solids. ICP-DOFMS is well suited for the analysis of laser-generated aerosols because it offers both high-speed mass analysis and simultaneous multi-elemental detection. Here, we evaluate the analytical performance of the LA-ICP-DOFMS instrument, equipped with a microchannel plate-based imaging detector, for the measurement of steady-state LA signals, as well as transient signals produced from single LA events. Steady-state detection limits are 1 mg g1, and absolute single-pulse LA detection limits are 200 fg for uranium; the system is shown capablemore » of performing time-resolved single-pulse LA analysis. By leveraging the benefits of simultaneous multi-elemental detection, we also attain a good shot-to-shot reproducibility of 6% relative standard deviation (RSD) and isotope-ratio precision of 0.3% RSD with a 10 s integration time.« less

Enzymatic saccharification of pretreated wheat straw: comparison of solids-recycling, sequential hydrolysis and batch hydrolysis.

PubMed

Pihlajaniemi, Ville; Sipponen, Satu; Sipponen, Mika H; Pastinen, Ossi; Laakso, Simo

2014-02-01

In the enzymatic hydrolysis of lignocellulose materials, the recycling of the solid residue has previously been considered within the context of enzyme recycling. In this study, a steady state investigation of a solids-recycling process was made with pretreated wheat straw and compared to sequential and batch hydrolysis at constant reaction times, substrate feed and liquid and enzyme consumption. Compared to batch hydrolysis, the recycling and sequential processes showed roughly equal hydrolysis yields, while the volumetric productivity was significantly increased. In the 72h process the improvement was 90% due to an increased reaction consistency, while the solids feed was 16% of the total process constituents. The improvement resulted primarily from product removal, which was equally efficient in solids-recycling and sequential hydrolysis processes. No evidence of accumulation of enzymes beyond the accumulation of the substrate was found in recycling. A mathematical model of solids-recycling was constructed, based on a geometrical series. Copyright © 2013 Elsevier Ltd. All rights reserved.

Entropy criteria applied to pattern selection in systems with free boundaries

NASA Astrophysics Data System (ADS)

Kirkaldy, J. S.

1985-10-01

The steady state differential or integral equations which describe patterned dissipative structures, typically to be identified with first order phase transformation morphologies like isothermal pearlites, are invariably degenerate in one or more order parameters (the lamellar spacing in the pearlite case). It is often observed that a different pattern is attained at the steady state for each initial condition (the hysteresis or metastable case). Alternatively, boundary perturbations and internal fluctuations during transition up to, or at the steady state, destroy the path coherence. In this case a statistical ensemble of imperfect patterns often emerges which represents a fluctuating but recognizably patterned and unique average steady state. It is cases like cellular, lamellar pearlite, involving an assembly of individual cell patterns which are regularly perturbed by local fluctuation and growth processes, which concern us here. Such weakly fluctuating nonlinear steady state ensembles can be arranged in a thought experiment so as to evolve as subsystems linking two very large mass-energy reservoirs in isolation. Operating on this discontinuous thermodynamic ideal, Onsager’s principle of maximum path probability for isolated systems, which we interpret as a minimal time correlation function connecting subsystem and baths, identifies the stable steady state at a parametric minimum or maximum (or both) in the dissipation rate. This nonlinear principle is independent of the Principle of Minimum Dissipation which is applicable in the linear regime of irreversible thermodynamics. The statistical argument is equivalent to the weak requirement that the isolated system entropy as a function of time be differentiable to the second order despite the macroscopic pattern fluctuations which occur in the subsystem. This differentiability condition is taken for granted in classical stability theory based on the 2nd Law. The optimal principle as applied to isothermal and forced velocity pearlites (in this case maximal) possesses a Le Chatelier (perturbation) Principle which can be formulated exactly via Langer’s conjecture that “each lamella must grow in a direction which is perpendicular to the solidification front”. This is the first example of such an equivalence to be experimentally and theoretically recognized in nonlinear irreversible thermodynamics. A further application to binary solidification cells is reviewed. In this case the optimum in the dissipation is a minimum and the closure between theory and experiment is excellent. Other applications in thermal-hydraulics, biology, and solid state physics are briefy described.

Nanoscale steady-state temperature gradients within polymer nanocomposites undergoing continuous-wave photothermal heating from gold nanorods.

PubMed

Maity, Somsubhra; Wu, Wei-Chen; Tracy, Joseph B; Clarke, Laura I; Bochinski, Jason R

2017-08-17

Anisotropically-shaped metal nanoparticles act as nanoscale heaters via excitation of a localized surface plasmon resonance, utilizing a photothermal effect which converts the optical energy into local heat. Steady-state temperatures within a polymer matrix embedded with gold nanorods undergoing photothermal heating using continuous-wave excitation are measured in the immediate spatial vicinity of the nanoparticle (referred to as the local temperature) from observing the rate of physical rotation of the asymmetric nanoparticles within the locally created polymer melt. Average temperatures across the entire (mostly solid) sample (referred to as the global temperature) are simultaneously observed using a fluorescence method from randomly dispersed molecular emitters. Comparing these two independent measurements in films having varying concentrations of nanorods reveals the interplay between the local and global temperatures, clearly demonstrating the capability of these material samples to sustain large steady-state spatial temperature gradients when experiencing continuous-wave excitation photothermal heating. These results are discussed quantitatively. Illustrative imaging studies of nanofibers under photothermal heating also support the presence of a large temperature gradient. Photothermal heating in this manner has potential utility in creating unique thermal processing conditions for outcomes such as driving chemical reactions, inducing crystallinity changes, or enhancing degradation processes in a manner unachievable by conventional heating methods.

RELAP5-3D Results for Phase I (Exercise 2) of the OECD/NEA MHTGR-350 MW Benchmark

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerhard Strydom

2012-06-01

The coupling of the PHISICS code suite to the thermal hydraulics system code RELAP5-3D has recently been initiated at the Idaho National Laboratory (INL) to provide a fully coupled prismatic Very High Temperature Reactor (VHTR) system modeling capability as part of the NGNP methods development program. The PHISICS code consists of three modules: INSTANT (performing 3D nodal transport core calculations), MRTAU (depletion and decay heat generation) and a perturbation/mixer module. As part of the verification and validation activities, steady state results have been obtained for Exercise 2 of Phase I of the newly-defined OECD/NEA MHTGR-350 MW Benchmark. This exercise requiresmore » participants to calculate a steady-state solution for an End of Equilibrium Cycle 350 MW Modular High Temperature Reactor (MHTGR), using the provided geometry, material, and coolant bypass flow description. The paper provides an overview of the MHTGR Benchmark and presents typical steady state results (e.g. solid and gas temperatures, thermal conductivities) for Phase I Exercise 2. Preliminary results are also provided for the early test phase of Exercise 3 using a two-group cross-section library and the Relap5-3D model developed for Exercise 2.« less

RELAP5-3D results for phase I (Exercise 2) of the OECD/NEA MHTGR-350 MW benchmark

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strydom, G.; Epiney, A. S.

2012-07-01

The coupling of the PHISICS code suite to the thermal hydraulics system code RELAP5-3D has recently been initiated at the Idaho National Laboratory (INL) to provide a fully coupled prismatic Very High Temperature Reactor (VHTR) system modeling capability as part of the NGNP methods development program. The PHISICS code consists of three modules: INSTANT (performing 3D nodal transport core calculations), MRTAU (depletion and decay heat generation) and a perturbation/mixer module. As part of the verification and validation activities, steady state results have been obtained for Exercise 2 of Phase I of the newly-defined OECD/NEA MHTGR-350 MW Benchmark. This exercise requiresmore » participants to calculate a steady-state solution for an End of Equilibrium Cycle 350 MW Modular High Temperature Reactor (MHTGR), using the provided geometry, material, and coolant bypass flow description. The paper provides an overview of the MHTGR Benchmark and presents typical steady state results (e.g. solid and gas temperatures, thermal conductivities) for Phase I Exercise 2. Preliminary results are also provided for the early test phase of Exercise 3 using a two-group cross-section library and the Relap5-3D model developed for Exercise 2. (authors)« less

Time effect of erosion by solid particle impingement on ductile materials

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1983-01-01

Erosion and morphological studies of several metals and alloys eroded by normal impingement jets of spherical glass beads and angular crushed-glass erodent particles were conducted. Erosion morphology (the width, depth, and width-depth ratio of the pit) was studied in order to fully investigate the effect of time on erosion rate. The eroded surfaces were studied with a scanning electron microscope, and surface profiles were measured with a profilometer. A large amount of experimental data reported in the literature was also analyzed in order to understand the effect of variables such as the type of device, the erodent particle size and shape, the impact velocity, and the abrasive charge on erosion-rate-versus-time curves. In the present experiments the pit-width-versus-time or pit-depth-versus-time curves were similar to erosion-versus-time curves for glass-bead impingement. The pit-depth-rate-versus-time curves were similar to erosion-rate-versus-time curves for crushed-glass impingement. Analysis of experimental data with two forms of glass resulted in four types of erosion-rate-versus-time curves: (1) incubation, acceleration, and steady-state periods (type I), (2) incubation, acceleration, deceleration, and steady-state periods (type III), (3) incubation, acceleration, peak rate, and deceleration periods (type IV), and (4) incubation, acceleration, steady-state, and deceleration periods (type V).

Development and Analysis of Hybrid Thermoelectric Refrigerator Systems

NASA Astrophysics Data System (ADS)

Saifizi, M.; Zakaria, M. S.; Yaacob, Sazali; Wan, Khairunizam

2018-03-01

Thermoelectric module (TEM) is a type of solid-state devices which has the capability to maintain the accuracy of small temperature variation application. In this study, a hybrid thermoelectric refrigerator system is introduced by utilizing TEMs; direct and air to air thermoelectric heat pump to cool down and maintain low temperature for vaccines storage. Two different materials which are aluminum and stainless steel are used as container in hybrid thermoelectric refrigerator (HTER) configuration to investigate the response of every system in transient and steady state mode. A proper temperature sensor calibration technique is implemented to make certain real time data acquisition of the systems are not affected very much from the noise generated. From step response analysis, it is indicated that HTER I (aluminum) has rapid settling time from transient to steady state than HTER II (stainless steel) since aluminum has better thermal conductivity as compared to stainless steel. It is found that HTER I is better in cooling capability with the same input current instead of HTER II which required a longer time to achieve steady state mode. Besides, in Pseudo Random Binary Sequence (PRBS) response analysis injected to both systems shows HTER I is very sensitive to current input as the sequence length of HTER I is shorter than HTER II. However both systems depict the varying temperature in the range of 4 oC due to differences in thermal conductivity of container.

Size and Shape of Solid Fuel Diffusion Flames in Very Low Speed Flows. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Foutch, David W.

1987-01-01

The effect of very low speed forced flows on the size and shape of a solid fuel diffusion flame are investigated experimentally. Flows due to natural convection are eliminated by performing the experiment in low gravity. The range of velocities tested is 1.5 cm/s to 6.3 cm/s and the mole fraction of oxygen in the O2/N2 atmosphere ranges from 0.15 to 0.19. The flames did not reach steady state in the 5.2 sec to which the experiment was limited. Despite limited data, trends in the transient flame temperature and, by means of extrapolation, the steady state flame size are deduced. As the flow velocity is reduced, the flames move farther from the fuel surface, and the transient flame temperature is lowered. As the oxygen concentration is reduced the flames move closer to the fuel sample and the transient flame temperature is reduced. With stand off distances up to 8.5 + or - 0.7 mm and thicknesses around 1 or 2 mm, these flames are much weaker than flames observed at normal gravity. Based on the performance of the equipment and several qualitative observations, suggestions for future work are made.

Comparisons of predicted steady-state levels in rooms with extended- and local-reaction bounding surfaces

NASA Astrophysics Data System (ADS)

Hodgson, Murray; Wareing, Andrew

2008-01-01

A combined beam-tracing and transfer-matrix model for predicting steady-state sound-pressure levels in rooms with multilayer bounding surfaces was used to compare the effect of extended- and local-reaction surfaces, and the accuracy of the local-reaction approximation. Three rooms—an office, a corridor and a workshop—with one or more multilayer test surfaces were considered. The test surfaces were a single-glass panel, a double-drywall panel, a carpeted floor, a suspended-acoustical ceiling, a double-steel panel, and glass fibre on a hard backing. Each test surface was modeled as of extended or of local reaction. Sound-pressure levels were predicted and compared to determine the significance of the surface-reaction assumption. The main conclusions were that the difference between modeling a room surface as of extended or of local reaction is not significant when the surface is a single plate or a single layer of material (solid or porous) with a hard backing. The difference is significant when the surface consists of multilayers of solid or porous material and includes a layer of fluid with a large thickness relative to the other layers. The results are partially explained by considering the surface-reflection coefficients at the first-reflection angles.

Dry-thermophilic anaerobic digestion of organic fraction of municipal solid waste: Methane production modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fdez-Gueelfo, L.A., E-mail: alberto.fdezguelfo@uca.es; Alvarez-Gallego, C.; Sales, D.

2012-03-15

Highlights: Black-Right-Pointing-Pointer Methane generation may be modeled by means of modified product generation model of Romero Garcia (1991). Black-Right-Pointing-Pointer Organic matter content and particle size influence the kinetic parameters. Black-Right-Pointing-Pointer Higher organic matter content and lower particle size enhance the biomethanization. - Abstract: The influence of particle size and organic matter content of organic fraction of municipal solid waste (OFMSW) in the overall kinetics of dry (30% total solids) thermophilic (55 Degree-Sign C) anaerobic digestion have been studied in a semi-continuous stirred tank reactor (SSTR). Two types of wastes were used: synthetic OFMSW (average particle size of 1 mm; 0.71more » g Volatile Solids/g waste), and OFMSW coming from a composting full scale plant (average particle size of 30 mm; 0.16 g Volatile Solids/g waste). A modification of a widely-validated product-generation kinetic model has been proposed. Results obtained from the modified-model parameterization at steady-state (that include new kinetic parameters as K, Y{sub pMAX} and {theta}{sub MIN}) indicate that the features of the feedstock strongly influence the kinetics of the process. The overall specific growth rate of microorganisms ({mu}{sub max}) with synthetic OFMSW is 43% higher compared to OFMSW coming from a composting full scale plant: 0.238 d{sup -1} (K = 1.391 d{sup -1}; Y{sub pMAX} = 1.167 L CH{sub 4}/gDOC{sub c}; {theta}{sub MIN} = 7.924 days) vs. 0.135 d{sup -1} (K = 1.282 d{sup -1}; Y{sub pMAX} = 1.150 L CH{sub 4}/gDOC{sub c}; {theta}{sub MIN} = 9.997 days) respectively. Finally, it could be emphasized that the validation of proposed modified-model has been performed successfully by means of the simulation of non-steady state data for the different SRTs tested with each waste.« less

Macrosegregation in aluminum alloy ingot cast by the semicontinuous direct chill method

NASA Technical Reports Server (NTRS)

Yu, H.; Granger, D. A.

1984-01-01

A theoretical model of the semicontinuous DC casting method is developed to predict the positive segregation observed at the subsurface and the negative segregation commonly found at the center of large commercial-size aluminum alloy ingot. Qualitative analysis of commercial-size aluminum alloy semicontinuous cast direct chill (DC) ingot is carried out. In the analysis, both positive segregation in the ingot subsurface and negative segregation at the center of the ingot are examined. Ingot subsurface macrosegregation is investigated by considering steady state casting of a circular cross-section binary alloy ingot. Nonequilibrium solidification is assumed with no solid diffusion, constant equilibrium partition ratio, and constant solid density.

Interfacing the Generalized Fluid System Simulation Program with the SINDA/G Thermal Program

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Palmiter, Christopher; Farmer, Jeffery; Lycans, Randall; Tiller, Bruce

2000-01-01

A general purpose, one dimensional fluid flow code has been interfaced with the thermal analysis program SINDA/G. The flow code, GFSSP, is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development was conducted in two phases. This paper describes the first (which allows for steady and quasi-steady - unsteady solid, steady fluid - conjugate heat transfer modeling). The second (full transient conjugate heat transfer modeling) phase of the interface development will be addressed in a later paper. Phase 1 development has been benchmarked to an analytical solution with excellent agreement. Additional test cases for each development phase demonstrate desired features of the interface. The results of the benchmark case, three additional test cases and a practical application are presented herein.

Further analytical study of hybrid rocket combustion

NASA Technical Reports Server (NTRS)

Hung, W. S. Y.; Chen, C. S.; Haviland, J. K.

1972-01-01

Analytical studies of the transient and steady-state combustion processes in a hybrid rocket system are discussed. The particular system chosen consists of a gaseous oxidizer flowing within a tube of solid fuel, resulting in a heterogeneous combustion. Finite rate chemical kinetics with appropriate reaction mechanisms were incorporated in the model. A temperature dependent Arrhenius type fuel surface regression rate equation was chosen for the current study. The governing mathematical equations employed for the reacting gas phase and for the solid phase are the general, two-dimensional, time-dependent conservation equations in a cylindrical coordinate system. Keeping the simplifying assumptions to a minimum, these basic equations were programmed for numerical computation, using two implicit finite-difference schemes, the Lax-Wendroff scheme for the gas phase, and, the Crank-Nicolson scheme for the solid phase.

Chamber measurement of surface-atmosphere trace gas exchange--Numerical evaluation of dependence on soil interfacial layer, and source/sink products

USGS Publications Warehouse

Hutchinson, G.L.; Livingston, G.P.; Healy, R.W.; Striegl, Robert G.

2000-01-01

We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere tace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulationshowed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steadystate chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

Understanding the vapor-liquid-solid growth and composition of ternary III-V nanowires and nanowire heterostructures

NASA Astrophysics Data System (ADS)

Dubrovskii, V. G.

2017-11-01

Based on the recent achievements in vapor-liquid-solid (VLS) synthesis, characterization and modeling of ternary III-V nanowires and axial heterostructures within such nanowires, we try to understand the major trends in their compositional evolution from a general theoretical perspective. Clearly, the VLS growth of ternary materials is much more complex than in standard vapor-solid epitaxy techniques, and even maintaining the necessary control over the composition of steady-state ternary nanowires is far from straightforward. On the other hand, VLS nanowires offer otherwise unattainable material combinations without introducing structural defects and hence are very promising for next-generation optoelectronic devices, in particular those integrated with a silicon electronic platform. In this review, we consider two main problems. First, we show how and by means of which parameters the steady-state composition of Au-catalyzed or self-catalyzed ternary III-V nanowires can be tuned to a desired value and why it is generally different from the vapor composition. Second, we present some experimental data and modeling results for the interfacial abruptness across axial nanowire heterostructures, both in Au-catalyzed and self-catalyzed VLS growth methods. Refined modeling allows us to formulate some general growth recipes for suppressing the unwanted reservoir effect in the droplet and sharpening the nanowire heterojunctions. We consider and refine two approaches developed to date, namely the regular crystallization model for a liquid alloy with a critical size of only one III-V pair at high supersaturations or classical binary nucleation theory with a macroscopic critical nucleus at modest supersaturations.

High-rate anaerobic treatment system for solid/lipid-rich wastewater using anaerobic baffled reactor with scum recovery.

PubMed

Fujihira, Takuya; Seo, Shogo; Yamaguchi, Takashi; Hatamoto, Masashi; Tanikawa, Daisuke

2018-04-27

A laboratory scale experiment was conducted to investigate the treatment of solid/lipid-rich wastewater with an anaerobic baffled reactor (ABR) and a down-flow hanging sponge (DHS) reactor. In this study, experimental periods were divided into three phases to explore efficient treatment of solids and lipids in wastewater. In ABR, >90% of the influent chemical oxygen demand (COD) was removed and >70% of the removed COD was converted to methane under steady-state conditions during each phase. During this period, >4.5 kg COD m -3  d -1 was achieved on an average in Phases 1 and 3. Biogas contributed to scum formation, and the scum was categorized into lipid-rich and sludge-containing types, which have energy potentials of 53.4 and 212 kcal/kg-wet weight, respectively. Therefore, by recovering solids and lipids, which formed persistent scum, ABR can be applied as a high-rate treatment for solid/lipid-rich wastewater. Copyright © 2018 Elsevier Ltd. All rights reserved.

Transient Catalytic Combustor Model With Detailed Gas and Surface Chemistry

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Dietrich, Daniel L.; Mellish, Benjamin P.; Miller, Fletcher J.; Tien, James S.

2005-01-01

In this work, we numerically investigate the transient combustion of a premixed gas mixture in a narrow, perfectly-insulated, catalytic channel which can represent an interior channel of a catalytic monolith. The model assumes a quasi-steady gas-phase and a transient, thermally thin solid phase. The gas phase is one-dimensional, but it does account for heat and mass transfer in a direction perpendicular to the flow via appropriate heat and mass transfer coefficients. The model neglects axial conduction in both the gas and in the solid. The model includes both detailed gas-phase reactions and catalytic surface reactions. The reactants modeled so far include lean mixtures of dry CO and CO/H2 mixtures, with pure oxygen as the oxidizer. The results include transient computations of light-off and system response to inlet condition variations. In some cases, the model predicts two different steady-state solutions depending on whether the channel is initially hot or cold. Additionally, the model suggests that the catalytic ignition of CO/O2 mixtures is extremely sensitive to small variations of inlet equivalence ratios and parts per million levels of H2.

A steady-state technique for studying the properties of free-burning wood fires

Treesearch

Wallace L. Fons; H.D. Bruce; W.Y. Pong

1961-01-01

A laboratory study was set up by the U.S. Forest Service with the ultimate objective of determining model laws for properties of wood fires, including rate of spread. This is a report of the first phase of the work, the development of a suitable bed of solid fuel and the technique of study. The bed chosen for initial study is in the form of long cribs of wood sticks...

Data and Modeling of Dendrites Subject to A Step Change in Pressure (TDSE)

NASA Technical Reports Server (NTRS)

Koss, Matthew B.; LaCombe, J. C.; Glicksman, M. E.; Pines, V.; Chait, A.

2003-01-01

There is considerable interest in dendritic solidification because of the influence dendrites have in the determination of microstructure, and thereby in the physical properties of cast metals and alloys. Current theories and models of dendritic growth generally couple diffusion effects in the melt with the physics of the interface. Data and subsequent analysis prior of the tip growth speed and radii of thermal succinonitrile dendrites in the near-convection free, on-orbit, free-fall environment demonstrate that these theories yield predictions that are reasonably in agreement with the results of experiment. However, data and analysis for assessing the interfacial physics component of theory are not sufficiently detailed or definitive. To study fundamental aspects of dendritic interface stability, we are measuring and modeling the kinetics and morphology of dendrites as they evolve from one well-defined steady state at a pre-set supercooling, through a transient stage, to a different well-defined steady state. More specifically, we subject succinonitrile dendrites, growing under steady-state conditions, to a rapid change in pressure. This leads to a rapid change in thermal driving force from the corresponding change in both the equilibrium melting temperature due to the Clapeyron effect, and a change in the far-field temperature due to adiabatic temperature changes in the bulk liquid and solid. Subsequently, we observe transformations from a well-characterized initial state into a new steady-state. Initial data reveal that the dendrite tip velocity changes almost as fast as the pressure charges, while the tip radius changes occur more slowly, taking from 10 60 seconds depending on the size of the step change and the final supercooling. Computer modeling of this process shows both agreements and disagreements with the experimental data. In making these observations and measurements, we are gaining new understandings of interfacial dynamics and state-selection physics.

Interface structure and contact melting in AgCu eutectic. A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bystrenko, O.; Kartuzov, V.

2017-12-01

Molecular dynamics simulations of the interface structure in binary AgCu eutectic were performed by using the realistic EAM potential. In simulations, we examined the time dependence of the total energy in the process of equilibration, the probability distributions, the composition profiles for the components, and the component diffusivities within the interface zone. It is shown that the relaxation to the equilibrium in the solid state is accompanied by the formation of the steady disordered diffusion zone at the boundary between the crystalline components. At higher temperatures, closer to the eutectic point, the increase in the width of the steady diffusion zone is observed. The particle diffusivities grow therewith to the numbers typical for the liquid metals. Above the eutectic point, the steady zone does not form, instead, the complete contact melting in the system occurs. The results of simulations indicate that during the temperature increase the phenomenon of contact melting is preceded by the similar process spatially localized in the vicinity of the interface.

Thermal Design, Analysis, and Testing of the Quench Module Insert Bread Board

NASA Technical Reports Server (NTRS)

Breeding Shawn; Khodabandeh, Julia; Turner, Larry D. (Technical Monitor)

2001-01-01

The science requirements for materials processing is to provide the desired PI requirements of thermal gradient, solid/liquid interface front velocity for a given processing temperature desired by the PI. Processing is performed by translating the furnace with the sample in a stationary position to minimize any disturbances to the solid/liquid interface front during steady state processing. Typical sample materials for this metals and alloys furnace are lead-tin alloys, lead-antimony alloys, and aluminum alloys. Samples must be safe to process and therefore typically are contained with hermetically sealed cartridge tubes (gas tight) with inner ceramic liners (liquid tight) to prevent contamination and/or reaction of the sample material with the cartridge tube.

Mass transfer of nonvolatile organic compounds from porous media

NASA Astrophysics Data System (ADS)

Khachikian, Crist Simon

This thesis presents data pertaining to the mass transfer of nonvolatile organic compounds from porous media. Physical properties of porous solids, including surface and pore areas, are studied. Information from these studies, along with dissolution data, are used to develop correlations relating the Sherwood Number to the Peclet Number. The contaminant used in this study is naphthalene; the solids used are Moffett Sand (MS), Borden Sand (BS), Lampblack (LB), and Silica Gel (SG). Surface area results indicate that contamination at 0.1% reduces the area of MS and SG by 48 and 37%, respectively, while contamination at 1.0% reduces the area of MS, BS, and SG by 59, 56, and 40%, respectively. Most of the reduction in area originates in the reduction of pore areas and volumes, where the contaminant precipitates. After long-term storage, surface areas did not recover to their original values due to an "irreversible" fraction of naphthalene. Treatment with heat or solvent or both was necessary to completely remove the contamination. For lampblack, treatment at 100°C decreased areas while treatment at 250°C increased them. Treatment at 250°°C probably opened pores while that at 100°C may have blocked more pores by redistributing the tar-like contaminant characteristic of lampblack. Contaminated MS and SG solids are packed in columns through which water is pumped. The effluent began at a relatively high concentration (˜70% of solubility) for both samples. However, SG column concentrations dropped quickly, never achieving steady state while the MS samples declined more gradually towards steady state. The high pore areas of the SG samples are believed to cause this behavior. The steady state portion of the MS dissolution history is used to develop mass transfer correlations. The correlation in this study differs from previous work in two major ways: (1) the exponent on the Pe is three times larger and (2) the limiting Sh is 106 times smaller. These results suggest that the dissolution mechanism here is different than in other studies, that is, dissolution is occurring from the contaminated pores which are inaccessible to the flowing water. This work can be used to assess the leaching potential of non-volatile organic impacted soils. Also, soil vapor extraction schemes which are hampered by observed long tails can be explained using the data in this thesis.

Solid-phase synthesis of self-assembling multivalent π-conjugated peptides

DOE PAGES

Sanders, Allix M.; Kale, Tejaswini S.; Katz, Howard E.; ...

2017-02-07

Here, we present a completely solid-phase synthetic strategy to create three- and four-fold peptide-appended π-electron molecules, where the multivalent oligopeptide presentation is dictated by the symmetries of reactive handles placed on discotic π-conjugated cores. Carboxylic acid and anhydride groups were viable amidation and imidation partners, respectively, and oligomeric π-electron discotic cores were prepared through Pd-catalyzed cross-couplings. Due to intermolecular hydrogen bonding between the three or four peptide axes, these π-peptide hybrids self-assemble into robust one-dimensional nanostructures with high aspect ratios in aqueous solution. The preparation of these systems via solid-phase methods will be detailed along with their self-assembly properties, asmore » revealed by steady-state spectroscopy and transmission electron microscopy and electrical characterization using field-effect transistor measurements.« less

Development of a Solid-Oxide Fuel Cell/Gas Turbine Hybrid System Model for Aerospace Applications

NASA Technical Reports Server (NTRS)

Freeh, Joshua E.; Pratt, Joseph W.; Brouwer, Jacob

2004-01-01

Recent interest in fuel cell-gas turbine hybrid applications for the aerospace industry has led to the need for accurate computer simulation models to aid in system design and performance evaluation. To meet this requirement, solid oxide fuel cell (SOFC) and fuel processor models have been developed and incorporated into the Numerical Propulsion Systems Simulation (NPSS) software package. The SOFC and reformer models solve systems of equations governing steady-state performance using common theoretical and semi-empirical terms. An example hybrid configuration is presented that demonstrates the new capability as well as the interaction with pre-existing gas turbine and heat exchanger models. Finally, a comparison of calculated SOFC performance with experimental data is presented to demonstrate model validity. Keywords: Solid Oxide Fuel Cell, Reformer, System Model, Aerospace, Hybrid System, NPSS

Assessment of Various Flow Solvers Used to Predict the Thermal Environment inside Space Shuttle Solid Rocket Motor Joints

NASA Technical Reports Server (NTRS)

Wang, Qun-Zhen; Cash, Steve (Technical Monitor)

2002-01-01

It is very important to accurately predict the gas pressure, gas and solid temperature, as well as the amount of O-ring erosion inside the space shuttle Reusable Solid Rocket Motor (RSRM) joints in the event of a leak path. The scenarios considered are typically hot combustion gas rapid pressurization events of small volumes through narrow and restricted flow paths. The ideal method for this prediction is a transient three-dimensional computational fluid dynamics (CFD) simulation with a computational domain including both combustion gas and surrounding solid regions. However, this has not yet been demonstrated to be economical for this application due to the enormous amount of CPU time and memory resulting from the relatively long fill time as well as the large pressure and temperature rising rate. Consequently, all CFD applications in RSRM joints so far are steady-state simulations with solid regions being excluded from the computational domain by assuming either a constant wall temperature or no heat transfer between the hot combustion gas and cool solid walls.

Strategies to achieve high-solids enzymatic hydrolysis of dilute-acid pretreated corn stover.

PubMed

Geng, Wenhui; Jin, Yongcan; Jameel, Hasan; Park, Sunkyu

2015-01-01

Three strategies were presented to achieve high solids loading while maximizing carbohydrate conversion, which are fed-batch, splitting/thickening, and clarifier processes. Enzymatic hydrolysis was performed at water insoluble solids (WIS) of 15% using washed dilute-acid pretreated corn stover. The carbohydrate concentration increased from 31.8 to 99.3g/L when the insoluble solids content increased from 5% to 15% WIS, while the final carbohydrate conversion was decreased from 78.4% to 73.2%. For the fed-batch process, a carbohydrate conversion efficiency of 76.8% was achieved when solid was split into 60:20:20 ratio, with all enzymes added first. For the splitting/thickening process, a carbohydrate conversion of 76.5% was realized when the filtrate was recycled to simulate a steady-state process. Lastly, the clarifier process was evaluated and the highest carbohydrate conversion of 81.4% was achieved. All of these results suggests the possibility of enzymatic hydrolysis at high solids to make the overall conversion cost-competitive. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evolution of clog formation with time in columns permeated with synthetic landfill leachate

NASA Astrophysics Data System (ADS)

VanGulck, Jamie F.; Rowe, R. Kerry

2004-11-01

Laboratory column tests conducted to gain insight regarding the biological and chemical clogging mechanisms in a porous medium are presented. To seed the porous medium with landfill bacteria, a mixture of Keele Valley Landfill and synthetic leachate permeated through the column under anaerobic conditions for the first 9 days of operation. After this, 100% synthetic leachate was used. The synthetic leachate approximated Keele Valley Landfill leachate in chemical composition but contained negligible suspended solids and bacteria compared with real leachate. The removal of volatile fatty acids (VFAs), primarily acetate, in leachate as it passed through the medium was highly correlated with the precipitation of calcium carbonate (CaCO 3(s)) from solution. The columns experienced a decrease in drainable porosity from an initial value of about 0.38 to less than 0.1 after steady state chemical oxygen demand (COD) removal, resulting in a five-order magnitude decrease in hydraulic conductivity. The decrease in drainable porosity prior to steady state COD removal was primarily due to the growth of a biofilm on the medium surface. After steady state COD removal, calcium precipitation was at least equally responsible for the decrease in drainable porosity as biofilm growth. Clog composition analyses showed that CaCO 3(s) was the dominant clog constituent and that 99% of the carbonate in the clog material was bound to calcium.

Laser Cooling of Solids

DTIC Science & Technology

2009-01-01

BN2 − CN3 + (1− ηe)BN2 (9) Here α(ν,N) is the interband absorption coefficient that in- cludes many-body and blocking factors. The recombination...the reso- nant absorption coefficient and αb is the unwanted parasitic (background) absorption coefficient . As will be derived in sections II and IV... coefficient of αb. It is straightforward to evaluate the steady-state solution to the above rate equations by setting the time derivatives to zero

A finite element analysis modeling tool for solid oxide fuel cell development: coupled electrochemistry, thermal and flow analysis in MARC®

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaleel, Mohammad A.; Lin, Zijing; Singh, Prabhakar

2004-05-03

A 3D simulation tool for modeling solid oxide fuel cells is described. The tool combines the versatility and efficiency of a commercial finite element analysis code, MARC{reg_sign}, with an in-house developed robust and flexible electrochemical (EC) module. Based upon characteristic parameters obtained experimentally and assigned by the user, the EC module calculates the current density distribution, heat generation, and fuel and oxidant species concentration, taking the temperature profile provided by MARC{reg_sign} and operating conditions such as the fuel and oxidant flow rate and the total stack output voltage or current as the input. MARC{reg_sign} performs flow and thermal analyses basedmore » on the initial and boundary thermal and flow conditions and the heat generation calculated by the EC module. The main coupling between MARC{reg_sign} and EC is for MARC{reg_sign} to supply the temperature field to EC and for EC to give the heat generation profile to MARC{reg_sign}. The loosely coupled, iterative scheme is advantageous in terms of memory requirement, numerical stability and computational efficiency. The coupling is iterated to self-consistency for a steady-state solution. Sample results for steady states as well as the startup process for stacks with different flow designs are presented to illustrate the modeling capability and numerical performance characteristic of the simulation tool.« less

Proteolytic bacterial dominance in a full-scale municipal solid waste anaerobic reactor assessed by 454 pyrosequencing technology.

PubMed

Cardinali-Rezende, Juliana; Rojas-Ojeda, Patricia; Nascimento, Andréa M A; Sanz, José L

2016-03-01

Biomethanization entails a good means to reduce the organic fraction (OF) derived from municipal solid wastes (MSW). The bacterial diversity of a full scale MSW anaerobic reactor located in Madrid (Spain) was investigated using high-throughput 454 pyrosequencing. Even though the proteolytic bacteria prevailed throughout all of the process, community shifts were observed from the start-up to the steady-state conditions, with an increasing biodiversity displayed over time. The Bacteroidetes and the Firmicutes were the majority phyla: 55.1 and 40.2% (start-up) and 18.7 and 78.7 (steady-state) of the total reads. The system's lack of evenness remains noteworthy as the sequences affiliated to the proteolytic non-saccharolytic Proteiniphylum, Gallicola and Fastidiosipila genera, together with the saccharolytic Saccharofermentans, were predominant on the system and this predominance appears to correlate with the presence of a high ammonium concentration. The 454 pyrosequencing revealed a great diversity of rare organisms which seemingly do not sustain any metabolic roles in the course of the OF-MSW degradation. However, this scarce and unique microbiota can confer great resilience to the system as a buffer against nutritional and environmental changing conditions, thus opening the door to increase the current knowledge about the bacterial community dynamics taking place during MSW treatment processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biochemomechanical poroelastic theory of avascular tumor growth

NASA Astrophysics Data System (ADS)

Xue, Shi-Lei; Li, Bo; Feng, Xi-Qiao; Gao, Huajian

2016-09-01

Tumor growth is a complex process involving genetic mutations, biochemical regulations, and mechanical deformations. In this paper, a thermodynamics-based nonlinear poroelastic theory is established to model the coupling among the mechanical, chemical, and biological mechanisms governing avascular tumor growth. A volumetric growth law accounting for mechano-chemo-biological coupled effects is proposed to describe the development of solid tumors. The regulating roles of stresses and nutrient transport in the tumor growth are revealed under different environmental constraints. We show that the mechano-chemo-biological coupling triggers anisotropic and heterogeneous growth, leading to the formation of layered structures in a growing tumor. There exists a steady state in which tumor growth is balanced by resorption. The influence of external confinements on tumor growth is also examined. A phase diagram is constructed to illustrate how the elastic modulus and thickness of the confinements jointly dictate the steady state of tumor volume. Qualitative and quantitative agreements with experimental observations indicate the developed model is capable of capturing the essential features of avascular tumor growth in various environments.

Modified septic tank-anaerobic filter unit as a two-stage onsite domestic wastewater treatment system.

PubMed

Sharma, Meena Kumari; Khursheed, Anwar; Kazmi, Absar Ahmad

2014-01-01

This study demonstrates the performance evaluation of a uniquely designed two-stage system for onsite treatment of domestic wastewater. The system consisted of two upflow anaerobic bioreactors, a modified septic tank followed by an upflow anaerobic filter, accommodated within a single cylindrical unit. The system was started up without inoculation at 24 h hydraulic retention time (HRT). It achieved a steady-state condition after 120 days. The system was observed to be remarkably efficient in removing pollutants during steady-state condition with the average removal efficiency of 88.6 +/- 3.7% for chemical oxygen demand, 86.3 +/- 4.9% for biochemical oxygen demand and 91.2 +/- 9.7% for total suspended solids. The microbial analysis revealed a high reduction (>90%) capacity of the system for indicator organism and pathogens. It also showed a very good endurance against imposed hydraulic shock load. Tracer study showed that the flow pattern was close to plug flow reactor. Mean HRT was also found to be close to the designed value.

Self-consistent modeling of CFETR baseline scenarios for steady-state operation

NASA Astrophysics Data System (ADS)

Chen, Jiale; Jian, Xiang; Chan, Vincent S.; Li, Zeyu; Deng, Zhao; Li, Guoqiang; Guo, Wenfeng; Shi, Nan; Chen, Xi; CFETR Physics Team

2017-07-01

Integrated modeling for core plasma is performed to increase confidence in the proposed baseline scenario in the 0D analysis for the China Fusion Engineering Test Reactor (CFETR). The steady-state scenarios are obtained through the consistent iterative calculation of equilibrium, transport, auxiliary heating and current drives (H&CD). Three combinations of H&CD schemes (NB + EC, NB + EC + LH, and EC + LH) are used to sustain the scenarios with q min > 2 and fusion power of ˜70-150 MW. The predicted power is within the target range for CFETR Phase I, although the confinement based on physics models is lower than that assumed in 0D analysis. Ideal MHD stability analysis shows that the scenarios are stable against n = 1-10 ideal modes, where n is the toroidal mode number. Optimization of RF current drive for the RF-only scenario is also presented. The simulation workflow for core plasma in this work provides a solid basis for a more extensive research and development effort for the physics design of CFETR.

Start-up, steady state performance and kinetic evaluation of a thermophilic integrated anaerobic-aerobic bioreactor (IAAB).

PubMed

Chan, Yi Jing; Chong, Mei Fong; Law, Chung Lim

2012-12-01

Thermophilic treatment of palm oil mill effluent (POME) was studied in a novel integrated anaerobic-aerobic bioreactor (IAAB). The IAAB was subjected to a program of steady-state operation over a range of organic loading rate (OLR)s, up to 30 g COD/L day in order to evaluate its treatment capacity. The thermophilic IAAB achieved high chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies of more than 99% for OLR up to 18.5 g COD/L day. High methane yield of 0.32 LCH(4) (STP)/g COD(removed) with compliance of the final treated effluent to the discharge limit were achieved. This is higher than that of the mesophilic system due to the higher maximum specific growth rate (μ(max)) of the thermophilic microorganisms. Besides, coupling the model of Grau second order model (anaerobic system) with the model of Monod (aerobic system) will completely define the IAAB system. Copyright © 2012 Elsevier Ltd. All rights reserved.

Benard convection in binary mixtures with Soret effects and solidification

NASA Technical Reports Server (NTRS)

Zimmermann, G.; Mueller, U.; Davis, S. H.

1992-01-01

Benard convection was studied in a two-component liquid which displayed Soret effects (Soret, 1879; DeGroot and Mazur, 1969) and in which the temperatures of the horizontal boundaries spanned the solidification temperature of the mixture. A steady basic state was observed, in which the layer is partly liquid (near the lower, heated plate) and partly solid (near the upper, cooled plate) with the interface being planar, and in which all transport is by conduction and diffusion. Linear stability of the basic state was examined to determine how the presence of solid and the ability of the material to solidify or melt under disturbance affects the critical conditions from the onset of instability. The theoretical results obtained for cases when the phase change is absent and when the Soret effects are absent (but the phase change is present) are compared with an experiment using alcohol-water mixtures.

Terahertz Measurement of the Water Content Distribution in Wood Materials

NASA Astrophysics Data System (ADS)

Bensalem, M.; Sommier, A.; Mindeguia, J. C.; Batsale, J. C.; Pradere, C.

2018-02-01

Recently, THz waves have been shown to be an effective technique for investigating the water diffusion within porous media, such as biomaterial or insulation materials. This applicability is due to the sufficient resolution for such applications and the safe levels of radiation. This study aims to achieve contactless absolute water content measurements at a steady state case in semi-transparent solids (wood) using a transmittance THz wave range setup. First, a calibration method is developed to validate an analytical model based on the Beer-Lambert law, linking the absorption coefficient, the density of the solid, and its water content. Then, an estimation of the water content on a local scale in a transient-state case (drying) is performed. This study shows that THz waves are an effective contactless, safe, and low-cost technique for the measurement of water content in a porous medium, such as wood.

Core Perylene Diimide Designs via Direct Bay- and ortho-(Poly)trifluoromethylation: Synthesis, Isolation, X-Ray Structures, Optical and Electronic Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clikeman, Tyler T.; Bukovsky, Eric V.; Wang, Xue-Bin

2015-09-22

We developed an efficient solvent- and catalyst-free direct polytrifluoromethylation of solid perylene-3,4,9,10-tetracarboxylic dianhydride that produced a new family of (poly)perfluoroalkyl bay- and ortho-substituted PDIs with two different imide substituents. Direct hydrogen substitution with CN group led to the synthesis of a cyanated perfluoroalkyl PDI derivative for the first time. Absorption, steady-state and time-resolved emission, X-ray diffraction, electrochemical, and gas-phase electron affinity data allowed for systematic studies of substitution effects at bay, ortho, and imide positions in the new PDIs. Solid-state packing showed remarkable variations in the intermolecular interactions that are important for charge transport and photophysical properties. Moreover, analysis ofmore » the electrochemical data for 143 electron poor PDIs, including newly reported compounds, revealed some general trends and peculiar effects from substituting electron-withdrawing groups at all three positions.« less

Core Perylene Diimide Designs via Direct Bay and Ortho (Poly)trifluoromethylation: Synthesis, Isolation, X-ray Structures, Optical and Electronic Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clikeman, Tyler T.; Bukovsky, Eric V.; Wang, Xue B.

2015-09-22

We developed an efficient solvent- and catalyst-free direct polytrifluoromethylation of solid perylene-3,4,9,10-tetracarboxylic dianhydride that produced a new family of (poly)perfluoroalkyl bay and ortho substituted PDIs with two different imide substituents. Direct hydrogen substitution with CN group led to the synthesis of a cyanated perfluoroalkyl PDI derivative for the first time. Absorption, steady-state and time-resolved emission, X-ray diffraction, electrochemical, and gas-phase electron affinity data allowed for systematic studies of substitution effects at bay, ortho, and imide positions in the new PDIs. Solid-state packing showed remarkable variations in the intermolecular interactions that are important for charge transport and photophysical properties. Analysis ofmore » the electrochemical data for 143 electron poor PDIs, including newly reported compounds, revealed some general trends and peculiar effects of electron withdrawing group substitution at all three positions.« less

Mimicking Nonequilibrium Steady States with Time-Periodic Driving

DTIC Science & Technology

2016-08-29

nonequilibrium steady states, and vice versa, within the theoretical framework of discrete-state stochastic thermodynamics . Nonequilibrium steady states...equilibrium [2], spontaneous relaxation towards equilibrium [3], nonequilibrium steady states generated by fixed thermodynamic forces [4], and stochastic pumps...paradigm, a system driven by fixed thermodynamic forces—such as temperature gradients or chemical potential differences— reaches a steady state in

Impact of fluid-rock chemical interactions on tracer transport in fractured rocks.

PubMed

Mukhopadhyay, Sumit; Liu, H-H; Spycher, N; Kennedy, B M

2013-11-01

In this paper, we investigate the impact of chemical interactions, in the form of mineral precipitation and dissolution reactions, on tracer transport in fractured rocks. When a tracer is introduced in fractured rocks, it moves through the fracture primarily by advection and it also enters the stagnant water of the surrounding rock matrix through diffusion. Inside the porous rock matrix, the tracer chemically interacts with the solid materials of the rock, where it can precipitate depending on the local equilibrium conditions. Alternatively, it can be dissolved from the solid phase of the rock matrix into the matrix pore water, diffuse into the flowing fluids of the fracture and is advected out of it. We show that such chemical interactions between the fluid and solid phases have significant impact on tracer transport in fractured rocks. We invoke the dual-porosity conceptualization to represent the fractured rocks and develop a semi-analytical solution to describe the transient transport of tracers in interacting fluid-rock systems. To test the accuracy and stability of the semi-analytical solution, we compare it with simulation results obtained with the TOUGHREACT simulator. We observe that, in a chemically interacting system, the tracer breakthrough curve exhibits a pseudo-steady state, where the tracer concentration remains more or less constant over a finite period of time. Such a pseudo-steady condition is not observed in a non-reactive fluid-rock system. We show that the duration of the pseudo-state depends on the physical and chemical parameters of the system, and can be exploited to extract information about the fractured rock system, such as the fracture spacing and fracture-matrix interface area. © 2013.

Mimicking Nonequilibrium Steady States with Time-Periodic Driving (Open Source)

DTIC Science & Technology

2016-05-18

nonequilibrium steady states, and vice versa, within the theoretical framework of discrete-state stochastic thermodynamics . Nonequilibrium steady states...equilibrium [2], spontaneous relaxation towards equilibrium [3], nonequilibrium steady states generated by fixed thermodynamic forces [4], and stochastic pumps...paradigm, a system driven by fixed thermodynamic forces—such as temperature gradients or chemical potential differences— reaches a steady state in

Variable-amplitude oscillatory shear response of amorphous materials.

PubMed

Perchikov, Nathan; Bouchbinder, Eran

2014-06-01

Variable-amplitude oscillatory shear tests are emerging as powerful tools to investigate and quantify the nonlinear rheology of amorphous solids, complex fluids, and biological materials. Quite a few recent experimental and atomistic simulation studies demonstrated that at low shear amplitudes, an amorphous solid settles into an amplitude- and initial-conditions-dependent dissipative limit cycle, in which back-and-forth localized particle rearrangements periodically bring the system to the same state. At sufficiently large shear amplitudes, the amorphous system loses memory of the initial conditions, exhibits chaotic particle motions accompanied by diffusive behavior, and settles into a stochastic steady state. The two regimes are separated by a transition amplitude, possibly characterized by some critical-like features. Here we argue that these observations support some of the physical assumptions embodied in the nonequilibrium thermodynamic, internal-variables based, shear-transformation-zone model of amorphous viscoplasticity; most notably that "flow defects" in amorphous solids are characterized by internal states between which they can make transitions, and that structural evolution is driven by dissipation associated with plastic deformation. We present a rather extensive theoretical analysis of the thermodynamic shear-transformation-zone model for a variable-amplitude oscillatory shear protocol, highlighting its success in accounting for various experimental and simulational observations, as well as its limitations. Our results offer a continuum-level theoretical framework for interpreting the variable-amplitude oscillatory shear response of amorphous solids and may promote additional developments.

Solid Rocket Motor Combustion Instability Modeling in COMSOL Multiphysics

NASA Technical Reports Server (NTRS)

Fischbach, Sean R.

2015-01-01

Combustion instability modeling of Solid Rocket Motors (SRM) remains a topic of active research. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process, acoustics, and steady-state gas dynamics. Recent advances in defining the energy transport of disturbances within steady flow-fields have been applied by combustion stability modelers to improve the analysis framework [1, 2, 3]. Employing this more accurate global energy balance requires a higher fidelity model of the SRM flow-field and acoustic mode shapes. The current industry standard analysis tool utilizes a one dimensional analysis of the time dependent fluid dynamics along with a quasi-three dimensional propellant grain regression model to determine the SRM ballistics. The code then couples with another application that calculates the eigenvalues of the one dimensional homogenous wave equation. The mean flow parameters and acoustic normal modes are coupled to evaluate the stability theory developed and popularized by Culick [4, 5]. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The current study employs the COMSOL multiphysics finite element framework to model the steady flow-field parameters and acoustic normal modes of a generic SRM. The study requires one way coupling of the CFD High Mach Number Flow (HMNF) and mathematics module. The HMNF module evaluates the gas flow inside of a SRM using St. Robert's law to model the solid propellant burn rate, no slip boundary conditions, and the hybrid outflow condition. Results from the HMNF model are verified by comparing the pertinent ballistics parameters with the industry standard code outputs (i.e. pressure drop, thrust, ect.). These results are then used by the coefficient form of the mathematics module to determine the complex eigenvalues of the Acoustic Velocity Potential Equation (AVPE). The mathematics model is truncated at the nozzle sonic line, where a zero flux boundary condition is self-satisfying. The remaining boundaries are modeled with a zero flux boundary condition, assuming zero acoustic absorption on all surfaces. The results of the steady-state CFD and AVPE analyses are used to calculate the linear acoustic growth rate as is defined by Flandro and Jacob [2, 3]. In order to verify the process implemented within COMSOL we first employ the Culick theory and compare the results with the industry standard. After the process is verified, the Flandro/Jacob energy balance theory is employed and results displayed.

Steady-state flow of solid CO2: preliminary results

USGS Publications Warehouse

Durham, William B.; Kirby, Stephen H.; Stern, Laura A.

1999-01-01

To help answer the question of how much solid CO2 exists in the Martian south polar cap, we performed a series of laboratory triaxial deformation experiments at constant displacement rate in compression on jacketed cylinders of pure, polycrystalline CO2. Test conditions were temperatures 150 −8 ≤ ε ≤4.3×10−4 s−1. Most of the measurements follow a constitutive law of the form ε = Aσnexp(−Q/RT), where σ is the applied differential stress, R is the gas constant, and the other constants have values as follows: A = 103 86 MPa−ns−1, n = 5.6, and Q = 33 kJ/mol. Solid CO2 is markedly weaker than water ice. Our results suggest that the south polar cap on Mars is unlikely to be predominately solid CO2, because the elevation and estimated age of the cap is difficult to reconcile with the very weak rheology of the material.

Combined anaerobic/aerobic digestion: effect of aerobic retention time on nitrogen and solids removal.

PubMed

Kim, Jongmin; Novak, John T

2011-09-01

A combined anaerobic/aerobic sludge digestion system was studied to determine the effect of aerobic solids retention time (SRT) on its solids and nitrogen removal efficiencies. After the anaerobic digester reached steady state, effluent from the anaerobic digester was fed to aerobic digesters that were operated at 2- to 5-day SRTs. The anaerobic system was fed with a mixture of primary and secondary sludge from a local municipal wastewater treatment plant. Both systems were fed once per a day. The aerobic reactor was continuously aerated with ambient air, maintaining dissolved oxygen level at 1.1 +/- 0.3 mg/L. At a 4-day or longer SRT, more than 11% additional volatile solids and 90% or greater ammonia were removed in the aerobic digester, while 32.8 mg-N/L or more nitrite/nitrate also was measured. Most total Kjeldahl nitrogen removal was via ammonia removal, while little organic nitrogen was removed in the aerobic digester.

Thermodynamic analysis of Direct Urea Solid Oxide Fuel Cell in combined heat and power applications

NASA Astrophysics Data System (ADS)

Abraham, F.; Dincer, I.

2015-12-01

This paper presents a comprehensive steady state modelling and thermodynamic analysis of Direct Urea Solid Oxide Fuel Cell integrated with Gas Turbine power cycle (DU-SOFC/GT). The use of urea as direct fuel mitigates public health and safety risks associated with the use of hydrogen and ammonia. The integration scheme in this study covers both oxygen ion-conducting solid oxide fuel cells (SOFC-O) and hydrogen proton-conducting solid oxide fuel cells (SOFC-H). Parametric case studies are carried out to investigate the effects of design and operating parameters on the overall performance of the system. The results reveal that the fuel cell exhibited the highest level of exergy destruction among other system components. Furthermore, the SOFC-O based system offers better overall performance than that with the SOFC-H option mainly due to the detrimental reverse water-gas shift reaction at the SOFC anode as well as the unique configuration of the system.

Model study on transesterification of soybean oil to biodiesel with methanol using solid base catalyst.

PubMed

Liu, Xuejun; Piao, Xianglan; Wang, Yujun; Zhu, Shenlin

2010-03-25

Modeling of the transesterification of vegetable oils to biodiesel using a solid base as a catalyst is very important because the mutual solubilities of oil and methanol will increase with the increasing biodiesel yield. The heterogeneous liquid-liquid-solid reaction system would become a liquid-solid system when the biodiesel reaches a certain content. In this work, we adopted a two-film theory and a steady state approximation assumption, then established a heterogeneous liquid-liquid-solid model in the first stage. After the diffusion coefficients on the liquid-liquid interface and the liquid-solid interface were calculated on the basis of the properties of the system, the theoretical value of biodiesel productivity changing with time was obtained. The predicted values were very near the experimental data, which indicated that the proposed models were suitable for the transesterification of soybean oil to biodiesel when solid bases were used as catalysts. Meanwhile, the model indicated that the transesterification reaction was controlled by both mass transfer and reaction. The total resistance will decrease with the increase in biodiesel yield in the liquid-liquid-solid stage. The solid base catalyst exhibited an activation energy range of 9-20 kcal/mol, which was consistent with the reported activation energy range of homogeneous catalysts.

Scattering of Microwaves by Steady-State Plasma Slabs, Columns, and Layers at Atmospheric Pressure

DTIC Science & Technology

1998-03-01

permeability unity is- (Fig 0) SÖ$ftS?S5 Pressure Plasmas Y=J7(er) . 2071 (1) where y is the complex propagation coefficient, w is the wave...a phase dependence expjtot-Yxl to a i„ ., permeability nnTty,^ J ’°SSy med’Um °f reIat<- ■j^r)^ • (1) where y is the complex propagation...preservation is an. issue. Some examples are food (solid or liquid) sterilization, pharmaceutical applications, and environmental applications ( soil

Temperature-Jump Relaxation Kinetics at Liquid/Solid Interfaces: Fluorescence Thermometry of Porous Silica Heated by a Joule Discharge

DTIC Science & Technology

1991-05-22

for understanding reaction mechanisms responsible for the steady-state behavior and determining the dispersion of rates in cases where inhomogeneities...derivatized by the following procedure. Three grams of the silica was placed in a dry reaction vessel consisting of a three neck flask, addition funnel...to the reaction vessel , taking care to avoid contact with the air. A five-fold molar equivalent excess of ODS (based on the silanol 8 density of the

Apparatus and process for controlling fluidized beds

DOEpatents

Rehmat, Amirali G.; Patel, Jitendra G.

1985-10-01

An apparatus and process for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance.

Apparatus for controlling fluidized beds

DOEpatents

Rehmat, Amirali G.; Patel, Jitendra G.

1987-05-12

An apparatus and process for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance.

Archimedes' law explains penetration of solids into granular media.

PubMed

Kang, Wenting; Feng, Yajie; Liu, Caishan; Blumenfeld, Raphael

2018-03-16

Understanding the response of granular matter to intrusion of solid objects is key to modelling many aspects of behaviour of granular matter, including plastic flow. Here we report a general model for such a quasistatic process. Using a range of experiments, we first show that the relation between the penetration depth and the force resisting it, transiently nonlinear and then linear, is scalable to a universal form. We show that the gradient of the steady-state part, K ϕ , depends only on the medium's internal friction angle, ϕ, and that it is nonlinear in μ = tan ϕ, in contrast to an existing conjecture. We further show that the intrusion of any convex solid shape satisfies a modified Archimedes' law and use this to: relate the zero-depth intercept of the linear part to K ϕ and the intruder's cross-section; explain the curve's nonlinear part in terms of the stagnant zone's development.

The effect of temperature and moisture on the amorphous-to-crystalline transformation of stavudine.

PubMed

Strydom, Schalk; Liebenberg, Wilna; Yu, Lian; de Villiers, Melgardt

2009-09-08

Stavudine is a nucleoside reverse transcriptase inhibitor active against HIV, and is known to exist in two polymorphic forms designated as forms I and II, and a hydrate form III. An amorphous solid of stavudine was successfully prepared and characterized during this investigation. A comprehensive evaluation of the stability of this amorphous solid showed that the amorphous solid transforms to either form II (anhydrous) or form III (hydrate) when exposed to temperature, in the absence or presence of moisture, respectively. The amorphous-to-hydrate transformation occurred at relatively low RH (>32%) and led to the formation of crystal aggregates of the hydrated form. Steady state growth rate analyses also showed that the amorphous-to-crystalline transformation occurs at a greater rate in the presence of moisture, compared to the transformation at the same temperature in a dry environment. Crystal growth studies showed that it is possible to stabilize the amorphous solid of stavudine against crystal transformations in the absence of moisture by coating it with poly(methyl methacrylate). However, this polymer coating could not prevent crystal growth from the amorphous solid during exposure to moisture.

On transient rheology and glacial isostasy

NASA Technical Reports Server (NTRS)

Yuen, David A.; Sabadini, Roberto C. A.; Gasperini, Paolo; Boschi, Enzo

1986-01-01

The effect of transient creep on the inference of long-term mantle viscosity is investigated using theoretical predictions from self-gravitating, layered earth models with Maxwell, Burgers' body, and standard linear solid rheologies. The interaction between transient and steady-state rheologies is studied. The responses of the standard linear solid and Burgers' body models to transient creep in the entire mantle, and of the Burgers' body and Maxwell models to creep in the lower mantle are described. The models' responses are examined in terms of the surface displacement, free air gravity anomaly, wander of the rotation pole, and the secular variation of the degree 2 zonal coefficient of the earth's gravitational potential field. The data reveal that transient creep cannot operate throughout the entire mantle.

Study of particle evolution from Composition B-3 detonation by time-resolved small angle x-ray scattering

NASA Astrophysics Data System (ADS)

Huber, R.; Podlesak, D.; Dattelbaum, D.; Firestone, M.; Gustavsen, R.; Jensen, B.; Ringstrand, B.; Watkins, E.; Bagge-Hansen, M.; Hodgin, R.; Lauderbach, L.; Willey, T.; van Buuren, T.; Graber, T.; Rigg, P.; Sinclair, N.; Seifert, S.

2017-06-01

High explosive (HE) detonations produce an assortment of gases (CO, CO2, N2) and solid carbon products (nanodiamond, graphite). The evolution of solid carbon particles, within the chemical reaction zone, help to propel the detonation wave forward. Due to the violent nature and short reaction times during HE detonations, experimental observation are limited. Through time-resolved small angle x-ray scattering (TRSAXS) we are able to observed nanocarbon formation on nanosecond time scales. This TRSAXS setup is the first of its kind in the United States at Argonne National Laboratory at the Advanced Photon Source in the Dynamic Compression Sector. From the empirical and analytical analysis of the x-ray scattering of an in-line detonation we are able to temporally follow morphology and size. Two detonation geometries were studied for the HE Comp B-3 (40% TNT/60% RDX), producing steady and overdriven conditions. Steady wave particle evolution plateaued by 2 microseconds, where overdriven condition particle size decreases at the collision of the two shock fronts then plateaus. Post detonation soot is also analyzed to confirm size and shape of nanocarbon formation from Comp B-3 detonations. LA-UR-17-21443.

Exergy optimization in a steady moving bed heat exchanger.

PubMed

Soria-Verdugo, A; Almendros-Ibáñez, J A; Ruiz-Rivas, U; Santana, D

2009-04-01

This work provides an energy and exergy optimization analysis of a moving bed heat exchanger (MBHE). The exchanger is studied as a cross-flow heat exchanger where one of the phases is a moving granular medium. The optimal MBHE dimensions and the optimal particle diameter are obtained for a range of incoming fluid flow rates. The analyses are carried out over operation data of the exchanger obtained in two ways: a numerical simulation of the steady-state problem and an analytical solution of the simplified equations, neglecting the conduction terms. The numerical simulation considers, for the solid, the convection heat transfer to the fluid and the diffusion term in both directions, and for the fluid only the convection heat transfer to the solid. The results are compared with a well-known analytical solution (neglecting conduction effects) for the temperature distribution in the exchanger. Next, the analytical solution is used to derive an expression for the exergy destruction. The optimal length of the MBHE depends mainly on the flow rate and does not depend on particle diameter unless they become very small (thus increasing sharply the pressure drop). The exergy optimal length is always smaller than the thermal one, although the difference is itself small.

A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state.

PubMed

Bencini, Andrea; Berni, Emanuela; Bianchi, Antonio; Fornasari, Patrizia; Giorgi, Claudia; Lima, Joao C; Lodeiro, Carlos; Melo, Maria J; de Melo, J Seixas; Parola, Antonio Jorge; Pina, Fernando; Pina, Joao; Valtancoli, Barbara

2004-07-21

The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.

Pseudo Steady-State Free Precession for MR-Fingerprinting.

PubMed

Assländer, Jakob; Glaser, Steffen J; Hennig, Jürgen

2017-03-01

This article discusses the signal behavior in the case the flip angle in steady-state free precession sequences is continuously varied as suggested for MR-fingerprinting sequences. Flip angle variations prevent the establishment of a steady state and introduce instabilities regarding to magnetic field inhomogeneities and intravoxel dephasing. We show how a pseudo steady state can be achieved, which restores the spin echo nature of steady-state free precession. Based on geometrical considerations, relationships between the flip angle, repetition and echo time are derived that suffice to the establishment of a pseudo steady state. The theory is tested with Bloch simulations as well as phantom and in vivo experiments. A typical steady-state free precession passband can be restored with the proposed conditions. The stability of the pseudo steady state is demonstrated by comparing the evolution of the signal of a single isochromat to one resulting from a spin ensemble. As confirmed by experiments, magnetization in a pseudo steady state can be described with fewer degrees of freedom compared to the original fingerprinting and the pseudo steady state results in more reliable parameter maps. The proposed conditions restore the spin-echo-like signal behavior typical for steady-state free precession in fingerprinting sequences, making this approach more robust to B 0 variations. Magn Reson Med 77:1151-1161, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Mechanism for multiplicity of steady states with distinct cell concentration in continuous culture of mammalian cells.

PubMed

Yongky, Andrew; Lee, Jongchan; Le, Tung; Mulukutla, Bhanu Chandra; Daoutidis, Prodromos; Hu, Wei-Shou

2015-07-01

Continuous culture for the production of biopharmaceutical proteins offers the possibility of steady state operations and thus more consistent product quality and increased productivity. Under some conditions, multiplicity of steady states has been observed in continuous cultures of mammalian cells, wherein with the same dilution rate and feed nutrient composition, steady states with very different cell and product concentrations may be reached. At those different steady states, cells may exhibit a high glycolysis flux with high lactate production and low cell concentration, or a low glycolysis flux with low lactate and high cell concentration. These different steady states, with different cell concentration, also have different productivity. Developing a mechanistic understanding of the occurrence of steady state multiplicity and devising a strategy to steer the culture toward the desired steady state is critical. We establish a multi-scale kinetic model that integrates a mechanistic intracellular metabolic model and cell growth model in a continuous bioreactor. We show that steady state multiplicity exists in a range of dilution rate in continuous culture as a result of the bistable behavior in glycolysis. The insights from the model were used to devise strategies to guide the culture to the desired steady state in the multiple steady state region. The model provides a guideline principle in the design of continuous culture processes of mammalian cells. © 2015 Wiley Periodicals, Inc.

Channelization in porous media driven by erosion and deposition.

PubMed

Jäger, R; Mendoza, M; Herrmann, H J

2017-01-01

We develop and validate a new model to study simultaneous erosion and deposition in three-dimensional porous media. We study the changes of the porous structure induced by the deposition and erosion of matter on the solid surface and find that when both processes are active, channelization in the porous structure always occurs. The channels can be stable or only temporary depending mainly on the driving mechanism. Whereas a fluid driven by a constant pressure drop in general does not form steady channels, imposing a constant flux always produces stable channels within the porous structure. Furthermore we investigate how changes of the local deposition and erosion properties affect the final state of the porous structure, finding that the larger the range of wall shear stress for which there is neither erosion nor deposition, the more steady channels are formed in the structure.

Finite element analysis of the effect of a non-planar solid-liquid interface on the lateral solute segregation during unidirectional solidification

NASA Technical Reports Server (NTRS)

Carlson, F. M.; Chin, L.-Y.; Fripp, A. L.; Crouch, R. K.

1982-01-01

The effect of solid-liquid interface shape on lateral solute segregation during steady-state unidirectional solidification of a binary mixture is calculated under the assumption of no convection in the liquid. A finite element technique is employed to compute the concentration field in the liquid and the lateral segregation in the solid with a curved boundary between the liquid and solid phases. The computational model is constructed assuming knowledge of the solid-liquid interface shape; no attempt is made to relate this shape to the thermal field. The influence of interface curvature on the lateral compositional variation is investigated over a range of system parameters including diffusivity, growth speed, distribution coefficient, and geometric factors of the system. In the limiting case of a slightly nonplanar interface, numerical results from the finite element technique are in good agreement with the analytical solutions of Coriell and Sekerka obtained by using linear theory. For the general case of highly non-planar interface shapes, the linear theory fails and the concentration field in the liquid as well as the lateral solute segregation in the solid can be calculated by using the finite element method.

Monitoring Thermal Performance of Hollow Bricks with Different Cavity Fillers in Difference Climate Conditions

NASA Astrophysics Data System (ADS)

Pavlík, Zbyšek; Jerman, Miloš; Fořt, Jan; Černý, Robert

2015-03-01

Hollow brick blocks have found widespread use in the building industry during the last decades. The increasing requirements to the thermal insulation properties of building envelopes given by the national standards in Europe led the brick producers to reduce the production of common solid bricks. Brick blocks with more or less complex systems of internal cavities replaced the traditional bricks and became dominant on the building ceramics market. However, contrary to the solid bricks where the thermal conductivity can easily be measured by standard methods, the complex geometry of hollow brick blocks makes the application of common techniques impossible. In this paper, a steady-state technique utilizing a system of two climatic chambers separated by a connecting tunnel for sample positioning is used for the determination of the thermal conductivity, thermal resistance, and thermal transmittance ( U value) of hollow bricks with the cavities filled by air, two different types of mineral wool, polystyrene balls, and foam polyurethane. The particular brick block is provided with the necessary temperature- and heat-flux sensors and thermally insulated in the tunnel. In the climatic chambers, different temperatures are set. After steady-state conditions are established in the measuring system, the effective thermal properties of the brick block are calculated using the measured data. Experimental results show that the best results are achieved with hydrophilic mineral wool as a cavity filler; the worst performance exhibits the brick block with air-filled cavities.

Localized Ignition And Subsequent Flame Spread Over Solid Fuels In Microgravity

NASA Technical Reports Server (NTRS)

Kashiwagi, T.; Nakamura, Y.; Prasad, K.; Baum, H.; Olson, S.; Fujita, O.; Nishizawa, K.; Ito, K.

2003-01-01

Localized ignition is initiated by an external radiant source at the middle of a thin solid sheet under external slow flow, simulating fire initiation in a spacecraft with a slow ventilation flow. Ignition behavior, subsequent transition simultaneously to upstream and downstream flame spread, and flame growth behavior are studied theoretically and experimentally. There are two transition stages in this study; one is the first transition from the onset of the ignition to form an initial anchored flame close to the sample surface, near the ignited area. The second transition is the flame growth stage from the anchored flame to a steady fire spread state (i.e. no change in flame size or in heat release rate) or a quasi-steady state, if either exists. Observations of experimental spot ignition characteristics and of the second transition over a thermally thin paper were made to determine the effects of external flow velocity. Both transitions have been studied theoretically to determine the effects of the confinement by a relatively small test chamber, of the ignition configuration (ignition across the sample width vs spot ignition), and of the external flow velocity on the two transitions over a thermally thin paper. This study is currently extending to two new areas; one is to include a thermoplastic sample such poly(methymethacrylate), PMMA, and the other is to determine the effects of sample thickness on the transitions. The recent results of these new studies on the first transition are briefly reported.

CFD Assessment of Forward Booster Separation Motor Ignition Overpressure on ET XT 718 Ice/Frost Ramp

NASA Technical Reports Server (NTRS)

Tejnil, Edward; Rogers, Stuart E.

2012-01-01

Computational fluid dynamics assessment of the forward booster separation motor ignition over-pressure was performed on the space shuttle external tank X(sub T) 718 ice/frost ramp using the flow solver OVERFLOW. The main objective of this study was the investigation of the over-pressure during solid rocket booster separation and its affect on the local pressure and air-load environments. Delta pressure and plume impingement were investigated as a possible contributing factor to the cause of the debris loss on shuttle missions STS-125 and STS-127. A simplified computational model of the Space Shuttle Launch Vehicle was developed consisting of just the external tank and the solid rocket boosters with separation motor nozzles and plumes. The simplified model was validated by comparison to full fidelity computational model of the Space Shuttle without the separation motors. Quasi steady-state plume solutions were used to calibrate the thrust of the separation motors. Time-accurate simulations of the firing of the booster-separation motors were performed. Parametric studies of the time-step size and the number of sub-iterations were used to find the best converged solution. The computed solutions were compared to previous OVERFLOW steady-state runs of the separation motors with reaction control system jets and to ground test data. The results indicated that delta pressure from the overpressure was small and within design limits, and thus was unlikely to have contributed to the foam losses.

THE INFLUENCE OF MAGNETIC FIELD GEOMETRY ON THE FORMATION OF CLOSE-IN EXOPLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, Jacob B., E-mail: jbsimon.astro@gmail.com

2016-08-20

Approximately half of Sun-like stars harbor exoplanets packed within a radius of ∼0.3 au, but the formation of these planets and why they form in only half of known systems are still not well understood. We employ a one-dimensional steady-state model to gain physical insight into the origin of these close-in exoplanets. We use Shakura and Sunyaev α values extracted from recent numerical simulations of protoplanetary disk accretion processes in which the magnitude of α , and thus the steady-state gas surface density, depend on the orientation of large-scale magnetic fields with respect to the disk’s rotation axis. Solving formore » the metallicity as a function of radius, we find that for fields anti-aligned with the rotation axis, the inner regions of our model disk often fall within a region of parameter space that is not suitable for planetesimal formation, whereas in the aligned case, the inner disk regions are likely to produce planetesimals through some combination of streaming instability and gravitational collapse, though the degree to which this is true depends on the assumed parameters of our model. More robustly, the aligned field case always produces higher concentrations of solids at small radii compared to the anti-aligned case. In the in situ formation model, this bimodal distribution of solid enhancement leads directly to the observed dichotomy in exoplanet orbital distances.« less

Total-dose radiation effects data for semiconductor devices, volume 3

NASA Technical Reports Server (NTRS)

Price, W. E.; Martin, K. E.; Nichols, D. K.; Gauthier, M. K.; Brown, S. F.

1982-01-01

Volume 3 of this three-volume set provides a detailed analysis of the data in Volumes 1 and 2, most of which was generated for the Galileo Orbiter Program in support of NASA space programs. Volume 1 includes total ionizing dose radiation test data on diodes, bipolar transistors, field effect transistors, and miscellaneous discrete solid-state devices. Volume 2 includes similar data on integrated circuits and a few large-scale integrated circuits. The data of Volumes 1 and 2 are combined in graphic format in Volume 3 to provide a comparison of radiation sensitivities of devices of a given type and different manufacturer, a comparison of multiple tests for a single data code, a comparison of multiple tests for a single lot, and a comparison of radiation sensitivities vs time (date codes). All data were generated using a steady-state 2.5-MeV electron source (Dynamitron) or a Cobalt-60 gamma ray source. The data that compose Volume 3 represent 26 different device types, 224 tests, and a total of 1040 devices. A comparison of the effects of steady-state electrons and Cobat-60 gamma rays is also presented.

Apparatus for the measurement of electrical resistivity, Seebeck coefficient, and thermal conductivity of thermoelectric materials between 300 K and 12 K

NASA Astrophysics Data System (ADS)

Martin, Joshua; Nolas, George S.

2016-01-01

We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials.

MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

NASA Technical Reports Server (NTRS)

Poirier, D. R.; Maples, A. L.

1985-01-01

Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys.

Quasi-steady state conditions in heterogeneous aquifers during pumping tests

NASA Astrophysics Data System (ADS)

Zha, Yuanyuan; Yeh, Tian-Chyi J.; Shi, Liangsheng; Huang, Shao-Yang; Wang, Wenke; Wen, Jet-Chau

2017-08-01

Classical Thiem's well hydraulic theory, other aquifer test analyses, and flow modeling efforts often assume the existence of ;quasi-steady; state conditions. That is, while drawdowns due to pumping continue to grow, the hydraulic gradient in the vicinity of the pumping well does not change significantly. These conditions have built upon two-dimensional and equivalent homogeneous conceptual models, but few field data have been available to affirm the existence of these conditions. Moreover, effects of heterogeneity and three-dimensional flow on this quasi-steady state concept have not been thoroughly investigated and discussed before. In this study, we first present a quantitative definition of quasi-steady state (or steady-shape conditions) and steady state conditions based on the analytical solution of two- or three-dimensional flow induced by pumping in unbounded, homogeneous aquifers. Afterward, we use a stochastic analysis to investigate the influence of heterogeneity on the quasi-steady state concept in heterogeneous aquifers. The results of the analysis indicate that the time to reach an approximate quasi-steady state in a heterogeneous aquifer could be quite different from that estimated based on a homogeneous model. We find that heterogeneity of aquifer properties, especially hydraulic conductivity, impedes the development of the quasi-steady state condition before the flow reaching steady state. Finally, 280 drawdown-time data from the hydraulic tomographic survey conducted at a field site corroborate our finding that the quasi-steady state condition likely would not take place in heterogeneous aquifers unless pumping tests last a long period. Research significance (1) Approximate quasi-steady and steady state conditions are defined for two- or three-dimensional flow induced by pumping in unbounded, equivalent homogeneous aquifers. (2) Analysis demonstrates effects of boundary condition, well screen interval, and heterogeneity of parameters on the existence of the quasi-steady, and validity of approximate quasi-steady concept. (3) Temporal evaluation of information content about heterogeneity in head observations are analyzed in heterogeneous aquifer. (4) 280 observed drawdown-time data corroborate the stochastic analysis that quasi-steady is difficult to reach in highly heterogeneous aquifers.

Using bioprocess stoichiometry to build a plant-wide mass balance based steady-state WWTP model.

PubMed

Ekama, G A

2009-05-01

Steady-state models are useful for design of wastewater treatment plants (WWTPs) because they allow reactor sizes and interconnecting flows to be simply determined from explicit equations in terms of unit operation performance criteria. Once the overall WWTP scheme is established and the main system defining parameters of the individual unit operations estimated, dynamic models can be applied to the connected unit operations to refine their design and evaluate their performance under dynamic flow and load conditions. To model anaerobic digestion (AD) within plant-wide WWTP models, not only COD and nitrogen (N) but also carbon (C) fluxes entering the AD need to be defined. Current plant-wide models, like benchmark simulation model No 2 (BSM2), impose a C flux at the AD influent. In this paper, the COD and N mass balance steady-state models of activated sludge (AS) organics degradation, nitrification and denitrification (ND) and anaerobic (AD) and aerobic (AerD) digestion of wastewater sludge are extended and linked with bioprocess transformation stoichiometry to form C, H, O, N, chemical oxygen demand (COD) and charge mass balance based models so that also C (and H and O) can be tracked through the whole WWTP. By assigning a stoichiometric composition (x, y, z and a in C(x)H(y)O(z)N(a)) to each of the five main influent wastewater organic fractions and ammonia, these, and the products generated from them via the biological processes, are tracked through the WWTP. The model is applied to two theoretical case study WWTPs treating the same raw wastewater (WW) to the same final sludge residual biodegradable COD. It is demonstrated that much useful information can be generated with the relatively simple steady-state models to aid WWTP layout design and track the different products exiting the WWTP via the solid, liquid and gas streams, such as aerobic versus anaerobic digestion of waste activated sludge, N loads in recycle streams, methane production for energy recovery and green house gas (CO(2), CH(4)) generation. To reduce trial and error usage of WWTP simulation software, it is recommended that they are extended to include pre-processors based on mass balance steady-state models to assist with WWTP layout design, unit operation selection, reactor sizing, option evaluation and comparison and wastewater characterization before dynamic simulation.

Estimating systemic exposure to levonorgestrel from an oral contraceptive.

PubMed

Basaraba, Cale N; Westhoff, Carolyn L; Pike, Malcolm C; Nandakumar, Renu; Cremers, Serge

2017-04-01

The gold standard for measuring oral contraceptive (OC) pharmacokinetics is the 24-h steady-state area under the curve (AUC). We conducted this study to assess whether limited sampling at steady state or measurements following use of one or two OCs could provide an adequate proxy in epidemiological studies for the progestin 24-h steady-state AUC of a particular OC. We conducted a 13-sample, 24-h pharmacokinetic study on both day 1 and day 21 of the first cycle of a monophasic OC containing 30-mcg ethinyl estradiol and 150-mcg levonorgestrel (LNG) in 17 normal-weight healthy White women and a single-dose 9-sample study of the same OC after a 1-month washout. We compared the 13-sample steady-state results with several steady-state and single-dose results calculated using parsimonious sampling schemes. The 13-sample steady-state 24-h LNG AUC was highly correlated with the steady-state 24-h trough value [r=0.95; 95% confidence interval (0.85, 0.98)] and with the steady-state 6-, 8-, 12- and 16-h values (0.92≤r≤0.95). The trough values after one or two doses were moderately correlated with the steady-state 24-h AUC value [r=0.70; 95% CI (0.27, 0.90) and 0.77; 95% CI (0.40, 0.92), respectively]. Single time-point concentrations at steady state and after administration of one or two OCs gave highly to moderately correlated estimates of steady-state LNG AUC. Using such measures could facilitate prospective pharmaco-epidemiologic studies of the OC and its side effects. A single time-point LNG concentration at steady state is an excellent proxy for complete and resource-intensive steady-state AUC measurement. The trough level after two single doses is a fair proxy for steady-state AUC. These results provide practical tools to facilitate large studies to investigate the relationship between systemic LNG exposure and side effects in a real-life setting. Copyright © 2017 Elsevier Inc. All rights reserved.

Enhancing emotional-based target prediction

NASA Astrophysics Data System (ADS)

Gosnell, Michael; Woodley, Robert

2008-04-01

This work extends existing agent-based target movement prediction to include key ideas of behavioral inertia, steady states, and catastrophic change from existing psychological, sociological, and mathematical work. Existing target prediction work inherently assumes a single steady state for target behavior, and attempts to classify behavior based on a single emotional state set. The enhanced, emotional-based target prediction maintains up to three distinct steady states, or typical behaviors, based on a target's operating conditions and observed behaviors. Each steady state has an associated behavioral inertia, similar to the standard deviation of behaviors within that state. The enhanced prediction framework also allows steady state transitions through catastrophic change and individual steady states could be used in an offline analysis with additional modeling efforts to better predict anticipated target reactions.

Steady- and non-steady-state carbonate-silicate controls on atmospheric CO2

USGS Publications Warehouse

Sundquist, E.T.

1991-01-01

Two contrasting hypotheses have recently been proposed for the past long-term relation between atmospheric CO2 and the carbonate-silicate geochemical cycle. One approach (Berner, 1990) suggests that CO2 levels have varied in a manner that has maintained chemical weathering and carbonate sedimentation at a steady state with respect to tectonically controlled decarbonation reactions. A second approach (Raymo et al., 1988), applied specificlly to the late Cenozoic, suggests a decrease in CO2 caused by an uplift-induced increase in chemical weathering, without regard to the rate of decarbonation. According to the steady-state (first) hypothesis, increased weathering and carbonate sedimentation are generally associated with increasing atmospheric CO2, whereas the uplift (second) hypothesis implies decreasing CO2 under the same conditions. An ocean-atmosphere-sediment model has been used to assess the response of atmospheric CO2 and carbonate sedimentation to global perturbations in chemical weathering and decarbonation reactions. Although this assessment is theoretical and cannot yet be related to the geologic record, the model simulations compare steady-state and non-steady-state carbonate-silicate cycle response. The e-fold response time of the 'CO2-weathering' feedback mechanism is between 300 and 400 ka. The response of carbonate sedimentation is much more rapid. These response times provide a measure of the strength of steady-state assumptions, and imply that certain systematic relations are sustained throughout steady-state and non-steady-state scenarios for the carbonate-silicate cycle. The simulations suggest that feedbacks can maintain the system near a steady state, but that non-steady-state effects may contribute to long-term trends. The steady-state and uplift hypotheses are not necessarily incompatible over time scales of a few million years. ?? 1991.

Sequential batch thermophilic solid-state anaerobic digestion of lignocellulosic biomass via recirculating digestate as inoculum - Part II: Microbial diversity and succession.

PubMed

Lin, Long; Yu, Zhongtang; Li, Yebo

2017-10-01

This study aimed to investigate the effect of recirculation of digestate as inoculum on the microbial communities in thermophilic solid-state anaerobic digestion (SS-AD) of yard trimmings. The SS-AD consisted of 4 consecutive runs (30days/run), with digestate from the previous run being used as the inoculum of the subsequent run. Bacterial and archaeal communities (day 0, 4, 8, 12, 20, and 30) were examined using Illumina sequencing of 16S rRNA genes. The results revealed substantial microbial succession toward increased diversity until run 3. The proportions of Firmicutes that contained cellulolytic bacteria doubled, which might explain the concomitantly increased cellulose degradation and volatile fatty acids (VFAs). Clostridia and Thermotogae appeared to correlate with VFAs. The VFA accumulation likely induced dynamic shifts of methanogens, particularly to hydrogenotrophic Methanothermobacter, implying that non-acetoclastic oxidative pathway dominated during the steady-state thermophilic SS-AD. This study suggested that recirculating SS-AD digestate might be an effective way for inoculation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Study of Solid-State Diffusion of Bi in Polycrystalline Sn Using Electron Probe Microanalysis

NASA Astrophysics Data System (ADS)

Delhaise, André M.; Perovic, Doug D.

2018-03-01

Current lead-free solders such as SAC305 exhibit degradation in microstructure, properties, and reliability. Current third-generation alloys containing bismuth (Bi) demonstrate preservation of strength after aging; this is accompanied by homogenization of the Bi precipitates in the tin (Sn) matrix, driven via solid-state diffusion. This study quantifies the diffusion of Bi in Sn. Diffusion couples were prepared by mating together polished samples of pure Sn and Bi. Couples were annealed at one of three temperatures, viz. 85°C for 7 days, 100°C for 2 days, or 125°C for 1 day. After cross-sectioning the couples to examine the diffusion microstructure and grain size, elemental analysis was performed using electron probe microanalysis. For this study, it was assumed that the diffusivity of Bi in Sn is concentration dependent, therefore inverse methods were used to solve Fick's non-steady-state diffusion equation. In addition, Darken analysis was used to extract the impurity diffusivity of Bi in Sn at each temperature, allowing estimation of the Arrhenius parameters D 0 and k A.

Pretreatment of a primary and secondary sludge blend at different thermal hydrolysis temperatures: Impacts on anaerobic digestion, dewatering and filtrate characteristics.

PubMed

Higgins, Matthew J; Beightol, Steven; Mandahar, Ushma; Suzuki, Ryu; Xiao, Steven; Lu, Hung-Wei; Le, Trung; Mah, Joshua; Pathak, Bipin; DeClippeleir, Haydee; Novak, John T; Al-Omari, Ahmed; Murthy, Sudhir N

2017-10-01

A study was performed to evaluate the effect of thermal hydrolysis pretreatment (THP) temperature on subsequent digestion performance and operation, as well as downstream parameters such as dewatering and cake quality. A blend of primary and secondary solids from the Blue Plains treatment plant in Washington, DC was dewatered to about 16% total solids (TS), and thermally hydrolyzed at five different temperatures 130, 140, 150, 160, 170 °C. The thermally hydrolyzed solids were then fed to five separate, 10 L laboratory digesters using the same feed concentration, 10.5% TS and a solids retention time (SRT) of 15 days. The digesters were operated over a six month period to achieve steady state conditions. The higher thermal hydrolysis temperatures generally improved the solids reduction and methane yields by about 5-6% over the temperature range. The increased temperature reduced viscosity of the solids and increased the cake solids after dewatering. The dissolved organic nitrogen and UV absorbance generally increased at the higher THP temperatures. Overall, operating at a higher temperature improved performance with a tradeoff of higher dissolved organic nitrogen and UV adsorbing materials in the return liquor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.

2012-01-01

Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.

Operating Deflection Shapes for the Space Shuttle Partial Stack Rollout

NASA Technical Reports Server (NTRS)

Buehrle, Ralph D.; Kappus, Kathy

2005-01-01

In November of 2003 a rollout test was performed to gain a better understanding of the dynamic environment for the Space Shuttle during transportation from the Vehicle Assembly Building to the launch pad. This was part of a study evaluating the methodology for including the rollout dynamic loads in the Space Shuttle fatigue life predictions. The rollout test was conducted with a partial stack consisting of the Crawler Transporter, Mobile Launch Platform, and the Solid Rocket Boosters with an interconnecting crossbeam. Instrumentation included over 100 accelerometers. Data was recorded for steady state speeds, start-ups and stops, and ambient wind excitations with the vehicle at idle. This paper will describe the operating deflection shape analysis performed using the measured acceleration response data. The response data for the steady state speed runs were dominated by harmonics of the forcing frequencies, which were proportional to the vehicle speed. Assuming a broadband excitation for the wind, analyses of the data sets with the vehicle at idle were used to estimate the natural frequencies and corresponding mode shapes. Comparisons of the measured modal properties with numerical predictions are presented.

Pulsed plasma solid propellant microthruster for the synchronous meteorological satellite. Task 4: Engineering model fabrication and test report

NASA Technical Reports Server (NTRS)

Guman, W. J. (Editor)

1972-01-01

Two flight prototype solid propellant pulsed plasma microthruster propulsion systems for the SMS satellite were fabricated, assembled and tested. The propulsion system is a completely self contained system requiring only three electrical inputs to operate: a 29.4 volt power source, a 28 volt enable signal and a 50 millsec long command fire signal that can be applied at any rate from 50 ppm to 110 ppm. The thrust level can be varied over a range 2.2 to 1 at constant impulse bit amplitude. By controlling the duration of the 28 volt enable either steady state thrust or a series of discrete impulse bits can be generated. A new technique of capacitor charging was implemented to reduce high voltage stress on energy storage capacitors.

Steady States, Fluctuation-Dissipation Theorems and Homogenization for Reversible Diffusions in a Random Environment

NASA Astrophysics Data System (ADS)

Mathieu, P.; Piatnitski, A.

2018-04-01

Prolongating our previous paper on the Einstein relation, we study the motion of a particle diffusing in a random reversible environment when subject to a small external forcing. In order to describe the long time behavior of the particle, we introduce the notions of steady state and weak steady state. We establish the continuity of weak steady states for an ergodic and uniformly elliptic environment. When the environment has finite range of dependence, we prove the existence of the steady state and weak steady state and compute its derivative at a vanishing force. Thus we obtain a complete `fluctuation-dissipation Theorem' in this context as well as the continuity of the effective variance.

Dielectrics for long term space exposure and spacecraft charging: A briefing

NASA Technical Reports Server (NTRS)

Frederickson, A. R.

1989-01-01

Charging of dielectrics is a bulk, not a surface property. Radiation driven charge stops within the bulk and is not quickly conducted to the surface. Very large electric fields develop in the bulk due to this stopped charge. At space radiation levels, it typically requires hours or days for the internal electric fields to reach steady state. The resulting electric fields are large enough to produce electrical failure within the insulator. This type failure is thought to produce nearly all electric discharge anomalies. Radiation also induces bond breakage, creates reactive radicals, displaces atoms and, in general, severely changes the chemistry of the solid state material. Electric fields can alter this process by reacting with charged species, driving them through the solid. Irradiated polymers often lose as much as a percent of their mass, or more, at exposures typical in space. Very different aging or contaminant emission can be induced by the stopped charge electric fields. These radiation effects are detailed.

A multi-level simulation platform of natural gas internal reforming solid oxide fuel cell-gas turbine hybrid generation system - Part II. Balancing units model library and system simulation

NASA Astrophysics Data System (ADS)

Bao, Cheng; Cai, Ningsheng; Croiset, Eric

2011-10-01

Following our integrated hierarchical modeling framework of natural gas internal reforming solid oxide fuel cell (IRSOFC), this paper firstly introduces the model libraries of main balancing units, including some state-of-the-art achievements and our specific work. Based on gPROMS programming code, flexible configuration and modular design are fully realized by specifying graphically all unit models in each level. Via comparison with the steady-state experimental data of Siemens-Westinghouse demonstration system, the in-house multi-level SOFC-gas turbine (GT) simulation platform is validated to be more accurate than the advanced power system analysis tool (APSAT). Moreover, some units of the demonstration system are designed reversely for analysis of a typically part-load transient process. The framework of distributed and dynamic modeling in most of units is significant for the development of control strategies in the future.

Steady state volcanism - Evidence from eruption histories of polygenetic volcanoes

NASA Technical Reports Server (NTRS)

Wadge, G.

1982-01-01

Cumulative volcano volume curves are presented as evidence for steady-state behavior at certain volcanoes and to develop a model of steady-state volcanism. A minimum criteria of five eruptions over a year was chosen to characterize a steady-state volcano. The subsequent model features a constant head of magmatic pressure from a reservoir supplied from depth, a sawtooth curve produced by the magma arrivals or discharge from the subvolcanic reservoir, large volume eruptions with long repose periods, and conditions of nonsupply of magma. The behavior of Mts. Etna, Nyamuragira, and Kilauea are described and show continuous levels of plasma output resulting in cumulative volume increases. Further discussion is made of steady-state andesitic and dacitic volcanism, long term patterns of the steady state, and magma storage, and the lack of a sufficient number of steady-state volcanoes in the world is taken as evidence that further data is required for a comprehensive model.

Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05

USGS Publications Warehouse

Iverson, R.M.; Dzurisin, D.; Gardner, C.A.; Gerlach, T.M.; LaHusen, R.G.; Lisowski, M.; Major, J.J.; Malone, S.D.; Messerich, J.A.; Moran, S.C.; Pallister, J.S.; Qamar, A.I.; Schilling, S.P.; Vallance, J.W.

2006-01-01

The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption. ??2006 Nature Publishing Group.

High-speed schlieren imaging of rocket exhaust plumes

NASA Astrophysics Data System (ADS)

Coultas-McKenney, Caralyn; Winter, Kyle; Hargather, Michael

2016-11-01

Experiments are conducted to examine the exhaust of a variety of rocket engines. The rocket engines are mounted in a schlieren system to allow high-speed imaging of the engine exhaust during startup, steady state, and shutdown. A variety of rocket engines are explored including a research-scale liquid rocket engine, consumer/amateur solid rocket motors, and water bottle rockets. Comparisons of the exhaust characteristics, thrust and cost for this range of rockets is presented. The variety of nozzle designs, target functions, and propellant type provides unique variations in the schlieren imaging.

Aerobic landfill bioreactor

DOEpatents

Hudgins, Mark P; Bessette, Bernard J; March, John; McComb, Scott T.

2000-01-01

The present invention includes a method of decomposing municipal solid waste (MSW) within a landfill by converting the landfill to aerobic degradation in the following manner: (1) injecting air via the landfill leachate collection system (2) injecting air via vertical air injection wells installed within the waste mass; (3) applying leachate to the waste mass using a pressurized drip irrigation system; (4) allowing landfill gases to vent; and (5) adjusting air injection and recirculated leachate to achieve a 40% to 60% moisture level and a temperature between 120.degree. F. and 140.degree. F. in steady state.

Aerobic landfill bioreactor

DOEpatents

Hudgins, Mark P; Bessette, Bernard J; March, John C; McComb, Scott T.

2002-01-01

The present invention includes a system of decomposing municipal solid waste (MSW) within a landfill by converting the landfill to aerobic degradation in the following manner: (1) injecting air via the landfill leachate collection system (2) injecting air via vertical air injection wells installed within the waste mass; (3) applying leachate to the waste mass using a pressurized drip irrigation system; (4) allowing landfill gases to vent; and (5) adjusting air injection and recirculated leachate to achieve a 40% to 60% moisture level and a temperature between 120.degree. F. and 140.degree. F. in steady state.

Mass balances for a biological life support system simulation model

NASA Technical Reports Server (NTRS)

Volk, Tyler; Rumel, John D.

1987-01-01

Design decisions to aid the development of future space-based biological life support systems (BLSS) can be made with simulation models. Here the biochemical stoichiometry is developed for: (1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible parts of plants; (2) food consumption and production of organic solids in urine, feces, and wash water by the humans; and (3) operation of the waste processor. Flux values for all components are derived for a steady-state system with wheat as the sole food source.

Apparatus for controlling fluidized beds

DOEpatents

Rehmat, A.G.; Patel, J.G.

1987-05-12

An apparatus and process are disclosed for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance. 2 figs.

The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases

NASA Technical Reports Server (NTRS)

Sagan, C.; Chyba, C.

1997-01-01

Atmospheric mixing ratios of approximately 10(-5 +/- 1) for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing.

Estimating Systemic Exposure to Levonorgestrel from an Oral Contraceptive

PubMed Central

Basaraba, Cale N; Westhoff, Carolyn L; Pike, Malcolm C; Nandakumar, Renu; Cremers, Serge

2017-01-01

Objective The gold standard for measuring oral contraceptive (OC) pharmacokinetics is the 24-hour steady-state area-under-the-curve (AUC). We conducted this study to assess whether limited sampling at steady state or measurements following use of one or two OCs could provide an adequate proxy in epidemiological studies for the progestin 24-hour steady-state AUC of a particular OC. Study Design We conducted a 13-sample, 24-hour pharmacokinetic study on both day 1 and day 21 of the first cycle of a monophasic OC containing 30 μg ethinyl estradiol and 150 μg levonorgestrel (LNG) in 17 normal-weight healthy white women, and a single-dose 9-sample study of the same OC after a one-month washout. We compared the 13-sample steady-state results with several steady-state and single-dose results calculated using parsimonious sampling schemes. Results The 13-sample steady-state 24-hour LNG AUC was highly correlated with the steady-state 24-hour trough value (r = 0.95; 95% CI [0.85, 0.98]) and with the steady-state 6, 8, 12 and 16-hour values (0.92 ≤ r ≤ 0.95). The trough values after one or two doses were moderately correlated with the steady-state 24-hour AUC value (r = 0.70; 95% CI [0.27, 0.90] and 0.77; 95% CI [0.40, 0.92], respectively). Conclusions Single time-point concentrations at steady-state and after administration of one or two OCs gave highly to moderately correlated estimates of steady-state LNG AUC. Using such measures could facilitate prospective pharmaco-epidemiologic studies of the OC and its side effects. PMID:28041990

Nonequilibrium steady states and resonant tunneling in time-periodically driven systems with interactions

NASA Astrophysics Data System (ADS)

Qin, Tao; Hofstetter, Walter

2018-03-01

Time-periodically driven systems are a versatile toolbox for realizing interesting effective Hamiltonians. Heating, caused by excitations to high-energy states, is a challenge for experiments. While most setups so far address the relatively weakly interacting regime, it is of general interest to study heating in strongly correlated systems. Using Floquet dynamical mean-field theory, we study nonequilibrium steady states (NESS) in the Falicov-Kimball model, with time-periodically driven kinetic energy or interaction. We systematically investigate the nonequilibrium properties of the NESS. For a driven kinetic energy, we show that resonant tunneling, where the interaction is an integer multiple of the driving frequency, plays an important role in the heating. In the strongly correlated regime, we show that this can be well understood using Fermi's golden rule and the Schrieffer-Wolff transformation for a time-periodically driven system. We furthermore demonstrate that resonant tunneling can be used to control the population of Floquet states to achieve "photodoping." For driven interactions introduced by an oscillating magnetic field near a widely adopted Feshbach resonance, we find that the double occupancy is strongly modulated. Our calculations apply to shaken ultracold-atom systems and to solid-state systems in a spatially uniform but time-dependent electric field. They are also closely related to lattice modulation spectroscopy. Our calculations are helpful to understand the latest experiments on strongly correlated Floquet systems.

Comparative photoluminescence study of close-packed and colloidal InP/ZnS quantum dots

NASA Astrophysics Data System (ADS)

Thuy, Ung Thi Dieu; Thuy, Pham Thi; Liem, Nguyen Quang; Li, Liang; Reiss, Peter

2010-02-01

This letter reports on the comparative photoluminescence study of InP/ZnS quantum dots in the close-packed solid state and in colloidal solution. The steady-state photoluminescence spectrum of the close-packed InP/ZnS quantum dots peaks at a longer wavelength than that of the colloidal ones. Time-resolved photoluminescence shows that the close-packed quantum dots possess a shorter luminescence decay time and strongly increased spectral shift with the time delayed from the excitation moment in comparison with the colloidal ones. The observed behavior is discussed on the basis of energy transfer enabled by the short interparticle distance between the close-packed quantum dots.

Multimode optical fibers: steady state mode exciter.

PubMed

Ikeda, M; Sugimura, A; Ikegami, T

1976-09-01

The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.

Dynamic fields near a crack tip growing in an elastic-perfectly-plastic solid

NASA Technical Reports Server (NTRS)

Nemat-Nasser, S.; Gao, Y. C.

1983-01-01

A full asymptotic solution is presented for the fields in the neighborhood of the tip of a steadily advancing crack in an incompressible elastic-perfectly-plastic solid. There are four findings for mode I crack growth in the plane strain condition. The first is that the entire crack tip in steady crack growth is surrounded by a plastic region and that no elastic unloading is predicted by the complete dynamic asymptotic solution. The second is that, in contrast to the quasi-static solution, the dynamic solution yields strain fields with a logarithmic singularity everywhere near the crack tip. The third is that whereas the stress field varies throughout the entire crack tip neighborhood, it does not exhibit behavior that can be approximated by a constant field followed by an essentially centered-fan field and then by another constant field, especially for small crack growth speeds. The fourth finding is that there are two shock fronts emanating from the crack tip across which certain stress and strain components undergo jump discontinuities. After reviewing the mode III steady-state crack growth, it is concluded that ductile fracture criteria for nonstationary cracks must be based on solutions that include the inertia effects and that for this purpose quasi-static solutions may be inadequate.

Lunar Laser Ranging: Glorious Past And A Bright Future

NASA Astrophysics Data System (ADS)

Shelus, Peter J.

Lunar Laser Ranging (LLR), a part of the NASA Apollo program, has beenon-going for more than 30 years. It provides the grist for a multi-disciplinarydata analysis mill. Results exist for solid Earth sciences, geodesy and geodynamics,solar system ephemerides, terrestrial and celestial reference frames, lunar physics,general relativity and gravitational theory. Combined with other data, it treatsprecession of the Earth''s spin axis, lunar induced nutation, polar motion/Earthrotation, Earth orbit obliquity to the ecliptic, intersection of the celestial equatorwith the ecliptic, luni-solar solid body tides, lunar tidal deceleration, lunar physicaland free librations, structure of the moon and energy dissipation in the lunar interior.LLR provides input to lunar surface cartography and surveying, Earth station and lunar retroreflector location and motion, mass of the Earth-moon system, lunar and terrestrial gravity harmonics and Love numbers, relativistic geodesic precession, and the equivalence principle of general relativity. With the passive nature of the reflectors and steady improvement in observing equipment and data analysis, LLR continues to provide state-of-the-art results. Gains are steady as the data-base expands. After more than 30 years, LLR remains the only active Apollo experiment. It is important to recognize examples of efficient and cost effective progress of research. LLR is just such an example.

Multiscale Transient and Steady-State Study of the Influence of Microstructure Degradation and Chromium Oxide Poisoning on Solid Oxide Fuel Cell Cathode Performance

NASA Astrophysics Data System (ADS)

Li, Guanchen; von Spakovsky, Michael R.; Shen, Fengyu; Lu, Kathy

2018-01-01

Oxygen reduction in a solid oxide fuel cell cathode involves a nonequilibrium process of coupled mass and heat diffusion and electrochemical and chemical reactions. These phenomena occur at multiple temporal and spatial scales, making the modeling, especially in the transient regime, very difficult. Nonetheless, multiscale models are needed to improve the understanding of oxygen reduction and guide cathode design. Of particular importance for long-term operation are microstructure degradation and chromium oxide poisoning both of which degrade cathode performance. Existing methods are phenomenological or empirical in nature and their application limited to the continuum realm with quantum effects not captured. In contrast, steepest-entropy-ascent quantum thermodynamics can be used to model nonequilibrium processes (even those far-from equilibrium) at all scales. The nonequilibrium relaxation is characterized by entropy generation, which can unify coupled phenomena into one framework to model transient and steady behavior. The results reveal the effects on performance of the different timescales of the varied phenomena involved and their coupling. Results are included here for the effects of chromium oxide concentrations on cathode output as is a parametric study of the effects of interconnect-three-phase-boundary length, oxygen mean free path, and adsorption site effectiveness. A qualitative comparison with experimental results is made.

Glass-water interaction: Effect of high-valence cations on glass structure and chemical durability

NASA Astrophysics Data System (ADS)

Hopf, J.; Kerisit, S. N.; Angeli, F.; Charpentier, T.; Icenhower, J. P.; McGrail, B. P.; Windisch, C. F.; Burton, S. D.; Pierce, E. M.

2016-05-01

Borosilicate glass is a durable solid, but it dissolves when in contact with aqueous fluids. The dissolution mechanism, which involves a variety of sequential reactions that occur at the solid-fluid interface, has important implications for the corrosion resistance of industrial and nuclear waste glasses. In this study, spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high-valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na2O-Al2O3-B2O3-HfO2-SiO2 system (e.g., Na/[Al + B] = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 (tetrahedral boron/total boron) and increases the amount of Si-O-Hf moieties in the glass. Results from flow-through experiments conducted under dilute and near-saturated conditions show a decrease of approximately 100× or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveals a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the stronger binding of Si sites that deposit on the surface from the influent when Hf is present in the glass. As a result, the residence time at the glass surface of these newly-formed Si sites is longer in the presence of Hf, which increases the density of anchor sites from which altered layers with higher Si densities can form. These results illustrate the importance of understanding solid-water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.

Preliminary results of geothermal desalting operations at the East Mesa test site Imperial Valley, California

NASA Technical Reports Server (NTRS)

Suemoto, S. H.; Mathias, K. E.

1974-01-01

The Bureau of Reclamation has erected at its Geothermal Resource Development site two experimental test vehicles for the purpose of desalting hot fluids of geothermal origin. Both plants have as a feed source geothermal well Mesa 6-1 drilled to a total depth of 8,030 feet and having a bottom hole temperature of 400 F. Formation fluid collected at the surface contained 24,800 mg/1 total dissolved solids. The dissolved solids consist mainly of sodium chloride. A multistage distillation (3-stage) plant has been operated intermittently for one year with no operational problems. Functioning at steady-state conditions with a liquid feed rate of 70 g/m and a temperature of 221 F, the final brine blowdown temperature was 169 F. Product water was produced at a rate of about 2 g/m; average total dissolved solids content of the product was 170 mg/1. A product quality of 27.5 mg/1 at a pH of 9.5 was produced from the first stage.

Energy transfer in aggregated CuInS2/ZnS core-shell quantum dots deposited as solid films

NASA Astrophysics Data System (ADS)

Gardelis, S.; Fakis, M.; Droseros, N.; Georgiadou, D.; Travlos, A.; Nassiopoulou, A. G.

2017-01-01

We report on the morphology and optical properties of CuInS2/ZnS core-shell quantum dots in solid films by means of AFM, SEM, HRTEM, steady state and time-resolved photoluminescence (PL) spectroscopy. The amount of aggregation of the CuInS2/ZnS QDs was controlled by changing the preparation conditions of the films. A red-shift of the PL spectrum of CuInS2/ZnS core-shell quantum dots, deposited as solid films on silicon substrates, is observed upon increasing the amount of aggregation. The presence of larger aggregates was found to lead to a larger PL red-shift. Besides, as the degree of aggregation increased, the PL decay became slower. We attribute the observed PL red-shift to energy transfer from the smaller to the larger dots within the aggregates, with the emission being realized via a long decay recombination mechanism (100-200 ns), the origin of which is discussed.

On the kinetics of the pack - Aluminization process

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.

1976-01-01

An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

Influence of an americium solid phase on americium concentrations in solutions

NASA Astrophysics Data System (ADS)

Rai, Dhanpat; Strickert, R. G.; Moore, D. A.; Serne, R. J.

1981-11-01

Americium-241 concentrations in solutions contacting contaminated sediments for up to 2 yr were measured as a function of pH. Steady-state concentrations were reached within a few days. The solubility-limited Am concentration was found to decrease approximately 10-fold with one unit increase in pH. The log equilibrium constant for the solubility of Am (soil) solid [Am (soil) + H + ⇌ Am (aq complex)+] was found to be -4.12. The predictions based upon thermodynamic data suggest that Am (aq complex)+ is likely to be Am(OH) 2+. Although the chemical formula of Am (soil) was not determined, it does not appear to be Am(OH) 3(a). Published data on sorption coefficients of Am by different rocks, soils, and minerals were critically evaluated. Final Am solution concentrations calculated from the sorption coefficients of a variety of earth materials with several solutions agreed well with the concentrations predicted from the solubility of Am (soil) solid, indicating that the sorption coefficient data are controlled by Am precipitation.

Modeling of tritium transport in a fusion reactor pin-type solid breeder blanket using the diffuse code

NASA Astrophysics Data System (ADS)

Martin, Rodger; Ghoniem, Nasr M.

1986-11-01

A pin-type fusion reactor blanket is designed using γ-LiAlO 2 solid tritium breeder. Tritium transport and diffusive inventory are modeled using the DIFFUSE code. Two approaches are used to obtain characteristic LiAlO 2 grain temperatures. DIFFUSE provides intragranular diffusive inventories which scale up to blanket size. These results compare well with a numerical analysis, giving a steady-state blanket tritium inventory of 13 g. Start-up transient inventories are modeled using DIFFUSE for both full and restricted coolant flow. Full flow gives rapid inventory buildup while restricted flow prevents this buildup. Inventories after shutdown are modeled: reduced cooling is found to have little effect on removing tritium, but preheating rapidly purges inventory. DIFFUSE provides parametric modeling of solid breeder density, radiation, and surface effects. 100% dense pins are found to give massive inventory and marginal tritium release. Only large trapping energies and concentrations significantly increase inventory. Diatomic surface recombination is only significant at high temperatures.

Experimental study of thermoacoustic effects on a single plate Part I: Temperature fields

NASA Astrophysics Data System (ADS)

Wetzel, M.; Herman, C.

The thermal interaction between a heated solid plate and the acoustically driven working fluid was investigated by visualizing and quantifying the temperature fields in the neighbourhood of the solid plate. A combination of holographic interferometry and high-speed cinematography was applied in the measurements. A better knowledge of these temperature fields is essential to develop systematic design methodologies for heat exchangers in oscillatory flows. The difference between heat transfer in oscillatory flows with zero mean velocity and steady-state flows is demonstrated in the paper. Instead of heat transfer from a heated solid surface to the colder bulk fluid, the visualized temperature fields indicated that heat was transferred from the working fluid into the stack plate at the edge of the plate. In the experiments, the thermoacoustic effect was visualized through the temperature measurements. A novel evaluation procedure that accounts for the influence of the acoustic pressure variations on the refractive index was applied to accurately reconstruct the high-speed, two-dimensional oscillating temperature distributions.

Illustrating the Steady-State Condition and the Single-Molecule Kinetic Method with the NMDA Receptor

ERIC Educational Resources Information Center

Kosman, Daniel J.

2009-01-01

The steady-state is a fundamental aspect of biochemical pathways in cells; indeed, the concept of steady-state is a definition of life itself. In a simple enzyme kinetic scheme, the steady-state condition is easy to define analytically but experimentally often difficult to capture because of its evanescent quality; the initial, constant velocity…

Spontaneous emission near the edge of a photonic band gap

NASA Astrophysics Data System (ADS)

John, Sajeev; Quang, Tran

1994-08-01

The spectral and dynamical features of spontaneous emission from two and three-level atoms in which one transition frequency lay near the edge of a photonic band gap (PBG) were derived. These features included temporal oscillations, fractionalized steady-state atomic population on the excited state, spectral splitting and subnatural bandwidth. The effect of N-1 unexcited atoms were also taken into account. The direct consequences of photon localization as embodied in the photon-atom bound state were observed. One feasible experimental accomplishment of these effects may ensue from laser-cooled atoms in the void regions of a PBG medium. Another option is the application of an organic impurity molecule such as pentacene. Such molecules were known to show extremely narrow linewidths when placed in fitting solid hosts.

Steady state and a general scale law of deformation

NASA Astrophysics Data System (ADS)

Huang, Yan

2017-07-01

Steady state deformation has been characterized based on the experimental results for dilute single-phase aluminium alloys. It was found that although characteristic properties such as flow stress and grain size remained constant with time, a continuous loss of grain boundaries occurred as an essential feature at steady state. A physical model, which takes into account the activity of grain boundary dislocations, was developed to describe the kinetics of steady state deformation. According to this model, the steady state as a function of strain rate and temperature defines the limit of the conventional grain size and strength relationship, i.e., the Hall-Petch relation holds when the grain size is larger than that at the steady state, and an inverse Hall-Petch relation takes over if grain size is smaller than the steady state value. The transition between the two relationships relating grain size and strength is a phenomenon that depends on deformation conditions, rather than an intrinsic property as generally perceived. A general scale law of deformation is established accordingly.

Phased array ghost elimination (PAGE) for segmented SSFP imaging with interrupted steady-state.

PubMed

Kellman, Peter; Guttman, Michael A; Herzka, Daniel A; McVeigh, Elliot R

2002-12-01

Steady-state free precession (SSFP) has recently proven to be valuable for cardiac imaging due to its high signal-to-noise ratio and blood-myocardium contrast. Data acquired using ECG-triggered, segmented sequences during the approach to steady-state, or return to steady-state after interruption, may have ghost artifacts due to periodic k-space distortion. Schemes involving several preparatory RF pulses have been proposed to restore steady-state, but these consume imaging time during early systole. Alternatively, the phased-array ghost elimination (PAGE) method may be used to remove ghost artifacts from the first several frames. PAGE was demonstrated for cardiac cine SSFP imaging with interrupted steady-state using a simple alpha/2 magnetization preparation and storage scheme and a spatial tagging preparation.

BLENDING ANALYSIS FOR RADIOACTIVE SALT WASTE PROCESSING FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S.

2012-05-10

Savannah River National Laboratory (SRNL) evaluated methods to mix and blend the contents of the blend tanks to ensure the contents are properly blended before they are transferred from the blend tank such as Tank 21 and Tank 24 to the Salt Waste Processing Facility (SWPF) feed tank. The tank contents consist of three forms: dissolved salt solution, other waste salt solutions, and sludge containing settled solids. This paper focuses on developing the computational model and estimating the operation time of submersible slurry pump when the tank contents are adequately blended prior to their transfer to the SWPF facility. Amore » three-dimensional computational fluid dynamics approach was taken by using the full scale configuration of SRS Type-IV tank, Tank 21H. Major solid obstructions such as the tank wall boundary, the transfer pump column, and three slurry pump housings including one active and two inactive pumps were included in the mixing performance model. Basic flow pattern results predicted by the computational model were benchmarked against the SRNL test results and literature data. Tank 21 is a waste tank that is used to prepare batches of salt feed for SWPF. The salt feed must be a homogeneous solution satisfying the acceptance criterion of the solids entrainment during transfer operation. The work scope described here consists of two modeling areas. They are the steady state flow pattern calculations before the addition of acid solution for tank blending operation and the transient mixing analysis during miscible liquid blending operation. The transient blending calculations were performed by using the 95% homogeneity criterion for the entire liquid domain of the tank. The initial conditions for the entire modeling domain were based on the steady-state flow pattern results with zero second phase concentration. The performance model was also benchmarked against the SRNL test results and literature data.« less

Characterizing potential water quality impacts from soils treated with dust suppressants.

PubMed

Beighley, R Edward; He, Yiping; Valdes, Julio R

2009-01-01

Two separate laboratory experiment series, surface runoff and steady-state seepage, were performed to determine if dust suppressant products can be applied to soils with an expected minimal to no negative impact on water quality. The experiments were designed to mimic arid field conditions and used two soils (clayey and sandy) and six different dust suppressants. The two experiments consisted of: (i) simulated rainfall (intensities of 18, 33, or 61 mm h(-1)) and associated runoff from soil trays at a surface slope of 33%; and (ii) steady-state, constant head seepage through soil columns. Both experiment series involved two product application scenarios and three application ages (i.e., to account for degradation effects) for a total of 126 surface runoff and 80 column experiments. One composite effluent sample was collected from each experiment and analyzed for pH, electrical conductivity, total suspended solids (TSS), total dissolved solids, dissolved oxygen, total organic carbon, nitrate, nitrite, and phosphate. Paired t tests at 1 and 5% levels of significance and project specific data quality objectives are used to compare water quality parameters from treated and untreated soils. Overall, the results from this laboratory scale study suggest that the studied dust suppressants have minimal potential for adverse impacts to selected water quality parameters. The primary impacts were increased TSS for two synthetic products from the surface runoff experiments on both soils. The increase in TSS was not expected based on previous studies and may be attributed to this study's focus on simulating real-world soil agitation/movement at an active construction site subjected to rough grading.

Investigation of possible effects of surface coal mining on hydrology and landscape stability in part of the Powder River structural basin, northeastern Wyoming

USGS Publications Warehouse

Bloyd, R.M.; Daddow, P.B.; Jordon, P.R.; Lowham, H.W.

1986-01-01

The effects of surface coal mining on the surface- and groundwater systems in a 5,400 sq mi area in the Powder River Basin, Wyoming, that includes 20 major coal mines were evaluated using three approaches: A surface water model, a landscape-stability analysis, and a groundwater model. A surface water model was developed for the Belle Fourche River basin. The Hydrological Simulation Program-Fortran model was used to simulate changes in streamflow and changes in dissolved-solids and sulfate concentrations. Simulated streamflows resulting from less than average rainfall were small, changes in flow from premining to during-mining and postmining conditions were less than 2.5%, and changes in mean dissolved-solids and sulfate concentrations ranged from 1 to 7%. A landscape-stability analysis resulted in regression relations to aid in the reconstruction of reclaimed drainage networks. Hypsometric analyses indicate the larger basins are relatively stable, and statistical data from these basins may be used to design the placement of material within a mined basin to approximate natural, stable landscapes in the area. The attempt to define and simulate the groundwater system in the area using a groundwater-flow model was unsuccessful. The steady-state groundwater-flow model could not be calibrated. The modeling effort failed principally because of insufficient quantity and quality of data to define the spatial distribution of aquifer properties; the hydraulic-head distribution within and between aquifers; and the rates of groundwater recharge and discharge, especially for steady-state conditions. (USGS)

Non-steady state diagenesis of organic and inorganic sulfur in lake sediments

NASA Astrophysics Data System (ADS)

Couture, Raoul-Marie; Fischer, Rachele; Van Cappellen, Philippe; Gobeil, Charles

2016-12-01

Sulfur controls the fate of many geochemical elements in lake sediments, including iron, phosphorus and environmentally important trace elements. We measured the speciation of pore-water and sediment-bound sulfur (aqueous sulfate and sulfides, elemental sulfur, iron monosulfide, pyrite, organic sulfur) and supporting geochemical variables (carbon, oxygen, iron) in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in Québec, using a combination of pore-water analyses, sequential extractions and X-ray absorption near edge structure. A non-steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of S transformations. Results suggest that the main source of S to the sediments is the settling of organic ester-sulfate (R-O-SO3-H). Hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter, releasing sulfide to the pore-water. Reduced solid-bound S species accumulate as thiols (R-SH) and iron sulfides in the perennially oxygenated and seasonally anoxic basin, respectively. The model-estimated rate constant for R-SH formation is lower than previously estimated for this particular lacustrine site, but similar to that proposed for marine shelf sediments. The solid sediment S profiles, however, carry the imprint of the time-dependent sulfate input to the lake. Iron sulfide enrichments formed during past decades of elevated atmospheric SO4 deposition are presently dissolving. In the sediments of the perennially oxygenated basin this reaction hampers the build-up of Fe(III) (oxy)hydroxide near the sediment-water interface.

Transient NOE enhancement in solid-state MAS NMR of mobile systems

NASA Astrophysics Data System (ADS)

Cui, Jiangyu; Li, Jun; Peng, Xinhua; Fu, Riqiang

2017-11-01

It has been known that the heteronuclear cross-relaxation affects the dilute S spin magnetization along the longitudinal direction, causing an overshoot phenomenon for those mobile systems in spin-lattice relaxation rate measurements. Here, we analyze the Solomon equations for an I-S system and derive the transient cross relaxation effect as to when an overshoot phenomenon would take place and what the maximum enhancement could be at the time of the overshoot. In order to utilize such a transient nuclear Overhauser effect (NOE), we first time apply it to dynamic solid samples by inverting the 1H magnetization prior to the excitation of the S spin. It is found that the overshoot depends on the ratio of the I and S spin-lattice relaxation rates, i.e. RSS /RII . When RSS /RII ≫ 1 , the maximum enhancement factor for transient NOE could be larger than that obtained in steady-state NOE experiments. Furthermore, transient NOE appears to be more efficient in terms of sensitivity enhancement of dilute spins in solid-state NMR of mobile systems than the traditional cross polarization scheme whose efficiency is greatly compromised by molecular mobility. A sample of natural abundance L-isoleucine amino acid, in which the spin-lattice relaxation rates for the four methyl carbons are different, has been used to demonstrate sensitivity enhancement factors under various experimental schemes.

Lignocellulose degradation during solid-state fermentation: Pleurotus ostreatus versus Phanerochaete chrysosporium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerem, Z.; Friesem, D.; Hadar, Y.

Lignocellulose degradation and activities related to lignin degradation were studied in the solid-state fermentation of cotton stalks by comparison two white rot fungi, Pleurotus ostreatus and Phanerochaete chrysosporium. P. chrysosporium grew vigorously, resulting in rapid, nonselective degradation of 55% of the organic components of the cotton stalks within 15 days. In contrast, P. ostreatus grew more slowly with obvious selectivity for lignin degradation and resulting in the degradation of only 20% of the organic matter after 30 days of incubation. The kinetics of {sup 14}C-lignin mineralization exhibited similar differences. In cultures of P. chrysosporium, mineralization ceased after 18 days, resultingmore » in the release of 12% of the total radioactivity as {sup 14}CO{sub 2}. In P. ostreatus, on the other hand, 17% of the total radioactivity was released in a steady rate throughout a period of 60 days of incubation. Laccase activity was only detected in water extracts of the P. ostreatus fermentation. No lignin peroxidase activity was detected in either the water extract or liquid cultures of this fungus. 2-Keto-4-thiomethyl butyric acid cleavage to ethylene correlated to lignin degradation in both fungi. A study of fungal activity under solid-state conditions, in contrast to those done under defined liquid culture, may help to better understand the mechanism involved in lignocellulose degradation.« less

Bioaccumulation factors and the steady state assumption for cesium isotopes in aquatic foodwebs near nuclear facilities.

PubMed

Rowan, D J

2013-07-01

Steady state approaches, such as transfer coefficients or bioaccumulation factors, are commonly used to model the bioaccumulation of (137)Cs in aquatic foodwebs from routine operations and releases from nuclear generating stations and other nuclear facilities. Routine releases from nuclear generating stations and facilities, however, often consist of pulses as liquid waste is stored, analyzed to ensure regulatory compliance and then released. The effect of repeated pulse releases on the steady state assumption inherent in the bioaccumulation factor approach has not been evaluated. In this study, I examine the steady state assumption for aquatic biota by analyzing data for two cesium isotopes in the same biota, one isotope in steady state (stable (133)Cs) from geologic sources and the other released in pulses ((137)Cs) from reactor operations. I also compare (137)Cs bioaccumulation factors for similar upstream populations from the same system exposed solely to weapon test (137)Cs, and assumed to be in steady state. The steady state assumption appears to be valid for small organisms at lower trophic levels (zooplankton, rainbow smelt and 0+ yellow perch) but not for older and larger fish at higher trophic levels (walleye). Attempts to account for previous exposure and retention through a biokinetics approach had a similar effect on steady state, upstream and non-steady state, downstream populations of walleye, but were ineffective in explaining the more or less constant deviation between fish with steady state exposures and non-steady state exposures of about 2-fold for all age classes of walleye. These results suggest that for large, piscivorous fish, repeated exposure to short duration, pulse releases leads to much higher (137)Cs BAFs than expected from (133)Cs BAFs for the same fish or (137)Cs BAFs for similar populations in the same system not impacted by reactor releases. These results suggest that the steady state approach should be used with caution in any situation where reactor releases are episodic or pulse in nature, even if the magnitude of these releases is small. Copyright © 2012. Published by Elsevier Ltd.

Steady shape analysis of tomographic pumping tests for characterization of aquifer heterogeneities

USGS Publications Warehouse

Bohling, Geoffrey C.; Zhan, Xiaoyong; Butler, James J.; Zheng, Li

2002-01-01

Hydraulic tomography, a procedure involving the performance of a suite of pumping tests in a tomographic format, provides information about variations in hydraulic conductivity at a level of detail not obtainable with traditional well tests. However, analysis of transient data from such a suite of pumping tests represents a substantial computational burden. Although steady state responses can be analyzed to reduce this computational burden significantly, the time required to reach steady state will often be too long for practical applications of the tomography concept. In addition, uncertainty regarding the mechanisms driving the system to steady state can propagate to adversely impact the resulting hydraulic conductivity estimates. These disadvantages of a steady state analysis can be overcome by exploiting the simplifications possible under the steady shape flow regime. At steady shape conditions, drawdown varies with time but the hydraulic gradient does not. Thus transient data can be analyzed with the computational efficiency of a steady state model. In this study, we demonstrate the value of the steady shape concept for inversion of hydraulic tomography data and investigate its robustness with respect to improperly specified boundary conditions.

Steady states and stability in metabolic networks without regulation.

PubMed

Ivanov, Oleksandr; van der Schaft, Arjan; Weissing, Franz J

2016-07-21

Metabolic networks are often extremely complex. Despite intensive efforts many details of these networks, e.g., exact kinetic rates and parameters of metabolic reactions, are not known, making it difficult to derive their properties. Considerable effort has been made to develop theory about properties of steady states in metabolic networks that are valid for any values of parameters. General results on uniqueness of steady states and their stability have been derived with specific assumptions on reaction kinetics, stoichiometry and network topology. For example, deep results have been obtained under the assumptions of mass-action reaction kinetics, continuous flow stirred tank reactors (CFSTR), concordant reaction networks and others. Nevertheless, a general theory about properties of steady states in metabolic networks is still missing. Here we make a step further in the quest for such a theory. Specifically, we study properties of steady states in metabolic networks with monotonic kinetics in relation to their stoichiometry (simple and general) and the number of metabolites participating in every reaction (single or many). Our approach is based on the investigation of properties of the Jacobian matrix. We show that stoichiometry, network topology, and the number of metabolites that participate in every reaction have a large influence on the number of steady states and their stability in metabolic networks. Specifically, metabolic networks with single-substrate-single-product reactions have disconnected steady states, whereas in metabolic networks with multiple-substrates-multiple-product reactions manifolds of steady states arise. Metabolic networks with simple stoichiometry have either a unique globally asymptotically stable steady state or asymptotically stable manifolds of steady states. In metabolic networks with general stoichiometry the steady states are not always stable and we provide conditions for their stability. In order to demonstrate the biological relevance we illustrate the results on the examples of the TCA cycle, the mevalonate pathway and the Calvin cycle. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solid Rocket Motor Combustion Instability Modeling in COMSOL Multiphysics

NASA Technical Reports Server (NTRS)

Fischbach, S. R.

2015-01-01

Combustion instability modeling of Solid Rocket Motors (SRM) remains a topic of active research. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process, acoustics, and steady-state gas dynamics. Recent advances in defining the energy transport of disturbances within steady flow-fields have been applied by combustion stability modelers to improve the analysis framework. Employing this more accurate global energy balance requires a higher fidelity model of the SRM flow-field and acoustic mode shapes. The current industry standard analysis tool utilizes a one dimensional analysis of the time dependent fluid dynamics along with a quasi-three dimensional propellant grain regression model to determine the SRM ballistics. The code then couples with another application that calculates the eigenvalues of the one dimensional homogenous wave equation. The mean flow parameters and acoustic normal modes are coupled to evaluate the stability theory developed and popularized by Culick. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The current study employs the COMSOL Multiphysics finite element framework to model the steady flow-field parameters and acoustic normal modes of a generic SRM. This work builds upon previous efforts to verify the use of the acoustic velocity potential equation (AVPE) laid out by Campos. The acoustic velocity potential (psi) describing the acoustic wave motion in the presence of an inhomogeneous steady high-speed flow is defined by, del squared psi - (lambda/c) squared psi - M x [M x del((del)(psi))] - 2((lambda)(M)/c + M x del(M) x (del)(psi) - 2(lambda)(psi)[M x del(1/c)] = 0. with M as the Mach vector, c as the speed of sound, and ? as the complex eigenvalue. The study requires one way coupling of the CFD High Mach Number Flow (HMNF) and mathematics module. The HMNF module evaluates the gas flow inside of a SRM using St. Robert's law to model the solid propellant burn rate, slip boundary conditions, and the supersonic outflow condition. Results from the HMNF model are verified by comparing the pertinent ballistics parameters with the industry standard code outputs (i.e. pressure drop, axial velocity, exit velocity). These results are then used by the coefficient form of the mathematics module to determine the complex eigenvalues of the AVPE. The mathematics model is truncated at the nozzle sonic line, where a zero flux boundary condition is self-satisfying. The remaining boundaries are modeled with a zero flux boundary condition, assuming zero acoustic absorption on all surfaces. The one way coupled analysis is perform four times utilizing geometries determined through traditional SRM modeling procedures. The results of the steady-state CFD and AVPE analyses are used to calculate the linear acoustic growth rate as is defined by Flandro and Jacob. In order to verify the process implemented within COMSOL we first employ the Culick theory and compare the results with the industry standard. After the process is verified, the Flandro/Jacob energy balance theory is employed and results displayed.

Topology optimisation for natural convection problems

NASA Astrophysics Data System (ADS)

Alexandersen, Joe; Aage, Niels; Andreasen, Casper Schousboe; Sigmund, Ole

2014-12-01

This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation. In order to facilitate topology optimisation, the Brinkman approach is taken to penalise velocities inside the solid domain and the effective thermal conductivity is interpolated in order to accommodate differences in thermal conductivity of the solid and fluid phases. The governing equations are discretised using stabilised finite elements and topology optimisation is performed for two different problems using discrete adjoint sensitivity analysis. The study shows that topology optimisation is a viable approach for designing heat sink geometries cooled by natural convection and micropumps powered by natural convection.

A new model for predicting moisture uptake by packaged solid pharmaceuticals.

PubMed

Chen, Y; Li, Y

2003-04-14

A novel mathematical model has been developed for predicting moisture uptake by packaged solid pharmaceutical products during storage. High density polyethylene (HDPE) bottles containing the tablet products of two new chemical entities and desiccants are investigated. Permeability of the bottles is determined at different temperatures using steady-state data. Moisture sorption isotherms of the two model drug products and desiccants at the same temperatures are determined and expressed in polynomial equations. The isotherms are used for modeling the time-humidity profile in the container, which enables the prediction of the moisture content of individual component during storage. Predicted moisture contents agree well with real time stability data. The current model could serve as a guide during packaging selection for moisture protection, so as to reduce the cost and cycle time of screening study.

Development of traceable measurement of the diffuse optical properties of solid reference standards for biomedical optics at National Institute of Standards and Technology.

PubMed

Lemaillet, Paul; Bouchard, Jean-Pierre; Allen, David W

2015-07-01

The development of a national reference instrument dedicated to the measurement of the scattering and absorption properties of solid tissue-mimicking phantoms used as reference standards is presented. The optical properties of the phantoms are measured with a double-integrating sphere setup in the steady-state domain, coupled with an inversion routine of the adding-doubling procedure that allows for the computation of the uncertainty budget for the measurements. The results are compared to the phantom manufacturer's values obtained by a time-resolved approach. The results suggest that the agreement between these two independent methods is within the estimated uncertainties. This new reference instrument will provide optical biomedical research laboratories with reference values for absolute diffuse optical properties of phantom materials.

Computational multiple steady states for enzymatic esterification of ethanol and oleic acid in an isothermal CSTR.

PubMed

Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya

2005-05-01

The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.

An Intuitive Approach to Steady-State Kinetics.

ERIC Educational Resources Information Center

Raines, Ronald T.; Hansen, David E.

1988-01-01

Attempts to provide an intuitive understanding of steady state kinetics. Discusses the meaning of steady state and uses free energy profiles to illustrate and follow complex kinetic and thermodynamic relationships. Provides examples with explanations. (MVL)

Effect of flaw size and temperature on the matrix cracking behavior of a brittle ceramic matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anandakumar, U.; Webb, J.E.; Singh, R.N.

The matrix cracking behavior of a zircon matrix - uniaxial SCS 6 fiber composite was studied as a function of initial flaw size and temperature. The composites were fabricated by a tape casting and hot pressing technique. Surface flaws of controlled size were introduced using a vicker`s indenter. The composite samples were tested in three point flexure at three different temperatures to study the non steady state and steady state matrix cracking behavior. The composite samples exhibited steady state and non steady matrix cracking behavior at all temperatures. The steady state matrix cracking stress and steady state crack size increasedmore » with increasing temperature. The results of the study correlated well with the results predicted by the matrix cracking models.« less

Differences between automatically detected and steady-state fractional flow reserve.

PubMed

Härle, Tobias; Meyer, Sven; Vahldiek, Felix; Elsässer, Albrecht

2016-02-01

Measurement of fractional flow reserve (FFR) has become a standard diagnostic tool in the catheterization laboratory. FFR evaluation studies were based on pressure recordings during steady-state maximum hyperemia. Commercially available computer systems detect the lowest Pd/Pa ratio automatically, which might not always be measured during steady-state hyperemia. We sought to compare the automatically detected FFR and true steady-state FFR. Pressure measurement traces of 105 coronary lesions from 77 patients with intermediate coronary lesions or multivessel disease were reviewed. In all patients, hyperemia had been achieved by intravenous adenosine administration using a dosage of 140 µg/kg/min. In 42 lesions (40%) automatically detected FFR was lower than true steady-state FFR. Mean bias was 0.009 (standard deviation 0.015, limits of agreement -0.02, 0.037). In 4 lesions (3.8%) both methods lead to different treatment recommendations, in all 4 cases instantaneous wave-free ratio confirmed steady-state FFR. Automatically detected FFR was slightly lower than steady-state FFR in more than one-third of cases. Consequently, interpretation of automatically detected FFR values closely below the cutoff value requires special attention.

Coupled laboratory experiments and numerical models for generating ice-depth profiles of steady-state hydrogen peroxide concentrations on radiolytically processed icy worlds.

NASA Astrophysics Data System (ADS)

Hand, K. P.; Carlson, R. W.

2007-12-01

The presence of hydrogen peroxide and condensed phase molecular oxygen on the surface of Europa is now well established [1,2] and laboratory experiments have repeatedly demonstrated the viability of various radiolytic processes for explaining the observations [see e.g. 3, 4]. To date, however, both the Europa observations and the laboratory work have been limited to only the upper few, or few tens of microns, of ice. The spectrum of charged particles incident on the surface of Europa penetrates deeper, and deposits energy over a much greater range, than any laboratory experiment has aimed to replicate [5, 6]. Here we present results from laboratory work on hydrogen peroxide production using energetic electrons (4 keV - 16 keV) and couple these results with a numerical model for the integrated steady-state density of hydrogen peroxide as a function of depth into the ice. Production rates and steady-state peroxide levels for a range of initial electron energies are used to generate functions for the number of peroxide molecules produced per initial electron as it penetrates through the ice. We examined the electron energy spectrum from 0.01 MeV to 10 MeV and accounted for electrons incident to the surface over the solid angle from cosine(theta) = 0.3-1.0, where theta is the angle from the normal to the surface. We found that, accounting for production and destruction as a function of energy deposition, steady-state hydrogen peroxide concentrations resulting from electron radiolysis likely increases by a factor of a few to an order of magnitude at a depth of a few hundred microns. In other words, the 0.13 percent by number abundance of peroxide observed by NIMS [1] may be a low-end value; at depth the peroxide concentration could increase to a few percent by number relative to water. [1] Carlson et al. 1999. [2] Spencer and Calvin, 2002. [3] Moore and Hudson, 2000. [4] Loeffler et al., 2006. [5] Cooper et al., 2001 [6] Paranicas et al., 2001.

Semi-brittle flow of granitoid fault rocks in experiments

NASA Astrophysics Data System (ADS)

Pec, Matej; Stünitz, Holger; Heilbronner, Renée.; Drury, Martyn

2016-03-01

Field studies and seismic data show that semi-brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so-called frictional-viscous transition. To understand the physical and chemical processes accommodating semi-brittle flow, we have performed an experimental study on synthetic granitoid fault rocks exploring a broad parameter space (temperature, T = 300, 400, 500, and 600°C, confining pressure, Pc ≈ 300, 500, 1000, and 1500 MPa, shear strain rate, γṡ ≈ 10-3, 10-4, 10-5, and 10-6 s-1, to finite shear strains, γ = 0-5). The experiments have been carried out using a granular material with grain size smaller than 200 µm with a little H2O added (0.2 wt %). Only two experiments (performed at the fastest strain rates and lowest temperatures) have failed abruptly right after reaching peak strength (τ ~ 1400 MPa). All other samples reach high shear stresses (τ ~ 570-1600 MPa) then weaken slightly (by Δτ ~ 10-190 MPa) and continue to deform at a more or less steady state stress level. Clear temperature dependence and a weak strain rate dependence of the peak as well as steady state stress levels are observed. In order to express this relationship, the strain rate-stress sensitivity has been fit with a stress exponent, assuming γ˙ ∝ τn and yields high stress exponents (n ≈ 10-140), which decrease with increasing temperature. The microstructures show widespread comminution, strain partitioning, and localization into slip zones. The slip zones contain at first nanocrystalline and partly amorphous material. Later, during continued deformation, fully amorphous material develops in some of the slip zones. Despite the mechanical steady state conditions, the fabrics in the slip zones and outside continue to evolve and do not reach a steady state microstructure below γ = 5. Within the slip zones, the fault rock material progressively transforms from a crystalline solid to an amorphous material. We present and interpret the experimental results both in terms of sliding friction and viscous flow, and we discuss the possible effect that the formation of nanocrystalline and amorphous layers may have on earthquake nucleation.

Unifying role of dissipative action in the dynamic failure of solids

NASA Astrophysics Data System (ADS)

Grady, Dennis E.

2015-04-01

A fourth-power law underlying the steady shock-wave structure and solid viscosity of condensed material has been observed for a wide range of metals and non-metals. The fourth-power law relates the steady-wave Hugoniot pressure to the fourth power of the strain rate during passage of the material through the structured shock wave. Preceding the fourth-power law was the observation in a shock transition that the product of the shock dissipation energy and the shock transition time is a constant independent of the shock pressure amplitude. Invariance of this energy-time product implies the fourth-power law. This property of the shock transition in solids was initially identified as a shock invariant. More recently, it has been referred to as the dissipative action, although no relationship to the accepted definitions of action in mechanics has been demonstrated. This same invariant property has application to a wider range of transient failure phenomena in solids. Invariance of this dissipation action has application to spall fracture, failure through adiabatic shear, shock compaction of granular media, and perhaps others. Through models of the failure processes, a clearer picture of the physics underlying the observed invariance is emerging. These insights in turn are leading to a better understanding of the shock deformation processes underlying the fourth-power law. Experimental result and material models encompassing the dynamic failure of solids are explored for the purpose of demonstrating commonalities leading to invariance of the dissipation action. Calculations are extended to aluminum and uranium metals with the intent of predicting micro-scale dynamics and spatial structure in the steady shock wave.

On the time to steady state: insights from numerical modeling

NASA Astrophysics Data System (ADS)

Goren, L.; Willett, S.; McCoy, S. W.; Perron, J.

2013-12-01

How fast do fluvial landscapes approach steady state after an application of tectonic or climatic perturbation? While theory and some numerical models predict that the celerity of the advective wave (knickpoint) controls the response time for perturbations, experiments and other landscape evolution models demonstrate that the time to steady state is much longer than the theoretically predicted response time. We posit that the longevity of transient features and the time to steady state are controlled by the stability of the topology and geometry of channel networks. Evolution of a channel network occurs by a combination of discrete capture events and continuous migration of water divides, processes, which are difficult to represent accurately in landscape evolution models. We therefore address the question of the time to steady state using the DAC landscape evolution model that solves accurately for the location of water divides, using a combination of analytical solution for hillslopes and low-order channels together with a numerical solution for higher order channels. DAC also includes an explicit capture criterion. We have tested fundamental predictions from DAC and show that modeled networks reproduce natural network characteristics such as the Hack's exponent and coefficient and the fractal dimension. We define two steady-state criteria: a topographic steady state, defined by global, pointwise steady elevation, and a topological steady state defined as the state in which no further reorganization of the drainage network takes place. Analyzing block uplift simulations, we find that the time to achieve either topographic or topological steady state exceeds by an order of magnitude the theoretical response time of the fluvial network. The longevity of the transient state is the result of the area feedback, by which, migration of a divide changes the local contributing area. This change propagates downstream as a slope adjustment, forcing further divide migrations and area change in adjacent tributaries and basins. In order to characterize the evolution of the drainage network on its way to steady state, we define a proxy to steady state elevation, χ, which is also the characteristic parameter of the transient stream power PDE. Through simulations of tectonic tilting we find that reorganization tends to minimize moments of the χ distribution of the landscape and of Δχ across divides.

Quantitative broadband absorption and scattering spectroscopy in turbid media by combined frequency-domain and steady state methodologies

DOEpatents

Tromberg, Bruce J [Irvine, CA; Berger, Andrew J [Rochester, NY; Cerussi, Albert E [Lake Forest, CA; Bevilacqua, Frederic [Costa Mesa, CA; Jakubowski, Dorota [Irvine, CA

2008-09-23

A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.

Steady-state entanglement in levitated optomechanical systems coupled to a higher order excited atomic ensemble

NASA Astrophysics Data System (ADS)

Chen, Aixi; Nie, Wenjie; Li, Ling; Zeng, Wei; Liao, Qinghong; Xiao, Xianbo

2017-11-01

We investigate the steady-state entanglement in an optomechanical system with a levitated dielectric nanosphere and a higher order excited atomic ensemble. The single nanosphere is trapped by an external harmonic dipole trap and coupled to the single-mode cavity field by the effective optomechanical coupling, which depends on the steady-state position of the nanosphere. We show that the steady-state optomechanical entanglement can be generated via the effective optomechanical interaction between the mechanical motion and the cavity mode. Further, these exist an optimal effective cavity detuning that maximizes the optomechanical entanglement. We also analyze in detail the influences of the excitation number of atoms, the radius of the nanosphere and the thermal noise strength on the steady-state optomechanical entanglement. It is found that the steady-state entanglement can be enhanced by increasing the excitation number of atoms and the radius of the nanosphere.

Design and experimental results of the 1-T Bitter Electromagnet Testing Apparatus (BETA)

NASA Astrophysics Data System (ADS)

Bates, E. M.; Birmingham, W. J.; Romero-Talamás, C. A.

2018-05-01

The Bitter Electromagnet Testing Apparatus (BETA) is a 1-Tesla (T) technical prototype of the 10 T Adjustable Long Pulsed High-Field Apparatus. BETA's final design specifications are highlighted in this paper which include electromagnetic, thermal, and stress analyses. We discuss here the design and fabrication of BETA's core, vessel, cooling, and electrical subsystems. The electrical system of BETA is composed of a scalable solid-state DC breaker circuit. Experimental results display the stable operation of BETA at 1 T. These results are compared to both analytical design and finite element calculations. Experimental results validate analytical magnet designing methods developed at the Dusty Plasma Laboratory. The theoretical steady state maxima and the limits of BETA's design are explored in this paper.

Design and experimental results of the 1-T Bitter Electromagnet Testing Apparatus (BETA).

PubMed

Bates, E M; Birmingham, W J; Romero-Talamás, C A

2018-05-01

The Bitter Electromagnet Testing Apparatus (BETA) is a 1-Tesla (T) technical prototype of the 10 T Adjustable Long Pulsed High-Field Apparatus. BETA's final design specifications are highlighted in this paper which include electromagnetic, thermal, and stress analyses. We discuss here the design and fabrication of BETA's core, vessel, cooling, and electrical subsystems. The electrical system of BETA is composed of a scalable solid-state DC breaker circuit. Experimental results display the stable operation of BETA at 1 T. These results are compared to both analytical design and finite element calculations. Experimental results validate analytical magnet designing methods developed at the Dusty Plasma Laboratory. The theoretical steady state maxima and the limits of BETA's design are explored in this paper.

Reliability analysis of component-level redundant topologies for solid-state fault current limiter

NASA Astrophysics Data System (ADS)

Farhadi, Masoud; Abapour, Mehdi; Mohammadi-Ivatloo, Behnam

2018-04-01

Experience shows that semiconductor switches in power electronics systems are the most vulnerable components. One of the most common ways to solve this reliability challenge is component-level redundant design. There are four possible configurations for the redundant design in component level. This article presents a comparative reliability analysis between different component-level redundant designs for solid-state fault current limiter. The aim of the proposed analysis is to determine the more reliable component-level redundant configuration. The mean time to failure (MTTF) is used as the reliability parameter. Considering both fault types (open circuit and short circuit), the MTTFs of different configurations are calculated. It is demonstrated that more reliable configuration depends on the junction temperature of the semiconductor switches in the steady state. That junction temperature is a function of (i) ambient temperature, (ii) power loss of the semiconductor switch and (iii) thermal resistance of heat sink. Also, results' sensitivity to each parameter is investigated. The results show that in different conditions, various configurations have higher reliability. The experimental results are presented to clarify the theory and feasibility of the proposed approaches. At last, levelised costs of different configurations are analysed for a fair comparison.

Inclusion of Paracetamol into β-cyclodextrin nanocavities in solution and in the solid state

NASA Astrophysics Data System (ADS)

El-Kemary, Maged; Sobhy, Saffaa; El-Daly, Samy; Abdel-Shafi, Ayman

2011-09-01

We report on steady-state UV-visible absorption and emission characteristics of Paracetamol, drug used as antipyretic agent, in water and within cyclodextrins (CDs): β-CD, 2-hydroxypropyl- β-CD (HP- β-CD) and 2,6-dimethyl- β-CD (Me- β-CD). The results reveal that Paracetamol forms a 1:1 inclusion complex with CD. Upon encapsulation, the emission intensity enhances, indicating a confinement effect of the nanocages on the photophysical behavior of the drug. Due to its methyl groups, the Me- β-CD shows the largest effect for the drug. The observed binding constant showing the following trend: Me- β-CD > HP- β-CD > β-CD. The less complexing effectiveness of HP- β-CD is due to the steric effect of the hydroxypropyl-substituents, which can hamper the inclusion of the guest molecules. The solid state inclusion complex was prepared by co-precipitation method and its characterization was investigated by Fourier transform infrared spectroscopy, 1H NMR and X-ray diffractometry. These approaches indicated that Paracetamol was able to form an inclusion complex with CDs, and the inclusion compounds exhibited different spectroscopic features and properties from Paracetamol.

ASYMPTOTIC STEADY-STATE SOLUTION TO A BOW SHOCK WITH AN INFINITE MACH NUMBER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yalinewich, Almog; Sari, Re’em

2016-08-01

The problem of a cold gas flowing past a stationary obstacle is considered. We study the bow shock that forms around the obstacle and show that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The profiles of the hydrodynamic variables in the interior of the shock are obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force on the obstacle is also calculated. Finally, we use these results to model the bow shock around an isolated neutron star.

Regular expansion solutions for small Peclet number heat or mass transfer in concentrated two-phase particulate systems

NASA Technical Reports Server (NTRS)

Yaron, I.

1974-01-01

Steady state heat or mass transfer in concentrated ensembles of drops, bubbles or solid spheres in uniform, slow viscous motion, is investigated. Convective effects at small Peclet numbers are taken into account by expanding the nondimensional temperature or concentration in powers of the Peclet number. Uniformly valid solutions are obtained, which reflect the effects of dispersed phase content and rate of internal circulation within the fluid particles. The dependence of the range of Peclet and Reynolds numbers, for which regular expansions are valid, on particle concentration is discussed.

Cryogenic-coolant He4-superconductor dynamic and static interactions

NASA Technical Reports Server (NTRS)

Caspi, S.; Chuang, C.; Kim, Y. I.; Allen, R. J.; Frederking, T. H. E.

1980-01-01

A composite superconducting material (NbTi-Cu) was evaluated with emphasis on post quench solid cooling interaction regimes. The quasi-steady runs confirm the existence of a thermodynamic limiting thickness for insulating coatings. Two distinctly different post quench regimes of coated composites are shown to relate to the limiting thickness. Only one regime,, from quench onset to the peak value, revealed favorable coolant states, in particular in He2. Transient recovery shows favorable recovery times from this post quench regime (not drastically different from bare conductors) for both single coated specimens and a coated conductor bundle.

Customized Steady-State Constraints for Parameter Estimation in Non-Linear Ordinary Differential Equation Models

PubMed Central

Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel

2016-01-01

Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization. PMID:27243005

Customized Steady-State Constraints for Parameter Estimation in Non-Linear Ordinary Differential Equation Models.

PubMed

Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel

2016-01-01

Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization.

Switching dynamics of TaOx-based threshold switching devices

NASA Astrophysics Data System (ADS)

Goodwill, Jonathan M.; Gala, Darshil K.; Bain, James A.; Skowronski, Marek

2018-03-01

Bi-stable volatile switching devices are being used as access devices in solid-state memory arrays and as the active part of compact oscillators. Such structures exhibit two stable states of resistance and switch between them at a critical value of voltage or current. A typical resistance transient under a constant amplitude voltage pulse starts with a slow decrease followed by a rapid drop and leveling off at a low steady state value. This behavior prompted the interpretation of initial delay and fast transition as due to two different processes. Here, we show that the entire transient including incubation time, transition time, and the final resistance values in TaOx-based switching can be explained by one process, namely, Joule heating with the rapid transition due to the thermal runaway. The time, which is required for the device in the conducting state to relax back to the stable high resistance one, is also consistent with the proposed mechanism.

Principles underlying the Fourth Power Nature of Structured Shock Waves

NASA Astrophysics Data System (ADS)

Grady, Dennis

2017-06-01

Steady structured shock waves in materials including metals, glasses, compounds and solid mixtures, when represented through plots of Hugoniot stress against a measure of the strain rate through which the Hugoniot state is achieved, have consistently demonstrated a dependence to the fourth power. A perhaps deeper observation is that the product of the energy dissipated through the transition to the Hugoniot state and the time duration of the Hugoniot state event exhibits invariance independent of the Hugoniot amplitude. Invariance of the energy-time product and the fourth-power trend are to first order equivalent. Further, constancy of this energy-time product is observed in other dynamic critical state failure events including spall fracture, dynamic compaction and adiabatic shear failure. The presentation pursues the necessary background exposing the foregoing shock physics observations and explores possible statistical physics principals that may underlie the collective dynamic observations.

Streaming current magnetic fields in a charged nanopore.

PubMed

Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W

2016-11-11

Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques.

Evolution of wear and friction along experimental faults

USGS Publications Warehouse

Boneh, Yeval; Chang, Jefferson C.; Lockner, David A.; Reches, Zeev

2014-01-01

We investigate the evolution of wear and friction along experimental faults composed of solid rock blocks. This evolution is analyzed through shear experiments along five rock types, and the experiments were conducted in a rotary apparatus at slip velocities of 0.002–0.97 m/s, slip distances from a few millimeters to tens of meters, and normal stress of 0.25–6.9 MPa. The wear and friction measurements and fault surface observations revealed three evolution phases: A) An initial stage (slip distances <50 mm) of wear by failure of isolated asperities associated with roughening of the fault surface; B) a running-in stage of slip distances of 1–3 m with intense wear-rate, failure of many asperities, and simultaneous reduction of the friction coefficient and wear-rate; and C) a steady-state stage that initiates when the fault surface is covered by a gouge layer, and during which both wear-rate and friction coefficient maintain quasi-constant, low levels. While these evolution stages are clearly recognizable for experimental faults made from bare rock blocks, our analysis suggests that natural faults “bypass” the first two stages and slip at gouge-controlled steady-state conditions.

A Monte Carlo Analysis of the Thrust Imbalance for the RSRMV Booster During Both the Ignition Transient and Steady State Operation

NASA Technical Reports Server (NTRS)

Foster, Winfred A., Jr.; Crowder, Winston; Steadman, Todd E.

2014-01-01

This paper presents the results of statistical analyses performed to predict the thrust imbalance between two solid rocket motor boosters to be used on the Space Launch System (SLS) vehicle. Two legacy internal ballistics codes developed for the Space Shuttle program were coupled with a Monte Carlo analysis code to determine a thrust imbalance envelope for the SLS vehicle based on the performance of 1000 motor pairs. Thirty three variables which could impact the performance of the motors during the ignition transient and thirty eight variables which could impact the performance of the motors during steady state operation of the motor were identified and treated as statistical variables for the analyses. The effects of motor to motor variation as well as variations between motors of a single pair were included in the analyses. The statistical variations of the variables were defined based on data provided by NASA's Marshall Space Flight Center for the upgraded five segment booster and from the Space Shuttle booster when appropriate. The results obtained for the statistical envelope are compared with the design specification thrust imbalance limits for the SLS launch vehicle

A Monte Carlo Analysis of the Thrust Imbalance for the Space Launch System Booster During Both the Ignition Transient and Steady State Operation

NASA Technical Reports Server (NTRS)

Foster, Winfred A., Jr.; Crowder, Winston; Steadman, Todd E.

2014-01-01

This paper presents the results of statistical analyses performed to predict the thrust imbalance between two solid rocket motor boosters to be used on the Space Launch System (SLS) vehicle. Two legacy internal ballistics codes developed for the Space Shuttle program were coupled with a Monte Carlo analysis code to determine a thrust imbalance envelope for the SLS vehicle based on the performance of 1000 motor pairs. Thirty three variables which could impact the performance of the motors during the ignition transient and thirty eight variables which could impact the performance of the motors during steady state operation of the motor were identified and treated as statistical variables for the analyses. The effects of motor to motor variation as well as variations between motors of a single pair were included in the analyses. The statistical variations of the variables were defined based on data provided by NASA's Marshall Space Flight Center for the upgraded five segment booster and from the Space Shuttle booster when appropriate. The results obtained for the statistical envelope are compared with the design specification thrust imbalance limits for the SLS launch vehicle.

Streaming current magnetic fields in a charged nanopore

NASA Astrophysics Data System (ADS)

Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W.

2016-11-01

Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques.

Probing Temperature Inside Planar SOFC Short Stack, Modules, and Stack Series

NASA Astrophysics Data System (ADS)

Yu, Rong; Guan, Wanbing; Zhou, Xiao-Dong

2017-02-01

Probing temperature inside a solid oxide fuel cell (SOFC) stack lies at the heart of the development of high-performance and stable SOFC systems. In this article, we report our recent work on the direct measurements of the temperature in three types of SOFC systems: a 5-cell short stack, a 30-cell stack module, and a stack series consisting of two 30-cell stack modules. The dependence of temperature on the gas flow rate and current density was studied under a current sweep or steady-state operation. During the current sweep, the temperature inside the 5-cell stack decreased with increasing current, while it increased significantly at the bottom and top of the 30-cell stack. During a steady-state operation, the temperature of the 5-cell stack was stable while it was increased in the 30-cell stack. In the stack series, the maximum temperature gradient reached 190°C when the gas was not preheated. If the gas was preheated and the temperature gradient was reduced to 23°C in the stack series with the presence of a preheating gas and segmented temperature control, this resulted in a low degradation rate.

Existence and instability of steady states for a triangular cross-diffusion system: A computer-assisted proof

NASA Astrophysics Data System (ADS)

Breden, Maxime; Castelli, Roberto

2018-05-01

In this paper, we present and apply a computer-assisted method to study steady states of a triangular cross-diffusion system. Our approach consist in an a posteriori validation procedure, that is based on using a fixed point argument around a numerically computed solution, in the spirit of the Newton-Kantorovich theorem. It allows to prove the existence of various non homogeneous steady states for different parameter values. In some situations, we obtain as many as 13 coexisting steady states. We also apply the a posteriori validation procedure to study the linear stability of the obtained steady states, proving that many of them are in fact unstable.

Effect of a solid solution on the steady-state creep behavior of an aluminum matrix composite

NASA Astrophysics Data System (ADS)

Pandey, A. B.; Mishra, R. S.; Mahajan, Y. R.

1996-02-01

The effect of an alloying element, 4 wt pct Mg, on the steady-state creep behavior of an Al-10 vol pct SiCp composite has been studied. The Al-4 wt pct Mg-10 vol pct SiCp composite has been tested under compression creep in the temperature range 573 to 673 K. The steady-state creep data of the composite show a transition in the creep behavior (regions I and II) depending on the applied stress at 623 and 673 K. The low stress range data (region I) exhibit a stress exponent of about 7 and an activation energy of 76.5 kJ mol-1. These values conform to the dislocation-climb-controlled creep model with pipe diffusion as a rate-controlling mechanism. The intermediate stress range data (region II) exhibit high and variable apparent stress exponents, 18 to 48, and activation energy, 266 kJ mol-1, at a constant stress, σ = 50 MPa, for creep of this composite. This behavior can be rationalized using a substructure-invariant model with a stress exponent of 8 and an activation energy close to the lattice self-diffusion of aluminum together with a threshold stress. The creep data of the Al-Mg-A12O3f composite reported by Dragone and Nix also conform to the substructure-invariant model. The threshold stress and the creep strength of the Al-Mg-SiCp, composite are compared with those of the Al-Mg-Al2O3f and 6061 Al-SiCp.w, composites and discussed in terms of the load-transfer mechanism. Magnesium has been found to be very effective in improving the creep resistance of the Al-SiCp composite.

Relating environmental availability to bioavailability: soil-type-dependent metal accumulation in the oligochaete Eisenia andrei.

PubMed

Peijnenburg, W J; Baerselman, R; de Groot, A C; Jager, T; Posthuma, L; Van Veen, R P

1999-11-01

Body residues are often better estimates of the amount of a chemical at the sites of toxic action in an organism than ambient soil concentrations, because bioavailability differences among soils are explicitly taken into account in considerations of body residues. Often, however, insufficient attention is paid to the rate and extent at which tissue concentrations respond to soil concentrations and soil characteristics. In this contribution the impact of soil characteristics on the environmental bioavailability of heavy metals for the oligochaete worm Eisenia andrei is reported. Uptake of As, Cd, Cr, Cu, Ni, Pb, and Zn in 20 Dutch field soils and in OECD artificial soil was quantified as a function of time. Internal metal concentrations varied less than the corresponding external levels. Metal uptake and elimination were both metal- and species-dependent. Worms typically attained steady-state concentrations rapidly for Cr, Cu, Ni, and Zn. Internal concentrations similar to those in the cultivation medium, linearly increasing body concentrations, or steady-state internal concentrations well above those in the cultivation medium were found for As, Cd, and Pb. Multivariate expressions were derived to describe uptake rate constants, steady-state concentrations, and bioaccumulation factors as a function of soil characteristics. Soil acidity is the most important solid-phase characteristic modulating the availability of As, Cd, and Pb. Although additional semimechanistic calculations yielded evidence of pore-water-related uptake of Cd and Pb modulated by competition between H(+) and metal ions at the active sites of the membranes, the findings for Cr, Cu, Ni, and Zn point to additional influences, among which is probably regulation. Copyright 1999 Academic Press.

Multi-Dimensional, Non-Pyrolyzing Ablation Test Problems

NASA Technical Reports Server (NTRS)

Risch, Tim; Kostyk, Chris

2016-01-01

Non-pyrolyzingcarbonaceous materials represent a class of candidate material for hypersonic vehicle components providing both structural and thermal protection system capabilities. Two problems relevant to this technology are presented. The first considers the one-dimensional ablation of a carbon material subject to convective heating. The second considers two-dimensional conduction in a rectangular block subject to radiative heating. Surface thermochemistry for both problems includes finite-rate surface kinetics at low temperatures, diffusion limited ablation at intermediate temperatures, and vaporization at high temperatures. The first problem requires the solution of both the steady-state thermal profile with respect to the ablating surface and the transient thermal history for a one-dimensional ablating planar slab with temperature-dependent material properties. The slab front face is convectively heated and also reradiates to a room temperature environment. The back face is adiabatic. The steady-state temperature profile and steady-state mass loss rate should be predicted. Time-dependent front and back face temperature, surface recession and recession rate along with the final temperature profile should be predicted for the time-dependent solution. The second problem requires the solution for the transient temperature history for an ablating, two-dimensional rectangular solid with anisotropic, temperature-dependent thermal properties. The front face is radiatively heated, convectively cooled, and also reradiates to a room temperature environment. The back face and sidewalls are adiabatic. The solution should include the following 9 items: final surface recession profile, time-dependent temperature history of both the front face and back face at both the centerline and sidewall, as well as the time-dependent surface recession and recession rate on the front face at both the centerline and sidewall. The results of the problems from all submitters will be collected, summarized, and presented at a later conference.

Low-dimensional Representation of Error Covariance

NASA Technical Reports Server (NTRS)

Tippett, Michael K.; Cohn, Stephen E.; Todling, Ricardo; Marchesin, Dan

2000-01-01

Ensemble and reduced-rank approaches to prediction and assimilation rely on low-dimensional approximations of the estimation error covariances. Here stability properties of the forecast/analysis cycle for linear, time-independent systems are used to identify factors that cause the steady-state analysis error covariance to admit a low-dimensional representation. A useful measure of forecast/analysis cycle stability is the bound matrix, a function of the dynamics, observation operator and assimilation method. Upper and lower estimates for the steady-state analysis error covariance matrix eigenvalues are derived from the bound matrix. The estimates generalize to time-dependent systems. If much of the steady-state analysis error variance is due to a few dominant modes, the leading eigenvectors of the bound matrix approximate those of the steady-state analysis error covariance matrix. The analytical results are illustrated in two numerical examples where the Kalman filter is carried to steady state. The first example uses the dynamics of a generalized advection equation exhibiting nonmodal transient growth. Failure to observe growing modes leads to increased steady-state analysis error variances. Leading eigenvectors of the steady-state analysis error covariance matrix are well approximated by leading eigenvectors of the bound matrix. The second example uses the dynamics of a damped baroclinic wave model. The leading eigenvectors of a lowest-order approximation of the bound matrix are shown to approximate well the leading eigenvectors of the steady-state analysis error covariance matrix.

Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems.

PubMed

Baranowski, M; Woźniak-Braszak, A; Jurga, K

2016-01-01

The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal. Copyright © 2015 Elsevier Inc. All rights reserved.

Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials

NASA Technical Reports Server (NTRS)

Camanho, Pedro P.; Davila, Carlos G.

2002-01-01

A new decohesion element with mixed-mode capability is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and non-self-similar growth of delaminations. A single relative displacement-based damage parameter is applied in a softening law to track the damage state of the interface and to prevent the restoration of the cohesive state during unloading. The softening law for mixed-mode delamination propagation can be applied to any mode interaction criterion such as the two-parameter power law or the three-parameter Benzeggagh-Kenane criterion. To demonstrate the accuracy of the predictions and the irreversibility capability of the constitutive law, steady-state delamination growth is simulated for quasistatic loading-unloading cycles of various single mode and mixed-mode delamination test specimens.

Contribution of highway capital to industry and national productivity growth

DOT National Transportation Integrated Search

1973-10-01

The report contains the authors initial efforts aimed at extending the steady state freeway model for optimizing freeway traffic flow to a non-steady state model. The steady-state model does not allow reaction to continuously changing conditions whic...

Microbial response to environmental gradients in a ceramic-based diffusion system.

PubMed

Wolfaardt, G M; Hendry, M J; Birkham, T; Bressel, A; Gardner, M N; Sousa, A J; Korber, D R; Pilaski, M

2008-05-01

A solid, porous matrix was used to establish steady-state concentration profiles upon which microbial responses to concentration gradients of nutrients or antimicrobial agents could be quantified. This technique relies on the development of spatially defined concentration gradients across a ceramic plate resulting from the diffusion of solutes through the porous ceramic matrix. A two-dimensional, finite-element numerical transport model was used to predict the establishment of concentration profiles, after which concentration profiles of conservative tracers were quantified fluorometrically and chemically at the solid-liquid interface to verify the simulated profiles. Microbial growth responses to nutrient, hypochloride, and antimicrobial concentration gradients were then quantified using epifluorescent or scanning confocal laser microscopy. The observed microbial response verified the establishment and maintenance of stable concentration gradients along the solid-liquid interface. These results indicate the ceramic diffusion system has potential for the isolation of heterogeneous microbial communities as well as for testing the efficacy of antimicrobial agents. In addition, the durability of the solid matrix allowed long-term investigations, making this approach preferable to conventional gel-stabilized systems that are impeded by erosion as well as expansion or shrinkage of the gel. Copyright 2008 Wiley Periodicals, Inc.

Development of a Moisture-in-Solid-Insulation Sensor for Power Transformers

PubMed Central

García, Belén; García, Diego; Robles, Guillermo

2015-01-01

Moisture is an important variable that must be kept under control to guarantee a safe operation of power transformers. Because of the hydrophilic character of cellulose, water mainly remains in the solid insulation, while just a few parts per million are dissolved in oil. The distribution of moisture between paper and oil is not static, but varies depending on the insulation temperature, and thus, water migration processes take place continuously during transformers operation. In this work, a sensor is presented that allows the determination of the moisture content of the transformer solid insulation in the steady state and during the moisture migration processes. The main objective of the design is that the electrodes of the sensor should not obstruct the movement of water from the solid insulation to the oil, so the proposed prototype uses a metallic-mesh electrode to do the measurements. The measurement setup is based on the characterization of the insulation dielectric response by means of the frequency dielectric spectroscopy (FDS) method. The sensitivity of the proposed sensor has been tested on samples with a moisture content within 1% to 5%, demonstrating the good sensitivity and repeatability of the measurements. PMID:25658393

Development of a moisture-in-solid-insulation sensor for power transformers.

PubMed

García, Belén; García, Diego; Robles, Guillermo

2015-02-04

Moisture is an important variable that must be kept under control to guarantee a safe operation of power transformers. Because of the hydrophilic character of cellulose, water mainly remains in the solid insulation, while just a few parts per million are dissolved in oil. The distribution of moisture between paper and oil is not static, but varies depending on the insulation temperature, and thus, water migration processes take place continuously during transformers operation. In this work, a sensor is presented that allows the determination of the moisture content of the transformer solid insulation in the steady state and during the moisture migration processes. The main objective of the design is that the electrodes of the sensor should not obstruct the movement of water from the solid insulation to the oil, so the proposed prototype uses a metallic-mesh electrode to do the measurements. The measurement setup is based on the characterization of the insulation dielectric response by means of the frequency dielectric spectroscopy (FDS) method. The sensitivity of the proposed sensor has been tested on samples with a moisture content within 1% to 5%, demonstrating the good sensitivity and repeatability of the measurements.

Dynamic effect of leachate recirculation on batch mode solid state anaerobic digestion: Influence of recirculated volume, leachate to substrate ratio and recirculation periodicity.

PubMed

Degueurce, Axelle; Trémier, Anne; Peu, Pascal

2016-09-01

Performances of batch mode solid state anaerobic digestion (SSAD) were investigated through several leachate recirculation strategies. Three parameters were shown to particularly influence methane production rates (MPR) and methane yields: the length of the interval between two recirculation events, the leachate to substrate (L:S) ratio and the volume of leachate recirculated. A central composite factor design was used to determine the influence of each parameter on methane production. Results showed that lengthening the interval between two recirculation events reduced methane yield. This effect can be counteracted by recirculating a large volume of leachate at a low L:S ratio. Steady methane production can be obtained by recirculating small amounts of leachate, and by lengthening the interval between two recirculations, regardless of the L:S ratio. However, several combinations of these parameters led to similar performances meaning that leachate recirculation practices can be modified as required by the specific constraints SSAD plants configurations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cascade aeroacoustics including steady loading effects

NASA Astrophysics Data System (ADS)

Chiang, Hsiao-Wei D.; Fleeter, Sanford

A mathematical model is developed to analyze the effects of airfoil and cascade geometry, steady aerodynamic loading, and the characteristics of the unsteady flow field on the discrete frequency noise generation of a blade row in an incompressible flow. The unsteady lift which generates the noise is predicted with a complex first-order cascade convected gust analysis. This model was then applied to the Gostelow airfoil cascade and variations, demonstrating that steady loading, cascade solidity, and the gust direction are significant. Also, even at zero incidence, the classical flat plate cascade predictions are unacceptable.

electromagnetics, eddy current, computer codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gartling, David

TORO Version 4 is designed for finite element analysis of steady, transient and time-harmonic, multi-dimensional, quasi-static problems in electromagnetics. The code allows simulation of electrostatic fields, steady current flows, magnetostatics and eddy current problems in plane or axisymmetric, two-dimensional geometries. TORO is easily coupled to heat conduction and solid mechanics codes to allow multi-physics simulations to be performed.

Critical threshold behavior for steady-state internal transport barriers in burning plasmas.

PubMed

García, J; Giruzzi, G; Artaud, J F; Basiuk, V; Decker, J; Imbeaux, F; Peysson, Y; Schneider, M

2008-06-27

Burning tokamak plasmas with internal transport barriers are investigated by means of integrated modeling simulations. The barrier sustainment in steady state, differently from the barrier formation process, is found to be characterized by a critical behavior, and the critical number of the phase transition is determined. Beyond a power threshold, alignment of self-generated and noninductively driven currents occurs and steady state becomes possible. This concept is applied to simulate a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor.

Adaptive particle-based pore-level modeling of incompressible fluid flow in porous media: a direct and parallel approach

NASA Astrophysics Data System (ADS)

Ovaysi, S.; Piri, M.

2009-12-01

We present a three-dimensional fully dynamic parallel particle-based model for direct pore-level simulation of incompressible viscous fluid flow in disordered porous media. The model was developed from scratch and is capable of simulating flow directly in three-dimensional high-resolution microtomography images of naturally occurring or man-made porous systems. It reads the images as input where the position of the solid walls are given. The entire medium, i.e., solid and fluid, is then discretized using particles. The model is based on Moving Particle Semi-implicit (MPS) technique. We modify this technique in order to improve its stability. The model handles highly irregular fluid-solid boundaries effectively. It takes into account viscous pressure drop in addition to the gravity forces. It conserves mass and can automatically detect any false connectivity with fluid particles in the neighboring pores and throats. It includes a sophisticated algorithm to automatically split and merge particles to maintain hydraulic connectivity of extremely narrow conduits. Furthermore, it uses novel methods to handle particle inconsistencies and open boundaries. To handle the computational load, we present a fully parallel version of the model that runs on distributed memory computer clusters and exhibits excellent scalability. The model is used to simulate unsteady-state flow problems under different conditions starting from straight noncircular capillary tubes with different cross-sectional shapes, i.e., circular/elliptical, square/rectangular and triangular cross-sections. We compare the predicted dimensionless hydraulic conductances with the data available in the literature and observe an excellent agreement. We then test the scalability of our parallel model with two samples of an artificial sandstone, samples A and B, with different volumes and different distributions (non-uniform and uniform) of solid particles among the processors. An excellent linear scalability is obtained for sample B that has more uniform distribution of solid particles leading to a superior load balancing. The model is then used to simulate fluid flow directly in REV size three-dimensional x-ray images of a naturally occurring sandstone. We analyze the quality and consistency of the predicted flow behavior and calculate absolute permeability, which compares well with the available network modeling and Lattice-Boltzmann permeabilities available in the literature for the same sandstone. We show that the model conserves mass very well and is stable computationally even at very narrow fluid conduits. The transient- and the steady-state fluid flow patterns are presented as well as the steady-state flow rates to compute absolute permeability. Furthermore, we discuss the vital role of our adaptive particle resolution scheme in preserving the original pore connectivity of the samples and their narrow channels through splitting and merging of fluid particles.

A Novel Chronic Opioid Monitoring Tool to Assess Prescription Drug Steady State Levels in Oral Fluid.

PubMed

Shaparin, Naum; Mehta, Neel; Kunkel, Frank; Stripp, Richard; Borg, Damon; Kolb, Elizabeth

2017-11-01

Interpretation limitations of urine drug testing and the invasiveness of blood toxicology have motivated the desire for the development of simpler methods to assess biologically active drug levels on an individualized patient basis. Oral fluid is a matrix well-suited for the challenge because collections are based on simple noninvasive procedures and drug concentrations better correlate to blood drug levels as oral fluid is a filtrate of the blood. Well-established pharmacokinetic models were utilized to generate oral fluid steady state concentration ranges to assess the interpretive value of the alternative matrix to monitor steady state plasma oxycodone levels. Paired oral fluid and plasma samples were collected from patients chronically prescribed oxycodone and quantitatively analyzed by liquid chromatography tandem mass spectrometry. Steady state plasma concentration ranges were calculated for each donor and converted to an equivalent range in oral fluid. Measured plasma and oral fluid oxycodone concentrations were compared with respective matrix-matched steady state ranges, using each plasma steady state classification as the control. A high degree of correlation was observed between matrices when classifying donors according to expected steady state oxycodone concentration. Agreement between plasma and oral fluid steady state classifications was observed in 75.6% of paired samples. This study supports novel application of basic pharmacokinetic knowledge to the pain management industry, simplifying and improving individualized drug monitoring and risk assessment through the use of oral fluid drug testing. Many benefits of established therapeutic drug monitoring in plasma can be realized in oral fluid for patients chronically prescribed oxycodone at steady state. © 2017 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Crystal growth and furnace analysis

NASA Technical Reports Server (NTRS)

Dakhoul, Youssef M.

1986-01-01

A thermal analysis of Hg/Cd/Te solidification in a Bridgman cell is made using Continuum's VAST code. The energy equation is solved in an axisymmetric, quasi-steady domain for both the molten and solid alloy regions. Alloy composition is calculated by a simplified one-dimensional model to estimate its effect on melt thermal conductivity and, consequently, on the temperature field within the cell. Solidification is assumed to occur at a fixed temperature of 979 K. Simplified boundary conditions are included to model both the radiant and conductive heat exchange between the furnace walls and the alloy. Calculations are performed to show how the steady-state isotherms are affected by: the hot and cold furnace temperatures, boundary condition parameters, and the growth rate which affects the calculated alloy's composition. The Advanced Automatic Directional Solidification Furnace (AADSF), developed by NASA, is also thermally analyzed using the CINDA code. The objective is to determine the performance and the overall power requirements for different furnace designs.

The measurement of the heat-transfer coefficient between high-temperature liquids and solid surfaces

NASA Astrophysics Data System (ADS)

Utigard, T. A.; Warczok, A.; Desclaux, P.

1994-01-01

Two experimental techniques were developed for the purpose of measuring the heat-transfer coefficient between liquid slags/salts and solid surfaces. This was carried out because the heat-transfer coefficient is important for the design and operation of metallurgical reactors. A “cold-finger” technique was developed for the purpose of carrying out heat-transfer measurements during steady-state conditions simulating heat fluxes through furnace sidewalls. A lump capacitance method was developed and tested for the purpose of simulating transient conditions. To determine the effect of fluid flow on the heat-transfer coefficient, nitrogen gas stirring was used. The two techniques were tested in molten (1) and NaNO3, (2) NaCl, (3) Na3AlF6, and (4) 2FeO·SiO2, giving consistent results. It was found that the heat-transfer coefficient increases with increasing bath superheat and stirring.

Simultaneous reflectometry and interferometry for measuring thin-film thickness and curvature

NASA Astrophysics Data System (ADS)

Arends, A. A.; Germain, T. M.; Owens, J. F.; Putnam, S. A.

2018-05-01

A coupled reflectometer-interferometer apparatus is described for thin-film thickness and curvature characterization in the three-phase contact line region of evaporating fluids. Validation reflectometry studies are provided for Au, Ge, and Si substrates and thin-film coatings of SiO2 and hydrogel/Ti/SiO2. For interferometry, liquid/air and solid/air interferences are studied, where the solid/air samples consisted of glass/air/glass wedges, cylindrical lenses, and molded polydimethylsiloxane lenses. The liquid/air studies are based on steady-state evaporation experiments of water and isooctane on Si and SiO2/Ti/SiO2 wafers. The liquid thin-films facilitate characterization of both (i) the nano-scale thickness of the absorbed fluid layer and (ii) the macro-scale liquid meniscus thickness, curvature, and curvature gradient profiles. For our validation studies with commercial lenses, the apparatus is shown to measure thickness profiles within 4.1%-10.8% error.

Application of the dynamic model of Saeman to an industrial rotary kiln incinerator: numerical and experimental results.

PubMed

Ndiaye, L G; Caillat, S; Chinnayya, A; Gambier, D; Baudoin, B

2010-07-01

In order to simulate granular materials structure in a rotary kiln under the steady-state regime, a mathematical model has been developed by Saeman (1951). This model enables the calculation of the bed profiles, the axial velocity and solids flow rate along the kiln. This model can be coupled with a thermochemical model, in the case of a reacting moving bed. This dynamic model was used to calculate the bed profile for an industrial size kiln and the model projections were validated by measurements in a 4 m diameter by 16 m long industrial rotary kiln. The effect of rotation speed under solids bed profile and the effect of the feed rate under filling degree were established. On the basis of the calculations and the experimental results a phenomenological relation for the residence time estimation was proposed for the rotary kiln. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Reversibility and criticality in amorphous solids

DOE PAGES

Regev, Ido; Weber, John; Reichhardt, Charles; ...

2015-11-13

The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaoticmore » behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.« less

Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization

NASA Astrophysics Data System (ADS)

Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

2015-09-01

Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160 K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea -eb - n } during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle. This study also shows the complexity of the MAS-DNP process and therefore the necessity to rely on numerical simulations for understanding parametric dependencies of the enhancements. Finally an extension of the spin system up to five spins allowed us to probe the first steps of the transfer of polarization from the nuclei coupled to the electrons to further away nuclei, demonstrating a decrease in the spin-diffusion barrier under MAS conditions.

Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization.

PubMed

Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

2015-09-01

Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea-eb-n} during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle. This study also shows the complexity of the MAS-DNP process and therefore the necessity to rely on numerical simulations for understanding parametric dependencies of the enhancements. Finally an extension of the spin system up to five spins allowed us to probe the first steps of the transfer of polarization from the nuclei coupled to the electrons to further away nuclei, demonstrating a decrease in the spin-diffusion barrier under MAS conditions. Copyright © 2015 Elsevier Inc. All rights reserved.

Ring-Down Spectroscopy for Characterizing a CW Raman Laser

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

2007-01-01

.A relatively simple technique for characterizing an all-resonant intracavity continuous-wave (CW) solid-state Raman laser involves the use of ring-down spectroscopy. As used here, characterizing signifies determining such parameters as threshold pump power, Raman gain, conversion efficiency, and quality factors (Q values) of the pump and Stokes cavity modes. Heretofore, in order to characterize resonant-cavity-based Raman lasers, it has usually been necessary to manipulate the frequencies and power levels of pump lasers and, in each case, to take several sets of measurements. In cases involving ultra-high-Q resonators, it also has been desirable to lock pump lasers to resonator modes to ensure the quality of measurement data. Simpler techniques could be useful. In the present ring-down spectroscopic technique, one infers the parameters of interest from the decay of the laser out of its steady state. This technique does not require changing the power or frequency of the pump laser or locking the pump laser to the resonator mode. The technique is based on a theoretical analysis of what happens when the pump laser is abruptly switched off after the Raman generation reaches the steady state. The analysis starts with differential equations for the evolution of the amplitudes of the pump and Stokes electric fields, leading to solutions for the power levels of the pump and Stokes fields as functions of time and of the aforementioned parameters. Among other things, these solutions show how the ring-down time depends, to some extent, on the electromagnetic energy accumulated in the cavity. The solutions are readily converted to relatively simple equations for the parameters as functions of quantities that can be determined from measurements of the time-dependent power levels. For example, the steady-state intracavity conversion efficiency is given by G1/G2 1 and the threshold power is given by Pin(G2/G1)2, where Pin is the steady-state input pump power immediately prior to abrupt switch-off, G1 is the initial rate of decay of the pump field, and G2 is the final rate of decay of the pump field. Hence, it is possible to determine all the parameters from a single ring-down scan, provided that the measurements taken in that scan are sufficiently accurate and complete.

The first effects of fluid inertia on flows in ordered and random arrays of spheres

NASA Astrophysics Data System (ADS)

Hill, Reghan J.; Koch, Donald L.; Ladd, Anthony J. C.

2001-12-01

Theory and lattice-Boltzmann simulations are used to examine the effects of fluid inertia, at small Reynolds numbers, on flows in simple cubic, face-centred cubic and random arrays of spheres. The drag force on the spheres, and hence the permeability of the arrays, is determined at small but finite Reynolds numbers, at solid volume fractions up to the close-packed limits of the arrays. For small solid volume fraction, the simulations are compared to theory, showing that the first inertial contribution to the drag force, when scaled with the Stokes drag force on a single sphere in an unbounded fluid, is proportional to the square of the Reynolds number. The simulations show that this scaling persists at solid volume fractions up to the close-packed limits of the arrays, and that the first inertial contribution to the drag force relative to the Stokes-flow drag force decreases with increasing solid volume fraction. The temporal evolution of the spatially averaged velocity and the drag force is examined when the fluid is accelerated from rest by a constant average pressure gradient toward a steady Stokes flow. Theory for the short- and long-time behaviour is in good agreement with simulations, showing that the unsteady force is dominated by quasi-steady drag and added-mass forces. The short- and long-time added-mass coefficients are obtained from potential-flow and quasi-steady viscous-flow approximations, respectively.

A Data Filter for Identifying Steady-State Operating Points in Engine Flight Data for Condition Monitoring Applications

NASA Technical Reports Server (NTRS)

Simon, Donald L.; Litt, Jonathan S.

2010-01-01

This paper presents an algorithm that automatically identifies and extracts steady-state engine operating points from engine flight data. It calculates the mean and standard deviation of select parameters contained in the incoming flight data stream. If the standard deviation of the data falls below defined constraints, the engine is assumed to be at a steady-state operating point, and the mean measurement data at that point are archived for subsequent condition monitoring purposes. The fundamental design of the steady-state data filter is completely generic and applicable for any dynamic system. Additional domain-specific logic constraints are applied to reduce data outliers and variance within the collected steady-state data. The filter is designed for on-line real-time processing of streaming data as opposed to post-processing of the data in batch mode. Results of applying the steady-state data filter to recorded helicopter engine flight data are shown, demonstrating its utility for engine condition monitoring applications.

Tailored parameter optimization methods for ordinary differential equation models with steady-state constraints.

PubMed

Fiedler, Anna; Raeth, Sebastian; Theis, Fabian J; Hausser, Angelika; Hasenauer, Jan

2016-08-22

Ordinary differential equation (ODE) models are widely used to describe (bio-)chemical and biological processes. To enhance the predictive power of these models, their unknown parameters are estimated from experimental data. These experimental data are mostly collected in perturbation experiments, in which the processes are pushed out of steady state by applying a stimulus. The information that the initial condition is a steady state of the unperturbed process provides valuable information, as it restricts the dynamics of the process and thereby the parameters. However, implementing steady-state constraints in the optimization often results in convergence problems. In this manuscript, we propose two new methods for solving optimization problems with steady-state constraints. The first method exploits ideas from optimization algorithms on manifolds and introduces a retraction operator, essentially reducing the dimension of the optimization problem. The second method is based on the continuous analogue of the optimization problem. This continuous analogue is an ODE whose equilibrium points are the optima of the constrained optimization problem. This equivalence enables the use of adaptive numerical methods for solving optimization problems with steady-state constraints. Both methods are tailored to the problem structure and exploit the local geometry of the steady-state manifold and its stability properties. A parameterization of the steady-state manifold is not required. The efficiency and reliability of the proposed methods is evaluated using one toy example and two applications. The first application example uses published data while the second uses a novel dataset for Raf/MEK/ERK signaling. The proposed methods demonstrated better convergence properties than state-of-the-art methods employed in systems and computational biology. Furthermore, the average computation time per converged start is significantly lower. In addition to the theoretical results, the analysis of the dataset for Raf/MEK/ERK signaling provides novel biological insights regarding the existence of feedback regulation. Many optimization problems considered in systems and computational biology are subject to steady-state constraints. While most optimization methods have convergence problems if these steady-state constraints are highly nonlinear, the methods presented recover the convergence properties of optimizers which can exploit an analytical expression for the parameter-dependent steady state. This renders them an excellent alternative to methods which are currently employed in systems and computational biology.

Method and apparatus for controlling current in inductive loads such as large diameter coils

DOEpatents

Riveros, Carlos A.

1981-01-01

A method and apparatus for controlling electric current in loads that are essentially inductive, such that sparking and "ringing" current problems are reduced or eliminated. The circuit apparatus employs a pair of solid state switches (each of which switch may be an array of connected or parallel solid state switching devices such as transistors) and means for controlling those switches such that a power supply supplying two d.c. voltages (e.g. positive 150 volts d.c. and negative 150 volts d.c.) at low resistance may be connected across an essentially inductive load (e.g. a 6 gauge wire loop one hundred meters in diameter) alternatively and such that the first solid state switch is turned off and the second is turned on such that both are not on at the same time but the first turned on and the other on in less time than the inductive time constant (L/R) so that the load is essentially always presented with a low resistance path across its input. In this manner a steady AC current may be delivered to the load at a frequency desired. Shut-off problems are avoided by gradually shortening the period of switching to less than the time constant so that the maximum energy contained in the inductive load is reduced to approximately zero and dissipated in the inherent resistance. The invention circuit may be employed by adjusting the timing of switching to deliver a desired waveform (such as sinusoidal) to the load.

40 CFR 1039.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Code of Federal Regulations, 2010 CFR

2010-07-01

...-state duty cycles, including ramped-modal testing? 1039.505 Section 1039.505 Protection of Environment... duty cycles, including ramped-modal testing? This section describes how to test engines under steady-state conditions. In some cases, we allow you to choose the appropriate steady-state duty cycle for an...

Internal Flow Analysis of Large L/D Solid Rocket Motors

NASA Technical Reports Server (NTRS)

Laubacher, Brian A.

2000-01-01

Traditionally, Solid Rocket Motor (SRM) internal ballistic performance has been analyzed and predicted with either zero-dimensional (volume filling) codes or one-dimensional ballistics codes. One dimensional simulation of SRM performance is only necessary for ignition modeling, or for motors that have large length to port diameter ratios which exhibit an axial "pressure drop" during the early burn times. This type of prediction works quite well for many types of motors, however, when motor aspect ratios get large, and port to throat ratios get closer to one, two dimensional effects can become significant. The initial propellant grain configuration for the Space Shuttle Reusable Solid Rocket Motor (RSRM) was analyzed with 2-D, steady, axi-symmetric computational fluid dynamics (CFD). The results of the CFD analysis show that the steady-state performance prediction at the initial burn geometry, in general, agrees well with 1-D transient prediction results at an early time, however, significant features of the 2-D flow are captured with the CFD results that would otherwise go unnoticed. Capturing these subtle differences gives a greater confidence to modeling accuracy, and additional insight with which to model secondary internal flow effects like erosive burning. Detailed analysis of the 2-D flowfield has led to the discovery of its hidden 1-D isentropic behavior, and provided the means for a thorough and simplified understanding of internal solid rocket motor flow. Performance parameters such as nozzle stagnation pressure, static pressure drop, characteristic velocity, thrust and specific impulse are discussed in detail and compared for different modeling and prediction methods. The predicted performance using both the 1-D codes and the CFD results are compared with measured data obtained from static tests of the RSRM. The differences and limitations of predictions using ID and 2-D flow fields are discussed and some suggestions for the design of large L/D motors and more critically, motors with port to throat ratios near one, are covered.

The Markov process admits a consistent steady-state thermodynamic formalism

NASA Astrophysics Data System (ADS)

Peng, Liangrong; Zhu, Yi; Hong, Liu

2018-01-01

The search for a unified formulation for describing various non-equilibrium processes is a central task of modern non-equilibrium thermodynamics. In this paper, a novel steady-state thermodynamic formalism was established for general Markov processes described by the Chapman-Kolmogorov equation. Furthermore, corresponding formalisms of steady-state thermodynamics for the master equation and Fokker-Planck equation could be rigorously derived in mathematics. To be concrete, we proved that (1) in the limit of continuous time, the steady-state thermodynamic formalism for the Chapman-Kolmogorov equation fully agrees with that for the master equation; (2) a similar one-to-one correspondence could be established rigorously between the master equation and Fokker-Planck equation in the limit of large system size; (3) when a Markov process is restrained to one-step jump, the steady-state thermodynamic formalism for the Fokker-Planck equation with discrete state variables also goes to that for master equations, as the discretization step gets smaller and smaller. Our analysis indicated that general Markov processes admit a unified and self-consistent non-equilibrium steady-state thermodynamic formalism, regardless of underlying detailed models.

Liquefaction process wherein solvents derived from the material liquefied and containing increased concentrations of donor species are employed

DOEpatents

Fant, B. T.; Miller, John D.; Ryan, D. F.

1982-01-01

An improved process for the liquefaction of solid carbonaceous materials wherein a solvent or diluent derived from the solid carbonaceous material being liquefied is used to form a slurry of the solid carbonaceous material and wherein the solvent or diluent comprises from about 65 to about 85 wt. % hydroaromatic components. The solvent is prepared by first separating a solvent or diluent distillate fraction from the liquefaction product, subjecting this distillate fraction to hydrogenation and then extracting the naphthenic components from the hydrogenated product. The extracted naphthenic components are then dehydrogenated and hydrotreated to produce additional hydroaromatic components. These components are combined with the solvent or diluent distillate fraction. The solvent may also contain hydroaromatic constituents prepared by extracting naphthenic components from a heavy naphtha, dehydrogenating the same and then hydrotreating the dehydrogenated product. When the amount of solvent produced in this manner exceeds that required for steady state operation of the liquefaction process a portion of the solvent or diluent distillated fraction will be withdrawn as product.

SOLID SOLUTION EFFECTS ON THE THERMAL PROPERTIES IN THE MgAl2O4-MgGa2O4

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Hara, Kelley; Smith, Jeffrey D; Sander, Todd P.

Solid solution eects on thermal conductivity within the MgO-Al2O3-Ga2O3 system were studied. Samples with systematically varied additions of MgGa2O4 to MgAl2O4 were prepared and the laser ash technique was used to determine thermal diusivity at temperatures between 200C and 1300C. Heat capacity as a function of temperature from room temperature to 800C was also determined using dierential scanning calorimetry. Solid solution in the MgAl2O4-MgGa2O4 system decreases the thermal conductivity up to 1000C. At 200C thermal conductivity decreased 24% with a 5 mol% addition of MgGa2O4 to the system. At 1000C the thermal conductivity decreased 13% with a 5 mol% addition.more » Steady state calculations showed a 12.5% decrease in heat ux with 5 mol% MgGa2O4 considered across a 12 inch thickness.« less

Characterization of Detonation Soot Produced During Steady and Overdriven Conditions for Three High Explosive Formulations

NASA Astrophysics Data System (ADS)

Podlesak, David; Amato, Ronald; Dattelbaum, Dana; Firestone, Millicent; Gustavsen, Richard; Huber, Rachel; Ringstrand, Bryan

2015-06-01

The detonation of high explosives (HE) produces a dense fluid of molecular gases and solid carbon. The solid detonation carbon contains various carbon allotropes such as detonation nanodiamonds, ``onion-like'' carbon, graphite and amorphous carbon, with the formation of the different forms dependent upon pressure, temperature and the environmental conditions of the detonation. We have collected solid carbon residues from controlled detonations of three HE formulations (Composition B-3, PBX 9501, and PBX 9502). Soot was collected from experiments designed to produce both steady and overdriven conditions, and from detonations in both an ambient (air) atmosphere and in an inert Ar atmosphere. Structural studies to glean the features of the solid carbon products have been performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Raman spectroscopy, small-angle X-ray scattering (SAXS), and X-Ray Pair Distribution Function measurements (PDF). Bulk soot was also analyzed for elemental and isotopic compositions. We will discuss differences in the structure and composition of the detonation carbon as a function of formulation, detonation conditions, and the surrounding atmosphere.

Stabilization of a spatially uniform steady state in two systems exhibiting Turing patterns

NASA Astrophysics Data System (ADS)

Konishi, Keiji; Hara, Naoyuki

2018-05-01

This paper deals with the stabilization of a spatially uniform steady state in two coupled one-dimensional reaction-diffusion systems with Turing instability. This stabilization corresponds to amplitude death that occurs in a coupled system with Turing instability. Stability analysis of the steady state shows that stabilization does not occur if the two reaction-diffusion systems are identical. We derive a sufficient condition for the steady state to be stable for any length of system and any boundary conditions. Our analytical results are supported with numerical examples.

Pseudo-compressibility methods for the incompressible flow equations

NASA Technical Reports Server (NTRS)

Turkel, Eli; Arnone, A.

1993-01-01

Preconditioning methods to accelerate convergence to a steady state for the incompressible fluid dynamics equations are considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Thus the steady state of the preconditioned system is the same as the steady state of the original system. The method is compared to other types of pseudo-compressibility. For finite difference methods preconditioning can change and improve the steady state solutions. An application to viscous flow around a cascade with a non-periodic mesh is presented.

Quantum thermodynamics of nanoscale steady states far from equilibrium

NASA Astrophysics Data System (ADS)

Taniguchi, Nobuhiko

2018-04-01

We develop an exact quantum thermodynamic description for a noninteracting nanoscale steady state that couples strongly with multiple reservoirs. We demonstrate that there exists a steady-state extension of the thermodynamic function that correctly accounts for the multiterminal Landauer-Büttiker formula of quantum transport of charge, energy, or heat via the nonequilibrium thermodynamic relations. Its explicit form is obtained for a single bosonic or fermionic level in the wide-band limit, and corresponding thermodynamic forces (affinities) are identified. Nonlinear generalization of the Onsager reciprocity relations are derived. We suggest that the steady-state thermodynamic function is also capable of characterizing the heat current fluctuations of the critical transport where the thermal fluctuations dominate. Also, the suggested nonequilibrium steady-state thermodynamic relations seemingly persist for a spin-degenerate single level with local interaction.

Integration of Steady-State and Temporal Gene Expression Data for the Inference of Gene Regulatory Networks

PubMed Central

Wang, Yi Kan; Hurley, Daniel G.; Schnell, Santiago; Print, Cristin G.; Crampin, Edmund J.

2013-01-01

We develop a new regression algorithm, cMIKANA, for inference of gene regulatory networks from combinations of steady-state and time-series gene expression data. Using simulated gene expression datasets to assess the accuracy of reconstructing gene regulatory networks, we show that steady-state and time-series data sets can successfully be combined to identify gene regulatory interactions using the new algorithm. Inferring gene networks from combined data sets was found to be advantageous when using noisy measurements collected with either lower sampling rates or a limited number of experimental replicates. We illustrate our method by applying it to a microarray gene expression dataset from human umbilical vein endothelial cells (HUVECs) which combines time series data from treatment with growth factor TNF and steady state data from siRNA knockdown treatments. Our results suggest that the combination of steady-state and time-series datasets may provide better prediction of RNA-to-RNA interactions, and may also reveal biological features that cannot be identified from dynamic or steady state information alone. Finally, we consider the experimental design of genomics experiments for gene regulatory network inference and show that network inference can be improved by incorporating steady-state measurements with time-series data. PMID:23967277

Oxidation and Volatilization of Silica-Formers in Water Vapor

NASA Technical Reports Server (NTRS)

Opila, E. J.; Gray, Hugh R. (Technical Monitor)

2002-01-01

At high temperatures SiC and Si3N4 react with water vapor to form a silica scale. Silica scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming silica and the other removing silica, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved, After steady state is achieved, the oxide found on the surface is a constant thickness and recession of the underlying material occurs at a linear rate. The steady state oxide thickness, the time to achieve steady state, and the steady state recession rate can all be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate can also be determined from parameters that describe a water vapor-containing environment. Accordingly, maps have been developed to show these steady state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of silica formers in water-vapor containing environments such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4

X-Ray Spectral Analysis of the Steady States of GRS1915+105

NASA Astrophysics Data System (ADS)

Peris, Charith S.; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa D.; Varnière, Peggy; Rodriguez, Jerome; Pooley, Guy

2016-05-01

We report on the X-ray spectral behavior within the steady states of GRS1915+105. Our work is based on the full data set of the source obtained using the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to these regions as steady-soft and steady-hard. GRS1915+105 displays significant curvature in the coronal component in both the soft and hard data within the RXTE/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius ({R}{{in}}), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations, we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes η ˜ 0.68+/- 0.35 and η ˜ 1.12+/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of the model parameters to the state definitions shows that almost all of the steady-soft observations match the criteria of either a thermal or steep power-law state, while a large portion of the steady-hard observations match the hard-state criteria when the disk fraction constraint is neglected.

40 CFR 1048.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Code of Federal Regulations, 2010 CFR

2010-07-01

...-state duty cycles, including ramped-modal testing? 1048.505 Section 1048.505 Protection of Environment... SPARK-IGNITION ENGINES Test Procedures § 1048.505 How do I test engines using steady-state duty cycles... some cases, we allow you to choose the appropriate steady-state duty cycle for an engine. In these...

X-ray spectral analysis of the steady states of GRS 1915+105

NASA Astrophysics Data System (ADS)

Peris, Charith; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa Dil; Varniere, Peggy; Rodriguez, Jerome; Pooley, Guy G.

2016-04-01

Of the black hole binaries (BHBs) discovered thus far, GRS 1915+105 stands out as an exceptional source primarily due to its wild X-ray variability, the diversity of which has not been replicated in any other stellar-mass black hole. Although extreme variability is commonplace in its light-curve, about half of the observations of GRS1915+105 show fairly steady X-ray intensity. We report on the X-ray spectral behavior within these steady observations. Our work is based on a vast RXTE/PCA data set obtained on GRS 1915+105 during the course of its entire mission and 10 years of radio data from the Ryle Telescope, which overlap the X-ray data. We find that the steady observations within the X-ray data set naturally separate into two regions in a color-color diagram, which we refer to as steady-soft and steady-hard. GRS 1915+105 displays significant curvature in the Comptonization component within the PCA band pass suggesting significantly heating from a hot disk present in all states. A new Comptonization model 'simplcut' was developed in order to model this curvature to best effect. A majority of the steady-soft observations display a roughly constant inner disk radius, remarkably reminiscent of canonical soft state black hole binaries. In contrast, the steady-hard observations display a growing disk truncation that is correlated to the mass accretion rate through the disk, which suggests a magnetically truncated disk. A comparison of X-ray model parameters to the canonical state definitions show that almost all steady-soft observations match the criteria of either thermal or steep power law state, while the thermal state observations dominate the constant radius branch. A large portion 80 % of the steady-hard observations matches the hard state criteria when the disk fraction constraint is neglected. These results combine to suggest that within the complexity of this source is a simpler underlying basis of states, which map to those observed in canonical BHBs.

Dynamics of a multimode semiconductor laser with optical feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koryukin, I. V.

A new model of a multi-longitudinal-mode semiconductor laser with weak optical feedback is proposed. This model generalizes the well-known Tang-Statz-deMars equations, which are derived from the first principles and adequately describe solid-state lasers to a semiconductor active medium. Steady states of the model and the spectrum of relaxation oscillations are found, and the laser dynamics in the chaotic regime of low-frequency fluctuations of intensity is investigated. It is established that the dynamic properties of the proposed model depend mainly on the carrier diffusion, which controls mode-mode coupling in the active medium via spread of gratings of spatial inversion. The resultsmore » obtained are compared with the predictions of previous semiphenomenological models and the scope of applicability of these models is determined.« less

Moessbauer spectra of ferrite catalysts used in oxidative dehydrogenation

NASA Technical Reports Server (NTRS)

Cares, W. R.; Hightower, J. W.

1971-01-01

Room temperature Mossbauer spectroscopy was used to examine bulk changes which occur in low surface area CoFe2O4 and CuFe2O4 catalysts as a result of contact with various mixtures of trans-2-butene and O2 during oxidative dehydrogenation reactions at about 420 C. So long as there was at least some O2 in the gas phase, the CoFe2O4 spectrum was essentially unchanged. However, the spectrum changed from a random spinel in the oxidized state to an inverse spinel as it was reduced by oxide ion removal. The steady state catalyst lies very near the fully oxidized state. More dramatic solid state changes occurred as the CuFe2O4 underwent reduction. Under severe reduction, the ferrite was transformed into Cu and Fe3O4, but it could be reversibly recovered by oxidation. An intense doublet located near zero velocity persisted in all spectra of CuFe2O4 regardless of the state of reduction.

From polariton condensates to highly photonic quantum degenerate states of bosonic matter

PubMed Central

Aßmann, Marc; Tempel, Jean-Sebastian; Veit, Franziska; Bayer, Manfred; Rahimi-Iman, Arash; Löffler, Andreas; Höfling, Sven; Reitzenstein, Stephan; Worschech, Lukas; Forchel, Alfred

2011-01-01

Bose–Einstein condensation (BEC) is a thermodynamic phase transition of an interacting Bose gas. Its key signatures are remarkable quantum effects like superfluidity and a phonon-like Bogoliubov excitation spectrum, which have been verified for atomic BECs. In the solid state, BEC of exciton–polaritons has been reported. Polaritons are strongly coupled light-matter quasiparticles in semiconductor microcavities and composite bosons. However, they are subject to dephasing and decay and need external pumping to reach a steady state. Accordingly the polariton BEC is a nonequilibrium process of a degenerate polariton gas in self-equilibrium, but out of equilibrium with the baths it is coupled to and therefore deviates from the thermodynamic phase transition seen in atomic BECs. Here we show that key signatures of BEC can even be observed without fulfilling the self-equilibrium condition in a highly photonic quantum degenerate nonequilibrium system. PMID:21245353

Understanding mechanisms of solid-state phase transformations by probing nuclear materials

NASA Astrophysics Data System (ADS)

Banerjee, Srikumar; Donthula, Harish

2018-04-01

In this review a few examples will be cited to illustrate that a study on a specific nuclear material sometimes lead to a better understanding of scientific phenomena of broader interests. Zirconium alloys offer some unique opportunities in addressing fundamental issues such as (i) distinctive features between displacive and diffusional transformations, (ii) characteristics of shuffle and shear dominated displacive transformations and (iii) nature of mixed-mode transformations. Whether a transformation is of first or higher order?" is often raised while classifying it. There are rare examples, such as Ni-Mo alloys, in which during early stages of ordering the system experiences tendencies for both first order and second order transitions. Studies on the order-disorder transitions under a radiation environment have established the pathway for the evolution of ordering. These studies have also identified the temperature range over which the chemically ordered state remains stable in steady state under radiation.

40 CFR 86.1363-2007 - Steady-state testing with a discrete-mode cycle.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Steady-state testing with a discrete-mode cycle. 86.1363-2007 Section 86.1363-2007 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Exhaust Test Procedures § 86.1363-2007 Steady-state testing with a discrete-mode cycle. This section...

AEROSOL GROWTH IN A STEADY-STATE, CONTINUOUS FLOW CHAMBER: APPLICATION TO STUDIES OF SECONDARY AEROSOL FORMATION

EPA Science Inventory

An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The s...

Analytical Solution of Steady State Equations for Chemical Reaction Networks with Bilinear Rate Laws

PubMed Central

Halász, Ádám M.; Lai, Hong-Jian; McCabe, Meghan M.; Radhakrishnan, Krishnan; Edwards, Jeremy S.

2014-01-01

True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher dimensional space. We show that the linearized version of the steady state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1. PMID:24334389

Solid H2 in the interstellar medium

NASA Astrophysics Data System (ADS)

Füglistaler, A.; Pfenniger, D.

2018-06-01

Context. Condensation of H2 in the interstellar medium (ISM) has long been seen as a possibility, either by deposition on dust grains or thanks to a phase transition combined with self-gravity. H2 condensation might explain the observed low efficiency of star formation and might help to hide baryons in spiral galaxies. Aims: Our aim is to quantify the solid fraction of H2 in the ISM due to a phase transition including self-gravity for different densities and temperatures in order to use the results in more complex simulations of the ISM as subgrid physics. Methods: We used molecular dynamics simulations of fluids at different temperatures and densities to study the formation of solids. Once the simulations reached a steady state, we calculated the solid mass fraction, energy increase, and timescales. By determining the power laws measured over several orders of magnitude, we extrapolated to lower densities the higher density fluids that can be simulated with current computers. Results: The solid fraction and energy increase of fluids in a phase transition are above 0.1 and do not follow a power law. Fluids out of a phase transition are still forming a small amount of solids due to chance encounters of molecules. The solid mass fraction and energy increase of these fluids are linearly dependent on density and can easily be extrapolated. The timescale is below one second, the condensation can be considered instantaneous. Conclusions: The presence of solid H2 grains has important dynamic implications on the ISM as they may be the building blocks for larger solid bodies when gravity is included. We provide the solid mass fraction, energy increase, and timescales for high density fluids and extrapolation laws for lower densities.

A complete second-order theory for the unsteady flow about an airfoil due to a periodic gust

NASA Technical Reports Server (NTRS)

Goldstein, M. E.; Atassi, H.

1976-01-01

A uniformly valid second-order theory is developed for calculating the unsteady incompressible flow that occurs when an airfoil is subjected to a convected sinusoidal gust. Explicit formulas for the airfoil response functions (i.e., fluctuating lift) are given. The theory accounts for the effect of the distortion of the gust by the steady-state potential flow around the airfoil, and this effect is found to have an important influence on the response functions. A number of results relevant to the general theory of the scattering of vorticity waves by solid objects are also presented.

One-dimensional thermohydraulic code THESEUS and its application to chilldown process simulation in two-phase hydrogen flows

NASA Astrophysics Data System (ADS)

Papadimitriou, P.; Skorek, T.

THESUS is a thermohydraulic code for the calculation of steady state and transient processes of two-phase cryogenic flows. The physical model is based on four conservation equations with separate liquid and gas phase mass conservation equations. The thermohydraulic non-equilibrium is calculated by means of evaporation and condensation models. The mechanical non-equilibrium is modeled by a full-range drift-flux model. Also heat conduction in solid structures and heat exchange for the full spectrum of heat transfer regimes can be simulated. Test analyses of two-channel chilldown experiments and comparisons with the measured data have been performed.

A Numerical Method for Incompressible Flow with Heat Transfer

NASA Technical Reports Server (NTRS)

Sa, Jong-Youb; Kwak, Dochan

1997-01-01

A numerical method for the convective heat transfer problem is developed for low speed flow at mild temperatures. A simplified energy equation is added to the incompressible Navier-Stokes formulation by using Boussinesq approximation to account for the buoyancy force. A pseudocompressibility method is used to solve the resulting set of equations for steady-state solutions in conjunction with an approximate factorization scheme. A Neumann-type pressure boundary condition is devised to account for the interaction between pressure and temperature terms, especially near a heated or cooled solid boundary. It is shown that the present method is capable of predicting the temperature field in an incompressible flow.

Long cycle life microporous spherical carbon anodes for sodium-ion batteries derived from furfuryl alcohol

DOE PAGES

Zhou, Dehua; Peer, Maryam; Yang, Zhenzhen; ...

2016-04-11

Spherical micron-sized carbon powders were synthesized from feedstock furfuryl alcohol and tested as anodes in sodium ion batteries (SIBs). A long cycle life of 1000 cycles is achievable with this carbon at C rate (3–4 mg cm –2 loading and i = 200 mA g –1) yielding a steady capacity of ca. 115 mA h g –1. Furthermore, the results from solid-state 23Na MAS NMR analyses of cycled electrodes indicate no correlation in voltage profiles with sodium site nature (graphene or nanopores), which is a new observation in SIB carbon anodes.

The simulation of a propulsive jet and force measurement using a magnetically suspended wind tunnel model

NASA Technical Reports Server (NTRS)

Garbutt, K. S.; Goodyer, M. J.

1994-01-01

Models featuring the simulation of exhaust jets were developed for magnetic levitation in a wind tunnel. The exhaust gas was stored internally producing a discharge of sufficient duration to allow nominal steady state to be reached. The gas was stored in the form of compressed gas or a solid rocket propellant. Testing was performed with the levitated models although deficiencies prevented the detection of jet-induced aerodynamic effects. Difficulties with data reduction led to the development of a new force calibration technique, used in conjunction with an exhaust simulator and also in separate high incidence aerodynamic tests.

Compositional effects on the chemorheological properties and forming behavior of aqueous alumina-poly(vinyl alcohol) gelcasting suspensions

NASA Astrophysics Data System (ADS)

Morissette, Sherry L.

A new gelcasting system based on aqueous, alumina-poly(vinyl alcohol) (PVA) suspensions cross-linked by an organotitanate coupling agent has been developed. Both the chemorheological properties and forming behavior of this system exhibited a strong compositional dependence. A sol- gel phase diagram was established, which yielded the critical titanium concentration [Ti] c required for gelation at a given PVA volume fraction, as well as the minimum PVA volume fraction ( fminPVA = 0.0245) and titanium PVA concentration ([Ti]min = 9.984 x 10--4 g Ti/ml) below which gelation was not observed irrespective of solution composition. The gelation time of suspensions of constant PVA volume fraction ( fsolnPVA ) decreased with increasing cross-linking agent concentration, PVA temperature, and solids volume fraction. The steady-state viscosity and elastic modulus of polymer solutions ( fsolnPVA = 0.05) of varying [Ti] were well described by the PVA percolation model, giving scaling exponents of 0.84 and 1.79, respectively. The steady-state elastic modulus of gel casting suspensions, which provides a measure of their handling strength in the as-gelled state, increased with increasing solids volume fraction. Gelcasting suspensions were used as feedstock for solid free-form fabrication (SFF) of ceramic components. The influence of processing conditions (e.g., tip diameter, mixing rate, table speed, etc.) and suspension rheology on deposition behavior was investigated. Continuous printablity was achieved for tip diameters ranging from dt = 0.254 -- 1.370 mm for all mixing rates (Rmix 5 -- 300 rpm) and suspension compositions (i.e., fAl2O3 = 0.45, φPVA = 0.275, [Ti] 0 -- 6.30 x 10--3 g Ti/ml) probed, where the minimum tip diameter for continuous printing was 0.203 mm. Printed lines were uniform with good edge definition. Line dimensions were independent of mixing rate for the given process conditions. The as-cast alumina volume fraction ( fAl2O3 ) depended on casting conditions and cross-linking agent concentration, where fAl2O3 decreased with increasing tip diameter and increased with increasing cross-linking agent concentration. Free-fomied Al2O3 components exhibited uniform particle packing and had minimal macro-defects (e.g., slumping or stair casing) and no detectable micro-defects (e.g., bubbles or cracking).

Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Naval Station Mayport, Florida

USGS Publications Warehouse

Halford, K.J.

1998-01-01

Ground-water flow through the surficial aquifer system at Naval Station Mayport near Jacksonville, Florida, was simulated with a two-layer finite-difference model as part of an investigation conducted by the U.S. Geological Survey. The model was calibrated to 229 water-level measurements from 181 wells during three synoptic surveys (July 17, 1995; July 31, 1996; and October 24, 1996). A quantifiable understanding of ground-water flow through the surficial aquifer was needed to evaluate remedial-action alternatives under consideration by the Naval Station Mayport to control the possible movement of contaminants from sites on the station. Multi-well aquifer tests, single-well tests, and slug tests were conducted to estimate the hydraulic properties of the surficial aquifer system, which was divided into three geohydrologic units?an S-zone and an I-zone separated by a marsh-muck confining unit. The recharge rate was estimated to range from 4 to 15 inches per year (95 percent confidence limits), based on a chloride-ratio method. Most of the simulations following model calibration were based on a recharge rate of 8 inches per year to unirrigated pervious areas. The advective displacement of saline pore water during the last 200 years was simulated using a particle-tracking routine, MODPATH, applied to calibrated steady-state and transient models of the Mayport peninsula. The surficial aquifer system at Naval Station Mayport has been modified greatly by natural and anthropogenic forces so that the freshwater flow system is expanding and saltwater is being flushed from the system. A new MODFLOW package (VAR1) was written to simulate the temporal variation of hydraulic properties caused by construction activities at Naval Station Mayport. The transiently simulated saltwater distribution after 200 years of displacement described the chloride distribution in the I-zone (determined from measurements made during 1993 and 1996) better than the steady-state simulation. The advective movement of contaminants from selected sites within the solid waste management units to discharge points was simulated using MODPATH. Most of the particles were discharged to the nearest surface-water feature after traveling less than 1,000 feet in the ground-water system. Most areas within 1,000 feet of a surface-water feature or storm sewer had traveltimes of less than 50 years, based on an effective porosity of 40 percent. Contributing areas, traveltimes, and pathlines were identified for 224 wells at Naval Station Mayport under steady-state and transient conditions by back-tracking a particle from the midpoint of the wetted screen of each well. Traveltimes to contributing areas that ranged between 15 and 50 years, estimated by the steady-state model, differed most from the transient traveltime estimates. Estimates of traveltimes and pathlines based on steady-state model results typically were 10 to 20 years more and about twice as long as corresponding estimates from the transient model. The models differed because the steady-state model simulated 1996 conditions when Naval Station Mayport had more impervious surfaces than at any earlier time. The expansion of the impervious surfaces increased the average distance between contributing areas and observation wells.

Motion of a Drop on a Solid Surface Due to a Wettability Gradient

NASA Technical Reports Server (NTRS)

Subramanian, R.; Moumen, Nadjoua; McLaughlin, John B.

2005-01-01

The hydrodynamic force experienced by a spherical-cap drop moving on a solid surface is obtained from two approximate analytical solutions and used to predict the quasi-steady speed of the drop in a wettability gradient. One solution is based on approximation of the shape of the drop as a collection of wedges, and the other is based on lubrication theory. Also, asymptotic results from both approximations for small contact angles, as well as an asymptotic result from lubrication theory that is good when the length scale of the drop is large compared with the slip length, are given. The results for the hydrodynamic force also can be used to predict the quasi-steady speed of a drop sliding down an incline.

MATHEMATICAL ANALYSIS OF STEADY-STATE SOLUTIONS IN COMPARTMENT AND CONTINUUM MODELS OF CELL POLARIZATION

PubMed Central

ZHENG, ZHENZHEN; CHOU, CHING-SHAN; YI, TAU-MU; NIE, QING

2013-01-01

Cell polarization, in which substances previously uniformly distributed become asymmetric due to external or/and internal stimulation, is a fundamental process underlying cell mobility, cell division, and other polarized functions. The yeast cell S. cerevisiae has been a model system to study cell polarization. During mating, yeast cells sense shallow external spatial gradients and respond by creating steeper internal gradients of protein aligned with the external cue. The complex spatial dynamics during yeast mating polarization consists of positive feedback, degradation, global negative feedback control, and cooperative effects in protein synthesis. Understanding such complex regulations and interactions is critical to studying many important characteristics in cell polarization including signal amplification, tracking dynamic signals, and potential trade-off between achieving both objectives in a robust fashion. In this paper, we study some of these questions by analyzing several models with different spatial complexity: two compartments, three compartments, and continuum in space. The step-wise approach allows detailed characterization of properties of the steady state of the system, providing more insights for biological regulations during cell polarization. For cases without membrane diffusion, our study reveals that increasing the number of spatial compartments results in an increase in the number of steady-state solutions, in particular, the number of stable steady-state solutions, with the continuum models possessing infinitely many steady-state solutions. Through both analysis and simulations, we find that stronger positive feedback, reduced diffusion, and a shallower ligand gradient all result in more steady-state solutions, although most of these are not optimally aligned with the gradient. We explore in the different settings the relationship between the number of steady-state solutions and the extent and accuracy of the polarization. Taken together these results furnish a detailed description of the factors that influence the tradeoff between a single correctly aligned but poorly polarized stable steady-state solution versus multiple more highly polarized stable steady-state solutions that may be incorrectly aligned with the external gradient. PMID:21936604

Solid effect in magic angle spinning dynamic nuclear polarization

NASA Astrophysics Data System (ADS)

Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

2012-08-01

For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω _0 ^{ - 2} field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.

An exact solution for the steady state phase distribution in an array of oscillators coupled on a hexagonal lattice

NASA Technical Reports Server (NTRS)

Pogorzelski, Ronald J.

2004-01-01

When electronic oscillators are coupled to nearest neighbors to form an array on a hexagonal lattice, the planar phase distributions desired for excitation of a phased array antenna are not steady state solutions of the governing non-linear equations describing the system. Thus the steady state phase distribution deviates from planar. It is shown to be possible to obtain an exact solution for the steady state phase distribution and thus determine the deviation from the desired planar distribution as a function of beam steering angle.

Preconditioning and the limit to the incompressible flow equations

NASA Technical Reports Server (NTRS)

Turkel, E.; Fiterman, A.; Vanleer, B.

1993-01-01

The use of preconditioning methods to accelerate the convergence to a steady state for both the incompressible and compressible fluid dynamic equations are considered. The relation between them for both the continuous problem and the finite difference approximation is also considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Hence, the steady state of the preconditioned system is the same as the steady state of the original system. For finite difference methods the preconditioning can change and improve the steady state solutions. An application to flow around an airfoil is presented.

Theoretical studies of solar-pumped lasers

NASA Technical Reports Server (NTRS)

Harries, W. L.

1982-01-01

Solar-pumped lasers were investigated by comparing experimental results from pulse experiments with steady state calculations. The time varying behavior of an IBr laser is studied. The analysis is only approximate, but indicates that conditions occurring in a pulsed experiment are quite different from those at steady state. The possibility of steady-state lasing in an IBr laser is determined. The effects of high temperatures on the quenching and recombination rates are examined. Although uncertainties in the values of the rate coefficients make it difficult to draw firm conclusions, it seems steady state running may be possible at high temperatures.

Quantification of the memory effect of steady-state currents from interaction-induced transport in quantum systems

NASA Astrophysics Data System (ADS)

Lai, Chen-Yen; Chien, Chih-Chun

2017-09-01

Dynamics of a system in general depends on its initial state and how the system is driven, but in many-body systems the memory is usually averaged out during evolution. Here, interacting quantum systems without external relaxations are shown to retain long-time memory effects in steady states. To identify memory effects, we first show quasi-steady-state currents form in finite, isolated Bose- and Fermi-Hubbard models driven by interaction imbalance and they become steady-state currents in the thermodynamic limit. By comparing the steady-state currents from different initial states or ramping rates of the imbalance, long-time memory effects can be quantified. While the memory effects of initial states are more ubiquitous, the memory effects of switching protocols are mostly visible in interaction-induced transport in lattices. Our simulations suggest that the systems enter a regime governed by a generalized Fick's law and memory effects lead to initial-state-dependent diffusion coefficients. We also identify conditions for enhancing memory effects and discuss possible experimental implications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grady, Dennis E.

A fourth-power law underlying the steady shock-wave structure and solid viscosity of condensed material has been observed for a wide range of metals and non-metals. The fourth-power law relates the steady-wave Hugoniot pressure to the fourth power of the strain rate during passage of the material through the structured shock wave. Preceding the fourth-power law was the observation in a shock transition that the product of the shock dissipation energy and the shock transition time is a constant independent of the shock pressure amplitude. Invariance of this energy-time product implies the fourth-power law. This property of the shock transition inmore » solids was initially identified as a shock invariant. More recently, it has been referred to as the dissipative action, although no relationship to the accepted definitions of action in mechanics has been demonstrated. This same invariant property has application to a wider range of transient failure phenomena in solids. Invariance of this dissipation action has application to spall fracture, failure through adiabatic shear, shock compaction of granular media, and perhaps others. Through models of the failure processes, a clearer picture of the physics underlying the observed invariance is emerging. These insights in turn are leading to a better understanding of the shock deformation processes underlying the fourth-power law. Experimental result and material models encompassing the dynamic failure of solids are explored for the purpose of demonstrating commonalities leading to invariance of the dissipation action. Calculations are extended to aluminum and uranium metals with the intent of predicting micro-scale dynamics and spatial structure in the steady shock wave.« less

Robust adaptive control for a hybrid solid oxide fuel cell system

NASA Astrophysics Data System (ADS)

Snyder, Steven

2011-12-01

Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices. They offer a number of advantages beyond those of most other fuel cells due to their high operating temperature (800-1000°C), such as internal reforming, heat as a byproduct, and faster reaction kinetics without precious metal catalysts. Mitigating fuel starvation and improving load-following capabilities of SOFC systems are conflicting control objectives. However, this can be resolved by the hybridization of the system with an energy storage device, such as an ultra-capacitor. In this thesis, a steady-state property of the SOFC is combined with an input-shaping method in order to address the issue of fuel starvation. Simultaneously, an overall adaptive system control strategy is employed to manage the energy sharing between the elements as well as to maintain the state-of-charge of the energy storage device. The adaptive control method is robust to errors in the fuel cell's fuel supply system and guarantees that the fuel cell current and ultra-capacitor state-of-charge approach their target values and remain uniformly, ultimately bounded about these target values. Parameter saturation is employed to guarantee boundedness of the parameters. The controller is validated through hardware-in-the-loop experiments as well as computer simulations.

Experimental measurements of U60 nanocluster stability in aqueous solution

NASA Astrophysics Data System (ADS)

Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

2015-05-01

In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the dissociation behavior of nanoclusters under a range of aqueous conditions.

40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part 51—Steady-State...

40 CFR Appendix II to Part 1039 - Steady-State Duty Cycles

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix... Appendix II to Part 1039—Steady-State Duty Cycles (a) The following duty cycles apply for constant-speed engines: (1) The following duty cycle applies for discrete-mode testing: D2 mode number Engine speed...

40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part 51—Steady-State...

40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part 51—Steady-State...

40 CFR Appendix II to Part 1039 - Steady-State Duty Cycles

Code of Federal Regulations, 2011 CFR

2011-07-01

... Appendix II to Part 1039—Steady-State Duty Cycles (a) The following duty cycles apply for constant-speed engines: (1) The following duty cycle applies for discrete-mode testing: D2 mode number Engine speed...(seconds) Engine speed Torque(percent) 1, 2 1a Steady-state 53 Engine governed 100. 1b Transition 20 Engine...

Characterization of detonation soot produced during steady and overdriven conditions for three high explosive formulations

NASA Astrophysics Data System (ADS)

Podlesak, David W.; Huber, Rachel C.; Amato, Ronald S.; Dattelbaum, Dana M.; Firestone, Millicent A.; Gustavsen, Richard L.; Johnson, Carl E.; Mang, Joseph T.; Ringstrand, Bryan S.

2017-01-01

The detonation of high explosives (HE) produces a dense fluid of molecular gases and solid carbon. The solid detonation carbon contains various carbon allotropes such as detonation nanodiamonds, onion-like carbon, graphite and amorphous carbon, with the formation of the different forms dependent upon pressure, temperature and the environmental conditions of the detonation. We have collected solid carbon residues from controlled detonations of three HE formulations (Composition B-3, PBX 9501, and PBX 9502). Soot was collected from experiments designed to produce both steady and overdriven conditions, and from detonations in both an ambient (air) atmosphere and in an inert Ar atmosphere. Differences in solid carbon residues were quantified using X-ray photoelectron spectroscopy and carbon isotope measurements. Environmental conditions, HE formulation, and peak pressures influenced the amount of and isotopic composition of the carbon in the soot. Detonations in an Ar atmosphere produced greater amounts of carbon soot with lower δ13C values than those in ambient air. Therefore, solid carbon residues continued to evolve after detonation due to excess oxygen in the ambient air detonations. As well, higher peak pressures in overdriven conditions produced less carbon soot with, in general, higher δ13C values. Consequently, while overdriven conditions only produced peak pressures for a limited duration, it was enough to influence the composition of the solid carbon residues.

Steady-state and quench-dependent relaxation of a quantum dot coupled to one-dimensional leads

NASA Astrophysics Data System (ADS)

Nuss, Martin; Ganahl, Martin; Evertz, Hans Gerd; Arrigoni, Enrico; von der Linden, Wolfgang

2013-07-01

We study the time evolution and steady state of the charge current in a single-impurity Anderson model, using matrix product states techniques. A nonequilibrium situation is imposed by applying a bias voltage across one-dimensional tight-binding leads. Focusing on particle-hole symmetry, we extract current-voltage characteristics from universal low-bias up to high-bias regimes, where band effects start to play a dominant role. We discuss three quenches, which after strongly quench-dependent transients yield the same steady-state current. Among these quenches we identify those favorable for extracting steady-state observables. The period of short-time oscillations is shown to compare well to real-time renormalization group results for a simpler model of spinless fermions. We find indications that many-body effects play an important role at high-bias voltage and finite bandwidth of the metallic leads. The growth of entanglement entropy after a certain time scale ∝Δ-1 is the major limiting factor for calculating the time evolution. We show that the magnitude of the steady-state current positively correlates with entanglement entropy. The role of high-energy states for the steady-state current is explored by considering a damping term in the time evolution.

Steady-state pattern electroretinogram and short-duration transient visual evoked potentials in glaucomatous and healthy eyes.

PubMed

Amarasekera, Dilru C; Resende, Arthur F; Waisbourd, Michael; Puri, Sanjeev; Moster, Marlene R; Hark, Lisa A; Katz, L Jay; Fudemberg, Scott J; Mantravadi, Anand V

2018-01-01

This study evaluates two rapid electrophysiological glaucoma diagnostic tests that may add a functional perspective to glaucoma diagnosis. This study aimed to determine the ability of two office-based electrophysiological diagnostic tests, steady-state pattern electroretinogram and short-duration transient visual evoked potentials, to discern between glaucomatous and healthy eyes. This is a cross-sectional study in a hospital setting. Forty-one patients with glaucoma and 41 healthy volunteers participated in the study. Steady-state pattern electroretinogram and short-duration transient visual evoked potential testing was conducted in glaucomatous and healthy eyes. A 64-bar-size stimulus with both a low-contrast and high-contrast setting was used to compare steady-state pattern electroretinogram parameters in both groups. A low-contrast and high-contrast checkerboard stimulus was used to measure short-duration transient visual evoked potential parameters in both groups. Steady-state pattern electroretinogram parameters compared were MagnitudeD, MagnitudeD/Magnitude ratio, and the signal-to-noise ratio. Short-duration transient visual evoked potential parameters compared were amplitude and latency. MagnitudeD was significantly lower in glaucoma patients when using a low-contrast (P = 0.001) and high-contrast (P < 0.001) 64-bar-size steady-state pattern electroretinogram stimulus. MagnitudeD/Magnitude ratio and SNR were significantly lower in the glaucoma group when using a high-contrast 64-bar-size stimulus (P < 0.001 and P = 0.010, respectively). Short-duration transient visual evoked potential amplitude and latency were not significantly different between the two groups. Steady-state pattern electroretinogram was effectively able to discern between glaucomatous and healthy eyes. Steady-state pattern electroretinogram may thus have a role as a clinically useful electrophysiological diagnostic tool. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

Time density curve analysis for C-arm FDCT PBV imaging.

PubMed

Kamran, Mudassar; Byrne, James V

2016-04-01

Parenchymal blood volume (PBV) estimation using C-arm flat detector computed tomography (FDCT) assumes a steady-state contrast concentration in cerebral vasculature for the scan duration. Using time density curve (TDC) analysis, we explored if the steady-state assumption is met for C-arm CT PBV scans, and how consistent the contrast-material dynamics in cerebral vasculature are across patients. Thirty C-arm FDCT datasets of 26 patients with aneurysmal-SAH, acquired as part of a prospective study comparing C-arm CT PBV with MR-PWI, were analysed. TDCs were extracted from the 2D rotational projections. Goodness-of-fit of TDCs to a steady-state horizontal-line-model and the statistical similarity among the individual TDCs were tested. Influence of the differences in TDC characteristics on the agreement of resulting PBV measurements with MR-CBV was calculated. Despite identical scan parameters and contrast-injection-protocol, the individual TDCs were statistically non-identical (p < 0.01). Using Dunn's multiple comparisons test, of the total 435 individual comparisons among the 30 TDCs, 330 comparisons (62%) reached statistical significance for difference. All TDCs deviated significantly (p < 0.01) from the steady-state horizontal-line-model. PBV values of those datasets for which the TDCs showed largest deviations from the steady-state model demonstrated poor agreement and correlation with MR-CBV, compared with the PBV values of those datasets for which the TDCs were closer to steady-state. For clinical C-arm CT PBV examinations, the administered contrast material does not reach the assumed 'ideal steady-state' for the duration of scan. Using a prolonged injection protocol, the degree to which the TDCs approximate the ideal steady-state influences the agreement of resulting PBV measurements with MR-CBV. © The Author(s) 2016.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, J.M.

Chemical phenomena occurring at boundaries between insulating solids and liquids (adsorption, partition, monolayer self-assembly, catalysis, and chemical reactions) are important to energy-related analytical chemistry. These phenomena are central to chromatography, solid-phase extraction, immobilized analytical reagents, and optical sensors. Chemical interactions in these processes cannot generally be identified solely by equilibrium surface concentrations, since the steady-state behavior does not reveal the mechanism or rates of surface reactions. Goal therefore is to develop surface-sensitive spectroscopies by which chemical kinetics at liquid/solid interfaces can be observed on time-scales from nanoseconds to seconds. In the first year, we have used Joule-discharge heating kinetics tomore » study pore structure of silica gels; effects of pore diameter, particle size, and chemical modification on pore connectivity were investigated. Temperature-jump relaxation measurements of sorption/desorption kinetics at liquid/solid interfaces were also carried out using Joule heating; kinetic barriers to sorption of ions from solution were found for both C18 and Cl surfaces. Through a collaboration with Fritz-Haber Institute in Berlin, we were able to acquire laser temperature-jump data on kinetics at liquid/solid interfaces using a colloidal sample. We also quantified the rate of migration of covalently attached ligands on silica surfaces; from the temperature dependence, the large energy barrier to migration was estimated. A review of applications of electronic spectroscopy (absorption and fluorescence) to reversed-phase chromatographic interfaces was published.« less

Improved design of anaerobic digesters for household biogas production in indonesia: one cow, one digester, and one hour of cooking per day.

PubMed

Usack, Joseph G; Wiratni, Wiratni; Angenent, Largus T

2014-01-01

A government-sponsored initiative in Indonesia to design and implement low-cost anaerobic digestion systems resulted in 21 full-scale systems with the aim to satisfy the cooking fuel demands of rural households owning at least one cow. The full-scale design consisted of a 0.3 m diameter PVC pipe, which was operated as a conventional plug-flow system. The system generated enough methane to power a cooking stove for ∼ 1 h. However, eventual clogging from solids accumulation inside the bioreactor proved to be a major drawback. Here, we improved the digester configuration to remedy clogging while maintaining system performance. Controlled experiments were performed using four 9-L laboratory-scale digesters operated at a temperature of 27 ± 1 °C, a volatile solids loading rate of 2.0 g VS · L(-1) · day(-1), and a 21-day hydraulic retention time. Two of the digesters were replicates of the original design (control digesters), while the other two digesters included internal mixing or effluent recycle (experimental digesters). The performance of each digester was compared based on methane yields, VS removal efficiencies, and steady-state solids concentrations during an operating period of 311 days. Statistical analyses revealed that internal mixing and effluent recycling resulted in reduced solids accumulation compared to the controls without diminishing methane yields or solids removal efficiencies.

Simulation of the Effect of Realistic Space Vehicle Environments on Binary Metal Alloys

NASA Technical Reports Server (NTRS)

Westra, Douglas G.; Poirier, D. R.; Heinrich, J. C.; Sung, P. K.; Felicelli, S. D.; Phelps, Lisa (Technical Monitor)

2001-01-01

Simulations that assess the effect of space vehicle acceleration environments on the solidification of Pb-Sb alloys are reported. Space microgravity missions are designed to provide a near zero-g acceleration environment for various types of scientific experiments. Realistically. these space missions cannot provide a perfect environment. Vibrations caused by crew activity, on-board experiments, support systems stems (pumps, fans, etc.), periodic orbital maneuvers, and water dumps can all cause perturbations to the microgravity environment. In addition, the drag on the space vehicle is a source of acceleration. Therefore, it is necessary to predict the impact of these vibration-perturbations and the steady-state drag acceleration on the experiments. These predictions can be used to design mission timelines. so that the experiment is run during times that the impact of the acceleration environment is acceptable for the experiment of interest. The simulations reported herein were conducted using a finite element model that includes mass, species, momentum, and energy conservation. This model predicts the existence of "channels" within the processing mushy zone and subsequently "freckles" within the fully processed solid, which are the effects of thermosolutal convection. It is necessary to mitigate thermosolutal convection during space experiments of metal alloys, in order to study and characterize diffusion-controlled transport phenomena (microsegregation) that are normally coupled with macrosegregation. The model allows simulation of steady-state and transient acceleration values ranging from no acceleration (0 g). to microgravity conditions (10(exp -6) to 10(exp -3) g), to terrestrial gravity conditions (1 g). The transient acceleration environments simulated were from the STS-89 SpaceHAB mission and from the STS-94 SpaceLAB mission. with on-orbit accelerometer data during different mission periods used as inputs for the simulation model. Periods of crew exercise, quiet (no crew activity), and nominal conditions from STS-89 were used as simulation inputs as were periods of nominal. overboard water-dump, and free-drift (no orbit maneuvering operations) from STS-94. Steady-state acceleration environments of 0.0 and 10(exp -6) to 10(exp -1) g were also simulated, to serve as a comparison to the transient data and to assess an acceptable magnitude for the steady-state vehicle drag

Solid oxide fuel cell short stack performance testing - Part A: Experimental analysis and μ-combined heat and power unit comparison

NASA Astrophysics Data System (ADS)

Mastropasqua, L.; Campanari, S.; Brouwer, J.

2017-12-01

The need to experimentally understand the detailed performance of SOFC stacks under operating conditions typical of commercial SOFC systems has prompted this two-part study. The steady state performance of a 6-cell short stack of yttria (Y2O3) stabilised zirconia (YSZ) with Ni/YSZ anodes and composite Sr-doped lanthanum manganite (LaMnO3, LSM)/YSZ cathodes is experimentally evaluated. In Part A, the stack characterisation is carried out by means of sensitivity analyses on the fuel utilisation factor and the steam-to-carbon ratio. Electrical and environmental performances are assessed and the results are compared with a commercial full-scale micro-CHP system, which comprises the same cells. The results show that the measured temperature dynamics of the short stack in a test stand environment are on the order of many minutes; therefore, one cannot neglect temperature dynamics for a precise measurement of the steady state polarisation behaviour. The overall polarisation performance is comparable to that of the full stack employed in the micro-CHP system, confirming the good representation that short-stack analyses can give of the entire SOFC module. The environmental performance is measured verifying the negligible values of NO emissions (<10 ppb) across the whole polarisation curve.

Start-up of membrane bioreactor and hybrid moving bed biofilm reactor-membrane bioreactor: kinetic study.

PubMed

Leyva-Díaz, J C; Poyatos, J M

2015-01-01

A hybrid moving bed biofilm reactor-membrane bioreactor (hybrid MBBR-MBR) system was studied as an alternative solution to conventional activated sludge processes and membrane bioreactors. This paper shows the results obtained from three laboratory-scale wastewater treatment plants working in parallel in the start-up and steady states. The first wastewater treatment plant was a MBR, the second one was a hybrid MBBR-MBR system containing carriers both in anoxic and aerobic zones of the bioreactor (hybrid MBBR-MBRa), and the last one was a hybrid MBBR-MBR system which contained carriers only in the aerobic zone (hybrid MBBR-MBRb). The reactors operated with a hydraulic retention time of 30.40 h. A kinetic study for characterizing heterotrophic biomass was carried out and organic matter and nutrients removals were evaluated. The heterotrophic biomass of the hybrid MBBR-MBRb showed the best kinetic performance in the steady state, with yield coefficient for heterotrophic biomass=0.30246 mg volatile suspended solids per mg chemical oxygen demand, maximum specific growth rate for heterotrophic biomass=0.00308 h(-1) and half-saturation coefficient for organic matter=3.54908 mg O2 L(-1). The removal of organic matter was supported by the kinetic study of heterotrophic biomass.

Feedback stabilization of an oscillating vertical cylinder by POD Reduced-Order Model

NASA Astrophysics Data System (ADS)

Tissot, Gilles; Cordier, Laurent; Noack, Bernd R.

2015-01-01

The objective is to demonstrate the use of reduced-order models (ROM) based on proper orthogonal decomposition (POD) to stabilize the flow over a vertically oscillating circular cylinder in the laminar regime (Reynolds number equal to 60). The 2D Navier-Stokes equations are first solved with a finite element method, in which the moving cylinder is introduced via an ALE method. Since in fluid-structure interaction, the POD algorithm cannot be applied directly, we implemented the fictitious domain method of Glowinski et al. [1] where the solid domain is treated as a fluid undergoing an additional constraint. The POD-ROM is classically obtained by projecting the Navier-Stokes equations onto the first POD modes. At this level, the cylinder displacement is enforced in the POD-ROM through the introduction of Lagrange multipliers. For determining the optimal vertical velocity of the cylinder, a linear quadratic regulator framework is employed. After linearization of the POD-ROM around the steady flow state, the optimal linear feedback gain is obtained as solution of a generalized algebraic Riccati equation. Finally, when the optimal feedback control is applied, it is shown that the flow converges rapidly to the steady state. In addition, a vanishing control is obtained proving the efficiency of the control approach.

Fault Wear by Damage Evolution During Steady-State Slip

NASA Astrophysics Data System (ADS)

Lyakhovsky, Vladimir; Sagy, Amir; Boneh, Yuval; Reches, Ze'ev

2014-11-01

Slip along faults generates wear products such as gouge layers and cataclasite zones that range in thickness from sub-millimeter to tens of meters. The properties of these zones apparently control fault strength and slip stability. Here we present a new model of wear in a three-body configuration that utilizes the damage rheology approach and considers the process as a microfracturing or damage front propagating from the gouge zone into the solid rock. The derivations for steady-state conditions lead to a scaling relation for the damage front velocity considered as the wear-rate. The model predicts that the wear-rate is a function of the shear-stress and may vanish when the shear-stress drops below the microfracturing strength of the fault host rock. The simulated results successfully fit the measured friction and wear during shear experiments along faults made of carbonate and tonalite. The model is also valid for relatively large confining pressures, small damage-induced change of the bulk modulus and significant degradation of the shear modulus, which are assumed for seismogenic zones of earthquake faults. The presented formulation indicates that wear dynamics in brittle materials in general and in natural faults in particular can be understood by the concept of a "propagating damage front" and the evolution of a third-body layer.

Three-dimensional modelling of leachate recirculation using vertical wells in bioreactor landfills.

PubMed

Feng, Shi-Jin; Chen, Zheng-Wei; Cao, Ben-Yi

2016-12-01

Bioreactor landfills use leachate recirculation to enhance the biodegradation of municipal solid waste and accelerate landfill stabilisation, which can provide significant environmental and economic benefits. Vertical wells are operated as a major method for leachate recirculation systems. The objectives of this article are to analyse the leachate migration in bioreactor landfills using vertical wells and to offer theoretical basis for the design of leachate recirculation systems. A three-dimensional numerical model was built using FLAC-3D, and this model can consider the saturated and unsaturated flow of leachate within anisotropic waste to reflect the actual conditions. First, main influence factors of leachate migration were analysed, including the vertical well height, hydraulic conductivity, and anisotropic coefficient, in a single-well recirculation system. Then, the effects of different configurations of a group-well system were studied and the optimal well spacing was obtained. Some key design parameters (e.g. the recirculation flow rate, volume of impact zone, radius of impact zone and time to reach steady state) were also evaluated. The results show that the hydraulic conductivity has a great impact on the optimal height of vertical wells and uniform configuration is the best option in terms of both volume of impact zone and time to reach steady state. © The Author(s) 2016.

Streaming current magnetic fields in a charged nanopore

PubMed Central

Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W.

2016-01-01

Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques. PMID:27833119

Adaptation to Cadmium by Klebsiella aerogenes Growing in Continuous Culture Proceeds Mainly via Formation of Cadmium Sulfide

PubMed Central

Aiking, Harry; Kok, Karin; van Heerikhuizen, Harm; van 't Riet, Jan

1982-01-01

The adaptation of Klebsiella aerogenes to high levels of cadmium was studied in continuous culture under conditions of glucose limitation. When up to 6 × 10−4 M cadmium was added to a culture in steady state, growth ceased instantaneously but resumed within 5 h (dilution rate, 0.1 h−1). When again in steady state, these adapted cells exhibited a far greater tolerance to cadmium than did unadapted cells (not previously exposed to cadmium) when tested on solid media containing different concentrations of cadmium. This relative insensitivity of adapted cells to cadmium was subsequently lost in continuous culture within 5 days after omitting cadmium from the influent medium. Thus, the phenomenon was an inducible physiological process. Adapted cells contained substantial amounts of cadmium (up to 2.4% of the bacterial dry weight). The cadmium content of the cells was dependent on growth conditions and was found to be proportional to the inorganic sulfide content of the cells in all cases. This suggested that formation of CdS is probably the most important mechanism of detoxification in this organism. The presence of large numbers of electron-dense granules on the cell surface (absent in cultures without added cadmium) provided additional support for this conclusion. Images PMID:16346119

Application of the finite element groundwater model FEWA to the engineered test facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craig, P.M.; Davis, E.C.

1985-09-01

A finite element model for water transport through porous media (FEWA) has been applied to the unconfined aquifer at the Oak Ridge National Laboratory Solid Waste Storage Area 6 Engineered Test Facility (ETF). The model was developed in 1983 as part of the Shallow Land Burial Technology - Humid Task (ONL-WL14) and was previously verified using several general hydrologic problems for which an analytic solution exists. Model application and calibration, as described in this report, consisted of modeling the ETF water table for three specialized cases: a one-dimensional steady-state simulation, a one-dimensional transient simulation, and a two-dimensional transient simulation. Inmore » the one-dimensional steady-state simulation, the FEWA output accurately predicted the water table during a long period in which there were no man-induced or natural perturbations to the system. The input parameters of most importance for this case were hydraulic conductivity and aquifer bottom elevation. In the two transient cases, the FEWA output has matched observed water table responses to a single rainfall event occurring in February 1983, yielding a calibrated finite element model that is useful for further study of additional precipitation events as well as contaminant transport at the experimental site.« less

Numerical Simulation of Combustion and Extinction of a Solid Cylinder in Low-Speed Cross Flow

NASA Technical Reports Server (NTRS)

Tien, J. S.; Yang, Chin Tien

1998-01-01

The combustion and extinction behavior of a diffusion flame around a solid fuel cylinder (PMMA) in low-speed forced flow in zero gravity was studied numerically using a quasi-steady gas phase model. This model includes two-dimensional continuity, full Navier Stokes' momentum, energy, and species equations with a one-step overall chemical reaction and second-order finite-rate Arrhenius kinetics. Surface radiation and Arrhenius pyrolysis kinetics are included on the solid fuel surface description and a parameter Phi, representing the percentage of gas-phase conductive heat flux going into the solid, is introduced into the interfacial energy balance boundary condition to complete the description for the quasi-steady gas-phase system. The model was solved numerically using a body-fitted coordinate transformation and the SIMPLE algorithm. The effects of varying freestream velocity and Phi were studied. These parameters have a significant effect on the flame structure and extinction limits. Two flame modes were identified: envelope flame and wake flame. Two kinds of flammability limits were found: quenching at low-flow speeds due to radiative loss and blow-off at high flow speeds due to insufficient gas residence time. A flammability map was constructed showing the existence of maximum Phi above which the solid is not flammable at any freestream velocity.

Prediction of elemental creep. [steady state and cyclic data from regression analysis

NASA Technical Reports Server (NTRS)

Davis, J. W.; Rummler, D. R.

1975-01-01

Cyclic and steady-state creep tests were performed to provide data which were used to develop predictive equations. These equations, describing creep as a function of stress, temperature, and time, were developed through the use of a least squares regression analyses computer program for both the steady-state and cyclic data sets. Comparison of the data from the two types of tests, revealed that there was no significant difference between the cyclic and steady-state creep strains for the L-605 sheet under the experimental conditions investigated (for the same total time at load). Attempts to develop a single linear equation describing the combined steady-state and cyclic creep data resulted in standard errors of estimates higher than obtained for the individual data sets. A proposed approach to predict elemental creep in metals uses the cyclic creep equation and a computer program which applies strain and time hardening theories of creep accumulation.

Absolute Steady-State Thermal Conductivity Measurements by Use of a Transient Hot-Wire System.

PubMed

Roder, H M; Perkins, R A; Laesecke, A; Nieto de Castro, C A

2000-01-01

A transient hot-wire apparatus was used to measure the thermal conductivity of argon with both steady-state and transient methods. The effects of wire diameter, eccentricity of the wire in the cavity, axial conduction, and natural convection were accounted for in the analysis of the steady-state measurements. Based on measurements on argon, the relative uncertainty at the 95 % level of confidence of the new steady-state measurements is 2 % at low densities. Using the same hot wires, the relative uncertainty of the transient measurements is 1 % at the 95 % level of confidence. This is the first report of thermal conductivity measurements made by two different methods in the same apparatus. The steady-state method is shown to complement normal transient measurements at low densities, particularly for fluids where the thermophysical properties at low densities are not known with high accuracy.

Quasi steady-state aerodynamic model development for race vehicle simulations

NASA Astrophysics Data System (ADS)

Mohrfeld-Halterman, J. A.; Uddin, M.

2016-01-01

Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.

Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X

NASA Astrophysics Data System (ADS)

Bosch, H.-S.; Wolf, R. C.; Andreeva, T.; Baldzuhn, J.; Birus, D.; Bluhm, T.; Bräuer, T.; Braune, H.; Bykov, V.; Cardella, A.; Durodié, F.; Endler, M.; Erckmann, V.; Gantenbein, G.; Hartmann, D.; Hathiramani, D.; Heimann, P.; Heinemann, B.; Hennig, C.; Hirsch, M.; Holtum, D.; Jagielski, J.; Jelonnek, J.; Kasparek, W.; Klinger, T.; König, R.; Kornejew, P.; Kroiss, H.; Krom, J. G.; Kühner, G.; Laqua, H.; Laqua, H. P.; Lechte, C.; Lewerentz, M.; Maier, J.; McNeely, P.; Messiaen, A.; Michel, G.; Ongena, J.; Peacock, A.; Pedersen, T. S.; Riedl, R.; Riemann, H.; Rong, P.; Rust, N.; Schacht, J.; Schauer, F.; Schroeder, R.; Schweer, B.; Spring, A.; Stäbler, A.; Thumm, M.; Turkin, Y.; Wegener, L.; Werner, A.; Zhang, D.; Zilker, M.; Akijama, T.; Alzbutas, R.; Ascasibar, E.; Balden, M.; Banduch, M.; Baylard, Ch.; Behr, W.; Beidler, C.; Benndorf, A.; Bergmann, T.; Biedermann, C.; Bieg, B.; Biel, W.; Borchardt, M.; Borowitz, G.; Borsuk, V.; Bozhenkov, S.; Brakel, R.; Brand, H.; Brown, T.; Brucker, B.; Burhenn, R.; Buscher, K.-P.; Caldwell-Nichols, C.; Cappa, A.; Cardella, A.; Carls, A.; Carvalho, P.; Ciupiński, Ł.; Cole, M.; Collienne, J.; Czarnecka, A.; Czymek, G.; Dammertz, G.; Dhard, C. P.; Davydenko, V. I.; Dinklage, A.; Drevlak, M.; Drotziger, S.; Dudek, A.; Dumortier, P.; Dundulis, G.; Eeten, P. v.; Egorov, K.; Estrada, T.; Faugel, H.; Fellinger, J.; Feng, Y.; Fernandes, H.; Fietz, W. H.; Figacz, W.; Fischer, F.; Fontdecaba, J.; Freund, A.; Funaba, T.; Fünfgelder, H.; Galkowski, A.; Gates, D.; Giannone, L.; García Regaña, J. M.; Geiger, J.; Geißler, S.; Greuner, H.; Grahl, M.; Groß, S.; Grosman, A.; Grote, H.; Grulke, O.; Haas, M.; Haiduk, L.; Hartfuß, H.-J.; Harris, J. H.; Haus, D.; Hein, B.; Heitzenroeder, P.; Helander, P.; Heller, R.; Hidalgo, C.; Hildebrandt, D.; Höhnle, H.; Holtz, A.; Holzhauer, E.; Holzthüm, R.; Huber, A.; Hunger, H.; Hurd, F.; Ihrke, M.; Illy, S.; Ivanov, A.; Jablonski, S.; Jaksic, N.; Jakubowski, M.; Jaspers, R.; Jensen, H.; Jenzsch, H.; Kacmarczyk, J.; Kaliatk, T.; Kallmeyer, J.; Kamionka, U.; Karaleviciu, R.; Kern, S.; Keunecke, M.; Kleiber, R.; Knauer, J.; Koch, R.; Kocsis, G.; Könies, A.; Köppen, M.; Koslowski, R.; Koshurinov, J.; Krämer-Flecken, A.; Krampitz, R.; Kravtsov, Y.; Krychowiak, M.; Krzesinski, G.; Ksiazek, I.; Kubkowska, M.; Kus, A.; Langish, S.; Laube, R.; Laux, M.; Lazerson, S.; Lennartz, M.; Li, C.; Lietzow, R.; Lohs, A.; Lorenz, A.; Louche, F.; Lubyako, L.; Lumsdaine, A.; Lyssoivan, A.; Maaßberg, H.; Marek, P.; Martens, C.; Marushchenko, N.; Mayer, M.; Mendelevitch, B.; Mertens, Ph.; Mikkelsen, D.; Mishchenko, A.; Missal, B.; Mizuuchi, T.; Modrow, H.; Mönnich, T.; Morizaki, T.; Murakami, S.; Musielok, F.; Nagel, M.; Naujoks, D.; Neilson, H.; Neubauer, O.; Neuner, U.; Nocentini, R.; Noterdaeme, J.-M.; Nührenberg, C.; Obermayer, S.; Offermanns, G.; Oosterbeek, H.; Otte, M.; Panin, A.; Pap, M.; Paquay, S.; Pasch, E.; Peng, X.; Petrov, S.; Pilopp, D.; Pirsch, H.; Plaum, B.; Pompon, F.; Povilaitis, M.; Preinhaelter, J.; Prinz, O.; Purps, F.; Rajna, T.; Récsei, S.; Reiman, A.; Reiter, D.; Remmel, J.; Renard, S.; Rhode, V.; Riemann, J.; Rimkevicius, S.; Riße, K.; Rodatos, A.; Rodin, I.; Romé, M.; Roscher, H.-J.; Rummel, K.; Rummel, Th.; Runov, A.; Ryc, L.; Sachtleben, J.; Samartsev, A.; Sanchez, M.; Sano, F.; Scarabosio, A.; Schmid, M.; Schmitz, H.; Schmitz, O.; Schneider, M.; Schneider, W.; Scheibl, L.; Scholz, M.; Schröder, G.; Schröder, M.; Schruff, J.; Schumacher, H.; Shikhovtsev, I. V.; Shoji, M.; Siegl, G.; Skodzik, J.; Smirnow, M.; Speth, E.; Spong, D. A.; Stadler, R.; Sulek, Z.; Szabó, V.; Szabolics, T.; Szetefi, T.; Szökefalvi-Nagy, Z.; Tereshchenko, A.; Thomsen, H.; Thumm, M.; Timmermann, D.; Tittes, H.; Toi, K.; Tournianski, M.; Toussaint, U. v.; Tretter, J.; Tulipán, S.; Turba, P.; Uhlemann, R.; Urban, J.; Urbonavicius, E.; Urlings, P.; Valet, S.; Van Eester, D.; Van Schoor, M.; Vervier, M.; Viebke, H.; Vilbrandt, R.; Vrancken, M.; Wauters, T.; Weissgerber, M.; Weiß, E.; Weller, A.; Wendorf, J.; Wenzel, U.; Windisch, T.; Winkler, E.; Winkler, M.; Wolowski, J.; Wolters, J.; Wrochna, G.; Xanthopoulos, P.; Yamada, H.; Yokoyama, M.; Zacharias, D.; Zajac, J.; Zangl, G.; Zarnstorff, M.; Zeplien, H.; Zoletnik, S.; Zuin, M.

2013-12-01

The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, currently under construction in Greifswald, Germany. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation under plasma conditions relevant for a fusion power plant. Steady-state operation of a fusion device, on the one hand, requires the implementation of special technologies, giving rise to technical challenges during the design, fabrication and assembly of such a device. On the other hand, also the physics development of steady-state operation at high plasma performance poses a challenge and careful preparation. The electron cyclotron resonance heating system, diagnostics, experiment control and data acquisition are prepared for plasma operation lasting 30 min. This requires many new technological approaches for plasma heating and diagnostics as well as new concepts for experiment control and data acquisition.

Could Flaring Stars Change Our Views of Their Planets?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

As the exoplanet count continues to increase, we are making progressively more measurements of exoplanets outer atmospheres through spectroscopy. A new study, however, reveals that these measurements may be influenced by the planets hosts.Spectra From TransitsExoplanet spectra taken as they transit their hosts can tell us about the chemical compositions of their atmospheres. Detailed spectroscopic measurements of planet atmospheres should become even more common with the next generation of missions, such as the James Webb Space Telescope (JWST), or Planetary Transits and Oscillations of Stars (PLATO).But is the spectrum that we measure in the brief moment of a planets transit necessarily representative of its spectrum all of the time? A team of scientists led by Olivia Venot (University of Leuven in Belgium) argue that it might not be, due to the influence of the planets stellar host.Atmospheric composition of a planet before flare impacts (dotted lines), during the steady state reached after a flare impact (dashed lines), and during the steady state reached after a second flare impact (solid lines). [Venot et al. 2016]The team suggests that when a hosts flares impact upon a planets atmosphere (especially likely in the case of active M-dwarfs that commonly harbor planetary systems), this activity may modify the chemical composition of the planets atmosphere. This would in turn alter the spectrum that we measure from the exoplanet.Modeling AtmospheresVenot and collaborators set out to test the effect of stellar flares on exoplanet atmospheres by modeling the atmospheres of two hypothetical planets orbiting the star AD Leo an active and flaring M dwarf located roughly 16 light-years away at two different distances. The team then examined what happened to the atmospheres, and to the resulting spectra that we would observe, when they were hit with a stellar flare typical of AD Leo.The difference in relative absorption between the initial steady-state and the instantaneous transmission spectra, obtained during the different phases of the flare. The left plot examines the impulsive and gradual phases, when the flare first impacts and then starts to pass. The peak photon flux occurs at 912 seconds. The right plot examines the return to a steady state over 1012 seconds, or roughly 30,000 years. [Adapted from Venot et al. 2016]The authors found that the planets atmospheric compositions were significantly affected by the incoming stellar flare. The sudden increase in incoming photon flux changed the chemical abundances of several important molecular species, like hydrogen and ammonia which resulted in changes to the spectrum that would be observed during the planets transit.Permanent ImpactIn addition to demonstrating that a planets atmospheric composition changes during and immediately after a flare impact, Venot and collaborators show that the chemical alteration isnt temporary: the planets atmosphere doesnt fully return to its original state after the flare passes. Instead, the authors find that it settles to a new steady-state composition that can be significantly different from the pre-flare composition.For a planet that is repeatedly hit by stellar flares, therefore, its atmospheric composition never actually settles to a steady state. Instead it is continually and permanently modified by its hosts activity.Venot and collaborators demonstrate that the variations of planetary spectra due to stellar flares should be easily detectable by future missions like JWST. We must therefore be careful about the conclusions we draw about planetary atmospheres from measurements of their spectra.CitationOlivia Venot et al 2016 ApJ 830 77. doi:10.3847/0004-637X/830/2/77

40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix..., App. II Appendix II to Part 1042—Steady-State Duty Cycles (a) The following duty cycles apply as specified in § 1042.505(b)(1): (1) The following duty cycle applies for discrete-mode testing: E3 mode No...

Min-By-Min Respiratory Exchange and Oxygen Uptake Kinetics During Steady-State Exercise in Subjects of High and Low Max VO2

ERIC Educational Resources Information Center

Weltman, Arthur; Katch, Victor

1976-01-01

No statistically meaningful differences in steady-state vo2 uptake for high and low max vo2 groups was indicated in this study, but a clear tendency was observed for the high max vo2 group to reach the steady-state at a faster rate. (MB)

Quantitative controls on submarine slope failure morphology

USGS Publications Warehouse

Lee, H.J.; Schwab, W.C.; Edwards, B.D.; Kayen, R.E.

1991-01-01

The concept of the steady-state of deformation can be applied to predicting the ultimate form a landslide will take. The steady-state condition, defined by a line in void ratio-effective stress space, exists at large levels of strain and remolding. Conceptually, if sediment initially exists with void ratio-effective stress conditions above the steady-state line, the sediment shear strength will decrease during a transient loading event, such as an earthquake or storm. If the reduced shear strength existing at the steady state is less than the downslope shear stress induced by gravity, then large-scale internal deformation, disintegration, and flow will occur. -from Authors

Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

PubMed

Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

2013-12-01

During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. © 2013 John Wiley & Sons Ltd.

Detection-enhanced steady state entanglement with ions.

PubMed

Bentley, C D B; Carvalho, A R R; Kielpinski, D; Hope, J J

2014-07-25

Driven dissipative steady state entanglement schemes take advantage of coupling to the environment to robustly prepare highly entangled states. We present a scheme for two trapped ions to generate a maximally entangled steady state with fidelity above 0.99, appropriate for use in quantum protocols. Furthermore, we extend the scheme by introducing detection of our dissipation process, significantly enhancing the fidelity. Our scheme is robust to anomalous heating and requires no sympathetic cooling.

Convection of tin in a Bridgman system. I - Flow characterization by effective diffusivity measurements

NASA Technical Reports Server (NTRS)

Sears, B.; Narayanan, R.; Anderson, T. J.; Fripp, A. L.

1992-01-01

An electrochemical titration method was used to investigate the dynamic states in a cylindrical layer of convecting tin. The liquid tin was contained in a cell, with curved boundaries made of quartz and flat boundaries made of a solid state electrolyte - yttria-stabilized zirconia (YSZ). The electrolyte acted as a window through which a trace amount of oxygen could be pumped in or out by the application of a constant voltage. The concentration at the YSZ interface was monitored by operating the electrochemical cell in the galvanic mode. Experimentally determined effective diffusivities of oxygen were compared with the molecular diffusivity. Dynamic states in the convective flow were thus inferred. Temperature measurements were simultaneously made in order to identify the onset of oscillations from a steady convective regime. The experiments were conducted for two different aspect ratios for various imposed temperature gradients and two different orientations with respect to gravity. Transcritical states were identified and comparison to two-dimensional numerical models were made.

Boundary condition computational procedures for inviscid, supersonic steady flow field calculations

NASA Technical Reports Server (NTRS)

Abbett, M. J.

1971-01-01

Results are given of a comparative study of numerical procedures for computing solid wall boundary points in supersonic inviscid flow calculatons. Twenty five different calculation procedures were tested on two sample problems: a simple expansion wave and a simple compression (two-dimensional steady flow). A simple calculation procedure was developed. The merits and shortcomings of the various procedures are discussed, along with complications for three-dimensional and time-dependent flows.

Steady-state MR imaging sequences: physics, classification, and clinical applications.

PubMed

Chavhan, Govind B; Babyn, Paul S; Jankharia, Bhavin G; Cheng, Hai-Ling M; Shroff, Manohar M

2008-01-01

Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reached: preexcitation signal (S-) from echo reformation; and postexcitation signal (S+), which consists of free induction decay. Depending on the signal sampled and used to form an image, steady-state sequences can be classified as (a) postexcitation refocused (only S+ is sampled), (b) preexcitation refocused (only S- is sampled), and (c) fully refocused (both S+ and S- are sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steady-state sequences have revolutionized cardiac imaging and have become the standard for anatomic functional cardiac imaging and for the assessment of myocardial viability because of their good signal-to-noise ratio and contrast-to-noise ratio and increased speed of acquisition. They are also useful in abdominal and fetal imaging and hold promise for interventional MR imaging. Because steady-state sequences are now commonly used in MR imaging, radiologists will benefit from understanding the underlying physics, classification, and clinical applications of these sequences.

Cyclone–anticyclone vortex asymmetry mechanism and linear Ekman friction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chefranov, S. G., E-mail: schefranov@mail.ru

2016-04-15

Allowance for the linear Ekman friction has been found to ensure a threshold (in rotation frequency) realization of the linear dissipative–centrifugal instability and the related chiral symmetry breaking in the dynamics of Lagrangian particles, which leads to the cyclone–anticyclone vortex asymmetry. An excess of the fluid rotation rate ω{sub 0} over some threshold value determined by the fluid eigenfrequency ω (i.e., ω{sub 0} > ω) is shown to be a condition for the realization of such an instability. A new generalization of the solution of the Karman problem to determine the steady-state velocity field in a viscous incompressible fluid abovemore » a rotating solid disk of large radius, in which the linear Ekman friction was additionally taken into account, has been obtained. A correspondence of this solution and the conditions for the realization of the dissipative–centrifugal instability of a chiral-symmetric vortex state and the corresponding cyclone–anticyclone vortex asymmetry has been shown. A generalization of the well-known spiral velocity distribution in an “Ekman layer” near a solid surface has been established for the case where the fluid rotation frequency far from the disk ω differs from the disk rotation frequency ω{sub 0}.« less

Summary of workshop 'Theory Meets Industry'—the impact of ab initio solid state calculations on industrial materials research

NASA Astrophysics Data System (ADS)

Wimmer, E.

2008-02-01

A workshop, 'Theory Meets Industry', was held on 12-14 June 2007 in Vienna, Austria, attended by a well balanced number of academic and industrial scientists from America, Europe, and Japan. The focus was on advances in ab initio solid state calculations and their practical use in industry. The theoretical papers addressed three dominant themes, namely (i) more accurate total energies and electronic excitations, (ii) more complex systems, and (iii) more diverse and accurate materials properties. Hybrid functionals give some improvements in energies, but encounter difficulties for metallic systems. Quantum Monte Carlo methods are progressing, but no clear breakthrough is on the horizon. Progress in order-N methods is steady, as is the case for efficient methods for exploring complex energy hypersurfaces and large numbers of structural configurations. The industrial applications were dominated by materials issues in energy conversion systems, the quest for hydrogen storage materials, improvements of electronic and optical properties of microelectronic and display materials, and the simulation of reactions on heterogeneous catalysts. The workshop is a clear testimony that ab initio computations have become an industrial practice with increasingly recognized impact.

Time density curve analysis for C-arm FDCT PBV imaging

PubMed Central

Byrne, James V

2016-01-01

Introduction Parenchymal blood volume (PBV) estimation using C-arm flat detector computed tomography (FDCT) assumes a steady-state contrast concentration in cerebral vasculature for the scan duration. Using time density curve (TDC) analysis, we explored if the steady-state assumption is met for C-arm CT PBV scans, and how consistent the contrast-material dynamics in cerebral vasculature are across patients. Methods Thirty C-arm FDCT datasets of 26 patients with aneurysmal-SAH, acquired as part of a prospective study comparing C-arm CT PBV with MR-PWI, were analysed. TDCs were extracted from the 2D rotational projections. Goodness-of-fit of TDCs to a steady-state horizontal-line-model and the statistical similarity among the individual TDCs were tested. Influence of the differences in TDC characteristics on the agreement of resulting PBV measurements with MR-CBV was calculated. Results Despite identical scan parameters and contrast-injection-protocol, the individual TDCs were statistically non-identical (p < 0.01). Using Dunn's multiple comparisons test, of the total 435 individual comparisons among the 30 TDCs, 330 comparisons (62%) reached statistical significance for difference. All TDCs deviated significantly (p < 0.01) from the steady-state horizontal-line-model. PBV values of those datasets for which the TDCs showed largest deviations from the steady-state model demonstrated poor agreement and correlation with MR-CBV, compared with the PBV values of those datasets for which the TDCs were closer to steady-state. Conclusion For clinical C-arm CT PBV examinations, the administered contrast material does not reach the assumed ‘ideal steady-state’ for the duration of scan. Using a prolonged injection protocol, the degree to which the TDCs approximate the ideal steady-state influences the agreement of resulting PBV measurements with MR-CBV. PMID:26769736

A minimal SATA III Host Controller based on FPGA

NASA Astrophysics Data System (ADS)

Liu, Hailiang

2018-03-01

SATA (Serial Advanced Technology Attachment) is an advanced serial bus which has a outstanding performance in transmitting high speed real-time data applied in Personal Computers, Financial Industry, astronautics and aeronautics, etc. In this express, a minimal SATA III Host Controller based on Xilinx Kintex 7 serial FPGA is designed and implemented. Compared to the state-of-art, registers utilization are reduced 25.3% and LUTs utilization are reduced 65.9%. According to the experimental results, the controller works precisely and steady with the reading bandwidth of up to 536 MB per second and the writing bandwidth of up to 512 MB per second, both of which are close to the maximum bandwidth of the SSD(Solid State Disk) device. The host controller is very suitable for high speed data transmission and mass data storage.

Dynamics of quantum correlation between separated nitrogen-vacancy centers embedded in plasmonic waveguide

PubMed Central

Yang, Wan-li; An, Jun-Hong; Zhang, Cheng-jie; Chen, Chang-yong; Oh, C. H.

2015-01-01

We investigate the dynamics of quantum correlation between two separated nitrogen vacancy centers (NVCs) placed near a one-dimensional plasmonic waveguide. As a common medium of the radiation field of NVCs propagating, the plasmonic waveguide can dynamically induce quantum correlation between the two NVCs. It is interesting to find that such dynamically induced quantum correlation can be preserved in the long-time steady state by locally applying individual driving on the two NVCs. In particular, we also show that a large degree of quantum correlation can be established by this scheme even when the distance between the NVCs is much larger than their operating wavelength. This feature may open new perspectives for devising active decoherence-immune solid-state optical devices and long-distance NVC-based quantum networks in the context of plasmonic quantum electrodynamics. PMID:26493045

Inverse Thermal Analysis of Titanium GTA Welds Using Multiple Constraints

NASA Astrophysics Data System (ADS)

Lambrakos, S. G.; Shabaev, A.; Huang, L.

2015-06-01

Inverse thermal analysis of titanium gas-tungsten-arc welds using multiple constraint conditions is presented. This analysis employs a methodology that is in terms of numerical-analytical basis functions for inverse thermal analysis of steady-state energy deposition in plate structures. The results of this type of analysis provide parametric representations of weld temperature histories that can be adopted as input data to various types of computational procedures, such as those for prediction of solid-state phase transformations. In addition, these temperature histories can be used to construct parametric function representations for inverse thermal analysis of welds corresponding to other process parameters or welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that provides for the inclusion of constraint conditions associated with both solidification and phase transformation boundaries.

Pressure Distribution and Performance Impacts of Aerospike Nozzles on Rotating Detonation Engines

DTIC Science & Technology

2017-06-01

design methodology at both on- and off-design conditions anticipated throughout the combustion cycle. Steady-state, non -reacting computational fluid...operation. Therefore, the nozzle contour was designed using a traditional, steady-state design methodology at both on- and off-design conditions...anticipated throughout the combustion cycle. Steady-state, non -reacting computational fluid dynamics (CFD) simulations were performed on various nozzle

Universal, computer facilitated, steady state oscillator, closed loop analysis theory and some applications to precision oscillators

NASA Technical Reports Server (NTRS)

Parzen, Benjamin

1992-01-01

The theory of oscillator analysis in the immittance domain should be read in conjunction with the additional theory presented here. The combined theory enables the computer simulation of the steady state oscillator. The simulation makes the calculation of the oscillator total steady state performance practical, including noise at all oscillator locations. Some specific precision oscillators are analyzed.

Steady state analysis of Boolean molecular network models via model reduction and computational algebra.

PubMed

Veliz-Cuba, Alan; Aguilar, Boris; Hinkelmann, Franziska; Laubenbacher, Reinhard

2014-06-26

A key problem in the analysis of mathematical models of molecular networks is the determination of their steady states. The present paper addresses this problem for Boolean network models, an increasingly popular modeling paradigm for networks lacking detailed kinetic information. For small models, the problem can be solved by exhaustive enumeration of all state transitions. But for larger models this is not feasible, since the size of the phase space grows exponentially with the dimension of the network. The dimension of published models is growing to over 100, so that efficient methods for steady state determination are essential. Several methods have been proposed for large networks, some of them heuristic. While these methods represent a substantial improvement in scalability over exhaustive enumeration, the problem for large networks is still unsolved in general. This paper presents an algorithm that consists of two main parts. The first is a graph theoretic reduction of the wiring diagram of the network, while preserving all information about steady states. The second part formulates the determination of all steady states of a Boolean network as a problem of finding all solutions to a system of polynomial equations over the finite number system with two elements. This problem can be solved with existing computer algebra software. This algorithm compares favorably with several existing algorithms for steady state determination. One advantage is that it is not heuristic or reliant on sampling, but rather determines algorithmically and exactly all steady states of a Boolean network. The code for the algorithm, as well as the test suite of benchmark networks, is available upon request from the corresponding author. The algorithm presented in this paper reliably determines all steady states of sparse Boolean networks with up to 1000 nodes. The algorithm is effective at analyzing virtually all published models even those of moderate connectivity. The problem for large Boolean networks with high average connectivity remains an open problem.

Steady state analysis of Boolean molecular network models via model reduction and computational algebra

PubMed Central

2014-01-01

Background A key problem in the analysis of mathematical models of molecular networks is the determination of their steady states. The present paper addresses this problem for Boolean network models, an increasingly popular modeling paradigm for networks lacking detailed kinetic information. For small models, the problem can be solved by exhaustive enumeration of all state transitions. But for larger models this is not feasible, since the size of the phase space grows exponentially with the dimension of the network. The dimension of published models is growing to over 100, so that efficient methods for steady state determination are essential. Several methods have been proposed for large networks, some of them heuristic. While these methods represent a substantial improvement in scalability over exhaustive enumeration, the problem for large networks is still unsolved in general. Results This paper presents an algorithm that consists of two main parts. The first is a graph theoretic reduction of the wiring diagram of the network, while preserving all information about steady states. The second part formulates the determination of all steady states of a Boolean network as a problem of finding all solutions to a system of polynomial equations over the finite number system with two elements. This problem can be solved with existing computer algebra software. This algorithm compares favorably with several existing algorithms for steady state determination. One advantage is that it is not heuristic or reliant on sampling, but rather determines algorithmically and exactly all steady states of a Boolean network. The code for the algorithm, as well as the test suite of benchmark networks, is available upon request from the corresponding author. Conclusions The algorithm presented in this paper reliably determines all steady states of sparse Boolean networks with up to 1000 nodes. The algorithm is effective at analyzing virtually all published models even those of moderate connectivity. The problem for large Boolean networks with high average connectivity remains an open problem. PMID:24965213

Open cycle traveling wave thermoacoustics: mean temperature difference at the regenerator interface.

PubMed

Weiland, Nathan T; Zinn, Ben T

2003-11-01

In an open cycle traveling wave thermoacoustic engine, the hot heat exchanger is replaced by a steady flow of hot gas into the regenerator to provide the thermal energy input to the engine. The steady-state operation of such a device requires that a potentially large mean temperature difference exist between the incoming gas and the solid material at the regenerator's hot side, due in part to isentropic gas oscillations in the open space adjacent to the regenerator. The magnitude of this temperature difference will have a significant effect on the efficiencies of these open cycle devices. To help assess the feasibility of such thermoacoustic engines, a numerical model is developed that predicts the dependence of the mean temperature difference upon the important design and operating parameters of the open cycle thermoacoustic engine, including the acoustic pressure, mean mass flow rate, acoustic phase angles, and conductive heat loss. Using this model, it is also shown that the temperature difference at the regenerator interface is approximately proportional to the sum of the acoustic power output and the conductive heat loss at this location.

Transitions between strongly correlated and random steady-states for catalytic CO-oxidation on surfaces at high-pressure

DOE PAGES

Liu, Da -Jiang; Evans, James W.

2015-04-02

We explore simple lattice-gas reaction models for CO-oxidation on 1D and 2D periodic arrays of surface adsorption sites. The models are motivated by studies of CO-oxidation on RuO 2(110) at high-pressures. Although adspecies interactions are neglected, the effective absence of adspecies diffusion results in kinetically-induced spatial correlations. A transition occurs from a random mainly CO-populated steady-state at high CO-partial pressure p CO, to a strongly-correlated near-O-covered steady-state for low p CO as noted. In addition, we identify a second transition to a random near-O-covered steady-state at very low p CO.

The steady-state visual evoked potential in vision research: A review

PubMed Central

Norcia, Anthony M.; Appelbaum, L. Gregory; Ales, Justin M.; Cottereau, Benoit R.; Rossion, Bruno

2015-01-01

Periodic visual stimulation and analysis of the resulting steady-state visual evoked potentials were first introduced over 80 years ago as a means to study visual sensation and perception. From the first single-channel recording of responses to modulated light to the present use of sophisticated digital displays composed of complex visual stimuli and high-density recording arrays, steady-state methods have been applied in a broad range of scientific and applied settings.The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science. PMID:26024451

Symmetry limit theory for cantilever beam-columns subjected to cyclic reversed bending

NASA Astrophysics Data System (ADS)

Uetani, K.; Nakamura, Tsuneyoshi

THE BEHAVIOR of a linear strain-hardening cantilever beam-column subjected to completely reversed plastic bending of a new idealized program under constant axial compression consists of three stages: a sequence of symmetric steady states, a subsequent sequence of asymmetric steady states and a divergent behavior involving unbounded growth of an anti-symmetric deflection mode. A new concept "symmetry limit" is introduced here as the smallest critical value of the tip-deflection amplitude at which transition from a symmetric steady state to an asymmetric steady state can occur in the response of a beam-column. A new theory is presented for predicting the symmetry limits. Although this transition phenomenon is phenomenologically and conceptually different from the branching phenomenon on an equilibrium path, it is shown that a symmetry limit may theoretically be regarded as a branching point on a "steady-state path" defined anew. The symmetry limit theory and the fundamental hypotheses are verified through numerical analysis of hysteretic responses of discretized beam-column models.

A general theory of kinetics and thermodynamics of steady-state copolymerization.

PubMed

Shu, Yao-Gen; Song, Yong-Shun; Ou-Yang, Zhong-Can; Li, Ming

2015-06-17

Kinetics of steady-state copolymerization has been investigated since the 1940s. Irreversible terminal and penultimate models were successfully applied to a number of comonomer systems, but failed for systems where depropagation is significant. Although a general mathematical treatment of the terminal model with depropagation was established in the 1980s, a penultimate model and higher-order terminal models with depropagation have not been systematically studied, since depropagation leads to hierarchically-coupled and unclosed kinetic equations which are hard to solve analytically. In this work, we propose a truncation method to solve the steady-state kinetic equations of any-order terminal models with depropagation in a unified way, by reducing them into closed steady-state equations which give the exact solution of the original kinetic equations. Based on the steady-state equations, we also derive a general thermodynamic equality in which the Shannon entropy of the copolymer sequence is explicitly introduced as part of the free energy dissipation of the whole copolymerization system.

Molecular control of steady-state dendritic cell maturation and immune homeostasis.

PubMed

Hammer, Gianna Elena; Ma, Averil

2013-01-01

Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.

Lineage tracing of murine adult hematopoietic stem cells reveals active contribution to steady-state hematopoiesis

PubMed Central

Chapple, Richard H.; Tseng, Yu-Jung; Hu, Tianyuan; Kitano, Ayumi; Takeichi, Makiko; Hoegenauer, Kevin A.

2018-01-01

Characterization of hematopoietic stem cells (HSCs) has advanced largely owing to transplantation assays, in which the developmental potential of HSCs is assessed generally in nonhomeostatic conditions. These studies established that adult HSCs extensively contribute to multilineage hematopoietic regeneration upon transplantation. On the contrary, recent studies performing lineage tracing of HSCs under homeostatic conditions have shown that adult HSCs may contribute far less to steady-state hematopoiesis than would be anticipated based on transplantation assays. Here, we used 2 independent HSC-lineage–tracing models to examine the contribution of adult HSCs to steady-state hematopoiesis. We show that adult HSCs contribute robustly to steady-state hematopoiesis, exhibiting faster efflux toward the myeloid lineages compared with lymphoid lineages. Platelets were robustly labeled by HSCs, reaching the same level of labeling as HSCs by 1 year of chase. Our results support the view that adult HSCs contribute to the continuous influx of blood cells during steady-state hematopoiesis. PMID:29848758

Steady State Condition in the Measurement of VO2and VCO2by Indirect Calorimetry.

PubMed

Cadena, M; Sacristan, E; Infante, O; Escalante, B; Rodriguez, F

2005-01-01

Resting Metabolic Rate (RMR) is computed using VO2and VCO2short time 15-minute window measurement with Indirect Calorimetry (IC) instruments designed with mixing chamber. Steady state condition using a 10% variation coefficient criteria is the main objective to achieve metabolic long time prediction reliability. This study address how susceptible is the steady state VO2, VCO2measurement condition to the clino-orthostatic physiological maneuver. 30 young healthy subjects were analyzed. Only 18 passed the 10% variation coefficient inclusive criteria. They were exposed to 10 minutes clino-stage and 10 minutes orthostage. The hypothesis tests show not statistical significance (p< 0.1) in the average and variance analysis. It is concluded that the steady state is not influenced by the patient position IC test, probably because IC mixing chamber instruments are insensitive to detect a mayor physiological dynamics changes that can modify the steady state definition.

Einstein's steady-state theory: an abandoned model of the cosmos

NASA Astrophysics Data System (ADS)

O'Raifeartaigh, Cormac; McCann, Brendan; Nahm, Werner; Mitton, Simon

2014-09-01

We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a `steady-state' model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein's steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.

Hybrid Rocket Performance Prediction with Coupling Method of CFD and Thermal Conduction Calculation

NASA Astrophysics Data System (ADS)

Funami, Yuki; Shimada, Toru

The final purpose of this study is to develop a design tool for hybrid rocket engines. This tool is a computer code which will be used in order to investigate rocket performance characteristics and unsteady phenomena lasting through the burning time, such as fuel regression or combustion oscillation. When phenomena inside a combustion chamber, namely boundary layer combustion, are described, it is difficult to use rigorous models for this target. It is because calculation cost may be too expensive. Therefore simple models are required for this calculation. In this study, quasi-one-dimensional compressible Euler equations for flowfields inside a chamber and the equation for thermal conduction inside a solid fuel are numerically solved. The energy balance equation at the solid fuel surface is solved to estimate fuel regression rate. Heat feedback model is Karabeyoglu's model dependent on total mass flux. Combustion model is global single step reaction model for 4 chemical species or chemical equilibrium model for 9 chemical species. As a first step, steady-state solutions are reported.

Axisymmetric shell analysis of the Space Shuttle solid rocket booster field joint

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.; Anderson, Melvin S.

1989-01-01

The Space Shuttle Challenger (STS 51-L) accident led to an intense investigation of the structural behavior of the solid rocket booster (SRB) tang and clevis field joints. The presence of structural deformations between the clevis inner leg and the tang, substantial enough to prevent the O-ring seals from eliminating hot gas flow through the joints, has emerged as a likely cause of the vehicle failure. This paper presents results of axisymmetric shell analyses that parametrically assess the structural behavior of SRB field joints subjected to quasi-steady-state internal pressure loading for both the original joint flown on mission STS 51-L and the redesigned joint recently flown on the Space Shuttle Discovery. Discussion of axisymmetric shell modeling issues and details is presented and a generic method for simulating contact between adjacent shells of revolution is described. Results are presented that identify the performance trends of the joints for a wide range of joint parameters.

One-step production of long-chain hydrocarbons from waste-biomass-derived chemicals using bi-functional heterogeneous catalysts.

PubMed

Wen, Cun; Barrow, Elizabeth; Hattrick-Simpers, Jason; Lauterbach, Jochen

2014-02-21

In this study, we demonstrate the production of long-chain hydrocarbons (C8+) from 2-methylfuran (2MF) and butanal in a single step reactive process by utilizing a bi-functional catalyst with both acid and metallic sites. Our approach utilizes a solid acid for the hydroalkylation function and as a support as well as a transition metal as hydrodeoxygenation catalyst. A series of solid acids was screened, among which MCM-41 demonstrated the best combination of activity and stability. Platinum nanoparticles were then incorporated into the MCM-41. The Pt/MCM-41 catalyst showed 96% yield for C8+ hydrocarbons and the catalytic performance was stable over four reaction cycles of 20 hour each. The reaction pathways for the production of long-chain hydrocarbons is probed with a combination of infrared spectroscopy and steady-state reaction experiments. It is proposed that 2MF and butanal go through hydroalkylation first on the acid site followed by hydrodeoxygenation to produce the hydrocarbon fuels.

Melt Convection Effects in the Bridgman Crystal Growth of an Alloy Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Simpson James E.; Garimella, Suresh V.; deGroh, Henry C., III; Abbaschian, Reza

1998-01-01

The solidification of a dilute bismuth-tin alloy under Bridgman crystal growth conditions is investigated in support of NASA's MEPHISTO space shuttle flight experiment. Computations are performed in two-dimensions with a uniform grid. The simulation includes the species-concentration, temperature and flow fields, as well as conduction in the ampoule. Fully transient simulations have been performed; no simplifying steady state approximations are used. Results are obtained under microgravity conditions for pure bismuth, and Bismuth-0.1 at.% Sn and Bi-1.0 at.% Sn alloys. The concentration dependence of the melting temperature is neglected; the solid/liquid interface temperature is assumed to be the melting temperature of pure bismuth for all cases studied. For the Bi-1.0 at.% Sn case the results indicate that a secondary convective cell, driven by solutal gradients, forms near the interface. The magnitude of the velocities in this cell increases with time; this causes increasing solute segregation at the liquid/solid interface.

Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate. Ph.D. Thesis - Va. Polytechnic Inst.

NASA Technical Reports Server (NTRS)

Byvik, C. E.

1971-01-01

The dynamic nuclear polarization of hydrogen nuclei by the solid effect in single crystals of samarium doped lanthanum magnesium nitrate (Sm:LMN) was studied theoretically and experimentally. The equations of evolution governing the dynamic nuclear polarization by the solid effect were derived in detail using the spin temperature theory and the complete expression for the steady state enhancement of the nuclear polarization was calculated. Experimental enhancements of the proton polarization were obtained for eight crystals at 9.2 GHz and liquid helium temperatures. The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181 was measured for a 1.1 percent Sm:LMN crystal at 3.0 K. The maximum enhancements extrapolated with the theory using the experimental data for peak enhancement versus microwave power and correcting for leakage, agree with the ideal enhancement (240 in this experiment) within experimental error for three of the crystals.

Determination of solid-propellant transient regression rates using a microwave Doppler shift technique

NASA Technical Reports Server (NTRS)

Strand, L. D.; Schultz, A. L.; Reedy, G. K.

1972-01-01

A microwave Doppler shift system, with increased resolution over earlier microwave techniques, was developed for the purpose of measuring the regression rates of solid propellants during rapid pressure transients. A continuous microwave beam is transmitted to the base of a burning propellant sample cast in a metal waveguide tube. A portion of the wave is reflected from the regressing propellant-flame zone interface. The phase angle difference between the incident and reflected signals and its time differential are continuously measured using a high resolution microwave network analyzer and related instrumentation. The apparent propellant regression rate is directly proportional to this latter differential measurement. Experiments were conducted to verify the (1) spatial and time resolution of the system, (2) effect of propellant surface irregularities and compressibility on the measurements, and (3) accuracy of the system for quasi-steady-state regression rate measurements. The microwave system was also used in two different transient combustion experiments: in a rapid depressurization bomb, and in the high-frequency acoustic pressure environment of a T-burner.

Shape-dependent guidance of active Janus particles by chemically patterned surfaces

NASA Astrophysics Data System (ADS)

Uspal, W. E.; Popescu, M. N.; Tasinkevych, M.; Dietrich, S.

2018-01-01

Self-phoretic chemically active Janus particles move by inducing—via non-equilibrium chemical reactions occurring on their surfaces—changes in the chemical composition of the solution in which they are immersed. This process leads to gradients in chemical composition along the surface of the particle, as well as along any nearby boundaries, including solid walls. Chemical gradients along a wall can give rise to chemi-osmosis, i.e., the gradients drive surface flows which, in turn, drive flow in the volume of the solution. This bulk flow couples back to the particle, and thus contributes to its self-motility. Since chemi-osmosis strongly depends on the molecular interactions between the diffusing molecular species and the wall, the response flow induced and experienced by a particle encodes information about any chemical patterning of the wall. Here, we extend previous studies on self-phoresis of a sphere near a chemically patterned wall to the case of particles with rod-like, elongated shape. We focus our analysis on the new phenomenology potentially emerging from the coupling—which is inoperative for a spherical shape—of the elongated particle to the strain rate tensor of the chemi-osmotic flow. Via detailed numerical calculations, we show that the dynamics of a rod-like particle exhibits a novel ‘edge-following’ steady state: the particle translates along the edge of a chemical step at a steady distance from the step and with a steady orientation. Moreover, within a certain range of system parameters, the edge-following state co-exists with a ‘docking’ state (the particle stops at the step, oriented perpendicular to the step edge), i.e., a bistable dynamics occurs. These findings are rationalized as a consequence of the competition between the fluid vorticity and the rate of strain by using analytical theory based on the point-particle approximation which captures quasi-quantitatively the dynamics of the system.

Modelling of slaughterhouse solid waste anaerobic digestion: determination of parameters and continuous reactor simulation.

PubMed

López, Iván; Borzacconi, Liliana

2010-10-01

A model based on the work of Angelidaki et al. (1993) was applied to simulate the anaerobic biodegradation of ruminal contents. In this study, two fractions of solids with different biodegradation rates were considered. A first-order kinetic was used for the easily biodegradable fraction and a kinetic expression that is function of the extracellular enzyme concentration was used for the slowly biodegradable fraction. Batch experiments were performed to obtain an accumulated methane curve that was then used to obtain the model parameters. For this determination, a methodology derived from the "multiple-shooting" method was successfully used. Monte Carlo simulations allowed a confidence range to be obtained for each parameter. Simulations of a continuous reactor were performed using the optimal set of model parameters. The final steady-states were determined as functions of the operational conditions (solids load and residence time). The simulations showed that methane flow peaked at a flow rate of 0.5-0.8 Nm(3)/d/m(reactor)(3) at a residence time of 10-20 days. Simulations allow the adequate selection of operating conditions of a continuous reactor. (c) 2010 Elsevier Ltd. All rights reserved.

Electro-convective versus electroosmotic instability in concentration polarization.

PubMed

Rubinstein, Isaak; Zaltzman, Boris

2007-10-31

Electro-convection is reviewed as a mechanism of mixing in the diffusion layer of a strong electrolyte adjacent to a charge-selective solid, such as an ion exchange (electrodialysis) membrane or an electrode. Two types of electro-convection in strong electrolytes may be distinguished: bulk electro-convection, due to the action of the electric field upon the residual space charge of a quasi-electro-neutral bulk solution, and convection induced by electroosmotic slip, due to electric forces acting in the thin electric double layer of either quasi-equilibrium or non-equilibrium type near the solid/liquid interface. According to recent studies, the latter appears to be the likely source of mixing in the diffusion layer, leading to 'over-limiting' conductance in electrodialysis. Electro-convection near a planar uniform charge selective solid/liquid interface sets on as a result of hydrodynamic instability of one-dimensional steady state electric conduction through such an interface. We compare the results of linear stability analysis obtained for instabilities of this kind appearing in the full electro-convective and limiting non-equilibrium electroosmotic formulations. The short- and long-wave aspects of these instabilities are discussed along with the wave number selection principles.

Biogasification of Walt Disney World biomass waste blend. Final report, January 1982-December 1985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biljetina, R.; Chynoweth, D.P.; Srivastava, V.J.

1986-10-01

The objective of the research is to develop efficient processes for conversion of biomass-waste blends to methane and other resources. To evaluate the technical and economic feasibility, an experimental test unit (ETU) was designed and operated at the Reedy Creek Wastewater Treatment Plant at Walt Disney World in Lake Buena Vista, Florida. The facility integrates a biomethanogenic-conversion process with a wastewater-treatment process employing water hyacinth ponds for secondary and tertiary treatment of sewage. Harvested water hyacinth is subsequently combined with sludge from the primary wastewater clarifier and fed at 1-wet-ton per day to the ETU digester. This results in themore » production of methane and other useful products. The digester was operated as a non-mixed, solids concentrating digester to encourage higher solids and microorganism retention times. Data collected during six steady-state operating periods confirmed earlier laboratory observations that this digester consistently produces 15 to 25% higher methane yields and conversions when compared to conventional stirred-tank digester. Digester operation was evaluated at different loading rates, solids blend ratios and feed configurations. Results from the program have provided a data base for the design of larger conversion systems.« less

A Poisson-like closed-form expression for the steady-state wealth distribution in a kinetic model of gambling

NASA Astrophysics Data System (ADS)

Garcia, Jane Bernadette Denise M.; Esguerra, Jose Perico H.

2017-08-01

An approximate but closed-form expression for a Poisson-like steady state wealth distribution in a kinetic model of gambling was formulated from a finite number of its moments, which were generated from a βa,b(x) exchange distribution. The obtained steady-state wealth distributions have tails which are qualitatively similar to those observed in actual wealth distributions.

The relationship between skin aging and steady state ultraweak photon emission as an indicator of skin oxidative stress in vivo.

PubMed

Gabe, Y; Osanai, O; Takema, Y

2014-08-01

Ultraweak photon emission (UPE) is one potential method to evaluate the oxidative status of the skin in vivo. However, little is known about how the daily oxidative stress of the skin is related to skin aging-related alterations in vivo. We characterized the steady state UPE and performed a skin survey. We evaluated the skin oxidative status by UPE, skin elasticity, epidermal thickness and skin color on the inner upper arm, the outer forearm, and the buttock of 70 Japanese volunteers. The steady state UPE at the three skin sites increased with age. Correlation analysis revealed that the steady state UPE only from the buttock was related to skin elasticity, which showed age-dependent changes. Moreover, analysis by age group indicated that b* values of the inner upper arm of subjects in their 20s were inversely correlated with UPE as occurred in buttock skin. In contrast, photoaged skin did not show a clear relationship with steady state UPE because the accumulation of sun-exposure might influence the sensitivity to oxidative stress. These results suggest that steady state UPE reflects not only intrinsic skin aging and cutaneous color but also the current oxidative status independent of skin aging. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Evaporation rate of nucleating clusters.

PubMed

Zapadinsky, Evgeni

2011-11-21

The Becker-Döring kinetic scheme is the most frequently used approach to vapor liquid nucleation. In the present study it has been extended so that master equations for all cluster configurations are included into consideration. In the Becker-Döring kinetic scheme the nucleation rate is calculated through comparison of the balanced steady state and unbalanced steady state solutions of the set of kinetic equations. It is usually assumed that the balanced steady state produces equilibrium cluster distribution, and the evaporation rates are identical in the balanced and unbalanced steady state cases. In the present study we have shown that the evaporation rates are not identical in the equilibrium and unbalanced steady state cases. The evaporation rate depends on the number of clusters at the limit of the cluster definition. We have shown that the ratio of the number of n-clusters at the limit of the cluster definition to the total number of n-clusters is different in equilibrium and unbalanced steady state cases. This causes difference in evaporation rates for these cases and results in a correction factor to the nucleation rate. According to rough estimation it is 10(-1) by the order of magnitude and can be lower if carrier gas effectively equilibrates the clusters. The developed approach allows one to refine the correction factor with Monte Carlo and molecular dynamic simulations.

Perception of steady-state vowels and vowelless syllables by adults and children

NASA Astrophysics Data System (ADS)

Nittrouer, Susan

2005-04-01

Vowels can be produced as long, isolated, and steady-state, but that is not how they are found in natural speech. Instead natural speech consists of almost continuously changing (i.e., dynamic) acoustic forms from which mature listeners recover underlying phonetic form. Some theories suggest that children need steady-state information to recognize vowels (and so learn vowel systems), even though that information is sparse in natural speech. The current study examined whether young children can recover vowel targets from dynamic forms, or whether they need steady-state information. Vowel recognition was measured for adults and children (3, 5, and 7 years) for natural productions of /dæd/, /dUd/ /æ/, /U/ edited to make six stimulus sets: three dynamic (whole syllables; syllables with middle 50-percent replaced by cough; syllables with all but the first and last three pitch periods replaced by cough), and three steady-state (natural, isolated vowels; reiterated pitch periods from those vowels; reiterated pitch periods from the syllables). Adults scored nearly perfectly on all but first/last three pitch period stimuli. Children performed nearly perfectly only when the entire syllable was heard, and performed similarly (near 80%) for all other stimuli. Consequently, children need dynamic forms to perceive vowels; steady-state forms are not preferred.

A stability analysis of the power-law steady state of marine size spectra.

PubMed

Datta, Samik; Delius, Gustav W; Law, Richard; Plank, Michael J

2011-10-01

This paper investigates the stability of the power-law steady state often observed in marine ecosystems. Three dynamical systems are considered, describing the abundance of organisms as a function of body mass and time: a "jump-growth" equation, a first order approximation which is the widely used McKendrick-von Foerster equation, and a second order approximation which is the McKendrick-von Foerster equation with a diffusion term. All of these yield a power-law steady state. We derive, for the first time, the eigenvalue spectrum for the linearised evolution operator, under certain constraints on the parameters. This provides new knowledge of the stability properties of the power-law steady state. It is shown analytically that the steady state of the McKendrick-von Foerster equation without the diffusion term is always unstable. Furthermore, numerical plots show that eigenvalue spectra of the McKendrick-von Foerster equation with diffusion give a good approximation to those of the jump-growth equation. The steady state is more likely to be stable with a low preferred predator:prey mass ratio, a large diet breadth and a high feeding efficiency. The effects of demographic stochasticity are also investigated and it is concluded that these are likely to be small in real systems.

EEMD-Based Steady-State Indexes and Their Applications to Condition Monitoring and Fault Diagnosis of Railway Axle Bearings

PubMed Central

Fan, Wei; Tsui, Kwok-Leung; Lin, Jianhui

2018-01-01

Railway axle bearings are one of the most important components used in vehicles and their failures probably result in unexpected accidents and economic losses. To realize a condition monitoring and fault diagnosis scheme of railway axle bearings, three dimensionless steadiness indexes in a time domain, a frequency domain, and a shape domain are respectively proposed to measure the steady states of bearing vibration signals. Firstly, vibration data collected from some designed experiments are pre-processed by using ensemble empirical mode decomposition (EEMD). Then, the coefficient of variation is introduced to construct two steady-state indexes from pre-processed vibration data in a time domain and a frequency domain, respectively. A shape function is used to construct a steady-state index in a shape domain. At last, to distinguish normal and abnormal bearing health states, some guideline thresholds are proposed. Further, to identify axle bearings with outer race defects, a pin roller defect, a cage defect, and coupling defects, the boundaries of all steadiness indexes are experimentally established. Experimental results showed that the proposed condition monitoring and fault diagnosis scheme is effective in identifying different bearing health conditions. PMID:29495446

Baroelectric Effects in Systems with Solid Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malov, Y.I.; Sherstnov, S.A.; Ukshe, E.A.

1985-07-01

This paper presents results obtained when measuring the baro-emf of the system Ag/1.1Na/sub 2/O.11A1/sub 2/O/sub 3//Ag at room temperature. The characteristic time dependence of the baro-emf is shown. In all cases the electrode experiencing the higher pressure was at the more negative potential. The signal decays slowly when the pressure is taken off; sometimes the emf will even change sign before the steady-state potential difference is established, which is close to zero. The effects of double-layer relaxation and elastic deformation of the electrolyte's rigid lattice evidently should determine the gradual decay of the emf after load removal.

Characterization of various two-phase materials based on thermal conductivity using modified transient plane source method

NASA Astrophysics Data System (ADS)

Jayachandran, S.; Prithiviraajan, R. N.; Reddy, K. S.

2017-07-01

This paper presents the thermal conductivity of various two-phase materials using modified transient plane source (MTPS) technique. The values are determined by using commercially available C-Therm TCi apparatus. It is specially designed for testing of low to high thermal conductivity materials in the range of 0.02 to 100 Wm-1K-1 within a temperature range of 223-473 K. The results obtained for the two-phase materials (solids, powders and liquids) are having an accuracy better than 5%. The transient method is one of the easiest and less time consuming method to determine the thermal conductivity of the materials compared to steady state methods.

TAP 1: A Finite Element Program for Steady-State Thermal Analysis of Convectively Cooled Structures

NASA Technical Reports Server (NTRS)

Thornton, E. A.

1976-01-01

The program has a finite element library of six elements: two conduction/convection elements to model heat transfer in a solid, two convection elements to model heat transfer in a fluid, and two integrated conduction/convection elements to represent combined heat transfer in tubular and plate/fin fluid passages. Nonlinear thermal analysis due to temperature dependent thermal parameters is performed using the Newton-Raphson iteration method. Program output includes nodal temperatures and element heat fluxes. Pressure drops in fluid passages may be computed as an option. A companion plotting program for displaying the finite element model and predicted temperature distributions is presented. User instructions and sample problems are presented in appendixes.

Bipolar pulse field for magnetic refrigeration

DOEpatents

Lubell, Martin S.

1994-01-01

A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies.

Steady State Advanced Tokamak (SSAT): The mission and the machine

NASA Astrophysics Data System (ADS)

Thomassen, K.; Goldston, R.; Nevins, B.; Neilson, H.; Shannon, T.; Montgomery, B.

1992-03-01

Extending the tokamak concept to the steady state regime and pursuing advances in tokamak physics are important and complementary steps for the magnetic fusion energy program. The required transition away from inductive current drive will provide exciting opportunities for advances in tokamak physics, as well as important impetus to drive advances in fusion technology. Recognizing this, the Fusion Policy Advisory Committee and the U.S. National Energy Strategy identified the development of steady state tokamak physics and technology, and improvements in the tokamak concept, as vital elements in the magnetic fusion energy development plan. Both called for the construction of a steady state tokamak facility to address these plan elements. Advances in physics that produce better confinement and higher pressure limits are required for a similar unit size reactor. Regimes with largely self-driven plasma current are required to permit a steady-state tokamak reactor with acceptable recirculating power. Reliable techniques of disruption control will be needed to achieve the availability goals of an economic reactor. Thus the central role of this new tokamak facility is to point the way to a more attractive demonstration reactor (DEMO) than the present data base would support. To meet the challenges, we propose a new 'Steady State Advanced Tokamak' (SSAT) facility that would develop and demonstrate optimized steady state tokamak operating mode. While other tokamaks in the world program employ superconducting toroidal field coils, SSAT would be the first major tokamak to operate with a fully superconducting coil set in the elongated, divertor geometry planned for ITER and DEMO.

Is steady-state capitalism viable? A review of the issues and an answer in the affirmative.

PubMed

Lawn, Philip

2011-02-01

Most ecological economists believe that the transition to a steady-state economy is necessary to ensure ecological sustainability and to maximize a nation's economic welfare. While some observers agree with the necessity of the steady-state economy, they are nonetheless critical of the suggestion made by ecological economists-in particular, Herman Daly-that a steady-state economy is compatible with a capitalist system. First, they believe that steady-state capitalism is based on the untenable assumption that growth is an optional rather than in-built element of capitalism. Second, they argue that capitalist notions of efficient resource allocation are too restrictive to facilitate the transition to an "ecological" or steady-state economy. I believe these observers are outright wrong with their first criticism and, because they misunderstand Daly's vision of a steady-state economy, are misplaced with their second criticism. The nature of a capitalist system depends upon the institutional framework that supports and shapes it. Hence, a capitalist system can exist in a wide variety of forms. Unfortunately, many observers fail to recognize that the current "growth imperative" is the result of capitalist systems everywhere being institutionally designed to grow. They need not be designed this way to survive and thrive. Indeed, because continued growth is both existentially undesirable and ecologically unsustainable, redesigning capitalist systems through the introduction of Daly-like institutions would prove to be capitalism's savior. What's more, it would constitute humankind's best hope of achieving sustainable development. © 2011 New York Academy of Sciences.

Understanding emotional transitions: the interpersonal consequences of changing emotions in negotiations.

PubMed

Filipowicz, Allan; Barsade, Sigal; Melwani, Shimul

2011-09-01

Research on the interpersonal functions of emotions has focused primarily on steady-state emotion rather than on emotional transitions, the movement between emotion states. The authors examined the influence of emotional transitions on social interactions and found that emotional transitions led to consistently different outcomes than their corresponding steady-state emotions. Across 2 computer-mediated negotiations and a face-to-face negotiation, participants negotiating with partners who displayed a "becoming angry" (happy to angry) emotional transition accepted worse negotiation outcomes yet formed better relational impressions of their partners than participants negotiating with partners who displayed steady-state anger. This relationship was mediated through 2 mechanisms: attributional and emotional contagion processes. The "becoming happy" (angry to happy) emotional transition as compared with steady-state happiness was not significantly related to differences in negotiation outcomes but was significantly related to differences in relational impressions, where perceivers of the "becoming happy" emotional transition gave their partners lower relational impression ratings than perceivers of steady-state happiness. PsycINFO Database Record (c) 2011 APA, all rights reserved.

Continuous-wave lasing in colloidal quantum dot solids enabled by facet-selective epitaxy.

PubMed

Fan, Fengjia; Voznyy, Oleksandr; Sabatini, Randy P; Bicanic, Kristopher T; Adachi, Michael M; McBride, James R; Reid, Kemar R; Park, Young-Shin; Li, Xiyan; Jain, Ankit; Quintero-Bermudez, Rafael; Saravanapavanantham, Mayuran; Liu, Min; Korkusinski, Marek; Hawrylak, Pawel; Klimov, Victor I; Rosenthal, Sandra J; Hoogland, Sjoerd; Sargent, Edward H

2017-04-06

Colloidal quantum dots (CQDs) feature a low degeneracy of electronic states at the band edges compared with the corresponding bulk material, as well as a narrow emission linewidth. Unfortunately for potential laser applications, this degeneracy is incompletely lifted in the valence band, spreading the hole population among several states at room temperature. This leads to increased optical gain thresholds, demanding high photoexcitation levels to achieve population inversion (more electrons in excited states than in ground states-the condition for optical gain). This, in turn, increases Auger recombination losses, limiting the gain lifetime to sub-nanoseconds and preventing steady laser action. State degeneracy also broadens the photoluminescence linewidth at the single-particle level. Here we demonstrate a way to decrease the band-edge degeneracy and single-dot photoluminescence linewidth in CQDs by means of uniform biaxial strain. We have developed a synthetic strategy that we term facet-selective epitaxy: we first switch off, and then switch on, shell growth on the (0001) facet of wurtzite CdSe cores, producing asymmetric compressive shells that create built-in biaxial strain, while still maintaining excellent surface passivation (preventing defect formation, which otherwise would cause non-radiative recombination losses). Our synthesis spreads the excitonic fine structure uniformly and sufficiently broadly that it prevents valence-band-edge states from being thermally depopulated. We thereby reduce the optical gain threshold and demonstrate continuous-wave lasing from CQD solids, expanding the library of solution-processed materials that may be capable of continuous-wave lasing. The individual CQDs exhibit an ultra-narrow single-dot linewidth, and we successfully propagate this into the ensemble of CQDs.

Spurious Numerical Solutions Of Differential Equations

NASA Technical Reports Server (NTRS)

Lafon, A.; Yee, H. C.

1995-01-01

Paper presents detailed study of spurious steady-state numerical solutions of differential equations that contain nonlinear source terms. Main objectives of this study are (1) to investigate how well numerical steady-state solutions of model nonlinear reaction/convection boundary-value problem mimic true steady-state solutions and (2) to relate findings of this investigation to implications for interpretation of numerical results from computational-fluid-dynamics algorithms and computer codes used to simulate reacting flows.

Electronic transport characterization of silicon wafers by spatially resolved steady-state photocarrier radiometric imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qian; University of the Chinese Academy of Sciences, Beijing 100039; Li, Bincheng, E-mail: bcli@ioe.ac.cn

2015-09-28

Spatially resolved steady-state photocarrier radiometric (PCR) imaging technique is developed to characterize the electronic transport properties of silicon wafers. Based on a nonlinear PCR theory, simulations are performed to investigate the effects of electronic transport parameters (the carrier lifetime, the carrier diffusion coefficient, and the front surface recombination velocity) on the steady-state PCR intensity profiles. The electronic transport parameters of an n-type silicon wafer are simultaneously determined by fitting the measured steady-state PCR intensity profiles to the three-dimensional nonlinear PCR model. The determined transport parameters are in good agreement with the results obtained by the conventional modulated PCR technique withmore » multiple pump beam radii.« less

A Waved Journal Bearing Concept-Evaluating Steady-State and Dynamic Performance with a Potential Active Control Alternative

NASA Technical Reports Server (NTRS)

Dimofte, Florin

1993-01-01

Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. The performance of generic waved bearings having either three or four waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of fluid film stability and dynamic coefficients. It was found that the bearing wave amplitude has an important influence on both the steady-state and the dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases.

[Specific features in realization of the principle of minimum energy dissipation during individual development].

PubMed

Zotin, A A

2012-01-01

Realization of the principle of minimum energy dissipation (Prigogine's theorem) during individual development has been analyzed. This analysis has suggested the following reformulation of this principle for living objects: when environmental conditions are constant, the living system evolves to a current steady state in such a way that the difference between entropy production and entropy flow (psi(u) function) is positive and constantly decreases near the steady state, approaching zero. In turn, the current steady state tends to a final steady state in such a way that the difference between the specific entropy productions in an organism and its environment tends to be minimal. In general, individual development completely agrees with the law of entropy increase (second law of thermodynamics).

Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection.

PubMed

Kitazumi, Yuki; Hamamoto, Katsumi; Noda, Tatsuo; Shirai, Osamu; Kano, Kenji

2015-01-01

The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.

Dissipative production of a maximally entangled steady state of two quantum bits.

PubMed

Lin, Y; Gaebler, J P; Reiter, F; Tan, T R; Bowler, R; Sørensen, A S; Leibfried, D; Wineland, D J

2013-12-19

Entangled states are a key resource in fundamental quantum physics, quantum cryptography and quantum computation. Introduction of controlled unitary processes--quantum gates--to a quantum system has so far been the most widely used method to create entanglement deterministically. These processes require high-fidelity state preparation and minimization of the decoherence that inevitably arises from coupling between the system and the environment, and imperfect control of the system parameters. Here we combine unitary processes with engineered dissipation to deterministically produce and stabilize an approximate Bell state of two trapped-ion quantum bits (qubits), independent of their initial states. Compared with previous studies that involved dissipative entanglement of atomic ensembles or the application of sequences of multiple time-dependent gates to trapped ions, we implement our combined process using trapped-ion qubits in a continuous time-independent fashion (analogous to optical pumping of atomic states). By continuously driving the system towards the steady state, entanglement is stabilized even in the presence of experimental noise and decoherence. Our demonstration of an entangled steady state of two qubits represents a step towards dissipative state engineering, dissipative quantum computation and dissipative phase transitions. Following this approach, engineered coupling to the environment may be applied to a broad range of experimental systems to achieve desired quantum dynamics or steady states. Indeed, concurrently with this work, an entangled steady state of two superconducting qubits was demonstrated using dissipation.

Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions.

PubMed

Takahashi, Hirohide; Miyagi, Atsushi; Redondo-Morata, Lorena; Scheuring, Simon

2016-11-01

With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca 2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Poiseuille flow of soft glasses in narrow channels: from quiescence to steady state.

PubMed

Chaudhuri, Pinaki; Horbach, Jürgen

2014-10-01

Using numerical simulations, the onset of Poiseuille flow in a confined soft glass is investigated. Starting from the quiescent state, steady flow sets in at a time scale which increases with a decrease in applied forcing. At this onset time scale, a rapid transition occurs via the simultaneous fluidization of regions having different local stresses. In the absence of steady flow at long times, creep is observed even in regions where the local stress is larger than the bulk yielding threshold. Finally, we show that the time scale to attain steady flow depends strongly on the history of the initial state.

Effect of wheelchair mass, tire type and tire pressure on physical strain and wheelchair propulsion technique.

PubMed

de Groot, Sonja; Vegter, Riemer J K; van der Woude, Lucas H V

2013-10-01

The purpose of this study was to evaluate the effect of wheelchair mass, solid vs. pneumatic tires and tire pressure on physical strain and wheelchair propulsion technique. 11 Able-bodied participants performed 14 submaximal exercise blocks on a treadmill with a fixed speed (1.11 m/s) within 3 weeks to determine the effect of tire pressure (100%, 75%, 50%, 25% of the recommended value), wheelchair mass (0 kg, 5 kg, or 10 kg extra) and tire type (pneumatic vs. solid). All test conditions (except pneumatic vs. solid) were performed with and without instrumented measurement wheels. Outcome measures were power output (PO), physical strain (heart rate (HR), oxygen uptake (VO2), gross mechanical efficiency (ME)) and propulsion technique (timing, force application). At 25% tire pressure PO and subsequently VO2 were higher compared to 100% tire pressure. Furthermore, a higher tire pressure led to a longer cycle time and contact angle and subsequently lower push frequency. Extra mass did not lead to an increase in PO, physical strain or propulsion technique. Solid tires led to a higher PO and physical strain. The solid tire effect was amplified by increased mass (tire × mass interaction). In contrast to extra mass, tire pressure and tire type have an effect on PO, physical strain or propulsion technique of steady-state wheelchair propulsion. As expected, it is important to optimize tire pressure and tire type. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Improved Design of Anaerobic Digesters for Household Biogas Production in Indonesia: One Cow, One Digester, and One Hour of Cooking per Day

PubMed Central

Usack, Joseph G.; Wiratni, Wiratni; Angenent, Largus T.

2014-01-01

A government-sponsored initiative in Indonesia to design and implement low-cost anaerobic digestion systems resulted in 21 full-scale systems with the aim to satisfy the cooking fuel demands of rural households owning at least one cow. The full-scale design consisted of a 0.3 m diameter PVC pipe, which was operated as a conventional plug-flow system. The system generated enough methane to power a cooking stove for ∼1 h. However, eventual clogging from solids accumulation inside the bioreactor proved to be a major drawback. Here, we improved the digester configuration to remedy clogging while maintaining system performance. Controlled experiments were performed using four 9-L laboratory-scale digesters operated at a temperature of 27 ± 1°C, a volatile solids loading rate of 2.0 g VS·L−1 ·day−1, and a 21-day hydraulic retention time. Two of the digesters were replicates of the original design (control digesters), while the other two digesters included internal mixing or effluent recycle (experimental digesters). The performance of each digester was compared based on methane yields, VS removal efficiencies, and steady-state solids concentrations during an operating period of 311 days. Statistical analyses revealed that internal mixing and effluent recycling resulted in reduced solids accumulation compared to the controls without diminishing methane yields or solids removal efficiencies. PMID:24715809

Bipolar pulse field for magnetic refrigeration

DOEpatents

Lubell, M.S.

1994-10-25

A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies. 2 figs.

Numerical Modeling of Reactive Multiphase Flow for FCC and Hot Gas Desulfurization Circulating Fluidized Beds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Aubrey L.

2005-07-01

This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFBmore » riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.« less

Steady-state kinetic modeling constrains cellular resting states and dynamic behavior.

PubMed

Purvis, Jeremy E; Radhakrishnan, Ravi; Diamond, Scott L

2009-03-01

A defining characteristic of living cells is the ability to respond dynamically to external stimuli while maintaining homeostasis under resting conditions. Capturing both of these features in a single kinetic model is difficult because the model must be able to reproduce both behaviors using the same set of molecular components. Here, we show how combining small, well-defined steady-state networks provides an efficient means of constructing large-scale kinetic models that exhibit realistic resting and dynamic behaviors. By requiring each kinetic module to be homeostatic (at steady state under resting conditions), the method proceeds by (i) computing steady-state solutions to a system of ordinary differential equations for each module, (ii) applying principal component analysis to each set of solutions to capture the steady-state solution space of each module network, and (iii) combining optimal search directions from all modules to form a global steady-state space that is searched for accurate simulation of the time-dependent behavior of the whole system upon perturbation. Importantly, this stepwise approach retains the nonlinear rate expressions that govern each reaction in the system and enforces constraints on the range of allowable concentration states for the full-scale model. These constraints not only reduce the computational cost of fitting experimental time-series data but can also provide insight into limitations on system concentrations and architecture. To demonstrate application of the method, we show how small kinetic perturbations in a modular model of platelet P2Y(1) signaling can cause widespread compensatory effects on cellular resting states.

A descriptive model of resting-state networks using Markov chains.

PubMed

Xie, H; Pal, R; Mitra, S

2016-08-01

Resting-state functional connectivity (RSFC) studies considering pairwise linear correlations have attracted great interests while the underlying functional network structure still remains poorly understood. To further our understanding of RSFC, this paper presents an analysis of the resting-state networks (RSNs) based on the steady-state distributions and provides a novel angle to investigate the RSFC of multiple functional nodes. This paper evaluates the consistency of two networks based on the Hellinger distance between the steady-state distributions of the inferred Markov chain models. The results show that generated steady-state distributions of default mode network have higher consistency across subjects than random nodes from various RSNs.

Thermodynamic analysis of a combined-cycle solar thermal power plant with manganese oxide-based thermochemical energy storage

NASA Astrophysics Data System (ADS)

Lei, Qi; Bader, Roman; Kreider, Peter; Lovegrove, Keith; Lipiński, Wojciech

2017-11-01

We explore the thermodynamic efficiency of a solar-driven combined cycle power system with manganese oxide-based thermochemical energy storage system. Manganese oxide particles are reduced during the day in an oxygen-lean atmosphere obtained with a fluidized-bed reactor at temperatures in the range of 750-1600°C using concentrated solar energy. Reduced hot particles are stored and re-oxidized during night-time to achieve continuous power plant operation. The steady-state mass and energy conservation equations are solved for all system components to calculate the thermodynamic properties and mass flow rates at all state points in the system, taking into account component irreversibilities. The net power block and overall solar-to-electric energy conversion efficiencies, and the required storage volumes for solids and gases in the storage system are predicted. Preliminary results for a system with 100 MW nominal solar power input at a solar concentration ratio of 3000, designed for constant round-the-clock operation with 8 hours of on-sun and 16 hours of off-sun operation and with manganese oxide particles cycled between 750 and 1600°C yield a net power block efficiency of 60.0% and an overall energy conversion efficiency of 41.3%. Required storage tank sizes for the solids are estimated to be approx. 5-6 times smaller than those of state-of-the-art molten salt systems.

Results of the ETV-1 breadboard tests under steady-state and transient conditions. [conducted in the NASA-LeRC Road Load Simulator

NASA Technical Reports Server (NTRS)

Sargent, N. B.; Dustin, M. O.

1981-01-01

Steady state tests were run to characterize the system and component efficiencies over the complete speed-torque capabilities of the propulsion system in both motoring and regenerative modes of operation. The steady state data were obtained using a battery simulator to separate the effects on efficiency caused by changing battery state-of-charge and component temperature. Transient tests were performed to determine the energy profiles of the propulsion system operating over the SAE J227a driving schedules.

Experimental investigation of cryogenic oscillating heat pipes.

PubMed

Jiao, A J; Ma, H B; Critser, J K

2009-07-01

A novel cryogenic heat pipe, oscillating heat pipe (OHP), which consists of an 4 × 18.5 cm evaporator, a 6 × 18.5 cm condenser, and 10 cm length of adiabatic section, has been developed and experimental characterization conducted. Experimental results show that the maximum heat transport capability of the OHP reached 380W with average temperature difference of 49 °C between the evaporator and condenser when the cryogenic OHP was charged with liquid nitrogen at 48% (v/v) and operated in a horizontal direction. The thermal resistance decreased from 0.256 to 0.112 while the heat load increased from 22.5 to 321.8 W. When the OHP was operated at a steady state and an incremental heat load was added to it, the OHP operation changed from a steady state to an unsteady state until a new steady state was reached. This process can be divided into three regions: (I) unsteady state; (II) transient state; and (III) new steady state. In the steady state, the amplitude of temperature change in the evaporator is smaller than that of the condenser while the temperature response keeps the same frequency both in the evaporator and the condenser. The experimental results also showed that the amplitude of temperature difference between the evaporator and the condenser decreased when the heat load increased.

Experimental investigation of cryogenic oscillating heat pipes

PubMed Central

Jiao, A.J.; Ma, H.B.; Critser, J.K.

2010-01-01

A novel cryogenic heat pipe, oscillating heat pipe (OHP), which consists of an 4 × 18.5 cm evaporator, a 6 × 18.5 cm condenser, and 10 cm length of adiabatic section, has been developed and experimental characterization conducted. Experimental results show that the maximum heat transport capability of the OHP reached 380W with average temperature difference of 49 °C between the evaporator and condenser when the cryogenic OHP was charged with liquid nitrogen at 48% (v/v) and operated in a horizontal direction. The thermal resistance decreased from 0.256 to 0.112 while the heat load increased from 22.5 to 321.8 W. When the OHP was operated at a steady state and an incremental heat load was added to it, the OHP operation changed from a steady state to an unsteady state until a new steady state was reached. This process can be divided into three regions: (I) unsteady state; (II) transient state; and (III) new steady state. In the steady state, the amplitude of temperature change in the evaporator is smaller than that of the condenser while the temperature response keeps the same frequency both in the evaporator and the condenser. The experimental results also showed that the amplitude of temperature difference between the evaporator and the condenser decreased when the heat load increased. PMID:20585410

Slow and deep respiration suppresses steady-state sympathetic nerve activity in patients with chronic heart failure: from modeling to clinical application.

PubMed

Harada, Daisuke; Asanoi, Hidetsugu; Takagawa, Junya; Ishise, Hisanari; Ueno, Hiroshi; Oda, Yoshitaka; Goso, Yukiko; Joho, Shuji; Inoue, Hiroshi

2014-10-15

Influences of slow and deep respiration on steady-state sympathetic nerve activity remain controversial in humans and could vary depending on disease conditions and basal sympathetic nerve activity. To elucidate the respiratory modulation of steady-state sympathetic nerve activity, we modeled the dynamic nature of the relationship between lung inflation and muscle sympathetic nerve activity (MSNA) in 11 heart failure patients with exaggerated sympathetic outflow at rest. An autoregressive exogenous input model was utilized to simulate entire responses of MSNA to variable respiratory patterns. In another 18 patients, we determined the influence of increasing tidal volume and slowing respiratory frequency on MSNA; 10 patients underwent a 15-min device-guided slow respiration and the remaining 8 had no respiratory modification. The model predicted that a 1-liter, step increase of lung volume decreased MSNA dynamically; its nadir (-33 ± 22%) occurred at 2.4 s; and steady-state decrease (-15 ± 5%), at 6 s. Actually, in patients with the device-guided slow and deep respiration, respiratory frequency effectively fell from 16.4 ± 3.9 to 6.7 ± 2.8/min (P < 0.0001) with a concomitant increase in tidal volume from 499 ± 206 to 1,177 ± 497 ml (P < 0.001). Consequently, steady-state MSNA was decreased by 31% (P < 0.005). In patients without respiratory modulation, there were no significant changes in respiratory frequency, tidal volume, and steady-state MSNA. Thus slow and deep respiration suppresses steady-state sympathetic nerve activity in patients with high levels of resting sympathetic tone as in heart failure. Copyright © 2014 the American Physiological Society.

Spatial variability of steady-state infiltration into a two-layer soil system on burned hillslopes

USGS Publications Warehouse

Kinner, D.A.; Moody, J.A.

2010-01-01

Rainfall-runoff simulations were conducted to estimate the characteristics of the steady-state infiltration rate into 1-m2 north- and south-facing hillslope plots burned by a wildfire in October 2003. Soil profiles in the plots consisted of a two-layer system composed of an ash on top of sandy mineral soil. Multiple rainfall rates (18.4-51.2 mm h-1) were used during 14 short-duration (30 min) and 2 long-duration simulations (2-4 h). Steady state was reached in 7-26 min. Observed spatially-averaged steady-state infiltration rates ranged from 18.2 to 23.8 mm h-1 for north-facing and from 17.9 to 36.0 mm h-1 for south-facing plots. Three different theoretical spatial distribution models of steady-state infiltration rate were fit to the measurements of rainfall rate and steady-state discharge to provided estimates of the spatial average (19.2-22.2 mm h-1) and the coefficient of variation (0.11-0.40) of infiltration rates, overland flow contributing area (74-90% of the plot area), and infiltration threshold (19.0-26 mm h-1). Tensiometer measurements indicated a downward moving pressure wave and suggest that infiltration-excess overland flow is the runoff process on these burned hillslope with a two-layer system. Moreover, the results indicate that the ash layer is wettable, may restrict water flow into the underlying layer, and increase the infiltration threshold; whereas, the underlying mineral soil, though coarser, limits the infiltration rate. These results of the spatial variability of steady-state infiltration can be used to develop physically-based rainfall-runoff models for burned areas with a two-layer soil system. ?? 2010 Elsevier B.V.

Steady states of a diode with counterstreaming electron and positron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ender, A. Ya.; Kuznetsov, V. I., E-mail: victor.kuznetsov@mail.ioffe.ru; Gruzdev, A. A.

2016-10-15

Steady states of a plasma layer with counterstreaming beams of oppositely charged particles moving without collisions in a self-consistent electric field are analyzed. The study is aimed at clarifying the mechanism of generation and reconstruction of pulsar radiation. Such a layer also models the processes occurring in Knudsen plasma diodes with counterstreaming electron and ion beams. The steady-state solutions are exhaustively classified. The existence of several solutions at the same external parameters is established.

Steady states of a diode with counterstreaming electron and positron beams

NASA Astrophysics Data System (ADS)

Ender, A. Ya.; Kuznetsov, V. I.; Gruzdev, A. A.

2016-10-01

Steady states of a plasma layer with counterstreaming beams of oppositely charged particles moving without collisions in a self-consistent electric field are analyzed. The study is aimed at clarifying the mechanism of generation and reconstruction of pulsar radiation. Such a layer also models the processes occurring in Knudsen plasma diodes with counterstreaming electron and ion beams. The steady-state solutions are exhaustively classified. The existence of several solutions at the same external parameters is established.

Transient and steady-state performance of a single turbojet combustor with four different fuel nozzles

NASA Technical Reports Server (NTRS)

Mccafferty, Richard J; Donlon, Richard H

1955-01-01

Acceleration and steady-state performance of a tubular combustor was evaluated at two simulated altitudes with four different fuel nozzles. Temperature response lag was observed with all the nozzles. Except for rich-limit blowout, the only combustion failures observed during acceleration were with a fuel nozzle that gave an interrupted flow delivery during the acceleration. This same nozzle, because of superior fuel atomization, gave the highest steady-state combustion efficiencies.

Lactate and Acrylate Metabolism by Megasphaera elsdenii under Batch and Steady-State Conditions

PubMed Central

Prabhu, Rupal; Altman, Elliot

2012-01-01

The growth of Megasphaera elsdenii on lactate with acrylate and acrylate analogues was studied under batch and steady-state conditions. Under batch conditions, lactate was converted to acetate and propionate, and acrylate was converted into propionate. Acrylate analogues 2-methyl propenoate and 3-butenoate containing a terminal double bond were similarly converted into their respective saturated acids (isobutyrate and butyrate), while crotonate and lactate analogues 3-hydroxybutyrate and (R)-2-hydroxybutyrate were not metabolized. Under carbon-limited steady-state conditions, lactate was converted to acetate and butyrate with no propionate formed. As the acrylate concentration in the feed was increased, butyrate and hydrogen formation decreased and propionate was increasingly generated, while the calculated ATP yield was unchanged. M. elsdenii metabolism differs substantially under batch and steady-state conditions. The results support the conclusion that propionate is not formed during lactate-limited steady-state growth because of the absence of this substrate to drive the formation of lactyl coenzyme A (CoA) via propionyl-CoA transferase. Acrylate and acrylate analogues are reduced under both batch and steady-state growth conditions after first being converted to thioesters via propionyl-CoA transferase. Our findings demonstrate the central role that CoA transferase activity plays in the utilization of acids by M. elsdenii and allows us to propose a modified acrylate pathway for M. elsdenii. PMID:23023753

A critical investigation of post-liquefaction strength and steady-state flow behavior of saturated soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jong, H.L.

1988-01-01

The first objective was to perform a critical evaluation of the recently proposed steady-state analysis methodology for evaluation of post-liquefaction stability of potentially liquefiable soils. This analysis procedure is based on direct comparison between the in-situ undrained residual (steady state) strength of soils in an embankment or foundation, and the driving shear stresses in these soils. A laboratory investigation was performed to investigate factors affecting steady-state strengths, and also to evaluate the validity of assumptions involved in correcting the results of laboratory steady-state strength tests on undisturbed samples for effects of sampling disturbance in order to estimate in-situ strengths. Next,more » a field case study was performed using the steady-state analysis and testing methodologies to analyze Lower San Fernando Dam, which suffered a liquefaction-induced slope failure as a results of a 1971 earthquake. This leads to the second objective which was to extend the Lower San Fernando Dam case study to consideration of analysis methods used to evaluate the likelihood of triggering liquefaction during an earthquake. Finally, a number of the high quality undisturbed samples were subjected to undrained cyclic testing in order to repeat an earlier (1973) study of the use of cyclic tests data to predict liquefaction behavior at Lower San Fernando Dam.« less

Multiple Steady States of Buoyancy Induced Flow in Cold Water and Their Stability.

NASA Astrophysics Data System (ADS)

El-Henawy, Ibrahim Mahmoud

In Chapters 1 and 2 the physical background and the literature related to buoyancy-induced flows are reviewed. An accurate representation, based upon experimental data, of the motion-causing buoyancy force, in the vicinity of maximum density in pure water at low temperatures, is used. This representation is an accurate and quite simple formulation due to Gebhart and Mollendorf (1977). Using the representation, we study, numerically, Chapter 3, a model for the laminar, boundary-layer flow arising from natural convection adjacent to a vertical isothermal flat surface submerged in quiescent cold water. The results demonstrate for the first time the existence of multiple steady-state solutions in a natural convection flow. The existence of these new multiple steady-state solutions led to an investigation of their stability. This is carried out in Chapter 4 by a mathematical method, different from that of the usual hydrodynamic stability approach, Lin (1955) and Razinand and Reid (1982). Three real eigenvalue and eigenvector pairs corresponding to the new steady-state -solutions were found. Each of these eigenvalues changes its algebraic sign at a particular limit point (point of vertical tangency, nose, knee) in the bifurcation diagrams found in Chapter 3. The results indicate that the new steady-state solutions are unstable and that the previously found steady-state solutions, Carey, Gebhart, and Mollendorf (1980), may be stable.

Prospective evaluation of haemoglobin oxygen saturation at rest and after exercise in paediatric sickle cell disease patients

PubMed Central

Campbell, Andrew; Minniti, Caterina P.; Nouraie, Mehdi; Arteta, Manuel; Rana, Sohail; Onyekwere, Onyinye; Sable, Craig; Ensing, Gregory; Dham, Niti; Luchtman-Jones, Lori; Kato, Gregory J.; Gladwin, Mark T.; Castro, Oswaldo L.; Gordeuk, Victor R.

2009-01-01

Summary Low steady state haemoglobin oxygen saturation in patients with sickle cell anaemia has been associated with the degree of anaemia and haemolysis. How much pulmonary dysfunction contributes to low saturation is not clear. In a prospective study of children and adolescents with sickle cell disease aged 3–20 years at steady state and matched controls, 52% of 391 patients versus 24% of 63 controls had steady state oxygen saturation <99% (P < 0·0001), 9% of patients versus no controls had saturation <95% (P = 0·008) and 8% of patients versus no controls had exercise-induced reduction in saturation ≥3%. Decreasing haemoglobin concentration (P ≤ 0·001) and increasing haemolysis (P ≤ 0·003) but not pulmonary function tests were independent predictors of both lower steady-state saturation and exercise-induced reduction in saturation. Neither history of stroke nor history of acute chest syndrome was significantly associated with lower steady-state oxygen saturation or exercise-induced reduction in saturation. Tricuspid regurgitation velocity was higher in patients with lower steady state haemoglobin oxygen saturation (P = 0·003) and with greater decline in oxygen saturation during the six-minute walk (P = 0·022). In conclusion, lower haemoglobin oxygen saturation is independently associated with increasing degrees of anaemia and haemolysis but not pulmonary function abnormalities among children and adolescents with sickle cell disease. PMID:19694721

Nitrogen Can Alleviate the Inhibition of Photosynthesis Caused by High Temperature Stress under Both Steady-State and Flecked Irradiance.

PubMed

Huang, Guanjun; Zhang, Qiangqiang; Wei, Xinghai; Peng, Shaobing; Li, Yong

2017-01-01

Nitrogen is one of the most important elements for plants and is closely related to photosynthesis. High temperature stress significantly inhibits photosynthesis under both steady-state and flecked irradiance. However, it is not known whether nitrogen can affect the decrease in photosynthesis caused by high temperature, especially under flecked irradiance. In the present study, a pot experiment was conducted under two nitrogen (N) supplies with rice plants, and the steady-state and dynamic photosynthesis rates were measured under 28 and 40°C. High temperature significantly increased leaf hydraulic conductance ( K leaf ) under high N supply (HN) but not under low N supply (LN). The increased K leaf maintained a constant leaf water potential (Ψ leaf ) and steady-state stomatal conductance ( g s,sat ) under HN, while the Ψ leaf and g s,sat significantly decreased under high temperature in LN conditions. This resulted in a more severe decrease in steady-state photosynthesis ( A sat ) under high temperature in the LN conditions. After shifting from low to high light, high temperature significantly delayed the recovery of photosynthesis, which resulted in more carbon loss under flecked irradiance. These effects were obtained under HN to a lesser extent than under LN supply. Therefore, it is concluded that nitrogen can alleviate the inhibition of photosynthesis caused by high temperature stress under both steady-state and flecked irradiance.

Quasi-steady-state voltammetry of rapid electron transfer reactions at the macroscopic substrate of the scanning electrochemical microscope.

PubMed

Nioradze, Nikoloz; Kim, Jiyeon; Amemiya, Shigeru

2011-02-01

We report on a novel theory and experiment for scanning electrochemical microscopy (SECM) to enable quasi-steady-state voltammetry of rapid electron transfer (ET) reactions at macroscopic substrates. With this powerful approach, the substrate potential is cycled widely across the formal potential of a redox couple while the reactant or product of a substrate reaction is amperometrically detected at the tip in the feedback or substrate generation/tip collection mode, respectively. The plot of tip current versus substrate potential features the retraceable sigmoidal shape of a quasi-steady-state voltammogram although a transient voltammogram is obtained at the macroscopic substrate. Finite element simulations reveal that a short tip-substrate distance and a reversible substrate reaction (except under the tip) are required for quasi-steady-state voltammetry. Advantageously, a pair of quasi-steady-state voltammograms is obtained by employing both operation modes to reliably determine all transport, thermodynamic, and kinetic parameters as confirmed experimentally for rapid ET reactions of ferrocenemethanol and 7,7,8,8-tetracyanoquinodimethane at a Pt substrate with ∼0.5 μm-radius Pt tips positioned at 90 nm-1 μm distances. Standard ET rate constants of ∼7 cm/s were obtained for the latter mediator as the largest determined for a substrate reaction by SECM. Various potential applications of quasi-steady-state voltammetry are also proposed.

Role of irregular otolith afferents in the steady-state nystagmus during off-vertical axis rotation

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Perachio, A. A.; Mustari, M. J.; Strunk, C. L.

1992-01-01

1. During constant velocity off-vertical axis rotations (OVAR) in the dark a compensatory ocular nystagmus is present throughout rotation despite the lack of a maintained signal from the semicircular canals. Lesion experiments and canal plugging have attributed the steady-state ocular nystagmus during OVAR to inputs from the otolith organs and have demonstrated that it depends on an intact velocity storage mechanism. 2. To test whether irregularly discharging otolith afferents play a crucial role in the generation of the steady-state eye nystagmus during OVAR, we have used anodal (inhibitory) currents bilaterally to selectively and reversibly block irregular vestibular afferent discharge. During delivery of DC anodal currents (100 microA) bilaterally to both ears, the slow phase eye velocity of the steady-state nystagmus during OVAR was reduced or completely abolished. The disruption of the steady-state nystagmus was transient and lasted only during the period of galvanic stimulation. 3. To distinguish a possible effect of ablation of the background discharge rates of irregular vestibular afferents on the velocity storage mechanism from specific contributions of the dynamic responses from irregular otolith afferents to the circuit responsible for the generation of the steady-state nystagmus, bilateral DC anodal galvanic stimulation was applied during optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN). No change in OKN and OKAN was observed.(ABSTRACT TRUNCATED AT 250 WORDS).

Pattern Formation in Diffusion Flames Embedded in von Karman Swirling Flows

NASA Technical Reports Server (NTRS)

Nayagam, Vedha

2006-01-01

Pattern formation is observed in nature in many so-called excitable systems that can support wave propagation. It is well-known in the field of combustion that premixed flames can exhibit patterns through differential diffusion mechanism between heat and mass. However, in the case of diffusion flames where fuel and oxidizer are separated initially there have been only a few observations of pattern formation. It is generally perceived that since diffusion flames do not possess an inherent propagation speed they are static and do not form patterns. But in diffusion flames close to their extinction local quenching can occur and produce flame edges which can propagate along stoichiometric surfaces. Recently, we reported experimental observations of rotating spiral flame edges during near-limit combustion of a downward-facing polymethylmethacrylate disk spinning in quiescent air. These spiral flames, though short-lived, exhibited many similarities to patterns commonly found in quiescent excitable media including compound tip meandering motion. Flame disks that grow or shrink with time depending on the rotational speed and in-depth heat loss history of the fuel disk have also been reported. One of the limitations of studying flame patterns with solid fuels is that steady-state conditions cannot be achieved in air at normal atmospheric pressure for experimentally reasonable fuel thickness. As a means to reproduce the flame patterns observed earlier with solid fuels, but under steady-state conditions, we have designed and built a rotating, porous-disk burner through which gaseous fuels can be injected and burned as diffusion flames. The rotating porous disk generates a flow of air toward the disk by a viscous pumping action, generating what is called the von K rm n boundary layer which is of constant thickness over the entire burner disk. In this note we present a map of the various dynamic flame patterns observed during the combustion of methane in air as a function of fuel flow rate and the burner rotational speed.

Glass-water interactions: Effect of high-valence cations on glass structure and chemical durability

DOE PAGES

Pierce, Eric M.; Kerisit, Sebastien N.; Charpentier, Thibault; ...

2016-02-27

Spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na 2O Al 2O 3 B 2O 3 HfO 2 SiO 2 system (e.g., Na/(Al+B) = 1.0 and HfO 2/SiO 2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N 4 and increasesmore » the amount of Si–O–Hf moieties in the glass. Results from flow through experiments conducted under dilute and near saturated conditions show a decrease of approximately 100 or more in the dissolution rate over the series from 0 to 20 mol% HfO 2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveal a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the formation of a low coordination Si sites when Si from the saturated solution adsorbs to Hf on the glass surface. The residence time of the newly formed low coordination Si sites is longer at the glass surface and increases the density of anchor sites from which altered layers with higher Si densities can form than in the absence of Hf. These results illustrate the importance of understanding solid water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.« less

Simulating the blast wave from detonation of a charge using a balloon of compressed air

NASA Astrophysics Data System (ADS)

Blanc, L.; Santana Herrera, S.; Hanus, J. L.

2018-07-01

This paper investigates a simple numerical method, based on the release of a pressurized spherical air volume, to predict or reproduce the main characteristics of the blast environment from the detonation of solid or gaseous charges. This approach aims to give an alternative to the use of a steady-state detonation model and a Jones-Wilkins-Lee equation of state to describe the expansion of the detonation products, especially when the explosive parameters are unknown and a TNT equivalent is used. The validity of the proposed approach is assessed through the comparison of predicted overpressure and impulse at different distances from the explosion with that of TNT and stoichiometric propane-oxygen explosions. It is also shown that, for gaseous detonations, a better agreement is obtained with the rationally optimized compressed balloon than with the use of a Jones-Wilkins-Lee model and a TNT equivalent mass.

Simulating the blast wave from detonation of a charge using a balloon of compressed air

NASA Astrophysics Data System (ADS)

Blanc, L.; Santana Herrera, S.; Hanus, J. L.

2017-11-01

This paper investigates a simple numerical method, based on the release of a pressurized spherical air volume, to predict or reproduce the main characteristics of the blast environment from the detonation of solid or gaseous charges. This approach aims to give an alternative to the use of a steady-state detonation model and a Jones-Wilkins-Lee equation of state to describe the expansion of the detonation products, especially when the explosive parameters are unknown and a TNT equivalent is used. The validity of the proposed approach is assessed through the comparison of predicted overpressure and impulse at different distances from the explosion with that of TNT and stoichiometric propane-oxygen explosions. It is also shown that, for gaseous detonations, a better agreement is obtained with the rationally optimized compressed balloon than with the use of a Jones-Wilkins-Lee model and a TNT equivalent mass.

Ultra-fast low concentration detection of Candida pathogens utilizing high resolution micropore chips.

PubMed

Mulero, Rafael; Lee, Dong Heun; Kutzler, Michele A; Jacobson, Jeffrey M; Kim, Min Jun

2009-01-01

Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the Candida species in a timely manner. Here we describe a novel method of detection using a solid-state micro-scale pore similar to the operational principles of a Coulter counter. With a steady electrolyte current flowing through the pore, measurements are taken of changes in the current corresponding to the shape of individual yeasts as they translocate or travel through the pore. The direct ultra-fast low concentration electrical addressing of C. albicans has established criteria for distinguishing individual yeast based on their structural properties, which may reduce the currently used methods' complexity for both identification and quantification capabilities in mixed blood samples.

Ultra-Fast Low Concentration Detection of Candida Pathogens Utilizing High Resolution Micropore Chips

PubMed Central

Mulero, Rafael; Lee, Dong Heun; Kutzler, Michele A.; Jacobson, Jeffrey M.; Kim, Min Jun

2009-01-01

Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the Candida species in a timely manner. Here we describe a novel method of detection using a solid-state micro-scale pore similar to the operational principles of a Coulter counter. With a steady electrolyte current flowing through the pore, measurements are taken of changes in the current corresponding to the shape of individual yeasts as they translocate or travel through the pore. The direct ultra-fast low concentration electrical addressing of C. albicans has established criteria for distinguishing individual yeast based on their structural properties, which may reduce the currently used methods’ complexity for both identification and quantification capabilities in mixed blood samples. PMID:22573974

Oxygen vacancies promoted interfacial charge carrier transfer of CdS/ZnO heterostructure for photocatalytic hydrogen generation.

PubMed

Xie, Ying Peng; Yang, Yongqiang; Wang, Guosheng; Liu, Gang

2017-10-01

The solid-state Z-scheme trinary/binary heterostructures show the advantage of utilizing the high-energy photogenerated charge carriers in photocatalysis. However, the key factors controlling such Z-scheme in the binary heterostructures are still unclear. In this paper, we showed that oxygen vacancies could act as an interface electron transfer mediator to promote the direct Z-scheme charge transfer process in binary semiconductor heterostructures of CdS/ZnS. Increasing the concentration of surface oxygen vacancies of ZnO crystal can greatly enhance photocatalytic hydrogen generation of CdS/ZnO heterostructure. This was attributed to the strengthened direct Z-scheme charge transfer process in CdS/ZnO, as evidenced by steady-state/time-resolved photoluminescence spectroscopy and selective photodeposition of metal particles on the heterostructure. Copyright © 2017 Elsevier Inc. All rights reserved.

Elements of an improved model of debris-flow motion

USGS Publications Warehouse

Iverson, R.M.

2009-01-01

A new depth-averaged model of debris-flow motion describes simultaneous evolution of flow velocity and depth, solid and fluid volume fractions, and pore-fluid pressure. Non-hydrostatic pore-fluid pressure is produced by dilatancy, a state-dependent property that links the depth-averaged shear rate and volumetric strain rate of the granular phase. Pore-pressure changes caused by shearing allow the model to exhibit rate-dependent flow resistance, despite the fact that the basal shear traction involves only rate-independent Coulomb friction. An analytical solution of simplified model equations shows that the onset of downslope motion can be accelerated or retarded by pore-pressure change, contingent on whether dilatancy is positive or negative. A different analytical solution shows that such effects will likely be muted if downslope motion continues long enough, because dilatancy then evolves toward zero, and volume fractions and pore pressure concurrently evolve toward steady states. ?? 2009 American Institute of Physics.

Silver-induced reconstruction of an adeninate-based metal-organic framework for encapsulation of luminescent adenine-stabilized silver clusters.

PubMed

Jonckheere, Dries; Coutino-Gonzalez, Eduardo; Baekelant, Wouter; Bueken, Bart; Reinsch, Helge; Stassen, Ivo; Fenwick, Oliver; Richard, Fanny; Samorì, Paolo; Ameloot, Rob; Hofkens, Johan; Roeffaers, Maarten B J; De Vos, Dirk E

2016-05-21

Bright luminescent silver-adenine species were successfully stabilized in the pores of the MOF-69A (zinc biphenyldicarboxylate) metal-organic framework, starting from the intrinsically blue luminescent bio-MOF-1 (zinc adeninate 4,4'-biphenyldicarboxylate). Bio-MOF-1 is transformed to the MOF-69A framework by selectively leaching structural adenine linkers from the original framework using silver nitrate solutions in aqueous ethanol. Simultaneously, bright blue-green luminescent silver-adenine clusters are formed inside the pores of the recrystallized MOF-69A matrix in high local concentrations. The structural transition and concurrent changes in optical properties were characterized using a range of structural, physicochemical and spectroscopic techniques (steady-state and time-resolved luminescence, quantum yield determination, fluorescence microscopy). The presented results open new avenues for exploring the use of MOFs containing luminescent silver clusters for solid-state lighting and sensor applications.

Effect of oxalate on the dissolution rates of oligoclase and tremolite (journal version)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mast, M.A.; Drever, J.I.

1987-01-01

The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22 deg C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of releasemore » of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si. The rate of dissolution of tremolite is independent of pH over the pH range 2-5, and decreases at higher pH. The rate of dissolution of oligoclase was independent of pH over the pH range 4-9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.« less

Neptunium(V) and neptunium(VI) solubilities in synthetic brines of interest to the Waste Isolation Pilot Plant (WIPP)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novak, C.F.; Nitsche, H.; Silber, H.B.

1996-12-31

The solubility of Np(V) and Np(VI) has been measured in three synthetic Na-K-Mg-Cl brines in the presence of CO{sub 2}(g). Experiments were prepared from oversaturation by adding an excess of NpO{sub 2}{sup +} or NpO{sub 2}{sup 2+} to the brines and allowing the neptunium solids to precipitate. Vessels were maintained in contact with fixed CO{sub 2}(g) partial pressures at constant pH and 24 {+-} 1 C. Dissolved Np(V) concentrations decreased several orders of magnitude within the first 100 days of the experiment, while dissolved Np(VI) concentrations decreased initially but then remained relatively constant for more than 400 days. The solidmore » phases formed in all experiments were identified by X-ray powder diffraction as KNpO{sub 2}CO{sub 3}{center_dot}xH{sub 2}O(s). Steady state concentrations for Np(V) are similar to those observed for Pu(V) in the same brines under the same conditions, where Pu occurs predominantly as Pu(V). Similarly, steady state concentrations for Np(VI), which was not reduced over a two year period, compare well with measured Pu(VI) concentrations in the same brines before the Pu(VI) was reduced to Pu(V).« less

Modeling biofiltration of VOC mixtures under steady-state conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baltzis, B.C.; Wojdyla, S.M.; Zarook, S.M.

1997-06-01

Treatment of air streams contaminated with binary volatile organic compound (VOC) mixtures in classical biofilters under steady-state conditions of operation was described with a general mathematical model. The model accounts for potential kinetic interactions among the pollutants, effects of oxygen availability on biodegradation, and biomass diversification in the filter bed. While the effects of oxygen were always taken into account, two distinct cases were considered for the experimental model validation. The first involves kinetic interactions, but no biomass differentiation, used for describing data from biofiltration of benzene/toluene mixtures. The second case assumes that each pollutant is treated by a differentmore » type of biomass. Each biomass type is assumed to form separate patches of biofilm on the solid packing material, thus kinetic interference does not occur. This model was used for describing biofiltration of ethanol/butanol mixtures. Experiments were performed with classical biofilters packed with mixtures of peat moss and perlite (2:3, volume:volume). The model equations were solved through the use of computer codes based on the fourth-order Runge-Kutta technique for the gas-phase mass balances and the method of orthogonal collocation for the concentration profiles in the biofilms. Good agreement between model predictions and experimental data was found in almost all cases. Oxygen was found to be extremely important in the case of polar VOCs (ethanol/butanol).« less

Smooth Approximation l 0-Norm Constrained Affine Projection Algorithm and Its Applications in Sparse Channel Estimation

PubMed Central

2014-01-01

We propose a smooth approximation l 0-norm constrained affine projection algorithm (SL0-APA) to improve the convergence speed and the steady-state error of affine projection algorithm (APA) for sparse channel estimation. The proposed algorithm ensures improved performance in terms of the convergence speed and the steady-state error via the combination of a smooth approximation l 0-norm (SL0) penalty on the coefficients into the standard APA cost function, which gives rise to a zero attractor that promotes the sparsity of the channel taps in the channel estimation and hence accelerates the convergence speed and reduces the steady-state error when the channel is sparse. The simulation results demonstrate that our proposed SL0-APA is superior to the standard APA and its sparsity-aware algorithms in terms of both the convergence speed and the steady-state behavior in a designated sparse channel. Furthermore, SL0-APA is shown to have smaller steady-state error than the previously proposed sparsity-aware algorithms when the number of nonzero taps in the sparse channel increases. PMID:24790588

[Study on balance group in steady-state extraction process of Chinese medicine and experimental verification to Houttuynia cordata].

PubMed

Liu, Wenlong; Zhang, Xili; He, Fuyuan; Zhang, Ping; Wang, Haiqin; Wu, Dezhi; Chen, Zuohong

2011-11-01

To establish and experimental verification the mathematical model of the balance groups that is the steady-state of traditional Chinese medicine in extraction. Using the entropy and genetic principles of statistics, and taking the coefficient of variation of GC fingerprint which is the naphtha of the Houttuynia cordata between strains in the same GAP place as a pivot to establish and verify the mathematical model was established of the balance groups that is the steady-state of traditional Chinese medicine in extraction. A mathematical model that is suitable for the balance groups of the steady-state of traditional Chinese medicine and preparation in extraction, and the balance groups which is 29 683 strains (approximately 118.7 kg) were gained with the same origin of H. cordata as the model drug. Under the GAP of quality control model, controlling the stability of the quality through further using the Hardy-Weinberg balance groups of the H. cordata between strains, the new theory and experiment foundation is established for the steady-state of traditional Chinese medicine in extraction and quality control.

In-situ shear stress indicator using heated strain gages at the flow boundary

NASA Astrophysics Data System (ADS)

Yeh, Chi-An; Yang, Fuling

2011-11-01

This work borrows the concept of hot-wire anemometry and sketch a technique that uses local heat transfer to infer the flow field and the corresponding stress. Conventional strain gages were mounted at the flow solid boundary as the heat source and acrylic boundary was chosen for its low thermal conductivity ensuring heat accumulation when a gage is energized. The gage would now work in slightly overheated state and its self-heating leads to an additional thermal strain. When exposed to a flow field, heat is brought away by local forced convection, resulting in deviations in gage signal from that developed in quiescent liquid. We have developed a facility to achieve synchronous gage measurements at different locations on a solid boundary. Three steady flow motions were considered: circular Couette flow, rectilinear uniform flow, and rectilinear oscillating flow. Preliminary tests show the gage reading does respond to the imposed flow through thermal effects and greater deviation was measured in flows of higher shear strain rates. The correlation between the gage signals and the imposed flow field is further examined by theoretical analysis. We also introduced a second solid boundary to the vicinity of the gage in the two rectilinear flows. The gage readings demonstrate rises in its magnitudes indicating wall amplification effect on the local shear strain, agreeing to the drag augmentation by a second solid boundary reported in many multiphase flow literatures.

Advanced continuous cultivation methods for systems microbiology.

PubMed

Adamberg, Kaarel; Valgepea, Kaspar; Vilu, Raivo

2015-09-01

Increasing the throughput of systems biology-based experimental characterization of in silico-designed strains has great potential for accelerating the development of cell factories. For this, analysis of metabolism in the steady state is essential as only this enables the unequivocal definition of the physiological state of cells, which is needed for the complete description and in silico reconstruction of their phenotypes. In this review, we show that for a systems microbiology approach, high-resolution characterization of metabolism in the steady state--growth space analysis (GSA)--can be achieved by using advanced continuous cultivation methods termed changestats. In changestats, an environmental parameter is continuously changed at a constant rate within one experiment whilst maintaining cells in the physiological steady state similar to chemostats. This increases the resolution and throughput of GSA compared with chemostats, and, moreover, enables following of the dynamics of metabolism and detection of metabolic switch-points and optimal growth conditions. We also describe the concept, challenge and necessary criteria of the systematic analysis of steady-state metabolism. Finally, we propose that such systematic characterization of the steady-state growth space of cells using changestats has value not only for fundamental studies of metabolism, but also for systems biology-based metabolic engineering of cell factories.

Effect of antacids on predicted steady-state cimetidine concentrations.

PubMed

Russell, W L; Lopez, L M; Normann, S A; Doering, P L; Guild, R T

1984-05-01

The purpose of this study was to evaluate effects of antacids on predicted steady-state concentrations of cimetidine. Ten healthy volunteers received in random order one week apart, cimetidine and cimetidine and antacid suspension. Blood was obtained at specified times and analyzed for cimetidine. Bioavailability was assessed by comparison of peak concentration, time to peak concentration, area under the curve, and time spent over 0.5 micrograms/ml. Single-dose data were extrapolated to steady-state using computer simulation. Concurrent administration of antacid suspension reduced parameters of bioavailability approximately 30%. When steady-state conditions were simulated, concentrations of cimetidine greater than or equal to 0.5 micrograms/ml were maintained for the entire dosing interval in seven of 10 subjects. These data suggest that temporal separation of cimetidine and antacid suspension may be unnecessary.

Interplay of interaction and disorder in the steady state of an open quantum system

NASA Astrophysics Data System (ADS)

Xu, Xiansong; Guo, Chu; Poletti, Dario

2018-04-01

Many types of dissipative processes can be found in nature or be engineered, and their interplay with a system can give rise to interesting phases of matter. Here we study the interplay among interaction, tunneling, and disorder in the steady state of a spin chain coupled to a tailored bath. We consider a dissipation which, in contrast to disorder, tends to generate a homogeneously polarized steady state. We find that the steady state can be highly sensitive even to weak disorder. We also establish that, in the presence of such dissipation, even in the absence of interaction, a finite amount of disorder is needed for localization. Last, we show that for strong disorder the system reveals signatures of localization both in the weakly and strong interacting regimes.

Shear-induced crystallization of a dense rapid granular flow: hydrodynamics beyond the melting point.

PubMed

Khain, Evgeniy; Meerson, Baruch

2006-06-01

We investigate shear-induced crystallization in a very dense flow of monodisperse inelastic hard spheres. We consider a steady plane Couette flow under constant pressure and neglect gravity. We assume that the granular density is greater than the melting point of the equilibrium phase diagram of elastic hard spheres. We employ a Navier-Stokes hydrodynamics with constitutive relations all of which (except the shear viscosity) diverge at the crystal-packing density, while the shear viscosity diverges at a smaller density. The phase diagram of the steady flow is described by three parameters: an effective Mach number, a scaled energy loss parameter, and an integer number m: the number of half-oscillations in a mechanical analogy that appears in this problem. In a steady shear flow the viscous heating is balanced by energy dissipation via inelastic collisions. This balance can have different forms, producing either a uniform shear flow or a variety of more complicated, nonlinear density, velocity, and temperature profiles. In particular, the model predicts a variety of multilayer two-phase steady shear flows with sharp interphase boundaries. Such a flow may include a few zero-shear (solidlike) layers, each of which moving as a whole, separated by fluidlike regions. As we are dealing with a hard sphere model, the granulate is fluidized within the "solid" layers: the granular temperature is nonzero there, and there is energy flow through the boundaries of the solid layers. A linear stability analysis of the uniform steady shear flow is performed, and a plausible bifurcation diagram of the system, for a fixed m, is suggested. The problem of selection of m remains open.

Exact results for Schrödinger cats in driven-dissipative systems and their feedback control

NASA Astrophysics Data System (ADS)

Minganti, Fabrizio; Bartolo, Nicola; Lolli, Jared; Casteels, Wim; Ciuti, Cristiano

2016-05-01

In quantum optics, photonic Schrödinger cats are superpositions of two coherent states with opposite phases and with a significant number of photons. Recently, these states have been observed in the transient dynamics of driven-dissipative resonators subject to engineered two-photon processes. Here we present an exact analytical solution of the steady-state density matrix for this class of systems, including one-photon losses, which are considered detrimental for the achievement of cat states. We demonstrate that the unique steady state is a statistical mixture of two cat-like states with opposite parity, in spite of significant one-photon losses. The transient dynamics to the steady state depends dramatically on the initial state and can pass through a metastable regime lasting orders of magnitudes longer than the photon lifetime. By considering individual quantum trajectories in photon-counting configuration, we find that the system intermittently jumps between two cats. Finally, we propose and study a feedback protocol based on this behaviour to generate a pure cat-like steady state.

Mathematical Analysis of Vehicle Delivery Scale of Bike-Sharing Rental Nodes

NASA Astrophysics Data System (ADS)

Zhai, Y.; Liu, J.; Liu, L.

2018-04-01

Aiming at the lack of scientific and reasonable judgment of vehicles delivery scale and insufficient optimization of scheduling decision, based on features of the bike-sharing usage, this paper analyses the applicability of the discrete time and state of the Markov chain, and proves its properties to be irreducible, aperiodic and positive recurrent. Based on above analysis, the paper has reached to the conclusion that limit state (steady state) probability of the bike-sharing Markov chain only exists and is independent of the initial probability distribution. Then this paper analyses the difficulty of the transition probability matrix parameter statistics and the linear equations group solution in the traditional solving algorithm of the bike-sharing Markov chain. In order to improve the feasibility, this paper proposes a "virtual two-node vehicle scale solution" algorithm which considered the all the nodes beside the node to be solved as a virtual node, offered the transition probability matrix, steady state linear equations group and the computational methods related to the steady state scale, steady state arrival time and scheduling decision of the node to be solved. Finally, the paper evaluates the rationality and accuracy of the steady state probability of the proposed algorithm by comparing with the traditional algorithm. By solving the steady state scale of the nodes one by one, the proposed algorithm is proved to have strong feasibility because it lowers the level of computational difficulty and reduces the number of statistic, which will help the bike-sharing companies to optimize the scale and scheduling of nodes.

Current Pressure Transducer Application of Model-based Prognostics Using Steady State Conditions

NASA Technical Reports Server (NTRS)

Teubert, Christopher; Daigle, Matthew J.

2014-01-01

Prognostics is the process of predicting a system's future states, health degradation/wear, and remaining useful life (RUL). This information plays an important role in preventing failure, reducing downtime, scheduling maintenance, and improving system utility. Prognostics relies heavily on wear estimation. In some components, the sensors used to estimate wear may not be fast enough to capture brief transient states that are indicative of wear. For this reason it is beneficial to be capable of detecting and estimating the extent of component wear using steady-state measurements. This paper details a method for estimating component wear using steady-state measurements, describes how this is used to predict future states, and presents a case study of a current/pressure (I/P) Transducer. I/P Transducer nominal and off-nominal behaviors are characterized using a physics-based model, and validated against expected and observed component behavior. This model is used to map observed steady-state responses to corresponding fault parameter values in the form of a lookup table. This method was chosen because of its fast, efficient nature, and its ability to be applied to both linear and non-linear systems. Using measurements of the steady state output, and the lookup table, wear is estimated. A regression is used to estimate the wear propagation parameter and characterize the damage progression function, which are used to predict future states and the remaining useful life of the system.

Enhancing the ABAQUS Thermomechanics Code to Simulate Steady and Transient Fuel Rod Behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. L. Williamson; D. A. Knoll

2009-09-01

A powerful multidimensional fuels performance capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth , gap heat transfer, and gap/plenum gas behavior during irradiation. The various modeling capabilities are demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multi-pellet fuel rod, during both steady and transient operation. Computational results demonstrate the importancemore » of a multidimensional fully-coupled thermomechanics treatment. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermo-mechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.« less

Experimental demonstration of revival of oscillations from death in coupled nonlinear oscillators.

PubMed

Senthilkumar, D V; Suresh, K; Chandrasekar, V K; Zou, Wei; Dana, Syamal K; Kathamuthu, Thamilmaran; Kurths, Jürgen

2016-04-01

We experimentally demonstrate that a processing delay, a finite response time, in the coupling can revoke the stability of the stable steady states, thereby facilitating the revival of oscillations in the same parameter space where the coupled oscillators suffered the quenching of oscillation. This phenomenon of reviving of oscillations is demonstrated using two different prototype electronic circuits. Further, the analytical critical curves corroborate that the spread of the parameter space with stable steady state is diminished continuously by increasing the processing delay. Finally, the death state is completely wiped off above a threshold value by switching the stability of the stable steady state to retrieve sustained oscillations in the same parameter space. The underlying dynamical mechanism responsible for the decrease in the spread of the stable steady states and the eventual reviving of oscillation as a function of the processing delay is explained using analytical results.

Pattern Formation in Keller-Segel Chemotaxis Models with Logistic Growth

NASA Astrophysics Data System (ADS)

Jin, Ling; Wang, Qi; Zhang, Zengyan

In this paper, we investigate pattern formation in Keller-Segel chemotaxis models over a multidimensional bounded domain subject to homogeneous Neumann boundary conditions. It is shown that the positive homogeneous steady state loses its stability as chemoattraction rate χ increases. Then using Crandall-Rabinowitz local theory with χ being the bifurcation parameter, we obtain the existence of nonhomogeneous steady states of the system which bifurcate from this homogeneous steady state. Stability of the bifurcating solutions is also established through rigorous and detailed calculations. Our results provide a selection mechanism of stable wavemode which states that the only stable bifurcation branch must have a wavemode number that minimizes the bifurcation value. Finally, we perform extensive numerical simulations on the formation of stable steady states with striking structures such as boundary spikes, interior spikes, stripes, etc. These nontrivial patterns can model cellular aggregation that develop through chemotactic movements in biological systems.

Experimental demonstration of revival of oscillations from death in coupled nonlinear oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senthilkumar, D. V., E-mail: skumarusnld@gmail.com; Centre for Nonlinear Science and Engineering, School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401; Suresh, K.

We experimentally demonstrate that a processing delay, a finite response time, in the coupling can revoke the stability of the stable steady states, thereby facilitating the revival of oscillations in the same parameter space where the coupled oscillators suffered the quenching of oscillation. This phenomenon of reviving of oscillations is demonstrated using two different prototype electronic circuits. Further, the analytical critical curves corroborate that the spread of the parameter space with stable steady state is diminished continuously by increasing the processing delay. Finally, the death state is completely wiped off above a threshold value by switching the stability of themore » stable steady state to retrieve sustained oscillations in the same parameter space. The underlying dynamical mechanism responsible for the decrease in the spread of the stable steady states and the eventual reviving of oscillation as a function of the processing delay is explained using analytical results.« less

Determination of the Steady State Leakage Current in Structures with Ferroelectric Ceramic Films

NASA Astrophysics Data System (ADS)

Podgornyi, Yu. V.; Vorotilov, K. A.; Sigov, A. S.

2018-03-01

Steady state leakage currents have been investigated in capacitor structures with ferroelectric solgel films of lead zirconate titanate (PZT) formed on silicon substrates with a lower Pt electrode. It is established that Pt/PZT/Hg structures, regardless of the PZT film thickness, are characterized by the presence of a rectifying contact similar to p-n junction. The steady state leakage current in the forward direction increases with a decrease in the film thickness and is determined by the ferroelectric bulk conductivity.

Revelations of X-ray spectral analysis of the enigmatic black hole binary GRS 1915+105

NASA Astrophysics Data System (ADS)

Peris, Charith; Remillard, Ronald A.; Steiner, James; Vrtilek, Saeqa Dil; Varniere, Peggy; Rodriguez, Jerome; Pooley, Guy

2016-01-01

Of the black hole binaries discovered thus far, GRS 1915+105 stands out as an exceptional source primarily due to its wild X-ray variability, the diversity of which has not been replicated in any other stellar-mass black hole. Although extreme variability is commonplace in its light-curve, about half of the observations of GRS1915+105 show fairly steady X-ray intensity. We report on the X-ray spectral behavior within these steady observations. Our work is based on a vast RXTE/PCA data set obtained on GRS 1915+105 during the course of its entire mission and 10 years of radio data from the Ryle Telescope, which overlap the X-ray data. We find that the steady observations within the X-ray data set naturally separate into two regions in a color-color diagram, which we refer to as steady-soft and steady-hard. GRS 1915+105 displays significant curvature in the Comptonization component within the PCA band pass suggesting significantly heating from a hot disk present in all states. A new Comptonization model 'simplcut' was developed in order to model this curvature to best effect. A majority of the steady-soft observations display a roughly constant inner radius; remarkably reminiscent of canonical soft state black hole binaries. In contrast, the steady-hard observations display a growing disk truncation that is correlated to the mass accretion rate through the disk, which suggests a magnetically truncated disk. A comparison of X-ray model parameters to the canonical state definitions show that almost all steady-soft observations match the criteria of either thermal or steep power law state, while the thermal state observations dominate the constant radius branch. A large portion (80%) of the steady-hard observations matches the hard state criteria when the disk fraction constraint is neglected. These results suggest that within the complexity of this source is a simpler underlying basis of states, which map to those observed in canonical black hole binaries. When represented in a color-color diagram, state assignments appear to map to ``A, B and C'' (Belloni et al. 2000) regions that govern fast variability cycles in GRS 1915+105 demonstrating a compelling link between short and long time scales in its phenomenology.

Dynamic weakening is limited by granular dynamics

NASA Astrophysics Data System (ADS)

Kuwano, O.; Hatano, T.

2011-12-01

Earthquakes are the result of the frictional instability of faults containing fine rock powders called gouge derived from attrition in past fault motions. Understanding the frictional instability of granular matter in terms of constitutive laws is thus important. Because of the importance of granular matter for industries and engineering, the friction of granular matter has been studied in the field of solid earth science and other fields, such as statistical physics. In solid earth science, the rate- and state-dependent friction law was established by laboratory experiments at a very low sliding velocity (μm/s to mm/s). Recent experiments conducted at sub-seismic to seismic sliding velocities (mm/s to m/s), however, show that frictional properties are much richer than those predicted by the rate- and state-dependent friction law. One of the most important findings in such experiments is the remarkable weakening due to mechano-chemical effects by frictional heating [Tullis, 2007]. In statistical physics, another empirical law holds for much faster deformation than the former, showing positive shear-rate dependence. Until Recently, friction of granular matter has been investigated independently in the fields of solid earth science and statistical physics, and thus the relation between these distinct constitutive laws is not clear. Recently, some experimental studies have been reported to connect the achievements in these two fields. For example, a laboratory experiment on dry glass beads under very low normal stress (0.02 to 0.05 MPa) in which the frictional heat is negligible reveals the transition from velocity-weakening friction at low sliding velocities to velocity-strengthening friction at high sliding velocities [Kuwano et al., 2011]. Importantly, the velocity-strengthening nature at high sliding velocities is quantitatively the same as those observed in simulations. The inelastic deformation of the grains therefore plays a vital role at high sliding velocities. In this study, we report a friction experiment under higher pressure (0.1 to 0.9 MPa), in which the frictional heat is significant. To clarify the effect of frictional heat in high-speed friction systematically, we investigated both the pressure and the velocity dependence of the friction coefficient over a wide range of sliding velocities ranging from aseismic to seismic slip velocities. We observed considerable weakening, described well by a flash-heating theory, above the sliding velocity of 1 cm/s regardless of pressure. At higher velocities, the velocity strengthening behavior replaced the velocity weakening behavior. This strengthening at higher velocities agrees with data from numerical simulations on sheared granular matter and is therefore described in terms of energy dissipation due to the inelastic deformation of grains. We propose a unified steady-state friction law that well describes the velocity and pressure dependence of the steady-state friction coefficient.

ESTIMATING SYSTEMIC EXPOSURE TO ETHINYL ESTRADIOL FROM AN ORAL CONTRACEPTIVE

PubMed Central

WESTHOFF, Carolyn L.; PIKE, Malcolm C.; TANG, Rosalind; DINAPOLI, Marianne N.; SULL, Monica; CREMERS, Serge

2015-01-01

Objectives This study was conducted to compare single-dose pharmacokinetics of ethinyl estradiol in an oral contraceptive to steady-state values, and to assess whether any simpler measures could provide an adequate proxy of the ‘gold standard’ 24-hour steady-state area-under-the-curve. Identifying a simple, less expensive, measure of systemic ethinyl estradiol exposure would be useful for larger studies designed to assess the relationship between an individual’s ethinyl estradiol exposure and her side effects. Study Design We conducted a 13 samples over 24 hours pharmacokinetic analysis on day 1 and day 21 of the first cycle of a monophasic oral contraceptive containing 30 mcg ethinyl estradiol and 150 mcg levonorgestrel in 17 non-obese healthy white women. We also conducted an abbreviated single dose 9-sample pharmacokinetic analysis after a month washout. Ethinyl estradiol was measured by liquid chromatography-tandem mass spectrometry. We compared results of full 13-sample steady-state pharmacokinetic analysis with results calculated using fewer samples (9 or 5) and following the single doses. We calculated Pearson correlation coefficients to evaluate the relationships between these estimates of systemic ethinyl estradiol exposure. Results The area-under-the-curve, maximum (Cmax), and 24-hour (C24) values were similar following the two single oral contraceptive doses (area-under-the-curve, r = 0.92). The steady-state 13-sample 24-hour area-under-the-curve was highly correlated with the average 9-sample area-under-the-curve after the two single doses (r = 0.81, p = 0.0002). This correlation remained the same if the number of samples was reduced to 4, taken at time 1, 2.5, 4 and 24 hours. The C24 at steady-state was highly correlated with the 24-hour steady-state area-under-the-curve (r = 0.92, p < 0.0001). The average of the C24 values following the two single doses was also quite highly correlated with the steady-state area-under-the-curve (r = 0.72, p = 0.0026). Conclusions Limited blood sampling, including results from two single doses, gave highly correlated estimates of an oral contraceptive user’s steady-state ethinyl estradiol exposure. PMID:25511238

Estimating systemic exposure to ethinyl estradiol from an oral contraceptive.

PubMed

Westhoff, Carolyn L; Pike, Malcolm C; Tang, Rosalind; DiNapoli, Marianne N; Sull, Monica; Cremers, Serge

2015-05-01

This study was conducted to compare single-dose pharmacokinetics of ethinyl estradiol in an oral contraceptive with steady-state values and to assess whether any simpler measures could provide an adequate proxy of the "gold standard" 24-hour steady-state area under the curve (AUC) value. Identification of a simple, less expensive measure of systemic ethinyl estradiol exposure would be useful for larger studies that are designed to assess the relationship between an individual's ethinyl estradiol exposure and side-effects. We collected 13 samples over 24 hours for pharmacokinetic analysis on days 1 and 21 of the first cycle of a monophasic oral contraceptive that contained 30 μg ethinyl estradiol and 150 μg levonorgestrel in 17 nonobese healthy white women. We also conducted an abbreviated single-dose 9-sample pharmacokinetic analysis after a month washout. Ethinyl estradiol was measured by liquid chromatography-tandem mass spectrometry. We compared results of a full 13-sample steady-state pharmacokinetic analysis with results that had been calculated with the use of fewer samples (9 or 5) and after the single doses. We calculated Pearson correlation coefficients to evaluate the relationships between these estimates of systemic ethinyl estradiol exposure. The AUC, maximum, and 24-hour values were similar after the 2 single oral contraceptive doses (AUC; r=0.92). The steady-state 13-sample 24-hour AUC value was correlated highly with the average 9-sample AUC value after the 2 single doses (r=0.81; P=.0002). This correlation remained the same if the number of single-dose samples was reduced to 4, taken at time 1, 2.5, 4, and 24 hours. The 24-hour value at steady-state was correlated highly with the 24-hour steady-state AUC value (r=0.92; P<.0001). The average of the 24-hour values after the 2 single doses was also correlated quite highly with the steady-state AUC value (r=0.72; P=.0026). Limited blood sampling, including results from 2 single doses, gave highly correlated estimates of an oral contraceptive user's steady-state ethinyl estradiol exposure. Copyright © 2015 Elsevier Inc. All rights reserved.

Glass–water interaction: Effect of high-valence cations on glass structure and chemical durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopf, J.; Kerisit, Sebastien N.; Angeli, F.

2016-05-15

Borosilicate glass is a durable solid, but it dissolves when in contact with aqueous fluids. The dissolution mechanism, which involves a variety of sequential reactions that occur at the solid-fluid interface, has important implications for the corrosion resistance of industrial and nuclear waste glasses. In this study, spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high–valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), withmore » the addition of the HVC element hafnium in the Na2O–Al2O3–B2O3–HfO2–SiO2 system (e.g., Na/[Al+B] = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 (tetrahedral boron/total boron) and increases the amount of Si—O—Hf moieties in the glass. Results from flow–through experiments conducted under dilute and near–saturated conditions show a decrease of approximately 100× or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveals a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the stronger binding of Si sites that deposit on the surface from the influent when Hf is present in the glass. As a result, the residence time at the glass surface of these newly-formed Si sites is longer in the presence of Hf, which increases the density of anchor sites from which altered layers with higher Si densities can form. These results illustrate the importance of understanding solid–water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.« less

On fast solid-body rotation of the solar core and differential (liquid-like) rotation of the solar surface

NASA Astrophysics Data System (ADS)

Pashitskii, E. A.

2017-07-01

On the basis of a two-component (two-fluid) hydrodynamic model, it is shown that the probable phenomenon of solar core rotation with a velocity higher than the average velocity of global rotation of the Sun, discovered by the SOHO mission, can be related to fast solid-body rotation of the light hydrogen component of the solar plasma, which is caused by thermonuclear fusion of hydrogen into helium inside the hot dense solar core. Thermonuclear fusion of four protons into a helium nucleus (α-particle) creates a large free specific volume per unit particle due to the large difference between the densities of the solar plasma and nuclear matter. As a result, an efficient volumetric sink of one of the components of the solar substance—hydrogen—forms inside the solar core. Therefore, a steady-state radial proton flux converging to the center should exist inside the Sun, which maintains a constant concentration of hydrogen as it burns out in the solar core. It is demonstrated that such a converging flux of hydrogen plasma with the radial velocity v r ( r) = -β r creates a convective, v r ∂ v φ/∂ r, and a local Coriolis, v r v φ/ r,φ nonlinear hydrodynamic forces in the solar plasma, rotating with the azimuthal velocity v φ. In the absence of dissipation, these forces should cause an exponential growth of the solid-body rotation velocity of the hydrogen component inside the solar core. However, friction between the hydrogen and helium components of the solar plasma due to Coulomb collisions of protons with α-particles results in a steady-state regime of rotation of the hydrogen component in the solar core with an angular velocity substantially exceeding the global rotational velocity of the Sun. It is suggested that the observed differential (liquid-like) rotation of the visible surface of the Sun (photosphere) with the maximum angular velocity at the equator is caused by sold-body rotation of the solar plasma in the radiation zone and strong turbulence in the tachocline layer, where the turbulent viscosity reaches its maximum value at the equator. There, the tachocline layer exerts the most efficient drag on the less dense outer layers of the solar plasma, which are slowed down due to the interaction with the ambient space plasma (solar wind).

An improved model for the combustion of AP composite propellants

NASA Technical Reports Server (NTRS)

Cohen, N. S.; Strand, L. D.

1981-01-01

This paper presents several improvements to the BDP model of steady-state burning of AP composite solid propellants. The Price-Boggs-Derr model of AP monopropellant burning is incorporated to represent the AP. A separate energy equation is written for the binder to permit a different surface temperature from the AP; this includes an analysis of the sharing of primary diffusion flame energy, and correction of a BDP model inconsistency in treating the binder regression rate. A method for assembling component contributions to calculate the burning rates of multimodal propellants is also presented. Results are shown in the form of representative burning rate curves, comparisons with data, and calculated internal details of interest. Ideas for future work are discussed in an Appendix.

The indirect electrochemical refining of lunar ores

NASA Technical Reports Server (NTRS)

Semkow, Krystyna W.; Sammells, Anthony F.

1987-01-01

Recent work performed on an electrolytic cell is reported which addresses the implicit limitations in various approaches to refining lunar ores. The cell uses an oxygen vacancy conducting stabilized zirconia solid electrolyte to effect separation between a molten salt catholyte compartment where alkali metals are deposited, and an oxygen-evolving anode of composition La(0.89)Sr(0.1)MnO3. The cell configuration is shown and discussed along with a polarization curve and a steady-state current-voltage curve. In a practical cell, cathodically deposited liquid lithium would be continuously removed from the electrolytic cell and used as a valuable reducing agent for ore refining under lunar conditions. Oxygen would be indirectly electrochemically extracted from lunar ores for breathing purposes.

Mass balances for a biological life support system simulation model

NASA Technical Reports Server (NTRS)

Volk, Tyler; Rummel, John D.

1987-01-01

Design decisions to aid the development of future space based biological life support systems (BLSS) can be made with simulation models. The biochemistry stoichiometry was developed for: (1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible parts of plants; (2) food consumption and production of organic solids in urine, feces, and wash water by the humans; and (3) operation of the waste processor. Flux values for all components are derived for a steady state system with wheat as the sole food source. The large scale dynamics of a materially closed (BLSS) computer model is described in a companion paper. An extension of this methodology can explore multifood systems and more complex biochemical dynamics while maintaining whole system closure as a focus.

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic System T-MATS

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei

2014-01-01

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically.

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS)

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei

2014-01-01

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically.

Coherent quantum dynamics in steady-state manifolds of strongly dissipative systems.

PubMed

Zanardi, Paolo; Campos Venuti, Lorenzo

2014-12-12

Recently, it has been realized that dissipative processes can be harnessed and exploited to the end of coherent quantum control and information processing. In this spirit, we consider strongly dissipative quantum systems admitting a nontrivial manifold of steady states. We show how one can enact adiabatic coherent unitary manipulations, e.g., quantum logical gates, inside this steady-state manifold by adding a weak, time-rescaled, Hamiltonian term into the system's Liouvillian. The effective long-time dynamics is governed by a projected Hamiltonian which results from the interplay between the weak unitary control and the fast relaxation process. The leakage outside the steady-state manifold entailed by the Hamiltonian term is suppressed by an environment-induced symmetrization of the dynamics. We present applications to quantum-computation in decoherence-free subspaces and noiseless subsystems and numerical analysis of nonadiabatic errors.

Fluctuations, Stratification and Stability in a Liquid Fluidized Bed at Low Reynolds Number

NASA Technical Reports Server (NTRS)

Segre, P. N.; McClymer, J. P.

2004-01-01

The sedimentation dynamics of extremely low polydispersity, non-colloidal, particles are studied in a liquid fluidized bed at low Reynolds number, Re much less than 1. When fluidized, the system reaches a steady state, defined where the local average volume fraction does not vary in time. In steady state, the velocity fluctuations and the particle concentrations are found to strongly depend on height. Using our results, we test a recently developed stability model for steady state sedimentation. The model describes the data well, and shows that in steady state there is a balancing of particle fluxes due to the fluctuations and the concentration gradient. Some results are also presented for the dependence of the concentration gradient in fluidized beds on particle size; the gradients become smaller as the particles become larger and fewer in number.

Acetylcholine-activated ionic currents in parasympathetic neurons of bullfrog heart.

PubMed

Tateishi, N; Kim, D K; Akaike, N

1990-05-01

1. The electrical and pharmacologic properties of acetylcholine (ACh)-induced current (IACh) were studied in the parasympathetic neurons isolated from bullfrog heart with the use of the concentration-clamp technique, which allows intracellular perfusion and rapid change of external solution within 2 ms under the single-electrode voltage-clamp condition. 2. The IACh consisted of an initial transient peak component and a successive steady-state plateau component. Both currents increased in a sigmoidal fashion with increasing ACh concentration. The dissociation constant (Kd value) and the Hill coefficient for each component were 2.2 X 10(-5) M and 1.6, respectively. 3. In the K(+)-free solution, the reversal potential (EACh) of IACh was close to the Na+ equilibrium potential (ENa). The current-voltage (I-V) relation showed inward rectification at positive potentials. 4. Nicotine mimicked only the peak component of IACh. However both peak and steady-state components were blocked nonselectively by the nicotinic blockers d-tubocurarine and hexamethonium. 5. Carbamylcholine (CCh) mimicked the steady-state component of IACh. The steady-state component was selectively inhibited by atropine at concentrations 1,000 times lower than that required for inhibition of the peak component. The steady state was blocked equally by either pirenzepine (M1 blocker) or AF-DX-116 (M2 blocker). 6. It was concluded that the IACh consisted of a peak component having double exponential activation and inactivation, mediated through the nicotinic actions, and a steady-state component having no inactivation, mediated through the muscarinic action.

Auditory steady-state response in cochlear implant patients.

PubMed

Torres-Fortuny, Alejandro; Arnaiz-Marquez, Isabel; Hernández-Pérez, Heivet; Eimil-Suárez, Eduardo

2018-03-19

Auditory steady state responses to continuous amplitude modulated tones at rates between 70 and 110Hz, have been proposed as a feasible alternative to objective frequency specific audiometry in cochlear implant subjects. The aim of the present study is to obtain physiological thresholds by means of auditory steady-state response in cochlear implant patients (Clarion HiRes 90K), with acoustic stimulation, on free field conditions and to verify its biological origin. 11 subjects comprised the sample. Four amplitude modulated tones of 500, 1000, 2000 and 4000Hz were used as stimuli, using the multiple frequency technique. The recording of auditory steady-state response was also recorded at 0dB HL of intensity, non-specific stimulus and using a masking technique. The study enabled the electrophysiological thresholds to be obtained for each subject of the explored sample. There were no auditory steady-state responses at either 0dB or non-specific stimulus recordings. It was possible to obtain the masking thresholds. A difference was identified between behavioral and electrophysiological thresholds of -6±16, -2±13, 0±22 and -8±18dB at frequencies of 500, 1000, 2000 and 4000Hz respectively. The auditory steady state response seems to be a suitable technique to evaluate the hearing threshold in cochlear implant subjects. Copyright © 2018 Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. Publicado por Elsevier España, S.L.U. All rights reserved.

Single-dose and steady-state pharmacokinetics of tenofovir disoproxil fumarate in human immunodeficiency virus-infected children.

PubMed

Hazra, Rohan; Balis, Frank M; Tullio, Antonella N; DeCarlo, Ellen; Worrell, Carol J; Steinberg, Seth M; Flaherty, John F; Yale, Kitty; Poblenz, Marianne; Kearney, Brian P; Zhong, Lijie; Coakley, Dion F; Blanche, Stephane; Bresson, Jean Louis; Zuckerman, Judith A; Zeichner, Steven L

2004-01-01

Tenofovir disoproxil fumarate (DF) is a potent nucleotide analog reverse transcriptase inhibitor approved for the treatment of human immunodeficiency virus (HIV)-infected adults. The single-dose and steady-state pharmacokinetics of tenofovir were evaluated following administration of tenofovir DF in treatment-experienced HIV-infected children requiring a change in antiretroviral therapy. Using increments of tenofovir DF 75-mg tablets, the target dose was 175 mg/m(2); the median administered dose was 208 mg/m(2). Single-dose pharmacokinetics were evaluated in 18 subjects, and the geometric mean area under the concentration-time curve from 0 h to infinity (AUC(0- infinity )) was 2,150 ng. h/ml and the geometric mean maximum concentration (C(max)) was 266 ng/ml. Subsequently, other antiretrovirals were added to each patient's regimen based upon treatment history and baseline viral resistance results. Steady-state pharmacokinetics were evaluated in 16 subjects at week 4. The steady-state, geometric mean AUC for the 24-h dosing interval was 2,920 ng. h/ml and was significantly higher than the AUC(0- infinity ) after the first dose (P = 0.0004). The geometric mean C(max) at steady state was 302 ng/ml. Tenofovir DF was generally very well tolerated. Steady-state tenofovir exposures in children receiving tenofovir DF-containing combination antiretroviral therapy approached values seen in HIV-infected adults (AUC, approximately 3,000 ng. h/ml; C(max), approximately 300 ng/ml) treated with tenofovir DF at 300 mg.

Ultrafiltration technology with a ceramic membrane for reactive dye removal: optimization of membrane performance.

PubMed

Alventosa-deLara, E; Barredo-Damas, S; Alcaina-Miranda, M I; Iborra-Clar, M I

2012-03-30

An ultrafiltration (UF) ceramic membrane was used to decolorize Reactive Black 5 (RB5) solutions at different dye concentrations (50 and 500 mg/L). Transmembrane pressure (TMP) and cross-flow velocity (CFV) were modified to study their influence on initial and steady-state permeate flux (J(p)) and dye rejection (R). Generally, J(p) increased with higher TMP and CFV and lower feed concentration, up to a maximum steady-state J(p) of 266.81 L/(m(2)h), obtained at 3 bar, 3m/s and 50mg/L. However, there was a TMP value (which changed depending on operating CFV and concentration) beyond which slight or no further increase in steady-state J(p) was observed. Similarly, the higher the CFV was, the more slightly the steady-state J(p) increased. Furthermore, the effectiveness of ultrafiltration treatment was evaluated through dye rejection coefficient. The results showed significant dye removals, regardless of the tested conditions, with steady-state R higher than 79.8% for the 50mg/L runs and around 73.2% for the 500 mg/L runs. Finally response surface methodology (RSM) was used to optimize membrane performance. At 50mg/L, a TMP of 4 bar and a CFV of 2.53 m/s were found to be the conditions giving the highest steady-state J(p), 255.86 L/(m(2)h), and the highest R, 95.2% simultaneously. Copyright © 2012 Elsevier B.V. All rights reserved.

Basin stability measure of different steady states in coupled oscillators

NASA Astrophysics Data System (ADS)

Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

2017-04-01

In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.

Using the properties of soil to speed up the start-up process, enhance process stability, and improve the methane content and yield of solid-state anaerobic digestion of alkaline-pretreated poplar processing residues.

PubMed

Yao, Yiqing; Luo, Yang; Li, Tian; Yang, Yingxue; Sheng, Hongmei; Virgo, Nolan; Xiang, Yun; Song, Yuan; Zhang, Hua; An, Lizhe

2014-01-01

Solid-state anaerobic digestion (SS-AD) was initially adopted for the treatment of municipal solid waste. Recently, SS-AD has been increasingly applied to treat lignocellulosic biomass, such as agricultural and forestry residues. However, studies on the SS-AD process are few. In this study, the process performance and methane yield from SS-AD of alkaline-pretreated poplar processing residues (PPRs) were investigated using the properties of soil, such as buffering capacity and nutritional requirements. The results showed that the lignocellulosic structures of the poplar sample were effectively changed by NaOH pretreatment, as indicated by scanning electron microscopy and Fourier transform infrared spectra analysis. The start-up was markedly hastened, and the process stability was enhanced. After NaOH pretreatment, the maximum methane yield (96.1 L/kg volatile solids (VS)) was obtained under a poplar processing residues-to-soil sample (P-to-S) ratio of 2.5:1, which was 29.9% and 36.1% higher than that of PPRs (74.0 L/kg VS) and that of experiments without NaOH pretreatment (70.6 L/kg VS), respectively. During steady state, the increase in the methane content of the experiment with a P-to-S ratio of 2.5:1 was 4.4 to 50.9% higher than that of the PPRs. Degradation of total solids and volatile solids ranged from 19.3 to 33.0% and from 34.9 to 45.9%, respectively. The maximum reductions of cellulose and hemicellulose were 52.6% and 42.9%, respectively, which were in accordance with the maximal methane yield. T 80 for the maximum methane yield for the experiments with NaOH pretreatment was 11.1% shorter than that for the PPRs. Pretreatment with NaOH and addition of soil led to a significant improvement in the process performance and the methane yield of SS-AD of PPRs. The changes in lignocellulosic structures induced by NaOH pretreatment led to an increase in methane yield. For the purpose of practical applications, SS-AD with soil addition is a convenient, economical, and practical technique.

An optimizing start-up strategy for a bio-methanator.

PubMed

Sbarciog, Mihaela; Loccufier, Mia; Vande Wouwer, Alain

2012-05-01

This paper presents an optimizing start-up strategy for a bio-methanator. The goal of the control strategy is to maximize the outflow rate of methane in anaerobic digestion processes, which can be described by a two-population model. The methodology relies on a thorough analysis of the system dynamics and involves the solution of two optimization problems: steady-state optimization for determining the optimal operating point and transient optimization. The latter is a classical optimal control problem, which can be solved using the maximum principle of Pontryagin. The proposed control law is of the bang-bang type. The process is driven from an initial state to a small neighborhood of the optimal steady state by switching the manipulated variable (dilution rate) from the minimum to the maximum value at a certain time instant. Then the dilution rate is set to the optimal value and the system settles down in the optimal steady state. This control law ensures the convergence of the system to the optimal steady state and substantially increases its stability region. The region of attraction of the steady state corresponding to maximum production of methane is considerably enlarged. In some cases, which are related to the possibility of selecting the minimum dilution rate below a certain level, the stability region of the optimal steady state equals the interior of the state space. Aside its efficiency, which is evaluated not only in terms of biogas production but also from the perspective of treatment of the organic load, the strategy is also characterized by simplicity, being thus appropriate for implementation in real-life systems. Another important advantage is its generality: this technique may be applied to any anaerobic digestion process, for which the acidogenesis and methanogenesis are, respectively, characterized by Monod and Haldane kinetics.

Pharmacokinetic Steady-States Highlight Interesting Target-Mediated Disposition Properties.

PubMed

Gabrielsson, Johan; Peletier, Lambertus A

2017-05-01

In this paper, we derive explicit expressions for the concentrations of ligand L, target R and ligand-target complex RL at steady state for the classical model describing target-mediated drug disposition, in the presence of a constant-rate infusion of ligand. We demonstrate that graphing the steady-state values of ligand, target and ligand-target complex, we obtain striking and often singular patterns, which yield a great deal of insight and understanding about the underlying processes. Deriving explicit expressions for the dependence of L, R and RL on the infusion rate, and displaying graphs of the relations between L, R and RL, we give qualitative and quantitive information for the experimentalist about the processes involved. Understanding target turnover is pivotal for optimising these processes when target-mediated drug disposition (TMDD) prevails. By a combination of mathematical analysis and simulations, we also show that the evolution of the three concentration profiles towards their respective steady-states can be quite complex, especially for lower infusion rates. We also show how parameter estimates obtained from iv bolus studies can be used to derive steady-state concentrations of ligand, target and complex. The latter may serve as a template for future experimental designs.

STEADY-STATE MODEL OF SOLAR WIND ELECTRONS REVISITED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Peter H.; Kim, Sunjung; Choe, G. S., E-mail: yoonp@umd.edu

2015-10-20

In a recent paper, Kim et al. put forth a steady-state model for the solar wind electrons. The model assumed local equilibrium between the halo electrons, characterized by an intermediate energy range, and the whistler-range fluctuations. The basic wave–particle interaction is assumed to be the cyclotron resonance. Similarly, it was assumed that a dynamical steady state is established between the highly energetic superhalo electrons and high-frequency Langmuir fluctuations. Comparisons with the measured solar wind electron velocity distribution function (VDF) during quiet times were also made, and reasonable agreements were obtained. In such a model, however, only the steady-state solution for themore » Fokker–Planck type of electron particle kinetic equation was considered. The present paper complements the previous analysis by considering both the steady-state particle and wave kinetic equations. It is shown that the model halo and superhalo electron VDFs, as well as the assumed wave intensity spectra for the whistler and Langmuir fluctuations, approximately satisfy the quasi-linear wave kinetic equations in an approximate sense, thus further validating the local equilibrium model constructed in the paper by Kim et al.« less

Noncontrast-enhanced renal angiography using multiple inversion recovery and alternating TR balanced steady-state free precession.

PubMed

Dong, Hattie Z; Worters, Pauline W; Wu, Holden H; Ingle, R Reeve; Vasanawala, Shreyas S; Nishimura, Dwight G

2013-08-01

Noncontrast-enhanced renal angiography techniques based on balanced steady-state free precession avoid external contrast agents, take advantage of high inherent blood signal from the T 2 / T 1 contrast mechanism, and have short steady-state free precession acquisition times. However, background suppression is limited; inflow times are inflexible; labeling region is difficult to define when tagging arterial flow; and scan times are long. To overcome these limitations, we propose the use of multiple inversion recovery preparatory pulses combined with alternating pulse repetition time balanced steady-state free precession to produce renal angiograms. Multiple inversion recovery uses selective spatial saturation followed by four nonselective inversion recovery pulses to concurrently null a wide range of background T 1 species while allowing for adjustable inflow times; alternating pulse repetition time steady-state free precession maintains vessel contrast and provides added fat suppression. The high level of suppression enables imaging in three-dimensional as well as projective two-dimensional formats, the latter of which has a scan time as short as one heartbeat. In vivo studies at 1.5 T demonstrate the superior vessel contrast of this technique. © 2012 Wiley Periodicals, Inc.

Hybrid Cascading Outage Analysis of Extreme Events with Optimized Corrective Actions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vallem, Mallikarjuna R.; Vyakaranam, Bharat GNVSR; Holzer, Jesse T.

2017-10-19

Power system are vulnerable to extreme contingencies (like an outage of a major generating substation) that can cause significant generation and load loss and can lead to further cascading outages of other transmission facilities and generators in the system. Some cascading outages are seen within minutes following a major contingency, which may not be captured exclusively using the dynamic simulation of the power system. The utilities plan for contingencies either based on dynamic or steady state analysis separately which may not accurately capture the impact of one process on the other. We address this gap in cascading outage analysis bymore » developing Dynamic Contingency Analysis Tool (DCAT) that can analyze hybrid dynamic and steady state behavior of the power system, including protection system models in dynamic simulations, and simulating corrective actions in post-transient steady state conditions. One of the important implemented steady state processes is to mimic operator corrective actions to mitigate aggravated states caused by dynamic cascading. This paper presents an Optimal Power Flow (OPF) based formulation for selecting corrective actions that utility operators can take during major contingency and thus automate the hybrid dynamic-steady state cascading outage process. The improved DCAT framework with OPF based corrective actions is demonstrated on IEEE 300 bus test system.« less

Modified fluctuation-dissipation and Einstein relation at nonequilibrium steady states

NASA Astrophysics Data System (ADS)

Chaudhuri, Debasish; Chaudhuri, Abhishek

2012-02-01

Starting from the pioneering work of Agarwal [G. S. Agarwal, Zeitschrift für PhysikEPJAFV1434-600110.1007/BF01391621 252, 25 (1972)], we present a unified derivation of a number of modified fluctuation-dissipation relations (MFDR) that relate response to small perturbations around nonequilibrium steady states to steady-state correlations. Using this formalism we show the equivalence of velocity forms of MFDR derived using continuum Langevin and discrete master equation dynamics. The resulting additive correction to the Einstein relation is exemplified using a flashing ratchet model of molecular motors.

Steady-state entanglement activation in optomechanical cavities

NASA Astrophysics Data System (ADS)

Farace, Alessandro; Ciccarello, Francesco; Fazio, Rosario; Giovannetti, Vittorio

2014-02-01

Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of nonclassical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.

Transition wave in the collapse of the San Saba bridge

NASA Astrophysics Data System (ADS)

Brun, Michele; Giaccu, Gian Felice; Movchan, Alexander; Slepyan, Leonid

2014-09-01

A domino wave is a well-known illustration of a transition wave, which appears to reach a stable regime of propagation. Nature also provides spectacular cases of gravity driven transition waves at large scale, observed in snow avalanches and landslides. On a different scale, the micro-structure level interaction between different constituents of the macro-system may influence critical regimes leading to instabilities in avalanche-like flow systems. Most transition waves observed in systems such as bulletproof vests, racing helmets under impact, shock-wave driven fracture in solids, are transient. For some structured waveguides a transition wave may stabilize to achieve a steady regime. Here we show that the failure of a long bridge is also driven by a transition wave that may allow for steady-state regimes. The recent observation of a failure of the San Saba Bridge in Texas provides experimental evidence supporting an elegant theory based on the notion of transition failure wave. No one would think of an analogy between a snow avalanche and a collapsing bridge. Despite an apparent controversy of such a comparison, these two phenomena can both be described in the framework of a model of the dynamic gravity driven transition fault.

Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

PubMed

Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

2017-11-01

An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

Appraisal of the water resources of Death Valley, California-Nevada

USGS Publications Warehouse

Miller, Glenn Allen

1977-01-01

The hydrologic system in Death Valley is probably in a steady-state condition--that is, recharge and discharge are equal, and net changes in the quantity of ground water in storage are not occurring. Recharge to ground water in the valley is derived from interbasin underflow and from local precipitation. The two sources may be of the same magnitude. Ground water beneath the valley moves toward the lowest area, a 200-square-mile saltpan, much of which is underlain by rock salt and other saline minerals, probably to depths of hundreds of feet or even more than 1,000 feet. Some water discharges from the saltpan by evaportranspiration. Water beneath the valley floor, excluding the saltpan, typically contains between 3,000 and 5,000 milligrams per liter of dissolved solids. Water from most springs and seeps in the mountains contains a few hundred to several hundred milligrams per liter of dissolved solids. Water from large springs that probably discharge from interbasin flow systems typically contains between 500 and 1,000 milligrams per liter dissolved solids. Present sites of intensive use by man are supplied by springs, with the exception of the Stovepipe Wells Hotel area. Potential sources of supply for this area include (1) Emigrant Spring area, (2) Cottonwood Spring, and (3) northern Mesquite Flat. (Woodard-USGS)

A mechanical energy analysis of gait initiation

NASA Technical Reports Server (NTRS)

Miller, C. A.; Verstraete, M. C.

1999-01-01

The analysis of gait initiation (the transient state between standing and walking) is an important diagnostic tool to study pathologic gait and to evaluate prosthetic devices. While past studies have quantified mechanical energy of the body during steady-state gait, to date no one has computed the mechanical energy of the body during gait initiation. In this study, gait initiation in seven normal male subjects was studied using a mechanical energy analysis to compute total body energy. The data showed three separate states: quiet standing, gait initiation, and steady-state gait. During gait initiation, the trends in the energy data for the individual segments were similar to those seen during steady-state gait (and in Winter DA, Quanbury AO, Reimer GD. Analysis of instantaneous energy of normal gait. J Biochem 1976;9:253-257), but diminished in amplitude. However, these amplitudes increased to those seen in steady-state during the gait initiation event (GIE), with the greatest increase occurring in the second step due to the push-off of the foundation leg. The baseline level of mechanical energy was due to the potential energy of the individual segments, while the cyclic nature of the data was indicative of the kinetic energy of the particular leg in swing phase during that step. The data presented showed differences in energy trends during gait initiation from those of steady state, thereby demonstrating the importance of this event in the study of locomotion.

Dispersion of a Nanoliter Bolus in Microfluidic Co-Flow.

PubMed

Conway, A J; Saadi, W M; Sinatra, F L; Kowalski, G; Larson, D; Fiering, J

2014-03-01

Microfluidic systems enable reactions and assays on the scale of nanoliters. However, at this scale nonuniformities in sample delivery become significant. To determine the fundamental minimum sample volume required for a particular device, a detailed understanding of mass transport is required. Co-flowing laminar streams are widely used in many devices, but typically only in the steady-state. Because establishing the co-flow steady-state consumes excess sample volume and time, there is a benefit to operating devices in the transient state, which predominates as the volume of the co-flow reactor decreases. Analysis of the co-flow transient has been neglected thus far. In this work we describe the fabrication of a pneumatically controlled microfluidic injector constructed to inject a discrete 50nL bolus into one side of a two-stream co-flow reactor. Using dye for image analysis, injections were performed at a range of flow rates from 0.5-10μL/min, and for comparison we collected the co-flow steady-state data for this range. The results of the image analysis were also compared against theory and simulations for device validation. For evaluation, we established a metric that indicates how well the mass distribution in the bolus injection approximates steady-state co-flow. Using such analysis, transient-state injections can approximate steady-state conditions within predefined errors, allowing straight forward measurements to be performed with reduced reagent consumption.

Co-digestion of ruminal content and blood from slaughterhouse industries: influence of solid concentration and ammonium generation.

PubMed

López, I; Passeggi, M; Borzacconi, L

2006-01-01

At the present time, organic solid wastes from industries and agricultural activities are considered to be promising substrates for biogas production via anaerobic digestion. Moreover solids stabilisation is required before reutilization or disposal. Slaughterhouses are among the most important industries in Uruguay and produce 150,000 tons of ruminal content (RC) and 30,000 tons of blood per year. In order to determine the influence of the solids and blood contents, the ammonia inhibition and the inoculum adaptation co-digestion batch tests were performed. A set of experiences with TS concentration of 2.5%, 5% and 7.5% and different ratios of RC/blood were carried out using an inoculum from an UASB reactor. In all experiences fast blood hydrolisation was observed. A higher methane production was detected in the experiences with higher TS content. However, the fraction of solids degradation was lower in these experiences. A plateau in the biogas production was found. The free ammonia level, which was above the reported inhibitory levels, could explain this behaviour. After the inhibition period the biogas production restarted probably due to the biomass acclimatisation to the ammonia. In order to determine the inoculum adaptation a new experiment was performed. The inoculum used was the sludge coming from the first set of experiences. Based upon batch tests a 3.5 m3 pilot reactor was designed and started up. Ammonia inhibition was avoided by the start-up strategy and in two weeks the biogas production was 3.5 m3/d. The VS stabilisation with a solid retention time of 20 days was of 43%. The pilot reactor working at steady state had a TS concentration of 3-4% with a ratio of RC/blood of 10:1 at the entrance.

Results of wind tunnel tests of an ASRM configured 0.03 scale Space Shuttle integrated vehicle model (47-OTS) in the AEDC 16-foot transonic wind tunnel, volume 2

NASA Technical Reports Server (NTRS)

Marroquin, J.; Lemoine, P.

1992-01-01

An experimental Aerodynamic and Aero-Acoustic loads data base was obtained at transonic Mach numbers for the Space Shuttle Launch Vehicle configured with the ASRM Solid Rocket Boosters as an increment to the current flight configuration (RSRB). These data were obtained during transonic wind tunnel tests (IA 613A) conducted in the Arnold Engineering Development Center 16-Foot transonic propulsion wind tunnel from March 27, 1991 through April 12, 1991. This test is the first of a series of two tests covering the Mach range from 0.6 to 3.5. Steady state surface static and fluctuating pressure distributions over the Orbiter, External Tank and Solid Rocket Boosters of the Shuttle Integrated Vehicle were measured. Total Orbiter forces, Wing forces and Elevon hinge moments were directly measured as well from force balances. Two configurations of Solid Rocket Boosters were tested, the Redesigned Solid Rocket Booster (RSRB) and the Advanced Solid Rocket Motor (ASRM). The effects of the position (i.e., top, bottom, top and bottom) of the Integrated Electronics Assembly (IEA) box, mounted on the SRB attach ring, were obtained on the ASRM configured model. These data were obtained with and without Solid Plume Simulators which, when used, matched as close as possible the flight derived pressures on the Orbiter and External Tank base. Data were obtained at Mach numbers ranging from 0.6 to 1.55 at a Unit Reynolds Number of 2.5 million per foot through model angles of attack from -8 to +4 degrees at sideslip angles of 0, +4 and -4 degrees.

Results of wind tunnel tests of an ASRM configured 0.03 scale Space Shuttle integrated vehicle model (47-OTS) in the AEDC 16-foot Transonic wind tunnel (IA613A), volume 1

NASA Technical Reports Server (NTRS)

Marroquin, J.; Lemoine, P.

1992-01-01

An experimental Aerodynamic and Aero-Acoustic loads data base was obtained at transonic Mach numbers for the Space Shuttle Launch Vehicle configured with the ASRM Solid Rocket Boosters as an increment to the current flight configuration (RSRB). These data were obtained during transonic wind tunnel tests (IA 613A) conducted in the Arnold Engineering Development Center 16-Foot transonic propulsion wind tunnel from March 27, 1991 through April 12, 1991. This test is the first of a series of two tests covering the Mach range from 0.6 to 3.5. Steady state surface static and fluctuating pressure distributions over the Orbiter, External Tank and Solid Rocket Boosters of the Shuttle Integrated Vehicle were measured. Total Orbiter forces, Wing forces and Elevon hinge moments were directly measured as well from force balances. Two configurations of Solid Rocket Boosters were tested, the Redesigned Solid Rocket Booster (RSRB) and the Advanced Solid Rocket Motor (ASRM). The effects of the position (i.e. top, bottom, top and bottom) of the Integrated Electronics Assembly (IEA) box, mounted on the SRB attach ring, were obtained on the ASRM configured model. These data were obtained with and without Solid Plume Simulators which, when used, matched as close as possible the flight derived pressures on the Orbiter and External Tank base. Data were obtained at Mach numbers ranging from 0.6 to 1.55 at a Unit Reynolds Number of 2.5 million per foot through model angles of attack from -8 to +4 degrees at sideslip angles of 0, +4 and -4 degrees.

Effect of Steady-State Faldaprevir on the Pharmacokinetics of Steady-State Methadone and Buprenorphine-Naloxone in Subjects Receiving Stable Addiction Management Therapy

PubMed Central

Joseph, David; Schobelock, Michael J.; Riesenberg, Robert R.; Vince, Bradley D.; Webster, Lynn R.; Adeniji, Abidemi; Elgadi, Mabrouk

2014-01-01

The effects of steady-state faldaprevir on the safety, pharmacokinetics, and pharmacodynamics of steady-state methadone and buprenorphine-naloxone were assessed in 34 healthy male and female subjects receiving stable addiction management therapy. Subjects continued receiving a stable oral dose of either methadone (up to a maximum dose of 180 mg per day) or buprenorphine-naloxone (up to a maximum dose of 24 mg-6 mg per day) and also received oral faldaprevir (240 mg) once daily (QD) for 8 days following a 480-mg loading dose. Serial blood samples were taken for pharmacokinetic analysis. The pharmacodynamics of the opioid maintenance regimens were evaluated by the objective and subjective opioid withdrawal scales. Coadministration of faldaprevir with methadone or buprenorphine-naloxone resulted in geometric mean ratios for the steady-state area under the concentration-time curve from 0 to 24 h (AUC0–24,ss), the steady-state maximum concentration of the drug in plasma (Cmax,ss), and the steady-state concentration of the drug in plasma at 24 h (C24,ss) of 0.92 to 1.18 for (R)-methadone, (S)-methadone, buprenorphine, norbuprenorphine, and naloxone, with 90% confidence intervals including, or very close to including, 1.00 (no effect), suggesting a limited overall effect of faldaprevir. Although individual data showed moderate variability in the exposures between subjects and treatments, there was no evidence of symptoms of opiate overdose or withdrawal either during the coadministration of faldaprevir with methadone or buprenorphine-naloxone or after faldaprevir dosing was stopped. Similar faldaprevir exposures were observed in the methadone- and buprenorphine-naloxone-treated subjects. In conclusion, faldaprevir at 240 mg QD can be coadministered with methadone or buprenorphine-naloxone without dose adjustment, although given the relatively narrow therapeutic windows of these agents, monitoring for opiate overdose and withdrawal may still be appropriate. (This study has been registered at ClinicalTrials.gov under registration no. NCT01637922.) PMID:25385094

A nodally condensed SUPG formulation for free-surface computation of steady-state flows constrained by unilateral contact - Application to rolling

NASA Astrophysics Data System (ADS)

Arora, Shitij; Fourment, Lionel

2018-05-01

In the context of the simulation of industrial hot forming processes, the resultant time-dependent thermo-mechanical multi-field problem (v →,p ,σ ,ɛ ) can be sped up by 10-50 times using the steady-state methods while compared to the conventional incremental methods. Though the steady-state techniques have been used in the past, but only on simple configurations and with structured meshes, and the modern-days problems are in the framework of complex configurations, unstructured meshes and parallel computing. These methods remove time dependency from the equations, but introduce an additional unknown into the problem: the steady-state shape. This steady-state shape x → can be computed as a geometric correction t → on the domain X → by solving the weak form of the steady-state equation v →.n →(t →)=0 using a Streamline Upwind Petrov Galerkin (SUPG) formulation. There exists a strong coupling between the domain shape and the material flow, hence, a two-step fixed point iterative resolution algorithm was proposed that involves (1) the computation of flow field from the resolution of thermo-mechanical equations on a prescribed domain shape and (2) the computation of steady-state shape for an assumed velocity field. The contact equations are introduced in the penalty form both during the flow computation as well as during the free-surface correction. The fact that the contact description is inhomogeneous, i.e., it is defined in the nodal form in the former, and in the weighted residual form in the latter, is assumed to be critical to the convergence of certain problems. Thus, the notion of nodal collocation is invoked in the weak form of the surface correction equation to homogenize the contact coupling. The surface correction algorithm is tested on certain analytical test cases and the contact coupling is tested with some hot rolling problems.

Higher Accuracy of the Lactate Minimum Test Compared to Established Threshold Concepts to Determine Maximal Lactate Steady State in Running.

PubMed

Wahl, Patrick; Zwingmann, Lukas; Manunzio, Christian; Wolf, Jacob; Bloch, Wilhelm

2018-05-18

This study evaluated the accuracy of the lactate minimum test, in comparison to a graded-exercise test and established threshold concepts (OBLA and mDmax) to determine running speed at maximal lactate steady state. Eighteen subjects performed a lactate minimum test, a graded-exercise test (2.4 m·s -1 start,+0.4 m·s -1 every 5 min) and 2 or more constant-speed tests of 30 min to determine running speed at maximal lactate steady state. The lactate minimum test consisted of an initial lactate priming segment, followed by a short recovery phase. Afterwards, the initial load of the subsequent incremental segment was individually determined and was increased by 0.1 m·s -1 every 120 s. Lactate minimum was determined by the lowest measured value (LM abs ) and by a third-order polynomial (LM pol ). The mean difference to maximal lactate steady state was+0.01±0.14 m·s -1 (LM abs ), 0.04±0.15 m·s -1 (LM pol ), -0.06±0.31 m·s 1 (OBLA) and -0.08±0.21 m·s 1 (mDmax). The intraclass correlation coefficient (ICC) between running velocity at maximal lactate steady state and LM abs was highest (ICC=0.964), followed by LM pol (ICC=0.956), mDmax (ICC=0.916) and OBLA (ICC=0.885). Due to the higher accuracy of the lactate minimum test to determine maximal lactate steady state compared to OBLA and mDmax, we suggest the lactate minimum test as a valid and meaningful concept to estimate running velocity at maximal lactate steady state in a single session for moderately up to well-trained athletes. © Georg Thieme Verlag KG Stuttgart · New York.

The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity

PubMed Central

Foster, Carl; Farland, Courtney V.; Guidotti, Flavia; Harbin, Michelle; Roberts, Brianna; Schuette, Jeff; Tuuri, Andrew; Doberstein, Scott T.; Porcari, John P.

2015-01-01

High intensity interval training (HIIT) has become an increasingly popular form of exercise due to its potentially large effects on exercise capacity and small time requirement. This study compared the effects of two HIIT protocols vs steady-state training on aerobic and anaerobic capacity following 8-weeks of training. Fifty-five untrained college-aged subjects were randomly assigned to three training groups (3x weekly). Steady-state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of ventilatory threshold (VT). Tabata (n = 21) completed eight intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15) completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s recovery, average PO = 90% VT. Each subject did 24 training sessions during 8 weeks. Results: There were significant (p < 0.05) increases in VO2max (+19, +18 and +18%) and PPO (+17, +24 and +14%) for each training group, as well as significant increases in peak (+8, + 9 and +5%) & mean (+4, +7 and +6%) power during Wingate testing, but no significant differences between groups. Measures of the enjoyment of the training program indicated that the Tabata protocol was significantly less enjoyable (p < 0.05) than the steady state and Meyer protocols, and that the enjoyment of all protocols declined (p < 0.05) across the duration of the study. The results suggest that although HIIT protocols are time efficient, they are not superior to conventional exercise training in sedentary young adults. Key points Steady state training equivalent to HIIT in untrained students Mild interval training presents very similar physiologic challenge compared to steady state training HIIT (particularly very high intensity variants were less enjoyable than steady state or mild interval training Enjoyment of training decreases across the course of an 8 week experimental training program PMID:26664271

The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity.

PubMed

Foster, Carl; Farland, Courtney V; Guidotti, Flavia; Harbin, Michelle; Roberts, Brianna; Schuette, Jeff; Tuuri, Andrew; Doberstein, Scott T; Porcari, John P

2015-12-01

High intensity interval training (HIIT) has become an increasingly popular form of exercise due to its potentially large effects on exercise capacity and small time requirement. This study compared the effects of two HIIT protocols vs steady-state training on aerobic and anaerobic capacity following 8-weeks of training. Fifty-five untrained college-aged subjects were randomly assigned to three training groups (3x weekly). Steady-state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of ventilatory threshold (VT). Tabata (n = 21) completed eight intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15) completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s recovery, average PO = 90% VT. Each subject did 24 training sessions during 8 weeks. There were significant (p < 0.05) increases in VO2max (+19, +18 and +18%) and PPO (+17, +24 and +14%) for each training group, as well as significant increases in peak (+8, + 9 and +5%) & mean (+4, +7 and +6%) power during Wingate testing, but no significant differences between groups. Measures of the enjoyment of the training program indicated that the Tabata protocol was significantly less enjoyable (p < 0.05) than the steady state and Meyer protocols, and that the enjoyment of all protocols declined (p < 0.05) across the duration of the study. The results suggest that although HIIT protocols are time efficient, they are not superior to conventional exercise training in sedentary young adults. Key pointsSteady state training equivalent to HIIT in untrained studentsMild interval training presents very similar physiologic challenge compared to steady state trainingHIIT (particularly very high intensity variants were less enjoyable than steady state or mild interval trainingEnjoyment of training decreases across the course of an 8 week experimental training program.

An Operational Definition of the Steady State in Enzyme Kinetics.

ERIC Educational Resources Information Center

Barnsley, E. A.

1990-01-01

The Briggs-Haldane assumption is used as the basis for the development of a kinetic model for enzyme catalysis. An alternative definition of the steady state and examples of realistic mechanisms are provided. (KR)

Vibration testing and analysis using holography

NASA Technical Reports Server (NTRS)

1971-01-01

Time average holography is useful in recording steady state vibrational mode patterns. Phase relationships under steady state conditions are measured with real time holography and special phase shifting techniques. Data from Michelson interferometer verify vibration amplitudes from holographic data.

Limiting Forces on Transit Trucks in Steady-State Curving

DOT National Transportation Integrated Search

1981-05-01

This study develops conservative bounds on wheel/rail forces and flange forces for several types of rigid and flexible trucks in steady-state curving conditions. The approximate analysis presented provides closed-form relations for estimating forces,...

Bifurcations in the theory of current transfer to cathodes of DC discharges and observations of transitions between different modes

NASA Astrophysics Data System (ADS)

Bieniek, M. S.; Santos, D. F. N.; Almeida, P. G. C.; Benilov, M. S.

2018-04-01

General scenarios of transitions between different spot patterns on electrodes of DC gas discharges and their relation to bifurcations of steady-state solutions are analyzed. In the case of cathodes of arc discharges, it is shown that any transition between different modes of current transfer is related to a bifurcation of steady-state solutions. In particular, transitions between diffuse and spot modes on axially symmetric cathodes, frequently observed in the experiment, represent an indication of the presence of pitchfork or fold bifurcations of steady-state solutions. Experimental observations of transitions on cathodes of DC glow microdischarges are analyzed and those potentially related to bifurcations of steady-state solutions are identified. The relevant bifurcations are investigated numerically and the computed patterns are found to conform to those observed in the course of the corresponding transitions in the experiment.

Steady-state performance analysis of fiber-optic ring resonator

NASA Astrophysics Data System (ADS)

Seraji, Faramarz E.

2009-01-01

This paper presents a full steady-state analysis of a fiber-optic ring resonator (FORR). Although in the literature the steady-state response of the FORR has been described, a detailed description of the same is not available. As an understanding of the different steady-state characteristics of the FORR is required to appreciate its characteristic response, in this paper, the expressions for the output and loop intensities, phase angles of the fields, conditions for resonance, output and loop intensities at resonance and off-resonance, finesse, and group delay of the FORR are given for different ideal and practical operating conditions of the resonator. Graphical plots of all the above characteristics are given, by highlighting the important results. The information presented in this paper will be helpful in explaining and understanding the pulse response of the resonator used in different applications of FORR.

Poissonian steady states: from stationary densities to stationary intensities.

PubMed

Eliazar, Iddo

2012-10-01

Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.

Reduction of Simulation Times for High-Q Structures using the Resonance Equation

DOE PAGES

Hall, Thomas Wesley; Bandaru, Prabhakar R.; Rees, Daniel Earl

2015-11-17

Simulating steady state performance of high quality factor (Q) resonant RF structures is computationally difficult for structures with sizes on the order of more than a few wavelengths because of the long times (on the order of ~ 0.1 ms) required to achieve steady state in comparison with maximum time step that can be used in the simulation (typically, on the order of ~ 1 ps). This paper presents analytical and computational approaches that can be used to accelerate the simulation of the steady state performance of such structures. The basis of the proposed approach is the utilization of amore » larger amplitude signal at the beginning to achieve steady state earlier relative to the nominal input signal. Finally, the methodology for finding the necessary input signal is then discussed in detail, and the validity of the approach is evaluated.« less

Steady-state solutions of a diffusive energy-balance climate model and their stability

NASA Technical Reports Server (NTRS)

Ghil, M.

1975-01-01

A diffusive energy-balance climate model, governed by a nonlinear parabolic partial differential equation, was studied. Three positive steady-state solutions of this equation are found; they correspond to three possible climates of our planet: an interglacial (nearly identical to the present climate), a glacial, and a completely ice-covered earth. Models similar to the main one are considered, and the number of their steady states was determined. All the models have albedo continuously varying with latitude and temperature, and entirely diffusive horizontal heat transfer. The stability under small perturbations of the main model's climates was investigated. A stability criterion is derived, and its application shows that the present climate and the deep freeze are stable, whereas the model's glacial is unstable. The dependence was examined of the number of steady states and of their stability on the average solar radiation.

SUPRATHERMAL SOLAR WIND ELECTRONS AND LANGMUIR TURBULENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sunjung; Yoon, Peter H.; Choe, G. S.

2016-09-01

The steady-state model recently put forth for the solar wind electron velocity distribution function during quiet time conditions, was originally composed of three population electrons (core, halo, and superhalo) with the core remaining nonresonant with any plasma waves while the halo and superhalo separately maintained steady-state resonance with whistler- and Langmuir-frequency range fluctuations, respectively. However, a recent paper demonstrates that whistler-range fluctuations in fact have no significant contribution. The present paper represents a consummation of the model in that a self-consistent model of the suprathermal electron population, which encompasses both the halo and the superhalo, is constructed solely on themore » basis of the Langmuir fluctuation spectrum. Numerical solutions to steady-state particle and wave kinetic equations are obtained on the basis of an initial trial electron distribution and Langmuir wave spectrum. Such a finding offers a self-consistent explanation for the observed steady-state electron distribution in the solar wind.« less

Poissonian steady states: From stationary densities to stationary intensities

NASA Astrophysics Data System (ADS)

Eliazar, Iddo

2012-10-01

Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.

The Effect of Impeller Type on Floc Size and Structure during Shear-Induced Flocculation

PubMed

Spicer; Keller; Pratsinis

1996-12-01

The effect of impeller type and shear rate on the evolution of floc size and structure during shear-induced flocculation of polystyrene particles with aluminum sulfate is investigated by image analysis. One radial flow (six-blade Rushton turbine) and two axial flow (three-blade fluid foil, four-blade 45° pitch) impeller configurations are examined. The steady state average floc size is shown to depend on the frequency of recirculation to the impeller zone and its characteristic velocity gradient. The concepts of fractal geometry are used to characterize the floc structure. For all impellers, the two-dimensional floc fractal dimension, Dpf, increases during floc growth, indicating formation of more open structures. Later on, Dpf levels off at a steady state value as breakage becomes significant and the floc size distribution approaches steady state. The shear rate does not affect the steady state Dpf of the flocs within experimental uncertainty.

Topological properties of a self-assembled electrical network via ab initio calculation

NASA Astrophysics Data System (ADS)

Stephenson, C.; Lyon, D.; Hübler, A.

2017-02-01

Interacting electrical conductors self-assemble to form tree like networks in the presence of applied voltages or currents. Experiments have shown that the degree distribution of the steady state networks are identical over a wide range of network sizes. In this work we develop a new model of the self-assembly process starting from the underlying physical interaction between conductors. In agreement with experimental results we find that for steady state networks, our model predicts that the fraction of endpoints is a constant of 0.252, and the fraction of branch points is 0.237. We find that our model predicts that these scaling properties also hold for the network during the approach to the steady state as well. In addition, we also reproduce the experimental distribution of nodes with a given Strahler number for all steady state networks studied.

The Steady-State Transport of Oxygen through Hemoglobin Solutions

PubMed Central

Keller, K. H.; Friedlander, S. K.

1966-01-01

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated. PMID:5943608

Realizing steady-state tokamak operation for fusion energy

NASA Astrophysics Data System (ADS)

Luce, T. C.

2011-03-01

Continuous operation of a tokamak for fusion energy has clear engineering advantages but requires conditions beyond those sufficient for a burning plasma. The fusion reactions and external sources must support both the pressure and the current equilibrium without inductive current drive, leading to demands on stability, confinement, current drive, and plasma-wall interactions that exceed those for pulsed tokamaks. These conditions have been met individually, and significant progress has been made in the past decade to realize scenarios where the required conditions are obtained simultaneously. Tokamaks are operated routinely without disruptions near pressure limits, as needed for steady-state operation. Fully noninductive sustainment with more than half of the current from intrinsic currents has been obtained for a resistive time with normalized pressure and confinement approaching those needed for steady-state conditions. One remaining challenge is handling the heat and particle fluxes expected in a steady-state tokamak without compromising the core plasma performance.

Pre-Steady-State Kinetic Analysis of Single-Nucleotide Incorporation by DNA Polymerases

PubMed Central

Su, Yan; Guengerich, F. Peter

2016-01-01

Pre-steady-state kinetic analysis is a powerful and widely used method to obtain multiple kinetic parameters. This protocol provides a step-by-step procedure for pre-steady-state kinetic analysis of single-nucleotide incorporation by a DNA polymerase. It describes the experimental details of DNA substrate annealing, reaction mixture preparation, handling of the RQF-3 rapid quench-flow instrument, denaturing polyacrylamide DNA gel preparation, electrophoresis, quantitation, and data analysis. The core and unique part of this protocol is the rationale for preparation of the reaction mixture (the ratio of the polymerase to the DNA substrate) and methods for conducting pre-steady-state assays on an RQF-3 rapid quench-flow instrument, as well as data interpretation after analysis. In addition, the methods for the DNA substrate annealing and DNA polyacrylamide gel preparation, electrophoresis, quantitation and analysis are suitable for use in other studies. PMID:27248785

Efficient steady-state solver for hierarchical quantum master equations

NASA Astrophysics Data System (ADS)

Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing

2017-07-01

Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.

Municipal solid waste management in Kurdistan Province, Iran.

PubMed

Abduli, Mohammad Ali; Nasrabadi, Touraj

2007-03-01

Kurdistan Province, with an area of 28,203 square kilometers, is located in a mountainous area in the western part of Iran. From 1967 to 1997, the urban population in the major eight cities of the Kurdistan Province-namely, Baneh, Bijar, Divan Darreh, Saghez, Sanandaj, Ghorveh, Kamyaran, and Marivan-increased from 102,250 to 705,715. The proportion of the population residing in urban areas increased 90 percent during this period. In most of the cities, solid waste handling remains primitive, and well-organized procedures for it have not been established. Traditional methods of disposal, with marginal inclusion of modern conveniences, appear to be the common practice. In general, the shortcomings of the prevailing practices can be summarized as follows: The municipal solid waste management systems (MSWMSs) in this province include unsegregated collection and open dumping of municipal solid wastes. Separation of municipal solid waste in this province is in the hands of scavengers. The MSWMSs in this province lack essential infrastructure. Thus, design and implementation of modern MSWMSs in this province are essential. Principal criteria for and methods of implementing these systems are as follows: (1) rationally evaluating all functional elements so that they operate in a steady-state or equilibrium manner; (2) creating all support elements for the MSWMS in each city; (3) introducing gradual privatization of MSWMS activities; (4) creating guidelines, regulations, and instructions for all elements of MSWMSs; and (5) giving priorities to source separation and recycling programs. This paper reviews the present status of MSWMSs in eight major cities of Kurdistan Province and outlines the principle guidelines and alternatives for MSWMSs.

Marginal states in a cubic autocatalytic reaction

NASA Astrophysics Data System (ADS)

Das, Debojyoti; Ghosh, Pushpita; Ray, Deb Shankar

2011-09-01

Marginal steady state belongs to a special class of states in nonlinear dynamics. To realize this state we consider a cubic autocatalytic reaction A + 2B → 3B in a continuous-stirred-tank-reactor, where the flow rate of the reactant A can be controlled to manipulate the dynamical behavior of the open system. We demonstrate that when the flow rate is weakly noisy the autocatalytic reaction admits of a steady state which is marginal in nature and is surrounded by infinite number of periodic trajectories. When the uncatalyzed reaction A → B is included in the reaction scheme, there exists a marginal steady state which is a critical state corresponding to the point of transition between the flow branch and the equilibrium branch, similar to gas-liquid critical point of transition. This state loses its stability in the weak noise limit.

Influence of the hypercycle on the error threshold: a stochastic approach.

PubMed

García-Tejedor, A; Sanz-Nuño, J C; Olarrea, J; Javier de la Rubia, F; Montero, F

1988-10-21

The role of fluctuations on the error threshold of the hypercycle has been studied by a stochastic approach on a very simplified model. For this model, the master equation was derived and its unique steady state calculated. This state implies the extinction of the system. But the actual time necessary to reach the steady state may be astronomically long whereas for times of experimental interest the system could be near some quasi-stationary states. In order to explore this possibility a Gillespie simulation of the stochastic process has been carried out. These quasi-stationary states correspond to the deterministic steady states of the system. The error threshold shifts towards higher values of the quality factor Q. Moreover, information about the fluctuations around the quasi-stationary states is obtained. The results are discussed in relation to the deterministic states.