Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation.

PubMed

Mauad, Cristiane R; Wagener, Angela de L R; Massone, Carlos G; Aniceto, Mayara da S; Lazzari, Letícia; Carreira, Renato S; Farias, Cássia de O

2015-02-15

Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement. Copyright © 2014 Elsevier B.V. All rights reserved.

Measurements of the cesium flow from a surface-plasma H/sup -/ ion source

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

Smith, H.V.; Allison, P.W.

1979-01-01

A surface ionization gauge (SIG) was constructed and used to measure the Cs/sup 0/ flow rate through the emission slit of a surface-plasma source (SPS) of H/sup -/ ions with Penning geometry. The equivalent cesium density in the SPS discharge is deduced from these flow measurements. For dc operation the optimum H/sup -/ current occurs at an equivalent cesium density of approx. 7 x 10/sup 12/ cm/sup -3/ (corresponding to an average cesium consumption rate of 0.5 mg/h). For pulsed operation the optimum H/sup -/ current occurs at an equivalent cesium density of approx. 2 x 10/sup 13/ cm/sup -3/more » (1-mg/h average cesium consumption rate). Cesium trapping by the SPS discharge was observed for both dc and pulsed operation. A cesium energy of approx. 0.1 eV is deduced from the observed time of flight to the SIG. In addition to providing information on the physics of the source, the SIG is a useful diagnostic tool for source startup and operation.« less

The effect of carrier gas flow rate and source cell temperature on low pressure organic vapor phase deposition simulation by direct simulation Monte Carlo method

PubMed Central

Wada, Takao; Ueda, Noriaki

2013-01-01

The process of low pressure organic vapor phase deposition (LP-OVPD) controls the growth of amorphous organic thin films, where the source gases (Alq3 molecule, etc.) are introduced into a hot wall reactor via an injection barrel using an inert carrier gas (N2 molecule). It is possible to control well the following substrate properties such as dopant concentration, deposition rate, and thickness uniformity of the thin film. In this paper, we present LP-OVPD simulation results using direct simulation Monte Carlo-Neutrals (Particle-PLUS neutral module) which is commercial software adopting direct simulation Monte Carlo method. By estimating properly the evaporation rate with experimental vaporization enthalpies, the calculated deposition rates on the substrate agree well with the experimental results that depend on carrier gas flow rate and source cell temperature. PMID:23674843

40 CFR 146.23 - Operating, monitoring, and reporting requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... pressure, flow rate, and cumulative volume at least with the following frequencies: (i) Weekly for produced..., flow rate and cumulative volume at reasonable intervals no greater than 30 days. (3) A demonstration of..., and any major changes in characteristics or sources of injected fluid. Previously submitted...

Utilizing Diffusion Theory to predict carbon dioxide concentration in an indoor environment

NASA Astrophysics Data System (ADS)

Kramer, Andrew R.

This research details a new method of relating sources of carbon dioxide to carbon dioxide concentration in a room operating in a reduced ventilation mode by utilizing Diffusion Theory. The theoretical basis of this research involved solving Fick's Second Law of Diffusion in spherical coordinates for a source of carbon dioxide flowing at a constant rate and located in the center of an impermeable spherical boundary. The solution was developed using a Laplace Transformation. A spherical diffusion test chamber was constructed and used to validate and benchmark the developed theory. The method was benchmarked by using Dispersion Coefficients for large carbon dioxide flow rates due to diffusion induced convection. The theoretical model was adapted to model a room operating with restricted ventilation in the presence of a known, constant source of carbon dioxide. The room was modeled as a sphere of volume equal to the room and utilized a Dispersion Coefficient that is consistent with published values. The developed Diffusion Model successfully predicted the spatial concentration of carbon dioxide in a room operating in a reduced ventilation mode in the presence of a source of carbon dioxide. The flow rates of carbon dioxide that were used in the room are comparable to the average flow rate of carbon dioxide from a person during quiet breathing, also known as the Tidal Breathing. This indicates the Diffusion Model developed from this research has the potential to correlate carbon dioxide concentration with static occupancy levels which can lead to energy savings through a reduction in air exchange rates when low occupancy is detected.

77 FR 30283 - Standards of Performance for New Stationary Sources, National Emission Standards for Hazardous...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-22

... timeline and exceedances of the pressure, temperature, and oxygen and/or nitrogen concentration are... (AMP) that consists of monitoring the inlet scrubbing liquid temperature, flow rate, and acid content... request consisting of monitoring the inlet scrubbing liquid temperature and flow rate and identifying...

40 CFR 63.645 - Test methods and procedures for miscellaneous process vents.

Code of Federal Regulations, 2010 CFR

2010-07-01

... TOC emission rate, as specified under paragraph (f) of this section, the sampling site shall be after... process vent TOC mass flow rate is less than 33 kilograms per day for an existing source or less than 6.8... shall determine the TOC mass flow rate by the following procedures: (1) The sampling site shall be...

A compact model for electroosmotic flows in microfluidic devices

NASA Astrophysics Data System (ADS)

Qiao, R.; Aluru, N. R.

2002-09-01

A compact model to compute flow rate and pressure in microfluidic devices is presented. The microfluidic flow can be driven by either an applied electric field or a combined electric field and pressure gradient. A step change in the ζ-potential on a channel wall is treated by a pressure source in the compact model. The pressure source is obtained from the pressure Poisson equation and conservation of mass principle. In the proposed compact model, the complex fluidic network is simplified by an electrical circuit. The compact model can predict the flow rate, pressure distribution and other basic characteristics in microfluidic channels quickly with good accuracy when compared to detailed numerical simulation. Using the compact model, fluidic mixing and dispersion control are studied in a complex microfluidic network.

Sources of debris flow material in burned areas

USGS Publications Warehouse

Santi, P.M.; deWolfe, V.G.; Higgins, J.D.; Cannon, S.H.; Gartner, J.E.

2008-01-01

The vulnerability of recently burned areas to debris flows has been well established. Likewise, it has been shown that many, if not most, post-fire debris flows are initiated by runoff and erosion and grow in size through erosion and scour by the moving debris flow, as opposed to landslide-initiated flows with little growth. To better understand the development and character of these flows, a study has been completed encompassing 46 debris flows in California, Utah, and Colorado, in nine different recently burned areas. For each debris flow, progressive debris production was measured at intervals along the length of the channel, and from these measurements graphs were developed showing cumulative volume of debris as a function of channel length. All 46 debris flows showed significant bulking by scour and erosion, with average yield rates for each channel ranging from 0.3 to 9.9??m3 of debris produced for every meter of channel length, with an overall average value of 2.5??m3/m. Significant increases in yield rate partway down the channel were identified in 87% of the channels, with an average of a three-fold increase in yield rate. Yield rates for short reaches of channels (up to several hundred meters) ranged as high as 22.3??m3/m. Debris was contributed from side channels into the main channels for 54% of the flows, with an average of 23% of the total debris coming from those side channels. Rill erosion was identified for 30% of the flows, with rills contributing between 0.1 and 10.5% of the total debris, with an average of 3%. Debris was deposited as levees in 87% of the flows, with most of the deposition occurring in the lower part of the basin. A median value of 10% of the total debris flow was deposited as levees for these cases, with a range from near zero to nearly 100%. These results show that channel erosion and scour are the dominant sources of debris in burned areas, with yield rates increasing significantly partway down the channel. Side channels are much more important sources of debris than rills. Levees are very common, but the size and effect on the amount of debris that reaches a canyon mouth is highly variable. ?? 2007 Elsevier B.V. All rights reserved.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R.

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. [Figure not available: see fulltext.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure.

PubMed

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. Graphical Abstract.

Flow Glottogram and Subglottal Pressure Relationship in Singers and Untrained Voices.

PubMed

Sundberg, Johan

2018-01-01

This article combines results from three earlier investigations of the glottal voice source during phonation at varying degrees of vocal loudness (1) in five classically trained baritone singers (Sundberg et al., 1999), (2) in 15 female and 14 male untrained voices (Sundberg et al., 2005), and (3) in voices rated as hyperfunctional by an expert panel (Millgård et al., 2015). Voice source data were obtained by inverse filtering. Associated subglottal pressures were estimated from oral pressure during the occlusion for the consonant /p/. Five flow glottogram parameters, (1) maximum flow declination rate (MFDR), (2) peak-to-peak pulse amplitude, (3) level difference between the first and the second harmonics of the voice source, (4) closed quotient, and (5) normalized amplitude quotient, were averaged across the singer subjects and related to associated MFDR values. Strong, quantitative relations, expressed as equations, are found between subglottal pressure and MFDR and between MFDR and each of the other flow glottogram parameters. The values for the untrained voices, as well as those for the voices rated as hyperfunctional, deviate systematically from the values derived from the equations. Copyright © 2018 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Chandra Observations of MS0440.5+0204 & MS0839.9+2938: Cooling Flow Clusters in Formation?

NASA Astrophysics Data System (ADS)

McNamara, Brian

2000-09-01

We propose to observe two redshift z~0.2 clusters, MS0839.9+2938 and MS0440+0204, discovered as bright X-ray sources in the Einstein Medium Sensitivity Survey. The cluster cores are structured in the X-ray and optical bands, and they harbor large cooling flows. Their central cluster galaxies contain luminous nebular emission systems, active star formation, and strong radio sources. Using the Chandra data, we will determine whether the large discrepancies between the X-ray cooling rates and optical star formation rates can be reconciled, and we will test the hypothesis that cooling flows form as cool, dense groups accrete into massive clusters.

High-bandwidth continuous-flow arc furnace

DOEpatents

Hardt, David E.; Lee, Steven G.

1996-01-01

A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics.

High-bandwidth continuous-flow arc furnace

DOEpatents

Hardt, D.E.; Lee, S.G.

1996-08-06

A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics. 4 figs.

Magma supply dynamics at Westdahl volcano, Alaska, modeled from satellite radar interferometry

USGS Publications Warehouse

Lu, Z.; Masterlark, Timothy; Dzurisin, D.; Rykhus, Russ; Wicks, C.

2003-01-01

A group of satellite radar interferograms that span the time period from 1991 to 2000 shows that Westdahl volcano, Alaska, deflated during its 1991-1992 eruption and is reinflating at a rate that could produce another eruption within the next several years. The rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days, respectively. This behavior is consistent with a deep, constant-pressure magma source connected to a shallow reservoir by a magma-filled conduit. An elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath Westdahl Peak. We propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir. The pressure gradient, and hence the flow rate, are greatest immediately after eruptions. Pressurization of the reservoir decreases both the pressure gradient and the flow rate, but eventually the reservoir ruptures and an eruption or intrusion ensues. The eruption rate is controlled partly by the pressure gradient between the reservoir and surface, and therefore it, too, decreases with time. When the supply of eruptible magma is exhausted, the eruption stops, the reservoir begins to repressurize at a high rate, and the cycle repeats. This model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems.

Constraints of nonresponding flows based on cross layers in the networks

NASA Astrophysics Data System (ADS)

Zhou, Zhi-Chao; Xiao, Yang; Wang, Dong

2016-02-01

In the active queue management (AQM) scheme, core routers cannot manage and constrain user datagram protocol (UDP) data flows by the sliding window control mechanism in the transport layer due to the nonresponsive nature of such traffic flows. However, the UDP traffics occupy a large part of the network service nowadays which brings a great challenge to the stability of the more and more complex networks. To solve the uncontrollable problem, this paper proposes a cross layers random early detection (CLRED) scheme, which can control the nonresponding UDP-like flows rate effectively when congestion occurs in the access point (AP). The CLRED makes use of the MAC frame acknowledgement (ACK) transmitting congestion information to the sources nodes and utilizes the back-off windows of the MAC layer throttling data rate. Consequently, the UDP-like flows data rate can be restrained timely by the sources nodes in order to alleviate congestion in the complex networks. The proposed CLRED can constrain the nonresponsive flows availably and make the communication expedite, so that the network can sustain stable. The simulation results of network simulator-2 (NS2) verify the proposed CLRED scheme.

Nonlinear Gravitational and Radiation Aspects in Nanoliquid with Exponential Space Dependent Heat Source and Variable Viscosity

NASA Astrophysics Data System (ADS)

Gireesha, B. J.; Kumar, P. B. Sampath; Mahanthesh, B.; Shehzad, S. A.; Abbasi, F. M.

2018-05-01

The nonlinear convective flow of kerosene-Alumina nanoliquid subjected to an exponential space dependent heat source and temperature dependent viscosity is investigated here. This study is focuses on augmentation of heat transport rate in liquid propellant rocket engine. The kerosene-Alumina nanoliquid is considered as the regenerative coolant. Aspects of radiation and viscous dissipation are also covered. Relevant nonlinear system is solved numerically via RK based shooting scheme. Diverse flow fields are computed and examined for distinct governing variables. We figured out that the nanoliquid's temperature increased due to space dependent heat source and radiation aspects. The heat transfer rate is higher in case of changeable viscosity than constant viscosity.

Nonlinear Gravitational and Radiation Aspects in Nanoliquid with Exponential Space Dependent Heat Source and Variable Viscosity

NASA Astrophysics Data System (ADS)

Gireesha, B. J.; Kumar, P. B. Sampath; Mahanthesh, B.; Shehzad, S. A.; Abbasi, F. M.

2018-02-01

The nonlinear convective flow of kerosene-Alumina nanoliquid subjected to an exponential space dependent heat source and temperature dependent viscosity is investigated here. This study is focuses on augmentation of heat transport rate in liquid propellant rocket engine. The kerosene-Alumina nanoliquid is considered as the regenerative coolant. Aspects of radiation and viscous dissipation are also covered. Relevant nonlinear system is solved numerically via RK based shooting scheme. Diverse flow fields are computed and examined for distinct governing variables. We figured out that the nanoliquid's temperature increased due to space dependent heat source and radiation aspects. The heat transfer rate is higher in case of changeable viscosity than constant viscosity.

Theory for source-responsive and free-surface film modeling of unsaturated flow

USGS Publications Warehouse

Nimmo, J.R.

2010-01-01

A new model explicitly incorporates the possibility of rapid response, across significant distance, to substantial water input. It is useful for unsaturated flow processes that are not inherently diffusive, or that do not progress through a series of equilibrium states. The term source-responsive is used to mean that flow responds sensitively to changing conditions at the source of water input (e.g., rainfall, irrigation, or ponded infiltration). The domain of preferential flow can be conceptualized as laminar flow in free-surface films along the walls of pores. These films may be considered to have uniform thickness, as suggested by field evidence that preferential flow moves at an approximately uniform rate when generated by a continuous and ample water supply. An effective facial area per unit volume quantitatively characterizes the medium with respect to source-responsive flow. A flow-intensity factor dependent on conditions within the medium represents the amount of source-responsive flow at a given time and position. Laminar flow theory provides relations for the velocity and thickness of flowing source-responsive films. Combination with the Darcy-Buckingham law and the continuity equation leads to expressions for both fluxes and dynamic water contents. Where preferential flow is sometimes or always significant, the interactive combination of source-responsive and diffuse flow has the potential to improve prediction of unsaturated-zone fluxes in response to hydraulic inputs and the evolving distribution of soil moisture. Examples for which this approach is efficient and physically plausible include (i) rainstorm-generated rapid fluctuations of a deep water table and (ii) space- and time-dependent soil water content response to infiltration in a macroporous soil. ?? Soil Science Society of America.

Aerodynamic performance of a low-speed wind tunnel.

PubMed

Frechen, F-B; Frey, M; Wett, M; Löser, C

2004-01-01

The determination of the odour mass flow emitted from a source is a very important step and forms the basis for all subsequent considerations and calculations. Wastewater treatment plants, as well as waste treatment facilities, consist of different kinds of odour sources. Unfortunately, most of the sources are passive sources, where no outward air flow-rate can be measured, but where odorants are obviously emitted. Thus, a type of sampling is required that allows to measure the emitted odour flow-rate (OFR). To achieve this, different methods are in use worldwide. Besides indirect methods, such as micrometeorological atmospheric dispersion models, which have not been used in Germany (in other countries due to different problems, direct methods are also used). Direct measurements include hood methods, commonly divided into static flux chambers, dynamic flux chambers and wind tunnels. The wind tunnel that we have been operating in principle since 1983 is different from all subsequent presented wind tunnels, in that we operate it at a considerably lower wind speed than the others. To describe the behaviour of this wind tunnel, measurement of the flow pattern in this low-speed tunnel are under way, and some initial results are presented here.

Oscillatory bedload transport: Data review and simple formulation

NASA Astrophysics Data System (ADS)

Hallermeier, Robert J.

1982-11-01

This review displays over 700 rates of sediment transport by oscillatory flow from 20 sources. Sediments include fine sands to pebbles, both of quartz and of lightweight materials, and the transport rates in water range over seven orders of magnitude. Most data are average gross (to and fro) bedload rates collinear with laboratory flow over a horizontal sediment bed, although other situations with net transport, suspended load, or oblique field waves are considered. As peak flow velocity nears twice the threshold velocity for sediment motion, bedload appears to be fully developed and the transport rate is near that given by a simple formula including flow frequency and peak velocity, and sediment size and density. At lesser peak velocities, bedload rates are markedly smaller and distinctly different regimes of sediment mobilization and transport may be identified.

The 1984 Mauna Loa eruption and planetary geolgoy

NASA Technical Reports Server (NTRS)

Moore, Henry J.

1987-01-01

In planetary geology, lava flows on the Moon and Mars are commonly treated as relatively simple systems. Some of the complexities of actual lava flows are illustrated using the main flow system of the 1984 Mauna Loa eruption. The outline, brief narrative, and results given are based on a number of sources. The implications of the results to planetary geology are clear. Volume flow rates during an eruption depend, in part, on the volatile content of the lava. These differ from the volume flow rates calculated from post eruption flow dimensions and the duration of the eruption and from those using models that assume a constant density. Mass flow rates might be more appropriate because the masses of volatiles in lavas are usually small, but variable and sometimes unknown densities impose severe restrictions on mass estimates.

Effects of episodic sediment supply on bedload transport rate in mountain rivers. Detecting debris flow activity using continuous monitoring

NASA Astrophysics Data System (ADS)

Uchida, Taro; Sakurai, Wataru; Iuchi, Takuma; Izumiyama, Hiroaki; Borgatti, Lisa; Marcato, Gianluca; Pasuto, Alessandro

2018-04-01

Monitoring of sediment transport from hillslopes to channel networks as a consequence of floods with suspended and bedload transport, hyperconcentrated flows, debris and mud flows is essential not only for scientific issues, but also for prevention and mitigation of natural disasters, i.e. for hazard assessment, land use planning and design of torrent control interventions. In steep, potentially unstable terrains, ground-based continuous monitoring of hillslope and hydrological processes is still highly localized and expensive, especially in terms of manpower. In recent years, new seismic and acoustic methods have been developed for continuous bedload monitoring in mountain rivers. Since downstream bedload transport rate is controlled by upstream sediment supply from tributary channels and bed-external sources, continuous bedload monitoring might be an effective tool for detecting the sediments mobilized by debris flow processes in the upper catchment and thus represent an indirect method to monitor slope instability processes at the catchment scale. However, there is poor information about the effects of episodic sediment supply from upstream bed-external sources on downstream bedload transport rate at a single flood time scale. We have examined the effects of sediment supply due to upstream debris flow events on downstream bedload transport rate along the Yotagiri River, central Japan. To do this, we have conducted continuous bedload observations using a hydrophone (Japanese pipe microphone) located 6.4 km downstream the lower end of a tributary affected by debris flows. Two debris flows occurred during the two-years-long observation period. As expected, bedload transport rate for a given flow depth showed to be larger after storms triggering debris flows. That is, although the magnitude of sediment supply from debris flows is not large, their effect on bedload is propagating >6 km downstream at a single flood time scale. This indicates that continuous bedload observations could be effective for detecting sediment supply as a consequence of debris flow events.

Rootless shield and perched lava pond collapses at Kīlauea Volcano, Hawai'i

USGS Publications Warehouse

Patrick, Matthew R.; Orr, Tim R.

2012-01-01

Effusion rate is a primary measurement used to judge the expected advance rate, length, and hazard potential of lava flows. At basaltic volcanoes, the rapid draining of lava stored in rootless shields and perched ponds can produce lava flows with much higher local effusion rates and advance velocities than would be expected based on the effusion rate at the vent. For several months in 2007–2008, lava stored in a series of perched ponds and rootless shields on Kīlauea Volcano, Hawai'i, was released episodically to produce fast-moving 'a'ā lava flows. Several of these lava flows approached Royal Gardens subdivision and threatened the safety of remaining residents. Using time-lapse image measurements, we show that the initial time-averaged discharge rate for one collapse-triggered lava flow was approximately eight times greater than the effusion rate at the vent. Though short-lived, the collapse-triggered 'a'ā lava flows had average advance rates approximately 45 times greater than that of the pāhoehoe flow field from which they were sourced. The high advance rates of the collapse-triggered lava flows demonstrates that recognition of lava accumulating in ponds and shields, which may be stored in a cryptic manner, is vital for accurately assessing short-term hazards at basaltic volcanoes.

Numerical simulation of two-dimensional flow over a heated carbon surface with coupled heterogeneous and homogeneous reactions

NASA Astrophysics Data System (ADS)

Johnson, Ryan Federick; Chelliah, Harsha Kumar

2017-01-01

For a range of flow and chemical timescales, numerical simulations of two-dimensional laminar flow over a reacting carbon surface were performed to understand further the complex coupling between heterogeneous and homogeneous reactions. An open-source computational package (OpenFOAM®) was used with previously developed lumped heterogeneous reaction models for carbon surfaces and a detailed homogeneous reaction model for CO oxidation. The influence of finite-rate chemical kinetics was explored by varying the surface temperatures from 1800 to 2600 K, while flow residence time effects were explored by varying the free-stream velocity up to 50 m/s. The reacting boundary layer structure dependence on the residence time was analysed by extracting the ratio of chemical source and species diffusion terms. The important contributions of radical species reactions on overall carbon removal rate, which is often neglected in multi-dimensional simulations, are highlighted. The results provide a framework for future development and validation of lumped heterogeneous reaction models based on multi-dimensional reacting flow configurations.

Steam distillation extraction of ginger essential oil: Study of the effect of steam flow rate and time process

NASA Astrophysics Data System (ADS)

Fitriady, Muhammad Arifuddin; Sulaswatty, Anny; Agustian, Egi; Salahuddin, Aditama, Deska Prayoga Fauzi

2017-01-01

In Indonesia ginger was usually used as a seasoning for dishes, an ingredient for beverage and a source of herbal medicines. Beside raw usage, ginger can be processed to obtain the essential oil which has many advantages such as proven to be an active antimicrobial and having an antioxidant ability. There are a lot of methods to extract essential oil from ginger, one of which is steam distillation. The aim of the current study was to investigate the effect of variation of time process and steam flow rate in the yield on ginger essential oil steam distillation extraction process. It was found that the best operation condition was 0.35 ml/s as the steam flow rate which yields 2.43% oil. The optimum time process was predicted at 7.5 hours. The composition of the oil was varied depend on the flow rate and every flow rate has its own major component contained in the oil. Curcumene composition in the oil was increased as increased steam flow rate applied, but the composition of camphene was decreased along with the increasing steam flow rate.

Effects of seawater flow rate and evaporation temperature on performance of Sherbet type ice making machine

NASA Astrophysics Data System (ADS)

Son, C. H.; Yoon, J. I.; Choi, K. H.; Lee, H. K.; Lee, K. S.; Moon, C. G.; Seol, S. H.

2018-01-01

This study analyzes performance of the sherbet type ice making machine using seawater with respect to seawater volumetric flow rate, evaporation temperature, cooling water inlet and seawater inlet temperature as variables. Cooling water inlet and seawater inlet temperature are set considering average temperature of South Korea and the equator regions. Volumetric flow rate of seawater range is 0.75-1.75 LPM in this experiment. The results obtained from the experiment are as follows. As the seawater volumetric flow rate increases, or seawater inlet temperature increases, evaporation capacity tends to increase. At the point of seawater inlet temperature of 27°C and volumetric flow rate of 1.0LPM, evaporation capacity is over 2kW. On the other hand, results of COP change tendency are different from that of evaporation capacity. It appears to increase until volumetric flow rate of 1.0LPM, and decrease gradually from volumetric flow rate of 1.5LPM. This is due to the increase of compressor work to keep the evaporation pressure in accordance with the temperature of heat source. As the evaporation temperature decreases from -8 to -15°C, the evaporation capacity increases, but the COP decreases.

Flow visualization and acoustic consequences of the air moving through a static model of the human larynx.

PubMed

Kucinschi, Bogdan R; Scherer, Ronald C; DeWitt, Kenneth J; Ng, Terry T M

2006-06-01

Flow visualization with smoke particles illuminated by a laser sheet was used to obtain a qualitative description of the air flow structures through a dynamically similar 7.5x symmetric static scale model of the human larynx (divergence angle of 10 deg, minimal diameter of 0.04 cm real life). The acoustic level downstream of the vocal folds was measured by using a condenser microphone. False vocal folds (FVFs) were included. In general, the glottal flow was laminar and bistable. The glottal jet curvature increased with flow rate and decreased with the presence of the FVFs. The glottal exit flow for the lowest flow rate showed a curved jet which remained laminar for all geometries. For the higher flow rates, the jet flow patterns exiting the glottis showed a laminar jet core, transitioning to vortical structures, and leading spatially to turbulent dissipation. This structure was shortened and tightened with an increase in flow rate. The narrow FVF gap lengthened the flow structure and reduced jet curvature via acceleration of the flow. These results suggest that laryngeal flow resistance and the complex jet flow structure exiting the glottis are highly affected by flow rate and the presence of the false vocal folds. Acoustic consequences are discussed in terms of the quadrupole- and dipole-type sound sources due to ordered flow structures.

Advection within shallow pore waters of a coastal lagoon, Florida

USGS Publications Warehouse

Cable, J.E.; Martin, Jonathan B.; Swarzenski, Peter W.; Lindenberg, Mary K.; Steward, Joel

2004-01-01

Ground water sources can be a significant portion of a local water budget in estuarine environments, particularly in areas with high recharge rates, transmissive aquifers, and permeable marine sediments. However, field measurements of ground water discharge are often incongruent with ground water flow modeling results, leaving many scientists unsure which estimates are accurate. In this study, we find that both measurements and model results are reasonable. The difference between estimates apparently results from the sources of water being measured and not the techniques themselves. In two locations in the Indian River Lagoon estuarine system, we found seepage meter rates similar to rates calculated from the geochemical tracers 222Rn and 226Ra. Ground water discharge rates ranged from 4 to 9 cm/d using seepage meters and 3 to 20 cm/d using 222Rn and 226Ra. In contrast, in comparisons to other studies where finite element ground water flow modeling was used, much lower ground water discharge rates of ∼0.05 to 0.15 cm/d were estimated. These low rates probably represent discharge of meteoric ground water from land-recharged aquifers, while the much higher rates measured with seepage meters, 222Rn, and 226Ra likely include an additional source of surface waters that regularly flush shallow (< 1 m depth) sediments. This resultant total flow of mixed land-recharged water and recirculated surface waters contributes to the total biogeochemical loading in this shallow estuarine environment.

The flow structure of jets from transient sources and implications for modeling short-duration explosive volcanic eruptions

NASA Astrophysics Data System (ADS)

Chojnicki, K. N.; Clarke, A. B.; Adrian, R. J.; Phillips, J. C.

2014-12-01

We used laboratory experiments to examine the rise process in neutrally buoyant jets that resulted from an unsteady supply of momentum, a condition that defines plumes from discrete Vulcanian and Strombolian-style eruptions. We simultaneously measured the analog-jet discharge rate (the supply rate of momentum) and the analog-jet internal velocity distribution (a consequence of momentum transport and dilution). Then, we examined the changes in the analog-jet velocity distribution over time to assess the impact of the supply-rate variations on the momentum-driven rise dynamics. We found that the analog-jet velocity distribution changes significantly and quickly as the supply rate varied, such that the whole-field distribution at any instant differed considerably from the time average. We also found that entrainment varied in space and over time with instantaneous entrainment coefficient values ranging from 0 to 0.93 in an individual unsteady jet. Consequently, we conclude that supply-rate variations exert first-order control over jet dynamics, and therefore cannot be neglected in models without compromising their capability to predict large-scale eruption behavior. These findings emphasize the fundamental differences between unsteady and steady jet dynamics, and show clearly that: (i) variations in source momentum flux directly control the dynamics of the resulting flow; (ii) impulsive flows driven by sources of varying flux cannot reasonably be approximated by quasi-steady flow models. New modeling approaches capable of describing the time-dependent properties of transient volcanic eruption plumes are needed before their trajectory, dilution, and stability can be reliably computed for hazards management.

Generalized Fluid System Simulation Program (GFSSP) - Version 6

NASA Technical Reports Server (NTRS)

Majumdar, Alok; LeClair, Andre; Moore, Ric; Schallhorn, Paul

2015-01-01

The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors, flow control valves and external body forces such as gravity and centrifugal. The thermo-fluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids, and 24 different resistance/source options are provided for modeling momentum sources or sinks in the branches. Users can introduce new physics, non-linear and time-dependent boundary conditions through user-subroutine.

Influence of turbulent fluctuations on non-equilibrium chemical reactions in the flow

NASA Astrophysics Data System (ADS)

Molchanov, A. M.; Yanyshev, D. S.; Bykov, L. V.

2017-11-01

In chemically nonequilibrium flows the problem of calculation of sources (formation rates) in equations for chemical species is of utter importance. Formation rate of each component is a non-linear function of mixture density, temperature and concentration of species. Thus the suggestion that the mean rate may be determined via mean values of the flow parameters could lead to significant errors. One of the most accurate approaches here is utilization of probability density function (PDF). In this paper the method for constructing such PDFs is developed. The developed model was verified by comparison with the experimental data. On the example of supersonic combustion it was shown that while the overall effect on the averaged flow field is often negligible, the point of ignition can be considerably shifted up the flow.

[Difference of water relationships of poplar trees in Zhangbei County, Hebei, China based on stable isotope and thermal dissipation method].

PubMed

Miao, Bo; Meng, Ping; Zhang, Jin Song; He, Fang Jie; Sun, Shou Jia

2017-07-18

The water sources and transpiration of poplar trees in Zhangbei County were measured using stable hydrogen isotope and thermal dissipation method. The differences in water relationships between dieback and non-dieback poplar trees were analyzed. The results showed that the dieback trees mainly used shallow water from 0-30 cm soil layer during growing season while the non-dieback trees mainly used water from 30-80 cm soil layer. There was a significant difference in water source between them. The non-dieback trees used more water from middle and deep soil layers than that of the dieback trees during the dry season. The percentage of poplar trees using water from 0-30 cm soil layer increased in wet season, and the increase of dieback trees was higher than that of non-dieback trees. The contributions of water from 30-180 cm soil layer of dieback and non-dieback trees both decreased in wet season. The sap flow rate of non-dieback trees was higher than that of dieback trees. There was a similar variation tend of sap flow rate between dieback and non-dieback trees in different weather conditions, but the start time of sap flow of non-dieback trees was earlier than that of dieback trees. Correlation analysis showed that the sap flow rate of either dieback or non-dieback poplar trees strongly related to soil temperature, wind speed, photosynthetically active radiation, relative humidity and air temperature. The sap flow rate of die-back poplar trees strongly negatively related to soil temperature and relative humidity, and strongly positively related to the other factors. The sap flow rate of non-dieback poplar trees only strongly negatively related to relative humidity but positively related to the other factors. The results revealed transpiration of both poplar trees was easily affected by environmental factors. The water consumption of dieback trees was less than non-dieback trees because the cumulative sap flow amount of dieback trees was lower. Reduced transpiration of dieback trees couldn't help to prevent poplar forest declining due to shallow water source.

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2012 CFR

2012-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2010 CFR

2010-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2011 CFR

2011-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

CALUTRON CONTROL DEVICE

DOEpatents

Baldwin, L.W.

1959-08-25

Several interlock and control circuits for a calutron are described. In one of the arrangements, the ton source cooling water flow is interlocked with the current supply to the heaters assoctated with the charge chamber, arc chamber, and electrode structure. When the ion source coolant flow rate exceeds a predetermined level, the heater associated with the charge chamber is energized. After the charge chamber has reached a predetermined temperature, the arc chamber heater is energized. Thereafter, the electrode structure heater is energized and the ion source is ready to have the operating voltages applied.

Patterns and age distribution of ground-water flow to streams

USGS Publications Warehouse

Modica, E.; Reilly, T.E.; Pollock, D.W.

1997-01-01

Simulations of ground-water flow in a generic aquifer system were made to characterize the topology of ground-water flow in the stream subsystem and to evaluate its relation to deeper ground-water flow. The flow models are patterned after hydraulic characteristics of aquifers of the Atlantic Coastal Plain and are based on numerical solutions to three-dimensional, steady-state, unconfined flow. The models were used to evaluate the effects of aquifer horizontal-to-vertical hydraulic conductivity ratios, aquifer thickness, and areal recharge rates on flow in the stream subsystem. A particle tracker was used to determine flow paths in a stream subsystem, to establish the relation between ground-water seepage to points along a simulated stream and its source area of flow, and to determine ground-water residence time in stream subsystems. In a geometrically simple aquifer system with accretion, the source area of flow to streams resembles an elongated ellipse that tapers in the downgradient direction. Increased recharge causes an expansion of the stream subsystem. The source area of flow to the stream expands predominantly toward the stream headwaters. Baseflow gain is also increased along the reach of the stream. A thin aquifer restricts ground-water flow and causes the source area of flow to expand near stream headwaters and also shifts the start-of-flow to the drainage basin divide. Increased aquifer anisotropy causes a lateral expansion of the source area of flow to streams. Ground-water seepage to the stream channel originates both from near- and far-recharge locations. The range in the lengths of flow paths that terminate at a point on a stream increase in the downstream direction. Consequently, the age distribution of ground water that seeps into the stream is skewed progressively older with distance downstream. Base flow ia an integration of ground water with varying age and potentially different water quality, depending on the source within the drainage basin. The quantitative results presented indicate that this integration can have a wide and complex residence time range and source distribution.

ION SOURCE FOR A CALUTRON

DOEpatents

Lofgren, E.J.

1959-04-14

This patcnt relates to calutron devices and deals particularly with the mechanism used to produce the beam of ions wherein a charge material which is a vapor at room temperature is used. A charge container located outside the tank is connected through several conduits to various points along the arc chamber of the ion source. In addition, the rate of flow of the vapor to the arc chamber is controlled by a throttle valve in each conduit. By this arrangement the arc can be regulated accurately and without appreciable time lag, inasmuch as the rate of vapor flow is immediately responsive to the manipulation of the throttle valves.

ANALYTICAL ASSESSMENT OF THE IMPACTS OF PARTIAL MASS DEPLETION IN DNAPL SOURCE ZONES (SAN FRANCISCO, CA)

EPA Science Inventory

Analytical solutions describing the time-dependent DNAPL source-zone mass and contaminant discharge rate are used as a flux-boundary condition in a semi-analytical contaminant transport model. These analytical solutions assume a power relationship between the flow-averaged sourc...

Impact of Pitot tube calibration on the uncertainty of water flow rate measurement

NASA Astrophysics Data System (ADS)

de Oliveira Buscarini, Icaro; Costa Barsaglini, Andre; Saiz Jabardo, Paulo Jose; Massami Taira, Nilson; Nader, Gilder

2015-10-01

Water utility companies often use Cole type Pitot tubes to map velocity profiles and thus measure flow rate. Frequent monitoring and measurement of flow rate is an important step in identifying leaks and other types of losses. In Brazil losses as high as 42% are common and in some places even higher values are found. When using Cole type Pitot tubes to measure the flow rate, the uncertainty of the calibration coefficient (Cd) is a major component of the overall flow rate measurement uncertainty. A common practice is to employ the usual value Cd = 0.869, in use since Cole proposed his Pitot tube in 1896. Analysis of 414 calibrations of Cole type Pitot tubes show that Cd varies considerably and values as high 0.020 for the expanded uncertainty are common. Combined with other uncertainty sources, the overall velocity measurement uncertainty is 0.02, increasing flowrate measurement uncertainty by 1.5% which, for the Sao Paulo metropolitan area (Brazil) corresponds to 3.5 × 107 m3/year.

Rotating coherent flow structures as a source for narrowband tip clearance noise from axial fans

NASA Astrophysics Data System (ADS)

Zhu, Tao; Lallier-Daniels, Dominic; Sanjosé, Marlène; Moreau, Stéphane; Carolus, Thomas

2018-03-01

Noise from axial fans typically increases significantly as the tip clearance is increased. In addition to the broadband tip clearance noise at the design flow rate, narrowband humps also associated with the tip flow are observed in the far-field acoustic spectra at lower flow rate. In this study, both experimental and numerical methods are used to shed more light on the noise generation mechanism of this narrowband tip clearance noise and provide a unified description of this source. Unsteady aeroacoustic predictions with the Lattice-Boltzmann Method (LBM) are successfully compared with experiment. Such a validation allows using LBM data to conduct a detailed modal analysis of the pressure field for detecting rotating coherent flow structures which might be considered as noise sources. As previously found in ring fans the narrowband humps in the far-field noise spectra are found to be related to the tip clearance noise that is generated by an interaction of coherent flow structures present in the tip region with the leading edge of the impeller blades. The visualization of the coherent structures shows that they are indeed part of the unsteady tip clearance vortex structures. They are hidden in a complex, spatially and temporally inhomogeneous flow field, but can be recovered by means of appropriate filtering techniques. Their pressure trace corresponds to the so-called rotational instability identified in previous turbomachinery studies, which brings a unified picture of this tip-noise phenomenon for the first time.

Preventing Bandwidth Abuse at the Router through Sending Rate Estimate-based Active Queue Management

DTIC Science & Technology

2007-06-01

behavior is growing in the Internet. These non-responsive sources can monopolize network bandwidth and starve the “congestion friendly” flows. Without...unnecessarily complex because most of the flows in the Internet are short flows usually termed as “web mice ” [7]. Moreover, having a separate queue for each

Qualitative modeling of silica plasma etching using neural network

NASA Astrophysics Data System (ADS)

Kim, Byungwhan; Kwon, Kwang Ho

2003-01-01

An etching of silica thin film is qualitatively modeled by using a neural network. The process was characterized by a 23 full factorial experiment plus one center point, in which the experimental factors and ranges include 100-800 W radio-frequency source power, 100-400 W bias power and gas flow rate ratio CHF3/CF4. The gas flow rate ratio varied from 0.2 to 5.0. The backpropagation neural network (BPNN) was trained on nine experiments and tested on six experiments, not pertaining to the original training data. The prediction ability of the BPNN was optimized as a function of the training parameters. Prediction errors are 180 Å/min and 1.33, for the etch rate and anisotropy models, respectively. Physical etch mechanisms were estimated from the three-dimensional plots generated from the optimized models. Predicted response surfaces were consistent with experimentally measured etch data. The dc bias was correlated to the etch responses to evaluate its contribution. Both the source power (plasma density) and bias power (ion directionality) strongly affected the etch rate. The source power was the most influential factor for the etch rate. A conflicting effect between the source and bias powers was noticed with respect to the anisotropy. The dc bias played an important role in understanding or separating physical etch mechanisms.

Spatial and Temporal Patterns of Dissolved Organic Matter Characteristics in the Upper Willamette River Basin, Oregon

NASA Astrophysics Data System (ADS)

Lee, B. S.; Lajtha, K.

2014-12-01

Dissolved organic matter (DOM) leaching through soil affects soil carbon sequestration and the carbon metabolism of receiving water bodies. Improving our understanding of the sources and fate of DOM at varying spatial and temporal patterns is crucial for land management decisions. However, little is known about how DOM sources change with land use types and seasonal flow patterns. In the Willamette River Basin (WRB), which is home to Oregon's major cities including Portland and Salem, forested headwaters transition to agricultural and urban land. The climate of WRB has a distinctive seasonal pattern with dry warm summers and wet winters driven by winter precipitation and snowmelt runoff between November and March. This study examined DOM fluorescence characteristic in stream water from 21 locations collected monthly and 16 locations collected seasonally to identify the sources and fate of DOM in the upper WRB in contrasting land uses. DOC and dissolved organic nitrogen concentrations increased as the flow rate increased during winter precipitation at all sites. This indicates that increased flow rate increased the connectivity between land and nearby water bodies. DOM fluorescent properties varied among land use types. During the first precipitation event after a long dry summer, a microbial DOM signature in agricultural areas increased along with nitrate concentrations. This may be because accumulated nutrients on land during the dry season flowed to nearby streams during the first rain event and promoted microbial growth in the streams. During the month of the highest flow rate in 2014, sampling sites near forest showed evidence of a greater terrestrial DOM signature compared to its signature during the dry season. This indicates fluorescent DOM characteristics in streams vary as the flow connectivity changes even within the same land type.

Salinization Sources Along the Lower Jordan River Under Draught Conditions

NASA Astrophysics Data System (ADS)

Holtzman, R.; Shavit, U.; Segal, M.; Vengosh, A.; Farber, E.; Gavrieli, I.

2003-12-01

The Lower Jordan River, once a flowing freshwater river, is suffering from an ongoing reduction of discharge and water quality. The river flows between the Sea of Galilee and the Dead Sea, an aerial distance of about 105 Km. The severe reduction is caused by an excessive exploitation of its sources and diversion of sewage and agricultural drainage into the river. The extreme low flows and low water quality threaten the natural existence of the river and its potential use for agriculture. In spite of its importance, little research has been done in the river. The objectives of the study were to measure the discharge and water composition along the river and to evaluate the main sources that control its flow and chemical characteristics. The hypothesis of the study was that interaction with subsurface flows significantly affects the river flow and chemical composition. The research is based on a detailed field study, which included flow rate measurements in the river and its tributaries, water sampling and analysis and mass balance calculations of water and solutes. A portable Acoustic Doppler Velocimeter (ADV) was used to measure velocities and bathymetry at different locations across the river sections. Due to accessibility constraints, a floating traverse construction, which enables the ADV's deployment from one bank of the river, was developed. It was found that flow rate ranges between 500-1,100 L/s in northern (upstream) sections and 300-1,650 L/s in the south. This low discharge represents a significant reduction from historical values and is lower than recent published estimations. This research represents base flows only, as the measurements were done during a period of two consecutive draught years. Calculated mass balance of water flows in the northern sections shows that the subsurface source contributes to the river around 200-670 L/s (30-80% of the river flow). Calculations of solute balance show that the subsurface flows add 20-50% of the mass of solutes (e.g. Sulfate) that flows in the river. The assumption of a hydraulic gradient that points at inflows from subsurface flows is encouraged by high water levels measured in nearby piezometers. Possible natural subsurface sources include shallow groundwater or rising of water from deep formations. The existence of adjacent thermal wells strengthens the reasonability of such water rise. Possible anthropogenic sources include return flows and effluents. The results are consistent and agree with the geochemical and isotopic analyses. It is concluded that the impact of the subsurface component on the Jordan River is significant and must be taken into consideration, for future water management schemes and implementation of the Peace Treaty between Israel and Jordan.

Influence of oxygen concentration, fuel composition, and strain rate on synthesis of carbon nanomaterials

NASA Astrophysics Data System (ADS)

Hou, Shuhn-Shyurng; Huang, Wei-Cheng

2015-02-01

This paper investigates the influence of flame parameters including oxygen concentration, fuel composition, and strain rate on the synthesis of carbon nanomaterials in opposed-jet ethylene diffusion flames with or without rigid-body rotation. In the experiments, a mixture of ethylene and nitrogen was introduced from the upper burner; meanwhile, a mixture of oxygen and nitrogen was supplied from the lower burner. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. With non-rotating opposed-jet diffusion flames, carbon nanotubes (CNTs) were successfully produced for oxygen concentrations in the range of 21-50 % at a fixed ethylene concentration of 20 %, and for ethylene concentrations ranging from 14 to 24 % at a constant oxygen concentration of 40 %. With rotating opposed-jet diffusion flames, the strain rate was varied by adjusting the angular velocities of the upper and lower burners. The strain rate governed by flow rotation greatly affects the synthesis of carbon nanomaterials [i.e., CNTs and carbon nano-onions (CNOs)] either through the residence time or carbon sources available. An increase in the angular velocity lengthened the residence time of the flow and thus caused the diffusion flame to experience a decreased strain rate, which in turn produced more carbon sources. The growth of multi-walled CNTs was achieved for the stretched flames experiencing a higher strain rate [i.e., angular velocity was equal to 0 or 1 rotations per second (rps)]. CNOs were synthesized at a lower strain rate (i.e., angular velocity was in the range of 2-5 rps). It is noteworthy that the strain rate controlled by flow rotation greatly influences the fabrication of carbon nanostructures owing to the residence time as well as carbon source. Additionally, more carbon sources and higher temperature are required for the synthesis of CNOs compared with those required for CNTs (i.e., about 605-625 °C for CNTs and 700-800 °C for CNOs).

Experimental Investigation of A Heat Pipe-Assisted Latent Heat Thermal Energy Storage System

NASA Astrophysics Data System (ADS)

Tiari, Saeed; Mahdavi, Mahboobe; Qiu, Songgang

2016-11-01

In the present work, different operation modes of a latent heat thermal energy storage system assisted by a heat pipe network were studied experimentally. Rubitherm RT55 enclosed by a vertical cylindrical container was used as the Phase Change Material (PCM). The embedded heat pipe network consisting of a primary heat pipe and an array of four secondary heat pipes were employed to transfer heat to the PCM. The primary heat pipe transports heat from the heat source to the heat sink. The secondary heat pipes transfer the extra heat from the heat source to PCM during charging process or retrieve thermal energy from PCM during discharging process. The effects of heat transfer fluid (HTF) flow rate and temperature on the thermal performance of the system were investigated for both charging and discharging processes. It was found that the HTF flow rate has a significant effect on the total charging time of the system. Increasing the HTF flow rate results in a remarkable increase in the system input thermal power. The results also showed that the discharging process is hardly affected by the HTF flow rate but HTF temperature plays an important role in both charging and discharging processes. The authors would like to acknowledge the financial supports by Temple University for the project.

Breakdown characteristics of atmospheric dielectric barrier discharge in gas flow condition

NASA Astrophysics Data System (ADS)

Fan, Zhihui; Yan, Huijie; Wang, Yuying; Liu, Yidi; Guo, Hongfei; Ren, Chunsheng

2018-05-01

Experimental investigations of the breakdown characteristics of plate-to-plate dielectric barrier discharge excited by an AC source at different gas flow conditions are carried out. The ignition voltage for the appearance of the very first discharge filament and the breakdown voltage in each discharge half cycle in continuous operation are examined. As revealed by the results of the indoor air experiment, the ignition voltage manifests a monotonous increase with the increase in the gas flow rate, while the breakdown voltage has a marked decline at the low gas flow rate and increases slightly as the gas flow rate is higher than 10 m/s. As regards the obvious decreases in the ignition voltage and breakdown voltage, the decrease in the humidity with the increase in the gas flow rate plays a dominant role. As regards the increase in breakdown voltage, the memory effect from the preceding discharge is considered. The losses of metastable particles, together with particles having high translational energy in the gas flow, are considered to be the most critical factors.

Accretion flow dynamics during 1999 outburst of XTE J1859+226—modeling of broadband spectra and constraining the source mass

NASA Astrophysics Data System (ADS)

Nandi, Anuj; Mandal, S.; Sreehari, H.; Radhika, D.; Das, Santabrata; Chattopadhyay, I.; Iyer, N.; Agrawal, V. K.; Aktar, R.

2018-05-01

We examine the dynamical behavior of accretion flow around XTE J1859+226 during the 1999 outburst by analyzing the entire outburst data (˜166 days) from RXTE Satellite. Towards this, we study the hysteresis behavior in the hardness intensity diagram (HID) based on the broadband (3-150 keV) spectral modeling, spectral signature of jet ejection and the evolution of Quasi-periodic Oscillation (QPO) frequencies using the two-component advective flow model around a black hole. We compute the flow parameters, namely Keplerian accretion rate (\\dot{m}d), sub-Keplerian accretion rate (\\dot{m}h), shock location (rs) and black hole mass (M_{bh}) from the spectral modeling and study their evolution along the q-diagram. Subsequently, the kinetic jet power is computed as L^{obs}_{jet} ˜3-6 ×10^{37} erg s^{-1} during one of the observed radio flares which indicates that jet power corresponds to 8-16% mass outflow rate from the disc. This estimate of mass outflow rate is in close agreement with the change in total accretion rate (˜14%) required for spectral modeling before and during the flare. Finally, we provide a mass estimate of the source XTE J1859+226 based on the spectral modeling that lies in the range of 5.2-7.9 M_{⊙} with 90% confidence.

Emplacement of inflated Pāhoehoe flows in the Naude's Nek Pass, Lesotho remnant, Karoo continental flood basalt province: use of flow-lobe tumuli in understanding flood basalt emplacement

NASA Astrophysics Data System (ADS)

Jay, Anne E.; Marsh, Julian S.; Fluteau, Frédéric; Courtillot, Vincent

2018-02-01

Physical volcanological features are presented for a 710-m-thick section, of the Naude's Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are `medial or distal to source' are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients.

PubMed

Matimati, Ignatious; Verboom, G Anthony; Cramer, Michael D

2014-01-01

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 μm mesh from which nutrients could move by diffusion or mass-flow (termed 'mass-flow' treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed 'interception' treatment). 'Mass-flow' plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (gs), 1.2-fold higher intercellular [CO2] (Ci), and 3.4-fold lower water use efficiency than 'interception' plants, despite comparable values of photosynthetic rate (A). E, gs, and Ci first increased and then decreased with increasing distance from the N source to values even lower than those of 'interception' plants. 'Mass-flow' plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties.

Improved Nitrogen Removal Effect In Continuous Flow A2/O Process Using Typical Extra Carbon Source

NASA Astrophysics Data System (ADS)

Wu, Haiyan; Gao, Junyan; Yang, Dianhai; Zhou, Qi; Cai, Bijing

2010-11-01

In order to provide a basis for optimal selection of carbon source, three typical external carbon sources (i.e. methanol, sodium acetate and leachate) were applied to examine nitrogen removal efficiency of continuous flow A2/O system with the influent from the effluent of grit chamber in the second Kunming wastewater treatment plant. The best dosage was determined, and the specific nitrogen removal rate and carbon consumption rate were calculated with regard to individual external carbon source in A2/O system. Economy and technology analysis was also conducted to select the suitable carbon source with a low operation cost. Experimental results showed that the external typical carbon source caused a remarkable enhancement of system nitrate degradation ability. In comparison with the blank test, the average TN and NH3-N removal efficiency of system with different dosing quantities of external carbon source was improved by 15.2% and 34.2%, respectively. The optimal dosage of methanol, sodium acetate and leachate was respectively up to 30 mg/L, 40 mg/L and 100 mg COD/L in terms of a high nitrogen degradation effect. The highest removal efficiency of COD, TN and NH3-N reached respectively 92.3%, 73.9% and 100% with methanol with a dosage of 30 mg/L. The kinetic analysis and calculation revealed that the greatest denitrification rate was 0.0107 mg TN/mg MLVSSṡd with sodium acetate of 60 mg/L. As to carbon consumption rate, however, the highest value occurred in the blank test with a rate of 0.1955 mg COD/mg MLVSSṡd. Also, further economic analysis proved leachate to be pragmatic external carbon source whose cost was far cheaper than methanol.

Analysis of flow in an observation well intersecting a single fracture

USGS Publications Warehouse

Lapcevic, P.A.; Novakowski, K.S.; Paillet, Frederick L.

1993-01-01

A semi-analytical model is developed to determine transmissivity and storativity from the interpretation of transient flow in an observation well due to pumping in a source well where the two wells are connected by a single fracture. Flow rate can be determined using a heat-pulse flowmeter located above the intersection of the fracture in the observation well. The results of a field experiment were interpreted using the new model and compared with drawdown data from the same test. Good agreement between the transmissivity estimates was observed whereas estimates of storativity were found to be better determined from the analysis of flow rate. ?? 1993.

PILOT SCALE WATER REUSE SYSTEM

EPA Science Inventory

The efficiency of the treatment technologies is expected to vary with the source water quality. By testing the technologies with various source waters, the research will quantify the limits of the technology: testing the flow rate variations with influent water quality, evalu...

The self-similar turbulent flow of low-pressure water vapor

NASA Astrophysics Data System (ADS)

Konyukhov, V. K.; Stepanov, E. V.; Borisov, S. K.

2018-05-01

We studied turbulent flows of water vapor in a pipe connecting two closed vessels of equal volume. The vessel that served as a source of water vapor was filled with adsorbent in the form of corundum ceramic balls. These ceramic balls were used to obtain specific conditions to lower the vapor pressure in the source vessel that had been observed earlier. A second vessel, which served as a receiver, was empty of either air or vapor before each vapor sampling. The rate of the pressure increase in the receiver vessel was measured in a series of six samplings performed with high precision. The pressure reduction rate in the source vessel was found to be three times lower than the pressure growth rate in the receiver vessel. We found that the pressure growth rates in all of the adjacent pairs of samples could be arranged in a combination that appeared to be identical for all pairs, and this revealed the existence of a rather interesting and peculiar self-similarity law for the sampling processes under consideration.

Nitrate removal performance of Diaphorobacter nitroreducens using biodegradable plastics as the source of reducing power

NASA Astrophysics Data System (ADS)

Khan, S. T.; Nagao, Y.; Hiraishi, A.

2015-02-01

Strain NA10BT and other two strains of the denitrifying betaproteobacterium Diaphorobacter nitroreducens were studied for the performance of solid-phase denitrification (SPD) using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and some other biodegradable plastics as the source of reducing power in wastewater treatment. Sequencing-batch SPD reactors with these organisms and PHBV granules or flakes as the substrate exhibited good nitrate removal performance. Vial tests using cultures from these parent reactors showed higher nitrate removal rates with PHBV granules (ca. 20 mg-NO3-- N g-1 [dry wt cells] h-1) than with PHBV pellets and flakes. In continuous-flow SPD reactors using strain NA10BT and PHBV flakes, nitrate was not detected even at a loading rate of 21 mg-NO3-- N L-1 h-1. This corresponded to a nitrate removal rate of 47 mg-NO3-- N g-1 (dry wt cells) h-1. In the continuous-flow reactor, the transcription level of the phaZ gene, coding for PHB depolymerase, decreased with time, while that of the nosZ gene, involved in denitrificaiton, was relatively constant. These results suggest that the bioavailability of soluble metabolites as electron donor and carbon sources increases with time in the continuous-flow SPD process, thereby having much higher nitrate removal rates than the process with fresh PHBV as the substrate.

Quantifying air distribution, ventilation effectiveness and airborne pollutant transport in an aircraft cabin mockup

NASA Astrophysics Data System (ADS)

Wang, Aijun

The health, safety and comfort of passengers during flight inspired this research into cabin air quality, which is closely related to its airflow distribution, ventilation effectiveness and airborne pollutant transport. The experimental facility is a full-scale aircraft cabin mockup. A volumetric particle tracking velocimetry (VPTV) technique was enhanced by incorporating a self-developed streak recognition algorithm. Two stable recirculation regions, the reverse flows above the seats and the main air jets from the air supply inlets formed the complicated airflow patterns inside the cabin mockup. The primary air flow was parallel to the passenger rows. The small velocity component in the direction of the cabin depth caused less net air exchange between the passenger rows than that parallel to the passenger rows. Different total air supply rate changed the developing behaviors of the main air jets, leading to different local air distribution patterns. Two indices, Local mean age of air and ventilation effectiveness factor (VEF), were measured at five levels of air supply rate and two levels of heating load. Local mean age of air decreased linearly with an increase in the air supply rate, while the VEF remained consistent when the air supply rate varied. The thermal buoyancy force from the thermal plume generated the upside plume flow, opposite to the main jet flow above the boundary seats and thus lowered the local net air exchange. The airborne transport dynamics depends on the distance between the source and the receptors, the relative location of pollutant source, and air supply rate. Exposure risk was significantly reduced with increased distance between source and receptors. Another possible way to decrease the exposure risk was to position the release source close to the exhaust outlets. Increasing the air supply rate could be an effective solution under some emergency situations. The large volume of data regarding the three-dimensional air velocities was visualized in the CAVE virtual environment. ShadowLight, a virtual reality application was used to import and navigate the velocity vectors through the virtual airspace. A real world demonstration and an active interaction with the three-dimensional air velocity data have been established.

Nonlinear radiative heat flux and heat source/sink on entropy generation minimization rate

NASA Astrophysics Data System (ADS)

Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Alsaedi, A.

2018-06-01

Entropy generation minimization in nonlinear radiative mixed convective flow towards a variable thicked surface is addressed. Entropy generation for momentum and temperature is carried out. The source for this flow analysis is stretching velocity of sheet. Transformations are used to reduce system of partial differential equations into ordinary ones. Total entropy generation rate is determined. Series solutions for the zeroth and mth order deformation systems are computed. Domain of convergence for obtained solutions is identified. Velocity, temperature and concentration fields are plotted and interpreted. Entropy equation is studied through nonlinear mixed convection and radiative heat flux. Velocity and temperature gradients are discussed through graphs. Meaningful results are concluded in the final remarks.

High-speed Particle Image Velocimetry Near Surfaces

PubMed Central

Lu, Louise; Sick, Volker

2013-01-01

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (> 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows. A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included. PMID:23851899

Accretion flows onto supermassive black holes

NASA Technical Reports Server (NTRS)

Begelman, Mitchell C.

1988-01-01

The radiative and hydrodynamic properties of an angular momentum-dominated accretion flow onto a supermassive black hole depend largely on the ratio of the accretion rate to the Eddington accretion rate. High values of this ratio favor optically thick flows which produce largely thermal radiation, while optically thin 'two-temperature' flows may be present in systems with small values of this ratio. Observations of some AGN suggest that thermal and nonthermal sources of radiation may be of comparable importance in the 'central engine'. Consideration is given to the possibilities for coexistence of different modes of accretion in a single flow. One intriguing possibility is that runaway pair production may cause an optically thick 'accretion annulus' to form at the center of a two-temperature inflow.

Effects of changes in pumping on regional groundwater-flow paths, 2005 and 2010, and areas contributing recharge to discharging wells, 1990–2010, in the vicinity of North Penn Area 7 Superfund site, Montgomery County, Pennsylvania

USGS Publications Warehouse

Senior, Lisa A.; Goode, Daniel J.

2017-06-06

A previously developed regional groundwater flow model was used to simulate the effects of changes in pumping rates on groundwater-flow paths and extent of recharge discharging to wells for a contaminated fractured bedrock aquifer in southeastern Pennsylvania. Groundwater in the vicinity of the North Penn Area 7 Superfund site, Montgomery County, Pennsylvania, was found to be contaminated with organic compounds, such as trichloroethylene (TCE), in 1979. At the time contamination was discovered, groundwater from the underlying fractured bedrock (shale) aquifer was the main source of supply for public drinking water and industrial use. As part of technical support to the U.S. Environmental Protection Agency (EPA) during the Remedial Investigation of the North Penn Area 7 Superfund site from 2000 to 2005, the U.S. Geological Survey (USGS) developed a model of regional groundwater flow to describe changes in groundwater flow and contaminant directions as a result of changes in pumping. Subsequently, large decreases in TCE concentrations (as much as 400 micrograms per liter) were measured in groundwater samples collected by the EPA from selected wells in 2010 compared to 2005‒06 concentrations.To provide insight on the fate of potentially contaminated groundwater during the period of generally decreasing pumping rates from 1990 to 2010, steady-state simulations were run using the previously developed groundwater-flow model for two conditions prior to extensive remediation, 1990 and 2000, two conditions subsequent to some remediation 2005 and 2010, and a No Pumping case, representing pre-development or cessation of pumping conditions. The model was used to (1) quantify the amount of recharge, including potentially contaminated recharge from sources near the land surface, that discharged to wells or streams and (2) delineate the areas contributing recharge that discharged to wells or streams for the five conditions.In all simulations, groundwater divides differed from surface-water divides, partly because of differences in stream elevations and because of geologic structure and pumping. In the 1990 and 2000 simulations, all recharge in and near the vicinity of North Penn Area 7 discharged to wells, but in the 2005 and 2010 simulations some recharge in this area discharged to streams, indicating possible discharge of contaminated groundwater from North Penn Area 7 sources to streams. As the amount of groundwater withdrawals by wells has declined since 1990, the area contributing recharge to wells in the vicinity of North Penn Area 7 has decreased.To determine the effect of changes in pumping on flow paths and possible flow-path-related contributions to the observed changes in spatial distribution of contaminants in groundwater from 2005 to 2010, the USGS conducted simulations using the previously developed regional groundwater-flow model using reported pumping and estimated recharge rates for 2005 and 2010. Flow paths from recharge at known contaminant source areas to discharge locations at wells or streams were simulated under steady-state conditions for the two periods. Simulated groundwater-flow paths shifted only slightly from 2005 to 2010 as a result of changes in pumping rates. These slight changes in groundwater-flow paths from known sources of contamination are not coincident with the spatial distribution of observed changes in TCE concentrations from 2005 to 2010, indicating that the decreases of TCE concentrations may be a result of other processes, such as source removal or degradation. Results of the simulations and the absence of increases in TCE-degradation-product concentrations indicate that the decreases of TCE concentrations observed in 2010 may be at least partly related to contaminant-source removal by soil excavation completed in 2005, although additional data would be needed to confirm this preliminary explanation.

Beaver-mediated lateral hydrologic connectivity, fluvial carbon and nutrient flux, and aquatic ecosystem metabolism

NASA Astrophysics Data System (ADS)

Wegener, Pam; Covino, Tim; Wohl, Ellen

2017-06-01

River networks that drain mountain landscapes alternate between narrow and wide valley segments. Within the wide segments, beaver activity can facilitate the development and maintenance of complex, multithread planform. Because the narrow segments have limited ability to retain water, carbon, and nutrients, the wide, multithread segments are likely important locations of retention. We evaluated hydrologic dynamics, nutrient flux, and aquatic ecosystem metabolism along two adjacent segments of a river network in the Rocky Mountains, Colorado: (1) a wide, multithread segment with beaver activity; and, (2) an adjacent (directly upstream) narrow, single-thread segment without beaver activity. We used a mass balance approach to determine the water, carbon, and nutrient source-sink behavior of each river segment across a range of flows. While the single-thread segment was consistently a source of water, carbon, and nitrogen, the beaver impacted multithread segment exhibited variable source-sink dynamics as a function of flow. Specifically, the multithread segment was a sink for water, carbon, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along the multithread relative to the single-thread segment. Our data suggest that beaver activity in wide valleys can create a physically complex hydrologic environment that can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. Given the widespread removal of beaver, determining the cumulative effects of these changes is a critical next step in restoring function in altered river networks.

Asm-Triggered too Observations of Z Sources at Low Accretion Rate

NASA Astrophysics Data System (ADS)

van der Klis, Michiel

We propose to perform a pointed observation if the ASM shows that a Z source has entered a state of low accretion rate. This would provide a unique opportunity to detect millisecond pulsations. In Sco X-1 we would expect to discover beat-frequency QPO, and could perform a unique high count rate study of them. At sufficiently low accretion rate it would be possible to study the accretion flow when the magnetospheric radius approaches the corotation radius. The frequency of the horizontal branch QPO should go to zero here, and centrifugal inhibition of the accretion should set in, providing direct tests of the magnetospheric model of Z sources.

Sources of nitrogen and phosphorous to northern San Francisco Bay

USGS Publications Warehouse

Hager, Stephen W.; Schemel, Laurence E.

1992-01-01

We studied nutrient sources to the Sacramento River and Suisun Bay (northern San Francisco Bay) and the influence which these sources have on the distributions of dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) in the river and bay. We found that agricultural return flow drains and a municipal wastewater treatment plant were the largest sources of nutrients to the river during low river flow. The Sutter and Colusa agricultural drains contributed about 70% of the transport of DIN and DRP by the river above Sacramento (about 20% of the total transport by the river) between August 8 and September 26, 1985. Further downstream, the Sacramento Regional Wastewater Treatment Plant discharged DIN and DRP at rates that were roughly 70% of total DIN and DRP transport by the river at that time. Concentrations at Rio Vista on the tidal river below the Sacramento plant and at the head of the estuary were related to the reciprocals of the river flows, indicating the importance of dilution of the Sacramento waste by river flows. During very dry years, elevated DIN and DRP concentrations were observed in Suisun Bay. We used a steady-state, one-dimensional, single-compartment box model of the bay, incorporating terms for advection, exchange, and waste input, to calculate a residual rate for all processes not included in the model. We found that the residual for DIN was related to concentrations of chlorophylla (Chla). The residual for DRP was also related to Chla at high concentrations of Chla, but showed significant losses of DRP at low Chla concentrations. These losses were typically equivalent to about 80% of the wastewater input rate.

The effect of toxic carbon source on the reaction of activated sludge in the batch reactor.

PubMed

Wu, Changyong; Zhou, Yuexi; Zhang, Siyu; Xu, Min; Song, Jiamei

2018-03-01

The toxic carbon source can cause higher residual effluent dissolved organic carbon than easily biodegraded carbon source in activated sludge process. In this study, an integrated activated sludge model is developed as the tool to understand the mechanism of toxic carbon source (phenol) on the reaction, regarding the carbon flows during the aeration period in the batch reactor. To estimate the toxic function of phenol, the microbial cells death rate (k death ) is introduced into the model. The integrated model was calibrated and validated by the experimental data and it was found the model simulations matched the all experimental measurements. In the steady state, the toxicity of phenol can result in higher microbial cells death rate (0.1637 h -1 vs 0.0028 h -1 ) and decay rate coefficient of biomass (0.0115 h -1 vs 0.0107 h -1 ) than acetate. In addition, the utilization-associated products (UAP) and extracellular polymeric substances (EPS) formation coefficients of phenol are higher than that of acetate, indicating that more carbon flows into the extracellular components, such as soluble microbial products (SMP), when degrading toxic organics. In the non-steady state of feeding phenol, the yield coefficient for growth and maximum specific growth rate are very low in the first few days (1-10 d), while the decay rate coefficient of biomass and microbial cells death rate are relatively high. The model provides insights into the difference of the dynamic reaction with different carbon sources in the batch reactor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

Space-Time Dependent Transport, Activation, and Dose Rates for Radioactivated Fluids.

NASA Astrophysics Data System (ADS)

Gavazza, Sergio

Two methods are developed to calculate the space - and time-dependent mass transport of radionuclides, their production and decay, and the associated dose rates generated from the radioactivated fluids flowing through pipes. The work couples space- and time-dependent phenomena, treated as only space- or time-dependent in the open literature. The transport and activation methodology (TAM) is used to numerically calculate space- and time-dependent transport and activation of radionuclides in fluids flowing through pipes exposed to radiation fields, and volumetric radioactive sources created by radionuclide motions. The computer program Radionuclide Activation and Transport in Pipe (RNATPA1) performs the numerical calculations required in TAM. The gamma ray dose methodology (GAM) is used to numerically calculate space- and time-dependent gamma ray dose equivalent rates from the volumetric radioactive sources determined by TAM. The computer program Gamma Ray Dose Equivalent Rate (GRDOSER) performs the numerical calculations required in GAM. The scope of conditions considered by TAM and GAM herein include (a) laminar flow in straight pipe, (b)recirculating flow schemes, (c) time-independent fluid velocity distributions, (d) space-dependent monoenergetic neutron flux distribution, (e) space- and time-dependent activation process of a single parent nuclide and transport and decay of a single daughter radionuclide, and (f) assessment of space- and time-dependent gamma ray dose rates, outside the pipe, generated by the space- and time-dependent source term distributions inside of it. The methodologies, however, can be easily extended to include all the situations of interest for solving the phenomena addressed in this dissertation. A comparison is made from results obtained by the described calculational procedures with analytical expressions. The physics of the problems addressed by the new technique and the increased accuracy versus non -space and time-dependent methods are presented. The value of the methods is also discussed. It has been demonstrated that TAM and GAM can be used to enhance the understanding of the space- and time-dependent mass transport of radionuclides, their production and decay, and the associated dose rates related to radioactivated fluids flowing through pipes.

Effects of high source flow and high pumping speed on gas source molecular beam epitaxy / chemical beam epitaxy

NASA Astrophysics Data System (ADS)

McCollum, M. J.; Jackson, S. L.; Szafranek, I.; Stillman, G. E.

1990-10-01

We report the growth of GaAs by molecular beam epitaxy (MBE), gas source molecular beam epitaxy (GSMBE), and chemical beam epitaxy (CBE) in an epitaxial III-V reactor which features high pumping speed. The system is comprised of a modified Perkin-Elmer 430P molecular beam epitaxy system and a custom gas source panel from Emcore. The growth chamber is pumped with a 7000 1/s (He) diffusion pump (Varian VHS-10 with Monsanto Santovac 5 oil). The gas source panel includes pressure based flow controllers (MKS 1150) allowing triethylaluminum (TEA), triethylgallium (TEG), and trimethylindium (TMI) to be supplied without the use of hydrogen. All source lines, including arsine and phosphine, are maintained below atmospheric pressure. The high pumping speed allows total system flow rates as high as 100 SCCM and V/III ratios as high as 100. The purity of GaAs grown by MBE in this system increases with pumping speed. GaAs layers grown by GSMBE with arsine flows of 10 and 20 SCCM have electron concentrations of 1 × 10 15 cm -3 (μ 77=48,000 cm 2/V·) and 2 × 10 14 cm -3 (μ 77=78,000 cm 2/V·s) respectively. El ectron concentration varies with hydride injector temperature such that the minimum in electron concentration occurs for less than complete cracking. The effect of V/III ratio and the use of a metal eutectic bubbler on residual carrier concentration in GaAs grown by CBE is presented. Intentional Si and Be doping of CBE grown GaAs is demonstrated at a high growth rate of 5.4 μm/h.

Flow rate and source reservoir identification from airborne chemical sampling of the uncontrolled Elgin platform gas release

NASA Astrophysics Data System (ADS)

Lee, James D.; Mobbs, Stephen D.; Wellpott, Axel; Allen, Grant; Bauguitte, Stephane J.-B.; Burton, Ralph R.; Camilli, Richard; Coe, Hugh; Fisher, Rebecca E.; France, James L.; Gallagher, Martin; Hopkins, James R.; Lanoiselle, Mathias; Lewis, Alastair C.; Lowry, David; Nisbet, Euan G.; Purvis, Ruth M.; O'Shea, Sebastian; Pyle, John A.; Ryerson, Thomas B.

2018-03-01

An uncontrolled gas leak from 25 March to 16 May 2012 led to evacuation of the Total Elgin wellhead and neighbouring drilling and production platforms in the UK North Sea. Initially the atmospheric flow rate of leaking gas and condensate was very poorly known, hampering environmental assessment and well control efforts. Six flights by the UK FAAM chemically instrumented BAe-146 research aircraft were used to quantify the flow rate. The flow rate was calculated by assuming the plume may be modelled by a Gaussian distribution with two different solution methods: Gaussian fitting in the vertical and fitting with a fully mixed layer. When both solution methods were used they compared within 6 % of each other, which was within combined errors. Data from the first flight on 30 March 2012 showed the flow rate to be 1.3 ± 0.2 kg CH4 s-1, decreasing to less than half that by the second flight on 17 April 2012. δ13CCH4 in the gas was found to be -43 ‰, implying that the gas source was unlikely to be from the main high pressure, high temperature Elgin gas field at 5.5 km depth, but more probably from the overlying Hod Formation at 4.2 km depth. This was deemed to be smaller and more manageable than the high pressure Elgin field and hence the response strategy was considerably simpler. The first flight was conducted within 5 days of the blowout and allowed a flow rate estimate within 48 h of sampling, with δ13CCH4 characterization soon thereafter, demonstrating the potential for a rapid-response capability that is widely applicable to future atmospheric emissions of environmental concern. Knowledge of the Elgin flow rate helped inform subsequent decision making. This study shows that leak assessment using appropriately designed airborne plume sampling strategies is well suited for circumstances where direct access is difficult or potentially dangerous. Measurements such as this also permit unbiased regulatory assessment of potential impact, independent of the emitting party, on timescales that can inform industry decision makers and assist rapid-response planning by government.

A Basic Experiment on the Aerodynamics of Sniffing

NASA Astrophysics Data System (ADS)

Settles, Gary S.; Kester, Douglas A.

1999-11-01

Our previous work (APS/DFD97:Ii1 and 98:FA10) used flow visualization to observe canine olfaction. The results raised some basic questions about the aerodynamics of sniffing, e.g. what flow rate is required, as a function of distance from a scent source, to acquire a detectable scent? Commercial sampler technology does not address such questions. A basic experiment was thus designed to investigate the aerodynamic phenomena and performance of sniffing. A stable thermal layer on a horizontal plane was used as a "scent" source per Reynolds Analogy. The detector was a thermocouple inside a sniffer tube. Flow patterns were observed by schlieren. Results show the importance of sniffer proximity to localize a scent source. A transient scent spike occurs at the sniff onset, followed by signal decline due to source depletion. Sniffing shows extreme sensitivity to disruptive air currents. Unstably-stratified scent sources (thermal plumes) are also considered. These results help us understand evolved sniffing behavior, and they suggest sampler design criteria for electronic-nose devices. (Research supported by DARPA.)

The flow of magnetohydrodynamic Maxwell nanofluid over a cylinder with Cattaneo-Christov heat flux model

NASA Astrophysics Data System (ADS)

Raju, C. S. K.; Sanjeevi, P.; Raju, M. C.; Ibrahim, S. M.; Lorenzini, G.; Lorenzini, E.

2017-11-01

A theoretical analysis is performed for studying the flow and heat and mass transfer characteristics of Maxwell fluid over a cylinder with Cattaneo-Christov and non-uniform heat source/sink. The Brownian motion and thermophoresis parameters also considered into account. Numerical solutions are carried out by using Runge-Kutta-based shooting technique. The effects of various governing parameters on the flow and temperature profiles are demonstrated graphically. We also computed the friction factor coefficient, local Nusselt and Sherwood numbers for the permeable and impermeable flow over a cylinder cases. It is found that the rising values of Biot number, non-uniform heat source/sink and thermophoresis parameters reduce the rate of heat transfer. It is also found that the friction factor coefficient is high in impermeable flow over a cylinder case when compared with the permeable flow over a cylinder case.

Kinetic instability of electrostatic ion cyclotron waves in inter-penetrating plasmas

NASA Astrophysics Data System (ADS)

Bashir, M. F.; Ilie, R.; Murtaza, G.

2018-05-01

The Electrostatic Ion Cyclotron (EIC) instability that includes the effect of wave-particle interaction is studied owing to the free energy source through the flowing velocity of the inter-penetrating plasmas. It is shown that the origin of this current-less instability is different from the classical current driven EIC instability. The threshold conditions applicable to a wide range of plasma parameters and the estimate of the growth rate are determined as a function of the normalized flowing velocity ( u0/vt f e ), the temperature ( Tf/Ts ) and the density ratios ( nf 0/ns 0 ) of flowing component to static one. The EIC instability is driven by either flowing electrons or flowing ions, depending upon the different Doppler shifted frequency domains. It is found that the growth rate for electron-driven instability is higher than the ion-driven one. However, in both cases, the denser (hotter) is the flowing plasma, the lesser (greater) is the growth rate. The possible applications related to the terrestrial solar plasma environment are also discussed.

Analogue experiments as benchmarks for models of lava flow emplacement

NASA Astrophysics Data System (ADS)

Garel, F.; Kaminski, E. C.; Tait, S.; Limare, A.

2013-12-01

During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flow advance and its velocity. The spreading of a lava flow, seen as a gravity current, depends on its "effective rheology" and on the effusion rate. Fast-computing models have arisen in the past decade in order to predict in near real time lava flow path and rate of advance. This type of model, crucial to mitigate volcanic hazards and organize potential evacuation, has been mainly compared a posteriori to real cases of emplaced lava flows. The input parameters of such simulations applied to natural eruptions, especially effusion rate and topography, are often not known precisely, and are difficult to evaluate after the eruption. It is therefore not straightforward to identify the causes of discrepancies between model outputs and observed lava emplacement, whereas the comparison of models with controlled laboratory experiments appears easier. The challenge for numerical simulations of lava flow emplacement is to model the simultaneous advance and thermal structure of viscous lava flows. To provide original constraints later to be used in benchmark numerical simulations, we have performed lab-scale experiments investigating the cooling of isoviscous gravity currents. The simplest experimental set-up is as follows: silicone oil, whose viscosity, around 5 Pa.s, varies less than a factor of 2 in the temperature range studied, is injected from a point source onto a horizontal plate and spreads axisymmetrically. The oil is injected hot, and progressively cools down to ambient temperature away from the source. Once the flow is developed, it presents a stationary radial thermal structure whose characteristics depend on the input flow rate. In addition to the experimental observations, we have developed in Garel et al., JGR, 2012 a theoretical model confirming the relationship between supply rate, flow advance and stationary surface thermal structure. We also provide experimental observations of the effect of wind the surface thermal structure of a viscous flow, that could be used to benchmark a thermal heat loss model. We will also briefly present more complex analogue experiments using wax material. These experiments present discontinuous advance behavior, and a dual surface thermal structure with low (solidified) vs. high (hot liquid exposed at the surface) surface temperatures regions. Emplacement models should tend to reproduce these two features, also observed on lava flows, to better predict the hazard of lava inundation.

Model for a transformer-coupled toroidal plasma source

NASA Astrophysics Data System (ADS)

Rauf, Shahid; Balakrishna, Ajit; Chen, Zhigang; Collins, Ken

2012-01-01

A two-dimensional fluid plasma model for a transformer-coupled toroidal plasma source is described. Ferrites are used in this device to improve the electromagnetic coupling between the primary coils carrying radio frequency (rf) current and a secondary plasma loop. Appropriate components of the Maxwell equations are solved to determine the electromagnetic fields and electron power deposition in the model. The effect of gas flow on species transport is also considered. The model is applied to 1 Torr Ar/NH3 plasma in this article. Rf electric field lines form a loop in the vacuum chamber and generate a plasma ring. Due to rapid dissociation of NH3, NHx+ ions are more prevalent near the gas inlet and Ar+ ions are the dominant ions farther downstream. NH3 and its by-products rapidly dissociate into small fragments as the gas flows through the plasma. With increasing source power, NH3 dissociates more readily and NHx+ ions are more tightly confined near the gas inlet. Gas flow rate significantly influences the plasma characteristics. With increasing gas flow rate, NH3 dissociation occurs farther from the gas inlet in regions with higher electron density. Consequently, more NH4+ ions are produced and dissociation by-products have higher concentrations near the outlet.

Unsteady Flow Dynamics and Acoustics of Two-Outlet Centrifugal Fan Design

NASA Astrophysics Data System (ADS)

Wong, I. Y. W.; Leung, R. C. K.; Law, A. K. Y.

2011-09-01

In this study, a centrifugal fan design with two flow outlets is investigated. This design aims to provide high mass flow rate but low noise performance. Two dimensional unsteady flow simulation with CFD code (FLUENT 6.3) is carried out to analyze the fan flow dynamics and its acoustics. The calculations were done using the unsteady Reynolds averaged Navier Stokes (URANS) approach in which effects of turbulence were accounted for using κ-ɛ model. This work aims to provide an insight how the dominant noise source mechanisms vary with a key fan geometrical paramters, namely, the ratio between cutoff distance and the radius of curvature of the fan housing. Four new fan designs were calculated. Simulation results show that the unsteady flow-induced forces on the fan blades are found to be the main noise sources. The blade force coefficients are then used to build the dipole source terms in Ffowcs Williams and Hawkings (FW-H) Equation for estimating their noise effects. It is found that one design is able to deliver a mass flow 34% more, but with sound pressure level (SPL) 10 dB lower, than the existing design .

Generalized Fluid System Simulation Program, Version 6.0

NASA Technical Reports Server (NTRS)

Majumdar, A. K.; LeClair, A. C.; Moore, A.; Schallhorn, P. A.

2013-01-01

The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependant flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors and external body forces such as gravity and centrifugal. The thermo-fluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids, and 24 different resistance/source options are provided for modeling momentum sources or sinks in the branches. This Technical Memorandum illustrates the application and verification of the code through 25 demonstrated example problems.

Generalized Fluid System Simulation Program, Version 5.0-Educational

NASA Technical Reports Server (NTRS)

Majumdar, A. K.

2011-01-01

The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors and external body forces such as gravity and centrifugal. The thermofluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the point, drag and click method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids and 21 different resistance/source options are provided for modeling momentum sources or sinks in the branches. This Technical Memorandum illustrates the application and verification of the code through 12 demonstrated example problems.

High frequency longitudinal profiling reveals hydrologic controls on solute sourcing, transport and processing in a karst river

NASA Astrophysics Data System (ADS)

Hensley, R. T.; Cohen, M. J.; Spangler, M.; Gooseff, M. N.

2017-12-01

The lower Santa Fe River is a large, karst river of north Florida, fed by numerous artesian springs and also containing multiple sink-rise systems. We performed repeated longitudinal profiles collecting very high frequency measurements of multiple stream parameters including temperature, dissolved oxygen, carbon dioxide, pH, dissolved organic matter, nitrate, ammonium, phosphate and turbidity. This high frequency dataset provided a spatially explicit understanding of solute sources and coupled biogeochemical processing rates along the 25 km study reach. We noted marked changes in river profiles as the river transitioned from low to high flow during the onset of the wet season. The role of lateral inflow from springs as the primary solute source was greatly reduced under high flow conditions. Effects of sink-rise systems, which under low flow conditions allow the majority of flow to bypass several kilometer long sections of the main channel, virtually disappeared under high flow conditions. Impeded light transmittance at high flow reduced primary production and by extension assimilatory nutrient uptake. This study demonstrates how high frequency longitudinal profiling can be used to observe how hydrologic conditions can alter groundwater-surface water interactions and modulate the sourcing, transport and biogeochemical processing of stream solutes.

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients

PubMed Central

Matimati, Ignatious

2014-01-01

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 μm mesh from which nutrients could move by diffusion or mass-flow (termed ‘mass-flow’ treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed ‘interception’ treatment). ‘Mass-flow’ plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (g s), 1.2-fold higher intercellular [CO2] (C i), and 3.4-fold lower water use efficiency than ‘interception’ plants, despite comparable values of photosynthetic rate (A). E, g s, and C i first increased and then decreased with increasing distance from the N source to values even lower than those of ‘interception’ plants. ‘Mass-flow’ plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties. PMID:24231035

Moment Analysis Characterizing Water Flow in Repellent Soils from On- and Sub-Surface Point Sources

NASA Astrophysics Data System (ADS)

Xiong, Yunwu; Furman, Alex; Wallach, Rony

2010-05-01

Water repellency has a significant impact on water flow patterns in the soil profile. Flow tends to become unstable in such soils, which affects the water availability to plants and subsurface hydrology. In this paper, water flow in repellent soils was experimentally studied using the light reflection method. The transient 2D moisture profiles were monitored by CCD camera for tested soils packed in a transparent flow chamber. Water infiltration experiments and subsequent redistribution from on-surface and subsurface point sources with different flow rates were conducted for two soils of different repellency degrees as well as for wettable soil. We used spatio-statistical analysis (moments) to characterize the flow patterns. The zeroth moment is related to the total volume of water inside the moisture plume, and the first and second moments are affinitive to the center of mass and spatial variances of the moisture plume, respectively. The experimental results demonstrate that both the general shape and size of the wetting plume and the moisture distribution within the plume for the repellent soils are significantly different from that for the wettable soil. The wetting plume of the repellent soils is smaller, narrower, and longer (finger-like) than that of the wettable soil compared with that for the wettable soil that tended to roundness. Compared to the wettable soil, where the soil water content decreases radially from the source, moisture content for the water-repellent soils is higher, relatively uniform horizontally and gradually increases with depth (saturation overshoot), indicating that flow tends to become unstable. Ellipses, defined around the mass center and whose semi-axes represented a particular number of spatial variances, were successfully used to simulate the spatial and temporal variation of the moisture distribution in the soil profiles. Cumulative probability functions were defined for the water enclosed in these ellipses. Practically identical cumulative probability functions (beta distribution) were obtained for all soils, all source types, and flow rates. Further, same distributions were obtained for the infiltration and redistribution processes. This attractive result demonstrates the competence and advantage of the moment analysis method.

Neutralization of an ion beam from the end-Hall ion source by a plasma electron source based on a discharge in crossed E × H fields

NASA Astrophysics Data System (ADS)

Dostanko, A. P.; Golosov, D. A.

2009-10-01

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm2 at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O2 or N2. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).

Selective Catalytic Combustion Sensors for Reactive Organic Analysis

NASA Technical Reports Server (NTRS)

Innes, W. B.

1971-01-01

Sensors involving a vanadia-alumina catalyst bed-thermocouple assembly satisfy requirements for simple, reproducible and rapid continuous analysis or reactive organics. Responses generally increase with temperature to 400 C and increase to a maximum with flow rate/catalyst volume. Selectivity decreases with temperature. Response time decreases with flow rate and increases with catalyst volume. At chosen optimum conditions calculated response which is additive and linear agrees better with photochemical reactivity than other methods for various automotive sources, and response to vehicle exhaust is insensitive to flow rate. Application to measurement of total reactive organics in vehicle exhaust as well as for gas chromatography detection illustrate utility. The approach appears generally applicable to high thermal effect reactions involving first order kinetics.

ACCRETION FLOW DYNAMICS OF MAXI J1659-152 FROM THE SPECTRAL EVOLUTION STUDY OF ITS 2010 OUTBURST USING THE TCAF SOLUTION

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

Debnath, Dipak; Molla, Aslam Ali; Chakrabarti, Sandip K.

2015-04-20

Transient black hole candidates are interesting objects to study in X-rays as these sources show rapid evolutions in their spectral and temporal properties. In this paper, we study the spectral properties of the Galactic transient X-ray binary MAXI J1659-152 during its very first outburst after discovery with the archival data of RXTE Proportional Counter Array instruments. We make a detailed study of the evolution of accretion flow dynamics during its 2010 outburst through spectral analysis using the Chakrabarti–Titarchuk two-component advective flow (TCAF) model as an additive table model in XSPEC. Accretion flow parameters (Keplerian disk and sub-Keplerian halo rates, shockmore » location, and shock strength) are extracted from our spectral fits with TCAF. We studied variations of these fit parameters during the entire outburst as it passed through three spectral classes: hard, hard-intermediate, and soft-intermediate. We compared our TCAF fitted results with standard combined disk blackbody (DBB) and power-law (PL) model fitted results and found that variations of disk rate with DBB flux and halo rate with PL flux are generally similar in nature. There appears to be an absence of the soft state, unlike what is seen in other similar sources.« less

Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae

2017-12-01

Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.

Growth rate of plasma-synthesized vertically aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Merkulov, Vladimir I.; Melechko, A. V.; Guillorn, M. A.; Lowndes, D. H.; Simpson, M. L.

2002-08-01

Vertically aligned carbon nanofibers (VACNFs) were synthesized by direct-current plasma enhanced chemical vapor deposition using acetylene and ammonia as the gas source. The mechanisms responsible for changing the nanofiber growth rate were studied and phenomenological models are proposed. The feedstock for VACNF growth is suggested to consist mainly of radicals formed in the plasma and not the unexcited acetylene gas molecules. The growth rate is shown to increase dramatically by changing the radical transport mechanism from diffusive to forced flow, which was accomplished by increasing the gas flow in the direction perpendicular to the substrate.

Ammonia Offgassing from SA9T

NASA Technical Reports Server (NTRS)

Monje, Oscar; Nolek, Sara D.; Wheeler, Raymond M.

2011-01-01

NH3 is a degradation product of SA9T, a solid-amine sorbent developed by Hamilton Sundstrand, that is continually emitted into the gas stream being conditioned by this sorbent. NH3 offgassing rates were measured using FTIR spectroscopy using a packed bed at similar contact times as offgassing tests conducted at Hamilton Sundstrand and at the Ames Research Center. The bed was challenged with moist air at several flow rates and humidities and NH3 concentration of the effluent was measured for several hours. The NH3 offgassing rates in open-loop testing were calculated from the steady state outlet NH3 concentration and flow rate. NH3 offgassing rates from SA9T were found to be influenced by the contact time with the adsorbent (flow rate) and by the humidity of the inlet gas stream, which are consistent with previous studies. Closed-loop vacuum-swing adsorption cycling rates verified that NH3 offgassing continues when a constant source of water vapor is present.

Radiative Effects on a Free Convective MHD Flow past a Vertically Inclined Plate with with Heat Source and Sink

NASA Astrophysics Data System (ADS)

Sambath, P.; Pullepu, Bapuji; Kannan, R. M.

2018-04-01

The impact of thermal radiation on unsteady laminar free convective MHD flow of a incompressible viscous fluid passes through a vertically inclined plate under the persuade of heat source and sink is presented here.Plate surface is considered to have variable wall temperature. The fluid regarded as gray absorbing / emitting, but non dispersing medium. The periphery layer dimensionless equations that administer the flow are evaluated by a finite difference implicit method called Crank Nicolson method. Numerical solutions are carried out for velocity, temperature, local shear stress, heat transfer rate for various values of the parameters (Pr, λ, Δ M, Rd ) are presented.

Additively manufactured MEMS multiplexed coaxial electrospray sources for high-throughput, uniform generation of core-shell microparticles.

PubMed

Olvera-Trejo, D; Velásquez-García, L F

2016-10-18

This study reports the first MEMS multiplexed coaxial electrospray sources in the literature. Coaxial electrospraying is a microencapsulation technology based on electrohydrodynamic jetting of two immiscible liquids, which allows precise control with low size variation of the geometry of the core-shell particles it generates, which is of great importance in numerous biomedical and engineering applications, e.g., drug delivery and self-healing composites. By implementing monolithic planar arrays of miniaturized coaxial electrospray emitters that work uniformly in parallel, the throughput of the compound microdroplet source is greatly increased, making the microencapsulation technology compatible with low-cost commercial applications. Miniaturized core-shell particle generators with up to 25 coaxial electrospray emitters (25 emitters cm -2 ) were fabricated via stereolithography, which is an additive manufacturing process that can create complex microfluidic devices at a small fraction of the cost per device and fabrication time associated with silicon-based counterparts. The characterization of devices with the same emitter structure but different array sizes demonstrates uniform array operation. Moreover, the data demonstrate that the per-emitter current is approximately proportional to the square root of the flow rate of the driving liquid, and it is independent of the flow rate of the driven liquid, as predicted by the theory. The core/shell diameters and the size distribution of the generated compound microparticles can be modulated by controlling the flow rates fed to the emitters.

Environmental conditions influence tissue regeneration rates in scleractinian corals.

PubMed

Sabine, Alexis M; Smith, Tyler B; Williams, Dana E; Brandt, Marilyn E

2015-06-15

Natural and anthropogenic factors may influence corals' ability to recover from partial mortality. To examine how environmental conditions affect lesion healing, we assessed several water quality parameters and tissue regeneration rates in corals at six reefs around St. Thomas, US Virgin Islands. We hypothesized that sites closer to developed areas would have poor water quality due to proximity to anthropogenic stresses, which would impede tissue regeneration. We found that water flow and turbidity most strongly influenced lesion recovery rates. The most impacted site, with high turbidity and low flow, recovered almost three times slower than the least impacted site, with low turbidity, high flow, and low levels of anthropogenic disturbance. Our results illustrate that in addition to lesion-specific factors known to affect tissue regeneration, environmental conditions can also control corals' healing rates. Resource managers can use this information to protect low-flow, turbid nearshore reefs by minimizing sources of anthropogenic stress. Copyright © 2015 Elsevier Ltd. All rights reserved.

Atmospheric Pressure Effects on Cryogenic Storage Tank Boil-Off

NASA Technical Reports Server (NTRS)

Sass, J. P.; Frontier, C. R.

2007-01-01

The Cryogenics Test Laboratory (CTL) at the Kennedy Space Center (KSC) routinely utilizes cryostat test hardware to evaluate comparative and absolute thermal conductivities of a wide array of insulation systems. The test method is based on measurement of the flow rate of gas evolved due to evaporative boil-off of a cryogenic liquid. The gas flow rate typically stabilizes after a period of a couple of hours to a couple of days, depending upon the test setup. The stable flow rate value is then used to calculate the thermal conductivity for the insulation system being tested. The latest set of identical cryostats, 1,000-L spherical tanks, exhibited different behavior. On a macro level, the flow rate did stabilize after a couple of days; however the stable flow rate was oscillatory with peak to peak amplitude of up to 25 percent of the nominal value. The period of the oscillation was consistently 12 hours. The source of the oscillation has been traced to variations in atmospheric pressure due to atmospheric tides similar to oceanic tides. This paper will present analysis of this phenomenon, including a calculation that explains why other cryostats are not affected by it.

Parametric investigations of plasma characteristics in a remote inductively coupled plasma system

NASA Astrophysics Data System (ADS)

Shukla, Prasoon; Roy, Abhra; Jain, Kunal; Bhoj, Ananth

2016-09-01

Designing a remote plasma system involves source chamber sizing, selection of coils and/or electrodes to power the plasma, designing the downstream tubes, selection of materials used in the source and downstream regions, locations of inlets and outlets and finally optimizing the process parameter space of pressure, gas flow rates and power delivery. Simulations can aid in spatial and temporal plasma characterization in what are often inaccessible locations for experimental probes in the source chamber. In this paper, we report on simulations of a remote inductively coupled Argon plasma system using the modeling platform CFD-ACE +. The coupled multiphysics model description successfully address flow, chemistry, electromagnetics, heat transfer and plasma transport in the remote plasma system. The SimManager tool enables easy setup of parametric simulations to investigate the effect of varying the pressure, power, frequency, flow rates and downstream tube lengths. It can also enable the automatic solution of the varied parameters to optimize a user-defined objective function, which may be the integral ion and radical fluxes at the wafer. The fast run time coupled with the parametric and optimization capabilities can add significant insight and value in design and optimization.

Correlating non-linear properties with spectral states of RXTE data: possible observational evidences for four different accretion modes around compact objects

NASA Astrophysics Data System (ADS)

Adegoke, Oluwashina; Dhang, Prasun; Mukhopadhyay, Banibrata; Ramadevi, M. C.; Bhattacharya, Debbijoy

2018-05-01

By analysing the time series of RXTE/PCA data, the non-linear variabilities of compact sources have been repeatedly established. Depending on the variation in temporal classes, compact sources exhibit different non-linear features. Sometimes they show low correlation/fractal dimension, but in other classes or intervals of time they exhibit stochastic nature. This could be because the accretion flow around a compact object is a non-linear general relativistic system involving magnetohydrodynamics. However, the more conventional way of addressing a compact source is the analysis of its spectral state. Therefore, the question arises: What is the connection of non-linearity to the underlying spectral properties of the flow when the non-linear properties are related to the associated transport mechanisms describing the geometry of the flow? This work is aimed at addressing this question. Based on the connection between observed spectral and non-linear (time series) properties of two X-ray binaries: GRS 1915+105 and Sco X-1, we attempt to diagnose the underlying accretion modes of the sources in terms of known accretion classes, namely, Keplerian disc, slim disc, advection dominated accretion flow and general advective accretion flow. We explore the possible transition of the sources from one accretion mode to others with time. We further argue that the accretion rate must play an important role in transition between these modes.

Destabilization of confined granular packings due to fluid flow

NASA Astrophysics Data System (ADS)

Monloubou, Martin; Sandnes, Bjørnar

2016-04-01

Fluid flow through granular materials can cause fluidization when fluid drag exceeds the frictional stress within the packing. Fluid driven failure of granular packings is observed in both natural and engineered settings, e.g. soil liquefaction and flowback of proppants during hydraulic fracturing operations. We study experimentally the destabilization and flow of an unconsolidated granular packing subjected to a point source fluid withdrawal using a model system consisting of a vertical Hele-Shaw cell containing a water-grain mixture. The fluid is withdrawn from the cell at a constant rate, and the emerging flow patterns are imaged in time-lapse mode. Using Particle Image Velocimetry (PIV), we show that the granular flow gets localized in a narrow channel down the center of the cell, and adopts a Gaussian velocity profile similar to those observed in dry grain flows in silos. We investigate the effects of the experimental parameters (flow rate, grain size, grain shape, fluid viscosity) on the packing destabilization, and identify the physical mechanisms responsible for the observed complex flow behaviour.

43 CFR 3272.11 - How do I describe the proposed utilization facility?

Code of Federal Regulations, 2011 CFR

2011-10-01

...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) GEOTHERMAL RESOURCE... proposed facility operations, including estimated total production and injection rates; estimated well flow... site(s); (e) The source, quality, and proposed consumption rate of water to be used during facility...

Model for a transformer-coupled toroidal plasma source

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

Rauf, Shahid; Balakrishna, Ajit; Chen Zhigang

2012-01-15

A two-dimensional fluid plasma model for a transformer-coupled toroidal plasma source is described. Ferrites are used in this device to improve the electromagnetic coupling between the primary coils carrying radio frequency (rf) current and a secondary plasma loop. Appropriate components of the Maxwell equations are solved to determine the electromagnetic fields and electron power deposition in the model. The effect of gas flow on species transport is also considered. The model is applied to 1 Torr Ar/NH{sub 3} plasma in this article. Rf electric field lines form a loop in the vacuum chamber and generate a plasma ring. Due tomore » rapid dissociation of NH{sub 3}, NH{sub x}{sup +} ions are more prevalent near the gas inlet and Ar{sup +} ions are the dominant ions farther downstream. NH{sub 3} and its by-products rapidly dissociate into small fragments as the gas flows through the plasma. With increasing source power, NH{sub 3} dissociates more readily and NH{sub x}{sup +} ions are more tightly confined near the gas inlet. Gas flow rate significantly influences the plasma characteristics. With increasing gas flow rate, NH{sub 3} dissociation occurs farther from the gas inlet in regions with higher electron density. Consequently, more NH{sub 4}{sup +} ions are produced and dissociation by-products have higher concentrations near the outlet.« less

Stabilization of flow past a rounded cylinder

NASA Astrophysics Data System (ADS)

Samtaney, Ravi; Zhang, Wei

2016-11-01

We perform global linear stability analysis on low-Re flow past a rounded cylinder. The cylinder corners are rounded with a radius R, normalized as R+ = R / D where D is the cylinder diameter, and its effect on the flow stability characteristics is investigated. We compute the critical Reynolds number (Recr) for the onset of first instability, and quantify the perturbation growth rate for the super-critical flows. It is found that the flow can be stabilized by partially rounding the cylinder. Compared with the square and circular cylinders, the partially rounded cylinder has a higher Recr , attaining a maximum at around R+ = 0 . 30 , and the perturbation growth rate of the super-critical flows is reduced for Re <= 100 . We perform sensitivity analysis to explore the source of the stabilization. The growth rate sensitivity to base flow modification has two different spatial structures: the growth rate is sensitive to the wake backflow in a large region for square-like cylinders (R+ -> 0 . 00), while only the near-wake backflow is crucial for circular-like cylinders (R+ -> 0 . 50). The stability analysis results are also verified with those of the direct simulations and very good agreement is achieved. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1394-01. The supercomputer Shaheen at KAUST was utilized for the simulations.

Experimental Measurements of Two-dimensional Planar Propagating Edge Flames

NASA Technical Reports Server (NTRS)

Villa-Gonzalez, Marcos; Marchese, Anthony J.; Easton, John W.; Miller, Fletcher J.

2007-01-01

The study of edge flames has received increased attention in recent years. This work reports the results of a recent study into two-dimensional, planar, propagating edge flames that are remote from solid surfaces (called here, free-layer flames, as opposed to layered flames along floors or ceilings). They represent an ideal case of a flame propagating down a flammable plume, or through a flammable layer in microgravity. The results were generated using a new apparatus in which a thin stream of gaseous fuel is injected into a low-speed laminar wind tunnel thereby forming a flammable layer along the centerline. An airfoil-shaped fuel dispenser downstream of the duct inlet issues ethane from a slot in the trailing edge. The air and ethane mix due to mass diffusion while flowing up towards the duct exit, forming a flammable layer with a steep lateral fuel concentration gradient and smaller axial fuel concentration gradient. We characterized the flow and fuel concentration fields in the duct using hot wire anemometer scans, flow visualization using smoke traces, and non-reacting, numerical modeling using COSMOSFloWorks. In the experiment, a hot wire near the exit ignites the ethane air layer, with the flame propagating downwards towards the fuel source. Reported here are tests with the air inlet velocity of 25 cm/s and ethane flows of 967-1299 sccm, which gave conditions ranging from lean to rich along the centerline. In these conditions the flame spreads at a constant rate faster than the laminar burning rate for a premixed ethane air mixture. The flame spread rate increases with increasing transverse fuel gradient (obtained by increasing the fuel flow rate), but appears to reach a maximum. The flow field shows little effect due to the flame approach near the igniter, but shows significant effect, including flow reversal, well ahead of the flame as it approaches the airfoil fuel source.

Two-Dimensional Microdischarge Jet Array in Air: Characterization and Inactivation of Virus

NASA Astrophysics Data System (ADS)

Nayak, Gaurav

Cold atmospheric pressure plasmas (CAPs) have proven to be quite effective for surface disinfection, wound healing and even cancer treatment in recent years. One of the major societal challenges faced today is related to illness caused by food-borne bacteria and viruses, particularly in minimally processed, fresh or ready-to-eat foods. Gastroenteritis outbreaks, caused, for example, by the human Norovirus (NV) is a growing concern. Current used technologies seem not to be fully effective. In this work we focus on a possible solution based on CAP technology for surface disinfection. Many discharge sources have been studied for disinfection and the two major challenges faced are the use of expensive noble gases (Ar/He) by many plasma sources and the difficulty to scale up the plasma devices. The efficacies of these devices also vary for different plasma sources, making it difficult to compare results from different research groups. Also, the interaction of plasma with the biological matter is not understood well, particularly for virus. In this work, a two-dimensional array of micro dielectric barrier discharge is used to treat Feline Calicivirus (FCV), which is a surrogate for human Norovirus. The plasma source can be operated with an air flow rate (up to 94 standard liters per minute or slm). The use of such discharge source also raises important scientific questions which are addressed in this work. These questions include the effect of gas flow rate on discharge properties and the production of reactive species responsible for virus inactivation and the underlying inactivation mechanism. The plasma source is characterized via several diagnostic techniques such as current voltage measurements for electrical characterization and power measurements, optical emission spectroscopy (OES) to determine the gas temperature, cross-correlation spectroscopy (CCS) for microdischarge evolution and timescales, UV absorption spectroscopy to measure the O3 density, absolute IR OES to measure the O2(a 1Deltag) density and spectrophotometry to estimate the NOx species density in aqueous medium. The results show that the discharge activity is strongly dependent on the gas flow rate particularly for gas residence times comparable to the applied high voltage cycle. The maximum difference in gas temperature at extreme plasma conditions do not exceed 50 K. The NO density is found to be reducing with smaller gas residence time. It is found that the reduced field E/N is dependent on the flow rate. The observed variation in the electric field is attributed to the change in the neutral gas densities. Both gas residence time and humidity have an impact on the space-charge distribution. The O 3 density is found to increase with increasing power density and saturates at higher power above 12 W, and the maximum density of 1022 m-3 is achieved at an intermediate flow rate of 20 slm. An optimal condition for O2(a 1Deltag) generation is found that is a balance between power and gas residence. Higher specific energy leads to higher increase of O2(a 1Deltag) density as compared to the O3 density. It is also observed that the O2(a 1Deltag) to O3 density ratio could be controlled by the flow rate from 0.7 to almost 0. The discharge source is used for FCV inactivation on surfaces (in the gas phase) and suspended in solution. Discharge power and treatment time have strong effect on the reduction in virus titer, while exposure distance or flow rate have negligible effect. Humidity plays a major effect on FCV inactivation on surfaces, leading to complete inactivation (>4 log10) within 3 minutes of treatment. FCV inactivation can be explained by O3 in gas phase and RNS in liquid phase. Nonetheless synergistic effects of ROS and RNS cannot be excluded, as similar production rates of O3 and NOx in discharge are determined. The O2(a 1Deltag) density at conditions used for FCV treatment is at least 2 orders of magnitude lower than the ozone density and is not a dominant factor in the inactivation.

Describing different styles of singing: a comparison of a female singer's voice source in "Classical", "Pop", "Jazz" and "Blues".

PubMed

Thalén, M; Sundberg, J

2001-01-01

The voice is apparently used in quite different manners in different styles of singing. Some of these differences concern the voice source, which varies considerably with loudness, pitch, and mode of phonation. We attempt to describe voice source differences between Classical, Pop, Jazz and Blues styles of singing as produced in a triad melody pattern by a professional female singer in soft, middle and loud phonation. An expert panel was asked to identify these triads as examples of either Classical, Pop, Jazz or Blues. The voice source was analysed by inverse filtering. Subglottal pressure Ps, closed quotient QClosed, glottal compliance (ratio between the air volume contained in a voice pulse and Ps), and the level difference between the two lowest source spectrum partials were analysed in the styles and in four modes of phonation: breathy, flow, neutral, and pressed. The same expert panel rated the degree of pressedness in the entire material. Averages across pitch were calculated for each mode and style and related to their total range of variation in the subject. The glottogram data showed a high correlation with the ratings of pressedness. Based on these correlations a pressedness factor was computed from the glottogram data. A phonation map was constructed with the axes representing mean adduction factor and mean Ps, respectively. In this map Classical was similar to flow phonation, Pop and Jazz to neutral and flow phonation, and Blues to pressed phonation.

40 CFR 463.24 - New source performance standards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... usage flow rate for cleaning processes at a new source times the following pollutant concentrations: Subpart B [Cleaning water] Concentration used to calculate NSPS Pollutant or pollutant property Maximum for any 1 day (mg/l) Maximum for monthly average (mg/l) BOD5 49 22 Oil and Grease 71 17 TSS 117 36 pH...

40 CFR 463.24 - New source performance standards.

Code of Federal Regulations, 2013 CFR

2013-07-01

... usage flow rate for cleaning processes at a new source times the following pollutant concentrations: Subpart B [Cleaning water] Concentration used to calculate NSPS Pollutant or pollutant property Maximum for any 1 day (mg/l) Maximum for monthly average (mg/l) BOD5 49 22 Oil and Grease 71 17 TSS 117 36 pH...

Impacts of Land Use/Cover Uncertainty on Predictions of Ecologically Relevant Flow Metrics

NASA Astrophysics Data System (ADS)

Kalin, L.; Dosdogru, F.

2016-12-01

Streamflow regimes are crucial parts of the ecological integrity in river systems. Although species are adopted to natural flow variability, permanent changes in flow regimes as a result of alterations in land use/cover of the watersheds can adversely impact ecosystem health. This study assessed the impacts of land use/cover (LULC) changes on ecologically relevant flow (ERF) metrics in the rapidly urbanizing upper Cahaba River basin in north-central Alabama. Cahaba River is the longest free-flowing river in the state of Alabama and is identified by the Nature Conservancy as one of the only eight "Hotspot of Biodiversity" in the contiguous United States. Cahaba River and its major tributaries support 69 rare and imperiled species, making it one of the most various aquatic ecosystems in the United States. SWAT model was used to generate daily streamflows, which were then fed into the Indicators of Hydrological Alterations (IHA) software to generate 38 key ERF metrics that capture high, low, and median flow, as well as flashiness, which are known to have significant impacts on flora and fauna. SWAT was calibrated and validated twice with two different sources of LULC. Model performances during calibration and validations were very good and were very similar with both LULC. The flow duration curves generated based on each LULC also look very similar. However, when we compared the ERF metrics significant differences were observed signifying the importance of LULC sources. The biggest differences were in Oct-Dec low flows, rise and fall rates of daily flows, annual maximum flow and average during month od October. This study shows that although model calibration can compensate for the differences in differences in LULC sources, when it comes to key ERF metrics the use of the most reliable LULC source is evident.

Influence of source parameters on the growth of metal nanoparticles by sputter-gas-aggregation

NASA Astrophysics Data System (ADS)

Khojasteh, Malak; Kresin, Vitaly V.

2017-11-01

We describe the production of size-selected manganese nanoclusters using a magnetron sputtering/aggregation source. Since nanoparticle production is sensitive to a range of overlapping operating parameters (in particular, the sputtering discharge power, the inert gas flow rates, and the aggregation length), we focus on a detailed map of the influence of each parameter on the average nanocluster size. In this way, it is possible to identify the main contribution of each parameter to the physical processes taking place within the source. The discharge power and argon flow supply the metal vapor, and argon also plays a crucial role in the formation of condensation nuclei via three-body collisions. However, the argon flow and the discharge power have a relatively weak effect on the average nanocluster size in the exiting beam. Here the defining role is played by the source residence time, governed by the helium supply (which raises the pressure and density of the gas column inside the source, resulting in more efficient transport of nanoparticles to the exit) and by the aggregation path length.

Aircraft Engine Sump Fire Mitigation, Phase 2

NASA Technical Reports Server (NTRS)

Rosenlieb, J. W.

1978-01-01

The effect of changes in the input parameters (air leakage flow rate and temperature and lubricating oil inlet flow rate and temperature) over a specified range on the flammability conditions within an aircraft engine bearing sump was investigated. An analytical study was performed to determine the effect of various parameters on the generation rate of oil vapor from oil droplets in a hot air stream flowing in a cylindrical tube. The ignition of the vapor-air mixture by an ignition source was considered. The experimental investigation demonstrated that fires would be ignited by a spark ignitor over the full range of air and oil flow rates and air temperatures evaluated. However, no fires could be ignited when the oil inlet temperature was maintained below 41.7 K (290 F). The severity of the fires ignited were found to be directly proportional to the hot air flow rate. Reasonably good correlation was found between the mixture temperature in the sump at the ignitor location and the flammability limits as defined by flammability theory; thus a fairly reliable experimental method of determining flammable conditions within a sump was demonstrated. The computerized mathematical model shows that oil droplet size and air temperature have the greatest influence on the generation rate of oil vapor.

40 CFR 60.424 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Ammonium Sulfate.../ton) of ammonium sulfate produced. cs = concentration of particulate matter, g/dscm (g/dscf). Qsd = volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P = production rate of ammonium sulfate, Mg/hr (ton...

40 CFR 60.404 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock.../ton) of phosphate rock feed. cs=concentration of particulate matter, g/dscm (g/dscf). Qsd=volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P=phosphate rock feed rate, Mg/hr (ton/hr). K=conversion...

40 CFR 60.404 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock.../ton) of phosphate rock feed. cs = concentration of particulate matter, g/dscm (g/dscf). Qsd = volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P=phosphate rock feed rate, Mg/hr (ton/hr). K...

40 CFR 60.404 - Test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock.../ton) of phosphate rock feed. cs=concentration of particulate matter, g/dscm (g/dscf). Qsd=volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P=phosphate rock feed rate, Mg/hr (ton/hr). K=conversion...

40 CFR 60.404 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock.../ton) of phosphate rock feed. cs=concentration of particulate matter, g/dscm (g/dscf). Qsd=volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P=phosphate rock feed rate, Mg/hr (ton/hr). K=conversion...

40 CFR 60.404 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Phosphate Rock.../ton) of phosphate rock feed. cs=concentration of particulate matter, g/dscm (g/dscf). Qsd=volumetric flow rate of effluent gas, dscm/hr (dscf/hr). P=phosphate rock feed rate, Mg/hr (ton/hr). K=conversion...

Debris flow susceptibility mapping using a qualitative heuristic method and Flow-R along the Yukon Alaska Highway Corridor, Canada

NASA Astrophysics Data System (ADS)

Blais-Stevens, A.; Behnia, P.

2016-02-01

This research activity aimed at reducing risk to infrastructure, such as a proposed pipeline route roughly parallel to the Yukon Alaska Highway Corridor (YAHC), by filling geoscience knowledge gaps in geohazards. Hence, the Geological Survey of Canada compiled an inventory of landslides including debris flow deposits, which were subsequently used to validate two different debris flow susceptibility models. A qualitative heuristic debris flow susceptibility model was produced for the northern region of the YAHC, from Kluane Lake to the Alaska border, by integrating data layers with assigned weights and class ratings. These were slope angle, slope aspect, surficial geology, plan curvature, and proximity to drainage system. Validation of the model was carried out by calculating a success rate curve which revealed a good correlation with the susceptibility model and the debris flow deposit inventory compiled from air photos, high-resolution satellite imagery, and field verification. In addition, the quantitative Flow-R method was tested in order to define the potential source and debris flow susceptibility for the southern region of Kluane Lake, an area where documented debris flow events have blocked the highway in the past (e.g. 1988). Trial and error calculations were required for this method because there was not detailed information on the debris flows for the YAHC to allow us to define threshold values for some parameters when calculating source areas, spreading, and runout distance. Nevertheless, correlation with known documented events helped define these parameters and produce a map that captures most of the known events and displays debris flow susceptibility in other, usually smaller, steep channels that had not been previously documented.

Debris flow susceptibility mapping using a qualitative heuristic method and Flow-R along the Yukon Alaska Highway Corridor, Canada

NASA Astrophysics Data System (ADS)

Blais-Stevens, A.; Behnia, P.

2015-05-01

This research activity aimed at reducing risk to infrastructure, such as a proposed pipeline route roughly parallel to the Yukon Alaska Highway Corridor (YAHC) by filling geoscience knowledge gaps in geohazards. Hence, the Geological Survey of Canada compiled an inventory of landslides including debris flow deposits, which were subsequently used to validate two different debris flow susceptibility models. A qualitative heuristic debris flow susceptibility model was produced for the northern region of the YAHC, from Kluane Lake to the Alaska border, by integrating data layers with assigned weights and class ratings. These were slope angle, slope aspect (derived from a 5 m × 5 m DEM), surficial geology, permafrost distribution, and proximity to drainage system. Validation of the model was carried out by calculating a success rate curve which revealed a good correlation with the susceptibility model and the debris flow deposit inventory compiled from air photos, high resolution satellite imagery, and field verification. In addition, the quantitative Flow-R method was tested in order to define the potential source and debris flow susceptibility for the southern region of Kluane Lake, an area where documented debris flow events have blocked the highway in the past (e.g., 1988). Trial and error calculations were required for this method because there was not detailed information on the debris flows for the YAHC to allow us to define threshold values for some parameters when calculating source areas, spreading, and runout distance. Nevertheless, correlation with known documented events helped define these parameters and produce a map that captures most of the known events and displays debris flow susceptibility in other, usually smaller, steep channels that had not been previously documented.

Generalized Fluid System Simulation Program, Version 5.0-Educational. Supplemental Information for NASA/TM-2011-216470. Supplement

NASA Technical Reports Server (NTRS)

Majumdar, A. K.

2011-01-01

The Generalized Fluid System Simulation Program (GFSSP) is a finite-volume based general-purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors and external body forces such as gravity and centrifugal. The thermofluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the point, drag and click method; the users can also run their models and post-process the results in the same environment. The integrated fluid library supplies thermodynamic and thermo-physical properties of 36 fluids and 21 different resistance/source options are provided for modeling momentum sources or sinks in the branches. This Technical Memorandum illustrates the application and verification of the code through 12 demonstrated example problems. This supplement gives the input and output data files for the examples.

Air exchange rates and migration of VOCs in basements and residences

PubMed Central

Du, Liuliu; Batterman, Stuart; Godwin, Christopher; Rowe, Zachary; Chin, Jo-Yu

2015-01-01

Basements can influence indoor air quality by affecting air exchange rates (AERs) and by the presence of emission sources of volatile organic compounds (VOCs) and other pollutants. We characterized VOC levels, AERs and interzonal flows between basements and occupied spaces in 74 residences in Detroit, Michigan. Flows were measured using a steady-state multi-tracer system, and 7-day VOC measurements were collected using passive samplers in both living areas and basements. A walkthrough survey/inspection was conducted in each residence. AERs in residences and basements averaged 0.51 and 1.52 h−1, respectively, and had strong and opposite seasonal trends, e.g., AERs were highest in residences during the summer, and highest in basements during the winter. Air flows from basements to occupied spaces also varied seasonally. VOC concentration distributions were right-skewed, e.g., 90th percentile benzene, toluene, naphthalene and limonene concentrations were 4.0, 19.1, 20.3 and 51.0 μg m−3, respectively; maximum concentrations were 54, 888, 1117 and 134 μg m−3. Identified VOC sources in basements included solvents, household cleaners, air fresheners, smoking, and gasoline-powered equipment. The number and type of potential VOC sources found in basements are significant and problematic, and may warrant advisories regarding the storage and use of potentially strong VOCs sources in basements. PMID:25601281

Sound production due to large-scale coherent structures

NASA Technical Reports Server (NTRS)

Gatski, T. B.

1979-01-01

The acoustic pressure fluctuations due to large-scale finite amplitude disturbances in a free turbulent shear flow are calculated. The flow is decomposed into three component scales; the mean motion, the large-scale wave-like disturbance, and the small-scale random turbulence. The effect of the large-scale structure on the flow is isolated by applying both a spatial and phase average on the governing differential equations and by initially taking the small-scale turbulence to be in energetic equilibrium with the mean flow. The subsequent temporal evolution of the flow is computed from global energetic rate equations for the different component scales. Lighthill's theory is then applied to the region with the flowfield as the source and an observer located outside the flowfield in a region of uniform velocity. Since the time history of all flow variables is known, a minimum of simplifying assumptions for the Lighthill stress tensor is required, including no far-field approximations. A phase average is used to isolate the pressure fluctuations due to the large-scale structure, and also to isolate the dynamic process responsible. Variation of mean square pressure with distance from the source is computed to determine the acoustic far-field location and decay rate, and, in addition, spectra at various acoustic field locations are computed and analyzed. Also included are the effects of varying the growth and decay of the large-scale disturbance on the sound produced.

Microplasma-based flowing atmospheric-pressure afterglow (FAPA) source for ambient desorption-ionization mass spectrometry.

PubMed

Zeiri, Offer M; Storey, Andrew P; Ray, Steven J; Hieftje, Gary M

2017-02-01

A new direct-current microplasma-based flowing atmospheric pressure afterglow (FAPA) source was developed for use in ambient desorption-ionization mass spectrometry. The annular-shaped microplasma is formed in helium between two concentric stainless-steel capillaries that are separated by an alumina tube. Current-voltage characterization of the source shows that this version of the FAPA operates in the normal glow-discharge regime. A glass surface placed in the path of the helium afterglow reaches temperatures of up to approximately 400 °C; the temperature varies with distance from the source and helium flow rate through the source. Solid, liquid, and vapor samples were examined by means of a time-of-flight mass spectrometer. Results suggest that ionization occurs mainly through protonation, with only a small amount of fragmentation and adduct formation. The mass range of the source was shown to extend up to at least m/z 2722 for singly charged species. Limits of detection for several small organic molecules were in the sub-picomole range. Examination of competitive ionization revealed that signal suppression occurs only at high (mM) concentrations of competing substances. Copyright © 2016 Elsevier B.V. All rights reserved.

Uranyl adsorption kinetics within silica gel: dependence on flow velocity and concentration

NASA Astrophysics Data System (ADS)

Dodd, Brandon M.; Tepper, Gary

2017-09-01

Trace quantities of a uranyl dissolved in water were measured using a simple optical method. A dilute solution of uranium nitrate dissolved in water was forced through nanoporous silica gel at fixed and controlled water flow rates. The uranyl ions deposited and accumulated within the silica gel and the uranyl fluorescence within the silica gel was monitored as a function of time using a light emitting diode as the excitation source and a photomultiplier tube detector. It was shown that the response time of the fluorescence output signal at a particular volumetric flow rate or average liquid velocity through the silica gel can be used to quantify the concentration of uranium in water. The response time as a function of concentration decreased with increasing flow velocity.

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

Pak, S.; Sites, J.R.

A Kaufman-type broad beam ion source, used for sputtering and etching purposes, has been operated with Ar, Kr,O/sub 2/ and N/sub 2/ gas inputs over a wide range of beam energies (200-1200 eV) and gas flow rates (1-10 sccm). The maximum ion beam current density for each gas saturates at about 2.5 mA/sq. cm. as gas flow is increased. The discharge threshold voltage necessary to produce a beam and the beam efficiency (beam current/molecular current), however, varied considerably. Kr had the lowest threshold and highest efficiency, Ar next, then N/sub 2/ and O/sub 2/. The ion beam current varied onlymore » weakly with beam energy for low gas flow rates, but showed a factor of two increase when the gas flow was higher.« less

Redistribution of blood within the body is important for thermoregulation in an ectothermic vertebrate (Crocodylus porosus).

PubMed

Seebacher, Frank; Franklin, Craig E

2007-11-01

Changes in blood flow are a principal mechanism of thermoregulation in vertebrates. Changes in heart rate will alter blood flow, although multiple demands for limited cardiac output may compromise effective thermoregulation. We tested the hypothesis that regional differences in blood flow during heating and cooling can occur independently from changes in heart rate. We measured heart rate and blood pressure concurrently with blood flow in the crocodile, Crocodylus porosus. We measured changes in blood flow by laser Doppler flowmetry, and by injecting coloured microspheres. All measurements were made under different heat loads, with and without blocking cholinergic and beta-adrenergic receptors (autonomic blockade). Heart rates were significantly faster during heating than cooling in the control animals, but not when autonomic receptors were blocked. There were no significant differences in blood flow distribution between the control and autonomic blockade treatments. In both treatments, blood flow was directed to the dorsal skin and muscle and away from the tail and duodenum during heating. When the heat source was switched off, there was a redistribution of blood from the dorsal surface to the duodenum. Blood flow to the leg skin and muscle, and to the liver did not change significantly with thermal state. Blood pressure was significantly higher during the autonomic blockade than during the control. Thermal time constants of heating and cooling were unaffected by the blockade of autonomic receptors. We concluded that animals partially compensated for a lack of differential heart rates during heating and cooling by redistributing blood within the body, and by increasing blood pressure to increase flow. Hence, measures of heart rate alone are insufficient to assess physiological thermoregulation in reptiles.

Inclusion of TCAF model in XSPEC to study accretion flow dynamics around black hole candidates

NASA Astrophysics Data System (ADS)

Debnath, Dipak; Chakrabarti, Sandip Kumar; Mondal, Santanu

Spectral and Temporal properties of black hole candidates can be well understood with the Chakrabarti-Titarchuk solution of two component advective flow (TCAF). This model requires two accretion rates, namely, the Keplerian disk accretion rate and the sub-Keplerian halo accretion rate, the latter being composed of a low angular momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disk rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for the first time we are able to create a user friendly version by implementing additive Table model FITS file into GSFC/NASA's spectral analysis software package XSPEC. This enables any user to extract physical parameters of accretion flows, such as two accretion rates, shock location, shock strength etc. for any black hole candidate. Most importantly, unlike any other theoretical model, we show that TCAF is capable of predicting timing properties from spectral fits, since in TCAF, a shock is responsible for deciding spectral slopes as well as QPO frequencies.

AMELIA CESTOL Test: Acoustic Characteristics of Circulation Control Wing with Leading-and Trailing-Edge Slot Blowing

NASA Technical Reports Server (NTRS)

Horne, Clifton; Burnside, Nathan J.

2013-01-01

Aeroacoustic measurements of the 11 % scale full-span AMELIA CESTOL model with leading- and trailing-edge slot blowing circulation control (CCW) wing were obtained during a recent test in the Arnold Engineering Development Center 40- by 80-Ft. Wind Tunnel at NASA Ames Research Center, Sound levels and spectra were acquired with seven in-flow microphones and a 48-element phased microphone array for a variety of vehicle configurations, CCW slot flow rates, and forward speeds, Corrections to the measurements and processing are in progress, however the data from selected configurations presented in this report confirm good measurement quality and dynamic range over the test conditions, Array beamform maps at 40 kts tunnel speed show that the trailing edge flap source is dominant for most frequencies at flap angles of 0deg and 60deg, The overall sound level for the 60deg flap was similar to the 0deg flap for most slot blowing rates forward of 90deg incidence, but was louder by up to 6 dB for downstream angles, At 100 kts, the in-flow microphone levels were louder than the sensor self-noise for the higher blowing rates, while passive and active background noise suppression methods for the microphone array revealed source levels as much as 20 dB lower than observed with the in-flow microphones,

The precession dynamo experiment at HZDR

NASA Astrophysics Data System (ADS)

Giesecke, A.; Albrecht, T.; Gerbeth, G.; Gundrum, T.; Nore, C.; Stefani, F.; Steglich, C.

2013-12-01

Most planets of the solar system are accompanied by a magnetic field with a large scale structure. These fields are generated by the dynamo effect, the process that provides for the transfer of kinetic energy from a flow of a conducting fluid into magnetic energy. In case of planetary dynamos it is generally assumed that these flows are driven by thermal and/or chemical convection but other driving sources like libration, tidal forcing or precession are possible as well. Precessional forcing, in particular, has been discussed since long as an at least additional power source for the geodynamo. A fluid flow of liquid sodium, solely driven by precession, will be the source for magnetic field generation in the next generation dynamo experiment currently under development at the Helmholz-Zentrum Dresden-Rossendorf (HZDR). In contrast to previous dynamo experiments no internal blades, propellers or complex systems of guiding tubes will be used for the optimization of the flow properties. However, in order to reach sufficiently high magnetic Reynolds numbers required for the onset of dynamo action rather large dimensions of the container are necessary making the construction of the experiment a challenge. At present state a small scale water experiment is running in order to estimate the hydrodynamic flow properties in dependence of precession angle and precession rate. The measurements are utilized in combination with numerical simulations of the hydrodynamic case as input data for kinematic simulations of the induction equation. The resulting growth rates and the corresponding critical magnetic Reynolds numbers will provide a restriction of the useful parameter regime and will allow an optimization of the experimental configuration.

Pigtail catheters used for percutaneous fluid drainage: comparison of performance characteristics.

PubMed

Macha, Douglas B; Thomas, John; Nelson, Rendon C

2006-03-01

To compare the performance characteristics of various single-lumen all-purpose pigtail drainage catheters. The following parameters were compared: flow rates between catheters of the same size, whether changing the fluid viscosity has any effect on catheter comparisons, the effect on flow of leaving an open three-way stopcock in the drainage pathway, the tendency of the catheters to kink, and catheter patency after kinking, as measured according to flow. All-purpose 8.0-, 8.3-, and 8.5-F (collectively referred to as 8-F); 10.0-, 10.2-, and 10.3-F (collectively referred to as 10-F); and 12.0-F pigtail drainage catheters from three manufacturers were evaluated. Data were compared by using two-tailed t tests after normal distributions were confirmed. P < .05 was considered to represent a significant difference. At comparison of the 8-F catheters, the C.R. Bard catheters demonstrated better flow rates than the Cook and Boston Scientific devices. Among the 10-F catheters, there were no significant differences in the flow rates of fluid with viscosity equivalent to that of water between the C.R. Bard and Boston Scientific catheters; however, both these catheter types demonstrated significantly (P < .05) better flow rates than the Cook devices. Among the 12-F catheters, the C.R. Bard catheters demonstrated significantly (P < .05) better flow rates than the other two catheter types. Changing the fluid viscosity caused no changes in comparison results. In all catheter groups, the presence of a stopcock significantly (P < .05) impaired flow. None of the evaluated catheters demonstrated a clear advantage in terms of patency or susceptibility to kinking. At comparison of the in vitro performances of catheters from different manufacturers, the C.R. Bard 8.0-F and Cook 10.2-F catheters had comparable flow rates, and flow rates through the C.R. Bard and Boston Scientific 10.0-F catheters were comparable to flow rates through the Cook and Boston Scientific 12.0-F catheters. Varying viscosity had no effect on comparisons of catheter flow rates; however, a stopcock between the vacuum source and the catheter was noted to impair flow rates in all brands and sizes of evaluated catheters. Copyright RSNA, 2006.

Simulation of Flow and Long-Term Plutonium (Pu) Transport in the Vadose Zone at the Savannah River National Laboratory (SRNL)

NASA Astrophysics Data System (ADS)

Demirkanli, I.; Molz, F. J.; Kaplan, D. I.; Fjeld, R. A.; Serkiz, S. M.

2006-05-01

An improved understanding of flow and radionuclide transport in vadose zone sediments is fundamental to all types of future planning involving radioactive materials. One way to obtain such understanding is to perform long-term experimental studies of Pu transport in complex natural systems. With this in mind, a series of field experiments were initiated at the SRNL in the early 1980s. Lysimeters containing sources of different Pu oxidation states were placed in the shallow subsurface and left open to the natural environment for 2 to 11 years. At the end of the experiments, Pu activities were measured along vertical cores obtained from the lysimeters. Pu distributions were anomalous in nature, with transport from oxidized Pu sources being less than expected, and a small fraction of Pu from reduced sources moving more. Laboratory studies with lysimeter sediments suggested that surface-mediated, oxidation/reduction (redox) reactions could be responsible for the anomalous behavior, and this hypothesis is tested by performing both steady-state and transient Pu transport simulations that include retardation along with first-order redox reactions on mineral surfaces. Based on the simulations, we conclude that the surface-mediated, redox hypothesis is consistent with the observed downward Pu activity profiles in the experiments, and such profiles are captured well by a steady-state, net downward, flow model. (Discussion is presented as to why a steady model appears to work in a highly transient flow environment.) The redox model explains how Pu(V/VI) sources release activity that moves downward more slowly than expected based on adsorptive retardation alone, and how Pu(III/IV) sources result in a small fraction of activity that moves downward more rapidly than expected. The calibrated parameter values were robust and relatively well-defined throughout all four sets of simulations. Pu(V/VI) (i.e., oxidized Pu)retardation factors were about 15, and reduced Pu(III/IV) retardation factors were about 10,000. For these values, ko (1st order oxidation rate) averaged 2.4x10-7/hr with a standard deviation of 1.6x10-7, and kr (reduction rate)was 7.1x10-4/hr with a standard deviation of 1.6x10-4. Preliminary transient flow simulations showed a very slight increase in the fitted reaction rate constants, but otherwise reproduced the steady-state results. To date, neither approach is able to simulate the observed Pu movement above the source.

Navy Nurse Corps manpower management model.

PubMed

Kinstler, Daniel P; Johnson, Raymond W; Richter, Anke; Kocher, Kathryn

2008-01-01

The Navy Nurse Corps is part of a team of professionals that provides high quality, economical health care to approximately 700,000 active duty Navy and Marine Corps members, as well as 2.6 million retired and family members. Navy Nurse Corps manpower management efficiency is critical to providing this care. This paper aims to focus on manpower planning in the Navy Nurse Corps. The Nurse Corps manages personnel primarily through the recruitment process, drawing on multiple hiring sources. Promotion rates at the lowest two ranks are mandated, but not at the higher ranks. Retention rates vary across pay grades. Using these promotion and attrition rates, a Markov model was constructed to model the personnel flow of junior nurse corps officers. Hiring sources were shown to have a statistically significant effect on promotion and retention rates. However, these effects were not found to be practically significant in the Markov model. Only small improvements in rank imbalances are possible given current recruiting guidelines. Allowing greater flexibility in recruiting practices, fewer recruits would generate a 25 percent reduction in rank imbalances, but result in understaffing. Recruiting different ranks at entry would generate a 65 percent reduction in rank imbalances without understaffing issues. Policies adjusting promotion and retention rates are more powerful in controlling personnel flows than adjusting hiring sources. These policies are the only means for addressing the fundamental sources of rank imbalances in the Navy Nurse Corps arising from current manpower guidelines. The paper shows that modeling to improve manpower management may enable the Navy Nurse Corps to more efficiently fulfill its mandate for high-quality healthcare.

Source model of volcanic tremor: two-phase flow instability in a pipe-valve system

NASA Astrophysics Data System (ADS)

Fujita, E.

2003-12-01

Volcanic tremor at a shallow depth beneath the volcano is inferred to link to hydrothermal activities powered by heat supply from magma. In this study, we developed numerical simulations of the instabilities of the water-steam two-phase flow in a pipe-valve system and considered the source mechanism of volcanic tremor. The experiments of two-phase flow by Veziroglu and Lee [1968] revealed the two kinds of oscillating modes, density wave oscillation with the period of a few seconds and pressure drop oscillation with the period of dozens of seconds. These modes were mainly controlled by the pressure difference between inlet and outlet, flux rate of fluid and heat supply rate. Especially, the former mode appears when the flux rate is small and the latter does when the pressure difference and heat supply rate are larger. We performed some preliminary numerical simulation of these oscillations in water-steam flow in a cylindrical conduit. As an example, we assume the flow in conduit of 4 m length with the valves at inlet and outlet with the conditions of non-slip at the wall. As initial conditions, the inlet and outlet pressures are fixed to be 1.2E5 Pa and 1.0E5 Pa, respectively, water temperature of 370 K, heat supply of 1.0E6 - 2.0E7W/m3. The friction except the valve area is assumed to be 1000kg/m3. After the heating condition becomes stable, we shut the valve at the outlet and detect the significant oscillation. In case of the heat supply of 1.1E7W/m3, density drop oscillation with the period of 0.16s has appeared. In this model, the oscillation originates from the density change due to vaporization, and its information arrives at the outlet with the velocity of two-phase flow. The cycle of heating and boiling controls the interval of the tremor occurrence and the period is determined by the length of the pipe and the flow velocity. The shut of valve physically corresponds to geometrical narrowing, choking, and non-linear effect of flow and/or surrounding medium.

A resettable in-line particle concentrator using AC electrokinetics for distributed monitoring of microalgae in source waters

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

Yuan, Quan; Purdue Univ., West Lafayette, IN; Wu, Jayne

Green algae have been studied as an important and effective biomarker to indicate water quality due to their sensitivity to toxic agents in freshwater sources. But, conventional methods to monitor algal physiology use a chlorophyll fluorometer whose use is hampered by high-cost, large footprint, and limited sensitivity for practical samples containing low algal concentration. In order to overcome these constraints, we developed a multi-level electrode platform for resettable trapping of algae via AC electro-osmosis (ACEO) and negative dielectrophoresis. Preliminary experiments were performed in freshwater with conductivity of 0.02 S/m. Algal trapping was demonstrated at a low voltage of 2 V.more » The concentration effect was experimentally verified by measuring the fluorescence intensity of algae and using hemocytometer counting chambers at the inlet and outlet of the multilevel microchannel lab-on-a-chip. An optimal frequency was found for trapping, which agrees with the frequency dependence of ACEO flow velocity. Through-flow rate and electrode dimensions were optimized as well. Trapping efficiencies within the range of 26% - 65% have been obtained. A maximum trapping rate of 182 cells/s was obtained with a flow rate of 20 l/min. Our lab-on-a-chip shows high potential for improving the limit of detection in algal monitoring and enabling the development of a portable, integrated and automated system for monitoring the quality of source drinking waters.« less

A resettable in-line particle concentrator using AC electrokinetics for distributed monitoring of microalgae in source waters

DOE PAGES

Yuan, Quan; Purdue Univ., West Lafayette, IN; Wu, Jayne; ...

2016-12-29

Green algae have been studied as an important and effective biomarker to indicate water quality due to their sensitivity to toxic agents in freshwater sources. But, conventional methods to monitor algal physiology use a chlorophyll fluorometer whose use is hampered by high-cost, large footprint, and limited sensitivity for practical samples containing low algal concentration. In order to overcome these constraints, we developed a multi-level electrode platform for resettable trapping of algae via AC electro-osmosis (ACEO) and negative dielectrophoresis. Preliminary experiments were performed in freshwater with conductivity of 0.02 S/m. Algal trapping was demonstrated at a low voltage of 2 V.more » The concentration effect was experimentally verified by measuring the fluorescence intensity of algae and using hemocytometer counting chambers at the inlet and outlet of the multilevel microchannel lab-on-a-chip. An optimal frequency was found for trapping, which agrees with the frequency dependence of ACEO flow velocity. Through-flow rate and electrode dimensions were optimized as well. Trapping efficiencies within the range of 26% - 65% have been obtained. A maximum trapping rate of 182 cells/s was obtained with a flow rate of 20 l/min. Our lab-on-a-chip shows high potential for improving the limit of detection in algal monitoring and enabling the development of a portable, integrated and automated system for monitoring the quality of source drinking waters.« less

Does Don Fisher's high-pressure manifold model account for phloem transport and resource partitioning?

PubMed Central

Patrick, John W.

2013-01-01

The pressure flow model of phloem transport envisaged by Münch (1930) has gained wide acceptance. Recently, however, the model has been questioned on structural and physiological grounds. For instance, sub-structures of sieve elements may reduce their hydraulic conductances to levels that impede flow rates of phloem sap and observed magnitudes of pressure gradients to drive flow along sieve tubes could be inadequate in tall trees. A variant of the Münch pressure flow model, the high-pressure manifold model of phloem transport introduced by Donald Fisher may serve to reconcile at least some of these questions. To this end, key predicted features of the high-pressure manifold model of phloem transport are evaluated against current knowledge of the physiology of phloem transport. These features include: (1) An absence of significant gradients in axial hydrostatic pressure in sieve elements from collection to release phloem accompanied by transport properties of sieve elements that underpin this outcome; (2) Symplasmic pathways of phloem unloading into sink organs impose a major constraint over bulk flow rates of resources translocated through the source-path-sink system; (3) Hydraulic conductances of plasmodesmata, linking sieve elements with surrounding phloem parenchyma cells, are sufficient to support and also regulate bulk flow rates exiting from sieve elements of release phloem. The review identifies strong circumstantial evidence that resource transport through the source-path-sink system is consistent with the high-pressure manifold model of phloem transport. The analysis then moves to exploring mechanisms that may link demand for resources, by cells of meristematic and expansion/storage sinks, with plasmodesmal conductances of release phloem. The review concludes with a brief discussion of how these mechanisms may offer novel opportunities to enhance crop biomass yields. PMID:23802003

Development and Evaluation of an Externally Air-Cooled Low-Flow torch and the Attenuation of Space Charge and Matrix Effects in Inductively Coupled Plasma Mass Spectrometry

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

Praphairaksit, Narong

2000-09-12

An externally air-cooled low-flow torch has been constructed and successfully demonstrated for applications in inductively coupled plasma mass spectrometry (ICP-MS). The torch is cooled by pressurized air flowing at ~70 L/min through a quartz air jacket onto the exterior of the outer tube. The outer gas flow rate and operating RF forward power are reduced considerably. Although plasmas can be sustained at the operating power as low as 400 W with a 2 L/min of outer gas flow, somewhat higher power and outer gas flows are advisable. A stable and analytical useful plasma can be obtained at 850 W withmore » an outer gas flow rate of ~4 L/min. Under these conditions, the air-cooled plasma produces comparable sensitivities, doubly charged ion ratios, matrix effects and other analytical merits as those produced by a conventional torch while using significantly less argon and power requirements. Metal oxide ion ratios are slightly higher with the air-cooled plasma but can be mitigated by reducing the aerosol gas flow rate slightly with only minor sacrifice in analyte sensitivity. A methodology to alleviate the space charge and matrix effects in ICP-MS has been developed. A supplemental electron source adapted from a conventional electron impact ionizer is added to the base of the skimmer. Electrons supplied from this source downstream of the skimmer with suitable amount and energy can neutralize the positive ions in the beam extracted from the plasma and diminish the space charge repulsion between them. As a result, the overall ion transmission efficiency and consequent analyte ion sensitivities are significantly improved while other important analytical aspects, such as metal oxide ion ratio, doubly charged ion ratio and background ions remain relatively unchanged with the operation of this electron source. This technique not only improves the ion transmission efficiency but also minimizes the matrix effects drastically. The matrix-induced suppression of signal for even the most troublesome combination of light analyte and heavy matrix elements can be attenuated from 90-99% to only 2-10% for 2 mM matrix solutions with an ultrasonic nebulizer. The supplemental electron current can be adjusted to ''titrate'' out the matrix effects as desired.« less

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering.

PubMed

Miller, Joseph D; Roy, Sukesh; Slipchenko, Mikhail N; Gord, James R; Meyer, Terrence R

2011-08-01

High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

NASA Astrophysics Data System (ADS)

Miller, Joseph D.; Roy, Sukesh; Slipchenko, Mikhail N.; Gord, James R.; Meyer, Terrence R.

2011-08-01

High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

Fixed-target protein serial microcrystallography with an x-ray free electron laser

PubMed Central

Hunter, Mark S.; Segelke, Brent; Messerschmidt, Marc; Williams, Garth J.; Zatsepin, Nadia A.; Barty, Anton; Benner, W. Henry; Carlson, David B.; Coleman, Matthew; Graf, Alexander; Hau-Riege, Stefan P.; Pardini, Tommaso; Seibert, M. Marvin; Evans, James; Boutet, Sébastien; Frank, Matthias

2014-01-01

We present results from experiments at the Linac Coherent Light Source (LCLS) demonstrating that serial femtosecond crystallography (SFX) can be performed to high resolution (~2.5 Å) using protein microcrystals deposited on an ultra-thin silicon nitride membrane and embedded in a preservation medium at room temperature. Data can be acquired at a high acquisition rate using x-ray free electron laser sources to overcome radiation damage, while sample consumption is dramatically reduced compared to flowing jet methods. We achieved a peak data acquisition rate of 10 Hz with a hit rate of ~38%, indicating that a complete data set could be acquired in about one 12-hour LCLS shift using the setup described here, or in even less time using hardware optimized for fixed target SFX. This demonstration opens the door to ultra low sample consumption SFX using the technique of diffraction-before-destruction on proteins that exist in only small quantities and/or do not produce the copious quantities of microcrystals required for flowing jet methods. PMID:25113598

Insights into asthenospheric anisotropy and deformation in Mainland China

NASA Astrophysics Data System (ADS)

Zhu, Tao

2018-03-01

Seismic anisotropy can provide direct constraints on asthenospheric deformation which also can be induced by the inherent mantle flow within our planet. Mantle flow calculations thus have been an effective tool to probe asthenospheric anisotropy. To explore the source of seismic anisotropy, asthenospheric deformation and the effects of mantle flow on seismic anisotropy in Mainland China, mantle flow models driven by plate motion (plate-driven) and by a combination of plate motion and mantle density heterogeneity (plate-density-driven) are used to predict the fast polarization direction of shear wave splitting. Our results indicate that: (1) plate-driven or plate-density-driven mantle flow significantly affects the predicted fast polarization direction when compared with simple asthenospheric flow commonly used in interpreting the asthenospheric source of seismic anisotropy, and thus new insights are presented; (2) plate-driven flow controls the fast polarization direction while thermal mantle flow affects asthenospheric deformation rate and local deformation direction significantly; (3) asthenospheric flow is an assignable contributor to seismic anisotropy, and the asthenosphere is undergoing low, large or moderate shear deformation controlled by the strain model, the flow plane/flow direction model or both in most regions of central and eastern China; and (4) the asthenosphere is under more rapid extension deformation in eastern China than in western China.

Investigation of a liquid-fed water resistojet plume

NASA Technical Reports Server (NTRS)

Manzella, D. H.; Carney, L. M.

1989-01-01

Measurements of mass flux and flow angle were taken throughout the forward flow region of the exhaust of a liquid-fed water resistojet using a quartz crystal microbalance (QCM). The resistojet operated at a mass flow rate of 0.1 g/s with a power input of 330 Watts. Measured values were compared to theoretical predictions obtained by employing a source flow approximation. Excellent agreement between predicted and measured mass flux values was attained; however, this agreement was highly dependent on knowledge of nozzle flow conditions. Measurements of the temperature at which the exhaust condensed on the QCM were obtained as a function of incident mass flux.

Role of hot oxygen in Venusian ionospheric ion energetics and supersonic antisunward flow

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

Knudsen, W.C.

1990-02-01

The column heating rate of the dayside Venus ionospheric ion gas resulting from transfer of energy from the hot oxygen component of the neutral atmosphere is estimated and found equal to that which, when inserted into ionospheric models at the ionopause, raises the calculated temperature to measured values. The transfer of energy is effected through resonant charge exchange between the relatively cold ionospheric O{sup +} ions and the hot oxygen neutrals. The hot oxygen density in the nightside hemisphere does not appear to play a significant role in the nightside ion energetics. The hot oxygen neutral gas flowing across themore » terminator from its dayside source to its nightside sink will exchange momentum with the antisunward flowing ionospheric gas. Although the flow rate of hot oxygen can be estimated only crudely, the estimated rate of deposition and absorption is comparable to that produced by the plasma pressure gradient and should be included in numerical studies of the terminator ionospheric wind.« less

Large Field of View PIV Measurements of Air Entrainment by SLS SMAT Water Sound Suppression System

NASA Astrophysics Data System (ADS)

Stegmeir, Matthew; Pothos, Stamatios; Bissell, Dan

2015-11-01

Water-based sound suppressions systems have been used to reduce the acoustic impact of space vehicle launches. Water flows at a high rate during launch in order to suppress Engine Generated Acoustics and other potentially damaging sources of noise. For the Space Shuttle, peak flow rates exceeded 900,000 gallons per minute. Such large water flow rates have the potential to induce substantial entrainment of the surrounding air, affecting the launch conditions and generating airflow around the launch vehicle. Validation testing is necessary to quantify this impact for future space launch systems. In this study, PIV measurements were performed to map the flow field above the SMAT sub-scale launch vehicle scaled launch stand. Air entrainment effects generated by a water-based sound suppression system were studied. Mean and fluctuating fluid velocities were mapped up to 1m above the test stand deck and compared to simulation results. Measurements performed with NASA MSFC.

Radiogenic heat production in sedimentary rocks of the Gulf of Mexico Basin, south Texas

USGS Publications Warehouse

McKenna, T.E.; Sharp, J.M.

1998-01-01

Radiogenic heat production within the sedimentary section of the Gulf of Mexico basin is a significant source of heat. Radiogenic heat should be included in thermal models of this basin (and perhaps other sedimentary basins). We calculate that radiogenic heat may contribute up to 26% of the overall surface heat-flow density for an area in south Texas. Based on measurements of the radioactive decay rate of ??-particles, potassium concentration, and bulk density, we calculate radiogenic heat production for Stuart City (Lower Cretaceous) limestones, Wilcox (Eocene) sandstones and mudrocks, and Frio (Oligocene) sandstones and mudrocks from south Texas. Heat production rates range from a low of 0.07 ?? 0.01 ??W/m3 in clean Stuart City limestones to 2.21 ?? 0.24??W/m3 in Frio mudrocks. Mean heat production rates for Wilcox sandstones, Frio sandstones, Wilcox mudrocks, and Frio mudrocks are 0.88, 1.19, 1.50, and 1.72 ??W/m3, respectively. In general, the mudrocks produce about 30-40% more heat than stratigraphically equivalent sandstones. Frio rocks produce about 15% more heat than Wilcox rocks per unit volume of clastic rock (sandstone/mudrock). A one-dimensional heat-conduction model indicates that this radiogenic heat source has a significant effect on subsurface temperatures. If a thermal model were calibrated to observed temperatures by optimizing basal heat-flow density and ignoring sediment heat production, the extrapolated present-day temperature of a deeply buried source rock would be overestimated.Radiogenic heat production within the sedimentary section of the Gulf of Mexico basin is a significant source of heat. Radiogenic heat should be included in thermal models of this basin (and perhaps other sedimentary basins). We calculate that radiogenic heat may contribute up to 26% of the overall surface heat-flow density for an area in south Texas. Based on measurements of the radioactive decay rate of ??-particles, potassium concentration, and bulk density, we calculate radiogenic heat production for Stuart City (Lower Cretaceous) limestones, Wilcox (Eocene) sandstones and mudrocks, and Frio (Oligocene) sandstones and mudrocks from south Texas. Heat production rates range from a low of 0.07??0.01 ??W/m3 in clean Stuart City limestones to 2.21??0.24 ??W/m3 in Frio mudrocks. Mean heat production rates for Wilcox sandstones, Frio sandstones, Wilcox mudrocks, and Frio mudrocks are 0.88, 1.19, 1.50, and 1.72 ??W/m3, respectively. In general, the mudrocks produce about 30-40% more heat than stratigraphically equivalent sandstones. Frio rocks produce about 15% more heat than Wilcox rocks per unit volume of clastic rock (sandstone/mudrock). A one-dimensional heat-conduction model indicates that this radiogenic heat source has a significant effect on subsurface temperatures. If a thermal model were calibrated to observed temperatures by optimizing basal heat-flow density and ignoring sediment heat production, the extrapolated present-day temperature of a deeply buried source rock would be overestimated.

Fast blood flow monitoring in deep tissues with real-time software correlators

PubMed Central

Wang, Detian; Parthasarathy, Ashwin B.; Baker, Wesley B.; Gannon, Kimberly; Kavuri, Venki; Ko, Tiffany; Schenkel, Steven; Li, Zhe; Li, Zeren; Mullen, Michael T.; Detre, John A.; Yodh, Arjun G.

2016-01-01

We introduce, validate and demonstrate a new software correlator for high-speed measurement of blood flow in deep tissues based on diffuse correlation spectroscopy (DCS). The software correlator scheme employs standard PC-based data acquisition boards to measure temporal intensity autocorrelation functions continuously at 50 – 100 Hz, the fastest blood flow measurements reported with DCS to date. The data streams, obtained in vivo for typical source-detector separations of 2.5 cm, easily resolve pulsatile heart-beat fluctuations in blood flow which were previously considered to be noise. We employ the device to separate tissue blood flow from tissue absorption/scattering dynamics and thereby show that the origin of the pulsatile DCS signal is primarily flow, and we monitor cerebral autoregulation dynamics in healthy volunteers more accurately than with traditional instrumentation as a result of increased data acquisition rates. Finally, we characterize measurement signal-to-noise ratio and identify count rate and averaging parameters needed for optimal performance. PMID:27231588

Hydrothermal fluid flow and deformation in large calderas: Inferences from numerical simulations

USGS Publications Warehouse

Hurwitz, S.; Christiansen, L.B.; Hsieh, P.A.

2007-01-01

Inflation and deflation of large calderas is traditionally interpreted as being induced by volume change of a discrete source embedded in an elastic or viscoelastic half-space, though it has also been suggested that hydrothermal fluids may play a role. To test the latter hypothesis, we carry out numerical simulations of hydrothermal fluid flow and poroelastic deformation in calderas by coupling two numerical codes: (1) TOUGH2 [Pruess et al., 1999], which simulates flow in porous or fractured media, and (2) BIOT2 [Hsieh, 1996], which simulates fluid flow and deformation in a linearly elastic porous medium. In the simulations, high-temperature water (350??C) is injected at variable rates into a cylinder (radius 50 km, height 3-5 km). A sensitivity analysis indicates that small differences in the values of permeability and its anisotropy, the depth and rate of hydrothermal injection, and the values of the shear modulus may lead to significant variations in the magnitude, rate, and geometry of ground surface displacement, or uplift. Some of the simulated uplift rates are similar to observed uplift rates in large calderas, suggesting that the injection of aqueous fluids into the shallow crust may explain some of the deformation observed in calderas.

Io - A volcanic flow model for the hot spot emission spectrum and a thermostatic mechanism

NASA Technical Reports Server (NTRS)

Sinton, V. M.

1982-01-01

The hot spots of Io are modeled as a steady state of active areas at 600 K, continuing creation of new lava flows and calderas, cooling off of recent flows and calderas, and the cessation of radiation of old flows and calderas from the accumulation of insulation added by resurfacing. There are three adjustable parameters in this model: the area of active sources at 600 K, the rate of production of new area that is cooling, and the temperature of cessation of emission as the result of resurfacing. The resurfacing rate sets constrains on this last parameter. The emission spectrum computed with reasonable values for these parameters is an excellent match to the spectrum from recent observations. A thermostatic mechanism is described whereby the volcanic activity is turned on for a long period of time and is then turned off for a nearly equal period. As a result the presently observed internal heat flow of approximately 1.5 W/sq m may be as much as twice the rate of production of internal heat. Thus the restrictions placed on theories of tidal dissipation by the observed heat flow may be partially relieved.

Formation of manganese nanoclusters in a sputtering/aggregation source and the roles of individual operating parameters

NASA Astrophysics Data System (ADS)

Khojasteh, Malak; Kresin, Vitaly V.

2016-12-01

We describe the production of size selected manganese nanoclusters using a dc magnetron sputtering/aggregation source. Since nanoparticle production is sensitive to a range of overlapping operating parameters (in particular, the sputtering discharge power, the inert gas flow rates, and the aggregation length) we focus on a detailed map of the influence of each parameter on the average nanocluster size. In this way it is possible to identify the main contribution of each parameter to the physical processes taking place within the source. The discharge power and argon flow supply the atomic vapor, and argon also plays the crucial role in the formation of condensation nuclei via three-body collisions. However, neither the argon flow nor the discharge power have a strong effect on the average nanocluster size in the exiting beam. Here the defining role is played by the source residence time, which is governed by the helium supply and the aggregation path length. The size of mass selected nanoclusters was verified by atomic force microscopy of deposited particles.

Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

PubMed

Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

2007-09-04

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

Time variability in Cenozoic reconstructions of mantle heat flow: Plate tectonic cycles and implications for Earth's thermal evolution

PubMed Central

Loyd, S. J.; Becker, T. W.; Conrad, C. P.; Lithgow-Bertelloni, C.; Corsetti, F. A.

2007-01-01

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by ∼0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past. PMID:17720806

A High Precision $3.50 Open Source 3D Printed Rain Gauge Calibrator

NASA Astrophysics Data System (ADS)

Lopez Alcala, J. M.; Udell, C.; Selker, J. S.

2017-12-01

Currently available rain gauge calibrators tend to be designed for specific rain gauges, are expensive, employ low-precision water reservoirs, and do not offer the flexibility needed to test the ever more popular small-aperture rain gauges. The objective of this project was to develop and validate a freely downloadable, open-source, 3D printed rain gauge calibrator that can be adjusted for a wide range of gauges. The proposed calibrator provides for applying low, medium, and high intensity flow, and allows the user to modify the design to conform to unique system specifications based on parametric design, which may be modified and printed using CAD software. To overcome the fact that different 3D printers yield different print qualities, we devised a simple post-printing step that controlled critical dimensions to assure robust performance. Specifically, the three orifices of the calibrator are drilled to reach the three target flow rates. Laboratory tests showed that flow rates were consistent between prints, and between trials of each part, while the total applied water was precisely controlled by the use of a volumetric flask as the reservoir.

METHOD OF OPERATING A CALUTRON

DOEpatents

Davidson, P.H.

1960-01-12

A method of operating an electromagnetic isotope separator of the calutron class is reported whereby uranium tetrachloride is produced at a controlled rate within the source rather than betng introduced therein as was formerly practiced. This is accomplished by placing a uranium-bearing material, such as uranium metal, uranium trichloride, or uranium carbide in the charge receptacle of the calutron, heating this material to about to produce uranium tetrachloride vapor at a rate controlled by the chlorine gas flow into the source. The vapor is subsequently ionized by an electric arc and mass separated by conventional calutron methods.

Erosion of steepland valleys by debris flows

USGS Publications Warehouse

Stock, J.D.; Dietrich, W.E.

2006-01-01

Episodic debris flows scour the rock beds of many steepland valleys. Along recent debris-flow runout paths in the western United States, we have observed evidence for bedrock lowering, primarily by the impact of large particles entrained in debris flows. This evidence may persist to the point at which debris-flow deposition occurs, commonly at slopes of less than ???0.03-0.10. We find that debris-flow-scoured valleys have a topographic signature that is fundamentally different from that predicted by bedrock river-incision models. Much of this difference results from the fact that local valley slope shows a tendency to decrease abruptly downstream of tributaries that contribute throughgoing debris flows. The degree of weathering of valley floor bedrock may also decrease abruptly downstream of such junctions. On the basis of these observations, we hypothesize that valley slope is adjusted to the long-term frequency of debris flows, and that valleys scoured by debris flows should not be modeled using conventional bedrock river-incision laws. We use field observations to justify one possible debris-flow incision model, whose lowering rate is proportional to the integral of solid inertial normal stresses from particle impacts along the flow and the number of upvalley debris-flow sources. The model predicts that increases in incision rate caused by increases in flow event frequency and length (as flows gain material) downvalley are balanced by rate reductions from reduced inertial normal stress at lower slopes, and stronger, less weathered bedrock. These adjustments lead to a spatially uniform lowering rate. Although the proposed expression leads to equilibrium long-profiles with the correct topographic signature, the crudeness with which the debris-flow dynamics are parameterized reveals that we are far from a validated debris-flow incision law. However, the vast extent of steepland valley networks above slopes of ???0.03-0.10 illustrates the need to understand debris-flow incision if we hope to understand the evolution of steep topography around the world. ?? 2006 Geological Society of America.

Rapid geomorphic change caused by glacial outburst floods and debris flows along Tahoma Creek, Mount Rainier, Washington, USA

USGS Publications Warehouse

Walder, J.S.; Driedger, C.L.

1994-01-01

As part of a hazards-assessment study, we examined the nature and rate of geomorphic change caused by outburst floods and debris flows along Tahoma Creek. Mount Rainier, since 1967. Archival aerial photographs of the area proved to be a rich source of qualitative geomorphic information. On the basis of limited direct evidence and considerations of stream hydrology, we conclude that nearly all of these debris flows began as outburst floods from South Tahoma Glacier. The water floods transformed to debris flows by incorporating large masses of sediment in a 2-km-long channel reach where the stream has incised proglacial sediments and debris-rich, stagnant glacier ice. Comparison of topographic maps for 1970 and 1991 shows that the average sediment flux out of the incised reach has been about 2 to 4 × 105 m3 a-1 corresponding to an average denudation rate in the upper part of the Tahoma Creek drainage basin of about 20 to 40 mm a-1, a value exceeded only rarely in basins affected by debris flows. However, little of this sediment has yet passed out of the Tahoma Creek basin. Comparison of geomorphic change at Tahoma Creek to that in two other alpine basins affected by outburst floods suggests that debris-rich stagnant ice can be an important source of sediment for debris flows as long as floods are frequent or channel slope is great.

Removal of unwanted fluid

NASA Astrophysics Data System (ADS)

Subudhi, Sudhakar; Sreenivas, K. R.; Arakeri, Jaywant H.

2013-01-01

This work is concerned with the removal of unwanted fluid through the source-sink pair. The source consists of fluid issuing out of a nozzle in the form of a jet and the sink is a pipe that is kept some distance from the source pipe. Of concern is the percentage of source fluid sucked through the sink. The experiments have been carried in a large glass water tank. The source nozzle diameter is 6 mm and the sink pipe diameter is either 10 or 20 mm. The horizontal and vertical separations and angles between these source and sink pipes are adjustable. The flow was visualized using KMnO4 dye, planer laser induced fluorescence and particle streak photographs. To obtain the effectiveness (that is percentage of source fluid entering the sink pipe), titration method is used. The velocity profiles with and without the sink were obtained using particle image velocimetry. The sink flow rate to obtain a certain effectiveness increase dramatically with lateral separation. The sink diameter and the angle between source and the sink axes don't influence effectiveness as much as the lateral separation.

Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan

NASA Astrophysics Data System (ADS)

Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn; Prata, Fred; Kazahaya, Ryunosuke; Nakamichi, Haruhisa; Iguchi, Masato

2017-12-01

Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Here we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan. Six infrasound stations deployed from 12-20 February 2015 recorded the explosions. We compute numerical Green's functions using 3-D Finite Difference Time Domain modeling and a high-resolution digital elevation model. The inversion, assuming a simple acoustic monopole source, provides realistic eruption masses and excellent fit to the data for the majority of the explosions. The inversion results are compared to independent eruption masses derived from ground-based ash collection and volcanic gas measurements. Assuming realistic flow densities, our infrasound-derived eruption masses for ash-rich eruptions compare favorably to the ground-based estimates, with agreement ranging from within a factor of two to one order of magnitude. Uncertainties in the time-dependent flow density and acoustic propagation likely contribute to the mismatch between the methods. Our results suggest that realistic and accurate infrasound-based eruption mass and mass flow rate estimates can be computed using the method employed here. If accurate volcanic flow parameters are known, application of this technique could be broadly applied to enable near real-time calculation of eruption mass flow rates and total masses. These critical input parameters for volcanic eruption modeling and monitoring are not currently available.

ACCRETION FLOW DYNAMICS OF MAXI J1836-194 DURING ITS 2011 OUTBURST FROM TCAF SOLUTION

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

Jana, Arghajit; Debnath, Dipak; Chakrabarti, Sandip K.

2016-03-20

The Galactic transient X-ray binary MAXI J1836-194 was discovered on 2011 August 29. Here we make a detailed study of the spectral and timing properties of its 2011 outburst using archival data from the RXTE Proportional Counter Array instrument. The evolution of accretion flow dynamics of the source during the outburst through spectral analysis with Chakrabarti–Titarchuk’s two-component advective flow (TCAF) solution as a local table model in XSPEC. We also fitted spectra with combined disk blackbody and power-law models and compared it with the TCAF model fitted results. The source is found to be in hard and hard-intermediate spectral states onlymore » during the entire phase of this outburst. No soft or soft-intermediate spectral states are observed. This could be due to the fact that this object belongs to a special class of sources (e.g., MAXI J1659-152, Swift J1753.5-0127, etc.) that have very short orbital periods and that the companion is profusely mass-losing or the disk is immersed inside an excretion disk. In these cases, flows in the accretion disk are primarily dominated by low viscous sub-Keplerian flow and the Keplerian rate is not high enough to initiate softer states. Low-frequency quasi-periodic oscillations (QPOs) are observed sporadically although as in normal outbursts of transient black holes, monotonic evolutions of QPO frequency during both rising and declining phases are observed. From the TCAF fits, we find the mass of the black hole in the range of 7.5–11 M{sub ⊙}, and from time differences between peaks of the Keplerian and sub-Keplerian accretion rates we obtain a viscous timescale for this particular outburst, ∼10 days.« less

Lava effusion rate definition and measurement: a review

USGS Publications Warehouse

Calvari, Sonia; Dehn, Jonathan; Harris, A.

2007-01-01

Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.

Ultra-Sensitive Biological Detection via Nanoparticle-Based Magnetically Amplified Surface Plasmon Resonance (Mag-SPR) Techniques

DTIC Science & Technology

2008-10-08

of reactant to ferrocene and xylene, a liquid carbon source, results in longer nanostructures in larger amount as shown in Fig. 2(g). These samples...with 6.5 mol% ferrocene and 100 mol% xylene. The flow rate was (e) 0.195 ml/hr, (f) 0.98 ml/hr, and (g) 1.95 ml/hr. (d) and (h) are HR-TEM images of...and ferrocene . The flow rate was (a) 0.195 ml/hr and (b) 1.95 ml/hr........................ 19  Fig. A-5. STEM EDS analysis of the CF specimen after

A diagonal implicit scheme for computing flows with finite-rate chemistry

NASA Technical Reports Server (NTRS)

Eberhardt, Scott; Imlay, Scott

1990-01-01

A new algorithm for solving steady, finite-rate chemistry, flow problems is presented. The new scheme eliminates the expense of inverting large block matrices that arise when species conservation equations are introduced. The source Jacobian matrix is replaced by a diagonal matrix which is tailored to account for the fastest reactions in the chemical system. A point-implicit procedure is discussed and then the algorithm is included into the LU-SGS scheme. Solutions are presented for hypervelocity reentry and Hydrogen-Oxygen combustion. For the LU-SGS scheme a CFL number in excess of 10,000 has been achieved.

The development of alum rates to enhance the remediation of phosphorus in fluvial systems following manure spills

USDA-ARS?s Scientific Manuscript database

Following the remediation of animal manure spills that reach surface waters, contaminated streambed sediments are often left in place and become a source for internal P loading within the stream in subsequent flow. The objective of this study was to develop treatment rates and combinations of alum a...

Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

NASA Technical Reports Server (NTRS)

Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

1995-01-01

Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

Tracking the evolution of stream DOM source during storm events using end member mixing analysis based on DOM quality

NASA Astrophysics Data System (ADS)

Yang, Liyang; Chang, Soon-Woong; Shin, Hyun-Sang; Hur, Jin

2015-04-01

The source of river dissolved organic matter (DOM) during storm events has not been well constrained, which is critical in determining the quality and reactivity of DOM. This study assessed temporal changes in the contributions of four end members (weeds, leaf litter, soil, and groundwater), which exist in a small forested watershed (the Ehwa Brook, South Korea), to the stream DOM during two storm events, using end member mixing analysis (EMMA) based on spectroscopic properties of DOM. The instantaneous export fluxes of dissolved organic carbon (DOC), chromophoric DOM (CDOM), and fluorescent components were all enhanced during peak flows. The DOC concentration increased with the flow rate, while CDOM and humic-like fluorescent components were diluted around the peak flows. Leaf litter was dominant for the DOM source in event 2 with a higher rainfall, although there were temporal variations in the contributions of the four end members to the stream DOM for both events. The contribution of leaf litter peaked while that of deeper soils decreased to minima at peak flows. Our results demonstrated that EMMA based on DOM properties could be used to trace the DOM source, which is of fundamental importance for understanding the factors responsible for river DOM dynamics during storm events.

Implementation of two-component advective flow solution in XSPEC

NASA Astrophysics Data System (ADS)

Debnath, Dipak; Chakrabarti, Sandip K.; Mondal, Santanu

2014-05-01

Spectral and temporal properties of black hole candidates can be explained reasonably well using Chakrabarti-Titarchuk solution of two-component advective flow (TCAF). This model requires two accretion rates, namely the Keplerian disc accretion rate and the halo accretion rate, the latter being composed of a sub-Keplerian, low-angular-momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disc rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for the first time, we made it user friendly by implementing it into XSPEC software of Goddard Space Flight Center (GSFC)/NASA. This enables any user to extract physical parameters of the accretion flows, such as two accretion rates, the shock location, the shock strength, etc., for any black hole candidate. We provide some examples of fitting a few cases using this model. Most importantly, unlike any other model, we show that TCAF is capable of predicting timing properties from the spectral fits, since in TCAF, a shock is responsible for deciding spectral slopes as well as quasi-periodic oscillation frequencies. L86

Intrinsically safe moisture blending system

DOEpatents

Hallman Jr., Russell L.; Vanatta, Paul D.

2012-09-11

A system for providing an adjustable blend of fluids to an application process is disclosed. The system uses a source of a first fluid flowing through at least one tube that is permeable to a second fluid and that is disposed in a source of the second fluid to provide the adjustable blend. The temperature of the second fluid is not regulated, and at least one calibration curve is used to predict the volumetric mixture ratio of the second fluid with the first fluid from the permeable tube. The system typically includes a differential pressure valve and a backpressure control valve to set the flow rate through the system.

Effect of a rotating propeller on the separation angle of attack

NASA Technical Reports Server (NTRS)

Boldman, D. R.; Iek, C.; Hwang, D. P.; Larkin, M.; Schweiger, P.

1993-01-01

The present study represents an extension of an earlier wind tunnel experiment performed with the P&W 17-in. Advanced Ducted Propeller (ADP) Simulator operating at Mach 0.2. In order to study the effects of a rotating propeller on the inlet flow, data were obtained in the UTRC 10- by 15-Foot Large Subsonic Wind Tunnel with the same hardware and instrumentation, but with the propellar removed. These new tests were performed over a range of flow rates which duplicated flow rates in the powered simulator program. The flow through the inlet was provided by a remotely located vacuum source. A comparison of the results of this flow-through study with the previous data from the powered simulator indicated that in the conventional inlet the propeller produced an increase in the separation angle of attack between 4.0 deg at a specific flow of 22.4 lb/sec-sq ft to 2.7 deg at a higher specific flow of 33.8 lb/sec-sq ft. A similar effect on separation angle of attack was obtained by using stationary blockage rather than a propeller.

A Tracking Analyst for large 3D spatiotemporal data from multiple sources (case study: Tracking volcanic eruptions in the atmosphere)

NASA Astrophysics Data System (ADS)

Gad, Mohamed A.; Elshehaly, Mai H.; Gračanin, Denis; Elmongui, Hicham G.

2018-02-01

This research presents a novel Trajectory-based Tracking Analyst (TTA) that can track and link spatiotemporally variable data from multiple sources. The proposed technique uses trajectory information to determine the positions of time-enabled and spatially variable scatter data at any given time through a combination of along trajectory adjustment and spatial interpolation. The TTA is applied in this research to track large spatiotemporal data of volcanic eruptions (acquired using multi-sensors) in the unsteady flow field of the atmosphere. The TTA enables tracking injections into the atmospheric flow field, the reconstruction of the spatiotemporally variable data at any desired time, and the spatiotemporal join of attribute data from multiple sources. In addition, we were able to create a smooth animation of the volcanic ash plume at interactive rates. The initial results indicate that the TTA can be applied to a wide range of multiple-source data.

Cyclic variations in nitrogen uptake rate of soybean plants: ammonium as a nitrogen source

NASA Technical Reports Server (NTRS)

Henry, L. T.; Raper, C. D. Jr

1989-01-01

When NO3- is the sole nitrogen source in flowing solution culture, the net rate of nitrogen uptake by nonnodulated soybean (Glycine max L. Merr. cv Ransom) plants cycles between maxima and minima with a periodicity of oscillation that corresponds with the interval of leaf emergence. Since soybean plants accumulate similar quantities of nitrogen when either NH4+ or NO3- is the sole source in solution culture controlled at pH 6.0, an experiment was conducted to determine if the oscillations in net rate of nitrogen uptake also occur when NH4+ is the nitrogen source. During a 21-day period of vegetative development, net uptake of NH4+ was measured daily by ion chromatography as depletion of NH4+ from a replenished nutrient solution containing 1.0 millimolar NH4+. The net rate of NH4+ uptake oscillated with a periodicity that was similar to the interval of leaf emergence. Instances of negative net rates of uptake indicate that the transition between maxima and minima involved changes in influx and efflux components of net NH4+ uptake.

Runoff phosphorus losses as related to phosphorus source, application method, and application rate on a Piedmont soil.

PubMed

Tarkalson, David D; Mikkelsen, Robert L

2004-01-01

Land application of animal manures and fertilizers has resulted in an increased potential for excessive P losses in runoff to nutrient-sensitive surface waters. The purpose of this research was to measure P losses in runoff from a bare Piedmont soil in the southeastern United States receiving broiler litter or inorganic P fertilizer either incorporated or surface-applied at varying P application rates (inorganic P, 0-110 kg P ha(-1); broiler litter, 0-82 kg P ha(-1)). Rainfall simulation was applied at a rate of 76 mm h(-1). Runoff samples were collected at 5-min intervals for 30 min and analyzed for reactive phosphorus (RP), algal-available phosphorus (AAP), and total phosphorus (TP). Incorporation of both P sources resulted in P losses not significantly different than the unfertilized control at all application rates. Incorporation of broiler litter decreased flow-weighted concentration of RP in runoff by 97% and mass loss of TP in runoff by 88% compared with surface application. Surface application of broiler litter resulted in runoff containing between 2.3 and 21.8 mg RP L(-1) for application rates of 8 to 82 kg P ha(-1), respectively. Mass loss of TP in runoff from surface-applied broiler litter ranged from 1.3 to 8.5 kg P ha(-1) over the same application rates. Flow-weighted concentrations of RP and mass losses of TP in runoff were not related to application rate when inorganic P fertilizer was applied to the soil surface. Results for this study can be used by P loss assessment tools to fine-tune P source, application rate, and application method site factors, and to estimate extreme-case P loss from cropland receiving broiler litter and inorganic P fertilizers.

A depth-averaged debris-flow model that includes the effects of evolving dilatancy. I. physical basis

USGS Publications Warehouse

Iverson, Richard M.; George, David L.

2014-01-01

To simulate debris-flow behaviour from initiation to deposition, we derive a depth-averaged, two-phase model that combines concepts of critical-state soil mechanics, grain-flow mechanics and fluid mechanics. The model's balance equations describe coupled evolution of the solid volume fraction, m, basal pore-fluid pressure, flow thickness and two components of flow velocity. Basal friction is evaluated using a generalized Coulomb rule, and fluid motion is evaluated in a frame of reference that translates with the velocity of the granular phase, vs. Source terms in each of the depth-averaged balance equations account for the influence of the granular dilation rate, defined as the depth integral of ∇⋅vs. Calculation of the dilation rate involves the effects of an elastic compressibility and an inelastic dilatancy angle proportional to m−meq, where meq is the value of m in equilibrium with the ambient stress state and flow rate. Normalization of the model equations shows that predicted debris-flow behaviour depends principally on the initial value of m−meq and on the ratio of two fundamental timescales. One of these timescales governs downslope debris-flow motion, and the other governs pore-pressure relaxation that modifies Coulomb friction and regulates evolution of m. A companion paper presents a suite of model predictions and tests.

A flowing atmospheric pressure afterglow as an ion source coupled to a differential mobility analyzer for volatile organic compound detection.

PubMed

Bouza, Marcos; Orejas, Jaime; López-Vidal, Silvia; Pisonero, Jorge; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo

2016-05-23

Atmospheric pressure glow discharges have been widely used in the last decade as ion sources in ambient mass spectrometry analyses. Here, an in-house flowing atmospheric pressure afterglow (FAPA) has been developed as an alternative ion source for differential mobility analysis (DMA). The discharge source parameters (inter-electrode distance, current and helium flow rate) determining the atmospheric plasma characteristics have been optimized in terms of DMA spectral simplicity with the highest achievable sensitivity while keeping an adequate plasma stability and so the FAPA working conditions finally selected were: 35 mA, 1 L min(-1) of He and an inter-electrode distance of 8 mm. Room temperature in the DMA proved to be adequate for the coupling and chemical analysis with the FAPA source. Positive and negative ions for different volatile organic compounds were tested and analysed by FAPA-DMA using a Faraday cup as a detector and proper operation in both modes was possible (without changes in FAPA operational parameters). The FAPA ionization source showed simpler ion mobility spectra with narrower peaks and a better, or similar, sensitivity than conventional UV-photoionization for DMA analysis in positive mode. Particularly, the negative mode proved to be a promising field of further research for the FAPA ion source coupled to ion mobility, clearly competitive with other more conventional plasmas such as corona discharge.

Determination of psychostimulants and their metabolites by electrochemistry linked on-line to flowing atmospheric pressure afterglow mass spectrometry.

PubMed

Smoluch, Marek; Mielczarek, Przemyslaw; Reszke, Edward; Hieftje, Gary M; Silberring, Jerzy

2014-09-07

The flowing atmospheric pressure afterglow (FAPA) ion source operates in the ambient atmosphere and has been proven to be a promising tool for direct and rapid determination of numerous compounds. Here we linked a FAPA-MS system to an electrochemical flow cell for the identification of drug metabolites generated electrochemically in order to study simulated metabolic pathways. Psychostimulants and their metabolites produced by electrochemistry (EC) were detected on-line by FAPA-MS. The FAPA source has never been used before for an on-line connection with liquid flow, neither for identification of products generated in an electrochemical flow cell. The system was optimized to achieve the highest ionization efficiency by adjusting several parameters, including distances and angles between the ion source and the outlet of the EC system, the high voltage for plasma generation, flow-rates, and EC parameters. Simulated metabolites from tested compounds [methamphetamine (MAF), para-methoxy-N-methylamphetamine (PMMA), dextromethorphan (DXM), and benzydamine (BAM)] were formed in the EC cell at various pH levels. In all cases the main products were oxidized substrates and compounds after N-demethylation. Generation of such products and their thorough on-line identification confirm that the cytochrome P450 - driven metabolism of pharmaceuticals can be efficiently simulated in an electrochemical cell; this approach may serve as a step towards predictive pharmacology using a fast and robust design.

Physical aspects of computing the flow of a viscous fluid

NASA Technical Reports Server (NTRS)

Mehta, U. B.

1984-01-01

One of the main themes in fluid dynamics at present and in the future is going to be computational fluid dynamics with the primary focus on the determination of drag, flow separation, vortex flows, and unsteady flows. A computation of the flow of a viscous fluid requires an understanding and consideration of the physical aspects of the flow. This is done by identifying the flow regimes and the scales of fluid motion, and the sources of vorticity. Discussions of flow regimes deal with conditions of incompressibility, transitional and turbulent flows, Navier-Stokes and non-Navier-Stokes regimes, shock waves, and strain fields. Discussions of the scales of fluid motion consider transitional and turbulent flows, thin- and slender-shear layers, triple- and four-deck regions, viscous-inviscid interactions, shock waves, strain rates, and temporal scales. In addition, the significance and generation of vorticity are discussed. These physical aspects mainly guide computations of the flow of a viscous fluid.

Migration of Amphitheater-Headed Valleys in Kauai Basalts: Wailua Falls as a Case Example

NASA Astrophysics Data System (ADS)

Pederson, D. T.; Blay, C.

2006-12-01

Amphitheater-headed valleys in Kauai basalts migrate upstream primarily because of weathering processes. Basalt weathering rates are enhanced by the presence of water and/or vegetation. When both weathering process are present, weathering rates are greater than the sum of the two processes. Because waterfalls can create an environment where vegetation growth is greatly inhibited by the impact of falling water, weathering rates may be much greater on each side of the falls where vegetation can grow. Sources of water for weathering include groundwater discharge, waterfall spray, and condensation of atmospheric water. Because basalts weather rapidly in tropical environments, streams require only the capability to transport smaller particle sizes to sustain amphitheater migration. It should be noted that most waterfalls occupy only a small fraction of the amphitheater head which further supports weathering as the principal agent in amphitheater development and migration. Lava flows building shield volcanos are usually episodic with crystallization and possible weathering occurring before the next flow. The rate of cooling of a flow determines the crystal size of minerals and in combination with the magma chemistry the susceptibility of a flow to weathering process as well as the strength of the rock. With time, soils and topography will develop on the now crystallized flow. Because clays are a product of basalt weathering, soils when buried by later flows, represent low permeability layers. Additionally, new flows may follow (and bury) surface drainage systems resulting in localized thicker flows that cool more slowly and have different properties then the adjacent thinner flows. Consequently, most amphitheater heads have significant heterogenieties, especially in a vertical section representing multiple basalt flows. Wailua Falls on Kauai will be used as a field example of amphitheater weathering processes and migration.

Episodic fluid flow in the Nankai accretionary complex: Timescale, geochemistry, flow rates, and fluid budget

USGS Publications Warehouse

Saffer, D.M.; Bekins, B.A.

1998-01-01

Down-hole geochemical anomalies encountered in active accretionary systems can be used to constrain the timing, rates, and localization of fluid flow. Here we combine a coupled flow and solute transport model with a kinetic model for smectite dehydration to better understand and quantify fluid flow in the Nankai accretionary complex offshore of Japan. Compaction of sediments and clay dehydration provide fluid sources which drive the model flow system. We explicitly include the consolidation rate of underthrust sediments in our calculations to evaluate the impact that variations in this unknown quantity have on pressure and chloride distribution. Sensitivity analysis of steady state pressure solutions constrains bulk and flow conduit permeabilities. Steady state simulations with 30% smectite in the incoming sedimentary sequence result in minimum chloride concentrations at site 808 of 550 mM, but measured chlorinity is as low as 447 mM. We simulate the transient effects of hydrofracture or a strain event by assuming an instantaneous permeability increase of 3-4 orders of magnitude along a flow conduit (in this case the de??collement), using steady state results as initial conditions. Transient results with an increase in de??collement permeability from 10-16 m2 to 10-13 m2 and 20% smectite reproduce the observed chloride profile at site 808 after 80-160 kyr. Modeled chloride concentrations are highly sensitive to the consolidation rate of underthrust sediments, such that rapid compaction of underthrust material leads to increased freshening. Pressures within the de??collement during transient simulations rise rapidly to a significant fraction of lithostatic and remain high for at least 160 kyr, providing a mechanism for maintaining high permeability. Flow rates at the deformation front for transient simulations are in good agreement with direct measurements, but steady state flow rates are 2-3 orders of magnitude smaller than observed. Fluid budget calculations indicate that nearly 71% of the incoming water in the sediments leaves the accretionary wedge via diffuse flow out the seafloor, 0-5% escapes by focused flow along the de??collement, and roughly 1% is subducted. Copyright 1998 by the American Geophysical Union.

Start-up Characteristics of Swallow-tailed Axial-grooved Heat Pipe under the conditions of Multiple Heat Sources

NASA Astrophysics Data System (ADS)

Zhang, Renping

2017-12-01

A mathematical model was developed for predicting start-up characteristics of Swallow-tailed Axial-grooved Heat Pipe under the conditions of Multiple Heat Sources. The effects of heat capacitance of heat source, liquid-vapour interfacial evaporation-condensation heat transfer, shear stress at the interface was considered in current model. The interfacial evaporating mass flow rate is based on the kinetic analysis. Time variations of evaporating mass rate, wall temperature and liquid velocity are studied from the start-up to steady state. The calculated results show that wall temperature demonstrates step transition at the junction between the heat source and non-existent heat source on the evaporator. The liquid velocity changes drastically at the evaporator section, however, it has slight variation at the evaporator section without heat source. When the effect of heat source is ignored, the numerical temperature demonstrates a quicker response. With the consideration of capacitance of the heat source, the data obtained from the proposed model agree well with the experimental results.

A model for assessing water quality risk in catchments prone to wildfire

NASA Astrophysics Data System (ADS)

Langhans, Christoph; Smith, Hugh; Chong, Derek; Nyman, Petter; Lane, Patrick; Sheridan, Gary

2017-04-01

Post-fire debris flows can have erosion rates up to three orders of magnitude higher than background rates. They are major sources of fine suspended sediment, which is critical to the safety of water supply from forested catchments. Fire can cover parts or all of these large catchments and burn severity is often heterogeneous. The probability of spatial and temporal overlap of fire disturbance and rainfall events, and the susceptibility of hillslopes to severe erosion determine the risk to water quality. Here we present a model to calculate recurrence intervals of high magnitude sediment delivery from runoff-generated debris flows to a reservoir in a large catchment (>100 km2) accounting for heterogeneous burn conditions. Debris flow initiation was modelled with indicators of surface runoff and soil surface erodibility. Debris flow volume was calculated with an empirical model, and fine sediment delivery was calculated using simple, expert-based assumptions. In a Monte-Carlo simulation, wildfire was modelled with a fire spread model using historic data on weather and ignition probabilities for a forested catchment in central Victoria, Australia. Multiple high intensity storms covering the study catchment were simulated using Intensity-Frequency-Duration relationships, and the runoff indicator calculated with a runoff model for hillslopes. A sensitivity analysis showed that fine sediment is most sensitive to variables related to the texture of the source material, debris flow volume estimation, and the proportion of fine sediment transported to the reservoir. As a measure of indirect validation, denudation rates of 4.6 - 28.5 mm ka-1 were estimated and compared well to other studies in the region. From the results it was extrapolated that in the absence of fire management intervention the critical sediment concentrations in the studied reservoir could be exceeded in intervals of 18 - 124 years.

Numerical study of supersonic combustion using a finite rate chemistry model

NASA Technical Reports Server (NTRS)

Chitsomboon, T.; Tiwari, S. N.; Kumar, A.; Drummond, J. P.

1986-01-01

The governing equations of two-dimensional chemically reacting flows are presented together with a global two-step chemistry model for H2-air combustion. The explicit unsplit MacCormack finite difference algorithm is used to advance the discrete system of the governing equations in time until convergence is attained. The source terms in the species equations are evaluated implicitly to alleviate stiffness associated with fast reactions. With implicit source terms, the species equations give rise to a block-diagonal system which can be solved very efficiently on vector-processing computers. A supersonic reacting flow in an inlet-combustor configuration is calculated for the case where H2 is injected into the flow from the side walls and the strut. Results of the calculation are compared against the results obtained by using a complete reaction model.

Low temperature growth of heavy boron-doped hydrogenated Ge epilayers and its application in Ge/Si photodetectors

NASA Astrophysics Data System (ADS)

Kuo, Wei-Cheng; Lee, Ming Jay; Wu, Mount-Learn; Lee, Chien-Chieh; Tsao, I.-Yu; Chang, Jenq-Yang

2017-04-01

In this study, heavily boron-doped hydrogenated Ge epilayers are grown on Si substrates at a low growth temperature (220 °C). The quality of the boron-doped epilayers is dependent on the hydrogen flow rate. The optical emission spectroscopic, X-ray diffraction and Hall measurement results demonstrate that better quality boron-doped Ge epilayers can be obtained at low hydrogen flow rates (0 sccm). This reduction in quality is due to an excess of hydrogen in the source gas, which breaks one of the Ge-Ge bonds on the Ge surface, leading to the formation of unnecessary dangling bonds. The structure of the boron doped Ge epilayers is analyzed by transmission electron microscopy and atomic force microscopy. In addition, the performance, based on the I-V characteristics, of Ge/Si photodetectors fabricated with boron doped Ge epilayers produced under different hydrogen flow rates was examined. The photodetectors with boron doped Ge epilayers produced with a low hydrogen flow rate (0 sccm) exhibited a higher responsivity of 0.144 A/W and a lower dark current of 5.33 × 10-7 A at a reverse bias of 1 V.

Uncertainty in hydrological signatures

NASA Astrophysics Data System (ADS)

McMillan, Hilary; Westerberg, Ida

2015-04-01

Information that summarises the hydrological behaviour or flow regime of a catchment is essential for comparing responses of different catchments to understand catchment organisation and similarity, and for many other modelling and water-management applications. Such information types derived as an index value from observed data are known as hydrological signatures, and can include descriptors of high flows (e.g. mean annual flood), low flows (e.g. mean annual low flow, recession shape), the flow variability, flow duration curve, and runoff ratio. Because the hydrological signatures are calculated from observed data such as rainfall and flow records, they are affected by uncertainty in those data. Subjective choices in the method used to calculate the signatures create a further source of uncertainty. Uncertainties in the signatures may affect our ability to compare different locations, to detect changes, or to compare future water resource management scenarios. The aim of this study was to contribute to the hydrological community's awareness and knowledge of data uncertainty in hydrological signatures, including typical sources, magnitude and methods for its assessment. We proposed a generally applicable method to calculate these uncertainties based on Monte Carlo sampling and demonstrated it for a variety of commonly used signatures. The study was made for two data rich catchments, the 50 km2 Mahurangi catchment in New Zealand and the 135 km2 Brue catchment in the UK. For rainfall data the uncertainty sources included point measurement uncertainty, the number of gauges used in calculation of the catchment spatial average, and uncertainties relating to lack of quality control. For flow data the uncertainty sources included uncertainties in stage/discharge measurement and in the approximation of the true stage-discharge relation by a rating curve. The resulting uncertainties were compared across the different signatures and catchments, to quantify uncertainty magnitude and bias, and to test how uncertainty depended on the density of the raingauge network and flow gauging station characteristics. The uncertainties were sometimes large (i.e. typical intervals of ±10-40% relative uncertainty) and highly variable between signatures. Uncertainty in the mean discharge was around ±10% for both catchments, while signatures describing the flow variability had much higher uncertainties in the Mahurangi where there was a fast rainfall-runoff response and greater high-flow rating uncertainty. Event and total runoff ratios had uncertainties from ±10% to ±15% depending on the number of rain gauges used; precipitation uncertainty was related to interpolation rather than point uncertainty. Uncertainty distributions in these signatures were skewed, and meant that differences in signature values between these catchments were often not significant. We hope that this study encourages others to use signatures in a way that is robust to data uncertainty.

Air-flow regulation system for a coal gasifier

DOEpatents

Fasching, George E.

1984-01-01

An improved air-flow regulator for a fixed-bed coal gasifier is provided which allows close air-flow regulation from a compressor source even though the pressure variations are too rapid for a single primary control loop to respond. The improved system includes a primary controller to control a valve in the main (large) air supply line to regulate large slow changes in flow. A secondary controller is used to control a smaller, faster acting valve in a secondary (small) air supply line parallel to the main line valve to regulate rapid cyclic deviations in air flow. A low-pass filter with a time constant of from 20 to 50 seconds couples the output of the secondary controller to the input of the primary controller so that the primary controller only responds to slow changes in the air-flow rate, the faster, cyclic deviations in flow rate sensed and corrected by the secondary controller loop do not reach the primary controller due to the high frequency rejection provided by the filter. This control arrangement provides at least a factor of 5 improvement in air-flow regulation for a coal gasifier in which air is supplied by a reciprocating compressor through a surge tank.

Numerical Simulation of Noise from Supersonic Jets Passing Through a Rigid Duct

NASA Technical Reports Server (NTRS)

Kandula, Max

2012-01-01

The generation, propagation and radiation of sound from a perfectly expanded Mach 2.5 cold supersonic jet flowing through an enclosed rigid-walled duct with an upstream J-deflector have been numerically simulated with the aid of OVERFLOW Navier-Stokes CFD code. A one-equation turbulence model is considered. While the near-field sound sources are computed by the CFD code, the far-field sound is evaluated by Kirchhoff surface integral formulation. Predictions of the farfield directivity of the OASPL (Overall Sound Pressure Level) agree satisfactorily with the experimental data previously reported by the author. Calculations also suggest that there is significant entrainment of air into the duct, with the mass flow rate of entrained air being about three times the jet exit mass flow rate.

Understanding Hydrological Processes in Variable Source Areas in the Glaciated Northeastern US Watersheds under Variable Climate Conditions

NASA Astrophysics Data System (ADS)

Steenhuis, T. S.; Azzaino, Z.; Hoang, L.; Pacenka, S.; Worqlul, A. W.; Mukundan, R.; Stoof, C.; Owens, E. M.; Richards, B. K.

2017-12-01

The New York City source watersheds in the Catskill Mountains' humid, temperate climate has long-term hydrological and water quality monitoring data It is one of the few catchments where implementation of source and landscape management practices has led to decreased phosphorus concentration in the receiving surface waters. One of the reasons is that landscape measures correctly targeted the saturated variable source runoff areas (VSA) in the valley bottoms as the location where most of the runoff and other nonpoint pollutants originated. Measures targeting these areas were instrumental in lowering phosphorus concentration. Further improvements in water quality can be made based on a better understanding of the flow processes and water table fluctuations in the VSA. For that reason, we instrumented a self-contained upland variable source watershed with a landscape characteristic of a soil underlain by glacial till at shallow depth similar to the Catskill watersheds. In this presentation, we will discuss our experimental findings and present a mathematical model. Variable source areas have a small slope making gravity the driving force for the flow, greatly simplifying the simulation of the flow processes. The experimental data and the model simulations agreed for both outflow and water table fluctuations. We found that while the flows to the outlet were similar throughout the year, the discharge of the VSA varies greatly. This was due to transpiration by the plants which became active when soil temperatures were above 10oC. We found that shortly after the temperature increased above 10oC the baseflow stopped and only surface runoff occurred when rainstorms exceeded the storage capacity of the soil in at least a portion of the variable source area. Since plant growth in the variable source area was a major variable determining the base flow behavior, changes in temperature in the future - affecting the duration of the growing season - will affect baseflow and related transport of nutrient and other chemicals many times more than small temperature related increases in potential evaporation rate. This in turn will directly change the water availability and pollutant transport in the many surface source watersheds with variable source area hydrology.

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

Khan, S. T.; Nagao, Y.; Hiraishi, A., E-mail: hiraishi@ens.tut.ac.jp

Strain NA10B{sup T} and other two strains of the denitrifying betaproteobacterium Diaphorobacter nitroreducens were studied for the performance of solid-phase denitrification (SPD) using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and some other biodegradable plastics as the source of reducing power in wastewater treatment. Sequencing-batch SPD reactors with these organisms and PHBV granules or flakes as the substrate exhibited good nitrate removal performance. Vial tests using cultures from these parent reactors showed higher nitrate removal rates with PHBV granules (ca. 20 mg-NO{sub 3}{sup −}‐N g{sup −1} [dry wt cells] h{sup −1}) than with PHBV pellets and flakes. In continuous-flow SPD reactors using strain NA10B{sup T}more » and PHBV flakes, nitrate was not detected even at a loading rate of 21 mg-NO{sub 3}{sup −}‐N L{sup −1} h{sup −1}. This corresponded to a nitrate removal rate of 47 mg-NO{sub 3}{sup −}‐N g{sup −1} (dry wt cells) h{sup −1}. In the continuous-flow reactor, the transcription level of the phaZ gene, coding for PHB depolymerase, decreased with time, while that of the nosZ gene, involved in denitrificaiton, was relatively constant. These results suggest that the bioavailability of soluble metabolites as electron donor and carbon sources increases with time in the continuous-flow SPD process, thereby having much higher nitrate removal rates than the process with fresh PHBV as the substrate.« less

A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed

USGS Publications Warehouse

Bukaveckas, P.A.; Likens, G.E.; Winter, T.C.; Buso, D.C.

1998-01-01

Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

Predictive onboard flow control for packet switching satellites

NASA Technical Reports Server (NTRS)

Bobinsky, Eric A.

1992-01-01

We outline two alternate approaches to predicting the onset of congestion in a packet switching satellite, and argue that predictive, rather than reactive, flow control is necessary for the efficient operation of such a system. The first method discussed is based on standard, statistical techniques which are used to periodically calculate a probability of near-term congestion based on arrival rate statistics. If this probability exceeds a present threshold, the satellite would transmit a rate-reduction signal to all active ground stations. The second method discussed would utilize a neural network to periodically predict the occurrence of buffer overflow based on input data which would include, in addition to arrival rates, the distributions of packet lengths, source addresses, and destination addresses.

Multiple coincident eruptive seismic tremor sources during the 2014-2015 eruption at Holuhraun, Iceland

NASA Astrophysics Data System (ADS)

Eibl, Eva P. S.; Bean, Christopher J.; Jónsdóttir, Ingibjörg; Höskuldsson, Armann; Thordarson, Thorvaldur; Coppola, Diego; Witt, Tanja; Walter, Thomas R.

2017-04-01

We analyze eruptive tremor during one of the largest effusive eruptions in historical times in Iceland (2014/2015 Holuhraun eruption). Seismic array recordings are compared with effusion rates deduced from Moderate Resolution Imaging Spectroradiometer recordings and ground video monitoring data and lead to the identification of three coexisting eruptive tremor sources. This contrasts other tremor studies that generally link eruptive tremor to only one source usually associated with the vent. The three sources are (i) a source that is stable in back azimuth and shows bursts with ramp-like decrease in amplitude at the beginning of the eruption: we link it to a process below the open vents where the bursts correlate with the opening of new vents and temporary increases in the lava fountaining height; (ii) a source moving by a few degrees per month while the tremor amplitude suddenly increases and decreases: back azimuth and slowness correlate with the growing margins of the lava flow field, whilst new contact with a river led to fast increases of the tremor amplitude; and (iii) a source moving by up to 25° southward in 4 days that cannot be related to any observed surface activity and might be linked to intrusions. We therefore suggest that eruptive tremor amplitudes/energies are used with caution when estimating eruptive volumes, effusion rates, or the eruption explosivity as multiple sources can coexist during the eruption phase. Our results suggest that arrays can monitor both the growth of a lava flow field and the activity in the vents.

Design and performance of a dynaniic gas flux chamber.

PubMed

Reichman, Rivka; Rolston, Dennis E

2002-01-01

Chambers are commonly used to measure the emission of many trace gases and chemicals from soil. An aerodynamic (flow through) chamber was designed and fabricated to accurately measure the surface flux of trace gases. Flow through the chamber was controlled with a small vacuum at the outlet. Due to the design using fans, a partition plate, and aerodynamic ends, air is forced to sweep parallel and uniform over the entire soil surface. A fraction of the air flowing inside the chamber is sampled in the outlet. The air velocity inside the chamber is controlled by fan speed and outlet suction flow rate. The chamber design resulted in a uniform distribution of air velocity at the soil surface. Steady state flux was attained within 5 min when the outlet air suction rate was 20 L/min or higher. For expected flux rates, the presence of the chamber did not affect the measured fluxes at outlet suction rates of around 20 L/min, except that the chamber caused some cooling of the surface in field experiments. Sensitive measurements of the pressure deficit across the soil layer in conjunction with measured fluxes in the source box and chamber outlet show that the outflow rate must be controlled carefully to minimize errors in the flux measurements. Both over- and underestimation of the fluxes are possible if the outlet flow rate is not controlled carefully. For this design, the chamber accurately measured steady flux at outlet air suction rates of approximately 20 L/min when the pressure deficit within the chamber with respect to the ambient atmosphere ranged between 0.46 and 0.79 Pa.

Development of a Distributed Source Contaminant Transport Model for ARAMS

DTIC Science & Technology

2005-09-01

runoff as a result of rainfall. The transfer of dissolved chemicals from the soil solution to overland flow is a rate-limited process ERDC/EL TN-ECMI...boundary layer that separates the stagnant soil solution and the moving overland flow (Wallach et al. 1988, 1989). Dissolution. Some chemicals may...layer (L/T) The mass transfer coefficient relates solute flux across the soil surface interface to the difference in concentration between the soil

Calibration and use of filter test facility orifice plates

NASA Astrophysics Data System (ADS)

Fain, D. E.; Selby, T. W.

1984-07-01

There are three official DOE filter test facilities. These test facilities are used by the DOE, and others, to test nuclear grade HEPA filters to provide Quality Assurance that the filters meet the required specifications. The filters are tested for both filter efficiency and pressure drop. In the test equipment, standard orifice plates are used to set the specified flow rates for the tests. There has existed a need to calibrate the orifice plates from the three facilities with a common calibration source to assure that the facilities have comparable tests. A project has been undertaken to calibrate these orifice plates. In addition to reporting the results of the calibrations of the orifice plates, the means for using the calibration results will be discussed. A comparison of the orifice discharge coefficients for the orifice plates used at the seven facilities will be given. The pros and cons for the use of mass flow or volume flow rates for testing will be discussed. It is recommended that volume flow rates be used as a more practical and comparable means of testing filters. The rationale for this recommendation will be discussed.

Simulation of ground-water flow in the Cedar River alluvial aquifer flow system, Cedar Rapids, Iowa

USGS Publications Warehouse

Turco, Michael J.; Buchmiller, Robert C.

2004-01-01

Model results indicate that the primary sources of inflow to the modeled area are infiltration from the Cedar River (53.0 percent) and regional flow in the glacial and bedrock materials (34.1 percent). The primary sources of outflow from the modeled area are discharge to the Cedar River (45.4 percent) and pumpage (44.8 percent). Current steady-state pumping rates have increased the flow of water from the Cedar River to the alluvial aquifer by 43.8 cubic feet per second. Steady-state and transient hypothetical pumpage scenarios were used to show the relation between changes in pumpage and changes in infiltration of water from the Cedar River. Results indicate that more than 99 percent of the water discharging from municipal wells infiltrates from the Cedar River, that the time required for induced river recharge to equilibrate with municipal pumpage may be 150 days or more, and that ground-water availability in the Cedar Rapids area will not be significantly affected by doubling current pumpage as long as there is sufficient flow in the Cedar River to provide recharge.

Activation rates for nonlinear stochastic flows driven by non-Gaussian noise

NASA Astrophysics Data System (ADS)

van den Broeck, C.; Hänggi, P.

1984-11-01

Activation rates are calculated for stochastic bistable flows driven by asymmetric dichotomic Markov noise (a two-state Markov process). This noise contains as limits both a particular type of non-Gaussian white shot noise and white Gaussian noise. Apart from investigating the role of colored noise on the escape rates, one can thus also study the influence of the non-Gaussian nature of the noise on these rates. The rate for white shot noise differs in leading order (Arrhenius factor) from the corresponding rate for white Gaussian noise of equal strength. In evaluating the rates we demonstrate the advantage of using transport theory over a mean first-passage time approach for cases with generally non-white and non-Gaussian noise sources. For white shot noise with exponentially distributed weights we succeed in evaluating the mean first-passage time of the corresponding integro-differential master-equation dynamics. The rate is shown to coincide in the weak noise limit with the inverse mean first-passage time.

Observation of improved and degraded confinement with driven flow on the LAPD

NASA Astrophysics Data System (ADS)

Schaffner, David

2012-10-01

External continuous control over azimuthal flow and flow shear has been achieved in a linear plasma device for the first time allowing for a careful study of the effect of flow shear on pressure-gradient-driven turbulence and transport in the edge of the Large Plasma Device (LAPD). The flow is controlled using biasable iris-like limiters situated axially between the cathode source and main plasma chamber. LAPD rotates spontaneously in the ion diamagnetic direction (IDD); positive limiter bias first reduces, then minimizes (producing a near-zero shear state), and finally reverses the flow into the electron diamagnetic direction (EDD). Degradation of particle confinement is observed in the minimum shearing state and reduction in turbulent particle flux is observed with increasing shearing in both flow directions. Near-complete suppression of turbulent particle flux is observed for shearing rates comparable to the turbulent autocorrelation rate measured in the minimum shear state. Turbulent flux suppression is dominated by amplitude reduction in low-frequency (>10kHz) density fluctuations and a reduction in the radial correlation length. An increase in fluctuations for the highest shearing states is observed with the emergence of a coherent mode which does not lead to net particle transport. Magnetic field is varied in order to explore whether and how field effects transport modification. Calculations of transport equations are used to predict density profiles given source and temperature profiles and can show the level of transport predicted to be necessary in order to produce the experimental density profiles observed. Finally, the variations of density fluctuations and radial correlation length are fit well with power-laws and compare favorably to simple models of shear suppression of transport.

Lattice Boltzmann modeling to explain volcano acoustic source.

PubMed

Brogi, Federico; Ripepe, Maurizio; Bonadonna, Costanza

2018-06-22

Acoustic pressure is largely used to monitor explosive activity at volcanoes and has become one of the most promising technique to monitor volcanoes also at large scale. However, no clear relation between the fluid dynamics of explosive eruptions and the associated acoustic signals has yet been defined. Linear acoustic has been applied to derive source parameters in the case of strong explosive eruptions which are well-known to be driven by large overpressure of the magmatic fluids. Asymmetric acoustic waveforms are generally considered as the evidence for supersonic explosive dynamics also for small explosive regimes. We have used Lattice-Boltzmann modeling of the eruptive fluid dynamics to analyse the acoustic wavefield produced by different flow regimes. We demonstrate that acoustic waveform well reproduces the flow dynamics of a subsonic fluid injection related to discrete explosive events. Different volumetric flow rate, at low-Mach regimes, can explain both the observed symmetric and asymmetric waveform. Hence, asymmetric waveforms are not necessarily related to the shock/supersonic fluid dynamics of the source. As a result, we highlight an ambiguity in the general interpretation of volcano acoustic signals for the retrieval of key eruption source parameters, necessary for a reliable volcanic hazard assessment.

Investigation on the Core Bypass Flow in a Very High Temperature Reactor

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

Hassan, Yassin

2013-10-22

Uncertainties associated with the core bypass flow are some of the key issues that directly influence the coolant mass flow distribution and magnitude, and thus the operational core temperature profiles, in the very high-temperature reactor (VHTR). Designers will attempt to configure the core geometry so the core cooling flow rate magnitude and distribution conform to the design values. The objective of this project is to study the bypass flow both experimentally and computationally. Researchers will develop experimental data using state-of-the-art particle image velocimetry in a small test facility. The team will attempt to obtain full field temperature distribution using racksmore » of thermocouples. The experimental data are intended to benchmark computational fluid dynamics (CFD) codes by providing detailed information. These experimental data are urgently needed for validation of the CFD codes. The following are the project tasks: • Construct a small-scale bench-top experiment to resemble the bypass flow between the graphite blocks, varying parameters to address their impact on bypass flow. Wall roughness of the graphite block walls, spacing between the blocks, and temperature of the blocks are some of the parameters to be tested. • Perform CFD to evaluate pre- and post-test calculations and turbulence models, including sensitivity studies to achieve high accuracy. • Develop the state-of-the art large eddy simulation (LES) using appropriate subgrid modeling. • Develop models to be used in systems thermal hydraulics codes to account and estimate the bypass flows. These computer programs include, among others, RELAP3D, MELCOR, GAMMA, and GAS-NET. Actual core bypass flow rate may vary considerably from the design value. Although the uncertainty of the bypass flow rate is not known, some sources have stated that the bypass flow rates in the Fort St. Vrain reactor were between 8 and 25 percent of the total reactor mass flow rate. If bypass flow rates are on the high side, the quantity of cooling flow through the core may be considerably less than the nominal design value, causing some regions of the core to operate at temperatures in excess of the design values. These effects are postulated to lead to localized hot regions in the core that must be considered when evaluating the VHTR operational and accident scenarios.« less

Development and analytical characterization of a Grimm-type glow discharge ion source operated with high gas flow rates and coupled to a mass spectrometer with high mass resolution1

NASA Astrophysics Data System (ADS)

Beyer, Claus; Feldmann, Ingo; Gilmour, Dave; Hoffmann, Volker; Jakubowski, Norbert

2002-10-01

A Grimm-type glow discharge ion source has been developed and was coupled to a commercial inductively coupled plasma mass spectrometer (ICP-MS) with high mass resolution (Axiom, ThermoElemental, Winsford, UK) by exchanging the front plate of the ICP-MS interface system only. In addition to high discharge powers of up to 70 W, which are typical for a Grimm-type design, this source could be operated with relative high gas flow rates of up to 240 ml min -1. In combination with a high discharge voltage the signal intensities are reaching a constant level within the first 20 s after the discharge has started. An analytical characterization of this source is given utilizing a calibration using the steel standard reference material NIST 1261A-1265A. The sensitivity for the investigated elements measured with a resolution of 4000 is in the range of 500-6000 cps μg -1 g -1, and a relative standard deviation (R.S.D.) of the measured isotope relative to Fe of less than 8% for the major and minor components of the sample has been achieved. Limits of detection at ng g -1 levels could be obtained.

Effects of variations in flow characteristics through W.P. Franklin Lock and Dam on downstream water quality in the Caloosahatchee River Estuary and in McIntyre Creek in the J.N. “Ding” Darling National Wildlife Refuge, southern Florida, 2010–13

USGS Publications Warehouse

Booth, Amanda C.; Soderqvist, Lars E.; Knight, Travis M.

2016-05-17

The U.S. Geological Survey studied water-quality trends at the mouth of McIntyre Creek, an entry point to the J.N. “Ding” Darling National Wildlife Refuge, to investigate correlations between flow rates and volumes through the W.P. Franklin Lock and Dam and water-quality constituents inside the refuge from March 2010 to December 2013. Outflow from Lake Okeechobee, and flows from Franklin Lock, tributaries to the Caloosahatchee River Estuary, and the Cape Coral canal system were examined to determine the sources and quantity of water to the study area. Salinity, temperature, dissolved-oxygen concentration, pH, turbidity, and chromophoric dissolved organic matter fluorescence (FDOM) were measured during moving-boat surveys and at a fixed location in McIntyre Creek. Chlorophyll fluorescence was also recorded in McIntyre Creek. Water-quality surveys were completed on 20 dates between 2011 and 2014 using moving-boat surveys.Franklin Lock contributed the majority of flow to the Caloosahatchee River. Between 2010 and 2013, the monthly mean flow rate at Franklin Lock ranged from 29 cubic feet per second in May 2011 to 10,650 cubic feet per second in August 2013. Instantaneous near-surface salinity in McIntyre Creek ranged from 12.9 parts per thousand on September 26, 2013, to 37.9 parts per thousand on June 27, 2011. Salinity in McIntyre Creek decreased with increasing flow rate through Franklin Lock. Flow rates through Franklin Lock explained 61 percent of the variation in salinity in McIntyre Creek. Salinity data from moving-boat surveys also indicate that an increase in flow rate at Franklin Lock decreases salinity in the Caloosahatchee River Estuary, and a reduction or elimination in flow increases salinity. The FDOM in McIntyre Creek was positively correlated with flow at Franklin Lock, and 54 percent of the variation in FDOM can be attributed to the flow rate through Franklin Lock. Data from moving-boat surveys indicate that FDOM increases when flow volume from Franklin Lock increases. The highest FDOM recorded during a survey was at Billy’s Creek. Chlorophyll fluorescence was positively correlated with flow at Franklin Lock, with 23 percent of the variation explained by the flow rate at Franklin Lock. An increase in flow rate at Franklin Lock resulted in a decrease in pH (21 percent of variation explained by flow rates). Data from the pH surveys indicate an increase in pH with distance from Franklin Lock. Turbidity and dissolved oxygen near the surface in McIntyre Creek were not correlated with flow rate at Franklin Lock. Moving-boat surveys did not document a change in turbidity or dissolved oxygen with a change in distance from the Franklin Lock. Correlations between Franklin Lock flow rate and water quality in McIntyre Creek indicate that releases at Franklin Lock affect water quality in the Caloosahatchee River Estuary and Ding Darling Refuge.

Neutral source and particle balance in the HSX edge

NASA Astrophysics Data System (ADS)

Stephey, Laurie; Kumar, Santhosh; Bader, Aaron; Akerson, Adrian; Schmitz, Oliver; Anderson, David; A, Simon; Talmadge, Joseph; Hegna, Chris

2015-11-01

The ability to control the neutral particle and impurity source in fusion devices is critical to obtaining high purity, high confinement plasmas. The neutral particle source defines the edge density gradients and plasma flows. To understand the relationship between the neutral particle source, plasma density gradients and plasma edge and core transport in HSX, a single reservoir particle balance is being used to provide a complete particle inventory. Detailed spectroscopic measurements of hydrogen and helium emission have yielded neutral and plasma profiles and ionization length estimations. The plasma puff source rate has been directly measured. To determine the recycling source rate, two specially designed limiters will be inserted to intercept 99% of the field lines, resulting in a well-defined LCFS and plasma interaction zone. Single limiter insertion resulted in a 50% reduction in global line emission, implying a reduction in wall recycling. Future camera and probe measurements will provide a recycling source rate. HSX neutral physics is also being investigated using EMC3-EIRENE. All results are discussed along with complementary plans for the Wendelstein 7-X startup phase. This work supported by US DOE Grant DE-FG02-93ER54222 and DE-SC0006103.

Time-resolved PIV measurements of the flow field in a stenosed, compliant arterial model

NASA Astrophysics Data System (ADS)

Geoghegan, P. H.; Buchmann, N. A.; Soria, J.; Jermy, M. C.

2013-05-01

Compliant (flexible) structures play an important role in several biological flows including the lungs, heart and arteries. Coronary heart disease is caused by a constriction in the artery due to a build-up of atherosclerotic plaque. This plaque is also of major concern in the carotid artery which supplies blood to the brain. Blood flow within these arteries is strongly influenced by the movement of the wall. To study these problems experimentally in vitro, especially using flow visualisation techniques, can be expensive due to the high-intensity and high-repetition rate light sources required. In this work, time-resolved particle image velocimetry using a relatively low-cost light-emitting diode illumination system was applied to the study of a compliant flow phantom representing a stenosed (constricted) carotid artery experiencing a physiologically realistic flow wave. Dynamic similarity between in vivo and in vitro conditions was ensured in phantom construction by matching the distensibility and the elastic wave propagation wavelength and in the fluid system through matching Reynolds ( Re) and Womersley number ( α) with a maximum, minimum and mean Re of 939, 379 and 632, respectively, and a α of 4.54. The stenosis had a symmetric constriction of 50 % by diameter (75 % by area). Once the flow rate reached a critical value, Kelvin-Helmholtz instabilities were observed to occur in the shear layer between the main jet exiting the stenosis and a reverse flow region that occurred at a radial distance of 0.34 D from the axis of symmetry in the region on interest 0-2.5 D longitudinally downstream from the stenosis exit. The instability had an axis-symmetric nature, but as peak flow rate was approached this symmetry breaks down producing instability in the flow field. The characteristics of the vortex train were sensitive not only to the instantaneous flow rate, but also to whether the flow was accelerating or decelerating globally.

Development of a primary diffusion source of organic vapors for gas analyzer calibration

NASA Astrophysics Data System (ADS)

Lecuna, M.; Demichelis, A.; Sassi, G.; Sassi, M. P.

2018-03-01

The generation of reference mixtures of volatile organic compounds (VOCs) at trace levels (10 ppt-10 ppb) is a challenge for both environmental and clinical measurements. The calibration of gas analyzers for trace VOC measurements requires a stable and accurate source of the compound of interest. The dynamic preparation of gas mixtures by diffusion is a suitable method for fulfilling these requirements. The estimation of the uncertainty of the molar fraction of the VOC in the mixture is a key step in the metrological characterization of a dynamic generator. The performance of a dynamic generator was monitored over a wide range of operating conditions. The generation system was simulated by a model developed with computational fluid dynamics and validated against experimental data. The vapor pressure of the VOC was found to be one of the main contributors to the uncertainty of the diffusion rate and its influence at 10-70 kPa was analyzed and discussed. The air buoyancy effect and perturbations due to the weighing duration were studied. The gas carrier flow rate and the amount of liquid in the vial were found to play a role in limiting the diffusion rate. The results of sensitivity analyses were reported through an uncertainty budget for the diffusion rate. The roles of each influence quantity were discussed. A set of criteria to minimize the uncertainty contribution to the primary diffusion source (25 µg min-1) were estimated: carrier gas flow rate higher than 37.7 sml min-1, a maximum VOC liquid mass decrease in the vial of 4.8 g, a minimum residual mass of 1 g and vial weighing times of 1-3 min. With this procedure a limit uncertainty of 0.5% in the diffusion rate can be obtained for VOC mixtures at trace levels (10 ppt-10 ppb), making the developed diffusion vials a primary diffusion source with potential to become a new reference material for trace VOC analysis.

Miniaturized Water Flow and Level Monitoring System for Flood Disaster Early Warning

NASA Astrophysics Data System (ADS)

Ifedapo Abdullahi, Salami; Hadi Habaebi, Mohamed; Surya Gunawan, Teddy; Rafiqul Islam, MD

2017-11-01

This study presents the performance of a prototype miniaturised water flow and water level monitoring sensor designed towards supporting flood disaster early warning systems. The design involved selection of sensors, coding to control the system mechanism, and automatic data logging and storage. During the design phase, the apparatus was constructed where all the components were assembled using locally sourced items. Subsequently, under controlled laboratory environment, the system was tested by running water through the inlet during which the flow rate and rising water levels are automatically recorded and stored in a database via Microsoft Excel using Coolterm software. The system is simulated such that the water level readings measured in centimeters is output in meters using a multiplicative of 10. A total number of 80 readings were analyzed to evaluate the performance of the system. The result shows that the system is sensitive to water level rise and yielded accurate measurement of water level. But, the flow rate fluctuates due to the manual water supply that produced inconsistent flow. It was also observed that the flow sensor has a duty cycle of 50% of operating time under normal condition which implies that the performance of the flow sensor is optimal.

Effect of a rotating propeller on the separation angle of attack and distortion in ducted propeller inlets

NASA Technical Reports Server (NTRS)

Boldman, D. R.; Iek, C.; Hwang, D. P.; Larkin, M.; Schweiger, P.

1993-01-01

The present study represents an extension of an earlier wind tunnel experiment performed with the P&W 17-in. Advanced Ducted Propeller (ADP) Simulator operating at Mach 0.2. In order to study the effects of a rotating propeller on the inlet flow, data were obtained in the UTRC 10- by 15-Foot Large Subsonic Wind Tunnel with the same hardware and instrumentation, but with the propeller removed. These new tests were performed over a range of flow rates which duplicated flow rates in the powered simulator program. The flow through the inlet was provided by a remotely located vacuum source. A comparison of the results of this flow-through study with the previous data from the powered simulator indicated that in the conventional inlet the propeller produced an increase in the separation angle of attack between 4.0 deg at a specific flow of 22.4 lb/sec-sq ft to 2.7 deg at a higher specific flow of 33.8 lb/sec-sq ft. A similar effect on separation angle of attack was obtained by using stationary blockage rather than a propeller.

A source-sink model of the generation of plate tectonics from non-Newtonian mantle flow

NASA Technical Reports Server (NTRS)

Bercovici, David

1995-01-01

A model of mantle convection which generates plate tectonics requires strain rate- or stress-dependent rheology in order to produce strong platelike flows with weak margins as well as strike-slip deformation and plate spin (i.e., toroidal motion). Here, we employ a simple model of source-sink driven surface flow to determine the form of such a rheology that is appropriate for Earth's present-day plate motions. In this model, lithospheric motion is treated as shallow layer flow driven by sources and sinks which correspond to spreading centers and subduction zones, respectively. Two plate motion models are used to derive the source sink field. As originally implied in the simpler Cartesian version of this model, the classical power law rheologies do not generate platelike flows as well as the hypothetical Whitehead-Gans stick-slip rheology (which incorporates a simple self-lubrication mechanism). None of the fluid rheologies examined, however, produce more than approximately 60% of the original maximum shear. For either plate model, the viscosity fields produced by the power law rheologies are diffuse, and the viscosity lows over strike-slip shear zones or pseudo-margins are not as small as over the prescribed convergent-divergent margins. In contrast, the stick-slip rheology generates very platelike viscosity fields, with sharp gradients at the plate boundaries, and margins with almost uniformly low viscosity. Power law rheologies with high viscosity contrasts, however, lead to almost equally favorable comparisons, though these also yield the least platelike viscosity fields. This implies that the magnitude of toroidal flow and platelike strength distributions are not necessarily related and thus may present independent constraints on the determination of a self-consistent plate-mantle rheology.

A source-sink model of the generation of plate tectonics from non-Newtonian mantle flow

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

Bercovici, D.

1995-02-01

A model of mantle convection which generates plate tectonics requires strain rate- or stress-dependent rheology in order to produce strong platelike flows with weak margins as well as strike-slip deformation and plate spin (i.e., toroidal motion). Here, we employ a simple model of source-sink driven surface flow to determine the form of such a rheology that is appropriate for Earth`s present-day plate motions. In this model, lithospheric motion is treated as shallow layer flow driven by sources and sinks which correspond to spreading centers and subduction zones, respectively. Two plate motion models are used to derive the source sink field.more » As originally implied in the simpler Cartesian version of this model, the classical power law rheologies do not generate platelike flows as well as the hypothetical Whitehead-Gans stick-slip rheology (which incorporates a simple self-lubrication mechanism). None of the fluid rheologies examined, however, produce more than approximately 60% of the original maximum shear. For either plate model, the viscosity fields produced by the power law rheologies are diffuse, and the viscosity lows over strike-slip shear zones or pseudo-margins are not as small as over the prescribed convergent-divergent margins. In contrast, the stick-slip rheology generates very platelike viscosity fields, with sharp gradients at the plate boundaries, and margins with almost uniformly low viscosity. Power law rheologies with high viscosity contrasts, however, lead to almost equally favorable comparisons, though these also yield the least platelike viscosity fields. This implies that the magnitude of toroidal flow and platelike strength distributions are not necessarily related and thus may present independent constraints on the determination of a self-consistent plate-mantle rheology.« less

Aluminum recycling in the United States in 2000

USGS Publications Warehouse

Plunkert, Patricia A.

2006-01-01

As one of a series of reports on metals recycling, this report discusses the flow of aluminum from production through its uses with particular emphasis on the recycling of industrial scrap (new scrap) and used products (old scrap) in 2000. This materials flow study includes a description of aluminum supply and demand factors for the United States to illustrate the extent of aluminum recycling and to identify recycling trends. Understanding the system of materials flow from source to ultimate disposition can assist in improving the management of natural resources in a manner that is compatible with sound environmental practices. In 2000, the old scrap recycling efficiency for aluminum was estimated to be 42 percent. Almost 60 percent of the aluminum that was recycled in 2000 came from new scrap, and the recycling rate was estimated to be 36 percent. The principal source of old scrap was recycled aluminum beverage cans.

Impact of typical steady-state conditions and transient conditions on flow ripple and its test accuracy for axial piston pump

NASA Astrophysics Data System (ADS)

Xu, Bing; Hu, Min; Zhang, Junhui

2015-09-01

The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ±6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.

The impact of flow focusing on gas hydrate accumulations in overpressured marine sediments

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

Nole, Michael; Daigle, Hugh; Cook, Ann

This study demonstrates the potential for flow focusing due to overpressuring in marine sedimentary environments to act as a significant methane transport mechanism from which methane hydrate can precipitate in large quantities in dipping sandstone bodies. Traditionally, gas hydrate accumulations in nature are discussed as resulting from either short-range diffusive methane migration or from long-range advective fluid transport sourced from depth. However, 3D simulations performed in this study demonstrate that a third migration mechanism, short-range advective transport, can provide a significant methane source that is unencumbered by limitations of the other two end-member mechanisms. Short-range advective sourcing is advantageous overmore » diffusion because it can convey greater amounts of methane to sands over shorter timespans, yet it is not necessarily limited by down-dip pore blocking in sands as is typical of updip advection from a deep source. These results are novel because they integrate pore size impacts on spatial solubility gradients, grid block properties that evolve through time, and methane sourcing through microbial methanogenesis into a holistic characterization of environments exposed to multiple methane hydrate sourcing mechanisms. We show that flow focusing toward sand bodies transports large quantities of methane, the magnitude of which are determined by the sand-clay solubility contrast, and generates larger quantities of hydrate in sands than a solely diffusive system; after depositing methane as hydrate, fluid exiting a sand body is depleted in methane and leaves a hydrate free region in its wake above the sand. Additionally, we demonstrate that in overpressured environments, hydrate growth is initially diffusively dominated before transitioning to an advection-dominated regime. The timescale and depth at which this transition takes place depends primarily on the rate of microbial metabolism and the sedimentation rate but only depends loosely on the degree of overpressuring.« less

An Assessment of Some Design Constraints on Heat Production of a 3D Conceptual EGS Model Using an Open-Source Geothermal Reservoir Simulation Code

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

Yidong Xia; Mitch Plummer; Robert Podgorney

2016-02-01

Performance of heat production process over a 30-year period is assessed in a conceptual EGS model with a geothermal gradient of 65K per km depth in the reservoir. Water is circulated through a pair of parallel wells connected by a set of single large wing fractures. The results indicate that the desirable output electric power rate and lifespan could be obtained under suitable material properties and system parameters. A sensitivity analysis on some design constraints and operation parameters indicates that 1) the fracture horizontal spacing has profound effect on the long-term performance of heat production, 2) the downward deviation anglemore » for the parallel doublet wells may help overcome the difficulty of vertical drilling to reach a favorable production temperature, and 3) the thermal energy production rate and lifespan has close dependence on water mass flow rate. The results also indicate that the heat production can be improved when the horizontal fracture spacing, well deviation angle, and production flow rate are under reasonable conditions. To conduct the reservoir modeling and simulations, an open-source, finite element based, fully implicit, fully coupled hydrothermal code, namely FALCON, has been developed and used in this work. Compared with most other existing codes that are either closed-source or commercially available in this area, this new open-source code has demonstrated a code development strategy that aims to provide an unparalleled easiness for user-customization and multi-physics coupling. Test results have shown that the FALCON code is able to complete the long-term tests efficiently and accurately, thanks to the state-of-the-art nonlinear and linear solver algorithms implemented in the code.« less

Bathyphotometer bioluminescence potential measurements: A framework for characterizing flow agitators and predicting flow-stimulated bioluminescence intensity

NASA Astrophysics Data System (ADS)

Latz, Michael I.; Rohr, Jim

2013-07-01

Bathyphotometer measurements of bioluminescence are used as a proxy for the abundance of luminescent organisms for studying population dynamics; the interaction of luminescent organisms with physical, chemical, and biological oceanographic processes; and spatial complexity especially in coastal areas. However, the usefulness of bioluminescence measurements has been limited by the inability to compare results from different bathyphotometer designs, or even the same bathyphotometer operating at different volume flow rates. The primary objective of this study was to compare measurements of stimulated bioluminescence of four species of cultured dinoflagellates, the most common source of bioluminescence in coastal waters, using two different bathyphotometer flow agitators as a function of bathyphotometer volume flow rate and dinoflagellate concentration. For both the NOSC and BIOLITE flow agitators and each species of dinoflagellate tested, there was a critical volume flow rate, above which average bioluminescence intensity, designated as bathyphotometer bioluminescence potential (BBP), remained relatively constant and scaled directly with dinoflagellate cell concentration. At supra-critical volume flow rates, the ratio of BIOLITE to NOSC BBP was nearly constant for the same species studied, but varied between species. The spatial pattern and residence time of flash trajectories within the NOSC flow agitator indicated the presence of dominant secondary recirculating flows, where most of the bioluminescence was detected. A secondary objective (appearing in the Appendix) was to study the feasibility of using NOSC BBP to scale flow-stimulated bioluminescence intensity across similar flow fields, where the contributing composition of luminescent species remained the same. Fully developed turbulent pipe flow was chosen because it is hydrodynamically well characterized. Average bioluminescence intensity in a 2.54-cm i.d. pipe was highly correlated with wall shear stress and BBP. This correlation, when further scaled by pipe diameter, effectively predicted bioluminescence intensity in fully developed turbulent flow in a 0.83-cm i.d. pipe. Determining similar correlations between other bathyphotometer flow agitators and flow fields will allow bioluminescence potential measurements to become a more powerful tool for the oceanographic community.

Method of remotely characterizing thermal properties of a sample

NASA Technical Reports Server (NTRS)

Heyman, Joseph S. (Inventor); Heath, D. Michele (Inventor); Welch, Christopher (Inventor); Winfree, William P. (Inventor); Miller, William E. (Inventor)

1992-01-01

A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

Reduction of exposure to ultrafine particles by kitchen exhaust hoods: the effects of exhaust flow rates, particle size, and burner position.

PubMed

Rim, Donghyun; Wallace, Lance; Nabinger, Steven; Persily, Andrew

2012-08-15

Cooking stoves, both gas and electric, are one of the strongest and most common sources of ultrafine particles (UFP) in homes. UFP have been shown to be associated with adverse health effects such as DNA damage and respiratory and cardiovascular diseases. This study investigates the effectiveness of kitchen exhaust hoods in reducing indoor levels of UFP emitted from a gas stove and oven. Measurements in an unoccupied manufactured house monitored size-resolved UFP (2 nm to 100 nm) concentrations from the gas stove and oven while varying range hood flow rate and burner position. The air change rate in the building was measured continuously based on the decay of a tracer gas (sulfur hexafluoride, SF(6)). The results show that range hood flow rate and burner position (front vs. rear) can have strong effects on the reduction of indoor levels of UFP released from the stove and oven, subsequently reducing occupant exposure to UFP. Higher range hood flow rates are generally more effective for UFP reduction, though the reduction varies with particle diameter. The influence of the range hood exhaust is larger for the back burner than for the front burner. The number-weighted particle reductions for range hood flow rates varying between 100 m(3)/h and 680 m(3)/h range from 31% to 94% for the front burner, from 54% to 98% for the back burner, and from 39% to 96% for the oven. Copyright © 2012 Elsevier B.V. All rights reserved.

Extreme erosion response after wildfire in the Upper Ovens, south-east Australia: Assessment of catchment scale connectivity by an intensive field survey

NASA Astrophysics Data System (ADS)

Box, Walter; Keestra, Saskia; Nyman, Petter; Langhans, Christoph; Sheridan, Gary

2015-04-01

South-eastern Australia is generally regarded as one of the world's most fire-prone environments because of its high temperatures, low rainfall and flammable native Eucalyptus forests. Modifications to the landscape by fire can lead to significant changes to erosion rates and hydrological processes. Debris flows in particular have been recognised as a process which increases in frequency as a result of fire. This study used a debris flow event in the east Upper Ovens occurred on the 28th of February 2013 as a case study for analysing sediment transport processes and connectivity of sediment sources and sinks. Source areas were identified using a 15 cm resolution areal imagery and a logistic regression model was made based on fire severity, aridity index and slope to predict locations of source areas. Deposits were measured by making cross-sections using a combination of a differential GPS and a total station. In total 77 cross-sections were made in a 14.1 km2 sub-catchment and distributed based on channel gradient and width. A more detailed estimation was obtained by making more cross-sections where the volume per area is higher. Particle size distribution between sources and sink areas were obtained by combination of field assessment, photography imagery analyses and sieve and laser diffraction. Sediment was locally eroded, transported and deposited depending on factors such as longitude gradient, stream power and the composition of bed and bank material. The role of headwaters as sediment sinks changed dramatically as a result of the extreme erosion event in the wildfire affected areas. Disconnected headwaters became connected to low order streams due to debris flow processes in the contributing catchment. However this redistribution of sediment from headwaters to the drainage network was confined to upper reaches of the Ovens. Below this upper part of the catchment the event resulted in redistribution of sediment already existing in the channel through a combination of debris flows and hyperconcentrated flows. These results indicate that there is a stepwise outflow of sediment influencing long-term erosion rates and landform development.

Extraction of astaxanthin from Euphausia pacific using subcritical 1, 1, 1, 2-tetrafluoroethane

NASA Astrophysics Data System (ADS)

Han, Yuqian; Ma, Qinchuan; Wang, Lan; Xue, Changhu

2012-12-01

Euphausia pacific is an important source of natural astaxanthin. Studies were carried out to assess the extractability of astaxanthin from E. pacific using subcritical 1, 1, 1, 2-tetrafluoroethane (R134a). To examine the effects of multiple process variables on the extraction yield, astaxanthin was extracted under various conditions of pressure (30-150 bar), temperature (303-343 K), time (10-50 min), flow rate (2-10 g min-1), moisture content (5.5%-63.61%), and particle size (0.25-0.109 mm). The results showed that the extraction yield increased with temperature, pressure, time and flow rate, but decreased with moisture content and particle size. A maximum yield of 87.74% was obtained under conditions of 100 bar, 333 K, and 30 min with a flow rate of 6 g min-1 and a moisture content of 5.5%. The substantial astaxanthin yield obtained under low-pressure conditions demonstrates that subcritical R134a is a good alternative to CO2 for extraction of astaxanthin from E. pacific.

Highly selective deuteration of pharmaceutically relevant nitrogen-containing heterocycles: a flow chemistry approach.

PubMed

Ötvös, Sándor B; Mándity, István M; Fülöp, Ferenc

2011-08-01

A simple and efficient flow-based technique is reported for the catalytic deuteration of several model nitrogen-containing heterocyclic compounds which are important building blocks of pharmacologically active materials. A continuous flow reactor was used in combination with on-demand pressure-controlled electrolytic D(2) production. The D(2) source was D(2)O, the consumption of which was very low. The experimental set-up allows the fine-tuning of pressure, temperature, and flow rate so as to determine the optimal conditions for the deuteration reactions. The described procedure lacks most of the drawbacks of the conventional batch deuteration techniques, and additionally is highly selective and reproducible.

TiCl4 as a source of TiO2 particles for laser anemometry measurements in hot gas

NASA Technical Reports Server (NTRS)

Weikle, Donald H.; Seasholtz, Richard G.; Oberle, Lawrence G.

1990-01-01

A method of reacting TiCl4 with water saturated gaseous nitrogen (GN2) at the entrance into a high temperature gas flow is described. The TiO2 particles formed are then entrained in the gas flow and used as seed particles for making laser anemometry (LA) measurements of the flow velocity distribution in the hot gas. Scanning electron microscope photographs of the TiO2 particles are shown. Data rate of the LA processor was measured to determine the amount of TiO2 formed. The TiCl4 and mixing gas flow diagram is shown. This work was performed in an open jet burner.

Catchment-wide impacts on water quality: the use of 'snapshot' sampling during stable flow

NASA Astrophysics Data System (ADS)

Grayson, R. B.; Gippel, C. J.; Finlayson, B. L.; Hart, B. T.

1997-12-01

Water quality is usually monitored on a regular basis at only a small number of locations in a catchment, generally focused at the catchment outlet. This integrates the effect of all the point and non-point source processes occurring throughout the catchment. However, effective catchment management requires data which identify major sources and processes. As part of a wider study aimed at providing technical information for the development of integrated catchment management plans for a 5000 km 2 catchment in south eastern Australia, a 'snapshot' of water quality was undertaken during stable summer flow conditions. These low flow conditions exist for long periods so water quality at these flow levels is an important constraint on the health of in-stream biological communities. Over a 4 day period, a study of the low flow water quality characteristics throughout the Latrobe River catchment was undertaken. Sixty-four sites were chosen to enable a longitudinal profile of water quality to be established. All tributary junctions and sites along major tributaries, as well as all major industrial inputs were included. Samples were analysed for a range of parameters including total suspended solids concentration, pH, dissolved oxygen, electrical conductivity, turbidity, flow rate and water temperature. Filtered and unfiltered samples were taken from 27 sites along the main stream and tributary confluences for analysis of total N, NH 4, oxidised N, total P and dissolved reactive P concentrations. The data are used to illustrate the utility of this sampling methodology for establishing specific sources and estimating non-point source loads of phosphorous, total suspended solids and total dissolved solids. The methodology enabled several new insights into system behaviour including quantification of unknown point discharges, identification of key in-stream sources of suspended material and the extent to which biological activity (phytoplankton growth) affects water quality. The costs and benefits of the sampling exercise are reviewed.

The Competition Between a Localised and Distributed Source of Buoyancy

NASA Astrophysics Data System (ADS)

Partridge, Jamie; Linden, Paul

2012-11-01

We propose a new mathematical model to study the competition between localised and distributed sources of buoyancy within a naturally ventilated filling box. The main controlling parameters in this configuration are the buoyancy fluxes of the distributed and local source, specifically their ratio Ψ. The steady state dynamics of the flow are heavily dependent on this parameter. For large Ψ, where the distributed source dominates, we find the space becomes well mixed as expected if driven by an distributed source alone. Conversely, for small Ψ we find the space reaches a stable two layer stratification. This is analogous to the classical case of a purely local source but here the lower layer is buoyant compared to the ambient, due to the constant flux of buoyancy emanating from the distributed source. The ventilation flow rate, buoyancy of the layers and also the location of the interface height, which separates the two layer stratification, are obtainable from the model. To validate the theoretical model, small scale laboratory experiments were carried out. Water was used as the working medium with buoyancy being driven directly by temperature differences. Theoretical results were compared with experimental data and overall good agreement was found. A CASE award project with Arup.

On-site SiH4 generator using hydrogen plasma generated in slit-type narrow gap

NASA Astrophysics Data System (ADS)

Takei, Norihisa; Shinoda, Fumiya; Kakiuchi, Hiroaki; Yasutake, Kiyoshi; Ohmi, Hiromasa

2018-06-01

We have been developing an on-site silane (SiH4) generator based on use of the chemical etching reaction between solid silicon (Si) and the high-density H atoms that are generated in high-pressure H2 plasma. In this study, we have developed a slit-type plasma source for high-efficiency SiH4 generation. High-density H2 plasma was generated in a narrow slit-type discharge gap using a 2.45 GHz microwave power supply. The plasma’s optical emission intensity distribution along the slit was measured and the resulting distribution was reflected by both the electric power distribution and the hydrogen gas flow. Because the Si etching rate strongly affects the SiH4 generation rate, the Si etching behavior was investigated with respect to variations in the experimental parameters. The weight etch rate increased monotonically with increasing input microwave power. However, the weight etch rate decreased with increasing H2 pressure and an increasing plasma gap. This reduction in the etch rate appears to be related to shrinkage of the plasma generation area because increased input power is required to maintain a constant plasma area with increasing H2 pressure and the increasing plasma gap. Additionally, the weight etch rate also increases with increasing H2 flow rate. The SiH4 generation rate of the slit-type plasma source was also evaluated using gas-phase Fourier transform infrared absorption spectroscopy and the material utilization efficiencies of both Si and the H2 gas for SiH4 gas formation were discussed. The main etch product was determined to be SiH4 and the developed plasma source achieved a SiH4 generation rate of 10 sccm (standard cubic centimeters per minute) at an input power of 900 W. In addition, the Si utilization efficiency exceeded 60%.

Inverse problem and variation method to optimize cascade heat exchange network in central heating system

NASA Astrophysics Data System (ADS)

Zhang, Yin; Wei, Zhiyuan; Zhang, Yinping; Wang, Xin

2017-12-01

Urban heating in northern China accounts for 40% of total building energy usage. In central heating systems, heat is often transferred from heat source to users by the heat network where several heat exchangers are installed at heat source, substations and terminals respectively. For given overall heating capacity and heat source temperature, increasing the terminal fluid temperature is an effective way to improve the thermal performance of such cascade heat exchange network for energy saving. In this paper, the mathematical optimization model of the cascade heat exchange network with three-stage heat exchangers in series is established. Aim at maximizing the cold fluid temperature for given hot fluid temperature and overall heating capacity, the optimal heat exchange area distribution and the medium fluids' flow rates are determined through inverse problem and variation method. The preliminary results show that the heat exchange areas should be distributed equally for each heat exchanger. It also indicates that in order to improve the thermal performance of the whole system, more heat exchange areas should be allocated to the heat exchanger where flow rate difference between two fluids is relatively small. This work is important for guiding the optimization design of practical cascade heating systems.

An optimized inverse modelling method for determining the location and strength of a point source releasing airborne material in urban environment

NASA Astrophysics Data System (ADS)

Efthimiou, George C.; Kovalets, Ivan V.; Venetsanos, Alexandros; Andronopoulos, Spyros; Argyropoulos, Christos D.; Kakosimos, Konstantinos

2017-12-01

An improved inverse modelling method to estimate the location and the emission rate of an unknown point stationary source of passive atmospheric pollutant in a complex urban geometry is incorporated in the Computational Fluid Dynamics code ADREA-HF and presented in this paper. The key improvement in relation to the previous version of the method lies in a two-step segregated approach. At first only the source coordinates are analysed using a correlation function of measured and calculated concentrations. In the second step the source rate is identified by minimizing a quadratic cost function. The validation of the new algorithm is performed by simulating the MUST wind tunnel experiment. A grid-independent flow field solution is firstly attained by applying successive refinements of the computational mesh and the final wind flow is validated against the measurements quantitatively and qualitatively. The old and new versions of the source term estimation method are tested on a coarse and a fine mesh. The new method appeared to be more robust, giving satisfactory estimations of source location and emission rate on both grids. The performance of the old version of the method varied between failure and success and appeared to be sensitive to the selection of model error magnitude that needs to be inserted in its quadratic cost function. The performance of the method depends also on the number and the placement of sensors constituting the measurement network. Of significant interest for the practical application of the method in urban settings is the number of concentration sensors required to obtain a ;satisfactory; determination of the source. The probability of obtaining a satisfactory solution - according to specified criteria -by the new method has been assessed as function of the number of sensors that constitute the measurement network.

Evaluation of compliance with national legislation on emissions in Portugal.

PubMed

Gomes, João F P

2005-04-01

More than 13 years after publication of the first air quality laws in Portugal and more than 10 years after the publication of the respective emission limits, it seems appropriate to analyze the degree of compliance by the Portuguese manufacturing industry. Using the data from emission measurements made regularly by the Instituto de Soldadura e Qualidade, the only officially accredited laboratory according to standard ISO 17025, I analyzed a set of approximately 400 sources in terms of compliance with the emission limits regarding total suspended particulates, sulfur dioxide, nitrogen oxides, and volatile organic compounds. I evaluated compliance through a nondimensional parameter and plotted it versus the emission flow rate to derive conclusions: the results indicate that emission limits are generally met regarding sulfur dioxide and nitrogen oxides but not for the other pollutants considered in this study. However, noncompliance occurs mainly for very low emission flow rates, which suggests some alterations in the emission limits, which are being revised at the moment. These alterations will include the exemption of measurements in minor sources.

Flows and hypoxic blackwater events in managed ephemeral river channels

NASA Astrophysics Data System (ADS)

Hladyz, Sally; Watkins, Susanne C.; Whitworth, Kerry L.; Baldwin, Darren S.

2011-04-01

SummaryAs pressure increases on the availability of water resources worldwide, especially in the face of climatic change, it is probable that the likelihood of streams undergoing at least some periods of drying will increase in arid and semi-arid regions. This has implications for the ongoing management of waterways in these areas. One area of concern is the potential occurrence of hypoxic blackwater events upon re-instatement of flows in creek and river channels following periods of drying. Hypoxic blackwater events are characterised by high levels of dissolved organic carbon (DOC), the metabolism of which results in low dissolved oxygen (DO) in the water column, which can cause fish and crustacean mortality. Therefore, understanding hypoxic blackwater events is important in order to reduce the potential for fish mortalities and other water quality impacts from both managed and natural flows. In this study, we set out to determine the factors that influenced the occurrence of a hypoxic blackwater event in the Edward-Wakool river system, in southern NSW, Australia during the previous austral summer (2008-2009). Standing stocks of plant litter, emergent macrophytes and river red gum saplings ( Eucalyptus camaldulensis Dehn.), as well as rates of litterfall, were determined in dry and inundated channels. A series of mesocosm experiments were undertaken to determine which carbon source was the greatest contributor to DOC and to DO depletion, and what loadings could result in hypoxia. These experiments were then used to create a simple algorithm relating carbon loading in a dry channel to DOC in the overlying water column following inundation. Results revealed that plant litter was the main contributor to water column DOC and to DO depletion. Litter loadings equal to or greater than 370 g m -2 were found to cause DO in a shallow (20 cm) water column at 20 °C to fall to zero within two days. This loading was approximately half of that found in dry channels in the Edward-Wakool system - thus, initial inundation of these channels at a low flow rate during summer (or when water temperature is equal to or greater than 20 °C) is highly likely to trigger a hypoxic blackwater event. In addition, one month of litterfall in summer was calculated to be sufficient to deliver enough carbon to dry channels to create a hypoxic blackwater event. These findings suggest that to reduce the likelihood of a hypoxic blackwater event occurring as a result of managed flows in ephemeral systems; (1) the principal source(s) of DOC as well as the pathway and timing of accumulation in dry channels should be identified, and (2) the timing of the re-instatement of flows in a dry channel should be considered in light of the timing of maximum rates of accumulation of the principal source(s) of DOC.

Characteristics of an Electron Cyclotron Resonance Plasma Source for the Production of Active Nitrogen Species in III-V Nitride Epitaxy

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

A simple analysis is provided to determine the characteristics of an electron cyclotron resonance (ECR) plasma source for the generation of active nitrogen species in the molecular beam epitaxy of III-V nitrides. The effects of reactor geometry, pressure, power, and flow rate on the dissociation efficiency and ion flux are presented. Pulsing the input power is proposed to reduce the ion flux.

Tunable Ionization Modes of a Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source.

PubMed

Badal, Sunil P; Michalak, Shawn D; Chan, George C-Y; You, Yi; Shelley, Jacob T

2016-04-05

Plasma-based ambient desorption/ionization sources are versatile in that they enable direct ionization of gaseous samples as well as desorption/ionization of analytes from liquid and solid samples. However, ionization matrix effects, caused by competitive ionization processes, can worsen sensitivity or even inhibit detection all together. The present study is focused on expanding the analytical capabilities of the flowing atmospheric-pressure afterglow (FAPA) source by exploring additional types of ionization chemistry. Specifically, it was found that the abundance and type of reagent ions produced by the FAPA source and, thus, the corresponding ionization pathways of analytes, can be altered by changing the source working conditions. High abundance of proton-transfer reagent ions was observed with relatively high gas flow rates and low discharge currents. Conversely, charge-transfer reagent species were most abundant at low gas flows and high discharge currents. A rather nonpolar model analyte, biphenyl, was found to significantly change ionization pathway based on source operating parameters. Different analyte ions (e.g., MH(+) via proton-transfer and M(+.) via charge-transfer) were formed under unique operating parameters demonstrating two different operating regimes. These tunable ionization modes of the FAPA were used to enable or enhance detection of analytes which traditionally exhibit low-sensitivity in plasma-based ADI-MS analyses. In one example, 2,2'-dichloroquaterphenyl was detected under charge-transfer FAPA conditions, which were difficult or impossible to detect with proton-transfer FAPA or direct analysis in real-time (DART). Overall, this unique mode of operation increases the number and range of detectable analytes and has the potential to lessen ionization matrix effects in ADI-MS analyses.

Reactive barrier system for nitrate removal from mine effluents in northern Sweden: Laboratory experiments

NASA Astrophysics Data System (ADS)

Herbert, Roger

2010-05-01

Laboratory column experiments have been conducted to determine nitrate removal rates from mine effluents by denitrification, with the purpose of providing initial data for the construction of a pilot scale reactive barrier system at the Malmberget iron mine, Sweden. Experiments were conducted at several different flow rates at 5C, 10C and room temperature; annual mean temperatures at the Malmberget site lie close to 0C. Columns were filled with an organic substrate consisting of sawdust mixed with sewage sludge, the source of denitrifying bacteria, supported by oven-dried clay pellets. Apparent denitrification rates, calculated from inflow and outflow nitrate concentrations and column hydraulic residence time, ranged from 5 to 13 mg N/L/d, with the lowest rates corresponding to the 5C experiments. These rates are, however, limited to a certain degree by the low flow rate and the supply of electrons acceptors (i.e. nitrate) to denitrifying bacteria. Results from the column experiment have been used to construct a barrier system in Malmberget, Sweden. Trial runs with the pilot-scale barrier will be conducted during 2010, with the purpose of determining the performance of the barrier as mean air temperatures increase from below to above 0C and saturated flow commences in the barrier. The barrier system is constructed as a rectangular container with steel sheet walls (9m length in flow direction, 1.5m deep), and the flow rate will be adjusted to a hydraulic residence time of 1 day. The pilot-scale barrier system currently lies above ground, but a permanent barrier system would be installed below the ground surface so that the system can be maintained at positive temperatures throughout the year.

Acoustic measurement of the Deepwater Horizon Macondo well flow rate

PubMed Central

Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M.; Techet, Alexandra H.; Yoerger, Dana R.; Whitcomb, Louis L.; Seewald, Jeffrey S.; Sylva, Sean P.; Fenwick, Judith

2012-01-01

On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well’s two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well’s oil flow rate was approximately 0.10 ± 0.017 m3 s-1 at seafloor conditions, or approximately 85 ± 15 kg s-1 (7.4 ± 1.3 Gg d-1), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s-1 (2.1 ± 0.37 Gg d-1) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s-1 (9.5 ± 1.6 Gg d-1). PMID:21903931

Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 2: Predicted emplacement processes and observations)

NASA Astrophysics Data System (ADS)

Head, James W.; Wilson, Lionel

2017-02-01

We utilize a theoretical analysis of the generation, ascent, intrusion and eruption of basaltic magma on the Moon to develop new insights into magma source depths, supply processes, transport and emplacement mechanisms via dike intrusions, and effusive and explosive eruptions. We make predictions about the intrusion and eruption processes and compare these with the range of observed styles of mare volcanism, and related features and deposits. Density contrasts between the bulk mantle and regions with a greater abundance of heat sources will cause larger heated regions to rise as buoyant melt-rich diapirs that generate partial melts that can undergo collection into magma source regions; diapirs rise to the base of the anorthositic crustal density trap (when the crust is thicker than the elastic lithosphere) or, later in history, to the base of the lithospheric rheological trap (when the thickening lithosphere exceeds the thickness of the crust). Residual diapiric buoyancy, and continued production and arrival of diapiric material, enhances melt volume and overpressurizes the source regions, producing sufficient stress to cause brittle deformation of the elastic part of the overlying lithosphere; a magma-filled crack initiates and propagates toward the surface as a convex upward, blade-shaped dike. The volume of magma released in a single event is likely to lie in the range 102 km3 to 103 km3, corresponding to dikes with widths of 40-100 m and both vertical and horizontal extents of 60-100 km, favoring eruption on the lunar nearside. Shallower magma sources produce dikes that are continuous from the source region to the surface, but deeper sources will propagate dikes that detach from the source region and ascend as discrete penny-shaped structures. As the Moon cools with time, the lithosphere thickens, source regions become less abundant, and rheological traps become increasingly deep; the state of stress in the lithosphere becomes increasingly contractional, inhibiting dike emplacement and surface eruptions. In contrast to small dike volumes and low propagation velocities in terrestrial environments, lunar dike propagation velocities are typically sufficiently high that shallow sill formation is not favored; local low-density breccia zones beneath impact crater floors, however, may cause lateral magma migration to form laccoliths (e.g., Vitello Crater) and sills (e.g., Humboldt Crater) in floor-fractured craters. Dikes emplaced into the shallow crust may stall and produce crater chains due to active and passive gas venting (e.g., Mendeleev Crater Chain) or, if sufficiently shallow, may create a near-surface stress field that forms linear and arcuate graben, often with pyroclastic and small-scale effusive eruptions (e.g., Rima Parry V). Effusive eruptions are modulated by effusion rates, eruption durations, cooling and supply limitations to flow length, and pre-existing topography. Relatively low effusion rate, cooling-limited flows lead to small shield volcanoes (e.g., Tobias Mayer, Milicius); higher effusion rate, cooling-limited flows lead to compound flow fields (e.g., most mare basins) and even higher effusion rate, long-duration flows lead to thermal erosion of the vent, effusion rate enhancement, and thermal erosion of the substrate to produce sinuous rilles (e.g., Rimae Prinz). Extremely high effusion rate flows on slopes lead to volume-limited flow with lengths of many hundreds of kilometers (e.g., the young Imbrium basin flows). Explosive, pyroclastic eruptions are common on the Moon. The low pressure environment in propagating dike crack-tips can cause gas formation at great depths and throughout dike ascent; at shallow crustal depths both the smelting reaction and the recently documented abundant magmatic volatiles in mare basalt magmas contribute to significant shallow degassing and pyroclastic activity associated with the dike as it erupts at the surface. Dikes penetrating to the surface produce a wide range of explosive eruption types whose manifestations are modulated by lunar environmental conditions: (1) terrestrial strombolian-style eruptions map to cinder/spatter cone-like constructs (e.g., Isis and Osiris); (2) Hawaiian-style eruptions map to broad flat pyroclastic blankets (e.g., Taurus-Littrow Apollo 17 dark mantle deposits); (3) gas-rich ultraplinian-like venting can cause Moon-wide dispersal of gas and foam droplets (e.g., many isolated glass beads in lunar soils); (4) vulcanian-like eruptions caused by solidification of magma in the dike tip, buildup of gas pressure and explosive disruption, can form dark-halo craters with mixed country rock (e.g., Alphonsus Crater floor); (5) ionian-like eruptions can be caused by artificial gas buildup in wide dikes, energetic explosive eruption and formation of a dark pyroclastic ring (e.g., Orientale dark ring); (6) multiple eruptions from many gas-rich fissures can form regional dark mantle deposits (e.g., Rima Bode, Sinus Aestuum); and (7) long duration, relatively high effusion rate eruptions accompanied by continuing pyroclastic activity cause a central thermally eroded lava pond and channel, a broader pyroclastic 'spatter' edifice, an even broader pyroclastic glass deposit and, if the eruption lasts sufficiently long, an associated inner thermally eroded vent and sinuous rille channel (e.g., Cobra Head and Aristarchus Plateau dark mantle). The asymmetric nearside-farside distribution of mare basalt deposits is most plausibly explained by crustal thickness differences; intrusion is favored on the thicker farside crust and extrusion is favored on the thinner nearside crust. Second-order effects include regional and global thermal structure (areal variations in lithospheric thickness as a function of time) and broad geochemical anomalies (the Procellarum-KREEP Terrain). Differences in mare basalt titanium content as a function of space and time are testimony to a laterally and vertically heterogeneous mantle source region. The rapidly decreasing integrated flux of mare basalts is a result of the thermal evolution of the Moon; continued cooling decreased diapiric rise and mantle melting, thickened the lithosphere, and caused the global state of stress to be increasingly contractional, all factors progressively inhibiting the generation, ascent and eruption of basaltic magma. Late-stage volcanic eruptions are typically widely separated in time and characterized by high-volume, high-effusion rate eruptions producing extensive volume-limited flows, a predictable characteristic of deep source regions below a thick lithosphere late in lunar history. This improved paradigm for the generation, ascent, intrusion and eruption of basaltic magma provides the basis for the broader interpretation of the lunar volcanic record in terms of variations in eruption conditions in space and time, and their relation to mantle heterogeneity and a more detailed understanding of lunar thermal evolution.

Controls on Lava Flow Morphology and Propagation: Using Laboratory Analogue Experiments

NASA Astrophysics Data System (ADS)

Peters, S.; Clarke, A. B.

2017-12-01

The morphology of lava flows is controlled by eruption rate, composition, cooling rate, and topography [Fink and Griffiths, 1990; Gregg and Fink, 2000, 2006]. Lava flows are used to understand how volcanoes, volcanic fields, and igneous provinces formed and evolved [Gregg and Fink., 1996; Sheth, 2006]. This is particularly important for other planets where compositional data is limited and historical context is nonexistent. Numerical modeling of lava flows remains challenging, but has been aided by laboratory analog experiments [Gregg and Keszrthelyi, 2004; Soule and Cashman, 2004]. Experiments using polyethylene glycol (PEG) 600 wax have been performed to understand lava flow emplacement [Fink and Griffiths, 1990, 1992; Gregg and Fink, 2000]. These experiments established psi (hereafter denoted by Ψ), a dimensionless parameter that relates crust formation and advection timescales of a viscous gravity current. Four primary flow morphologies corresponding to discreet Ψ ranges were observed. Gregg and Fink [2000] also investigated flows on slopes and found that steeper slopes increase the effective effusion rate producing predicted morphologies at lower Ψ values. Additional work is needed to constrain the Ψ parameter space, evaluate the predictive capability of Ψ, and determine if the preserved flow morphology can be used to indicate the initial flow conditions. We performed 514 experiments to address the following controls on lava flow morphology: slope (n = 282), unsteadiness/pulsations (n = 58), slope & unsteadiness/pulsations (n = 174), distal processes, and emplacement vs. post-emplacement morphologies. Our slope experiments reveal a similar trend to Gregg and Fink [2000] with the caveat that very high and very low local & source eruption rates can reduce the apparent predictive capability of Ψ. Predicted Ψ morphologies were often produced halfway through the eruption. Our pulse experiments are expected to produce morphologies unique to each eruption rate and promote tube formation and compound flows. Post-emplacement morphologies are modified by a variety of factors (e.g. solidification, deflation), which may not preserve the initial morphology produced during an eruption. Relating this morphology to the eruption conditions is pertinent to understanding the evolution of planetary surfaces.

Rate decline curves analysis of multiple-fractured horizontal wells in heterogeneous reservoirs

NASA Astrophysics Data System (ADS)

Wang, Jiahang; Wang, Xiaodong; Dong, Wenxiu

2017-10-01

In heterogeneous reservoir with multiple-fractured horizontal wells (MFHWs), due to the high density network of artificial hydraulic fractures, the fluid flow around fracture tips behaves like non-linear flow. Moreover, the production behaviors of different artificial hydraulic fractures are also different. A rigorous semi-analytical model for MFHWs in heterogeneous reservoirs is presented by combining source function with boundary element method. The model are first validated by both analytical model and simulation model. Then new Blasingame type curves are established. Finally, the effects of critical parameters on the rate decline characteristics of MFHWs are discussed. The results show that heterogeneity has significant influence on the rate decline characteristics of MFHWs; the parameters related to the MFHWs, such as fracture conductivity and length also can affect the rate characteristics of MFHWs. One novelty of this model is to consider the elliptical flow around artificial hydraulic fracture tips. Therefore, our model can be used to predict rate performance more accurately for MFHWs in heterogeneous reservoir. The other novelty is the ability to model the different production behavior at different fracture stages. Compared to numerical and analytic methods, this model can not only reduce extensive computing processing but also show high accuracy.

Demonstration of a high repetition rate capillary discharge waveguide

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

Gonsalves, A. J., E-mail: ajgonsalves@lbl.gov; Pieronek, C.; Daniels, J.

2016-01-21

A hydrogen-filled capillary discharge waveguide operating at kHz repetition rates is presented for parameters relevant to laser plasma acceleration (LPA). The discharge current pulse was optimized for erosion mitigation with laser guiding experiments and MHD simulation. Heat flow simulations and measurements showed modest temperature rise at the capillary wall due to the average heat load at kHz repetition rates with water-cooled capillaries, which is promising for applications of LPAs such as high average power radiation sources.

Design and setup of intermittent-flow respirometry system for aquatic organisms.

PubMed

Svendsen, M B S; Bushnell, P G; Steffensen, J F

2016-01-01

Intermittent-flow respirometry is an experimental protocol for measuring oxygen consumption in aquatic organisms that utilizes the best features of closed (stop-flow) and flow-through respirometry while eliminating (or at least reducing) some of their inherent problems. By interspersing short periods of closed-chamber oxygen consumption measurements with regular flush periods, accurate oxygen uptake rate measurements can be made without the accumulation of waste products, particularly carbon dioxide, which may confound results. Automating the procedure with easily available hardware and software further reduces error by allowing many measurements to be made over long periods thereby minimizing animal stress due to acclimation issues. This paper describes some of the fundamental principles that need to be considered when designing and carrying out automated intermittent-flow respirometry (e.g. chamber size, flush rate, flush time, chamber mixing, measurement periods and temperature control). Finally, recent advances in oxygen probe technology and open source automation software will be discussed in the context of assembling relatively low cost and reliable measurement systems. © 2015 The Fisheries Society of the British Isles.

Recent improvements of the French liquid micro-flow reference facility

NASA Astrophysics Data System (ADS)

Florestan, Ogheard; Sandy, Margot; Julien, Savary

2018-02-01

According to the mission of the national reference laboratory, LNE-CETIAT achieved in 2012 the construction and accreditation of a modern and innovative calibration laboratory based on the gravimetric method. The measurement capabilities cover a flow rate range for liquid from 10 kg · h-1 down to 1 g · h-1 with expanded relative uncertainties from 0.1% to 0.6% (k  =  2). Since 2012, several theoretical and experimental studies have allowed a better knowledge and control over uncertainty sources and have decreased calibration time. When dealing with liquid micro-flow using a reference method such as the gravimetric method, several difficulties have to be overcome. The main improvements described in this paper relate to the enhancement of the evaporation trap system, the merging of the four dedicated measurement lines into one, and the implementation of a gravimetric dynamic ‘flying’ method for the calculation of the reference flow rate. The evaporation-avoiding system has been replaced by an oil layer in order to remove the possibility of condensation of water on both the weighed vessel and the immersed capillary. The article describes the experimental method used to quantify the effect of surface tension of water/oil/air interfaces on the weighed mass. The traditional static gravimetric method has been upgraded by a dynamic ‘flying’ gravimetric method. The article presents the newly implemented method, its validation and its advantages compared to the static method. The four dedicated weighing devices, dispatched over four sub-ranges of flow rate, have been merged leading to the use of only one weighing scale with the same uncertainties on the reference flow rate. The article discusses the new uncertainty budget over the full flow rate range capability. Finally, the article discusses the improvements still under development and the general prospects of liquid micro-flow metrology.

Cross diffusion and exponential space dependent heat source impacts in radiated three-dimensional (3D) flow of Casson fluid by heated surface

NASA Astrophysics Data System (ADS)

Zaigham Zia, Q. M.; Ullah, Ikram; Waqas, M.; Alsaedi, A.; Hayat, T.

2018-03-01

This research intends to elaborate Soret-Dufour characteristics in mixed convective radiated Casson liquid flow by exponentially heated surface. Novel features of exponential space dependent heat source are introduced. Appropriate variables are implemented for conversion of partial differential frameworks into a sets of ordinary differential expressions. Homotopic scheme is employed for construction of analytic solutions. Behavior of various embedding variables on velocity, temperature and concentration distributions are plotted graphically and analyzed in detail. Besides, skin friction coefficients and heat and mass transfer rates are also computed and interpreted. The results signify the pronounced characteristics of temperature corresponding to convective and radiation variables. Concentration bears opposite response for Soret and Dufour variables.

Deposition of amorphous carbon thin films by aerosol-assisted CVD method

NASA Astrophysics Data System (ADS)

Fadzilah, A. N.; Dayana, K.; Rusop, M.

2018-05-01

This paper reports on the deposition of amorphous carbon (a-C) by Aerosol-assisted Chemical Vapor Deposition (AACVD) using natural source of camphor oil as the precursor material. 4 samples were deposited at 4 different deposition flow rate from 15 sccm to 20 sccm, with 5 sccm interval for each sample. The analysis includes the electrical, optical and structural analysis of the data. The a-C structure which came from the manipulation of synthesis parameter was characterized by the solar simulator system, UV-VIS-NIR, Raman spectroscope and AFM. The properties of a-C are highly dependent on the deposition techniques and deposition parameters; hence the influences of gas flow rate were studied.

Advancements in solar stills for enhanced flow rate

NASA Astrophysics Data System (ADS)

Mishra, Sourav; Dubey, Maneesh; Raghuwanshi, Jitendra; Sharma, Vipin

2018-05-01

All over the world there is a scarcity of water and it is difficult to access potable water. Due to this most of the people are affected by diseases that are caused due to drinking of polluted water. There are technologies through which we can purify polluted water but the only problem is these technologies uses electrical energy. Since solar energy is abundant in nature therefore we can use solar as an energy source in solar stills for water distillation. Solar stills can be used in village areas where there is no electricity. It is simple and also economic in construction. This article addresses advancement in solar distillation and usage of nanofluids for enhancement in flow rate.

Evaluating Nitrate Contributions From Different Land Use Types Across a Regional Watershed Using Flow and Transport Models

NASA Astrophysics Data System (ADS)

Spansky, M. C.; Hyndman, D. W.; Long, D. T.; Pijanowski, B. C.

2004-05-01

Regional inputs of non-point source pollutants to groundwater, such as agriculturally-derived nitrate, have typically proven difficult to model due to sparse concentration data and complex system dynamics. We present an approach to evaluate the relative contribution of various land use types to groundwater nitrate across a regional Michigan watershed using groundwater flow and transport models. The models were parameterized based on land use data, and calibrated to a 20 year database of nitrate measured in drinking water wells. The database spans 1983-2003 and contains approximately 27,000 nitrate records for the five major counties encompassed by the watershed. The Grand Traverse Bay Watershed (GTBW), located in the northwest Lower Peninsula of Michigan, was chosen for this research. Groundwater flow and nitrate transport models were developed for the GTBW using MODFLOW2000 and RT3D, respectively. In a preliminary transport model, agricultural land uses were defined as the sole source of groundwater nitrate. Nitrate inputs were then refined to reflect variations in nitrogen loading rates for different agriculture types, including orchards, row crops, and pastureland. The calibration dataset was created by assigning spatial coordinates to each water well sample using address matching from a geographic information system (GIS). Preliminary results show that there is a significant link between agricultural sources and measured groundwater nitrate concentrations. In cases where observed concentrations remain significantly higher than simulated values, other sources of nitrate (e.g. septic tanks or abandoned agricultural fields) will be evaluated. This research will eventually incorporate temporal variations in fertilizer application rates and changing land use patterns to better represent fluid and solute fluxes at a regional scale.

The effect of inlet boundary conditions in image-based CFD modeling of aortic flow

NASA Astrophysics Data System (ADS)

Madhavan, Sudharsan; Kemmerling, Erica Cherry

2016-11-01

CFD of cardiovascular flow is a growing and useful field, but simulations are subject to a number of sources of uncertainty which must be quantified. Our work focuses on the uncertainty introduced by the selection of inlet boundary conditions in an image-based, patient-specific model of the aorta. Specifically, we examined the differences between plug flow, fully developed parabolic flow, linear shear flows, skewed parabolic flow profiles, and Womersley flow. Only the shape of the inlet velocity profile was varied-all other parameters were held constant between simulations, including the physiologically realistic inlet flow rate waveform and outlet flow resistance. We found that flow solutions with different inlet conditions did not exhibit significant differences beyond 1 . 75 inlet diameters from the aortic root. Time averaged wall shear stress (TAWSS) was also calculated. The linear shear velocity boundary condition solution exhibited the highest spatially averaged TAWSS, about 2 . 5 % higher than the fully developed parabolic velocity boundary condition, which had the lowest spatially averaged TAWSS.

Simulation results for a multirate mass transfer modell for immiscible displacement of two fluids in highly heterogeneous porous media

NASA Astrophysics Data System (ADS)

Tecklenburg, Jan; Neuweiler, Insa; Dentz, Marco; Carrera, Jesus; Geiger, Sebastian

2013-04-01

Flow processes in geotechnical applications do often take place in highly heterogeneous porous media, such as fractured rock. Since, in this type of media, classical modelling approaches are problematic, flow and transport is often modelled using multi-continua approaches. From such approaches, multirate mass transfer models (mrmt) can be derived to describe the flow and transport in the "fast" or mobile zone of the medium. The porous media is then modeled with one mobile zone and multiple immobile zones, where the immobile zones are connected to the mobile zone by single rate mass transfer. We proceed from a mrmt model for immiscible displacement of two fluids, where the Buckley-Leverett equation is expanded by a sink-source-term which is nonlocal in time. This sink-source-term models exchange with an immobile zone with mass transfer driven by capillary diffusion. This nonlinear diffusive mass transfer can be approximated for particular imbibition or drainage cases by a linear process. We present a numerical scheme for this model together with simulation results for a single fracture test case. We solve the mrmt model with the finite volume method and explicit time integration. The sink-source-term is transformed to multiple single rate mass transfer processes, as shown by Carrera et. al. (1998), to make it local in time. With numerical simulations we studied immiscible displacement in a single fracture test case. To do this we calculated the flow parameters using information about the geometry and the integral solution for two phase flow by McWorther and Sunnada (1990). Comparision to the results of the full two dimensional two phase flow model by Flemisch et. al. (2011) show good similarities of the saturation breakthrough curves. Carrera, J., Sanchez-Vila, X., Benet, I., Medina, A., Galarza, G., and Guimera, J.: On matrix diffusion: formulations, solution methods and qualitative effects, Hydrogeology Journal, 6, 178-190, 1998. Flemisch, B., Darcis, M., Erbertseder, K., Faigle, B., Lauser, A. et al.: Dumux: Dune for multi-{Phase, Component, Scale, Physics, ...} flow and transport in porous media, Advances in Water Resources, 34, 1102-1112, 2011. McWhorter, D. B., and Sunada, D. K.: Exact integral solutions for two-phase flow, Water Resources Research, 26(3), 399-413, 1990.

Development of a Distributed Source Containment Transport, Transformation, and Fate (CTT&F) Sub-Model for Military Installations

DTIC Science & Technology

2007-08-01

includes soil erodibility terms from the Universal Soil Lass Equation ( USLE ) for estimating the overland sediment transport capacity (for both the x and y...q = unit flow rate of water = va h [L2/T] vc = critical velocity for erosion overland [L/T] K = USLE soil erodibility factor C = USLE soil ...cover factor P = USLE soil management practice factor Be = width of eroding surface in flow direction [L]. In channels, sediment particles can be

Quasiparticle pair creation in unstable superflow

NASA Astrophysics Data System (ADS)

Elser, Veit

1995-06-01

Landau's instability mechanism in superflow is considered with special attention given to the role of nonuniformity in the flow. Linear stability analysis applied to the first in a series of approximate microscopic equations for the superfluid reveals a growth rate for Landau's instability proportional to the shear in the flow. In a quasiparticle description, the shear acts as a source of particle pair creation. The observation of roton-pair creation in experiments with electron bubbles in helium is offered as evidence of this phenomenon.

Continental-scale river flow in climate models

NASA Technical Reports Server (NTRS)

Miller, James R.; Russell, Gary L.; Caliri, Guilherme

1994-01-01

The hydrologic cycle is a major part of the global climate system. There is an atmospheric flux of water from the ocean surface to the continents. The cycle is closed by return flow in rivers. In this paper a river routing model is developed to use with grid box climate models for the whole earth. The routing model needs an algorithm for the river mass flow and a river direction file, which has been compiled for 4 deg x 5 deg and 2 deg x 2.5 deg resolutions. River basins are defined by the direction files. The river flow leaving each grid box depends on river and lake mass, downstream distance, and an effective flow speed that depends on topography. As input the routing model uses monthly land source runoff from a 5-yr simulation of the NASA/GISS atmospheric climate model (Hansen et al.). The land source runoff from the 4 deg x 5 deg resolution model is quartered onto a 2 deg x 2.5 deg grid, and the effect of grid resolution is examined. Monthly flow at the mouth of the world's major rivers is compared with observations, and a global error function for river flow is used to evaluate the routing model and its sensitivity to physical parameters. Three basinwide parameters are introduced: the river length weighted by source runoff, the turnover rate, and the basinwide speed. Although the values of these parameters depend on the resolution at which the rivers are defined, the values should converge as the grid resolution becomes finer. When the routing scheme described here is coupled with a climate model's source runoff, it provides the basis for closing the hydrologic cycle in coupled atmosphere-ocean models by realistically allowing water to return to the ocean at the correct location and with the proper magnitude and timing.

Experimental study on rotating instability mode characteristics of axial compressor tip flow

NASA Astrophysics Data System (ADS)

Tian, Jie; Yao, Dan; Wu, Yadong; Ouyang, Hua

2018-04-01

This paper investigates the rotating instabilities that occurred on the single-stage axial compressor designed for aerodynamic performance validation, which was tested with two sets of circumferential measuring points in combination. Circumferential mode characteristics of compressors are usually too high to be captured experimentally, and aliasing of the circumferential mode order occurs when not enough sensors are used. A calibration and prediction method to capture the higher circumferential mode of unsteady flow in a compressor was proposed. Unsteady pressure fluctuations near the tip region in an axial compressor were studied, and high circumferential mode characteristics were captured on both the blade passing frequency (BPF) and the rotational instability frequency (RIF) under different flow rate conditions based on this novel method. The characteristic RI spectrum with a broadband hump was present in a large range of flow conditions. Both the frequency range and the dominant circumferential mode order decreased as the flow rate decreased. Based on the calibrated mode characteristics, a rotating aerodynamic source model is used to explain the side-by-side peak of RIF spectrum and rotating characteristics of RI. The calibration and prediction method of the high circumferential mode is beneficial for the research of unsteady flow in an axial compressor.

Pump-Flow-Probe X-Ray Absorption Spectroscopy as a Tool for Studying Intermediate States of Photocatalytic Systems.

PubMed

Smolentsev, Grigory; Guda, Alexander; Zhang, Xiaoyi; Haldrup, Kristoffer; Andreiadis, Eugen; Chavarot-Kerlidou, Murielle; Canton, Sophie E; Nachtegaal, Maarten; Artero, Vincent; Sundstrom, Villy

2013-08-29

A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXAS beamline of the Swiss Light Source. It allows recording X-ray absorption spectra with a time resolution of tens of microseconds and high detection efficiency for samples with sub-mM concentrations. A continuous wave laser is used for the photoexcitation, with the distance between laser and X-ray beams and velocity of liquid flow determining the time delay, while the focusing of both beams and the flow speed define the time resolution. This method is compared with the alternative measurement technique that utilizes a 1 kHz repetition rate laser and multiple X-ray probe pulses. Such an experiment was performed at beamline 11ID-D of the Advanced Photon Source. Advantages, limitations and potential for improvement of the pump-flow-probe setup are discussed by analyzing the photon statistics. Both methods, with Co K-edge probing were applied to the investigation of a cobaloxime-based photo-catalytic reaction. The interplay between optimizing for efficient photoexcitation and time resolution as well as the effect of sample degradation for these two setups are discussed.

Pump-Flow-Probe X-Ray Absorption Spectroscopy as a Tool for Studying Intermediate States of Photocatalytic Systems

PubMed Central

Smolentsev, Grigory; Guda, Alexander; Zhang, XIaoyi; Haldrup, Kristoffer; Andreiadis, Eugen; Chavarot-Kerlidou, Murielle; Canton, Sophie E.; Nachtegaal, Maarten; Artero, Vincent; Sundstrom, Villy

2014-01-01

A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXAS beamline of the Swiss Light Source. It allows recording X-ray absorption spectra with a time resolution of tens of microseconds and high detection efficiency for samples with sub-mM concentrations. A continuous wave laser is used for the photoexcitation, with the distance between laser and X-ray beams and velocity of liquid flow determining the time delay, while the focusing of both beams and the flow speed define the time resolution. This method is compared with the alternative measurement technique that utilizes a 1 kHz repetition rate laser and multiple X-ray probe pulses. Such an experiment was performed at beamline 11ID-D of the Advanced Photon Source. Advantages, limitations and potential for improvement of the pump-flow-probe setup are discussed by analyzing the photon statistics. Both methods, with Co K-edge probing were applied to the investigation of a cobaloxime-based photo-catalytic reaction. The interplay between optimizing for efficient photoexcitation and time resolution as well as the effect of sample degradation for these two setups are discussed. PMID:24443663

In situ formation of leak-free polyethylene glycol (PEG) membranes in microfluidic fuel cells.

PubMed

Ho, W F; Lim, K M; Yang, K-L

2016-11-29

Membraneless microfluidic fuel cells operated under two co-laminar flows often face serious fuel cross-over problems, especially when flow rates are close to zero. In this study, we show that polyethylene glycol (PEG) monomers can be cross-linked inside microfluidic channels to form leak-free PEG membranes, which prevent mixing of two incompatible electrolyte solutions while allowing diffusion of certain molecules (e.g. glucose) and ions. By using PEG monomers of different molecular weights and cross-linking conditions, we are able to tailor selectivity of the membrane to allow passage of glucose while blocking larger molecules such as trypan blue. As a proof of principle, a microfluidic fuel cell with a PEG membrane and two incompatible electrolytes (acid and base) is demonstrated. Thanks to the leak-free nature of the PEG membrane, these two electrolytes do not mix together even at very slow flow rates. This microfluidic fuel cell is able to generate a voltage up to ∼450 mV from 10 mM of glucose with a flow rate of 20 μL min -1 . This microfluidic fuel cell is potentially useful as a miniature power source for many applications.

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

NASA Astrophysics Data System (ADS)

Nayak, Gaurav; Santos Sousa, João; Bruggeman, Peter J.

2017-03-01

The production of singlet delta oxygen (O2(a 1Δg)) is of growing interest for many applications. We report on the measurement of O2(a 1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a 1Δg) production. Different O2(a 1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a 1Δg) densities are discussed. The flow rate also allows for control of the O2(a 1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

Acetate enhances startup of a H₂-producing microbial biocathode.

PubMed

Jeremiasse, Adriaan W; Hamelers, Hubertus V M; Croese, Elsemiek; Buisman, Cees J N

2012-03-01

H(2) can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease MEC capital costs, a cathode is needed that is made of low-cost material and produces H(2) at high rate. A microbial biocathode is a low-cost candidate, but suffers from a long startup and a low H(2) production rate. In this study, the effects of cathode potential and carbon source on microbial biocathode startup were investigated. Application of a more negative cathode potential did not decrease the startup time of the biocathode. If acetate instead of bicarbonate was used as carbon source, the biocathode started up more than two times faster. The faster startup was likely caused by a higher biomass yield for acetate than for bicarbonate, which was supported by thermodynamic calculations. To increase the H(2) production rate, a flow through biocathode fed with acetate was investigated. This biocathode produced 2.2 m(3) H(2) m(-3)  reactor day(-1) at a cathode potential of -0.7 V versus NHE, which was seven times that of a parallel flow biocathode of a previous study. Copyright © 2011 Wiley Periodicals, Inc.

NOAA Propagation Database Value in Tsunami Forecast Guidance

NASA Astrophysics Data System (ADS)

Eble, M. C.; Wright, L. M.

2016-02-01

The National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research (NCTR) has developed a tsunami forecasting capability that combines a graphical user interface with data ingestion and numerical models to produce estimates of tsunami wave arrival times, amplitudes, current or water flow rates, and flooding at specific coastal communities. The capability integrates several key components: deep-ocean observations of tsunamis in real-time, a basin-wide pre-computed propagation database of water level and flow velocities based on potential pre-defined seismic unit sources, an inversion or fitting algorithm to refine the tsunami source based on the observations during an event, and tsunami forecast models. As tsunami waves propagate across the ocean, observations from the deep ocean are automatically ingested into the application in real-time to better define the source of the tsunami itself. Since passage of tsunami waves over a deep ocean reporting site is not immediate, we explore the value of the NOAA propagation database in providing placeholder forecasts in advance of deep ocean observations. The propagation database consists of water elevations and flow velocities pre-computed for 50 x 100 [km] unit sources in a continuous series along all known ocean subduction zones. The 2011 Japan Tohoku tsunami is presented as the case study

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

Anand, Venu, E-mail: venuanand@cense.iisc.ernet.in, E-mail: venuanand83@gmail.com; Shivashankar, S. A.; Nair, Aswathi R.

Gas discharge plasmas used for thinfilm deposition by plasma-enhanced chemical vapor deposition (PECVD) must be devoid of contaminants, like dust or active species which disturb the intended chemical reaction. In atmospheric pressure plasma systems employing an inert gas, the main source of such contamination is the residual air inside the system. To enable the construction of an atmospheric pressure plasma (APP) system with minimal contamination, we have carried out fluid dynamic simulation of the APP chamber into which an inert gas is injected at different mass flow rates. On the basis of the simulation results, we have designed and builtmore » a simple, scaled APP system, which is capable of holding a 100 mm substrate wafer, so that the presence of air (contamination) in the APP chamber is minimized with as low a flow rate of argon as possible. This is examined systematically by examining optical emission from the plasma as a function of inert gas flow rate. It is found that optical emission from the plasma shows the presence of atmospheric air, if the inlet argon flow rate is lowered below 300 sccm. That there is minimal contamination of the APP reactor built here, was verified by conducting an atmospheric pressure PECVD process under acetylene flow, combined with argon flow at 100 sccm and 500 sccm. The deposition of a polymer coating is confirmed by infrared spectroscopy. X-ray photoelectron spectroscopy shows that the polymer coating contains only 5% of oxygen, which is comparable to the oxygen content in polymer deposits obtained in low-pressure PECVD systems.« less

Inferred vs Realized Patterns of Gene Flow: An Analysis of Population Structure in the Andros Island Rock Iguana

PubMed Central

Colosimo, Giuliano; Knapp, Charles R.; Wallace, Lisa E.; Welch, Mark E.

2014-01-01

Ecological data, the primary source of information on patterns and rates of migration, can be integrated with genetic data to more accurately describe the realized connectivity between geographically isolated demes. In this paper we implement this approach and discuss its implications for managing populations of the endangered Andros Island Rock Iguana, Cyclura cychlura cychlura. This iguana is endemic to Andros, a highly fragmented landmass of large islands and smaller cays. Field observations suggest that geographically isolated demes were panmictic due to high, inferred rates of gene flow. We expand on these observations using 16 polymorphic microsatellites to investigate the genetic structure and rates of gene flow from 188 Andros Iguanas collected across 23 island sites. Bayesian clustering of specimens assigned individuals to three distinct genotypic clusters. An analysis of molecular variance (AMOVA) indicates that allele frequency differences are responsible for a significant portion of the genetic variance across the three defined clusters (Fst =  0.117, p0.01). These clusters are associated with larger islands and satellite cays isolated by broad water channels with strong currents. These findings imply that broad water channels present greater obstacles to gene flow than was inferred from field observation alone. Additionally, rates of gene flow were indirectly estimated using BAYESASS 3.0. The proportion of individuals originating from within each identified cluster varied from 94.5 to 98.7%, providing further support for local isolation. Our assessment reveals a major disparity between inferred and realized gene flow. We discuss our results in a conservation perspective for species inhabiting highly fragmented landscapes. PMID:25229344

Aeroacoustic model of a modulation fan with pitching blades as a sound generator.

PubMed

Du, Lin; Jing, Xiaodong; Sun, Xiaofeng; Song, Weihua

2014-10-01

This paper is to develop an aeroacoustic model for a type of modulation fan termed as rotary subwoofer that is capable of radiating low-frequency sound at high sound pressure levels. The rotary subwoofer is modeled as a baffled monopole whose source strength is specified by the fluctuating mass flow rate produced by the pitching blades that rotate at constant speed. An immersed boundary method is established to simulate the detailed unsteady flow around the blades and also to estimate the source strength for the prediction of the far-field sound pressure level (SPL). The numerical simulation shows that the rotary subwoofer can output oscillating air flow that is in phase with the pitching motion of the blades. It is found that flow separation is more likely to occur on the pitching blades at higher modulation frequency, resulting in the reduction of the radiated SPL. Increasing the maximum blade excursion is one of the most effective means to enhance the sound radiation, but this effect can also be compromised by the flow separation. As the modulation frequency increases, correspondingly increasing the rotational speed or using larger blade solidity is beneficial to suppressing the flow separation and thus improving the acoustic performance of the rotary subwoofer.

Quartz Crystal Microbalance Based System for High-Sensitivity Differential Sputter Yield Measurements (Preprint)

DTIC Science & Technology

2009-08-20

at low ion energies require appropriate ion sources. For example, past work using QCM sensors employed a magnetron as an ion source 32,33 . The...and for data logging. Detailed discussion of the QCM sensor is provided in Section IID. Figure 1. Schematic diagram of the experimental set-up...mass flow rate of 0.5 sccm. The PBN was biased negatively relative to ground potential. D. QCM Sensor and Temperature Control In deposition mode

Computational Fluid Dynamics (CFD) study of the 4th generation prototype of a continuous flow Ventricular Assist Device (VAD).

PubMed

Song, Xinwei; Wood, Houston G; Olsen, Don

2004-04-01

The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.

Effects of flow field on the metabolic characteristics of Streptomyces lincolnensis in the industrial fermentation of lincomycin.

PubMed

Li, Xiao; Zhang, Jiang; Tan, Ya-Li; Li, Zhi-Hong; Yu, Xue-Feng; Xia, Jian-Ye; Chu, Ju; Ge, You-Qun

2013-01-01

In this work, the flow field in the existing fermentor with radial-flow impellers (C1) was studied using the computational fluid dynamics (CFD) software package Fluent, then the fermentor with radial-axial flow impellers (C2) was constructed and was compared with the C1 fermentor by CFD and experimental research. The simulation results revealed that the flow field in C2 fermentor had characteristics such as higher turbulent kinetic energy, gas holdup and shear rates. Metabolic variables of Streptomyces lincolnensis in the two fermentors such as carbon and nitrogen source consumption rates, specific growth rates (μ), hyphae morphologies, and lincomycin productivities were further explored. The correlation analysis between the experimental measurements and the simulation results indicated that the hyphae clustering and dry cell weight (DCW) decreasing at production stage were eliminated in C2 fermentor, which had higher gas volumetric mass transfer coefficient (K(L)a), dissolved oxygen (DO) concentration and consumption rates of nutrient materials. When C2 was employed in the fermentor, the specific growth rate of S. lincolnensis at growth stage was higher, and the maintenance metabolism together with secondary metabolism at production stage was kept at higher levels. As a result, the yield of lincomycin was achieved 7039 μg ml(-1) when the 60 m(3) industrial fermentor was equipped with C2, which was increased by 46% compared to that obtained in the C1 fermentor. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Rarefied gas electro jet (RGEJ) micro-thruster for space propulsion

NASA Astrophysics Data System (ADS)

Blanco, Ariel; Roy, Subrata

2017-11-01

This article numerically investigates a micro-thruster for small satellites which utilizes plasma actuators to heat and accelerate the flow in a micro-channel with rarefied gas in the slip flow regime. The inlet plenum condition is considered at 1 Torr with flow discharging to near vacuum conditions (<0.05 Torr). The Knudsen numbers at the inlet and exit planes are ~0.01 and ~0.1, respectively. Although several studies have been performed in micro-hallow cathode discharges at constant pressure, to our knowledge, an integrated study of the glow discharge physics and resulting fluid flow of a plasma thruster under these low pressure and low Knudsen number conditions is yet to be reported. Numerical simulations of the charge distribution due to gas ionization processes and the resulting rarefied gas flow are performed using an in-house code. The mass flow rate, thrust, specific impulse, power consumption and the thrust effectiveness of the thruster are predicted based on these results. The ionized gas is modelled using local mean energy approximation. An electrically induced body force and a thermal heating source are calculated based on the space separated charge distribution and the ion Joule heating, respectively. The rarefied gas flow with these electric force and heating source is modelled using density-based compressible flow equations with slip flow boundary conditions. The results show that a significant improvement of specific impulse can be achieved over highly optimized cold gas thrusters using the same propellant.

A Class of Exact Solutions of the Boussinesq Equation for Horizontal and Sloping Aquifers

NASA Astrophysics Data System (ADS)

Bartlett, M. S.; Porporato, A.

2018-02-01

The nonlinear equation of Boussinesq (1877) is a foundational approach for studying groundwater flow through an unconfined aquifer, but solving the full nonlinear version of the Boussinesq equation remains a challenge. Here, we present an exact solution to the full nonlinear Boussinesq equation that not only applies to sloping aquifers but also accounts for source and sink terms such as bedrock seepage, an often significant flux in headwater catchments. This new solution captures the hysteretic relationship (a loop rating curve) between the groundwater flow rate and the water table height, which may be used to provide a more realistic representation of streamflow and groundwater dynamics in hillslopes. In addition, the solution provides an expression where the flow recession varies based on hillslope parameters such as bedrock slope, bedrock seepage, aquifer recharge, plant transpiration, and other factors that vary across landscape types.

Nonlinear Dynamics of Turbulent Thermals in Shear Flow

NASA Astrophysics Data System (ADS)

Ingel, L. Kh.

2018-03-01

The nonlinear integral model of a turbulent thermal is extended to the case of the horizontal component of its motion relative to the medium (e.g., thermal floating-up in shear flow). In contrast to traditional models, the possibility of a heat source in the thermal is taken into account. For a piecewise constant vertical profile of the horizontal velocity of the medium and a constant vertical velocity shear, analytical solutions are obtained which describe different modes of dynamics of thermals. The nonlinear interaction between the horizontal and vertical components of thermal motion is studied because each of the components influences the rate of entrainment of the surrounding medium, i.e., the growth rate of the thermal size and, hence, its mobility. It is shown that the enhancement of the entrainment of the medium due to the interaction between the thermal and the cross flow can lead to a significant decrease in the mobility of the thermal.

Fuel cell generator with fuel electrodes that control on-cell fuel reformation

DOEpatents

Ruka, Roswell J [Pittsburgh, PA; Basel, Richard A [Pittsburgh, PA; Zhang, Gong [Murrysville, PA

2011-10-25

A fuel cell for a fuel cell generator including a housing including a gas flow path for receiving a fuel from a fuel source and directing the fuel across the fuel cell. The fuel cell includes an elongate member including opposing first and second ends and defining an interior cathode portion and an exterior anode portion. The interior cathode portion includes an electrode in contact with an oxidant flow path. The exterior anode portion includes an electrode in contact with the fuel in the gas flow path. The anode portion includes a catalyst material for effecting fuel reformation along the fuel cell between the opposing ends. A fuel reformation control layer is applied over the catalyst material for reducing a rate of fuel reformation on the fuel cell. The control layer effects a variable reformation rate along the length of the fuel cell.

Theory of plasma contractors for electrodynamic tethered satellite systems

NASA Technical Reports Server (NTRS)

Parks, D. E.; Katz, I.

1986-01-01

Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source for example requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

Occurrence and transport of tetracycline, sulfonamide, quinolone, and macrolide antibiotics in the Haihe River Basin, China.

PubMed

Luo, Yi; Xu, Lin; Rysz, Michal; Wang, Yuqiu; Zhang, Hao; Alvarez, Pedro J J

2011-03-01

The occurrence and transport of 12 antibiotics (from the tetracycline, sulfonamide, quinolone, and macrolide families) was studied in a 72-km stretch of the Haihe River, China, and in six of its tributaries. Aqueous and sediment samples were analyzed by HPLC-MS/MS. Sulfonamides were detected at the highest concentrations (24-385 ng/L) and highest frequencies (76-100%). Eight of the 12 antibiotics likely originated from veterinary applications in swine farms and fishponds, and concentrations at these sources (0.12-47 μg/L) were 1-2 orders of magnitude higher than in the effluent of local wastewater treatment plants. Sulfachloropyridazine (SCP) was detected in all swine farm and fishpond samples (maximum concentration 47 μg/L), which suggests its potential usefulness to indicate livestock source pollution in the Haihe River basin. Hydrological and chemical factors that may influence antibiotic distribution in the Haihe River were considered by multiple regression analysis. River flow rate exerted the most significant effect on the first-order attenuation coefficient (K) for sulfonamides, quinolones, and macrolides, with higher flow rates resulting in higher K, probably due to dilution. For tetracyclines, sediment total organic matter and cation exchange capacity exerted a greater impact on K than flow rate, indicating that adsorption to sediments plays an important role in attenuating tetracycline migration. Overall, the predominance of sulfonamides in the Haihe River underscores the need to consider regulating their veterinary use and improving the management and treatment of associated releases.

Detailed design of a quiet high flow fan

NASA Technical Reports Server (NTRS)

Soltau, J. D.; Orelup, M. J.; Beguhn, A. A.; Wiles, F. M.; Anderson, M. J.

1977-01-01

A single stage fan was designed to demonstrate the noise abatement properties of near-sonic inlet flow and long-chord stator vanes for the reduction of both upstream and downstream propagated fan source noise. It is designed to produce a pressure ratio of 1.653:1 with an adiabatic efficiency of 83.9%. The fan has a 508 mm inlet diameter with a hub/tip ratio of 0.426 and a design tip speed of 533.4 m/sec. The design inlet specific flow rate is 219.71 kg/sec sq m and there are 10 tandem stator vanes with a combined aspect ratio of 0.54.

The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus.

PubMed

Franklin, Craig E; Seebacher, Frank

2003-04-01

The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23 degrees C and (3) heated via convective transfer by increasing water temperature from 23 degrees C to 35 degrees C. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23 degrees C. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (<0.5 degrees C) resulted in Q(10) values greater than 4000, calling into question the usefulness of this measure on heart rate during the initial stages of heating and cooling. In the later phases of heating and cooling, heart rate changed with body temperature, with Q(10) values of 2-3. The magnitude of the heart rate response differed between treatments, with radiant heating during submergence eliciting the smallest response. The heart rate of C. porosus outside of the 'rapid response' periods was found to be a function of the heat load experienced at the animal surface, as well as on the mode of heat transfer. Heart rate increased or decreased rapidly when C. porosus experienced large positive (above 25 W) or negative (below -15 W) heat loads, respectively, in all treatments. For heat loads between -15 W and 20 W, the increase in heart rate was smaller for the 'unnatural' heating by convection in water compared with either treatment using radiant heating. Our data indicate that changes in heart rate constitute a thermoregulatory mechanism that is modulated in response to the thermal environment occupied by the animal, but that heart rate during heating and cooling is, in part, controlled independently of body temperature.

Flow Analysis Tool White Paper

NASA Technical Reports Server (NTRS)

Boscia, Nichole K.

2012-01-01

Faster networks are continually being built to accommodate larger data transfers. While it is intuitive to think that implementing faster networks will result in higher throughput rates, this is often not the case. There are many elements involved in data transfer, many of which are beyond the scope of the network itself. Although networks may get bigger and support faster technologies, the presence of other legacy components, such as older application software or kernel parameters, can often cause bottlenecks. Engineers must be able to identify when data flows are reaching a bottleneck that is not imposed by the network and then troubleshoot it using the tools available to them. The current best practice is to collect as much information as possible on the network traffic flows so that analysis is quick and easy. Unfortunately, no single method of collecting this information can sufficiently capture the whole endto- end picture. This becomes even more of a hurdle when large, multi-user systems are involved. In order to capture all the necessary information, multiple data sources are required. This paper presents a method for developing a flow analysis tool to effectively collect network flow data from multiple sources and provide that information to engineers in a clear, concise way for analysis. The purpose of this method is to collect enough information to quickly (and automatically) identify poorly performing flows along with the cause of the problem. The method involves the development of a set of database tables that can be populated with flow data from multiple sources, along with an easyto- use, web-based front-end interface to help network engineers access, organize, analyze, and manage all the information.

40 CFR 98.173 - Calculating GHG emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... associated requirements for Tier 4 in subpart C of this part (General Stationary Fuel Combustion Sources). (b... basis (% CO2). Q = Hourly stack gas volumetric flow rate (scfh). %H2O = Hourly moisture percentage in... vented through the same stack as any combustion unit or process equipment that reports CO2 emissions...

40 CFR 98.173 - Calculating GHG emissions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... associated requirements for Tier 4 in subpart C of this part (General Stationary Fuel Combustion Sources). (b..., dry basis (% CO2). Q = Hourly stack gas volumetric flow rate (scfh). %H2O = Hourly moisture percentage... reduction furnace are vented through the same stack as any combustion unit or process equipment that reports...

40 CFR 98.173 - Calculating GHG emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... associated requirements for Tier 4 in subpart C of this part (General Stationary Fuel Combustion Sources). (b... basis (% CO2). Q = Hourly stack gas volumetric flow rate (scfh). %H2O = Hourly moisture percentage in... vented through the same stack as any combustion unit or process equipment that reports CO2 emissions...

Advancements in Afterbody Radiative Heating Simulations for Earth Entry

NASA Technical Reports Server (NTRS)

Johnston, Christopher O.; Panesi, Marco; Brandis, Aaron M.

2016-01-01

Four advancements to the simulation of backshell radiative heating for Earth entry are presented. The first of these is the development of a flow field model that treats electronic levels of the dominant backshell radiator, N, as individual species. This is shown to allow improvements in the modeling of electron-ion recombination and two-temperature modeling, which are shown to increase backshell radiative heating by 10 to 40%. By computing the electronic state populations of N within the flow field solver, instead of through the quasi-steady state approximation in the radiation code, the coupling of radiative transition rates to the species continuity equations for the levels of N, including the impact of non-local absorption, becomes feasible. Implementation of this additional level of coupling between the flow field and radiation codes represents the second advancement presented in this work, which is shown to increase the backshell radiation by another 10 to 50%. The impact of radiative transition rates due to non-local absorption indicates the importance of accurate radiation transport in the relatively complex flow geometry of the backshell. This motivates the third advancement, which is the development of a ray-tracing radiation transport approach to compute the radiative transition rates and divergence of the radiative flux at every point for coupling to the flow field, therefore allowing the accuracy of the commonly applied tangent-slab approximation to be assessed for radiative source terms. For the sphere considered at lunar-return conditions, the tangent-slab approximation is shown to provide a sufficient level of accuracy for the radiative source terms, even for backshell cases. This is in contrast to the agreement between the two approaches for computing the radiative flux to the surface, which differ by up to 40%. The final advancement presented is the development of a nonequilibrium model for NO radiation, which provides significant backshell radiation at velocities below 10 km/s. The developed model reduces the nonequilibrium NO radiation by 50% relative to the previous model.

Effects of Convective Solute and Impurity Transport in Protein Crystal Growth

NASA Technical Reports Server (NTRS)

Vekilov, Peter G.; Thomas, Bill R.; Rosenberger, Franz

1998-01-01

High-resolution optical interferometry was used to investigate the effects of forced solution convection on the crystal growth kinetics of the model protein lysozyme. Most experiments were conducted with 99.99% pure protein solutions. To study impurity effects, approx. 1% of lysozyme dimer (covalently bound) was added in some cases. We show that the unsteady kinetics, corresponding to bunching of growth steps, can be characterized by the Fourier components of time traces of the growth rate. Specific Fourier spectra are uniquely determined by the solution conditions (composition, temperature, and flow rate) and the growth layer source activity. We found that the average step velocity and growth rate increase by approx. I0% with increasing flow rate, as a result of the enhanced solute supply to the interface. More importantly, faster convective transport results in lower fluctuation amplitudes. This observation supports our rationale for system-dependent effects of transport on the structural perfection of protein crystals. We also found that solution flow rates greater than 500 microns/s result in stronger fluctuations while the average growth rate is decreased. This can lead to growth cessation at low supersaturations. With the intentionally contaminated solutions, these undesirable phenomena occurred at about half the flow rates required in pure solutions. Thus, we conclude that they are due to enhanced convective supply of impurities that are incorporated into the crystal during growth. Furthermore, we found that the impurity effects are reduced at higher crystal growth rates. Since the exposure time of terraces is inversely proportional to the growth rate, this observation suggests that the increased kinetics instability results from impurity adsorption on the interface. Finally, we provide evidence relating earlier observations of "slow protein crystal growth kinetics" to step bunch formation in response to nonsteady step generation.

Flow Measurement

NASA Technical Reports Server (NTRS)

1988-01-01

Macrodyne, Inc.'s laser velocimeter (LV) is a system used in wind tunnel testing of aircraft, missiles and spacecraft employing electro optical techniques to probe the flow field as the tunnel blows air over a model of flight vehicle and to determine velocity of air and its direction at many points around the model. However, current state-of-the-art minicomputers cannot handle the massive flow of real time data from several sources simultaneously. Langley developed instrument Laser Velocimeter Autocovariance Buffer Interface (LVABI). LVABI is interconnecting instrument between LV and computer. It acquires data from as many as six LV channels at high real time data rates, stores it in memory and sends it to computer on command. LVABI has application in variety of research, industrial and defense functions requiring precise flow measurement.

Rossby waves and two-dimensional turbulence in a large-scale zonal jet

NASA Technical Reports Server (NTRS)

Shepherd, Theodor G.

1987-01-01

Homogeneous barotropic beta-plane turbulence is investigated, taking into account the effects of spatial inhomogeneity in the form of a zonal shear flows. Attention is given to the case of zonal flows that are barotropically stable and of larger scale than the resulting transient eddy field. Numerical simulations reveal that large-scale zonal flows alter the picture of classical beta-plane turbulence. It is found that the disturbance field penetrates to the largest scales of motion, that the larger disturbance scales show a tendency to meridional rather than zonal anisotropy, and that the initial spectral transfer rate away from an isotropic intermediate-scale source is enhanced by the shear-induced transfer associated with straining by the zonal flow.

A new approach for flow-through respirometry measurements in humans

PubMed Central

Ingebrigtsen, Jan P.; Bergouignan, Audrey; Ohkawara, Kazunori; Kohrt, Wendy M.; Lighton, John R. B.

2010-01-01

Indirect whole room calorimetry is commonly used in studies of human metabolism. These calorimeters can be configured as either push or pull systems. A major obstacle to accurately calculating gas exchange rates in a pull system is that the excurrent flow rate is increased above the incurrent flow rate, because the organism produces water vapor, which also dilutes the concentrations of respiratory gasses in the excurrent sample. A common approach to this problem is to dry the excurrent gasses prior to measurement, but if drying is incomplete, large errors in the calculated oxygen consumption will result. The other major potential source of error is fluctuations in the concentration of O2 and CO2 in the incurrent airstream. We describe a novel approach to measuring gas exchange using a pull-type whole room indirect calorimeter. Relative humidity and temperature of the incurrent and excurrent airstreams are measured continuously using high-precision, relative humidity and temperature sensors, permitting accurate measurement of water vapor pressure. The excurrent flow rates are then adjusted to eliminate the flow contribution from water vapor, and respiratory gas concentrations are adjusted to eliminate the effect of water vapor dilution. In addition, a novel switching approach is used that permits constant, uninterrupted measurement of the excurrent airstream while allowing frequent measurements of the incurrent airstream. To demonstrate the accuracy of this approach, we present the results of validation trials compared with our existing system and metabolic carts, as well as the results of standard propane combustion tests. PMID:20200135

Denitrification and dilution along fracture flowpaths influence the recovery of a bedrock aquifer from nitrate contamination.

PubMed

Kim, Jonathan J; Comstock, Jeff; Ryan, Peter; Heindel, Craig; Koenigsberger, Stephan

2016-11-01

In 2000, elevated nitrate concentrations ranging from 12 to 34mg/L NO3N were discovered in groundwater from numerous domestic bedrock wells adjacent to a large dairy farm in central Vermont. Long-term plots and contours of nitrate vs. time for bedrock wells showed "little/no", "moderate", and "large" change patterns that were spatially separable. The metasedimentary bedrock aquifer is strongly anisotropic and groundwater flow is controlled by fractures, bedding/foliation, and basins and ridges in the bedrock surface. Integration of the nitrate concentration vs. time data and the physical and chemical aquifer characterization suggest two nitrate sources: a point source emanating from a waste ravine and a non-point source that encompasses the surrounding fields. Once removed, the point source of NO3 (manure deposited in a ravine) was exhausted and NO3 dropped from 34mg/L to <10mg/L after ~10years; however, persistence of NO3 in the 3 to 8mg/L range (background) reflects the long term flux of nitrates from nutrients applied to the farm fields surrounding the ravine over the years predating and including this study. Inferred groundwater flow rates from the waste ravine to either moderate change wells in basin 2 or to the shallow bedrock zone beneath the large change wells are 0.05m/day, well within published bedrock aquifer flow rates. Enrichment of (15)N and (18)O in nitrate is consistent with lithotrophic denitrification of NO3 in the presence of dissolved Mn and Fe. Once the ravine point-source was removed, denitrification and dilution collectively were responsible for the down-gradient decrease of nitrate in this bedrock aquifer. Denitrification was most influential when NO3N was >10mg/L. Our multidisciplinary methods of aquifer characterization are applicable to groundwater contamination in any complexly-deformed and metamorphosed bedrock aquifer. Copyright © 2016 Elsevier B.V. All rights reserved.

Atomic layer deposition of zirconium silicate films using zirconium tetrachloride and tetra-n-butyl orthosilicate

NASA Astrophysics Data System (ADS)

Kim, Won-Kyu; Kang, Sang-Woo; Rhee, Shi-Woo; Lee, Nae-In; Lee, Jong-Ho; Kang, Ho-Kyu

2002-11-01

Atomic layer chemical vapor deposition of zirconium silicate films with a precursor combination of ZrCl4 and tetra-n-butyl orthosilicate (TBOS) was studied for high dielectric gate insulators. The effect of deposition conditions, such as deposition temperature, pulse time for purge and precursor injection on the deposition rate per cycle, and composition of the film were studied. At 400 °C, the growth rate saturated to 1.35 Å/cycle above 500 sccm of the argon purge flow rate. The growth rate, composition ratio ((Zr/Zr+Si)), and impurity contents (carbon and chlorine) saturated with the increase of the injection time of ZrCl4 and TBOS and decreased with the increased deposition temperature from 300 to 500 °C. The growth rate, composition ratio, carbon, and chlorine contents of the Zr silicate thin films deposited at 500 °C were 1.05 Å/cycle, 0.23, 1.1 at. %, and 2.1 at. %, respectively. It appeared that by using only zirconium chloride and silicon alkoxide sources, the content of carbon and chlorine impurities could not be lowered below 1%. It was also found that the incorporation rate of metal from halide source was lower than alkoxide source.

Relationship between eruption plume heights and seismic source amplitudes of eruption tremors and explosion events

NASA Astrophysics Data System (ADS)

Mori, A.; Kumagai, H.

2016-12-01

It is crucial to analyze and interpret eruption tremors and explosion events for estimating eruption size and understanding eruption phenomena. Kumagai et al. (EPS, 2015) estimated the seismic source amplitudes (As) and cumulative source amplitudes (Is) for eruption tremors and explosion events at Tungurahua, Ecuador, by the amplitude source location (ASL) method based on the assumption of isotropic S-wave radiation in a high-frequency band (5-10 Hz). They found scaling relations between As and Is for eruption tremors and explosion events. However, the universality of these relations is yet to be verified, and the physical meanings of As and Is are not clear. In this study, we analyzed the relations between As and Is for eruption tremors and explosion events at active volcanoes in Japan, and estimated As and Is by the ASL method. We obtained power-law relations between As and Is, in which the powers were different between eruption tremors and explosion events. These relations were consistent with the scaling relations at Tungurahua volcano. Then, we compared As with maximum eruption plume heights (H) during eruption tremors analyzed in this study, and found that H was proportional to 0.21 power of As. This relation is similar to the plume height model based on the physical process of plume rise, which indicates that H is proportional to 0.25 power of volumetric flow rate for plinian eruptions. This suggests that As may correspond to volumetric flow rate. If we assume a seismic source with volume changes and far-field S-wave, As is proportional to the source volume rate. This proportional relation and the plume height model give rise to the relation that H is proportional to 0.25 power of As. These results suggest that we may be able to estimate plume heights in realtime by estimating As during eruptions from seismic observations.

Hydrogeologic investigations of the Sierra Vista subwatershed of the Upper San Pedro Basin, Cochise County, southeast Arizona

USGS Publications Warehouse

Pool, Donald R.; Coes, Alissa L.

1999-01-01

The hydrogeologic system in the Sierra Vista subwatershed of the Upper San Pedro Basin in southeastern Arizona was investigated for the purpose of developing a better understanding of stream-aquifer interactions. The San Pedro River is an intermittent stream that supports a narrow corridor of riparian vegetation. Withdrawal of ground water will result in reduced discharge from the basin through reduced base flow and evapotranspiration; however, the rate and location of reduced discharge are uncertain. The investigation resulted in better definition of distributions of silt and clay in the regional aquifer; changes in seasonal precipitation, runoff, and base flow in the San Pedro River; sources of base flow; and regional water-level changes. Regional ground-water flow is separated into deep-confined and shallow-unconfined systems by silt and clay. Precipitation, runoff, and base flow declined at the Charleston streamflow-gaging station from 1936 through 1997 for the months of June through October. Base flow at the Charleston station during 1996 and 1997 was primarily supplied by ground water recharged near the San Pedro River during recent major runoff and by minor contributions from the regional aquifer. The decline in base flow, about 2 cubic feet per second, has several probable causes including declining runoff and recharge near the river during June through October and increased interception of ground-water flow to the river by wells and phreatophytes. Water levels in wells throughout the regional aquifer generally declined at rates of 0.2 to 0.5 feet per year between 1940 and the mid-1980's, which corresponded with a period of below-average winter precipitation. Water levels in wells in the Fort Huachuca and Sierra Vista areas declined at rates that were faster than regional rates of decline through 1998 and caused diversion of ground-water flow that would have discharged along perennial stream reaches.

Observations and initial modeling of lava-SO2 interactions at Prometheus, Io

NASA Astrophysics Data System (ADS)

Milazzo, M. P.; Keszthelyi, L. P.; McEwen, A. S.

2001-12-01

We present observations and initial modeling of the lava-SO2 interactions at the flow fronts in the Prometheus region of Io. Recent high-resolution observations of Prometheus reveal a compound flow field with many active flow lobes. Many of the flow lobes are associated with bright streaks of what is interpreted to be volatilized and recondensed SO2 radiating away from the hot lava. Lower-resolution color data show diffuse blue to violet areas, also near the active flow front, perhaps from active venting of SO2. Not clearly visible in any of the images is a single source vent for the active plume. While the size of the proposed vent is probably near the limit of the resolution, we expected to see radial or concentric albedo patterns or other evidence for gas and entrained particles above the flow field. The lack of an obvious plume vent, earlier suggestions that the Prometheus-type plumes may originate from the advancing flow lobes, and the high-resolution images showing evidence for large-scale volatilization of the SO2-rich substrate at Prometheus encouraged us to develop a model to quantify the heat transfer between a basaltic lava flow and a substrate of SO2 snow. We calculate that the vaporization rate of SO2 snow is 2.5×10-6ms-1 per unit area. Using an estimated 5 m2s-1 lava coverage rate (from change detection images), we show that the gas production rate of SO2 at the flow fronts is enough to produce a resurfacing rate of ~0.24 cm yr-1 at the annulus of Prometheus. This is much less than other estimates of resurfacing by the Prometheus plume. While not easily explaining the main Prometheus plume, our model readily accounts for the bright streaks.

Accelerated uplift and magmatic intrusion of the Yellowstone caldera, 2004 to 2006

USGS Publications Warehouse

Chang, Wu-Lung; Smith, Robert B.; Wicks, Charles; Farrell, J.M.; Puskas, C.M.

2007-01-01

The Yellowstone caldera began a rapid episode of ground uplift in mid-2004, revealed by Global Positioning System and interferometric synthetic aperture radar measurements, at rates up to 7 centimeters per year, which is over three times faster than previously observed inflation rates. Source modeling of the deformation data suggests an expanding volcanic sill of ???1200 square kilometers at a 10-kilometer depth beneath the caldera, coincident with the top of a seismically imaged crustal magma chamber. The modeled rate of source volume increase is 0.1 cubic kilometer per year, similar to the amount of magma intrusion required to supply the observed high heat flow of the caldera. This evidence suggests magma recharge as the main mechanism for the accelerated uplift, although pressurization of magmatic fluids cannot be ruled out.

FloWave.US: validated, open-source, and flexible software for ultrasound blood flow analysis.

PubMed

Coolbaugh, Crystal L; Bush, Emily C; Caskey, Charles F; Damon, Bruce M; Towse, Theodore F

2016-10-01

Automated software improves the accuracy and reliability of blood velocity, vessel diameter, blood flow, and shear rate ultrasound measurements, but existing software offers limited flexibility to customize and validate analyses. We developed FloWave.US-open-source software to automate ultrasound blood flow analysis-and demonstrated the validity of its blood velocity (aggregate relative error, 4.32%) and vessel diameter (0.31%) measures with a skeletal muscle ultrasound flow phantom. Compared with a commercial, manual analysis software program, FloWave.US produced equivalent in vivo cardiac cycle time-averaged mean (TAMean) velocities at rest and following a 10-s muscle contraction (mean bias <1 pixel for both conditions). Automated analysis of ultrasound blood flow data was 9.8 times faster than the manual method. Finally, a case study of a lower extremity muscle contraction experiment highlighted the ability of FloWave.US to measure small fluctuations in TAMean velocity, vessel diameter, and mean blood flow at specific time points in the cardiac cycle. In summary, the collective features of our newly designed software-accuracy, reliability, reduced processing time, cost-effectiveness, and flexibility-offer advantages over existing proprietary options. Further, public distribution of FloWave.US allows researchers to easily access and customize code to adapt ultrasound blood flow analysis to a variety of vascular physiology applications. Copyright © 2016 the American Physiological Society.

Energy balance in the core of the Saturn plasma sheet: H2O chemistry

NASA Astrophysics Data System (ADS)

Shemansky, D. E.; Yoshii, J.; Liu, X.

2011-10-01

A model of the weakly ionized plasma at Saturn has been developed to investigate the properties of the system. Energy balance is a critical consideration. The present model is based on two sources of mass, H2O, and HI. H2O is a variable. HI is a significant volume of gas flowing through the plasma imposed by the source at Saturn [1,2,3]. The energy sources are solar radiation and heterogeneous magnetosphere electrons. The model calculations produce energy rates, species partitioning, and relaxation lifetimes. For the first time the state of the ambient plasma sheet electrons is directly connected to the energy forcing functions. Within limits of knowledge, the predicted state of the core region of the plasma sheet in neutral and ionized gas corresponds satisfactorily to observation. The dominant ions in these calculations are H2O+ and H3O+ with lifetimes of several days. The lifetime of H2O is roughly 60 days. In calculations carried out so far the predicted source rate for H2O is lower than the rates quoted from the Enceladus encounters.

An Empirical Temperature Variance Source Model in Heated Jets

NASA Technical Reports Server (NTRS)

Khavaran, Abbas; Bridges, James

2012-01-01

An acoustic analogy approach is implemented that models the sources of jet noise in heated jets. The equivalent sources of turbulent mixing noise are recognized as the differences between the fluctuating and Favre-averaged Reynolds stresses and enthalpy fluxes. While in a conventional acoustic analogy only Reynolds stress components are scrutinized for their noise generation properties, it is now accepted that a comprehensive source model should include the additional entropy source term. Following Goldstein s generalized acoustic analogy, the set of Euler equations are divided into two sets of equations that govern a non-radiating base flow plus its residual components. When the base flow is considered as a locally parallel mean flow, the residual equations may be rearranged to form an inhomogeneous third-order wave equation. A general solution is written subsequently using a Green s function method while all non-linear terms are treated as the equivalent sources of aerodynamic sound and are modeled accordingly. In a previous study, a specialized Reynolds-averaged Navier-Stokes (RANS) solver was implemented to compute the variance of thermal fluctuations that determine the enthalpy flux source strength. The main objective here is to present an empirical model capable of providing a reasonable estimate of the stagnation temperature variance in a jet. Such a model is parameterized as a function of the mean stagnation temperature gradient in the jet, and is evaluated using commonly available RANS solvers. The ensuing thermal source distribution is compared with measurements as well as computational result from a dedicated RANS solver that employs an enthalpy variance and dissipation rate model. Turbulent mixing noise predictions are presented for a wide range of jet temperature ratios from 1.0 to 3.20.

Baseflow separation in a premontane transitional rainforest using stable isotope techniques

NASA Astrophysics Data System (ADS)

Miller, G. R.; DuMont, A.; Roark, E.; Cahill, A. T.; Brumbelow, J. K.

2013-12-01

Hydrologic, geologic, and biologic processes are critical to understanding the ecosystem in the tropical premontane transitional forests of Costa Rica. Precipitation is significantly lower during the dry season, and incoming rainfall can be completely intercepted and re-evaporated by the canopy during light events. These canopy processes can affect the rates of runoff and infiltration by changing the quantity and timing of rainfall reaching the ground surface. However, the resulting partitioning of stream water sources between event-water and baseflow from groundwater is not well quantified due to limited accessibility and complex subsurface conditions. This study focuses on research conducted at the Texas A&M Soltis Center for Education and Research, near San Ramón, Costa Rica. We have monitored a 2.2 ha watershed there, measuring precipitation and transpiration rates for over two years, and groundwater levels and stream flow rates for nearly one year. Precipitation rates for the watershed averaged 4.4 m/yr since 2010. Stream flow (runoff, spring flow, and baseflow) averaged 0.09 m^3/sec during the 2012-2013 wet seasons. At 1.2 mm/day, transpiration was a relatively minor component of the water budget. Over a 40-day span during summer 2013, we collected a combination of daily and rain-event based samples from locations throughout the watershed. Sources included: the main stream and two small tributaries, groundwater from piezometers, pore water from suction lysimeters, throughfall and stemflow from under canopy collection systems, and xylem water from 8 tree species across the watershed. We then measured stable isotope fractions (δ18O and δD) in the water using a Picarro L2120i CRDS. Isotope ratios for all surface water averaged -5.50‰ for δ18O and -28.00‰ for δD, while that measured under baseflow conditions were -5.45‰ for δ18O and -29.18‰ for δD. These results indicate that baseflow is the dominate source of stream water even in the wet season. We additionally conclude that despite the ubiquity of low permeability Andisols in this watershed, groundwater transport to the stream is characterized by short residence times attributable to macropore/fracture flow in the subsurface.

Three-Dimensional Numerical Simulation on Passively Excited Flows by Distributed Local Hot Sources Settled at the D" Layer Below Hotspots and/or Large-Scale Cool Masses at Subduction Zones Within the Static Layered Mantle

NASA Astrophysics Data System (ADS)

Eguchi, T.; Matsubara, K.; Ishida, M.

2001-12-01

To unveil dynamic process associated with three-dimensional unsteady mantle convection, we carried out numerical simulation on passively exerted flows by simplified local hot sources just above the CMB and large-scale cool masses beneath smoothed subduction zones. During the study, we used our individual code developed with the finite difference method. The basic three equations are for the continuity, the motion with the Boussinesq (incompressible) approximation, and the (thermal) energy conservation. The viscosity of our model is sensitive to temperature. To get time integration with high precision, we used the Newton method. In detail, the size and thermal energy of the hot or cool sources are not uniform along the latitude, because we could not select uniform local volumes assigned for the sources within the finite difference grids throughout the mantle. Our results, thus, accompany some latitude dependence. First, we treated the case of the hotspots, neglecting the contribution of the subduction zones. The local hot sources below the currently active hotspots were settled as dynamic driving forces included in the initial condition. Before starting the calculation, we assumed that the mantle was statically layered with zero velocity component. The thermal anomalies inserted instantaneously in the initial condition do excite dynamically passive flows. The type of the initial hot sources was not 'plume' but 'thermal.' The simulation results represent that local upwelling flows which were directly excited over the initial heat sources reached the upper mantle by approximately 30 My during the calculation. Each of the direct upwellings above the hotspots has its own dynamic potential to exert concentric down- and up-welling flows, alternately, at large distances. Simultaneously, the direct upwellings interact mutually within the spherical mantle. As an interesting feature, we numerically observed secondary upwellings somewhere in a wide region covering east Eurasia to the Bering Sea where no hot sources were initially input. It seems that the detailed location of the secondary upwellings depends partly on the numerical parameters such as the radial profile of mantle viscosity especially at the D" layer, etc., because the secondary flows are provoked by dynamic interaction among the distributed direct upwellings just above the CMB. Our results suggest that if we assume not only non-zero time delays during the input of the local hot sources but also parameters related with the difference of their historical surface flux rates, the pattern of the passively excited flows will be different from that obtained with the simultaneously settled hot sources stated above. Second, we simultaneously incorporated simplified thermal anomaly models associated with both the distributed local hotspots and the global subduction zones, as dynamic origins in the initial condition for the static layered mantle. In this case, the simulation result represents that the pattern of secondary radial flows, being different from those in the earlier case, is sensitive to the relative strength between the positive dynamic buoyancy integrated over all of the local hot sources below the hotspots and the total negative buoyancy beneath the subduction zones.

Exploring Inflated Pahohoe Lava Flow Morphologies and the Effects of Cooling Using a New Simulation Approach

NASA Technical Reports Server (NTRS)

Glaze, L. S.; Baloga, S. M.

2014-01-01

Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts.

From Magma Fracture to a Seismic Magma Flow Meter

NASA Astrophysics Data System (ADS)

Neuberg, J. W.

2007-12-01

Seismic swarms of low-frequency events occur during periods of enhanced volcanic activity and have been related to the flow of magma at depth. Often they precede a dome collapse on volcanoes like Soufriere Hills, Montserrat, or Mt St Helens. This contribution is based on the conceptual model of magma rupture as a trigger mechanism. Several source mechanisms and radiation patterns at the focus of a single event are discussed. We investigate the accelerating event rate and seismic amplitudes during one swarm, as well as over a time period of several swarms. The seismic slip vector will be linked to magma flow parameters resulting in estimates of magma flux for a variety of flow models such as plug flow, parabolic- or friction controlled flow. In this way we try to relate conceptual models to quantitative estimations which could lead to estimations of magma flux at depth from seismic low-frequency signals.

Transient Point Infiltration In The Unsaturated Zone

NASA Astrophysics Data System (ADS)

Buecker-Gittel, M.; Mohrlok, U.

The risk assessment of leaking sewer pipes gets more and more important due to urban groundwater management and environmental as well as health safety. This requires the quantification and balancing of transport and transformation processes based on the water flow in the unsaturated zone. The water flow from a single sewer leakage could be described as a point infiltration with time varying hydraulic conditions externally and internally. External variations are caused by the discharge in the sewer pipe as well as the state of the leakage itself. Internal variations are the results of microbiological clogging effects associated with the transformation processes. Technical as well as small scale laboratory experiments were conducted in order to investigate the water transport from an transient point infiltration. From the technical scale experiment there was evidence that the water flow takes place under transient conditions when sewage infiltrates into an unsaturated soil. Whereas the small scale experiments investigated the hydraulics of the water transport and the associated so- lute and particle transport in unsaturated soils in detail. The small scale experiment was a two-dimensional representation of such a point infiltration source where the distributed water transport could be measured by several tensiometers in the soil as well as by a selective measurement of the discharge at the bottom of the experimental setup. Several series of experiments were conducted varying the boundary and initial con- ditions in order to derive the important parameters controlling the infiltration of pure water from the point source. The results showed that there is a significant difference between the infiltration rate in the point source and the discharge rate at the bottom, that could be explained by storage processes due to an outflow resistance at the bottom. This effect is overlayn by a decreasing water content decreases over time correlated with a decreasing infiltration rate. As expected the initial conditions mainly affects the time scale for the water transport. Additionally, the influence of preferential flow paths on the discharge distribution could be found due to the heterogenieties caused by the filling and compaction process of the sandy soil.

Monitoring Enzymatic Reactions in Real Time Using Venturi Easy Ambient Sonic-Spray Ionization Mass Spectrometry

PubMed Central

2016-01-01

We developed a technique to monitor spatially confined surface reactions with mass spectrometry under ambient conditions, without the need for voltage or organic solvents. Fused-silica capillaries immersed in an aqueous solution, positioned in close proximity to each other and the functionalized surface, created a laminar flow junction with a resulting reaction volume of ∼5 pL. The setup was operated with a syringe pump, delivering reagents to the surface through a fused-silica capillary. The other fused-silica capillary was connected to a Venturi easy ambient sonic-spray ionization source, sampling the resulting analytes at a slightly higher flow rate compared to the feeding capillary. The combined effects of the inflow and outflow maintains a chemical microenvironment, where the rate of advective transport overcomes diffusion. We show proof-of-concept where acetylcholinesterase was immobilized on an organosiloxane polymer through electrostatic interactions. The hydrolysis of acetylcholine by acetylcholinesterase into choline was monitored in real-time for a range of acetylcholine concentrations, fused-silica capillary geometries, and operating flow rates. Higher reaction rates and conversion yields were observed with increasing acetylcholine concentrations, as would be expected. PMID:27249533

Paper pump for passive and programmable transport

PubMed Central

Wang, Xiao; Hagen, Joshua A.; Papautsky, Ian

2013-01-01

In microfluidic systems, a pump for fluid-driving is often necessary. To keep the size of microfluidic systems small, a pump that is small in size, light-weight and needs no external power source is advantageous. In this work, we present a passive, simple, ultra-low-cost, and easily controlled pumping method based on capillary action of paper that pumps fluid through conventional polymer-based microfluidic channels with steady flow rate. By using inexpensive cutting tools, paper can be shaped and placed at the outlet port of a conventional microfluidic channel, providing a wide range of pumping rates. A theoretical model was developed to describe the pumping mechanism and aid in the design of paper pumps. As we show, paper pumps can provide steady flow rates from 0.3 μl/s to 1.7 μl/s and can be cascaded to achieve programmable flow-rate tuning during the pumping process. We also successfully demonstrate transport of the most common biofluids (urine, serum, and blood). With these capabilities, the paper pump has the potential to become a powerful fluid-driving approach that will benefit the fielding of microfluidic systems for point-of-care applications. PMID:24403999

Laboratory simulations of cumulus cloud flows explain the entrainment anomaly

NASA Astrophysics Data System (ADS)

Narasimha, Roddam; Diwan, Sourabh S.; Subrahmanyam, Duvvuri; Sreenivas, K. R.; Bhat, G. S.

2010-11-01

In the present laboratory experiments, cumulus cloud flows are simulated by starting plumes and jets subjected to off-source heat addition in amounts that are dynamically similar to latent heat release due to condensation in real clouds. The setup permits incorporation of features like atmospheric inversion layers and the active control of off-source heat addition. Herein we report, for the first time, simulation of five different cumulus cloud types (and many shapes), including three genera and three species (WMO Atlas 1987), which show striking resemblance to real clouds. It is known that the rate of entrainment in cumulus cloud flows is much less than that in classical plumes - the main reason for the failure of early entrainment models. Some of the previous studies on steady-state jets and plumes (done in a similar setup) have attributed this anomaly to the disruption of the large-scale turbulent structures upon the addition of off-source heat. We present estimates of entrainment coefficients from these measurements which show a qualitatively consistent variation with height. We propose that this explains the observed entrainment anomaly in cumulus clouds; further experiments are planned to address this question in the context of starting jets and plumes.

Microfluidic oscillators with widely tunable periods

PubMed Central

Kim, Sung-Jin; Yokokawa, Ryuji; Takayama, Shuichi

2013-01-01

We present experiments and theory of a constant flow-driven microfluidic oscillator with widely tunable oscillation periods. This oscillator converts two constant input-flows from a syringe pump into an alternating, periodic output-flow with oscillation periods that can be adjusted to between 0.3 s to 4.1 h by tuning an external membrane capacitor. This capacitor allows multiple adjustable periods at a given input flow-rate, thus providing great flexibility in device operation. Also, we show that a sufficiently large external capacitance, relative to the internal capacitance of the microfluidic valve itself, is a critical requirement for oscillation. These widely tunable microfluidic oscillators are envisioned to be broadly useful for the study of biological rhythms, as on-chip timing sources for microfluidic logic circuits, and other applications that require variation in timed flow switching. PMID:23429765

Transient Characteristics of a Fluidic Device for Circulatory Jet Flow.

PubMed

Phan, Hoa Thanh; Dinh, Thien Xuan; Bui, Phong Nhu; Dau, Van Thanh

2018-03-13

In this paper, we report on the design, simulation, and experimental analysis of a miniaturized device that can generate multiple circulated jet flows. The device is actuated by a lead zirconate titanate (PZT) diaphragm. The flows in the device were studied using three-dimensional transient numerical simulation with the programmable open source OpenFOAM and was comparable to the experimental result. Each flow is verified by two hotwires mounted at two positions inside each consisting chamber. The experiment confirmed that the flow was successfully created, and it demonstrated good agreement with the simulation. In addition, a prospective application of the device as an angular rate sensor is also demonstrated. The device is robust, is minimal in size, and can contribute to the development of multi-axis fluidic inertial sensors, fluidic amplifiers, gas mixing, coupling, and analysis.

Transient Characteristics of a Fluidic Device for Circulatory Jet Flow

PubMed Central

Phan, Hoa Thanh; Dinh, Thien Xuan; Bui, Phong Nhu

2018-01-01

In this paper, we report on the design, simulation, and experimental analysis of a miniaturized device that can generate multiple circulated jet flows. The device is actuated by a lead zirconate titanate (PZT) diaphragm. The flows in the device were studied using three-dimensional transient numerical simulation with the programmable open source OpenFOAM and was comparable to the experimental result. Each flow is verified by two hotwires mounted at two positions inside each consisting chamber. The experiment confirmed that the flow was successfully created, and it demonstrated good agreement with the simulation. In addition, a prospective application of the device as an angular rate sensor is also demonstrated. The device is robust, is minimal in size, and can contribute to the development of multi-axis fluidic inertial sensors, fluidic amplifiers, gas mixing, coupling, and analysis. PMID:29534014

Streamflow sensitivity to water storage changes across Europe

NASA Astrophysics Data System (ADS)

Berghuijs, Wouter R.; Hartmann, Andreas; Woods, Ross A.

2016-03-01

Terrestrial water storage is the primary source of river flow. We introduce storage sensitivity of streamflow (ɛS), which for a given flow rate indicates the relative change in streamflow per change in catchment water storage. ɛS can be directly derived from streamflow observations. Analysis of 725 catchments in Europe reveals that ɛS is high in, e.g., parts of Spain, England, Germany, and Denmark, whereas flow regimes in parts of the Alps are more resilient (that is, less sensitive) to storage changes. A regional comparison of ɛS with observations indicates that ɛS is significantly correlated with variability of low (R2 = 0.41), median (R2 = 0.27), and high flow conditions (R2 = 0.35). Streamflow sensitivity provides new guidance for a changing hydrosphere where groundwater abstraction and climatic changes are altering water storage and flow regimes.

On numerical model of time-dependent processes in three-dimensional porous heat-releasing objects

NASA Astrophysics Data System (ADS)

Lutsenko, Nickolay A.

2016-10-01

The gas flows in the gravity field through porous objects with heat-releasing sources are investigated when the self-regulation of the flow rate of the gas passing through the porous object takes place. Such objects can appear after various natural or man-made disasters (like the exploded unit of the Chernobyl NPP). The mathematical model and the original numerical method, based on a combination of explicit and implicit finite difference schemes, are developed for investigating the time-dependent processes in 3D porous energy-releasing objects. The advantage of the numerical model is its ability to describe unsteady processes under both natural convection and forced filtration. The gas cooling of 3D porous objects with different distribution of heat sources is studied using computational experiment.

Towards a Numerical Description of Volcano Aeroacoustic Source Processes using Lattice Boltzmann Strategies

NASA Astrophysics Data System (ADS)

Brogi, F.; Malaspinas, O.; Bonadonna, C.; Chopard, B.; Ripepe, M.

2015-12-01

Low frequency (< 20Hz) acoustic measurements have a great potential for the real time characterization of volcanic plume source parameters. Using the classical source theory, acoustic data can be related to the exit velocity of the volcanic jet and to mass eruption rate, based on the geometric constrain of the vent and the mixture density. However, the application of the classical acoustic source models to volcanic explosive eruptions has shown to be challenging and a better knowledge of the link between the acoustic radiation and actual volcanic fluid dynamics processes is required. New insights into this subject could be given by the study of realistic aeroacoustic numerical simulations of a volcanic jet. Lattice Boltzmann strategies (LBS) provide the opportunity to develop an accurate, computationally fast, 3D physical model for a volcanic jet. In the field of aeroacoustic applications, dedicated LBS has been proven to have the low dissipative properties needed for capturing the weak acoustic pressure fluctuations. However, due to the big disparity in magnitude between the flow and the acoustic disturbances, even weak spurious noise sources in simulations can ruin the accuracy of the acoustic predictions. Reflected waves from artificial boundaries defined around the flow region can have significant influence on the flow field and overwhelm the acoustic field of interest. In addition, for highly multiscale turbulent flows, such as volcanic plumes, the number of grid points needed to represent the smallest scales might become intractable and the most complicated physics happen only in small portions of the computational domain. The implementation of the grid refinement, in our model allow us to insert local finer grids only where is actually needed and to increase the size of the computational domain for running more realistic simulations. 3D LBS model simulations for turbulent jet aeroacoustics have been accurately validated. Both mean flow and acoustic results are in good agreement with theory and experimental data available in the literature.

Capture Versus Capture Zones: Clarifying Terminology Related to Sources of Water to Wells.

PubMed

Barlow, Paul M; Leake, Stanley A; Fienen, Michael N

2018-03-15

The term capture, related to the source of water derived from wells, has been used in two distinct yet related contexts by the hydrologic community. The first is a water-budget context, in which capture refers to decreases in the rates of groundwater outflow and (or) increases in the rates of recharge along head-dependent boundaries of an aquifer in response to pumping. The second is a transport context, in which capture zone refers to the specific flowpaths that define the three-dimensional, volumetric portion of a groundwater flow field that discharges to a well. A closely related issue that has become associated with the source of water to wells is streamflow depletion, which refers to the reduction in streamflow caused by pumping, and is a type of capture. Rates of capture and streamflow depletion are calculated by use of water-budget analyses, most often with groundwater-flow models. Transport models, particularly particle-tracking methods, are used to determine capture zones to wells. In general, however, transport methods are not useful for quantifying actual or potential streamflow depletion or other types of capture along aquifer boundaries. To clarify the sometimes subtle differences among these terms, we describe the processes and relations among capture, capture zones, and streamflow depletion, and provide proposed terminology to distinguish among them. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. Groundwater published by Wiley Periodicals, Inc. on behalf of National Ground Water Association.

The recruiter's excitement--features of thoracic vibrations during the honey bee's waggle dance related to food source profitability.

PubMed

Hrncir, Michael; Maia-Silva, Camila; Mc Cabe, Sofia I; Farina, Walter M

2011-12-01

The honey bee's waggle dance constitutes a remarkable example of an efficient code allowing social exploitation of available feeding sites. In addition to indicating the position (distance, direction) of a food patch, both the occurrence and frequency of the dances depend on the profitability of the exploited resource (sugar concentration, solution flow rate). During the waggle dance, successful foragers generate pulsed thoracic vibrations that putatively serve as a source of different kinds of information for hive bees, who cannot visually decode dances in the darkness of the hive. In the present study, we asked whether these vibrations are a reliable estimator of the excitement of the dancer when food profitability changes in terms of both sugar concentration and solution flow rate. The probability of producing thoracic vibrations as well as several features related to their intensity during the waggle phase (pulse duration, velocity amplitude, duty cycle) increased with both these profitability variables. The number of vibratory pulses, however, was independent of sugar concentration and reward rate exploited. Thus, pulse number could indeed be used by dance followers as reliable information about food source distance, as suggested in previous studies. The variability of the dancer's thoracic vibrations in relation to changes in food profitability suggests their role as an indicator of the recruiter's motivational state. Hence, the vibrations could make an important contribution to forager reactivation and, consequently, to the organisation of collective foraging processes in honey bees.

Photoacoustic thermal flowmetry with a single light source

NASA Astrophysics Data System (ADS)

Liu, Wei; Lan, Bangxin; Hu, Leo; Chen, Ruimin; Zhou, Qifa; Yao, Junjie

2017-09-01

We report a photoacoustic thermal flowmetry based on optical-resolution photoacoustic microscopy (OR-PAM) using a single laser source for both thermal tagging and photoacoustic excitation. When an optically absorbing medium is flowing across the optical focal zone of OR-PAM, a small volume of the medium within the optical focus is repeatedly illuminated and heated by a train of laser pulses with a high repetition rate. The average temperature of the heated volume at each laser pulse is indicated by the photoacoustic signal excited by the same laser pulse due to the well-established linear relationship between the Grueneisen coefficient and the local temperature. The thermal dynamics of the heated medium volume, which are closely related to the flow speed, can therefore be measured from the time course of the detected photoacoustic signals. Here, we have developed a lumped mathematical model to describe the time course of the photoacoustic signals as a function of the medium's flow speed. We conclude that the rising time constant of the photoacoustic signals is linearly dependent on the flow speed. Thus, the flow speed can be quantified by fitting the measured photoacoustic signals using the derived mathematical model. We first performed proof-of-concept experiments using defibrinated bovine blood flowing in a plastic tube. The experiment results have demonstrated that the proposed method has high accuracy (˜±6%) and a wide range of measurable flow speeds. We further validated the method by measuring the blood flow speeds of the microvasculature in a mouse ear in vivo.

A field evaluation of subsurface and surface runoff. II. Runoff processes

USGS Publications Warehouse

Pilgrim, D.H.; Huff, D.D.; Steele, T.D.

1978-01-01

Combined use of radioisotope tracer, flow rate, specific conductance and suspended-sediment measurements on a large field plot near Stanford, California, has provided more detailed information on surface and subsurface storm runoff processes than would be possible from any single approach used in isolation. Although the plot was surficially uniform, the runoff processes were shown to be grossly nonuniform, both spatially over the plot, and laterally and vertically within the soil. The three types of processes that have been suggested as sources of storm runoff (Horton-type surface runoff, saturated overland flow, and rapid subsurface throughflow) all occurred on the plot. The nonuniformity of the processes supports the partial- and variable-source area concepts. Subsurface storm runoff occurred in a saturated layer above the subsoil horizon, and short travel times resulted from flow through macropores rather than the soil matrix. Consideration of these observations would be necessary for physically realistic modeling of the storm runoff process. ?? 1978.

Biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium: Rhodopirillum rubrum.

PubMed

Younesi, Habibollah; Najafpour, Ghasem; Ku Ismail, Ku Syahidah; Mohamed, Abdul Rahman; Kamaruddin, Azlina Harun

2008-05-01

Hydrogen may be considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas (syngas) to hydrogen was demonstrated in continuous stirred tank bioreactor (CSTBR) utilizing acetate as a carbon source. An anaerobic photosynthetic bacterium, Rhodospirillum rubrum catalyzed water-gas shift reaction which was applied for the bioconversion of syngas to hydrogen. The continuous fermentation of syngas in the bioreactor was continuously operated at various gas flow rates and agitation speeds, for the period of two months. The gas flow rates were varied from 5 to 14 ml/min. The agitation speeds were increasingly altered in the range of 150-500 rpm. The pH and temperature of the bioreactor was set at 6.5 and 30 degrees C. The liquid flow rate was kept constant at 0.65 ml/min for the duration of 60 days. The inlet acetate concentration was fed at 4 g/l into the bioreactor. The hydrogen production rate and yield were 16+/-1.1 mmol g(-1)cell h(-1) and 87+/-2.4% at fixed agitation speed of 500 rpm and syngas flow rate of 14 ml/min, respectively. The mass transfer coefficient (KLa) at this condition was approximately 72.8h(-1). This new approach, using a biocatalyst was considered as an alternative method of conventional Fischer-Tropsch synthetic reactions, which were able to convert syngas into hydrogen.

Dynamics of dissolved organic matter during four storm events in two forest streams: source, export, and implications for harmful disinfection byproduct formation.

PubMed

Yang, Liyang; Hur, Jin; Lee, Sonmin; Chang, Soon-Woong; Shin, Hyun-Sang

2015-06-01

Dynamics of river dissolved organic matter (DOM) during storm events have profound influences on the downstream aquatic ecosystem and drinking water safety. This study investigated temporal variations in DOM during four storm events in two forest headwater streams (the EH and JH brooks, South Korea) and the impacts on the disinfection byproducts (DBPs) formation potential. The within-event variations of most DOM quantity parameters were similar to the flow rate in the EH but not in the larger JH brook. The dissolved organic carbon (DOC) showed clockwise and counterclockwise hysteresis with the flow rate in the EH and JH brooks, respectively, indicating the importance of both flow path and DOM source pool size in determining the effects of storm events. The stream DOM became less aromatic/humified from the first to the last event in both brooks, probably due to the increasing fresh plant pool and the decreasing leaf litter pool during the course of rainy season. The DOC export during each event increased 1.3-2.7- and 1.1-7.0-fold by stormflows in the EH and JH brooks, respectively. The leaf litter and soil together was the major DOM source, particularly during early events. The enhanced DOM export probably increases the risks of DBPs formation in disinfection, as indicated by a strong correlation observed between DOC and trihalomethanes formation potential (THMFP). High correlations between two humic-like fluorescent components and THMFP further suggested the potential of assessing THMFP with in situ fluorescence sensors during storms.

Insight into the effect of screw dislocations and oxygen vacancy defects on the optical nonlinear refraction response in chemically grown ZnO/Al2O3 films

NASA Astrophysics Data System (ADS)

Agrawal, Arpana; Saroj, Rajendra K.; Dar, Tanveer A.; Baraskar, Priyanka; Sen, Pratima; Dhar, Subhabrata

2017-11-01

We report the effect of screw dislocations and oxygen vacancy defects on the optical nonlinear refraction response of ZnO films grown on a sapphire substrate at various oxygen flow rates using the chemical vapor deposition technique. The nonlinear refraction response was investigated in the off-resonant regime using a CW He-Ne laser source to examine the role of the intermediate bandgap states. It has been observed that the structural defects strongly influence the optical nonlinearity in the off-resonant regime. Nonlinearity has been found to improve as the oxygen flow rate is lowered from 2 sccm to 0.3 sccm. From photoluminescence studies, we observe that the enhanced defect density of the electronic defect levels due to the increased concentration of structural defects (with the decrease in the oxygen flow rate) is responsible for this improved optical nonlinearity along with the thermal effect. This suggests that defect engineering is an effective way to tailor the nonlinearity of ZnO films and their utility for optoelectronic device applications.

Analytical modeling of operating characteristics of premixing-prevaporizing fuel-air mixing passages. Volume 1: Analysis and results

NASA Technical Reports Server (NTRS)

Anderson, O. L.; Chiappetta, L. M.; Edwards, D. E.; Mcvey, J. B.

1982-01-01

A model for predicting the distribution of liquid fuel droplets and fuel vapor in premixing-prevaporizing fuel-air mixing passages of the direct injection type is reported. This model consists of three computer programs; a calculation of the two dimensional or axisymmetric air flow field neglecting the effects of fuel; a calculation of the three dimensional fuel droplet trajectories and evaporation rates in a known, moving air flow; a calculation of fuel vapor diffusing into a moving three dimensional air flow with source terms dependent on the droplet evaporation rates. The fuel droplets are treated as individual particle classes each satisfying Newton's law, a heat transfer, and a mass transfer equation. This fuel droplet model treats multicomponent fuels and incorporates the physics required for the treatment of elastic droplet collisions, droplet shattering, droplet coalescence and droplet wall interactions. The vapor diffusion calculation treats three dimensional, gas phase, turbulent diffusion processes. The analysis includes a model for the autoignition of the fuel air mixture based upon the rate of formation of an important intermediate chemical species during the preignition period.

Using host-associated genetic markers to investigate sources of fecal contamination in two Vermont streams

USGS Publications Warehouse

Medalie, Laura; Matthews, Leslie J.; Stelzer, Erin A.

2011-01-01

The use of host-associated Bacteroidales-based 16S ribosomal ribonucleic acid genetic markers was investigated as a tool for providing information to managers on sources of bacterial impairment in Vermont streams. The study was conducted during 2009 in two watersheds on the U.S. Environmental Protection Agency's 303(d) List of Impaired Waters, the Huntington and the Mettawee Rivers. Streamwater samples collected during high-flow and base-flow conditions were analyzed for concentrations of Escherichia coli (E. coli) and Bacteroidales genetic markers (General AllBac, Human qHF183 and BacHum, Ruminant BoBac, and Canid BacCan) to identify humans, ruminants, and canids as likely or unlikely major sources of fecal contamination. Fecal reference samples from each of the potential source groups, as well as from common species of wildlife, were collected during the same season and from the same watersheds as water samples. The results were combined with data from other states to assess marker cross reaction and to relate marker results to E. coli, the regulated water-quality parameter, with a higher degree of statistical significance. Results from samples from the Huntington River collected under different flow conditions on three dates indicated that humans were unlikely to be a major source of fecal contamination, except for a single positive result at one station that indicated the potential for human sources. Ruminants (deer, moose, cow, or sheep) were potential sources of fecal contamination at all six stations on the Huntington River during one high-flow event and at all but two stations during the other high-flow event. Canids were potential sources of fecal contamination at some stations during two high-flow events, with genetic-marker concentrations in samples from two of the six stations showing consistent positive results for canids for both storm dates. A base-flow sample showed no evidence of major fecal contamination in the Huntington River from humans, ruminants, or canids. Results from samples from the Mettawee River watershed collected during high-flow conditions (12 storm samples on 2 dates at 6 stations) indicated that there was no evidence of fecal contamination from humans in seven samples and possible evidence in five samples. Results for humans were positive for only one station during both storm events. For two of the five samples with evidence for human fecal contamination, results for two different human genetic markers agreed, but results from three samples were inconsistent. In samples from five of the six Mettawee stations, ruminants were a potential source of fecal contamination on at least one of the three sampled dates, including three positive results for the base-flow sample. Yet samples from all of the stations that showed positive results for ruminants did so for only one or two of the three sampled dates. Samples from only one of the six stations gave consistent results, which were negative for ruminants for all three dates. In the Mettawee River base-flow sample, humans were an unlikely source of major fecal contamination. Factors that may influence results and conclusions include the timing of sample collection relative to the storm event; variability of E. coli and Bacteroidales concentrations in fecal reference samples and in water; sampling and analytical errors; the potential cross reactivity of host-associated genetic markers; and different persistence and survival rates of E. coli bacteria and Bacteroidales genetic markers on land, in water, and by season. These factors interfere with the ability to directly relate Bacteroidales concentrations to E. coli concentrations in river samples. It must be recognized that while use of Bacteroidales genetic markers as a source tracking tool coupled with the interpretive approach described in this report cannot be used quantitatively to pinpoint sources, it can be used to exclude potential sources as major contributors to fecal contamination.

Improving the Efficiency of DASC by Adding CeO2/CuO Hybrid Nanoparticles in Water

NASA Astrophysics Data System (ADS)

Midhun Mohan, V.; Sajeeb, A. M.

Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO-water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CuO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20cc/min to 100cc/min and with CeO2/CuO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1 and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20cc/min to 100cc/min for hybrid CeO2/CuO (1:1)-water nanofluid. The results also showed an increase in efficiency of 13.8%, 18.1%, 24.3%, 24.9% and 26.1% with hybrid combination of CeO2/CuO at ratios 1:0, 1:0.5, 1:1, 0.5:1 and 0:1, respectively, in comparison with water at a flow rate of 100cc/min.

Determination of the effect of source intensity profile on speckle contrast using coherent spatial frequency domain imaging

PubMed Central

Rice, Tyler B.; Konecky, Soren D.; Owen, Christopher; Choi, Bernard; Tromberg, Bruce J.

2012-01-01

Laser Speckle Imaging (LSI) is fast, noninvasive technique to image particle dynamics in scattering media such as biological tissue. While LSI measurements are independent of the overall intensity of the laser source, we find that spatial variations in the laser source profile can impact measured flow rates. This occurs due to differences in average photon path length across the profile, and is of significant concern because all lasers have some degree of natural Gaussian profile in addition to artifacts potentially caused by projecting optics. Two in vivo measurement are performed to show that flow rates differ based on location with respect to the beam profile. A quantitative analysis is then done through a speckle contrast forward model generated within a coherent Spatial Frequency Domain Imaging (cSFDI) formalism. The model predicts remitted speckle contrast as a function of spatial frequency, optical properties, and scattering dynamics. Comparison with experimental speckle contrast images were done using liquid phantoms with known optical properties for three common beam shapes. cSFDI is found to accurately predict speckle contrast for all beam shapes to within 5% root mean square error. Suggestions for improving beam homogeneity are given, including a widening of the natural beam Gaussian, proper diffusing glass spreading, and flat top shaping using microlens arrays. PMID:22741080

Removal of lead, cadmium, zinc, and copper from industrial wastewater by carbon developed from walnut, hazelnut, almond, pistachio shell, and apricot stone.

PubMed

Kazemipour, Maryam; Ansari, Mehdi; Tajrobehkar, Shabnam; Majdzadeh, Majdeh; Kermani, Hamed Reihani

2008-01-31

In this work, adsorption of copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) that exist in industrial wastewater onto the carbon produced from nutshells of walnut, hazelnut, pistachio, almond, and apricot stone has been investigated. All the agricultural shell or stone used were ground, sieved to a defined size range, and carbonized in an oven. Time and temperature of heating were optimized at 15 min and 800 degrees C, respectively, to reach maximum removal efficiency. Removal efficiency was optimized regarding to the initial pH, flow rate, and dose of adsorbent. The maximum removal occurred at pH 6-10, flow rate of 3 mL/min, and 0.1g of the adsorbent. Capacity of carbon sources for removing cations will be considerably decreased in the following times of passing through them. Results showed that the cations studied significantly can be removed by the carbon sources. Efficiency of carbon to remove the cations from real wastewater produced by copper industries was also studied. Finding showed that not only these cations can be removed considerably by the carbon sources noted above, but also removing efficiency are much more in the real samples. These results were in adoption to those obtained by standard mixture synthetic wastewater.

Microbial Source Module (MSM): Documenting the Science ...

EPA Pesticide Factsheets

The Microbial Source Module (MSM) estimates microbial loading rates to land surfaces from non-point sources, and to streams from point sources for each subwatershed within a watershed. A subwatershed, the smallest modeling unit, represents the common basis for information consumed and produced by the MSM which is based on the HSPF (Bicknell et al., 1997) Bacterial Indicator Tool (EPA, 2013b, 2013c). Non-point sources include numbers, locations, and shedding rates of domestic agricultural animals (dairy and beef cows, swine, poultry, etc.) and wildlife (deer, duck, raccoon, etc.). Monthly maximum microbial storage and accumulation rates on the land surface, adjusted for die-off, are computed over an entire season for four land-use types (cropland, pasture, forest, and urbanized/mixed-use) for each subwatershed. Monthly point source microbial loadings to instream locations (i.e., stream segments that drain individual sub-watersheds) are combined and determined for septic systems, direct instream shedding by cattle, and POTWs/WWTPs (Publicly Owned Treatment Works/Wastewater Treatment Plants). The MSM functions within a larger modeling system that characterizes human-health risk resulting from ingestion of water contaminated with pathogens. The loading estimates produced by the MSM are input to the HSPF model that simulates flow and microbial fate/transport within a watershed. Microbial counts within recreational waters are then input to the MRA-IT model (Soller et

Hydrogeochemical processes governing the origin, transport and fate of major and trace elements from mine wastes and mineralized rock to surface waters

USGS Publications Warehouse

Nordstrom, D. Kirk

2011-01-01

Mobility of potential or actual contaminants from mining and mineral processing activities depends on (1) occurrence: is the mineral source of the contaminant actually present? (2) abundance: is the mineral present in sufficient quantity to make a difference? (3) reactivity: what are the energetics, rates, and mechanisms of sorption and mineral dissolution and precipitation relative to the flow rate of the water? and (4) hydrology: what are the main flow paths for contaminated water? Estimates of relative proportions of minerals dissolved and precipitated can be made with mass-balance calculations if minerals and water compositions along a flow path are known. Combined with discharge, these mass-balance estimates quantify the actual weathering rate of pyrite mineralization in the environment and compare reasonably well with laboratory rates of pyrite oxidation except when large quantities of soluble salts and evaporated mine waters have accumulated underground. Quantitative mineralogy with trace-element compositions can substantially improve the identification of source minerals for specific trace elements through mass balances. Post-dissolution sorption and precipitation (attenuation) reactions depend on the chemical behavior of each element, solution composition and pH, aqueous speciation, temperature, and contact-time with mineral surfaces. For example, little metal attenuation occurs in waters of low pH (2, and redox-sensitive oxyanions (As, Sb, Se, Mo, Cr, V). Once dissolved, metal and metalloid concentrations are strongly affected by redox conditions and pH. Iron is the most reactive because it is rapidly oxidized by bacteria and archaea and Fe(III) hydrolyzes and precipitates at low pH (1–3) which is related directly to its first hydrolysis constant, pK1 = 2.2. Several insoluble sulfate minerals precipitate at low pH including anglesite, barite, jarosite, alunite and basaluminite. Aluminum hydrolyzes near pH 5 (pK1 = 5.0) and provides buffering and removal of Al by mineral precipitation from pH 4–5.5. Dissolved sulfate behaves conservatively because the amount removed from solution by precipitation is usually too small relative to the high concentrations in the water column and relative to the flow rate of the water.

Responses to deceleration during car following: roles of optic flow, warnings, expectations, and interruptions.

PubMed

DeLucia, Patricia R; Tharanathan, Anand

2009-12-01

More than 25% of accidents are rear-end collisions. It is essential to identify the factors that contribute to such collisions. One such factor is a driver's ability to respond to the deceleration of the car ahead. In Experiment 1, we measured effects of optic flow information and discrete visual and auditory warnings (brake lights, tones) on responses to deceleration during car following. With computer simulations of car-following scenes, university students pressed a button when the lead car decelerated. Both classes of information affected responses. Observers relied on discrete warnings when optic flow information was relatively less effective as determined by the lead car's headway and deceleration rate. This is consistent with DeLucia's (2008) conceptual framework of space perception that emphasized the importance of viewing distance and motion (and task). In Experiment 2, we measured responses to deceleration after a visual interruption. Scenes were designed to tease apart the role of expectations and optic flow. Responses mostly were consistent with optic flow information presented after the interruption rather than with putative mental expectations that were set up by the lead car's motion prior to the interruption. The theoretical implication of the present results is that responses to deceleration are based on multiple sources of information, including optical size, optical expansion rate and tau, and discrete warnings that are independent of optic flow. The practical implication is that in-vehicle collision-avoidance warning systems may be more useful when optic flow is less effective (e.g., slow deceleration rates), implicating a role for adaptive collision-warning systems. Copyright 2009 APA

Impact of EPR systems on information flow in Finnish health centers.

PubMed

Mäkelä, Kari; Virjo, Irma; Aho, Juhani; Kalliola, Pentti; Kurunmäki, Harri; Uusitalo, Leena; Valli, Markku; Ylinen, Suvi

2013-03-01

We studied how well healthcare personnel in healthcare centers (HCs) in the South Ostrobothnia region of Finland are able to obtain patient information thorough electronic patient record (EPR) systems. This study followed the changes in availability of patient information during a 7-year period, from 2003 to the end of 2010. The patient group studied focused on those involved in anticoagulant (AC) treatment. A structured questionnaire was sent in 2003 to the staff of 15 HCs. The questionnaire dealt with access and availability of patient information from the EPR. Respondents were asked to rate how often they obtain information concerning AC treatment from various sources. In total, 1,114 questionnaires were sent, and 860 answers were received; the response rate was 77%. A repeat study was conducted in 2010, and 932 responses were obtained (response rate, 56%). Paper-based AC treatment cards carried by the patients were an important information source for 75.0% of the respondents in 2003 and 55.4% in 2010. For all new AC treatments, the EPR was a primary information source for 33.3% of respondents in 2003 and 60.2% in 2010. This study indicated that during the study period there was an improvement in access to EPR but that this did not always improve the overall availability of data. Results show that problems in information flow from secondary care to the HCs persist. Almost half of the patients dealt with in the HCs were affected by at least some problems. In the 7 years covered by this study, EPR systems have become more important as information sources for clinical data, but there is still room for improvement.

Simulated ground-water flow and sources of water in the Killbuck Creek Valley near Wooster, Wayne County, Ohio

USGS Publications Warehouse

Breen, K.J.; Kontis, A.L.; Rowe, G.L.; Haefner, R.J.

1995-01-01

The stratified-drift aquifer in the 3,000-ft (feet)-wide and 100-ft-deep buried valley of Killbuck Creek near Wooster in northeastern Ohio was studied. The stratified drift with adjacent sandstone and shale bedrock produce a system of ground-water flow representative of the western part of the glaciated north-eastern United States. The stratified-drift aquifer is an excellent source of water for municipal and industrial wells. The aquifer is recharged locally by water from precipitation on the valley floor and uplands, by infiltration from streams, and by lateral flow to the valley from the uplands. As a result, the aquifer is vulnerable to surface or subsurface spills of contaminants in the valley or the adjacent uplands. Quality of water in the stratified drift is affected by influx of water from bedrock lateral to or beneath the valley. This influx is controlled, in part, by the pumping stress placed on the stratified-drift aquifer. Hydrogeologic and aqueous-geochemical data were analyzed to establish the framework necessary for stead-state and transient simulations of ground-water flow in stratified drift and bedrock with a three-layer ground-water-flow model. A new model routine, the Variable-Recharge procedure, was developed to simulate areal recharge and the contribution of the uplands to the drift system. This procedure allows for water applied to land surface to infiltrate or to be rejected. Rejected recharge and ground water discharged when the water table is at land surface form surface runoff-this excess upland water can be redirected as runoff to other parts of the model. Infiltration of streamwater, areal recharge to uplands and valley, and lateral subsurface flow from the uplands to the valley are sources of water to the stratufued0druft aquifer. Water is removed from the stratified-drift aquifer at Wooster primarily by production wells pumping at a rate of approximately 8.5 ft3/s (cubic feet per second). The ground-water budget resulting from two types of simulations of ground-water flow in this study indicates the primary sources of water to the wells are recharge at or near land surface and lateral subsurface flow from the shale and sandstone bedrock. Components of recharge at land surface include induced infiltration from streams, precipitation on the valley floor, and infiltration of unchanneled upland runoff that reaches the valley floor. The steady-state simulation was designed to represent conditions during the fall of 1984. The transient simulation was designed to represent an 11-day snowmelt event, 23 February to 5 March 1985, that caused water levels to rise significantly throughout the valley. Areal recharge to the valley and flow from the uplands to the valley were determined through the Variable-Recharge procedure. The total steady-state recharge to the valley was 12.5 ft3/s. Upland sources, areal valley recharge, and induced infiltration from Killnuck Creek accounted for 63, 23, and 8 percent, respectively, of the valley recharge. An analysis of the simulated vertical flow to the buried stratified drift through surficial slit, clay, and fine sand indicates that about 75 percent of the total recharge to the buried deposits is the sum of areally extensive, relatively small flows less than about 0.01 ft? /s per model node), whereas about 25 percent of the recharge results from a really restricted, relatively large flows (greater than about 0.01 ft? /s per model node). The large-magnitude flows are located primarily beneath Clear and Little Killbuck Creeks where seepage provides abundant recharge and the surficial sediments grade into coarser alluvial-fan deposits. Chemical and isotopic studies of ground water and streamwater combined with measurements of stream infiltration provide independent support for the conclusions derived from computer simulation of ground-water flow. In addition, the chemical and isotopic studies helped quantity the rate and pathways of infiltrating water from

Recent paleoseismicity record in Prince William Sound, Alaska, USA

NASA Astrophysics Data System (ADS)

Kuehl, Steven A.; Miller, Eric J.; Marshall, Nicole R.; Dellapenna, Timothy M.

2017-12-01

Sedimentological and geochemical investigation of sediment cores collected in the deep (>400 m) central basin of Prince William Sound, along with geochemical fingerprinting of sediment source areas, are used to identify earthquake-generated sediment gravity flows. Prince William Sound receives sediment from two distinct sources: from offshore (primarily Copper River) through Hinchinbrook Inlet, and from sources within the Sound (primarily Columbia Glacier). These sources are found to have diagnostic elemental ratios indicative of provenance; Copper River Basin sediments were significantly higher in Sr/Pb and Cu/Pb, whereas Prince William Sound sediments were significantly higher in K/Ca and Rb/Sr. Within the past century, sediment gravity flows deposited within the deep central channel of Prince William Sound have robust geochemical (provenance) signatures that can be correlated with known moderate to large earthquakes in the region. Given the thick Holocene sequence in the Sound ( 200 m) and correspondingly high sedimentation rates (>1 cm year-1), this relationship suggests that sediments within the central basin of Prince William Sound may contain an extraordinary high-resolution record of paleoseismicity in the region.

Moth-inspired navigation algorithm in a turbulent odor plume from a pulsating source.

PubMed

Liberzon, Alexander; Harrington, Kyra; Daniel, Nimrod; Gurka, Roi; Harari, Ally; Zilman, Gregory

2018-01-01

Some female moths attract male moths by emitting series of pulses of pheromone filaments propagating downwind. The turbulent nature of the wind creates a complex flow environment, and causes the filaments to propagate in the form of patches with varying concentration distributions. Inspired by moth navigation capabilities, we propose a navigation strategy that enables a flier to locate an upwind pulsating odor source in a windy environment using a single threshold-based detection sensor. This optomotor anemotaxis strategy is constructed based on the physical properties of the turbulent flow carrying discrete puffs of odor and does not involve learning, memory, complex decision making or statistical methods. We suggest that in turbulent plumes from a pulsating point source, an instantaneously measurable quantity referred as a "puff crossing time", improves the success rate as compared to the navigation strategies based on temporally regular zigzags due to intermittent contact, or an "internal counter", that do not use this information. Using computer simulations of fliers navigating in turbulent plumes of the pulsating point source for varying flow parameters such as turbulent intensities, plume meandering and wind gusts, we obtained statistics of navigation paths towards the pheromone sources. We quantified the probability of a successful navigation as well as the flight parameters such as the time spent searching and the total flight time, with respect to different turbulent intensities, meandering or gusts. The concepts learned using this model may help to design odor-based navigation of miniature airborne autonomous vehicles.

The silent base flow and the sound sources in a laminar jet.

PubMed

Sinayoko, Samuel; Agarwal, Anurag

2012-03-01

An algorithm to compute the silent base flow sources of sound in a jet is introduced. The algorithm is based on spatiotemporal filtering of the flow field and is applicable to multifrequency sources. It is applied to an axisymmetric laminar jet and the resulting sources are validated successfully. The sources are compared to those obtained from two classical acoustic analogies, based on quiescent and time-averaged base flows. The comparison demonstrates how the silent base flow sources shed light on the sound generation process. It is shown that the dominant source mechanism in the axisymmetric laminar jet is "shear-noise," which is a linear mechanism. The algorithm presented here could be applied to fully turbulent flows to understand the aerodynamic noise-generation mechanism. © 2012 Acoustical Society of America

Understanding the flowing atmospheric-pressure afterglow (FAPA) ambient ionization source through optical means.

PubMed

Shelley, Jacob T; Chan, George C-Y; Hieftje, Gary M

2012-02-01

The advent of ambient desorption/ionization mass spectrometry (ADI-MS) has led to the development of a large number of atmospheric-pressure ionization sources. The largest group of such sources is based on electrical discharges; yet, the desorption and ionization processes that they employ remain largely uncharacterized. Here, the atmospheric-pressure glow discharge (APGD) and afterglow of a helium flowing atmospheric-pressure afterglow (FAPA) ionization source were examined by optical emission spectroscopy. Spatial emission profiles of species created in the APGD and afterglow were recorded under a variety of operating conditions, including discharge current, electrode polarity, and plasma-gas flow rate. From these studies, it was found that an appreciable amount of atmospheric H(2)O vapor, N(2), and O(2) diffuses through the hole in the plate electrode into the discharge to become a major source of reagent ions in ADI-MS analyses. Spatially resolved plasma parameters, such as OH rotational temperature (T(rot)) and electron number density (n(e)), were also measured in the APGD. Maximum values for T(rot) and n(e) were found to be ~1100 K and ~4×10(19) m(-3), respectively, and were both located at the pin cathode. In the afterglow, rotational temperatures from OH and N(2)(+) yielded drastically different values, with OH temperatures matching those obtained from infrared thermography measurements. The higher N(2)(+) temperature is believed to be caused by charge-transfer ionization of N(2) by He(2)(+). These findings are discussed in the context of previously reported ADI-MS analyses with the FAPA source. © American Society for Mass Spectrometry, 2011

Understanding the Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source through Optical Means

NASA Astrophysics Data System (ADS)

Shelley, Jacob T.; Chan, George C.-Y.; Hieftje, Gary M.

2012-02-01

The advent of ambient desorption/ionization mass spectrometry (ADI-MS) has led to the development of a large number of atmospheric-pressure ionization sources. The largest group of such sources is based on electrical discharges; yet, the desorption and ionization processes that they employ remain largely uncharacterized. Here, the atmospheric-pressure glow discharge (APGD) and afterglow of a helium flowing atmospheric-pressure afterglow (FAPA) ionization source were examined by optical emission spectroscopy. Spatial emission profiles of species created in the APGD and afterglow were recorded under a variety of operating conditions, including discharge current, electrode polarity, and plasma-gas flow rate. From these studies, it was found that an appreciable amount of atmospheric H2O vapor, N2, and O2 diffuses through the hole in the plate electrode into the discharge to become a major source of reagent ions in ADI-MS analyses. Spatially resolved plasma parameters, such as OH rotational temperature (Trot) and electron number density (ne), were also measured in the APGD. Maximum values for Trot and ne were found to be ~1100 K and ~4 × 1019 m-3, respectively, and were both located at the pin cathode. In the afterglow, rotational temperatures from OH and N{2/+} yielded drastically different values, with OH temperatures matching those obtained from infrared thermography measurements. The higher N{2/+} temperature is believed to be caused by charge-transfer ionization of N2 by He{2/+}. These findings are discussed in the context of previously reported ADI-MS analyses with the FAPA source.

Shear flow of angular grains: acoustic effects and nonmonotonic rate dependence of volume.

PubMed

Lieou, Charles K C; Elbanna, Ahmed E; Langer, J S; Carlson, J M

2014-09-01

Naturally occurring granular materials often consist of angular particles whose shape and frictional characteristics may have important implications on macroscopic flow rheology. In this paper, we provide a theoretical account for the peculiar phenomenon of autoacoustic compaction-nonmonotonic variation of shear band volume with shear rate in angular particles-recently observed in experiments. Our approach is based on the notion that the volume of a granular material is determined by an effective-disorder temperature known as the compactivity. Noise sources in a driven granular material couple its various degrees of freedom and the environment, causing the flow of entropy between them. The grain-scale dynamics is described by the shear-transformation-zone theory of granular flow, which accounts for irreversible plastic deformation in terms of localized flow defects whose density is governed by the state of configurational disorder. To model the effects of grain shape and frictional characteristics, we propose an Ising-like internal variable to account for nearest-neighbor grain interlocking and geometric frustration and interpret the effect of friction as an acoustic noise strength. We show quantitative agreement between experimental measurements and theoretical predictions and propose additional experiments that provide stringent tests on the new theoretical elements.

40 CFR Table 5 to Subpart Mmmmm of... - Continuous Compliance With Emission Limits and Operating Limits

Code of Federal Regulations, 2010 CFR

2010-07-01

... performance test. v. If you use a venturi scrubber, maintaining the daily average pressure drop across the.... Each new or reconstructed flame lamination affected source using a scrubber a. Maintain the daily average scrubber inlet liquid flow rate above the minimum value established during the performanceb...

40 CFR 98.173 - Calculating GHG emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... associated requirements for Tier 4 in subpart C of this part (General Stationary Fuel Combustion Sources). (b... stack gas volumetric flow rate (scfh). %H2O = Hourly moisture percentage in the stack gas. (iii) You... Tier 4 methodology in subpart C of this part, or through the same stack as any combustion unit or...

40 CFR 98.173 - Calculating GHG emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... associated requirements for Tier 4 in subpart C of this part (General Stationary Fuel Combustion Sources). (b... basis (% CO2). Q = Hourly stack gas volumetric flow rate (scfh). %H2O = Hourly moisture percentage in... furnace are vented through the same stack as any combustion unit or process equipment that reports CO2...

LINES OF EVIDENCE FOR NA FOR ORGANIC COMPOUNDS AND THE USE OF COMPOUND SPECIFIC ISOTOPE ANALYSIS

EPA Science Inventory

The strongest line of evidence is a reduction in concentration over time. However, this only provides evidence of natural attenuation of the source area. It is difficult to determine the rate of natural attenuation through biodegradation with distance along a flow path in the a...

40 CFR 60.5225 - What are the monitoring and calibration requirements for compliance with my operating limits?

Code of Federal Regulations, 2012 CFR

2012-07-01

... SOURCES Emission Guidelines and Compliance Times for Existing Sewage Sludge Incineration Units Model Rule... monitoring system according to your monitoring plan required under § 60.4880. Additionally: (i) For carrier gas flow rate monitors (for activated carbon injection), during the performance test conducted...

40 CFR Table 2 of Subpart Bbbbbbb... - Initial Compliance Demonstration Methods With the Emission Reduction and PM Concentration...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Emission Standards for Hazardous Air Pollutants for Area Sources: Chemical Preparations Industry Other... less; or c. Provide engineering calculations, such as mass balance and flow rate calculations, that demonstrate that the control device is capable of reducing PM concentration from the chemical preparations...

40 CFR Table 2 of Subpart Bbbbbbb... - Initial Compliance Demonstration Methods With the Emission Reduction and PM Concentration...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Emission Standards for Hazardous Air Pollutants for Area Sources: Chemical Preparations Industry Other... less; or c. Provide engineering calculations, such as mass balance and flow rate calculations, that demonstrate that the control device is capable of reducing PM concentration from the chemical preparations...

40 CFR Table 2 of Subpart Bbbbbbb... - Initial Compliance Demonstration Methods With the Emission Reduction and PM Concentration...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Emission Standards for Hazardous Air Pollutants for Area Sources: Chemical Preparations Industry Other... less; or c. Provide engineering calculations, such as mass balance and flow rate calculations, that demonstrate that the control device is capable of reducing PM concentration from the chemical preparations...

40 CFR Table 2 of Subpart Bbbbbbb... - Initial Compliance Demonstration Methods With the Emission Reduction and PM Concentration...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Emission Standards for Hazardous Air Pollutants for Area Sources: Chemical Preparations Industry Other... less; or c. Provide engineering calculations, such as mass balance and flow rate calculations, that demonstrate that the control device is capable of reducing PM concentration from the chemical preparations...

40 CFR Table 2 of Subpart Bbbbbbb... - Initial Compliance Demonstration Methods With the Emission Reduction and PM Concentration...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Emission Standards for Hazardous Air Pollutants for Area Sources: Chemical Preparations Industry Other... less; or c. Provide engineering calculations, such as mass balance and flow rate calculations, that demonstrate that the control device is capable of reducing PM concentration from the chemical preparations...

77 FR 44204 - Approval and Promulgation of Air Quality Implementation Plans; Maryland; Control of Iron and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-27

... to approve revisions to the Maryland State Implementation Plan (SIP) submitted by the Maryland... (Sparrows Point) is the only sintering plant located in the State of Maryland, and therefore the only source... compliance with specified pressure drop and flow rate operating parameters. EPA is approving these revisions...

40 CFR 60.203 - Monitoring of operations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for the Phosphate..., calibrate, maintain, and operate a monitoring device which can be used to determine the mass flow of... maintain a daily record of equivalent P2O5 feed by first determining the total mass rate in Mg/hr of...

40 CFR Table 5 to Subpart Mmmmm of... - Continuous Compliance With Emission Limits and Operating Limits

Code of Federal Regulations, 2011 CFR

2011-07-01

.... Each new or reconstructed flame lamination affected source using a scrubber a. Maintain the daily average scrubber inlet liquid flow rate above the minimum value established during the performanceb. Maintain the daily average scrubber effluent pH within the operating range established during the...

Influence of radiation on MHD peristaltic blood flow through a tapered channel in presence of slip and joule heating

NASA Astrophysics Data System (ADS)

Ahamad, N. Ameer; Ravikumar, S.; Govindaraju, Kalimuthu

2017-07-01

The aim of the present attempt was to investigate an effect of slip and joule heating on MHD peristaltic Newtonian fluid through an asymmetric vertical tapered channel under influence of radiation. The Mathematical modeling is investigated by utilizing long wavelength and low Reynolds number assumptions. The effects of Hartmann number, porosity parameter, volumetric flow rate, radiation parameter, non uniform parameter, shift angle, Prandtl number, Brinkman number, heat source/sink parameter on temperature characteristics are presented graphically and discussed in detail.

Development of a miniature microwave electron cyclotron resonance plasma ion thruster for exospheric micro-propulsion

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

Dey, Indranuj, E-mail: indranuj@aees.kyushu-u.ac.jp; Toyoda, Yuji; Yamamoto, Naoji

A miniature microwave electron cyclotron resonance plasma source [(discharge diameter)/(microwave cutoff diameter) < 0.3] has been developed at Kyushu University to be used as an ion thruster in micro-propulsion applications in the exosphere. The discharge source uses both radial and axial magnetostatic field confinement to facilitate electron cyclotron resonance and increase the electron dwell time in the volume, thereby enhancing plasma production efficiency. Performance of the ion thruster is studied at 3 microwave frequencies (1.2 GHz, 1.6 GHz, and 2.45 GHz), for low input powers (<15 W) and small xenon mass flow rates (<40 μg/s), by experimentally measuring the extractedmore » ion beam current through a potential difference of ≅1200 V. The discharge geometry is found to operate most efficiently at an input microwave frequency of 1.6 GHz. At this frequency, for an input power of 8 W, and propellant (xenon) mass flow rate of 21 μg/s, 13.7 mA of ion beam current is obtained, equivalent to an calculated thrust of 0.74 mN.« less

The Green's function in a channel with a sound-absorbing cover in the case of a uniform flow

NASA Astrophysics Data System (ADS)

Sobolev, A. F.

2012-07-01

We study the modal structure of an acoustic field of a point source as function of channel wall admittance in the case of a two-dimensional channel. The characteristic equation for determining the eigen-values corresponding to the boundary problem is studied in the form of this equation's dependence on the admittance, which varies in the entire complex plane. All modes, without exception, existing in the channel and forming the source field are classified based on the obtained topography of the characteristic equation. The expressions that describe the amplitudes and spatial distribution of the hydrodynamic modes, attenuation rate (for stable modes), or increment (for unstable modes) were obtained as functions of the wall admittance and flow velocity. It is shown that in addition to the hydrodynamic unstable modes existing downstream from the source, hydrodynamic unstable modes exist upstream from the source at any admittance. They appear only when the admittance has an elastic character. It is shown that hydrodynamic modes are induced only in the case when the source is located close to the wall or on the wall. The amplitude of these modes decreases exponentially with distance from the wall.

Investigation on heat transfer analysis and its effect on a multi-mode, beam-wave interaction for a 140 GHz, MW-class gyrotron

NASA Astrophysics Data System (ADS)

Liu, Qiao; Liu, Yinghui; Chen, Zhaowei; Niu, Xinjian; Li, Hongfu; Xu, Jianhua

2018-04-01

The interaction cavity of a 140 GHz, 1 MW continuous wave gyrotron developed in UESTC will be loaded with a very large heat load in the inner surface during operation. In order to reduce the heat, the axial wedge grooves of the outside surface of the cavity are considered and employed as the heat radiation structure. Thermoanalysis and structural analysis were discussed in detail to obtain the effects of heat on the cavity. In thermoanalysis, the external coolant-flow rates ranging from 20 L/min to 50 L/min were considered, and the distribution of wall loading was loaded as the heat flux source. In structural analysis, the cavity's deformation caused by the loads of heat and pressure was calculated. Compared with a non-deformed cavity, the effects of deformation on the performance of a cavity were discussed. For a cold-cavity, the results show that the quality factor would be reduced by 72, 89, 99 and 171 at the flow rates of 50 L/min, 40 L/min, 30 L/min and 20 L/min, respectively. Correspondingly, the cold-cavity frequencies would be decreased by 0.13 GHz, 0.15 GHz, 0.19 GHz and 0.38 GHz, respectively. For a hot-cavity, the results demonstrate that the output port frequencies would be dropped down, but the offset would be gradually decreased with increasing coolant-flow rate. Meanwhile, the output powers would be reduced dramatically with decreasing coolant-flow rate. In addition, when the coolant-flow rate reaches 40 L/min, the output power and the frequency are just reduced by 30 kW and 0.151 GHz, respectively.

Experimental calibration and validation of sewer/surface flow exchange equations in steady and unsteady flow conditions

NASA Astrophysics Data System (ADS)

Rubinato, Matteo; Martins, Ricardo; Kesserwani, Georges; Leandro, Jorge; Djordjević, Slobodan; Shucksmith, James

2017-09-01

The linkage between sewer pipe flow and floodplain flow is recognised to induce an important source of uncertainty within two-dimensional (2D) urban flood models. This uncertainty is often attributed to the use of empirical hydraulic formulae (the one-dimensional (1D) weir and orifice steady flow equations) to achieve data-connectivity at the linking interface, which require the determination of discharge coefficients. Because of the paucity of high resolution localised data for this type of flows, the current understanding and quantification of a suitable range for those discharge coefficients is somewhat lacking. To fulfil this gap, this work presents the results acquired from an instrumented physical model designed to study the interaction between a pipe network flow and a floodplain flow. The full range of sewer-to-surface and surface-to-sewer flow conditions at the exchange zone are experimentally analysed in both steady and unsteady flow regimes. Steady state measured discharges are first analysed considering the relationship between the energy heads from the sewer flow and the floodplain flow; these results show that existing weir and orifice formulae are valid for describing the flow exchange for the present physical model, and yield new calibrated discharge coefficients for each of the flow conditions. The measured exchange discharges are also integrated (as a source term) within a 2D numerical flood model (a finite volume solver to the 2D Shallow Water Equations (SWE)), which is shown to reproduce the observed coefficients. This calibrated numerical model is then used to simulate a series of unsteady flow tests reproduced within the experimental facility. Results show that the numerical model overestimated the values of mean surcharge flow rate. This suggests the occurrence of additional head losses in unsteady conditions which are not currently accounted for within flood models calibrated in steady flow conditions.

Amphoteric Ion-Exchange Membranes with Significantly Improved Vanadium Barrier Properties for All-Vanadium Redox Flow Batteries.

PubMed

Nibel, Olga; Rojek, Tomasz; Schmidt, Thomas J; Gubler, Lorenz

2017-07-10

All-vanadium redox flow batteries (VRBs) have attracted considerable interest as promising energy-storage devices that can allow the efficient utilization of renewable energy sources. The membrane, which separates the porous electrodes in a redox flow cell, is one of the key components in VRBs. High rates of crossover of vanadium ions and water through the membrane impair the efficiency and capacity of a VRB. Thus, membranes with low permeation rate of vanadium species and water are required, also characterized by low resistance and stability in the VRB environment. Here, we present a new design concept for amphoteric ion-exchange membranes, based on radiation-induced grafting of vinylpyridine into an ethylene tetrafluoroethylene base film and a two-step functionalization to introduce cationic and anionic exchange sites, respectively. During long-term cycling, redox flow cells containing these membranes showed higher efficiency, less pronounced electrolyte imbalance, and significantly reduced capacity decay compared to the cells with the benchmark material Nafion 117. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of the Dynamic Pressure Response of Fuels in Microchannels

NASA Astrophysics Data System (ADS)

Haendler, Brenda; Pisano, Albert; Liepmann, Dorian

2004-11-01

In order to create a self-pumping fuel vaporization and delivery systems for a MEMS rotary engine power system, the dynamic pressure response due to phase eruption of fuels in micro channels must be characterized. Testing is done using micro channels with diameters the same order of magnitude as the critical bubble radius, a constant mass flow rate syringe pump, and a steady heat source. Pressure changes in the micro channel due to the periodic movement of the phase change meniscus are measured for a variety of flow conditions. A discrete Fourier transform is performed on the data to determine the dominant frequencies in the signal. Critical trends are discussed comparing both the frequency and the amplitude of the pressure spikes for a variety of temperatures and flow rates. The results presented on the trends in the pressure signature due to phase eruption for fuels are then related back to the fuel delivery system, which is using a nozzle-diffuser design to accomplish positive flow rectification given the periodic pressure condition at the phase eruption interface.

Effect of N2 flow during deposition on p-type ZnO film

NASA Astrophysics Data System (ADS)

Lin, Chiung-Wei; Liu, Bor-Chang

2017-01-01

In this study, the influence of a nitrogen source on p-type conductive ZnO films was studied. Rapid thermal oxidation was conducted to oxidize ZnN films and convert them to ZnO films. When an as-deposited ZnN film was prepared at a high nitrogen gas flow rate, the converted ZnO film possessed many acceptors and showed stable p-type conduction. This p-type conduction was attributed to the nitrogen gas flow providing many “No” states, which act as acceptors within the processed ZnO film. It was found that the as-deposited ZnN film prepared at a high nitrogen gas flow rate is oxidized slightly so that only a few nitrogen atoms were replaced by oxygen. The carrier concentration and mobility of the optimized oxidized ZnN film were 9.76 × 1017 cm-3 and 62.78 cm2 V-1 s-1, respectively. A good rectified current-voltage characteristic with a turn-on voltage of 3.65 V was achieved for the optimized ZnO:N/ZnO junction.

Effect of Cooling Units on the Performance of an Automotive Exhaust-Based Thermoelectric Generator

NASA Astrophysics Data System (ADS)

Su, C. Q.; Zhu, D. C.; Deng, Y. D.; Wang, Y. P.; Liu, X.

2017-05-01

Currently, automotive exhaust-based thermoelectric generators (AETEGs) are a hot topic in energy recovery. In order to investigate the influence of coolant flow rate, coolant flow direction and cooling unit arrangement in the AETEG, a thermoelectric generator (TEG) model and a related test bench are constructed. Water cooling is adopted in this study. Due to the non-uniformity of the surface temperature of the heat source, the coolant flow direction would affect the output performance of the TEG. Changing the volumetric flow rate of coolant can increase the output power of multi-modules connected in series or/and parallel as it can improve the temperature uniformity of the cooling unit. Since the temperature uniformity of the cooling unit has a strong influence on the output power, two cooling units are connected in series or parallel to research the effect of cooling unit arrangements on the maximum output power of the TEG. Experimental and theoretical analyses reveal that the net output power is generally higher with cooling units connected in parallel than cooling units connected in series in the cooling system with two cooling units.

Computational Aerodynamic Simulations of a Spacecraft Cabin Ventilation Fan Design

NASA Technical Reports Server (NTRS)

Tweedt, Daniel L.

2010-01-01

Quieter working environments for astronauts are needed if future long-duration space exploration missions are to be safe and productive. Ventilation and payload cooling fans are known to be dominant sources of noise, with the International Space Station being a good case in point. To address this issue cost effectively, early attention to fan design, selection, and installation has been recommended, leading to an effort by NASA to examine the potential for small-fan noise reduction by improving fan aerodynamic design. As a preliminary part of that effort, the aerodynamics of a cabin ventilation fan designed by Hamilton Sundstrand has been simulated using computational fluid dynamics codes, and the computed solutions analyzed to quantify various aspects of the fan aerodynamics and performance. Four simulations were performed at the design rotational speed: two at the design flow rate and two at off-design flow rates. Following a brief discussion of the computational codes, various aerodynamic- and performance-related quantities derived from the computed flow fields are presented along with relevant flow field details. The results show that the computed fan performance is in generally good agreement with stated design goals.

Three dimensional investigation of the shock train structure in a convergent-divergent nozzle

NASA Astrophysics Data System (ADS)

Mousavi, Seyed Mahmood; Roohi, Ehsan

2014-12-01

Three-dimensional computational fluid dynamics analyses have been employed to study the compressible and turbulent flow of the shock train in a convergent-divergent nozzle. The primary goal is to determine the behavior, location, and number of shocks. In this context, full multi-grid initialization, Reynolds stress turbulence model (RSM), and the grid adaption techniques in the Fluent software are utilized under the 3D investigation. The results showed that RSM solution matches with the experimental data suitably. The effects of applying heat generation sources and changing inlet flow total temperature have been investigated. Our simulations showed that changes in the heat generation rate and total temperature of the intake flow influence on the starting point of shock, shock strength, minimum pressure, as well as the maximum flow Mach number.

Demonstration that a new flow sensor can operate in the clinical range for cerebrospinal fluid flow

PubMed Central

Raj, Rahul; Lakshmanan, Shanmugamurthy; Apigo, David; Kanwal, Alokik; Liu, Sheng; Russell, Thomas; Madsen, Joseph R.; Thomas, Gordon A.; Farrow, Reginald C.

2015-01-01

A flow sensor has been fabricated and tested that is capable of measuring the slow flow characteristic of the cerebrospinal fluid in the range from less than 4 mL/h to above 100 mL/h. This sensor is suitable for long-term implantation because it uses a wireless external spectrometer to measure passive subcutaneous components. The sensors are pressure-sensitive capacitors, in the range of 5 pF with an air gap at atmospheric pressure. Each capacitor is in series with an inductor to provide a resonant frequency that varies with flow rate. At constant flow, the system is steady with drift <0.3 mL/h over a month. At variable flow rate, V̇, the resonant frequency, f0, which is in the 200–400 MHz range, follows a second order polynomial with respect to V̇. For this sensor system the uncertainty in measuring f0 is 30 kHz which corresponds to a sensitivity in measuring flow of ΔV̇= 0.6 mL/hr. Pressures up to 20 cm H2O relative to ambient pressure were also measured. An implantable twin capacitor system is proposed that can measure flow, which is fully compensated for all hydrostatic pressures. For twin capacitors, other sources of systematic variation within clinical range, such as temperature and ambient pressure, are smaller than our sensitivity and we delineate a calibration method that should maintain clinically useful accuracy over long times. PMID:26543321

Optimizing Natural Gas Networks through Dynamic Manifold Theory and a Decentralized Algorithm: Belgium Case Study

NASA Astrophysics Data System (ADS)

Koch, Caleb; Winfrey, Leigh

2014-10-01

Natural Gas is a major energy source in Europe, yet political instabilities have the potential to disrupt access and supply. Energy resilience is an increasingly essential construct and begins with transmission network design. This study proposes a new way of thinking about modelling natural gas flow. Rather than relying on classical economic models, this problem is cast into a time-dependent Hamiltonian dynamics discussion. Traditional Natural Gas constraints, including inelastic demand and maximum/minimum pipe flows, are portrayed as energy functions and built into the dynamics of each pipe flow. Doing so allows the constraints to be built into the dynamics of each pipeline. As time progresses in the model, natural gas flow rates find the minimum energy, thus the optimal gas flow rates. The most important result of this study is using dynamical principles to ensure the output of natural gas at demand nodes remains constant, which is important for country to country natural gas transmission. Another important step in this study is building the dynamics of each flow in a decentralized algorithm format. Decentralized regulation has solved congestion problems for internet data flow, traffic flow, epidemiology, and as demonstrated in this study can solve the problem of Natural Gas congestion. A mathematical description is provided for how decentralized regulation leads to globally optimized network flow. Furthermore, the dynamical principles and decentralized algorithm are applied to a case study of the Fluxys Belgium Natural Gas Network.

Dynamic Pore-Scale Imaging of Reactive Transport in Heterogeneous Carbonates at Reservoir Conditions Across Multiple Dissolution Regimes

NASA Astrophysics Data System (ADS)

Menke, H. P.; Bijeljic, B.; Andrew, M. G.; Blunt, M. J.

2014-12-01

Sequestering carbon in deep geologic formations is one way of reducing anthropogenic CO2 emissions. When supercritical CO2 mixes with brine in a reservoir, the acid generated has the potential to dissolve the surrounding pore structure. However, the magnitude and type of dissolution are condition dependent. Understanding how small changes in the pore structure, chemistry, and flow properties affect dissolution is paramount for successful predictive modelling. Both 'Pink Beam' synchrotron radiation and a Micro-CT lab source are used in dynamic X-ray microtomography to investigate the pore structure changes during supercritical CO2 injection in carbonate rocks of varying heterogeneity at high temperatures and pressures and various flow-rates. Three carbonate rock types were studied, one with a homogeneous pore structure and two heterogeneous carbonates. All samples are practically pure calcium carbonate, but have widely varying rock structures. Flow-rate was varied in three successive experiments by over an order of magnitude whlie keeping all other experimental conditions constant. A 4-mm carbonate core was injected with CO2-saturated brine at 10 MPa and 50oC. Tomographic images were taken at 30-second to 20-minute time-resolutions during a 2 to 4-hour injection period. A pore network was extracted using a topological analysis of the pore space and pore-scale flow modelling was performed directly on the binarized images with connected pathways and used to track the altering velocity distributions. Significant differences in dissolution type and magnitude were found for each rock type and flowrate. At the highest flow-rates, the homogeneous carbonate was seen to have predominately uniform dissolution with minor dissolution rate differences between the pores and pore throats. Alternatively, the heterogeneous carbonates which formed wormholes at high flow rates. At low flow rates the homogeneous rock developed wormholes, while the heterogeneous samples showed evidence of compact dissolution. This study serves as a unique benchmark for pore-scale reactive transport modelling directly on the binarized Micro-CT images. Dynamic pore-scale imaging methods offer advantages in helping explain the dominant processes at the pore scale so that they may be up-scaled for accurate model prediction.

Qualification of a sublimation tool applied to the case of metalorganic chemical vapor deposition of In{sub 2}O{sub 3} from In(tmhd){sub 3} as a solid precursor

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

Szkutnik, P. D., E-mail: pierre.szkutnik@cea.fr; Jiménez, C.; Angélidès, L.

2016-02-15

A solid delivery system consisting of a source canister, a gas management, and temperature controlled enclosure designed and manufactured by Air Liquide Electronics Systems was tested in the context of gas-phase delivery of the In(tmhd){sub 3} solid precursor. The precursor stream was delivered to a thermal metalorganic chemical vapor deposition reactor to quantify deposition yield under various conditions of carrier gas flow and sublimation temperature. The data collected allowed the determination of characteristic parameters such as the maximum precursor flow rate (18.2 mg min{sup −1} in specified conditions) and the critical mass (defined as the minimum amount of precursor ablemore » to attain the maximum flow rate) found to be about 2.4 g, as well as an understanding of the influence of powder distribution inside the canister. Furthermore, this qualification enabled the determination of optimal delivery conditions which allowed for stable and reproducible precursor flow rates over long deposition times (equivalent to more than 47 h of experiment). The resulting In{sub 2}O{sub 3} layers was compared with those elaborated via pulsed liquid injection obtained in the same chemical vapor deposition chamber and under the same deposition conditions.« less

Assessment of Component-level Emission Measurements ...

EPA Pesticide Factsheets

Oil and natural gas (ONG) production facilities have the potential to emit a substantial amount of greenhouse gasses, hydrocarbons and hazardous air pollutants into the atmosphere. These emissions come from a wide variety of sources including engine exhaust, combustor gases, atmospheric venting from uncontrolled tanks and leaks. Engine exhaust, combustor gases and atmospheric tank venting are included in the initial estimation of a production facilities cumulative emissions. However, there is a large amount of uncertainty associated with magnitude and composition of leaks at these facilities. In order to understand the environmental impacts of these emissions we must first be able characterize the emission flow rate and chemical composition of these leaks/venting. A number of recent publications regarding emission flow rate measurements of components at ONG production facilities have brought into question the validity of such measurements and the sampling methodology. An accurate methodology for quantifying hydrocarbon leaks/venting is needed to support both emission inventories and environmental compliance. This interim report will summarize recent results from a small leak survey completed at ONG production facilities in Utah to characterize their flow rate and chemical composition using a suite of instruments using a high volume sampler (Bacharach Hi Flow Sampler; Bacharach, Inc.), as well as infrared (IR) cameras, a photoionization detector (PID), a fl

Facilitated strontium transport by remobilization of strontium-containing secondary precipitates in Hanford Site subsurface.

PubMed

Wang, Guohui; Um, Wooyong

2013-03-15

Significantly enhanced immobilization of radionuclides (such as (90)Sr and (137)Cs) due to adsorption and coprecipitation with neo-formed colloid-sized secondary precipitates has been reported at the U.S. Department of Energy's Hanford Site. However, the stability of these secondary precipitates containing radionuclides in the subsurface under changeable field conditions is not clear. Here, the authors tested the remobilization possibility of Sr-containing secondary precipitates (nitrate-cancrinite) in the subsurface using saturated column experiments under different geochemical and flow conditions. The columns were packed with quartz sand that contained secondary precipitates (nitrate-cancrinite containing Sr), and leached using colloid-free solutions under different flow rates, varying pH, and ionic strength conditions. The results indicate remobilization of the neo-formed secondary precipitates could be possible given a change of pH of ionic strength and flow rate conditions. The remobility of the neo-formed precipitates increased with the rise in the leaching solution flow rate and pH (in a range of pH 4-11), as well as with decreasing solution ionic strength. The increased mobility of Sr-containing secondary precipitates with changing background conditions can be a potential source for additional radionuclide transport in Hanford Site subsurface environments. Published by Elsevier B.V.

Time-Ordered Networks Reveal Limitations to Information Flow in Ant Colonies

PubMed Central

Blonder, Benjamin; Dornhaus, Anna

2011-01-01

Background An important function of many complex networks is to inhibit or promote the transmission of disease, resources, or information between individuals. However, little is known about how the temporal dynamics of individual-level interactions affect these networks and constrain their function. Ant colonies are a model comparative system for understanding general principles linking individual-level interactions to network-level functions because interactions among individuals enable integration of multiple sources of information to collectively make decisions, and allocate tasks and resources. Methodology/Findings Here we show how the temporal and spatial dynamics of such individual interactions provide upper bounds to rates of colony-level information flow in the ant Temnothorax rugatulus. We develop a general framework for analyzing dynamic networks and a mathematical model that predicts how information flow scales with individual mobility and group size. Conclusions/Significance Using thousands of time-stamped interactions between uniquely marked ants in four colonies of a range of sizes, we demonstrate that observed maximum rates of information flow are always slower than predicted, and are constrained by regulation of individual mobility and contact rate. By accounting for the ordering and timing of interactions, we can resolve important difficulties with network sampling frequency and duration, enabling a broader understanding of interaction network functioning across systems and scales. PMID:21625450

High geothermal heat flux in close proximity to the Northeast Greenland Ice Stream.

PubMed

Rysgaard, Søren; Bendtsen, Jørgen; Mortensen, John; Sejr, Mikael K

2018-01-22

The Greenland ice sheet (GIS) is losing mass at an increasing rate due to surface melt and flow acceleration in outlet glaciers. Currently, there is a large disagreement between observed and simulated ice flow, which may arise from inaccurate parameterization of basal motion, subglacial hydrology or geothermal heat sources. Recently it was suggested that there may be a hidden heat source beneath GIS caused by a higher than expected geothermal heat flux (GHF) from the Earth's interior. Here we present the first direct measurements of GHF from beneath a deep fjord basin in Northeast Greenland. Temperature and salinity time series (2005-2015) in the deep stagnant basin water are used to quantify a GHF of 93 ± 21 mW m -2 which confirm previous indirect estimated values below GIS. A compilation of heat flux recordings from Greenland show the existence of geothermal heat sources beneath GIS and could explain high glacial ice speed areas such as the Northeast Greenland ice stream.

Hydraulic responses to extreme drought conditions in three co-dominant tree species in shallow soil over bedrock.

PubMed

Kukowski, Kelly R; Schwinning, Susanne; Schwartz, Benjamin F

2013-04-01

An important component of the hydrological niche involves the partitioning of water sources, but in landscapes characterized by shallow soils over fractured bedrock, root growth is highly constrained. We conducted a study to determine how physical constraints in the root zone affected the water use of three tree species that commonly coexist on the Edwards Plateau of central Texas; cedar elm (Ulmus crassifolia), live oak (Quercus fusiformis), and Ashe juniper (Juniperus ashei). The year of the study was unusually dry; minimum predawn water potentials measured in August were -8 MPa in juniper, less than -8 MPa in elm, and -5 MPa in oak. All year long, species used nearly identical water sources, based on stable isotope analysis of stem water. Sap flow velocities began to decline simultaneously in May, but the rate of decline was fastest for oak and slowest for juniper. Thus, species partitioned water by time when they could not partition water by source. Juniper lost 15-30 % of its stem hydraulic conductivity, while percent loss for oak was 70-75 %, and 90 % for elm. There was no tree mortality in the year of the study, but 2 years later, after an even more severe drought in 2011, we recorded 34, 14, 6, and 1 % mortality among oak, elm, juniper, and Texas persimmon (Diospyros texana), respectively. Among the study species, mortality rates ranked in the same order as the rate of sap flow decline in 2009. Among the angiosperms, mortality rates correlated with wood density, lending further support to the hypothesis that species with more cavitation-resistant xylem are more susceptible to catastrophic hydraulic failure under acute drought.

Failure and life cycle evaluation of watering valves.

PubMed

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-09-01

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves' internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a 'drying out' period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure.

Failure and Life Cycle Evaluation of Watering Valves

PubMed Central

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-01-01

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves’ internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a ‘drying out’ period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure. PMID:22330720

Treatment of radioactive liquid waste (Co-60) by sorption on Zeolite Na-A prepared from Iraqi kaolin.

PubMed

Mustafa, Yasmen A; Zaiter, Maysoon J

2011-11-30

Iraqi synthetic zeolite type Na-A has been suggested as ion exchange material to treat cobalt-60 in radioactive liquid waste which came from neutron activation for corrosion products. Batch experiments were conducted to find out the equilibrium isotherm for source sample. The equilibrium isotherm for radioactive cobalt in the source sample showed unfavorable type, while the equilibrium isotherm for the total cobalt (the radioactive and nonradioactive cobalt) in the source sample showed a favorable type. The ability of Na-A zeolite to remove cobalt from wastewater was checked for high cobalt concentration (822 mg/L) in addition to low cobalt concentration in the source sample (0.093 mg/L). A good fitting for the experimental data with Langmuir equilibrium model was observed. Langmuir constant qm which is related to monolayer adsorption capacity for low and high cobalt concentration was determined to be 0.021 and 140 mg/g(zeolite). The effects of important design variables on the zeolite column performance were studied these include initial concentration, flow rate, and bed depth. The experimental results have shown that high sorption capacity can be obtained at high influent concentration, low flow rate, and high bed depth. Higher column performance was obtained at higher bed depth. Thomas model was employed to predict the breakthrough carves for the above variables. A good fitting was observed with correlation coefficients between 0.915 and 0.985. Copyright © 2011 Elsevier B.V. All rights reserved.

Use of dust fall filters as passive samplers for metal concentrations in air for communities near contaminated mine tailings

PubMed Central

Beamer, P.I.; Sugeng, A. J.; Kelly, M.D.; Lothrop, N.; Klimecki, W.; Wilkinson, S.T.; Loh, M.

2014-01-01

Mine tailings are a source of metal exposures in many rural communities. Multiple air samples are necessary to assess the extent of exposures and factors contributing to these exposures. However, air sampling equipment is costly and requires trained personnel to obtain measurements, limiting the number of samples that can be collected. Simple, low-cost methods are needed to allow for increased sample collection. The objective of our study was to assess if dust fall filters can serve as passive air samplers and be used to characterize potential exposures in a community near contaminated mine tailings. We placed filters in cylinders, concurrently with active indoor air samplers, in 10 occupied homes. We calculated an estimated flow rate by dividing the mass on each dust fall filter by the bulk air concentration and the sampling duration. The mean estimated flow rate for dust fall filters was significantly different during sampling periods with precipitation. The estimated flow rate was used to estimate metal concentration in the air of these homes, as well as in 31 additional homes in another rural community impacted by contaminated mine tailings. The estimated air concentrations had a significant linear association with the measured air concentrations for beryllium, manganese and arsenic (p<0.05), whose primary source in indoor air is resuspended soil from outdoors. In the second rural community, our estimated metal concentrations in air were comparable to active air sampling measurements taken previously. This passive air sampler is a simple low-cost method to assess potential exposures near contaminated mining sites. PMID:24469149

Convective heat transfer in a porous enclosure saturated by nanofluid with different heat sources

NASA Astrophysics Data System (ADS)

Muthtamilselvan, M.; Sureshkumar, S.

2018-03-01

The present study is proposed to investigate the effects of various lengths and different locations of the heater on the left sidewall in a square lid-driven porous cavity filled with nanofluid. A higher temperature is maintained on the left wall where three different lengths and three different locations of the heat source are considered for the analysis. The right wall is kept at a lower temperature while the top and bottom walls, and the remaining portions of the heated wall are adiabatic. The governing equations are solved by finite volume method. The results show that among the different lengths of the heat source, an enhancement in the heat transfer rate is observed only for the length LH = 1/3 of the heat source. In the case of location of the heat source, the overall heat transfer rate is increased when the heat source is located at the top of the hot wall. For Ri = 1 and 0.01, a better heat transfer rate is obtained when the heat source is placed at the top of the hot wall whereas for Ri = 100, it occurs when the heating portion is at the middle of the hot wall. As the solid volume fraction increases, the viscosity of the fluid is increased, which causes a reduction in the flow intensity. An addition of nanoparticles in the base fluid enhances the overall heat transfer rate significantly for all Da considered. The permeability of the porous medium plays a major role in convection of nanofluid than porosity. A high heat transfer rate (57.26%) is attained for Da = 10-1 and χ = 0.06.

An analytical approach for the simulation of flow in a heterogeneous confined aquifer with a parameter zonation structure

NASA Astrophysics Data System (ADS)

Huang, Ching-Sheng; Yeh, Hund-Der

2016-11-01

This study introduces an analytical approach to estimate drawdown induced by well extraction in a heterogeneous confined aquifer with an irregular outer boundary. The aquifer domain is divided into a number of zones according to the zonation method for representing the spatial distribution of a hydraulic parameter field. The lateral boundary of the aquifer can be considered under the Dirichlet, Neumann or Robin condition at different parts of the boundary. Flow across the interface between two zones satisfies the continuities of drawdown and flux. Source points, each of which has an unknown volumetric rate representing the boundary effect on the drawdown, are allocated around the boundary of each zone. The solution of drawdown in each zone is expressed as a series in terms of the Theis equation with unknown volumetric rates from the source points. The rates are then determined based on the aquifer boundary conditions and the continuity requirements. The estimated aquifer drawdown by the present approach agrees well with a finite element solution developed based on the Mathematica function NDSolve. As compared with the existing numerical approaches, the present approach has a merit of directly computing the drawdown at any given location and time and therefore takes much less computing time to obtain the required results in engineering applications.

Phosphorus recovery from municipal wastewater: An integrated comparative technological, environmental and economic assessment of P recovery technologies.

PubMed

Egle, L; Rechberger, H; Krampe, J; Zessner, M

2016-11-15

Phosphorus (P) is an essential and limited resource. Municipal wastewater is a promising source of P via reuse and could be used to replace P derived from phosphate rocks. The agricultural use of sewage sludge is restricted by legislation or is not practiced in several European countries due to environmental risks posed by organic micropollutants and pathogens. Several technologies have been developed in recent years to recover wastewater P. However, these technologies target different P-containing flows in wastewater treatment plants (effluent, digester supernatant, sewage sludge, and sewage sludge ash), use diverse engineering approaches and differ greatly with respect to P recycling rate, potential of removing or destroying pollutants, product quality, environmental impact and cost. This work compares 19 relevant P recovery technologies by considering their relationships with existing wastewater and sludge treatment systems. A combination of different methods, such as material flow analysis, damage units, reference soil method, annuity method, integrated cost calculation and a literature study on solubility, fertilizing effects and handling of recovered materials, is used to evaluate the different technologies with respect to technical, ecological and economic aspects. With regard to the manifold origins of data an uncertainty concept considering validity of data sources is applied. This analysis revealed that recovery from flows with dissolved P produces clean and plant-available materials. These techniques may even be beneficial from economic and technical perspectives under specific circumstances. However, the recovery rates (a maximum of 25%) relative to the wastewater treatment plant influent are relatively low. The approaches that recover P from sewage sludge apply complex technologies and generally achieve effective removal of heavy metals at moderate recovery rates (~40-50% relative to the WWTP input) and comparatively high costs. Sewage sludge ash is the most promising P source, with recovery rates of 60-90% relative to the wastewater P. The costs highly depend on the purity requirements of the recycled products but can be kept comparatively low, especially if synergies with existing industrial processes are exploited. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

NASA-Modified Precipitation Products to Improve EPA Nonpoint Source Water Quality Modeling for the Chesapeake Bay

NASA Technical Reports Server (NTRS)

Nigro, Joseph; Toll, David; Partington, Ed; Ni-Meister, Wenge; Lee, Shihyan; Gutierrez-Magness, Angelica; Engman, Ted; Arsenault, Kristi

2010-01-01

The Environmental Protection Agency (EPA) has estimated that over 20,000 water bodies within the United States do not meet water quality standards. Ninety percent of the impairments are typically caused by nonpoint sources. One of the regulations in the Clean Water Act of 1972 requires States to monitor the Total Maximum Daily Load (TMDL), or the amount of pollution that can be carried by a water body before it is determined to be "polluted", for any watershed in the U.S.. In response to this mandate, the EPA developed Better Assessment Science Integrating Nonpoint Sources (BASINS) as a Decision Support Tool (DST) for assessing pollution and to guide the decision making process for improving water quality. One of the models in BASINS, the Hydrological Simulation Program -- Fortran (HSPF), computes daily stream flow rates and pollutant concentration at each basin outlet. By design, precipitation and other meteorological data from weather stations serve as standard model input. In practice, these stations may be unable to capture the spatial heterogeneity of precipitation events especially if they are few and far between. An attempt was made to resolve this issue by substituting station data with NASA modified/NOAA precipitation data. Using these data within HSPF, stream flow was calculated for seven watersheds in the Chesapeake Bay Basin during low flow periods, convective storm periods, and annual flows. In almost every case, the modeling performance of HSPF increased when using the NASA-modified precipitation data, resulting in better stream flow statistics and, ultimately, in improved water quality assessment.

CrossWater - Modelling micropollutant loads from different sources in the Rhine basin

NASA Astrophysics Data System (ADS)

Moser, Andreas; Bader, Hans-Peter; Fenicia, Fabrizio; Scheidegger, Ruth; Stamm, Christian

2016-04-01

The pressure on rivers from micropollutants (MPs) originating from various sources is a growing environmental issue and requiring political regulations. The challenges for the water management are numerous, particularly for international water basins. Spatial knowledge of MP sources and the water quality are prerequisites for an effective water quality policy. In this study we analyze the sources of MPs in the international Rhine basin in Europe, and model their transport to the streams. The spatial patterns of MP loads and concentrations from different use classes are investigated with a mass flow analysis and compared to the territorial jurisdictions that shape the spatial arrangement of water management. The source area of MPs depends on the specific use of a compound. Here, we focus on i) herbicides from agricultural land use, ii) biocides from material protection on buildings and iii) human pharmaceuticals from households. The total mass of MPs available for release to the stream network is estimated from statistical application and consumption data. The available mass of MPs is spatially distributed to the catchments areas based on GIS data of agricultural land use, vector data of buildings and wastewater treatment plant (WWTP) locations, respectively. The actual release of MPs to the stream network is calculated with empirical loss rates related to river discharge for agricultural herbicides and to precipitation for biocides. For the pharmaceuticals the release is coupled to the human metabolism rates and elimination rates in WWTP. The released loads from the catchments are propagated downstream with hydraulic routing. Water flow, transport and fate of the substances are simulated within linked river reaches. Time series of herbicide concentrations and loads are simulated for the main rivers in the Rhine basin. Accordingly the loads from the primary catchments are aggregated and constitute lateral or upstream input to the simulated river reaches. Pronounced differences in the spatial patterns of concentrations in the aquatic system are observed between the different compounds. The comparison with measurements from monitoring stations along the Rhine yield satisfactory results.

Simulations of the origin of fluid pressure, fracture gen­ eration, and the movement of fluids in the Uinta Basin, Utah

USGS Publications Warehouse

Bredehoeft, J.D.; Wesley, J.B.; Fouch, T.D.

1994-01-01

The Altamont oil field in the deep Uinta basin is known to have reservoir fluid pressures that approach lithostatic. One explanation for this high pore-fluid pressure is the generation of oil from kerogen in the Green River oil shale at depth. A three-dimensional simulation of flow in the basin was done to test this hypothesis.In the flow simulation, oil generation is included as a fluid source. The kinetics of oil generation from oil shale is a function of temperature. The temperature is controlled by (1) the depth of sediment burial and (2) the geothermal gradient.Using this conceptual model, the pressure buildup results from the trade-off between the rate of oil generation and the flow away from the source volume. The pressure increase depends primarily on (1) the rate of the oil-generation reaction and (2) the permeability of the reservoir rocks. A sensitivity analysis was performed in which both of these parameters were systematically varied. The reservoir permeability must be lower than most of the observed data for the pressure to build up to near lithostatic.The results of the simulations indicated that once oil generation was initiated, the pore pressure built up rapidly to near lithostatic. We simulated hydrofractures in that part of the system in which the pressures approach lithostatic by increasing both the horizontal and the vertical permeability by an order of magnitude. Because the simulated hydrofractures were produced by the high pore pressure, they were restricted to the Altamont field. A new flow system was established in the vicinity of the reservoir; the maximum pore pressure was limited by the least principal stress. Fluids moved vertically up and down and laterally outward away from the source of oil generation. The analysis indicated that, assuming that one is willing to accept the low values of permeability, oil generati n can account for the observed high pressures at Altamont field.

Applying the new HIT results to tokamak and solar plasmas

NASA Astrophysics Data System (ADS)

Jarboe, Thomas; Sutherland, Derek; Hossack, Aaron; Nelson, Brian; Morgan, Kyle; Chris, Hansen; Benedett, Thomas; Everson, Chris; Penna, James

2016-10-01

Understanding sustainment of stable equilibria with helicity injection in HIT-SI has led to a simple picture of several tokamak features. Perturbations cause a viscous-like force on the current that flattens the λ profile, which sustains and stabilizes the equilibrium. An explanation of the mechanism is based on two properties of stable, ideal, two-fluid, magnetized plasma. First, the electron fluid is frozen to magnetic fields and, therefore, current flow is also magnetic field flow. Second, for a stable equilibrium the structure perpendicular to the flux surface resists deformation. Thus toroidal current is from electrons frozen in nested, rotating resilient flux surfaces. Only symmetric flux surfaces allow free differential current flow. Perturbations cause interference of the flux surfaces. Thus, perturbations cause forces that oppose differential electron rotation and forced differential flow produces a symmetrizing force against perturbations and instability. This mechanism can explain the level of field error that spoils tokamak performance and the rate of poloidal flux loss in argon-induced disruptions in DIII-D. This new understanding has led to an explanation of the source of the solar magnetic fields and the power source for the chromosphere, solar wind and corona. Please place in spheromak and FRC section with other HIT posters.

MR imaging of apparent 3He gas transport in narrow pipes and rodent airways

NASA Astrophysics Data System (ADS)

Minard, Kevin R.; Jacob, Richard E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

2008-10-01

High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Nevertheless, flow splitting at airway branches is still evident and use of 3D vector flow mapping is shown to reveal surprising detail that highlights the correlation between gas dynamics and lung structure.

Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on earth

NASA Technical Reports Server (NTRS)

Komar, P. D.

1979-01-01

The hydraulics of channelized water flows on Mars and the resulting sediment transport rates are calculated, and similar computations are performed for such terrestrial analogs as the Mississippi River and the catastrophic Lake Missoula floods that formed the Channeled Scabland in eastern Washington State. The morphologies of deep-sea channels formed by catastrophic turbidity currents are compared with the Martian channels, many similarities are pointed out, and the hydraulics of the various flows are compared. The results indicate that the velocities, discharges, bottom shear stresses, and sediment-transport capacity of water flows along the Martian channels would be comparable to those of the oceanic turbidity currents and the Lake Missoula floods. It is suggested that the submarine canyons from which turbidity currents originate are the terrestrial counterparts to the chaotic-terrain areas or craters that serve as sources for many of the Martian channels.

Monodisperse microdroplet generation and stopping without coalescence

DOEpatents

Beer, Neil Reginald

2015-04-21

A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.

Monodisperse microdroplet generation and stopping without coalescence

DOEpatents

Beer, Neil Reginald

2016-02-23

A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.

Rheology of arc dacite lavas: experimental determination at low strain rates

NASA Astrophysics Data System (ADS)

Avard, Geoffroy; Whittington, Alan G.

2012-07-01

Andesitic-dacitic volcanoes exhibit a large variety of eruption styles, including explosive eruptions, endogenous and exogenous dome growth, and kilometer-long lava flows. The rheology of these lavas can be investigated through field observations of flow and dome morphology, but this approach integrates the properties of lava over a wide range of temperatures. Another approach is through laboratory experiments; however, previous studies have used higher shear stresses and strain rates than are appropriate to lava flows. We measured the apparent viscosity of several lavas from Santiaguito and Bezymianny volcanoes by uniaxial compression, between 1,109 and 1,315 K, at low shear stress (0.085 to 0.42 MPa), low strain rate (between 1.1 × 10-8 and 1.9 × 10-5 s-1), and up to 43.7 % total deformation. The results show a strong variability of the apparent viscosity between different samples, which can be ascribed to differences in initial porosity and crystallinity. Deformation occurs primarily by compaction, with some cracking and/or vesicle coalescence. Our experiments yield apparent viscosities more than 1 order of magnitude lower than predicted by models based on experiments at higher strain rates. At lava flow conditions, no evidence of a yield strength is observed, and the apparent viscosity is best approached by a strain rate- and temperature-dependent power law equation. The best fit for Santiaguito lava, for temperatures between 1,164 and 1,226 K and strain rates lower than 1.8 × 10-4 s-1, is log {η_{{app}}} = - 0.738 + 9.24 × {10^3}{/}T(K) - 0.654 \\cdot log dot{\\varepsilon } where η app is apparent viscosity and dot{\\varepsilon } is strain rate. This equation also reproduced 45 data for a sample from Bezymianny with a root mean square deviation of 0.19 log unit Pa s. Applying the rheological model to lava flow conditions at Santiaguito yields calculated apparent viscosities that are in reasonable agreement with field observations and suggests that internal shear heating may be significant ongoing heat source within these flows, enabling highly viscous lava to travel long distances.

Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions.

PubMed

Gui, P; Inamori, R; Matsumura, M; Inamori, Y

2007-01-01

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.

Norwood with right ventricle-to-pulmonary artery conduit is more effective than Norwood with Blalock-Taussig shunt for hypoplastic left heart syndrome: mathematic modeling of hemodynamics.

PubMed

Mroczek, Tomasz; Małota, Zbigniew; Wójcik, Elżbieta; Nawrat, Zbigniew; Skalski, Janusz

2011-12-01

The introduction of right ventricle to pulmonary artery (RV-PA) conduit in the Norwood procedure for hypoplastic left heart syndrome resulted in a higher survival rate in many centers. A higher diastolic aortic pressure and a higher mean coronary perfusion pressure were suggested as the hemodynamic advantage of this source of pulmonary blood flow. The main objective of this study was the comparison of two models of Norwood physiology with different types of pulmonary blood flow sources and their hemodynamics. Based on anatomic details obtained from echocardiographic assessment and angiographic studies, two three-dimensional computer models of post-Norwood physiology were developed. The finite-element method was applied for computational hemodynamic simulations. Norwood physiology with RV-PA 5-mm conduit and Blalock-Taussig shunt (BTS) 3.5-mm shunt were compared. Right ventricle work, wall stress, flow velocity, shear rate stress, energy loss and turbulence eddy dissipation were analyzed in both models. The total work of the right ventricle after Norwood procedure with the 5-mm RV-PA conduit was lower in comparison to the 3.5-mm BTS while establishing an identical systemic blood flow. The Qp/Qs ratio was higher in the BTS group. Hemodynamic performance after Norwood with the RV-PA conduit is more effective than after Norwood with BTS. Computer simulations of complicated hemodynamics after the Norwood procedure could be helpful in establishing optimal post-Norwood physiology. Copyright © 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Contaminant concentration versus flow velocity: drivers of biodegradation and microbial growth in groundwater model systems.

PubMed

Grösbacher, Michael; Eckert, Dominik; Cirpka, Olaf A; Griebler, Christian

2018-06-01

Aromatic hydrocarbons belong to the most abundant contaminants in groundwater systems. They can serve as carbon and energy source for a multitude of indigenous microorganisms. Predictions of contaminant biodegradation and microbial growth in contaminated aquifers are often vague because the parameters of microbial activity in the mathematical models used for predictions are typically derived from batch experiments, which don't represent conditions in the field. In order to improve our understanding of key drivers of natural attenuation and the accuracy of predictive models, we conducted comparative experiments in batch and sediment flow-through systems with varying concentrations of contaminant in the inflow and flow velocities applying the aerobic Pseudomonas putida strain F1 and the denitrifying Aromatoleum aromaticum strain EbN1. We followed toluene degradation and bacterial growth by measuring toluene and oxygen concentrations and by direct cell counts. In the sediment columns, the total amount of toluene degraded by P. putida F1 increased with increasing source concentration and flow velocity, while toluene removal efficiency gradually decreased. Results point at mass transfer limitation being an important process controlling toluene biodegradation that cannot be assessed with batch experiments. We also observed a decrease in the maximum specific growth rate with increasing source concentration and flow velocity. At low toluene concentrations, the efficiencies in carbon assimilation within the flow-through systems exceeded those in the batch systems. In all column experiments the number of attached cells plateaued after an initial growth phase indicating a specific "carrying capacity" depending on contaminant concentration and flow velocity. Moreover, in all cases, cells attached to the sediment dominated over those in suspension, and toluene degradation was performed practically by attached cells only. The observed effects of varying contaminant inflow concentration and flow velocity on biodegradation could be captured by a reactive-transport model. By monitoring both attached and suspended cells we could quantify the release of new-grown cells from the sediments to the mobile aqueous phase. Studying flow velocity and contaminant concentrations as key drivers of contaminant transformation in sediment flow-through microcosms improves our system understanding and eventually the prediction of microbial biodegradation at contaminated sites.

Characterization of the Oum Er Rbia (Morocco) high basin karstic water sources by using solid state nuclear track detectors and radon as a natural tracer.

PubMed

Khalil, N; Misdaq, M A; Berrazzouk, S; Mania, J

2002-06-01

Uranium and thorium contents as well as radon alpha-activities per unit volume were evaluated inside different water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted alpha-particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranyl nitrate (UO2(NO3)26H2O) standard solutions. A relationship between water radon concentration and water transmission of different water sources belonging to two regions of the Middle Atlas (Morocco) water reservoir was found. The influence of the water flow rate as well as the permeability and fracture system of the host rocks of the sources studied was investigated.

A dual-phantom system for validation of velocity measurements in stenosis models under steady flow.

PubMed

Blake, James R; Easson, William J; Hoskins, Peter R

2009-09-01

A dual-phantom system is developed for validation of velocity measurements in stenosis models. Pairs of phantoms with identical geometry and flow conditions are manufactured, one for ultrasound and one for particle image velocimetry (PIV). The PIV model is made from silicone rubber, and a new PIV fluid is made that matches the refractive index of 1.41 of silicone. Dynamic scaling was performed to correct for the increased viscosity of the PIV fluid compared with that of the ultrasound blood mimic. The degree of stenosis in the models pairs agreed to less than 1%. The velocities in the laminar flow region up to the peak velocity location agreed to within 15%, and the difference could be explained by errors in ultrasound velocity estimation. At low flow rates and in mild stenoses, good agreement was observed in the distal flow fields, excepting the maximum velocities. At high flow rates, there was considerable difference in velocities in the poststenosis flow field (maximum centreline differences of 30%), which would seem to represent real differences in hydrodynamic behavior between the two models. Sources of error included: variation of viscosity because of temperature (random error, which could account for differences of up to 7%); ultrasound velocity estimation errors (systematic errors); and geometry effects in each model, particularly because of imperfect connectors and corners (systematic errors, potentially affecting the inlet length and flow stability). The current system is best placed to investigate measurement errors in the laminar flow region rather than the poststenosis turbulent flow region.

Discharge Characterization of 40 cm-Microwave ECR Ion Source and Neutralizer

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.; Britton, Melissa

2003-01-01

Discharge characteristics of a 40 cm, 2.45 GHz Electron Cyclotron Resonance (ECR) ion thruster discharge chamber and neutralizer were acquired. Thruster bulk discharge plasma characteristics were assessed using a single Langmuir probe. Total extractable ion current was measured as a function of input microwave power and flow rate. Additionally, radial ion current density profiles at the thruster.s exit plane were characterized using five equally spaced Faraday probes. Distinct low and high density operating modes were observed as discharge input power was varied from 0 to 200 W. In the high mode, extractable ion currents as high as 0.82 A were measured. Neutralizer emission current was characterized as a function of flow rate and microwave power. Neutralizer extraction currents as high as 0.6 A were measured.

Looking Deeper Into Hydrologic Connectivity and Streamflow Generation: A Groundwater Hydrologist's Perspective.

NASA Astrophysics Data System (ADS)

Gardner, W. P.

2016-12-01

In this presentation the definition of hydraulic connection will be explored with a focus on the role of deep groundwater in streamflow generation and its time and space limits. Regional groundwater flow paths can be important sources of baseflow and potentially event response in surface water systems. This deep groundwater discharge plays an important role in determining how the watershed responds to climatic forcing, whether watersheds are a carbon source or sink and can be significant for watershed geochemistry and nutrient loading. These flow paths potentially "connect" to surface water systems and saturated soil zones at large distances, and over long time scales. However, these flow paths are challenging to detect, especially with hydraulic techniques. Here we will discuss some of the basic physical processes that affect the hydraulic signal along a groundwater flow path and their implications for the definition of hydrologic connection. Methods of measuring hydraulic connection using groundwater head response and their application in detecting regional groundwater discharge will be discussed. Environmental tracers are also a powerful method for identifying connected flowpaths in groundwater systems, and are commonly used to determine flow connection and flow rates in groundwater studies. Isotopic tracer methods for detecting deep, regional flow paths in watersheds will be discussed, along with observations of deep groundwater discharge in shallow alluvial systems around the world. The goal of this talk is to discuss hydraulic and hydrologic connection from a groundwater hydrologist's perspective, spark conversation on the meaning of hydrologic connection, the processes which govern hydraulic response and methods to measure flow connections and flux.

Breakdown of doublet recirculation and direct line drives by far-field flow in reservoirs: implications for geothermal and hydrocarbon well placement

NASA Astrophysics Data System (ADS)

Weijermars, R.; van Harmelen, A.

2016-07-01

An important real world application of doublet flow occurs in well design of both geothermal and hydrocarbon reservoirs. A guiding principle for fluid management of injection and extraction wells is that mass balance is commonly assumed between the injected and produced fluid. Because the doublets are considered closed loops, the injection fluid is assumed to eventually reach the producer well and all the produced fluid ideally comes from stream tubes connected to the injector of the well pair making up the doublet. We show that when an aquifer background flow occurs, doublets will rarely retain closed loops of fluid recirculation. When the far-field flow rate increases relative to the doublet's strength, the area occupied by the doublet will diminish and eventually vanishes. Alternatively, rather than using a single injector (source) and single producer (sink), a linear array of multiple injectors separated by some distance from a parallel array of producers can be used in geothermal energy projects as well as in waterflooding of hydrocarbon reservoirs. Fluid flow in such an arrangement of parallel source-sink arrays is shown to be macroscopically equivalent to that of a line doublet. Again, any far-field flow that is strong enough will breach through the line doublet, which then splits into two vortices. Apart from fundamental insight into elementary flow dynamics, our new results provide practical clues that may contribute to improve the planning and design of doublets and direct line drives commonly used for flow management of groundwater, geothermal and hydrocarbon reservoirs.

Ascorbate elevates perfusion pressure in the bovine extraocular long posterior ciliary artery: role of endothelium-derived hyperpolarizing factor (EDHF).

PubMed

Stirrat, Alison; Nelli, Silvia; McGuckin, Alicia; Ho, Vivian Wing Man; Wilson, William S; Martin, William

2006-03-18

Ascorbate blocks agonist-induced, endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilatation in the bovine perfused ciliary artery and this is associated with a rise in perfusion pressure. We now report the origins of this ascorbate-induced rise in perfusion pressure. In segments of ciliary artery perfused at 2.5 ml/min, the addition of ascorbate (10-150 microM) enhanced U46619-induced perfusion pressure. Ascorbate produced no enhancement in the absence of U46619, suggesting that its effects resulted not from a constrictor action but through removal of a tonic vasodilator influence. Experiments revealed the endothelial source of this vasodilator influence, and EDHF, but not nitric oxide or prostanoids, appeared to be involved. The ascorbate-induced enhancement of vasoconstrictor tone was not seen in a static myograph or in segments perfused at low rates of flow, but was seen at flow rates of 2.5 ml(-1) and above. We conclude that ascorbate augments vasoconstrictor tone through inhibition of flow-induced EDHF activity.

Mixed convection flow of couple stress nanofluid over oscillatory stretching sheet with heat absorption/generation effects

NASA Astrophysics Data System (ADS)

Khan, Sami Ullah; Shehzad, Sabir Ali; Rauf, Amar; Ali, Nasir

2018-03-01

The aim of this article is to highlight the unsteady mixed convective couple stress nanoliquid flow passed through stretching surface. The flow is generated due to periodic oscillations of sheet. An appropriate set of dimensionless variables are used to reduce the independent variables in governing equations arising from mathematical modeling. An analytical solution has been computed by employing the technique of homotopy method. The outcomes of various sundry parameters like couple stress parameter, the ratio of angular velocity to stretching rate, thermophoresis parameter, Hartmann number, Prandtl number, heat source/sink parameter, Schmidt number described graphically and in tabular form. It is observed that the velocity profile increases by increasing mixed convection parameter and concentration buoyancy parameter. The temperature enhances for larger values of Hartmann number and Brownian. The concentration profile increases by increasing thermophoresis parameter. Results show that wall shear stress increases by increasing couple stress parameter and ratio of oscillating frequency to stretching rate.

40 CFR Table 2 to Subpart Mmmmm of... - Operating Limits for New or Reconstructed Flame Lamination Affected Sources

Code of Federal Regulations, 2010 CFR

2010-07-01

... scrubber, maintain the daily average pressure drop across the venturi within the operating range value... . . . You must . . . 1. Scrubber a. Maintain the daily average scrubber inlet liquid flow rate above the minimum value established during the performance test. b. Maintain the daily average scrubber effluent pH...

40 CFR Table 2 to Subpart Mmmmm of... - Operating Limits for New or Reconstructed Flame Lamination Affected Sources

Code of Federal Regulations, 2011 CFR

2011-07-01

... . . . You must . . . 1. Scrubber a. Maintain the daily average scrubber inlet liquid flow rate above the minimum value established during the performance test. b. Maintain the daily average scrubber effluent pH... scrubber, maintain the daily average pressure drop across the venturi within the operating range value...

Dusk/dawn atmospheric asymmetries on tidally-locked satellites: O2 at Europa

NASA Astrophysics Data System (ADS)

Oza, Apurva V.; Johnson, Robert E.; Leblanc, François

2018-05-01

We use a simple analytic model to examine the effect of the atmospheric source properties on the spatial distribution of a volatile in a surface-bounded atmosphere on a satellite that is tidally-locked to its planet. Spatial asymmetries in the O2 exosphere of Europa observed using the Hubble Space Telescope appear to reveal on average a dusk enhancement in the near-surface ultraviolet auroral emissions. Since the hop distances in these ballistic atmospheres are small, we use a 1-D mass conservation equation to estimate the latitudinally-averaged column densities produced by suggested O2 sources. Although spatial asymmetries in the plasma flow and in the surface properties certainly affect the spatial distribution of the near-surface aurora, the dusk enhancements at Europa can be understood using a relatively simple thermally-dependent source. Such a source is consistent with the fact that radiolytically produced O2 permeates their porous regoliths and is not so sensitive to the local production rate from ice. The size of the shift towards dusk is determined by the ratio of the rotation rate and atmospheric loss rate. A thermally-dependent source emanating from a large reservoir of O2 permeating Europa's icy regolith is consistent with the suggestion that its subsurface ocean might be oxidized by subduction of such radiolytic products.

A noninvasive optical system for the measurement of xylem and phloem sap flow in woody plants of small stem size.

PubMed

Helfter, Carole; Shephard, Jonathon D; Martinez-Vilalta, Jordi; Mencuccini, Maurizio; Hand, Duncan P

2007-02-01

Over the past 70 years, heat has been widely used as a tracer for estimating the flow of water in woody and herbaceous plants. However, most commercially available techniques for monitoring whole plant water use are invasive and the measurements are potentially flawed because of wounding of the xylem tissue. The study of photosynthate transport in the phloem remains in its infancy, and little information about phloem transport rates is available owing to the fragility of the vascular tissue. The aim of our study was to develop a compact, stand-alone non-invasive system allowing for direct detection of phloem and xylem sap movement. The proposed method uses a heat pulse as a tracer for sap flow. Heat is applied to the surface of the stem with a near-infrared laser source, and heat propagation is monitored externally by means of an infrared camera. Heat pulse velocities are determined from the thermometric data and related to the more useful quantity, mass flow rate. Simulation experiments on the xylem tissue of severed silver birch (Betula pendula Roth.) branch segments were performed to assess the feasibility of the proposed approach, highlight the characteristics of the technique and outline calibration strategies. Good agreement between imposed and measured flow rates was achieved leading to experimentation with live silver birch and oak (Quercus robur L.) saplings. It was demonstrated that water flow through xylem vessels can be monitored non-invasively on an intact stem with satisfactory accuracy despite simultaneous sugar transport in the phloem. In addition, it was demonstrated that the technique allows for unequivocal detection of phloem flow velocities.

Heterogeneity in leaf litter decomposition in a temporary Mediterranean stream during flow fragmentation.

PubMed

Abril, Meritxell; Muñoz, Isabel; Menéndez, Margarita

2016-05-15

In temporary Mediterranean streams, flow fragmentation during summer droughts originates an ephemeral mosaic of terrestrial and aquatic habitat types. The heterogeneity of habitat types implies a particular ecosystem functioning in temporary streams that is still poorly understood. We assessed the initial phases of leaf litter decomposition in selected habitat types: running waters, isolated pools and moist and dry streambed sediments. We used coarse-mesh litter bags containing Populus nigra leaves to examine decomposition rates, microbial biomass, macroinvertebrate abundance and dissolved organic carbon (DOC) release rates in each habitat type over an 11-day period in late summer. We detected faster decomposition rates in aquatic (running waters and isolated pools) than in terrestrial habitats (moist and dry streambed sediments). Under aquatic conditions, decomposition was characterized by intense leaching and early microbial colonization, which swiftly started to decompose litter. Microbial colonization in isolated pools was primarily dominated by bacteria, whereas in running waters fungal biomass predominated. Under terrestrial conditions, leaves were most often affected by abiotic processes that resulted in small mass losses. We found a substantial decrease in DOC release rates in both aquatic habitats within the first days of the study, whereas DOC release rates remained relatively stable in the moist and dry sediments. This suggests that leaves play different roles as a DOC source during and after flow fragmentation. Overall, our results revealed that leaf decomposition is heterogeneous during flow fragmentation, which has implications related to DOC utilization that should be considered in future regional carbon budgets. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydrologic and Water-Quality Characterization and Modeling of the Onondaga Lake Basin, Onondaga County, New York

USGS Publications Warehouse

Coon, William F.; Reddy, James E.

2008-01-01

Onondaga Lake in Onondaga County, New York, has been identified as one of the Nation?s most contaminated lakes as a result of industrial and sanitary-sewer discharges and stormwater nonpoint sources, and has received priority cleanup status under the national Water Resources Development Act of 1990. A basin-scale precipitation-runoff model of the Onondaga Lake basin was identified as a desirable water-resources management tool to better understand the processes responsible for the generation of loads of sediment and nutrients that are transported to Onondaga Lake. During 2003?07, the U.S. Geological Survey (USGS) developed a model based on the computer program, Hydrological Simulation Program?FORTRAN (HSPF), which simulated overland flow to, and streamflow in, the major tributaries of Onondaga Lake, and loads of sediment, phosphorus, and nitrogen transported to the lake. The simulation period extends from October 1997 through September 2003. The Onondaga Lake basin was divided into 107 subbasins and within these subbasins, the land area was apportioned among 19 pervious and impervious land types on the basis of land use and land cover, hydrologic soil group (HSG), and aspect. Precipitation data were available from three sources as input to the model. The model simulated streamflow, water temperature, concentrations of dissolved oxygen, and concentrations and loads of sediment, orthophosphate, total phosphorus, nitrate, ammonia, and organic nitrogen in the four major tributaries to Onondaga Lake?Onondaga Creek, Harbor Brook, Ley Creek, and Ninemile Creek. Simulated flows were calibrated to data from nine USGS streamflow-monitoring sites; simulated nutrient concentrations and loads were calibrated to data collected at six of the nine streamflow-monitoring sites. Water-quality samples were collected, processed, and analyzed by personnel from the Onondaga County Department of Water Environment Protection. Several time series of flow, and sediment and nutrient loads were generated for known sources of these constituents, including the Tully Valley mudboils (flow and sediment), Otisco Lake (flow and nutrients), the Marcellus wastewater-treatment plant (flow and nutrients), and springs from carbonate bedrock (flow). Runoff from the impervious sewered areas of the City of Syracuse was adjusted for the quantity that was treatable at the county wastewater-treatment plant; the excess flows were routed to nearby streams through combined-sanitary-and-storm-sewer overflows. The mitigative effects that the Onondaga Reservoir and Otisco Lake were presumed to have on loads of sediment and particulate constituents were simulated by adjustment of parameter values that controlled sediment settling rates, deposition, and scour in the reservoir and lake. Graphical representations of observed and simulated data, and relevant statistics, were compared to assess model performance. Simulated daily and monthly streamflows were rated ?very good? (within 10 percent of observed flows) at all calibration sites, except Onondaga Creek at Cardiff, which was rated ?fair? (10?15 percent difference). Simulations of monthly average water temperatures were rated ?very good? (within 7 percent of observed temperatures) at all sites. No observed data were available by which to directly assess the model?s simulation of suspended sediment loads. Available measured total suspended solids data provided an indirect means of comparison but, not surprisingly, yielded only ?fair? to ?poor? ratings (greater than 30 percent difference) for simulated monthly sediment loads at half the water-quality calibration sites. Simulations of monthly orthophosphate loads ranged from ?very good? (within 15 percent of measured loads) at three sites to ?poor? (greater than 35 percent difference) at one site; simulations of ammonia nitrogen loads ranged from ?very good? at one site to ?fair? (25?35 percent difference) at two sites. Simulations of monthly total phosphorus, nitrate, and or

Pollen-Mediated Gene Flow in Maize: Implications for Isolation Requirements and Coexistence in Mexico, the Center of Origin of Maize.

PubMed

Baltazar, Baltazar M; Castro Espinoza, Luciano; Espinoza Banda, Armando; de la Fuente Martínez, Juan Manuel; Garzón Tiznado, José Antonio; González García, Juvencio; Gutiérrez, Marco Antonio; Guzmán Rodríguez, José Luis; Heredia Díaz, Oscar; Horak, Michael J; Madueño Martínez, Jesús Ignacio; Schapaugh, Adam W; Stojšin, Duška; Uribe Montes, Hugo Raúl; Zavala García, Francisco

2015-01-01

Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives.

Pollen-Mediated Gene Flow in Maize: Implications for Isolation Requirements and Coexistence in Mexico, the Center of Origin of Maize

PubMed Central

Gutiérrez, Marco Antonio; Guzmán Rodríguez, José Luis; Horak, Michael J.; Madueño Martínez, Jesús Ignacio; Schapaugh, Adam W.; Stojšin, Duška; Uribe Montes, Hugo Raúl

2015-01-01

Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives. PMID:26162097

Effect of saline waste solution infiltration rates on uranium retention and spatial distribution in Hanford sediments.

PubMed

Wan, Jiamin; Tokunaga, Tetsu K; Kim, Yongman; Wang, Zheming; Lanzirotti, Antonio; Saiz, Eduardo; Serne, R Jeffrey

2008-03-15

The accidental overfilling of waste liquid from tank BX-102 at the Hanford Site in 1951 put about 10 t of U(VI) into the vadose zone. In order to understand the dominant geochemical reactions and transport processes that occurred during the initial infiltration and to help understand current spatial distribution, we simulated the waste liquid spilling event in laboratory sediment columns using synthesized metal waste solution. We found that, as the plume propagated through sediments, pH decreased greatly (as much as 4 units) at the moving plume front. Infiltration flow rates strongly affect U behavior. Slower flow rates resulted in higher sediment-associated U concentrations, and higher flow rates (> or =5 cm/day) permitted practically unretarded U transport. Therefore, given the very high Ksat of most of Hanford formation, the low permeability zones within the sediment could have been most important in retaining high concentrations of U during initial release into the vadose zone. Massive amount of colloids, including U-colloids, formed at the plume fronts. Total U concentrations (aqueous and colloid) within plume fronts exceeded the source concentration by up to 5-fold. Uranium colloid formation and accumulation at the neutralized plume front could be one mechanism responsible for highly heterogeneous U distribution observed in the contaminated Hanford vadose zone.

Development of vacuum ultraviolet absorption spectroscopy system for wide measurement range of number density using a dual-tube inductively coupled plasma light source

NASA Astrophysics Data System (ADS)

Kuwahara, Akira; Matsui, Makoto; Yamagiwa, Yoshiki

2012-12-01

A vacuum ultraviolet absorption spectroscopy system for a wide measurement range of atomic number densities is developed. Dual-tube inductively coupled plasma was used as a light source. The probe beam profile was optimized for the target number density range by changing the mass flow rate of the inner and outer tubes. This system was verified using cold xenon gas. As a result, the measurement number density range was extended from the conventional two orders to five orders of magnitude.

Technical aspects and clinical implications of high frequency jet ventilation with a solenoid valve.

PubMed

Carlon, G C; Miodownik, S; Ray, C; Kahn, R C

1981-01-01

High frequency jet ventilation (HFJV) is an incompletely studied technique of mechanical respiratory support. The authors have built a ventilator based on a solenoid valve, that allows independent selection of respiratory rate and inspiratory/expiratory ratio. The ventilator can be synchronized to the heart rate. Humidification is provided by warm saline dripped in front of the injector nozzle, so that the jet stream itself acts as a nebulizer. Tube diameter, length, and deformability are fundamental determinants of inspiratory flow rate and wave form. Cannula kinking and inadequate humidification were the most significant sources of complications.

Development of a Model for Dynamic Recrystallization Consistent with the Second Derivative Criterion.

PubMed

Imran, Muhammad; Kühbach, Markus; Roters, Franz; Bambach, Markus

2017-11-02

Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain-hardening rate as a function of flow stress. Various models are available that can predict the evolution of flow stress from incipient plastic flow up to steady-state deformation in the presence of DRX. Some of these models have been implemented into finite element codes and are widely used for the design of metal forming processes, but their consistency with the SDC has not been investigated. This work identifies three sources of inconsistencies that models for DRX may exhibit. For a consistent modeling of the DRX kinetics, a new strain-hardening model for the hardening stages III to IV is proposed and combined with consistent recrystallization kinetics. The model is devised in the Kocks-Mecking space based on characteristic transition in the strain-hardening rate. A linear variation of the transition and inflection points is observed for alloy 800H at all tested temperatures and strain rates. The comparison of experimental and model results shows that the model is able to follow the course of the strain-hardening rate very precisely, such that highly accurate flow stress predictions are obtained.

Development of a Model for Dynamic Recrystallization Consistent with the Second Derivative Criterion

PubMed Central

Imran, Muhammad; Kühbach, Markus; Roters, Franz; Bambach, Markus

2017-01-01

Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain-hardening rate as a function of flow stress. Various models are available that can predict the evolution of flow stress from incipient plastic flow up to steady-state deformation in the presence of DRX. Some of these models have been implemented into finite element codes and are widely used for the design of metal forming processes, but their consistency with the SDC has not been investigated. This work identifies three sources of inconsistencies that models for DRX may exhibit. For a consistent modeling of the DRX kinetics, a new strain-hardening model for the hardening stages III to IV is proposed and combined with consistent recrystallization kinetics. The model is devised in the Kocks-Mecking space based on characteristic transition in the strain-hardening rate. A linear variation of the transition and inflection points is observed for alloy 800H at all tested temperatures and strain rates. The comparison of experimental and model results shows that the model is able to follow the course of the strain-hardening rate very precisely, such that highly accurate flow stress predictions are obtained. PMID:29099068

Use of Interrupted Helium Flow in the Analysis of Vapor Samples with Flowing Atmospheric-Pressure Afterglow-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Storey, Andrew P.; Zeiri, Offer M.; Ray, Steven J.; Hieftje, Gary M.

2017-02-01

The flowing atmospheric-pressure afterglow (FAPA) source was used for the mass-spectrometric analysis of vapor samples introduced between the source and mass spectrometer inlet. Through interrupted operation of the plasma-supporting helium flow, helium consumption is greatly reduced and dynamic gas behavior occurs that was characterized by schlieren imaging. Moreover, mass spectra acquired immediately after the onset of helium flow exhibit a signal spike before declining and ultimately reaching a steady level. This initial signal appears to be due to greater interaction of sample vapor with the afterglow of the source when helium flow resumes. In part, the initial spike in signal can be attributed to a pooling of analyte vapor in the absence of helium flow from the source. Time-resolved schlieren imaging of the helium flow during on and off cycles provided insight into gas-flow patterns between the FAPA source and the MS inlet that were correlated with mass-spectral data.

Use of Interrupted Helium Flow in the Analysis of Vapor Samples with Flowing Atmospheric-Pressure Afterglow-Mass Spectrometry.

PubMed

Storey, Andrew P; Zeiri, Offer M; Ray, Steven J; Hieftje, Gary M

2017-02-01

The flowing atmospheric-pressure afterglow (FAPA) source was used for the mass-spectrometric analysis of vapor samples introduced between the source and mass spectrometer inlet. Through interrupted operation of the plasma-supporting helium flow, helium consumption is greatly reduced and dynamic gas behavior occurs that was characterized by schlieren imaging. Moreover, mass spectra acquired immediately after the onset of helium flow exhibit a signal spike before declining and ultimately reaching a steady level. This initial signal appears to be due to greater interaction of sample vapor with the afterglow of the source when helium flow resumes. In part, the initial spike in signal can be attributed to a pooling of analyte vapor in the absence of helium flow from the source. Time-resolved schlieren imaging of the helium flow during on and off cycles provided insight into gas-flow patterns between the FAPA source and the MS inlet that were correlated with mass-spectral data. Graphical Abstract ᅟ.

Performance of the subsurface flow constructed wetlands for pretreatment of slightly polluted source water.

PubMed

Yang, Xu; Zhang, Xueping; Wang, Jifu; Zhao, Guangying; Wang, Baojian

2014-05-01

The slightly polluted source water of Yellow River was pretreated in a horizontal subsurface flow constructed wetland (HSFCW) and a lateral subsurface flow constructed wetland (LSFCW) in the Ji'nan city Reservoir, Shandong, China. During almost one years run, the results showed that at the hydraulic loading rate of 1 m/day, the removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4 (+)-N) and total phosphorus (TP) in the HSFCW were 48.9, 51.4, 48.7 and 48.9 %, respectively, and the corresponding removal efficiencies in the LSFCW were 50.51, 53.12, 50.44 and 50.83 %, respectively. The HSFCW and LSFCW had a similar high potential for nutrients removal and LSFCW was slightly better. According to the China standard for surface water resources (GB3838-2002), mean effluent COD can reach the Class I (≤ 15 mg/L), and NH4 (+)-N and TP and TN can reach nearly the Class I (≤ 0.015 mg/L), the Class III (≤ 0.05 mg/L) and the Class IV (≤ 1.5 mg/L), respectively. It can be concluded that the slightly polluted source water from Reservoir was pretreated well by the constructed wetland.

Air change rates and interzonal flows in residences, and the need for multi-zone models for exposure and health analyses.

PubMed

Du, Liuliu; Batterman, Stuart; Godwin, Christopher; Chin, Jo-Yu; Parker, Edith; Breen, Michael; Brakefield, Wilma; Robins, Thomas; Lewis, Toby

2012-12-12

Air change rates (ACRs) and interzonal flows are key determinants of indoor air quality (IAQ) and building energy use. This paper characterizes ACRs and interzonal flows in 126 houses, and evaluates effects of these parameters on IAQ. ACRs measured using weeklong tracer measurements in several seasons averaged 0.73 ± 0.76 h(-1) (median = 0.57 h(-1), n = 263) in the general living area, and much higher, 1.66 ± 1.50 h(-1) (median = 1.23 h(-1), n = 253) in bedrooms. Living area ACRs were highest in winter and lowest in spring; bedroom ACRs were highest in summer and lowest in spring. Bedrooms received an average of 55 ± 18% of air from elsewhere in the house; the living area received only 26 ± 20% from the bedroom. Interzonal flows did not depend on season, indoor smoking or the presence of air conditioners. A two-zone IAQ model calibrated for the field study showed large differences in pollutant levels between the living area and bedroom, and the key parameters affecting IAQ were emission rates, emission source locations, air filter use, ACRs, interzonal flows, outdoor concentrations, and PM penetration factors. The single-zone models that are commonly used for residences have substantial limitations and may inadequately represent pollutant concentrations and exposures in bedrooms and potentially other environments other where people spend a substantial fraction of time.

Air Change Rates and Interzonal Flows in Residences, and the Need for Multi-Zone Models for Exposure and Health Analyses

PubMed Central

Du, Liuliu; Batterman, Stuart; Godwin, Christopher; Chin, Jo-Yu; Parker, Edith; Breen, Michael; Brakefield, Wilma; Robins, Thomas; Lewis, Toby

2012-01-01

Air change rates (ACRs) and interzonal flows are key determinants of indoor air quality (IAQ) and building energy use. This paper characterizes ACRs and interzonal flows in 126 houses, and evaluates effects of these parameters on IAQ. ACRs measured using weeklong tracer measurements in several seasons averaged 0.73 ± 0.76 h−1 (median = 0.57 h−1, n = 263) in the general living area, and much higher, 1.66 ± 1.50 h−1 (median = 1.23 h−1, n = 253) in bedrooms. Living area ACRs were highest in winter and lowest in spring; bedroom ACRs were highest in summer and lowest in spring. Bedrooms received an average of 55 ± 18% of air from elsewhere in the house; the living area received only 26 ± 20% from the bedroom. Interzonal flows did not depend on season, indoor smoking or the presence of air conditioners. A two-zone IAQ model calibrated for the field study showed large differences in pollutant levels between the living area and bedroom, and the key parameters affecting IAQ were emission rates, emission source locations, air filter use, ACRs, interzonal flows, outdoor concentrations, and PM penetration factors. The single-zone models that are commonly used for residences have substantial limitations and may inadequately represent pollutant concentrations and exposures in bedrooms and potentially other environments other where people spend a substantial fraction of time. PMID:23235286

Particle velocity measurements with macroscopic fluorescence imaging in lymph tissue mimicking microfluidic phantoms

NASA Astrophysics Data System (ADS)

Hennessy, Ricky; Koo, Chiwan; Ton, Phuc; Han, Arum; Righetti, Raffaella; Maitland, Kristen C.

2011-03-01

Ultrasound poroelastography can quantify structural and mechanical properties of tissues such as stiffness, compressibility, and fluid flow rate. This novel ultrasound technique is being explored to detect tissue changes associated with lymphatic disease. We have constructed a macroscopic fluorescence imaging system to validate ultrasonic fluid flow measurements and to provide high resolution imaging of microfluidic phantoms. The optical imaging system is composed of a white light source, excitation and emission filters, and a camera with a zoom lens. The field of view can be adjusted from 100 mm x 75 mm to 10 mm x 7.5 mm. The microfluidic device is made of polydimethylsiloxane (PDMS) and has 9 channels, each 40 μm deep with widths ranging from 30 μm to 200 μm. A syringe pump was used to propel water containing 15 μm diameter fluorescent microspheres through the microchannels, with flow rates ranging from 0.5 μl/min to 10 μl/min. Video was captured at a rate of 25 frames/sec. The velocity of the microspheres in the microchannels was calculated using an algorithm that tracked the movement of the fluorescent microspheres. The imaging system was able to measure particle velocities ranging from 0.2 mm/sec to 10 mm/sec. The range of flow velocities of interest in lymph vessels is between 1 mm/sec to 10 mm/sec; therefore our imaging system is sufficient to measure particle velocity in phantoms modeling lymphatic flow.

Rapid determination of tartaric acid in wines.

PubMed

Bastos, Sandra S T; Tafulo, Paula A R; Queirós, Raquel B; Matos, Cristina D; Sales, M Goreti F

2009-08-01

A flow-spectrophotometric method is proposed for the routine determination of tartaric acid in wines. The reaction between tartaric acid and vanadate in acetic media is carried out in flowing conditions and the subsequent colored complex is monitored at 475 nm. The stability of the complex and the corresponding formation constant are presented. The effect of wavelength and pH was evaluated by batch experiments. The selected conditions were transposed to a flow-injection analytical system. Optimization of several flow parameters such as reactor lengths, flow-rate and injection volume was carried out. Using optimized conditions, a linear behavior was observed up to 1000 microg mL(-1) tartaric acid, with a molar extinction coefficient of 450 L mg(-1) cm(-1) and +/- 1 % repeatability. Sample throughput was 25 samples per hour. The flow-spectrophotometric method was satisfactorily applied to the quantification of TA in wines from different sources. Its accuracy was confirmed by statistical comparison to the conventional Rebelein procedure and to a certified analytical method carried out in a routine laboratory.

A theoretical evaluation of rigid baffles in suppression of combustion instability

NASA Technical Reports Server (NTRS)

Baer, M. R.; Mitchell, C. E.

1976-01-01

An analytical technique for the prediction of the effects of rigid baffles on the stability of liquid propellant combustors is presented. A three dimensional combustor model characterized by a concentrated combustion source at the chamber injector and a constant Mach number nozzle is used. The linearized partial differential equations describing the unsteady flow field are solved by an eigenfunction matching method. Boundary layer corrections to this unsteady flow are used to evaluate viscous and turbulence effects within the flow. An integral stability relationship is then employed to predict the decay rate of the oscillations. Results show that sufficient dissipation exists to indicate that the proper mechanism of baffle damping is a fluid dynamic loss. The response of the dissipation model to varying baffle blade length, mean flow Mach number and oscillation amplitude is examined.

Non-domestic phosphorus release in rivers during low-flow: Mechanisms and implications for sources identification

NASA Astrophysics Data System (ADS)

Dupas, Rémi; Tittel, Jörg; Jordan, Phil; Musolff, Andreas; Rode, Michael

2018-05-01

A common assumption in phosphorus (P) load apportionment studies is that P loads in rivers consist of flow independent point source emissions (mainly from domestic and industrial origins) and flow dependent diffuse source emissions (mainly from agricultural origin). Hence, rivers dominated by point sources will exhibit highest P concentration during low-flow, when flow dilution capacity is minimal, whereas rivers dominated by diffuse sources will exhibit highest P concentration during high-flow, when land-to-river hydrological connectivity is maximal. Here, we show that Soluble Reactive P (SRP) concentrations in three forested catchments free of point sources exhibited seasonal maxima during the summer low-flow period, i.e. a pattern expected in point source dominated areas. A load apportionment model (LAM) is used to show how point sources contribution may have been overestimated in previous studies, because of a biogeochemical process mimicking a point source signal. Almost twenty-two years (March 1995-September 2016) of monthly monitoring data of SRP, dissolved iron (Fe) and nitrate-N (NO3) were used to investigate the underlying mechanisms: SRP and Fe exhibited similar seasonal patterns and opposite to that of NO3. We hypothesise that Fe oxyhydroxide reductive dissolution might be the cause of SRP release during the summer period, and that NO3 might act as a redox buffer, controlling the seasonality of SRP release. We conclude that LAMs may overestimate the contribution of P point sources, especially during the summer low-flow period, when eutrophication risk is maximal.

Influence of Magnetic Topology on Mars' Ionospheric Structure

NASA Astrophysics Data System (ADS)

Adams, D.; Xu, S.; Mitchell, D. L.; Fillingim, M. O.; Lillis, R. J.; Andersson, L.; Fowler, C. M.; Benna, M.; Connerney, J. E. P.; Elrod, M. K.; Girazian, Z.; Vogt, M.

2017-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been in Mars' orbit since September 2014 (>1 Mars year), and has collected particle and field data within the ionosphere over wide ranges of altitudes, latitudes, and local times. This study uses MAVEN data to (1) analyze the influence of magnetic topology on the day-side ionosphere and (2) identify the sources of the night-side ionosphere. On the day side, magnetic strength and elevation angle are commonly used as proxies for magnetic topology. In this study, we use pitch-angle-resolved suprathermal electron measurements by the Solar Wind Electron Analyzer (SWEA) to directly deduce the magnetic topology instead of using a proxy. On the night side, the main sources of ionospheric plasma are bulk transport and plasma pressure gradient flow from the day side, as well as in situ production by electron impact ionization (EII). Plasma transport at Mars is complicated by the presence of intense crustal magnetic fields. Closed crustal magnetic fields form isolated plasma environments ("miniature magnetospheres") that inhibit external sources of cold ionospheric plasma as well as suprathermal (ionizing) electrons. Inside these closed magnetic loops, we study how the plasma evolves with bulk flow transport as the only source. By comparing closed and non-closed magnetic configurations, the effects of pressure gradient flow and EII can be distinguished. Finally, the densities of O2+, O+, and NO+, as measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS), are examined. Inside miniature magnetospheres on the night side, the abundances of these species are found to be primarily controlled by the different recombination rates, as there is little plasma created within these regions by EII or transported from the neighboring regions by plasma pressure gradient flow.

Jasminum polyanthum Franch. as a natural source of (-)-methyl jasmonate: an alternative to the use of the synthetic standard.

PubMed

Blanch, Gracia Patricia; Flores, Gema; Caja, Maria del Mar; Ruiz del Castillo, Maria Luisa

2009-01-01

Methyl jasmonate (MJ) contains two chiral centres at C-3 and C-7 in its chemical structure, which implies that it can exist in four possible stereoisomeric forms, namely (+)-MJ, (-)-MJ, (+)-epiMJ and (-)-epiMJ. The absolute configuration of the two side chains of MJ affects the biological activity associated with this compound. To isolate pure (-)-MJ from a natural source, Jasminum polyanthum Franch., with the intention of increasing the knowledge about its biological properties, including its effect on the biosynthesis of plant metabolites. The method used was based on steam distillation extraction (SDE) as an extraction technique followed by high-performance liquid chromatography (HPLC) as a purification procedure. The HPLC flow-rate as well as the number of fractions accumulated were optimised to achieve the concentration and purity required. The employment of 0.3 mL/min as HPLC flow-rate and the accumulation of three HPLC fractions allowed the required enantiomeric purity (95%) and concentration (0.36 mg/L in each HPLC fraction) to efficiently obtain (-)-methyl jasmonate from Jasminum polyanthum Franch. to be achieved. The approach proposed may enable the properties and effect of pure (-)-MJ on plant responses to be studied. The use of a natural source to obtain (-)-MJ is presented as an alternative to the enantioselective synthesis and enantiomeric resolution from the standard racaemic mixture.

Strontium Co-precipitation During Biomineralization of Calcite in Porous Media Using Differing Treatment Strategies

NASA Astrophysics Data System (ADS)

Lauchnor, E. G.; Schultz, L.; Mitchell, A.; Cunningham, A. B.; Gerlach, R.

2013-12-01

The process of ureolytically-induced calcium carbonate mineralization has been shown in laboratory studies to be effective in co-precipitation of heavy metals and radionuclides. During this process, the microbially catalyzed hydrolysis of urea increases alkalinity and pH, thus promoting CaCO3 precipitation in the presence of dissolved calcium. One proposed application of biomineralization includes the remediation of radionuclides such as strontium, which can be co-precipitated in situ within calcite. Strontium is of concern at several US DOE sites where it is a radioactive product of uranium fission and groundwater contaminant. Our research focuses on promoting attached bacteria, or biofilms, in subsurface environments where they serve as immobilized catalysts in biomineralization and can aide in co-precipitation of some contaminants. In this work, flat plate reactors with 1 mm etched flow channels designed to mimic a porous medium environment were used. Reactors were inoculated with the model ureolytic bacterium Sporosarcina pasteurii and addition of urea, calcium and strontium containing fluid was performed to induce biomineralization. Continuous flow and stopped-flow injection strategies were investigated to evaluate differences in strontium co-precipitation efficiency. During stopped-flow experiments, injection of cementation fluid containing urea, Ca2+ and Sr2+ was alternated with growth nutrients for stimulation of microbial activity. Control parameters such as urea and calcium concentration and injection flow rate are currently being varied to optimize rate and efficiency of strontium co-precipitation. Ureolytically induced calcite precipitation and strontium incorporation in the calcite was verified by chemical and mineralogical analyses, including X-ray diffraction and ICP-MS. Strontium co-precipitation efficiency was similar under different injection strategies. Alternating calcium-containing fluid with growth nutrients allowed for continued viability of the ureolytic biofilms and also insured that bacterially-induced mineralization was still occurring after 60 days of operation. Batch rate experiments demonstrated the effective use of alternative sources of substrates for biomineralization, which are economical for use in field-scale remediation. Fertilizer has been shown to be an effective urea source and several economical carbon and nutrient sources such as molasses and whey are being evaluated for stimulating ureolytic microorganisms. This research demonstrates on a bench scale the use of different injection strategies to control precipitation of calcium carbonate, as well as the feasibility of strontium co-precipitation in porous media. The ongoing optimization of strontium co-precipitation will lead to additional work on potential remediation of other heavy metal groundwater contaminants.

Culvert analysis program for indirect measurement of discharge

USGS Publications Warehouse

Fulford, Janice M.; ,

1993-01-01

A program based on the U.S. Geological Survey (USGS) methods for indirectly computing peak discharges through culverts allows users to employ input data formats used by the water surface profile program (WSPRO). The program can be used to compute discharge rating surfaces or curves that describe the behavior of flow through a particular culvert or to compute discharges from measurements of upstream of the gradually varied flow equations and has been adapted slightly to provide solutions that minimize the need for the user to determine between different flow regimes. The program source is written in Fortran 77 and has been run on mini-computers and personal computers. The program does not use or require graphics capability, a color monitor, or a mouse.

Sandia’s Current Energy Conversion module for the Flexible-Mesh Delft3D flow solver v. 1.0

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

Chartand, Chris; Jagers, Bert

The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around a MHK arrays while quantifying environmental responses. As an augmented version of the Dutch company, Deltares’s, environmental hydrodynamics code, Delft3D, SNL-Delft3D-CEC-FM includes a new module that simulates energy conversion (momentum withdrawal) by MHK current energy conversion devices with commensurate changes in the turbulent kinetic energy and its dissipation rate. SNL-Delft3D-CEC-FM modified the Delft3D flexible mesh flow solver, DFlowFM.

Computational and Experimental Investigation of Contaminant Plume Response to DNAPL Source Zone Architecture and Depletion in Porous and Fractured Media

DTIC Science & Technology

2013-09-01

Mass in the Rock Matrix. Table 4.8.5.1: Flow and Transport Parameters Used for TCE Dissolution Modeling in Discrete Fracture Approach. Table 4.8.5.2...represent the flow rate over time. Figure 4.8.4.5: The Profile of Estimated Diffusing TCE Front into the Rock Matrix. Figure 4.8.5.1: a) Mesh Used for TCE...fractured rocks . The work of Illman et al. (2009) motivates us to conduct a laboratory fractured rock block experiment in which a large number of pumping

Three dimensional radiative flow of magnetite-nanofluid with homogeneous-heterogeneous reactions

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Rashid, Madiha; Alsaedi, Ahmed

2018-03-01

Present communication deals with the effects of homogeneous-heterogeneous reactions in flow of nanofluid by non-linear stretching sheet. Water based nanofluid containing magnetite nanoparticles is considered. Non-linear radiation and non-uniform heat sink/source effects are examined. Non-linear differential systems are computed by Optimal homotopy analysis method (OHAM). Convergent solutions of nonlinear systems are established. The optimal data of auxiliary variables is obtained. Impact of several non-dimensional parameters for velocity components, temperature and concentration fields are examined. Graphs are plotted for analysis of surface drag force and heat transfer rate.

Numerical investigations of the unsteady blood flow in the end-to-side arteriovenous fistula for hemodialysis.

PubMed

Jodko, Daniel; Obidowski, Damian; Reorowicz, Piotr; Jóźwik, Krzysztof

2016-01-01

The aim of this study was to investigate the blood flow in the end-to-side arteriovenous (a-v) fistula, taking into account its pulsating nature and the patient-specific geometry of blood vessels. Computational Fluid Dynamics (CFD) methods were used for this analysis. DICOM images of the fistula, obtained from the angio-computed tomography, were a source of the data applied to develop a 3D geometrical model of the fistula. The model was meshed, then the ANSYS CFX v. 15.0 code was used to perform simulations of the flow in the vessels under analysis. Mesh independence tests were conducted. The non-Newtonian rheological model of blood and the Shear Stress Transport model of turbulence were employed. Blood vessel walls were assumed to be rigid. Flow patterns, velocity fields, the volume flow rate, the wall shear stress (WSS) propagation on particular blood vessel walls were shown versus time. The maximal value of the blood velocity was identified in the anastomosis - the place where the artery is connected to the vein. The flow rate was calculated for all veins receiving blood. The blood flow in the geometrically complicated a-v fistula was simulated. The values and oscillations of the WSS are the largest in the anastomosis, much lower in the artery and the lowest in the cephalic vein. A strong influence of the mesh on the results concerning the maximal and area-averaged WSS was shown. The relation between simulations of the pulsating and stationary flow under time-averaged flow conditions was presented.

Optimization of a Nafion Membrane-Based System for Removal of Chloride and Fluoride from Lunar Regolith-Derived Water

NASA Technical Reports Server (NTRS)

Anthony, Stephen M.; Santiago-Maldonado, Edgardo; Captain, James G.; Pawate, Ashtamurthy S.; Kenis, Paul J. A.

2012-01-01

A long-term human presence in space will require self-sustaining systems capable of producing oxygen and potable water from extraterrestrial sources. Oxygen can be extracted from lunar regolith, and water contaminated with hydrochloric and hydrofluoric acids is produced as an intermediate in this process. We investigated the ability of Nafion proton exchange membranes to remove hydrochloric and hydrofluoric acids from water. The effect of membrane thickness, product stream flow rate, and acid solution temperature and concentration on water flux, acid rejection, and water and acid activity were studied. The conditions that maximized water transport and acid rejection while minimizing resource usage were determined by calculating a figure of merit. Water permeation is highest at high solution temperature and product stream flow rate across thin membranes, while chloride and fluoride permeation are lowest at low acid solution temperature and concentration across thin membranes. The figure of merit varies depending on the starting acid concentration; at low concentration, the figure of merit is highest across a thin membrane, while at high concentration, the figure of merit is highest at low solution temperature. In all cases, the figure of merit increases with increasing product stream flow rate.

Controlled boiling on Enceladus. 1. Model of the vapor-driven jets

NASA Astrophysics Data System (ADS)

Nakajima, Miki; Ingersoll, Andrew P.

2016-07-01

Plumes of water vapor and ice particles have been observed from the so-called tiger stripes at the south polar terrain (SPT) of Saturn's satellite, Enceladus. The observed high salinity (∼0.5-2%) of the ice particles in the plumes may indicate that the plumes originate from a subsurface liquid ocean. Additionally, the SPT is the source of strong infrared radiation (∼4.2 GW), which is especially intense near (within tens of meters) the tiger stripes. This could indicate that the radiation is associated with plume activity, but the connection remains unclear. Here we investigate the constraints that plume observations place on the widths of the cracks, the depth to the liquid-vapor interface, and the mechanisms controlling plume variability. We solve the fluid dynamics of the flow in the crack and the interaction between the flow and ice walls assuming that the flows of water vapor and ice particles originate from a few kilometers deep liquid ocean. For a crack with a uniform width, we find that our model could explain the observed vapor mass flow rate of the plumes when the crack width is 0.05-0.075 m. A wider crack is not favorable because it would produce a higher vapor mass flow rate than the observed value, but it may be allowed if there are some flows that do not reach the surface of Enceladus either due to condensation on the icy walls or the tortuosity of the crack. The observed heat flow can be explained if the total crack length is approximately 1.7 × 500 km. A tapering crack (a crack which is ∼1 m wide at the bottom of the flow and sharply becomes 0.05-0.075 m at shallower depths) can also explain the observed vapor mass flow rate and heat flow. Widths of 1 m or more are necessary to avoid freezing at the liquid-vapor interface, as shown in our paired paper (Ingersoll and Nakajima [2016] Icarus). The observed intense heat flow along the tiger stripes can be explained by the latent heat release due to vapor condensation onto the ice walls near the surface. The resulting buildup of ice causes the vents to seal themselves on time scales less than a year. We also find that the ice to vapor ratio of the plumes is sensitive to the ice mass fraction at the bottom of the flow (liquid-vapor interface). We find that the total mass flow rate of the plumes becomes larger when the crack width is larger, which is consistent with the observation that the flow rate increases near the orbital apocenter, where the crack is expected to be widest.

Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

NASA Astrophysics Data System (ADS)

Smith, Hugh G.; Sheridan, Gary J.; Nyman, Petter; Child, David P.; Lane, Patrick N. J.; Hotchkis, Michael A. C.; Jacobsen, Geraldine E.

2012-02-01

Fine sediment supply has been identified as an important factor contributing to the initiation of runoff-generated debris flows after fire. However, despite the significance of fines for post-fire debris flow generation, no investigations have sought to quantify sources of this material in debris flow affected catchments. In this study, we employ fallout radionuclides ( 137Cs, 210Pb ex and 239,240Pu) as tracers to measure proportional contributions of fine sediment (< 10 μm) from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post-fire debris flows in two forest catchments in southeastern Australia. While 137Cs and 210Pb ex have been widely used in sediment tracing studies, application of Pu as a tracer represents a recent development and was limited to only one catchment. The ranges in estimated proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment were 22-69% and 32-74%. The greater susceptibility of 210Pb ex to apparent reductions in the ash content of channel deposits relative to hillslope sources resulted in its exclusion from the final analysis. No systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points. Instead, spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits. Linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges. Hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions. This indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments. In contrast, material stored within channels that was deposited during subsequent surges was predominantly channel-derived. The results demonstrate that fallout radionuclide tracers may provide unique information on changing source contributions of fine sediment during debris flow events.

Comparison of PDF and Moment Closure Methods in the Modeling of Turbulent Reacting Flows

NASA Technical Reports Server (NTRS)

Norris, Andrew T.; Hsu, Andrew T.

1994-01-01

In modeling turbulent reactive flows, Probability Density Function (PDF) methods have an advantage over the more traditional moment closure schemes in that the PDF formulation treats the chemical reaction source terms exactly, while moment closure methods are required to model the mean reaction rate. The common model used is the laminar chemistry approximation, where the effects of turbulence on the reaction are assumed negligible. For flows with low turbulence levels and fast chemistry, the difference between the two methods can be expected to be small. However for flows with finite rate chemistry and high turbulence levels, significant errors can be expected in the moment closure method. In this paper, the ability of the PDF method and the moment closure scheme to accurately model a turbulent reacting flow is tested. To accomplish this, both schemes were used to model a CO/H2/N2- air piloted diffusion flame near extinction. Identical thermochemistry, turbulence models, initial conditions and boundary conditions are employed to ensure a consistent comparison can be made. The results of the two methods are compared to experimental data as well as to each other. The comparison reveals that the PDF method provides good agreement with the experimental data, while the moment closure scheme incorrectly shows a broad, laminar-like flame structure.

Effect of the gas flow rate on the spatiotemporal distribution of Ar(1s5) absolute densities in a ns pulsed plasma jet impinging on a glass surface

NASA Astrophysics Data System (ADS)

Gazeli, K.; Bauville, G.; Fleury, M.; Jeanney, P.; Neveu, O.; Pasquiers, S.; Santos Sousa, J.

2018-06-01

This work presents spatial (axial-z and transversal-y) and temporal distributions of Ar(1s5) metastable absolute densities in an atmospheric pressure argon micro-plasma jet impinging on an ungrounded glass surface. Guided streamers are generated with a DBD device driven by pulsed positive high voltages of 6 kV in amplitude, 224 +/- 3 ns in FWHM and 20 kHz in frequency. The argon flow rate is varied between 200 and 600 sccm. The glass plate is placed at 5 mm away from the reactor’s nozzle and perpendicular to the streamers propagation. At these conditions, a diffuse stable discharge is established after the passage of the streamers allowing the quantification of the Ar(1s5) absolute density by means of a conventional TDLAS technique coupled with emission spectroscopy and ICCD imaging. The good reproducibility of the absorption signals is demonstrated. The experiments show the strong dependence of the maximum density ({0.5-4}× {10}13 {{{cm}}}-3) on the gas flow rate and the axial and transversal position. At 200 sccm, high maximum densities (> 2.4× {10}13 {{{cm}}}-3) are obtained in a small area close to the plasma source, while with increasing flow rate this area expands towards the glass plate. In the transversal direction, density maxima are obtained in a small zone around the propagation axis of the streamers. Finally, a noticeable increase is measured on the Ar(1s5) effective lifetime close to the glass surface by varying the flow rate from 200 to 600 sccm. In overall, the effective lifetime varies between ∼25 and ∼550 ns, depending on the gas flow rate and the values of z and y coordinates. The results obtained suggest that the present system can be implemented in various applications and particularly in what concerns the detection of weakly volatile organic compounds present in trace amounts on different surfaces.

EVALUATION OF ENGINEERING CONTROLS FOR THE MIXING OF FLAVORINGS CONTAINING DIACETYL AND OTHER VOLATILE INGREDIENTS

PubMed Central

Hirst, Deborah V.L.; Dunn, Kevin H.; Shulman, Stanley A.; Hammond, Duane R.; Sestito, Nicholas

2015-01-01

Exposures to diacetyl, a primary ingredient of butter flavoring, have been shown to cause respiratory disease among workers who mix flavorings. This study focused on evaluating ventilation controls designed to reduce emissions from the flavor mixing tanks, the major source of diacetyl in the plants. Five exhaust hood configurations were evaluated in the laboratory: standard hinged lid-opened, standard hinged lid-closed, hinged lid-slotted, dome with 38-mm gap, and dome with 114-mm gap. Tracer gas tests were performed to evaluate quantitative capture efficiency for each hood. A perforated copper coil was used to simulate an area source within the 1.2-meter diameter mixing tank. Capture efficiencies were measured at four hood exhaust flow rates (2.83, 5.66, 11.3, and 17.0 cubic meters per minute) and three cross draft velocities (0, 30, and 60 meters per minute). All hoods evaluated performed well with capture efficiencies above 90% for most combinations of exhaust volume and cross drafts. The standard hinged lid was the least expensive to manufacture and had the best average capture efficiency (over 99%) in the closed configuration for all exhaust flow rates and cross drafts. The hinged lid-slotted hood had some of the lowest capture efficiencies at the low exhaust flow rates compared to the other hood designs. The standard hinged lid performed well, even in the open position, and it provided a flexible approach to controlling emissions from mixing tanks. The dome hood gave results comparable to the standard hinged lid but it is more expensive to manufacture. The results of the study indicate that emissions from mixing tanks used in the production of flavorings can be controlled using simple inexpensive exhaust hoods. PMID:24649880

Impact of Air Injection on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Tom

2007-01-01

The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

Fine structure of microwave spike bursts and associated cross-field energy transport

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Dulk, G. A.; Pritchett, P. L.

1988-01-01

The characteristics of the maser emission from a driven system where energetic electrons continue to flow through the source region is investigated using electronic particle simulations. It is shown that, under appropriate conditions, the maser can efficiently radiate a significant portion of the energy of the fast electrons in a very short time. The radiation is emitted in pulses even though the flow of electrons through the system is at a constant rate. The mission of these pulses is proposed as the source of the fine structure. Under other conditions the dominant maser emission changes from fundamental x-mode to either fundamental z-mode or to electrostatic upper hybrid or Bernstein modes. The bulk of the emission from the maser instability cannot propagate across field lines in this regime, and hence strong local plasma heating is expected, with little energy transport across the magnetic field lines.

Near-field transport of {sup 129}I from a point source in an in-room disposal vault

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

Kolar, M.; Leneveu, D.M.; Johnson, L.H.

1995-12-31

A very small number of disposal containers of heat generating nuclear waste may have initial manufacturing defects that would lead to pin-hole type failures at the time of or shortly after emplacement. For sufficiently long-lived containers, only the initial defects need to be considered in modeling of release rates from the disposal vault. Two approaches to modeling of near-field mass transport from a single point source within a disposal room have been compared: the finite-element code MOTIF (A Model Of Transport In Fractured/porous media) and a boundary integral method (BIM). These two approaches were found to give identical results formore » a simplified model of the disposal room without groundwater flow. MOTIF has then been used to study the effects of groundwater flow on the mass transport out of the emplacement room.« less

Radiation effects on the mixed convection flow induced by an inclined stretching cylinder with non-uniform heat source/sink.

PubMed

Hayat, Tasawar; Qayyum, Sajid; Alsaedi, Ahmed; Asghar, Saleem

2017-01-01

This study investigates the mixed convection flow of Jeffrey liquid by an impermeable inclined stretching cylinder. Thermal radiation and non-uniform heat source/sink are considered. The convective boundary conditions at surface are imposed. Nonlinear expressions of momentum, energy and concentration are transformed into dimensionless systems. Convergent homotopic solutions of the governing systems are worked out by employing homotopic procedure. Impact of physical variables on the velocity, temperature and concentration distributions are sketched and discussed. Numerical computations for skin friction coefficient, local Nusselt and Sherwood numbers are carried out. It is concluded that velocity field enhances for Deborah number while reverse situation is observed regarding ratio of relaxation to retardation times. Temperature and heat transfer rate are enhanced via larger thermal Biot number. Effect of Schmidt number on the concentration and local Sherwood number is quite reverse.

Radiation effects on the mixed convection flow induced by an inclined stretching cylinder with non-uniform heat source/sink

PubMed Central

Hayat, Tasawar; Qayyum, Sajid; Alsaedi, Ahmed; Asghar, Saleem

2017-01-01

This study investigates the mixed convection flow of Jeffrey liquid by an impermeable inclined stretching cylinder. Thermal radiation and non-uniform heat source/sink are considered. The convective boundary conditions at surface are imposed. Nonlinear expressions of momentum, energy and concentration are transformed into dimensionless systems. Convergent homotopic solutions of the governing systems are worked out by employing homotopic procedure. Impact of physical variables on the velocity, temperature and concentration distributions are sketched and discussed. Numerical computations for skin friction coefficient, local Nusselt and Sherwood numbers are carried out. It is concluded that velocity field enhances for Deborah number while reverse situation is observed regarding ratio of relaxation to retardation times. Temperature and heat transfer rate are enhanced via larger thermal Biot number. Effect of Schmidt number on the concentration and local Sherwood number is quite reverse. PMID:28441392

Improved security monitoring method for network bordary

NASA Astrophysics Data System (ADS)

Gao, Liting; Wang, Lixia; Wang, Zhenyan; Qi, Aihua

2013-03-01

This paper proposes a network bordary security monitoring system based on PKI. The design uses multiple safe technologies, analysis deeply the association between network data flow and system log, it can detect the intrusion activities and position invasion source accurately in time. The experiment result shows that it can reduce the rate of false alarm or missing alarm of the security incident effectively.

Hybrid Method for Power Control Simulation of a Single Fluid Plasma Thruster

NASA Astrophysics Data System (ADS)

Jaisankar, S.; Sheshadri, T. S.

2018-05-01

Propulsive plasma flow through a cylindrical-conical diverging thruster is simulated by a power controlled hybrid method to obtain the basic flow, thermodynamic and electromagnetic variables. Simulation is based on a single fluid model with electromagnetics being described by the equations of potential Poisson, Maxwell and the Ohm's law while the compressible fluid dynamics by the Navier Stokes in cylindrical form. The proposed method solved the electromagnetics and fluid dynamics separately, both to segregate the two prominent scales for an efficient computation and for the delivery of voltage controlled rated power. The magnetic transport is solved for steady state while fluid dynamics is allowed to evolve in time along with an electromagnetic source using schemes based on generalized finite difference discretization. The multistep methodology with power control is employed for simulating fully ionized propulsive flow of argon plasma through the thruster. Numerical solution shows convergence of every part of the solver including grid stability causing the multistep hybrid method to converge for a rated power delivery. Simulation results are reasonably in agreement with the reported physics of plasma flow in the thruster thus indicating the potential utility of this hybrid computational framework, especially when single fluid approximation of plasma is relevant.

The simulated air flow pattern around a moving animal transport vehicle as the basis for a prospective biosecurity risk assessment.

PubMed

Seedorf, Jens; Schmidt, Ralf-Gunther

2017-08-01

Research that investigates bioaerosol emissions from animal transport vehicles (ATVs) and their importance in the spread of harmful airborne agents while the ATVs travel on roads is limited. To investigate the dynamical behaviour of theoretically released particles from a moving ATV, the open-source computational fluid dynamics (CFD) software OpenFOAM was used to calculate the external and internal air flow fields with passive and forced ventilated openings of a common ATV moving at a speed of 80 km/h. In addition to a computed flow rate of approximately 40,000 m 3 /h crossing the interior of the ATV, the visualization of the trajectories has demonstrated distinct patterns of the spatial distribution of potentially released bioaerosols in the vicinity of the ATV. Although the front openings show the highest air flow to the outside, the recirculations of air masses between the interior of the ATV and the atmosphere also occur, which complicate the emission and the dispersion characterizations. To specify the future emission rates of ATVs, a database of bioaerosol concentrations within the ATV is necessary in conjunction with high-performance computing resources to simulate the potential dispersion of bioaerosols in the environment.

Performance evaluation of a ground-source heat pump system utilizing a flowing well and estimation of suitable areas for its installation in Aizu Basin, Japan

NASA Astrophysics Data System (ADS)

Shrestha, Gaurav; Uchida, Youhei; Kuronuma, Satoru; Yamaya, Mutsumi; Katsuragi, Masahiko; Kaneko, Shohei; Shibasaki, Naoaki; Yoshioka, Mayumi

2017-08-01

Development of a ground-source heat pump (GSHP) system with higher efficiency, and evaluation of its operating performance, is essential to expand the growth of GSHP systems in Japan. A closed-loop GSHP system was constructed utilizing a flowing (artesian) well as a ground heat exchanger (GHE). The system was demonstrated for space-heating and space-cooling of a room (area 126.7 m2) in an office building. The average coefficient of performance was found to be 4.5 for space-heating and 8.1 for space-cooling. The maximum heat exchange rate was 70.8 W/m for space-heating and 57.6 W/m for space-cooling. From these results, it was determined that a GSHP system with a flowing well as a GHE can result in higher performance. With this kind of highly efficient system, energy saving and cost reduction can be expected. In order to assess appropriate locations for the installation of similar kinds of GSHP systems in Aizu Basin, a suitability map showing the distribution of groundwater up-flowing areas was prepared based on the results of a regional-scale three-dimensional analytical model. Groundwater up-flowing areas are considered to be suitable because the flowing well can be constructed at these areas. Performance evaluation of the GSHP system utilizing the flowing well, in conjunction with the prepared suitability map for its installation, can assist in the promotion of GSHP systems in Japan.

Female reproductive success variation in a Pseudotsuga menziesii seed orchard as revealed by pedigree reconstruction from a bulk seed collection.

PubMed

El-Kassaby, Yousry A; Funda, Tomas; Lai, Ben S K

2010-01-01

The impact of female reproductive success on the mating system, gene flow, and genetic diversity of the filial generation was studied using a random sample of 801 bulk seed from a 49-clone Pseudotsuga menziesii seed orchard. We used microsatellite DNA fingerprinting and pedigree reconstruction to assign each seed's maternal and paternal parents and directly estimated clonal reproductive success, selfing rate, and the proportion of seed sired by outside pollen sources. Unlike most family array mating system and gene flow studies conducted on natural and experimental populations, which used an equal number of seeds per maternal genotype and thus generating unbiased inferences only on male reproductive success, the random sample we used was a representative of the entire seed crop; therefore, provided a unique opportunity to draw unbiased inferences on both female and male reproductive success variation. Selfing rate and the number of seed sired by outside pollen sources were found to be a function of female fertility variation. This variation also substantially and negatively affected female effective population size. Additionally, the results provided convincing evidence that the use of clone size as a proxy to fertility is questionable and requires further consideration.

On the sources of drift in a turbine-based spirometer.

PubMed

Ha, Jonathan K; Perlow, Daniel B; Yi, Byong Yong; Yu, Cedric X

2008-08-21

A systematic study on the sources of drift in a turbine-based spirometer (VMM-400) is presented. The study utilized an air-tight cylinder to pump air through the spirometer in a precise and programmable manner. Factors contributing to the drift were isolated and quantified. The drift due to imbalance in the electronics and the mechanical blade increased from 1% per breathing cycle to as much as 10% when the flow rate decreased from 0.24 to 0.08 l s(-1). A temperature difference of 16 degrees between the ambient and the air in the cylinder contributed about 3.5%. Most significantly, a difference in the breathing between inhalation and exhalation could produce a drift of 40% per breathing cycle, or even higher, depending on the extent of the breathing asymmetry. The origin of this drift was found to be rooted in the differential response of the spirometer to the different flow rate. Some ideas and suggestions for a correction strategy are provided for future work. The present work provides an important first step for eventual utilization of a spirometer as a stand-alone breathing surrogate for gating or tracking radiation therapy.

Selecting remediation goals by assessing the natural attenuation capacity of groundwater systems

USGS Publications Warehouse

Chapelle, Francis H.; Bradley, Paul M.

1998-01-01

Remediation goals for the source areas of a chlorinated ethene‐contaminated groundwater plume were identified by assessing the natural attenuation capacity of the aquifer system. The redox chemistry of the site indicates that sulfate‐reducing (H2 ∼ 2 nanomoles [nM]) per liter conditions near the contaminant source grade to Fe(III)‐reducing conditions (H2 ∼ 0.5 nM) downgradient of the source. Sulfate‐reducing conditions facilitate the initial reduction of perchloroethene (PCE) to trichloroethene (TCE), cis‐dichloroethene (cis‐DCE), and vinyl chloride (VC). Subsequently, the Fe(III)‐reducing conditions drive the oxidation of cis‐DCE and VC to carbon dioxide and chloride. This sequence gives the aquifer a substantial capacity for biodegrading chlorinated ethenes. Natural attenuation capacity (the slope of the steady‐state contaminant concentration profile along a groundwater flowpath) is a function of biodegradation rates, aquifer dispersive characteristics, and groundwater flow velocity. The natural attenuation capacity at the Kings Bay, Georgia site was assessed by estimating groundwater flowrates (∼0.23 ± 0.12 m/d) and aquifer dispersivity (∼1 m) from hydrologic and scale considerations. Apparent biodegradation rate constants (PCE and TCE ∼ 0.01 d−1; cis‐DCE and VC ∼ 0.025 d−1) were estimated from observed contaminant concentration changes along aquifer flowpaths. A boundary‐value problem approach was used to estimate levels to which contaminant concentrations in the source areas must be lowered (by engineered removal), or groundwater flow velocities lowered (by pumping) for the natural attenuation capacity to achieve maximum concentration limits (MCLs) prior to reaching a predetermined regulatory point of compliance.

Simulations of groundwater flow, transport, and age in Albuquerque, New Mexico, for a study of transport of anthropogenic and natural contaminants (TANC) to public-supply wells

USGS Publications Warehouse

Heywood, Charles E.

2013-01-01

Vulnerability to contamination from manmade and natural sources can be characterized by the groundwater-age distribution measured in a supply well and the associated implications for the source depths of the withdrawn water. Coupled groundwater flow and transport models were developed to simulate the transport of the geochemical age-tracers carbon-14, tritium, and three chlorofluorocarbon species to public-supply wells in Albuquerque, New Mexico. A separate, regional-scale simulation of transport of carbon-14 that used the flow-field computed by a previously documented regional groundwater flow model was calibrated and used to specify the initial concentrations of carbon-14 in the local-scale transport model. Observations of the concentrations of each of the five chemical species, in addition to water-level observations and measurements of intra-borehole flow within a public-supply well, were used to calibrate parameters of the local-scale groundwater flow and transport models. The calibrated groundwater flow model simulates the mixing of “young” groundwater, which entered the groundwater flow system after 1950 as recharge at the water table, with older resident groundwater that is more likely associated with natural contaminants. Complexity of the aquifer system in the zone of transport between the water table and public-supply well screens was simulated with a geostatistically generated stratigraphic realization based upon observed lithologic transitions at borehole control locations. Because effective porosity was simulated as spatially uniform, the simulated age tracers are more efficiently transported through the portions of the simulated aquifer with relatively higher simulated hydraulic conductivity. Non-pumping groundwater wells with long screens that connect aquifer intervals having different hydraulic heads can provide alternate pathways for contaminant transport that are faster than the advective transport through the aquifer material. Simulation of flow and transport through these wells requires time discretization that adequately represents periods of pumping and non-pumping. The effects of intra-borehole flow are not fully represented in the simulation because it employs seasonal stress periods, which are longer than periods of pumping and non-pumping. Further simulations utilizing daily pumpage data and model stress periods may help quantify the relative effects of intra-borehole versus advective aquifer flow on the transport of contaminants near the public-supply wells. The fraction of young water withdrawn from the studied supply well varies with simulated pumping rates due to changes in the relative contributions to flow from different aquifer intervals. The advective transport of dissolved solutes from a known contaminant source to the public-supply wells was simulated by using particle-tracking. Because of the transient groundwater flow field, scenarios with alternative contaminant release times result in different simulated-particle fates, most of which are withdrawn from the aquifer at wells that are between the source and the studied supply well. The relatively small effective porosity required to simulate advective transport from the simulated contaminant source to the studied supply well is representative of a preferential pathway and not the predominant aquifer effective porosity that was estimated by the calibration of the model to observed chemical-tracer concentrations.

Investigating source water Cryptosporidium concentration, species and infectivity rates during rainfall-runoff in a multi-use catchment.

PubMed

Swaffer, Brooke A; Vial, Hayley M; King, Brendon J; Daly, Robert; Frizenschaf, Jacqueline; Monis, Paul T

2014-12-15

Protozoan pathogens present a significant human health concern, and prevention of contamination into potable networks remains a key focus for drinking water providers. Here, we monitored the change in Cryptosporidium concentration in source water during high flow events in a multi-use catchment. Furthermore, we investigated the diversity of Cryptosporidium species/genotypes present in the source water, and delivered an oocyst infectivity fraction. There was a positive and significant correlation between Cryptosporidium concentration and flow (ρ = 0.756) and turbidity (ρ = 0.631) for all rainfall-runoff events, despite variable source water pathogen concentrations. Cell culture assays measured oocyst infectivity and suggested an overall source water infectious fraction of 3.1%. No infectious Cryptosporidium parvum or Cryptosporidium hominis were detected, although molecular testing detected C. parvum in 7% of the samples analysed using PCR-based molecular techniques. Twelve Cryptosporidium species/genotypes were identified using molecular techniques, and were reflective of the host animals typically found in remnant vegetation and agricultural areas. The inclusion of molecular approaches to identify Cryptosporidium species and genotypes highlighted the diversity of pathogens in water, which originated from various sources across the catchment. We suggest this mixing of runoff water from a range of landuses containing diverse Cryptosporidium hosts is a key explanation for the often-cited difficulty forming strong pathogen-indicator relationships. Copyright © 2014 Elsevier Ltd. All rights reserved.

A new lumped-parameter model for flow in unsaturated dual-porosity media

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

Zimmerman, Robert W.; Hadgu, Teklu; Bodvarsson, Gudmundur S.

A new lumped-parameter approach to simulating unsaturated flow processes in dual-porosity media such as fractured rocks or aggregated soils is presented. Fluid flow between the fracture network and the matrix blocks is described by a non-linear equation that relates the imbibition rate to the local difference in liquid-phase pressure between the fractures and the matrix blocks. Unlike a Warren-Root-type equation, this equation is accurate in both the early and late time regimes. The fracture/matrix interflow equation has been incorporated into an existing unsaturated flow simulator, to serve as a source/sink term for fracture gridblocks. Flow processes are then simulated usingmore » only fracture gridblocks in the computational grid. This new lumped-parameter approach has been tested on two problems involving transient flow in fractured/porous media, and compared with simulations performed using explicit discretization of the matrix blocks. The new procedure seems to accurately simulate flow processes in unsaturated fractured rocks, and typically requires an order of magnitude less computational time than do simulations using fully-discretized matrix blocks. [References: 37]« less

What do male singers mean by modal and falsetto register? An investigation of the glottal voice source.

PubMed

Salomão, Gláucia Laís; Sundberg, Johan

2009-01-01

The voice source differs between modal and falsetto registers, but singers often try to reduce the associated timbral differences, some even doubting that there are any. A total of 54 vowel sounds sung in falsetto and modal register by 13 male more or less experienced choir singers were analyzed by inverse filtering and electroglottography. Closed quotient, maximum flow declination rate, peak-to-peak airflow amplitude, normalized amplitude quotient, and level difference between the two lowest source spectrum partials were determined, and systematic differences were found in all singers, regardless of experience of singing. The observations seem compatible with previous observations of thicker vocal folds in modal register.

Effects of oblique air flow on burning rates of square ethanol pool fires.

PubMed

Tao, Changfa; He, Yaping; Li, Yuan; Wang, Xishi

2013-09-15

The effects of downward airflow on the burning rate and/or burning intensity of square alcohol pool fires for different airflow speeds and directions have been studied experimentally in an inclined wind tunnel. An interesting flame-wrapping phenomenon, caused by impingement of air flow, was observed. The mass burning intensity was found to increase with the airflow speed and the impinging angle. The fuel pan rim temperatures were also measured to study the effect of wind direction and speed on heat transfer from the flame to the fuel source. A model based on heat transfer analysis was developed to correlate the burning intensity with the pan rim characteristic temperature. A good correlation was established between the model results and the experimental results. Copyright © 2013 Elsevier B.V. All rights reserved.

Flow behavior and mobility of contaminated waste rock materials in the abandoned Imgi mine in Korea

NASA Astrophysics Data System (ADS)

Jeong, S. W.; Wu, Y.-H.; Cho, Y. C.; Ji, S. W.

2018-01-01

Incomplete mine reclamation can cause ecological and environmental impacts. This paper focuses on the geotechnical and rheological characteristics of waste rock materials, which are mainly composed of sand-size particles, potentially resulting in mass movement (e.g., slide or flow) and extensive acid mine drainage. To examine the potential for contaminant mobilization resulting from physicochemical processes in abandoned mines, a series of scenario-based debris flow simulations was conducted using Debris-2D to identify different hazard scenarios and volumes. The flow behavior of waste rock materials was examined using a ball-measuring rheometric apparatus, which can be adapted for large particle samples, such as debris flow. Bingham yield stresses determined in controlled shear rate mode were used as an input parameter in the debris flow modeling. The yield stresses ranged from 100 to 1000 Pa for shear rates ranging from 10- 5 to 102 s- 1. The results demonstrated that the lowest yield stress could result in high mobility of debris flow (e.g., runout distance > 700 m from the source area for 60 s); consequently, the material contaminants may easily reach the confluence of the Suyoung River through a mountain stream. When a fast slide or debris flow occurs at or near an abandoned mine area, it may result in extremely dynamic and destructive geomorphological changes. Even for the highest yield stress of debris flow simulation (i.e., τy = 2000 Pa), the released debris could flow into the mountain stream; therefore, people living near abandoned mines may become exposed to water pollution throughout the day. To maintain safety at and near abandoned mines, the physicochemical properties of waste materials should be monitored, and proper mitigation measures post-mining should be considered in terms of both their physical damage and chemical pollution potential.

Tracing groundwater recharge sources in the northwestern Indian alluvial aquifer using water isotopes (δ18O, δ2H and 3H)

NASA Astrophysics Data System (ADS)

Joshi, Suneel Kumar; Rai, Shive Prakash; Sinha, Rajiv; Gupta, Sanjeev; Densmore, Alexander Logan; Rawat, Yadhvir Singh; Shekhar, Shashank

2018-04-01

Rapid groundwater depletion from the northwestern Indian aquifer system in the western Indo-Gangetic basin has raised serious concerns over the sustainability of groundwater and the livelihoods that depend on it. Sustainable management of this aquifer system requires that we understand the sources and rates of groundwater recharge, however, both these parameters are poorly constrained in this region. Here we analyse the isotopic (δ18O, δ2H and tritium) compositions of groundwater, precipitation, river and canal water to identify the recharge sources, zones of recharge, and groundwater flow in the Ghaggar River basin, which lies between the Himalayan-fed Yamuna and Sutlej River systems in northwestern India. Our results reveal that local precipitation is the main source of groundwater recharge. However, depleted δ18O and δ2H signatures at some sites indicate recharge from canal seepage and irrigation return flow. The spatial variability of δ18O, δ2H, d-excess, and tritium reflects limited lateral connectivity due to the heterogeneous and anisotropic nature of the aquifer system in the study area. The variation of tritium concentration with depth suggests that groundwater above c. 80 mbgl is generally modern water. In contrast, water from below c. 80 mbgl is a mixture of modern and old waters, and indicates longer residence time in comparison to groundwater above c. 80 mbgl. Isotopic signatures of δ18O, δ2H and tritium suggest significant vertical recharge down to a depth of 320 mbgl. The spatial and vertical variations of isotopic signature of groundwater reveal two distinct flow patterns in the aquifer system: (i) local flow (above c. 80 mbgl) throughout the study area, and (ii) intermediate and regional flow (below c. 80 mbgl), where water recharges aquifers through large-scale lateral flow as well as vertical infiltration. The understanding of spatial and vertical recharge processes of groundwater in the study area provides important base-line knowledge for developing a sustainable groundwater management plan for the northwestern Indian aquifer system.

Influence of Nano-Fluid and Receiver Modification in Solar Parabolic Trough Collector Performance

NASA Astrophysics Data System (ADS)

Dharani Kumar, M.; Yuvaraj, G.; Balaji, D.; Pravinraj, R.; shanmugasundaram, Prabhu

2018-02-01

Utilization of natural renewal sources in India is very high over the past decades. Solar power is a prime source of energy available plenty in the world. In this work solar energy is modified into thermal energy by using copper absorber tube with fins. Due to low heat transfer coefficient results leading to higher thermal losses and lower thermal efficiency. In order to increase the heat transfer coefficient copper receiver tube with fins is used and as well as solid has higher thermal conductivity compare to fluid (Tio2) nano fluid is used to improve the heat transfer rate. The analyses have been carried out and take the account of parameters such as solar radiation with time variation, mass flow rate of water, temperatures.

Compact and Thermosensitive Nature-inspired Micropump

PubMed Central

Kim, Hyejeong; Kim, Kiwoong; Lee, Sang Joon

2016-01-01

Liquid transportation without employing a bulky power source, often observed in nature, has been an essential prerequisite for smart applications of microfluidic devices. In this report, a leaf-inspired micropump (LIM) which is composed of thermo-responsive stomata-inspired membrane (SIM) and mesophyll-inspired agarose cryogel (MAC) is proposed. The LIM provides a durable flow rate of 30 μl/h · cm2 for more than 30 h at room temperature without external mechanical power source. By adapting a thermo-responsive polymer, the LIM can smartly adjust the delivery rate of a therapeutic liquid in response to temperature changes. In addition, as the LIM is compact, portable, and easily integrated into any liquid, it might be utilized as an essential component in advanced hand-held drug delivery devices. PMID:27796357

Low temperature ECR-CVD of SiN X for III-V device passivation

NASA Astrophysics Data System (ADS)

Lee, J. W.; MacKenzie, K.; Johnson, D.; Shul, R. J.; Pearton, S. J.; Ren, F.

1998-06-01

Electron Cyclotron Resonance SiH 4/N 2 and SiH 4/NH 3 discharges have been employed for deposition of SiN X over a range of temperatures (25-120°C), source powers (200-700 W), pressures (15-40 mTorr), SiH 4 percentages (20-50%) and additional Ar flow rates (0-30 sccm). Deposition rates were in the range 100-700 Å min -1, with refractive indices of 1.7-2.3. The SiH 4/N 2 chemistry allowed a wider process window for tailoring the stress in the SiN X films, with chuck temperature, ECR source power, chamber pressure, SiH 4 composition and Ar addition all producing a transition from compressive to tensile stress, or vice-versa.

Impact of particle emissions of new laser printers on modeled office room

NASA Astrophysics Data System (ADS)

Koivisto, Antti J.; Hussein, Tareq; Niemelä, Raimo; Tuomi, Timo; Hämeri, Kaarle

2010-06-01

In this study, we present how an indoor aerosol model can be used to characterize particle emitter and predict influence of the source on indoor air quality. Particle size-resolved emission rates were quantified and the source's influence on indoor air quality was estimated by using office model simulations. We measured particle emissions from three modern laser printers in a flow-through chamber. Measured parameters were used as input parameters for an indoor aerosol model, which we then used to quantify the particle emission rates. The same indoor aerosol model was used to simulate the effect of the particle emission source inside an office model. The office model consists of a mechanically ventilated empty room and the particle source. The aerosol from the ventilation air was a filtered urban background aerosol. The effect of the ventilation rate was studied using three different ventilation ratios 1, 2 and 3 h -1. According to the model, peak emission rates of the printers exceeded 7.0 × 10 8 s -1 (2.5 × 10 12 h -1), and emitted mainly ultrafine particles (diameter less than 100 nm). The office model simulation results indicate that a print job increases ultrafine particle concentration to a maximum of 2.6 × 10 5 cm -3. Printer-emitted particles increased 6-h averaged particle concentration over eleven times compared to the background particle concentration.

Strength and deformation mechanisms of rhyolitic glass at lower seismogenic zone conditions

NASA Astrophysics Data System (ADS)

Proctor, B.; Lockner, D. A.; Lowenstern, J. B.; Beeler, N. M.

2017-12-01

Although its relevance to coseismic earthquake source properties is still debated, frictional melting and the production of quenched glass called pseudotachylyte is a recurring process in some earthquake source regions. To investigate how glassy materials affect the post- and interseismic- strength and stability of faults, rhyolitic obsidian gouges were sheared under dry and wet conditions from 200 °C to 300 °C at effective normal stresses up to 200 MPa. Velocity-stepping and slide-hold slide tests were performed for up to three days. Dry glass gouges exhibited a brittle rheology at all conditions tested, exhibiting friction values and microstructures consistent with siliciclastic materials. Likewise, wet glass gouges at 200 °C exhibited a brittle rheology. In contrast, wet gouges at 300 °C transitioned from brittle sliding to linear-viscous (Newtonian) flow at strain rates < 3x10-4 s-1, indicating melt-like behavior well below the equilibrium melting temperature. The melt ranged from 2.1x1011 to 2.6x1012 Pa-s. The molten gouges transitioned back to glass when strain rates were increased, which, in some cases, promoted extreme strengthening. The molten gouges were fully welded with rod-shaped microlites rotated and boudinaged into the flow direction. There was very little evidence for nucleation of new phases within the glass or metasomatic alteration. Fourier transform infrared spectroscopy along with electron backscatter imaging demonstrate that hydration of the glass by diffusion of pore water was the dominant process reducing the viscosity and promoting melt flow. As much as 5 wt% water diffused into the nominally anhydrous glass. These results may provide insight into postseismic-slip behaviors and challenge some interpretations of fault kinematics which assume pseudotachylyte formation and flow is solely coseismic.

A unified assessment of hydrological and biogeochemical responses in research watersheds in Eastern Puerto Rico using runoff-concentration relations

USGS Publications Warehouse

Stallard, Robert F.; Murphy, Sheila F.

2014-01-01

An examination of the relation between runoff rate, R, and concentration, C, of twelve major constituents in four small watersheds in eastern Puerto Rico demonstrates a consistent pattern of responses. For solutes that are not substantially bioactive (alkalinity, silica, calcium, magnesium, sodium, and chloride), the log(R)–log(C) relation is almost linear and can be described as a weighted average of two sources, bedrock weathering and atmospheric deposition. The slope of the relation for each solute depends on the respective source contributions to the total river load. If a solute were strictly derived from bedrock weathering, the slope would be −0.3 to −0.4, whereas if strictly derived from atmospheric deposition, the slope would be approximately −0.1. The bioactive constituents (dissolved organic carbon, nitrate, sulfate, and potassium), which are recycled by plants and concentrated in shallow soil, demonstrate nearly flat or downward-arched log(R)–log(C) relations. The peak of the arch represents a transition from dominantly soil-matrix flow to near-surface macropore flow, and finally to overland flow. At highest observed R (80 to >90 mm/h), essentially all reactive surfaces have become wetted, and the input rate of C becomes independent of R (log(R)–log(C) slope of –1). The highest R are tenfold greater than any previous study. Slight clockwise hysteresis for many solutes in the rivers with riparian zones or substantial hyporheic flows indicates that these settings may act as mixing end-members. Particulate constituents (suspended sediment and particulate organic carbon) show slight clockwise hysteresis, indicating mobilization of stored sediment during rising stage.

The contribution of skin blood flow in warming the skin after the application of local heat; the duality of the Pennes heat equation.

PubMed

Petrofsky, Jerrold; Paluso, Dominic; Anderson, Devyn; Swan, Kristin; Yim, Jong Eun; Murugesan, Vengatesh; Chindam, Tirupathi; Goraksh, Neha; Alshammari, Faris; Lee, Haneul; Trivedi, Moxi; Hudlikar, Akshay N; Katrak, Vahishta

2011-04-01

As predicted by the Pennes equation, skin blood flow is a major contributor to the removal of heat from an external heat source. This protects the skin from erythema and burns. But, for a person in a thermally neutral room, the skin is normally much cooler than arterial blood. Therefore, if skin blood flow (BF) increases, it should initially warm the skin paradoxically. To examine this phenomenon, 10 young male and female subjects participated in a series of experiments to examine the contribution of skin blood flow in the initial warming the skin after the application of local heat. Heat flow was measured by the use of a thermode above the brachioradialis muscle. The thermode was warmed by constant temperature water at 44°C entering the thermode at a water flow rate of 100 cm(3)/min. Skin temperature was measured by a thermistor and blood flow in the underlying skin was measured by a laser Doppler imager in single point mode. The results of the experiments showed that, when skin temperature is cool (31-32°C), the number of calories being transferred to the skin from the thermode cannot account for the rise in skin temperature alone. A significant portion of the rise in skin temperature is due to the warm arterialized blood traversing the skin from the core areas of the body. However, as skin temperature approaches central core temperature, it becomes less of a heat source and more of a heat sync such that when skin temperature is at or above core temperature, the blood flow to the skin, as predicted by Pennes, becomes a heat sync pulling heat from the thermode. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Shear band formation in plastic bonded explosive (PBX)

NASA Astrophysics Data System (ADS)

Dey, T. N.; Johnson, J. N.

1998-07-01

Adiabatic shear bands can be a source of ignition and lead to detonation. At low to moderate deformation rates, 10-1000 s-1, two other mechanisms can also give rise to shear bands. These mechanisms are: 1) softening caused by micro-cracking and 2) a constitutive response with a non-associated flow rule as is observed in granular material such as soil. Brittle behavior at small strains and the granular nature of HMX suggest that PBX-9501 constitutive behavior may be similar to sand. A constitutive model for the first of these mechanisms is studied in a series of calculations. This viscoelastic constitutive model for PBX-9501 softens via a statistical crack model. A sand model is used to provide a non-associated flow rule and detailed results will be reported elsewhere. Both models generate shear band formation at 1-2% strain at nominal strain rates at and below 1000 s-1. Shear band formation is suppressed at higher strain rates. Both mechanisms may accelerate the formation of adiabatic shear bands.

Theoretical study of turbulent channel flow - Bulk properties, pressure fluctuations, and propagation of electromagnetic waves

NASA Technical Reports Server (NTRS)

Canuto, V. M.; Hartke, G. J.; Battaglia, A.; Chasnov, J.; Albrecht, G. F.

1990-01-01

In this paper, we apply two theoretical turbulence models, DIA and the recent GISS model, to study properties of a turbulent channel flow. Both models provide a turbulent kinetic energy spectral function E(k) as the solution of a non-linear equation; the two models employ the same source function but different closures. The source function is characterized by a rate n sub s (k) which is derived from the complex eigenvalues of the Orr-Sommerfeld (OS) equation in which the basic flow is taken to be of a Poiseuille type. The O-S equation is solved for a variety of Reynolds numbers corresponding to available experimental data. A physical argument is presented whereby the central line velocity characterizing the basic flow, U0 sup L, is not to be identified with the U0 appearing in the experimental Reynolds number. The theoretical results are compared with two types of experimental data: (1) turbulence bulk properties, and (2) properties that depend strongly on the structure of the turbulence spectrum at low wave numbers. The only existing analytical expression for Pi (k) cannot be used in the present case because it applies to the case of a flat plate, not a finite channel.

In situ cosmogenic radiocarbon production and 2-D ice flow line modeling for an Antarctic blue ice area

NASA Astrophysics Data System (ADS)

Buizert, Christo; Petrenko, Vasilii V.; Kavanaugh, Jeffrey L.; Cuffey, Kurt M.; Lifton, Nathaniel A.; Brook, Edward J.; Severinghaus, Jeffrey P.

2012-06-01

Radiocarbon measurements at ice margin sites and blue ice areas can potentially be used for ice dating, ablation rate estimates and paleoclimatic reconstructions. Part of the measured signal comes from in situ cosmogenic 14C production in ice, and this component must be well understood before useful information can be extracted from 14C data. We combine cosmic ray scaling and production estimates with a two-dimensional ice flow line model to study cosmogenic 14C production at Taylor Glacier, Antarctica. We find (1) that 14C production through thermal neutron capture by nitrogen in air bubbles is negligible; (2) that including ice flow patterns caused by basal topography can lead to a surface 14C activity that differs by up to 25% from the activity calculated using an ablation-only approximation, which is used in all prior work; and (3) that at high ablation margin sites, solar modulation of the cosmic ray flux may change the strength of the dominant spallogenic production by up to 10%. As part of this effort we model two-dimensional ice flow along the central flow line of Taylor Glacier. We present two methods for parameterizing vertical strain rates, and assess which method is more reliable for Taylor Glacier. Finally, we present a sensitivity study from which we conclude that uncertainties in published cosmogenic production rates are the largest source of potential error. The results presented here can inform ongoing and future 14C and ice flow studies at ice margin sites, including important paleoclimatic applications such as the reconstruction of paleoatmospheric 14C content of methane.

A Detailed Study of Debris Flow Source Areas in the Northern Colorado Front Range.

NASA Astrophysics Data System (ADS)

Arana-Morales, A.; Baum, R. L.; Godt, J.

2014-12-01

Nearly continuous, heavy rainfall occurred during 9-13 September 2013 causing flooding and widespread landslides and debris flows in the northern Colorado Front Range. Whereas many recent studies have identified erosion as the most common process leading to debris flows in the mountains of Colorado, nearly all of the debris flows mapped in this event began as small, shallow landslides. We mapped the boundaries of 415 September 2013 debris flows in the Eldorado Springs and Boulder 7.5-minute quadrangles using 0.5-m-resolution satellite imagery. We characterized the landslide source areas of six debris flows in the field as part of an effort to identify what factors controlled their locations. Four were on a dip slope in sedimentary rocks in the Pinebrook Hills area, near Boulder, and the other two were in granitic rocks near Gross Reservoir. Although we observed no obvious geomorphic differences between the source areas and surrounding non-landslide areas, we noted several characteristics that the source areas all had in common. Slopes of the source areas ranged from 28° to 35° and most occurred on planar or slightly concave slopes that were vegetated with grass, small shrubs, and sparse trees. The source areas were shallow, irregularly shaped, and elongated downslope: widths ranged from 4 to 9 m, lengths from 6 to 40 m and depths ranged from 0.7 to 1.2 m. Colluvium was the source material for all of the debris flows and bedrock was exposed in the basal surface of all of the source areas. We observed no evidence for concentrated surface runoff upslope from the sources. Local curvature and roughness of bedrock and surface topography, and depth distribution and heterogeneity of the colluvium appear to have controlled the specific locations of these shallow debris-flow source areas. The observed distribution and characteristics of the source areas help guide ongoing efforts to model initiation of the debris flows.

Modeling of plasma and thermo-fluid transport in hybrid welding

NASA Astrophysics Data System (ADS)

Ribic, Brandon D.

Hybrid welding combines a laser beam and electrical arc in order to join metals within a single pass at welding speeds on the order of 1 m min -1. Neither autonomous laser nor arc welding can achieve the weld geometry obtained from hybrid welding for the same process parameters. Depending upon the process parameters, hybrid weld depth and width can each be on the order of 5 mm. The ability to produce a wide weld bead increases gap tolerance for square joints which can reduce machining costs and joint fitting difficulty. The weld geometry and fast welding speed of hybrid welding make it a good choice for application in ship, pipeline, and aerospace welding. Heat transfer and fluid flow influence weld metal mixing, cooling rates, and weld bead geometry. Cooling rate affects weld microstructure and subsequent weld mechanical properties. Fluid flow and heat transfer in the liquid weld pool are affected by laser and arc energy absorption. The laser and arc generate plasmas which can influence arc and laser energy absorption. Metal vapors introduced from the keyhole, a vapor filled cavity formed near the laser focal point, influence arc plasma light emission and energy absorption. However, hybrid welding plasma properties near the opening of the keyhole are not known nor is the influence of arc power and heat source separation understood. A sound understanding of these processes is important to consistently achieving sound weldments. By varying process parameters during welding, it is possible to better understand their influence on temperature profiles, weld metal mixing, cooling rates, and plasma properties. The current literature has shown that important process parameters for hybrid welding include: arc power, laser power, and heat source separation distance. However, their influence on weld temperatures, fluid flow, cooling rates, and plasma properties are not well understood. Modeling has shown to be a successful means of better understanding the influence of processes parameters on heat transfer, fluid flow, and plasma characteristics for arc and laser welding. However, numerical modeling of laser/GTA hybrid welding is just beginning. Arc and laser welding plasmas have been previously analyzed successfully using optical emission spectroscopy in order to better understand arc and laser plasma properties as a function of plasma radius. Variation of hybrid welding plasma properties with radial distance is not known. Since plasma properties can affect arc and laser energy absorption and weld integrity, a better understanding of the change in hybrid welding plasma properties as a function of plasma radius is important and necessary. Material composition influences welding plasma properties, arc and laser energy absorption, heat transfer, and fluid flow. The presence of surface active elements such as oxygen and sulfur can affect weld pool fluid flow and bead geometry depending upon the significance of heat transfer by convection. Easily vaporized and ionized alloying elements can influence arc plasma characteristics and arc energy absorption. The effects of surface active elements on heat transfer and fluid flow are well understood in the case of arc and conduction mode laser welding. However, the influence of surface active elements on heat transfer and fluid flow during keyhole mode laser welding and laser/arc hybrid welding are not well known. Modeling has been used to successfully analyze the influence of surface active elements during arc and conduction mode laser welding in the past and offers promise in the case of laser/arc hybrid welding. A critical review of the literature revealed several important areas for further research and unanswered questions. (1) The understanding of heat transfer and fluid flow during hybrid welding is still beginning and further research is necessary. (2) Why hybrid welding weld bead width is greater than that of laser or arc welding is not well understood. (3) The influence of arc power and heat source separation distance on cooling rates during hybrid welding are not known. (4) Convection during hybrid welding is not well understood despite its importance to weld integrity. (5) The influence of surface active elements on weld geometry, weld pool temperatures, and fluid flow during high power density laser and laser/arc hybrid welding are not known. (6) Although the arc power and heat source separation distance have been experimentally shown to influence arc stability and plasma light emission during hybrid welding, the influence of these parameters on plasma properties is unknown. (7) The electrical conductivity of hybrid welding plasmas is not known, despite its importance to arc stability and weld integrity. In this study, heat transfer and fluid flow are analyzed for laser, gas tungsten arc (GTA), and laser/GTA hybrid welding using an experimentally validated three dimensional phenomenological model. By evaluating arc and laser welding using similar process parameters, a better understanding of the hybrid welding process is expected. The role of arc power and heat source separation distance on weld depth, weld pool centerline cooling rates, and fluid flow profiles during CO2 laser/GTA hybrid welding of 321 stainless steel are analyzed. Laser power is varied for a constant heat source separation distance to evaluate its influence on weld temperatures, weld geometry, and fluid flow during Nd:YAG laser/GTA hybrid welding of A131 structural steel. The influence of oxygen and sulfur on keyhole and weld bead geometry, weld temperatures, and fluid flow are analyzed for high power density Yb doped fiber laser welding of (0.16 %C, 1.46 %Mn) mild steel. Optical emission spectroscopy was performed on GTA, Nd:YAG laser, and Nd:YAG laser/GTA hybrid welding plasmas for welding of 304L stainless steel. Emission spectroscopy provides a means of determining plasma temperatures and species densities using deconvoluted measured spectral intensities, which can then be used to calculate plasma electrical conductivity. In this study, hybrid welding plasma temperatures, species densities, and electrical conductivities were determined using various heat source separation distances and arc currents using an analytical method coupled calculated plasma compositions. As a result of these studies heat transfer by convection was determined to be dominant during hybrid welding of steels. The primary driving forces affecting hybrid welding fluid flow are the surface tension gradient and electromagnetic force. Fiber laser weld depth showed a negligible change when increasing the (0.16 %C, 1.46 %Mn) mild steel sulfur concentration from 0.006 wt% to 0.15 wt%. Increasing the dissolved oxygen content in weld pool from 0.0038 wt% to 0.0257 wt% increased the experimental weld depth from 9.3 mm to 10.8 mm. Calculated partial pressure of carbon monoxide increased from 0.1 atm to 0.75 atm with the 0.0219 wt% increase in dissolved oxygen in the weld metal and may explain the increase in weld depth. Nd:YAG laser/GTA hybrid welding plasma temperatures were calculated to be approximately between 7927 K and 9357 K. Increasing the Nd:YAG laser/GTA hybrid welding heat source separation distance from 4 mm to 6 mm reduced plasma temperatures between 500 K and 900 K. Hybrid welding plasma total electron densities and electrical conductivities were on the order of 1 x 1022 m-3 and 3000 S m-1, respectively.

Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

NASA Astrophysics Data System (ADS)

Smith, Hugh; Sheridan, Gary; Nyman, Petter; Child, David; Lane, Patrick; Hotchkis, Michael

2013-04-01

The supply of fine sediment and ash has been identified as an important factor contributing to the initiation of runoff-generated debris flows after fire. However, despite the significance of fines for post-fire debris flow generation, no investigations have sought to quantify sources of this material in debris flow affected catchments. In this study, we employ fallout radionuclides (Cs-137, excess Pb-210 and Pu-239,240) as tracers to measure proportional contributions of fine sediment (<10 μm) from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post-fire debris flows in two forest catchments in southeastern Australia. While Cs-137 and excess Pb-210 have been widely used in sediment tracing studies, application of Pu as a tracer represents a recent development and was limited to only one catchment. The estimated range in hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment was 22-69% and 32-74%, respectively. No systematic change in the source contributions to debris flow deposits was observed with distance downstream from channel initiation points. Instead, spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits. Linking the sediment tracing with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges. Hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions. This indicated the importance of hillslope runoff and sediment supply for debris flow generation in both catchments. In contrast, material stored within channels that was deposited during subsequent surges was predominantly channel-derived. The results demonstrate that fallout radionuclide tracers may provide unique information on the changing source contributions of fine sediment during debris flow events.

The noise and flow characteristics of inverted-profile coannular jets

NASA Technical Reports Server (NTRS)

Tanna, H. K.; Tester, B. J.; Lau, J. C.

1979-01-01

A basic understanding of the noise reduction mechanisms in shock-free inverted-velocity-profile coannular jets was studied. Acoustic measurements are first conducted in an anechoic facility to isolate the effects of inverted velocity and inverted temperature for coannular jets having constant total thrust, mass flow rate and exit area. To obtain physical explanations of the measured noise changes, several types of experiments are conducted. These include (1) source location experiments using the polar correlation technique, (2) mean flow surveys using a combination pressure/temperature probe, and (3) detailed mean flow and turbulence measurements using a two-point four-channel laser velocimeter. The results from these experiments are presented and discussed in detail. Finally, the measured variations of coannular jet mixing noise with fan-to-primary velocity ratio and static temperature ratio are interpreted by utilizing the results from the various experimental phases in conjunction with the existing Lockheed single jet noise prediction model.

Experimental investigation of turbine disk cavity aerodynamics and heat transfer

NASA Technical Reports Server (NTRS)

Daniels, W. A.; Johnson, B. V.

1993-01-01

An experimental investigation of turbine disk cavity aerodynamics and heat transfer was conducted to provide an experimental data base that can guide the aerodynamic and thermal design of turbine disks and blade attachments for flow conditions and geometries simulating those of the space shuttle main engine (SSME) turbopump drive turbines. Experiments were conducted to define the nature of the aerodynamics and heat transfer of the flow within the disk cavities and blade attachments of a large scale model simulating the SSME turbopump drive turbines. These experiments include flow between the main gas path and the disk cavities, flow within the disk cavities, and leakage flows through the blade attachments and labyrinth seals. Air was used to simulate the combustion products in the gas path. Air and carbon dioxide were used to simulate the coolants injected at three locations in the disk cavities. Trace amounts of carbon dioxide were used to determine the source of the gas at selected locations on the rotors, the cavity walls, and the interstage seal. The measurements on the rotor and stationary walls in the forward and aft cavities showed that the coolant effectiveness was 90 percent or greater when the coolant flow rate was greater than the local free disk entrainment flow rate and when room temperature air was used as both coolant and gas path fluid. When a coolant-to-gas-path density ratio of 1.51 was used in the aft cavity, the coolant effectiveness on the rotor was also 90 percent or greater at the aforementioned condition. However, the coolant concentration on the stationary wall was 60 to 80 percent at the aforementioned condition indicating a more rapid mixing of the coolant and flow through the rotor shank passages. This increased mixing rate was attributed to the destabilizing effects of the adverse density gradients.

Transverse bacterial migration induced by chemotaxis in a packed column with structured physical heterogeneity.

PubMed

Wang, Meng; Ford, Roseanne M

2009-08-01

The significance of chemotaxis in directing bacterial migration toward contaminants in natural porous media was investigated under groundwater flow conditions. A laboratory-scale column, with a coarse-grained sand core surrounded by a fine-grained annulus, was used to simulate natural aquifers with strata of different hydraulic conductivities. A chemoattractant source was placed along the central axis of the column to model contaminants trapped in the heterogeneous subsurface. Chemotactic bacterial strains, Escherichia coli HCB1 and Pseudomonas putida F1, introduced into the column by a pulse injection, were found to alter their transport behaviors under the influence of the attractant chemical emanating from the central source. For E. coil HCB1, approximately 18% more of the total population relative to the control without attractant exited the column from the coarse sand layer due to the chemotactic effects of alpha-methylaspartate under an average fluid velocity of 5.1 m/d. Although P. putida F1 demonstrated no observable changes in migration pathways with the model contaminant acetate under the same flow rate, when the flow rate was reduced to 1.9 m/d, approximately 6-10% of the population relative to the control migrated from the fine sand layer toward attractant into the coarse sand layer. Microbial transport properties were further quantified by a mathematical model to examine the significance of bacterial motility and chemotaxis under different hydrodynamic conditions, which suggested important considerations for strain selection and practical operation of bioremediation schemes.

Design and Feasibility Analysis of a Self-Sustaining Biofiltration System for Removal of Low Concentration N2O Emitted from Wastewater Treatment Plants.

PubMed

Yoon, Hyun; Song, Min Joon; Yoon, Sukhwan

2017-09-19

N 2 O is a potent greenhouse gas and ozone-depletion agent. In this study, a biofiltration system was designed for removal of N 2 O emitted at low concentrations (<200 ppmv) from wastewater treatment plants. The proposed biofiltration system utilizes untreated wastewater from the primary sedimentation basin as the source of electron donor and nutrients and energy requirement is minimized by utilizing gravitational force and pressure differential to direct liquid medium and gas through the biofilter. The experiments performed with laboratory-scale biofilter in two different configurations confirmed the feasibility of the biofiltration system. The biofilter operated with cycling of raw wastewater exhibited up to 94% and 53% removal efficiency with 100 ppmv N 2 O in N 2 and air, respectively, as the feed gas, corroborating that untreated wastewater can serve as a robust source of electron donor and nutrients. The laboratory-scale biofilter operated with a continuous flow-through of synthetic wastewater attained >99.9% removal of N 2 O from N 2 background at the gas flow rate up to 2,000 mL·min -1 and >50% N 2 O removal from air background at the gas flow rate of 200 mL·min -1 . nosZ-containing bacterial genera including Flavobacterium (5.92%), Pseudomonas (4.26%) and Bosea (2.39%) were identified in the biofilm samples collected from the oxic biofilter, indicating these organisms were responsible for N 2 O removal.

The carrier gas pressure effect in a laminar flow diffusion chamber, homogeneous nucleation of n-butanol in helium.

PubMed

Hyvärinen, Antti-Pekka; Brus, David; Zdímal, Vladimír; Smolík, Jiri; Kulmala, Markku; Viisanen, Yrjö; Lihavainen, Heikki

2006-06-14

Homogeneous nucleation rate isotherms of n-butanol+helium were measured in a laminar flow diffusion chamber at total pressures ranging from 50 to 210 kPa to investigate the effect of carrier gas pressure on nucleation. Nucleation temperatures ranged from 265 to 280 K and the measured nucleation rates were between 10(2) and 10(6) cm(-3) s(-1). The measured nucleation rates decreased as a function of increasing pressure. The pressure effect was strongest at pressures below 100 kPa. This negative carrier gas effect was also temperature dependent. At nucleation temperature of 280 K and at the same saturation ratio, the maximum deviation between nucleation rates measured at 50 and 210 kPa was about three orders of magnitude. At nucleation temperature of 265 K, the effect was negligible. Qualitatively the results resemble those measured in a thermal diffusion cloud chamber. Also the slopes of the isothermal nucleation rates as a function of saturation ratio were different as a function of total pressure, 50 kPa isotherms yielded the steepest slopes, and 210 kPa isotherms the shallowest slopes. Several sources of inaccuracies were considered in the interpretation of the results: uncertainties in the transport properties, nonideal behavior of the vapor-carrier gas mixture, and shortcomings of the used mathematical model. Operation characteristics of the laminar flow diffusion chamber at both under-and over-pressure were determined to verify a correct and stable operation of the device. We conclude that a negative carrier gas pressure effect is seen in the laminar flow diffusion chamber and it cannot be totally explained with the aforementioned reasons.

Pollen-mediated gene flow from transgenic to non-transgenic switchgrass (Panicum virgatum L.) in the field.

PubMed

Millwood, Reginald; Nageswara-Rao, Madhugiri; Ye, Rongjian; Terry-Emert, Ellie; Johnson, Chelsea R; Hanson, Micaha; Burris, Jason N; Kwit, Charles; Stewart, C Neal

2017-05-02

Switchgrass is C 4 perennial grass species that is being developed as a cellulosic bioenergy feedstock. It is wind-pollinated and considered to be an obligate outcrosser. Genetic engineering has been used to alter cell walls for more facile bioprocessing and biofuel yield. Gene flow from transgenic cultivars would likely be of regulatory concern. In this study we investigated pollen-mediated gene flow from transgenic to nontransgenic switchgrass in a 3-year field experiment performed in Oliver Springs, Tennessee, U.S.A. using a modified Nelder wheel design. The planted area (0.6 ha) contained sexually compatible pollen source and pollen receptor switchgrass plants. One hundred clonal switchgrass 'Alamo' plants transgenic for an orange-fluorescent protein (OFP) and hygromycin resistance were used as the pollen source; whole plants, including pollen, were orange-fluorescent. To assess pollen movement, pollen traps were placed at 10 m intervals from the pollen-source plot in the four cardinal directions extending to 20 m, 30 m, 30 m, and 100 m to the north, south, west, and east, respectively. To assess pollination rates, nontransgenic 'Alamo 2' switchgrass clones were planted in pairs adjacent to pollen traps. In the eastward direction there was a 98% decrease in OFP pollen grains from 10 to 100 m from the pollen-source plot (Poisson regression, F1,8 = 288.38, P < 0.0001). At the end of the second and third year, 1,820 F 1 seeds were collected from pollen recipient-plots of which 962 (52.9%) germinated and analyzed for their transgenic status. Transgenic progeny production detected in each pollen-recipient plot decreased with increased distance from the edge of the transgenic plot (Poisson regression, F1,15 = 12.98, P < 0.003). The frequency of transgenic progeny detected in the eastward plots (the direction of the prevailing wind) ranged from 79.2% at 10 m to 9.3% at 100 m. In these experiments we found transgenic pollen movement and hybridization rates to be inversely associated with distance. However, these data suggest pollen-mediated gene flow is likely to occur up to, at least, 100 m. This study gives baseline data useful to determine isolation distances and other management practices should transgenic switchgrass be grown commercially in relevant environments.

Temperature stabilized effusion cell evaporation source for thin film deposition and molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Tiedje, H. F.; Brodie, D. E.

2000-05-01

A simple effusion cell evaporation source for thin film deposition and molecular-beam epitaxy is described. The source consists of a crucible with a thermocouple temperature sensor heated by a resistive crucible heater. Radiation heat transfer from the crucible to the thermocouple produces a consistent and reproducible thermocouple temperature for a given crucible temperature, without direct contact between the thermocouple and the crucible. The thermocouple temperature is somewhat less than the actual crucible temperature because of heat flow from the thermocouple junction along the thermocouple lead wires. In a typical case, the thermocouple temperature is 1007 °C while the crucible is at 1083 °C. The crucible temperature stability is estimated from the measured sensitivity of the evaporation rate of indium to temperature, and the observed variations in the evaporation rate for a fixed thermocouple temperature. The crucible temperature peak-to-peak variation over a one hour period is 1.2 °C. Machined molybdenum crucibles were used in the indium and copper sources for depositing CuInSe2 thin films for solar cells.

A Workflow to Model Microbial Loadings in Watersheds ...

EPA Pesticide Factsheets

Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated with 1) land-applied manure on undeveloped areas from domestic animals; 2) direct shedding on undeveloped lands by domestic animals and wildlife; 3) urban or engineered areas; and 4) point sources that directly discharge to streams from septic systems and shedding by domestic animals. A microbial source module, which houses these formulations, is linked within a workflow containing eight models and a set of databases that form a loosely configured modeling infrastructure which supports watershed-scale microbial source-to-receptor modeling by focusing on animal-impacted catchments. A hypothetical example application – accessing, retrieving, and using real-world data – demonstrates the ability of the infrastructure to automate many of the manual steps associated with a standard watershed assessment, culminating with calibrated flow and microbial densities at the pour point of a watershed. Presented at 2016 Biennial Conference, International Environmental Modelling & Software Society.

Effects of Abandoned Coal-Mine Drainage on Streamflow and Water Quality in the Shamokin Creek Basin, Northumberland and Columbia Counties, Pennsylvania, 1999-2001

USGS Publications Warehouse

Cravotta,, Charles A.; Kirby, Carl S.

2003-01-01

This report assesses the contaminant loading, effects to receiving streams, and possible remedial alternatives for abandoned mine drainage (AMD) within the upper Shamokin Creek Basin in east-central Pennsylvania. The upper Shamokin Creek Basin encompasses an area of 54 square miles (140 square kilometers) within the Western Middle Anthracite Field, including and upstream of the city of Shamokin. Elevated concentrations of acidity, metals, and sulfate in the AMD from flooded underground anthracite coal mines and (or) unreclaimed culm (waste rock) piles degrade the aquatic ecosystem and water quality of Shamokin Creek to its mouth and along many of its tributaries within the upper basin. Despite dilution by unpolluted streams that more than doubles the streamflow of Shamokin Creek in the lower basin, AMD contamination and ecological impairment persist to its mouth on the Susquehanna River at Sunbury, 20 miles (32 kilometers) downstream from the mined area. Aquatic ecological surveys were conducted by the U.S. Geological Survey (USGS) in cooperation with Bucknell University (BU) and the Northumberland County Conservation District (NCCD) at six stream sites in October 1999 and repeated in 2000 and 2001 on Shamokin Creek below Shamokin and at Sunbury. In 1999, fish were absent from Quaker Run and Shamokin Creek upstream of its confluence with Carbon Run; however, creek chub (Semotilus atromaculatus) were present within three sampled reaches of Carbon Run. During 1999, 2000, and 2001, six or more species of fish were identified in Shamokin Creek below Shamokin and at Sunbury despite elevated concentrations of dissolved iron and ironencrusted streambeds at these sites. Data on the flow rate and chemistry for 46 AMD sources and 22 stream sites throughout the upper basin plus 1 stream site at Sunbury were collected by the USGS with assistance from BU and the Shamokin Creek Restoration Alliance (SCRA) during low base-flow conditions in August 1999 and high baseflow conditions in March 2000. The water-quality data were used to determine priority ranks of the AMD sources on the basis of loadings of iron, manganese, and aluminum and to identify possible remedial alternatives, including passive-treatment options, for consideration by water-resource managers. The ranking sequence for the top AMD sources based on the high base-flow data generally matched that based on the low base-flow data. The contaminant loadings generally increased with flow, and 10 previously identified intermittent AMD sources were not discharging during the low base-flow sampling period. The top 3 AMD sources (SR19, SR12, and SR49) on the basis of dissolved metals loading in March 2000 accounted for more than 50 percent of the metals loading to Shamokin Creek, whereas the top 15 AMD sources accounted for more than 98 percent of the metals loading. When sampled in March 2000, these AMD sources had flow rates ranging from 0.7 to 19 cubic feet per second (1,138 to 32,285 liters per minute) and pH from 3.5 to 6.1 standard units. Only 1 of the top 15 AMD sources (SR21) was net alkaline (alkalinity > acidity); the others were net acidic and will require additional alkalinity to facilitate metals removal and maintain near-neutral pH. For the top 15 AMD sources, dissolved iron was the principal source of acidity and metals loading; concentrations of iron ranged from 10 to 57 milligrams per liter. Dissolved manganese ranged from 1.9 to 7.4 milligrams per liter. Dissolved aluminum exceeded 3.9 milligrams per liter at seven of the sites but was less than 0.2 milligram per liter at seven others. Alkalinity can be acquired by the dissolution of limestone and (or) bacterial sulfate reduction within various passive-treatment systems including anoxic or oxic limestone drains, limestone- lined channels, or compost wetlands. Subsequently, the gradual oxidation and consequent precipitation of iron and manganese can be accommodated within settling ponds or aerobic wetlands. Assum

Combined corona discharge and UV photoionization source for ion mobility spectrometry.

PubMed

Bahrami, Hamed; Tabrizchi, Mahmoud

2012-08-15

An ion mobility spectrometer is described which is equipped with two non-radioactive ion sources, namely an atmospheric pressure photoionization and a corona discharge ionization source. The two sources cannot only run individually but are additionally capable of operating simultaneously. For photoionization, a UV lamp was mounted parallel to the axis of the ion mobility cell. The corona discharge electrode was mounted perpendicular to the UV radiation. The total ion current from the photoionization source was verified as a function of lamp current, sample flow rate, and drift field. Simultaneous operation of the two ionization sources was investigated by recording ion mobility spectra of selected samples. The design allows one to observe peaks from either the corona discharge or photoionization individually or simultaneously. This makes it possible to accurately compare peaks in the ion mobility spectra from each individual source. Finally, the instrument's capability for discriminating two peaks appearing in approximately identical drift times using each individual ionization source is demonstrated. Copyright © 2012 Elsevier B.V. All rights reserved.

Critical transport issues for improving the performance of aqueous redox flow batteries

NASA Astrophysics Data System (ADS)

Zhou, X. L.; Zhao, T. S.; An, L.; Zeng, Y. K.; Wei, L.

2017-01-01

As the fraction of electricity generated from intermittent renewable sources (such as solar and wind) grows, developing reliable energy storage technologies to store electrical energy in large scale is of increasing importance. Redox flow batteries are now enjoying a renaissance and regarded as a leading technology in providing a well-balanced solution for current daunting challenges. In this article, state-of-the-art studies of the complex multicomponent transport phenomena in aqueous redox flow batteries, with a special emphasis on all-vanadium redox flow batteries, are reviewed and summarized. Rather than elaborating on the details of previous experimental and numerical investigations, this article highlights: i) the key transport issues in each battery's component that need to be tackled so that the rate capability and cycling stability of flow batteries can be significantly improved, ii) the basic mechanisms that control the active species/ion/electron transport behaviors in each battery's component, and iii) the key experimental and numerical findings regarding the correlations between the multicomponent transport processes and battery performance.

Modular GIS Framework for National Scale Hydrologic and Hydraulic Modeling Support

NASA Astrophysics Data System (ADS)

Djokic, D.; Noman, N.; Kopp, S.

2015-12-01

Geographic information systems (GIS) have been extensively used for pre- and post-processing of hydrologic and hydraulic models at multiple scales. An extensible GIS-based framework was developed for characterization of drainage systems (stream networks, catchments, floodplain characteristics) and model integration. The framework is implemented as a set of free, open source, Python tools and builds on core ArcGIS functionality and uses geoprocessing capabilities to ensure extensibility. Utilization of COTS GIS core capabilities allows immediate use of model results in a variety of existing online applications and integration with other data sources and applications.The poster presents the use of this framework to downscale global hydrologic models to local hydraulic scale and post process the hydraulic modeling results and generate floodplains at any local resolution. Flow forecasts from ECMWF or WRF-Hydro are downscaled and combined with other ancillary data for input into the RAPID flood routing model. RAPID model results (stream flow along each reach) are ingested into a GIS-based scale dependent stream network database for efficient flow utilization and visualization over space and time. Once the flows are known at localized reaches, the tools can be used to derive the floodplain depth and extent for each time step in the forecast at any available local resolution. If existing rating curves are available they can be used to relate the flow to the depth of flooding, or synthetic rating curves can be derived using the tools in the toolkit and some ancillary data/assumptions. The results can be published as time-enabled spatial services to be consumed by web applications that use floodplain information as an input. Some of the existing online presentation templates can be easily combined with available online demographic and infrastructure data to present the impact of the potential floods on the local community through simple, end user products. This framework has been successfully used in both the data rich environments as well as in locales with minimum available spatial and hydrographic data.

A simulation-based study on different control strategies for variable speed pump in distributed ground source heat pump systems

DOE PAGES

Liu, Xiaobing; Zheng, O'Neill; Niu, Fuxin

2016-01-01

Most commercial ground source heat pump systems (GSHP) in the United States are in a distributed configuration. These systems circulate water or an anti-freeze solution through multiple heat pump units via a central pumping system, which usually uses variable speed pump(s). Variable speed pumps have potential to significantly reduce pumping energy use; however, the energy savings in reality could be far away from its potential due to improper pumping system design and controls. In this paper, a simplified hydronic pumping system was simulated with the dynamic Modelica models to evaluate three different pumping control strategies. This includes two conventional controlmore » strategies, which are to maintain a constant differential pressure across either the supply and return mains, or at the most hydraulically remote heat pump; and an innovative control strategy, which adjusts system flow rate based on the demand of each heat pump. The simulation results indicate that a significant overflow occurs at part load conditions when the variable speed pump is controlled to main a constant differential pressure across the supply and return mains of the piping system. On the other hand, an underflow occurs at part load conditions when the variable speed pump is controlled to maintain a constant differential pressure across the furthest heat pump. The flow-demand-based control can provide needed flow rate to each heat pump at any given time, and with less pumping energy use than the two conventional controls. Finally, a typical distributed GSHP system was studied to evaluate the energy saving potential of applying the flow-demand-based pumping control strategy. This case study shows that the annual pumping energy consumption can be reduced by 62% using the flow-demand-based control compared with that using the conventional pressure-based control to maintain a constant differential pressure a cross the supply and return mains.« less

Conduit enlargement in an eogenetic karst aquifer

NASA Astrophysics Data System (ADS)

Moore, Paul J.; Martin, Jonathan B.; Screaton, Elizabeth J.; Neuhoff, Philip S.

2010-11-01

SummaryMost concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigates dissolution within a 6-km long conduit system in the eogenetic Upper Floridan aquifer of north-central Florida that begins with a continuous source of allogenic recharge at the Santa Fe River Sink and discharges from a first-magnitude spring at the Santa Fe River Rise. Three sources of water to the conduit include the allogenic recharge, diffuse recharge through epikarst, and mineralized water upwelling from depth. Results of sampling and inverse modeling using PHREEQC suggest that dissolution within the conduit is episodic, occurring only during 30% of 16 sampling times between March 2003 and April 2007. During low flow conditions, carbonate saturated water flows from the matrix to the conduit, restricting contact between undersaturated allogenic water with the conduit wall. When gradients reverse during high flow conditions, undersaturated allogenic recharge enters the matrix. During these limited periods, estimates of dissolution within the conduit suggest wall retreat averages about 4 × 10 -6 m/day, in agreement with upper estimates of maximum wall retreat for telogenetic karst. Because dissolution is episodic, time-averaged dissolution rates in the sink-rise system results in a wall retreat rate of about 7 × 10 -7 m/day, which is at the lower end of wall retreat for telogenetic karst. Because of the high permeability matrix, conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre-existing conduits such as those in telogenetic karst, but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes. These observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks.

Average Heating Rate of Hot Atmospheres in Distant Galaxy Clusters by Radio AGN: Evidence for Continuous AGN Heating

NASA Astrophysics Data System (ADS)

Ma, Cheng-Jiun; McNamara, B.; Nulsen, P.; Schaffer, R.

2011-09-01

X-ray observations of nearby clusters and galaxies have shown that energetic feedback from AGN is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 -- 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in 400SD, but cannot rule out the presence of weak cooling flows. The average jet power of central radio AGN is approximately 2 10^{44} erg/s. The jet power corresponds to an average heating of approximately 0.2 keV/particle for gas within R_500. Assuming the current AGN heating rate remained constant out to redshifts of about 2, these figures would rise by a factor of two. Our results show that the integrated energy injected from radio AGN outbursts in clusters is statistically significant compared to the excess entropy in hot atmospheres that is required for the breaking of self-similarity in cluster scaling relations. It is not clear that central AGN in 400SD clusters are maintained by a self-regulated feedback loop at the base of a cooling flow. However, they may play a significant role in preventing the development of strong cooling flows at early epochs.

Advancement of atmospheric-vacuum interfaces for mass spectrometers with a focus on increasing gas throughput for improving sensitivity.

PubMed

Prasad, Satendra; Wouters, Eloy R; Dunyach, Jean-Jacques

2015-08-18

Ion sampling from an electrospray ionization (ESI) source was improved by increasing gas conductance of the MS inlet by 4.3-fold. Converting the gas throughput (Q) into sensitivity improvement was dependent on ion desolvation and handling of the gas load. Desolvation was addressed by using a novel slot shaped inlet that exhibited desolvation properties identical to the 0.58 mm i.d capillary. An assay tailored for "small molecules" at high chromatographic flow rate (500 μL/min) yielded a compound dependent 6.5 to 14-fold signal gain while analysis at nano chromatographic flow rate (300 nL/min) showed 2 to 3.5-fold improvement for doubly charged peptides. Improvement exceeding the Q (4.3-fold) at high chromatographic flow rate was explained by superior sampling of the spatially dispersed ion spray when using the slot shaped capillary. Sensitivity improvement across a wide range of chromatographic flow rate confirmed no compromise in ion desolvation with the increase in Q. Another improvement included less overflow of gas into the mass analyzer from the foreline region owing to the slot shape of the capillary. By doubling the roughing pump capacity and operating the electrodynamic ion funnel (EDIF) at ∼4 Torr, a single pumping stage was sufficient to handle the gas load. The transport of solvent clusters from the LC effluent into the mass analyzer was prevented by a "wavy shaped" transfer quadrupole and was compared with a benchmark approach that delivered ions orthogonally into a differentially pumped dual EDIF at comparable gas Q.

Better Than Nothing: A Rational Approach for Minimizing the Impact of Outflow Strategy on Cerebrovascular Simulations.

PubMed

Chnafa, C; Brina, O; Pereira, V M; Steinman, D A

2018-02-01

Computational fluid dynamics simulations of neurovascular diseases are impacted by various modeling assumptions and uncertainties, including outlet boundary conditions. Many studies of intracranial aneurysms, for example, assume zero pressure at all outlets, often the default ("do-nothing") strategy, with no physiological basis. Others divide outflow according to the outlet diameters cubed, nominally based on the more physiological Murray's law but still susceptible to subjective choices about the segmented model extent. Here we demonstrate the limitations and impact of these outflow strategies, against a novel "splitting" method introduced here. With our method, the segmented lumen is split into its constituent bifurcations, where flow divisions are estimated locally using a power law. Together these provide the global outflow rate boundary conditions. The impact of outflow strategy on flow rates was tested for 70 cases of MCA aneurysm with 0D simulations. The impact on hemodynamic indices used for rupture status assessment was tested for 10 cases with 3D simulations. Differences in flow rates among the various strategies were up to 70%, with a non-negligible impact on average and oscillatory wall shear stresses in some cases. Murray-law and splitting methods gave flow rates closest to physiological values reported in the literature; however, only the splitting method was insensitive to arbitrary truncation of the model extent. Cerebrovascular simulations can depend strongly on the outflow strategy. The default zero-pressure method should be avoided in favor of Murray-law or splitting methods, the latter being released as an open-source tool to encourage the standardization of outflow strategies. © 2018 by American Journal of Neuroradiology.

40 CFR 1065.545 - Validation of proportional flow control for batch sampling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of the estimate, SEE, of the sample flow rate versus the total flow rate. For each test interval, demonstrate that SEE was less than or equal to 3.5% of the mean sample flow rate. (b) For any pair of flow meters, use recorded sample and total flow rates, where total flow rate means the raw exhaust flow rate...

Drinking, driving, and crashing: a traffic-flow model of alcohol-related motor vehicle accidents.

PubMed

Gruenewald, Paul J; Johnson, Fred W

2010-03-01

This study examined the influence of on-premise alcohol-outlet densities and of drinking-driver densities on rates of alcohol-related motor vehicle crashes. A traffic-flow model is developed to represent geographic relationships between residential locations of drinking drivers, alcohol outlets, and alcohol-related motor vehicle crashes. Cross-sectional and time-series cross-sectional spatial analyses were performed using data collected from 144 geographic units over 4 years. Data were obtained from archival and survey sources in six communities. Archival data were obtained within community areas and measured activities of either the resident population or persons visiting these communities. These data included local and highway traffic flow, locations of alcohol outlets, population density, network density of the local roadway system, and single-vehicle nighttime (SVN) crashes. Telephone-survey data obtained from residents of the communities were used to estimate the size of the resident drinking and driving population. Cross-sectional analyses showed that effects relating on-premise densities to alcohol-related crashes were moderated by highway trafficflow. Depending on levels of highway traffic flow, 10% greater densities were related to 0% to 150% greater rates of SVN crashes. Time-series cross-sectional analyses showed that changes in the population pool of drinking drivers and on-premise densities interacted to increase SVN crash rates. A simple traffic-flow model can assess the effects of on-premise alcohol-outlet densities and of drinking-driver densities as they vary across communities to produce alcohol-related crashes. Analyses based on these models can usefully guide policy decisions on the sitting of on-premise alcohol outlets.

Gravimetric system using high-speed double switching valves for low liquid flow rates

NASA Astrophysics Data System (ADS)

Cheong, Kar-Hooi; Doihara, Ryouji; Shimada, Takashi; Terao, Yoshiya

2018-07-01

This paper presents a gravimetric system developed to perform the static weighing with flying-start-and-stop (SW-FSS) calibration method at low liquid flow rates using a pair of identical high-speed switching valves as a flow diverter. Features of the gravimetric system comprise three main components: a pair of switching valves that divert the working liquid between two symmetrical flow paths; a weighing vessel equipped with an overflow inner vessel and enclosed in a weighing chamber; and a liquid discharge mechanism comprising a discharge tube and a discharge pump, used with a multi-purpose bin. These are described with an explanation of the design considerations behind each feature. The overflow inner vessel is designed with a notch in its wall and is positioned so that it does not come into contact with the liquid surface of the accumulated liquid in the weighing vessel or the side wall of the weighing vessel to obtain a good repeatability of the interactive effects between the feeding tube and the submerging working liquid, thus ensuring a correct mass reading of the liquid collection. A performance test showed that, in terms of contribution to the overall uncertainty of the standard flow rate, the pair of switching valves is capable of performing SW-FSS satisfactorily with small relative timing errors within %. However, the mass loss due to evaporation is considered a major source of error of the gravimetric system, showing a maximum error of 0.011% under the most evaporative condition tested for the longest liquid collection time of the gravimetric system.

Micro pumping with cardiomyocyte-polymer hybrid.

PubMed

Park, Jungyul; Kim, Il Chaek; Baek, Jeongeun; Cha, Misun; Kim, Jinseok; Park, Sukho; Lee, Junghoon; Kim, Byungkyu

2007-10-01

This paper presents a hybrid micropump actuated by the up-down motion of a dome shaped cell-polymer membrane composite. The contractile force induced from self-beating cardiomyocytes cultured on the membrane causes shrinkage and relaxation of a microchamber, leading to a flow in a microchannel. Flow direction is controlled by the geometry of diffuser/nozzle in the microchannel. The fabrication process is noninvasive to cells, thus, cardiomyocytes can robustly maintain their activity for a long time. The fluid motion in the microchannel was monitored by tracking 2 microm polystyrene beads. A net flow rate of 0.226 nl min(-1) was obtained in our microscale device. Our device demonstrates a unique performance of a cell-microdevice hybrid lab-on-a-chip that does not require any external power source, preventing electrical or heat shock to analytes.

Bn and Si-Doped Bn Coatings on Woven Fabrics

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.; Scott, John M.; Wheeler, Donald R.; Chayka, Paul V.; Gray, Hugh R. (Technical Monitor)

2002-01-01

A computer controlled, pulsed chemical vapor infiltration (CVI) system has been developed to deposit BN from a liquid borazine (B3N3H6) source, as well as silicon doped BN coatings using borazine and a silicon source, into 2-D woven ceramic fabric preforms. The coating process was evaluated as a function of deposition temperature, pressure, and precursor flow rate. Coatings were characterized by field emission scanning electron microscopy, electron dispersive spectroscopy and Auger spectroscopy. By controlling the reactant feed ratios, Si incorporation could be controlled over the range of 6-24 atomic percent.

Distribution of "Compound" and "Simple" Flows in the Deccan Traps (India)

NASA Astrophysics Data System (ADS)

Vanderkluysen, L.; Self, S.; Jay, A. E.; Sheth, H. C.; Clarke, A. B.

2014-12-01

The Deccan Traps are a dominantly mafic large igneous province (LIP) that, prior to erosion, covered ~1 million km2 of west-central India with lava flows. The type sections of the Western Ghats escarpment, where the Deccan lava pile reaches a maximum reconstructed stratigraphic thickness of ~3400 m, are subdivided into eleven formations defined on chemo-stratigraphic grounds. Earlier work recognized that emplacement of Deccan basalt flows primarily occurs following two main modes: as a stack of meter-sized pāhoehoe toes and lobes, termed "compound" flows; or as inflated sheet lobes tens to hundreds of meters in width and meters to tens of meters in height, previously termed "simple" flows. Initially, the distribution of small lobes and sheet lobes in the Deccan was thought to be controlled by distance from source, but later work suggested the distribution to be mainly controlled along stratigraphic, formational boundaries, with six of the lower formations being composed exclusively of compound flows, and the upper 4-5 formations being wholly built of sheet lobes. This simple stratigraphic subdivision of lava flow morphologies has also been documented in the volcanic architecture of other LIPs, e.g., the Etendeka, the Ethiopian Traps, and in the Faeroe Islands (North Atlantic LIP). Upon examination of eight sections carefully logged along the Western Ghats, this traditional view must be challenged. Where the lower Deccan formations crop out, we found that as much as 65% of the exposed thickness (below the Khandala Formation) is made up of sheet lobes, from 40% in the Bhimashankar Formation to 75% in the Thakurvadi Formation. Near the bottom of the sequence, 25% of the Neral Formation is composed of sheet lobes ≥15 m in thickness. This distribution in lava flow morphology does not seem to be noticeably affected by the inferred distance to the source (based on the location of similar-composition dikes for each formation). Several mechanisms have been proposed to explain the development of compound flows and inflated sheet lobes, involving one or more of the following factors: underlying slope, varying effusion rate, and source geometry. Analogue experiments are currently under way to test the relative influence of each of these factors in the development of different lava flow morphologies in LIPs.

Oxygen Mass Flow Rate Generated for Monitoring Hydrogen Peroxide Stability

NASA Technical Reports Server (NTRS)

Ross, H. Richard

2002-01-01

Recent interest in propellants with non-toxic reaction products has led to a resurgence of interest in hydrogen peroxide for various propellant applications. Because peroxide is sensitive to contaminants, material interactions, stability and storage issues, monitoring decomposition rates is important. Stennis Space Center (SSC) uses thermocouples to monitor bulk fluid temperature (heat evolution) to determine reaction rates. Unfortunately, large temperature rises are required to offset the heat lost into the surrounding fluid. Also, tank penetration to accomodate a thermocouple can entail modification of a tank or line and act as a source of contamination. The paper evaluates a method for monitoring oxygen evolution as a means to determine peroxide stability. Oxygen generation is not only directly related to peroxide decomposition, but occurs immediately. Measuring peroxide temperature to monitor peroxide stability has significant limitations. The bulk decomposition of 1% / week in a large volume tank can produce in excess of 30 cc / min. This oxygen flow rate corresponds to an equivalent temperature rise of approximately 14 millidegrees C, which is difficult to measure reliably. Thus, if heat transfer were included, there would be no temperature rise. Temperature changes from the surrounding environment and heat lost to the peroxide will also mask potential problems. The use of oxygen flow measurements provides an ultra sensitive technique for monitoring reaction events and will provide an earlier indication of an abnormal decomposition when compared to measuring temperature rise.

Twenty years of experience in monitoring 41Ar in a research reactor and decrease of its discharge into the environment.

PubMed

Fukui, M

2004-04-01

The radioactive gas 41Ar has been produced at high concentration by neutron activation near the reactor core in the Kyoto University Research Reactor. A pipe line for an exhaust stream, so-called sweep gas, was fabricated at the construction of the reactor in 1964 in order to exhale 41Ar from the facilities above to the environment. Other exhaust lines with decay tanks were established separately from the sweep line for both the cold neutron source in 1986 and the heavy-water tank in 1996, respectively, because a higher amount of 41Ar was thought to be produced from these facilities due to the improvement. As a result, a slight change in the flow rate of the exhaust was found to have a great deal of influence on both the 41Ar concentration in the reactor room and the rate of emission from the stack. By monitoring the exhaust air from the decay tanks, the mechanism for decreasing the emission was clarified together with identifying an obstacle, i.e., the condensate against the steady state flow, formed in the exhaust pipe. By setting the flow rate suitably in the exhaust line, the rate of 41Ar emission from the biological shielding into both the work place in the reactor room and the environment has been controlled as low as reasonably achievable.

Spatio-temporal models to determine association between Campylobacter cases and environment

PubMed Central

Sanderson, Roy A; Maas, James A; Blain, Alasdair P; Gorton, Russell; Ward, Jessica; O’Brien, Sarah J; Hunter, Paul R; Rushton, Stephen P

2018-01-01

Abstract Background Campylobacteriosis is a major cause of gastroenteritis in the UK, and although 70% of cases are associated with food sources, the remainder are probably associated with wider environmental exposure. Methods In order to investigate wider environmental transmission, we conducted a spatio-temporal analysis of the association of human cases of Campylobacter in the Tyne catchment with weather, climate, hydrology and land use. A hydrological model was used to predict surface-water flow in the Tyne catchment over 5 years. We analysed associations between population-adjusted Campylobacter case rate and environmental factors hypothesized to be important in disease using a two-stage modelling framework. First, we investigated associations between temporal variation in case rate in relation to surface-water flow, temperature, evapotranspiration and rainfall, using linear mixed-effects models. Second, we used the random effects for the first model to quantify how spatial variation in static landscape features of soil and land use impacted on the likely differences between subcatchment associations of case rate with the temporal variables. Results Population-adjusted Campylobacter case rates were associated with periods of high predicted surface-water flow, and during above average temperatures. Subcatchments with cattle on stagnogley soils, and to a lesser extent sheep plus cattle grazing, had higher Campylobacter case rates. Conclusions Areas of stagnogley soils with mixed livestock grazing may be more vulnerable to both Campylobacter spread and exposure during periods of high rainfall, with resultant increased risk of human cases of the disease. PMID:29069406

Improved Calibration Of Acoustic Plethysmographic Sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Davis, David C.

1993-01-01

Improved method of calibration of acoustic plethysmographic sensors involves acoustic-impedance test conditions like those encountered in use. Clamped aluminum tube holds source of sound (hydrophone) inside balloon. Test and reference sensors attached to outside of balloon. Sensors used to measure blood flow, blood pressure, heart rate, breathing sounds, and other vital signs from surfaces of human bodies. Attached to torsos or limbs by straps or adhesives.

Guidance for the Development of Air Force Storm Water Sampling Programs

DTIC Science & Technology

1993-09-01

38 Storm Water Quality Monitoring ................. 39 Determining Flow Rate ....................... 42 Weirs and Flumes... water quality monitoring it is not possible to analyze the entire nmoff from a drainage basin. The objective of water quality sampling is to collect a...development of storm water pollution prevention plans. Best management practices can also be developed to control the pollution sources identified. In storm

40 CFR 423.15 - New source performance standards (NSPS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... sources shall not exceed the quantity determined by multiplying the flow of low volume waste sources times... metal cleaning wastes shall not exceed the quantity determined by multiplying the flow of chemical metal... transport water shall not exceed the quantity determined by multiplying the flow of the bottom ash transport...

Ionization based multi-directional flow sensor

DOEpatents

Chorpening, Benjamin T [Morgantown, WV; Casleton, Kent H [Morgantown, WV

2009-04-28

A method, system, and apparatus for conducting real-time monitoring of flow (airflow for example) in a system (a hybrid power generation system for example) is disclosed. The method, system and apparatus measure at least flow direction and velocity with minimal pressure drop and fast response. The apparatus comprises an ion source and a multi-directional collection device proximate the ion source. The ion source is configured to generate charged species (electrons and ions for example). The multi-directional collection source is configured to determine the direction and velocity of the flow in real-time.

Geometric optimization of microreactor chambers to increase the homogeneity of the velocity field

NASA Astrophysics Data System (ADS)

Pálovics, Péter; Ender, Ferenc; Rencz, Márta

2018-06-01

In this work microfluidic flow-through chambers are investigated. They are filled with magnetic nanoparticle (MNP) suspension in order to facilitate enzymatic reactions. The enzyme is immobilized on the surface of the MNPs. These reactions have been found to be flow rate dependent. To overcome this issue various chamber geometries have been examined and optimized geometries have been designed and tested experimentally. The investigation is supported with dedicated CFD simulations using the open source software OpenFOAM. The paper presents the theoretical background and the results of the simulations. The simulations have been verified with measurements and these too are presented in the paper.

Nonintrusive Temperature and Velocity Measurements in a Hypersonic Nozzle Flow

NASA Technical Reports Server (NTRS)

OByrne, S.; Danehy, P. M.; Houwing, A. F. P.

2002-01-01

Distributions of nitric oxide vibrational temperature, rotational temperature and velocity have been measured in the hypersonic freestream at the exit of a conical nozzle, using planar laser-induced fluorescence. Particular attention has been devoted to reducing the major sources of systematic error that can affect fluorescence tempera- ture measurements, including beam attenuation, transition saturation effects, laser mode fluctuations and transition choice. Visualization experiments have been performed to improve the uniformity of the nozzle flow. Comparisons of measured quantities with a simple one-dimensional computation are made, showing good agreement between measurements and theory given the uncertainty of the nozzle reservoir conditions and the vibrational relaxation rate.

Wind-energy recovery by a static Scherbius induction generator

NASA Astrophysics Data System (ADS)

Smith, G. A.; Nigim, K. A.

1981-11-01

The paper describes a technique for controlling a doubly fed induction generator driven by a windmill, or other form of variable-speed prime mover, to provide power generation into the national grid system. The secondary circuit of the generator is supplied at a variable frequency from a current source inverter which for test purposes is rated to allow energy recovery, from a simulated windmill, from maximum speed to standstill. To overcome the stability problems normally associated with doubly fed machines a novel signal generator, which is locked in phase with the rotor EMF, controls the secondary power to provide operation over a wide range of subsynchronous and supersynchronous speeds. Consideration of power flow enables the VA rating of the secondary power source to be determined as a function of the gear ratio and online operating range of the system. A simple current source model is used to predict performance which is compared with experimental results. The results indicate a viable system, and suggestions for further work are proposed.

Disturbance Source Separation in Shear Flows Using Blind Source Separation Methods

NASA Astrophysics Data System (ADS)

Gluzman, Igal; Cohen, Jacob; Oshman, Yaakov

2017-11-01

A novel approach is presented for identifying disturbance sources in wall-bounded shear flows. The method can prove useful for active control of boundary layer transition from laminar to turbulent flow. The underlying idea is to consider the flow state, as measured in sensors, to be a mixture of sources, and to use Blind Source Separation (BSS) techniques to recover the separate sources and their unknown mixing process. We present a BSS method based on the Degenerate Unmixing Estimation Technique. This method can be used to identify any (a priori unknown) number of sources by using the data acquired by only two sensors. The power of the new method is demonstrated via numerical and experimental proofs of concept. Wind tunnel experiments involving boundary layer flow over a flat plate were carried out, in which two hot-wire anemometers were used to separate disturbances generated by disturbance generators such as a single dielectric barrier discharge plasma actuator and a loudspeaker.

1 K cryostat with sub-millikelvin stability based on a pulse-tube cryocooler

NASA Astrophysics Data System (ADS)

DeMann, A.; Mueller, Sara; Field, S. B.

2016-01-01

A cryogenic system has been designed and tested that reaches a temperature below 1.1 K, with an rms temperature stability of 25 μ K. In this system a commercial pulse-tube cryocooler is used to liquify helium gas supplied from an external source. This liquid helium enters a 1 K pot through a large-impedance capillary tube, similar to a conventional 1 K system operated from a liquid helium bath. Unlike a conventional system, however, the molar flow rate of the system can be varied by changing the pressure of the incoming helium. This allows for a trade-off between helium usage and cooling power, which has a maximum value of 27 mW. The measured cooling power and fraction of helium exiting the capillary as liquid agree well with predictions based on an isenthalpic model of helium flow through the capillary. The system is simple to use and inexpensive to operate: The system can be cooled to base temperature in about 3 h and, with a flow rate giving a cooling power of 13 mW, the helium cost is around 6 per day.

Nonnormality increases variance of gravity waves trapped in a tilted box

NASA Astrophysics Data System (ADS)

Harlander, Uwe; Borcia, Ion Dan; Krebs, Andreas

2017-04-01

We study the prototype problem of internal gravity waves in a square domain tilted with respect to the gravity vector by an angle theta. Only when theta is zero regular normal modes exist, for all other angles wave attractors and singularities dominate the flow. We show that the linear operator of the governing PDE becomes non-normal for nonzero theta giving rise to non-modal transient growth. This growth depends on the underlying norm: for the variance norm significant growth rates can be found whereas for the energy norm, no growth is possible since there is no source for energy (in contrast to shear fows, for which the mean flow feeds the perturbations). We continue by showing that the nonnormality of the system matrix is increasing with theta and reaches a maximum when theta is 45 degree. Moreover, the growth rate is increasing as can be expected from the increasing nonnormality of the matrix. Our results imply that at least the most simple wave attractors can be seen as those initial flow fields that gain most of the variance during a given time period.

Large springs of east Tennessee

USGS Publications Warehouse

Sun, Pao-chang P.; Criner, J.H.; Poole, J.L.

1963-01-01

Springs constitute an important source of water in east Tennessee, and many individual springs are capable of supplying the large quantities needed for municipal and industrial supplies. Most of the springs in east Tennessee issue from solution openings and fractured and faulted zones in limestone and dolomite of the Knox Group, Chickamauga Limestone, and Conasauga Group. The ability of these rocks to yield a sustained flow of water to springs is dependent on a system of interconnected openings through which water can infiltrate from the land surface and move to points of natural discharge. Ninety springs were selected for detailed study, and 84 of these are analyzed in terms of magnitude and variability of discharge. Of the 84 springs analyzed, 4 flow at an average rate of 10 to 100 cfs (cubic feet per second), 62 at an average rate of 1 to 10 cfs, and 18 at an average rate of 1 cfs or less. Of the 90 springs, 75 are variable in their discharge; that is, the ratio of their fluctuations to their average discharges exceeds 100 percent. Mathematical analysis of the flow recession curve of Mill Spring near Jefferson City shows that the hydrologic system contributing to the flow of the spring has an effective capacity of about 70 million cubic feet of water. The rate of depletion of this volume of water, in the absence of significant precipitation, averages 0.0056 cfs per day between the time when the hydrologic system is full and the time when the spring ceases to flow. From such a curve it is possible to determine at any time the residual volume of water remaining in the system and the expected rate of decrease in discharge from that time to cessation of flow. Correlation of discharge measurements of 22 springs with those of Mill Spring shows that rough approximations of discharge can be projected for springs for which few measurements are available. Seventeen of the springs analyzed in this manner show good correlation with Mill Spring: that is, their coefficients of correlation were 0.70 or better as compared with a perfect correlation factor of 1.00.

On the Disappearance of Kilohertz Quasi-periodic Oscillations at a High Mass Accretion Rate in Low-Mass X-Ray Binaries

NASA Astrophysics Data System (ADS)

Cui, Wei

2000-05-01

For all sources in which the phenomenon of kilohertz quasi-periodic oscillation (kHz QPO) is observed, the QPOs disappear abruptly when the inferred mass accretion rate exceeds a certain threshold. Although the threshold cannot at present be accurately determined (or even quantified) observationally, it is clearly higher for bright Z sources than for faint atoll sources. Here we propose that the observational manifestation of kHz QPOs requires direct interaction between the neutron star magnetosphere and the Keplerian accretion disk and that the cessation of kHz QPOs at a high accretion rate is due to the lack of such an interaction when the Keplerian disk terminates at the last stable orbit and yet the magnetosphere is pushed farther inward. The threshold is therefore dependent on the magnetic field strength-the stronger the magnetic field, the higher the threshold. This is certainly in agreement with the atoll/Z paradigm, but we argue that it is also generally true, even for individual sources within each (atoll or Z) category. For atoll sources, the kHz QPOs also seem to vanish at a low accretion rate. Perhaps the ``disengagement'' between the magnetosphere and the Keplerian disk also takes place under such circumstances because of, for instance, the presence of quasi-spherical advection-dominated accretion flow (ADAF) close to the neutron star. Unfortunately, in this case, the estimation of the accretion rate threshold would require a knowledge of the physical mechanisms that cause the disengagement. If the ADAF is responsible, the threshold is likely dependent on the magnetic field of the neutron star.

Conjunctive-use optimization model of the Mississippi River Valley alluvial aquifer of northeastern Arkansas

USGS Publications Warehouse

Czarnecki, John B.; Clark, Brian R.; Reed, Thomas B.

2003-01-01

The Mississippi River Valley alluvial aquifer is a water-bearing assemblage of gravels and sands that underlies about 32,000 square miles of Missouri, Kentucky, Tennessee, Mississippi, Louisiana, and Arkansas. Because of the heavy demands placed on the aquifer, several large cones of depression over 100 feet deep have formed in the potentiometric surface, resulting in lower well yields and degraded water quality in some areas. A ground-water flow model of the alluvial aquifer was previously developed for an area covering 14,104 square miles, extending northeast from the Arkansas River into the northeast corner of Arkansas and parts of southeastern Missouri. The flow model showed that continued ground-water withdrawals at rates commensurate with those of 1997 could not be sustained indefinitely without causing water levels to decline below half the original saturated thickness of the aquifer. To develop estimates of withdrawal rates that could be sustained in compliance with the constraints of critical ground-water area designation, conjunctive-use optimization modeling was applied to the flow model of the alluvial aquifer in northeastern Arkansas. Ground-water withdrawal rates form the basis for estimates of sustainable yield from the alluvial aquifer and from rivers specified within the alluvial aquifer model. A management problem was formulated as one of maximizing the sustainable yield from all ground-water and surface-water withdrawal cells within limits imposed by plausible withdrawal rates, and within specified constraints involving hydraulic head and streamflow. Steady-state flow conditions were selected because the maximized withdrawals are intended to represent sustainable yield of the system (a rate that can be maintained indefinitely). Within the optimization model, 11 rivers are specified. Surface-water diversion rates that occurred in 2000 were subtracted from specified overland flow at the appropriate river cells. Included in these diversions were the planned diversions of 63,339,248 ft3/d for the Bayou Meto project area and 55,078,367 ft3/d for the Grand Prairie project area, which factor in an additional 30 and 40 percent transmission loss, respectively. Streamflow constraints were specified at all 1,165 river cells based on average 7-day minimum flows for 10 years. Sustainable yield for all rivers ranged from 0 (Current, Little Red, and Bayou Meto Rivers) to almost 5 billion cubic feet per day for the Arkansas River. Total sustainable yield from all rivers combined was 12.8 billion cubic feet per day, which represents a substantial source for supplementing ground water to meet the total water demand. Sustainable-yield estimates are affected by the allowable upper limit on withdrawals from wells specified in the optimization model. Ground-water withdrawal rates were allowed to vary as much as 200 percent of the withdrawal rate in 1997. As the overall upper limit on withdrawals is increased, the sustainable yield generally increases. Tests with the optimization model show that without limits on pumping, wells adjacent to sources of water would have optimized withdrawal rates that were orders of magnitude larger than rates corresponding to those of 1997. The sustainable yield from ground water for the entire study area while setting the maximum upper limit as the amount withdrawn in 1997 is 360 million cubic feet per day, which is only about 57 percent of the amount withdrawn in 1997 (635.6 million cubic feet per day). Optimal sustainable yields from within the Bayou Meto irrigation project area and within the Grand Prairie irrigation project area are 18.1 and 9.1 million cubic feet per day, respectively, assuming a maximum allowable withdrawal rate equal to 1997 rates. These values of sustainable yield represent 35 and 30 percent respectively of the amount pumped from these project areas in 1997. Unmet demand (defined as the difference between the optimized withdrawal rate or sustainable yield, a

Environmental factors and flow paths related to Escherichia coli concentrations at two beaches on Lake St. Clair, Michigan, 2002–2005

USGS Publications Warehouse

Holtschlag, David J.; Shively, Dawn; Whitman, Richard L.; Haack, Sheridan K.; Fogarty, Lisa R.

2008-01-01

Regression analyses and hydrodynamic modeling were used to identify environmental factors and flow paths associated with Escherichia coli (E. coli) concentrations at Memorial and Metropolitan Beaches on Lake St. Clair in Macomb County, Mich. Lake St. Clair is part of the binational waterway between the United States and Canada that connects Lake Huron with Lake Erie in the Great Lakes Basin. Linear regression, regression-tree, and logistic regression models were developed from E. coli concentration and ancillary environmental data. Linear regression models on log10 E. coli concentrations indicated that rainfall prior to sampling, water temperature, and turbidity were positively associated with bacteria concentrations at both beaches. Flow from Clinton River, changes in water levels, wind conditions, and log10 E. coli concentrations 2 days before or after the target bacteria concentrations were statistically significant at one or both beaches. In addition, various interaction terms were significant at Memorial Beach. Linear regression models for both beaches explained only about 30 percent of the variability in log10 E. coli concentrations. Regression-tree models were developed from data from both Memorial and Metropolitan Beaches but were found to have limited predictive capability in this study. The results indicate that too few observations were available to develop reliable regression-tree models. Linear logistic models were developed to estimate the probability of E. coli concentrations exceeding 300 most probable number (MPN) per 100 milliliters (mL). Rainfall amounts before bacteria sampling were positively associated with exceedance probabilities at both beaches. Flow of Clinton River, turbidity, and log10 E. coli concentrations measured before or after the target E. coli measurements were related to exceedances at one or both beaches. The linear logistic models were effective in estimating bacteria exceedances at both beaches. A receiver operating characteristic (ROC) analysis was used to determine cut points for maximizing the true positive rate prediction while minimizing the false positive rate. A two-dimensional hydrodynamic model was developed to simulate horizontal current patterns on Lake St. Clair in response to wind, flow, and water-level conditions at model boundaries. Simulated velocity fields were used to track hypothetical massless particles backward in time from the beaches along flow paths toward source areas. Reverse particle tracking for idealized steady-state conditions shows changes in expected flow paths and traveltimes with wind speeds and directions from 24 sectors. The results indicate that three to four sets of contiguous wind sectors have similar effects on flow paths in the vicinity of the beaches. In addition, reverse particle tracking was used for transient conditions to identify expected flow paths for 10 E. coli sampling events in 2004. These results demonstrate the ability to track hypothetical particles from the beaches, backward in time, to likely source areas. This ability, coupled with a greater frequency of bacteria sampling, may provide insight into changes in bacteria concentrations between source and sink areas.