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1

Optimal mixing in recirculation zones  

Microsoft Academic Search

Coarse-scale mixing in a recirculation zone is described with a simple vortex model. Time-dependent forcing is employed to change the vortex motion and mixing properties. An optimal mixing problem is defined in which the flux across the recirculation region shall be maximized under the side-constraints of bounded vortex motion and bounded actuation. Concepts of control theory and chaotic advection are

Bernd R. Noack; Igor Mezic; Gilead Tadmor; Andrzej Banaszuk

2004-01-01

2

Fuel evaporation rate in intense recirculation zones  

Microsoft Academic Search

An expression is derived for the mean liquid fuel concentration in a flow region with intense recirculation rates. The expression makes it possible to evaluate liquid fuel evaporation rates. Finite fuel concentrations are predicted even for residence times greater than the critical value for single drops. The mean fuel evaporation rate may, therefore, be significantly smaller than that for single

I. T. Osgerby

1975-01-01

3

An investigation of the establishment of a recirculation zone by swirling flows within a conical duct  

SciTech Connect

This paper reports an investigation carried out on the recirculation zones established in concial chambers with radial vaned inlet swirlers. The boundaries of the recirculation zones established in various conical chambers of different cone angles are presented for different inlet swirl numbers and an optimum cone angle which gives a reasonably short length of the recirculation zone with maximum pressure recovery is suggested. The inlet swirl number is also optimized for a fairly high swirl strength within the recirculation zone and the inlet swirl number for which the recirculation completely disappears is also estimated. In addition to this, an equation is curve-fit to the experimental data which correlates the length of the recirculation zone for any given cone angle and inlet swirl number.

Rama Mohan, P.; Vara Prasad, C.M.

1983-01-01

4

Particle capture by turbulent recirculation zones measured using long-time Lagrangian particle tracking  

NASA Astrophysics Data System (ADS)

We have measured the trajectories of particles into, and around, the recirculation zone formed in water flowing through a sudden pipe expansion with radius ratio 1:3.7, at Reynolds numbers between 5,960 and 41,700 over a range of particle Stokes number (here defined as St = {{T_{{f}} }/{tau_{{p} }}} , where T f is an appropriate mean or turbulent timescale of the fluid flow and a particle relaxation time, ?p,) between 6.2 and 51 and drift parameter between 0.3 and 2.8. The particles were thus weakly inertial but nevertheless heavy with a diameter about an order of magnitude larger than the Kolmogorov scale. Trajectories of particles, released individually into the flow, were taken in a Lagrangian framework by a three-dimensional particle tracking velocimeter using a single 25 Hz framing rate intensified CCD camera. Trajectories are quantified by the axial distribution of the locations of particle axial velocity component reversal and the probability distributions of trajectory angle and curvature. The effect of increasing the drift parameter was to reduce the tendency for particles to enter the recirculation zone. For centreline release, the proportion of particles entering the recirculation zone and acquiring a negative velocity decreased from about 80% to none and from about 66% to none, respectively, as the drift parameter increased from 0.3 to 2.8. Almost half of the particles experienced a relatively large change of direction corresponding to a radius of curvature of their trajectory comparable to, or smaller than, the radius of the downstream pipe. This was due to the interaction between these particles and eddies of this size in the downstream pipe and provides experimental evidence that particles are swept by large eddies into the recirculation zone over 1.0 < Z^{*} < 2.5, where Z^{*} is axial distance from the expansion plane normalized by the downstream pipe diameter, which was well upstream of the reattachment point at the wall ( Z^{*} ? 3. 5 ). Once inside the recirculation zone, the particle motion was governed more by the drift parameter than by the Stokes number.

Siu, Y. W.; Taylor, A. M. K. P.

2011-07-01

5

Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame  

Microsoft Academic Search

To examine the effect of the flow field within the recirculation zone on flame structure, the characteristic velocity fields\\u000a of methane\\/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle\\u000a image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame.\\u000a However, the distance of the two

Xin Gu; Shusheng Zang; Bing Ge

2008-01-01

6

Flow Field Features of the Induced Recirculation Zone using Planar Jet Injection.  

NASA Astrophysics Data System (ADS)

The objective of the present work is to study the recirculation bubble induced by injecting a planar jet in to a channel flow. The work is motivated by the desire to provide a flame stabilization environment for ramjet engines without the use of a sudden expansion or bluff-body which incurs drag penalties. A planar jet issuing into a cross flow is used to create a recirculation zone reminiscent of the flow field created downstream of a rearward-facing step configuration which is used in a current ramjet/scramjet systems. The effect of confinement at high momentum flux ratios leads to a saturation of the control of the recirculation bubble size and strength. Comparison to a rearward-facing step flow shows the current method produces higher turbulence levels and larger integral length scales. It is clear that the flow field produced with fluidic injection has potential for flame anchoring and enhancing combustion rates.

Ahmed, Kareem; Forliti, David; Moody, Jack

2006-11-01

7

Vortex formation and recirculation zones in left anterior descending artery stenoses: computational fluid dynamics analysis  

NASA Astrophysics Data System (ADS)

Flow patterns may affect the potential of thrombus formation following plaque rupture. Computational fluid dynamics (CFD) were employed to assess hemodynamic conditions, and particularly flow recirculation and vortex formation in reconstructed arterial models associated with ST-elevation myocardial infraction (STEMI) or stable coronary stenosis (SCS) in the left anterior descending coronary artery (LAD). Results indicate that in the arterial models associated with STEMI, a 50% diameter stenosis immediately before or after a bifurcation creates a recirculation zone and vortex formation at the orifice of the bifurcation branch, for most of the cardiac cycle, thus allowing the creation of stagnating flow. These flow patterns are not seen in the SCS model with an identical stenosis. Post-stenotic recirculation in the presence of a 90% stenosis was evident at both the STEMI and SCS models. The presence of 90% diameter stenosis resulted in flow reduction in the LAD of 51.5% and 35.9% in the STEMI models and 37.6% in the SCS model, for a 10 mmHg pressure drop. CFD simulations in a reconstructed model of stenotic LAD segments indicate that specific anatomic characteristics create zones of vortices and flow recirculation that promote thrombus formation and potentially myocardial infarction.

Katritsis, D. G.; Theodorakakos, A.; Pantos, I.; Andriotis, A.; Efstathopoulos, E. P.; Siontis, G.; Karcanias, N.; Redwood, S.; Gavaises, M.

2010-03-01

8

Prediction of central recirculation zone size for a complete burner-quarl-furnace system  

SciTech Connect

In the swirl flow burning process of fuels, the central recirculation zone plays an important role in flame stabilization by providing a hot flow of recirculated combustion products, which reduce both the length of flame and the stabilized flame distance from the burner mouth. In this paper, a new modified swirl number, S exp xx, related to the characteristic size of the burner quarl, is introduced to correlate the isothermal and burning flows. Using a well-known two-dimensional computational model, the isothermal flow pattern in a complete burner-quarl-furnace system is computed. On this basis, the theoretical swirl number S exp xx is calculated and used as a correlation parameter for predicting the central recirculation zone size in burning flow conditions. Experimental tests for both nonreacting and reacting flows on the same complete burner-quarl-furnace system, for comparing the theoretical and experimental swirl number s exp xx, have been conducted, and the validity of this new correlation parameter has been proved. 11 references.

Cristea, E.B.

1987-03-01

9

Capture Zone Analyses of Two Airlift Recirculation Wells in the Southern Sector of A/M Area  

SciTech Connect

This report documents a series of capture zone analyses performed to access the expected overall performance of two (of the twelve) vertical airlift recirculation wells (ARWs) (specifically, SSR-011 and SRR-012) located in the Southern Sector of A/M Area.

Aleman, S.E.

1999-09-14

10

Comparison of Finite Difference Calculations of a Large Region of Recirculating Flow Near an Airfoil Trailing Edge.  

National Technical Information Service (NTIS)

Calculations are presented for a turbulent boundary layer which separates upstream of a sharp trailing edge and results in a large region of recirculating flow and a curved downstream wake. The solutions obtained from two procedures that solve finite diff...

L. Reis B. E. Thompson

1986-01-01

11

Central recirculation zone analysis in an unconfined tangential swirl burner with varying degrees of premixing  

NASA Astrophysics Data System (ADS)

Swirl-stabilised combustion is one of the most widely used techniques for flame stabilisation, uses ranging from gas turbine combustors to pulverised coal-fired power stations. In gas turbines, lean premixed systems are of especial importance, giving the ability to produce low NOx systems coupled with wide stability limits. The common element is the swirl burner, which depends on the generation of an aerodynamically formed central recirculation zone (CRZ) and which serves to recycle heat and active chemical species to the root of the flame as well as providing low-velocity regions where the flame speed can match the local flow velocity. Enhanced mixing in and around the CRZ is another beneficial feature. The structure of the CRZ and hence that of the associated flames, stabilisation and mixing processes have shown to be extremely complex, three-dimensional and time dependent. The characteristics of the CRZ depend very strongly on the level of swirl (swirl number), burner configuration, type of flow expansion, Reynolds number (i.e. flowrate) and equivalence ratio. Although numerical methods have had some success when compared to experimental results, the models still have difficulties at medium to high swirl levels, with complex geometries and varied equivalence ratios. This study thus focuses on experimental results obtained to characterise the CRZ formed under varied combustion conditions with different geometries and some variation of swirl number in a generic swirl burner. CRZ behaviour has similarities to the equivalent isothermal state, but is strongly dependent on equivalence ratio, with interesting effects occurring with a high-velocity fuel injector. Partial premixing and combustion cause more substantive changes to the CRZ than pure diffusive combustion.

Valera-Medina, A.; Syred, N.; Kay, P.; Griffiths, A.

2011-06-01

12

Evaluation of numerical strategies for large eddy simulation of particulate two-phase recirculating flows  

NASA Astrophysics Data System (ADS)

Predicting particle dispersion in recirculating two-phase flows is a key issue for reacting flows and a potential application of large eddy simulation (LES) methods. In this study, Euler/Euler and Euler/Lagrange LES approaches are compared in the bluff body configuration from Borée et al. [J. Borée, T. Ishima, I. Flour, The effect of mass loading and inter-particle collisions on the development of the polydispersed two-phase flow downstream of a confined bluff body, J. Fluid Mech. 443 (2001) 129 165] where glass beads are injected into a complex recirculating flow. These tests are performed for non-reacting, non-evaporating sprays but are mandatory validations before computing realistic combustion chambers. Two different codes (one explicit and compressible and the other implicit and incompressible) are also tested on the same configuration. Results show that the gas flow is well predicted by both codes. The dispersed phase is also well predicted by both codes but the Lagrangian approach predicts root-mean-square values more accurately than the Eulerian approach. The effects of mesh, solvers and numerical schemes are discussed for each method.

Riber, E.; Moureau, V.; García, M.; Poinsot, T.; Simonin, O.

2009-02-01

13

Velocity characteristics of a swirling recirculating flow  

SciTech Connect

The isothermal recirculating flow downstream of a model swirl burner is studied making use of a laser-Doppler velocimeter. The arrangement was designed to incorporate the injection of liquid fuel into a gas flame characterized by a large recirculation zone attached to the burner head and to allow a detailed analysis of turbulent transport processes in a strongly swirled recirculating flow. The results show that turbulent mixing in the present flow is not dominated by large-scale motions or precession. The production of turbulent kinetic energy depends upon mechanisms of shear-generated turbulence but is influenced by streamline curvature in the zone of mean shear. Inspection of the terms in the conservation equations for the turbulent stresses allows quantification of the extent to which the interaction of normal stresses and normal strains influence the flow and suggests the likely magnitude of turbulent diffusion and dissipation. 53 refs.

Heitor, M.V.; Moreira, A.L.N. (Karlsruhe, Universitaet (Germany))

1992-05-01

14

Exhaust recirculation  

Microsoft Academic Search

An exhaust gas recirculation system for the reduction of nitrogen oxides in automobile exhaust is described that provides for the reduction of recirculation during engine idling without the prior-art complexities of moving parts. The system also achieves preheating and improved mixing and carburetion of the fuel-air mixture in the inlet header. Exhaust gases are recycled by means of a swirl

Sarto

1974-01-01

15

Recirculation regeneration  

Microsoft Academic Search

Disclosed are improved recirculating sorption bed systems of the type in which one sorption bed is in sorption duty while another is being regenerated thermally by a recirculating regeneration loop. The regeneration loop includes a cooler\\/condenser, a heater, and a tertiary sorption bed. The tertiary bed takes up sorbate from the coolant stream that may contain sorbate as a result

Oliker

1984-01-01

16

Recirculating rotary gas compressor  

DOEpatents

A positive displacement, recirculating Roots-type rotary gas compressor which operates on the basis of flow work compression. The compressor includes a pair of large diameter recirculation conduits (24 and 26) which return compressed discharge gas to the compressor housing (14), where it is mixed with low pressure inlet gas, thereby minimizing adiabatic heating of the gas. The compressor includes a pair of involutely lobed impellers (10 and 12) and an associated port configuration which together result in uninterrupted flow of recirculation gas. The large diameter recirculation conduits equalize gas flow velocities within the compressor and minimize gas flow losses. The compressor is particularly suited to applications requiring sustained operation at higher gas compression ratios than have previously been feasible with rotary pumps, and is particularly applicable to refrigeration or other applications requiring condensation of a vapor.

Weinbrecht, John F. (601 Oakwood Loop, NE., Albuquerque, NM 87123)

1992-01-01

17

Recirculating rotary gas compressor  

DOEpatents

A positive displacement, recirculating Roots-type rotary gas compressor is described which operates on the basis of flow work compression. The compressor includes a pair of large diameter recirculation conduits which return compressed discharge gas to the compressor housing, where it is mixed with low pressure inlet gas, thereby minimizing adiabatic heating of the gas. The compressor includes a pair of involutely lobed impellers and an associated port configuration which together result in uninterrupted flow of recirculation gas. The large diameter recirculation conduits equalize gas flow velocities within the compressor and minimize gas flow losses. The compressor is particularly suited to applications requiring sustained operation at higher gas compression ratios than have previously been feasible with rotary pumps, and is particularly applicable to refrigeration or other applications requiring condensation of a vapor. 12 figs.

Weinbrecht, J.F.

1992-02-25

18

Wind Effect, Recirculation and Thermal Flow Field of a Direct Air-cooled Condenser for a Large Power Plant  

NASA Astrophysics Data System (ADS)

The thermal effect experiments were carried out of a direct air-cooled system in the low speed wind tunnel. The influence of effect factors on recirculation is also discussion, after that the relationship between the thermal flow field structure and recirculation ratio under the cooling tower is analyzed. At last, the engineering measures to reduce or avoid recirculation are proposed. For certain conditions the experimental measurement shows close agreement with numerical values.

Zhao, W. L.; Liu, P. Q.; Duan, H. S.; Zhu, J. Y.

2011-09-01

19

Rupture Zones of Large South American Earthquakes and Some Predictions  

Microsoft Academic Search

This study attempts to forecast likely locations for large shallow South American earthquakes in the near future by examining the past space-time pattern of occurrence of large (M _ 7.7) earthquakes, the lateral extent of their rupture zones, and, where possible, the direction of rupture propagation. Rupture zones of large shallow earthquakes generally abut and do not overlap. Patterns of

John A. Kelleher

1972-01-01

20

Plastic zone and pileup around large indentations  

SciTech Connect

Mechanical properties of cold-worked molybdenum, grade 4 titanium, and an {alpha}-{beta} titanium alloy are measured with tensile tests and by indentations using conical indenters with 105, 120, and 137 deg included angles. The extent of plastic deformation and pileup around an indentation is measured using profilometry. Various models predicting the extent of plastic deformation and pileup are compared to the actual measured values. As inferred from indentation, the calculated yield strength of the material from the mean pressure does not correlate well to the yield strength measured by tensile testing. The plastic zone size surrounding an indentation can also be used to determine the yield strength of the material, and this does correlate to the yield strength measured by tensile tests. Furthermore, the extent of plastic deformation is relatively independent of the included angle of the indenter for the range of materials used in this system. Models predicting the amount of pileup at the edges of the indentation appear to approach but overestimate the actual amount of pileup in the materials tested.

Bahr, D.F.; Gerberich, W.W. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science

1996-12-01

21

Noncharacteristic behavior and complex recurrence of large subduction zone earthquakes  

Microsoft Academic Search

The last few years have been remarkable with respect to the number of large underthrusting earthquakes in subduction zones that reruptured plate boundary segments that failed in previous great events. Availability of modern seismic data for two consecutive large earthquakes rupturing the same portion of the plate interface provides the opportunity to compare the spatial distribution of moment release for

Susan Y. Schwartz

1999-01-01

22

Large-Area Zone Plate Fabrication with Optical Lithography  

NASA Astrophysics Data System (ADS)

Zone plates as condenser optics for x-ray microscopes offer simple optical designs for both illumination and spectral resolution when used as a linear monochromator. However, due to the long write times for electron beam lithography, both the availability and the size of zone plates for condensers have been limited. Since the resolution provided by the linear monochromator scales almost linearly with the diameter of the zone plate, the full potential for zone plate monochromators as illumination systems for x-ray microscopes has not been achieved. For example, the 10-mm-diameter zone plate has demonstrated a spectral resolution of E/?E = 700 [1], but with a 26-mm-diameter zone plate, the calculated spectral resolution is higher than E/?E = 3000. These large-area zone plates are possible to fabricate with the leading edge semiconductor lithography tools such as those available at the College of Nanoscale Science and Engineering at the University at Albany. One of the lithography tools available is the ASML TWINSCAN XT: 1950i with 37-nm resolution [2]. A single 300-mm wafer can contain more than 60 fields, each with a large area condenser, and the throughput of the tool can be more than one wafer every minute.

Denbeaux, G.

2011-09-01

23

Large-Area Zone Plate Fabrication with Optical Lithography  

SciTech Connect

Zone plates as condenser optics for x-ray microscopes offer simple optical designs for both illumination and spectral resolution when used as a linear monochromator. However, due to the long write times for electron beam lithography, both the availability and the size of zone plates for condensers have been limited. Since the resolution provided by the linear monochromator scales almost linearly with the diameter of the zone plate, the full potential for zone plate monochromators as illumination systems for x-ray microscopes has not been achieved. For example, the 10-mm-diameter zone plate has demonstrated a spectral resolution of E/{Delta}E = 700[1], but with a 26-mm-diameter zone plate, the calculated spectral resolution is higher than E/{Delta}E = 3000. These large-area zone plates are possible to fabricate with the leading edge semiconductor lithography tools such as those available at the College of Nanoscale Science and Engineering at the University at Albany. One of the lithography tools available is the ASML TWINSCAN XT: 1950i with 37-nm resolution [2]. A single 300-mm wafer can contain more than 60 fields, each with a large area condenser, and the throughput of the tool can be more than one wafer every minute.

Denbeaux, G. [College of Nanoscale Science and Engineering, University at Albany, 255 Fuller Road, Albany, NY 12203 (United States)

2011-09-09

24

Hydro-mechanical behavior of Municipal Solid Waste subject to leachate recirculation in a large-scale compression reactor cell  

SciTech Connect

The paper presents the results of a laboratory experiment on Municipal Solid Waste (MSW) subjected to one-dimensional compression in a 1 m{sup 3} instrumented cell. The focus was on the hydro-mechanical behavior of the material under conditions of confinement and leachate percolation that replicate those found in real-scale landfills. The operation of the apparatus is detailed together with the testing methodology and the monitoring program. Two samples of waste were tested: the first extended over a period of 10 months ('Control Test') and the second for 22 months ('Enhanced Test' with leachate recirculation). Consolidation data is reported with regard to both short-term (stress-dependent) and long-term (time-dependent) settlements. A discussion follows based on the derived values of primary and secondary compression ratios. Correlations between compression parameters and the biodegradation process are presented. In particular, results clearly highlight the effect of leachate recirculation on waste settlement: 24% secondary deformation reached after slightly less than 2 years (equivalent to a 5-fold increase in compressibility) and 17.9% loss of dry matter. Comparisons are proposed considering the results derived from the few monitoring programs conducted on experimental bioreactors worldwide. Finally, the hydraulic characterization of waste is discussed with regard to the evaluation of effective porosity and permeability.

Olivier, Franck [Environment, Energy and Waste Research Center (CREED), 291, avenue Dreyfous Ducas, 78520 Limay (France) and Laboratoire LIRIGM - Maison des Geosciences, 1381, rue de la piscine 38400 Saint-Martin d'Heres (France)]. E-mail: franck.olivier@ujf-grenoble.fr; Gourc, Jean-Pierre [Laboratoire LIRIGM - Maison des Geosciences, 1381, rue de la piscine 38400 Saint-Martin d'Heres (France)]. E-mail: gourc@ujf-grenoble.fr

2007-07-01

25

Hydro-mechanical behavior of municipal solid waste subject to leachate recirculation in a large-scale compression reactor cell.  

PubMed

The paper presents the results of a laboratory experiment on Municipal Solid Waste (MSW) subjected to one-dimensional compression in a 1 m3 instrumented cell. The focus was on the hydro-mechanical behavior of the material under conditions of confinement and leachate percolation that replicate those found in real-scale landfills. The operation of the apparatus is detailed together with the testing methodology and the monitoring program. Two samples of waste were tested: the first extended over a period of 10 months ('Control Test') and the second for 22 months ('Enhanced Test' with leachate recirculation). Consolidation data is reported with regard to both short-term (stress-dependent) and long-term (time-dependent) settlements. A discussion follows based on the derived values of primary and secondary compression ratios. Correlations between compression parameters and the biodegradation process are presented. In particular, results clearly highlight the effect of leachate recirculation on waste settlement: 24% secondary deformation reached after slightly less than 2 years (equivalent to a 5-fold increase in compressibility) and 17.9% loss of dry matter. Comparisons are proposed considering the results derived from the few monitoring programs conducted on experimental bioreactors worldwide. Finally, the hydraulic characterization of waste is discussed with regard to the evaluation of effective porosity and permeability. PMID:16563727

Olivier, Franck; Gourc, Jean-Pierre

2006-03-23

26

Evidence for large earthquakes at the Cascadia subduction zone  

Microsoft Academic Search

Large, historically unprecedented earthquakes at the Cascadia subduction zone in western North America have left signs of sudden land level change, tsunamis, and strong shaking in coastal sediments. The coastal geological evidence suggests that many of the earthquakes occurred at the boundary between the overriding North American plate and the subducting Juan de Fuca plate. This hypothesis is consistent with

John J. Clague

1997-01-01

27

Recirculating flow and sedimentation in the Colorado River in Grand Canyon, Arizona  

Microsoft Academic Search

Debris fans debouching into the bottom of Grand Canyon create rapids and flow separation in the Colorado River. The patterns of flow and the behavior of recirculation zones formed by flow separation are consistent throughout the Canyon's length. Zones of recirculating flow occur along the margin of channel expansions. Recirculation zones are comprised of one primary eddy; secondary eddies and

John C. Schmidt

1990-01-01

28

A satellite magnetic perspective of subduction zones, large igneous provinces, rifts, and diffuse plate boundary zones  

NASA Astrophysics Data System (ADS)

Large and intermediate-scale tectonic features such as subduction zones, large igneous provinces, rifts, and diffuse plate boundary zones are often seen to have a magnetic signature visible from the perspective of near-Earth magnetic field satellites such as CHAMP and Orsted. Why do these tectonic features have a magnetic signature, while others do not? A new model of the lithospheric field (MF-6, Maus et al., 2008) extending to spherical harmonic degree 120 (333 km wavelength) has been used to evaluate the magnetic state of the lithosphere under the assumption that the magnetization is either induced (with a seismic starting model), or remanent (with a minimum norm approach). Some of the features identified from these images include the Tethyan and NE Siberian diffuse plate boundary zones, the Red Sea rift, and Cretaceous rift basins developed on the West African shield. Almost without exception, subduction zones exhibit a magnetic signature, as do many large igneous provinces. In this talk we discuss some of the new insights this magnetic perspective provides, and speculate on the controls which determine whether tectonic features will be expressed magnetically.

Purucker, M. E.; Whaler, K. A.

2008-12-01

29

Flume simulation of sedimentation in recirculating flow  

SciTech Connect

A 4-m-wide flume at the University of Tsukuba Environmental Research Center was used to simulate flow conditions near debris fans in bedrock gorges. Flow was constricted to 2 m by a semicircular obstruction. During the authors experiments (discharge = 600 L/sec; Froude number of constricted flow = 1) a zone of recirculating current extended 25-30 m downstream from the separation point at the constriction. The pattern and velocity of surface flow was determined using time-lapse photography; subsurface velocity was measured with a two-dimensional electromagnetic current meter. During 32-hr of run time, a fine, very coarse sand mixture was fed into the flow at a rate between 0.5-1 kg/sec. Oscillation ripples developed beneath the separation surface that bounds the recirculation zone, and upstream-migrating dunes and ripples developed within the recirculation zone upstream from the reattachment point. A mid-channel expansion bar was deposited downstream from the reattachment point. Sedimentation within the recirculation zone continued by vertical aggradation and by upstream migration of dunes and ripples. Sediments within the recirculation zone were areally sorted with the finest sediment deposited near the separation point. These patterns are consistent with field observations of bars along the Colorado River in the Grand Canyon.

Schmidt, J.C. (Middlebury College, VT (USA)); Rubin, D.M. (Geological Survey, Menlo Park, CA (USA)); Ikeda, H. (Univ. of Tsukuba (Japan))

1990-05-01

30

Validation for a recirculation model.  

PubMed

Recent Clean Air Act regulations designed to reduce volatile organic compound (VOC) emissions have placed new restrictions on painting operations. Treating large volumes of air which contain dilute quantities of VOCs can be expensive. Recirculating some fraction of the air allows an operator to comply with environmental regulations at reduced cost. However, there is a potential impact on employee safety because indoor pollutants will inevitably increase when air is recirculated. A computer model was developed, written in Microsoft Excel 97, to predict compliance costs and indoor air concentration changes with respect to changes in the level of recirculation for a given facility. The model predicts indoor air concentrations based on product usage and mass balance equations. This article validates the recirculation model using data collected from a C-130 aircraft painting facility at Hill Air Force Base, Utah. Air sampling data and air control cost quotes from vendors were collected for the Hill AFB painting facility and compared to the model's predictions. The model's predictions for strontium chromate and isocyanate air concentrations were generally between the maximum and minimum air sampling points with a tendency to predict near the maximum sampling points. The model's capital cost predictions for a thermal VOC control device ranged from a 14 percent underestimate to a 50 percent overestimate of the average cost quotes. A sensitivity analysis of the variables is also included. The model is demonstrated to be a good evaluation tool in understanding the impact of recirculation. PMID:11318387

LaPuma, P T

2001-04-01

31

Recirculating Electron Beam Linac.  

National Technical Information Service (NTIS)

One method to achieve a high gradient, linear induction accelerator is to recirculate the electron beam in phase with a repeating accelerating voltage. A two-cavity recirculating accelerator has been designed and operated in a single-pass mode. The protot...

W. K. Tucker S. L. Shope D. E. Hasti

1987-01-01

32

Lattice Design for the LHEC Recirculating Linac  

SciTech Connect

In this paper, we present a lattice design for the Large Hadron Electron Collider (LHeC) recirculating linac. The recirculating linac consists of one roughly 3-km long linac hosting superconducting RF (SRF) accelerating cavities, two arcs and one transfer line for the recirculation. In two passes through a pulsed SRF linac the electron beam can get a maximum energy of 140 GeV. Alternatively, in the Energy Recovery Linac (ERL) option the beam passes through a CW linac four times (two passes for acceleration and two for deceleration) for a maximum energy of 60 GeV.

Sun, Yipeng; /CERN; Eide, Anders; /CERN; Zimmermann, Frank; /CERN; Adolphsen, Chris; /SLAC

2011-05-20

33

33 CFR 165.839 - Safety Zone; Large Cruise Ships; Lower Mississippi River, Southwest Pass Sea Buoy to Mile Marker...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Safety Zone; Large Cruise Ships; Lower Mississippi River, Southwest...165.839 Safety Zone; Large Cruise Ships; Lower Mississippi River, Southwest...are established around all large cruise ships transiting between the Southwest...

2013-07-01

34

Quiet Zone within a Seismic Gap near Western Nicaragua: Possible Location of a Future Large Earthquake  

Microsoft Academic Search

A 5700-square-kilometer quiet zone occurs in the midst of the locations of more than 4000 earthquakes off the Pacific coast of Nicaragua. The region is indicated by the seismic gap technique to be a likely location for an earthquake of magnitude larger than 7. The quiet zone has existed since at least 1950; the last large earthquake originating from this

David H. Harlow; Randall A. White; Ines Lucia Cifuentes; Arturo Aburto Q

1981-01-01

35

Exhaust gas recirculation apparatus  

Microsoft Academic Search

Apparatus is disclosed for recirculating combustion exhaust gases to the burner region of a Stirling cycle hot-gas engine to lower combustion temperature and reduct NO\\/sub x\\/ formation includes a first wall separating the exhaust gas stream from the inlet air stream, a second wall separating the exhaust gas stream from the burner region, and low flow resistance ejectors formed in

R. A. Egnell; B. L. Hansson

1981-01-01

36

33 CFR 165.1318 - Security and Safety Zone Regulations, Large Passenger Vessel Protection, Captain of the Port...  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Security and Safety Zone Regulations, Large Passenger Vessel...SECURITY (CONTINUED) PORTS AND WATERWAYS SAFETY REGULATED NAVIGATION AREAS AND LIMITED...District § 165.1318 Security and Safety Zone Regulations, Large Passenger...

2013-07-01

37

Airlift recirculation well test results -- Southern sector  

SciTech Connect

Chlorinated solvents used in the A and M-Areas at the Savannah River Site (SRS) from 1952--1982 have contaminated the groundwater under the site. A plume of groundwater contaminated with trichloroethylene (TCE) and perchloroethylene (PCE) in the Lost Lake aquifer is moving generally southward with the natural flow of groundwater. To comply with the requirements of the current SCDHEC Part B Permit, a series of wells is being installed to contain and treat the plume. Airlift Recirculation Wells (ARW) are a new and innovative technology with potential for more cost effective implementation than conventional pump and treat systems. Two Airlift Recirculation Wells have been installed and tested to quantify performance parameters needed to locate a line of these wells along the leading edge of the contaminant plume. The wells proved to be very sensitive to proper development, but after this requirement was met, performance was very good. The Zone of Capture has been estimated to be within a radius of 130--160 ft. around the wells. Thus a line of wells spaced at 250 ft. intervals could intercept the contaminant plume. At SSR-012, TCE was stripped from the groundwater at approximately 1.2 lb./day. The longer term effect of the recirculation wells upon the plume and the degree of recirculation within the aquifer itself will require additional data over a longer time period for an accurate review. Data collection is ongoing.

White, R.M.; Hiergesell, R.A.

1997-08-01

38

Hydraulics of recirculating well pairs for ground water remediation.  

PubMed

Recirculating well pairs are a proven means of implementing bioremediation and may also be useful for applying other in situ ground water remediation technologies. A bromide tracer test was performed to characterize the hydraulic performance of a recirculating well pair installed at Moffett Field, California. In particular, we estimate two important properties of the recirculating well pair: (1) the fraction of captured water that is recycled between the wells, and (2) the travel-time distribution of ground water in the induced zone of recirculation. We also develop theoretical estimates of these two properties and demonstrate they depend upon a dimensionless pumping rate, denoted xi. The bromide breakthrough curve predicted from theory agrees well with that determined experimentally at Moffett Field. The minimum travel time between the wells is denoted t(min). In theory, t(min) depends inversely on Q, the pumping rate in the recirculating wells, and is proportional to a2, the square of the distance between the wells. Both the experimental and theoretical travel-time distributions indicate that at least half the recirculating water travels between the wells along fast flowpaths (travel time < 2*t(min)). Therefore, when designing recirculating well pairs, engineers should ensure that t(min) will be sufficiently high to allow biologically mediated reactions (or other in situ remediation processes) sufficient time to proceed. PMID:15584301

Cunningham, Jeffrey A; Hoelen, Thomas P; Hopkins, Gary D; Lebrón, Carmen A; Reinhard, Martin

39

Monitoring of Leachate Recirculation in a Bioreactor Using Electrical Resistivity  

NASA Astrophysics Data System (ADS)

The bioreactor is a concept of waste landfill management consisting in speeding up the biodegradation by optimizing the moisture content through leachate recirculation. Electrical resistivity tomography (ERT) is carried out with fast resistivity-meter (Syscal Pro, IRIS Instruments, developed in the framework of the research project CERBERE 01V0665-69, funded by the French Research Ministry) to monitor leachate recirculation. During a recirculation period waste moisture increases, so that electrical resistivity may decrease, but at the same time temperature and mineralization of both waste and leachate become intermixed. If waste temperature is much higher than leachate temperature electrical resistivity will not decrease as much as if the temperature difference was smaller. If leachate mineralization (i.e. leachate conductivity) is higher than that of wet waste in the landfill, electrical resistivity will tend to decrease. Otherwise for example after an addition of rain water into the leachate storage or in case of very wet waste, the resistivities of each medium (leachate and wet waste) can be almost the same, so that leachate mineralization will not have a great influence on waste resistivity. Resistivity measurements were performed during 85 minutes injection trials (with a discharge of 20 m3 h-1) where leachate was injected through a vertical borehole perforated between 1.85 and 4.15 m. Three first measurements are made during the injection (3, 30 and 60 minutes from the beginning of the injection) and the two other after the injection period (8 and 72 minutes after the end of the injection). Apparent and interpreted resistivity variations that occurred during injection trials, expressed as the relative differences (in %) between apparent, respectively interpreted, resistivity during injection and apparent, respectively interpreted, resistivity before injection (reference measurement) show the formation of a plume (a negative anomaly: resistivity decreases with increasing moisture content). The positive anomaly could be explained by an increasing of biogas proportion in waste porosity. For this experiment, leachate temperature is relatively cold (between 5 and 10° C, as the injection trials take place at the end of October), leachate conductivity is about 9200 ? S cm-1 (i.e. a resistivity of 1.1 ? m) and waste resistivity in the borehole region is about 80 ? m. This is a situation where the temperature difference between waste and leachate is large and the resistivity difference between waste and leachate is high. The resistivity variation is essentially due to waste moisture increase. ERT method allows leachate diffusion to be seen through the waste mass and the influence zone of the leachate recirculation system to be determined.

Grellier, S.; Bureau, N.; Robain, H.; Tabbagh, A.; Camerlynck, C.; Guerin, R.

2004-05-01

40

Exhaust gas recirculation control valve  

Microsoft Academic Search

An exhaust gas recirculation control valve for preventing carbon and the like contained in the exhaust gas from attaching to the inner wall surface of exhaust gas paths, through which the exhaust gas from an engine of a motor car passes, thus decreasing the diameters of the paths with time. This exhaust gas recirculation control valve is provided in a

Masuda

1982-01-01

41

Hydroxyl time series and recirculation in turbulent nonpremixed swirling flames  

SciTech Connect

Time-series measurements of OH, as related to accompanying flow structures, are reported using picosecond time-resolved laser-induced fluorescence (PITLIF) and particle-imaging velocimetry (PIV) for turbulent, swirling, nonpremixed methane-air flames. The [OH] data portray a primary reaction zone surrounding the internal recirculation zone, with residual OH in the recirculation zone approaching chemical equilibrium. Modeling of the OH electronic quenching environment, when compared to fluorescence lifetime measurements, offers additional evidence that the reaction zone burns as a partially premixed flame. A time-series analysis affirms the presence of thin flamelet-like regions based on the relation between swirl-induced turbulence and fluctuations of [OH] in the reaction and recirculation zones. The OH integral time-scales are found to correspond qualitatively to local mean velocities. Furthermore, quantitative dependencies can be established with respect to axial position, Reynolds number, and global equivalence ratio. Given these relationships, the OH time-scales, and thus the primary reaction zone, appear to be dominated by convection-driven fluctuations. Surprisingly, the OH time-scales for these nominally swirling flames demonstrate significant similarities to previous PITLIF results in nonpremixed jet flames. (author)

Guttenfelder, Walter A.; Laurendeau, Normand M.; Ji, Jun; King, Galen B.; Gore, Jay P. [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-1288 (United States); Renfro, Michael W. [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139 (United States)

2006-10-15

42

77 FR 65816 - Safety Zone; Large Cruise Ships; Lower Mississippi River, Southwest Pass Sea Buoy to Mile Marker...  

Federal Register 2010, 2011, 2012, 2013

...1625-AA00 Safety Zone; Large Cruise Ships; Lower Mississippi River, Southwest Pass...moving safety zone around large cruise ships as they transit the Lower Mississippi River between the Port of New Orleans Cruise Ship Terminal, mile marker 96.0, and...

2012-10-31

43

77 FR 29254 - Safety Zones, Large Cruise Ships; Lower Mississippi River, Southwest Pass Sea Buoy to Mile Marker...  

Federal Register 2010, 2011, 2012, 2013

...1625-AA00 Safety Zones, Large Cruise Ships; Lower Mississippi River, Southwest Pass...moving safety zone around large cruise ships as they transit the Lower Mississippi River between the Port of New Orleans Cruise Ship Terminal, mile marker 96.0 and the...

2012-05-17

44

Exhaust gas recirculation apparatus  

SciTech Connect

Apparatus is disclosed for recirculating combustion exhaust gases to the burner region of a Stirling cycle hot-gas engine to lower combustion temperature and reduct NO/sub x/ formation includes a first wall separating the exhaust gas stream from the inlet air stream, a second wall separating the exhaust gas stream from the burner region, and low flow resistance ejectors formed in the first and second walls for admitting the inlet air to the burner region and for entraining and mixing with the inlet air portion of the exhaust gas stream. In a preferred embodiment the ejectors are arranged around the periphery of a cylindrical burner region and oriented to admit the air/exhaust gas mixture tangentially to promote mixing. In another preferred embodiment a single annular ejector surrounds and feeds the air/exhaust gas mixture to a cylindrical burner region. The annular ejector includes an annular plate with radially-directed flow passages to provide an even distribution of the air/exhaust gas mixture to the burner region.

Egnell, R.A.; Hansson, B.L.

1981-07-14

45

Dogbone geometry for recirculating accelerators.  

National Technical Information Service (NTIS)

Most scenarios for accelerating muons require recirculating acceleration. A racetrack shape for the accelerator requires particles with lower energy in early passes to traverse almost the same length of arc as particles with the highest energy. This extra...

S. Berg Johnstone Summers

2001-01-01

46

Floating zone growth of large single crystals of SrFeO  

NASA Astrophysics Data System (ADS)

The Fe4+-containing cubic perovskite phase SrFeO is of interest both for its high-temperature, oxygen-conducting properties as a solid oxide fuel cell component, and at low temperatures, where it exhibits a plethora of helical magnetic phases and a candidate Skyrmion lattice. However, a sequence of structural phase transitions encountered on cooling to room temperature has limited the size of single crystals. We report the floating-zone growth and oxygen-annealing of multiple-cubic-centimetre-sized single crystals of SrFeO, suitable for inelastic neutron scattering and other measurement techniques requiring large sample volumes.

Peets, D. C.; Kim, Jung-hwa; Reehuis, M.; Dosanjh, P.; Keimer, B.

2012-12-01

47

Classification of lymphocytes recirculating in the spleen.  

PubMed Central

After washing out remaining blood cells using cold perfusate, pig spleens were connected to a closed-circuit normothermic perfusion system. Recirculating lymphocytes migrated out and rapidly established an equilibrium with the splenic extravascular lymphoid tissues. Comparison of the subpopulations among these lymphocytes with those in the blood at time of removal of the spleen, showed the absence of Null cells and reduced numbers of weakly E-rosetting cells among splenic emigrants. The proportion of other B- and T-cell subpopulations were increased in a way which might be explained by non-recirculation of these two subpopulations. Autologous blood lymphocytes labelled with fluorescein isothiocyanate and introduced into spleen perfusions rapidly established equilibrium (approximately 15%-25%, well within 1 hr) and at the end of perfusion were concentrated in the marginal zones. The fluorescent lymphocytes remaining in the perfusate showed a marked enrichment of Null cells suggesting that these cells do not home to splenic extravascular lymphoid tissues in agreement with the hypothesis that Null cells are absent from splenic emigrants because they are nonrecirculating cells. Images Figure 1 Figure 2

Binns, R M; Pabst, R; Licence, S T

1981-01-01

48

Classification of lymphocytes recirculating in the spleen.  

PubMed

After washing out remaining blood cells using cold perfusate, pig spleens were connected to a closed-circuit normothermic perfusion system. Recirculating lymphocytes migrated out and rapidly established an equilibrium with the splenic extravascular lymphoid tissues. Comparison of the subpopulations among these lymphocytes with those in the blood at time of removal of the spleen, showed the absence of Null cells and reduced numbers of weakly E-rosetting cells among splenic emigrants. The proportion of other B- and T-cell subpopulations were increased in a way which might be explained by non-recirculation of these two subpopulations. Autologous blood lymphocytes labelled with fluorescein isothiocyanate and introduced into spleen perfusions rapidly established equilibrium (approximately 15%-25%, well within 1 hr) and at the end of perfusion were concentrated in the marginal zones. The fluorescent lymphocytes remaining in the perfusate showed a marked enrichment of Null cells suggesting that these cells do not home to splenic extravascular lymphoid tissues in agreement with the hypothesis that Null cells are absent from splenic emigrants because they are nonrecirculating cells. PMID:6795107

Binns, R M; Pabst, R; Licence, S T

1981-10-01

49

Rupture process of large earthquakes in the northern Mexico subduction zone  

NASA Astrophysics Data System (ADS)

The Cocos plate subducts beneath North America at the Mexico trench. The northernmost segment of this trench, between the Orozco and Rivera fracture zones, has ruptured in a sequence of five large earthquakes from 1973 to 1985; the Jan. 30, 1973 Colima event ( M s 7.5) at the northern end of the segment near Rivera fracture zone; the Mar. 14, 1979 Petatlan event ( M s 7.6) at the southern end of the segment on the Orozco fracture zone; the Oct. 25, 1981 Playa Azul event ( M s 7.3) in the middle of the Michoacan “gap”; the Sept. 19, 1985 Michoacan mainshock ( M s 8.1); and the Sept. 21, 1985 Michoacan aftershock ( M s 7.6) that reruptured part of the Petatlan zone. Body wave inversion for the rupture process of these earthquakes finds the best: earthquake depth; focal mechanism; overall source time function; and seismic moment, for each earthquake. In addition, we have determined spatial concentrations of seismic moment release for the Colima earthquake, and the Michoacan mainshock and aftershock. These spatial concentrations of slip are interpreted as asperities; and the resultant asperity distribution for Mexico is compared to other subduction zones. The body wave inversion technique also determines the Moment Tensor Rate Functions; but there is no evidence for statistically significant changes in the moment tensor during rupture for any of the five earthquakes. An appendix describes the Moment Tensor Rate Functions methodology in detail. The systematic bias between global and regional determinations of epicentral locations in Mexico must be resolved to enable plotting of asperities with aftershocks and geographic features. We have spatially “shifted” all of our results to regional determinations of epicenters. The best point source depths for the five earthquakes are all above 30 km, consistent with the idea that the down-dip edge of the seismogenic plate interface in Mexico is shallow compared to other subduction zones. Consideration of uncertainties in the focal mechanisms allows us to state that all five earthquakes occurred on fault planes with the same strike (N65°W to N70°W) and dip (15±3°), except for the smaller Playa Azul event at the down-dip edge which has a steeper dip angle of 20 to 25°. However, the Petatlan earthquake does “prefer” a fault plane that is rotated to a more east-west orientation—one explanation may be that this earthquake is located near the crest of the subducting Orozco fracture zone. The slip vectors of all five earthquakes are similar and generally consistent with the NUVEL-predicted Cocos-North America convergence direction of N33°E for this segment. The most important deviation is the more northerly slip direction for the Petatlan earthquake. Also, the slip vectors from the Harvard CMT solutions for large and small events in this segment prefer an overall convergence direction of about N20°E to N25°E. All five earthquakes share a common feature in the rupture process: each earthquake has a small initial precursory arrival followed by a large pulse of moment release with a distinct onset. The delay time varies from 4 s for the Playa Azul event to 8 s for the Colima event. While there is some evidence of spatial concentration of moment release for each event, our overall asperity distribution for the northern Mexico segment consists of one clear asperity, in the epicentral region of the 1973 Colima earthquake, and then a scattering of diffuse and overlapping regions of high moment release for the remainder of the segment. This character is directly displayed in the overlapping of rupture zones between the 1979 Petatlan event and the 1985 Michoacan aftershock. This character of the asperity distribution is in contrast to the widely spaced distinct asperities in the northern Japan-Kuriles Islands subduction zone, but is somewhat similar to the asperity distributions found in the central Peru and Santa Cruz Islands subduction zones. Subduction of the Orozco fracture zone may strongly affect the seismogenic character as the overlapping rupture zones are located on the

Ruff, Larry J.; Miller, Angus D.

1994-03-01

50

The South ``West'' Pacific Convergence Zone: Large-scale feedback on atmospheric subsidence to the east  

NASA Astrophysics Data System (ADS)

Three semi-permanent convective cloud bands exist in the Southern Hemisphere extending southeastward from the equator, through the tropics, and into the subtropics. The most prominent of these features occurs in the South Pacific during summer and is referred to as the South Pacific Convergence Zone (SPCZ). Similar cloud bands, with less intensity, exist in the South Indian and Atlantic basins. To the east of each convective zone is a large-scale region of atmospheric subsidence. We attempt to explain the physical mechanisms that promote the diagonal orientation of the SPCZ and also teleconnections that may exist with stratocumulus cloud cover in the southeastern Pacific. It is argued that slowly varying sea surface temperature patterns produce upper tropospheric wind fields that vary substantially in longitude (?U/?x). Regions where 200 hPa zonal winds decrease with longitude (i.e., negative zonal stretching deformation, or ?U/?x<0) reduce the group speed of the eastward propagating synoptic (3-6 day period) Rossby waves and locally increase the wave energy density. Such a region of wave accumulation occurs in the vicinity of the SPCZ (see Figure), thus providing a hypothesis for the diagonal orientation and a physical basis for earlier observations that the zone traps eastward propagating synoptic disturbances. Controlled numerical experiments and composites of observed life cycles of synoptic waves confirm that disturbances slow in the SPCZ. From the hypothesis comes a more general theory accounting for the SPCZ’s spatial orientation and the lack of disturbances to the east. December-February climatology of 200 hPa zonal winds (shading) and negative zonal stretching deformation (red contours). Large black box located at 20°S-35°S, 165°W-135°W encloses the diagonal region of the SPCZ. 240 W m-2 OLR contour outlined by blue lines.

Widlansky, M. J.; Webster, P. J.; Hoyos, C.

2010-12-01

51

Vertical stress transfer after large subduction zone earthquakes: 2007 Tocopilla /North Chile case study  

NASA Astrophysics Data System (ADS)

Large interplate subduction zone earthquakes occur on fault planes within the seismogenic interface which, in the case of Northern Chile, usually start to break at the down dip end of the coupled interface, propagating towards the trench. Although the rupture is a horizontally oriented process, some vertical connectivity between the interface and the upper crust should be expected. We study two clusters of aftershock seismicity from the Mw 7.7, 2007, Tocopilla earthquake in Northern Chile Both clusters seem to align along vertical profiles in the upper crust above the main shock rupture plane. The first cluster has a rather dissipative character at the up-dip limit of the rupture plane in the off-shore area around the Peninsula of Mejillones. It developed in the early stage of the aftershock sequence. The second cluster lies above the pronounced aftershock sequence of a secondary large Mw 6.9 slab-push event on 16th of December 2007. This type of compressional event can occur after large thrust earthquakes. A comparison of the epicentral distribution of the crustal events belonging to the aftershock sequence suggests a possible relation to the Cerro Fortuna Fault in the Coastal Cordillera which is a subsidiary fault strand of the major Atacama Fault Zone. We compute the Coulomb stress change on the respective faults of both clusters analyzed to see where slip is promoted or inhibited due to the slip on the subduction interface. We then combine these results with the spatial and temporal aftershock distribution, focal mechanism solutions, b-value mappings and geological evidences to understand the process behind the ascending seismicity clusters and their relation to the main shock of the major Tocopilla event.

Eggert, S.; Sobiesiak, M.; Victor, P.

2011-12-01

52

Decoupling of lithospheric plates along the Hellenic subduction zone and repeat times of large earthquakes  

NASA Astrophysics Data System (ADS)

The subduction zone along the Hellenic arc is the most active in the entire Mediterranean region producing shallow, interplate and intermediate-depth earthquakes with magnitudes of instrumental earthquakes up to about 7.2. Very large, possibly interplate, historical earthquakes assigning magnitudes up to about 8.0 occurred in 365 and 1303 in the western and eastern segments of the Hellenic arc, respectively. Such earthquakes produced also large tsunamis which propagated up to remote places of the eastern Mediterranean basin. The generation of large earthquakes and their repeat times depend on the degree of lithospheric decoupling. We quantify the degree of decoupling as the ratio of aseismic slip rate over the plate motion rate; where aseismic slip rate equals plate motion rate minus seismic slip rate. From the lateral and vertical distribution of modern seismicity, along with large scale morphotectonic features, we determined a number of main segments along the plate interface in the Hellenic arc and calculated the degree of decoupling in each one of these segments by using an updated historical earthquake catalog and GPS data to calculate the seismic slip rate and the plate motion rate. The degree of decoupling is then used as a measure of the seismic potential accumulated as well as to control if it is consistent with the historical seismicity rate with profound forecasting consequences.

Daskalaki, Elena; Papadopoulos, Gerassimos; Siettos, Constantinos

2013-04-01

53

Times of increased probability of large earthquakes ( Ms ? 7.5) along the Mexican subduction zone  

NASA Astrophysics Data System (ADS)

Using the method of pattern recognition of infrequent events, we explore the possibility of identifying the times of increased probability (TIP) of occurrence of large earthquakes ( Ms ? 7.5) along the Mexican subduction zone. A TIP refers to a 5 year period within which a strong earthquake has a high probability of occurrence. We analyzed the seismicity for the regions of Chiapas-Eastern Oaxaca (91-97°W, Region 1), Western Oaxaca-Guerrero (97-102°W, Region 2), and Michoacan-Colima-Jalisco (102-106°W, Region 3) for the time interval 1970-1991 with the National Oceanic and Atmospheric Administration seismic catalog as the source data. The premonitory intermediate-term seismic activation to identify a TIP was measured using the algorithm M8. Three out of the five earthquakes of Ms ? 7.5 that occurred during the studied period are diagnosed by algorithm M8, and for the Region 3 segment a TIP is identified that will end between 1994 and 1996. We consider the area between the Western Colima gap and the Jalisco region (103.7-106.0°W) as the zone where the forecast earthquake has a higher than usual probability of occurrence. Our results by no means constitute a definitive earthquake prediction but suggest the need for detailed seismic analysis and the study of other geophysical precursors along the Colima-Jalisco segment.

Novelo-Casanova, David A.; Alvarez-Moctezuma, Jose

1995-01-01

54

Contamination of port zone sediments by metals from Large Marine Ecosystems of Brazil.  

PubMed

Sediment contamination by metals poses risks to coastal ecosystems and is considered to be problematic to dredging operations. In Brazil, there are differences in sedimentology along the Large Marine Ecosystems in relation to the metal distributions. We aimed to assess the extent of Al, Fe, Hg, Cd, Cr, Cu, Ni, Pb and Zn contamination in sediments from port zones in northeast (Mucuripe and Pecém) and southeast (Santos) Brazil through geochemical analyses and sediment quality ratings. The metal concentrations found in these port zones were higher than those observed in the continental shelf or the background values in both regions. In the northeast, metals were associated with carbonate, while in Santos, they were associated with mud. Geochemical analyses showed enrichments in Hg, Cd, Cu, Ni and Zn, and a simple application of international sediment quality guidelines failed to predict their impacts, whereas the use of site-specific values that were derived by geochemical and ecotoxicological approaches seemed to be more appropriate in the management of the dredged sediments. PMID:22306311

Buruaem, Lucas M; Hortellani, Marcos A; Sarkis, Jorge E; Costa-Lotufo, Leticia V; Abessa, Denis M S

2012-02-04

55

The impact of building recirculation rates on secondary organic aerosols generated by indoor chemistry  

Microsoft Academic Search

Numerous investigators have documented increases in the concentrations of airborne particles as a consequence of ozone\\/terpene reactions in indoor environments. This study examines the effect of building recirculation rates on the concentrations of secondary organic aerosol (SOA) resulting from reactions between indoor limonene and ozone. The experiments were conducted in a large environmental chamber using four recirculation rates (11, 14,

M. S. Zuraimi; C. J. Weschler; K. W. Tham; M. O. Fadeyi

2007-01-01

56

A combustion concept for oxyfuel processes with low recirculation rate – Experimental validation  

Microsoft Academic Search

Oxyfuel combustion is a technology for Carbon Capture & Storage from coal fired power plants. One drawback is the large necessary amount of recirculation of cold flue gases into the combustion chamber to avoid inadmissible high flame temperatures. The new concept of Controlled Staging with Non-stoichiometric Burners (CSNB) makes a reduction of the recirculation rate possible without inadmissible high flame

Valentin Becher; Jan-Peter Bohn; Adrian Goanta; Hartmut Spliethoff

2011-01-01

57

Large-scale modeling of reactive solute transport in fracture zones of granitic bedrocks.  

PubMed

Final disposal of high-level radioactive waste in deep repositories located in fractured granite formations is being considered by several countries. The assessment of the safety of such repositories requires using numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the Redox Zone Experiment carried out at the underground laboratory of Aspö in Sweden. This experiment aimed at evaluating the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Most chemical species showed dilution trends except for bicarbonate and sulphate which unexpectedly increased with time. Molinero and Samper [Molinero, J. and Samper, J. Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Aspö (Sweden). J. Hydraul. Res., 42, Extra Issue, 157-172] presented a two-dimensional water flow and solute transport finite element model which reproduced measured drawdowns and dilution curves of conservative species. Here we extend their model by using a reactive transport which accounts for aqueous complexation, acid-base, redox processes, dissolution-precipitation of calcite, quartz, hematite and pyrite, and cation exchange between Na+ and Ca2+. The model provides field-scale estimates of cation exchange capacity of the fracture zone and redox potential of groundwater recharge. It serves also to identify the mineral phases controlling the solubility of iron. In addition, the model is useful to test the relevance of several geochemical processes. Model results rule out calcite dissolution as the process causing the increase in bicarbonate concentration and reject the following possible sources of sulphate: (1) pyrite dissolution, (2) leaching of alkaline sulphate-rich waters from a nearby rock landfill and (3) dissolution of iron monosulphides contained in Baltic seafloor sediments. Based on these results, microbially mediated processes are postulated as the most likely hypothesis to explain the measured increase of dissolved bicarbonates and sulphates after tunnel construction. PMID:16337025

Molinero, Jorge; Samper, Javier

2005-12-05

58

Large-scale modeling of reactive solute transport in fracture zones of granitic bedrocks  

NASA Astrophysics Data System (ADS)

Final disposal of high-level radioactive waste in deep repositories located in fractured granite formations is being considered by several countries. The assessment of the safety of such repositories requires using numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the Redox Zone Experiment carried out at the underground laboratory of Äspö in Sweden. This experiment aimed at evaluating the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Most chemical species showed dilution trends except for bicarbonate and sulphate which unexpectedly increased with time. Molinero and Samper [Molinero, J. and Samper, J. Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Äspö (Sweden). J. Hydraul. Res., 42, Extra Issue, 157 172] presented a two-dimensional water flow and solute transport finite element model which reproduced measured drawdowns and dilution curves of conservative species. Here we extend their model by using a reactive transport which accounts for aqueous complexation, acid base, redox processes, dissolution precipitation of calcite, quartz, hematite and pyrite, and cation exchange between Na+ and Ca2+. The model provides field-scale estimates of cation exchange capacity of the fracture zone and redox potential of groundwater recharge. It serves also to identify the mineral phases controlling the solubility of iron. In addition, the model is useful to test the relevance of several geochemical processes. Model results rule out calcite dissolution as the process causing the increase in bicarbonate concentration and reject the following possible sources of sulphate: (1) pyrite dissolution, (2) leaching of alkaline sulphate-rich waters from a nearby rock landfill and (3) dissolution of iron monosulphides contained in Baltic seafloor sediments. Based on these results, microbially mediated processes are postulated as the most likely hypothesis to explain the measured increase of dissolved bicarbonates and sulphates after tunnel construction.

Molinero, Jorge; Samper, Javier

2006-01-01

59

Repeated large Slow Slip Events at the southcentral Alaska subduction zone  

NASA Astrophysics Data System (ADS)

We identify and study an ongoing Slow Slip Event (SSE) in the southcentral Alaska subduction zone using GPS measurements. This is the second large SSE in this region since modern geodetic measurements became available in 1993. We divide the ongoing SSE into two phases according to their transient displacement time evolution; their slip distributions are similar to each other but slip rates are slightly different. This ongoing SSE occurs downdip of the main asperity that ruptured in the 1964 Alaska earthquake, on the same part of the subduction interface as the earlier 1998–2001 SSE. The average slip rate of this SSE is ˜4–5 cm/yr, with a cumulative moment magnitude of Mw 7.5 (Mw 7.3 and Mw 7.1 For Phases I and II, respectively) through the end of 2012. The time and space dependence of the GPS displacements suggest that the slip area remained nearly the same during Phase I, while the slip rate increased with time. The SSEs occur on a transitional section of the subduction plate interface between the fully locked updip part and the freely slipping deeper part. During the 1964 earthquake, slip on the region of the SSE was much lower than slip in the updip region. Based on this observation and the repeated SSEs, we conclude that this part of the interface slips repeatedly in SSEs throughout the interseismic period and does not build up a large slip deficit to be released through large slip in earthquakes.

Fu, Yuning; Freymueller, Jeffrey T.

2013-08-01

60

In Situ Biotreatment of TBA with Recirculation/Oxygenation  

PubMed Central

The potential for in situ biodegradation of tert-butyl alcohol (TBA) by creation of aerobic conditions in the subsurface with recirculating well pairs was investigated in two field studies conducted at Vandenberg Air Force Base (VAFB). In the first experiment, a single recirculating well pair with bromide tracer and oxygen amendment successfully delivered oxygen to the subsurface for 42 days. TBA concentrations were reduced from approximately 500 ?g/L to below the detection limit within the treatment zone and the treated water was detected in a monitoring transect several meters downgradient. In the second experiment, a site-calibrated model was used to design a double recirculating well pair with oxygen amendment, which successfully delivered oxygen to the subsurface for 291 days and also decreased TBA concentrations to below the detection limit. Methylibium petroleiphilum strain PM1, a known TBA-degrading bacterium, was detectable at the study site but addition of oxygen had little impact on the already low baseline population densities, suggesting that there was not enough carbon within the groundwater plume to support significant new growth in the PM1 population. Given favorable hydrogeologic and geochemical conditions, the use of recirculating well pairs to introduce dissolved oxygen into the subsurface is a viable method to stimulate in situ biodegradation of TBA or other aerobically-degradable aquifer contaminants.

North, Katharine P.; Mackay, Douglas M.; Kayne, Julian S.; Petersen, Daniel; Rasa, Ehsan; Rastegarzadeh, Laleh; Holland, Reef B.; Scow, Kate M.

2012-01-01

61

Preliminary Study on Emittance Growth in the LHEC Recirculating Linac  

SciTech Connect

In this paper, we estimate the emittance growth in the LHeC recirculating Linac, the lattice design of which is presented in another paper of IPAC10 proceedings. The possible sources for emittance growth included here are: energy spread from RF acceleration in the SRF (superconducting RF) linac together with large chromatic effects from the lattice, and synchrotron radiation (SR) fluctuations in the recirculating arcs. 6-D multi-particle tracking is launched to calculate the emittance from the statistical point of view. The simulation results are also compared with a theoretical estimation.

Sun, Yi-Peng; Adolphsen, Chris; /SLAC; Zimmermann, Frank; /CERN

2011-05-20

62

Coseismic Slip Distributions of Great or Large Earthquakes in the Northern Japan to Kurile Subduction Zone  

NASA Astrophysics Data System (ADS)

Slip distributions of great and large earthquakes since 1963 along the northern Japan and Kuril trenches are examined to study the recurrence of interplate, intraslab and outer-rise earthquakes. The main findings are that the large earthquakes in 1991 and 1995 reruptured the 1963 great Urup earthquake source, and the 2006, 2007 and 2009 Simshir earthquakes were all different types. We also identify three seismic gaps. The northern Japan to southern Kurile trenches have been regarded as a typical subduction zone with spatially and temporally regular recurrence of great (M>8) interplate earthquakes. The source regions were grouped into six segments by Utsu (1972; 1984). The Headquarters for Earthquake Research Promotion of the Japanese government (2004) divided the southern Kurile subduction zone into four regions and evaluated future probabilities of great interplate earthquakes. Besides great interplate events, however, many large (M>7) interplate, intraslab, outer-rise and tsunami earthquakes have also occurred in this region. Harada, Ishibashi, and Satake (2010, 2011) depicted the space-time pattern of M>7 earthquakes along the northern Japan to Kuril trench, based on the relocated mainshock-aftershock distributions of all types of earthquakes occurred since 1913. The space-time pattern is more complex than that had been considered conventionally. Each region has been ruptured by a M8-class interplate earthquake or by multiple M7-class events. In this study, in order to examine more detail space pattern, or rupture areas, of M>7 earthquakes since 1963 (WWSSN waveform data have been available since this year), we estimated cosiesmic slip distributions by the Kikuchi and Kanamori's (2003) teleseismic body wave inversion method. The WWSSN waveform data were used for earthquakes before 1990, and digital teleseismic waveform data compiled by the IRIS were used for events after 1990. Main-shock hypocenters that had been relocated by our previous study were used as initial rupture points. Some preliminary results are as follows. Offshore Urup Is. is source region of the 1963 Urup earthquake (M 8.5). Large interplate earthquakes occurred in the eastern and western part of the 1963 source region in 1991 (M 7.6) and 1995 (M 7.9), respectively. Their aftershock areas almost re-occupied the 1963 aftershock area. The 1963, 1991, and 1995 coseismic slip distributions show that the southwestern asperity of the 1963 event seems to be re-ruptured by the 1995 earthquake. The 2009 Simushir earthquake (M 7.4) with reverse faulting occurred within the aftershock area of the 2007 great outer-rise event (M 8.1). The 2007 and 2009 coseismic slip distributions show that the 2007 normal faulting occurred in the shallower part of the Pacific plate and the 2009 reverse intraplate faulting occurred in the deeper part. Giant (the 2011 Tohoku earthquake of M 9.0), great and large interplate earthquakes occurred in the Kurile to Japan subduction zone after 1990s successively. The aftershock areas and coseismic slip distributions clearly show that only three seismic gaps (offshore Aomori pref., offshore eastern Hokkaido to Etorofu Is., and offshore between Urup and Simushir Is.) have remained in this region.

Harada, T.; Satake, K.; Ishibashi, K.

2011-12-01

63

NET DISSOLVED ORGANIC CARBON PRODUCTION IN RECIRCULATING SALMONID CULTURE SYSTEM  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ozonating a coldwater recirculating system (RAS) can help control the accumulation of fine suspended solids, micro-organisms, and components of dissolved organic carbon (DOC) that can negatively impact fish health and production efficiency. Ozone can oxidize relatively large non-biodegradable organ...

64

History Matters: The Large Scale Landscape Setting of the Boulder Creek Critical Zone Observatory (Invited)  

NASA Astrophysics Data System (ADS)

The architecture of the critical zone depends upon the structural geologic and climatic history of a site. We document these controls in the vicinity of the Boulder Creek Critical Zone Observatory (BcCZO), and show that events in its geologic history reaching back to the Laramide have left a strong legacy in the landscape and its critical zone architecture. The Laramide orogeny brought crystalline >1Gyr rocks to the surface by motion along listric faults both east and west of the range crest. This manifests itself in the juxtaposition of crystalline rocks of the range against younger sedimentary rocks of the Denver Basin. More subtly, the rocks have also been subjected to significant strain upon passing through major bends and ramps in the thrust faults, leading to brittle cracking of the rocks. They therefore arrive in the near-surface pre-crushed. Post-Laramide evolution of the range resulted in reduction of relief within the crystalline core of the range, and construction of a sedimentary ramp built of weathered debris. Accumulation of sediment ended with deposition of the Ogallala formation and similar clastic sedimentary units derived from the crystalline core of the Rockies. Subsequent late Cenozoic abandonment of this depositional surface and significant exhumation of the western Great Plains resulted in the cutting out of a large wedge of the easily eroded sedimentary rocks. This exhumation event could result from either a change in the hydrologic system in the headwaters, or more likely from the climatically induced reduction in sediment supply from the crystalline range. Simple models show how the latter would generate a wedge-shaped exhumation pattern that is both deepest and widest against the range. The relevance to the BcCZO is two-fold. First, it may be a reduction in regolith production rate and/or grain size that promotes the exhumation of the western Plains. Second, the rapid exhumation adjacent to the range served as a drop in base level for all rivers draining the range, which in turn induced a wave of fluvial erosion that propagates into the range. All rivers draining the range display convexities reflecting the modern edge of this wave of incision. The knickzones of rivers with the highest drainage areas have bitten most deeply into the range. The landscape immediately adjacent to the river segments outboard of the knickzones has been rejuvenated. Hillslopes are steeper, are dominated by bedrock exposures and display regolith of variable thickness. Roughly simultaneously with the exhumation of the Plains, the upper drainages have been glaciated, repeatedly scouring the weathered carapace from the glacial troughs; 10Be concentrations in glacial polish suggest that >3 m of erosion occurred in the last glacial cycle. The BcCZO exploits this landscape history by addressing the differences in critical zone development in three settings in the landscape: the glacially scoured headwaters, the re-excited outer edge of the range adjacent to the major streams, and the landscape between these zones of excitement, in which slow post-Laramide decay of the landscape reigns.

Anderson, R. S.; Wobus, C. W.; Berlin, M. M.; Duehnforth, M.; Tucker, G. E.; Anderson, S. P.

2009-12-01

65

Effect of solar rotation on turbulent transfer of the large-scale magnetic field in the convective zone  

NASA Astrophysics Data System (ADS)

The turbulent transfer of the large-scale magnetic field is investigated in the density-stratified convective zone with due regard for turbulence anisotropy excited by solar rotation. It is found that the transfer directions of poloidal and toroidal components of the magnetic field do not coincide in the rotating convective envelope. The values of different transfer velocity components of the magnetic fields for the Spruit convective zone model are calculated. The possible role of the transport effects in the large-scale field dynamics over a solar cycle is discussed.

Kichatinov, L. L.; Krivodubs'kii, V. N.

1991-12-01

66

Reconstruction of a large deep-crustal terrane: Implications for the Snowbird tectonic zone and early growth of Laurentia  

NASA Astrophysics Data System (ADS)

The ˜2800-km-long Snowbird tectonic zone is a well-recognized but still enigmatic feature in the western Canadian Shield. It has been interpreted as a Paleoproterozoic continental suture or an Archean strike-slip fault system, but here we suggest that the distinctive geometry of the central Snowbird tectonic zone is primarily due to the interaction of crosscutting Paleoproterozoic intracontinental thrust and strike-slip shear zones having a length of hundreds of kilometers. First, a major zone of thrust-sense shearing, coeval with early continent-continent collision between the Superior and western Churchill provinces, accommodated uplift of a large exposure of granulite facies lower continental crust. Younger strike-slip shear zones, perhaps analogous to Asian fault systems behind the Himalayan orogen, offset the thrust zone. Thus, the current geometry and distribution of deep-crustal rocks in this region represent a relatively late stage in the tectonic evolution of the western Churchill province rather than an accretionary one. Earlier structures oriented at a high angle to the Snowbird tectonic zone may record the fundamental accretionary history in this part of Laurentia.

Mahan, K. H.; Williams, M. L.

2005-05-01

67

Large, pre-digital earthquakes of the Bonin-Mariana subduction zone, 1930-1974  

NASA Astrophysics Data System (ADS)

The Bonin-Mariana subduction zone is the end-member example of a decoupled system, as described by Uyeda and Kanamori (1979), with no interplate thrust solutions of moments greater than 8 × 1025 dyn cm known in the CMT catalog, although a number of earthquakes are reported with assigned magnitudes around or above 7, both during the WWSSN period and the historical pre-1962 era. We present a systematic study of these events, including relocation and inversion of moment tensors. We obtain 15 new moment tensor solutions, featuring a wide variety of focal mechanisms both in the fore-arc and the outer rise, and most importantly a shallow-dipping interplate thrust mechanism with a moment of 4 × 1027 dyn cm for the event of 28 December 1940 at a location 175 km East of Pagan. Our results show that the modern CMT catalog still undersamples the seismicity of the Mariana arc, which is thus not immune to relatively large, albeit rare, interplate thrust events, with moments 40 times that of the largest Global-CMT solution. Frequency-magnitude relations would then suggest a return time of 320 years for a magnitude 8 interplate thrust faulting earthquake in the Bonin-Mariana system.

Okal, Emile A.; Reymond, Dominique; Hongsresawat, Sutatcha

2013-02-01

68

Comparison of slip distribution of large slow slip events in Guerrero subduction zone  

Microsoft Academic Search

Aseismic slow slip events (SSEs) have been reported in most of the well geodetically instrumented subduction zones worldwide (Japan, Cascadia, Mexico, New Zealand, Costa Rica, Alaska). For most of the observed SSEs, the slip distribution on the subduction interface was inferred from the surface GPS displacements to be located at the downdip extension of the seismogenic zone, in the conditionally

F. Cotton; M. Vergnolle; O. Thollon; M. Campillo; I. Manighetti; N. Cotte; A. Walpersdorf; V. Kostoglodov

2008-01-01

69

Wood storage within the active zone of a large European gravel-bed river  

Microsoft Academic Search

Wood storage within the active zone of the dynamic, gravel-bed, Fiume Tagliamento, Italy, was investigated at eight sites along the river's main stem. The quantity, nature, and mode of wood storage revealed a number of trends related to active zone morphology, cover type, and distance from the river's source. Relatively small quantities of wood were stored on open-gravel surfaces (estimates

A. M. Gurnell; G. E. Petts; D. M. Hannah; B. P. G. Smith; P. J. Edwards; J. Kollmann; J. V. Ward; K. Tockner

2000-01-01

70

Exhaust gas recirculation valve assembly  

SciTech Connect

This paper describes an exhaust gas recirculation valve assembly. It comprises: a base having an exhaust gas chamber through which exhaust gas passes; a pintle valve assembly having a valve member disposed within the exhaust gas chamber and a valve stem extending outwardly of the chamber through an opening therein; an actuator, maintained in a fixed relationship to the base, coupling means, extending between the valve stem and the armature and configured to allow lateral movement of the valve stem relative to the armature to compensate for misalignment of the actuator relative to the base thereby preventing the misalignment from affecting the reciprocal operation of the pintle valve assembly relative to the base.

Grey, T.J.; Braun, C.N.; Palmer, D.O.

1991-06-04

71

Recirculation in multiple wave conversions  

SciTech Connect

A one-dimensional multiple wave-conversion model is constructed that allows energy recirculation in ray phase space. Using a modular eikonal approach, the connection coefficients for this model are calculated by ray phase-space methods. Analytical results (confirmed numerically) show that all connection coefficients exhibit interference effects that depend on an interference phase, calculated from the coupling constants and the area enclosed by the intersecting rays. This conceptual model, which focuses on the topology of intersecting rays in phase space, is used to investigate how mode conversion between primary and secondary waves is modified by the presence of a tertiary wave.

Brizard, A. J. [Department of Chemistry and Physics, Saint Michael's College, Colchester, Vermont 05439 (United States); Kaufman, A. N. [Department of Physics and Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Tracy, E. R. [Department of Physics, College of William and Mary, Williamsburg, Virginia 23187-8795 (United States)

2008-08-15

72

Recirculation in multiple wave conversions  

SciTech Connect

A one-dimensional multiple wave-conversion model is constructed that allows energy recirculation in ray phase space. Using a modular eikonal approach, the connection coefficients for this model are calculated by ray phase-space methods. Analytical results (confirmed numerically) show that all connection coefficients exhibit interference effects that depend on an interference phase, calculated from the coupling constants and the area enclosed by the intersecting rays. This conceptual model, which focuses on the topology of intersecting rays in phase space, is used to investigate how mode conversion between primary and secondary waves is modified by the presence of a tertiary wave.

Kaufman, A. N.; Brizard, A.J.; Kaufman, A.N.; Tracy, E.R.

2008-07-30

73

Transition and acoustic response of recirculation structures in an unconfined co-axial isothermal swirling flow  

NASA Astrophysics Data System (ADS)

This paper reports the first observations of transition from a pre-vortex breakdown (Pre-VB) flow reversal to a fully developed central toroidal recirculation zone in a non-reacting, double-concentric swirling jet configuration and its response to longitudinal acoustic excitation. This transition proceeds with the formation of two intermediate, critical flow regimes. First, a partially penetrated vortex breakdown bubble (VBB) is formed that indicates the first occurrence of an enclosed structure as the centre jet penetration is suppressed by the growing outer roll-up eddy; resulting in an opposed flow stagnation region. Second, a metastable transition structure is formed that marks the collapse of inner mixing vortices. In this study, the time-averaged topological changes in the coherent recirculation structures are discussed based on the non-dimensional modified Rossby number (Rom) which appears to describe the spreading of the zone of swirl influence in different flow regimes. Further, the time-mean global acoustic response of pre-VB and VBB is measured as a function of pulsing frequency using the relative aerodynamic blockage factor (i.e., maximum radial width of the inner recirculation zone). It is observed that all flow modes except VBB are structurally unstable as they exhibit severe transverse radial shrinkage (~20%) at the burner Helmholtz resonant modes (100-110 Hz). In contrast, all flow regimes show positional instability as seen by the large-scale, asymmetric spatial shifting of the vortex core centres. Finally, the mixing transfer function M (f) and magnitude squared coherence ?2(f) analysis is presented to determine the natural coupling modes of the system dynamic parameters (u', p'), i.e., local acoustic response. It is seen that the pre-VB flow mode exhibits a narrow-band, low pass filter behavior with a linear response window of 100-105 Hz. However, in the VBB structure, presence of critical regions such as the opposed flow stagnation region alters the linearity range with the structure showing a response even at higher pulsing frequencies (100-300 Hz).

Santhosh, R.; Miglani, Ankur; Basu, Saptarshi

2013-08-01

74

3D Modeling of Strong Ground Motion in the Pacific Northwest From Large Earthquakes in the Cascadia Subduction Zone  

Microsoft Academic Search

The Cascadia subduction zone in the Pacific Northwest, USA, generates Great (megathrust) earthquakes with a recurrence period of about 500 years, most recently the M~9 event on January 26, 1700. Since no earthquake of such magnitude has occurred in the Pacific Northwest since the deployment of strong ground motion instruments, a large uncertainty is associated with the ground motions expected

K. B. Olsen; A. Geisselmeyer; W. J. Stephenson; P. M. Mai

2007-01-01

75

Times of increased probability of large earthquakes ( M s ? 7.5) along the Mexican subduction zone  

Microsoft Academic Search

Using the method of pattern recognition of infrequent events, we explore the possibility of identifying the times of increased probability (TIP) of occurrence of large earthquakes (Ms ? 7.5) along the Mexican subduction zone. A TIP refers to a 5 year period within which a strong earthquake has a high probability of occurrence. We analyzed the seismicity for the regions

David A. Novelo-Casanova; Jose Alvarez-Moctezuma

1995-01-01

76

Gas recirculator for acyclic machines  

NASA Astrophysics Data System (ADS)

The present invention relates to acyclic machines of the type using liquid metal collectors, and more particularly to an improvement for retaining the liquid metal in such machines. Radial type acyclic motors and generators generally include a metallic disk rotor rotating on a shaft between electromagnetic stator poles excited by field coils wound concentric with the shaft. Instead of solid brush, current collectors at the rotor periphery, liquid metal collectors are sometimes used to close the electrical current loop between the shaft and the rotor, and an inert pressurized cover gas fills the gaps between the rotating components and the stationary housing. A cover has recirculator in an acyclic generator having liquid metal collectors for reducing entrainment of the liquid metal in the gas. Radial passages in the stator housing provide natural recirculating paths for the cover gas to flow radially outward along the sides of the rotor and return inwardly through the passages. Scoops or lips located inward of the liquid metal collector divert the outward gas flow into the passages to minimize contact of the gas with the liquid metal.

Balsa, T. F.

1985-05-01

77

Effects of a large northern European no-take zone on flatfish populations(a.).  

PubMed

In March 2006, a 360?km(2) no-take zone (NTZ) was established north of Gotland in the central Baltic Sea, with the purpose to scientifically evaluate the effects of a fishing ban on flatfish populations. A monitoring programme was set up to study the populations in the NTZ and in a reference area east of Gotland where the fishing pressure was high. The programme included fishing with multimesh survey nets, modelling of potential larval export and estimation of fish consumption by large marine predators. Overall, the results showed a clear positive effect of the NTZ on turbot Scophthalmus maximus, with higher densities in the closed area compared with the fished area and also higher densities after closure compared with before. The NTZ also had older individuals and a more even sex ratio. This, in combination with a high potential for larval export from the NTZ to Gotland, shows that the marine reserve may be important for maintaining a viable S. maximus stock at Gotland. Also, for flounder Platichthys flesus, the densities were higher in the NTZ compared to the reference area and there was a net larval export to the fished area. For both species, density-dependent growth was evident, with a lower length at age in the closed area. Potential predation by grey seal Halichoerus grypus and great cormorant Phalacrocorax carbo sinesis on flatfishes, that could hamper the evaluation of the marine reserve, was also addressed. Taken together, the results show that there are clear benefits of the fishing ban for both flatfish species within the NTZ, while the net effects on fisheries are difficult to quantify. PMID:24090556

Florin, A-B; Bergström, U; Ustups, D; Lundström, K; Jonsson, P R

2013-05-31

78

A Study of NO{sub x} Reduction by Fuel Injection Recirculation  

SciTech Connect

Flue-gas recirculation (FGR) is a well-known method used to control oxides of nitrogen (NO{sub X}) in industrial burner applications. Recent small- and large-scale experiments in natural-gas fired boilers have shown that introducing the recirculated flue gases with the fuel results in a much greater reduction in NO{sub X}, per unit mass of gas recirculated, in comparison to introducing the flue gases with the combustion air. That fuel injection recirculation (FIR) is more effective than windbox FGR is quite remarkable. At present, however, there is no definitive understanding of why FIR is more effective than conventional FGR. The objective of the present investigation is to ascertain whether or not chemical and/or molecular transport effects alone can explain the differences in NO{sub X} reduction observed between FIR and FGR by studying laminar diffusion flames. The purpose of studying laminar flames is to isolate chemical effects from the effects of turbulent mixing and heat transfer, which are inherent in practical boilers. Numerical simulations of H{sub 2}-air and CH{sub 4}-air counterflow diffusion flames using full kinetics were performed and NO{sub X} emission indices calculated for various conditions. Studies were conducted in which a N{sub 2} diluent was added either on the fuel- or air-side of the flame for conditions of either fixed initial velocities or fixed fuel mass flux. Results from these simulation studies indicate that a major factor in diluent effectiveness is the differential effect on flame zone residence times associated with fuel-side verses air-side dilution. Simulations in which flow velocities were fixed as diluent was added either to the air or fuel stream showed lower NO{sub X} emissions for air-side dilution; however, if instead, fuel mass fluxes were fixed as diluent was added, which results in an increase in the velocity of the streams, fuel-side dilution was more effective. These results were independent of whether H{sub 2} or Ch{sub 4} was used as the fuel.

Feese, J.J.; Turns, S.R.

1996-08-01

79

Initial water budget: the key to detaching large volumes of eclogitized oceanic crust in subduction zones?  

NASA Astrophysics Data System (ADS)

The Mesozoic, Neotethyan ophiolites and eclogites from the Zermatt-Saas area (ZS, Western Alps) represent a complete sequence of subducted lithosphere and the largest and deepest known piece of exhumed oceanic lithosphere so far (Bucher et al., 2005; Angiboust et al., 2009). Pervasive hydrothermal processes and seafloor alteration, which led to the incorporation of large amounts of fluid bound in the hydrated, upper layers of the oceanic crust, enabled the development of moderately (lawsonite eclogites) or strongly hydrated parageneses (glaucophanites, chloritoschists). Although their exhumation may have been facilitated by the highly buoyant continental units underlying the ZS ophiolite (e.g., Monte Rosa) and/or the mechanically weak (and light) surrounding serpentinites, none of the other major ophiolite bodies from the same subduction zone (eg, Monviso, Voltri) show the same characteristics (ie, continuous mafic slices and abundant lawsonite). We therefore investigated the extent to which the hydration of the oceanic lithosphere may be a major parameter controlling exhumation, a process largely overlooked up to now. Internally, the ZS ophiolite is made up of a series of tectonics slices of oceanic crust (150-300m thick) which are systematically separated by a 5 to 100-m thick serpentinite slivers. This stack of slices is separated from the underlying eclogitized continental crust (e.g., Monte Rosa) by a thick (~500m) serpentinite sole. Field observations, textural relationships and pseudosection modelling reveal that lawsonite (now pseudomorphed by clinozoisite) was abundant and widespread in mafic eclogites when the ophiolite detached from the slab at c. 550°C and 24 kbar. Comparison between fresh eclogitic samples and thermodynamic modelling suggests that (i) water remained in excess from burial to eclogitic peak conditions, (ii) the lightest eclogitized metabasalts correspond to the portions of oceanic crust where metasomatism was most intense, (iii) crystallization of widespread hydrated parageneses (such as lawsonite, glaucophane and phengite), instead of garnet and omphacite, decreased rock density by 5 to 10 % and subsequently enhanced its flottability. We propose that this density decrease acted as an efficient force to prevent these slices from irreversibly sinking into the mantle. Penetrative serpentinization of the slab mantle harzburgites during ridge-processes (Li et al., 2004) likely facilitated the detachment of theses slices from the downgoing slab and their stacking in the serpentinized subduction channel at pressures between 15-20 kbar. Exhumation of the underlying positively buoyant continental crust later dragged this "frozen" nappe-stack towards the surface.

Angiboust, Samuel; Agard, Philippe

2010-05-01

80

Turbulent transfer of the large-scale magnetic field in the rotating convective zone of the sun  

NASA Astrophysics Data System (ADS)

Consideration is given to the problem of the turbulent transfer of the large-scale magnetic field in a density-stratified convective zone, with the turbulence anisotropy excited by the sun's rotation taken into account. The anisotropy parameter (the Coriolis number - reciprocal of the Rossby number) and the transfer velocity components for the Spruit convective zone model are calculated. The transfer directions of the poloidal and toroidal components of the mean magnetic field do not coincide. The possible role of the turbulent transfer effects in the observed redistribution of magnetic fields over a solar cycle is discussed.

Krivodubskij, V. N.

1992-08-01

81

A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces  

Microsoft Academic Search

A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 l of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary

Salah Jellali; Hocine Benremita; Paul Muntzer; Olivier Razakarisoa; Gerhard Schäfer

2003-01-01

82

Determining fault zone structure and examining earthquake early warning signals using large datasets of seismograms  

NASA Astrophysics Data System (ADS)

Seismic signals associated with near-fault waveforms are examined to determine fault zone structure and scaling of earthquake properties with event magnitude. The subsurface structure of faults is explored using fault zone head and/or trapped waves, while various signals from the early parts of seismograms are investigated to find out the extent to which they scale with magnitude. Fault zone trapped waves are observed in three arrays of instruments across segments of the San Jacinto fault. Similarly to previous fault zone trapped wave studies, the low velocity damage zones are found to be 100-200m wide and extend to a depth of ˜3-5km. Observation and modeling indicate that the damage zone was asymmetric around the fault trace. A similar sense of damage asymmetry was observed using detailed geological mapping by Dor et al. (2006) nearby on the San Jacinto fault at Anza. Travel time analysis and arrival time inversions of fault zone head waves were used to produce high resolution images of the fault structure of the San Andreas fault south of Hollister. The contrast of P wave velocities across the fault was found to be ˜50% in the shallow section, lowering to 10-20% below 3 km, with the southwest side having faster velocities. Inversions making use of different subsets of stations suggest that a low velocity damage zone also exists in this area and that it is more prominent on the faster velocity side of the fault. The patterns of damage from these studies of fault zone head waves and trapped waves are consistent (Ben-Zion and Shi, 2005) with the theoretical prediction that earthquake ruptures on these fault sections have statistically-preferred propagation directions. The early parts of P waveforms are examined for signals that have previously been proposed to scale with the final event magnitude. Data from Turkey and a deep South African gold mine show that scaling is present in signals related to the maximum displacement amplitude and frequency content. The high sampling rate of the instruments in the gold mine enables the reduction of the time window in which measurements are made to below the estimated rupture duration of the largest events. Using increasingly small time windows has only a minimal effect on the scaling of the signals with event magnitude, implying that the size of earthquakes is affected statistically by some property of the early part of the rupture.

Lewis, Michael Antony

83

Large two-dimensional laboratory experiment with biodegradation of a PCE source zone  

NASA Astrophysics Data System (ADS)

To investigate the effects of bioremediation on DNAPL source zones, we carried out an experiment in a two-dimensional tank filled with sand. A microbial assemblage originating from a contaminated field site was used for inoculation without enrichment. Injection of 250 ml PCE into the tank yielded a residual zone of PCE with a pool at the bottom. After this injection, the tank was continuously flushed with anaerobic water containing sufficient electron donor and various nutrients. Chlorinated ethenes analysis, microbial groups counting, and the visual observation of the colored PCE show that PCE was degraded in the source zone. Bio-enhanced dissolution occurred as cDCE concentrations were measured four times the solubility limit of PCE and because the PCE solubility limit in the source zone increased. Degradation of cDCE to VC and ethene occurred when PCE concentrations were low (<0.1 mM). After one year of experiment, approximately 135 ml of chlorinated ethenes were removed from the tank. PCE left in the tank was 90 ml and was only present in the pool. keywords: 2D tank experiment, PCE-DNAPL, reductive dechlorination, source zone, bio-enhanced dissolution, mobilization.

Langevoort, M.; Hassanizadeh, S.; Kleingeld, P.; Heimovaara, T.; Leijnse, T.

2008-12-01

84

Demand Shifting with Thermal Mass in Large Commercial Buildings in a California Hot Climate Zone  

Microsoft Academic Search

The potential for using building thermal mass for load shifting and peak energy demand reduction has been demonstrated in a number of simulation, laboratory, and field studies. Previous Lawrence Berkeley National Laboratory research has demonstrated that the approach is very effective in cool and moderately warm climate conditions (California Climate Zones 2-4). However, this method had not been tested in

Peng Xu; Rongxin Yin; Carrie Brown; DongEun Kim

2009-01-01

85

Seismically active fracture zones and distribution of large accumulations of metals in the central part of Andean South America  

Microsoft Academic Search

The analysis of the geometry of distribution of earthquake foci in the central part of Andean South America between 18? and\\u000a 34?S made the delineation of several seismically active fracture zones in the continental wedge overlying the subducting Nazca\\u000a plate possible. Correlation of their position with the distribution of hypogene accumulations of metals revealed that the\\u000a majority of large mineral

V. Hanuš; J. Van?k; A. Špi?ák

2000-01-01

86

Fabrication of large-area CCD detectors on high-purity, float-zone silicon  

Microsoft Academic Search

One of the problems with the fabrication of radiation detectors on high-purity, float-zone silicon is that such material is more susceptible to the formation of dislocations during high-temperature processing than Czochralski-grown material. We describe here the impact of dislocations on the electrical performance of a 1024 × 1024-pixel CCD imager that we have developed as the principal detector for the

J. A. Gregory; B. E. Burke; M. J. Cooper; B. B. Kosicki

1996-01-01

87

Recirculating cross-correlation detector  

DOEpatents

A digital cross-correlation detector is provided in which two time-varying signals are correlated by repetitively comparing data samples stored in digital form to detect correlation between the two signals. The signals are sampled at a selected rate converted to digital form, and stored in separate locations in separate memories. When the memories are filled, the data samples from each memory are first fed word-by-word through a multiplier and summing circuit and each result is compared to the last in a peak memory circuit and if larger than the last is retained in the peak memory. Then the address line to leading signal memory is offset by one byte to affect one sample period delay of a known amount in that memory and the data in the two memories are then multiplied word-by-word once again and summed. If a new result is larger than a former sum, it is saved in the peak memory together with the time delay. The recirculating process continues with the address of the one memory being offset one additional byte each cycle until the address is shifted through the length of the memory. The correlation between the two signals is indicated by the peak signal stored in the peak memory together with the delay time at which the peak occurred. The circuit is faster and considerably less expensive than comparable accuracy correlation detectors.

Andrews, W.H. Jr.; Roberts, M.J.

1985-01-18

88

High Power Picosecond Laser Pulse Recirculation.  

National Technical Information Service (NTIS)

We designed and constructed a nonlinear crystal-based short pulse recirculation cavity that traps the second harmonic of an incident high power laser. This scheme aims to increase the efficiency of Compton-scattering based light sources.

C. Brown D. Gibson F. Hartemann I. Jovanovic M. Y. Shverdin S. Anderson

2007-01-01

89

Weak Compliance Undermines the Success of No-Take Zones in a Large Government-Controlled Marine Protected Area  

PubMed Central

The effectiveness of marine protected areas depends largely on whether people comply with the rules. We quantified temporal changes in benthic composition, reef fish biomass, and fishing effort among marine park zones (including no-take areas) to assess levels of compliance following the 2005 rezoning of the government-controlled Karimunjawa National Park (KNP), Indonesia. Four years after the rezoning awareness of fishing regulations was high amongst local fishers, ranging from 79.5±7.9 (SE) % for spatial restrictions to 97.7±1.2% for bans on the use of poisons. Despite this high awareness and strong compliance with gear restrictions, compliance with spatial restrictions was weak. In the four years following the rezoning reef fish biomass declined across all zones within KNP, with >50% reduction within the no-take Core and Protection Zones. These declines were primarily driven by decreases in the biomass of groups targeted by local fishers; planktivores, herbivores, piscivores, and invertivores. These declines in fish biomass were not driven by changes in habitat quality; coral cover increased in all zones, possibly as a result of a shift in fishing gears from those which can damage reefs (i.e., nets) to those which cause little direct damage (i.e., handlines and spears). Direct observations of fishing activities in 2009 revealed there was limited variation in fishing effort between zones in which fishing was allowed or prohibited. The apparent willingness of the KNP communities to comply with gear restrictions, but not spatial restrictions is difficult to explain and highlights the complexities of the social and economic dynamics that influence the ecological success of marine protected areas. Clearly the increased and high awareness of fishery restrictions following the rezoning is a positive step. The challenge now is to understand and foster the conditions that may facilitate compliance with spatial restrictions within KNP and marine parks worldwide.

Campbell, Stuart J.; Hoey, Andrew S.; Maynard, Jeffrey; Kartawijaya, Tasrif; Cinner, Joshua; Graham, Nicholas A. J.; Baird, Andrew H.

2012-01-01

90

Re-circulating linac vacuum system  

Microsoft Academic Search

The vacuum system for a proposed 2.5 GeV, 10?A re-circulating linac synchrotron light source is readily achievable with conventional vacuum hardware and established fabrication processes. Some of the difficult technical challenges associated with synchrotron light source storage rings are sidestepped by the relatively low beam current and short beam lifetime requirements of a re-circulating linac. This minimal lifetime requirement leads

Russell P. Wells; John N. Corlett; Alexander A. Zholents

2003-01-01

91

Recirculation control valve replacement cuts maintenance costs  

Microsoft Academic Search

This article describes how replacement of boiler feed pump recirculation control valves solves a maintenance problem on Baldwin Unit 3. All three of Illinois Power`s Baldwin power plant units had the same boiler feed pump (BFP) valve design when they went into commercial operation. The original BFP recirculation valves were a top-guided plug, single-port cage design using a tapered plug

M. E. Liefer; H. L. Miller; R. E. Katz

1995-01-01

92

Towards measuring large-scale hydraulic properties of the seismogenic Gole Larghe Fault Zone at 8 km depth  

NASA Astrophysics Data System (ADS)

Fluid flow along fault zones is a major issue in structural geology and seismology. The permeability of fault rocks can be measured in laboratory experiments (e.g. Mitchell et al., this meeting) but its upscaling to large scale structures is not an easy task. On the other hand, in-situ measurements of permeability have been carried out just at relatively shallow depths, only exceptionally up to 3 km for active tectonic settings (e.g. SAFOD), whilst deeper experiments have been performed only in the stable continental crust (e.g. KTB). In this contribution we combine field and microstructural observations, fracture network modelling techniques borrowed from the oil industry, and geochemistry, in order to characterize the (possibly transient) hydraulic structure of the Gole Larghe Fault Zone (GLFZ, Italian Southern Alps), exhumed from ca. 8 km where it was characterized by a well-documented seismic activity. Our strategy consists of: (1) quantitative field characterization of the large- and meso-scale fault and fracture network of the GLFZ, combining DGPS scanlines and image analysis; (2) evaluation of the aperture of fractures based on microstructural and mechanical considerations; (3) reconstruction of realistic Discrete Fracture Network (DFN) 3D models; (4) output in terms of upscaled hydraulic parameters; (5) calibration based on the observed large scale fluid-rock interaction pattern. In this contribution we present the first results of this study performed on the GLFZ, which reveals a composite, heterogeneous, and highly anisotropic hydraulic structure.

Bistacchi, Andrea; Mittempergher, Silvia; Smith, Steve; Di Toro, Giulio; Mitchell, Tom; Nielsen, Stefan

2013-04-01

93

Chronology and dynamics of a large silicic magmatic system. Central Taupo volcanic zone, New Zealand  

SciTech Connect

The central Taupo Volcanic Zone in New Zealand is a region of intense Quaternary silicic volcanism accompanying rapid extension of continental crust. At least 34 caldera-forming ignimbrite eruptions have produced a complex sequence of relatively short-lived, nested, and/or overlapping volcanic centers over 1.6 m.y. Silicic volcanism at Taupo is similar to the Yellowstone system in size, longevity, thermal flux, and magma output rate. However, Taupo contrasts with Yellowstone in the exceptionally high frequency, but small size, of caldera-forming eruptions. This contrast reflects the thin, rifted nature of the crust, which precludes the development of long-term magmatic cycles at Taupo. 11 refs., 4 figs., 1 tab.

Houghton, B.F.; Wilson, C.J.N. (Wairakei Research Center, Taupo (New Zealand)); McWilliams, M.O. (Stanford Univ., CA (United States)); Lanphere, M.A.; Pringle, M.S. (Geological Survey, Menlo Park, CA (United States)); Weaver, S.D. (Univ. of Canterbury, Christchurch (New Zealand)); Briggs, R.M. (Univ. of Waikato, Hamilton (New Zealand))

1995-01-01

94

Longitudinal dynamics in high frequency ffag recirculating accelerators  

NASA Astrophysics Data System (ADS)

A recirculating accelerator accelerates the beam by passing through accelerating cavities multiple times. An FFAG recirculating accelerator uses a single arc to connect the linacs together, as opposed to multiple arcs for the different energies. For most scenarios using high-frequency RF, it is impractical to change the phase of the RF on each pass, at least for lower energy accelerators. Ideally, therefore, the WAG arc will be isochronous, so that the particles come back to the same phase (on-crest) on each linac pass. However, it is not possible to make the FFAG arcs isochronous (compared to the RF period) over a large energy range. This paper demonstrates that one can nonetheless make an WAG recirculating accelerator work. Given the arc's path length as a function of energy and the number of turns to accelerate for, one can find the minimum voltage (and corresponding initial conditions) required to accelerate a reference particle to the desired energy. I also briefly examine how the longitudinal acceptance varies with the number of turns that one accelerates.

Berg, S.

2002-04-01

95

LONGITUDINAL DYNAMICS IN HIGH FREQUENCY FFAG RECIRCULATING ACCELERATORS.  

SciTech Connect

A recirculating accelerator accelerates the beam by passing through accelerating cavities multiple times. An FFAG recirculating accelerator uses a single arc to connect the linacs together, as opposed to multiple arcs for the different energies. For most scenarios using high-frequency RF, it is impractical to change the phase of the RF on each pass, at least for lower energy accelerators. Ideally, therefore, the WAG arc will be isochronous, so that the particles come back to the same phase (on-crest) on each linac pass. However, it is not possible to make the FFAG arcs isochronous (compared to the RF period) over a large energy range. This paper demonstrates that one can nonetheless make an WAG recirculating accelerator work. Given the arc's path length as a function of energy and the number of turns to accelerate for, one can find the minimum voltage (and corresponding initial conditions) required to accelerate a reference particle to the desired energy. I also briefly examine how the longitudinal acceptance varies with the number of turns that one accelerates.

BERG,J.S.

2002-04-08

96

Organic carbon oxidation induced by large-scale shallow water intrusion into a vertical fracture zone at the Äspö Hard Rock Laboratory (Sweden)  

Microsoft Academic Search

Entrance tunnel construction at the Äspö Hard Rock Laboratory opened a conductive vertical fracture zone at a depth of 70 m on March 13, 1991. Three weeks later a sharp dilution front corresponding to 80% shallow water inflow to the originally saline fracture zone arrived at the entrance tunnel depth. In spite of this large inflow of shallow water, the

Steven Banwart; Eva-Lena Tullborg; Karsten Pedersen; Erik Gustafsson; Marcus Laaksoharju; Ann-Chatrin Nilsson; Bill Wallin; Peter Wikberg

1996-01-01

97

An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas  

NASA Astrophysics Data System (ADS)

Large-scale coal and gas outbursts post a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution. A steep gradient of gas pressure in the low-permeability zone and the high gas pressure in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

An, F. H.; Cheng, Y. P.

2013-09-01

98

Interface shape, heat transfer and fluid flow in the floating zone growth of large silicon crystals with the needle-eye technique  

Microsoft Academic Search

A computer simulation is carried out to study the interface shape, heat transfer and fluid flow in the floating zone (FZ) growth of large (> 100 mm) Si crystals with the needle-eye technique and with feed\\/crystal rotation. Natural convection, thermocapillary convection, electromagnetic (EM) forces and rotation in the melt are considered. The unknown shape of the molten zone is calculated

Alfred Mühlbauer; Andris Muiznieks; Janis Virbulis; Anke Lüdge; Helge Riemann

1995-01-01

99

Deformations Associated With Large Interplate Earthquakes Along the Sumatra-Andaman Subduction Zone  

NASA Astrophysics Data System (ADS)

Since the occurrence of the 2004 Sumatra-Andaman earthquake (Mw9.2), the Sumatra-Andaman Subduction zone has attracted geophysicists' attention. We have been carrying on CGPS observation in Thailand and Myanmar to detect postseismic deformation following this gigantic event. Since CGPS on land is not enough to clarify the detailed image of postseismic deformation, we also make InSAR analyses in Andaman and Phuket Islands. On September 12, 2007, another Mw8.4 event occurred SW off Sumatra. We report deformations observed with GPS and SAR including co- and postseismic deformation following this event. We have analyzed CGPS data up to the end of 2007 and detected postseismic displacements all over the Indochina peninsula. Phuket, which suffered from about 26cm coseismic displacement, has shifted by 26cm southwestward till July, 2007. Postseismic transient is clearly recognized and already exceeds coseismic movements at remote sites such as Bangkok and Chiang Mai in Thailand. We processed ALOS/PALSAR data in Andaman and Phuket islands. No remarkable deformation is found in Andaman and Phuket Islands, since the operation period of ALOS/PALSAR is not long enough and the wavelength of postseismic deformation may be much longer than the swath. We try to synthesize the postseismic displacement using a 3-D viscoelastic FEM model. Its results imply that viscoelastic relaxation in mantle with a typical mantle viscosity may play an important role for the observed postseismic transients except during the first six month. An extremely low viscosity is not required beneath the Andaman Sea, though this back arc is now actively opening. Coseismic motion following the 2007 Sumatra event is detected north of Benkgulu on the coast of southern Sumatra with InSAR. The largest LOS displacement of about 35cm is observed 100km NW of Bengkulu. Coseismic westward displacements of 3.5cm from the 2007 Sumatra event are also observed at Singapore, whose epicentral distance is about 700km, with CGPS. The observed fringe can be simulated by a plane fault model gently dipping northeastward with a 10m slip. On the other hand, the maximum of postseismic LOS displacement is shifted about 50km south from the coseismic maximum and significant fringes are more localized than the coseismic ones. The shift and localization of fringe are difficult to understand with an afterslip on deeper extension of coseismic fault plane. There is a slight disturbance in fringes along the Sumatran fault in the coseismic image, although it might be a topographic error. We will continue monitoring crustal deformations in the Sumatra-Andaman subduction zone with GPS and InSAR in order to reveal stress transfer.

Hashimoto, M.; Fukushima, Y.; Katagi, T.; Hashizume, M.; Satomura, M.; Wu, P.; Kato, T.

2008-12-01

100

Experimental characterization of the initial zone of an annular jet with a very large diameter ratio  

NASA Astrophysics Data System (ADS)

This article presents an experimental investigation of a large diameter ratio annular air jet by particle image velocimetry, Laser Doppler Anemometry, hot-wire anemometry and time-resolved tomography. Annular jets consist of a round nozzle with an obstacle placed in its center. These jets are thus defined by an external and an internal diameter corresponding to the round nozzle lips and the diameter of the obstacle, respectively. The ratio between these two diameters defines the behavior of the flow across a characteristic diameter called diameter ratio. In most industrial applications these jets have large diameter ratios, superior to 0.7.

Danlos, Amélie; Lalizel, Gildas; Patte-Rouland, Béatrice

2012-12-01

101

Experimental characterization of the initial zone of an annular jet with a very large diameter ratio  

NASA Astrophysics Data System (ADS)

This article presents an experimental investigation of a large diameter ratio annular air jet by particle image velocimetry, Laser Doppler Anemometry, hot-wire anemometry and time-resolved tomography. Annular jets consist of a round nozzle with an obstacle placed in its center. These jets are thus defined by an external and an internal diameter corresponding to the round nozzle lips and the diameter of the obstacle, respectively. The ratio between these two diameters defines the behavior of the flow across a characteristic diameter called diameter ratio. In most industrial applications these jets have large diameter ratios, superior to 0.7.

Danlos, Amélie; Lalizel, Gildas; Patte-Rouland, Béatrice

2013-01-01

102

Isotopic variation of fishes in freshwater and estuarine zones of a large subtropical coastal lagoon  

Microsoft Academic Search

We used stable C and N isotope ratios of tissues from 29 fish species from a large subtropical lagoon in southern Brazil to examine spatial variability in isotopic composition and vertical trophic structure across freshwater and estuarine habitats. Nitrogen isotope ratios indicated a smooth gradation in trophic positions among species, with most fishes occupying the secondary and tertiary consumer level.

A. M. Garcia; D. J. Hoeinghaus; J. P. Vieira; K. O. Winemiller

2007-01-01

103

The Hardangerfjord Shear Zone in SW Norway and the North Sea: a large-scale low-angle shear zone in the Caledonian crust  

Microsoft Academic Search

The Hardangerfjord Shear Zone is a more than 600 km long low-angle extensional structure that affects the South Norway and North Sea Caledonides. The ductile shear zone, which shows total maximum onshore displacement of the order of 10-15 km, is primarily a basement structure with an associated passive, monoclinal fold structure of the overlying Caledonian nappes. Deep seismic data indicate

HAAKON F OSSEN; C HARLES A. H URICH

2005-01-01

104

Relevance of large litter bag burial for the study of leaf breakdown in the hyporheic zone  

Microsoft Academic Search

Particulate organic matter is the major source of energy for most low-order streams, but a large part of this litter is buried\\u000a within bed sediment during floods and thus become poorly available for benthic food webs. The fate of this buried litter is\\u000a little studied. In most cases, measures of breakdown rates consist of burying a known mass of litter

Pierre Marmonier; Christophe Piscart; Pierre Emmanuel Sarriquet; Didier Azam; Eric Chauvet

2010-01-01

105

Large multicellular filamentous bacteria under the oxygen minimum zone of the eastern South Pacific: a forgotten biosphere  

NASA Astrophysics Data System (ADS)

In the soft reduced sediments of the continental shelf, below the oxygen minimum zone (OMZ) of the eastern South Pacific (ESP), peculiar microbial communities have been disclosed which include a variety of large prokaryotes, protists and small metazoans. Dominant among the prokaryotes are large multi-cellular filamentous bacteria which, according to their size range, are roughly divided into megabacteria and macrobacteria. The former group is made up of a few species of Gamma Proteobacteria of the genera Thioploca and Beggiatoa and the second group includes a diversity of phenotypes. Protists include ciliates, flagellates, and foraminifers and the metazoans are mostly nematodes and small polychaetes. A significant similarity has been found in the exploitation of the area/volume relationship among these large bacteria and their fossil analog forms as described from pre-Cambrian rocks. For the same reason, the latter have mostly been referred to as algae or cyanobacteria in the literature. The presence of these seemingly ancient bacteria in the sediments of the oxygen minimum zones of the ESP, one of the most productive but also ecologically most inefficient marine ecosystems of the world, suggests that such setting must have prevailed throughout the geological history of the planet allowing for their survival and further that it might be considered an analog of Proterozoic ocean conditions. These non-cyanobacterial communities offer an alternative hypothesis to students of the evolution of life on Earth and may be of special interest to astrobiologists looking for life or traces of life in terrestrial or extraterrestrial environments since these do not necessarily imply a photosynthesis-based metabolism.

Gallardo, Victor Ariel; Espinoza, Carola

2007-10-01

106

Primary mediastinal (thymic) large B-cell lymphoma: a short review with brief discussion of mediastinal gray zone lymphoma.  

PubMed

Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is a subtype of diffuse large B-cell lymphoma (DLBCL). It commonly presents as a bulky lesion in the anterior-superior mediastinum with symptoms related to local invasion or compression. Microscopic examination typically shows infiltration of medium-large cells surrounded by collagen fibrosis. The neoplastic cells express B-cell markers, and CD30 often shows heterogeneous staining. Comparative genomic hybridization has identified gains in loci of 9p24 and 2p15 as well as Xp11.4-21 and Xq24-26. Amplification of REL and BCL11A at 2p as well as elevated expression of JAK2, PDL1, and PDL2 at 9p has been demonstrated. Nodular sclerosis classic Hodgkin lymphoma needs to be differentiated from PMBCL and cases with overlapped features have been described as mediastinal gray zone lymphoma. Primary mediastinal (thymic) large B-cell lymphoma carries a favorable prognosis in comparison to conventional DLBCL. PMID:21366467

Hutchinson, Charles Blake; Wang, Endi

2011-03-01

107

Large-scale perfusion culture process for suspended mammalian cells that uses a centrifuge with multiple settling zones.  

PubMed

A high-cell-density perfusion culture process, using a novel centrifuge, was developed. The centrifuge has spiral multiple settling zones to separate cells from culture medium. Because of the multiple zones, the separation area can be efficiently increased without enlarging the diameter of the centrifuge. The centrifuge used in this study had a separation capacity of 2600 ml culture medium min -1 at 100 g of the centrifugal force. A new cell separation and withdrawal method was also developed. The cells separated in the centrifuge can be withdrawn easily from the centrifuge with no cell clogging by feeding a liquid carrier such as a perfluorocarbon into the centrifuge and pushing the cells out with the liquid carrier. By this culture process, monoclonal antibodies were produced with mouse-human hybridoma X87X at a cell density of about 8 x 10(6) cells ml -1 for 25 days. This centrifuge culture shows promise as a large-scale perfusion culture process. (Himmelfarb et al. 1969; Feder and Tolbert 1983) usually have the problem of filter clogging, and perfusion culture processes with gravitational cell settling (Tokashiki and Arai 1989) are limited in scale-up because of low separation efficiency. Recently centrifugal separation of cells from culture medium has been used for perfusion culture processes (Hamamoto et al. 1989; Tokashiki et al. 1990; Apelman 1992; Jäger 1992). This process essentially has a high separation efficiency and can avoid further operational problems, such as filter clogging, by the type of filtration. To investigate the scale-up feasibility of the centrifuge culture system, we have developed a new type of centrifuge with four layers of spiral cell-settling zones to increase the separation area, and a novel cell separation and withdrawal method using a perfluorocarbon. PMID:8737569

Takamatsu, H; Hamamoto, K; Ishimaru, K; Yokoyama, S; Tokashiki, M

1996-05-01

108

Large shield volcanos on Venus: The effect of neutral buoyancy zone development on evolution and altitude distribution  

NASA Astrophysics Data System (ADS)

The Magellan mission to Venus has emphasized the importance of volcanism in shaping the surface of the planet. Volcanic plains make up 80 percent of the terrain and hundreds of regions of localized eruptions have been identified. Large volcanos, defined as edifices with diameters greater than 100 km, are the sites of some of the most voluminous eruptions. Head et al. have identified 158 of these structures. Their spatial distribution is neither random nor arranged in linear chains as on the Earth; large volcanos on Venus are concentrated in two large, near-equatorial clusters that are also the site of many other forms of volcanic activity. The set of conditions that must be met on Venus that controls the change from widespread, distributed volcanism to focused, shield-building volcanism is not well understood. Future studies of transitional features will help to address this problem. It is likely, however, that the formation and evolution of a neutral buoyancy zone (NBZ) plays an important role in both determining the style of the volcanism and the development of the volcanic feature once it has begun to erupt. Head and Wilson have suggested that the high surface pressure on Venus may inhibit volatile exsolution, which may influence the density distribution of the upper crust and hence control the nature and location of a NBZ. The extreme variations in pressure with elevation may result in significantly different characteristics of such a NBZ at different locations on the planet. In order to test these ideas regarding the importance of NBZ development in the evolution of a large shield and to determine the style of volcanism, three large volcanos that occur at different basal elevations were examined and the distribution of large volcanos as a function of altitude was determined.

Keddie, S.; Head, James W., III

1992-12-01

109

Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA  

Microsoft Academic Search

The New Madrid seismic zone (NMSZ) is an intraplate right-lateral strike-slip and thrust fault system contained mostly within the Mississippi Alluvial Valley. The most recent earthquake sequence in the zone occurred in 1811–1812 and had estimated moment magnitudes of 7–8 (e.g., [Johnston, A.C., 1996. Seismic moment assessment of stable continental earthquakes, Part 3: 1811–1812 New Madrid, 1886 Charleston, and 1755

Margaret J. Guccione

2005-01-01

110

Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA  

Microsoft Academic Search

The New Madrid seismic zone (NMSZ) is an intraplate right-lateral strike-slip and thrust fault system contained mostly within the Mississippi Alluvial Valley. The most recent earthquake sequence in the zone occurred in 1811 1812 and had estimated moment magnitudes of 7 8 (e.g., [Johnston, A.C., 1996. Seismic moment assessment of stable continental earthquakes, Part 3: 1811 1812 New Madrid, 1886

Margaret J. Guccione

2005-01-01

111

Large and rapid melt-induced velocity changes in the ablation zone of the Greenland Ice Sheet.  

PubMed

Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades. PMID:18599784

van de Wal, R S W; Boot, W; van den Broeke, M R; Smeets, C J P P; Reijmer, C H; Donker, J J A; Oerlemans, J

2008-07-01

112

33 CFR 159.127 - Safety coliform count: Recirculating devices.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Safety coliform count: Recirculating devices...Testing § 159.127 Safety coliform count: Recirculating devices...device must have less than 240 fecal coliform bacteria per 100 milliliters....

2009-07-01

113

33 CFR 159.127 - Safety coliform count: Recirculating devices.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Safety coliform count: Recirculating devices...Testing § 159.127 Safety coliform count: Recirculating devices...device must have less than 240 fecal coliform bacteria per 100 milliliters....

2010-07-01

114

Longitudinal dynamics in high frequency ffag recirculating accelerators..  

National Technical Information Service (NTIS)

A recirculating accelerator accelerates the beam by passing through accelerating cavities multiple times. An FFAG recirculating accelerator uses a single arc to connect the linacs together, as opposed to multiple arcs for the different energies. For most ...

S. Berg

2002-01-01

115

River Food Web Response to Large-Scale Riparian Zone Manipulations  

PubMed Central

Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks.

Wootton, J. Timothy

2012-01-01

116

River food web response to large-scale riparian zone manipulations.  

PubMed

Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks. PMID:23284786

Wootton, J Timothy

2012-12-20

117

Production of cobia in recirculating systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

Only limited information exists with respect to rearing juvenile cobia Rachycentron canadum to stocker and marketable sizes using recirculating aquaculture systems (RAS). To investigate this topic, two rearing trials were conducted using commercial scale RAS. In Trial 1, juvenile cobia (29 g) we...

118

Multipoint measurements of large electric fields and shears in the Auroral zone  

NASA Astrophysics Data System (ADS)

This work presents results from the Auroral Turbulence II (AT II) sounding rocket launched from the Poker Flat Research Range, near Fairbanks, Alaska, on February 11, 1997. The rocket consisted of three identically instrumented payloads that reached an apogee of 550 km and flew through several arc structures in a pre-midnight auroral breakup. Three payload measurements were desired to separate the temporal from spatial aspects of auroral forms, and to investigate three dimensional flows and fields that cannot be resolved using traditional single point measurements. The focus of this study has been in the structure and changes in the dc electric field. Although the AT II payloads traversed many auroral arc structures, most of the forms had negligible electric fields associated with them. The one exception was when the payloads crossed a large, stable arc at nearly 500 km altitude. In the middle region of the arc, and near the poleward boundary, the payloads measured significant electric fields, as much as 450 mV/m in the poleward region of the arc. The payloads also measured different electric field structures, while approximately three kilometers apart, indicating a gradient in the field between measurements. Spectral analysis of the ac electric field data show broadband electrostatic waves in the regions of enhanced dc electric field. The multiple measurements indicate a region of spatially localized electric field, electric field shear and wave activity that both drifts in space and changes amplitude temporally. In-situ changes in the electric field are examined in parallel with all-sky imagery obtained near the footpoint of the payload trajectories. We have determined that there are errors in the dc electric field measurements that are most likely explained by a shadowing of the potential spheres by the payload. Despite the uncertainty in absolute, magnitudes of the dc field, there are clear differences in the field signatures between payload measurements that can be shown to be spatial shears. The shear in the localized electric field, the observed broadband electrostatic waves, and the low field aligned currents measured by the magnetometers indicate an instability mechanism responsible for the wave growth. The most likely candidate, given the environment, is the inhomogeneous energy density driven instability (IEDDI), which we believe to be responsible for the observed electrostatic waves observed near the oxygen cyclotron frequency.

Pietrowski, David

2000-10-01

119

Toluene removal in membrane bioreactors under recirculating and non-recirculating liquid conditions  

Microsoft Academic Search

A single-, dual- and multiple-tube dense phase silicone rubber membrane bioreactor were investigated for control of toluene-contaminated\\u000a air under circulating and non-recirculating liquid conditions. A mathematical model was developed to describe the system.\\u000a The reactors were seeded with a mixed bacterial consortium isolated from activated sludge and capable of aromatic biodegradation.\\u000a After operating with recirculating liquid nutrient solution, the reactors

Ellen England; Mark W. Fitch; Melanie Mormile; Michael Roberts

2005-01-01

120

Pressure mediated diesel engine exhaust gas recirculation control system  

Microsoft Academic Search

A diesel engine includes an air intake system, an exhaust system , and an exhaust gas recirculation conduit which leads from the exhaust system to the intake system. An exhaust gas recirculation control valve, which includes a first diaphragm chamber, is mounted in the exhaust gas recirculation conduit so as to regulate the flow of exhaust gas through it. The

1983-01-01

121

3D Modeling of Strong Ground Motion in the Pacific Northwest From Large Earthquakes in the Cascadia Subduction Zone  

NASA Astrophysics Data System (ADS)

The Cascadia subduction zone in the Pacific Northwest, USA, generates Great (megathrust) earthquakes with a recurrence period of about 500 years, most recently the M~9 event on January 26, 1700. Since no earthquake of such magnitude has occurred in the Pacific Northwest since the deployment of strong ground motion instruments, a large uncertainty is associated with the ground motions expected from such event. To decrease this uncertainty, we have carried out the first 3D simulations of megathrust earthquakes (Mw8.5 and Mw9.0) rupturing along the Cascadia subduction zone. The simulations were carried out in a recently developed 3D velocity model of the region of dimensions 1050 km by 550 km, discretized into 2 billion 250 m3 cubes with a minimum S-wave velocity of 625 m/s. The model includes the subduction slab, accretionary sediments, local sedimentary basins, and the ocean layer. About 6 minutes of wave propagation for each scenario consumed about 24 Wall-clock hours using a parallel fourth-order finite-difference method with 1600 processors on the San Diego Supercomputer Center Datastar supercomputer. The source descriptions for the Mw9.0 scenarios were designed by mapping the inversion results for the December 26, 2004 M9+ Sumatra-Andaman Islands earthquake (Ji, 2006) onto a 950 km by 150 km large rupture for the Pacific Northwest model. Simulations were carried out for hypocenters located toward the northern and southern ends of the subduction zone. In addition, we simulated two M8.5 events with a source area of 275 km by 150 km located in the northern and central parts of the model area. The sources for the M8.5 events were generated using the pseudo-dynamic model by Guatteri et al. (2004). All sources used spatially-variable slip, rise time and rupture velocity. Three major metropolitan areas are located in the model region, namely Seattle (3 million+ people), Vancouver (2 million+ people), and Portland (2 million+ people), all located above sedimentary basins amplifying the waves incident from the subduction zone. The estimated peak ground velocities (PGVs) for frequencies less than 0.5 Hz vary significantly with the assumed rise time. Using a mean rise of 32 s, as estimated from source inversion of the 2004 M9+ Sumatra-Andeman event (Ji, 2006), PGVs reached 40 cm/s in Seattle and 10 cm/s in Vancouver and Portland. However, if the mean rise time is decreased to about 14 s, as suggested by the empirical regression by Somerville et al. (1999), PGVs are increased by 2-3 times at these locations. For the Mw8.5 events, PGVs would reach about 10 cm/s in Seattle, and about 5 cm/s in Vancouver and Portland. Combined with extended duration of the shaking exceeding 1 minute for the Mw8.5 events and 2 minutes for the Mw9 events, these long-period ground motions may inflict significant damage on the built environment, in particular on the highrises in downtown Seattle. However, the strongest shaking arrives 1-2 minutes after the earthquake nucleates, indicating that an early warning system in place may help mitigate loss of life in case of a megathrust earthquake in the Pacific Northwest. Additional efforts should analyse the simulated displacements on the ocean bottom for tsunami generation potential.

Olsen, K. B.; Geisselmeyer, A.; Stephenson, W. J.; Mai, P. M.

2007-12-01

122

On the stability of a recirculation bubble and its application in compact combustion  

NASA Astrophysics Data System (ADS)

A 2D channel flow expands asymmetrically via a sudden expansion splitter plate, the Reynolds number based on the channel height and mean velocity is 1.47 x 10^4. A recirculation bubble generated by a momenturm-driven counter flowing secondary stream located downstream of the sudden expansion is experimentally investigated by means of hot-wire anemometry and PIV. It is conjectured that the fluid field created is one of a separated region of locally absolutely unstable flow. This separated region is the result of both the partial stagnation of the main flow due to the spreading of the second counter-current flow as well as the entrainment of the secondary jet. The secondary stream augments the initial shear layer that has been created after the expansion and a separation bubble appears. This secondary jet creates a control mechanism for the fluid field. The low-velocity zone downstream of the expansion that has been created is necessary for flame anchoring, and the large turbulence levels recorded (total turbulence levels exceeding 100% of the inlet velocity) dramatically increase mixing and may lead to more efficient compact combustion in backward-facing step-combustors.

Anderson, Matt; Strykowski, Paul

2009-11-01

123

Development of large-field high-resolution hard x-ray imaging microscopy and microtomography with Fresnel zone plate objective  

NASA Astrophysics Data System (ADS)

A hard x-ray imaging microscope system of high spatial resolution and large field of view (FOV) has been developed at the beamline 37 XU of SPring-8. By utilizing the 30 m-long experimental station, large magnification can be attained with a large diameter Fresnel zone plate (FZP) objective. Some configurations of microscope systems were tested. In a typical condition, a magnification of 133 and a FOV of 123 ?m are attained using a FZP with a diameter of 310 ?m and an outermost zone width of 100 nm, and the spatial resolution evaluated by observing resolution test chart is 160 nm in full pitch of periodic object with an exposure time of 1 s. When a FZP with an outermost zone width of 50 nm is used, a spatial resolution better than 100 nm is achieved. Phase-contrast imaging by Zernike's method was also tested, and three dimensional measurement by computer tomography (CT) method was also carried out.

Suzuki, Yoshio; Takeuchi, Akihisa; Terada, Yasuko; Uesugi, Kentaro; Tamura, Shigeharu

2013-09-01

124

Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan Fault Zone Based on Seismic Moment Accumulation/Release Model  

PubMed Central

Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7?±?0.3)?×?1017?N?m/yr, and a recurrence interval of 3900?±?400?yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

Zhang, Shimin

2013-01-01

125

Estimation of recurrence interval of large earthquakes on the central Longmen Shan fault zone based on seismic moment accumulation/release model.  

PubMed

Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7?±?0.3)?×?10¹??N?m/yr, and a recurrence interval of 3900?±?400?yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region. PMID:23878524

Ren, Junjie; Zhang, Shimin

2013-06-26

126

Numerical Study of Frictional Properties and the Role of Cohesive End-Zones in Large Strike- Slip Earthquakes  

NASA Astrophysics Data System (ADS)

Cohesive end-zones (CEZs) are regions of increased frictional strength and/or cohesion near the peripheries of faults that cause slip distributions to taper toward the fault-tip. Laboratory results, field observations, and theoretical models suggest an important role for CEZs in small-scale fractures and faults; however, their role in crustal-scale faulting and associated large earthquakes is less thoroughly understood. We present a numerical study of the potential role of CEZs on slip distributions in large, multi-segmented, strike-slip earthquake ruptures including the 1992 Landers Earthquake (Mw 7.2) and 1999 Hector Mine Earthquake (Mw 7.1). Displacement discontinuity is calculated using a quasi-static, 2D plane-strain boundary element (BEM) code for a homogeneous, isotropic, linear-elastic material. Friction is implemented by enforcing principles of complementarity. Model results with and without CEZs are compared with slip distributions measured by combined inversion of geodetic, strong ground motion, and teleseismic data. Stepwise and linear distributions of increasing frictional strength within CEZs are considered. The incorporation of CEZs in our model enables an improved match to slip distributions measured by inversion, suggesting that CEZs play a role in governing slip in large, strike-slip earthquakes. Additionally, we present a parametric study highlighting the very great sensitivity of modeled slip magnitude to small variations of the coefficient of friction. This result suggests that, provided a sufficiently well-constrained stress tensor and elastic moduli for the surrounding rock, relatively simple models could provide precise estimates of the magnitude of frictional strength. These results are verified by comparison with geometrically comparable finite element (FEM) models using the commercial code ABAQUS. In FEM models, friction is implemented by use of both Lagrange multipliers and penalty methods.

Lovely, P. J.; Mutlu, O.; Pollard, D. D.

2007-12-01

127

Breathing of a coral cay: Tracing tidally driven seawater recirculation in permeable coral reef sediments  

Microsoft Academic Search

Coral reefs are characterized by high gross productivity in spite of low nutrient concentrations. This apparent paradox may be partially reconciled if seawater recirculation in permeable sediments over large (meters) and long (hours to days) scales is an important source of recycled nitrogen and phosphorus to coral reefs. In this paper we use radon (222Rn, a natural tracer) to quantify

Isaac R. Santos; Dirk Erler; Douglas Tait; Bradley D. Eyre

2010-01-01

128

Re-circulating linac vacuum system  

SciTech Connect

The vacuum system for a proposed 2.5 GeV, 10{Mu}A recirculating linac synchrotron light source [1] is readily achievable with conventional vacuum hardware and established fabrication processes. Some of the difficult technical challenges associated with synchrotron light source storage rings are sidestepped by the relatively low beam current and short beam lifetime requirements of a re-circulating linac. This minimal lifetime requirement leads directly to relatively high limits on the background gas pressure through much of the facility. The 10{Mu}A average beam current produces very little synchrotron radiation induced gas desorption and thus the need for an ante-chamber in the vacuum chamber is eliminated. In the arc bend magnets, and the insertion devices, the vacuum chamber dimensions can be selected to balance the coherent synchrotron radiation and resistive wall wakefield effects, while maintaining the modest limits on the gas pressure and minimal outgassing.

Wells, Russell P.; Corlett, John N.; Zholents, Alexander A.

2003-05-09

129

Recirculation control valve replacement cuts maintenance costs  

SciTech Connect

This article describes how replacement of boiler feed pump recirculation control valves solves a maintenance problem on Baldwin Unit 3. All three of Illinois Power`s Baldwin power plant units had the same boiler feed pump (BFP) valve design when they went into commercial operation. The original BFP recirculation valves were a top-guided plug, single-port cage design using a tapered plug and seat arrangement. This design failed in Unit 1 during the first year of operation, so a redesigned set of internals was installed in 1973. The new internals used a drilled-hole cage and were designed to resist cavitation and erosion. This same design was initially installed in the Unit 2 and Unit 3 valves. During initial unit startup and throughout the years, cavitation and erosion of the valve internals resulted in leaks.

Liefer, M.E.; Miller, H.L.; Katz, R.E.

1995-07-01

130

Preoperational test report, recirculation condenser cooling systems  

SciTech Connect

This represents a preoperational test report for Recirculation Condenser Systems, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The four system provide condenser cooling water for vapor space cooling of tanks AY1O1, AY102, AZ1O1, AZ102. Each system consists of a valved piping loop, a pair of redundant recirculation pumps, a closed-loop evaporative cooling tower, and supporting instrumentation; equipment is located outside the farm on concrete slabs. Piping is routed to the each ventilation condenser inside the farm via below-grade concrete trenches. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.

Clifton, F.T.

1997-11-04

131

High Power Picosecond Laser Pulse Recirculation  

SciTech Connect

We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

2010-04-12

132

Recirculating, suppressor T cells in transplantation tolerance  

PubMed Central

An adoptive transfer system was used to examine the capacity of cellular inocula from rats fully tolerant of Ag-B antigens to transfer tolerance to irradiated recipients. Permanent tolerance in these irradiated recipients involved specific suppression of the regenerating immune response. Cells obtained from tissues rich in recirculating lymphocytes were the most effective suppressors. Highly purified inocula of T cells from tolerant donors were potent suppressors in irradiated hosts, but were not capable of direct suppression of peripheral antigen-sensitive T cells.. The role of the thymus in maintaining the complement of recirculating suppressor T cells in tolerant animals was examined after adult thymectomy. Thymectomized tolerant rats did not reject their tolerated grafts, and the longevity of the suppression in tolerant rats was confirmed by showing that adoptive transfer of cells from thymectomized tolerant donors was effective in suppressing irradiated recipients up to 180 days after thymectomy. Cellular inocula from these donors appeared to lose their suppressor function marginally faster than they lost effector function (as measured by their capacity to mediate rejection of third party control grafts). Thymectomy made tolerant rats more vulnerable to the termination of tolerance by challenge with normal cells. Transplantation tolerance is maintained in adult rats by long-lived rapidly recirculating suppressor T cells. The target for the suppressor action of these cells is probably the precursor of alloantigen- sensitive lymphocytes, and the effect of suppression may be deletion or inactivation of the relevant clone of these cells.

1977-01-01

133

Stereoscopic PIV using optical flow: application to a cavity recirculation  

NASA Astrophysics Data System (ADS)

Open cavity flows are a class of wall-bounded flows marked by a recirculation vortex, large velocity gradients, and internal three-dimensional (3D) features. That complex structure results in the combination of an upper shear layer, which can develop a Kelvin-Helmholtz-like instability interacting with walls, the flow injection inside the cavity, the recirculation vortex development, and, for some geometries and Reynolds numbers, a centrifugal Taylor-Görtler-like instability. In order to explore this flow, experimental measurements of the three components of velocity are addressed with stereoscopic two-dimensional particle image velocimetry (3C-2D PIV) using an optical flow algorithm. This technique is a valuable diagnostic tool for quantitative instantaneous description of 3D flows, as those dominated by vortex motion. PIV camera calibration is based on a pinhole model using a single target and camera focal length. The challenging issue is that the studied flow is wall-bounded and subject to laser reflections, which can alter the quality of particle images. A treatment of recorded frames is addressed to get the correct velocity field. PIV measurements are carried out in two orthogonal planes to catch the flow structure and vortex dynamics. Time development of Taylor-Görtler-like vortices is also confronted to the results obtained in previous studies.

Douay, Christelle L.; Faure, Thierry M.; Lusseyran, François

2013-08-01

134

Tide-driven dynamics of ephemeral fluid mud deposits in troughs of large, subaqueous dunes in an estuarine turbidity zone  

NASA Astrophysics Data System (ADS)

Near-bed density stratification due to suspended, fine-grained cohesive sediments and the formation of fluid mud layers are frequently observed in tide-dominated estuaries. Significant progress was made during the past years in terms of the description and parameterization of fluid mud related sediment transport processes. However, only few studies present in-situ measurements of the spatiotemporal distribution of estuarine fluid mud deposits. Due to the tidal excursion, settling of cohesive sediments during slack water and the formation of fluid mud is also expected to occur in tidal channels, located upstream and downstream of the tidally averaged location of the estuarine turbidity zone and characterized by coarser bed sediments and mobile bedforms. In the Weser estuary (Southern North Sea, Germany), high resolution sediment echo sounder and acoustic Doppler current profiler measurements revealed ephemeral fluid mud deposits in troughs of large, ebb-directed, subaqueous dunes during flood slack water. The spatial distribution of fluid mud deposits correlated with the location of the turbidity zone, shifted upstream during the flood phase. Density stratification, induced by the accumulation of suspended sediments in dune troughs, was initially observed 1.2h before flood slack water. Sediment concentrations in the fluid mud layer ranged from 25g/l below the lutocline to a maximum concentration of 70g/l at the river bed, validated by Rumohr-type gravity coring. During the early ebb phase internal waves were observed as current velocities exceeded 0.2m/s, measured 1m above the lutocline. Fluid mud remained in dune troughs for approximately 2h after slack water and was not entrained until current velocities exceeded 0.45m/s. According to the local gradient Richardson number, calculated on the basis of average current velocities, the corresponding density gradient was stable with respect to shear instabilities during entrainment. Entrainment of fluid mud is explained to be induced by the development of the dune specific turbulent flow field downstream of the dune crest and advection of strong turbulent stresses in direction of the lutocline. Indicating high suspended sediment concentrations near the bed, lutoclines were observed for 3.5h during the tidal cycle around slack water. The associated fluid mud deposits are considered to affect the grain size distribution in dune troughs in terms of matrix infilling and the formation of mud drapes, embedded in cross-strata as found to be preserved in the sedimentary record.

Becker, M.; Schrottke, K.; Bartholomä, A.; Ernstsen, V. B.; Winter, C.; Hebbeln, D.

2012-04-01

135

Highly-resolved large eddy simulation of the nonreacting flow in an asymmetric vortex combustor  

NASA Astrophysics Data System (ADS)

In this paper, we present a computational investigation of the nonreacting flow structure inside a novel asymmetric vortex combustor that was recently proposed by the authors. Large Eddy Simulation using the Smagorinsky-Lilly subgrid turbulence closure has been used to study such flow. A computational grid of 2.22×106 cells was used to ensure that the resolved turbulence kinetic energy is fairly more than 80% of the total turbulence kinetic energy budget. The flow was found to exhibit a central recirculation zone, and two secondary recirculation zones in the asymmetry regions. The vortex structure was found to be a completely forced vortex field. The effect of turbulence on the size and structure of the statistically averaged mean flow phenomena has been analyzed as discussed.

Saqr, Khalid M.; Wahid, M. A.; Sies, Mohsin M.

2012-06-01

136

Ground Motion Simulation for a Large Active Fault System using Empirical Green's Function Method and the Strong Motion Prediction Recipe - a Case Study of the Noubi Fault Zone -  

Microsoft Academic Search

The 1995 Hyogo-ken Nambu Earthquake (1995) near Kobe, Japan, spurred research on strong motion prediction. To mitigate damage caused by large earthquakes, a highly precise method of predicting future strong motion waveforms is required. In this study, we applied empirical Green's function method to forward modeling in order to simulate strong ground motion in the Noubi Fault zone and examine

M. Kuriyama; T. Kumamoto; M. Fujita

2005-01-01

137

Impact of nitrate-enhanced leachate recirculation on gaseous releases from a landfill bioreactor cell.  

PubMed

This study evaluates the impact of nitrate injection on a full scale landfill bioreactor through the monitoring of gaseous releases and particularly N(2)O emissions. During several weeks, we monitored gas concentrations in the landfill gas collection system as well as surface gas releases with a series of seven static chambers. These devices were directly connected to a gas chromatograph coupled to a flame ionisation detector and an electron capture detector (GC-FID/ECD) placed directly on the field. Measurements were performed before, during and after recirculation of raw leachate and nitrate-enhanced leachate. Raw leachate recirculation did not have a significant effect on the biogas concentrations (CO(2), CH(4) and N(2)O) in the gas extraction network. However, nitrate-enhanced leachate recirculation induced a marked increase of the N(2)O concentrations in the gas collected from the recirculation trench (100-fold increase from 0.2 ppm to 23 ppm). In the common gas collection system however, this N(2)O increase was no more detectable because of dilution by gas coming from other cells or ambient air intrusion. Surface releases through the temporary cover were characterized by a large spatial and temporal variability. One automated chamber gave limited standard errors over each experimental period for N(2)O releases: 8.1 +/- 0.16 mg m(-2) d(-1) (n = 384), 4.2 +/- 0.14 mg m(-2) d(-1) (n = 132) and 1.9 +/- 0.10 mg m(-2) d(-1) (n = 49), during, after raw leachate and nitrate-enhanced leachate recirculation, respectively. No clear correlation between N(2)O gaseous surface releases and recirculation events were evidenced. Estimated N(2)O fluxes remained in the lower range of what is reported in the literature for landfill covers, even after nitrate injection. PMID:19297142

Tallec, G; Bureau, C; Peu, P; Benoist, J C; Lemunier, M; Budka, A; Presse, D; Bouchez, T

2009-03-17

138

Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA  

NASA Astrophysics Data System (ADS)

The New Madrid seismic zone (NMSZ) is an intraplate right-lateral strike-slip and thrust fault system contained mostly within the Mississippi Alluvial Valley. The most recent earthquake sequence in the zone occurred in 1811 1812 and had estimated moment magnitudes of 7 8 (e.g., [Johnston, A.C., 1996. Seismic moment assessment of stable continental earthquakes, Part 3: 1811 1812 New Madrid, 1886 Charleston, and 1755 Lisbon. Geophysical Journal International 126, 314 344; Johnston, A.C., Schweig III, E.S, 1996. The enigma of the New Madrid earthquakes of 1811 1812. Annual Reviews of Earth and Planetary Sciences 24, 339 384; Hough, S.E., Armbruster, J.G., Seeber, L., Hough, J.F., 2000. On the modified Mercalli intensities and magnitudes of the New Madrid earthquakes. Journal of Geophysical Research 105 (B10), 23,839 23,864; Tuttle, M.P., 2001. The use of liquefaction features in paleoseismology: Lessons learned in the New Madrid seismic zone, central United States. Journal of Seismology 5, 361 380]). Four earlier prehistoric earthquakes or earthquake sequences have been dated A.D. 1450 ± 150, 900 ± 100, 300 ± 200, and 2350 B.C. ± 200 years using paleoliquefaction features, particularly those associated with native American artifacts, and in some cases surface deformation ([Craven, J. A. 1995. Paleoseismology study in the New Madrid seismic zone using geological and archeological features to constrain ages of liquefaction deposits. M.S thesis, University of Memphis, Memphis, TN, U.S.A.; Tuttle, M.P., Lafferty III, R.H., Guccione, M.J., Schweig III, E.S., Lopinot, N., Cande, R., Dyer-Williams, K., Haynes, M., 1996. Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone, central United States. Geoarchaeology 11, 451 480; Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43(2002), 313 349; Tuttle, M.P., Schweig, E.S., Sims, J.D., Lafferty, R.H., Wolf, L.W., Haynes, M.L., 2002. The earthquake potential of the New Madrid seismic zone, Bulletin of the Seismological Society of America, v 92, n. 6, p. 2080 2089; Tuttle, M.P., Schweig III, E.S., Campbell, J., Thomas, P.M., Sims, J.D., Lafferty III, R.H., 2005. Evidence for New Madrid earthquakes in A.D. 300 and 2350 B.C. Seismological Research Letters 76, 489 501]). The two most recent prehistoric and the 2350 B.C. events were probably also earthquake sequences with approximately the same magnitude as the historic sequence. Surface deformation (faulting and folding) in an alluvial setting provides many examples of stream response to gradient changes that can also be used to date past earthquake events. Stream responses include changes in channel morphology, deviations in the channel path from the regional gradient, changes in the direction of flow, anomalous longitudinal profiles, and aggradation or incision of the channel ([Merritts, D., Hesterberg, T, 1994. Stream networks and long-term surface uplift in the New Madrid seismic zone. Science 265, 1081 1084.; Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43 (2002), 313 349]). Uplift or depression of the floodplain affects the frequency of flooding and thus the thickness and style of vertical accretion or drowning of a meander scar to form a lake. Vegetation may experience trauma, mortality, and in some cases growth enhancement due to ground failure during the earthquake and hydrologic changes after the earthquake ([VanArdale, R.B., Stahle, D.W., Cleaveland, M.K., Guccione, M.J., 1998. Earthquake signals in tree-ring data from the New Madrid seismic zone and implications for paleoseismicity. Geology 26, 515 518]). Identification and dating these physical and biologic responses allows source areas to be identified and seismic events to be dated. Seven fault segments are recognized by microseismicity and geomorphology. Surface faulting

Guccione, Margaret J.

2005-10-01

139

Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff  

Microsoft Academic Search

The Rainier Mesa ash-flow is a large (1200 km3), 11.6 My old, chemically zoned unit that ranges in composition from 55 to 76% SiO2 --- one of the largest chemical ranges ever observed in a large volume ash-flow sheet. Two chemical trends occur in this sheet, a low silica (55 66% SiO2) and a high silica (>66% SiO2) trend. Ninety

Kristin T. Huysken; Thomas A. Vogel; Paul W. Layer

1994-01-01

140

Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff  

Microsoft Academic Search

The Rainier Mesa ash-flow is a large (1200 km3), 11.6 My old, chemically zoned unit that ranges in composition from 55 to 76% SiO2 — one of the largest chemical ranges ever observed in a large volume ash-flow sheet. Two chemical trends occur in this sheet, a low silica (55–66% SiO2) and a high silica (>66% SiO2) trend. Ninety per

Kristin T. Huysken; Thomas A. Vogel; Paul W. Layer

1994-01-01

141

Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff  

Microsoft Academic Search

The Rainier Mesa ash-flow is a large (1200 km3), 11.6 My old, chemically zoned unit that ranges in composition from 55 to 76% SiO2 - one of the largest chemical ranges ever observed in a large volume ash-flow sheet. Two chemical trends occur in this sheet, a low silica (55-66% SiO2) and a high silica (>66% SiO2) trend. Ninety per

Kristin T. Huysken; Thomas A. Vogel; Paul W. Layer

1994-01-01

142

Computational fluid dynamics analysis of external recirculation flow at updraft gasifier using ejector  

NASA Astrophysics Data System (ADS)

Gasification process at updraft gasifier produces the amount of more tar than the other gasifier type. To reduce tar at updraft gasifier, it is carried out recirculation of pirolysis gas into combustion zone. Ejector is an equipment used to entrain the secondary fluid flow by moving momentum and energy from high velocity of primary flow (jet). Research carries out the simulation of isothermal 3D using Computational Fluid Dynamics (CFD) to obtain the maximum of recirculation flow at updraft gasifier using ejector. The result of simulation shows that change of nozzle diameter gives great influence at change of total flow for resirculation compared with the change of diameter and length of mixing area and nozzle exit position (NXP). The maximum of resirculation flow 81 lpm at nozzle diameter 0.75 cm.

Vidiana, Fajri; Surjosatyo, Adi; Nugroho, Yulianto Sulistyo

2012-06-01

143

A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces.  

PubMed

A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 1 of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary zone into underlying groundwater. The mass transfer of TCE vapors from the vadose zone to the atmosphere was quantified using a vertical flux chamber. A special soil water sampler was used to monitor transport across the capillary fringe. Experimental data indicated that TCE in the unsaturated zone was mainly transported to the atmosphere and this exchange reduced significantly the potential for groundwater pollution. The maximum measured TCE flux to the atmosphere was about 3 g/m(2)/day. Observed and calculated fluxes based on vertical TCE vapor concentration gradients and Fick's law were in good agreement. This confirms that TCE vapor transport under the experimental conditions was governed essentially by molecular diffusion. TCE vapors also caused a lower, but significant contamination of the underlying groundwater by dispersion across the capillary fringe with a corresponding maximum flux of about 0.1 g/m(2)/day. This mass transfer to groundwater is partly uncertain due to an inadvertent entry of some nonaqueous phase liquid (NAPL) from the source area into the saturated zone. Application of an analytical solution to estimate the TCE flux from the unsaturated zone to the groundwater indicated that this phenomenon is not only influenced by molecular diffusion but also by vertical dispersion. The mass balance indicates that, under the given experimental conditions (e.g. proximity of the source emplacement relative to the soil surface, relatively high permeable porous medium), nearly 95% of the initial TCE mass was transferred to the atmosphere. PMID:12498573

Jellali, Salah; Benremita, Hocine; Muntzer, Paul; Razakarisoa, Olivier; Schäfer, Gerhard

2003-01-01

144

The use of large loop excision of the transformation zone in management problems of cervical intraepithelial neoplasia.  

PubMed

We studied 2 groups of women whose management is controversial: those with cervical intraepithelial neoplasia (CIN) grade 2 or 3 on smear, but only CIN grade 1 or no abnormality on target biopsy (Group 1), and those with persistent CIN grade 1 on smear and up to CIN 1 on biopsy (Group 2). We set out to assess whether large loop excision of the transformation zone (LLETZ) was an acceptable method of treating these 2 groups of women. A review of 100 consecutive patients was undertaken. There were 71 women in Group 1 and 29 women in Group 2. The LLETZ procedures were performed under local analgesia and no immediate problems were encountered. Delayed haemorrhage requiring vaginal packing and admission to hospital occurred in 1 patient. In Group 1, histopathology of the LLETZ biopsies showed CIN 2 or 3 in 29 (40.8%) of the women, CIN 1 in 24 (33.8%) and no CIN in 18 (25.3%), and in Group 2, CIN 2 or 3 was seen in 5 (17.2%) of the women, CIN 1 in 11 (37.9%) and no CIN in 13 (44.8%). At 12 months completed follow-up, 4 patients in Group 1 had recurrent CIN 1 or equivocal CIN 1 and 1 patient from Group 2 had recurrent CIN 1, giving an overall recurrence rate of 5 of the 94 patients who completed follow-up (5%). We concluded that LLETZ was a useful procedure in both groups. In Group 1 the provision of a histological diagnosis on the LLETZ biopsy was a check on the accuracy of the cervical smear report. In Group 2, LLETZ offered the advantage of rapidly returning the smear to normal in most patients, and the diagnosis and treatment of those women who actually had a high-grade lesion. PMID:9761146

Ehsani, N; Golbang, P; Papadakis, T; Scurry, J; Muldowney, L; Allen, D; Planner, R

1998-08-01

145

Oligomerization state of S100B at nanomolar concentration determined by large-zone analytical gel filtration chromatography.  

PubMed Central

S100B is a Ca(2+)-binding protein known to be a non-covalently associated dimer, S100B(beta beta), at high concentrations (0.2-3.0 mM) under reducing conditions. The solution structure of apo-S100B (beta beta) shows that the subunits associate in an antiparallel manner to form a tightly packed hydrophobic core at the dimer interface involving six of eight helices and the C-terminal loop (Drohat AC, Amburgey JC, Abildgaard F, Starich MR, Baldisseri D, Weber DJ. 1996. Solution structure of rat apo-S100B (beta beta) as determined by NMR spectroscopy. Biochemistry 35:11577-11588). The C-terminal loop, however, is also known to participate in the binding of S100B to target proteins, so its participation in the dimer interface raises questions as to the physiological relevance of dimeric S100B (beta beta). Therefore, we investigated the oligomerization state of S100B at low concentrations (1-10,000 nM) using large-zone analytical gel filtration chromatography with 35S-labeled S100B. We found that S100B exists (> 99%) as a non-covalently associated dimer, S100B (beta beta), at 1 nM subunit concentration (500 pM dimer) in the presence or absence of saturating levels of Ca2+, which implies a dissociation constant in the picomolar range or lower. These results demonstrate for the first time that in reducing environments and at physiological concentrations, S100B exists as dimeric S100B (beta beta) in the presence or absence of Ca2+, and that the non-covalent dimer is most likely the form of S100B presented to target proteins.

Drohat, A. C.; Nenortas, E.; Beckett, D.; Weber, D. J.

1997-01-01

146

Exhaust gas recirculation system for an internal combustion engine  

DOEpatents

An exhaust gas recirculation system for an internal combustion engine comprises an exhaust driven turbocharger having a low pressure turbine outlet in fluid communication with an exhaust gas conduit. The turbocharger also includes a low pressure compressor intake and a high pressure compressor outlet in communication with an intake air conduit. An exhaust gas recirculation conduit fluidly communicates with the exhaust gas conduit to divert a portion of exhaust gas to a low pressure exhaust gas recirculation branch extending between the exhaust gas recirculation conduit and an engine intake system for delivery of exhaust gas thereto. A high pressure exhaust gas recirculation branch extends between the exhaust gas recirculation conduit and the compressor intake and delivers exhaust gas to the compressor for mixing with a compressed intake charge for delivery to the intake system.

Wu, Ko-Jen

2013-05-21

147

Non-premixed conditions in the flameholding recirculation region behind a step in supersonic flow  

NASA Astrophysics Data System (ADS)

Flameholding in supersonic flow depends on local conditions in the recirculation region, and on mass transfer into and out of this region. Large gradients in local gas composition and temperature exist in the recirculation region. Hence, stability parameter correlations developed for premixed flames cannot be used to determine blowout stability limits for non-premixed flames encountered in practical devices. In the present study, mixture samples were extracted at different locations in the recirculation region and the shear layer formed behind a rearward-facing step in supersonic flow, and analyzed by mass spectrometry to determine the species concentration distribution in the region. The point-wise mass spectrometer measurements were complemented by acetone planar laser-induced fluorescence (PLIF) measurements to get a planar distribution of fuel mole fraction in the recirculation region. Non-reacting flow tests and combustion experiments were performed by varying various fuel related parameters such as injection location, injection pressure and fuel type. Fuel injection upstream of the step was not effective in supplying enough fuel to the recirculation region and did not sustain the flame in combustion experiments. Fuel injection at the step base was effective in sustaining the flame. For base injection, the local fuel mole fraction in the recirculation region determined from experiments was an order of magnitude higher than the global fuel mole fraction based on total moles of air flowing through the test section and total fuel injected in the test section. This suggests substantial difference in flame stability curve for non-premixed conditions in the scramjet engine compared to premixed flow. For base injection, fuel remained in the recirculation region even at higher injection pressure. Due to slower diffusion rate, the heavier fuel had higher local mole fraction in the recirculation region compared to lighter fuel for a unit global fuel mole fraction injected in the test section. Hence fuel molecular weight will affect the non-premixed flame stability limits in scramjet engine; the heavier fuel will have better fuel-lean and worse fuel-rich stability limit compared to lighter fuel. This is in addition to the fact that a lighter fuel such as hydrogen has a much wider flame stability limit than a heavier fuel such as propane. The data obtained in the study can help develop a stability parameter for non-premixed flames and validate computational models.

Thakur, Amit

148

Monitoring of Leachate Recirculation in a Bioreactor Using Electrical Resistivity  

Microsoft Academic Search

The bioreactor is a concept of waste landfill management consisting in speeding up the biodegradation by optimizing the moisture content through leachate recirculation. Electrical resistivity tomography (ERT) is carried out with fast resistivity-meter (Syscal Pro, IRIS Instruments, developed in the framework of the research project CERBERE 01V0665-69, funded by the French Research Ministry) to monitor leachate recirculation. During a recirculation

S. Grellier; N. Bureau; H. Robain; A. Tabbagh; C. Camerlynck; R. Guerin

2004-01-01

149

FULL-SCALE EXPERIENCES WITH LEACHATE RECIRCULATING LANDFILLS: CASE STUDIES  

Microsoft Academic Search

Leachate recirculation has been shown in lysimeter, pilot-scale and full-scale investigations to reduce the time required for waste stabilization, improve leachate quality, provide the opportunity for leachate volume reduction, and to enhance the rate of gas production. New generation full-scale landfills are implementing recirculation as a leachate management tool with increasing frequency. Leachate recirculation techniques used at full-scale landfills include

Debra R. Reinhart

1996-01-01

150

Landslide zoning over large areas from a sample inventory by means of scale-dependent terrain units  

NASA Astrophysics Data System (ADS)

A procedure is proposed to produce landslide distribution zoning maps to be considered preparatory to susceptibility, hazard and risk zoning maps, based on 1) the results from a statistical multivariate analysis of a landslide inventory, which must be available for only a portion of the territory to be zoned, and 2) the use of appropriately defined terrain mapping units. The units are divided into terrain computational units (TCUs) and terrain zoning units (TZUs), whose size is related to the scale of zoning. The procedure comprises three phases: calibration, validation and prediction. The purpose of the prediction phase is the application of a calibrated and validated statistical model in a territory, previously recognized as viable on the basis of 'a-priori applicability maps,' for which no information is available regarding the distribution of landslides or where the information provided by the landslides inventory is unreliable or heterogeneous. The proposed procedure is applied to two case studies in southern Italy for the analysis and zoning of slow-moving landslides at 1:25,000 and 1:100,000 scales, respectively. The first case study illustrates the applicability of the procedure. The aim of the second case study is to address the part of the procedure related to the evaluation of the computational maps at the end of the calibration and validation phases.

Calvello, Michele; Cascini, Leonardo; Mastroianni, Sabrina

2013-01-01

151

Recirculating Linear Accelerators for Future Muon Facilities  

SciTech Connect

Neutrino Factories (NF) and Muon Colliders (MC) require rapid acceleration of short-lived muons to multi-GeV and TeV energies. A Recirculating Linear Accelerator (RLA) that uses superconducting RF structures can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the RF cavities, leading to greater cost effectiveness.

S.A. Bogacz, K.B.Beard, R.P. Johnson

2010-05-01

152

Practice review of five bioreactor/recirculation landfills.  

PubMed

Five landfills were analyzed to provide a perspective of current practice and technical issues that differentiate bioreactor and recirculation landfills in North America from conventional landfills. The bioreactor and recirculation landfills were found to function in much the same manner as conventional landfills, with designs similar to established standards for waste containment facilities. Leachate generation rates, leachate depths and temperatures, and liner temperatures were similar for landfills operated in a bioreactor/recirculation or conventional mode. Gas production data indicate accelerated waste decomposition from leachate recirculation at one landfill. Ambiguities in gas production data precluded a definitive conclusion that leachate recirculation accelerated waste decomposition at the four other landfills. Analysis of leachate quality data showed that bioreactor and recirculation landfills generally produce stronger leachate than conventional landfills during the first two to three years of recirculation. Thereafter, leachate from conventional and bioreactor landfills is similar, at least in terms of conventional indicator variables (BOD, COD, pH). While the BOD and COD decreased, the pH remained around neutral and ammonia concentrations remained elevated. Settlement data collected from two of the landfills indicate that settlements are larger and occur much faster in landfills operated as bioreactors or with leachate recirculation. The analysis also indicated that more detailed data collection over longer time periods is needed to draw definitive conclusions regarding the effects of bioreactor and recirculation operations. For each of the sites in this study, some of the analyses were limited by sparseness or ambiguity in the data sets. PMID:16766174

Benson, C H; Barlaz, M A; Lane, D T; Rawe, J M

2006-06-12

153

Recirculating Planar Magnetron Modeling and Experiments  

NASA Astrophysics Data System (ADS)

We present simulations and initial experimental results of a new class of crossed field device: Recirculating Planar Magnetrons (RPM) [1]. Two geometries of RPM are being explored: 1) Dual planar-magnetrons connected by a recirculating section with axial magnetic field and transverse electric field, and 2) Planar cathode and anode-cavity rings with radial magnetic field and axial electric field. These RPMs have numerous advantages for high power microwave generation by virtue of larger area cathodes and anodes. The axial B-field RPM can be configured in either the conventional or inverted (faster startup) configuration. Two and three-dimensional EM PIC simulations show rapid electron spoke formation and microwave oscillation in pi-mode. Smoothbore prototype axial-B RPM experiments are underway using the MELBA accelerator at parameters of -300 kV, 1-20 kA and pulselengths of 0.5-1 microsecond. Implementation and operation of the first RPM slow wave structure, operating at 1GHz, will be discussed. [4pt] [1] Patent pending

Franzi, Matthew; Gilgenbach, Ronald; Hoff, Brad; French, Dave; Lau, Y. Y.

2011-11-01

154

Recirculating linac free-electron laser driver  

NASA Astrophysics Data System (ADS)

This paper describes the design of a recirculating linac as a driver for the suite of seeded free-electron lasers (FELs) proposed in the UK New Light Source (NLS) project. The choice of superconducting technology for NLS is required in order to deliver bunches at high repetition rates up to 1 MHz. This raises the question of whether a shorter linac in recirculating mode can deliver the beam quality required for seeded FELs. To design such a facility, careful layout choices and optimizations must be made to ensure emittance growth is minimized. Effects leading to emittance dilution include chromatic transport terms, incoherent and coherent synchrotron radiation. The design outlined here is based on a modular philosophy to separate beam injection and extraction from a three stage compression scheme. The design uses many novel design concepts and optimizations to deliver the necessary high peak currents while preserving beam quality for seeded FELs. Start-to-end simulations including the FELs show that the necessary pulse coherence and output power can be provided from the beam thus generated.

Williams, Peter H.; Angal-Kalinin, Deepa; Dunning, David J.; Jones, James K.; Thompson, Neil R.

2011-05-01

155

High-resolution genomic profiling reveals clonal evolution and competition in gastrointestinal marginal zone B-cell lymphoma and its large cell variant.  

PubMed

We studied marginal zone B-cell lymphomas of the gastrointestinal tract including seven small cell lymphomas, eight large cell areas of composite lymphomas and 13 large cell variants using SNP array profiling. We found an increase of genomic complexity with lymphoma progression from small to large cytology, and identified gains of prominent (proto) oncogenes such as REL, BCL11A, ETS1, PTPN1, PTEN and KRAS which were found exclusively in the large cell variants. Copy numbers of ADAM3A, SCAPER and SIRPB1 were varying between the three different modes of presentation, hence suggestive for aberrations associated with progression from small to large cell lymphoma. The number of aberrations was slightly higher in the large cell part of composite lymphomas than in large cell lymphomas, suggesting that clonal selection takes place and that composite lymphomas are in a transition state. To further investigate this, we comparatively analyzed samples of two morphologically different regions of the same small cell tumor with a BIRC3-MALT1 translocation, as well as material acquired at two different time points from one composite lymphoma. We found genomic heterogeneity in both cases, supporting the theory of competing subclones in the evolution and progression of extranodal marginal zone B-cell lymphoma. PMID:22890838

Flossbach, Lucia; Holzmann, Karlheinz; Mattfeldt, Torsten; Buck, Michaela; Lanz, Karin; Held, Michael; Möller, Peter; Barth, Thomas F E

2012-09-01

156

Plume Generation Zones at the margins of Large Low Shear Velocity Provinces on the core mantle boundary  

NASA Astrophysics Data System (ADS)

Large Igneous Province (LIP) eruption sites of the past 300 My lie vertically above 1% slow shear wave velocity ( Vs) contours bounding the African and Pacific Large Low Shear Velocity Provinces (LLSVPs) at the core-mantle boundary (CMB), or in the cases of the Siberian and Columbia River LIPs, bounding one or other of two smaller, Low Shear Velocity Provinces (LSVPs). Steep gradients in Vs at the CMB coincide with those 1% slow contours. The sites of 24 active hotspot volcanoes project down to the same narrowly defined borders of the LLSVPs at the CMB. Plumes that have generated LIPs and major hotspot volcanoes have risen only from the immediate neighbourhoods of the 1% slow Vs contours at the CMB which thus define Plume Generation Zones (PGZs). PGZs projected vertically upward approximately match the + 10 m elevation contour of the geoid showing that the LLSVPs are a dominant control on the positively elevated geoid. Minima in the frequency distribution of shear wave velocities in the lowermost mantle near Vs = - 1% indicate that regions with more negative velocities, forming ˜ 2% of total mantle mass, are likely to be of material compositionally different from the rest of the mantle. Because all LIP eruption sites with ages younger than 300 Ma lie above the borders of LLSVPs or LSVPs at the CMB, PGZ footprints are inferred to have remained in the same places for the past 300 My. Because no plumes have risen from the interior of the LLSVPs and because no lithospheric slabs have penetrated those bodies the volumes of the LLSVPs are inferred to have also remained unchanged for the past 300 My. Because the LLSVPs are the dominant control on the positively elevated areas of the geoid those too must have remained as they now are since 300 Ma. The LLSVPs are not rising buoyant objects but stable features of the deep mantle. LIPs have been erupted throughout the past 2.5 Gy indicating that PGZs comparable to those of the past 0.3 Gy and LLSVPs (of which PGZs mark the margins at the CMB) have also existed for at least that long. LLSVPs could thus form the isolated reservoir invoked by some to explain the distinctive isotopic compositions of terrestrial rocks. PGZs lie at places where the boundaries of: (i) The outer core, (ii) one of the LLSVPs or LSVPs, and (iii) the seismically faster part of the deep mantle meet. Horizontal temperature gradients across the steeply inclined margins to the LLSVPs, the interiors of which are hotter than the surrounding mantle, at the CMB are key controls for the generation of plumes. Near the CMB the association of the high temperature of the outer core with an inclined thermal boundary layer at the margins of LLSVPs facilitates the generation of mantle plumes in the PGZs.

Burke, Kevin; Steinberger, Bernhard; Torsvik, Trond H.; Smethurst, Mark A.

2008-01-01

157

Extreme Precipitation Events in Southeastern South America and Large-Scale Convective Patterns in the South Atlantic Convergence Zone  

Microsoft Academic Search

The occurrence of daily extreme precipitation events in southeast South America (São Paulo, Brazil) and the spatial features of convective activity in the South Atlantic convergence zone (SACZ) are investigated. Precipitation data from surface stations in São Paulo state from 1979 to 1996 are used to determine the frequency of occurrence of extremely heavy daily precipitation events. Daily averages of

Leila M. V. Carvalho; Charles Jones; Brant Liebmann

2002-01-01

158

Fixed Field Alternating Gradient recirculator for heavy ion fusion  

SciTech Connect

A heavy ion fusion driver is considered in which a beam is passed repeatedly through a LIA (linear induction accelerator) by recirculating with two spiral sector FFAG (Fixed Field Alternating Gradient) 180 degree bends. The driver consists of three such rings: a 10--100 MeV low energy ring (LER), a 100--1000 MeV medium energy ring (MER), and a 1--10 GeV high energy ring (HER). Using a scaling field of 14 kG and taking the length of the straight sections to equal the path length in the bends, the circumference of the three rings would be 187, 590, and 1890 meters. Four matching sections in each of the three rings provide the interface between the two straight sections accommodating the LIA and the FFAG bends. These matching sections consist of dipoles which provide a dispersion free match between the linear induction accelerator and the energy dependent equilibrium orbits of the FFAG ring. The advantage in the use of the spiral sector FFAG over other recirculator concepts is that the fields are time invariant. This removes the problems associated with time dependent field penetration into the vacuum chamber and the large amount of energy which must be expended to change the magnetic field on the small time scale associated with the required pulse repetition frequency. The disadvantage, as we show in this work is the relatively weak alternating gradient focusing. The FFAG will not accommodate the level of beam current possible in a separate function lattice of bending magnets and quadrupoles.

Paul, A.C.; Neil, V.K.

1991-03-01

159

The benefits of flue gas recirculation in waste incineration  

Microsoft Academic Search

Flue gas recirculation in the incinerator combustion chamber is an operative technique that offers substantial benefits in managing waste incineration. The advantages that can be obtained are both economic and environmental and are determined by the low flow rate of fumes actually emitted if compared to the flue gas released when recirculation is not conducted. Simulations of two incineration processes,

Giuseppe Liuzzo; Nicola Verdone; Marco Bravi

2007-01-01

160

Energy savings from air recirculation in peanut curing  

SciTech Connect

A thin-layer peanut drying simulation model was adapted to incorporate air recirculation. Laboratory crop dryers were designed and constructed to conduct experiments to verify the model. Five batches of peanuts were dried using different recirculation strategies. The model successfully predicted the results.

Cook, D.F.; Cundiff, J.S.; Vaughan, D.H.

1982-12-01

161

Energy conservation by partial recirculation of peanut drying air  

SciTech Connect

Conventional, recirculating, and intermittent type peanut dryers were compared in a three-year study. Comparisons indicate that partial recirculation of peanut drying air may reduce energy consumption per unit of water removed by approximately 25% while also reducing required drying time and maintaining high quality.

Young, J.H.

1983-06-01

162

Longitudinal dynamics in high frequency ffag recirculating accelerators  

Microsoft Academic Search

A recirculating accelerator accelerates the beam by passing through accelerating cavities multiple times. An FFAG recirculating accelerator uses a single arc to connect the linacs together, as opposed to multiple arcs for the different energies. For most scenarios using high-frequency RF, it is impractical to change the phase of the RF on each pass, at least for lower energy accelerators.

S. Berg

2002-01-01

163

THE BMI16 RECIRCULATING GAS LOOP INSTALLED AT THE ETR  

Microsoft Academic Search

A developmental program was conducted to provide and in-pile loop ; facility for use in evaluating gas-cooledreactor fuel asubassemblies. The ; program included the design, construction, and installation of a recirculating ; gas loop which is located in a 6 by 6-in. facility in the aluminum reflector of ; the ETR. The loop system was designed to recirculate the primary

J. V. Baum; G. A. Francis

1960-01-01

164

Leachate Recirculation Using Permeable Blankets in Engineered Landfills  

Microsoft Academic Search

Subsurface leachate recirculation or liquid injection methods for municipal solid waste MSW landfills are horizontal trenches, vertical wells, and permeable blankets. In this study, results of field-scale testing and numerical modeling of a recently developed subsurface leachate recirculation system called permeable blankets have been presented. In the field, at a MSW landfill located in Michigan, the travel of injected leachate

Mazen M. Haydar; Milind V. Khire

2007-01-01

165

How many histological levels should be examined from tissue blocks originating in cone biopsy and large loop excision of the transformation zone specimens of cervix?  

Microsoft Academic Search

Aims—To establish the value of examining additional histological levels in cone biopsy and large loop excision of the transformation zone (LLETZ) specimens of cervix.Methods—Three deeper levels were examined from 200 consecutive cone biopsy and LLETZ specimens reported by a single pathologist.Results—Examination of the first deeper level resulted in cervical intraepithelial neoplasia (CIN) being identified for the first time in five

M K Heatley

2001-01-01

166

Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Äspö (Sweden)  

Microsoft Academic Search

157-172 Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Äspö (Sweden) Jorge Molinero E.T.S. Ingenieros de Caminos Canales y Puertos, Campus de Elvina Universidadde A Coruña 15192 A Coruña Spain E-mail: molinero@iccp.udc.es Javier Samper E.T.S. Ingenieros de Caminos Canales y Puertos, Campus de Elvina Universidad de A Coruna, 15192 A Coruna,

Jorge Molinero; Javier Samper

2004-01-01

167

Spatially explicit estimation of soil denitrification rates and land use effects in the riparian buffer zone of the large Guanting reservoir  

Microsoft Academic Search

An important function of riparian ecosystems, usually characterized as nitrate-loaded wetland environments, is nitrogen removal by denitrification. Riparian buffer zones around large dams and water reservoirs are also recognized as hotspots for emission of nitrogen (N2) and nitrous oxide (N2O), the latter being a strong greenhouse gas. Research has proven that land use has an important effect on soil denitrification.

Xuelei Wang; Shengtian Yang; C. M. Mannaerts; Yunfei Gao; Jianxia Guo

2009-01-01

168

NGL recovery being hiked by natural-gasoline recirculation  

SciTech Connect

Construction will be completed later this year at two compression plants operated by Lagoven, S.A., to install natural-gasoline recirculation to improve NGL recovery. The project is the result of a study of condensate-stream recirculation and absorber operations at the compression plants Tia Juana 2 (PCTJ-2) and Tia Juana 3 (PCTJ-3), offshore Lake Maracaibo in western Venezuela. The PCTJ-2 and PCTJ-3 gas compression plants have two systems: gas compression and NGL extraction. Previous analysis of the NGL extraction and fractionation processes of Lagoven determined that there are two practical and attractive alternatives for the recirculation of the condensate streams in PCTJ-2 and 3: recirculation of natural gasoline from the Ule LPG plant; recirculation of a conditioned condensate from the de-ethanizer tower of each plant. Both alternatives are discussed. Also described are fractionation capacity, and modifications for adding absorption and fractionation.

Rivas M, M.; Bracho, J.L. [Lagoven S.A., Maracaibo (Venezuela); Murray, J.E. [Murray (James E.), Corpus Christi, TX (United States)

1997-07-07

169

Recirculating Linac Accelerators For Future Muon Facilities  

SciTech Connect

Neutrino Factories (NF) and Muon Colliders (MC) require rapid acceleration of shortlived muons to multi-GeV and TeV energies. A Recirculating Linear Accelerator (RLA) that uses superconducting RF structures can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the RF cavities, leading to greater cost effectiveness. We discuss the optics and technical requirements for RLA designs, using RF cavities capable of simultaneous acceleration of both m+ and m- species. The design will include the optics for the multi-pass linac and droplet-shaped return arcs.

Yves Roblin, Alex Bogacz, Vasiliy Morozov, Kevin Beard

2012-04-01

170

Mixing in a stratified recirculating flow  

SciTech Connect

Experiments were conducted to study the mixing processes and circulation patterns in a stratified, lid-driven cavity flow. This flow is different from those reported in the literature in three ways, viz., recirculation is a dominant feature, temperature is used as the stratification device, and the upper and lower boundaries are held at different constant temperatures. For the geometric configuration used entrainment rate E is proportional to Ri/sup -7/5/. Taylor-Goertler-like vortices above the thermocline are significant contributors to the mixing process. In addition, the number of circulation cells expected in this stratified flow can be estimated by use of the bulk Richardson number Ri/sub b/.

Koseff, J.R.; Rhee, H.; Street, R.L.

1983-01-01

171

Recirculating Molten Metal Supply System And Method  

DOEpatents

The melter furnace includes a heating chamber (16), a pump chamber (18), a degassing chamber (20), and a filter chamber (22). The pump chamber (18) is located adjacent the heating chamber (16) and houses a molten metal pump (30). The degassing chamber (20) is located adjacent and in fluid communication with the pump chamber (18), and houses a degassing mechanism (36). The filter chamber (22) is located adjacent and in fluid communication with the degassing chamber (20). The filter chamber (22) includes a molten metal filter (38). The melter furnace (12) is used to supply molten metal to an externally located holder furnace (14), which then recirculates molten metal back to the melter furnace (12).

Kinosz, Michael J. (Apollo, PA); Meyer, Thomas N. (Murrysville, PA)

2003-07-01

172

Near-surface recirculation over Georges Bank  

NASA Astrophysics Data System (ADS)

Satellite-tracked drifters with drogues centered near-surface (5 m) and below the seasonal thermocline (50 m) were launched during late winter and spring of 1988 and 1989 in the northern Great South Channel in the western Gulf of Maine to investigate the regional circulation as part of the South Channel Ocean Productivity Experiment (SCOPEX). Many of the near-surface drifters became entrained in the clockwise gyre over Georges Bank, and eight drifters made a total of 16 complete circuits around the bank during the stratified season. The average recirculation period of these eight drifters was 48 days, and the average drifter speed around the bank was 12 cm s -1. There is no clear evidence from the drifter data that the strength of the clockwise gyre over the bank increased with time during the stratified season. On average, these drifters (i) followed a relatively narrow path around the bank, except over the eastern end of the bank where three preferred paths were observed, (ii) moved fastest over the northern and southern flanks of the bank, (iii) did not enter a core area of 3500 km 2 centered at 41°17'N, 68°00'W, approximately 30 km southwest of the topographic center of the bank, and (iv) stopped circling the bank by the end of November, due in part to strong wind events that appeared to drive drifters off the bank. Curiously, none of the near-surface drifters moved from the southern flank of Georges Bank onto the New England shelf as might be expected from continuity of flow along the outer shelf; instead, the drifters that circled the bank tended to move off the bank along its southern flank. None of the drifters with drogues centered at 50 m appeared to recirculate around Georges Bank.

Limeburner, Richard; Beardsley, Robert C.

173

Large tectonic rotations since the Early Miocene in a convergent plate-boundary zone, South Island, New Zealand  

Microsoft Academic Search

A palaeomagnetic study in part of the New Zealand plate-boundary zone provides new constraints on the temporal and spatial distribution of Neogene and Quaternary tectonic rotations. Thermal demagnetization of samples from Cretaceous basaltic dykes, Palaeocene-Oligocene micritic limestone, and Miocene and Pliocene siltstones in the Marlborough region, South Island, have defined stable, high-temperature magnetic components, which are interpreted as the primary

Sara Vickery; Simon Lamb

1995-01-01

174

33 CFR 165.1317 - Security and Safety Zone; Large Passenger Vessel Protection, Puget Sound and adjacent waters...  

Code of Federal Regulations, 2010 CFR

...Large Passenger Vessel Protection, Puget Sound and adjacent waters, Washington...Large Passenger Vessel Protection, Puget Sound and adjacent waters, Washington...notice by the Captain of the Port Puget Sound. Captain of the Port...

2009-07-01

175

Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone  

NASA Astrophysics Data System (ADS)

Results pertaining to the response of the equatorial and low latitude ionosphere to a major geomagnetic storm that occurred on 15 May 2005 are presented. These results are also the first from the Indian zone in terms of (i) GPS derived total electron content (TEC) variations following the storm (ii) Local low latitude electrodynamics response to penetration of high latitude convection electric field (iii) effect of storm induced traveling atmospheric disturbances (TAD's) on GPS-TEC in equatorial ionization anomaly (EIA) zone. Data set comprising of ionospheric TEC obtained from GPS measurements, ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N, Geog. Long. 77.21° E), ground based magnetometers in equatorial and low latitude stations and solar wind data obtained from Advanced Composition Explorer (ACE) has been used in the present study. GPS receivers located at Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E) and Hyderabad (Geog. Lat. 17.33° N, Geog. Long. 78.47° E) have been used for wider spatial coverage in the Indian zone. Storm induced features in vertical TEC (VTEC) have been obtained comparing them with the mean VTEC of quiet days. Variations in solar wind parameters, as obtained from ACE and in the SYM-H index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main phase of the storm commenced at 06:00 UT on 15 May with a sudden southward turning of the Z-component of interplanetary magnetic field (IMF-Bz) and subsequent decrease in SYM-H index. The dawn-to-dusk convection electric field of high latitude origin penetrated to low and equatorial latitudes simultaneously as corroborated by the magnetometer data from the Indian zone. Subsequent northward turning of the IMF-Bz, and the penetration of the dusk-to-dawn electric field over the dip equator is also discernible. Response of the low latitude ionosphere to this storm may be characterized in terms of (i) enhanced background level of VTEC as compared to the mean VTEC, (ii) peaks in VTEC and foF2 within two hours of prompt penetration of electric field and (iii) wave-like modulations in VTEC and sudden enhancement in hmF2 within 4-5 h in to the storm. These features have been explained in terms of the modified fountain effect, local low latitude electrodynamic response to penetration electric field and the TIDs, respectively. The study reveals a strong positive ionospheric storm in the Indian zone on 15 May 2005. Consequences of such major ionospheric storms on the systems that use satellite based navigation solutions in low latitude, are also discussed.

Dashora, N.; Sharma, S.; Dabas, R. S.; Alex, S.; Pandey, R.

2009-05-01

176

Recirculating Linac Acceleration - End-to-End Simulation  

SciTech Connect

A conceptual design of a high-pass-number Recirculating Linear Accelerator (RLA) for muons is presented. The scheme involves three superconducting linacs (201 MHz): a single pass linear Pre-accelerator followed by a pair multi-pass (4.5-pass)'Dogbone' RLAs. Acceleration starts after ionization cooling at 220 MeV/c and proceeds to 12.6 GeV. The Pre-accelerator captures a large muon phase space and accelerates muons to relativistic energies, while adiabatically decreasing the phase-space volume, so that effective acceleration in the RLA is possible. The RLA further compresses and shapes up the longitudinal and transverse phase-spaces, while increasing the energy. Appropriate choice of multi-pass linac optics based on FODO focusing assures large number of passes in the RLA. The proposed 'Dogbone' configuration facilitates simultaneous acceleration of both mu{sup +}- species through the requirement of mirror symmetric optics of the return 'droplet' arcs. Finally, presented end-to-end simulation validates the efficiency and acceptance of the accelerator system.

Bogacz, S. Alex [Center for Advanced Studies of Accelerators, Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)

2010-03-30

177

Recirculating Linac Acceleration-End-to-End Simulation  

NASA Astrophysics Data System (ADS)

A conceptual design of a high-pass-number Recirculating Linear Accelerator (RLA) for muons is presented. The scheme involves three superconducting linacs (201 MHz): a single pass linear Pre-accelerator followed by a pair multi-pass (4.5-pass) `Dogbone' RLAs. Acceleration starts after ionization cooling at 220 MeV/c and proceeds to 12.6 GeV. The Pre-accelerator captures a large muon phase space and accelerates muons to relativistic energies, while adiabatically decreasing the phase-space volume, so that effective acceleration in the RLA is possible. The RLA further compresses and shapes up the longitudinal and transverse phase-spaces, while increasing the energy. Appropriate choice of multi-pass linac optics based on FODO focusing assures large number of passes in the RLA. The proposed `Dogbone' configuration facilitates simultaneous acceleration of both ?+/- species through the requirement of mirror symmetric optics of the return `droplet' arcs. Finally, presented end-to-end simulation validates the efficiency and acceptance of the accelerator system.

Bogacz, S. Alex

2010-03-01

178

Large Eddy Simulations of forced ignition of a non-premixed bluff-body methane flame with Conditional Moment Closure  

SciTech Connect

Large Eddy Simulations (LES) of forced ignition of a bluff-body stabilised non-premixed methane flame using the Conditional Moment Closure (CMC) turbulent combustion model have been performed. The aim is to investigate the feasibility of the use of CMC/LES for ignition problems and to examine which, if any, of the characteristics already observed in related experiments could be predicted. A three-dimensional formulation of the CMC equation was used with simple and detailed chemical mechanisms, and sparks with different parameters (location, size) were used. It was found that the correct pattern of flame expansion and overall flame appearance were predicted with reasonable accuracy with both mechanisms, but the detailed mechanism resulted in expansion rates closer to the experiment. Moreover, the distribution of OH was predicted qualitatively accurately, with patches of high and low concentration in the recirculation zone during the ignition transient, consistent with experimental data. The location of the spark relative to the recirculation zone was found to determine the pattern of the flame propagation and the total time for the flame stabilisation. The size was also an important parameter, since it was found that the flame extinguishes when the spark is very small, in agreement with expectations from experiment. The stabilisation mechanism of the flame was dominated by the convection and sub-grid scale diffusion of hot combustion products from the recirculation zone to the cold gases that enter the burner, as revealed by analysis of the CMC equation. (author)

Triantafyllidis, A.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom); Eggels, R.L.G.M. [Rolls Royce Deutschland, Blankenfelde-Mahlow (Germany)

2009-12-15

179

Blow-by gas recirculating apparatus  

SciTech Connect

A blow-by gas recirculating apparatus for returning blow-by gases from the crankcase of an internal combustion engine to an intake passage thereof is described comprising: a cylinder head; a cylinder head cover mounted on the engine cylinder head; a DOHC valve mechanism housed in the cylinder head; a shield panel attached to the cylinder head cover in substantially covering relation to the DOHC valve mechanism; a breather chamber defined between the cylinder head cover and the shield panel and communicating with both the interior of the cylinder head and an air intake unit of the internal combustion engine; the breather chamber extending longitudinally of the cylinder head cover and comprising a central first, second and third chamber sections each extending longitudinally substantially the full length of the cylinder head; and the second and third breather chamber sections being located one on each side of the first breather chamber section, the first through third breather chamber sections being interconnected by passages for causing blow-by gas passing from the interior of the cylinder head to flow longitudinally for substantially the entire length of the cylinder head cover through each of the first, second and third breather chambers, in that order, to the intake unit of the internal combustion engine.

Kato, H.

1988-01-26

180

Recirculating cooling water solute depletion models  

SciTech Connect

Chromates have been used for years to inhibit copper corrosion in the plant Recirculating Cooling Water (RCW) system. However, chromates have become an environmental problem in recent years both in the chromate removal plant (X-616) operation and from cooling tower drift. In response to this concern, PORTS is replacing chromates with Betz Dianodic II, a combination of phosphates, BZT, and a dispersant. This changeover started with the X-326 system in 1989. In order to control chemical concentrations in X-326 and in systems linked to it, we needed to be able to predict solute concentrations in advance of the changeover. Failure to predict and control these concentrations can result in wasted chemicals, equipment fouling, or increased corrosion. Consequently, Systems Analysis developed two solute concentration models. The first simulation represents the X-326 RCW system by itself; and models the depletion of a solute once the feed has stopped. The second simulation represents the X-326, X-330, and the X-333 systems linked together by blowdown. This second simulation represents the concentration of a solute in all three systems simultaneously. 4 figs.

Price, W.T.

1990-03-16

181

Characterizing a large shear-zone with seismic and magnetotelluric methods: The case of the Dead Sea Transform  

USGS Publications Warehouse

Seismic tomography, imaging of seismic scatterers, and magnetotelluric soundings reveal a sharp lithologic contrast along a ???10 km long segment of the Arava Fault (AF), a prominent fault of the southern Dead Sea Transform (DST) in the Middle East. Low seismic velocities and resistivities occur on its western side and higher values east of it, and the boundary between the two units coincides partly with a seismic scattering image. At 1-4 km depth the boundary is offset to the east of the AF surface trace, suggesting that at least two fault strands exist, and that slip occurred on multiple strands throughout the margin's history. A westward fault jump, possibly associated with straightening of a fault bend, explains both our observations and the narrow fault zone observed by others. Copyright 2005 by the American Geophysical Union.

Maercklin, N.; Bedrosian, P. A.; Haberland, C.; Ritter, O.; Ryberg, T.; Weber, M.; Weckmann, U.

2005-01-01

182

Future of recirculating systems in the US aquaculture industry  

SciTech Connect

Recirculating systems consist of a culture unit, a recirculating pump, and a treatment block which facilitate extended re-use of water in the rearing of aquatic animals. As water re-use is extended from a few hours to months or even years, the complexity of the treatment block increases. Classified as either `open` with greater than 10 percent water replacement per day or `closed` with less than 10 percent daily replacement, most recirculating systems include aerators, clarifiers, and biofilters as key core elements. The aquaculture industry is increasingly facing a variety of socio-economic issues which will dramatically influence its future development. These problems range from increased competition for water rights through price depression and foreign imports to predation by protected migratory birds. As water-use, environmental, and conservation conflicts grow, the cost differences between the flow-through and closed production technologies will narrow, increasing the industry`s use of recirculating systems.

Malone, R.F.

1994-08-01

183

Dynamics of Microorganism Populations in Recirculating Nutrient Solutions.  

National Technical Information Service (NTIS)

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, ...

R. F. Strayer

1994-01-01

184

Recirculating Peritoneal Dialysis with a Subcutaneous Peritoneal Catheter.  

National Technical Information Service (NTIS)

Ten end stage renal disease patients, 9 of whom were diabetic, were treated with peritoneal dialysis via a subcutaneous peritoneal catheter. Three dialysis formats were used: Intermittent peritoneal dialysis (IPD), recirculating peritoneal dialysis (RPD),...

R. L. Stephen S. C. Jacobsen C. Kablitz W. J. Kolff

1977-01-01

185

Nitric Oxide Formation in Combustion Processes with Strong Recirculation.  

National Technical Information Service (NTIS)

The principal objective of the combustion experiments was to obtain information on the nitric oxide formation process in a continuous flow combustion system in which the flame is stabilized by recirculation. Specifically, the factors affecting nitric oxid...

C. T. Bowman L. S. Cohen M. N. Director

1973-01-01

186

Fuel cell stack with an integral ejector for reactant gas recirculation  

Microsoft Academic Search

A stack of fuel cells operating on gaseous reactants includes an ejector in integral heat exchange relationship with the stack for recirculating one of the reactant gases through the cells of the stack. The recirculating reactant is continuously heated by waste heat from the cells as it recirculates thereby preventing condensation of water from the recirculating reactant gas and thereby

Grasso

1976-01-01

187

The Pebble Recirculation Experiment (PREX) for the AHTR  

SciTech Connect

Conceptual design studies for the liquid-salt cooled Advanced High Temperature Reactor (AHTR) have identified three candidate TRISO fuel geometries: prismatic, pebble, and stringer fuels. This paper presents experimental results from the integral Pebble Recirculation Experiment (PREX) that verifies the viability of pebble recirculation in a Pebble Bed AHTR (PB-AHTR). The experiments conducted include injection and extraction of buoyant pebbles, measurements of packing density and pressure losses, and observations of pebble landing dynamics and bed formation. (authors)

Bardet, P.; An, J.Y.; Franklin, J.T.; Huang, D.; Lee, K.; Mai, A.; Toulouse, M.; Peterson, P.F. [Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1730 (United States)

2007-07-01

188

33 CFR 165.1318 - Security and Safety Zone Regulations, Large Passenger Vessel Protection, Portland, OR Captain of...  

Code of Federal Regulations, 2010 CFR

...the United States, in Portland, OR at the Columbia River Bar âCâ buoy and extending eastward on the Columbia River to Kennewick, WA and upriver through Lewiston, ID on the Snake River. (d) Compliance. The large passenger vessel...

2009-07-01

189

Diagnostic study of the Fram Strait marginal ice zone during summer from 1983 and 1984 Marginal Ice Zone Experiment Lagrangian observations  

NASA Astrophysics Data System (ADS)

From 1984 Marginal Ice Zone Experiment observations in Fram Strait, three main results concerning large scale, mesoscale, and summer marginal ice zone (MIZ) features are presented and discussed in this paper. Regarding the large scale, the main conclusion is that the East Greenland Current (EGC) is a narrow, stable current, in contradiction with past results presenting the EGC as a broad and unstable current. In the mesoscale, the West Spitsbergen Current (WSC) and the Norwegian Current are the main generators for eddies in Fram Strait. These eddies propagate northwestward, preferentially following topographic features like fracture zones, which are quite abundant in this region. In our opinion, these WSC eddies represent an important part of the Atlantic water recirculation in Fram Strait. When approaching the east Greenland continental slope, they interact with the EGC and they form well-developed eddies. These ice edge eddies associated with ice edge tongues are quite recognizable with remote sensing techniques. The summer marginal ice zone in Fram Strait is clearly characterized by sea ice concentrations from 1/10 to 3/10 and floe sizes limited to 1 km or less. There is a well-defined limit which separates the pack ice from the MIZ where no big ice floes are ever recorded. The breaking action of waves and swell propagating into the ice are likely to be the only mechanisms explaining such a drastic filtering effect. According to their amplitudes and directions, winds and eddies act in the MIZ in shrinking or stretching this zone.

Gascard, Jean-Claude; Kergomard, Claude; Jeannin, Pierre-FrançOis; Fily, Michel

1988-04-01

190

Use of a small TSK GSW high-performance liquid chromatographic column for large-zone chromatographic studies of monomer-oligomer equilibria of membrane protein.  

PubMed

A TSK GSWP size-exclusion high-performance liquid chromatography "pre-column" (75 mm x 7.5 mm) was used for large-zone chromatographic studies of the effect of ligands on the monomer-oligomer equilibrium in sarcoplasmic reticulum Ca-ATPase solubilized in a non-ionic detergent. The monomer-dimer association constants determined for the Ca2+-occluded E1 P[Ca2] and vanadate-reacted E2V forms were 2-3 fold lower than the association constant of the E1Ca2 form (bound Ca2+ is freely exchangeable). With the TSK GSWP column, large-zone chromatography was rapid and required only small quantities of protein. This column was found to be useful also for studies in the presence of phospholipid, provided that the influence of lipid binding, per se, on the partition coefficient of the protein in the column was taken into consideration. This opens new possibilities for studies of membrane proteins under non-denaturing conditions. PMID:2843556

Vilsen, B; Andersen, J P

1988-06-17

191

Constraints on strain rates during large-scale mid-crustal shearing: An example from the basal Vaddas shear zone, northern Caledonides  

NASA Astrophysics Data System (ADS)

The Caledonian orogen in Scandinavia is characterized by large-scale crustal nappe stacks which were emplaced east-/southeast-wards onto the Baltica shield. Whereas original thrust relationships are generally obscured by syn- to post-collisional extensional deformation in the southern and central Scandinavian Caledonides, several large-scale thrust systems are well-preserved in the northern Scandinavian Caledonides in Troms and Finnmark. One example is the mid-crustal Vaddas shear zone, which emplaced the Vaddas nappe on top of the Kalak nappe complex. In this contribution we present a structural, petrological and geochronological analysis of the rocks under- and overlying the Vaddas shear zone in northern Troms, in order to estimate the strain rate associated with thrusting along this major shear zone. The Vaddas nappe above the investigated shear zone consists mainly of Upper Ordovician to Silurian metasediments, which were deposited in a marine environment and which were intruded by voluminous gabbroic intrusions, before they were sheared off from their substratum and transported on top of the Kalak nappe complex during the Caledonian orogeny. PT conditions from one of these gabbroic bodies indicate that the body intruded the metasediments at ~9 kbar (Getsinger et al., subm to G3), which corresponds to a depth of ~34 km. U-Pb SIMS dating of zircons from this gabbro indicate that intrusion occurred at 439±2 Ma. The Vaddas nappe is separated from the Kalak nappe by an at least ~150 m thick, amphibolite-facies shear zone with a subhorizontal fabric and top-to-the-SE shear sense. It has developed within the lowest part of the Vaddas nappe as well as the upper part of the Kalak nappe complex and PT calculations indicate that final shearing occurred at ~450° C and ~6 kbar (depth of ~23 km). U-Pb TIMS dating of titanites, which grow parallel to the shear fabric in the Kalak nappe complex, gives 206Pb/238U ages ranging from 442±1 to 429±1 Ma, indicating that shearing probably commenced right after intrusion of the Vaddas gabbros and continued over a period of ~10 m.y. Assuming an original dip of the Vaddas shear zone of 30° , the horizontal displacement would be ~23 km as the most conservative assumption (i.e. for a highest thrust angle) for the depth difference of 11 km between intrusion of the gabbro and late shear deformation. Given the thickness of the shear zone of 150 m and the time for the shearing of ~10 m.y., a strain rate of ~5*10-13 s-1 can be estimated. As suggested, this is a conservative estimate, so that strain rates may well have been faster. These strain rates appear to be similar to those of Alpine nappes, so that it is suggested that Caledonian nappe stacking has probably taken place at the same rates or even faster than Alpine ones. Given the fact that the transport distances in the Caledonides are far greater than in the Alps, this would suggest that the Caledonian orogeny has taken place over a longer period of time than in the Alps.

Gasser, Deta; Stünitz, Holger; Nasipuri, Pritam; Menegon, Luca

2013-04-01

192

Management of Large Soft-tissue Wounds with Negative Pressure Therapy—Lessons Learned from the War Zone  

Microsoft Academic Search

The recent conflicts in Afghanistan and Iraq have demonstrated that body armor has led to increase survival of combatants but the extremity injuries have been alarming. The increased numbers of extremity injuries have led to the acceptance and use of negative pressure therapy (NPT) in managing large wounds. This article reviews some of the lessons learned in treating wounds of

David Esquivel; M MACHEN

2008-01-01

193

Management of Large Soft-tissue Wounds with Negative Pressure Therapy—Lessons Learned from the War Zone  

Microsoft Academic Search

The recent conflicts in Afghanistan and Iraq have demonstrated that body armor has led to increase survival of combatants but the extremity injuries have been alarming. The increased numbers of extremity injuries have led to the acceptance and use of negative pressure therapy (NPT) in managing large wounds. This article reviews some of the lessons learned in treating wounds of

Miguel A. Pirela-Cruz; M. Shaun Machen; David Esquivel; Steve Warinsky

194

The Origin of Olivine B-Type Fabric in Naturally Deformed Peridotite: Insight from the Ronda Large-Scale Mantle Shear Zone (spain)  

NASA Astrophysics Data System (ADS)

Strain-induced olivine Lattice Preferred Orientation (LPO) mostly controls the propagation of seismic waves in the mantle. Hence, it strongly affects the imaging of mantle structures through analyzing of elastic waves coming from deep earthquakes (Ismaïl and Mainprice, 1998). Understanding the relationships between mantle deformation and olivine LPO is thus crucial to objectively interpret the deep mantle structures. Here, based on detailed documentation of olivine LPOs in the Ronda peridotite (southern Spain), we provide evidences of flow-normal a-axis LPO, i.e., B-type fabric, within a kilometer-scale ductile shear zone. This fabric occurs upon entering the shear zone and describes a progressive transition from A-type fabric (parallel-flow a-axis LPO) to B-type fabric. While B-type fabrics have been described from several localities, to our knowledge this is the first olivine fabric transition ever observed in naturally deformed peridotites. Furthermore, while the olivine fabric strength (Jindex) increases in the A-type fabric domain towards the center of the shear zone, the Jindex progressively decreases in the B-type fabric domain. Based on deformation experiments, A-type fabric occurs during high-temperature/low-stress deformation of anhydrous olivine aggregates (Jung and Karato, 2001). In contrast, the B-type fabrics have been observed under a wide range of conditions: 1) at high-temperature/low stress conditions in the presence of melt (Kohlstedt and Holtzman, 2009); 2) at high-stress in the presence of water (Jung and Karato, 2001); 3) under dry conditions at very high pressure (> 3 GPa; Jung et al., 2009); and 4) during diffusion-creep in the presence of orthopyroxene (Sundberg and Cooper, 2008). In our natural example, we conclude that the B-type fabric arises from enhancing diffusion creep at the expense of dislocation creep, because: 1) the B-type fabric is observed to overprint the typical fabric of anhydrous peridotite (A-type), 2) the Ronda peridotites were deformed at pressures lower than 2 GPa at sub-solidus conditions (Garrido et al., 2011), and 3) the A-type/B-type transition correlates with a decrease of temperature, grain size and fabric strength (Jindex) towards the inner shear zone. Our results moreover indicate that B-type fabric is somehow related to large-scale mantle shear zones, and hence it could characterize a signature of lithosphere-scale mantle strain localization.

Précigout, J.; Hirth, G.

2011-12-01

195

Visualisation of isothermal large coherent structures in a swirl burner  

SciTech Connect

Lean premixed combustion using swirl flame stabilisation is widespread amongst gas turbine manufacturers. The use of swirl mixing and flame stabilisation is also prevalent in many other non-premixed systems. Problems that emerge include loss of stabilisation as a function of combustor geometry and thermo-acoustic instabilities. Coherent structures and their relationship with combustion processes have been a concern for decades due to their complex nature. This paper thus adopts an experimental approach to characterise large coherent structures in swirl burners under isothermal conditions so as to reveal the effects of swirl in a number of geometries and cold flow patterns that are relevant in combustion. Aided by techniques such as Hot Wire Anemometry, High Speed Photography and Particle Image Velocimetry, the recognition of several structures was achieved in a 100 kW swirl burner model. Several varied, interacting, structures developed in the field as a consequence of the configurations used. New structures never observed before were identified, the results not only showing the existence of very well defined large structures, but also their dependency on geometrical and flow parameters. The PVC is confirmed to be a semi-helical structure, contrary to previous simulations performed on the system. The appearance of secondary recirculation zones and suppression of the vortical core as a consequence of geometrical constrictions are presented as a mechanism of flow control. The asymmetry of the Central Recirculation Zone in cold flows is observed in all the experiments, with its elongation dependent on Re and swirl number used. (author)

Valera-Medina, A.; Syred, N.; Griffiths, A. [School of Engineering, Cardiff University, Queen's Building, The Parade, Cardiff, Wales CF24 3AA (United Kingdom)

2009-09-15

196

Large-Scale Numerical Modeling of Flow and Transport in a Deep Unsaturated-Zone System for Natural and Artificial Recharge Analysis  

NASA Astrophysics Data System (ADS)

Investigations of deep unsaturated-zone systems have increased in recent years owing to a variety of issues including nuclear waste management, contaminant remediation, and population increases in semi-arid lands. While substantial insights have been realized in our understanding of such complex systems, challenges still remain in our ability to accurately simulate large-scale flow and transport processes. In the San Gorgonio Pass area near Beaumont, California, overdraft of ground-water resources has led to the development of a program that uses surface spreading of water from the California aqueduct to artificially recharge the local aquifer. The issues being addressed in the program are the characterization of the unsaturated zone beneath the artificial recharge ponds and the amount, timing, and location of artificially recharged water reaching the water table, including the interception of nitrates from nearby septic systems. A measurement scheme using surface and subsurface instrumentation and laboratory analyses was implemented to develop conceptual and numerical models of the deep unsaturated zone. The initial conceptual model was tested using a numerical model and was then modified to account for in situ measurements of temperature and matric potential. Transient one-dimensional flow modeling of vertical infiltration could reproduce the measured temperature and matric potential profiles, but could not account for all conceptual model components. Steady-state two-dimensional flow modeling more easily reproduced the temperature and matric potential profiles when cold-water infiltration occurred in a nearby (25 m) ephemeral stream. In either model, the hydraulic conductivity of a perching layer critical to the timing of recharge was estimated by inverse fitting the temperature profile between the perched water and the water table. A transient three-dimensional flow model that accounts for all components of the conceptual model was developed from the experience gained using the one and two-dimensional models, and was used to predict the amount, timing, and location of the artificial recharge for the San Gorgonio Pass area. Sensitivity analysis of space-time discretization was performed to illustrate the ability of existing models to accurately simulate large-scale hydrologic processes in the unsaturated zone.

Ellett, K. M.; Ellett, K. M.; Flint, A. L.; Flint, A. L.; Hopmans, J. W.

2001-12-01

197

Phosphorus dynamics at multiple time scales in the pelagic zone of a large shallow lake in Florida, USA  

Microsoft Academic Search

Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension,\\u000a at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column\\u000a transparency,

Karl E. Havens; Kang-Ren Jin; Nenad Iricanin; R. Thomas James

198

Phosphorus dynamics at multiple time scales in the pelagic zone of a large shallow lake in Florida, USA  

Microsoft Academic Search

Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension,\\u000a at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column\\u000a transparency,

Karl E. Havens; Kang-Ren Jin; Nenad Iricanin; R. Thomas James

2007-01-01

199

Role of Differential Air Pressure Zones in the Control of Aerosols in a Large Animal Isolation Facility  

PubMed Central

The uncontrolled transmission of hog cholera in a large animal isolation facility, designed to control the movement of aerosols within and between individual wings of a multiunit building, indicated the need for a critical study of aerosol behavior under existing conditions of operation. Studies with aerosols of Escherichia coli B T3 bacteriophage (T3 coliphage) conclusively demonstrated the impossibility of obtaining the desired control by means of a “static” air balance relationship between adjacent areas within the facility. Modifications needed to provide the desired control of the air-handling system are outlined and discussed. Images Fig. 1 Fig. 2 Fig. 3

Sullivan, James F.; Songer, Joseph R.

1966-01-01

200

Influence of leachate recirculation on aerobic and anaerobic decomposition of solid wastes.  

PubMed

In this study, the effect of leachate recirculation on aerobic and anaerobic degradation of municipal solid wastes is determined by four laboratory-scale landfill reactors. The options studied and compared with the traditional anaerobic landfill are: leachate recirculation, landfill aeration, and aeration with leachate recirculation. Leachate quality is regularly monitored by the means of pH, alkalinity, total dissolved solids, conductivity, oxidation-reduction potential, chloride, chemical oxygen demand, ammonia, and total Kjeldahl nitrogen, in addition to generated leachate quantity. Aerobic leachate recirculated landfill appears to be the most effective option in the removal of organic matter and ammonia. The main difference between aerobic recirculated and non-recirculated landfill options is determined at leachate quantity. Recirculation is more effective on anaerobic degradation of solid waste than aerobic degradation. Further studies are going on to determine the optimum operational conditions for aeration and leachate recirculation rates, also with the operational costs of aeration and recirculation. PMID:17023112

Bilgili, M Sinan; Demir, Ahmet; Ozkaya, Bestamin

2006-09-10

201

Acceleration schedules for a recirculating heavy-ion accelerator  

SciTech Connect

Recent advances in solid-state switches have made it feasible to design programmable, high-repetition-rate pulsers for induction accelerators. These switches could lower the cost of recirculating induction accelerators, such as the ''small recirculator'' at Lawrence Livermore National Laboratory (LLNL), by substantially reducing the number of induction modules. Numerical work is reported here to determine what effects the use of fewer pulsers at higher voltage would have on the beam quality of the LLNL small recirculator. Lattices with different numbers of pulsers are examined using the fluid/envelope code CIRCE, and several schedules for acceleration and compression are compared for each configuration. For selected schedules, the phase-space dynamics is also studied using the particle-in-cell code WARP3d.

Sharp, W.M.; Grote, D.P.

2002-05-01

202

Thermal and bifurcation characteristics of heat-recirculating conversion of gaseous fuels  

NASA Astrophysics Data System (ADS)

The paper investigates the possibility of utilisation of heat-recirculating systems for fuel conversions having low net thermal effect. The experimental part is conducted with an electrically heated heat exchanger. It is shown that heat-recirculating systems can operate under superadiabatic conditions. Their thermal characteristics are provided by means of the dependencies of heat recirculation ratio on process parameters. Further, the heat-recirculating catalytic combustion system is characterised via combustion bifurcation diagrams. The similarities and differences of both those heat-recirculating systems are qualitatively compared and explained. Bifurcation characteristics proves to be useful tools in concise description of practical complex heat-recirculating fuel conversion systems in energy generation.

Budzianowski, Wojciech

2010-07-01

203

Evolution of the vertical profile and flux of large sea-salt particles in a coastal zone  

NASA Astrophysics Data System (ADS)

In the vicinity of the North Carolina Outer Banks we observed both steady onshore flow conditions and a continental air mass transition into a marine boundary layer. Using the CIRPAS Twin Otter aircraft, we measured changes in the column burden of sea salt as the air mass was advected out to sea. We also measured the flux of whitecap-generated sea-salt particles in neutrally stable atmosphere at wind speeds of 4, 8, and 12 m s-1. Production of salt particles as small as 0.27 ?m in diameter was observed. Furthermore, we measured salt particle size distributions at various wind speeds during along shore wind and near steady state conditions. Using these measurements as a frame of reference, we discuss the very large differences in the reported size and flux of sea salt presented in the literature. The disagreement in reported salt fluxes is larger for smaller- sized particles (almost an order of magnitude) and is most likely due to assumptions made when the fluxes were computed, especially the particle dry deposition velocity and air mass history. However, for giant salt particles with short atmospheric lifetimes (>˜10 ?m in diameter), there is general agreement between fluxes and size distributions measured in this study and previous ones. Reported salt particle size distributions in the literature also vary considerably under similar steady wind and stability conditions. From these and our results it is clear that no more than half of the variance in salt particle concentration can be explained by wind speed alone, suggesting that the idea of "steady state" in the marine boundary layer rarely exists at midlatitudes.

Reid, Jeffrey S.; Jonsson, Haflidi H.; Smith, Michael H.; Smirnov, Alexander

2001-06-01

204

Radiocarbon and geochemical constraints on shallow groundwater recharge in a large arid zone river, Cooper Creek, SW Queensland, Australia  

NASA Astrophysics Data System (ADS)

In the arid and semi-arid internally drained Lake Eyre Basin of central Australia, large mud dominated anabranching river systems transport monsoon derived floodwaters into the centre of the continent during the summer months, and subsequently spend much of the year under low to no flow conditions. Cooper Creek has the largest catchment in this basin, and in south west Queensland has a wide (20-60km) floodplain and multiple channel system. Enlarged channel segments, known as waterholes or billabongs, can retain water throughout much of the dry season, and their mud base can often be scoured during floods into the underlying sandy alluvium where the shallow groundwater table exists ~3-5m below the base of the waterholes. Little is known of the groundwater recharge mechanisms in this ecologically important and hydrologically unregulated river system, thus a number of piezometer transects were construct across the floodplain between two waterholes to investigate groundwater recharge processes in further detail. Samples recovered from all piezometers were analysed for major-trace element, water stable isotopes (?2H and ?180), 3H and 14C. Water stable isotopes reveal shallow groundwater is recharged by high magnitude, low frequency monsoonal flood events, with minor evaporative enrichment probably linked to recent smaller flooding events. 14C dating of dissolved inorganic carbon reveals recharge is most effective beneath the deepest channel segments of the waterholes, and that residence time of the shallow groundwater increases with distance from major waterholes, with the post 1950's 14C bomb pulse signature present only in close proximity to the channels. 3H allows further refinement of the shallow groundwater residence times, with no 3H detected in groundwater over ~500m from the waterholes, indicating groundwater recharge is slow and restricted to major flooding events. The increase in groundwater residence time with distance from waterholes, is also accompanied by an abrupt increase in salinity, and suggests recent recharge has formed local freshwater lenses above the regional, more saline groundwater. This increase in salinity with increasing distance from the waterholes is not accompanied by an increase on the evaporative signal of water stable isotopes, suggesting evapotranspiration is the dominant mechanism of salinisation within the shallow groundwater beneath the floodplains and minor channels. This study demonstrates that detailed chemical analysis of groundwaters from arid and semi arid areas can provide a useful estimate of recharge where the remote location makes traditional detailed borehole monitoring difficult or impossible to achieve.

Larsen, Joshua; Cendón, Dioni; Nanson, Gerald; Jones, Brian

2010-05-01

205

Metasomatism and fluid flow in ductile fault zones  

NASA Astrophysics Data System (ADS)

Observed major element metasomatism in 5 amphibolite facies ductile fault zones can be explained as the inevitable consequence of aqueous fluid flow along normal temperature gradients under conditions of local chemical equilibrium. The metasomatism does not require the infiltration of chemically exotic fluids. Calculations suggest that metasomatized ductile fault zones are typically infiltrated by ˜105 moles H2O/cm2, fluid flow is in the direction of decreasing temperature, and fluids contain about 1.0 molal total chloride. Where available, stable isotopic alteration data confirm both flow direction and fluid fluxes calculated from major element metasomatism. The fluid fluxes inferred from metasomatism do not require large-scale fluid recirculation or mantle sources if significant lateral fluid flow occurs in the deep crust. Time-integrated fluid fluxes are combined with estimates of flow duration to constrain average flow rates and average permeabilities. Rocks in ductile fault zones are probably much more permeable during metasomatism (average permeabilities of 10-17 to 10-15 m2) than rocks normally are during regional metamorphism (10-21 to 10-18 m2). Estimated average fluid flow rates (3.5×10-3 to 0.35 m/yr) are insufficient, however, to significantly elevate ambient temperatures within ductile faults. Fluid flow in the direction of decreasing temperature may increase the ductility of silicate rocks by adding K to the rocks and thereby driving mica-forming reactions.

Dipple, Gregory M.; Ferry, John M.

1992-11-01

206

Recirculating beam-breakup thresholds for polarized higher-order modes with optical coupling  

NASA Astrophysics Data System (ADS)

Here we will derive the general theory of the beam-breakup (BBU) instability in recirculating linear accelerators with coupled beam optics and with polarized higher-order dipole modes. The bunches do not have to be at the same radio-frequency phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where beam currents become very large and coupled optics are used on purpose to increase the threshold current. This theory can be used for the analysis of phase errors of recirculated bunches, and of errors in the optical coupling arrangement. It is shown how the threshold current for a given linac can be computed and a remarkable agreement with tracking data is demonstrated. General formulas are then analyzed for several analytically solvable problems: (a) Why can different higher order modes (HOM) in one cavity couple and why can they then not be considered individually, even when their frequencies are separated by much more than the resonance widths of the HOMs? For the Cornell ERL as an example, it is noted that optimum advantage is taken of coupled optics when the cavities are designed with an x-y HOM frequency splitting of above 50 MHz. The simulated threshold current is then far above the design current of this accelerator. To justify that the simulation can represent an actual accelerator, we simulate cavities with 1 to 8 modes and show that using a limited number of modes is reasonable. (b) How does the x-y coupling in the particle optics determine when modes can be considered separately? (c) How much of an increase in threshold current can be obtained by coupled optics and why does the threshold current for polarized modes diminish roughly with the square root of the HOMs’ quality factors. Because of this square root scaling, polarized modes with coupled optics increase the threshold current more effectively for cavities that have rather large HOM quality factors, e.g. those without very elaborate HOM absorbers. (d) How does multiple-turn recirculation interfere with the threshold improvements obtained with a coupled optics? Furthermore, the orbit deviations produced by cavity misalignments are also generalized to coupled optics. It is shown that the BBU instability always occurs before the orbit excursion becomes very large.

Hoffstaetter, Georg H.; Bazarov, Ivan V.; Song, Changsheng

2007-04-01

207

Developments in recirculation systems for Mediterranean fish species  

Microsoft Academic Search

Nowadays, most European commercial hatcheries use recirculating water systems for all the different stages of Mediterranean fish rearing, from breeders to fingerlings several grams in weight. Despite a higher initial investment relative to flow-through systems, this technology reduces production costs mainly because much less energy is required for heating and the survival rate of the fingerlings is much higher. The

Jean Paul Blancheton

2000-01-01

208

An Inexpensive Recirculating Aquaculture System with Multiple Use Capabilities.  

ERIC Educational Resources Information Center

|Describes the construction of an inexpensive recirculating aquaculture system that can hold up to 46 pounds of fish, invertebrates, and mussels for classroom use. The system is versatile, requires little maintenance, and can be used for both teaching and research purposes. (WRM)|

Scurlock, Gerald Don, Jr.; Cook, S. Bradford; Scurlock, Carrie Ann

1999-01-01

209

10 Commercially Feasible Urban Recirculating Aquaculture: Addressing the Marine Sector  

Microsoft Academic Search

With the global collapse of marine fisheries and the environmental issues associated with net-pen aquaculture practices, there is a pressing need to develop fully contained and environmentally sus- tainable approaches to producing seafood. Recirculating aquaculture systems (RAS), which provide this approach, have been widely used over the last two decades to farm freshwater species. However, the cost associated with the

Yonathan Zohar; Yossi Tal; Harold Schreier; Colin Steven; John Stubblefield

210

Amplified recirculating circuits for pseudo-continuous wave generation  

Microsoft Academic Search

An analysis of amplified recirculating structures for producing a pseudo-continuous wave, PCW, signal is presented. Experimentations with amplification provided by EDFA and SOA are shown. Both the hold-on function and the switch-off function are analyzed. The comparison between structures with different amplifiers shows better duration performances for EDFAs, but faster all-optical operation capabilities for SOAs.

Paola Parolari; Lucia Marazzi; Pierpaolo Boffi; Mario Martinelli

1999-01-01

211

An Inexpensive Recirculating Aquaculture System with Multiple Use Capabilities.  

ERIC Educational Resources Information Center

Describes the construction of an inexpensive recirculating aquaculture system that can hold up to 46 pounds of fish, invertebrates, and mussels for classroom use. The system is versatile, requires little maintenance, and can be used for both teaching and research purposes. (WRM)

Scurlock, Gerald Don, Jr.; Cook, S. Bradford; Scurlock, Carrie Ann

1999-01-01

212

Exhaust gas recirculation control system for an internal combustion engine  

Microsoft Academic Search

An exhaust gas recirculation control system is disclosed for particular application to a diesel engine, which includes a combination of a fuel injection pump having a movable fuel amount determining element whose position regulates the amount of fuel injected, a conversion device having a fixed orifice and a variable orifice provided downstream of the fixed orifice and whose effective opening

1981-01-01

213

Dynamics of microorganism populations in recirculating nutrient solutions  

Microsoft Academic Search

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are

R. F. Strayer

1994-01-01

214

EVALUATION OF A PAINT SPRAY BOOTH UTILIZING AIR RECIRCULATION  

EPA Science Inventory

The objective of this project was to evaluate the effectiveness of the recirculating air spray booth process at the Deere and Company facility in Davenport, Iowa. The effort involved a field measurement program and subsequent analysis of flow rates and emission data from the spra...

215

Wastewater Renovation in Buried and Recirculating Sand Filters  

Microsoft Academic Search

A replicated, multiyear field study was conducted to assess the re- duction of N, P and microbial indicators by a recirculating sand filter (RSF) and bu ried mu ltilayer sa nd filter patterned after the RU CK filter. The RSF's received 38 L m -~ d-1 of septic tank effluent, while the buried sand filters were loaded at 76 L

A. J. Gold; B. E. Lamb; G. W. Loomis; J. R. Boyd; V. J. Cabelli; C. G. McKiel

1992-01-01

216

PROTOTYPE RECIRCULATION PUMP TESTS. PATHFINDER ATOMIC POWER PLANT SUMMARY REPORT  

Microsoft Academic Search

Results of tests performed on the Pathfinder Atomic Power Plant ; recirculation prototype pump and its components are presented. Tests included a ; preliminary seal test, a serrated bushing test, a cold performance test, and a ; hot loop test. Results indicated thut the pump should give trouble-free service ; in the field if operated as intended and within the

R. Haugen; D. J. Nolan

1961-01-01

217

PATHFINDER ATOMIC POWER PLANT PROTOTYPE RECIRCULATION PUMP REPORT  

Microsoft Academic Search

The development and testing of a centrifugal pump suitable for use in ; the recirculation system which forces core coolant and moderator through the core ; at a high rate are described. The prototype is a vertical single-stage ; centrifugal pump driven by a 400-hp induction motor. The pump has an overhung ; impeller which contains a journal for a

R. A. Haugen; D. J. Nolan

1962-01-01

218

Using exhaust gas recirculation in internal combustion engines: a review  

Microsoft Academic Search

The aim of this work is to review the potential of exhaust gas recirculation (EGR) to reduce the exhaust emissions, particularly NOX emissions, and to delimit the application range of this technique. A detailed analysis of previous and current results of EGR effects on the emissions and performance of Diesel engines, spark ignition engines and duel fuel engines is introduced.

G. H. Abd-Alla

2002-01-01

219

Selecting materials for recirculation valves used in secondary recovery service  

Microsoft Academic Search

It would be desirable to recommend an optimum combination of trim materials for use in recirculating valves handling seawater and\\/or hydrogen sulfide, but each application must be judged independently. The design engineer on each project must determine what materials will be best in the application, depending on the problem expected. Valve cavitation can be eliminated by using the proper valve

M. Schumacher; J. Gossett

1983-01-01

220

Recirculation in the Fram Strait and transports of water in and north of the Fram Strait derived from CTD data  

NASA Astrophysics Data System (ADS)

The volume, heat and freshwater transports in the Fram Strait are estimated from geostrophic computations based on summer hydrographic data from 1984, 1997, 2002 and 2004. In these years, in addition to the usually sampled section along 79° N, a section between Greenland and Svalbard was sampled further north. Quasi-closed boxes bounded by the two sections and Greenland and Svalbard can then be formed. Applying conservation constraints on these boxes provides barotropic reference velocities. The net volume flux is southward and varies between 2 and 4 Sv. The recirculation of Atlantic water is about 2 Sv. Heat is lost to the atmosphere and the heat loss from the area between the sections averaged over the four years is about 10 TW. The net heat (temperature) transport is 20 TW northward into the Arctic Ocean, with large interannual differences. The mean net freshwater added between the sections is 40 mSv and the mean freshwater transport southward across 79° N is less than 60 mSv, indicating that most of the liquid freshwater leaving the Arctic Ocean through Fram Strait in summer is derived from sea ice melt in the northern vicinity of the strait. In 1997, 2001 and 2003 meridional sections along 0° longitude were sampled and in 2003 two smaller boxes can be formed, and the recirculation of Atlantic water in the strait is estimated by geostrophic computations and continuity constraints. The recirculation is weaker close to 80° N than close to 78° N, indicating that the recirculation is mainly confined to the south of 80° N. This is supported by the observations in 1997 and 2001, when only the northern part of the meridional section, from 79° N to 80° N, can be computed with the constraints applied. The recirculation is found strongest close to 79° N.

Marnela, M.; Rudels, B.; Houssais, M.-N.; Beszczynska-Möller, A.; Eriksson, P. B.

2013-05-01

221

Effect of Two-Stage Injection on Unburned Hydrocarbon and Carbon Monoxide Emissions in Smokeless Low-Temperature Diesel Combustion with UltraHigh Exhaust Gas Recirculation  

Microsoft Academic Search

The unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions from smokeless low-temperature diesel combustion (LTC) with ultra-high exhaust gas recirculation (EGR) can be attributed to lowered combustion temperatures as well as to under-mixing of fuel-rich mixture along the combustion chamber walls, overly mixed fuel-lean mixture at the spray tails, and fuel missing the piston bowl and entering the squish zones.

T Li; M Suzuki; H Ogawa

2010-01-01

222

Exhaust gas recirculation control system for a compression-ignition internal combustion engine  

Microsoft Academic Search

An exhaust gas recirculation control system for a compression ignition internal combustion engine or diesel engine including an intake throttle valve in an intake passage and an exhaust gas recirculation passage opening downstream of the intake throttle valve, comprises a shut-off valve in the exhaust gas recirculation passage so that the shut-off valve is closed in the proximity of a

H. Fujii; M. Shinzawa; J. Teranuma; S. Yasuhara

1981-01-01

223

Low NOx Combustion of DME by Means of Flue Gas Recirculation  

Microsoft Academic Search

This study focuses on the fundamental characteristics of DME (Dimethyl Ether) combustion aiming at development of low-NOx combustion technology with flue gas recirculation, FGR. The flue gas is recirculated into the combustion chamber to reduce the oxygen concentration and to suppress the combustion gas temperature, so that NOx emission is significantly reduced. The fuel gas recirculation at high mixing ratio,

Ryosuke Matsumoto; Mamoru Ozawa; Shinya Terada; Takenori Iio

2008-01-01

224

Hydraulic study on recirculation loops using computational fluid dynamics (CFD). Design optimization and turbulence reduction  

Microsoft Academic Search

A full scope study of the recirculation system flow of a BWR6 nuclear plant is essential, to completing the characterisation and understanding the dynamics of the flow and specially the bistable flow in the recirculation loop.The finite element model serves to study the sensitivity of the design and to reduce turbulence at the connection between the recirculation pump impulsion piping

Carlos Julián Gavilán Moreno

2009-01-01

225

Zoning Study.  

National Technical Information Service (NTIS)

The study analyzes existing zoned properties in the Shreveport Standard Metropolitan Statistical Area to determine if current development justifies the amount of such zoning. It reviews administrative procedures and policies used in carrying out zoning ch...

1968-01-01

226

Quantifying turbulent wall shear stress in a stenosed pipe using large eddy simulation.  

PubMed

Large eddy simulation was applied for flow of Re=2000 in a stenosed pipe in order to undertake a thorough investigation of the wall shear stress (WSS) in turbulent flow. A decomposition of the WSS into time averaged and fluctuating components is proposed. It was concluded that a scale resolving technique is required to completely describe the WSS pattern in a subject specific vessel model, since the poststenotic region was dominated by large axial and circumferential fluctuations. Three poststenotic regions of different WSS characteristics were identified. The recirculation zone was subject to a time averaged WSS in the retrograde direction and large fluctuations. After reattachment there was an antegrade shear and smaller fluctuations than in the recirculation zone. At the reattachment the fluctuations were the largest, but no direction dominated over time. Due to symmetry the circumferential time average was always zero. Thus, in a blood vessel, the axial fluctuations would affect endothelial cells in a stretched state, whereas the circumferential fluctuations would act in a relaxed direction. PMID:20887027

Gårdhagen, Roland; Lantz, Jonas; Carlsson, Fredrik; Karlsson, Matts

2010-06-01

227

The species-specific structure of microanatomical compartments in the human spleen: strongly sialoadhesin-positive macrophages occur in the perifollicular zone, but not in the marginal zone.  

PubMed Central

The microanatomical structure of human and rat splenic white pulp is compared, with special emphasis on the localization of the marginal zone occupied by immunoglobulin M (IgM)+ IgD-/dull B lymphocytes and its specialized macrophages. Our study reveals that in contrast to rats, the marginal zone of humans primarily exists in the vicinity of primary and secondary splenic follicles and that it is almost absent around the periarteriolar T-cell zones. We demonstrate that in humans there is an additional compartment, the perifollicular zone, located between the marginal zone and the red pulp. The perifollicular zone is a dynamic region of variable cellular and phenotypic composition, which can be regarded either as a part of the red pulp or of the follicles. In most cases the perifollicular zone appears as a compartment of the red pulp containing erythrocyte-filled spaces which differ from the typical red pulp sinusoids. Similar to the splenic cords, the perifollicular zone mostly harbours scattered B and T lymphocytes. However, sometimes B lymphocytes clearly predominate in the perifollicular area. In addition, strongly sialoadhesin-positive macrophages form sheaths around capillaries in the perifollicular zone. Such capillary sheaths are not observed in rats. In humans weakly sialoadhesin-positive macrophages are also present in the perifollicular zone and in the red pulp. In some specimens sialoadhesin is, however, strongly expressed by a large number of dispersed perifollicular macrophages. Interestingly, in striking contrast to rats, the human marginal zone does not contain sialoadhesin-positive macrophages and marginal metallophilic macrophages are also absent in humans. Thus, sialoadhesin-positive macrophages and IgM+ IgD- memory B lymphocytes both share the marginal zone as a common compartment in rats, while they occupy different compartments in humans. We show that the human splenic marginal zone does not contain a marginal sinus and assume that in humans the perifollicular region is the compartment where antigen and recirculating lymphocytes enter the organ. Images Figure 1 Figure 2 Figure 3

Steiniger, B; Barth, P; Herbst, B; Hartnell, A; Crocker, P R

1997-01-01

228

Displacement of large-scale open solar magnetic fields from the zone of active longitudes and the heliospheric storm of November 3-10, 2004: 2. "Explosion" of singularity and dynamics of sunspot formation and energy release  

NASA Astrophysics Data System (ADS)

A more detailed scenario of one stage (August-November 2004) of the quasibiennial MHD process "Origination ... and dissipation of the four-sector structure of the solar magnetic field" during the decline phase of cycle 23 has been constructed. It has been indicated that the following working hypothesis on the propagation of an MHD disturbance westward (in the direction of solar rotation) and eastward (toward the zone of active longitudes) with the displacement of the large-scale open solar magnetic field (LOSMF) from this zone can be constructed based on LOSMF model representations and data on sunspot formation, flares, active filaments, and coronal ejections as well as on the estimated contribution of sporadic energy release to the flare luminosity and kinetic energy of ejections: (1) The "explosion" of the LOSMF singularity and the formation in the explosion zone of an anemone active region (AR), which produced the satellite sunspot formation that continued west and east of the "anemone," represented a powerful and energy-intensive source of MHD processes at this stage. (2) This resulted in the origination of two "governing" large-scale MHD processes, which regulated various usual manifestations of solar activity: the fast LOSMF along the neutral line in the solar atmosphere, strongly affecting the zone of active longitudes, and the slow LOSMF in the outer layers of the convection zone. The fronts of these processes were identified by powerful (about 1031 erg) coronal ejections. (3) The collision of a wave reflected from the zone of active longitudes with the eastern front of the hydromagnetic impulse of the convection zone resulted in an increase in LOSMF magnetic fluxes, origination of an active sector boundary in the zone of active longitudes, shear-convergent motions, and generation and destabilization of the flare-productive AR 10696 responsible for the heliospheric storm of November 3-10, 2004.

Ivanov, K. G.

2010-12-01

229

Large-scale separation of antipsychotic alkaloids from Rauwolfia tetraphylla L. by pH-zone-refining fast centrifugal partition chromatography.  

PubMed

pH-zone-refining centrifugal partition chromatography was successively applied in the large-scale separation of close R(f) antipsychotic indole alkaloids directly from CHCl(3) fraction of Rauwolfia tetraphylla leaves. Two experiments with increasing mass from 500 mg to 3 g of crude alkaloid extracts (1C) of R. tetraphylla were carried out in normal-displacement mode using a two-phase solvent system composed of methyl tert-butyl ether/ACN/water (4:1:5, v/v/v) where HCl (12 mM) was added to the lower aqueous stationary phase as a retainer and triethylamine (5 mM) to the organic mobile phase as an eluter. The two centrifugal partition chromatography separations afforded a total of 162.6 mg of 10-methoxytetrahydroalstonine (1) and 296.5 mg of isoreserpiline (2) in 97% and 95.5% purity, respectively, along with a 400.9 mg mixture of ?-yohimbine and reserpiline (3 and 4). Further, this mixture was resolved over medium pressure LC using TLC grade silica gel H (average particle size 10 ?m), which afforded 160.4 mg of ?-yohimbine (3) and 150.2 mg of reserpiline (4) in >95% purities. The purity of the isolated antipsychotic alkaloids was analyzed by high-performance LC and their structures were characterized on the basis of their 1D, 2D NMR and electrospray ionization-mass spectroscopic data. PMID:23335460

Maurya, Anupam; Gupta, Shikha; Srivastava, Santosh K

2012-11-29

230

A new technique for 100-fold increase in the FSR of optical recirculating delay line filters using a time compression unit.  

PubMed

A new technique that increases the free spectral range (FSR) of a recirculating delay line filter, is presented. The concept is based on a time-compression unit, which is used in conjunction with a frequency-shifting recirculating loop that generates multi-spectral characteristics, and the idea exploits the optical wavelength domain by wavelength-to-time mapping of the taps using an oppositely time-oriented dispersive element so that the taps travel different lengths, to time compress the tap separation. This technique solves, for the first time, the long-standing problem of the small FSR limitation in recirculating microwave photonic delay line filters, opening the way to realize the main functionalities required in microwave photonic filters. Experimental results are presented which demonstrate a large 100-fold increase in the FSR of the bandpass filter response. PMID:23188320

Nguyen, T A; Chan, E H W; Minasian, R A

2012-10-01

231

External Mass Transfer Model for a Recirculated Packed-Bed Batch Reactor on the Hydrolysis of Palm Olein Using Immobilized Lipase  

Microsoft Academic Search

The application of immobilized enzyme in organic synthesis is gaining popularity as it offers advantages over conventional chemical reactions. A recirculated packed-bed batch reactor (RPBBR) can be used for immobilized enzyme systems. However, external mass transfer limitation is significant in an RPBBR, especially at large scales. This study investigated the external mass transfer coefficients in an RPBBR. The effect of

Chew Yin Hoon; Lee Chew Tin

232

An evaluation of horizontal recirculation using single-well tests, pumping tests, tracer tests, and the colloidal borescope  

SciTech Connect

Extensive hydrodynamic testing was performed as part of a program to evaluate horizontal recirculation as a means of removing contaminants from thin, interbedded aquifers. Two test sites, each containing a pair of horizontal recirculation wells, were evaluated using various hydraulic tests. Results of these evaluations showed that ground water was intercepted more than 100 feet beyond the wells, and that the hydraulic gradient increased by more than two orders of magnitude. Aquifer heterogeneity, however, controlled the efficiency and uniformity of ground water flow. Heterogeneity was assessed with a variety of techniques. Bromide tracer tests and the colloidal borescope provided the most useful data. For example, at an uncontaminated site, the leading edge of the bromide tracer traversed the 100 feet between the injection and extraction wells in 21 hours, and the peak bromide concentration was observed in 2.6 days, compared with the four days predicted by a pumping test. The resulting maximum velocity calculation was consistent with measurements made with the borescope in preferential flow zones. Data obtained from a highly contaminated location indicated that assessments of aquifer heterogeneity are further complicated by the presence of DNAPL. Very low flow occurred in a highly contaminated zone, despite the fact that lithologic descriptions indicated that this region contained permeable sand and gravel.

Korte, N.; Kearl, P.M.; Siegrist, R.L.; Muck, M.T.; Schlosser, R.M.

2000-12-31

233

Research on leachate recirculation from different types of landfills  

SciTech Connect

Landfills can produce a great amount of leachate containing highly concentrated organic matter. This is especially true for the initial leachate from landfilled municipal solid wastes (MSW) that generally has concentrations of COD{sub Cr} and BOD{sub 5} up to 80,000 and 50,000 mg/L, respectively. The leachate could be disposed by means of recirculating technique, which decomposes the organics through the action of proliferating microorganisms and thereby purifies the leachate, and simultaneously accelerates organic decomposition through water saturation control. Data from experimental results indicated that leachate recirculating could reduce the organic concentration considerably, with a maximum reduction rate of COD{sub Cr} over 95%; and, using a semi-aerobic process, NH{sub 3}-N concentration of treated leachate could be under 10 mg/L. In addition, the organic concentration in MSW decreased greatly.

Wang Qi [Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, No. 8 of Dayangfang, Chaoyang District, Beijing 100012 (China) and Faculty of Engineering, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180 (Japan)]. E-mail: wangqi@craes.org.cn; Matsufuji, Yasushi [Faculty of Engineering, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180 (Japan); Dong Lu [Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, No. 8 of Dayangfang, Chaoyang District, Beijing 100012 (China); Huang Qifei [Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, No. 8 of Dayangfang, Chaoyang District, Beijing 100012 (China); Hirano, Fumiaki [Faculty of Engineering, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180 (Japan); Tanaka, Ayako [Faculty of Engineering, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180 (Japan)

2006-07-01

234

Closed recirculating system for shrimp-mollusk polyculture  

Microsoft Academic Search

This paper deals with a new system of aquaculture, i.e., a closed recirculating system for shrimp-mollusk polyculture. The\\u000a culture system consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir. During the production cycle,\\u000a water circulated between the shrimp and mollusk ponds, and the reservoir compensated for water loss from seepage and evaporation.\\u000a Constricted tagelus,Sinonovacula constricta, was selected

Xiongfei Wu; Zhidong Zhao; Deshang Li; Kangmei Chang; Zhuanshang Tong; Liegang Si; Kaichong Xu; Bailin Ge

2005-01-01

235

Energy utilization and recirculation of currant-finishing wastewater  

Microsoft Academic Search

In this study, a new method for the treatment of currant-finishing wastewater was proposed in the context of the “clean technology” concept. This method consisted of two stages. In the first stage, the currant-finishing wastewater was recirculated in the currant-wash process and in the second stage this wastewater was utilized for the production of energy through anaerobic digestion. Recycling ratios

A. G. Vlyssides; E. M. P. Barampouti; S. T. Mai

2007-01-01

236

A fiber optic recirculating memory loop operating at microwave frequencies  

Microsoft Academic Search

The use of optical fibers as the delay line elements in high-frequency memory loops provides light-weight and small-size devices with long time delays. The authors present a performance analysis and experimental results on a 2-6 GHz fiber-optic recirculating delay line. It is shown that microseconds delays can be achieved using the fiber-optic memory loop (FOML) in the 2 to 6

I. Koffman; P. R. Herczfeld; A. S. Daryoush; B. Even-Or; R. Markowitz

1988-01-01

237

Parasite infections in recirculated rainbow trout ( Oncorhynchus mykiss) farms  

Microsoft Academic Search

Parasite infections in recirculated rainbow trout farms were monitored through 22 months. Parameters such as temperature, mortality, pH, nitrite and ammonia-concentrations, use of formalin, mortality and feed conversion ratio were also monitored. Due to introduction of rainbow trout from traditional earth ponds into the new systems, all farms were found to be infected with a number of parasitic organisms known from

Thomas R. Jørgensen; Thomas B. Larsen; Kurt Buchmann

2009-01-01

238

A continuous recirculating culture system for planktonic copepods  

Microsoft Academic Search

The calanoid copepods, Acartia clausiGiesbrecht and Acartia tonsaDana, are maintained at high densities in continuous culture at 15°C. Synthetic sea-water medium is recirculated through filters and a foam tower which limits accumulation of dissolved wastes and various metabolites. The ciliate Euplotes vannusMüller is associated in culture with the copepods, and effectively controls bacterial population and accumulation of algal debris. The

E. J. Zillioux

1969-01-01

239

Recirculating, passive micromixer with a novel sawtooth structure.  

PubMed

A microfluidic device capable of recirculating nano to microlitre volumes in order to efficiently mix solutions is described. The device consists of molded polydimethyl siloxane (PDMS) channels with pressure inlet and outlet holes sealed by a glass lid. Recirculation is accomplished by a repeatedly reciprocated flow over an iterated sawtooth structure. The sawtooth structure serves to change the fluid velocity of individual streamlines differently depending on whether the fluid is flowing backwards or forward over the structure. Thus, individual streamlines can be accelerated or decelerated relative to the other streamlines to allow sections of the fluid to interact that would normally be linearly separated. Low Reynolds numbers imply that the process is reversible, neglecting diffusion. Computer simulations were carried out using FLUENT. Subsequently, fluorescent indicators were employed to experimentally verify these numerical simulations of the recirculation principal. Finally, mixing of a carboxyfluorescein labeled DMSO plug with an unlabeled DMSO plug across an immiscible hydrocarbon plug was investigated. At cycling rates of 1 Hz across five sawtooth units, the time was recorded to reach steady state in the channels, i.e. until both DMSO plugs had the same fluorescence intensity. In the case of the sawtooth structures, steady state was reached five times faster than in channels without sawtooth structures, which verified what would be expected based on numerical simulations. The microfluidic mixer is unique due to its versatility with respect to scaling, its potential to also mix solutions containing small particles such as beads and cells, and its ease of fabrication and use. PMID:16450034

Nichols, Kevin P; Ferullo, Julia R; Baeumner, Antje J

2005-12-08

240

Cyclone reactor with internal separation and axial recirculation  

DOEpatents

A cyclone combustor apparatus contains a circular partition plate containing a central circular aperture is described. The partition plate divides the apparatus into a cylindrical precombustor chamber and a combustor chamber. A coal-water slurry is passed axially into the inlet end of the precombustor chamber, and primary air is passed tangentially into said chamber to establish a cyclonic air flow. Combustion products pass through the partition plate aperture and into the combustor chamber. Secondary air may also be passed tangentially into the combustor chamber adjacent the partition plate to maintain the cyclonic flow. Flue gas is passed axially out of the combustor chamber at the outlet end and ash is withdrawn tangentially from the combustor chamber at the outlet end. A first mixture of flue gas and ash may be tangentially withdrawn from the combustor chamber at the outlet end and recirculated to the axial inlet of the precombustor chamber with the coal-water slurry. A second mixture may be tangentially withdrawn from the outlet end and passed to a heat exchanger for cooling. Cooled second mixture is then recirculated to the axial inlet of the precombustor chamber. In another embodiment a single cyclone combustor chamber is provided with both the recirculation streams of the first mixture and the second mixture. 10 figs.

Becker, F.E.; Smolensky, L.A.

1988-07-19

241

Branching of Atlantic Water within the Greenland-Spitsbergen Passage: An estimate of recirculation  

NASA Astrophysics Data System (ADS)

Atlantic Water (AW) supplies the largest source of heat, mass, and salt to the Arctic Ocean via Fram Strait (Greenland-Spitsbergen Passage), yet it represents only a fraction of the Atlantic Water that resides in the Greenland, Iceland, Norwegian, and Barents Seas. This is a result of both the branching of the central core of AW along its northward flow and the modification of its T-S signature through air-sea-ice interactions and internal mixing. This paper addresses the quantitative analysis of the three dominant Atlantic Water cores within Fram Strait and north of 76°N using an 11-year (1977 to 1987) hydrographic database. Spatial variations of heat, volume, and salt along its flow path of some 600 km showed that the major core of Atlantic Water that directly enters the Arctic Ocean (Svalbard branch) did not extend past 20°E. Of the 9719 km3 of Atlantic Water existing within the region, one third resided within the Svalbard branch; the remainder, 22% and 45%, were held within the Return Atlantic Current and the Yermak branches, respectively. Restricting the analysis to a southern limit of 79°N effectively removed the Return Atlantic Current and showed a nearly equal split between the two remaining branches. Work completed by Bourke et al. (1988) indicated that the Yermak branch is largely recirculated to the south; if true, this analysis supports Rudels' (1987) model estimate of a 50% recirculation of AW within this region.

Manley, T. O.

1995-10-01

242

A recirculating linac-based facility for ultrafast X-ray science  

SciTech Connect

We present an updated design for a proposed source of ultra-fast synchrotron radiation pulses based on a recirculating superconducting linac, in particular the incorporation of EUV and soft x-ray production. The project has been named LUX - Linac-based Ultrafast X-ray facility. The source produces intense x-ray pulses with duration of 10-100 fs at a 10 kHz repetition rate, with synchronization of 10 s fs, optimized for the study of ultra-fast dynamics. The photon range covers the EUV to hard x-ray spectrum by use of seeded harmonic generation in undulators, and a specialized technique for ultra-short-pulse photon production in the 1-10 keV range. High-brightness rf photocathodes produce electron bunches which are optimized either for coherent emission in free-electron lasers, or to provide a large x/y emittance ration and small vertical emittance which allows for manipulation to produce short-pulse hard x-rays. An injector linac accelerates the beam to 120 MeV, and is followed by four passes through a 600-720 MeV recirculating linac. We outline the major technical components of the proposed facility.

Corlett, J.N; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Green, M.A.; Heimann, P.; Leone, S.; Lidia, S.; Li, D.; Ratti, A.; Robinson, K.; Schoenlein, R.; Staples, J.; Wan, W.; Wells, R.; Wolski, A.; Zholents, A.; Placidi, M.; Pirkl, W.; Parmigiani, F.

2003-05-06

243

A Recirculating Linac-Based Facility for Ultrafast X-Ray Science  

SciTech Connect

We present an updated design for a proposed source of ultra-fast synchrotron radiation pulses based on a recirculating superconducting linac [1,2], in particular the incorporation of EUV and soft x-ray production. The project has been named LUX--Linac-based Ultrafast X-ray facility. The source produces intense x-ray pulses with duration of 10-100 fs at a 10 kHz repetition rate, with synchronization of 10's fs, optimized for the study of ultra-fast dynamics. The photon range covers the EUV to hard x-ray spectrum by use of seeded harmonic generation in undulators, and a specialized technique for ultra-short pulse photon production in the 1-10 keV range. High brightness rf photocathodes produce electron bunches which are optimized either for coherent emission in free electron lasers, or to provide a large x/y emittance ration and small vertical emittance which allows for manipulation to produce short-pulse hard x-rays. An injector linac accelerates the beam to 120 MeV, and is followed by f our passes through a 600-720 MeV recirculating linac. We outline the major technical components of the proposed facility.

J. N. Corlett; W. A. Barletta; S. DeSantis; L. Doolittle; W. M. Fawley; M.A. Green; P. Heimann; S. Leone; S. Lidia; D. Li; A. Ratti; K. Robinson; R. Schoenlein; J. Staples; W. Wan; R. Wells; A.Wolski; A. Zholents; F. Parmigiani; M. Placidi; W. Pirkl; R. A. Rimmer; S. Wang

2003-05-01

244

Flow and recirculation of Antarctic Intermediate Water across the Rio Grande Rise  

NASA Astrophysics Data System (ADS)

The flow of the low-salinity Antarctic Intermediate Water (AAIW) at 700-1150 m depth across the Rio Grande Rise and the lower Santos Plateau is studied under the auspices of the World Ocean Circulation Experiment (WOCE) in the context of the Deep Basin Experiment. Our data set consists of several hydrographic sections, a collection of 15 RAFOS float trajectories, and records from 14 moored current meters. The data were gathered during different intervals between 1990 and 1994. The inferred flow field strongly supports a basinwide anticyclonic recirculation cell in the subtropical South Atlantic underneath the wind-driven gyre. Its center, which appears to be southeast of the Rio Grande Rise, separates the eastward advection of AAIW below the South Atlantic Current from the westward flowing, recirculating AAIW. The two near-shelf limbs closing the circumference of AAIW flow are formed in the east by the deep Benguela Current, potentially modulated by salty inflow of Indian Ocean Intermediate Water, and in the west by the Brazil Current system. Further important circulation elements are the Brazil-Falkland (Malvinas) Confluence Zone at 40°S and an unnamed divergence at 28°S close to the 1000 m isobath. The resulting broad southward flow of AAIW augments the share of modified, i.e., saltier, intermediate water in the source region of the South Atlantic Current, while the smaller northward flow marks the source of a narrow equatorward Western Intermediate Boundary Current, ultimately leaving the South Atlantic. This shelf-trapped jet is clearly documented in hydrographic data from 19°S and in nearby current meter records. The jet contrasts a sluggish flow across this latitude east of 35°W. A continuous flow of AAIW from its subpolar region in the southwestern Argentine Basin all along the western slope toward the equator appears unlikely between 35°S and 25°S.

Boebel, Olaf; Schmid, Claudia; Zenk, Walter

1997-09-01

245

The Southern Part of the Southern Volcanic Zone (SSVZ; 42-46S) of the Andes: History of Medium and Large Explosive Holocene Eruptions  

NASA Astrophysics Data System (ADS)

Chaitén volcano is one of 13 large volcanic centers, and numerous small cones, comprising the southern part of the Andean Southern Volcanic Zone (SVZ), that results from the subduction of the Nazca plate (at 7.8 cm/yr) between the landward extension of the Chiloé FZ at 42S and the Chile Rise - Trench triple junction at 46S. Chaitén is a rhyolite dome inside a 3 km diameter caldera located 15 km west of the larger Michinmahuida stratovolcano. Other stratovolcanoes in the SSVZ include Yate, Hornopirén, Corcovado, Yanteles, Melimoyu, Mentolat, Cay and Macá. Hudson volcano, the southernmost in the Southern SVZ, is a large 10 km caldera, while Huequi and Hualaihué - Cordón Cabrera are a group of small aligned cinder cones possibly related to a larger eroded volcanic complex. Prior to the May 2008 eruption of Chaitén, the only well documented historic eruptions in this segment of the Andean arc were the explosive eruption of Hudson in August 1991 (Naranjo et al. 1993), and two eruptions of Michinmahuida in 1742 and 1834-35. Tephra deposits provide evidence of 11 prehistoric explosive Holocene eruptions of the southernmost SSVZ Hudson volcano, including two large eruptions near <6700 and <3600 BP (Naranjo and Stern 1998). The 6700 BP eruption produced greater than 18 km3 of andesitic tephra, possibly the largest Holocene eruption in all the southern Andes. Although Hudson is clearly the most active of the Southern SVZ volcanoes in terms of both volume and frequency of explosive eruptions, tephra deposits indicate that seven of the other SSVZ volcanoes, including Chaitén, also have had medium to large Holocene explosive eruptions (Naranjo and Stern 2004). Three of these eruptions were from Corcovado at approximately <9190, <7980 and <6870 BP, one from Yanteles at <9180 BP, two from Melimoyu at <2740 and <1750 BP, one from Mentolat at <6960 and one from Macá at <1540 BP. Two other eruptions, at <6350 and <3820 BP, we interpret as having been produced by Michinmahuida, because no evidence of tephra from this eruption is found around the Chaitén volcano. The younger and larger of these eruptions (MIC2) generated rhyolites similar in composition to those erupted from Chaitén, suggesting some possible relation between the Michinmahuida and Chaitén magma plumbing systems. Chaitén erupted at approximately <9370 BP based on dating of charcoal within the pyroclastic flow deposit produced by this eruption. This deposit decreases from 3.5 m thick 10 km north of the volcano to 1.5 m thick 30 km north of the volcano, and is covered by a 1.65 to 0.3 m thick tehra fall deposit of rhyolite pumice capped by a thin layer of dark mafic scoria. We consider the pre-May 2008 rhyolite obsidian dome to have formed at this time, or at least before 5610 BP, the age of pre-historic occupation sites with obsidian artifacts fashioned from this obsidian (Stern et al. 2002). Both the thickness of this deposit and the size of the dome in the crater prior to the May 2008 eruption suggest that the current event is not yet as large as the 9370 BP event, which ended with the eruption of a more mafic magma. Thus the current eruption cycle may have a way to go yet before it is complete. Naranjo et al. 1993, Boletin No 44, SERNAGEOMIN, 50 p. Naranjo and Stern 1998, Bull Volcanology 59: 291-306. Naranjo and Stern 2004, Revista Geologica de Chile 31: 225-240. Stern et al. 2002, Anales del Intituto de la Patagonia 30: 167-174.

Stern, C. R.; Naranjo, J. A.

2008-12-01

246

Air pollution in the shore zone of a Large Alpine Lake - 1 - Road dust and urban aerosols at Lake Tahoe, California-Nevada  

NASA Astrophysics Data System (ADS)

Concentrated human activity and limited atmospheric mixing create a high potential for airborne pollutant impacts to alpine lakes developed as mountain resorts. Lake Tahoe is a major alpine resort straddling the California-Nevada border, receiving more than two million visitors each year. The lake's clarity has declined substantially since the inception of intense development in the Tahoe basin in the 1970s. The 2002-2004 Lake Tahoe Atmospheric Deposition Study (LTADS) was conducted as part of a multi-agency effort to develop a water quality management plan for the lake. Estimating aerosol deposition to the lake requires detailed knowledge of the spatial and temporal patterns of aerosol concentration, size distribution, and chemical composition over the entire basin - and developing a management plan requires also that the sources of the aerosols be known with considerable specificity. In lieu of the intensive measurement network implied by this level of detail, we hypothesized that a set of measurements to characterized the temporal, spatial, and size distribution patterns of particles in ambient air and in local emissions in the vicinity of Lake Tahoe could be used to extrapolate long time series of simple measurements to an annual aerosol deposition computation. Here we report the results of our detailed aerosol measurement campaign. Our results show that there are strong systematic and repeating gradients in aerosol loading that occur as functions of location, land use, traffic activity, and time of day, and that road dust is a major source of aerosols around the lake. In addition, we observed strong consistency of particle size distributions as a function of source type, largely independent of particle concentrations. Finally, we demonstrated the use of particle counters to directly observe downwind dispersion and deposition of particles. Together, these findings support the use of imputed location- and time-specific size distributions in annual aerosol deposition calculations, even though particle size distributions were not directly measured in the LTADS baseline monitoring program, and that program was conducted at only a limited set of sites in the Tahoe basin. Two companion articles in this journal issue describe the overall findings of the LTADS study (Dolislager et al., "Overview of the Lake Tahoe Atmospheric Deposition Study") and the results of measurements taken on the lake itself (VanCuren et al., "Air Pollution in the Shore Zone of a Large Alpine Lake - 2 - Local and Regional Pollutant Distribution over Lake Tahoe California-Nevada").

VanCuren, R.; Pederson, J.; Lashgari, A.; Dolislager, L.; McCauley, E.

2012-01-01

247

Characteristics of velocity pulsations in a turbulent recirculated melt flow  

NASA Astrophysics Data System (ADS)

For the modern industrial applications it is necessary to develop and investigate metallic and oxide materials of high purity or predicted composition. Such materials can be produced by the induction melting method, especially in inductor and cold crucible furnaces. Measurements taken in experimental furnaces show that the velocity pulsations dominate for the heat and mass exchange in the melt, especially in a zone between typical upper and lower eddies. Understanding of the pulsation mechanism and development of models to estimate the exchange characteristics are very important for the development and optimisation of industrial furnaces. The authors present experimental results and propose a simple 3D large eddy simulation (LES) model of the induction furnace that can be adapted to qualitative analysis of experimental data. Tables 2, Figs 13, Refs 7.

Kirpo, M.; Jakovics, A.; Baake, E.

2005-06-01

248

A study of NO{sub x} reduction by fuel injection recirculation. Final report, January 1995--June 1996  

SciTech Connect

Flue-gas recirculation (FGR) is a well-known method used to control oxides of nitrogen (NO{sub x}) in industrial burner applications. Recent small- and large-scale experiments in natural-gas fired boilers have shown that introducing the recirculated flue gases with the fuel results in a much greater reduction in NO{sub x}, per unit mass of gas recirculated, in comparison to introducing the flue gases with the combustion air. That fuel injection recirculation (FIR) is more effective than windbox FGR is quite remarkable. At present, however, there is no definitive understanding of why FIR is more effective than conventional FGR. The objective of the present investigation is to ascertain whether or not chemical and/or molecular transport effects alone can explain the differences in NO{sub x} reduction observed between FIR and FGR by studying laminar diffusion flames. The purpose of studying laminar flames is to isolate chemical effects from the effects of turbulent mixing and heat transfer, which are inherent in practical boilers. The results of both the numerical simulations and the experiments suggest that, although molecular transport and chemical kinetic phenomena are affected by the location of diluent addition depending on flow conditions, the greater effectiveness of FIR over FGR in practical applications may result from differences in turbulent mixing and heat transfer. Further research is required to understand how differences in diluent-addition location affect NO{sub x} production in turbulent flames. The present study, however, provides an underlying basis for understanding how flow conditions can affect flame chemistry. 51 figs., 7 tabs.

Feese, J.J.; Turns, S.R.

1996-08-01

249

Method and apparatus for affecting a recirculation zone in a cross flow  

SciTech Connect

Disclosed is a cross flow apparatus including a surface and at least one outlet located at the surface. The cross flow apparatus further includes at least one guide at the surface configured to direct an intersecting flow flowing across the surface and increase a velocity of a cross flow being expelled from the at least one outlet downstream from the at least one outlet.

Bathina, Mahesh (Andhra Pradesh, IN); Singh, Ramanand (Uttar Pradesh, IN)

2012-07-17

250

Investigation of groundwater recirculation for the removal of RDX from the Pantex Plant perched aquifer  

SciTech Connect

The Pantex Plant near Amarillo, Texas, is a US Department of Energy (DOE) facility that has been in operation since 1942. Past and present operations at Pantex include the creation of chemical high explosives components for nuclear weapons and assembly and disassembly of nuclear weapons. The Pantex Plant is underlain by the Ogallala aquifer, which in this area, consists of the main water-bearing unit and a perched water zone. These are separated by a fine-grained zone of low permeability. Multiple contaminant plumes containing high explosive (HE) compounds have been detected in the perched aquifer beneath the plant. The occurrence of these contaminants is the result of past waste disposal practices at the facility. RDX is an HE compound, which has been detected in the groundwater of the perched aquifer at significant concentrations. A pilot-scale, dual-phase extraction treatment system has been installed at one location at the plant, east of Zone 12, to test the effectiveness of such a system on the removal of these contaminants from the subsurface. A tracer test using a conservative tracer, bromide (Br), was conducted at the treatment site in 1996. In addition to the bromide, RDX and water elevations in the aquifer were monitored. Using data from the tracer test and other relevant data from the investigations at Pantex, flow and contaminant transport in the perched aquifer were simulated with groundwater models. The flow was modeled using MODFLOW and the transport of contaminants in the aqueous phase was modeled using MT3D. Modeling the perched aquifer had been conducted to characterize the flow in the perched aquifer; estimate RDX retardation in the perched aquifer; and evaluate the use of groundwater re-circulation to enhance the extraction of RDX from the perched aquifer.

Woods, A.L. [ed.; Barnes, D.L. [Amarillo National Resource Center for Plutonium, TX (United States); Boles, K.M.; Charbeneau, R.J. [Univ. of Texas, Austin, TX (United States); Black, S.; Rainwater, K. [Texas Tech Univ., Lubbock, TX (United States). Water Resources Center

1998-07-01

251

Xenon recirculation systems for next-generation lithography tools  

NASA Astrophysics Data System (ADS)

Next generation lithography tools designed to pattern critical dimensions at <45nm will require extreme ultraviolet (EUV) light sources. Xenon is currently a strong candidate for the source medium for production of EUV light at 13.5nm. A consistent supply of ultra high purity xenon is required for efficient light source production. Several factors must be considered in the overall operating costs of the EUV tool: The high cost of xenon (typically ~$4/litre); The quantities required for EUV source production, which are typically 4slpm for Laser Produced Plasma (LPP) and 300sccm for Gas Discharge Produced Plasma (GDPP). On the basis of these figures the annual xenon cost would typically be approximately $11M/year for LPP, $1M/year for GDPP. Therefore recycling of xenon offers a significant operating cost reduction. This type of re-circulation system is not restricted to high xenon throughput applications, but can be scaled in size, and hence cost, for application to lower throughput process applications. Additional applications in mainstream silicon processing including a new development in dielectric etch using xenon could also benefit from re-circulation. Present research indicates that for a typical recipe, 675sccm xenon is required per wafer pass, this equates to an annual cost of $0.6M. BOC Edwards has designed & built a series of five fully integrated xenon re-circulation systems for lithography applications. Each system has been custom designed to exact application requirements, including liquid/solid xenon filament production. Additionally, an important footprint reduction has been achieved during the design evolution, which ideally suits dielectric etch applications.

Greenwood, Joanne R.; Mennie, Darren; Hughes, Carolyn; Lee, Ron

2004-05-01

252

SOA gate array recirculating buffer with fiber delay loop.  

PubMed

We present a compact variable delay buffer for storage of 40 byte packets. The recirculating buffer is based on an InP SOA gate array two-by-two switch which provides greater than 40 dB of extinction, sub-nanosecond switching, and fiber-to-fiber gain. The switch is used with a fiber delay loop 450 centimeters, or 23 ns, in length. The buffer is demonstrated with greater than 98% packet recovery at 40 Gb/s for up to 184 ns of storage. PMID:18545559

Burmeister, Emily F; Mack, John P; Poulsen, Henrik N; Klamkin, Jonathan; Coldren, Larry A; Blumenthal, Daniel J; Bowers, John E

2008-06-01

253

Demonstration of spray booth recirculation and partitioning -- Phase 2  

SciTech Connect

Acurex Environmental was contracted by the US EPA to demonstrate an advanced pollution control cost reduction strategy at a US Marine Corps maintenance facility in Barstow, CA. One booth was modified and two new booths were built and manifolded into a single air pollution control device. This SERDP funded project grew out of previous studies by the EPA and DoD to evaluate and develop economic volatile organic compound (VOC) control technologies for painting facilities. This first application of partitioned recirculating booth in a high volume production environment fulfills a stated SERDP goal of transferring promising design concepts into reliable production applications.

Proffitt, D.; Clayton, R.K.; Ayer, J.

1996-12-31

254

Development of beam position monitors for heavy ion recirculators  

SciTech Connect

Work is underway at the Lawrence Livermore National Laboratory to design and build a small-scale, heavy ion recirculating induction accelerator. An essential part of this design work is the development of small nonintercepting diagnostics to measure beam current and position. This paper describes some of this work, with particular emphasis on the development of a small capacitive probe beam position monitor to resolve beam position to the 100 {mu}m level in a 6 cm diameter beam pipe. Initial measured results with an 80 keV potassium ion beam are presented.

Deadrick, F.J.; Barnard, J.J. [Lawrence Livermore National Lab., CA (United States); Fessenden, T.J. [Lawrence Berkeley Lab., CA (United States); Meridith, J.W. [EG and G Energy Measurements, Inc., Pleasanton, CA (United States). Amador Valley Operations; Rintamaki, J. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering

1995-04-25

255

[Analysis of effect of sludge recirculation on setting efficiency in horizontal sedimentation tank].  

PubMed

The problem that the present sediment theory does not consider sludge recirculation effect on the efficiency of particle settling is studied. Based on the longitudinal mixing settling theory, an imperfect sediment model that takes reflux ratio in consideration is built. According to the established model, the study analyzes the effect of sludge recirculation taken by suction dredge on particle setting, in horizontal sedimentation tank. Specifically, the relation between overplus of sewerage suspension and sedimentation rate was chosen as an example. Shown as a result, when sludge recirculation is not taken in consideration, efficiency of particle settling is 72.8%. However, when sludge recirculation increases from 0.5 to 3.0, efficiency of particle settling decreases from 71.1% to 50.9%, which is smaller than efficiency of particle settling without recirculation; and when sludge recirculation is 3.0, efficiency of particle settling is 50.9%, which is approximately 30% less than efficiency of particle settling without recirculation. So, sludge recirculation make efficiency of particle settling is smaller than efficiency of particle settling without recirculation, and the efficiency of particle settling reduces with the increase of reflux ratio. PMID:17633172

Zou, Zhi-hong; Zhang, Wei; Sui, Jun

2007-05-01

256

Recirculation-aeration: Bibliography for aquaculture. Bibliographies and literature of agriculture (Final)  

SciTech Connect

The bibliography includes literature citations through 1992 related to water recirculation and aeration in aquaculture. The focus is on filtration, aeration, and circulation techniques in various aquaculture situations.

Perschbacher, P.W.; Powell, R.V.; Freeman, D.W.; Lorio, W.J.; Hanfman, D.T.

1993-08-01

257

THE SANTA RITA FAULT ZONE: EVIDENCE FOR LARGE MAGNITUDE EARTHQUAKES WITH VERY LONG RECURRENCE INTERVALS, BASIN AND RANGE PROVINCE OF SOUTHEASTERN ARIZONA  

Microsoft Academic Search

A discontinuous zone of subdued, west-facing fault scarps offset Quaternary alluvium along 58 km of the western piedmont of the Santa Rita Mountains, south of Tucson, Arizona. Scarps trend NE to N-S and are 1 to 6 km basinward from the deeply embayed mountain front. Scarp heights range from 1 to 7 m, and maximum scarp slope angles range from

PHILIP A. PEARTHREE; SUSANNA S. CALVO

258

Optical characteristics of different Bragg planes of 3D polystyrene photonic crystals in the LU and LK path of the first Brillouin zone of close packed fcc structure with large band gap depth and steeper band edges  

Microsoft Academic Search

We report the angle dependent transmission spectral characteristics of 331 nm diameter polystyrene (PS) photonic crystals (PhCs) with large band gap depth and steeper band edges which allow one to identify different Bragg planes promptly. The spectral characteristics recorded in the clock-wise (CW) and anti clock-wise (ACW) directions follow the LK and LU paths in the first Brillouin zone (FBZ)

K. Shadak Alee; Carina B. M; Sriram G; Narayana Rao Desai

2010-01-01

259

The Effects of Canopy Leaf Area Index on Airflow Across Forest Edges: Large-eddy Simulation and Analytical Results  

NASA Astrophysics Data System (ADS)

The structure of turbulent flows along a transition between tall-forested canopies and forest clearings continues to be an active research topic in canopy turbulence. The difficulties in describing the turbulent flow along these transitions stem from the fact that the vertical structure of the canopy and its leaf area distribution cannot be ignored or represented by an effective roughness length. Large-eddy simulation (LES) runs were performed to explore the effect of a homogeneous variation in the forest leaf area index (LAI) on the turbulent flow across forest edges. A nested grid numerical method was used to ensure the development of a deep boundary layer above the forest while maintaining a sufficiently high resolution in the region close to the ground. It was demonstrated that the LES here predicted first-order and second-order mean velocity statistics within the canopy that agree with reported Reynolds-Averaged Navier-Stokes (RANS) model results, field and laboratory experiments. In the simulations reported here, the LAI was varied between 2 and 8 spanning a broad range of observed LAI in terrestrial ecosystems. By increasing the forest LAI, the mean flow properties both within the forest and in the clearing near the forest edge were altered in two fundamental ways: near the forest edge and into the clearing, the flow statistical properties resembled the so-called back-facing step (BFS) flow with a mean recirculation zone near the edge. Another recirculation zone sets up downstream of the clearing as the flow enters the tall forest canopy. The genesis of this within-forest recirculation zone can be primarily described using the interplay between the mean pressure gradients (forcing the flow) and the drag force (opposing the flow). Using the LES results, a simplified analytical model was also proposed to explain the location of the recirculation zone inside the canopy and its dependence on the forest LAI. Furthermore, a simplified scaling argument that decomposes the mean velocity at the outflow edge into a superposition of ‘exit flow’ and BFS-like flow with their relative importance determined by LAI was explored.

Cassiani, M.; Katul, G. G.; Albertson, J. D.

2008-03-01

260

Pulsed power performance of the new RLA (Recirculating Linear Accelerator)  

NASA Astrophysics Data System (ADS)

The Recirculating Linear Accelerator (RLA) is returning to operation with a new electron beam injector and a modified accelerating cavity. Upon completion of our experimental program the RLA will capture the injected beam on an IFR guiding plasma channel in either a spiral or a closed racetrack drift tube. The relativistic beam will be efficiently recirculated for up to four passes through two or more accelerating cavities, in phase with the ringing cavity voltage waveforms, and thereby increased in energy to 10 MeV before being extracted. The inductively isolated four-stage injector was designed to produce beam parameters of 4 MeV, 10 to 20 kA, and 40 to 55 ns FWHM. The three-line radial cavity is being modified to improve the 1 MV accelerating voltage pulse shape while an advanced cavity design study is in progress. The actual versus predicted pulsed-power performance of the RLA injector and cavity and the associated driving hardware is discussed.

Smith, D. L.; Mazarakis, M. G.; Bennett, L. F.; Olson, W. R.

261

Liquid flow focused by a gas: Jetting, dripping, and recirculation  

NASA Astrophysics Data System (ADS)

The liquid cone-jet mode can be produced upon stimulation by a coflowing gas sheath. Most applications deal with the jet breakup, leading to either of two droplet generation regimes: Jetting and dripping. The cone-jet flow pattern is explored by direct axisymmetric volume of fluid (VOF) numerical simulation; its evolution is studied as the liquid flow rate is increased around the jetting-dripping transition. As observed in other focused flows such as electrospraying cones upon steady thread emission, the flow displays a strong recirculating pattern within the conical meniscus; it is shown to play a role on the stability of the system, being a precursor to the onset of dripping. Close to the minimum liquid flow rate for steady jetting, the recirculation cell penetrates into the feed tube. Both the jet diameter and the size of the cell are accurately estimated by a simple theoretical model. In addition, the transition from jetting to dripping is numerically analyzed in detail in some illustrative cases, and compared, to good agreement, with a set of experiments.

Herrada, Miguel A.; Gañán-Calvo, Alfonso M.; Ojeda-Monge, Antonio; Bluth, Benjamin; Riesco-Chueca, Pascual

2008-09-01

262

Design of a scaled recirculator for Heavy Ion Inertial Fusion  

NASA Astrophysics Data System (ADS)

An alternative concept for Heavy Ion Inertial Fusion (HIF) is the use of a recirculator to accelerate ion beams to energies in the range of 50-100 GeV [1]. The physics of an ion recirculator can be explored by means of scaled experiments in a compact machine like the existing University of Maryland Electron Ring (UMER). UMER has been successfully used for the study of the fundamental physics of space-charge-dominated transport using a 10 keV electron beam with up to 100 mA of current (or 10 nC per a 100 ns pulse) [2]. Due to the low energy and high perveance, the UMER beam accesses the same range of intensities as an HIF driver. In this paper we report on a computational study for the design of an acceleration stage for UMER using an induction cell. Using the two-dimensional transverse slice model in the particle-in-cell code WARP we show that it is possible to accelerate the UMER beam up to 20 keV without major modifications to the machine. Such acceleration enables future experiments on transverse resonance crossing and studies on longitudinal pulse behavior.

Fiuza, K.; Beaudoin, B.; Bernal, S.; Haber, I.; Kishek, R. A.; O'Shea, P. G.; Papadopoulos, C.; Sutter, D.; Wu, C.

2010-08-01

263

Subduction of fracture zones  

NASA Astrophysics Data System (ADS)

Since Wilson proposed in 1965 the existence of a new class of faults on the ocean floor, namely transform faults, the geodynamic effects and importance of fracture zone subduction is still little studied. It is known that oceanic plates are characterized by numerous fracture zones, and some of them have the potential to transport into subduction zones large volumes of water-rich serpentinite, providing a fertile water source for magma generated in subduction-related arc volcanoes. In most previous geodynamic studies, subducting plates are considered to be homogeneous, and there is no clear indication how the subduction of a fracture zone influences the melting pattern in the mantle wedge and the slab-derived fluids distribution in the subarc mantle. Here we show that subduction of serpentinized fracture zones plays a significant role in distribution of melt and fluids in the mantle wedge above the slab. Using high-resolution tree-dimensional coupled petrological-termomechanical simulations of subduction, we show that fluids, including melts and water, vary dramatically in the region where a serpentinized fracture zone enters into subduction. Our models show that substantial hydration and partial melting tend to concentrate where fracture zones are being subducted, creating favorable conditions for partially molten hydrous plumes to develop. These results are consistent with the along-arc variability in magma source compositions and processes in several regions, as the Aleutian Arc, the Cascades, the Southern Mexican Volcanic Arc, and the Andean Southern Volcanic Zone.

Constantin Manea, Vlad; Gerya, Taras; Manea, Marina; Zhu, Guizhi; Leeman, William

2013-04-01

264

Prospects of large-scale noble metal mineralization in the Upper Selemdzha minerogenic zone (by the example of the Malomyr and Sagur-Semertak ore clusters)  

NASA Astrophysics Data System (ADS)

The Upper Selemdzha minerogenic zone, which has the potential for noble metal mineralization in the Upper Amur, has been studied. It is confined to the thick strata of Paleozoic terrigeneous-sedimentary rocks (sandstones, siltstones, clay schists, packages of their thin rhythmical interlayering, sedimentary breccias, and conglomerates) in the Tokura subzone of the Selemdzha-Kerbinsk zone in the Amur-Okhotsk area of the Mongol-Okhotsk system, overlain by Early Cretaceous volcanogenic sedimentary rocks and intruded by Early Cretaceous quartz diorites, granodiorites, and dacites. In the Malomyr and Sagur-Semertak ore clusters, there are a few known potential deposits of noble metals and ore occurrences; when studied and prospected, they can exhibit vein-veinlet noble metal mineralization with rich contents of gold and platinoids in ore columns and metasomatic deposits.

Melnikov, A. V.; Agafonenko, S. G.; Babichev, I. V.; Piskunov, Yu. G.; Moiseenko, V. G.

2013-04-01

265

Balloon measurements of x-rays in the auroral zone. III. High time resolution studies. [Time resolution of large Nai(Tl) detectors  

Microsoft Academic Search

The main objective of the experiment is to examine temporal features in the auroral zone X-ray fluxes above 30 keV photon energy with resolution to intervals as short as a few milliseconds. It is primarily desired to apply high-resolution analysis to small and moderate auroral X-ray fluxes which occur with much greater frequency than do extremely high fluxes. The X-ray

K. A. Anderson; D. W. Milton

1964-01-01

266

Studying coastal recirculation with a simplified analytical land-sea breeze model  

Microsoft Academic Search

The diurnal cycle of the land and sea breeze is of high importance in determining many aspects of the living conditions in coastal areas. One of these aspects is the buildup of air pollutants concentrations due to air mass recirculation. In order to study the main factors governing the recirculation of an air mass under land-sea breeze conditions, a single

Ilan Levy; Uri Dayan; Yitzhak Mahrer

2008-01-01

267

Recirculation injection by nonlinear gating for high-power laser pulses  

Microsoft Academic Search

The average power and efficiency of processes that exhibit low interaction cross section and low optical loss can often be enhanced by recirculating the laser pulse in the cavity. Inverse Compton scattering of the photon pulse on an electron bunch, harmonic generation, and spectroscopy represent examples of such processes. Methods for laser recirculation that enhance the interaction efficiency have been

Igor Jovanovic; Miro Shverdin; David Gibson; Curtis Brown

2008-01-01

268

A Review Article: Access Recirculation Among End Stage Renal Disease Patients Undergoing Maintenance Hemodialysis  

PubMed Central

Background The presence of arterio-venous (A-V) fistula recirculation among hemodialysis (HD) patients markedly decrease adequacy of dialysis. Objectives The present article summarize some of observations about clinical significance, causes, the most common techniques for measurement, and main source of pitfall in calculation of access recirculation. Materials and Methods A variety of literature sources such as PubMed, Current Content, Scopus, Embase, and Iranmedex; with key words such as inadequate dialysis and arterio-venous fistula access recirculation were used to collect current data. Manuscripts published in English language as full-text articles or as abstract form were included in our review study. Results Any access recirculation among HD patients should be considered abnormal and if it presents prompt investigation should be performed for its causes. There are two most common techniques for accurate assessment of access recirculation: Urea (or chemical) and nonurea-based method by ultrasound dilution technique. The most common causes of access recirculation are the presence of high-grade venous stenosis, inadequate arterial blood flow rate, close proximity, or misdirection of arterial and venous needles placement by HD staff especially in new vascular accesses due to a lack of familiarity with the access anatomy. Conclusions The presence of access recirculation among HD patients can lead to significant inadequate dialysis thereby resulting in reducing the survival of these patients. Therefore, periodic assessment of access recirculation should be performed in HD wards.

Zeraati, Abbasali; Beladi Mousavi, Seyed Seifollah; Beladi Mousavi, Marzieh

2013-01-01

269

Exhaust gas recirculation control system for a diesel engine and control method therefor  

Microsoft Academic Search

In an exhaust gas recirculation control system in which a fuel injection quantity is determined on the basis of engine speed and engine load, a throttle-closed range is determined on the basis of engine speed and fuel injection quantity. An exhaust gas recirculation control valve has an electromagnetically operable valve actuator, the duty cycle of which is controlled by a

Y. Kawamura; T. Nakagawa; M. Nakajima; G. Shioyama

1984-01-01

270

Recirculation of Air Pollutants During Lake Breeze Events in Chicago  

NASA Astrophysics Data System (ADS)

Chicago is located at the southwestern end of Lake Michigan and experiences lake breezes on a regular basis during the summer months. In order to study transport and evolution of air pollution during such lake breeze events reactive trace gases NOx and ozone were measured as well as aerosol samples collected in summer 2003. The aerosol samples were analyzed for major ionic species by ion chromatography and for elemental species by total reflection X-ray fluorescence spectrometry. Several lake breeze events occurred during the field collections with one set of events on June 30 and July 1, 2003 standing out due to high levels of NOx and some aerosol species such as nitrate, iron and lead. The fully coupled chemistry-meteorology model WRF/CHEM was applied to simulate atmospheric conditions on these two days. The simulations show that a temperature and wind field front developed in the course of the lake breeze event creating a local cell of about 150km in diameter. Air and pollutants trapped in this cell appear to be re-circulating above Chicago and western Lake Michigan. The model results provide important insight on the evolution of ozone precursors, photolysis rates and ozone production during transport above the lake, and allow for quantifying the influence of this recirculation on the observed levels of local pollutants in Chicago. Whereas the June 30/July 1, 2003 lake breeze seems to be very pronounced, other lake breeze situations showed also enhanced NOx and nitrate mixing ratios compared to non-lake breeze days. Interestingly ozone mixing ratios were found to be lower in average during lake breeze events as compared to non-lake breeze conditions. To understand the development of the local lake breeze cell and possible recirculation of pollutants we plan to simulate temperature, wind field and pollutant level on other lake breeze days as well. Satellite data from the moderate resolution imaging spectrometer (MODIS) and Atmospheric Infrared Sounder (AIRS) will be used to highlight the general atmospheric distribution of aerosols and relative humidity within the region.

Schmeling, M.; Hodzic, A.; Massie, S. T.

2009-12-01

271

Segmentation of the southern part of the Outer Hebrides Fault Zone (NW Scotland). Implications on the seismotectonic behaviour of large-scale crustal faults  

NASA Astrophysics Data System (ADS)

The crustal-scale Outer Hebrides Fault Zone (OHFZ) in NW Scotland is a complex fault zone which cuts Precambrian gneisses and which was active, with varied kinematics, at several epochs between the Proterozoic and the Mesozoic. It is outlined by a series of fault rocks formed under ductile to brittle conditions. The southern part of the Outer Hebrides Fault Zone, exposed in South Uist, Eriskay and Barra, is outlined by pseudotachylytes and cataclasites presumably formed by reverse motion during the brittle stages of the Caledonian orogeny about 430 Ma ago. Analysis of published geological maps and detailed field mapping between latitudes N56°54' and N57°17' show that the OHFZ consists of two segments. Between N57°07' and N57°17', the northern segment emplaces a banded granulite-textured metadiorite, forming the so-called Corodale gneiss, upon Lewisian gneiss. This fault segment is characterised by moderate deformation in the footwall. The hanging-wall consists of a pseudotachylyte sole whose thickness is comprised between 2 and 10 m and which is overlain by a cataclastic zone whose thickness ranges from a few meters to more than 50 m, locally reaching 250 m. Between N56°54' and N57°07', the hanging-wall and footwall of the southern segment both consist of Lewisian gneiss but with different metamorphic grades. Unlike the northern segment, the southern segment is characterized by numerous pseudotachylyte-bearing thrust surfaces along which the pseudotachylyte thickness seldom exceeds 0.5 m. In summary, seismic deformation along the northern segment appears localized and is associated with significant cataclasis, whereas along the southern segment, seismic deformation is essentially distributed, with limited formation of pseudotachylyte and very little cataclasis. The segmentation likely reflects the contrasted mineralogical compositions and the texture of the rocks from the hanging-wall. The Corodale gneiss mainly consists of an assemblage of minerals (opx-cpx-gt-pl) whose friction melting susceptibilities are higher than the mineralogical assemblage of the Lewisian gneiss (qz-pl-kf- bi and minor hbl-px). Similarly, unlike the Lewisian gneiss, the Corodale gneiss is devoid of any planar fabric. These differences may account for the preferred development of cataclasites in Corodale gneiss. The segmentation is further discussed by comparison with modern earthquake ruptures.

Souquiere, F.; Fabbri, O.

2008-12-01

272

Numerical investigation of recirculation in the UTSI MHD combustor  

SciTech Connect

Numerical studies were carried out to investigate the gross structure of flow in cylindrical combustors. The combustor configurations studied are variations of a working design used at the University of Tennessee Space Institute to burn pulverized coal at temperatures in excess of 3000K for generation of a plasma feeding a magnetohydrodynamic channel. The numerical studies were conducted for an isothermal fluid; the main objective of the calculations was to study the effect of the oxidant injection pattern on the gross structure of recirculating flows within the combustor. The calculations illustrate the basic features of the flow in combustors of this type and suggest implications for the injection of coal and oxidizer in this type of combustor.

Schulz, R.J.; Lee, J.J.; Giel, T.V. Jr.

1983-09-01

273

Dynamics of microorganism populations in recirculating nutrient solutions.  

PubMed

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are root surfaces, hardware surfaces (biofilms), and solution suspension. Numbers of bacteria on root surfaces usually exceed those from the other habitats by several orders of magnitude. Gram negative bacteria dominate the microflora with fungal counts usually much lower. Trends typically show a decrease in counts with increasing time unless stressed plants increase root exudates. Important microbial activities include carbon mineralization and nitrogen transformations. Important detrimental interactions include competition with plants, and human and plant pathogenesis. PMID:11540206

Strayer, R F

1994-11-01

274

Recycling crop residues for use in recirculating hydroponic crop production.  

PubMed

As part of bioregenerative life support feasibility testing by NASA, crop residues are being used to resupply elemental nutrients to recirculating hydroponic crop production systems. Methods for recovering nutrients from crop residues have evolved from water soaking (leaching) to rapid aerobic bioreactor processing. Leaching residues recovered the majority of elements but it also recovered significant amounts of soluble organics. The high organic content of leachates was detrimental to plant growth. Aerobic bioreactor processing reduced the organic content ten-fold, which reduced or eliminated phytotoxic effects. Wheat and potato production studies were successful using effluents from reactors having with 8- to 1-day retention times. Aerobic bioreactor effluents supplied at least half of the crops elemental mass needs in these studies. Descriptions of leachate and effluent mineral content, biomass productivity, microbial activity, and nutrient budgets for potato and wheat are presented. PMID:11541570

Mackowiak, C L; Garland, J L; Sager, J C

1996-12-01

275

Dynamics of microorganism populations in recirculating nutrient solutions  

NASA Astrophysics Data System (ADS)

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are root surfaces, hardware surfaces (biofilms), and solution suspension. Numbers of bacteria on root surfaces usually exceed those from the other habitats by several orders of magnitude. Gram negative bacteria dominate the microflora with fungal counts usually much lower. Trends typically show a decrease in counts with increasing time unless stressed plants increase root exudates. Important microbial activities include carbon mineralization and nitrogen transformations. Important detrimental interactions include competition with plants, and human and plant pathogenesis.

Strayer, R. F.

1994-11-01

276

Requirements for longitudinal HOM damping in superconducting recirculating linacs  

SciTech Connect

Transverse beam breakup provides the primary current limitation in the operation of superconducting recirculating linacs and requires the significant damping of transverse-deflecting higher order modes. The need to damp the coexisting longitudinal HOMs in these nominally isochronous machines, however, is not as clear. Isochronicity implies that energy variations induced by excitation of longitudinal modes do not translate directly into position and current modulations. Such modulations, if present, could enhance the initial excitation, effectively closing a potentially unstable feedback loop. Design optimization of cavity structures may suggest that no longitudinal damping be provided. On the other hand, easing of the isochronicity requirement may provide desired flexibility in lattice design. In this note, limits are placed on the requirements for longitudinal HOM damping and on the tolerances for isochronicity which are driven by possible longitudinal multipass phenomena. 2 refs., 1 fig.

Bisognano, J.J.; Fripp, M.L.

1989-01-01

277

Experiments With Recirculating Target for F-18 Production  

NASA Astrophysics Data System (ADS)

Approximately 10 ml of O-18 water was loaded in an apparatus containing a 5 ml storage vessel, pump, silver target attached to a cyclotron, filter, backpressure regulator, conductivity meter, several valves and ion exchange cartridges. The water was continuously pumped through the target during proton bombardment at a rate 5 ml/min. Continuous irradiation with beam current ranging from 10 to 50 uA was conducted while pressure, temperature and conductivity were continuously monitored. The results indicate that recirculating of the target water can increase production of F-18 in relation to consumed O-18 water material. It can also increase productivity by eliminating idle periods for re-filling the target. A backpressure regulator can precisely control target pressure. This method also allows for continuous monitoring of the target material temperature, pressure, conductivity and accumulated radioactivity. Results of these observations provide important information about target performance and physical processes taking place inside the target.

Kiselev, M. Y.

2003-08-01

278

RECENT PROGRESS TOWARD A MUON RECIRCULATING LINEAR ACCELERATOR  

SciTech Connect

Both Neutrino Factories (NF) and Muon Colliders (MC) require very rapid acceleration due to the short lifetime of muons. After a capture and bunching section, a linac raises the energy to about 900 MeV, and is followed by one or more Recirculating Linear Accelerators (RLA), possibly followed by a Rapid Cycling Synchnotron (RCS) or Fixed-Field Alternating Gradient (FFAG) ring. A RLA reuses the expensive RF linac section for a number of passes at the price of having to deal with different energies within the same linac. Various techniques including pulsed focusing quadruopoles, beta frequency beating, and multipass arcs have been investigated via simulations to improve the performance and reduce the cost of such RLAs.

Slawomir Bogacz, Vasiliy Morozov, Yves Roblin, Kevin Beard

2012-07-01

279

Selecting materials for recirculation valves used in secondary recovery service  

SciTech Connect

It would be desirable to recommend an optimum combination of trim materials for use in recirculating valves handling seawater and/or hydrogen sulfide, but each application must be judged independently. The design engineer on each project must determine what materials will be best in the application, depending on the problem expected. Valve cavitation can be eliminated by using the proper valve for the pressures to be encountered. Then, the designer or material specifier can concentrate on selecting the best combination out of the many available materials to provide the necessary balance of resistance to corroion, erosion, and stress corrosion cracking under severe conditions. These materials selection guidelines do not guarantee the performance of valves designed according to these guidelines.

Schumacher, M.; Gossett, J.

1983-02-28

280

Momentum and heat transfer in a complex recirculating flow  

SciTech Connect

Three-dimensional and turbulent recirculating flows in enclosed spaces occur in many engineering situations. Accurate measurements of momentum- and heat-transfer characteristics are needed for direct engineering-design applications and for developments of numerical-simulation codes of these flows. A facility to generate recirculating flows driven by buoyancy and/or shear forces in a rectangular cavity was constructed to model such flows. Also, a visualization technique, involving temperature-sensitive liquid-crystal microcapsules, was developed to visualize the temperature and velocity fields simultaneously in any flow plane. Two flow cases were studied: (1) natural convection driven by buoyancy in a bottom-heated cavity, with Gr = 2.4 10/sup 7/, and (2) mixed-convection driven by shear force from a moving lid and buoyancy, with Gr = 2.4 x 10/sup 7/ and Re = 3200. In the mixed-convection case, Gr/Re/sup 2/ = 2.3, indicating that buoyancy and shear forces acting on the flow are comparable. In addition to the flow/temperature visualizations, measurements were made of velocity, temperature, and surface heat flux. Overall heat-transfer measurements were conducted for a wide range of the mixed-convection parameter, Gr/Re/sup 2/, in the cavity. Smooth transitions were found from natural convection to forced convection. The mixed convection regime was found in 0.5 < Gr/Re/sup 2/ < 80, the upper found of 80 being larger than that of flat plate data (about 10). This was probably due to heat-transfer enhancement by the TGL vortices.

Rhee, H.S.

1987-01-01

281

Quantitative investigations of the Missouri gravity low: A possible expression of a large, Late Precambrian batholith intersecting the New Madrid seismic zone  

USGS Publications Warehouse

Analysis of gravity and magnetic anomaly data helps characterize the geometry and physical properties of the source of the Missouri gravity low, an important cratonic feature of substantial width (about 125 km) and length (> 600 km). Filtered anomaly maps show that this prominent feature extends NW from the Reelfoot rift to the Midcontinent Rift System. Geologic reasoning and the simultaneous inversion of the gravity and magnetic data lead to an interpretation that the gravity anomaly reflects an upper crustal, 11-km-thick batholith with either near vertical or outward dipping boundaries. Considering the modeled characteristics of the batholith, structural fabric of Missouri, and relations of the batholith with plutons and regions of alteration, a tectonic model for the formation of the batholith is proposed. The model includes a mantle plume that heated the crust during Late Precambrian and melted portions of lower and middle crust, from which the low-density granitic rocks forming the batholith were partly derived. The batholith, called the Missouri batholith, may be currently related to the release of seismic energy in the New Madrid seismic zone (earthquake concentrations occur at the intersection of the Missouri batholith and the New Madrid seismic zone). Three qualitative mechanical models are suggested to explain this relationship with seismicity. Copyright 1996 by the American Geophysical Union.

Hildenbrand, T. G.; Griscom, A.; Van Schmus, W. R.; Stuart, W. D.

1996-01-01

282

Lycos Zone  

NSDL National Science Digital Library

In the tradition of Yahooligans (reviewed in the March 22, 1996 Scout Report) and other so-called "green spaces," Lycos has created a new online safe haven for young users which is fairly self-contained, with the exception of the advertisements. (In response to criticisms regarding aggressive marketing to children at similar sites, Lycos claims that the ads are clearly marked and will not collect any personal information.) The site is composed of four sections: the Fun and Games Zone, the Homework Zone, the New and Cool Zone, and an area for parents and teachers. The first two sections are fairly deep, with numerous resources and activities aimed at various age levels. Some links in the Homework Zone lead users outside the site, but they are first presented with a gateway page informing them that they are leaving and offering advice on not divulging personal information.

283

Apparatus for controlling recirculated exhaust gas quantities in self-igniting internal combustion engines  

SciTech Connect

An apparatus is described for controlling recirculated exhaust gas quantities in self-igniting internal combustion engines which have a fuel injection pump. Two parameters, the rpm (preferably via the rpm-dependent suction chamber pressure) and the position of the quantity-adjusting device, are obtained from the fuel injection pump and delivered to a performance-graph memory in which a control value for the recirculated exhaust gas quantity is stored in accordance with these parameters. A recirculated exhaust gas quantity control device is actuated in accordance with the recalled control value.

Eheim, F.

1982-06-08

284

Design of a computerized, temperature-controlled, recirculating aquaria system  

USGS Publications Warehouse

We built a recirculating aquaria system with computerized temperature control to maintain static temperatures, increase temperatures 1 ??C/day, and maintain diel temperature fluctuations up to 10 ??C. A LabVIEW program compared the temperature recorded by thermocouples in fish tanks to a desired set temperature and then calculated the amount of hot or cold water to add to tanks to reach or maintain the desired temperature. Intellifaucet?? three-way mixing valves controlled temperature of the input water and ensured that all fish tanks had the same turnover rate. The system was analyzed over a period of 50 days and was fully functional for 96% of that time. Six different temperature treatments were run simultaneously in 18, 72 L fish tanks and temperatures stayed within 0.5 ??C of set temperature. We used the system to determine the upper temperature tolerance of fishes, but it could be used in aquaculture, ecological studies, or other aquatic work where temperature control is required. ?? 2005 Elsevier B.V. All rights reserved.

Widmer, A. M.; Carveth, C. J.; Keffler, J. W.; Bonar, S. A.

2006-01-01

285

Energy utilization and recirculation of currant-finishing wastewater.  

PubMed

In this study, a new method for the treatment of currant-finishing wastewater was proposed in the context of the "clean technology" concept. This method consisted of two stages. In the first stage, the currant-finishing wastewater was recirculated in the currant-wash process and in the second stage this wastewater was utilized for the production of energy through anaerobic digestion. Recycling ratios from 0 to 95% were examined. By increasing the recycling ratio, effluent's COD increased from 3808 to 43,722mg/l, effluent's BOD from 681 to 5378mg/l, total sugars from 2.57 to 42.13g/l, total phosphorous from 0.79 to 5.14mg/l and total Kjeldahl nitrogen from 7.36 to 51.9mg/l while fresh water addition decreased from 6 to 0.3kg per kg of currants processed. The optimum recycling ratio range for the wastewater energy utilization proved to be 30-40%. In this range, the mass of COD and sugars digested was maximized resulting in the highest biogas production. Thus, the proposed system could be promising since water consumption is minimized and wastewater energy utilization is achieved rendering the process almost energetically self-sufficient. PMID:17316987

Vlyssides, A G; Barampouti, E M P; Mai, S T

2007-01-18

286

Recent advances in AMTEC recirculating test cell performance  

NASA Astrophysics Data System (ADS)

The alkali metal thermal to electric converter (AMTEC) is an electrochemical device for the direct conversion of thermal energy to electrical energy with efficiencies potentially near Carnot. The future usefulness of AMTEC for space power conversion depends on the efficiency of the devices. Systems studies have projected from 15% to 35% thermal to electric conversion efficiencies, and one experiment has demonstrated 19% efficiency for a short period of time. A recent experiment in a recirculating test cell (RCT) has demonstrated sustained conversion efficiencies as high as 13.2%. The cell was operated at lower current and 12% efficiency for over 1700 hours at the time of this writing. The cell required a maturation period of 355 hours at high temperature. During this period, the cell was operated once at 12% efficiency but was generally operated at lower powers. The maturation period ended with the formation of a reflective sodium film on the condenser surface which reduced the parasitic thermal losses in the cell. After maturation, the cell demonstrated the first experimental demonstration of the maximum efficiency occuring at a lower current than the maximum power. The cell also demonstrated an unexpected decrease in parasitic loss with increasing cell current. The decrease in parasitic loss resulted from the development of a more reflective sodium film at higher sodium fluxes.

Underwood, Mark L.; Williams, Roger M.; Ryan, Margaret A.; Jeffries-Nakamura, Barbara; O'Connor, Dennis

1993-01-01

287

Franchise Zone  

NSDL National Science Digital Library

Entrepreneur.com's new service, Franchise Zone, claims to be the "Online Franchise Authority." Featured on the site is Franchise Zone's collection of over 900 franchise opportunities, ranging from financial services to pet businesses. Browseable by name of company as well as by company sector, each franchise is described in detail, including its products or services, company background, costs and fees, number of national and international units, and corporate information. The site also offers news and advice for those looking to buy into a franchise including news-making franchises, the Entrepreneur's Guide to Franchising, an expert advice column, and interactive discussions.

288

Cooling Tower Recirculation as Influenced by the Local Atmospheric Flow Field, a Numerical Study.  

National Technical Information Service (NTIS)

A survey of the literature shows that existing methods of numerically modeling cooling tower plume recirculation ignore the aerodynamic effects of the atmospheric flow over the cooling tower. This investigation describes a method of numerically modeling c...

B. R. Becker

1979-01-01

289

Combining dialysate and blood recirculation to boost uremic toxin removal: theory and simulation study.  

PubMed

Emerging concepts in renal replacement therapies such as daily hemodialysis (HD) and wearable artificial kidney (WAK) meet the challenges derived from the aging of renal disease population. The successful results of blood recirculation to improve the dialysis clearance of medium-high uremic toxins suggest that this technique could be used both in daily HD and WAK. However, blood recirculation induces a reduction of small solutes clearance. This work analyzes the ability of a nonregenerated recirculating dialysate technique to avoid that reduction. The study uses in silico simulations with in vitro data from several commercial dialyzers and very compact dialyzer models derived from them. The resulting combined optimization system (recirculating blood-dialysate system [RBDS]) reached low solute dialysance improvements above 100% in different scenarios. Our outcomes show the RBDS performs best with very compact dialyzers, in agreement with the requirements of daily HD and WAK. PMID:17924986

Prado, Manuel; Roa, Laura

2007-10-08

290

TO RATING FIXED-FILM BIOFILTERS USED IN RECIRCULATING AQUACULTURE SYSTEMS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A standardized methodology for evaluating and rating biofilters is proposed to simplify design of recirculating systems. This methodology will allow engineers to compare biofilters options and accurately predict performance before construction. The methodology is based upon an increasing recognized ...

291

High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays  

SciTech Connect

Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.

Jovanovic, I; Shverdin, M; Gibson, D; Brown, C

2007-04-17

292

Leachate Recirculation at the Nanticoke Sanitary Landfill Using a Bioreactor Trench.  

National Technical Information Service (NTIS)

A one-year landfill leachate recirculation demonstration project was conducted in a 20-acre cell at the Broome County, NY, Nanticoke Landfill using a retrofit bioreactor trench design concept to introduce landfill leachate to the surrounding refuse mass. ...

J. J. Pagano R. J. Scrudato G. M. Sumner

1998-01-01

293

Solvent extraction in a static bed with solvent recirculation and longitudinal mixing  

NASA Astrophysics Data System (ADS)

A numerical solution has been obtained for extraction from a static bed with solvent recirculation, where allowance is made for the longitudinal mixing and for the variable mass-transfer coefficient in the solid.

Minchev, A.; Penchev, I.; Tsibranska, I.

1986-10-01

294

DEVELOPMENT OF A NOVEL STRATEGY FOR CLEARING FISH PATHOGENS FROM RECIRCULATING AQUACULTURE SYSTEMS USING BACTERIOPHAGE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biosecurity is more easily managed in environmentally controlled recirculating aquaculture systems (RAS) facilities. However, pathogenic organisms still invade systems and result in significant losses. Current RAS disinfection strategies include delivering medicated feeds to culture animals, incre...

295

Comparison of recirculation configurations for biological nutrient removal in a membrane bioreactor.  

PubMed

A 12-L lab-scale membrane bioreactor (MBR), consisting of an anaerobic and anoxic compartment followed by an oxic plate-frame membrane compartment, was evaluated for carbonaceous and nutrient removals by varying the recirculation of mixed liquor and permeate. The hydraulic retention times (HRTs) for the anaerobic, anoxic, and oxic compartments were 2, 2, and 8h, respectively. The solids residence time (SRT) for the oxic compartment was 25 days. Five different recirculation configurations were tested by recirculating mixed liquor and/or permeate recirculation equal to the influent flow rate (identified as 100%) into different locations of the anaerobic and anoxic compartments. Of the five configurations, the configuration with 100% mixed liquor recirculation to the anaerobic compartment and 100% permeate recirculation to the anoxic compartment gave the highest percentage removal with an average 92.3+/-0.5% soluble chemical oxygen demand (sCOD), 75.6+/-0.4% total nitrogen (TN), and 62.4+/-1.3% total phosphorus (TP) removal. When the mixed liquor and permeate recirculation rates were varied for the same configuration, the highest TP removal was obtained for 300% mixed liquor recirculation and 100% permeate recirculation (300%/100%) with a TP removal of 88.1+/-1.3% while the highest TN removal (90.3+/-0.3%) was obtained for 200%/300% recirculation. TN and TP concentrations as low as 4.2+/-0.1 and 1.4+/-0.2mg/L respectively were obtained. Mass loading rates were generally low in the range of 0.11-0.22kgCOD/kgMLSS/d due to high biomass concentrations within the oxic reactor (approx. 8000mg/L). The BioWin model was calibrated against one set of the experimental data and was found to predict the experimental data of effluent TN, TP, and NO(3)(-)-N but over-predicted sCOD and NH(3)-N for various recirculation rates. The anoxic heterotrophic yield for the calibrated model was 0.2kg biomass COD/kg COD utilized while the maximum growth rates were found to be 0.45day(-1) for mu(max-autotroph), 3.2day(-1) for mu(max-heterotroph), and 1.5day(-1) for mu(max-PAO). PMID:17991508

Bekir Ersu, Cagatayhan; Ong, Say Kee; Arslankaya, Ertan; Brown, Patrick

2007-10-18

296

Large Pore Ion and Metabolite-Permeable Channel Regulation of Postnatal Ventricular Zone Neural Stem and Progenitor Cells: Interplay between Aquaporins, Connexins, and Pannexins?  

PubMed Central

The birth of new neurons from unspecialized neural stem and progenitor cells surrounding the lateral ventricles occurs throughout postnatal life. This process, termed neurogenesis, is complex and multistepped, encompassing several types of cellular behaviours, such as proliferation, differentiation, and migration. These behaviours are influenced by numerous factors present in the unique, permissive microenvironment. A major cellular mechanism for sensing the plethora of environmental cues directing this process is the presence of different channel forming proteins spanning the plasma membrane. So-called large pore membrane channels, which are selective for the passage of specific types of small molecules and ions, are emerging as an important subgroup of channel proteins. Here, we focus on the roles of three such large pore channels, aquaporin 4, connexin 43, and pannexin 1. We highlight both their independent functions as well as the accumulating evidence for crosstalk between them.

Wicki-Stordeur, Leigh E.; Swayne, Leigh Anne

2012-01-01

297

A Model for Large-Amplitude Internal Solitary Waves with Trapped Cores  

NASA Astrophysics Data System (ADS)

Large-amplitude internal solitary waves in continuously stratified systems can be found by solution of the Dubreil-Jacotin-Long (DJL) equation. For finite ambient density gradients at the surface (bottom) for waves of depression (elevation) these solutions may develop recirculating cores above a critical phase speed (or amplitude). The critical point is defined by incipient overturning where the surface (bottom) velocity above (below) the crest equals the phase speed. Within the recirculation zone the fluid density is outside the ambient range, is statically unstable, and thus unphysical. This situation is rectified by reformulating the problem once incipient overturning appears. A finite core of uniform density and velocity, but unknown shape, is assumed. The density is arbitrary, but generally should be equal to that of the separating streamline via the Prandtl-Batchelor theorem. The core velocity is set equal to the phase speed (plug flow). A pressure matching condition is invoked at the core boundary and the exterior flow satisfies the DJL equation. Simultaneous numerical solution of the DJL equation and the core condition results in the exterior flow and the core height, length, and shape. Properties of the model solutions are discussed as are numerical solutions of the time-dependent, nonhydrostatic equations with the model solutions as initial conditions.

Helfrich, K. R.; White, B. L.

2008-12-01

298

Biologically Plausible Error-Driven Learning Using Local Activation Differences: The Generalized Recirculation Algorithm  

Microsoft Academic Search

The error backpropagation learning algorithm (BP) is generally considered biologically implausible because it does not use locally available, activation-based variables. A version of BP that can be computed locally using bidirectional activation recirculation (Hinton and McClelland 1988) instead of backpropagated error derivatives is more biologically plausible. This paper presents a generalized version of the recirculation algorithm (GeneRec), which overcomes several

Randall C. O'Reilly

1996-01-01

299

Picosecond Pulse Recirculation for High Average Brightness Thomson Scattering-based Gamma-ray Sources  

SciTech Connect

Pulse recirculation has been successfully demonstrated with the interaction laser system of LLNL's Thomson-Radiated Extreme X-ray (T-REX) source. The recirculation increased twenty-eight times the intensity of the light coming out of the laser system, demonstrating the capability of increasing the gamma-ray flux emitted by T-REX. The technical approach demonstrated could conceivably increase the average gamma-ray flux output by up to a hundred times.

Semenov, V

2009-05-28

300

Stress fields during the evolution of large-scale strike-slip systems and tectonic slivers, Atacama Fault Zone, northern Chile  

Microsoft Academic Search

Tectonic evolution of crustal slivers generated during oblique subduction involves a series of translations and rotations. Slivers are defined by large-scale strike-slip faults, whereas internal blocks are by the faulting pattern related to the fault system. Translations and rotations are then likely to accommodate the internal deformation caused by external forces. The Atacama Fault System (AFS), a crustal-scale strike-slip fault

E. E. Veloso; R. Gomila

2009-01-01

301

Enhanced leachate recirculation and stabilization in a pilot landfill bioreactor in Taiwan.  

PubMed

This study focused on the treatment of municipal solid waste (MSW) by modification and recirculation of leachate from a simulated landfill bioreactor. Hydrogen peroxide was added to recirculated leachate to maintain a constant oxygen concentration as the leachate passed again through the simulated landfill bioreactor. The results showed that leachate recirculation increased the dissolved oxygen concentration in the test landfill bioreactor. Over a period of 405 days, the biochemical oxygen demand (BOD(5)) in the collected leachate reduced by 99.7%, whereas the chemical oxygen demand (COD) reduced by 96%. The BOD(5)/COD ratio at the initial stage of 0.9 improved to 0.09 under aerobic conditions (leachate recirculation with added hydrogen peroxide) compared with the anaerobic test cell 0.11 (leachate recirculation alone without hydrogen peroxide). The pH increased from 5.5 to 7.6, and the degradation rate of organic carbon was 93%. Leachate recirculation brings about the biodegradation of MSW comparatively faster than the conventional landfill operation. The addition of a constant concentration of hydrogen peroxide was found to further increase the biodegradation. This increased biodegradation rate ultimately enables an MSW landfill to reach a stable state sooner and free up the land for further reuse. PMID:22767874

Huang, Fu-Shih; Hung, Jui-Min; Lu, Chih-Jen

2012-07-05

302

Temporal and spatial pore water pressure distribution surrounding a vertical landfill leachate recirculation well.  

PubMed

Addition of liquids into landfilled waste can result in an increase in pore water pressure, and this in turn may increase concerns with respect to geotechnical stability of the landfilled waste mass. While the impact of vertical well leachate recirculation on landfill pore water pressures has been mathematically modeled, measurements of these systems in operating landfills have not been reported. Pressure readings from vibrating wire piezometers placed in the waste surrounding a liquids addition well at a full-scale operating landfill in Florida were recorded over a 2-year period. Prior to the addition of liquids, measured pore pressures were found to increase with landfill depth, an indication of gas pressure increase and decreasing waste permeability with depth. When liquid addition commenced, piezometers located closer to either the leachate injection well or the landfill surface responded more rapidly to leachate addition relative to those far from the well and those at deeper locations. After liquid addition stopped, measured pore pressures did not immediately drop, but slowly decreased with time. Despite the large pressures present at the bottom of the liquid addition well, much smaller pressures were measured in the surrounding waste. The spatial variation of the pressures recorded in this study suggests that waste permeability is anisotropic and decreases with depth. PMID:21655145

Kadambala, Ravi; Townsend, Timothy G; Jain, Pradeep; Singh, Karamjit

2011-05-24

303

Advanced Horizontal Well Recirculation Systems for Geothermal Energy Recovery in Sedimentary Formations  

SciTech Connect

There is increased recognition that geothermal energy resources are more widespread than previously thought, with potential for providing a significant amount of sustainable clean energy worldwide. Recent advances in drilling, completion, and production technology from the oil and gas industry can now be applied to unlock vast new geothermal resources, with some estimates for potential electricity generation from geothermal energy now on the order of 2 million megawatts. Terralog USA, in collaboration with the University of California, Irvine (UCI), are currently investigating advanced design concepts for paired horizontal well recirculation systems, optimally configured for geothermal energy recovery in permeable sedimentary and crystalline formations of varying structure and material properties. This two-year research project, funded by the US Department of Energy, includes combined efforts for: 1) Resource characterization; 2) Small and large scale laboratory investigations; 3) Numerical simulation at both the laboratory and field scale; and 4) Engineering feasibility studies and economic evaluations. The research project is currently in its early stages. This paper summarizes our technical approach and preliminary findings related to potential resources, small-scale laboratory simulation, and supporting numerical simulation efforts.

Mike Bruno; Russell L. Detwiler; Kang Lao; Vahid Serajian; Jean Elkhoury; Julia Diessl; Nicky White

2012-09-30

304

Kink zone localization, structurally-controlled instability, and large-scale rock slope failure at the Mt. Gorsa porphyry quarry (Trentino, Italy)  

NASA Astrophysics Data System (ADS)

Rock slope failure is controlled by rock mass strength and anisotropy, and by slope-scale persistent fractures with different spacing, eventually resulting in complex mechanisms as large-scale flexural toppling, block toppling, and kink band slumping. Despite these mechanisms have been studied, their interplay in large rock slope failure is often difficult to ascertain in complex geological settings. We studied the 250 m high porphyry quarry slopes of Mt. Gorsa (Trentino, Italy). Two slopes facing to N and E are carved in Permian rhyolithic ignimbrites, providing spectacular exposures of the inherited geological structure. Despite the strong intact rock, rock mass has a complex structure due to the occurrence of thermal cooling joints, persistent tectonic fractures, and joint sets. Evidence of ongoing displacement of the northern quarry face in 2003 motivated geotechnical and geophysical site investigation, and the initiation of displacement monitoring activities. GB-InSAR measurements using a LiSALab system captured large-scale slope dilation involving 400.000 m3. Further GB-InSAR measurements have been carried out since 2010. In order to understand the mechanisms governing large-scale deformation and failure of the northern slope, we carried out a comprehensive field and modelling study exploiting terrestrial photo mapping, field structural analysis and discontinuity surveys at different locations. On the northern face, 190 Geological Strength Index (GSI) surveys along benches, DEM structural analysis (COLTOP3D), and analysis of GB-InSAR data were carried out, and relationships among rock mass quality, 2003 landslide extent, and measured displacements established. Data show that slope instability is locally constrained by close and persistent cooling joints steeply dipping to the south (K1), persistent fault surfaces moderately dipping to the NNW (K2), and joint sets steeply dipping to NE and WNW (K3 and K4). NNW-dipping, top-to-N kink bands up to 2m wide also occur at depth and are exposed on the eastern slope. Close to the northern quarry face, structurally-controlled instabilities (sliding, flexural toppling, block toppling) occur inside individual kinematic domains ranging from tens to thousands cubic meters, leading to significant rock mass degradation (GSI < 35-40) and to disintegrated and weathered rock masses in areas undergoing largest displacements. We investigated the links between local structurally-controlled failure and large-scale rock slope failure using different Finite-Element modelling approaches implemented in the softwares Phase2 v.8 (Rocscience Inc.) and ELFEN (Rockfield Inc.). Performed modelling tasks include: continuum models (Phase, ELFEN), continuum-based jointed rock models (Phase), and hybrid continuum-discrete models (ELFEN). A continuum-based SSR (Shear Strength reduction) back-analysis of the 2003 instability, calibrated on landslide geometry and GB-InSAR displacements, shows that reduced rock mass properties (GSI < 35-40) observed where local-scale structurally-controlled instability occurs, were a pre-requisite for the 2003 global slope instability. Jointed rock and hybrid models suggest that slope excavation results in shear strain localisation along inherited fault surfaces and newly-formed kink bands at different depths. At depths less than some tens of meters, these interact with K1 resulting in step-path failure surfaces, sliding and toppling. Globally, these processes result in dilation and rock mass damage, which in turn promote the required conditions for global slope failure.

Agliardi, F.; Crosta, G. B.; Meloni, F.; Valle, C.; Rivolta, C.; Leva, D.

2012-04-01

305

Constructed wetlands as recirculation filters in large-scale shrimp aquaculture  

Microsoft Academic Search

Effluent waters from shrimp aquaculture, which can contain elevated levels of phosphorus, ammonia, nitrate, and organics, must be managed properly if shrimp aquaculture is to achieve sustainability. Constructed wetlands are ecologically beneficial, low cost treatment alternatives proven capable of reducing suspended solids, biochemical oxygen demand (BOD), nitrogen, phosphorus and heavy metals from wastewater of many sources. The goal of this

David Rogers Tilley; Harish Badrinarayanan; Ronald Rosati; Jiho Son

2002-01-01

306

All currently used measurements of recirculation in blood access by chemical methods are flawed due to intradialytic disequilibrium or recirculation at low flow  

Microsoft Academic Search

Blood flows and recirculations with standard and reversed direction of lines were measured by chemical (urea and creatinine) and ultrasound dilution (saline) methods in 47 chronic hemodialysis patients. Thirty- seven patients had 47 dual-lumen, central vein (CV) catheters: 32 were PermCath (Quinton Instruments Company, Seattle, WA), 6 were Access Cath (MEDCOMP, Harleysville, PA), 3 were Soft Cell PC (Vas Cath,

ZJ Twardowski; JC Van Stone; JD Haynie

1998-01-01

307

Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre  

NASA Astrophysics Data System (ADS)

Data from the Kuroshio Extension Observatory (KEO) surface mooring are used to analyze the balance of processes affecting the upper ocean heat content and surface mixed layer temperature variations in the Recirculation Gyre (RG) south of the Kuroshio Extension (KE). Cold and dry air blowing across the KE and its warm RG during winter cause very large heat fluxes out of the ocean that result in the erosion of the seasonal thermocline in the RG. Some of this heat is replenished through horizontal heat advection, which may enable the seasonal thermocline to begin restratifying while the net surface heat flux is still acting to cool the upper ocean. Once the surface heat flux begins warming the ocean, restratification occurs rapidly due to the low thermal inertia of the shallow mixed layer depth. Enhanced diffusive mixing below the mixed layer tends to transfer some of the mixed layer heat downward, eroding and potentially modifying sequestered subtropical mode water and even the deeper waters of the main thermocline during winter. Diffusivity at the base of the mixed layer, estimated from the residual of the mixed layer temperature balance, is roughly 3×10-4 m2/s during the summer and up to two orders of magnitude larger during winter. The enhanced diffusivities appear to be due to large inertial shear generated by wind events associated with winter storms and summer tropical cyclones. The diffusivity's seasonality is likely due to seasonal variations in stratification just below the mixed layer depth, which is large during the summer when the seasonal thermocline is fully developed and low during the winter when the mixed layer extends to the top of the thermocline.

Cronin, Meghan F.; Bond, Nicholas A.; Thomas Farrar, J.; Ichikawa, Hiroshi; Jayne, Steven R.; Kawai, Yoshimi; Konda, Masanori; Qiu, Bo; Rainville, Luc; Tomita, Hiroyuki

2013-01-01

308

Earthquake hazards on the cascadia subduction zone  

Microsoft Academic Search

Large subduction earthquakes on the Cascadia subduction zone pose a potential seismic hazard. Very young oceanic lithosphere (10 million years old) is being subducted beneath North America at a rate of approximately 4 centimeters per year. The Cascadia subduction zone shares many characteristics with subduction zones in southern Chile, southwestern Japan, and Colombia, where comparably young oceanic lithosphere is also

T. H. Heaton; S. H. Hartzell

1987-01-01

309

Electron recirculation in electrostatic multicusp systems: II. System performance scaling of one-dimensional rollover wells  

SciTech Connect

In an earlier paper a comprehensive study was made of the recirculation and losses of electrons in their flow through simple inverse power-law potential wells bounded by similarly inverse power-law dependent magnetic fields. This study examined electron flow and loss behavior in the simplest approximation invoked to describe Polywell confinement systems. The importance of this study, and of the present paper, is that the power balance in Polywell systems is determined entirely by the rate of electron losses; if these are large, then the system can not yield net power. Thus it is of interest to determine those conditions that results in small losses, and to design experiments and systems to attempt to achieve and operate at these most favorable conditions, in order to test and prove the efficacy of the system for the generation of net power from fusion reactions. The outline and summary of this problem presented is generally repeated here, with some modifications to clarify particular physics issues of most concern, in order to avoid having to refer to the earlier document for this general description. As noted, a large body of work has been undertaken over the past 35 or so years in the study of general cusp confinement of plasmas. Nearly all of this has examined single particle electron (or ion) motion or the motion of particles in neutral plasmas within cusped magnetic systems, generally without internal electric potential fields.**INVALID KEYWORDS: controlled nuclear fusion, electron flux, plasma devices, confinement, performance, engineering, scaling factor, multicusp systems, polywell systems

Bussard, R.W.; King, K.E.

1992-01-01

310

Low NOx Combustion of DME by Means of Flue Gas Recirculation  

NASA Astrophysics Data System (ADS)

This study focuses on the fundamental characteristics of DME (Dimethyl Ether) combustion aiming at development of low-NOx combustion technology with flue gas recirculation, FGR. The flue gas is recirculated into the combustion chamber to reduce the oxygen concentration and to suppress the combustion gas temperature, so that NOx emission is significantly reduced. The fuel gas recirculation at high mixing ratio, however, may lead to unstable combustion of conventional fuels, methane or city gas. On the other hand, DME has very high potential of applicability for the flue gas recirculation even at high mixing ratio because of its high burning velocity and low ignition temperature. Combustion tests were conducted with laboratory-scale 11kW combustor. The maximum FGR ratio is 85% at the initial air ratio of 1.5 with preheated diluted air about 600K. The NOx emission reduced to 13ppm at 0%-O2, which corresponds to about 9% of NOx emission at FGR=0%. The stable combustion is sustained even in the low oxygen concentration by preheating diluted-air up to near the auto-ignition temperature of DME. Finally, the effect of the flue gas recirculation on the NOx and CO emission is discussed with reference to the industrial-scale water-tube boilers.

Matsumoto, Ryosuke; Ozawa, Mamoru; Terada, Shinya; Iio, Takenori

311

Large eddy simulation of the unsteady flow-field in an idealized human mouth-throat configuration.  

PubMed

The present study concerns the simulation and analysis of the flow field in the upper human respiratory system in order to gain an improved understanding of the complex flow field with respect to the process affecting drug delivery for medical treatment of the human air system. For this purpose, large eddy simulation (LES) is chosen because of its powerful performance in the transitional range of laminar and turbulent flow fields. The average gas velocity in a constricted tube is compared with experimental data (Ahmed and Giddens, 1983) and numerical data from Reynolds-averaged Navier-Stokes (RANS) equations coupled with low Reynolds number (LRN) ?-? model (Zhang and Kleinstreuer, 2003) and LRN shear-stress transport ?-? model (Jayaraju et al., 2007), for model validation. The present study emphasizes on the instantaneous flow field, where the simulations capture different scales of secondary vortices in different flow zones including recirculation zones, the laryngeal jet zone, the mixing zone, and the wall shear layer. It is observed that the laryngeal jet tail breaks up, and the unsteady motion of laryngeal jet is coupled with the unsteady distribution of secondary vortices in the jet boundary. The present results show that it is essential to study the unsteady flow field since it strongly affects the particle flow in the human upper respiratory system associated with drug delivery for medical treatment. PMID:21937045

Cui, X G; Gutheil, E

2011-09-19

312

Field evaluation of a horizontal well recirculation system for groundwater treatment: Field demonstration at X-701B Portsmouth Gaseous Diffusion Plant, Piketon, Ohio  

SciTech Connect

This report describes the field-scale demonstration performed as part of the project, In Situ Treatment of Mixed Contaminants in Groundwater. This project was a 3{1/2} year effort comprised of laboratory work performed at Oak Ridge National Laboratory and fieldwork performed at the US Department of Energy (DOE) Portsmouth Gaseous Diffusion Plant (PORTS). The overall goal of the project was to evaluate in situ treatment of groundwater using horizontal recirculation coupled with treatment modules. Specifically, horizontal recirculation was tested because of its application to thin, interbedded aquifer zones. Mixed contaminants were targeted because of their prominence at DOE sites and because they cannot be treated with conventional methods. The project involved several research elements, including treatment process evaluation, hydrodynamic flow and transport modeling, pilot testing at an uncontaminated site, and full-scale testing at a contaminated site. This report presents the results of the work at the contaminated site, X-701B at PORTS. Groundwater contamination at X-701B consists of trichloroethene (TCE) (concentrations up to 1800 mg/L) and technetium-998 (Tc{sup 99}) (activities up to 926 pCi/L).

Korte, N.; Muck, M.; Kearl, P.; Siegrist, R.; Schlosser, R.; Zutman, J. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); Houk, T. [Lockheed Martin Energy Systems, Piketon, OH (United States). Portsmouth Gaseous Diffusion Plant] [Lockheed Martin Energy Systems, Piketon, OH (United States). Portsmouth Gaseous Diffusion Plant

1998-08-01

313

Distributed model of solid waste anaerobic digestion: effects of leachate recirculation and pH adjustment.  

PubMed

A distributed model of solid waste digestion in a 1-D bioreactor with leachate recirculation and pH adjustment was developed to analyze the balance between the rates of polymer hydrolysis/acidogenesis and methanogenesis during the anaerobic digestion of municipal solid waste (MSW). The model was calibrated on previously published experimental data generated in 2-L reactors filled with shredded refuse and operated with leachate recirculation and neutralization. Based on model simulations, both waste degradation and methane production were stimulated when inhibition was prevented rapidly from the start, throughout the reactor volume, by leachate recirculation and neutralization. An optimal strategy to reduce the time needed for solid waste digestion is discussed. PMID:12432582

Vavilin, Vasily A; Rytov, Sergey V; Lokshina, Ljudmila Ya; Pavlostathis, Spyros G; Barlaz, Morton A

2003-01-01

314

Apparatus for controlling an exhaust recirculation device in internal combustion engines  

SciTech Connect

An apparatus is proposed for controlling an exhaust recirculation device in internal combustion engines, in which a throttle device in an exhaust recirculation line is opened on the condition that the position of the load-adjusting lever of a fuel injection pump associated with the engine falls below a maximum load position and that the adjusting member of an rpm governor of the fuel injection pump is below a predetermined deflection position and/or is operated above a lower rpm value. With an embodiment of this kind, the control of exhaust recirculation quantities can be performed in a simple and functionally reliable manner for the various operational points of the engine with the greatest possible approximation of the permissible values.

Greiner, M.; Krieger, K.; Schiller, G.; Walk, W.; Walz, L.

1983-02-15

315

Monte Carlo simulation of energization of Jovian trapped electrons by recirculation  

NASA Astrophysics Data System (ADS)

The recirculation model for particle acceleration in the Jovian magnetosphere is studied by means of Monte Carlo simulation. The recirculation model combines the conventional radial and pitch angle diffusion processes with the essentially energy-conserving latitudinal diffusion in low altitudes and the pitch angle scattering in the plasma disk. This process has been proposed to explain the pitch angle and spectral characteristics of MeV electrons observed by Pioneer in the Jovian magnetosphere. The simulation confirms that the dumbbell-type anisotropy and the high-energy tail of the energy spectrum can be produced from the recirculation process if the rate of the low-altitude cross-L diffusion is comparable to that of the conventional radial diffusion.

Fujimoto, M.; Nishida, A.

1990-04-01

316

Recirculation Gyres In The Labrador Sea and Their Influence On Deep Convection  

NASA Astrophysics Data System (ADS)

Recent observations in the Labrador and Irminger Seas have revealed energetic, weakly sheared cyclonic recirculation gyres just offshore of the boundary currents that flow around the subpolar North Atlantic. The data suggest that these features, which dominate the circulation in the interior of the Labrador and Irminger Seas, play an active role in isolating deep convection. The driving mechanism for these recircula- tion gyres and their influence on the formation and circulation of water masses within the Labrador and Irminger Seas are the main subjects of this study. To investigate these issues, a regional numerical model of the area of interest is used, which is idealized but designed to retain the essential features of the Labrador and Irminger Seas. The recirculation gyres appear to be predominantly forced by intense cyclonic wind events that develop along the east coast of Greenland during winter. The resulting oceanic response is a so-called beta-plume: an elongated cyclonic gyre that follows the topography around Greenland and into the Labrador Sea. Recirculations develop in the Irminger and Labrador Seas, in crude agreement with the observations. Despite the strong seasonality of the forcing the circulation persists year-round, as a consequence of slow Rossby-wave adjustment and interaction with the continental slope. Having established a plausible forcing mechanism for the recirculation gyres, we sub- sequently incorporate buoyancy forcing to investigate the influence of the recirculation gyres on deep convection. Key features of the recirculations that may result in favor- able conditions for localized deep convection, like the trapping of water masses and preconditioning of the stratification, are addressed.

Spall, M. A.; Katsman, C. A.; Pickart, R. S.

317

The impact of recirculation, ventilation and filters on secondary organic aerosols generated by indoor chemistry  

NASA Astrophysics Data System (ADS)

This study examined the impact of recirculation rates (7 and 14 h -1), ventilation rates (1 and 2 h -1), and filtration on secondary organic aerosols (SOAs) generated by ozone of outdoor origin reacting with limonene of indoor origin. Experiments were conducted within a recirculating air handling system that serviced an unoccupied, 236 m 3 environmental chamber configured to simulate an office; either no filter, a new filter or a used filter was located downstream of where outdoor air mixed with return air. For otherwise comparable conditions, the SOA number and mass concentrations at a recirculation rate of 14 h -1 were significantly smaller than at a recirculation rate of 7 h -1. This was due primarily to lower ozone concentrations, resulting from increased surface removal, at the higher recirculation rate. Increased ventilation increased outdoor-to-indoor transport of ozone, but this was more than offset by the increased dilution of SOA derived from ozone-initiated chemistry. The presence of a particle filter (new or used) strikingly lowered SOA number and mass concentrations compared with conditions when no filter was present. Even though the particle filter in this study had only 35% single-pass removal efficiency for 100 nm particles, filtration efficiency was greatly amplified by recirculation. SOA particle levels were reduced to an even greater extent when an activated carbon filter was in the system, due to ozone removal by the carbon filter. These findings improve our understanding of the influence of commonly employed energy saving procedures on occupant exposures to ozone and ozone-derived SOA.

Fadeyi, M. O.; Weschler, C. J.; Tham, K. W.

318

Water recirculation and good management: potential methods to avoid disease outbreaks with Flavobacterium psychrophilum.  

PubMed

Flavobacterium psychrophilum infections cause high mortality among rainbow trout, Oncorhynchus mykiss, fry in Danish fish farms and hatcheries. Hatcheries based entirely on bore-hole water recirculation systems have been suggested as a possibility for eliminating F. psychrophilum or at least keeping the amount of this bacterium low. The occurrence of the bacterium in a bore-hole water recirculation system was compared with a combined bore-hole water and stream water flow-through system in a hatchery where outbreaks of rainbow trout fry syndrome caused by F. psychrophilum often occurred. Broodfish, unfertilized and fertilized eggs, eyed eggs and fry, as well as water samples from the tanks/troughs with broodfish/fry, were examined. Suspect yellow bacterial colonies were either confirmed or rejected as F. psychrophilum by growth characteristics and by PCR. As both virulent and less virulent F. psychrophilum isolates are known, isolates were characterized. The isolates were ribotyped and grouped according to ribotyping patterns. Representatives of the groups were serotyped. Fry isolates were very homogeneous whereas isolates from broodfish were heterogeneous, whether the isolates originated from external surfaces of the fish (mucus from skin and gills, haemorrhages and ulcers) or internal organs. Flavobacterium psychrophilum was isolated from broodfish in both water systems; 56% of investigated broodfish from the borehole/flowthrough system and 36% from the recirculation facility harboured the bacterium. In the recirculation system, the bacterium was isolated from fish (ulcers, milt, liver, abdominal cavity) kept in the system for 11 months. Flavobacterium psychrophilum was found in milt and ovarian fluid as well as on the surface of fertilized eggs, but not inside the eggs. Fry also harboured F. psychrophilum, but in the water recirculation system the bacterium was first isolated from the fry after they had been graded. Flavobacterium psychrophilum was found regularly in other parts of the hatchery (outside the recirculation facility), including at the time of grading, suggesting that the occurrence of F. psychrophilum in the fry recirculation facility was due to contamination from the borehole/flow-through hatchery. It is suggested that the combination of bore-hole water recirculation systems and good management procedures (including egg disinfection) is a possible method for hatcheries to avoid disease outbreaks due to F. psychrophilum. PMID:19238756

Madsen, L; Dalsgaard, I

2008-11-01

319

Hybrid heat exchange for the compression capture of CO2 from recirculated flue gas  

SciTech Connect

An approach proposed for removal of CO2 from flue gas cools and compresses a portion of a recirculated flue-gas stream, condensing its volatile materials for capture. Recirculating the flue gas concentrates SOx, H2O and CO2 while dramatically reducing N2 and NOx, enabling this approach, which uses readily available industrial components. A hybrid system of indirect and direct-contact heat exchange performs heat and mass transfer for pollutant removal and energy recovery. Computer modeling and experimentation combine to investigate the thermodynamics, heat and mass transfer, chemistry and engineering design of this integrated pollutant removal (IPR) system.

Oryshchyn, Danylo B.; Ochs, Thomas L.; Summers, Cathy A.

2004-01-01

320

A computer model of the energy-current loss instabilities in a recirculating accelerator system  

NASA Astrophysics Data System (ADS)

The computer program called ESRA (energy stability in a recirculating accelerator FELs) has been written to model bunches of particles in longitudinal phase space traversing a recirculating accelerator and the associated rf changes and aperture current losses. This code addresses stability issues and determines the transport, noise, feedback and other parameters for which these FEL systems are stable or unstable. A representative system is modeled, the Novosibirisk high power FEL race-track microtron for photochemical research. The system is stable with prudent choice of parameters.

Edighoffer, J. A.; Kim, K.-J.

1995-02-01

321

Effect of room air recirculation delay on the decay rate of tracer gas concentration  

SciTech Connect

Tracer gas measurements are commonly used to estimate the fresh air exchange rate in a room or building. Published tracer decay methods account for fresh air supply, infiltration, and leaks in ductwork. However, the time delay associated with a ventilation system recirculating tracer back to the room also affects the decay rate. We present an analytical study of tracer gas decay in a well-mixed, mechanically-ventilated room with recirculation. The analysis shows that failing to account for delays can lead to under- or over-estimates of the fresh air supply, depending on whether the decay rate calculation includes the duct volume.

Kristoffersen, A.R.; Gadgil, A.J.; Lorenzetti, D.M.

2004-05-01

322

Development of low cost all glass recirculation systems for environmental applications.  

PubMed

Some simple glassware has been developed for recirculation of liquid medium. These glassware have wider applications and have been tested in experiments involving leaching, biodegradation, and desulfurization. The fabrication cost is minimum and can be developed in a small glassware workshop. Such a development has certain advantages as no separate mechanical devices are needed, the flow can be easily monitored due to transparency of the apparatus, acidic or alkaline medium can also be circulated. The paper discusses the development, design and fabrication of some specialized glass recirculation systems and its environmental applications. PMID:13677063

Kshirsagar, P S; Pandya, G H

2002-10-01

323

Earthquake hazards on the Cascadia subduction zone  

Microsoft Academic Search

Large subjection earthquakes on the Cascadia subduction zone pose a potential seismic hazard. Very young oceanic lithosphere (10 million years old) is being subducted beneath North America at a rate of approximately 4 cm per year. Very large subduction earthquakes, ranging in energy magnitude M(w) between 8 and 9.5 have occurred along these other subduction zones. If the Cascadia subjection

Thomas H. Heaton; Stephen H. Hartzell

1987-01-01

324

A Mathematical Model of Solute Coupled Water Transport in Toad Intestine Incorporating Recirculation of the Actively Transported Solute  

PubMed Central

A mathematical model of an absorbing leaky epithelium is developed for analysis of solute coupled water transport. The non-charged driving solute diffuses into cells and is pumped from cells into the lateral intercellular space (lis). All membranes contain water channels with the solute passing those of tight junction and interspace basement membrane by convection-diffusion. With solute permeability of paracellular pathway large relative to paracellular water flow, the paracellular flux ratio of the solute (influx/outflux) is small (2–4) in agreement with experiments. The virtual solute concentration of fluid emerging from lis is then significantly larger than the concentration in lis. Thus, in absence of external driving forces the model generates isotonic transport provided a component of the solute flux emerging downstream lis is taken up by cells through the serosal membrane and pumped back into lis, i.e., the solute would have to be recirculated. With input variables from toad intestine (Nedergaard, S., E.H. Larsen, and H.H. Ussing, J. Membr. Biol. 168:241–251), computations predict that 60–80% of the pumped flux stems from serosal bath in agreement with the experimental estimate of the recirculation flux. Robust solutions are obtained with realistic concentrations and pressures of lis, and with the following features. Rate of fluid absorption is governed by the solute permeability of mucosal membrane. Maximum fluid flow is governed by density of pumps on lis-membranes. Energetic efficiency increases with hydraulic conductance of the pathway carrying water from mucosal solution into lis. Uphill water transport is accomplished, but with high hydraulic conductance of cell membranes strength of transport is obscured by water flow through cells. Anomalous solvent drag occurs when back flux of water through cells exceeds inward water flux between cells. Molecules moving along the paracellular pathway are driven by a translateral flow of water, i.e., the model generates pseudo-solvent drag. The associated flux-ratio equation is derived.

Larsen, Erik Hviid; S?rensen, Jakob Balslev; S?rensen, Jens N?rkaer

2000-01-01

325

Control of a turbocharged Diesel engine fitted with high pressure and low pressure exhaust gas recirculation systems  

Microsoft Academic Search

Exhaust gas recirculation is an effective way for reducing nitric oxides emissions in Diesel engine achieving low temperature combustion (LTC). Two strategies can be applied to recirculate burnt gas in a turbocharged Diesel engine using the high pressure loop or the low pressure loop. This paper describes a generic model based control structure for Diesel engines with dual-loop exhaust gas

Olivier Grondin; Philippe Moulin; Jonathan Chauvin

2009-01-01

326

Observer design of critical states for air path flow regulation in a variable geometry turbocharger exhaust gas recirculation diesel engine  

Microsoft Academic Search

Modern automotive diesel engines rely on control strategies that must optimally manage the flows of fresh air and recirculated exhaust gas to achieve the best trade-off between torque demand and engine out emissions. An important aspect of the gas exchange regulation problem is the complex interaction between the variable geometry turbocharger (VGT) and the exhaust gas recirculation (EGR) valve and

B C Glenn; D Upadhyay; V I Utkin; G N Washington; M B Hopka

2011-01-01

327

High rate algal pond treatment for water reuse in a marine fish recirculation system: Water purification and fish health  

Microsoft Academic Search

Regardless of the degree of closure of a recirculation system, effluents are produced and replacement water is needed, which limits the possibility of locating a seawater production system away from the shoreline. At the Palavas Ifremer station, in the south of France, a High Rate Algal Pond (HRAP) was operated during several years to treat the effluent from a recirculating

E. Metaxa; G. Deviller; P. Pagand; C. Alliaume; C. Casellas; J. P. Blancheton

2006-01-01

328

SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES  

SciTech Connect

The research program conducted at the West Virginia University Engine and Emissions Research Laboratory (EERL) is working towards the verification and optimization of an approach to remove nitric oxides from the exhaust gas of lean burn natural gas engines. This project was sponsored by the US Department of Energy, National Energy Technology Laboratory (NETL) under contract number: DE-FC26-02NT41608. Selective NOx Recirculation (SNR) involves three main steps. First, NOx is adsorbed from the exhaust stream, followed by periodic desorption from the aftertreatment medium. Finally the desorbed NOx is passed back into the intake air stream and fed into the engine, where a percentage of the NOx is decomposed. This reporting period focuses on the NOx decomposition capability in the combustion process. Although researchers have demonstrated NOx reduction with SNR in other contexts, the proposed program is needed to further understand the process as it applies to lean burn natural gas engines. SNR is in support of the Department of Energy goal of enabling future use of environmentally acceptable reciprocating natural gas engines through NOx reduction under 0.1 g/bhp-hr. The study of decomposition of oxides of nitrogen (NOx) during combustion in the cylinder was conducted on a 1993 Cummins L10G 240 hp lean burn natural gas engine. The engine was operated at different air/fuel ratios, and at a speed of 800 rpm to mimic a larger bore engine. A full scale dilution tunnel and analyzers capable of measuring NOx, CO{sub 2}, CO, HC concentrations were used to characterize the exhaust gas. Commercially available nitric oxide (NO) was used to mimic the NOx stream from the desorption process through a mass flow controller and an injection nozzle. The same quantity of NOx was injected into the intake and exhaust line of the engine for 20 seconds at various steady state engine operating points. NOx decomposition rates were obtained by averaging the peak values at each set point minus the baseline and finding the ratio between the injected NO amounts. It was observed that the air/fuel ratio, injected NO quantity and engine operating points affected the NOx decomposition rates of the natural gas engine. A highest NOx decomposition rate of 27% was measured from this engine. A separate exploratory tests conducted with a gasoline engine with a low air/fuel ratio yielded results that suggested, that high NOx decomposition rates may be possible if a normally lean burn engine were operated at conditions closer to stoichiometric, with high exhaust gas recirculation (EGR) for a brief period of time during the NOx decomposition phase and with a wider range of air/fuel ratios. Chemical kinetic model predictions using CHEMKIN were performed to relate the experimental data with the established rate and equilibrium models. NOx decomposition rates from 35% to 42% were estimated using the CHEMKIN software. This provided insight on how to maximize NOx decomposition rates for a large bore engine. In the future, the modeling will be used to examine the effect of higher NO{sub 2}/NO ratios that are associated with lower speed and larger bore lean burn operation.

Nigel Clark; Gregory Thompson; Richard Atkinson; Chamila Tissera; Matt Swartz; Emre Tatli; Ramprabhu Vellaisamy

2005-01-01

329

Leachate recirculation: moisture content assessment by means of a geophysical technique  

Microsoft Academic Search

Bioreactor technology is a waste treatment concept consisting in speeding up the biodegradation of landfilled waste by optimizing its moisture content through leachate recirculation. The measurement of variations in waste moisture content is critical in the design and control of bioreactors. Conventional methods such as direct physical sampling of waste reach their limits due to the interference with the waste

Roger Guérin; Marie Laure Munoz; Christophe Aran; Claire Laperrelle; Mustapha Hidra; Eric Drouart; Solenne Grellier

2004-01-01

330

Use of Hydroponics to Maintain Quality of Recirculated Water in a Fish Culture System  

Microsoft Academic Search

Fish production, biofiltration, and hydroponics were linked in a closed system of recirculating water. Fish tanks were stocked with channel catfish (Ictalurus punctatus) and the fish were fed daily. A revolving plate-type biofilter was used. Three field varieties of tomatoes (Lycopericon esculentum) were planted in outdoor hydroponic tanks. Three production units were operated during the 1976 growing season. All significant

William M. Lewis; John H. Yopp; Harold L. Schramm JR; Alan M. Brandenburg

1978-01-01

331

Compact, Pi-Mode Extraction Scheme for the Axial B-Field Recirculating Planar Magnetron.  

National Technical Information Service (NTIS)

A recirculating planar magnetron (RPM), operating in the pi-mode and utilizing a compact, waveguide-based extraction scheme was simulated using ICEPIC. At an applied voltage of 300 kV and B-field of 0.140T, output power of the six-module RPM was 565 MW wi...

B. W. Hoff D. M. French G. Greening M. Franzi R. M. Gilgenbach

2012-01-01

332

Modelling and Optimisation of Eurycoma longifolia Extraction Utilising a Recirculating Flow Extractor  

Microsoft Academic Search

In this study, Tongkat Ali was extracted with a newly designed recirculating flow extractor with temperature and flow rate as the operating parameters. The optimum duration and ratio for extraction were found to be 90 min and 40:1 w\\/w, respectively. The determination of optimal operating parameter value for this extractor was based on maximum percentage extract yield and solid diffusivity,

Mohd Ajib Mohtar; Sivakumar Kumaresan; Mohd Roji Sarmidi; Ramlan Abdul Aziz

2007-01-01

333

Laboratory Investigation of Submarine Groundwater Flow and Recirculation Patterns in Coastal Aquifers  

Microsoft Academic Search

Submarine groundwater discharge (SGWD) is an important discharge process occurring in the vicinity of the saltwater-freshwater boundary in coastal unconfined aquifers. It is now well established that the SGWD has a regional freshwater flow component and a re-circulated saltwater flow component. In an unconfined aquifer, the freshwater and saltwater regions are separated by a distinct interface and freshwater flow occurs

P. Clement; R. R. Goswami; M. B. Hogan

2005-01-01

334

CHEMICAL EXPERIENCE WITH THE RECIRCULATION COOLING SYSTEM OF THE NRX THERMAL SHIELDS  

Microsoft Academic Search

The mild steel thermal shields in the NRX reactor were cooled for the ; first eight years by Ottawa River water with added phosphate, alkali and ; chlorine, on a once-through basis. In the summer of 1955 the cooling system was ; changed to recirculation, and this report deals with chemical and corrosion ; results obtained since that time. Considerable

Allison

1959-01-01

335

Biological degradation of MSW in a methanogenic reactor using treated leachate recirculation  

Microsoft Academic Search

With a methanogenic reactor using treated leachate recirculation, the effects of 12 effective microorganisms (EMs), isolated from Hangzhou Tianzhiling landfill, on the degradation of municipal solid waste (MSW) were investigated. The preliminary experiment indicated that the EMs increased the biodegradability of MSW, enhanced 24% of organic mass effluent from the landfill reactor, and shortened methane production period to about 91

Ruo He; Dong-sheng Shen; Jun-qin Wang; Yong-hua He; Yin-mei Zhu

2005-01-01

336

Removal efficiency and balance of nitrogen in a recirculating aquaculture system integrated with constructed wetlands  

Microsoft Academic Search

The nitrogen (N) balance for aquaculture is an important aspect, especially in China, and it is attributed to the eutrophication in many freshwater bodies. In recent years, constructed wetlands (CWs) have been widely used in wastewater treatment and ecosystem restoration. A recirculating aquaculture system (RAS) consisting of CWs and 4 fish ponds was set up in Wuhan, China. Channel catfish

Fei Zhong; Wei Liang; Tao Yu; Shui P. Cheng; Feng He; Zhen B. Wu

2011-01-01

337

A semi-recirculating, integrated system for the culture of fish and seaweed  

Microsoft Academic Search

Biofiltration allows for environmentally sustainable mariculture. An intensive, biofiltered recirculating integrated system producing fish and seaweed on a semi-commercial scale was evaluated with respect to production and to nutrient and heat budgets. The system consisted of abalone (Haliotis discus hannai) and sea urchin (Paracentrotus lividus) tanks, an intensive fishpond (Sparus aurata), and a three-stage Ulva lactuca biofilter, which cleaned and

Andreas Schuenhoff; Muki Shpigel; Ingrid Lupatsch; Arik Ashkenazi; Flower E Msuya; Amir Neori

2003-01-01

338

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines  

Microsoft Academic Search

Selective NOx Recirculation (SNR) involves cooling the engine exhaust gas and then adsorbing the oxides of nitrogen (NOx) from the exhaust stream, followed by the periodic desorption of NOx. By returning the desorbed, concentrated NOx into the engine intake and through the combustion chamber, a percentage of the NOx is decomposed during the combustion process. An initial study of NOx

Nigel Clark; Gregory Thompson; Richard Atkinson; Richard Turton; Chamila Tissera; Emre Tatli; Andy Zimmerman

2005-01-01

339

Fulminant hepatic failure following marijuana drug abuse: Molecular adsorbent recirculation system therapy  

PubMed Central

Marijuana is used for psychoactive and recreational purpose. We report a case of fulminant hepatic failure following marijuana drug abuse who recovered following artificial support systems for acute liver failure. There is no published literature of management of marijuana intoxication with molecular adsorbent recirculation system (MARS). MARS is effective and safe in patients with fulminant hepatic failure following marijuana intoxication.

Swarnalatha, G.; Pai, S.; Ram, R.; Dakshinamurty, K. V.

2013-01-01

340

Tissue engineering of human cartilage and osteochondral composites using recirculation bioreactors  

Microsoft Academic Search

Chondrocytes isolated from human foetal epiphyseal cartilage were seeded dynamically into polyglycolic acid (PGA) scaffolds and cultured in recirculation column bioreactors to produce tissue-engineered cartilage. Several culture techniques with the potential to provide endogenous growth factors and other conditions beneficial for de novo cartilage synthesis were investigated. Osteochondral composite constructs were generated by seeding separate PGA scaffolds with either foetal

Nastaran Mahmoudifar; Pauline M. Doran

2005-01-01

341

Response of Bacterial Biofilms in Recirculating Aquaculture Systems to Various Sanitizers  

Microsoft Academic Search

Pathogenic microorganisms may be incorporated into biofilms found in aquaculture systems, causing recurring exposure to potential disease agents. Aerobic plate counts, the presence of Enterobacteriaceae, and the presence of Escherichia coli, modified to express a green fluorescent protein (GFP E. coli), was used to evaluate the effectiveness of various sanitizers in decreasing bacterial incorporation into newly generated biofilms in recirculating

Robin K. King; George J. Flick Jr; Stephen A. Smith; Merle D. Pierson; Gregory D. Boardman; Charles W. Coale Jr

2008-01-01

342

Electron Recirculation in Electrostatic Multicusp Systems: II - System Performance Scaling of One-Dimensional 'Rollover' Wells.  

National Technical Information Service (NTIS)

In an earlier paper a comprehensive study was made of the recirculation and losses of electrons in their flow through simple inverse power-law potential wells bounded by similarly inverse power-law dependent magnetic fields. This study examined electron f...

R. W. Bussard K. E. King

1992-01-01

343

Electron recirculation in electrostatic multicusp systems: II. System performance scaling of one-dimensional rollover wells  

Microsoft Academic Search

In an earlier paper a comprehensive study was made of the recirculation and losses of electrons in their flow through simple inverse power-law potential wells bounded by similarly inverse power-law dependent magnetic fields. This study examined electron flow and loss behavior in the simplest approximation invoked to describe Polywell confinement systems. The importance of this study, and of the present

R. W. Bussard; K. E. King

1992-01-01

344

Suction-recirculation device for stabilizing particle flows within a solar powered solid particle receiver  

DOEpatents

A suction-recirculation device for stabilizing the flow of a curtain of blackened heat absorption particles falling inside of a solar receiver with an open aperture. The curtain of particles absorbs the concentrated heat from a solar mirror array reflected up to the receiver on a solar power tower. External winds entering the receiver at an oblique angle can destabilize the particle curtain and eject particles. A fan and ductwork is located behind the back wall of the receiver and sucks air out through an array of small holes in the back wall. Any entrained particles are separated out by a conventional cyclone device. Then, the air is recirculated back to the top of the receiver by injecting the recycled air through an array of small holes in the receiver's ceiling and upper aperture front wall. Since internal air is recirculated, heat losses are minimized and high receiver efficiency is maintained. Suction-recirculation velocities in the range of 1-5 m/s are sufficient to stabilize the particle curtain against external wind speeds in excess of 10 m/s.

Kolb, Gregory J. (Albuquerque, NM)

2012-02-07

345

A local grid refinement method for three-dimensional turbulent recirculating flows  

Microsoft Academic Search

A local grid refinement method is presented and applied to a three-dimensional turbulent recirculating flow. It is based on the staggered grid arrangement. The computational domain is covered by block-structured subgrids of different refinement levels. The exchange of information between the subgrids is fully conservative and all grids are treated implicitly. This allows for a simultaneous solution of one variable

G. Papadakis; G. Bergeles

1999-01-01

346

Phase-noise suppression in an interferometric fiber optic sensor with recirculating paths  

Microsoft Academic Search

We report a modified all-fiber Mach-Zehnder interferometer configuration incorporating recirculating fiber paths in both the signal and reference arms. This system can be operated using a time-division based interrogation approach to yield a self phase-noise compensated sensor.

Michael J. Marrone; Alan D. Kersey

1992-01-01

347

Fulminant hepatic failure following marijuana drug abuse: Molecular adsorbent recirculation system therapy.  

PubMed

Marijuana is used for psychoactive and recreational purpose. We report a case of fulminant hepatic failure following marijuana drug abuse who recovered following artificial support systems for acute liver failure. There is no published literature of management of marijuana intoxication with molecular adsorbent recirculation system (MARS). MARS is effective and safe in patients with fulminant hepatic failure following marijuana intoxication. PMID:24049281

Swarnalatha, G; Pai, S; Ram, R; Dakshinamurty, K V

2013-09-01

348

A Tracer Method for Evaluating Recirculation of Pollutant Releases in Buildings  

Microsoft Academic Search

A method is introduced for evaluating recirculation in a building ventilation system from pollutant emissions in or near the building. Tracer was released at a known rate at the point of pollutant emission. Using measured tracer concentrations, the tracer release rate, and an estimate of the pollutant release rate, pollutant concentrations were estimated at the locations in the building where

James P. Rydock; Ove Hermansen

2002-01-01

349

A nucleonic oil debris monitor for detecting metal in recirculating lubricating systems  

Microsoft Academic Search

Metallic debris sensors have been developed for recirculating oil lubrication systems. The in-line monitors apply the principle of X-ray fluorescence. The nucleonic oil debris monitors (ODM's) have been designed and fabricated for use with test cell operations involving aircraft transmissions and gear boxes. ODM's were tested to evaluate their sensitivity, accuracy, and response to lubricant temperature over the range of

R. W. Harman

1974-01-01

350

Performance of Twin Central Venous Catheters: Influence of the Inversion of Inlet and Outlet on Recirculation  

Microsoft Academic Search

Background: The use of a central venous catheter as a permanent vascular access is constantly growing. The recirculation rate in this type of vascular access varies depending on the site of insertion, the length of the catheter, the blood flow and the time elapsed since catheter insertion. When the in\\/out flow of the lumens of the catheter is reduced, it

Catherine Lasseur; Philippe Chauveau; Hervé Bonarek; Luc Perrault; Christian Combe

2002-01-01

351

Improvement of anaerobic digester performance by wastewater recirculation through an aerated membrane.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Swine wastewater from an anaerobic digester was recirculated through a silicone hose located in an external aeration chamber to determine its effect on wastewater malodorants and biogas composition. The silicone hose acted as a semipermeable membrane for the passage of small molecules. In the first...

352

Evaluation of a Revolving Plate Type Biofilter for Use in Recirculated Fish Production and Holding Units  

Microsoft Academic Search

Based on information gained from a pilot model, two identical revolving plate filters were designed to be evaluated for use in a recirculated fish production system. Each unit consisted of a fiberglass tank containing 787 liters of water; a biofilter having 60 plates, each 51 cm in diameter, rotated at 6 rpm; and a settling tank. The total water volume

William M. Lewis; Gerard L. Buynak

1976-01-01

353

Dynamic tuning of optical waveguides with electrowetting pumps and recirculating fluid channels  

Microsoft Academic Search

We have developed an approach for using electrowetting actuation in recirculating fluidic channels to achieve dynamic tuning of optical fiber structures. The electrically controlled and fully reversible motion of the fluids and lubricants in these channels alters the refractive index profile experienced by the optical waveguide modes of the fiber. When combined with in-fiber gratings and etched fibers, this fluidic

P. Mach; T. Krupenkin; S. Yang; J. A. Rogers

2002-01-01

354

Stream cleaning for specific foulants in open recirculating cooling water systems  

Microsoft Academic Search

Together with corrosion, fouling is the most predominant problem in open recirculating cooling water systems. There are basically 5 different types of fouling deposits which form in cooling water systems, as follows: (1) inorganic scale deposits arising from the mineral content of the makeup water; (2) iron salts and oxides consisting of corrosion products from active corrosion sites in the

D. R. Sexsmith; E. Q. Petrey

1971-01-01

355

Effect of cooling the recirculated exhaust gases on diesel engine emissions  

Microsoft Academic Search

Although combustion is essential in most energy generation processes, it is one of the major causes of air pollution. Spiral fin exhaust pipes were designed to study the effect of cooling the recirculated exhaust gases (EGR) of Diesel engines on the chemical composition of the exhaust gases and the reduction in the percentages of pollutant emissions. The gases examined in

Nidal H. Abu-Hamdeh

2003-01-01

356

Control system for engine exhaust gas recirculation according to engine opertional condition  

Microsoft Academic Search

A control system comprising a flow control valve provided in an exhaust gas recirculation passage, an electromechanical valve-actuator for actuating the flow control valve and a control circuit including function generators and an adder, optionally combined with a multiplier, for producing a control signal to operate the valve-actuator. Each function generator receives a signal representing one of several variables related

Aono

1978-01-01

357

Growth and survival of juvenile cobia, Rachycentron canadum, at different salinities in a recirculating aquaculture system  

Microsoft Academic Search

Cobia (Rachycentron canadum) is an emerging aquaculture candidate for both offshore cage culture and land-based systems such as recirculating aquaculture systems. The ability to grow cobia at salinities other than oceanic (?34 ppt) could present culturists with additional production opportunities with this species. Culture at low salinities could also reduce the incidence of disease and simplify water management. In two

Matthew J. Resley; Kenneth A. Webb; G. Joan Holt

2006-01-01

358

Growth of juvenile cobia, Rachycentron canadum, at three different densities in a recirculating aquaculture system  

Microsoft Academic Search

Cobia (Rachycentron canadum) is an excellent aquaculture candidate and culture of this species continues to develop worldwide. Current culture practices generally include larviculture and production of early juveniles on land with final growout occurring in ocean cages. Data indicate that production and\\/or growout of juveniles in land based recirculating systems may be hampered by growth depression in fish held at

Kenneth A. Webb; Glenn M. Hitzfelder; Cynthia K. Faulk; G. Joan Holt

2007-01-01

359

Growth and survival of larval and juvenile cobia Rachycentron canadum in a recirculating raceway system  

Microsoft Academic Search

Cobia Rachycentron canadum is a fast-growing, pelagic marine species that has recently attracted aquaculturists in both the research and commercial sectors. The typical method of grow-out for this species is in outdoor systems where production is limited to locations and seasons conducive for adequate growth and survival. Expanding the culture of cobia to indoor recirculating aquaculture systems (RAS) would allow

Cynthia K. Faulk; Jeffrey B. Kaiser; G. Joan Holt

2007-01-01

360

Recirculation of process streams in fuel ethanol production from softwood based on simultaneous saccharification and fermentation.  

PubMed

The effect of process stream recirculation on ethanol production from steam- pretreated softwood based on simultaneous saccharification and fermentation (SSF) was investigated for two process configurations. In the first configuration, a part of the stillage stream after distillation was recycled and, in the second configuration, the liquid after SSF was recycled. The aim was to minimize the energy consumption in the distillation of the fermentation broth and in the evaporation of the stillage, as well as the use of fresh water. However, recirculation leads to an increased concentration of nonvolatiles in the first configuration, and of both volatiles and nonvolatiles in the second configuration. These substances might be inhibitory to the enzymes and the yeast in SSF. When 60% of the fresh water was replaced by stillage, the ethanol yield and the productivity were the same as for the configuration without recirculation. The ethanol production cost was reduced by 17%. In the second configuration, up to 40% of the fresh water could be replaced without affecting the final ethanol yield, although the initial ethanol productivity decreased. The ethanol production cost was reduced by 12%. At higher degrees of recirculation, fermentation was clearly inhibited, resulting in a decrease in ethanol yield while hydrolysis seemed unaffected. PMID:12018307

Alkasrawi, Malek; Galbe, Mats; Zacchi, Guido

2002-01-01

361

Design and Evaluation of Recirculating Water Systems for Maintenance and Propagation of Freshwater Mussels  

Microsoft Academic Search

A complete system for culturing, rearing, and holding juvenile and adult freshwater mussels (Unionidae) was designed and evaluated for use at hatcheries and research facilities. The system includes air delivery, water conditioning and delivery, algal culturing and automated algal feed delivery, and air-driven water-recirculating units. These systems are appropriate for holding and conditioning adult mussels for spawning, as well as

William F. Henley; Lora L. Zimmerman; Richard J. Neves; Mark R. Kidd

2001-01-01

362

Recirculation subtraction for analysis of left-to-right-cardiac shunts: concise communication  

SciTech Connect

The object of this study is to improve the techniques for describing the lung dilution curve for shunt quantification by separating the effects of systemic recirculation on the curve from those of direct shunt return. The time of the systemic recirculation peak was estimated by determination of transit times from the right and left ventricles and lung. A gamma variate fit based on the distribution of points at that segment was applied to the recirculation curve and subtracted from the original lung dilution curve. Similar gamma variate fitting was performed for both primary and shunt curves. Rather than fitting the gamma variate of the shunt curve by the leading edge only, a larger portion could now be used since the trailing edge of the curve is clearer following recirculation subtraction. The algorithm is completely automatic, requiring no operator intervention or selection of curve-fitting regions. The correlation coefficient for comparison of the dilution-curve analysis with oximetry determinations was 0.92 in a series of 29 patients.

Houser, T.S.; MacIntyre, W.J.; Cook, S.A.; Go, R.T.; Moodie, D.S.; Ceimo, J.; Gallagher, J.H.

1981-12-01

363

Molecular Determinants Controlling Homeostatic Recirculation and Tissue-Specific Trafficking of Lymphocytes  

Microsoft Academic Search

The homeostasis of the immune system is maintained by the recirculation of naïve lymphocytes through the secondary lymphoid tissues, such as the lymph nodes, Peyer’s patches, and spleen. Upon insult by pathogens or antigens, lymphocytes become activated, and the regulated trafficking of these cells results in the integration of systemic and regional immune responses. The exquisite specificity of such lymphocyte

Toshiyuki Tanaka; Yukihiko Ebisuno; Naotoshi Kanemitsu; Eiji Umemoto; Bo-gie Yang; Myoung-ho Jang; Masayuki Miyasaka

2004-01-01

364

Temperate Oceans: Light Zones  

NSDL National Science Digital Library

This reference provides an overview of the three zones into which the ocean can be divided based on the amount of light recieved: the sunlit (or euphotic) zone, the twilight (or disphotic) zone, and the midnight (or aphotic) zone. The descriptions are accompanied by diagrams and a brief listing of the organisms that live in each zone.

365

Re-circulation artefact at the carotid bulb can be differentiated from true stenosis.  

PubMed

Re-circulation artefact developing secondary to vortex flow at the bulb of the internal carotid artery is very difficult to distinguish from true stenotic defect on two-dimensional Fourier transformed time-of-flight magnetic resonance angiography (2D-FT TOF MRA). The purpose of our study is to identify appropriate distinguishing features of re-circulation artefact. We included 45 extracranial carotid arteries collected from 25 patients who underwent both 2D-FT TOF MRA and contrast medium based angiography. Review of the 45 vessels demonstrated re-circulation artefact in 21 vessels, true stenotic defect in 8 vessels, and no filling defect in 16 vessels on 2D-FT TOF MRA. We compared the findings of re-circulation artefact and true stenotic defect in 29 vessels excluding the 16 vessels without filling defect. The following were evaluated: (1) preservation of posterior wall contour; (2) marginal character of filling defect; (3) darkness of filling defect; (4) involvement of common carotid artery by filling defect; (5) size of filling defect. In four out of the five evaluated items, statistically significant difference was present between re-circulation artefact group and true stenotic defect group (p<0.01 in all four items, chi(2) analysis). Re-circulation artefact demonstrated the preservation of the posterior wall contour (19/21), ill-defined margin (19/21), less dark defect (18/21), and no involvement of the common carotid artery (19/21). On the contrary true stenotic defect demonstrated focal loss of posterior wall contour (8/8), sharp margin (8/8), dark defect (8/8), and involvement of common carotid artery (4/8). No significant difference was noted in the size of the defect between the two groups (p>0.05). The specificity of 2D-FT TOF MRA for carotid stenosis was markedly increased after application of above signs. These distinguishing signs are very helpful in differentiating re-circulation artefact from true stenotic defect. PMID:15238400

Ahn, K J; You, W J; Lee, J H; Kang, B J; Kim, Y J; Kim, B S; Hahn, S T

2004-07-01

366

Marginal Zone Lymphoma  

MedlinePLUS

Marginal Zone Lymphoma Overview Lymphoma is the most common blood cancer. The two main forms of lymphoma are Hodgkin lymphoma (HL) ... types of marginal zone lymphoma: Extranodal marginal zone lymphoma or mucosa-associated lymphoid tissue (MALT) is the ...

367

The bottom intertidal zone  

NSDL National Science Digital Library

The bottom intertidal area remains under water except during low tides. This zone is most abundant of the intertidal zones and contains seaweeds and other plants, invertebrates, and fishes. The bottom zone is subject to the most intense wave action.

Katie Hale (CSUF;Biological Sciences)

2007-06-08

368

Zone separator for multiple zone vessels  

DOEpatents

A solids-gas contact vessel, having two vertically disposed distinct reaction zones, includes a dynamic seal passing solids from an upper to a lower zone and maintaining a gas seal against the transfer of the separate treating gases from one zone to the other, and including a stream of sealing fluid at the seal.

Jones, John B. (Grand Junction, CO)

1983-02-01

369

Wind tunnel investigation on the retention of air pollutants in three-dimensional recirculation zones in urban areas  

Microsoft Academic Search

The article discusses an experimental investigation of turbulent dispersion processes in a typical three-dimensional urban geometry, in reduced scale, in neutrally stable conditions. Wind tunnel experiments were carried out for characterizing the flow and the dispersion of a pollutant around a scaled model (1:400) of a group of eight 10-floor buildings surrounding a square. The situation corresponded to the dispersion

Marcos Sebastião de Paula Gomes; André Augusto Isnard; José Maurício do Carmo Pinto

2007-01-01

370

Fluid Image Velocimetry of the Flow in the Recirculation Zone of a Bluff Body Stabilized and Controlled Burner  

Microsoft Academic Search

Combustion instabilities have been encountered in almost all of the propulsion system development programs. In typical liquid fueled combustors, the most dangerous oscillations are at the frequency of 80-500 Hz. This low-frequency \\

B. Golovanevsky; Y. Levy

371

Effects of non-uniform root zone salinity on water use, Na+ recirculation, and Na+ and H+ flux in cotton  

PubMed Central

A new split-root system was established through grafting to study cotton response to non-uniform salinity. Each root half was treated with either uniform (100/100?mM) or non-uniform NaCl concentrations (0/200 and 50/150?mM). In contrast to uniform control, non-uniform salinity treatment improved plant growth and water use, with more water absorbed from the non- and low salinity side. Non-uniform treatments decreased Na+ concentrations in leaves. The [Na+] in the ‘0’ side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the ‘0’ side phloem was girdled, suggesting that the increased [Na+] in the ‘0’ side roots was possibly due to transportation of foliar Na+ to roots through phloem. Plants under non-uniform salinity extruded more Na+ from the root than those under uniform salinity. Root Na+ efflux in the low salinity side was greatly enhanced by the higher salinity side. NaCl-induced Na+ efflux and H+ influx were inhibited by amiloride and sodium orthovanadate, suggesting that root Na+ extrusion was probably due to active Na+/H+ antiport across the plasma membrane. Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na+ concentration, transport of excessive foliar Na+ to the low salinity side, and enhanced Na+ efflux from the low salinity root.

Kong, Xiangqiang; Luo, Zhen; Dong, Hezhong; Eneji, A. Egrinya

2012-01-01

372

Simultaneous water desalination and electricity generation in a microbial desalination cell with electrolyte recirculation for pH control.  

PubMed

A recirculation microbial desalination cell (rMDC) was designed and operated to allow recirculation of solutions between the anode and cathode chambers. This recirculation avoided pH imbalances that could inhibit bacterial metabolism. The maximum power density was 931±29mW/m(2) with a 50mM phosphate buffer solution (PBS) and 776±30mW/m(2) with 25mM PBS. These power densities were higher than those obtained without recirculation of 698±10mW/m(2) (50mM PBS) and 508±11mW/m(2) (25mM PBS). The salt solution (20g/L NaCl) was reduced in salinity by 34±1% (50mM) and 37±2% (25mM) with recirculation (rMDC), and by 39±1% (50mM) and 25±3% (25mM) without recirculation (MDC). These results show that electrolyte recirculation using an rMDC is an effective method to increase power and achieve efficient desalination by eliminating pH imbalances. PMID:22200556

Qu, Youpeng; Feng, Yujie; Wang, Xin; Liu, Jia; Lv, Jiangwei; He, Weihua; Logan, Bruce E

2011-11-25

373

Heat transport dynamics at a sandy intertidal zone  

NASA Astrophysics Data System (ADS)

Intertidal zones are spatially complex and temporally dynamic environments. Coastal groundwater discharge, including submarine groundwater discharge, may provide stabilizing conditions for intertidal zone permeable sediments. In this study, we integrated detailed time series temperature observations, porewater pressure measurements, and two-dimensional electrical resistivity tomography profiles to understand the coupled hydraulic-thermal regime of a tropical sandy intertidal zone in a fringing coral reef lagoon (Rarotonga, Cook Islands). We found three heating patterns across the 15 m study transect over tidal and diel periods: (1) a highly variable thermal regime dominated by swash infiltration and changes in saturation state in the upper foreshore with net heat import into the sediment, (2) a groundwater-supported underground stable, cool region just seaward of the intertidal slope break also importing heat into the subsurface, and (3) a zone of seawater recirculation that sustained consistently warm subsurface temperatures that exported heat across the sediment-water interface. Simple calculations suggested thermal conduction as the main heat transport mechanism for the shallow intertidal sediment, but deeper and/or multidimensional groundwater flow was required to explain temperature patterns beyond 20 cm depth. Temperature differences between the distinct hydrodynamic zones of the foreshore site resulted in significant thermal gradients that persisted beyond tidal and diel periods. The thermal buffering of intertidal zones by coastal groundwater systems, both at surface seeps and in the shallow subsurface, can be responsible for thermal refugia for some coastal organisms and hotspots for biogeochemical reactions.

Befus, Kevin M.; Cardenas, M. Bayani; Erler, Dirk V.; Santos, Isaac R.; Eyre, Bradley D.

2013-06-01

374

A modified adaptive grid method for recirculating flows  

NASA Astrophysics Data System (ADS)

In this study, a method of equidistribution of a weight function for grid adaption is modified to produce a smoother grid which yields a more accurate solution. In the original scheme the weight function was estimated on each grid independently and a large variation in the values of the weight function could generate a highly skewed and nonuniform grid which produced large errors. In this study, the weight function is smoothed by coupling neighboring weight functions. Abrupt changes in the weight function are alleviated and a smoother grid distribution is obtained. With relatively minor modifications of the original weight function, it is demonstrated in this study that the solution can be improved. The test cases presented are the one-dimensional convection-diffusion equation, a laminar polar cavity flow, a laminar backward-facing step flow and a turbulent reacting sudden expansion pipe flow. Numerical efficiencies ranging from factors of five to 10 are achieved over uniform grid methods.

Lee, D.; Tsuei, Y. M.

1992-04-01

375

Root Apex Transition Zone As Oscillatory Zone  

PubMed Central

Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone.

Baluska, Frantisek; Mancuso, Stefano

2013-01-01

376

Root apex transition zone as oscillatory zone.  

PubMed

Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone. PMID:24106493

Baluška, František; Mancuso, Stefano

2013-10-02

377

Laboratory Investigation of Submarine Groundwater Flow and Recirculation Patterns in Coastal Aquifers  

NASA Astrophysics Data System (ADS)

Submarine groundwater discharge (SGWD) is an important discharge process occurring in the vicinity of the saltwater-freshwater boundary in coastal unconfined aquifers. It is now well established that the SGWD has a regional freshwater flow component and a re-circulated saltwater flow component. In an unconfined aquifer, the freshwater and saltwater regions are separated by a distinct interface and freshwater flow occurs above the interface and saltwater flow occurs beneath the interface. Under natural conditions, the interface is at a dynamic equilibrium established by the movement of fresh and saltwater flows. Currently, there is a considerable controversy in the estimated values of these fresh and saltwater flow rates. For example, in a classic field study, Moore (Nature, v.380, p.612-614, 1996) discovered very high rates (much higher than estimated regional freshwater flux) of SGWD into a coastal aquifer. Younger (Nature, v.382, p.121-122, 1996) argued that only four percent of the SGWD estimated by Moore is from the land (fresh groundwater) and the rest of SGWD is of marine origin. The objective of this work is develop a physical model for a coastal unconfined aquifer and perform careful studies to visualize the freshwater and saltwater flow patterns near a coastal interface. We conducted laboratory studies of the saltwater intrusion phenomenon in two flow tanks filled with a homogeneous porous medium. Our small tank has dimensions of 53 cm x 32 cm x 2.7 cm, and our large tank has dimensions of 110 cm x 65 cm x 5 cm. By completing experiments in two difference scales we hope to address the scaling issues related to this complex flow problem. Our experimental setup allowed us to quantify both freshwater and seawater fluxes; further, the circulation patterns of seawater and the discharge patterns of freshwater were also observed. Tracer studies were conducted to quantify the residence times. In this presentation, we will present the data collected from our experiments and correlate the observed fluxes and circulation patterns with certain dimensional parameters. SGWD can be an important phenomenon that controls the overall nutrient budgets of coastal water. Our study would aid in developing a better understanding of seawater circulation and its relationship to SGWD.

Clement, P.; Goswami, R. R.; Hogan, M. B.

2005-12-01

378

Compressibility and shear strength of municipal solid waste under short-term leachate recirculation operations.  

PubMed

This paper describes a comprehensive laboratory study performed to investigate the compressibility and shear strength properties of 1.5-year-old municipal solid waste (MSW) exhumed from a landfill cell where low amounts of leachate were recirculated. The study results are compared with results from a previous study on fresh MSW collected from the same landfill and data from previous studies with known MSW age to assess the variation in properties due to degradation. Laboratory testing was conducted on shredded landfilled and fresh MSW that consisted of similar particle-size distribution, with maximum particle size less than 40 mm and approximately 80% of the waste consisting of particles ranging from 10 to 20 mm. Standard Proctor, compressibility, direct shear, and triaxial consolidated undrained (CU) shear tests were conducted in general accordance with the American Society of Testing and Materials Standard Procedures. These tests were conducted with samples at an in-situ moisture content of 44% (dry weight basis) as well as elevated moisture contents of 60, 80 and 100% (dry weight basis). Standard Proctor compaction tests yielded a maximum dry density of 600 kg/m(3) at 77% optimum moisture content for landfilled MSW compared to the 420 kg/m(3) maximum dry density at 70% optimum moisture content for fresh MSW. Compression ratio values for landfilled MSW varied in a close range of 0.19-0.24 with a slight increasing trend with increase in moisture content; however, for fresh waste they were in the close range of 0.24-0.33 with no definitive correlation with moisture content. Based on direct shear tests, drained cohesion and friction angle were varied in the range of 12-64 kPa and 31-35 degrees for landfilled MSW and 31-64 kPa and 26-30 degrees for fresh MSW. Neither cohesion nor friction angle demonstrated any correlation with the moisture content. Based on triaxial CU tests, the average total strength parameters (TSP) were found to be 39 kPa and 12 degrees for landfilled MSW and 32 kPa and 12 degrees for fresh MSW, while effective strength parameters (ESP) were 34 kPa and 23 degrees for landfilled MSW and 32 kPa and 16 degrees for fresh MSW. This study was limited to small-scale laboratory testing using MSW samples with the specimen size relative to the maximum particle size in the range of 1.6 to 2.6; therefore, large-scale laboratory and field studies are recommended to systematically assess the influence of composition, particle size distribution and specimen size on the geotechnical properties of MSW. PMID:19423596

Reddy, Krishna R; Gangathulasi, Janardhanan; Parakalla, Naveen S; Hettiarachchi, Hiroshan; Bogner, Jean E; Lagier, Thomas

2009-05-07

379

A Spatial Model for Marine Park Zoning  

Microsoft Academic Search

The complexity of stakeholder interests, governing structures, and biophysical processes often present challenges in adopting multiple-use approaches in the management of large marine areas. Marine zoning plans provide a mechanism for ensuring the realization of conservation objectives under spatially varying levels of resource use. The need for a systematic and transparent approach to zone planning highlights the role of Geographical

Eleanor M. Bruce; Ian G. Eliot

2006-01-01

380

Two- and three-dimensional simulations of aerosol transport and deposition in alveolar zone of human lung  

SciTech Connect

We simulate two- and three-dimensional (2D and 3D) aerosol transport for different particle diameters within alveolated ducts. In agreement with previous studies, the 2D-computed velocity field shows that the flow inside the alveoli is negligible compared with that in the central channel of the ducts and that a recirculation zone is set up in each alveolus. The calculated particle trajectories indicate that in the 2D and 3D simulations the particles do not deposit uniformly on the alveolar walls. For <0.5-{mu}m-diameter particles, simulations show that particles are mainly located near the entrance of the alveoli. This suggests that local and mean aerosol concentrations may be substantially different. For large particles we show that the gravity field significantly affects deposition. Aerosol dispersion is also computed, and the simulations are compared with the classical one-dimensional (1D) approach with use of the trumpet model, with additional terms for deposition. The 3D model simulates total deposition that is intermediate between 1D and 2D models. The differences between 2D and 3D data are attributed to the inclusion of azimuthal alveolar walls in the 3D duct and the change from 2D- to 3D-particle motions. Finally, our work suggests that the 1D model may introduce large errors in the location of deposited particles. 16 refs., 12 figs., 3 tabs.

Darquenne, C.; Paiva, M. [Universite Libre de Bruxelles, Brussels (Belgium)

1996-04-01

381

Design of multifamily solar domestic hot water systems using recirculating distribution  

SciTech Connect

This paper describes a study designed to quantify the effect of daily domestic hot water loads and system design on the performance of solar domestic hot water systems employing a recirculating distribution system. A solar domestic hot water system judged representative of the systems funded by the HUD Solar Demonstration Program, along with a modification to this system, was modeled using the TRNSYS simulation computer program. Results of simulations over a representative climatic period show that daily domestic hot water usage significantly affects solar system performance. Notable improvement in system performance can be obtained by the use of a recirculation return to solar storage system configuration within a specific range of daily domestic hot water loads. An optimum system was developed from parametric variations of system design and modeled on an annual basis. Comparison is made to modeled system performance of the original design.

Wedekind, D.R.

1982-01-01

382

Identification and origin of plant pathogenic microorganisms in recirculating nutrient solutions  

NASA Astrophysics Data System (ADS)

Avoidance of root-infecting microorganisms was originally considered one of the advantages of cultivation of crops in a soilless, recirculating nutrient solution. However, to date, four viral, three bacterial and 21 fungal pathogens have been identified as causal agents of root disease in hydroponically-grown crops. Root-infecting fungi, particularly those which produce a motile stage known as a zoospore, have been the primary pathogens associated with extensive crop losses. Documented sources of these root pathogens in hydroponic systems include peat, surface water such as rivers and streams, and insects. The severity of disease caused by these introduced root pathogens is primarily governed by the genetic susceptibility of each crop and the temperature of the recirculating nutrient solution.

Stanghellini, M. E.; Rasmussen, S. L.

1994-11-01

383

Possible interactions between recirculated landfill leachate and the stabilized organic fraction of municipal solid waste.  

PubMed

The stabilized organic fraction of municipal solid waste (SOFMSW) is a product of the mechanical/biological treatment (MBT) of mixed municipal solid waste (MMSW). SOFMSW is considered a 'grey' compost and the presence of pollutants (particularly heavy metals) and residual glass and plastic normally prevents agricultural use, making landfills the typical final destination for SOFMSW. Recirculation of leachate in landfills can be a cost-effective management option, but the long-term sustainability of such a practice must be verified. Column tests were carried out to examine the effect of SOFMSW on leachate recirculation. The results indicate that organic matter may be biologically degraded and metals (copper and zinc) are effectively entrapped through a combination of physical (adsorption), biological (bacterial sulfate reduction), and chemical (precipitation of metal sulfides) processes, while other chemicals (i.e. ammonia nitrogen and chloride) are essentially unaffected by filtration through SOFMSW. PMID:22351654

Calabrò, Paolo S; Mancini, Giuseppe

2012-02-20

384

Thermal-hydraulic tests of a recirculation cooling installation for the Rostov nuclear power station  

NASA Astrophysics Data System (ADS)

Results obtained from thermal-hydraulic tests of the recirculation cooling installation used as part of the air cooling system under the containments of the Rostov nuclear power station Units 3 and 4 are presented. The operating modes of the installation during normal operation (air cooling on the surface of finned tubes), under the conditions of anticipated operational occurrences (air cooling and steam condensation from a steam-air mixture), and during an accident (condensation of pure steam) are considered. Agreement is obtained between the results of tests and calculations carried out according to the recommendations given in the relevant regulatory documents. A procedure of carrying out thermal calculation for the case of steam condensation from a steam-air mixture on the surface of fins is proposed. The possibility of efficient use of the recirculation cooling installation in the system for reducing emergency pressure under the containment of a nuclear power station is demonstrated.

Balunov, B. F.; Balashov, V. A.; Il'in, V. A.; Krayushnikov, V. V.; Lychakov, V. D.; Meshalkin, V. V.; Ustinov, A. N.; Shcheglov, A. A.

2013-09-01

385

Removal of sodium chloride from human urine via batch recirculation electrodialysis at constant applied voltage.  

PubMed

The removal of sodium chloride (NaCl) from human urine using a six-compartment electrodialysis cell with batch recirculation mode of operation for use in advanced life support systems (ALSS) was studied. From the results obtained, batch recirculation at constant applied voltage yields high values (approximately 94% of NaCl removal. Based on the results, the initial rate of NaCl removal was correlated to a power function of the applied voltage: -r=2.0 x 10(-4)E(3.8). With impedance spectroscopy methods, it was also found that the anion membranes were more affected by fouling with an increase of the ohmic resistance of almost 11% compared with 7.4% for the cationic ones. PMID:14632001

Gordils-Striker, Nilda E; Colon, Guillermo

2003-01-01

386

Performance and operation of a rotating biological contactor in a tilapia recirculating aquaculture system  

Microsoft Academic Search

This paper describes the performance characteristics of an industrial-scale air-driven rotating biological contactor (RBC) installed in a recirculating aquaculture system (RAS) rearing tilapia at 28°C. This three-staged RBC system was configured with stages 1 and 2 possessing approximately the same total surface area and stage 3 having approximately 25% smaller. The total surface area provided by the RBC equaled 13,380m2.

Brian L. Brazil

2006-01-01

387

Characterization of a biofilm bacterium from a recirculation system for European lobster ( Homarus gammarus)  

Microsoft Academic Search

The European lobster (Homarus gammarus) is often stored live in re-circulation systems. Previously bio-films and fouling has been reported to occur during storage of live aquatic animals. This investigation profiled a bacterium isolated from a bio-film observed on the carapace of live lobster and on the sub-water surfaces of the holding facility. Molecular analysis using a universal 16s rRNA primer

Jennifer E. Welsh; Pauline A. King; Eugene MacCarthy

2011-01-01

388

High gradient magnetic beneficiation of dry pulverized coal via upwardly directed recirculating fluidization  

DOEpatents

This invention relates to an improved device and method for the high gradient magnetic beneficiation of dry pulverized coal, for the purpose of removing sulfur and ash from the coal whereby the product is a dry environmentally acceptable, low-sulfur fuel. The process involves upwardly directed recirculating air fluidization of selectively sized powdered coal in a separator having sections of increasing diameters in the direction of air flow, with magnetic field and flow rates chosen for optimum separations depending upon particulate size.

Eissenberg, David M. (Oak Ridge, TN); Liu, Yin-An (Opelika, AL)

1980-01-01

389

Ozone degradation of alkylbenzene sulfonate in aqueous solutions using a stirred tank reactor with recirculation  

Microsoft Academic Search

The degradation of linear alkylbenzene sulfonates (LAS) in aqueous solutions by ozone has been investigated. The ozonation process was performed in a stirred tank reactor with recirculation which simulates the clean-in-place process used in many industrial facilities. The gas-liquid mass transfer of ozone in a buffer solution at different temperatures (25–55°C) was also studied in the same device, revealing that

Encarnación Jurado-Alameda; José M. Vicaria; Deisi Altmajer-Vaz; Germán Luzón; José L. Jiménez-Pérez; Ignacio Moya-Ramírez

2012-01-01

390

Design of adiabatic wigglers for recirculating-beam free- electron lasers and adiabatic beam bunchers  

Microsoft Academic Search

We present the design of an adiabatic free-electron laser, which enables effective electron beam recirculation, and, therefore, very high efficiency. The free-electron laser uses an electron beam to amplify coherent radiation, is tunable, and is capable of high output power. An adiabatic free-electron laser preserves the longitudinal energy spread of an electron beam by trapping and detrapping the beam over

Scott Alan Hendrickson

1997-01-01

391

Recirculating Accelerator Driver for a High-Power Free-Electron Laser: A Design Overview  

Microsoft Academic Search

Jefferson Lab is building an infrared free-electron laser to produce light at nominal wavelength and power of 3 mum and 1 kW, respectively. A superconducting linac will drive the laser, generating a continuous-wave electron beam at nominal average current of 5 mA and energy of 42 MeV. A transport lattice will recirculate the beam back to the linac for deceleration

C. L. Bohn

1997-01-01

392

Modelling strongly swirling recirculating jet flow with Reynolds-stress transport closures  

Microsoft Academic Search

The paper examines the performance of four variants of the Reynolds-stress-transport closure when applied to the computation of a strongly swirling, recirculating free jet. The models differ principally in the way mean strain is held to affect the pressure-strain correlation. Two variants are new - one combining the stress-production and convection tensors so as to yield an objective tensor which

S. Fu; B. E. Launder; M. A. Leschziner

1987-01-01

393

Recirculating loop for experimental evaluation of EDFA saturated regime effects on optical communication systems  

Microsoft Academic Search

We demonstrate an optical-fiber recirculating loop for experimental simulation of long-haul optical communication systems using cascaded erbium-doped fiber amplifiers (EDFA's) operating in the gain saturation regime. The loop contains sections of dispersion shifted fibers (DSF's), standard fiber, and a set of in-line devices, such as tuning filters, optical amplifiers, polarization controllers, and a variable attenuator. The main results presented here

Claudio Mazzali; Hugo L. Fragnito

1998-01-01

394

Combination of a bead filter and rotating biological contactor in a recirculating fish culture system  

Microsoft Academic Search

The performance of the combination of a floating bead filter and an RBC employing 1-inch diameter N?orpac® tube media was evaluated in an intensive pilot scale recirculating system stocked with tilapia. The combination maintained favorable water quality, attaining practically complete TAN and NO2-N removal. The average overall removal across the FBF-RBC combination was 60·6 g TAN\\/day and 59·6 g NO2-N\\/day,

Aurelio A. delos Reyes; Thomas B. Lawson

1996-01-01

395

Amplifier and resonator dynamics of a low-Reynolds-number recirculation bubble in a global framework  

Microsoft Academic Search

The stability behaviour of a low-Reynolds-number recirculation flow developing in a curved channel is investigated using a global formulation of hydrodynamic stability theory. Both the resonator and amplifier dynamics are investigated. The resonator dynamics, which results from the ability of the flow to self-sustain perturbations, is studied through a modal stability analysis. In agreement with the literature, the flow becomes

OLIVIER M ARQUET; JEAN-MARC C HOMAZ; LAURENT J ACQUIN

2008-01-01

396

Study of atmospheric stagnation, recirculation and ventilation potential at Narora Atomic Power Station NPP site.  

PubMed

The atmosphere is an important pathway to be considered in assessment of the environmental impact of radioactivity releases from nuclear facilities. The estimation of concentration of released effluents in air and possible ground contamination needs an understanding of relevant atmospheric dispersion. This paper describes the meteorological characteristics of Narora Atomic Power Station (NAPS) Nuclear Power Project site by using the integral parameters developed by Allwine and Whiteman (Atmospheric Environment 28(4):713-721, 1994). Meteorological data measured during the period 2006-2010 were analysed. The integral quantities related to the occurrence of stagnation, recirculation and ventilation characteristics were studied for the NAPS site to assess the dilution potential of the atmosphere. Wind run and recirculation factors were calculated for a 24-h transport time using 5 years of hourly surface measurements of wind speed and direction. The occurrence of stagnation, recirculation and ventilation characteristics during 2006-2010 at the NAPS site is observed to be 33.8, 19.5 and 34.7 % of the time, respectively. The presence of strong winds with predominant wind direction NW and WNW during winter and summer seasons leads to higher ventilation (48.1 and 44.3 %) and recirculation (32.6 % of the summer season). The presence of more dispersed light winds during pre-winter season with predominant wind directions W and WNW results in more stagnation (59.7 % of the pre-winter season). Thus, this study will serve as an essential meteorological tool to understand the transport mechanism of atmospheric radioactive effluent release from any nuclear industry during the pre-operational as well as operational phase. PMID:22821255

Kumar, Deepak; Kumar, Avinash; Kumar, Vimal; Kumar, Jaivender; Ravi, P M

2012-07-21

397

Constructions of Optical Queues With a Limited Number of Recirculations--Part I: Greedy Constructions  

Microsoft Academic Search

In this two-part paper, we consider SDL constructions of optical queues with\\u000aa limited number of recirculations through the optical switches and the fiber\\u000adelay lines. We show that the constructions of certain types of optical queues,\\u000aincluding linear compressors, linear decompressors, and 2-to-1 FIFO\\u000amultiplexers, under a simple packet routing scheme and under the constraint of\\u000aa limited number

Jay Cheng; Cheng-Shang Chang; Sheng-Hua Yang; Tsz-Hsuan Chao; Duan-Shin Lee; Ching-Ming Lien

2010-01-01

398

RECIRCULATING - REDUCING AND ALKALINITY PRODUCING SYSTEM (RERAPS) FOR THE TREATMENT OF ACIDIC COAL PILE RUNOFF 1  

Microsoft Academic Search

The treatment of acidic coal pile runoff (CPR) using an alternative constructed wetland design was evaluated. This alternative design, which provided improved wetland performance, was based on the partial re-circulation of treated water into a detention basin located immediately upstream from a Reducing and Alkalinity Producing System (RAPS). This modification created a semi-passive RAPS-based system we refer to as a

William E. Garrett; Alfred A. Bartolucci; Robert R. Pitt; Michael E. Vermace

2002-01-01

399

Recirculation pump discharge line break tests at ROSA-III for a boiling water reactor  

Microsoft Academic Search

Three loss-of-coolant accident (LOCA) tests were conducted at the Rig of Safety Assessment (ROSA)-III test facility, which simulates boiling water reactor (BWR)\\/6-251 with a volumetric scaling factor of 1\\/424. The fundamental features of the recirculation pump discharge line break LOCA and the effects of break areas on the features are investigated. It has been confirmed experimentally that the LOCA phenomena

M. Suzuki; Y. Anoda; H. Kumamaru; H. Nakamura; M. Shiba; K. Tasaka

1985-01-01

400

Noncardiogenic pulmonary edema induced by a molecular adsorbent recirculating system: case report  

Microsoft Academic Search

Noncardiogenic pulmonary edema is a well-recognized manifestation of acute lung injury which has been related, among others, to blood or blood-product transfusion, intravenous contrast injection, air embolism, and drug ingestion. We describe two cases of noncardiogenic pulmonary edema after use of a molecular adsorbent recirculating system, a cell-free dialysis technique. Patients in this series presented at our institution to be

Cataldo Doria; Lucio MandalÀ; Victor L. Scott; Ignazio R. Marino; Salvatore Gruttadauria; Roberto Miraglia; Claudio H. Vitale; Jan Smith

2003-01-01

401

Accelerated landfill waste decomposition by external leachate recirculation from an old landfill cell.  

PubMed

This research is focused on the management of moisture regime for a young landfill site in terms of leachate recirculation which entails the containment, collection and reinjection of leachate back into the landfill to promote in situ anaerobic biological treatment. Moreover, an innovative leachate management strategy was developed by using leachate recirculation from a mature landfill site into a young landfill site to provide accelerated waste stabilization. For this purpose, two reactors simulating young and old landfills were used in the laboratory. These reactors were loaded with shredded and compacted municipal solid waste with a typical composition determined for Istanbul Region. Both reactors were operated in a constant temperature room at 32 degrees C to enhance the growth of anaerobic microorganisms. Moreover, water was added to the reactors in order to simulate the annual rainfall. The reactor having the properties of old landfills was used as a control reactor. The reactor which represented the characteristics of young landfill was operated under four operational stages to enhance the activity of methanogenic population and accelerate waste stabilization. Results of this study indicated that the utilization of leachate recirculation enhanced waste stabilization in the young landfill by increasing the uniformity, and providing additional substrate and nutrients. Additions of buffer solutions of KOH and Na2CO3 together with leachate recirculation enhanced further waste stabilization and prevented possible acid inhibition. The utilization of external leachate recycled from the old landfill having desired acclimated anaerobic microorganisms, low organic content and higher buffer capacity into a young landfill could be a promising leachate management strategy for faster and controlled waste stabilization. PMID:12926691

Suna Erses, A; Onay, T T

2003-01-01

402

The Kuroshio Extension Northern Recirculation Gyre: Profiling Float Measurements and Forcing Mechanism  

Microsoft Academic Search

Middepth, time-mean circulation in the western North Pacific Ocean (28°-45°N, 140°-165°E) is investi- gated using drift information from the profiling floats deployed in the Kuroshio Extension System Study (KESS) and the International Argo programs. A well-defined, cyclonic recirculation gyre (RG) is found to exist north of the Kuroshio Extension jet, confined zonally between the Japan Trench (?145°E) and the Shatsky

Bo Qiu; Shuiming Chen; Peter Hacker; Nelson G. Hogg; Steven R. Jayne; Hideharu Sasaki

2008-01-01

403

A Sodium Bicarbonate Dosing Methodology for pH Management in Freshwater-Recirculating Aquaculture Systems  

Microsoft Academic Search

High-density water-recirculating aquaculture systems with hydraulic retention times above about 5 d must be monitored for alkalinity, and in the vast majority of cases, the alkalinity must be adjusted upwards to assure maintenance of desirable pH levels. Sodium bicarbonate is the preferred additive for increasing alkalinity because it is inexpensive, dissolves rapidly, and is safe for both personnel and fish.

J. Clay Loyless; Ronald F. Malone

1997-01-01

404

Heat and mass transfer in turbulent flows with several recirculated flow eddies  

Microsoft Academic Search

Numerical modeling of the concentration and temperature distribution in axial symmetrical systems with several recirculated flow eddies, which is based on various 2D stationary k-? models and commercial codes, e.g. ANSYS and FLUENT, leads to results, which are significantly different from experimental data. Therefore additional user-defined subroutines were included in the commercial program code to improve the turbulent heat and

E. Baake; B. Nacke; A. Jakovics; A. Umbrashko

2001-01-01

405

Studies in Support of Recirculating Bed Reactors for the Processing of Coal. Quarterly Report, July--October 1976.  

National Technical Information Service (NTIS)

This quarterly report summarizes the contract goals, engineering design philosophy, and progress by task. Task I, coal mixer modelling studies, to be done in a cold model of a recirculating bed reactor, will examine mixing by isokinetically sampling the e...

T. W. Bierl L. J. Gaydos

1976-01-01

406

A Laboratory Model of Exchange and Mixing Between Western Boundary Layers and Sub-basin Recirculation Gyres  

NASA Astrophysics Data System (ADS)

Chaotic advection is suggested as a possible mechanism for fluid exchange and mix- ing among a western boundary current and sub-basin recirculation gyres. Applications include the North Atlantic deep western boundary current and its adjacent mesoscale recirculation gyres. Visualization and quantification of certain aspects of chaotic ad- vection in a laboratory analog are described. Effective invariant manifolds and turn- stile lobes are revealed by careful introduction of dye. Transports and flushing times for the recirculations can be estimated using these objects. The effective diffusivity of the flow field is calculated and it is shown that configurations favorable for chaotic advection (i.e., flows with hyperbolic trajectories) undergo substantially more mixing than those that are not. The experiments suggest how tracers in deep western boundary currents might be transported into and out of neighboring recirculations.

Deese, H.; Pratt, L.; Helfrich, K.

407

Deflecting RF Cavity Design foir a Recirculating Linac Based Facility for Ultrafast X-Ray Science (LUX).  

National Technical Information Service (NTIS)

We report on superconducting deflecting RF cavity designs for a Recirculating Linac Based Facility for Ultrafast X-ray Science (LUX) at Lawrence Berkeley National Laboratory. The deflecting cavities operate in the lowest dipole mode and are required to pr...

D. Li J. N. Corlett

2003-01-01

408

A Numerical Model for the Prediction of Two Dimensional Unsteady Flows of Multicomponent Gases with Strong Buoyancy Effects and Recirculation.  

National Technical Information Service (NTIS)

In this report a numerical model is developed for the prediction of two dimensional, unsteady, buoyancy driven flows with recirculation. The model makes use of the full elliptic equations for mass, species, momentum and energy balance. The full equation o...

M. L. Doria

1974-01-01

409

Vadose zone microbiology  

SciTech Connect

The vadose zone is defined as the portion of the terrestrial subsurface that extends from the land surface downward to the water table. As such, it comprises the surface soil (the rooting zone), the underlying subsoil, and the capillary fringe that directly overlies the water table. The unsaturated zone between the rooting zone and the capillary fringe is termed the "intermediate zone" (Chapelle, 1993). The vadose zone has also been defined as the unsaturated zone, since the sediment pores and/or rock fractures are generally not completely water filled, but instead contain both water and air. The latter characteristic results in the term "zone of aeration" to describe the vadose zone. The terms "vadose zone," "unsaturated zone", and "zone of aeration" are nearly synonymous, except that the vadose zone may contain regions of perched water that are actually saturated. The term "subsoil" has also been used for studies of shallow areas of the subsurface immediately below the rooting zone. This review focuses almost exclusively on the unsaturated region beneath the soil layer since there is already an extensive body of literature on surface soil microbial communities and process, e.g., Paul and Clark (1989), Metting (1993), Richter and Markowitz, (1995), and Sylvia et al. (1998); whereas the deeper strata of the unsaturated zone have only recently come under scrutiny for their microbiological properties.

Kieft, Thomas L.; Brockman, Fred J.

2001-01-17

410

Analysis of the sodium recirculation theory of solute-coupled water transport in small intestine  

PubMed Central

Our previous mathematical model of solute-coupled water transport through the intestinal epithelium is extended for dealing with electrolytes rather than electroneutral solutes. A 3Na+–2K+ pump in the lateral membranes provides the energy-requiring step for driving transjunctional and translateral flows of water across the epithelium with recirculation of the diffusible ions maintained by a 1Na+-1K+–2Cl? cotransporter in the plasma membrane facing the serosal compartment. With intracellular non-diffusible anions and compliant plasma membranes, the model describes the dependence on membrane permeabilities and pump constants of fluxes of water and electrolytes, volumes and ion concentrations of cell and lateral intercellular space (lis), and membrane potentials and conductances. Simulating physiological bioelectrical features together with cellular and paracellular fluxes of the sodium ion, computations predict that the concentration differences between lis and bathing solutions are small for all three ions. Nevertheless, the diffusion fluxes of the ions out of lis significantly exceed their mass transports. It is concluded that isotonic transport requires recirculation of all three ions. The computed sodium recirculation flux that is required for isotonic transport corresponds to that estimated in experiments on toad small intestine. This result is shown to be robust and independent of whether the apical entrance mechanism for the sodium ion is a channel, a SGLT1 transporter driving inward uphill water flux, or an electroneutral Na+–K+–2Cl? cotransporter.

Larsen, Erik Hviid; S?rensen, Jakob Balslev; S?rensen, Jens N?rkaer

2002-01-01

411

Apparatus for controlling the exhaust gas recirculation rate in an internal combustion engine  

SciTech Connect

An apparatus is proposed for controlling the exhaust recirculation rate in an internal combustion engine, in particular an engine with auto-ignition, which includes preferably one mixture valve in the area of the discharge opening of the exhaust recirculation line and which is characterized in that the control is accomplished via the mixture valve position ahead of the inlet valves in accordance with the concentration of at least one component of the air-exhaust gas mixture and/or at least one component of the exhaust gas. Thus it is possible to operate the engine with a relatively emission-free exhaust. An exhaust gas reservoir is further provided, with which peaks in the exhaust gas concentration due to a dynamic driving mode can be intercepted. Finally, it is also proposed that the exhaust recirculation be realized solely via a pressure, which can be controlled in open-loop or closed-loop fashion, in the exhaust line by means of a valve.

Muller, K.; Linder, E.; Maurer, H.; Rieger, F.

1984-01-24

412

Biofouling reduction in recirculating cooling systems through biofiltration of process water.  

PubMed

Biofouling is a serious problem in industrial recirculating cooling systems. It damages equipment, through biocorrosion, and causes clogging and increased energy consumption, through decreased heat transfer. In this research a fixed-bed biofilter was developed which removed assimilable organic carbon (AOC) from process water, thus limiting the major substrate for the growth of biofouling. The biofilter was tested in a laboratory model recirculating cooling water system, including a heat exchanger and a cooling tower. A second identical model system without a biofilter served as a reference. Both installations were challenged with organic carbon (sucrose and yeast extract) to provoke biofouling. The biofilter improved the quality of the recirculating cooling water by reducing the AOC content, the ATP concentration, bacterial numbers (30-40 fold) and the turbidity (OD660). The process of biofouling in the heat exchangers, the process water pipelines and the cooling towers, was monitored by protein increase, heat transfer resistance, and chlorine demanded for maintenance. This revealed that biofouling was lower in the system with the biofilter compared to the reference installation. It was concluded that AOC removal through biofiltration provides an attractive, environmental-friendly means to reduce biofouling in industrial cooling systems. PMID:12688686

Meesters, K P H; Van Groenestijn, J W; Gerritse, J

2003-02-01

413

Performance of anaerobic hybrid reactors for the treatment of complex phenolic wastewaters with biogas recirculation.  

PubMed

This study investigates the application of a novel anaerobic hybrid reactor (AHR) configuration, incorporating support media for biomass immobilisation and biogas recirculation for improved mixing towards the anaerobic treatment of complex phenolic wastewater. Synthetic coal wastewater with an average phenolics and COD concentration of 752 and 2240 mg L(-1) was used as substrate. Biogas recirculation was employed at four different rates of 11.25, 16.87, 25.30 and 37.95 L d(-1) for 100 days. Phenolics and COD removal improved with increase in biogas recirculation. After 120 days of continuous operation, the results revealed that a high amount (14.0 g VSS) of biomass was able to attach itself to the support medium. The investigated AHR configuration achieved phenolics and COD removal efficiencies of 95% and 92% respectively at a hydraulic retention time (HRT) of 0.33 d. The corresponding average methane production obtained in this study was 0.02 mol methane g(-1) COD. PMID:23232220

Ramakrishnan, Anushuya; Surampalli, Rao Y

2012-11-16

414

Effects of Flue-Gas Recirculation on NOx Production and Performance of Pulse Combustion Hot-Water Boilers  

Microsoft Academic Search

Two hot-water boilers with rated inputs of 147 and 220 kW had NOx emissions near 40 and 50 ppm (3% O2), respectively, without flue-gas recirculation. With recirculation, NOx was reduced to 20-25 ppm for the larger boiler and to less than 20 ppm for the smaller one. Emissions of CO were not correlated with NOx; they depended on overall equivalence

Y. MICHEL; F. E. BELLES

1993-01-01

415

Duration of a large Mafic intrusion and heat transfer in the lower crust: A SHRIMP U-Pb zircon Study in the Ivrea-Verbano Zone (Western Alps, Italy)  

USGS Publications Warehouse

The Ivrea-Verbano Zone in the western Italian Alps contains one of the world's classic examples of ponding of mantle-derived, mafic magma in the deep crust. Within it, a voluminous, composite mafic pluton, the Mafic Complex, intruded lower-crustal, high-grade paragneiss of the Kinzigite Formation during Permian-Carboniferous time, and is now exposed in cross-section as a result of Alpine uplift. The age of the intrusion is still debated because the results of geochronological studies in the last three decades on different rock types and with various dating techniques range from 250 to about 300 Ma. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age determinations on 12 samples from several locations within the Mafic Complex were performed to better constrain the age of the igneous event. The results indicate a long history of magma emplacement and cooling, which reconciles the spread in previously published ages. The main intrusive phase took place at 288 ?? 4 Ma, causing a perturbation of the deep-crustal geotherm, which relaxed to the Sm-Nd closure temperature in garnet-free mafic rocks after about 15-20 Myr of sub-solidus cooling at c. 270 Ma. These results suggest that large, deep crustal plutons, such as those identified geophysically at depths of 10-20 km within extended continental crust (e.g. Yellowstone, Rio Grande Rift, Basin and Range) may have formed rapidly but induced a prolonged thermal perturbation. In addition, the data indicate that a significant thermal event affected the country rock of the Mafic Complex at about 310 Ma. The occurrence of an upper amphibolite- to granulite-facies thermal event in the Kinzigite Formation prior to the main intrusive phase of the Mafic Complex has been postulated by several workers, and is corroborated by other geochronological investigations. However, it remains uncertain whether this event (1) was part of a prolonged perturbation of the deep-crustal geotherm, which started long before the onset of intrusion of the Mafic Complex, or (2) corresponded to the intrusion of the first sills of the Mafic Complex, or (3) was related to an earlier, independent thermal pulse. ?? The Author 2007. Published by Oxford University Press. All rights reserved.

Peressini, G.; Quick, J. E.; Sinigoi, S.; Hofmann, A. W.; Fanning, M.

2007-01-01

416

Apparatus for controlling the recirculated exhaust gas quantities and the injection quantity in auto-igniting internal combustion engines  

SciTech Connect

An apparatus is proposed which serves the purpose of controlling the exhaust gas recirculation quantity and the injection quantity in auto-igniting internal combustion engines. In this apparatus, an arbitrarily actuatable throttle valve is provided in the intake manifold, downstream of which a control pressure is withdrawn from the intake manifold and used to actuate a pneumatic adjustment device which determines the position of the quantity adjustment device of a fuel injection pump. This control pressure simultaneously serves to actuate an exhaust gas recirculation valve and acts counter to the force of a restoring spring in the work chamber of a second pneumatic adjustment device. Thus, during idling and at full-load of the engine, little exhaust gas or none at all is recirculated and at mediumload and rpm the exhaust gas recirculation quantity is controlled in accordance with the induced air quantity, that is, according to load and rpm; at the same time, in the same sense, the suction pressure which actuates the quantity adjustment device is a standard for load and rpm, that is, for the induced air quantity. Thus with increasing suction pressure less fuel is injected, and more exhaust gas is recirculated, and at a desired high load level the power output of the engine is not impaired by exhaust gas recirculation.

Straubel, M.

1981-12-08

417

Apparatus for controlling the recirculated exhaust gas quantities and the injection quantity in auto-igniting internal combustion engines  

SciTech Connect

An apparatus is proposed which serves the purpose of controlling the exhaust gas recirculation quantity and the injection quantity in auto-igniting internal combustion engines. In this apparatus, an arbitrarily actuatable throttle valve is provided in the intake manifold, downstream of which a control pressure is withdrawn from the intake manifold and used to actuate a pneumatic adjustment device which determines the position of the quantity adjustment device of a fuel injection pump. This control pressure simultaneously serves to actuate an exhaust gas recirculation valve and acts counter to the force of a restoring spring in the work chamber of a second pneumatic adjustment device. Thus, during idling and at full-load of the engine, little exhaust gas or none at all is recirculated and at mediumload and rpm the exhaust gas recirculation quantity is controlled in accordance with the induced air quantity, that is, according to load and rpm; at the same time, in the same sense, the suction pressure which actuates the quantity adjustment device is a standard for load and rpm, that is, for the induced air quantity. Thus with increasing suction pressure less fuel is injected, and more exhaust gas is recirculated, and at a desired high load level the power output of the engine is not impaired by exhaust gas recirculation.

Straubel, M.

1982-10-19

418

The recirculating lymphocyte pool of the rat: a systematic description of the migratory behaviour of recirculating lymphocytes.  

PubMed Central

A comprehensive study of lymphocyte traffic in AO rats was performed under conditions as near to the physiological state as was practicable. In the light of previous results on the effect of environmental factors on the migratory behaviour of lymphocytes, thoracic duct cells were passed from blood to lymph in an intermediate rat before injection into a series of recipients for examination at time intervals from 1 min to 24 hr. At 1, 2 and 5 min after injection most of the labelled cells were in the blood, lungs and liver. The concentrations in these compartments fell over the next 25 min as the cells entered the spleen, lymph nodes (LN) and Peyer's patches according to a regular pattern. The peak localization in these latter organs occurred between 1 hr and 18 hr. Each organ had a characteristic time pattern of lymphocyte localization. Entry into mesenteric LN lagged behind other LN until 2.5 hr after injection following which mesenteric LN localization easily outstripped that in other LN to reach a delayed peak at 18 hr. Intravenously injected lymphocytes began to reappear in thoracic duct lymph in large numbers earlier than in previous studies so that the time taken for most T lymphocytes to cross LN from blood to lymph fell within the broad time band of 4-18 hr. Lymphocytes took on average 5-10 min to cross high endothelial venules when entering LN from the blood.

Smith, M E; Ford, W L

1983-01-01

419

Nonlinear thermal analysis with a boundary element zone condensation technique  

Microsoft Academic Search

This paper presents a substantially more economical technique for the boundary element analysis (BEA) of a large class of nonlinear heat transfer problems including those with temperature dependent conductivity, temperature dependent convection coefficients, and radiation boundary conditions. The technique involves an exact static condensation of boundary element zones in a multi-zone boundary element model. The condensed boundary element zone contributions

J. H. Kane; H. Wang; B. L. K. Kumar

1990-01-01

420

Recipe for Hypoxia: Playing the Dead Zone Game  

ERIC Educational Resources Information Center

|Dead zones--areas experiencing low levels of dissolved oxygen--are growing in shallow ocean waters around the world. Research has shown that dead zones form as a result of a specific type of pollution, called nutrient enrichment or eutrophication, and are found in almost every coastal zone where humans have large populations. Concepts related to…

Kastler, Jessica A.

2009-01-01

421

76 FR 42048 - Safety Zones; Swimming Events in Captain of the Port Boston Zone  

Federal Register 2010, 2011, 2012, 2013

...USCG-2011-0533] RIN 1625-AA00 Safety Zones; Swimming Events in Captain of the Port Boston...of the Port (COTP) Boston Zone for swimming events. This action is necessary to...navigable waters from the hazardous nature of swimming events such as large numbers of...

2011-07-18

422

THE SPECIFIC SELECTION OF RECIRCULATING LYMPHOCYTES BY ANTIGEN IN NORMAL AND PREIMMUNIZED RATS  

PubMed Central

Thoracic duct lymphocytes (TDL) from normal rats will restore a primary antibody response to sheep erythrocytes (SRBC) in irradiated recipients and cause a graft-versus-host reaction in F1 hybrid rats; lymphocytes from rats immunized with either tetanus toxoid or dinitrophenylated bovine gamma globulin (DNP BGG) will generate specific antibody after cell transfer and challenge. The ability of TDL to mediate each of these responses is severely depressed by giving a single intravenous dose of the specific antigen shortly before cannulation of the thoracic duct, although the lymphocyte donors themselves respond normally. The injection of antigen does not decrease the output of lymphocytes in the thoracic duct and the effect is specific for the antigen injected. The findings are most readily accounted for by assuming that small subpopulations of specific lymphocytes are selected from the recirculating pool by antigen which has localized in lymphoid tissue. The observation that passive antibody abolishes selection by SRBC supports this interpretation. The strong selection exerted by a subcutaneous injection of SRBC in Freund's complete adjuvant, which induces delayed hypersensitivity but little early antibody, suggests that a common cell type may be involved in the induction of both delayed hypersensitivity and antibody formation. The anti-DNP antibody response generated by TDL from rats immunized with DNP BGG was abolished by a selecting injection of the homologous conjugate. The response was depressed to a smaller degree by injections of either BGG or dinitrophenylated human serum albumin, suggesting that carrier-specific (T) and hapten-specific (B) lymphocytes could be separately selected from the recirculating pool. The regional selection of recirculating lymphocytes by antigen may explain a number of phenomena in which the prior injection of antigen has been found to inhibit a subsequent immune response.

Rowley, D. A.; Gowans, J. L.; Atkins, R. C.; Ford, W. L.; Smith, Marilyn E.

1972-01-01

423

Two-group interfacial area transport equation in large diameter pipes  

NASA Astrophysics Data System (ADS)

The closure relations for the two-group interfacial area transport equation (LATE) by which the changes of interfacial area concentration can be dynamically modeled are set forth in this thesis for the case of large diameter pipes. In the two-group formulation, the sources and sink terms are established by mechanistic modeling of the intra-group and inter-group transport of the bubbles based on five major bubble interaction mechanisms. These mechanisms are bubble coalescence as a result of random collision, RC, wake entrainment, WE, bubble break-up due to turbulent impact, TI, small bubble shearing-off of large bubbles, SO, and bubble break-up due to surface instability for large bubbles, SI. The models developed are supported by experiments using a four-sensor conductivity probe in large diameter test sections, 10.16 cm and 15.24 cm in diameter. A total of 31 different flow conditions under atmospheric pressure are examined in the bubbly to churn-turbulent flow regimes. The local flow parameters measured by the multi-sensor conductivity probe include the local time-averaged void fraction, interfacial area concentration, bubble Sauter mean diameter, interfacial velocity, and interface frequency for the two groups of bubbles. The model is evaluated against the extensive database and good agreement is obtained between the model predictions and the experimental data. The average error based on the total interfacial area concentration is around 7.0% for interfacial area concentration in both test sections. Recirculation in the large pipes is given special treatment in the measurement analysis. Using upwards and downwards facing probes, information on the missing bubble signals is obtained which is used to correct the local data by either the Effective Bubble Number or Intrusiveness Factor Method. The correction to void fraction is found to be about a 12% increase in the local area averaged value, while interfacial area concentration may increase upwards of 60% in the recirculation zones. Comparison of the model predictions with the corrected data are reasonably good. Scaling of the IATE and application of the newly developed models to smaller pipe sizes is also discussed with emphasis on the model dependencies on the length scales of the flow.

Smith, Todd Ryan

2002-01-01

424

Recirculating Beam Breakup Study for the 12 GeV Upgrade at Jefferson Lab  

SciTech Connect

Two new high gradient C100 cryomodules with a total of 16 new cavities were installed at the end of the CEBAF south linac during the 2011 summer shutdown as part of the 12-GeV upgrade project at Jefferson Lab. We surveyed the higher order modes (HOMs) of these cavities in the Jefferson Lab cryomodule test facility and CEBAF tunnel. We then studied recirculating beam breakup (BBU) in November 2011 to evaluate CEBAF low energy performance, measure transport optics, and evaluate BBU thresholds due to these HOMs. This paper discusses the experiment setup, cavity measurements, machine setup, optics measurements, and lower bounds on BBU thresholds by new cryomodules.

Ilkyoung Shin, Todd Satogata, Shahid Ahmed, Slawomir Bogacz, Mircea Stirbet, Haipeng Wang, Yan Wang, Byung Yunn, Ryan Bodenstein

2012-07-01

425

Dynamic tuning of optical waveguides with electrowetting pumps and recirculating fluid channels  

NASA Astrophysics Data System (ADS)

We have developed an approach for using electrowetting actuation in recirculating fluidic channels to achieve dynamic tuning of optical fiber structures. The electrically controlled and fully reversible motion of the fluids and lubricants in these channels alters the refractive index profile experienced by the optical waveguide modes of the fiber. When combined with in-fiber gratings and etched fibers, this fluidic system yields dynamically adjustable narrow and broadband fiber filters, respectively. The nonmechanical operation of these systems, their ability to support switching speeds on the order of milliseconds, and their excellent optical characteristics indicate a promising potential for electrowetting-actuated fluidic tuning in optical fiber devices and other photonic components.

Mach, P.; Krupenkin, T.; Yang, S.; Rogers, J. A.

2002-07-01

426

Determination of nitrate ion content in recirculating water in petroleum refineries and petrochemical plants  

SciTech Connect

A method for determining nitrate ions, using a 2,6-diacetaminopyridine solution in concentrated sulfuric acid, was investigated. Potassium nitrate solutions with nitrate ion contents of 1 mg/ml, including a 2% aqueous solution of sulfamic acid, a 0.5% solution of antimony trioxide in concentrated sulfuric acid, were used. The solutions were mixed with a 1-4 ml sample of recirculating water in two 25 ml flasks. The optical density of the solution was measured relative to the zero standard of the scale of the calibration curve. Nitrate ion content was measured by the calibration curve, from data obtained in a series of 25-ml volumetric flasks.

Sukhova, N.S.; Bokova, Z.I.

1987-11-01

427

Effects of Exhaust Gas Recirculation on SI Engines at Wide Open Throttle  

NASA Astrophysics Data System (ADS)

Exhaust gas recirculation, a charge dilution technique, has proven to be an effective method of reducing NOx emissions and fuel consumption of spark ignition engines. Wide open throttle operation also increases overall engine efficiency by reducing the pumping losses caused by throttling. In this study, the emissions and fuel economy benefits of exhaust gas recirculation (EGR) at wide open throttle conditions were quantified using a 2.4L port-injected engine. Engine performance and emissions data were recorded as the percentage of EGR in the intake charge was increased from zero to just above thirty percent (the EGR limit). This EGR percentage, in-cylinder pressure measurements, and the temperatures and pressures of the intake and exhaust were all recorded to ensure stable operating conditions. These tests were performed with a stoichiometric air-fuel ratio at a constant speed of 2000 rpm at wide open throttle. The variation of brake specific fuel consumption and emissions (in particular NOx) with increasing EGR percentages was analyzed.

Bronson, Sydney; Puzinauskas, Paulius

2011-11-01

428

Investigation of sludge re-circulating clarifiers design and optimization through numerical simulation.  

PubMed

In steam thermal power plants (TPP) with open re-circulating wet cooling towers, elimination of water hardness and suspended solids (SS) is performed in clarifiers. Most of these clarifiers are of high efficiency sludge re-circulating type (SRC) with capacity between 500-1,500 m3/hr. Improper design and/or mal-operation of clarifiers in TPPs results in working conditions below design capacity or production of soft water with improper quality (hardness and S.S.). This causes accumulation of deposits in heat exchangers, condenser tubes, cooling and service water pipes and boiler tubes as well as increasing the ionic load of water at the demineralizing system inlet. It also increases the amount of chemical consumptions and produces more liquid and solid waste. In this regard, a software program for optimal design and simulation of SRCs has been developed. Then design parameters of existing SRCs in four TPPs in Iran were used as inputs to developed software program and resulting technical specifications were compared with existing ones. In some cases improper design was the main cause of poor outlet water quality. In order to achieve proper efficiency, further investigations were made to obtain control parameters as well as design parameters for both mal-designed and/or mal-operated SRCs. PMID:14753549

Davari, S; Lichayee, M J

2003-01-01

429

Nitrification in brackish water recirculating aquaculture system integrated with activated packed bed bioreactor.  

PubMed

Recirculation aquaculture systems (RAS) depend on nitrifying biofilters for the maintenance of water quality, increased biosecurity and environmental sustainability. To satisfy these requirements a packed bed bioreactor (PBBR) activated with indigenous nitrifying bacterial consortia has been developed and commercialized for operation under different salinities for instant nitrification in shrimp and prawn hatchery systems. In the present study the nitrification efficiency of the bioreactor was tested in a laboratory level recirculating aquaculture system for the rearing of Penaeus monodon for a period of two months under higher feeding rates and no water exchange. Rapid setting up of nitrification was observed during the operation, as the volumetric total ammonia nitrogen removal rates (VTR) increased with total ammonia nitrogen (TAN) production in the system. The average Volumetric TAN Removal Rates (VTR) at the feeding rate of 160 g/day from 54-60th days of culture was 0.1533+/-0.0045 kg TAN/m(3)/day. The regression between VTR and TAN explained 86% variability in VTR (P<0.001). The laboratory level RAS demonstrated here showed high performance both in terms of shrimp biomass yield and nitrification and environmental quality maintenance. Fluorescent in-situ Hybridization analysis of the reactor biofilm ensured the presence of autotrophic nitrifier groups such as Nitrosococcus mobilis lineage, Nitrobacter spp and phylum Nitrospira, the constituent members present in the original consortia used for activating the reactors. This showed the stability of the consortia on long term operation. PMID:20150717

Rejish Kumar, V J; Joseph, Valsamma; Philip, Rosamma; Bright Singh, I S

2010-01-01

430

Fate of saline ions in a planted landfill site with leachate recirculation.  

PubMed

Recirculation of leachate on a covered landfill site planted with willows or other highly evapotranspirative woody plants is an inexpensive option for leachate management. In our study, a closed landfill leachate recirculation system was established on a rehabilitated municipal solid waste landfill site with planted landfill cover. The main objective of the study was to evaluate the sustainability of the system with regard to high hydraulic loads of the landfill leachate on the landfill cover and high concentrations of saline ions, especially potassium (K(+)), sodium (Na(+)) and chloride (Cl(-)), in leachate. The results of intensive monitoring, implemented during May 2004 and September 2007, including leachate, soil and plant samples, showed a high sustainability of the system regarding saline ions with the precipitation regime of the studied region. Saline ion concentrations in leachates varied between 132 and 2592mg Cl(-) L(-1), 69 and 1310mg Na(+) L(-1) and between 66 and 2156mg K(+) L(-1), with mean values of 1010, 632 and 686mg L(-1), re