Inverse and Direct Energy Cascades in Three-Dimensional Magnetohydrodynamic Turbulence at Low Magnetic Reynolds Number

NASA Astrophysics Data System (ADS)

Baker, Nathaniel T.; Pothérat, Alban; Davoust, Laurent; Debray, François

2018-06-01

This experimental study analyzes the relationship between the dimensionality of turbulence and the upscale or downscale nature of its energy transfers. We do so by forcing low-R m magnetohydrodynamic turbulence in a confined channel, while precisely controlling its dimensionality by means of an externally applied magnetic field. We first identify a specific length scale l^⊥ c that separates smaller 3D structures from larger quasi-2D ones. We then show that an inverse energy cascade of horizontal kinetic energy along horizontal scales is always observable at large scales, and that it extends well into the region of 3D structures. At the same time, a direct energy cascade confined to the smallest and strongly 3D scales is observed. These dynamics therefore appear not to be simply determined by the dimensionality of individual scales, nor by the forcing scale, unlike in other studies. In fact, our findings suggest that the relationship between kinematics and dynamics is not universal and may strongly depend on the forcing and dissipating mechanisms at play.

A Method for Estimating 2D Horizontal Shortening at Wrinkle Ridges from Remote Sensing Data: Results from the Yakima Fold Belt (Columbia Plateau)

NASA Astrophysics Data System (ADS)

Mege, D.

1999-03-01

Field data and length/displacement scaling laws applied to the Yakima fold belt on the Columbia Plateau are used to demonstrate a method for estimating surface shortening of wrinkle ridge areas. Application to martian wrinkle ridges is given in another abstract.

Shape dependence of slip length on patterned hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Gu, Xiaokun; Chen, Min

2011-08-01

The effects of solid-liquid interfacial shape on the boundary velocity slip of patterned hydrophobic surfaces are investigated. The scaling law in literature is extended to demonstrate the role of such shape, indicating a decrease of the effective slip length with increasing interfacial roughness. A patterned surface with horizontally aligned carbon nanotube arrays reaches an effective slip length of 83 nm, by utilizing large intrinsic slippage of carbon nanotube while keeping away from the negative effects of interfacial curvature through the flow direction. The results emphasize the importance of avoiding the solid-liquid interfacial roughness in low-friction patterned surface design and manufacture.

Horizontal and vertical structure of reactive bromine events probed by bromine monoxide MAX-DOAS

NASA Astrophysics Data System (ADS)

Simpson, William R.; Peterson, Peter K.; Frieß, Udo; Sihler, Holger; Lampel, Johannes; Platt, Ulrich; Moore, Chris; Pratt, Kerri; Shepson, Paul; Halfacre, John; Nghiem, Son V.

2017-08-01

Heterogeneous photochemistry converts bromide (Br-) to reactive bromine species (Br atoms and bromine monoxide, BrO) that dominate Arctic springtime chemistry. This phenomenon has many impacts such as boundary-layer ozone depletion, mercury oxidation and deposition, and modification of the fate of hydrocarbon species. To study environmental controls on reactive bromine events, the BRomine, Ozone, and Mercury EXperiment (BROMEX) was carried out from early March to mid-April 2012 near Barrow (Utqiaġvik), Alaska. We measured horizontal and vertical gradients in BrO with multiple-axis differential optical absorption spectroscopy (MAX-DOAS) instrumentation at three sites, two mobile and one fixed. During the campaign, a large crack in the sea ice (an open lead) formed pushing one instrument package ˜ 250 km downwind from Barrow (Utqiaġvik). Convection associated with the open lead converted the BrO vertical structure from a surface-based event to a lofted event downwind of the lead influence. The column abundance of BrO downwind of the re-freezing lead was comparable to upwind amounts, indicating direct reactions on frost flowers or open seawater was not a major reactive bromine source. When these three sites were separated by ˜ 30 km length scales of unbroken sea ice, the BrO amount and vertical distributions were highly correlated for most of the time, indicating the horizontal length scales of BrO events were typically larger than ˜ 30 km in the absence of sea ice features. Although BrO amount and vertical distribution were similar between sites most of the time, rapid changes in BrO with edges significantly smaller than this ˜ 30 km length scale episodically transported between the sites, indicating BrO events were large but with sharp edge contrasts. BrO was often found in shallow layers that recycled reactive bromine via heterogeneous reactions on snowpack. Episodically, these surface-based events propagated aloft when aerosol extinction was higher (> 0.1 km-1); however, the presence of aerosol particles aloft was not sufficient to produce BrO aloft. Highly depleted ozone (< 1 nmol mol-1) repartitioned reactive bromine away from BrO and drove BrO events aloft in cases. This work demonstrates the interplay between atmospheric mixing and heterogeneous chemistry that affects the vertical structure and horizontal extent of reactive bromine events.

Spatial structure of plasma density perturbations, induced in the ionosphere modified by powerful HF radio waves: Review of experimental results

NASA Astrophysics Data System (ADS)

Frolov, Vladimir

2015-06-01

In the review, the results of experimental studies of spatial structure of small-, middle-, and large scale plasma density perturbations induced in the ionosphere by its pumping by powerful HF O-mode (ordinary) radio waves, are analyzed. It is shown that the region with induced plasma density perturbations occupied all ionosphere body from its E-region up to the topside ionosphere in the height and it has the horizontal length of about of 300-500 km. Peculiarities of generation of artificial ionosphere irregularities of different scale-lengths in the magnetic zenith region are stated. Experimental results obtained under conditions of ionosphere periodical pumping when the generation of travel ionosphere disturbances is revealed are also discussed.

Large-scale variability of wind erosion mass flux rates at Owens Lake 1. Vertical profiles of horizontal mass fluxes of wind-eroded particles with diameter greater than 50 μm

USGS Publications Warehouse

Gillette, Dale A.; Fryrear, D.W.; Xiao, Jing Bing; Stockton, Paul; Ono, Duane; Helm, Paula J.; Gill, Thomas E; Ley, Trevor

1997-01-01

A field experiment at Owens (dry) Lake, California, tested whether and how the relative profiles of airborne horizontal mass fluxes for >50-μm wind-eroded particles changed with friction velocity. The horizontal mass flux at almost all measured heights increased proportionally to the cube of friction velocity above an apparent threshold friction velocity for all sediment tested and increased with height except at one coarse-sand site where the relative horizontal mass flux profile did not change with friction velocity. Size distributions for long-time-averaged horizontal mass flux samples showed a saltation layer from the surface to a height between 30 and 50 cm, above which suspended particles dominate. Measurements from a large dust source area on a line parallel to the wind showed that even though the saltation flux reached equilibrium ∼650 m downwind of the starting point of erosion, weakly suspended particles were still input into the atmosphere 1567 m downwind of the starting point; thus the saltating fraction of the total mass flux decreased after 650 m. The scale length difference and ratio of 70/30 suspended mass flux to saltation mass flux at the farthest down wind sampling site confirm that suspended particles are very important for mass budgets in large source areas and that saltation mass flux can be a variable fraction of total horizontal mass flux for soils with a substantial fraction of <100-μm particles.

Propagation and damping of Alfvén waves in low solar atmosphere

NASA Astrophysics Data System (ADS)

Ryu, Chang-Mo; Huynh, Cong Tuan

2017-10-01

Propagation and damping of Alfvén waves in the inner solar corona are studied using a 2D magnetohydrodynamics (MHD) simulation code with realistic density and temperature profiles in a uniform background magnetic field. A linear wave is launched by ascribing a sinusoidal fluid motion at about 1000 km from the surface of the Sun, which is shown to generate Alfvénic wave motions along the height. The 2D MHD simulation shows that for B0 ≈ 3 G, Alfvén waves of about 10-2 Hz with an infinite horizontal length-scale can penetrate into the corona, transferring about 90 per cent their energies. This raises the possibility that the wave can be dissipated by various physical processes. The results show that the propagating wave can effectively damp via viscosity in the lower region of the corona, if a horizontal scale of granular size is incorporated.

A spatial length scale analysis of turbulent temperature and velocity fluctuations within and above an orchard canopy

USGS Publications Warehouse

Wang, Y.S.; Miller, D.R.; Anderson, D.E.; Cionco, R.M.; Lin, J.D.

1992-01-01

Turbulent flow within and above an almond orchard was measured with three-dimensional wind sensors and fine-wire thermocouple sensors arranged in a horizontal array. The data showed organized turbulent structures as indicated by coherent asymmetric ramp patterns in the time series traces across the sensor array. Space-time correlation analysis indicated that velocity and temperature fluctuations were significantly correlated over a transverse distance more than 4m. Integral length scales of velocity and temperature fluctuations were substantially greater in unstable conditions than those in stable conditions. The coherence spectral analysis indicated that Davenport's geometric similarity hypothesis was satisfied in the lower frequency region. From the geometric similarity hypothesis, the spatial extents of large ramp structures were also estimated with the coherence functions.

On effects of topography in rotating flows

NASA Astrophysics Data System (ADS)

Burmann, Fabian; Noir, Jerome; Jackson, Andrew

2017-11-01

Both, seismological studies and geodynamic arguments suggest that there is significant topography at the core mantle boundary (CMB). This leads to the question whether the topography of the CMB could influence the flow in the Earth's outer core. As a preliminary experiment, we investigate the effects of bottom topography in the so-called Spin-Up, where motion of a contained fluid is created by a sudden increase of rotation rate. Experiments are performed in a cylindrical container mounted on a rotating table and quantitative results are obtained with particle image velocimetry. Several horizontal length scales of topography (λ) are investigated, ranging from cases where λ is much smaller then the lateral extend of the experiment (R) to cases where λ is a fraction of R. We find that there is an optimal λ that creates maximum dissipation of kinetic energy. Depending on the length scale of the topography, kinetic energy is either dissipated in the boundary layer or in the bulk of the fluid. Two different phases of fluid motion are present: a starting flow in the from of solid rotation (phase I), which is later replaced by meso scale vortices on the length scale of bottom topography (phase II).

Mid-tropospheric Spectral Length-scale Analysis of Many Constituents from Aircraft, Satellite and Model Results During the 2013 SENEX Field Study.

NASA Astrophysics Data System (ADS)

McKeen, S. A.; Angevine, W. M.; Ahmadov, R.; Frost, G. J.; Kim, S. W.; Cui, Y.; McDonald, B.; Trainer, M.; Holloway, J. S.; Ryerson, T. B.; Peischl, J.; Gambacorta, A.; Barnet, C. D.; Smith, N.; Pierce, R. B.

2016-12-01

This study presents preliminary comparisons of satellite, aircraft, and model variance spectra for meteorological, thermodynamic and gas-phase species collected during the 2013 Southeastern Nexus Air Quality Experiment (SENEX). Fourier analysis of 8 constituents collected at 1 Hz by the NOAA W-P3 aircraft in the 25 to 200 km length-scale range exhibit properties consistent with previous scale dependence studies: when spectra are averaged over several 500 mb flight legs, very linear dependence is found on log-log plots of spectral density versus inverse length-scale. Derived slopes for wind speed, temperature, H2O, CO, CO2, CH4, NOy and O3 all fall within ±30% and close to the slope of -5/3 predicted from dimensional scaling theory of isotropic turbulence. Qualitative differences are seen when a similar analysis, without quality control, is applied to a preliminary set of NUCAPS satellite retrievals over the continental U.S. during SENEX. While 500mb water vapor and column integrated water show slopes close to the -5/3 value in the 200 to 1000 km length-scale range, other quantities show significantly shallower slopes, suggesting the need for rigorous quality control. Results from WRF-Chem regional air quality model simulations at 500mb show the model is unable to account for variance on length-scales less than 6ΔX, where ΔX is the model horizontal resolution (12km). Comparisons with satellite data in the 200 to 1000km range show slopes consistent with the -5/3 power law for species such as CO, CH4 and CO2 that do not undergo reinitialization, suggesting potential for future application.

Visual and visually mediated haptic illusions with Titchener's ⊥.

PubMed

Landwehr, Klaus

2014-05-01

For a replication and expansion of a previous experiment of mine, 14 newly recruited participants provided haptic and verbal estimates of the lengths of the two lines that make up Titchener's ⊥. The stimulus was presented at two different orientations (frontoparallel vs. horizontal) and rotated in steps of 45 deg around 2π. Haptically, the divided line of the ⊥ was generally underestimated, especially at a horizontal orientation. Verbal judgments also differed according to presentation condition and to which line was the target, with the overestimation of the undivided line ranging between 6.2 % and 15.3 %. The results are discussed with reference to the two-visual-systems theory of perception and action, neuroscientific accounts, and also recent historical developments (the use of handheld touchscreens, in particular), because the previously reported "haptic induction effect" (the scaling of haptic responses to the divided line of the ⊥, depending on the length of the undivided one) did not replicate.

Mw7.7 2013 Balochistan Earthquake. Slip-Distribution and Deformation Field in Oblique Tectonic Context

NASA Astrophysics Data System (ADS)

Klinger, Y.; Vallage, A.; Grandin, R.; Delorme, A.; Rosu, A. M.; Pierro-Deseilligny, M.

2014-12-01

The Mw7.7 2013 Balochistan earthquake ruptured 200 km of the Hoshab fault, the southern end of the Chaman fault. Azimuth of the fault changes by more than 30° along rupture, from a well-oriented strike-slip fault to a more thrust prone direction. We use the MicMac optical image software to correlate pairs of Landsat images taken before and after the earthquake to access to the horizontal displacement field associated with the earthquake. We combine the horizontal displacement with radar image correlation in range and radar interferometry to derive the co-seismic slip on the fault. The combination of these different datasets actually provides the 3D displacement field. We note that although the earthquake was mainly strike-slip all along the rupture length, some vertical motion patches exist, which locations seem to be controlled by kilometric-scale variations of the fault geometry. 5 pairs of SPOT images were also correlated to derive a 2.5m pixel-size horizontal displacement field, providing unique opportunity to look at deformation in the near field and to obtain high-resolution strike-slip and normal slip-distributions. We note a significant difference, especially in the normal component, between the slip localized at depth on the fault plane and the slip localized closer to the surface, with more apparent slip at the surface. A high-resolution map of ground rupture allows us to locate the distribution of the deformation over the whole rupture length. The rupture map also highlights multiple fault geometric complexities where we could quantify details of the slip distribution. At the rupture length-scale, the local azimuth variations between segments have a large impact on the expression of the localized slip at the surface. The combination of those datasets gives an overview of the large distribution of the deformation in the near field, corresponding to the co-seismic damage zone.

Characteristics of Upper Quadrant Posture of Young Women with Temporomandibular Disorders

PubMed Central

Uritani, Daisuke; Kawakami, Tetsuji; Inoue, Tomohiro; Kirita, Tadaaki

2014-01-01

[Purpose] This study aimed to investigate the characteristics of upper quadrant posture of young women with temporomandibular disorders. [Subjects] The participants were 19 female patients with temporomandibular disorders (patient group: mean age, 30.1 years) and 14 controls (control group: mean age, 24.6 years). [Methods] Outcome measures were the neck inclination angle (formed by a line connecting C7 and the ear tragus with a horizontal line), the angle of the shoulder (formed by a line connecting C7 and the acromial angle with a horizontal line), the cranial rotation angle (formed by a line connecting the ear tragus and the corner of the eye with a horizontal line), and the neck-length/shoulder-width ratio [the ratio of the neck length (from C7 to the tragus) to the width of the shoulder between the acromial angle]. The maximum range of mouth opening was measured using a scale. [Results] The neck inclination angle and maximum range of mouth opening were significantly smaller in the patient group than in the control group. No significant differences were observed in the other outcome measures between the two groups. [Conclusion] Temporomandibular disorders with limited mouth opening in young females are associated with the head position relative to the trunk. PMID:25276038

Geostatistical Analysis of Mesoscale Spatial Variability and Error in SeaWiFS and MODIS/Aqua Global Ocean Color Data

NASA Astrophysics Data System (ADS)

Glover, David M.; Doney, Scott C.; Oestreich, William K.; Tullo, Alisdair W.

2018-01-01

Mesoscale (10-300 km, weeks to months) physical variability strongly modulates the structure and dynamics of planktonic marine ecosystems via both turbulent advection and environmental impacts upon biological rates. Using structure function analysis (geostatistics), we quantify the mesoscale biological signals within global 13 year SeaWiFS (1998-2010) and 8 year MODIS/Aqua (2003-2010) chlorophyll a ocean color data (Level-3, 9 km resolution). We present geographical distributions, seasonality, and interannual variability of key geostatistical parameters: unresolved variability or noise, resolved variability, and spatial range. Resolved variability is nearly identical for both instruments, indicating that geostatistical techniques isolate a robust measure of biophysical mesoscale variability largely independent of measurement platform. In contrast, unresolved variability in MODIS/Aqua is substantially lower than in SeaWiFS, especially in oligotrophic waters where previous analysis identified a problem for the SeaWiFS instrument likely due to sensor noise characteristics. Both records exhibit a statistically significant relationship between resolved mesoscale variability and the low-pass filtered chlorophyll field horizontal gradient magnitude, consistent with physical stirring acting on large-scale gradient as an important factor supporting observed mesoscale variability. Comparable horizontal length scales for variability are found from tracer-based scaling arguments and geostatistical decorrelation. Regional variations between these length scales may reflect scale dependence of biological mechanisms that also create variability directly at the mesoscale, for example, enhanced net phytoplankton growth in coastal and frontal upwelling and convective mixing regions. Global estimates of mesoscale biophysical variability provide an improved basis for evaluating higher resolution, coupled ecosystem-ocean general circulation models, and data assimilation.

Influence of eye rotation on peripheral eye length measurement obtained with a partial coherence interferometry instrument.

PubMed

Verkicharla, Pavan K; Suheimat, Marwan; Mallen, Edward A H; Atchison, David A

2014-01-01

The eye rotation approach for measuring peripheral eye length leads to concern about whether the rotation influences results, such as through pressure exerted by eyelids or extra-ocular muscles. This study investigated whether this approach is valid. Peripheral eye lengths were measured with a Lenstar LS 900 biometer for eye rotation and no-eye rotation conditions (head rotation for horizontal meridian and instrument rotation for vertical meridian). Measurements were made for 23 healthy young adults along the horizontal visual field (± 30°) and, for a subset of eight participants along the vertical visual field (± 25°). To investigate the influence of the duration of eye rotation, for six participants measurements were made at 0, 60, 120, 180 and 210 s after eye rotation to ± 30° along horizontal and vertical visual fields. Peripheral eye lengths were not significantly different for the conditions along the vertical meridian (F1,7 = 0.16, p = 0.71). The peripheral eye lengths for the conditions were significantly different along the horizontal meridian (F1,22 = 4.85, p = 0.04), although not at individual positions (p ≥ 0.10) and were not important. There were no apparent differences between the emmetropic and myopic groups. There was no significant change in eye length at any position after maintaining position for 210 s. Eye rotation and no-eye rotation conditions were similar for measuring peripheral eye lengths along horizontal and vertical visual field meridians at ± 30° and ± 25°, respectively. Either condition can be used to estimate retinal shape from peripheral eye lengths. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Anisotropy of Observed and Simulated Turbulence in Marine Stratocumulus

NASA Astrophysics Data System (ADS)

Pedersen, J. G.; Ma, Y.-F.; Grabowski, W. W.; Malinowski, S. P.

2018-02-01

Anisotropy of turbulence near the top of the stratocumulus-topped boundary layer (STBL) is studied using large-eddy simulation (LES) and measurements from the POST and DYCOMS-II field campaigns. Focusing on turbulence ˜100 m below the cloud top, we see remarkable similarity between daytime and nocturnal flight data covering different inversion strengths and free-tropospheric conditions. With λ denoting wavelength and zt cloud-top height, we find that turbulence at λ/zt≃0.01 is weakly dominated by horizontal fluctuations, while turbulence at λ/zt>1 becomes strongly dominated by horizontal fluctuations. Between are scales at which vertical fluctuations dominate. Typical-resolution LES of the STBL (based on POST flight 13 and DYCOMS-II flight 1) captures observed characteristics of below-cloud-top turbulence reasonably well. However, using a fixed vertical grid spacing of 5 m, decreasing the horizontal grid spacing and increasing the subgrid-scale mixing length leads to increased dominance of vertical fluctuations, increased entrainment velocity, and decreased liquid water path. Our analysis supports the notion that entrainment parameterizations (e.g., in climate models) could potentially be improved by accounting more accurately for anisotropic deformation of turbulence in the cloud-top region. While LES has the potential to facilitate improved understanding of anisotropic cloud-top turbulence, sensitivity to grid spacing, grid-box aspect ratio, and subgrid-scale model needs to be addressed.

Steady Fluid Flow to a Radial System of Horizontal Wells

NASA Astrophysics Data System (ADS)

Morozov, P. E.

2018-03-01

A semi-analyticalmethod for determining the productivity of a radial system of horizontal wells in an anisotropic reservoir is proposed. Calculation results for the productivity and distribution of fluid flow along the length of the wellbores of the radial system of horizontal wells using the proposed method are compared with the data of experimental studies based on electrolytic simulation and engineering formulas. The effects of the number of wellbores, their location in the reservoir, and the hydraulic pressure loss on the distribution of the fluid flow along the length of horizontal wellbores are investigated.

Noise characteristics of upper surface blown configurations. Experimental program and results

NASA Technical Reports Server (NTRS)

Brown, W. H.; Searle, N.; Blakney, D. F.; Pennock, A. P.; Gibson, J. S.

1977-01-01

An experimental data base was developed from the model upper surface blowing (USB) propulsive lift system hardware. While the emphasis was on far field noise data, a considerable amount of relevant flow field data were also obtained. The data were derived from experiments in four different facilities resulting in: (1) small scale static flow field data; (2) small scale static noise data; (3) small scale simulated forward speed noise and load data; and (4) limited larger-scale static noise flow field and load data. All of the small scale tests used the same USB flap parts. Operational and geometrical variables covered in the test program included jet velocity, nozzle shape, nozzle area, nozzle impingement angle, nozzle vertical and horizontal location, flap length, flap deflection angle, and flap radius of curvature.

SUPERGRANULATION AS THE LARGEST BUOYANTLY DRIVEN CONVECTIVE SCALE OF THE SUN

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

Cossette, Jean-Francois; Rast, Mark P.

The origin of solar supergranulation remains a mystery. Unlike granulation, the size of which is comparable to both the thickness of the radiative boundary layer and local scale-height in the photosphere, supergranulation does not reflect any obvious length scale of the solar convection zone. Moreover, recent observations of flows in the photosphere using Doppler imaging or correlation or feature tracking show a monotonic decrease in horizontal flow power at scales larger than supergranulation. Both local area and global spherical shell simulations of solar convection by contrast show the opposite, an increase in horizontal flow amplitudes to a low wavenumber. Wemore » examine these disparities and investigate how the solar supergranulation may arise as a consequence of nonlocal heat transport by cool diving plumes. Using three-dimensional anelastic simulations with surface driving, we show that the kinetic energy of the largest convective scales in the upper layers of a stratified domain reflects the depth of transition from strong buoyant driving to adiabatic stratification below caused by the dilution of the granular downflows. This depth is quite shallow because of the rapid increase of the mean density below the photosphere. We interpret the observed monotonic decrease in solar convective power at scales larger than supergranulation to be a consequence of this rapid transition, with the supergranular scale the largest buoyantly driven mode of convection in the Sun.« less

Description of signature scales in a floating wind turbine model wake subjected to varying turbulence intensity

NASA Astrophysics Data System (ADS)

Kadum, Hawwa; Rockel, Stanislav; Holling, Michael; Peinke, Joachim; Cal, Raul Bayon

2017-11-01

The wake behind a floating model horizontal axis wind turbine during pitch motion is investigated and compared to a fixed wind turbine wake. An experiment is conducted in an acoustic wind tunnel where hot-wire data are acquired at five downstream locations. At each downstream location, a rake of 16 hot-wires was used with placement of the probes increasing radially in the vertical, horizontal, and diagonally at 45 deg. In addition, the effect of turbulence intensity on the floating wake is examined by subjecting the wind turbine to different inflow conditions controlled through three settings in the wind tunnel grid, a passive and two active protocols, thus varying in intensity. The wakes are inspected by statistics of the point measurements, where the various length/time scales are considered. The wake characteristics for a floating wind turbine are compared to a fixed turbine, and uncovering its features; relevant as the demand for exploiting deep waters in wind energy is increasing.

Sediment Transport at Density Fronts in Shallow Water: A Continuation of N00014-08-1-0846

DTIC Science & Technology

2013-09-30

flats in Puget Sound, coordinated with other researchers in the Tidal Flats DRI. Focused observations of the shallow density front and its evolution...an evaluation of effects of complex topography on wind correlation length scales and implications for coastal ocean modeling (Raubenheimer et al...as the integrated potential energy anomaly Φ (Simpson et al. 1990), varied with the Simpson number, , where g is gravity, ∂ρ/∂x is the horizontal

Material transport in a wind and buoyancy forced mixed layer

NASA Astrophysics Data System (ADS)

Mensa, J. A.; Özgökmen, T.; Poje, A. C.; Imberger, J.

2016-02-01

Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (|u10|=5ms-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(l), than those reported by Okubo (1970), while the wind- and buoyancy forced case shows a good agreement with Okubo's diffusivity amplitude, and scaling consistent with Richardson's 4/3rd law, kD(l) l4/3. The modelling results provide a framework for measuring material dispersion by mixed layer flow in future observational programs.

Material transport in a convective surface mixed layer under weak wind forcing

NASA Astrophysics Data System (ADS)

Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

2015-12-01

Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

Smagorinsky-type diffusion in a high-resolution GCM

NASA Astrophysics Data System (ADS)

Schaefer-Rolffs, Urs; Becker, Erich

2013-04-01

The parametrization of the (horizontal) momentum diffusion is a paramount component of a Global Circulation Model (GCM). Aside from friction in the boundary layer, a relevant fraction of kinetic energy is dissipated in the free atmosphere, and it is known that a linear harmonic turbulence model is not sufficient to obtain a reasonable simulation of the kinetic energy spectrum. Therefore, often empirical hyper-diffusion schemes are employed, regardless of disadvantages like the violation of energy conservation and the second law of thermodynamics. At IAP we have developed an improved parametrization of the horizontal diffusion that is based on Smagorinsky's nonlinear and energy conservation formulation. This approach is extended by the dynamic Smagorinsky model (DSM) of M. Germano. In this new scheme, the mixing length is no longer a prescribed parameter but calculated dynamically from the resolved flow such as to preserve scale invariance for the horizontal energy cascade. The so-called Germano identity is solved by a tensor norm ansatz which yields a positive definite frictional heating. We present results from an investigation using the DSM as a parametrization of horizontal diffusion in a high-resolution version of the Kühlungborn Mechanistic general Circulation Model (KMCM) with spectral truncation at horizontal wavenumber 330. The DSM calculates the Smagorinsky parameter cS independent from the resolution scale. We find that this method yields an energy spectrum that exhibits a pronounced transition from a synoptic -3 to a mesoscale -5-3 slope at wavenumbers around 50. At the highest wavenumber end, a behaviour similar to that often obtained by tuning the hyper-diffusion is achieved self-consistently. This result is very sensitive to the explicit choice of the test filter in the DSM.

Applicability of a diffusion model to lateral transport in the terrestrial and lunar exospheres.

NASA Technical Reports Server (NTRS)

Hodges, R. R., Jr.

1972-01-01

Kinetic theory is used to determine a series expansion of the vertical flux of particles in an exosphere in terms of time and space derivatives of particle concentration, exobase velocity, and temperature. For sufficiently large scale variations of these parameters in time and space, the series can be truncated to a form that is similar to a diffusion equation. Owing to this analogy, it is possible to unite the mathematical description of molecular diffusion, which governs thermospheric flow, and the corresponding exospheric equation by using effective transport coefficients which change smoothly with altitude through the transition from thermosphere to exosphere. A new definition of the exobase for lateral flow emerges from the analogy of exospheric and thermospheric diffusion, as the altitude where the horizontal mean free path length equals the mean horizontal extent of ballistic trajectories of the transported gas, as opposed to the scale height of the dominant gas which determines the exobase for escape. It is shown that the approximation of exospheric lateral flow as a diffusion process is applicable to global scale problems concerning terrestrial helium and heavier gases, and lunar gases heavier than helium.

Self-similar mixing in stratified plane Couette flow for varying Prandtl number

NASA Astrophysics Data System (ADS)

Caulfield, C. P.; Zhou, Qi; Taylor, John

2017-11-01

We investigate fully developed turbulence in statically stable stratified plane Couette flows (the flow between two horizontal plates a distance 2 h apart moving at velocities +/-U0 and held at densities ρa -/+ρ0) using direct numerical simulations at a range of Prandtl numbers Pr ≡ ν / κ ∈ { 0.7 , 7 , 70 } and Reynolds numbers Re ≡U0 h / ν ∈ [ 865 , 280000 ] . We observe significant effects of Pr on the heat and momentum fluxes across the channel gap and on the mean temperature and velocity profile, which can be described through a mixing length model using Monin-Obukhov (M-O) similarity theory. We employ M-O theory to formulate similarity scalings for various flow diagnostics in the gap interior. The mid-channel-gap gradient Richardson number Rig is determined by the length scale ratio h / L , where L is the Obukhov length scale. When h / L >> 1 , Rig asymptotes to a maximum characteristic value of approximately 0.2, for very high Re and for a range of Pr and bulk Richardson number Ri = gρ0 h /(ρaU02) . The flux Richardson number Rif = Rig , implying that such turbulent flows do not access the (strongly) `layered anisotropic stratified turbulence' regime, and that the turbulent Prandtl number is approximately one.

Spectral decomposition of internal gravity wave sea surface height in global models

NASA Astrophysics Data System (ADS)

Savage, Anna C.; Arbic, Brian K.; Alford, Matthew H.; Ansong, Joseph K.; Farrar, J. Thomas; Menemenlis, Dimitris; O'Rourke, Amanda K.; Richman, James G.; Shriver, Jay F.; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis

2017-10-01

Two global ocean models ranging in horizontal resolution from 1/12° to 1/48° are used to study the space and time scales of sea surface height (SSH) signals associated with internal gravity waves (IGWs). Frequency-horizontal wavenumber SSH spectral densities are computed over seven regions of the world ocean from two simulations of the HYbrid Coordinate Ocean Model (HYCOM) and three simulations of the Massachusetts Institute of Technology general circulation model (MITgcm). High wavenumber, high-frequency SSH variance follows the predicted IGW linear dispersion curves. The realism of high-frequency motions (>0.87 cpd) in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest-resolution runs of each model (1/25° HYCOM and 1/48° MITgcm) with dynamic height variance frequency spectral density computed from nine in situ profiling instruments. These high-frequency motions are of particular interest because of their contributions to the small-scale SSH variability that will be observed on a global scale in the upcoming Surface Water and Ocean Topography (SWOT) satellite altimetry mission. The variance at supertidal frequencies can be comparable to the tidal and low-frequency variance for high wavenumbers (length scales smaller than ˜50 km), especially in the higher-resolution simulations. In the highest-resolution simulations, the high-frequency variance can be greater than the low-frequency variance at these scales.

Experimental investigation of turbulent diffusion of slightly buoyant droplets in locally isotropic turbulence

NASA Astrophysics Data System (ADS)

Gopalan, Balaji; Malkiel, Edwin; Katz, Joseph

2008-09-01

High-speed inline digital holographic cinematography is used for studying turbulent diffusion of slightly buoyant 0.5-1.2 mm diameter diesel droplets and 50 μm diameter neutral density particles. Experiments are performed in a 50×50×70 mm3 sample volume in a controlled, nearly isotropic turbulence facility, which is characterized by two dimensional particle image velocimetry. An automated tracking program has been used for measuring velocity time history of more than 17 000 droplets and 15 000 particles. For most of the present conditions, rms values of horizontal droplet velocity exceed those of the fluid. The rms values of droplet vertical velocity are higher than those of the fluid only for the highest turbulence level. The turbulent diffusion coefficient is calculated by integration of the ensemble-averaged Lagrangian velocity autocovariance. Trends of the asymptotic droplet diffusion coefficient are examined by noting that it can be viewed as a product of a mean square velocity and a diffusion time scale. To compare the effects of turbulence and buoyancy, the turbulence intensity (ui') is scaled by the droplet quiescent rise velocity (Uq). The droplet diffusion coefficients in horizontal and vertical directions are lower than those of the fluid at low normalized turbulence intensity, but exceed it with increasing normalized turbulence intensity. For most of the present conditions the droplet horizontal diffusion coefficient is higher than the vertical diffusion coefficient, consistent with trends of the droplet velocity fluctuations and in contrast to the trends of the diffusion timescales. The droplet diffusion coefficients scaled by the product of turbulence intensity and an integral length scale are a monotonically increasing function of ui'/Uq.

Experimental data for the slug two-phase flow characteristics in horizontal pipeline.

PubMed

Mohmmed, Abdalellah O; Nasif, Mohammad S; Al-Kayiem, Hussain H

2018-02-01

The data presented in this article were the basis for the study reported in the research articles entitled "Statistical assessment of experimental observation on the slug body length and slug translational velocity in a horizontal pipe" (Al-Kayiem et al., 2017) [1] which presents an experimental investigation of the slug velocity and slug body length for air-water tow phase flow in horizontal pipe. Here, in this article, the experimental set-up and the major instruments used for obtaining the computed data were explained in details. This data will be presented in the form of tables and videos.

Evolution of Pull-Apart Basins and Their Scale Independence

NASA Astrophysics Data System (ADS)

Aydin, Atilla; Nur, Amos

1982-02-01

Pull-apart basins or rhomb grabens and horsts along major strike-slip fault systems in the world are generally associated with horizontal slip along faults. A simple model suggests that the width of the rhombs is controlled by the initial fault geometry, whereas the length increases with increasing fault displacement. We have tested this model by analyzing the shapes of 70 well-defined rhomb-like pull-apart basins and pressure ridges, ranging from tens of meters to tens of kilometers in length, associated with several major strike-slip faults in the western United States, Israel, Turkey, Iran, Guatemala, Venezuela, and New Zealand. In conflict with the model, we find that the length to width ratio of these basins is a constant value of approximately 3; these basins become wider as they grow longer with increasing fault offset. Two possible mechanisms responsible for the increase in width are suggested: (1) coalescence of neighboring rhomb grabens as each graben increases its length and (2) formation of fault strands parallel to the existing ones when large displacements need to be accommodated. The processes of formation and growth of new fault strands promote interaction among the new faults and between the new and preexisting faults on a larger scale. Increased displacement causes the width of the fault zone to increase resulting in wider pull-apart basins.

Tornadoes and downbursts in the context of generalized planetary scales

NASA Technical Reports Server (NTRS)

Fujita, T. T.

1981-01-01

In order to cover a wide range of horizontal dimensions of airflow, the paper proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, I, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet. Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20,000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent, mesoscale disturbances.

Tornadoes and Downbursts in the Context of Generalized Planetary Scales.

NASA Astrophysics Data System (ADS)

Fujita, T. Theodore

1981-08-01

In order to cover a wide range of horizontal dimensions of airflow, the author proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, 1, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet.Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20 000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent. mesoscale disturbances.

Assignment of boundary conditions in embedded ground water flow models

USGS Publications Warehouse

Leake, S.A.

1998-01-01

Many small-scale ground water models are too small to incorporate distant aquifer boundaries. If a larger-scale model exists for the area of interest, flow and head values can be specified for boundaries in the smaller-scale model using values from the larger-scale model. Flow components along rows and columns of a large-scale block-centered finite-difference model can be interpolated to compute horizontal flow across any segment of a perimeter of a small-scale model. Head at cell centers of the larger-scale model can be interpolated to compute head at points on a model perimeter. Simple linear interpolation is proposed for horizontal interpolation of horizontal-flow components. Bilinear interpolation is proposed for horizontal interpolation of head values. The methods of interpolation provided satisfactory boundary conditions in tests using models of hypothetical aquifers.Many small-scale ground water models are too small to incorporate distant aquifer boundaries. If a larger-scale model exists for the area of interest, flow and head values can be specified for boundaries in the smaller-scale model using values from the larger-scale model. Flow components along rows and columns of a large-scale block-centered finite-difference model can be interpolated to compute horizontal flow across any segment of a perimeter of a small-scale model. Head at cell centers of the larger.scale model can be interpolated to compute head at points on a model perimeter. Simple linear interpolation is proposed for horizontal interpolation of horizontal-flow components. Bilinear interpolation is proposed for horizontal interpolation of head values. The methods of interpolation provided satisfactory boundary conditions in tests using models of hypothetical aquifers.

Comparisons of a standard galaxy model with stellar observations in five fields

NASA Technical Reports Server (NTRS)

Bahcall, J. N.; Soneira, R. M.

1984-01-01

Modern data on the distribution of stellar colors and on the number of stars as a function of apparent magnitude in five directions in the Galaxy are analyzed. It is found that the standard model is consistent with all the available data. Detailed comparisons with the data for five separate fields are presented. The bright end of the spheroid luminosity function and the blue tip of the spheroid horizontal branch are analyzed. The allowed range of the disk scale heights and of fluctuations in the volume density is determined, and a lower limit is set on the disk scale length. Calculations based on the thick disk model of Gilmore and Reid (1983) are presented.

Turbulence scalings in pipe flows exhibiting polymer-induced drag reduction

NASA Astrophysics Data System (ADS)

Zadrazil, Ivan; Markides, Christos

2014-11-01

Non-intrusive laser based diagnostics technique, namely Particle Image Velocimetry, was used to in detail characterise polymer induced drag reduction in a turbulent pipe flow. The effect of polymer additives was investigated in a pneumatically-driven flow facility featuring a horizontal pipe test section of inner diameter 25.3 mm and length 8 m. Three high molecular weight polymers (2, 4 and 8 MDa) at concentrations of 5 - 250 wppm were used at Reynolds numbers from 35000 to 210000. The PIV derived results show that the level of drag reduction scales with different normalised turbulence parameters, e.g. streamwise and spanwise velocity fluctuations, vorticity or Reynolds stresses. These scalings are dependent of the distance from the wall, however, are independent of the Reynolds numbers range investigated.

Directionally asymmetric self-assembly of cadmium sulfide nanotubes using porous alumina nanoreactors: need for chemohydrodynamic instability at the nanoscale.

PubMed

Varghese, Arthur; Datta, Shouvik

2012-05-01

We explore nanoscale hydrodynamical effects on synthesis and self-assembly of cadmium sulfide nanotubes oriented along one direction. These nanotubes are synthesized by horizontal capillary flow of two different chemical reagents from opposite directions through nanochannels of porous anodic alumina which are used primarily as nanoreactors. We show that uneven flow of different chemical precursors is responsible for directionally asymmetric growth of these nanotubes. On the basis of structural observations using scanning electron microscopy, we argue that chemohydrodynamic convective interfacial instability of multicomponent liquid-liquid reactive interface is necessary for sustained nucleation of these CdS nanotubes at the edges of these porous nanochannels over several hours. However, our estimates clearly suggest that classical hydrodynamics cannot account for the occurrence of such instabilities at these small length scales. Therefore, we present a case which necessitates further investigation and understanding of chemohydrodynamic fluid flow through nanoconfined channels in order to explain the occurrence of such interfacial instabilities at nanometer length scales.

Horizontal movements, migration patterns, and population structure of whale sharks in the Gulf of Mexico and northwestern Caribbean sea.

PubMed

Hueter, Robert E; Tyminski, John P; de la Parra, Rafael

2013-01-01

Whale sharks, Rhincodon typus, aggregate by the hundreds in a summer feeding area off the northeastern Yucatan Peninsula, Mexico, where the Gulf of Mexico meets the Caribbean Sea. The aggregation remains in the nutrient-rich waters off Isla Holbox, Isla Contoy and Isla Mujeres, Quintana Roo for several months in the summer and then dissipates between August and October. Little has been known about where these sharks come from or migrate to after they disperse. From 2003-2012, we used conventional visual tags, photo-identification, and satellite tags to characterize the basic population structure and large-scale horizontal movements of whale sharks that come to this feeding area off Mexico. The aggregation comprised sharks ranging 2.5-10.0 m in total length and included juveniles, subadults, and adults of both sexes, with a male-biased sex ratio (72%). Individual sharks remained in the area for an estimated mean duration of 24-33 days with maximum residency up to about 6 months as determined by photo-identification. After leaving the feeding area the sharks showed horizontal movements in multiple directions throughout the Gulf of Mexico basin, the northwestern Caribbean Sea, and the Straits of Florida. Returns of individual sharks to the Quintana Roo feeding area in subsequent years were common, with some animals returning for six consecutive years. One female shark with an estimated total length of 7.5 m moved at least 7,213 km in 150 days, traveling through the northern Caribbean Sea and across the equator to the South Atlantic Ocean where her satellite tag popped up near the Mid-Atlantic Ridge. We hypothesize this journey to the open waters of the Mid-Atlantic was for reproductive purposes but alternative explanations are considered. The broad movements of whale sharks across multiple political boundaries corroborates genetics data supporting gene flow between geographically distinct areas and underscores the need for management and conservation strategies for this species on a global scale.

Turbulent Flow Structure Inside a Canopy with Complex Multi-Scale Elements

NASA Astrophysics Data System (ADS)

Bai, Kunlun; Katz, Joseph; Meneveau, Charles

2015-06-01

Particle image velocimetry laboratory measurements are carried out to study mean flow distributions and turbulent statistics inside a canopy with complex geometry and multiple scales consisting of fractal, tree-like objects. Matching the optical refractive indices of the tree elements with those of the working fluid provides unobstructed optical paths for both illuminations and image acquisition. As a result, the flow fields between tree branches can be resolved in great detail, without optical interference. Statistical distributions of mean velocity, turbulence stresses, and components of dispersive fluxes are documented and discussed. The results show that the trees leave their signatures in the flow by imprinting wake structures with shapes similar to the trees. The velocities in both wake and non-wake regions significantly deviate from the spatially-averaged values. These local deviations result in strong dispersive fluxes, which are important to account for in canopy-flow modelling. In fact, we find that the streamwise normal dispersive flux inside the canopy has a larger magnitude (by up to four times) than the corresponding Reynolds normal stress. Turbulent transport in horizontal planes is studied in the framework of the eddy viscosity model. Scatter plots comparing the Reynolds shear stress and mean velocity gradient are indicative of a linear trend, from which one can calculate the eddy viscosity and mixing length. Similar to earlier results from the wake of a single tree, here we find that inside the canopy the mean mixing length decreases with increasing elevation. This trend cannot be scaled based on a single length scale, but can be described well by a model, which considers the coexistence of multi-scale branches. This agreement indicates that the multi-scale information and the clustering properties of the fractal objects should be taken into consideration in flows inside multi-scale canopies.

Horizontal visibility graphs generated by type-I intermittency

NASA Astrophysics Data System (ADS)

Núñez, Ángel M.; Luque, Bartolo; Lacasa, Lucas; Gómez, Jose Patricio; Robledo, Alberto

2013-05-01

The type-I intermittency route to (or out of) chaos is investigated within the horizontal visibility (HV) graph theory. For that purpose, we address the trajectories generated by unimodal maps close to an inverse tangent bifurcation and construct their associated HV graphs. We show how the alternation of laminar episodes and chaotic bursts imprints a fingerprint in the resulting graph structure. Accordingly, we derive a phenomenological theory that predicts quantitative values for several network parameters. In particular, we predict that the characteristic power-law scaling of the mean length of laminar trend sizes is fully inherited by the variance of the graph degree distribution, in good agreement with the numerics. We also report numerical evidence on how the characteristic power-law scaling of the Lyapunov exponent as a function of the distance to the tangent bifurcation is inherited in the graph by an analogous scaling of block entropy functionals defined on the graph. Furthermore, we are able to recast the full set of HV graphs generated by intermittent dynamics into a renormalization-group framework, where the fixed points of its graph-theoretical renormalization-group flow account for the different types of dynamics. We also establish that the nontrivial fixed point of this flow coincides with the tangency condition and that the corresponding invariant graph exhibits extremal entropic properties.

Spectral characteristics of background error covariance and multiscale data assimilation

DOE PAGES

Li, Zhijin; Cheng, Xiaoping; Gustafson, Jr., William I.; ...

2016-05-17

The steady increase of the spatial resolutions of numerical atmospheric and oceanic circulation models has occurred over the past decades. Horizontal grid spacing down to the order of 1 km is now often used to resolve cloud systems in the atmosphere and sub-mesoscale circulation systems in the ocean. These fine resolution models encompass a wide range of temporal and spatial scales, across which dynamical and statistical properties vary. In particular, dynamic flow systems at small scales can be spatially localized and temporarily intermittent. Difficulties of current data assimilation algorithms for such fine resolution models are numerically and theoretically examined. Ourmore » analysis shows that the background error correlation length scale is larger than 75 km for streamfunctions and is larger than 25 km for water vapor mixing ratios, even for a 2-km resolution model. A theoretical analysis suggests that such correlation length scales prevent the currently used data assimilation schemes from constraining spatial scales smaller than 150 km for streamfunctions and 50 km for water vapor mixing ratios. Moreover, our results highlight the need to fundamentally modify currently used data assimilation algorithms for assimilating high-resolution observations into the aforementioned fine resolution models. Lastly, within the framework of four-dimensional variational data assimilation, a multiscale methodology based on scale decomposition is suggested and challenges are discussed.« less

Grasp and index finger reach zone during one-handed smartphone rear interaction: effects of task type, phone width and hand length.

PubMed

Lee, Songil; Kyung, Gyouhyung; Lee, Jungyong; Moon, Seung Ki; Park, Kyoung Jong

2016-11-01

Recently, some smartphones have introduced index finger interaction functions on the rear surface. The current study investigated the effects of task type, phone width, and hand length on grasp, index finger reach zone, discomfort, and muscle activation during such interaction. We considered five interaction tasks (neutral, comfortable, maximum, vertical, and horizontal strokes), two device widths (60 and 90 mm) and three hand lengths. Horizontal (vertical) strokes deviated from the horizontal axis in the range from -10.8° to -13.5° (81.6-88.4°). Maximum strokes appeared to be excessive as these caused 43.8% greater discomfort than did neutral strokes. The 90-mm width also appeared to be excessive as it resulted in 12.3% increased discomfort relative to the 60-mm width. The small-hand group reported 11.9-18.2% higher discomfort ratings, and the percent maximum voluntary exertion of their flexor digitorum superficialis muscle, pertaining to index finger flexion, was also 6.4% higher. These findings should be considered to make smartphone rear interaction more comfortable. Practitioner Summary: Among neutral, comfortable, maximum, horizontal, and vertical index finger strokes on smartphone rear surfaces, maximum vs. neutral strokes caused 43.8% greater discomfort. Horizontal (vertical) strokes deviated from the horizontal (vertical) axis. Discomfort increased by 12.3% with 90-mm- vs. 60-mm-wide devices. Rear interaction regions of five commercialised smartphones should be lowered 20 to 30 mm for more comfortable rear interaction.

A new species of Astyanax (Characiformes: Characidae) from Costa Rica and Panama, with a key to the lower Central American species of the genus.

PubMed

Angulo, A; Santos, A C; López, M; Langeani, F; Mcmahan, C D

2018-06-01

Astyanax anai, a new species of characid fish, is described from the Sixaola River basin, eastern Costa Rica-western Panama, Central America. The new species can be distinguished from all other congeners by the following combination of characters: premaxillary teeth 4-5 at the inner series and 4-6 at the outer series; maxillary teeth tricuspid, 2-4; predorsal scale series irregular and incomplete, with an unscaled space behind tip of supraoccipital process and 12-14 scales; lateral line scales 34-39; humeral region with a conspicuous black and rounded to horizontally ovate spot and two diffuse brown and vertically elongate bars (the first through the rounded to horizontally ovate spot, the second 2-4 scales behind the first); body depth 36·6-42·3% of standard length (L S ); midlateral stripe formed by a series of 10-14 anteriorly-directed dermal herringbone, or chevron-shaped, marks, most apparent in juveniles and in preserved specimens, extending above the lateral line from the black humeral spot or just behind it (from the second vertical bar) to the caudal peduncle; scale rows from lateral line to base of first dorsal-fin ray 8-9; scale rows from lateral line to base of pelvic fin 7-8; pre-anal distance 53·9-61·9% of L S ; total anal-fin elements 29-33; caudal spot elongated, rhomboid or rectangular, with its anterior margin surpassing the middle of the caudal peduncle, usually reaching the anal-fin insertion, posteriorly covering 4-7 principal caudal-fin rays and not extending onto the ventral and dorsal margins of the caudal peduncle, covering 3-5 horizontal scale rows. In order to test the phylogenetic relationships of the new taxon in relation to the other North and Central American species of the genus, a new phylogenetic hypothesis based on a reanalysis of the morphological matrix by Schmitter-Soto (2016) is proposed. A key to the lower Central American (southern Nicaragua to eastern Panama) species of Astyanax is also provided. © 2018 The Fisheries Society of the British Isles.

Geometry of tracer trajectories in turbulent rotating convection

NASA Astrophysics Data System (ADS)

Alards, Kim; Rajaei, Hadi; Kunnen, Rudie; Toschi, Federico; Clercx, Herman

2016-11-01

In Rayleigh-Bénard convection rotation is known to cause transitions in flow structures and to change the level of anisotropy close to the horizontal plates. To analyze this effect of rotation, we collect curvature and torsion statistics of passive tracer trajectories in rotating Rayleigh-Bénard convection, using both experiments and direct numerical simulations. In previous studies, focusing on homogeneous isotropic turbulence (HIT), curvature and torsion PDFs are found to reveal pronounced power laws. In the center of the convection cell, where the flow is closest to HIT, we recover these power laws, regardless of the rotation rate. However, near the top plate, where we expect the flow to be anisotropic, the scaling of the PDFs deviates from the HIT prediction for lower rotation rates. This indicates that anisotropy clearly affects the geometry of tracer trajectories. Another effect of rotation is observed as a shift of curvature and torsion PDFs towards higher values. We expect this shift to be related to the length scale of typical flow structures. Using curvature and torsion statistics, we can characterize how these typical length scales evolve under rotation and moreover analyze the effect of rotation on more complicated flow characteristics, such as anisotropy.

Factors Influencing Perception of Facial Attractiveness: Gender and Dental Education.

PubMed

Jung, Ga-Hee; Jung, Seunggon; Park, Hong-Ju; Oh, Hee-Kyun; Kook, Min-Suk

2018-03-01

This study was conducted to investigate the gender- and dental education-specific differences in perception of facial attractiveness for varying ratio of lower face contour. Two hundred eleven students (110 male respondents and 110 female respondents; aged between 20-38 years old) were requested to rate facial figures with alterations to the bigonial width and the vertical length of the lower face. We produced a standard figure which is based on the "golden ratio" and 4 additional series of figures with either horizontal or vertical alterations to the contour of lower face. The preference for each figure was evaluated using a Visual Analog Scale. The Kruskal Wallis test was used for differences in the preferences for each figure and the Mann-Whitney U test was used to evaluate gender-specific differences and differences by dental education. In general, the highest preference score was indicated for the standard figure, whereas facial figure with large bigonial width and chin length had the lowest score.Male respondents showed significantly higher preference score for facial contour that had a 0.1 proportional increase in the facial height-bigonial width ratio over that of the standard figure.For horizontal alterations to the facial profiles, there were no significant differences in the preferences by the level of dental education. For vertically altered images, the average Visual Analog Scale was significantly lower among the dentally-educated for facial image that had a proportional 0.22 and 0.42 increase in the ratio between the vertical length of the chin and the lip. Generally, the standard image based on the golden ratio was the most. Slender face was appealed more to males than to females, and facial image with an increased lower facial height were perceived to be much less attractive to the dentally-educated respondents, which suggests that the dental education might have some influence in sensitivity to vertical changes in lower face.

Inter-Comparison of WRF Model Simulated Winds and MISR Stereoscopic Winds Embedded within Mesoscale von Kármán Wake Vortices

NASA Astrophysics Data System (ADS)

Horvath, A.; Nunalee, C. G.; Mueller, K. J.

2014-12-01

Several distinct wake regimes are possible when considering atmospheric flow past a steep mountainous island. Of these regimes, coherent vortex shedding in low-Froude number flow is particularly interesting because it can produce laterally focused paths of counter rotating eddies capable of extending downstream for hundreds of kilometers (i.e., a von Kármán vortex street). Given the spatial scales of atmospheric von Kármán vortices, which typically lies on the interface of the meso-scale and the micro-scale, they are uniquely challenging to model using conventional numerical weather prediction platforms. In this presentation, we present high resolution (1-km horizontally) numerical modeling results using the Weather Research and Forecasting (WRF) model, of multiple real-world von Kármán vortex shedding events associated with steep islands (e.g., Madeira island, Gran Canaria island, etc.). In parallel, we also present corresponding cloud-motion wind and cloud-top height measurements from the satellite-based Multiangle Imaging SpectroRadiometer (MISR) instrument. The MISR stereo algorithm enables experimental retrieval of the horizontal wind vector (both along-track and cross-track components) at 4.4-km resolution, in addition to the operational 1.1-km resolution cross-track wind and cloud-top height products. These products offer the fidelity appropriate for inter-comparison with the numerically simulated vortex streets. In general, we find an agreement between the instantaneous simulated cloud level winds and the MISR stereoscopic winds; however, discrepancies in the vortex street length and localized horizontal wind shear were documented. In addition, the simulated fields demonstrate sensitivity to turbulence closure and input terrain height data.

Determination of real-time predictors of the wind turbine wake meandering

NASA Astrophysics Data System (ADS)

Muller, Yann-Aël; Aubrun, Sandrine; Masson, Christian

2015-03-01

The present work proposes an experimental methodology to characterize the unsteady properties of a wind turbine wake, called meandering, and particularly its ability to follow the large-scale motions induced by large turbulent eddies contained in the approach flow. The measurements were made in an atmospheric boundary layer wind tunnel. The wind turbine model is based on the actuator disc concept. One part of the work has been dedicated to the development of a methodology for horizontal wake tracking by mean of a transverse hot wire rake, whose dynamic response is adequate for spectral analysis. Spectral coherence analysis shows that the horizontal position of the wake correlates well with the upstream transverse velocity, especially for wavelength larger than three times the diameter of the disc but less so for smaller scales. Therefore, it is concluded that the wake is actually a rather passive tracer of the large surrounding turbulent structures. The influence of the rotor size and downstream distance on the wake meandering is studied. The fluctuations of the lateral force and the yawing torque affecting the wind turbine model are also measured and correlated with the wake meandering. Two approach flow configurations are then tested: an undisturbed incoming flow (modelled atmospheric boundary layer) and a disturbed incoming flow, with a wind turbine model located upstream. Results showed that the meandering process is amplified by the presence of the upstream wake. It is shown that the coherence between the lateral force fluctuations and the horizontal wake position is significant up to length scales larger than twice the wind turbine model diameter. This leads to the conclusion that the lateral force is a better candidate than the upstream transverse velocity to predict in real time the meandering process, for either undisturbed (wake free) or disturbed incoming atmospheric flows.

An experimental study of the Rayleigh-Taylor instability critical wave length

NASA Astrophysics Data System (ADS)

Kong, Xujing; Wang, Youchun; Zhang, Shufei; Xu, Hongkun

1992-06-01

A physical model has been constructed to represent the condensate film pattern on a horizontal downward-facing surface with fins, which is based on visual observation in experiment. The results of analysis using this model confirms the validity of the critical wave length formula obtained from Rayleigh-Taylor stability analysis. This formula may be used as a criterion to design horizontal downward-facing surfaces with fins that can best destabilize the condensate film, thus enhancing condensation heat transfer.

The influence of idealized surface heterogeneity on virtual turbulent flux measurements

NASA Astrophysics Data System (ADS)

De Roo, Frederik; Mauder, Matthias

2018-04-01

The imbalance of the surface energy budget in eddy-covariance measurements is still an unsolved problem. A possible cause is the presence of land surface heterogeneity, which affects the boundary-layer turbulence. To investigate the impact of surface variables on the partitioning of the energy budget of flux measurements in the surface layer under convective conditions, we set up a systematic parameter study by means of large-eddy simulation. For the study we use a virtual control volume approach, which allows the determination of advection by the mean flow, flux-divergence and storage terms of the energy budget at the virtual measurement site, in addition to the standard turbulent flux. We focus on the heterogeneity of the surface fluxes and keep the topography flat. The surface fluxes vary locally in intensity and these patches have different length scales. Intensity and length scales can vary for the two horizontal dimensions but follow an idealized chessboard pattern. Our main focus lies on surface heterogeneity of the kilometer scale, and one order of magnitude smaller. For these two length scales, we investigate the average response of the fluxes at a number of virtual towers, when varying the heterogeneity length within the length scale and when varying the contrast between the different patches. For each simulation, virtual measurement towers were positioned at functionally different positions (e.g., downdraft region, updraft region, at border between domains, etc.). As the storage term is always small, the non-closure is given by the sum of the advection by the mean flow and the flux-divergence. Remarkably, the missing flux can be described by either the advection by the mean flow or the flux-divergence separately, because the latter two have a high correlation with each other. For kilometer scale heterogeneity, we notice a clear dependence of the updrafts and downdrafts on the surface heterogeneity and likewise we also see a dependence of the energy partitioning on the tower location. For the hectometer scale, we do not notice such a clear dependence. Finally, we seek correlators for the energy balance ratio in the simulations. The correlation with the friction velocity is less pronounced than previously found, but this is likely due to our concentration on effectively strongly to freely convective conditions.

Association of X-ray arches with chromospheric neutral lines

NASA Technical Reports Server (NTRS)

Mcintosh, P. S.; Krieger, A. S.; Nolte, J. T.; Vaiana, G.

1976-01-01

Daily maps of magnetic neutral lines derived from H-alpha observations have been superimposed on solar X-ray images for the period from June 15 to 30, 1973. Nearly all X-ray-emitting structures consist of systems of arches covering chromospheric neutral lines. Areas of low emissivity, coronal holes, appear as the areas between arcades of arches. The presence of a coronal hole, therefore, is determined by the spacing between neutral lines and the scale of the arches over those neutral lines. X-ray emissivity on the solar disk extends from neutral lines in proportion to the vertical and horizontal scale of the arches over those neutral lines. Increasing scale of arches corresponds with increasing age of magnetic fields associated with the neutral line. All X-ray filament cavities coincided with neutral lines, but filaments appeared under cavities for only part of their length and for only a fraction of the disk passage.

Buoyancy-driven convection around chemical fronts traveling in covered horizontal solution layers.

PubMed

Rongy, L; Goyal, N; Meiburg, E; De Wit, A

2007-09-21

Density differences across an autocatalytic chemical front traveling horizontally in covered thin layers of solution trigger hydrodynamic flows which can alter the concentration profile. We theoretically investigate the spatiotemporal evolution and asymptotic dynamics resulting from such an interplay between isothermal chemical reactions, diffusion, and buoyancy-driven convection. The studied model couples the reaction-diffusion-convection evolution equation for the concentration of an autocatalytic species to the incompressible Stokes equations ruling the evolution of the flow velocity in a two-dimensional geometry. The dimensionless parameter of the problem is a solutal Rayleigh number constructed upon the characteristic reaction-diffusion length scale. We show numerically that the asymptotic dynamics is one steady vortex surrounding, deforming, and accelerating the chemical front. This chemohydrodynamic structure propagating at a constant speed is quite different from the one obtained in the case of a pure hydrodynamic flow resulting from the contact between two solutions of different density or from the pure reaction-diffusion planar traveling front. The dynamics is symmetric with regard to the middle of the layer thickness for positive and negative Rayleigh numbers corresponding to products, respectively, lighter or heavier than the reactants. A parametric study shows that the intensity of the flow, the propagation speed, and the deformation of the front are increasing functions of the Rayleigh number and of the layer thickness. In particular, the asymptotic mixing length and reaction-diffusion-convection speed both scale as square root Ra for Ra>5. The velocity and concentration fields in the asymptotic dynamics are also found to exhibit self-similar properties with Ra. A comparison of the dynamics in the case of a monostable versus bistable kinetics is provided. Good agreement is obtained with experimental data on the speed of iodate-arsenous acid fronts propagating in horizontal capillaries. We furthermore compare the buoyancy-driven dynamics studied here to Marangoni-driven deformation of traveling chemical fronts in solution open to the air in the absence of gravity previously studied in the same geometry [L. Rongy and A. De Wit, J. Chem. Phys. 124, 164705 (2006)].

Horizontal Movements, Migration Patterns, and Population Structure of Whale Sharks in the Gulf of Mexico and Northwestern Caribbean Sea

PubMed Central

Hueter, Robert E.; Tyminski, John P.; de la Parra, Rafael

2013-01-01

Whale sharks, Rhincodon typus, aggregate by the hundreds in a summer feeding area off the northeastern Yucatan Peninsula, Mexico, where the Gulf of Mexico meets the Caribbean Sea. The aggregation remains in the nutrient-rich waters off Isla Holbox, Isla Contoy and Isla Mujeres, Quintana Roo for several months in the summer and then dissipates between August and October. Little has been known about where these sharks come from or migrate to after they disperse. From 2003–2012, we used conventional visual tags, photo-identification, and satellite tags to characterize the basic population structure and large-scale horizontal movements of whale sharks that come to this feeding area off Mexico. The aggregation comprised sharks ranging 2.5–10.0 m in total length and included juveniles, subadults, and adults of both sexes, with a male-biased sex ratio (72%). Individual sharks remained in the area for an estimated mean duration of 24–33 days with maximum residency up to about 6 months as determined by photo-identification. After leaving the feeding area the sharks showed horizontal movements in multiple directions throughout the Gulf of Mexico basin, the northwestern Caribbean Sea, and the Straits of Florida. Returns of individual sharks to the Quintana Roo feeding area in subsequent years were common, with some animals returning for six consecutive years. One female shark with an estimated total length of 7.5 m moved at least 7,213 km in 150 days, traveling through the northern Caribbean Sea and across the equator to the South Atlantic Ocean where her satellite tag popped up near the Mid-Atlantic Ridge. We hypothesize this journey to the open waters of the Mid-Atlantic was for reproductive purposes but alternative explanations are considered. The broad movements of whale sharks across multiple political boundaries corroborates genetics data supporting gene flow between geographically distinct areas and underscores the need for management and conservation strategies for this species on a global scale. PMID:23991000

Study on load-bearing characteristics of a new pile group foundation for an offshore wind turbine.

PubMed

Lang, Ruiqing; Liu, Run; Lian, Jijian; Ding, Hongyan

2014-01-01

Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.

Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine

PubMed Central

Liu, Run; Lian, Jijian; Ding, Hongyan

2014-01-01

Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect. PMID:25250375

A prototype fully polarimetric 160-GHz bistatic ISAR compact radar range

NASA Astrophysics Data System (ADS)

Beaudoin, C. J.; Horgan, T.; DeMartinis, G.; Coulombe, M. J.; Goyette, T.; Gatesman, A. J.; Nixon, William E.

2017-05-01

We present a prototype bistatic compact radar range operating at 160 GHz and capable of collecting fullypolarimetric radar cross-section and electromagnetic scattering measurements in a true far-field facility. The bistatic ISAR system incorporates two 90-inch focal length, 27-inch-diameter diamond-turned mirrors fed by 160 GHz transmit and receive horns to establish the compact range. The prototype radar range with its modest sized quiet zone serves as a precursor to a fully developed compact radar range incorporating a larger quiet zone capable of collecting X-band bistatic RCS data and 3D imagery using 1/16th scale objects. The millimeter-wave transmitter provides 20 GHz of swept bandwidth in the single linear (Horizontal/Vertical) polarization while the millimeter-wave receiver, that is sensitive to linear Horizontal and Vertical polarization, possesses a 7 dB noise figure. We present the design of the compact radar range and report on test results collected to validate the system's performance.

Impact of Resolution on the Representation of Precipitation Variability Associated With the ITCZ

NASA Astrophysics Data System (ADS)

De Benedetti, Marc; Moore, G. W. K.

2017-12-01

The Intertropical Convergence Zone (ITCZ) is responsible for most of the weather and climate in equatorial regions along with many tropical-midlatitude interactions. It is therefore important to understand how models represent its structure and variability. Most ITCZ-associated precipitation is convective, making it unclear how horizontal resolution impacts its representation. To assess this, we introduce a novel technique that involves calculation of the precipitation field's decorrelation length scale (DCLS) using model data sets that share a common lineage with horizontal resolutions from 16 to 160 km. All resolutions captured the ITCZ's mean structure; however, imprints of topography, such as Hawaii and sea surface temperature, including the variability associated with upwelling cold water off the coast of South America, are more clearly represented at higher resolutions. The DCLS analysis indicates that there are changes in the spatial variability of the ITCZ's precipitation that are not reflected in its mean structure, thus confirming its utility as a diagnostic.

Wind turbine blade shear web disbond detection using rotor blade operational sensing and data analysis.

PubMed

Myrent, Noah; Adams, Douglas E; Griffith, D Todd

2015-02-28

A wind turbine blade's structural dynamic response is simulated and analysed with the goal of characterizing the presence and severity of a shear web disbond. Computer models of a 5 MW offshore utility-scale wind turbine were created to develop effective algorithms for detecting such damage. Through data analysis and with the use of blade measurements, a shear web disbond was quantified according to its length. An aerodynamic sensitivity study was conducted to ensure robustness of the detection algorithms. In all analyses, the blade's flap-wise acceleration and root-pitching moment were the clearest indicators of the presence and severity of a shear web disbond. A combination of blade and non-blade measurements was formulated into a final algorithm for the detection and quantification of the disbond. The probability of detection was 100% for the optimized wind speed ranges in laminar, 30% horizontal shear and 60% horizontal shear conditions. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Estimation of turbulence characteristics of the low-level eyewall and outer-core regions in intense Hurricanes Allen (1980) and Hugo (1989)

NASA Astrophysics Data System (ADS)

Zhang, J. A.; Marks, F. D.; Montgomery, M.; Lorsolo, S.

2010-12-01

Turbulent transport processes in the atmospheric boundary layer play an important role in the intensification and maintenance of a hurricane vortex. However, direct measurement of turbulence in the hurricane boundary layer has been scarce. This study analyzes the flight-level data collected by research aircraft that penetrated the eyewalls of Category 5 Hurricane Hugo (1989) and Category 4 Hurricane Allen (1980) between 1 km and the sea surface. Momentum flux, turbulent kinetic energy (TKE) and vertical eddy diffusivity are estimated before and during the eyewall penetrations. Spatial scales of turbulent eddies are determined through spectral analysis. The turbulence parameters estimated for the eyewall penetration leg are found to be nearly an order of magnitude larger than those for the leg outside the eyewall at similar altitudes. In the low-level intense eyewall region, the horizontal length scale of dominant turbulent eddies is found to be between 500 - 3000 m and the corresponding vertical length scale is approximately 100 - 200 m. The results suggest also that it is unwise to include the eyewall vorticity maximum (EVM) in the turbulence parameter estimation, since the EVMs are likely to be quasi two-dimensional vortex structures that are embedded within the three dimensional turbulence on the inside edge of the eyewall.

Bacterial chromosome organization and segregation

PubMed Central

Badrinarayanan, Anjana; Le, Tung BK; Laub, Michael T

2016-01-01

If fully stretched out, a typical bacterial chromosome would be nearly one millimeter long, or approximately 1000 times the length of a cell. Not only must cells massively compact their genetic material, but they must also organize their DNA in a manner that is compatible with a range of cellular processes, including DNA replication, DNA repair, homologous recombination, and horizontal gene transfer. Recent work, driven in part by technological advances, has begun to reveal the general principles of chromosome organization in bacteria. Here, drawing on studies of many different organisms, we review the emerging picture of how bacterial chromosomes are structured at multiple length-scales, highlighting the functions of various DNA-binding proteins and impact of physical forces. Additionally, we discuss the spatial dynamics of chromosomes, particularly during their segregation to daughter cells. Although there has been tremendous progress, we also highlight gaps that remain in understanding chromosome organization and segregation. PMID:26566111

Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.

Large-scale horizontal flows from SOUP observations of solar granulation

NASA Technical Reports Server (NTRS)

November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.; Ferguson, S. H.

1987-01-01

Using high resolution time sequence photographs of solar granulation from the SOUP experiment on Spacelab 2, large scale horizontal flows were observed in the solar surface. The measurement method is based upon a local spatial cross correlation analysis. The horizontal motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of granulation from a sunspot penumbra into surrounding photosphere is a striking new discovery. Both the supergranulation pattern and cellular structures having the scale of mesogranulation are seen. The vertical flows that are inferred by continuity of mass from these observed horizontal flows have larger upflow amplitudes in cell centers than downflow amplitudes at cell boundaries.

Stratified turbulence diagnostics for high-Reynolds-number momentum wakes

NASA Astrophysics Data System (ADS)

Diamessis, Peter; Zhou, Qi

2017-11-01

We analyze a large-eddy simulation (LES) dataset of the turbulent wake behind a sphere of diameter D translating at speed U in a linearly stratified Boussinesq fluid with buoyancy frequency N. These simulations are performed at Reynolds numbers Re ≡ UD / ν ∈ { 5 ×103 , 105 , 4 ×105 } and various Froude numbers Fr ≡ 2 U /(ND) . The recently obtained data at Re = 4 ×105 , the highest Re attained so far in either simulation or laboratory, and Fr ∈ { 4 , 16 } enable us to systematically investigate the effects of Reynolds number on this prototypical localized stratified turbulent shear flow. Our analysis focuses on the time evolution of various diagnostics of stratified turbulence, such as the horizontal and vertical integral length scales, turbulent kinetic energy and its dissipation rate ɛ, and the local rate of shear between the spontaneously formed layers of vorticity within the larger-scale quasi-horizontal flow structures. This leads to a discussion of the transitions between distinct stratified flow regimes (Brethouwer et al. 2007) in the appropriately defined phase diagram, and we highlight the dynamical role of the Gibson number Gi = ɛ /(νN2) , and its dependence on the body-based Reynolds number Re . ONR Grants N00014-13-1-0665 and N00014-15-1-2513.

Scintillation index and performance analysis of wireless optical links over non-Kolmogorov weak turbulence based on generalized atmospheric spectral model.

PubMed

Cang, Ji; Liu, Xu

2011-09-26

Based on the generalized spectral model for non-Kolmogorov atmospheric turbulence, analytic expressions of the scintillation index (SI) are derived for plane, spherical optical waves and a partially coherent Gaussian beam propagating through non-Kolmogorov turbulence horizontally in the weak fluctuation regime. The new expressions relate the SI to the finite turbulence inner and outer scales, spatial coherence of the source and spectral power-law and then used to analyze the effects of atmospheric condition and link length on the performance of wireless optical communication links. © 2011 Optical Society of America

7 CFR 51.573 - Damage.

Code of Federal Regulations, 2014 CFR

2014-01-01

... the maximum allowed for any one defect, shall be considered as damage: (a) Growth cracks when more than 2 branches are affected by growth cracks which are over one-half inch in length, or when more than 6 branches have growth cracks; (b) Horizontal cracks when more than 3 branches have horizontal...

7 CFR 51.573 - Damage.

Code of Federal Regulations, 2013 CFR

2013-01-01

... the maximum allowed for any one defect, shall be considered as damage: (a) Growth cracks when more than 2 branches are affected by growth cracks which are over one-half inch in length, or when more than 6 branches have growth cracks; (b) Horizontal cracks when more than 3 branches have horizontal...

URBAN MORPHOLOGY FOR HOUSTON TO DRIVE MODELS-3/CMAQ AT NEIGHBORHOOD SCALES

EPA Science Inventory

Air quality simulation models applied at various horizontal scales require different degrees of treatment in the specifications of the underlying surfaces. As we model neighborhood scales ( 1 km horizontal grid spacing), the representation of urban morphological structures (e....

Simulation of Mesoscale Cellular Convection in Marine Stratocumulus. Part I: Drizzling Conditions

DOE PAGES

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.; ...

2018-01-01

This study uses eddy-permitting simulations to investigate the mechanisms that promote mesoscale variability of moisture in drizzling stratocumulus-topped marine boundary layers. Simulations show that precipitation tends to increase horizontal scales. Analysis of terms in the prognostic equation for total water mixing ratio variance indicates that moisture stratification plays a leading role in setting horizontal scales. This result is supported by simulations in which horizontal mean thermodynamic profiles are strongly nudged to their initial well-mixed state, which limits cloud scales. It is found that the spatial variability of subcloud moist cold pools surprisingly tends to respond to, rather than determine, themore » mesoscale variability, which may distinguish them from dry cold pools associated with deeper convection. Finally, simulations also indicate that moisture stratification increases cloud scales specifically by increasing latent heating within updrafts, which increases updraft buoyancy and favors greater horizontal scales.« less

Simulation of Mesoscale Cellular Convection in Marine Stratocumulus. Part I: Drizzling Conditions

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

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.

This study uses eddy-permitting simulations to investigate the mechanisms that promote mesoscale variability of moisture in drizzling stratocumulus-topped marine boundary layers. Simulations show that precipitation tends to increase horizontal scales. Analysis of terms in the prognostic equation for total water mixing ratio variance indicates that moisture stratification plays a leading role in setting horizontal scales. This result is supported by simulations in which horizontal mean thermodynamic profiles are strongly nudged to their initial well-mixed state, which limits cloud scales. It is found that the spatial variability of subcloud moist cold pools surprisingly tends to respond to, rather than determine, themore » mesoscale variability, which may distinguish them from dry cold pools associated with deeper convection. Finally, simulations also indicate that moisture stratification increases cloud scales specifically by increasing latent heating within updrafts, which increases updraft buoyancy and favors greater horizontal scales.« less

Effect of buoyancy on the motion of long bubbles in horizontal tubes

NASA Astrophysics Data System (ADS)

Atasi, Omer; Khodaparast, Sepideh; Scheid, Benoit; Stone, Howard A.

2017-09-01

As a confined long bubble translates along a horizontal liquid-filled tube, a thin film of liquid is formed on the tube wall. For negligible inertial and buoyancy effects, respectively, small Reynolds (Re) and Bond (Bo) numbers, the thickness of the liquid film depends only on the flow capillary number (Ca). However, buoyancy effects are no longer negligible as the diameter of the tube reaches millimeter length scales, which corresponds to finite values of Bo. We perform experiments and theoretical analysis for a long bubble in a horizontal tube to investigate the effect of Bond number (0.05

The growth of ultralong and highly blue luminescent gallium oxide nanowires and nanobelts, and direct horizontal nanowire growth on substrates.

PubMed

Kuo, Chi-Liang; Huang, Michael H

2008-04-16

We report the growth of ultralong β-Ga(2)O(3) nanowires and nanobelts on silicon substrates using a vapor phase transport method. The growth was carried out in a tube furnace, with gallium metal serving as the gallium source. The nanowires and nanobelts can grow to lengths of hundreds of nanometers and even millimeters. Their full lengths have been captured by both scanning electron microscope (SEM) and optical images. X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) images have been used to study the crystal structures of these nanowires and nanobelts. Strong blue emission from these ultralong nanostructures can be readily observed by irradiation with an ultraviolet (UV) lamp. Diffuse reflectance spectroscopy measurements gave a band gap of 4.56 eV for these nanostructures. The blue emission shows a band maximum at 470 nm. Interestingly, by annealing the silicon substrates in an oxygen atmosphere to form a thick SiO(2) film, and growing Ga(2)O(3) nanowires over the sputtered gold patterned regions, horizontal Ga(2)O(3) nanowire growth in the non-gold-coated regions can be observed. These horizontal nanowires can grow to as long as over 10 µm in length. Their composition has been confirmed by TEM characterization. This represents one of the first examples of direct horizontal growth of oxide nanowires on substrates.

Is increased residual shank length a competitive advantage for elite transtibial amputee long jumpers?

PubMed

Nolan, Lee; Patritti, Benjamin L; Stana, Laura; Tweedy, Sean M

2011-07-01

The purpose of this study was to evaluate the extent to which residual shank length affects long jump performance of elite athletes with a unilateral transtibial amputation. Sixteen elite, male, long jumpers with a transtibial amputation were videoed while competing in major championships (World Championships 1998, 2002 and Paralympic Games, 2004). The approach, take-off, and landing of each athlete's best jump was digitized to determine residual and intact shank lengths, jump distance, and horizontal and vertical velocity of center of mass at touchdown. Residual shank length ranged from 15 cm to 38 cm. There were weak, nonsignificant relationships between residual shank length and (a) distance jumped (r = 0.30), (b) horizontal velocity (r = 0.31), and vertical velocity (r = 0.05). Based on these results, residual shank length is not an important determinant of long jump performance, and it is therefore appropriate that all long jumpers with transtibial amputation compete in the same class. The relationship between residual shank length and key performance variables was stronger among athletes that jumped off their prosthetic leg (N = 5), and although this result must be interpreted cautiously, it indicates the need for further research.

Ocean Winds and Turbulent Air-Sea Fluxes Inferred From Remote Sensing

NASA Technical Reports Server (NTRS)

Bourassa, Mark A.; Gille, Sarah T.; Jackson, Daren L.; Roberts, J. Brent; Wick, Gary A.

2010-01-01

Air-sea turbulent fluxes determine the exchange of momentum, heat, freshwater, and gas between the atmosphere and ocean. These exchange processes are critical to a broad range of research questions spanning length scales from meters to thousands of kilometers and time scales from hours to decades. Examples are discussed (section 2). The estimation of surface turbulent fluxes from satellite is challenging and fraught with considerable errors (section 3); however, recent developments in retrievals (section 3) will greatly reduce these errors. Goals for the future observing system are summarized in section 4. Surface fluxes are defined as the rate per unit area at which something (e.g., momentum, energy, moisture, or CO Z ) is transferred across the air/sea interface. Wind- and buoyancy-driven surface fluxes are called surface turbulent fluxes because the mixing and transport are due to turbulence. Examples of nonturbulent processes are radiative fluxes (e.g., solar radiation) and precipitation (Schmitt et al., 2010). Turbulent fluxes are strongly dependent on wind speed; therefore, observations of wind speed are critical for the calculation of all turbulent surface fluxes. Wind stress, the vertical transport of horizontal momentum, also depends on wind direction. Stress is very important for many ocean processes, including upper ocean currents (Dohan and Maximenko, 2010) and deep ocean currents (Lee et al., 2010). On short time scales, this horizontal transport is usually small compared to surface fluxes. For long-term processes, transport can be very important but again is usually small compared to surface fluxes.

Large-scale horizontal flows from SOUP observations of solar granulation

NASA Astrophysics Data System (ADS)

November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.; Ferguson, S. H.

1987-09-01

Using high-resolution time-sequence photographs of solar granulation from the SOUP experiment on Spacelab 2 the authors observed large-scale horizontal flows in the solar surface. The measurement method is based upon a local spatial cross correlation analysis. The horizontal motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of granulation from a sunspot penumbra into the surrounding photosphere is a striking new discovery. Both the supergranulation pattern and cellular structures having the scale of mesogranulation are seen. The vertical flows that are inferred by continuity of mass from these observed horizontal flows have larger upflow amplitudes in cell centers than downflow amplitudes at cell boundaries.

Drop impact on inclined superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Choi, Wonjae; Leclear, Sani; Leclear, Johnathon; Abhijeet, .; Park, Kyoo-Chul

We report an empirical study and dimensional analysis on the impact patterns of water drops on inclined superhydrophobic surfaces. While the classic Weber number determines the spreading and recoiling dynamics of a water drop on a horizontal / smooth surface, for a superhydrophobic surface, the dynamics depends on two distinct Weber numbers, each calculated using the length scale of the drop or of the pores on the surface. Impact on an inclined superhydrophobic surface is even more complicated, as the velocity that determines the Weber number is not necessarily the absolute speed of the drop but the velocity components normal and tangential to the surface. We define six different Weber numbers, using three different velocities (absolute, normal and tangential velocities) and two different length scales (size of the drop and of the texture). We investigate the impact patterns on inclined superhydrophobic surfaces with three different types of surface texture: (i) posts, (ii) ridges aligned with and (iii) ridges perpendicular to the impact direction. Results suggest that all six Weber numbers matter, but affect different parts of the impact dynamics, ranging from the Cassie-Wenzel transition, maximum spreading, to anisotropic deformation. We acknowledge financial support from the Office of Naval Research (ONR) through Contract 3002453812.

7 CFR 51.586 - Serious damage.

Code of Federal Regulations, 2010 CFR

2010-01-01

... allowed for any one defect, shall be considered as serious damage: (a) Growth cracks when more than 4 branches are affected by growth cracks which are over one-half inch in length, or when more than 8 branches have growth cracks; (b) Horizontal cracks when more than 5 branches have horizontal cracks which are...

7 CFR 51.586 - Serious damage.

Code of Federal Regulations, 2011 CFR

2011-01-01

... allowed for any one defect, shall be considered as serious damage: (a) Growth cracks when more than 4 branches are affected by growth cracks which are over one-half inch in length, or when more than 8 branches have growth cracks; (b) Horizontal cracks when more than 5 branches have horizontal cracks which are...

7 CFR 51.586 - Serious damage.

Code of Federal Regulations, 2012 CFR

2012-01-01

... allowed for any one defect, shall be considered as serious damage: (a) Growth cracks when more than 4 branches are affected by growth cracks which are over one-half inch in length, or when more than 8 branches have growth cracks; (b) Horizontal cracks when more than 5 branches have horizontal cracks which are...

10. MOVABLE BED SEDIMENTATION MODELS. DOGTOOTH BEND MODEL (MODEL SCALE: ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. MOVABLE BED SEDIMENTATION MODELS. DOGTOOTH BEND MODEL (MODEL SCALE: 1' = 400' HORIZONTAL, 1' = 100' VERTICAL), AND GREENVILLE BRIDGE MODEL (MODEL SCALE: 1' = 360' HORIZONTAL, 1' = 100' VERTICAL). - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

Growth of high-aspect ratio horizontally-aligned ZnO nanowire arrays.

PubMed

Soman, Pranav; Darnell, Max; Feldman, Marc D; Chen, Shaochen

2011-08-01

A method of fabricating horizontally-aligned zinc-oxide (ZnO) nanowire (NW) arrays with full control over the width and length is demonstrated. SEM images reveal the hexagonal structure typical of zinc oxide NWs. Arrays of high-aspect ratio horizontal ZnO NWs are fabricated by making use of the lateral overgrowth from dot patterns created by electron beam lithography (EBL). An array of patterned wires are lifted off and transferred to a flexible PDMS substrate with possible applications in several key nanotechnology areas.

Direct and inverse energy cascades in a forced rotating turbulence experiment

NASA Astrophysics Data System (ADS)

Campagne, Antoine; Gallet, Basile; Moisy, Frédéric; Cortet, Pierre-Philippe

2014-12-01

We present experimental evidence for a double cascade of kinetic energy in a statistically stationary rotating turbulence experiment. Turbulence is generated by a set of vertical flaps, which continuously injects velocity fluctuations towards the center of a rotating water tank. The energy transfers are evaluated from two-point third-order three-component velocity structure functions, which we measure using stereoscopic particle image velocimetry in the rotating frame. Without global rotation, the energy is transferred from large to small scales, as in classical three-dimensional turbulence. For nonzero rotation rates, the horizontal kinetic energy presents a double cascade: a direct cascade at small horizontal scales and an inverse cascade at large horizontal scales. By contrast, the vertical kinetic energy is always transferred from large to small horizontal scales, a behavior reminiscent of the dynamics of a passive scalar in two-dimensional turbulence. At the largest rotation rate, the flow is nearly two-dimensional, and a pure inverse energy cascade is found for the horizontal energy. To describe the scale-by-scale energy budget, we consider a generalization of the Kármán-Howarth-Monin equation to inhomogeneous turbulent flows, in which the energy input is explicitly described as the advection of turbulent energy from the flaps through the surface of the control volume where the measurements are performed.

Horizontal heat fluxes over complex terrain computed using a simple mixed-layer model and a numerical model

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

Kimura, Fujio; Kuwagata, Tuneo

1995-02-01

The thermally induced local circulation over a periodic valley is simulated by a two-dimensional numerical model that does-not include condensational processes. During the daytime of a clear, calm day, heat is transported from the mountainous region to the valley area by anabatic wind and its return flow. The specific humidity is, however, transported in an inverse manner. The horizontal exchange rate of sensible heat has a horizontal scale similarity, as long as the horizontal scale is less than a critical width of about 100 km. The sensible heat accumulated in an atmospheric column over an arbitrary point can be estimatedmore » by a simple model termed the uniform mixed-layer model (UML). The model assumes that the potential temperature is both vertically and horizontally uniform in the mixed layer, even over the complex terrain. The UML model is valid only when the horizontal scale of the topography is less than the critical width and the maximum difference in the elevation of the topography is less than about 1500 m. Latent heat is accumulated over the mountainous region while the atmosphere becomes dry over the valley area. When the horizontal scale is close to the critical width, the largest amount of humidity is accumulated during the late afternoon over the mountainous region. 18 refs., 15 figs., 1 tab.« less

Eye-Tracking Reveals that the Strength of the Vertical-Horizontal Illusion Increases as the Retinal Image Becomes More Stable with Fixation

PubMed Central

Chouinard, Philippe A.; Peel, Hayden J.; Landry, Oriane

2017-01-01

The closer a line extends toward a surrounding frame, the longer it appears. This is known as a framing effect. Over 70 years ago, Teodor Künnapas demonstrated that the shape of the visual field itself can act as a frame to influence the perceived length of lines in the vertical-horizontal illusion. This illusion is typically created by having a vertical line rise from the center of a horizontal line of the same length creating an inverted T figure. We aimed to determine if the degree to which one fixates on a spatial location where the two lines bisect could influence the strength of the illusion, assuming that the framing effect would be stronger when the retinal image is more stable. We performed two experiments: the visual-field and vertical-horizontal illusion experiments. The visual-field experiment demonstrated that the participants could discriminate a target more easily when it was presented along the horizontal vs. vertical meridian, confirming a framing influence on visual perception. The vertical-horizontal illusion experiment determined the effects of orientation, size and eye gaze on the strength of the illusion. As predicted, the illusion was strongest when the stimulus was presented in either its standard inverted T orientation or when it was rotated 180° compared to other orientations, and in conditions in which the retinal image was more stable, as indexed by eye tracking. Taken together, we conclude that the results provide support for Teodor Künnapas’ explanation of the vertical-horizontal illusion. PMID:28392764

A detailed model for simulation of catchment scale subsurface hydrologic processes

NASA Technical Reports Server (NTRS)

Paniconi, Claudio; Wood, Eric F.

1993-01-01

A catchment scale numerical model is developed based on the three-dimensional transient Richards equation describing fluid flow in variably saturated porous media. The model is designed to take advantage of digital elevation data bases and of information extracted from these data bases by topographic analysis. The practical application of the model is demonstrated in simulations of a small subcatchment of the Konza Prairie reserve near Manhattan, Kansas. In a preliminary investigation of computational issues related to model resolution, we obtain satisfactory numerical results using large aspect ratios, suggesting that horizontal grid dimensions may not be unreasonably constrained by the typically much smaller vertical length scale of a catchment and by vertical discretization requirements. Additional tests are needed to examine the effects of numerical constraints and parameter heterogeneity in determining acceptable grid aspect ratios. In other simulations we attempt to match the observed streamflow response of the catchment, and we point out the small contribution of the streamflow component to the overall water balance of the catchment.

Trains of large Kelvin-Helmholtz billows observed in the Kuroshio above a seamount

NASA Astrophysics Data System (ADS)

Chang, Ming-Huei; Jheng, Sin-Ya; Lien, Ren-Chieh

2016-08-01

Trains of large Kelvin-Helmholtz (KH) billows within the Kuroshio current at ~230 m depth off southeastern Taiwan and above a seamount were observed by shipboard instruments. The trains of large KH billows were present in a strong shear band along the 0.55 m s-1 isotach within the Kuroshio core; they are presumably produced by flow interactions with the rapidly changing topography. Each individual billow, resembling a cat's eye, had a horizontal length scale of 200 m, a vertical scale of 100 m, and a timescale of 7 min, near the local buoyancy frequency. Overturns were observed frequently in the billow cores and the upper eyelids. The turbulent kinetic energy dissipation rates estimated using the Thorpe scale had an average value of O(10-4) W kg-1 and a maximum value of O(10-3) W kg-1. The turbulence mixing induced by the KH billows may exchange Kuroshio water with the surrounding water masses.

Buoyancy forcing and the MOC: insights from experiments, simulations and global models

NASA Astrophysics Data System (ADS)

White, B. L.; Passaggia, P. Y.; Zemskova, V.

2017-12-01

The driving forces behind the Meridional Overturning Circulation (MOC) have been widely debated, with wind-driven upwelling, surface buoyancy fluxes due to heating/cooling/freshwater input, and vertical diffusion due to turbulent mixing all thought to play significant roles. To explore the specific role of buoyancy forcing we present results from experiments and simulations of Horizontal Convection (HC), where a circulation is driven by differential buoyancy forcing applied along a horizontal surface. We interpret these results using energy budgets based on the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. We first describe HC experiments driven by the diffusion of salt in water across membranes localized at the surface, at Schmidt numbers {Sc}≈ 610 and Rayleigh numbers in the range 1012 < Ra=Δ b L3/(ν κ ) < 1017, where ν is the kinematic viscosity of water, κ is the diffusion coefficient of salt, L=[.5,2,5]m is the length of the different tanks and Δ b=g(ρ salt}-ρ {fresh}/ρ_{fresh is the reduced gravity difference. We show that the scaling follows a Nu ˜ Ra1/4 type scaling recently theorized by Shishkina et; al. (2016). We then present numerical results for rotating horizontal convection with a zonally re-entrant channel to represent the Southern Ocean branch of the MOC. While the zonal wind stress profile is important to the spatial pattern of the circulation, perhaps surprisingly, the energy budget shows only a weak dependence on the magnitude of the wind input, suggesting that surface APE generation by buoyancy forcing is dominant in driving the overturning circulation.

Evaluating the Individualism and Collectivism Scale for use in mainland China.

PubMed

Chen, Guo-Hai

2007-08-01

A Chinese translation of the 27-item Individualism and Collectivism Scale was administered in southern mainland China to 626 Chinese university students (210 men and 416 women) with a mean age of 19.9 yr. (SD = 1.5). From analysis of the responses to these items, the prior four factors, Horizontal Individualism, Vertical Individualism, Horizontal Collectivism, and Vertical Collectivism, did not clearly emerge in the Chinese sample. Further research on the viability of the scale and conceptualization of the horizontal and vertical distinction in the Chinese context is recommended.

Horizontal sliding of kilometre-scale hot spring area during the 2016 Kumamoto earthquake

PubMed Central

Tsuji, Takeshi; Ishibashi, Jun’ichiro; Ishitsuka, Kazuya; Kamata, Ryuichi

2017-01-01

We report horizontal sliding of the kilometre-scale geologic block under the Aso hot springs (Uchinomaki area) caused by vibrations from the 2016 Kumamoto earthquake (Mw 7.0). Direct borehole observations demonstrate the sliding along the horizontal geological formation at ~50 m depth, which is where the shallowest hydrothermal reservoir developed. Owing to >1 m northwest movement of the geologic block, as shown by differential interferometric synthetic aperture radar (DInSAR), extensional open fissures were generated at the southeastern edge of the horizontal sliding block, and compressional deformation and spontaneous fluid emission from wells were observed at the northwestern edge of the block. The temporal and spatial variation of the hot spring supply during the earthquake can be explained by the horizontal sliding and borehole failures. Because there was no strain accumulation around the hot spring area prior to the earthquake and gravitational instability could be ignored, the horizontal sliding along the low-frictional formation was likely caused by seismic forces from the remote earthquake. The insights derived from our field-scale observations may assist further research into geologic block sliding in horizontal geological formations. PMID:28218298

Turbulent dispersion of slightly buoyant oil droplets and turbulent breakup of crude oil droplets mixed with dispersants

NASA Astrophysics Data System (ADS)

Gopalan, Balaji

In part I, high speed in-line digital holographic cinematography is used for studying turbulent diffusion of slightly buoyant 0.5-1.2 mm diameter diesel droplets (specific gravity of 0.85) and 50 mum diameter neutral density particles. Experiments are performed in a 50x50x70 mm3 sample volume in a controlled, nearly isotropic turbulence facility, which is characterized by 2-D PIV. An automated tracking program has been used for measuring velocity time history of more than 17000 droplets and 15000 particles. The PDF's of droplet velocity fluctuations are close to Gaussian for all turbulent intensities ( u'i ). The mean rise velocity of droplets is enhanced or suppressed, compared to quiescent rise velocity (Uq), depending on Stokes number at lower turbulence levels, but becomes unconditionally enhanced at higher turbulence levels. The horizontal droplet velocity rms exceeds the fluid velocity rms for most of the data, while the vertical ones are higher than the fluid only at the highest turbulence level. The scaled droplet horizontal diffusion coefficient is higher than the vertical one, for 1 < u'i /Uq < 5, consistent with trends of the droplet velocity fluctuations. Conversely, the scaled droplet horizontal diffusion timescale is smaller than the vertical one due to crossing trajectories effect. The droplet diffusion coefficients scaled by the product of turbulence intensity and an integral length scale is a monotonically increasing function of u'i /Uq. Part II of this work explains the formation of micron sized droplets in turbulent flows from crude oil droplets pre-mixed with dispersants. Experimental visualization shows that this breakup starts with the formation of very long and quite stable, single or multiple micro threads that trail behind millimeter sized droplets. These threads form in regions with localized increase in concentration of surfactant, which in turn depends on the flow around the droplet. The resulting reduction of local surface tension, aided by high oil viscosity and stretching by the flow, suppresses capillary breakup and explains the stability of these threads. Due to increasing surface area and diffusion of dispersants into the continuous phase, the threads eventually breakup into ˜3 mum droplets.

A new estimator for VLBI baseline length repeatability

NASA Astrophysics Data System (ADS)

Titov, O.

2009-11-01

The goal of this paper is to introduce a more effective technique to approximate for the “repeatability-baseline length” relationship that is used to evaluate the quality of geodetic VLBI results. Traditionally, this relationship is approximated by a quadratic function of baseline length over all baselines. The new model incorporates the mean number of observed group delays of the reference radio sources (i.e. estimated as global parameters) used in the estimation of each baseline. It is shown that the new method provides a better approximation of the “repeatability-baseline length” relationship than the traditional model. Further development of the new approach comes down to modeling the repeatability as a function of two parameters: baseline length and baseline slewing rate. Within the framework of this new approach the station vertical and horizontal uncertainties can be treated as a function of baseline length. While the previous relationship indicated that the station vertical uncertainties are generally 4-5 times larger than the horizontal uncertainties, the vertical uncertainties as determined by the new method are only larger by a factor of 1.44 over all baseline lengths.

Simulation analysis of receptive-field size of retinal horizontal cells by ionic current model.

PubMed

Aoyama, Toshihiro; Kamiyama, Yoshimi; Usui, Shiro

2005-01-01

The size of the receptive field of retinal horizontal cells changes with the state of dark/light adaptation. We have used a mathematical model to determine how changes in the membrane conductance affect the receptive-field properties of horizontal cells. We first modeled the nonlinear membrane properties of horizontal cells based on ionic current mechanisms. The dissociated horizontal cell model reproduced the voltage-current (V-I) relationships for various extracellular glutamate concentrations measured in electrophysiological studies. Second, a network horizontal cell model was also described, and it reproduced the V-I relationship observed in vivo. The network model showed a bell-shaped relationship between the receptive-field size and constant glutamate concentration. The simulated results suggest that the calcium current is a candidate for the bell-shaped length constant relationship.

Intensity and angle-of-arrival spectra of laser light propagating through axially homogeneous buoyancy-driven turbulence.

PubMed

Pawar, Shashikant S; Arakeri, Jaywant H

2016-08-01

Frequency spectra obtained from the measurements of light intensity and angle of arrival (AOA) of parallel laser light propagating through the axially homogeneous, axisymmetric buoyancy-driven turbulent flow at high Rayleigh numbers in a long (length-to-diameter ratio of about 10) vertical tube are reported. The flow is driven by an unstable density difference created across the tube ends using brine and fresh water. The highest Rayleigh number is about 8×10⁹. The aim of the present work is to find whether the conventional Obukhov-Corrsin scaling or Bolgiano-Obukhov (BO) scaling is obtained for the intensity and AOA spectra in the case of light propagation in a buoyancy-driven turbulent medium. Theoretical relations for the frequency spectra of log amplitude and AOA fluctuations developed for homogeneous isotropic turbulent media are modified for the buoyancy-driven flow in the present case to obtain the asymptotic scalings for the high and low frequency ranges. For low frequencies, the spectra of intensity and vertical AOA fluctuations obtained from measurements follow BO scaling, while scaling for the spectra of horizontal AOA fluctuations shows a small departure from BO scaling.

Stratified mixing by microorganisms

NASA Astrophysics Data System (ADS)

Wagner, Gregory; Young, William; Lauga, Eric

2013-11-01

Vertical mixing is of fundamental significance to the general circulation, climate, and life in the ocean. In this work we consider whether organisms swimming at low Reynolds numbers might collectively contribute substantially to vertical mixing. Scaling analysis indicates that the mixing efficiency η, or the ratio between the rate of potential energy conversion and total work done on the fluid, should scale with η ~(a / l) 3 as a / l --> 0 , where a is the size of the organism and l = (νκ /N2)1/4 is an intrinsic length scale of a stratified fluid with kinematic viscosity ν, tracer diffusivity κ, and buoyancy frequency N2. A regularized singularity model demonstrates this scaling, indicating that in this same limit η ~ 1.2 (a / l) 3 for vertical swimming and η ~ 0.14 (a / l ) 3 for horizontal swimming. The model further predicts the absolute maximum mixing efficiency of an ensemble of randomly oriented organisms is around 6% and that the greatest mixing efficiencies in the ocean (in regions of strong salt-stratification) are closer to 0.1%, implying that the total contribution of microorganisms to vertical ocean mixing is negligible.

Lava flow topographic measurements for radar data interpretation

NASA Technical Reports Server (NTRS)

Campbell, Bruce A.; Garvin, James B.

1993-01-01

Topographic profiles at 25- and 5-cm horizontal resolution for three sites along a lava flow on Kilauea Volcano are presented, and these data are used to illustrate techniques for surface roughness analysis. Height and slope distributions and the height autocorrelation function are evaluated as a function of varying lowpass filter wavelength for the 25-cm data. Rms slopes are found to increase rapidly with decreasing topographic scale and are typically much higher than those found by modeling of Magellan altimeter data for Venus. A more robust description of the surface roughness appears to be the ratio of rms height to surface height correlation length. For all three sites this parameter falls within the range of values typically found from model fits to Magellan altimeter waveforms. The 5-cm profile data are used to estimate the effect of small-scale roughness on quasi-specular scattering.

On the nonlinear dynamics of trolling-mode AFM: Analytical solution using multiple time scales method

NASA Astrophysics Data System (ADS)

Sajjadi, Mohammadreza; Pishkenari, Hossein Nejat; Vossoughi, Gholamreza

2018-06-01

Trolling mode atomic force microscopy (TR-AFM) has resolved many imaging problems by a considerable reduction of the liquid-resonator interaction forces in liquid environments. The present study develops a nonlinear model of the meniscus force exerted to the nanoneedle of TR-AFM and presents an analytical solution to the distributed-parameter model of TR-AFM resonator utilizing multiple time scales (MTS) method. Based on the developed analytical solution, the frequency-response curves of the resonator operation in air and liquid (for different penetration length of the nanoneedle) are obtained. The closed-form analytical solution and the frequency-response curves are validated by the comparison with both the finite element solution of the main partial differential equations and the experimental observations. The effect of excitation angle of the resonator on horizontal oscillation of the probe tip and the effect of different parameters on the frequency-response of the system are investigated.

Competitive Self-Assembly Manifests Supramolecular Darwinism in Soft-Oxometalates

NASA Astrophysics Data System (ADS)

Das, Santu; Kumar, Saurabh; Mallick, Apabrita; Roy, Soumyajit

2015-09-01

Topological transformation manifested in inorganic materials shows manifold possibilities. In our present work, we show a clear topological transformation in a soft-oxometalate (SOM) system which was formed from its polyoxometalate (POM) precursor [PMo12@Mo72Fe30]. This topological transformation was observed due to time dependent competitive self-assembly of two different length scale soft-oxometalate moieties formed from this two-component host-guest reaction. We characterized different morphologies by scanning electron microscopy, electron dispersive scattering spectroscopy, dynamic light scattering, horizontal attenuated total reflection-infrared spectroscopy and Raman spectroscopy. The predominant structure is selected by its size in a sort of supramolecular Darwinian competition in this process and is described here.

Buckling of a Flexible Strip Sliding on a Frictional Base

NASA Astrophysics Data System (ADS)

Huynen, Alexandre; Marck, Julien; Denoel, Vincent; Detournay, Emmanuel

2013-03-01

The main motivation for this contribution is the buckling of a drillstring sliding on the bottom of the horizontal section of borehole. The open questions that remain today are related to the determination of the onset of instability, and to the conditions under which different modes of constrained buckling occur. In this presentation, we are concerned by a two-dimensional version of this problem; namely, the sliding of a flexible strip being fed inside a conduit. The ribbon, which has a flexural rigidity EI and a weight per unit length w, is treated as an inextensible elastica of negligible thickness. The contact between the ribbon and the wall of the conduit is characterized by a friction coefficient μ. First, we report the result of a stability analysis that aims at determining the critical inserted length of the ribbon l* (μ) (scaled by the characteristic length λ =(EI / w) 1 / 3) at which there is separation between the strip and the conduit bottom, as well as the buckling mode. Next, the relationship between the feeding force F and the inserted length l after bifurcation is computed. Finally, the results of a ``kitchen table'' experiment involving a strip of silicon rubber being pushed on a plank are reported and compared with predictions.

Analysis of the NASA/MSFC Airborne Doppler Lidar results from San Gorgonio Pass, California

NASA Technical Reports Server (NTRS)

Cliff, W. C.; Skarda, J. R.; Renne, D. S.; Sandusky, W. F.

1984-01-01

Two days during July of 1981 the NASA/MSFC Airborne Doppler Lidar System (ADLS) was flown aboard the NASA/AMES Convair 990 on the east side of San Gorgonio Pass California, near Palm Springs, to measure and investigate the accelerated atmospheric wind field discharging from the pass. The vertical and horizontal extent of the fast moving atmospheric flow discharging from the San Gorgonio Pass were examined. Conventional ground measurements were also taken during the tests to assist in validating the ADLS results. This particular region is recognized as a high wind resource region and, as such, a knowledge of the horizontal and vertical extent of this flow was of interest for wind energy applications. The statistics of the atmospheric flow field itself as it discharges from the pass and then spreads out over the desert were also of scientific interests. This data provided the first spatial data for ensemble averaging of spatial correlations to compute longitudinal and lateral integral length scales in the longitudinal and lateral directions for both components.

Segregation physics of a macroscale granular ratchet

NASA Astrophysics Data System (ADS)

Bhateja, Ashish; Sharma, Ishan; Singh, Jayant K.

2017-05-01

New experiments with multigrain mixtures in a laterally shaken, horizontal channel show complete axial segregation of species. The channel consists of multiple concatenated trapeziums, and superficially resembles microratchets wherein asymmetric geometries and potentials transport, and sort, randomly agitated microscopic particles. However, the physics of our macroscale granular ratchet is fundamentally different, as macroscopic segregation is gravity driven. Our observations are not explained by classical granular segregation theories either. Motivated by the experiments, extensive parallelized discrete element simulations reveal that the macroratchet differentiates grains through hierarchical bidirectional segregation over two different time scales: Grains rapidly sort vertically into horizontal bands spanning the channel's length that, subsequently, slowly separate axially, driven by strikingly gentle, average interfacial pressure gradients acting over long distances. At its maximum, the pressure gradient responsible for axial separation was due to a change in height of about two big grain diameters (d =7 mm) over a meter-long channel. The strong directional segregation achieved by the granular macroratchet has practical importance, while identifying the underlying new physics will further our understanding of granular segregation in industrial and geophysical processes.

Snow stratigraphic heterogeneity within ground-based passive microwave radiometer footprints: Implications for emission modeling

NASA Astrophysics Data System (ADS)

Rutter, Nick; Sandells, Mel; Derksen, Chris; Toose, Peter; Royer, Alain; Montpetit, Benoit; Langlois, Alex; Lemmetyinen, Juha; Pulliainen, Jouni

2014-03-01

Two-dimensional measurements of snowpack properties (stratigraphic layering, density, grain size, and temperature) were used as inputs to the multilayer Helsinki University of Technology (HUT) microwave emission model at a centimeter-scale horizontal resolution, across a 4.5 m transect of ground-based passive microwave radiometer footprints near Churchill, Manitoba, Canada. Snowpack stratigraphy was complex (between six and eight layers) with only three layers extending continuously throughout the length of the transect. Distributions of one-dimensional simulations, accurately representing complex stratigraphic layering, were evaluated using measured brightness temperatures. Large biases (36 to 68 K) between simulated and measured brightness temperatures were minimized (-0.5 to 0.6 K), within measurement accuracy, through application of grain scaling factors (2.6 to 5.3) at different combinations of frequencies, polarizations, and model extinction coefficients. Grain scaling factors compensated for uncertainty relating optical specific surface area to HUT effective grain size inputs and quantified relative differences in scattering and absorption properties of various extinction coefficients. The HUT model required accurate representation of ice lenses, particularly at horizontal polarization, and large grain scaling factors highlighted the need to consider microstructure beyond the size of individual grains. As variability of extinction coefficients was strongly influenced by the proportion of large (hoar) grains in a vertical profile, it is important to consider simulations from distributions of one-dimensional profiles rather than single profiles, especially in sub-Arctic snowpacks where stratigraphic variability can be high. Model sensitivity experiments suggested that the level of error in field measurements and the new methodological framework used to apply them in a snow emission model were satisfactory. Layer amalgamation showed that a three-layer representation of snowpack stratigraphy reduced the bias of a one-layer representation by about 50%.

Thermal convection of liquid metal in a long inclined cylinder

NASA Astrophysics Data System (ADS)

Teimurazov, Andrei; Frick, Peter

2017-11-01

The turbulent convection of low-Prandtl-number fluids (Pr=0.0083 ) in a long cylindrical cell, heated at one end face and cooled at the other, inclined to the vertical at angle β , 0 ≤β ≤π /2 with step π /20 , is studied numerically by solving the Oberbeck-Boussinesq equations with the large-eddy-simulation approach for small-scale turbulence. The cylinder length is L =5 D , where D is the diameter. The Rayleigh number, determined by the cylinder diameter, is of the order of 5 ×106 . We show that the structure of the flow strongly depends on the inclination angle. A stable large-scale circulation (LSC) slightly disturbed by small-scale turbulence exists in the horizontal cylinder. The deviation from a horizontal position provides strong amplification of both LSC and small-scale turbulence. The energy of turbulent pulsations increases monotonically with decreasing inclination angle β , matching the energy of the LSC at β ≈π /5 . The intensity of the LSC has a wide, almost flat, maximum for an inclined cylinder and slumps approaching the vertical position, in which the LSC vanishes. The dependence of the Nusselt number on the inclination angle has a maximum at β ≈7 π /20 and generally follows the dependence of the intensity of LSC on the inclination. This indicates that the total heat transport is highly determined by LSC. We examine the applicability of idealized thermal boundary conditions (BCs) for modeling a real experiment with liquid sodium flows. Therefore, the simulations are done with two types of temperature BCs: fixed face temperature and fixed heat flux. The intensity of the LSC is slightly higher in the latter case and leads to a corresponding increase of the Nusselt number and enhancement of temperature pulsations.

Non-pumping reactive wells filled with mixing nano and micro zero-valent iron for nitrate removal from groundwater: Vertical, horizontal, and slanted wells

NASA Astrophysics Data System (ADS)

Hosseini, Seiyed Mossa; Tosco, Tiziana; Ataie-Ashtiani, Behzad; Simmons, Craig T.

2018-03-01

Non-pumping reactive wells (NPRWs) filled by zero-valent iron (ZVI) can be utilized for the remediation of groundwater contamination of deep aquifers. The efficiency of NPRWs mainly depends on the hydraulic contact time (HCT) of the pollutant with the reactive materials, the extent of the well capture zone (Wcz), and the relative hydraulic conductivity of aquifer and reactive material (Kr). We investigated nitrate removal from groundwater using NPRWs filled by ZVI (in nano and micro scales) and examined the effect of NPRWs orientations (i.e. vertical, slanted, and horizontal) on HCT and Wcz. The dependence of HCT on Wcz for different Kr values was derived theoretically for a homogeneous and isotropic aquifer, and verified using particle tracking simulations performed using the semi-analytical particle tracking and pathlines model (PMPATH). Nine batch experiments were then performed to investigate the impact of mixed nano-ZVI, NZVI (0 to 2 g l-1) and micro-ZVI, MZVI (0 to 4 g l-1) on the nitrate removal rate (with initial NO3-=132 mg l-1). The NPRWs system was tested in a bench-scale sand medium (60 cm length × 40 cm width × 25 cm height) for three orientations of NPRWs (vertical, horizontal, and slanted with inclination angle of 45°). A mixture of nano/micro ZVI, was used, applying constant conditions of pore water velocity (0.024 mm s-1) and initial nitrate concentration (128 mg l-1) for five pore volumes. The results of the batch tests showed that mixing nano and micro Fe0 outperforms these individual materials in nitrate removal rates. The final products of nitrate degradation in both batch and bench-scale experiments were NO2-, NH4+, and N2(gas). The results of sand-box experiments indicated that the slanted NPRWs have a higher nitrate reduction rate (57%) in comparison with vertical (38%) and horizontal (41%) configurations. The results also demonstrated that three factors have pivotal roles in expected HCT and Wcz, namely the contrast between the hydraulic conductivity of aquifer and reactive materials within the wells, the mass of Fe0 in the NPRWs, and the orientation of NPRWs adopted. A trade-off between these factors should be considered to increase the efficiency of remediation using the NPRWs system.

Reservoir characterization of the Mt. Simon Sandstone, Illinois Basin, USA

USGS Publications Warehouse

Frailey, S.M.; Damico, J.; Leetaru, H.E.

2011-01-01

The integration of open hole well log analyses, core analyses and pressure transient analyses was used for reservoir characterization of the Mt. Simon sandstone. Characterization of the injection interval provides the basis for a geologic model to support the baseline MVA model, specify pressure design requirements of surface equipment, develop completion strategies, estimate injection rates, and project the CO2 plume distribution.The Cambrian-age Mt. Simon Sandstone overlies the Precambrian granite basement of the Illinois Basin. The Mt. Simon is relatively thick formation exceeding 800 meters in some areas of the Illinois Basin. In the deeper part of the basin where sequestration is likely to occur at depths exceeding 1000 m, horizontal core permeability ranges from less than 1 ?? 10-12 cm 2 to greater than 1 ?? 10-8 cm2. Well log and core porosity can be up to 30% in the basal Mt. Simon reservoir. For modeling purposes, reservoir characterization includes absolute horizontal and vertical permeability, effective porosity, net and gross thickness, and depth. For horizontal permeability, log porosity was correlated with core. The core porosity-permeability correlation was improved by using grain size as an indication of pore throat size. After numerous attempts to identify an appropriate log signature, the calculated cementation exponent from Archie's porosity and resistivity relationships was used to identify which porosity-permeability correlation to apply and a permeability log was made. Due to the relatively large thickness of the Mt. Simon, vertical permeability is an important attribute to understand the distribution of CO2 when the injection interval is in the lower part of the unit. Only core analyses and specifically designed pressure transient tests can yield vertical permeability. Many reservoir flow models show that 500-800 m from the injection well most of the CO2 migrates upward depending on the magnitude of the vertical permeability and CO2 injection rate (CO2 velocity). Assigning a specific value of vertical permeability to model cells is dependent on the vertical height of the model cell. Measured vertical permeability on core is scale dependent, such that lower vertical permeability is expected over longer core lengths compared to smaller lengths. Consequently, a series of vertical permeability tests were conducted on whole core varying in lengths of samples from 7 cm to 30 cm that showed vertical perm could change by an order of magnitude over a 30 cm height. For one well, the results from a series of pressure transient tests over a perforated interval much smaller than the gross thickness (<2%) confirmed the core-log based geologic model for vertical and horizontal permeability. A partial penetration model was used to estimate the horizontal and vertical permeability over a portion of the modeled area using series and parallel flow averaging techniques. ?? 2011 Published by Elsevier Ltd.

HIGH-RESOLUTION DATASET OF URBAN CANOPY PARAMETERS FOR HOUSTON, TEXAS

EPA Science Inventory

Urban dispersion and air quality simulation models applied at various horizontal scales require different levels of fidelity for specifying the characteristics of the underlying surfaces. As the modeling scales approach the neighborhood level (~1 km horizontal grid spacing), the...

Human factors evaluation of the HL-20 full-scale model

NASA Astrophysics Data System (ADS)

Willshire, Kelli F.; Simonsen, Lisa C.; Willshire, William L., Jr.

1993-09-01

The human factors testing of the HL-20 personnel launch system full-scale model was conducted in both the vertical and horizontal positions at NASA Langley Research Center. Three main areas of testing were considered: an anthropometric fit evaluation, the ingress and egress of a 10-person crew, and pilot viewing. The subjects, ranging from the 5th to 95th percentile size, had sufficient clearance in the model, with the exception of the last two rows of seats and the cockpit area. Adjustable seat heights and/or placement of the seats farther forward would provide more headroom. In the horizontal position, the model's seat placement and aisle width allowed a quick and orderly 10-person egress for the no-keel (a structural support running the length on the aisle), 6-in.-high keel, and 12-in.-high keel conditions. Egress times were less than 20 s. For the vertical position, the model's long cylindrical shape with the ladder in the ceiling allowed a quick and orderly egress with average times less than 30 s. Ingress and egress procedures were demonstrated using shuttle partial-pressure suits. The reduced mobility experienced while wearing the suits did increase egress times, although they still remained acceptable. The window arrangement for pilot viewing was found to be reasonably acceptable, although slight modifications, such as an increased downward view, is desirable.

PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL CLAPBOARD SIDING AND HAS A SHEET METAL ROOF. NOTE THE TWO OPENINGS THAT RUN THE LENGTH OF THE BRIDGE; ONE IS AT THE EAVES AND THE OTHER IS ABOUT 4’ ABOVE THE DECK. - Dreibelbis Station Bridge, Spanning Maiden Creek, Balthaser Road (TR 745), Lenhartsville, Berks County, PA

A geostatistical analysis of small-scale spatial variability in bacterial abundance and community structure in salt marsh creek bank sediments

NASA Technical Reports Server (NTRS)

Franklin, Rima B.; Blum, Linda K.; McComb, Alison C.; Mills, Aaron L.

2002-01-01

Small-scale variations in bacterial abundance and community structure were examined in salt marsh sediments from Virginia's eastern shore. Samples were collected at 5 cm intervals (horizontally) along a 50 cm elevation gradient, over a 215 cm horizontal transect. For each sample, bacterial abundance was determined using acridine orange direct counts and community structure was analyzed using randomly amplified polymorphic DNA fingerprinting of whole-community DNA extracts. A geostatistical analysis was used to determine the degree of spatial autocorrelation among the samples, for each variable and each direction (horizontal and vertical). The proportion of variance in bacterial abundance that could be accounted for by the spatial model was quite high (vertical: 60%, horizontal: 73%); significant autocorrelation was found among samples separated by 25 cm in the vertical direction and up to 115 cm horizontally. In contrast, most of the variability in community structure was not accounted for by simply considering the spatial separation of samples (vertical: 11%, horizontal: 22%), and must reflect variability from other parameters (e.g., variation at other spatial scales, experimental error, or environmental heterogeneity). Microbial community patch size based upon overall similarity in community structure varied between 17 cm (vertical) and 35 cm (horizontal). Overall, variability due to horizontal position (distance from the creek bank) was much smaller than that due to vertical position (elevation) for both community properties assayed. This suggests that processes more correlated with elevation (e.g., drainage and redox potential) vary at a smaller scale (therefore producing smaller patch sizes) than processes controlled by distance from the creek bank. c2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

EXAMINATION OF MODEL PREDICTIONS AT DIFFERENT HORIZONTAL GRID RESOLUTIONS

EPA Science Inventory

While fluctuations in meteorological and air quality variables occur on a continuum of spatial scales, the horizontal grid spacing of coupled meteorological and photochemical models sets a lower limit on the spatial scales that they can resolve. However, both computational costs ...

Direct and inverse energy cascades in a forced rotating turbulence experiment

NASA Astrophysics Data System (ADS)

Campagne, Antoine; Gallet, Basile; Moisy, Frédéric; Cortet, Pierre-Philippe

2014-11-01

Turbulence in a rotating frame provides a remarkable system where 2D and 3D properties may coexist, with a possible tuning between direct and inverse cascades. We present here experimental evidence for a double cascade of kinetic energy in a statistically stationary rotating turbulence experiment. Turbulence is generated by a set of vertical flaps which continuously injects velocity fluctuations towards the center of a rotating water tank. The energy transfers are evaluated from two-point third-order three-component velocity structure functions, which we measure using stereoscopic PIV in the rotating frame. Without global rotation, the energy is transferred from large to small scales, as in classical 3D turbulence. For nonzero rotation rates, the horizontal kinetic energy presents a double cascade: a direct cascade at small horizontal scales and an inverse cascade at large horizontal scales. By contrast, the vertical kinetic energy is always transferred from large to small horizontal scales, a behavior reminiscent of the dynamics of a passive scalar in 2D turbulence. At the largest rotation rate, the flow is nearly 2D and a pure inverse energy cascade is found for the horizontal energy.

Effects of varying inter-limb spacing to limb length ratio in metachronal swimming

NASA Astrophysics Data System (ADS)

Lai, Hong Kuan; Merkel, Rachael; Santhanakrishnan, Arvind

2016-11-01

Crustaceans such as shrimp, krill and crayfish swim by rhythmic paddling of four to five pairs of closely spaced limbs. Each pair is phase-shifted in time relative to the neighboring pair, resulting in a metachronal wave that travels in the direction of animal motion. The broad goal of this study is to investigate how the mechanical design of the swimming limbs affect scalability of metachronal swimming in terms of limb-based Reynolds number (Re). A scaled robotic model of metachronal paddling was developed, consisting of four pairs of hinged acrylic plates actuated using stepper motors that were immersed in a rectangular tank containing water-glycerin fluid medium. 2D PIV measurements show that the propulsive jets transition from being primarily horizontal (thrust-producing direction) at Re of order 10 to angled vertically at Re of order 100. The ratio of inter-limb spacing to limb length among metachronal swimming organisms ranges between 0.2 to 0.65. 2D PIV will be used to examine the jets generated between adjacent limbs for varying inter-limb spacing to limb length ratios. The effect of increasing this ratio to beyond the biologically observed range will be discussed.

Physical controls and depth of emplacement of igneous bodies: A review

NASA Astrophysics Data System (ADS)

Menand, Thierry

2011-03-01

The formation and growth of magma bodies are now recognised as involving the amalgamation of successive, discrete pulses such as sills. Sills would thus represent the building blocks of larger plutons ( sensu lato). Mechanical and thermal considerations on the incremental development of these plutons raise the issue of the crustal levels at which magma can stall and accumulate as sills. Reviewing the mechanisms that could a priori explain sill formation, it is shown that principal physical controls include: rigidity contrast, where sills form at the interface between soft strata overlaid by comparatively stiffer strata; rheology anisotropy, where sills form within the weakest ductile zones; and rotation of deviatoric stress, where sills form when the minimum compressive stress becomes vertical. Comparatively, the concept of neutral buoyancy is unlikely to play a leading control in the emplacement of sills, although it could assist their formation. These different controls on sill formation, however, do not necessarily operate on the same length scale. The length scale associated with the presence of interfaces separating upper stiffer layers from lower softer ones determines the depth at which rigidity-controlled sills will form. On another hand, the emplacement depths for rheology-controlled sills are likely to be determined by the distribution of the weakest ductile zones. Whereas the emplacement depth of stress-controlled sills is determined by a balance between the horizontal maximum compressive stress, which favours sill formation, and the buoyancy of their feeder dykes, which drives magma vertically. Ultimately, the depth at which a sill forms depends on whether crustal anisotropy or stress rotation is the dominant control, i.e. which of these processes operates at the smallest length scale. Using dimensional analysis, it is shown that sill formation controlled by remote stress rotation would occur on length scales of hundreds of meters or greater. This therefore suggests that crustal heterogeneities and their associated anisotropy are likely to play a larger role than remote stress rotation in controlling sill emplacement, unless these heterogeneities are several hundred meters or more apart. This also reinforces the role of local stress barriers, owing to interactions between deviatoric stress and crustal heterogeneities, in the formation of sills.

Turbulent premixed combustion in V-shaped flames: Characteristics of flame front

NASA Astrophysics Data System (ADS)

Kheirkhah, S.; Gülder, Ö. L.

2013-05-01

Flame front characteristics of turbulent premixed V-shaped flames were investigated experimentally using the Mie scattering and the particle image velocimetry techniques. The experiments were performed at mean streamwise exit velocities of 4.0, 6.2, and 8.6 m/s, along with fuel-air equivalence ratios of 0.7, 0.8, and 0.9. Effects of vertical distance from the flame-holder, mean streamwise exit velocity, and fuel-air equivalence ratio on statistics of the distance between the flame front and the vertical axis, flame brush thickness, flame front curvature, and angle between tangent to the flame front and the horizontal axis were studied. The results show that increasing the vertical distance from the flame-holder and the fuel-air equivalence ratio increase the mean and root-mean-square (RMS) of the distance between the flame front and the vertical axis; however, increasing the mean streamwise exit velocity decreases these statistics. Spectral analysis of the fluctuations of the flame front position depicts that the normalized and averaged power-spectrum-densities collapse and show a power-law relation with the normalized wave number. The flame brush thickness is linearly correlated with RMS of the distance between the flame front and the vertical axis. Analysis of the curvature of the flame front data shows that the mean curvature is independent of the experimental conditions tested and equals to zero. Values of the inverse of the RMS of flame front curvature are similar to those of the integral length scale, suggesting that the large eddies in the flow make a significant contribution in wrinkling of the flame front. Spectral analyses of the flame front curvature as well as the angle between tangent to the flame front and the horizontal axis show that the power-spectrum-densities feature a peak. Value of the inverse of the wave number pertaining to the peak is larger than that of the integral length scale.

Towards GPS orbit accuracy of tens of centimeters

NASA Technical Reports Server (NTRS)

Lichten, Stephen M.

1990-01-01

In this paper, CASA Uno orbit results are presented utilizing data from four continents. Refinements in orbit modeling, combined with the availability of a worldwide tracking network and the dense distribution of tracking sites in North and South America, have improved orbit determination precision to about 60 cm (per component) for four of the seven GPS satellites tracked in CASA Uno. The orbit results are consistent with California baseline repeatabilities, which are at the few mm level in horizontal and length, and 1-2 cm in the vertical. Baseline comparisons with VLBI provide a measure of orbit accuracy, showing sub-cm agreement in length and 1.5 cm agreement in the horizontal.

Fine-scale multi-species aggregations of oceanic zooplankton

NASA Astrophysics Data System (ADS)

Haury, L. R.; Wiebe, P. H.

1982-07-01

Sixteen Longhurst-Hardy Plankton Recorder tows were taken at different depths in the northwest Atlantic for analysis of fine-scale horizontal patchiness. Abundant species were non-randomly distributed in patches with scales of tens to hundreds of meters. Positive correlations between species abundances dominated, indicating that the patches were multi-species associations. Most horizontal pattern appeared to be of biological origin.

Addressing scale dependence in roughness and morphometric statistics derived from point cloud data.

NASA Astrophysics Data System (ADS)

Buscombe, D.; Wheaton, J. M.; Hensleigh, J.; Grams, P. E.; Welcker, C. W.; Anderson, K.; Kaplinski, M. A.

2015-12-01

The heights of natural surfaces can be measured with such spatial density that almost the entire spectrum of physical roughness scales can be characterized, down to the morphological form and grain scales. With an ability to measure 'microtopography' comes a demand for analytical/computational tools for spatially explicit statistical characterization of surface roughness. Detrended standard deviation of surface heights is a popular means to create continuous maps of roughness from point cloud data, using moving windows and reporting window-centered statistics of variations from a trend surface. If 'roughness' is the statistical variation in the distribution of relief of a surface, then 'texture' is the frequency of change and spatial arrangement of roughness. The variance in surface height as a function of frequency obeys a power law. In consequence, roughness is dependent on the window size through which it is examined, which has a number of potential disadvantages: 1) the choice of window size becomes crucial, and obstructs comparisons between data; 2) if windows are large relative to multiple roughness scales, it is harder to discriminate between those scales; 3) if roughness is not scaled by the texture length scale, information on the spacing and clustering of roughness `elements' can be lost; and 4) such practice is not amenable to models describing the scattering of light and sound from rough natural surfaces. We discuss the relationship between roughness and texture. Some useful parameters which scale vertical roughness to characteristic horizontal length scales are suggested, with examples of bathymetric point clouds obtained using multibeam from two contrasting riverbeds, namely those of the Colorado River in Grand Canyon, and the Snake River in Hells Canyon. Such work, aside from automated texture characterization and texture segmentation, roughness and grain size calculation, might also be useful for feature detection and classification from point clouds.

Highly Unstable Double-Diffusive Finger Convection in a Hele-Shaw Cell: Baseline Experimental Data for Evaluation of Numerical Models

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

PRINGLE,SCOTT E.; COOPER,CLAY A.; GLASS JR.,ROBERT J.

An experimental investigation was conducted to study double-diffusive finger convection in a Hele-Shaw cell by layering a sucrose solution over a more-dense sodium chloride (NaCl) solution. The solutal Rayleigh numbers were on the order of 60,000, based upon the height of the cell (25 cm), and the buoyancy ratio was 1.2. A full-field light transmission technique was used to measure a dye tracer dissolved in the NaCl solution. They analyze the concentration fields to yield the temporal evolution of length scales associated with the vertical and horizontal finger structure as well as the mass flux. These measures show a rapidmore » progression through two early stages to a mature stage and finally a rundown period where mass flux decays rapidly. The data are useful for the development and evaluation of numerical simulators designed to model diffusion and convection of multiple components in porous media. The results are useful for correct formulation at both the process scale (the scale of the experiment) and effective scale (where the lab-scale processes are averaged-up to produce averaged parameters). A fundamental understanding of the fine-scale dynamics of double-diffusive finger convection is necessary in order to successfully parameterize large-scale systems.« less

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

NASA Astrophysics Data System (ADS)

Tian, H.; Potts, H. E.; Marsch, E.; Attie, R.; He, J.-S.

2010-09-01

Aims: We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere. Methods: A highly efficient feature-tracking technique called balltracking has been applied for the first time to the image sequences obtained by TRACE (transition region and coronal explorer) in the passband of white light and the three ultraviolet passbands centered at 1700 Å, 1600 Å, and 1550 Å. The resulting velocity fields have been spatially smoothed and temporally averaged in order to reveal horizontal supergranule-scale motions that may exist at the emission heights of these passbands. Results: We find indeed a high correlation between the horizontal velocities derived in the white-light and ultraviolet passbands. The horizontal velocities derived from the chromospheric and photospheric emission are comparable in magnitude. Conclusions: The horizontal motions derived in the UV passbands might indicate the existence of a supergranule-scale magneto-convection in the chromosphere, which may shed new light on the study of mass and energy supply to the corona and solar wind at the height of the chromosphere. However, it is also possible that the apparent motions reflect the chromospheric brightness evolution as produced by acoustic shocks which might be modulated by the photospheric granular motions in their excitation process, or advected partly by the supergranule-scale flow towards the network while propagating upward from the photosphere. To reach a firm conclusion, it is necessary to investigate the role of granular motions in the excitation of shocks through numerical modeling, and future high-cadence chromospheric magnetograms must be scrutinized.

Estimation of the Latitude, the Gnomon`s Length and Position About Sinbeop-Jipyeong-Ilgu in the Late of Joseon Dynasty

NASA Astrophysics Data System (ADS)

Mihn, Byeong-Hee; Lee, Yong Sam; Kim, Sang Hyuk; Choi, Won-Ho; Ham, Seon Young

2017-06-01

In this study, the characteristics of a horizontal sundial from the Joseon Dynasty were investigated. Korea’s Treasure No. 840 (T840) is a Western-style horizontal sundial where hour-lines and solar-term-lines are engraved. The inscription of this sundial indicates that the latitude (altitude of the north celestial pole) is 37° 39´, but the gnomon is lost. In the present study, the latitude of the sundial and the length of the gnomon were estimated based only on the hour-lines and solar-termlines of the horizontal sundial. When statistically calculated from the convergent point obtained by extending the hourlines, the latitude of this sundial was 37° 15´ ± 26´, which showed a 24´ difference from the record of the inscription. When it was also assumed that a convergent point is changeable, the estimation of the sundial’s latitude was found to be sensitive to the variation of this point. This study found that T840 used a vertical gnomon, that is, perpendicular to the horizontal plane, rather than an inclined triangular gnomon, and a horn-shaped mark like a vertical gnomon is cut on its surface. The length of the gnomon engraved on the artifact was 43.1 mm, and in the present study was statistically calculated as 43.7 ± 0.7 mm. In addition, the position of the gnomon according to the original inscription and our calculation showed an error of 0.3 mm.

Atmospheric flow over two-dimensional bluff surface obstructions

NASA Technical Reports Server (NTRS)

Bitte, J.; Frost, W.

1976-01-01

The phenomenon of atmospheric flow over a two-dimensional surface obstruction, such as a building (modeled as a rectangular block, a fence or a forward-facing step), is analyzed by three methods: (1) an inviscid free streamline approach, (2) a turbulent boundary layer approach using an eddy viscosity turbulence model and a horizontal pressure gradient determined by the inviscid model, and (3) an approach using the full Navier-Stokes equations with three turbulence models; i.e., an eddy viscosity model, a turbulence kinetic-energy model and a two-equation model with an additional transport equation for the turbulence length scale. A comparison of the performance of the different turbulence models is given, indicating that only the two-equation model adequately accounts for the convective character of turbulence. Turbulence flow property predictions obtained from the turbulence kinetic-energy model with prescribed length scale are only insignificantly better than those obtained from the eddy viscosity model. A parametric study includes the effects of the variation of the characteristics parameters of the assumed logarithmic approach velocity profile. For the case of the forward-facing step, it is shown that in the downstream flow region an increase of the surface roughness gives rise to higher turbulence levels in the shear layer originating from the step corner.

Computational Fluid Dynamics Based Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2015-01-01

Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

Engineering survey planning for the alignment of a particle accelerator: part II. Design of a reference network and measurement strategy

NASA Astrophysics Data System (ADS)

Junqueira Leão, Rodrigo; Raffaelo Baldo, Crhistian; Collucci da Costa Reis, Maria Luisa; Alves Trabanco, Jorge Luiz

2018-03-01

The building blocks of particle accelerators are magnets responsible for keeping beams of charged particles at a desired trajectory. Magnets are commonly grouped in support structures named girders, which are mounted on vertical and horizontal stages. The performance of this type of machine is highly dependent on the relative alignment between its main components. The length of particle accelerators ranges from small machines to large-scale national or international facilities, with typical lengths of hundreds of meters to a few kilometers. This relatively large volume together with micrometric positioning tolerances make the alignment activity a classical large-scale dimensional metrology problem. The alignment concept relies on networks of fixed monuments installed on the building structure to which all accelerator components are referred. In this work, the Sirius accelerator is taken as a case study, and an alignment network is optimized via computational methods in terms of geometry, densification, and surveying procedure. Laser trackers are employed to guide the installation and measure the girders’ positions, using the optimized network as a reference and applying the metric developed in part I of this paper. Simulations demonstrate the feasibility of aligning the 220 girders of the Sirius synchrotron to better than 0.080 mm, at a coverage probability of 95%.

Evidences for Skeletal Structures in the Ocean from the Images Analyzed by Multilevel Dynamical Contrasting Method

NASA Astrophysics Data System (ADS)

Rantsev-Kartinov, Valentin A.

2004-11-01

An analysis of databases of photographic images of ocean's surface, taken from various altitudes and for various types of rough ocean surface, revealed the presence of an ocean's skeletal structures (OSS) = http://www.arxiv.org/ftp/physics/papers/0401/0401139.pdf [1] Rantsev-Kartinov V.A., Preprint, which exhibit a tendency toward self-similarity of structuring at various length scales (i.e., within various ``generations''). The topology of the OSS appears to be identical to that of skeletal structures which have been formerly found in a wide range of length scales, media and for various phenomena (Phys. Lett. A, 2002, 306). The typical OSS consists of separate identical blocks which are linked together to form a network. Two types of such blocks are found: (i) a coaxial tubular (CT) structures with internal radial bonds, and (ii) a cartwheel-like structures, located either on an axle or in the edges of the CT blocks. The OSSs differ from the formerly found SSs only by the fact that OSS, in their interior, are filled in with closely packed OSSs of a smaller size. We specially discuss the phenomenon of skeletal blocks in the form of vertically/horizontally oriented floating cylinders. The size of these observed blocks is shown to grow with increasing rough water.

CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2015-01-01

Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

Background Adjusted Alignment-Free Dissimilarity Measures Improve the Detection of Horizontal Gene Transfer.

PubMed

Tang, Kujin; Lu, Yang Young; Sun, Fengzhu

2018-01-01

Horizontal gene transfer (HGT) plays an important role in the evolution of microbial organisms including bacteria. Alignment-free methods based on single genome compositional information have been used to detect HGT. Currently, Manhattan and Euclidean distances based on tetranucleotide frequencies are the most commonly used alignment-free dissimilarity measures to detect HGT. By testing on simulated bacterial sequences and real data sets with known horizontal transferred genomic regions, we found that more advanced alignment-free dissimilarity measures such as CVTree and [Formula: see text] that take into account the background Markov sequences can solve HGT detection problems with significantly improved performance. We also studied the influence of different factors such as evolutionary distance between host and donor sequences, size of sliding window, and host genome composition on the performances of alignment-free methods to detect HGT. Our study showed that alignment-free methods can predict HGT accurately when host and donor genomes are in different order levels. Among all methods, CVTree with word length of 3, [Formula: see text] with word length 3, Markov order 1 and [Formula: see text] with word length 4, Markov order 1 outperform others in terms of their highest F 1 -score and their robustness under the influence of different factors.

Development of Gridded Fields of Urban Canopy Parameters for Advanced Urban Meteorological and Air Quality Models

EPA Science Inventory

Urban dispersion and air quality simulation models applied at various horizontal scales require different levels of fidelity for specifying the characteristics of the underlying surfaces. As the modeling scales approach the neighborhood level (~1 km horizontal grid spacing), the...

Functional analyses of the primate upper cervical vertebral column.

PubMed

Nalley, Thierra K; Grider-Potter, Neysa

2017-06-01

Recent work has highlighted functional correlations between direct measures of head and neck posture and primate cervical bony morphology. Primates with more horizontal necks exhibit middle and lower cervical vertebral features that indicate increased mechanical advantage for deep nuchal musculature and mechanisms for column curvature formation and maintenance. How features of the C1 and C2 reflect quantified measures of posture have yet to be examined. This study incorporates bony morphology from the upper cervical levels from 20 extant primate species in order to investigate further how posture correlates with cervical vertebrae morphology. Results from phylogenetic generalized least-squares analyses indicate that few vertebral features exhibit a significant relationship with posture when accounting for differences in size. When size-adjusted traits were correlated with posture, vertebral variation had a stronger relationship with neck posture than head posture variables. Two C1 traits-relative posterior arch length and superior facet curvature-were correlated with neck posture variables. Relative posterior arch length exhibits a positive relationship with neck posture, while superior articular facet curvature demonstrates a negative relationship, such that as the neck becomes more horizontal, the greater the facet curvature. Four C2 features were also correlated with neck posture: relative pedicle and lamina lengths, relative superior facet orientation, and dens orientation. Relative pedicle and lamina lengths become craniocaudally longer as the neck becomes more horizontal. Relative C2 superior facet orientation and dens orientation exhibit negative correlations with posture, such that as the neck becomes more horizontal, the superior facet becomes more caudally inclined and the dens more dorsally inclined. These results produce a similar functional signal observed in the middle and lower cervical spine. Modeling the cervical vertebrae of more pronograde taxa within a sigmoidal spinal column model is further discussed and may prove useful in refining and testing future hypotheses of primate cervical mechanics. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Comparative Analysis of Selected Mechanical Aspects of the Ice Skating Stride.

ERIC Educational Resources Information Center

Marino, G. Wayne

This study quantitatively analyzes selected aspects of the skating strides of above-average and below-average ability skaters. Subproblems were to determine how stride length and stride rate are affected by changes in skating velocity, to ascertain whether the basic assumption that stride length accurately approximates horizontal movement of the…

NEUTRON-IRRADIATED STRUCTURES

DOEpatents

Ashley, E.L.; Ashley, J.W.; Bowker, H.W.; Hall, R.H.; Kendall, J.W.

1959-02-01

A moderator structure is described for a nuclear reactor of the heterogensous type wherein a large mass of moderator is provided with channels therethrough for the introduction of uranium serving as nuclear fuel and for the passage of a cooling fluid. The structure is comprised of blocks of moderator material in superposed horizontal layers, the blocks of each layer being tied together with spaces between them and oriented to have horizontal Wigner growth. The ties are strips of moderator material, the same as the blocks, with transverse Wigner growth, disposed horizontally along lines crossing at vertical axes of the blocks. The blocks are preferably rectangular with a larger or length dimension transverse to the directions of Wiguer growth and are stood on end to provide for horizontal growth.

Comparison of ophthalmic measurements obtained via high-frequency ultrasound imaging in four species of snakes.

PubMed

Hollingsworth, Steven R; Holmberg, Bradford J; Strunk, Anneliese; Oakley, Alicia D; Sickafoose, Leann M; Kass, Philip H

2007-10-01

To measure the dimensions of the eyes of living snakes by use of high-frequency ultrasound imaging and correlate those measurements with age, length, and weight. Animals-14 clinically normal snakes. Species, age, length, weight, and horizontal spectacle diameter were recorded, and each snake underwent physical and ophthalmic examinations; ultrasonographic examination of both eyes was performed by use of a commercially available ultrasound unit and a 50-MHz transducer. Ultrasonographic measurements included spectacle thickness, subspectacular space depth, corneal thickness, anterior chamber depth, lens thickness, vitreous cavity depth, and globe length. All measurements were made along the visual axis. 2 corn snakes, 5 California king snakes, 1 gopher snake, and 6 ball pythons were examined. There were no significant differences within or between the species with regard to mean spectacle thickness, corneal thickness, or subspectacular space depth. However, mean horizontal spectacle diameter, anterior chamber depth, and axial globe length differed among the 4 species; for each measurement, ball pythons had significantly larger values than California king snakes. Spectacle thickness, subspectacular space depth, and corneal thickness were similar among the species of snake examined and did not vary significantly with age, length, or weight. Measurements of these dimensions can potentially serve as baseline values to evaluate snakes of these species with a retained spectacle, subspectacular abscess, or subspectacular fluid accumulation. Anterior chamber depth and axial length appeared variable among species, but axial length did not vary with age, length, or weight in the species studied.

Environmental drivers of epibenthic megafauna on a deep temperate continental shelf: A multiscale approach

NASA Astrophysics Data System (ADS)

Lacharité, Myriam; Metaxas, Anna

2018-03-01

Evaluating the role of abiotic factors in influencing the distribution of deep-water (>75-100 m depth) epibenthic megafaunal communities at mid-to-high latitudes is needed to estimate effects of environmental change, and support marine spatial planning since these factors can be effectively mapped. Given the disparity in scales at which these factors operate, incorporating multiple spatial and temporal scales is necessary. In this study, we determined the relative importance of 3 groups of environmental drivers at different scales (sediment, geomorphology, and oceanography) on epibenthic megafauna on a deep temperate continental shelf in the eastern Gulf of Maine (northwest Atlantic). Twenty benthic photographic transects (range: 611-1021 m; total length surveyed: 18,902 m; 996 images; average of 50 ± 16 images per transect) were performed in July and August 2009 to assess the abundance, composition and diversity of these communities. Surficial geology was assessed using seafloor imagery processed with a novel approach based on computer vision. A bathymetric terrain model (horizontal resolution: 100 m) was used to derive bathymetric variability in the vicinity of transects (1.5, 5 km). Oceanography at the seafloor (temperature, salinity, current speed, current direction) over 10 years (1999-2008) was determined using empirical (World Ocean Database 2013) and modelled data (Finite-Volume Community Ocean Model; 45 vertical layers; horizontal resolution: 1.7-9.5 km). The relative influence of environmental drivers differed between community traits. Abundance was enhanced primarily by swift current speeds, while higher diversity was observed in coarser and more heterogeneous substrates. In both cases, the role of geomorphological features was secondary to these drivers. Environmental variables were poor predictors of change in community composition at the scale of the eastern Gulf of Maine. This study demonstrated the need for explicitly incorporating scales into habitat modelling studies in these regions, and targeting specific drivers for community traits of interest.

High stability integrated Tri-axial fluxgate sensor with suspended technology

NASA Astrophysics Data System (ADS)

Wang, Chen; Teng, Yuntian; Wang, Xiaomei; Fan, Xiaoyong; Wu, Qiong

2017-04-01

The relative geomagnetic record of China Geomagnetic Network of China(GNC) has been digitized, network, meanwhile achieving second data acquisition and storage during after 9th five-year and 10th five-year plan upgraded. Currently the relative record in geomagnetic observatories are generally two sets of the same type instrument with parallel observation, which could distinguish the differential between observation instrument failures and environmental interference, and ensure the continuity and integrity of the observation data. Fluxgate magnetometer has become mainstream equipment for relative geomagnetic record because of its low noise, high sensitivity, and fast response. There is a problem about data inconsistency by the same type of instrument in the same station though few years observation data analysis. The researchers have done a lot of experiments and found three main error sources:1. The instrument performances, due to the limitation of manufacturing and assembly process level it is difficult to ensure the orthogonality of the instrument; other performances of scale, zero offset and temperature coefficient; 2. horizontal error, which introduced by the initial installation process due to horizontal adjustment and pillar tilling due to long-term observations; 3.The observation environment, the temperature and humidity, power supply system. The new fluxgate magnetometer uses special nonmagnetic gimbaled (made by beryllium / bronze material) construction for suspension, so the fluxgate sensor is fixed at the suspended platform in order to automatically keep the horizontal level. The advantage of this design is to eliminate horizontal error introduced by the initial installation process due to horizontal adjustment and pillar tilling due to long-term observations. The signal processing circuit board is fixed on the top of the suspended platform with certain distance to ensure the static and dynamic magnetic field produced by circuit board no effect to the sensor, so we could get flexible instrument due to signal attenuation resulting signal transmission cable limited length.

Design of a sensor network for structural health monitoring of a full-scale composite horizontal tail

NASA Astrophysics Data System (ADS)

Gao, Dongyue; Wang, Yishou; Wu, Zhanjun; Rahim, Gorgin; Bai, Shengbao

2014-05-01

The detection capability of a given structural health monitoring (SHM) system strongly depends on its sensor network placement. In order to minimize the number of sensors while maximizing the detection capability, optimal design of the PZT sensor network placement is necessary for structural health monitoring (SHM) of a full-scale composite horizontal tail. In this study, the sensor network optimization was simplified as a problem of determining the sensor array placement between stiffeners to achieve the desired the coverage rate. First, an analysis of the structural layout and load distribution of a composite horizontal tail was performed. The constraint conditions of the optimal design were presented. Then, the SHM algorithm of the composite horizontal tail under static load was proposed. Based on the given SHM algorithm, a sensor network was designed for the full-scale composite horizontal tail structure. Effective profiles of cross-stiffener paths (CRPs) and uncross-stiffener paths (URPs) were estimated by a Lamb wave propagation experiment in a multi-stiffener composite specimen. Based on the coverage rate and the redundancy requirements, a seven-sensor array-network was chosen as the optimal sensor network for each airfoil. Finally, a preliminary SHM experiment was performed on a typical composite aircraft structure component. The reliability of the SHM result for a composite horizontal tail structure under static load was validated. In the result, the red zone represented the delamination damage. The detection capability of the optimized sensor network was verified by SHM of a full-scale composite horizontal tail; all the diagnosis results were obtained in two minutes. The result showed that all the damage in the monitoring region was covered by the sensor network.

Numerical Modeling and Experimental Analysis of Scale Horizontal Axis Marine Hydrokinetic (MHK) Turbines

NASA Astrophysics Data System (ADS)

Javaherchi, Teymour; Stelzenmuller, Nick; Seydel, Joseph; Aliseda, Alberto

2013-11-01

We investigate, through a combination of scale model experiments and numerical simulations, the evolution of the flow field around the rotor and in the wake of Marine Hydrokinetic (MHK) turbines. Understanding the dynamics of this flow field is the key to optimizing the energy conversion of single devices and the arrangement of turbines in commercially viable arrays. This work presents a comparison between numerical and experimental results from two different case studies of scaled horizontal axis MHK turbines (45:1 scale). In the first case study, we investigate the effect of Reynolds number (Re = 40,000 to 100,000) and Tip Speed Ratio (TSR = 5 to 12) variation on the performance and wake structure of a single turbine. In the second case, we study the effect of the turbine downstream spacing (5d to 14d) on the performance and wake development in a coaxial configuration of two turbines. These results provide insights into the dynamics of Horizontal Axis Hydrokinetic Turbines, and by extension to Horizontal Axis Wind Turbines in close proximity to each other, and highlight the capabilities and limitations of the numerical models. Once validated at laboratory scale, the numerical model can be used to address other aspects of MHK turbines at full scale. Supported by DOE through the National Northwest Marine Renewable Energy Center.

Hydrodynamic studies on two wiggling hydrofoils in an oblique arrangement

NASA Astrophysics Data System (ADS)

Lin, Xingjian; He, Guoyi; He, Xinyi; Wang, Qi; Chen, Longsheng

2018-06-01

The propulsive performance of an oblique school of fish is numerically studied using an immersed boundary technique. The effect of the spacing and wiggling phase on the hydrodynamics of the system is investigated. The hydrodynamics of the system is deeply affected by the spacing between each fish in the school. When the horizontal separation is smaller than the length of the fish body, the downstream fish exhibits a larger thrust coefficient and greater propulsive efficiency than the isolated fish. However, the corresponding values for the upstream fish are smaller. The opposite behavior occurs when the horizontal separation increases beyond the length of fish body. The propulsive performance of the entire oblique school of fish can be substantially enhanced when the separations are optimized.

Method for culturing mammalian cells in a horizontally rotated bioreactor

NASA Technical Reports Server (NTRS)

Schwarz, Ray P. (Inventor); Wolf, David A. (Inventor); Trinh, Tinh T. (Inventor)

1992-01-01

A bio-reactor system where cell growth microcarrier beads are suspended in a zero head space fluid medium by rotation about a horizontal axis and where the fluid is continuously oxygenated from a tubular membrane which rotates on a shaft together with rotation of the culture vessel. The oxygen is continuously throughput through the membrane and disbursed into the fluid medium along the length of the membrane.

Proof of the Wave Nature of Plants

NASA Astrophysics Data System (ADS)

Wagner, Orvin

2008-03-01

I assume plants operate with a set of frequencies. These frequencies and the means of these frequencies are equal in all directions. We can then write (vh/λ)avh=(vv/λ)avv where the subscripts h and v represent horizontal and vertical respectively and av is average,. or vv/vh=(1/λh)av/(1/λv)av. I use an internodal spacing as λ/2 or the the distance between adjacent branches, leaves, etc. The ratios, vv/vh, are ratios of small integers for sufficient samplings. For example, for Ponderosa pine the ratio is 3/1 or for delicious apple 4/3. Note that these ratios represent the shape of the tree or other plant and their interactions with gravity. These ratios are derivable by other means such as use the ratio of # of horizontal needles per unit length from a horizontal sample to the # of needles per unit length from a vertical sample from p-pine. Or measure the vertical and horizontal velocities. My literature provides many other proofs of the wave nature of plants. I suggest that the waves in and related waves outside of plants (outside 4.9 m/s) are a dark matter related since they travel at such low velocities. See my present web site at home.budget.net/˜oedphd.

Electromagnetically levitated vibration isolation system for the manufacturing process of silicon monocrystals

NASA Technical Reports Server (NTRS)

Kanemitsu, Yoichi; Watanabe, Katsuhide; Yano, Kenichi; Mizuno, Takayuki

1994-01-01

This paper introduces a study on an Electromagnetically Levitated Vibration Isolation System (ELVIS) for isolation control of large-scale vibration. This system features no mechanical contact between the isolation table and the installation floor, using a total of four electromagnetic actuators which generate magnetic levitation force in the vertical and horizontal directions. The configuration of the magnet for the vertical direction is designed to prevent any generation of restoring vibratory force in the horizontal direction. The isolation system is set so that vibration control effects due to small earthquakes can be regulated to below 5(gal) versus horizontal vibration levels of the installation floor of up t 25(gal), and those in the horizontal relative displacement of up to 30 (mm) between the floor and levitated isolation table. In particular, studies on the relative displacement between the installation floor and the levitated isolation table have been made for vibration control in the horizontal direction. In case of small-scale earthquakes (Taft wave scaled: max. 25 gal), the present system has been confirmed to achieve a vibration isolation to a level below 5 gal. The vibration transmission ratio of below 1/10 has been achieved versus continuous micro-vibration (approx. one gal) in the horizontal direction on the installation floor.

On the coupled unsaturated-saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

NASA Astrophysics Data System (ADS)

Liang, Xiuyu; Zhan, Hongbin; Zhang, You-Kuan; Liu, Jin

2017-03-01

Conventional models of pumping tests in unconfined aquifers often neglect the unsaturated flow process. This study concerns the coupled unsaturated-saturated flow process induced by vertical, horizontal, and slant wells positioned in an unconfined aquifer. A mathematical model is established with special consideration of the coupled unsaturated-saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace-finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W) during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant) in unconfined aquifers affected from above by the unsaturated flow process.

Collection Efficiency and Ice Accretion Characteristics of Two Full Scale and One 1/4 Scale Business Jet Horizontal Tails

NASA Technical Reports Server (NTRS)

Bidwell, Colin S.; Papadakis, Michael

2005-01-01

Collection efficiency and ice accretion calculations have been made for a series of business jet horizontal tail configurations using a three-dimensional panel code, an adaptive grid code, and the NASA Glenn LEWICE3D grid based ice accretion code. The horizontal tail models included two full scale wing tips and a 25 percent scale model. Flow solutions for the horizontal tails were generated using the PMARC panel code. Grids used in the ice accretion calculations were generated using the adaptive grid code ICEGRID. The LEWICE3D grid based ice accretion program was used to calculate impingement efficiency and ice shapes. Ice shapes typifying rime and mixed icing conditions were generated for a 30 minute hold condition. All calculations were performed on an SGI Octane computer. The results have been compared to experimental flow and impingement data. In general, the calculated flow and collection efficiencies compared well with experiment, and the ice shapes appeared representative of the rime and mixed icing conditions for which they were calculated.

A mechanical model for complex fault patterns induced by fluid overpressures due to dehydration reaction within evaporitic rocks

NASA Astrophysics Data System (ADS)

de Paola, N.; Collettini, C.; Trippetta, F.; Barchi, M. R.; Minelli, G.

2006-12-01

Complex fault patterns, i.e. faults which exhibit a diverse range of strikes, may develop under a weak/absent regional tectonic field (e.g. polygonal faults). We studied a complex synsedimentary fault pattern, geometrically similar to polygonal fault systems, developed during an early Jurassic faulting episode and exposed in the Umbria-Marche Apennines (Italy). Along the passive margin of the African plate, these faults disrupt the Early Jurassic platform overlying the Triassic Evaporites, and bound the subsiding basins where a pelagic succession was successively deposited. We digitised the fault pattern at the regional scale on the grounds of the available geological maps, characterising each fault in terms of attitude, length and throw (i.e. vertical displacement). Fault statistical analysis shows a largely scattered orientation, a high grade of fragmentation, an average length of about 10 km and a constant length/displacement ratio. The measured stratigraphic throw ranges from 300 m to 700 m leading to very low long-term fault slip rates (less than 0.1 mm/yr). We propose a mechanical model where Jurassic faulting has been strongly influenced by the onset of dehydration of the Triassic Evaporites, made of interbedded gypsum layers and dolostones. Dehydration, i.e. anhydritization of the gypsum rich layers, initiated during burial at 1000 m of depth. During initial phases of dehydration increasing fluid pressures trapped at the gypsum-dolostones interface, promote hydrofracturing and faulting within the dolostone layers and subsequent fluid release. Fluid expulsion produces volume contraction of the dehydrating rocks causing vertical thinning and horizontal isotropic extension. This state of non-plane strain is accommodated within the composite gypsum-dolostones sequence by a mix of ductile (flowage and boudinage) and brittle (hydrofracturing and faulting) deformation processes. The stress field caused by the former processes, consistent with an almost isotropic stress distribution within the horizontal plane, explains well the studied complex fault pattern and seems to be dominant over the far-field regional extensional tectonics.

Stratospheric Horizontal Wavenumber Spectra of Winds, Potential Temperature, and Atmospheric Tracers Observed by High-Altitude Aircraft

NASA Technical Reports Server (NTRS)

Bacmeister, Julio T.; Eckermann, Stephen D.; Newman, Paul A.; Lait, Leslie; Chan, K. R.; Loewenstein, Max; Proffitt, Michael H.; Gary, Bruce L.

1996-01-01

Horizontal wavenumber power spectra of vertical and horizontal wind velocities, potential temperatures, and ozone and N(2)O mixing ratios, as measured in the mid-stratosphere during 73 ER-2 flights (altitude approx. 20km) are presented. The velocity and potential temperature spectra in the 100 to 1-km wavelength range deviate significantly from the uniform -5/3 power law expected for the inverse energy-cascade regime of two-dimensional turbulence and also for inertial-range, three-dimensional turbulence. Instead, steeper spectra approximately consistent with a -3 power law are observed at horizontal scales smaller than 3 km for all velocity components as well as potential temperature. Shallower spectra are observed at scales longer than 6 km. For horizontal velocity and potential temperature the spectral indices at longer scales are between -1.5 and -2.0. For vertical velocity the spectrum at longer scales become flat. It is argued that the observed velocity and potential temperature spectra are consistent with gravity waves. At smaller scales, the shapes are also superficially consistent with a Lumley-Shur-Weinstock buoyant subrange of turbulence and/or nonlinear gravity waves. Contemporaneous spectra of ozone and N(sub 2)O mixing ratio in the 100 to 1-km wavelength range do conform to an approximately uniform -5/3 power law. It is argued that this may reflect interactions between gravity wave air-parcel displacements and laminar or filamentary structures in the trace gas mixing ratio field produced by enstropy-cascading two-dimensional turbulence.

The three-zone composite productivity model for a multi-fractured horizontal shale gas well

NASA Astrophysics Data System (ADS)

Qi, Qian; Zhu, Weiyao

2018-02-01

Due to the nano-micro pore structures and the massive multi-stage multi-cluster hydraulic fracturing in shale gas reservoirs, the multi-scale seepage flows are much more complicated than in most other conventional reservoirs, and are crucial for the economic development of shale gas. In this study, a new multi-scale non-linear flow model was established and simplified, based on different diffusion and slip correction coefficients. Due to the fact that different flow laws existed between the fracture network and matrix zone, a three-zone composite model was proposed. Then, according to the conformal transformation combined with the law of equivalent percolation resistance, the productivity equation of a horizontal fractured well, with consideration given to diffusion, slip, desorption, and absorption, was built. Also, an analytic solution was derived, and the interference of the multi-cluster fractures was analyzed. The results indicated that the diffusion of the shale gas was mainly in the transition and Fick diffusion regions. The matrix permeability was found to be influenced by slippage and diffusion, which was determined by the pore pressure and diameter according to the Knudsen number. It was determined that, with the increased half-lengths of the fracture clusters, flow conductivity of the fractures, and permeability of the fracture network, the productivity of the fractured well also increased. Meanwhile, with the increased number of fractures, the distance between the fractures decreased, and the productivity slowly increased due to the mutual interfere of the fractures.

No evidence of inhibition of horizontal gene transfer by CRISPR-Cas on evolutionary timescales.

PubMed

Gophna, Uri; Kristensen, David M; Wolf, Yuri I; Popa, Ovidiu; Drevet, Christine; Koonin, Eugene V

2015-09-01

The CRISPR (clustered, regularly, interspaced, short, palindromic repeats)-Cas (CRISPR-associated genes) systems of archaea and bacteria provide adaptive immunity against viruses and other selfish elements and are believed to curtail horizontal gene transfer (HGT). Limiting acquisition of new genetic material could be one of the sources of the fitness cost of CRISPR-Cas maintenance and one of the causes of the patchy distribution of CRISPR-Cas among bacteria, and across environments. We sought to test the hypothesis that the activity of CRISPR-Cas in microbes is negatively correlated with the extent of recent HGT. Using three independent measures of HGT, we found no significant dependence between the length of CRISPR arrays, which reflects the activity of the immune system, and the estimated number of recent HGT events. In contrast, we observed a significant negative dependence between the estimated extent of HGT and growth temperature of microbes, which could be explained by the lower genetic diversity in hotter environments. We hypothesize that the relevant events in the evolution of resistance to mobile elements and proclivity for HGT, to which CRISPR-Cas systems seem to substantially contribute, occur on the population scale rather than on the timescale of species evolution.

FANNING OUT OF THE SOLAR f-MODE IN THE PRESENCE OF NON-UNIFORM MAGNETIC FIELDS?

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

Singh, Nishant K.; Brandenburg, Axel; Rheinhardt, Matthias, E-mail: nishant@nordita.org

2014-11-01

We show that in the presence of a magnetic field that is varying harmonically in space, the fundamental mode, or f-mode, in a stratified layer is altered in such a way that it fans out in the diagnostic kω diagram, with mode power also within the fan. In our simulations, the surface is defined by a temperature and density jump in a piecewise isothermal layer. Unlike our previous work (Singh et al. 2014), where a uniform magnetic field was considered, here we employ a non-uniform magnetic field together with hydromagnetic turbulence at length scales much smaller than those of themore » magnetic field. The expansion of the f-mode is stronger for fields confined to the layer below the surface. In some of those cases, the kω diagram also reveals a new class of low-frequency vertical stripes at multiples of twice the horizontal wavenumber of the background magnetic field. We argue that the study of the f-mode expansion might be a new and sensitive tool to determine subsurface magnetic fields with azimuthal or other horizontal periodicity.« less

Anisotropic perception of visual angle: implications for the horizontal-vertical illusion, overconstancy of size, and the moon illusion.

PubMed

Higashiyama, A

1992-03-01

Three experiments investigated anisotropic perception of visual angle outdoors. In Experiment 1, scales for vertical and horizontal visual angles ranging from 20 degrees to 80 degrees were constructed with the method of angle production (in which the subject reproduced a visual angle with a protractor) and the method of distance production (in which the subject produced a visual angle by adjusting viewing distance). In Experiment 2, scales for vertical and horizontal visual angles of 5 degrees-30 degrees were constructed with the method of angle production and were compared with scales for orientation in the frontal plane. In Experiment 3, vertical and horizontal visual angles of 3 degrees-80 degrees were judged with the method of verbal estimation. The main results of the experiments were as follows: (1) The obtained angles for visual angle are described by a quadratic equation, theta' = a + b theta + c theta 2 (where theta is the visual angle; theta', the obtained angle; a, b, and c, constants). (2) The linear coefficient b is larger than unity and is steeper for vertical direction than for horizontal direction. (3) The quadratic coefficient c is generally smaller than zero and is negatively larger for vertical direction than for horizontal direction. And (4) the obtained angle for visual angle is larger than that for orientation. From these results, it was possible to predict the horizontal-vertical illusion, over-constancy of size, and the moon illusion.

Application of Statistical Learning Theory to Plankton Image Analysis

DTIC Science & Technology

2006-06-01

linear distance interval from 1 to 40 pixels and two directions formula (horizontal & vertical, and diagonals), EF2 is EF with 7 ex- ponential distance...and four directions formula (horizontal, vertical and two diagonals). It is clear that exponential distance inter- val works better than the linear ...PSI - PS by Vincent, linear and pseudo opening and closing spectra, each has 40 elements, total feature length of 160. PS2 - PS modified from Mei- jster

Saturation of the anisoplanatic error in horizontal imaging scenarios

NASA Astrophysics Data System (ADS)

Beck, Jeffrey; Bos, Jeremy P.

2017-09-01

We evaluate the piston-removed anisoplanatic error for smaller apertures imaging over long horizontal paths. Previous works have shown that the piston and tilt compensated anisoplanatic error saturates to values less than one squared radian. Under these conditions the definition of the isoplanatic angle is unclear. These works focused on nadir pointing telescope systems with aperture sizes between five meters and one half meter. We directly extend this work to horizontal imaging scenarios with aperture sizes smaller than one half meter. We assume turbulence is constant along the imaging path and that the ratio of the aperture size to the atmospheric coherence length is on the order of unity.

A new front-face optical cell for measuring weak fluorescent emissions with time resolution in the picosecond time scale.

PubMed

Gryczynski, Z; Bucci, E

1993-11-01

Recent developments of ultrafast fluorimeters allow measuring time-resolved fluorescence on the picosecond time scale. This implies one is able to monitor lifetimes and anisotropy decays of highly quenched systems and of systems that contain fluorophores having lifetimes in the subnanosecond range; both systems that emit weak signals. The combination of weak signals and very short lifetimes makes the measurements prone to distortions which are negligible in standard fluorescence experiments. To cope with these difficulties, we have designed a new optical cell for front-face optics which offers to the excitation beam a horizontal free liquid surface in the absence of interactions with optical windows. The new cell has been tested with probes of known lifetimes and anisotropies. It proved very useful in detecting tryptophan fluorescence in hemoglobin. If only diluted samples are available, which cannot be used in front-face optics, regular square geometry can still be utilized by inserting light absorbers into a cuvette of 1 cm path length.

Application of aerial photography to the study of small scale upper ocean phenomena

NASA Technical Reports Server (NTRS)

Ichiye, T.; Carnes, M.

1981-01-01

The industrial waste dumped 180 n. miles south of Galveston was monitored in July 1977 by water sampling, hydrographic measurements, acoustic tracking on board two vessels, and by aerial photography. The plume of the waste diffused vertically and horizontally. Photodensitometry of aerial photos of the plume showed lateral dispersion of the plume in agreement with two other methods: acoustic tracking of the waste suspensoid and transmissometer sampling. In addition, the method showed small scale features like the lateral and longitudinal variations in the photodensity, indicating the waste concentration. This waste concentration showed periodic changes in its axial distance, with the spectral peak at about 160 m wave length. It shows a sharp increase at the windward edge of the plume as do the acoustic records. This phenomenon is explained in terms of the shearing current near the surface together with vertical diffusion. The periodic change along the axis is explained in terms of the Langmuir circulation and in terms of internal ship waves.

A Unified Theory for Plants and Plant Structure

NASA Astrophysics Data System (ADS)

Wagner, Orvin E.

1998-04-01

The wave theory provides for quantization of plant structure. If one measures many spacings between plant structures it becomes apparent that certain spacings repeat from plant to plant. These spacings are associated with certain discrete frequencies associated with plant operation. When a branch grows it extend by one or more of discrete half wavelengths associated with permitted frequencies. If conditions are optimum it grows by the larger permitted half wavelengths. The angle that the branch makes with the vertical also determines the length because vertical wave velocities are in general larger than horizontal wave velocities as mentioned in the previous abstract. It also appears that cell dimensions are determined by permitted wavelengths. In conifer fiber cells it appears that there is an exact ratio between the average reciprocals of vertical lengths and horizontal reciprocal averages with a value of 1.50 in the data taken so far. Similar ratios for external structure spacings include 1.50, 1.25, 1.33, 1.66, 3.0, These ratios appear to represent ratios of vertical to horizontal velocities (Wagner 1996). See the Wagner web page.

Mesoscale model response to random, surface-based perturbations — A sea-breeze experiment

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Pielke, R. A.; Miller, W. F.; Lee, T. J.

1990-09-01

The introduction into a mesoscale model of random (in space) variations in roughness length, or random (in space and time) surface perturbations of temperature and friction velocity, produces a measurable, but barely significant, response in the simulated flow dynamics of the lower atmosphere. The perturbations are an attempt to include the effects of sub-grid variability into the ensemble-mean parameterization schemes used in many numerical models. Their magnitude is set in our experiments by appeal to real-world observations of the spatial variations in roughness length and daytime surface temperature over the land on horizontal scales of one to several tens of kilometers. With sea-breeze simulations, comparisons of a number of realizations forced by roughness-length and surface-temperature perturbations with the standard simulation reveal no significant change in ensemble mean statistics, and only small changes in the sea-breeze vertical velocity. Changes in the updraft velocity for individual runs, of up to several cms-1 (compared to a mean of 14 cms-1), are directly the result of prefrontal temperature changes of 0.1 to 0.2K, produced by the random surface forcing. The correlation and magnitude of the changes are entirely consistent with a gravity-current interpretation of the sea breeze.

Physical Properties of Umbral Dots Observed in Sunspots: A Hinode Observation

NASA Astrophysics Data System (ADS)

Yadav, Rahul; Mathew, Shibu K.

2018-04-01

Umbral dots (UDs) are small-scale bright features observed in the umbral part of sunspots and pores. It is well established that they are manifestations of magnetoconvection phenomena inside umbrae. We study the physical properties of UDs in different sunspots and their dependence on decay rate and filling factor. We have selected high-resolution, G-band continuum filtergrams of seven sunspots from Hinode to study their physical properties. We have also used Michelson Doppler Imager (MDI) continuum images to estimate the decay rate of selected sunspots. An identification and tracking algorithm was developed to identify the UDs in time sequences. The statistical analysis of UDs exhibits an averaged maximum intensity and effective diameter of 0.26 I_{QS} and 270 km. Furthermore, the lifetime, horizontal speed, trajectory length, and displacement length (birth-death distance) of UDs are 8.19 minutes, 0.5 km s-1, 284 km, and 155 km, respectively. We also find a positive correlation between intensity-diameter, intensity-lifetime, and diameter-lifetime of UDs. However, UD properties do not show any significant relation with the decay rate or filling factor.

Anomalous behaviors during infiltration into heterogeneous porous media

NASA Astrophysics Data System (ADS)

Aarão Reis, F. D. A.; Bolster, D.; Voller, V. R.

2018-03-01

Flow and transport in heterogeneous porous media often exhibit anomalous behavior. A physical analog example is the uni-directional infiltration of a viscous liquid into a horizontal oriented Hele-Shaw cell containing through thickness flow obstacles; a system designed to mimic a gravel/sand medium with impervious inclusions. When there are no obstacles present or the obstacles form a multi-repeating pattern, the change of the length of infiltration F with time t tends to follow a Fickian like scaling, F ∼t1/2 . In the presence of obstacle fields laid out as Sierpinski carpet fractals, infiltration is anomalous, i.e., F ∼ tn, n ≠ 1/2. Here, we study infiltration into such Hele-Shaw cells. First we investigate infiltration into a square cell containing one fractal carpet and make the observation that it is possible to generate both sub (n < 1/2) and super (n > 1/2) diffusive behaviors within identical heterogeneity configurations. We show that this can be explained in terms of a scaling analysis developed from results of random-walk simulations in fractal obstacles; a result indicating that the nature of the domain boundary controls the exponent n of the resulting anomalous transport. Further, we investigate infiltration into a rectangular cell containing several repeats of a given Sierpinski carpet. At very early times, before the liquid encounters any obstacles, the infiltration is Fickian. When the liquid encounters the first (smallest scale) obstacle the infiltration sharply transitions to sub-diffusive. Subsequently, around the time where the liquid has sampled all of the heterogeneity length scales in the system, there is a rapid transition back to Fickian behavior. An explanation for this second transition is obtained by developing a simplified infiltration model based on the definition of a representative averaged hydraulic conductivity.

Nonequilibrium relaxations within the ground-state manifold in the antiferromagnetic Ising model on a triangular lattice.

PubMed

Kim, Eunhye; Lee, Sung Jong; Kim, Bongsoo

2007-02-01

We present an extensive Monte Carlo simulation study on the nonequilibrium kinetics of triangular antiferromagnetic Ising model within the ground state ensemble which consists of sectors, each of which is characterized by a unique value of the string density p through a dimer covering method. Building upon our recent work [Phys. Rev. E 68, 066127 (2003)] where we considered the nonequilibrium relaxation observed within the dominant sector with p=2/3, we here focus on the nonequilibrium kinetics within the minor sectors with p<2/3. The initial configurations are chosen as those in which the strings are straight and evenly distributed. In the minor sectors, we observe a characteristic spatial anisotropy in both equilibrium and nonequilibrium spatial correlations. We observe emergence of a critical relaxation region (in the spatial and temporal domain) which grows as p deviates from p=2/3. Spatial anisotropy appears in the equilibrium spatial correlation with the characteristic length scale xi(e,V)(p) diverging with vanishing string density as xi(e,V)(p) approximately p(-2) along the vertical direction, while along the horizontal direction the spatial length scale diverges as xi(e,H) approximately p(-1). Analytic forms for the anisotropic equilibrium correlation functions are given. We also find that the spin autocorrelation function A(t) shows a simple scaling behavior A(t)=A(t/tau(A)(p)), where the time scale tau(A)(p) shows a power-law divergence with vanishing p as tau(A)(p) approximately p(-phi) with phi approximately or equal to 4. These features can be understood in terms of random walk nature of the fluctuations of the strings within the typical separation between neighboring strings.

Dayton Aircraft Cabin Fire Model, Version 3, Volume I. Physical Description.

DTIC Science & Technology

1982-06-01

contact to any surface directly above a burning element, provided that the current flame length makes contact possible. For fires originating on the...no extension of the flames horizontally beneath the surface is considered. The equation for computing the flame length is presented in Section 5. For...high as 0.3. The values chosen for DACFIR3 are 0.15 for Ec and 0.10 for E P. The Steward model is also used to compute flame length , hf, for the fire

Knotting probability of a shaken ball-chain.

PubMed

Hickford, J; Jones, R; du Pont, S Courrech; Eggers, J

2006-11-01

We study the formation of knots on a macroscopic ball chain, which is shaken on a horizontal plate at 12 times the acceleration of gravity. We find that above a certain critical length, the knotting probability is independent of chain length, while the time to shake out a knot increases rapidly with chain length. The probability of finding a knot after a certain time is the result of the balance of these two processes. In particular, the knotting probability tends to a constant for long chains.

Effects of vertical shear in modelling horizontal oceanic dispersion

NASA Astrophysics Data System (ADS)

Lanotte, A. S.; Corrado, R.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

2016-02-01

The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ˜ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

Validation of buoyancy driven spectral tensor model using HATS data

NASA Astrophysics Data System (ADS)

Chougule, A.; Mann, J.; Kelly, M.; Larsen, G. C.

2016-09-01

We present a homogeneous spectral tensor model for wind velocity and temperature fluctuations, driven by mean vertical shear and mean temperature gradient. Results from the model, including one-dimensional velocity and temperature spectra and the associated co-spectra, are shown in this paper. The model also reproduces two-point statistics, such as coherence and phases, via cross-spectra between two points separated in space. Model results are compared with observations from the Horizontal Array Turbulence Study (HATS) field program (Horst et al. 2004). The spectral velocity tensor in the model is described via five parameters: the dissipation rate (ɛ), length scale of energy-containing eddies (L), a turbulence anisotropy parameter (Γ), gradient Richardson number (Ri) representing the atmospheric stability and the rate of destruction of temperature variance (ηθ).

Insights Into Layering in the Cratonic Lithosphere Beneath Western Australia

NASA Astrophysics Data System (ADS)

Sun, Weijia; Fu, Li-Yun; Saygin, Erdinc; Zhao, Liang

2018-02-01

The characteristics of internal lithospheric discontinuities carry crucial information regarding the origin and evolution of the lithosphere. However, the formation and mechanisms of the midlithosphere discontinuity (MLD) are still enigmatic and controversial. We investigate the midlithospheric discontinuities beneath the Archean Western Australian Craton, which represents one of the oldest continents on the globe, using a novel receiver-based reflectivity approach combined with other geophysical information comprising tomographic P and S wave velocity, radial anisotropy, electrical resistivity, and heat flow data. The MLD is rather shallow with a depth of 68-82 km. Multiple prominent discontinuities are observed in the lithospheric mantle using constructed high-frequency (0.5-4 Hz) P wave reflectivities. These multiple discontinuities coincide well with the broad-scale reduction of relative P and SV wave velocities at the top of the graded transition zone from the lithosphere to the asthenosphere. Strong radial anisotropy in the upper lithosphere mantle tends to be weak across the MLD, which might reflect quasi-laminar lithospheric heterogeneity behavior with a horizontal correlation length that is greater than its vertical correlation length. Broad-scale electrical resistivity variations show little coherence with the MLD. Given these various geophysical observations, the upper lithosphere exhibits rigid and elastic properties above the MLD, while the lower lithosphere tends to be ductile and rheological or viscous. A model comprising quasi-laminar lithospheric heterogeneity could effectively represent the MLD characteristics beneath the Archean continent.

Integrated Approach to Drilling Project in Unconventional Reservoir Using Reservoir Simulation

NASA Astrophysics Data System (ADS)

Stopa, Jerzy; Wiśniowski, Rafał; Wojnarowski, Paweł; Janiga, Damian; Skrzypaszek, Krzysztof

2018-03-01

Accumulation and flow mechanisms in unconventional reservoir are different compared to conventional. This requires a special approach of field management with drilling and stimulation treatments as major factor for further production. Integrated approach of unconventional reservoir production optimization assumes coupling drilling project with full scale reservoir simulation for determine best well placement, well length, fracturing treatment design and mid-length distance between wells. Full scale reservoir simulation model emulate a part of polish shale - gas field. The aim of this paper is to establish influence of technical factor for gas production from shale gas field. Due to low reservoir permeability, stimulation treatment should be direct towards maximizing the hydraulic contact. On the basis of production scenarios, 15 stages hydraulic fracturing allows boost gas production over 1.5 times compared to 8 stages. Due to the possible interference of the wells, it is necessary to determine the distance between the horizontal parts of the wells trajectories. In order to determine the distance between the wells allowing to maximize recovery factor of resources in the stimulated zone, a numerical algorithm based on a dynamic model was developed and implemented. Numerical testing and comparative study show that the most favourable arrangement assumes a minimum allowable distance between the wells. This is related to the volume ratio of the drainage zone to the total volume of the stimulated zone.

Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability

NASA Astrophysics Data System (ADS)

Chougule, Abhijit; Mann, Jakob; Kelly, Mark; Larsen, Gunner C.

2018-06-01

A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate ɛ , the length scale of energy-containing eddies L, a turbulence anisotropy parameter Γ, the Richardson number Ri, and the normalized rate of destruction of temperature variance η _θ ≡ ɛ _θ /ɛ . Here, the latter two parameters are collapsed into a single atmospheric stability parameter z / L using Monin-Obukhov similarity theory, where z is the height above the Earth's surface, and L is the Obukhov length corresponding to Ri,η _θ. Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale ˜ 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.

Increase in the Accuracy of Calculating Length of Horizontal Cable SCS in Civil Engineering

NASA Astrophysics Data System (ADS)

Semenov, A.

2017-11-01

A modification of the method for calculating the horizontal cable consumption of SCS established at civil engineering facilities is proposed. The proposed procedure preserves the prototype simplicity and provides a 5 percent accuracy increase. The values of the achieved accuracy are justified, their compliance with the practice of real projects is proved. The method is brought to the level of the engineering algorithm and formalized in the form of 12/70 rule.

International transferability of accident modification functions for horizontal curves.

PubMed

Elvik, Rune

2013-10-01

Studies of the relationship between characteristics of horizontal curves and accident rate have been reported in several countries. The characteristic most often studied is the radius of a horizontal curve. Functions describing the relationship between the radius of horizontal curves and accident rate have been developed in Australia, Canada, Denmark, Germany, Great Britain, New Zealand, Norway, Portugal, Sweden, and the United States. Other characteristics of horizontal curves that have been studied include deflection angle, curve length, the presence of transition curves, super-elevation in curves and distance to adjacent curves. This paper assesses the international transferability of mathematical functions (accident modification functions) that have been developed to relate the radius of horizontal curves to their accident rate. The main research problem is whether these functions are similar, which enhances international transferability, or dissimilar, which reduces international transferability. Accident modification functions for horizontal curve radius developed in the countries listed above are synthesised. The sensitivity of the functions to other characteristics of curves than radius is examined. Accident modification functions developed in different countries have important similarities. The functions diverge with respect to accident rate in the sharpest curves. Copyright © 2013 Elsevier Ltd. All rights reserved.

The nonlinear oil-water two-phase flow behavior for a horizontal well in triple media carbonate reservoir

NASA Astrophysics Data System (ADS)

Wang, Yong; Tao, Zhengwu; Chen, Liang; Ma, Xin

2017-10-01

Carbonate reservoir is one of the important reservoirs in the world. Because of the characteristics of carbonate reservoir, horizontal well has become a key technology for efficiently developing carbonate reservoir. Establishing corresponding mathematical models and analyzing transient pressure behaviors of this type of well-reservoir configuration can provide a better understanding of fluid flow patterns in formation as well as estimations of important parameters. A mathematical model for a oil-water two-phase flow horizontal well in triple media carbonate reservoir by conceptualizing vugs as spherical shapes are presented in this article. A semi-analytical solution is obtained in the Laplace domain using source function theory, Laplace transformation, and superposition principle. Analysis of transient pressure responses indicates that seven characteristic flow periods of horizontal well in triple media carbonate reservoir can be identified. Parametric analysis shows that water saturation of matrix, vug and fracture system, horizontal section length, and horizontal well position can significantly influence the transient pressure responses of horizontal well in triple media carbonate reservoir. The model presented in this article can be applied to obtain important parameters pertinent to reservoir by type curve matching.

The vertical dependence in the horizontal variability of salinity and temperature at the ocean surface

NASA Astrophysics Data System (ADS)

Asher, W.; Drushka, K.; Jessup, A. T.; Clark, D.

2016-02-01

Satellite-mounted microwave radiometers measure sea surface salinity (SSS) as an area-averaged quantity in the top centimeter of the ocean over the footprint of the instrument. If the horizontal variability in SSS is large inside this footprint, sub-grid-scale variability in SSS can affect comparison of the satellite-retrieved SSS with in situ measurements. Understanding the magnitude of horizontal variability in SSS over spatial scales that are relevant to the satellite measurements is therefore important. Horizontal variability of SSS at the ocean surface can be studied in situ using data recorded by thermosalinographs (TSGs) that sample water from a depth of a few meters. However, it is possible measurements made at this depth might underestimate the horizontal variability at the surface because salinity and temperature can become vertically stratified in a very near surface layer due to the effects of rain, solar heating, and evaporation. This vertical stratification could prevent horizontal gradients from propagating to the sampling depths of ship-mounted TSGs. This presentation will discuss measurements made using an underway salinity profiling system installed on the R/V Thomas Thompson that made continuous measurements of SSS and SST in the Pacific Ocean. The system samples at nominal depths of 2-m, 3-m, and 5-m, allowing the depth dependence of the horizontal variability in SSS and SST to be measured. Horizontal variability in SST is largest at low wind speeds during daytime, when a diurnal warm layer forms. In contrast, the diurnal signal in the variability of SSS was smaller with variability being slightly larger at night. When studied as a function of depth, the results show that over 100-km scales, the horizontal variability in both SSS and SST at a depth of 2 m is approximately a factor of 4 higher than the variability at 5 m.

Natural convection and radiation heat transfer from an array of inclined pin fins

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

Alessio, M.E.; Kaminski, D.A.

1989-02-01

Natural convection and radiation from an air-cooled, highly populated pin-fin array were studied experimentally. the effects of pin density, pin length, and the angle of the pin to the horizontal were measured. Previous work by Sparrow and Vemuri treated the case of a vertical base plate with horizontal fins. recently, Sparrow and Vemuri (1986) extended their study to include results for vertical fins with a horizontal down-facing base plate, as well as vertical fins with a horizontal up-facing base plate. In this study, the base plate is maintained in a vertical position and the angle of the pins is variedmore » from the horizontal. The main intent of this study was to compare the performance of inclined pin fins with straight pin fins. In all cases studied, the straight, horizontal fins were superior to the inclined fins. It was possible to obtain a single general correlation of the test data. While this correlation is recommended within the range of parameters that were tested here, one significant parameter, the size of the base plate, was not varied.« less

The relation between knee flexion angle and anterior cruciate ligament femoral tunnel characteristics: a cadaveric study comparing a standard and a far anteromedial portal.

PubMed

Alavekios, Damon; Peterson, Alexander; Patton, John; McGarry, Michelle H; Lee, Thay Q

2014-11-01

The purpose of this study was to compare the anterior cruciate ligament (ACL) femoral tunnel characteristics between 2 common arthroscopic portals used for ACL reconstruction, a standard anteromedial portal and a far anteromedial portal. Seven cadaveric knees were used. A 1.25-mm Kirschner wire was drilled through the center of the ACL femoral footprint and through the distal femur from the standard anteromedial and far anteromedial portals at knee flexion angles of 100°, 120°, and 140°. No formal tunnels were drilled. Each tunnel exit point was marked with a colored pin. After all tunnels were created, the specimens were digitized with a MicroScribe device (Revware, Raleigh, NC) to measure the tunnel length; distance to the posterior femoral cortical wall (posterior cortical margin); and tunnel orientation in the sagittal, coronal, and axial planes. The standard anteromedial portal resulted in a longer tunnel length, a less horizontal tunnel in the coronal plane, and a greater posterior cortical margin compared with the far anteromedial portal at all knee flexion angles. For both portal locations, the tunnel length and posterior cortical margin increased, and the tunnel position became more horizontal in the coronal plane, more anterior in the sagittal plane, and less horizontal in the transverse plane as knee flexion increased. Portal position affects femoral tunnel characteristics, with results favoring the more laterally positioned standard anteromedial portal at all flexion angles. Increasing the knee flexion angle leads to a longer femoral tunnel length and posterior femoral cortical margin with either portal position. Understanding how portal positioning and knee flexion angle affect femoral tunnel orientation and characteristics may lead to improved surgical outcomes after ACL reconstruction. Published by Elsevier Inc.

Recent horizontal transfer of mellifera subfamily mariner transposons into insect lineages representing four different orders shows that selection acts only during horizontal transfer.

PubMed

Lampe, David J; Witherspoon, David J; Soto-Adames, Felipe N; Robertson, Hugh M

2003-04-01

We report the isolation and sequencing of genomic copies of mariner transposons involved in recent horizontal transfers into the genomes of the European earwig, Forficula auricularia; the European honey bee, Apis mellifera; the Mediterranean fruit fly, Ceratitis capitata; and a blister beetle, Epicauta funebris, insects from four different orders. These elements are in the mellifera subfamily and are the second documented example of full-length mariner elements involved in this kind of phenomenon. We applied maximum likelihood methods to the coding sequences and determined that the copies in each genome were evolving neutrally, whereas reconstructed ancestral coding sequences appeared to be under selection, which strengthens our previous hypothesis that the primary selective constraint on mariner sequence evolution is the act of horizontal transfer between genomes.

Influence of different peg length in glenoid bone loss: A biomechanical analysis regarding primary stability of the glenoid baseplate in reverse shoulder arthroplasty.

PubMed

Königshausen, M; Jettkant, B; Sverdlova, N; Ehlert, C; Gessmann, J; Schildhauer, T A; Seybold, D

2015-01-01

There is no biomechanical basis to determine the influence of different length of the central peg of the baseplate anchored within the native scapula in glenoid defect reconstruction in cases of degenerative or posttraumatic glenoid bone loss in reversed shoulder arthroplasty. The purpose of this study was to analyse the stability of different peg lengths used in glenoid bone loss in reversed shoulder arthroplasty. Different lengths of metaglene pegs with different depths of peg anchorage performed with or without metaglene screws in sawbone foam blocks were loaded in vertical and horizontal directions for differentiating load capacities. Simulated physiological loadings were then applied to the peg implants to determine the limits of loading in each depth of anchorage. The loading capacity of the implant was reduced as less of the peg was anchored. The vertically loaded implants showed a significantly higher stability, in contrast to those loaded horizontally at a corresponding peg length and depth of anchorage (p < 0.05). The tests revealed that the metaglene screws are more essential for primary stability than is the peg particularly in the vertically directed loadings (2/3 anchored: peg contributed to 28% of the stability, 1/3 anchorage: peg contributed to 12%). Under the second test conditions, the lowest depth of peg anchorage (1/3) resulted in 322 Newtons [N] in the long peg with a vertical loading direction, and in 130 N in the long peg with a horizontal loading direction (p < 0.05). The pegs should be anchored as deeply as possible into the native scapula bone stock. The metaglene screws play a major role in the initial stability, in contrast to the peg, and they become more important when the depth of the peg anchorage is reduced. If possible, four metaglene screws should be used in cases of uncontained bone loss to guarantee the highest stability.

23 CFR 658.9 - National Network criteria.

Code of Federal Regulations, 2014 CFR

2014-04-01

... length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry. (5) The route consists of lanes designed to be...

23 CFR 658.9 - National Network criteria.

Code of Federal Regulations, 2011 CFR

2011-04-01

... length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry. (5) The route consists of lanes designed to be...

23 CFR 658.9 - National Network criteria.

Code of Federal Regulations, 2010 CFR

2010-04-01

... length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry. (5) The route consists of lanes designed to be...

23 CFR 658.9 - National Network criteria.

Code of Federal Regulations, 2012 CFR

2012-04-01

... length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry. (5) The route consists of lanes designed to be...

23 CFR 658.9 - National Network criteria.

Code of Federal Regulations, 2013 CFR

2013-04-01

... length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry. (5) The route consists of lanes designed to be...

Atmospheric gravity waves with small vertical-to-horizotal wavelength ratios

NASA Astrophysics Data System (ADS)

Song, I. S.; Jee, G.; Kim, Y. H.; Chun, H. Y.

2017-12-01

Gravity wave modes with small vertical-to-horizontal wavelength ratios of an order of 10-3 are investigated through the systematic scale analysis of governing equations for gravity wave perturbations embedded in the quasi-geostrophic large-scale flow. These waves can be categorized as acoustic gravity wave modes because their total energy is given by the sum of kinetic, potential, and elastic parts. It is found that these waves can be forced by density fluctuations multiplied by the horizontal gradients of the large-scale pressure (geopotential) fields. These theoretical findings are evaluated using the results of a high-resolution global model (Specified Chemistry WACCM with horizontal resolution of 25 km and vertical resolution of 600 m) by computing the density-related gravity-wave forcing terms from the modeling results.

Scale Properties of Anisotropic and Isotropic Turbulence in the Urban Surface Layer

NASA Astrophysics Data System (ADS)

Liu, Hao; Yuan, Renmin; Mei, Jie; Sun, Jianning; Liu, Qi; Wang, Yu

2017-11-01

The scale properties of anisotropic and isotropic turbulence in the urban surface layer are investigated. A dimensionless anisotropic tensor is introduced and the turbulent tensor anisotropic coefficient, defined as C, where C = 3d3 + 1 (d3 is the minimum eigenvalue of the tensor) is used to characterize the turbulence anisotropy or isotropy. Turbulence is isotropic when C ≈ 1, and anisotropic when C ≪ 1. Three-dimensional velocity data collected using a sonic anemometer are analyzed to obtain the anisotropic characteristics of atmospheric turbulence in the urban surface layer, and the tensor anisotropic coefficient of turbulent eddies at different spatial scales calculated. The analysis shows that C is strongly dependent on atmospheric stability ξ = (z-zd)/L_{{it{MO}}}, where z is the measurement height, zd is the displacement height, and L_{{it{MO}}} is the Obukhov length. The turbulence at a specific scale in unstable conditions (i.e., ξ < 0) is closer to isotropic than that at the same scale under stable conditions. The maximum isotropic scale of turbulence is determined based on the characteristics of the power spectrum in three directions. Turbulence does not behave isotropically when the eddy scale is greater than the maximum isotropic scale, whereas it is horizontally isotropic at relatively large scales. The maximum isotropic scale of turbulence is compared to the outer scale of temperature, which is obtained by fitting the temperature fluctuation spectrum using the von Karman turbulent model. The results show that the outer scale of temperature is greater than the maximum isotropic scale of turbulence.

Mars Exploration Rover Landing Site Hectometer Slopes

NASA Astrophysics Data System (ADS)

Haldemann, A. F.; Anderson, F. S.

2002-12-01

The Mars Exploration Rover (MER) airbag landing system imposes a maximum slope of 5 degrees over 100 m length-scales. This limit avoids dangerous changes in elevation over the horizontal travel distance of the lander on its parachute between the time of the last radar altimeter detection of the surface and the time the retro-rockets fire and the bridle to the airbags is cut. Stereo imagery from the MGS MOC can provide information at this length scale, but MOC stereo coverage is sparse, even when targeted to MER landing sites. Additionally, MGS spacecraft stability issues affect the DEMs at precisely the hectometric length-scale1. The MOLA instrument provides global coverage pulse-width measurements2 over a single MOLA-pulse footprint, which is about 100 m in diameter. However, the pulse spread only provides an upper bound on the 100 m slope. We chose another approach. We sample the inter-pulse root-mean-square (RMS) height deviations for MOLA track segments restricted to pixels of 0.1 deg latitude by 0.1 deg longitude. Then, under the assumption of self-affine topography, we determine the scale-dependence of the RMS deviations and extrapolate that behavior over the range of 300 m to 1.2 km downward to the 100 m scale. Shepard et al.3 clearly summarize the statistical properties of the RMS deviation (noting that it also goes by the name structure function, variogram or Allan deviation), and we follow their nomenclature. The RMS deviation is a useful measure in that it can be directly converted to RMS-slope for a given length-scale. We map the results of this self-affine extrapolation method for each of the proposed MER landing sites as well as Viking Lander 1 (VL1) and Pathfiner (MPF). In order of decreasing average hectometer RMS-slopes, Melas (about 4.5 degrees) > Elysium EP80 > Gusev > MPF > Elysium EP78 > VL1 > Athabasca > Isidis > Hematite (about 1 degree). We also map the scaling parameter (Hurst exponent); its behavior in the MER landing site regions is interesting in how it ties together the regional behavior of kilometer slopes (directly measured with MOLA) with the decameter and meter slopes (locally derived from stereo image analysis or radar scattering). 1Kirk, R. L., E. Howington-Kraus, and B. A. Archinal, Int. Arch. Photogramm. Remote Sens., XXVIII(B4), 476 (CD-ROM), 2001; Kirk, R. L., E. Howington-Kraus, and B. A. Archinal, Lunar Planet Sci., XXXIII, abs 1988, 2002. 2Garvin, J. B., and J. J. Frawley, Lunar Planet. Sci., XXXI, abs 1884, 2000. 3Shepard, M. K., R. A. Brackett, and R. E. Arvidson, J. Geophys. Res., 100, 11709-11718, 1995.; Shepard, M. K., et al., J. Geophys. Res., 106, 32777-32796, 2001.

Correlation-based regularization and gradient operators for (joint) inversion on unstructured meshes

NASA Astrophysics Data System (ADS)

Jordi, Claudio; Doetsch, Joseph; Günther, Thomas; Schmelzbach, Cedric; Robertsson, Johan

2017-04-01

When working with unstructured meshes for geophysical inversions, special attention should be paid to the design of the operators that are used for regularizing the inverse problem and coupling of different property models in joint inversions. Regularization constraints for inversions on unstructured meshes are often defined in a rather ad-hoc manner and usually only involve the cell to which the operator is applied and its direct neighbours. Similarly, most structural coupling operators for joint inversion, such as the popular cross-gradients operator, are only defined in the direct neighbourhood of a cell. As a result, the regularization and coupling length scales and strength of these operators depend on the discretization as well as cell sizes and shape. Especially for unstructured meshes, where the cell sizes vary throughout the model domain, the dependency of the operator on the discretization may lead to artefacts. Designing operators that are based on a spatial correlation model allows to define correlation length scales over which an operator acts (called footprint), reducing the dependency on the discretization and the effects of variable cell sizes. Moreover, correlation-based operators can accommodate for expected anisotropy by using different length scales in horizontal and vertical directions. Correlation-based regularization operators also known as stochastic regularization operators have already been successfully applied to inversions on regular grids. Here, we formulate stochastic operators for unstructured meshes and apply them in 2D surface and 3D cross-well electrical resistivity tomography data inversion examples of layered media. Especially for the synthetic cross-well example, improved inversion results are achieved when stochastic regularization is used instead of a classical smoothness constraint. For the case of cross-gradients operators for joint inversion, the correlation model is used to define the footprint of the operator and weigh the contributions of the property values that are used to calculate the cross-gradients. In a first series of synthetic-data tests, we examined the mesh dependency of the cross-gradients operators. Compared to operators that are only defined in the direct neighbourhood of a cell, the dependency on the cell size of the cross-gradients calculation is markedly reduced when using operators with larger footprints. A second test with synthetic models focussed on the effect of small-scale variabilities of the parameter value on the cross-gradients calculation. Small-scale variabilities that are superimposed on a global trend of the property value can potentially degrade the cross-gradients calculation and destabilize joint inversion. We observe that the cross-gradients from operators with footprints larger than the length scale of the variabilities are less affected compared to operators with a small footprint. In joint inversions on unstructured meshes, we thus expect the correlation-based coupling operators to ensure robust coupling on a physically meaningful scale.

Improvement of gray-scale representation of horizontally scanning holographic display using error diffusion.

PubMed

Matsumoto, Yuji; Takaki, Yasuhiro

2014-06-15

Horizontally scanning holography can enlarge both screen size and viewing zone angle. A microelectromechanical-system spatial light modulator, which can generate only binary images, is used to generate hologram patterns. Thus, techniques to improve gray-scale representation in reconstructed images should be developed. In this study, the error diffusion technique was used for the binarization of holograms. When the Floyd-Steinberg error diffusion coefficients were used, gray-scale representation was improved. However, the linearity in the gray-scale representation was not satisfactory. We proposed the use of a correction table and showed that the linearity was greatly improved.

The Influence of a Lower Heated Tube on Nucleate Pool Boiling from a Horizontal Tube

DTIC Science & Technology

1992-06-01

9 C. CONDENSER SECTION .................................... 12 D. COOLING SECTION...lower tube kc thermal conductivity of copper L active boiling tube length Lu non-boiling tube length x Nu Nusselt number p tube outside wall perimeter Pr...teflon endplates. 2. A condenser , assembled using a similar Pyrex-glass tee with aluminum endplates. 3. A reservoir for R- 114 liquid storage. 4. A

[Geographic variation of seed morphological traits of Picea schrenkiana var. tianschanica in Tianshan Mountains, Xinjiang of Northwest China].

PubMed

Liu, Gui-Feng; Zang, Run-Guo; Liu, Hua; Bai, Zhi-Qiang; Guo, Zhong-Jun; Ding, Yi

2012-06-01

Taking the Picea schrenkiana var. tianschanica forests at three sites with different longitudes (Zhaosu, Tianchi, and Qitai) in Tianshan Mountains as the objects, the cones were collected along an altitudinal gradient to analyze the variation of their seed morphological traits (seed scale length and width, seed scale length/width ratio, seed wing length and width, seed wing length/ width ratio, seed length and width, and seed length/width ratio). All the seed traits except seed width tended to decrease with increasing altitude. The seed traits except seed wing width, seed width, and seed length/width ratio all had significant negative correlations with altitude. Seed scale length and width and seed scale length/width ratio had significant positive correlations with longitude. Seed scale length, seed scale length/width ratio, and seed wing length/width ratio had significant negative correlations with slope degree. No significant correlations were observed between the seed traits except seed wing width and the slope aspect. Altitude was the main factor affecting the seed scale length, seed scale length/width ratio, and seed wing length/width ratio.

7 CFR 1755.507 - Aerial cable services.

Code of Federal Regulations, 2010 CFR

2010-01-01

....5 kilogram/meter (kg/m)] except when equivalent combinations of greater span lengths with cable... horizontal runs, cable clamps shall be placed not more than 16 in. (400 mm) apart for cable diameters equal...

Impacts of the horizontal and vertical grids on the numerical solutions of the dynamical equations - Part 1: Nonhydrostatic inertia-gravity modes

NASA Astrophysics Data System (ADS)

Konor, Celal S.; Randall, David A.

2018-05-01

We have used a normal-mode analysis to investigate the impacts of the horizontal and vertical discretizations on the numerical solutions of the nonhydrostatic anelastic inertia-gravity modes on a midlatitude f plane. The dispersion equations are derived from the linearized anelastic equations that are discretized on the Z, C, D, CD, (DC), A, E and B horizontal grids, and on the L and CP vertical grids. The effects of both horizontal grid spacing and vertical wavenumber are analyzed, and the role of nonhydrostatic effects is discussed. We also compare the results of the normal-mode analyses with numerical solutions obtained by running linearized numerical models based on the various horizontal grids. The sources and behaviors of the computational modes in the numerical simulations are also examined.Our normal-mode analyses with the Z, C, D, A, E and B grids generally confirm the conclusions of previous shallow-water studies for the cyclone-resolving scales (with low horizontal wavenumbers). We conclude that, aided by nonhydrostatic effects, the Z and C grids become overall more accurate for cloud-resolving resolutions (with high horizontal wavenumbers) than for the cyclone-resolving scales.A companion paper, Part 2, discusses the impacts of the discretization on the Rossby modes on a midlatitude β plane.

Migration of the Cratering Flow-Field Center with Implications for Scaling Oblique Impacts

NASA Technical Reports Server (NTRS)

Anderson, J. L. B.; Schultz, P. H.; Heineck, J. T.

2004-01-01

Crater-scaling relationships are used to predict many cratering phenomena such as final crater diameter and ejection speeds. Such nondimensional relationships are commonly determined from experimental impact and explosion data. Almost without exception, these crater-scaling relationships have used data from vertical impacts (90 deg. to the horizontal). The majority of impact craters, however, form by impacts at angles near 45 deg. to the horizontal. While even low impact angles result in relatively circular craters in sand targets, the effects of impact angle have been shown to extend well into the excavation stage of crater growth. Thus, the scaling of oblique impacts needs to be investigated more thoroughly in order to quantify fully how impact angle affects ejection speed and angle. In this study, ejection parameters from vertical (90 deg.) and 30 deg. oblique impacts are measured using three-dimensional particle image velocimetry (3D PIV) at the NASA Ames Vertical Gun Range (AVGR). The primary goal is to determine the horizontal migration of the cratering flow-field center (FFC). The location of the FFC at the time of ejection controls the scaling of oblique impacts. For vertical impacts the FFC coincides with the impact point (IP) and the crater center (CC). Oblique impacts reflect a more complex, horizontally migrating flow-field. A single, stationary point-source model cannot be used accurately to describe the evolution of the ejection angles from oblique impacts. The ejection speeds for oblique impacts also do not follow standard scaling relationships. The migration of the FFC needs to be understood and incorporated into any revised scaling relationships.

Large perceptual distortions of locomotor action space occur in ground-based coordinates: Angular expansion and the large-scale horizontal-vertical illusion.

PubMed

Klein, Brennan J; Li, Zhi; Durgin, Frank H

2016-04-01

What is the natural reference frame for seeing large-scale spatial scenes in locomotor action space? Prior studies indicate an asymmetric angular expansion in perceived direction in large-scale environments: Angular elevation relative to the horizon is perceptually exaggerated by a factor of 1.5, whereas azimuthal direction is exaggerated by a factor of about 1.25. Here participants made angular and spatial judgments when upright or on their sides to dissociate egocentric from allocentric reference frames. In Experiment 1, it was found that body orientation did not affect the magnitude of the up-down exaggeration of direction, suggesting that the relevant orientation reference frame for this directional bias is allocentric rather than egocentric. In Experiment 2, the comparison of large-scale horizontal and vertical extents was somewhat affected by viewer orientation, but only to the extent necessitated by the classic (5%) horizontal-vertical illusion (HVI) that is known to be retinotopic. Large-scale vertical extents continued to appear much larger than horizontal ground extents when observers lay sideways. When the visual world was reoriented in Experiment 3, the bias remained tied to the ground-based allocentric reference frame. The allocentric HVI is quantitatively consistent with differential angular exaggerations previously measured for elevation and azimuth in locomotor space. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Large perceptual distortions of locomotor action space occur in ground-based coordinates: Angular expansion and the large-scale horizontal-vertical illusion

PubMed Central

Klein, Brennan J.; Li, Zhi; Durgin, Frank H.

2015-01-01

What is the natural reference frame for seeing large-scale spatial scenes in locomotor action space? Prior studies indicate an asymmetric angular expansion in perceived direction in large-scale environments: Angular elevation relative to the horizon is perceptually exaggerated by a factor of 1.5, whereas azimuthal direction is exaggerated by a factor of about 1.25. Here participants made angular and spatial judgments when upright or on their sides in order to dissociate egocentric from allocentric reference frames. In Experiment 1 it was found that body orientation did not affect the magnitude of the up-down exaggeration of direction, suggesting that the relevant orientation reference frame for this directional bias is allocentric rather than egocentric. In Experiment 2, the comparison of large-scale horizontal and vertical extents was somewhat affected by viewer orientation, but only to the extent necessitated by the classic (5%) horizontal-vertical illusion (HVI) that is known to be retinotopic. Large-scale vertical extents continued to appear much larger than horizontal ground extents when observers lay sideways. When the visual world was reoriented in Experiment 3, the bias remained tied to the ground-based allocentric reference frame. The allocentric HVI is quantitatively consistent with differential angular exaggerations previously measured for elevation and azimuth in locomotor space. PMID:26594884

Horizontal geometrical reaction time model for two-beam nacelle LiDARs

NASA Astrophysics Data System (ADS)

Beuth, Thorsten; Fox, Maik; Stork, Wilhelm

2015-06-01

Wind energy is one of the leading sustainable energies. To attract further private and state investment in this technology, a broad scaled drop of the cost of energy has to be enforced. There is a trend towards using Laser Doppler Velocimetry LiDAR systems for enhancing power output and minimizing downtimes, fatigue and extreme forces. Since most used LiDARs are horizontally setup on a nacelle and work with two beams, it is important to understand the geometrical configuration which is crucial to estimate reaction times for the actuators to compensate wind gusts. In the beginning of this article, the basic operating modes of wind turbines are explained and the literature on wind behavior is analyzed to derive specific wind speed and wind angle conditions in relation to the yaw angle of the hub. A short introduction to the requirements for the reconstruction of the wind vector length and wind angle leads to the problem of wind shear detection of angled but horizontal homogeneous wind fronts due to the spatial separation of the measuring points. A distance is defined in which the wind shear of such homogeneous wind fronts is not present which is used as a base to estimate further distance calculations. The reaction time of the controller and the actuators are having a negative effect on the effective overall reaction time for wind regulation as well. In the end, exemplary calculations estimate benefits and disadvantages of system parameters for wind gust regulating LiDARs for a wind turbine of typical size. An outlook shows possible future improvements concerning the vertical wind behavior.

Lattice Boltzmann methods applied to large-scale three-dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

USGS Publications Warehouse

Michael Sukop,; Cunningham, Kevin J.

2014-01-01

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 × 0.4 × 17 m (2.72 m3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s−1. This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Lattice Boltzmann methods applied to large-scale three-dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

NASA Astrophysics Data System (ADS)

Sukop, Michael C.; Cunningham, Kevin J.

2014-11-01

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 × 0.4 × 17 m (2.72 m3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s-1. This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Anatomic motor point localization for partial quadriceps block in spasticity.

PubMed

Albert, T; Yelnik, A; Colle, F; Bonan, I; Lassau, J P

2000-03-01

To identify the location of the vastus intermedius nerve and its motor point (point M) and to precisely identify its coordinates in relation to anatomic surface landmarks. Descriptive study. Anatomy institute of a university school of medicine. Twenty-nine adult cadaver limbs immobilized in anatomic position. Anatomic dissection to identify point M. Anatomic surface landmarks were point F, the issuing point of femoral nerve under the inguinal ligament; point R, the middle of superior edge of the patella; segment FR, which corresponds to thigh length; point M', point M orthogonal projection on segment FR. Absolute vertical coordinate, distance FM, relative vertical coordinate compared to the thigh length, FM'/FR ratio; absolute horizontal coordinate, distance MM'. The absolute vertical coordinate was 11.7+/-2 cm. The relative vertical coordinate was at .29+/-.04 of thigh length. The horizontal coordinate was at 2+/-.5 cm lateral to the FR line. Point M can be defined with relative precision by two coordinates. Application and clinical interest of nerve blocking using these coordinates in quadriceps spasticity should be studied.

Influences of drizzle on stratocumulus cloudiness and organization [Influences of drizzle on cloudiness and stratocumulus organization

DOE PAGES

Zhou, Xiaoli; Heus, Thijs; Kollias, Pavlos

2017-06-06

Large-eddy simulations are used to study the influence of drizzle on stratocumulus organization, based on measurements made as part of the Second Dynamics and Chemistry of the Marine Stratocumulus field study-II. Cloud droplet number concentration ( N c) is prescribed and considered as the proxy for different aerosol loadings. Our study shows that the amount of cloudiness does not decrease linearly with precipitation rate. An N c threshold is observed below which the removal of cloud water via precipitation efficiently reduces cloud depth, allowing evaporation to become efficient and quickly remove the remaining thin clouds, facilitating a fast transition frommore » closed cells to open cells. Using Fourier analysis, stratocumulus length scales are found to increase with drizzle rates. Raindrop evaporation below 300 m lowers the cloud bases and amplifies moisture variances in the subcloud layer, while it does not alter the horizontal scales in the cloud layer, suggesting that moist cold pool dynamic forcings are not essential for mesoscale organization of stratocumulus. Furthermore, the cloud scales are greatly increased when the boundary layer is too deep to maintain well mixed.« less

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

DOE PAGES

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang; ...

2017-04-20

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed in this paper. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humiditymore » differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Finally, clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.« less

Influences of drizzle on stratocumulus cloudiness and organization [Influences of drizzle on cloudiness and stratocumulus organization

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

Zhou, Xiaoli; Heus, Thijs; Kollias, Pavlos

Large-eddy simulations are used to study the influence of drizzle on stratocumulus organization, based on measurements made as part of the Second Dynamics and Chemistry of the Marine Stratocumulus field study-II. Cloud droplet number concentration ( N c) is prescribed and considered as the proxy for different aerosol loadings. Our study shows that the amount of cloudiness does not decrease linearly with precipitation rate. An N c threshold is observed below which the removal of cloud water via precipitation efficiently reduces cloud depth, allowing evaporation to become efficient and quickly remove the remaining thin clouds, facilitating a fast transition frommore » closed cells to open cells. Using Fourier analysis, stratocumulus length scales are found to increase with drizzle rates. Raindrop evaporation below 300 m lowers the cloud bases and amplifies moisture variances in the subcloud layer, while it does not alter the horizontal scales in the cloud layer, suggesting that moist cold pool dynamic forcings are not essential for mesoscale organization of stratocumulus. Furthermore, the cloud scales are greatly increased when the boundary layer is too deep to maintain well mixed.« less

Cloud microphysical relationships and their implication on entrainment and mixing mechanism for the stratocumulus clouds measured during the VOCALS project

DOE PAGES

Yum, Seong Soo; Wang, Jian; Liu, Yangang; ...

2015-05-27

Cloud microphysical data obtained from G-1 aircraft flights over the southeastern pacific during the VOCALS-Rex field campaign were analyzed for evidence of entrainment mixing of dry air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at 1 Hz and 40 Hz. The dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurementsmore » were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing, the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top.« less

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

NASA Astrophysics Data System (ADS)

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang; Lu, Chunsong

2017-09-01

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humidity differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

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

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed in this paper. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humiditymore » differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Finally, clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.« less

Deviations from Equilibrium in Daytime Atmospheric Boundary Layer Turbulence arising from Nonstationary Mesoscale Forcing

NASA Astrophysics Data System (ADS)

Jayaraman, Balaji; Brasseur, James; Haupt, Sue; Lee, Jared

2016-11-01

LES of the "canonical" daytime atmospheric boundary layer (ABL) over flat topography is developed as an equilibrium ABL with steady surface heat flux, Q0 and steady unidirectional "geostrophic" wind vector Vg above a capping inversion. A strong inversion layer in daytime ABL acts as a "lid" that sharply separates 3D "microscale" ABL turbulence at the O(10) m scale from the quasi-2D "mesoscale" turbulent weather eddies (O(100) km scale). While "canonical" ABL is equilibrium, quasi-stationary and characterized statistically by the ratio of boundary layer depth (zi) to Obukhov length scale (- L) , the real mesoscale influences (Ug and Q0) that force a true daytime ABL are nonstationary at both diurnal and sub-diurnal time scales. We study the consequences of this non-stationarity on ABL dynamics by forcing ABL LES with realistic WRF simulations over flat Kansas terrain. Considering horizontal homogeneity, we relate the mesoscale and geostrophic winds, Ug and Vg, and systematically study the ABL turbulence response to non-steady variations in Q0 and Ug. We observe significant deviations from equilibrium, that manifest in many ways, such as the formation of "roll" eddies purely from changes in mesoscale wind direction that are normally associated with increased surface heat flux. Support from DOE. Compute resources from Penn State ICS.

A Critical Characteristic in the Transverse Galloping Pattern

PubMed Central

Wei, Xiaohui; Long, Yongjun; Wang, Chunlei; Wang, Shigang

2015-01-01

Transverse gallop is a common gait used by a large number of quadrupeds. This paper employs the simplified dimensionless quadrupedal model to discuss the underlying mechanism of the transverse galloping pattern. The model is studied at different running speeds and different values of leg stiffness, respectively. If the horizontal running speed reaches up to a critical value at a fixed leg stiffness, or if the leg stiffness reaches up to a critical value at a fixed horizontal speed, a key property would emerge which greatly reduces the overall mechanical forces of the dynamic system in a proper range of initial pitch angular velocities. Besides, for each horizontal speed, there is an optimal stiffness of legs that can reduce both the mechanical loads and the metabolic cost of transport. Furthermore, different body proportions and landing distance lags of a pair of legs are studied in the transverse gallop. We find that quadrupeds with longer length of legs compared with the length of the body are more suitable to employ the transverse galloping pattern, and the landing distance lag of a pair of legs could reduce the cost of transport and the locomotion frequency. PMID:27087773

Simulation of Boundary-Layer Cumulus and Stratocumulus Clouds using a Cloud-Resolving Model With Low- and Third-Order Turbulence Closures

NASA Technical Reports Server (NTRS)

Xu, Kuan-Man; Cheng, Anning

2007-01-01

The effects of subgrid-scale condensation and transport become more important as the grid spacings increase from those typically used in large-eddy simulation (LES) to those typically used in cloud-resolving models (CRMs). Incorporation of these effects can be achieved by a joint probability density function approach that utilizes higher-order moments of thermodynamic and dynamic variables. This study examines how well shallow cumulus and stratocumulus clouds are simulated by two versions of a CRM that is implemented with low-order and third-order turbulence closures (LOC and TOC) when a typical CRM horizontal resolution is used and what roles the subgrid-scale and resolved-scale processes play as the horizontal grid spacing of the CRM becomes finer. Cumulus clouds were mostly produced through subgrid-scale transport processes while stratocumulus clouds were produced through both subgrid-scale and resolved-scale processes in the TOC version of the CRM when a typical CRM grid spacing is used. The LOC version of the CRM relied upon resolved-scale circulations to produce both cumulus and stratocumulus clouds, due to small subgrid-scale transports. The mean profiles of thermodynamic variables, cloud fraction and liquid water content exhibit significant differences between the two versions of the CRM, with the TOC results agreeing better with the LES than the LOC results. The characteristics, temporal evolution and mean profiles of shallow cumulus and stratocumulus clouds are weakly dependent upon the horizontal grid spacing used in the TOC CRM. However, the ratio of the subgrid-scale to resolved-scale fluxes becomes smaller as the horizontal grid spacing decreases. The subcloud-layer fluxes are mostly due to the resolved scales when a grid spacing less than or equal to 1 km is used. The overall results of the TOC simulations suggest that a 1-km grid spacing is a good choice for CRM simulation of shallow cumulus and stratocumulus.

Large-scale anisotropy in stably stratified rotating flows

DOE PAGES

Marino, R.; Mininni, P. D.; Rosenberg, D. L.; ...

2014-08-28

We present results from direct numerical simulations of the Boussinesq equations in the presence of rotation and/or stratification, both in the vertical direction. The runs are forced isotropically and randomly at small scales and have spatial resolutions of up tomore » $1024^3$ grid points and Reynolds numbers of $$\\approx 1000$$. We first show that solutions with negative energy flux and inverse cascades develop in rotating turbulence, whether or not stratification is present. However, the purely stratified case is characterized instead by an early-time, highly anisotropic transfer to large scales with almost zero net isotropic energy flux. This is consistent with previous studies that observed the development of vertically sheared horizontal winds, although only at substantially later times. However, and unlike previous works, when sufficient scale separation is allowed between the forcing scale and the domain size, the total energy displays a perpendicular (horizontal) spectrum with power law behavior compatible with $$\\sim k_\\perp^{-5/3}$$, including in the absence of rotation. In this latter purely stratified case, such a spectrum is the result of a direct cascade of the energy contained in the large-scale horizontal wind, as is evidenced by a strong positive flux of energy in the parallel direction at all scales including the largest resolved scales.« less

Time and length scales within a fire and implications for numerical simulation

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

TIESZEN,SHELDON R.

2000-02-02

A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principlesmore » solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.« less

Revisiting Gill's Circulation. Dynamic Response to Diabatic Heating of Different Horizontal Extents

NASA Astrophysics Data System (ADS)

Reboredo, B.; Bellon, G.

2017-12-01

The horizontal extent of diabatic heating associated with the MJO is thought to be crucial to its development, and the inability of GCMs to simulate the spatial, horizontal organization of clouds is considered a leading hypothesis to explain their limited capacity to simulate MJO events. This prevents the MJO large-circulation response from developing and feeding back on the development of clouds. We apply mid-tropospheric heating of different size in simple linear and non-linear models of the tropical atmosphere following Gill's seminal work on heat-induced tropical circulations. Results show that there is a scale for which the characteristic circulation {Γ c} for the vertical advection of moisture to produce the latent heat mean {Q} gives a rough estimate of the real world MJO scale. Overturning circulation flow rates above {Γ c} account for a circulation that transports more moisture than necessary to be maintained, and below {Γ c}, circulation would not transport enough moisture to maintain circulation. This dynamic scale might constrain the size of the spatially-organised convection necessary to the development of an MJO event. However, other effects are expected to modulate this scale, such as vertical advection of moisture anomalies, horizontal advection, evaporation, radiative heating, and sensible heat fluxes.

Effect of Fluid Flow on Zinc Electrodeposits from Acid Chloride Electrolytes. M.S. Thesis

NASA Technical Reports Server (NTRS)

Abdelmassir, A. A.

1982-01-01

Zinc was deposited potentiostatically from acid chloride baths. Once bath chemistry and electrochemistry were controlled, the study was focused on convective mass transfer at horizontal electrodes and its effect on cell performance. A laser schlieren imaging technique allowed in situ observations of flow patterns and their correlation with current transients. Convection was turbulent and mass transfer as a function of Rayleigh number was well correlated by: Sh = 0.14 R to the 1/3 power. Similarly, convection initiation time was correlated by DT/d squared = 38 Ra to the -2/3 power. Time scale of fluctuations was about half the initiation time. Taking the boundary layer thickness as a characteristic length, a critical Rayleigh number for the onset of convection was deduced: Ra sub CR = 5000. Placing the anode on the top of the cathode completely changed the flow pattern but kept the I-t curves identical whereas the use of a cathode grid doubled the limiting current. A well defined plateau in the current voltage curves suggested that hydrogen evolution has been successfully inhibited. Finally, long time deposition showed that convection at horizontal electrodes increased the induction time for dentrite growth by at least a factor of 2 with respect to a vertical wire.

Fractal properties and denoising of lidar signals from cirrus clouds

NASA Astrophysics Data System (ADS)

van den Heuvel, J. C.; Driesenaar, M. L.; Lerou, R. J. L.

2000-02-01

Airborne lidar signals of cirrus clouds are analyzed to determine the cloud structure. Climate modeling and numerical weather prediction benefit from accurate modeling of cirrus clouds. Airborne lidar measurements of the European Lidar in Space Technology Experiment (ELITE) campaign were analyzed by combining shots to obtain the backscatter at constant altitude. The signal at high altitude was analyzed for horizontal structure of cirrus clouds. The power spectrum and the structure function show straight lines on a double logarithmic plot. This behavior is characteristic for a Brownian fractal. Wavelet analysis using the Haar wavelet confirms the fractal aspects. It is shown that the horizontal structure of cirrus can be described by a fractal with a dimension of 1.8 over length scales that vary 4 orders of magnitude. We use the fractal properties in a new denoising method. Denoising is required for future lidar measurements from space that have a low signal to noise ratio. Our wavelet denoising is based on the Haar wavelet and uses the statistical fractal properties of cirrus clouds in a method based on the maximum a posteriori (MAP) probability. This denoising based on wavelets is tested on airborne lidar signals from ELITE using added Gaussian noise. Superior results with respect to averaging are obtained.

Dispersion/dilution enhances phytoplankton blooms in low-nutrient waters

NASA Astrophysics Data System (ADS)

Lehahn, Yoav; Koren, Ilan; Sharoni, Shlomit; D'Ovidio, Francesco; Vardi, Assaf; Boss, Emmanuel

2017-03-01

Spatial characteristics of phytoplankton blooms often reflect the horizontal transport properties of the oceanic turbulent flow in which they are embedded. Classically, bloom response to horizontal stirring is regarded in terms of generation of patchiness following large-scale bloom initiation. Here, using satellite observations from the North Pacific Subtropical Gyre and a simple ecosystem model, we show that the opposite scenario of turbulence dispersing and diluting fine-scale (~1-100 km) nutrient-enriched water patches has the critical effect of regulating the dynamics of nutrients-phytoplankton-zooplankton ecosystems and enhancing accumulation of photosynthetic biomass in low-nutrient oceanic environments. A key factor in determining ecological and biogeochemical consequences of turbulent stirring is the horizontal dilution rate, which depends on the effective eddy diffusivity and surface area of the enriched patches. Implementation of the notion of horizontal dilution rate explains quantitatively plankton response to turbulence and improves our ability to represent ecological and biogeochemical processes in oligotrophic oceans.

A dimensional comparison between embedded 3D-printed and silicon microchannels

NASA Astrophysics Data System (ADS)

O'Connor, J.; Punch, J.; Jeffers, N.; Stafford, J.

2014-07-01

The subject of this paper is the dimensional characterization of embedded microchannel arrays created using contemporary 3D-printing fabrication techniques. Conventional microchannel arrays, fabricated using deep reactive ion etching techniques (DRIE) and wet-etching (KOH), are used as a benchmark for comparison. Rectangular and trapezoidal cross-sectional shapes were investigated. The channel arrays were 3D-printed in vertical and horizontal directions, to examine the influence of print orientation on channel characteristics. The 3D-printed channels were benchmarked against Silicon channels in terms of the following dimensional characteristics: cross-sectional area (CSA), perimeter, and surface profiles. The 3D-printed microchannel arrays demonstrated variances in CSA of 6.6-20% with the vertical printing approach yielding greater dimensional conformity than the horizontal approach. The measured CSA and perimeter of the vertical channels were smaller than the nominal dimensions, while the horizontal channels were larger in both CSA and perimeter due to additional side-wall roughness present throughout the channel length. This side-wall roughness caused significant shape distortion. Surface profile measurements revealed that the base wall roughness was approximately the resolution of current 3D-printers. A spatial periodicity was found along the channel length which appeared at different frequencies for each channel array. This paper concludes that vertical 3D-printing is superior to the horizontal printing approach, in terms of both dimensional fidelity and shape conformity and can be applied in microfluidic device applications.

Numerical simulation of tidal dispersion around a coastal headland

USGS Publications Warehouse

Signell, R.P.; Geyer, W. Rockwell; Cheng, Ralph T.

1990-01-01

Tidal flows around headlands can exhibit strong spatial gradients in the Eulerian currents, resulting in complex Lagrangian trajectories and dispersion of the vertically integrated flow. This typically occurs when the horizontal length scale of the headland is comparable to or smaller than the tidal excursion. The effects of these headlands on dispersion are investigated using a depthaveraged hydrodynamic model combined with a particle tracking model. The dispersion of patches of fluid is found to vary by more than an order of magnitude, depending both on position and tidal phase at the time of release. This is due to the infrequent interaction of material with the strongly sheared flow at the tip of the headland, where flow separation occurs during times of maximum tidal flow. Spreading of these patches over many tidal cycles is not Gaussian, but rather shows a patchy, streaky structure.

Characterization of meter-scale spatial variability of riverbed hydraulic conductivity in a lowland river (Aa River, Belgium)

NASA Astrophysics Data System (ADS)

Ghysels, Gert; Benoit, Sien; Awol, Henock; Jensen, Evan Patrick; Debele Tolche, Abebe; Anibas, Christian; Huysmans, Marijke

2018-04-01

An improved general understanding of riverbed heterogeneity is of importance for all groundwater modeling studies that include river-aquifer interaction processes. Riverbed hydraulic conductivity (K) is one of the main factors controlling river-aquifer exchange fluxes. However, the meter-scale spatial variability of riverbed K has not been adequately mapped as of yet. This study aims to fill this void by combining an extensive field measurement campaign focusing on both horizontal and vertical riverbed K with a detailed geostatistical analysis of the meter-scale spatial variability of riverbed K . In total, 220 slug tests and 45 standpipe tests were performed at two test sites along the Belgian Aa River. Omnidirectional and directional variograms (along and across the river) were calculated. Both horizontal and vertical riverbed K vary over several orders of magnitude and show significant meter-scale spatial variation. Horizontal K shows a bimodal distribution. Elongated zones of high horizontal K along the river course are observed at both sections, indicating a link between riverbed structures, depositional environment and flow regime. Vertical K is lognormally distributed and its spatial variability is mainly governed by the presence and thickness of a low permeable organic layer at the top of the riverbed. The absence of this layer in the center of the river leads to high vertical K and is related to scouring of the riverbed by high discharge events. Variograms of both horizontal and vertical K show a clear directional anisotropy with ranges along the river being twice as large as those across the river.

Film condensation in a horizontal rectangular duct

NASA Technical Reports Server (NTRS)

Lu, Qing; Suryanarayana, N. V.

1993-01-01

Condensation heat transfer in a horizontal rectangular duct was experimentally and analytically investigated. To prevent the dripping of condensate on the film, the experiment was conducted inside a horizontal rectangular duct with vapor condensing only on the bottom cooled plate of the duct. R-113 and FC-72 (Fluorinert Electronic Fluid developed by the 3M Company) were used as the condensing fluids. The experimental program included measurements of film thickness, local and average heat transfer coefficients, wave length, wave speed, and a study of wave initiation. The measured film thickness was used to obtain the local heat transfer coefficient. The wave initiation was studied both with condensation and with an adiabatic air-liquid flow. The test sections used in both experiments were identical.

Design and Analysis of Horizontal Axial Flow Motor Shroud

NASA Astrophysics Data System (ADS)

Wang, Shiming; Shen, Yu

2018-01-01

The wind turbine diffuser can increase the wind energy utilization coefficient of the wind turbine, and the addition of the shroud to the horizontal axis wind turbine also plays a role of accelerating the flow of the condensate. First, the structure of the shroud was designed and then modeled in gambit. The fluent software was used to establish the mathematical model for simulation. The length of the shroud and the opening angle of the shroud are analyzed to determine the best shape of the shroud. Then compared the efficiency with or without the shroud, through the simulation and the experiment of the water tank, it is confirmed that the horizontal axis of the shroud can improve the hydrodynamic performance.

Peripheral Refraction, Peripheral Eye Length, and Retinal Shape in Myopia.

PubMed

Verkicharla, Pavan K; Suheimat, Marwan; Schmid, Katrina L; Atchison, David A

2016-09-01

To investigate how peripheral refraction and peripheral eye length are related to retinal shape. Relative peripheral refraction (RPR) and relative peripheral eye length (RPEL) were determined in 36 young adults (M +0.75D to -5.25D) along horizontal and vertical visual field meridians out to ±35° and ±30°, respectively. Retinal shape was determined in terms of vertex radius of curvature Rv, asphericity Q, and equivalent radius of curvature REq using a partial coherence interferometry method involving peripheral eye lengths and model eye raytracing. Second-order polynomial fits were applied to RPR and RPEL as functions of visual field position. Linear regressions were determined for the fits' second order coefficients and for retinal shape estimates as functions of central spherical refraction. Linear regressions investigated relationships of RPR and RPEL with retinal shape estimates. Peripheral refraction, peripheral eye lengths, and retinal shapes were significantly affected by meridian and refraction. More positive (hyperopic) relative peripheral refraction, more negative RPELs, and steeper retinas were found along the horizontal than along the vertical meridian and in myopes than in emmetropes. RPR and RPEL, as represented by their second-order fit coefficients, correlated significantly with retinal shape represented by REq. Effects of meridian and refraction on RPR and RPEL patterns are consistent with effects on retinal shape. Patterns derived from one of these predict the others: more positive (hyperopic) RPR predicts more negative RPEL and steeper retinas, more negative RPEL predicts more positive relative peripheral refraction and steeper retinas, and steeper retinas derived from peripheral eye lengths predict more positive RPR.

Effect of volumetric radiation on natural convection in a cavity with a horizontal fin using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Tighchi, Hashem Ahmadi; Sobhani, Masoud; Esfahani, Javad Abolfazli

2018-01-01

The lattice Boltzmann method (LBM) is presented for the effects of volumetric radiation on laminar natural convection in a square cavity with a horizontal fin on the hot wall containing an absorbing, emitting and scattering medium. Accordingly, the flow, energy and radiative equations are solved by separate distribution functions in the LBM. A parametric study is performed: the effects of Rayleigh number and radiative parameters, such as extinction coefficient and scattering albedo on the flow and temperature fields are investigated. It is found that the isotherms become dense near the cold wall, due to highly participating properties and Rayleigh number. Also, the Nusselt number ratio (NNR) on the clod wall is examined for values of fin length and height. The maximum NNR is found at the longest fin length and near top wall for a given Rayleigh number.

Impacts of the horizontal and vertical grids on the numerical solutions of the dynamical equations – Part 1: Nonhydrostatic inertia–gravity modes

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

Konor, Celal S.; Randall, David A.

We have used a normal-mode analysis to investigate the impacts of the horizontal and vertical discretizations on the numerical solutions of the nonhydrostatic anelastic inertia–gravity modes on a midlatitude f plane. The dispersion equations are derived from the linearized anelastic equations that are discretized on the Z, C, D, CD, (DC), A, E and B horizontal grids, and on the L and CP vertical grids. The effects of both horizontal grid spacing and vertical wavenumber are analyzed, and the role of nonhydrostatic effects is discussed. We also compare the results of the normal-mode analyses with numerical solutions obtained by runningmore » linearized numerical models based on the various horizontal grids. The sources and behaviors of the computational modes in the numerical simulations are also examined.Our normal-mode analyses with the Z, C, D, A, E and B grids generally confirm the conclusions of previous shallow-water studies for the cyclone-resolving scales (with low horizontal wavenumbers). We conclude that, aided by nonhydrostatic effects, the Z and C grids become overall more accurate for cloud-resolving resolutions (with high horizontal wavenumbers) than for the cyclone-resolving scales.A companion paper, Part 2, discusses the impacts of the discretization on the Rossby modes on a midlatitude β plane.« less

Impacts of the horizontal and vertical grids on the numerical solutions of the dynamical equations – Part 1: Nonhydrostatic inertia–gravity modes

DOE PAGES

Konor, Celal S.; Randall, David A.

2018-05-08

We have used a normal-mode analysis to investigate the impacts of the horizontal and vertical discretizations on the numerical solutions of the nonhydrostatic anelastic inertia–gravity modes on a midlatitude f plane. The dispersion equations are derived from the linearized anelastic equations that are discretized on the Z, C, D, CD, (DC), A, E and B horizontal grids, and on the L and CP vertical grids. The effects of both horizontal grid spacing and vertical wavenumber are analyzed, and the role of nonhydrostatic effects is discussed. We also compare the results of the normal-mode analyses with numerical solutions obtained by runningmore » linearized numerical models based on the various horizontal grids. The sources and behaviors of the computational modes in the numerical simulations are also examined.Our normal-mode analyses with the Z, C, D, A, E and B grids generally confirm the conclusions of previous shallow-water studies for the cyclone-resolving scales (with low horizontal wavenumbers). We conclude that, aided by nonhydrostatic effects, the Z and C grids become overall more accurate for cloud-resolving resolutions (with high horizontal wavenumbers) than for the cyclone-resolving scales.A companion paper, Part 2, discusses the impacts of the discretization on the Rossby modes on a midlatitude β plane.« less

Final bubble lengths for aqueous foam coarsened in a horizontal cylinder

NASA Astrophysics Data System (ADS)

Sebag, V.; Roth, A. E.; Durian, D. J.

2011-12-01

We report on length statistics measured for bubbles in the equilibrium bamboo state, achieved by the coarsening of aqueous foam in long cylindrical tubes, such that the soap films are all flat and perpendicular to the axis of the tube. The average bubble length is found to be 0.88 times the tube diameter, independent of variation of the liquid filling fraction by a factor of nearly three. The actual distribution is well-approximated by a shifted Rayleigh form, with a minimum bubble size of 0.28 tube diameters. And, perhaps surprisingly, no correlations are found in the lengths of neighboring bubbles. The observed length distribution agrees with that of Fortes et al. for short bubbles, but not for long bubbles.

Parametrization of Drag and Turbulence for Urban Neighbourhoods with Trees

NASA Astrophysics Data System (ADS)

Krayenhoff, E. S.; Santiago, J.-L.; Martilli, A.; Christen, A.; Oke, T. R.

2015-08-01

Urban canopy parametrizations designed to be coupled with mesoscale models must predict the integrated effect of urban obstacles on the flow at each height in the canopy. To assess these neighbourhood-scale effects, results of microscale simulations may be horizontally-averaged. Obstacle-resolving computational fluid dynamics (CFD) simulations of neutrally-stratified flow through canopies of blocks (buildings) with varying distributions and densities of porous media (tree foliage) are conducted, and the spatially-averaged impacts on the flow of these building-tree combinations are assessed. The accuracy with which a one-dimensional (column) model with a one-equation (-) turbulence scheme represents spatially-averaged CFD results is evaluated. Individual physical mechanisms by which trees and buildings affect flow in the column model are evaluated in terms of relative importance. For the treed urban configurations considered, effects of buildings and trees may be considered independently. Building drag coefficients and length scale effects need not be altered due to the presence of tree foliage; therefore, parametrization of spatially-averaged flow through urban neighbourhoods with trees is greatly simplified. The new parametrization includes only source and sink terms significant for the prediction of spatially-averaged flow profiles: momentum drag due to buildings and trees (and the associated wake production of turbulent kinetic energy), modification of length scales by buildings, and enhanced dissipation of turbulent kinetic energy due to the small scale of tree foliage elements. Coefficients for the Santiago and Martilli (Boundary-Layer Meteorol 137: 417-439, 2010) parametrization of building drag coefficients and length scales are revised. Inclusion of foliage terms from the new parametrization in addition to the Santiago and Martilli building terms reduces root-mean-square difference (RMSD) of the column model streamwise velocity component and turbulent kinetic energy relative to the CFD model by 89 % in the canopy and 71 % above the canopy on average for the highest leaf area density scenarios tested: . RMSD values with the new parametrization are less than 20 % of mean layer magnitude for the streamwise velocity component within and above the canopy, and for above-canopy turbulent kinetic energy; RMSD values for within-canopy turbulent kinetic energy are negligible for most scenarios. The foliage-related portion of the new parametrization is required for scenarios with tree foliage of equal or greater height than the buildings, and for scenarios with foliage below roof height for building plan area densities less than approximately 0.25.

A parametric study on the benefits of drilling horizontal and multilateral wells in coalbed methane reservoirs

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

Maricic, N.; Mohaghegh, S.D.; Artun, E.

2008-12-15

Recent years have witnessed a renewed interest in development of coalbed methane (CBM) reservoirs. Optimizing CBM production is of interest to many operators. Drilling horizontal and multilateral wells is gaining Popularity in many different coalbed reservoirs, with varying results. This study concentrates on variations of horizontal and multilateral-well configurations and their potential benefits. In this study, horizontal and several multilateral drilling patterns for CBM reservoirs are studied. The reservoir parameters that have been studied include gas content, permeability, and desorption characteristics. Net present value (NPV) has been used as the yard stick for comparing different drilling configurations. Configurations that havemore » been investigated are single-, dual-, tri-, and quad-lateral wells along with fishbone (also known as pinnate) wells. In these configurations, the total length of horizontal wells and the spacing between laterals (SBL) have been studied. It was determined that in the cases that have been studied in this paper (all other circumstances being equal), quadlateral wells are the optimum well configuration.« less

Controls on groundwater flow in the Bengal Basin of India and Bangladesh: Regional modeling analysis

USGS Publications Warehouse

Michael, H.A.; Voss, C.I.

2009-01-01

Groundwater for domestic and irrigation purposes is produced primarily from shallow parts of the Bengal Basin aquifer system (India and Bangladesh), which contains high concentrations of dissolved arsenic (exceeding worldwide drinking water standards), though deeper groundwater is generally low in arsenic. An essential first step for determining sustainable management of the deep groundwater resource is identification of hydrogeologic controls on flow and quantification of basin-scale groundwater flow patterns. Results from groundwater modeling, in which the Bengal Basin aquifer system is represented as a single aquifer with higher horizontal than vertical hydraulic conductivity, indicate that this anisotropy is the primary hydrogeologic control on the natural flowpath lengths. Despite extremely low hydraulic gradients due to minimal topographic relief, anisotropy implies large-scale (tens to hundreds of kilometers) flow at depth. Other hydrogeologic factors, including lateral and vertical changes in hydraulic conductivity, have minor effects on overall flow patterns. However, because natural hydraulic gradients are low, the impact of pumping on groundwater flow is overwhelming; modeling indicates that pumping has substantially changed the shallow groundwater budget and flowpaths from predevelopment conditions. ?? Springer-Verlag 2009.

Wind-Tunnel Investigation of the Static Longitudinal Stability Characteristics of a 0.15-Scale Model of the Hermes A-1E2 Missile at High Subsonic Mach Numbers

NASA Technical Reports Server (NTRS)

Alford, William J., Jr.

1952-01-01

The static longitudinal stability characteristics of a 0.15-scale model of the Hermes A-lE2 missile have been determined in the Langley high-speed 7- by 10-foot tunnel over a Mach number range of 0.50 to 0.98, corresponding to Reynolds numbers, based on body length, of 12.3 x 10(exp 6) to 17.1 x 10(exp 6). This paper presents results obtained with body alone and body-fins combinations at 0 degrees (one set of fins vertical and the other set horizontal) and 45 degree angle of roll. The results indicate that the addition of the fins to the body insures static longitudinal stability and provides essentially linear variations of the lift and pitching moment at small angles of attack throughout the Mach number range. The slopes of the lift and pitching-moment curves vary slightly with Mach number and show only small effects due to the angle of roll.

Controls on groundwater flow in the Bengal Basin of India and Bangladesh: regional modeling analysis

NASA Astrophysics Data System (ADS)

Michael, Holly A.; Voss, Clifford I.

2009-11-01

Groundwater for domestic and irrigation purposes is produced primarily from shallow parts of the Bengal Basin aquifer system (India and Bangladesh), which contains high concentrations of dissolved arsenic (exceeding worldwide drinking water standards), though deeper groundwater is generally low in arsenic. An essential first step for determining sustainable management of the deep groundwater resource is identification of hydrogeologic controls on flow and quantification of basin-scale groundwater flow patterns. Results from groundwater modeling, in which the Bengal Basin aquifer system is represented as a single aquifer with higher horizontal than vertical hydraulic conductivity, indicate that this anisotropy is the primary hydrogeologic control on the natural flowpath lengths. Despite extremely low hydraulic gradients due to minimal topographic relief, anisotropy implies large-scale (tens to hundreds of kilometers) flow at depth. Other hydrogeologic factors, including lateral and vertical changes in hydraulic conductivity, have minor effects on overall flow patterns. However, because natural hydraulic gradients are low, the impact of pumping on groundwater flow is overwhelming; modeling indicates that pumping has substantially changed the shallow groundwater budget and flowpaths from predevelopment conditions.

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

Leger, M.; Morvan, J.M.; Thibaut, M.

Restoration of a geologic structure at earlier times is a good means to criticize, and next to improve, its interpretation. Restoration softwares already exist in 2D, but a lot of work remains to be done in 3D. The authors focus on the interbedding slip phenomenon, with bed-length and volume conservation. They unfold a (geometrical) foliation by optimizing following least-squares criteria: horizontalness, bed-length and volume conservation, under equality constraints related to the position of the ``binding`` or ``pin-surface``

A new blind snake of the genus Letheobia (Serpentes: Typhlopidae) from Rwanda with redescriptions of L. gracilis (Sternfeld, 1910) and L. graueri (Sternfeld, 1912) and the introduction of a non-invasive preparation procedure for scanning electron microscopy in zoology.

PubMed

Dehling, J Maximilian; Hinkel, Harald H; Ensikat, Hans-jÜrgen; Babilon, Kenny; Fischer, Eberhard

2018-02-11

A new species of blind snake in the genus Letheobia is described from Akagera National Park in eastern Rwanda. The new species is most similar to species of the L. gracilis complex, particularly L. gracilis and L. graueri. It differs from all other species of the genus by a unique combination of morphological characters, including the highest number of middorsal scale rows (834) and the most extreme elongation (total-length/midbody-width ratio 131) of all species in the genus and of any species of snake in the world; 22-22-22 longitudinal scale rows; snout in dorsal profile rounded, in lateral profile bluntly rounded with an angular horizontal edge ventrally; rostral broad, posteriorly rounded; eyes invisible; supralabial imbrication pattern T-0; tail short (1.3 percent of total length) with an apical spine; and a pink life colouration. The holotype of the new species was collected in gallery forest at a lake shore surrounded by savanna at 1300 m elevation. We produced scanning electron microscope images of the heads of the investigated specimens applying a liquid-substitution preparation procedure which does not require coating or drying and thus does not irreversibly damage the investigated samples. The obtained images allow an easy and more accurate examination of the scalation.

Horizontal Directional Drilling-Length Detection Technology While Drilling Based on Bi-Electro-Magnetic Sensing.

PubMed

Wang, Yudan; Wen, Guojun; Chen, Han

2017-04-27

The drilling length is an important parameter in the process of horizontal directional drilling (HDD) exploration and recovery, but there has been a lack of accurate, automatically obtained statistics regarding this parameter. Herein, a technique for real-time HDD length detection and a management system based on the electromagnetic detection method with a microprocessor and two magnetoresistive sensors employing the software LabVIEW are proposed. The basic principle is to detect the change in the magnetic-field strength near a current coil while the drill stem and drill-stem joint successively pass through the current coil forward or backward. The detection system consists of a hardware subsystem and a software subsystem. The hardware subsystem employs a single-chip microprocessor as the main controller. A current coil is installed in front of the clamping unit, and two magneto resistive sensors are installed on the sides of the coil symmetrically and perpendicular to the direction of movement of the drill pipe. Their responses are used to judge whether the drill-stem joint is passing through the clamping unit; then, the order of their responses is used to judge the movement direction. The software subsystem is composed of a visual software running on the host computer and a software running in the slave microprocessor. The host-computer software processes, displays, and saves the drilling-length data, whereas the slave microprocessor software operates the hardware system. A combined test demonstrated the feasibility of the entire drilling-length detection system.

Horizontal Directional Drilling-Length Detection Technology While Drilling Based on Bi-Electro-Magnetic Sensing

PubMed Central

Wang, Yudan; Wen, Guojun; Chen, Han

2017-01-01

The drilling length is an important parameter in the process of horizontal directional drilling (HDD) exploration and recovery, but there has been a lack of accurate, automatically obtained statistics regarding this parameter. Herein, a technique for real-time HDD length detection and a management system based on the electromagnetic detection method with a microprocessor and two magnetoresistive sensors employing the software LabVIEW are proposed. The basic principle is to detect the change in the magnetic-field strength near a current coil while the drill stem and drill-stem joint successively pass through the current coil forward or backward. The detection system consists of a hardware subsystem and a software subsystem. The hardware subsystem employs a single-chip microprocessor as the main controller. A current coil is installed in front of the clamping unit, and two magneto resistive sensors are installed on the sides of the coil symmetrically and perpendicular to the direction of movement of the drill pipe. Their responses are used to judge whether the drill-stem joint is passing through the clamping unit; then, the order of their responses is used to judge the movement direction. The software subsystem is composed of a visual software running on the host computer and a software running in the slave microprocessor. The host-computer software processes, displays, and saves the drilling-length data, whereas the slave microprocessor software operates the hardware system. A combined test demonstrated the feasibility of the entire drilling-length detection system. PMID:28448445

Do the angle and length of the eustachian tube influence the development of chronic otitis media?

PubMed

Dinç, Aykut Erdem; Damar, Murat; Uğur, Mehmet Birol; Öz, Ibrahim Ilker; Eliçora, Sultan Şevik; Bişkin, Sultan; Tutar, Hakan

2015-09-01

To compare the eustachian tube (ET) angle (ETa) and length (ETl) of ears with and without chronic otitis media (COM), and to determine the relationship between ET anatomy and the development of COM. A retrospective case-control study. The study group comprised 125 patients (age range, 8-79 years; 64 males and 61 females) with 124 normal ears and 126 diseased ears, including ears with chronic suppurative otitis media (CSOM) with central perforation, intratympanic tympanosclerosis (ITTS), cholesteatoma, and a tympanic membrane with retraction pockets (TMRP). ET angle and length were measured using computed tomography employing the multiplanar reconstruction technique. The ETa was significantly more horizontal in diseased versus normal ears of all study groups (P = .030), and there was no group difference in ETl (P = .160). ETl was shorter in CSOM versus ITTS ears and normal ears (P = .007 and P = .003, respectively) and in cholesteatoma versus TMRP ears (P = .014). In the unilateral COM group, there were no significant differences in the ETa or ETl of diseased versus contralateral normal ears (P = .155 and P = .710, respectively). The ETa was significantly more horizontal in childhood-onset diseased versus normal ears (P = .027), and there was no group difference in ETl (P = .732). The ETa (P = .002) and ETl (P < .001) were significantly greater in males than females. A more horizontal ETa and shorter ETl could be contributory (though not significantly) etiological factors in the development of COM. 3b. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

A new species of Hyphessobrycon (Characiformes, Characidae) from the upper Guaviare River, Orinoco River Basin, Colombia

PubMed Central

García-Alzate, Carlos A.; Urbano-Bonilla, Alexander; Taphorn, Donald C.

2017-01-01

Abstract Hyphessobrycon klausanni sp. n. is described from small drainages of the upper Guaviare River (Orinoco River Basin) in Colombia. It differs from all congeners by having a wide, conspicuous, dark lateral stripe extending from the anterior margin of the eye across the body and continued through the middle caudal-fin rays, and that covers (vertically) three or four horizontal scale rows. It also differs by having an orange-yellow stripe extending from the anterosuperior margin of the eye to the caudal peduncle above the lateral line in life. It differs from all other species of Hyphessobrycon that have a similar dark lateral stripe: H. cyanotaenia, H. loretoensis, H. melanostichos, H. nigricinctus, H. herbertaxelrodi, H. eschwartzae, H. montogoi, H. psittacus, H. metae, H. margitae, H. vanzolinii, and H. peruvianus in having only three or four pored scales in the lateral line, 21 to 24 lateral scales and six teeth in the inner premaxillary row. Hyphessobrycon klausanni differs from H. loretoensis in having seven to eight maxillary teeth (vs. three to four) and in having a longer caudal peduncle (12.4–17.0% SL vs. 4.6–8.0% SL). Additionally Hyphessobrycon klausanni can be distinguished from the other species of Hyphessobrycon with a dark lateral stripe from the Orinoco River Basin (H. metae and H. acaciae) in having two teeth in the outer premaxillary row (vs. three to four) and 10 branched pectoral–fin rays (vs. 11 to 12). It further differs from H. metae by the length of the snout (17.6–22.8% HL vs. 9.9–15.2% HL) and by the length of the caudal peduncle (12.4–17.0% SL vs. 7.3–11.8% SL). PMID:28769647

Hydraulic Roughness and Flow Resistance in a Subglacial Conduit

NASA Astrophysics Data System (ADS)

Chen, Y.; Liu, X.; Mankoff, K. D.

2017-12-01

The hydraulic roughness significantly affects the flow resistance in real subglacial conduits, but has been poorly understood. To address this knowledge gap, this paper first proposes a procedure to define and quantify the geometry roughness, and then relates such a geometry roughness to the hydraulic roughness based on a series of computational fluid dynamics (CFD) simulations. The results indicate that by using the 2nd order structure function, the roughness field can be well quantified by the powers of the scaling-law, the vertical and horizontal length scales of the structure functions. The vertical length scale can be further chosen as the standard deviation of the roughness field σr. The friction factors calculated from either total drag force or the linear decreasing pressure agree very well with those calculated from traditional rough pipe theories when the equivalent hydraulic roughness height is corrected as ks = (1.1 ˜ 1.5)σr. This result means that the fully rough pipe resistance formula λ = [2 log(D0/2ks) + 1.74]-2, and the Moody diagram are still valid for the friction factor estimation in subglacial conduits when σr /D0<18% and ks/D0<22%. The results further show that when a proper hydraulic roughness is determined, the total flow resistance corresponding to the given hydraulic roughness height can be accurately modelled by using a rough wall function. This suggests that the flow resistance for the longer realistic subglacial conduits with large sinuosity and cross-sectional variations may be correctly predicted by CFD simulations. The results also show that the friction factors from CFD modeling are much larger than those determined from traditional rough pipe theories when σr /D0>20%.

Correlation Tests of the Ditching Behavior of an Army B-24D Airplane and a 1/16-size Model

NASA Technical Reports Server (NTRS)

Jarvis, George A.; Fisher, Lloyd J.

1946-01-01

Behaviors of both model and full-scale airplanes were ascertained by making visual observations, by recording time histories of decelerations, and by taking motion picture records of ditchings. Results are presented in form of sequence photographs and time-history curves for attitudes, vertical and horizontal displacements, and longitudinal decelerations. Time-history curves for attitudes and horizontal and vertical displacements for model and full-scale tests were in agreement; maximum longitudinal decelerations for both ditchings did not occur at same part of run; full-scale maximum deceleration was 50 percent greater.

Stress Distribution Around Single Short Dental Implants: A Finite Element Study.

PubMed

Vidya Bhat, S; Premkumar, Priyanka; Kamalakanth Shenoy, K

2014-12-01

Bone height restrictions are more common in the posterior regions of the mandible, because of either bone resorption resulting from tooth loss or even anatomic limitations, such as the position of the inferior alveolar nerve. In situations where adequate bone height is not available in the posterior mandible region, smaller lengths of implants may have to be used but it has been reported that the use of long implants (length ≥10 mm) is a positive factor in osseointegration and authors have reported failures with short implants. Hence knowledge about the stress generated on the bone with different lengths of implants needs scientific evaluation. The purpose of this study was to compare and evaluate the influence of different lengths of implants on stress upon bone in mandibular posterior area. A 3 D finite element model was made of the posterior mandible using the details from a CT scan, using computer software (ANSYS 12). Four simulated implants with lengths 6 mm, 8 mm, 10 mm and 13 mm were placed in the centre of the bone. A static vertical force of 250 N and a static horizontal force of 100 N were applied. The stress generated in the cortical and cancellous bone around the implant were recorded and evaluated with the help of ANSYS. In this study, Von Mises stress on a 6 mm implant under a static vertical load of 250 N appeared to be almost in the same range of 8 and 10 mm implant which were more as compared to 13 mm implant. Von Mises stress on a 6mm implant under a static horizontal load of 100 N appeared to be less when compared to 8, 10 and 13 mm implants. From the results obtained it may be inferred that under static horizontal loading conditions, shorter implants receive lesser load and thus may tend to transfer more stresses to the surrounding bone. While under static vertical loading the shorter implants bear more loads and comparatively transmit lesser load to the surrounding bone.

[Effects of ridge-cultivation and plastic film mulching on root distribution and yield of spring maize in hilly area of central Sichuan basin, China.

PubMed

Zha, Li; Xie, Meng Lin; Zhu, Min; Dou, Pan; Cheng, Qiu Bo; Wang, Xing Long; Yuan, Ji Chao; Kong, Fan Lei

2016-03-01

A field experiment was conducted to study the effects of planting pattern (ridge culture, flatten culture, furrow culture) and film mulching on the distribution of spring maize root system and their influence on the yield of spring maize in the hilly area of central Sichuan basin. The results showed that ridge and film mulching had great influence on root morphology and root distribution of maize. The root length, root surface area and root volume of film mulching was 42.3%, 50.0%, 57.4% higher than those of no film mulching at jointing stage. The film mulching significantly increased the dry mass of root in vertical and horizontal distribution, and increased the root allocation ratio in deeper soil layer (20-40 cm) and the allocation ratio of wide row (0-20 cm) in horizontal direction. The effects of planting pattern on root growth and root distribution differed by film mulching. With film mulching, the ridge culture significantly increased the root dry mass in each soil layer and enlarged the distribution percentage of wide row (20-40 cm) in horizontal direction, as well as the dry mass of root in horizontal distribution and the root allocation ratio of wide row. The root mass under film mulching was in the order of ridge culture>flatten culture>furrow culture. Without film mulching, the furrow culture significantly increased root dry mass of narrow row (0-40 cm), and the root mass under no film mulching was in the order of furrow culture > ridge culture >flatten culture. As for the spike characteristics and maize yield, the filming mulching mea-sures reduced the corn bald length while increased the spike length, grain number, 1000-grain mass and yield. The yield under film mulching was in the order of ridge culture>flatten culture> furrow culture, while it was furrow culture > flatten culture > ridge culture under no film mulching. The reason for yield increase under ridge culture with film mulching was that it increased root weight especially in deep soil, and promoted the root allocation ratio in deeper soil and wide row (20-40 cm) in horizontal direction. The ridge-furrow culture without film mulching was helpful to root growth and increased the maize yield.

An Idealized Test of the Response of the Community Atmosphere Model to Near-Grid-Scale Forcing Across Hydrostatic Resolutions

NASA Astrophysics Data System (ADS)

Herrington, A. R.; Reed, K. A.

2018-02-01

A set of idealized experiments are developed using the Community Atmosphere Model (CAM) to understand the vertical velocity response to reductions in forcing scale that is known to occur when the horizontal resolution of the model is increased. The test consists of a set of rising bubble experiments, in which the horizontal radius of the bubble and the model grid spacing are simultaneously reduced. The test is performed with moisture, through incorporating moist physics routines of varying complexity, although convection schemes are not considered. Results confirm that the vertical velocity in CAM is to first-order, proportional to the inverse of the horizontal forcing scale, which is consistent with a scale analysis of the dry equations of motion. In contrast, experiments in which the coupling time step between the moist physics routines and the dynamical core (i.e., the "physics" time step) are relaxed back to more conventional values results in severely damped vertical motion at high resolution, degrading the scaling. A set of aqua-planet simulations using different physics time steps are found to be consistent with the results of the idealized experiments.

A Composite Medium Approximation for Moisture Tension-Dependent Anisotropy in Unsaturated Layered Sediments

NASA Astrophysics Data System (ADS)

Pruess, K.

2001-12-01

Sedimentary formations often have a layered structure in which hydrogeologic properties have substantially larger correlation length in the bedding plane than perpendicular to it. Laboratory and field experiments and observations have shown that even small-scale layering, down to millimeter-size laminations, can substantially alter and impede the downward migration of infiltrating liquids, while enhancing lateral flow. The fundamental mechanism is that of a capillary barrier: at increasingly negative moisture tension (capillary suction pressure), coarse-grained layers with large pores desaturate more quickly than finer-grained media. This strongly reduces the hydraulic conductivity of the coarser (higher saturated hydraulic conductivity) layers, which then act as barriers to downward flow, forcing water to accumulate and spread near the bottom of the overlying finer-grained material. We present a "composite medium approximation" (COMA) for anisotropic flow behavior on a typical grid block scale (0.1 - 1 m or larger) in finite-difference models. On this scale the medium is conceptualized as consisting of homogeneous horizontal layers with uniform thickness, and capillary equilibrium is assumed to prevail locally. Directionally-dependent relative permeabilities are obtained by considering horizontal flow to proceed via "conductors in parallel," while vertical flow involves "resistors in series." The model is formulated for the general case of N layers, and implementation of a simplified two-layer (fine-coarse) approximation in the multiphase flow simulator TOUGH2 is described. The accuracy of COMA is evaluated by comparing numerical simulations of plume migration in 1-D and 2-D unsaturated flow with results of fine-grid simulations in which all layers are discretized explicitly. Applications to water seepage and solute transport at the Hanford site are also described. This work was supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098 through Memorandum Purchase Order 248861-A-B2 between Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory.

Influence of Tennis Racquet Kinematics on Ball Topspin Angular Velocity and Accuracy during the Forehand Groundstroke

PubMed Central

Kwon, Sunku; Pfister, Robin; Hager, Ronald L.; Hunter, Iain; Seeley, Matthew K.

2017-01-01

Forehand groundstroke effectiveness is important for tennis success. Ball topspin angular velocity (TAV) and accuracy are important for forehand groundstroke effectiveness, and have been extensively studied, previously; despite previous, quality studies, it was unclear whether certain racquet kinematics relate to ball TAV and shot accuracy during the forehand groundstroke. This study evaluated potential relationships between (1) ball TAV and (2) forehand accuracy, and five measures of racquet kinematics: racquet head impact angle (i.e., closed or open face), horizontal and vertical racquet head velocity before impact, racquet head trajectory (resultant velocity direction, relative to horizontal) before impact, and hitting zone length (quasi-linear displacement, immediately before and after impact). Thirteen collegiate-level tennis players hit forehand groundstrokes in a biomechanics laboratory, where racquet kinematics and ball TAV were measured, and on a tennis court, to assess accuracy. Correlational statistics were used to evaluate potential relationships between racquet kinematics, and ball TAV (mixed model) and forehand accuracy (between-subjects model; α = 0.05). We observed an average (1) racquet head impact angle, (2) racquet head trajectory before impact, relative to horizontal, (3) racquet head horizontal velocity before impact, (4) racquet head vertical velocity before impact, and (5) hitting zone length of 80.4 ± 3.6˚, 18.6 ± 4.3˚, 15.4 ± 1.4 m·s-1, 6.6 ± 2.2 m·s-1, and 79.8 ± 8.6 mm, respectively; and an average ball TAV of 969 ± 375 revolutions per minute. Only racquet head impact angle and racquet head vertical velocity, before impact, significantly correlated with ball TAV (p < 0.01). None of the observed racquet kinematics significantly correlated to the measures of forehand accuracy. These results confirmed mechanical logic and indicate that increased ball TAV is associated with a more closed racquet head impact angle (ranging from 70 to 85˚, relative to the ground) and increased racquet head vertical velocity before impact. Key points The study confirmed previous research that two key racquet kinematic variables, near impact, are significantly correlated to ball topspin angular velocity, during the forehand groundstroke: racquet head impact angle (i.e., open or closed racquet face) and racquet vertical velocity, before impact. The trajectory (direction of resultant velocity) and horizontal velocity of the racquet head before impact, and length of hitting zone were not significantly correlated to ball topspin angular velocity, or shot placement accuracy, during the tennis forehand groundstroke, for skilled male players. Hitting zone length was smaller than expected for skilled tennis players performing the forehand groundstroke. PMID:29238250

Mechanical and deformation analyses of pile foundation for supporting structure of off-shore wind turbine at Changhua coast in Taiwan

NASA Astrophysics Data System (ADS)

Wang, W. C.; Lin, D. G.

2015-12-01

This study investigates the bearing capacities and mechanical behaviors of pile foundation installed on the seabed of wind farm near Chang-Hua coast of western Taiwan for the supporting structure of offshore wind turbine. A series of three-dimensional (3-D) numerical modeling of pile foundation subjected to various types of combined loading were carried out using Plaix-3D finite element program to investigate the interactive behaviors between soil and pile. In the numerical modeling, pile diameter, pile length and pile spacing were selected as design parameters to inspect their effects on the bearing capacities and deformation behaviors of the pile foundation. For a specific design parameter combination, one can obtain the corresponding loading-displacement curve, various ultimate bearing capacities, V-H (Vertical-Horizontal combined loading) ultimate bearing capacity envelope, and p-ycurve of pile foundation. Numerical results indicate that: (1) Large displacement and plastic points at ultimate state mostly distribute and concentrate in the topsoil of seabed and around pile head. (2) The soil resistance on the soil-pile interface is ascending with the increases of depth, pile diameter and pile length. (3) The vertical and horizontal bearing capacities of pile group increase significantly with the increase of pile diameter. (4) The vertical and bending moment capacities of pile group increase greatly with the increase of pile length whereas the horizontal capacity is almost insensitive to pile length. (5) The bending moment of pile is highly influenced by the pile spacing. (6) For different design parameters, the shape of ultimate bearing capacity envelopes of pile group on V-H plane is similar while the envelopes will expand as the design parameters increase. For different loading levels of bending moment, the envelopes on V-H plane will contract gradually as the bending moment loading increasing.

PULSE AMPLITUDE ANALYSERS

DOEpatents

Lewis, I.A.D.

1956-05-15

This patent pentains to an electrical pulse amplitude analyzer, capable of accepting input pulses having a separation between adjacent pulses in the order of one microsecond while providing a large number of channels of classification. In its broad aspect the described pulse amplitude analyzer utilizes a storage cathode ray tube und control circuitry whereby the amplitude of the analyzed pulses controls both the intensity and vertical defiection of the beam to charge particular spots in horizontal sectors of the tube face as the beam is moved horizontally across the tube face. As soon as the beam has swept the length of the tube the information stored therein is read out by scanning individually each horizontal sector corresponding to a certain range of pulse amplitudes and applying the output signal from each scan to separate indicating means.

Spatial Variation of Diapycnal Diffusivity Estimated From Seismic Imaging of Internal Wave Field, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Dickinson, Alex; White, N. J.; Caulfield, C. P.

2017-12-01

Bright reflections are observed within the upper 1,000 m of the water column along a seismic reflection profile that traverses the northern margin of the Gulf of Mexico. Independent hydrographic calibration demonstrates that these reflections are primarily caused by temperature changes associated with different water masses that are entrained into the Gulf along the Loop Current. The internal wave field is analyzed by automatically tracking 1,171 reflections, each of which is greater than 2 km in length. Power spectra of the horizontal gradient of isopycnal displacement, ϕξx, are calculated from these tracked reflections. At low horizontal wave numbers (kx<10-2 cpm), ϕξx∝kx-0.2±0.6, in agreement with hydrographic observations of the internal wave field. The turbulent spectral subrange is rarely observed. Diapycnal diffusivity, K, is estimated from the observed internal wave spectral subrange of each tracked reflection using a fine-scale parametrization of turbulent mixing. Calculated values of K vary between 10-8 and 10-4 m2 s-1 with a mean value of K˜4×10-6 m2 s-1. The spatial distribution of turbulent mixing shows that K˜10-7 m2 s-1 away from the shelf edge in the upper 300 m where stratification is strong. Mixing is enhanced by up to 4 orders of magnitude adjacent to the shoaling bathymetry of the continental slope. This overall pattern matches that determined by analyzing nearby suites of CTD casts. However, the range of values recovered by spectral analysis of the seismic image is greater as a consequence of significantly better horizontal resolution.

Maximal liquid bridges between horizontal cylinders

NASA Astrophysics Data System (ADS)

Cooray, Himantha; Huppert, Herbert E.; Neufeld, Jerome A.

2016-08-01

We investigate two-dimensional liquid bridges trapped between pairs of identical horizontal cylinders. The cylinders support forces owing to surface tension and hydrostatic pressure that balance the weight of the liquid. The shape of the liquid bridge is determined by analytically solving the nonlinear Laplace-Young equation. Parameters that maximize the trapping capacity (defined as the cross-sectional area of the liquid bridge) are then determined. The results show that these parameters can be approximated with simple relationships when the radius of the cylinders is small compared with the capillary length. For such small cylinders, liquid bridges with the largest cross-sectional area occur when the centre-to-centre distance between the cylinders is approximately twice the capillary length. The maximum trapping capacity for a pair of cylinders at a given separation is linearly related to the separation when it is small compared with the capillary length. The meniscus slope angle of the largest liquid bridge produced in this regime is also a linear function of the separation. We additionally derive approximate solutions for the profile of a liquid bridge, using the linearized Laplace-Young equation. These solutions analytically verify the above-mentioned relationships obtained for the maximization of the trapping capacity.

Global Positioning System Antenna Fixed Height Tripod Adapter

NASA Technical Reports Server (NTRS)

Dinardo, Steven J.; Smith, Mark A.

1997-01-01

An improved Global Positioning em antenna adaptor allows fixed antenna height measurements by removably attaching an adaptor plate to a conventional surveyor's tripod. Antenna height is controlled by an antenna boom which is a fixed length rod. The antenna is attached to one end of the boom. The opposite end of the boom tapers to a point sized to fit into a depression at the center of survey markers. The boom passes through the hollow center of a universal ball joint which is mounted at the center of the adaptor plate so that the point of the rod can be fixed in the marker's central depression. The mountains of the ball joint allow the joint to be moved horizontally in any direction relative to the tripod. When the ball joint is moved horizontally, the angle between the boom and the vertical changes because the boom's position is fixed at its lower end. A spirit level attached to the rod allows an operator to determine when the boom is plumb. The position of the ball joint is adjusted horizontally until the boom is plumb. At that time the antenna is positioned exactly over the center of the monument and the elevation of the antenna is precisely set by the length of the boom.

Large-scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability

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

Bhat, Pallavi; Ebrahimi, Fatima; Blackman, Eric G.

Here, we study the dynamo generation (exponential growth) of large-scale (planar averaged) fields in unstratified shearing box simulations of the magnetorotational instability (MRI). In contrast to previous studies restricted to horizontal (x–y) averaging, we also demonstrate the presence of large-scale fields when vertical (y–z) averaging is employed instead. By computing space–time planar averaged fields and power spectra, we find large-scale dynamo action in the early MRI growth phase – a previously unidentified feature. Non-axisymmetric linear MRI modes with low horizontal wavenumbers and vertical wavenumbers near that of expected maximal growth, amplify the large-scale fields exponentially before turbulence and high wavenumbermore » fluctuations arise. Thus the large-scale dynamo requires only linear fluctuations but not non-linear turbulence (as defined by mode–mode coupling). Vertical averaging also allows for monitoring the evolution of the large-scale vertical field and we find that a feedback from horizontal low wavenumber MRI modes provides a clue as to why the large-scale vertical field sustains against turbulent diffusion in the non-linear saturation regime. We compute the terms in the mean field equations to identify the individual contributions to large-scale field growth for both types of averaging. The large-scale fields obtained from vertical averaging are found to compare well with global simulations and quasi-linear analytical analysis from a previous study by Ebrahimi & Blackman. We discuss the potential implications of these new results for understanding the large-scale MRI dynamo saturation and turbulence.« less

Large-scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability

DOE PAGES

Bhat, Pallavi; Ebrahimi, Fatima; Blackman, Eric G.

2016-07-06

Here, we study the dynamo generation (exponential growth) of large-scale (planar averaged) fields in unstratified shearing box simulations of the magnetorotational instability (MRI). In contrast to previous studies restricted to horizontal (x–y) averaging, we also demonstrate the presence of large-scale fields when vertical (y–z) averaging is employed instead. By computing space–time planar averaged fields and power spectra, we find large-scale dynamo action in the early MRI growth phase – a previously unidentified feature. Non-axisymmetric linear MRI modes with low horizontal wavenumbers and vertical wavenumbers near that of expected maximal growth, amplify the large-scale fields exponentially before turbulence and high wavenumbermore » fluctuations arise. Thus the large-scale dynamo requires only linear fluctuations but not non-linear turbulence (as defined by mode–mode coupling). Vertical averaging also allows for monitoring the evolution of the large-scale vertical field and we find that a feedback from horizontal low wavenumber MRI modes provides a clue as to why the large-scale vertical field sustains against turbulent diffusion in the non-linear saturation regime. We compute the terms in the mean field equations to identify the individual contributions to large-scale field growth for both types of averaging. The large-scale fields obtained from vertical averaging are found to compare well with global simulations and quasi-linear analytical analysis from a previous study by Ebrahimi & Blackman. We discuss the potential implications of these new results for understanding the large-scale MRI dynamo saturation and turbulence.« less

Relationship between macroscopic and microphysical properties for mixed-phase and ice clouds over the Southern Ocean in ORCAS campaign

NASA Astrophysics Data System (ADS)

Diao, M.; Jensen, J. B.

2017-12-01

Mixed-phase and ice clouds play very important roles in regulating the atmospheric radiation over the Southern Ocean. Previously, in-situ observations over this remote region are limited, and a few of the available observation-based analyses mainly focused on the cloud microphysical properties. The relationship between macroscopic and microphysical properties for both mixed-phase and ice clouds have not been thoroughly investigated based on in-situ observations. In this work, the aircraft-based observations from the NSF O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) field campaign (Jan - Feb 2016) will be used to analyze the cloud macroscopic properties on the microscale to mesoscale, including the distributions of cloud chord length, the patchiness of clouds, and the spatial ratios of adjacent cloud segments in mixed phase and pure ice phase. In addition, these macroscopic properties will be analyzed in relation to the relative humidity (RH) background, such as the average and maximum RH inside clouds, as well as the probability density function (PDF) of in-cloud RH. We found that the clouds with larger horizontal scales are often associated with larger magnitudes of average and maximum in-cloud RH values. In addition, when decomposing the contributions from the spatial variabilities of water vapor and temperature to the variability of RH, the water vapor heterogeneities are found to have the most dominant impact on RH variability. Sensitivities of the cloud macroscopic and microphysical properties to the horizontal resolutions of the observations will be shown, including the impacts on the patchiness of clouds, cloud fraction, frequencies of ice supersaturation, and the PDFs of RH. These sensitivity analyses will provide useful information on the comparisons among multi-scale observations and simulations.

Estimating the Instantaneous Drag-Wind Relationship for a Horizontally Homogeneous Canopy

NASA Astrophysics Data System (ADS)

Pan, Ying; Chamecki, Marcelo; Nepf, Heidi M.

2016-07-01

The mean drag-wind relationship is usually investigated assuming that field data are representative of spatially-averaged metrics of statistically stationary flow within and above a horizontally homogeneous canopy. Even if these conditions are satisfied, large-eddy simulation (LES) data suggest two major issues in the analysis of observational data. Firstly, the streamwise mean pressure gradient is usually neglected in the analysis of data from terrestrial canopies, which compromises the estimates of mean canopy drag and provides misleading information for the dependence of local mean drag coefficients on local velocity scales. Secondly, no standard approach has been proposed to investigate the instantaneous drag-wind relationship, a critical component of canopy representation in LES. Here, a practical approach is proposed to fit the streamwise mean pressure gradient using observed profiles of the mean vertical momentum flux within the canopy. Inclusion of the fitted mean pressure gradient enables reliable estimates of the mean drag-wind relationship. LES data show that a local mean drag coefficient that characterizes the relationship between mean canopy drag and the velocity scale associated with total kinetic energy can be used to identify the dependence of the local instantaneous drag coefficient on instantaneous velocity. Iterative approaches are proposed to fit specific models of velocity-dependent instantaneous drag coefficients that represent the effects of viscous drag and the reconfiguration of flexible canopy elements. LES data are used to verify the assumptions and algorithms employed by these new approaches. The relationship between mean canopy drag and mean velocity, which is needed in models based on the Reynolds-averaged Navier-Stokes equations, is parametrized to account for both the dependence on velocity and the contribution from velocity variances. Finally, velocity-dependent drag coefficients lead to significant variations of the calculated displacement height and roughness length with wind speed.

Ballasting pipeline moving in horizontal well as method of control sticking phenomenon

NASA Astrophysics Data System (ADS)

Toropov, V. S.; Toropov, E. S.

2018-05-01

The mechanism of the phenomenon of sticking a pipeline moving in a well while pulled by the facility horizontal directional drilling is investigated. A quantitative evaluation of the force arising from sticking is given. At the same time, the working hypothesis takes a view of the combined effect of adhesion and friction interactions as the reasons that cause this phenomenon. As a measure to control the occurrence of sticking and to reduce the resistance force to movement of the pipeline in the well, several methods of ballasting the working pipeline are proposed, depending on the profile of the well and the ratio of the length of the curved sections of the inlet and outlet and the straight horizontal sections of the profile. It is shown that for crossings, which profile contains an extended horizontal section, it is possible to partially fill the pipeline with water to achieve zero buoyancy, and for crossings with curvature along the entire profile, the ballasting efficiency will be minimal.

Comparison of Large eddy dynamo simulation using dynamic sub-grid scale (SGS) model with a fully resolved direct simulation in a rotating spherical shell

NASA Astrophysics Data System (ADS)

Matsui, H.; Buffett, B. A.

2017-12-01

The flow in the Earth's outer core is expected to have vast length scale from the geometry of the outer core to the thickness of the boundary layer. Because of the limitation of the spatial resolution in the numerical simulations, sub-grid scale (SGS) modeling is required to model the effects of the unresolved field on the large-scale fields. We model the effects of sub-grid scale flow and magnetic field using a dynamic scale similarity model. Four terms are introduced for the momentum flux, heat flux, Lorentz force and magnetic induction. The model was previously used in the convection-driven dynamo in a rotating plane layer and spherical shell using the Finite Element Methods. In the present study, we perform large eddy simulations (LES) using the dynamic scale similarity model. The scale similarity model is implement in Calypso, which is a numerical dynamo model using spherical harmonics expansion. To obtain the SGS terms, the spatial filtering in the horizontal directions is done by taking the convolution of a Gaussian filter expressed in terms of a spherical harmonic expansion, following Jekeli (1981). A Gaussian field is also applied in the radial direction. To verify the present model, we perform a fully resolved direct numerical simulation (DNS) with the truncation of the spherical harmonics L = 255 as a reference. And, we perform unresolved DNS and LES with SGS model on coarser resolution (L= 127, 84, and 63) using the same control parameter as the resolved DNS. We will discuss the verification results by comparison among these simulations and role of small scale fields to large scale fields through the role of the SGS terms in LES.

Supergranulation, a convective phenomenon

NASA Astrophysics Data System (ADS)

Udayashankar, Paniveni

2015-08-01

Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection ,Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2004, MNRAS, 347, 1279-12814) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2005, Solar Physics, 231, 1-105) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2010, MNRAS, 402, Issue 1, 424-428

Supergranular Convection

NASA Astrophysics Data System (ADS)

Udayashankar, Paniveni

2015-12-01

Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Here the opacity is so large that heat flux transport is mainly by convection rather than by photon diffusion. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection , Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2004, MNRAS, 347, 1279-12814) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2005, Solar Physics, 231, 1-105) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2010, MNRAS, 402, Issue 1, 424-428

Effects of Word Width and Word Length on Optimal Character Size for Reading of Horizontally Scrolling Japanese Words

PubMed Central

Teramoto, Wataru; Nakazaki, Takuyuki; Sekiyama, Kaoru; Mori, Shuji

2016-01-01

The present study investigated, whether word width and length affect the optimal character size for reading of horizontally scrolling Japanese words, using reading speed as a measure. In Experiment 1, three Japanese words, each consisting of four Hiragana characters, sequentially scrolled on a display screen from right to left. Participants, all Japanese native speakers, were instructed to read the words aloud as accurately as possible, irrespective of their order within the sequence. To quantitatively measure their reading performance, we used rapid serial visual presentation paradigm, where the scrolling rate was increased until the participants began to make mistakes. Thus, the highest scrolling rate at which the participants’ performance exceeded 88.9% correct rate was calculated for each character size (0.3°, 0.6°, 1.0°, and 3.0°) and scroll window size (5 or 10 character spaces). Results showed that the reading performance was highest in the range of 0.6° to 1.0°, irrespective of the scroll window size. Experiment 2 investigated whether the optimal character size observed in Experiment 1 was applicable for any word width and word length (i.e., the number of characters in a word). Results showed that reading speeds were slower for longer than shorter words and the word width of 3.6° was optimal among the word lengths tested (three, four, and six character words). Considering that character size varied depending on word width and word length in the present study, this means that the optimal character size can be changed by word width and word length in scrolling Japanese words. PMID:26909052

Effects of Word Width and Word Length on Optimal Character Size for Reading of Horizontally Scrolling Japanese Words.

PubMed

Teramoto, Wataru; Nakazaki, Takuyuki; Sekiyama, Kaoru; Mori, Shuji

2016-01-01

The present study investigated, whether word width and length affect the optimal character size for reading of horizontally scrolling Japanese words, using reading speed as a measure. In Experiment 1, three Japanese words, each consisting of four Hiragana characters, sequentially scrolled on a display screen from right to left. Participants, all Japanese native speakers, were instructed to read the words aloud as accurately as possible, irrespective of their order within the sequence. To quantitatively measure their reading performance, we used rapid serial visual presentation paradigm, where the scrolling rate was increased until the participants began to make mistakes. Thus, the highest scrolling rate at which the participants' performance exceeded 88.9% correct rate was calculated for each character size (0.3°, 0.6°, 1.0°, and 3.0°) and scroll window size (5 or 10 character spaces). Results showed that the reading performance was highest in the range of 0.6° to 1.0°, irrespective of the scroll window size. Experiment 2 investigated whether the optimal character size observed in Experiment 1 was applicable for any word width and word length (i.e., the number of characters in a word). Results showed that reading speeds were slower for longer than shorter words and the word width of 3.6° was optimal among the word lengths tested (three, four, and six character words). Considering that character size varied depending on word width and word length in the present study, this means that the optimal character size can be changed by word width and word length in scrolling Japanese words.

Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Brunner, D.; Kuang, A. Q.; LaBombard, B.; Burke, W.

2017-07-01

A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density—through use of a mirror Langmuir probe bias system—combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. In addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.

Seismic, satellite, and site observations of internal solitary waves in the NE South China Sea.

PubMed

Tang, Qunshu; Wang, Caixia; Wang, Dongxiao; Pawlowicz, Rich

2014-06-20

Internal solitary waves (ISWs) in the NE South China Sea (SCS) are tidally generated at the Luzon Strait. Their propagation, evolution, and dissipation processes involve numerous issues still poorly understood. Here, a novel method of seismic oceanography capable of capturing oceanic finescale structures is used to study ISWs in the slope region of the NE SCS. Near-simultaneous observations of two ISWs were acquired using seismic and satellite imaging, and water column measurements. The vertical and horizontal length scales of the seismic observed ISWs are around 50 m and 1-2 km, respectively. Wave phase speeds calculated from seismic observations, satellite images, and water column data are consistent with each other. Observed waveforms and vertical velocities also correspond well with those estimated using KdV theory. These results suggest that the seismic method, a new option to oceanographers, can be further applied to resolve other important issues related to ISWs.

Large scale production of densified hydrogen to the triple point and below

NASA Astrophysics Data System (ADS)

Swanger, A. M.; Notardonato, W. U.; E Fesmire, J.; Jumper, K. M.; Johnson, W. L.; Tomsik, T. M.

2017-12-01

Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage technology at NASA Kennedy Space Center led to the production of large quantities of densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. Overall densification performance of the system is explored, and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing, and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. The phenomenon, observed at two fill levels, is detailed herein. The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed.

The Principle and Structure of the Gyupyo(Gnomon) of King Sejong's Reign in Choson Dynasty

NASA Astrophysics Data System (ADS)

Lee, Yong Sam; Jeong, Jang Hae; Kim, Chun-Hwey; Kim, Sang Hyuk

2006-09-01

For a reconstruct draft of the Gyupyo (Gnomon) in King Sejong Era, we collected a lot of documents of the Choson Dynasty. With the result we made a reduced model by 1/10 and drawing set for the Gnomon in Sejong Era. It is composed of the Gyu, Yongpyo, Hoengryang (a beam), Yeongbu and granitic prop. You can read the scale where the shadow of vertically-standing stick touches the horizontal Gyu. A Shadow-Definer (Yeongbu) was used to focus the shadow cast by the sun's center, measuring the (gnomon) shadow length precisely. A Yeongbu is made of a leaf of copper in the middle of which is pierced a pin-hole for the tiny optical image of the sun which tilted to face the incident sunlight, used the principle of the a pin-hole camera and Scheimplug principle.

Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

PubMed

Jenke, T; Cronenberg, G; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H

2014-04-18

We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14  eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20  μm (95% C.L.).

Large Scale Production of Densified Hydrogen to the Triple Point and Below

NASA Technical Reports Server (NTRS)

Swanger, A. M.; Notardonato, W. U.; Fesmire, J. E.; Jumper, K. M.; Johnson, W. L.; Tomsik, T. M.

2017-01-01

Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage technology at NASA Kennedy Space Center led to the production of large quantities of densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. Overall densification performance of the system is explored, and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing, and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. The phenomenon, observed at two fill levels, is detailed herein. The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed.

CATS Version 2 Aerosol Feature Detection and Applications for Data Assimilation

NASA Technical Reports Server (NTRS)

Nowottnick, Ed; Yorks, John; McGill, Matt; Scott, Stan; Palm, Stephen; Hlavka, Dennis; Hart, William; Selmer, Patrick; Kupchock, Andrew; Pauly, Rebecca

2017-01-01

Using GEOS-5, we are developing a 1D ENS approach for assimilating CATS near real time observations of total attenuated backscatter at 1064 nm: a) After performing a 1-ENS assimilation of a cloud-free profile, the GEOS-5 analysis closely followed observed total attenuated backscatter. b) Vertical localization length scales were varied for the well-mixed PBL and the free troposphere After assimilating a cloud free segment of a CATS granule, the fine detail of a dust event was obtained in the GEOS-5 analysis for both total attenuated backscatter and extinction. Future Work: a) Explore horizontal localization and test within a cloudy aerosol layer. b) Address noisy analysis increments in the free troposphere where both CATS and GEOS-5 aerosol loadings are low. c) Develop a technique to screen CATS ground return from profiles. d) "Dynamic" lidar ratio that will evolve in conjunction with simulated aerosol mixtures.

Crystallization process of a three-dimensional complex plasma

NASA Astrophysics Data System (ADS)

Steinmüller, Benjamin; Dietz, Christopher; Kretschmer, Michael; Thoma, Markus H.

2018-05-01

Characteristic timescales and length scales for phase transitions of real materials are in ranges where a direct visualization is unfeasible. Therefore, model systems can be useful. Here, the crystallization process of a three-dimensional complex plasma under gravity conditions is considered where the system ranges up to a large extent into the bulk plasma. Time-resolved measurements exhibit the process down to a single-particle level. Primary clusters, consisting of particles in the solid state, grow vertically and, secondarily, horizontally. The box-counting method shows a fractal dimension of df≈2.72 for the clusters. This value gives a hint that the formation process is a combination of local epitaxial and diffusion-limited growth. The particle density and the interparticle distance to the nearest neighbor remain constant within the clusters during crystallization. All results are in good agreement with former observations of a single-particle layer.

The impact of resolution on the dynamics of the martian global atmosphere: Varying resolution studies with the MarsWRF GCM

NASA Astrophysics Data System (ADS)

Toigo, Anthony D.; Lee, Christopher; Newman, Claire E.; Richardson, Mark I.

2012-09-01

We investigate the sensitivity of the circulation and thermal structure of the martian atmosphere to numerical model resolution in a general circulation model (GCM) using the martian implementation (MarsWRF) of the planetWRF atmospheric model. We provide a description of the MarsWRF GCM and use it to study the global atmosphere at horizontal resolutions from 7.5° × 9° to 0.5° × 0.5°, encompassing the range from standard Mars GCMs to global mesoscale modeling. We find that while most of the gross-scale features of the circulation (the rough location of jets, the qualitative thermal structure, and the major large-scale features of the surface level winds) are insensitive to horizontal resolution over this range, several major features of the circulation are sensitive in detail. The northern winter polar circulation shows the greatest sensitivity, showing a continuous transition from a smooth polar winter jet at low resolution, to a distinct vertically “split” jet as resolution increases. The separation of the lower and middle atmosphere polar jet occurs at roughly 10 Pa, with the split jet structure developing in concert with the intensification of meridional jets at roughly 10 Pa and above 0.1 Pa. These meridional jets appear to represent the separation of lower and middle atmosphere mean overturning circulations (with the former being consistent with the usual concept of the “Hadley cell”). Further, the transition in polar jet structure is more sensitive to changes in zonal than meridional horizontal resolution, suggesting that representation of small-scale wave-mean flow interactions is more important than fine-scale representation of the meridional thermal gradient across the polar front. Increasing the horizontal resolution improves the match between the modeled thermal structure and the Mars Climate Sounder retrievals for northern winter high latitudes. While increased horizontal resolution also improves the simulation of the northern high latitudes at equinox, even the lowest model resolution considered here appears to do a good job for the southern winter and southern equinoctial pole (although in detail some discrepancies remain). These results suggest that studies of the northern winter jet (e.g., transient waves and cyclogenesis) will be more sensitive to global model resolution that those of the south (e.g., the confining dynamics of the southern polar vortex relevant to studies of argon transport). For surface winds, the major effect of increased horizontal resolution is in the superposition of circulations forced by local-scale topography upon the large-scale surface wind patterns. While passive predictions of dust lifting are generally insensitive to model horizontal resolution when no lifting threshold is considered, increasing the stress threshold produces significantly more lifting in higher resolution simulations with the generation of finer-scale, higher-stress winds due primarily to better-resolved topography. Considering the positive feedbacks expected for radiatively active dust lifting, we expect this bias to increase when such feedbacks are permitted.

Internal Gravity Waves Forced by an Isolated Mountain

NASA Astrophysics Data System (ADS)

Nikitina, L.; Campbell, L.

2009-12-01

Density-stratified fluid flow over topography such as mountains, hills and ridges may give rise to internal gravity waves which transport and distribute energy away from their source and have profound effects on the general circulation of the atmosphere and ocean. Much of our knowledge of internal gravity wave dynamics has been acquired from theoretical studies involving mathematical analyses of simplified forms of the governing equations, as well as numerical simulations at varying levels of approximation. In this study, both analytical and numerical methods are used to examine the nonlinear dynamics of gravity waves forced by an isolated mountain. The topography is represented by a lower boundary condition on a two-dimensional rectangular domain and the waves are represented as a perturbation to the background shear flow, thus allowing the use of weakly-nonlinear and multiple-scale asymptotic analyzes. The waves take the form of a packet, localized in the horizontal direction and comprising a continuous spectrum of horizontal wavenumbers centered at zero. For horizontally-localized wave packets, such as those forced by a mountain range with multiple peaks, there are generally two horizontal scales, the fast (short) scale which is defined by the oscillations within the packet and the slow (large) scale which is defined by the horizontal extent of the packet. In the case of an isolated mountain that we examine here, the multiple-scaling procedure is simplified by the absence of a fast spatial scale. The problem is governed by two small parameters that define the height and width of the mountain and approximate solutions are derived in terms of these parameters. Numerical solutions are also carried out to simulate nonlinear critical-level interactions such as the transfer of energy to the background flow by the wave packet, wave reflection and static instability and, eventually, wave breaking leading to turbulence. It is found that for waves forced by an isolated mountain the time frame within which these nonlinear effects become significant depends on both the mountain height and width and that they begin to occur at least an order of magnitude later and the configuration thus remains stable longer than in the case of waves forced by a mountain range of equivalent height.

A dynamic subgrid-scale parameterization of the effective wall stress in atmospheric boundary layer flows over multiscale, fractal-like surfaces

NASA Astrophysics Data System (ADS)

Anderson, William; Meneveau, Charles

2010-05-01

A dynamic subgrid-scale (SGS) parameterization for hydrodynamic surface roughness is developed for large-eddy simulation (LES) of atmospheric boundary layer (ABL) flow over multiscale, fractal-like surfaces. The model consists of two parts. First, a baseline model represents surface roughness at horizontal length-scales that can be resolved in the LES. This model takes the form of a force using a prescribed drag coefficient. This approach is tested in LES of flow over cubes, wavy surfaces, and ellipsoidal roughness elements for which there are detailed experimental data available. Secondly, a dynamic roughness model is built, accounting for SGS surface details of finer resolution than the LES grid width. The SGS boundary condition is based on the logarithmic law of the wall, where the unresolved roughness of the surface is modeled as the product of local root-mean-square (RMS) of the unresolved surface height and an unknown dimensionless model coefficient. This coefficient is evaluated dynamically by comparing the plane-average hydrodynamic drag at two resolutions (grid- and test-filter scale, Germano et al., 1991). The new model is tested on surfaces generated through superposition of random-phase Fourier modes with prescribed, power-law surface-height spectra. The results show that the method yields convergent results and correct trends. Limitations and further challenges are highlighted. Supported by the US National Science Foundation (EAR-0609690).

Multi Scale Modeling of Continuous Aramid Fiber Reinforced Polymer Matrix Composites Used in Ballistic Protection Applications

DTIC Science & Technology

2014-11-16

related to identification of the type and the extent of data generated at a finer length scale to the adjacent coarser length scale, as well as seamless ...data generated at a finer length scale to the adjacent coarser length scale, as well as seamless integration of different length scales into a unified...composite laminate consisting of 32 laminae and impacted (at a 0° obliquity angle and an incident velocity of 500 m/s) by a 0.30 caliber steel

Atmospheric circulation of brown dwarfs and directly imaged extrasolar giant planets with active clouds

NASA Astrophysics Data System (ADS)

Tan, Xianyu; Showman, Adam

2016-10-01

Observational evidence have suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys for brown dwarfs showed that near-IR brightness variability is common for L and T dwarfs. Directly imaged EGPs share similar observations, and can be viewed as low-gravity versions of BDs. Clouds are believed to play the major role in shaping the thermal structure, dynamics and near-IR flux of these atmospheres. So far, only a few studies have been devoted to atmospheric circulation and the implications for observations of BDs and directly EGPs, and yet no global model includes a self-consistent active cloud formation. Here we present preliminary results from the first global circulation model applied to BDs and directly imaged EGPs that can properly treat absorption and scattering of radiation by cloud particles. Our results suggest that horizontal temperature differences on isobars can reach up to a few hundred Kelvins, with typical horizontal length scale of the temperature and cloud patterns much smaller than the radius of the object. The combination of temperature anomaly and cloud pattern can result in moderate disk-integrated near-IR flux variability. Wind speeds can reach several hundred meters per second in cloud forming layers. Unlike Jupiter and Saturn, we do not observe stable zonal jet/banded patterns in our simulations. Instead, our simulated atmospheres are typically turbulent and dominated by transient vortices. The circulation is sensitive to the parameterized cloud microphysics. Under some parameter combinations, global-scale atmospheric waves can be triggered and maintained. These waves induce global-scale temperature anomalies and cloud patterns, causing large (up to several percent) disk-integrated near-IR flux variability. Our results demonstrate that the commonly observed near-IR brightness variability for BDs and directly imaged EGPs can be explained by the typical cloud-induced turbulent circulation, and in particular, the large flux variability for some objects can be attributed to the global-scale patterns of temperature anomaly and cloud formation caused by atmospheric waves.

Evaluating 20th Century precipitation characteristics between multi-scale atmospheric models with different land-atmosphere coupling

NASA Astrophysics Data System (ADS)

Phillips, M.; Denning, A. S.; Randall, D. A.; Branson, M.

2016-12-01

Multi-scale models of the atmosphere provide an opportunity to investigate processes that are unresolved by traditional Global Climate Models while at the same time remaining viable in terms of computational resources for climate-length time scales. The MMF represents a shift away from large horizontal grid spacing in traditional GCMs that leads to overabundant light precipitation and lack of heavy events, toward a model where precipitation intensity is allowed to vary over a much wider range of values. Resolving atmospheric motions on the scale of 4 km makes it possible to recover features of precipitation, such as intense downpours, that were previously only obtained by computationally expensive regional simulations. These heavy precipitation events may have little impact on large-scale moisture and energy budgets, but are outstanding in terms of interaction with the land surface and potential impact on human life. Three versions of the Community Earth System Model were used in this study; the standard CESM, the multi-scale `Super-Parameterized' CESM where large-scale parameterizations have been replaced with a 2D cloud-permitting model, and a multi-instance land version of the SP-CESM where each column of the 2D CRM is allowed to interact with an individual land unit. These simulations were carried out using prescribed Sea Surface Temperatures for the period from 1979-2006 with daily precipitation saved for all 28 years. Comparisons of the statistical properties of precipitation between model architectures and against observations from rain gauges were made, with specific focus on detection and evaluation of extreme precipitation events.

Analysis of the moments of the sensitivity function for resistivity over a homogeneous half-space: Rules of thumb for pseudoposition, offline sensitivity and resolution

NASA Astrophysics Data System (ADS)

Butler, S. L.

2017-08-01

It is instructive to consider the sensitivity function for a homogeneous half space for resistivity since it has a simple mathematical formula and it does not require a priori knowledge of the resistivity of the ground. Past analyses of this function have allowed visualization of the regions that contribute most to apparent resistivity measurements with given array configurations. The horizontally integrated form of this equation gives the sensitivity function for an infinitesimally thick horizontal slab with a small resistivity contrast and analysis of this function has admitted estimates of the depth of investigation for a given electrode array. Recently, it has been shown that the average of the vertical coordinate over this function yields a simple formula that can be used to estimate the depth of investigation. The sensitivity function for a vertical inline slab has also been previously calculated. In this contribution, I show that the sensitivity function for a homogeneous half-space can also be integrated so as to give sensitivity functions to semi-infinite vertical slabs that are perpendicular to the array axis. These horizontal sensitivity functions can, in turn, be integrated over the spatial coordinates to give the mean horizontal positions of the sensitivity functions. The mean horizontal positions give estimates for the centres of the regions that affect apparent resistivity measurements for arbitrary array configuration and can be used as horizontal positions when plotting pseudosections even for non-collinear arrays. The mean of the horizontal coordinate that is perpendicular to a collinear array also gives a simple formula for estimating the distance over which offline resistivity anomalies will have a significant effect. The root mean square (rms) widths of the sensitivity functions are also calculated in each of the coordinate directions as an estimate of the inverse of the resolution of a given array. For depth and in the direction perpendicular to the array, the rms thickness is shown to be very similar to the mean distance. For the direction parallel to the array, the rms thickness is shown to be proportional to the array length and similar to the array length divided by 2 for many arrays. I expect that these formulas will provide useful rules of thumb for estimating the centres and extents of regions influencing apparent resistivity measurements for survey planning and for education.

Multifractal Analysis of the Small Time-Scale Boundary-Layer Characteristics of the Wind: the Anisotropy and Extremes

NASA Astrophysics Data System (ADS)

Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

2012-12-01

Under various physical conditions (mean temperature and velocity gradients, stratification and rotation) atmospheric turbulent flows remain intrinsically anisotropic. The immediate vicinity of physical boundaries rises to a greater complexity of the anisotropy effects. In this paper we address the issue of the scaling anisotropy of the wind velocity fields within the atmospheric boundary layer (ABL). Under the universal multifractal (UM) framework we compare the small time-scale (0.1 to 1,000 seconds) boundary-layer characteristics of the wind for two different case studies. The first case study consisted of a single mast located within a wind farm in Corsica, France. Three sonic anemometers were installed on the mast at 22, 23 and 43m, measuring three-dimensional wind velocity data at 10Hz. Wakes, complex terrain and buoyancy forces influenced the measurements. The second case study (GROWIAN experiment in Germany) consisted of an array of propeller anemometers measuring wind speed inflow data at 2.5Hz over flat terrain. The propeller anemometers were positioned vertically at 10, 50, 75, 100, 125 and 150m with four horizontal measurements taken at 75, 100 and 125m. The spatial distribution allowed us to calculate the horizontal and vertical shear structure functions of the horizontal wind. Both case studies are within a kilometre from the sea. For the first case study (10Hz measurements in a wind farm test site) the high temporal resolution of the data meant we observed Kolmogorov scaling from 0.2 seconds (with intermittency correction) right up to 1,000 seconds at which point a scaling break occurred. After the break we observed a scaling power law of approximately 2, which is in agreement with Bolgiano-Obukhov scaling theory with intermittency correction. However, for the second case study (2.5Hz on flat terrain) we only observed Kolmogorov scaling from 6.4 seconds (also with intermittency correction). The spectra of horizontal velocity components remain anisotropic over high frequencies, where u1 most scales as Bolgiano-Obukhov and u2 scales as Kolmogorov. The scaling law of the vertical shears of the horizontal wind in the array varied from Kolmogorov to Bolgiano-Obukhov with height depending on the condition of stability. We interpret the results with the UM anisotropic model that greatly enhances our understanding of the ABL structure. Comparing the two case studies we found in both cases the multifractality parameter of about 1.6, which remains close to the estimates obtained for the free atmosphere. From the UM parameters, the exponent of the power law of the distribution of the extremes can be predicted. Over small scales, this exponent is of about 7.5 for the wind velocity, which is a crucial result for applications within the field of wind energy.

Scanning dimensional measurement using laser-trapped microsphere with optical standing-wave scale

NASA Astrophysics Data System (ADS)

Michihata, Masaki; Ueda, Shin-ichi; Takahashi, Satoru; Takamasu, Kiyoshi; Takaya, Yasuhiro

2017-06-01

We propose a laser trapping-based scanning dimensional measurement method for free-form surfaces. We previously developed a laser trapping-based microprobe for three-dimensional coordinate metrology. This probe performs two types of measurements: a tactile coordinate and a scanning measurement in the same coordinate system. The proposed scanning measurement exploits optical interference. A standing-wave field is generated between the laser-trapped microsphere and the measured surface because of the interference from the retroreflected light. The standing-wave field produces an effective length scale, and the trapped microsphere acts as a sensor to read this scale. A horizontal scan of the trapped microsphere produces a phase shift of the standing wave according to the surface topography. This shift can be measured from the change in the microsphere position. The dynamics of the trapped microsphere within the standing-wave field was estimated using a harmonic model, from which the measured surface can be reconstructed. A spherical lens was measured experimentally, yielding a radius of curvature of 2.59 mm, in agreement with the nominal specification (2.60 mm). The difference between the measured points and a spherical fitted curve was 96 nm, which demonstrates the scanning function of the laser trapping-based microprobe for free-form surfaces.

Large Kelvin-Helmholtz Billow Trains Observed in the Kuroshio above a Seamount

NASA Astrophysics Data System (ADS)

Chang, M. H.; Jheng, S. Y.; Lien, R. C.

2016-02-01

Trains of large Kelvin-Helmholtz (KH) billows were observed within the Kuroshio core, off southeastern Taiwan, at 230-m depth above a seamount in shipboard echo sounder, ADCP, and LADCP/CTD profiling, and moored ADCP measurements. The large KH billow trains were present in a strong shear band along 0.55 ms-1 isotach within the Kuroshio core as a result of the Kuroshio current interacting with the rapid changing topography. Each individual billow, resembling a cats' eye, had a horizontal length scale of 200 m and a vertical amplitude scale of 100 m, and a propagation timescale of 7 minutes, near local buoyancy period. Overturns were frequently observed in both the billow core and the upper eyelid. The shear instability criterion (Ri < 0.25) was reached in the billow core. The dissipation rate of turbulent kinetic energy in the core and in the eyelid is comparable at an average value of O(10-4) WKg-1 and a maximum value of O(10-3) WKg-1. The KH billows derive energy from the Kuroshio kinetic energy. The corresponding turbulence mixing allows the water mass exchange between the Kuroshio and the surrounding water. These small-scale processes play an important role in the energy and water mass budgets within the Kuroshio.

Statistical characteristics of austral summer cyclones in Southern Ocean

NASA Astrophysics Data System (ADS)

Liu, Na; Fu, Gang; Kuo, Ying-Hwa

2012-06-01

Characteristics of cyclones and explosively developing cyclones (or `bombs') over the Southern Ocean in austral summer (December, January and February) from 2004 to 2008 are analyzed by using the Final Analysis (FNL) data produced by the National Centers for Environmental Prediction (NCEP) of the United States. Statistical results show that both cyclones and explosively developing cyclones frequently develop in January, and most of them occur within the latitudinal zone between 55°S and 70°S. These cyclones gradually approach the Antarctic Continent from December to February. Generally cyclones and bombs move east-southeastward with some exceptions of northeastward movement. The lifetime of cyclones is around 2-6 d, and the horizontal scale is about 1000 km. Explosive cyclones have the lifetime of about 1 week with the horizontal scale reaching up to 3000 km. Compared with cyclones developed in the Northern Hemisphere, cyclones over the southern ocean have much higher occurrence frequency, lower central pressure and larger horizontal scale, which may be caused by the unique geographical features of the Southern Hemisphere.

Challenge toward the prediction of typhoon behaviour and down pour

NASA Astrophysics Data System (ADS)

Takahashi, K.; Onishi, R.; Baba, Y.; Kida, S.; Matsuda, K.; Goto, K.; Fuchigami, H.

2013-08-01

Mechanisms of interactions among different scale phenomena play important roles for forecasting of weather and climate. Multi-scale Simulator for the Geoenvironment (MSSG), which deals with multi-scale multi-physics phenomena, is a coupled non-hydrostatic atmosphere-ocean model designed to be run efficiently on the Earth Simulator. We present simulation results with the world-highest 1.9km horizontal resolution for the entire globe and regional heavy rain with 1km horizontal resolution and 5m horizontal/vertical resolution for urban area simulation. To gain high performance by exploiting the system capabilities, we propose novel performance evaluation metrics introduced in previous studies that incorporate the effects of the data caching mechanism between CPU and memory. With a useful code optimization guideline based on such metrics, we demonstrate that MSSG can achieve an excellent peak performance ratio of 32.2% on the Earth Simulator with the single-core performance found to be a key to a reduced time-to-solution.

Large-scale horizontally aligned ZnO microrod arrays with controlled orientation, periodic distribution as building blocks for chip-in piezo-phototronic LEDs.

PubMed

Guo, Zhen; Li, Haiwen; Zhou, Lianqun; Zhao, Dongxu; Wu, Yihui; Zhang, Zhiqiang; Zhang, Wei; Li, Chuanyu; Yao, Jia

2015-01-27

A novel method of fabricating large-scale horizontally aligned ZnO microrod arrays with controlled orientation and periodic distribution via combing technology is introduced. Horizontally aligned ZnO microrod arrays with uniform orientation and periodic distribution can be realized based on the conventional bottom-up method prepared vertically aligned ZnO microrod matrix via the combing method. When the combing parameters are changed, the orientation of horizontally aligned ZnO microrod arrays can be adjusted (θ = 90° or 45°) in a plane and a misalignment angle of the microrods (0.3° to 2.3°) with low-growth density can be obtained. To explore the potential applications based on the vertically and horizontally aligned ZnO microrods on p-GaN layer, piezo-phototronic devices such as heterojunction LEDs are built. Electroluminescence (EL) emission patterns can be adjusted for the vertically and horizontally aligned ZnO microrods/p-GaN heterojunction LEDs by applying forward bias. Moreover, the emission color from UV-blue to yellow-green can be tuned by investigating the piezoelectric properties of the materials. The EL emission mechanisms of the LEDs are discussed in terms of band diagrams of the heterojunctions and carrier recombination processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterizing Variability in Long Period Horizontal Tilt Noise Through Coherence Analysis

NASA Astrophysics Data System (ADS)

Rohde, M. D.; Ringler, A. T.; Hutt, C. R.; Wilson, D.; Holland, A. A.

2016-12-01

Tilt induced horizontal noise fundamentally limits a wide variety of seismological studies. This noise source is not well characterized or understood and the spatial variability has yet to be well constrained. Long-period (i.e., greater than 100 seconds period) horizontal seismic noise is generally known to be of greater magnitude than long-period vertical seismic noise due to tilt noise. As a result, many studies only make use of the vertical seismic wavefield as opposed to all three axes. The main source of long-period horizontal seismic noise is hypothesized to be tilt due to atmospheric pressure variation. Reducing horizontal tilt noise could lead to improved resolution of torsional earth modes and other long-period horizontal seismic signals that are often dominated by tilt noise, as well as better construction of seismic isolation systems for sensitive scientific experiments. We looked at a number of small aperture array configurations. For each array we installed eight Streckeisen STS-2 broadband seismometers in the Albuquerque Seismological Laboratory (ASL) underground vault. The data from these array configurations was used to characterize the long period horizontal tilt noise over a spatially small scale. Sensors were installed approximately 1 to 10 meters apart depending on the array configuration. Coherence as a function of frequency was calculated between sensors, of which we examine the frequency band between 10 and 500 seconds. We observed complexity in the pair-wise coherence with respect to frequency, seismometer axis, and time, even for spatially close sensors. We present some possible explanations for the large variability in our coherence observations and demonstrate how these results can be applied to find potentially low horizontal noise locations over small spatial scales, such as in stations with multiple co-located sensors within the Global Seismographic Network.

Sea-ice deformation in a coupled ocean-sea-ice model and in satellite remote sensing data

NASA Astrophysics Data System (ADS)

Spreen, Gunnar; Kwok, Ron; Menemenlis, Dimitris; Nguyen, An T.

2017-07-01

A realistic representation of sea-ice deformation in models is important for accurate simulation of the sea-ice mass balance. Simulated sea-ice deformation from numerical simulations with 4.5, 9, and 18 km horizontal grid spacing and a viscous-plastic (VP) sea-ice rheology are compared with synthetic aperture radar (SAR) satellite observations (RGPS, RADARSAT Geophysical Processor System) for the time period 1996-2008. All three simulations can reproduce the large-scale ice deformation patterns, but small-scale sea-ice deformations and linear kinematic features (LKFs) are not adequately reproduced. The mean sea-ice total deformation rate is about 40 % lower in all model solutions than in the satellite observations, especially in the seasonal sea-ice zone. A decrease in model grid spacing, however, produces a higher density and more localized ice deformation features. The 4.5 km simulation produces some linear kinematic features, but not with the right frequency. The dependence on length scale and probability density functions (PDFs) of absolute divergence and shear for all three model solutions show a power-law scaling behavior similar to RGPS observations, contrary to what was found in some previous studies. Overall, the 4.5 km simulation produces the most realistic divergence, vorticity, and shear when compared with RGPS data. This study provides an evaluation of high and coarse-resolution viscous-plastic sea-ice simulations based on spatial distribution, time series, and power-law scaling metrics.

Submesoscale-selective compensation of fronts in a salinity-stratified ocean.

PubMed

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-02-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world's upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity.

Finite-size scaling above the upper critical dimension in Ising models with long-range interactions

NASA Astrophysics Data System (ADS)

Flores-Sola, Emilio J.; Berche, Bertrand; Kenna, Ralph; Weigel, Martin

2015-01-01

The correlation length plays a pivotal role in finite-size scaling and hyperscaling at continuous phase transitions. Below the upper critical dimension, where the correlation length is proportional to the system length, both finite-size scaling and hyperscaling take conventional forms. Above the upper critical dimension these forms break down and a new scaling scenario appears. Here we investigate this scaling behaviour by simulating one-dimensional Ising ferromagnets with long-range interactions. We show that the correlation length scales as a non-trivial power of the linear system size and investigate the scaling forms. For interactions of sufficiently long range, the disparity between the correlation length and the system length can be made arbitrarily large, while maintaining the new scaling scenarios. We also investigate the behavior of the correlation function above the upper critical dimension and the modifications imposed by the new scaling scenario onto the associated Fisher relation.

Modeling the MJO rain rates using parameterized large scale dynamics: vertical structure, radiation, and horizontal advection of dry air

NASA Astrophysics Data System (ADS)

Wang, S.; Sobel, A. H.; Nie, J.

2015-12-01

Two Madden Julian Oscillation (MJO) events were observed during October and November 2011 in the equatorial Indian Ocean during the DYNAMO field campaign. Precipitation rates and large-scale vertical motion profiles derived from the DYNAMO northern sounding array are simulated in a small-domain cloud-resolving model using parameterized large-scale dynamics. Three parameterizations of large-scale dynamics --- the conventional weak temperature gradient (WTG) approximation, vertical mode based spectral WTG (SWTG), and damped gravity wave coupling (DGW) --- are employed. The target temperature profiles and radiative heating rates are taken from a control simulation in which the large-scale vertical motion is imposed (rather than directly from observations), and the model itself is significantly modified from that used in previous work. These methodological changes lead to significant improvement in the results.Simulations using all three methods, with imposed time -dependent radiation and horizontal moisture advection, capture the time variations in precipitation associated with the two MJO events well. The three methods produce significant differences in the large-scale vertical motion profile, however. WTG produces the most top-heavy and noisy profiles, while DGW's is smoother with a peak in midlevels. SWTG produces a smooth profile, somewhere between WTG and DGW, and in better agreement with observations than either of the others. Numerical experiments without horizontal advection of moisture suggest that that process significantly reduces the precipitation and suppresses the top-heaviness of large-scale vertical motion during the MJO active phases, while experiments in which the effect of cloud on radiation are disabled indicate that cloud-radiative interaction significantly amplifies the MJO. Experiments in which interactive radiation is used produce poorer agreement with observation than those with imposed time-varying radiative heating. Our results highlight the importance of both horizontal advection of moisture and cloud-radiative feedback to the dynamics of the MJO, as well as to accurate simulation and prediction of it in models.

Effects of step-feeding and intermittent aeration on organics and nitrogen removal in a horizontal subsurface flow constructed wetland.

PubMed

Patil, Sagar; Chakraborty, Saswati

2017-03-21

The effect of step feed strategy and intermittent aeration on removal of chemical oxygen demand (COD) and nitrogen was investigated in a laboratory scale horizontal subsurface flow constructed wetland (HSSFCW). Wetland was divided into four zones along the length (zone I to IV), and influent was introduced into first and third zones by step feeding. Continuous study was carried out in four phases. In phases I to III, 30% of influent was bypassed to zone III for denitrification along with organics removal. Intermittent aeration was provided only in zone II at 2.5 L/min for 4 h/day, during phases II, III and IV. In phase I, 87% COD and 43% NH 4 + -N (ammonia-nitrogen) removal were obtained from influents of 331 and 30 mg/L, respectively. In phase II study, external aeration resulted in 97% COD and 71% NH 4 + -N removal in the wetland. In phase IV, 40% of feed was delivered to zone III. Higher supply of organic in zone III resulted in higher denitrification, and total nitrogen removal rate increased to 70% from 56%. In the final effluent, concentration of NO 3 - -N was 9-11 mg/L in phase I to III and decreased to 4 mg/L in phase IV. Batch study showed that COD and NH 4 + -N removal followed first order kinetics in different zones of wetland.

CVD-grown horizontally aligned single-walled carbon nanotubes: synthesis routes and growth mechanisms.

PubMed

Ibrahim, Imad; Bachmatiuk, Alicja; Warner, Jamie H; Büchner, Bernd; Cuniberti, Gianaurelio; Rümmeli, Mark H

2012-07-09

Single-walled carbon nanotubes (SWCNTs) have attractive electrical and physical properties, which make them very promising for use in various applications. For some applications however, in particular those involving electronics, SWCNTs need to be synthesized with a high degree of control with respect to yield, length, alignment, diameter, and chirality. With this in mind, a great deal of effort is being directed to the precision control of vertically and horizontally aligned nanotubes. In this review the focus is on the latter, horizontally aligned tubes grown by chemical vapor deposition (CVD). The reader is provided with an in-depth review of the established vapor deposition orientation techniques. Detailed discussions on the characterization routes, growth parameters, and growth mechanisms are also provided. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of macropore structure of Malan loess in NW China based on 3D pipe models constructed by using computed tomography technology

NASA Astrophysics Data System (ADS)

Li, Yanrong; He, Shengdi; Deng, Xiaohong; Xu, Yongxin

2018-04-01

Malan loess is a grayish yellow or brownish yellow, clastic, highly porous and brittle late Quaternary sediment formed by the accumulation of windblown dust. The present-day pore structure of Malan loess is crucial for understanding the loessification process in history, loess strengths and mechanical behavior. This study employed a modern computed tomography (CT) device to scan Malan loess samples, which were obtained from the east part of the Loess Plateau of China. A sophisticated and efficient workflow for processing the CT images and constructing 3D pore models was established by selecting and programming relevant mathematical algorithms in MATLAB, such as the maximum entropy method, medial axis method, and node recognition algorithm. Individual pipes within the Malan loess were identified and constructed by partitioning and recombining links in the 3D pore model. The macropore structure of Malan loess was then depicted using quantitative parameters. The parameters derived from 2D images of CT scanning included equivalent radius, length and aspect ratio of pores, porosity, and pore distribution entropy, whereas those derived from the constructed 3D structure models included porosity, coordination number, node density, pipe radius, length, length density, dip angle, and dip direction. The analysis of these parameters revealed that Malan loess is a strongly anisotropic geomaterial with a dense and complex network of pores and pipes. The pores discovered on horizontal images, perpendicular to the vertical direction, were round and relatively uniform in shape and size and evenly distributed, whereas the pores discovered on vertical images varied in shape and size and were distributed in clusters. The pores showed good connectivity in vertical direction and formed vertically aligned pipes but displayed weak connectivity in horizontal directions. The pipes in vertical direction were thick, long, and straight compared with those in horizontal directions. These results were in good agreement with both numerical simulation and laboratory permeability tests, which indicate that Malan loess is more permeable in the vertical direction than in the horizontal directions.

Evaluation of the Operational Multi-scale Environment model with Grid Adaptivity (OMEGA) for use in Wind Energy Applications in the Great Basin of Nevada

NASA Astrophysics Data System (ADS)

King, Kristien C.

In order to further assess the wind energy potential for Nevada, the accuracy of a computational meteorological model, the Operational Multi-scale Environment model with Grid Adaptivity (OMEGA), was evaluated by comparing simulation results with data collected from a wind monitoring tower near Tonopah, NV. The state of Nevada is characterized by high mountains and low-lying valleys, therefore, in order to determine the wind potential for the state, meteorological models that predict the wind must be able to accurately represent and account for terrain features and simulate topographic forcing with accuracy. Topographic forcing has a dominant role in the development and modification of mesoscale flows in regions of complex terrain, like Tonopah, especially at the level of wind turbine blade heights (~80 m). Additionally, model factors such as horizontal resolution, terrain database resolution, model physics, time of model initialization, stability regime, and source of initial conditions may each affect the ability of a mesoscale model to forecast winds correctly. The observational tower used for comparison was located at Stone Cabin, Nevada. The tower had both sonic anemometers and cup anemometers installed at heights of 40 m, 60 m, and 80 m above the surface. During a previous experiment, tower data were collected for the period February 9 through March 10, 2007 and compared to model simulations using the MM5 and WRF models at a number of varying horizontal resolutions. In this previous research, neither the MM5 nor the WRF showed a significant improvement in ability to forecast wind speed with increasing horizontal grid resolution. The present research evaluated the ability of OMEGA to reproduce point winds as compared to the observational data from the Stone Cabin Tower at heights of 40 m, 60 m, and 80 m. Unlike other mesoscale atmospheric models, OMEGA incorporates an unstructured triangular adaptive grid which allows for increased flexibility and accuracy in characterizing areas of complex terrain. Model sensitivity to horizontal grid resolution, initial conditions, and time of initialization were tested. OMEGA was run over three different horizontal grid resolutions with minimum horizontal edge lengths of: 18 km, 6 km, and 2 km. For each resolution, the model was initialized using both the Global Forecasting System (GFS) and North American Regional Reanalysis (NARR) to determine model sensitivity to initial conditions. For both the NARR and GFS initializations, the model was started at both 0000 UTC and 1200 UTC to determine the effect of start time and stability regime on the performance of the model. An additional intensive study into the model's performance was also conducted by a detailed evaluation of model results during two separate 24-hour periods, the first a period where the model performed well and the second a period where the model performed poorly, to determine which atmospheric factors most affect the predictive ability of the OMEGA model. The statistical results were then compared with the results from the MM5 and WRF simulations to determine the most appropriate model for wind energy potential studies in complex terrain.

Water-vapour variability within a convective boundary-layer assessed by large-eddy simulations and IHOP_2002 observations

NASA Astrophysics Data System (ADS)

Couvreux, F.; Guichard, F.; Redelsperger, J. L.; Kiemle, C.; Masson, V.; Lafore, J. P.; Flamant, C.

2005-10-01

This study presents a comprehensive analysis of the variability of water vapour in a growing convective boundary-layer (CBL) over land, highlighting the complex links between advection, convective activity and moisture heterogeneity in the boundary layer. A Large-eddy Simulation (LES) is designed, based on observations, and validated, using an independent data-set collected during the International H2O Project (IHOP 2002) fieldexperiment. Ample information about the moisture distribution in space and time, as well as other important CBL parameters are acquired by mesonet stations, balloon soundings, instruments on-board two aircraft and the DLR airborne water-vapour differential-absorption lidar. Because it can deliver two-dimensional cross-sections at high spatial resolution (140 m horizontal, 200 m vertical), the airborne lidar offers valuable insights of small-scale moisture-variability throughout the CBL. The LES is able to reproduce the development of the CBL in the morning and early afternoon, as assessed by comparisons of simulated mean profiles of key meteorological variables with sounding data. Simulated profiles of the variance of water-vapour mixing-ratio were found to be in good agreement with the lidar-derived counterparts. Finally, probability-density functions of potential temperature, vertical velocity and water-vapour mixing-ratio calculated from the LES show great consistency with those derived from aircraft in situ measurements in the middle of the CBL. Downdraughts entrained from above the CBL are governing the scale of moisture variability. Characteristic length-scales are found to be larger for water-vapour mixing-ratio than for temperature.The observed water-vapour variability exhibits contributions from different scales. The influence of the mesoscale (larger than LES domain size, i.e. 10 km) on the smaller-scale variability is assessed using LES and observations. The small-scale variability of water vapour is found to be important and to be driven by the dynamics of the CBL. Both lidar observations and LES evidence that dry downdraughts entrained from above the CBL are governing the scale of moisture variability. Characteristic length-scales are found to be larger for water-vapour mixing-ratio than for temperature and vertical velocity. In particular, intrusions of drier free-troposphere air from above the growing CBL impose a marked negative skewness on the water-vapour distribution within it, both as observed and in the simulation.

ANALYTICAL SOLUTION TO SATURATED FLOW IN A FINITE STRATIFIED AQUIFER

EPA Science Inventory

An analytical solution for the flow of water in a saturated-stratified aquitard-aquifer-aquitard system of finite length is presented. The analytical solution assumes one-dimensional horizontal flow in the aquifer and two-dimensional flow in the aquitards. Several examples are gi...

A lithographically patterned capacitor with horizontal nanowires of length 2.5 mm.

PubMed

Yan, Wenbo; Thai, Mya Le; Dutta, Rajen; Li, Xiaowei; Xing, Wendong; Penner, Reginald M

2014-04-09

A symmetrical hybrid capacitor consisting of interdigitated, horizontal nanowires is described. Each of the 750 nanowires within the capacitor is 2.5 mm in length, consisting of a gold nanowire core (40 × ≈200 nm) encapsulated within a hemicylindrical shell of δ-phase MnO2 (thickness = 60-220 nm). These Au@δ-MnO2 nanowires are patterned onto a planar glass surface using lithographically patterned nanowire electrodeposition (LPNE). A power density of 165 kW/kg and energy density of 24 Wh/kg were obtained for a typical nanowire array in which the MnO2 shell thickness was 68 ± 8 nm. Capacitors incorporating these ultralong nanowires lost ≈10% of their capacity rapidly, during the first 20 discharge cycles, and then retained 90% of their maximum capacity for the ensuing 6000 cycles. The ability of capacitors consisting of ultralong Au@δ-MnO2 nanowires to simultaneously deliver high power and high capacity with acceptable cycle life is demonstrated.

Level-crossing statistics of the horizontal wind speed in the planetary surface boundary layer

NASA Astrophysics Data System (ADS)

Edwards, Paul J.; Hurst, Robert B.

2001-09-01

The probability density of the times for which the horizontal wind remains above or below a given threshold speed is of some interest in the fields of renewable energy generation and pollutant dispersal. However there appear to be no analytic or conceptual models which account for the observed power law form of the distribution of these episode lengths over a range of over three decades, from a few tens of seconds to a day or more. We reanalyze high resolution wind data and demonstrate the fractal character of the point process generated by the wind speed level crossings. We simulate the fluctuating wind speed by a Markov process which approximates the characteristics of the real (non-Markovian) wind and successfully generates a power law distribution of episode lengths. However, fundamental questions concerning the physical basis for this behavior and the connection between the properties of a continuous-time stochastic process and the fractal statistics of the point process generated by its level crossings remain unanswered.

The Effects of a Geomagnetic Storm on Thermospheric Circulation.

DTIC Science & Technology

1987-01-01

frequency. .*. p air density. olU 2 Pedersen and Hall conductivities. a P height intergrated Pedersen conductivity. horizontal viscous stress. * east...equations need to be ex- ,n~panded upon. The energy density is: (.2 1 + V2). I~i~iCPT +<V 2 . The horizontal viscous stress, including molecular and...with Z=0 at 80 km and Z=14.4 at 450 km for a total of 49 levels each 0.3 of a scale height apart. Also, the horizontal wind velocity, gas energy

Design and test of 1/5th scale horizontal axis tidal current turbine

NASA Astrophysics Data System (ADS)

Liu, Hong-wei; Zhou, Hong-bin; Lin, Yong-gang; Li, Wei; Gu, Hai-gang

2016-06-01

Tidal current energy is prominent and renewable. Great progress has been made in the exploitation technology of tidal current energy all over the world in recent years, and the large scale device has become the trend of tidal current turbine (TCT) for its economies. Instead of the similarity to the wind turbine, the tidal turbine has the characteristics of high hydrodynamic efficiency, big thrust, reliable sealing system, tight power transmission structure, etc. In this paper, a 1/5th scale horizontal axis tidal current turbine has been designed, manufactured and tested before the full scale device design. Firstly, the three-blade horizontal axis rotor was designed based on traditional blade element momentum theory and its hydrodynamic performance was predicted in numerical model. Then the power train system and stand-alone electrical control unit of tidal current turbine, whose performances were accessed through the bench test carried out in workshop, were designed and presented. Finally, offshore tests were carried out and the power performance of the rotor was obtained and compared with the published literatures, and the results showed that the power coefficient was satisfactory, which agrees with the theoretical predictions.

Length scale effects and multiscale modeling of thermally induced phase transformation kinetics in NiTi SMA

NASA Astrophysics Data System (ADS)

Frantziskonis, George N.; Gur, Sourav

2017-06-01

Thermally induced phase transformation in NiTi shape memory alloys (SMAs) shows strong size and shape, collectively termed length scale effects, at the nano to micrometer scales, and that has important implications for the design and use of devices and structures at such scales. This paper, based on a recently developed multiscale model that utilizes molecular dynamics (MDs) simulations at small scales and MD-verified phase field (PhF) simulations at larger scales, reports results on specific length scale effects, i.e. length scale effects in martensite phase fraction (MPF) evolution, transformation temperatures (martensite and austenite start and finish) and in the thermally cyclic transformation between austenitic and martensitic phase. The multiscale study identifies saturation points for length scale effects and studies, for the first time, the length scale effect on the kinetics (i.e. developed internal strains) in the B19‧ phase during phase transformation. The major part of the work addresses small scale single crystals in specific orientations. However, the multiscale method is used in a unique and novel way to indirectly study length scale and grain size effects on evolution kinetics in polycrystalline NiTi, and to compare the simulation results to experiments. The interplay of the grain size and the length scale effect on the thermally induced MPF evolution is also shown in this present study. Finally, the multiscale coupling results are employed to improve phenomenological material models for NiTi SMA.

a Numerical Simulation of a Tornado-Scale Vortex in a Three-Dimensional Cloud Model

NASA Astrophysics Data System (ADS)

Wicker, Louis John

1990-01-01

One of the more spectacular and elusive events of nature is the tornado. Usually spawned by a highly organized, lasting, and rotating thunderstorm called a "supercell", tornadoes are one of the most destructive atmospheric phenomena. Tornadoes almost always have length and time scales smaller than the measurable scales within the observing network of surface stations, conventional radar, Doppler radar and satellites. Therefore direct observations of tornadoes and their parent features are rarely obtained. Consequently, understanding of these phenomena will generally have to come from theoretical work, laboratory experiments, and numerical simulations. In this thesis we seek to understand the process of tornadogenesis within the context of a fully three-dimensional cloud model. Very high horizontal and vertical resolution is used to capture a developing tornado-scale vortex during the simulation of a strongly rotating supercell storm simulated within the 3 April 1964 environment from Witchita Fall, Texas. To better represent the influence of surface friction on the vortex flow, a simple surface layer parametrization of the vertical fluxes of horizontal momentum is added to the model. Results from the simulation show that a tornado -scale vortex forms along the western edge of the mesocyclone, intensifies and rotates cyclonically around the center of the mesocyclone over a several minute period. The inclusion of the surface layer parameterization increases the low -level velocity convergence. Surface vertical vorticity is greater than 0.43 s^{-1} for thirty seconds and greater than 0.3 s^ {-1} for several minutes. During tornadogenesis, pressures at the surface fall 3-4 mb in thirty seconds and a pressure gradient develops of over 7 mb from the outer edge of the tornado to the center. A vortex tube extends from the surface to over 2.5 km aloft and tilts to the northwest. Analyses show that tornadogenesis occurs when the vertical velocity gradients along the western side of the mesocyclone increase and that the principle mechanism for intensifying the vertical vorticity is convergence. Analyses also show that the development of the occlusion updraft along the western edge of the mesocyclone is related to advection of warm air southwestward over the gust front and the lowering of pressure aloft within the mesocyclone core.

"Spilling Over": Fish Swimming Kinematics in Cylinder Wakes

NASA Astrophysics Data System (ADS)

Wilson, C. A.; Muhawenimana, V.; Cable, J.

2016-12-01

Our understanding of fish swimming kinematics and behaviour in turbulent altered and pseudo-natural flows remains incomplete. This study aims to examine velocity, turbulence and wake metrics that govern fish stability and other behavioural traits in the turbulent wake of a horizontal cylinder. In a free surface flume, the swimming behaviour of Nile tilapia (Oreochromis niloticus, Silver strain) was monitored over a range of cylinder diameter (D) Reynolds numbers from 2.8 x103 to 25.8 x103. Spills, defined as loss of both balance and posture, were inversely correlated with fish length and weight; where smaller fish in the 50th percentile of standard length, lost balance more often and accounted for 65% of the total number (533) of spills. Additionally, the bigger fish in the 95th percentile, experienced <0.5% of all recorded spills. Such findings are in keeping with a previous study where the spill occurrence increased with decreasing fish length to eddy size ratio. Fish spent the majority of station holding time within a two diameter (2D) distance closest to the flume bed and in a downstream distance of 3D to 6D from the cylinder. The frequency of occurrence of spills increased with increasing Reynolds number for the whole fish population until an intermediate Reynolds number of 11.5 x103 was reached, where the frequency in spills steadily declined with increasing Reynolds number until the end of the test duration. The spill frequency-Reynolds number relationship indicates a shift in cylinder wake dynamics. Further analysis of the measured velocity statistics will help determine the intensity, periodicity and the turbulence length scale of the wake structure and their correlations with the observed fish swimming kinematics.

Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study.

PubMed

Vuletić, T; Dolanski Babić, S; Ivek, T; Grgicin, D; Tomić, S; Podgornik, R

2010-07-01

Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as c(HA)(-0.5) and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kilohertz range also varies with HA concentration as c(HA)(-0.5) which differs from the case of DNA (c(DNA)(-0.25)). The observed behavior suggests that the relaxation in the kilohertz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kilohertz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.

Net Force of an Ideal Conductor on an Element of a Line of Charge Moving With Extreme Relativistic Speed

ERIC Educational Resources Information Center

Cawley, Robert

1978-01-01

Considers the problem of determining the force on an element of a finite length line of charge moving horizontally with extreme relativistic speed through an evacuated space above an infinite plane ideal conducting surface. (SL)

Forced convection and flow boiling with and without enhancement devices for top-side-heated horizontal channels

NASA Technical Reports Server (NTRS)

Boyd, Ronald D., Sr.; Turknett, Jerry C.

1989-01-01

The effect of enhancement devices on flow boiling heat transfer in coolant channels, which are heated either from the top side or uniformly was studied. Studies are completed of the variations in the local (axial and circumferential) and mean heat transfer coefficients in horizontal, top-heated coolant channels with smooth walls and internal heat transfer enhancement devices. The working fluid is freon-11. The objectives are to: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls; (2) examine the effect of channel diameter (and the length-to-diameter aspect ratio) variations for the smooth wall channel; and (3) develop and improved data reduction analysis. The case of the top-heated, horizontal flow channel with smooth wall (1.37 cm inside diameter, and 122 cm heated length) was completed. The data were reduced using a preliminary analysis based on the heated hydraulic diameter. Preliminary examination of the local heat transfer coefficient variations indicated that there are significant axial and circumferential variations. However, it appears that the circumferential variation is more significant than the axial ones. In some cases, the circumferential variations were as much as a factor of ten. The axial variations rarely exceeded a factor of three.

Correlation between solar flare productivity and photospheric vector magnetic fields

NASA Astrophysics Data System (ADS)

Cui, Yanmei; Wang, Huaning

2008-11-01

Studying the statistical correlation between the solar flare productivity and photospheric magnetic fields is very important and necessary. It is helpful to set up a practical flare forecast model based on magnetic properties and improve the physical understanding of solar flare eruptions. In the previous study ([Cui, Y.M., Li, R., Zhang, L.Y., He, Y.L., Wang, H.N. Correlation between solar flare productivity and photospheric magnetic field properties 1. Maximum horizontal gradient, length of neutral line, number of singular points. Sol. Phys. 237, 45 59, 2006]; from now on we refer to this paper as ‘Paper I’), three measures of the maximum horizontal gradient, the length of the neutral line, and the number of singular points are computed from 23990 SOHO/MDI longitudinal magnetograms. The statistical relationship between the solar flare productivity and these three measures is well fitted with sigmoid functions. In the current work, the three measures of the length of strong-shear neutral line, total unsigned current, and total unsigned current helicity are computed from 1353 vector magnetograms observed at Huairou Solar Observing Station. The relationship between the solar flare productivity and the current three measures can also be well fitted with sigmoid functions. These results are expected to be beneficial to future operational flare forecasting models.

Application of a tri-axial accelerometry-based portable motion recorder for the quantitative assessment of hippotherapy in children and adolescents with cerebral palsy

PubMed Central

Mutoh, Tomoko; Mutoh, Tatsushi; Takada, Makoto; Doumura, Misato; Ihara, Masayo; Taki, Yasuyuki; Tsubone, Hirokazu; Ihara, Masahiro

2016-01-01

[Purpose] This case series aims to evaluate the effects of hippotherapy on gait and balance ability of children and adolescents with cerebral palsy using quantitative parameters for physical activity. [Subjects and Methods] Three patients with gait disability as a sequela of cerebral palsy (one female and two males; age 5, 12, and 25 years old) were recruited. Participants received hippotherapy for 30 min once a week for 2 years. Gait parameters (step rate, step length, gait speed, mean acceleration, and horizontal/vertical displacement ratio) were measured using a portable motion recorder equipped with a tri-axial accelerometer attached to the waist before and after a 10-m walking test. [Results] There was a significant increase in step length between before and after a single hippotherapy session. Over the course of 2 year intervention, there was a significant increase in step rate, gait speed, step length, and mean acceleration and a significant improvement in horizontal/vertical displacement ratio. [Conclusion] The data suggest that quantitative parameters derived from a portable motion recorder can track both immediate and long-term changes in the walking ability of children and adolescents with cerebral palsy undergoing hippotherapy. PMID:27821971

Impact of horizontal and vertical localization scales on microwave sounder SAPHIR radiance assimilation

NASA Astrophysics Data System (ADS)

Krishnamoorthy, C.; Balaji, C.

2016-05-01

In the present study, the effect of horizontal and vertical localization scales on the assimilation of direct SAPHIR radiances is studied. An Artificial Neural Network (ANN) has been used as a surrogate for the forward radiative calculations. The training input dataset for ANN consists of vertical layers of atmospheric pressure, temperature, relative humidity and other hydrometeor profiles with 6 channel Brightness Temperatures (BTs) as output. The best neural network architecture has been arrived at, by a neuron independence study. Since vertical localization of radiance data requires weighting functions, a ANN has been trained for this purpose. The radiances were ingested into the NWP using the Ensemble Kalman Filter (EnKF) technique. The horizontal localization has been taken care of, by using a Gaussian localization function centered around the observed coordinates. Similarly, the vertical localization is accomplished by assuming a function which depends on the weighting function of the channel to be assimilated. The effect of both horizontal and vertical localizations has been studied in terms of ensemble spread in the precipitation. Aditionally, improvements in 24 hr forecast from assimilation are also reported.

Feasibility of Sensing Tropospheric Ozone with MODIS 9.6 Micron Observations

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Iacovazzi, R., Jr.; Moon-Yoo, Jung

2004-01-01

With the infrared observations made by the Moderate Resolution Imaging Spectrometer (MODIS) on board the EOS-Aqua satellite, which include the 9.73 micron channel, a method is developed to deduce horizontal patterns of tropospheric ozone in cloud free conditions on a scale of about 100 km. It is assumed that on such small scale, at a given instant, horizontal changes in stratospheric ozone are small compared to that in the troposphere. From theoretical simulations it is found that uncertainties in the land surface emissivity and the vertical thermal stratification in the troposphere can lead to significant errors in the inferred tropospheric ozone. Because of this reason in order to derive horizontal patterns of tropospheric ozone in a given geographic area a tuning of this method is necessary with the help of a few dependent cases. After tuning, this method is applied to independent cases of MODIS data taken over Los Angeles basin in cloud free conditions to derive horizontal distribution of ozone in the troposphere. Preliminary results indicate that the derived patterns of ozone resemble crudely the patterns of surface ozone reported by EPA.

The role of vertical shear on the horizontal oceanic dispersion

NASA Astrophysics Data System (ADS)

Lanotte, A. S.; Corrado, R.; Lacorata, G.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

2015-09-01

The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of South Mediterranean is investigated by means of observative and model data. In-situ current measurements reveal that vertical velocity gradients in the upper mixed layer decorrelate quite fast (∼ 1 day), whereas basin-scale ocean circulation models tend to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion simulated by an eddy-permitting ocean model, like, e.g., the Mediterranean Forecasting System, is mosty affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out; (2) poorly resolved time variability of vertical velocity profiles in the upper layer. For the case study we have analysed, we show that a suitable use of kinematic parameterisations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

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

Li, Fuyu; Collins, William D.; Wehner, Michael F.

High-resolution climate models have been shown to improve the statistics of tropical storms and hurricanes compared to low-resolution models. The impact of increasing horizontal resolution in the tropical storm simulation is investigated exclusively using a series of Atmospheric Global Climate Model (AGCM) runs with idealized aquaplanet steady-state boundary conditions and a fixed operational storm-tracking algorithm. The results show that increasing horizontal resolution helps to detect more hurricanes, simulate stronger extreme rainfall, and emulate better storm structures in the models. However, increasing model resolution does not necessarily produce stronger hurricanes in terms of maximum wind speed, minimum sea level pressure, andmore » mean precipitation, as the increased number of storms simulated by high-resolution models is mainly associated with weaker storms. The spatial scale at which the analyses are conducted appears to have more important control on these meteorological statistics compared to horizontal resolution of the model grid. When the simulations are analyzed on common low-resolution grids, the statistics of the hurricanes, particularly the hurricane counts, show reduced sensitivity to the horizontal grid resolution and signs of scale invariant.« less

Why the long face? The importance of vertical image structure for biological "barcodes" underlying face recognition.

PubMed

Spence, Morgan L; Storrs, Katherine R; Arnold, Derek H

2014-07-29

Humans are experts at face recognition. The mechanisms underlying this complex capacity are not fully understood. Recently, it has been proposed that face recognition is supported by a coarse-scale analysis of visual information contained in horizontal bands of contrast distributed along the vertical image axis-a biological facial "barcode" (Dakin & Watt, 2009). A critical prediction of the facial barcode hypothesis is that the distribution of image contrast along the vertical axis will be more important for face recognition than image distributions along the horizontal axis. Using a novel paradigm involving dynamic image distortions, a series of experiments are presented examining famous face recognition impairments from selectively disrupting image distributions along the vertical or horizontal image axes. Results show that disrupting the image distribution along the vertical image axis is more disruptive for recognition than matched distortions along the horizontal axis. Consistent with the facial barcode hypothesis, these results suggest that human face recognition relies disproportionately on appropriately scaled distributions of image contrast along the vertical image axis. © 2014 ARVO.

Deformation sequences of the Day Nui Con Voi metamorphic belt, northern Vietnam

NASA Astrophysics Data System (ADS)

Yeh, M. W.; Lee, T. Y.; Lo, C. H.; Chung, S. L.; Lan, C. Y.; Lee, J. C.; Lin, T. S.; Lin, Y. J.

2003-04-01

The correlation of structure, microstructure and metamorphic assemblages is of fundamental importance to the understanding of the complex tectonic history and kinematics of the Day Nui Con Voi (DNCV) metamorphic belt in Vietnam along the Ailao Shan-Red River (ASRR) shear zone as it provides constraints on the relative timing of the deformation, kinematics and metamorphism. High-grade metamorphic rocks of amphibolite faces showed consistent deformation sequences of three folding events followed by one brittle deformation through all four cross sections from Lao Cai to Viet Tri indicated the DNCV belt experienced similar deformation condition throughout its length. The first deformation event, D1, produced up-right folds (locally preserved) with sub-vertical, NE-SW striking axial planes with dextral sense of shear probably formed during the early phase of the lowermost Triassic Indosinian orogeny. Followed by this compressional event is a gravitational collapsing event, D2, which is the major deformation and metamorphic event characterized by kyanite grade metamorphism and large scale horizontal folds with NW-SE (320) striking sub-horizontal axial pane showing sinsistral sense of shear most likely formed during the Oligocene-Miocene SE extrusion of Indochina peninsula. The 3rd folding event, D3, is a post-metamorphism doming event with NW-SE (310) striking sub-vertical axial plane that folded/tilted the once sub-horizontal D2 axial planes into shallowly (<30 degrees) NE dipping on the NE limb, and SW dipping on the SW limb possibly due to left-lateral movement of the N-S trending Xian Shui He fault system in Mid-Miocene. The outward decreasing of the metamorphic grade from kyanite to garnet then biotite indicated the D3 occurred post metamorphism. Reactivation of the sub-horizontal D2 fold axial planes showed dextral sense of shear possibly due to Late Miocene-Pliocene right-lateral movement of the ASRR shear zone. This right lateral movement continuously deformed the DNCV with brittle fractures such as joints and normal faults (D4) striking NE-SW to E-W and NW-SE.

Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide.

PubMed

Chang, Ken-Wei; Huang, Chia-Chien

2016-01-20

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ± 20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS.

Geostatistical analysis of regional hydraulic conductivity variations in the Snake River Plain aquifer, eastern Idaho

USGS Publications Warehouse

Welhan, J.A.; Reed, M.F.

1997-01-01

The regional spatial correlation structure of bulk horizontal hydraulic conductivity (Kb) estimated from published transmissivity data from 79 open boreholes in the fractured basalt aquifer of the eastern Snake River Plain was analyzed with geostatistical methods. The two-dimensional spatial correlation structure of In Kb shows a pronounced 4:1 range anisotropy, with a maximum correlation range in the north-northwest- south-southeast direction of about 6 km. The maximum variogram range of In Kb is similar to the mean length of flow groups exposed at the surface. The In Kb range anisotropy is similar to the mean width/length ratio of late Quaternary and Holocene basalt lava flows and the orientations of the major volcanic structural features on the eastern Snake River Plain. The similarity between In Kb correlation scales and basalt flow dimensions and between basalt flow orientations and correlation range anisotropy suggests that the spatial distribution of zones of high hydraulic conductivity may be controlled by the lateral dimensions, spatial distribution, and interconnection between highly permeable zones which are known to occur between lava flows within flow groups. If hydraulic conductivity and lithology are eventually shown to be cross correlative in this geologic setting, it may be possible to stochastically simulate hydraulic conductivity distributions, which are conditional on a knowledge of volcanic stratigraphy.

Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

NASA Astrophysics Data System (ADS)

Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

2016-09-01

An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

Intra-Wellbore Head Losses in a Horizontal Well with both Kinematic and Frictional Effects in an Anisotropic Confined Aquifer between Two Streams

NASA Astrophysics Data System (ADS)

Wang, Q.; Zhan, H.

2017-12-01

Horizontal drilling becomes an appealing technology for water exploration or aquifer remediation in recent decades, due to the decreasing operational cost and many technical advantages over the vertical wells. However, many previous studies on the flow into horizontal wells were based on the uniform flux boundary condition (UFBC) for treating horizontal wells, which could not reflect the physical processes of flow inside the well accurately. In this study, we investigated transient flow into a horizontal well in an anisotropic confined aquifer between two streams for three types of boundary conditions of treating the horizontal well, including UFBC, uniform head boundary condition (UHBC), and mixed-type boundary condition (MTBC). The MTBC model considered both kinematic and frictional effects inside the horizontal well, in which the kinematic effect referred to the accelerational and fluid inflow effects. The new solution of UFBC was derived by superimposing the point sink/source solutions along the axis of the horizontal well with a uniform strength. The solutions of UHBC and MTBC were obtained by a hybrid analytical-numerical method, and an iterative method was proposed to determine the minimum well segment number required to yield sufficiently accurate answer. The results showed that the differences among the UFBC, UHBC, MTBCFriction and MTBC solutions were obvious, in which MTBCFriction represented the solutions considering the frictional effect but ignoring the kinematic effect. The MTBCFriction and MTBC solutions were sensitive to the flow rate, and the difference of these two solutions increases with the flow rate, suggesting that the kinematic effect could not be ignored for studying flow to a horizontal well, especially when the flow rate is great. The well specific inflow (WSI) (which is the inflow per unit screen length at a specified location of the horizontal well) increased with the distance along the wellbore for the MTBC model at early stage, while the minimum WSI moved to the well center with time going, following a cubic polynomial function.

Local magnitude scale for earthquakes in Turkey

NASA Astrophysics Data System (ADS)

Kılıç, T.; Ottemöller, L.; Havskov, J.; Yanık, K.; Kılıçarslan, Ö.; Alver, F.; Özyazıcıoğlu, M.

2017-01-01

Based on the earthquake event data accumulated by the Turkish National Seismic Network between 2007 and 2013, the local magnitude (Richter, Ml) scale is calibrated for Turkey and the close neighborhood. A total of 137 earthquakes (Mw > 3.5) are used for the Ml inversion for the whole country. Three Ml scales, whole country, East, and West Turkey, are developed, and the scales also include the station correction terms. Since the scales for the two parts of the country are very similar, it is concluded that a single Ml scale is suitable for the whole country. Available data indicate the new scale to suffer from saturation beyond magnitude 6.5. For this data set, the horizontal amplitudes are on average larger than vertical amplitudes by a factor of 1.8. The recommendation made is to measure Ml amplitudes on the vertical channels and then add the logarithm scale factor to have a measure of maximum amplitude on the horizontal. The new Ml is compared to Mw from EMSC, and there is almost a 1:1 relationship, indicating that the new scale gives reliable magnitudes for Turkey.

Orthodontically induced eruption of a horizontally impacted maxillary central incisor.

PubMed

Rizzatto, Susana Maria Deon; de Menezes, Luciane Macedo; Allgayer, Susiane; Batista, Eraldo Luiz; Freitas, Maria Perpétua Mota; Loro, Raphael Carlos Drumond

2013-07-01

This case report presents the clinical features and periodontal findings in a patient with a horizontally impacted maxillary central incisor that had been exposed and aligned after a closed-eruption surgical technique. By combining 3 treatment stages-maxillary expansion, crown exposure surgery, and induced eruption-the horizontally impacted incisor was successfully moved into proper position. The patient finished treatment with a normal and stable occlusion between the maxillary and mandibular arches, and an adequate width of attached gingiva, even in the area surrounding the crown. The 5-year follow-up of stability and periodontal health demonstrated esthetic and functional outcomes after orthodontically induced tooth eruption. Clinical evaluation showed that the treated central incisor had periodontal clinical variables related to visible plaque, bleeding on probing, width of attached gingiva, and crown length that resembled the contralateral incisor. Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Safer Ski Jumps: Design of Landing Surfaces and Clothoidal In-Run Transitions

DTIC Science & Technology

2010-06-01

MINIMIZATION ......................................................................................... 9 B. DETERMINATION OF SKIER VELOCITY AT TAKEOFF...Spiral Flatness, Clothoid Length, and Angle From Horizontal ..................... 68 c. Free Body Diagram of a Skier in Clothoidal Transition...1 Figure 2. Ski jump in Einsiedeln, Switzerland, from [5] ................................................ 2 Figure 3. A skier performing

Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia : supplemental report.

DOT National Transportation Integrated Search

2006-01-01

A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current 12-ton posted load restriction of the bridge (instituted ...

Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia.

DOT National Transportation Integrated Search

2004-01-01

A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current load rating of the bridge could be raised and to document...

30 CFR 77.213 - Draw-off tunnel escapeways.

Code of Federal Regulations, 2011 CFR

2011-07-01

....213 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES... horizontal it shall be equipped with a ladder which runs the full length of the inclined portion of the...

Towards a global accurate model for horizontal and vertical elastic response of the Earth to seasonal hydrology derived from GRACE

NASA Astrophysics Data System (ADS)

Chanard, K.; Fleitout, L.; Calais, E.; Barbot, S.; Avouac, J. P.

2016-12-01

Elastic deformation of the Earth induced by seasonal variations in hydrology is now well established. We compute the vertical and horizontal deformation induced by large variations of continental water storage at a set of 195 globally distributed continuous Global Positioning System (cGPS) stations. Seasonal loading is derived from the Gravity and Recovery Climate experiment (GRACE) equivalent water height data, where we first account for non observable degree-1 components using previous results (Swenson et al., 2010). While the vertical displacements are well predicted by the model, the horizontal components are systematically underpredicted and out-of- phase with the observations. This global result confirms previous difficulties to predict horizontal seasonal site positions at a regional scale. We discuss possible contributions to this misfit (thermal expansion, draconitic effects, etc.) and show a dramatic improvement when we derive degree-one deformation plus reference frame differences between model and observations. The fit in phase and amplitude of the seasonal deformation model to the horizontal GPS measurements is improved and the fit to the vertical component is not affected. However, the amplitude of global seasonal horizontal displacement remains slightly underpredicted. We explore several hypothesis including the validity of a purely elastic model derived from seismic estimates at an annual time scale. We show that mantle volume variations due to mineral phase transitions may play a role in the seasonal deformation and, as a by-product, use this seasonal deformation to provide a lower bound of the transient astenospheric viscosity. Our study aims at providing an accurate model for horizontal and vertical seasonal deformation of the Earth induced by variations in surface hydrology derived from GRACE.

Long-term variation of horizontal phase velocity and propagation direction of mesospheric and thermospheric gravity waves by using airglow images obtained at Shigarkai, Japan

NASA Astrophysics Data System (ADS)

Takeo, D.; Kazuo, S.; Hujinami, H.; Otsuka, Y.; Matsuda, T. S.; Ejiri, M. K.; Yamamoto, M.; Nakamura, T.

2016-12-01

Atmospheric gravity waves generated in the lower atmosphere transport momentum into the upper atmosphere and release it when they break. The released momentum drives the global-scale pole-to-pole circulation and causes global mass transport. Vertical propagation of the gravity waves and transportation of momentum depend on horizontal phase velocity of gravity waves according to equation about dispersion relation of waves. Horizontal structure of gravity waves including horizontal phase velocity can be seen in the airglow images, and there have been many studies about gravity waves by using airglow images. However, long-term variation of horizontal phase velocity spectrum of gravity waves have not been studied yet. In this study, we used 3-D FFT method developed by Matsuda et al., (2014) to analyze the horizontal phase velocity spectrum of gravity waves by using 557.7-nm (altitude of 90-100 km) and 630.0-nm (altitude of 200-300 km) airglow images obtained at Shigaraki MU Observatory (34.8 deg N, 136.1 deg E) over 16 years from October 1, 1998 to July 26, 2015. Results about 557.7-nm shows clear seasonal variation of propagation direction of gravity waves in the mesopause region. Between summer and winter, there are propagation direction anisotropies which probably caused by filtering due to zonal mesospheric jet and by difference of latitudinal location of wave sources relative to Shigaraki. Results about 630.0-nm shows clear negative correlation between the yearly power spectrum density of horizontal phase velocity and sunspot number. This negative correlation with solar activity is consistent with growth rate of the Perkins instability, which may play an important role in generating the nighttime medium-scale traveling ionospheric disturbances at middle latitudes.

A comparison of VLBI with the ICE-3G glacial rebound model

NASA Technical Reports Server (NTRS)

James, Thomas S.; Lambert, Anthony

1993-01-01

Crustal motion predicted by the ICE-3G glacial rebound model exhibits a pattern of tangential (horizontal) divergence away from the centers of uplift, which in North America and Europe are located around Hudson Bay and the Gulf of Bothnia. Tangential velocities reach peak magnitudes of 1-2 mm/yr, and must be included when predicting VLBI baseline length change rates due to postglacial rebound. Out of 18 observed VLBI baselines examined three are situated such that their predicted length rates are around their 2 sigma uncertainties or greater. It is encouraging that two of these baselines exhibit predicted length rates within 2 sigma of the observed rates.

Nonlinear critical-layer evolution of a forced gravity wave packet

NASA Astrophysics Data System (ADS)

Campbell, L. J.; Maslowe, S. A.

2003-10-01

In this paper, numerical simulations are presented of the nonlinear critical-layer evolution of a forced gravity wave packet in a stratified shear flow. The wave packet, localized in the horizontal direction, is forced at the lower boundary of a two-dimensional domain and propagates vertically towards the critical layer. The wave mean-flow interactions in the critical layer are investigated numerically and contrasted with the results obtained using a spatially periodic monochromatic forcing. With the horizontally localized forcing, the net absorption of the disturbance at the critical layer continues for large time and the onset of the nonlinear breakdown is delayed compared with the case of monochromatic forcing. There is an outward flux of momentum in the horizontal direction so that the horizontal extent of the packet increases with time. The extent to which this happens depends on a number of factors including the amplitude and horizontal length of the forcing. It is also seen that the prolonged absorption of the disturbance stabilizes the solution to the extent that it is always convectively stable; the local Richardson number remains positive well into the nonlinear regime. In this respect, our results for the localized forcing differ from those in the case of monochromatic forcing where significant regions with negative Richardson number appear.

Orthognathic Surgery and Rhinoplasty to Address Nasomaxillary Hypoplasia.

PubMed

Veeramani, Anamika; Sawh, Raj; Steinbacher, Derek M

2017-11-01

The treatment of nasomaxillary hypoplasia is challenging. The phenotype of Binder "syndrome" includes the following: midfacial hypoplasia, class III malocclusion, small or absent anterior nasal spine, flattened nose, horizontal nostrils, short columella, acute nasolabial angle, and a flat frontonasal angle. A staged approach is used, with orthognathic surgery to achieve vertical maxillary length and sagittal advancement, followed by rhinoplasty aimed to increase nasal tip projection, rotation, and columellar length. This article details the diagnosis and treatment of nasomaxillary hypoplasia, demonstrating the senior author's (D.M.S.) preferred approach and technical steps. Therapeutic, V.

Role of medium heterogeneity and viscosity contrast in miscible flow regimes and mixing zone growth: A computational pore-scale approach

NASA Astrophysics Data System (ADS)

Afshari, Saied; Hejazi, S. Hossein; Kantzas, Apostolos

2018-05-01

Miscible displacement of fluids in porous media is often characterized by the scaling of the mixing zone length with displacement time. Depending on the viscosity contrast of fluids, the scaling law varies between the square root relationship, a sign for dispersive transport regime during stable displacement, and the linear relationship, which represents the viscous fingering regime during an unstable displacement. The presence of heterogeneities in a porous medium significantly affects the scaling behavior of the mixing length as it interacts with the viscosity contrast to control the mixing of fluids in the pore space. In this study, the dynamics of the flow and transport during both unit and adverse viscosity ratio miscible displacements are investigated in heterogeneous packings of circular grains using pore-scale numerical simulations. The pore-scale heterogeneity level is characterized by the variations of the grain diameter and velocity field. The growth of mixing length is employed to identify the nature of the miscible transport regime at different viscosity ratios and heterogeneity levels. It is shown that as the viscosity ratio increases to higher adverse values, the scaling law of mixing length gradually shifts from dispersive to fingering nature up to a certain viscosity ratio and remains almost the same afterwards. In heterogeneous media, the mixing length scaling law is observed to be generally governed by the variations of the velocity field rather than the grain size. Furthermore, the normalization of mixing length temporal plots with respect to the governing parameters of viscosity ratio, heterogeneity, medium length, and medium aspect ratio is performed. The results indicate that mixing length scales exponentially with log-viscosity ratio and grain size standard deviation while the impact of aspect ratio is insignificant. For stable flows, mixing length scales with the square root of medium length, whereas it changes linearly with length during unstable flows. This scaling procedure allows us to describe the temporal variation of mixing length using a generalized curve for various combinations of the flow conditions and porous medium properties.

Spatiotemporal Variability of Turbulence Kinetic Energy Budgets in the Convective Boundary Layer over Both Simple and Complex Terrain

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

Rai, Raj K.; Berg, Larry K.; Pekour, Mikhail

The assumption of sub-grid scale (SGS) horizontal homogeneity within a model grid cell, which forms the basis of SGS turbulence closures used by mesoscale models, becomes increasingly tenuous as grid spacing is reduced to a few kilometers or less, such as in many emerging high-resolution applications. Herein, we use the turbulence kinetic energy (TKE) budget equation to study the spatio-temporal variability in two types of terrain—complex (Columbia Basin Wind Energy Study [CBWES] site, north-eastern Oregon) and flat (ScaledWind Farm Technologies [SWiFT] site, west Texas) using the Weather Research and Forecasting (WRF) model. In each case six-nested domains (three domains eachmore » for mesoscale and large-eddy simulation [LES]) are used to downscale the horizontal grid spacing from 10 km to 10 m using the WRF model framework. The model output was used to calculate the values of the TKE budget terms in vertical and horizontal planes as well as the averages of grid cells contained in the four quadrants (a quarter area) of the LES domain. The budget terms calculated along the planes and the mean profile of budget terms show larger spatial variability at CBWES site than at the SWiFT site. The contribution of the horizontal derivative of the shear production term to the total production shear was found to be 45% and 15% of the total shear, at the CBWES and SWiFT sites, respectively, indicating that the horizontal derivatives applied in the budget equation should not be ignored in mesoscale model parameterizations, especially for cases with complex terrain with <10 km scale.« less

Radial bisection of words and lines in right-brain-damaged patients with spatial neglect.

PubMed

Veronelli, Laura; Arduino, Lisa S; Girelli, Luisa; Vallar, Giuseppe

2017-09-01

The bisection of lines positioned radially (with the two ends of the line close and far, with respect to the participant's body) has been less investigated than that of lines placed horizontally (with their two ends left and right, with respect to the body's midsagittal plane). In horizontal bisection, patients with left neglect typically show a rightward bias for both lines and words, greater with longer stimuli. As for radial bisection, available data indicate that neurologically unimpaired participants make a distal error, while results from right-brain-damaged patients with left spatial neglect are contradictory. We investigated the bisection of radially oriented words, with the prediction that, during bisection, linguistic material would be recoded to its canonical left-to-right format in reading, with the performance of neglect patients being similar to that for horizontal words. Thirteen right-brain-damaged patients (seven with left spatial neglect) and fourteen healthy controls were asked to manually bisect 40 radial and 40 horizontal words (5-10 letters), and 80 lines, 40 radial and 40 horizontal, of comparable length. Right-brain-damaged patients with spatial neglect exhibited a proximal bias in the bisection of short radial words, with the proximal part corresponding to the final right part of horizontally oriented words. This proximal error was not found in patients without neglect and healthy controls. For bisection, short radial words may be recoded to the canonical orthographic horizontal format, unveiling the impact of left neglect on radially oriented stimuli. © 2015 The British Psychological Society.

Test Report for MSFC Test No. 83-2: Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster filament wound case and external TVC PCD

NASA Technical Reports Server (NTRS)

1983-01-01

Water impact tests using a 12.5 inch diameter model representing a 8.56 percent scale of the Space Shuttle Solid Rocket Booster configuration were conducted. The two primary objectives of this SRB scale model water impact test program were: 1. Obtain cavity collapse applied pressure distributions for the 8.56 percent rigid body scale model FWC pressure magnitudes as a function of full-scale initial impact conditions at vertical velocities from 65 to 85 ft/sec, horizontal velocities from 0 to 45 ft/sec, and angles from -10 to +10 degrees. 2. Obtain rigid body applied pressures on the TVC pod and aft skirt internal stiffener rings at initial impact and cavity collapse loading events. In addition, nozzle loads were measured. Full scale vertical velocities of 65 to 85 ft/sec, horizontal velocities of 0 to 45 ft/sec, and impact angles from -10 to +10 degrees simulated.

Length-scale dependent mechanical properties of Al-Cu eutectic alloy: Molecular dynamics based model and its experimental verification

NASA Astrophysics Data System (ADS)

Tiwary, C. S.; Chakraborty, S.; Mahapatra, D. R.; Chattopadhyay, K.

2014-05-01

This paper attempts to gain an understanding of the effect of lamellar length scale on the mechanical properties of two-phase metal-intermetallic eutectic structure. We first develop a molecular dynamics model for the in-situ grown eutectic interface followed by a model of deformation of Al-Al2Cu lamellar eutectic. Leveraging the insights obtained from the simulation on the behaviour of dislocations at different length scales of the eutectic, we present and explain the experimental results on Al-Al2Cu eutectic with various different lamellar spacing. The physics behind the mechanism is further quantified with help of atomic level energy model for different length scale as well as different strain. An atomic level energy partitioning of the lamellae and the interface regions reveals that the energy of the lamellae core are accumulated more due to dislocations irrespective of the length-scale. Whereas the energy of the interface is accumulated more due to dislocations when the length-scale is smaller, but the trend is reversed when the length-scale is large beyond a critical size of about 80 nm.

The Impacts of an Observationally-Based Cloud Fraction and Condensate Overlap Parameterization on a GCM's Cloud Radiative Effect

NASA Technical Reports Server (NTRS)

Oreopoulos, Lazaros; Lee, Dongmin; Norris, Peter; Yuan, Tianle

2011-01-01

It has been shown that the details of how cloud fraction overlap is treated in GCMs has substantial impact on shortwave and longwave fluxes. Because cloud condensate is also horizontally heterogeneous at GCM grid scales, another aspect of cloud overlap should in principle also be assessed, namely the vertical overlap of hydrometeor distributions. This type of overlap is usually examined in terms of rank correlations, i.e., linear correlations between hydrometeor amount ranks of the overlapping parts of cloud layers at specific separation distances. The cloud fraction overlap parameter and the rank correlation of hydrometeor amounts can be both expressed as inverse exponential functions of separation distance characterized by their respective decorrelation lengths (e-folding distances). Larger decorrelation lengths mean that hydrometeor fractions and probability distribution functions have high levels of vertical alignment. An analysis of CloudSat and CALIPSO data reveals that the two aspects of cloud overlap are related and their respective decorrelation lengths have a distinct dependence on latitude that can be parameterized and included in a GCM. In our presentation we will contrast the Cloud Radiative Effect (CRE) of the GEOS-5 atmospheric GCM (AGCM) when the observationally-based parameterization of decorrelation lengths is used to represent overlap versus the simpler cases of maximum-random overlap and globally constant decorrelation lengths. The effects of specific overlap representations will be examined for both diagnostic and interactive radiation runs in GEOS-5 and comparisons will be made with observed CREs from CERES and CloudSat (2B-FLXHR product). Since the radiative effects of overlap depend on the cloud property distributions of the AGCM, the availability of two different cloud schemes in GEOS-5 will give us the opportunity to assess a wide range of potential cloud overlap consequences on the model's climate.

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

PubMed

Kocabas, Coskun; Hur, Seung-Hyun; Gaur, Anshu; Meitl, Matthew A; Shim, Moonsub; Rogers, John A

2005-11-01

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.

Large-scale deformation associated with ridge subduction

USGS Publications Warehouse

Geist, E.L.; Fisher, M.A.; Scholl, D. W.

1993-01-01

Continuum models are used to investigate the large-scale deformation associated with the subduction of aseismic ridges. Formulated in the horizontal plane using thin viscous sheet theory, these models measure the horizontal transmission of stress through the arc lithosphere accompanying ridge subduction. Modelling was used to compare the Tonga arc and Louisville ridge collision with the New Hebrides arc and d'Entrecasteaux ridge collision, which have disparate arc-ridge intersection speeds but otherwise similar characteristics. Models of both systems indicate that diffuse deformation (low values of the effective stress-strain exponent n) are required to explain the observed deformation. -from Authors

Mesoscopic Length Scale Controls the Rheology of Dense Suspensions

NASA Astrophysics Data System (ADS)

Bonnoit, Claire; Lanuza, Jose; Lindner, Anke; Clement, Eric

2010-09-01

From the flow properties of dense granular suspensions on an inclined plane, we identify a mesoscopic length scale strongly increasing with volume fraction. When the flowing layer height is larger than this length scale, a diverging Newtonian viscosity is determined. However, when the flowing layer height drops below this scale, we evidence a nonlocal effective viscosity, decreasing as a power law of the flow height. We establish a scaling relation between this mesoscopic length scale and the suspension viscosity. These results support recent theoretical and numerical results implying collective and clustered granular motion when the jamming point is approached from below.

Mesoscopic length scale controls the rheology of dense suspensions.

PubMed

Bonnoit, Claire; Lanuza, Jose; Lindner, Anke; Clement, Eric

2010-09-03

From the flow properties of dense granular suspensions on an inclined plane, we identify a mesoscopic length scale strongly increasing with volume fraction. When the flowing layer height is larger than this length scale, a diverging Newtonian viscosity is determined. However, when the flowing layer height drops below this scale, we evidence a nonlocal effective viscosity, decreasing as a power law of the flow height. We establish a scaling relation between this mesoscopic length scale and the suspension viscosity. These results support recent theoretical and numerical results implying collective and clustered granular motion when the jamming point is approached from below.

The role of plasma density scale length on the laser pulse propagation and scattering in relativistic regime

NASA Astrophysics Data System (ADS)

Pishdast, Masoud; Ghasemi, Seyed Abolfazl; Yazdanpanah, Jamal Aldin

2017-10-01

The role of plasma density scale length on two short and long laser pulse propagation and scattering in under dense plasma have been investigated in relativistic regime using 1 D PIC simulation. In our simulation, different density scale lengths and also two short and long pulse lengths with temporal pulse duration τL = 60 fs and τL = 300 fs , respectively have been used. It is found that laser pulse length and density scale length have considerable effects on the energetic electron generation. The analysis of total radiation spectrum reveals that, for short laser pulses and with reducing density scale length, more unstable electromagnetic modes grow and strong longitudinal electric field generates which leads to the generation of more energetic plasma particles. Meanwhile, the dominant scattering mechanism is Raman scattering and tends to Thomson scattering for longer laser pulse.

Quasi-Continuum Reduction of Field Theories: A Route to Seamlessly Bridge Quantum and Atomistic Length-Scales with Continuum

DTIC Science & Technology

2016-04-01

AFRL-AFOSR-VA-TR-2016-0145 Quasi-continuum reduction of field theories: A route to seamlessly bridge quantum and atomistic length-scales with...field theories: A route to seamlessly bridge quantum and atomistic length-scales with continuum Principal Investigator: Vikram Gavini Department of...calculations on tens of thousands of atoms, and enable continuing efforts towards a seamless bridging of the quantum and continuum length-scales

Horizontal Residual Mean Circulation: Evaluation of Spatial Correlations in Coarse Resolution Ocean Models

NASA Astrophysics Data System (ADS)

Li, Y.; McDougall, T. J.

2016-02-01

Coarse resolution ocean models lack knowledge of spatial correlations between variables on scales smaller than the grid scale. Some researchers have shown that these spatial correlations play a role in the poleward heat flux. In order to evaluate the poleward transport induced by the spatial correlations at a fixed horizontal position, an equation is obtained to calculate the approximate transport from velocity gradients. The equation involves two terms that can be added to the quasi-Stokes streamfunction (based on temporal correlations) to incorporate the contribution of spatial correlations. Moreover, these new terms do not need to be parameterized and is ready to be evaluated by using model data directly. In this study, data from a high resolution ocean model have been used to estimate the accuracy of this HRM approach for improving the horizontal property fluxes in coarse-resolution ocean models. A coarse grid is formed by sub-sampling and box-car averaging the fine grid scale. The transport calculated on the coarse grid is then compared to the transport on original high resolution grid scale accumulated over a corresponding number of grid boxes. The preliminary results have shown that the estimate on coarse resolution grids roughly match the corresponding transports on high resolution grids.

Submesoscale-selective compensation of fronts in a salinity-stratified ocean

PubMed Central

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-01-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world’s upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity. PMID:29507874

Ultrasound biomicroscopy for determining visian implantable contact lens length in phakic IOL implantation.

PubMed

Choi, Ki Hwan; Chung, Song Ee; Chung, Tae Young; Chung, Eui Sang

2007-04-01

To assess the efficacy of the ultrasound biomicroscopic (UBM) method in estimating the sulcus-to-sulcus horizontal diameter for Visian Implantable Contact Lens (ICL, model V4) length determination to obtain optimal ICL vault. The results of postoperative ICL vaults in 30 eyes of 18 patients were retrospectively analyzed. In 17 eyes, ICL length was determined using the conventional method, and in 13 eyes, ICL length was determined using the UBM method. The UBM method was carried out by measuring the sulcus to limbus distance on each side by 50 MHz UBM and adding the white-to-white diameter by caliper or Orbscan. The ICL vaults were measured using the UBM method at 1 and 6 months postoperatively and the results were compared between the two groups. Ideal ICL vault was defined as vault between 250 and 750 microm. The relation between the ICL vault, footplate location, and ICL power was also investigated. In the UBM method group, ICL vault was within the ideal range in all 13 (100%) eyes at 1 and 6 months postoperatively, whereas in the conventional method group, 10 (58.8%) eyes showed ideal vault at 1 month postoperatively (P = .01) and 9 (52.9%) eyes showed ideal vault at 6 months postoperatively (P < .01). The ideal ICL footplate location was achieved in the ciliary sulcus in 11 (84.6%) eyes of the UBM method group and 10 (64.7%) eyes of the conventional method group. However, the differences between the two groups were not statistically significant. The ICL vault was not significantly affected by the ICL power. Implantable Contact Lens length determined by the UBM method achieved significantly more ideal ICL vault than that of the conventional white-to-white method. The UBM method is superior to the conventional method in terms of predicting the sulcus-to-sulcus horizontal diameter for ICL length determination.

Up, Down, and All Around: Scale-Dependent Spatial Variation in Rocky-Shore Communities of Fildes Peninsula, King George Island, Antarctica

PubMed Central

Valdivia, Nelson; Díaz, María J.; Holtheuer, Jorge; Garrido, Ignacio; Huovinen, Pirjo; Gómez, Iván

2014-01-01

Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and predicted environmental changes in Antarctica. PMID:24956114

Modeling dolomitized carbonate-ramp reservoirs: A case study of the Seminole San Andres unit. Part 2 -- Seismic modeling, reservoir geostatistics, and reservoir simulation

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

Wang, F.P.; Dai, J.; Kerans, C.

1998-11-01

In part 1 of this paper, the authors discussed the rock-fabric/petrophysical classes for dolomitized carbonate-ramp rocks, the effects of rock fabric and pore type on petrophysical properties, petrophysical models for analyzing wireline logs, the critical scales for defining geologic framework, and 3-D geologic modeling. Part 2 focuses on geophysical and engineering characterizations, including seismic modeling, reservoir geostatistics, stochastic modeling, and reservoir simulation. Synthetic seismograms of 30 to 200 Hz were generated to study the level of seismic resolution required to capture the high-frequency geologic features in dolomitized carbonate-ramp reservoirs. Outcrop data were collected to investigate effects of sampling interval andmore » scale-up of block size on geostatistical parameters. Semivariogram analysis of outcrop data showed that the sill of log permeability decreases and the correlation length increases with an increase of horizontal block size. Permeability models were generated using conventional linear interpolation, stochastic realizations without stratigraphic constraints, and stochastic realizations with stratigraphic constraints. Simulations of a fine-scale Lawyer Canyon outcrop model were used to study the factors affecting waterflooding performance. Simulation results show that waterflooding performance depends strongly on the geometry and stacking pattern of the rock-fabric units and on the location of production and injection wells.« less

Studies of the relationship between environmental forcing and the structure and dynamics of tornado-like vortices

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

Nolan, David S.; Almgren, Ann S.; Bell, John B.

Axisymmetric numerical simulations continue to provide insight into how the structure, dynamics, and maximum wind speeds of tornadoes, and other convectively-maintained vortices, are influenced by the surrounding environment. This work is continued with a new numerical model of axisymmetric incompressible flow that incorporates adaptive mesh refinement. The model dynamically increases or decreases the resolution in regions of interest as determined by a specified refinement criterion. Here, the criterion used is based on the cell Reynolds number dx dv / nu, so that the flow is guaranteed to be laminar on the scale of the local grid spacing. The model ismore » used to investigate how the altitude and shape of the convective forcing, the size of the domain, and the effective Reynolds number (based on the choice of the eddy viscosity nu) influence the structure and dynamics of the vortex. Over a wide variety of domain and forcing geometries,the vortex Reynolds number Gamma / nu (the ratio of the far-field circulation to the eddy viscosity) is shown to be the most important parameter for determining vortex structure and behavior. Furthermore,it is found that the vertical scale of the convective forcing only affects the vortex inasmuch as this vertical scale contributes to the total strength of the convective forcing. The horizontal scale of the convective forcing, however, is found to be the fundamental length scale in the problem, in that it can determine both the circulation of the fluid that is drawn into the vortex core, and also influences the depth of the swirling boundary layer. Higher mean wind speeds are sustained as the eddy viscosity is decreased; however, it is observed that the highest wind speeds are found in the high-swirl, two-celled vortex regime rather than in the low-swirl, one-celled regime, which is in contrast with some previous results. The conclusions drawn from these results are applied to dimensional simulations with scales similar to the mesocyclone/thunderstorm environment. Tornado-like vortices are reproduced, using a constant eddy viscosity with such values as 40 m2s-1, which have maximum wind speeds, radii of maximum winds, and boundary layer depths which are quite similar to those recently observed with portable Doppler radar. Based on the results of both nondimensional and tornado-scale simulations, scaling laws are empirically derived for the internal length scales in tornado-like vortices, such as the depth of the boundary layer and the radius of maximum winds.« less

Viscosity stratification and the aspect ratio of convection rolls

NASA Astrophysics Data System (ADS)

Morris, S. J. S.

2005-11-01

To clarify a mechanism by which earth's low--viscosity layer may increase the wavelength of mantle convection cells, we analyse the clockwise isothermal cellular motion driven by a uniform shear stress of magnitude τ applied at each end of a rectangle of height 2D and length L. The viscosity μ is a given piecewise-constant function of depth; within a low--viscosity channel of thickness d located at the top of the layer, μ=mμ1; elsewhere, within the `core', μ=μ1. We show that in the double limit d/D->0, m->0, this two--layer flow is equivalent to one in single layer of viscosity μ1 with a new boundary condition at its top representing the interaction of the channel and core flows. Let x=x*/L, y=y*/D and ψ= μ1ψ*/ τD^2. Then the stream function ψ for the core motion satisfies the b.v.p. ψyyyy+2 2̂ψxxyy+ 4̂ψxxxx=0; at |x|=1 , ψ=0, α^2ψxx=-1; at y=0 , ψ=0=ψyy; at y=1, ψyy- 2̂ψxx=0 , and ψyyy+3 2̂ψyxx= 3ɛψ. Here α=D/L and ɛ=mD^3/d^3. We find that for ɛ->0, the motion has two horizontal scales, namely D and L1= D/&1/2 ̂D. If the rectangle length L˜L1, fluid sinks at one end and rises at the other; those end flows occur on the scale D, and are connected by a long--wave flow on the scale L1. The cellular motion is closed within the low--viscosity layer. We have extended this method to treat convection rolls in a fluid of infinite Prandtl number. Our predicted heat flows agree well with those found in numerical simulations by Lenardic, Richards & Busse et al (2005) (J. Geophys. Res., to appear).

7 CFR 51.586 - Serious damage.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Growth cracks when more than 4 branches are affected by growth cracks which are over one-half inch in length, or when more than 8 branches have growth cracks; (b) Horizontal cracks when more than 5 branches..., whichever is less, has more than 3 distinct hair-like lines more than 3 inches long occurring on the outer...

7 CFR 51.586 - Serious damage.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Growth cracks when more than 4 branches are affected by growth cracks which are over one-half inch in length, or when more than 8 branches have growth cracks; (b) Horizontal cracks when more than 5 branches..., whichever is less, has more than 3 distinct hair-like lines more than 3 inches long occurring on the outer...

77 FR 55773 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-11

...) inspections for cracking of the left and right rib hinge bearing lugs of the aft face of the center section of... bearing lugs of the aft face of the center section of the horizontal stabilizer; measuring crack length...). Recognition That Reporting of Findings Is Not Required American Airlines stated it recognizes that reporting...

Cloud Size Distributions from Multi-sensor Observations of Shallow Cumulus Clouds

NASA Astrophysics Data System (ADS)

Kleiss, J.; Riley, E.; Kassianov, E.; Long, C. N.; Riihimaki, L.; Berg, L. K.

2017-12-01

Combined radar-lidar observations have been used for almost two decades to document temporal changes of shallow cumulus clouds at the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Facility's Southern Great Plains (SGP) site in Oklahoma, USA. Since the ARM zenith-pointed radars and lidars have a narrow field-of-view (FOV), the documented cloud statistics, such as distributions of cloud chord length (or horizontal length scale), represent only a slice along the wind direction of a region surrounding the SGP site, and thus may not be representative for this region. To investigate this impact, we compare cloud statistics obtained from wide-FOV sky images collected by ground-based observations at the SGP site to those from the narrow FOV active sensors. The main wide-FOV cloud statistics considered are cloud area distributions of shallow cumulus clouds, which are frequently required to evaluate model performance, such as routine large eddy simulation (LES) currently being conducted by the ARM LASSO (LES ARM Symbiotic Simulation and Observation) project. We obtain complementary macrophysical properties of shallow cumulus clouds, such as cloud chord length, base height and thickness, from the combined radar-lidar observations. To better understand the broader observational context where these narrow FOV cloud statistics occur, we compare them to collocated and coincident cloud area distributions from wide-FOV sky images and high-resolution satellite images. We discuss the comparison results and illustrate the possibility to generate a long-term climatology of cloud size distributions from multi-sensor observations at the SGP site.

Radiation incident on tilted collectors

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

Robinson, P.J.

1981-12-01

For solar energy system design purposes, observations of solar radiation on a horizontal surface must be converted to values on a tilted energy collector. An empirical conversion relationship, introduced by Liu and Jordan (1960) and based on short-term data for a single station, and has been widely adopted throughout the nation. The spatial variations of the coefficients of this relationship and their stability with record length on North Carolina. Minor variations in coefficients result from changes in record length, but the differences have little impact on the design or performance of a solar energy system. Similarly, minor variations occur betweenmore » coastal and inland sites but are insufficient to alter system designs. Hence a single relationship is appropriate for the area investigated. These SOLMET results indicate a greater proportion of direct radiation for a given total horizontal radiation amount than do Collares-Pereira and Rabl (1979), who used short period records from a few widely scattered stations to refine the original national relationship. The difference may reflect variations in data quality or regional differences in atmospheric transmission characteristics.« less

Tactical decisions for changeable cuttlefish camouflage: visual cues for choosing masquerade are relevant from a greater distance than visual cues used for background matching.

PubMed

Buresch, Kendra C; Ulmer, Kimberly M; Cramer, Corinne; McAnulty, Sarah; Davison, William; Mäthger, Lydia M; Hanlon, Roger T

2015-10-01

Cuttlefish use multiple camouflage tactics to evade their predators. Two common tactics are background matching (resembling the background to hinder detection) and masquerade (resembling an uninteresting or inanimate object to impede detection or recognition). We investigated how the distance and orientation of visual stimuli affected the choice of these two camouflage tactics. In the current experiments, cuttlefish were presented with three visual cues: 2D horizontal floor, 2D vertical wall, and 3D object. Each was placed at several distances: directly beneath (in a circle whose diameter was one body length (BL); at zero BL [(0BL); i.e., directly beside, but not beneath the cuttlefish]; at 1BL; and at 2BL. Cuttlefish continued to respond to 3D visual cues from a greater distance than to a horizontal or vertical stimulus. It appears that background matching is chosen when visual cues are relevant only in the immediate benthic surroundings. However, for masquerade, objects located multiple body lengths away remained relevant for choice of camouflage. © 2015 Marine Biological Laboratory.

Droplet evaporation on a horizontal substrate under gravity field by mesoscopic modeling.

PubMed

Xie, Chiyu; Zhang, Jianying; Bertola, Volfango; Wang, Moran

2016-02-01

The evaporation of water drop deposited on a horizontal substrate is investigated using a lattice Boltzmann method (LBM) for multiphase flows with a large-density ratio. To account for the variation of evaporation flux distribution along the drop interface, a novel evaporation scheme is introduced into the LBM framework, and validated by comparison with experimental data. We aim at discovering the effect of gravity on the evaporating drop in detail, and various evaporation conditions are considered as well as different wetting properties of the substrates. An effective diameter is introduced as an indicator of the critical drop size under which gravity is negligible. Our results show that such critical diameter is much smaller than the capillary length, which has been widely accepted as the critical size in previous and current works. The critical diameter is found to be almost independent of the evaporation conditions and the surface wettability. A correlation between this critical diameter and the capillary length is also proposed for easy use in applications. Copyright © 2015 Elsevier Inc. All rights reserved.

Estimating unconsolidated sediment cover thickness by using the horizontal distance to a bedrock outcrop as secondary information

NASA Astrophysics Data System (ADS)

Kitterød, Nils-Otto

2017-08-01

Unconsolidated sediment cover thickness (D) above bedrock was estimated by using a publicly available well database from Norway, GRANADA. General challenges associated with such databases typically involve clustering and bias. However, if information about the horizontal distance to the nearest bedrock outcrop (L) is included, does the spatial estimation of D improve? This idea was tested by comparing two cross-validation results: ordinary kriging (OK) where L was disregarded; and co-kriging (CK) where cross-covariance between D and L was included. The analysis showed only minor differences between OK and CK with respect to differences between estimation and true values. However, the CK results gave in general less estimation variance compared to the OK results. All observations were declustered and transformed to standard normal probability density functions before estimation and back-transformed for the cross-validation analysis. The semivariogram analysis gave correlation lengths for D and L of approx. 10 and 6 km. These correlations reduce the estimation variance in the cross-validation analysis because more than 50 % of the data material had two or more observations within a radius of 5 km. The small-scale variance of D, however, was about 50 % of the total variance, which gave an accuracy of less than 60 % for most of the cross-validation cases. Despite the noisy character of the observations, the analysis demonstrated that L can be used as secondary information to reduce the estimation variance of D.

Retrieving mesospheric winds and gravity waves using high resolution radar measurements of polar mesospheric summer echoes with MAARSY

NASA Astrophysics Data System (ADS)

Stober, G.; Sommer, S.; Schult, C.; Chau, J. L.; Latteck, R.

2013-12-01

The Middle Atmosphere Alomar Radar System (MAARSY) located at the northern Norwegian island of Andøya (69.3 ° N, 16° E) observes polar mesosphere summer echoes (PMSE) on a regular basis. This backscatter turned out to be an ideal tracer of atmospheric dynamics and to investigate the wind field at the mesosphere/lower thermosphere (MLT) at high spatial and temporal scales. MAARSY is dedicated to explore the polar mesosphere at such high resolution and employs an active phased array antenna with the capability to steer the beam on a pulse-to-pulse basis, which permits to perform systematic scanning of PMSE and to investigate the horizontal structure of the backscatter. The radar also uses a 16 channel receiver system for interferometric applications e.g. mean angle of arrival analysis or coherent radar imaging. Here we present measurements using these features of MAARSY to study the wind field at the MLT applying sophisticated wind analysis algorithms such as velocity azimuth display or volume velocity processing to derive gravity wave parameters such as horizontal wave length, phase speed and propagation direction. Further, we compare the interferometrically corrected and uncorrected wind measurements to emphasize the importance to account for likely edge effects using PMSE as tracer of the dynamics. The observations indicate huge deviations from the nominal beam pointing direction at the upper and lower edges of the PMSE altering the wind analysis.

Inherent length-scales of periodic solar wind number density structures

NASA Astrophysics Data System (ADS)

Viall, N. M.; Kepko, L.; Spence, H. E.

2008-07-01

We present an analysis of the radial length-scales of periodic solar wind number density structures. We converted 11 years (1995-2005) of solar wind number density data into radial length series segments and Fourier analyzed them to identify all spectral peaks with radial wavelengths between 72 (116) and 900 (900) Mm for slow (fast) wind intervals. Our window length for the spectral analysis was 9072 Mm, approximately equivalent to 7 (4) h of data for the slow (fast) solar wind. We required that spectral peaks pass both an amplitude test and a harmonic F-test at the 95% confidence level simultaneously. From the occurrence distributions of these spectral peaks for slow and fast wind, we find that periodic number density structures occur more often at certain radial length-scales than at others, and are consistently observed within each speed range over most of the 11-year interval. For the slow wind, those length-scales are L ˜ 73, 120, 136, and 180 Mm. For the fast wind, those length-scales are L ˜ 187, 270 and 400 Mm. The results argue for the existence of inherent radial length-scales in the solar wind number density.

Flow Environment Study Near the Empennage of a 15-Percent Scale Helicopter Model

NASA Technical Reports Server (NTRS)

Gorton, Susan Althoff; Berry, John D.; Hodges, W. Todd; Reis, Deane G.

2000-01-01

Development of advanced rotorcraft configurations has highlighted a need for high-quality experimental data to support the development of flexible and accurate analytical design tools. To provide this type of data, a test program was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a 15-percent scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with laser velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady angle of attack variations of over 30 degrees due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the tail fan were made for a low-speed flight condition using conventional LV techniques. The velocity data show an accelerated flow near the tail fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane.

Aerodynamic Characteristics of a 0.5-Scale Model of the Fairchild XSAM-N-2 Lark Missile at High Subsonic Speeds

NASA Technical Reports Server (NTRS)

Martin, Andrew; Hunter, Harlo A.

1949-01-01

An investigation was conducted to determine the longitudinal- and lateral-stability characteristics of a 0.5-scale moue1 of the Fairchild Lark missile, The model was tested with 0 deg and with 22.5 deg of roll. Three horizontal wings having NACA 16-009, 16-209, and 64A-209 sections were tested. Pressures were measured on both pointed and blunt noses. The wind-tunnel-test data indicate that rolling the missile 22.5 deg. had no serious effect on the static longitudinal stability. The desired maneuvering acceleration could not be attained with any of the horizontal wings tested, even with the horizontal wing flaps deflected 50 deg. The flaps on the 64A-209 wing (with small trailing-edge angles and flat sides) were effective at all flap deflections, while the flaps on the 16-series wings (with large trailing-edge angles) lost effectiveness at small flap deflections. The data showed that rolling moment existed when the vertical wing flaps were deflected with the model at other than zero angle of attack. A similar rolling moment probably would be found . with the horizontal wing flaps deflected and the model yawed.

A digital photogrammetric method for measuring horizontal surficial movements on the slumgullion earthflow, Hinsdale county, Colorado

USGS Publications Warehouse

Powers, P.S.; Chiarle, M.; Savage, W.Z.

1996-01-01

The traditional approach to making aerial photographic measurements uses analog or analytic photogrammetric equipment. We have developed a digital method for making measurements from aerial photographs which uses geographic information system (GIS) software, and primarily DOS-based personal computers. This method, which is based on the concept that a direct visual comparison can be made between images derived from two sets of aerial photographs taken at different times, was applied to the surface of the active portion of the Slumgullion earthflow in Colorado to determine horizontal displacement vectors from the movements of visually identifiable objects, such as trees and large rocks. Using this method, more of the slide surface can be mapped in a shorter period of time than using the standard photogrammetric approach. More than 800 horizontal displacement vectors were determined on the active earthflow surface using images produced by our digital photogrammetric technique and 1985 (1:12,000-scale) and 1990 (1:6,000-scale) aerial photographs. The resulting displacement field shows, with a 2-m measurement error (??? 10%), that the fastest moving portion of the landslide underwent 15-29 m of horizontal displacement between 1985 and 1990. Copyright ?? 1996 Elsevier Science Ltd.

Focus of a multilayer Laue lens with an aperture of 102 microns determined by ptychography at beamline 1-BM at the Advanced Photon Source

NASA Astrophysics Data System (ADS)

Macrander, Albert; Wojcik, Michael; Maser, Jörg; Bouet, Nathalie; Conley, Raymond

2017-09-01

Ptychography was used to determine the focus of a Multilayer-Laue-Lens (MLL) at beamline 1-BM at the Advanced Photon Source (APS). The MLL had a record aperture of 102 microns with 15170 layers. The measurements were made at 12 keV. The focal length was 9.6 mm, and the outer-most zone was 4 nm thick. MLLs with ever larger apertures are under continuous development since ever longer focal lengths, ever larger working distances, and ever increased flux in the focus are desired. A focus size of 25 nm was determined by ptychographic phase retrieval from a gold grating sample with 1 micron lines and spaces over 3.0 microns horizontal distance. The MLL was set to focus in the horizontal plane of the bending magnet beamline. A CCD with 13.0 micron pixel size positioned 1.13 m downstream of the sample was used to collect the transmitted intensity distribution. The beam incident on the MLL covered the whole 102 micron aperture in the horizontal focusing direction and 20 microns in the vertical direction. 160 iterations of the difference map algorithm were sufficient to obtain a reconstructed image of the sample. The present work highlights the utility of a bending magnet source at the APS for performing coherence-based experiments. Use of ptychography at 1-BM on MLL optics opens the way to study diffraction-limited imaging of other hard x-ray optics.

Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

NASA Astrophysics Data System (ADS)

Yang, Zhuqiang; Bi, Qincheng; Guo, Yong; Liu, Zhaohui; Yan, Jianguo

2013-07-01

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2ṡs), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

Numerical Modeling of Methane Leakage from a Faulty Natural Gas Well into Fractured Tight Formations.

PubMed

Moortgat, Joachim; Schwartz, Franklin W; Darrah, Thomas H

2018-03-01

Horizontal drilling and hydraulic fracturing have enabled hydrocarbon recovery from unconventional reservoirs, but led to natural gas contamination of shallow groundwaters. We describe and apply numerical models of gas-phase migration associated with leaking natural gas wells. Three leakage scenarios are simulated: (1) high-pressure natural gas pulse released into a fractured aquifer; (2) continuous slow leakage into a tilted fractured formation; and (3) continuous slow leakage into an unfractured aquifer with fluvial channels, to facilitate a generalized evaluation of natural gas transport from faulty natural gas wells. High-pressure pulses of gas leakage into sparsely fractured media are needed to produce the extensive and rapid lateral spreading of free gas previously observed in field studies. Transport in fractures explains how methane can travel vastly different distances and directions laterally away from a leaking well, which leads to variable levels of methane contamination in nearby groundwater wells. Lower rates of methane leakage (≤1 Mcf/day) produce shorter length scales of gas transport than determined by the high-pressure scenario or field studies, unless aquifers have low vertical permeabilities (≤1 millidarcy) and fractures and bedding planes have sufficient tilt (∼10°) to allow a lateral buoyancy component. Similarly, in fractured rock aquifers or where permeability is controlled by channelized fluvial deposits, lateral flow is not sufficiently developed to explain fast-developing gas contamination (0-3 months) or large length scales (∼1 km) documented in field studies. Thus, current efforts to evaluate the frequency, mechanism, and impacts of natural gas leakage from faulty natural gas wells likely underestimate contributions from small-volume, low-pressure leakage events. © 2018, National Ground Water Association.

Scaling analysis of cloud and rain water in marine stratocumulus and implications for scale-aware microphysical parameterizations

NASA Astrophysics Data System (ADS)

Witte, M.; Morrison, H.; Jensen, J. B.; Bansemer, A.; Gettelman, A.

2017-12-01

The spatial covariance of cloud and rain water (or in simpler terms, small and large drops, respectively) is an important quantity for accurate prediction of the accretion rate in bulk microphysical parameterizations that account for subgrid variability using assumed probability density functions (pdfs). Past diagnoses of this covariance from remote sensing, in situ measurements and large eddy simulation output have implicitly assumed that the magnitude of the covariance is insensitive to grain size (i.e. horizontal resolution) and averaging length, but this is not the case because both cloud and rain water exhibit scale invariance across a wide range of scales - from tens of centimeters to tens of kilometers in the case of cloud water, a range that we will show is primarily limited by instrumentation and sampling issues. Since the individual variances systematically vary as a function of spatial scale, it should be expected that the covariance follows a similar relationship. In this study, we quantify the scaling properties of cloud and rain water content and their covariability from high frequency in situ aircraft measurements of marine stratocumulus taken over the southeastern Pacific Ocean aboard the NSF/NCAR C-130 during the VOCALS-REx field experiment of October-November 2008. First we confirm that cloud and rain water scale in distinct manners, indicating that there is a statistically and potentially physically significant difference in the spatial structure of the two fields. Next, we demonstrate that the covariance is a strong function of spatial scale, which implies important caveats regarding the ability of limited-area models with domains smaller than a few tens of kilometers across to accurately reproduce the spatial organization of precipitation. Finally, we present preliminary work on the development of a scale-aware parameterization of cloud-rain water subgrid covariability based in multifractal analysis intended for application in large-scale model microphysics schemes.

Seismic, satellite, and site observations of internal solitary waves in the NE South China Sea

PubMed Central

Tang, Qunshu; Wang, Caixia; Wang, Dongxiao; Pawlowicz, Rich

2014-01-01

Internal solitary waves (ISWs) in the NE South China Sea (SCS) are tidally generated at the Luzon Strait. Their propagation, evolution, and dissipation processes involve numerous issues still poorly understood. Here, a novel method of seismic oceanography capable of capturing oceanic finescale structures is used to study ISWs in the slope region of the NE SCS. Near-simultaneous observations of two ISWs were acquired using seismic and satellite imaging, and water column measurements. The vertical and horizontal length scales of the seismic observed ISWs are around 50 m and 1–2 km, respectively. Wave phase speeds calculated from seismic observations, satellite images, and water column data are consistent with each other. Observed waveforms and vertical velocities also correspond well with those estimated using KdV theory. These results suggest that the seismic method, a new option to oceanographers, can be further applied to resolve other important issues related to ISWs. PMID:24948180

Flux canceling in three-dimensional radiative magnetohydrodynamic simulations

NASA Astrophysics Data System (ADS)

Thaler, Irina; Spruit, H. C.

2017-05-01

We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.

Development of subminiature multi-sensor hot-wire probes

NASA Technical Reports Server (NTRS)

Westphal, Russell V.; Ligrani, Phillip M.; Lemos, Fred R.

1988-01-01

Limitations on the spatial resolution of multisensor hot wire probes have precluded accurate measurements of Reynolds stresses very near solid surfaces in wind tunnels and in many practical aerodynamic flows. The fabrication, calibration and qualification testing of very small single horizontal and X-array hot-wire probes which are intended to be used near solid boundaries in turbulent flows where length scales are particularly small, is described. Details of the sensor fabrication procedure are reported, along with information needed to successfully operate the probes. As compared with conventional probes, manufacture of the subminiature probes is more complex, requiring special equipment and careful handling. The subminiature probes tested were more fragile and shorter lived than conventional probes; they obeyed the same calibration laws but with slightly larger experimental uncertainty. In spite of these disadvantages, measurements of mean statistical quantities and spectra demonstrate the ability of the subminiature sensors to provide the measurements in the near wall region of turbulent boundary layers that are more accurate than conventional sized probes.

Scale dependence of the 200-mb divergence inferred from EOLE data.

NASA Technical Reports Server (NTRS)

Morel, P.; Necco, G.

1973-01-01

The EOLE experiment with 480 constant-volume balloons distributed over the Southern Hemisphere approximately at the 200-mb level, has provided a unique, highly accurate set of tracer trajectories in the general westerly circulation. The trajectories of neighboring balloons are analyzed to estimate the horizontal divergence from the Lagrangian derivative of the area of one cluster. The variance of the divergence estimates results from two almost comparable effects: the true divergence of the horizontal flow and eddy diffusion due to small-scale, two-dimensional turbulence. Taking this into account, the rms divergence is found to be of the order of 0.00001 per sec and decreases logarithmically with cluster size. This scale dependence is shown to be consistent with the quasi-geostrophic turbulence model of the general circulation in midlatitudes.

Irreversible transport in the stratosphere by internal waves of short vertical wavelength

NASA Technical Reports Server (NTRS)

Danielsen, Edwin F.; Hipskind, R. S.; Starr, Walter L.; Vedder, James F.; Gaines, Steven E.; Kley, Dieter; Kelley, Ken K.

1991-01-01

Measurements performed during stratospheric flights of the U-2 aircraft confirm that cross-jet transport is dominated by waves, not by large-scale circulations. Monotonic gradients of trace constituents normal to the jet axis, with upper stratospheric tracers increasing poleward and tropospheric tracers increasing equatorward, are augmented by large-scale confluence as the jet intensifies during cyclogenesis. These gradients are rotated, intensified, and significantly increased in areas as their mixing ratio surfaces are folded by the differential transport of a very low frequency transverse wave. The quasi-horizontal transport produces a laminar structure with stable layers rich in upper stratospheric tracers alternating vertically with less stable layers rich in tropospheric tracers. The transport proceeds toward irreversibility at higher frequency, shear-gravity waves extend the folding to smaller horizontal scales.

Simultaneous electric-field measurements on nearby balloons.

NASA Technical Reports Server (NTRS)

Mozer, F. S.

1972-01-01

Electric-field payloads were flown simultaneously on two balloons from Great Whale River, Canada, on September 21, 1971, to provide data at two points in the upper atmosphere that differed in altitude by more than one atmospheric density scale height and in horizontal position by 30-140 km. The altitude dependences in the two sets of data prove conclusively that the vertical electric field at balloon altitudes stems from fair-weather atmospheric electricity sources and that the horizontal fields are mapped down ionospheric fields, since the weather-associated horizontal fields were smaller than 2 mV/m.

Local magnitude scale for Valle Medio del Magdalena region, Colombia

NASA Astrophysics Data System (ADS)

Londoño, John Makario; Romero, Jaime A.

2017-12-01

A local Magnitude (ML) scale for Valle Medio del Magdalena (VMM) region was defined by using 514 high quality earthquakes located at VMM area and inversion of 2797 amplitude values of horizontal components of 17 stations seismic broad band stations, simulated in a Wood-Anderson seismograph. The derived local magnitude scale for VMM region was: ML =log(A) + 1.3744 ∗ log(r) + 0.0014776 ∗ r - 2.397 + S Where A is the zero-to-peak amplitude in nm in horizontal components, r is the hypocentral distance in km, and S is the station correction. Higher values of ML were obtained for VMM region compared with those obtained with the current formula used for ML determination, and with California formula. With this new scale ML values are adjusted to local conditions beneath VMM region leading to more realistic ML values. Moreover, with this new ML scale the seismicity caused by tectonic or fracking activity at VMM region can be monitored more accurately.

Solute-specific scaling of inorganic nitrogen and phosphorus uptake in streams

NASA Astrophysics Data System (ADS)

Hall, R. O., Jr.; Baker, M. A.; Rosi-Marshall, E. J.; Tank, J. L.; Newbold, J. D.

2013-11-01

Stream ecosystem processes such as nutrient cycling may vary with stream position in the network. Using a scaling approach, we examined the relationship between stream size and nutrient uptake length, which represents the mean distance that a dissolved solute travels prior to removal from the water column. Ammonium (NH4+) uptake length increased proportionally with stream size measured as specific discharge (discharge/stream width) with a scaling exponent = 1.01. In contrast, uptake lengths for nitrate (NO3-) and soluble reactive phosphorus (SRP) increased more rapidly than increases in specific discharge (scaling exponents = 1.19 for NO3- and 1.35 for SRP). Additionally, the ratio of inorganic nitrogen (N) uptake length to SRP uptake length declined with stream size; there was relatively lower demand for SRP compared to N as stream size increased. Finally, we related the scaling of uptake length with specific discharge to that of stream length using Hack's law and downstream hydraulic geometry. Ammonium uptake length increased less than proportionally with distance from the headwaters, suggesting a strong role for larger streams and rivers in regulating nutrient transport.

Rotating Apparatus for Isoelectric Focusing

NASA Technical Reports Server (NTRS)

Bier, M.

1986-01-01

Remixing of separated fractions prevented. Improved isoelectric focusing apparatus helps to prevent electro-osmosis and convection, both of which cause remixing of separated fractions. Fractionating column segmented and rotated about horizontal axis: Only combined effects of both features fully effective in making good separations. Improved apparatus slowly rotated continuously or rocked (at rotational amplitude of at least 180 degrees) about its horizontal axis so average gravitational vector experienced by fluid is zero and convection is therefore suppressed. Electro-osmosis suppressed and convection further suppressed by separating column into disklike compartments along its length with filters. Experiments have shown dimensions of apparatus not critical. Typical compartment and column volumes are 2 and 40 ml, respectively. Rotation speeds lie between 3 and 30 rpm.

Convection with a simple chemically reactive passive scalar

NASA Astrophysics Data System (ADS)

Herring, J. R.; Wyngaard, J. C.

Convection between horizontal stress-free perfectly conducting plates is examined in the turbulent regime for air. Results are presented for an additional scalar undergoing simple linear decay. We discuss qualitative aspects of the flow in terms of spectral and three-dimensional contour maps of the velocity and scalar fields. The horizontal mean profiles of scalar gradients and fluxes agree rather well with simple mixing-length concepts. Further, the mean profiles for a range of the destruction-rate parameter are shown to be nearly completely characterized by the boundary fluxes. Finally, we shall use the present numerical data as a basis for exploring a generalization of eddy-diffusion concepts so as to properly incorporate non-local effects.

Some effects of horizontal discretization on linear baroclinic and symmetric instabilities

NASA Astrophysics Data System (ADS)

Barham, William; Bachman, Scott; Grooms, Ian

2018-05-01

The effects of horizontal discretization on linear baroclinic and symmetric instabilities are investigated by analyzing the behavior of the hydrostatic Eady problem in ocean models on the B and C grids. On the C grid a spurious baroclinic instability appears at small wavelengths. This instability does not disappear as the grid scale decreases; instead, it simply moves to smaller horizontal scales. The peak growth rate of the spurious instability is independent of the grid scale as the latter decreases. It is equal to cf /√{Ri} where Ri is the balanced Richardson number, f is the Coriolis parameter, and c is a nondimensional constant that depends on the Richardson number. As the Richardson number increases c increases towards an upper bound of approximately 1/2; for large Richardson numbers the spurious instability is faster than the Eady instability. To suppress the spurious instability it is recommended to use fourth-order centered tracer advection along with biharmonic viscosity and diffusion with coefficients (Δx) 4 f /(32√{Ri}) or larger where Δx is the grid scale. On the B grid, the growth rates of baroclinic and symmetric instabilities are too small, and converge upwards towards the correct values as the grid scale decreases; no spurious instabilities are observed. In B grid models at eddy-permitting resolution, the reduced growth rate of baroclinic instability may contribute to partially-resolved eddies being too weak. On the C grid the growth rate of symmetric instability is better (larger) than on the B grid, and converges upwards towards the correct value as the grid scale decreases.

The Snakelike Chain Character of Unstructured RNA

PubMed Central

Jacobson, David R.; McIntosh, Dustin B.; Saleh, Omar A.

2013-01-01

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod “wormlike chain” (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a “snakelike chain,” characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. PMID:24314087

Identifying Conventionally Sub-Seismic Faults in Polygonal Fault Systems

NASA Astrophysics Data System (ADS)

Fry, C.; Dix, J.

2017-12-01

Polygonal Fault Systems (PFS) are prevalent in hydrocarbon basins globally and represent potential fluid pathways. However the characterization of these pathways is subject to the limitations of conventional 3D seismic imaging; only capable of resolving features on a decametre scale horizontally and metres scale vertically. While outcrop and core examples can identify smaller features, they are limited by the extent of the exposures. The disparity between these scales can allow for smaller faults to be lost in a resolution gap which could mean potential pathways are left unseen. Here the focus is upon PFS from within the London Clay, a common bedrock that is tunnelled into and bears construction foundations for much of London. It is a continuation of the Ieper Clay where PFS were first identified and is found to approach the seafloor within the Outer Thames Estuary. This allows for the direct analysis of PFS surface expressions, via the use of high resolution 1m bathymetric imaging in combination with high resolution seismic imaging. Through use of these datasets surface expressions of over 1500 faults within the London Clay have been identified, with the smallest fault measuring 12m and the largest at 612m in length. The displacements over these faults established from both bathymetric and seismic imaging ranges from 30cm to a couple of metres, scales that would typically be sub-seismic for conventional basin seismic imaging. The orientations and dimensions of the faults within this network have been directly compared to 3D seismic data of the Ieper Clay from the offshore Dutch sector where it exists approximately 1km below the seafloor. These have typical PFS attributes with lengths of hundreds of metres to kilometres and throws of tens of metres, a magnitude larger than those identified in the Outer Thames Estuary. The similar orientations and polygonal patterns within both locations indicates that the smaller faults exist within typical PFS structure but are sub-seismic in conventional imaging techniques. These unseen faults could create additional unseen pathways that impact construction in London via water ingress and influence fluid migration within hydrocarbon basins.

Experimental evidence for two thermodynamic length scales in neutralized polyacrylate gels

NASA Astrophysics Data System (ADS)

Horkay, Ferenc; Hecht, Anne-Marie; Grillo, Isabelle; Basser, Peter J.; Geissler, Erik

2002-11-01

The small angle neutron scattering (SANS) behavior of fully neutralized sodium polyacrylate gels is investigated in the presence of calcium ions. Analysis of the SANS response reveals the existence of three characteristic length scales, two of which are of thermodynamic origin, while the third length is associated with the frozen-in structural inhomogeneities. This latter contribution exhibits power law behavior with a slope of about -3.6, reflecting the presence of interfaces. The osmotically active component of the scattering signal is defined by two characteristic length scales, a correlation length ξ and a persistence length L.

Scaling Effects on Materials Tribology: From Macro to Micro Scale.

PubMed

Stoyanov, Pantcho; Chromik, Richard R

2017-05-18

The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale.

Scaling Effects on Materials Tribology: From Macro to Micro Scale

PubMed Central

Stoyanov, Pantcho; Chromik, Richard R.

2017-01-01

The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale. PMID:28772909

Length scale effects of friction in particle compaction using atomistic simulations and a friction scaling model

NASA Astrophysics Data System (ADS)

Stone, T. W.; Horstemeyer, M. F.

2012-09-01

The objective of this study is to illustrate and quantify the length scale effects related to interparticle friction under compaction. Previous studies have shown as the length scale of a specimen decreases, the strength of a single crystal metal or ceramic increases. The question underlying this research effort continues the thought—If there is a length scale parameter related to the strength of a material, is there a length scale parameter related to friction? To explore the length scale effects of friction, molecular dynamics (MD) simulations using an embedded atom method potential were performed to analyze the compression of two spherical FCC nickel nanoparticles at different contact angles. In the MD model study, we applied a macroscopic plastic contact formulation to determine the normal plastic contact force at the particle interfaces and used the average shear stress from the MD simulations to determine the tangential contact forces. Combining this information with the Coulomb friction law, we quantified the MD interparticle coefficient of friction and showed good agreement with experimental studies and a Discrete Element Method prediction as a function of contact angle. Lastly, we compared our MD simulation friction values to the tribological predictions of Bhushan and Nosonovsky (BN), who developed a friction scaling model based on strain gradient plasticity and dislocation-assisted sliding that included a length scale parameter. The comparison revealed that the BN elastic friction scaling model did a much better job than the BN plastic scaling model of predicting the coefficient of friction values obtained from the MD simulations.

How much a galaxy knows about its large-scale environment?: An information theoretic perspective

NASA Astrophysics Data System (ADS)

Pandey, Biswajit; Sarkar, Suman

2017-05-01

The small-scale environment characterized by the local density is known to play a crucial role in deciding the galaxy properties but the role of large-scale environment on galaxy formation and evolution still remain a less clear issue. We propose an information theoretic framework to investigate the influence of large-scale environment on galaxy properties and apply it to the data from the Galaxy Zoo project that provides the visual morphological classifications of ˜1 million galaxies from the Sloan Digital Sky Survey. We find a non-zero mutual information between morphology and environment that decreases with increasing length-scales but persists throughout the entire length-scales probed. We estimate the conditional mutual information and the interaction information between morphology and environment by conditioning the environment on different length-scales and find a synergic interaction between them that operates up to at least a length-scales of ˜30 h-1 Mpc. Our analysis indicates that these interactions largely arise due to the mutual information shared between the environments on different length-scales.

The mechanics of granitoid systems and maximum entropy production rates.

PubMed

Hobbs, Bruce E; Ord, Alison

2010-01-13

A model for the formation of granitoid systems is developed involving melt production spatially below a rising isotherm that defines melt initiation. Production of the melt volumes necessary to form granitoid complexes within 10(4)-10(7) years demands control of the isotherm velocity by melt advection. This velocity is one control on the melt flux generated spatially just above the melt isotherm, which is the control valve for the behaviour of the complete granitoid system. Melt transport occurs in conduits initiated as sheets or tubes comprising melt inclusions arising from Gurson-Tvergaard constitutive behaviour. Such conduits appear as leucosomes parallel to lineations and foliations, and ductile and brittle dykes. The melt flux generated at the melt isotherm controls the position of the melt solidus isotherm and hence the physical height of the Transport/Emplacement Zone. A conduit width-selection process, driven by changes in melt viscosity and constitutive behaviour, operates within the Transport Zone to progressively increase the width of apertures upwards. Melt can also be driven horizontally by gradients in topography; these horizontal fluxes can be similar in magnitude to vertical fluxes. Fluxes induced by deformation can compete with both buoyancy and topographic-driven flow over all length scales and results locally in transient 'ponds' of melt. Pluton emplacement is controlled by the transition in constitutive behaviour of the melt/magma from elastic-viscous at high temperatures to elastic-plastic-viscous approaching the melt solidus enabling finite thickness plutons to develop. The system involves coupled feedback processes that grow at the expense of heat supplied to the system and compete with melt advection. The result is that limits are placed on the size and time scale of the system. Optimal characteristics of the system coincide with a state of maximum entropy production rate. This journal is © 2010 The Royal Society

Size-dependent elastic/inelastic behavior of enamel over millimeter and nanometer length scales.

PubMed

Ang, Siang Fung; Bortel, Emely L; Swain, Michael V; Klocke, Arndt; Schneider, Gerold A

2010-03-01

The microstructure of enamel like most biological tissues has a hierarchical structure which determines their mechanical behavior. However, current studies of the mechanical behavior of enamel lack a systematic investigation of these hierarchical length scales. In this study, we performed macroscopic uni-axial compression tests and the spherical indentation with different indenter radii to probe enamel's elastic/inelastic transition over four hierarchical length scales, namely: 'bulk enamel' (mm), 'multiple-rod' (10's microm), 'intra-rod' (100's nm with multiple crystallites) and finally 'single-crystallite' (10's nm with an area of approximately one hydroxyapatite crystallite). The enamel's elastic/inelastic transitions were observed at 0.4-17 GPa depending on the length scale and were compared with the values of synthetic hydroxyapatite crystallites. The elastic limit of a material is important as it provides insights into the deformability of the material before fracture. At the smallest investigated length scale (contact radius approximately 20 nm), elastic limit is followed by plastic deformation. At the largest investigated length scale (contact size approximately 2 mm), only elastic then micro-crack induced response was observed. A map of elastic/inelastic regions of enamel from millimeter to nanometer length scale is presented. Possible underlying mechanisms are also discussed. (c) 2009 Elsevier Ltd. All rights reserved.

Horizontal acquisition of transposable elements and viral sequences: patterns and consequences.

PubMed

Gilbert, Clément; Feschotte, Cédric

2018-04-01

It is becoming clear that most eukaryotic transposable elements (TEs) owe their evolutionary success in part to horizontal transfer events, which enable them to invade new species. Recent large-scale studies are beginning to unravel the mechanisms and ecological factors underlying this mode of transmission. Viruses are increasingly recognized as vectors in the process but also as a direct source of genetic material horizontally acquired by eukaryotic organisms. Because TEs and endogenous viruses are major catalysts of variation and innovation in genomes, we argue that horizontal inheritance has had a more profound impact in eukaryotic evolution than is commonly appreciated. To support this proposal, we compile a list of examples, including some previously unrecognized, whereby new host functions and phenotypes can be directly attributed to horizontally acquired TE or viral sequences. We predict that the number of examples will rapidly grow in the future as the prevalence of horizontal transfer in the life cycle of TEs becomes even more apparent, firmly establishing this form of non-Mendelian inheritance as a consequential facet of eukaryotic evolution. Copyright © 2018 Elsevier Ltd. All rights reserved.

Automated analysis of timber access road alternatives.

Treesearch

Doyle Burke

1974-01-01

The evaluation of timber access road alternatives is one of the primary tasks in timber harvest planning and design. During the planning stages, it is also one of the most difficult to accomplish quantitatively because a basis for comparison is related to such values as grade, length, horizontal and vertical curvature, and volumes of excavation and embankment. Within...

Technique of Axillary Use of a Combat Ready Clamp to Stop Junctional Bleeding

DTIC Science & Technology

2013-01-01

compressed parallel to—but not on—the clavicle (Fig. 4). 5. Adjust the horizontal arm length by using its locking pin. 6. Adjust the vertical arm by...arm adjustment for square disk head contact atop the target. Fig. 4. Placing the square disk head atop the target, parallel to—but not on—the clavicle

Decay Times and Quality Factors for a Resonance Apparatus

ERIC Educational Resources Information Center

Stephens, Heather; Tam, Austin; Moloney, Michael

2011-01-01

The commercial resonance demonstration apparatus shown in Fig. 1 exhibits curious behavior. It consists of three pairs of slender spring-steel rods attached to a horizontal bar. When one of the rods is pulled aside and released, the rod of corresponding length is excited into visible motion, but the other rods remain apparently stationary. This…

Predicting catastrophes of non-autonomous networks with visibility graphs and horizontal visibility

NASA Astrophysics Data System (ADS)

Zhang, Haicheng; Xu, Daolin; Wu, Yousheng

2018-05-01

Prediction of potential catastrophes in engineering systems is a challenging problem. We first attempt to construct a complex network to predict catastrophes of a multi-modular floating system in advance of their occurrences. Response time series of the system can be mapped into an virtual network by using visibility graph or horizontal visibility algorithm. The topology characteristics of the networks can be used to forecast catastrophes of the system. Numerical results show that there is an obvious corresponding relationship between the variation of topology characteristics and the onset of catastrophes. A Catastrophe Index (CI) is proposed as a numerical indicator to measure a qualitative change from a stable state to a catastrophic state. The two approaches, the visibility graph and horizontal visibility algorithms, are compared by using the index in the reliability analysis with different data lengths and sampling frequencies. The technique of virtual network method is potentially extendable to catastrophe predictions of other engineering systems.

The effect of single-horn glaze ice on the vortex structures in the wake of a horizontal axis wind turbine

NASA Astrophysics Data System (ADS)

Jin, Zhe-Yan; Dong, Qiao-Tian; Yang, Zhi-Gang

2015-02-01

The present study experimentally investigated the effect of a simulated single-horn glaze ice accreted on rotor blades on the vortex structures in the wake of a horizontal axis wind turbine by using the stereoscopic particle image velocimetry (Stereo-PIV) technique. During the experiments, four horizontal axis wind turbine models were tested, and both "free-run" and "phase-locked" Stereo-PIV measurements were carried out. Based on the "free-run" measurements, it was found that because of the simulated single-horn glaze ice, the shape, vorticity, and trajectory of tip vortices were changed significantly, and less kinetic energy of the airflow could be harvested by the wind turbine. In addition, the "phase-locked" results indicated that the presence of simulated single-horn glaze ice resulted in a dramatic reduction of the vorticity peak of the tip vortices. Moreover, as the length of the glaze ice increased, both root and tip vortex gaps were found to increase accordingly.

Equatorial ion composition, 140-200 km, based on Atmosphere Explorer E data

NASA Technical Reports Server (NTRS)

Miller, N. J.; Grebowsky, J. M.; Hedin, A. E.; Spencer, N. W.

1993-01-01

We have used in situ measurements of ion composition and horizontal winds, taken from equatorial orbiting Atmosphere Explorer E in eccentric orbit during 1975-1976 to investigate the bottomside ionosphere at altitudes 140-200 km. Representative daytime altitude profiles of ionization were stable against wide variations in horizontal wind patterns. Special features that sometimes appeared in the structured nightside ionization were apparent ion composition waves, intermediate layers of enhanced ionization, and ionization depletions similar to equatorial ionization bubbles. Apparent ion composition waves displayed a horizontal wave length of about 650 km. Enhanced layers of ionization appeared to be newly separated from the bottomside midnight F layer; its ions were primarily NO(+) and O2(+) without significant densities of metallic ions, an indication that metallic ions are not required to produce the layers at altitudes above 140 km. Equatorial ionization depletions were observed at lower altitudes than previously reported and displayed molecular ion depletions as well as O(+) depletions.

Groundwater flow to a horizontal or slanted well in an unconfined aquifer

NASA Astrophysics Data System (ADS)

Zhan, Hongbin; Zlotnik, Vitaly A.

2002-07-01

New semianalytical solutions for evaluation of the drawdown near horizontal and slanted wells with finite length screens in unconfined aquifers are presented. These fully three-dimensional solutions consider instantaneous drainage or delayed yield and aquifer anisotropy. As a basis, solution for the drawdown created by a point source in a uniform anisotropic unconfined aquifer is derived in Laplace domain. Using superposition, the point source solution is extended to the cases of the horizontal and slanted wells. The previous solutions for vertical wells can be described as a special case of the new solutions. Numerical Laplace inversion allows effective evaluation of the drawdown in real time. Examples illustrate the effects of well geometry and the aquifer parameters on drawdown. Results can be used to generate type curves from observations in piezometers and partially or fully penetrating observation wells. The proposed solutions and software are useful for the parameter identification, design of remediation systems, drainage, and mine dewatering.

Coarsening of stripe patterns: variations with quench depth and scaling.

PubMed

Tripathi, Ashwani K; Kumar, Deepak

2015-02-01

The coarsening of stripe patterns when the system is evolved from random initial states is studied by varying the quench depth ε, which is a measure of distance from the transition point of the stripe phase. The dynamics of the growth of stripe order, which is characterized by two length scales, depends on the quench depth. The growth exponents of the two length scales vary continuously with ε. The decay exponents for free energy, stripe curvature, and densities of defects like grain boundaries and dislocations also show similar variation. This implies a breakdown of the standard picture of nonequilibrium dynamical scaling. In order to understand the variations with ε we propose an additional scaling with a length scale dependent on ε. The main contribution to this length scale comes from the "pinning potential," which is unique to systems where the order parameter is spatially periodic. The periodic order parameter gives rise to an ε-dependent potential, which can pin defects like grain boundaries, dislocations, etc. This additional scaling provides a compact description of variations of growth exponents with quench depth in terms of just one exponent for each of the length scales. The relaxation of free energy, stripe curvature, and the defect densities have also been related to these length scales. The study is done at zero temperature using Swift-Hohenberg equation in two dimensions.

Influence of Tennis Racquet Kinematics on Ball Topspin Angular Velocity and Accuracy during the Forehand Groundstroke.

PubMed

Kwon, Sunku; Pfister, Robin; Hager, Ronald L; Hunter, Iain; Seeley, Matthew K

2017-12-01

Forehand groundstroke effectiveness is important for tennis success. Ball topspin angular velocity (TAV) and accuracy are important for forehand groundstroke effectiveness, and have been extensively studied, previously; despite previous, quality studies, it was unclear whether certain racquet kinematics relate to ball TAV and shot accuracy during the forehand groundstroke. This study evaluated potential relationships between (1) ball TAV and (2) forehand accuracy, and five measures of racquet kinematics: racquet head impact angle (i.e., closed or open face), horizontal and vertical racquet head velocity before impact, racquet head trajectory (resultant velocity direction, relative to horizontal) before impact, and hitting zone length (quasi-linear displacement, immediately before and after impact). Thirteen collegiate-level tennis players hit forehand groundstrokes in a biomechanics laboratory, where racquet kinematics and ball TAV were measured, and on a tennis court, to assess accuracy. Correlational statistics were used to evaluate potential relationships between racquet kinematics, and ball TAV (mixed model) and forehand accuracy (between-subjects model; α = 0.05). We observed an average (1) racquet head impact angle, (2) racquet head trajectory before impact, relative to horizontal, (3) racquet head horizontal velocity before impact, (4) racquet head vertical velocity before impact, and (5) hitting zone length of 80.4 ± 3.6˚, 18.6 ± 4.3˚, 15.4 ± 1.4 m·s -1 , 6.6 ± 2.2 m·s -1 , and 79.8 ± 8.6 mm, respectively; and an average ball TAV of 969 ± 375 revolutions per minute. Only racquet head impact angle and racquet head vertical velocity, before impact, significantly correlated with ball TAV (p < 0.01). None of the observed racquet kinematics significantly correlated to the measures of forehand accuracy. These results confirmed mechanical logic and indicate that increased ball TAV is associated with a more closed racquet head impact angle (ranging from 70 to 85˚, relative to the ground) and increased racquet head vertical velocity before impact.

Interactions between a fractal tree-like object and hydrodynamic turbulence: flow structure and characteristic mixing length

NASA Astrophysics Data System (ADS)

Meneveau, C. V.; Bai, K.; Katz, J.

2011-12-01

The vegetation canopy has a significant impact on various physical and biological processes such as forest microclimate, rainfall evaporation distribution and climate change. Most scaled laboratory experimental studies have used canopy element models that consist of rigid vertical strips or cylindrical rods that can be typically represented through only one or a few characteristic length scales, for example the diameter and height for cylindrical rods. However, most natural canopies and vegetation are highly multi-scale with branches and sub-branches, covering a wide range of length scales. Fractals provide a convenient idealization of multi-scale objects, since their multi-scale properties can be described in simple ways (Mandelbrot 1982). While fractal aspects of turbulence have been studied in several works in the past decades, research on turbulence generated by fractal objects started more recently. We present an experimental study of boundary layer flow over fractal tree-like objects. Detailed Particle-Image-Velocimetry (PIV) measurements are carried out in the near-wake of a fractal-like tree. The tree is a pre-fractal with five generations, with three branches and a scale reduction factor 1/2 at each generation. Its similarity fractal dimension (Mandelbrot 1982) is D ~ 1.58. Detailed mean velocity and turbulence stress profiles are documented, as well as their downstream development. We then turn attention to the turbulence mixing properties of the flow, specifically to the question whether a mixing length-scale can be identified in this flow, and if so, how it relates to the geometric length-scales in the pre-fractal object. Scatter plots of mean velocity gradient (shear) and Reynolds shear stress exhibit good linear relation at all locations in the flow. Therefore, in the transverse direction of the wake evolution, the Boussinesq eddy viscosity concept is appropriate to describe the mixing. We find that the measured mixing length increases with increasing streamwise locations. Conversely, the measured eddy viscosity and mixing length decrease with increasing elevation, which differs from eddy viscosity and mixing length behaviors of traditional boundary layers or canopies studied before. In order to find an appropriate length for the flow, several models based on the notion of superposition of scales are proposed and examined. One approach is based on spectral distributions. Another more practical approach is based on length-scale distributions evaluated using fractal geometry tools. These proposed models agree well with the measured mixing length. The results indicate that information about multi-scale clustering of branches as it occurs in fractals has to be incorporated into models of the mixing length for flows through canopies with multiple scales. The research is supported by National Science Foundation grant ATM-0621396 and AGS-1047550.

Turbulent thermal superstructures in Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Stevens, Richard J. A. M.; Blass, Alexander; Zhu, Xiaojue; Verzicco, Roberto; Lohse, Detlef

2018-04-01

We report the observation of superstructures, i.e., very large-scale and long living coherent structures in highly turbulent Rayleigh-Bénard convection up to Rayleigh Ra=109 . We perform direct numerical simulations in horizontally periodic domains with aspect ratios up to Γ =128 . In the considered Ra number regime the thermal superstructures have a horizontal extend of six to seven times the height of the domain and their size is independent of Ra. Many laboratory experiments and numerical simulations have focused on small aspect ratio cells in order to achieve the highest possible Ra. However, here we show that for very high Ra integral quantities such as the Nusselt number and volume averaged Reynolds number only converge to the large aspect ratio limit around Γ ≈4 , while horizontally averaged statistics such as standard deviation and kurtosis converge around Γ ≈8 , the integral scale converges around Γ ≈32 , and the peak position of the temperature variance and turbulent kinetic energy spectra only converge around Γ ≈64 .

Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide

PubMed Central

Chang, Ken-Wei; Huang, Chia-Chien

2016-01-01

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ±20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS. PMID:26786972

Seawater Upconing Under a Pumping Horizontal Well in a Confined Coastal Aquifer

NASA Astrophysics Data System (ADS)

Sun, D.; Zhan, H.

2003-12-01

Coastal margins are one of the nation­_s greatest natural resources and economic assets. Due to increasing concentration of human settlements and economic activities in the coastal margins, it is critical to find better technologies of managing the coastal groundwater resources. Coastal aquifers always have saline water underneath the fresh water. This phenomenon substantially limits the groundwater pumping rates using traditional vertical wells because of the upconing of the fresh/saline water interfaces and the potential of sea water intrusion. With the advancement of horizontal well technology, we propose to use long-screen (kilometers) horizontal wells in coastal aquifers to increase groundwater supply and prevent sea water intrusion into those wells. In this study, we have developed two mathematical models to predict the equilibrium location of upconed sharp interfaces due to pumping horizontal wells based on the linear model of Muskat (1982) and the non-linear model of Dagan and Bear (1968) which described the upcoming due to a partially penetrating vertical pumping well. The horizontal well solution is obtained by integrating the point sink solution along the horizontal well axis. The linear solution based on Muskat­_s model (1982) is acquired by neglecting the pressure field variation caused by the change of the fresh/saline water interface, while the nonlinear solution includes that variation. The computed interface profiles based on these two models are compared with those of vertical wells. The critical pumping rate is calculated and the sensitivity of the interface profile on aquifer anisotropy, horizontal well depth, and horizontal well length is tested. References: G. Dagan and J. Bear, Solving the problem of local interface upcoming in a coastal aquifer by the method of small perturbations, J. Hydraulic Research, 6, 15-44, 1968. Muskat, M, The flow of homogeneous Fluids Through Porous Media, International Human Resources Development Corporation, Boston, 763 PP, 1982.

The snakelike chain character of unstructured RNA.

PubMed

Jacobson, David R; McIntosh, Dustin B; Saleh, Omar A

2013-12-03

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod "wormlike chain" (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a "snakelike chain," characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Length-scale dependent mechanical properties of Al-Cu eutectic alloy: Molecular dynamics based model and its experimental verification

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

Tiwary, C. S., E-mail: cst.iisc@gmail.com; Chattopadhyay, K.; Chakraborty, S.

2014-05-28

This paper attempts to gain an understanding of the effect of lamellar length scale on the mechanical properties of two-phase metal-intermetallic eutectic structure. We first develop a molecular dynamics model for the in-situ grown eutectic interface followed by a model of deformation of Al-Al{sub 2}Cu lamellar eutectic. Leveraging the insights obtained from the simulation on the behaviour of dislocations at different length scales of the eutectic, we present and explain the experimental results on Al-Al{sub 2}Cu eutectic with various different lamellar spacing. The physics behind the mechanism is further quantified with help of atomic level energy model for different lengthmore » scale as well as different strain. An atomic level energy partitioning of the lamellae and the interface regions reveals that the energy of the lamellae core are accumulated more due to dislocations irrespective of the length-scale. Whereas the energy of the interface is accumulated more due to dislocations when the length-scale is smaller, but the trend is reversed when the length-scale is large beyond a critical size of about 80 nm.« less

Taming active turbulence with patterned soft interfaces.

PubMed

Guillamat, P; Ignés-Mullol, J; Sagués, F

2017-09-15

Active matter embraces systems that self-organize at different length and time scales, often exhibiting turbulent flows apparently deprived of spatiotemporal coherence. Here, we use a layer of a tubulin-based active gel to demonstrate that the geometry of active flows is determined by a single length scale, which we reveal in the exponential distribution of vortex sizes of active turbulence. Our experiments demonstrate that the same length scale reemerges as a cutoff for a scale-free power law distribution of swirling laminar flows when the material evolves in contact with a lattice of circular domains. The observed prevalence of this active length scale can be understood by considering the role of the topological defects that form during the spontaneous folding of microtubule bundles. These results demonstrate an unexpected strategy for active systems to adapt to external stimuli, and provide with a handle to probe the existence of intrinsic length and time scales.Active nematics consist of self-driven components that develop orientational order and turbulent flow. Here Guillamat et al. investigate an active nematic constrained in a quasi-2D geometrical setup and show that there exists an intrinsic length scale that determines the geometry in all forcing regimes.

Log-Normal Turbulence Dissipation in Global Ocean Models

NASA Astrophysics Data System (ADS)

Pearson, Brodie; Fox-Kemper, Baylor

2018-03-01

Data from turbulent numerical simulations of the global ocean demonstrate that the dissipation of kinetic energy obeys a nearly log-normal distribution even at large horizontal scales O (10 km ) . As the horizontal scales of resolved turbulence are larger than the ocean is deep, the Kolmogorov-Yaglom theory for intermittency in 3D homogeneous, isotropic turbulence cannot apply; instead, the down-scale potential enstrophy cascade of quasigeostrophic turbulence should. Yet, energy dissipation obeys approximate log-normality—robustly across depths, seasons, regions, and subgrid schemes. The distribution parameters, skewness and kurtosis, show small systematic departures from log-normality with depth and subgrid friction schemes. Log-normality suggests that a few high-dissipation locations dominate the integrated energy and enstrophy budgets, which should be taken into account when making inferences from simplified models and inferring global energy budgets from sparse observations.

Numerical simulation of turbulent convective flow over wavy terrain

NASA Astrophysics Data System (ADS)

Dörnbrack, A.; Schumann, U.

1993-09-01

By means of a large-eddy simulation, the convective boundary layer is investigated for flows over wavy terrain. The lower surface varies sinusoidally in the downstream direction while remaining constant in the other. Several cases are considered with amplitude δ up to 0.15 H and wavelength λ of H to 8 H, where H is the mean fluid-layer height. At the lower surface, the vertical heat flux is prescribed to be constant and the momentum flux is determined locally from the Monin-Obukhov relationship with a roughness length z o=10-4 H. The mean wind is varied between zero and 5 w *, where w * is the convective velocity scale. After rather long times, the flow structure shows horizontal scales up to 4 H, with a pattern similar to that over flat surfaces at corresponding shear friction. Weak mean wind destroys regular spatial structures induced by the surface undulation at zero mean wind. The surface heating suppresses mean-flow recirculation-regions even for steep surface waves. Short surface waves cause strong drag due to hydrostatic and dynamic pressure forces in addition to frictional drag. The pressure drag increases slowly with the mean velocity, and strongly with δ/ H. The turbulence variances increase mainly in the lower half of the mixed layer for U/w *>2.

The delineation and interpretation of the Earth's gravity field

NASA Technical Reports Server (NTRS)

Marsh, Bruce D.

1987-01-01

The geoid and topographic fields of the central Pacific were delineated and shown to correlate closely at intermediate wavelengths (500 to 2500 km). The associated admittance shows that anomalies having wavelengths less than about 1000 km are probably supported by the elastic strength of the lithosphere. Larger wavelength anomalies are due to dynamic effects in the sublithosphere. Direct modeling of small scale convection in the asthenosphere shows that the amplitudes of observed geoid and topographic anomalies can be independently matched, but that the observed admittance cannot. Only by imposing an initial regional variation in the thermal regime is it possible to match the admittance. It is proposed that this variation may be due to differences in the onset time of convection beneath the lithosphere of different ages. That is, convection beneath thickening lithosphere is strongly dependent on the rate of thickening (V) relative to the rise time for convection. The critical Rayleigh number contains the length scale K/V, where K is thermal diffusivity. Young, fast growing lithosphere stabilizes the underlying asthenosphere unless it has an unusually low viscosity. Lithosphere of different age, separated by fracture zones, will go unstable at different times, producing regional horizontal temperature gradient that may strongly influence convection. Laboratory and numerical experiments are proposed to study this form of convection and its influence on the geoid.

Convection due to an unstable density difference across a permeable membrane

NASA Astrophysics Data System (ADS)

Puthenveettil, Baburaj A.; Arakeri, Jaywant H.

We study natural convection driven by unstable concentration differences of sodium chloride (NaCl) across a horizontal permeable membrane at Rayleigh numbers (Ra) of 1010 to 1011 and Schmidt number (Sc)=600. A layer of brine lies over a layer of distilled water, separated by the membrane, in square-cross-section tanks. The membrane is permeable enough to allow a small flow across it at higher driving potentials. Based on the predominant mode of transport across the membrane, three regimes of convection, namely an advection regime, a diffusion regime and a combined regime, are identified. The near-membrane flow in all the regimes consists of sheet plumes formed from the unstable layers of fluid near the membrane. In the advection regime observed at higher concentration differences (Bb) show a common log-normal probability density function at all Ra. We propose a phenomenology which predicts /line{lambda}_b sqrt{Z_w Z_{V_i}}, where Zw and Z_{V_i} are, respectively, the near-wall length scales in Rayleighnard convection (RBC) and due to the advection velocity. In the combined regime, which occurs at intermediate values of C/2)4/3. At lower driving potentials, in the diffusion regime, the flux scaling is similar to that in turbulent RBC.

Atmospheric waves on Venus as seen by the Venus Express Radio Science Experiment VeRa

NASA Astrophysics Data System (ADS)

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-09-01

Next to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves and turbulence play a significant role in the development and maintenance of atmospheric super rotation.

Small-Scale Gravity Waves in ER-2 MMS/MTP Wind and Temperature Measurements during CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Wang, L.; Alexander, M. J.; Bui, T. P.; Mahoney, M. J.

2006-01-01

Lower stratospheric wind and temperature measurements made from NASA's high-altitude ER-2 research aircraft during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at the aircraft's flight level (typically approximately 20 km altitude). For a given flight segment, the S-transform (a Gaussian wavelet transform) was used to search for and identify small horizontal scale GW events, and to estimate their apparent horizontal wavelengths. The horizontal propagation directions of the events were determined using the Stokes parameter method combined with the cross S-transform analysis. The vertical temperature gradient was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100GW events were identified. They were generally high frequency waves with vertical wavelength of approximately 5 km and horizontal wavelength generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, approximately 20% of them had very short horizontal wavelength, very high intrinsic frequency, and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream of the locations of the events observed at the aircraft level. Finally, a probability density function of the reversible cooling rate due to GWs was obtained in this study, which may be useful for cirrus cloud models.

Examining Changes to the Madden-Julian Oscillation in a Warmer Climate Using CMIP5 Models

NASA Astrophysics Data System (ADS)

Rushley, Stephanie

Five models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) that reasonably represent the Madden-Julian Oscillation (MJO) are used to examine the response of the MJO to greenhouse gas induced warming. Changes in the MJO's amplitude, zonal scale, and phase speed are examined using daily-mean precipitation during boreal winter (November to April) when the MJO is strongest. The MJO precipitation variance increases with tropics mean surface temperature. However, the westward moving waves of the same temporal and spatial scales increase at about the same rate, suggesting that the maintenance mechanism for the MJO does not change with warming. On the other hand, a robust increase in phase speed of the MJO is found with a rate of 5-12% per degree of surface warming. The robust increase in the MJO phase speed are examined using the linear moisture wave theory of Adames and Kim (2016). In this theory, the MJO phase speed is determined by the horizontal moisture gradient in the lower troposphere, the gross dry stability, the convective moisture adjustment timescale, and zonal wavenumber of the MJO. All CMIP5 models examined show an increase in the horizontal humidity gradient, the gross dry stability and the convective moisture adjustment timescale, while exhibiting a decrease in the zonal wavenumber of the MJO. The increase in the horizontal humidity gradient and zonal scale of the MJO act to increase the speed of the MJO by enhancing horizontal moisture advection associated with the MJO, while the gross dry stability and convective moisture adjustment timescale act to slow down the MJO by dampening the horizontal moisture advection process. In all the models, the combined effects of the four key parameters act to speed up the MJO, matching the calculated phase speed changes with warming in the models.

Tectonic stress in the plates

NASA Technical Reports Server (NTRS)

Richardson, R. M.; Solomon, S. C.; Sleep, N. H.

1979-01-01

In the present paper, the basic set of global intraplate stress orientation data is plotted and tabulated. Although the global intraplate stress field is complicated, several large-scale patterns can be seen. Much of stable North America is characterized by an E-W to NE-SW trend for the maximum compressive stress. South American lithosphere beneath the Andes, and perhaps farther east in the stable interior, has horizontal compressive stresses trending E-W to NW-SE. Western Europe north of the Alps is characterized by a NW-SE trending maximum horizontal compression, while Asia has the maximum horizontal compressive stress trending more nearly N-S, especially near the Himalayan front.

Estimation of radiative forcing and chore length of shallow convective clouds (SCC) based on broadband pyranometer measurement network

NASA Astrophysics Data System (ADS)

Shi, H.

2017-12-01

We presented a method to identify and calculate cloud radiative forcing (CRF) and horizontal chore length (L) of shallow convective clouds (SCC) using a network of 9 broadband pyranometers. The analyzing data was collected from the SCC campaign during two years summers (2015 2016) at Baiqi site over Inner Mongolia grassland. The network of pyranometers was operated across a spatial domain covering 42.16-42.30° N and 114.83-114.98° E. The SCC detection method was verified by observer reports and cameras, which showed that the detection method and human observations were in agreement about 75 %. The differences between the SCC detection method and human observations can be responsible for following factors: 1) small or dissipating clouds can be neglected for the value of 1 min of temporal resolution of pyranometer; 2) human observation recorded weather conditions four times every day; 3) SCC was indistinguishable from coexistence of SCC and Cirrus (Ci); 4) the SCC detection method is weighted toward clouds crossing the sun's path, while the human observer can view clouds over the entire sky. The deviation of L can be attributed to two factors: 1) the accuracy of wind speed at height of SCC and the ratio of horizontal and vertical length play a key role in determine values of L; 2) the effect of variance of solar zenith angle can be negligible. The downwelling shortwave CRF of SCC was -134.1 Wm-2. The average value of L of SCC was 1129 m. Besides, the distribution of normalized cloud chore length agreed well with power-law fit.

Comparing 3D foot scanning with conventional measurement methods.

PubMed

Lee, Yu-Chi; Lin, Gloria; Wang, Mao-Jiun J

2014-01-01

Foot dimension information on different user groups is important for footwear design and clinical applications. Foot dimension data collected using different measurement methods presents accuracy problems. This study compared the precision and accuracy of the 3D foot scanning method with conventional foot dimension measurement methods including the digital caliper, ink footprint and digital footprint. Six commonly used foot dimensions, i.e. foot length, ball of foot length, outside ball of foot length, foot breadth diagonal, foot breadth horizontal and heel breadth were measured from 130 males and females using four foot measurement methods. Two-way ANOVA was performed to evaluate the sex and method effect on the measured foot dimensions. In addition, the mean absolute difference values and intra-class correlation coefficients (ICCs) were used for precision and accuracy evaluation. The results were also compared with the ISO 20685 criteria. The participant's sex and the measurement method were found (p < 0.05) to exert significant effects on the measured six foot dimensions. The precision of the 3D scanning measurement method with mean absolute difference values between 0.73 to 1.50 mm showed the best performance among the four measurement methods. The 3D scanning measurements showed better measurement accuracy performance than the other methods (mean absolute difference was 0.6 to 4.3 mm), except for measuring outside ball of foot length and foot breadth horizontal. The ICCs for all six foot dimension measurements among the four measurement methods were within the 0.61 to 0.98 range. Overall, the 3D foot scanner is recommended for collecting foot anthropometric data because it has relatively higher precision, accuracy and robustness. This finding suggests that when comparing foot anthropometric data among different references, it is important to consider the differences caused by the different measurement methods.

[Exploration of three-dimensional biometric measurement of emmetropic adult eye-ball by using magnetic resonance imaging technology].

PubMed

Xu, Hai-Ming; Zhou, Yun-Xin; Shi, Ming-Guang

2008-11-01

To study biometric measurements of emmetropic adult eyes with magnetic resonance imaging technology (MRI). MRI technology, with super-resolution, hyper-speed imaging and the integration of the thin-scanning layer, is applied to measure the three-dimensional biometric parameters of the eyeball. From January to December, 2003, emmetropic eyes from 31 normal Chinese adults (16 males and 15 females) aged from 18 to 32 years old (23.32 +/- 3.32) were successfully measured to obtain the volume of the eyeball and vitreous cavity; inner dimensions of the eye, including the anterior-posterior, vertical and horizontal diameters. The length of ocular axis was measured by A-echo too. Data was analyzed by SPSS 11.0 statistical software. The volume of the eyeball, anterior chamber, lens and the vitreous cavity is (6.013 +/- 0.449) ml, (0.348 +/- 0.020) ml, (0.183 +/- 0.015) ml, and (5.482 +/- 0.440) ml, respectively. The length of anterior-posterior diameter of the vitreous cavity is (16.008 +/- 0.707) mm. The ocular inner dimensions of horizontal, vertical and anterior-posterior planes were (22.455 +/- 0.983) mm, (23.290 +/- 0.815) mm and (22.619 +/- 0.912) mm, respectively. The length of the ocular axis is (23.10 +/- 0.92) mm (with MRI & Orbscan II) and (23.67 +/- 0.82) mm (with A-echo). The value of the ocular length in emmetropic eye measured with both MRI + Orbscan II and the (A-echo) in the present study is very close to the value of the Bennett-Rabbitts schematic eye (24.09 mm). MRI technology is valuable for obtaining more reliable and precise data in the study of ocular physiology and clinical ophthalmology.

Control and prediction components of movement planning in stuttering vs. nonstuttering adults

PubMed Central

Daliri, Ayoub; Prokopenko, Roman A.; Flanagan, J. Randall; Max, Ludo

2014-01-01

Purpose Stuttering individuals show speech and nonspeech sensorimotor deficiencies. To perform accurate movements, the sensorimotor system needs to generate appropriate control signals and correctly predict their sensory consequences. Using a reaching task, we examined the integrity of these control and prediction components, separately, for movements unrelated to the speech motor system. Method Nine stuttering and nine nonstuttering adults made fast reaching movements to visual targets while sliding an object under the index finger. To quantify control, we determined initial direction error and end-point error. To quantify prediction, we calculated the correlation between vertical and horizontal forces applied to the object—an index of how well vertical force (preventing slip) anticipated direction-dependent variations in horizontal force (moving the object). Results Directional and end-point error were significantly larger for the stuttering group. Both groups performed similarly in scaling vertical force with horizontal force. Conclusions The stuttering group's reduced reaching accuracy suggests limitations in generating control signals for voluntary movements, even for non-orofacial effectors. Typical scaling of vertical force with horizontal force suggests an intact ability to predict the consequences of planned control signals. Stuttering may be associated with generalized deficiencies in planning control signals rather than predicting the consequences of those signals. PMID:25203459

Performance of Renormalization Group Algebraic Turbulence Model on Boundary Layer Transition Simulation

NASA Technical Reports Server (NTRS)

Ahn, Kyung H.

1994-01-01

The RNG-based algebraic turbulence model, with a new method of solving the cubic equation and applying new length scales, is introduced. An analysis is made of the RNG length scale which was previously reported and the resulting eddy viscosity is compared with those from other algebraic turbulence models. Subsequently, a new length scale is introduced which actually uses the two previous RNG length scales in a systematic way to improve the model performance. The performance of the present RNG model is demonstrated by simulating the boundary layer flow over a flat plate and the flow over an airfoil.

Analyzing the Multiscale Processes in Tropical Cyclone Genesis Associated with African Easterly Waves using the PEEMD. Part I: Downscaling Processes

NASA Astrophysics Data System (ADS)

Wu, Y.; Shen, B. W.; Cheung, S.

2016-12-01

Recent advance in high-resolution global hurricane simulations and visualizations have collectively suggested the importance of both downscaling and upscaling processes in the formation and intensification of TCs. To reveal multiscale processes from massive volume of global data for multiple years, a scalable Parallel Ensemble Empirical Mode Decomposition (PEEMD) method has been developed for the analysis. In this study, the PEEMD is applied to analyzing 10-year (2004-2013) ERA-Interim global 0.750 resolution reanalysis data to explore the role of the downscaling processes in tropical cyclogenesis associated with African Easterly Waves (AEWs). Using the PEEMD, raw data are decomposed into oscillatory Intrinsic Function Modes (IMFs) that represent atmospheric systems of the various length scales and the trend mode that represents a non-oscillatory large scale environmental flow. Among oscillatory modes, results suggest that the third oscillatory mode (IMF3) is statistically correlated with the TC/AEW scale systems. Therefore, IMF3 and trend mode are analyzed in details. Our 10-year analysis shows that more than 50% of the AEW associated hurricanes reveal the association of storms' formation with the significant downscaling shear transfer from the larger-scale trend mode to the smaller scale IMF3. Future work will apply the PEEMD to the analysis of higher-resolution datasets to explore the role of the upscaling processes provided by the convection (or TC) in the development of the TC (or AEW). Figure caption: The tendency for horizontal wind shear for the total winds (black line), IMF3 (blue line), and trend mode (red line) and SLP (black dotted line) along the storm track of Helene (2006).

Estimating the components of the sensible heat budget of a tall forest canopy in complex terrain

NASA Astrophysics Data System (ADS)

Moderow, U.; Feigenwinter, C.; Bernhofer, C.

2007-04-01

Ultrasonic wind measurements, sonic temperature and air temperature data at two heights in the advection experiment MORE II were used to establish a complete budget of sensible heat including vertical advection, horizontal advection and horizontal turbulent flux divergence. MORE II took place at the long-term Carbo-Europe IP site in Tharandt, Germany. During the growing period of 2003 three additional towers were established to measure all relevant parameters for an estimation of advective fluxes, primarily of CO2. Additionally, in relation to other advection experiments, a calculation of the horizontal turbulent flux divergence is proposed and the relation of this flux to atmospheric stability and friction velocity is discussed. In order to obtain a complete budget, different scaling heights for horizontal advection and horizontal turbulent flux divergence are tested. It is shown that neglecting advective fluxes may lead to incorrect results. If advective fluxes are taken into account, the sensible heat budget based upon vertical turbulent flux and storage change only, is reduced by approximately 30%. Additional consideration of horizontal turbulent flux divergence would in turn add 5 10% to this sum (i.e., the sum of vertical turbulent flux plus storage change plus horizontal and vertical advection). In comparison with available energy horizontal advection is important at night whilst horizontal turbulent flux divergence is rather insignificant. Obviously, advective fluxes typically improve poor nighttime energy budget closure and might change ecosystem respiration fluxes considerably.

Some techniques for reducing the tower shadow of the DOE/NASA mod-0 wind turbine tower. [wind tunnel tests to measure effects of tower structure on wind velocity

NASA Technical Reports Server (NTRS)

Burley, R. R.; Savino, J. M.; Wagner, L. H.; Diedrich, J. H.

1979-01-01

Wind speed profile measurements to measure the effect of a wind turbine tower on the wind velocity are presented. Measurements were made in the wake of scale models of the tower and in the wake of certain full scale components to determine the magnitude of the speed reduction (tower shadow). Shadow abatement techniques tested on the towers included the removal of diagonals, replacement of diagonals and horizontals with round cross section members, installation of elliptical shapes on horizontal members, installation of airfoils on vertical members, and application of surface roughness to vertical members.

Robot-Applied Resistance Augments the Effects of Body Weight-Supported Treadmill Training on Stepping and Synaptic Plasticity in a Rodent Model of Spinal Cord Injury.

PubMed

Hinahon, Erika; Estrada, Christina; Tong, Lin; Won, Deborah S; de Leon, Ray D

2017-08-01

The application of resistive forces has been used during body weight-supported treadmill training (BWSTT) to improve walking function after spinal cord injury (SCI). Whether this form of training actually augments the effects of BWSTT is not yet known. To determine if robotic-applied resistance augments the effects of BWSTT using a controlled experimental design in a rodent model of SCI. Spinally contused rats were treadmill trained using robotic resistance against horizontal (n = 9) or vertical (n = 8) hind limb movements. Hind limb stepping was tested before and after 6 weeks of training. Two control groups, one receiving standard training (ie, without resistance; n = 9) and one untrained (n = 8), were also tested. At the terminal experiment, the spinal cords were prepared for immunohistochemical analysis of synaptophysin. Six weeks of training with horizontal resistance increased step length, whereas training with vertical resistance enhanced step height and movement velocity. None of these changes occurred in the group that received standard (ie, no resistance) training or in the untrained group. Only standard training increased the number of step cycles and shortened cycle period toward normal values. Synaptophysin expression in the ventral horn was highest in rats trained with horizontal resistance and in untrained rats and was positively correlated with step length. Adding robotic-applied resistance to BWSTT produced gains in locomotor function over BWSTT alone. The impact of resistive forces on spinal connections may depend on the nature of the resistive forces and the synaptic milieu that is present after SCI.

Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

USGS Publications Warehouse

Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

2013-01-01

The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

Prefabricated Vertical Drain (PVD) and Deep Cement Mixing (DCM)/Stiffened DCM (SDCM) techniques for soft ground improvement

NASA Astrophysics Data System (ADS)

Bergado, D. T.; Long, P. V.; Chaiyaput, S.; Balasubramaniam, A. S.

2018-04-01

Soft ground improvement techniques have become most practical and popular methods to increase soil strength, soil stiffness and reduce soil compressibility including the soft Bangkok clay. This paper focuses on comparative performances of prefabricated vertical drain (PVD) using surcharge, vacuum and heat preloading as well as the cement-admixed clay of Deep Cement Mixing (DCM) and Stiffened DCM (SDCM) methods. The Vacuum-PVD can increase the horizontal coefficient of consolidation, Ch, resulting in faster rate of settlement at the same magnitudes of settlement compared to Conventional PVD. Several field methods of applying vacuum preloading are also compared. Moreover, the Thermal PVD and Thermal Vacuum PVD can increase further the coefficient of horizontal consolidation, Ch, with the associated reduction of kh/ks values by reducing the drainage retardation effects in the smear zone around the PVD which resulted in faster rates of consolidation and higher magnitudes of settlements. Furthermore, the equivalent smear effect due to non-uniform consolidation is also discussed in addition to the smear due to the mechanical installation of PVDs. In addition, a new kind of reinforced deep mixing method, namely Stiffened Deep Cement Mixing (SDCM) pile is introduced to improve the flexural resistance, improve the field quality control, and prevent unexpected failures of the Deep Cement Mixing (DCM) pile. The SDCM pile consists of DCM pile reinforced with the insertion of precast reinforced concrete (RC) core. The full scale test embankment on soft clay improved by SDCM and DCM piles was also analysed. Numerical simulations using the 3D PLAXIS Foundation finite element software have been done to understand the behavior of SDCM and DCM piles. The simulation results indicated that the surface settlements decreased with increasing lengths of the RC cores, and, at lesser extent, increasing sectional areas of the RC cores in the SDCM piles. In addition, the lateral movements decreased by increasing the lengths (longer than 4 m) and, the sectional areas of the RC cores in the SDCM piles. The results of the numerical simulations closely agreed with the observed data and successfully verified the parameters affecting the performances and behavior of both SDCM and DCM piles.

Flow to partially penetrating wells in unconfined heterogeneous aquifers: Mean head and interpretation of pumping tests

NASA Astrophysics Data System (ADS)

Dagan, G.; Lessoff, S. C.

2011-06-01

A partially penetrating well of length Lw and radius Rw starts to pump at constant discharge Qw at t = 0 from an unconfined aquifer of thickness D. The aquifer is of random and stationary conductivity characterized by KG (geometric mean), σY2 (log conductivity variance), and I and Iv (the horizontal and vertical integral scales). The flow problem is solved under a few simplifying assumptions commonly adopted in the literature for homogeneous media: Rw/Lw ≪ 1, linearization of the free surface condition, and constant drainable porosity n. Additionally, it is assumed that Rw/I < 1 and Lw/Iv ≫ 1 (to simplify the well boundary conditions) and that a first-order approximation in σY2 (extended to finite σY2 on a conjectural basis) is adopted. The solution is obtained for the mean head field and the associated water table equation. The main result of the analysis is that the flow domain can be divided into three zones for : (1) the neighborhood of the well R ≪ I, where = (Qw/LwKA)h0(R, z, tKefuv/nD), with h0 being the zero-order solution pertaining to a homogeneous and isotropic aquifer, KA being the conductivity arithmetic mean, and Kefuv being the effective vertical conductivity in mean uniform flow, (2) an exterior zone R ⪆ I in which ?H? = (Qw/LwKefuh)h0(R?, z, tKefuv/nD), with Kefuh being the horizontal effective conductivity, and (3) an intermediate zone in which the solution requires a few numerical quadratures, not carried out here. The application to pumping tests reveals that identification of the aquifer parameters for homogeneous and anisotropic aquifers by commonly used methods can be applied for the drawdown measured in an observation well of length Low?Iv (to ensure exchange of space and ensemble head averages) in the second zone in order to identify Kefuh, Kefuv, and n. In contrast, the use of the drawdown in the well (first zone) leads to an overestimation of Kefuh by the factor KA/Kefuh.

Empirical scaling of the length of the longest increasing subsequences of random walks

NASA Astrophysics Data System (ADS)

Mendonça, J. Ricardo G.

2017-02-01

We provide Monte Carlo estimates of the scaling of the length L n of the longest increasing subsequences of n-step random walks for several different distributions of step lengths, short and heavy-tailed. Our simulations indicate that, barring possible logarithmic corrections, {{L}n}∼ {{n}θ} with the leading scaling exponent 0.60≲ θ ≲ 0.69 for the heavy-tailed distributions of step lengths examined, with values increasing as the distribution becomes more heavy-tailed, and θ ≃ 0.57 for distributions of finite variance, irrespective of the particular distribution. The results are consistent with existing rigorous bounds for θ, although in a somewhat surprising manner. For random walks with step lengths of finite variance, we conjecture that the correct asymptotic behavior of L n is given by \\sqrt{n}\\ln n , and also propose the form for the subleading asymptotics. The distribution of L n was found to follow a simple scaling form with scaling functions that vary with θ. Accordingly, when the step lengths are of finite variance they seem to be universal. The nature of this scaling remains unclear, since we lack a working model, microscopic or hydrodynamic, for the behavior of the length of the longest increasing subsequences of random walks.

INTERCOMPARISON STUDY OF ATMOSPHERIC MERCURY MODELS: 1. COMPARISON OF MODELS WITH SHORT-TERM MEASUREMENTS

EPA Science Inventory

Five regional scale models with a horizontal domain covering the European continent and its surrounding seas, one hemispheric and one global scale model participated in an atmospheric mercury modelling intercomparison study. Model-predicted concentrations in ambient air were comp...

EFFECTS OF INTENSE, SHORT DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND

EPA Science Inventory

Microtopography describes variations in soil surface elevation (nim or cm) for a scale of a few meters of horizontal distance, Small-scale (few centimeters) changes in vegetation communities synchronized with the elevation differences were observed in drained marsh (Zedler & Zedl...

IMPLEMENTATION OF AN URBAN CANOPY PARAMETERIZATION FOR FINE-SCALE SIMULATIONS

EPA Science Inventory

The Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) (Grell et al. 1994) has been modified to include an urban canopy parameterization (UCP) for fine-scale urban simulations ( 1 - km horizontal grid spacing ). The UCP accounts for dr...

Structure of large-scale flows and their oscillation in the thermal convection of liquid gallium.

PubMed

Yanagisawa, Takatoshi; Yamagishi, Yasuko; Hamano, Yozo; Tasaka, Yuji; Yoshida, Masataka; Yano, Kanako; Takeda, Yasushi

2010-07-01

This investigation observed large-scale flows in liquid gallium and the oscillation with Rayleigh-Bénard convection. An ultrasonic velocity profiling method was used to visualize the spatiotemporal flow pattern of the liquid gallium in a horizontally long rectangular vessel. Measuring the horizontal component of the flow velocity at several lines, an organized roll-like structure with four cells was observed in the 1×10(4)-2×10(5) range of Rayleigh numbers, and the rolls show clear oscillatory behavior. The long-term fluctuations in temperature observed in point measurements correspond to the oscillations of the organized roll structure. This flow structure can be interpreted as the continuous development of the oscillatory instability of two-dimensional roll convection that is theoretically investigated around the critical Rayleigh number. Both the velocity of the large-scale flows and the frequency of the oscillation increase proportional to the square root of the Rayleigh number. This indicates that the oscillation is closely related to the circulation of large-scale flow.

Tip vortices in the actuator line model

NASA Astrophysics Data System (ADS)

Martinez, Luis; Meneveau, Charles

2017-11-01

The actuator line model (ALM) is a widely used tool to represent the wind turbine blades in computational fluid dynamics without the need to resolve the full geometry of the blades. The ALM can be optimized to represent the `correct' aerodynamics of the blades by choosing an appropriate smearing length scale ɛ. This appropriate length scale creates a tip vortex which induces a downwash near the tip of the blade. A theoretical frame-work is used to establish a solution to the induced velocity created by a tip vortex as a function of the smearing length scale ɛ. A correction is presented which allows the use of a non-optimal smearing length scale but still provides the downwash which would be induced using the optimal length scale. Thanks to the National Science Foundation (NSF) who provided financial support for this research via Grants IGERT 0801471, IIA-1243482 (the WINDINSPIRE project) and ECCS-1230788.

Growth of primary motor neurons on horizontally aligned carbon nanotube thin films and striped patterns

NASA Astrophysics Data System (ADS)

Roberts, Megan J.; Leach, Michelle K.; Bedewy, Mostafa; Meshot, Eric R.; Copic, Davor; Corey, Joseph M.; Hart, A. John

2014-06-01

Objective. Carbon nanotubes (CNTs) are attractive for use in peripheral nerve interfaces because of their unique combination of strength, flexibility, electrical conductivity and nanoscale surface texture. Here we investigated the growth of motor neurons on thin films of horizontally aligned CNTs (HACNTs). Approach. We cultured primary embryonic rat motor neurons on HACNTs and performed statistical analysis of the length and orientation of neurites. We next presented motor neurons with substrates of alternating stripes of HACNTs and SiO2. Main results. The neurons survived on HACNT substrates for up to eight days, which was the full duration of our experiments. Statistical analysis of the length and orientation of neurites indicated that the longest neurites on HACNTs tended to align with the CNT direction, although the average neurite length was similar between HACNTs and glass control substrates. We observed that when motor neurons were presented with alternating stripes of HACNTs and SiO2, the proportion of neurons on HACNTs increases over time, suggesting that neurons selectively migrate toward and adhere to the HACNT surface. Significance. The behavior of motor neurons on CNTs has not been previously investigated, and we show that aligned CNTs could provide a viable interface material to motor neurons. Combined with emerging techniques to build complex hierarchical structures of CNTs, our results suggest that organised CNTs could be incorporated into nerve grafts that use physical and electrical cues to guide regenerating axons.

Shallow Cumulus Variability at the ARM Eastern North Atlantic Site

NASA Astrophysics Data System (ADS)

Lamer, K.; Kollias, P.; Ghate, V. P.; Luke, E. P.

2016-12-01

Cumulus clouds play a critical role in modulating the radiative and hydrological budget of the lower troposphere. These clouds, which are ubiquitous in regions of large-scale subsidence over the oceans, tend to be misrepresented in global climate models. Island-based, long-term, high-resolution ground-based observations can provide valuable insights on the factors controlling their macroscopic and microphysical properties and subsequenlty assist in model evaluation and guidance. Previous studies, limited to fair-weather cumuli over land, revealed that their fractional coverage is only weakly correlated with several parameters; the best ones being complex dynamical characteristics of the subcloud layer (vertical velocity skewness and eddy coherence). Other studies noted a relationship between cumuli depth and their propensity to precipitate. The current study will expand on such analysis by performing detail characterization of the full spectrum of shallow cumulus fields from non-precipitating to precipitating in the context of the large-scale forcing (i.e. thermodynamic structure and subsidence rates). Two years of ground-based remote sensing observations collected at the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) site are used to document macroscopic (cloud depth, cord length, cover), microphysical (liquid water path, cloud base rain rate) and dynamical (cloud base mass flux, eddy dissipation rate) cumuli properties. The observed variability in shallow cumulus is examined in relation to the variability of the large-scale environment as captured by the humidity profile, the magnitude of the low-level horizontal winds and near-surface aerosol conditions.

Modeling of Ceiling Fire Spread and Thermal Radiation.

DTIC Science & Technology

1981-10-01

under a PMMA ceiling and flame lengths under an inert ceiling are found to be in reasonable agreement with full-scale behavior. Although fire spread...5 3 Flame Lengths under Full-Scale Ceilings 12 4 Correlation of Flame Length under Inert Ceilings 16 5 Correlation of Flame Length under No 234 Model...Ceilings 17 6 Correlation of Flame Length under No B8811 Model Ceilings 18 7 Correlation of Flame Length under No. 223 Model Ceilings 19 8

Drilling side holes from a borehole

NASA Technical Reports Server (NTRS)

Collins, E. R., Jr.

1980-01-01

Machine takes long horizontal stratum samples from confines of 21 cm bore hole. Stacked interlocking half cylindrical shells mate to form rigid thrust tube. Drive shaft and core storage device is flexible and retractable. Entire machine fits in 10 meter length of steel tube. Machine could drill drainage or ventilation holes in coal mines, or provide important information for geological, oil, and geothermal surveys.

Tracheid dimensions in rootwood of southern pine

Treesearch

Floyd G. Manwiller

1972-01-01

In samples from 20 trees aged 12 to 89 years, rootwood tracheids were one-third longer and one-third larger in diameter and had walls 18 percent thinner and lumens almost two-thirds larger than stemwood tracheids measured at stump height. Tracheids from horizontal roots were longer and had thicker walls than those from roots of other orientations; length, cell diameter...

33 CFR 84.05 - Horizontal positioning and spacing of lights.

Code of Federal Regulations, 2011 CFR

2011-07-01

... forward light must be placed not more than one half of the length of the vessel from the stem. (b) On a... forward masthead lights. They shall be placed at or near the side of the vessel. (c) When the lights prescribed in Rule 27(b)(i) are placed vertically between the forward masthead light(s) and the after...

33 CFR 84.05 - Horizontal positioning and spacing of lights.

Code of Federal Regulations, 2010 CFR

2010-07-01

... forward light must be placed not more than one half of the length of the vessel from the stem. (b) On a... forward masthead lights. They shall be placed at or near the side of the vessel. (c) When the lights prescribed in Rule 27(b)(i) are placed vertically between the forward masthead light(s) and the after...

Some Mathematics and Physics in the Garden

ERIC Educational Resources Information Center

De Luca, R.

2012-01-01

Observing the way a watering hose is wrapped on a rotating cylinder, a catenary shape is detected for the suspended portion of the hose. We calculate the angle [alpha] the tangent to the curve at the highest point of the suspended portion makes with the horizontal. By means of this quantity, the length of the suspended and dragged portions of the…

Natural Length Scales Shape Liquid Phase Continuity in Unsaturated Flows

NASA Astrophysics Data System (ADS)

Assouline, S.; Lehmann, P. G.; Or, D.

2015-12-01

Unsaturated flows supporting soil evaporation and internal drainage play an important role in various hydrologic and climatic processes manifested at a wide range of scales. We study inherent natural length scales that govern these flow processes and constrain the spatial range of their representation by continuum models. These inherent length scales reflect interactions between intrinsic porous medium properties that affect liquid phase continuity, and the interplay among forces that drive and resist unsaturated flow. We have defined an intrinsic length scale for hydraulic continuity based on pore size distribution that controls soil evaporation dynamics (i.e., stage 1 to stage 2 transition). This simple metric may be used to delineate upper bounds for regional evaporative losses or the depth of soil-atmosphere interactions (in the absence of plants). A similar length scale governs the dynamics of internal redistribution towards attainment of field capacity, again through its effect on hydraulic continuity in the draining porous medium. The study provides a framework for guiding numerical and mathematical models for capillary flows across different scales considering the necessary conditions for coexistence of stationarity (REV), hydraulic continuity and intrinsic capillary gradients.

Root diversity in alpine plants: root length, tensile strength and plant age

NASA Astrophysics Data System (ADS)

Pohl, M.; Stroude, R.; Körner, C.; Buttler, A.; Rixen, C.

2009-04-01

A high diversity of plant species and functional groups is hypothesised to increase the diversity of root types and their subsequent effects for soil stability. However, even basic data on root characteristics of alpine plants are very scarce. Therefore, we determined important root characteristics of 13 plant species from different functional groups, i.e. grasses, herbs and shrubs. We excavated the whole root systems of 62 plants from a machine-graded ski slope at 2625 m a.s.l. and analysed the rooting depth, the horizontal root extension, root length and diameter. Single roots of plant species were tested for tensile strength. The age of herbs and shrubs was determined by growth-ring analysis. Root characteristics varied considerably between both plant species and functional groups. The rooting depth of different species ranged from 7.2 ± 0.97 cm to 20.5 ± 2.33 cm, but was significantly larger in the herb Geum reptans (70.8 ± 10.75 cm). The woody species Salix breviserrata reached the highest horizontal root extensions (96.8 ± 25.5 cm). Most plants had their longest roots in fine diameter classes (0.5

A Large-eddy Simulation Study of Vertical Axis Wind Turbine Wakes in the Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Shamsoddin, Sina; Porté-Agel, Fernando

2016-04-01

Vertical axis wind turbines (VAWTs) offer some advantages over their horizontal axis counterparts, and are being considered as a viable alternative to conventional horizontal axis wind turbines (HAWTs). Nevertheless, a relative shortage of scientific, academic and technical investigations of VAWTs is observed in the wind energy community with respect to HAWTs. Having this in mind, in this work, we aim to study the wake of a single VAWT, placed in the atmospheric boundary layer, using large-eddy simulation (LES) coupled with actuator line model (ALM). It is noteworthy that this is the first time that such a study is being performed. To do this, for a typical 1 MW VAWT design, first, the variation of power coefficient with both the chord length of the blades and the tip-speed ratio is analyzed using LES-ALM, and an optimum combination of chord length and tip-speed ratio is obtained. Subsequently, the wake of a VAWT with these optimum specifications is thoroughly examined by showing different relevant mean and turbulent wake flow statistics. Keywords: vertical axis wind turbine (VAWT); VAWT wake; Atmospheric Boundary Layer (ABL); large eddy simulation (LES); actuator line model (ALM); turbulence.

Atmospheric energetics in regions of intense convective activity

NASA Technical Reports Server (NTRS)

Fuelberg, H. E.

1977-01-01

Synoptic-scale budgets of kinetic and total potential energy are computed using 3- and 6-h data at nine times from NASA's fourth Atmospheric Variability Experiment (AVE IV). Two intense squall lines occurred during the period. Energy budgets for areas that enclose regions of intense convection are shown to have systematic changes that relate to the life cycles of the convection. Some of the synoptic-scale energy processes associated with the convection are found to be larger than those observed in the vicinity of mature cyclones. Volumes enclosing intense convection are found to have large values of cross-contour conversion of potential to kinetic energy and large horizontal export of kinetic energy. Although small net vertical transport of kinetic energy is observed, values at individual layers indicate large upward transport. Transfer of kinetic energy from grid to subgrid scales of motion occurs in the volumes. Latent heat release is large in the middle and upper troposphere and is thought to be the cause of the observed cyclic changes in the budget terms. Total potential energy is found to be imported horizontally in the lower half of the atmosphere, transported aloft, and then exported horizontally. Although local changes of kinetic energy and total potential energy are small, interaction between volumes enclosing convection with surrounding larger volumes is quite large.

Transport Loss Estimation of Fine Particulate Matter in Sampling Tube Based on Numerical Computation

NASA Astrophysics Data System (ADS)

Luo, L.; Cheng, Z.

2016-12-01

In-situ measurement of PM2.5 physical and chemical properties is one substantial approach for the mechanism investigation of PM2.5 pollution. Minimizing PM2.5 transport loss in sampling tube is essential for ensuring the accuracy of the measurement result. In order to estimate the integrated PM2.5 transport efficiency in sampling tube and optimize tube designs, the effects of different tube factors (length, bore size and bend number) on the PM2.5 transport were analyzed based on the numerical computation. The results shows that PM2.5 mass concentration transport efficiency of vertical tube with flowrate at 20.0 L·min-1, bore size at 4 mm, length at 1.0 m was 89.6%. However, the transport efficiency will increase to 98.3% when the bore size is increased to 14 mm. PM2.5 mass concentration transport efficiency of horizontal tube with flowrate at 1.0 L·min-1, bore size at 4mm, length at 10.0 m is 86.7%, increased to 99.2% with length at 0.5 m. Low transport efficiency of 85.2% for PM2.5 mass concentration is estimated in bend with flowrate at 20.0 L·min-1, bore size at 4mm, curvature angle at 90o. Laminar flow of air in tube through keeping the ratio of flowrate (L·min-1) and bore size (mm) less than 1.4 is beneficial to decrease the PM2.5 transport loss. For the target of PM2.5 transport efficiency higher than 97%, it is advised to use vertical sampling tubes with length less than 6.0 m for the flowrates of 2.5, 5.0, 10.0 L·min-1 and bore size larger than 12 mm for the flowrates of 16.7 or 20.0 L·min-1. For horizontal sampling tubes, tube length is decided by the ratio of flowrate and bore size. Meanwhile, it is suggested to decrease the amount of the bends in tube of turbulent flow.

Failure analysis of fuel cell electrodes using three-dimensional multi-length scale X-ray computed tomography

NASA Astrophysics Data System (ADS)

Pokhrel, A.; El Hannach, M.; Orfino, F. P.; Dutta, M.; Kjeang, E.

2016-10-01

X-ray computed tomography (XCT), a non-destructive technique, is proposed for three-dimensional, multi-length scale characterization of complex failure modes in fuel cell electrodes. Comparative tomography data sets are acquired for a conditioned beginning of life (BOL) and a degraded end of life (EOL) membrane electrode assembly subjected to cathode degradation by voltage cycling. Micro length scale analysis shows a five-fold increase in crack size and 57% thickness reduction in the EOL cathode catalyst layer, indicating widespread action of carbon corrosion. Complementary nano length scale analysis shows a significant reduction in porosity, increased pore size, and dramatically reduced effective diffusivity within the remaining porous structure of the catalyst layer at EOL. Collapsing of the structure is evident from the combination of thinning and reduced porosity, as uniquely determined by the multi-length scale approach. Additionally, a novel image processing based technique developed for nano scale segregation of pore, ionomer, and Pt/C dominated voxels shows an increase in ionomer volume fraction, Pt/C agglomerates, and severe carbon corrosion at the catalyst layer/membrane interface at EOL. In summary, XCT based multi-length scale analysis enables detailed information needed for comprehensive understanding of the complex failure modes observed in fuel cell electrodes.

Guided Growth of Horizontal ZnSe Nanowires and their Integration into High-Performance Blue-UV Photodetectors.

PubMed

Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

2015-07-15

Perfectly aligned horizontal ZnSe nano-wires are obtained by guided growth, and easily integrated into high-performance blue-UV photodetectors. Their crystal phase and crystallographic orientation are controlled by the epitaxial relations with six different sapphire planes. Guided growth paves the way for the large-scale integration of nanowires into optoelectronic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating the effect of compression on solute transport through degrading municipal solid waste

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

Woodman, N.D., E-mail: n.d.woodman@soton.ac.uk; Rees-White, T.C.; Stringfellow, A.M.

2014-11-15

Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to themore » presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.« less

Explosion source strong ground motions in the Mississippi embayment

USGS Publications Warehouse

Langston, C.A.; Bodin, P.; Powell, C.; Withers, M.; Horton, S.; Mooney, W.

2006-01-01

Two strong-motion arrays were deployed for the October 2002 Embayment Seismic Excitation Experiment to study the spatial variation of strong ground motions in the deep, unconsolidated sediments of the Mississippi embayment because there are no comparable strong-motion data from natural earthquakes in the area. Each linear array consisted of eight three-component K2 accelerographs spaced 15 m apart situated 1.2 and 2.5 kin from 2268-kg and 1134-kg borehole explosion sources, respectively. The array data show distinct body-wave and surface-wave arrivals that propagate within the thick, unconsolidated sedimentary column, the high-velocity basement rocks, and small-scale structure near the surface. Time-domain coherence of body-wave and surface-wave arrivals is computed for acceleration, velocity, and displacement time windows. Coherence is high for relatively low-frequency verticalcomponent Rayleigh waves and high-frequency P waves propagating across the array. Prominent high-frequency PS conversions seen on radial components, a proxy for the direct S wave from earthquake sources, lose coherence quickly over the 105-m length of the array. Transverse component signals are least coherent for any ground motion and appear to be highly scattered. Horizontal phase velocity is computed by using the ratio of particle velocity to estimates of the strain based on a plane-wave-propagation model. The resulting time-dependent phase-velocity map is a useful way to infer the propagation mechanisms of individual seismic phases and time windows of three-component waveforms. Displacement gradient analysis is a complementary technique for processing general spatial-array data to obtain horizontal slowness information.

Spatial statistics of hydrography and water chemistry in a eutrophic boreal lake based on sounding and water samples.

PubMed

Leppäranta, Matti; Lewis, John E; Heini, Anniina; Arvola, Lauri

2018-06-04

Spatial variability, an essential characteristic of lake ecosystems, has often been neglected in field research and monitoring. In this study, we apply spatial statistical methods for the key physics and chemistry variables and chlorophyll a over eight sampling dates in two consecutive years in a large (area 103 km 2 ) eutrophic boreal lake in southern Finland. In the four summer sampling dates, the water body was vertically and horizontally heterogenic except with color and DOC, in the two winter ice-covered dates DO was vertically stratified, while in the two autumn dates, no significant spatial differences in any of the measured variables were found. Chlorophyll a concentration was one order of magnitude lower under the ice cover than in open water. The Moran statistic for spatial correlation was significant for chlorophyll a and NO 2 +NO 3 -N in all summer situations and for dissolved oxygen and pH in three cases. In summer, the mass centers of the chemicals were within 1.5 km from the geometric center of the lake, and the 2nd moment radius ranged in 3.7-4.1 km respective to 3.9 km for the homogeneous situation. The lateral length scales of the studied variables were 1.5-2.5 km, about 1 km longer in the surface layer. The detected spatial "noise" strongly suggests that besides vertical variation also the horizontal variation in eutrophic lakes, in particular, should be considered when the ecosystems are monitored.

Clustering of vertically constrained passive particles in homogeneous isotropic turbulence.

PubMed

De Pietro, Massimo; van Hinsberg, Michel A T; Biferale, Luca; Clercx, Herman J H; Perlekar, Prasad; Toschi, Federico

2015-05-01

We analyze the dynamics of small particles vertically confined, by means of a linear restoring force, to move within a horizontal fluid slab in a three-dimensional (3D) homogeneous isotropic turbulent velocity field. The model that we introduce and study is possibly the simplest description for the dynamics of small aquatic organisms that, due to swimming, active regulation of their buoyancy, or any other mechanism, maintain themselves in a shallow horizontal layer below the free surface of oceans or lakes. By varying the strength of the restoring force, we are able to control the thickness of the fluid slab in which the particles can move. This allows us to analyze the statistical features of the system over a wide range of conditions going from a fully 3D incompressible flow (corresponding to the case of no confinement) to the extremely confined case corresponding to a two-dimensional slice. The background 3D turbulent velocity field is evolved by means of fully resolved direct numerical simulations. Whenever some level of vertical confinement is present, the particle trajectories deviate from that of fluid tracers and the particles experience an effectively compressible velocity field. Here, we have quantified the compressibility, the preferential concentration of the particles, and the correlation dimension by changing the strength of the restoring force. The main result is that there exists a particular value of the force constant, corresponding to a mean slab depth approximately equal to a few times the Kolmogorov length scale η, that maximizes the clustering of the particles.

Influence of a step-change increase of peat moisture content on the horizontal propagation of smouldering fires

NASA Astrophysics Data System (ADS)

Prat-Guitart, Nuria; Belcher, Claire M.; Hadden, Rory M.; Rein, Guillermo; Yearsley, Jon M.

2015-04-01

In shallow layers of peat, the transition between moss species causes a step-change of the horizontal distribution of peat moisture content. Post-fire studies in peatlands have reported shallow layers being consumed in irregular distributions. The unburned areas were found to be patches of wet Sphagnum moss. Our laboratory scale study analyses the effect of a horizontal step-change in moisture content on the spread of smouldering. We designed a laboratory-scale experiment (20×18×5 cm) within an insulated box filled with milled peat. Peat was ignited on one side of the box from which the smouldering fire horizontally self-propagates through a region of dry peat (MC1) and then through a wetter region of peat (MC2). An infrared camera, a webcam and thermocouples monitor the position of the smouldering fire spreading horizontally. The experiment was repeated with peats at different moisture content combinations to analyse the smouldering behaviour on a range of moisture content step-change conditions. The data analysis estimates the burned area and examines smouldering fire behaviour across a wide range of moisture content combinations reproducing realistic scenarios. We found that the area burned depends on peat moisture content before the step-change (MC1) as well as the increase in moisture of the step-change itself (difference between MC1 and MC2). Our study assists in researching the influence of peat moisture content on the spread of smouldering in peatland fire and contributes to a better understanding of the post-fire peatland landscape, helping to reconstruct smouldering fire events.

Horizontal Heat Impact of Urban Structures on the Surface Soil Layer and Its Diurnal Patterns under Different Micrometeorological Conditions

PubMed Central

Zhou, Hongxuan; Hu, Dan; Wang, Xiaolin; Han, Fengsen; Li, Yuanzheng; Wu, Xiaogang; Ma, Shengli

2016-01-01

The temperature of the surface soil layer around different orientation walls was investigated horizontally along several construction-soil micro-gradients in Beijing, China. On a diurnal scale, similar fluctuating trends in T0 and T50 (temperature of surface soil layer, 0 and 0.5 m from the building baseline) adjacent to the external walls of buildings with the same orientation usually appeared under similar micrometeorological conditions. The difference between T0 and T50 (ΔT0–50) can be considered an indicator of the intensity of the horizontal heat effects: higher ΔT0–50 values correspond to greater intensities. The values of ΔT0–50 for south-, north-, east- and west-facing sides of buildings were highest on sunny days in summer and exhibited values of 6.61 K, 1.64 K, 5.93 K and 2.76 K, respectively. The scope of horizontal heat impacts (Sh) changed on a diurnal scale between zero and the maximum, which fluctuated with the micrometeorological conditions. The maximum values of Sh were 0.30, 0.15, 0.20 and 0.20 m for south-, north-, east-, and west-facing walls. The ΔT0–50 was related to solar radiation, horizontal heat flux, relative humidity, wind speed, soil moisture differences and air temperature; the relative importance of these factors was 36.22%, 31.80%, 19.19%, 2.67%, 3.68% and 6.44%, respectively. PMID:26728627

Surface Roughness of the Moon Derived from Multi-frequency Radar Data

NASA Astrophysics Data System (ADS)

Fa, W.

2011-12-01

Surface roughness of the Moon provides important information concerning both significant questions about lunar surface processes and engineering constrains for human outposts and rover trafficabillity. Impact-related phenomena change the morphology and roughness of lunar surface, and therefore surface roughness provides clues to the formation and modification mechanisms of impact craters. Since the Apollo era, lunar surface roughness has been studied using different approaches, such as direct estimation from lunar surface digital topographic relief, and indirect analysis of Earth-based radar echo strengths. Submillimeter scale roughness at Apollo landing sites has been studied by computer stereophotogrammetry analysis of Apollo Lunar Surface Closeup Camera (ALSCC) pictures, whereas roughness at meter to kilometer scale has been studied using laser altimeter data from recent missions. Though these studies shown lunar surface roughness is scale dependent that can be described by fractal statistics, roughness at centimeter scale has not been studied yet. In this study, lunar surface roughnesses at centimeter scale are investigated using Earth-based 70 cm Arecibo radar data and miniature synthetic aperture radar (Mini-SAR) data at S- and X-band (with wavelengths 12.6 cm and 4.12 cm). Both observations and theoretical modeling show that radar echo strengths are mostly dominated by scattering from the surface and shallow buried rocks. Given the different penetration depths of radar waves at these frequencies (< 30 m for 70 cm wavelength, < 3 m at S-band, and < 1 m at X-band), radar echo strengths at S- and X-band will yield surface roughness directly, whereas radar echo at 70-cm will give an upper limit of lunar surface roughness. The integral equation method is used to model radar scattering from the rough lunar surface, and dielectric constant of regolith and surface roughness are two dominate factors. The complex dielectric constant of regolith is first estimated globally using the regolith composition and the relation among the dielectric constant, bulk density, and regolith composition. The statistical properties of lunar surface roughness are described by the root mean square (RMS) height and correlation length, which represent the vertical and horizontal scale of the roughness. The correlation length and its scale dependence are studied using the topography data from laser altimeter observations from recent lunar missions. As these two parameters are known, surface roughness (RMS slope) can be estimated by minimizing the difference between the observed and modeled radar echo strength. Surface roughness of several regions over Oceanus Procellarum and southeastern highlands on lunar nearside are studied, and preliminary results show that maira is smoother than highlands at 70 cm scale, whereas the situation turns opposite at 12 and 4 cm scale. Surface roughness of young craters is in general higher than that of maria and highlands, indicating large rock population produced during impacting process.

[Alteration of profile of treatment of the public psychiatric hospitals of Belo Horizonte, Brazil, in the context of mental health care reform].

PubMed

Coelho, Vívian Andrade Araújo; Volpe, Fernando Madalena; Diniz, Sabrina Stephanie Lana; Silva, Eliane Mussel da; Cunha, Cristiane de Freitas

2014-08-01

This article seeks to describe the profile of treatment and internment in public psychiatric hospitals in Belo Horizonte, Brazil, from 2002 to 2011. The changes in the characteristics of treatment and the profiles of the patients treated are analyzed in the context of health care reform. It is a study of temporal series with trend analysis by means of linear regression. There was a reduction in the total of patients treated in the period under scrutiny. Inversely, there was an increase in internments with a reduction in length of stay, though no change in readmission rates. Patients from Belo Horizonte prevailed, however a relative increase in demand from the surrounding area was observed. There was a reversal in the prevalence of morbidity switching from psychotic disorders to disorders resulting from the use of alcohol and/or other drugs. The alteration observed in the profile of treatment in public psychiatric hospitals in Belo Horizonte was concomitant with the progressive implementation of community mental health services, which have probably met the demand that was formerly directed to these hospitals. Currently the psychiatric hospital is not the first, much less the only venue for treatment in the mental health network in Minas Gerais.

Impact of Variable-Resolution Meshes on Regional Climate Simulations

NASA Astrophysics Data System (ADS)

Fowler, L. D.; Skamarock, W. C.; Bruyere, C. L.

2014-12-01

The Model for Prediction Across Scales (MPAS) is currently being used for seasonal-scale simulations on globally-uniform and regionally-refined meshes. Our ongoing research aims at analyzing simulations of tropical convective activity and tropical cyclone development during one hurricane season over the North Atlantic Ocean, contrasting statistics obtained with a variable-resolution mesh against those obtained with a quasi-uniform mesh. Analyses focus on the spatial distribution, frequency, and intensity of convective and grid-scale precipitations, and their relative contributions to the total precipitation as a function of the horizontal scale. Multi-month simulations initialized on May 1st 2005 using ERA-Interim re-analyses indicate that MPAS performs satisfactorily as a regional climate model for different combinations of horizontal resolutions and transitions between the coarse and refined meshes. Results highlight seamless transitions for convection, cloud microphysics, radiation, and land-surface processes between the quasi-uniform and locally- refined meshes, despite the fact that the physics parameterizations were not developed for variable resolution meshes. Our goal of analyzing the performance of MPAS is twofold. First, we want to establish that MPAS can be successfully used as a regional climate model, bypassing the need for nesting and nudging techniques at the edges of the computational domain as done in traditional regional climate modeling. Second, we want to assess the performance of our convective and cloud microphysics parameterizations as the horizontal resolution varies between the lower-resolution quasi-uniform and higher-resolution locally-refined areas of the global domain.

Impact of Variable-Resolution Meshes on Regional Climate Simulations

NASA Astrophysics Data System (ADS)

Fowler, L. D.; Skamarock, W. C.; Bruyere, C. L.

2013-12-01

The Model for Prediction Across Scales (MPAS) is currently being used for seasonal-scale simulations on globally-uniform and regionally-refined meshes. Our ongoing research aims at analyzing simulations of tropical convective activity and tropical cyclone development during one hurricane season over the North Atlantic Ocean, contrasting statistics obtained with a variable-resolution mesh against those obtained with a quasi-uniform mesh. Analyses focus on the spatial distribution, frequency, and intensity of convective and grid-scale precipitations, and their relative contributions to the total precipitation as a function of the horizontal scale. Multi-month simulations initialized on May 1st 2005 using NCEP/NCAR re-analyses indicate that MPAS performs satisfactorily as a regional climate model for different combinations of horizontal resolutions and transitions between the coarse and refined meshes. Results highlight seamless transitions for convection, cloud microphysics, radiation, and land-surface processes between the quasi-uniform and locally-refined meshes, despite the fact that the physics parameterizations were not developed for variable resolution meshes. Our goal of analyzing the performance of MPAS is twofold. First, we want to establish that MPAS can be successfully used as a regional climate model, bypassing the need for nesting and nudging techniques at the edges of the computational domain as done in traditional regional climate modeling. Second, we want to assess the performance of our convective and cloud microphysics parameterizations as the horizontal resolution varies between the lower-resolution quasi-uniform and higher-resolution locally-refined areas of the global domain.

Horizontal Contraction of Oceanic Lithosphere Tested Using Azimuths of Transform Faults

NASA Astrophysics Data System (ADS)

Gordon, R. G.; Mishra, J. K.

2012-12-01

A central hypothesis or approximation of plate tectonics is that the plates are rigid, which implies that oceanic lithosphere does not contract horizontally as it cools (hereinafter "no contraction"). An alternative hypothesis is that vertically averaged tensional thermal stress in the competent lithosphere is fully relieved by horizontal thermal contraction (hereinafter "full contraction"). These two hypotheses predict different azimuths for transform faults. We build on prior predictions of horizontal thermal contraction of oceanic lithosphere as a function of age to predict the bias induced in transform-fault azimuths by full contraction for 140 azimuths of transform faults that are globally distributed between 15 plate pairs. Predicted bias increases with the length of adjacent segments of mid-ocean ridges and depends on whether the adjacent ridges are stepped, crenellated, or a combination of the two. All else being equal, the bias decreases with the length of a transform fault and modestly decreases with increasing spreading rate. The value of the bias varies along a transform fault. To correct the observed transform-fault azimuths for the biases, we average the predicted values over the insonified portions of each transform fault. We find the bias to be as large as 2.5°, but more typically is ≤ 1.0°. We test whether correcting for the predicted biases improves the fit to plate motion data. To do so, we determine the sum-squared normalized misfit for various values of γ, which we define to be the fractional multiple of bias predicted for full contraction. γ = 1 corresponds to the full contraction, while γ = 0 corresponds to no contraction. We find that the minimum in sum-squared normalized misfit is obtained for γ = 0.9 ±0.4 (95% confidence limits), which excludes the hypothesis of no contraction, but is consistent with the hypothesis of full contraction. Application of the correction reduces but does not eliminate the longstanding misfit between the azimuth of the Kane transform fault with respect to those of the other North America-Nubia transform faults. We conclude that significant ridge-parallel horizontal thermal contraction occurs in young oceanic lithosphere and that it is accommodated by widening of transform-fault valleys, which causes biases in transform-fault azimuths up to 2.5°.

Surface rupture and slip variation induced by the 2010 El Mayor-Cucapah earthquake, Baja California, quantified using COSI-Corr analysis on pre- and post-earthquake LiDAR acquisitions

NASA Astrophysics Data System (ADS)

Leprince, S.; Hudnut, K. W.; Akciz, S. O.; Hinojosa-Corona, A.; Fletcher, J. M.

2011-12-01

One-hundred and three years after the publication of the Lawson report on the Great 1906 earthquake, accurate documentation of surface deformation along the entire length of an earthquake is still challenging. Analysis of pre- and post-earthquake topographic data provides an opportunity to deliver the full 3D displacement field of the ground's surface. However, direct differencing of a pre- and post-earthquake digital topography model (DEM) generally leads to biased estimation of the vertical component of the deformation. Indeed, if the earthquake also produced significant horizontal motion, or if the pre- and post-earthquake DEM acquisitions exhibit non-negligible horizontal mis-registration, then the vertical offset measured by direct differencing will be biased by the local topography gradient. To overcome this limitation, we use the COSI-Corr sub-pixel correlation algorithm to estimate the relative horizontal offset between the pre- and post- 2010 El Mayor - Cucapah earthquake high resolution LiDAR acquisitions. Compensating for the horizontal offset between the two LiDAR acquisitions allows us to estimate unbiased measurements of the vertical component of the surface fault rupture induced by the El Mayor-Cucapah earthquake. We will also show the limitations of the available data set, such as aircraft jitter artifacts, which impaired accurate measurements of the horizontal component of the surface deformation. This analysis shows an unprecedented view of the complete vertical slip component of the rupture induced by the Mw 7.2 2010 El Mayor-Cucapah earthquake, sampled at every 5 m, over a length of about 100 km, and with a vertical accuracy of a few centimeters. Using sampling bins as narrow as 150 m and 1.5 km long, variations in the vertical component of an oblique slip earthquake are presented, with breaks along multiple fault-strands showing opposite dip directions and diffuse boundaries. With the availability of high precision pre- and post-earthquake data, COSI-Corr has the ability to accurately document the variability of 3D surface slip along strike of an earthquake rupture. Such data can be used to investigate the causes of this variability, and improve our understanding of its influence on the pattern of ground shaking.

Stress anisotropy analysis and its effect on unconventional resource development in Montney play, Kakwa, Canada

NASA Astrophysics Data System (ADS)

Tak, Heewon; Choi, Jaewon; Jo, Sohyun; Hwang, Sukyeon

2017-04-01

Stress anisotropy analysis is important for estimating both stress regime and fracture geometry for the efficient development of unconventional resources. Despite being within the same play, different areas can have different stress regimes, which can affect drilling decisions. The Montney play is located in Canada between British Columbia and Alberta. In British Columbia it is known for its ductile shale and high horizontal stress anisotropy because of the Rocky Mountains; however, in Alberta, it has different geological characteristics with some studies finding weak horizontal stress anisotropy. Therefore, we studied the horizontal stress anisotropy using full azimuth seismic and well data in the Kakwa area in order to establish a drilling plan. Minimal horizontal anisotropy was discovered within the area and the direction of maximum horizontal anisotropy corresponded with the regional scale (i.e., NE-SW). The induced fractures were assumed to have a normal stress regime because of the large depth (> 3000 m). Additionally, because of the very high brittleness (Young's modulus > 9) and relatively weak horizontal stress anisotropy, the fracture geometry in the Kakwa area was estimated as complex or complex planar, as opposed to simply planar.

Fission track length distributions in multi-system thermochronology (Invited)

NASA Astrophysics Data System (ADS)

Gleadow, A. J.; Seiler, C.

2013-12-01

Fission track length distributions contain a unique record of past temperature variations and therefore play a key role in low-temperature thermochronology, for which there is no exact equivalent in any other method. Confined track lengths closely approximate the true etchable ranges of latent fission tracks [1] and are therefore favoured for fission track studies, but they still have a number of practical limitations. These include small numbers of suitable tracks, especially when only horizontal confined tracks are measured. Using only track-in-track events for measurement further limits the sample size. These restrictions become acute for low track-density samples, where length measurements may be impossible. Irradiating the surface with 252Cf tracks [2] can substantially increase the number of confined tracks, but many researchers do not have access to a Cf source. An even more significant issue has emerged from inter-laboratory comparison experiments that demonstrate a disturbingly poor reproducibility of length measurements between observers [3], a problem compounded by a lack of standardisation in measurement techniques. As a result, individual observers may measure different positions for the end of a track, contributing significantly to variability, and consequently blurring the thermal histories obtained. New digital microscopes open up important opportunities for improved track length measurements by reducing restrictions on sample size, and eliminating some sources of inter-observer bias. We have developed a track length measurement system that enables precise determination of vertical as well as horizontal track dimensions, allowing 3D lengths to be obtained. Lengths are measured on captured image stacks that can be analysed easily and may also be shared, for greater standardisation between laboratories. Length measurements are highly reproducible between different observers using this system, suggesting that at least one source of variability can be eliminated. The selection of lengths for imaging, however, still remains a source of potential bias between observers. The new measurement system also enables measurement of 3D lengths of surface-intersecting ';semi-tracks', the distributions of which have been well understood theoretically [1,4], but have not been used in practice because of difficulties of measuring vertical dimensions on older microscopes. Semi-track lengths are, of course, a degraded measure compared to confined tracks because they are randomly truncated. However, this is more than compensated by their very much greater abundance, by a factor of >60, compared to confined tracks. They are also more amenable to semi- or fully-automated measurement techniques than confined tracks. Moreover the distribution characteristics of semi-track lengths relative to confined track lengths are well understood so that in principle the two types could be used together in modelling thermal histories. The implementation of these new approaches for track length measurement should significantly improve the precision and standardisation of track length measurements at every stage of their utilisation, from annealing studies to thermal history modelling of unknowns. [1] Galbraith (2003) Statistics for FT Analysis, Chapman & Hall [2] Donelick et al. (2005) Rev Min Geochem 58, 49-94 [3] Ketcham et al. (2009) Ear Planet Sci Lett 284, 504-515 [4] Jonckheere & Van den haute (1999) Rad Meas 30, 155-179

Technology summary of the in situ bioremediation demonstration (methane biostimulation) via horizontal wells at the Savannah River Site Integrated Demonstration Project

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

Hazen, T.C.; Looney, B.B.; Fliermans, C.B.

1994-06-01

The US Department of Energy, Office of Technology Development, has been sponsoring full-scale environmental restoration technology demonstrations for the past 4 years. The Savannah River Site Integrated Demonstration focuses on ``Clean-up of Soils ad Groundwater Contaminated with Chlorinated VOCs.`` Several laboratories including our own had demonstrated the ability of methanotrophic bacteria to completely degrade or mineralize chlorinated solvents, and these bacteria were naturally found in soil and aquifer material. Thus the test consisted of injection of methane mixed with air into the contaminated aquifer via a horizontal well and extraction from the vadose zone via a parallel horizontal well.

CFD analysis of a Darrieus wind turbine

NASA Astrophysics Data System (ADS)

Niculescu, M. L.; Cojocaru, M. G.; Pricop, M. V.; Pepelea, D.; Dumitrache, A.; Crunteanu, D. E.

2017-07-01

The Darrieus wind turbine has some advantages over the horizontal-axis wind turbine. Firstly, its tip speed ratio is lower than that of the horizontal-axis wind turbine and, therefore, its noise is smaller, privileging their placement near populated areas. Secondly, the Darrieus wind turbine does needs no orientation mechanism with respect to wind direction in contrast to the horizontal-axis wind turbine. However, the efficiency of the Darrieus wind turbine is lower than that of the horizontal-axis wind turbine since its aerodynamics is much more complex. With the advances in computational fluids and computers, it is possible to simulate the Darrieus wind turbine more accurately to understand better its aerodynamics. For these reasons, the present papers deals with the computational aerodynamics of a Darrieus wind turbine applying the state of the art of CFD methods (anisotropic turbulence models, transition from laminar to turbulent, scale adaptive simulation) to better understand its unsteady behavior.

Horizontal and vertical dimensions of individualism-collectivism: a comparison of African Americans and European Americans.

PubMed

Komarraju, Meera; Cokley, Kevin O

2008-10-01

The current study examined ethnic differences in horizontal and vertical dimensions of individualism and collectivism among 96 African American and 149 European American college students. Participants completed the 32-item Singelis et al. (1995) Individualism/Collectivism Scale. Multivariate analyses of variance results yielded a main effect for ethnicity, with African Americans being significantly higher on horizontal individualism and European Americans being higher on horizontal collectivism and vertical individualism. A moderated multiple regression analysis indicated that ethnicity significantly moderated the relationship between individualism and collectivism. Individualism and collectivism were significantly and positively associated among African Americans, but not associated among European Americans. In addition, collectivism was related to grade point average for African Americans but not for European Americans. Contrary to the prevailing view of individualism-collectivism being unipolar, orthogonal dimensions, results provide support for individualism-collectivism to be considered as unipolar, related dimensions for African Americans.

Tests of crustal divergence models for Aphrodite Terra, Venus

NASA Technical Reports Server (NTRS)

Grimm, Robert E.; Solomon, Sean C.

1989-01-01

This paper discusses the characteristics of Aphrodite Terra, the highland region of Venus which is considered to be a likely site of mantle upwelling, active volcanism, and extensional tectonics, and examines the relation of these features to three alternative kinematic models for the interaction of mantle convection with the surface. These the 'vertical tectonics' model, in which little horizontal surface displacement results from mantle flow; the 'plate divergence' model, in which shear strain from large horizontal displacements is accommodated only in narrow zones of deformation; and the 'distributed deformation' model, in which strain from large horizontal motions is broadly accommodated. No convincing observational evidence was found to support the rigid-plate divergence, while the evidence of large-scale horizontal motions of Aphrodite argues against purely vertical tectonics. A model is proposed, involving a broad disruption of a thin lithosphere. In such a model, lineaments are considered to be surface manifestations of mantle convective flow.

New powerful statistics for alignment-free sequence comparison under a pattern transfer model.

PubMed

Liu, Xuemei; Wan, Lin; Li, Jing; Reinert, Gesine; Waterman, Michael S; Sun, Fengzhu

2011-09-07

Alignment-free sequence comparison is widely used for comparing gene regulatory regions and for identifying horizontally transferred genes. Recent studies on the power of a widely used alignment-free comparison statistic D2 and its variants D*2 and D(s)2 showed that their power approximates a limit smaller than 1 as the sequence length tends to infinity under a pattern transfer model. We develop new alignment-free statistics based on D2, D*2 and D(s)2 by comparing local sequence pairs and then summing over all the local sequence pairs of certain length. We show that the new statistics are much more powerful than the corresponding statistics and the power tends to 1 as the sequence length tends to infinity under the pattern transfer model. Copyright © 2011 Elsevier Ltd. All rights reserved.

New Powerful Statistics for Alignment-free Sequence Comparison Under a Pattern Transfer Model

PubMed Central

Liu, Xuemei; Wan, Lin; Li, Jing; Reinert, Gesine; Waterman, Michael S.; Sun, Fengzhu

2011-01-01

Alignment-free sequence comparison is widely used for comparing gene regulatory regions and for identifying horizontally transferred genes. Recent studies on the power of a widely used alignment-free comparison statistic D2 and its variants D2∗ and D2s showed that their power approximates a limit smaller than 1 as the sequence length tends to infinity under a pattern transfer model. We develop new alignment-free statistics based on D2, D2∗ and D2s by comparing local sequence pairs and then summing over all the local sequence pairs of certain length. We show that the new statistics are much more powerful than the corresponding statistics and the power tends to 1 as the sequence length tends to infinity under the pattern transfer model. PMID:21723298

Fluid dynamics structures in a fire environment observed in laboratory-scale experiments

Treesearch

J. Lozano; W. Tachajapong; D.R. Weise; S. Mahalingam; M. Princevac

2010-01-01

Particle Image Velocimetry (PIV) measurements were performed in laboratory-scale experimental fires spreading across horizontal fuel beds composed of aspen (Populus tremuloides Michx) excelsior. The continuous flame, intermittent flame, and thermal plume regions of a fire were investigated. Utilizing a PIV system, instantaneous velocity fields for...

Fate of estrone in laboratory-scale constructed wetlands

USDA-ARS?s Scientific Manuscript database

A horizontal, subsurface, laboratory-scale constructed wetland (CW) consisting of four cells in series was used to determine the attenuation of the steroid hormone estrone (E1) present in animal wastewater. Liquid swine manure diluted 1:80 with farm pond water and dosed with [14C]E1 flowed through ...

Large-area few-layer hexagonal boron nitride prepared by quadrupole field aided exfoliation

NASA Astrophysics Data System (ADS)

Lun Lu, Han; Zhi Rong, Min; Qiu Zhang, Ming

2018-03-01

A quadrupole electric field-mediated exfoliation method is proposed to convert micron-sized hexagonal boron nitride (h-BN) powder into few-layer hexagonal boron nitride nanosheets (h-BNNS). Under optimum conditions (400 Hz, 40 V, 32 μg ml-1, sodium deoxycholate, TAE medium), the h-BN powders (thickness >200 nm, horizontal scale ˜10 μm) are successfully exfoliated into 0.5-4 nm (1-10 layers) thick h-BNNS with the same horizontal scale. Dynamic laser scattering and atomic force microscope data show that the yield is 47.6% (for the portion with the thickness of 0.5-6 nm), and all of the vertical sizes are reduced to smaller than 18 nm (45 layers).

Λ(t)CDM model as a unified origin of holographic and agegraphic dark energy models

NASA Astrophysics Data System (ADS)

Chen, Yun; Zhu, Zong-Hong; Xu, Lixin; Alcaniz, J. S.

2011-04-01

Motivated by the fact that any nonzero Λ can introduce a length scale or a time scale into Einstein's theory, r=ct=3/|Λ|. Conversely, any cosmological length scale or time scale can introduce a Λ(t), Λ(t)=3/rΛ2(t)=3/(c2tΛ2(t)). In this Letter, we investigate the time varying Λ(t) corresponding to the length scales, including the Hubble horizon, the particle horizon and the future event horizon, and the time scales, including the age of the universe and the conformal time. It is found out that, in this scenario, the Λ(t)CDM model can be taken as the unified origin of the holographic and agegraphic dark energy models with interaction between the matter and the dark energy, where the interacting term is determined by Q=-ρ. We place observational constraints on the Λ(t)CDM models originating from different cosmological length scales and time scales with the recently compiled “Union2 compilation” which consists of 557 Type Ia supernovae (SNIa) covering a redshift range 0.015⩽z⩽1.4. In conclusion, an accelerating expansion universe can be derived in the cases taking the Hubble horizon, the future event horizon, the age of the universe and the conformal time as the length scale or the time scale.

Avoiding early revision rhytidectomy: a biomechanical comparison of tissue plication suture techniques.

PubMed

White, Jeremy B; Barraja, Mathieu; Mengesha, Tewodros; Bose, Sumit; Ashktorab, Samaneh; Bahn, Ryan; Vallance, Ryan; Lindsey, William H

2008-12-01

Manipulation and suspension of the superficial musculoaponeurotic system (SMAS) is performed by 74% of rhytidectomy surgeons. Multiple variations in suture techniques are employed in this task, but they have never been evaluated for differences in their ability to withstand stress. To compare the biomechanical properties of two different suture techniques that are used in SMAS plications during rhytidectomy: a double-layered running locking (DRL) stitch and multiple horizontal mattress stitches. Fourteen horizontal mattress plications, in rows of six sutures, and comparable lengths of 16 DRL stitch plications of pig skin samples, were stressed using a tensometer with grip displacement increasing at a constant rate of 0.5 cm/Min. The required force to cause plication failure was recorded for each sample at three suture break points. There was no significant difference between the two groups in the force required to cause the initial suture failure. Unlike the horizontal mattress plication, an initial break seemed to cause minimal to no distortion of the DRL tissue plication. When results were normalized by the initial break forces to account for small variations in tissue properties, the force ratio required to cause a second suture break was significantly larger in the DRL group than in the horizontal mattress technique. This is evidenced by the average second to first break force ratios of 1.62 vs. 1.13 for the DRL and horizontal mattress stitches, respectively, with a P-value of .60. The mean ratios of third to first break forces for the DRL and horizontal mattress groups were 2.08 and 0.91, respectively, with a P-value of .08. The DRL stitch requires more force than the horizontal mattress stitch to cause significant failure of tissue plication. This technique may enable plastic surgeons to avoid early revision rhytidectomy due to suture failure, and to create a long-lasting, youthful cosmetic result.

Similarity and Scale Invariance of Velocity and Temperature Structure Functions within and above Dense Canopies

NASA Astrophysics Data System (ADS)

Ghannam, K.; Katul, G. G.; Chamecki, M.

2016-12-01

The scale-wise properties of turbulent flow statistics are conventionally quantified using the structure function D_ss (r)= <〖(Δs)〗^2 > describing velocity (s=u) or scalar (s=c) concentration increments Δs=s(x+r)-s(x) at various scales or separation distances r, where <.> is Reynolds averaging over coordinates of statistical homogeneity. For locally homogeneous and isotropic turbulence, the structure function can unfold statistical invariance of the form D_ss (βr)=β^p D_ss (r) as has been demonstrated by Kolmogorov's theory for the inertial subrange in the absence of intermittency corrections. For scales larger than inertial, scale invariance need not hold though universal scaling properties can still emerge provided an appropriate length and velocity scales are identified. One recent study on the structure function of the streamwise velocity (s=u) in smooth and rough wall-bounded flows argued that a logarithmic scaling of the form D_ss/(u_*^2 )=A+B ln(r/l_ɛ ) exists at any height z above the wall (or roughness elements), with,l_ɛ,〖 u〗_*, A and B being a dissipation length scale, the friction velocity, and two similarity constants to be determined. Whether this scaling is valid across all atmospheric stability regimes in the roughness sublayer (RSL) and the possible co-existence of length scales other than l_ɛ that collapse D_ss (r) for velocity and temperature frames the scope of this work. Using year-round field measurements within and above an Amazonian canopy, the work here explores the aforementioned scaling for the streamwise (s=u) and vertical velocity (s=w) components, along with its extension to active scalars (s=T, the air temperature) inside canopies and in the RSL above canopies. While the premise is that a length scale such as l_ɛ may serve as a master closure length scale for turbulent momentum and heat flux budgets, the role of the vorticity thickness, the Obukhov length, the adjustment length scale, and height z are also explored for various scale (or r) regimes. Because the RSL blends D_ss (r) from its form inside the canopy to its form in the well-studied atmospheric surface layer, the scaling laws derived here offer a new perspective on the thickness of the RSL for momentum and scalars and its variations with atmospheric stability.

Constant Stress Drop Fits Earthquake Surface Slip-Length Data

NASA Astrophysics Data System (ADS)

Shaw, B. E.

2011-12-01

Slip at the surface of the Earth provides a direct window into the earthquake source. A longstanding controversy surrounds the scaling of average surface slip with rupture length, which shows the puzzling feature of continuing to increase with rupture length for lengths many times the seismogenic width. Here we show that a more careful treatment of how ruptures transition from small circular ruptures to large rectangular ruptures combined with an assumption of constant stress drop provides a new scaling law for slip versus length which (1) does an excellent job fitting the data, (2) gives an explanation for the large crossover lengthscale at which slip begins to saturate, and (3) supports constant stress drop scaling which matches that seen for small earthquakes. We additionally discuss how the new scaling can be usefully applied to seismic hazard estimates.

Understanding the k-5/3 to k-2.4 spectral break in aircraft wind data

NASA Astrophysics Data System (ADS)

Pinel, J.; Lovejoy, S.; Schertzer, D. J.; Tuck, A.

2010-12-01

A fundamental issue in atmospheric dynamics is to understand how the statistics of fluctuations of various fields vary with their space-time scale. The classical - and still “standard” model - dates back to Kraichnan and Charney’s work on 2-D and geostrophic (quasi 2-D) turbulence at the end of the 1960’s and early 1970’s. It postulates an isotropic 2-D turbulent regime at large scales and an isotropic 3D regime at small scales separated by a “dimensional transition” (once called a “mesoscale gap”) near the pressure scale height of ≈10 km. By the early 1980’s a quite different model emerged, the 23/9-D scaling model in which the dynamics were postulated to be dominated (over wide scale ranges) by a strongly anisotropic scale invariant cascade mechanism with structures becoming flatter and flatter at larger and larger scales in a scaling manner: the isotropy assumptions were discarded but the scaling and cascade assumptions retained. Today, thanks to the revolution in geodata and atmospheric models - both in quality and quantity - the 23/9-D model can explain the observed horizontal cascade structures in remotely sensed radiances, in meteorological “reanalyses”, in meteorological models, in high resolution drop sonde vertical analyses, of lidar vertical sections etc. All of these analyses directly contradict the standard model which predicts drastic “dimensional transitions” for scalar quantities. Indeed, until recently the only unexplained feature was a scale break in aircraft spectra of the (vector) horizontal wind somewhere between about 40 and 200 km. However - contrary to repeated claims - and thanks to a reanalysis of the historical papers - the transition that had been observed since the 1980’s was not between k^-5/3 and k^-3 but rather between k^-5/3 and k^-2.4. By 2009, the standard model was thus hanging by a thread. This was cut when careful analysis of scientific aircraft data allowed the 23/9-D model to explain the large scale k-2.4 regime as an artefact of the aircraft following a sloping trajectory: at large enough scales, the spectrum is simply dominated by vertical rather than horizontal fluctuations which have the required k^-2.4 form. Since aircraft frequently follow gently sloping isobars, this neatly explains the last obstacle to wide range anisotropic scaling models finally opening the door to an urgently needed consensus on the statistical structure of the atmosphere. However, objections remain: at large enough scales do isobaric and isoheight spectra really have different exponents? In this presentation we attempted to study this issue in more detail than before by analyzed data measured by commercial aircrafts through the Tropospheric Airborne Meteorological Data Reporting (TAMDAR) system over CONUS during year 2009. The TAMDAR system allows us to calculate the statistical properties of the wind field on constant pressure and altitude levels. Various statistical exponents were calculated (velocity increment in terms of horizontal, vertical displacement, pressure and time) and we show here what we learned and how this analysis can help with solving this question.

Holographic Lens for Pilot’s Head-Up Display

DTIC Science & Technology

1976-02-01

holog; rdm lens. The dynamically-stabilized recording apparatus for the full- scale transmission hologram lens was designed and assembled in Phase 2...8217LjI for which the fringe visibility measured is 0.707 ........... 25 3 Coherence lengjth for TEMQ is 3.5 cm........27 4 Masured sinkile frequency...horizontal focal surfaces ofthe T90-N8-21.9 hologram lens . . . . . . . 118 41 Chief ray efficiency measured as a function of vertical and horizontal field

Variability at Multiple Scales: Using an Array of Current and Pressure Sensor Equipped Inverted Echo Sounders to Measure the Ocean

DTIC Science & Technology

2016-11-29

travel time between the seafloor and the sea surface; bottom pressure and temperature; and near-bottom horizontal currents hourly for up to 5 years...pressure and current sensors (CPIESs). CPIESs (Figure 1) are moored instruments that measure (1) the round-trip acoustic travel time between the...measurements of surface-to-bottom round-trip acoustic- travel time (’c), bottom pressure and temperature, and near-bottom horizontal currents

Variability at Multiple Scales: Using an Array of Current- and Pressure-Sensor Equipped Inverted Echo Sounders to Measure the Ocean

DTIC Science & Technology

2016-11-29

travel time between the seafloor and the sea surface; bottom pressure and temperature; and near-bottom horizontal currents hourly for up to 5 years...pressure and current sensors (CPIESs). CPIESs (Figure 1) are moored instruments that measure (1) the round-trip acoustic travel time between the...measurements of surface-to-bottom round-trip acoustic- travel time (’c), bottom pressure and temperature, and near-bottom horizontal currents

Investigation of the scaling characteristics of LANDSAT temperature and vegetation data: a wavelet-based approach

NASA Astrophysics Data System (ADS)

Rathinasamy, Maheswaran; Bindhu, V. M.; Adamowski, Jan; Narasimhan, Balaji; Khosa, Rakesh

2017-10-01

An investigation of the scaling characteristics of vegetation and temperature data derived from LANDSAT data was undertaken for a heterogeneous area in Tamil Nadu, India. A wavelet-based multiresolution technique decomposed the data into large-scale mean vegetation and temperature fields and fluctuations in horizontal, diagonal, and vertical directions at hierarchical spatial resolutions. In this approach, the wavelet coefficients were used to investigate whether the normalized difference vegetation index (NDVI) and land surface temperature (LST) fields exhibited self-similar scaling behaviour. In this study, l-moments were used instead of conventional simple moments to understand scaling behaviour. Using the first six moments of the wavelet coefficients through five levels of dyadic decomposition, the NDVI data were shown to be statistically self-similar, with a slope of approximately -0.45 in each of the horizontal, vertical, and diagonal directions of the image, over scales ranging from 30 to 960 m. The temperature data were also shown to exhibit self-similarity with slopes ranging from -0.25 in the diagonal direction to -0.20 in the vertical direction over the same scales. These findings can help develop appropriate up- and down-scaling schemes of remotely sensed NDVI and LST data for various hydrologic and environmental modelling applications. A sensitivity analysis was also undertaken to understand the effect of mother wavelets on the scaling characteristics of LST and NDVI images.

Orientation dependent modulation of apparent speed: a model based on the dynamics of feed-forward and horizontal connectivity in V1 cortex.

PubMed

Seriès, Peggy; Georges, Sébastien; Lorenceau, Jean; Frégnac, Yves

2002-11-01

Psychophysical and physiological studies suggest that long-range horizontal connections in primary visual cortex participate in spatial integration and contour processing. Until recently, little attention has been paid to their intrinsic temporal properties. Recent physiological studies indicate, however, that the propagation of activity through long-range horizontal connections is slow, with time scales comparable to the perceptual scales involved in motion processing. Using a simple model of V1 connectivity, we explore some of the implications of this slow dynamics. The model predicts that V1 responses to a stimulus in the receptive field can be modulated by a previous stimulation, a few milliseconds to a few tens of milliseconds before, in the surround. We analyze this phenomenon and its possible consequences on speed perception, as a function of the spatio-temporal configuration of the visual inputs (relative orientation, spatial separation, temporal interval between the elements, sequence speed). We show that the dynamical interactions between feed-forward and horizontal signals in V1 can explain why the perceived speed of fast apparent motion sequences strongly depends on the orientation of their elements relative to the motion axis and can account for the range of speed for which this perceptual effect occurs (Georges, Seriès, Frégnac and Lorenceau, this issue).

Rainfall From Resolved Rather Than Parameterized Processes Better Represents the Present-Day and Climate Change Response of Moderate Rates in the Community Atmosphere Model

DOE PAGES

Kooperman, Gabriel J.; Pritchard, Michael S.; O'Brien, Travis A.; ...

2018-04-01

Deficiencies in the parameterizations of convection used in global climate models often lead to a distorted representation of the simulated rainfall intensity distribution (i.e., too much rainfall from weak rain rates). While encouraging improvements in high percentile rainfall intensity have been found as the horizontal resolution of the Community Atmosphere Model is increased to ~25 km, we demonstrate no corresponding improvement in the moderate rain rates that generate the majority of accumulated rainfall. Using a statistical framework designed to emphasize links between precipitation intensity and accumulated rainfall beyond just the frequency distribution, we show that CAM cannot realistically simulate moderatemore » rain rates, and cannot capture their intensification with climate change, even as resolution is increased. However, by separating the parameterized convective and large-scale resolved contributions to total rainfall, we find that the intensity, geographic pattern, and climate change response of CAM's large-scale rain rates are more consistent with observations (TRMM 3B42), superparameterization, and theoretical expectations, despite issues with parameterized convection. Increasing CAM's horizontal resolution does improve the representation of total rainfall intensity, but not due to changes in the intensity of large-scale rain rates, which are surprisingly insensitive to horizontal resolution. Rather, improvements occur through an increase in the relative contribution of the large-scale component to the total amount of accumulated rainfall. Analysis of sensitivities to convective timescale and entrainment rate confirm the importance of these parameters in the possible development of scale-aware parameterizations, but also reveal unrecognized trade-offs from the entanglement of precipitation frequency and total amount.« less

Rainfall From Resolved Rather Than Parameterized Processes Better Represents the Present-Day and Climate Change Response of Moderate Rates in the Community Atmosphere Model

NASA Astrophysics Data System (ADS)

Kooperman, Gabriel J.; Pritchard, Michael S.; O'Brien, Travis A.; Timmermans, Ben W.

2018-04-01

Deficiencies in the parameterizations of convection used in global climate models often lead to a distorted representation of the simulated rainfall intensity distribution (i.e., too much rainfall from weak rain rates). While encouraging improvements in high percentile rainfall intensity have been found as the horizontal resolution of the Community Atmosphere Model is increased to ˜25 km, we demonstrate no corresponding improvement in the moderate rain rates that generate the majority of accumulated rainfall. Using a statistical framework designed to emphasize links between precipitation intensity and accumulated rainfall beyond just the frequency distribution, we show that CAM cannot realistically simulate moderate rain rates, and cannot capture their intensification with climate change, even as resolution is increased. However, by separating the parameterized convective and large-scale resolved contributions to total rainfall, we find that the intensity, geographic pattern, and climate change response of CAM's large-scale rain rates are more consistent with observations (TRMM 3B42), superparameterization, and theoretical expectations, despite issues with parameterized convection. Increasing CAM's horizontal resolution does improve the representation of total rainfall intensity, but not due to changes in the intensity of large-scale rain rates, which are surprisingly insensitive to horizontal resolution. Rather, improvements occur through an increase in the relative contribution of the large-scale component to the total amount of accumulated rainfall. Analysis of sensitivities to convective timescale and entrainment rate confirm the importance of these parameters in the possible development of scale-aware parameterizations, but also reveal unrecognized trade-offs from the entanglement of precipitation frequency and total amount.

The Turbulent Structure of the Atmosphere: Vorticity, Winds and Temperature Emerge From Molecular Motion

NASA Astrophysics Data System (ADS)

Tuck, A. F.; Hovde, S. J.; Lovejoy, S.; Schertzer, D.

2007-12-01

Application of generalized scale invariance to horizontal airborne observations of winds, temperature, ozone and humidity reveals the atmosphere as a random, non-Gaussian Levy process, having mean scaling exponents H (conservation), C1 (intermittency) and alpha (Levy) of 0.56, 0.05 and 1.6 respectively in the cases of winds and temperature. A correlation between the intermittency of temperature and the ozone photodissociation rate in the Arctic lower stratosphere is interpreted in terms of the ring currents of non-equilibrium statistical mechanics in which vortices, fluid dynamical behavior, emerge from thermalized populations of Maxwellian molecules subjected to an anisotropy in the form of a flux. The emergence of jet streams and the definition of atmospheric temperature are examined in the light of these results. The vertical scaling of wind, temperature and humidity is examined through the depth of the troposphere using data observed by GPS dropsondes from the NOAA Gulfstream 4 aircraft over the eastern Pacific Ocean in boreal winter. The results exclude isotropic turbulence in the atmosphere, and reveal the structure of static, moist static and dynamic (Richardson number) stabilities to be sparse fractal sets. Each stable layer contains a set of smaller scale unstable sublayers, each of which in turn contains a set of stable sub-sublayers and so on. The moist static stability scales differently to the dry static stability in the lower troposphere. As with the 'horizontal' data, the 'vertical' data reveal a correlation between H for horizontal wind and measures of jet stream strength. It is pointed out that these results provide potentially a new way of testing numerical models of the atmosphere.

Rainfall From Resolved Rather Than Parameterized Processes Better Represents the Present-Day and Climate Change Response of Moderate Rates in the Community Atmosphere Model

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

Kooperman, Gabriel J.; Pritchard, Michael S.; O'Brien, Travis A.

Deficiencies in the parameterizations of convection used in global climate models often lead to a distorted representation of the simulated rainfall intensity distribution (i.e., too much rainfall from weak rain rates). While encouraging improvements in high percentile rainfall intensity have been found as the horizontal resolution of the Community Atmosphere Model is increased to ~25 km, we demonstrate no corresponding improvement in the moderate rain rates that generate the majority of accumulated rainfall. Using a statistical framework designed to emphasize links between precipitation intensity and accumulated rainfall beyond just the frequency distribution, we show that CAM cannot realistically simulate moderatemore » rain rates, and cannot capture their intensification with climate change, even as resolution is increased. However, by separating the parameterized convective and large-scale resolved contributions to total rainfall, we find that the intensity, geographic pattern, and climate change response of CAM's large-scale rain rates are more consistent with observations (TRMM 3B42), superparameterization, and theoretical expectations, despite issues with parameterized convection. Increasing CAM's horizontal resolution does improve the representation of total rainfall intensity, but not due to changes in the intensity of large-scale rain rates, which are surprisingly insensitive to horizontal resolution. Rather, improvements occur through an increase in the relative contribution of the large-scale component to the total amount of accumulated rainfall. Analysis of sensitivities to convective timescale and entrainment rate confirm the importance of these parameters in the possible development of scale-aware parameterizations, but also reveal unrecognized trade-offs from the entanglement of precipitation frequency and total amount.« less

Driven, underdamped Frenkel-Kontorova model on a quasiperiodic substrate

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

Vanossi, A.; Ro''der, J.; Bishop, A. R.

2001-01-01

We consider the underdamped dynamics of a chain of atoms subject to a dc driving force and a quasiperiodic substrate potential. The system has three inherent length scales which we take to be mutually incommensurate. We find that when the length scales are related by the spiral mean (a cubic irrational) there exists a value of the interparticle interaction strength above which the static friction is zero. When the length scales are related by the golden mean (a quadratic irrational) the static friction is always nonzero. >From considerations based on the connection of this problem to standard map theory, wemore » postulate that zero static friction is generally possible for incommensurate ratios of the length scales involved. However, when the length scales are quadratic irrationals, or have some commensurability with each other, the static friction will be nonzero for all choices of interaction parameters. We also comment on the nature of the depinning mechanisms and the steady states achieved by the moving chain.« less

Brillouin Scattering of Picosecond Laser Pulses in Preformed, Short-Scale-Length Plasmas

NASA Astrophysics Data System (ADS)

Gaeris, A. C.; Fisher, Y.; Delettrez, J. A.; Meyerhofer, D. D.

1996-11-01

Brillouin scattering (BS) has been studied in short-scale-length, preformed plasmas. The backscattered and specularly reflected light resulting from the interaction of high-power picosecond pulses with preformed silicon plasmas has been measured. A first laser pulse forms a short-scale-length plasma -- without significant BS -- while a second delayed pulse interacts with an expanded, drifting underdense region of the plasma with density scale length (0 <= Ln <= 600 λ _L). The pulses are generated at λ L = 1054 nm, with intensities up to 10^16 W/cm^2. The backscattered light spectra, threshold intensities, and enhanced reflectivities have been determined for different plasma-density scale lengths and are compared to Liu, Rosenbluth, and White's(C. S. Liu, M. N. Rosenbluth, and R. B. White, Phys. Fluids 17, 1211 (1974).) WKB treatment of stimulated Brillouin scattering in inhomogeneous drifting plasmas. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

Experiments on integral length scale control in atmospheric boundary layer wind tunnel

NASA Astrophysics Data System (ADS)

Varshney, Kapil; Poddar, Kamal

2011-11-01

Accurate predictions of turbulent characteristics in the atmospheric boundary layer (ABL) depends on understanding the effects of surface roughness on the spatial distribution of velocity, turbulence intensity, and turbulence length scales. Simulation of the ABL characteristics have been performed in a short test section length wind tunnel to determine the appropriate length scale factor for modeling, which ensures correct aeroelastic behavior of structural models for non-aerodynamic applications. The ABL characteristics have been simulated by using various configurations of passive devices such as vortex generators, air barriers, and slot in the test section floor which was extended into the contraction cone. Mean velocity and velocity fluctuations have been measured using a hot-wire anemometry system. Mean velocity, turbulence intensity, turbulence scale, and power spectral density of velocity fluctuations have been obtained from the experiments for various configuration of the passive devices. It is shown that the integral length scale factor can be controlled using various combinations of the passive devices.

Reynolds number scaling of straining motions in turbulence

NASA Astrophysics Data System (ADS)

Elsinga, Gerrit; Ishihara, T.; Goudar, M. V.; da Silva, C. B.; Hunt, J. C. R.

2017-11-01

Strain is an important fluid motion in turbulence as it is associated with the kinetic energy dissipation rate, vorticity stretching, and the dispersion of passive scalars. The present study investigates the scaling of the turbulent straining motions by evaluating the flow in the eigenframe of the local strain-rate tensor. The analysis is based on DNS of homogeneous isotropic turbulence covering a Reynolds number range Reλ = 34.6 - 1131. The resulting flow pattern reveals a shear layer containing tube-like vortices and a dissipation sheet, which both scale on the Kolmogorov length scale, η. The vorticity stretching motions scale on the Taylor length scale, while the flow outside the shear layer scales on the integral length scale. These scaling results are consistent with those in wall-bounded flow, which suggests a quantitative universality between the different flows. The overall coherence length of the vorticity is 120 η in all directions, which is considerably larger than the typical size of individual vortices, and reflects the importance of spatial organization at the small scales. Transitions in flow structure are identified at Reλ 45 and 250. Below these respective Reynolds numbers, the small-scale motions and the vorticity stretching motions appear underdeveloped.

Longitudinal growth of skeletal myotubes in vitro in a new horizontal mechanical cell stimulator

NASA Technical Reports Server (NTRS)

Vandenburgh, Herman H.; Karlisch, Patricia

1989-01-01

A tissue-culture model system for growing skeletal-muscle cells under more dynamic conditions than found in normal tissue-culture environments is described. A computerized device presented allows mechanical stimulation of the cell's substratum by 300 to 400 pct in length in the horizontal plane. Cell growth rates and skeletal-muscle organogenesis are stimulated in this in vitro system. It is noted that longitudinal myotube growth observed is accompanied by increased rates of cell proliferation and myoblast fusion. Prestretching the collagen-coated substratum before cell plating is shown to lead to increased cell proliferation, myotube orientation, and longitudinal myotube growth. The effects of substratum stretching on myogenesis in the model system are also assessed and attributed to alterations in the cell's extracellular matrix.

REACTOR MODERATOR STRUCTURE

DOEpatents

Fraas, A.P.; Tudor, J.J.

1963-08-01

An improved moderator structure for nuclear reactors consists of moderator blocks arranged in horizontal layers to form a multiplicity of vertically stacked columns of blocks. The blocks in each vertical column are keyed together, and a ceramic grid is disposed between each horizontal layer of blocks. Pressure plates cover- the lateral surface of the moderator structure in abutting relationship with the peripheral terminal lengths of the ceramic grids. Tubular springs are disposed between the pressure plates and a rigid external support. The tubular springs have their axes vertically disposed to facilitate passage of coolant gas through the springs and are spaced apart a selected distance such that at sonae preselected point of spring deflection, the sides of the springs will contact adjacent springs thereby causing a large increase in resistance to further spring deflection. (AEC)

Influence of Turbulent Flow and Fractal Scaling on Effective Permeability of Fracture Network

NASA Astrophysics Data System (ADS)

Zhu, J.

2017-12-01

A new approach is developed to calculate hydraulic gradient dependent effective permeability of a fractal fracture network where both laminar and turbulent flows may occur in individual fractures. A critical fracture length is used to distinguish flow characteristics in individual fractures. The developed new solutions can be used for the case of a general scaling relationship, an extension to the linear scaling. We examine the impact on the effective permeability of the network of fractal fracture network characteristics, which include the fractal scaling coefficient and exponent, fractal dimension, ratio of minimum over maximum fracture lengths. Results demonstrate that the developed solution can explain more variations of the effective permeability in relation to the fractal dimensions estimated from the field observations. At high hydraulic gradient the effective permeability decreases with the fractal scaling exponent, but increases with the fractal scaling exponent at low gradient. The effective permeability increases with the scaling coefficient, fractal dimension, fracture length ratio and maximum fracture length.

End-monomer Dynamics in Semiflexible Polymers

PubMed Central

Hinczewski, Michael; Schlagberger, Xaver; Rubinstein, Michael; Krichevsky, Oleg; Netz, Roland R.

2009-01-01

Spurred by an experimental controversy in the literature, we investigate the end-monomer dynamics of semiflexible polymers through Brownian hydrodynamic simulations and dynamic mean-field theory. Precise experimental observations over the last few years of end-monomer dynamics in the diffusion of double-stranded DNA have given conflicting results: one study indicated an unexpected Rouse-like scaling of the mean squared displacement (MSD) 〈r2(t)〉 ~ t1/2 at intermediate times, corresponding to fluctuations at length scales larger than the persistence length but smaller than the coil size; another study claimed the more conventional Zimm scaling 〈r2(t)〉 ~ t2/3 in the same time range. Using hydrodynamic simulations, analytical and scaling theories, we find a novel intermediate dynamical regime where the effective local exponent of the end-monomer MSD, α(t) = d log〈r2(t)〉/d log t, drops below the Zimm value of 2/3 for sufficiently long chains. The deviation from the Zimm prediction increases with chain length, though it does not reach the Rouse limit of 1/2. The qualitative features of this intermediate regime, found in simulations and in an improved mean-field theory for semiflexible polymers, in particular the variation of α(t) with chain and persistence lengths, can be reproduced through a heuristic scaling argument. Anomalously low values of the effective exponent α are explained by hydrodynamic effects related to the slow crossover from dynamics on length scales smaller than the persistence length to dynamics on larger length scales. PMID:21359118

Bupivacaine injection remodels extraocular muscles and corrects comitant strabismus.

PubMed

Miller, Joel M; Scott, Alan B; Danh, Kenneth K; Strasser, Dirk; Sane, Mona

2013-12-01

To evaluate the clinical effectiveness and anatomic changes resulting from bupivacaine injection into extraocular muscles to treat comitant horizontal strabismus. Prospective, observational clinical series. Thirty-one comitant horizontal strabismus patients. Nineteen patients with esotropia received bupivacaine injections in the lateral rectus muscle, and 12 patients with exotropia received bupivacaine injections in the medial rectus. Sixteen of these, with large strabismus angles, also received botulinum type A toxin injections in the antagonist muscle at the same treatment session. A second treatment was given to 13 patients who had residual strabismus after the first treatment. Clinical alignment measures and muscle volume, maximum cross-sectional area, and shape derived from magnetic resonance imaging, with follow-up examinations for up to 3 years. At an average of 15.3 months after the final treatment, original misalignment was reduced by 10.5 prism diopters (Δ; 6.0°) with residual deviations of 10Δ or less in 53% of patients. A single treatment with bupivacaine alone reduced misalignment at 11.3 months by 4.7Δ (2.7°) with residual deviations of 10Δ or less in 50% of patients. Alignment corrections were remarkably stable over follow-ups for as long as 3 years. Six months after bupivacaine injection, muscle volume had increased by 6.6%, and maximum cross-sectional area had increased by 8.5%, gradually relaxing toward pretreatment values thereafter. Computer modeling with Orbit 1.8 (Eidactics, San Francisco, CA) suggested that changes in agonist and antagonist muscle lengths were responsible for the enduring changes in eye alignment. Bupivacaine injection alone or together with botulinum toxin injection in the antagonist muscle improves eye alignment in comitant horizontal strabismus by inducing changes in rectus muscle structure and length. Copyright © 2013 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Intrapetrous Internal Carotid Artery: Evaluation of Exposure, Mobilization and Surgical Maneuvers Feasibility from a Retrosigmoid Approach in a Cadaveric Model.

PubMed

Scerrati, Alba; Ercan, Serdar; Wu, Pengfei; Zhang, Jun; Ammirati, Mario

2016-07-01

To provide a quantification of the exposure of the vertical and horizontal segments of the intrapetrous carotid artery (IPCA) and to evaluate the possibilities of its mobilization and of performing surgical maneuvers on it using the retrosigmoid approach. Twelve surgical dissections were performed bilaterally on 6 fresh cadavers. Predissection computed tomography (CT) scans with bone fiducials for intraoperative navigation were acquired. A retrosigmoid craniectomy was performed. The inframeatal space was drilled, the horizontal (HoIPCA) and vertical (VeIPCA) segments of the IPCA were exposed, and their measurements were recorded. The carotid canal was enlarged, the artery was carefully detached from the bone, and a vessel loop was inserted in order to mobilize its horizontal segment. Afterwards we performed different surgical maneuvers: We inflated a 5-French Fogarty balloon to compress the IPCA and repaired a 7-mm arteriotomy with a running suture. Specimens underwent a new CT scan to evaluate the amount of bone removal and the integrity of the inner ear structures. The HoIPCA and VeIPCA were exposed and anatomically preserved in all specimens without injuring the surrounding neurovascular structures. The HoIPCA presented an average length of 24.89 mm (range: 19.41-31.47 mm), and the VeIPCA presented an average length of 10.07 mm (range: 8.92-11.58 mm). The possibility of IPCA mobilization and the feasibility of performing surgical maneuvers were demonstrated. Postdissection CT scan showed the preservation of inner ear structures. Exposure and mobilization of the IPCA using a retrosigmoid approach are feasible and could represent a viable option for the possibility of reaching a total resection of selected skull base tumors, even when involvement of the carotid canal is present. Published by Elsevier Inc.

Multifractal Analysis of Velocity Vector Fields and a Continuous In-Scale Cascade Model

NASA Astrophysics Data System (ADS)

Fitton, G.; Tchiguirinskaia, I.; Schertzer, D.; Lovejoy, S.

2012-04-01

In this study we have compared the multifractal analyses of small-scale surface-layer wind velocities from two different datasets. The first dataset consists of six-months of wind velocity and temperature measurements at the heights 22, 23 and 43m. The measurements came from 3D sonic anemometers with a 10Hz data output rate positioned on a mast in a wind farm test site subject to wake turbulence effects. The location of the test site (Corsica, France) meant the large scale structures were subject to topography effects that therefore possibly caused buoyancy effects. The second dataset (Germany) consists of 300 twenty minute samples of horizontal wind velocity magnitudes simultaneously recorded at several positions on two masts. There are eight propeller anemometers on each mast, recording velocity magnitude data at 2.5Hz. The positioning of the anemometers is such that there are effectively two grids. One grid of 3 rows by 4 columns and a second of 5 rows by 2 columns. The ranges of temporal scale over which the analyses were done were from 1 to 103 seconds for both datasets. Thus, under the universal multifractal framework we found both datasets exhibit parameters α ≈ 1.5 and C1 ≈ 0.1. The parameters α and C1, measure respectively the multifractality and mean intermittency of the scaling field. A third parameter, H, quantifies the divergence from conservation of the field (e.g. H = 0 for the turbulent energy flux density). To estimate the parameters we used the ratio of the scaling moment function of the energy flux and of the velocity increments. This method was particularly useful when estimating the parameter α over larger scales. In fact it was not possible to obtain a reasonable estimate of alpha using the usual double trace moment method. For each case the scaling behaviour of the wind was almost isotropic when the scale ranges remained close to the sphero-scale. For the Corsica dataset this could be seen by the agreement of the spectral exponents of the order of 1.5 for all three components. Given we have only the horizontal wind components over a grid for the Germany dataset the comparable probability distributions of horizontal and vertical velocity increments shows the field is isotropic. The Germany dataset allows us to compare the spatial velocity increments with that of the temporal. We briefly mentioned above that the winds in Corsica were subject to vertical forcing effects over large scales. This means the velocity field scaled as 11/5 i.e. Bolgiano-Obukhov instead of Kolmogorov's. To test this we were required to invoke Taylor's frozen turbulence hypothesis since the data was a one point measurement. Having vertical and horizontal velocity increments means we can further justify the claims of an 11/5 scaling law for vertical shears of the velocity and test the validity of the Taylor's hypothesis. We used the results to first simulate the velocity components using continuous in-scale cascades and then discuss the reconstruction of the full vector fields.

[Principles of the EOS™ X-ray machine and its use in daily orthopedic practice].

PubMed

Illés, Tamás; Somoskeöy, Szabolcs

2012-02-26

The EOS™ X-ray machine, based on a Nobel prize-winning invention in Physics in the field of particle detection, is capable of simultaneously capturing biplanar X-ray images by slot scanning of the whole body in an upright, physiological load-bearing position, using ultra low radiation doses. The simultaneous capture of spatially calibrated anterioposterior and lateral images allows the performance of a three-dimensional (3D) surface reconstruction of the skeletal system by a special software. Parts of the skeletal system in X-ray images and 3D-reconstructed models appear in true 1:1 scale for size and volume, thus spinal and vertebral parameters, lower limb axis lengths and angles, as well as any relevant clinical parameters in orthopedic practice could be very precisely measured and calculated. Visualization of 3D reconstructed models in various views by the sterEOS 3D software enables the presentation of top view images, through which one can analyze the rotational conditions of lower limbs, joints and spine deformities in horizontal plane and this provides revolutionary novel possibilities in orthopedic surgery, especially in spine surgery.

Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics.

PubMed

Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

2016-01-18

We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37-0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics.

Photon Transport in One-Dimensional Incommensurately Epitaxial CsPbX 3 Arrays

DOE PAGES

Wang, Yiping; Sun, Xin; Shivanna, Ravichandran; ...

2016-11-16

One-dimensional nanoscale epitaxial arrays serve as a great model in studying fundamental physics and for emerging applications. With an increasing focus laid on the Cs-based inorganic halide perovskite out of its outstanding material stability, we have applied vapor phase epitaxy to grow well aligned horizontal CsPbX 3 (X: Cl, Br, or I or their mixed) nanowire arrays in large scale on mica substrate. The as-grown nanowire features a triangular prism morphology with typical length ranging from a few tens of micrometers to a few millimeters. Structural analysis reveals that the wire arrays follow the symmetry of mica substrate through incommensuratemore » epitaxy, paving a way for a universally applicable method to grow a broad family of halide perovskite materials. We have studied the unique photon transport in the one-dimensional structure in the all-inorganic Cs-based perovskite wires via temperature dependent and spatially resolved photoluminescence. Furthermore, epitaxy of well oriented wire arrays in halide perovskite would be a promising direction for enabling the circuit-level applications of halide perovskite in high-performance electro-optics and optoelectronics.« less

Large Scale Production of Densified Hydrogen Using Integrated Refrigeration and Storage

NASA Technical Reports Server (NTRS)

Notardonato, William U.; Swanger, Adam Michael; Jumper, Kevin M.; Fesmire, James E.; Tomsik, Thomas M.; Johnson, Wesley L.

2017-01-01

Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage (IRAS) technology at NASA Kennedy Space Center led to the production of large quantities of solid densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. System energy balances and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing (up to 1 K), and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. Twenty silicon diode temperature sensors were recorded over approximately one month for testing at two different fill levels (33 67). The phenomenon, observed at both two fill levels, is described and presented detailed and explained herein., and The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed.

Mechanical krill models for studying coordinated swimming

NASA Astrophysics Data System (ADS)

Montague, Alice; Lai, Hong Kuan; Samaee, Milad; Santhanakrishnan, Arvind

2016-11-01

The global biomass of Homo sapiens is about a third of the biomass of Euphausia superba, commonly known as the Antarctic krill. Krill participate in organized social behavior. Propulsive jets generated by individual krill in a school have been suggested to be important in providing hydrodynamic sensory cues. The importance of body positions and body angles on the wakes generated is challenging to study in free swimming krill. Our solution to study the flow fields of multiple krill was to develop mechanical krill robots. We designed krillbots using mostly 3D printed parts that are actuated by stepper motors. The krillbot limb lengths, angles, inter-limb spacing and pleopod stroke frequency were dynamically scaled using published data on free-swimming krill kinematics. The vertical and horizontal spacing between krillbots, as well as the body angle, are adjustable. In this study, we conducted particle image velocimetry (PIV) measurements with two tethered krillbots in a flow tank with no background flow. One krillbot was placed above and behind the other. Both krillbots were at a zero-degree body angle. Wake-body interactions visualized from PIV data will be presented.

Fiber-Optic Network Observations of Earthquake Wavefields

NASA Astrophysics Data System (ADS)

Lindsey, Nathaniel J.; Martin, Eileen R.; Dreger, Douglas S.; Freifeld, Barry; Cole, Stephen; James, Stephanie R.; Biondi, Biondo L.; Ajo-Franklin, Jonathan B.

2017-12-01

Our understanding of subsurface processes suffers from a profound observation bias: seismometers are sparse and clustered on continents. A new seismic recording approach, distributed acoustic sensing (DAS), transforms telecommunication fiber-optic cables into sensor arrays enabling meter-scale recording over tens of kilometers of linear fiber length. We analyze cataloged earthquake observations from three DAS arrays with different horizontal geometries to demonstrate some possibilities using this technology. In Fairbanks, Alaska, we find that stacking ground motion records along 20 m of fiber yield a waveform that shows a high degree of correlation in amplitude and phase with a colocated inertial seismometer record at 0.8-1.6 Hz. Using an L-shaped DAS array in Northern California, we record the nearly vertically incident arrival of an earthquake from The Geysers Geothermal Field and estimate its backazimuth and slowness via beamforming for different phases of the seismic wavefield. Lastly, we install a fiber in existing telecommunications conduits below Stanford University and show that little cable-to-soil coupling is required for teleseismic P and S phase arrival detection.

Improved scheme for parametrization of convection in the Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME)

NASA Astrophysics Data System (ADS)

Meneguz, Elena; Thomson, David; Witham, Claire; Kusmierczyk-Michulec, Jolanta

2015-04-01

NAME is a Lagrangian atmospheric dispersion model used by the Met Office to predict the dispersion of both natural and man-made contaminants in the atmosphere, e.g. volcanic ash, radioactive particles and chemical species. Atmospheric convection is responsible for transport and mixing of air resulting in a large exchange of heat and energy above the boundary layer. Although convection can transport material through the whole troposphere, convective clouds have a small horizontal length scale (of the order of few kilometres). Therefore, for large-scale transport the horizontal scale on which the convection exists is below the global NWP resolution used as input to NAME and convection must be parametrized. Prior to the work presented here, the enhanced vertical mixing generated by non-resolved convection was reproduced by randomly redistributing Lagrangian particles between the cloud base and cloud top with probability equal to 1/25th of the NWP predicted convective cloud fraction. Such a scheme is essentially diffusive and it does not make optimal use of all the information provided by the driving meteorological model. To make up for these shortcomings and make the parametrization more physically based, the convection scheme has been recently revised. The resulting version, presented in this paper, is now based on the balance equation between upward, entrainment and detrainment fluxes. In particular, upward mass fluxes are calculated with empirical formulas derived from Cloud Resolving Models and using the NWP convective precipitation diagnostic as closure. The fluxes are used to estimate how many particles entrain, move upward and detrain. Lastly, the scheme is completed by applying a compensating subsidence flux. The performance of the updated convection scheme is benchmarked against available observational data of passive tracers. In particular, radioxenon is a noble gas that can undergo significant long range transport: this study makes use of observations of the isotope 133Xe available at International Monitoring System stations around the South Pacific Ocean. In addition, timeseries of modelled output concentrations obtained using NAME on a grid of 25 km size are compared with those obtained with FLEXPART, another well-known atmospheric dispersion model used by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) and other scientific communities. Findings are discussed and discrepancies investigated.