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Sample records for hemispherical roughness element

  1. Global stability and sensitivity analysis of boundary-layer flows past a hemispherical roughness element

    NASA Astrophysics Data System (ADS)

    Citro, V.; Giannetti, F.; Luchini, P.; Auteri, F.

    2015-08-01

    We study the full three-dimensional instability mechanism past a hemispherical roughness element immersed in a laminar Blasius boundary layer. The inherent three-dimensional flow pattern beyond the Hopf bifurcation is characterized by coherent vortical structures usually called hairpin vortices. Direct numerical simulation results are used to analyze the formation and the shedding of hairpin vortices inside the shear layer. The first bifurcation is investigated by global-stability tools. We show the spatial structure of the linear direct and adjoint global eigenmodes of the linearized Navier-Stokes equations and use the structural-sensitivity field to locate the region where the instability mechanism acts. The core of this instability is found to be symmetric and spatially localized in the region immediately downstream of the roughness element. The effect of the variation of the ratio between the obstacle height k and the boundary layer thickness δk ∗ is also considered. The resulting bifurcation scenario is found to agree well with previous experimental investigations. A limit regime for k / δk ∗ < 1 . 5 is attained where the critical Reynolds number is almost constant, Rek ≈ 580. This result indicates that, in these conditions, the only important parameter identifying the bifurcation is the unperturbed (i.e., without the roughness element) velocity slope at the wall.

  2. NO PLIF Study of Hypersonic Transition Over a Discrete Hemispherical Roughness Element

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Bathel, Brett F.; Ivey, Christopher; Inman, Jennifer A.; Jones, Stephen B.

    2009-01-01

    Nitric oxide (NO) planar laser-induced fluorescence (PLIF) has been use to investigate the hypersonic flow over a flat plate with and without a 2-mm (0.08-in) radius hemispherical trip. In the absence of the trip, for all angles of attack and two different Reynolds numbers, the flow was observed to be laminar and mostly steady. Boundary layer thicknesses based on the observed PLIF intensity were measured and compared with a CFD computation, showing agreement. The PLIF boundary layer thickness remained constant while the NO flowrate was varied by a factor of 3, indicating non-perturbative seeding of NO. With the hemispherical trip in place, the flow was observed to be laminar but unsteady at the shallowest angle of attack and lowest Reynolds number and appeared vigorously turbulent at the steepest angle of attack and highest Reynolds number. Laminar corkscrew-shaped vortices oriented in the streamwise direction were frequently observed to transition the flow to more turbulent structures.

  3. Heat Transfer Variation on Protuberances and Surface Roughness Elements

    NASA Technical Reports Server (NTRS)

    Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.

    1995-01-01

    In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.

  4. Elastoplastic deformation of a roughness element

    NASA Astrophysics Data System (ADS)

    Murashov, M. V.; Kornev, Yu. V.

    2014-03-01

    The problem of using the mechanical properties determined in a macroexperiment in contact models for micron-sized roughness elements is considered. For a sample of commercial-purity AD1 aluminum, the penetration depths of an indenter into a rough surface element that are determined in a physical experiment and in a three-dimensional finite element simulation are compared. It is found that, with allowance for certain assumptions, the application of the properties determined in a macroexperiment requires their correction to take into account the cold work hardening of the surface layer in the sample material and the size effect.

  5. Hypersonic Viscous Flow Over Large Roughness Elements

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan; Choudhari, Meelan M.

    2009-01-01

    Viscous flow over discrete or distributed surface roughness has great implications for hypersonic flight due to aerothermodynamic considerations related to laminar-turbulent transition. Current prediction capability is greatly hampered by the limited knowledge base for such flows. To help fill that gap, numerical computations are used to investigate the intricate flow physics involved. An unstructured mesh, compressible Navier-Stokes code based on the space-time conservation element, solution element (CESE) method is used to perform time-accurate Navier-Stokes calculations for two roughness shapes investigated in wind tunnel experiments at NASA Langley Research Center. It was found through 2D parametric study that at subcritical Reynolds numbers, spontaneous absolute instability accompanying by sustained vortex shedding downstream of the roughness is likely to take place at subsonic free-stream conditions. On the other hand, convective instability may be the dominant mechanism for supersonic boundary layers. Three-dimensional calculations for both a rectangular and a cylindrical roughness element at post-shock Mach numbers of 4.1 and 6.5 also confirm that no self-sustained vortex generation from the top face of the roughness is observed, despite the presence of flow unsteadiness for the smaller post-shock Mach number case.

  6. Hypersonic Viscous Flow Over Large Roughness Elements

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan; Choudhari, Meelan M.

    2009-01-01

    Viscous flow over discrete or distributed surface roughness has great implications for hypersonic flight due to aerothermodynamic considerations related to laminar-turbulent transition. Current prediction capability is greatly hampered by the limited knowledge base for such flows. To help fill that gap, numerical computations are used to investigate the intricate flow physics involved. An unstructured mesh, compressible Navier-Stokes code based on the space-time conservation element, solution element (CESE) method is used to perform time-accurate Navier-Stokes calculations for two roughness shapes investigated in wind tunnel experiments at NASA Langley Research Center. It was found through 2D parametric study that at subcritical Reynolds numbers of the boundary layers, absolute instability resulting in vortex shedding downstream, is likely to weaken at supersonic free-stream conditions. On the other hand, convective instability may be the dominant mechanism for supersonic boundary layers. Three-dimensional calculations for a rectangular or cylindrical roughness element at post-shock Mach numbers of 4.1 and 6.5 also confirm that no self-sustained vortex generation is present.

  7. Elemental Water Impact Test: Phase 1 20-Inch Hemisphere

    NASA Technical Reports Server (NTRS)

    Vassilakos, Gregory J.

    2015-01-01

    Spacecraft are being designed based on LS-DYNA simulations of water landing impacts. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 1 of the EWIT series featured water impact tests of a 20-inch hemisphere dropped from heights of 5 feet and 10 feet. The hemisphere was outfitted with an accelerometer and three pressure gages. The focus of this report is the correlation of analytical models against test data.

  8. Transition Experiments on Blunt Bodies with Isolated Roughness Elements in Hypersonic Free Flight

    NASA Technical Reports Server (NTRS)

    Reda, Daniel C.; Wilder, Michael C.; Prabhu, Dinesh K.

    2010-01-01

    Smooth titanium hemispheres with isolated three-dimensional (3D) surface roughness elements were flown in the NASA Ames hypersonic ballistic range through quiescent CO2 and air environments. Global surface intensity (temperature) distributions were optically measured and thermal wakes behind individual roughness elements were analyzed to define tripping effectiveness. Real-gas Navier-Stokes calculations of model flowfields, including laminar boundary layer development in these flowfields, were conducted predict key dimensionless parameters used to correlate transition on blunt bodies in hypersonic flow. For isolated roughness elements totally immersed within the laminar boundary layer, critical roughness Reynolds numbers for flights in air were found to be higher than those measured for flights in CO2, i.e., it was easier to trip the CO2 boundary layer to turbulence. Tripping effectiveness was found to be dependent on trip location within the subsonic region of the blunt body flowfield, with effective tripping being most difficult to achieve for elements positioned closest to the stagnation point. Direct comparisons of critical roughness Reynolds numbers for 3D isolated versus 3D distributed roughness elements for flights in air showed that distributed roughness patterns were significantly more effective at tripping the blunt body laminar boundary layer to turbulence.

  9. Effect of surface morphology on drag and roughness sublayer in flows over regular roughness elements

    NASA Astrophysics Data System (ADS)

    Placidi, Marco; Ganapathisubramani, Bharathram

    2014-11-01

    The effects of systematically varied roughness morphology on bulk drag and on the spatial structure of turbulent boundary layers are examined by performing a series of wind tunnel experiments. In this study, rough surfaces consisting of regularly and uniformly distributed LEGO™ bricks are employed. Twelve different patterns are adopted in order to methodically examine the individual effects of frontal solidity (λF, frontal area of the roughness elements per unit wall-parallel area) and plan solidity (λP, plan area of roughness elements per unit wall-parallel area), on both the bulk drag and the turbulence structure. A floating element friction balance based on Krogstad & Efros (2010) was designed and manufactured to measure the drag generated by the different surfaces. In parallel, high resolution planar and stereoscopic Particle Image Velocimetry (PIV) was applied to investigate the flow features. This talk will focus on the effects of each solidity parameter on the bulk drag and attempt to relate the observed trends to the flow structures in the roughness sublayer. Currently at City University London.

  10. Convective Enhancement of Icing Roughness Elements in Stagnation Region Flows

    NASA Technical Reports Server (NTRS)

    Hughes, Michael T.; McClain, Stephen T.; Vargas, Mario; Broeren, Andy

    2015-01-01

    To improve existing ice accretion simulation codes, more data regarding ice roughness and its effects on convective heat transfer are required. To build on existing research on this topic, this study used the Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. Using the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with 3 surfaces, each with a different representation of ice roughness: 1) a control surface with no ice roughness, 2) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 10x, and 3) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 25x. Temperature data from the tests were recorded using an infrared camera and thermocouples imbedded in the test plate. From the temperature data, a convective heat transfer coefficient map was created for each case. Additional testing was also performed to validate the VIST's flow quality. These tests included five-hole probe and hot-wire probe velocity traces to provide flow visualization and to study boundary layer formation on the various test surfaces. The knowledge gained during the experiments will help improve ice accretion codes by providing heat transfer coefficient validation data and by providing flow visualization data helping understand current and future experiments performed in the VIST.

  11. Adjustment of roughness sublayer in turbulent flows over two-dimensional idealised roughness elements

    NASA Astrophysics Data System (ADS)

    HO, Yat-Kiu; LIU, Chun-Ho

    2015-04-01

    The atmospheric boundary layer (ABL) immediately above the urban canopy is the roughness sublayer (RSL). In this layer, flows and turbulence are strongly affected by the roughness elements beneath, e.g. building obstacles. The wind flows over urban areas could be represented by conventional logarithmic law of the wall (log-law) in the neutrally stratified ABL. However, in the RSL region, the vertical wind profile deviates from that predicted from log-law and the effect could be extended from ground level up to several canopy heights. As a result, the Monin-Obukhov similarity theory (MOST) fails and an additional length scale is required to describe the flows. The key aim of this study is to introduce a simple wind profile model which accounts for the effect of the RSL in neutral stratification using wind tunnel experiments. Profile measurements of wind speeds and turbulence quantities over various two-dimensional (2D) idealised roughness elements are carried out in an open-circuit wind tunnel with test section of size 560 mm (width) × 560 mm (height) × 6 m (length). The separation between the roughness elements is varied systematically so that ten different types of surface forms are adopted. The velocity measurements are obtained by hot-wire anemometry using X-probe design (for UW- measurements) with a constant temperature anemometer. For each configuration, eight vertical profiles are collected over the canopy, including solid boundaries and cavities of the roughness elements. Firstly, we compute the measurement results using conventional MOST to determine different roughness parameters. Afterwards, we derive the RSL height from the Reynolds stress profiles. Since the profiles taken from different locations of the canopy are eventually converged with increasing height, we use this 'congregated height' to define the RSL height. Next, we introduce an alternative function, i.e. power-law function, instead of MOST, to describe the velocity profile in attempt to

  12. Connections Between the Spring Breakup of the Southern Hemisphere Polar Vortex, Stationary Waves, and Air-sea Roughness

    NASA Technical Reports Server (NTRS)

    Garfinkel, Chaim I.; Oman, Luke David; Barnes, Elizabeth A.; Waugh, Darryn W.; Hurwitz, Margaret H.; Molod, Andrea M.

    2013-01-01

    A robust connection between the drag on surface-layer winds and the stratospheric circulation is demonstrated in NASA's Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). Specifically, an updated parameterization of roughness at the air-sea interface, in which surface roughness is increased for moderate wind speeds (4ms to 20ms), leads to a decrease in model biases in Southern Hemispheric ozone, polar cap temperature, stationary wave heat flux, and springtime vortex breakup. A dynamical mechanism is proposed whereby increased surface roughness leads to improved stationary waves. Increased surface roughness leads to anomalous eddy momentum flux convergence primarily in the Indian Ocean sector (where eddies are strongest climatologically) in September and October. The localization of the eddy momentum flux convergence anomaly in the Indian Ocean sector leads to a zonally asymmetric reduction in zonal wind and, by geostrophy, to a wavenumber-1 stationary wave pattern. This tropospheric stationary wave pattern leads to enhanced upwards wave activity entering the stratosphere. The net effect is an improved Southern Hemisphere vortex: the vortex breaks up earlier in spring (i.e., the spring late-breakup bias is partially ameliorated) yet is no weaker in mid-winter. More than half of the stratospheric biases appear to be related to the surface wind speed biases. As many other chemistry climate models use a similar scheme for their surface layer momentum exchange and have similar biases in the stratosphere, we expect that results from GEOSCCM may be relevant for other climate models.

  13. Flow formed by spanwise gaps between roughness elements

    NASA Technical Reports Server (NTRS)

    Logan, E.; Lin, S. H.; Islam, O.

    1985-01-01

    Measurements of the three mean velocity components and the three Reynolds shear stresses were made in the region downstream of gaps between wall-mounted roughness elements of square cross section and high aspect ratio in a thick turbulent boundary layer. The effect of small and large gaps was studied in a wind tunnel at a Reynolds number of 3600, based on obstacle height and free-stream velocity. The small gap produces retardation of the gap flow as with a two-dimensional roughness element, but a definite interaction between gap and wake flows is observed. The interaction is more intense for the large gap than for the small. Both gaps generate a secondary crossflow which moves fluid away from the centerline in the wall region and toward the centerline in the outer (y greater than 1.5H) region.

  14. The Effect of Volumetric Porosity on Roughness Element Drag

    NASA Astrophysics Data System (ADS)

    Gillies, John; Nickling, William; Nikolich, George; Etyemezian, Vicken

    2016-04-01

    Much attention has been given to understanding how the porosity of two dimensional structures affects the drag force exerted by boundary-layer flow on these flow obstructions. Porous structures such as wind breaks and fences are typically used to control the sedimentation of sand and snow particles or create micro-habitats in their lee. Vegetation in drylands also exerts control on sediment transport by wind due to aerodynamic effects and interaction with particles in transport. Recent research has also demonstrated that large spatial arrays of solid three dimensional roughness elements can be used to reduce sand transport to specified targets for control of wind erosion through the effect of drag partitioning and interaction of the moving sand with the large (>0.3 m high) roughness elements, but porous elements may improve the effectiveness of this approach. A thorough understanding of the role porosity plays in affecting the drag force on three-dimensional forms is lacking. To provide basic understanding of the relationship between the porosity of roughness elements and the force of drag exerted on them by fluid flow, we undertook a wind tunnel study that systematically altered the porosity of roughness elements of defined geometry (cubes, rectangular cylinders, and round cylinders) and measured the associated change in the drag force on the elements under similar Reynolds number conditions. The elements tested were of four basic forms: 1) same sized cubes with tubes of known diameter milled through them creating three volumetric porosity values and increasing connectivity between the tubes, 2) cubes and rectangular cylinders constructed of brass screen that nested within each other, and 3) round cylinders constructed of brass screen that nested within each other. The two-dimensional porosity, defined as the ratio of total surface area of the empty space to the solid surface area of the side of the element presented to the fluid flow was conserved at 0.519 for

  15. Observations on the Growth of Roughness Elements Into Icing Feathers

    NASA Technical Reports Server (NTRS)

    Vargas, Mario; Tsao, Jen, Ching

    2007-01-01

    This work presents the results of an experiment conducted in the Icing Research Tunnel at NASA Glenn Research Center to understand the process by which icing feathers are formed in the initial stages of ice accretion formation on swept wings. Close-up photographic data were taken on an aluminum NACA 0012 swept wing tip airfoil. Two types of photographic data were obtained: time sequence close-up photographic data during the run and close-up photographic data of the ice accretion at the end of each run. Icing runs were conducted for short ice accretion times from 10 to 180 sec. The time sequence close-up photographic data was used to study the process frame by frame and to create movies of how the process developed. The movies confirmed that at glaze icing conditions in the attachment line area icing feathers develop from roughness elements. The close-up photographic data at the end of each run showed that roughness elements change into a pointed shape with an upstream facet and join on the side with other elements having the same change to form ridges with pointed shape and upstream facet. The ridges develop into feathers when the upstream facet grows away to form the stem of the feather. The ridges and their growth into feathers were observed to form the initial scallop tips present in complete scallops.

  16. The effect of roughness elements on wind erosion: The importance of surface shear stress distribution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Representation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Drag partitioning schemes are used to account for roughness by scaling the soil entrainment threshold by the ratio of shear stress on roughness elements to that on the veg...

  17. Elements of cognitive rehabilitation after right hemisphere stroke.

    PubMed

    Calvanio, R; Levine, D; Petrone, P

    1993-02-01

    There are two basic approaches to cognitive training: (1) impairment training and (2) task specific training. Impairment training addresses impairments common to a number of tasks and attempts to offer a general benefit to all of the tasks at once. Task specific training focuses on the impairments that arise in a single task and attempts to improve performance on that task. Impairment training of spatial disorders following right hemisphere stroke has shown some success when curricula are properly designed. The success, however, is quite limited because of normal cognitive constraints and those occurring after brain damage. Task specific training in conjunction with the combined application of various cognitive principles appears more promising, but as yet, only a few studies exist. The neurologic factors are likely to be the same factors that influence recovery. The factors that influence trainability are lesion topography (size and location of the focus plus premorbid atrophy), lesion chronicity, and the presence of additional cognitive impairments (anosognosia, confusion, and abulia). Other interventions that may be beneficial, even for training resistant patients, include behavior modification, cognitive prostheses, and drugs. PMID:8441373

  18. Laminar-Turbulent Transition Behind Discrete Roughness Elements in a High-Speed Boundary Layer

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan M.; Li, Fei; Wu, Minwei; Chang, Chau-Lyan; Edwards, Jack R., Jr.; Kegerise, Michael; King, Rudolph

    2010-01-01

    Computations are performed to study the flow past an isolated roughness element in a Mach 3.5, laminar, flat plate boundary layer. To determine the effects of the roughness element on the location of laminar-turbulent transition inside the boundary layer, the instability characteristics of the stationary wake behind the roughness element are investigated over a range of roughness heights. The wake flow adjacent to the spanwise plane of symmetry is characterized by a narrow region of increased boundary layer thickness. Beyond the near wake region, the centerline streak is surrounded by a pair of high-speed streaks with reduced boundary layer thickness and a secondary, outer pair of lower-speed streaks. Similar to the spanwise periodic pattern of streaks behind an array of regularly spaced roughness elements, the above wake structure persists over large distances and can sustain strong enough convective instabilities to cause an earlier onset of transition when the roughness height is sufficiently large. Time accurate computations are performed to clarify additional issues such as the role of the nearfield of the roughness element during the generation of streak instabilities, as well as to reveal selected details of their nonlinear evolution. Effects of roughness element shape on the streak amplitudes and the interactions between multiple roughness elements aligned along the flow direction are also investigated.

  19. Wake Instabilities Behind Discrete Roughness Elements in High Speed Boundary Layers

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Li, Fei; Chang, Chau-Lyan; Norris, Andrew; Edwards, Jack

    2013-01-01

    Computations are performed to study the flow past an isolated, spanwise symmetric roughness element in zero pressure gradient boundary layers at Mach 3.5 and 5.9, with an emphasis on roughness heights of less than 55 percent of the local boundary layer thickness. The Mach 5.9 cases include flow conditions that are relevant to both ground facility experiments and high altitude flight ("cold wall" case). Regardless of the Mach number, the mean flow distortion due to the roughness element is characterized by long-lived streamwise streaks in the roughness wake, which can support instability modes that did not exist in the absence of the roughness element. The higher Mach number cases reveal a variety of instability mode shapes with velocity fluctuations concentrated in different localized regions of high base flow shear. The high shear regions vary from the top of a mushroom shaped structure characterizing the centerline streak to regions that are concentrated on the sides of the mushroom. Unlike the Mach 3.5 case with nearly same values of scaled roughness height k/delta and roughness height Reynolds number Re(sub kk), the odd wake modes in both Mach 5.9 cases are significantly more unstable than the even modes of instability. Additional computations for a Mach 3.5 boundary layer indicate that the presence of a roughness element can also enhance the amplification of first mode instabilities incident from upstream. Interactions between multiple roughness elements aligned along the flow direction are also explored.

  20. The Long Range Persistence of Wakes Behind a Row of Roughness Elements

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Sescu, Adrian; Duck, Peter W.; Choudhari, Meelan

    2010-01-01

    We consider a periodic array of relatively small roughness elements whose spanwise separation is of the order of the local boundary-layer thickness and construct a local asymptotic high-Reynolds-number solution that is valid in the vicinity of the roughness. The resulting flow decays on the very short streamwise length scale of the roughness, but the solution eventually becomes invalid at large downstream distances and a new solution has to be constructed in the downstream region. This latter result shows that the roughness-generated wakes can persist over very long streamwise distances, which are much longer than the distance between the roughness elements and the leading edge. Detailed numerical results are given for the far wake structure.

  1. Computations of Disturbance Amplification Behind Isolated Roughness Elements and Comparison with Measurements

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Li, Fei; Bynum, Michael; Kegerise, Michael; King, Rudolph

    2015-01-01

    Computations are performed to study laminar-turbulent transition due to isolated roughness elements in boundary layers at Mach 3.5 and 5.95, with an emphasis on flow configurations for which experimental measurements from low disturbance wind tunnels are available. The Mach 3.5 case corresponds to a roughness element with right-triangle planform with hypotenuse that is inclined at 45 degrees with respect to the oncoming stream, presenting an obstacle with spanwise asymmetry. The Mach 5.95 case corresponds to a circular roughness element along the nozzle wall of the Purdue BAMQT wind tunnel facility. In both cases, the mean flow distortion due to the roughness element is characterized by long-lived streamwise streaks in the roughness wake, which can support instability modes that did not exist in the absence of the roughness element. The linear amplification characteristics of the wake flow are examined towards the eventual goal of developing linear growth correlations for the onset of transition.

  2. Direct numerical simulation of instabilities in parallel flow with spherical roughness elements

    NASA Technical Reports Server (NTRS)

    Deanna, R. G.

    1992-01-01

    Results from a direct numerical simulation of laminar flow over a flat surface with spherical roughness elements using a spectral-element method are given. The numerical simulation approximates roughness as a cellular pattern of identical spheres protruding from a smooth wall. Periodic boundary conditions on the domain's horizontal faces simulate an infinite array of roughness elements extending in the streamwise and spanwise directions, which implies the parallel-flow assumption, and results in a closed domain. A body force, designed to yield the horizontal Blasius velocity in the absence of roughness, sustains the flow. Instabilities above a critical Reynolds number reveal negligible oscillations in the recirculation regions behind each sphere and in the free stream, high-amplitude oscillations in the layer directly above the spheres, and a mean profile with an inflection point near the sphere's crest. The inflection point yields an unstable layer above the roughness (where U''(y) is less than 0) and a stable region within the roughness (where U''(y) is greater than 0). Evidently, the instability begins when the low-momentum or wake region behind an element, being the region most affected by disturbances (purely numerical in this case), goes unstable and moves. In compressible flow with periodic boundaries, this motion sends disturbances to all regions of the domain. In the unstable layer just above the inflection point, the disturbances grow while being carried downstream with a propagation speed equal to the local mean velocity; they do not grow amid the low energy region near the roughness patch. The most amplified disturbance eventually arrives at the next roughness element downstream, perturbing its wake and inducing a global response at a frequency governed by the streamwise spacing between spheres and the mean velocity of the most amplified layer.

  3. Optimization of dynamic roughness elements for reducing drag in a laminar boundary layer

    NASA Astrophysics Data System (ADS)

    Sayadi, Taraneh; Sayadi, Peter

    2015-11-01

    Roughness elements can serve as controllers in both laminar and turbulent regimes to, for example, reduce the skin friction or drag. In this study, adjoint-based optimization is employed to extract the optimal shape of roughness elements for reducing drag, in a laminar setting, given an initial condition. The roughness elements considered here are of the ``dynamic'' type, varying both in space and time, which allows control over the spatial distribution of the roughness but also the inherent timescales of the flow. Dynamic roughness is modeled here using the linearized boundary conditions previously introduced by McKeon (2008), where the no-slip and impermeability boundary conditions are replaced by stream-wise and wall-normal distributions at the wall. The adjoint equation is then implemented using the discretized approach by Fosas et al. (2012). This approach is particularly efficient, since the linearized operators are computed simply by using the local differentiation technique, without explicitly forming the resulting matrices for both forward and adjoint operators. Using the described framework we investigate the effect of the initial condition on the spatial distribution of the roughness elements and their variation in time as the drag coefficient is minimized.

  4. Application research of rough sets in the multi-elemental cooperative spatial analysis

    NASA Astrophysics Data System (ADS)

    Li, Wenjing; Wang, Qiao; Lin, Zhiyong

    2009-10-01

    Multi-elemental cooperative analysis can not only brings a large number of relevant information but fuzz up key elements, so valid data excavating tools are needed to find element information which influences entities the most. Based on the sample of bus site setting in a city, this paper employs Rough Sets method to analyze multi-elemental cooperation which influence bus site grade and calculate importance of each element. Thus, multi-elemental cooperative analysis can be realized. Compared with conventional multi-parameter analysis, this method based on data self-adapting is intelligent, high-efficiency and have no use for manual intervention.

  5. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    SciTech Connect

    Song, Junho; Hynynen, Kullervo

    2009-04-14

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100x100x80 mm{sup 3} with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  6. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    NASA Astrophysics Data System (ADS)

    Song, Junho; Hynynen, Kullervo

    2009-04-01

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100×100×80 mm3 with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  7. Transitional flow in the wake of a moderate to large height cylindrical roughness element

    NASA Astrophysics Data System (ADS)

    Plogmann, B.; Würz, W.; Krämer, E.

    2015-12-01

    The effect of an isolated, cylindrical roughness on the stability of an airfoil boundary layer has been studied based on particle image velocimetry and hot-wire anemometry. The investigated roughness elements range from a sub-critical to a super-critical behavior with regard to the critical roughness Reynolds number. For the sub-critical case, the nonlinear disturbance growth in the near wake is governed by oblique Tollmien-Schlichting (TS) type modes. Further downstream, these disturbance modes are, however, damped with the mean flow stabilization and no dominant modes persist in the far wake. By contrast, in the transitional configuration the disturbance growth is increased, but still associated with a TS-type instability in the near-wake centerline region of the low-aspect (height-to-diameter) ratio element. That is, the disturbances in the centerline region show a similar behavior as known for 2D elements, whereas in the outer spanwise domain a Kelvin-Helmholtz (KH) type, shear-layer instability is found, as previously reported for larger aspect ratio isolated elements. With increasing height and, thereby, aspect ratio of the roughness, the KH-type instability domain extends toward the centerline and, accordingly, the TS-type instability domain decreases. For high super-critical cases, transition is already triggered in the wall-normal and spanwise shear layers upstream and around the roughness. In the immediate wake, periodic shear-layer disturbances roll up into a—for isolated elements characteristic—shedding of vortices, which was not present at the lower roughness Reynolds number cases due to the decreased aspect ratio and, thereby, different instability mechanism.

  8. Flow transition with 2-D roughness elements in a 3-D channel

    NASA Technical Reports Server (NTRS)

    Liu, Zhining; Liu, Chaoquin; Mccormick, Stephen F.

    1993-01-01

    We develop a new numerical approach to study the spatially evolving instability of the streamwise dominant flow in the presence of roughness elements. The difficulty in handling the flow over the boundary surface with general geometry is removed by using a new conservative form of the governing equations and an analytical mapping. The numerical scheme uses second-order backward Euler in time, fourth-order central differences in all three spatial directions, and boundary-fitted staggered grids. A three-dimensional channel with multiple two-dimensional-type roughness elements is employed as the test case. Fourier analysis is used to decompose different Fourier modes of the disturbance. The results show that surface roughness leads to transition at lower Reynolds number than for smooth channels.

  9. High-Speed Boundary-Layer Transition Induced by an Isolated Roughness Element

    NASA Technical Reports Server (NTRS)

    Kegerise, Michael A.; Owens, Lewis R.; King, Rudolph A.

    2010-01-01

    Progress on an experimental effort to quantify the instability mechanisms associated with roughness-induced transition in a high-speed boundary layer is reported in this paper. To simulate the low-disturbance environment encountered during high-altitude flight, the experimental study was performed in the NASA-Langley Mach 3.5 Supersonic Low-Disturbance Tunnel. A flat plate trip sizing study was performed first to identify the roughness height required to force transition. That study, which included transition onset measurements under both quiet and noisy freestream conditions, confirmed the sensitivity of roughness-induced transition to freestream disturbance levels. Surveys of the laminar boundary layer on a 7deg half-angle sharp-tipped cone were performed via hot-wire anemometry and pitot-pressure measurements. The measured mean mass-flux and Mach-number profiles agreed very well with computed mean-flow profiles. Finally, surveys of the boundary layer developing downstream of an isolated roughness element on the cone were performed. The measurements revealed an instability in the far wake of the roughness element that grows exponentially and has peak frequencies in the 150 to 250 kHz range.

  10. An Investigation of the Effect of a Highly Favorable Pressure Gradient on Boundary-Layer Transition as Caused by Various Types of Roughnesses on a 10-foot-Diameter Hemisphere at Subsonic Speeds

    NASA Technical Reports Server (NTRS)

    Peterson, John B., Jr.; Horton, Elmer A.

    1959-01-01

    Tests were made on a 10-foot-diameter hemispherical nose at Reynolds numbers up to 10 x 10(exp 6) and at a maximum Mach number of about 0.1 to determine the effects of a highly favorable pressure gradient on boundary-layer transition caused by roughness. Both two-dimensional and three-dimensional roughness particles were used, and the transition of the boundary layer was determined by hot-wire anemometers. The roughness Reynolds number for transition R(sub k,t) caused by three-dimensional particles such as Carborundum grains, spherical particles, and rimmed craters was found. The results show that for particles immersed in the boundary layer, R(sub k,t) is independent of the particle size or position on the hemispherical nose and depends mainly on the height-to-width ratio of the particle. The values of R(sub k,t) found on the hemispherical nose compare closely with those previously found on a flat plate and on airfoils with roughness. For two-dimensional roughness, the ratio of roughness height to boundary-layer displacement thickness necessary to cause transition was found to increase appreciably as the roughness was moved forward on the nose. Also included in the investigation were studies of the spread of turbulence behind a single particle of roughness and the effect of holes such as pressure orifices.

  11. Trace element analysis of rough diamond by LA-ICP-MS: a case of source discrimination?

    PubMed

    Dalpé, Claude; Hudon, Pierre; Ballantyne, David J; Williams, Darrell; Marcotte, Denis

    2010-11-01

    Current profiling of rough diamond source is performed using different physical and/or morphological techniques that require strong knowledge and experience in the field. More recently, chemical impurities have been used to discriminate diamond source and with the advance of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) empirical profiling of rough diamonds is possible to some extent. In this study, we present a LA-ICP-MS methodology that we developed for analyzing ultra-trace element impurities in rough diamond for origin determination ("profiling"). Diamonds from two sources were analyzed by LA-ICP-MS and were statistically classified by accepted methods. For the two diamond populations analyzed in this study, binomial logistic regression produced a better overall correct classification than linear discriminant analysis. The results suggest that an anticipated matrix match reference material would improve the robustness of our methodology for forensic applications. PMID:20681965

  12. Electrochemical machining process for forming surface roughness elements on a gas turbine shroud

    DOEpatents

    Lee, Ching-Pang; Johnson, Robert Alan; Wei, Bin; Wang, Hsin-Pang

    2002-01-01

    The back side recessed cooling surface of a shroud defining in part the hot gas path of a turbine is electrochemically machined to provide surface roughness elements and spaces therebetween to increase the heat transfer coefficient. To accomplish this, an electrode with insulating dielectric portions and non-insulating portions is disposed in opposition to the cooling surface. By passing an electrolyte between the cooling surface and electrode and applying an electrical current between the electrode and a shroud, roughness elements and spaces therebetween are formed in the cooling surface in opposition to the insulating and non-insulating portions of the electrode, hence increasing the surface area and heat transfer coefficient of the shroud.

  13. Infrared thermography of transition due to isolated roughness elements in hypersonic flows

    NASA Astrophysics Data System (ADS)

    Avallone, F.; Schrijer, F. F. J.; Cardone, G.

    2016-02-01

    Boundary layer transition in high-speed flows is a phenomenon that despite extensive research over the years is still extremely hard to predict. The presence of protrusions or gaps can lead to an accelerated laminar-to-turbulent transition enhancing the thermal loads and the skin friction coefficient. In the current investigation, inverse heat transfer measurements using infrared thermography are performed on the flow past different roughness geometries in the form of cylinders and diamond at free stream Mach number equal to 7.5, h/δ ranging between 0.5 and 0.9 (where h is the roughness height and δ is the boundary layer thickness), and Reθ ranging between 1305 and 2450. The roughness elements are positioned on a 5° ramp placed at zero angle of attack. The measurements indicate that the roughness geometry influences the transitional pattern while the frontal area influences both the transition location and the maximum value of the Stanton number along the centreline. Moreover, there is a strong connection between the streamwise centreline Stanton number and the spreading of the wake width. In particular, the transition process is characterized by an approximately constant wake width. Differently, the wake width spreads at the location where the streamwise centreline Stanton number reaches the turbulent level. This point corresponds to a local maximum of the wake amplitude defined as one half of the maximum spanwise variation of the Stanton number.

  14. Bubble-induced sheet cavitation inception on an isolated roughness element

    NASA Astrophysics Data System (ADS)

    van Rijsbergen, Martijn; Slot, Jesse

    2015-12-01

    The nucleation process on an isolated roughness element, located at the point of minimum pressure of a NACA 0015 hydrofoil was studied experimentally and computationally. The objective of this study was to investigate the working mechanism of bubble-induced sheet cavitation inception. High-speed micro-scale observations show the generation of a streak of cavitation—attached to the roughness element—in the wake of the bubble. Below its critical diameter, the bubble can detach from the streak cavity and travel on while the streak cavity remains. The solutions of a Rayleigh-Plesset equation along a streamline extracted from a RANS calculation show strong similarities with the experimental observations, but a factor 5 to 10 higher frame rate is needed to validate the calculations.

  15. Computational Study of Laminar Flow Control on a Subsonic Swept Wing Using Discrete Roughness Elements

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; Streett, Craig L.; Carpenter, Mark H.

    2011-01-01

    A combination of parabolized stability equations and secondary instability theory has been applied to a low-speed swept airfoil model with a chord Reynolds number of 7.15 million, with the goals of (i) evaluating this methodology in the context of transition prediction for a known configuration for which roughness based crossflow transition control has been demonstrated under flight conditions and (ii) of analyzing the mechanism of transition delay via the introduction of discrete roughness elements (DRE). Roughness based transition control involves controlled seeding of suitable, subdominant crossflow modes, so as to weaken the growth of naturally occurring, linearly more unstable crossflow modes. Therefore, a synthesis of receptivity, linear and nonlinear growth of stationary crossflow disturbances, and the ensuing development of high frequency secondary instabilities is desirable to understand the experimentally observed transition behavior. With further validation, such higher fidelity prediction methodology could be utilized to assess the potential for crossflow transition control at even higher Reynolds numbers, where experimental data is currently unavailable.

  16. The effect of a small isolated roughness element on the forces on a sphere in uniform flow

    NASA Astrophysics Data System (ADS)

    Norman, A. K.; McKeon, B. J.

    2011-10-01

    The effect of an isolated roughness element on the forces on a sphere was examined for a Reynolds number range of 5 × 104 < Re < 5 × 105 using a novel sting-mounted sphere apparatus. The roughness element was a circular cylinder, and its width and height was varied to be 1, 2, and 4% of the sphere diameter. At subcritical Re, a lateral force is produced in the direction of the roughness, while at supercritical Re, the force is in the opposite direction. This is caused by asymmetric boundary layer separation, as shown using particle image velocimetry. At supercritical Re, a roughness element that is only 1% the sphere diameter produces a lift to drag ratio of almost one. It was found that the isolated roughness element has the largest effect on the lateral forces when it is located between a streamwise angle of about 40° and 80°. In addition to the mean forces, the unsteady forces were also measured. It was found that at subcritical Re, vortex shedding is aligned to the plane of the roughness element. In addition, the probability distribution of the forces was nearly Gaussian for subcritical Re, but for supercritical Re, the skewness and kurtosis deviate from Gaussian, and the details are dependent on the roughness size. A simple model developed for the vortical structure formed behind the roughness element can be extended to explain aspects of nominally smooth sphere flow, in which external disturbances perturb the sphere boundary layer in an azimuthally local sense. These results also form the basis of comparison for an investigation into the effectiveness of a moving isolated roughness element for manipulating sphere flow.

  17. Using Large-Scale Roughness Elements to Control Sand and Dust Flux at the Keeler Dunes, Keeler, CA

    NASA Astrophysics Data System (ADS)

    Gillies, John; McCarley-Holder, Grace

    2014-05-01

    Controlling dust emission from areas that subsequently degrade air quality and threaten human and animal health and reduce the quality of life for people residing in proximity to such sources is necessary, but also challenging. Recent research has indicated that arrays of large roughness elements (height >0.3 m) can be used effectively to modulate sand transport and the associated dust emissions. Prediction of the rate of sand flux reduction as a function of downwind distance upon entering an array of roughness elements, and the equilibrium flux reduction in the interior of the array is possible using the known geometric properties of the roughness elements, their number, and published relationships. Air quality in the town of Keeler, CA (36 deg 29' 17.92" N, 117 deg 52' 24.62" W) is degraded by levels of particulate matter <10 µm aerodynamic diameter (PM10) during periods of elevated wind speeds due to sand transport and dust emissions in the nearby Keeler Dunes. A demonstration project was designed to evaluate the effectiveness of an array of roughness elements composed of solid elements and managed vegetation to meet sand and dust flux reduction criteria. This project has two major goals: 1) to demonstrate that solid roughness elements placed on areas of the Keeler Dunes immediately arrest sand movement to specified levels (target of 85% reduction), and 2) to assess whether native plant species, planted in the sheltered area of the solid roughness elements can effectively thrive and subsequently replace the solid roughness to achieve the desired sand flux reduction control efficiency. This poster describes the results related mostly to objective one, as considerable time has to pass before sufficient data will be obtained to evaluate the success of the planted and managed vegetation to achieve a control level provided by the solid element roughness array.

  18. Stability of the laminar boundary-layer flow behind a roughness element

    NASA Astrophysics Data System (ADS)

    Shin, Yong-su; Rist, Ulrich; Krämer, Ewald

    2015-01-01

    Roughness elements in laminar boundary layers generate both high shear layers and streaky structures. Because these phenomena interact, it is difficult to precisely ascertain the dominant instability mechanisms. With the goal of explicating such interactions, we study the stability of a laminar boundary layer subject to a single roughness element at a Reynolds number subcritical of bypass transition. Our work involves two parts: bi-global linear stability theory (LST) analysis and corroborating experimental measurements. Linear stability analysis of a flat-plate boundary layer perturbed by streamwise streaks reveals the presence of several unstable modes. Of the dominant two modes, one exhibits spanwise symmetry and the other is antisymmetric. These modes are termed `varicose' and `sinuous,' respectively. Corroborating experiments were conducted in the laminar water channel of the University of Stuttgart. By simultaneously traversing two hot-film probes, we are able to confirm the presence of both eigenmodes predicted by LST and to extract relevant data for each: eigenvalues, eigenfunctions, growth rates and phase distributions. The main part of the experiments has been performed under `natural' conditions, i.e., in the absence of external forcing. As the amplitude of the sinuous part of the results is much smaller than the varicose one and hence affected by measurement noise, a case with asymmetric external forcing is presented as well. Despite some deficiencies of the setup, it is possible to enhance the sinuous mode with respect to the unforced case and to confirm its existence as an eigenmode of the flow.

  19. Investigation of turbulent wedges generated by different single surface roughness elements

    NASA Astrophysics Data System (ADS)

    Traphan, Dominik; Meinlschmidt, Peter; Lutz, Otto; Peinke, Joachim; Gülker, Gerd

    2013-11-01

    It is known that small faults on rotor blades of wind turbines can cause significant power loss. In order to better understand the governing physical effects, in this experimental study, the formation of a turbulent wedge over a flat plate induced by single surface roughness elements is under investigation. The experiments are performed at different ambient pressure gradients, thus allowing conclusions about the formation of a turbulent wedge over an airfoil. With respect to typical initial faults on operating airfoils, the roughness elements are modified in both size and shape (raised or recessed). None intrusive experimental methods, such as stereoscopic PIV and LDA, enable investigations based on temporally and spatially highly resolved velocity measurements. In this way, a spectral analysis of the turbulent boundary layer is performed and differences in coherent structures within the wedge are identified. These findings are correlated with global measurements of the wedge carried out by infrared thermography. This correlation aims to enable distinguishing the cause and main properties of a turbulent wedge by the easy applicable method of infrared thermography, which is of practical relevance in the field of condition monitoring of wind turbines.

  20. Validated heat-transfer and pressure-drop prediction methods based on the discrete-element method: Phase 2, two-dimensional rib roughness

    SciTech Connect

    James, C.A.; Hodge, B.K.; Taylor, R.P.

    1993-05-01

    Surface roughness is a commonly used approach for enhancing the rate of heat transfer of surfaces, such as in heat-exchanger tubes. Because the improved thermal performance of roughened surfaces is at the expense of increased flow resistance (increased pressure drop or friction factor), accurate prediction techniques for determining the friction factors and Nusselt numbers for roughened surfaces are required if such features are to be considered as design options. This report presents the results of the second phase of a research program sponsored by Argonne National Laboratory to validate models for the prediction of friction factors and Nusselt numbers for fully developed turbulent flow in enhanced heat-exchanger tubes. The first phase was concerned with validating a roughness model for turbulent flow in tubes internally roughened with three-dimensional distributed roughness elements, such as sandgrains, spheres, hemispheres, and cones. The second phase is concerned with devising and validating methods for the prediction of friction factors and Nusselt numbers for turbulent flow in tubes internally roughened with repeated, two-dimensional ribs aligned perpendicular to the flow. The ribs are spaced sufficiently far apart that the leeward-side separated flow reattaches to the wall before again separating in order to negotiate the next rib. This heat-transfer enhancement mechanism is called the separation and reattachment mechanism, after Rabas (1989). This work is limited to rectangular rib shapes.

  1. Investigations of Effects of Surface Temperature and Single Roughness Elements on Boundary-Layer Transition

    NASA Technical Reports Server (NTRS)

    Liepmann, Hans W; Fila, Gertrude H

    1947-01-01

    The laminar boundary layer and the position of the transition point were investigated on a heated flat plate. It was found that the Reynolds number of transition decreased as the temperature of the plate is increased. It is shown from simple qualitative analytical considerations that the effect of variable viscosity in the boundary layer due to the temperature difference produces a velocity profile with an inflection point if the wall temperature is higher than the free-stream temperature. This profile is confirmed by measurements. The instability of inflection-point profiles is discussed. Studies of the flow in the wake of large, two-dimensional roughness elements are presented. It is shown that a boundary-layer can separate and reattach itself to the wall without having transition take place.

  2. The Effects of Surface Roughness on the NEAR XRS Elemental Results: Monte-Carlo Modeling

    NASA Technical Reports Server (NTRS)

    Lin, Lucy F.; Nittler, Larry R.

    2011-01-01

    The objective of the NEAR-Shoemaker X-ray Gamma-Ray Spec1roscopy ("XGRS") investigation was to determine the elemental composition of the near-Earth asteroid 433 Eros. The X-ray Spectrometer (XRS) system measured the characteristic fluorescence of six major elements (Mg, Al, Si, S, Ca, Fe) in the 1-10 keV energy range excited by the interaction of solar X-rays with the upper 100 microns of the surface of 433 Eros. Various investigators, using both laboratory experiments and computer simulations have established that X-ray fluorescent line ratios can be influenced by small-scale surface roughness at high incidence or emission angles. The effect on the line ratio is specific to the geometry, excitation spectrum, and composition involved, In general, however, the effect is only substantial for ratios of lines with a significant energy difference between them: Fe/Si and Ca/Si are much more likely to be affected than AI/Si or Mg/Si. We apply a Monte-Carlo code to the specific geometry and spectrum of a major NEAR XRS solar flare observation, using an H chondrite composition as the substrate. The seventeen most abundant elements were included in the composition model, from oxygen to titanium.

  3. Structure of two-dimensional and three-dimensional turbulent boundary layers with sparsely distributed roughness elements

    NASA Astrophysics Data System (ADS)

    George, Jacob

    The present study deals with the effects of sparsely distributed three-dimensional elements on two-dimensional (2-D) and three-dimensional (3-D) turbulent boundary layers (TBL) such as those that occur on submarines, ship hulls, etc. This study was achieved in three parts: Part 1 dealt with the cylinders when placed individually in the turbulent boundary layers, thereby considering the effect of a single perturbation on the TBL; Part 2 considered the effects when the same individual elements were placed in a sparse and regular distribution, thus studying the response of the flow to a sequence of perturbations; and in Part 3, the distributions were subjected to 3-D turbulent boundary layers, thus examining the effects of streamwise and spanwise pressure gradients on the same perturbed flows as considered in Part 2. The 3-D turbulent boundary layers were generated by an idealized wing-body junction flow. Detailed 3-velocity-component Laser-Doppler Velocimetry (LDV) and other measurements were carried out to understand and describe the rough-wall flow structure. The measurements include mean velocities, turbulence quantities (Reynolds stresses and triple products), skin friction, surface pressure and oil flow visualizations in 2-D and 3-D rough-wall flows for Reynolds numbers, based on momentum thickness, greater than 7000. Very uniform circular cylindrical roughness elements of 0.38mm, 0.76mm and 1.52mm height (k) were used in square and diagonal patterns, yielding six different roughness geometries of rough-wall surface. For the 2-D rough-wall flows, the roughness Reynolds numbers, k +, based on the element height (k) and the friction velocity (Utau), range from 26 to 131. Results for the 2-D rough-wall flows reveal that the velocity-defect law is similar for both smooth and rough surfaces, and the semi-logarithmic velocity-distribution curve is shifted by an amount DeltaU/U, depending on the height of the roughness element, showing that Delta U/Utau is a function

  4. A hybrid computational approach for the interactions between river flow and porous sediment bed covered with large roughness elements

    NASA Astrophysics Data System (ADS)

    Liu, X.

    2013-12-01

    In many natural and human-impacted rivers, the porous sediment beds are either fully or partially covered by large roughness elements, such as gravels and boulders. The existence of these large roughness elements, which are in direct contact with the turbulent river flow, changes the dynamics of mass and momentum transfer across the river bed. It also impacts the overall hydraulics in the river channel and over time, indirectly influences the geomorphological evolution of the system. Ideally, one should resolve each of these large roughness elements in a computational fluid model. This approach is apparently not feasible due to the prohibitive computational cost. Considering a typical river bed with armoring, the distribution of sediment sizes usually shows significant vertical variations. Computationally, it poses great challenge to resolve all the size scales. Similar multiscale problem exists in the much broader porous media flow field. To cope with this, we propose a hybrid computational approach where the large surface roughness elements are resolved using immersed boundary method and sediment layers below (usually finer) are modeled by adding extra drag terms in momentum equations. Large roughness elements are digitized using a 3D laser scanner. They are put into the computational domain using the collision detection and rigid body dynamics algorithms which guarantees realistic and physically-correct spatial arrangement of the surface elements. Simulation examples have shown the effectiveness of the hybrid approach which captures the effect of the surface roughness on the turbulent flow as well as the hyporheic flow pattern in and out of the bed.

  5. How do macro-roughness elements affect bed-load sediment motion?

    NASA Astrophysics Data System (ADS)

    Radice, Alessio; Campagnol, Jenny

    2015-04-01

    Experimental results are here presented for bed-load particle motion in the presence of macro-roughness elements (MREs). Experiments were performed at the Hydraulics Laboratory of the Politecnico di Milano using plastic particles (size of 3 mm) as bed-load sediment that was fed into a rectangular-section, pressurized duct. The bottom of the duct was covered with a number of MREs, represented by concrete semi-spheres (diameter of 35 mm) that were not mobilized by the hydrodynamic conditions used. The experiments thus mimicked the transport of fine sediment in the presence of immobile boulders, that is one possible idealized representation of the granulometric variability found in natural water courses. The work is part of a project devoted to the characterization of particle kinematics for different roughness of the bed, undertaken within a long-term cooperation with the Environmental and Industrial Fluid Mechanics group at the University of Aberdeen (UK). Different flow conditions were tested. For each, MREs were placed in two different arrangements, corresponding to triangular grids with variable side length (130 mm and 100 mm). Colour of sediment was appropriately chosen (white grains over black background) to enable bed-load particles to be tracked by an image processing software (Streams, developed by the University of Canterbury, New Zealand). Particle kinematics was described using typical quantities: path length and tortuosity, path-averaged and instantaneous velocity components in the stream-wise and transverse directions, duration of motion events. The collected database was considerably wide, in terms of both measured particle paths and instantaneous velocity values. Results are discussed in terms of the measured kinematic properties and also comparing the sediment motion to that obtained for the same hydrodynamic conditions and in the absence of MREs. A discussion is made about comparability of the different scenarios, as the presence/absence of the MREs

  6. Turbulence analysis of rough wall channel flows based on direct numerical simulation

    SciTech Connect

    Mishra, A. V.; Bolotnov, I. A.

    2012-07-01

    Direct numerical simulation (DNS) of rough wall channel flows was performed for various surface roughnesses. The goal of the presented research is to investigate the effect of nucleating bubbles in subcooled boiling conditions on the turbulence. The nucleating bubbles are represented by hemispherical roughness elements at the wall. The stabilized finite element based code, PHASTA, is used to perform the simulations. Validation against theoretical, experimental and numerical data is performed for smooth channel flow and rectangular rod type of roughness. The presence of roughness elements affects the flow structure within the roughness sublayer, which is estimated to be 5 times the height of roughness elements. DNS observations are consistent with this result and demonstrate the flow homogeneity above 50 viscous units. The influence of roughness elements layout and density on the turbulence parameters is also demonstrated and analyzed. (authors)

  7. Using trace elements in skin to discriminate the populations of minke whales in southern hemisphere.

    PubMed

    Kunito, Takashi; Watanabe, Izumi; Yasunaga, Genta; Fujise, Yoshihiro; Tanabe, Shinsuke

    2002-03-01

    Concentrations of 12 trace elements (V, Cr, Mn, Cu, Zn, Se, Rb, Sr, Cd, Cs, Ba, and Hg) were determined in liver and skin tissues of minke whales from various regions within the Antarctic Ocean. Cd concentrations in livers of southern minke whale were apparently higher than those in cetaceans from other regions, while Hg concentrations were lower. There were significant positive correlations between body length and concentrations of Cd and Hg in the liver. The concentrations of all trace elements in the skin were lower than those in other cetaceans reported previously. Significant positive correlations between liver and skin were found for Cr, Mn, Cu, Zn, Rb, Cd, and Cs, implying that the concentrations of these trace elements in the skin reflect those of internal organs. Large interannual variation of the accumulation pattern of trace elements in the skin was observed for the southern minke whales from Area V. There were significant differences in the skin element concentrations among Areas III, IV, and V, especially for males. Also, discriminant analysis between geographically two different groups collected during 1995/1996 austral summer season, based on the concentrations of trace elements in the skin, allowed for a correct classification of 90% of these minke whales. These results suggest that measurement of trace elements in skin samples could provide valuable information on the status of contamination and possible geographic differences in the accumulation levels in southern minke whales. PMID:11824827

  8. Application of Plenoptic PIV for 3D Velocity Measurements Over Roughness Elements in a Refractive Index Matched Facility

    NASA Astrophysics Data System (ADS)

    Thurow, Brian; Johnson, Kyle; Kim, Taehoon; Blois, Gianluca; Best, Jim; Christensen, Ken

    2014-11-01

    The application of Plenoptic PIV in a Refractive Index Matched (RIM) facility housed at Illinois is presented. Plenoptic PIV is an emerging 3D diagnostic that exploits the light-field imaging capabilities of a plenoptic camera. Plenoptic cameras utilize a microlens array to measure the position and angle of light rays captured by the camera. 3D/3C velocity fields are determined through application of the MART algorithm for volume reconstruction and a conventional 3D cross-correlation PIV algorithm. The RIM facility is a recirculating tunnel with a 62.5% aqueous solution of sodium iodide used as the working fluid. Its resulting index of 1.49 is equal to that of acrylic. Plenoptic PIV was used to measure the 3D velocity field of a turbulent boundary layer flow over a smooth wall, a single wall-mounted hemisphere and a full array of hemispheres (i.e. a rough wall) with a k/ δ ~ 4.6. Preliminary time averaged and instantaneous 3D velocity fields will be presented. This material is based upon work supported by the National Science Foundation under Grant No. 1235726.

  9. Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

    NASA Astrophysics Data System (ADS)

    Pettit, J. R.; Walker, A. E.; Lowe, M. J. S.

    2015-03-01

    Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.

  10. Improved detection of rough defects for ultrasonic NDE inspections based on finite element modeling of elastic wave scattering

    SciTech Connect

    Pettit, J. R.; Walker, A.; Lowe, M. J. S.

    2014-02-18

    Defects which posses rough surfaces greatly affect ultrasonic wave scattering behaviour, often reducing the magnitude of reflected signals. Ultrasonic inspections rely upon this response for detecting and sizing flaws. For safety critical components reliable characterisation is crucial. Therefore, providing an accurate means to predict reductions in signal amplitude is essential. An extension of Kirchhoff theory has formed the basis for the UK power industry inspection justifications. However, it is widely recognised that these predictions are pessimistic owing to analytical approximations. A numerical full field modelling approach does not fall victim to such limitations. Here, a Finite Element model is used to aid in setting a non-conservative reporting threshold during the inspection of a large pressure vessel forging that might contain embedded rough defects. The ultrasonic response from multiple rough surfaces defined by the same statistical class is calculated for normal incident compression waves. The approach is validated by comparing coherent scattering with predictions made by Kirchhoff theory. At lower levels of roughness excellent agreement is observed, whilst higher values confirm the pessimism of Kirchhoff theory. Furthermore, the mean amplitude in the specular direction is calculated. This represents the information obtained during an inspection, indicating that reductions due to increasing roughness are significantly less than the coherent component currently being used.

  11. Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

    SciTech Connect

    Pettit, J. R.; Lowe, M. J. S.; Walker, A. E.

    2015-03-31

    Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.

  12. Heat Transfer Enhancement in a Solar Air Heater with Roughened Duct Having Arc-Shaped Elements as Roughness Element on the Absorber Plate

    NASA Astrophysics Data System (ADS)

    Singh, Anil Prakash; Goel, Varun; Vashishtha, Siddhartha; Kumar, Amit

    2016-07-01

    An experimental study has been carried out for the heat transfer and friction characteristics for arc shaped roughness element used in solar air heaters. Duct has an aspect ratio (W/H) of 11, relative roughness pitch (p/e) range of 4-16, relative roughness height (e/D) range of 0.027-0.045, Reynolds number ( Re) range of 2200-22,000 and arc angle (α) was kept constant at 60°. The effects of Re, relative roughness pitch (p/e) and relative roughness height (e/D) on heat transfer and friction factor have been discussed. The results obtained for Nusselt number and friction factor has been compared with smooth solar air heater to see the enhancement in heat transfer and friction factor and it is found out that considerable enhancement takes place in case of heat transfer as well as in friction factor. Correlations were also developed for Nusselt number and friction factor. Thermo-hydraulic performance parameter is also calculated for the same.

  13. Heat Transfer Enhancement in a Solar Air Heater with Roughened Duct Having Arc-Shaped Elements as Roughness Element on the Absorber Plate

    NASA Astrophysics Data System (ADS)

    Singh, Anil Prakash; Goel, Varun; Vashishtha, Siddhartha; Kumar, Amit

    2016-05-01

    An experimental study has been carried out for the heat transfer and friction characteristics for arc shaped roughness element used in solar air heaters. Duct has an aspect ratio (W/H) of 11, relative roughness pitch (p/e) range of 4-16, relative roughness height (e/D) range of 0.027-0.045, Reynolds number (Re) range of 2200-22,000 and arc angle (α) was kept constant at 60°. The effects of Re, relative roughness pitch (p/e) and relative roughness height (e/D) on heat transfer and friction factor have been discussed. The results obtained for Nusselt number and friction factor has been compared with smooth solar air heater to see the enhancement in heat transfer and friction factor and it is found out that considerable enhancement takes place in case of heat transfer as well as in friction factor. Correlations were also developed for Nusselt number and friction factor. Thermo-hydraulic performance parameter is also calculated for the same.

  14. Towards transition modelling for supersonic laminar flow control based on spanwise periodic roughness elements.

    PubMed

    Choudhari, Meelan; Chang, Chau-Lyan; Jiang, Li

    2005-05-15

    Laminar flow control (LFC) is one of the key enabling technologies for quiet and efficient supersonic aircraft. Recent work at Arizona State University (ASU) has led to a novel concept for passive LFC, which employs distributed leading edge roughness to limit the growth of naturally dominant crossflow instabilities in a swept-wing boundary layer. Predicated on nonlinear modification of the mean boundary-layer flow via controlled receptivity, the ASU concept requires a holistic prediction approach that accounts for all major stages within transition in an integrated manner. As a first step in developing an engineering methodology for the design and optimization of roughness-based supersonic LFC, this paper reports on canonical findings related to receptivity plus linear and nonlinear development of stationary crossflow instabilities on a Mach 2.4, 73 degrees swept airfoil with a chord Reynolds number of 16.3 million. PMID:16105770

  15. Finite element modeling of the surface roughness of 5052 Al alloy subjected to a surface severe plastic deformation process

    SciTech Connect

    Dai, K.; Villegas, J.; Stone, Z.; Shaw, L. . E-mail: lshaw@mail.ims.uconn.edu

    2004-12-01

    The surface of 5052 Al alloy plates is severely plastically deformed via multiple impacts by high-velocity tungsten carbide/cobalt (Wc/Co) balls in a surface nanocrystallization and hardening (SNH) process. The surface roughness of 5052 Al alloy plates as a function of the impacting ball size and processing time has been evaluated via non-contact 3D profilometry. A three-dimensional finite element (FE) model has been developed to simulate the formation of peaks and valleys during the SNH process. The peak-to-valley distance predicted from the FEM matches the maximum PV value measured experimentally quite well, indicating that surface roughening of 5052 Al alloy plates during the SNH process using WC/Co balls is mainly dictated by the indentation process of the impacting balls. The implications of this surface roughening mechanism in the final surface roughness, processing time, related microstructure change, and property alteration are discussed.

  16. Wall-drag measurements of smooth- and rough-wall turbulent boundary layers using a floating element

    NASA Astrophysics Data System (ADS)

    Baars, W. J.; Squire, D. T.; Talluru, K. M.; Abbassi, M. R.; Hutchins, N.; Marusic, I.

    2016-05-01

    The mean wall shear stress, overline{τ }_w, is a fundamental variable for characterizing turbulent boundary layers. Ideally, overline{τ }_w is measured by a direct means and the use of floating elements has long been proposed. However, previous such devices have proven to be problematic due to low signal-to-noise ratios. In this paper, we present new direct measurements of overline{τ }_w where high signal-to-noise ratios are achieved using a new design of a large-scale floating element with a surface area of 3 m (streamwise) × 1 m (spanwise). These dimensions ensure a strong measurement signal, while any error associated with an integral measurement of overline{τ }_w is negligible in Melbourne's large-scale turbulent boundary layer facility. Wall-drag induced by both smooth- and rough-wall zero-pressure-gradient flows are considered. Results for the smooth-wall friction coefficient, C_f ≡ overline{τ }_w/q_{∞}, follow a Coles-Fernholz relation C_f = [ 1/κ ln ( Re_{θ }) + C] ^{-2} to within 3 % (κ = 0.38 and C = 3.7) for a momentum thickness-based Reynolds number, Re_{θ } > 15{,}000. The agreement improves for higher Reynolds numbers to <1 % deviation for Re_{θ } > 38{,}000. This smooth-wall benchmark verification of the experimental apparatus is critical before attempting any rough-wall studies. For a rough-wall configuration with P36 grit sandpaper, measurements were performed for 10{,}500< Re_{θ } < 88{,}500, for which the wall-drag indicates the anticipated trend from the transitionally to the fully rough regime.

  17. Experimental investigation of the modification of the flow field, past instream vegetation elements, for distinct bedsurface roughness.

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos; Yagci, Oral; Kitsikoudis, Vasileios; Koursari, Eftychia

    2015-04-01

    The presence of vegetation in rivers and estuaries has important implications for the modification of the flow field and sediment transport. In-stream vegetation has the potential to regulate the morphology and ecological health of a surface water body, and as such it finds a wide range of applications. Even though a number of controls influencing the local flow field past aquatic vegetation elements or patches of instream vegetation have been identified (such as shape, areal density, size and flexibility), conclusive evidence is lacking, particularly on how sediment transport processes are affected. Here, an experimental study is designed to identify how the flow field past different types of elements simulating in-stream emergent vegetation is modified. Two sets of experiments are conducted, each with a distinct value of high and low hydraulic roughness for the bed surface. In both experiments a rigid cylindrical element, a patch of rigid tubes and a plant shaped element (Cupressus Macrocarpa), simulating instream emergent vegetation are utilized. The flow field is measured at various locations downstream the element and average and turbulent flow statistics are obtained at near bed, mid-flow depth and near the water surface regions. It is found that different structural aspects of the elements, particularly the geometry, can significantly affect the flow field downstream the elements. Specifically, the average flow profiles are practically restored to near ambient flow conditions at about 5 diameters downstream the rigid element, while this happens at longer distances for the other elements. The flow structures shed past the elements are also very distinct, as confirmed via appropriately designed fluorescent dye flow visualizations. Potential ecosystem feedbacks and implications for formation of geospatial patterns are also discussed.

  18. Brain Hemispheric Functioning.

    ERIC Educational Resources Information Center

    Roeper Review, 1981

    1981-01-01

    Four articles consider brain hemisphere functioning of gifted students as it relates to gifted programs; alternation of education methodologies; spatial ability as an element of intellectual gifted functioning; and the interaction between hemisphere specialization, imagery, creative imagination, and sex differentiation. (SB)

  19. Mechanics of hemispherical electronics

    NASA Astrophysics Data System (ADS)

    Wang, Shuodao; Xiao, Jianliang; Jung, Inhwa; Song, Jizhou; Ko, Heung Cho; Stoykovich, Mark P.; Huang, Yonggang; Hwang, Keh-Chih; Rogers, John A.

    2009-11-01

    A simple analytical model is established for the development of hemisphere electronics, which has many important applications in electronic-eye cameras and related curvilinear systems. The photodetector arrays, made in planar mesh layouts with conventional techniques, are deformed and transferred onto a hemisphere. The model gives accurately the positions of photodetectors on the hemisphere, and has been validated by experiments and finite element analysis. The results also indicate very small residual strains in the photodetectors. The model provides a tool to define a pattern of photodetectors in the planar, as-fabricated layout to yield any desired spatial configuration on the hemisphere.

  20. Wind Tunnel Measurements of Turbulent Boundary Layer over Hypothetical Urban Roughness Elements

    NASA Astrophysics Data System (ADS)

    Ho, Y. K.; Liu, C. H.

    2012-04-01

    Urban morphology affects the near-ground atmospheric boundary layer that in turn modifies the wind flows and pollutant dispersion over urban areas. A number of numerical models (large-eddy simulation, LES and k-ɛ turbulence models) have been developed to elucidate the transport processes in and above urban street canyons. To complement the modelling results, we initiated a wind tunnel study to examine the influence of idealized urban roughness on the flow characteristics and pollutant dispersion mechanism over 2D idealized street canyons placed in cross flows. Hot-wire anemometry (HWA) was employed in this study to measure the flows over 2D street canyons in the wind tunnel in our university. Particular focus in the beginning stage was on the fabrication of hot-wire probes, data acquisition system, and signal processing technique. Employing the commonly adopted hot-wire universal function, we investigated the relationship in between and developed a scaling factor which could generalize the output of our hot-wire probes to the standardized one as each hot-wire probes has its unique behaviour. Preliminary experiments were performed to measure the wind flows over street canyons of unity aspect ratio. Vertical profiles of the ensemble average velocity and fluctuations at three different segments over the street canyons were collected. The results were then compared with our LES that show a good argument with each other. Additional experiments are undertaken to collect more data in order to formulate the pollutant dispersion mechanism of street canyons and urban areas.

  1. An experimental study of the flow through and over two dimensional rectangular roughness elements: Deductions for urban boundary layer parameterizations and exchange processes

    NASA Astrophysics Data System (ADS)

    Neophytou, M. K.-A.; Markides, C. N.; Fokaides, P. A.

    2014-08-01

    This paper investigates the flow through and over two-dimensional rectangular roughness elements, arranged in a building-street canyon geometry through a series of experiments. Geometries of different packing densities of the roughness elements (λp) were examined and the packing density values ranged from λp = 0.30 to 0.67. The purpose of the work is: (i) to investigate the flow physics observed both at the boundary layer scale as well as at the scale within the roughness elements for a range of packing densities, (ii) to deduce parameterizations of the adjusted rough boundary layer and their variation with a change in the packing density, and (iii) given a particular interest in and application to the urban atmosphere, a final aim at the roughness-element scale is to deduce the variation of the breathability with the packing density variation. Particle image velocimetery measurements of the velocity flow field as well as the turbulent kinetic energy and the Reynolds Stress (within and up to well-above the street canyons) were conducted. The results reveal qualitative flow features as well as features of the adjusted boundary layer structure—in particular the roughness and inertial sublayers, which can be associated with the surface roughness length, zero-plane displacement thickness, and the friction velocity. The lowest friction velocities are exhibited in the geometries with the highest- and lowest packing densities while the maximum friction velocities are observed in the medium-packed geometries. The exchange processes and breathability at the level of the roughness elements top were characterized and quantified by a mean exchange velocity. The results show that unlike friction velocity, the normalized exchange velocity (over the mean bulk velocity) for the most dense and sparse geometries differ by more than 80%, with the denser-packed geometries exhibiting lower exchange velocities; this is shown to be related with the thickness of the developed

  2. Multigrid methods and high order finite difference for flow in transition - Effects of isolated and distributed roughness elements

    NASA Technical Reports Server (NTRS)

    Liu, C.; Liu, Z.

    1993-01-01

    The high order finite difference and multigrid methods have been successfully applied to direct numerical simulation (DNS) for flow transition in 3D channels and 3D boundary layers with 2D and 3D isolated and distributed roughness in a curvilinear coordinate system. A fourth-order finite difference technique on stretched and staggered grids, a fully-implicit time marching scheme, a semicoarsening multigrid method associated with line distributive relaxation scheme, and a new treatment of the outflow boundary condition, which needs only a very short buffer domain to damp all wave reflection, are developed. These approaches make the multigrid DNS code very accurate and efficient. This makes us not only able to do spatial DNS for the 3D channel and flat plate at low computational costs, but also able to do spatial DNS for transition in the 3D boundary layer with 3D single and multiple roughness elements. Numerical results show good agreement with the linear stability theory, the secondary instability theory, and a number of laboratory experiments.

  3. Bursting process of large- and small-scale structures in turbulent boundary layer perturbed by a cylinder roughness element

    NASA Astrophysics Data System (ADS)

    Tang, Zhanqi; Jiang, Nan; Zheng, Xiaobo; Wu, Yanhua

    2016-05-01

    Hot-wire measurements on a turbulent boundary layer flow perturbed by a wall-mounted cylinder roughness element (CRE) are carried out in this study. The cylindrical element protrudes into the logarithmic layer, which is similar to those employed in turbulent boundary layers by Ryan et al. (AIAA J 49:2210-2220, 2011. doi: 10.2514/1.j051012) and Zheng and Longmire (J Fluid Mech 748:368-398, 2014. doi: 10.1017/jfm.2014.185) and in turbulent channel flow by Pathikonda and Christensen (AIAA J 53:1-10, 2014. doi: 10.2514/1.j053407). The similar effects on both the mean velocity and Reynolds stress are observed downstream of the CRE perturbation. The series of hot-wire data are decomposed into large- and small-scale fluctuations, and the characteristics of large- and small-scale bursting process are observed, by comparing the bursting duration, period and frequency between CRE-perturbed case and unperturbed case. It is indicated that the CRE perturbation performs the significant impact on the large- and small-scale structures, but within the different impact scenario. Moreover, the large-scale bursting process imposes a modulation on the bursting events of small-scale fluctuations and the overall trend of modulation is not essentially sensitive to the present CRE perturbation, even the modulation extent is modified. The conditionally averaging fluctuations are also plotted, which further confirms the robustness of the bursting modulation in the present experiments.

  4. Receptivity of a laminar boundary layer to the interaction of a three-dimensional roughness element with time-harmonic free-stream disturbances

    NASA Technical Reports Server (NTRS)

    Tadjfar, M.; Bodonyi, R. J.

    1992-01-01

    Receptivity of a laminar boundary layer to the interaction of time-harmonic free-stream disturbances with a 3D roughness element is studied. The 3D nonlinear triple-deck equations are solved numerically to provide the basic steady-state motion. At high Reynolds numbers, the governing equations for the unsteady motion are the unsteady linearized 3D triple-deck equations. These equations can only be solved numerically. In the absence of any roughness element, the free-stream disturbances, to the first order, produce the classical Stokes flow, in the thin Stokes layer near the wall (on the order of our lower deck). However, with the introduction of a small 3D roughness element, the interaction between the hump and the Stokes flow introduces a spectrum of all spatial disturbances inside the boundary layer.

  5. Finite Element Method Simulations of the Near-Field Enhancement at the Vicinity of Fractal Rough Metallic Surfaces

    SciTech Connect

    Micic, Miodrag; Klymyshyn, Nicholas A.; Lu, H PETER.

    2004-03-04

    Near-field optical enhancement at metal surfaces and methods such as surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS), fluorescent quenching and enhancement, and various near-field scanning microscopies (NSOM) all depend on a metals surface properties, mainly on its morphology and SPR resonant frequency. We report on simulations of the influence of different surface morphologies on electromagnetic field enhancements at the rough surfaces of noble metals and also evaluate the optimal conditions for the generation of a surface-enhanced Raman signal of absorbed species on a metallic substrate. All simulations were performed with a classical electrodynamics approach using the full set of Maxwells equations, which were solved with the three-dimensional finite element method (FEM). Two different classes of surfaces where modeled using fractals, representing diffusion limited aggregation growth dendritic structures, such as one on the surface of electrodes, and second one representing the sponge-like structure used to model surfaces of particles with high porosity, such as metal coated catalyst supports. The simulations depict the high inhomogeneity of an enhanced electromagnetic field as both a field enhancement and field attenuation near the surface. While the diffusion limited aggregation dendritical fractals enhanced the near-field electromagnetic field, the sponge fractals significantly reduced the local electromagnetic field intensity. Moreover, the fractal orders of the fractal objects did not significantly alter the total enhancement, and the distribution of a near-field enhancement was essentially invariant to the changes in the angle of an incoming laser beam.

  6. Transverse Crack Modeling of Continuously Casted Slabs through Finite Element Method in Roughing Rolling at Wide Strip Mill

    NASA Astrophysics Data System (ADS)

    Pesin, A.; Salganik, V.; Pustovoytov, D.

    2010-06-01

    In the pipe billet production at the wide strip mills of hot rolling big metal losses are caused by surface defects that affect most parts of the finished strips. The rolling surface defects are referred to the breach of steelmaking technology. Specialists mostly face defects of metal surface such as "scab" and "crack". The only area suffered from these defects is a slab edge. This area has the least surface temperature at the unbending of the continuous-casting machine, and together with deep buckles made by reciprocating motion of the crystallizer it is mostly subjected to transverse cracks that can be up to several millimeters. Each surface defect of the continuously casted slab will further turn into the surface defect of the strip bar. For some grade sets, mostly made of pipe steel grades the amount of strips with these defects can reach up to 60-70%. The area that is mostly prone to these defects is the edge of the strip. The work reveals investigation of the form change peculiarities in the transverse cracks of the continuously casted slab in roughing rolling in the horizontal rollers. The finite element method with software DEFORM 3D V6.1 has been applied in modeling. The work gives a form change mechanism of transverse cracks of slabs in deformation. Further crack growth in rolling is assessed due to Cockroft-Latham criteria.

  7. Simulation of the enhancement factor from an individual 3D hemisphere-on-post field emitter by using finite elements method.

    PubMed

    Roveri, D S; Sant'Anna, G M; Bertan, H H; Mologni, J F; Alves, M A R; Braga, E S

    2016-01-01

    This paper presents a 3D computational framework for evaluating electrostatic properties of a single field emitter characterized by the hemisphere-on-post geometry. Numerical simulations employed the finite elements method by using Ansys-Maxwell software. Extensive parametric simulations were focused on the threshold distance from which the emitter field enhancement factor (γ) becomes independent from the anode-substrate gap (G). This investigation allowed demonstrating that the ratio between G and the emitter height (h) is a reliable reference for a broad range of emitter dimensions; furthermore, results permitted establishing G/h ≥ 2.2 as the threshold condition for setting the anode without affecting γ. PMID:26555324

  8. Right Hemisphere and Left Hemisphere: Pedagogical Implications for CSL Reading.

    ERIC Educational Resources Information Center

    Mickel, Stanley L.

    Students can be taught to read Chinese more efficiently and accurately by using the specific capabilities of the right and left hemispheres of the brain. The right hemisphere is the site of image and pattern recognition, and students can be taught to use those capacities to process individual characters efficiently by watching for the element of…

  9. The 3D flow structures generated by a pair of cubic roughness elements in a turbulent channel flow resolved using holographic microscopy

    NASA Astrophysics Data System (ADS)

    Gao, Jian; Katz, Joseph

    2015-11-01

    In studies of turbulent flows over rough walls, considerable efforts have been put on the overall effects of roughness parameters such as roughness height and spatial arrangement on the mean profiles and turbulence statistics. However there is very little experimental data on the generation, evolution, and interaction among roughness-initiated turbulent structures, which are essential for elucidating the near-wall turbulence production. As a first step, we approach this problem experimentally by applying digital holographic microscopy (DHM) to measure the flow and turbulence around a pair of cubic roughness elements embedded in the inner part of a high Reynolds number turbulent channel flow (Reτ = 2000 - 5000). The ratio of half-channel height (h) to cube height (a) is 25, and the cubes are aligned in the spanwise direction, and separated by 1.5 a. DHM provides high-resolution three-dimensional (3D) three-component (3C) velocity distributions. The presentation discusses methods to improve the data accuracy, both during the hologram acquisition and particle tracking phases. First, we compare and mutually validate velocity fields obtained from a two-view DHM system. Subsequently, during data processing, the seven criteria used for particle tracking is validated and augmented by planar tracking of particle image projections. Sample results reveal instantaneous 3D velocity fields and vortical structures resolved in fine details of several wall units. Funded by NSF and ONR.

  10. Right Hemisphere Brain Damage

    MedlinePlus

    ... Language and Swallowing / Disorders and Diseases Right Hemisphere Brain Damage [ en Español ] What is right hemisphere brain ... right hemisphere brain damage ? What is right hemisphere brain damage? Right hemisphere brain damage (RHD) is damage ...

  11. Measurement and calculation of fluid dynamic characteristics of rough-wall turbulent boundary-layer flows

    SciTech Connect

    Hosni, M.H. . Dept. of Mechanical Engineering); Coleman, H.W. . Mechanical Engineering Dept.); Taylor, R.P. . Mechanical and Nuclear Engineering Dept.)

    1993-09-01

    Experimental measurements of profiles of mean velocity and distributions of boundary-layer thickness and skin friction coefficient from aerodynamically smooth, transitionally rough, and fully rough turbulent boundary-layer flows are presented for four surfaces-three rough and one smooth. The rough surfaces are composed of 1.27 mm diameter hemispheres spaced in staggered arrays 2, 4, and 10 base diameters apart, respectively, on otherwise smooth walls. The current incompressible turbulent boundary-layer rough-wall air flow data are compared with previously published results on another, similar rough surface. It is shown that fully rough mean velocity profiles collapse together when scaled as a function of momentum thickness, as was reported previously. However, this similarity cannot be used to distinguish roughness flow regimes, since a similar degree of collapse is observed in the transitionally rough regimes, since a similar degree of collapse is observed in the transitionally rough data. Observation of the new data shows that scaling on the momentum thickness alone is not sufficient to produce similar velocity profiles for flows over surfaces of different roughness character. The skin friction coefficient data versus the ratio of the momentum thickness to roughness height collapse within the data uncertainty, irrespective of roughness flow regime, with the data for each rough surface collapsing to a different curve. Calculations made using the previously published discrete element prediction method are compared with data from the rough surfaces with well-defined roughness elements, and it is shown that the calculations are in good agreement with the data.

  12. Experimental study of noise emitted by circular cylinders with large roughness

    NASA Astrophysics Data System (ADS)

    Alomar, Antoni; Angland, David; Zhang, Xin; Molin, Nicolas

    2014-12-01

    The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe's roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.

  13. Effects of Alloying Elements on Microstructure, Hardness, Wear Resistance, and Surface Roughness of Centrifugally Cast High-Speed Steel Rolls

    NASA Astrophysics Data System (ADS)

    Ha, Dae Jin; Sung, Hyo Kyung; Park, Joon Wook; Lee, Sunghak

    2009-11-01

    A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up to 25 vol pct) of carbides, such as MC, M2C, and M7C3 carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous. The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent, and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively.

  14. Full Wave Analysis of RF Signal Attenuation in a Lossy Rough Surface Cave using a High Order Time Domain Vector Finite Element Method

    SciTech Connect

    Pingenot, J; Rieben, R; White, D; Dudley, D

    2005-10-31

    We present a computational study of signal propagation and attenuation of a 200 MHz planar loop antenna in a cave environment. The cave is modeled as a straight and lossy random rough wall. To simulate a broad frequency band, the full wave Maxwell equations are solved directly in the time domain via a high order vector finite element discretization using the massively parallel CEM code EMSolve. The numerical technique is first verified against theoretical results for a planar loop antenna in a smooth lossy cave. The simulation is then performed for a series of random rough surface meshes in order to generate statistical data for the propagation and attenuation properties of the antenna in a cave environment. Results for the mean and variance of the power spectral density of the electric field are presented and discussed.

  15. Critical assessment of finite element analysis applied to metal-oxide interface roughness in oxidising zirconium alloys

    NASA Astrophysics Data System (ADS)

    Platt, P.; Frankel, P.; Gass, M.; Preuss, M.

    2015-09-01

    As a nuclear fuel cladding material, zirconium alloys act as a barrier between the fuel and pressurised steam or lithiated water environment. Controlling degradation mechanisms such as oxidation is essential to extending the in-service lifetime of the fuel. At temperatures of ∼360 °C zirconium alloys are known to exhibit cyclical, approximately cubic corrosion kinetics. With acceleration in the oxidation kinetics occurring every ∼2 μm of oxide growth, and being associated with the formation of a network of lateral cracks. Finite element analysis has been used previously to explain the lateral crack formation by the development of localised out-of-plane tensile stresses at the metal-oxide interface. This work uses the Abaqus finite element code to assess critically current approaches to representing the oxidation of zirconium alloys, with relation to undulations at the metal-oxide interface and localised stress generation. This includes comparison of axisymmetric and 3D quartered modelling approaches, and investigates the effect of interface geometry and plasticity in the metal substrate. Particular focus is placed on the application of the anisotropic strain tensor used to represent the oxidation mechanism, which is typically applied with a fixed coordinate system. Assessment of the impact of the tensor showed that 99% of the localised tensile stresses originated from the out-of-plane component of the strain tensor, rather than the in-plane expansion as was previously thought. Discussion is given to the difficulties associated with this modelling approach and the requirements for future simulations of the oxidation of zirconium alloys.

  16. [Hemispheric specialisation versus inter-hemispheric communication].

    PubMed

    Belin, C; Faure, S; Mayer, E

    2008-05-01

    The first part of this article covers the main discoveries that led to the concept of hemispheric specialisation, from Egyptian antiquity to present times, through the pivotal XIXth century period that saw the attribution of specific cognitive functions to the left and right hemispheres. Next, this dichotomous conception of cerebral function, attributing a given process to a hemisphere and hypothesising callosal transmission, is discussed in the light of recent studies on language comprehension. Present day knowledge suggesting an alternative to the structuralist view of hemispheric specialisation in the form of dynamic, complementary sharing of labour, and of cooperation through transcortical neural networks, is then considered. Finally, the role of the corpus callosum in interhemispheric communication is briefly covered. An emphasis is placed on the diversity of this structure that is at the origin of highly different functions (fibre size, homotopic vs heterotopic connections). Ultimately, we contrast the view of a corpus callosum serving as an information transmitting channel with that of a fibre tract co-activating the non-engaged hemisphere and preparing it for potential stimulation. In this manner, the corpus callosum minimises disparities in the distribution of attention between the two hemispheres. PMID:18675041

  17. Investigation of the influence of a step change in surface roughness on turbulent heat transfer

    NASA Technical Reports Server (NTRS)

    Taylor, Robert P.; Coleman, Hugh W.; Taylor, J. Keith; Hosni, M. H.

    1991-01-01

    The use is studied of smooth heat flux gages on the otherwise very rough SSME fuel pump turbine blades. To gain insights into behavior of such installations, fluid mechanics and heat transfer data were collected and are reported for a turbulent boundary layer over a surface with a step change from a rough surface to a smooth surface. The first 0.9 m length of the flat plate test surface was roughened with 1.27 mm hemispheres in a staggered, uniform array spaced 2 base diameters apart. The remaining 1.5 m length was smooth. The effect of the alignment of the smooth surface with respect to the rough surface was also studied by conducting experiments with the smooth surface aligned with the bases or alternatively with the crests of the roughness elements. Stanton number distributions, skin friction distributions, and boundary layer profiles of temperature and velocity are reported and are compared to previous data for both all rough and all smooth wall cases. The experiments show that the step change from rough to smooth has a dramatic effect on the convective heat transfer. It is concluded that use of smooth heat flux gages on otherwise rough surfaces could cause large errors.

  18. Hemispheric Asymmetries in Substorm Recovery Time Scales

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

    2009-01-01

    Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

  19. Roughness of stable, armored gravel beds

    NASA Astrophysics Data System (ADS)

    Gomez, Basil

    1993-11-01

    The grain roughness of stable armored beds that formed in a laboratory flume under a range of steady flow conditions on rounded, flat and angular gravel is analyzed. Gravel roughness geometry is determined from bed surface profiles and vertical photographs. These techniques have been employed in field situations. Thus the methodology is potentially applicable to the analysis of grain roughness in natural gravel bed channels. The description of representative roughness geometry is also analogous to that used to characterize artificial roughness arrays. Armor roughness increases with increasing flow. Armored surfaces composed of angular gravel are roughest, and surfaces formed of flat gravel offer least resistance to the flow. Stable armored beds may exhibit a tendency to maximize the ratio of the shear due to drag on representative roughness elements to total shear. Roughness concentration is strongly correlated with the energy slope, and there is a linear increase in equivalent roughness height with increasing roughness concentration. The friction factor for an armored surface varies in a linear manner with representative roughness geometry. The equation defining this relation is probably similar to that used to characterize variations in the friction factor with artificial roughness geometry at low roughness concentrations. However, to reconcile the relations for artificial and natural roughness completely, it may be necessary to explicitly consider the contribution to flow resistance made by roughness shape, background roughness, and blocking in shallow flows.

  20. Heat transfer in the turbulent boundary layer with a step change in surface roughness

    NASA Technical Reports Server (NTRS)

    Taylor, Robert P.; Taylor, J. K.; Coleman, Hugh W.; Hosni, M. H.

    1991-01-01

    Measurements of Stanton numbers, velocity profiles, temperature profiles, and turbulence intensity profiles are reported for turbulent flat plate boundary layer flows with a step change in surface roughness. The first 0.9 m length of the test surface is roughened with 1.27 mm diameter hemispheres spaced 2 base diameters apart in a staggered array. The remaining 1.5 m length is smooth. The experiments show that the step change from a rough to a smooth surface has a dramatic effect on the convective heat transfer. In many cases, the Stanton number drops below the smooth-wall correlation immediately downstream of the change in roughness. The Stanton number measurements are compared with predictions using the discrete element method with excellent results.

  1. Analysis and testing for rotordynamic coefficients of turbulent annular seals with different, directionally homogeneous surface-roughness treatment for rotor and stator elements

    NASA Technical Reports Server (NTRS)

    Childs, D. W.; Kim, C. H.

    1984-01-01

    A theory is presented, based on a simple modification of Hirs' turbulent lubrication equations, to account for different but directionally-homogeneous surface roughness treatments for the rotor and stator of annular seals. The theoretical results agree with von Pragenau's predictions that a damper seal which uses a smooth rotor and a rough stator yields more net damping than a conventional seal which has the same roughness for both the rotor and stator. Experimental results for four stators confirm that properly-designed roughened stators yield higher net damping values and substantially less leakage than seals with smooth surfaces. The best seal from both damping and leakage viewpoints uses a round-hole-pattern stator. Initial results for this stator suggest that, within limits, seals can be designed to yield specified ratios of stiffness to damping.

  2. Radar-aeolian roughness project

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

    1991-01-01

    The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

  3. Io's Kanehekili Hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color composite of Io, acquired by Galileo during its ninth orbit (C9) of Jupiter, shows the hemisphere of Io which is centered at longitude 52 degrees. The dark feature just to the lower right of the center of the disk is called Kanehekili. Named after an Hawaiian thunder god, Kanehekili contains two persistent high temperature hot spots and a 'new' active volcanic plume. NASA's Voyager spacecraft returned images of nine active plumes during its 1979 flyby of this dynamic satellite. To date, Galileo's plume monitoring observations have shown continued activity at four of those nine plume locations as well as new activity at six other locations.

    North is to the top of the picture which combines images acquired using violet, green, and near-infrared (756 micrometers) filters. The resolution is 21 kilometers per picture element. The images were taken on June 27, 1997 at a range of 1,033,000 kilometers by the solid state imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  4. Hemispherical micro-resonators from atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Gray, Jason M.; Houlton, John P.; Gertsch, Jonas C.; Brown, Joseph J.; Rogers, Charles T.; George, Steven M.; Bright, Victor M.

    2014-12-01

    Hemispherical shell micro-resonators may be used as gyroscopes to potentially enable precision inertial navigation and guidance at low cost and size. Such devices require a high degree of symmetry and large quality factors (Q). Fabricating the devices from atomic layer deposition (ALD) facilitates symmetry through ALD’s high conformality and low surface roughness. To maximize Q, the shells’ geometry is optimized using finite element method (FEM) studies to reduce thermoelastic dissipation and anchor loss. The shells are fabricated by etching hemispherical molds in Si (1 1 1) substrates with a 2:7:1 volumetric ratio of hydrofluoric:nitric:acetic acids, and conformally coating and patterning the molds with ALD Al2O3. The Al2O3 shells are then released from the surrounding Si substrate with an SF6 plasma. The resulting shells typically have radii around 50 µm and thicknesses close to 50 nm. The shells are highly symmetric, with radial deviations between 0.22 and 0.49%, and robust enough to be driven on resonance at amplitudes 10 × their thickness, sufficient to visualize the resonance mode shapes in an SEM. Resonance frequencies are around 60 kHz, with Q values between 1000 and 2000. This Q is lower than the 106 predicted by FEM, implying that Q is being limited by unmodeled sources of energy loss, most likely from surface effects or material defects.

  5. Southern hemisphere observations

    NASA Astrophysics Data System (ADS)

    Orchiston, Wayne

    Because of insurmountable problems associated with absolute dating, the non-literate cultures of the Southern Hemisphere can contribute little to Applied Historical Astronomy, although Maori traditions document a possible supernova dating to the period 1000-1770 AD. In contrast, the abundant nineteenth century solar, planetary, cometary and stellar observational data provided by Southern Hemisphere professional and amateur observatories can serve as an invaluable mine of information for present-day astronomers seeking to incorporate historical data in their investigations.

  6. Hemispherical Laue camera

    DOEpatents

    Li, James C. M.; Chu, Sungnee G.

    1980-01-01

    A hemispherical Laue camera comprises a crystal sample mount for positioning a sample to be analyzed at the center of sphere of a hemispherical, X-radiation sensitive film cassette, a collimator, a stationary or rotating sample mount and a set of standard spherical projection spheres. X-radiation generated from an external source is directed through the collimator to impinge onto the single crystal sample on the stationary mount. The diffracted beam is recorded on the hemispherical X-radiation sensitive film mounted inside the hemispherical film cassette in either transmission or back-reflection geometry. The distances travelled by X-radiation diffracted from the crystal to the hemispherical film are the same for all crystal planes which satisfy Bragg's Law. The recorded diffraction spots or Laue spots on the film thereby preserve both the symmetry information of the crystal structure and the relative intensities which are directly related to the relative structure factors of the crystal orientations. The diffraction pattern on the exposed film is compared with the known diffraction pattern on one of the standard spherical projection spheres for a specific crystal structure to determine the orientation of the crystal sample. By replacing the stationary sample support with a rotating sample mount, the hemispherical Laue camera can be used for crystal structure determination in a manner previously provided in conventional Debye-Scherrer cameras.

  7. Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

    NASA Technical Reports Server (NTRS)

    Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

    1987-01-01

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  8. Measurement and calculation of surface roughness effects on turbulent flow and heat transfer

    NASA Astrophysics Data System (ADS)

    Hosni, Mohammad Hosein

    Fluid dynamics and heat transfer data for turbulent boundary layer flow of air over a smooth surface and three well-defined rough surfaces were taken in the Turbulent Heat Transfer Test Facility (THTTF) for x-Reynolds numbers ranging up to 10,000,000. The smooth wall data provided base line data for comparison with the data from rough surfaces. The three rough surfaces were composed of 1.27 mm diameter hemispheres spaced 2, 4, and 10 diameters apart, respectively, in staggered arrays on otherwise smooth flat plates. Skin friction coefficient distributions and boundary layer profiles of mean velocity and Reynolds stresses were obtained using hot-wire anemometry. The THTTF heat transfer data taken in aerodynamically smooth, transitionally rough, and fully rough flow regimes over the three well-defined rough surfaces for freestream velocities of 6, 12, 28, 43, 58, and 67 m/s were compared with the data sets taken at Stanford University using a single well-defined rough surface. It was observed that the Stanton numbers for a given surface collapse together in x-Reynolds number coordinates as the freestream velocity increases, with the Stanton number level being larger for rougher surfaces. The THTTF heat transfer data and the Stanford data were used to modify the roughness energy transport model in the discrete element prediction method. This method was used in calculation of the fluid dynamics and heat transfer for the THTTF and Stanford surfaces. The predictions were in excellent agreement with all data sets within the data uncertainty.

  9. Electrokinetic transport in microchannels with random roughness

    SciTech Connect

    Wang, Moran; Kang, Qinjun

    2008-01-01

    We present a numerical framework to model the electrokinetic transport in microchannels with random roughness. The three-dimensional microstructure of the rough channel is generated by a random generation-growth method with three statistical parameters to control the number density, the total volume fraction, and the anisotropy characteristics of roughness elements. The governing equations for the electrokinetic transport are solved by a high-efficiency lattice Poisson?Boltzmann method in complex geometries. The effects from the geometric characteristics of roughness on the electrokinetic transport in microchannels are therefore modeled and analyzed. For a given total roughness volume fraction, a higher number density leads to a lower fluctuation because of the random factors. The electroosmotic flow rate increases with the roughness number density nearly logarithmically for a given volume fraction of roughness but decreases with the volume fraction for a given roughness number density. When both the volume fraction and the number density of roughness are given, the electroosmotic flow rate is enhanced by the increase of the characteristic length along the external electric field direction but is reduced by that in the direction across the channel. For a given microstructure of the rough microchannel, the electroosmotic flow rate decreases with the Debye length. It is found that the shape resistance of roughness is responsible for the flow rate reduction in the rough channel compared to the smooth channel even for very thin double layers, and hence plays an important role in microchannel electroosmotic flows.

  10. Transition Experiments on Blunt Bodies with Distributed Roughness in Hypersonic Free Flight in Carbon Dioxide

    NASA Technical Reports Server (NTRS)

    Wilder, Michael C.; Reda, Daniel C.; Prabhu, Dinesh K.

    2015-01-01

    Blunt-body geometries were flown through carbon dioxide in the NASA Ames Hypervelocity Free Flight Aerodynamic Facility to investigate the influence of distributed surface roughness on transition to turbulence in CO2-dominated atmospheres, such as those of Mars and Venus. Tests were also performed in air for direct comparison with archival results. Models of hemispherical and spherically-blunted large-angle conical geometries were flown at speeds between 2.8 km/s and 5.1 km/s and freestream pressures between 50 Torr and 228 Torr. Transition fronts were determined from global surface heat flux distributions measured using thermal imaging techniques. Distributed surface roughness was produced by grit-blasting the model surfaces. Real-gas Navier-Stokes solutions were used to calculate non-dimensional correlating parameters at the measured transition onset locations. Transition-onset locations correlated well with a constant roughness Reynolds number based on the mean roughness element height. The critical roughness Reynolds number for transition onset determined for flight in CO2 was 223 +/- 25%. This mean value is lower than the critical value of 250 +/- 20% previously-established from tests conducted in air, but within the bounds of the expected measurement uncertainty.

  11. Rough-wall turbulent boundary layers in the transition regime

    NASA Technical Reports Server (NTRS)

    Bandyopadhyay, Promode R.

    1987-01-01

    An experimental investigation of turbulent boundary layers over two-dimensional spanwise groove and three-dimensional sandgrain roughnesses in the transition regime between hydraulically smooth and fully rough conditions is presented. It is found that a self-preserving state can be reached in boundary layers developing over both d-type groove and sandgrain roughnesses, and that the drag of a k-type rough wall can be reduced by lowering the spanwise aspect ratio of the roughness elements. The two roughness Reynolds numbers defining the boundaries of the transition regime of the k-type roughnesses are shown to decrease with increasing roughness-element spanwise aspect ratio, and the upper critical transition Reynolds number is shown to determine the roughness behavior in both the transition and fully rough regime.

  12. Hemispheric lateralization in reasoning.

    PubMed

    Turner, Benjamin O; Marinsek, Nicole; Ryhal, Emily; Miller, Michael B

    2015-11-01

    A growing body of evidence suggests that reasoning in humans relies on a number of related processes whose neural loci are largely lateralized to one hemisphere or the other. A recent review of this evidence concluded that the patterns of lateralization observed are organized according to two complementary tendencies. The left hemisphere attempts to reduce uncertainty by drawing inferences or creating explanations, even at the cost of ignoring conflicting evidence or generating implausible explanations. Conversely, the right hemisphere aims to reduce conflict by rejecting or refining explanations that are no longer tenable in the face of new evidence. In healthy adults, the hemispheres work together to achieve a balance between certainty and consistency, and a wealth of neuropsychological research supports the notion that upsetting this balance results in various failures in reasoning, including delusions. However, support for this model from the neuroimaging literature is mixed. Here, we examine the evidence for this framework from multiple research domains, including an activation likelihood estimation analysis of functional magnetic resonance imaging studies of reasoning. Our results suggest a need to either revise this model as it applies to healthy adults or to develop better tools for assessing lateralization in these individuals. PMID:26426534

  13. Experimental Investigation of the Problem of Surface Roughness

    NASA Technical Reports Server (NTRS)

    Schlichting, H

    1937-01-01

    Based on the universal laws of turbulent velocity distribution at rough and smooth walls, there is in the present work presented a method that allows surface roughness tests and in particular, measurements on the roughness of ship surfaces to be carried out in a much simpler manner. The types of roughness investigated were in the form of flat, rough plates installed in a square-section rectangular channel, the other three walls always being smooth. Twenty-one plates of various roughness were investigated, the roughness elements being the following: spheres of diameter 0.41 and 0.21, respectively, spherical segments, cones, and "short" and "long" angles.

  14. Extensive wetting due to roughness

    SciTech Connect

    Yost, F.G.; Michael, J.R.; Eisenmann, E.T. . Center for Solder Science and Technology)

    1995-01-01

    Typically, a small mass of eutectic Sn-Pb solder wets a copper surface and flows radially outward to form a hemispherical shape with a contact angle of approx. 15--20 deg. When a similar mass of solder wets and thick electroless copper coated substrate, rapid radial flow commences and surprising new effects occur. Thick coats of electroless copper have a nodular surface structure and spreading on it does not subside until all solder is consumed. When the nodular structure is wetted by solder a coastline'' with many nearby islands'' are defined. Photos of regions at the wetting front were taken in the backscatter imaging mode of an SEM. These images show that solder wets the valleys between the surface nodules forming a delicate, lacy arrangement. The geometry of this coastal'' solder structure is described as fractal-like having a dimension D = 1.38 making it similar to drying fronts and cloud configurations. The importance of surface roughness in wetting phenomena is discussed in the light of an extensive history on the subject. It is shown that for spontaneous flow, assisted by roughness, the surface geometry must consist of local angles that are larger than the equilibrium contact angle. Kinetics of the wetting process are demonstrated by image analysis of wetted area taken from videotaped experiments. These experimental kinetics are shown to be similar in form to flow in open channel capillaries.

  15. Hemispherical Stokes polarimeter for early cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Lemaillet, Paul; Ramella-Roman, Jessica C.

    2011-03-01

    Optimal treatment of skin cancer before it reaches metastasis depends critically on early diagnosis of the melanoma. Valuable information for this diagnosis can be obtained from the analysis of skin roughness. This information can aid in determining the necessity for skin removal. For this purpose, we developed a hemispherical imaging Stokes polarimeter designed to monitor skin cancer based on a roughness assessment of the epidermis. Our setup is composed of 16 out-of-plane polarized light illuminations tubes that contain a three color LED and a vertical polarizer, a Stokes polarimeter that contains 2 liquid crystal retarders, a reference vertical polarizer and a fast acquisition camera. The Stokes polarimeter was calibrated using a set of well-known input polarization states. Each illumination polarizer was positioned using a roughness gold standard and a facet model describing the principal angle of polarization of the analyzed light as a function of the angle of incidence. A set of phantoms mimicking the optical properties of skin at 633 nm as well as skin roughness was built using wax as the bulk material, titanium dioxide as the scatterer and a black dye as the absorber. Images of these phantoms are presented and they are analyzed using a facet model.

  16. Music, Hemisphere Preference and Imagery.

    ERIC Educational Resources Information Center

    Stratton, Valerie N.; Zalanowski, Annette H.

    Two experiments were conducted to determine a possible relationship between the right hemisphere, music perception, and mental imagery. The first experiment compared two groups of college students, one of which showed a preference for left hemisphere thinking (n=22) and the other a preference for right hemisphere thinking (n=20), in order to test…

  17. Brain Hemisphericity and Developmental Dyslexia

    ERIC Educational Resources Information Center

    Vlachos, Filippos; Andreou, Eleni; Delliou, Afroditi

    2013-01-01

    The present study examined the link between brain hemisphericity and dyslexia in secondary school students, using the Preference Test (PT), a widely used self-report index of preferred hemisphere thinking styles. The hypothesis was that differences would be revealed between the dyslexic group and their peers in hemispheric preference. A total of…

  18. Comparing Experiment and Computation of Hypersonic Laminar Boundary Layers with Isolated Roughness

    NASA Technical Reports Server (NTRS)

    Bathel, Brett F.; Iyer, Prahladh S.; Mahesh, Krishnan; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Johansen, Craig T.

    2014-01-01

    Streamwise velocity profile behavior in a hypersonic laminar boundary layer in the presence of an isolated roughness element is presented for an edge Mach number of 8.2. Two different roughness element types are considered: a 2-mm tall, 4-mm diameter cylinder, and a 2-mm radius hemisphere. Measurements of the streamwise velocity behavior using nitric oxide (NO) planar laser-induced fluorescence (PLIF) molecular tagging velocimetry (MTV) have been performed on a 20-degree wedge model. The top surface of this model acts as a flat-plate and is oriented at 5 degrees with respect to the freestream flow. Computations using direct numerical simulation (DNS) of these flows have been performed and are compared to the measured velocity profiles. Particular attention is given to the characteristics of velocity profiles immediately upstream and downstream of the roughness elements. In these regions, the streamwise flow can experience strong deceleration or acceleration. An analysis in which experimentally measured MTV profile displacements are compared with DNS particle displacements is performed to determine if the assumption of constant velocity over the duration of the MTV measurement is valid. This assumption is typically made when reporting MTV-measured velocity profiles, and may result in significant errors when comparing MTV measurements to computations in regions with strong deceleration or acceleration. The DNS computations with the cylindrical roughness element presented in this paper were performed with and without air injection from a rectangular slot upstream of the cylinder. This was done to determine the extent to which gas seeding in the MTV measurements perturbs the boundary layer flowfield.

  19. Triton's Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This polar projection of Triton's southern hemisphere provides a view of the southern polar cap and bright equatorial fringe. The margin of the cap is scalloped and ranges in latitude from +10 degrees to -30 degrees. The bright fringe is closely associated with the cap's margin; from it, diffuse bright rays extend north-northeast for hundreds of kilometers. The bright fringe probably consists of very fresh nitrogen frost or snow, and the rays consist of bright-fringe materials that were redistributed by north-moving Coriolis-deflected winds.

  20. Modeling surface roughness scattering in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim

    2015-09-28

    Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.

  1. MOLA Global roughness map of Mars

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The median of slopes in 35-km windows indicate the typical roughness on 300-meter baselines. The rougher nature of the heavily cratered terrain in the Southern Hemisphere is apparent, as well as that of Valles Marineris (12S, 289E) canyon walls and the Olympus Mons (18N, 227E) aureole deposits. The Northern Lowlands are smooth, especially Amazonis Planitia (16N, 202E), a region to the west of Olympus Mons, were typical median slopes on these baselines are often smaller than 0.1 degree. A shaded relief map of the topography is overlaid is monochrome.

  2. Neptune's Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This photograph of Neptune's southern hemisphere was taken by the narrow-angle camera on NASA's Voyager 2 when the spacecraft was 4.2 million km (2.6 million miles) from the planet. The smallest features that can be seen are 38 km (24 miles) across. The almond-shaped structure at the left is a large cloud system that has been seen for several weeks. Internal details in the feature have become increasingly apparent as Voyager 2 has approached. Systems with similar shapes in Jupiter's atmosphere rotate about their centers, rolling in the local winds that increase toward the south. However, the wispy nature of the white central clouds in this Neptunian feature make confirmation of the system's rotation difficult. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  3. A Left-Hemisphere Model for Right-Hemisphere Programmers.

    ERIC Educational Resources Information Center

    Krantz, Gordon C.

    The paper presents an action-and-decision (left-hemisphere) algorithm as a model for planning by holistic, intuitive (right-hemisphere) managers of service programs, including programs for exceptional children. Because the model is not based upon an established literature in the field of service to exceptional individuals, and because it appears…

  4. Roughness and function

    NASA Astrophysics Data System (ADS)

    Thomas, T. R.

    2014-01-01

    A function map is used to locate applications of roughness in separation-velocity space. The importance of roughness in contact mechanics is demonstrated and versions of the plasticity index are introduced and compared. Case studies of roughness and function are presented from tribology and the life sciences. Tribological examples are taken from the automotive industry and include the manufacture of vehicle bodies, and drive train tribology, particularly cylinder liner, cam and gearbox friction and wear. From the life sciences, problems of prosthetic fixation and tribology are shown to depend on roughness. The interaction of haptics and surface finish is described and illustrated. A number of other areas of application are listed. Finally the likely future importance of structured surfaces is discussed.

  5. Rough Fresnel zone plates over metallic surfaces.

    PubMed

    Salgado-Remacha, Francisco Javier; Sanchez-Brea, Luis Miguel; Alvarez-Rios, Francisco Javier; Bernabeu, Eusebio

    2010-04-01

    We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome-glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh-Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results. PMID:20357856

  6. Callisto Hemispherical Globes

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The images used for the base of this globe were chosen from the best image quality and moderate resolution coverage supplied by Galileo SSI and Voyager 1 and 2 (Batson, 1987; Becker and others, 1998; Becker and others, 1999; Becker and others, 2001). The digital map was produced using Integrated Software for Imagers and Spectrometers (ISIS) (Eliason, 1997; Gaddis and others, 1997; Torson and Becker, 1997). The individual images were radiometrically calibrated and photometrically normalized using a Lunar-Lambert function with empirically derived values (McEwen, 1991; Kirk and others, 2000). A linear correction based on the statistics of all overlapping areas was then applied to minimize image brightness variations. The image data were selected on the basis of overall image quality, reasonable original input resolution (from 20 km/pixel for gap fill to as much as 150 m/pixel), and availability of moderate emission/incidence angles for topography. Although consistency was achieved where possible, different filters were included for global image coverage as necessary: clear for Voyager 1 and 2; clear and green (559 nm) for Galileo SSI. Individual images were projected to a Sinusoidal Equal-Area projection at an image resolution of 1.0 kilometer/pixel, and a final global mosaic was constructed in this same projection. The final mosaic was enhanced using commercial software. The global mosaic was then reprojected so that the entire surface of Callisto is portrayed in a manner suitable for the production of a globe. A specialized program was used to create the 'flower petal' appearance of the images; the area of each petal from 0 to 75 degrees latitude is in the Transverse Mercator projection, and the area from 75 to 90 degrees latitude is in the Lambert Azimuthal Equal-Area projection. The projections for adjacent petals overlap by 2 degrees of longitude, so that some features are shown twice. The northern hemisphere is shown on the left, and the southern hemisphere is

  7. Europa Hemispherical Globes

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The images used for the base of this globe were chosen from coverage supplied by the Galileo solid-state imaging (SSI) camera and Voyager 1 and 2 spacecraft. The individual images were radiometrically calibrated and photometrically normalized using a Lunar-Lambert function with empirically derived values. A linear correction based on the statistics of all overlapping areas was then applied to minimize image brightness variations. The image data were selected on the basis of overall image quality, reasonable original input resolution (from 20 km/pixel for gap fill to as much as 200 m/pixel), and availability of moderate emission/incidence angles for topography. Although consistency was achieved where possible, different filters were included for global image coverage as necessary: clear/blue for Voyager 1 and 2, and clear, near-IR (757 nm), and green (559 nm) for Galileo SSI. Individual images were projected to a Sinusoidal Equal-Area projection at an image resolution of 500 m/pixel, and a final global mosaic was constructed in this same Sinusoidal projection.

    The global mosaic was then reprojected so that the entire surface of Europa is portrayed in a manner suitable for the production of a globe. A specialized program was used to create the 'flower petal' appearance of the images; the area of each petal from 0 to 75 degrees latitude is in the Transverse Mercator projection, and the area from 75 to 90 degrees latitude is in the Lambert Azimuthal Equal-Area projection. The projections for adjacent petals overlap by 2 degrees of longitude, so that some features are shown twice.

    Names shown on the globe are approved by the International Astronomical Union. The number, size, and placement of text were chosen for a 9-inch globe. A complete list of Europa nomenclature can be found at the Gazetteer of Planetary Nomenclature at http://planetarynames.wr.usgs.gov. The northern hemisphere is shown on the left, and the southern hemisphere is shown on the right.

  8. Callisto's Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    These views of Callisto's southern hemisphere were taken by the Near Infrared Mapping Spectrometer just after closest approach in orbit G8 on May 6, 1997. These false color images show surface compositional differences, red = more ice, blue = less ice.

    The upper left view contains Buri, a crater with a diameter of about 60 km. In the infrared spectrum, Buri and the rays that extend from the crater have high abundance of water ice compared to the surrounding region. The center view, a large (200 km or 120 mile diameter) unnamed impact crater with a distinct ring or circle around it reveals a complex mix of ice and non-ice materials. This is possibly due to impact excavation of the ice-rich subsurface which suggests that the darker material is just a thin surface covering caused by impact debris or a lag deposit from which the ice has evaporated away. The infrared data shows spectral signatures for both sulfur and carbon as two potential materials which could play a part in the complicated make-up of Callisto's surface.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  9. Europa's Leading Hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image of Europa's leading hemisphere was obtained by the solid state imaging (CCD) system on board NASA's Galileo spacecraft during its seventh orbit of Jupiter. In the upper left part of the image is Tyre, a multi-ringed structure that may have formed as a result of an ancient impact. Also visible are numerous lineaments that extend for over 1000 kilometers. The limb, or edge, of Europa in this image can be used by scientists to constrain the radius and shape of the satellite. North is to the top of the picture and the sun illuminates the surface from the right. The image, centered at -40 latitude and 180 longitude, covers an area approximately 2000 by 1300 kilometers. The finest details that can be discerned in this picture are about 6.6 kilometers across. The images were taken on April 3, 1997 at 17 hours, 42 minutes, 19 seconds Universal Time when the spacecraft was at a range of 31,8628 kilometers.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  10. Detonation in TATB Hemispheres

    SciTech Connect

    Druce, B; Souers, P C; Chow, C; Roeske, F; Vitello, P; Hrousis, C

    2004-03-17

    Streak camera breakout and Fabry-Perot interferometer data have been taken on the outer surface of 1.80 g/cm{sup 3} TATB hemispherical boosters initiated by slapper detonators at three temperatures. The slapper causes breakout to occur at 54{sup o} at ambient temperatures and 42{sup o} at -54 C, where the axis of rotation is 0{sup o}. The Fabry velocities may be associated with pressures, and these decrease for large timing delays in breakout seen at the colder temperatures. At room temperature, the Fabry pressures appear constant at all angles. Both fresh and decade-old explosive are tested and no difference is seen. The problem has been modeled with reactive flow. Adjustment of the JWL for temperature makes little difference, but cooling to -54 C decreases the rate constant by 1/6th. The problem was run both at constant density and with density differences using two different codes. The ambient code results show that a density difference is probably there but it cannot be quantified.

  11. Fault Roughness Records Strength

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Candela, T.; Kirkpatrick, J. D.

    2014-12-01

    Fault roughness is commonly ~0.1-1% at the outcrop exposure scale. More mature faults are smoother than less mature ones, but the overall range of roughness is surprisingly limited which suggests dynamic control. In addition, the power spectra of many exposed fault surfaces follow a single power law over scales from millimeters to 10's of meters. This is another surprising observation as distinct structures such as slickenlines and mullions are clearly visible on the same surfaces at well-defined scales. We can reconcile both observations by suggesting that the roughness of fault surfaces is controlled by the maximum strain that can be supported elastically in the wallrock. If the fault surface topography requires more than 0.1-1% strain, it fails. Invoking wallrock strength explains two additional observations on the Corona Heights fault for which we have extensive roughness data. Firstly, the surface is isotropic below a scale of 30 microns and has grooves at larger scales. Samples from at least three other faults (Dixie Valley, Mount St. Helens and San Andreas) also are isotropic at scales below 10's of microns. If grooves can only persist when the walls of the grooves have a sufficiently low slope to maintain the shape, this scale of isotropy can be predicted based on the measured slip perpendicular roughness data. The observed 30 micron scale at Corona Heights is consistent with an elastic strain of 0.01 estimated from the observed slip perpendicular roughness with a Hurst exponent of 0.8. The second observation at Corona Heights is that slickenlines are not deflected around meter-scale mullions. Yielding of these mullions at centimeter to meter scale is predicted from the slip parallel roughness as measured here. The success of the strain criterion for Corona Heights supports it as the appropriate control on fault roughness. Micromechanically, the criterion implies that failure of the fault surface is a continual process during slip. Macroscopically, the

  12. Shear Stress Partitioning in Airflow over Rough Surfaces: Roughness Form Effects and Influence on the Distribution of Shear Stress

    NASA Astrophysics Data System (ADS)

    Gillies, J. A.; Nickling, W. G.; King, J.

    2004-12-01

    Roughness elements distributed across a surface can significantly decrease the entrainment and transport of underlying fine-grained sediments by wind. The parameterization of roughness effects on wind erosion thresholds and sediment transport is critical to the development of models that can provide realistic predictions of sediment thresholds and fluxes due to wind erosion. Raupach et al. (1993) present a model for predicting the protective role of roughness elements in terms of a threshold friction velocity ratio as a function of the roughness geometry and the aerodynamic properties of the surface and roughness elements. The predictive capacity of this model remains uncertain and the work presented here represents part of an on-going effort of our group to improve the parameterization of the Raupach et al. (1993) model. To gain additional understanding of how roughness elements influence the magnitude and nature of the shear stress acting on the surface among the elements and evaluate strength and weaknesses of the roughness density parameter to characterize these effects, a wind tunnel study using model roughness arrays of similar roughness density composed of cube-shaped elements of different length dimensions was undertaken. Roughness density is defined as the total frontal area of all the elements to the total surface area that they occupy. Shear stress in the above element air flow was determined from vertical wind speed profile measurements. Point measurements of near surface shear stresses within the roughness array were made with simple omni-directional skin friction meters in order to investigate the partitioning of shear stress to the intervening surface. The results suggest that the roughness density parameter has severe limitations in describing the shear stress partitioning for these regularly arrayed rough surfaces. For surfaces with identical roughness densities, the surface composed of more and smaller elements was observed to have average and

  13. Mesoscale roughness of Venus

    NASA Technical Reports Server (NTRS)

    Garvin, J. B.; Frawley, James J.

    1994-01-01

    The global distribution of multi-kilometer (approx. 9 km) length scale 'roughness' (hereafter mesoscale roughness or MR) on Venus can be estimated from the Magellan global altimetry dataset (GxDR) and then compared with MR data derived for Earth from 5' ETOP5 data and for Mars (from USGS Mars DTM dataset). The mesoscale roughness parameter (MR) represents the RMS variance in meters of the actual planetary surface topography relative to the best fitting tangent plane defined on the basis of a 3x3 pixel sliding window. The best-fit plane was computed using a least-squares solution which minimizes delta H, the sum of the squares of the differences between the 9 local elevation values (H(sub i)), and the elevation of best-fit plane at the same grid location. Using the best-fit plane and delta H, we have computed the RMS 'roughness' var(delta R), where this parameter is always minimized on the basis of its calculation using least squares. We have called this 'ruggedness' parameter the Mesoscale Roughness (MR) because it is directly related to the high-frequency variance of topography after mesoscale slopes and tilts (i.e., for Venus, the baseline over which MR is computed (dx) is approx. 8.8 km and dx for Earth is approx. 9.3 km) are removed. As such, MR represents the degree to which a planetary surface is more rugged than approximately 10 km scale facets or tilts. It should not be confused with the radar 'RMS Roughness' parameter computed at 0.1 to 10 m length scales on the basis of the Magellan radar altimeter echo. We will use our MR parameter to investigate the global ruggedness properties of Venus as they relate to geological provinces and in comparison with the spatial pattern of MR for Earth and Mars.

  14. The Southern Hemisphere VLBI experiment

    SciTech Connect

    Preston, R.A.; Meier, D.L.; Louie, A.P.; Morabito, D.D.; Skjerve, L.; Slade, M.A.; Niell, A.E.; Wehrle, A.E.; Jauncey, D.L.; Tzioumis, A.K.; Haystack Observatory, Westford, MA; California Univ., Los Angeles; CSIRO, Div. of Radiophysics, Epping; Sydney Univ.; Manchester Victoria Univ., Jodrell Bank )

    1989-07-01

    Six radio telescopes were operated as the first Southern Hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 GHz. This array provided VLBI modeling and hybrid imaging of celestial radio sources in the Southern Hemisphere, high-accuracy VLBI geodesy between Southern Hemisphere sites, and subarcsecond radio astrometry of celestial sources south of declination -45 deg. The goals and implementation of the array are discussed, the methods of modeling and hybrid image production are explained, and the VLBI structure of the sources that were observed is summarized. 36 refs.

  15. Bio-inspired hemispherical compound eye camera

    NASA Astrophysics Data System (ADS)

    Xiao, Jianliang; Song, Young Min; Xie, Yizhu; Malyarchuk, Viktor; Jung, Inhwa; Choi, Ki-Joong; Liu, Zhuangjian; Park, Hyunsung; Lu, Chaofeng; Kim, Rak-Hwan; Li, Rui; Crozier, Kenneth B.; Huang, Yonggang; Rogers, John A.

    2014-03-01

    Compound eyes in arthropods demonstrate distinct imaging characteristics from human eyes, with wide angle field of view, low aberrations, high acuity to motion and infinite depth of field. Artificial imaging systems with similar geometries and properties are of great interest for many applications. However, the challenges in building such systems with hemispherical, compound apposition layouts cannot be met through established planar sensor technologies and conventional optics. We present our recent progress in combining optics, materials, mechanics and integration schemes to build fully functional artificial compound eye cameras. Nearly full hemispherical shapes (about 160 degrees) with densely packed artificial ommatidia were realized. The number of ommatidia (180) is comparable to those of the eyes of fire ants and bark beetles. The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors, which were fabricated in the planar geometries and then integrated and elastically transformed to hemispherical shapes. Imaging results and quantitative ray-tracing-based simulations illustrate key features of operation. These general strategies seem to be applicable to other compound eye devices, such as those inspired by moths and lacewings (refracting superposition eyes), lobster and shrimp (reflecting superposition eyes), and houseflies (neural superposition eyes).

  16. Archimedes and the Magdeburg Hemispheres

    ERIC Educational Resources Information Center

    Hayn, Carl H.

    1975-01-01

    Weights suspended from a lever arm separate evacuated hemispheres allowing estimation of atmospheric pressure to within five percent of the barometric reading. An illustration and a reference to von Guericke's demonstration are provided. (GH)

  17. Brain Hemispheres and Thinking Styles.

    ERIC Educational Resources Information Center

    Gray, Esther Cappon

    1980-01-01

    The author reviews some research, particularly that of Roger Sperry, substantiating the existence of different thinking styles in the two brain hemispheres and the development of this differentiation in infancy and childhood. She draws some implications for elementary teaching. (SJL)

  18. Free form hemispherical shaped charge

    DOEpatents

    Haselman, L.C. Jr.

    1996-06-04

    A hemispherical shaped charge has been modified such that one side of the hemisphere is spherical and the other is aspherical allowing a wall thickness variation in the liner. A further modification is to use an elongated hemispherical shape. The liner has a thick wall at its pole and a thin wall at the equator with a continually decreasing wall thickness from the pole to the equator. The ratio of the wall thickness from the pole to the equator varies depending on liner material and HE shape. Hemispherical shaped charges have previously been limited to spherical shapes with no variations in wall thicknesses. By redesign of the basic liner thicknesses, the jet properties of coherence, stability, and mass distribution have been significantly improved. 8 figs.

  19. Free form hemispherical shaped charge

    DOEpatents

    Haselman, Jr., Leonard C.

    1996-01-01

    A hemispherical shaped charge has been modified such that one side of the hemisphere is spherical and the other is aspherical allowing a wall thickness variation in the liner. A further modification is to use an elongated hemispherical shape. The liner has a thick wall at its pole and a thin wall at the equator with a continually decreasing wall thickness from the pole to the equator. The ratio of the wall thickness from the pole to the equator varies depending on liner material and HE shape. Hemispherical shaped charges have previously been limited to spherical shapes with no variations in wall thicknesses. By redesign of the basic liner thicknesses, the jet properties of coherence, stability, and mass distribution have been significantly improved.

  20. Northern Hemisphere Slopes from Mars Orbiter Laser Altimeter

    NASA Astrophysics Data System (ADS)

    Aharonson, O.; Zuber, M. T.

    1998-12-01

    Slopes, slope distributions, and macroscale surface roughness in the northern hemisphere of Mars have been measured from topographic profiles collected by the Mars Orbiter Laser Altimeter (MOLA) in the capture orbit, aerobraking hiatus and Science Phasing Orbit phases of the Mars Global Surveyor mission. The distribution function of slopes indicates that portions of the Martian surface fall into statistically distinct categories, distinguished by the histograms of both point-to-point slopes and of longer wavelength (10 and 100 km) slopes. Roughness correlates with elevation such that low regions tend to exhibit low roughness. Areas such as southern hemisphere highlands, dichotomy boundary terrains, and northern hemisphere lowlands all posses unique slope distribution signatures. The slope distribution within the Amazonis Planitia region, particularly member 3 of the Arcadia formation, displays an unusually smooth character. This region of anomalously low thermal inertia and low radar backscatter cross-section exhibits an rms variation in topography of <2 m over a 100-km baseline. Previous interpretations have suggested that this area is composed of accumulation of fine dust. Statistical comparison with other planetary surfaces of varying origin indicates that Amazonis most closely resembles in its smoothness the heavily sedimented surfaces on the Earth, i.e. oceanic abyssal plains and basins characterized by fluvial deposition. The smoothest measured volcanic surfaces as measured by altimetry on the Moon, Venus, and Mars are all significantly rougher than Amazonis. Saharan sand sheets are rougher by a factor of about three. Other regions in the Martian northern hemisphere that exhibit clear evidence of aeolian deposition are rougher than Amazonis as well.

  1. Rough surface reconstruction for ultrasonic NDE simulation

    SciTech Connect

    Choi, Wonjae; Shi, Fan; Lowe, Michael J. S.; Skelton, Elizabeth A.; Craster, Richard V.

    2014-02-18

    The reflection of ultrasound from rough surfaces is an important topic for the NDE of safety-critical components, such as pressure-containing components in power stations. The specular reflection from a rough surface of a defect is normally lower than it would be from a flat surface, so it is typical to apply a safety factor in order that justification cases for inspection planning are conservative. The study of the statistics of the rough surfaces that might be expected in candidate defects according to materials and loading, and the reflections from them, can be useful to develop arguments for realistic safety factors. This paper presents a study of real rough crack surfaces that are representative of the potential defects in pressure-containing power plant. Two-dimensional (area) values of the height of the roughness have been measured and their statistics analysed. Then a means to reconstruct model cases with similar statistics, so as to enable the creation of multiple realistic realizations of the surfaces, has been investigated, using random field theory. Rough surfaces are reconstructed, based on a real surface, and results for these two-dimensional descriptions of the original surface have been compared with those from the conventional model based on a one-dimensional correlation coefficient function. In addition, ultrasonic reflections from them are simulated using a finite element method.

  2. Heat Transfer and Friction-Factor Methods Turbulent Flow Inside Pipes 3d Rough

    Energy Science and Technology Software Center (ESTSC)

    1994-01-21

    Three-dimensional roughened internally enhanced tubes have been shown to be one of the most energy efficient for turbulent, forced convection applications. However, there is only one prediction method presented in the open literature and that is restricted to three-dimensional sand-grain roughness. Other roughness types are being proposed: hemispherical sectors, truncated cones, and full and truncated pyramids. There are no validated heat-transfer and friction-factor prediction methods for these different roughness shapes that can be used inmore » the transition and fully rough region. This program calculates the Nusselt number and friction factor values, for a broad range of three-dimensional roughness types such as hemispherical sectors, truncated cones, and full and truncated pyramids. Users of this program are heat-exchangers designers, enhanced tubing suppliers, and research organizations or academia who are developing or validating prediction methods.« less

  3. Western Hemisphere Knowledge Partnerships

    NASA Astrophysics Data System (ADS)

    Malone, T. F.

    2001-05-01

    , and application of knowledge concerning the nature of -- and interaction among -- matter, living organisms, energy, information, and human behavior. This strategy calls for innovative partnerships among the physical, biological, health, and social sciences, engineering, and the humanities. New kinds of partnership must also be forged among academia, business and industry, governments, and nongovernmental organizations. Geophysicists can play an important role in these partnerships. A focus for these partnerships is to manage the individual economic productivity that drives both human development and global change. As world population approaches stability during the twenty-first century, individual economic productivity will be the critical link between the human and the natural systems on planet Earth. AGU is among a core group of individuals and institutions proposing Western Hemisphere Knowledge Partnerships (WHKP) to test the hypothesis that knowledge, broadly construed, is an important organizing principle in choosing a path into the future. The WHKP agenda includes: (1) life-long learning, (2) the health and resilience of natural ecosystems, (3) eco-efficiency in economic production and consumption, (4) extension of national income accounts, (5) environmentally benign sources of energy, (6) delivery of health care, (7) intellectual property rights, and (8) networks for action by local communities.Collaboratories and distance education technologies will be major tools. A panel of experts will explore this proposal.

  4. Roughness Induced Transition in a Supersonic Boundary Layer

    NASA Technical Reports Server (NTRS)

    Balakumar, Ponnampalam; Kergerise, Michael A.

    2013-01-01

    Direct numerical simulation is used to investigate the transition induced by threedimensional isolated roughness elements in a supersonic boundary layer at a free stream Mach number of 3.5. Simulations are performed for two different configurations: one is a square planform roughness and the other is a diamond planform roughness. The mean-flow calculations show that the roughness induces counter rotating streamwise vortices downstream of the roughness. These vortices persist for a long distance downstream and lift the low momentum fluid from the near wall region and place it near the outer part of the boundary layer. This forms highly inflectional boundary layer profiles. These observations agree with recent experimental observations. The receptivity calculations showed that the amplitudes of the mass-flux fluctuations near the neutral point for the diamond shape roughness are the same as the amplitude of the acoustic disturbances. They are three times smaller for the square shape roughness.

  5. Random rough surface photofabrication

    NASA Astrophysics Data System (ADS)

    Brissonneau, Vincent; Escoubas, Ludovic; Flory, François; Berginc, Gérard

    2011-10-01

    Random rough surfaces are of primary interest for their optical properties: reducing reflection at the interface or obtaining specific scattering diagram for example. Thus controlling surface statistics during the fabrication process paves the way to original and specific behaviors of reflected optical waves. We detail an experimental method allowing the fabrication of random rough surfaces showing tuned statistical properties. A two-step photoresist exposure process was developed. In order to initiate photoresist polymerization, an energy threshold needs to be reached by light exposure. This energy is brought by a uniform exposure equipment comprising UV-LEDs. This pre-exposure is studied by varying parameters such as optical power and exposure time. The second step consists in an exposure based on the Gray method.1 The speckle pattern of an enlarged scattered laser beam is used to insolate the photoresist. A specific photofabrication bench using an argon ion laser was implemented. Parameters such as exposure time and distances between optical components are discussed. Then, we describe how we modify the speckle-based exposure bench to include a spatial light modulator (SLM). The SLM used is a micromirror matrix known as Digital Micromirror Device (DMD) which allows spatial modulation by displaying binary images. Thus, the spatial beam shape can be tuned and so the speckle pattern on the photoresist is modified. As the photoresist photofabricated surface is correlated to the speckle pattern used to insolate, the roughness parameters can be adjusted.

  6. Measurement and Correlation of Ice Accretion Roughness

    NASA Technical Reports Server (NTRS)

    Anderson, David N.; Hentschel, Daniel B.; Ruff, Gary A.

    2003-01-01

    Measurements were taken of the roughness characteristics of ice accreted on NACA 0012 airfoils in the NASA Glenn Icing Research Tunnel (IRT). Tests were conducted with size scaled, using models with chords of 26.7, 53.3, and 80.0 cm, and with liquid-water content scaled, both according to previously-tested scaling methods. The width of the smooth zone which forms on either side of the leading edge of the airfoil and the diameter of the roughness elements are presented in non-dimensional form as functions of the accumulation parameter. The smooth-zone width was found to decrease with increasing accumulation parameter. The roughness-element diameter increased with accumulation parameter until a plateau was reached. This maximum diameter was about 0.06 times twice the model leading-edge radius. Neither smooth-zone width nor element diameter were affected by a change in freezing fraction from 0.2 to 0.4. Both roughness characteristics appeared to scale with model size and with liquid-water content.

  7. Investigation of wall-bounded turbulence over sparsely distributed roughness

    NASA Astrophysics Data System (ADS)

    Placidi, Marco; Ganapathisubramani, Bharath

    2011-11-01

    The effects of sparsely distributed roughness elements on the structure of a turbulent boundary layer are examined by performing a series of Particle Image Velocimetry (PIV) experiments in a wind tunnel. From the literature, the best way to characterise a rough wall, especially one where the density of roughness elements is sparse, is unclear. In this study, rough surfaces consisting of sparsely and uniformly distributed LEGO® blocks are used. Five different patterns are adopted in order to examine the effects of frontal solidity (λf, frontal area of the roughness elements per unit wall-parallel area), plan solidity (λp, plan area of roughness elements per unit wall-parallel area) and the geometry of the roughness element (square and cylindrical elements), on the turbulence structure. The Karman number, Reτ , has been matched, at the value of approximately 2300, in order to compare across the different cases. In the talk, we will present detailed analysis of mean and rms velocity profiles, Reynolds stresses and quadrant decomposition.

  8. Estimating aerodynamic resistance of rough surfaces from angular reflectance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model wh...

  9. Computational Analysis for Roughness-Based Transition Control

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; Edwards, Jack R., Jr.

    2009-01-01

    Suitably placed discrete roughness elements are known to delay or hasten the onset of transition, depending on requirements. In this paper, 2D eigenvalue analysis is used to study the effects of surface roughness in the context of transition delay over subsonic and supersonic swept wing configurations, as well as boundarylayer tripping on the forebody of a hypersonic air breathing vehicle.

  10. Characteristics of surface roughness associated with leading edge ice accretion

    NASA Technical Reports Server (NTRS)

    Shin, Jaiwon

    1994-01-01

    Detailed size measurements of surface roughness associated with leading edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data was obtained from icing tests conducted in the Icing Research Tunnel (IRT) at NASA Lewis Research Center (LeRC) using a NACA 0012 airfoil. Measurements include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The height of roughness grows as the air temperature and the liquid water content increase, however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very initial stage of the ice accretion process.

  11. Surface roughness effects on equilibrium temperature.

    NASA Technical Reports Server (NTRS)

    Houchens, A. F.; Hering, R. G.

    1972-01-01

    An analysis is presented for evaluation of equilibrium temperature distribution on radiatively adiabatic, adjoint planes which are uniformly irradiated by a collimated solar flux. The analysis employs a semigrey spectral model. Radiation properties for surface emitted radiation are obtained from the expressions of electromagnetic theory for smooth surfaces. Rough surface properties for solar radiation are given by the Beckmann bidirectional reflectance model. Numerical solutions to the governing equations yield equilibrium temperature distributions for a range of the influencing parameters. Surface roughness has little influence on equilibrium temperature for materials with high values for solar absorptance. However, for low or intermediate values of solar absorptance, roughness effects on the spatial distribution of reflected solar radiation can significantly alter equilibrium temperature particularly at surface elements where radiant interaction is small.

  12. One-way implodable tag capsule with hemispherical beaded end cap for LWR fuel manufacturing

    DOEpatents

    Gross, K.; Lambert, J.

    1999-04-06

    A capsule is disclosed containing a tag gas in a zircaloy body portion having a hemispherical top curved toward the bottom of the body portion. The hemispherical top has a rupturable portion upon exposure to elevated gas pressure and the capsule is positioned within a fuel element in a nuclear reactor. 3 figs.

  13. The work budget of rough faults

    NASA Astrophysics Data System (ADS)

    Newman, Patrick J.; Ashley Griffith, W.

    2014-12-01

    Faults in nature have measurable roughness at many scales and are not planar as generally idealized. We utilize the boundary element method to model the geomechanical response of synthetic rough faults in an isotropic, linear elastic continuum to external tectonic loading in terms of the work budget. Faults are generated with known fractal roughness parameters, including the root mean square slope (β), a measure of roughness amplitude, and the Hurst exponent (H), a measure of geometric self-similarity. Energy within the fault models is partitioned into external work (Wext), internal elastic strain energy (Wint), gravitational work (Wgrav), frictional work (Wfric), and seismic energy (Wseis). Results confirm that Wext, or work done on the external model boundaries, is smallest for a perfectly planar fault, and steadily increases with increasing β. This pattern is also observed in Wint, the energy expended in deforming the host rock. The opposite is true for gravitational work, or work done against gravity in uplifting host rock, as well as with frictional work, or energy dissipated with frictional slip on the fault, and Wseis, or seismic energy released during slip events. Effects of variation in H are not as large as for β, but Wgrav, Wfric, and Wseis increase with increasing H, with Wint and Wext decreasing across the same range. Remarkably, however, for a narrow range of roughness amplitudes which are commonly observed along natural faults, the total work of the system remains approximately constant, while slightly larger than the total work of a planar fault. Faults evolve toward the most mechanically efficient configuration; therefore we argue that this range of roughness amplitudes may represent an energy barrier, preventing faults from removing asperities and evolving to smooth, planar discontinuities. A similar conclusion is drawn from simulations at relatively shallow depths, with results showing that shallower faults have larger energy barriers, and can

  14. Determination of Joint Roughness Coefficients Using Roughness Parameters

    NASA Astrophysics Data System (ADS)

    Jang, Hyun-Sic; Kang, Seong-Seung; Jang, Bo-An

    2014-11-01

    This study used precisely digitized standard roughness profiles to determine roughness parameters such as statistical and 2D discontinuity roughness, and fractal dimensions. Our methods were based on the relationship between the joint roughness coefficient (JRC) values and roughness parameters calculated using power law equations. Statistical and 2D roughness parameters, and fractal dimensions correlated well with JRC values, and had correlation coefficients of over 0.96. However, all of these relationships have a 4th profile (JRC 6-8) that deviates by more than ±5 % from the JRC values given in the standard roughness profiles. This indicates that this profile is statistically different than the others. We suggest that fractal dimensions should be measured within the entire range of the divider, instead of merely measuring values within a suitable range. Normalized intercept values also correlated with the JRC values, similarly to the fractal dimension values discussed above. The root mean square first derivative values, roughness profile indexes, 2D roughness parameter, and fractal dimension values decreased as the sampling interval increased. However, the structure function values increased very rapidly with increasing sampling intervals. This indicates that the roughness parameters are not independent of the sampling interval, and that the different relationships between the JRC values and these roughness parameters are dependent on the sampling interval.

  15. RELATIONSHIP BETWEEN THE AERODYNAMIC ROUGHNESS LENGTH AND THE ROUGHNESS DENSITY IN CASES OF LOW ROUGHNESS DENSITY

    EPA Science Inventory

    This paper presents measurements of roughness length performed in a wind tunnel for low roughness density. The experiments were performed with both compact and porous obstacles (clusters), in order to simulate the behavior of sparsely vegetated surfaces.

  16. Seasonal hemispherical SWIR airglow imaging

    NASA Astrophysics Data System (ADS)

    Allen, Jeffrey; Dayton, David C.; Gonglewski, John D.; Myers, Michael M.; Nolasco, Rudolph

    2011-09-01

    Airglow luminescence in the SWIR region due to upper atmospheric recombination of solar excited molecules is a well accepted phenomenon. While the intensity appears broadly uniform over the whole sky hemisphere, we are interested in variations in four areas: 1) fine periodic features known as gravity waves, 2) broad patterns across the whole sky, 3) temporal variations in the hemispheric mean irradiance over the course of the night, and 4) long term seasonal variations in the mean irradiance. An experiment is described and results presented covering a full year of high resolution hemispheric SWIR irradiance images. An automated gimbal views 45 hemispheric positions, using 30 second durations, and repeats approximately every half hour through out the night. The gimbal holds co-mounted and bore-sighted visible and SWIR cameras. Measuring airglow with respect to spatial, temporal, and seasonal variations will facilitate understanding its behavior and possible benefits, such as night vision and predicting upper atmosphere turbulence. The measurements were performed in a tropical marine location on the island of Kauai Hi.

  17. Characteristics of density currents over regular and irregular rough surfaces

    NASA Astrophysics Data System (ADS)

    Bhaganagar, K.

    2013-12-01

    Direct numerical simulation is used as a tool to understand the effect of surface roughness on the propagation of density currents. Simulations have been performed for lock-exchange flow with gate separating the dense and the lighter fluid. As the lock is released the dense fluid collapses with the lighter fluid on the top, resulting in formation of horizontally evolving density current. The talk will focus on the fundamental differences between the propagation of the density current over regular and irregular rough surfaces. The flow statistics and the flow structures are discussed. The results have revealed the spacing between the roughness elements is an important factor in classifying the density currents. The empirical relations of the front velocity and location for the dense and sparse roughness have been evaluated in terms of the roughness height, spacing between the elements and the initial amount of lock fluid. DNS results for a dense current flowing over a (a) smooth and (b) rough bottom with egg-carton roughness elements in a regular configuration. In these simulations the lock-exchange box is located in the middle of the channel and has two gates which allow two dense currents to be generated, one moving to the right and one to the left side of the channel. Note how the dense current interface presents smaller structures when over a rough bottom (right).

  18. Thermal Stability of Ice on Ceres with Rough Topography

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.; Aharonson, Oded

    2015-11-01

    The dwarf planet Ceres may have an ice-rich crust, and subsurface ice exposed by impacts or endogenic activity would be subject to sublimation. The “bright spots” recently discovered by the Dawn mission on the illuminated surface of Ceres have prompted speculation regarding their possible icy composition and the youthful age this might imply. Furthermore, sublimation of ice at the surface or in the interior of Ceres could explain water vapor observed on more than one occasion in the exosphere. We investigated the possible distribution and lifetimes of water ice and other volatiles on Ceres using detailed thermal models, including realistic thermophysical properties and surface roughness.Topographic shadowing creates polar cold traps where a small, but non-negligible fraction (~0.4%) of Ceres' surface is perennially below the ~110 K criterion for 1 Gyr of H2O ice stability. These areas are found above 60° latitude. Other molecules (CH3OH, NH3, SO2, CO2) may be cold-trapped in smaller abundances. A model for the transport, gravitational escape and photoionization of H2O molecules suggests net accumulation in the cold traps. At latitudes 0° - 30°, ice is stable under solar illumination only briefly (~10-100 yr), unless it has high albedo and thermal inertia, in which case lifetimes of > 104 yr are possible.Buried ice is stable within a meter for > 1 Gyr at latitudes higher than ~50°. An illuminated polar cap of water ice would be stable within a few degrees of the poles only if it maintained a high albedo (> 0.5) at present obliquity. If the obliquity exceeded 5° in the geologically recent past, then a putative polar cap would have been erased. Finally, a small hemispheric asymmetry exists due to the timing of Ceres' perihelion passage, which would lead to a detectable enhancement of ice in the northern hemisphere if the orbital elements vary slowly relative to the ice accumulation rate. Our model results are potentially testable during the Dawn science

  19. On the Mean Flow Behaviour in the Presence of Regional-Scale Surface Roughness Heterogeneity

    NASA Astrophysics Data System (ADS)

    Yang, Xiang I. A.

    2016-05-01

    A suite of large-eddy simulations of the neutral atmospheric boundary layer is conducted to study the mean flow response to the presence of surface roughness heterogeneity at regional scales (surface roughness heterogeneity on the scale of several boundary-layer heights). The roughness heterogeneity is imposed using alternating rough wall patches with numerically resolved rectangular roughness elements of different packing densities. The flow near the surface is found to adjust rapidly, reaching equilibrium conditions at distances on the order of a single inter-roughness element spacing. Despite the regional heterogeneity in surface roughness, it is often desirable to parametrize the entire rough wall using one single effective roughness height. To develop such a parametrization the model of Bou-Zeid et al. [Water Resources Research 40(2):1, 2004] is extended to incorporate the displacement height, d. Predictions from this parametrization are compared with the simulations, with reasonably good agreement.

  20. Optical roughness measurements on specially designed roughness standards

    NASA Astrophysics Data System (ADS)

    Danzl, R.; Helmli, F.; Rubert, P.; Prantl, M.

    2008-09-01

    The measurement of surface texture is one of the most common and important ways to judge the quality of a technical surface. In order to verify whether a metrology device is able to measure certain types of roughness accurately, various roughness standards with calibrated roughness values are available. While almost all roughness standards produced so far have been designed for tactile systems we demonstrate how the optical metrology device InfiniteFocus can be applied to special roughness standards that have been artificially roughened. Experiments are performed on standards with periodic structure and the results of the optical system are compared to the calibrated values obtained by tactile systems with different tip radius. Additionally the profile-based measurements are compared to area-based measurements conform to a recently developed ISO standard draft. Finally roughness measurements on real surfaces are presented.

  1. Hemispheric ultra-wideband antenna.

    SciTech Connect

    Brocato, Robert Wesley

    2006-04-01

    This report begins with a review of reduced size ultra-wideband (UWB) antennas and the peculiar problems that arise when building a UWB antenna. It then gives a description of a new type of UWB antenna that resolves these problems. This antenna, dubbed the hemispheric conical antenna, is similar to a conventional conical antenna in that it uses the same inverted conical conductor over a ground plane, but it also uses a hemispheric dielectric fill in between the conductive cone and the ground plane. The dielectric material creates a fundamentally new antenna which is reduced in size and much more rugged than a standard UWB conical antenna. The creation of finite-difference time domain (FDTD) software tools in spherical coordinates, as described in SAND2004-6577, enabled this technological advance.

  2. Focal hemisphere and visuoperceptual categorization.

    PubMed Central

    Bisiach, E; Capitani, E; Spinnler, H

    1975-01-01

    Visuoperceptual categorization was investigated in patients with unilateral brain damage by a task in which meaningless shapes had to be classified with reference to a number of prototype patterns. Right brain-damaged subjects with visual field defect turned out to have a narrower categorization span. As this outcome seems to be scarcely consonant with a lower level disorder of visual processing, a major competence of the right hemisphere is suggested for visuoperceptual categorization. PMID:1206421

  3. Roughness characteristics of natural channels

    USGS Publications Warehouse

    Barnes, Harry Hawthorne

    1967-01-01

    Color photographs and descriptive data are presented for 50 stream channels for which roughness coefficients have been determined. All hydraulic computations involving flow in open channels require an evaluation of the roughness characteristics of the channel. In the absence of a satisfactory quantitative procedure this evaluation remains chiefly an art. The ability to evaluate roughness coefficients must be developed through experience. One means of gaining this experience is by examining and becoming acquainted with the appearance of some typical channels whose roughness coefficients are known. The photographs and data contained in this report represent a wide range of channel conditions. Familiarity with the appearance, geometry, and roughness characteristics of these channels will improve the engineer's ability to select roughness coefficients for other channels .

  4. Classifying Southern Hemisphere extratropical cyclones

    NASA Astrophysics Data System (ADS)

    Catto, Jennifer

    2015-04-01

    There is a wide variety of flavours of extratropical cyclones in the Southern Hemisphere, with differing structures and lifecycles. Previous studies have classified these manually using upper level flow features or satellite data. In order to be able to evaluate climate models and understand how extratropical cyclones might change in the future, we need to be able to use an automated method to classify cyclones. Extratropical cyclones have been identified in the Southern Hemisphere from the ERA-Interim reanalysis dataset with a commonly used identification and tracking algorithm that employs 850hPa relative vorticity. A clustering method applied to large-scale fields from ERA-Interim at the time of cyclone genesis (when the cyclone is first identified), has been used to objectively classify these cyclones in the Southern Hemisphere. This simple method is able to separate the cyclones into classes with quite different development mechanisms and lifecycle characteristics. Some of the classes seem to coincide with previous manual classifications on shorter timescales, showing their utility for climate model evaluation and climate change studies.

  5. Awake right hemisphere brain surgery.

    PubMed

    Hulou, M Maher; Cote, David J; Olubiyi, Olutayo I; Smith, Timothy R; Chiocca, E Antonio; Johnson, Mark D

    2015-12-01

    We report the indications and outcomes of awake right hemispheric brain surgery, as well as a rare patient with crossed aphasia. Awake craniotomies are often performed to protect eloquent cortex. We reviewed the medical records for 35 of 96 patients, in detail, who had awake right hemisphere brain operations. Intraoperative cortical mapping of motor and/or language function was performed in 29 of the 35 patients. A preoperative speech impairment and left hand dominance were the main indicators for awake right-sided craniotomies in patients with right hemisphere lesions. Four patients with lesion proximity to eloquent areas underwent awake craniotomies without cortical mapping. In addition, one patient had a broncho-pulmonary fistula, and another had a recent major cardiac procedure that precluded awake surgery. An eloquent cortex representation was identified in 14 patients (48.3%). Postoperatively, seven of 17 patients (41.1%) who presented with weakness, experienced improvements in their motor functions, 11 of 16 (68.7%) with seizures became seizure-free, and seven of nine (77.7%) with moderate to severe headaches and one of two with a visual field deficit improved significantly. There were also improvements in speech and language functions in all patients who presented with speech difficulties. A right sided awake craniotomy is an excellent option for left handed patients, or those with right sided cortical lesions that result in preoperative speech impairments. When combined with intraoperative cortical mapping, both speech and motor function can be well preserved. PMID:26279501

  6. Hemispheric Assymeries in Auroral Precipitation

    NASA Astrophysics Data System (ADS)

    Mende, S. B.

    2014-12-01

    It is widely accepted that the space weather related electrodynamic forcing of the geospace environment acts through the high geomagnetic latitude regions. At high latitudes inter-hemispheric asymmetries are largely due to the differences in solar illumination, the direction of the solar wind and interplanetary magnetic field components and to a lesser extent, due to differences between the two hemispheric internal fields. So far most research regarding interhemispheric differences concentrated on learning about the basic magnetosphere-ionosphere coupling mechanisms. It has been well established that sunlit conditions affect the energy flux of auroral precipitation resulting from the reduction in the mean energy of the auroral electrons in the sunlit summer hemisphere. This can be explained by the partial shorting out of the particle accelerating fields by the sunlight induced conductivity. It has also been found that sunlit conditions reduce the particle fluxes and therefore the associated field aligned currents. Unless the precipitation-induced conductivities overwhelm the sunlit component of conductivity, this would imply that the magnetospheric current generator responds to the ionospheric load in a highly non-linear manner. Interhemispheric currents may also play an important role that has not been fully explored. Interhemispheric asymmetries in substorm morphology have been explored critically because conjugacy implies that substorms have a common source at equatorial latitudes. In some cases the lack of conjugacy of substorms could be explained by considering the magnitude and direction of the IMF.

  7. Right Hemisphere Dominance in Visual Statistical Learning

    ERIC Educational Resources Information Center

    Roser, Matthew E.; Fiser, Jozsef; Aslin, Richard N.; Gazzaniga, Michael S.

    2011-01-01

    Several studies report a right hemisphere advantage for visuospatial integration and a left hemisphere advantage for inferring conceptual knowledge from patterns of covariation. The present study examined hemispheric asymmetry in the implicit learning of new visual feature combinations. A split-brain patient and normal control participants viewed…

  8. Brain Hemispheric Functions and the Native American.

    ERIC Educational Resources Information Center

    Ross, Allen Chuck

    1982-01-01

    Uses brain research conducted by Dr. Roger Sperry to show that traditional Native Americans are more dominant in right hemisphere thinking, setting them apart from a modern left hemisphere-oriented society (especially emphasized in schools). Describes some characteristics of Native American thinking that illustrate a right hemisphere orientation…

  9. Hemispheric Laterality in Music and Math

    ERIC Educational Resources Information Center

    Szirony, Gary Michael; Burgin, John S.; Pearson, L. Carolyn

    2008-01-01

    Hemispheric laterality may be a useful concept in teaching, learning, training, and in understanding more about human development. To address this issue, a measure of hemispheric laterality was compared to musical and mathematical ability. The Human Information Processing Survey (HIPS) instrument, designed to measure hemispheric laterality, was…

  10. Solvation forces between rough surfaces

    SciTech Connect

    Frink, L.J.; van Swol, F.

    1998-04-01

    We investigate the role of surface roughness on solvation forces and solvation free energies. Roughness is introduced by dividing a surface into an array of square tiles that are then randomly displaced in the direction perpendicular to the wall. The integrated wall strength of these tiled surfaces is independent of the surface roughness and hence this class of rough walls is ideally suited for isolating roughness effects. We use grand canonical Monte Carlo simulations of a Lennard-Jones fluid confined in a slit pore with rough walls to generate the solvation interactions as a function of roughness, tile size, and surface area. The simulation data are compared to a simple superposition approximation of smooth wall solvation interactions (obtained from simulation or density functional theory), based on a distribution of wall separations. We find that this approximation provides a surprisingly accurate route to the solvation interaction of rough surfaces. In general, increased roughness leads to a reduction of oscillations in the solvation forces and surface free energies. However, nonmonotonic behavior of the oscillation amplitude with roughness can be observed for finite surfaces. The washing out of the oscillations found for large surface roughness produces a solvation force that exhibits a broad repulsive peak with separation. The broad repulsion is a consequence of the resistance to squeezing out fluid from the smallest gaps between two opposing rough surfaces. It is as much a reflection of packing effects as are the solvation oscillations for perfectly smooth pores. In addition, we present results for patterned and undulating surfaces produced by an analogous modification of the one-body external field for smooth walls. Finally, we discuss the implications of our results for a number of experimental systems including self-assembled monolayers, microporous materials, protein solutions, and DNA crystals. {copyright} {ital 1998 American Institute of Physics.}

  11. Roughness Measurement of Dental Materials

    NASA Astrophysics Data System (ADS)

    Shulev, Assen; Roussev, Ilia; Karpuzov, Simeon; Stoilov, Georgi; Ignatova, Detelina; See, Constantin von; Mitov, Gergo

    2016-06-01

    This paper presents a roughness measurement of zirconia ceramics, widely used for dental applications. Surface roughness variations caused by the most commonly used dental instruments for intraoral grinding and polishing are estimated. The applied technique is simple and utilizes the speckle properties of the scattered laser light. It could be easily implemented even in dental clinic environment. The main criteria for roughness estimation is the average speckle size, which varies with the roughness of zirconia. The algorithm used for the speckle size estimation is based on the normalized autocorrelation approach.

  12. Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

    NASA Technical Reports Server (NTRS)

    Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

    1987-01-01

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  13. Investigation of wall-bounded turbulence over regularly distributed roughness

    NASA Astrophysics Data System (ADS)

    Placidi, Marco; Ganapathisubramani, Bharathram

    2012-11-01

    The effects of regularly distributed roughness elements on the structure of a turbulent boundary layer are examined by performing a series of Planar (high resolution l+ ~ 30) and Stereoscopic Particle Image Velocimetry (PIV) experiments in a wind tunnel. An adequate description of how to best characterise a rough wall, especially one where the density of roughness elements is sparse, is yet to be developed. In this study, rough surfaces consisting of regularly and uniformly distributed LEGO® blocks are used. Twelve different patterns are adopted in order to systematically examine the effects of frontal solidity (λf, frontal area of the roughness elements per unit wall-parallel area) and plan solidity (λp, plan area of roughness elements per unit wall-parallel area), on the turbulence structure. The Karman number, Reτ , is approximately 4000 across the different cases. Spanwise 3D vector fields at two different wall-normal locations (top of the canopy and within the log-region) are also compared to examine the spanwise homogeneity of the flow across different surfaces. In the talk, a detailed analysis of mean and rms velocity profiles, Reynolds stresses, and quadrant decomposition for the different patterns will be presented.

  14. How surface roughness affects chemical transfer from soil to surface runoff?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil surface roughness affects transport processes, e.g., runoff generation, infiltration, sediment detachment, etc., occurring on the surface. Nevertheless, how soil roughness affects chemical transport is less known. In this study, we partitioned roughness elements into mounds which diverge water ...

  15. Detailed Cloud Patterns in Martian Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Cold and cloudy mornings; cool, hazy afternoons. High winds aloft and weather fronts moving slowly to the east. It is winter in the Martian northern hemisphere. One of the many reasons to study Mars is that, at times, its weather is very 'Earth-like.' At this time of the Martian year, clouds are abundant, especially in the morning and especially in the high northern latitudes. Clouds and fogs are also observed in low-lying areas farther to the south, in some lowlands they are as far south as the equator.

    The above color composite images, obtained by Mars Global Surveyor's camera on June 4, 1998, illustrate this Martian 'weather report.' Most of the thick, white clouds seen here occur north of latitude 35oN (roughly equivalent to Albuquerque NM, Memphis TN, and Charlotte, NC). Fog (seen as bright orange because it is lighter than the ground but some of the ground is still visible) occupies the lowest portions of the Kasei Valles outflow channel around 30oN and at 25oN.

    Several different types of cloud features are seen. The repetitious, wash-board pattern of parallel lines are 'gravity wave clouds'. These commonly form, in the lee--downwind side-- of topographic features such as mountain ranges (on Earth) or crater rims (on Mars), under very specific atmospheric conditions (low temperatures, high humidity, and high wind speeds). In this area, the wave clouds are lower in the atmosphere than some of the other clouds. These other clouds show attributes reflecting more the regional weather pattern, occasionally showing the characteristic 'slash' shape (southwest to northeast) of a weather front. These clouds probably contain mostly crystals of water ice but, depending on the temperature at high altitude (and more likely closer to the pole), some could also contain frozen carbon dioxide ('dry ice').

    MOC images 34501 (the red wide angle image) and 34502 (the blue wide angle image) were obtained on Mars Global Surveyor's 345th orbit about the planet

  16. Electric analysis of a conducting hemisphere

    NASA Astrophysics Data System (ADS)

    Yang, Mimi X.; Yang, Fuqian

    2016-05-01

    Using Legendre polynomials, the boundary value problem of a charged, conducting hemisphere in an infinite space was reduced to the solution of an infinite system of linear, algebraic equations. Analytical solutions of electric charge and electric stress on the surface of the hemisphere were obtained. The numerical analysis revealed non-uniform distributions of the electric charge and electric stress over the surface of the hemisphere with local singularities at the edge of the hemisphere. Both the electric charge and electric stress distributions were expressed in terms of the power function with respect to the distance to the nearest hemisphere edge. The power index for the flat surface is larger than that corresponding to the spherical surface. Numerical result of the capacitance of the conducting hemisphere is the same as the result reported in the literature. There is no net force acting on the hemisphere.

  17. Effect of surface roughness pattern on transient mixed elastohydrodynamic lubrication

    NASA Astrophysics Data System (ADS)

    Torabi, Amir; Akbarzadeh, Saleh; Salimpour, Mohammad Reza; Taei, Morteza

    2016-03-01

    Besides the surface roughness of two contacting surfaces, the surface roughness pattern i.e. longitudinal, transverse and isotropic significantly influences the tribological performance of the mechanical element. Their impression is more pronounced under the mixed elasto-hydrodynamic lubrication condition. The cam and flat follower mechanism is a typical sample in which adverse tribological conditions, including direct boundary interactions occurs. In this paper, the effect of surface roughness pattern on the film thickness and friction coefficient in a cam follower mechanism is investigated. Asperity interaction and friction coefficient analysis is conducted based on a novel elasto-plastic model. The lubrication model is qualitatively compared with the experimental results obtained from the pin on disk experiments for various surface roughness orientations. The results of transient lubrication analysis for a cam and follower lubrication problem are presented. It is shown that the longitudinal surface roughness pattern has a more desirable tribological performance than transverse surface pattern.

  18. Generalizing roughness: experiments with flow-oriented roughness

    NASA Astrophysics Data System (ADS)

    Trevisani, Sebastiano

    2015-04-01

    Surface texture analysis applied to High Resolution Digital Terrain Models (HRDTMs) improves the capability to characterize fine-scale morphology and permits the derivation of useful morphometric indexes. An important indicator to be taken into account in surface texture analysis is surface roughness, which can have a discriminant role in the detection of different geomorphic processes and factors. The evaluation of surface roughness is generally performed considering it as an isotropic surface parameter (e.g., Cavalli, 2008; Grohmann, 2011). However, surface texture has often an anisotropic character, which means that surface roughness could change according to the considered direction. In some applications, for example involving surface flow processes, the anisotropy of roughness should be taken into account (e.g., Trevisani, 2012; Smith, 2014). Accordingly, we test the application of a flow-oriented directional measure of roughness, computed considering surface gravity-driven flow. For the calculation of flow-oriented roughness we use both classical variogram-based roughness (e.g., Herzfeld,1996; Atkinson, 2000) as well as an ad-hoc developed robust modification of variogram (i.e. MAD, Trevisani, 2014). The presented approach, based on a D8 algorithm, shows the potential impact of considering directionality in the calculation of roughness indexes. The use of flow-oriented roughness could improve the definition of effective proxies of impedance to flow. Preliminary results on the integration of directional roughness operators with morphometric-based models, are promising and can be extended to more complex approaches. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. Cavalli, M. & Marchi, L. 2008, "Characterization of the surface morphology of an alpine alluvial fan using airborne LiDAR", Natural Hazards and Earth System Science, vol. 8, no. 2, pp. 323-333. Grohmann, C

  19. Instability of a Supersonic Boundary-Layer with Localized Roughness

    NASA Technical Reports Server (NTRS)

    Marxen, Olaf; Iaccarino, Gianluca; Shaqfeh, Eric S. G.

    2010-01-01

    A localized 3-D roughness causes boundary-layer separation and (weak) shocks. Most importantly, streamwise vortices occur which induce streamwise (low U, high T) streaks. Immersed boundary method (volume force) suitable to represent roughness element in DNS. Favorable comparison between bi-global stability theory and DNS for a "y-mode" Outlook: Understand the flow physics (investigate "z-modes" in DNS through sinuous spanwise forcing, study origin of the beat in DNS).

  20. Remote Control Southern Hemisphere SSA Observatory

    NASA Astrophysics Data System (ADS)

    Ritchie, I.; Pearson, M.; Sang, J.

    2013-09-01

    EOS Space Systems (EOSSS) is a research and development company which has developed custom observatories, camera and telescope systems for space surveillance since 1996, as well as creating several evolutions of systems control software for control of observatories and laser tracking systems. Our primary reserach observatory is the Space Reserach Centre (SRC) at Mount Stromlo Asutralia. The current SRC control systems are designed such that remote control can be offered for real time data collection, noise filtering and flexible session management. Several imaging fields of view are available simultaneously for tracking orbiting objects, with real time imaging to Mag 18. Orbiting objects can have the centroids post processed into orbital determination/ orbital projection (OD/OP) elements. With or without laser tracking of orbiting objects, they can be tracked in terminator conditions and their OD/OP data created, then enhanced by proprietary methods involving ballistic coefficient estimation and OD convergence pinning, using a priori radar elements. Sensors in development include a thermal imager for satellite thermal signature detection. Extending laser tracking range by use of adaptive optics beam control is also in development now. This Southern Hemisphere observatory is in a unique position to facilitate the study of space debris, either stand-alone or as part of a network such as Falcon. Current national and international contracts will enhance the remote control capabilities further, creating a resource ready to go for a wide variety of SSA missions.

  1. Boundary-layer receptivity of sound with roughness

    NASA Technical Reports Server (NTRS)

    Saric, William S.; Hoos, Jon A.; Radeztsky, Ronald H.

    1991-01-01

    An experimental study of receptivity was carried out using an acoustical disturbance in the freestream. The receptivity was enhanced by using a uniform two-dimensional roughness strip (tape). The roughness strip generated the local adjustment in the flow needed to couple the long-wavelength sound wave with the short-wavelength T-S wave. The method proved to be highly sensitive, with slight changes in the forcing frequency or in the height of the 2D roughness element having a strong effect on the amplitude of the observed T-S wave.

  2. Ice Roughness in Short Duration SLD Icing Events

    NASA Technical Reports Server (NTRS)

    McClain, Stephen T.; Reed, Dana; Vargas, Mario; Kreeger, Richard E.; Tsao, Jen-Ching

    2014-01-01

    Ice accretion codes depend on models of roughness parameters to account for the enhanced heat transfer during the ice accretion process. While mitigating supercooled large droplet (SLD or Appendix O) icing is a significant concern for manufacturers seeking future vehicle certification due to the pending regulation, historical ice roughness studies have been performed using Appendix C icing clouds which exhibit mean volumetric diameters (MVD) much smaller than SLD clouds. Further, the historical studies of roughness focused on extracting parametric representations of ice roughness using multiple images of roughness elements. In this study, the ice roughness developed on a 21-in. NACA 0012 at 0deg angle of attack exposed to short duration SLD icing events was measured in the Icing Research Tunnel at the NASA Glenn Research Center. The MVD's used in the study ranged from 100 micrometer to 200 micrometers, in a 67 m/s flow, with liquid water contents of either 0.6 gm/cubic meters or 0.75 gm/cubic meters. The ice surfaces were measured using a Romer Absolute Arm laser scanning system. The roughness associated with each surface point cloud was measured using the two-dimensional self-organizing map approach developed by McClain and Kreeger (2013) resulting in statistical descriptions of the ice roughness.

  3. Does surface roughness amplify wetting?

    SciTech Connect

    Malijevský, Alexandr

    2014-11-14

    Any solid surface is intrinsically rough on the microscopic scale. In this paper, we study the effect of this roughness on the wetting properties of hydrophilic substrates. Macroscopic arguments, such as those leading to the well-known Wenzel's law, predict that surface roughness should amplify the wetting properties of such adsorbents. We use a fundamental measure density functional theory to demonstrate the opposite effect from roughness for microscopically corrugated surfaces, i.e., wetting is hindered. Based on three independent analyses we show that microscopic surface corrugation increases the wetting temperature or even makes the surface hydrophobic. Since for macroscopically corrugated surfaces the solid texture does indeed amplify wetting there must exist a crossover between two length-scale regimes that are distinguished by opposite response on surface roughening. This demonstrates how deceptive can be efforts to extend the thermodynamical laws beyond their macroscopic territory.

  4. Measuring Roughnesses Of Optical Surfaces

    NASA Technical Reports Server (NTRS)

    Coulter, Daniel R.; Al-Jumaily, Gahnim A.; Raouf, Nasrat A.; Anderson, Mark S.

    1994-01-01

    Report discusses use of scanning tunneling microscopy and atomic force microscopy to measure roughnesses of optical surfaces. These techniques offer greater spatial resolution than other techniques. Report notes scanning tunneling microscopes and atomic force microscopes resolve down to 1 nm.

  5. Electroformation of uranium hemispherical shells

    SciTech Connect

    Marshall, S.L.; Redey, L.; Vandegrift, G.F.; Vissers, D.R.

    1989-11-01

    This effort was directed at developing an electrochemical process for forming uniform and dendrite-free deposits of uranium from molten salts. This process is to be used for the electroformation of free-standing hemispherical shells of uranium for nuclear applications. Electrodeposition of uranium onto a substrate was accomplished with a fused chloride mixture containing 42 wt% UCl{sub 3} and a fused chloride-fluoride mixture containing 4 wt % UF{sub 4}. Under pulsed potential control at 504{degree}C, the chloride-fluoride mixture yielded the widest range of plating conditions for which dendrites could be avoided. Bipolar current pulse plating with both electrolytes gave good results, and successful application of this technique to a large tubular cathode has been demonstrated. 24 refs., 10 figs.

  6. Hemispheric Asymmetries: The Comparative View

    PubMed Central

    Ocklenburg, Sebastian; Güntürkün, Onur

    2012-01-01

    Hemispheric asymmetries play an important role in almost all cognitive functions. For more than a century, they were considered to be uniquely human but now an increasing number of findings in all vertebrate classes make it likely that we inherited our asymmetries from common ancestors. Thus, studying animal models could provide unique insights into the mechanisms of lateralization. We outline three such avenues of research by providing an overview of experiments on left–right differences in the connectivity of sensory systems, the embryonic determinants of brain asymmetries, and the genetics of lateralization. All these lines of studies could provide a wealth of insights into our own asymmetries that should and will be exploited by future analyses. PMID:22303295

  7. Audiotactile interactions in roughness perception.

    PubMed

    Guest, Steve; Catmur, Caroline; Lloyd, Donna; Spence, Charles

    2002-09-01

    The sounds produced when we touch textured surfaces frequently provide information regarding the structure of those surfaces. It has recently been demonstrated that the perception of the texture of the hands can be modified simply by manipulating the frequency content of such touch-related sounds. We investigated whether similar auditory manipulations change people's perception of the roughness of abrasive surfaces (experiment 1). Participants were required to make speeded, forced-choice discrimination responses regarding the roughness of a series of abrasive samples which they touched briefly. Analysis of discrimination errors verified that tactile roughness perception was modulated by the frequency content of the auditory feedback. Specifically, attenuating high frequencies led to a bias towards an increased perception of tactile smoothness. In experiment 2, we replicated the rubbing-hands manipulation of previous experimenters while participants rated either the perceived roughness or wetness of their hands. The wetness scale data replicated the results in the literature, while the roughness scale data replicated the result from experiment 1. A final experiment showed that delaying the auditory feedback from the hand-rubbing reduced the magnitude of this parchment-skin illusion. These experiments demonstrate the dramatic effect that auditory frequency manipulations can have on the perceived tactile roughness and moistness of surfaces, and are consistent with the proposal that different auditory perceptual dimensions may have varying salience for different surfaces. PMID:12195518

  8. Roughness reduction on aspheric surfaces

    NASA Astrophysics Data System (ADS)

    Kiontke, S.; Kokot, Sebastian

    2015-02-01

    For a lot of applications like spectrometer and high power laser roughness as an important parameter has been discussed over and over again. Especially for high power systems the surface quality is crucial for determining the damage threshold and therefore the field of application. Above that, it has often been difficult to compare roughness measurements because of different measurement methods and the usage of filters and surface fits. Measurement results differ significantly depending on filters and especially on the measured surface size. Insights will be given how values behave depending on the quality of surface and the size of measured area. Many applications require a high quality of roughness in order to reduce scattering. Some of them in order to prevent from damage like high power laser applications. Others like spectrometers seek to increase the signal-to-noise ratio. Most of them have already been built with spherical surfaces. With higher demands on efficiency and more sophisticated versions aspherical surfaces need to be employed. Therefore, the high requirement in roughness known from spherical surfaces is also needed on aspherical surfaces. For one thing, the constant change of curvature of an aspherical surface accounts for the superior performance, for another thing, it prevents from using classical polishing technics, which guarantied this low roughness. New methods need to be qualified. In addition, also results of a new manufacturing process will be shown allowing low roughness on aspheric even with remarkable departure from the best fit sphere.

  9. Determining Surface Roughness in Urban Areas Using Lidar Data

    NASA Technical Reports Server (NTRS)

    Holland, Donald

    2009-01-01

    An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland security models. The developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant. In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a point, whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

  10. Shape of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter (MOLA)

    NASA Astrophysics Data System (ADS)

    Zuber, Maria T.; Smith, David E.; Phillips, Roger J.; Solomon, Sean C.; Banerdt, W. Bruce; Neumann, Gregory A.; Aharonson, Oded

    1998-12-01

    Eighteen profiles of ˜N-S-trending topography from the Mars Orbiter Laser Altimeter (MOLA) are used to analyze the shape of Mars' northern hemisphere. MOLA observations show smaller northern hemisphere flattening than previously thought. The hypsometric distribution is narrowly peaked with >20% of the surface lying within 200 m of the mean elevation. Low elevation correlates with low surface roughness, but the elevation and roughness may reflect different mechanisms. Bouguer gravity indicates less variability in crustal thickness and/or lateral density structure than previously expected. The 3.1-km offset between centers of mass and figure along the polar axis results in a pole-to-equator slope at all longitudes. The N-S slope distribution also shows a subtle longitude-dependent variation that may represent the antipodal effect of the formation of Tharsis.

  11. The left hemisphere and the selection of learned actions.

    PubMed

    Rushworth, M F; Nixon, P D; Wade, D T; Renowden, S; Passingham, R E

    1998-01-01

    The left hemisphere's dominance for movement is well known. The basis of its dominance is less clear. We have tested 16 left hemisphere (LH) patients, 17 right hemisphere (RH) patients and 12 neurologically normal controls on a battery of five tasks. The tasks were based on animal lesion and recording studies, and human imaging and magnetic stimulation studies that identified two distributed systems that are important for the selection of motor responses and object-oriented responses. The LH patients were impaired on three response selection tasks: learning to select between joystick movement responses instructed by visual cues; learning to select between analogous object-oriented responses instructed by visual cues; learning to select movements in a sequence. Although we replicated the finding that LH damage impairs sequencing, some of the impaired tasks had no sequencing element. We therefore argue that the LH deficits are best explained as an impairment of response selection. This was confirmed by showing that LH subjects were unimpaired on a more demanding task-object discrimination learning-which imposed a greater memory load but had no response selection element. Moreover, the LH deficits could not be attributed to disorganization of movement kinematics. The lesions of the impaired LH group were widespread but always included the distributed systems known to be important for response selection-the dorsolateral frontal and parietal cortices, striatum, thalamus and white matter fascicles. PMID:9533383

  12. Homotopic Language Reorganization in the Right Hemisphere after Early Left Hemisphere Injury

    ERIC Educational Resources Information Center

    Tivarus, Madalina E.; Starling, Sarah J.; Newport, Elissa L.; Langfitt, John T.

    2012-01-01

    To determine the areas involved in reorganization of language to the right hemisphere after early left hemisphere injury, we compared fMRI activation patterns during four production and comprehension tasks in post-surgical epilepsy patients with either left (LH) or right hemisphere (RH) speech dominance (determined by Wada testing) and healthy…

  13. On the Effects of Surface Roughness on Boundary Layer Transition

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan M.; Li, Fei; Chang, Chau-Lyan; Edwards, Jack

    2009-01-01

    Surface roughness can influence laminar-turbulent transition in many different ways. This paper outlines selected analyses performed at the NASA Langley Research Center, ranging in speed from subsonic to hypersonic Mach numbers and highlighting the beneficial as well as adverse roles of the surface roughness in technological applications. The first theme pertains to boundary-layer tripping on the forebody of a hypersonic airbreathing configuration via a spanwise periodic array of trip elements, with the goal of understanding the physical mechanisms underlying roughness-induced transition in a high-speed boundary layer. The effect of an isolated, finite amplitude roughness element on a supersonic boundary layer is considered next. The other set of flow configurations examined herein corresponds to roughness based laminar flow control in subsonic and supersonic swept wing boundary layers. A common theme to all of the above configurations is the need to apply higher fidelity, physics based techniques to develop reliable predictions of roughness effects on laminar-turbulent transition.

  14. Fantasy and the Brain's Right Hemisphere.

    ERIC Educational Resources Information Center

    Shuman, R. Baird

    While the left hemisphere of the brain is responsible for logical and verbal activity, the right brain is the center of much of human feeling and emotion. Its vision is holistic rather than segmented or compartmentalized. Although schools today are geared almost exclusively to training the brain's left hemisphere, fantasy literature can provide…

  15. The Cost of Action Miscues: Hemispheric Asymmetries

    ERIC Educational Resources Information Center

    Shenal, Brian V.; Hinze, Stephan; Heilman, Kenneth M.

    2012-01-01

    Adaptive behaviors require preparation and when necessary inhibition or alteration of actions. The right hemisphere has been posited to be dominant for preparatory motor activation. This experiment was designed to learn if there are hemispheric asymmetries in the control of altered plans of actions. Cues, both valid and invalid, which indicate the…

  16. Surface forces: Surface roughness in theory and experiment

    SciTech Connect

    Parsons, Drew F. Walsh, Rick B.; Craig, Vincent S. J.

    2014-04-28

    A method of incorporating surface roughness into theoretical calculations of surface forces is presented. The model contains two chief elements. First, surface roughness is represented as a probability distribution of surface heights around an average surface height. A roughness-averaged force is determined by taking an average of the classic flat-surface force, weighing all possible separation distances against the probability distributions of surface heights. Second the model adds a repulsive contact force due to the elastic contact of asperities. We derive a simple analytic expression for the contact force. The general impact of roughness is to amplify the long range behaviour of noncontact (DLVO) forces. The impact of the elastic contact force is to provide a repulsive wall which is felt at a separation between surfaces that scales with the root-mean-square (RMS) roughness of the surfaces. The model therefore provides a means of distinguishing between “true zero,” where the separation between the average centres of each surface is zero, and “apparent zero,” defined by the onset of the repulsive contact wall. A normal distribution may be assumed for the surface probability distribution, characterised by the RMS roughness measured by atomic force microscopy (AFM). Alternatively the probability distribution may be defined by the histogram of heights measured by AFM. Both methods of treating surface roughness are compared against the classic smooth surface calculation and experimental AFM measurement.

  17. A combined experimental and numerical investigation of roughness induced supersonic boundary layer transition

    NASA Astrophysics Data System (ADS)

    Zhao, Yunfei; Liu, Wei; Xu, Dan; Gang, Dundian; Yi, Shihe

    2016-01-01

    The effect of surface roughness on boundary layer transition is of great importance to hypersonic vehicles. In this paper, both experimental and numerical methods are used to investigate the laminar-turbulent transition of a Mach 3 flat-plate boundary layer induced by isolated roughness element. Good agreements are achieved between experimental data and high-order numerical simulations. It is observed that, with increasing height of roughness, the transition tends to move forward. Two different types of transition mechanisms are found according to the height of the roughness elements. For the smallest roughness height of h=1 mm, the shear layer instability in the wake region appears to be the leading mechanism for transition to turbulence. For two larger roughness elements of h=2 mm and h=4 mm, strong unsteadiness is developed from the upstream separation zone and transition is immediately accomplished, which indicates that the absolute instability in upstream separation zone dominates the transition.

  18. Roughness effects in uncompensated antiferromagnets

    SciTech Connect

    Charilaou, M.; Hellman, F.

    2015-02-28

    Monte Carlo simulations show that roughness in uncompensated antiferromagnets decreases not just the surface magnetization but also the net magnetization and particularly strongly affects the temperature dependence. In films with step-type roughness, each step creates a new compensation front that decreases the global net magnetization. The saturation magnetization decreases non-monotonically with increasing roughness and does not scale with the surface area. Roughness in the form of surface vacancies changes the temperature-dependence of the magnetization; when only one surface has vacancies, the saturation magnetization will decrease linearly with surface occupancy, whereas when both surfaces have vacancies, the magnetization is negative and exhibits a compensation point at finite temperature, which can be tuned by controlling the occupancy. Roughness also affects the spin-texture of the surfaces due to long-range dipolar interactions and generates non-collinear spin configurations that could be used in devices to produce locally modified exchange bias. These results explain the strongly reduced magnetization found in magnetometry experiments and furthers our understanding of the temperature-dependence of exchange bias.

  19. UV Observations of Hemispheric Asymmetry

    NASA Astrophysics Data System (ADS)

    Schaefer, R. K.; Paxton, L. J.; Wolven, B. C.; Zhang, Y.; Romeo, G.

    2015-12-01

    Asymmetry in the auroral patterns can be an important diagnostic for understanding the dynamics of solar wind interaction with the magnetosphere-ionosphere-thermosphere system (e.g., Newel and Meng, 1998; Fillingrim et al., 2005). Molecular nitrogen emission in the UV Lyman-Birge-Hopfield bands can be used to determine energy flux and electron mean energy (Sotirelis, et al, 2013) and thereby Hall and Pederson integrated conductances (Gjerloev, et al., 2014). UV imagery provided by the 4 SSUSI instruments on the Defense Meteorological Satellite Program (DMSP) F16-F19 spacecraft provide two dimensional maps of this emission at different local times. Often there are near simultaneous observations of both poles by some combination of the satellites. (see figure 1) The SSUSI auroral data products are well suited to this study, as they have the following features.: - dayglow has been subtracted on dayside aurora - electron energy flux and mean energy are pre-calculated - individual arcs have been identified through image processing. In order to intercompare data from multiple satellites, we must first ensure that the instrument calibrations are consistent. In this work we show that the instruments are consistently calibrated, and that results generated from the SSUSI data products can be trusted. Several examples of storm time asymmetries captured by the SSUSI instruments will be discussed. Fillingim, M. O., G. K. Parks, H. U. Frey, T. J. Immel, and S. B. Mende (2005), Hemispheric asymmetry of the afternoon electron aurora, Geophys. Res. Lett., 32, L03113, doi:10.1029/2004GL021635. Gjerloev, J., Schaefer, R., Paxton, L, and Zhang, Y. (2014), A comprehensive empirical model of the ionospheric conductivity derived from SSUSI/GUVI, SuperMAG and SuperDARN data, SM51G-4339, Fall 2014 AGU meeting, San Francisco. Newell, P. T., and C.-I. Meng (1988), Hemispherical asymmetry in cusp precipitation near solstices, J. Geophys. Res., 93(A4), 2643-2648, doi:10.1029/JA093iA04p02643

  20. Modeling of surface roughness effects on glaze ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian; Potapczuk, M.

    1989-01-01

    The cause and effects of roughness on accreting glaze ice surfaces were studied with microvideo observations. Distinct zones of surface water behavior were observed, including a smooth wet zone in the stagnation region with a uniform water film, a rough zone where surface tension effects caused coalescence of surface water into stationary beads, and a zone where roughness elements grow into horn shapes. In addition, a zone where surface water ran back as rivulets and a dry zone where rime feathers formed were observed. The locations and behaviors of these zones are discussed. A simple multizone modification to the glaze ice accretion model is proposed to include spatial variability in surface roughness. Two test cases using the multizone model showed significant improvements for the prediction of glaze ice shapes.

  1. Reciprocal organization of the cerebral hemispheres

    PubMed Central

    McGilchrist, Iain

    2010-01-01

    The cerebral hemispheres are anatomically and neurophysiologically asymmetrical. The evolutionary basis for these differences remains uncertain. There are, however, highly consistent differences between the hemispheres, evident in reptiles, birds, and mammals, as well as in humans, in the nature of the attention each applies to the environment. This permits the simultaneous application of precisely focused, but narrow, attention, needed for grasping food or prey, with broad, open, and uncommitted attention, needed to watch out for predators and to interpret the intentions of conspecifics. These different modes of attention can account for a very wide range of repeated observations relating to hemisphere specialization, and suggest that hemisphere differences lie not in discrete functional domains as such, but distinct modes of functioning within any one domain. These modes of attention are mutually incompatible, and their application depends on inhibitory transmission in the corpus callosum. There is also an asymmetry of interaction between the hemispheres at the phenomenological level. PMID:21319495

  2. Mola's First Observations of the Southern Hemisphere Topography of Mars

    NASA Technical Reports Server (NTRS)

    Smith, David E.; Zuber, M. T.

    1999-01-01

    Towards the end of February 1999, the Mars Global Surveyor (MGS) spacecraft is expected to enter a near-circular polar orbit around Mars at an altitude of about 400 km. At this time the Mars Orbiter Laser Altimeter (MOLA) will begin near-continuous operation and acquire topography of the full planet. The initial areas of study will be concentrated in the southern hemisphere with particular interest in the polar region near the targeted landing site of the Mars Polar Lander. In addition to topography, MOLA matched filter pulse width data will be used to assess foot-print-scale surface roughness in the region. Such observations will also be applied in future studies for assessment of the Mars '01 landing site in the latitude range 15 degrees south to 5 degrees north.

  3. Temporal variation of hemispheric solar rotation

    NASA Astrophysics Data System (ADS)

    Xie, Jing-Lan; Shi, Xiang-Jun; Xu, Jing-Chen

    2012-02-01

    The daily sunspot numbers of the whole disk as well as the northern and southern hemispheres from 1945 January 1 to 2010 December 31 are used to investigate the temporal variation of rotational cycle length through the continuous wavelet transformation analysis method. Auto-correlation function analysis of daily hemispheric sunspot numbers shows that the southern hemisphere rotates faster than the northern hemisphere. The results obtained from the wavelet transformation analysis are that no direct relationship exists between the variation trend of the rotational cycle length and the solar activity in the two hemispheres and that the rotational cycle length of both hemispheres has no significant period appearing at 11yr, but has a significant period of about 7.6 yr. Analysis concerning the solar cycle dependence of the rotational cycle length shows that acceleration seems to appear before the minimum time of solar activity in the whole disk and the northern hemisphere, respectively. Furthermore, the cross-correlation study indicates that the rotational cycle length of the two hemispheres has different phases, and that the rotational cycle length of the whole disk as well as the northern and southern hemispheres, also has phase shifts with corresponding solar activity. In addition, the temporal variation of the north-south (N-S) asymmetry of the rotational cycle length is also studied. This displays the same variation trend as the N-S asymmetry of solar activity in a solar cycle, as well as in the considered time interval, and has two significant periods of 7.7 and 17.5 yr. Moreover, the rotational cycle length and the N-S asymmetry of solar activity are highly correlated. It is inferred that the northern hemisphere should rotate faster at the beginning of solar cycle 24.

  4. Recent Studies of Runway Roughness

    NASA Technical Reports Server (NTRS)

    Morris, Garland; Hall, Albert W.

    1965-01-01

    Recent studies of NASA research related to aircraft operating problems on rough runways are presented. Some of these investigations were conducted cooperatively with the airport operators, with the Federal Aviation Agency, and with the U.S. Air Force. The studies show that criteria based on power spectral levels of runway-profile data are not sufficient to define acceptable levels of runway roughness from the piloting viewpoint. Because of the large variation in response characteristics between various types of aircraft, a runway may be acceptable for some aircraft and unacceptable for others. A criterion for roughness, therefore, should be expressed in terms of aircraft response - preferably, cockpit acceleration. A criterion suggested is that the maximum vertical acceleration in the cockpit should not exceed +/- 0.4 g for sections of the runway where precise aircraft control is required.

  5. Wetting phenomena on rough substrates

    NASA Astrophysics Data System (ADS)

    Li, Hao; Kardar, Mehran

    1990-10-01

    We consider wetting phenomena in the vicinity of rough substrates. The quenched random geometry of the substrate is assumed to be a self-affine fractal with a roughness exponent of ζS. Asymptotic critical properties on approaching complete and critical wetting transitions are studied by combining the replica method with scaling and renormalization-group arguments. We find new critical behavior, controlled by a zero-temperature fixed point, when ζS exceeds the thermal roughness exponent of the emerging wetting layer. The possibility of an effective dimensional reduction due to randomness is considered. In two dimensions a number of exact results are obtained by using a many-body transfer-matrix technique.

  6. Ontogenesis of hemispheric specialization: apraxia associated with congenital left hemisphere lesions.

    PubMed

    Nass, R

    1983-12-01

    In adults apraxia is more common after left-hemisphere damage. The engram for control of skilled motor movements has therefore been considered a specialized function of the left hemisphere. The ontogenesis of motor control was studied in a group of prepubertal children with congenital unilateral hemispheric lesions. Left-hemisphere lesions caused greater impairment of rapid independent finger movements, suggesting that specialization for motor control is innately programmed in the left hemisphere. No subject evidenced apraxia to verbal command, but adult-like performance is not yet expected at the age the group was tested, and effects of side of lesion could appear later. PMID:6664762

  7. On the effect of surface roughness on the vapor flow under Leidenfrost-levitated droplets

    SciTech Connect

    Prat, M.; Schmitz, P.; Poulikakos, D.

    1995-09-01

    In this paper a theoretical investigation is reported on the effect of surface roughness on the phenomenon of Leidenfrost-levitation of droplets above a hot surface. The problem is solved first approximately using a macroscopic approach in which the roughness is replaced by a semi-empirical slip conditions of the Beavers-Joseph type. Next, a microscopic model which determines the vapor flow in the close vicinity of the rough surface is solved numerically. Three basic periodic roughnesses are examined: triangular, rectangular, and semi-cylindrical. The effect of the relative size of the droplet and the roughness elements on the vapor flow is investigated in the course of the study.

  8. The Asgard Hemisphere of Callisto

    NASA Technical Reports Server (NTRS)

    1997-01-01

    False color view of a portion of the leading hemisphere of Jupiter's moon Callisto as seen through the infrared filters of the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. North is to the top of the picture and the sun illuminates the surface from the east. More recent impacts have excavated bright, relatively clean ice from beneath Callisto's battered surface. Callisto's dark mottled appearance may be due to contamination by non-ice components contributed by impactors or concentrated in a residue as ice is removed. This color composite image is centered on longitude 139 West and encompasses an area about 1000 miles (1600 kilometers) by 2470 miles (4000 kilometers). The images were obtained on November 3rd, 1996.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  9. HEMISPHERIC CENTER FOR ENVIRONMENTAL TECHNOLOGY

    SciTech Connect

    M.A. Ebadian

    1999-10-31

    The Deactivation and Decommissioning (D&D) Technology Assessment Program (TAP) was developed to provide detailed, comparable data for environmental technologies and to disseminate this data to D&D professionals in a manner that will facilitate the review and selection of technologies to perform decontamination and decommissioning. The objectives for this project include the following: Determine technology needs through review of the Site Technology Coordination Group (STCG) information and other applicable websites and needs databases; Perform a detailed review of industries that perform similar activities as those required in D&D operations to identify additional technologies; Define the technology assessment program for characterization and waste management problem sets; Define the data management program for characterization, dismantlement, and waste management problem sets; Evaluate baseline and innovative technologies under standard test conditions at Florida International University's Hemispheric Center for Environmental Technology (FIU-HCET) and other locations and collect data in the areas of performance, cost, health and safety, operations and maintenance, and primary and secondary waste generation; Continue to locate, verify, and incorporate technology performance data from other sources into the multimedia information system; and Develop the conceptual design for a dismantlement technology decision analysis tool for dismantlement technologies.

  10. Effect of surface roughness on characteristics of spherical shock waves

    NASA Technical Reports Server (NTRS)

    Huber, Paul W; Mcfarland, Donald R

    1955-01-01

    An investigation has been conducted on a small-scale test layout in which direct observation of the shock wave movement with time could be made in order to determine the effects of surface roughness on the characteristics of spherical shock waves. Data were obtained with 15-gram pentolite charges at four heights of burst, both for a smooth surface and for a surface completely covered with pyramid-shaped roughness elements. The observations resulted in determinations of shock peak overpressure and Mach stem height as a function of distance for each test. Comparison of the smooth-surface data with those obtained for the extremely rough condition showed a small net effort of roughness on the shock peak overpressures at the surface for all burst heights, the effect being to lower the overpressures. The effect of surface roughness on the Mach stem formation and growth was to delay the formation at the greatest charge height and to lower the height of the Mach stem for all heights.Comparison of the free-air shock peak overpressures with larger scale data showed good similarity of the overpressure-distance relationships. The data did not fit a geometrical similarity parameter for the path of the triple point at different heights of burst suggested by other investigators. A simple similarity parameter (relating the horizontal distance to the theoretical point of Mach formation) was found which showed only a small influence of burst height on the path of the triple point. While the data presented provide knowledge of the effect of many surface-roughness elements on the overall shock characteristics, the data do not provide insight into the details of the air-flow characteristics along the surface, nor the relative contribution of individual roughness elements to the results obtained.

  11. Hemispheric sunspot unit area: comparison with hemispheric sunspot number and sunspot area

    SciTech Connect

    Li, K. J.; Xiang, N. B.; Qu, Z. N.; Xie, J. L.

    2014-03-01

    The monthly mean northern and southern hemispheric sunspot numbers (SNs) and sunspot areas (SAs) in the time interval of 1945 January to 2012 December are utilized to construct the monthly northern and southern hemispheric sunspot unit areas (SUAs), which are defined as the ratio of hemispheric SA to SN. Hemispheric SUAs are usually found to rise at the beginning and to fall at the ending time of a solar cycle more rapidly, forming a more irregular cycle profile than hemispheric SNs and SAs, although it also presents Schwabe-cycle-like hemispheric SNs and SAs. Sunspot activity (SN, SA, and SUA) is found asynchronously and is asymmetrically distributed in the northern and southern hemispheres, and hemispheric SNs, SAs, and SUAs are not in phase in the two hemispheres. The similarity of hemispheric SNs and SAs is found to be much more obvious than that of hemispheric SUAs and SNs (or SAs), and also for their north-south asymmetry. A notable feature is found for the behavior of the SUA around the minimum time of cycle 24: the SUA rapidly decreases from the cycle maximum value to the cycle minimum value of sunspot cycles 19-24 within just 22 months.

  12. Large Craters in Callisto's Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    NASA's Galileo spacecraft provides a new view of this heavily cratered region in the southern hemisphere of the icy Jovian satellite Callisto. The region was not observed by NASA's Voyager spacecraft. Craters ranging in diameter from the 1.85 kilometer (1.13 mile) limit of resolution up to more than 70 kilometers (43 miles) can be observed in this image. Although all craters are generally round in outline, details in their structures vary with both size and relative age. Bright spots in the center of smaller craters (up to approximately 20 kilometers (12 miles)) are central peaks. Larger craters (up to the 51 kilometer (31 mile) wide crater in the east central part of the image) exhibit central pits or depressions. The largest crater, called Thrainn, has a diameter of 74 kilometers (45 miles) and is located in the southernmost corner of the image. This crater contains a broad central uplift, or dome, and has a highly eroded rim. In contrast, the 70 kilometer (43 mile) crater Audr, located along the northern margin of the image, is flat-bottomed, and has a less degraded and generally rounder rim. If erosional or degradational forces have been roughly constant with time on Callisto, scientists viewing this image can assume that Audr is relatively younger than Thrainn by noting the less degraded or fresher appearance of its rim. The differences in crater floor features between these two similarly sized craters could have been produced by differences in the impacting bodies that produced them, differences in the crustal materials in which the craters formed, or simply by a gradual evolution of crater floor shape with time.

    North is to the top of the image which was taken by the Galileo spacecraft's solid state imaging (CCD) system during its eighth orbit around Jupiter on May 6th, 1997. The center of the image is located at 34 degrees south latitude, 84 degrees west longitude, and was taken when the spacecraft was approximately 48,430 kilometers (29,542 miles) from

  13. Hemispheric View of Venus Centered at the North Pole

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The hemispheric view of Venus, as revealed by more than a decade of radar investigations culminating in the 1990-1994 Magellan mission, is centered on the North Pole. The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of this image is about 3 km. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from the Earth-based Arecibo radar in a region centered roughly on 0 degree latitude and longitude, and with a neutral tone elsewhere (primarily near the south pole). The composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions. An orthographic projection was used, simulating a distant view of one hemisphere of the planet. The Magellan mission was managed for NASA by Jet Propulsion Laboratory (JPL), Pasadena, CA. Data processed by JPL, the Massachusetts Institute of Technology, Cambridge, MA, and the U.S. Geological Survey, Flagstaff, AZ.

  14. Hemispheric View of Venus Centered at 270 Degrees East Longitude

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The hemispheric view of Venus, as revealed by more than a decade of radar investigations culminating in the 1990-1994 Magellan mission, is centered at 270 degrees east longitude. The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of this image is about 3 km. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from the Earth-based Arecibo radar in a region centered roughly on 0 degree latitude and longitude, and with a neutral tone elsewhere (primarily near the south pole). The composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions. An orthographic projection was used, simulating a distant view of one hemisphere of the planet. The Magellan mission was managed for NASA by Jet Propulsion Laboratory (JPL), Pasadena, CA. Data processed by JPL, the Massachusetts Institute of Technology, Cambridge, MA, and the U.S. Geological Survey, Flagstaff, AZ.

  15. Hemispheric View of Venus Centered at 90 Degrees East Longitude

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The hemispheric view of Venus, as revealed by more than a decade of radar investigations culminating in the 1990-1994 Magellan mission, is centered at 90 degrees east longitude. The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of this image is about 3 km. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from the Earth-based Arecibo radar in a region centered roughly on 0 degree latitude and longitude, and with a neutral tone elsewhere (primarily near the south pole). The composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions. An orthographic projection was used, simulating a distant view of one hemisphere of the planet. The Magellan mission was managed for NASA by Jet Propulsion Laboratory (JPL), Pasadena, CA. Data processed by JPL, the Massachusetts Institute of Technology, Cambridge, MA, and the U.S. Geological Survey, Flagstaff, AZ.

  16. Hemispheric View of Venus Centered at 180 Degrees East Longitude

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The hemispheric view of Venus, as revealed by more than a decade of radar investigations culminating in the 1990-1994 Magellan mission, is centered at 180 degrees east longitude. The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of this image is about 3 km. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from the Earth-based Arecibo radar in a region centered roughly on 0 degree latitude and longitude, and with a neutral tone elsewhere (primarily near the south pole). The composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions. An orthographic projection was used, simulating a distant view of one hemisphere of the planet. The Magellan mission was managed for NASA by Jet Propulsion Laboratory (JPL), Pasadena, CA. Data processed by JPL, the Massachusetts Institute of Technology, Cambridge, MA, and the U.S. Geological Survey, Flagstaff, AZ.

  17. Hemispheric View of Venus Centered at 0 Degrees East Longitude

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The hemispheric view of Venus, as revealed by more than a decade of radar investigations culminating in the 1990-1994 Magellan mission, is centered at 0 degrees east longitude. The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of this image is about 3 km. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from the Earth-based Arecibo radar in a region centered roughly on 0 degree latitude and longitude, and with a neutral tone elsewhere (primarily near the south pole). The composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions. An orthographic projection was used, simulating a distant view of one hemisphere of the planet. The Magellan mission was managed for NASA by Jet Propulsion Laboratory (JPL), Pasadena, CA. Data processed by JPL, the Massachusetts Institute of Technology, Cambridge, MA, and the U.S. Geological Survey, Flagstaff, AZ.

  18. Shock/shock interference on a transpiration cooled hemispherical model

    NASA Technical Reports Server (NTRS)

    Nowak, Robert J.; Wieting, Allan R.; Holden, Michael S.

    1990-01-01

    Experimental results are presented which show the effectiveness of transpiration cooling in reducing the peak heat flux caused by an impinging shock on a bow shock of a hemispherical model. The 12-inch diameter hemispherical transpiration model with helium coolant was tested in the Calspan 48-inch Hypersonic Shock Tunnel at nominal Mach 12.1 and freestream unit Reynolds number of 0.33 x 10 to the 6th/ft. An incident shock wave, generated by a blunt flat-plate shock generator inclined at 10 deg to the freestream, intersected the bow shock of the model to produce shock/shock interference. The stagnation heat flux without coolant or shock/shock interference was about 1.6 times a smooth surface laminar prediction due to effective roughness of the coolant ejection slots. A coolant mass flux 31 percent of the freestream mass flux reduced the stagnation heat flux to zero without shock/shock interference. However, for the same coolant mass flux and with shock/shock interference the peak heat flux was only reduced 8.3 percent, even though the total integrated heat load was reduced.

  19. Northern hemisphere dust storms on Mars

    NASA Technical Reports Server (NTRS)

    James, P. B.

    1993-01-01

    Dust storms in the northern hemisphere of Mars appear to be less common than the more familiar southern hemisphere storms, and essentially, no activity north of about 30 latittude has been documented. The data are, however, subject to an observational bias because Mars is near aphelion during oppositions, which occur during the most likely seasons for dust activity in the north. The amount of dust activity in the northern hemisphere is clearly very relevant to the role of atmospheric transport in the dust cycle. The classic global storms that occur during spring in the southern hemisphere are observed to transport dust from sources in the southern hemisphere to sinks or temporary depositories in the north. The question of whether atmospheric transport can close the dust cycle, i.e., return the dust to the southern hemisphere sources on some timescale, is clearly relevant to the solution of the puzzle of how the dust storm cycle is modulated, i.e., why storms occur in some years but not in others. There are data that suggest that the spring/early summer season in the northern hemisphere of Mars during the year following the major 1977 storms observed by Viking was very dusty. A number of observations of the vicinity of the receding north polar cap showed clear evidence of substantial dust activity in the sub-Arctic region.

  20. Nanowetting of rough superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Lamb, R. N.; Cookson, D. J.

    2007-12-01

    Small angle x-ray scattering has been used to investigate the in situ immersive wetting of ultrarough surfaces which exhibit superhydrophobicity with extreme water contact angle (θA=169°). Reduced scattering contrast observed from rough surfaces when partially or totally wetted reveals significant physical differences between superhydrophobic surfaces not otherwise apparent from conventional contact angle measurements.

  1. Plant Communities of Rough Rock.

    ERIC Educational Resources Information Center

    Jacobs, Linda

    A unit of study on plants grown in the Navajo community of Rough Rock, Arizona, is presented in sketches providing the common Navajo name for the plant, a literal English translation, the English name of the plant, and the Latin name. A brief description of each plant includes where the plant grows, how the Navajos use the plant, and the color and…

  2. Estimating surface roughness using stereophotogrammetry

    NASA Astrophysics Data System (ADS)

    David, V.; Krasa, J.

    2009-04-01

    At the Department of Drainage, Irrigation and Landscape Engineering (CTU Prague) we use several mathematical models for soil erosion, sediment transport and surface runoff assessment. Here we continuously struggle for successful models parameterizations. One of the typical coefficients usually taken from literature instead of measurements is surface roughness, eg. Manning roughness (Maidment, 1993). Roughness is a key to surface runoff velocity and surface runoff depth estimation but often it is very roughly estimated. Within the COST 22 Action research we focused on estimating actual surface roughness using stereophotogrammetry. Our aim was to set up a simple low cost system useful for roughness measurements in nature conditions - mainly on agricultural fields. Our system consists of Canon EOS 400 digital camera with angle viewfinder, two robust tripods and a horizontal bar with sliding 3D tripod head. We tested different camera heights and focal distances as well as various parallaxes to obtain reasonable results. Finally we shot the surfaces from 1600 millimeters with 24 and 35 mm lens and parallaxes close to 100 mm. For 3D scene development we use Geomatica 10 GIS and its OrthoEngine module. Testing the proper system and many variables of the 3D scene modelling was an important part of the first year of the project. For these purposes we first prepared a calibrated and known 3D surface consisting of 70 by 70 cm grid and several geometrical objects of different sizes and shapes. Preparing the correct lighting conditions, finding the resolving power of the system and solving the problems with low contrast areas of measured surfaces was a time consuming but interesting task. After the system calibration we started with the actual terrain measurements. Our setup, system testing and preliminary results of the roughness computations are presented on the poster. Acknowledgement This research was acomplished within national COST project OC189 „Flood risk and its

  3. Compact Autonomous Hemispheric Vision System

    NASA Technical Reports Server (NTRS)

    Pingree, Paula J.; Cunningham, Thomas J.; Werne, Thomas A.; Eastwood, Michael L.; Walch, Marc J.; Staehle, Robert L.

    2012-01-01

    Solar System Exploration camera implementations to date have involved either single cameras with wide field-of-view (FOV) and consequently coarser spatial resolution, cameras on a movable mast, or single cameras necessitating rotation of the host vehicle to afford visibility outside a relatively narrow FOV. These cameras require detailed commanding from the ground or separate onboard computers to operate properly, and are incapable of making decisions based on image content that control pointing and downlink strategy. For color, a filter wheel having selectable positions was often added, which added moving parts, size, mass, power, and reduced reliability. A system was developed based on a general-purpose miniature visible-light camera using advanced CMOS (complementary metal oxide semiconductor) imager technology. The baseline camera has a 92 FOV and six cameras are arranged in an angled-up carousel fashion, with FOV overlaps such that the system has a 360 FOV (azimuth). A seventh camera, also with a FOV of 92 , is installed normal to the plane of the other 6 cameras giving the system a > 90 FOV in elevation and completing the hemispheric vision system. A central unit houses the common electronics box (CEB) controlling the system (power conversion, data processing, memory, and control software). Stereo is achieved by adding a second system on a baseline, and color is achieved by stacking two more systems (for a total of three, each system equipped with its own filter.) Two connectors on the bottom of the CEB provide a connection to a carrier (rover, spacecraft, balloon, etc.) for telemetry, commands, and power. This system has no moving parts. The system's onboard software (SW) supports autonomous operations such as pattern recognition and tracking.

  4. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  5. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  6. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  7. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  8. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Rough diamond. 592.310 Section 592... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply...

  9. Amplitude modulation of streamwise velocity fluctuations in the roughness sublayer: evidence from large-eddy simulations

    NASA Astrophysics Data System (ADS)

    Awasthi, Ankit; Anderson, William

    2015-11-01

    Large-scale motions in the logarithmic region of turbulent boundary layers amplitude modulate the viscous sublayer (Marusic et al., 2010: Science; Mathis et al., 2009: J. Fluid Mech.). This finding has promising implications for large-eddy simulation of wall-bounded turbulence at high Reynolds number (wherein the turbulence integral length exhibits linear proportionality with wall-normal elevation). Existing amplitude modulation studies have addressed smooth wall flows, though high Reynolds number rough wall flows are ubiquitous. Under such conditions, roughness-scale vortices ablate the viscous sublayer and result in the roughness sublayer. The roughness sublayer depth scales with aggregate element height, k, and is typically 2k ~ 3k. Above this, Townsend's Hypothesis dictates that the logarithmic layer is unaffected by the roughness sublayer. Here, we present large-eddy simulation results of turbulent channel flow over rough walls. We follow the decoupling procedure of Mathis et al., 2009: J. Fluid Mech., and present evidence that outer-layer dynamics amplitude modulate the roughness sublayer. Below the roughness element height, we report enormous sensitivity to element proximity. Above the elements, but within the roughness sublayer, topography dependence rapidly declines. This work was supported by the Air Force Office of Scientific Research, Turbulence and Transition Program (PM: Dr. R. Ponnoppan) under Grant # FA9550-14-1-0101. Computational resources were provided by the Texas Adv. Comp. Center at the Univ. of Texas.

  10. Parametric Flow Visualization of Dynamic Roughness Effects

    NASA Astrophysics Data System (ADS)

    Jakkali, Vinay

    The ever growing need in the aircraft industry to enhance the performance of a flight vehicle has led to active areas of research which focus on the control of the local boundary layer by both passive and active methods. An effective flow control mechanism can improve the performance of a flight vehicle in various ways, one of which is eliminating boundary layer separation. To be effective the mechanism not only needs to control the boundary layer as desired, but also use less energy than the resulting energy savings. In this study, the effectiveness of an active flow control technique known as dynamic roughness (DR) has been explored to eliminate the laminar separation bubble near the leading edge and also to eliminate the stall on a NACA 0012 airfoil wing. As opposed to static roughness, dynamic roughness utilizes small time-dependent deforming elements or humps with displacement amplitudes that are on the order of the local boundary layer height to energize the local boundary layer. DR is primarily characterized by the maximum amplitude and operating frequency. A flow visualization study was conducted on a 2D NACA 0012 airfoil model at different angles of attack, and also varying the Reynolds number and DR actuation frequency with fixed maximum DR amplitude. The experimental results from this study suggests that DR is an effective method of reattaching a totally separated boundary layer. In addition, this study discusses some of the fundamental physics behind the working of DR and proposes some non-dimensional terms that may help to explain the driving force behind the mechanism.

  11. Hemispherical total emissivity of Hastelloy N with different surface conditions

    NASA Astrophysics Data System (ADS)

    Gordon, Andrew J.; Walton, Kyle L.; Ghosh, Tushar K.; Loyalka, Sudarshan K.; Viswanath, Dabir S.; Tompson, Robert V.

    2012-07-01

    The hemispherical total emissivity of Hastelloy N (a candidate structural material for Next Generation Nuclear Plants (NGNPs), particularly for the molten fluoride cooled reactors) was measured using an experimental set-up that was constructed in accordance with the standard ASTM C835-06. The material surface conditions included: (i) 'as received' (original) sample from the supplier; (ii) samples with increased surface roughness through sand blasting; (iii) oxidized surface, and (iv) samples coated with graphite powder. The emissivity of the as received samples varied from around 0.22 to 0.28 in the temperature range of 473 K to 1498 K. The emissivity increased when the roughness of the surface increased compared to an as received sample. When Hastelloy N was oxidized in air at 1153 K or coated with graphite powder, its emissivity increased substantially. The sample sand blasted with 60 grit beads and sprinkled with graphite powder showed an increase of emissivity from 0.2 to 0.60 at 473 K and from 0.25 to 0.67 at 1473 K. The oxidized surface showed a similar behavior: an increase in emissivity compared to an unoxidized sample. This increase in emissivity has strong favorable safety implications in terms of decay heat removal in post-accident environments. The data were compared with another Hastelloy family member, Hastelloy X.

  12. Modeling of surface roughness effects on glaze ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian M.; Potapczuk, Mark

    1990-01-01

    A series of experimental investigations focused on studying the cause and effect of roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1 to 4 inch diameter cylinders in three icing wind tunnels (the Data Products of New England six inch test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film; a rough zone where surface tension effects caused coalescence of surface water into stationary beads; a horn zone where roughness elements grow into horn shapes; a runback zone where surface water ran back as rivulets; and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary layer transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multi-zone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness.

  13. Simulation of Turbulent Boundary Layer Flow with Large Roughness

    NASA Astrophysics Data System (ADS)

    Johnson, Erika; Subramanian, Chelakara

    2006-11-01

    Several studies indicate that in situations where surface roughness is very strong, the friction velocity scaling for the mean and turbulent velocities are not satisfactory. Subramanian et al showed a dramatic effect of a strong irregular roughened surface on the turbulent properties. The log-law relation in the overlap region was distorted. A significant pressure gradient normal to the surface was observed with a concomitant increase in normal turbulent stress, v^'2 . The pressure gradient velocity scale, uP, was suggested as a better alternative for capturing the effects of this roughness induced pressure gradient. Here, we performed a numerical simulation of a roughened boundary layer to gain more insight on the correlation between the wall normal pressure gradient and normal turbulent stress, v^'2 and further validate this new pressure gradient velocity scale, uP for different types of roughness. A two-dimensional flat plate computational model with strong regular (k-type) roughness, was constructed in GAMBIT and a CFD analysis performed using FLUENT, version 6.2. The roughness elements cause the pressure near the wall to increase suddenly at the first element and then decrease gradually similar to experiments. The variation of this normal pressure gradient is well correlated with the normal turbulent stress v^'2 variation. Application of the uP as scaling parameter for other non-equilibrium flows such as with suction and blowing is also investigated.

  14. Structure of rough-wall turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Bandyopadhyay, Promode R.; Watson, Ralph D.

    1988-01-01

    Recent experiments have shown that, in rough-wall turbulent boundary layers, drag varies systematically with the spanwise aspect ratio lambda(z) (span/height) of roughness elements. In this paper, the effect of lambda(z) on turbulence structure has been examined. Based on lambda(z), the roughness in a transversely grooved surface with lambda(z) much greater than 1 is the opposite extreme of model plant canopies with lambda(z) much less than 1, studied in wind tunnels, whereas sandgrain is an intermediate type. Second-, third-, and fourth-order turbulence moments have been measured in turbulent boundary layers over transversely grooved and smooth surfaces and compared with available turbulence structure measurements over other types of surfaces. The near-wall turbulence structure is found to vary with lambda(z). The instantaneous motions involved in the flux of shear stress near the wall in smooth and transversely grooved surfaces are opposite in sign to those in three-dimensional roughness. The former is explained in terms of hairpin vortices alone, while the latter group is modeled to have an additional vortex (the so-called necklace vortex which straddles a three-dimensional roughness element near its base).

  15. Electromagnetic scattering and depolarization across rough surfaces: Full wave analysis

    NASA Astrophysics Data System (ADS)

    Bahar, Ezekiel; Huang, Guorong; Lee, Bom Son

    1995-05-01

    Full wave solutions are derived for vertically and horizontally polarized waves diffusely scattered across an interface that is two-dimensionally rough separating two different propagating media. Since the normal to the rough surface is not restricted to the reference plane of incidence, the waves are depolarized upon scattering; and the single scattered radiation fields are expressed as integrals of a surface element transmission scattering matrix that also accounts for coupling between the vertically and horizontally polarized waves. The integrations are over the rough surface area as well as the complete two-dimensional wave spectra of the radiation fields. The full wave solutions satisfy the duality and reciprocity relationships in electromagnetic theory, and the surface element scattering matrix is invariant to coordinate transformations. It is shown that in the high-frequency limit the full wave solutions reduce to the physical optics solutions, while in the low-frequency limit (for small mean square heights and slopes) the full wave solutions reduce to Rice's (1951) small perturbation solutions. Thus, the full wave solution accounts for specular point scattering as well as diffuse, Bragg-type scattering in a unified, self-consistent manner. It is therefore not necessary to use hybrid, perturbation and physical optics approaches (based on two-scale models of composite surfaces with large and small roughness scales) to determine the like- and cross-polarized fields scattered across the rough surface.

  16. Hemispherical color differences on Pluto and Charon

    NASA Technical Reports Server (NTRS)

    Binzel, Richard P.

    1988-01-01

    Time-resolved multicolor photometric observations of Pluto-Charon mutual events have been used to derive individual colors for these two bodies and to investigate the degree of color differences between their synchronous facing and opposite hemispheres. Pluto is significantly redder than Charon, where direct measurements of the anti-Charon hemisphere of Pluto and the Pluto-facing hemisphere of Charon yield B-V magnitudes of 0.867 + or - 0.008 and 0.700 + or - 0.010, respectively. Both Pluto and Charon are found to have relatively uniform longitudinal color distributions with 1-sigma upper limits of 2 percent and 5 percent, respectively, for any large-scale hemispherical color asymmetries. Thus, a previous suspicion of a significant color asymmetry on Charon is not confirmed. Instead the data may be attributed to a direct detection of polar caps on Pluto.

  17. Huge Filament Rises From Sun's Northern Hemisphere

    NASA Video Gallery

    On August 1, 2010 following a C3-class solar flare from sunspot 1092, an enormous magnetic filament stretching across the sun's northern hemisphere erupted. This 304 angstrom video shows that filam...

  18. Recovering two languages with the right hemisphere.

    PubMed

    Marini, Andrea; Galetto, Valentina; Tatu, Karina; Duca, Sergio; Geminiani, Giuliano; Sacco, Katiuscia; Zettin, Marina

    2016-08-01

    Converging evidence suggests that the right hemisphere (RH) plays an important role in language recovery from aphasia after a left hemisphere (LH) lesion. In this longitudinal study we describe the neurological, cognitive, and linguistic profile of A.C., a bilingual who, after a severe traumatic brain injury, developed a form of fluent aphasia that affected his two languages (i.e., Romanian and Italian). The trauma-induced parenchymal atrophy led to an exceptional ventricular dilation that, gradually, affected the whole left hemisphere. A.C. is now recovering both languages relying only on his right hemisphere. An fMRI experiment employing a bilingual covert verb generation task documented the involvement of the right middle temporal gyrus in processes of lexical selection and access. This case supports the hypothesis that the RH plays a role in language recovery from aphasia when the LH has suffered massive lesions. PMID:27289209

  19. Southern Hemisphere Polygonal Patterned Ground

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On Earth, periglacial is a term that refers to regions and processes where cold climate contributes to the evolution of landforms and landscapes. Common in periglacial environments on Earth, such as the arctic of northern Canada,Siberia, and Alaska, is a phenomenon called patterned ground. The 'patterns' in patterned ground often take the form of large polygons, each bounded by either troughs or ridges made up of rock particles different in size from those seen in the interior of the polygon. On Earth, many polygons in periglacial environments are directly linked to water: they typically form from stresses induced by repeated freezing and thawing of water, contraction from stress induced by changing temperatures, and sorting of rocks brought to the surface along polygon boundaries by the freeze-thaw processes. Although not exclusively formed by freezing and thawing of water, that is often the dominant mechanism on Earth.

    Polygons similar to those found in Earth's arctic and antarctic regions are also found in the polar regions of Mars. Typically, they occur on crater floors, or on intercrater plains, between about 60o and 80o latitude. The polygons are best seen when bright frost or dark sand has been trapped in the troughs that form the polygon boundaries. Three examples of martian polygons seen by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) are shown here. Each is located in the southern hemisphere:(left) Polygon troughs highlighted by frost as the south polar cap retreats during spring. The circular features are the locations of buried craters that were originally formed by meteor impact. This image, E09-00029, is located at 75.1oS, 331.3oW, and was acquired on 1 October 2001.(center) Summertime view of polygons, highlighted by dark, windblown sand, on the floor of a crater at 71.2oS, 282.6oW. The image, E12-02319, was obtained on 21January 2002.(right) Polygon troughs highlighted by the retreating south polar frost cap during southern summer

  20. A Giant Storm in Saturn's Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Fischer, G.; Gurnett, D. A.; Zarka, P. M.; Dyudina, U. A.; Ingersoll, A. P.; Ewald, S. P.; Porco, C.; Wesley, A.; Go, C.; Delcroix, M.

    2011-12-01

    Beginning on December 5, 2010, an extraordinary thunderstorm developed as observed via the radio signatures of lightning using the Radio and Plasma Wave Science (RPWS) instrument and the appearance of a convective cloud in Cassini's Imaging Science System (ISS) images. These instruments as well as amateur astronomers across the globe have continued to track this storm to the present. The storm is extraordinary in that it is the first observed by Cassini in the northern hemisphere near 35 degrees planetocentric north latitude and is, by far, the largest storm observed by Cassini during its mission at Saturn and is comparable to the Great White Spot (GWS) storms observed approximately once per Saturn year. The development from the barely visible indications on December 5 to a storm of GWS status occurred over about 3 weeks. Expansion of the storm in latitude within a latitudinal gradient in the wind system of the planet resulted in an elongated eastward tail which entirely circled the planet by February 2011. The primary active cell lies in a relatively localized area around the main plume of high altitude clouds that overshoot the ammonia cloud layer due to strong vertical convection, although other, weaker cells occasionally develop within the tail. The lightning flash rate of this storm peaked at an order of magnitude higher than previously recorded storms with strokes occurring at the rate of 10 per second and the total power estimated for the storm is comparable to Saturn's total emitted power, making it a significant element of the planet's energy budget. That this storm occurred a year or so after northern vernal equinox suggests a seasonal change in the location of Saturn's thunderstorms. We will summarize observations of this extraordinary storm and update its progress as it is ongoing at the time of this writing.

  1. The estimation of surface roughness with the utilization of Mueller matrix

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Gu, Guohua; Zhou, Xiaojun; Xu, Fuyuan; Ren, Kan

    2016-05-01

    Roughness is an important parameter to describe the microtopography of target surface. In the field of roughness detection, constraints on traditional methods are significant. Meanwhile, polarization imaging technology is gradually mature in recent years. In this paper, a method of roughness estimation with Mueller matrix is presented. Battery of lenses with fixed orientation have been introduced to produce a facula on the measured surface. Polarized information of each pixel can be obtained with the lenses of known position. According to the polarized information and Lambertian model, Stocks vector, Mueller matrix, and reflected Mueller matrix of each pixel can be acquired. Therefore, the roughness information of target surface can be obtained according to the relationship between roughness information and elements of matrix. Experimental results show that with the proposed method, efficiency of roughness detection can be improved without precision deducing. It can lay a foundation for extending the application of roughness into the field of object identification.

  2. Polymer Transport Near Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Bloom, Moses; Whitmer, Jonathan; Luijten, Erik

    2011-03-01

    The rheology of dilute polymer solutions under confinement is important in biology, medicine, microfluidic device design, synthetic polymer processing, and even geologic porous media. However, the solution's specific interactions with the confining surface are poorly understood. This situation is exacerbated for composite nanoparticles, such as polymer/metallic hybrids. Using multi-particle collision dynamics, we find a rich array of transport regimes depending on small-scale surface roughness and the specific surface/solute interactions. These factors couple to hydrodynamic conditions, including flow strength and confinement geometry in unexpected ways. Our findings may be relevant to transport phenomena in certain rough-walled capillaries, such as the distribution of various nanoconjugates in vivo.

  3. Northern Hemisphere forcing of Southern Hemisphere climate during the last deglaciation.

    PubMed

    He, Feng; Shakun, Jeremy D; Clark, Peter U; Carlson, Anders E; Liu, Zhengyu; Otto-Bliesner, Bette L; Kutzbach, John E

    2013-02-01

    According to the Milankovitch theory, changes in summer insolation in the high-latitude Northern Hemisphere caused glacial cycles through their impact on ice-sheet mass balance. Statistical analyses of long climate records supported this theory, but they also posed a substantial challenge by showing that changes in Southern Hemisphere climate were in phase with or led those in the north. Although an orbitally forced Northern Hemisphere signal may have been transmitted to the Southern Hemisphere, insolation forcing can also directly influence local Southern Hemisphere climate, potentially intensified by sea-ice feedback, suggesting that the hemispheres may have responded independently to different aspects of orbital forcing. Signal processing of climate records cannot distinguish between these conditions, however, because the proposed insolation forcings share essentially identical variability. Here we use transient simulations with a coupled atmosphere-ocean general circulation model to identify the impacts of forcing from changes in orbits, atmospheric CO(2) concentration, ice sheets and the Atlantic meridional overturning circulation (AMOC) on hemispheric temperatures during the first half of the last deglaciation (22-14.3 kyr BP). Although based on a single model, our transient simulation with only orbital changes supports the Milankovitch theory in showing that the last deglaciation was initiated by rising insolation during spring and summer in the mid-latitude to high-latitude Northern Hemisphere and by terrestrial snow-albedo feedback. The simulation with all forcings best reproduces the timing and magnitude of surface temperature evolution in the Southern Hemisphere in deglacial proxy records. AMOC changes associated with an orbitally induced retreat of Northern Hemisphere ice sheets is the most plausible explanation for the early Southern Hemisphere deglacial warming and its lead over Northern Hemisphere temperature; the ensuing rise in atmospheric CO(2

  4. Surface roughness of anodized titanium coatings.

    SciTech Connect

    Dugger, Michael Thomas; Chinn, Douglas Alan

    2010-10-01

    Samples of grade five 6Al4V titanium alloy were coated with two commercial fluoropolymer anodizations (Tiodize and Canadize) and compared. Neither coating demonstrates significant outgassing. The coatings show very similar elemental analysis, except for the presence of lead in the Canadize coating, which may account for its lower surface friction in humid environments. Surface roughness has been compared by SEM, contact profilometry, optical profilometry, power spectral density and bidirectional scattering distribution function (BSDF). The Tiodize film is slightly smoother by all measurement methods, but the Canadize film shows slightly less scatter at all angles of incidence. Both films exhibited initial friction coefficients of 0.2 to 0.4, increasing to 0.4 to 0.8 after 1000 cycles of sliding due to wear of the coating and ball. The coatings are very similar and should behave identically in most applications.

  5. Meaningful surface roughness and quality tolerances

    NASA Astrophysics Data System (ADS)

    Aikens, David M.

    2010-08-01

    Most tolerances on optical elements can be derived or calculated from the application requirements using computeraided optical design programs. For surface quality and surface roughness, however, there are few guidelines or tools for calculating appropriate tolerances. Typically, we simply use a legacy specification (e.g. 60-40 and 3 A RMS) with little thought for either the cost of achieving the specification or the penalty for failing to achieve it. Often these legacy specifications are ambiguous, unnecessarily costly and in some cases completely meaningless. This paper provides some basic rules and equations for calculation of the real or perceived impact of these specifications, and some guidelines for the initiate (and for some of us veterans as well) as to how to compose a meaningful tolerance.

  6. Sensing roughness and polish direction

    NASA Astrophysics Data System (ADS)

    Jakobsen, M. L.; Olesen, A. S.; Larsen, H. E.; Stubager, J.; Hanson, S. G.; Pedersen, T. F.; Pedersen, H. C.

    2016-04-01

    As a part of the work carried out on a project supported by the Danish council for technology and innovation, we have investigated the option of smoothing standard CNC machined surfaces. In the process of constructing optical prototypes, involving custom-designed optics, the development cost and time consumption can become relatively large numbers in a research budget. Machining the optical surfaces directly is expensive and time consuming. Alternatively, a more standardized and cheaper machining method can be used, but then the object needs to be manually polished. During the polishing process the operator needs information about the RMS-value of the surface roughness and the current direction of the scratches introduces by the polishing process. The RMS-value indicates to the operator how far he is from the final finish, and the scratch orientation is often specified by the customer in order to avoid complications during the casting process. In this work we present a method for measuring the RMS-values of the surface roughness while simultaneously determining the polishing direction. We are mainly interested in the RMS-values in the range from 0 - 100 nm, which corresponds to the finish categories of A1, A2 and A3. Based on simple intensity measurements we estimates the RMS-value of the surface roughness, and by using a sectioned annual photo-detector to collect the scattered light we can determine the direction of polishing and distinguish light scattered from random structures and light scattered from scratches.

  7. Boundary Layer Receptivity due to Roughness and Freestream Sound for Supersonic Flows over Axisymmetric Cones

    NASA Technical Reports Server (NTRS)

    Balakumar, P.

    2008-01-01

    The receptivity of supersonic boundary layers due to the interaction of a two-dimensional acoustic wave with a three-dimensional roughness is numerically investigated over a 5-degree sharp tipped straight cone at a free stream Mach number of 3.5 and a high Reynolds number of 10(exp 6)/inch. Both the steady and unsteady solutions are obtained by solving the full Navier-Stokes equations using the fifth-order accurate weighted essentially non-oscillatory (WENO) scheme for spatial discretization and using third-order total-variation-diminishing (TVD) Runge-Kutta scheme for temporal integration. The simulations are performed with different roughness heights and roughness locations. The steady computations with the roughness reveal that the perturbations induced by the roughness remain very close to the wall and do not penetrate to the outer part of the boundary layer. The effects of the roughness persist for about 10 boundary layer thicknesses downstream of each element. The unsteady simulation shows the generation of unstable three-dimensional first mode disturbances within a short distance from the roughness. However, the amplitudes of the instability waves are very small near the neutral point, on the order of 10(exp -4) compared to the free stream disturbances. The receptivity coefficients due to the roughness elements located very close to the tip are one order of magnitude smaller than those due to the roughness elements located closer to the neutral point.

  8. Direct simulation of open-channel flow in the fully rough regime: focus on fluid-roughness interaction

    NASA Astrophysics Data System (ADS)

    Mazzuoli, Marco; Uhlmann, Markus

    2015-04-01

    The interaction between an incompressible open-channel flow at Reb = 6900 and rigid spheres of size k+ = 120 mounted in square arrangement on the bottom, has been investigated by means of Direct Numerical Simulation (DNS) for the purpose of contributing to the knowledge of the basic mechanism of sediment transport. The shift generated by the roughness on mean velocity profile in the log-region is in the range of values characterizing the Fully-Rough Regime (FRR). First, average quantities (i.e. flow velocity, shear-stress distribution on the sphere surface, force and torque acting on the spheres) are analyzed exploiting the spatial periodicity of the arrangement of roughness elements. Then, spatial and temporal fluctuations of the quantities are studied. Results are compared with those obtained for a similar DNS at Reb = 2900, which is in the Transitionally-Rough Regime (TRR). Although the largest fluctuations of the velocity components are observed ~ 8 wall units below the crest of the spheres in the FRR, their effect on the drag and lift fluctuations acting on individual spheres is weaker than in the TRR. Nonetheless, the lift coefficient in the FRR case was found the 24% larger than in the TRR case. The characteristics of vortex structures in the vicinity of roughness elements are also investigated. Differences in the flow structure between the two simulations in the TRR and in the FRR reflect on the stress distribution on the surface of the spheres. Finally, the arrangement of the roughness elements might play a key role in the modulation of turbulence.

  9. Interactions between surface roughness and airflow turbulence affecting drying dynamics of rough porous surfaces

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Kirchner, James; Or, Dani

    2016-04-01

    Evaporative drying of porous surfaces interacting with turbulent airflows is common in various industrial and natural applications. The intrinsic relief and roughness of natural porous surfaces are likely to influence the structure of interacting turbulent airflow boundary layers, and thus affect rates and patterns of heat and vapor fluxes from the surface. These links have been formalized in new mechanistic models that consider intermittent and localized turbulence-induced boundary layers, resulting in rich surface evaporation and energy exchange dynamics. The models were evaluated experimentally by systematically varying surface roughness elements in drying experiments of wavy and bluff-body covered sand surfaces in a wind tunnel. Thermal infrared signatures of localized evaporative fluxes as well as mean evaporative mass losses were recorded. The resulting patterns were in good agreement with model predictions for local and surface averaged turbulent exchange rates. Experimental and theoretical results suggest that evaporative water losses from wavy sand surfaces can be either enhanced or suppressed (relative to a flat surface), due to the complex interplay between the local boundary layer thickness and internal limitations on water flow to the evaporating surface. For sand surfaces covered by isolated cylindrical elements (bluff bodies), model predictions and measurements show persistent enhancement of evaporative fluxes from bluff-rough surfaces compared to a flat surface under similar conditions. This enhancement is attributed to the formation of vortices that thin the boundary layer over part of the interacting surface footprint. The implications of this study for interpreting and upscaling evapotranspiration rates from terrestrial surfaces will be discussed.

  10. Discrete Roughness Effects on Shuttle Orbiter at Mach 6

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Hamilton, H. Harris, II

    2002-01-01

    Discrete roughness boundary layer transition results on a Shuttle Orbiter model in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel have been reanalyzed with new boundary layer calculations to provide consistency for comparison to other published results. The experimental results were previously obtained utilizing the phosphor thermography system to monitor the status of the boundary layer via global heat transfer images of the Orbiter windward surface. The size and location of discrete roughness elements were systematically varied along the centerline of the 0.0075-scale model at an angle of attack of 40 deg and the boundary layer response recorded. Various correlative approaches were attempted, with the roughness transition correlations based on edge properties providing the most reliable results. When a consistent computational method is used to compute edge conditions, transition datasets for different configurations at several angles of attack have been shown to collapse to a well-behaved correlation.

  11. The effect of surface roughness on Triton's volatile distribution

    NASA Technical Reports Server (NTRS)

    Yelle, Roger V.

    1992-01-01

    Calculations of radiative equilibrium temperatures on Triton's rough surface suggest that significant condensation of N2 may be occurring in the northern equatorial regions, despite their relatively dark appearance. The bright frost is not apparent in the Voyager images because it tends to be concentrated in relatively unilluminated facets of the surface. This patchwork of bright frost-covered regions and darker bare ground may be distributed on scales smaller than that of the Voyager resolution; as a result the northern equatorial regions may appear relatively dark. This hypothesis also accounts for the observed wind direction in the Southern Hemisphere because it implies that the equatorial regions are warmer than the south polar regions.

  12. HEMISPHERIC CENTER FOR ENVIRONMENTAL TECHNOLOGY

    SciTech Connect

    M.A. Ebadian

    1999-04-30

    The final data package has been completed for the Mississippi State University, DIAL FTP Wall Depth Removal Characterization Technology. The package has been sent to DIAL for comments. Work is progressing on completing the transfer of glove boxes and tanks from Rocky Flats to FIU-HCET for the purpose of performing size reduction technology assessments. Vendors are being identified and security measures are being put in place to meet the High Risk Property criteria required by Rocky Flats. The FIU-HCET Technology Assessment Program has been included as one of 11 verification programs across the US and Canada described in the Interstate Technology Regulatory Cooperation (ITRC) document, ''Multi-state Evaluation of Elements Important to the Verification of Remediation Technologies'', dated January 1999. FIU-HCET will also participate in a panel discussion on technology verification programs at the International Environmental Technology Expo '99.

  13. A right hemisphere dominance for bimanual grasps.

    PubMed

    Le, Ada; Niemeier, Matthias

    2013-01-01

    To find points on the surface of an object that ensure a stable grasp, it would be most effective to employ one area in one cortical hemisphere. But grasping the object with both hands requires control through both hemispheres. To better understand the control mechanisms underlying this "bimanual grasping", here we examined how the two hemispheres coordinate their control processes for bimanual grasping depending on visual field. We asked if bimanual grasping involves both visual fields equally or one more than the other. To test this, participants fixated either to the left or right of an object and then grasped or pushed it off a pedestal. We found that when participants grasped the object in the right visual field, maximum grip aperture (MGA) was larger and more variable, and participants were slower to react and to show MGA compared to when they grasped the object in the left visual field. In contrast, when participants pushed the object we observed no comparable visual field effects. These results suggest that grasping with both hands, specifically the computation of grasp points on the object, predominantly involves the right hemisphere. Our study provides new insights into the interactions of the two hemispheres for grasping. PMID:23109083

  14. Hemispheric lateralization of semantic feature distinctiveness

    PubMed Central

    Reilly, M.; Machado, N.; Blumstein, S. E.

    2015-01-01

    Recent models of semantic memory propose that the semantic representation of concepts is based, in part, on a network of features. In this view, a feature that is distinctive for an object (a zebra has stripes) is processed differently from a feature that is shared across many objects (a zebra has four legs). The goal of this paper is to determine whether there are hemispheric differences in such processing. In a feature verification task, participants responded ‘yes’ or ‘no’ following concepts which were presented to a single visual field (left or right) paired with a shared or distinctive feature. Both hemispheres showed faster reaction times to shared features than to distinctive features, although right hemisphere responses were significantly slower overall and particularly in the processing of distinctive features. These findings support models of semantic processing in which the dominant left hemisphere more efficiently performs highly discriminating ‘fine’ encoding, in contrast to the right hemisphere which performs less discriminating ‘coarse’ encoding. PMID:26022059

  15. Optical receivers using rough reflectors

    NASA Technical Reports Server (NTRS)

    Vilnrotter, V. A.

    1985-01-01

    This report examines the possible use of rough, or nondiffraction-limited, reflectors for collecting optical signals. It is shown that in the absence of background radiation, the reflector's surface quality has little effect on the performance of a properly designed receiver, but that the presence of even small amounts of background radiation can lead to severe performance degradation. Techniques are suggested for improving receiver performance in high-background environments, and bounds and approximations to the exact error-probability expressions are derived.

  16. Approximating the detection limit of an infrared spectroscopic imaging microscope operating in an attenuated total reflection (ATR) modality: theoretical and empirical results for an instrument using a linear array detector and a 1.5 millimeter germanium hemisphere internal reflection element.

    PubMed

    Lanzarotta, Adam

    2015-01-01

    Theoretical and empirical detection limits have been estimated for aripiprazole (analyte) in alpha lactose monohydrate (matrix model pharmaceutical formulation) using a micro-attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopic imaging instrument equipped with a linear array detector and a 1.5 mm germanium hemisphere internal reflection element (IRE). The instrument yielded a theoretical detection limit of 0.0035% (35 parts per million (ppm)) when operating under diffraction-limited conditions, which was 49 times lower than what was achieved with a traditional macro-ATR instrument operating under practical conditions (0.17%, 1700 ppm). However, these results may not be achievable for most analyses because the detection limits will be particle size limited, rather than diffraction limited, for mixtures with average particle diameters greater than 8.3 μm (most pharmaceutical samples). For example, a theoretical detection limit of 0.028% (280 ppm) was calculated for an experiment operating under particle size-limited conditions where the average particle size was 23.4 μm. These conditions yielded a detection limit of 0.022% (220 ppm) when measured empirically, which was close to the theoretical value and only eight times lower than that of a faster, more simplistic macro-ATR instrument. Considering the longer data acquisition and processing times characteristic of the micro-ATR imaging approach (minutes or even hours versus seconds), the cost-benefit ratio may not often be favorable for the analysis of analytes in matrices that exhibit only a few overlapping absorptions (low-interfering matrices such as alpha lactose monohydrate) using this technique compared to what can be achieved using macro-ATR. However, the advantage was significant for detecting analytes in more complex matrices (those that exhibited several overlapping absorptions with the analyte) because the detection limit of the macro-ATR approach was highly formulation

  17. The effect of bottom roughness on scalar transport in aquatic ecosystems: implications for reproduction and recruitment in the benthos.

    PubMed

    Quinn, Noel P; Ackerman, Josef D

    2015-03-21

    Bottom roughness can influence gamete and larval transport in benthic organisms. For example the ratio of the roughness spacing (λ) and roughness height (k) determines the type of roughness flow regime created in two dimensional (2D) flows: λ/k<8 results in skimming flow; λ/k~8 results in wake interference flow; and λ/k>8 results in isolated roughness flow. Computational fluid dynamic modeling (COMSOL K-ε) was used to examine the effect of roughness geometry (e.g., a gradient in angularity provided by square, triangular and round 2D bottom roughness elements) on the prediction of roughness flow regime using biologically relevant λ/k ratios. In addition, a continuously released scalar (a proxy for gametes and larvae) in a coupled convection-diffusion model was used to determine the relationship among roughness geometry, λ/k ratios, and scalar transport (relative scalar transport, RT=ratio of scalar measured downstream in a series of roughness elements placed in tandem). The modeled roughness flow regimes fit closely with theoretical predictions using the square and triangle geometries, but the round geometry required a lower λ/k ratio than expected for skimming flow. Relative transport of the scalar was consistent with the modeled flow regimes, however significant differences in RT were found among the roughness flows for each geometry, and significantly lower RT values were observed for skimming flow in the round geometry. The λ/k ratio provides an accurate means of classifying flow in and around the roughness elements, whereas RT indicates the nature of scalar transport and retention. These results indicate that the spatial configuration of bottom roughness is an important determinant of gamete/larval transport in terms of whether the scalar will be retained among roughness elements or transported downstream. PMID:25596514

  18. Mapping number to space in the two hemispheres of the avian brain.

    PubMed

    Rugani, Rosa; Vallortigara, Giorgio; Regolin, Lucia

    2016-09-01

    Pre-verbal infants and non-human animals associate small numbers with the left space and large numbers with the right space. Birds and primates, trained to identify a given position in a sagittal series of identical positions, whenever required to respond on a left/right oriented series, referred the given position starting from the left end. Here, we extended this evidence by selectively investigating the role of either cerebral hemisphere, using the temporary monocular occlusion technique. In birds, lacking the corpus callosum, visual input is fed mainly to the contralateral hemisphere. We trained 4-day-old chicks to identify the 4th element in a sagittal series of 10 identical elements. At test, the series was identical but left/right oriented. Test was conducted in right monocular, left monocular or binocular condition of vision. Right monocular chicks pecked at the 4th right element; left monocular and binocular chicks pecked at the 4th left element. Data on monocular chicks demonstrate that both hemispheres deal with an ordinal (sequential) task. Data on binocular chicks indicate that the left bias is linked to a right hemisphere dominance, that allocates the attention toward the left hemispace. This constitutes a first step towards understanding the neural basis of number space mapping. PMID:27246250

  19. One-way implodable tag capsule with hemispherical beaded end cap for LWR fuel manufacturing

    DOEpatents

    Gross, Kenny; Lambert, John

    1999-01-01

    A capsule containing a tag gas in a zircaloy body portion having a hemispical top curved toward the bottom of the body portion. The hemispherical top has a rupturable portion upon exposure to elevated gas pressure and the capsule is positioned within a fuel element in a nuclear reactor.

  20. Diffusion-induced line-edge roughness

    NASA Astrophysics Data System (ADS)

    Stewart, Michael D.; Schmid, Gerard M.; Goldfarb, Dario L.; Angelopoulos, Marie; Willson, C. Grant

    2003-06-01

    As feature dimensions shrink, line edge roughness has become an increasing concern in semiconductor fabrication. There are numerous potential contributors to line edge roughness throughout the lithographic process and any measured roughness value on a printed device feature is, like the feature itself, a convolved function of every processing step. When the full lithographic process is used to study line edge roughness, it can be difficult to isolate the contribution to final roughness from any individual processing step or factor. To gain a more fundamental understanding of roughness generation that is specifically related to photoresist chemistry and formulation it is necessary to design experiments that separate out exposure related issues like mask dimension variation or local dose variation ("shot noise"). This can be accomplished using previously reported experimental protocols for bilayer film stack creation. The bilayer experimental approach has been used to study the effect of variations in such factors as post exposure bake time, photoacid generator loading, and developer concentration on roughness generation. Surface roughness of the developed film stacks is measured via atomic force microscopy. Surface roughness of developed bilayer film stacks may be considered analogous to sidewall roughness of printed features. An acrylate-based 193nm photoresist resin and an APEX-type resin are used in these experiments. In addition to experimental results, results from mesoscale lithographic simulations are used to gain further insight into diffusion induced roughness and how roughness in the latent image is modified during the development step.

  1. Intelligent Information Retrieval Using Rough Set Approximations.

    ERIC Educational Resources Information Center

    Srinivasan, Padmini

    1989-01-01

    Describes rough sets theory and discusses the advantages it offers for information retrieval, including the implicit inclusion of Boolean logic, term weighting, ranked retrieval output, and relevance feedback. Rough set formalism is compared to Boolean, vector, and fuzzy models of information retrieval and a small scale evaluation of rough sets is…

  2. Structural contribution to the roughness of supersmooth crystal surface

    SciTech Connect

    Butashin, A. V.; Muslimov, A. E. Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E.

    2013-05-15

    Technological advances in processing crystals (Si, sapphire {alpha}-Al{sub 2}O{sub 3}, SiC, GaN, LiNbO{sub 3}, SrTiO{sub 3}, etc.) of substrate materials and X-ray optics elements make it possible to obtain supersmooth surfaces with a periodicity characteristic of the crystal structure. These periodic structures are formed by atomically smooth terraces and steps of nano- and subnanometer sizes, respectively. A model surface with such nanostructures is proposed, and the relations between its roughness parameters and the height of atomic steps are determined. The roughness parameters calculated from these relations almost coincide with the experimental atomic force microscopy (AFM) data obtained from 1 Multiplication-Sign 1 and 10 Multiplication-Sign 10 {mu}m areas on the surface of sapphire plates with steps. The minimum roughness parameters for vicinal crystal surfaces, which are due to the structural contribution, are calculated based on the approach proposed. A comparative analysis of the relief and roughness parameters of sapphire plate surfaces with different degrees of polishing is performed. A size effect is established: the relief height distribution changes from stochastic to regular with a decrease in the surface roughness.

  3. Crosshatch roughness distortions on a hypersonic turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Peltier, S. J.; Humble, R. A.; Bowersox, R. D. W.

    2016-04-01

    The effects of periodic crosshatch roughness (k+ = 160) on a Mach 4.9 turbulent boundary layer (Reθ = 63 000) are examined using particle image velocimetry. The roughness elements generate a series of alternating shock and expansion waves, which span the entire boundary layer, causing significant (up to +50% and -30%) variations in the Reynolds shear stress field. Evidence of the hairpin vortex organization of incompressible flows is found in the comparative smooth-wall boundary layer case (Reθ = 47 000), and can be used to explain several observations regarding the rough-wall vortex organization. In general, the rough-wall boundary layer near-wall vortices no longer appear to be well-organized into streamwise-aligned packets that straddle relatively low-speed regions like their smooth-wall counterpart; instead, they lean farther away from the wall, become more spatially compact, and their populations become altered. In the lower half of the boundary layer, the net vortex swirling strength and outer-scaled Reynolds stresses increase relative to the smooth-wall case, and actually decrease in the outer half of the boundary layer, as ejection and entrainment processes are strengthened and weakened in these two regions, respectively. A spectral analysis of the data suggests a relative homogenizing of the most energetic scales near Λ = ˜ 0.5δ across the rough-wall boundary layer.

  4. Single Mode Lasing from Hybrid Hemispherical Microresonators

    PubMed Central

    Chen, Rui; Van Duong Ta; Sun, Han Dong

    2012-01-01

    Enormous attention has been paid to optical microresonators which hold a great promise for microlasers as well as fundamental studies in cavity quantum electrodynamics. Here we demonstrate a three-dimensional (3D) hybrid microresonator combining self-assembled hemispherical structure with a planar reflector. By incorporating dye molecules into the hemisphere, optically pumped lasing phenomenon is observed at room temperature. We have studied the lasing behaviors with different cavity sizes, and particularly single longitudinal mode lasing from hemispheres with diameter ∼15 μm is achieved. Detailed characterizations indicate that the lasing modes shift under varying pump densities, which can be well-explained by frequency shift and mode hopping. This work provides a versatile approach for 3D confined microresonators and opens an opportunity to realize tunable single mode microlasers. PMID:22540027

  5. Calibration of surface roughness standards

    NASA Astrophysics Data System (ADS)

    Thalmann, R.; Nicolet, A.; Meli, F.; Picotto, G. B.; Matus, M.; Carcedo, L.; Hemming, B.; Ganioglu, O.; De Chiffre, L.; Saraiva, F.; Bergstrand, S.; Zelenika, S.; Tonmueanwai, A.; Tsai, C.-L.; Shihua, W.; Kruger, O.; de Souza, M. M.; Salgado, J. A.; Ramotowski, Z.

    2016-01-01

    The key comparison EURAMET.L-K8.2013 on roughness was carried out in the framework of a EURAMET project starting in 2013 and ending in 2015. It involved the participation of 17 National Metrology Institutes from Europe, Asia, South America and Africa representing four regional metrology organisations. Five surface texture standards of different type were circulated and on each of the standards several roughness parameters according to the standard ISO 4287 had to be determined. 32 out of 395 individual results were not consistent with the reference value. After some corrective actions the number of inconsistent results could be reduced to 20, which correspond to about 5% of the total and can statistically be expected. In addition to the material standards, two softgauges were circulated, which allow to test the software of the instruments used in the comparison. The comparison results help to support the calibraton and measurement capabilities (CMCs) of the laboratories involved in the CIPM MRA. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  6. Characterization of Ice Roughness From Simulated Icing Encounters

    NASA Technical Reports Server (NTRS)

    Anderson, David N.; Shin, Jaiwon

    1997-01-01

    Detailed measurements of the size of roughness elements on ice accreted on models in the NASA Lewis Icing Research Tunnel (IRT) were made in a previous study. Only limited data from that study have been published, but included were the roughness element height, diameter and spacing. In the present study, the height and spacing data were found to correlate with the element diameter, and the diameter was found to be a function primarily of the non-dimensional parameters freezing fraction and accumulation parameter. The width of the smooth zone which forms at the leading edge of the model was found to decrease with increasing accumulation parameter. Although preliminary, the success of these correlations suggests that it may be possible to develop simple relationships between ice roughness and icing conditions for use in ice-accretion-prediction codes. These codes now require an ice-roughness estimate to determine convective heat transfer. Studies using a 7.6-cm-diameter cylinder and a 53.3-cm-chord NACA 0012 airfoil were also performed in which a 1/2-min icing spray at an initial set of conditions was followed by a 9-1/2-min spray at a second set of conditions. The resulting ice shape was compared with that from a full 10-min spray at the second set of conditions. The initial ice accumulation appeared to have no effect on the final ice shape. From this result, it would appear the accreting ice is affected very little by the initial roughness or shape features.

  7. Right hemisphere grey matter structure and language outcomes in chronic left hemisphere stroke.

    PubMed

    Xing, Shihui; Lacey, Elizabeth H; Skipper-Kallal, Laura M; Jiang, Xiong; Harris-Love, Michelle L; Zeng, Jinsheng; Turkeltaub, Peter E

    2016-01-01

    The neural mechanisms underlying recovery of language after left hemisphere stroke remain elusive. Although older evidence suggested that right hemisphere language homologues compensate for damage in left hemisphere language areas, the current prevailing theory suggests that right hemisphere engagement is ineffective or even maladaptive. Using a novel combination of support vector regression-based lesion-symptom mapping and voxel-based morphometry, we aimed to determine whether local grey matter volume in the right hemisphere independently contributes to aphasia outcomes after chronic left hemisphere stroke. Thirty-two left hemisphere stroke survivors with aphasia underwent language assessment with the Western Aphasia Battery-Revised and tests of other cognitive domains. High-resolution T1-weighted images were obtained in aphasia patients and 30 demographically matched healthy controls. Support vector regression-based multivariate lesion-symptom mapping was used to identify critical language areas in the left hemisphere and then to quantify each stroke survivor's lesion burden in these areas. After controlling for these direct effects of the stroke on language, voxel-based morphometry was then used to determine whether local grey matter volumes in the right hemisphere explained additional variance in language outcomes. In brain areas in which grey matter volumes related to language outcomes, we then compared grey matter volumes in patients and healthy controls to assess post-stroke plasticity. Lesion-symptom mapping showed that specific left hemisphere regions related to different language abilities. After controlling for lesion burden in these areas, lesion size, and demographic factors, grey matter volumes in parts of the right temporoparietal cortex positively related to spontaneous speech, naming, and repetition scores. Examining whether domain general cognitive functions might explain these relationships, partial correlations demonstrated that grey matter

  8. Effective lifetime of NOx produced by energetic particle precipitation in the winter hemisphere

    NASA Astrophysics Data System (ADS)

    Antonius Marszalek, Markus; Nesse Tyssøy, Hilde; Hibbins, Robert; Ødegaard, Linn-Krisitine; Sandanger, Marit; Stadsnes, Johan

    2015-04-01

    Energetic particle precipitation (EPP) into the atmosphere impacts the chemical composition in the middle atmosphere. However, the EPP effects are not restrained to the area it is produced, but will be transported both horizontally and vertically by the background winds and waves. To address the aspect of horizontal transport we use the simple empirical horizontal wind model, HWM07, to trace the approximate trajectories the air parcels take around the polar region. We limit our focus to the winter hemisphere. We parameterize the NOx production based on the energy deposition estimated from particle measurements on the NOAA Polar Orbiting Environmental Satellites (POES). We estimate the evolution of the EPP-produced NOx taking into consideration sunlight exposure. The results give a rough estimate of the lifetime of NOx produced during a precipitation event and its hemispherical distribution in the aftermath of an event compared to its local production.

  9. Influence of wall roughness on the hydrodynamics in a circulating fluidized bed

    SciTech Connect

    Zhou, J.; Grace, J.R.; Brereton, C.H.M.; Lim, C.J.

    1996-04-01

    Many efforts have been made to explore the particle and gas behavior in circulating fluidized beds during the last decade. Glicksman et al. (1991) reported that protrusions as small as one particle diameter may cause a change in the voidage of a circulating fluidized bed. Since the walls of CFB combustors and other commercial CFB reactors can be quite rough, with roughness elements sometimes several times the mean particle diameter, the roughness could have a significant influence on the hydrodynamics, affecting mixing, gas-solid contacting, and heat and mass transfer in circulating fluidized-bed processes. It is therefore important to explore the influence of wall roughness on riser hydrodynamics. No other previous work has been reported on this topic. Here, the influence of wall roughness on CFB hydrodynamics is identified by comparing the experimental results from a riser with rough walls with those from the same riser having smooth surfaces.

  10. Effect of nanoscale patterned interfacial roughness on interfacial toughness.

    SciTech Connect

    Zimmerman, Jonathan A.; Moody, Neville Reid; Mook, William M.; Kennedy, Marian S.; Bahr, David F.; Zhou, Xiao Wang; Reedy, Earl David, Jr.

    2007-09-01

    The performance and the reliability of many devices are controlled by interfaces between thin films. In this study we investigated the use of patterned, nanoscale interfacial roughness as a way to increase the apparent interfacial toughness of brittle, thin-film material systems. The experimental portion of the study measured the interfacial toughness of a number of interfaces with nanoscale roughness. This included a silicon interface with a rectangular-toothed pattern of 60-nm wide by 90-nm deep channels fabricated using nanoimprint lithography techniques. Detailed finite element simulations were used to investigate the nature of interfacial crack growth when the interface is patterned. These simulations examined how geometric and material parameter choices affect the apparent toughness. Atomistic simulations were also performed with the aim of identifying possible modifications to the interfacial separation models currently used in nanoscale, finite element fracture analyses. The fundamental nature of atomistic traction separation for mixed mode loadings was investigated.

  11. Turbulence in rough-wall boundary layers: universality issues

    NASA Astrophysics Data System (ADS)

    Amir, Mohammad; Castro, Ian P.

    2011-08-01

    Wind tunnel measurements of turbulent boundary layers over three-dimensional rough surfaces have been carried out to determine the critical roughness height beyond which the roughness affects the turbulence characteristics of the entire boundary layer. Experiments were performed on three types of surfaces, consisting of an urban type surface with square random height elements, a diamond-pattern wire mesh and a sand-paper type grit. The measurements were carried out over a momentum thickness Reynolds number ( Re θ) range of 1,300-28,000 using two-component Laser Doppler anemometry (LDA) and hot-wire anemometry (HWA). A wide range of the ratio of roughness element height h to boundary layer thickness δ was covered (0.04 ≤ h/δ ≤ 0.40). The results confirm that the mean profiles for all the surfaces collapse well in velocity defect form up to surprisingly large values of h/δ, perhaps as large as 0.2, but with a somewhat larger outer layer wake strength than for smooth-wall flows, as previously found. At lower h/δ, at least up to 0.15, the Reynolds stresses for all surfaces show good agreement throughout the boundary layer, collapsing with smooth-wall results outside the near-wall region. With increasing h/δ, however, the turbulence above the near-wall region is gradually modified until the entire flow is affected. Quadrant analysis confirms that changes in the rough-wall boundary layers certainly exist but are confined to the near-wall region at low h/δ; for h/δ beyond about 0.2 the quadrant events show that the structural changes extend throughout much of the boundary layer. Taken together, the data suggest that above h/δ ≈ 0.15, the details of the roughness have a weak effect on how quickly (with rising h/δ) the turbulence structure in the outer flow ceases to conform to the classical boundary layer behaviour. The present results provide support for Townsend's wall similarity hypothesis at low h/δ and also suggest that a single critical roughness

  12. Influence of a Two-scale Surface Roughness on a Neutral Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Salizzoni, Pietro; Soulhac, Lionel; Mejean, Patrick; Perkins, Richard J.

    2008-04-01

    Flow in the urban boundary layer is strongly influenced by the surface roughness, which is composed principally of isolated buildings or groups of buildings. Previous research has shown that the flow regime depends on the characteristic height of these obstacles ( H), and the spacing between them ( W). In reality, the urban boundary layer contains roughness elements with a wide range of length scales; in many practical situations these can be classified into large-scale roughness—buildings, or groups of buildings—and small-scale roughness, such as street furniture and elements on the façades and roofs. It is important to understand how the small-scale roughness might modify mass and momentum transfer in the urban boundary layer, but relatively little information is available concerning the potential interaction between large- and small-scale roughness elements in the different flow regimes. This problem has been studied using wind-tunnel experiments, by measuring vertical velocity profiles over a two-dimensional obstacle array, adding small-scale roughness elements to the top of larger parallel square bars. The experiments were performed for different cavity aspect ratios: the results show that the small-scale roughness increases the turbulence intensities and the momentum transfer when the large-scale obstacles are closely packed ( H/ W > 1) but it has very little effect for more widely-spaced obstacles ( H/ W < 1).

  13. A vision of graded hemispheric specialization.

    PubMed

    Behrmann, Marlene; Plaut, David C

    2015-11-01

    Understanding the process by which the cerebral hemispheres reach their mature functional organization remains challenging. We propose a theoretical account in which, in the domain of vision, faces and words come to be represented adjacent to retinotopic cortex by virtue of the need to discriminate among homogeneous exemplars. Orthographic representations are further constrained to be proximal to typically left-lateralized language-related information to minimize connectivity length between visual and language areas. As reading is acquired, orthography comes to rely more heavily (albeit not exclusively) on the left fusiform region to bridge vision and language. Consequently, due to competition from emerging word representations, face representations that were initially bilateral become lateralized to the right fusiform region (albeit, again, not exclusively). We review recent research that describes constraints that give rise to this graded hemispheric arrangement. We then summarize empirical evidence from a variety of studies (behavioral, evoked response potential, functional imaging) across different populations (children, adolescents, and adults; left handers and individuals with developmental dyslexia) that supports the claims that hemispheric lateralization is graded rather than binary and that this graded organization emerges dynamically over the course of development. Perturbations of this system either during development or in adulthood provide further insights into the principles governing hemispheric organization. PMID:26199998

  14. Meaning Apprehension in the Cerebral Hemispheres

    ERIC Educational Resources Information Center

    Kandhadai, Padmapriya A.

    2009-01-01

    When we hear a word, it is remarkable how we store, activate and rapidly retrieve a vast amount of relevant information within a few hundred milliseconds. This thesis examines how meaning is processed in parallel--but with critical differences--between the two hemispheres of the brain. Event-related brain potentials (ERP) were used to examine…

  15. Right Hemisphere Specialization for Color Detection

    ERIC Educational Resources Information Center

    Sasaki, Hitoshi; Morimoto, Akiko; Nishio, Akira; Matsuura, Sumie

    2007-01-01

    Three experiments were carried out to investigate hemispheric asymmetry in color processing among normal participants. In Experiment 1, it was shown that the reaction times (RTs) of the dominant and non-dominant hands assessed using a visual target presented at the central visual field, were not significantly different. In Experiment 2, RTs of…

  16. Hemispheric differences in the mesostriatal dopaminergic system

    PubMed Central

    Molochnikov, Ilana; Cohen, Dana

    2014-01-01

    The mesostriatal dopaminergic system, which comprises the mesolimbic and the nigrostriatal pathways, plays a major role in neural processing underlying motor and limbic functions. Multiple reports suggest that these processes are influenced by hemispheric differences in striatal dopamine (DA) levels, DA turnover and its receptor activity. Here, we review studies which measured the concentration of DA and its metabolites to examine the relationship between DA imbalance and animal behavior under different conditions. Specifically, we assess evidence in support of endogenous, inter-hemispheric DA imbalance; determine whether the known anatomy provides a suitable substrate for this imbalance; examine the relationship between DA imbalance and animal behavior; and characterize the symmetry of the observed inter-hemispheric laterality in the nigrostriatal and the mesolimbic DA systems. We conclude that many studies provide supporting evidence for the occurrence of experience-dependent endogenous DA imbalance which is controlled by a dedicated regulatory/compensatory mechanism. Additionally, it seems that the link between DA imbalance and animal behavior is better characterized in the nigrostriatal than in the mesolimbic system. Nonetheless, a variety of brain and behavioral manipulations demonstrate that the nigrostriatal system displays symmetrical laterality whereas the mesolimbic system displays asymmetrical laterality which supports hemispheric specialization in rodents. The reciprocity of the relationship between DA imbalance and animal behavior (i.e., the capacity of animal training to alter DA imbalance for prolonged time periods) remains controversial, however, if confirmed, it may provide a valuable non-invasive therapeutic means for treating abnormal DA imbalance. PMID:24966817

  17. Hemispheric Differences in Processing Handwritten Cursive

    ERIC Educational Resources Information Center

    Hellige, Joseph B.; Adamson, Maheen M.

    2007-01-01

    Hemispheric asymmetry was examined for native English speakers identifying consonant-vowel-consonant (CVC) non-words presented in standard printed form, in standard handwritten cursive form or in handwritten cursive with the letters separated by small gaps. For all three conditions, fewer errors occurred when stimuli were presented to the right…

  18. Rethinking a Right Hemisphere Deficit in ADHD

    ERIC Educational Resources Information Center

    Hale, T. Sigi; Loo, Sandra K.; Zaidel, Eran; Hanada, Grant; Macion, James; Smalley, Susan L.

    2009-01-01

    Introduction: Early observations from lesion studies suggested right hemisphere (RH) dysfunction in ADHD. However, a strictly right-lateralized deficit has not been well supported. An alternatively view suggests increased R greater than L asymmetry of brain function and abnormal interhemispheric interaction. If true, RH pathology in ADHD should…

  19. Hemisphere jet mass distribution at finite Nc

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshikazu; Hatta, Yoshitaka; Ueda, Takahiro

    2016-05-01

    We perform the leading logarithmic resummation of nonglobal logarithms for the single-hemisphere jet mass distribution in e+e- annihilation including the finite-Nc corrections. The result is compared with the previous all-order result in the large-Nc limit as well as fixed-order perturbative calculations.

  20. Civilisations of the Left Cerebral Hemisphere?

    ERIC Educational Resources Information Center

    Racle, Gabriel L.

    Research conducted by Tadanobu Tsunoda on auditory and visual sensation, designed to test and understand the functions of the cerebral hemispheres, is discussed. Tsunoda discovered that the Japanese responses to sounds by the left and the right sides of the brain are very different from the responses obtained from people from other countries. His…

  1. Hemisphere and gender differences in mental rotation.

    PubMed

    Uecker, A; Obrzut, J E

    1993-05-01

    Hemisphere and gender differences in mental rotation for tachistoscopically presented stimuli were assessed in 40 right-handed university students. Twenty male and 20 female subjects each were individually administered (via computer) a mental rotation task which included 10 stimulus presentations at each of eight angular disorientations (0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, and 315 degrees) in each visual half-field (VHF) for a total of 160 trials. Analyses of variance performed on reaction time and accuracy data revealed only a main effect for orientation. A typical mental rotation function for both the left VHF and the right VHF for both genders resulted; however, no gender x visual field interaction was found. Lack of hemisphere and gender differences provide further evidence questioning the interpretation of right-hemisphere male superiority for spatial tasks. Investigation into factors such as task complexity, stimulus familiarity, and task demands may lend further insight into hemisphere and gender differences in mental rotation. PMID:8499111

  2. Creative Cognitive Processes and Hemispheric Specialization.

    ERIC Educational Resources Information Center

    Poreh, A. M.; Whitman, R. D.

    1991-01-01

    The relationship between creative thought processes and hemispheric asymmetry was examined in 47 right-handed male undergraduates. Four factors were identified, accounting for 75 percent of the total variance: Verbal Divergent Thinking Factor, Nonverbal Divergent Thinking Factor, Convergent Verbal Search Factor, and Cognitive Complexity Factor.…

  3. Hemispheric Coupling: Comparing Dynamo Simulations and Observations

    NASA Astrophysics Data System (ADS)

    Norton, A. A.; Charbonneau, P.; Passos, D.

    2014-12-01

    Numerical simulations that reproduce solar-like magnetic cycles can be used to generate long-term statistics. The variations in north-south hemispheric solar cycle synchronicity and amplitude produced in simulations has not been widely compared to observations. The observed limits on solar cycle amplitude and phase asymmetry show that hemispheric sunspot area production is no more than 20 % asymmetric for cycles 17-23 and that phase lags do not exceed 20 % (or two years) of the total cycle period, as determined from Royal Greenwich Observatory sunspot data. Several independent studies have found a long-term trend in phase values as one hemisphere leads the other for, on average, four cycles. Such persistence in phase is not indicative of a stochastic phenomenon. We compare these observational findings to the magnetic cycle found in a numerical simulation of solar convection recently produced with the EULAG-MHD model. This long "millennium simulation" spans more than 1600 years and generated 40 regular, sunspot-like cycles. While the simulated cycle length is too long (˜40 yrs) and the toroidal bands remain at too high of latitudes (>30°), some solar-like aspects of hemispheric asymmetry are reproduced. The model is successful at reproducing the synchrony of polarity inversions and onset of cycle as the simulated phase lags do not exceed 20 % of the cycle period. The simulated amplitude variations between the north and south hemispheres are larger than those observed in the Sun, some up to 40 %. An interesting note is that the simulations also show that one hemisphere can persistently lead the other for several successive cycles, placing an upper bound on the efficiency of transequatorial magnetic coupling mechanisms. These include magnetic diffusion, cross-equatorial mixing within latitudinally-elongated convective rolls (a.k.a. "banana cells") and transequatorial meridional flow cells. One or more of these processes may lead to magnetic flux cancellation whereby

  4. Genetic biomarkers for brain hemisphere differentiation in Parkinson's Disease

    NASA Astrophysics Data System (ADS)

    Hourani, Mou'ath; Mendes, Alexandre; Berretta, Regina; Moscato, Pablo

    2007-11-01

    This work presents a study on the genetic profile of the left and right hemispheres of the brain of a mouse model of Parkinson's disease (PD). The goal is to characterize, in a genetic basis, PD as a disease that affects these two brain regions in different ways. Using the same whole-genome microarray expression data introduced by Brown et al. (2002) [1], we could find significant differences in the expression of some key genes, well-known to be involved in the mechanisms of dopamine production control and PD. The problem of selecting such genes was modeled as the MIN (α,β)—FEATURE SET problem [2]; a similar approach to that employed previously to find biomarkers for different types of cancer using gene expression microarray data [3]. The Feature Selection method produced a series of genetic signatures for PD, with distinct expression profiles in the Parkinson's model and control mice experiments. In addition, a close examination of the genes composing those signatures shows that many of them belong to genetic pathways or have ontology annotations considered to be involved in the onset and development of PD. Such elements could provide new clues on which mechanisms are implicated in hemisphere differentiation in PD.

  5. 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

  6. Influence of variations in extratropical wintertime teleconnections on Northern Hemisphere temperature

    SciTech Connect

    Hurrell, J.W.

    1997-11-01

    The purpose of this paper to illustrate and quantify the relationship between the circulation changes and surface temperature anomalies in the northern hemisphere during winter. Multivariate linear regression was used to regress three indices on the northern hemisphere extratropical temperature anomolies for each winter since 1935. The indices regressed were the North Atlantic Oscillation, the North Pacific, and the Southern Oscillation; these were selected because they relate to well understood circulation anomolies that have persisted for much of the past two decades. Elements of the temperature anomaly pattern since the mid-1970s resemble the greenhouse warming fingerprint predicted by some general circulation models; however, it is difficult to assess the cause. The changes in circulation since the mid-1970s have resulted in a particular surface temperature anomaly pattern that has amplified the hemispheric-averaged warming because of the interaction with land and ocean. 7 refs., 3 figs.

  7. A tunable hemispherical platform for non-stretching curved flexible electronics and optoelectronics

    SciTech Connect

    Zhuang, Jinda; Ju, Y. Sungtaek

    2014-07-28

    One major challenge in incorporating flexible electronics or optoelectronics on curved surfaces is the requirement of significant stretchability. We report a tunable platform for incorporating flexible and yet non-stretching device layers on a hemisphere. In this configuration, an array of planar petals contractively maps onto the surface of an inflatable hemisphere through elastocapillary interactions mediated by an interface liquid. A mechanical model is developed to elucidate the dependence of the conformality of the petal structures on their elastic modulus and thickness and the liquid surface tension. The modeling results are validated against experimental results obtained using petal structures of different thicknesses, restoring elastic spring elements of different spring constants, and liquids with different surface tension coefficients. Our platform will enable facile integration of non-stretching electronic and optoelectronic components prepared using established planar fabrication techniques on tunable hemispherical surfaces.

  8. Martian surface roughness and stratigraphy

    NASA Astrophysics Data System (ADS)

    Beyer, Ross Alan

    2004-12-01

    Orbital datasets can be combined and manipulated to learn about the three- dimensional structure of planetary surfaces, and the processes that have acted on them. The Mars Orbital Camera (MOC) is providing high-resolution images. These images allow qualitative inspection of features, and contain quantitative information about the shape of the surface. Using a photoclinometry technique derived from a lunar-Lambert photometric function, I am able to obtain estimates of the down-sun slope of each pixel in an image. This technique was calibrated against synthetic topography, compared to an area photoclinometry technique, and applied to the Viking and Pathfinder landing sites. It is a robust technique for obtaining the roughness and slope characteristics of large areas. It was applied to the potential landing sites for the Mars Exploration Rovers to evaluate site safety. The slopes from this point photoclinometry technique can be used to obtain a rough estimate of topography, which I used in a number of studies where topographic information was crucial. MOC images have shown that layering is pervasive on the martian surface. Mars Orbital Laser Altimeter (MOLA) data can be registered to MOC images to provide elevation constraints on layer outcrops. Such layers are observed in eastern Coprates Chasma both in the chasma rim and in a flat-topped massif. Observations indicate that the chasma stratigraphy consists of thin sequences of resistant layers and intervening thicker sequences of relatively less resistant layers. More resistant units cap the massif against erosion and result in steeper slopes than the weaker units would otherwise allow. These resistant layers can be used as stratigraphic markers which have allowed me to measure the subsidence and tilting of the massif relative to the chasma walls, providing evidence for tectonic motion in this portion of the Valles Marineris. These outcrops indicate that some of these layers may be analogus to terristrial flood

  9. Hemispheric Bias in Earth's response to orbital forcing

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Rajarshi; DeConto, Rob

    2014-05-01

    Today, there is an unequal distribution of land and water between the two hemispheres. The Northern Hemisphere has about 68% of the total landmass on earth, while the Southern hemisphere has less than half of the northern hemisphere land (~32%). It is observed that the Southern Hemisphere climates tend to be slightly milder than those in the Northern Hemisphere at similar latitudes, except in the Antarctic which is colder than the Arctic. This variance in climate can be attributed to two reasons: the current precessional configuration of the earth; and the fact that the Southern Hemisphere has significantly more ocean and much less land. The objective of this paper is to determine a hemispheric bias in climate due to unequal land distribution in the Northern and Southern Hemispheres. In this study, we use physically based climate models to gain insights into the role of Northern Hemisphere landmass distribution affecting the Southern Hemisphere climate and vice versa. We use hypothetical symmetric earth models in which landmass distribution is mirrored along the equator. We use these hypothetical landmass distributions to run a control simulation to provide the boundary conditions for a number of branched runs with a range of modified orbital parameters. The aim is to isolate the effects of the modified landmass distribution from the usual effects of orbital forcing. Using a Northern-Hemisphere symmetric earth model and a Southern-Hemisphere symmetric earth model, we are able to draw conclusions regarding the Northern influence on Southern Hemisphere and vice versa. With this information, a hemispheric bias map is constructed which has the potential to reveal useful insights into many unsolved climate problems. Precession and Obliquity effects are also studied in isolation on the calculated hemispheric bias. An improved understanding of the hemispheric bias caused by continental distribution will help associate past climates to paleocontinental reconstructions with

  10. Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances

    NASA Technical Reports Server (NTRS)

    Balakumar, P.

    2013-01-01

    Boundary-layer receptivity and stability of Mach 6 flows over smooth and rough seven-degree half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances is considered. The effects of three-dimensional isolated roughness on the receptivity and stability are also simulated. The results for the smooth cone show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast acoustic waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. Distributed roughness elements located near the nose region decreased the receptivity of the second mode generated by the slow acoustic wave by a small amount. Roughness elements distributed across the continuous spectrum increased the receptivity of the second mode generated by the slow and fast acoustic waves and the vorticity wave. The largest increase occurred for the vorticity wave. Roughness elements distributed across the synchronization point did not change the receptivity of the second modes generated by the acoustic waves. The receptivity of the second mode generated by the vorticity wave increased in this case, but the increase is lower than that occurred with the roughness elements located across the continuous spectrum. The simulations with an isolated roughness element showed that the second mode waves generated by the acoustic disturbances are not influenced by the small roughness element. Due to the interaction, a three-dimensional wave is generated. However, the amplitude is orders of magnitude smaller than the two-dimensional wave.

  11. Choosing words: left hemisphere, right hemisphere, or both? Perspective on the lateralization of word retrieval.

    PubMed

    Riès, Stéphanie K; Dronkers, Nina F; Knight, Robert T

    2016-04-01

    Language is considered to be one of the most lateralized human brain functions. Left hemisphere dominance for language has been consistently confirmed in clinical and experimental settings and constitutes one of the main axioms of neurology and neuroscience. However, functional neuroimaging studies are finding that the right hemisphere also plays a role in diverse language functions. Critically, the right hemisphere may also compensate for the loss or degradation of language functions following extensive stroke-induced damage to the left hemisphere. Here, we review studies that focus on our ability to choose words as we speak. Although fluidly performed in individuals with intact language, this process is routinely compromised in aphasic patients. We suggest that parceling word retrieval into its subprocesses-lexical activation and lexical selection-and examining which of these can be compensated for after left hemisphere stroke can advance the understanding of the lateralization of word retrieval in speech production. In particular, the domain-general nature of the brain regions associated with each process may be a helpful indicator of the right hemisphere's propensity for compensation. PMID:26766393

  12. The 2011 Northern Hemisphere Solar Maximum

    NASA Astrophysics Data System (ADS)

    Altrock, Richard C.

    2013-01-01

    Altrock (1997, Solar Phys. 170, 411) discusses a process in which Fe XIV 530.3 nm emission features appear at high latitudes and gradually migrate towards the equator, merging with the sunspot "butterfly diagram". In cycles 21 - 23 solar maximum occurred when the number of Fe XIV emission regions per day > 0.19 (averaged over 365 days and both hemispheres) first reached latitudes 18°, 21° and 21°, for an average of 20° ± 1.7°. Another high-latitude process is the "Rush to the Poles" of polar crown prominences and their associated coronal emission, including Fe XIV. The Rush is a harbinger of solar maximum (cf. Altrock, 2003, Solar Phys. 216, 343). Solar maximum in cycles 21 - 23 occurred when the center line of the Rush reached a critical latitude. These latitudes were 76°, 74° and 78°, respectively, for an average of 76° ± 2°. Cycle 24 displays an intermittent Rush that is only well-defined in the northern hemisphere. In 2009 an initial slope of 4.6°/yr was found in the north, compared to an average of 9.4 ± 1.7 °/yr in the previous three cycles. However, in 2010 the slope increased to 7.5°/yr. Extending that rate to 76° ± 2° indicates that the solar maximum smoothed sunspot number in the northern hemisphere already occurred at 2011.6 ± 0.3. In the southern hemisphere the Rush is very poorly defined. A linear fit to several maxima would reach 76° in the south at 2014.2. In 1999, persistent Fe XIV coronal emission connected with the ESC appeared near 70° in the north and began migrating towards the equator at a rate 40% slower than the previous two solar cycles. A fit to the early ESC would not reach 20° until 2019.8. However, in 2009 and 2010 an acceleration occurred. Currently the greatest number of emission regions is at 21° in the north and 24°in the south. This indicates that solar maximum is occurring now in the north but not yet in the south. The latest global smoothed sunspot numbers show an inflection point in late 2011, which

  13. Equivalent impedance of a rough interface

    NASA Astrophysics Data System (ADS)

    Zhuk, N. P.; Tret'iakov, O. A.

    1987-10-01

    An equivalent-impedance (EI) dyad is constructed for a rough and plane (on the average) interface dividing two plane-stratified magnetodielectric media. Its characteristics are related to those of a smooth surface and to the scattering properties of the roughnesses. It is shown that the Hermitian part of an EI dyad is formed through field scattering by roughnesses into the propagating natural modes of the regular medium.

  14. Estimating aerodynamic roughness over complex salt pan and sandur dust emitting surfaces

    NASA Astrophysics Data System (ADS)

    Nield, Joanna; King, James; Wiggs, Giles; Leyland, Julian; Bryant, Robert; Chiverrell, Richard; Darby, Stephen; Eckardt, Frank; Thomas, David; Vircavs, Larisa; Washington, Richard

    2014-05-01

    Salt pan and sandur surfaces typically consist of complex patterns of small-scale roughness which differ to more commonly studied larger roughness elements. It is important to understand how these surfaces interact with the wind as both sandar and salt pans (or playas) are potential dust emitters, and so improving our understanding of surface-atmosphere interactions over surfaces in these areas is vital. These complexly patterned surfaces are also relative flat, lack vegetation and typically have a large fetch which makes them the ideal experimental surfaces to develop empirical estimations of aerodynamic roughness from terrestrial laser scanner (TLS) datasets. We investigated 20 surfaces with element heights ranging from 1 to 199mm during four field campaigns. Co-located anemometer towers at each location measured actual aerodynamic roughness to compare to a myriad of surface metrics derived from TLS datasets. Using cluster analysis height, shape, spacing and variability metric groups were compared to decipher which best estimated aerodynamic roughness. When height metrics were employed, it was found that over 90% of the variability was explained and height is a better predictor than both shape and spacing. This finding is in juxtaposition to wind erosion models that assume the spacing of larger-scale isolated roughness elements is most important in determining aerodynamic roughness. The study recognizes that when small-scale surface roughness is accurately quantified (with millimetre accuracy using TLS), height is most significance for estimating aerodynamic roughness, irrespective of comparator metric choice. This has very significant implications for the development of aerodynamic roughness predictors which are fundamental to the efficiency of wind erosion models, and, particularly, dust emission schemes in climate models.

  15. Pollutant Plume Dispersion in the Atmospheric Boundary Layer over Idealized Urban Roughness

    NASA Astrophysics Data System (ADS)

    Wong, Colman C. C.; Liu, Chun-Ho

    2013-05-01

    The Gaussian model of plume dispersion is commonly used for pollutant concentration estimates. However, its major parameters, dispersion coefficients, barely account for terrain configuration and surface roughness. Large-scale roughness elements (e.g. buildings in urban areas) can substantially modify the ground features together with the pollutant transport in the atmospheric boundary layer over urban roughness (also known as the urban boundary layer, UBL). This study is thus conceived to investigate how urban roughness affects the flow structure and vertical dispersion coefficient in the UBL. Large-eddy simulation (LES) is carried out to examine the plume dispersion from a ground-level pollutant (area) source over idealized street canyons for cross flows in neutral stratification. A range of building-height-to-street-width (aspect) ratios, covering the regimes of skimming flow, wake interference, and isolated roughness, is employed to control the surface roughness. Apart from the widely used aerodynamic resistance or roughness function, the friction factor is another suitable parameter that measures the drag imposed by urban roughness quantitatively. Previous results from laboratory experiments and mathematical modelling also support the aforementioned approach for both two- and three-dimensional roughness elements. Comparing the UBL plume behaviour, the LES results show that the pollutant dispersion strongly depends on the friction factor. Empirical studies reveal that the vertical dispersion coefficient increases with increasing friction factor in the skimming flow regime (lower resistance) but is more uniform in the regimes of wake interference and isolated roughness (higher resistance). Hence, it is proposed that the friction factor and flow regimes could be adopted concurrently for pollutant concentration estimate in the UBL over urban street canyons of different roughness.

  16. Asymmetric auroral intensities in the Earth's Northern and Southern hemispheres

    NASA Astrophysics Data System (ADS)

    Laundal, K. M.; Østgaard, N.

    2009-07-01

    It is commonly assumed that the aurora borealis (Northern Hemisphere) and aurora australis (Southern Hemisphere) are mirror images of each other because the charged particles causing the aurora follow the magnetic field lines connecting the two hemispheres. The particles are believed to be evenly distributed between the two hemispheres, from the source region in the equatorial plane of the magnetosphere. Although it has been shown that similar auroral features in the opposite hemispheres can be displaced tens of degree in longitude and that seasonal effects can cause differences in global intensity, the overall auroral patterns were still similar. Here we report observations that clearly contradict the common assumption about symmetric aurora: intense spots are seen at dawn in the Northern summer Hemisphere, and at dusk in the Southern winter Hemisphere. The asymmetry is interpreted in terms of inter-hemispheric currents related to seasons, which have been predicted but hitherto had not been seen.

  17. Cortical Hemisphere Registration Via Large Deformation Diffeomorphic Metric Curve Mapping

    PubMed Central

    Qiu, Anqi; Miller, Michael I.

    2010-01-01

    We present large deformation diffeomorphic metric curve mapping (LDDMM-Curve) for registering cortical hemispheres. We showed global cortical hemisphere matching and evaluated the mapping accuracy in five subregions of the cortex in fourteen MRI scans. PMID:18051058

  18. Simplified Approach to Predicting Rough Surface Transition

    NASA Technical Reports Server (NTRS)

    Boyle, R. J.; Stripf, M.

    2009-01-01

    Turbine vane heat transfer predictions are given for smooth and rough vanes where the experimental data show transition moving forward on the vane as the surface roughness physical height increases. Consistent with smooth vane heat transfer, the transition moves forward for a fixed roughness height as the Reynolds number increases. Comparisons are presented with published experimental data. Some of the data are for a regular roughness geometry with a range of roughness heights, Reynolds numbers, and inlet turbulence intensities. The approach taken in this analysis is to treat the roughness in a statistical sense, consistent with what would be obtained from blades measured after exposure to actual engine environments. An approach is given to determine the equivalent sand grain roughness from the statistics of the regular geometry. This approach is guided by the experimental data. A roughness transition criterion is developed, and comparisons are made with experimental data over the entire range of experimental test conditions. Additional comparisons are made with experimental heat transfer data, where the roughness geometries are both regular and statistical. Using the developed analysis, heat transfer calculations are presented for the second stage vane of a high pressure turbine at hypothetical engine conditions.

  19. Simplified Approach to Predicting Rough Surface Transition

    NASA Technical Reports Server (NTRS)

    Boyle, Robert J.; Stripf, Matthias

    2009-01-01

    Turbine vane heat transfer predictions are given for smooth and rough vanes where the experimental data show transition moving forward on the vane as the surface roughness physical height increases. Consiste nt with smooth vane heat transfer, the transition moves forward for a fixed roughness height as the Reynolds number increases. Comparison s are presented with published experimental data. Some of the data ar e for a regular roughness geometry with a range of roughness heights, Reynolds numbers, and inlet turbulence intensities. The approach ta ken in this analysis is to treat the roughness in a statistical sense , consistent with what would be obtained from blades measured after e xposure to actual engine environments. An approach is given to determ ine the equivalent sand grain roughness from the statistics of the re gular geometry. This approach is guided by the experimental data. A roughness transition criterion is developed, and comparisons are made with experimental data over the entire range of experimental test co nditions. Additional comparisons are made with experimental heat tran sfer data, where the roughness geometries are both regular as well a s statistical. Using the developed analysis, heat transfer calculatio ns are presented for the second stage vane of a high pressure turbine at hypothetical engine conditions.

  20. Rough set models of Physarum machines

    NASA Astrophysics Data System (ADS)

    Pancerz, Krzysztof; Schumann, Andrew

    2015-04-01

    In this paper, we consider transition system models of behaviour of Physarum machines in terms of rough set theory. A Physarum machine, a biological computing device implemented in the plasmodium of Physarum polycephalum (true slime mould), is a natural transition system. In the behaviour of Physarum machines, one can notice some ambiguity in Physarum motions that influences exact anticipation of states of machines in time. To model this ambiguity, we propose to use rough set models created over transition systems. Rough sets are an appropriate tool to deal with rough (ambiguous, imprecise) concepts in the universe of discourse.

  1. Socioeconomic and environmental impacts of landslides in the Western Hemisphere

    USGS Publications Warehouse

    Schuster, Robert L.; Highland, Lynn M.

    2001-01-01

    In spite of improvements in recognition, prediction, mitigative measures, and warning systems, economic losses and casualties due to landslides in the Western Hemisphere appear to be growing as a result of increasing development of landslide-prone areas due to population pressures. This paper notes outstanding examples of socioeconomic losses in the Americas. Landslides impact the following elements of the natural environment: (1) the topography/morphology of both the subaerial and submarine surfaces of the Earth, (2) rivers, streams, forests, and grasslands, and (3) habitats of native fauna, both on the Earth?s surface and in its streams and oceans. Environmental disturbances are results of general tendency toward degradation of the Earth?s surface by gravitational mass wasting and erosion.

  2. Electron-energy losses in hemispherical targets

    SciTech Connect

    Aizpurua, J.; Rivacoba, A.; Apell, S.P.

    1996-07-01

    In the framework of classical dielectric theory, the hemispherical geometry is studied. Calculations on surface modes are carried out for isolated Drude-like hemispheres. The convergence of the results with respect to the number of coupled terms in the expressions of the potential is discussed. The electron-energy-loss probability is studied for Al and Ag particles involving this geometry. The surface modes and hence the energy-loss probability are given by coupled expressions, the physical meaning of which is the coupling among multipolar terms, because of the particular geometry. The results obtained here present a good quantitative agreement with experiments in the case of clear surfaces (Ag) and provide a qualitative understanding for the experiments in Al, in terms of the position and impact parameter of the beam. This allows us to set the validity of the dielectric theory for cases that seemed to question it. {copyright} {ital 1996 The American Physical Society.}

  3. Metastability of Northern Hemisphere Teleconnection modes

    NASA Astrophysics Data System (ADS)

    Risbey, James; O'Kane, Terence; Monselesan, Didier; Franzke, Christian; Horenko, Ilia

    2014-05-01

    This work applies the FEM-BV-VARX method to study of the large scale modes of variability in the Northern Hemisphere as manifest in 500hPa geopotential height fields. The FEM-BV-VARX method identifies metastable states of the system. The results for regional domains confirm that the teleconnection modes referred to as the NAO in the Atlantic domain, PNA in the Pacific domain, and Scandanavian blocking in the Eurasian domain, all exhibit metastability. For the full Northern Hemisphere domain the metastable state combines the AO and a midlatitude circumglobal wavetrain pattern. These results are shown in a set of reanalysis products from NCEP; the 20th century reanalysis, NNR1, and the CFSR coupled reanalysis. The reanalysis products are all able to simulate the structure and temporal switching of regime states. Decadal and multidecadal regimes are clearly apparent in the model affiliation sequence of metastable states and correspond to known transition points for the teleconnection modes.

  4. Mesoscale Temperature Fluctuations in the Southern Hemisphere Stratosphere

    NASA Technical Reports Server (NTRS)

    Gary, Bruce L.

    2008-01-01

    Isentrope surfaces in the Southern Hemisphere stratosphere reveal that air parcels undergo mesoscale temperature fluctuations that depend on latitude and season. The largest temperature fluctuations occur at high latitude winter, whereas the smallest fluctuations occur at high latitude summer. This is the same pattern found for the Northern Hemisphere stratosphere. However, the amplitude of the seasonal dependence in the Southern Hemisphere is only 37% of the Northern Hemisphere's seasonal amplitude.

  5. Quaternary glaciations in the Northern Hemisphere

    SciTech Connect

    Sibrava, V.; Bowen, D.Q.; Richmond, G.M.

    1987-01-01

    This volume presents the final report of Project 24 of the International Geological Correlation Programme. The publication is drawn from the contributions of leading individual scientist as well as from scientific research teams. It reflects the present state of knowledge of the Quaternary Glaciations in the Northern Hemisphere and their correlation in space and time, as well as providing a unique summary of climatic change.

  6. Hemispheric modulations of the attentional networks.

    PubMed

    Spagna, Alfredo; Martella, Diana; Fuentes, Luis J; Marotta, Andrea; Casagrande, Maria

    2016-10-01

    Although several recent studies investigated the hemispheric contributions to the attentional networks using the Attention Network Test (ANT), the role of the cerebral hemispheres in modulating the interaction among them remains unclear. In this study, two lateralized versions of this test (LANT) were used to investigate theal effects on the attentional networks under different conflict conditions. One version, the LANTI-A, presented arrows as target and flankers, while the other version, the LANTI-F, had fruits as target and flankers. Data collected from forty-seven participants confirmed well-known results on the efficiency and interactions among the attentional networks. Further, a left visual field advantage was found when a target occurred in an unattended location (e.g. invalid trials), only with the LANTI-F, but not with LANTI-A. The present study adds more evidence to the hemispheric asymmetry of the orienting of attention, and further reveals patterns of interactions between the attentional networks and the visual fields across different conflicting conditions, underlying the dynamic control of attention in complex environments. PMID:27566000

  7. Casimir Effect in Hemisphere Capped Tubes

    NASA Astrophysics Data System (ADS)

    Bezerra de Mello, E. R.; Saharian, A. A.

    2016-02-01

    In this paper we investigate the vacuum densities for a massive scalar field with general curvature coupling in background of a (2 + 1)-dimensional spacetime corresponding to a cylindrical tube with a hemispherical cap. A complete set of mode functions is constructed and the positive-frequency Wightman function is evaluated for both the cylindrical and hemispherical subspaces. On the base of this, the vacuum expectation values of the field squared and energy-momentum tensor are investigated. The mean field squared and the normal stress are finite on the boundary separating two subspaces, whereas the energy density and the parallel stress diverge as the inverse power of the distance from the boundary. For a conformally coupled field, the vacuum energy density is negative on the cylindrical part of the space. On the hemisphere, it is negative near the top and positive close to the boundary. In the case of minimal coupling the energy density on the cup is negative. On the tube it is positive near the boundary and negative at large distances. Though the geometries of the subspaces are different, the Casimir pressures on the separate sides of the boundary are equal and the net Casimir force vanishes. The results obtained may be applied to capped carbon nanotubes described by an effective field theory in the long-wavelength approximation.

  8. Hemisphericity Research: An Overview with Some Implications for Problem Solving.

    ERIC Educational Resources Information Center

    Myers, John T.

    1982-01-01

    Research on cerebral hemisphericity and lateral dominance is reviewed, and relationships between right and left hemispheric modes of information processing as well as problem solving techniques are discussed. Conclusions focus mainly on need for educators to know information processing differences of the two hemispheres to teach children problem…

  9. The Influence of Context on Hemispheric Recruitment during Metaphor Processing

    ERIC Educational Resources Information Center

    Diaz, Michele T.; Hogstrom, Larson J.

    2011-01-01

    Although the left hemisphere's prominence in language is well established, less emphasis has been placed on possible roles for the right hemisphere. Behavioral, patient, and neuroimaging research suggests that the right hemisphere may be involved in processing figurative language. Additionally, research has demonstrated that context can modify…

  10. Evidence for Right Hemisphere Phonology in a Backward Masking Task

    ERIC Educational Resources Information Center

    Halderman, Laura K.

    2011-01-01

    The extent to which orthographic and phonological processes are available during the initial moments of word recognition within each hemisphere is under specified, particularly for the right hemisphere. Few studies have investigated whether each hemisphere uses orthography and phonology under constraints that restrict the viewing time of words and…

  11. Flexible Contrast Gain Control in the Right Hemisphere

    ERIC Educational Resources Information Center

    Okubo, Matia; Nicholls, Michael E. R.

    2005-01-01

    This study investigates whether the right hemisphere has more flexible contrast gain control settings for the identification of spatial frequency. Right-handed participants identified 1 and 9 cycles per degree sinusoidal gratings presented either to the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH).…

  12. Hemisphericity, Cognitive Set, and Susceptibility to Subliminal Perception

    ERIC Educational Resources Information Center

    Sackeim, Harold A.; And Others

    1977-01-01

    Examines the role of hemisphericity, that is, the tendency habitually to activate one or the other cerebral hemispheres regardless of the appropriateness of that hemisphere for task demands, and cognitive set as moderating variables in susceptibility to subliminal perception. (Author/RK)

  13. Brain Hemisphere Dominance: Building the Whole-Brain Singer

    ERIC Educational Resources Information Center

    Boyd, Amanda R.

    2012-01-01

    The concept of brain hemisphere dominance serves as the basis for many educational learning theories. The dominant brain hemisphere guides the learning process, but both hemispheres are necessary for true learning to take place. This treatise outlines and analyzes the dominance factor, a learning theory developed by Dr. Carla Hannaford, which…

  14. Hemispheric Asymmetries in the Activation and Monitoring of Memory Errors

    ERIC Educational Resources Information Center

    Giammattei, Jeannette; Arndt, Jason

    2012-01-01

    Previous research on the lateralization of memory errors suggests that the right hemisphere's tendency to produce more memory errors than the left hemisphere reflects hemispheric differences in semantic activation. However, all prior research that has examined the lateralization of memory errors has used self-paced recognition judgments. Because…

  15. Hemispheric asymmetry in event knowledge activation during incremental language comprehension: A visual half-field ERP study.

    PubMed

    Metusalem, Ross; Kutas, Marta; Urbach, Thomas P; Elman, Jeffrey L

    2016-04-01

    During incremental language comprehension, the brain activates knowledge of described events, including knowledge elements that constitute semantic anomalies in their linguistic context. The present study investigates hemispheric asymmetries in this process, with the aim of advancing our understanding of the neural basis and functional properties of event knowledge activation during incremental comprehension. In a visual half-field event-related brain potential (ERP) experiment, participants read brief discourses in which the third sentence contained a word that was either highly expected, semantically anomalous but related to the described event (Event-Related), or semantically anomalous but unrelated to the described event (Event-Unrelated). For both visual fields of target word presentation, semantically anomalous words elicited N400 ERP components of greater amplitude than did expected words. Crucially, Event-Related anomalous words elicited a reduced N400 relative to Event-Unrelated anomalous words only with left visual field/right hemisphere presentation. This result suggests that right hemisphere processes are critical to the activation of event knowledge elements that violate the linguistic context, and in doing so informs existing theories of hemispheric asymmetries in semantic processing during language comprehension. Additionally, this finding coincides with past research suggesting a crucial role for the right hemisphere in elaborative inference generation, raises interesting questions regarding hemispheric coordination in generating event-specific linguistic expectancies, and more generally highlights the possibility of functional dissociation of event knowledge activation for the generation of elaborative inferences and for linguistic expectancies. PMID:26878980

  16. Wetting properties of molecularly rough surfaces

    SciTech Connect

    Svoboda, Martin; Lísal, Martin; Malijevský, Alexandr

    2015-09-14

    We employ molecular dynamics simulations to study the wettability of nanoscale rough surfaces in systems governed by Lennard-Jones (LJ) interactions. We consider both smooth and molecularly rough planar surfaces. Solid substrates are modeled as a static collection of LJ particles arranged in a face-centered cubic lattice with the (100) surface exposed to the LJ fluid. Molecularly rough solid surfaces are prepared by removing several strips of LJ atoms from the external layers of the substrate, i.e., forming parallel nanogrooves on the surface. We vary the solid-fluid interactions to investigate strongly and weakly wettable surfaces. We determine the wetting properties by measuring the equilibrium droplet profiles that are in turn used to evaluate the contact angles. Macroscopic arguments, such as those leading to Wenzel’s law, suggest that surface roughness always amplifies the wetting properties of a lyophilic surface. However, our results indicate the opposite effect from roughness for microscopically corrugated surfaces, i.e., surface roughness deteriorates the substrate wettability. Adding the roughness to a strongly wettable surface shrinks the surface area wet with the liquid, and it either increases or only marginally affects the contact angle, depending on the degree of liquid adsorption into the nanogrooves. For a weakly wettable surface, the roughness changes the surface character from lyophilic to lyophobic due to a weakening of the solid-fluid interactions by the presence of the nanogrooves and the weaker adsorption of the liquid into the nanogrooves.

  17. Optical methods for cylindrical rough surface testing

    NASA Astrophysics Data System (ADS)

    Perez Quintian, F.; Rebollo, Maria A.; Gaggioli, Nestor G.; Raffo, C. A.

    1999-07-01

    This work studies theoretically the scattering of light from cylindrical rough surfaces. It is shown, for the conical diffraction configuration, that the mean intensity on an observation plane perpendicular to the cylinder longitudinal axis, is related to the statistical parameters that characterize the surface: the roughness (sigma) and the correlation length T.

  18. Roughness configuration matters for aeolian sediment flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The parameterisation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Roughness effects are typically represented by bulk drag-partitioning schemes that scale the threshold friction velocity (u*t) for soil entrainment by the ratio of s...

  19. Wetting properties of molecularly rough surfaces.

    PubMed

    Svoboda, Martin; Malijevský, Alexandr; Lísal, Martin

    2015-09-14

    We employ molecular dynamics simulations to study the wettability of nanoscale rough surfaces in systems governed by Lennard-Jones (LJ) interactions. We consider both smooth and molecularly rough planar surfaces. Solid substrates are modeled as a static collection of LJ particles arranged in a face-centered cubic lattice with the (100) surface exposed to the LJ fluid. Molecularly rough solid surfaces are prepared by removing several strips of LJ atoms from the external layers of the substrate, i.e., forming parallel nanogrooves on the surface. We vary the solid-fluid interactions to investigate strongly and weakly wettable surfaces. We determine the wetting properties by measuring the equilibrium droplet profiles that are in turn used to evaluate the contact angles. Macroscopic arguments, such as those leading to Wenzel's law, suggest that surface roughness always amplifies the wetting properties of a lyophilic surface. However, our results indicate the opposite effect from roughness for microscopically corrugated surfaces, i.e., surface roughness deteriorates the substrate wettability. Adding the roughness to a strongly wettable surface shrinks the surface area wet with the liquid, and it either increases or only marginally affects the contact angle, depending on the degree of liquid adsorption into the nanogrooves. For a weakly wettable surface, the roughness changes the surface character from lyophilic to lyophobic due to a weakening of the solid-fluid interactions by the presence of the nanogrooves and the weaker adsorption of the liquid into the nanogrooves. PMID:26374050

  20. Computational Methods for Rough Classification and Discovery.

    ERIC Educational Resources Information Center

    Bell, D. A.; Guan, J. W.

    1998-01-01

    Rough set theory is a new mathematical tool to deal with vagueness and uncertainty. Computational methods are presented for using rough sets to identify classes in datasets, finding dependencies in relations, and discovering rules which are hidden in databases. The methods are illustrated with a running example from a database of car test results.…

  1. Testing the Language of German Cerebral Palsy Patients with Right Hemispheric Language Organization after Early Left Hemispheric Damage

    ERIC Educational Resources Information Center

    Schwilling, Eleonore; Krageloh-Mann, Ingeborg; Konietzko, Andreas; Winkler, Susanne; Lidzba, Karen

    2012-01-01

    Language functions are generally represented in the left cerebral hemisphere. After early (prenatally acquired or perinatally acquired) left hemispheric brain damage language functions may be salvaged by reorganization into the right hemisphere. This is different from brain lesions acquired in adulthood which normally lead to aphasia. Right…

  2. The turbulent thermal boundary layer with an abrupt change from a rough to a smooth wall

    NASA Technical Reports Server (NTRS)

    Taylor, Robert P.; Taylor, J. K.; Hosni, M. H.; Coleman, Hugh W.

    1993-01-01

    The work reported here was motivated by concern over the use of smooth heat flux gages for heat transfer measurements on the otherwise rough turbine blades. Stanton number distributions and boundary layer profiles of mean temperature, mean velocity, and turbulence intensity are reported for a surface with a step change from a rough to a smooth surface. In most cases, the Stanton number immediately downstream of the change in roughness drops below the all-smooth-wall data at the same x-Reynolds number. The alignment of the smooth surface between the bases and crests of the roughness elements is shown to have only a weak effect on the Stanton number distribution. It is concluded that the use of smooth heat flux gages on otherwise rough surfaces can cause large errors. It is recommended that heat transfer data collected in this manner be used with caution.

  3. Spherical wave reflection in layered media with rough interfaces: Three-dimensional modeling.

    PubMed

    Pinson, Samuel; Cordioli, Julio; Guillon, Laurent

    2016-08-01

    In the context of sediment characterization, layer interface roughnesses may be responsible for sound-speed profile measurement uncertainties. To study the roughness influence, a three-dimensional (3D) modeling of a layered seafloor with rough interfaces is necessary. Although roughness scattering has an abundant literature, 3D modeling of spherical wave reflection on rough interfaces is generally limited to a single interface (using Kirchhoff-Helmholtz integral) or computationally expensive techniques (finite difference or finite element method). In this work, it is demonstrated that the wave reflection over a layered medium with irregular interfaces can be modeled as a sum of integrals over each interface. The main approximations of the method are the tangent-plane approximation, the Born approximation (multiple reflection between interfaces are neglected) and flat-interface approximation for the transmitted waves into the sediment. The integration over layer interfaces results in a method with reasonable computation cost. PMID:27586741

  4. Casimir effect with rough metallic mirrors

    SciTech Connect

    Neto, Paulo A. Maia; Lambrecht, Astrid; Reynaud, Serge

    2005-07-15

    We calculate the second-order roughness correction to the Casimir energy for two parallel metallic mirrors. Our results may also be applied to the plane-sphere geometry used in most experiments. The metallic mirrors are described by the plasma model, with arbitrary values for the plasma wavelength, the mirror separation, and the roughness correlation length, with the roughness amplitude remaining the smallest length scale for perturbation theory to hold. From the analysis of the intracavity field fluctuations, we obtain the Casimir energy correction in terms of generalized reflection operators, which account for diffraction and polarization coupling in the scattering by the rough surfaces. We present simple analytical expressions for several limiting cases, as well as numerical results that allow for a reliable calculation of the roughness correction in real experiments. The correction is larger than the result of the proximity force approximation, which is obtained from our theory as a limiting case (very smooth surfaces)

  5. Surface roughness and infrared emission from the lunar surface

    NASA Astrophysics Data System (ADS)

    Vogler, Karl Joseph

    1994-01-01

    In order to understand thermal infrared spectra of the moon and solid-surfaced planetary bodies in terms of surface roughness and composition, a two-part project involving thermophysical computer models and infrared photometry has been pursued. The computer models calculate the infrared radiation emitted by an atmosphereless body with a macroscopically rough surface using radiative heat transfer methods. Multiple scattering of incident solar radiation, and multiple scattering and remission of thermal infrared radiation onto surrounding surface elements are included in the model. Surface roughness is modeled as paraboloidal holes characterized by a fractional coverage of a spherical object and a single depth-to-diameter ratio. Thermal emission from the rough surface is anisotropic and deviates from a gray body emission assumed by standard thermal models. The model explains to first-order published, mid infrared, measurements of the moon and Galilean Satellites. Surface composition is included by using results from Hapke for reflectance and emittance properties of a particulate surface. It is concluded that negative surface relief is required to explain the continuum behavior of the lunar thermal spectrum. An infrared photometer was constructed from an existing design and was configured in order to perform whole disk photometry of the moon at various phase angles. Measurements at 5.03, 8.4 and 11.5 micron were made at seven phase angles, ranging from -151 deg 55 min to 53 deg 27 min. The thermophysical computer models were modified so that disk-integrated emission as a function of phase angle could be calculated. Effects due to thermal inertia of the surface are not included in this simplified version of the model. The model calculations compare favorably with measurements of the moon made by the author, Sarri and Shorthill and Murdock. It is concluded that surface roughness is necessary in explaining the shape of the lunar thermal emission with phase angle.

  6. Hemispheric specialization for linguistic processing of sung speech.

    PubMed

    Yelle, Serena K; Grimshaw, Gina M

    2009-02-01

    The two hemispheres of the brain play complementary roles in song perception, with the left hemisphere specialized for processing the linguistic aspects of song and the right hemisphere specialized for the processing of melody. However, very little is known about how language and melody interact. The present study tested the hypothesis that right hemisphere linguistic processing would be facilitated by the presence of melody. In a dichotic listening paradigm, participants (8 men, 43 women) performed a linguistic task while listening to spoken or sung speech. Contrary to the hypothesis, left hemisphere specialization for linguistic processing was identical whether the sentences were spoken or sung. PMID:19425463

  7. Croll revisited: Why is the northern hemisphere warmer than the southern hemisphere?

    NASA Astrophysics Data System (ADS)

    Kang, Sarah M.; Seager, Richard; Frierson, Dargan M. W.; Liu, Xiaojuan

    2015-03-01

    The question of why, in the annual-mean, the northern hemisphere (NH) is warmer than the southern hemisphere (SH) is addressed, revisiting an 1870 paper by James Croll. We first show that ocean is warmer than land in general which, acting alone, would make the SH, with greater ocean fraction, warmer. Croll was aware of this and thought it was caused by greater specific humidity and greenhouse trapping over ocean than over land. However, for any given temperature, it is shown that greenhouse trapping is actually greater over land. Instead, oceans are warmer than land because of the smaller surface albedo. However, hemispheric differences in planetary albedo are negligible because the impact of differences in land-sea fraction are offset by the SH ocean and land reflecting more than their NH counterparts. In the absence of a role for albedo differences it is shown that, in agreement with Croll, northward cross-equatorial ocean heat transport (X-OHT) is critical for the warmer NH. This is examined in a simple box model based on the energy budget of each hemisphere. The hemispheric difference forced by X-OHT is enhanced by the positive water vapor-greenhouse feedback, and is partly compensated by the southward atmospheric energy transport. Due to uncertainties in the ocean data, a range of X-OHT is considered. A X-OHT of larger than 0.5 PW is needed to explain the warmer NH solely by X-OHT. For smaller X-OHT, a larger basic state greenhouse trapping in the NH, conceived as imposed by continental geometry, needs to be imposed. Numerical experiments with a GCM coupled to a slab ocean provide evidence that X-OHT is fundamentally important in determining the hemispheric differences in temperature. Therefore, despite some modifications to his theory, analysis of modern data confirms Croll's 140-year-old theory that the warmer NH is partly because of northward X-OHT.

  8. Inter-Hemispherical Currents for Realistic Model of Ionospheric Conductivity

    NASA Astrophysics Data System (ADS)

    Lyatsky, S.; Khazanov, G. V.

    2013-12-01

    We present results of modeling of the global 3-D ionosphere-magnetosphere current system including in addition to the R1 and R2 field-aligned currents also inter-hemispherical currents. The inter-hemispherical currents flow between Northern and Southern conjugate ionospheres in case of a North-South asymmetry in ionospheric conductivity in two hemispheres. These currents link together the ionospheric currents in two hemispheres, so the currents observed in one hemisphere can provide us with information about currents in the opposite hemisphere, which is especially important when their magnitude can not be obtained from direct observation (e.g., in Antarctica). In this study, we investigate the generation of the inter-hemispherical currents for several distributions of ionospheric conductivity in two hemispheres including a simplified model of ionospheric conductivity, which is important for better understanding of the expected distribution and magnitude of these currents, and a more realistic model of ionospheric conductivity, which is observed during magnetospheric substorms, when the geometry of the inter-hemispherical currents is more complicated. Simulation results show that the inter-hemispherical currents during substorms could play a very significant role, and neglecting these currents does not allow obtaining the correct picture of 3-D magnetosphere-ionosphere current system. These currents are an important part of 3-D field-aligned current system, and they are especially strong during summer-winter months, when they are comparable in magnitude with the R2 currents (about ~0.5 MA). Inter-hemispherical currents map. Left panel is related to Northern hemisphere, right panel to Southern. R1 and R2 currents are not shown; their locations are indicated by the red and blue dashed circles, respectively. The inter-hemispherical currents appear inside the auroral zone in the region of conductivity gradient. The currents in both hemispheres are equal in magnitude and

  9. On the receptivity problem for Goertler vortices: Vortex motions induced by wall roughness

    NASA Technical Reports Server (NTRS)

    Denier, James P.; Hall, Philip; Seddougui, Sharon

    1990-01-01

    The receptivity problem for Goertler vortices induced by wall roughness is investigated. The roughness is modelled by small amplitude perturbations to the curved wall over which the flow takes place. The amplitude of these perturbations is taken to be sufficiently small for the induced Goertler vortices to be described by linear theory. The roughness is assumed to vary in the spanwise direction on the boundary layer lengthscale, while in the flow direction the corresponding variation is on the lengthscale over which the wall curvature varies. In fact the latter condition can be relaxed to allow for a faster streamwise roughness variation so long as the variation does not become as fast as that in the spanwise direction. The function which describes the roughness is assumed to be such that its spanwise and streamwise dependences can be separated; this enables progress by taking Fourier or Laplace transforms where appropriate. The cases of isolated and distributed roughness elements are investigated and the coupling coefficient which relates the amplitude of the forcing and the induced vortex amplitude is found asymptotically in the small wavelength limit. It is shown that this coefficient is exponentially small in the latter limit so that it is unlikely that this mode can be stimulated directly by wall roughness. The situation at 0(1) wavelengths is quite different and this is investigated numerically for different forcing functions. It is found that an isolated roughness element induces a vortex field which grows within a wedge at a finite distance downstream of the element. However, immediately downstream of the obstacle the disturbed flow produced by the element decays in amplitude. The receptivity problem at larger Goertler numbers appropriate to relatively large wall curvature is discussed in detail.

  10. Hubble Spots Northern Hemispheric Clouds on Uranus

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Using visible light, astronomers for the first time this century have detected clouds in the northern hemisphere of Uranus. The newest images, taken July 31 and Aug. 1, 1997 with NASA Hubble Space Telescope's Wide Field and Planetary Camera 2, show banded structure and multiple clouds. Using these images, Dr. Heidi Hammel (Massachusetts Institute of Technology) and colleagues Wes Lockwood (Lowell Observatory) and Kathy Rages (NASA Ames Research Center) plan to measure the wind speeds in the northern hemisphere for the first time.

    Uranus is sometimes called the 'sideways' planet, because its rotation axis tipped more than 90 degrees from the planet's orbit around the Sun. The 'year' on Uranus lasts 84 Earth years, which creates extremely long seasons - winter in the northern hemisphere has lasted for nearly 20 years. Uranus has also been called bland and boring, because no clouds have been detectable in ground-based images of the planet. Even to the cameras of the Voyager spacecraft in 1986, Uranus presented a nearly uniform blank disk, and discrete clouds were detectable only in the southern hemisphere. Voyager flew over the planet's cloud tops near the dead of northern winter (when the northern hemisphere was completely shrouded in darkness).

    Spring has finally come to the northern hemisphere of Uranus. The newest images, both the visible-wavelength ones described here and those taken a few days earlier with the Near Infrared and Multi-Object Spectrometer (NICMOS) by Erich Karkoschka (University of Arizona), show a planet with banded structure and detectable clouds.

    Two images are shown here. The 'aqua' image (on the left) is taken at 5,470 Angstroms, which is near the human eye's peak response to wavelength. Color has been added to the image to show what a person on a spacecraft near Uranus might see. Little structure is evident at this wavelength, though with image-processing techniques, a small cloud can be seen near the planet's northern limb

  11. HUBBLE SPOTS NORTHERN HEMISPHERIC CLOUDS ON URANUS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Using visible light, astronomers for the first time this century have detected clouds in the northern hemisphere of Uranus. The newest images, taken July 31 and Aug. 1, 1997 with NASA Hubble Space Telescope's Wide Field and Planetary Camera 2, show banded structure and multiple clouds. Using these images, Dr. Heidi Hammel (Massachusetts Institute of Technology) and colleagues Wes Lockwood (Lowell Observatory) and Kathy Rages (NASA Ames Research Center) plan to measure the wind speeds in the northern hemisphere for the first time. Uranus is sometimes called the 'sideways' planet, because its rotation axis is tipped more than 90 degrees from the planet's orbit around the Sun. The 'year' on Uranus lasts 84 Earth years, which creates extremely long seasons - winter in the northern hemisphere has lasted for nearly 20 years. Uranus has also been called bland and boring, because no clouds have been detectable in ground-based images of the planet. Even to the cameras of the Voyager spacecraft in 1986, Uranus presented a nearly uniform blank disk, and discrete clouds were detectable only in the southern hemisphere. Voyager flew over the planet's cloud tops near the dead of northern winter (when the northern hemisphere was completely shrouded in darkness). Spring has finally come to the northern hemisphere of Uranus. The newest images, both the visible-wavelength ones described here and those taken a few days earlier with the Near Infrared and Multi-Object Spectrometer (NICMOS) by Erich Karkoschka (University of Arizona), show a planet with banded structure and detectable clouds. Two images are shown here. The 'aqua' image (on the left) is taken at 5,470 Angstroms, which is near the human eye's peak response to wavelength. Color has been added to the image to show what a person on a spacecraft near Uranus might see. Little structure is evident at this wavelength, though with image-processing techniques, a small cloud can be seen near the planet's northern limb (rightmost

  12. Hemispherical Capsule Implosions for Fast Ignition*

    NASA Astrophysics Data System (ADS)

    Hanson, D. L.; Vesey, R. A.; Sinars, D. B.; Adams, R. G.; Cuneo, M. E.; Porter, J. L.; Slutz, S. A.; Johnston, R. R.; Wenger, D. F.; Schroen, D. G.

    2003-10-01

    The fast ignitor approach to ICF ignition separates the fuel assembly and fast heating processes. After compressing the fuel with the main driver, the fuel is ignited using a focused electron or ion beam generated by a fast, ultra-high power laser pulse. This significantly relaxes the drive symmetry, energy, and shock timing requirements compared to hot spot ignition. A hemispherical capsule target is a fast ignitor geometry well-adapted to symmetric fuel compression by a single-ended z-pinch radiation drive. The hemispherical capsule implodes radially, constrained at its equator by a flat high-density surface (a special case of the spherical capsule "cone-focus" geometry). This glide plane is mounted on a hollow pedestal that provides a plasma-free, short-pulse laser path to the compressed fuel core region. In experiments on the Z accelerator at Sandia, we are studying implosions of 2.0-mm-diameter, 60-micron-thick hemispherical capsules in cylindrical secondary hohlraums heated to 90-100 eV from one end by a 120 TW wire-array z-pinch. Analysis of ZBL 6.7 keV point-projection backlighter images of pole-hot implosions in a tall secondary and 6.18 keV monochromatic crystal backlighter images of more symmetric implosions in a short secondary will be presented. We will also discuss progress on the development of a cryogenic liquid fuel target for this fast ignitor compression geometry. * Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  13. Phenological Changes in the Southern Hemisphere

    PubMed Central

    Chambers, Lynda E.; Altwegg, Res; Barbraud, Christophe; Barnard, Phoebe; Beaumont, Linda J.; Crawford, Robert J. M.; Durant, Joel M.; Hughes, Lesley; Keatley, Marie R.; Low, Matt; Morellato, Patricia C.; Poloczanska, Elvira S.; Ruoppolo, Valeria; Vanstreels, Ralph E. T.; Woehler, Eric J.; Wolfaardt, Anton C.

    2013-01-01

    Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand), South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias), although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa) and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially and logistically

  14. On the roughness measurement on knee prostheses.

    PubMed

    Jaber, Sami Abdel; Ruggiero, Alessandro; Battaglia, Santina; Affatato, Saverio

    2015-01-01

    The majority of total knee replacements currently implanted present an articulation composed of two metal parts, femoral and tibial components, between which there is a polyethylene insert serving as a bearing surface. The finishing surface of the metal components is a very important factor in minimizing the polyethylene wear rate and, later, the gradual production of metal and plastic debris. Considering the role of surface roughness on volumetric wear rates, the purpose of this study is to develop a protocol for the roughness characterization of total knee prosthesis (TKP) metal components, taking into consideration a limited number of points on each surface. Six mobile TKP of different sizes (three size 2 and three size 6) were tested on a knee joint simulator to compare the wear behavior of each group. After 2 million cycles the weight loss by the polyethylene inserts was measured with gravimetric method and the surface roughness of the metallic components was assessed in terms of average surface roughness, Ra, skewness, Rsk, and total roughness, Rt. Roughness measurement involved 29 points on each femoral condyle and 26 points on each metal tibial plate. The data collected has shown an increased roughness upon wear testing for both the investigated TKP sizes. No statistical differences were observed between the two groups for both the parameters Ra, Rsk, and Rt. The surface of all metallic components became more negatively skewed, indicating diminishing peaks. The various parameters were correlated to the volumetric loss using a linear regression analysis. PMID:25588764

  15. Thermal contact conductance of spherical, rough metals

    SciTech Connect

    Lambert, M.A.; Fletcher, L.S.

    1996-12-31

    Junction thermal conductance is an important consideration in such applications as thermally induced stresses in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, gas turbine and internal combustion engine cooling, and cryogenic liquid storage. A fundamental problem in analyzing and predicting junction thermal conductance is thermal contact conductance of non-flat, rough metals. Workable models have been previously derived for the limiting idealized cases of flat, rough and spherical, smooth surfaces. However, until now, no tractable models have been advanced for non-flat, rough surfaces (so called engineering surfaces) which are much more commonly dealt with in practice. The present investigation details the synthesis of previously derived models for macroscopically non-uniform thermal contact conductance and contact of non-flat, rough spheres, into a thermo-mechanical model, its refinement, and its presentation in an easily applied format. The present model is compared to representative experimental conductance results form the literature for stainless steel 304 with widely varying flatness deviation and roughness. Also included in the comparisons is a previous, often cited model for flat, rough metals to which the present model reduces in the limit of flat surfaces. The present model agrees well with the experimental results over the wide ranges of flatness deviation and roughness for which data was available. Conversely, the previous, well known model becomes increasingly overpredictive with increasing flatness deviation.

  16. Circular single domains in hemispherical Permalloy nanoclusters

    SciTech Connect

    Araujo, Clodoaldo I. L de Fonseca, Jakson M.; Sinnecker, João P.; Delatorre, Rafael G.; Garcia, Nicolas; Pasa, André A.

    2014-11-14

    We have studied ferromagnetic Permalloy clusters obtained by electrodeposition on n-type silicon. Magnetization measurements reveal hysteresis loops almost independent on temperature and very similar in shape to those obtained in nanodisks with diameter bigger than 150 nm. The spin configuration for the ground state, obtained by micromagnetic simulation, shows topological vortices with random chirality and polarization. This behavior in the small diameter clusters (∼80 nm) is attributed to the Dzyaloshinskii-Moriya interaction that arises in its hemispherical geometries. This magnetization behavior can be utilized to explain the magnetoresistance measured with magnetic field in plane and out of sample plane.

  17. Hemispheric asymmetries in reading Korean: task matters.

    PubMed

    Vaid, J; Park, K

    1997-06-01

    Native Korean readers were studied in a visual half-field paradigm. Subjects were to make speeded judgments on Hangul (syllabic) and Hanzza (logographic) scripts based on phonetic or visual properties of the stimuli. A task by visual field interaction was obtained indicating that, for both scripts, responses on the phonetic task were faster in the right visual field, whereas no visual field differences were found on the visual task. Script type did not interact with visual field. The results support a task-based account of hemispheric differences in verbal processing. PMID:9184098

  18. The genus Platychara from the Western Hemisphere

    USGS Publications Warehouse

    Peck, R.E.; Forester, R.M.

    1979-01-01

    The systematics of four species belonging to the genus Platychara (Charophyta) from the Western Hemisphere is discussed. Three of the species, as defined herein, occur in Cretaceous and Paleocene rocks from Mexico through South America. The type species, P. compressa (Peck and Reker) Grambast, also of Cretaceous and Paleocene age, is herein restricted to deposits north of Mexico. These latter restrictions geographically separate P. compressa and P. perlata as presently defined but the relationship between these two species is still uncertain. A new species, P. grambastii, is proposed for specimens from Maestrichtian sediments in Jamaica. ?? 1979.

  19. Turbulent flow in smooth and rough pipes.

    PubMed

    Allen, J J; Shockling, M A; Kunkel, G J; Smits, A J

    2007-03-15

    Recent experiments at Princeton University have revealed aspects of smooth pipe flow behaviour that suggest a more complex scaling than previously noted. In particular, the pressure gradient results yield a new friction factor relationship for smooth pipes, and the velocity profiles indicate the presence of a power-law region near the wall and, for Reynolds numbers greater than about 400x103 (R+>9x103), a logarithmic region further out. New experiments on a rough pipe with a honed surface finish with krms/D=19.4x10-6, over a Reynolds number range of 57x103-21x106, show that in the transitionally rough regime this surface follows an inflectional friction factor relationship rather than the monotonic relationship given in the Moody diagram. Outer-layer scaling of the mean velocity data and streamwise turbulence intensities for the rough pipe show excellent collapse and provide strong support for Townsend's outer-layer similarity hypothesis for rough-walled flows. The streamwise rough-wall spectra also agree well with the corresponding smooth-wall data. The pipe exhibited smooth behaviour for ks+ < or =3.5, which supports the suggestion that the original smooth pipe was indeed hydraulically smooth for ReD< or =24x106. The relationship between the velocity shift, DeltaU/utau, and the roughness Reynolds number, ks+, has been used to generalize the form of the transition from smooth to fully rough flow for an arbitrary relative roughness krms/D. These predictions apply for honed pipes when the separation of pipe diameter to roughness height is large, and they differ significantly from the traditional Moody curves. PMID:17244585

  20. Layering of ionic liquids on rough surfaces

    NASA Astrophysics Data System (ADS)

    Sheehan, Alexis; Jurado, L. Andres; Ramakrishna, Shivaprakash N.; Arcifa, Andrea; Rossi, Antonella; Spencer, Nicholas D.; Espinosa-Marzal, Rosa M.

    2016-02-01

    Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (<9 nm RMS) in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by atomic force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact.Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (<9 nm RMS) in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by atomic force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact. Electronic supplementary information (ESI) available: Optimized geometries and sizes for [HMIM] Ntf2, SEM images of the smooth and rough colloids, frequency of occurrence of layering in the resolved force-distance curves for all investigated systems with [HMIM] Ntf2, layer size and layering force measured with a sharp tip on mica for the same IL, and results of the kinetics experiments. See DOI: 10.1039/c5nr07805a

  1. The importance of wall-normal Reynolds stress in turbulent rough channel flows

    NASA Astrophysics Data System (ADS)

    Orlandi, P.

    2013-11-01

    In this paper, it is demonstrated by DNS of turbulent rough channels that a proportionality between widetilde{u}_2^' |_w (the wall-normal Reynolds stress widetilde{u}_2^' =< u_2^' 2} rangle ^{1/2} at the top of the roughness elements) and the roughness function does exist. This observation confirmed by experiments allows the derivation of a simple expression for the velocity profile in the log-region. This parameterization of rough walls through widetilde{u}_2^' |_w is suggested by the direct link between wall structures and partial ^2 widetilde{u_2^' }}^2/partial x^22. Identification of the wall structures, near smooth and different kinds of rough surfaces, demonstrates flow isotropization near rough walls, corroborated by profiles of partial ^2 widetilde{u_2^' }}^2/partial x^22, is depicted by visualizations of ∇2p. The relationship between the roughness function and widetilde{u}_2^' |_w allows the derivation of a new kind of Moody diagram, useful in the prediction of friction factors of rough flows at high Reynolds numbers.

  2. Non-linear boundary-layer receptivity due to distributed surface roughness

    NASA Technical Reports Server (NTRS)

    Amer, Tahani Reffet; Selby, Gregory V.

    1995-01-01

    The process by which a laminar boundary layer internalizes the external disturbances in the form of instability waves is known as boundary-layer receptivity. The objective of the present research was to determine the effect of acoustic excitation on boundary-layer receptivity for a flat plate with distributed variable-amplitude surface roughness through measurements with a hot-wire probe. Tollmien-Schlichting (T-S) mode shapes due to surface-roughness receptivity have also been determined, analyzed, and shown to be in agreement with theory and other experimental work. It has been shown that there is a linear relationship between the surface roughness and receptivity for certain roughness configurations with constant roughness wavelength. In addition, strong nonlinear receptivity effects exist for certain surface roughness configurations over a band where the surface roughness and T-S wavelength are matched. The results from the present experiment follow the trends predicted by theory and other experimental work for linear receptivity. In addition, the results show the existence of nonlinear receptivity effects for certain combinations of surface roughness elements.

  3. Non-linear boundary-layer receptivity due to distributed surface roughness

    NASA Technical Reports Server (NTRS)

    Amer, Tahani Reffet

    1995-01-01

    The process by which a laminar boundary layer internalizes the external disturbances in the form of instability waves is known as boundary-layer receptivity. The objective of the present research was to determine the effect of acoustic excitation on boundary-layer receptivity for a flat plate with distributed variable-amplitude surface roughness through measurements with a hot-wire probe. Tollmien-Schlichting mode shapes due to surface roughness receptivity have also been determined, analyzed, and shown to be in agreement with theory and other experimental work. It has been shown that there is a linear relationship between the surface roughness and receptivity for certain roughness configurations with constant roughness wavelength. In addition, strong non-linear receptivity effects exist for certain surface roughness configurations over a band where the surface roughness and T-S wavelength are matched. The results from the present experiment follow the trends predicted by theory and other experimental work for linear receptivity. In addition, the results show the existence of non-linear receptivity effects for certain combinations of surface roughness elements.

  4. Understanding EUV mask blank surface roughness induced LWR and associated roughness requirement

    SciTech Connect

    Yan, Pei-Yang; Zhang, Guojing; Gullickson, Eric M.; Goldberg, Kenneth A.; Benk, Markus P.

    2015-03-01

    Extreme ultraviolet lithography (EUVL) mask multi-layer (ML) blank surface roughness specification historically comes from blank defect inspection tool requirement. Later, new concerns on ML surface roughness induced wafer pattern line width roughness (LWR) arise. In this paper, we have studied wafer level pattern LWR as a function of EUVL mask surface roughness via High-NA Actinic Reticle Review Tool. We found that the blank surface roughness induced LWR at current blank roughness level is in the order of 0.5nm 3σ for NA=0.42 at the best focus. At defocus of ±40nm, the corresponding LWR will be 0.2nm higher. Further reducing EUVL mask blank surface roughness will increase the blank cost with limited benefit in improving the pattern LWR, provided that the intrinsic resist LWR is in the order of 1nm and above.

  5. Numerical Schemes for Rough Parabolic Equations

    SciTech Connect

    Deya, Aurelien

    2012-04-15

    This paper is devoted to the study of numerical approximation schemes for a class of parabolic equations on (0,1) perturbed by a non-linear rough signal. It is the continuation of Deya (Electron. J. Probab. 16:1489-1518, 2011) and Deya et al. (Probab. Theory Relat. Fields, to appear), where the existence and uniqueness of a solution has been established. The approach combines rough paths methods with standard considerations on discretizing stochastic PDEs. The results apply to a geometric 2-rough path, which covers the case of the multidimensional fractional Brownian motion with Hurst index H>1/3.

  6. Giant persistent photoconductivity in rough silicon nanomembranes.

    PubMed

    Feng, Ping; Mönch, Ingolf; Harazim, Stefan; Huang, Gaoshan; Mei, Yongfeng; Schmidt, Oliver G

    2009-10-01

    This paper reports the observation of giant persistent photoconductivity from rough Si nanomembranes. When exposed to light, the current in p-type Si nanomembranes is enhanced by roughly 3 orders of magnitude in comparison with that in the dark and can persist for days at a high conductive state after the light is switched off. An applied gate voltage can tune the persistent photocurrent and accelerate the response to light. By analyzing the band structure of the devices and the surfaces through various coatings, we attribute the observed effect to hole-localized regions in Si nanomembranes due to the rough surfaces, where light can activate the confined holes. PMID:19637888

  7. Nanoscale roughness micromilled silica evanescent refractometer.

    PubMed

    Carpenter, Lewis G; Cooper, Peter A; Holmes, Christopher; Gawith, Corin B E; Gates, James C; Smith, Peter G R

    2015-01-26

    We demonstrate machining of precision slots in silica with nanoscale roughness for applications in photonics. Using our in-house developed milling system we have achieved machined slots with surface roughness of 3.0 nm (Sa) and 17 µm depth of cut. This result represents eight times improvement in surface roughness and forty times increase in depth of cut than previously reported. We also demonstrate integration of these milled slots with UV-written waveguides and Bragg gratings to create optical refractometers, based on monitoring Fabry-Pérot spectral fringe changes. PMID:25835860

  8. Generation of nearly hemispherical and high gain azimuthally symmetric patterns with printed circuit antennas

    NASA Astrophysics Data System (ADS)

    Yang, Hung Yu; Alexopoulos, Nicolaos G.

    1987-08-01

    Patttern shaping techniques are discussed for printed circuit antennas such as microstrip dipoles and slot elements. Crossed printed circuit dipoles or a combination of a printed circuit dipole and a slot are employed. It is demonstrated that with the proper choice of substrate or substrate-superstrate parameters it is possible to generate: (1) nearly hemispherical patterns, (2) high-gain azimuthally symmetric patterns, and (3) nearly sec theta patterns.

  9. X-ray fluorescence from rough rocky surfaces of asteroids

    NASA Astrophysics Data System (ADS)

    Okada, T.

    2014-07-01

    X-ray fluorescence (XRF) from orbit is a frequently-used technique to determine the elemental composition of atmosphereless planetary bodies. So far, XRF observations have been conducted for asteroids by the Near-Earth Asteroid Rendezvous Shoemaker mission at (433) Eros [1] and the Hayabusa mission at (25143) Itokawa [2]. There has been difficulties to interpret the XRF data to derive the composition quantitatively. One of the reasons is the surface-roughness effect. We have investigated the XRF intensity influenced by a powdery surface as an analogue to fine regolith [3,4]. However, the surfaces of asteroids explored by the spacecraft at, e.g., (25143) Itokawa or (433) Eros, were not always covered with fine regolith but with pebbles or boulders. Thus, we have performed laboratory experiments to study the roughness effect for rocky surfaces to interpret the XRF observations of those asteroids and the observations of future missions. For the powdery surface, we have obtained the following results: 1) the XRF with lower energy is more effective for the same roughness; 2) the XRF intensity decreases for rougher surfaces but converges to a constant value almost 50--60 % of that of a flat surface; and 3) the XRF intensity decreases for larger phase angles, but does not change so for a varying incident angle when when the phase angle remains fixed. We started the experiments for rocky surfaces to investigate the elemental composition of natural unprepared rocks as well as ground rocks for past and future planetary missions. We prepared the basaltic rock samples with different surface roughness. The roughness of the rock surface is measured with a laser microscope to obtain the three-dimensional surface features and characterize the roughness in <10, 30, 60, 100-micron scales by a rectangular function as in our previous studies. We used the X-ray generator (RIGAKU RINT-2000) using an X-ray tube of Cr-target (V-filter) at 20 kV and 10mA, and detected with the Si-PIN diode

  10. Hemispheric specialization in dogs for processing different acoustic stimuli.

    PubMed

    Siniscalchi, Marcello; Quaranta, Angelo; Rogers, Lesley J

    2008-01-01

    Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions. PMID:18843371

  11. Inter-hemispheric temperature variability over the past millennium

    NASA Astrophysics Data System (ADS)

    Neukom, Raphael; Gergis, Joëlle; Karoly, David J.; Wanner, Heinz; Curran, Mark; Elbert, Julie; González-Rouco, Fidel; Linsley, Braddock K.; Moy, Andrew D.; Mundo, Ignacio; Raible, Christoph C.; Steig, Eric J.; van Ommen, Tas; Vance, Tessa; Villalba, Ricardo; Zinke, Jens; Frank, David

    2014-05-01

    The Earth's climate system is driven by a complex interplay of internal chaotic dynamics and natural and anthropogenic external forcing. Recent instrumental data have shown a remarkable degree of asynchronicity between Northern Hemisphere and Southern Hemisphere temperature fluctuations, thereby questioning the relative importance of internal versus external drivers of past as well as future climate variability. However, large-scale temperature reconstructions for the past millennium have focused on the Northern Hemisphere, limiting empirical assessments of inter-hemispheric variability on multi-decadal to centennial timescales. Here, we introduce a new millennial ensemble reconstruction of annually resolved temperature variations for the Southern Hemisphere based on an unprecedented network of terrestrial and oceanic palaeoclimate proxy records. In conjunction with an independent Northern Hemisphere temperature reconstruction ensemble, this record reveals an extended cold period (1594-1677) in both hemispheres but no globally coherent warm phase during the pre-industrial (1000-1850) era. The current (post-1974) warm phase is the only period of the past millennium where both hemispheres are likely to have experienced contemporaneous warm extremes. Our analysis of inter-hemispheric temperature variability in an ensemble of climate model simulations for the past millennium suggests that models tend to overemphasize Northern Hemisphere-Southern Hemisphere synchronicity by underestimating the role of internal ocean-atmosphere dynamics, particularly in the ocean-dominated Southern Hemisphere. Our results imply that climate system predictability on decadal to century timescales may be lower than expected based on assessments of external climate forcing and Northern Hemisphere temperature variations alone.

  12. A hemisphere array for non-invasive ultrasound brain therapy and surgery

    NASA Astrophysics Data System (ADS)

    Clement, G. T.; Sun, Jie; Giesecke, Tonia; Hynynen, Kullervo

    2000-12-01

    Ultrasound phased arrays may offer a method for non-invasive deep brain surgery through the skull. In this study a hemispherical phased array system is developed to test the feasibility of trans-skull surgery. The hemispherical shape is incorporated to maximize the penetration area on the skull surface, thus minimizing unwanted heating. Simulations of a 15 cm radius hemisphere divided into 11, 64, 228 and 512 elements are presented. It is determined that 64 elements are sufficient for correcting scattering and reflection caused by trans-skull propagation. An optimal operating frequency near 0.7 MHz is chosen for the array from numerical and experimental thermal gain measurements comparing the power between the transducer focus and the skull surface. A 0.665 MHz air-backed PZT array is constructed and evaluated. The array is used to focus ultrasound through an ex vivo human skull and the resulting fields are measured before and after phase correction of the transducer elements. Finally, to demonstrate the feasibility of trans-skull therapy, thermally induced lesions are produced through a human skull in fresh tissue placed at the ultrasound focus inside the skull.

  13. Hemispheric specialization for handwriting in right handers.

    PubMed

    Mack, L; Gonzalez Rothi, L J; Heilman, K M

    1993-01-01

    Hand preference may be related to either lateralized language, movement representations, or both. Anatomic and behavioral studies have revealed that whereas each hemisphere has motor control of the contralateral distal and proximal limb movements, this same hemisphere's control over the ipsilateral limb is limited to proximal movements. This differential proximal-versus-distal organization may have functional implications such that when right handers write with their left hand they must be use more proximal musculature than when they write with their right hand. If hand preference is related to lateralized movement representations, right handers may also use more proximal than distal movements when drawing with their left than with their right hand. If one uses distal musculature to write or draw, the elbow travels through space less than if one uses proximal musculature. We studied 12 right handers by having them write and draw with their right and left hands and measured the spatial amplitude of their elbow movements. We found that when writing or drawing, right handers moved their left elbow more than their right. These results suggest that it is the lateralized movement representations that may be primarily responsible for writing hand preference. PMID:8424864

  14. Flow past 2-D Hemispherical Rigid Canopies

    NASA Astrophysics Data System (ADS)

    Carnasciali, Maria-Isabel

    2013-11-01

    The flow past a 2-dimensional rigid hemispherical shape is investigated using PIV. Flow field measurements and images were generated with the use of a Thermoflow® apparatus. Results of this study are compared to prior work (APS DFD 2012 Session E9.00003) which employed CFD to investigate the flow in the near wake of hemispherical parachutes. The various sized gaps/open areas were positioned at distinct locations. The work presented here is part of a larger research project to investigate flow fields in deceleration devices and parachutes. Understanding the pitch-stability of parachutes is essential for accurate design and implementation of these deceleration devices but they present a difficult system to analyze. The flexibility of the parachute fabric results in large variations in the parachute geometry leading to complex fluid-structure interactions. Such flow, combined with flow through gaps and open areas, has been postulated to shed alternating vortices causing pitching/oscillations of the canopy. The results presented provide some insight into which geometric features affect vortex shedding and may enable the redesign of the baseline parachute to minimize instabilities.

  15. Effect of Surface Roughness on Hydrodynamic Bearings

    NASA Technical Reports Server (NTRS)

    Majumdar, B. C.; Hamrock, B. J.

    1981-01-01

    A theoretical analysis on the performance of hydrodynamic oil bearings is made considering surface roughness effect. The hydrodynamic as well as asperity contact load is found. The contact pressure was calculated with the assumption that the surface height distribution was Gaussian. The average Reynolds equation of partially lubricated surface was used to calculate hydrodynamic load. An analytical expression for average gap was found and was introduced to modify the average Reynolds equation. The resulting boundary value problem was then solved numerically by finite difference methods using the method of successive over relaxation. The pressure distribution and hydrodynamic load capacity of plane slider and journal bearings were calculated for various design data. The effects of attitude and roughness of surface on the bearing performance were shown. The results are compared with similar available solution of rough surface bearings. It is shown that: (1) the contribution of contact load is not significant; and (2) the hydrodynamic and contact load increase with surface roughness.

  16. Simplified models for mask roughness induced LER

    SciTech Connect

    McClinton, Brittany; Naulleau, Patrick

    2011-02-21

    The ITRS requires < 1.2nm line-edge roughness (LER) for the 22nm half-pitch node. Currently, we can consistently achieve only about 3nm LER. Further progress requires understanding the principle causes of LER. Much work has already been done on how both the resist and LER on the mask effect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane, and factor into LER limits. Presently, mask-roughness induced LER is studied via full 2D aerial image modeling and subsequent analysis of the resulting image. This method is time consuming and cumbersome. It is, therefore, the goal of this research to develop a useful 'rule-of-thumb' analytic model for mask roughness induced LER to expedite learning and understanding.

  17. Surface roughness effects on bidirectional reflectance

    NASA Technical Reports Server (NTRS)

    Smith, T. F.; Hering, R. G.

    1972-01-01

    An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. A facility capable of irradiating a sample from normal to grazing incidence and recording plane of incidence bidirectional reflectance measurements was developed. Samples consisting of glass, aluminum alloy, and stainless steel materials were selected for examination. Samples were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Mechanical surface roughness parameters, rms heights and rms slopes, evaluated from digitized surface profile measurements are less than 1.0 micrometers and 0.28, respectively. Rough surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle of incidence and wavelength of incident energy within the spectral range of 1 to 14 micrometers are reported. The Beckmann bidirectional reflectance model is compared with reflectance measurements to establish its usefulness in describing the magnitude and spatial distribution of energy reflected from rough surfaces.

  18. How supercontinents and superoceans affect seafloor roughness.

    PubMed

    Whittaker, Joanne M; Müller, R Dietmar; Roest, Walter R; Wessel, Paul; Smith, Walter H F

    2008-12-18

    Seafloor roughness varies considerably across the world's ocean basins and is fundamental to controlling the circulation and mixing of heat in the ocean and dissipating eddy kinetic energy. Models derived from analyses of active mid-ocean ridges suggest that ocean floor roughness depends on seafloor spreading rates, with rougher basement forming below a half-spreading rate threshold of 30-35 mm yr(-1) (refs 4, 5), as well as on the local interaction of mid-ocean ridges with mantle plumes or cold-spots. Here we present a global analysis of marine gravity-derived roughness, sediment thickness, seafloor isochrons and palaeo-spreading rates of Cretaceous to Cenozoic ridge flanks. Our analysis reveals that, after eliminating effects related to spreading rate and sediment thickness, residual roughness anomalies of 5-20 mGal remain over large swaths of ocean floor. We found that the roughness as a function of palaeo-spreading directions and isochron orientations indicates that most of the observed excess roughness is not related to spreading obliquity, as this effect is restricted to relatively rare occurrences of very high obliquity angles (>45 degrees ). Cretaceous Atlantic ocean floor, formed over mantle previously overlain by the Pangaea supercontinent, displays anomalously low roughness away from mantle plumes and is independent of spreading rates. We attribute this observation to a sub-Pangaean supercontinental mantle temperature anomaly leading to slightly thicker than normal Late Jurassic and Cretaceous Atlantic crust, reduced brittle fracturing and smoother basement relief. In contrast, ocean crust formed above Pacific superswells, probably reflecting metasomatized lithosphere underlain by mantle at only slightly elevated temperatures, is not associated with basement roughness anomalies. These results highlight a fundamental difference in the nature of large-scale mantle upwellings below supercontinents and superoceans, and their impact on oceanic crustal

  19. Initiative learning algorithm based on rough set

    NASA Astrophysics Data System (ADS)

    Wang, Guoyin; He, Xiao

    2003-03-01

    Rough set theory is emerging as a new tool for dealing with fuzzy and uncertain data. In this paper, a theory is developed to express, measure and process uncertain information and uncertain knowledge based on our result about the uncertainty measure of decision tables and decision rule systems. Based on Skowron"s propositional default rule generation algorithm, we develop an initiative learning model with rough set based initiative rule generation algorithm. Simulation results illustrate its efficiency.

  20. Predicting bed form roughness: the influence of lee side angle

    NASA Astrophysics Data System (ADS)

    Lefebvre, Alice; Winter, Christian

    2016-04-01

    Flow transverse bedforms (ripples and dunes) are ubiquitous in rivers and coastal seas. Local hydrodynamics and transport conditions depend on the size and geometry of these bedforms, as they constitute roughness elements at the bed. Bedform influence on flow energy must be considered for the understanding of flow dynamics, and in the development and application of numerical models. Common estimations or predictors of form roughness (friction factors) are based mostly on data of steep bedforms (with angle-of-repose lee slopes), and described by highly simplified bedform dimensions (heights and lengths). However, natural bedforms often are not steep, and differ in form and hydraulic effect relative to idealised bedforms. Based on systematic numerical model experiments, this study shows how the hydraulic effect of bedforms depends on the flow structure behind bedforms, which is determined by the bedform lee side angle, aspect ratio and relative height. Simulations reveal that flow separation behind bedform crests and, thus, a hydraulic effect is induced at lee side angles steeper than 11 to 18° depending on relative height, and that a fully developed flow separation zone exists only over bedforms with a lee side angle steeper than 24°. Furthermore, the hydraulic effect of bedforms with varying lee side angle is evaluated and a reduction function to common friction factors is proposed. A function is also developed for the Nikuradse roughness (k s), and a new equation is proposed which directly relates k s to bedform relative height, aspect ratio and lee side angle.

  1. Roughness Based Crossflow Transition Control: A Computational Assessment

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; Streett, Craig L.; Carpenter, Mark H.

    2009-01-01

    A combination of parabolized stability equations and secondary instability theory has been applied to a low-speed swept airfoil model with a chord Reynolds number of 7.15 million, with the goals of (i) evaluating this methodology in the context of transition prediction for a known configuration for which roughness based crossflow transition control has been demonstrated under flight conditions and (ii) of analyzing the mechanism of transition delay via the introduction of discrete roughness elements (DRE). Roughness based transition control involves controlled seeding of suitable, subdominant crossflow modes, so as to weaken the growth of naturally occurring, linearly more unstable crossflow modes. Therefore, a synthesis of receptivity, linear and nonlinear growth of stationary crossflow disturbances, and the ensuing development of high frequency secondary instabilities is desirable to understand the experimentally observed transition behavior. With further validation, such higher fidelity prediction methodology could be utilized to assess the potential for crossflow transition control at even higher Reynolds numbers, where experimental data is currently unavailable.

  2. Comparison of aerodynamically and model-derived roughness lengths (zo) over diverse surfaces, central Mojave Desert, California, USA

    USGS Publications Warehouse

    MacKinnon, D.J.; Clow, G.D.; Tigges, R.K.; Reynolds, R.L.; Chavez, P.S., Jr.

    2004-01-01

    The vulnerability of dryland surfaces to wind erosion depends importantly on the absence or the presence and character of surface roughness elements, such as plants, clasts, and topographic irregularities that diminish wind speed near the surface. A model for the friction velocity ratio has been developed to account for wind sheltering by many different types of co-existing roughness elements. Such conditions typify a monitored area in the central Mojave Desert, California, that experiences frequent sand movement and dust emission. Two additional models are used to convert the friction velocity ratio to the surface roughness length (zo) for momentum. To calculate roughness lengths from these models, measurements were made at 11 sites within the monitored area to characterize the surface roughness element. Measurements included (1) the number of roughness species (e.g., plants, small-scale topography, clasts), and their associated heights and widths, (2) spacing among species, and (3) vegetation porosity (a measurement of the spatial distribution of woody elements of a plant). Documented or estimated values of drag coefficients for different species were included in the modeling. At these sites, wind-speed profiles were measured during periods of neutral atmospheric stability using three 9-m towers with three or four calibrated anemometers on each. Modeled roughness lengths show a close correspondence (correlation coefficient, 0.84-0.86) to the aerodynamically determined values at the field sites. The geometric properties of the roughness elements in the model are amenable to measurement at much higher temporal and spatial resolutions using remote-sensing techniques than can be accomplished through laborious ground-based methods. A remote-sensing approach to acquire values of the modeled roughness length is particularly important for the development of linked surface/atmosphere wind-erosion models sensitive to climate variability and land-use changes in areas such

  3. Slip and accommodation coefficients from rarefaction and roughness in rotating microscale disk flows

    NASA Astrophysics Data System (ADS)

    Blanchard, Danny; Ligrani, Phil

    2007-06-01

    Accommodation coefficients are determined from experimental results and analysis based on the Navier-Stokes equations for rotation-induced flows in C-shaped fluid chamber passages formed between a rotating disk and a stationary surface. A first-order boundary condition is used to model the slip flow. The fluid chamber passage height ranges from 6.85to29.2μm to give Knudsen numbers from 0.0025 to 0.031 for air and helium. In all cases, roughness size is large compared to molecular mean free path. The unique method presented for deducing tangential momentum accommodation coefficients gives values with less uncertainty compared to procedures that rely on flows in stationary tubes and channels. When channel height is defined at the tops of the roughness elements, slip velocity magnitudes and associated accommodation coefficients are a result of rarefaction at solid-gas interfaces and shear at the gas-gas interfaces. With this arrangement, tangential accommodation coefficients obtained with this approach decrease, and slip velocity magnitudes increase, at a particular value of Knudsen number, as the level of surface roughness increases. At values of the mean roughness height greater than 500nm, accommodation coefficients then appear to be lower in air flows than in helium flows, when compared for a particular roughness configuration. When channel height is defined midway between the crests and troughs of the roughness elements, nondimensional pressure rise data show little or no dependence on the level of disk surface roughness and working fluid. With this arrangement, slip is largely independent of surface roughness magnitude and mostly due to rarefaction, provided the appropriate channel height is chosen to define the roughness height.

  4. Topographic roughness of the northern high latitudes of Mercury from MESSENGER Laser Altimeter data

    NASA Astrophysics Data System (ADS)

    Fa, Wenzhe; Cai, Yuzhen; Xiao, Zhiyong; Tian, Wei

    2016-04-01

    We investigated topographic roughness for the northern hemisphere (>45°N) of Mercury using high-resolution topography data acquired by the Mercury Laser Altimeter (MLA) on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Our results show that there are distinct differences in the bidirectional slope and root-mean-square (RMS) height among smooth plains (SP), intercrater plains (ICP), and heavily cratered terrain (HCT), and that the ratios of the bidirectional slope and RMS height among the three geologic units are both about 1:2:2.4. Most of Mercury's surface exhibits fractal-like behavior on the basis of the linearity in the deviograms, with median Hurst exponents of 0.66, 0.80, and 0.81 for SP, ICP, and HCT, respectively. The median differential slope map shows that smooth plains are smooth at kilometer scale and become rough at hectometer scale, but they are always rougher than lunar maria at the scales studied. In contrast, intercrater plains and heavily cratered terrain are rough at kilometer scale and smooth at hectometer scale, and they are rougher than lunar highlands at scale <˜2 km but smoother at >˜2 km. We suggest that these scale-dependent roughness characteristics are mainly caused by the difference in density and shape of impact craters between Mercury and the Moon.

  5. Hemisphere asymmetry in parasympathetic control of the heart.

    PubMed

    Wittling, W; Block, A; Genzel, S; Schweiger, E

    1998-05-01

    Hemisphere asymmetry in the control of parasympathetic outflow to the sino-atrial node of the heart was studied in healthy human subjects using lateralized film presentation for selective sensory stimulation of the hemispheres and power spectral analysis of heart rate variability as a measure of vagal tone. There was a clear and consistent left hemisphere predominance in the control of parasympathetic modulation of cardiac activity which cannot be attributed to differences in emotional processing. Supplementing previous findings of our research group, the present study indicates that control of autonomic cardiac activity at the level of the cerebral cortex seems to be characterized by a division of responsibility between both hemispheres, sympathetic activity being mainly controlled by the right hemisphere and parasympathetic activity being under the left hemisphere's main control. PMID:9699952

  6. Paleoceanography. Antarctic role in Northern Hemisphere glaciation.

    PubMed

    Woodard, Stella C; Rosenthal, Yair; Miller, Kenneth G; Wright, James D; Chiu, Beverly K; Lawrence, Kira T

    2014-11-14

    Earth's climate underwent a major transition from the warmth of the late Pliocene, when global surface temperatures were ~2° to 3°C higher than today, to extensive Northern Hemisphere glaciation (NHG) ~2.73 million years ago (Ma). We show that North Pacific deep waters were substantially colder (4°C) and probably fresher than the North Atlantic Deep Water before the intensification of NHG. At ~2.73 Ma, the Atlantic-Pacific temperature gradient was reduced to <1°C, suggesting the initiation of stronger heat transfer from the North Atlantic to the deep Pacific. We posit that increased glaciation of Antarctica, deduced from the 21 ± 10-meter sea-level fall from 3.15 to 2.75 Ma, and the development of a strong polar halocline fundamentally altered deep ocean circulation, which enhanced interhemispheric heat and salt transport, thereby contributing to NHG. PMID:25342658

  7. Voyager 1 Jupiter Southern Hemisphere Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This movie shows a portion of Jupiter in the southern hemisphere over 17Jupiter days. Above the white belt, notice the series of atmospheric vortices headed west. Even these early approach frames show wild dynamics in the roiling environment south of the white belt. Notice the small tumbling white cloud near the center.

    As Voyager 1 approached Jupiter in 1979, it took images of the planet at regular intervals. This sequence is made from 17 images taken once every Jupiter rotation period (about 10 hours). These images were acquired in the Blue filter around Feb. 1, 1979. The spacecraft was about 37 million kilometers from Jupiter at that time.

    This time-lapse movie was produced at JPL by the Image Processing Laboratory in 1979.

  8. Dynamics of charged hemispherical soap bubbles

    NASA Astrophysics Data System (ADS)

    Hilton, J. E.; van der Net, A.

    2009-04-01

    Raising the potential of a charged hemispherical soap bubble over a critical limit causes deformation of the bubble into a cone and ejection of a charged liquid jet. This is followed by a mode which has not previously been observed in bubbles, in which a long cylindrical liquid film column is created and collapses due to a Rayleigh-Plateau instability creating child bubbles. We show that the formation of the column and subsequent creation of child bubbles is due to a drop in potential caused by the ejection of charge from the system via the jet. Similar dynamics may occur in microscopic charged liquid droplets (electrospray processes), causing the creation of daughter droplets and long liquid spindles.

  9. A simple EHF hemispheric coverage antenna

    NASA Astrophysics Data System (ADS)

    Lee, J. C.

    1994-08-01

    A circulary polarized, axially symmetric, wide-beam radiator is required in many applications, including TT&C for UAV's and satellites. This report discusses some existing wide-beam antenna designs including divergent lenses and reflectors and introduces a new antenna design. Using a simple dielectric ring in conjunction with a dielectric loaded circular waveguide opening, a near ideal, axially symmetric, hemispheric coverage antenna with circular polarization of good axial ratio and wide-band impedance match is realized. Mechanically, the antenna is small, lightweight, and low cost. The dielectric used is the common Rexolite. Since no lossy materials or resonant scatterers are used, the antenna performance is inherently broadband and low loss. A K sub a-band prototype as well as compact designs for both Q- and K-bands are described.

  10. Interpretation of recent Southern Hemisphere climate change.

    PubMed

    Thompson, David W J; Solomon, Susan

    2002-05-01

    Climate variability in the high-latitude Southern Hemisphere (SH) is dominated by the SH annular mode, a large-scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. We present evidence that recent trends in the SH tropospheric circulation can be interpreted as a bias toward the high-index polarity of this pattern, with stronger westerly flow encircling the polar cap. It is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex, which are due largely to photochemical ozone losses. During the summer-fall season, the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia and to the cooling over eastern Antarctica and the Antarctic plateau. PMID:11988571

  11. Fault slip distribution and fault roughness

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Renard, François; Schmittbuhl, Jean; Bouchon, Michel; Brodsky, Emily E.

    2011-11-01

    We present analysis of the spatial correlations of seismological slip maps and fault topography roughness, illuminating their identical self-affine exponent. Though the complexity of the coseismic spatial slip distribution can be intuitively associated with geometrical or stress heterogeneities along the fault surface, this has never been demonstrated. Based on new measurements of fault surface topography and on statistical analyses of kinematic inversions of slip maps, we propose a model, which quantitatively characterizes the link between slip distribution and fault surface roughness. Our approach can be divided into two complementary steps: (i) Using a numerical computation, we estimate the influence of fault roughness on the frictional strength (pre-stress). We model a fault as a rough interface where elastic asperities are squeezed. The Hurst exponent ?, characterizing the self-affinity of the frictional strength field, approaches ?, where ? is the roughness exponent of the fault surface in the direction of slip. (ii) Using a quasi-static model of fault propagation, which includes the effect of long-range elastic interactions and spatial correlations in the frictional strength, the spatial slip correlation is observed to scale as ?, where ? represents the Hurst exponent of the slip distribution. Under the assumption that the origin of the spatial fluctuations in frictional strength along faults is the elastic squeeze of fault asperities, we show that self-affine geometrical properties of fault surface roughness control slip correlations and that ?. Given that ? for a wide range of faults (various accumulated displacement, host rock and slip movement), we predict that ?. Even if our quasi-static fault model is more relevant for creeping faults, the spatial slip correlations observed are consistent with those of seismological slip maps. A consequence is that the self-affinity property of slip roughness may be explained by fault geometry without considering

  12. The Right Hemisphere in Esthetic Perception

    PubMed Central

    Bromberger, Bianca; Sternschein, Rebecca; Widick, Page; Smith, William; Chatterjee, Anjan

    2011-01-01

    Little about the neuropsychology of art perception and evaluation is known. Most neuropsychological approaches to art have focused on art production and have been anecdotal and qualitative. The field is in desperate need of quantitative methods if it is to advance. Here, we combine a quantitative approach to the assessment of art with modern voxel-lesion-symptom-mapping methods to determine brain–behavior relationships in art perception. We hypothesized that perception of different attributes of art are likely to be disrupted by damage to different regions of the brain. Twenty participants with right hemisphere damage were given the Assessment of Art Attributes, which is designed to quantify judgments of descriptive attributes of visual art. Each participant rated 24 paintings on 6 conceptual attributes (depictive accuracy, abstractness, emotion, symbolism, realism, and animacy) and 6 perceptual attributes (depth, color temperature, color saturation, balance, stroke, and simplicity) and their interest in and preference for these paintings. Deviation scores were obtained for each brain-damaged participant for each attribute based on correlations with group average ratings from 30 age-matched healthy participants. Right hemisphere damage affected participants’ judgments of abstractness, accuracy, and stroke quality. Damage to areas within different parts of the frontal parietal and lateral temporal cortices produced deviation in judgments in four of six conceptual attributes (abstractness, symbolism, realism, and animacy). Of the formal attributes, only depth was affected by inferior prefrontal damage. No areas of brain damage were associated with deviations in interestingness or preference judgments. The perception of conceptual and formal attributes in artwork may in part dissociate from each other and from evaluative judgments. More generally, this approach demonstrates the feasibility of quantitative approaches to the neuropsychology of art. PMID:22016728

  13. Hemispherical Resonator Gyro: an IRU for Cassini

    NASA Astrophysics Data System (ADS)

    Litty, Edward C.; Gresham, Lennor L.; Toole, Patrick A.; Beisecker, Debra A.

    1996-10-01

    The JPL Inertial Reference Unit (IRU) is the single most sophisticated assembly on the Cassini spacecraft. At the core of the IRU is the state-of-the-art, Litton Hemispherical Resonator Gyro (HRG). Launched in October 1997, Cassini's trajectory utilizes gravity assist maneuvers around Venus (two), Earth, and Jupiter over a seven year period, arriving at Saturn in June 2004. Its tour of the Saturnian system will last an additional four years. Although the Stellar Reference Unit (SRU) provides the ultimate reference for the spacecraft Attitude and Articulation Control System (AACS) and can be used to control the spacecraft under benign conditions, the Cassini IRU is essential during maneuvers and fault recovery operations, and for precision attitude stabilization during science data acquisition. Therefore, IRU reliability over the long Cassini mission is a critical concern. Following an extensive evaluation of possible alternatives, the Hemispherical Resonator Gyro (HRG) based IRU developed by Litton Guidance and Control Systems, was chosen for the Cassini mission. The HRG is an attitude rate sensor that has no physical wear-out mechanisms. Based on a principle first described by G. H. Bryan (1890) in his paper, 'On Beats in the Vibrations of a Revolving Cylinder or Bell', the HRG is created by vibrating a quartz resonator. This paper discusses the theory and modifications required to the design of the standard Space Inertial Reference Unit to adapt it to meet the requirements of the Cassini mission and the AACS interface. The Cassini mission is the first use of an IRU for a deep space planetary mission that does not use a spun-mass sensor.

  14. The right hemisphere in esthetic perception.

    PubMed

    Bromberger, Bianca; Sternschein, Rebecca; Widick, Page; Smith, William; Chatterjee, Anjan

    2011-01-01

    Little about the neuropsychology of art perception and evaluation is known. Most neuropsychological approaches to art have focused on art production and have been anecdotal and qualitative. The field is in desperate need of quantitative methods if it is to advance. Here, we combine a quantitative approach to the assessment of art with modern voxel-lesion-symptom-mapping methods to determine brain-behavior relationships in art perception. We hypothesized that perception of different attributes of art are likely to be disrupted by damage to different regions of the brain. Twenty participants with right hemisphere damage were given the Assessment of Art Attributes, which is designed to quantify judgments of descriptive attributes of visual art. Each participant rated 24 paintings on 6 conceptual attributes (depictive accuracy, abstractness, emotion, symbolism, realism, and animacy) and 6 perceptual attributes (depth, color temperature, color saturation, balance, stroke, and simplicity) and their interest in and preference for these paintings. Deviation scores were obtained for each brain-damaged participant for each attribute based on correlations with group average ratings from 30 age-matched healthy participants. Right hemisphere damage affected participants' judgments of abstractness, accuracy, and stroke quality. Damage to areas within different parts of the frontal parietal and lateral temporal cortices produced deviation in judgments in four of six conceptual attributes (abstractness, symbolism, realism, and animacy). Of the formal attributes, only depth was affected by inferior prefrontal damage. No areas of brain damage were associated with deviations in interestingness or preference judgments. The perception of conceptual and formal attributes in artwork may in part dissociate from each other and from evaluative judgments. More generally, this approach demonstrates the feasibility of quantitative approaches to the neuropsychology of art. PMID:22016728

  15. Hemispheric asymmetries of the Venus plasma environment

    NASA Astrophysics Data System (ADS)

    Jarvinen, R.; Kallio, E.; Dyadechkin, S.

    2013-07-01

    We study the Venus-solar wind interaction and the hemispheric asymmetries of the Venus plasma environment in the global HYB-Venus hybrid simulation. We concentrate especially on the role of the flow-aligned interplanetary magnetic field (IMF) component (i.e., the Parker spiral angle or the IMF cone angle) and analyze the dawn-dusk and Esw asymmetries between four magnetic quadrants around Venus. Using the simulation model, we study two upstream condition cases in detail: the perpendicular IMF to the solar wind flow case and the nominal Parker spiral case (dominant flow-aligned IMF component). Several differences and similarities were found in these two simulation runs. Common features of the Venus plasma environment between the two cases include asymmetric magnetic barrier and tail lobes and asymmetric planetary ion escape in the direction of the solar wind convection electric field. Further, protons of planetary origin and of solar wind origin were found to follow similar velocity patterns in the Venus plasma wake in both cases. The differences when the IMF flow-aligned component is dominating compared to the perpendicular IMF case, the so-called (magnetic) dawn-dusk asymmetries, include the parallel bow shock and the foreshock region, the asymmetric magnetic barrier, the asymmetric tail current system, and the asymmetric central tail current sheet. Further, the escaping planetary H+ and O+ ion fluxes are concentrated more on the hemisphere of the parallel bow shock. When interpreting in situ plasma and magnetic observations from Venus, the features of at least these two basic IMF configurations should be considered.

  16. Particle transport and adjustments of the boundary layer over rough surfaces with an unrestricted, upwind supply of sediment

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl

    1998-10-01

    Most natural surfaces containing non-erodible roughness elements are considerably more complex than those studied in modelling exercises and wind tunnel simulations. Unlike idealized roughness elements, which are uniform in size, shape (i.e., spheres or cylinders) and spacing, natural elements are challenging to measure in 3-dimensional space. Similarly, most deflation lag surfaces, such those as found on sandar and beaches, are spatially heterogeneous open systems in which sediment transport from an external supply is very likely. The development of irregular deflation lag surfaces, and the transport of sediment over these surfaces from an upwind source of sediment, was studied in a series of wind tunnel simulations. Surfaces prepared with crushed gravel and natural beach shingle respond conservatively in terms of the adjustment to the deflation and deposition of sediment. Deflation lag surfaces, prepared with no spacing between the roughness elements (i.e., close packed), demonstrate little to no change in coverage with the introduction of particles from an upwind source. Neither the element type nor the friction velocity affect this outcome. As the center-to-center element spacing increases to 60 mm, infilling of the lag surface eventually is observed, with the element coverage reduced by a factor between 2 and 4. For a given threshold ratio ( Rt), the roughness density ( λ) is smaller than observed in previous simulation studies based on idealized roughness elements.

  17. An analytical study of the effects of surface roughness on a compressible turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Khan, Z. H.

    1983-12-01

    A previous study on the effect of surface roughness on the turbulent boundary layer, using a FORTRAN code, ITRACT, solved for the characteristics of a laminar, transitional and turbulent boundary layer on smooth surfaces. The present study investigates the influence of surface roughness on a compressible turbulent boundary layer and then extends the usefulness of ITRACT by including in it the optional capability of rough-surface boundary-layer calculations. Surface roughness was represented by distributed sources and sinks in the appropriate governing equations. The most important term is a sink term in the mean momentum equation, representing the form drag due to the roughness element. Governing boundary-layer equations for continuity, momentum, and energy were derived in a form to account for blockage effects due to roughness elements. The modified governing equations were then transformed using Probstein-Elliott and Levy-Lees transformations. The resulting equations, with appropriate boundary conditions, were solved by finite-difference techniques to determine the nondimensional velocity components and temperature at a finite number of nodes in the boundary-layer flow field.

  18. Effect on surface roughness of zerodur material in atmospheric pressure plasma jet processing

    NASA Astrophysics Data System (ADS)

    Jin, H. L.; Wang, B.; Zhang, F. H.

    2010-10-01

    Zerodur material is considered as the ideal material in the high performance optic systems because of its excellent thermal stability characteristics. This paper deals with the impacting factors on the zerodur material surface roughness during atmospheric pressure plasma jet(APPJ) processing. At first, based on multiphase and multi-component in zerodur material, the effect on the zerodur surface chemical components and surface roughness is studied when the element contained Si is etched during the chemical machining process. The change of surface microcosmic topography is observed, it is proved that the technology of atmospheric pressure plasma jet can modify the surface roughness of zerodur material. Moreover, in consideration of the re-deposition phenomenon in the machining process, the composition of the re-deposition are studied and the genesis of the re-deposition were analysed. Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray spectrometry (EDX) were utilized to obtain the elemental composition of the sample powder residuum on zerodur surface. The relationship between substrate roughness and the process parameters is established based on the experimental results. Experimental results indicate that it is beneficial to add certain amount O2 to modify the surface roughness of zerodur material. This finding provides an important basis for the improvement of surface roughness in APPJ of zerodur material.

  19. Effect of plate roughness on the field near RPC plates

    NASA Astrophysics Data System (ADS)

    Jash, A.; Majumdar, N.; Mukhopadhyay, S.; Chattopadhyay, S.

    2016-06-01

    The inner surfaces of the electrodes encompassing the gas volume of a Resistive Plate Chamber (RPC) have been found to exhibit asperities with, grossly, three kind of features. The desired uniform electric field within the gas volume of RPC is expected to be affected due to the presence of these asperities, which will eventually affect the final response from the detector. In this work, an attempt has been made to model the highly complex roughness of the electrode surfaces and compute its effect on the electrostatic field within RPC gas chamber. The calculations have been performed numerically using Finite Element Method (FEM) and Boundary Element Method (BEM) and the two methods have been compared in this context.

  20. An Experimental Study of Roughness-Induced Instabilities in a Supersonic Boundary Layer

    NASA Technical Reports Server (NTRS)

    Kegerise, Michael A.; King, Rudolph A.; Choudhari, Meelan; Li, Fei; Norris, Andrew

    2014-01-01

    Progress on an experimental study of laminar-to-turbulent transition induced by an isolated roughness element in a supersonic laminar boundary layer is reported in this paper. Here, the primary focus is on the effects of roughness planform shape on the instability and transition characteristics. Four different roughness planform shapes were considered (a diamond, a circle, a right triangle, and a 45 degree fence) and the height and width of each one was held fixed so that a consistent frontal area was presented to the oncoming boundary layer. The nominal roughness Reynolds number was 462 and the ratio of the roughness height to the boundary layer thickness was 0.48. Detailed flow- field surveys in the wake of each geometry were performed via hot-wire anemometry. High- and low-speed streaks were observed in the wake of each roughness geometry, and the modified mean flow associated with these streak structures was found to support a single dominant convective instability mode. For the symmetric planform shapes - the diamond and circular planforms - the instability characteristics (mode shapes, growth rates, and frequencies) were found to be similar. For the asymmetric planform shapes - the right-triangle and 45 degree fence planforms - the mode shapes were asymmetrically distributed about the roughness-wake centerline. The instability growth rates for the asymmetric planforms were lower than those for the symmetric planforms and therefore, transition onset was delayed relative to the symmetric planforms.

  1. Direct numerical simulation of a turbulent pipe with systematically varied three-dimensional roughness

    NASA Astrophysics Data System (ADS)

    Chan, Leon; MacDonald, Michael; Chung, Daniel; Hutchins, Nicholas; Ooi, Andrew

    2014-11-01

    Direct Numerical Simulations (DNS) are conducted at low to medium Reynolds numbers for a turbulent pipe flow with roughness. The roughness, which is comprised of three-dimensional sinusoidal elements, causes a downward shift in the mean velocity profile known as the Hama roughness function ΔU+ . In engineering applications, ΔU+ (which is related to the coefficient of drag Cf) is an important parameter as it is used to quantify the increase in drag and the decrease in efficiency. To have a better understanding of roughness and how it affects the flow, a range of numerical studies were conducted where the roughness height h+, wavelength λ+ and Reynolds number of the flow are varied. For the range of cases simulated, it is found that the roughness average height ka+ (which is proportional to h+) is strongly correlated to the roughness function ΔU+ whereas λ+ has a weaker influence on the flow. Results from simulations of more complicated surfaces comprised of two superimposed modes of different wavelength are also presented. Analysis of the turbulence statistics convincingly supports Townsend's outer-layer hypothesis for all of the cases simulated.

  2. Roughness-induced generation of crossflow vortices in three-dimensional boundary layers

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan

    1993-01-01

    The receptivity theory of Goldstein and Ruban is extended within the nonasymptotic (quasi-parallel) framework of Zavol'skii et al to predict the roughness-induced generation of stationary and nonstationary instability waves in three-dimensional, incompressible boundary layers. The influence of acoustic-wave orientation, as well as that of different types of roughness geometries, including isolated roughness elements, periodic arrays, and two-dimensional lattices of compact roughness shapes, as well as random, but spatially homogeneous roughness distributions, is examined. The parametric study for the Falkner-Skan-Cooke family of boundary layers supports our earlier conjecture that the initial amplitudes of roughness-induced stationary vortices are likely to be significantly larger than the amplitudes of similarly induced nonstationary vortices in the presence of acoustic disturbances in the free stream. Maximum unsteady receptivity occurs when the acoustic velocity fluctuation is aligned with the wavenumber vector of the unsteady vortex mode. On the other hand, roughness arrays that are oriented somewhere close to the group velocity direction are likely to produce higher instability amplitudes. Limitations of the nonasymptotic theory are discussed, and future work is suggested.

  3. Correlation of Windspeed and Antarctic Surface Roughness

    NASA Astrophysics Data System (ADS)

    Stockham, Mark; Anita Collaboration

    2015-04-01

    When electromagnetic waves interact with a media interface the transmitted and reflected portions of the incoming wave depend on the incident angle of the wave and wavelength (as well as the material properties of the media). The roughness of the surface of Antarctica affects the radio frequency signals received by airborne experiments, such as the balloon-borne experiment ANITA (ANtarctic Impulsive Transient Antenna) which observes the reflected radio waves from cosmic ray-induced extensive air showers (EAS). Roughness of a given scale can cause decoherence of the reflected signal and is an important effect to understand when estimating the amplitude of the incoming wave based on the reflected wave. It is challenging to get a survey of surface roughness over many of the areas that these experiments are likely to pass over. Correlating historical wind speed records with statistical roughness as observed by the backscatter of satellite [Rémy F, Parouty S. Remote Sensing. 2009] and airborne experiments operating at different frequencies can possibly be used to predict time-dependent surface roughness with surface wind speed as the input. These correlations will be presented for a variety of areas on the Antarctic ice shelf. NASA Grant NNX11AC47G.

  4. Interfacial roughness in ceramic matrix composites

    SciTech Connect

    Jero, P.D.; Parthasarathy, T.A.; Kerans, R.J.

    1992-08-01

    Recent work using push-out and push-back tests has shown that interfacial roughness contributes substantially to the sliding friction in at least some ceramic matrix composites (CMC's). Other work examining frictional heating of CMC's during cyclic fatigue has shown the important role that interfacial friction plays, and further that the interface is degraded upon extended cycling. From this it is apparent that interfacial roughness may play a key role in determining composite behavior. Although the observation of a seating drop during fiber push-back gives some information about the amplitude and spatial extent of the interfacial roughness, actual measurement of the roughness has proven difficult due to its extremely fine scale. In the present work, a laser interferometer has been used to examine the roughness of composite interfaces (both fiber and matrix) as well as virgin fibers. In addition, long range (mm scale) push-out tests have been followed by interferometric characterization to examine the severity and rate of interfacial degradation associated with fiber sliding. 4 refs.

  5. Mathematical modeling of surface roughness in magnetic abrasive finishing of BK7 optical glass.

    PubMed

    Pashmforoush, Farzad; Rahimi, Abdolreza; Kazemi, Mehdi

    2015-10-01

    Magnetic abrasive finishing (MAF) is one of the advanced machining processes efficiently used to finish hard-to-machine materials. Simulation and modeling of the process is of particular importance to understand the mechanics of material removal and consequently achieve a high-quality surface with a minimum of surface defects. Hence, in this paper, we performed a numerical-experimental study to mathematically model the surface roughness during the MAF of BK7 optical glass. For this purpose, the initial roughness profile was estimated using fast Fourier transform (FFT) and a Gaussian filter. We obtained the final surface profile based on the material removal mechanisms and the corresponding chipping depth values evaluated by finite element analysis. We then validated experimentally the simulation results in terms of the arithmetic average surface roughness (R(a ). The comparison between the obtained results demonstrates that the theoretical and experimental findings are in good agreement when predicting the parameters' effect on surface roughness behavior. PMID:26479596

  6. On roughness-induced transition - Facts, views, and speculations

    NASA Technical Reports Server (NTRS)

    Morkovin, Mark V.

    1990-01-01

    Roughness is considered as a steady passive device, and it is shown that roughness-induced separation is specifically sensitive to unsteady environmental forcing. The two-dimensional isolated roughness causing local upstream and downstream separations is considered, along with flows associated with the two-dimensional roughness and their relevance to the problem of distributed roughness. The difference between the two-dimensional isolated roughness and a three-dimensional isolated roughness at all Reynolds numbers is underlined, and the mechanisms and parameter conditions of a sudden breakdown of hairpin eddies are discussed, as well as flows over distributed roughness.

  7. Reconstructed and simulated temperature asymmetry between continents in both hemispheres over the last centuries

    NASA Astrophysics Data System (ADS)

    Goosse, Hugues

    2016-05-01

    Available proxy-based temperature reconstructions covering the past millennium display contrasted evolutions between the continents. The difference is particularly large between the two hemispheres. When driven by realistic natural and anthropogenic forcings, climate models tend to simulate a more spatially homogenous temperature response. This is associated with a relatively good agreement between model results and reconstructions in the Northern Hemisphere but a low consistency in the Southern Hemisphere. Here, simulations with data assimilations are performed to analyse the causes of this apparent disagreement. It shows that, when the uncertainties are taken into account, states of the climate system compatible with the forcing estimates, the reconstructions and the model physics can be obtained over the past millennium, except for the twentieth century in Antarctica where the simulated warming is always much larger than in the reconstructions. Such states consistent with all sources of information can be achieved even if the uncertainties of the reconstructions are underestimated. Although, well within the range of the proxy-based reconstructions, the temperatures obtained after data assimilation display more similar developments between the hemispheres than in those reconstructions. Ensuring the compatibility does not require to systematically reduce the model response to the forcing or to strongly enhance the model internal variability. From those results, there is thus no reason to suspect that the model is strongly biased in one aspect or another. The constraint imposed by the data assimilation is too low to unambiguously identify the origin of each feature displayed in the reconstructions but, as expected, changes in atmospheric circulation likely played a role in many of them. Furthermore, ocean heat uptake and release as well as oceanic heat transport are key elements to understand the delayed response of the Southern Hemisphere compared to the northern

  8. Numerical Simulation of Roughness-Induced Transient Growth in a Laminar Boundary Layer

    NASA Technical Reports Server (NTRS)

    Fischer, Paul; Choudhari, Meelan

    2004-01-01

    Numerical simulations are used to examine the roughness-induced transient growth in a laminar boundary-layer flow. Based on the spectral element method, these simulations model the stationary disturbance field associated with a nonsmooth roughness geometry, such as the spanwise periodic array of circular disks used by White and co-workers during a series of wind tunnel experiments at Case Western Reserve University. Besides capturing the major trends from the recent measurements by White and Ergin, the simulations provide additional information concerning the relative accuracy of the experimental findings derived from two separate wall-finding procedures. The paper also explores the dependence of transient growth on geometric characteristics of the roughness distribution, including the height and planform shape of the roughness element and the ratio of roughness due to spacing between an adjacent pair of elements. Results are used for a preliminary assessment of the differences between recently reported theoretical results of Tumin and Reshotko and the measurements by White and Ergin.

  9. The geological interpretation of photometric surface roughness

    NASA Technical Reports Server (NTRS)

    Helfenstein, Paul

    1988-01-01

    A computer-generated km-scale relief map, whose topographic facets on scales of less than a few m are assumed to have smooth particulate surfaces, is the basis of the present investigation of the relationship between photometrically-derived values of Hapke's (1984) roughness parameter theta and topographic scale. The addition of m-km scale-range relief to the otherwise smooth surface alters integral photometric behavior in a way that is consistent with Hapke's equation; the roughness characterized by theta is an integral property over all scales up to the resolution limit of the photometric data used in its determination. With sufficient phase angle coverage, theta can distinguish terrains with very different integral roughnesses.

  10. Discrete Roughness Transition for Hypersonic Flight Vehicles

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Horvath, Thomas J.

    2007-01-01

    The importance of discrete roughness and the correlations developed to predict the onset of boundary layer transition on hypersonic flight vehicles are discussed. The paper is organized by hypersonic vehicle applications characterized in a general sense by the boundary layer: slender with hypersonic conditions at the edge of the boundary layer, moderately blunt with supersonic, and blunt with subsonic. This paper is intended to be a review of recent discrete roughness transition work completed at NASA Langley Research Center in support of agency flight test programs. First, a review is provided of discrete roughness wind tunnel data and the resulting correlations that were developed. Then, results obtained from flight vehicles, in particular the recently flown Hyper-X and Shuttle missions, are discussed and compared to the ground-based correlations.

  11. Wetting on rough self-affine surfaces

    NASA Astrophysics Data System (ADS)

    Palasantzas, George

    1995-05-01

    In this paper, we present a general investigation of the effective potential for complete wetting on self-affine rough surfaces. The roughness effect is investigated by means of the height-height correlation model in Fourier space ~(1+aξ2q2)-1-H. The parameters H and ξ are, respectively, the roughness exponent and the substrate in-plane correlation length. It is observed that the effect of H on the free interface profile is significant for ξ>ξ) regime is characterized by a power-law scaling ~Y-2.

  12. Hemispheric Asymmetry in the Efficiency of Attentional Networks

    ERIC Educational Resources Information Center

    Asanowicz, Dariusz; Marzecova, Anna; Jaskowski, Piotr; Wolski, Piotr

    2012-01-01

    Despite the fact that hemispheric asymmetry of attention has been widely studied, a clear picture of this complex phenomenon is still lacking. The aim of the present study was to provide an efficient and reliable measurement of potential hemispheric asymmetries of three attentional networks, i.e. alerting, orienting and executive attention.…

  13. A Hemispheric Asymmetry for the Unconscious Perception of Emotion

    ERIC Educational Resources Information Center

    Smith, Stephen D.; Bulman-Fleming, M. Barbara

    2004-01-01

    Previous research has demonstrated that hemispheric asymmetries for conscious visual perception do not lead to asymmetries for unconscious visual perception. These studies utilized emotionally neutral items as stimuli. The current research utilized both emotionally negative and neutral stimuli to assess hemispheric differences for conscious and…

  14. Hemispheric Differences in the Organization of Memory for Text Ideas

    ERIC Educational Resources Information Center

    Long, Debra L.; Johns, Clinton L.; Jonathan, Eunike

    2012-01-01

    The goal of this study was to examine hemispheric asymmetries in episodic memory for discourse. Access to previously comprehended information is essential for mapping incoming information to representations of "who did what to whom" in memory. An item-priming-in-recognition paradigm was used to examine differences in how the hemispheres represent…

  15. Disentangling the Relationship between Hemispheric Asymmetry and Cognitive Performance

    ERIC Educational Resources Information Center

    Hirnstein, Marco; Leask, Stuart; Rose, Jonas; Hausmann, Markus

    2010-01-01

    It is widely believed that advantages of hemispheric asymmetries originated in better cognitive processing, hence it is often implied that the relationship between hemispheric asymmetry and cognitive performance is linearly positive: the higher the degree of lateralization in a specific cognitive domain, the better the performance in a…

  16. Hemispheric Differences in the Effects of Context on Vowel Perception

    ERIC Educational Resources Information Center

    Sjerps, Matthias J.; Mitterer, Holger; McQueen, James M.

    2012-01-01

    Listeners perceive speech sounds relative to context. Contextual influences might differ over hemispheres if different types of auditory processing are lateralized. Hemispheric differences in contextual influences on vowel perception were investigated by presenting speech targets and both speech and non-speech contexts to listeners' right or left…

  17. ERP Evidence of Hemispheric Independence in Visual Word Recognition

    ERIC Educational Resources Information Center

    Nemrodov, Dan; Harpaz, Yuval; Javitt, Daniel C.; Lavidor, Michal

    2011-01-01

    This study examined the capability of the left hemisphere (LH) and the right hemisphere (RH) to perform a visual recognition task independently as formulated by the Direct Access Model (Fernandino, Iacoboni, & Zaidel, 2007). Healthy native Hebrew speakers were asked to categorize nouns and non-words (created from nouns by transposing two middle…

  18. The Joint Development of Hemispheric Lateralization for Words and Faces

    ERIC Educational Resources Information Center

    Dundas, Eva M.; Plaut, David C.; Behrmann, Marlene

    2013-01-01

    Consistent with long-standing findings from behavioral studies, neuroimaging investigations have identified a region of the inferior temporal cortex that, in adults, shows greater face selectivity in the right than left hemisphere and, conversely, a region that shows greater word selectivity in the left than right hemisphere. What has not been…

  19. Assessment of Hemispheric Dominance for Language at Three Ages.

    ERIC Educational Resources Information Center

    Tegano, Deborah Walker

    The purposes of this study were to assess the development of hemispheric dominance for language function among children of 4, 7, and 10 years of age and to determine whether age predicts hemispheric dominance. Within 2 weeks of the beginning of data collection, middle-class subjects selected from private nursery schools and elementary schools…

  20. Hemispheric Specialization and the Language Abilities of Autistic Children.

    ERIC Educational Resources Information Center

    Dawson, Geraldine; And Others

    1986-01-01

    Autistic children's direction of hemispheric asymmetry in response to linguistic stimuli differed significantly from that of normal subjects, showing reversed but not necessarily reduced patterns. Autistic children with more advanced language abilities were more likely to exhibit a normal direction of hemispheric asymmetry. Implications are…

  1. ROUGHNESS LENGTHS FOR THE SAVANNAH RIVER SITE

    SciTech Connect

    Hunter, C.

    2012-03-28

    Surface roughness values for the areas surrounding the H, D and N-Area meteorological towers were computed from archived 2010 meteorological data. These 15-minute-averaged data were measured with cup anemometers and bidirectional wind vanes (bivanes) 61 m above the surface. The results of the roughness calculation using the standard deviation of elevation angle {sigma}{sub E}, and applying the simple formula based on tree canopy height, gave consistent estimates for roughness around the H-Area tower in the range of 1.76 to 1.86 m (95% confidence interval) with a mean value of 1.81 m. Application of the {sigma}{sub E} method for the 61-m level at D and N-Areas gave mean values of 1.71 and 1.81 with confidence ranges of 1.62-1.81 and 1.73-1.88 meters, respectively. Roughness results are azimuth dependent, and thus are presented as averages over compass sectors spanning 22.5 degrees. Calculated values were compared to other methods of determining roughness, including the standard deviation of the azimuth direction, {sigma}{sub A}, and standard deviation of the wind speed, {sigma}{sub U}. Additional data was obtained from a sonic anemometer at 61-m on the H-Area tower during a period of a few weeks in 2010. Results from the sonic anemometer support our use of {sigma}{sub E} to calculate roughness. Based on the H-Area tower results, a surface roughness of 1.8 m using is recommended for use in dispersion modeling applications that consider the impacts of a contaminant release to individuals along the Site boundary. The canopy surrounding the H-Area tower is relatively uniform (i.e., little variance in roughness by upwind direction), and data supplied by the U.S. Forest Service at Savannah River show that the canopy height and composition surrounding the H-Area tower is reasonably representative of forested areas throughout the SRS reservation. For dispersion modeling analyses requiring assessments of a co-located worker within the respective operations area, recommended

  2. Laws of Flow in Rough Pipes

    NASA Technical Reports Server (NTRS)

    Nikuradse, J

    1950-01-01

    An experimental investigation is made of the turbulent flow of water in pipes with various degrees of relative roughness. The pipes range in size from 25 to 100 millimeters in diameter and from 1800 to 7050 millimeters in length. Flow velocities permitted Reynolds numbers from about 10 (sup. 4) to 10 (sup. 6). The laws of resistance and velocity distributions were obtained as a function of relative roughness and Reynolds number. Mixing length, as described by Prandtl's mixing-length formula, is discussed in relation to the experimental results.

  3. Rough and Steep Terrain Lunar Surface Mobility

    NASA Technical Reports Server (NTRS)

    Wilcox, Brian

    2005-01-01

    In the summer of 2004, the NASA Exploration Systems Mission Directorate conducted an open call for projects relevant to human and robotic exploration of the Earth-Moon and Mars systems. A project entitled 'Rough and Steep Terrain Lunar Surface Mobility' was submitted by JPL and accepted by NASA. The principal investigator of this project describes the robotic vehicle being developed for this effort, which includes six 'wheels-on-legs' so that it can roll efficiently on relatively smooth terrain but walk (using locked wheels as footpads) when "the going gets rough".

  4. Roughness Perception of Haptically Displayed Fractal Surfaces

    NASA Technical Reports Server (NTRS)

    Costa, Michael A.; Cutkosky, Mark R.; Lau, Sonie (Technical Monitor)

    2000-01-01

    Surface profiles were generated by a fractal algorithm and haptically rendered on a force feedback joystick, Subjects were asked to use the joystick to explore pairs of surfaces and report to the experimenter which of the surfaces they felt was rougher. Surfaces were characterized by their root mean square (RMS) amplitude and their fractal dimension. The most important factor affecting the perceived roughness of the fractal surfaces was the RMS amplitude of the surface. When comparing surfaces of fractal dimension 1.2-1.35 it was found that the fractal dimension was negatively correlated with perceived roughness.

  5. Evaluation of Dry, Rough Vacuum Pumps

    NASA Technical Reports Server (NTRS)

    Hunter, Brian

    2006-01-01

    This document provides information on the testing and evaluation of thirteen dry rough vacuum pumps of various designs and from various manufacturers. Several types of rough vacuum pumps were evaluated, including scroll, roots, and diaphragm pumps. Tests included long term testing, speed curve generation, voltage variance, vibrations emissions and susceptibility, electromagnetic interference emissions and susceptibility, static leak rate, exhaust restriction, response/recovery time tests, and a contamination analysis for scroll pumps. Parameters were found for operation with helium, which often is not provided from the manufacturer

  6. Surface roughness effects in elastohydrodynamic contacts

    NASA Technical Reports Server (NTRS)

    Tripp, J. H.; Hamrock, B. J.

    1985-01-01

    Surface roughness effects in full-film EHL contacts were studied. A flow factor modification to the Reynolds equation was applied to piezoviscous-elastic line contacts. Results for ensemble-averaged film shape, pressure distribution, and other mechanical quantities were obtained. Asperities elongated in the flow direction by a factor exceeding two decreased both film shape and pressure extrema at constant load; isotropic or transverse asperities increased these extrema. The largest effects are displayed by traction, which increased by over 5% for isotropic or transverse asperities and by slightly less for longitudinal roughness.

  7. Fused silica fine grinding with low roughness

    NASA Astrophysics Data System (ADS)

    Dai, Lei; Gu, Yongqiang; Wu, Di

    2014-08-01

    Lithography-optics is one of the most complex optical systems. The fine grinding process is the most important step before polishing. Roughness and sub-surface damage (SSD) are essential outputs of fine grinding. We demonstrate the method that use fix abrasive cup tool with CNC grinding machine to complete the fine grinding process, even instead of lapping process. And experiment sample roughness can reach 23.40nm rms and Ra 18.554nm. The SSD estimate is about 2 μm which is also smaller than commercial lapping process. The fine grinding output can satisfy the lithography optic fabrication demands and efficiently reduce the polishing time.

  8. Surface roughness evolution of nanocomposite thin films

    SciTech Connect

    Turkin, A. A.; Pei, Y. T.; Shaha, K. P.; Chen, C. Q.; Vainshtein, D. I.; Hosson, J. Th. M. de

    2009-01-01

    An analysis of dynamic roughening and smoothening mechanisms of thin films grown with pulsed-dc magnetron sputtering is presented. The roughness evolution has been described by a linear stochastic equation, which contains the second- and fourth-order gradient terms. Dynamic smoothening of the growing interface is explained by ballistic effects resulting from impingements of ions to the growing thin film. These ballistic effects are sensitive to the flux and energy of impinging ions. The predictions of the model are compared with experimental data, and it is concluded that the thin film roughness can be further controlled by adjusting waveform, frequency, and width of dc pulses.

  9. Venus surface roughness and Magellan stereo data

    NASA Technical Reports Server (NTRS)

    Maurice, Kelly E.; Leberl, Franz W.; Norikane, L.; Hensley, Scott

    1994-01-01

    Presented are results of some studies to develop tools useful for the analysis of Venus surface shape and its roughness. Actual work was focused on Maxwell Montes. The analyses employ data acquired by means of NASA's Magellan satellite. The work is primarily concerned with deriving measurements of the Venusian surface using Magellan stereo SAR. Roughness was considered by means of a theoretical analyses based on digital elevation models (DEM's), on single Magellan radar images combined with radiometer data, and on the use of multiple overlapping Magellan radar images from cycles 1, 2, and 3, again combined with collateral radiometer data.

  10. Inkjet printed superparamagnetic polymer composite hemispheres with programmed magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Ergeneman, Olgaç; Peters, Christian; Gullo, Maurizio R.; Jacot-Descombes, Loïc; Gervasoni, Simone; Özkale, Berna; Fatio, Philipe; Cadarso, Victor J.; Mastrangeli, Massimo; Pané, Salvador; Brugger, Jürgen; Hierold, Christofer; Nelson, Bradley J.

    2014-08-01

    We present the fabrication and characterization of large arrays of inkjet-printed superparamagnetic polymer composite (SPMPC) hemispherical microstructures. SPMPCs are appealing for applications in microsystems and nanorobotics due to the added functionality of polymers and the significant magnetic attributes of embedded nanostructures. SPMPC-based microarchitectures can be used to perform different functions wirelessly in various media (e.g. water, solvents) using external magnetic fields: handling and assembling small objects, delivering drugs or biomass, or sensing specific physical or chemical changes. In this work superparamagnetic magnetite nanoparticles are dispersed in SU-8 to form magnetic hemispheres. Magnetically anisotropic hemispheres as well as standard SPMPC hemispheres are fabricated. Magnetic anisotropy is programmed by applying a magnetic field during curing. The distribution of nanoparticles inside the polymer matrix and magnetic characteristics of the SPMPC are investigated. Magnetic manipulation of hemispheres is demonstrated at liquid-liquid interfaces. Different assembly strategies to form lines or geometric shapes from hemispheres as well as their independent dynamic control are demonstrated. Finally, a two-interface assembly strategy is demonstrated to assemble hemispheres into complete spheres for advanced self-assembly tasks.We present the fabrication and characterization of large arrays of inkjet-printed superparamagnetic polymer composite (SPMPC) hemispherical microstructures. SPMPCs are appealing for applications in microsystems and nanorobotics due to the added functionality of polymers and the significant magnetic attributes of embedded nanostructures. SPMPC-based microarchitectures can be used to perform different functions wirelessly in various media (e.g. water, solvents) using external magnetic fields: handling and assembling small objects, delivering drugs or biomass, or sensing specific physical or chemical changes. In this

  11. Atmospheric Blocking in the Northern Hemisphere.

    NASA Astrophysics Data System (ADS)

    Knox, John Lewis

    Blocking is generally understood as the obstruction on a large scale of the normal west - to - east motion of mid-latitude pressure systems. It is a persistent phenomenon lasting from one to several weeks and the resulting prolonged weather regimes may have serious economic and social consequences. The recent Northern Hemisphere winters, starting with 1976 -77, featured unusually large circulation anomalies, many of which can be directly related to prolonged episodes of large scale blocking. The intent of this study is to investigate the statistics and certain diagnostics of blocking in the Northern Hemisphere. The first of the three primary objectives is to present and interpret the spatial and temporal distribution of blocking during the past 33 years. We develop objective identification criteria, adaptable to machine processing methods, by relating the blocking anticyclone to its associated positive anomaly of 5-day mean 500MB height. Anomalies meeting the criteria are called 'blocking signatures.' We present the seasonal frequency of occurrence of these signatures by longitude and by area. The results are in good agreement with published studies for the oceans, but they also reveal a high frequency of blocking signatures over the Northeastern Canadian Archipelago. This result, dubbed the 'Baffin Island Paradox' is further investigated and rationalized. A catalogue has been prepared which identifies the date, centre location and magnitude of every blocking signature which occurred from January 1, 1946 to December 31, 1978. A supplementary Catalogue identifies sequences of these signatures corresponding to actual blocking episodes. The second objective is to investigate whether regions with high incidence of blocking, in either the developing or the mature stage, features non-Gaussian distributions of 5-day mean geopotential. During winter, fields of significantly low kurtosis are found in certain mid-latitude regions where the genesis and amplification of

  12. Inferring the thermal-infrared hemispheric emission from a sparsely-vegetated surface by directional measurements

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Susskind, J.; Brakke, T.; Kimes, D.; Pielke, R.; Lee, T. J.

    1995-01-01

    The thermal-infrared (longwave) emission from a vegetated terrain is generally anisotropic, i.e., the emission temperature varies with the view direction. If a directional measurement of temperature is considered to be equal to the effective temperature of the hemispheric emission, then the estimate of the latter can be significantly in error. The view-direction (zenith angle theta(sub eq) at which the emission equivalence does hold is determined in our modeling study. In a two-temperature field-of-view (soil and plants), theta(sub eq) falls in a narrow range depending on plant density and canopy architecture. Theta(sub eq) does not depend on soil and (uniform) plant temperatures nor on their ratio, even though the pattern of emission vs. the view direction depends crucially on this ratio. For a sparse canopy represented as thin, vertical cylindrical stalks (or vertical blades uniformly distributed in azimuth) with horizontal facets, theta(sub eq) ranges from 48 to 53 deg depending on the optical density of the vertical elements alone. When plant elements are modeled as small spheres, theta(sub eq) lies between 53 to 57 deg (for the same values of the canopy optical density). Only for horizontal leaves (a truly planophile canopy) is the temperature measured from any direction equal to the temperature of the hemispheric emission. When the emission temperature changes with optical depth within the canopy at a specified rate, theta(sub eq) depends to some extent on that rate. For practically any sparsely vegetated surface, a directional measurement at the zenith angle of 50 deg offers an appropriate evaluation of the hemispheric emission, since the error in the estimate will, at most, only slightly exceed 1% (around 4 W/sq m). Estimates of the hemispheric emission through a nadir measurement, on the other hand, can be in error in some cases by about 10%, i.e., on the order of 40 W/sq m.

  13. Topography of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Zuber, M. T.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Muhleman, D. O.; Pettengill, G. H.; Phillips, R. J.; Solomon, S. C.; Zwally, H. J.; Banerdt, W. B.; Duxbury, T. C.

    1998-01-01

    The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50 degrees is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the channel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in low-lying areas such as Valles Marineris.

  14. Topography of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter.

    PubMed

    Smith, D E; Zuber, M T; Frey, H V; Garvin, J B; Head, J W; Muhleman, D O; Pettengill, G H; Phillips, R J; Solomon, S C; Zwally, H J; Banerdt, W B; Duxbury, T C

    1998-03-13

    The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50 degrees is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the channel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in low-lying areas such as Valles Marineris. PMID:9497281

  15. Beyond Hemispheric Dominance: Brain Regions Underlying the Joint Lateralization of Language and Arithmetic to the Left Hemisphere

    ERIC Educational Resources Information Center

    Pinel, Philippe; Dehaene, Stanislas

    2010-01-01

    Language and arithmetic are both lateralized to the left hemisphere in the majority of right-handed adults. Yet, does this similar lateralization reflect a single overall constraint of brain organization, such an overall "dominance" of the left hemisphere for all linguistic and symbolic operations? Is it related to the lateralization of specific…

  16. Hemispheric Contributions to Lexical Ambiguity Resolution in a Discourse Context: Evidence from Individuals with Unilateral Left and Right Hemisphere Lesions

    ERIC Educational Resources Information Center

    Grindrod, C.M.; Baum, S.R.

    2005-01-01

    In the present study, a cross-modal semantic priming task was used to investigate the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use a discourse context to resolve lexically ambiguous words. Subjects first heard four-sentence discourse passages ending…

  17. Europa's Northern Trailing Hemisphere: Lineament Stratigraphic Framework

    NASA Technical Reports Server (NTRS)

    Figueredo, P. H.; Hare, T.; Ricq, E.; Strom, K.; Greeley, R.; Tanaka, K.; Senske, D.

    2004-01-01

    Knowledge of the global distribution of Europan geologic units in time and space is a necessary step for the synthesis of the results of the Galileo mission and in preparation for future exploration (namely, by JIMO) of the satellite. We have initiated the production of the first Global Geological Map of Europa. As a base map, we use the recently published global photomosaic of Europa (U.S.G.S. Map I-2757) and additional Galileo SSI images at their original resolution. The map is being produced entirely on GIS format for analysis and combination with other datasets [1]. One of the main objectives of this project is to establish a global stratigraphic framework for Europa. In the absence of a well-developed cratering record, this goal will be achieved using the satellite s global network of lineaments (ridges, ridge complexes and bands; cf. [2]). Here we present the preliminary stratigraphic framework synthesized from the sequence of lineaments derived for the northern trailing hemisphere of Europa (Figure 1, below), and we discuss its significance and some emerging implications.

  18. Bright Ray Craters in Ganymede's Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    1979-01-01

    GANYMEDE COLOR PHOTOS: This color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The images show detail on the surface with a resolution of four and a half km. This picture is of a region in the northern hemisphere near the terminator. It shows a variety of impact structures, including both razed and unrazed craters, and the odd, groove-like structures discovered by Voyager in the lighter regions. The most striking features are the bright ray craters which have a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young craters have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas suggests that here, too, there is cleaner ice. We see ray craters with all sizes of ray patterns, ranging from extensive systems of the crater in the southern part of this picture, which has rays at least 300-500 kilometers long, down to craters which have only faint remnants of bright ejects patterns (such as several of the craters in the southern half of PIA01516; P21262). This variation suggests that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact. JPL manages and controls the Voyager project for NASA's Office of Space Science.

  19. Objectively classifying Southern Hemisphere extratropical cyclones

    NASA Astrophysics Data System (ADS)

    Catto, Jennifer

    2016-04-01

    There has been a long tradition in attempting to separate extratropical cyclones into different classes depending on their cloud signatures, airflows, synoptic precursors, or upper-level flow features. Depending on these features, the cyclones may have different impacts, for example in their precipitation intensity. It is important, therefore, to understand how the distribution of different cyclone classes may change in the future. Many of the previous classifications have been performed manually. In order to be able to evaluate climate models and understand how extratropical cyclones might change in the future, we need to be able to use an automated method to classify cyclones. Extratropical cyclones have been identified in the Southern Hemisphere from the ERA-Interim reanalysis dataset with a commonly used identification and tracking algorithm that employs 850 hPa relative vorticity. A clustering method applied to large-scale fields from ERA-Interim at the time of cyclone genesis (when the cyclone is first detected), has been used to objectively classify identified cyclones. The results are compared to the manual classification of Sinclair and Revell (2000) and the four objectively identified classes shown in this presentation are found to match well. The relative importance of diabatic heating in the clusters is investigated, as well as the differing precipitation characteristics. The success of the objective classification shows its utility in climate model evaluation and climate change studies.

  20. Volcanoes and volcanic provinces - Martian western hemisphere

    NASA Technical Reports Server (NTRS)

    Scott, D. H.

    1982-01-01

    The recognition of some Martian landforms as volcanoes is based on their morphology and geologic setting. Other structures, however, may exhibit classic identifying features to a varying or a less degree; these may be only considered provisionally as having a volcanic origin. Regional geologic mapping of the western hemisphere of Mars from Viking images has revealed many more probable volcanoes and volcanotectonic features than were recognized on Mariner 9 pictures. These abundant volcanoes have been assigned to several distinct provinces on the basis of their areal distribution. Although the Olympus-Tharsis region remains as the principle center of volcanism on Mars, four other important provinces are now also recognized: the lowland plains, Tempe Terra plateau, southern highlands (in the Phaethontis and Thaumasia quadrangles), and a probable ignimbrite province, situated along the highland-lowland boundary in Amazonis Planitia. Volcanoes in any one province vary in morphlogy, size, and age, but volcanoes in each province tend to have common characteristics that distinguish that particular group.

  1. Modeling Hemispheric Detonation Experiments in 2-Dimensions

    SciTech Connect

    Howard, W M; Fried, L E; Vitello, P A; Druce, R L; Phillips, D; Lee, R; Mudge, S; Roeske, F

    2006-06-22

    Experiments have been performed with LX-17 (92.5% TATB and 7.5% Kel-F 800 binder) to study scaling of detonation waves using a dimensional scaling in a hemispherical divergent geometry. We model these experiments using an arbitrary Lagrange-Eulerian (ALE3D) hydrodynamics code, with reactive flow models based on the thermo-chemical code, Cheetah. The thermo-chemical code Cheetah provides a pressure-dependent kinetic rate law, along with an equation of state based on exponential-6 fluid potentials for individual detonation product species, calibrated to high pressures ({approx} few Mbars) and high temperatures (20000K). The parameters for these potentials are fit to a wide variety of experimental data, including shock, compression and sound speed data. For the un-reacted high explosive equation of state we use a modified Murnaghan form. We model the detonator (including the flyer plate) and initiation system in detail. The detonator is composed of LX-16, for which we use a program burn model. Steinberg-Guinan models5 are used for the metal components of the detonator. The booster and high explosive are LX-10 and LX-17, respectively. For both the LX-10 and LX-17, we use a pressure dependent rate law, coupled with a chemical equilibrium equation of state based on Cheetah. For LX-17, the kinetic model includes carbon clustering on the nanometer size scale.

  2. Surface roughness scattering in multisubband accumulation layers

    NASA Astrophysics Data System (ADS)

    Fu, Han; Reich, K. V.; Shklovskii, B. I.

    2016-06-01

    Accumulation layers with very large concentrations of electrons where many subbands are filled became recently available due to ionic liquid and other new methods of gating. The low-temperature mobility in such layers is limited by the surface roughness scattering. However, theories of roughness scattering so far dealt only with the small-density single subband two-dimensional electron gas (2DEG). Here we develop a theory of roughness-scattering limited mobility for the multisubband large concentration case. We show that with growing 2D electron concentration n the surface dimensionless conductivity σ /(2 e2/h ) first decreases as ∝n-6 /5 and then saturates as ˜(d aB/Δ2)≫1 , where d and Δ are the characteristic length and height of the surface roughness and aB is the effective Bohr radius. This means that in spite of the shrinkage of the 2DEG thickness and the related increase of the scattering rate the 2DEG remains a good metal.

  3. Surface roughness modulations by submesoscale currents

    NASA Astrophysics Data System (ADS)

    Rascle, Nicolas; Chapron, Bertrand; Nouguier, Frederic; Ponte, Aurelien; Mouche, Alexis; Molemaker, Jeroen

    2016-04-01

    At times, high resolution images of sea surface roughness can provide stunning details of submesoscale upper ocean dynamics. As interpreted, transformations of short scale wind waves by horizontal current gradients are responsible for those spectacular observations. Here we present two major advances towards the quantitative interpretation of those observations. First, we show that surface roughness variations mainly trace two particular characteristics of the current gradient tensor, the divergence and the strain in the wind direction. Local vorticity and shear in the wind direction should not affect short scale roughness distribution and would not be detectable. Second, we discuss the effect of the viewing direction using sets of quasi-simultaneous sun glitter images, taken from different satellites to provide different viewing configurations. We show that upwind and crosswind viewing observations can be markedly different. As further confirmed with idealized numerical simulations, this anisotropy well traces surface current strain area, while more isotropic contrasts likely trace areas dominated by surface divergence conditions. These findings suggest the potential to directly observe surface currents at submesoscale by using surface roughness observations at multiple azimuth viewing angles. They also pave the way towards a better understanding of the coupling between ocean, waves and atmosphere at high resolution.

  4. Thermal smoothing of rough surfaces in vacuo

    NASA Technical Reports Server (NTRS)

    Wahl, G.

    1986-01-01

    The derivation of equations governing the smoothing of rough surfaces, based on Mullins' (1957, 1960, and 1963) theories of thermal grooving and of capillarity-governed solid surface morphology is presented. As an example, the smoothing of a one-dimensional sine-shaped surface is discussed.

  5. Particle Sliding on a Rough Incline

    ERIC Educational Resources Information Center

    Zurcher, Ulrich

    2007-01-01

    We study a particle sliding on a rough inclined plane as an example of a mechanical problem with nonholonomic constraint. The particle is launched in an arbitrary direction so that its motion has both a horizontal and a "vertical" (i.e., up- and downhill) direction. The friction force acts along the instantaneous velocity, so that the horizontal…

  6. Three-tier rough superhydrophobic surfaces.

    PubMed

    Cao, Yuanzhi; Yuan, Longyan; Hu, Bin; Zhou, Jun

    2015-08-01

    A three-tier rough superhydrophobic surface was fabricated by growing hydrophobic modified (fluorinated silane) zinc oxide (ZnO)/copper oxide (CuO) hetero-hierarchical structures on silicon (Si) micro-pillar arrays. Compared with the other three control samples with a less rough tier, the three-tier surface exhibits the best water repellency with the largest contact angle 161° and the lowest sliding angle 0.5°. It also shows a robust Cassie state which enables the water to flow with a speed over 2 m s(-1). In addition, it could prevent itself from being wetted by the droplet with low surface tension (mixed water and ethanol 1:1 in volume) which reveals a flow speed of 0.6 m s(-1) (dropped from the height of 2 cm). All these features prove that adding another rough tier on a two-tier rough surface could futher improve its water-repellent properties. PMID:26184512

  7. Uranus’ Hemispheric Asymmetries in Polar Cloud and Circulation Structures

    NASA Astrophysics Data System (ADS)

    Hammel, Heidi B.; Sromovsky, Lawrence; Fry, Pat; de Pater, Imke

    2015-11-01

    We report on the north polar region of Uranus in the post-equinoctial era. Near-IR imaging with Keck 2 using NIRC2 in 2012-2014 revealed numerous small bright features, as well as small dark features, between 50 degrees N and the north pole. Tracking of these features yielded circulation patterns, with the remarkable result that the region from 60 degrees to at least 83 degrees rotates about the northern pole as a solid body, with a drift rate of 4.1 degrees/hour westward relative to the interior (Sromovsky et al. 2015, Icarus 258, 192-223). For the south pole, the same latitude region had dramatically different characteristics, as judged by 1986 Voyager and 2003 Keck observations. The southern region showed no discrete near-IR features; detailed circulation measurements in that region were based solely on low-contrast features in re-analyzed Voyager images (Karkoschka, 2015, Icarus 250, 294-307). They revealed a large gradient in drift rates, with values reaching twice that seen in the corresponding northern region.The north-south asymmetry in circulation and cloud structure/morphology is surprising because the distribution of upper tropospheric methane is relatively symmetric: roughly constant over a region from 30 S to 30 N, and then declining at higher latitudes in both hemispheres. The methane distribution suggests symmetric down-welling motion in both polar regions, which would inhibit formation of condensation clouds there, in contrast to the observed dichotomy. Some asymmetry may be an effect of seasonal forcing, since the north versus south polar measurements were made during different seasons. If so, then major changes can be expected in the north polar region as Uranus proceeds toward its 2030 northern summer solstice. Hubble STIS observations expected in October of 2015 will further examine the vertical distribution and stability of the polar methane abundances. Future high-resolution imaging with Earth-based facilities will be able to track circulation

  8. 14 CFR 25.1517 - Rough air speed, VRA.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rough air speed, VRA. 25.1517 Section 25... Limitations § 25.1517 Rough air speed, VRA. A rough air speed, VRA, for use as the recommended turbulence... rough air encounters will not cause the overspeed warning to operate too frequently. In the absence of...

  9. 14 CFR 25.1517 - Rough air speed, VRA.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rough air speed, VRA. 25.1517 Section 25... Limitations § 25.1517 Rough air speed, VRA. A rough air speed, VRA, for use as the recommended turbulence... rough air encounters will not cause the overspeed warning to operate too frequently. In the absence of...

  10. 7 CFR 51.707 - Slightly rough texture.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Other Than Florida, California, and Arizona) Definitions § 51.707 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively... 7 Agriculture 2 2013-01-01 2013-01-01 false Slightly rough texture. 51.707 Section...

  11. 7 CFR 51.707 - Slightly rough texture.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Other Than Florida, California, and Arizona) Definitions § 51.707 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively... 7 Agriculture 2 2014-01-01 2014-01-01 false Slightly rough texture. 51.707 Section...

  12. 7 CFR 51.645 - Slightly rough texture.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., and Arizona) Definitions § 51.645 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2010-01-01 2010-01-01 false Slightly rough texture. 51.645 Section...

  13. 7 CFR 51.707 - Slightly rough texture.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., and Arizona) Definitions § 51.707 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2010-01-01 2010-01-01 false Slightly rough texture. 51.707 Section...

  14. 7 CFR 51.707 - Slightly rough texture.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., and Arizona) Definitions § 51.707 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2011-01-01 2011-01-01 false Slightly rough texture. 51.707 Section...

  15. 7 CFR 51.645 - Slightly rough texture.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., and Arizona) Definitions § 51.645 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2011-01-01 2011-01-01 false Slightly rough texture. 51.645 Section...

  16. 7 CFR 51.645 - Slightly rough texture.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Other Than Florida, California, and Arizona) Definitions § 51.645 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively... 7 Agriculture 2 2014-01-01 2014-01-01 false Slightly rough texture. 51.645 Section...

  17. 7 CFR 51.645 - Slightly rough texture.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Other Than Florida, California, and Arizona) Definitions § 51.645 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively... 7 Agriculture 2 2013-01-01 2013-01-01 false Slightly rough texture. 51.645 Section...

  18. 7 CFR 51.645 - Slightly rough texture.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., and Arizona) Definitions § 51.645 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2012-01-01 2012-01-01 false Slightly rough texture. 51.645 Section...

  19. 7 CFR 51.707 - Slightly rough texture.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., and Arizona) Definitions § 51.707 Slightly rough texture. Slightly rough texture means that the skin is not smooth or fairly smooth but is not excessively rough or excessively thick, or materially... 7 Agriculture 2 2012-01-01 2012-01-01 false Slightly rough texture. 51.707 Section...

  20. Physically-based Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

    NASA Astrophysics Data System (ADS)

    Li, Li; Gaiser, Peter; Allard, Richard; Posey, Pamela; Hebert, David; Richter-Menge, Jacqueline; Polashenski, Christopher; Claffey, Keran

    2016-04-01

    The observations of sea ice thickness and ice surface roughness are critical for our understanding of the state of the changing Arctic. Currently, the Radar and/or LiDAR data of sea ice freeboard are used to infer sea ice thickness via isostasy. The underlying assumption is that the LiDAR signal returns at the air/snow interface and radar signal at the snow/ice interface. The elevations of these interfaces are determined based on LiDAR/Radar return waveforms. However, the commonly used threshold-based surface detection techniques are empirical in nature and work well only over level/smooth sea ice. Rough sea ice surfaces can modify the return waveforms, resulting in significant Electromagnetic (EM) bias in the estimated surface elevations, and thus large errors in the ice thickness retrievals. To understand and quantify such sea ice surface roughness effects, a combined EM rough surface and volume scattering model was developed to simulate radar returns from the rough sea ice 'layer cake' structure. A waveform matching technique was also developed to fit observed waveforms to a physically-based waveform model and subsequently correct the roughness induced EM bias in the estimated freeboard. This new EM Bias Corrected (EMBC) algorithm was able to better retrieve surface elevations and estimate the surface roughness parameter simultaneously. Both the ice thickness and surface roughness retrievals are validated using in-situ data. For the surface roughness retrievals, we applied this EMBC algorithm to co-incident LiDAR/Radar measurements collected during a Cryosat-2 under-flight by the NASA IceBridge missions. Results show that not only does the waveform model fit very well to the measured radar waveform, but also the roughness parameters derived independently from the LiDAR and radar data agree very well for both level and deformed sea ice. For sea ice thickness retrievals, validation based on in-situ data from the coordinated CRREL/NRL field campaign demonstrates

  1. Comparative analysis of different measurement techniques for characterizing soil surface roughness in agricultural soils

    NASA Astrophysics Data System (ADS)

    Martinez-Agirre, Alex; Álvarez-Mozos, Jesús; Valle, José Manuel; Rodríguez, Álvaro; Giménez, Rafael

    2016-04-01

    Soil surface roughness can be defined as the variation in soil surface elevations, and as such, it is a key element in hydrology and soil erosion processes. In agricultural soils, roughness is mainly an anthropic factor determined by the type of tillage and management. Roughness is also a property with a high spatial variability, since the same type of tillage can result in surfaces with different roughness depending on the physical characteristics of the soil and atmospheric conditions. In order to quantify roughness and to parameterize its role in different processes, different measurement techniques have been used and several parameters have been proposed in the literature. The objective of this work is to evaluate different measurement techniques and assess their accuracy and suitability for quantifying surface roughness in agricultural soils. With this aim, a comparative analysis of three roughness measurement techniques has been carried out; (1) laser profilometer, (2) convergent photogrammetry and (3) terrestrial laser scanner. Roughness measurements were done in 3 experimental plots (5x5 meters) with different tillage treatments (representing different roughness conditions) obtained with typical agricultural tools. The laser profilometer registered vertically the distance from a reference bar down to the surface. It had a vertical accuracy of 1.25 mm, a sampling interval of 5 mm and a total length profile of 5 m. Eight profiles were taken per plot, four in parallel to tillage direction and four in perpendicular. Convergent photogrammetry consisted of 20-30 images taken per plot from a height of 5-10 m above ground (using an elevation platform), leading to point clouds of ~25 million points per plot. Terrestrial laser scanner measurements were taken from the four sides of each plot at a measurement height of ~1.75 m above ground. After orientating and corregistering the four scans, point clouds of ~60 million points were obtained per plot. The comparative

  2. Soil surface roughness decay in contrasting climates, tillage types and management systems

    NASA Astrophysics Data System (ADS)

    Vidal Vázquez, Eva; Bertol, Ildegardis; Tondello Barbosa, Fabricio; Paz-Ferreiro, Jorge

    2014-05-01

    Soil surface roughness describes the variations in the elevation of the soil surface. Such variations define the soil surface microrelief, which is characterized by a high spatial variability. Soil surface roughness is a property affecting many processes such as depression storage, infiltration, sediment generation, storage and transport and runoff routing. Therefore the soil surface microrelief is a key element in hydrology and soil erosion processes at different spatial scales as for example at the plot, field or catchment scale. In agricultural land soil surface roughness is mainly created by tillage operations, which promote to different extent the formation of microdepressions and microelevations and increase infiltration and temporal retention of water. The decay of soil surface roughness has been demonstrated to be mainly driven by rain height and rain intensity, and to depend also on runoff, aggregate stability, soil reface porosity and soil surface density. Soil roughness formation and decay may be also influenced by antecedent soil moisture (either before tillage or rain), quantity and type of plant residues over the soil surface and soil composition. Characterization of the rate and intensity of soil surface roughness decay provides valuable information about the degradation of the upper most soil surface layer before soil erosion has been initiated or at the very beginning of soil runoff and erosion processes. We analyzed the rate of decay of soil surface roughness from several experiments conducted in two regions under temperate and subtropical climate and with contrasting land use systems. The data sets studied were obtained both under natural and simulated rainfall for various soil tillage and management types. Soil surface roughness decay was characterized bay several parameters, including classic and single parameters such as the random roughness or the tortuosity and parameters based on advanced geostatistical methods or on the fractal theory. Our

  3. Observations of Seafloor Roughness in a Tidally Modulated Inlet

    NASA Astrophysics Data System (ADS)

    Lippmann, T. C.; Hunt, J.

    2014-12-01

    The vertical structure of shallow water flows are influenced by the presence of a bottom boundary layer, which spans the water column for long period waves or mean flows. The nature of the boundary is determined in part by the roughness elements that make up the seafloor, and includes sometimes complex undulations associated with regular and irregular shaped bedforms whose scales range several orders of magnitude from orbital wave ripples (10-1 m) to mega-ripples (100 m) and even larger features (101-103) such as sand waves, bars, and dunes. Modeling efforts often parameterize the effects of roughness elements on flow fields, depending on the complexity of the boundary layer formulations. The problem is exacerbated by the transient nature of bedforms and their large spatial extent and variability. This is particularly important in high flow areas with large sediment transport, such as tidally dominated sandy inlets like New River Inlet, NC. Quantification of small scale seafloor variability over large spatial areas requires the use of mobile platforms that can measure with fine scale (order cm) accuracy in wide swaths. The problem is difficult in shallow water where waves and currents are large, and water clarity is often limited. In this work, we present results from bathymetric surveys obtained with the Coastal Bathymetry Survey System, a personal watercraft equipped with a Imagenex multibeam acoustic echosounder and Applanix POS-MV 320 GPS-aided inertial measurement unit. This system is able to measure shallow water seafloor bathymetry and backscatter intensity with very fine scale (10-1 m) resolution and over relatively large scales (103 m) in the presence of high waves and currents. Wavenumber spectra show that the noise floor of the resolved multibeam bathymetry is on the order of 2.5 - 5 cm in amplitude, depending on water depths ranging 2 - 6 m, and about 30 cm in wavelength. Seafloor roughness elements are estimated from wavenumber spectra across the inlet

  4. (An)isotropy of the Hubble diagram: comparing hemispheres

    NASA Astrophysics Data System (ADS)

    Schwarz, D. J.; Weinhorst, B.

    2007-11-01

    Aims:We test the isotropy of the Hubble diagram. At small redshifts, this is possible without assumptions on the cosmic inventory and provides a fundamental test of the cosmological principle. At higher redshift we check for the self-consistency of the ΛCDM model. Methods: At small redshifts, we use public supernovae (SNe) Ia data to determine the deceleration parameter q0 and the SN calibration on opposite hemispheres. For the complete data sets we fit ΩM and the SN calibration on opposite hemispheres. Results: A statistically significant anisotropy of the Hubble diagram at redshifts z < 0.2 is discovered (>95%C.L.). While data from the North Galactic hemisphere favour the accelerated expansion of the Universe, data from the South Galactic hemisphere are not conclusive. The hemispheric asymmetry is maximal toward a direction close to the equatorial poles. The discrepancy between the equatorial North and South hemispheres shows up in the SN calibration. For the ΛCDM model fitted to all available SNe, we find the same asymmetry. Conclusions: The alignment of discrepancies between hemispheric Hubble diagrams with the equatorial frame seems to point toward a systematic error in the SN search, observation, analysis or data reduction. We also find that our model independent test cannot exclude the case of the deceleration of the expansion at a statistically significant level.

  5. What Does the Right Hemisphere Know about Phoneme Categories?

    PubMed Central

    Wolmetz, Michael; Poeppel, David; Rapp, Brenda

    2015-01-01

    Innate auditory sensitivities and familiarity with the sounds of language give rise to clear influences of phonemic categories on adult perception of speech. With few exceptions, current models endorse highly left-hemisphere-lateralized mechanisms responsible for the influence of phonemic category on speech perception, based primarily on results from functional imaging and brain-lesion studies. Here we directly test the hypothesis that the right hemisphere does not engage in phonemic analysis. By using fMRI to identify cortical sites sensitive to phonemes in both word and pronounceable nonword contexts, we find evidence that right-hemisphere phonemic sensitivity is limited to a lexical context. We extend the interpretation of these fMRI results through the study of an individual with a left-hemisphere lesion who is right-hemisphere reliant for initial acoustic and phonetic analysis of speech. This individual’s performance revealed that the right hemisphere alone was insufficient to allow for typical phonemic category effects but did support the processing of gradient phonetic information in lexical contexts. Taken together, these findings confirm previous claims that the right temporal cortex does not play a primary role in phoneme processing, but they also indicate that lexical context may modulate the involvement of a right hemisphere largely tuned for less abstract dimensions of the speech signal. PMID:20350179

  6. Hemispherical power asymmetry: parameter estimation from cosmic microwave background WMAP5 data

    SciTech Connect

    Lew, Bartosz

    2008-09-15

    We re-examine the evidence for hemispherical power asymmetry, detected in the cosmic microwave background (CMB) WMAP (Wilkinson Microwave Anisotropy Probe) data using a new method. We use a data filtering, preprocessing, and a statistical approach different from those used previously, and pursue an independent method of parameter estimation. First, we analyze the hemispherical variance ratios and compare these with simulated distributions. Secondly, working within a previously proposed CMB bipolar modulation model, we constrain model parameters: the amplitude and the orientation of the modulation field, as a function of various multipole bins. Finally, we select three ranges of multipoles leading to the most anomalous signals, and we process a hundred corresponding Gaussian random field (GRF) simulations, treated as observational data, to further test the statistical significance and robustness of the hemispherical power asymmetry. For our analysis we use the Internally Linearly Coadded (ILC) full sky map, and the KQ75 cut sky V channel foreground reduced map of the WMAP five-year data (V5). We constrain the modulation parameters using a generic maximum a posteriori method. In particular, we find differences in hemispherical power distribution, which when described in terms of a model with a bipolar modulation field, exclude the field amplitude value of the isotropic model, A = 0, at the confidence level of {approx}99.5% ({approx}99.4%) in the multipole range l element of [7,19] (l element of [7,79]) for the V5 data, and at the confidence level of {approx}99.9% in the multipole range l element of [7,39] for the ILC5 data, with best-fit (modal probability distribution function) values in these particular multipole ranges of A = 0.21 (A = 0.21) and A = 0.15 respectively. However, we also point out that similar or larger significances (in terms of rejecting the isotropic model) and large best-fit modulation amplitudes are obtained in GRF simulations as well, which

  7. Combination of Stokes polarized light imaging, roughness metrics and morphological features for the detection of melanoma

    NASA Astrophysics Data System (ADS)

    Ghassemi, P.; Shupp, J. W.; Venna, S.; Boisvert, M. E.; Flanagan, K. E.; Jordan, M. H.; Ramella-Roman, J. C.

    2012-02-01

    Skin cancer is the most common and most rapidly increasing form of cancer in the world. Optimal treatment of skin cancer before it reaches metastasis depends critically on early diagnosis. Usually physicians will measure some outward features to diagnose malignancy of pigmented skin lesion. These are mostly morphological features like border irregularity, size, shape, and color. Valuable information can be obtained from the analysis of skin roughness. Previously, we developed a hemispherical imaging Stokes polarimeter to monitor skin cancer based on a roughness assessment of the epidermis. In this study, Stokes images were analyzed to measure polarization properties of skin samples such as the principal angle of the polarization ellipse and the degree of polarization. A processing algorithm based on morphological operators was also developed and applied on Stokes images to extract shape information. Finally, an appropriate classifier was designed to determine the type of lesion based on morphological features as well as the roughness information. Clinical evaluation of the technique was performed on patients with benign nevi, melanocytic nevi, melanoma, and normal skin.

  8. A hemispherical dynamo model: Implications for the Martian crustal magnetization

    NASA Astrophysics Data System (ADS)

    Dietrich, W.; Wicht, J.

    2013-04-01

    Mars Global Surveyor measurements revealed that the Martian crust is strongly magnetized in the southern hemisphere while the northern hemisphere is virtually void of magnetization. Two possible reasons have been suggested for this dichotomy: a once more or less homogeneously magnetization may have been destroyed in the northern hemisphere by, for example, resurfacing or impacts. The alternative theory we further explore here assumes that the dynamo itself produced a hemispherical field (Stanley et al., 2008; Amit et al., 2011). We use numerical dynamo simulations to study under which conditions a spatial variation of the heat flux through the core-mantle boundary (CMB) may yield a strongly hemispherical surface field. We assume that the early Martian dynamo was exclusively driven by secular cooling and we mostly concentrate on a cosine CMB heat flux pattern with a minimum at the north pole, possibly caused by the impacts responsible for the northern lowlands. This pattern consistently triggers a convective mode which is dominated by equatorially anti-symmetric and axisymmetric (EAA, Landeau and Aubert, 2011) thermal winds. Convective up- and down-wellings and thus radial magnetic field production then tend to concentrate in the southern hemisphere which is still cooled efficiently while the northern hemisphere remains hot. The dynamo changes from an α2 for a homogeneous CMB heat flux to an αΩ-type in the hemispherical configuration. These dynamos reverse on time scales of about 10 kyrs. This too fast to allow for the more or less unidirectional magnetization of thick crustal layer required to explain the strong magnetization in the southern hemisphere.

  9. Lateral erosion in an experimental bedrock channel: The influence of bed roughness on erosion by bed load impacts

    NASA Astrophysics Data System (ADS)

    Fuller, Theodore K.; Gran, Karen B.; Sklar, Leonard S.; Paola, Chris

    2016-05-01

    Physical experiments were conducted to evaluate the efficacy of bed load particle impacts as a mechanism of lateral bedrock erosion. In addition, we explored how changes in channel bed roughness, as would occur during development of an alluvial cover, influence rates of lateral erosion. Experimental channels were constructed to have erodible walls and a nonerodible bed using different mixtures of sand and cement. Bed roughness was varied along the length of the channel by embedding sediment particles of different size in the channel bed mixture. Lateral wall erosion from clear-water flow was negligible. Lateral erosion during periods in which bed load was supplied to the channel removed as much as 3% of the initial wetted cross-sectional area. The vertical distribution of erosion was limited to the base of the channel wall, producing channels with undercut banks. The addition of roughness elements to an otherwise smooth bed caused rates of lateral erosion to increase by as much as a factor of 7 during periods of bed load supply. However, a minimum roughness element diameter of approximately half the median bed load particle diameter was required before a substantial increase in erosion was observed. Beyond this minimum threshold size, further increases in the relative size of roughness elements did not substantially change the rate of wall erosion despite changes in total boundary shear stress. The deflection of saltating bed load particles into the channel wall by fixed roughness elements is hypothesized to be the driver of the observed increase in lateral erosion rates.

  10. Effective impedance spectra for predicting rough sea effects on atmospheric impulsive sounds.

    PubMed

    Boulanger, Patrice; Attenborough, Keith

    2005-02-01

    Two methods of calculating the effective impedance spectra of acoustically hard, randomly rough, two-dimensional surfaces valid for acoustic wavelengths large compared with the roughness scales have been explored. The first method uses the complex excess attenuation spectrum due to a point source above a rough boundary predicted by a boundary element method (BEM) and solves for effective impedance roots identified by a winding number integral method. The second method is based on an analytical theory in which the contributions from random distributions of surface scatterers are summed to obtain the total scattered field. Effective impedance spectra deduced from measurements of the complex excess attenuation above 2D randomly rough surfaces formed by semicylinders and wedges have been compared to predictions from the two approaches. Although the analytical theory gives relatively poor predictions, BEM-deduced effective impedance spectra agree tolerably well with measured data. Simple polynomials have been found to fit BEM-deduced spectra for surfaces formed by intersecting parabolas corresponding to average roughness heights between 0.25 and 7.5 m and for five incidence angles for each average height. Predicted effects of sea-surface roughness on sonic boom profiles and rise time are comparable to those due to turbulence and molecular relaxation effects. PMID:15759695

  11. Influence of rough and smooth walls on macroscale flows in tumblers.

    PubMed

    D'Ortona, Umberto; Thomas, Nathalie; Zaman, Zafir; Lueptow, Richard M

    2015-12-01

    Walls in discrete element method simulations of granular flows are sometimes modeled as a closely packed monolayer of fixed particles, resulting in a rough wall rather than a geometrically smooth wall. An implicit assumption is that the resulting rough wall differs from a smooth wall only locally at the particle scale. Here we test this assumption by considering the impact of the wall roughness at the periphery of the flowing layer on the flow of monodisperse particles in a rotating spherical tumbler. We find that varying the wall roughness significantly alters average particle trajectories even far from the wall. Rough walls induce greater poleward axial drift of particles near the flowing layer surface but decrease the curvature of the trajectories. Increasing the volume fill level in the tumbler has little effect on the axial drift for rough walls but increases the drift while reducing curvature of the particle trajectories for smooth walls. The mechanism for these effects is related to the degree of local slip at the bounding wall, which alters the flowing layer thickness near the walls, affecting the particle trajectories even far from the walls near the equator of the tumbler. Thus, the proper choice of wall conditions is important in the accurate simulation of granular flows, even far from the bounding wall. PMID:26764677

  12. Roughness effects on thermal-infrared emissivities estimated from remotely sensed images

    NASA Astrophysics Data System (ADS)

    Mushkin, Amit; Danilina, Iryna; Gillespie, Alan R.; Balick, Lee K.; McCabe, Matthew F.

    2007-10-01

    Multispectral thermal-infrared images from the Mauna Loa caldera in Hawaii, USA are examined to study the effects of surface roughness on remotely retrieved emissivities. We find up to a 3% decrease in spectral contrast in ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) 90-m/pixel emissivities due to sub-pixel surface roughness variations on the caldera floor. A similar decrease in spectral contrast of emissivities extracted from MASTER (MODIS/ASTER Airborne Simulator) ~12.5-m/pixel data can be described as a function of increasing surface roughness, which was measured remotely from ASTER 15-m/pixel stereo images. The ratio between ASTER stereo images provides a measure of sub-pixel surface-roughness variations across the scene. These independent roughness estimates complement a radiosity model designed to quantify the unresolved effects of multiple scattering and differential solar heating due to sub-pixel roughness elements and to compensate for both sub-pixel temperature dispersion and cavity radiation on TIR measurements.

  13. The orbicularis oculi response after hemispheral damage.

    PubMed Central

    Berardelli, A; Accornero, N; Cruccu, G; Fabiano, F; Guerrisi, V; Manfredi, M

    1983-01-01

    The corneal and blink reflexes were evaluated in 20 normal subjects and in 30 patients with motor deficits secondary to unilateral hemispheral lesions of vascular origin. In the normal population there were no differences between subjects below and subjects above 50 years of age. In the patients the reflex evoked by electrical stimulation of the cornea of the clinically affected side was depressed in 24 out of 30 cases. The depression mainly affected the afferent branch of the circuit, which triggers both homolateral and contralateral orbicularis oculi discharge (afferent abnormality). In three cases the depression was exerted concomitantly on the efferent branch (afferent and efferent abnormality) and only in one case was it limited to the efferent branch (efferent abnormality). The late R2 component of the blink reflex was depressed in 15 out of 30 patients. The early R1 component was slightly facilitated on the affected side. The changes of the corneal reflex and of the R2 component of blink reflex were similar, but the blink reflex had a greater safety factor. The patients with an abnormal corneal reflex had more extensive damage than had the patients with normal corneal response, as shown by computer tomography, but the site of the lesion was comparable in the two groups. Conduction through the brain stem circuits mediating the orbicularis oculi response is normally under pyramidal facilitatory influences while facial motoneurons are subjected to pyramidal inhibition. After pyramidal damage the transmission of impulses in the brain stem was slowed down, ultimately to a degree that abolished the reflex. Removal of pyramidal inhibition on facial motoneurons is probably the basis of the slight facilitation of the R1 component of the blink reflex. Images PMID:6311988

  14. Heat Transfer Measurements on Surfaces with Natural Ice Castings and Modeled Roughness

    NASA Technical Reports Server (NTRS)

    Breuer, Kenneth S.; Torres, Benjamin E.; Orr, D. J.; Hansman, R. John

    1997-01-01

    An experimental method is described to measure and compare the convective heat transfer coefficient of natural and simulated ice accretion roughness and to provide a rational means for determining accretion-related enhanced heat transfer coefficients. The natural ice accretion roughness was a sample casting made from accretions at the NASA Lewis Icing Research Tunnel (IRT). One of these castings was modeled using a Spectral Estimation Technique (SET) to produce three roughness elements patterns that simulate the actual accretion. All four samples were tested in a flat-plate boundary layer at angle of attack in a "dry" wind tunnel test. The convective heat transfer coefficient was measured using infrared thermography. It is shown that, dispite some problems in the current data set, the method does show considerable promise in determining roughness-induced heat transfer coefficients, and that, in addition to the roughness height and spacing in the flow direction, the concentration and spacing of elements in the spanwise direction are important parameters.

  15. Micro PIV measurements of turbulent flow over 2D structured roughness

    NASA Astrophysics Data System (ADS)

    Hartenberger, Joel; Perlin, Marc

    2015-11-01

    We investigate the turbulent boundary layer over surfaces with 2D spanwise square and triangular protrusions having nominal heights of 100 - 300 microns for Reynolds numbers ranging from Reτ ~ 1500 through Reτ ~ 4500 using a high speed, high magnification imaging system. Micro PIV analysis gives finely resolved velocity fields of the flow (on the order of 10 microns between vectors) enabling a detailed look at the inner region as well as the flow in the immediate vicinity of the roughness elements. Additionally, planar PIV with lower resolution is performed to capture the remainder of the boundary layer to the freestream flow. Varying the streamwise distance between individual roughness elements from one to ten times the nominal heights allows investigation of k-type and d-type roughness in both the transitionally rough and fully rough regimes. Preliminary results show a shift in the mean velocity profile similar to the results of previous studies. Turbulent statistics will be presented also. The authors would like to acknowledge the support of NAVSEA which funded this project through the Naval Engineering Education Center (NEEC).

  16. Roughness Based Crossflow Transition Control for a Swept Airfoil Design Relevant to Subsonic Transports

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.; Carpenter, Mark H.; Malik, Mujeeb R.; Eppink, Jenna; Chang, Chau-Lyan; Streett, Craig L.

    2010-01-01

    A high fidelity transition prediction methodology has been applied to a swept airfoil design at a Mach number of 0.75 and chord Reynolds number of approximately 17 million, with the dual goal of an assessment of the design for the implementation and testing of roughness based crossflow transition control and continued maturation of such methodology in the context of realistic aerodynamic configurations. Roughness based transition control involves controlled seeding of suitable, subdominant crossflow modes in order to weaken the growth of naturally occurring, linearly more unstable instability modes via a nonlinear modification of the mean boundary layer profiles. Therefore, a synthesis of receptivity, linear and nonlinear growth of crossflow disturbances, and high-frequency secondary instabilities becomes desirable to model this form of control. Because experimental data is currently unavailable for passive crossflow transition control for such high Reynolds number configurations, a holistic computational approach is used to assess the feasibility of roughness based control methodology. Potential challenges inherent to this control application as well as associated difficulties in modeling this form of control in a computational setting are highlighted. At high Reynolds numbers, a broad spectrum of stationary crossflow disturbances amplify and, while it may be possible to control a specific target mode using Discrete Roughness Elements (DREs), nonlinear interaction between the control and target modes may yield strong amplification of the difference mode that could have an adverse impact on the transition delay using spanwise periodic roughness elements.

  17. Combinatorial Block Copolymer Ordering on Tunable Rough

    SciTech Connect

    Kulkarni M. M.; Yager K.; Sharma, A.; Karim, A.

    2012-05-01

    Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period of

  18. Musical priming by the right hemisphere post-callosotomy.

    PubMed

    Tramo, M J; Bharucha, J J

    1991-01-01

    The hemispheric representation of auditory functions mediating the perception of harmony in music was investigated in two split-brain patients using a musical chord priming task. Previous experiments in normal subjects had demonstrated that the harmonic context established by a prime chord influences the accuracy of target chord intonation judgements. Only the right hemisphere of each callosotomy patient manifested the normal interaction between harmonic relatedness and intonation. The results raise the possibility that associative auditory functions which generate expectancies for harmonic progression in music are lateralized within the right hemisphere. PMID:1857503

  19. On hemispheric differences in evoked potentials to speech stimuli

    NASA Technical Reports Server (NTRS)

    Galambos, R.; Benson, P.; Smith, T. S.; Schulman-Galambos, C.; Osier, H.

    1975-01-01

    Confirmation is provided for the belief that evoked potentials may reflect differences in hemispheric functioning that are marginal at best. Subjects were right-handed and audiologically normal men and women, and responses were recorded using standard EEG techniques. Subjects were instructed to listen for the targets while laying in a darkened sound booth. Different stimuli, speech and tone signals, were used. Speech sounds were shown to evoke a response pattern that resembles that to tone or clicks. Analysis of variances on peak amplitude and latency measures showed no significant differences between hemispheres, however, a Wilcoxon test showed significant differences in hemispheres for certain target tasks.

  20. Analysis of grounding systems in soils with hemispherical layering

    SciTech Connect

    Ma, J.; Dawalibi, F.P. ); Daily, W.K. )

    1993-10-01

    A theoretical model for the analysis of grounding systems located inside or near hemispherical soil heterogeneities is presented for the first time. Exact closed-form analytical expressions for the earth potential calculations due to current sources in different regions of this soil structure have been obtained. Numerical results are presented for different grounding systems and for different types of hemispherical soil volumes. The results clearly show that these finite hemispherical soil heterogeneities have a significant influence on the performance of grounding systems. The results obtained are in agreement with well known simple case results and converge asymptotically to the uniform soil case.

  1. Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications

    SciTech Connect

    Naulleau, P. P.; George, Simi A.

    2009-02-13

    Line-edge roughness (LER) and the related effect of contact size variation remain as significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. LER is typically viewed as a resist problem; however, recent simulation results have shown that the mask can indeed be an important contributor. Problems arise from both mask absorber LER as well as mask multilayer roughness leading to random phase variations in the reflected beam (see Fig. 1). The latter effect is especially important as higher coherence off-axis illumination conditions are used and defocus is considered. Here we describe these effect in detail and explore how they will impact EUV mask requirements for the 22-nm half-pitch node and beyond. Figure 2 shows modeling results for 22-nm lines printed in a 0.32-numerical aperture system with 100-nm defocus assuming a mask with 0.24-nm rms multilayer roughness and no absorber edge roughness (unlike the example in Fig. 1). The impact of the phase roughness on the printed line-edge roughness is clearly evident and demonstrates the basic problem with mask roughness. The more detailed modeling-based analysis to be presented will account for performance throughout the process window as well as non-stochastic resist effects. We note that the mean-field resist effect is important to consider because, in practice, the resist is the limiting resolution element in the system and therefore dominates the mask-error enhancement factor (MEEF). As is typically the case with projection-optic-induced MEEF, the resist-induced MEEF will lead to even tighter mask requirements. Note that we do not consider resist stochastic effects since the purpose of this study is isolate mask-induced sources of image-plane roughness.

  2. Hemispherical emissivity of V, Nb, Ta, Mo, and W from 300 to 1000 K

    NASA Technical Reports Server (NTRS)

    Cheng, S. X.; Hanssen, L. M.; Riffe, D. M.; Sievers, A. J.; Cebe, P.

    1987-01-01

    The hemispherical emissivities of five transition elements, V, Nb, Ta, Mo, and W, have been measured from 300 to 1000 K, complementing earlier higher-temperature results. These low-temperature data, which are similar, are fitted to a Drude model in which the room-temperature parameters have been obtained from optical measurements and the temperature dependence of the dc resistivity is used as input to calculate the temperature dependence of the emissivity. A frequency-dependent free-carrier relaxation rate is found to have a similar magnitude for all these elements. For temperatures larger than 1200 K the calculated emissivity is always greater than the measured value, indicating that the high-temperature interband features of transition elements are much weaker than those determined from room-temperature measurements.

  3. Fresnel diffraction of aperture with rough edge

    NASA Astrophysics Data System (ADS)

    Cui, Yuwei; Zhang, Wei; Wang, Junhong; Zhang, Meina; Teng, Shuyun

    2015-06-01

    The Fresnel diffraction of an aperture with a rough edge is studied in this paper. Circular and elliptical apertures with sinusoidal and random edges are chosen as examples to investigate the influence of the aperture edge on the diffraction. The numerical calculation results indicate intuitively the variations of the transverse and longitude diffraction intensity distributions with the edge parameters of the aperture. The data files of aperture models are obtained through the numerical calculations, and the aperture samples are obtained with the help of a liquid crystal light modulator (LCLM). Thus, the practical experiments of the diffractions of apertures with rough edges are carried out. The measured results are consistent with the calculated ones. The approximate analytic expressions of the diffraction by the modified aperture are deduced on the basis of the Fresnel diffraction theory and the statistic optics, and the reasonable explanations for the influence of edge parameters on the diffraction are given through the theoretical analysis.

  4. Simulating photomask edge roughness and corner rounding

    NASA Astrophysics Data System (ADS)

    Adam, Konstantinos; Socha, Robert J.; Pistor, Thomas V.; Neureuther, Andrew R.

    1997-07-01

    Corner rounding and edge roughness of a rectangular opening at a glass-chrome mask are simulated with TEMPEST. The intensity patterns on the image plane are extracted and compared for these defects at several degrees of fabrication-induced imperfection. A 4X - DUV lithography printing system is assumed with NA equals 0.6 and (sigma) equals 0.5. The prototypical geometry simulate was a 4 micrometers X 1 micrometers line on the mask. The results indicate that the rounding of the corners does not decrease the printed area by more than 2 percent for a 0.4 micrometers radius corner rounding and that roughness should not be a concern, at least in DUV, since it does not crucially affect the linewidth of the printed area.

  5. Surface Roughness Reduction on Divinylbenzene Foam Shells

    NASA Astrophysics Data System (ADS)

    Streit, Jon; Karnes, John; Motta, Brian; Petta, Nicole

    2009-11-01

    Inertial fusion energy targets for the Naval Research Laboratory's High Average Power Laser Program require millimeter-scale, low density foam capsules with a gas permeation barrier and an outer surface roughness less than 50 nm RMS. Divinylbenzene (DVB) foam is a candidate for the capsule wall material, but its porous, open celled surface has been both too rough and difficult to seal. To overcome this difficulty we have repurposed a previously reported dual stage initiator emulsion microencapsulation method, adding an additional step that enhances the surface of the foam capsules. Using both low and high temperature initiators allows the DVB foam to gel in the low temperature stage and a water soluble monomer to be added and polymerized during the high temperature stage without breaking down the emulsion. This method forms a submicron skin that covers the open celled DVB foam surface, resulting in a superior substrate for gas permeation barrier deposition.

  6. Boltzmann active walkers and rough surfaces

    NASA Astrophysics Data System (ADS)

    Pochy, R. D.; Kayser, D. R.; Aberle, L. K.; Lam, L.

    1993-06-01

    An active walker model (AWM) was recently proposed by Freimuth and Lam for the generation of various filamentary patterns. In an AWM, the walker changes the landscape as it walks, and its steps are in turn influenced by the changing landscape. The landscape so obtained is a rough surface. In this paper, the properties of such a rough surface (with average height conserved) generated by a Boltzmann active walker in 1 + 1 dimensions is investigated in detail. The scaling properties of the surface thickness σ T is found to belong to a new class quite different from other types of fractal surfaces. For example, σ T is independent of the system size L, but is a function of the “temperature” T. Soliton propagation is found when T = 0.

  7. Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record

    NASA Astrophysics Data System (ADS)

    Scafetta, N.; West, B. J.

    2006-09-01

    We study the solar impact on 400 years of a global surface temperature record since 1600. This period includes the pre-industrial era (roughly 1600-1800 or 1600-1900), when negligible amount of anthropogenic-added climate forcing was present and the sun realistically was the only climate force affecting climate on a secular scale, and the industrial era (roughly since 1800-1900), when anthropogenic-added climate forcing has been present in some degree. We use a recent secular Northern Hemisphere temperature reconstruction (Moberg et al., 2005), three alternative total solar irradiance (TSI) proxy reconstructions (Lean et al., 1995; Lean, 2000; Wang et al., 2005) and a scale-by-scale transfer climate sensitivity model to solar changes (Scafetta and West, 2005, 2006). The phenomenological approach we propose is an alternative to the more traditional computer-based climate model approach, and yields results proven to be almost independent on the secular TSI proxy reconstruction used. We find good correspondence between global temperature and solar induced temperature curves during the pre-industrial period such as the cooling periods occurring during the Maunder Minimum (1645-1715) and the Dalton Minimum (1795-1825). The sun might have contributed approximately 50% of the observed global warming since 1900 (Scafetta and West, 2006). We briefly discuss the global cooling that occurred from the medieval maximum (~1000-1100 AD) to the 17th century minimum.

  8. Replicated mask surface roughness effects on EUV lithographic patterning and line edge roughness

    NASA Astrophysics Data System (ADS)

    George, Simi A.; Naulleau, Patrick P.; Gullikson, Eric M.; Mochi, Iacopo; Salmassi, Farhad; Goldberg, Kenneth A.; Anderson, Erik H.

    2011-04-01

    To quantify the roughness contributions to speckle, a programmed roughness substrate was fabricated with a number of areas having different roughness magnitudes. The substrate was then multilayer coated. Atomic force microscopy (AFM) surface maps were collected before and after multilayer deposition. At-wavelength reflectance and total integrated scattering measurements were also completed. Angle resolved scattering based power spectral densities are directly compared to the AFM based power spectra. We show that AFM overpredicts the roughness in the picometer measurements range. The mask was then imaged at-wavelength for the direct characterization of the aerial image speckle using the SEMATECH Berkeley Actinic Inspection Tool (AIT). Modeling was used to test the effectiveness of the different metrologies in predicting the measured aerial-image speckle. AIT measured contrast values are 25% or more than the calculated image contrast values obtained using the measured rms roughness input. The extent to which the various metrologies can be utilized for specifying tolerable roughness limits on EUV masks is still to be determined. Further modeling and measurements are being planned.

  9. Replicated mask surface roughness effects on EUV lithographic pattering and line edge roughness

    SciTech Connect

    George, Simi A.; Naulleau, Patrick P.; Gullikson, Eric M.; Mochi, Iacopo; Salmassi, Farhad; Goldberg, Kenneth A.; Anderson, Erik H.

    2011-03-11

    To quantify the roughness contributions to speckle, a programmed roughness substrate was fabricated with a number of areas having different roughness magnitudes. The substrate was then multilayer coated. Atomic force microscopy (AFM) surface maps were collected before and after multilayer deposition. At-wavelength reflectance and total integrated scattering measurements were also completed. Angle resolved scattering based power spectral densities are directly compared to the AFM based power spectra. We show that AFM overpredicts the roughness in the picometer measurements range. The mask was then imaged at-wavelength for the direct characterization of the aerial image speckle using the SEMATECH Berkeley Actinic Inspection Tool (AIT). Modeling was used to test the effectiveness of the different metrologies in predicting the measured aerial-image speckle. AIT measured contrast values are 25% or more than the calculated image contrast values obtained using the measured rms roughness input. The extent to which the various metrologies can be utilized for specifying tolerable roughness limits on EUV masks is still to be determined. Further modeling and measurements are being planned.

  10. Recovery of ribophorins and ribosomes in "inverted rough" vesicles derived from rat liver rough microsomes

    PubMed Central

    1982-01-01

    Treatment of rat liver rough microsomes (3.5 mg of protein/ml) with sublytical concentrations (0.08%) of the neutral detergent Triton X-100 caused a lateral displacement of bound ribosomes and the formation of ribosomal aggregates on the microsomal surface. At slightly higher detergent concentrations (0.12-0.16%) membrane areas bearing ribosomal aggregates invaginated into the microsomal lumen and separated from the rest of the membrane. Two distinct classes of vesicles could be isolated by density gradient centrifugation from microsomes treated with 0.16% Triton X-100: one with ribosomes bound to the inner membrane surfaces ("inverted rough" vesicles) and another with no ribosomes attached to the membranes. Analysis of the fractions showed that approximately 30% of the phospholipids and 20-30% of the total membrane protein were released from the membranes by this treatment. Labeling with avidin-ferritin conjugates demonstrated that concanavalin A binding sites, which in native rough microsomes are found in the luminal face of the membranes, were present on the outer surface of the inverted rough vesicles. Freeze-fracture electron microscopy showed that both fracture faces had similar concentrations of intramembrane particles. SDS PAGE analysis of the two vesicle subfractions demonstrated that, of all the integral microsomal membrane proteins, only ribophorins I and II were found exclusively in the inverted rough vesicles bearing ribosomes. These observations are consistent with the proposal that ribophorins are associated with the ribosomal binding sites characteristic of rough microsomal membranes. PMID:7068749

  11. Rough primes and rough conversations: evidence for a modality-specific basis to mental metaphors

    PubMed Central

    Denke, Claudia; Heinze, Hans-Jochen; Rotte, Michael

    2014-01-01

    How does our brain organize knowledge? Traditional theories assume that our knowledge is represented abstractly in an amodal conceptual network of formal logic symbols. The theory of embodied cognition challenges this view and argues that conceptual representations that constitute our knowledge are grounded in sensory and motor experiences. We tested this hypothesis by examining how the concept of social coordination is grounded metaphorically in the tactile sensation of roughness. Participants experienced rough or smooth touch before being asked to judge an ambiguous social interaction. Results revealed that rough touch made social interactions appear more difficult and adversarial, consistent with the rough metaphor. This impact of tactile cues on social impressions was accompanied by a network including primary and secondary somatosensory cortices, amygdala, hippocampus and inferior prefrontal cortex. Thus, the roughness of tactile stimulation affected metaphor-relevant (but not metaphor-irrelevant) behavioral and neural responses. Receiving touch from a rough object seems to trigger the application of associated ontological concepts (or scaffolds) even for unrelated people and situations (but not to unrelated or more general feelings). Since this priming was based on somatosensory brain areas, our results provide support for the theory that sensorimotor grounding is intrinsic to cognitive processes. PMID:24097375

  12. Mimas - Photometric roughness and albedo map

    NASA Technical Reports Server (NTRS)

    Verbiscer, Anne J.; Veverka, Joseph

    1992-01-01

    The backscattering phase function asssociated with bright icy satellites may render Hapke's (1986) isotropic approximation to multiple scattering inadequate. A reanalysis is accordingly conducted here of the Voyager observations of Mimas, using a modification to Hapke's equation that accommodates anisotropic multiple scattering, in order to characterize the physical and photometric properties of the heavily cratered icy surface. The roughness parameter of Mimas is in this way redefined, and an accurate albedo map is obtained which deminstrates small latitudinal and longitudinal albedo variations.

  13. Radiative transfer model for contaminated rough slabs.

    PubMed

    Andrieu, François; Douté, Sylvain; Schmidt, Frédéric; Schmitt, Bernard

    2015-11-01

    We present a semi-analytical model to simulate the bidirectional reflectance distribution function (BRDF) of a rough slab layer containing impurities. This model has been optimized for fast computation in order to analyze massive hyperspectral data by a Bayesian approach. We designed it for planetary surface ice studies but it could be used for other purposes. It estimates the bidirectional reflectance of a rough slab of material containing inclusions, overlaying an optically thick media (semi-infinite media or stratified media, for instance granular material). The inclusions are assumed to be close to spherical and constituted of any type of material other than the ice matrix. It can be any other type of ice, mineral, or even bubbles defined by their optical constants. We assume a low roughness and we consider the geometrical optics conditions. This model is thus applicable for inclusions larger than the considered wavelength. The scattering on the inclusions is assumed to be isotropic. This model has a fast computation implementation and thus is suitable for high-resolution hyperspectral data analysis. PMID:26560577

  14. Wenzel Wetting on Slippery Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Stogin, Birgitt; Dai, Xianming; Wong, Tak-Sing

    2015-11-01

    Liquid repellency is an important surface property used in a wide range of applications including self-cleaning, anti-icing, anti-biofouling, and condensation heat transfer, and is characterized by apparent contact angle (θ*) and contact angle hysteresis (Δθ*). The Wenzel equation (1936) predicts θ* of liquids in the Wenzel state, and is one of the most fundamental equations in the wetting field. However, droplets in the Wenzel state on conventional rough surfaces exhibit large Δθ* , making it difficult to experimentally verify the model with precision. As a result, precise verification of the Wenzel wetting model has remained an open scientific question for the past 79 years. Here we introduce a new class of liquid-infused surfaces called slippery rough surfaces -- surfaces with significantly reduced Δθ* compared to conventional rough surfaces--and use them to experimentally assess the Wenzel equation with the highest precision to date. We acknowledge the funding support by National Science Foundation (NSF) CAREER Award #: 1351462 and Office of Navy Research MURI Award #: N00014-12-1-0875. Stogin acknowledges the support from the NSF Graduate Research Fellowship (Grant No. DGE1255832).

  15. Soil Surface Roughness through Image Analysis

    NASA Astrophysics Data System (ADS)

    Tarquis, A. M.; Saa-Requejo, A.; Valencia, J. L.; Moratiel, R.; Paz-Gonzalez, A.; Agro-Environmental Modeling

    2011-12-01

    Soil erosion is a complex phenomenon involving the detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude and importance of these processes depends on several factors being one of them surface micro-topography, usually quantified trough soil surface roughness (SSR). SSR greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. The methods commonly used to measure SSR involve measuring point elevation using a pin roughness meter or laser, both of which are labor intensive and expensive. Lately a simple and inexpensive technique based on percentage of shadow in soil surface image has been developed to determine SSR in the field in order to obtain measurement for wide spread application. One of the first steps in this technique is image de-noising and thresholding to estimate the percentage of black pixels in the studied area. In this work, a series of soil surface images have been analyzed applying several de-noising wavelet analysis and thresholding algorithms to study the variation in percentage of shadows and the shadows size distribution. Funding provided by Spanish Ministerio de Ciencia e Innovación (MICINN) through project no. AGL2010- 21501/AGR and by Xunta de Galicia through project no INCITE08PXIB1621 are greatly appreciated.

  16. Modeling superhydrophobic surfaces comprised of random roughness

    NASA Astrophysics Data System (ADS)

    Samaha, M. A.; Vahedi Tafreshi, H.; Gad-El-Hak, M.

    2011-11-01

    We model the performance of superhydrophobic surfaces comprised of randomly distributed roughness that resembles natural surfaces, or those produced via random deposition of hydrophobic particles. Such a fabrication method is far less expensive than ordered-microstructured fabrication. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridge configurations for pipe flows. The present results are compared with other theoretical and experimental studies. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. Financial support from DARPA, contract number W91CRB-10-1-0003, is acknowledged.

  17. Flow over a Biomimetic Surface Roughness Microgeometry

    NASA Astrophysics Data System (ADS)

    Warncke Lang, Amy; Hidalgo, Pablo; Westcott, Matthew

    2006-11-01

    Certain species of sharks (e.g. shortfin mako and common hammerhead) have a skin structure that could result in a bristling of their denticles (scales) during increased swimming speeds (Bechert, D. W., Bruse, M., Hage, W. and Meyer, R. 2000, Fluid mechanics of biological surfaces and their technological application. Naturwissenschaften 80:157-171). This unique surface geometry results in a three-dimensional array of cavities* (d-type roughness geometry) forming within the surface and has been given the acronym MAKO (Micro-roughness Array for Kinematic Optimization). Possible mechanisms leading to drag reduction over the shark's body by this unique roughness geometry include separation control thereby reducing pressure drag, skin friction reduction (via the `micro-air bearing' effect first proposed by Bushnell (AIAA 83-0227)), as well as possible transition delay in the boundary layer. Initial work is confined to scaling up the geometry from 0.2 mm on the shark skin to 2 cm, with a scaling down in characteristic velocity from 10 - 20 m/s to 10 - 20 cm/s for laminar flow boundary layer water tunnel studies. Support for this research by NSF SGER grant CTS-0630489 and a University of Alabama RAC grant is gratefully acknowledged. * Patent pending.

  18. Poleward bound: biological impacts of Southern Hemisphere glaciation.

    PubMed

    Fraser, Ceridwen I; Nikula, Raisa; Ruzzante, Daniel E; Waters, Jonathan M

    2012-08-01

    Postglacial recolonisation patterns are well documented for the Northern Hemisphere biota, but comparable processes in the Southern Hemisphere have only recently been examined. In the largely terrestrial Northern Hemisphere, recession of ice after the Last Glacial Maximum (LGM) allowed various taxa, including slow-moving terrestrial species, to migrate poleward. By contrast, the Southern Hemisphere polar region is completely ringed by ocean, and recolonisation of Antarctica and the sub-Antarctic islands has thus presented considerable challenges. Although a few highly dispersive marine species have been able to recolonise postglacially, most surviving high-latitude taxa appear to have persisted throughout glacial maxima in local refugia. These contrasting patterns highlight the importance of habitat continuity in facilitating biological range shifts in response to climate change. PMID:22658874

  19. Geological Mapping of the Encounter Hemisphere on Pluto

    NASA Astrophysics Data System (ADS)

    White, O. L.; Moore, J. M.; Stern, S. A.; Weaver, H. A.; Olkin, C. B.; Ennico, K.; Young, L. A.; Cheng, A. F.; New Horizons GGI Theme Team

    2016-06-01

    We present mapping of Pluto's encounter hemisphere performed to date (focusing on Sputnik Planum and the immediately surrounding area) and offer preliminary descriptions of terrains further afield that will be the subject of future mapping.

  20. Summer Temperature Anomalies for the Northern Hemisphere, 1955-2011

    NASA Video Gallery

    This visualization shows a flat map of the Earth with summertime temperature anomalies for the Northern Hemisphere. This analysis compares observed seasonal mean temperatures (June-July-August) to ...

  1. Metaliteral dreaming: a right hemisphere dominant linguistic activity.

    PubMed

    Arenson, K

    1990-06-01

    Many dream reports, which take the form of propositional speech, are more meaningful if understood as metaliteral speech. To achieve this understanding the speech sounds must be decoded according to different linguistic rules than govern propositional speech. The basic rules for metaliteral speech were outlined in a recent paper. Those rules came from empirical observation. This paper proposes that the right hemisphere is dominant for the linguistic activity of metaliteral speech because, in one way or another, the rules all seem to depend on the cognitive use of right hemisphere functions, or sometimes, on the absence of left hemisphere functions. The proposed theory rejects an exclusive role for the right hemisphere in metaliteral behavior. By recognizing the subordinate role of the left, the puzzles are solved of the story-like quality to dream reports and the central role of prosody in decoding metaliteral speech. PMID:2197651

  2. Light scattering by irregular particles much larger than the wavelength with wavelength-scale surface roughness.

    PubMed

    Grynko, Yevgen; Shkuratov, Yuriy; Förstner, Jens

    2016-08-01

    We simulate light scattering by random irregular particles that have dimensions much larger than the wavelength of incident light at the size parameter of X=200 using the discontinuous Galerkin time domain method. A comparison of the DGTD solution for smoothly faceted particles with that obtained with a geometric optics model shows good agreement for the scattering angle curves of intensity and polarization. If a wavelength-scale surface roughness is introduced, diffuse scattering at rough interface results in smooth and featureless curves for all scattering matrix elements which is consistent with the laboratory measurements of real samples. PMID:27472601

  3. Aerodynamic roughness measured in the field and simulated in a wind tunnel

    NASA Technical Reports Server (NTRS)

    Sullivan, Robert; Greeley, Ronald

    1992-01-01

    This study evaluates how well values of aerodynamic surface roughness, z sub 0, measured over scale models in wind tunnels correlate with values of z sub 0 measured at full scale in the field. A field experiment was conducted in which values of z sub 0 and u* (wind friction speed) were measured over three arrays of non-erodible roughness elements on a dry lake bed. Wind profiles were measured by ten anemometers on a 15 m mast under thermally neutral atmospheric conditions. Values of z sub 0 increased from .00014 m (dry lake bed only) to .026 m with increasing roughness element density. The three roughness element arrays were simulated at 1/10 and 1/20 scale in an open-circuit atmospheric boundary-layer wind tunnel. Velocities were measured with a boundary-layer pitot-tube rake from the same relative position within the scale model arrays as the anemometers were relative to the field arrays. Each array at each scale was sampled three times at five freestream velocities. Average values of z sub 0 for each model array at each scale were compared with full-scale values of z sub 0 obtained in the field. The field vs. wind tunnel correspondence of z sub 0 is found to be z sub 0 field = 0.2661 x (z sub(0 model) x scale(exp -1))exp .8159.

  4. Highly regioselective hydroformylation with hemispherical chelators.

    PubMed

    Sémeril, David; Matt, Dominique; Toupet, Loïc

    2008-01-01

    The hemispherical diphosphites (R,R)- or (S,S)-5,11,17,23-tetra-tert-butyl-25,27-di(OR)-26,28-bis(1,1'-binaphthyl-2,2'-dioxyphosphanyloxy)calix[4]arene (R=OPr, OCH(2)Ph, OCH(2)-naphtyl, O-fluorenyl; R=H, R'=OPr) (L(R)), all with C(2) symmetry, have been synthesised starting from the appropriate di-O-alkylated calix[4]arene precursor. In the presence of [Rh(acac)(CO)(2)], these ligands straightforwardly provide chelate complexes in which the metal centre sits in a molecular pocket defined by two naphthyl planes related by the C(2) axis and the two apically situated R groups. Hydroformylation of octene with the L(Pr)/Rh system turned out to be highly regioselective, the linear-to-branched (l:b) aldehyde ratio reaching 58:1. The l:b ratio significantly increased when the propyl groups were replaced by -CH(2)Ph (l:b=80) or -CH(2)naphthyl (l:b=100) groups, that is, with substituents able to sterically interact with the apical metal sites, but without inducing an opening of the cleft nesting the catalytic centre. The trend to preferentially form the aldehyde the shape of which fits with the shape of the catalytic pocket was further confirmed in the hydroformylation of styrene, for which, in contrast to catalysis with conventional diphosphanes, the linear aldehyde was the major product (up to ca. 75 % linear aldehyde). In the hydroformylation of trans-2-octene with the L(benzyl)/Rh system, combined isomerisation/hydroformylation led to a remarkably high l:b aldehyde ratios of 25, thus showing that isomerisation is more effective than hydroformylation. Unusually large amounts of linear products were also observed with all the above diphosphites in the tandem hydroformylation/amination of styrene (l:b of ca. 3:1) as well as in the hydroformylation of allyl benzyl ether (l:b ratio up to 20). PMID:18686280

  5. RIGHT HEMISPHERIC FUNCTION IN NORMALS, AFFECTIVE DISORDER AND SCHIZOPHRENIA

    PubMed Central

    Borde, Milind; Roy, Amal; Davis, Elizabeth J.B.; Davis, Rachel

    1996-01-01

    The happy-sad chimeric faces test has been established as a useful test of right hemispheric function. It is known to elicit a left hemifacial bias (LHF bias) in right handed subjects. 41 normals and 19 manic, depressive and schizophrenic patients each were tested. All subjects were strictly right handed. Normals and depressives showed significant LHF bias. Monies and schizophrenics did not show significant LHF Bias. This suggests right hemispheric dysfunction in both mania and schizophrenia. PMID:21584135

  6. Fault zone roughness controls slip stability

    NASA Astrophysics Data System (ADS)

    Harbord, Christopher; Nielsen, Stefan; De Paola, Nicola

    2016-04-01

    Fault roughness is an important control factor in the mechanical behaviour of fault zones, in particular the frictional slip stability and subsequent earthquake nucleation. Despite this, there is little experimental quantification as to the effects of varying roughness upon rate- and state-dependant friction (RSF). Utilising a triaxial deformation apparatus and a novel adaptation of the direct shear methodology to simulate initially bare faults in Westerly Granite, we performed a series of velocity step frictional sliding experiments. Initial root mean square roughnesses (Sq) was varied in the range 6x10‑7 ‑ 2.4x10‑5 m. We also investigated the effects upon slip stability of normal stress variation in the range σn = 30 ‑ 200 MPa, and slip velocity between 0.1 ‑ 10 μm s‑1. A transition from stable sliding to unstable slip (manifested by stick-slip and slow slip events) was observed, depending on the parameter combination, thus covering the full spectrum of fault slip behaviours. At low normal stress (σn = 30MPa) smooth faults (Sq< 1x10‑6 m) are conditional unstable (stress drops on slow slip events upon velocity increase), with strongly velocity weakening friction. When normal stress is increased to intermediate values (σn = 100 ‑ 150 MPa), smooth faults (Sq< 1x10‑6 m) are fully unstable and generate seismic stick-slip behaviour. However at higher normal stress (σn = 200 MPa) a transition from unstable to stable sliding is observed for smooth faults, which is not expected using RSF stability criteria. At all conditions sliding is stable for rough faults (Sq> 1x10‑6 m). We find that instability can develop when the ratio of fault to critical stiffness kf kc > 10, or, alternatively, even when a ‑ b > 0 at σn = 150MPa, suggesting that bare surfaces may not strictly obey the R+S stability condition. Additionally we present white light interferometry and SEM analysis of experimentally deformed samples which provide information about the

  7. Different Effects of Roughness (Granularity) and Hydrophobicity

    NASA Astrophysics Data System (ADS)

    Shirtcliffe, Neil; McHale, Glen; Hamlett, Christopher; Newton, Michael

    2010-05-01

    With thanks to Stefan Doerr and Jorge Mataix-Solera for their invitation Superhydrophobicity is an interesting effect that appears to be simple on the outset; increased surface area from roughness increases interfacial area and therefore energy loss or gain. More extreme roughness prevents total wetting, resulting in gas pockets present at the surface and a drastic change in the properties of the system. Increases in complexity of the system, by adding porosity (granularity), allowing the structures to move, varying the shape of the roughness or the composition of the liquid used often has unexpected effects. Here we will consider a few of these related to complex topography. Overhanging features are commonly used in test samples as they perform better in some tests than simple roughness. It has been shown to be a prerequisite for superoleophobic surfaces as it allows liquids to be suspended for contact angles considerably below 90°. It also allows trapping of gas in lower layers even if the first layer is flooded. This is important in soils as a fixed bed of granules behaves just like a surface with overhanging roughness. Using simple geometry it is possible to predict at what contact angle penetration will occur. Plants have some structured superhydrophobic surfaces and we have shown that some use them in conjunction with other structured surfaces to control water flows. This allows some plants to survive in difficult environments and shows us how subtly different structures interact completely differently with water. Long fibres can either cause water droplets to roll over a plant surface or halt it in its tracks. Implications of this in soils include predicting when particles will adhere more strongly to water drops and why organic fibrous material may play a greater role in the behaviour of water in soils than may be expected from the amount present. The garden snail uses a biosurfactant that is very effective at wetting surfaces and can crawl over most

  8. Characterization of surface roughness effects on pressure drop in single-phase flow in minichannels

    NASA Astrophysics Data System (ADS)

    Kandlikar, Satish G.; Schmitt, Derek; Carrano, Andres L.; Taylor, James B.

    2005-10-01

    Roughness features on the walls of a channel wall affect the pressure drop of a fluid flowing through that channel. This roughness effect can be described by (i) flow area constriction and (ii) increase in the wall shear stress. Replotting the Moody's friction factor chart with the constricted flow diameter results in a simplified plot and yields a single asymptotic value of friction factor for relative roughness values of ɛ /D>0.03 in the fully developed turbulent region. After reviewing the literature, three new roughness parameters are proposed (maximum profile peak height Rp, mean spacing of profile irregularities RSm, and floor distance to mean line Fp). Three additional parameters are presented to consider the localized hydraulic diameter variation (maximum, minimum, and average) in future work. The roughness ɛ is then defined as Rp+Fp. This definition yields the same value of roughness as obtained from the sand-grain roughness [H. Darcy, Recherches Experimentales Relatives au Mouvement de L'Eau dans les Tuyaux (Mallet-Bachelier, Paris, France, 1857); J. T. Fanning, A Practical Treatise on Hydraulic and Water Supply Engineering (Van Nostrand, New York, 1877, revised ed. 1886); J. Nikuradse, "Laws of flow in rough pipes" ["Stromungsgesetze in Rauen Rohren," VDI-Forschungsheft 361 (1933)]; Beilage zu "Forschung auf dem Gebiete des Ingenieurwesens," Ausgabe B Band 4, English translation NACA Tech. Mem. 1292 (1937)]. Specific experiments are conducted using parallel sawtooth ridge elements, placed normal to the flow direction, in aligned and offset configurations in a 10.03mm wide rectangular channel with variable gap (resulting hydraulic diameters of 325μm-1819μm with Reynolds numbers ranging from 200 to 7200 for air and 200 to 5700 for water). The use of constricted flow diameter extends the applicability of the laminar friction factor equations to relative roughness values (sawtooth height) up to 14%. In the turbulent region, the aligned and offset

  9. The effects of roughness and offset on fracture compliance ratio

    NASA Astrophysics Data System (ADS)

    Ahmadi, M.; Taleghani, A. Dahi; Sayers, C. M.

    2016-04-01

    Fractures are a source of extra compliance in the rock mass. The mechanical properties of the rock matrix as well as the propagation of seismic waves inside the rock medium are dependent on the magnitude of roughness and offset between the imperfect fracture interfaces. Fracture compliance can estimate the degree of contact between fracture faces, type of fluid filling the fracture and the fracture roughness. To characterize these fracture properties, compliance ratio, known by the ratio of normal-to-shear compliance, can be a potential tool in the subsurface studies to improve the well layout design. The focus of this study is to illustrate how the compliance ratio of a rough fracture, with or without the offset between the fracture faces, can diverge from the compliance ratio of a fracture with smooth interface. Quasi-static and dynamic methods are two common ways to calculate the compliance. The former calculates the compliance by measuring the change in the displacement with the applied stress, while the latter estimates the compliance through monitoring the changes in propagation of seismic waves. To compare the compliance ratios of fractures with imperfect and smooth interfaces in an infinite medium, a numerical finite-element model is built in commercial finite-element software. The imperfect interface of the fracture is modeled with saw-tooth-like structures where they can be partially or fully in contact. The defined saw-tooth-like structures of contact asperities impose an in-plane asymmetry in the shear direction. This asymmetry causes two different values for the compliance in shear direction, known as the soft and stiff shear compliance. Our numerical simulations suggest the increase in the degree of contact between the fracture faces increases the compliance ratio in the stiff direction more than the soft direction. The compliance ratio of the fracture with the imperfect interface is larger than the compliance ratio of the smooth fracture. We suggest

  10. Hemispheric asymmetry in the efficiency of attentional networks.

    PubMed

    Asanowicz, Dariusz; Marzecová, Anna; Jaśkowski, Piotr; Wolski, Piotr

    2012-07-01

    Despite the fact that hemispheric asymmetry of attention has been widely studied, a clear picture of this complex phenomenon is still lacking. The aim of the present study was to provide an efficient and reliable measurement of potential hemispheric asymmetries of three attentional networks, i.e. alerting, orienting and executive attention. Participants (N=125) were tested with the Lateralized Attention Network Test (LANT) that allowed us to investigate the efficiency of the networks in both visual fields (VF). We found a LVF advantage when a target occurred in an unattended location, which seems to reflect right hemisphere superiority in control of the reorienting of attention. Furthermore, a LVF advantage in conflict resolution was observed, which may indicate hemispheric asymmetry of the executive network. No VF effect for alerting was found. The results, consistent with the common notion of general right hemisphere dominance for attention, provide a more detailed account of hemispheric asymmetries of the attentional networks than previous studies using the LANT task. PMID:22475579

  11. Category Membership and Semantic Coding in the Cerebral Hemispheres.

    PubMed

    Turner, Casey E; Kellogg, Ronald T

    2016-01-01

    Although a gradient of category membership seems to form the internal structure of semantic categories, it is unclear whether the 2 hemispheres of the brain differ in terms of this gradient. The 2 experiments reported here examined this empirical question and explored alternative theoretical interpretations. Participants viewed category names centrally and determined whether a closely related or distantly related word presented to either the left visual field/right hemisphere (LVF/RH) or the right visual field/left hemisphere (RVF/LH) was a member of the category. Distantly related words were categorized more slowly in the LVF/RH relative to the RVF/LH, with no difference for words close to the prototype. The finding resolved past mixed results showing an unambiguous typicality effect for both visual field presentations. Furthermore, we examined items near the fuzzy border that were sometimes rejected as nonmembers of the category and found both hemispheres use the same category boundary. In Experiment 2, we presented 2 target words to be categorized, with the expectation of augmenting the speed advantage for the RVF/LH if the 2 hemispheres differ structurally. Instead the results showed a weakening of the hemispheric difference, arguing against a structural in favor of a processing explanation. PMID:27424416

  12. Phase Relationships of Solar Hemispheric Toroidal and Poloidal Cycles

    NASA Astrophysics Data System (ADS)

    Muraközy, J.

    2016-08-01

    The solar northern and southern hemispheres exhibit differences in their intensities and time profiles of the activity cycles. The time variation of these properties was studied in a previous article covering the data from Cycles 12–23. The hemispheric phase lags exhibited a characteristic variation: the leading role was exchanged between hemispheres every four cycles. The present work extends the investigation of this variation using the data of Staudacher and Schwabe in Cycles 1–4 and 7–10 as well as Spörer’s data in Cycle 11. The previously observed variation cannot be clearly recognized using the data of Staudacher, Schwabe, and Spörer. However, it is more interesting that the phase lags of the reversals of the magnetic fields at the poles follow the same variations as those of the hemispheric cycles in Cycles 12–23, i.e., one of the hemispheres leads in four cyles and the leading role jumps to the opposite hemisphere in the next four cycles. This means that this variation is a long-term property of the entire solar dynamo mechanism, for both the toroidal and poloidal fields, which hints at an unidentified component of the process responsible for the long-term memory.

  13. Stereotyping, self-affirmation, and the cerebral hemispheres.

    PubMed

    Shrira, Ilan; Martin, Leonard L

    2005-06-01

    The authors used the processing characteristics of the left and right cerebral hemispheres to gain some insight into the relation between self-affirmation and stereotyping. In Study 1, self-affirmation led to greater stereotyping (of a librarian) and to greater left hemisphere activation, which in turn mediated the self-affirmation/stereotyping relationship. Study 2 replicated these results but also found that self-affirmation decreased stereotyping for a stigmatized target. However, relative hemisphere activation did not mediate this self-affirmation/stereotyping relationship. These studies showed that self-affirmation can either increase or decrease stereotyping depending on the status of the target and that relative hemisphere activation may provide clues as to underlying processes of stereotyping. In both studies, relative hemisphere activation was assessed using a line bisection task. Discussion focuses on possible mechanisms of different kinds of stereotyping and on the ways in which a consideration of relative hemisphere activation could help researchers gain insights into those mechanisms. PMID:15833910

  14. Evidence of inter-hemispheric temperature contrasts over the last millennium from a new Southern Hemisphere multi-proxy reconstruction

    NASA Astrophysics Data System (ADS)

    Neukom, Raphael; Gergis, Joëlle; Karoly, David; Wanner, Heinz; Curran, Mark; Elbert, Julie; González-Rouco, Fidel; Linsley, Braddock; Moy, Andrew; Mundo, Ignacio; Raible, Christoph; Steig, Eric; van Ommen, Tas; Vance, Tessa; Villalba, Ricardo; Zinke, Jens; Frank, David

    2014-05-01

    The instrumental temperature record shows distinct inter-hemispheric temperature differences superimposed on the common warming trend over the last 150 years. Asynchronicity between the hemispheres is also suggested by millennial-scale analyses over the last deglaciation and the Holocene, indicating a significant modulation of the response to external forcing by internal climate system variability on multiple temporal scales. However, on multi-decadal to centennial times-scales, quantitative analyses on inter-hemispheric temperature variability are largely missing due to the lack of hemispheric-scale high-resolution reconstructions from the Southern Hemisphere. We introduce a new annually resolved multi-proxy ensemble reconstruction of Southern Hemisphere mean temperatures over the last 1000 years. The reconstruction is based on an unprecedented network of 325 proxy records yielding 111 temperature sensitive predictors. In 99.7% of the reconstruction ensemble members, the warmest decade of the last millennium occurs after 1970. Comparing our results with an ensemble of Northern Hemisphere mean reconstructions, we identify periods, where both hemispheres simultaneously exhibit extreme temperatures (defined as exceeding ±1 standard deviations of 1000-2000 temperatures). The only pre-industrial period where >33% of ensemble members indicate globally synchronous extremes is the cold phase between 1594 and 1677. Simultaneous warm temperatures are only identified in the years after 1974 (1979) where more than 66% (90%) of ensemble members indicate extreme warmth. This suggests existence of a globally coherent peak 'Little Ice Age', but no consistent 'Medieval Climate Anomaly' during last 1000 years. We then compare our ensemble of temperature reconstructions to an ensemble of 24 climate model simulations. While the simulated globally consistent cold periods coincide with major volcanic eruptions, the simulations do not account for key features of reconstructed

  15. Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials: Hastelloy X, Haynes 230, and Alloy 617

    NASA Astrophysics Data System (ADS)

    Maynard, Raymond K.

    An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emissivity of structural materials of interest in Very High Temperature Reactor (VHTR) systems. The system was tested with304 stainless steel as well as for oxidized and un-oxidized nickel, and good reproducibility and agreement with the literature data was found. Emissivity of Hastelloy X was measured under different conditions that included: (i) "as received" (original sample) from the supplier; (ii) with increased surface roughness; (iii) oxidized, and; (iv) graphite coated. Measurements were made over a wide range of temperatures. Hastelloy X, as received from the supplier, was cleaned before additional roughening of the surface and coating with graphite. The emissivity of the original samples (cleaned after received) varied from around 0.18 to 0.28 in the temperature range of 473 K to 1498 K. The apparent emissivity increased only slightly as the roughness of the surface increased (without corrections for the increased surface area due to the increased surface roughness). When Hastelloy X was coated with graphite or oxidized however, its emissivity was observed to increase substantially. With a deposited graphite layer on the Hastelloy, emissivity increased from 0.2 to 0.53 at 473 K and from 0.25 to 0.6 at 1473 K; a finding that has strong favorable safety implications in terms of decay heat removal in post-accident VHTR environments. Although initial oxidation of Hastelloy X increased the emissivity prolonged oxidation did not significantly increase emissivity. However as there is some oxidation of Hastelloy X used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in post-accident VHTR environments. The total hemispherical emissivity of Haynes 230 alloy, which is regarded as a leading candidate material for heat exchangers in VHTR systems, was measured under various surface

  16. Non-conjugate aurora and inter hemispheric currents

    NASA Astrophysics Data System (ADS)

    Reistad, J. P.; Østgaard, N.; Laundal, K. M.; Oksavik, K.

    2012-04-01

    We look at large scale auroral features using global imagers to obtain simultaneous pictures of both the southern and northern auroral ovals in the ultra violet part of the spectra. During the years 2001 and 2002 the IMAGE satellite was in a favourable position for imaging the aurora borealis (Northern Hemisphere) and the POLAR satellite with its large field-of-view VIS Earth camera had a sporadic coverage of the aurora australis (Southern Hemisphere). In total 19 hours of simultaneous global imaging from different seasons are analysed searching for non-conjugacy in the night side sector. By non-conjugate aurora we mean auroral features appearing in one hemisphere only, or significant differences in intensity between the hemispheres for the same auroral feature. We suggest that our observed large scale asymmetries can be explained in terms of inter hemispheric currents (IHC). Coherent with our earlier findings, we list three possible candidates for producing such inter hemispheric currents based on observations. 1) Hemispherical differences in the solar wind dynamo due to IMF Bx and tilt angle producing different strength of region 1 currents in the conjugate he mispheres, 2) Hemispherical differences in conductivity controlled by the tilt angle only giving rise to IHC on closed field lines, and 3) Field-aligned current components induced by the penetration of the IMF By into the closed magnetosphere. Most of the observed non-conjugate aurora in our dataset can be explained by these candidates only. The IMF By penetration candidate is considered closer. We search for evidence in our data that IMF By < 0 (By > 0) can induce an IHC producing stronger aurora on the polar boundary in the Northern (Southern) Hemisphere. Also a second IHC component are predicted from the theory, mapping to the equatorward part of the oval and opposite directed along the magnetic field lines. Using a much larger dataset for one hemisphere only, we show whether these predicted currents can

  17. Receptivity to Roughness, Acoustic, and Vortical Disturbances in Supersonic Boundary Layers Over Swept Wings

    NASA Technical Reports Server (NTRS)

    Balakumar, Ponnampalam; King, Rudolph A.

    2011-01-01

    The receptivity and interaction of stationary and traveling crossflow instability of three-dimensional supersonic boundary layers over a swept biconvex wing with a blunt leading edge are numerically investigated for a freestream Mach number of 3. The steady and unsteady flow fields are obtained by solving the full Navier-Stokes equations. The receptivity of the boundary layer to surface roughness, freestream acoustic waves, and freestream vorticity waves are numerically investigated. The initial amplitudes of the stationary vortices generated by 1 micron roughness elements is about 2000 times larger than the initial amplitudes of the traveling disturbances generated by vortical disturbances. The interaction of stationary and traveling disturbances was investigated by solving the equations with both surface roughness and vortical disturbances. When the initial amplitudes of the stationary disturbances are large compared to the traveling disturbances, the stationary vortex dominates the perturbation field. When the amplitudes are comparable, the traveling vortex prevails and the stationary vortex is suppressed.

  18. A new method for modeling rough membrane surface and calculation of interfacial interactions.

    PubMed

    Zhao, Leihong; Zhang, Meijia; He, Yiming; Chen, Jianrong; Hong, Huachang; Liao, Bao-Qiang; Lin, Hongjun

    2016-01-01

    Membrane fouling control necessitates the establishment of an effective method to assess interfacial interactions between foulants and rough surface membrane. This study proposed a new method which includes a rigorous mathematical equation for modeling membrane surface morphology, and combination of surface element integration (SEI) method and the composite Simpson's approach for assessment of interfacial interactions. The new method provides a complete solution to quantitatively calculate interfacial interactions between foulants and rough surface membrane. Application of this method in a membrane bioreactor (MBR) showed that, high calculation accuracy could be achieved by setting high segment number, and moreover, the strength of three energy components and energy barrier was remarkably impaired by the existence of roughness on the membrane surface, indicating that membrane surface morphology exerted profound effects on membrane fouling in the MBR. Good agreement between calculation prediction and fouling phenomena was found, suggesting the feasibility of this method. PMID:26519696

  19. Patchy Janus particles with tunable roughness and composition via vapor-assisted deposition of macromolecules

    NASA Astrophysics Data System (ADS)

    Shepard, Kimberly B.; Christie, Dane A.; Sosa, Chris L.; Arnold, Craig B.; Priestley, Rodney D.

    2015-03-01

    Here, we present a technique for the fabrication of patchy Janus particles utilizing a vapor-assisted macromolecular deposition technique, termed Matrix Assisted Pulsed Laser Evaporation (MAPLE). Using this technique, both inorganic and organic precursor particles, immobilized on a surface, are functionalized on one hemisphere with nanodroplets of a desired polymer, thus forming particles with a patchy Janus morphology and textured surface topology. This fabrication method is flexible with respect to the chemical identity of the precursor particle and the selection of the deposited polymer. By tuning MAPLE deposition parameters, e.g., target composition or deposition time, the Janus anisotropy and roughness (i.e., patchiness) can be tuned, thus enabling greater control over the particles' behavior for applications as nanoparticle surfactants for stabilization of emulsions and foams.

  20. Four-parameter model for polarization-resolved rough-surface BRDF.

    PubMed

    Renhorn, Ingmar G E; Hallberg, Tomas; Bergström, David; Boreman, Glenn D

    2011-01-17

    A modeling procedure is demonstrated, which allows representation of polarization-resolved BRDF data using only four parameters: the real and imaginary parts of an effective refractive index with an added parameter taking grazing incidence absorption into account and an angular-scattering parameter determined from the BRDF measurement of a chosen angle of incidence, preferably close to normal incidence. These parameters allow accurate predictions of s- and p-polarized BRDF for a painted rough surface, over three decades of variation in BRDF magnitude. To characterize any particular surface of interest, the measurements required to determine these four parameters are the directional hemispherical reflectance (DHR) for s- and p-polarized input radiation and the BRDF at a selected angle of incidence. The DHR data describes the angular and polarization dependence, as well as providing the overall normalization constraint. The resulting model conserves energy and fulfills the reciprocity criteria. PMID:21263641

  1. Rough Evaluation Structure: Application of Rough Set Theory to Generate Simple Rules for Inconsistent Preference Relation

    NASA Astrophysics Data System (ADS)

    Gehrmann, Andreas; Nagai, Yoshimitsu; Yoshida, Osamu; Ishizu, Syohei

    Since management decision-making becomes complex and preferences of the decision-maker frequently becomes inconsistent, multi-attribute decision-making problems were studied. To represent inconsistent preference relation, the concept of evaluation structure was introduced. We can generate simple rules to represent inconsistent preference relation by the evaluation structures. Further rough set theory for the preference relation was studied and the concept of approximation was introduced. One of our main aims of this paper is to introduce a concept of rough evaluation structure for representing inconsistent preference relation. We apply rough set theory to the evaluation structure, and develop a method for generating simple rules for inconsistent preference relations. In this paper, we introduce concepts of totally ordered information system, similarity class of preference relation, upper and lower approximation of preference relations. We also show the properties of rough evaluation structure and provide a simple example. As an application of rough evaluation structure, we analyze questionnaire survey of customer preferences about audio players.

  2. Plume Dispersion over Idealized Urban-liked Roughness with Height Variation: an LES Approach

    NASA Astrophysics Data System (ADS)

    Wong, Colman Ching Chi; Liu, Chun-Ho

    2013-04-01

    Human activities (e.g. vehicular emission) are the primary pollutant sources affecting the health and living quality of stakeholders in modern compact cities. Gaussian plume dispersion model is commonly used for pollutant distribution estimate that works well over rural areas with flat terrain. However, its major parameters, dispersion coefficients, exclude the effect of surface roughness that unavoidably prone to error handling the pollutant transport in the urban boundary layer (UBL) over building roughness. Our recent large-eddy simulation (LES) has shown that urban surfaces affect significantly the pollutant dispersion over idealized, identical two-dimensional (2D) street canyons of uniform height. As an extension to our on-going effort, this study is conceived to investigate how rough urban surfaces, which are constructed by 2D street canyons of non-uniform height, modify the UBL pollutant dispersion . A series of LESs with idealized roughness elements of non-uniform heights were performed in neutral stratification. Building models with two different heights were placed alternatively in the computational domain to construct 2D street canyons in cross flows. The plume dispersion from a ground-level passive pollutant source over more realistic urban areas was then examined. Along with the existing building-height-to-street-width (aspect) ratio (AR), a new parameter, building-height variability (BHV), is used to measure the building height unevenness. Four ARs (1, 0.5, 0.25 and 0.125) and three BHVs (20%, 40% and 60%) were considered in this study. Preliminary results show that BHV greatly increases the aerodynamic roughness of the hypothetical urban surfaces for narrow street canyons. Analogous to our previous findings, the air exchange rate (ACH) of street canyons increases with increasing friction factor, implying that street-level ventilation could be improved by increasing building roughness via BHV. In addition, the parameters used in dispersion coefficient

  3. Roughness characterization of the galling of metals

    NASA Astrophysics Data System (ADS)

    Hubert, C.; Marteau, J.; Deltombe, R.; Chen, Y. M.; Bigerelle, M.

    2014-09-01

    Several kinds of tests exist to characterize the galling of metals, such as that specified in ASTM Standard G98. While the testing procedure is accurate and robust, the analysis of the specimen's surfaces (area=1.2 cm) for the determination of the critical pressure of galling remains subject to operator judgment. Based on the surface's topography analyses, we propose a methodology to express the probability of galling according to the macroscopic pressure load. After performing galling tests on 304L stainless steel, a two-step segmentation of the S q parameter (root mean square of surface amplitude) computed from local roughness maps (100 μ m× 100 μ m) enables us to distinguish two tribological processes. The first step represents the abrasive wear (erosion) and the second one the adhesive wear (galling). The total areas of both regions are highly relevant to quantify galling and erosion processes. Then, a one-parameter phenomenological model is proposed to objectively determine the evolution of non-galled relative area A e versus the pressure load P, with high accuracy ({{A}e}=100/(1+a{{P}2}) with a={{0.54}+/- 0.07}× {{10}-3} M P{{a}-2} and with {{R}2}=0.98). From this model, the critical pressure of galling is found to be equal to 43MPa. The {{S}5 V} roughness parameter (the five deepest valleys in the galled region's surface) is the most relevant roughness parameter for the quantification of damages in the ‘galling region’. The significant valleys’ depths increase from 10 μm-250 μm when the pressure increases from 11-350 MPa, according to a power law ({{S}5 V}=4.2{{P}0.75}, with {{R}2}=0.93).

  4. Quantifying surface roughness over debris covered ice

    NASA Astrophysics Data System (ADS)

    Quincey, Duncan; Rounce, David; Ross, Andrew

    2016-04-01

    Aerodynamic roughness length (z0) remains a major uncertainty when determining turbulent heat fluxes over glacier surfaces, and can vary by an order of magnitude even within a small area and through the melt season. Defining z0 over debris-covered ice is particularly complex, because the surface may comprise clasts of greatly varying size, and the broader-scale surface relief can be similarly heterogeneous. Several recent studies have used Structure from Motion to data model debris-covered surfaces at the centimetric scale and calculate z0 based on measurements of surface microtopography. However, few have validated these measurements with independent vertical wind profile measurements, or considered how the measurements vary over a range of different surface types or scales of analysis. Here, we present the results of a field investigation conducted on the debris covered Khumbu Glacier during the post-monsoon season of 2015. We focus on two sites. The first is characterised by gravels and cobbles supported by a fine sandy matrix. The second comprises cobbles and boulders separated by voids. Vertical profiles of wind speed measured over both sites enable us to derive measurements of aerodynamic roughness that are similar in magnitude, with z0 at the second site exceeding that at the first by < 1 cm. During our observation period, snow covered the second site for three days, but the impact on z0 is small, implying that roughness is predominantly determined by major rock size obstacles rather than the general form of the surface. To complement these aerodynamic measurements we also conducted a Structure from Motion survey across each patch and calculated z0 using microtopographic methods published in a range of recent studies. We compare the outputs of each of these algorithms with each other and with the aerodynamic measurements, assess how they perform over a range of scales, and evaluate the validity of using microtopographic methods where aerodynamic measurements

  5. Effective field model of roughness in magnetic nano-structures

    SciTech Connect

    Lepadatu, Serban

    2015-12-28

    An effective field model is introduced here within the micromagnetics formulation, to study roughness in magnetic structures, by considering sub-exchange length roughness levels as a perturbation on a smooth structure. This allows the roughness contribution to be separated, which is found to give rise to an effective configurational anisotropy for both edge and surface roughness, and accurately model its effects with fine control over the roughness depth without the explicit need to refine the computational cell size to accommodate the roughness profile. The model is validated by comparisons with directly roughened structures for a series of magnetization switching and domain wall velocity simulations and found to be in excellent agreement for roughness levels up to the exchange length. The model is further applied to vortex domain wall velocity simulations with surface roughness, which is shown to significantly modify domain wall movement and result in dynamic pinning and stochastic creep effects.

  6. 7 CFR 51.776 - Slightly rough texture.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Definitions § 51.776 Slightly rough texture. Slightly rough texture means that the skin may be slightly thick but not excessively thick, materially ridged or grooved. “Slightly thick” means that the...

  7. 7 CFR 51.776 - Slightly rough texture.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Definitions § 51.776 Slightly rough texture. Slightly rough texture means that the skin may be slightly thick but not excessively thick, materially ridged or grooved. “Slightly thick” means that the...

  8. Correlation between roughness and porosity in rocks

    NASA Astrophysics Data System (ADS)

    Rebollo, M. A.; Hogert, E. N.; Albano, J.; Raffo, C. A.; Gaggioli, N. G.

    1996-02-01

    The porosity of rocks is a very important parameter in the determination of the performance of oil wells. Optical methods allow us to study surface roughness and different materials that have surface properties with random characteristics. Therefore, we have extended these applications to porosity analysis. In our method, we have used the speckle produced by the scattered light from a porous rock, illuminated by a laser beam, and found a linear relationship between the decorrelation of the speckle intensity distribution and the porosity magnitude. In this paper we present the results for samples extracted from oil wells in Argentina.

  9. Protein Translocation across the Rough Endoplasmic Reticulum

    PubMed Central

    Mandon, Elisabet C.; Trueman, Steven F.; Gilmore, Reid

    2013-01-01

    The rough endoplasmic reticulum is a major site of protein biosynthesis in all eukaryotic cells, serving as the entry point for the secretory pathway and as the initial integration site for the majority of cellular integral membrane proteins. The core components of the protein translocation machinery have been identified, and high-resolution structures of the targeting components and the transport channel have been obtained. Research in this area is now focused on obtaining a better understanding of the molecular mechanism of protein translocation and membrane protein integration. PMID:23251026

  10. Polarimetric thermal emission from rough surfaces

    NASA Technical Reports Server (NTRS)

    Johnson, J. T.; Kong, J. A.; Shin, R. T.; Staelin, D. H.; Yueh, S. H.; Nghiem, S. V.; Kwok, R.; Oneill, K.; Lohanick, A.

    1993-01-01

    Recent theoretical works have suggested the potential of passive polarimetry in the remote sensing of geophysical media. It was shown that the third Stokes parameter U of the thermal emission may become larger for azimuthally asymmetric fields of observation. In order to investigate the potential applicability of passive polarimetry to the remote sensing of ocean surface, measurements of the polarimetric thermal emission from a sinusoidal water surface and a numerical study of the polarimetric thermal emission from randomly rough ocean surfaces were performed. Measurements of sinusoidal water surface thermal emission were performed using a sinusoidal water surface which was created by placing a thin sheet of fiberglass with a sinusoidal profile in two dimensions extended infinitely in the third dimension onto a water surface. The theory of thermal emission from a 'two-layer' periodic surface is derived and the exact solution is performed using both the extended boundary condition method (EBC) and the method of moments (MOM). The theoretical predictions are found to be in good agreement with the experimental results once the effects of the radiometer antenna pattern are included and the contribution of background noise to the measurements is modeled. The experimental results show that the U parameter indicates the direction of periodicity of the water surface and can approach values of up to 30 K for the surface observed. Next, a numerical study of polarimetric thermal emission from randomly rough surfaces was performed. A Monte Carlo technique utilizing an exact method for calculating thermal emission was chosen for the study to avoid any of the limitations of the commonly used approximate methods in rough surface scattering. In this Monte Carlo technique, a set of finite rough surface profiles in two dimensions with desired statistics was generated and extended periodically. The polarimetric thermal emission from each surface of the set was then calculated using

  11. Mold Cavity Roughness vs. Flow of Polymer

    NASA Astrophysics Data System (ADS)

    Stanek, Michal; Manas, Miroslav; Manas, David

    2009-07-01

    Injection molding represents such a way of polymer processing that requires injection of polymer melt into the mold cavity with very high injection rate. The fluidity of polymers is affected by many parameters (mold design, melt temperature, injection rate and pressure). The main objective of this paper is the study of influence of surface roughness of mold cavity of the polymer melts flow. Evaluation of set of data obtained by experiments where the testing conditions were widely changed shows that quality of cavity surface affects on the length of flow.

  12. Investigations of Titan's topography and surface roughness

    NASA Astrophysics Data System (ADS)

    Sharma, Priyanka

    Saturn's moon, Titan is a geomorphologically active planetary object, and its surface is influenced by multiple processes like impact cratering, fluvial and aeolian erosion, lacustrine processes, tectonics, cryovolcanism and mantling. Disentangling the processes that compete to shape Titan's landscape is difficult in the absence of global topography data. In this thesis, I utilize techniques in topographic statistics, fractal theory, study of terrestrial analogs and landscape evolution modeling to characterize Titan's topography and surface roughness and investigate the relative roles of surface processes in sculpting its landscape. I mapped the shorelines of 290 North Polar Titanian lakes using the Cassini Synthetic Aperture Radar dataset. The fractal dimensions of the shorelines were calculated via the divider/ruler method and box-counting method, at length scales of (1--10) km and found to average 1.27 and 1.32, respectively. The inferred power-spectral exponent of Titan's topography was found to be ≤ 2, which is lower than the values obtained from the global topography of the Earth or Venus. In order to interpret fractal dimensions of Titan's shorelines in terms of the surficial processes at work, I repeated a similar statistical analysis with 114 terrestrial analogous lakes formed by different processes, using C-band radar backscatter data from the Shuttle Radar Topography Mission (SRTM). I found different lake generation mechanisms on Earth produce 'statistically different' shorelines; however, no specific set of processes could be identified for forming Titanian lake basins. Using the Cassini RADAR altimetry data, I investigated Titan's global surface roughness and calculated median absolute slopes, average relief and Hurst exponent (H) for the surface of Titan. I detected a clear trend with latitude in these roughness parameters. Equatorial regions had the smallest slopes, lowest values of H and smallest intra-footprint relief, compared to the mid

  13. Impact of Endothelium Roughness on Blood Flow

    PubMed Central

    Park, Sangwoo; Intaglietta, Marcos; Tartakovsky, Daniel M.

    2012-01-01

    Cell free layer (CFL), a plasma layer bounded by the red blood cell (RBC) core and the endothelium, plays an important physiological role. Its width affects the effective blood viscosity as well as the scavenging and production of nitric oxide (NO). Measurements of the CFL and its spatio-temporal variability are highly uncertain, exhibiting random fluctuations. Yet traditional models of blood flow and NO scavenging treat the CFL’s bounding surfaces as deterministic and smooth. We investigate the effects of the endothelium roughness and uncertain (random) spatial variability on blood flow and estimates of effective blood viscosity. PMID:22300799

  14. Robust surface roughness indices and morphological interpretation

    NASA Astrophysics Data System (ADS)

    Trevisani, Sebastiano; Rocca, Michele

    2016-04-01

    Geostatistical-based image/surface texture indices based on variogram (Atkison and Lewis, 2000; Herzfeld and Higginson, 1996; Trevisani et al., 2012) and on its robust variant MAD (median absolute differences, Trevisani and Rocca, 2015) offer powerful tools for the analysis and interpretation of surface morphology (potentially not limited to solid earth). In particular, the proposed robust index (Trevisani and Rocca, 2015) with its implementation based on local kernels permits the derivation of a wide set of robust and customizable geomorphometric indices capable to outline specific aspects of surface texture. The stability of MAD in presence of signal noise and abrupt changes in spatial variability is well suited for the analysis of high-resolution digital terrain models. Moreover, the implementation of MAD by means of a pixel-centered perspective based on local kernels, with some analogies to the local binary pattern approach (Lucieer and Stein, 2005; Ojala et al., 2002), permits to create custom roughness indices capable to outline different aspects of surface roughness (Grohmann et al., 2011; Smith, 2015). In the proposed poster, some potentialities of the new indices in the context of geomorphometry and landscape analysis will be presented. At same time, challenges and future developments related to the proposed indices will be outlined. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. Grohmann, C.H., Smith, M.J., Riccomini, C., 2011. Multiscale Analysis of Topographic Surface Roughness in the Midland Valley, Scotland. IEEE Transactions on Geoscience and Remote Sensing 49, 1220-1213. Herzfeld, U.C., Higginson, C.A., 1996. Automated geostatistical seafloor classification - Principles, parameters, feature vectors, and discrimination criteria. Computers and Geosciences, 22 (1), pp. 35-52. Lucieer, A., Stein, A., 2005. Texture-based landform segmentation of LiDAR imagery

  15. Speckle pattern texture analysis method to measure surface roughness

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I.; Sadovoy, A.; Doronin, A.; Meglinski, I.

    2013-02-01

    Speckle pattern texture analysis method is applied to measure surface roughness of human skin. The method is based on analyzing of a gray level co-occurrence matrix occurred from a speckle image of a rough surface. Paper with different surface roughness is used as a skin phantom. The roughness is controlled by profilometry measurements. The developed methodology could find wide application in dermatology and tissue diagnostics.

  16. Application of rough set for medical images data mining

    NASA Astrophysics Data System (ADS)

    Wang, Shuyan; Wang, Chunmei; Chen, Yan

    2010-08-01

    To study the application of Rough set algorithm for diagnosis breast cancer, attribute reduction strategies of rough set are applied to the data mining of the mammography classification, proposes a medical images classifier based on association rules. Attribute reduction strategies of rough set for medical image data mining are realized. The experiment results are given. The experimental results show that the system performs well in accuracy, verified the great potential of rough set in assistant medical treatment.

  17. 7 CFR 51.1014 - Excessively rough texture.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Excessively rough texture. 51.1014 Section 51.1014 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards....1014 Excessively rough texture. Excessively rough texture means that the skin is badly ridged or...

  18. 7 CFR 51.1014 - Excessively rough texture.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Excessively rough texture. 51.1014 Section 51.1014 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards....1014 Excessively rough texture. Excessively rough texture means that the skin is badly ridged or...

  19. 7 CFR 51.1169 - Slightly rough texture.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... rough texture. Slightly rough texture means that the skin is not of smooth texture but is not materially... 7 Agriculture 2 2011-01-01 2011-01-01 false Slightly rough texture. 51.1169 Section 51.1169 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE...

  20. 7 CFR 51.1169 - Slightly rough texture.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... rough texture. Slightly rough texture means that the skin is not of smooth texture but is not materially... 7 Agriculture 2 2010-01-01 2010-01-01 false Slightly rough texture. 51.1169 Section 51.1169 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE...