Boundary Layer Flow Over a Moving Wavy Surface

NASA Astrophysics Data System (ADS)

Hendin, Gali; Toledo, Yaron

2016-04-01

Boundary Layer Flow Over a Moving Wavy Surface Gali Hendin(1), Yaron Toledo(1) January 13, 2016 (1)School of Mechanical Engineering, Tel-Aviv University, Israel Understanding the boundary layer flow over surface gravity waves is of great importance as various atmosphere-ocean processes are essentially coupled through these waves. Nevertheless, there are still significant gaps in our understanding of this complex flow behaviour. The present work investigates the fundamentals of the boundary layer air flow over progressive, small-amplitude waves. It aims to extend the well-known Blasius solution for a boundary layer over a flat plate to one over a moving wavy surface. The current analysis pro- claims the importance of the small curvature and the time-dependency as second order effects, with a meaningful impact on the similarity pattern in the first order. The air flow over the ocean surface is modelled using an outer, inviscid half-infinite flow, overlaying the viscous boundary layer above the wavy surface. The assumption of a uniform flow in the outer layer, used in former studies, is now replaced with a precise analytical solution of the potential flow over a moving wavy surface with a known celerity, wavelength and amplitude. This results in a conceptual change from former models as it shows that the pressure variations within the boundary layer cannot be neglected. In the boundary layer, time-dependent Navier-Stokes equations are formulated in a curvilinear, orthogonal coordinate system. The formulation is done in an elaborate way that presents additional, formerly neglected first-order effects, resulting from the time-varying coordinate system. The suggested time-dependent curvilinear orthogonal coordinate system introduces a platform that can also support the formulation of turbulent problems for any surface shape. In order to produce a self-similar Blasius-type solution, a small wave-steepness is assumed and a perturbation method is applied. Consequently, a novel self-similar solution is obtained from the first order set of equations. A second order solution is also obtained, stressing the role of small curvature on the boundary layer flow. The proposed model and solution for the boundary layer problem overlaying a moving wavy surface can also be used as a base flow for stability problems that can develop in a boundary layer, including phases of transitional states.

Upper Campanian suspected silicified seismite related to the Syrian Arc tectonic system in the Middle East

NASA Astrophysics Data System (ADS)

Lewy, Zeev

2010-06-01

The formation of the rare 'homogenous linear structures' in chert beds in the Phosphate Member of the Mishash Formation in central and southern Israel is reevaluated based on new samples from Har Omer, Arava Valley. These are of 4-6 cm thick chert beds in which the upper and lower surfaces form dense subparallel low ridges in contrast to the planar surfaces of other chert layers alternating with other lithologies. The ridges were suggested to have formed by advancing silicification fronts replacing the original sediment by microquartz without specifying the control on the ridged pattern and its regional orientation. One sample exhibits different color internal folds attesting to a multiple wavy mobilization of the silica-bearing liquid, probably composed of individual tiny crystallites of silicified calcareous micrite dispersed in seawater. This interpreted 'soup' of microquartz crystallites is corroborated by examples of a plastic deformation and mobilization in a muddy state of the siliceous Mishash Formation unconsolidated sediment. E-W dominant orientation of the ridges in central and southern Israel cannot be related to a simple diffusive diagenetic process and probably was initiated by N-S trending seismic surface waves during the Syrian Arc tectonic activity in the Middle East. Accordingly, this seismically induced sedimentary structure (seismite) formed through the vertical mobilization of silica-rich liquid replacing seawater in-between the sedimentary particles, advancing in a wavy upper and lower front triggered by a seismic event.

Natural convection of Al2O3-water nanofluid in a wavy enclosure

NASA Astrophysics Data System (ADS)

Leonard, Mitchell; Mozumder, Aloke K.; Mahmud, Shohel; Das, Prodip K.

2017-06-01

Natural convection heat transfer and fluid flow inside enclosures filled with fluids, such as air, water or oil, have been extensively analysed for thermal enhancement and optimisation due to their applications in many engineering problems, including solar collectors, electronic cooling, lubrication technologies, food processing and nuclear reactors. In comparison, little effort has been given to the problem of natural convection inside enclosures filled with nanofluids, while the addition of nanoparticles into a fluid base to alter thermal properties can be a feasible solution for many heat transfer problems. In this study, the problem of natural convection heat transfer and fluid flow inside a wavy enclosure filled with Al2O3-water nanofluid is investigated numerically using ANSYS-FLUENT. The effects of surface waviness and aspect ratio of the wavy enclosure on the heat transfer and fluid flow are analysed for various concentrations of Al2O3 nanoparticles in water. Flow fields and temperature fields are investigated and heat transfer rate is examined for different values of Rayleigh number. Results show that heat transfer within the enclosure can be enhanced by increasing surface waviness, aspect ratio or nanoparticles volume fraction. Changes in surface waviness have little effect on the heat transfer rate at low Rayleigh numbers, but when Ra ≥ 105 heat transfer increases with the increase of surface waviness from zero to higher values. Increasing the aspect ratio causes an increase in heat transfer rate, as the Rayleigh number increases the effect of changing aspect ratio is more apparent with the greatest heat transfer enhancement seen at higher Rayleigh numbers. Nanoparticles volume fraction has a little effect on the average Nusselt number at lower Rayleigh numbers when Ra ≥ 105 average Nusselt number increases with the increase of volume fraction. These findings provide insight into the heat transfer effects of using Al2O3-water nanofluid as a heat transfer medium and the effects of changing geometrical parameters, which will help in developing novel geometries with enhanced and controlled heat-transfer for solar collectors, electronic cooling, and food processing industries.

Drag of two-dimensional small-amplitude symmetric and asymmetric wavy walls in turbulent boundary layers

NASA Technical Reports Server (NTRS)

Lin, J. C.; Walsh, M. J.; Balasubramanian, R.

1984-01-01

Included are results of an experimental investigation of low-speed turbulent flow over multiple two-dimensional transverse rigid wavy surfaces having a wavelength on the order of the boundary-layer thickness. Data include surface pressure and total drag measurements on symmetric and asymmetric wall waves under a low-speed turbulent boundary-layer flow. Several asymmetric wave configurations exhibited drag levels below the equivalent symmetric (sine) wave. The experimental results compare favorably with numerical predictions from a Reynolds-averaged Navier-Stokes spectral code. The reported results are of particular interest for the estimation of drag, the minimization of fabrication waviness effects, and the study of wind-wave interactions.

Influence of Ply Waviness on Fatigue Life of Tapered Composite Flexbeam Laminates

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.

1999-01-01

Nonlinear tapered flexbeam laminates, with significant ply waviness, were cut from a full-size composite rotor hub flexbeam. The specimens were tested under combined axial tension and cyclic bending loads. All of the specimens had wavy plies through the center and near the surfaces (termed marcelled areas), although for some of the specimens the surface marcels were very obvious, and for others they were much smaller. The specimens failed by first developing cracks through the marcels at the surfaces, and then delaminations grew from those cracks, in both directions. Delamination failure occurred in these specimens at significantly shorter fatigue lives than similar specimens without waviness, tested in ref. 2. A 2D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. In addition, the FE model duplicated the waviness observed in one of the test specimens. The model was analyzed using a geometrically nonlinear FE code. Modifications were made to the original model to reduce the amplitude of the marcels near the surfaces. The analysis was repeated for each modification. Comparisons of the interlaminar normal stresses, sigma(sub n), in the various models showed that under combined axial-tension and cyclic-bending loading, for marcels of the same aspect ratio, sigma(sub n) stresses increased as the distance along the taper, from thick to thin end, increased. For marcels of the same aspect ratio and at the same X-location along the taper, sigma(sub n) stresses decreased as the distance from the surface into the flexbeam interior increased. A technique was presented for determining the smallest acceptable marcel aspect ratio at various locations in the flexbeam.

Simulation of leakage through mechanical sealing device

NASA Astrophysics Data System (ADS)

Tikhomorov, V. P.; Gorlenko, O. A.; Izmerov, M. A.

2018-03-01

The procedure of mathematical modeling of leakage through the mechanical seal taking into account waviness and roughness is considered. The percolation process is represented as the sum of leakages through a gap between wavy surfaces and percolation through gaps formed by fractal roughness, i.e. the total leakage is determined by the slot model and filtration leakage. Dependences of leaks on the contact pressure of corrugated and rough surfaces of the mechanical seal elements are presented.

Effect of perforation on flow past a conic cylinder at \\varvec{Re} = 100 : wavy vortex and sign laws

NASA Astrophysics Data System (ADS)

Lin, L. M.; Zhong, X. F.; Wu, Y. X.

2018-04-01

In order to find the intrinsic physical mechanism of the original Kármán vortex wavily distorted across the span due to the introduction of three-dimensional (3-D) geometric disturbances, a flow past a peak-perforated conic shroud is numerically simulated at a Reynolds number of 100. Based on previous work by Meiburg and Lasheras (1988), the streamwise and vertical interactions with spanwise vortices are introduced and analyzed. Then vortex-shedding patterns in the near wake for different flow regimes are reinspected and illustrated from the view of these two interactions. Generally, in regime I, spanwise vortices are a little distorted due to the weak interaction. Then in regime II, spanwise vortices, even though curved obviously, are still shed synchronously with moderate streamwise and vertical interactions. But in regime III, violently wavy spanwise vortices in some vortex-shedding patterns, typically an Ω -type vortex, are mainly attributed to the strong vertical interactions, while other cases, such as multiple vortex-shedding patterns in sub-regime III-D, are resulted from complex streamwise and vertical interactions. A special phenomenon, spacial distribution of streamwise and vertical components of vorticity with specific signs in the near wake, is analyzed based on two models of streamwise and vertical vortices in explaining physical reasons of top and bottom shear layers wavily varied across the span. Then these two models and above two interactions are unified. Finally two sign laws are summarized: the first sign law for streamwise and vertical components of vorticity is positive in the upper shear layer, but negative in the lower shear layer, while the second sign law for three vorticity components is always negative in the wake.

Optimal design of wavy microchannel and comparison of heat transfer characteristics with zigzag and straight geometries

NASA Astrophysics Data System (ADS)

Parlak, Zekeriya

2018-05-01

Design concept of microchannel heat exchangers is going to plan with new flow microchannel configuration to reduce the pressure drop and improve heat transfer performance. The study aims to find optimum microchannel design providing the best performance of flow and heat transfer characterization in a heat sink. Therefore, three different types of microchannels in which water is used, straight, wavy and zigzag have been studied. The optimization operation has been performed to find optimum geometry with ANSYS's Response Surface Optimization Tool. Primarily, CFD analysis has been performed by parameterizing a wavy microchannel geometry. Optimum wavy microchannel design has been obtained by the response surface created for the range of velocity from 0.5 to 5, the range of amplitude from 0.06 to 0.3, the range of microchannel height from 0.1 to 0.2, the range of microchannel width from 0.1 to 0.2 and range of sinusoidal wave length from 0.25 to 2.0. All simulations have been performed in the laminar regime for Reynolds number ranging from 100 to 900. Results showed that the Reynolds number range corresponding to the industrial pressure drop limits is between 100 and 400. Nu values obtained in this range for optimum wavy geometry were found at a rate of 10% higher than those of the zigzag channel and 40% higher than those of the straight channels. In addition, when the pressure values of the straight channel did not exceed 10 kPa, the inlet pressure data calculated for zigzag and wavy channel data almost coincided with each other.

Underwater Rays

ERIC Educational Resources Information Center

Cepic, Mojca

2008-01-01

Light beams in wavy unclear water, also called underwater rays, and caustic networks of light formed at the bottom of shallow water are two faces of a single phenomenon. Derivation of the caustic using only simple geometry, Snell's law and simple derivatives accounts for observations such as the existence of the caustic network on vertical walls,…

Real-Time Curvature Defect Detection on Outer Surfaces Using Best-Fit Polynomial Interpolation

PubMed Central

Golkar, Ehsan; Prabuwono, Anton Satria; Patel, Ahmed

2012-01-01

This paper presents a novel, real-time defect detection system, based on a best-fit polynomial interpolation, that inspects the conditions of outer surfaces. The defect detection system is an enhanced feature extraction method that employs this technique to inspect the flatness, waviness, blob, and curvature faults of these surfaces. The proposed method has been performed, tested, and validated on numerous pipes and ceramic tiles. The results illustrate that the physical defects such as abnormal, popped-up blobs are recognized completely, and that flames, waviness, and curvature faults are detected simultaneously. PMID:23202186

DT-CWT Robust Filtering Algorithm for The Extraction of Reference and Waviness from 3-D Nano Scalar Surfaces

NASA Astrophysics Data System (ADS)

Ren, Zhi Ying.; Gao, ChengHui.; Han, GuoQiang.; Ding, Shen; Lin, JianXing.

2014-04-01

Dual tree complex wavelet transform (DT-CWT) exhibits superiority of shift invariance, directional selectivity, perfect reconstruction (PR), and limited redundancy and can effectively separate various surface components. However, in nano scale the morphology contains pits and convexities and is more complex to characterize. This paper presents an improved approach which can simultaneously separate reference and waviness and allows an image to remain robust against abnormal signals. We included a bilateral filtering (BF) stage in DT-CWT to solve imaging problems. In order to verify the feasibility of the new method and to test its performance we used a computer simulation based on three generations of Wavelet and Improved DT-CWT and we conducted two case studies. Our results show that the improved DT-CWT not only enhances the robustness filtering under the conditions of abnormal interference, but also possesses accuracy and reliability of the reference and waviness from the 3-D nano scalar surfaces.

Wavy Architecture Thin-Film Transistor for Ultrahigh Resolution Flexible Displays.

PubMed

Hanna, Amir Nabil; Kutbee, Arwa Talal; Subedi, Ram Chandra; Ooi, Boon; Hussain, Muhammad Mustafa

2018-01-01

A novel wavy-shaped thin-film-transistor (TFT) architecture, capable of achieving 70% higher drive current per unit chip area when compared with planar conventional TFT architectures, is reported for flexible display application. The transistor, due to its atypical architecture, does not alter the turn-on voltage or the OFF current values, leading to higher performance without compromising static power consumption. The concept behind this architecture is expanding the transistor's width vertically through grooved trenches in a structural layer deposited on a flexible substrate. Operation of zinc oxide (ZnO)-based TFTs is shown down to a bending radius of 5 mm with no degradation in the electrical performance or cracks in the gate stack. Finally, flexible low-power LEDs driven by the respective currents of the novel wavy, and conventional coplanar architectures are demonstrated, where the novel architecture is able to drive the LED at 2 × the output power, 3 versus 1.5 mW, which demonstrates the potential use for ultrahigh resolution displays in an area efficient manner. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Forecasting of Machined Surface Waviness on the Basis of Self-oscillations Analysis

NASA Astrophysics Data System (ADS)

Belov, E. B.; Leonov, S. L.; Markov, A. M.; Sitnikov, A. A.; Khomenko, V. A.

2017-01-01

The paper states a problem of providing quality of geometrical characteristics of machined surfaces, which makes it necessary to forecast the occurrence and amount of oscillations appearing in the course of mechanical treatment. Objectives and tasks of the research are formulated. Sources of oscillation onset are defined: these are coordinate connections and nonlinear dependence of cutting force on the cutting velocity. A mathematical model of forecasting steady-state self-oscillations is investigated. The equation of the cutter tip motion is a system of two second-order nonlinear differential equations. The paper shows an algorithm describing a harmonic linearization method which allows for a significant reduction of the calculation time. In order to do that it is necessary to determine the amplitude of oscillations, frequency and a steady component of the first harmonic. Software which allows obtaining data on surface waviness parameters is described. The paper studies an example of the use of the developed model in semi-finished lathe machining of the shaft made from steel 40H which is a part of the BelAZ wheel electric actuator unit. Recommendations on eliminating self-oscillations in the process of shaft cutting and defect correction of the surface waviness are given.

Nonlinear analysis and dynamic compensation of stylus scanning measurement with wide range

NASA Astrophysics Data System (ADS)

Hui, Heiyang; Liu, Xiaojun; Lu, Wenlong

2011-12-01

Surface topography is an important geometrical feature of a workpiece that influences its quality and functions such as friction, wearing, lubrication and sealing. Precision measurement of surface topography is fundamental for product quality characterizing and assurance. Stylus scanning technique is a widely used method for surface topography measurement, and it is also regarded as the international standard method for 2-D surface characterizing. Usually surface topography, including primary profile, waviness and roughness, can be measured precisely and efficiently by this method. However, by stylus scanning method to measure curved surface topography, the nonlinear error is unavoidable because of the difference of horizontal position of the actual measured point from given sampling point and the nonlinear transformation process from vertical displacement of the stylus tip to angle displacement of the stylus arm, and the error increases with the increasing of measuring range. In this paper, a wide range stylus scanning measurement system based on cylindrical grating interference principle is constructed, the originations of the nonlinear error are analyzed, the error model is established and a solution to decrease the nonlinear error is proposed, through which the error of the collected data is dynamically compensated.

On the Effect of Rigid Swept Surface Waves on Turbulent Drag

NASA Technical Reports Server (NTRS)

Denison, M.; Wilkinson, S. P.; Balakumar, P.

2015-01-01

Passive turbulent drag reduction techniques are of interest as a cost effective means to improve air vehicle fuel consumption. In the past, rigid surface waves slanted at an angle from the streamwise direction were deemed ineffective to reduce skin friction drag due to the pressure drag that they generate. A recent analysis seeking similarities to the spanwise shear stress generated by spatial Stokes layers suggested that there may be a range of wavelength, amplitude, and orientation in which the wavy surface would reduce turbulent drag. The present work explores, by experiments and Direct Numerical Simulations (DNS), the effect of swept wavy surfaces on skin friction and pressure drag. Plates with shallow and deep wave patterns were rapid-prototyped and tested using a drag balance in the 7x11 inch Low-Speed Wind Tunnel at the NASA LaRC Research Center. The measured drag o set between the wavy plates and the reference at plate is found to be within the experimental repeatability limit. Oil vapor flow measurements indicate a mean spanwise flow over the deep waves. The turbulent flow in channels with at walls, swept wavy walls and spatial Stokes spanwise velocity forcing was simulated at a friction Reynolds number of two hundred. The time-averaged and dynamic turbulent flow characteristics of the three channel types are compared. The drag obtained for the channel with shallow waves is slightly larger than for the at channel, within the range of the experiments. In the case of the large waves, the simulation over predicts the drag. The shortcomings of the Stokes layer analogy model for the estimation of the spanwise shear stress and drag are discussed.

Acoustic Receptivity of a Blasius Boundary Layer with 2-D and Oblique Surface Waviness

NASA Technical Reports Server (NTRS)

King, Rudolph A.; Breuer, Kenneth S.

2000-01-01

An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on a flat plate in the presence of two-dimensional (2-D) and oblique (3-D) surface waviness. The effect of the non-localized surface roughness geometry and acoustic wave amplitude on the receptivity process was explored. The surface roughness had a well defined wavenumber spectrum with fundamental wavenumber k (sub w). A planar downstream traveling acoustic wave was created to temporally excite the flow near the resonance frequency of an unstable eigenmode corresponding to k (sub ts) = k (sub w). The range of acoustic forcing levels, epsilon, and roughness heights, DELTA h, examined resulted in a linear dependence of receptivity coefficients; however, the larger values of the forcing combination epsilon dot DELTA h resulted in subsequent nonlinear development of the Tollmien-Schlichting (T-S) wave. This study provided the first experimental evidence of a marked increase in the receptivity coefficient with increasing obliqueness of the surface waviness in excellent agreement with theory. Detuning of the 2-D and oblique disturbances was investigated by varying the streamwise wall-roughness wavenumber a,, and measuring the T-S response. For the configuration where laminar-to-turbulent breakdown occurred, the breakdown process was found to be dominated by energy at the fundamental and harmonic frequencies, indicative of K-type breakdown.

Structural ordering and interface morphology in symmetrically strained(GaIn)As/Ga(PAs) superlattices grown on off-oriented GaAs(100)

NASA Astrophysics Data System (ADS)

Giannini, C.; Tapfer, L.; Zhuang, Y.; de Caro, L.; Marschner, T.; Stolz, W.

1997-02-01

In this work we investigate the structural properties of symmetrically strained (GaIn)As/GaAs/Ga(PAs)/GaAs superlattices by means of x-ray diffraction, reciprocal-space mapping, and x-ray reflectivity. The multilayers were grown by metalorganic vapor-phase epitaxy on (001) GaAs substrates intentionally off-oriented towards one of the nearest <110> directions. High-resolution triple-crystal reciprocal-space maps recorded for different azimuth angles in the vicinity of the (004) Bragg diffraction clearly show a double periodicity of the x-ray peak intensity that can be ascribed to a lateral and a vertical periodicity occurring parallel and perpendicular to the growth surface. Moreover, from the intensity modulation of the satellite peaks, a lateral-strain gradient within the epilayer unit cell is found, varying from a tensile to a compressive strain. Thus, the substrate off-orientation promotes a lateral modulation of the layer thickness (ordered interface roughness) and of the lattice strain, giving rise to laterally ordered macrosteps. In this respect, contour maps of the specular reflected beam in the vicinity of the (000) reciprocal lattice point were recorded in order to inspect the vertical and lateral interface roughness correlation. A semiquantitative analysis of our results shows that the interface morphology and roughness is greatly influenced by the off-orientation angle and the lateral strain distribution. Two mean spatial wavelengths can be determined, one corresponding exactly to the macrostep periodicity and the other indicating a further interface waviness along the macrosteps. The same spatial periodicities were found on the surface by atomic-force-microscopy images confirming the x-ray results and revealing a strong vertical correlation of the interfaces up to the outer surface.

Study of the Effect of Turbulence and Large Obstacles on the Evaporation from Bare Soil Surface through Coupled Free-flow and Porous-medium Flow Model

NASA Astrophysics Data System (ADS)

Gao, B.; Smits, K. M.

2017-12-01

Evaporation is a strongly coupled exchange process of mass, momentum and energy between the atmosphere and the soil. Several mechanisms influence evaporation, such as the atmospheric conditions, the structure of the soil surface, and the physical properties of the soil. Among the previous studies associated with evaporation modeling, most efforts use uncoupled models which simplify the influences of the atmosphere and soil through the use of resistance terms. Those that do consider the coupling between the free flow and porous media flow mainly consider flat terrain with grain-scale roughness. However, larger obstacles, which may form drags or ridges allowing normal convective air flow through the soil, are common in nature and may affect the evaporation significantly. Therefore, the goal of this work is to study the influence of large obstacles such as wavy surfaces on the flow behavior within the soil and exchange processes to the atmosphere under turbulent free-flow conditions. For simplicity, the soil surface with large obstacles are represented by a simple wavy surface. To do this, we modified a previously developed theory for two-phase two-component porous-medium flow, coupling it to single-phase two-component turbulent flow to simulate and analyze the evaporation from wavy soil surfaces. Detailed laboratory scale experiments using a wind tunnel interfaced with a porous media tank were carried out to test the modeling results. The characteristics of turbulent flow across a permeable wavy surface are discussed. Results demonstrate that there is an obvious recirculation zone formed at the surface, which is special because of the accumulation of water vapor and the thicker boundary layer in this area. In addition, the influences of both the free flow and porous medium on the evaporation are also analyzed. The porous medium affects the evaporation through the amount of water it can provide to the soil surface; while the atmosphere influences the evaporation through the gradients formed within the boundary layer. This study gives a primary cognition on the evaporation from bare soil surface with obstacles. Ongoing work will include a deep understanding of the mechanisms which may provide the basis for land-atmosphere study on field scale.

Direct Numerical Simulation of Oscillatory Flow Over a Wavy, Rough, and Permeable Bottom

NASA Astrophysics Data System (ADS)

Mazzuoli, Marco; Blondeaux, Paolo; Simeonov, Julian; Calantoni, Joseph

2018-03-01

The results of a direct numerical simulation of oscillatory flow over a wavy bottom composed of different layers of spherical particles are described. The amplitude of wavy bottom is much smaller in scale than typical bed forms such as sand ripples. The spherical particles are packed in such a way to reproduce a bottom profile observed during an experiment conducted in a laboratory flow tunnel with well-sorted coarse sand. The amplitude and period of the external forcing flow as well as the size of the particles are set equal to the experimental values and the computed velocity field is compared with the measured velocity profiles. The direct numerical simulation allows for the evaluation of quantities, which are difficult to measure in a laboratory experiment (e.g., vorticity, seepage flow velocity, and hydrodynamic force acting on sediment particles). In particular, attention is focused on the coherent vortex structures generated by the vorticity shed by both the spherical particles and the bottom waviness. Results show that the wavy bottom triggers transition to turbulence. Moreover, the forces acting on the spherical particles are computed to investigate the mechanisms through which they are possibly mobilized by the oscillatory flow. It was found that forces capable of mobilizing surface particles are strongly correlated with the particle position above the mean bed elevation and the passage of coherent vortices above them.

Recrystallization and modification of the stainless-steel surface relief under photonic heat load in powerful plasma discharges

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

Budaev, V. P., E-mail: budaev@mail.ru; Martynenko, Yu. V.; Khimchenko, L. N.

Targets made of ITER-grade 316L(N)-IG stainless steel and Russian-grade 12Cr18Ni10Ti stainless steel with a close composition were exposed at the QSPA-T plasma gun to plasma photonic radiation pulses simulating conditions of disruption mitigation in ITER. After a large number of pulses, modification of the stainless-steel surface was observed, such as the formation of a wavy structure, irregular roughness, and cracks on the target surface. X-ray and optic microscopic analyses of targets revealed changes in the orientation and dimensions of crystallites (grains) over a depth of up to 20 μm for 316L(N)-IG stainless steel after 200 pulses and up to 40more » μm for 12Cr18Ni10Ti stainless steel after 50 pulses, which is significantly larger than the depth of the layer melted in one pulse (∼10 μm). In a series of 200 tests of ITER-grade 316L(N)-IG ITER stainless steel, a linear increase in the height of irregularity (roughness) with increasing number of pulses at a rate of up to ∼1 μm per pulse was observed. No alteration in the chemical composition of the stainless-steel surface in the series of tests was revealed. A model is developed that describes the formation of wavy irregularities on the melted metal surface with allowance for the nonlinear stage of instability of the melted layer with a vapor/plasma flow above it. A decisive factor in this case is the viscous flow of the melted metal from the troughs to tops of the wavy structure. The model predicts saturation of the growth of the wavy structure when its amplitude becomes comparable with its wavelength. Approaches to describing the observed stochastic relief and roughness of the stainless-steel surface formed in the series of tests are considered. The recurrence of the melting-solidification process in which mechanisms of the hill growth compete with the spreading of the material from the hills can result in the formation of a stochastic relief.« less

Simulation of an active underwater imaging through a wavy sea surface

NASA Astrophysics Data System (ADS)

Gholami, Ali; Saghafifar, Hossein

2018-06-01

A numerical simulation for underwater imaging through a wavy sea surface has been done. We have used a common approach to model the sea surface elevation and its slopes as an important source of image disturbance. The simulation algorithm is based on a combination of ray tracing and optical propagation, which has taken to different approaches for downwelling and upwelling beams. The nature of randomly focusing and defocusing property of surface waves causes a fluctuated irradiance distribution as an illuminating source of immersed object, while it gives rise to a great disturbance on the image through a coordinate change of image pixels. We have also used a modulation transfer function based on Well's small angle approximations to consider the underwater optical properties effect on the transferring of the image. As expected, the absorption effect reduces the light intensity and scattering decreases image contrast by blurring the image.

Generation of wavy structure on lipid membrane by peripheral proteins: a linear elastic analysis.

PubMed

Mahata, Paritosh; Das, Sovan Lal

2017-05-01

We carry out a linear elastic analysis to study wavy structure generation on lipid membrane by peripheral membrane proteins. We model the lipid membrane as linearly elastic and anisotropic material. The hydrophobic insertion by proteins into the lipid membrane has been idealized as penetration of rigid rod-like inclusions into the membrane and the electrostatic interaction between protein and membrane has been modeled by a distributed surface traction acting on the membrane surface. With the proposed model we study curvature generation by several binding domains of peripheral membrane proteins containing BAR domains and amphipathic alpha-helices. It is observed that electrostatic interaction is essential for curvature generation by the BAR domains. © 2017 Federation of European Biochemical Societies.

Laser micropolishing of AISI 304 stainless steel surfaces for cleanability and bacteria removal capability

NASA Astrophysics Data System (ADS)

De Giorgi, Chiara; Furlan, Valentina; Demir, Ali Gökhan; Tallarita, Elena; Candiani, Gabriele; Previtali, Barbara

2017-06-01

In this work, laser micropolishing (LμP) was employed to reduce the surface roughness and waviness of cold-rolled AISI 304 stainless steel sheets. A pulsed fibre laser operating in the ns regime was used and the influence of laser parameters in a N2-controlled atmospheres was evaluated. In the optimal conditions, the surface remelting induced by the process allowed to reduce the surface roughness by closing cracks and defects formed during the rolling process. Other conditions that did not improve the surface quality were analysed for defect typology. Moreover, laser treatments allowed the production of more hydrophobic surfaces, and no surface chemistry modification was identified. Surface cleanability was investigated with Escherichia coli (E. coli), evaluating the number of residual bacteria adhering to the substrate after a washing procedure. These results showed that LμP is a suitable way to lower the average surface roughness by about 58% and average surface waviness by approximately 38%. The LμP process proved to be effective on the bacteria cleanability as approximately five times fewer bacteria remained on the surfaces treated with the optimized LμP parameters compared to the untreated surfaces.

Theoretical investigation of the electronic structure and quantum transport in the graphene-C(111) diamond surface system.

PubMed

Selli, Daniele; Baburin, Igor; Leoni, Stefano; Zhu, Zhen; Tománek, David; Seifert, Gotthard

2013-10-30

We investigate the interaction of a graphene monolayer with the C(111) diamond surface using ab initio density functional theory. To accommodate the lattice mismatch between graphene and diamond, the overlayer deforms into a wavy structure that binds strongly to the diamond substrate. The detached ridges of the wavy graphene overlayer behave electronically as free-standing polyacetylene chains with delocalized π electrons, separated by regions containing only sp(3) carbon atoms covalently bonded to the (111) diamond surface. We performed quantum transport calculations for different geometries of the system to study how the buckling of the graphene layer and the associated bonding to the diamond substrate affect the transport properties. The system displays high carrier mobility along the ridges and a wide transport gap in the direction normal to the ridges. These intriguing, strongly anisotropic transport properties qualify the hybrid graphene-diamond system as a viable candidate for electronic nanodevices.

Reconstruction of Laser-Induced Surface Topography from Electron Backscatter Diffraction Patterns.

PubMed

Callahan, Patrick G; Echlin, McLean P; Pollock, Tresa M; De Graef, Marc

2017-08-01

We demonstrate that the surface topography of a sample can be reconstructed from electron backscatter diffraction (EBSD) patterns collected with a commercial EBSD system. This technique combines the location of the maximum background intensity with a correction from Monte Carlo simulations to determine the local surface normals at each point in an EBSD scan. A surface height map is then reconstructed from the local surface normals. In this study, a Ni sample was machined with a femtosecond laser, which causes the formation of a laser-induced periodic surface structure (LIPSS). The topography of the LIPSS was analyzed using atomic force microscopy (AFM) and reconstructions from EBSD patterns collected at 5 and 20 kV. The LIPSS consisted of a combination of low frequency waviness due to curtaining and high frequency ridges. The morphology of the reconstructed low frequency waviness and high frequency ridges matched the AFM data. The reconstruction technique does not require any modification to existing EBSD systems and so can be particularly useful for measuring topography and its evolution during in situ experiments.

Broad bandwidth vibration energy harvester based on thermally stable wavy fluorinated ethylene propylene electret films with negative charges

NASA Astrophysics Data System (ADS)

Zhang, Xiaoqing; Sessler, Gerhard M.; Ma, Xingchen; Xue, Yuan; Wu, Liming

2018-06-01

Wavy fluorinated ethylene propylene (FEP) electret films with negative charges were prepared by a patterning method followed by a corona charging process. The thermal stability of these films was characterized by the surface potential decay with annealing time at elevated temperatures. The results show that thermally stable electret films can be made by corona charging followed by pre-aging treatment. Vibration energy harvesters having a very simple sandwich structure, consisting of a central wavy FEP electret film and two outside metal plates, were designed and their performance, including the resonance frequency, output power, half power bandwidth, and device stability, was investigated. These harvesters show a broad bandwidth as well as high output power. Their performance can be further improved by using a wavy-shaped counter electrode. For an energy harvester with an area of 4 cm2 and a seismic mass of 80 g, the output power referred to 1 g (g is the gravity of the earth), the resonance frequency, and the 3 dB bandwidth are 1.85 mW, 90 Hz, and 24 Hz, respectively. The output power is sufficient to power some electronic devices. Such devices may be embedded in shoe soles, carpets or seat cushions where the flexibility is required and large force is available.

An experimental study on flow friction and heat transfer of water in sinusoidal wavy silicon microchannels

NASA Astrophysics Data System (ADS)

Huang, Houxue; Wu, Huiying; Zhang, Chi

2018-05-01

Sinusoidal wavy microchannels have been known as a more heat transfer efficient heat sink for the cooling of electronics than normal straight microchannels. However, the existing experimental study on wavy silicon microchannels with different phase differences are few. As a result of this, in this paper an experimental study has been conducted to investigate the single phase flow friction and heat transfer of de-ionized water in eight different sinusoidal wavy silicon microchannels (SWSMCs) and one straight silicon microchannel (SMC). The SWSMCs feature different phase differences (α  =  0 to π) and different relative wavy amplitudes (β  =  A/l  =  0.05 to 0.4), but the same average hydraulic diameters (D h  =  160 µm). It is found that both flow friction constant fRe and the Nusselt number depend on the phase difference and relative wavy amplitude. For sinusoidal wavy microchannels with a relative wavy amplitude (β  =  0.05), the Nusselt number increased noticeably with the phase difference for Re  >  250, but the effect was insignificant for Re  <  250 however, both pressure drop and apparent flow friction constant fRe increased with the increase in phase difference. For sinusoidal wavy microchannels with 0 phase difference, the increase in relative wavy amplitude obtained by reducing the wavy wave length induced higher pressure drop and apparent friction constant fRe, while the Nusselt number increased with relative wavy amplitude for Re  >  300. The results indicate that the thermal resistances of sinusoidal wavy silicon microchannels were generally lower than that of straight silicon microchannels, and the thermal resistance decreased with the increase in relative wavy amplitude. The enhancement of thermal performance is attributed to the flow re-circulation occurring in the corrugation troughs and the secondary flows or Dean vortices introduced by curved channels. It is concluded that silicon sinusoidal wavy microchannels provide higher heat transfer rate albeit with a higher flow friction, making it a better choice for the cooling of high heat flux electronics.

Evaluation of Rock Joint Coefficients

NASA Astrophysics Data System (ADS)

Audy, Ondřej; Ficker, Tomáš

2017-10-01

A computer method for evaluation of rock joint coefficients is described and several applications are presented. The method is based on two absolute numerical indicators that are formed by means of the Fourier replicas of rock joint profiles. The first indicator quantifies the vertical depth of profiles and the second indicator classifies wavy character of profiles. The absolute indicators have replaced the formerly used relative indicators that showed some artificial behavior in some cases. This contribution is focused on practical computations testing the functionality of the newly introduced indicators.

Formation of temperature front in stably stratified turbulence

NASA Astrophysics Data System (ADS)

Kimura, Yoshifumi; Sullivan, Peter; Herring, Jackson

2016-11-01

An important feature of stably stratified turbulence is the significant influence of internal gravity waves which makes stably stratified turbulence unique compared to homogeneous isotropic turbulence. In this paper, we investigate the genesis of temperature fronts-a crucial subject both practically and fundamentally-in stably stratified turbulence using Direct Numerical Simulations (DNS) of the Navier-Stokes equation under the Boussinesq approximation with 10243 grid points. Vertical profiles of temperature fluctuations show almost vertically periodic sawtooth wavy structures with negative and positive layers stacked together with clear boundaries implying a sharp temperature fronts. The sawtooth waves consist of gradual decreasing temperature fluctuations with rapid recovery to a positive value as the frontal boundary is crossed vertically. This asymmetry of gradients comes from the structure that warm temperature region lies on top of cool temperature region, and can be verified in the skewed probability density function (PDF) of vertical temperature gradient. We try to extract the flow structures and mechanism for the formation and maintenance of the strong temperature front numerically.

Numerical studies of laminar and turbulent drag reduction, part 2

NASA Technical Reports Server (NTRS)

Balasubramanian, R.; Orszag, S. A.

1983-01-01

The flow over wave shaped surfaces is studied using a Navier Stokes solver. Detailed comparisons with theoretical results are presented, including the stability of a laminar flow over wavy surfaces. Drag characteristics of nonplanar surfaces are predicted using the Navier-Stokes solver. The secondary instabilities of wall bounded and free shear flows are also discussed.

Lithography-Free Fabrication of Reconfigurable Substrate Topography For Contact Guidance

PubMed Central

Pholpabu, Pitirat; Kustra, Stephen; Wu, Haosheng; Balasubramanian, Aditya; Bettinger, Christopher J.

2014-01-01

Mammalian cells detect and respond to topographical cues presented in natural and synthetic biomaterials both in vivo and in vitro. Micro- and nano-structures influence the adhesion, morphology, proliferation, migration, and differentiation of many phenotypes. Although the mechanisms that underpin cell-topography interactions remain elusive, synthetic substrates with well-defined micro- and nano-structures are important tools to elucidate the origin of these responses. Substrates with reconfigurable topography are desirable because programmable cues can be harmonized with dynamic cellular responses. Here we present a lithography-free fabrication technique that can reversibly present topographical cues using an actuation mechanism that minimizes the confounding effects of applied stimuli. This method utilizes strain-induced buckling instabilities in bi-layer substrate materials with rigid uniform silicon oxide membranes that are thermally deposited on elastomeric substrates. The resulting surfaces are capable of reversible of substrates between three distinct states: flat substrates (A = 1.53 ± 0.55 nm, Rms = 0.317 ± 0.048 nm); parallel wavy grating arrays (A|| = 483.6 ± 7.8 nm and λ|| = 4.78 ± 0.16 μm); perpendicular wavy grating arrays (A⊥ = 429.3 ± 5.8 nm; λ⊥ = 4.95 ± 0.36 μm). The cytoskeleton dynamics of 3T3 fibroblasts in response to these surfaces was measured using optical microscopy. Fibroblasts cultured on dynamic substrates that are switched from flat to topographic features (FLAT-WAVY) exhibit a robust and rapid change in gross morphology as measured by a reduction in circularity from 0.30 ± 0.13 to 0.15 ± 0.08 after 5 min. Conversely, dynamic substrate sequences of FLAT-WAVY-FLAT do not significantly alter the gross steady-state morphology. Taken together, substrates that present topographic structures reversibly can elucidate dynamic aspects of cell-topography interactions. PMID:25468368

Temperature dependent evolution of wrinkled single-crystal silicon ribbons on shape memory polymers.

PubMed

Wang, Yu; Yu, Kai; Qi, H Jerry; Xiao, Jianliang

2017-10-25

Shape memory polymers (SMPs) can remember two or more distinct shapes, and thus can have a lot of potential applications. This paper presents combined experimental and theoretical studies on the wrinkling of single-crystal Si ribbons on SMPs and the temperature dependent evolution. Using the shape memory effect of heat responsive SMPs, this study provides a method to build wavy forms of single-crystal silicon thin films on top of SMP substrates. Silicon ribbons obtained from a Si-on-insulator (SOI) wafer are released and transferred onto the surface of programmed SMPs. Then such bilayer systems are recovered at different temperatures, yielding well-defined, wavy profiles of Si ribbons. The wavy profiles are shown to evolve with time, and the evolution behavior strongly depends on the recovery temperature. At relatively low recovery temperatures, both wrinkle wavelength and amplitude increase with time as evolution progresses. Finite element analysis (FEA) accounting for the thermomechanical behavior of SMPs is conducted to study the wrinkling of Si ribbons on SMPs, which shows good agreement with experiment. Merging of wrinkles is observed in FEA, which could explain the increase of wrinkle wavelength observed in the experiment. This study can have important implications for smart stretchable electronics, wrinkling mechanics, stimuli-responsive surface engineering, and advanced manufacturing.

Thermal control of electroosmotic flow in a microchannel through temperature-dependent properties.

PubMed

Kwak, Ho Sang; Kim, Hyoungsoo; Hyun, Jae Min; Song, Tae-Ho

2009-07-01

A numerical investigation is conducted on the electroosmotic flow and associated heat transfer in a two-dimensional microchannel. The objective of this study is to explore a new conceptual idea that is control of an electroosmotic flow by using a thermal field effect through the temperature-dependent physical properties. Two exemplary problems are examined: a flow in a microchannel with a constant vertical temperature difference between two horizontal walls and a flow in a microchannel with the wall temperatures varying horizontally in a sinusoidal manner. The results of numerical computations showed that a proper control of thermal field may be a viable means to manipulate various non-plug-like flow patterns. A constant vertical temperature difference across the channel produces a shear flow. The horizontally-varying thermal condition results in spatial variation of physical properties to generate fluctuating flow patterns. The temperature variation at the wall with alternating vertical temperature gradient induces a wavy flow.

Porosimetry and packing morphology of vertically-aligned carbon nanotube arrays via impedance spectroscopy.

PubMed

Mutha, Heena K; Lu, Yuan; Stein, Itai; Cho, H Jeremy; Suss, Matthew; Laoui, Tahar; Thompson, Carl; Wardle, Brian; Wang, Evelyn

2016-12-13

Vertically aligned one-dimensional nanostructure arrays are promising in many applications such as electrochemical systems, solar cells, and electronics, taking advantage of high surface area per unit volume, nanometer length scale packing, and alignment leading to high conductivity. However, many devices need to optimize arrays for device performance by selecting an appropriate morphology. Developing a simple, non-invasive tool for understanding the role of pore volume distribution and interspacing would aid in the optimization of nanostructure morphologies in electrodes. In this work, we combined electrochemical impedance spectroscopy (EIS) with capacitance measurements and porous electrode theory to conduct in situ porosimetry of vertically-aligned carbon nanotubes (VA-CNTs) non-destructively. We utilized the EIS measurements with a pore size distribution model to quantify the average and dispersion of inter-CNT spacing (Γ), stochastically, in carpets that were mechanically densified from 1.7 × 10¹⁰ tubes/cm² to 4.5 × 10¹¹ tubes/cm². Our analysis predicts that the inter-CNT spacing ranges from over 100 ± 50 nm in sparse carpets to sub 10 ± 5 nm in packed carpets. Our results suggest that waviness of CNTs leads to variations in the inter-CNT spacing, which can be significant in sparse carpets. This methodology can be used to predict the performance of many nanostructured devices, including supercapacitors, batteries, solar cells, and semiconductor electronics. Copyright 2016 IOP Publishing Ltd.

Estimation of Effective Directional Strength of Single Walled Wavy CNT Reinforced Nanocomposite

NASA Astrophysics Data System (ADS)

Bhowmik, Krishnendu; Kumar, Pranav; Khutia, Niloy; Chowdhury, Amit Roy

2018-03-01

In this present work, single walled wavy carbon nanotube reinforced into composite has been studied to predict the effective directional strength of the nanocomposite. The effect of waviness on the overall Young’s modulus of the composite has been analysed using three dimensional finite element model. Waviness pattern of carbon nanotube is considered as periodic cosine function. Both long (continuous) and short (discontinuous) carbon nanotubes are being idealized as solid annular tube. Short carbon nanotube is modelled with hemispherical cap at its both ends. Representative Volume Element models have been developed with different waviness, height fractions, volume fractions and modulus ratios of carbon nanotubes. Consequently a micromechanics based analytical model has been formulated to derive the effective reinforcing modulus of wavy carbon nanotubes. In these models wavy single walled wavy carbon nanotubes are considered to be aligned along the longitudinal axis of the Representative Volume Element model. Results obtained from finite element analyses are compared with analytical model and they are found in good agreement.

Stretchable Ag electrodes with mechanically tunable optical transmittance on wavy-patterned PDMS substrates

PubMed Central

Ko, Eun-Hye; Kim, Hyo-Joong; Lee, Sang-Mok; Kim, Tae-Woong; Kim, Han-Ki

2017-01-01

We report on semi-transparent stretchable Ag films coated on a wavy-patterned polydimethylsiloxane (PDMS) substrate for use as stretchable electrodes for stretchable and transparent electronics. To improve the mechanical stretchability of the Ag films, we optimized the wavy-pattern of the PDMS substrate as a function of UV-ozone treatment time and pre-strain of the PDMS substrate. In addition, we investigated the effect of the Ag thickness on the mechanical stretchability of the Ag electrode formed on the wavy-patterned PDMS substrate. The semi-transparent Ag films formed on the wavy-patterned PDMS substrate showed better stretchability (strain 20%) than the Ag films formed on a flat PDMS substrate because the wavy pattern effectively relieved strain. In addition, the optical transmittance of the Ag electrode on the wavy-patterned PDMS substrate was tunable based on the degree of stretching for the PDMS substrate. In particular, it was found that the wavy-patterned PDMS with a smooth buckling was beneficial for a precise patterning of Ag interconnectors. Furthermore, we demonstrated the feasibility of semi-transparent Ag films on wavy-patterned PDMS as stretchable electrodes for the stretchable electronics based on bending tests, hysteresis tests, and dynamic fatigue tests. PMID:28436426

Summary of Drag Characteristics of Practical-Construction Wing Sections

NASA Technical Reports Server (NTRS)

Quinn, John H , Jr

1948-01-01

The effect of several parameters on the drag characteristics of practical-construction wing sections have been considered and evaluated. The effects considered were those of surface roughness, surface waviness, compressive load, and de-icers. The data were obtained from a number of tests in the Langley two-dimensional low-turbulence tunnels.

Measurement of Interfacial Profiles of Wavy Film Flow on Inclined Wall

NASA Astrophysics Data System (ADS)

Rosli, N.; Amagai, K.

2016-02-01

Falling liquid films on inclined wall present in many industrial processes such as in food processing, seawater desalination and electronic devices manufacturing industries. In order to ensure an optimal efficiency of the operation in these industries, a fundamental study on the interfacial flow profiles of the liquid film is of great importance. However, it is generally difficult to experimentally predict the interfacial profiles of liquid film flow on inclined wall due to the instable wavy flow that usually formed on the liquid film surface. In this paper, the liquid film surface velocity was measured by using a non-intrusive technique called as photochromic dye marking method. This technique utilizes the color change of liquid containing the photochromic dye when exposed to the UV light source. The movement of liquid film surface marked by the UV light was analyzed together with the wave passing over the liquid. As a result, the liquid film surface was found to slightly shrink its gradual movement when approached by the wave before gradually move again after the intersection with the wave.

Failure Behavior of Unidirectional Composites under Compression Loading: Effect of Fiber Waviness

PubMed Central

Yue, Chee Yoon

2017-01-01

The key objective of this work is to highlight the effect of manufacturing-induced fiber waviness defects on the compressive failure of glass fiber-reinforced unidirectional specimens. For this purpose, in-plane, through-thickness waviness defects (with different waviness severities) are induced during the manufacturing of the laminate. Numerical and experimental results show that the compressive strength of the composites decreases as the severity of the waviness defects increases. A reduction of up to 75% is noted with a wave severity of 0.075. Optical and scanning electron microscopy observations of the failed specimens reveal that kink-bands are created in the wavy regions and lead to failure. PMID:28783057

Wavy carbon: A new series of carbon structures explored by quantum chemical calculations

NASA Astrophysics Data System (ADS)

Ohno, Koichi; Satoh, Hiroko; Iwamoto, Takeaki; Tokoyama, Hiroaki; Yamakado, Hideo

2015-10-01

A new carbon family adopting wavy structures has been found by quantum chemical calculations. The key motif of this family is a condensed four-membered ring. Periodically wavy-carbon sheets (wavy-Cn sheets, n = 2, 6, and 8) as well as wavy-C36 tube were found to be very similar to the previously reported prism-Cn carbon tubes (n = 5, 6, and 8) in several respects, including the relative energies per one carbon atom with respect to graphene, CC bond lengths, and CCC bond angles. Because of very high relative energies with respect to graphene (206-253 kJ mol-1), the wavy-carbons may behave as energy reserving materials.

Characterization of waviness in wind turbine blades using air coupled ultrasonics

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

Chakrapani, Sunil Kishore; Dayal, Vinay; Hsu, David K.

2011-06-23

Waviness in glass fiber reinforced composite is of great interest in composite research, since it results in the loss of stiffness. Several NDE techniques have been used previously to detect waviness. This work is concerned with waves normal to the plies in a composite. Air-coupled ultrasonics was used to detect waviness in thick composites used in the manufacturing of wind turbine blades. Composite samples with different wave aspect ratios were studied. Different wavy samples were characterized, and a three step process was developed to make sure the technique is field implementable. This gives us a better understanding of the effectmore » of waviness in thick composites, and how it affects the life and performance of the composite.« less

A High-Performance Lithium-Ion Battery Anode Based on the Core-Shell Heterostructure of Silicon-Coated Vertically Aligned Carbon Nanofibers

DTIC Science & Technology

2013-01-01

nanotubes ( MWCNTs ) using chemical vapour deposition (CVD) to form a hybrid Si– MWCNT structure consisting of 54 to 57 wt% of Si.16 The initial specic...retained less than 70% aer 100 cycles.16 The wavy and partially entangled structure may still have prevented uniform Si deposition deep into the MWCNT ...silicon shells, as illustrated in Fig. 1. The VACNFs are a special type of MWCNTs which are grown with DC-biased plasma chemical vapour deposition (PECVD

Cutin plays a role in differentiation of endosperm-derived callus of kiwifruit.

PubMed

Popielarska-Konieczna, Marzena; Kozieradzka-Kiszkurno, Małgorzata; Bohdanowicz, Jerzy

2011-11-01

Cutin fluorescence, after auramine O treatment, was detected on the surface of organogenic areas (protuberances) of endosperm derived callus induced on Murashige and Skoog medium with thidiazuron (0.5 mg l(-1)) in darkness. Electron micrographs of the protuberances revealed cuticle, visible as a dark-staining layer, and amorphous waxes on the cell wall. In some cases the cells of the epidermis-like layer and shoot buds at early stages of development showed thick and characteristically wavy cutin. This waviness corresponds with the wrinkled appearance of the cell wall as observed by scanning electron microscopy. The role of multivesicular bodies in cutin production and transfer to the plasma membrane is discussed.

An Experimental Study of the Influence of in-Plane Fiber Waviness on Unidirectional Laminates Tensile Properties

NASA Astrophysics Data System (ADS)

Zhao, Cong; Xiao, Jun; Li, Yong; Chu, Qiyi; Xu, Ting; Wang, Bendong

2017-12-01

As one of the most common process induced defects of automated fiber placement, in-plane fiber waviness and its influences on mechanical properties of fiber reinforced composite lack experimental studies. In this paper, a new approach to prepare the test specimen with in-plane fiber waviness is proposed in consideration of the mismatch between the current test standard and actual fiber trajectory. Based on the generation mechanism of in-plane fiber waviness during automated fiber placement, the magnitude of in-plane fiber waviness is characterized by axial compressive strain of prepreg tow. The elastic constants and tensile strength of unidirectional laminates with in-plane fiber waviness are calculated by off-axis and maximum stress theory. Experimental results show that the tensile properties infade dramatically with increasing magnitude of the waviness, in good agreement with theoretical analyses. When prepreg tow compressive strain reaches 1.2%, the longitudinal tensile modulus and strength of unidirectional laminate decreased by 25.5% and 57.7%, respectively.

On the study of wavy leading-edge vanes to achieve low fan interaction noise

NASA Astrophysics Data System (ADS)

Tong, Fan; Qiao, Weiyang; Xu, Kunbo; Wang, Liangfeng; Chen, Weijie; Wang, Xunnian

2018-04-01

The application of wavy leading-edge vanes to reduce a single-stage axial fan noise is numerically studied. The aerodynamic and acoustic performance of the fan is numerically investigated using a hybrid unsteady Reynolds averaged Navier-Stokes (URANS)/acoustic analogy method (Goldstein equations). First, the hybrid URANS/Goldstein method is developed and successfully validated against experiment results. Next, numerical simulations are performed to investigate the noise reduction effects of the wavy leading-edge vanes. The aerodynamic and acoustic performance is assessed for a fan with vanes equipped with two different wavy leading-edge profiles and compared with the performance of conventional straight leading-edge vanes. Results indicate that a fan with wavy leading-edge vanes produces lower interaction noise than the baseline fan without a significant loss in aerodynamic performance. In fact, it is demonstrated that wavy leading-edge vanes have the potential to lead to both aerodynamic and acoustic improvements. The two different wavy leading-edge profiles are shown to successfully reduce the fan tone sound power level by 1.2 dB and 4.3 dB, respectively. Fan efficiency is also improved by about 1% with one of the tested wavy leading-edge profiles. Large eddy simulation (LES) is also performed for a simplified fan stage model to assess the effects of wavy leading-edge vanes on the broadband fan noise. Results indicate that the overall sound power level of a fan can be reduced by about 4 dB with the larger wavy leading-edge profile. Finally, the noise reduction mechanisms are investigated and analysed. It is found that the wavy leading-edge profiles can induce significant streamwise vorticity around the leading-edge protuberances and reduce pressure fluctuations (especially at locations of wavy leading-edge hills) and unsteady forces on the stator vanes. The underlying mechanism of the reduced pressure fluctuations is also discussed by examining the magnitude-squared coherence between the velocity and pressure fluctuations in the vicinity of the noise sources. Moreover, a reduction in the correlation level of the wall pressure fluctuations along the vane leading-edge is observed, as well as destructive phase interference along the vane leading-edge.

Impact of initial surface parameters on the final quality of laser micro-polished surfaces

NASA Astrophysics Data System (ADS)

Chow, Michael; Bordatchev, Evgueni V.; Knopf, George K.

2012-03-01

Laser micro-polishing (LμP) is a new laser-based microfabrication technology for improving surface quality during a finishing operation and for producing parts and surfaces with near-optical surface quality. The LμP process uses low power laser energy to melt a thin layer of material on the previously machined surface. The polishing effect is achieved as the molten material in the laser-material interaction zone flows from the elevated regions to the local minimum due to surface tension. This flow of molten material then forms a thin ultra-smooth layer on the top surface. The LμP is a complex thermo-dynamic process where the melting, flow and redistribution of molten material is significantly influenced by a variety of process parameters related to the laser, the travel motions and the material. The goal of this study is to analyze the impact of initial surface parameters on the final surface quality. Ball-end micromilling was used for preparing initial surface of samples from H13 tool steel that were polished using a Q-switched Nd:YAG laser. The height and width of micromilled scallops (waviness) were identified as dominant parameter affecting the quality of the LμPed surface. By adjusting process parameters, the Ra value of a surface, having a waviness period of 33 μm and a peak-to-valley value of 5.9 μm, was reduced from 499 nm to 301 nm, improving the final surface quality by 39.7%.

Modeling Solar Energetic Particle Transport near a Wavy Heliospheric Current Sheet

NASA Astrophysics Data System (ADS)

Battarbee, Markus; Dalla, Silvia; Marsh, Mike S.

2018-02-01

Understanding the transport of solar energetic particles (SEPs) from acceleration sites at the Sun into interplanetary space and to the Earth is an important question for forecasting space weather. The interplanetary magnetic field (IMF), with two distinct polarities and a complex structure, governs energetic particle transport and drifts. We analyze for the first time the effect of a wavy heliospheric current sheet (HCS) on the propagation of SEPs. We inject protons close to the Sun and propagate them by integrating fully 3D trajectories within the inner heliosphere in the presence of weak scattering. We model the HCS position using fits based on neutral lines of magnetic field source surface maps (SSMs). We map 1 au proton crossings, which show efficient transport in longitude via HCS, depending on the location of the injection region with respect to the HCS. For HCS tilt angles around 30°–40°, we find significant qualitative differences between A+ and A‑ configurations of the IMF, with stronger fluences along the HCS in the former case but with a distribution of particles across a wider range of longitudes and latitudes in the latter. We show how a wavy current sheet leads to longitudinally periodic enhancements in particle fluence. We show that for an A+ IMF configuration, a wavy HCS allows for more proton deceleration than a flat HCS. We find that A‑ IMF configurations result in larger average fluences than A+ IMF configurations, due to a radial drift component at the current sheet.

Laser-induced nonlinear crystalline waveguide on glass fiber format and diode-pumped second harmonic generation

NASA Astrophysics Data System (ADS)

Shi, Jindan; Feng, Xian

2018-03-01

We report a diode pumped self-frequency-doubled nonlinear crystalline waveguide on glass fiber. A ribbon fiber has been drawn on the glass composition of 50GeO2-25B2O3-25(La,Yb)2O3. Surface channel waveguides have been written on the surface of the ribbon fiber, using space-selective laser heating method with the assistance of a 244 nm CW UV laser. The Raman spectrum of the written area indicates that the waveguide is composed of structure-deformed nonlinear (La,Yb)BGeO5 crystal. The laser-induced surface wavy cracks have also been observed and the forming mechanism of the wavy cracks has been discussed. Efficient second harmonic generation has been observed from the laser-induced crystalline waveguide, using a 976 nm diode pump. 13 μW of 488 nm output has been observed from a 17 mm long waveguide with 26.0 mW of launched diode pump power, corresponding to a normalized conversion efficiency of 4.4%W-1.

A novel zebrafish mutant with wavy-notochord: an effective biological index for monitoring the copper pollution of water from natural resources.

PubMed

Chen, Yau-Hung; Lin, Ji-Sheng

2011-02-01

We identified a novel zebrafish mutant that has wavy-notochord phenotypes, such as severely twisted notochord and posterior malformations, but has normal melanocytes. Histological evidences showed that proliferating vacuolar cells extended their growth to the muscle region, and consequently caused the wavy-notochord phenotypes. Interestingly, those malformations can be greatly reversed by exposure with copper, suggesting that copper plays an important role on wavy-notochord phenotypes. In addition, after long-term copper exposure, the surviving larvae derived from wavy-notochord mutants displayed bone malformations, such as twisted axial skeleton and osteophyte. These phenotypic changes and molecular evidences of wavy-notochord mutants are highly similar to those embryos whose lysyl oxidases activities have been inactivated. Taken together, we propose that (i) the putative mutated genes of this wavy-notochord mutant might be highly associated with the lysyl oxidase genes in zebrafish; and (ii) this fish model is an effective tool for monitoring copper pollution of water from natural resources. Copyright © 2009 Wiley Periodicals, Inc.

Effects of cone surface waviness and freestream noise on transition in supersonic flow

NASA Technical Reports Server (NTRS)

Morrisette, E. L.; Creel, T. R., Jr.; Chen, F.-J.

1986-01-01

A comparison of transition on wavy-wall and smooth-wall cones in a Mach 3.5 wind tunnel is made under conditions of either low freestream noise (quiet flow) or high freestream noise (noisy flow). The noisy flow compares to that found in conventional wind tunnels while the quiet flow gives transitional Reynolds numbers on smooth sharp cones comparable to those found in flight. The waves were found to have a much smaller effect on transition than similar sized trip wires. A satisfatory correlating parameter for the effect of waves on transition was simply the wave height-to-length ratio. A given value of this ratio was found to cause the same percentage change in transition location in quiet and noisy flows.

Analysis of the reflection of a micro drop fiber sensor

NASA Astrophysics Data System (ADS)

Sun, Weimin; Liu, Qiang; Zhao, Lei; Li, Yingjuan; Yuan, Libo

2005-01-01

Micro drop fiber sensors are effective tools for measuring characters of liquids. These types of sensors are wildly used in biotechnology, beverage and food markets. For a fiber micro drop sensor, the signal of the output light is wavy with two peaks, normally. Carefully analyzing the wavy process can identify the liquid components. Understanding the reason of forming this wavy signal is important to design a suitable sensing head and to choose a suitable signal-processing method. The dripping process of a type of liquids is relative to the characters of the liquid and the shape of the sensing head. The quasi-Gauss model of the light field from the input-fiber end is used to analyse the distribution of the light field in the liquid drop. In addition, considering the characters of the liquid to be measured, the dripping process of the optical signal from the output-fiber end can be expected. The reflection surface of the micro drop varies as serials of spheres with different radiuses and global centers. The intensity of the reflection light changes with the shape of the surface. The varying process of the intensity relates to the tense, refractive index, transmission et al. To support the analyse above, an experimental system is established. In the system, LED is chosen as the light source and the PIN transform the light signal to the electrical signal, which is collected by a data acquisition card. An on-line testing system is made to check the theory discussed above.

Role of large-scale slip in mode II fracture of bimaterial interface produced by diffusion bonding

NASA Astrophysics Data System (ADS)

Fox, M. R.; Ghosh, A. K.

2001-08-01

Bimaterial interfaces present in diffusion-bonded (and in-situ) composites are often not flat interfaces. The unevenness of the interface can result not only from interface reaction products but also from long-range waviness associated with the surfaces of the component phases bonded together. Experimental studies aimed at determining interface mechanical properties generally ignore the departure in the local stress due to waviness and assume a theoretically flat interface. Furthermore, the commonly used testing methods involving superimposed tension often renders the interface so extremely brittle that if microplastic effects were present it becomes impossible to perceive them. This article examines the role of waviness of the interface and microplastic effects on crack initiation. To do this, a test was selected that provides significant stability against crack growth by superimposing compressive stresses. Mode II interface fracture was studied for NiAl/Mo model laminates using a recently developed asymmetrically loaded shear (ALS) interface shear test. The ALS test may be viewed as opposite of the laminate bend test. In the bend test, shear at the interface is created via tension on one surface of the bend, while in the ALS test, shear is created by compression on one side of the interface relative to the other. Normal to the interface, near the crack tip, an initially compressive state is replaced by slight tension due to Poisson’s expansion of the unbonded part of the compressed beam.

A comprehensive dynamic model of double-row spherical roller bearing—Model development and case studies on surface defects, preloads, and radial clearance

NASA Astrophysics Data System (ADS)

Cao, M.; Xiao, J.

2008-02-01

Bearing excitation is one of the most important mechanical sources for vibration and noise generation in machine systems of a broad range of industries. Although extensively investigated, accurately predicting the vibration/acoustic behavior of bearings remains a challenging task because of its complicated nonlinear behaviors. While some ground work has been laid out on single-row deep-grooved ball (DGB) bearing, comprehensive modeling effort on spherical roller bearing (SRB) has yet to be carried out. This is mainly due to the facts that SRB system carries one more extra degree of freedom (DOF) on the moving race (could be either inner or outer race) and in general has more rolling elements compared with DGB. In this study, a comprehensive SRB excitation source model is developed. In addition to the vertical and horizontal displacements considered in previous investigations, the impacts of axial displacement/load are addressed by introducing the DOF in the axial shaft direction. Hence, instead of being treated as pre-assumed constants, the roller-inner/outer race contact angles are formulated as functions of the axial displacement of the moving race to reflect their dependence on the axial movement. The approach presented in this paper accounts for the point contacts between rollers and inner/outer races, as well as line contacts when the loads on individual rollers exceed the limit for point contact. A detailed contact-damping model reflecting the influences of the surface profiles and the speeds of the both contacting elements is developed and applied in the SRB model. Waviness of all the contact surfaces (including inner race, outer race, and rollers) is included and compared in this analysis. Extensive case studies are carried out to reveal the impacts of surface waviness, radial clearance, surface defects, and loading conditions on the force and displacement responses of the SRB system. System design guidelines are recommended based on the simulation results. This model is also applicable for bearing health monitoring, as demonstrated by the numerical case studies showing the frequency response of the system with moderate-to-large point defects on both inner and outer races, as well as the rollers. Comparisons between the simulation results and some conclusions reflecting common sense available in open literature serves as first hand partial validation of the developed model. Future validation efforts and further improvement directions are also provided. The comprehensive model developed in this investigation is a useful tool for machine system design, optimization, and performance evaluation.

Development of a Mobile Robot with Wavy Movement by Rotating Bars

NASA Astrophysics Data System (ADS)

Kitagawa, Ato; Zhang, Liang; Eguchi, Takashi; Tsukagoshi, Hideyuki

A mobile robot with a new type of movement called wavy movement is proposed in this paper. Wavy movement can be readily realized by many bars or crosses which are rotating at equivalent speeds, and the robot with simple structure and easy control method is able to ascend and descend stairs by covering the corners of stairs within separate wave shapes between touching points. The principle of wavy movement, the mechanism, and the experimental result of the proposed robot are discussed.

Models for Electromagnetic Scattering from the Sea at Extremely Low Grazing Angles

DTIC Science & Technology

1987-12-31

34 wedgy " rather than a "wavy" surface. this author found such a surface to have the expected k-minus-four spectrum. but with a spectral scale factor that...zero grazing angle across the top of the wedge (Fig. 19b. correspond- ing to the normal wedgy sea of our low-angle model.) We see that the polarization

Level-Set Simulation of Viscous Free Surface Flow Around a Commercial Hull Form

DTIC Science & Technology

2005-04-15

Abstract The viscous free surface flow around a 3600 TEU KRISO Container Ship is computed using the finite volume based multi-block RANS code, WAVIS...developed at KRISO . The free surface is captured with the Level-set method and the realizable k-ε model is employed for turbulence closure. The...computations are done for a 3600 TEU container ship of Korea Research Institute of Ships & Ocean Engineering, KORDI (hereafter, KRISO ) selected as

Subsurface damage in precision ground ULE(R) and Zerodur(R) surfaces.

PubMed

Tonnellier, X; Morantz, P; Shore, P; Baldwin, A; Evans, R; Walker, D D

2007-09-17

The total process cycle time for large ULE((R)) and Zerodur((R))optics can be improved using a precise and rapid grinding process, with low levels of surface waviness and subsurface damage. In this paper, the amounts of defects beneath ULE((R)) and Zerodur((R) )surfaces ground using a selected grinding mode were compared. The grinding response was characterised by measuring: surface roughness, surface profile and subsurface damage. The observed subsurface damage can be separated into two distinct depth zones, which are: 'process' and 'machine dynamics' related.

A parametric study of variables that affect fiber microbuckling initiation in composite laminates. I - Analyses. II - Experiments

NASA Technical Reports Server (NTRS)

Guynn, E. G.; Ochoa, Ozden O.; Bradley, Walter L.

1992-01-01

The effects of the stacking sequence (orientation of plies adjacent to the 0-deg plies), free surfaces, fiber/matrix interfacial bond strength, initial fiber waviness, resin-rich regions, and nonlinear shear constitutive behavior of the resin on the initiation of fiber microbuckling in thermoplastic composites were investigated using nonlinear geometric and nonlinear 2D finite-element analyses. Results show that reductions in the resin shear tangent modulus, large amplitudes of the initial fiber waviness, and debonds each cause increases in the localized matrix shear strains; these increases lead in turn to premature initiation of fiber microbuckling. The numerical results are compared to experimental data obtained using three thermoplastic composite material systems: (1) commercial APC-2, (2) QUADRAX Unidirectional Interlaced Tape, and AU4U/PEEK.

Wave propagation reversal for wavy vortices in wide-gap counter-rotating cylindrical Couette flow.

PubMed

Altmeyer, S; Lueptow, Richard M

2017-05-01

We present a numerical study of wavy supercritical cylindrical Couette flow between counter-rotating cylinders in which the wavy pattern propagates either prograde with the inner cylinder or retrograde opposite the rotation of the inner cylinder. The wave propagation reversals from prograde to retrograde and vice versa occur at distinct values of the inner cylinder Reynolds number when the associated frequency of the wavy instability vanishes. The reversal occurs for both twofold and threefold symmetric wavy vortices. Moreover, the wave propagation reversal only occurs for sufficiently strong counter-rotation. The flow pattern reversal appears to be intrinsic in the system as either periodic boundary conditions or fixed end wall boundary conditions for different system sizes always result in the wave propagation reversal. We present a detailed bifurcation sequence and parameter space diagram with respect to retrograde behavior of wavy flows. The retrograde propagation of the instability occurs when the inner Reynolds number is about two times the outer Reynolds number. The mechanism for the retrograde propagation is associated with the inviscidly unstable region near the inner cylinder and the direction of the global average azimuthal velocity. Flow dynamics, spatio-temporal behavior, global mean angular velocity, and torque of the flow with the wavy pattern are explored.

Can deformation of a polymer film with a rigid coating model geophysical processes?

NASA Astrophysics Data System (ADS)

Volynskii, A. L.; Bazhenov, S. L.

2007-12-01

The structural and mechanical behavior of polymer films with a thin rigid coating is analyzed. The behavior of such systems under applied stress is accompanied by the formation of a regular wavy surface relief and by regular fragmentation of the coating. The above phenomena are shown to be universal. Both phenomena (stress-induced development of a regular wavy surface relief and regular fragmentation of the coating) are provided by the specific features of mechanical stress transfer from a compliant soft support to a rigid thin coating. The above phenomena are associated with a specific structure of the system, which is referred to as “a rigid coating on a soft substratum” system (RCSS). Surface microrelief in RCSS systems is similar to the ocean floor relief in the vicinity of mid-oceanic ridges. Thus, the complex system composed of a young oceanic crust and upper Earth's mantle may be considered as typically “a solid coating on a soft substratum” system. Specific features of the ocean floor relief are analyzed in terms of the approach advanced for the description of the structural mechanical behavior of polymer films with a rigid coating. This analysis allowed to estimate the strength of an ocean floor.

Locomotion of Paramecium in patterned environments

NASA Astrophysics Data System (ADS)

Park, Eun-Jik; Eddins, Aja; Kim, Junil; Yang, Sung; Jana, Saikat; Jung, Sunghwan

2011-10-01

Ciliary organisms like Paramecium Multimicronucleatum locomote by synchronized beating of cilia that produce metachronal waves over their body. In their natural environments they navigate through a variety of environments especially surfaces with different topology. We study the effects of wavy surfaces patterned on the PDMS channels on the locomotive abilities of Paramecium by characterizing different quantities like velocity amplitude and wavelength of the trajectories traced. We compare this result with the swimming characteristics in straight channels and draw conclusions about the effects of various patterned surfaces.

Annealing of (DU-10Mo)-Zr Co-Rolled Foils

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

Pacheco, Robin Montoya; Alexander, David John; Mccabe, Rodney James

2017-01-20

Producing uranium-10wt% molybdenum (DU-10Mo) foils to clad with Al first requires initial bonding of the DU-10Mo foil to zirconium (Zr) by hot rolling, followed by cold rolling to final thickness. Rolling often produces wavy (DU-10Mo)-Zr foils that should be flattened before further processing, as any distortions could affect the final alignment and bonding of the Al cladding to the Zr co-rolled surface layer; this bonding is achieved by a hot isostatic pressing (HIP) process. Distortions in the (DU-10Mo)-Zr foil may cause the fuel foil to press against the Al cladding and thus create thinner or thicker areas in the Almore » cladding layer during the HIP cycle. Post machining is difficult and risky at this stage in the process since there is a chance of hitting the DU-10Mo. Therefore, it is very important to establish a process to flatten and remove any waviness. This study was conducted to determine if a simple annealing treatment could flatten wavy foils. Using the same starting material (i.e. DU-10Mo coupons of the same thickness), five different levels of hot rolling and cold rolling, combined with five different annealing treatments, were performed to determine the effect of these processing variables on flatness, bonding of layers, annealing response, microstructure, and hardness. The same final thickness was reached in all cases. Micrographs, textures, and hardness measurements were obtained for the various processing combinations. Based on these results, it was concluded that annealing at 650°C or higher is an effective treatment to appreciably reduce foil waviness.« less

The Influence of Multiple Nested Layer Waviness on the Compression Strength of Double Nested Wave Formations in a Carbon Fiber Composite Laminate

NASA Astrophysics Data System (ADS)

Khan, Z. M.; Adams, D. O.; Anas, S.

2016-01-01

As advanced composite materials having superior physical and mechanical properties are being developed, the optimization of their processing techniques is eagerly sought. One of the most common defects arising during processing of structural composites is layer waviness. The layer waviness is more pronounced in thick-section flat and cylindrical laminates, which are extensively used in large wind turbine blades, submersibles, and space platforms. The layer waviness undulates the entire layer of a multidirectional laminate in the throughthe-thickness direction, leading to a gross deterioration of its compressive strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wavy 0° layers were fabricated in an IM/8551-7 carbon-epoxy composite laminate on a steel mold by using a single-step fabrication procedure. The test laminates were cured on a heated press according to the specific curing cycle of epoxy. Their static compression testing was performed using a NASA short block compression fixture on an MTS servohydraulic machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of the composite laminate. The experimental and analytical results obtained revealed that the reduction in the compression strength of composite laminate was constant after the fraction of the wavy 0° layers exceeded 35%. This analysis indicated that the percentage of the 0° wavy layer may be used to estimate the reduction in the compression strength of a double nested wave formation in a composite laminate.

Strain measurement in the wavy-ply region of an externally pressurized cross-ply composite ring

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

Gascoigne, H.E.; Abdallah, M.G.

1996-07-01

Ply-level strains are determined in the cross-section of an externally pressurized cross-ply (3:1 circumferential to axial fiber ratio) graphite-epoxy ring containing an isolated circumferential wavy region. A special test fixture was used which permitted measuring orthogonal displacement components in the wavy area using moire interferometry as the pressure was increased. Strain components were determined at selected locations in the wavy area up to approximately90% of failure pressure. The study shows: (1) large interlaminar shear strains, which are non-existent in the perfect ring, are present near the wave inflection points; (2) the wavy plies generate increased interlaminar normal compressive strains inmore » both circumferential and axial plies along a radial line coinciding with maximum wave amplitude; and (3) nonlinear strain response begins at approximately 60% of failure pressure.« less

Intensification of heat transfer across falling liquid films

NASA Astrophysics Data System (ADS)

Ruyer-Quil, Christian; Cellier, Nicolas; Stutz, Benoit; Caney, Nadia; Bandelier, Philippe; Locie Team; Legi Team

2017-11-01

The wavy motion of a liquid film is well known to intensify heat or mass transfers. Yet, if film thinning and wave merging are generally invoked, the physical mechanisms which enable this intensification are still unclear. We propose a systematic investigation of the impact of wavy motions on the heat transfer across 2D falling films on hot plates as a function of the inlet frequency and flow parameters. Computations over extended domains and for sufficient durations to achieve statistically established flows have been made possible by low-dimensional modeling and the development of a fast temporal solver based on graph optimizations. Heat transfer has been modeled using the weighted residual technique as a set of two evolution equations for the free-surface temperature and the wall heat flux. This new model solves the shortcomings of previous attempts, namely their inability to capture the onset of thermal boundary layers in large-amplitude waves and their limitation to low Prandtl numbers. Our study reveals that heat transfer is enhanced at the crests of the waves and that heat transfer intensification is maximum at the maximum of density of wave crests, which does not correspond to the natural wavy regime (no inlet forcing). Supports from Institut Universitaire de France and Région Auvergne-Rhones-Alpes are warmly acknowledged.

Analysis of spatial and temporal spectra of liquid film surface in annular gas-liquid flow

NASA Astrophysics Data System (ADS)

Alekseenko, Sergey; Cherdantsev, Andrey; Heinz, Oksana; Kharlamov, Sergey; Markovich, Dmitriy

2013-09-01

Wavy structure of liquid film in annular gas-liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

Power collection reduction by mirror surface nonflatness and tracking error for a central receiver solar power system.

PubMed

McFee, R H

1975-07-01

The effects of random waviness, curvature, and tracking error of plane-mirror heliostats in a rectangular array around a central-receiver solar power system are determined by subdividing each mirror into 484 elements, assuming the slope of each element to be representative of the surface slope average at its location, and summing the contributions of all elements and then of all mirrors in the array. Total received power and flux density distribution are computed for a given sun location and set of array parameter values. Effects of shading and blocking by adjacent mirrors are included in the calculation. Alt-azimuth mounting of the heliostats is assumed. Representative curves for two receiver diameters and two sun locations indicate a power loss of 20% for random waviness, curvature, and tracking error of 0.1 degrees rms, 0.002 m(-1), and 0.5 degrees , 3sigma, respectively, for an 18.2-m diam receiver and 0.3 degrees rms, 0.005 m(-1), and greater than 1 degrees , respectively, for a 30.4-m diam receiver.

Characterization of technical surfaces by structure function analysis

NASA Astrophysics Data System (ADS)

Kalms, Michael; Kreis, Thomas; Bergmann, Ralf B.

2018-03-01

The structure function is a tool for characterizing technical surfaces that exhibits a number of advantages over Fourierbased analysis methods. So it is optimally suited for analyzing the height distributions of surfaces measured by full-field non-contacting methods. The structure function is thus a useful method to extract global or local criteria like e. g. periodicities, waviness, lay, or roughness to analyze and evaluate technical surfaces. After the definition of line- and area-structure function and offering effective procedures for their calculation this paper presents examples using simulated and measured data of technical surfaces including aircraft parts.

Effect of topography on wind turbine power and load fluctuations

NASA Astrophysics Data System (ADS)

Santoni, Christian; Ciri, Umberto; Leonardi, Stefano

2015-11-01

Onshore wind turbines produce more than 17 GW in the US, which constitutes 4 . 4 % of all the energy produced. Sites selection is mostly determined by the atmospheric conditions and the topographical characteristics of the region. While the effect of the atmospheric boundary layer had been widely studied, less attention has been given to the effect of the topography on the wind turbine aerodynamics. To address how the topography affects the flow, Large Eddy Simulations of the flow over a wind turbine placed over wavy wall are performed. The wavelength of the wavy terrain, λ, is 1 . 7 D where D is the turbine rotor diameter. Two different values of the height of the wavy wall, a / D = 0 . 05 and a / D = 0 . 10 have been considered. In addition, two positions of the turbine with respect to the wavy wall had been studied, on the crest and trough of the wavy wall and compared with a wind turbine over a flat wall. For the turbine located at the crest, the pressure gradient due to the wavy wall caused a recirculation behind the wind tower 2 . 5 D larger than that of the smooth wall. When placed at the trough of the wavy terrain, the favorable pressure gradient increases the wake velocity near the wall and promotes entrainment into the turbine wake. Numerical simulations were performed on XSEDE TACC, Grant CTS070066. This work was supported by the NSF, grant IIA-1243482 (WINDINSPIRE).

The waviness of the extratropical jet and daily weather extremes

NASA Astrophysics Data System (ADS)

Röthlisberger, Matthias; Martius, Olivia; Pfahl, Stephan

2016-04-01

In recent years the Northern Hemisphere mid-latitudes have experienced a large number of weather extremes with substantial socio-economic impact, such as the European and Russian heat waves in 2003 and 2010, severe winter floods in the United Kingdom in 2013/2014 and devastating winter storms such as Lothar (1999) and Xynthia (2010) in Central Europe. These have triggered an engaged debate within the scientific community on the role of human induced climate change in the occurrence of such extremes. A key element of this debate is the hypothesis that the waviness of the extratropical jet is linked to the occurrence of weather extremes, with a wavier jet stream favouring more extremes. Previous work on this topic is expanded in this study by analyzing the linkage between a regional measure of jet waviness and daily temperature, precipitation and wind gust extremes. We show that indeed such a linkage exists in many regions of the world, however this waviness-extremes linkage varies spatially in strength and sign. Locally, it is strong only where the relevant weather systems, in which the extremes occur, are affected by the jet waviness. Its sign depends on how the frequency of occurrence of the relevant weather systems is correlated with the occurrence of high and low jet waviness. These results go beyond previous studies by noting that also a decrease in waviness could be associated with an enhanced number of some weather extremes, especially wind gust and precipitation extremes over western Europe.

The Microstructural Evolution of Fatigue Cracks in FCC Metals

NASA Astrophysics Data System (ADS)

Gross, David William

The microstructural evolution during fatigue crack propagation was investigated in a variety of planar and wavy slip FCC metals. The planar materials included Haynes 230, Nitronic 40, and 316 stainless steel, and the wavy materials included pure nickel and pure copper. Three different sets of experiments were performed to fully characterize the microstructural evolution. The first, performed on Haynes 230, mapped the strain field ahead a crack tip using digital image correlation and electron backscatter diffraction techniques. Focused ion beam (FIB) lift-out techniques were then utilized to extract transmission electron microscopy (TEM) samples at specific distances from the crack tip. TEM investigations compared the measured strain to the microstructure. Overall, the strain measured via DIC and EBSD was only weakly correlated to the density of planar slip bands in the microstructure. The second set of experiments concerned the dislocation structure around crack tips. This set of experiments was performed on all the materials. The microstructure at arrested fatigue cracks on the free surface was compared to the microstructure found beneath striations on the fracture surfaces by utilizing FIB micromachining to create site-specific TEM samples. The evolved microstructure depended on the slip type. Strong agreement was found between the crack tip microstructure at the free surface and the fracture surface. In the planar materials, the microstructure in the plastic zone consisted of bands of dislocations or deformation twins, before transitioning to a refined sub-grain microstructure near the crack flank. The sub-grain structure extended 300-500 nm away from the crack flank in all the planar slip materials studied. In contrast, the bulk structure in the wavy slip material consisted of dislocation cells and did not transition to a different microstructure as the crack tip was approached. The strain in wavy slip was highest near the crack tip, as the misorientations between the dislocation cells increased and the cell size decreased as the crack flank was approached. The final set of experiments involved reloading the arrested crack tips in monotonic tension. This was performed on both the Haynes 230 and 316 stainless steel. This technique exposed the fracture surface and location of the arrested crack tip away from the free surface, allowing for a sample to be extracted via FIB micromachining and TEM evaluation of the microstructure. This permitted the crack tip microstructure to be investigated without exposing the microstructure to crack closure or free surface effects. These experiments confirmed what was inferred from the earlier experiments, namely that the banded structure was a product of the crack tip plastic zone and the refined structure was a product of the strain associated with crack advance. Overall the microstructural complexity presented in this work was much higher than would be predicted by current models of fatigue crack propagation. It is recommended that future models attempt to simulate interactions between the dislocations emitted during fatigue crack growth and the pre-existing microstructure to more accurately simulate the processes occurring at the crack tip during crack growth.

Experimental investigation of defect criticality in FRP laminate composites

NASA Astrophysics Data System (ADS)

Joyce, Peter James

1999-11-01

This work examines the defect criticality of fiber reinforced polymer Composites. The objective is to determine the sensitivity of the finished composite to various process-induced defects. This work focuses on two different classes of process-induced defects; (1) fiber waviness in high performance carbon-fiber reinforced unidirectional composites and (2) void volume in low cost glass-fabric reinforced composites. The role of fiber waviness in the compressive response of unidirectional composites has been studied by a number of other investigators. Because of difficulties associated with producing real composites with varying levels of fiber waviness, most experimental studies of fiber waviness have evaluated composites with artificially induced fiber waviness. Furthermore, most experimental studies have been concentrated on the effects of out-of-plane fiber waviness. The objective of this work is to evaluate the effects of in-plane fiber waviness naturally occurring in autoclave consolidated thermoplastic laminates. The first phase of this project involved the development of a simple technique for measuring the resulting fiber waviness levels. An experimental investigation of the compression strength reduction in composites with in-plane fiber waviness followed. The experimental program included carbon-fiber reinforced thermoplastic composites manufactured from prepreg tape by hand layup, and carbon-fiber and glass-fiber reinforced composites manufactured from an experimental powder towpreg by filament winding and autoclave consolidation. The compression specimens exhibited kink band failure in the prepreg composite and varying amounts of longitudinal splitting and kink banding in the towpreg composites. The compression test results demonstrated the same trend as predicted by microbudding theory but the overall quantitative correlation was poor. The second thrust of this research evaluated void effects in resin transfer molded composites. Much of the existing literature in this area has focused on composites with unidirectional fiber reinforcement. In this program, the influence of void volume on the mechanical behavior of RTM composites with plain weave reinforcement was investigated. The experimental program demonstrated that the effects of void volume are negligible in terms of the fiber dominated properties. Interlaminar shear strength tests on the other hand demonstrated a linear dependence on void volume in the range tested.

Modeling of normal contact of elastic bodies with surface relief taken into account

NASA Astrophysics Data System (ADS)

Goryacheva, I. G.; Tsukanov, I. Yu

2018-04-01

An approach to account the surface relief in normal contact problems for rough bodies on the basis of an additional displacement function for asperities is considered. The method and analytic expressions for calculating the additional displacement function for one-scale and two-scale wavy relief are presented. The influence of the microrelief geometric parameters, including the number of scales and asperities density, on additional displacements of the rough layer is analyzed.

Surface inspection system for carriage parts

NASA Astrophysics Data System (ADS)

Denkena, Berend; Acker, Wolfram

2006-04-01

Quality standards are very high in carriage manufacturing, due to the fact, that the visual quality impression is highly relevant for the purchase decision for the customer. In carriage parts even very small dents can be visible on the varnished and polished surface by observing reflections. The industrial demands are to detect these form errors on the unvarnished part. In order to meet the requirements, a stripe projection system for automatic recognition of waviness and form errors is introduced1. It bases on a modified stripe projection method using a high resolution line scan camera. Particular emphasis is put on achieving a short measuring time and a high resolution in depth, aiming at a reliable automatic recognition of dents and waviness of 10 μm on large curved surfaces of approximately 1 m width. The resulting point cloud needs to be filtered in order to detect dents. Therefore a spatial filtering technique is used. This works well on smoothly curved surfaces, if frequency parameters are well defined. On more complex parts like mudguards the method is restricted by the fact that frequencies near the define dent frequencies occur within the surface as well. To allow analysis of complex parts, the system is currently extended by including 3D CAD models into the process of inspection. For smoothly curved surfaces, the measuring speed of the prototype is mainly limited by the amount of light produced by the stripe projector. For complex surfaces the measuring speed is limited by the time consuming matching process. Currently, the development focuses on the improvement of the measuring speed.

Investigation of Fiber Waviness in a Thick Glass Composite Beam Using THz NDE

NASA Technical Reports Server (NTRS)

Anastasi, Robert F.

2008-01-01

Fiber waviness in laminated composite material is introduced during manufacture because of uneven curing, resin shrinkage, or ply buckling caused by bending the composite lay-up into its final shape prior to curing. The resulting waviness has a detrimental effect on mechanical properties, therefore this condition is important to detect and characterize. Ultrasonic characterization methods are difficult to interpret because elastic wave propagation is highly dependent on ply orientation and material stresses. By comparison, the pulsed terahertz response of the composite is shown to provide clear indications of the fiber waviness. Pulsed Terahertz NDE is an electromagnetic inspection method that operates in the frequency range between 300 GHz and 3 THz. Its propagation is influenced by refractive index variations and interfaces. This work applies pulsed Terahertz NDE to the inspection of a thick composite beam with fiber waviness. The sample is a laminated glass composite material approximately 15mm thick with a 90-degree bend. Terahertz response from the planar section, away from the bend, is indicative of a homogeneous material with no major reflections from internal plies, while the multiple reflections at the bend area correspond to the fiber waviness. Results of these measurements are presented for the planar and bend areas.

In situ observations of wave pumping of sediments in the Yellow River Delta with a newly developed benthic chamber

NASA Astrophysics Data System (ADS)

Zhang, Shaotong; Jia, Yonggang; Zhang, Yaqi; Liu, Xiaolei; Shan, Hongxian

2018-03-01

A specially designed benthic chamber for the field observation of sediment resuspension that is caused by the wave-induced oscillatory seepage effect (i.e., the wave pumping of sediments) is newly developed. Observational results from the first sea trial prove that the geometry design and skillful instrumentation of the chamber well realize the goal of monitoring the wave pumping of sediments (WPS) continuously. Based on this field dataset, the quantitative contribution of the WPS to the total sediment resuspension is estimated to be 20-60% merely under the continuous action of normal waves (Hs ≤ 1.5 m) in the subaqueous Yellow River Delta (YRD). Such a large contribution invalidates a commonly held opinion that sediments are purely eroded from the seabed surface by the horizontal "shearing effect" from the wave orbital or current velocities. In fact, a considerable amount of sediments could originate from the shallow subsurface of seabed driven by the vertical "pumping effect" of the wave-generated seepage flows during wavy periods. According to the new findings, an improved conceptual model for the resuspension mechanisms of silty sediments under various hydrodynamics is proposed for the first time.

Slug-flow dynamics with phase change heat transfer in compact heat exchangers with oblique wavy walls

NASA Astrophysics Data System (ADS)

Morimoto, Kenichi; Kinoshita, Hidenori; Matsushita, Ryo; Suzuki, Yuji

2017-11-01

With abundance of low-temperature geothermal energy source, small-scale binary-cycle power generation system has gained renewed attention. Although heat exchangers play a dominant role in thermal efficiency and the system size, the optimum design strategy has not been established due to complex flow phenomena and the lack of versatile heat transfer models. In the present study, the concept of oblique wavy walls, with which high j/f factor is achieved by strong secondary flows in single-phase system, is extended to two-phase exchangers. The present analyses are based on evaporation model coupled to a VOF technique, and a train of isolated bubbles is generated under the controlled inlet quality. R245fa is adopted as a low boiling-point working media, and two types of channels are considered with a hydraulic diameter of 4 mm: (i) a straight circular pipe and (ii) a duct with oblique wavy walls. The focus is on slug-flow dynamics with evaporation under small capillary but moderate Weber numbers, where the inertial effect as well as the surface tension is of significance. A possible direction of the change in thermo-physical properties is explored by assuming varied thermal conductivity. Effects of the vortical motions on evaporative heat transfer are highlighted. This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Effect of the cross sectional aspect ratio on the flow past a twisted cylinder

NASA Astrophysics Data System (ADS)

Jung, Jae Hwan; Yoon, Hyun Sik

2013-11-01

The cross-flow around twisted cylinders of cross sectional aspect ratio (A/B) from 1 to 2.25 is investigated at a subcritical Reynolds number (Re) of 3000 using large eddy simulation (LES). The flow past a corresponding smooth and wavy cylinder is also calculated for comparison and validation against experimental data. The effect of twisted surface assessed in terms of the mean drag and root-mean-square (RMS) value of fluctuating lift. The shear layer of the twisted cylinder covering the recirculation region is more elongated than those of the smooth and the wavy cylinder. Successively, vortex shedding of the twisted cylinder is considerably suppressed, compared with those of the smooth and the wavy cylinder. The maximum drag reduction of up to 13% compared with a smooth cylinder is obtained at a certain cross sectional aspect ratio. The fluctuating lift coefficient of the twisted cylinder is also significantly suppressed. We found that the cross sectional cross sectional aspect ratio (A/B) plays an essential role in determining the vortical structures behind the twisted cylinder which has a significant effect on the reduction of the fluctuating lift and suppression of flow-induced vibration. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) through GCRC-SOP (No. 2011-0030013).

Effect of Surface Waviness on Transition in Three-Dimensional Boundary-Layer Flow

NASA Technical Reports Server (NTRS)

Masad, Jamal A.

1996-01-01

The effect of a surface wave on transition in three-dimensional boundary-layer flow over an infinite swept wing was studied. The mean flow computed using interacting boundary-layer theory, and transition was predicted using linear stability theory coupled with the empirical eN method. It was found that decreasing the wave height, sweep angle, or freestream unit Reynolds number, and increasing the freestream Mach number or suction level all stabilized the flow and moved transition onset to downstream locations.

Influence of a white noise at channel inlet on the parallel and wavy convective instabilities of Poiseuille-Rayleigh-Bénard flows

NASA Astrophysics Data System (ADS)

Nicolas, Xavier; Zoueidi, Noussaiba; Xin, Shihe

2012-08-01

The present paper concerns Poiseuille-Rayleigh-Bénard mixed convection flows in horizontal rectangular air-filled channels of large spanwise aspect ratio (W/H ≥ 10) and it focuses on the primary and secondary thermoconvective instabilities made of steady longitudinal and unsteady wavy rolls for 100 ≤ Re ≤ 200, 3000 < Ra < 15 000, Pr = 0.7, and W/H = 10. Time linear stability analysis of longitudinal rolls and 3D nonlinear numerical simulations using a specially tailored finite difference code is performed for this purpose. A bibliographical review, linear stability analysis and 3D numerical simulations allow establishing the full stability diagram for Re ≤ 300 and Ra ≤ 20 000. The linear stability analysis indicates that the critical Rayleigh number Ra≈*(Re) of the neutral curve between longitudinal and wavy rolls for W/H = 10 is increased at least by a factor of 1.5 in comparison with infinite W/H. The numerical study shows that the usual definitions of growth lengths for longitudinal rolls are inappropriate and it explains the discrepancies observed on wall Nusselt numbers in the literature between experimental and numerical results for the fully developed longitudinal rolls: Nusselt number decreasing at Ra > 8000 is due to spanwise oscillations of thermoconvective rolls that favor a bulk temperature homogenization. Because they are a convective instability, wavy rolls and their space and time development are studied numerically by maintaining at channel inlet, a permanent random excitation: it is designed to cover all the modes and allows detecting the wavy roll modes that are naturally amplified by the flow and those that are damped. Wavy roll patterns are characterized with respect to its three control parameters: Re, the relative distance ɛ to the critical Rayleigh number Ra≈*, and the excitation magnitude Aexc. The growth length of the wavy rolls is shown to correlate with ɛ-0.72 and Log(Aexc). The frequency, wave number, and phase velocity of the most amplified mode, the wall averaged Nusselt number and the spanwise displacements of the wavy rolls are independent of Aexc in the fully developed zone, but depend a lot on ɛ for ɛ < 2 and nearly stabilize for ɛ > 2 (i.e., Ra > 3Ra≈*). Correlation laws as a function of Re, ɛ, and Aexc are proposed for most of the exploited quantities. Numerical simulations performed are in a good agreement with experimental results on the wavy rolls obtained by Pabiou et al. ["Wavy secondary instability of longitudinal rolls in Rayleigh-Bénard-Poiseuille flows," J. Fluid Mech. 542, 175 (2005), 10.1017/S0022112005006154]. Finally, wavy roll characteristics are shown to be potentially interesting to better homogenize the vapor depositions in the horizontal rectangular chemical vapor deposition reactors used to make thin coatings on heated substrates from gaseous components.

Stretchable Lithium-Ion Batteries Enabled by Device-Scaled Wavy Structure and Elastic-Sticky Separator

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

Liu, Wei; Chen, Jun; Chen, Zheng

Fast developments and substantial achievements have been shaping the field of wearable electronic devices, resulting in the persistent requirement for stretchable lithium-ion batteries (LIBs). Despite recent progress in stretchable electrodes, stretching full batteries, including electrodes, separator, and sealing material, remains a great challenge. Here, a simple design concept for stretchable LIBs via a wavy structure at the full battery device scale is reported. All components including the package are capable of being reversibly stretched by folding the entire pouch cell into a wavy shape with polydimethylsiloxane filled in each valley region. In addition, the stretchable, sticky, and porous polyurethane/poly(vinylidene fluoride)more » membrane is adopted as a separator for the first time, which can maintain intimate contact between electrodes and separator to continuously secure ion pathway under dynamic state. Commercial cathode, anode, and package can be utilized in this rationally designed wavy battery to enable stretchability. The results indicate good electrochemical performances and long-term stability at repeatable release–stretch cycles. A high areal capacity of 3.6 mA h cm -2 and energy density of up to 172 W h L -1 can be achieved for the wavy battery. The promising results of the cost-effective wavy battery with high stretchability shed light on the development of stretchable energy storages.« less

Stretchable Lithium-Ion Batteries Enabled by Device-Scaled Wavy Structure and Elastic-Sticky Separator

DOE PAGES

Liu, Wei; Chen, Jun; Chen, Zheng; ...

2017-07-17

Fast developments and substantial achievements have been shaping the field of wearable electronic devices, resulting in the persistent requirement for stretchable lithium-ion batteries (LIBs). Despite recent progress in stretchable electrodes, stretching full batteries, including electrodes, separator, and sealing material, remains a great challenge. Here, a simple design concept for stretchable LIBs via a wavy structure at the full battery device scale is reported. All components including the package are capable of being reversibly stretched by folding the entire pouch cell into a wavy shape with polydimethylsiloxane filled in each valley region. In addition, the stretchable, sticky, and porous polyurethane/poly(vinylidene fluoride)more » membrane is adopted as a separator for the first time, which can maintain intimate contact between electrodes and separator to continuously secure ion pathway under dynamic state. Commercial cathode, anode, and package can be utilized in this rationally designed wavy battery to enable stretchability. The results indicate good electrochemical performances and long-term stability at repeatable release–stretch cycles. A high areal capacity of 3.6 mA h cm -2 and energy density of up to 172 W h L -1 can be achieved for the wavy battery. The promising results of the cost-effective wavy battery with high stretchability shed light on the development of stretchable energy storages.« less

Effects of assumed tow architecture on the predicted moduli and stresses in woven composites

NASA Technical Reports Server (NTRS)

Chapman, Clinton Dane

1994-01-01

This study deals with the effect of assumed tow architecture on the elastic material properties and stress distributions of plain weave woven composites. Specifically, the examination of how a cross-section is assumed to sweep-out the tows of the composite is examined in great detail. The two methods studied are extrusion and translation. This effect is also examined to determine how sensitive this assumption is to changes in waviness ratio. 3D finite elements were used to study a T300/Epoxy plain weave composite with symmetrically stacked mats. 1/32nd of the unit cell is shown to be adequate for analysis of this type of configuration with the appropriate set of boundary conditions. At low waviness, results indicate that for prediction of elastic properties, either method is adequate. At high waviness, certain elastic properties become more sensitive to the method used. Stress distributions at high waviness ratio are shown to vary greatly depending on the type of loading applied. At low waviness, both methods produce similar results.

The Arabidopsis WAVY GROWTH 2 protein modulates root bending in response to environmental stimuli.

PubMed

Mochizuki, Susumu; Harada, Akiko; Inada, Sayaka; Sugimoto-Shirasu, Keiko; Stacey, Nicola; Wada, Takuji; Ishiguro, Sumie; Okada, Kiyotaka; Sakai, Tatsuya

2005-02-01

To understand how the direction of root growth changes in response to obstacles, light, and gravity, we characterized an Arabidopsis thaliana mutant, wavy growth 2 (wav2), whose roots show a short-pitch pattern of wavy growth on inclined agar medium. The roots of the wav2 mutant bent with larger curvature than those of the wild-type seedlings in wavy growth and in gravitropic and phototropic responses. The cell file rotations of the root epidermis of wav2-1 in the wavy growth pattern were enhanced in both right-handed and left-handed rotations. WAV2 encodes a protein belonging to the BUD EMERGENCE 46 family with a transmembrane domain at the N terminus and an alpha/beta-hydrolase domain at the C terminus. Expression analyses showed that mRNA of WAV2 was expressed strongly in adult plant roots and seedlings, especially in the root tip, the cell elongation zone, and the stele. Our results suggest that WAV2 is not involved in sensing environmental stimuli but that it negatively regulates stimulus-induced root bending through inhibition of root tip rotation.

Numerical simulations and linear stability analysis of a boundary layer developed on wavy surfaces

NASA Astrophysics Data System (ADS)

Siconolfi, Lorenzo; Camarri, Simone; Fransson, Jens H. M.

2015-11-01

The development of passive methods leading to a laminar to turbulent transition delay in a boundary layer (BL) is a topic of great interest both for applications and academic research. In literature it has been shown that a proper and stable spanwise velocity modulation can reduce the growth rate of Tollmien-Schlichting (TS) waves and delay transition. In this study, we investigate numerically the possibility of obtaining a stabilizing effect of the TS waves through the use of a spanwise sinusoidal modulation of a flat plate. This type of control has been already successfully investigated experimentally. An extensive set of direct numerical simulations is carried out to study the evolution of a BL flow developed on wavy surfaces with different geometric characteristics, and the results will be presented here. Moreover, since this configuration is characterized by a slowly-varying flow field in streamwise direction, a local stability analysis is applied to define the neutral stability curves for the BL flow controlled by this type of wall modifications. These results give the possibility of investigating this control strategy and understanding the effect of the free parameters on the stabilization mechanism.

Analytical and numerical techniques for predicting the interfacial stresses of wavy carbon nanotube/polymer composites

NASA Astrophysics Data System (ADS)

Yazdchi, K.; Salehi, M.; Shokrieh, M. M.

2009-03-01

By introducing a new simplified 3D representative volume element for wavy carbon nanotubes, an analytical model is developed to study the stress transfer in single-walled carbon nanotube-reinforced polymer composites. Based on the pull-out modeling technique, the effects of waviness, aspect ratio, and Poisson ratio on the axial and interfacial shear stresses are analyzed in detail. The results of the present analytical model are in a good agreement with corresponding results for straight nanotubes.

Flaser and wavy bedding in ephemeral streams: a modern and an ancient example

NASA Astrophysics Data System (ADS)

Martin, A. J.

2000-10-01

Flaser and wavy bedding are sedimentary structures characterized by alternating rippled sand and mud layers. These structures often are considered to form mostly in tidally influenced environments; published examples from fluvial environments are rare. Flaser and wavy bedding were found in two ephemeral stream deposits: the Jurassic Kayenta Formation and the modern wash in Seven Mile Canyon, both located in southeastern Utah, USA. These examples demonstrate that flaser bedding can form and be preserved in ephemeral streams.

Momentum and buoyancy transfer in atmospheric turbulent boundary layer over wavy water surface - Part 1: Harmonic wave

NASA Astrophysics Data System (ADS)

Troitskaya, Yu. I.; Ezhova, E. V.; Zilitinkevich, S. S.

2013-10-01

The surface-drag and mass-transfer coefficients are determined within a self-consistent problem of wave-induced perturbations and mean fields of velocity and density in the air, using a quasi-linear model based on the Reynolds equations with down-gradient turbulence closure. Investigation of a harmonic wave propagating along the wind has disclosed that the surface drag is generally larger for shorter waves. This effect is more pronounced in the unstable and neutral stratification. The stable stratification suppresses turbulence, which leads to weakening of the momentum and mass transfer.

Film condensation in a horizontal rectangular duct

NASA Technical Reports Server (NTRS)

Lu, Qing; Suryanarayana, N. V.

1992-01-01

Condensation heat transfer in an annular flow regime with and without interfacial waves was experimentally investigated. The study included measurements of heat transfer rate with condensation of vapor flowing inside a horizontal rectangular duct and experiments on the initiation of interfacial waves in condensation, and adiabatic air-liquid flow. An analytical model for the condensation was developed to predict condensate film thickness and heat transfer coefficients. Some conclusions drawn from the study are that the condensate film thickness was very thin (less than 0.6 mm). The average heat transfer coefficient increased with increasing the inlet vapor velocity. The local heat transfer coefficient decreased with the axial distance of the condensing surface, with the largest change at the leading edge of the test section. The interfacial shear stress, which consisted of the momentum shear stress and the adiabatic shear stress, appeared to have a significant effect on the heat transfer coefficients. In the experiment, the condensate flow along the condensing surface experienced a smooth flow, a two-dimensional wavy flow, and a three-dimensional wavy flow. In the condensation experiment, the local wave length decreased with the axial distance of the condensing surface and the average wave length decreased with increasing inlet vapor velocity, while the wave speed increased with increasing vapor velocity. The heat transfer measurements are reliable. And, the ultrasonic technique was effective for measuring the condensate film thickness when the surface was smooth or had waves of small amplitude.

Forensic surface metrology: tool mark evidence.

PubMed

Gambino, Carol; McLaughlin, Patrick; Kuo, Loretta; Kammerman, Frani; Shenkin, Peter; Diaczuk, Peter; Petraco, Nicholas; Hamby, James; Petraco, Nicholas D K

2011-01-01

Over the last several decades, forensic examiners of impression evidence have come under scrutiny in the courtroom due to analysis methods that rely heavily on subjective morphological comparisons. Currently, there is no universally accepted system that generates numerical data to independently corroborate visual comparisons. Our research attempts to develop such a system for tool mark evidence, proposing a methodology that objectively evaluates the association of striated tool marks with the tools that generated them. In our study, 58 primer shear marks on 9 mm cartridge cases, fired from four Glock model 19 pistols, were collected using high-resolution white light confocal microscopy. The resulting three-dimensional surface topographies were filtered to extract all "waviness surfaces"-the essential "line" information that firearm and tool mark examiners view under a microscope. Extracted waviness profiles were processed with principal component analysis (PCA) for dimension reduction. Support vector machines (SVM) were used to make the profile-gun associations, and conformal prediction theory (CPT) for establishing confidence levels. At the 95% confidence level, CPT coupled with PCA-SVM yielded an empirical error rate of 3.5%. Complementary, bootstrap-based computations for estimated error rates were 0%, indicating that the error rate for the algorithmic procedure is likely to remain low on larger data sets. Finally, suggestions are made for practical courtroom application of CPT for assigning levels of confidence to SVM identifications of tool marks recorded with confocal microscopy. Copyright © 2011 Wiley Periodicals, Inc.

Femtosecond laser-induced ripple patterns for homogenous nanostructuring of pyrolytic carbon heart valve implant

NASA Astrophysics Data System (ADS)

Stępak, Bogusz; Dzienny, Paulina; Franke, Volker; Kunicki, Piotr; Gotszalk, Teodor; Antończak, Arkadiusz

2018-04-01

Laser-induced periodic surface structures (LIPSS) are highly periodic wavy surface features which are frequently smaller than incident light wavelength that bring possibility of nanostructuring of many materials. In this paper the possibility of using them to homogeneously structure the surface of artificial heart valve made of PyC was examined. By changing laser irradiation parameters such like energy density and pulse separation the most suitable conditions were established for 1030 nm wavelength. A wide spectrum of periodicities and geometries was obtained. Interesting side effects like creating a thin shell-like layer were observed. Modified surfaces were examined using EDX and Raman spectroscopy to determine change in elemental composition of surface.

Compression failure of angle-ply laminates

NASA Technical Reports Server (NTRS)

Peel, Larry D.; Hyer, Michael W.; Shuart, Mark J.

1991-01-01

The present work deals with modes and mechanisms of failure in compression of angle-ply laminates. Experimental results were obtained from 42 angle-ply IM7/8551-7a specimens with a lay-up of ((plus or minus theta)/(plus or minus theta)) sub 6s where theta, the off-axis angle, ranged from 0 degrees to 90 degrees. The results showed four failure modes, these modes being a function of off-axis angle. Failure modes include fiber compression, inplane transverse tension, inplane shear, and inplane transverse compression. Excessive interlaminar shear strain was also considered as an important mode of failure. At low off-axis angles, experimentally observed values were considerably lower than published strengths. It was determined that laminate imperfections in the form of layer waviness could be a major factor in reducing compression strength. Previously developed linear buckling and geometrically nonlinear theories were used, with modifications and enhancements, to examine the influence of layer waviness on compression response. The wavy layer is described by a wave amplitude and a wave length. Linear elastic stress-strain response is assumed. The geometrically nonlinear theory, in conjunction with the maximum stress failure criterion, was used to predict compression failure and failure modes for the angle-ply laminates. A range of wave length and amplitudes were used. It was found that for 0 less than or equal to theta less than or equal to 15 degrees failure was most likely due to fiber compression. For 15 degrees less than theta less than or equal to 35 degrees, failure was most likely due to inplane transverse tension. For 35 degrees less than theta less than or equal to 70 degrees, failure was most likely due to inplane shear. For theta less than 70 degrees, failure was most likely due to inplane transverse compression. The fiber compression and transverse tension failure modes depended more heavily on wave length than on wave amplitude. Thus using a single parameter, such as a ratio of wave amplitude to wave length, to describe waviness in a laminate would be inaccurate. Throughout, results for AS4/3502, studied previously, are included for comparison. At low off-axis angles, the AS4/3502 material system was found to be less sensitive to layer waviness than IM7/8551-7a. Analytical predictions were also obtained for laminates with waviness in only some of the layers. For this type of waviness, laminate compression strength could also be considered a function of which layers in the laminate were wavy, and where those wavy layers were. Overall, the geometrically nonlinear model correlates well with experimental results.

In-Situ Waviness Characterization of Metal Plates by a Lateral Shearing Interferometric Profilometer

PubMed Central

Frade, María; Enguita, José María; Álvarez, Ignacio

2013-01-01

Characterizing waviness in sheet metal is a key process for quality control in many industries, such as automotive and home appliance manufacturing. However, there is still no known technique able to work in an automated in-floor inspection system. The literature describes many techniques developed in the last three decades, but most of them are either slow, only able to work in laboratory conditions, need very short (unsafe) working distances, or are only able to estimate certain waviness parameters. In this article we propose the use of a lateral shearing interferometric profilometer, which is able to obtain a 19 mm profile in a single acquisition, with sub-micron precision, in an uncontrolled environment, and from a working distance greater than 90 mm. This system allows direct measurement of all needed waviness parameters even with objects in movement. We describe a series of experiments over several samples of steel plates to validate the sensor and the processing method, and the results are in close agreement with those obtained with a contact stylus device. The sensor is an ideal candidate for on-line or in-machine fast automatic waviness assessment, reducing delays and costs in many metalworking processes. PMID:23584120

In-situ waviness characterization of metal plates by a lateral shearing interferometric profilometer.

PubMed

Frade, María; Enguita, José María; Alvarez, Ignacio

2013-04-12

Characterizing waviness in sheet metal is a key process for quality control in many industries, such as automotive and home appliance manufacturing. However, there is still no known technique able to work in an automated in-floor inspection system. The literature describes many techniques developed in the last three decades, but most of them are either slow, only able to work in laboratory conditions, need very short (unsafe) working distances, or are only able to estimate certain waviness parameters. In this article we propose the use of a lateral shearing interferometric profilometer, which is able to obtain a 19 mm profile in a single acquisition, with sub-micron precision, in an uncontrolled environment, and from a working distance greater than 90 mm. This system allows direct measurement of all needed waviness parameters even with objects in movement. We describe a series of experiments over several samples of steel plates to validate the sensor and the processing method, and the results are in close agreement with those obtained with a contact stylus device. The sensor is an ideal candidate for on-line or in-machine fast automatic waviness assessment, reducing delays and costs in many metalworking processes.

Simulation of oceanic whitecaps and their reflectance characteristics in the short wavelength infrared.

PubMed

Schwenger, Frédéric; Repasi, Endre

2017-02-20

The knowledge of the spatial energy (or power) distribution of light beams reflected at the dynamic sea surface is of great practical interest in maritime environments. For the estimation of the light energy reflected into a specific spatial direction a lot of parameters need to be taken into account. Both whitecap coverage and its optical properties have a large impact upon the calculated value. In published literature, for applications considering vertical light propagation paths, such as bathymetric lidar, the reflectance of sea surface and whitecaps are approximated by constant values. For near-horizontal light propagation paths the optical properties of the sea surface and the whitecaps must be considered in greater detail. The calculated light energy reflected into a specific direction varies statistically and depends largely on the dynamics of the wavy sea surface and the dynamics of whitecaps. A 3D simulation of the dynamic sea surface populated with whitecaps is presented. The simulation considers the evolution of whitecaps depending on wind speed and fetch. The radiance calculation of the maritime scene (open sea/clear sky) populated with whitecaps is done in the short wavelength infrared spectral band. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of a light beam at the sea surface in the absence of whitecaps is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For whitecaps, a specific BRDF is used by taking into account their shadowing function. To ensure the credibility of the simulation, the whitecap coverage is determined from simulated image sequences for different wind speeds and compared to whitecap coverage functions from literature. The impact of whitecaps on the radiation balance for bistatic configuration of light source and receiver is calculated for a different incident (zenith/azimuth angles) of the light beam and is presented for two different wind speeds.

Experimental Evaluation of Journal Bearing Stability and New Gas Wave Bearing Materials

NASA Technical Reports Server (NTRS)

Keith, Theo G., Jr.; Dimofte, Florin

1998-01-01

A gas journal bearing, with a wavy surfaces was tested in a range of speeds up to 18,000 RPM to determine its stability in an unloaded condition as a function of the wave amplitude. The bearing, was 50 mm in diameter, 58 mm long and had 0.01 65 mm radial clearance. Three waves were created on the inner surface by deforming the bearing sleeve. The ratio of the wave amplitude to the radial clearance (the wave amplitude ratio) was varied from zero to 0.3.

Industrial inspection of specular surfaces using a new calibration procedure

NASA Astrophysics Data System (ADS)

Aswendt, Petra; Hofling, Roland; Gartner, Soren

2005-06-01

The methodology of phase encoded reflection measurements has become a valuable tool for the industrial inspection of components with glossy surfaces. The measuring principle provides outstanding sensitivity for tiny variations of surface curvature so that sub-micron waviness and flaws are reliably detected. Quantitative curvature measurements can be obtained from a simple approach if the object is almost flat. 3D-objects with a high aspect ratio require more effort to determine both coordinates and normal direction of a surface point unambiguously. Stereoscopic solutions have been reported using more than one camera for a certain surface area. This paper will describe the combined double camera steady surface approach (DCSS) that is well suited for the implementation in industrial testing stations

Influence of homogeneous magnetic fields on the flow of a ferrofluid in the Taylor-Couette system.

PubMed

Altmeyer, S; Hoffmann, Ch; Leschhorn, A; Lücke, M

2010-07-01

We investigate numerically the influence of a homogeneous magnetic field on a ferrofluid in the gap between two concentric, independently rotating cylinders. The full Navier-Stokes equations are solved with a combination of a finite difference method and a Galerkin method. Structure, dynamics, symmetry properties, bifurcation, and stability behavior of different vortex structures are investigated for axial and transversal magnetic fields, as well as combinations of them. We show that a transversal magnetic field modulates the Taylor vortex flow and the spiral vortex flow. Thus, a transversal magnetic field induces wavy structures: wavy Taylor vortex flow (wTVF) and wavy spiral vortex flow. In contrast to the classic wTVF, which is a secondarily bifurcating structure, these magnetically generated wavy Taylor vortices are pinned by the magnetic field, i.e., they are stationary and they appear via a primary forward bifurcation out of the basic state of circular Couette flow.

Stability of Wavy Films in Gas-Liquid Two-Phase Flows at Normal and Microgravity Conditions

NASA Technical Reports Server (NTRS)

Balakotaiah, V.; Jayawardena, S. S.

1996-01-01

For flow rates of technological interest, most gas-liquid flows in pipes are in the annular flow regime, in which, the liquid moves along the pipe wall in a thin, wavy film and the gas flows in the core region. The waves appearing on the liquid film have a profound influence on the transfer rates, and hence on the design of these systems. We have recently proposed and analyzed two boundary layer models that describe the characteristics of laminar wavy films at high Reynolds numbers (300-1200). Comparison of model predictions to 1-g experimental data showed good agreement. The goal of our present work is to understand through a combined program of experimental and modeling studies the characteristics of wavy films in annular two-phase gas-liquid flows under normal as well as microgravity conditions in the developed and entry regions.

High power CO II lasers and their material processing applications at Centre for Advanced Technology, India

NASA Astrophysics Data System (ADS)

Nath, A. K.; Paul, C. P.; Rao, B. T.; Kau, R.; Raghu, T.; Mazumdar, J. Dutta; Dayal, R. K.; Mudali, U. Kamachi; Sastikumar, D.; Gandhi, B. K.

2006-01-01

We have developed high power transverse flow (TF) CW CO II lasers up to 15kW, a high repetition rate TEA CO II laser of 500Hz, 500W average power and a RF excited fast axial flow CO II laser at the Centre for Advanced Technology and have carried out various material processing applications with these lasers. We observed very little variation of discharge voltage with electrode gap in TF CO II lasers. With optimally modulated laser beam we obtained better results in laser piercing and cutting of titanium and resolidification of 3 16L stainless steel weld-metal for improving intergranular corrosion resistance. We carried out microstructure and phase analysis of laser bent 304 stainless steel sheet and optimum process zones were obtained. We carried out laser cladding of 316L stainless steel and Al-alloy substrates with Mo, WC, and Cr IIC 3 powder to improve their wear characteristics. We developed a laser rapid manufacturing facility and fabricated components of various geometries with minimum surface roughness of 5-7 microns Ra and surface waviness of 45 microns between overlapped layers using Colmonoy-6, 3 16L stainless steel and Inconel powders. Cutting of thick concrete blocks by repeated laser glazing followed by mechanical scrubbing process and drilling holes on a vertical concrete with laser beam incident at an optimum angle allowing molten material to flow out under gravity were also done. Some of these studies are briefly presented here.

Spatially averaged flow over a wavy boundary revisited

USGS Publications Warehouse

McLean, S.R.; Wolfe, S.R.; Nelson, J.M.

1999-01-01

Vertical profiles of streamwise velocity measured over bed forms are commonly used to deduce boundary shear stress for the purpose of estimating sediment transport. These profiles may be derived locally or from some sort of spatial average. Arguments for using the latter procedure are based on the assumption that spatial averaging of the momentum equation effectively removes local accelerations from the problem. Using analogies based on steady, uniform flows, it has been argued that the spatially averaged velocity profiles are approximately logarithmic and can be used to infer values of boundary shear stress. This technique of using logarithmic profiles is investigated using detailed laboratory measurements of flow structure and boundary shear stress over fixed two-dimensional bed forms. Spatial averages over the length of the bed form of mean velocity measurements at constant distances from the mean bed elevation yield vertical profiles that are highly logarithmic even though the effect of the bottom topography is observed throughout the water column. However, logarithmic fits of these averaged profiles do not yield accurate estimates of the measured total boundary shear stress. Copyright 1999 by the American Geophysical Union.

interThermalPhaseChangeFoam-A framework for two-phase flow simulations with thermally driven phase change

NASA Astrophysics Data System (ADS)

Nabil, Mahdi; Rattner, Alexander S.

The volume-of-fluid (VOF) approach is a mature technique for simulating two-phase flows. However, VOF simulation of phase-change heat transfer is still in its infancy. Multiple closure formulations have been proposed in the literature, each suited to different applications. While these have enabled significant research advances, few implementations are publicly available, actively maintained, or inter-operable. Here, a VOF solver is presented (interThermalPhaseChangeFoam), which incorporates an extensible framework for phase-change heat transfer modeling, enabling simulation of diverse phenomena in a single environment. The solver employs object oriented OpenFOAM library features, including Run-Time-Type-Identification to enable rapid implementation and run-time selection of phase change and surface tension force models. The solver is packaged with multiple phase change and surface tension closure models, adapted and refined from earlier studies. This code has previously been applied to study wavy film condensation, Taylor flow evaporation, nucleate boiling, and dropwise condensation. Tutorial cases are provided for simulation of horizontal film condensation, smooth and wavy falling film condensation, nucleate boiling, and bubble condensation. Validation and grid sensitivity studies, interfacial transport models, effects of spurious currents from surface tension models, effects of artificial heat transfer due to numerical factors, and parallel scaling performance are described in detail in the Supplemental Material (see Appendix A). By incorporating the framework and demonstration cases into a single environment, users can rapidly apply the solver to study phase-change processes of interest.

Waves on White: Ice or Clouds?

NASA Technical Reports Server (NTRS)

2005-01-01

As it passed over Antarctica on December 16, 2004, the Multi-angle Imaging SpectroRadiometer (MISR) on NASA's Terra satellite captured this image showing a wavy pattern in a field of white. At most other latitudes, such wavy patterns would likely indicate stratus or stratocumulus clouds. MISR, however, saw something different. By using information from several of its multiple cameras (each of which views the Earth's surface from a different angle), MISR was able to tell that what looked like a wavy cloud pattern was actually a wavy pattern on the ice surface. One of MISR's cloud classification products, the Angular Signature Cloud Mask (ASCM), correctly identified the rippled area as being at the surface.

In this image pair, the view from MISR's most oblique backward-viewing camera is on the left, and the color-coded image on the right shows the results of the ASCM. The colors represent the level of certainty in the classification. Areas that were classed as cloudy with high confidence are white, and areas where the confidence was lower are yellow; dark blue shows confidently clear areas, while light blue indicates clear with lower confidence. The ASCM works particularly well at detecting clouds over snow and ice, but also works well over ocean and land. The rippled area on the surface which could have been mistaken for clouds are actually sastrugi -- long wavelike ridges of snow formed by the wind and found on the polar plains. Usually sastrugi are only several centimeters high and several meters apart, but large portions of East Antarctica are covered by mega-sastrugi ice fields, with dune-like features as high as four meters separated by two to five kilometers. The mega-sastrugi fields are a result of unusual snow accumulation and redistribution processes influenced by the prevailing winds and climate conditions. MISR imagery indicates that these mega sastrugi were stationary features between 2002 and 2004.

Being able to distinguish clouds from snow or ice-covered surfaces is important in order to adequately characterize the radiation balance of the polar regions. However, detecting clouds using spaceborne detectors over snow and ice surfaces is notoriously difficult, because the surface may often be as bright and as cold as the overlying clouds, and because polar atmospheric temperature inversions sometimes mean that clouds are warmer than the underlying snow or ice surface. The Angular Signature Cloud Mask (ASCM) was developed based on the Band-Differenced Angular Signature (BDAS) approach, introduced by Di Girolamo and Davies (1994) and updated for MISR application by Di Girolamo and Wilson (2003). BDAS uses both spectral and angular changes in reflectivity to distinguish clouds from the background, and the ASCM calculates the difference between the 446 and 866 nanometer reflectances at MISR's two most oblique cameras that view forward-scattered light. New land thresholds for the ASCM are planned for delivery later this year.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82o north and 82o south latitude. This image area covers about 277 kilometers by 421 kilometers in the interior of the East Antarctic ice sheet. These data products were generated from a portion of the imagery acquired during Terra orbit 26584 and utilize data from within blocks 159 to 161 within World Reference System-2 path 63.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Electron acceleration behind a wavy dipolarization front

NASA Astrophysics Data System (ADS)

Wu, Mingyu; Lu, Quanming; Volwerk, Martin; Nakamura, Rumi; Zhang, Tielong

2018-02-01

In this paper, with the in-situ observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes we report a wavy dipolarization front (DF) event, where the DF has different magnetic structures and electron distributions at different y positions in the Geocentric Solar Magnetospheric (GSM) coordinates. At y ˜2.1RE (RE is the radius of Earth), the DF has a relatively simple structure, which is similar to that of a conventional DF. At y ˜3.0RE, the DF is revealed to have a multiple DF structure, where the plasma exhibits a vortex flow. Such a wavy DF could be the results of the interchange instability. The different structure of such a wavy DF at different sites has a great effect on electron acceleration. Fermi acceleration can occur at the site of the DF with a simple or multiple DF structure, while betatron acceleration as a local process has the contribution to energetic electrons only at the site of the DF with a simple structure.

An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites.

PubMed

Christian, W J R; DiazDelaO, F A; Atherton, K; Patterson, E A

2018-05-01

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect.

Identification of flow structures in fully developed canonical and wavy channels by means of modal decomposition techniques

NASA Astrophysics Data System (ADS)

Ghebali, Sacha; Garicano-Mena, Jesús; Ferrer, Esteban; Valero, Eusebio

2018-04-01

A Dynamic Mode Decomposition (DMD) of Direct Numerical Simulations (DNS) of fully developed channel flows is undertaken in order to study the main differences in flow features between a plane-channel flow and a passively “controlled” flow wherein the mean friction was reduced relative to the baseline by modifying the geometry in order to generate a streamwise-periodic spanwise pressure gradient, as is the case for an oblique wavy wall. The present analysis reports POD and DMD modes for the plane channel, jointly with the application of a sparsity-promoting method, as well as a reconstruction of the Reynolds shear stress with the dynamic modes. Additionally, a dynamic link between the streamwise velocity fluctuations and the friction on the wall is sought by means of a composite approach both in the plane and wavy cases. One of the DMD modes associated with the wavy-wall friction exhibits a meandering motion which was hardly identifiable on the instantaneous friction fluctuations.

Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates.

PubMed

Bauer, Christina T; Kroner, Elmar; Fleck, Norman A; Arzt, Eduard

2015-10-23

Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.

Molecular genetics of root gravitropism and waving in Arabidopsis thaliana

NASA Technical Reports Server (NTRS)

Sedbrook, J.; Boonsirichai, K.; Chen, R.; Hilson, P.; Pearlman, R.; Rosen, E.; Rutherford, R.; Batiza, A.; Carroll, K.; Schulz, T.;

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux

NASA Technical Reports Server (NTRS)

Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.

2002-01-01

The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid contact only in wetting fronts, located in the troughs of the interfacial waves. CHF commenced when wetting fronts near the outlet were lifted off the wall. The Interfacial Lift-off model is shown to be an effective tool for predicting the effects of body force on CHF at high velocities.

Meteorite Impact "Earthquake" Features (Rock Liquefaction, Surface Wave Deformations, Seismites) from Ground Penetrating Radar (GPR) and Geoelectric Complex Resistivity/Induced Polarization (IP) Measurements, Chiemgau (Alpine Foreland, Southeast Germany)

NASA Astrophysics Data System (ADS)

Ernstson, K.; Poßekel, J.

2017-12-01

Densely spaced GPR and complex resistivity measurements on a 30,000 square meters site in a region of enigmatic sinkhole occurrences in unconsolidated Quaternary sediments have featured unexpected and highlighting results from both a meteorite impact research and an engineering geology point of view. The GPR measurements and a complex resistivity/IP electrical imaging revealed extended subrosion depressions related with a uniformly but in various degrees of intensity deformed loamy and gravelly ground down to at least 10 m depth. Two principle observations could be made from both the GPR high-resolution measurements and the more integrating resistivity and IP soundings with both petrophysical evidences in good complement. Subrosion can be shown to be the result of prominent sandy-gravelly intrusions and extrusions typical of rock liquefaction processes well known to occur during strong earthquakes. Funnel-shaped structures with diameters up to 25 m near the surface and reaching down to the floating ground water level at 10 m depth were measured. GPR radargrams could trace prominent gravelly-material transport bottom-up within the funnels. Seen in both GPR tomography and resistivity/IP sections more or less the whole investigated area is overprinted by wavy deformations of the unconsolidated sediments with wavelengths of the order of 5 - 10 m and amplitudes up to half a meter, likewise down to 10 m depth. Substantial earthquakes are not known in this region. Hence, the observed heavy underground disorder is considered the result of the prominent earthquake shattering that must have occurred during the Holocene (Bronze Age/Celtic era) Chiemgau meteorite impact event that produced a 60 km x 30 km sized crater strewn field directly hosting the investigated site. Depending on depth and size of floating aquifers local concentrations of rock liquefaction and seismic surface waves (probably LOVE waves) to produce the wavy deformations could develop, when the big disintegrated meteoroid (a loosely bound asteroid or a comet of roughly estimated 1 km size) hit the ground. The observations in the Chiemgau area emphasize that studied paleoliquefaction features and wavy deformations (e.g. seismites) need not necessarily have originated solely from paleoseismicity but can provide a recognizable regional impact signature.

Nonlinear dynamic modeling of rotor system supported by angular contact ball bearings

NASA Astrophysics Data System (ADS)

Wang, Hong; Han, Qinkai; Zhou, Daning

2017-02-01

In current bearing dynamic models, the displacement coordinate relations are usually utilized to approximately obtain the contact deformations between the rolling element and raceways, and then the nonlinear restoring forces of the rolling bearing could be calculated accordingly. Although the calculation efficiency is relatively higher, the accuracy is lower as the contact deformations should be solved through iterative analysis. Thus, an improved nonlinear dynamic model is presented in this paper. Considering the preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication, load distribution analysis is solved iteratively to more accurately obtain the contact deformations and angles between the rolling balls and raceways. The bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. Dynamic tests upon a typical rotor system supported by two angular contact ball bearings are conducted to verify the model. Through comparisons, the differences between the nonlinear dynamic model and current models are also pointed out. The effects of axial preload, rotor eccentricity and inner/outer waviness amplitudes on the dynamic response are discussed in detail.

Evidence for the interaction of the IRS 16 wind with the ionized and molecular gas at the Galactic center

NASA Technical Reports Server (NTRS)

Yusef-Zadeh, Farhad; Wardle, Mark

1993-01-01

We present a number of high-resolution radio images showing evidence for the dynamical interaction of the outflow arising from the IRS 16 complex with the ionized gas associated with the Northern Arm of Sgr A West, and with the northwestern segment of the circumnuclear molecular disk which engulfs the inner few parsecs of the Galactic center. We suggest that the wind disturbs the dynamics of the Northern Arm within 0.1 pc of the center, is responsible for the waviness of the arm at larger distances, and is collimated by Sgr A West and the circumnuclear disk. The waviness is discussed in terms of the Rayleigh-Taylor instability induced by the ram pressure of the wind incident on the surface of the Northern Arm. Another consequence of this interaction is the strong mid-IR polarization of the Northern Arm in the vicinity of the IRS 16 complex which is explained as a result of the ram pressure of the wind compressing the gas and the magnetic field.

Enhanced piezoelectricity and stretchability in energy harvesting devices fabricated from buckled PZT ribbons.

PubMed

Qi, Yi; Kim, Jihoon; Nguyen, Thanh D; Lisko, Bozhena; Purohit, Prashant K; McAlpine, Michael C

2011-03-09

The development of a method for integrating highly efficient energy conversion materials onto soft, biocompatible substrates could yield breakthroughs in implantable or wearable energy harvesting systems. Of particular interest are devices which can conform to irregular, curved surfaces, and operate in vital environments that may involve both flexing and stretching modes. Previous studies have shown significant advances in the integration of highly efficient piezoelectric nanocrystals on flexible and bendable substrates. Yet, such inorganic nanomaterials are mechanically incompatible with the extreme elasticity of elastomeric substrates. Here, we present a novel strategy for overcoming these limitations, by generating wavy piezoelectric ribbons on silicone rubber. Our results show that the amplitudes in the waves accommodate order-of-magnitude increases in maximum tensile strain without fracture. Further, local probing of the buckled ribbons reveals an enhancement in the piezoelectric effect of up to 70%, thus representing the highest reported piezoelectric response on a stretchable medium. These results allow for the integration of energy conversion devices which operate in stretching mode via reversible deformations in the wavy/buckled ribbons.

Dynamic modeling of moment wheel assemblies with nonlinear rolling bearing supports

NASA Astrophysics Data System (ADS)

Wang, Hong; Han, Qinkai; Luo, Ruizhi; Qing, Tao

2017-10-01

Moment wheel assemblies (MWA) have been widely used in spacecraft attitude control and large angle slewing maneuvers over the years. Understanding and controlling vibration of MWAs is a crucial factor to achieving the desired level of payload performance. Dynamic modeling of a MWA with nonlinear rolling bearing supports is conducted. An improved load distribution analysis is proposed to more accurately obtain the contact deformations and angles between the rolling balls and raceways. Then, the bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. The effects of preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication could all be reflected in the nonlinear bearing forces. Considering the mass imbalances of the flywheel, flexibility of supporting structures and rolling bearing nonlinearity, the dynamic model of a typical MWA is established based upon the energy theorem. Dynamic tests are conducted to verify the nonlinear dynamic model. The influences of flywheel mass eccentricity and inner/outer waviness amplitudes on the dynamic responses are discussed in detail. The obtained results would be useful for the design and vibration control of the MWA system.

Self-assembled tunable networks of sticky colloidal particles

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

Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim

Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

Novel seed adaptations of a monocotyledon seagrass in the wavy sea.

PubMed

Soong, Keryea; Chiu, Shau-Ting; Chen, Ching-Nen Nathan

2013-01-01

Returning to the sea, just like invasion of land, has occurred in many groups of animals and plants. For flowering plants, traits adapted to the terrestrial environments have to change or adopt a new function to allow the plants to survive and prosper in the sea where water motion tends to rotate and move seeds. In this investigation, how seeds of the seagrass Thalassia hemprichii (Hydrocharitaceae), a common monocotyledon in the Indo-Pacific, adapt to the wavy environment was studied. Mature seeds were collected from Dongsha Atoll in South China Sea. The effects of light qualities on seed germination, the seed morphology, the unipolar distribution of starch granules in the endosperms and growth of root hair-like filamentous cells from basal surface of the seeds were all found to differ from those of terrestrial monocotyledons. Physiologically, germination of the seeds was stimulated by blue light rather than red light. Morphologically, the bell-shaped seeds coupled with the unipolar distribution of starch granules in the enlarged bases helped maintain their upright posture on the tidal seafloor. Growth of root hair-like filamentous cells from the basal surface of the seeds prior to primary root growth served to attach onto sediments, providing leverage and attachment required by the primary roots to insert into sediments. These filamentous cells grasped coral sand but not silicate sand, demonstrating a habitat preference of this species.

Novel Seed Adaptations of a Monocotyledon Seagrass in the Wavy Sea

PubMed Central

Soong, Keryea; Chiu, Shau-Ting; Chen, Ching-Nen Nathan

2013-01-01

Returning to the sea, just like invasion of land, has occurred in many groups of animals and plants. For flowering plants, traits adapted to the terrestrial environments have to change or adopt a new function to allow the plants to survive and prosper in the sea where water motion tends to rotate and move seeds. In this investigation, how seeds of the seagrass Thalassia hemprichii (Hydrocharitaceae), a common monocotyledon in the Indo-Pacific, adapt to the wavy environment was studied. Mature seeds were collected from Dongsha Atoll in South China Sea. The effects of light qualities on seed germination, the seed morphology, the unipolar distribution of starch granules in the endosperms and growth of root hair-like filamentous cells from basal surface of the seeds were all found to differ from those of terrestrial monocotyledons. Physiologically, germination of the seeds was stimulated by blue light rather than red light. Morphologically, the bell-shaped seeds coupled with the unipolar distribution of starch granules in the enlarged bases helped maintain their upright posture on the tidal seafloor. Growth of root hair-like filamentous cells from the basal surface of the seeds prior to primary root growth served to attach onto sediments, providing leverage and attachment required by the primary roots to insert into sediments. These filamentous cells grasped coral sand but not silicate sand, demonstrating a habitat preference of this species. PMID:24040188

Effects of a wavy neutral sheet on cosmic ray anisotropies

NASA Technical Reports Server (NTRS)

Kota, J.; Jokipii, J. R.

1985-01-01

The first results of a three-dimensional numerical code calculating cosmic ray anisotropies is presented. The code includes diffusion, convection, adiabatic cooling, and drift in an interplanetary magnetic field model containing a wavy neutral sheet. The 3-D model can reproduce all the principal observations for a reasonable set of parameters.

An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites

PubMed Central

DiazDelaO, F. A.; Atherton, K.

2018-01-01

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect. PMID:29892446

Temperature dependency of double material gate oxide (DMGO) symmetric dual-k spacer (SDS) wavy FinFET

NASA Astrophysics Data System (ADS)

Pradhan, K. P.; Priyanka; Sahu, P. K.

2016-01-01

Symmetric Dual-k Spacer (SDS) Trigate Wavy FinFET is a novel hybrid device that combines three significant and advanced technologies i.e., ultra-thin-body (UTB), FinFET, and symmetric spacer engineering on a single silicon on insulator (SOI) platform. This innovative architecture promises to enhance the device performance as compared to conventional FinFET without increasing the chip area. For the first time, we have incorporated two different dielectric materials (SiO2, and HfO2) as gate oxide to analyze the effect on various performance metrics of SDS wavy FinFET. This work evaluates the response of double material gate oxide (DMGO) on parameters like mobility, on current (Ion), transconductance (gm), transconductance generation factor (TGF), total gate capacitance (Cgg), and cutoff frequency (fT) in SDS wavy FinFET. This work also reveals the presence of biasing point i.e., zero temperature coefficient (ZTC) bias point. The ZTC bias point is that point where the device parameters become independent of temperature. The impact of operating temperature (T) on above said various performances are also subjected to extensive analysis. This further validates the reliability of DMGO-SDS FinFET and its application opportunities involved in modeling analog/RF circuits for a broad range of temperature applications. From extensive 3-D device simulation, we have determined that the inclusion of DMGO in SDS wavy FinFET is superior in performance.

Flow analysis for efficient design of wavy structured microchannel mixing devices

NASA Astrophysics Data System (ADS)

Kanchan, Mithun; Maniyeri, Ranjith

2018-04-01

Microfluidics is a rapidly growing field of applied research which is strongly driven by demands of bio-technology and medical innovation. Lab-on-chip (LOC) is one such application which deals with integrating bio-laboratory on micro-channel based single fluidic chip. Since fluid flow in such devices is restricted to laminar regime, designing an efficient passive modulator to induce chaotic mixing for such diffusion based flow is a major challenge. In the present work two-dimensional numerical simulation of viscous incompressible flow is carried out using immersed boundary method (IBM) to obtain an efficient design for wavy structured micro-channel mixing devices. The continuity and Navier-Stokes equations governing the flow are solved by fractional step based finite volume method on a staggered Cartesian grid system. IBM uses Eulerian co-ordinates to describe fluid flow and Lagrangian co-ordinates to describe solid boundary. Dirac delta function is used to couple both these co-ordinate variables. A tether forcing term is used to impose the no-slip boundary condition on the wavy structure and fluid interface. Fluid flow analysis by varying Reynolds number is carried out for four wavy structure models and one straight line model. By analyzing fluid accumulation zones and flow velocities, it can be concluded that straight line structure performs better mixing for low Reynolds number and Model 2 for higher Reynolds number. Thus wavy structures can be incorporated in micro-channels to improve mixing efficiency.

Apple Snail: a Bio Cleaner of the Water Free Surface.

NASA Astrophysics Data System (ADS)

Bassiri, Golnaz

2005-11-01

Oil spills from tankers represent a threat for shorelines and marine life. Despite continuing research, there has been little change in the fundamental technology for dealing with oil spills. An experimental investigation of the feeding strategy of Apple snails from the water free surface, called surface film feeding, is being studied motivated by the need to develop new techniques to recover oil spills. To feed on floating food (usually a thin layer of microorganisms), the apple snail forms a funnel with its foot and pulls the free surface toward the funnel. High speed imaging and particle image velocimetry were used in the present investigation to measure the free surface motion and to investigate the mechanism used by the apple snails to pull the free surface. The results suggest that the snail pulls the free surface via the wavy motion of the muscles in its funnel.

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests.

PubMed

Forquin, Pascal; Zinszner, Jean-Luc

2017-01-28

Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the 'wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, 'wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests

NASA Astrophysics Data System (ADS)

Forquin, Pascal; Zinszner, Jean-Luc

2017-01-01

Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the `wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, `wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

The wavy growth 3 E3 ligase family controls the gravitropic response in Arabidopsis roots.

PubMed

Sakai, Tatsuya; Mochizuki, Susumu; Haga, Ken; Uehara, Yukiko; Suzuki, Akane; Harada, Akiko; Wada, Takuji; Ishiguro, Sumie; Okada, Kiyotaka

2012-04-01

Regulation of the root growth pattern is an important control mechanism during plant growth and propagation. To better understand alterations in root growth direction in response to environmental stimuli, we have characterized an Arabidopsis thaliana mutant, wavy growth 3 (wav3), whose roots show a short-pitch pattern of wavy growth on inclined agar medium. The wav3 mutant shows a greater curvature of root bending in response to gravity, but a smaller curvature in response to light, suggesting that it is a root gravitropism-enhancing mutation. This wav3 phenotype also suggests that enhancement of the gravitropic response in roots strengthens root tip impedance after contact with the agar surface and/or causes an increase in subsequent root bending in response to obstacle-touching stimulus in these mutants. WAV3 encodes a protein with a RING finger domain, and is mainly expressed in root tips. RING-containing proteins often function as an E3 ubiquitin ligase, and the WAV3 protein shows such activity in vitro. There are three genes homologous to WAV3 in the Arabidopsis genome [EMBRYO SAC DEVELOPMENT ARREST 40 (EDA40), WAVH1 and WAVH2 ], and wav3 wavh1 wavh2 triple mutants show marked root gravitropism abnormalities. This genetic study indicates that WAV3 functions positively rather than negatively in root gravitropism, and that enhancement of the gravitropic response in wav3 roots is dependent upon the function of WAVH2 in the absence of WAV3. Hence, our results demonstrate that the WAV3 family of proteins are E3 ligases that are required for root gravitropism in Arabidopsis. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Local differentiation of cell wall matrix polysaccharides in sinuous pavement cells: its possible involvement in the flexibility of cell shape.

PubMed

Sotiriou, P; Giannoutsou, E; Panteris, E; Galatis, B; Apostolakos, P

2018-03-01

The distribution of homogalacturonans (HGAs) displaying different degrees of esterification as well as of callose was examined in cell walls of mature pavement cells in two angiosperm and two fern species. We investigated whether local cell wall matrix differentiation may enable pavement cells to respond to mechanical tension forces by transiently altering their shape. HGA epitopes, identified with 2F4, JIM5 and JIM7 antibodies, and callose were immunolocalised in hand-made or semithin leaf sections. Callose was also stained with aniline blue. The structure of pavement cells was studied with light and transmission electron microscopy (TEM). In all species examined, pavement cells displayed wavy anticlinal cell walls, but the waviness pattern differed between angiosperms and ferns. The angiosperm pavement cells were tightly interconnected throughout their whole depth, while in ferns they were interconnected only close to the external periclinal cell wall and intercellular spaces were developed between them close to the mesophyll. Although the HGA epitopes examined were located along the whole cell wall surface, the 2F4- and JIM5- epitopes were especially localised at cell lobe tips. In fern pavement cells, the contact sites were impregnated with callose and JIM5-HGA epitopes. When tension forces were applied on leaf regions, the pavement cells elongated along the stretching axis, due to a decrease in waviness of anticlinal cell walls. After removal of tension forces, the original cell shape was resumed. The presented data support that HGA epitopes make the anticlinal pavement cell walls flexible, in order to reversibly alter their shape. Furthermore, callose seems to offer stability to cell contacts between pavement cells, as already suggested in photosynthetic mesophyll cells. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

7 CFR 29.3152 - Lugs or Cutters (C Group).

Code of Federal Regulations, 2014 CFR

2014-01-01

... percent uniform, and 15 percent injury tolerance. C4L Fair Buff Lugs. Thin, mature to ripe, firm to open... percent injury tolerance. C5L Low Buff Lugs. Thin, mature, firm to open, wavy dull finish, pale color... Fair Tan Lugs. Medium to thin body, mature to ripe, firm to open, wavy to even, moderate finish, weak...

7 CFR 29.3152 - Lugs or Cutters (C Group).

Code of Federal Regulations, 2013 CFR

2013-01-01

... percent uniform, and 15 percent injury tolerance. C4L Fair Buff Lugs. Thin, mature to ripe, firm to open... percent injury tolerance. C5L Low Buff Lugs. Thin, mature, firm to open, wavy dull finish, pale color... Fair Tan Lugs. Medium to thin body, mature to ripe, firm to open, wavy to even, moderate finish, weak...

7 CFR 29.3152 - Lugs or Cutters (C Group).

Code of Federal Regulations, 2012 CFR

2012-01-01

... percent uniform, and 15 percent injury tolerance. C4L Fair Buff Lugs. Thin, mature to ripe, firm to open... percent injury tolerance. C5L Low Buff Lugs. Thin, mature, firm to open, wavy dull finish, pale color... Fair Tan Lugs. Medium to thin body, mature to ripe, firm to open, wavy to even, moderate finish, weak...

On the parameters influencing air-water gas exchange

NASA Astrophysics Data System (ADS)

JäHne, Bernd; Münnich, Karl Otto; BöSinger, Rainer; Dutzi, Alfred; Huber, Werner; Libner, Peter

1987-02-01

Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k ∝ Sc-⅔ to k ∝ Sc-½indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes.

A flexible, stretchable and shape-adaptive approach for versatile energy conversion and self-powered biomedical monitoring.

PubMed

Yang, Po-Kang; Lin, Long; Yi, Fang; Li, Xiuhan; Pradel, Ken C; Zi, Yunlong; Wu, Chih-I; He, Jr-Hau; Zhang, Yue; Wang, Zhong Lin

2015-07-01

A flexible triboelectric nanogenerator (FTENG) based on wavy-structured Kapton film and a serpentine electrode on stretchable substrates is presented. The as-fabricated FTENG is capable of harvesting ambient mechanical energy via both compressive and stretching modes. Moreover, the FTENG can be a bendable power source to work on curved surfaces; it can also be adaptively attached onto human skin for monitoring gentle body motions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.

Flow over a traveling wavy foil with a passively flapping flat plate

NASA Astrophysics Data System (ADS)

Liu, Nansheng; Peng, Yan; Liang, Youwen; Lu, Xiyun

2012-05-01

Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.

Floating compression of Ag nanowire networks for effective strain release of stretchable transparent electrodes

NASA Astrophysics Data System (ADS)

Pyo, Jun Beom; Kim, Byoung Soo; Park, Hyunchul; Kim, Tae Ann; Koo, Chong Min; Lee, Jonghwi; Son, Jeong Gon; Lee, Sang-Soo; Park, Jong Hyuk

2015-10-01

Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant electrodes for dielectric elastomer actuators. The study demonstrates their promising potential to provide improved performance for soft electronic devices.Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant electrodes for dielectric elastomer actuators. The study demonstrates their promising potential to provide improved performance for soft electronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03814f

Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP) Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method

PubMed Central

Gao, Hang; Wang, Xu; Guo, Dongming; Liu, Ziyuan

2018-01-01

Laser induced damage threshold (LIDT) is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP) crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT), followed by water dissolution ultra-precision polishing (WDUP) and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD) analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal. PMID:29534032

On the influence of airfoil deviations on the aerodynamic performance of wind turbine rotors

NASA Astrophysics Data System (ADS)

Winstroth, J.; Seume, J. R.

2016-09-01

The manufacture of large wind turbine rotor blades is a difficult task that still involves a certain degree of manual labor. Due to the complexity, airfoil deviations between the design airfoils and the manufactured blade are certain to arise. Presently, the understanding of the impact of manufacturing uncertainties on the aerodynamic performance is still incomplete. The present work analyzes the influence of a series of airfoil deviations likely to occur during manufacturing by means of Computational Fluid Dynamics and the aeroelastic code FAST. The average power production of the NREL 5MW wind turbine is used to evaluate the different airfoil deviations. Analyzed deviations include: Mold tilt towards the leading and trailing edge, thick bond lines, thick bond lines with cantilever correction, backward facing steps and airfoil waviness. The most severe influences are observed for mold tilt towards the leading and thick bond lines. By applying the cantilever correction, the influence of thick bond lines is almost compensated. Airfoil waviness is very dependent on amplitude height and the location along the surface of the airfoil. Increased influence is observed for backward facing steps, once they are high enough to trigger boundary layer transition close to the leading edge.

Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics.

PubMed

Ding, Yang; Batista, Bruno; Steinbock, Oliver; Cartwright, Julyan H E; Cardoso, Silvana S S

2016-08-16

To model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a 2D microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about one order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms.

Experimental observations and finite element analysis of the initiation of fiber microbuckling in notched composite laminates

NASA Technical Reports Server (NTRS)

Guynn, E. Gail; Bradley, Walter L.; Ochoa, Ozden O.

1990-01-01

A better understanding of the factors that affect the semi-circular edge-notched compressive strength is developed, and the associated failure mode(s) of thermoplastic composite laminates with multidirectional stacking sequences are identified. The primary variables in this investigation are the resin nonlinear shear constitutive behavior, stacking sequence (orientation of plies adjacent to the 0 degree plies), resin-rich regions between the 0 degree plies and the off-axis supporting plies, fiber/matrix interfacial bond strength, and initial fiber waviness. Two thermoplastic composite material systems are used in this investigation. The materials are the commercial APC-2 (AS4/PEEK) and a poor interface experimental material, AU4U/PEEK, designed for this investigation. Notched compression specimens are studied at 21, 77, and 132 C. Geometric and material nonlinear two-dimensional finite element analysis is used to model the initiation of fiber microbuckling of both the ideal straight fiber and the more realistic initially wavy fiber. The effects of free surface, fiber constitutive properties, matrix constitutive behavior, initial fiber curvature, and fiber/matrix interfacial bond strength on fiber microbuckling initiation strain levels are considered.

Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence.

PubMed

Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

2016-11-14

The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, k L , and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, k L for the wind-driven wavy gas-liquid interface is generally proportional to Sc -0.5 , and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking.

Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence

PubMed Central

Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

2016-01-01

The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, kL, and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, kL for the wind-driven wavy gas-liquid interface is generally proportional to Sc−0.5, and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking. PMID:27841325

Near-field interaction of colloid near wavy walls

NASA Astrophysics Data System (ADS)

Luo, Yimin; Serra, Francesca; Wong, Denise; Steager, Edward; Stebe, Kathleen

Anisotropic media can be used to manipulate colloids, in tandem with carefully designed boundary conditions. For example, in bulk nematic liquid crystal, a wall with homeotropic anchoring repels a colloid with the same anchoring; yet by changing the surface topography from planar to concave, one can turn repulsion into attraction. We explore the behaviors of micro-particles with associated topological defects (hedgehogs or Saturn rings) near wavy walls. The walls locally excite disturbance, which decays into bulk. The range of influence is related to the curvature. The distortion can be used to position particles, either directly on the structure or at a distance away, based on the ``splay-matching'' rules. When distortion becomes stronger through the deepening of the well, the splay field created by the wall can prompt transformation from a Saturn ring to a hedgehog. We combine wells of different wavelength and depth to direct colloid movement. We apply a magnetic field to reset the initial position of ferromagnetic colloids and subsequently release them to probe the elastic energy landscape. Our platform enables manipulation, particle selection, and a detailed study of defect structure under the influence of curvature. Army Research Office.

Indirect evaporative coolers with enhanced heat transfer

DOEpatents

Kozubal, Eric; Woods, Jason; Judkoff, Ron

2015-09-22

A separator plate assembly for use in an indirect evaporative cooler (IEC) with an air-to-air heat exchanger. The assembly includes a separator plate with a first surface defining a dry channel and a second surface defining a wet channel. The assembly includes heat transfer enhancements provided on the first surface for increasing heat transfer rates. The heat transfer enhancements may include slit fins with bodies extending outward from the first surface of separator plate or may take other forms including vortex generators, offset strip fins, and wavy fins. In slit fin implementations, the separator plate has holes proximate to each of the slit fins, and the separator plate assembly may include a sealing layer applied to the second surface of the separator plate to block air flow through the holes. The sealing layer can be a thickness of adhesive, and a layer of wicking material is applied to the adhesive.

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang-Condell, Hannah; Wilner, David; Andrews, Sean; Kraus, Adam; Dahm, Scott;

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang, Condell, Hannah; Wilner, David; Andrews, Sean; Dahm, Scott; Robitaille,Thomas

2012-01-01

We present Keck/NIRC2 K(sub s) band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.3 - 2.5" (approx equals 35 - 280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to r approx equals 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50 - 100% brighter at r = 35 - 80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model fur a single dust belt including a phase function with two components and a 5 - 10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry and the profile at wider separations (r > 110 AU). Although there may be a1ternate explanations, agreement between the SW disk brightness peak and disk's peak rom emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1 - 1 mm-sized grains at approx equal 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

Credit PSR. View looking north northeast (12°) across surface remains ...

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

Credit PSR. View looking north northeast (12°) across surface remains of North Base swimming pool. The southeast edge of the pool appearing in the foreground may seem to be a sidewalk to the casual observer; the wavy inside edge of this walk matches the pool side visible in historic construction photos (See HAER photo CA-170-Q-2). The telephone pole in the midground of the view is inside the pool proper. Building 4312 (Liquid Oxygen Repair Facility) appears in left background, Building 4456 (Fire House No. 4) in middle background, and Building 4444 (Communications Building) in right background - Edwards Air Force Base, North Base, Swimming Pool, Second Street, Boron, Kern County, CA

Simulation of a 3D Turbulent Wavy Channel based on the High-order WENO Scheme

NASA Astrophysics Data System (ADS)

Tsai, Bor-Jang; Chou, Chung-Chyi; Tsai, Yeong-Pei; Chuang, Ying Hung

2018-02-01

Passive interest turbulent drag reduction, effective means to improve air vehicle fuel consumption costs. Most turbulent problems happening to the nature and engineering applications were exactly the turbulence problem frequently caused by one or more turbulent shear flows. This study was operated with incompressible 3-D channels with cyclic wavy boundary to explore the physical properties of turbulence flow. This research measures the distribution of average velocity, instant flowing field shapes, turbulence and pressure distribution, etc. Furthermore, the systematic computation and analysis for the 3-D flow field was also implemented. It was aimed to clearly understand the turbulence fields formed by wavy boundary of tube flow. The purpose of this research is to obtain systematic structural information about the turbulent flow field and features of the turbulence structure are discussed.

Development of a wavy Stark velocity filter for studying interstellar chemistry

NASA Astrophysics Data System (ADS)

Okada, Kunihiro; Takada, Yusuke; Kimura, Naoki; Wada, Michiharu; Schuessler, Hans A.

2017-08-01

Cold polar molecules are key to both the understanding of fundamental physics and the characterization of the chemical evolution of interstellar clouds. To facilitate such studies over a wide range of temperatures, we developed a new type of Stark velocity filter for changing the translational and rotational temperatures of velocity-selected polar molecules without changing the output beam position. The translational temperature of guided polar molecules can be significantly varied by exchanging the wavy deflection section with one having a different radius of the curvature and a different deflection angle. Combining in addition a temperature variable gas cell with the wavy Stark velocity filter enables to observe the translational and rotational temperature dependence of the reaction-rate constants of cold ion-polar molecule reactions over the interesting temperature range of 10-100 K.

Surface Structure Formation in Direct Chill (DC) Casting of Al Alloys

NASA Astrophysics Data System (ADS)

Bayat, Nazlin; Carlberg, Torbjörn

2014-05-01

The aim of this study is to increase the understanding of the surface zone formation during direct chill (DC) casting of aluminum billets produced by the air slip technology. The depth of the shell zone, with compositions deviating from the bulk, is of large importance for the subsequent extrusion productivity and quality of final products. The surface microstructures of 6060 and 6005 aluminum alloys in three different surface appearances—defect free, wavy surface, and spot defects—were studied. The surface microstructures and outer appearance, segregation depth, and phase formation were investigated for the mentioned cases. The results were discussed and explained based on the exudation of liquid metal through the mushy zone and the fact that the exudated liquid is contained within a surface oxide skin. Outward solidification in the surface layer was quantitatively analyzed, and the oxide skin movements explained meniscus line formation. Phases forming at different positions in the segregation zone were analyzed and coupled to a cellular solidification in the exudated layer.

Modeling glacial flow on and onto Pluto's Sputnik Planitia

NASA Astrophysics Data System (ADS)

Umurhan, O. M.; Howard, A. D.; Moore, J. M.; Earle, A. M.; White, O. L.; Schenk, P. M.; Binzel, R. P.; Stern, S. A.; Beyer, R. A.; Nimmo, F.; McKinnon, W. B.; Ennico, K.; Olkin, C. B.; Weaver, H. A.; Young, L. A.

2017-05-01

Observations of Pluto's surface made by the New Horizons spacecraft indicate present-day N2 ice glaciation in and around the basin informally known as Sputnik Planitia. Motivated by these observations, we have developed an evolutionary glacial flow model of solid N2 ice that takes into account its published thermophysical and rheological properties. This model assumes that glacial ice flows laminarly and has a low aspect ratio which permits a vertically integrated mathematical formulation. We assess the conditions for the validity of laminar N2 ice motion by revisiting the problem of the onset of solid-state buoyant convection of N2 ice for a variety of bottom thermal boundary conditions. Subject to uncertainties in N2 ice rheology, N2 ice layers are estimated to flow laminarly for thicknesses less than 400-1000 m. The resulting mass-flux formulation for when the N2 ice flows as a laminar dry glacier is characterized by an Arrhenius-Glen functional form. The flow model developed is used here to qualitatively answer some questions motivated by features we interpret to be a result of glacial flow found on Sputnik Planitia. We find that the wavy transverse dark features found along the northern shoreline of Sputnik Planitia may be a transitory imprint of shallow topography just beneath the ice surface suggesting the possibility that a major shoreward flow event happened relatively recently, within the last few hundred years. Model results also support the interpretation that the prominent darkened features resembling flow lobes observed along the eastern shoreline of the Sputnik Planitia basin may be the result of a basally wet N2 glacier flowing into the basin from the pitted highlands of eastern Tombaugh Regio.

Hydrotectonics; principles and relevance

USGS Publications Warehouse

Kopf, R.W.

1982-01-01

Hydrotectonics combines the principles of hydraulics and rock mechanics. The hypothesis assumes that: (1) no faults are truly planar, (2) opposing noncongruent wavy wallrock surfaces form chambers and bottlenecks along the fault, and (3) most thrusting occurs beneath the water table. These physical constraints permit the following dynamics. Shear displacement accompanying faulting must constantly change the volume of each chamber. Addition of ground water liquefies dry fault breccia to a heavy incompressible viscous muddy breccia I call fault slurry. When the volume of a chamber along a thrust fault decreases faster than its fault slurry can escape laterally, overpressurized slurry is hydraulically injected into the base of near-vertical fractures in the otherwise impervious overriding plate. Breccia pipes commonly form where such fissures intersect. Alternating decrease and increase in volume of the chamber subjects this injection slurry to reversible surges that not only raft and abrade huge clasts sporadically spalled from the walls of the conduit but also act as a forceful hydraulic ram which periodically widens the conduit and extends its top. If the pipe perforates a petroleum reservoir, leaking hydrocarbons float to its top. Sudden faulting may generate a powerful water hammer that can be amplified at some distal narrow ends of the anastomosing plumbing system, where the shock may produce shatter cones. If vented on the Earth's surface, the muddy breccia, now called extrusion slurry, forms a mud volcano. This hypothesis suggests that many highly disturbed features presently attributed to such catastrophic processes as subsurface explosions or meteorite impacts are due to the rheology of tectonic slurry in an intermittently reactivated pressure-relief tube rooted in a powerful reciprocating hydrotectonic pump activated by a long-lived deep-seated thrust fault.

Investigation of the foam influence on the wind-wave momentum exchange and cross-polarization microwave radar return within laboratory modeling of atmosphere-ocean boundary layer

NASA Astrophysics Data System (ADS)

Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim; Ermoshkin, Alexey

2016-04-01

The effect of foam presence on the transfer processes and the parameters of the surface roughness within the laboratory simulation of wind-wave interaction was carried out on the Thermostratified Wind-Wave Tank (TSWiWaT) IAP, using a specially designed foam generator. The parameters of air flow profiles and waves elevation were measured with scanning Pitot gauge and wire wave gauges respectively in the range of equivalent wind speed U10 from 12 to 38 m/s (covering strong winds) on the clean water and with foam. It was shown that the foam reduces the amplitudes and slopes of the waves in comparison with the clean water in the hole range of wind speeds investigated, and the peak frequency and wave numbers remain almost constant. The drag coefficient calculating by profiling method demonstrated similar behavior (almost independent on U10) for case of foam and increased compared with clear water, particularly noticeable for low wind speeds. Simultaneously the investigations of influence of the foam on the peculiarity of the microwave radio back scattering of X-diapason was investigated. These measurements were carried for different sensing angles (30, 40 i 50 degrees from vertical) and for four polarizations: co-polarized HH and VV, and de-polarized HV and VH. It was shown that foam leads to decrease of specific radar cross section of the wavy surface in comparison with clean water. The work was supported by the Russian Foundation for Basic Research (grants No. 15-35-20953, 14-05-00367, 16-55-52022) and project ASIST of FP7. The experiment is supported by Russian Science Foundation (Agreement No. 15-17-20009), radilocation measurments are partially supported by Russian Science Foundation (Agreement No. 14-17-00667).

Stimulation of Cl- uptake and morphological changes in gill mitochondria-rich cells in freshwater tilapia (Oreochromis mossambicus).

PubMed

Chang, Il-Chi; Wei, Yuan-Yaw; Chou, Fong-In; Hwang, Pung-Pung

2003-01-01

The purpose of the present article is to examine the relationships between ion uptakes and morphologies of gill mitochondria-rich (MR) cells in freshwater tilapia. Tilapia were acclimated to three different artificial freshwaters (high Na [10 mM], high Cl [7.5 mM]; high Na, low Cl [0.02-0.07 mM], and low Na [0.5 mM], low Cl) for 1 wk, and then morphological measurements of gill MR cells were made and ion influxes were determined. The number and the apical size of wavy-convex MR cells positively associated with the level of Cl(-) influx. Conversely, Na(+) influx showed no positive correlation with the morphologies of MR cells. The dominant MR cell type in tilapia gills changed from deep-hole to wavy-convex within 6 h after acute transfer from a high-Cl(-) to a low-Cl(-) environment. Deep-hole MR cells became dominant 24-96 h after acute transfer from a low-Cl(-) to a high-Cl(-) environment. We conclude that wavy-convex MR cells associate with Cl(-) uptake but not Na(+) uptake, and the rapid formation of wavy-convex MR cells reflects the timely stimulation of Cl(-) uptake to recover the homeostasis of internal Cl(-) levels on acute challenge with low environmental Cl(-).

Gravity Wave Seeding of Equatorial Plasma Bubbles

NASA Technical Reports Server (NTRS)

Singh, Sardul; Johnson, F. S.; Power, R. A.

1997-01-01

Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

Is fault surface roughness indicative of fault mechanisms? Observations from experimental Limestone faults

NASA Astrophysics Data System (ADS)

Sagy, A.; Tesei, T.; Collettini, C.

2016-12-01

Geometrical irregularity of contacting surfaces is a fundamental factor controlling friction and energy dissipation during sliding. We performed direct shear experiments on 20x20 cm limestone surfaces by applying constant normal load (40-200 kN) and sliding velocity 1-300 µm/s. Before shearing, the surfaces were polished with maximal measured amplitudes of less than 0.1 mm. After shear, elongated islands of shear zones are observed, characterized by grooves ploughed into the limestone surfaces and by layers of fine grain wear. These structures indicate that the contact areas during shear are scattered and occupy a limited portion of the entire surface area. The surfaces was scanned by a laser profilometer that measures topography using 640 parallel beams in a single run, offer up to 10 µm accuracy and working ranges of 200 mm. Two distinctive types of topographical end members are defined: rough wavy sections and smooth polished ones. The rough zones display ridges with typical amplitudes of 0.1-1 mm that cross the grooves perpendicular to the slip direction. These features are associated with penetrative brittle damage and with fragmentation. The smoother zones display reflective mirror-like surfaces bordered by topographical sharp steps at heights of 0.3-0.5 mm. These sections are localized inside the wear layer or between the wear layer and the host rock, and are not associated with observed penetrative damage. Preliminary statistical analysis suggests that the roughness of the ridges zones can be characterized using a power-low relationship between profile length and mean roughness, with relatively high values of Hurst exponents (e.g. H > 0.65) parallel to the slip direction. The polished zones, on the other hand, corresponded to lower values of Hurst exponents (e.g. H ≤ 0.6). Both structural and roughness measurements indicate that the distinctive topographic variations on the surfaces reflect competing mechanical processes which occur simultaneously during shear. The wavy ridged zone is the surface expression of penetrative cracking and fragmentation which widen the shear zone, while the smooth zones reflect localized flow and plastic deformation of the wear material. The similarity in topography of shear structures between experimental and natural faults suggests similar mechanical processes.

Credit USAF, ca. 1943. Original housed in the Muroc Flight ...

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

Credit USAF, ca. 1943. Original housed in the Muroc Flight Test Base, Unit History, 1 September 1942 - 30 June 1945. Alfred F. Simpson Historical Research Agency. United States Air Force. Maxwell AFB, Alabama. Historic view looking northeast along southeast edge of swimming pool during construction. The wavy edge of the pool visible here remains as a ground surface feature in 1995. Building in the background is the second Bachelor Officers' Quarters (T-15) built in 1943 - Edwards Air Force Base, North Base, Swimming Pool, Second Street, Boron, Kern County, CA

Establishment of a Continuous Wave Laser Welding Process

DTIC Science & Technology

1976-10-01

gas channel . A stiff bridge clamp with threaded force points was used on half inch plate welds to iron out waviness in the test coupons. Several...34 back up channel * 10.5kW on work 11-17 ^^^^^^^ ■ u u mi u.üiijüuiiiii IK««,,.! umm j,- u.jipiHi^iMii.ijii.ijiji j! J u„„, On each of four days...welded at 40 ipm using maximum available power on the surface (12.6 KV7 for the F/7 optical system) . Contours improved but porosity formed in the

Escape jumping by three age-classes of water striders from smooth, wavy and bubbling water surfaces.

PubMed

Ortega-Jimenez, Victor Manuel; von Rabenau, Lisa; Dudley, Robert

2017-08-01

Surface roughness is a ubiquitous phenomenon in both oceanic and terrestrial waters. For insects that live at the air-water interface, such as water striders, non-linear and multi-scale perturbations produce dynamic surface deformations which may impair locomotion. We studied escape jumps of adults, juveniles and first-instar larvae of the water strider Aquarius remigis on smooth, wave-dominated and bubble-dominated water surfaces. Effects of substrate on takeoff jumps were substantial, with significant reductions in takeoff angles, peak translational speeds, attained heights and power expenditure on more perturbed water surfaces. Age effects were similarly pronounced, with the first-instar larvae experiencing the greatest degradation in performance; age-by-treatment effects were also significant for many kinematic variables. Although commonplace in nature, perturbed water surfaces thus have significant and age-dependent effects on water strider locomotion, and on behavior more generally of surface-dwelling insects. © 2017. Published by The Company of Biologists Ltd.

Influence of surface roughness and waviness on film thickness and pressure distribution in elastohydrodynamic contacts

NASA Technical Reports Server (NTRS)

Chow, L. S. H.; Cheng, H. S.

1976-01-01

The Christensen theory of a stochastic model for hydrodynamic lubrication of rough surfaces was extended to elastohydrodynamic lubrication between two rollers. Solutions for the reduced pressure at the entrance as a function of the ratio of the average nominal film thickness to the rms surface roughness, were obtained numerically. Results were obtained for purely transverse as well as purely longitudinal surface roughness for cases with or without slip. The reduced pressure was shown to decrease slightly by considering longitudinal surface roughness. The same approach was used to study the effect of surface roughness on lubrication between rigid rollers and lubrication of an infinitely wide slider bearing. Using the flow balance concept, the perturbed Reynolds equation, was derived and solved for the perturbed pressure distribution. In addition, Cheng's numerical scheme was modified to incorporate a single two-dimensional elastic asperity on the stationary surface. The perturbed pressures obtained by these three different models were compared.

Post-modelling of images from a laser-induced wavy boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2015-12-01

Processes like laser keyhole welding, remote fusion laser cutting or laser drilling are governed by a highly dynamic wavy boiling front that was recently recorded by ultra-high speed imaging. A new approach has now been established by post-modelling of the high speed images. Based on the image greyscale and on a cavity model the three-dimensional front topology is reconstructed. As a second step the Fresnel absorptivity modulation across the wavy front is calculated, combined with the local projection of the laser beam. Frequency polygons enable additional analysis of the statistical variations of the properties across the front. Trends like shadow formation and time dependency can be studied, locally and for the whole front. Despite strong topology modulation in space and time, for lasers with 1 μm wavelength and steel the absorptivity is bounded to a narrow range of 35-43%, owing to its Fresnel characteristics.

Selective laser melting in heat exchanger development - experimental investigation of heat transfer and pressure drop characteristics of wavy fins

NASA Astrophysics Data System (ADS)

Kuehndel, J.; Kerler, B.; Karcher, C.

2018-04-01

To improve performance of heat exchangers for vehicle applications, it is necessary to increase the air side heat transfer. Selective laser melting gives rise to be applied for fin development due to: i) independency of conventional tooling ii) a fast way to conduct essential experimental studies iii) high dimensional accuracy iv) degrees of freedom in design. Therefore, heat exchanger elements with wavy fins were examined in an experimental study. Experiments were conducted for air side Reynolds number range of 1400-7400, varying wavy amplitude and wave length of the fins at a constant water flow rate of 9.0 m3/h. Heat transfer and pressure drop characteristics were evaluated with Nusselt Number Nu and Darcy friction factor ψ as functions of Reynolds number. Heat transfer and pressure drop correlations were derived from measurement data obtained by regression analysis.

Compression failure of angle-ply laminates

NASA Technical Reports Server (NTRS)

Peel, L. D.; Hyer, M. W.; Shuart, M. J.

1992-01-01

Test results from the compression loading of (+ or - Theta/ - or + Theta)(sub 6s) angle-ply IM7-8551-7a specimens, 0 less than or = Theta less than or = 90 degs, are presented. The observed failure strengths and modes are discussed, and typical stress-strain relations shown. Using classical lamination theory and the maximum stress criterion, an attempt is made to predict failure stress as a function of Theta. This attempt results in poor correlation with test results and thus a more advanced model is used. The model, which is based on a geometrically nonlinear theory, and which was taken from previous work, includes the influence of observed layer waviness. The waviness is described by the wave length and the wave amplitude. The theory is briefly described and results from the theory are correlated with test results. It is shown that by using levels of waviness observed in the specimens, the correlation between predictions and observations is good.

Processing vertical size disparities in distinct depth planes.

PubMed

Duke, Philip A; Howard, Ian P

2012-08-17

A textured surface appears slanted about a vertical axis when the image in one eye is horizontally enlarged relative to the image in the other eye. The surface appears slanted in the opposite direction when the same image is vertically enlarged. Two superimposed textured surfaces with different horizontal size disparities appear as two surfaces that differ in slant. Superimposed textured surfaces with equal and opposite vertical size disparities appear as a single frontal surface. The vertical disparities are averaged. We investigated whether vertical size disparities are averaged across two superimposed textured surfaces in different depth planes or whether they induce distinct slants in the two depth planes. In Experiment 1, two superimposed textured surfaces with different vertical size disparities were presented in two depth planes defined by horizontal disparity. The surfaces induced distinct slants when the horizontal disparity was more than ±5 arcmin. Thus, vertical size disparities are not averaged over surfaces with different horizontal disparities. In Experiment 2 we confirmed that vertical size disparities are processed in surfaces away from the horopter, so the results of Experiment 1 cannot be explained by the processing of vertical size disparities in a fixated surface only. Together, these results show that vertical size disparities are processed separately in distinct depth planes. The results also suggest that vertical size disparities are not used to register slant globally by their effect on the registration of binocular direction of gaze.

[Study on exogenous hormones inducing parthenocarpy fruit growth and development and quality of Siraitia grosvenorii].

PubMed

Huang, Jie; Tu, Dong-ping; Ma, Xiao-jun; Mo, Chang-ming; Pan, Li-mei; Bai, Long-hua; Feng, Shi-xin

2015-09-01

To explore the growth and development and analyze the quality of the parthenocarpy fruit induced by exogenous hormones of Siraitia grosvenorii. the horizontal and vertical diameter, volume of the fruit were respectively measured by morphological and the content of endogenous hormones were determined by ELISA. The size and seed and content of mogrosides of mature fruit were determined. The results showed that the fruit of parthenocarpy was seedless and its growth and development is similar to the diploid fruit by hand pollination and triploid fruit by hand pollination or hormones. But the absolute value of horizontal and vertical diameter, volume of parthenocarpy fruit was less than those of fruit by hand pollination, while triploid was opposite. The content of IAA, ABA and ratio of ABA/GA was obviously wavy. At 0-30 d the content of IAA and ABA of parthenocarpy fruit first reduced then increased, content of IAA and GA parthenocarpy fruit was higher than that of fruit by hand pollination. Mogrosides of parthenocarpy fruit was close to pollination fruit. Hormones can induce S. grosvenorii parthenocarpy to get seedless fruit and the fruit shape and size and quality is close to normal diploid fruit by hand pollination and better than triploid fruit by hormone or hand pollination.

Analysis of the tail structures of comet P/Halley 1910 II

NASA Astrophysics Data System (ADS)

Voelzke, Marcos Rincon; Izaguirre, Liberdade

2012-07-01

Eight hundred and eighty six images from September 1909 to May 1911 are analysed for the purpose of identifying, measuring and correlating the morphological structures along the plasma tail of P/Halley. These images are from the Atlas of Comet Halley 1910 II (Donn et al., 1986). A systematic visual analysis revealed 304 wavy structures along the main tail and 164 along the secondary tails, 41 solitary waves (solitons), 13 Swan-like tails, 26 disconnection events (DEs), 166 knots (regions of higher density of matter) and six shells. While the wavy structures denote undulations or a train of waves, the solitons refer to the formations usually denominated kinks. In general, it is possible to associate the occurrence of a DE and/or a Swan-Tail with the occurrence of a knot, but the last one may occur independently. It is also possible to say that the solitons occur in association with the wavy structures, but the reverse is not true. The 26 DEs documented in 26 different images allowed the derivation of two onsets of DEs (Table 1), i.e., the time when the comet supposedly crossed a frontier between magnetic sectors of the solar wind (Brandt and Snow, 2000). Both onsets of DEs were determined after the perihelion passage with an average of the corrected velocities Vc equal to (57 ± 15) km/s. The mean value of the corrected wavelength c measured in 70 different wavy structures is equal to (1.7 ± 0.1) x 10^6 km and the mean amplitude A of the wave (measured in the same 70 wavy structures cited above) is equal to (1.4 ± 0.1) x 10^5 km. The mean value of the corrected cometocentric phase velocity Vpc measured in 20 different wavy structures is equal to (168 ± 28) km/s. The average value of the corrected velocities Vkc of the knots measured in 36 different images is equal to (128 ± 12) km/s. There is a tendancy for A and c to increase with increasing cometocentric distance. The results of this work agree with the earlier research from Voelzke and Matsuura (1998), which analysed comet P/Halley's tail structures in its last apparition in 1986.

Morphological analysis of the tail structures of comet P/Halley 1910 II

NASA Astrophysics Data System (ADS)

Voelzke, M. R.; Izaguirre, L. S.

2012-05-01

For the purpose of identifying, measuring and correlating the morphological structures along the plasma tail of P/Halley 886 images from September 1909 to May 1911 are analysed. These images are from the Atlas of Comet Halley 1910 II (Donn et al., 1986). A systematic visual analysis revealed 304 wavy structures along the main tail and 164 along the secondary tails, 41 solitary waves (solitons), 13 Swan-like tails, 26 disconnection events (DEs), 166 knots (regions of higher density of matter) and six shells. While the wavy structures denote undulations or a train of waves, the solitons refer to the formations usually denominated as kinks. In general, it is possible to associate the occurrence of a DE and/or a Swan-Tail with the occurrence of a knot, but the last one may occur independently. It is also possible to say that the solitons occur in association with the wavy structures, but the reverse is not true. The 26 DEs documented in 26 different images allowed the derivation of two onsets of DEs (Table 1), i.e., the time when the comet supposedly crossed a frontier between magnetic sectors of the solar wind (Brandt and Snow, 2000). Both onsets of DEs were determined after the perihelion passage with an average of the corrected velocities Vc equal to (57±15) km s-1. The mean value of the corrected wavelength λc measured in 70 different wavy structures is equal to (1.7±0.1)×106 km and the mean amplitude A of the wave (measured in the same 70 wavy structures cited above) is equal to (1.4±0.1)×105 km. The mean value of the corrected cometocentric phase velocity Vpc measured in 20 different wavy structures is equal to (168±28) km s-1. The average value of the corrected velocities Vkc of the knots measured in 36 different images is equal to (128±12) km s-1. There is a tendency for A and λc to increase with increasing cometocentric distance. The results of this work agree with the earlier research from Voelzke and Matsuura (1998), which analysed comet P/Halley's tail structures in its last apparition in 1986.

Temporal Evolution of the Morphological Tail Structures of Comet P/Halley 1910 II

NASA Astrophysics Data System (ADS)

Izaguirre, L. S.; Voelzke, M. R.

2004-08-01

Eight hundred and eighty six images from September 1909 to May 1911 are analysed for the purpose of identifying, measuring and correlating the morphological structures along the plasma tail of P/Halley. These images are from the Atlas of Comet Halley 1910 II (Donn et al., 1986). A systematic visual analysis revealed 304 wavy structures (Yi et al., 1998) along the main tail and 164 along the secondary tails, 41 solitary waves (solitons) (Roberts, 1985), 13 Swan-like tails (Jockers, 1985), 26 disconnection events (DEs) (Voelzke, 2002a), 166 knots (Voelzke et al., 1997) and six shells (Schulz and Schlosser, 1989). While the wavy structures denote undulations or a train of waves, the solitons refer to the formations usually denominated kinks (Tomita et al., 1987). In general, it is possible to associate the occurrence of a DE and/or a Swan-Tail with the occurrence of a knot, but the last one may occur independently. It is also possible to say that the solitons occur in association with the wavy structures, but the reverse is not true. The 26 DEs documented in 26 different images allowed the derivation of two onsets of DEs, i.e., the time when the comet supposedly crossed a frontier between magnetic sectors of the solar wind (Brandt and Snow, 2000). Both onsets of DEs were determined after the perihelion passage with an average of the corrected velocities Vc equal to (57 ± 15) km s-1. The mean value of the corrected wavelength lc measured in 70 different wavy structures is equal to (1.7 ± 0.1) x 10^6 km and the mean amplitude A of the wave (measured in the same 70 wavy structures cited above) is equal to (1.4 ± 0.1) x 10^5 km. The mean value of the corrected cometocentric phase velocity Vpc measured in 20 different wavy structures is equal to (168 ± 28) km s-1. The average value of the corrected velocities Vkc of the knots measured in 36 different images is equal to (128 ± 12) km s-1. There is a tendency for A and lc to increase with increasing cometocentric distance. The preliminary results of this work agree with the earlier research from Voelzke and Matsuura (1998), which analysed comet P/Halley's tail structures in its last apparition in 1986.

Radar sea reflection for low-e targets

NASA Astrophysics Data System (ADS)

Chow, Winston C.; Groves, Gordon W.

1998-09-01

Modeling radar signal reflection from a wavy sea surface uses a realistic characteristic of the large surface features and parameterizes the effect of the small roughness elements. Representation of the reflection coefficient at each point of the sea surface as a function of the Specular Deviation Angle is, to our knowledge, a novel approach. The objective is to achieve enough simplification and retain enough fidelity to obtain a practical multipath model. The 'specular deviation angle' as used in this investigation is defined and explained. Being a function of the sea elevations, which are stochastic in nature, this quantity is also random and has a probability density function. This density function depends on the relative geometry of the antenna and target positions, and together with the beam- broadening effect of the small surface ripples determined the reflectivity of the sea surface at each point. The probability density function of the specular deviation angle is derived. The distribution of the specular deviation angel as function of position on the mean sea surface is described.

Active Stabilization of Aeromechanical Systems

DTIC Science & Technology

1993-01-05

rotatingUsing the linearized forms of the equations of motion in the stall the compressed reverse flow comes from the annular space upstream and...and temperatures of the two opposite flows, I tential. This is a baroclinic instability deforms the ring into a wavy motion . I~dol)_ This front was...1989. Fig. 14, and 1990a, Fig, 17). The wavy motion of the S (2+ () front is then developed into Rossby waves, the velocity field If we define of which

Adaptive lenticular microlens array based on voltage-induced waves at the surface of polyvinyl chloride/dibutyl phthalate gels.

PubMed

Xu, Miao; Jin, Boya; He, Rui; Ren, Hongwen

2016-04-18

We report a new approach to preparing a lenticular microlens array (LMA) using polyvinyl chloride (PVC)/dibutyl phthalate (DBP) gels. The PVD/DBP gels coated on a glass substrate form a membrane. With the aid of electrostatic repulsive force, the surface of the membrane can be reconfigured with sinusoidal waves by a DC voltage. The membrane with wavy surface functions as a LMA. By switching over the anode and cathode, the convex shape of each lenticular microlens in the array can be converted to the concave shape. Therefore, the LMA can present a large dynamic range. The response time is relatively fast and the driving voltage is low. With the advantages of compact structure, optical isotropy, and good mechanical stability, our LMA has potential applications in imaging, information processing, biometrics, and displays.

Cassini/VIMS observes rough surfaces on Titan's Punga Mare in specular reflection.

PubMed

Barnes, Jason W; Sotin, Christophe; Soderblom, Jason M; Brown, Robert H; Hayes, Alexander G; Donelan, Mark; Rodriguez, Sebastien; Mouélic, Stéphane Le; Baines, Kevin H; McCord, Thomas B

Cassini /VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of [Formula: see text] cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.

A New Tool for Quality Control

NASA Technical Reports Server (NTRS)

1988-01-01

Diffracto, Ltd. is now offering a new product inspection system that allows detection of minute flaws previously difficult or impossible to observe. Called D-Sight, it represents a revolutionary technique for inspection of flat or curved surfaces to find such imperfections as dings, dents and waviness. System amplifies defects, making them highly visible to simplify decision making as to corrective measures or to identify areas that need further study. CVA 3000 employs a camera, high intensity lamps and a special reflective screen to produce a D- Sight image of light reflected from a surface. Image is captured and stored in a computerized vision system then analyzed by a computer program. A live image of surface is projected onto a video display and compared with a stored master image to identify imperfections. Localized defects measuring less than 1/1000 of an inch are readily detected.

Numerical study of Wavy Blade Section for Wind Turbines

NASA Astrophysics Data System (ADS)

Kobæk, C. M.; Hansen, M. O. L.

2016-09-01

The Wavy Blade concept is inspired by the unique flipper of a humpback whale, characterized by the tubercles located at the leading edge. It has been suggested that this shape may have been a result of a natural selection process, since this flipper under some circumstances can produce higher lift than a flipper having a smooth trailing edge and thus could be potentially beneficial when catching food. A thorough literature study of the Wavy Blade concept is made and followed by CFD computations of two wavy blade geometries and a comparison with their baseline S809 airfoil at conditions more relevant for modern wind turbines. The findings in the literature from geometries similar to the hump back whale flipper indicate that the aerodynamic performance can be improved at high angles of attack, but sometimes at the expense of a lower lift slope and increased drag before stall. The numerical results for a blade section based on the S809 airfoil are, however, not as promising as some of the findings reported in the literature for the whale flipper at high angles of attack. These first CFD computations using a thicker airfoil and a higher Reynolds number than the whale flipper indicate that the results may very well depend on the actual airfoil geometry and perhaps also the Reynolds number, and future studies are necessary in order to illuminate this further.

Dynamic response of a lenticular microlens array using a polyvinyl chloride gel

NASA Astrophysics Data System (ADS)

Li, Xiaolong; Zhou, Zuowei; Ren, Hongwen

2017-12-01

We prepared a lenticular microlens array (LMA) using a polyvinyl chloride (PVC) gel and an interdigitated electrode. By applying a DC voltage to the electrode, the surface of the PVC gel can be waved with an LMA character. When the voltage is removed, the wavy PVC gel can recover its flat surface gradually. With the aid of a polarity-inverted voltage, the recovering time can be largely reduced. The LMA can present a stable dynamic response when it is repetitively impacted by a pulse voltage. The experimental results are given, and the mechanism of reducing the dynamic response time is explained. Our LMA with improved response time has potential applications in sensing, beam steering, biometrics, and displays.

Melt layer formation in stainless steel under transient thermal loads

NASA Astrophysics Data System (ADS)

Steudel, I.; Klimov, N. S.; Linke, J.; Loewenhoff, Th.; Pintsuk, G.; Pitts, R. A.; Wirtz, M.

2015-08-01

To investigate the performance of stainless steel under transient thermal events, such as photon pulses caused by disruptions mitigated by massive gas injection (MGI), the material has been exposed to electron beam loads with ITER relevant power densities slightly above the melting threshold (245 MW/m2) and a pulse duration of 3 ms (Sugihara et al., 2012; Klimov et al., 2013; Pitts et al., 2013). The samples were manufactured from different steel grades with slightly modified chemical composition. To investigate the effect of repetitive surface heat loads on the melting process and the melt motion, identical heat pulses in the range of 100-3000 were applied. All tested materials showed intense melt-induced surface roughening, driven by repeated shallow surface melting up to several ten micrometre and fast re-solidification with epitaxial grain growth. During the liquid phase, melt motion induced by cohesive forces results in the formation of a wavy surface structure with apexes. Further experiments have been performed to study the effects of non-perpendicular surfaces or leading edges.

Nanostructured β-type titanium alloy fabricated by ultrasonic nanocrystal surface modification.

PubMed

Kheradmandfard, Mehdi; Kashani-Bozorg, Seyed Farshid; Kim, Chang-Lae; Hanzaki, Abbas Zarei; Pyoun, Young-Shik; Kim, Jung-Hyong; Amanov, Auezhan; Kim, Dae-Eun

2017-11-01

The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy, which is a promising material for biomedical applications, was treated with the ultrasonic nanocrystal surface modification (UNSM) technique to enhance its hardness. As a result, a gradient nanostructured (GNS) layer was generated in the surface; the microstructure of the top surface layer consisted of nanoscale lamellae with a width of about 60-200nm. In addition, there were lamellar grains consisting of nanostructured subgrains having unclear and wavy boundaries. The treated surface exhibited a hardness value of ∼385HV compared to 190HV for the untreated alloy. It was further determined that highly dense deformation twins were generated at a depth of ∼40-150µm below the UNSM-treated surface. These deformation twins led to a significant work hardening effect which aided in enhancing the mechanical properties. It was also found that UNSM treatment resulted in the formation of micropatterns on the surface, which would be beneficial for high bioactivity and bone regeneration performance of TNTZ implants. Copyright © 2017 Elsevier B.V. All rights reserved.

Darcy Flow in a Wavy Channel Filled with a Porous Medium

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

Gray, Donald D; Ogretim, Egemen; Bromhal, Grant S

2013-05-17

Flow in channels bounded by wavy or corrugated walls is of interest in both technological and geological contexts. This paper presents an analytical solution for the steady Darcy flow of an incompressible fluid through a homogeneous, isotropic porous medium filling a channel bounded by symmetric wavy walls. This packed channel may represent an idealized packed fracture, a situation which is of interest as a potential pathway for the leakage of carbon dioxide from a geological sequestration site. The channel walls change from parallel planes, to small amplitude sine waves, to large amplitude nonsinusoidal waves as certain parameters are increased. Themore » direction of gravity is arbitrary. A plot of piezometric head against distance in the direction of mean flow changes from a straight line for parallel planes to a series of steeply sloping sections in the reaches of small aperture alternating with nearly constant sections in the large aperture bulges. Expressions are given for the stream function, specific discharge, piezometric head, and pressure.« less

Ultrasonic NDE Simulation for Composite Manufacturing Defects

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Juarez, Peter D.

2016-01-01

The increased use of composites in aerospace components is expected to continue into the future. The large scale use of composites in aerospace necessitates the development of composite-appropriate nondestructive evaluation (NDE) methods to quantitatively characterize defects in as-manufactured parts and damage incurred during or post manufacturing. Ultrasonic techniques are one of the most common approaches for defect/damage detection in composite materials. One key technical challenge area included in NASA's Advanced Composite's Project is to develop optimized rapid inspection methods for composite materials. Common manufacturing defects in carbon fiber reinforced polymer (CFRP) composites include fiber waviness (in-plane and out-of-plane), porosity, and disbonds; among others. This paper is an overview of ongoing work to develop ultrasonic wavefield based methods for characterizing manufacturing waviness defects. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with in-plane fiber waviness (also known as marcelling). Wavefield data processing methods are applied to the simulation data to explore possible routes for quantitative defect characterization.

Predicting the mixed-mode I/II spatial damage propagation along 3D-printed soft interfacial layer via a hyperelastic softening model

NASA Astrophysics Data System (ADS)

Liu, Lei; Li, Yaning

2018-07-01

A methodology was developed to use a hyperelastic softening model to predict the constitutive behavior and the spatial damage propagation of nonlinear materials with damage-induced softening under mixed-mode loading. A user subroutine (ABAQUS/VUMAT) was developed for numerical implementation of the model. 3D-printed wavy soft rubbery interfacial layer was used as a material system to verify and validate the methodology. The Arruda - Boyce hyperelastic model is incorporated with the softening model to capture the nonlinear pre-and post- damage behavior of the interfacial layer under mixed Mode I/II loads. To characterize model parameters of the 3D-printed rubbery interfacial layer, a series of scarf-joint specimens were designed, which enabled systematic variation of stress triaxiality via a single geometric parameter, the slant angle. It was found that the important model parameter m is exponentially related to the stress triaxiality. Compact tension specimens of the sinusoidal wavy interfacial layer with different waviness were designed and fabricated via multi-material 3D printing. Finite element (FE) simulations were conducted to predict the spatial damage propagation of the material within the wavy interfacial layer. Compact tension experiments were performed to verify the model prediction. The results show that the model developed is able to accurately predict the damage propagation of the 3D-printed rubbery interfacial layer under complicated stress-state without pre-defined failure criteria.

Split off-specular reflection and surface scattering from woven materials

NASA Astrophysics Data System (ADS)

Pont, Sylvia C.; Koenderink, Jan J.

2003-03-01

We measured radiance distributions for black lining cloth and copper gauze using the convenient technique of wrapping the materials around a circular cylinder, irradiating it with a parallel light source and collecting the scattered radiance by a digital camera. One family of parallel threads (weave or weft) was parallel to the cylinder generator. The most salient features for such glossy plane weaves are a splitting up of the reflection peak due to the wavy variations in local slopes of the threads around the cylinders and a surface scattering lobe due to the threads that run along the cylinder. These scattering characteristics are quite different from the (off-)specular peaks and lobes that were found before for random rough specular surfaces. The split off-specular reflection is due to the regular structures in our samples of man-made materials. We derived simple approximations for these reflectance characteristics using geometrical optics.

Gage for micromachining system

DOEpatents

Miller, Donald M.

1979-02-27

A gage for measuring the contour of the surface of an element of a micromachining tool system and of a work piece machined by the micromachining tool system. The gage comprises a glass plate containing two electrical contacts and supporting a steel ball resting against the contacts. As the element or workpiece is moved against the steel ball, the very slight contact pressure causes an extremely small movement of the steel ball which breaks the electrical circuit between the two contacts. The contour information is supplied to a dedicated computer controlling the micromachining tool so that the computer knows the contour of the element and the work piece to an accuracy of .+-. 25 nm. The micromachining tool system with X- and omega-axes is used to machine spherical, aspherical, and irregular surfaces with a maximum contour error of 100 nanometers (nm) and surface waviness of no more than 0.8 nm RMS.

Self-ordering of InAs nanostructures on (631)A/B GaAs substrates

NASA Astrophysics Data System (ADS)

Eugenio-López, Eric; Alejandro Mercado-Ornelas, Christian; Kisan Patil, Pallavi; Cortes-Mestizo, Irving Eduardo; Ángel Espinoza-Figueroa, José; Gorbatchev, Andrei Yu; Shimomura, Satoshi; Ithsmel Espinosa-Vega, Leticia; Méndez-García, Víctor Hugo

2018-02-01

The high order self-organization of quantum dots is demonstrated in the growth of InAs on a GaAs(631)-oriented crystallographic plane. The unidimensional ordering of the quantum dots (QDs) strongly depends on the As flux beam equivalent pressure (P As) and the cation/anion terminated surface, i.e., A- or B-type GaAs(631). The self-organization of QDs occurs for both surface types along [\\bar{1}13], while the QD shape and size distribution were found to be different for the self-assembly on the A- and B-type surfaces. In addition, the experiments showed that any misorientation from the (631) plane, which results from the buffer layer waviness, does not allow a high order of unidimensional arrangements of QDs. The optical properties were studied by photoluminescence spectroscopy, where good correspondence was obtained between the energy transitions and the size of the QDs.

Unsteady viscous effects in the flow over an oscillating surface. [mathematical model

NASA Technical Reports Server (NTRS)

Lerner, J. I.

1972-01-01

A theoretical model for the interaction of a turbulent boundary layer with an oscillating wavy surface over which a fluid is flowing is developed, with an application to wind-driven water waves and to panel flutter in low supersonic flow. A systematic methodology is developed to obtain the surface pressure distribution by considering separately the effects on the perturbed flow of a mean shear velocity profile, viscous stresses, the turbulent Reynolds stresses, compressibility, and three-dimensionality. The inviscid theory is applied to the wind-water wave problem by specializing to traveling-wave disturbances, and the pressure magnitude and phase shift as a function of the wave phase speed are computed for a logarithmic mean velocity profile and compared with inviscid theory and experiment. The results agree with experimental evidence for the stabilization of the panel motion due to the influence of the unsteady boundary layer.

Analysis of the tail structures of comet P/Halley 1910 II

NASA Astrophysics Data System (ADS)

Voelzke, M. R.; Izaguirre, L. S.

Eight hundred and eighty six images from September 1909 to May 1911 are analysed for the purpose of identifying, measuring and correlating the morphological structures along the plasma tail of P/Halley. These images are from the Atlas of Comet Halley 1910 II (Donn et al. 1986). A systematic visual analysis revealed 304 wavy structures along the main tail and 164 along the secondary tails, 41 solitary waves (solitons), 13 Swan-like tails, 26 disconnection events (DEs), 166 knots and six shells. While the wavy structures denote undulations or a train of waves, the solitons refer to the formations usually denominated kinks. In general, it is possible to associate the occurrence of a DE and/or a Swan-Tail with the occurrence of a knot, but the last one may occur independently. It is also possible to say that the solitons occur in association with the wavy structures, but the reverse is not true. The 26 DEs documented in 26 different images allowed the derivation of two onsets of DEs, i.e., the time when the comet supposedly crossed a frontier between magnetic sectors of the solar wind. Both onsets of DEs were determined after the perihelion passage with an average of the corrected velocities Vc equal to (57 ± 15) km s-1. The mean value of the corrected wavelength λ c measured in 70 different wavy structures is equal to (1.7 ± 0.1) × 106 km and the mean amplitude A of the wave (measured in the same 70 wavy structures cited above) is equal to (1.4 ± 0.1) × 105 km. The mean value of the corrected cometocentric phase velocity Vpc measured in 20 different wavy structures is equal to (168 ± 28) km s-1. The average value of the corrected velocities Vkc of the knots measured in 36 different images is equal to (128 ± 12) km s-1. There is a tendency for A and λ c to increase with increasing cometocentric distance. The preliminary results of this work agree with the earlier research from Voelzke and Matsuura (1998), which analysed comet P/Halley's tail structures in its last apparition in 1986. Donn, B., Rahe, J. and Brandt, J.C. (1986) Atlas of Comet Halley 1910 II. NASA SP-488, NASA Scientific and Technical Information Branch, 1-600. Voelzke, M.R. and Matsuura, O.T. (1998) Planet. Space Sci. 46 (8), 835-841.

Flow and heat transfer enhancement in tube heat exchangers

NASA Astrophysics Data System (ADS)

Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

2015-11-01

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

Characterization of Nonlinear Effects in Optically Pumped Vertical Cavity Surface Emitting Lasers

DTIC Science & Technology

1993-12-01

Vertical Cavity Surface Emitting Lasers ( VCSELs ) are an exciting...lines A-3 X AFIT/GEOiENP/93 D-01 Abstract The nonlinear characteristics of optically pumped Vertical Cavity Surface Emitting Lasers ( VCSELs ) are...uniformity of the VCSEL fabrication. xi Characterization of Nonlinear Effects in Optically Pumped Vertical Cavity Surface Emitting Lasers

The flow of a thin liquid film on a stationary and rotating disk. I - Experimental analysis and flow visualization

NASA Technical Reports Server (NTRS)

Thomas, S.; Faghri, A.; Hankey, W.

1990-01-01

The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed was 0-300 RPM and the flow rate was 7.0-15.0 LPM. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Surface waves were found in the supercritical and subcritical regions at all flow rates studied. When the rotational speed of the disk is low, a standing wave at the edge of the disk was present. As the rotational speed increased, the surface waves changed from the wavy-laminar region to a region in which the waves ran nearly radially across the disk on top of a thin substrate of fluid.

Suppressing Taylor vortices in a Taylor-Couette flow system with free surface

NASA Astrophysics Data System (ADS)

Bouabdallah, A.; Oualli, H.; Mekadem, M.; Gad-El-Hak, M.

2016-11-01

Taylor-Couette flows have been extensively investigated due to their many industrial applications, such as catalytic reactors, electrochemistry, photochemistry, biochemistry, and polymerization. Mass transfer applications include extraction, tangential filtration, crystallization, and dialysis. A 3D study is carried out to simulate a Taylor-Couette flow with a rotating and pulsating inner cylinder. We utilize FLUENT to simulate the incompressible flow with a free surface. The study reveals that flow structuring is initiated with the development of an Ekman vortex at low Taylor number, Ta = 0 . 01 . For all encountered flow regimes, the Taylor vortices are systematically inhibited by the pulsatile motion of the inner cylinder. A spectral analysis shows that this pulsatile motion causes a rapid decay of the free surface oscillations, from a periodic wavy movement to a chaotic one, then to a fully turbulent motion. This degenerative free surface behavior is interpreted as the underlying mechanism responsible for the inhibition of the Taylor vortices.

Fog Collection on Polyethylene Terephthalate (PET) Fibers: Influence of Cross Section and Surface Structure.

PubMed

Azad, M A K; Krause, Tobias; Danter, Leon; Baars, Albert; Koch, Kerstin; Barthlott, Wilhelm

2017-06-06

Fog-collecting meshes show a great potential in ensuring the availability of a supply of sustainable freshwater in certain arid regions. In most cases, the meshes are made of hydrophilic smooth fibers. Based on the study of plant surfaces, we analyzed the fog collection using various polyethylene terephthalate (PET) fibers with different cross sections and surface structures with the aim of developing optimized biomimetic fog collectors. Water droplet movement and the onset of dripping from fiber samples were compared. Fibers with round, oval, and rectangular cross sections with round edges showed higher fog-collection performance than those with other cross sections. However, other parameters, for example, width, surface structure, wettability, and so forth, also influenced the performance. The directional delivery of the collected fog droplets by wavy/v-shaped microgrooves on the surface of the fibers enhances the formation of a water film and their fog collection. A numerical simulation of the water droplet spreading behavior strongly supports these findings. Therefore, our study suggests the use of fibers with a round cross section, a microgrooved surface, and an optimized width for an efficient fog collection.

Scanning electron microscopic observations of 'fractured' biodegradable plates and screws.

PubMed

Kosaka, Masaaki; Uemura, Fumiko; Tomemori, Shoko; Kamiishi, Hiroshi

2003-02-01

We encountered two out of 100 cases in which implanted biodegradable plates and screws had fractured within 1 month postoperatively. Failure of the material was confirmed through clinical symptoms, radiographs or CT findings. In addition, four specimens obtained from these two cases were examined with regard to their ultrastructure using scanning electron microscopy. Several principal patterns of the fractured surface were found: (1) gradual cracking, i.e. 'circular stair' and, (2) tortuous threads, i.e. a wavy line. It is conceivable that the material may not have been hit by major sudden forces but a disproportion between the thread configuration and the drilled hole may have led to screw loosening and torsion. Subsequently, the threads were deformed in a 'wavy' manner, finally leading to cracking and fracture of plates and screws. Fractures of plates and screws due to these instabilities are thought to be distinguishable from material resorption. In the application of biodegradable materials, more than two screws per single bone segment should be used as a principle of plate-fixation technique in order to avoid a stability-compromising situation, particularly in the stress-bearing areas of the maxillofacial region. Moreover, three-dimensional fixation using more than two plates is recommended in the facial skeleton e.g. zygomatic tripod. Intermaxillary fixation should also be considered to reinforce initial stability in stress-bearing areas.

Numerical evaluations of the effect of leading-edge protuberances on the static and dynamic stall characteristics of an airfoil

NASA Astrophysics Data System (ADS)

Cai, C.; Zuo, Z. G.; Liu, S. H.; Wu, Y. L.; Wang, F. B.

2013-12-01

Wavy leading edge modifications of airfoils through imitating humpback whale flippers has been considered as a viable passive way to control flow separation. In this paper, flows around a baseline 634-021 airfoil and one with leading-edge sinusoidal protuberances were simulated using S-A turbulence model. When studying the static stall characteristics, it is found that the modified airfoil does not stall in the traditional manner, with increasing poststall lift coefficients. At high angles of attack, the flows past the wavy leading edge stayed attached for a distance, while the baseline foil is in a totally separated flow condition. On this basis, the simulations of pitch characteristic were carried out for both foils. At high angles of attack mild variations in lift and drag coefficients of the modified foil can be found, leading to a smaller area of hysteresis loop. The special structure of wavy leading edge can help maintain high consistency of the flow field in dynamic pitching station within a particular range of angles of attack.

A comparative rugoscopic study of the dentate and edentulous individuals in the South Indian population.

PubMed

Rajguru, Jagdish Prasad; Misra, Satya Ranjan; Somayaji, Nagaveni S; Masthan, K M K; Babu, Aravindha N; Mohanty, Neeta

2014-01-01

This study analyzes the rugae pattern in dentulous and edentulous patients and also evaluates the association of rugae pattern between males and females. This study aims to investigate rugae patterns in dentulous and edentulous patients of both sexes in South Indian population and to find whether palatoscopy is a useful tool in human identification. Four hundred outpatients from Sree Balaji Dental College and Hospital, Chennai, were included in the study. The study group was equally divided between the sexes, which was further categorized into 100 dentulous and edentulous patients, respectively. The edentulous male showed the highest mean of wavy pattern and total absence of circular pattern while the edentulous female group showed the highest mean of curved pattern and total absence of nonspecific pattern, while dentate population showed similar value as that of the overall population such as straight, wavy, and curved patterns. The present study concludes that there is similar rugae pattern of distribution between male and female dentate population while there is varied pattern between the sexes of edentulous population. However, the most predominant patterns were straight, wavy, and circular patterns.

Vertical axis wind turbine airfoil

DOEpatents

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Investigations of Optical Properties of Active Regions in Vertical Cavity Surface Emitting Lasers Grown by MBE

DTIC Science & Technology

2002-06-03

Molecular beam epitaxy ; Planar microcavities; Vertical cavity surface emitting lasers 1... Vertical Cavity Surface Emitting Lasers Grown by MBE DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the...S-581 83 Linkiping, Sweden Abstract The design of the vertical cavity surface emitting lasers ( VCSELs ) needs proper tuning of many

Rayleigh-Bénard convection with uniform vertical magnetic field.

PubMed

Basak, Arnab; Raveendran, Rohit; Kumar, Krishna

2014-09-01

We present the results of direct numerical simulations of Rayleigh-Bénard convection in the presence of a uniform vertical magnetic field near instability onset. We have done simulations in boxes with square as well as rectangular cross sections in the horizontal plane. We have considered the horizontal aspect ratio η=L(y)/L(x)=1 and 2. The onset of the primary and secondary instabilities are strongly suppressed in the presence of the vertical magnetic field for η=1. The Nusselt number Nu scales with the Rayleigh number Ra close to the primary instability as [{Ra-Ra(c)(Q)}/Ra(c)(Q)](0.91), where Ra(c)(Q) is the threshold for onset of stationary convection at a given value of the Chandrasekhar number Q. Nu also scales with Ra/Q as (Ra/Q)(μ). The exponent μ varies in the range 0.39≤μ≤0.57 for Ra/Q≥25. The primary instability is stationary as predicted by Chandrasekhar. The secondary instability is temporally periodic for Pr=0.1 but quasiperiodic for Pr=0.025 for moderate values of Q. Convective patterns for higher values of Ra consist of periodic, quasiperiodic, and chaotic wavy rolls above the onset of the secondary instability for η=1. In addition, stationary as well as time-dependent cross rolls are observed, as Ra is further raised. The ratio r(o)/Pr is independent of Q for smaller values of Q. The delay in the onset of the oscillatory instability is significantly reduced in a simulation box with η=2. We also observe inclined stationary rolls for smaller values of Q for η=2.

Summary of past experience in natural laminar flow and experimental program for resilient leading edge

NASA Technical Reports Server (NTRS)

Carmichael, B. H.

1979-01-01

The potential of natural laminar flow for significant drag reduction and improved efficiency for aircraft is assessed. Past experience with natural laminar flow as reported in published and unpublished data and personal observations of various researchers is summarized. Aspects discussed include surface contour, waviness, and smoothness requirements; noise and vibration effects on boundary layer transition, boundary layer stability criteria; flight experience with natural laminar flow and suction stabilized boundary layers; and propeller slipstream, rain, frost, ice and insect contamination effects on boundary layer transition. The resilient leading edge appears to be a very promising method to prevent leading edge insect contamination.

Hypersonic Boundary-Layer Transition for X-33 Phase 2 Vehicle

NASA Technical Reports Server (NTRS)

Thompson, Richard A.; Hamilton, Harris H., II; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

1998-01-01

A status review of the experimental and computational work performed to support the X-33 program in the area of hypersonic boundary-layer transition is presented. Global transition fronts are visualized using thermographic phosphor measurements. Results are used to derive transition correlations for "smooth body" and discrete roughness data and a computational tool is developed to predict transition onset for X-33 using these results. The X-33 thermal protection system appears to be conservatively designed for transition effects based on these studies. Additional study is needed to address concerns related to surface waviness. A discussion of future test plans is included.

Attributes and origins of ancient submarine slides and filled embayments: examples from the Gulf Coast basin

USGS Publications Warehouse

Morton, Robert

1993-01-01

Submarine slides exhibit landward-dipping, wavy, mounded, and chaotic seismic reflections that are manifestations of slump blocks and other mass transport material. Composition of these internally derived slide deposits depends on the composition of the preexisting shelf margin. Embayment fill above the slide consists mostly of externally derived mudstones and sandstones deposited by various disorganized slope processes, as well as more organized submarine channel-levee systems. Thickest slope sandstones, which are potential hydrocarbon reservoirs, commonly occur above the basal slide mudstones where seismic reflections change from chaotic patterns to overlying wavy or subhorizontal reflections.

Enhancement of surface migration by Mg doping in the metalorganic vapor phase epitaxy of N-polar (000\\bar{1}) GaN/sapphire

NASA Astrophysics Data System (ADS)

Tanikawa, Tomoyuki; Shojiki, Kanako; Aisaka, Takashi; Kimura, Takeshi; Kuboya, Shigeyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi

2014-01-01

With respect to N-polar (000\\bar{1}) GaN grown on a sapphire substrate, the effects of Mg doping on the surface morphology, and the optical, and electrical properties are precisely investigated. By doping Mg, hillocks observed on the surface of (000\\bar{1}) GaN can be suppressed, while step bunching becomes severe. The atomic terrace width is extended with increasing Mg/Ga precursor ratio. Mg doping can promote the surface migration of Ga adatoms on a GaN surface during growth. In the case of heavily Mg-doped GaN, atomic steps become wavy. From photoluminescence spectra, the dominant transition was found to change from near-band-edge transition to donor-acceptor-pair transition. Hall-effect measurement shows p-type conduction at room temperature for a sample grown with the Mg/Ga precursor ratio of 4.5 × 10-3. The activation energy is 143 meV, which is comparable to that of Mg in the conventional Ga-polar (0001) GaN.

About the relevance of waviness, agglomeration, and strain on the electrical behavior of polymer composites filled with carbon nanotubes evaluated by a Monte-Carlo simulation

NASA Astrophysics Data System (ADS)

Román, Sebastián; Lund, Fernando; Bustos, Javier; Palza, Humberto

2018-01-01

In several technological applications, carbon nanotubes (CNT) are added to a polymer matrix in order to develop electrically conductive composite materials upon percolation of the CNT network. This percolation state depends on several parameters such as particle characteristics, degree of dispersion, and filler orientation. For instance, CNT aggregation is currently avoided because it is thought that it will have a negative effect on the electrical behavior despite some experimental evidence showing the contrary. In this study, the effect of CNT waviness, degree of agglomeration, and external strain, on the electrical percolation of polymer composites is studied by a three dimensional Monte-Carlo simulation. The simulation shows that the percolation threshold of CNT depends on the particle waviness, with rigid particles displaying the lowest values. Regarding the effect of CNT dispersion, our numerical results confirm that low levels of agglomeration reduce the percolation threshold of the composite. However, the threshold is shifted to larger values at high agglomeration states because of the appearance of isolated areas of high CNT concentrations. These results imply, therefore, an optimum of agglomeration that further depends on the waviness and concentration of CNT. Significantly, CNT agglomeration can further explain the broad percolation transition found in these systems. When an external strain is applied to the composites, the percolation concentration shifts to higher values because CNT alignment increases the inter-particle distances. The strain sensitivity of the composites is affected by the percolation state of CNT showing a maximum value at certain filler concentration. These results open up the discussion about the relevance in polymer composites of the dispersion state of CNT and filler flexibility towards electrically conductive composites.

Molecular dynamics simulations of the effect of waviness and agglomeration of CNTs on interface strength of thermoset nanocomposites.

PubMed

Alian, A R; Meguid, S A

2017-02-08

Most existing molecular dynamics simulations in nanoreinforced composites assume carbon nanotubes (CNTs) to be straight and uniformly dispersed within thermoplastics. In reality, however, CNTs are typically curved, agglomerated and aggregated as a result of van der Waal interactions and electrostatic forces. In this paper, we account for both curvature and agglomeration of CNTs in extensive molecular dynamic (MD) simulations. The purpose of these simulations is to evaluate the influence of waviness and agglomeration of these curved and agglomerated CNTs on the interfacial strength of thermoset nanocomposite and upon their load transfer capability. Two aspects of the work were accordingly examined. In the first, realistic carbon nanotubes (CNTs) of the same length but varied curvatures were embedded in thermoset polymer composites and simulations of pull-out tests were conducted to evaluate the corresponding interfacial shear strength (ISS). In the second, the effect of the agglomerate size upon the ISS was determined using bundles of CNTs of different diameters. The results of our MD simulations revealed the following. The pull-out force of the curved CNTs is significantly higher than its straight counterpart and increases further with the increase in the waviness of the CNTs. This is attributed to the added pull-out energy dissipated in straightening the CNTs during the pull-out process. It also reveals that agglomeration of CNTs leads to a reduction in the ISS and poor load transferability, and that this reduction is governed by the size of the agglomerate. The simulation results were also used to develop a generalized relation for the ISS that takes into consideration the effect of waviness and agglomeration of CNTs of CNT-polymer composites.

Bistable Vertical-Cavity Surface-Emitting Laser. Structures on GaAs and Si Substrates

DTIC Science & Technology

1994-06-01

vertical - cavity surface - emitting lasers ( VCSELs ) [1,5,6 of publications below], fabrication processes to realize low...May 91 through 1 June 94 R&T Number: Contract / Grant Number: N00014-91-J-1952 Contract / Grant Title: Bistable Vertical - Cavity Surface - Emitting Laser ...T.J. Rogers, B.G. Streetman, S.C. Smith, and R.D. Burnham, "Cascadabity of an Optically Iathing Vertical - Cavity Surface - Emitting Laser

Structure and microhardness of the plasma sprayed composite coatings after combined treatment

NASA Astrophysics Data System (ADS)

Ivannikov, A. Yu; Kalita, V. I.; Komlev, D. I.; Radyuk, A. A.; Bagmutov, V. P.; Zakharov, I. N.; Parshev, S. N.; Denisevich, D. S.

2018-04-01

The principal aim of this study was to evaluate the effect of combination of electromechanical treatment (EMT) and ultrasonic treatment on structure and microhardness of air plasma sprayed composite coatings from Ni–20Cr alloy and R6M5 high speed steel (HSS). The results of the microstructural studies showed fundamental changes of the treated by the EMT plasma sprayed coating with the formation of nanostructured crystalline phases. As a consequence of the coating thus formed, the number of pores in the coating structure reduced from 10.0±1.5% to 2.0±0.5%, the surface microhardness increased from 3100±500 MPa to 7900±400 MPa. Additional ultrasonic treatment on the selected mode decreased surface waviness, which was formed on the surface of the plasma sprayed composite coatings after the EMT. The obtained results revealed the high potential of the combined treatment for post-treatment of the plasma sprayed coatings.

Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics

NASA Astrophysics Data System (ADS)

van Hinsberg, Nils Paul; Charbonneau-Grandmaison, Marie

2015-07-01

The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported.

Laser induced periodic surface structures on pyrolytic carbon prosthetic heart valve

NASA Astrophysics Data System (ADS)

Stepak, Bogusz D.; Łecka, Katarzyna M.; Płonek, Tomasz; Antończak, Arkadiusz J.

2016-12-01

Laser-induced periodic surface structures (LIPSS) can appear in different forms such as ripples, grooves or cones. Those highly periodic wavy surface features which are frequently smaller than incident light wavelength bring possibility of nanostructuring of many different materials. Furthermore, by changing laser parameters one can obtain wide spectrum of periodicities and geometries. The aim of this research was to determine possibility of nanostructuring pyrolytic carbon (PyC) heart valve leaflets using different irradiation conditions. The study was performed using two laser sources with different pulse duration (15 ps, 450 fs) as well as different wavelengths (1064, 532, 355 nm). Both low and high spatial frequency LIPSS were observed for each set of irradiation parameters. In case femtosecond laser pulses we obtained deep subwavelength ripple period which was even ten times smaller than applied wavelength. Obtained ripple period was ranging from 90 up to 860 nm. Raman spectra revealed the increase of disorder after laser irradiation which was comparable for both pico- and femtosecond laser.

Large-Diameter InGaAs/AlGaAs Vertical-Cavity Surface-Emitting Lasers with Low Threshold Current Density Fabricated Using a Simple Chemical Etch Process

DTIC Science & Technology

1994-03-01

Epitaxial structure of vertical cavity surface - emitting laser ( VCSEL ...diameter (75 tum < d< 150 prm) vertical - cavity surface - emitting lasers fabricated from an epitaxial structure containing a single In0 .2Ga 8.,As quantum...development of vertical - cavity surface - emitting lasers ( VCSELs ) [1] has enabled III-V semiconductor technology to be applied to cer- tain optical

Does trampoline or hard surface jumping influence lower extremity alignment?

PubMed

Akasaka, Kiyokazu; Tamura, Akihiro; Katsuta, Aoi; Sagawa, Ayako; Otsudo, Takahiro; Okubo, Yu; Sawada, Yutaka; Hall, Toby

2017-12-01

[Purpose] To determine whether repetitive trampoline or hard surface jumping affects lower extremity alignment on jump landing. [Subjects and Methods] Twenty healthy females participated in this study. All subjects performed a drop vertical jump before and after repeated maximum effort trampoline or hard surface jumping. A three-dimensional motion analysis system and two force plates were used to record lower extremity angles, moments, and vertical ground reaction force during drop vertical jumps. [Results] Knee extensor moment after trampoline jumping was greater than that after hard surface jumping. There were no significant differences between trials in vertical ground reaction force and lower extremity joint angles following each form of exercise. Repeated jumping on a trampoline increased peak vertical ground reaction force, hip extensor, knee extensor moments, and hip adduction angle, while decreasing hip flexion angle during drop vertical jumps. In contrast, repeated jumping on a hard surface increased peak vertical ground reaction force, ankle dorsiflexion angle, and hip extensor moment during drop vertical jumps. [Conclusion] Repeated jumping on the trampoline compared to jumping on a hard surface has different effects on lower limb kinetics and kinematics. Knowledge of these effects may be useful in designing exercise programs for different clinical presentations.

Does trampoline or hard surface jumping influence lower extremity alignment?

PubMed Central

Akasaka, Kiyokazu; Tamura, Akihiro; Katsuta, Aoi; Sagawa, Ayako; Otsudo, Takahiro; Okubo, Yu; Sawada, Yutaka; Hall, Toby

2017-01-01

[Purpose] To determine whether repetitive trampoline or hard surface jumping affects lower extremity alignment on jump landing. [Subjects and Methods] Twenty healthy females participated in this study. All subjects performed a drop vertical jump before and after repeated maximum effort trampoline or hard surface jumping. A three-dimensional motion analysis system and two force plates were used to record lower extremity angles, moments, and vertical ground reaction force during drop vertical jumps. [Results] Knee extensor moment after trampoline jumping was greater than that after hard surface jumping. There were no significant differences between trials in vertical ground reaction force and lower extremity joint angles following each form of exercise. Repeated jumping on a trampoline increased peak vertical ground reaction force, hip extensor, knee extensor moments, and hip adduction angle, while decreasing hip flexion angle during drop vertical jumps. In contrast, repeated jumping on a hard surface increased peak vertical ground reaction force, ankle dorsiflexion angle, and hip extensor moment during drop vertical jumps. [Conclusion] Repeated jumping on the trampoline compared to jumping on a hard surface has different effects on lower limb kinetics and kinematics. Knowledge of these effects may be useful in designing exercise programs for different clinical presentations. PMID:29643592

Wavy-Planform Helicopter Blades Make Less Noise

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.

2004-01-01

Wavy-planform rotor blades for helicopters have been investigated for the first time in an effort to reduce noise. Two of the main sources of helicopter noise are blade/vortex interaction (BVI) and volume displacement. (The noise contributed by volume displacement is termed thickness noise.) The reduction in noise generated by a wavyplanform blade, relative to that generated by an otherwise equivalent straight-planform blade, affects both main sources: (1) the BVI noise is reduced through smoothing and defocusing of the aerodynamic loading on the blade and (2) the thickness noise is reduced by reducing gradients of thickness with respect to listeners on the ground.

On transonic flow past a wave-shaped wall

NASA Technical Reports Server (NTRS)

Kaplan, Carl

1953-01-01

This report is an extension of a previous investigation (described in NACA rep. 1069) concerned with the solution of the nonlinear differential equation for transonic flow past a wavy wall. In the present work several new notions are introduced which permit the solution of the recursion formulas arising from the method of integration in series. In addition, a novel numerical tests of convergence, applied to the power series (in transonic similarity parameter) representing the local Mach number distribution at the boundary, indicates that smooth symmetrical potential flow past the wavy wall is no longer possible once the critical value of the stream Mach number has been exceeded.

Wavy and Cycloidal Lineament Formation on Europa from Combined Diurnal and Nonsynchronous Stresses

NASA Technical Reports Server (NTRS)

Gleeson, Damhnait; Crawford, Zane; Barr, Amy C.; Mullen, McCall; Pappalardo, Robert T.; Prockter, Louise M.; Stempel, Michelle M.; Wahr, John

2005-01-01

In a companion abstract, we show that fractures propagated into combined diurnal and nonsynchronous rotation (NSR) stress fields can be cycloidal, "wavy," or arcuate in planform as the relative proportion of NSR stress in increased. These transitions occur as NSR stress accumulates over approx. 0 to 10 deg of ice shell rotation, for average fracture propagation speeds of approx. 1 to 3 m/s. Here we consider the NSR speed parameter space for these morphological transitions, and explore the effects on cycloids of adding NSR to diurnal stress. Fitting individual Europan lineaments can constrain the combined NSR plus diurnal stress field at the time of formation.

MHD natural convection of hybrid nanofluid in an open wavy cavity

NASA Astrophysics Data System (ADS)

Ashorynejad, Hamid Reza; Shahriari, Alireza

2018-06-01

In this paper, natural convection heat transfer of Al2O3-Cu/water hybrid nanofluid within open wavy cavity and subjected to a uniform magnetic field is examined by adopting the lattice Boltzmann method scheme. The left wavy wall is heated sinusoidal, while the right wall is open and maintained to the ambient conditions. The top and the bottom horizontal walls are smooth and insulated against heat and mass. The influence of solid volume fraction of nanoparticles (φ = 0, 0.02, 0.04), Rayleigh number (Ra = 103, 104, 105), Hartmann number (Ha = 0, 30, 60, 90) and phase deviation (Φ = 0, π/4, π/2, 3π/4) are investigated on flow and heat transfer fields. The results proved that the Nusselt number decreases with the increase of the Hartmann number, but it increases by the increment of Rayleigh number and nanoparticle volume fraction. The magnetic field rises or falls the effect produced by the presence of nanoparticles with respect to Rayleigh number. At Ra = 103, the effect of the raising phase deviation on heat transfer is erratic while it has a positive role in the improvement of nanoparticles effect at Ra = 105.

Experimental investigation of wavy leading edges on rod-aerofoil interaction noise

NASA Astrophysics Data System (ADS)

Chen, Weijie; Qiao, Weiyang; Tong, Fan; Wang, Liangfeng; Wang, Xunnian

2018-05-01

Experimental studies are performed to investigate the effect of wavy leading edges on rod-aerofoil interaction noise in an open-jet anechoic wind tunnel. NACA 0012 aerofoils with straight and wavy leading edges (denoted by SLE and WLE, respectively) are embedded in the wake of a circular rod. The WLEs are in the form of sinusoidal profiles of amplitude, A, and wavelength, W. Parametric studies of the amplitude and wavelength characteristics are conducted to understand the effect of WLEs on noise reduction. It is observed that the sound power reduction level is sensitive to both the amplitude and wavelength of the WLEs. The WLE with the largest amplitude and smallest wavelength can achieve the most considerable noise reduction effect of up to 4 dB. The influences of rod diameter, d, and free-stream velocity, U0, on the noise reduction effect of the WLEs are also investigated. In addition, a parametric study of the influence of separating rod-aerofoil distance on the acoustic radiation of the SLE case and on the sound power reduction level of the WLE cases is performed. It is found that a critical spacing exists where the acoustic radiation and noise reduction can be divided into two different "modes".

A note on flow reversal in a wavy channel filled with anisotropic porous material

NASA Astrophysics Data System (ADS)

Karmakar, Timir; Raja Sekhar, G. P.

2017-07-01

Viscous flow through a symmetric wavy channel filled with anisotropic porous material is investigated analytically. Flow inside the porous bed is assumed to be governed by the anisotropic Brinkman equation. It is assumed that the ratio of the channel width to the wavelength is small (i.e. δ2≪1). The problem is solved up to O(δ2) assuming that δ2λ2≪1, where λ is the anisotropic ratio. The key purpose of this paper is to study the effect of anisotropic permeability on flow near the crests of the wavy channel which causes flow reversal. We present a detailed analysis of the flow reversal at the crests. The ratio of the permeabilities (anisotropic ratio) is responsible for the flow separation near the crests of the wall where viscous forces are effective. For a flow configuration (say, low amplitude parameter) in which there is no separation if the porous media is isotropic, introducing anisotropy causes flow separation. On the other hand, interestingly, flow separation occurs even in the case of isotropic porous medium if the amplitude parameter a is large.

A Comparative Rugoscopic Study of the Dentate and Edentulous Individuals in the South Indian Population

PubMed Central

Rajguru, Jagdish Prasad; Somayaji, Nagaveni S.; Masthan, K. M. K.; Babu, Aravindha N.; Mohanty, Neeta

2014-01-01

This study analyzes the rugae pattern in dentulous and edentulous patients and also evaluates the association of rugae pattern between males and females. Aims and Objectives. This study aims to investigate rugae patterns in dentulous and edentulous patients of both sexes in South Indian population and to find whether palatoscopy is a useful tool in human identification. Materials and Methods. Four hundred outpatients from Sree Balaji Dental College and Hospital, Chennai, were included in the study. The study group was equally divided between the sexes, which was further categorized into 100 dentulous and edentulous patients, respectively. Results. The edentulous male showed the highest mean of wavy pattern and total absence of circular pattern while the edentulous female group showed the highest mean of curved pattern and total absence of nonspecific pattern, while dentate population showed similar value as that of the overall population such as straight, wavy, and curved patterns. Conclusion. The present study concludes that there is similar rugae pattern of distribution between male and female dentate population while there is varied pattern between the sexes of edentulous population. However, the most predominant patterns were straight, wavy, and circular patterns. PMID:24605051

Stretchable interconnections for flexible electronic systems.

PubMed

Jianhui, Lin; Bing, Yan; Xiaoming, Wu; Tianling, Ren; Litian, Liu

2009-01-01

Sensors, actuators and integrated circuits (IC) can be encapsulated together on an elastic substrate, which makes a flexible electronic system. In this system, electrical interconnections that can sustain large and reversible stretching are in great need. This paper is devoted to the fabrication of highly stretchable metal interconnections. Transfer printing technology is utilized, which mainly involves the transfer of 100-nm-thick gold ribbons from silicon wafers to pre-stretched elastic substrates. After the elastic substrates relax from the pre-strain, the gold ribbons buckle and form wavy geometries. These wavy geometries change in shapes to accommodate the applied strain and can be reversely stretched without cracks or fractures occurring, which will greatly raise the stretchability of the gold ribbons. As an application example, some of these wavy ribbons can accommodate high levels of stretching (up to 100%) and bending (with curvature radius down to 1.20 mm). Moreover, the efficiency and reliability of the transfer, especially for slender ribbons, have been increased due to the improvement of the technology. All the characteristics above will permit making stretchable gold conductors as interconnections for flexible electronic systems such as implantable medical systems and smart clothes.

Preliminary SEM Observations on the Surface of Elastomeric Impression Materials after Immersion or Ozone Disinfection

PubMed Central

Prombonas, Anthony; Yannikakis, Stavros; Karampotsos, Thanasis; Katsarou, Martha-Spyridoula; Drakoulis, Nikolaos

2016-01-01

Introduction Surface integrity of dental elastomeric impression materials that are subjected to disinfection is of major importance for the quality of the final prosthetic restorations. Aim The aim of this qualitative Scanning Electronic Microscopy (SEM) study was to reveal the effects of immersion or ozone disinfection on the surface of four dental elastomeric impression materials. Materials and Methods Four dental elastomeric impression material brands were used (two vinyl polysiloxane silicones, one polyether, and one vinyl polyether silicone). Total of 32 specimens were fabricated, eight from each impression material. Specimens were immersion (0.525% sodium hypochlorite solution or 0.3% benzalkonium chloride solution) or ozone disinfected or served as controls and examined with SEM. Results Surface degradation was observed on several speci-mens disinfected with 0.525% sodium hypochlorite solution. Similar wavy-wrinkling surface structures were observed in almost all specimens, when treated either with 0.3% benzalkonium chloride solution or ozone. Conclusion The SEM images obtained from this study revealed that both immersion disinfectants and ozone show similar impression material surface alterations. Ozone seems to be non-inferior as compared to immersion disinfectants, but superior as to environmental protection. PMID:28208993

Surface tension profiles in vertical soap films

NASA Astrophysics Data System (ADS)

Adami, N.; Caps, H.

2015-01-01

Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed by introducing deformable elastic objets in the films. The shape adopted by those objects once set in the film is related to the surface tension value at a given vertical position by numerically solving the adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position is predicted by simple modeling that takes into account the mechanical equilibrium of the films coupled to previous thickness measurements.

Optimization of Surface Roughness and Wall Thickness in Dieless Incremental Forming Of Aluminum Sheet Using Taguchi

NASA Astrophysics Data System (ADS)

Hamedon, Zamzuri; Kuang, Shea Cheng; Jaafar, Hasnulhadi; Azhari, Azmir

2018-03-01

Incremental sheet forming is a versatile sheet metal forming process where a sheet metal is formed into its final shape by a series of localized deformation without a specialised die. However, it still has many shortcomings that need to be overcome such as geometric accuracy, surface roughness, formability, forming speed, and so on. This project focus on minimising the surface roughness of aluminium sheet and improving its thickness uniformity in incremental sheet forming via optimisation of wall angle, feed rate, and step size. Besides, the effect of wall angle, feed rate, and step size to the surface roughness and thickness uniformity of aluminium sheet was investigated in this project. From the results, it was observed that surface roughness and thickness uniformity were inversely varied due to the formation of surface waviness. Increase in feed rate and decrease in step size will produce a lower surface roughness, while uniform thickness reduction was obtained by reducing the wall angle and step size. By using Taguchi analysis, the optimum parameters for minimum surface roughness and uniform thickness reduction of aluminium sheet were determined. The finding of this project helps to reduce the time in optimising the surface roughness and thickness uniformity in incremental sheet forming.

Natural laminar flow hits smoother air

NASA Technical Reports Server (NTRS)

Holmes, B. J.

1985-01-01

Natural laminar flow (NLF) may be attained in aircraft with lower cost, weight, and maintenance penalties than active flow laminarization by means of a slot suction system. A high performance general aviation jet aircraft possessing a moderate degree of NLF over wing, fuselage, empennage and engine nacelles will accrue a 24 percent reduction in total aircraft drag in the cruise regime. NASA-Langley has conducted NLF research centered on the use of novel airfoil profiles as well as composite and milled aluminum alloy construction methods which minimize three-dimensional aerodynamic surface roughness and waviness. It is noted that higher flight altitudes intrinsically reduce unit Reynolds numbers, thereby minimizing turbulence for a given cruise speed.

Collagen fibril arrangement and size distribution in monkey oral mucosa

PubMed Central

OTTANI, V.; FRANCHI, M.; DE PASQUALE, V.; LEONARDI, L.; MOROCUTTI, M.; RUGGERI, A.

1998-01-01

Collagen fibre organisation and fibril size were studied in the buccal gingival and hard palate mucosa of Macacus rhesus monkey. Light and electron microscopy analysis showed connective papillae exhibiting a similar inner structure in the different areas examined, but varying in distribution, shape and size. Moving from the deep to surface layers of the buccal gingival mucosa (free and attached portions), large collagen fibril bundles became smaller and progressively more wavy with decreasing collagen fibril diameter. This gradual diameter decrease did not occur in the hard palate mucosa (free portion, rugae and interrugal regions) where the fibril diameter remained constant. A link between collagen fibril diameter and mechanical function is discussed. PMID:9688498

Optical assessment of nonimaging concentrators.

PubMed

Timinger, A; Kribus, A; Ries, H; Smith, T; Walther, M

2000-11-01

An optical measurement method for nonimaging radiation concentrators is proposed. A Lambertian light source is placed in the exit aperture of the concentrator. Looking into the concentrator's entrance aperture from a remote position, one can photograph the transmission patterns. The patterns show the transmission of radiation through the concentrator with the full resolution of the four-dimensional phase space of geometric optics. By matching ray-tracing simulations to the measurement, one can achieve detailed and accurate information about the geometry of the concentrator. This is a remote, noncontact measurement and can be performed in situ for installed concentrators. Additional information regarding small-scale reflector waviness and surface reflectivity can also be obtained from the same measurement with additional analysis.

Buckling analysis of stiff thin films suspended on a substrate with tripod surface relief structure

NASA Astrophysics Data System (ADS)

Yu, Qingmin; Chen, Furong; Li, Ming; Cheng, Huanyu

2017-09-01

A wavy configuration is a simple yet powerful structural design strategy, which has been widely used in flexible and stretchable electronics. A buckled structure created from a prestretch-contact-release process represents an early effort. Substrates with engineered surface relief structures (e.g., rectangular islands or tripod structure) have enabled stretchability to the devices without sacrificing their electric performance (e.g., high areal coverage for LEDs/photovoltaics/batteries/supercapacitors). In particular, the substrate with a tripod surface relief structure allows wrinkled devices to be suspended on a soft tripod substrate. This minimizes the contact area between devices and the deformed substrate, which contributes to a significantly reduced interfacial stress/strain. To uncover the underlying mechanism of such a design, we exploit the energy method to analytically investigate the buckling and postbuckling behaviors of stiff films suspended on a stretchable polymeric substrate with a tripod surface relief structure. Validated by finite element analysis, the predications from such an analytical study elucidate the deformed profile and maximum strain in the buckled and postbuckled stiff thin device films, providing a useful toolkit for future experimental designs.

Analysis of enamel rod end patterns on tooth surface for personal identification--ameloglyphics.

PubMed

Manjunath, Krishnappa; Sivapathasundharam, Balasundharam; Saraswathi, Thillai R

2012-05-01

Ameloglyphics is the study of enamel rod end patterns on a tooth surface. Our aim was to study the in vivo analysis of enamel rod end patterns on tooth surfaces for personal identification. In this study, the maxillary left canine and 1st premolar of 30 men and 30 women were included. The cellulose acetate peel technique was used to record enamel rod endings on tooth surfaces. Photomicrographs of the acetate peel imprint were subjected to VeriFinger Standard SDK v5.0 software for obtaining enamel rod end patterns. All 120 enamel rod end patterns were subjected to visual analysis and biometric analysis. Biometric analysis revealed that the enamel rod end pattern is unique for each tooth in an individual. It shows both intra- and interindividual variation. Enamel rod end patterns were unique between the male and female subjects. Visual analysis showed that wavy branched subpattern was the predominant subpattern observed among examined teeth. Hence, ameloglyphics is a reliable technique for personal identification. © 2012 American Academy of Forensic Sciences.

Measurement of the residual stress in hot rolled strip using strain gauge method

NASA Astrophysics Data System (ADS)

Kumar, Lokendra; Majumdar, Shrabani; Sahu, Raj Kumar

2017-07-01

Measurement of the surface residual stress in a flat hot rolled steel strip using strain gauge method is considered in this paper. Residual stresses arise in the flat strips when the shear cut and laser cut is applied. Bending, twisting, central buckled and edge waviness is the common defects occur during the cutting and uncoiling process. These defects arise due to the non-uniform elastic-plastic deformation, phase transformation occurring during cooling and coiling-uncoiling process. The residual stress analysis is very important because with early detection it is possible to prevent an object from failure. The goal of this paper is to measure the surface residual stress in flat hot rolled strip using strain gauge method. The residual stress was measured in the head and tail end of hot rolled strip considering as a critical part of the strip.

Spreading of triboelectrically charged granular matter

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Sane, A.; Gohil, Smita.; Bandaru, P. R.; Bhattacharya, S.; Ghosh, Shankar

2014-06-01

We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures.

Characterization of low thermal conductivity PAN-based carbon fibers

NASA Technical Reports Server (NTRS)

Katzman, Howard A.; Adams, P. M.; Le, T. D.; Hemminger, Carl S.

1992-01-01

The microstructure and surface chemistry of eight low thermal conductivity (LTC) PAN-based carbon fibers were determined and compared with PAN-based fibers heat treated to higher temperatures. Based on wide-angle x ray diffraction, the LTC PAN fibers all appear to have a similar turbostratic structure with large 002 d-spacings, small crystallite sizes, and moderate preferred orientation. Limited small-angle x ray scattering (SAXS) results indicate that, with the exception of LTC fibers made by BASF, the LTC fibers do not have well developed pores. Transmission electron microscopy shows that the texture of the two LTC PAN-based fibers studied (Amoco T350/23X and /25X) consists of multiple sets of parallel, wavy, bent layers that interweave with each other forming a complex three dimensional network oriented randomly around the fiber axis. X ray photoelectron spectroscopy (XPS) analysis finds correlations between heat treated temperatures and the surface composition chemistry of the carbon fiber samples.

Analyzing and Post-modelling the High Speed Images of a Wavy Laser Induced Boiling Front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

The boiling front in laser materials processing like remote fusion cutting, keyhole welding or drilling can nowadays be recorded by high speed imaging. It was recently observed that bright waves flow down the front. Several complex physical mechanisms are associated with a stable laser-induced boiling front, like beam absorption, shadowing, heating, ablation pressure, fluid flow, etc. The evidence of dynamic phenomena from high speed imaging is closely linked to these phenomena. As a first step, the directly visible phenomena were classified and analyzed. This has led to the insight that the appearance of steady flow of the bright front peaks is a composition of many short flashing events of 20-50 μs duration, though composing a rather constant melt film flow downwards. Five geometrical front shapes of bright and dark domains were categorized, for example long inclined dark valleys. In addition, the special top and bottom regions of the front are distinguished. As a second step, a new method of post-modelling based on the greyscale variation of the images was applied, to approximately reconstruct the topology of the wavy front and subsequently to calculate the absorption across the front. Despite certain simplifications this kind of analysis provides a variety of additional information, including statistical analysis. In particular, the model could show the sensitivity of front waves to the formation of shadow domains and the robustness of fiber lasers to keep most of an irradiated steel surface in an absorptivity window between 35 to 43%.

Histological study of some Echium vulgare, Pulmonaria officinalis and Symphytum officinale populations.

PubMed

Papp, Nóra; Bencsik, Tímea; Németh, Kitti; Gyergyák, Kinga; Sulc, Alexandra; Farkas, Agnes

2011-10-01

Plants living in different ecological habitats can show significant variability in their histological and phytochemical characters. The main histological features of various populations of three medicinal plants from the Boraginaceae family were studied. Stems, petioles and leaves were investigated by light microscopy in vertical and transverse sections. The outline of the epidermal cells, as well as the shape and cell number of trichomes was studied in leaf surface casts. Differences were measured among the populations of Echium vulgare in the width and height of epidermis cells in the stem, petiole and leaf, as well as in the size of palisade cells in the leaves. Among the populations of Pulmonaria officinalis significant differences were found in the length of trichomes and in the slightly or strongly wavy outline of epidermal radial cell walls. Populations of Symphytum officinale showed variance in the height of epidermal cells in leaves and stems, length of palisade cells and number of intercellular spaces in leaves, and the size of the central cavity in the stem. Boraginaceae bristles were found to be longer in plants in windy/shady habitats as opposed to sunny habitats, both in the leaves and stems ofP. officinalis and S. officinale, which might be connected to varying levels of exposure to wind. Longer epidermal cells were detected in the leaves and stems of both E. vulgare and S. officinale plants living in shady habitats, compared with shorter cells in sunny habitats. Leaf mesophyll cells were shorter in shady habitats as opposed to longer cells in sunny habitats, both in E. vulgare and S. officinale. This combination of histological characters may contribute to the plant's adaptation to various amounts of sunshine. The reported data prove the polymorphism of the studied taxa, as well as their ability to adapt to various ecological circumstances.

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials.

PubMed

Chun, Hyungphil; Dybtsev, Danil N; Kim, Hyunuk; Kim, Kimoon

2005-06-06

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.

Numerical and Experimental Studies on the Explosive Welding of Tungsten Foil to Copper

PubMed Central

Zhou, Qiang; Feng, Jianrui; Chen, Pengwan

2017-01-01

This work verifies that the W foil could be successfully welded on Cu through conventional explosive welding, without any cracks. The microstructure was observed through scanning electron microscopy (SEM), optical microscopy and energy-dispersive X-ray spectrometry (EDS). The W/Cu interface exhibited a wavy morphology, and no intermetallic or transition layer was observed. The wavy interface formation, as well as the distributions of temperature, pressure and plastic strain at the interface were studied through numerical simulation with Smoothed Particle Hydrodynamics (SPH). The welding mechanism of W/Cu was analyzed according to the numerical results and experimental observation, which was in accordance with the indentation mechanism proposed by Bahrani. PMID:28832527

Study of heat exchange in cooling systems of heat-stressed structures

NASA Astrophysics Data System (ADS)

Vikulin, A. V.; Yaroslavtsev, N. L.; Zemlyanaya, V. A.

2017-01-01

Increasing working parameters of the cycle of gas-turbine engines, complicating design of gas-turbine plants, as well as growing aerodynamic, thermal, static, and dynamic loads, necessitate the development of promising cooling systems for heat-stressed structures. This work is devoted to an experimental study of heat exchange in ducts equipped with systems of inclined and cross walls (fins). It has been found that an increase in the Reynolds number Re from 3000 to 20000 leads to a decrease in the heat exchange, which is characterized by the relative Nusselt number overline{Nu}, by 19-30% at the angle of inclination of the walls φ = 0, 40°, 50°, and 90° if the length of the walls x w is comparable to the spacing b s and by 12-15% at φ = 30° and 90° if x w ≫ b s. If cross walls are used in cooling ducts, the length of the walls x w plays the governing role; an increase in this characteristic from 1.22 × 10-3 to 3.14 × 10-3 m leads to an increase in the intensity of heat exchange by 30-40% and to a decrease in the capacity of the entire system of the walls. It has been shown that, on surfaces with wavy fins, the intensity of heat exchange is closest to that determined in the models under study. For example, values of the Colborne criterion StPr2/3 for ducts equipped with wavy fins and for the models under study differ only slightly (by 2-20% depending on the value of the angle φ). However, the difference for surfaces with short plate fins and ducts equipped with inclined walls is high (30-40%). This is due to the design features of these surfaces and to the severe effect of the inlet portion on heat exchange, since the surfaces are characterized by a higher ratio of the duct length to the hydraulic diameter L/d h at small fin thicknesses ((0.1-0.15) × 10-3 m). The experimental results can be used in developing designs of nozzle and rotor blades of high-temperature gas turbines in gas-turbine engines and plants.

14 CFR 23.443 - Gust loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Vertical Surfaces § 23.443 Gust loads. (a) Vertical surfaces must be designed to withstand, in unaccelerated flight at speed V C... computed as follows: ER09FE96.000 Where— Lvt=Vertical surface loads (lbs.); ER09FE96.001 ER09FE96.002 Ude...

14 CFR 23.443 - Gust loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Vertical Surfaces § 23.443 Gust loads. (a) Vertical surfaces must be designed to withstand, in unaccelerated flight at speed V C... computed as follows: ER09FE96.000 Where— Lvt=Vertical surface loads (lbs.); ER09FE96.001 ER09FE96.002 Ude...

14 CFR 23.443 - Gust loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Vertical Surfaces § 23.443 Gust loads. (a) Vertical surfaces must be designed to withstand, in unaccelerated flight at speed V C... computed as follows: ER09FE96.000 Where— Lvt=Vertical surface loads (lbs.); ER09FE96.001 ER09FE96.002 Ude...

14 CFR 23.443 - Gust loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Vertical Surfaces § 23.443 Gust loads. (a) Vertical surfaces must be designed to withstand, in unaccelerated flight at speed V C... computed as follows: ER09FE96.000 Where— Lvt=Vertical surface loads (lbs.); ER09FE96.001 ER09FE96.002 Ude...

14 CFR 23.443 - Gust loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Vertical Surfaces § 23.443 Gust loads. (a) Vertical surfaces must be designed to withstand, in unaccelerated flight at speed V C... computed as follows: ER09FE96.000 Where— Lvt=Vertical surface loads (lbs.); ER09FE96.001 ER09FE96.002 Ude...

49 CFR 571.10 - Designation of seating positions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... maximum width of a seating surface measured in a zone extending from a transverse vertical plane 150 mm (5.9 inches) behind the front leading surface of that seating surface to a transverse vertical plane... (5.5 inches), as measured in each transverse vertical plane within that measurement zone, or (B) A...

Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

DOEpatents

Bryan, R.P.; Esherick, P.; Jewell, J.L.; Lear, K.L.; Olbright, G.R.

1997-04-29

A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications. 9 figs.

Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

DOEpatents

Bryan, Robert P.; Esherick, Peter; Jewell, Jack L.; Lear, Kevin L.; Olbright, Gregory R.

1997-01-01

A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications.

Reduction of Surface Errors over a Wide Range of Spatial Frequencies Using a Combination of Electrolytic In-Process Dressing Grinding and Magnetorheological Finishing

NASA Astrophysics Data System (ADS)

Kunimura, Shinsuke; Ohmori, Hitoshi

We present a rapid process for producing flat and smooth surfaces. In this technical note, a fabrication result of a carbon mirror is shown. Electrolytic in-process dressing (ELID) grinding with a metal bonded abrasive wheel, then a metal-resin bonded abrasive wheel, followed by a conductive rubber bonded abrasive wheel, and finally magnetorheological finishing (MRF) were performed as the first, second, third, and final steps, respectively in this process. Flatness over the whole surface was improved by performing the first and second steps. After the third step, peak to valley (PV) and root mean square (rms) values in an area of 0.72 x 0.54 mm2 on the surface were improved. These values were further improved after the final step, and a PV value of 10 nm and an rms value of 1 nm were obtained. Form errors and small surface irregularities such as surface waviness and micro roughness were efficiently reduced by performing ELID grinding using the above three kinds of abrasive wheels because of the high removal rate of ELID grinding, and residual small irregularities were reduced by short time MRF. This process makes it possible to produce flat and smooth surfaces in several hours.

Effects of Blank Curvature and Tool Conditions on the Spring Back of Thin Sheet Panel Formed through Local Embossing and Edge L-Bending

NASA Astrophysics Data System (ADS)

Park, Keecheol; Park, Jongyoun; Nam, Jaebok

2011-08-01

Due to the application of thinner sheet steels, the stamped panels in the forming process, generally, are severely distorted. The wavy shape of embossed panel finally converted to residual stress embedded in the panel at final forming (edge L-bending) and it is known as the cause of twisting and oil canning of spring backed panel. Another important source of stamped shape deviation is the curvature of blank. The effects of blank curvature on the shape defects (panel curvature and twisting) after stamping were investigated from defective panel analysis, model experiment and stamping simulation. And the effect of tool conditions (BHF and bead height change) on spring backed shape of real TV bottom chassis were studied. The initial curvature of blank was remained in the flat area of stamped panels as width directional curvature. It converted from length direction curvature of blank. The curvature of initial blank reduced the wavy shape after local emboss forming, but twisting after edge L-bending was increased at large blank curvature cases. The effects of emboss forming conditions, the forming heights and blank holding force were studied and it was found that the wavy shape of stamped sheet was rapidly changed although the forming conditions altered very small amount.

Investigation of Interface Bonding Mechanism of an Explosively Welded Tri-Metal Titanium/Aluminum/Magnesium Plate by Nanoindentation

NASA Astrophysics Data System (ADS)

Zhang, T. T.; Wang, W. X.; Zhou, J.; Cao, X. Q.; Yan, Z. F.; Wei, Y.; Zhang, W.

2018-04-01

A tri-metal titanium/aluminum/magnesium (Ti/Al/Mg) cladding plate, with an aluminum alloy interlayer plate, was fabricated for the first time by explosive welding. Nanoindentation tests and associated microstructure analysis were conducted to investigate the interface bonding mechanisms of the Ti/Al/Mg cladding plate. A periodic wavy bonding interface (with an amplitude of approximately 30 μm and a wavelength of approximately 160 μm) without a molten zone was formed between the Ti and Al plates. The bonding interface between the Al and the Mg demonstrated a similar wavy shape, but the wave at this location was much larger with an amplitude of approximately 390 μm and a wavelength of approximately 1580 μm, and some localized melted zones also existed at this location. The formation of the wavy interface was found to result from a severe deformation at the interface, which was caused by the strong impact or collision. The nanoindentation tests showed that the material hardness decreased with increasing distance from the bonding interface. Material hardness at a location was found to be correlated with the degree of plastic deformation at that site. A larger plastic deformation was correlated with an increase in hardness.

Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system

PubMed Central

Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

2015-01-01

We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638

Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system.

PubMed

Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

2015-12-21

We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices.

Massive formation of square array junctions dramatically alters cell shape but does not cause lens opacity in the cav1-KO mice.

PubMed

Biswas, Sondip K; Brako, Lawrence; Lo, Woo-Kuen

2014-08-01

The wavy square array junctions are composed of truncated aquaporin-0 (AQP0) proteins typically distributed in the deep cortical and nuclear fibers in wild-type lenses. These junctions may help maintain the narrowed extracellular spaces between fiber cells to minimize light scattering. Herein, we investigate the impact of the cell shape changes, due to abnormal formation of extensive square array junctions, on the lens opacification in the caveolin-1 knockout mice. The cav1-KO and wild-type mice at age 1-22 months were used. By light microscopy examinations, cav1-KO lenses at age 1-18 months were transparent in both cortical and nuclear regions, whereas some lenses older than 18 months old exhibited nuclear cataracts. Scanning EM consistently observed the massive formation of ridge-and-valley membrane surfaces in young fibers at approximately 150 μm deep in all cav1-KO lenses studied. In contrast, the typical ridge-and-valleys were only seen in mature fibers deeper than 400 μm in wild-type lenses. The resulting extensive ridge-and-valleys dramatically altered the overall cell shape in cav1-KO lenses. Remarkably, despite dramatic shape changes, these deformed fiber cells remained intact and made close contact with their neighboring cells. By freeze-fracture TEM, ridge-and-valleys exhibited the typical orthogonal arrangement of 6.6 nm square array intramembrane particles and displayed the narrowed extracellular spaces. Immunofluorescence analysis showed that AQP0 C-terminus labeling was significantly decreased in outer cortical fibers in cav1-KO lenses. However, freeze-fracture immunogold labeling showed that the AQP0 C-terminus antibody was sparsely distributed on the wavy square array junctions, suggesting that the cleavage of AQP0 C-termini might not yet be complete. The cav1-KO lenses with nuclear cataracts showed complete cellular breakdown and large globule formation in the lens nucleus. This study suggests that despite dramatic cell shape changes, the massive formation of wavy square array junctions in intact fibers may provide additional adhesive support for maintaining the narrowed extracellular spaces that are crucial for the transparency of cav1-KO lenses. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fabrication of precision high quality facets on molecular beam epitaxy material

DOEpatents

Petersen, Holly E.; Goward, William D.; Dijaili, Sol P.

2001-01-01

Fabricating mirrored vertical surfaces on semiconductor layered material grown by molecular beam epitaxy (MBE). Low energy chemically assisted ion beam etching (CAIBE) is employed to prepare mirrored vertical surfaces on MBE-grown III-V materials under unusually low concentrations of oxygen in evacuated etching atmospheres of chlorine and xenon ion beams. UV-stabilized smooth-surfaced photoresist materials contribute to highly vertical, high quality mirrored surfaces during the etching.

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

NASA Astrophysics Data System (ADS)

Anderson, William; Meneveau, Charles

2010-05-01

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

Vibration analysis of paper machine's asymmetric tube roll supported by spherical roller bearings

NASA Astrophysics Data System (ADS)

Heikkinen, Janne E.; Ghalamchi, Behnam; Viitala, Raine; Sopanen, Jussi; Juhanko, Jari; Mikkola, Aki; Kuosmanen, Petri

2018-05-01

This paper presents a simulation method that is used to study subcritical vibrations of a tube roll in a paper machine. This study employs asymmetric 3D beam elements based on the Timoshenko beam theory. An asymmetric beam model accounts for varying stiffness and mass distributions. Additionally, a detailed rolling element bearing model defines the excitations arising from the set of spherical roller bearings at both ends of the rotor. The results obtained from the simulation model are compared against the results from the measurements. The results indicate that the waviness of the bearing rolling surfaces contributes significantly to the subcritical vibrations while the asymmetric properties of the tube roll have only a fractional effect on the studied vibrations.

Regional difference of the vertical structure of seasonal thermocline and its impact on sea surface temperature in the North Pacific

NASA Astrophysics Data System (ADS)

Yamaguchi, R.; Suga, T.

2016-12-01

Recent observational studies show that, during the warming season, a large amount of heat flux is penetrated through the base of thin mixed layer by vertical eddy diffusion, in addition to penetration of solar radiation [1]. In order to understand this heat penetration process due to vertical eddy diffusivity and its contribution to seasonal variation of sea surface temperature, we investigated the evolution of thermal stratification below the summertime thin mixed layer (i.e. evolution of seasonal thermocline) and its vertical structure in the North Pacific using high vertical resolution temperature profile observed by Argo floats. We quantified the vertical structure of seasonal thermocline as deviations from the linear structure where the vertical gradient of temperature is constant, that is, "shape anomaly". The shape anomaly is variable representing the extent of the bend of temperature profiles. We found that there are larger values of shape anomaly in the region where the seasonal sea surface temperature warming is relatively faster. To understand the regional difference of shape anomalies, we investigated the relationship between time changes in shape anomalies and net surface heat flux and surface kinetic energy flux. From May to July, the analysis indicated that, in a large part of North Pacific, there's a tendency for shape anomalies to develop strongly (weakly) under the conditions of large (small) downward net surface heat flux and small (large) downward surface kinetic energy flux. Since weak (strong) development of shape anomalies means efficient (inefficient) downward heat transport from the surface, these results suggest that the regional difference of the downward heat penetration below mixed layer is explained reasonably well by differences in surface heat forcing and surface wind forcing in a vertical one dimensional framework. [1] Hosoda et al. (2015), J. Oceanogr., 71, 541-556.

Coda-wave and ambient noise interferometry using an offset vertical array at Iwanuma site, northeast Japan

NASA Astrophysics Data System (ADS)

Minami, K.; Yamamoto, M.; Nishimura, T.; Nakahara, H.; Shiomi, K.

2013-12-01

Seismic interferometry using vertical borehole arrays is a powerful tool to estimate the shallow subsurface structure and its time lapse changes. However, the wave fields surrounding borehole arrays are non-isotropic due to the existence of ground surface and non-uniform distribution of sources, and do not meet the requirements of the seismic interferometry in a strict sense. In this study, to examine differences between wave fields of coda waves and ambient noise, and to estimate their effects on the results of seismic interferometry, we conducted a temporal seismic experiment using zero-offset and offset vertical arrays. We installed two 3-components seismometers (hereafter called Surface1 and Surface2) at the ground surface in the vicinity of NIED Iwanuma site (Miyagi Pref., Japan). Surface1 is placed just above the Hi-net downhole seismometer whose depth is 101 m, and Surface2 is placed 70 m away from Surface1. To extract the wave propagation between these 3 seismometers, we compute the cross-correlation functions (CCFs) of coda-wave and ambient noise for each pair of the zero-offset vertical (Hi-net-Surface1), finite-offset vertical (Hi-net-Surface2), and horizontal (Surface1-Surface2) arrays. We use the frequency bands of 4-8, 8-16 Hz in the CCF computation. The characteristics of obtained CCFs are summarized as follows; (1) in all frequency bands, the peak lag times of CCFs from coda waves are almost the same between the vertical and offset-vertical arrays irrespective of different inter-station distance, and those for the horizontal array are around 0 s. (2) the peak lag times of CCFs from ambient noise show slight differences, that is, those obtained from the vertical array are earlier than those from the offset-vertical array, and those from the horizontal array are around 0.05 s. (3) the peak lag times of CCFs for the vertical array obtained from ambient noise analyses are earlier than those from the coda-wave analyses. These results indicate that wave fields of coda-wave are mainly composed of vertically propagating waves, while those of ambient noise are composed of both vertically and horizontally propagating waves. To explain these characteristics of the CCFs obtained from different wave fields, we conducted a numerical simulation of interferometry based on the concept of stationary phase. Here, we assume isotropic upward incidence of SV-wave into a homogeneous half-space, and compute CCFs for the zero-offset and finite-offset vertical arrays by taking into account the reflection and conversion of P-SV waves at the free surface. Due to the effectively non-isotropic wave field, the simulated CCF for the zero-offset vertical array shows slight delay in peak lag time and its amplitudes decrease in the acausal part. On the other hand, the simulated CCF for finite-offset vertical array shows amplitude decrease and no peak lag time shift. These results are consistent with the difference in peak lag times obtained from coda-wave and ambient noise analyses. Our observations and theoretical consideration suggest that the careful consideration of wave fields is important in the application of seismic interferometry to borehole array data.

Low Threshold Voltage Continuous Wave Vertical-Cavity Surface-Emitting Lasers

DTIC Science & Technology

1993-04-26

Data are presented demonstrating a design and fabrication process for the realization of low- threshold , high-output vertical-cavity surface-emitting...layers), the low series resistance of the design results in a bias voltage on o 1.8 V at a threshold current of 1.9 mA for 10-micrometer-diam devices.... Vertical-cavity surface-emitting lasers.

Manipulating the structure and mechanical properties of thermoplastic polyurethane/polycaprolactone hybrid small diameter vascular scaffolds fabricated via electrospinning using an assembled rotating collector.

PubMed

Mi, Hao-Yang; Jing, Xin; Yu, Emily; Wang, Xiaofeng; Li, Qian; Turng, Lih-Sheng

2018-02-01

The success of blood vessel transplants with vascular scaffolds (VSs) highly depends on their structure and mechanical properties. The fabrication of small diameter vascular scaffolds (SDVSs) mimicking the properties of native blood vessels has been a challenge. Herein, we propose a facile method to fabricate thermoplastic polyurethane (TPU)/polycaprolactone (PCL) hybrid SDVSs via electrospinning using a modified rotating collector. By varying the ratio between the TPU and the PCL, and changing the electrospinning volume, SDVSs with a wavy configuration and different properties could be obtained. Detailed investigation revealed that certain TPU/PCL hybrid SDVSs closely resembled the mechanical behaviors of blood vessels due to the presence of a wavy region and the combination of flexible TPU and rigid PCL, which mimicked the properties of elastin and collagen in blood vessels. The fabricated TPU/PCL SDVSs achieved lumen diameters of 1-3mm, wall thicknesses of 100-570µm, circumferential moduli of 1-6MPa, ultimate strengths of 2-8MPa, over 250% elongation-at-break values, toe regions of 5.3-9.4%, high recoverability, and compliances close to those of human veins. Moreover, these TPU/PCL SDVSs possessed sufficient suture retention strength and burst pressure to fulfill transplantation requirements and maintain normal blood flow. Human endothelial cell culture revealed good biocompatibility of the scaffolds, and cells were able to grow on the inner surface of the tubular scaffolds, indicating promising prospects for use as tissue-engineered vascular grafts. Copyright © 2017 Elsevier Ltd. All rights reserved.

Joining sheet aluminum AA6061-T4 to cast magnesium AM60B by vaporizing foil actuator welding: Input energy, interface, and strength

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

Liu, Bert; Vivek, Anupam; Daehn, Glenn S.

Dissimilar joining of sheet aluminum AA6061-T4 to cast magnesium AM60B was achieved by vaporizing foil actuator welding (VFAW). Three input energy levels were used (6, 8, and 10 kJ), and as a trend, higher input energies resulted in progressively higher flyer velocities, more pronounced interfacial wavy features, larger weld zones, higher peel strengths, and higher peel energies. In all cases, weld cross section revealed a soundly bonded interface characterized by well-developed wavy features and lack of voids and continuous layers of intermetallic compounds (IMCs). At 10 kJ input energy, flyer speed of 820 m/s, peel strength of 22.4 N/mm, andmore » peel energy of 5.2 J were obtained. In lap-shear, failure occurred in AA6061- T4 flyer at 97% of the base material’s peak tensile load. Peel samples failed along the weld interface, and the AM60B-side of the fracture surface showed thin, evenly-spaced lines of Al residuals which had been torn out of the base AA6061-T4 in a ductile fashion and transferred over to the AM60B side, indicating very strong AA6061-T4/AM60B bond in these areas. Furthermore, this work demonstrates VFAW’s capability in joining dissimilar lightweight metals such as Al/Mg, which is expected to be a great enabler in the ongoing push for vehicle weight reduction.« less

Joining sheet aluminum AA6061-T4 to cast magnesium AM60B by vaporizing foil actuator welding: Input energy, interface, and strength

DOE PAGES

Liu, Bert; Vivek, Anupam; Daehn, Glenn S.

2017-09-19

Dissimilar joining of sheet aluminum AA6061-T4 to cast magnesium AM60B was achieved by vaporizing foil actuator welding (VFAW). Three input energy levels were used (6, 8, and 10 kJ), and as a trend, higher input energies resulted in progressively higher flyer velocities, more pronounced interfacial wavy features, larger weld zones, higher peel strengths, and higher peel energies. In all cases, weld cross section revealed a soundly bonded interface characterized by well-developed wavy features and lack of voids and continuous layers of intermetallic compounds (IMCs). At 10 kJ input energy, flyer speed of 820 m/s, peel strength of 22.4 N/mm, andmore » peel energy of 5.2 J were obtained. In lap-shear, failure occurred in AA6061- T4 flyer at 97% of the base material’s peak tensile load. Peel samples failed along the weld interface, and the AM60B-side of the fracture surface showed thin, evenly-spaced lines of Al residuals which had been torn out of the base AA6061-T4 in a ductile fashion and transferred over to the AM60B side, indicating very strong AA6061-T4/AM60B bond in these areas. Furthermore, this work demonstrates VFAW’s capability in joining dissimilar lightweight metals such as Al/Mg, which is expected to be a great enabler in the ongoing push for vehicle weight reduction.« less

Structural Imaging around the SMS Deposit by the Multi-Source ZVCS Survey Method in the Izena Hole, Mid-Okinawa Trough

NASA Astrophysics Data System (ADS)

Tara, K.; Asakawa, E.; Murakami, F.; Tsukahara, H.; Saito, S.; Lee, S.; Katou, M.; Jamali Hondori, E.; Sumi, T.; Kadoshima, K.; Kose, M.

2017-12-01

Seafloor Massive Sulfide (SMS) deposits typically show rugged topography such as abundant chimney structures and sulfide mounds. However, buried SMS deposits are not well studied because of few efficient methods to detect and characterize them. Therefore, we proposed a Zero-offset Vertical Cable Seismic (ZVCS) survey using a Sparker and a Remotely Operated Vehicle (ROV) which was equipped with autonomous hydrophone arrays and a sub-bottom profiler (SBP). Zero-offset shooting and near-bottom recording can acquire high resolution acoustic data that could separate the reflection and scattered wave by vertically towed hydrophone arrays. We conducted the multi-source ZVCS survey in the Hakurei site, where the existence of the exposed and the buried SMS deposits has been reported, in Izena Hole, the Mid-Okinawa Trough, during the exploration cruise JM16-04. We obtained the two source's cross-sections of the buried SMS that enabled us to identify the area from the viewpoint of seismic facies. Buried SMS area is characterized by wavy to subparallel internal configuration and semi-continuously reflections. These features suggest that results from collapse of original sedimentary structure and hydrothermal alteration. Previous our exploration of the entire Izena Hole by the Autonomous Cable Seismic (ACS) were conducted in the JM16-02. Comparison between the ZVCS and ACS results gave us not only structural features in the surrounding area of SMS, but also the hydrothermal system of the Izena Hole. These results suggest that the hydrothermal circulation in the Izena Hole is vertically limited to the fracture zone caused by the depression and the buried SMS occurs in a sedimentary layer in the fracture zone. We conclude that ZVCS and ACS imaging of the shallow sub-seafloor structures will be useful for discussion about the geological background of SMS deposits.

Experimental Study and Fractal Analysis on the Anisotropic Performance of Explosively Welded Interfaces of 304 Stainless Steel/245 Carbon Steel

NASA Astrophysics Data System (ADS)

Fu, Yanshu; Qiu, Yaohui; Li, Yulong

2018-03-01

The mechanical anisotropy of an explosive welding composite plate made of 304 stainless steel/245 steel was studied through shear experiments performed on explosively welded wavy interfaces along several orientation angles. The results indicated that the strength and the fracture energy of samples significantly varied with the orientation angles. The fracture surfaces of all samples were observed using a scanning electron microscope and through three-dimensional structure microscopy. The periodic features of all the fracture surfaces were clearly shown in different fracture modes. The fractal dimension of the fracture surfaces was calculated based on the fractal geometry by the box-counting method in MATLAB. The cohesive element model was used to analyze the fracture energy according to the physical dependence of the fractal dimension on thermodynamic entropy and interface separation energy. The fracture energy was an exponential function of the fractal dimension value, which was in good agreement with the experimental results. All results were validated for effective use in the application of anisotropy analysis to the welded interface and structural optimization of explosively welded composite plates.

Topological and morphological analysis of gamma rays irradiated chitosan-poly (vinyl alcohol) blends using atomic force microscopy

NASA Astrophysics Data System (ADS)

Bhatt, Rinkesh; Bisen, D. S.; Bajpai, R.; Bajpai, A. K.

2017-04-01

In the present communication, binary blends of poly (vinyl alcohol) (PVA) and chitosan (CS) were prepared by solution cast method and the roughness parameters of PVA, native CS and CS-PVA blend films were determined using atomic force microscopy (AFM). Moreover, the changes in the morphology of the samples were also investigated after irradiation of gamma rays at absorbed dose of 1 Mrad and 10 Mrad for the scanning areas of 5×5 μm2, 10×10 μm2 and 20×20 μm2. Amplitude, statistical and spatial parameters, including line, 3D and 2D image profiles of the experimental surfaces were examined and compared to un-irradiated samples. For gamma irradiated CS-PVA blends the larger waviness over the surface was found as compared to un-irradiated CS-PVA blends but the values of average roughness for both the films were found almost same. The coefficient of skewness was positive for gamma irradiated CS-PVA blends which revealed the presence of more peaks than valleys on the blend surfaces.

Joint properties of a tool machining process to guarantee fluid-proof abilities

NASA Astrophysics Data System (ADS)

Bataille, C.; Deltombe, R.; Jourani, A.; Bigerelle, M.

2017-12-01

This study addressed the impact of rod surface topography in contact with reciprocating seals. Rods were tooled with and without centreless grinding. All rods tooled with centreless grinding were fluid-proof, in contrast to rods tooled without centreless grinding that either had leaks or were fluid-proof. A method was developed to analyse the machining signature, and the software Mesrug™ was used in order to discriminate roughness parameters that can be used to characterize the sealing functionality. According to this surface roughness analysis, a fluid-proof rod tooled without centreless grinding presents aperiodic large plateaus, and the relevant roughness parameter for characterizing the sealing functionality is the density of summits S DS. Increasing the density of summits counteracts leakage, which may be because motif decomposition integrates three topographical components: circularity (perpendicular long-wave roughness), longitudinal waviness, and roughness thanks to the Wolf pruning algorithm. A 3D analytical contact model was applied to analyse the contact area of each type of sample with the seal surface. This model provides a leakage probability, and the results were consistent with the interpretation of the topographical analysis.

Experimental Study and Fractal Analysis on the Anisotropic Performance of Explosively Welded Interfaces of 304 Stainless Steel/245 Carbon Steel

NASA Astrophysics Data System (ADS)

Fu, Yanshu; Qiu, Yaohui; Li, Yulong

2018-05-01

The mechanical anisotropy of an explosive welding composite plate made of 304 stainless steel/245 steel was studied through shear experiments performed on explosively welded wavy interfaces along several orientation angles. The results indicated that the strength and the fracture energy of samples significantly varied with the orientation angles. The fracture surfaces of all samples were observed using a scanning electron microscope and through three-dimensional structure microscopy. The periodic features of all the fracture surfaces were clearly shown in different fracture modes. The fractal dimension of the fracture surfaces was calculated based on the fractal geometry by the box-counting method in MATLAB. The cohesive element model was used to analyze the fracture energy according to the physical dependence of the fractal dimension on thermodynamic entropy and interface separation energy. The fracture energy was an exponential function of the fractal dimension value, which was in good agreement with the experimental results. All results were validated for effective use in the application of anisotropy analysis to the welded interface and structural optimization of explosively welded composite plates.

Pressure and heating-rate distributions on a corrugated surface in a supersonic turbulent boundary layer

NASA Technical Reports Server (NTRS)

Sawyer, J. W.

1977-01-01

Drag and heating rates on wavy surfaces typical of current corrugated plate designs for thermal protection systems were determined experimentally. Pressure-distribution, heating-rate, and oil-flow tests were conducted in the Langley Unitary Plan wind tunnel at Mach numbers of 2.4 and 4.5 with the corrugated surface exposed to both thick and thin turbulent boundary layers. Tests were conducted with the corrugations at cross-flow angles from 0 deg to 90 deg to the flow. Results show that for cross-flow angles of 30 deg or less, the pressure drag coefficients are less than the local flat-plate skin-friction coefficients and are not significantly affected by Mach number, Reynolds number, or boundary-layer thickness over the ranges investigated. For cross-flow angles greater than 30 deg, the drag coefficients increase significantly with cross-flow angle and moderately with Reynolds number. Increasing the Mach number causes a significant reduction in the pressure drag. The average and peak heating penalties due to the corrugated surface are small for cross-flow angles of 10 deg or less but are significantly higher for the larger cross-flow angles.

Tool wear compensation scheme for DTM

NASA Astrophysics Data System (ADS)

Sandeep, K.; Rao, U. S.; Balasubramaniam, R.

2018-04-01

This paper is aimed to monitor tool wear in diamond turn machining (DTM), assess effects of tool wear on accuracies of the machined component, and develop compensation methodology to enhance size and shape accuracies of a hemispherical cup. In order to find change in the centre and radius of tool with increasing wear of tool, a MATLAB program is used. In practice, x-offsets are readjusted by DTM operator for desired accuracy in the cup and the results of theoretical model show that change in radius and z-offset are insignificant however x-offset is proportional to the tool wear and this is what assumed while resetting tool offset. Since we could not measure the profile of tool; therefore we modeled our program for cup profile data. If we assume no error due to slide and spindle of DTM then any wear in the tool will be reflected in the cup profile. As the cup data contains surface roughness, therefore random noise similar to surface waviness is added. It is observed that surface roughness affects the centre and radius but pattern of shifting of centre with increase in wear of tool remains similar to the ideal condition, i.e. without surface roughness.

Boattail Plates With Non-Rectangular Geometries For Reducing Aerodynamic Base Drag Of A Bluff Body In Ground Effect

DOEpatents

Ortega, Jason M.; Sabari, Kambiz

2006-03-07

An apparatus for reducing the aerodynamic base drag of a bluff body having a leading end, a trailing end, a top surface, opposing left and right side surfaces, and a base surface at the trailing end substantially normal to a longitudinal centerline of the bluff body, with the base surface joined (1) to the left side surface at a left trailing edge, (2) to the right side surface at a right trailing edge, and (3) to the top surface at a top trailing edge. The apparatus includes left and right vertical boattail plates which are orthogonally attached to the base surface of the bluff body and inwardly offset from the left and right trailing edges, respectively. This produces left and right vertical channels which generate, in a flowstream substantially parallel to the longitudinal centerline, respective left and right vertically-aligned vortical structures, with the left and right vertical boattail plates each having a plate width defined by a rear edge of the plate spaced from the base surface. Each plate also has a peak plate width at a location between top and bottom ends of the plate corresponding to a peak vortex of the respective vertically-aligned vortical structures.

Vertical shear-wave velocity profiles generated from spectral analysis of surface waves : field examples

DOT National Transportation Integrated Search

2003-04-01

Surface wave (Rayleigh wave) seismic data were acquired at six separate bridge sites in southeast Missouri. Each acquired surface wave data set was processed (spectral analysis of surface waves; SASW) and transformed into a site-specific vertical she...

Topography reconstruction of specular surfaces

NASA Astrophysics Data System (ADS)

Kammel, Soren; Horbach, Jan

2005-01-01

Specular surfaces are used in a wide variety of industrial and consumer products like varnished or chrome plated parts of car bodies, dies, molds or optical components. Shape deviations of these products usually reduce their quality regarding visual appearance and/or technical performance. One reliable method to inspect such surfaces is deflectometry. It can be employed to obtain highly accurate values representing the local curvature of the surfaces. In a deflectometric measuring system, a series of illumination patterns is reflected at the specular surface and is observed by a camera. The distortions of the patterns in the acquired images contain information about the shape of the surface. This information is suited for the detection and measurement of surface defects like bumps, dents and waviness with depths in the range of a few microns. However, without additional information about the distances between the camera and each observed surface point, a shape reconstruction is only possible in some special cases. Therefore, the reconstruction approach described in this paper uses data observed from at least two different camera positions. The data obtained is used separately to estimate the local surface curvature for each camera position. From the curvature values, the epipolar geometry for the different camera positions is recovered. Matching the curvature values along the epipolar lines yields an estimate of the 3d position of the corresponding surface points. With this additional information, the deflectometric gradient data can be integrated to represent the surface topography.

Linearly Polarized Dual-Wavelength Vertical-External-Cavity Surface-Emitting Laser (Postprint)

DTIC Science & Technology

2007-03-01

Lamb, Jr., Laser Physics Addison-Wesley, Reading, MA, 1974, pp. 125-126. 7A. E. Siegman , Lasers University Sciences Books, Sausalito, CA, 1986, pp...AFRL-RY-WP-TP-2008-1171 LINEARLY POLARIZED DUAL-WAVELENGTH VERTICAL-EXTERNAL-CAVITY SURFACE-EMITTING LASER (Postprint) Li Fan, Mahmoud...LINEARLY POLARIZED DUAL-WAVELENGTH VERTICAL-EXTERNAL- CAVITY SURFACE-EMITTING LASER (Postprint) 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT NUMBER 5c

Transformational electronics are now reconfiguring

NASA Astrophysics Data System (ADS)

Rojas, Jhonathan P.; Hussain, Aftab M.; Arevalo, A.; Foulds, I. G.; Torres Sevilla, Galo A.; Nassar, Joanna M.; Hussain, Muhammad M.

2015-05-01

Current developments on enhancing our smart living experience are leveraging the increased interest for novel systems that can be compatible with foldable, wrinkled, wavy and complex geometries and surfaces, and thus become truly ubiquitous and easy to deploy. Therefore, relying on innovative structural designs we have been able to reconfigure the physical form of various materials, to achieve remarkable mechanical flexibility and stretchability, which provides us with the perfect platform to develop enhanced electronic systems for application in entertainment, healthcare, fitness and wellness, military and manufacturing industry. Based on these novel structural designs we have developed a siliconbased network of hexagonal islands connected through double-spiral springs, forming an ultra-stretchable (~1000%) array for full compliance to highly asymmetric shapes and surfaces, as well as a serpentine design used to show an ultrastretchable (~800%) and flexible, spatially reconfigurable, mobile, metallic thin film copper (Cu)-based, body-integrated and non-invasive thermal heater with wireless controlling capability, reusability, heating-adaptability and affordability due to low-cost complementary metal oxide semiconductor (CMOS)-compatible integration.

Vortex generation and wave-vortex interaction over a concave plate with roughness and suction

NASA Technical Reports Server (NTRS)

Bertolotti, Fabio

1993-01-01

The generation and amplification of vortices by surface homogeneities, both in the form of surface waviness and of wall-normal velocity, is investigated using the nonlinear parabolic stability equations. Transients and issues of algebraic growth are avoided through the use of a similarity solution as initial condition for the vortex. In the absence of curvature, the vortex decays as the square root of 1/x when flowing over streamwise aligned riblets of constant height, and grows as the square root of x when flowing over a corresponding streamwise aligned variation of blowing/suction transpiration velocity. However, in the presence of wall inhomogeneities having both streamwise and spanwise periodicity, the growth of the vortex can be much larger. In the presence of curvature, the vortex develops into a Gortler vortex. The 'direct' and 'indirect' interaction mechanisms possible in wave-vortex interaction are presented. The 'direct' interaction does not lead to strong resonance with the flow conditions investigated. The 'indirect' interaction leads to K-type transition.

Cell directional migration and oriented division on three-dimensional laser-induced periodic surface structures on polystyrene.

PubMed

Wang, Xuefeng; Ohlin, Christian A; Lu, Qinghua; Hu, Jun

2008-05-01

The extracellular matrix in animal tissues usually provides a three-dimensional structural support to cells in addition to performing various other important functions. In the present study, wavy submicrometer laser-irradiated periodic surface structures (LIPSS) were produced on a smooth polystyrene film by polarized laser irradiation with a wavelength of 266 nm. Rat C6 glioma cells exhibited directional migration and oriented division on laser-irradiated polystyrene, which was parallel to the direction of LIPSS. However, rat C6 glioma cells on smooth polystyrene moved in a three-step invasion cycle, with faster migration speed than that on laser-irradiated polystyrene. In addition, focal adhesions examined by immunostaining focal adhesion kinase in human epithelial carcinoma HeLa cells were punctuated on smooth polystyrene, whereas dash-like on laser-irradiated polystyrene. We hypothesized that LIPSS on laser-irradiated polystyrene acted as an anisotropic and persistent mechanical stimulus to guide cell anisotropic spreading, migration and division through focal adhesions.

Growth and quantum transport properties of vertical Bi2Se3 nanoplate films on Si substrates.

PubMed

Li, Mingze; Wang, Zhenhua; Yang, Liang; Pan, Desheng; Li, Da; Gao, Xuan P A; Zhang, Zhidong

2018-08-03

Controlling the growth direction (planar versus vertical) and surface-to-bulk ratio can lead to lots of unique properties for two-dimensional layered materials. We report a simple method to fabricate continuous films of vertical Bi 2 Se 3 nanoplates on Si substrate and investigate the quantum transport properties of such films. In contrast to (001) oriented planar Bi 2 Se 3 nanoplate film, vertical Bi 2 Se 3 nanoplate films are enclosed by (015) facets, which possess high surface-to-bulk ratio that can enhance the quantum transport property of topological surface states. And by controlling the compactness of vertical Bi 2 Se 3 nanoplates, we realized an effective tuning of the weak antilocalization effect from topological surface states in Bi 2 Se 3 films. Our work paves a way for exploring the unique transport properties of this unconventional structure topological insulator film.

Molecular genetic investigations of root gravitropism and other complex growth behaviors using Arabidopsis and Brachypodium as models

NASA Astrophysics Data System (ADS)

Masson, Patrick; Barker, Richard; Miller, Nathan; Su, Shih-Hao; Su, Shih-Heng

2016-07-01

When growing on hard surfaces, Arabidopsis roots tend to grown downward, as dictated by positive gravitropism. At the same time, surface-derived stimuli promote a wavy pattern of growth that is superimposed to a rightward root-skewing trend. This behavior is believed to facilitate obstacle avoidance in soil. To better understand these complex behaviors, we have isolated and characterized mutations that affect them. Some of these mutations were shown to affect gravitropism whereas others did not. Within the latter group, most of the mutations affected mechanisms that control anisotropic cell expansion. We have also characterized mutations that affect early steps of gravity signal transduction within the gravity-sensing columella cells of the root cap. Upon reorientation within the gravity field, starch-filled plastids sediment to the bottom-side of these cells, triggering a pathway that leads to re-localization of auxin efflux facilitators to the bottom membrane. Lateral auxin transport toward the bottom flank ensues, leading to gravitropic curvature. Several of the mutations we characterized affect genes that encode proteins associated with the vesicle trafficking pathway needed for this cell polarization. Other mutations were shown to affect components of the plastid outer envelope protein import complex (TOC). Their functional analysis suggests an active role for plastids in gravity signal transduction, beyond a simple contribution as sedimenting gravity susceptors. Because most cultivated crops are monocots, not dicots like Arabidopsis, we have also initiated studies of root-growth behavior with Brachypodium distachyon. When responding to a gravistimulus, the roots of Brachypodium seedlings develop a strong downward curvature that proceeds until the tip reaches a ~50-degree curvature. At that time, an oscillatory tip movement occurs while the root continues its downward reorientation. These root-tip oscillations also occur if roots are allowed to simply grow downward on vertical surfaces, or fully embedded in agar-containing medium. Brachypodium distachyon accessions differ in their gravisensitivity, kinetics of gravitropism and occurrence, periodicity and amplitude of tip oscillations. Mathematical models are being built to fit the data, and used to estimate growth, gravitropism and oscillation parameters for incorporation into Genome-Wide Association Study (GWAS) algorithms aimed at identifying contributing loci. This work was supported by grants from the National Aeronautics and Space Administration (NASA) and from the National Science Foundation (NSF).

Trajectories of charged dust grains in the cometary environment

NASA Astrophysics Data System (ADS)

Horanyi, M.; Mendis, D. A.

1985-07-01

Using a simple model of the particles and fields environment of a comet, the trajectories of the smallest (micron- and submicron-sized) dust grains that are expected to be released from a cometary nucleus are calculated. It is shown that electromagnetic forces play a crucial role in the dynamics of these particles. The present calculations indicate not only the asymmetry of the sunward dust envelopes that have been suggested earlier by other authors, but they also indicate the possible existence of wavy dust features far down the tail, reminiscent of the peculiar wavy dust feature observed in the dust tail of Comet Ikeya-Seki 1965f. The importance of these findings in studying the lower end of the cometary dust mass spectrum during the forthcoming fly-by missions to Comet Halley is underscored.

Confocal laser scanning microscopy and area-scale analysis used to quantify enamel surface textural changes from citric acid demineralization and salivary remineralization in vitro.

PubMed

Austin, R S; Giusca, C L; Macaulay, G; Moazzez, R; Bartlett, D W

2016-02-01

This paper investigates the application of confocal laser scanning microscopy to determine the effect of acid-mediated erosive enamel wear on the micro-texture of polished human enamel in vitro. Twenty polished enamel samples were prepared and subjected to a citric acid erosion and pooled human saliva remineralization model. Enamel surface microhardness was measured using a Knoop hardness tester, which confirmed that an early enamel erosion lesion was formed which was then subsequently completely remineralized. A confocal laser scanning microscope was used to capture high-resolution images of the enamel surfaces undergoing demineralization and remineralization. Area-scale analysis was used to identify the optimal feature size following which the surface texture was determined using the 3D (areal) texture parameter Sa. The Sa successfully characterized the enamel erosion and remineralization for the polished enamel samples (P<0.001). Areal surface texture characterization of the surface events occurring during enamel demineralization and remineralization requires optical imaging instrumentation with lateral resolution <2.5 μm, applied in combination with appropriate filtering in order to remove unwanted waviness and roughness. These techniques will facilitate the development of novel methods for measuring early enamel erosion lesions in natural enamel surfaces in vivo. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Trampoline Effect: Observations and Modeling

NASA Astrophysics Data System (ADS)

Guyer, R.; Larmat, C. S.; Ulrich, T. J.

2009-12-01

The Iwate-Miyagi earthquake at site IWTH25 (14 June 2008) had large, asymmetric at surface vertical accelerations prompting the sobriquet trampoline effect (Aoi et. al. 2008). In addition the surface acceleration record showed long-short waiting time correlations and vertical-horizontal acceleration correlations. A lumped element model, deduced from the equations of continuum elasticity, is employed to describe the behavior at this site in terms of a surface layer and substrate. Important ingredients in the model are the nonlinear vertical coupling between the surface layer and the substrate and the nonlinear horizontal frictional coupling between the surface layer and the substrate. The model produces results in qualitative accord with observations: acceleration asymmetry, Fourier spectrum, waiting time correlations and vertical acceleration-horizontal acceleration correlations. [We gratefully acknowledge the support of the U. S. Department of Energy through the LANL/LDRD Program for this work].

Tricho-Dento-Osseous Syndrome: Diagnosis and Dental Management

PubMed Central

Al-Batayneh, Ola B.

2012-01-01

Tricho-dento-osseous (TDO) syndrome is a rare, autosomal dominant disorder principally characterised by curly hair at infancy, severe enamel hypomineralization and hypoplasia and taurodontism of teeth, sclerotic bone, and other defects. Diagnostic criteria are based on the generalized enamel defects, severe taurodontism especially of the mandibular first permanent molars, an autosomal dominant mode of inheritance, and at least one of the other features (i.e., nail defects, bone sclerosis, and curly, kinky or wavy hair present at a young age that may straighten out later). Confusion with amelogenesis imperfecta is common; however, taurodontism is not a constant feature of any of the types of amelogenesis imperfecta. Management of TDO requires a team approach, proper documentation, and a long-term treatment and follow-up plan. The aim of treatment is to prevent problems such as sensitivity, caries, dental abscesses, and loss of occlusal vertical dimension through attrition of hypoplastic tooth structure. Another aim is to restore function of the dentition and enhance the esthetics and self-esteem of the patient. This paper proposes treatment approaches that include preventive, restorative, endodontic, prosthetic, and surgical options to management. In addition, it sheds light on the difficulties faced during dental treatment of such cases. PMID:22969805

Mass transfer in thin films under counter-current gas: experiments and numerical study

NASA Astrophysics Data System (ADS)

Lucquiaud, Mathieu; Lavalle, Gianluca; Schmidt, Patrick; Ausner, Ilja; Wehrli, Marc; O Naraigh, Lennon; Valluri, Prashant

2016-11-01

Mass transfer in liquid-gas stratified flows is strongly affected by the waviness of the interface. For reactive flows, the chemical reactions occurring at the liquid-gas interface also influence the mass transfer rate. This is encountered in several technological applications, such as absorption units for carbon capture. We investigate the absorption rate of carbon dioxide in a liquid solution. The experimental set-up consists of a vertical channel where a falling film is sheared by a counter-current gas flow. We measure the absorption occurring at different flow conditions, by changing the liquid solution, the liquid flow rate and the gas composition. With the aim to support the experimental results with numerical simulations, we implement in our level-set flow solver a novel module for mass transfer taking into account a variant of the ghost-fluid formalism. We firstly validate the pure mass transfer case with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we analyse the absorption rate in reactive flows, and try to reproduce the experimental results by means of numerical simulations to explore the active role of the waves at the interface.

Steerable vertical to horizontal energy transducer for mobile robots

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Feddema, John T.

2001-01-01

The present invention provides a steerable vertical to horizontal energy transducer for mobile robots that less complex and requires less power than two degree of freedom tilt mechanisms. The present invention comprises an end effector that, when mounted with a hopping actuator, translates along axis (typically vertical) actuation into combined vertical and horizontal motion. The end effector, or foot, mounts with an end of the actuator that moves toward the support surface (typically a floor or the earth). The foot is shaped so that the first contact with the support surface is off the axis of the actuator. Off-axis contact with the support surface generates an on-axis force (typically resulting in vertical motion) and a moment orthogonal to the axis. The moment initiates a horizontal tumbling motion, and tilts the actuator so that its axis is oriented with a horizontal component and continued actuation generates both vertical and horizontal force.

Preparation of multilayered nanocrystalline thin films with composition-modulated interfaces

NASA Astrophysics Data System (ADS)

Biro, D.; Barna, P. B.; Székely, L.; Geszti, O.; Hattori, T.; Devenyi, A.

2008-06-01

The properties of multilayer thin film structures depend on the morphology and structure of interfaces. A broad interface, in which the composition is varying, can enhance, e.g., the hardness of multilayer thin films. In the present experiments multilayers of TiAlN and CrN as well as TiAlN, CrN and MoS 2 were studied by using unbalanced magnetron sputter sources. The sputter sources were arranged side by side on an arc. This arrangement permits development of a transition zone between the layers, where the composition changes continuously. The multilayer system was deposited by one-fold oscillating movement of substrates in front of sputter sources. Thicknesses of layers could be changed both by oscillation frequency and by the power applied to sputter sources. Ti/Al: 50/50 at%, pure chromium and MoS 2 targets were used in the sputter sources. The depositions were performed in an Ar-N 2 mixture at 0.22 Pa working pressure. The sputtering power of the TiAl source was feed-back adjusted in fuzzy-logic mode in order to avoid fluctuation of the TiAl target sputter rate due to poisoning of the target surface. Structure characterization of films deposited on <1 0 0> Si wafers covered by thermally grown SiO 2 was performed by cross-sectional transmission electron microscopy. At first a 100 nm thick Cr base layer was deposited on the substrate to improve adhesion, which was followed by a CrN transition layer. The CrN transition layer was followed by a 100 nm thick TiAlN/CrN multilayer system. The TiAlN/CrN/MoS 2 multilayer system was deposited on the surface of this underlayer system. The underlayer systems Cr, CrN and TiAlN/CrN were crystalline with columnar structure according to the morphology of zone T of the structure zone models. The column boundaries contained segregated phases showing up in the under-focused TEM images. The surface of the underlayer system was wavy due to dome-shaped columns. The nanometer-scaled TiAlN/CrN/MoS 2 multilayer system followed this waviness. Crystallinity of the TiAlN and CrN layers in the multilayer system decreases with increasing thickness of the MoS 2 layer.

Support mechanism for a mirrored surface or other arrangement

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

Cutburth, R.W.

1987-02-03

A mechanism is described for supporting first means including a planer surface for movement relative to a vertical plane defined by particular intersecting x and y axes which extend horizontally and vertically, respectively, the mechanism comprising: (a) second means including a plurality of segments of an annular surface which forms part of a sphere whose center defines the intersection of the x and y axes. The annular surface defines a z axis extending through the intersection of the x and y axes perpendicular to the vertical plane; (b) third means connecting the planer surface including first means with the secondmore » means such that the planer surface is positionably within the vertical plane and is itself intersected by the z axis at a particular point thereon. The third means includes bearing means disposed between the first means and the segments of the annular surface of the second means for allowing the first means to move in any direction on the annular surface segments including certain specific directions which allow the planer surface to pivot back and forth to a limited extent about both the x and y axes relative to the vertical plane; and (c) fourth means interconnecting the first and second means and cooperating with the third means for limiting the movement of the first means to the certain specific directions.« less

Vertical distributions of aerosols under different weather conditions: Analysis of in-situ aircraft measurements in Beijing, China

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Ma, XinCheng; Tie, Xuexi; Huang, Mengyu; Zhao, Chunsheng

In this study, aerosol vertical distributions of 17 in-situ aircraft measurements during 2005 and 2006 springs are analyzed. The 17 flights are carefully selected to exclude dust events, and the analyses are focused on the vertical distributions of aerosol particles associated with anthropogenic activities. The results show that the vertical distributions of aerosol particles are strongly affected by weather and meteorological conditions, and 3 different types of aerosol vertical distributions corresponding to different weather systems are defined in this study. The measurement with a flat vertical gradient and low surface aerosol concentrations is defined as type-1; a gradual decrease of aerosols with altitudes and modest surface aerosol concentrations is defined as type-2; a sharp vertical gradient (aerosols being strongly depressed in the PBL) with high surface aerosol concentrations is defined as type-3. The weather conditions corresponding to the 3 different aerosol types are high pressure, between two high pressures, and low pressure systems (frontal inversions), respectively. The vertical mixing and horizontal transport for the 3 different vertical distributions are analyzed. Under the type-1 condition, the vertical mixing and horizontal transport were rapid, leading to strong dilution of aerosols in both vertical and horizontal directions. As a result, the aerosol concentrations in PBL (planetary boundary layer) were very low, and the vertical distribution was flat. Under the type-2 condition, the vertical mixing was strong and there was no strong barrier at the PBL height. The horizontal transport (wind flux) was modest. As a result, the aerosol concentrations were gradually reduced with altitude, with modest surface aerosol concentrations. Under the type-3 condition, there was a cold front near the region. As a result, a frontal inversion associated with weak vertical mixing appeared at the top of the inversion layer, forming a very strong barrier to prevent aerosol particles being exchanged from the PBL height to the free troposphere. As a result, the aerosol particles were strongly depressed in the PBL height, producing high surface aerosol concentrations. The measured vertical aerosol distributions have important implications for studying the effects of aerosols on photochemistry. The J[O 3] values are reduced by 11%, 48%, and 50%, under the type-1, type-2, and type-3 conditions, respectively. This result reveals that atmospheric oxidant capacity (OH concentrations) is modestly reduced under the type-1 condition, but is significantly reduced under the type-2 and type-3 conditions. This result also suggests that the effect of aerosol particles on surface solar flux is an integrated column effect, and detailed vertical distributions of aerosol particles are very important for assessing the impacts of aerosol on photochemistry.

Modeling the oxidative capacity of the atmosphere of the south coast air basin of California. 1. Ozone formation metrics.

PubMed

Griffin, Robert J; Revelle, Meghan K; Dabdub, Donald

2004-02-01

Metrics associated with ozone (O3) formation are investigated using the California Institute of Technology (CIT) three-dimensional air-quality model. Variables investigated include the O3 production rate (P(O3)), O3 production efficiency (OPE), and total reactivity (the sum of the reactivity of carbon monoxide (CO) and all organic gases that react with the hydroxyl radical). Calculations are spatially and temporally resolved; surface-level and vertically averaged results are shown for September 9, 1993 for three Southern California locations: Central Los Angeles, Azusa, and Riverside. Predictions indicate increasing surface-level O3 concentrations with distance downwind, in line with observations. Surface-level and vertically averaged P(O3) values peak during midday and are highest downwind; surface P(O3) values are greater than vertically averaged values. Surface OPEs generally are highest downwind and peak during midday in downwind locations. In contrast, peaks occur in early morning and late afternoon in the vertically averaged case. Vertically averaged OPEs tend to be greater than those for the surface. Total reactivities are highest in upwind surface locations and peak during rush hours; vertically averaged reactivities are smaller and tend to be more uniform temporally and spatially. Total reactivity has large contributions from CO, alkanes, alkenes, aldehydes, unsubstituted monoaromatics, and secondary organics. Calculations using estimated emissions for 2010 result in decreases in P(O3) values and reactivities but increases in OPEs.

A three-dimensional architecture of vertically aligned multilayer graphene facilitates heat dissipation across joint solid surfaces

NASA Astrophysics Data System (ADS)

Liang, Qizhen; Yao, Xuxia; Wang, Wei; Wong, C. P.

2012-02-01

Low operation temperature and efficient heat dissipation are important for device life and speed in current electronic and photonic technologies. Being ultra-high thermally conductive, graphene is a promising material candidate for heat dissipation improvement in devices. In the application, graphene is expected to be vertically stacked between contact solid surfaces in order to facilitate efficient heat dissipation and reduced interfacial thermal resistance across contact solid surfaces. However, as an ultra-thin membrane-like material, graphene is susceptible to Van der Waals forces and usually tends to be recumbent on substrates. Thereby, direct growth of vertically aligned free-standing graphene on solid substrates in large scale is difficult and rarely available in current studies, bringing significant barriers in graphene's application as thermal conductive media between joint solid surfaces. In this work, a three-dimensional vertically aligned multi-layer graphene architecture is constructed between contacted Silicon/Silicon surfaces with pure Indium as a metallic medium. Significantly higher equivalent thermal conductivity and lower contact thermal resistance of vertically aligned multilayer graphene are obtained, compared with those of their recumbent counterpart. This finding provides knowledge of vertically aligned graphene architectures, which may not only facilitate current demanding thermal management but also promote graphene's widespread applications such as electrodes for energy storage devices, polymeric anisotropic conductive adhesives, etc.

Vertical coherence and forward scattering from the sea surface and the relation to the directional wave spectrum.

PubMed

Dahl, Peter H; Plant, William J; Dall'Osto, David R

2013-09-01

Results of an experiment to measure vertical spatial coherence from acoustic paths interacting once with the sea surface but at perpendicular azimuth angles are presented. The measurements were part of the Shallow Water 2006 program that took place off the coast of New Jersey in August 2006. An acoustic source, frequency range 6-20 kHz, was deployed at depth 40 m, and signals were recorded on a 1.4 m long vertical line array centered at depth 25 m and positioned at range 200 m. The vertical array consisted of four omni-directional hydrophones and vertical coherences were computed between pairs of these hydrophones. Measurements were made over four source-receiver bearing angles separated by 90°, during which sea surface conditions remained stable and characterized by a root-mean-square wave height of 0.17 m and a mixture of swell and wind waves. Vertical coherences show a statistically significant difference depending on source-receiver bearing when the acoustic frequency is less than about 12 kHz, with results tending to fade at higher frequencies. This paper presents field observations and comparisons of these observations with two modeling approaches, one based on bistatic forward scattering and the other on a rough surface parabolic wave equation utilizing synthetic sea surfaces.

The Functional Anatomy of Nerves Innervating the Ventral Grooved Blubber of Fin Whales (Balaenoptera Physalus).

PubMed

Vogl, Wayne; Petersen, Hannes; Adams, Arlo; Lillie, Margo A; Shadwick, Robert E

2017-11-01

Nerves that supply the floor of the oral cavity in rorqual whales are extensible to accommodate the dramatic changes in tissue dimensions that occur during "lunge feeding" in this group. We report here that the large nerves innervating the muscle component of the ventral grooved blubber (VGB) in fin whales are branches of cranial nerve VII (facial nerve). Therefore, the muscles of the VGB are homologous to second branchial arch derived muscles, which in humans include the muscles of "facial expression." We speculate, based on the presence of numerous foramina on the dorsolateral surface of the mandibular bones, that general sensation from the VGB likely is carried by branches of the mandibular division (V3) of cranial nerve V (trigeminal nerve), and that these small branches travel in the lipid-rich layer directly underlying the skin. We show that intercostal and phrenic nerves, which are not extensible, have a different wall and nerve core morphology than the large VGB nerves that are branches of VII. Although these VGB nerves are known to have two levels of waviness, the intercostal and phrenic nerves have only one in which the nerve fascicles in the nerve core are moderately wavy. In addition, the VGB nerves have inner and outer parts to their walls with numerous large elastin fibers in the outer part, whereas intercostal and phrenic nerves have single walls formed predominantly of collagen. Our results illustrate that overall nerve morphology depends greatly on location and the forces to which the structures are exposed. Anat Rec, 300:1963-1972, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Can dead man tooth do tell tales? Tooth prints in forensic identification.

PubMed

Christopher, Vineetha; Murthy, Sarvani; Ashwinirani, S R; Prasad, Kulkarni; Girish, Suragimath; Vinit, Shashikanth Patil

2017-01-01

We know that teeth trouble us a lot when we are alive, but they last longer for thousands of years even after we are dead. Teeth being the strongest and resistant structure are the most significant tool in forensic investigations. Patterns of enamel rod end on the tooth surface are known as tooth prints. This study is aimed to know whether these tooth prints can become a forensic tool in personal identification such as finger prints. A study has been targeted toward the same. In the present in-vivo study, acetate peel technique has been used to obtain the replica of enamel rod end patterns. Tooth prints of upper first premolars were recorded from 80 individuals after acid etching using cellulose acetate strips. Then, digital images of the tooth prints obtained at two different intervals were subjected to biometric conversion using Verifinger standard software development kit version 6.5 software followed by the use of Automated Fingerprint Identification System (AFIS) software for comparison of the tooth prints. Similarly, each individual's finger prints were also recorded and were subjected to the same software. Further, recordings of AFIS scores obtained from images were statistically analyzed using Cronbach's test. We observed that comparing two tooth prints taken from an individual at two intervals exhibited similarity in many cases, with wavy pattern tooth print being the predominant type. However, the same prints showed dissimilarity when compared with other individuals. We also found that most of the individuals with whorl pattern finger print showed wavy pattern tooth print and few loop type fingerprints showed linear pattern of tooth prints. Further more experiments on both tooth prints and finger prints are required in establishing an individual's identity.

Can dead man tooth do tell tales? Tooth prints in forensic identification

PubMed Central

Christopher, Vineetha; Murthy, Sarvani; Ashwinirani, S. R.; Prasad, Kulkarni; Girish, Suragimath; Vinit, Shashikanth Patil

2017-01-01

Background: We know that teeth trouble us a lot when we are alive, but they last longer for thousands of years even after we are dead. Teeth being the strongest and resistant structure are the most significant tool in forensic investigations. Patterns of enamel rod end on the tooth surface are known as tooth prints. Aim: This study is aimed to know whether these tooth prints can become a forensic tool in personal identification such as finger prints. A study has been targeted toward the same. Settings and Design: In the present in-vivo study, acetate peel technique has been used to obtain the replica of enamel rod end patterns. Materials and Methods: Tooth prints of upper first premolars were recorded from 80 individuals after acid etching using cellulose acetate strips. Then, digital images of the tooth prints obtained at two different intervals were subjected to biometric conversion using Verifinger standard software development kit version 6.5 software followed by the use of Automated Fingerprint Identification System (AFIS) software for comparison of the tooth prints. Similarly, each individual's finger prints were also recorded and were subjected to the same software. Statistical Analysis: Further, recordings of AFIS scores obtained from images were statistically analyzed using Cronbach's test. Results: We observed that comparing two tooth prints taken from an individual at two intervals exhibited similarity in many cases, with wavy pattern tooth print being the predominant type. However, the same prints showed dissimilarity when compared with other individuals. We also found that most of the individuals with whorl pattern finger print showed wavy pattern tooth print and few loop type fingerprints showed linear pattern of tooth prints. Conclusions: Further more experiments on both tooth prints and finger prints are required in establishing an individual's identity. PMID:28584483

Morphology and Structural Characterization of Carbon Nanowalls Grown via VHF-PECVD

NASA Astrophysics Data System (ADS)

Akmal Hasanudin, M.; Wahab, Y.; Ismail, A. K.; Zahid Jamal, Z. A.

2018-03-01

A 150 MHz very high frequency plasma enhanced chemical vapor deposition (150 MHz VHF-PECVD) system was utilized to fabricate two-dimensional carbon nanostructure from the mixture of methane and hydrogen. Morphology and structural properties of the grown nanostructure were investigated by FESEM imaging and Raman spectroscopy. Carbon nanowalls (CNW) with dense and wavy-like structure were successfully synthesized. The wavy-like morphology of CNW was found to be more distinct during growth at small electrode spacing and denser with increasing deposition time due to better flux of hydrocarbon radicals to the substrate and higher rate of reaction, respectively. Typical characteristics of CNW were observed from strong D band, narrow bandwidth of G band and single broad peak of 2D band of Raman spectra indicating the presence of disordered nanocrystalline graphite structure with high degree of graphitization.

An acoustofluidic micromixer via bubble inception and cavitation from microchannel sidewalls.

PubMed

Ozcelik, Adem; Ahmed, Daniel; Xie, Yuliang; Nama, Nitesh; Qu, Zhiguo; Nawaz, Ahmad Ahsan; Huang, Tony Jun

2014-05-20

During the deep reactive ion etching process, the sidewalls of a silicon mold feature rough wavy structures, which can be transferred onto a polydimethylsiloxane (PDMS) microchannel through the soft lithography technique. In this article, we utilized the wavy structures of PDMS microchannel sidewalls to initiate and cavitate bubbles in the presence of acoustic waves. Through bubble cavitation, this acoustofluidic approach demonstrates fast, effective mixing in microfluidics. We characterized its performance by using viscous fluids such as poly(ethylene glycol) (PEG). When two PEG solutions with a resultant viscosity 54.9 times higher than that of water were used, the mixing efficiency was found to be 0.92, indicating excellent, homogeneous mixing. The acoustofluidic micromixer presented here has the advantages of simple fabrication, easy integration, and capability to mix high-viscosity fluids (Reynolds number: ~0.01) in less than 100 ms.

Learning in settings with partial feedback and the wavy recency effect of rare events.

PubMed

Plonsky, Ori; Erev, Ido

2017-03-01

Analyses of human learning reveal a discrepancy between the long- and the short-term effects of outcomes on subsequent choice. The long-term effect is simple: favorable outcomes increase the choice rate of an alternative whereas unfavorable outcomes decrease it. The short-term effects are more complex. Favorable outcomes can decrease the choice rate of the best option. This pattern violates the positive recency assumption that underlies the popular models of learning. The current research tries to clarify the implications of these results. Analysis of wide sets of learning experiments shows that rare positive outcomes have a wavy recency effect. The probability of risky choice after a successful outcome from risk-taking at trial t is initially (at t+1) relatively high, falls to a minimum at t+2, then increases for about 15 trials, and then decreases again. Rare negative outcomes trigger a wavy reaction when the feedback is complete, but not under partial feedback. The difference between the effects of rare positive and rare negative outcomes and between full and partial feedback settings can be described as a reflection of an interaction of an effort to discover patterns with two other features of human learning: surprise-triggers-change and the hot stove effect. A similarity-based descriptive model is shown to capture well all these interacting phenomena. In addition, the model outperforms the leading models in capturing the outcomes of data used in the 2010 Technion Prediction Tournament. Copyright © 2017 Elsevier Inc. All rights reserved.

Studies on Normal and Microgravity Annular Two Phase Flows

NASA Technical Reports Server (NTRS)

Balakotaiah, V.; Jayawardena, S. S.; Nguyen, L. T.

1999-01-01

Two-phase gas-liquid flows occur in a wide variety of situations. In addition to normal gravity applications, such flows may occur in space operations such as active thermal control systems, power cycles, and storage and transfer of cryogenic fluids. Various flow patterns exhibiting characteristic spatial and temporal distribution of the two phases are observed in two-phase flows. The magnitude and orientation of gravity with respect to the flow has a strong impact on the flow patterns observed and on their boundaries. The identification of the flow pattern of a flow is somewhat subjective. The same two-phase flow (especially near a flow pattern transition boundary) may be categorized differently by different researchers. Two-phase flow patterns are somewhat simplified in microgravity, where only three flow patterns (bubble, slug and annular) have been observed. Annular flow is obtained for a wide range of gas and liquid flow rates, and it is expected to occur in many situations under microgravity conditions. Slug flow needs to be avoided, because vibrations caused by slugs result in unwanted accelerations. Therefore, it is important to be able to accurately predict the flow pattern which exists under given operating conditions. It is known that the wavy liquid film in annular flow has a profound influence on the transfer of momentum and heat between the phases. Thus, an understanding of the characteristics of the wavy film is essential for developing accurate correlations. In this work, we review our recent results on flow pattern transitions and wavy films in microgravity.

Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

DTIC Science & Technology

2015-07-16

SECURITY CLASSIFICATION OF: The InAs quantum dot (QD) grown on GaAs substrates represents a highly performance active region in the 1 - 1.3 µm...2015 Approved for Public Release; Distribution Unlimited Final Report: Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface...ABSTRACT Final Report: Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene Report

The effect of Ga pre-deposition on Si (111) surface for InAs nanowire selective area hetero-epitaxy

NASA Astrophysics Data System (ADS)

Liu, Ziyang; Merckling, Clement; Rooyackers, Rita; Franquet, Alexis; Richard, Olivier; Bender, Hugo; Vila, María; Rubio-Zuazo, Juan; Castro, Germán R.; Collaert, Nadine; Thean, Aaron; Vandervorst, Wilfried; Heyns, Marc

2018-04-01

Vertical InAs nanowires (NWs) grown on a Si substrate are promising building-blocks for next generation vertical gate-all-around transistor fabrication. We investigate the initial stage of InAs NW selective area epitaxy (SAE) on a patterned Si (111) substrate with a focus on the interfacial structures. The direct epitaxy of InAs NWs on a clean Si (111) surface is found to be challenging. The yield of vertical InAs NWs is low, as the SAE is accompanied by high proportions of empty holes, inclined NWs, and irregular blocks. In contrast, it is improved when the NW contains gallium, and the yield of vertical InxGa1-xAs NWs increased with higher Ga content. Meanwhile, unintentional Ga surface contamination on a patterned Si substrate induces high yield vertical InAs NW SAE, which is attributed to a GaAs-like seeding layer formed at the InAs/Si interface. The role of Ga played in the III-V NW nucleation on Si is further discussed. It stabilizes the B-polarity on a non-polar Si (111) surface and enhances the nucleation. Therefore, gallium incorporation on a Si surface is identified as an important enabler for vertical InAs NW growth. A new method for high yield (>99%) vertical InAs NW SAE on Si using an InGaAs nucleation layer is proposed based on this study.

Vertical Distributions of Coccolithophores, PIC, POC, Biogenic Silica, and Chlorophyll a Throughout the Global Ocean.

PubMed

Balch, William M; Bowler, Bruce C; Drapeau, David T; Lubelczyk, Laura C; Lyczkowski, Emily

2018-01-01

Coccolithophores are a critical component of global biogeochemistry, export fluxes, and seawater optical properties. We derive globally significant relationships to estimate integrated coccolithophore and coccolith concentrations as well as integrated concentrations of particulate inorganic carbon (PIC) from their respective surface concentration. We also examine surface versus integral relationships for other biogeochemical variables contributed by all phytoplankton (e.g., chlorophyll a and particulate organic carbon) or diatoms (biogenic silica). Integrals are calculated using both 100 m integrals and euphotic zone integrals (depth of 1% surface photosynthetically available radiation). Surface concentrations are parameterized in either volumetric units (e.g., m -3 ) or values integrated over the top optical depth. Various relationships between surface concentrations and integrated values demonstrate that when surface concentrations are above a specific threshold, the vertical distribution of the property is biased to the surface layer, and when surface concentrations are below a specific threshold, the vertical distributions of the properties are biased to subsurface maxima. Results also show a highly predictable decrease in explained-variance as vertical distributions become more vertically heterogeneous. These relationships have fundamental utility for extrapolating surface ocean color remote sensing measurements to 100 m depth or to the base of the euphotic zone, well beyond the depths of detection for passive ocean color remote sensors. Greatest integrated concentrations of PIC, coccoliths, and coccolithophores are found when there is moderate stratification at the base of the euphotic zone.

Vertical Distributions of Coccolithophores, PIC, POC, Biogenic Silica, and Chlorophyll a Throughout the Global Ocean

PubMed Central

Bowler, Bruce C.; Drapeau, David T.; Lubelczyk, Laura C.; Lyczkowski, Emily

2018-01-01

Abstract Coccolithophores are a critical component of global biogeochemistry, export fluxes, and seawater optical properties. We derive globally significant relationships to estimate integrated coccolithophore and coccolith concentrations as well as integrated concentrations of particulate inorganic carbon (PIC) from their respective surface concentration. We also examine surface versus integral relationships for other biogeochemical variables contributed by all phytoplankton (e.g., chlorophyll a and particulate organic carbon) or diatoms (biogenic silica). Integrals are calculated using both 100 m integrals and euphotic zone integrals (depth of 1% surface photosynthetically available radiation). Surface concentrations are parameterized in either volumetric units (e.g., m−3) or values integrated over the top optical depth. Various relationships between surface concentrations and integrated values demonstrate that when surface concentrations are above a specific threshold, the vertical distribution of the property is biased to the surface layer, and when surface concentrations are below a specific threshold, the vertical distributions of the properties are biased to subsurface maxima. Results also show a highly predictable decrease in explained‐variance as vertical distributions become more vertically heterogeneous. These relationships have fundamental utility for extrapolating surface ocean color remote sensing measurements to 100 m depth or to the base of the euphotic zone, well beyond the depths of detection for passive ocean color remote sensors. Greatest integrated concentrations of PIC, coccoliths, and coccolithophores are found when there is moderate stratification at the base of the euphotic zone. PMID:29576683

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

Jeon, Sangmin; Desikan, Ramya; Thundat, Thomas George

Young's equation, which is commonly used for determining the contact angle of liquid drops on a solid surface, ignores the vertical component of the surface energy. Although this force is extremely small and its effect on the solid can be ignored, it plays a significant role for flexible surfaces such as microcantilevers. A gold-coated silicon microcantilever and a dodecanethiol coated silicon microcantilever were used to detect real-time formation of nanobubbles on their surfaces when exposed to air-rich water. As air nanobubbles form on the surfaces of the cantilever, the cantilever undergoes bending, and we relate this to the vertical componentmore » of surface energy in Young's equation. This implies that the vertical component of the surface tension should be considered for flexible solid surfaces, and the formation of nanobubbles should be avoided when cantilevers are used as sensors to avoid artifacts.« less

Trace Element Cycling in Lithogenic Particles at Station ALOHA

NASA Astrophysics Data System (ADS)

Morton, P. L.; Weisend, R.; Landing, W. M.; Fitzsimmons, J. N.; Hayes, C. T.; Boyle, E. A.

2014-12-01

Trace element cycling in marine particles is influenced by atmospheric deposition, vertical export, biological uptake and remineralization, scavenging, and lateral transport processes. To investigate the cycling of lithogenic particles in the central North Pacific Ocean, surface and vertical profile samples of marine suspended particulate matter (SPM) were collected July-August 2012 during the HOE-DYLAN cruises at Station ALOHA. In the late summer, atmospheric dust inputs from the Gobi desert (which peak during the spring, April-May) were sparse, as indicated by low surface particulate Ti (pTi) concentrations. In contrast, surface pAl concentrations did not follow pTi trends as expected, but appear to be dominated by scavenging/uptake of dissolved Al during diatom blooms. Surface pMn concentrations were low, but vertical profiles of pMn and pMn/pTi reveal a strong sedimentary source at 200 m, originating from the Hawaiian continental shelf through a combination of redox mobilization and resuspension processes. The redox active elements Ce and Co can have chemistries similar to that of Mn, but in these samples the pCe and pCo distributions were distinct from Mn and each other in both surface trends and vertical profiles. Surface pREE (e.g., La, Ce, Pr) were highest during the earliest sampling events and quickly decreased to consistently low concentrations, while vertical distributions were characterized by scavenging onto biotic particles and mid-depth inputs. The surface particulate Co trend is similar to those of pAl and pP, while the pCo vertical profiles reflect surface enrichment but low concentrations and little variability at depth. A second, complementary poster is also being presented which examines the biological influence over particulate trace element cycling (Weisend et al., "Particulate Trace Element Cycling in a Diatom Bloom at Station ALOHA").

Investigation of CaCO3 fouling in plate heat exchangers

NASA Astrophysics Data System (ADS)

Li, Wei; Zhou, Kan; Manglik, Raj M.; Li, Guan-Qiu; Bergles, Arthur E.

2016-11-01

An experimental investigation, coupled with theoretical modeling of CaCO3 fouling in plate-and-frame type heat exchangers (PHEs) have been conducted. Four different plates, made of SS-304, are used in two different surface patterns (chevron and zig-zag) of varying corrugation severity (waviness depth and pitch) and area enhancement. They were further characterized in clean, non-fouled convection by their measured heat transfer coefficients and friction factors in the Reynolds number range of 600-6000. The flow-fouling experiments delineate the effects of temperature and plate-surface geometry on growth rates and stabilization of fouling resistance, along with the anti-fouling behavior of plates coated with a hydrophobic PTFE (Teflon) film. Moreover, the microscopic structure of fouling deposits is mapped in a scanning-electron microscope. Corrugated plates with the largest height-to-pitch ratio and hydraulic diameter are found to have the lowest fouling growth rate and resistance; Teflon-film coating of plate surface is also found to mitigate fouling relative to the performance of bare stainless steel plates. Finally, a semi-empirical fouling model, based on the Prandtl-Taylor analogy, has been devised to describe the experimental data and provide a predictive tool.

Mutations in Arabidopsis thaliana genes involved in the tryptophan biosynthesis pathway affect root waving on tilted agar surfaces

NASA Technical Reports Server (NTRS)

Rutherford, R.; Gallois, P.; Masson, P. H.

1998-01-01

Arabidopsis thaliana roots grow in a wavy pattern upon a slanted surface. A novel mutation in the anthranilate synthase alpha 1 (ASA1) gene, named trp5-2wvc1, and mutations in the tryptophan synthase alpha and beta 1 genes (trp3-1 and trp2-1, respectively) confer a compressed root wave phenotype on tilted agar surfaces. When trp5-2wvc1 seedlings are grown on media supplemented with anthranilate metabolites, their roots wave like wild type. Genetic and pharmacological experiments argue that the compressed root wave phenotypes of trp5-2wvc1, trp2-1 and trp3-1 seedlings are not due to reduced IAA biosynthetic potential, but rather to a deficiency in L-tryptophan (L-Trp), or in a L-Trp derivative. Although the roots of 7-day-old seedlings possess higher concentrations of free L-Trp than the shoot as a whole, trp5-2wvc1 mutants show no detectable alteration in L-Trp levels in either tissue type, suggesting that a very localized shortage of L-Trp, or of a L-Trp-derived compound, is responsible for the observed phenotype.

Research status and future trends on surface pre-grouting technology in reforming wall rock of vertical shafts in coal mines in China

NASA Astrophysics Data System (ADS)

Wang, Hua

2018-02-01

In the mine construction, the surface pre-grouting technology is an important method to prevent water blast in excavation process of vertical shaft when the shaft must pass through the thick, water-rich and high water-pressure bedrock aquifer. It has been nearly 60 years since the technology was used to reform wall rock of vertical shaft in coal mine in China for the first time, and the existing technology can basically meet the needs of constructing 1000m deep vertical shaft. Firstly, the article introduces that in view of Magg’s spherical seepage theory and Karol’s spherical seepage theory, Chinese scholars found that the diffusion of grout from borehole into the surrounding strata in horizontal direction is irregular through a lot of research and engineering practice of using the surface pre-grouting technology to reform wall rock of vertical shafts, and put forward the selecting principles of grout’s effective diffusion radius in one grouting engineering; Secondly, according to the shape of the grouting boreholes, surface pre-grouting technology of vertical shaft is divided into two stages: vertical borehole stage and S-type borehole stage. Thirdly, the development status of grouting materials and grouting equipment for the technology is introduced. Fourthly, grouting mode, stage height and pressure of the technology are introduced. Finally, it points out that with the increasing depth of coal mining in China, the technology of reforming wall rock of 1000~2000m deep vertical shafts will face many problems, such as grouting theory, grouting equipment, grouting finishing standard, testing and evaluation of grouting effect, and so on. And it put forward a preliminary approach to solving these problems. This paper points out future research directions of the surface pre-grouting technology in China.

Hydrophobic properties of a wavy rough substrate.

PubMed

Carbone, G; Mangialardi, L

2005-01-01

The wetting/non-wetting properties of a liquid drop in contact with a chemically hydrophobic rough surface (thermodynamic contact angle theta(e)>pi/2) are studied for the case of an extremely idealized rough profile: the liquid drop is considered to lie on a simple sinusoidal profile. Depending on surface geometry and pressure values, it is found that the Cassie and Wenzel states can coexist. But if the amplitude h of the substrate is sufficiently large the only possible stable state is the Cassie one, whereas if h is below a certain critical value hcr a transition to the Wenzel state occurs. Since in many potential applications of such super-hydrophobic surfaces, liquid drops often collide with the substrate (e.g. vehicle windscreens), in the paper the critical drop pressure pW is calculated at which the Cassie state is no longer stable and the liquid jumps into full contact with the substrate (Wenzel state). By analyzing the asymptotic behavior of the systems in the limiting case of a large substrate corrugation, a simple criterion is also proposed to calculate the minimum height asperity h necessary to prevent the Wenzel state from being formed, to preserve the super-hydrophobic properties of the substrate, and, hence, to design a robust super-hydrophobic surface.

Different stages and status of vertical transporting process of Cu in Jiaozhou Bay

NASA Astrophysics Data System (ADS)

Yang, Dongfang; Li, Haixia; Wang, Qi; Zhang, Xiaolong; Ding, Jun

2017-12-01

Understanding the stages and status of vertical transporting process of pollutant in marine bay is essential to pollution control. This paper analyzed the stages and status of Cu’s vertical transporting process in waters in Jiaozhou Bay. Results showed that the vertical transporting process in waters in Jiaozhou Bay included four stages of 1) Cu was imported to the bay by major sources, 2) Cu was transported to surface waters, 3) Cu was transported from surface waters to sediment in sea bottom, and 4) Cu was fixed and buried in sediment. Furthermore, Cu’s vertical transporting process could be divided into seven status in detail, and he characteristics of the vertical transport process of Cu were also analyzed.

Production of Near-Mirror Surface Quality by Precision Grinding

NASA Technical Reports Server (NTRS)

Dimofte, Florin; Krantz, Timothy

2003-01-01

Mechanical components such as gears and bearings operate with the working surfaces in intimate contact with a mating part. The performance of such components will be influenced by the quality of the working surface. In general, a smoother surface will perform better than a rougher surface since the lubrication conditions are improved. For example, surfaces with a special near-mirror quality finish of low roughness performed better than ground surfaces when tested using a block-on-ring arrangement. Bearings with near-mirror quality have been tested and analyzed; lower running torques were measured and improved fatigue life was anticipated. Experiments have been done to evaluate the performance of gears with improved, low roughness surface finishing. The measured performance improvements include an increased scuffing (scoring) load capacity by a factor of 1.6, a 30-percent reduction of gear tooth running friction, and longer fatigue lives by a factor of about four. One can also anticipate that near-mirror quality surface finishing could improve the performance of other mechanical components such as mechanical seals and heavily loaded journal bearings. Given these demonstrated benefits, capable and economical methods for the production of mechanical components with near-mirror quality surfaces are desired. One could propose the production of near-mirror quality surfaces by several methods such as abrasive polishing, chemical assisted polishing, or grinding. Production of the surfaces by grinding offers the possibility to control the macro-geometry (form), waviness, and surface texture with one process. The present study was carried out to investigate the possibility of producing near-mirror quality surfaces by grinding. The present study makes use of a specially designed grinding machine spindle to improve the surface quality relative to the quality produced when using a spindle of conventional design.

The Modelling Analysis of the Response of Convective Transport of Energy and Water to Multiscale Surface Heterogeneity over Tibetan Plateau

NASA Astrophysics Data System (ADS)

SUN, G.; Hu, Z.; Ma, Y.; Ma, W.

2017-12-01

The land-atmospheric interactions over a heterogeneous surface is a tricky issue for accurately understanding the energy-water exchanges between land surface and atmosphere. We investigate the vertical transport of energy and water over a heterogeneous land surface in Tibetan Plateau during the evolution of the convective boundary layer using large eddy simulation (WRF_LES). The surface heterogeneity is created according to remote sensing images from high spatial resolution LandSat ETM+ images. The PBL characteristics over a heterogeneous surface are analyzed in terms of secondary circulations under different background wind conditions based on the horizontal and vertical distribution and evolution of wind. The characteristics of vertical transport of energy and heat over a heterogeneous surface are analyzed in terms of the horizontal distribution as well as temporal evolution of sensible and latent heat fluxes at different heights under different wind conditions on basis of the simulated results from WRF_LES. The characteristics of the heat and water transported into the free atmosphere from surface are also analyzed and quantified according to the simulated results from WRF_LES. The convective transport of energy and water are analyzed according to horizontal and vertical distributions of potential temperature and vapor under different background wind conditions. With the analysis based on the WRF_LES simulation, the performance of PBL schemes of mesoscale simulation (WRF_meso) is evaluated. The comparison between horizontal distribution of vertical fluxes and domain-averaged vertical fluxes of the energy and water in the free atmosphere is used to evaluate the performance of PBL schemes of WRF_meso in the simulation of vertical exchange of energy and water. This is an important variable because only the energy and water transported into free atmosphere is able to influence the regional and even global climate. This work would will be of great significance not only for understanding the land atmosphere interactions over a heterogeneous surface by evaluating and improving the performance PBL schemes in WRF-meso, but also for the understanding the profound effect of Tibetan Plateau on the regional and global climate.

Kokopelli Crater on Ceres

NASA Image and Video Library

2017-12-14

This image obtained by NASA's Dawn spacecraft shows a field of small craters next to Kokopelli Crater, seen at bottom right in this image, on dwarf planet Ceres. The small craters overlay a smooth, wavy material that represents ejecta from nearby Dantu Crater. The small craters were formed by blocks ejected in the Dantu impact event, and likely from the Kokopelli impact as well. Kokopelli is named after the fertility deity who presides over agriculture in the tradition of the Pueblo people from the southwestern United States. The crater measures 21 miles (34 kilometers) in diameter. Dawn took this image during its first extended mission on August 11, 2016, from its low-altitude mapping orbit, at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 20 degrees north latitude, 123 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21915

Thermobaricity, cabbeling, and water-mass conversion

NASA Astrophysics Data System (ADS)

McDougall, Trevor J.

1987-05-01

The efficient mixing of heat and salt along neutral surfaces (by mesoscale eddies) is shown to lead to vertical advection through these neutral surfaces. This is due to the nonlinearities of the equation of state of seawater through terms like ∂2ρ/∂θ∂p (thermobaric effect) and ∂2ρ/∂ θ2 (cabbeling). Cabbeling always causes a sinking or downwelling of fluid through neutral surfaces, whereas thermobaricity can lead to a vertical velocity (relative to neutral surfaces) of either sign. In this paper it is shown that for reasonable values of the lateral scalar diffusivity (especially below a depth of 1000 m), these two processes cause vertical velocities of the order of 10-7 m s-1 through neutral surfaces (usually downward!) and cause water-mass conversion of a magnitude equal to that caused by a vertical diffusivity of 10-4 m2 s-1 (often equivalent to a negative diffusivity). Both thermobaricity and cabbeling can occur in the presence of any nonzero amount of small-scale turbulence and so will not be detected by microstructure measurements. The conservation equations for tracers are considered in a nonorthogonal coordinate frame that moves with neutral surfaces in the ocean. Since only mixing processes cause advection across neutral surfaces, it is useful to regard this vertical advection as a symptom of various mixing processes rather than as a separate physical process. It is possible to derive conservative equations for scalars that do not contain the vertical advective term explicity. In these conservation equations, the terms that represent mixing processes are substantially altered. It is argued that this form of the conservation equations is the most appropriate when considering water-mass transformation, and some examples are given of its application in the North Atlantic. It is shown that the variation of the vertical diffusivity with height does not cause water-mass transformation. Also, salt fingering is often 3-4 times more effective at changing the potential temperature of a water mass than would be implied by simply calculating the vertical derivative of the fingering heat flux.

Optoelectronic Materials Center

DTIC Science & Technology

1991-06-11

surface - emitting GaAs/AIGaAs vertical - cavity laser (TJ- VCSEL ) incorporating wavelength-resonant...multi-quantum well, vertical cavity surface - emitted laser . This structure consists entirely of undoped epilayers, thus simplifying the problems of... cavity surface - emitting lasers ( VCSELs ) for doubling and for parallel optical data processing. Progress - GaAIAs/GaAs and InGaAs/GaAs RPG- VCSEL

Miniature modular microwave end-to-end receiver

NASA Technical Reports Server (NTRS)

Sukamto, Lin M. (Inventor); Cooley, Thomas W. (Inventor); Janssen, Michael A. (Inventor); Parks, Gary S. (Inventor)

1993-01-01

An end-to-end microwave receiver system contained in a single miniature hybrid package mounted on a single heatsink is presented. It includes an input end connected to a microwave receiver antenna and an output end which produces a digital count proportional to the amplitude of a signal of a selected microwave frequency band received at the antenna and corresponding to one of the water vapor absorption lines near frequencies of 20 GHz or 30 GHz. The hybrid package is on the order of several centimeters in length and a few centimeters in height and width. The package includes an L-shaped carrier having a base surface, a vertical wall extending up from the base surface and forming a corner therewith, and connection pins extending through the vertical wall. Modular blocks rest on the base surface against the vertical wall and support microwave monolithic integrated circuits on top surfaces thereof connected to the external connection pins. The modular blocks lie end-to-end on the base surface so as to be modularly removable by sliding along the base surface beneath the external connection pins away from the vertical wall.

Optimization of freeform surfaces using intelligent deformation techniques for LED applications

NASA Astrophysics Data System (ADS)

Isaac, Annie Shalom; Neumann, Cornelius

2018-04-01

For many years, optical designers have great interests in designing efficient optimization algorithms to bring significant improvement to their initial design. However, the optimization is limited due to a large number of parameters present in the Non-uniform Rationaly b-Spline Surfaces. This limitation was overcome by an indirect technique known as optimization using freeform deformation (FFD). In this approach, the optical surface is placed inside a cubical grid. The vertices of this grid are modified, which deforms the underlying optical surface during the optimization. One of the challenges in this technique is the selection of appropriate vertices of the cubical grid. This is because these vertices share no relationship with the optical performance. When irrelevant vertices are selected, the computational complexity increases. Moreover, the surfaces created by them are not always feasible to manufacture, which is the same problem faced in any optimization technique while creating freeform surfaces. Therefore, this research addresses these two important issues and provides feasible design techniques to solve them. Finally, the proposed techniques are validated using two different illumination examples: street lighting lens and stop lamp for automobiles.

Composite Characterization Using Ultrasonic Wavefield Techniques

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Juarez, Peter D.; Seebo, Jeffrey P.

2016-01-01

The large-scale use of composite components in aerospace applications is expected to continue due to the benefits of composite materials, such as reduced weight, increased strength, and tailorability. NASA's Advanced Composites Project (ACP) has the goals of reducing the timeline for certification of composite materials and enabling the expanded use of advanced composite materials. A key technical challenge area for accomplishing these goals is the need for nondestructive evaluation and materials characterization techniques that are optimized for rapid inspection and detailed defect/damage characterization in composite materials. This presentation will discuss ongoing research investigating the use of ultrasonic wavefield techniques for the characterization of defects such as fiber waviness and delamination damage. Ongoing work includes the development of realistic ultrasonic simulation tools for use in predicting the inspectability of composites and optimizing inspection methodologies. Recent studies on detecting/characterizing delamination damage and fiber waviness via wavefield methods will be described.

An Acoustofluidic Micromixer via Bubble Inception and Cavitation from Microchannel Sidewalls

PubMed Central

2015-01-01

During the deep reactive ion etching process, the sidewalls of a silicon mold feature rough wavy structures, which can be transferred onto a polydimethylsiloxane (PDMS) microchannel through the soft lithography technique. In this article, we utilized the wavy structures of PDMS microchannel sidewalls to initiate and cavitate bubbles in the presence of acoustic waves. Through bubble cavitation, this acoustofluidic approach demonstrates fast, effective mixing in microfluidics. We characterized its performance by using viscous fluids such as poly(ethylene glycol) (PEG). When two PEG solutions with a resultant viscosity 54.9 times higher than that of water were used, the mixing efficiency was found to be 0.92, indicating excellent, homogeneous mixing. The acoustofluidic micromixer presented here has the advantages of simple fabrication, easy integration, and capability to mix high-viscosity fluids (Reynolds number: ∼0.01) in less than 100 ms. PMID:24754496

A note concerning the onset of three dimensionality and time dependence in Goertler vortices

NASA Technical Reports Server (NTRS)

Bassom, Andrew P.; Seddougui, Sharon O.

1989-01-01

Recently Hall and Seddougui (1989) considered the secondary instability of large amplitude Goertler vortices in a growing boundary layer evolving into a three-dimensional flow with wavy vortex boundaries. They obtained a pair of coupled, linear ordinary differential equations for this instability which constituted an eigenproblem for the wavelength and frequency of this wavy mode. Investigations into the nonlinear version of this problem by Seddougui and Bassom have revealed several omissions in the numerical work of Hall and Seddougui. These issues are addressed in this note. In particular, it is found that many neutrally stable modes are possible. The properties of such modes are derived in a high wavenumber limit and it is shown that the combination of the results of Hall and Seddougui and the modifications made here lead to conclusions which are consistent with the available experimental observations.

Histologic characterization of canine dilated cardiomyopathy.

PubMed

Tidholm, A; Jönsson, L

2005-01-01

Dilated cardiomyopathy (DCM), characterized by chamber dilatation and myocardial systolic and diastolic dysfunction, is one of the most common heart diseases in dogs. The clinical diagnosis is based on findings on echocardiographic and Doppler examinations, with the active exclusion of other acquired or congenital heart diseases. However, the echocardiographic criteria for the diagnosis of DCM are not wholly specific for the disease, and histologic examination may be necessary for final diagnosis. Review of reports on histologic findings in dogs with clinically diagnosed DCM reveals two histologically distinct forms of DCM: 1) cardiomyopathy of Boxers and Doberman Pinschers, corresponding to the "fatty infiltration-degenerative" type and 2) the form seen in many giant, large-, and medium-sized breeds, including some Boxers and Doberman Pinschers, classified as the "attenuated wavy fiber" type of DCM. The histologic changes of the attenuated wavy fiber type of DCM may precede clinical and echocardiographic signs of heart disease, thus indicating an early stage of DCM.

The Fluid Mechanics of a Wavy-Wall Bioreactor

NASA Astrophysics Data System (ADS)

Sucosky, Philippe; Bilgen, Bahar; Aleem, Alexander; Neitzel, Paul; Barabino, Gilda

2004-11-01

Bioreactors are devices used for the production of mammalian tissue in vitro. Although mixing has been shown to stimulate the growth of cartilage constructs, high shear-stress levels can damage the cells. In order to enhance mixing while minimizing shear, a wavy-wall bioreactor (WWB) featuring a sinusoidal internal profile has been designed. The turbulent hydrodynamic environment produced in this device is investigated experimentally using particle-image velocimetry. A model bioreactor made of acrylic and filled with an index-matching solution of zinc iodide is used to compensate for the refraction of light at the walls. The flow observed in different planes is shown to be periodic, spatially dependent, and dominated by mean-shear rather than Reynolds stresses in the vicinity of constructs. Finally, a comparison between the mean-shear stresses obtained in the WWB and in a standard spinner flask reveals similar stress levels near the construct walls.

Investigation on the Interface Morphologies of Explosive Welding of Inconel 625 to Steel A516 Plates

NASA Astrophysics Data System (ADS)

Mousavi, S. A. A. Akbari; Zareie, H. R.

2011-01-01

The purpose of this study is to produce composite plates by explosive cladding process. This is a process in which the controlled energy of explosives is used to create a metallic bond between two similar or dissimilar materials. The welding conditions were tailored through parallel geometry route with different operational parameters. In this investigation, a two-pronged study was adopted to establish the conditions required for producing successful solid state welding: (a) Analytical calculations to determine the weldability domain or welding window; (b) Metallurgical investigations of explosive welding experiments carried out under different explosive ratios to produce both wavy and straight interfaces. The analytical calculations confirm the experimental results. Optical microscopy studies show that a transition from a smooth to wavy interface occurs with an increase in explosive ratio. SEM studies show that the interface was outlined by characteristic sharp transition between two materials.

Underwater sky image as remote sensing instrument of sea roughness parameters and its variability

NASA Astrophysics Data System (ADS)

Molkov, Alexander A.; Dolin, Lev S.; Kapustin, Ivan A.; Sergievskaya, Irina A.; Shomina, Olga V.

2016-10-01

At present a sufficient amount of methods is offered for determining the characteristics of sea roughness in accordance with optical images of wavy water surface obtained from different near-shore constructions, sea platforms, vessels, aircraft and satellites. The most informative elements in this case are solar path and peripheral areas of the image free from sun glitters. However, underwater images of the surface obtained with the help of optical receiver located at a certain depth contain apart from the mentioned elements one more informative element- Snell's window. It is an underwater sky image which distortions of border contain information on roughness characteristics and serve as the indicator of its variability. The research offers the method for determining energy spectra of wind waves in accordance with the second statistical moment of Snell's window image. The results of testing of the offered method are provided based on natural images registered in the course of trip to the Black Sea under conditions of different wind and wave environment for clear surface and surface covered by surfactant films. For both cases frequency spectra of surface slopes are recovered and their good coincidence to the spectra received by processing of signals from a string wave recorder is established. Efficiency of application of the offered method for tasks of remote monitoring and environmental control of natural reservoirs is shown.

Quasi-Geostrophic Diagnosis of Mixed-Layer Dynamics Embedded in a Mesoscale Turbulent Field

NASA Astrophysics Data System (ADS)

Chavanne, C. P.; Klein, P.

2016-02-01

A new quasi-geostrophic model has been developed to diagnose the three-dimensional circulation, including the vertical velocity, in the upper ocean from high-resolution observations of sea surface height and buoyancy. The formulation for the adiabatic component departs from the classical surface quasi-geostrophic framework considered before since it takes into account the stratification within the surface mixed-layer that is usually much weaker than that in the ocean interior. To achieve this, the model approximates the ocean with two constant-stratification layers : a finite-thickness surface layer (or the mixed-layer) and an infinitely-deep interior layer. It is shown that the leading-order adiabatic circulation is entirely determined if both the surface streamfunction and buoyancy anomalies are considered. The surface layer further includes a diabatic dynamical contribution. Parameterization of diabatic vertical velocities is based on their restoring impacts of the thermal-wind balance that is perturbed by turbulent vertical mixing of momentum and buoyancy. The model skill in reproducing the three-dimensional circulation in the upper ocean from surface data is checked against the output of a high-resolution primitive-equation numerical simulation. Correlation between simulated and diagnosed vertical velocities are significantly improved in the mixed-layer for the new model compared to the classical surface quasi-geostrophic model, reaching 0.9 near the surface.

Hybrid radiator cooling system

DOEpatents

France, David M.; Smith, David S.; Yu, Wenhua; Routbort, Jules L.

2016-03-15

A method and hybrid radiator-cooling apparatus for implementing enhanced radiator-cooling are provided. The hybrid radiator-cooling apparatus includes an air-side finned surface for air cooling; an elongated vertically extending surface extending outwardly from the air-side finned surface on a downstream air-side of the hybrid radiator; and a water supply for selectively providing evaporative cooling with water flow by gravity on the elongated vertically extending surface.

Violent transient sloshing-wave interaction with a baffle in a three-dimensional numerical tank

NASA Astrophysics Data System (ADS)

Xue, Mi-An; Zheng, Jinhai; Lin, Pengzhi; Xiao, Zhong

2017-08-01

A finite difference model for solving Navier Stokes equations with turbulence taken into account is used to investigate viscous liquid sloshing-wave interaction with baffles in a tank. The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.

Estimating shallow subsidence in microtidal salt marshes of the southeastern United States: Kaye and Barghoorn revisited

USGS Publications Warehouse

Cahoon, D.R.; Reed, D.J.; Day, J.W.

1995-01-01

Simultaneous measurements of vertical accretion and change in surface elevation relative to a shallow (3-5 m) subsurface datum were made in selected coastal salt marshes of Louisiana, Florida, and North Carolina to quantitatively test Kaye and Barghoorn's contention that vertical accretion is not a good surrogate for surface elevation change because of autocompaction of the substrate. Rates of subsidence of the upper 3-5 m of marsh substrate were calculated for each marsh as the difference between vertical accretion and elevation change measured with feldspar marker horizons and a sedimentation-erosion table. Surface elevation change was significantly lower than vertical accretion at each site after 2 years, indicating a significant amount of shallow subsidence had occurred, ranging from 0.45 to 4.90 cm. The highest rate of shallow subsidence occurred in the Mississippi delta. Results confirm Kaye and Barghoorn's contention that vertical accretion is not generally a good surrogate for elevation change because of processes occurring in the upper few meters of the substrate, including not only compaction but also apparently shrink-swell from water storage and/or plant production--decomposition at some sites. Indeed, surface elevation change was completely decoupled from vertical accretion at the Florida site. The assumption of a 1:1 relationship between accretionary and substrate processes. Consequently, the potential for coastal marsh submergence should be expressed as an elevation deficit based on direct measures of surface elevation change rather than accretion deficits. These findings also indicate the need for greater understanding of the influence of subsurface and small-scale hydrologic processes on marsh surface elevation.

Multiphoton microscopy observations of 3D elastin and collagen fiber microstructure changes during pressurization in aortic media.

PubMed

Sugita, Shukei; Matsumoto, Takeo

2017-06-01

Elastin and collagen fibers play important roles in the mechanical properties of aortic media. Because knowledge of local fiber structures is required for detailed analysis of blood vessel wall mechanics, we investigated 3D microstructures of elastin and collagen fibers in thoracic aortas and monitored changes during pressurization. Using multiphoton microscopy, autofluorescence images from elastin and second harmonic generation signals from collagen were acquired in media from rabbit thoracic aortas that were stretched biaxially to restore physiological dimensions. Both elastin and collagen fibers were observed in all longitudinal-circumferential plane images, whereas alternate bright and dark layers were observed along the radial direction and were recognized as elastic laminas (ELs) and smooth muscle-rich layers (SMLs), respectively. Elastin and collagen fibers are mainly oriented in the circumferential direction, and waviness of collagen fibers was significantly higher than that of elastin fibers. Collagen fibers were more undulated in longitudinal than in radial direction, whereas undulation of elastin fibers was equibiaxial. Changes in waviness of collagen fibers during pressurization were then evaluated using 2-dimensional fast Fourier transform in mouse aortas, and indices of waviness of collagen fibers decreased with increases in intraluminal pressure. These indices also showed that collagen fibers in SMLs became straight at lower intraluminal pressures than those in EL, indicating that SMLs stretched more than ELs. These results indicate that deformation of the aorta due to pressurization is complicated because of the heterogeneity of tissue layers and differences in elastic properties of ELs, SMLs, and surrounding collagen and elastin.

Direct observation for atomically flat and ordered vertical {111} side-surfaces on three-dimensionally figured Si(110) substrate using scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Yang, Haoyu; Hattori, Azusa N.; Ohata, Akinori; Takemoto, Shohei; Hattori, Ken; Daimon, Hiroshi; Tanaka, Hidekazu

2017-11-01

A three-dimensional Si{111} vertical side-surface structure on a Si(110) wafer was fabricated by reactive ion etching (RIE) followed by wet-etching and flash-annealing treatments. The side-surface was studied with scanning tunneling microscopy (STM) in atomic scale for the first time, in addition to atomic force microscopy (AFM), scanning electron microscopy (SEM), and low-energy electron diffraction (LEED). AFM and SEM showed flat and smooth vertical side-surfaces without scallops, and STM proved the realization of an atomically-flat 7 × 7-reconstructed structure, under optimized RIE and wet-etching conditions. STM also showed that a step-bunching occurred on the produced {111} side-surface corresponding to a reversely taped side-surface with a tilt angle of a few degrees, but did not show disordered structures. Characteristic LEED patterns from both side- and top-reconstructed surfaces were also demonstrated.

The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running.

PubMed

Boey, Hannelore; Aeles, Jeroen; Schütte, Kurt; Vanwanseele, Benedicte

2017-06-01

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

Decoration of vertical graphene with aerosol nanoparticles for gas sensing

NASA Astrophysics Data System (ADS)

Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

2015-08-01

A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

Application of Particle Image Velocimetry and Reference Image Topography to jet shock cells using the hydraulic analogy

NASA Astrophysics Data System (ADS)

Kumar, Vaibhav; Ng, Ivan; Sheard, Gregory J.; Brocher, Eric; Hourigan, Kerry; Fouras, Andreas

2011-08-01

This paper examines the shock cell structure, vorticity and velocity field at the exit of an underexpanded jet nozzle using a hydraulic analogy and the Reference Image Topography technique. Understanding the flow in this region is important for the mitigation of screech, an aeroacoustic problem harmful to aircraft structures. Experiments are conducted on a water table, allowing detailed quantitative investigation of this important flow regime at a greatly reduced expense. Conventional Particle Image Velocimetry is employed to determine the velocity and vorticity fields of the nozzle exit region. Applying Reference Image Topography, the wavy water surface is reconstructed and when combined with the hydraulic analogy, provides a pressure map of the region. With this approach subtraction of surfaces is used to highlight the unsteady regions of the flow, which is not as convenient or quantitative with conventional Schlieren techniques. This allows a detailed analysis of the shock cell structures and their interaction with flow instabilities in the shear layer that are the underlying cause of jet screech.

Viscoacoustic model for near-field ultrasonic levitation.

PubMed

Melikhov, Ivan; Chivilikhin, Sergey; Amosov, Alexey; Jeanson, Romain

2016-11-01

Ultrasonic near-field levitation allows for contactless support and transportation of an object over vibrating surface. We developed an accurate model predicting pressure distribution in the gap between the surface and levitating object. The formulation covers a wide range of the air flow regimes: from viscous squeezed flow dominating in small gap to acoustic wave propagation in larger gap. The paper explains derivation of the governing equations from the basic fluid dynamics. The nonreflective boundary conditions were developed to properly define air flow at the outlet. Comparing to direct computational fluid dynamics modeling our approach allows achieving good accuracy while keeping the computation cost low. Using the model we studied the levitation force as a function of gap distance. It was shown that there are three distinguished flow regimes: purely viscous, viscoacoustic, and acoustic. The regimes are defined by the balance of viscous and inertial forces. In the viscous regime the pressure in the gap is close to uniform while in the intermediate viscoacoustic and the acoustic regimes the pressure profile is wavy. The model was validated by a dedicated levitation experiment and compared to similar published results.

Viscoacoustic model for near-field ultrasonic levitation

NASA Astrophysics Data System (ADS)

Melikhov, Ivan; Chivilikhin, Sergey; Amosov, Alexey; Jeanson, Romain

2016-11-01

Ultrasonic near-field levitation allows for contactless support and transportation of an object over vibrating surface. We developed an accurate model predicting pressure distribution in the gap between the surface and levitating object. The formulation covers a wide range of the air flow regimes: from viscous squeezed flow dominating in small gap to acoustic wave propagation in larger gap. The paper explains derivation of the governing equations from the basic fluid dynamics. The nonreflective boundary conditions were developed to properly define air flow at the outlet. Comparing to direct computational fluid dynamics modeling our approach allows achieving good accuracy while keeping the computation cost low. Using the model we studied the levitation force as a function of gap distance. It was shown that there are three distinguished flow regimes: purely viscous, viscoacoustic, and acoustic. The regimes are defined by the balance of viscous and inertial forces. In the viscous regime the pressure in the gap is close to uniform while in the intermediate viscoacoustic and the acoustic regimes the pressure profile is wavy. The model was validated by a dedicated levitation experiment and compared to similar published results.

Certification aspects of airplanes which may operate with significant natural laminar flow

NASA Technical Reports Server (NTRS)

Gabriel, Edward A.; Tankesley, Earsa L.

1986-01-01

Recent research by NASA indicates that extensive natural laminar flow (NLF) is attainable on modern high performance airplanes currently under development. Modern airframe construction methods and materials, such as milled aluminum skins, bonded aluminum skins, and composite materials, offer the potential for production of aerodynamic surfaces having waviness and roughness below the values which are critical for boundary layer transition. Areas of concern with the certification aspects of Natural Laminar Flow (NLF) are identified to stimulate thought and discussion of the possible problems. During its development, consideration has been given to the recent research information available on several small business and experimental airplanes and the certification and operating rules for general aviation airplanes. The certification considerations discussed are generally applicable to both large and small airplanes. However, from the information available at this time, researchers expect more extensive NLF on small airplanes because of their lower operating Reynolds numbers and cleaner leading edges (due to lack of leading-edge high lift devices). Further, the use of composite materials for aerodynamic surfaces, which will permit incorporation of NLF technology, is currently beginning to appear in small airplanes.

Seasonal Mass Changes and Crustal Vertical Deformations Constrained by GPS and GRACE in Northeastern Tibet

PubMed Central

Pan, Yuanjin; Shen, Wen-Bin; Hwang, Cheinway; Liao, Chaoming; Zhang, Tengxu; Zhang, Guoqing

2016-01-01

Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs), in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE) mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA) contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet. PMID:27490550

Cloud vertical distribution from combined surface and space radar-lidar observations at two Arctic atmospheric observatories

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

Liu, Yinghui; Shupe, Matthew D.; Wang, Zhien

Detailed and accurate vertical distributions of cloud properties (such as cloud fraction, cloud phase, and cloud water content) and their changes are essential to accurately calculate the surface radiative flux and to depict the mean climate state. Surface and space-based active sensors including radar and lidar are ideal to provide this information because of their superior capability to detect clouds and retrieve cloud microphysical properties. In this study, we compare the annual cycles of cloud property vertical distributions from space-based active sensors and surface-based active sensors at two Arctic atmospheric observatories, Barrow and Eureka. Based on the comparisons, we identifymore » the sensors' respective strengths and limitations, and develop a blended cloud property vertical distribution by combining both sets of observations. Results show that surface-based observations offer a more complete cloud property vertical distribution from the surface up to 11 km above mean sea level (a.m.s.l.) with limitations in the middle and high altitudes; the annual mean total cloud fraction from space-based observations shows 25-40 % fewer clouds below 0.5 km than from surface-based observations, and space-based observations also show much fewer ice clouds and mixed-phase clouds, and slightly more liquid clouds, from the surface to 1 km. In general, space-based observations show comparable cloud fractions between 1 and 2 km a.m.s.l., and larger cloud fractions above 2 km a.m.s.l. than from surface-based observations. A blended product combines the strengths of both products to provide a more reliable annual cycle of cloud property vertical distributions from the surface to 11 km a.m.s.l. This information can be valuable for deriving an accurate surface radiative budget in the Arctic and for cloud parameterization evaluation in weather and climate models. Cloud annual cycles show similar evolutions in total cloud fraction and ice cloud fraction, and lower liquid-containing cloud fraction at Eureka than at Barrow; the differences can be attributed to the generally colder and drier conditions at Eureka relative to Barrow.« less

Cloud vertical distribution from combined surface and space radar-lidar observations at two Arctic atmospheric observatories

DOE PAGES

Liu, Yinghui; Shupe, Matthew D.; Wang, Zhien; ...

2017-05-16

Detailed and accurate vertical distributions of cloud properties (such as cloud fraction, cloud phase, and cloud water content) and their changes are essential to accurately calculate the surface radiative flux and to depict the mean climate state. Surface and space-based active sensors including radar and lidar are ideal to provide this information because of their superior capability to detect clouds and retrieve cloud microphysical properties. In this study, we compare the annual cycles of cloud property vertical distributions from space-based active sensors and surface-based active sensors at two Arctic atmospheric observatories, Barrow and Eureka. Based on the comparisons, we identifymore » the sensors' respective strengths and limitations, and develop a blended cloud property vertical distribution by combining both sets of observations. Results show that surface-based observations offer a more complete cloud property vertical distribution from the surface up to 11 km above mean sea level (a.m.s.l.) with limitations in the middle and high altitudes; the annual mean total cloud fraction from space-based observations shows 25-40 % fewer clouds below 0.5 km than from surface-based observations, and space-based observations also show much fewer ice clouds and mixed-phase clouds, and slightly more liquid clouds, from the surface to 1 km. In general, space-based observations show comparable cloud fractions between 1 and 2 km a.m.s.l., and larger cloud fractions above 2 km a.m.s.l. than from surface-based observations. A blended product combines the strengths of both products to provide a more reliable annual cycle of cloud property vertical distributions from the surface to 11 km a.m.s.l. This information can be valuable for deriving an accurate surface radiative budget in the Arctic and for cloud parameterization evaluation in weather and climate models. Cloud annual cycles show similar evolutions in total cloud fraction and ice cloud fraction, and lower liquid-containing cloud fraction at Eureka than at Barrow; the differences can be attributed to the generally colder and drier conditions at Eureka relative to Barrow.« less

Spatial Light Modulators with Arbitrary Quantum Well Profiles

DTIC Science & Technology

1991-01-14

vertical cavity surface emitting lasers ( VCSEL ) is also...aDlications stemming from the research effort. An application of the MBE compositional grading technique to vertical cavity surface emitting lasers was described in section 2e. G. Other statements ... cavity surface emitting laser ( VCSEL ). This uses compositionally graded Bragg reflectors to reduce the electrical resistance of the mirrors

Quantitative RHEED Studies of MBE Growth of 3-5 Compounds

DTIC Science & Technology

1991-06-03

Vertical - Cavity Surface - Emitting Laser Using Molecular Beam Epitaxial ...Growth of Vertical Cavity Surface - emitting Lasers Our work under this ARO contract on the control of MBE growth has enhanced our ability to grow...pattern about the surface structure of nearly perfect crystals prepared by Molecular Beam Epitaxy ( MBE ) and to use these techniques

Simulations of vertical disruptions with VDE code: Hiro and Evans currents

NASA Astrophysics Data System (ADS)

Li, Xujing; Di Hu Team; Leonid Zakharov Team; Galkin Team

2014-10-01

The recently created numerical code VDE for simulations of vertical instability in tokamaks is presented. The numerical scheme uses the Tokamak MHD model, where the plasma inertia is replaced by the friction force, and an adaptive grid numerical scheme. The code reproduces well the surface currents generated at the plasma boundary by the instability. Five regimes of the vertical instability are presented: (1) Vertical instability in a given plasma shaping field without a wall; (2) The same with a wall and magnetic flux ΔΨ|plX< ΔΨ|Xwall(where X corresponds to the X-point of a separatrix); (3) The same with a wall and magnetic flux ΔΨ|plX> ΔΨ|Xwall; (4) Vertical instability without a wall with a tile surface at the plasma path; (5) The same in the presence of a wall and a tile surface. The generation of negative Hiro currents along the tile surface, predicted earlier by the theory and measured on EAST in 2012, is well-reproduced by simulations. In addition, the instability generates the force-free Evans currents at the free plasma surface. The new pattern of reconnection of the plasma with the vacuum magnetic field is discovered. This work is supported by US DoE Contract No. DE-AC02-09-CH11466.

Accurate pressure gradient calculations in hydrostatic atmospheric models

NASA Technical Reports Server (NTRS)

Carroll, John J.; Mendez-Nunez, Luis R.; Tanrikulu, Saffet

1987-01-01

A method for the accurate calculation of the horizontal pressure gradient acceleration in hydrostatic atmospheric models is presented which is especially useful in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The present method is shown to be exact if the potential temperature lapse rate is constant between the vertical pressure integration limits. The technique is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. A fixed vertical grid and a dynamic grid defined by the significant levels in the vertical temperature distribution are employed.

Electrochemical Control of Peptide Self-Organization on Atomically Flat Solid Surfaces: A Case Study with Graphite.

PubMed

Seki, Takakazu; So, Christopher R; Page, Tamon R; Starkebaum, David; Hayamizu, Yuhei; Sarikaya, Mehmet

2018-02-06

The nanoscale self-organization of biomolecules, such as proteins and peptides, on solid surfaces under controlled conditions is an important issue in establishing functional bio/solid soft interfaces for bioassays, biosensors, and biofuel cells. Electrostatic interaction between proteins and surfaces is one of the most essential parameters in the adsorption and self-assembly of proteins on solid surfaces. Although the adsorption of proteins has been studied with respect to the electrochemical surface potential, the self-assembly of proteins or peptides forming well-organized nanostructures templated by lattice structure of the solid surfaces has not been studied in the relation to the surface potential. In this work, we utilize graphite-binding peptides (GrBPs) selected by the phage display method to investigate the relationship between the electrochemical potential of the highly ordered pyrolytic graphite (HOPG) and peptide self-organization forming long-range-ordered structures. Under modulated electrical bias, graphite-binding peptides form various ordered structures, such as well-ordered nanowires, dendritic structures, wavy wires, amorphous (disordered) structures, and islands. A systematic investigation of the correlation between peptide sequence and self-organizational characteristics reveals that the presence of the bias-sensitive amino acid modules in the peptide sequence has a significant effect on not only surface coverage but also on the morphological features of self-assembled structures. Our results show a new method to control peptide self-assembly by means of applied electrochemical bias as well as peptide design-rules for the construction of functional soft bio/solid interfaces that could be integrated in a wide range of practical implementations.

Observations and Numerical Modeling of the Jovian Ribbon

NASA Technical Reports Server (NTRS)

Cosentino, R. G.; Simon, A.; Morales-Juberias, R.; Sayanagi, K. M.

2015-01-01

Multiple wavelength observations made by the Hubble Space Telescope in early 2007 show the presence of a wavy, high-contrast feature in Jupiter's atmosphere near 30 degrees North. The "Jovian Ribbon," best seen at 410 nanometers, irregularly undulates in latitude and is time-variable in appearance. A meridional intensity gradient algorithm was applied to the observations to track the Ribbon's contour. Spectral analysis of the contour revealed that the Ribbon's structure is a combination of several wavenumbers ranging from k equals 8-40. The Ribbon is a dynamic structure that has been observed to have spectral power for dominant wavenumbers which vary over a time period of one month. The presence of the Ribbon correlates with periods when the velocity of the westward jet at the same location is highest. We conducted numerical simulations to investigate the stability of westward jets of varying speed, vertical shear, and background static stability to different perturbations. A Ribbon-like morphology was best reproduced with a 35 per millisecond westward jet that decreases in amplitude for pressures greater than 700 hectopascals and a background static stability of N equals 0.005 per second perturbed by heat pulses constrained to latitudes south of 30 degrees North. Additionally, the simulated feature had wavenumbers that qualitatively matched observations and evolved throughout the simulation reproducing the Jovian Ribbon's dynamic structure.

Temperature characteristics at altitudes of 5-80 km with a self-calibrated Rayleigh-rotational Raman lidar: A summer case study

NASA Astrophysics Data System (ADS)

Li, Yajuan; Lin, Xin; Yang, Yong; Xia, Yuan; Xiong, Jun; Song, Shalei; Liu, Linmei; Chen, Zhenwei; Cheng, Xuewu; Li, Faquan

2017-02-01

Temperature profiles at altitudes of 5-80 km are obtained with a self-calibrated Rayleigh-rotational Raman lidar over Wuhan, China (30.5°N, 114.5°E). By using the synchronous Rayleigh lidar temperature, rotational Raman temperature in the lower atmosphere could be calibrated and retrieved, which is free of other instruments (like local radiosondes). The results are comparable to the radiosonde calibration method. Based on the self-calibration approach, one-night (August 4-5, 2014) lidar temperature profiles are presented with radiosondes, NRLMSISE-00 model and TIMED/SABER data. Some interesting temperature characteristics have been present for studies of waves propagating from near ground level into the mesosphere. Temperature perturbations are found to increase exponentially with a scale height of 10 km. The wavy structure shows minimal perturbations ('nodes') at some altitudes of 39, 52, 64 and 73 km. Dominant wavelengths and temperature variations are also analyzed at different time and altitudes. By comparison of the temperature and associate perturbations from the tropopause up to the stratopause, different amplitudes, phase fronts and vertical wavelengths are discovered as well. These discoveries indicate that some waves may originate in the lower atmosphere and propagate upward with decreasing static stability.

Vertical electro-absorption modulator design and its integration in a VCSEL

NASA Astrophysics Data System (ADS)

Marigo-Lombart, L.; Calvez, S.; Arnoult, A.; Thienpont, H.; Almuneau, G.; Panajotov, K.

2018-04-01

Electro-absorption modulators, either embedded in CMOS technology or integrated with a semiconductor laser, are of high interest for many applications such as optical communications, signal processing and 3D imaging. Recently, the integration of a surface-normal electro-absorption modulator into a vertical-cavity surface-emitting laser has been considered. In this paper we implement a simple quantum well electro-absorption model and design and optimize an asymmetric Fabry-Pérot semiconductor modulator while considering all physical properties within figures of merit. We also extend this model to account for the impact of temperature on the different parameters involved in the calculation of the absorption, such as refractive indices and exciton transition broadening. Two types of vertical modulator structures have been fabricated and experimentally characterized by reflectivity and photocurrent measurements demonstrating a very good agreement with our model. Finally, preliminary results of an electro-absorption modulator vertically integrated with a vertical-cavity surface-emitting laser device are presented, showing good modulation performances required for high speed communications.

Diel changes in the near-surface biomass of zooplankton and the carbon content of vertical migrants

NASA Astrophysics Data System (ADS)

Hays, Graeme C.; Harris, Roger P.; Head, Robert N.

Zooplankton biomass and the carbon content of vertical migrants were measured in the NE Atlantic (36.5°N, 19.2°W) between 11 and 18 July 1996 as part of the Plankton Reactivity in the Marine Environment (PRIME) programme. The increase in zooplankton biomass near the surface (0-100 m) at night compared to during the day suggested that diel vertical migration was an important feature at this site. For three species of vertically migrant copepods, Pleuromamma pisekii, P. gracilis and P. abdominalis, the carbon content of individuals collected at dusk was significantly less than for individuals collected at dawn, with this reduction being 6.2, 7.3 and 14.8%, respectively. This dawn-dusk reduction in carbon content is consistent with the diel pattern of feeding and fasting exhibited by vertical migrants and supports the suggestion that migrating zooplankton will cause an active export of carbon from the surface layers.

Earth-atmosphere system and surface reflectivities in arid regions from LANDSAT multispectral scanner measurements

NASA Technical Reports Server (NTRS)

Otterman, J.; Fraser, R. S.

1976-01-01

Programs for computing atmospheric transmission and scattering solar radiation were used to compute the ratios of the Earth-atmosphere system (space) directional reflectivities in the vertical direction to the surface reflectivity, for the four bands of the LANDSAT multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa and Central America from the spectral radiance levels measured by the LANDSAT MSS. From these space reflectivities, surface vertical reflectivities were computed applying the pertinent graphs. These surface reflectivities were used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory measurements.

The significance of vertical moisture diffusion on drifting snow sublimation near snow surface

NASA Astrophysics Data System (ADS)

Huang, Ning; Shi, Guanglei

2017-12-01

Sublimation of blowing snow is an important parameter not only for the study of polar ice sheets and glaciers, but also for maintaining the ecology of arid and semi-arid lands. However, sublimation of near-surface blowing snow has often been ignored in previous studies. To study sublimation of near-surface blowing snow, we established a sublimation of blowing snow model containing both a vertical moisture diffusion equation and a heat balance equation. The results showed that although sublimation of near-surface blowing snow was strongly reduced by a negative feedback effect, due to vertical moisture diffusion, the relative humidity near the surface does not reach 100 %. Therefore, the sublimation of near-surface blowing snow does not stop. In addition, the sublimation rate near the surface is 3-4 orders of magnitude higher than that at 10 m above the surface and the mass of snow sublimation near the surface accounts for more than half of the total snow sublimation when the friction wind velocity is less than about 0.55 m s-1. Therefore, the sublimation of near-surface blowing snow should not be neglected.

Scattering-type scanning near-field optical microscopy with reconstruction of vertical interaction

PubMed Central

Wang, Le; Xu, Xiaoji G.

2015-01-01

Scattering-type scanning near-field optical microscopy provides access to super-resolution spectroscopic imaging of the surfaces of a variety of materials and nanostructures. In addition to chemical identification, it enables observations of nano-optical phenomena, such as mid-infrared plasmons in graphene and phonon polaritons in boron nitride. Despite the high lateral spatial resolution, scattering-type near-field optical microscopy is not able to provide characteristics of near-field responses in the vertical dimension, normal to the sample surface. Here, we present an accurate and fast reconstruction method to obtain vertical characteristics of near-field interactions. For its first application, we investigated the bound electromagnetic field component of surface phonon polaritons on the surface of boron nitride nanotubes and found that it decays within 20 nm with a considerable phase change in the near-field signal. The method is expected to provide characterization of the vertical field distribution of a wide range of nano-optical materials and structures. PMID:26592949

Film flow and heat transfer during condensation of steam on inclined and vertical nonround tubes

NASA Astrophysics Data System (ADS)

Nikitin, N. N.; Semenov, V. P.

2008-03-01

We describe a mathematical model for calculating heat transfer during film condensation of stagnant steam on inclined and vertical smooth tubes with cross sections of arbitrary shape that takes into account the action of surface tension forces. The heat-transfer coefficients are calculated, and the hydrodynamic pattern is presented in which a condensate film flows over the surface of nonround inclined and vertical tubes with cross-section of different shapes.

3-D profilometer using a CCD linear image sensor: application to skin surface topography measurement.

PubMed

Nita, D; Mignot, J; Chuard, M; Sofa, M

1998-08-01

Measurement of cutaneous surface topography can be made by three-dimensional (3-D) profilometry. Different equipment is used for this measurement. The magnitude of the vertical scale required, which can vary from several tens of micrometers (microrelief) to several millimeters (skin pathologies), depends also on the precision required and the duration of acquisition time. Over the last few years, different apparatuses have been produced, with a vertical range that is most frequently used for classical industrial applications, i.e., 0-1000 μm. The system developed here has a wide range of about 7 mm and is accurate enough to analyse each of the different skin surfaces that fall in this range without changing magnification. An optical principle, operating without any contact with a skin replica, allows a precise measurement with a high scanning speed. The profilometer has a vertical sensitivity of 4 μm within a vertical range of 7 mm. This sensitivity is lower than that of a mechanical or focusing profilometer, but the vertical range is wider. The system has several advantages: because of its verticale range, it can measure large surfaces with great roughness variations; the initial position of the replica beneath the profilometer must be within the 7 mm vertical range; and skin topography can be quantified, without contact, in a short time.

High Temperature Monitoring the Height of Condensed Water in Steam Pipes

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; Badescu, Mircea; Bao, Xiaoqi; Sherrit, Stewart; Widholm, Scott; Ostlund, Patrick; Blosiu, Julian

2011-01-01

An in-service health monitoring system is needed for steam pipes to track through their wall the condensation of water. The system is required to measure the height of the condensed water inside the pipe while operating at temperatures that are as high as 250 deg. C. The system needs to be able to make real time measurements while accounting for the effects of cavitation and wavy water surface. For this purpose, ultrasonic wave in pulse-echo configuration was used and reflected signals were acquired and auto-correlated to remove noise from the data and determine the water height. Transmitting and receiving the waves is done by piezoelectric transducers having Curie temperature that is significantly higher than 250 deg. C. Measurements were made at temperatures as high as 250 deg. C and have shown the feasibility of the test method. This manuscript reports the results of this feasibility study.

Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors

DOE PAGES

Bartel, N.; Chen, M.; Utgikar, V. P.; ...

2015-04-04

A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimummore » combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well.« less

Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors

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

Bartel, N.; Chen, M.; Utgikar, V. P.

A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimummore » combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well.« less

Face-seal lubrication: 1: Proposed and published models

NASA Technical Reports Server (NTRS)

Ludwig, L. P.

1976-01-01

The numerous published theories on the mechanism of hydrodynamic lubrication of face seals were reviewed. These theories employ either an inclined-slider-bearing macrogeometry or an inclined-slider-bearing microgeometry to produce hydrodynamic pressure that separates the surfaces of the primary seal. Secondary seal friction and primary ring inertia effects are not considered. Hypothetical seal operating models were devised to include secondary seal friction and primary ring inertia effects. It was hypothesized that these effects induce relative angular misalinement of the primary seal faces and that this misalinement is, in effect, an inclined slider macrogeometry. Stable running was postulated for some of these hypothetical operating models. In others, periodic loss of hydrodynamic lubrication was postulated to be possible with certain combinations of waviness and angular misalinement. Application of restrictions that apply to seal operation led to a hydrodynamic governing equation for the new model that is a two-dimensional, time-dependent Reynolds equation with the short-bearing approximation.

Comparative performance of solar thermal power generation concepts

NASA Technical Reports Server (NTRS)

Wen, L.; Wu, Y. C.

1976-01-01

A performance comparison is made between the central receiver system (power tower) and a distributed system using either dishes or troughs and lines to transport fluids to the power station. These systems were analyzed at a rated capacity of 30 MW of thermal energy delivered in the form of superheated steam at 538 C (1000 F) and 68 atm (1000 psia), using consistent weather data, collector surface waviness, pointing error, and electric conversion efficiency. The comparisons include technical considerations for component requirements, land utilization, and annual thermal energy collection rates. The relative merits of different representative systems are dependent upon the overall conversion as expressed in the form of performance factors in this paper. These factors are essentially indices of the relative performance effectiveness for different concepts based upon unit collector area. These performance factors enable further economic tradeoff studies of systems to be made by comparing them with projected production costs for these systems.

A function-driven characterization of printed conductors on PV cells

NASA Astrophysics Data System (ADS)

Bellotti, Roberto; Furin, Valentina; Maras, Claire; Bartolo Picotto, Gian; Ribotta, Luigi

2018-06-01

Nowadays the development in photovoltaic (PV) cells manufacturing requires increasingly sophisticated technologies, and in order to avoid efficiency losses in PV cell, printing techniques of the front contacts have to be well controlled. To this purpose, printed linear conductors (PLCs) on a PV standard cell are characterized by morphology- and resistance-based measurements, creating a well-calibrated test structure towards the development of an application-oriented material measure. It can be noticed that morphology and texture parameters determined by stylus and optical profilers are well in agreement, and the resistance calculated from the reconstructed cross-section area matches quite well the measured resistance of fingers. Uncertainties of about 14% to 17% are estimated for local measurements of morphology-based and measured resistance of finger segments up to 5 mm length. Fingers characterized by somewhat larger roughness/waviness values (, , ) show some local irregularities, which may degrade the electrical contact of the PV front surface.

A path planning method used in fluid jet polishing eliminating lightweight mirror imprinting effect

NASA Astrophysics Data System (ADS)

Li, Wenzong; Fan, Bin; Shi, Chunyan; Wang, Jia; Zhuo, Bin

2014-08-01

With the development of space technology, the design of optical system tends to large aperture lightweight mirror with high dimension-thickness ratio. However, when the lightweight mirror PV value is less than λ/10 , the surface will show wavy imprinting effect obviously. Imprinting effect introduced by head-tool pressure has become a technological barrier in high-precision lightweight mirror manufacturing. Fluid jet polishing can exclude outside pressure. Presently, machining tracks often used are grating type path, screw type path and pseudo-random path. On the edge of imprinting error, the speed of adjacent path points changes too fast, which causes the machine hard to reflect quickly, brings about new path error, and increases the polishing time due to superfluous path. This paper presents a new planning path method to eliminate imprinting effect. Simulation results show that the path of the improved grating path can better eliminate imprinting effect compared to the general path.

Henneguya laterocapsulata Landsberg, 1987 (Myxosporea, Myxozoa) in cultured hybrid African catfish: Ultrastructure of the parasite-host interface.

PubMed

Obiekezie, A; Schmahl, G

1993-02-19

The ultrastructure of the host-parasite interface was studied in Henneguya laterocapsulata, parasitizing the skin of hybrid catfishes (Clarias gariepinus × Heterobranchus bidorsalis) in Nigeria. The plasmodia were located between malpighian cells, which are the main elements of the multilayered fish epidermis, and were bordered by a single cell membrane. The desmosomal junctions between the malpighian cells were forced apart by finger-like protrusions of the Plasmodium. These plasmodial protrusions finally ran into the host cell without disrupting of the host cell membrane and formed network-like extensions. At the margin of the plasmodium an extensive vacuolization occurred, leading to a wavy surface. Infections with H. laterocapsulata may be an adverse factor in the large-scale production of hybrid catfish fingerlings used for aquaculture in Africa. Copyright © 1993 Gustav Fischer Verlag · Stuttgart · Jena · New York. Published by Elsevier GmbH.. All rights reserved.

Dynamics of anisotropic particles under waves

NASA Astrophysics Data System (ADS)

Dibenedetto, Michelle; Ouellette, Nicholas; Koseff, Jeffrey

2017-11-01

We present results on anisotropic particles in wavy flows in order to gain insight into the transport and mixing of microplastic particles in the near-shore environment. From theory and numerical simulations, we find that the rate of alignment of the particles is not constant and depends strongly on their initial orientation; thus, variations in initial particle orientation result in dispersion of anisotropic-particle plumes. We find that this dispersion is a function of the particle's eccentricity and the ratio of the settling and wave time scales. Experiments in which non-spherical particles of various shapes are released under surface gravity waves were also performed. Our main goal is to explore the effects of particle shape under various wave scenarios. We vary the aspect ratio of the particle in our experiments while holding other variables constant. Our results demonstrate that particle shape can be important when predicting transport.

Unconventional magnetisation texture in graphene/cobalt hybrids

DOE PAGES

Vu, A. D.; Coraux, J.; Chen, G.; ...

2016-04-26

Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent alreadymore » a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.« less

Seaglider surveys at Ocean Station Papa: Diagnosis of upper-ocean heat and salt balances using least squares with inequality constraints

NASA Astrophysics Data System (ADS)

Pelland, Noel A.; Eriksen, Charles C.; Cronin, Meghan F.

2017-06-01

Heat and salt balances in the upper 200 m are examined using data from Seaglider spatial surveys June 2008 to January 2010 surrounding a NOAA surface mooring at Ocean Station Papa (OSP; 50°N, 145°W). A least-squares approach is applied to repeat Seaglider survey and moored measurements to solve for unknown or uncertain monthly three-dimensional circulation and vertical diffusivity. Within the surface boundary layer, the estimated heat and salt balances are dominated throughout the surveys by turbulent flux, vertical advection, and for heat, radiative absorption. When vertically integrated balances are considered, an estimated upwelling of cool water balances the net surface input of heat, while the corresponding large import of salt across the halocline due to upwelling and diffusion is balanced by surface moisture input and horizontal import of fresh water. Measurement of horizontal gradients allows the estimation of unresolved vertical terms over more than one annual cycle; diffusivity in the upper-ocean transition layer decreases rapidly to the depth of the maximum near-surface stratification in all months, with weak seasonal modulation in the rate of decrease and profile amplitude. Vertical velocity is estimated to be on average upward but with important monthly variations. Results support and expand existing evidence concerning the importance of horizontal advection in the balances of heat and salt in the Gulf of Alaska, highlight time and depth variability in difficult-to-measure vertical transports in the upper ocean, and suggest avenues of further study in future observational work at OSP.

Vertical electromagnetic profiling (VEMP)

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

Lytle, R.J.

1984-08-01

Vertical seismic profiling (VSP) is based upon reception measurements performed in a borehole with a source near the ground surface. This technology has seen a surge in application and development in the last decade. The analogous concept of vertical electromagnetic profiling (VEMP) consists of reception measurements performed in a borehole with a source near the ground surface. Although the electromagnetic concept has seen some application, this technology has not been as systematically developed and applied as VSP. Vertical electromagnetic profiling provides distinct and complementary data due to sensing different physical parameters than seismic profiling. Certain of the advantages of VEMPmore » are presented. 28 references, 7 figures.« less

The molecular dynamics simulation of ion-induced ripple growth

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

Suele, P.; Heinig, K.-H.

The wavelength-dependence of ion-sputtering induced growth of repetitive nanostructures, such as ripples has been studied by molecular dynamics (MD) simulations in Si. The early stage of the ion erosion driven development of ripples has been simulated on prepatterned Si stripes with a wavy surface. The time evolution of the height function and amplitude of the sinusoidal surface profile has been followed by simulated ion-sputtering. According to Bradley-Harper (BH) theory, we expect correlation between the wavelength of ripples and the stability of them. However, we find that in the small ripple wavelength ({lambda}) regime BH theory fails to reproduce the resultsmore » obtained by molecular dynamics. We find that at short wavelengths ({lambda}<35 nm) the adatom yield drops hence no surface diffusion takes place which is sufficient for ripple growth. The MD simulations predict that the growth of ripples with {lambda}>35 nm is stabilized in accordance with the available experimental results. According to the simulations, few hundreds of ion impacts in {lambda} long and few nanometers wide Si ripples are sufficient for reaching saturation in surface growth for for {lambda}>35 nm ripples. In another words, ripples in the long wavelength limit seems to be stable against ion-sputtering. A qualitative comparison of our simulation results with recent experimental data on nanopatterning under irradiation is attempted.« less

Deriving Surface NO2 Mixing Ratios from DISCOVER-AQ ACAM Observations: A Method to Assess Surface NO2 Spatial Variability

NASA Astrophysics Data System (ADS)

Silverman, M. L.; Szykman, J.; Chen, G.; Crawford, J. H.; Janz, S. J.; Kowalewski, M. G.; Lamsal, L. N.; Long, R.

2015-12-01

Studies have shown that satellite NO2 columns are closely related to ground level NO2 concentrations, particularly over polluted areas. This provides a means to assess surface level NO2 spatial variability over a broader area than what can be monitored from ground stations. The characterization of surface level NO2 variability is important to understand air quality in urban areas, emissions, health impacts, photochemistry, and to evaluate the performance of chemical transport models. Using data from the NASA DISCOVER-AQ campaign in Baltimore/Washington we calculate NO2 mixing ratios from the Airborne Compact Atmospheric Mapper (ACAM), through four different methods to derive surface concentration from column measurements. High spectral resolution lidar (HSRL) mixed layer heights, vertical P3B profiles, and CMAQ vertical profiles are used to scale ACAM vertical column densities. The derived NO2 mixing ratios are compared to EPA ground measurements taken at Padonia and Edgewood. We find similar results from scaling with HSRL mixed layer heights and normalized P3B vertical profiles. The HSRL mixed layer heights are then used to scale ACAM vertical column densities across the DISCOVER-AQ flight pattern to assess spatial variability of NO2 over the area. This work will help define the measurement requirements for future satellite instruments.

Assessing the impacts of seasonal and vertical atmospheric conditions on air quality over the Pearl River Delta region

NASA Astrophysics Data System (ADS)

Tong, Cheuk Hei Marcus; Yim, Steve Hung Lam; Rothenberg, Daniel; Wang, Chien; Lin, Chuan-Yao; Chen, Yongqin David; Lau, Ngar Cheung

2018-05-01

Air pollution is an increasingly concerning problem in many metropolitan areas due to its adverse public health and environmental impacts. Vertical atmospheric conditions have strong effects on vertical mixing of air pollutants, which directly affects surface air quality. The characteristics and magnitude of how vertical atmospheric conditions affect surface air quality, which are critical to future air quality projections, have not yet been fully understood. This study aims to enhance understanding of the annual and seasonal sensitivities of air pollution to both surface and vertical atmospheric conditions. Based on both surface and vertical meteorological characteristics provided by 1994-2003 monthly dynamic downscaling data from the Weather and Research Forecast Model, we develop generalized linear models (GLMs) to study the relationships between surface air pollutants (ozone, respirable suspended particulates, and sulfur dioxide) and atmospheric conditions in the Pearl River Delta (PRD) region. Applying Principal Component Regression (PCR) to address multi-collinearity, we study the contributions of various meteorological variables to pollutants' concentration levels based on the loading and model coefficient of major principal components. Our results show that relatively high pollutant concentration occurs under relatively low mid-level troposphere temperature gradients, low relative humidity, weak southerly wind (or strong northerly wind) and weak westerly wind (or strong easterly wind). Moreover, the correlations vary among pollutant species, seasons, and meteorological variables at various altitudes. In general, pollutant sensitivity to meteorological variables is found to be greater in winter than in other seasons, and the sensitivity of ozone to meteorology differs from that of the other two pollutants. Applying our GLMs to anomalous air pollution episodes, we find that meteorological variables up to mid troposphere (∼700 mb) play an important role in influencing surface air quality, pinpointing the significant and unique associations between meteorological variables at higher altitudes and surface air quality.

Arthropod vertical stratification in temperate deciduous forests: Implications for conservation oriented management

Treesearch

Ulyshen Michael

2011-01-01

Studies on the vertical distribution patterns of arthropods in temperate deciduous forests reveal highly stratified (i.e., unevenly vertically distributed) communities. These patterns are determined by multiple factors acting simultaneously, including: (1) time (forest age, season, time of day); (2) forest structure (height, vertical foliage complexity, plant surface...

A Study of Dean Vortex Development and Structure in a Curved Rectangular Channel with Aspect Ratio of 40 at Dean Numbers up to 430

NASA Technical Reports Server (NTRS)

Ligrani, Phillip M.

1994-01-01

Flow in a curved channel with mild curvature, an aspect ratio of 40 to 1, and an inner to outer radius ratio of 0.979 is studied at Dean numbers De ranging from 35 to 430. For positions from the start of curvature ranging from 85 to 145 degrees, the sequence of transition events begins with curved channel Poiseuille flow at De less than 40-64. As the Dean number increases, observations show initial development of Dean vortex pairs, followed by symmetric vortex pairs which, when viewed in spanwise/radial planes, cover the entire channel height (De=90-100). At De from 40 to 125-130, the vortex pairs often develop intermittent waviness in the form of vortex undulations. Splitting and merging of vortex pairs is also observed over the same experimental conditions as well as at higher De. When Dean numbers range from 130 to 185-200, the undulating wavy mode is replaced by a twisting mode with higher amplitudes of oscillation and shorter wavelengths. The twisting wavy mode results in the development of regions where turbulence intensity is locally augmented at Dean numbers from 150 to 185-200, principally in the upwash regions between the two individual vortices which make up each vortex pair. These turbulent regions eventually increase in intensity and spatial extent as the Dean number increases further, until individual regions merge together so that the entire cross section of the channel contains chaotic turbulent motions. When Dean numbers then reach 400-435, spectra of velocity fluctuations then evidence fully turbulent flow.

Effect of superficial harrowing on surface properties of sand with rubber and waxed-sand with fibre riding arena surfaces: a preliminary study.

PubMed

Tranquille, C A; Walker, V A; Hernlund, E; Egenvall, A; Roepstorff, L; Peterson, M L; Murray, R C

2015-01-01

A recent epidemiological study identified various aspects of arena surfaces and arena surface maintenance that were related to risk of injury in horses and that arena maintenance is important in reducing injury risk. However, there has been little research into how properties of arena surfaces change with harrowing. This study aimed to compare the properties of different arena surface types pre- and post-harrowing. The Orono Biomechanical Surface Tester fitted with accelerometers and a single- and a three-axis load cell was used to test 11 arenas with two different surfaces types, sand with rubber (SR) and waxed-sand with fibre (WSF). Three drop tests were carried out at 10 standardised locations on each arena. Mixed models were created to assess the effect of surface type, pre- or post-harrowing, and drop number on the properties of the surface, including maximum horizontal deceleration, maximum vertical deceleration, maximum vertical load and maximum horizontal load. Post-harrowing, none of the parameters were altered significantly on SR. On WSF, maximum vertical deceleration and maximum vertical load significantly decreased post-harrowing. The differences in the effects of superficial harrowing on SR and WSF could be attributed to the different compositions and sizes of the surface material. The results suggest that different maintenance techniques may be more suitable for different surface types and that the effects of superficial harrowing are short-lived due to the rapid re-compaction of the surface with repeated drops on WSF. Further work is required to determine the effects of other maintenance techniques, and on other surface types. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fine Scale Baleen Whale Behavior Observed via Tagging Over Daily Time Scales

DTIC Science & Technology

2012-09-30

right whales and sei whales) and the diel vertical migration behavior of their copepod prey. I hypothesize that (1) right whales track the diel...vertical migration of copepods by feeding near the bottom during the day and at the surface at night, and (2) sei whales are unable to feed on copepods at...depth during the day, and are therefore restricted to feeding on copepods at the surface only. Because copepod diel vertical migration is variable

Fine Scale Baleen Whale Behavior Observed via Tagging Over Daily Time Scales

DTIC Science & Technology

2013-09-30

sei whales) and the diel vertical migration behavior of their copepod prey. I hypothesize that (1) right whales track the diel vertical migration of... copepods by feeding near the bottom during the day and at the surface at night, and (2) sei whales are unable to feed on copepods at depth during the...day, and are therefore restricted to feeding on copepods at the surface only. Because copepod diel vertical migration is variable over time (days to

Vertical incidence of slow Ne 10+ ions on an LiF surface: Suppression of the trampoline effect

NASA Astrophysics Data System (ADS)

Wirtz, Ludger; Lemell, Christoph; Reinhold, Carlos O.; Hägg, Lotten; Burgdörfer, Joachim

2001-08-01

We present a Monte Carlo simulation of the neutralization of a slow Ne 10+ ion in vertical incidence on an LiF(1 0 0) surface. The rates for resonant electron transfer between surface F - ions and the projectile are calculated using a classical trajectory Monte Carlo simulation. We investigate the influence of the hole mobility on the neutralization sequence. It is shown that backscattering above the surface due to the local positive charge up of the surface ("trampoline effect") does not take place.

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

PubMed Central

Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

2015-01-01

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode

NASA Astrophysics Data System (ADS)

Hsin, Wei

New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.

Influence of packing density and surface roughness of vertically-aligned carbon nanotubes on adhesive properties of gecko-inspired mimetics.

PubMed

Chen, Bingan; Zhong, Guofang; Oppenheimer, Pola Goldberg; Zhang, Can; Tornatzky, Hans; Esconjauregui, Santiago; Hofmann, Stephan; Robertson, John

2015-02-18

We have systematically studied the macroscopic adhesive properties of vertically aligned nanotube arrays with various packing density and roughness. Using a tensile setup in shear and normal adhesion, we find that there exists a maximum packing density for nanotube arrays to have adhesive properties. Too highly packed tubes do not offer intertube space for tube bending and side-wall contact to surfaces, thus exhibiting no adhesive properties. Likewise, we also show that the surface roughness of the arrays strongly influences the adhesion properties and the reusability of the tubes. Increasing the surface roughness of the array strengthens the adhesion in the normal direction, but weakens it in the shear direction. Altogether, these results allow progress toward mimicking the gecko's vertical mobility.

Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature

NASA Technical Reports Server (NTRS)

Choudhari, Meelan

1992-01-01

Acoustic receptivity of a Blasius boundary layer in the presence of distributed surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a small band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary layer flow. The location, and width, of this most receptive band of wavenumbers corresponds to a relative detuning of O(R sub l.b.(exp -3/8)) with respect to the lower-neutral instability wavenumber at the frequency under consideration, R sub l.b. being the Reynolds number based on a typical boundary-layer thickness at the lower branch of the neutral stability curve. Surface imperfections in the form of discrete mode waviness in this range of wavenumbers lead to initial instability amplitudes which are O(R sub l.b.(exp 3/8)) larger than those caused by a single, isolated roughness element. In contrast, irregularities with a continuous spatial spectrum produce much smaller instability amplitudes, even compared to the isolated case, since the increase due to the resonant nature of the response is more than that compensated for by the asymptotically small band-width of the receptivity process. Analytical expressions for the maximum possible instability amplitudes, as well as their expectation for an ensemble of statistically irregular surfaces with random phase distributions, are also presented.

Interference phenomena in the refraction of a surface polariton by vertical dielectric barriers

NASA Technical Reports Server (NTRS)

Shen, T. P.; Wallis, R. F.; Maradudin, A. A.; Stegeman, G. I.

1984-01-01

A normal mode analysis is used to calculate the transmission and reflection coefficients for a surface polariton propagating along the interface between a surface active medium and a dielectric and incident normally on a vertical dielectric barrier of finite thickness or a thin dielectric film of finite length. The efficiencies of conversion of the surface polariton into transmitted and reflected bulk waves are also determined. The radiation patterns associated with the latter waves are presented.

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking Part II: Microstructure characterization

NASA Astrophysics Data System (ADS)

Unfried-Silgado, Jimy; Ramirez, Antonio J.

2014-03-01

In part II of this work is evaluated the as-welded microstructure of Ni-Cr-Fe alloys, which were selected and modeled in part I. Detailed characterization of primary and secondary precipitates, subgrain and grain structures, partitioning, and grain boundary morphology were developed. Microstructural characterization was carried out using optical microscopy, SEM, TEM, EBSD, and XEDS techniques. These results were analyzed and compared to modeling results displaying a good agreement. The Hf additions produced the highest waviness of grain boundaries, which were related to distribution of Hf-rich carbonitrides. Experimental evidences about Mo distribution into crystal lattice have provided information about its possible role in ductility-dip cracking (DDC). Characterization results of studied alloys were analyzed and linked to their DDC resistance data aiming to establish relationships between as-welded microstructure and hot deformation performance. Wavy grain boundaries, primary carbides distribution, and strengthened crystal lattice are metallurgical characteristics related to high DDC resistance.

Effects of geometrical parameters on thermal-hydraulic performance of wavy microtube

NASA Astrophysics Data System (ADS)

Khoshvaght-Aliabadi, Morteza; Chamanroy, Zohreh

2018-03-01

Laminar flow and heat transfer characteristics of water flow through wavy microtubes (WMTs) with different values of wave length ( l) and wave amplitude ( a) are investigated experimentally. The tested WMTs are fabricated from copper microtube with the internal diameter of 914 μm. Experiments encompass the Reynolds numbers from 640 to 1950. In order to validate the experimental setup and create a base line for comparison, initial tests are also carried out for a straight microtube. The results show that both the heat transfer coefficient and the pressure drop are strongly affected by the studied geometrical factors. For a given Reynolds number, these parameters increase as the wave length decreases and the wave amplitude increases. However, in the studied ranges, the effect of wave amplitude is more than that of wave length. A considerable thermal-hydraulic factor of 1.78 is obtained for a WMT with l = 14.3 mm and a = 6 mm. Finally, correlations are developed to predict the Colburn factor and friction factor of water flow in the WMTs.

A flexible ligand-based wavy layered metal-organic framework for lithium-ion storage.

PubMed

An, Tiance; Wang, Yuhang; Tang, Jing; Wang, Yang; Zhang, Lijuan; Zheng, Gengfeng

2015-05-01

A substantial challenge for direct utilization of metal-organic frameworks (MOFs) as lithium-ion battery anodes is to maintain the rigid MOF structure during lithiation/delithiation cycles. In this work, we developed a flexible, wavy layered nickel-based MOF (C20H24Cl2N8Ni, designated as Ni-Me4bpz) by a solvothermal approach of 3,3',5,5'-tetramethyl-4,4'-bipyrazole (H2Me4bpz) with nickel(II) chloride hexahydrate. The obtained MOF materials (Ni-Me4bpz) with metal azolate coordination mode provide 2-dimensional layered structure for Li(+) intercalation/extraction, and the H2Me4bpz ligands allow for flexible rotation feature and structural stability. Lithium-ion battery anodes made of the Ni-Me4bpz material demonstrate excellent specific capacity and cycling performance, and the crystal structure is well preserved after the electrochemical tests, suggesting the potential of developing flexible layered MOFs for efficient and stable electrochemical storage. Copyright © 2015 Elsevier Inc. All rights reserved.

Auxetic hexachiral structures with wavy ligaments for large elasto-plastic deformation

NASA Astrophysics Data System (ADS)

Zhu, Yilin; Wang, Zhen-Pei; Hien Poh, Leong

2018-05-01

The hexachiral structure is in-plane isotropic in small deformation. When subjected to large elasto-plastic deformation, however, the hexachiral structure tends to lose its auxeticity and/or isotropy—properties which are desirable in many potential applications. The objective of this study is to improve these two mechanical properties, without significantly compromising the effective yield stress, in the regime with significant material and geometrical nonlinearity effects. It is found that the deformation mechanisms underlying the auxeticity and isotropy properties of a hexachiral structure are largely influenced by the extent of rotation of the central ring in a unit cell. To facilitate the development of this deformation mechanism, an improved design with wavy ligaments is proposed. The improved performance of the proposed hexachiral structure is demonstrated. An initial study on possible applications as a protective material is next carried out, where the improved hexachiral design is shown to exhibit higher specific energy absorption capacity compared to the original design, as well as standard honeycomb structures.

A numerical assessment of rough surface scattering theories. I - Horizontal polarization. II - Vertical polarization

NASA Technical Reports Server (NTRS)

Rodriguez, Ernesto; Kim, Yunjin; Durden, Stephen L.

1992-01-01

A numerical evaluation is presented of the regime of validity for various rough surface scattering theories against numerical results obtained by employing the method of moments. The contribution of each theory is considered up to second order in the perturbation expansion for the surface current. Considering both vertical and horizontal polarizations, the unified perturbation method provides best results among all theories weighed.

D.R.O.P: The Durable Reconnaissance and Observation Platform

NASA Technical Reports Server (NTRS)

McKenzie, Clifford; Parness, Aaron

2011-01-01

Robots can provide a remote presence in areas that are either inaccessible or too dangerous for humans. However, robots are often limited by their ability to adapt to the terrain or resist environmental factors. The Durable Reconnaissance and Observation Platform (DROP) is a lightweight robot that addresses these challenges with the capability to survive falls from significant heights, carry a useable payload, and traverse a variety of surfaces, including climbing vertical surfaces like wood, stone, and concrete. DROP is manufactured using a combination of rapid prototyping and shape deposition manufacturing. It uses microspine technology to create a new wheel-like design for vertical climbing. To date, DROP has successfully engaged several vertical surfaces, hanging statically without assistance, and traversed horizontal surfaces at approximately 30 cm/s. Unassisted vertical climbing is capable on surfaces up to 85deg at a rate of approximately 25cm*s(sup -1). DROP can also survive falls from up to 3 meters and has the ability to be thrown off of and onto rooftops. Future efforts will focus on improving the microspine wheels, selecting more resilient materials, customizing the controls, and performing more rigorous and quantifiable testing.

Dependence of Hurricane intensity and structures on vertical resolution and time-step size

NASA Astrophysics Data System (ADS)

Zhang, Da-Lin; Wang, Xiaoxue

2003-09-01

In view of the growing interests in the explicit modeling of clouds and precipitation, the effects of varying vertical resolution and time-step sizes on the 72-h explicit simulation of Hurricane Andrew (1992) are studied using the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model (i.e., MM5) with the finest grid size of 6 km. It is shown that changing vertical resolution and time-step size has significant effects on hurricane intensity and inner-core cloud/precipitation, but little impact on the hurricane track. In general, increasing vertical resolution tends to produce a deeper storm with lower central pressure and stronger three-dimensional winds, and more precipitation. Similar effects, but to a less extent, occur when the time-step size is reduced. It is found that increasing the low-level vertical resolution is more efficient in intensifying a hurricane, whereas changing the upper-level vertical resolution has little impact on the hurricane intensity. Moreover, the use of a thicker surface layer tends to produce higher maximum surface winds. It is concluded that the use of higher vertical resolution, a thin surface layer, and smaller time-step sizes, along with higher horizontal resolution, is desirable to model more realistically the intensity and inner-core structures and evolution of tropical storms as well as the other convectively driven weather systems.

[Three-dimensional vertically aligned CNTs coated by Ag nanoparticles for surface-enhanced Raman scattering].

PubMed

Zhang, Xiao-Lei; Zhang, Jie; Fan, Tuo; Ren, Wen-Jie; Lai, Chun-Hong

2014-09-01

In order to make surface-enhanced Raman scattering (SERS) substrates contained more "hot spots" in a three-dimensional (3D) focal volume, and can be adsorbed more probe molecules and metal nanoparticles, to obtain stronger Raman spectral signal, a new structure based on vertically aligned carbon nanotubes (CNTs) coated by Ag nanoparticles for surface Raman enhancement is presented. The vertically aligned CNTs are synthesized by chemical vapor deposition (CVD). A silver film is first deposited on the vertically aligned CNTs by magnetron sputtering. The samples are then annealed at different temperature to cause the different size silver nanoparticles to coat on the surface and sidewalls of vertically aligned CNTs. The result of scanning electron microscopy(SEM) shows that Ag nanoparticles are attached onto the sidewalls and tips of the vertically aligned CNTs, as the annealing temperature is different , pitch size, morphology and space between the silver nanoparticles is vary. Rhodamine 6G is served as the probe analyte. Raman spectrum measurement indicates that: the higher the concentration of R6G, the stronger the Raman intensity, but R6G concentration increase with the enhanced Raman intensity varies nonlinearly; when annealing temperature is 450 °C, the average size of silver nanoparticles is about 100 to 120 nm, while annealing temperature is 400 °C, the average size is about 70 nm, and the Raman intensity of 450 °C is superior to the annealing temperature that of 400 °C and 350 °C.

Periodic bedforms generated by sublimation on terrestrial and martian ice sheets under the influence of the turbulent atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Bordiec, Maï; Carpy, Sabrina; Perret, Laurent; Bourgeois, Olivier; Massé, Marion

2017-04-01

The redistribution of surface ice induced the wind flow may lead to the development and migration of periodic bedforms, or "ice ripples", at the surface of ice sheets. In certain cold and dry environments, this redistribution need not involve solid particle transport but may be dominated by sublimation and condensation, inducing mass transfers between the ice surface and the overlying steady boundary layer turbulent flow. These mass transfers diffuse the water vapour sublimated from the ice into the atmosphere and become responsible for the amplification and propagation of ripples in a direction perpendicular to their crests. Such ice ripples, 24 cm in wavelength, have been described in the so-called Blue Ice Areas of Antarctica. In order to understand the mechanisms that generate and develop these periodic bedforms on terrestrial glaciers and to evaluate the plausibility that similar bedforms may develop on Mars, we performed a linear stability analysis applied to a turbulent boundary layer flow perturbed by a wavy ice surface. The model is developed as follow. We first solve the flow dynamics using numerical methods analogous to those used in sand wave models assuming that the airflow is similar in both problems. We then add the transport/diffusion equation of water vapour following the same scheme. We use the Reynolds-averaged description of the equation with a Prandtl-like closure. We insert a damping term in the exponential formula of the Van Driest mixing length, depending on the pressure gradient felt by the flow and related to the thickness of the viscous sublayer at the ice-atmosphere interface. This formulation is an efficient way to properly represent the transitional regime under which the ripples grow. Once the mass flux of water vapour is solved, the phase shift between the ripples crests and the maximum of the flux can be deduced for different environments. The temporal evolution of the ice surface can be expressed from these quantities to infer the growth rate, migration direction and velocity of the ripples. The present approach has been first used to model the atmospheric flow developing over wavy terrestrial ice bedforms in the Blue Ice Areas of Antarctica. Both the predicted preferential wavelength and propagation direction of the ice ripple have been found to be in agreement with the observations. The present model has subsequently been applied to the same flow configuration but on Mars. Ice ripples are indeed likely to exist there, given that temperature and pressure conditions in the martian atmosphere favors sublimation/condensation as the dominant mass-transport process. The model has proved able to predict not only the development of ice-ripple on Mars (i.e it showed that some most amplified wavelength also exist under Martian atmospheric conditions) but also both their wavelength and propagation direction. The preferential wavelength of ices-ripples on the Martian polar caps appears to be much larger than on the Earth. Finally, a good match between the most likely ice-ripple wavelength predicted by the model and those deduced from recent available observations of the surface of Martian polar caps is shown.

Mechanism for Surface Warming in the Equatorial Pacific during 1994-95

NASA Technical Reports Server (NTRS)

Rienecker, Michele M.; Borovikov, Anna; Schopf, Paul S.

1999-01-01

Mechanisms controlling the variation in sea surface temperature warm event in the equatorial Pacific were investigated through ocean model simulations. In addition, the mechanisms of the climatological SST cycle were investigated. The dominant mechanisms governing the seasonal cycle of SST vary significantly across the basin. In the western Pacific the annual cycle of SST is primarily in response to external heat flux. In the central basin the magnitude of zonal advection is comparable to that of the external heat flux. In the eastern basin the role of zonal advection is reduced and the vertical mixing is more important. In the easternmost equatorial Pacific the vertical entrainment contribution is as large as that of vertical diffusion. The model estimate of the vertical mixing contribution to the mixed layer heat budget compared well with estimates obtained by analysis of observations using the same diagnostic vertical mixing scheme. During 1994- 1995 the largest positive SST anomaly was observed in the mid-basin and was related to reduced latent heat flux due to weak surface winds. In the western basin the initial warming was related to enhanced external heating and reduced cooling effects of both vertical mixing and horizontal advection associated with weaker than usual wind stress. In the eastern Pacific where winds were not significantly anomalous throughout 1994-1995, only a moderate warm surface anomaly was detected. This is in contrast to strong El Nino events where the SST anomaly is largest in the eastern basin and, as shown by previous studies, the anomaly is due to zonal advection rather than anomalous surface heat flux. The end of the warm event was marked by cooling in July 1995 everywhere across the equatorial Pacific.

Venus spherical harmonic gravity model to degree and order 60

NASA Technical Reports Server (NTRS)

Konopliv, Alex S.; Sjogren, William L.

1994-01-01

The Magellan and Pioneer Venus Orbiter radiometric tracking data sets have been combined to produce a 60th degree and order spherical harmonic gravity field. The Magellan data include the high-precision X-band gravity tracking from September 1992 to May 1993 and post-aerobraking data up to January 5, 1994. Gravity models are presented from the application of Kaula's power rule for Venus and an alternative a priori method using surface accelerations. Results are given as vertical gravity acceleration at the reference surface, geoid, vertical Bouguer, and vertical isostatic maps with errors for the vertical gravity and geoid maps included. Correlation of the gravity with topography for the different models is also discussed.

Effects of morphological control on the characteristics of vertical-type OTFTs using Alq3.

PubMed

Kim, Young Do; Park, Jong Wook; Kang, In Nam; Oh, Se Young

2008-09-01

We have fabricated vertical-type organic thin-film transistors (OTFTs) using tris-(8-hydroxyquinoline) aluminum (Alq(3)) as an n-type active material. Vertical-type OTFT using Alq(3) has a layered structure of Al(source electrode)/Alq(3)(active layer)/Al(gate electrode)/Alq(3)(active layer)/ITO glass(drain electrode). Alq(3) thin films containing various surface morphologies could be obtained by the control of evaporation rate and substrate temperature. The effects of the morphological control of Alq(3) thin layer on the grain size and the flatness of film surface were investigated. The characteristics of vertical-type OTFT significantly influenced the growth condition of Alq(3) layer.

A Vertical Diffusion Scheme to estimate the atmospheric rectifier effect

NASA Astrophysics Data System (ADS)

Chen, Baozhang; Chen, Jing M.; Liu, Jane; Chan, Douglas; Higuchi, Kaz; Shashkov, Alexander

2004-02-01

The magnitude and spatial distribution of the carbon sink in the extratropical Northern Hemisphere remain uncertain in spite of much progress made in recent decades. Vertical CO2 diffusion in the planetary boundary layer (PBL) is an integral part of atmospheric CO2 transport and is important in understanding the global CO2 distribution pattern, in particular, the rectifier effect on the distribution [Keeling et al., 1989; Denning et al., 1995]. Attempts to constrain carbon fluxes using surface measurements and inversion models are limited by large uncertainties in this effect governed by different processes. In this study, we developed a Vertical Diffusion Scheme (VDS) to investigate the vertical CO2 transport in the PBL and to evaluate CO2 vertical rectification. The VDS was driven by the net ecosystem carbon flux and the surface sensible heat flux, simulated using the Boreal Ecosystem Productivity Simulator (BEPS) and a land surface scheme. The VDS model was validated against half-hourly CO2 concentration measurements at 20 m and 40 m heights above a boreal forest, at Fraserdale (49°52'29.9''N, 81°34'12.3''W), Ontario, Canada. The amplitude and phase of the diurnal/seasonal cycles of simulated CO2 concentration during the growing season agreed closely with the measurements (linear correlation coefficient (R) equals 0.81). Simulated vertical and temporal distribution patterns of CO2 concentration were comparable to those measured at the North Carolina tower. The rectifier effect, in terms of an annual-mean vertical gradient of CO2 concentration in the atmosphere that decreases from the surface to the top of PBL, was found at Fraserdale to be about 3.56 ppmv. Positive covariance between the seasonal cycles of plant growth and PBL vertical diffusion was responsible for about 75% of the effect, and the rest was caused by covariance between their diurnal cycles. The rectifier effect exhibited strong seasonal variations, and the contribution from the diurnal cycle was mostly confined to the surface layer (less than 300 m).

Vertical profiles in NO3 and N2O5 measured from an aircraft: Results from the NOAA P-3 and surface platforms during the New England Air Quality Study 2004

NASA Astrophysics Data System (ADS)

Brown, Steven S.; Dubé, William P.; Osthoff, Hans D.; Stutz, Jochen; Ryerson, Thomas B.; Wollny, Adam G.; Brock, Charles A.; Warneke, Carsten; de Gouw, Joost A.; Atlas, Eliot; Neuman, J. Andrew; Holloway, John S.; Lerner, Brian M.; Williams, Eric J.; Kuster, William C.; Goldan, Paul D.; Angevine, Wayne M.; Trainer, Michael; Fehsenfeld, Frederick C.; Ravishankara, A. R.

2007-11-01

The nocturnal nitrogen oxides, NO3 and N2O5, are important to the chemical transformation and transport of NOx, O3 and VOC. Their concentrations, sources and sinks are known to be vertically stratified in the nighttime atmosphere. In this paper, we report vertical profiles for NO3 and N2O5 measured from an aircraft (the NOAA P-3) as part of the New England Air Quality Study in July and August 2004. The aircraft data are compared to surface measurements made in situ from a ship and by long-path DOAS. Consistent with previous, vertically resolved studies of NO3 and N2O5, the aircraft measurements show that these species occur at larger concentrations and are longer lived aloft than they are at the surface. The array of in situ measurements available on the P-3 allows for investigation of the mechanisms that give rise to the observed vertical gradients. Selected vertical profiles from this campaign illustrate the role of biogenic VOC, particularly isoprene and dimethyl sulfide, both within and above the nocturnal and/or marine boundary layer. Gradients in relative humidity and aerosol surface may also create a vertical gradient in the rate of N2O5 hydrolysis. Low-altitude intercepts of power plant plumes showed strong vertical stratification, with plume depths of 80 m. The efficiency of N2O5 hydrolysis within these plumes was an important factor determining the low-level NOx and O3 transport or loss at night. Averages of nocturnal O3, NO2, NO3 and N2O5 binned according to altitude were consistent with the trends from individual profiles. While production rates of NO3 peaked near the surface, lifetimes of NO3 and N2O5 were maximum aloft, particularly in the free troposphere. Variability in NO3 and N2O5 was large and exceeded that of NO2 or O3 because of inhomogeneous distribution of NOx emissions and NO3 and N2O5 sinks.

The Sinuosity of Atmospheric Circulation over North America and its Relationship to Arctic Climate Change and Extreme Events

NASA Astrophysics Data System (ADS)

Vavrus, S. J.; Wang, F.; Martin, J. E.; Francis, J. A.

2015-12-01

Recent research has suggested a relationship between mid-latitude weather and Arctic amplification (AA) of global climate change via a slower and wavier extratropical circulation inducing more extreme events. To test this hypothesis and to quantify the waviness of the extratropical flow, we apply a novel application of the geomorphological concept of sinuosity (SIN) over greater North America. SIN is defined as the ratio of the curvilinear length of a geopotential height contour to the perimeter of its equivalent latitude, where the contour and the equivalent latitude enclose the same area. We use 500 hPa daily heights from reanalysis and model simulations to calculate past and future SIN. The circulation exhibits a distinct annual cycle of maximum SIN (waviness) in summer and a minimum in winter, inversely related to the annual cycle of zonal wind speed. Positive trends in SIN have emerged in recent decades during winter and summer at several latitude bands, generally collocated with negative trends in zonal wind speeds. High values of SIN coincide with many prominent extreme-weather events, including Superstorm Sandy. RCP8.5 simulations (2006-2100) project a dipole pattern of zonal wind changes that varies seasonally. In winter, AA causes inflated heights over the Arctic relative to mid-latitudes and an associated weakening (strengthening) of the westerlies north (south) of 40N. The AA signal in summer is strongest over upper-latitude land, promoting localized atmospheric ridging aloft with lighter westerlies to the south and stronger zonal winds to the north. The changes in wind speeds in both seasons are inversely correlated with SIN, indicating a wavier circulation where the flow weakens. In summer the lighter winds over much of the U. S. resemble circulation anomalies observed during extreme summer heat and drought. Such changes may be linked to enhanced heating of upper-latitude land surfaces caused by earlier snow melt during spring-summer.

BUFR TABLE A

Science.gov Websites

Surface data - sea 2 Vertical soundings (other than satellite) 3 Vertical soundings (satellite) 4 Single level upper-air data (other than satellite) 5 Single level upper-air data (satellite) 6 Radar data 7 tables, complete replacement or update 12 Surface data (satellite) 13 Forecasts 14 Warnings 15-19

CONTOURITES IN LAKE SUPERIOR

EPA Science Inventory

Contour currents influence sedimentation in an area 15 km wide and 65 km long at the base of the slope off the Keweenaw Peninsula in Lake Superior, northwestern Michigan. Seismic-reflection profiles (3.5 kHz) from this area show distinct wavy reflectors in a scoured trough at a d...

Successive reactive liquid flow episodes in a layered intrusion (Unit 9, Rum Eastern Layered Intrusion, Scotland)

NASA Astrophysics Data System (ADS)

Leuthold, Julien; Blundy, Jon; Holness, Marian

2014-05-01

We will present a detailed microstructural and geochemical study of reactive liquid flow in Unit 9 of the Rum Eastern Layered Intrusion. In the study region, Unit 9 comprises an underlying lens-like body of peridotite overlain by a sequence of troctolite and gabbro (termed allivalite), with some local and minor anorthosite. The troctolite is separated from the overlying gabbro by a distinct, sub-horizontal, undulose horizon (the major wavy horizon). Higher in the stratigraphy is another, similar, horizon (the minor wavy horizon) that separates relatively clinopyroxene-poor gabbro from an overlying gabbro. To the north of the peridotite lens, both troctolite and gabbro grade into poikilitic gabbro. Clinopyroxene habit in the allivalite varies from thin rims around olivine in troctolite, to equigranular crystals in gabbro, to oikocrysts in the poikilitic gabbro. The poikilitic gabbros contain multiple generations of clinopyroxene, with Cr-rich (~1.1 wt.% Cr2O3), anhedral cores with moderate REE concentrations (core1) overgrown by an anhedral REE-depleted second generation with moderate Cr (~0.7 wt.% Cr2O3) (core2). These composite cores are rimmed by Cr-poor (~0.2 wt.% Cr2O3) and REE-poor to moderate clinopyroxene. We interpret these microstructures as a consequence of two separate episodes of partial melting triggered by the intrusion of hot olivine-phyric picrite to form the discontinuous lenses that comprise the Unit 9 peridotite. Loss of clinopyroxene-saturated partial melt from the lower part of the allivalite immediately following the early stages of sill intrusion resulted in the formation of clinopyroxene-poor gabbro. The spatial extent of clinopyroxene loss is marked by the minor wavy horizon. A further partial melting event stripped out almost all clinopyroxene from the lowest allivalite, to form a troctolite, with the major wavy horizon marking the extent of melting during this second episode. The poikilitic gabbro formed from clinopyroxene-saturated melt moving upwards and laterally through the cumulate pile. The Rum layered intrusion is an open intrusive complex, composed of individual partially molten zones, evolving independently. The Rum layered intrusion offers a direct overview of processes taking place in shallow intra-plate and ridge magma chambers. Intrusion of hot magma into a pre-existing cumulate pile results in the modification both the incoming liquid and the host-rock cumulates. Our study highlights the necessity of considering this type of process when modelling the geochemistry of lavas erupted from magma chambers subject to repeated replenishment.

Adsorption to Fish Sperm of Vertically Transmitted Fish Viruses

NASA Astrophysics Data System (ADS)

Mulcahy, Dan; Pascho, Ronald J.

1984-07-01

More than 99 percent of a vertically transmitted fish rhabdovirus, infectious hematopoietic necrosis virus, was removed from suspension in less than 1 minute by adsorption to the surface membrane of sperm from two genera of salmonid fishes. The vertically transmitted, infectious pancreatic necrosis virus adsorbed to a lesser degree, but no adsorption occurred with a second fish rhabdovirus that is not vertically transmitted. Such adsorption may be involved in vertical transmission of these viruses.

Adsorption to fish sperm of vertically transmitted fish viruses

USGS Publications Warehouse

Mulcahy, D.; Pascho, R.J.

1984-01-01

More than 99 percent of a vertically transmitted fish rhabdovirus, infectious hematopoietic necrosis virus, was removed from suspension in less than 1 minute by adsorption to the surface membrane of sperm from two genera of salmonid fishes. The vertically transmitted, infectious pancreatic necrosis virus adsorbed to a lesser degree, but no adsorption occurred with a second fish rhabdovirus that is not vertically transmitted. Such adsorption may be involved in vertical transmission of these viruses.

Influence of surface flattening on biodiversity of terrestrial arthropods during early stages of brown coal spoil heap restoration.

PubMed

Moradi, Jabbar; Potocký, Pavel; Kočárek, Petr; Bartuška, Martin; Tajovský, Karel; Tichánek, Filip; Frouz, Jan; Tropek, Robert

2018-08-15

Heterogeneity of environmental conditions is the crucial factor supporting biodiversity in various habitats, including post-mining sites. The effects of micro-topographic heterogeneity on biodiversity and conservation potential of arthropod communities in post-industrial habitats had not been studied before now. At one of the largest European brown coal spoil heaps, we sampled eight groups of terrestrial arthropods with different life strategies (moths, spiders, ground beetles, ants, orthopteroids, centipedes, millipedes, and woodlice), in successionally young plots (5-18 y), with a heterogeneous wavy surface after heaping, and compared the communities with plots flattened by dozing. A combination of the standardized quantitative sampling, using two different methods, and a paired design of the plot selection enabled a robust analysis. Altogether, we recorded 380 species of the focal arthropods, 15 of them nationally threatened. We revealed the importance of the micro-topographic heterogeneity for the formation of the biodiversity of arthropods in their secondary refuges. The communities with higher biodiversity and conservation value were detected in the plots with heterogeneous surfaces; exceptions were ground beetles and millipedes. The surface flattening, often the first step of technical reclamation projects, thus suppress biodiversity of most terrestrial arthropods during the restoration of post-mining sites. Since the communities of both surface types differed, the proportional presence on both surfaces could be more efficient in supporting the local biodiversity. We suggest reducing the surface dozing for the cases with other concerns only, to achieve a proportional representation of both surface types. Such a combination of different restoration approaches would, thus, efficiently support high biodiversity of groups with various needs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Glistening-region model for multipath studies

NASA Astrophysics Data System (ADS)

Groves, Gordon W.; Chow, Winston C.

1998-07-01

The goal is to achieve a model of radar sea reflection with improved fidelity that is amenable to practical implementation. The geometry of reflection from a wavy surface is formulated. The sea surface is divided into two components: the smooth `chop' consisting of the longer wavelengths, and the `roughness' of the short wavelengths. Ordinary geometric reflection from the chop surface is broadened by the roughness. This same representation serves both for forward scatter and backscatter (sea clutter). The `Road-to-Happiness' approximation, in which the mean sea surface is assumed cylindrical, simplifies the reflection geometry for low-elevation targets. The effect of surface roughness is assumed to make the sea reflection coefficient depending on the `Deviation Angle' between the specular and the scattering directions. The `specular' direction is that into which energy would be reflected by a perfectly smooth facet. Assuming that the ocean waves are linear and random allows use of Gaussian statistics, greatly simplifying the formulation by allowing representation of the sea chop by three parameters. An approximation of `low waves' and retention of the sea-chop slope components only through second order provides further simplification. The simplifying assumptions make it possible to take the predicted 2D ocean wave spectrum into account in the calculation of sea-surface radar reflectivity, to provide algorithms for support of an operational system for dealing with target tracking in the presence of multipath. The product will be of use in simulated studies to evaluate different trade-offs in alternative tracking schemes, and will form the basis of a tactical system for ship defense against low flyers.

Beam steering via resonance detuning in coherently coupled vertical cavity laser arrays

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

Johnson, Matthew T., E-mail: matthew.johnson.9@us.af.mil; Siriani, Dominic F.; Peun Tan, Meng

2013-11-11

Coherently coupled vertical-cavity surface-emitting laser arrays offer unique advantages for nonmechanical beam steering applications. We have applied dynamic coupled mode theory to show that the observed temporal phase shift between vertical-cavity surface-emitting array elements is caused by the detuning of their resonant wavelengths. Hence, a complete theoretical connection between the differential current injection into array elements and the beam steering direction has been established. It is found to be a fundamentally unique beam-steering mechanism with distinct advantages in efficiency, compactness, speed, and phase-sensitivity to current.

Perceiving the vertical distances of surfaces by means of a hand-held probe.

PubMed

Chan, T C; Turvey, M T

1991-05-01

Nine experiments were conducted on the haptic capacity of people to perceive the distances of horizontal surfaces solely on the basis of mechanical stimulation resulting from contacting the surfaces with a vertically held rod. Participants touched target surfaces with rods inside a wooden cabinet and reported the perceived surface location with an indicator outside the cabinet. The target surface, rod, and the participant's hand were occluded, and the sound produced in exploration was muffled. Properties of the probe (length, mass, moment of inertia, center of mass, and shape) were manipulated, along with surface distance and the method and angle of probing. Results suggest that for the most common method of probing, namely, tapping, perceived vertical distance is specific to a particular relation among the rotational inertia of the probe, the distance of the point of contact with the surface from the probe's center of percussion, and the inclination at contact of the probe to the surface. They also suggest that the probe length and the distance probed are independently perceivable. The results were discussed in terms of information specificity versus percept-percept coupling and parallels between selective attention in haptic and visual perception.

Terrestrial water storage variations and surface vertical deformation derived from GPS and GRACE observations in Nepal and Himalayas

NASA Astrophysics Data System (ADS)

Pan, Y.; Shen, W.; Hwang, C.

2015-12-01

As an elastic Earth, the surface vertical deformation is in response to hydrological mass change on or near Earth's surface. The continuous GPS (CGPS) records show surface vertical deformations which are significant information to estimate the variation of terrestrial water storage. We compute the loading deformations at GPS stations based on synthetic models of seasonal water load distribution and then invert the synthetic GPS data for surface mass distribution. We use GRACE gravity observations and hydrology models to evaluate seasonal water storage variability in Nepal and Himalayas. The coherence among GPS inversion results, GRACE and hydrology models indicate that GPS can provide quantitative estimates of terrestrial water storage variations by inverting the surface deformation observations. The annual peak-to-peak surface mass change derived from GPS and GRACE results reveal seasonal loads oscillations of water, snow and ice. Meanwhile, the present uplifting of Nepal and Himalayas indicates the hydrology mass loss. This study is supported by National 973 Project China (grant Nos. 2013CB733302 and 2013CB733305), NSFC (grant Nos. 41174011, 41429401, 41210006, 41128003, 41021061).

The impact of vertical shear on the sensitivity of tropical cyclogenesis to environmental rotation and thermodynamic state

DOE PAGES

Zhou, Wenyu

2015-11-19

Here, the impact of vertical wind shear on the sensitivity of tropical cyclogenesis to environmental rotation and thermodynamic state is investigated through idealized cloud-resolving simulations of the intensification of an incipient vortex. With vertical shear, tropical cyclones intensify faster with a higher Coriolis parameter, f, irrespective of the environmental thermodynamic state. The vertical shear develops a vertically tilted vortex, which undergoes a precession process with the midlevel vortices rotating cyclonically around the surface center. With a higher f, the midlevel vortices are able to rotate continuously against the vertical shear, leading to the realignment of the tilted vortex and rapidmore » intensification. With a lower f, the rotation is too slow such that the midlevel vortices are advected away from the surface center and the intensification is suppressed. The parameter, Χ b, measuring the effect from the low-entropy downdraft air on the boundary layer entropy, is found to be a good indicator of the environmental thermodynamic favorability for tropical cyclogenesis in vertical shear. Without vertical shear, tropical cyclones are found to intensify faster with a lower f by previous studies. We show this dependency on f is sensitive to the environmental thermodynamic state. The thermodynamical favorability for convection can be measured by Χ m, which estimates the time it takes for surface fluxes to moisten the midtroposphere. A smaller Χ m not only leads to a faster intensification due to a shorter period for moist preconditioning of the inner region but also neutralizes the faster intensification with a lower f due to enhanced peripheral convection.« less

The impact of vertical shear on the sensitivity of tropical cyclogenesis to environmental rotation and thermodynamic state

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

Zhou, Wenyu

Here, the impact of vertical wind shear on the sensitivity of tropical cyclogenesis to environmental rotation and thermodynamic state is investigated through idealized cloud-resolving simulations of the intensification of an incipient vortex. With vertical shear, tropical cyclones intensify faster with a higher Coriolis parameter, f, irrespective of the environmental thermodynamic state. The vertical shear develops a vertically tilted vortex, which undergoes a precession process with the midlevel vortices rotating cyclonically around the surface center. With a higher f, the midlevel vortices are able to rotate continuously against the vertical shear, leading to the realignment of the tilted vortex and rapidmore » intensification. With a lower f, the rotation is too slow such that the midlevel vortices are advected away from the surface center and the intensification is suppressed. The parameter, Χ b, measuring the effect from the low-entropy downdraft air on the boundary layer entropy, is found to be a good indicator of the environmental thermodynamic favorability for tropical cyclogenesis in vertical shear. Without vertical shear, tropical cyclones are found to intensify faster with a lower f by previous studies. We show this dependency on f is sensitive to the environmental thermodynamic state. The thermodynamical favorability for convection can be measured by Χ m, which estimates the time it takes for surface fluxes to moisten the midtroposphere. A smaller Χ m not only leads to a faster intensification due to a shorter period for moist preconditioning of the inner region but also neutralizes the faster intensification with a lower f due to enhanced peripheral convection.« less

Measuring orthometric water heights from lightweight Unmanned Aerial Vehicles (UAVs)

NASA Astrophysics Data System (ADS)

Bandini, Filippo; Olesen, Daniel; Jakobsen, Jakob; Reyna-Gutierrez, Jose Antonio; Bauer-Gottwein, Peter

2016-04-01

A better quantitative understanding of hydrologic processes requires better observations of hydrological variables, such as surface water area, water surface level, its slope and its temporal change. However, ground-based measurements of water heights are restricted to the in-situ measuring stations. Hence, the objective of remote sensing hydrology is to retrieve these hydraulic variables from spaceborne and airborne platforms. The forthcoming Surface Water and Ocean Topography (SWOT) satellite mission will be able to acquire water heights with an expected accuracy of 10 centimeters for rivers that are at least 100 m wide. Nevertheless, spaceborne missions will always face the limitations of: i) a low spatial resolution which makes it difficult to separate water from interfering surrounding areas and a tracking of the terrestrial water bodies not able to detect water heights in small rivers or lakes; ii) a limited temporal resolution which limits the ability to determine rapid temporal changes, especially during extremes. Unmanned Aerial Vehicles (UAVs) are one technology able to fill the gap between spaceborne and ground-based observations, ensuring 1) high spatial resolution; 2) tracking of the water bodies better than any satellite technology; 3) timing of the sampling which only depends on the operator 4) flexibility of the payload. Hence, this study focused on categorizing and testing sensors capable of measuring the range between the UAV and the water surface. The orthometric height of the water surface is then retrieved by subtracting the height above water measured by the sensors from the altitude above sea level retrieved by the onboard GPS. The following sensors were tested: a) a radar, b) a sonar c) a laser digital-camera based prototype developed at Technical University of Denmark. The tested sensors comply with the weight constraint of small UAVs (around 1.5 kg). The sensors were evaluated in terms of accuracy, maximum ranging distance and beam divergence. The sonar demonstrated a maximum ranging distance of 10 m, the laser prototype of 15 m, whilst the radar is potentially able to measure the range to water surface from a height up to 50 m. After numerous test flights above a lake with an approximately horizontal water surface, estimation of orthometric water height error, including overall accuracy of the system GPS-sensors, was possible. The RTK GPS system proved able to deliver a relative vertical accuracy better than 5-7 cm. The radar confirmed to have the best reliability with an accuracy which is generally few cm (0.7-1.3% of the ranging distance). Whereas the accuracy of the sonar and laser varies from few cm (0.7-1.6% of the ranging distance) to some tens of cm because sonar measurements are generally influenced by noise and turbulence generated by the propellers of the UAV and the laser prototype is affected by drone vibrations and water waviness. However, the laser prototype demonstrated the lowest beam divergence, which is required to measure unconventional remote sensing targets, such as sinkholes and Mexican cenotes, and to clearly distinguish between rivers and interfering surroundings, such as riparian vegetation.

Dislocation mechanism based model for stage II fatigue crack propagation rate

NASA Technical Reports Server (NTRS)

Mazumdar, P. K.

1986-01-01

Repeated plastic deformation, which of course depends on dislocation mechanism, at or near the crack tip leads to the fatigue crack propagation. By involving the theory of thermally activated flow and the cumulative plastic strain criterion, an effort is made here to model the stage II fatigue crack propagation rate in terms of the dislocation mechanism. The model, therefore, provides capability to ascertain: (1) the dislocation mechanism (and hence the near crack tip microstructures) assisting the crack growth, (2) the relative resistance of dislocation mechanisms to the crack growth, and (3) the fracture surface characteristics and its interpretation in terms of the dislocation mechanism. The local microstructure predicted for the room temperature crack growth in copper by this model is in good agreement with the experimental results taken from the literature. With regard to the relative stability of such dislocation mechanisms as the cross-slip and the dislocation intersection, the model suggests an enhancement of crack growth rate with an ease of cross-slip which in general promotes dislocation cell formation and is common in material which has high stacking fault energy (produces wavy slips). Cross-slip apparently enhances crack growth rate by promoting slip irreversibility and fracture surface brittleness to a greater degree.

Implications of diamond-turned versus diamond-ground mold fabrication techniques on precision-molded optics

NASA Astrophysics Data System (ADS)

Mertus, Lou; Symmons, Alan

2012-10-01

In recent years, the trend within the molded optics community has been an overall advancement in the capability to diamond grind molds using a variety of grinding techniques. Improvements in grinding equipment, materials and tooling have enabled higher quality ceramic and carbide molds and thereby lenses. Diamond turned molds from ductile metals are still used prevalently throughout the molding industry. Each technology presents a unique set of advantages and disadvantages whether used for precision injection molding of plastic optics or precision glass molding. This paper reviews the manufacturing techniques for each approach and applicable molding process. The advantages and disadvantages of each are compared and analyzed. The subtle differences that exist in optics molded from each technique and the impact they have on the performance in various applications is reviewed. Differences stemming from tooling material properties, material-specific minor defects, as well as cutting and grinding process-induced artifacts are described in detail as well as their influence on the roughness, waviness, and form errors present on the molded surface. A comparison with results between similar surfaces for both diamond grinding and diamond turning is presented.

Surface activation of graphene oxide nanosheets by ultraviolet irradiation for highly efficient anti-bacterials

NASA Astrophysics Data System (ADS)

Veerapandian, Murugan; Zhang, Linghe; Krishnamoorthy, Karthikeyan; Yun, Kyusik

2013-10-01

A comprehensive investigation of anti-bacterial properties of graphene oxide (GO) and ultraviolet (UV) irradiated GO nanosheets was carried out. Microscopic characterization revealed that the GO nanosheet-like structures had wavy features and wrinkles or thin grooves. Fundamental surface chemical states of GO nanosheets (before and after UV irradiation) were investigated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Minimum inhibitory concentration (MIC) results revealed that UV irradiated GO nanosheets have more pronounced anti-bacterial behavior than GO nanosheets and standard antibiotic, kanamycin. The MIC of UV irradiated GO nanosheets was 0.125 μg ml-1 for Escherichia coli and Salmonella typhimurium, 0.25 μg ml-1 for Bacillus subtilis and 0.5 μg ml-1 for Enterococcus faecalis, ensuring its potential as an anti-infective agent for controlling the growth of pathogenic bacteria. The minimum bactericidal concentration of normal GO nanosheets was determined to be two-fold higher than its corresponding MIC value, indicating promising bactericidal activity. The mechanism of anti-bacterial action was evaluated by measuring the enzymatic activity of β-d-galactosidase for the hydrolysis of o-nitrophenol-β-d-galactopyranoside.

Space fabrication demonstration system

NASA Technical Reports Server (NTRS)

1978-01-01

The lower right aluminum beam cap roll forming mill was delivered and installed in the beam builder. The beam was brought to full operational status and beams of one to six bay lengths were produced to demonstrate full system capability. Although the cap flange waviness problem persists, work is progressing within cost and schedule.

Waves in Nature, Lasers to Tsumanis and Beyond

ScienceCinema

LLNL - University of California Television

2017-12-09

Waves are everywhere. Microwaves, laser beams, music, tsunamis. Electromagnetic waves emanating from the Big Bang fill the universe. Learn about the similarities and difference in all of these wavy phenomena with Ed Moses and Rick Sawicki, Lawrence Livermore National Laboratory scientists Series: Science on Saturday [10/2006] [Science] [Show ID: 11541

Waves in Nature, Lasers to Tsumanis and Beyond

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

LLNL - University of California Television

2008-05-01

Waves are everywhere. Microwaves, laser beams, music, tsunamis. Electromagnetic waves emanating from the Big Bang fill the universe. Learn about the similarities and difference in all of these wavy phenomena with Ed Moses and Rick Sawicki, Lawrence Livermore National Laboratory scientists Series: Science on Saturday [10/2006] [Science] [Show ID: 11541

Section Height Determination Methods of the Isotopographic Surface in a Complex Terrain Relief

ERIC Educational Resources Information Center

Syzdykova, Guldana D.; Kurmankozhaev, Azimhan K.

2016-01-01

A new method for determining the vertical interval of isotopographic surfaces on rugged terrain was developed. The method is based on the concept of determining the differentiated size of the vertical interval using spatial-statistical properties inherent in the modal characteristic, the degree of variability of apical heights and the chosen map…

Time-dynamics of the two-color emission from vertical-external-cavity surface-emitting lasers

NASA Astrophysics Data System (ADS)

Chernikov, A.; Wichmann, M.; Shakfa, M. K.; Scheller, M.; Moloney, J. V.; Koch, S. W.; Koch, M.

2012-01-01

The temporal stability of a two-color vertical-external-cavity surface-emitting laser is studied using single-shot streak-camera measurements. The collected data is evaluated via quantitative statistical analysis schemes. Dynamically stable and unstable regions for the two-color operation are identified and the dependence on the pump conditions is analyzed.

Transverse Mode Dynamics and Ultrafast Modulation of Vertical-Cavity Surface-Emitting Lasers

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

2002-01-01

We show that multiple transverse mode dynamics of VCSELs (Vertical-Cavity Surface-Emitting Lasers) can be utilized to generate ultrafast intensity modulation at a frequency over 100 GHz, much higher than the relaxation oscillation frequency. Such multimode beating can be greatly enhanced by taking laser output from part of the output facet.

Optical Characterization of IV-VI Mid-Infrared VCSEL

DTIC Science & Technology

2002-01-01

vertical cavity surface emitting laser ( VCSEL ). A power...il quantum well (QW) devices [5], there has little progress until recently in developing mid-IR vertical cavity surface emitting laser ( VCSEL ). This...structures and PbSrSe thin films were grown on Bat; (111) substrates by molecular beam epitaxy ( MBE ) and characterized by Fourier transform infi-ared

Lunar vertical-shaft mining system

NASA Technical Reports Server (NTRS)

Introne, Steven D. (Editor); Krause, Roy; Williams, Erik; Baskette, Keith; Martich, Frederick; Weaver, Brad; Meve, Jeff; Alexander, Kyle; Dailey, Ron; White, Matt

1994-01-01

This report proposes a method that will allow lunar vertical-shaft mining. Lunar mining allows the exploitation of mineral resources imbedded within the surface. The proposed lunar vertical-shaft mining system is comprised of five subsystems: structure, materials handling, drilling, mining, and planning. The structure provides support for the exploration and mining equipment in the lunar environment. The materials handling subsystem moves mined material outside the structure and mining and drilling equipment inside the structure. The drilling process bores into the surface for the purpose of collecting soil samples, inserting transducer probes, or locating ore deposits. Once the ore deposits are discovered and pinpointed, mining operations bring the ore to the surface. The final subsystem is planning, which involves the construction of the mining structure.

Orbits on a Concave Frictionless Surface

DTIC Science & Technology

2007-01-01

resistance. Because mechanical energy is conserved (for the system of ball and earth), the sum of the kinetic (K) and gravitational potential (U) energies...effects occur when a ball rolls without slipping on the surface of a rotating flat plate ,7 on the inner surface of a vertical cylinder such as a golf...The simple example of a ball in vertical freefall illustrates why this is necessary and how to perform the conversion. The method is then applied to

Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

NASA Astrophysics Data System (ADS)

Chizhevsky, V. N.

2018-01-01

For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

Climate change for the last 1,000 years inferred from borehole temperatures

NASA Astrophysics Data System (ADS)

Kitaoka, K.; Arimoto, H.; Hamamoto, H.; Taniguchi, M.; Takeuchi, T.

2013-12-01

Subsurface temperatures are an archive of temperature changes occurred at the ground surface in the recent past (Lachenbruch and Marshall, 1986; Pollack, 1993). In order to investigate the local surface temperature histories in Osaka Plane, Japan, we observed subsurface temperatures in existing boreholes, using a thermometer logger. Many temperature-depth profiles within 200 m depth from the ground surface have been obtained, but they show considerable variability. The geological formations in the area consist of horizontally stratified sedimentary layers of about 1,000 m in thickness overlaid on bedrock of granite. There exists a vertical disordered structure in the formations, which may be relating to an active fault (Uemachi fault) in the bedrock (Takemura, et al, 2013). It is considered that groundwater in the horizontal layers cannot move vertically, but can move vertically along the vertical disordered zone. Various temperature profiles might be related to occurrence of vertical groundwater flow in the zone. Analytical models of subsurface temperature which include heat conduction and convection due to vertical groundwater flow in the zone have been constructed under the boundary conditions of prescribing time dependent surface temperature and uniform geothermal flux from greater depths. To solve as one-dimensional problem, heat transfer between the vertical zone and the surrounding medium of no groundwater flow is assumed. Prescribing surface temperatures were given as exponential and periodic functions of the time. Climate change can be considered to comprise both natural and artificial changes. Artificial change, which occurs by the increasing combustion of fossil fuels, is considered roughly to be an exponential increase of the ground surface temperature during the last 150 years. Natural change, which can correlate to solar activity (Lassen and Friis-Christensen, 1995), is assumed roughly to be periodic with the period of about 1200 y at the minimum time of 1620 AD for the last 2,000 years, based on the proxy data in literature (Kitagawa, 1995; Moberg, et al, 2005). Analytical solutions have been obtained by applying a superimpose method. Optimum values of parameters included in the model have been obtained by fitting the solutions to the data of temperature-depth profiles by a least-square method. As a result, the amplitude of natural oscillation in the area is about 0.8 degree in average, which is in agreement with the result of tree ring analysis of Yakushima cedar (Kitagawa, 1995). Greater upward groundwater flow rates (up to 1.0 m/y, Darcy flux) are seen along the vertical disordered structure. However, the increasing rate of ground surface temperature is greater than that in atmospheric temperature during the last 140 years at Osaka Meteorological Observatory, Japan Meteorological Agency. The high increasing rate of the ground surface temperature suggests that the change in atmospheric temperature is influenced by the change in long wave radiation from the ground surface.

[Ecological basis of epiphytic Dendrobium officinale growth on cliff].

PubMed

Liu, Xiu-Juan; Zhu, Yan; Si, Jin-Ping; Wu, Ling-Shang; Cheng, Xue-Liang

2016-08-01

In order to make Dendrobium officinale return to the nature, the temperature and humidity in whole days of the built rock model with different slopes and aspects in the natural distribution of wild D. officinale in Tianmu Mountain were recorded by MH-WS01 automatic recorder. The results showed that the slope has a significant impact on the extreme temperature on the surface of the rocks. In summer, the extreme temperature on the surface of horizontal or soft rock can reach to 69.4 ℃, while the temperatures were lower than 50 ℃ on the vertical rock. In winter, the temperatures on the surface of vertical rock were higher and the low temperature duration was shorter than those on the horizontal or soft rock. Also, the humidity of the rocks was significantly influenced by the slope. The monthly average humidity on the surface of vertical rock was above 80%RH. Furthermore, the aspect had a significant impact on the temperature and humidity on the surface of the rocks, but had no significant effect on the daily mean temperature and extreme temperature on the surface of vertical rock. Therefore, the slope affects the survival of D. officinale by affecting the extreme temperature of rocks and affects the growth of D. officinale by affecting the humidity. The choice of slope is the key to the success of cliff epiphytic cultivation for D. officinale. Copyright© by the Chinese Pharmaceutical Association.

Slingram EMI prospection: Are vertical orientated devices a suitable solution in archaeological and pedological prospection?

NASA Astrophysics Data System (ADS)

Thiesson, Julien; Rousselle, Gabrielle; Simon, François Xavier; Tabbagh, Alain

2011-12-01

Electromagnetic induction (EMI) is one of the geophysical techniques widely used in soil studies, the slingram devices being held horizontally over the soil surface, i.e. with the coils located at the same height above the ground surface. Our study aims assessing the abilities of slingram devices when held vertically. 1D and 3D modelling have been achieved in order to compare the theoretical responses of vertical devices to the horizontal ones. Some comparative surveys were also undertaken in archaeological contexts to confirm the reliability of theoretical conclusions. Both approaches show that vertical slingram devices are suitable for survey and can constitute an alternative to the usual horizontal orientation. We give a table in Appendix A which contains the calibration coefficient allowing transforming of the values given by some of commercially available devices which would be advantageous to use in vertical orientation

Models for extracting vertical crustal movements from leveling data

NASA Technical Reports Server (NTRS)

Holdahl, S. H.

1978-01-01

Various adjustment strategies are being used in North America to obtain vertical crustal movements from repeated leveling. The more successful models utilize polynomials or multiquadric analysis to describe elevation change with a velocity surface. Other features permit determination of nonlinear motions, motions associated with earthquakes or episodes, and vertical motions of blocks where boundaries are prespecified. The preferred models for estimating crustal motions permit the use of detached segments of releveling to govern the shape of a velocity surface and allow for input from nonleveling sources such as tide gages and paired lake gages. Some models for extracting vertical crustal movements from releveling data are also excellent for adjusting leveling networks, and permit mixing old and new data in areas exhibiting vertical motion. The new adjustment techniques are more general than older static models and will undoubtedly be used routinely in the future as the constitution of level networks becomes mainly relevelings.

Characterizing groundwater/surface-water interactions in the interior of Jianghan Plain, central China

NASA Astrophysics Data System (ADS)

Du, Yao; Ma, Teng; Deng, Yamin; Shen, Shuai; Lu, Zongjie

2018-06-01

Quantifying groundwater/surface-water interactions is essential for managing water resources and revealing contaminant fate. There has been little concern on the exchange between streams and aquifers through an extensive aquitard thus far. In this study, hydrogeologic calculation and tritium modeling were jointly applied to characterize such interactions through an extensive aquitard in the interior of Jianghan Plain, an alluvial plain of Yangtze River, China. One groundwater simulation suggested that the lateral distance of influence from the river was about 1,000 m; vertical flow in the aquitard followed by lateral flow in the aquifer contributed significantly more ( 90%) to the aquifer head change near the river than lateral bank storage in the aquitard followed by infiltration. The hydrogeologic calculation produced vertical fluxes of the order 0.01 m/day both near and farther from the river, suggesting that similar shorter-lived (half-monthly) vertical fluxes occur between the river and aquitard near the river, and between the surface end members and aquitard farther from the river. Tritium simulation based on the OTIS model produced an average groundwater residence time of about 15 years near the river and a resulting vertical flux of the order 0.001 m/day. Another tritium simulation based on a dispersion model produced a vertical flux of the order 0.0001 m/day away from the river, coupled with an average residence time of around 90 years. These results suggest an order of magnitude difference for the longer-lived (decadal) vertical fluxes between surface waters and the aquifer near and away from the river.

Characterizing groundwater/surface-water interactions in the interior of Jianghan Plain, central China

NASA Astrophysics Data System (ADS)

Du, Yao; Ma, Teng; Deng, Yamin; Shen, Shuai; Lu, Zongjie

2018-01-01

Quantifying groundwater/surface-water interactions is essential for managing water resources and revealing contaminant fate. There has been little concern on the exchange between streams and aquifers through an extensive aquitard thus far. In this study, hydrogeologic calculation and tritium modeling were jointly applied to characterize such interactions through an extensive aquitard in the interior of Jianghan Plain, an alluvial plain of Yangtze River, China. One groundwater simulation suggested that the lateral distance of influence from the river was about 1,000 m; vertical flow in the aquitard followed by lateral flow in the aquifer contributed significantly more ( 90%) to the aquifer head change near the river than lateral bank storage in the aquitard followed by infiltration. The hydrogeologic calculation produced vertical fluxes of the order 0.01 m/day both near and farther from the river, suggesting that similar shorter-lived (half-monthly) vertical fluxes occur between the river and aquitard near the river, and between the surface end members and aquitard farther from the river. Tritium simulation based on the OTIS model produced an average groundwater residence time of about 15 years near the river and a resulting vertical flux of the order 0.001 m/day. Another tritium simulation based on a dispersion model produced a vertical flux of the order 0.0001 m/day away from the river, coupled with an average residence time of around 90 years. These results suggest an order of magnitude difference for the longer-lived (decadal) vertical fluxes between surface waters and the aquifer near and away from the river.

Near Surface Seismic Hazard Characterization in the Presence of High Velocity Contrasts

NASA Astrophysics Data System (ADS)

Gribler, G.; Mikesell, D.; Liberty, L. M.

2017-12-01

We present new multicomponent surface wave processing techniques that provide accurate characterization of near-surface conditions in the presence of large lateral or vertical shear wave velocity boundaries. A common problem with vertical component Rayleigh wave analysis in the presence of high contrast subsurface conditions is Rayleigh wave propagation mode misidentification due to an overlap of frequency-phase velocity domain dispersion, leading to an overestimate of shear wave velocities. By using the vertical and horizontal inline component signals, we isolate retrograde and prograde particle motions to separate fundamental and higher mode signals, leading to more accurate and confident dispersion curve picks and shear wave velocity estimates. Shallow, high impedance scenarios, such as the case with shallow bedrock, are poorly constrained when using surface wave dispersion information alone. By using a joint inversion of dispersion and horizontal-to-vertical (H/V) curves within active source frequency ranges (down to 3 Hz), we can accurately estimate the depth to high impedance boundaries, a significant improvement compared to the estimates based on dispersion information alone. We compare our approach to body wave results that show comparable estimates of bedrock topography. For lateral velocity contrasts, we observe horizontal polarization of Rayleigh waves identified by an increase in amplitude and broadening of the horizontal spectra with little variation in the vertical component spectra. The horizontal spectra offer a means to identify and map near surface faults where there is no topographic or clear body wave expression. With these new multicomponent active source seismic data processing and inversion techniques, we better constrain a variety of near surface conditions critical to the estimation of local site response and seismic hazards.

Profiling Transboundary Aerosols over Taiwan and Assessing Their Radiative Effects

NASA Technical Reports Server (NTRS)

Wang, Sheng-Hsiang; Lin, Neng-Huei; Chou, Ming-Dah; Tsay, Si-Chee; Welton, Ellsworth J.; Hsu, N. Christina; Giles, David M.; Liu, Gin-Rong; Holben, Brent N.

2010-01-01

A synergistic process was developed to study the vertical distributions of aerosol optical properties and their effects on solar heating using data retrieved from ground-based radiation measurements and radiative transfer simulations. Continuous MPLNET and AERONET observations were made at a rural site in northern Taiwan from 2005 to 2007. The aerosol vertical extinction profiles retrieved from ground-based lidar measurements were categorized into near-surface, mixed, and two-layer transport types, representing 76% of all cases. Fine-mode (Angstrom exponent, alpha, approx.1.4) and moderate-absorbing aerosols (columnar single-scattering albedo approx.0.93, asymmetry factor approx.0.73 at 440 nm wavelength) dominated in this region. The column-integrated aerosol optical thickness at 500 nm (tau(sub 500nm)) ranges from 0.1 to 0.6 for the near-surface transport type, but can be doubled in the presence of upper-layer aerosol transport. We utilize aerosol radiative efficiency (ARE; the impact on solar radiation per unit change of tau(sub 500nm)) to quantify the radiative effects due to different vertical distributions of aerosols. Our results show that the ARE at the top-of-atmosphere (-23 W/ sq m) is weakly sensitive to aerosol vertical distributions confined in the lower troposphere. On the other hand, values of the ARE at the surface are -44.3, -40.6 and -39.7 W/sq m 38 for near-surface, mixed, and two-layer transport types, respectively. Further analyses show that the impact of aerosols on the vertical profile of solar heating is larger for the near-surface transport type than that of two-layer transport type. The impacts of aerosol on the surface radiation and the solar heating profiles have implications for the stability and convection in the lower troposphere.

Use of In Situ Cloud Condensation Nuclei, Extinction, and Aerosol Size Distribution Measurements to Test a Method for Retrieving Cloud Condensation Nuclei Profiles From Surface Measurements

NASA Technical Reports Server (NTRS)

Ghan, Stephen J.; Rissman, Tracey A.; Ellman, Robert; Ferrare, Richard A.; Turner, David; Flynn, Connor; Wang, Jian; Ogren, John; Hudson, James; Jonsson, Haflidi H.;

A two-dimensional hydrodynamic model of turbulent transfer of CO2 and H2O over a heterogeneous land surface

NASA Astrophysics Data System (ADS)

Mukhartova, Yu. V.; Krupenko, A. S.; Mangura, P. A.; Levashova, N. T.

2018-01-01

A two-dimensional hydrodynamic model was developed and applied to describe turbulent fluxes of CO2 and H2O within the atmospheric surface layer over a heterogeneous land surface featuring mosaic vegetation and complex topography. Numerical experiments were carried out with a 4.5-km profile that crosses a hilly region in the central part of European Russia, with the diverse land-use patterns (bare soil, crop areas, grasslands, and forests). The results showed very strong variability of the vertical and horizontal turbulent CO2 and H2O fluxes. The standard deviations of the vertical fluxes were estimated for separate profile sections with uniform vegetation cover for daylight conditions in summer, and they were comparable with the mean vertical fluxes for corresponding sections. The highest horizontal turbulent fluxes occurred at the boundaries between different plant communities and at irregularities in surface profile. In some cases, these fluxes reached 10-20% of the absolute values of the mean vertical fluxes for corresponding profile sections. Significant errors in estimating the local and integrated fluxes e.g. when using the eddy covariance technique, can result from ignoring the surface topography, even in the case of relatively large plots with uniform vegetation cover.

Non-closure of the surface energy balance explained by phase difference between vertical velocity and scalars of large atmospheric eddies

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

Gao, Zhongming; Liu, Heping; Katul, Gabriel G.

It is now accepted that large-scale turbulent eddies impact the widely reported non-closure of the surface energy balance when latent and sensible heat fluxes are measured using the eddy covariance method in the atmospheric surface layer (ASL). However, a mechanistic link between large eddies and non-closure of the surface energy balance remains a subject of inquiry. Here, measured 10 Hz time series of vertical velocity, air temperature, and water vapor density collected in the ASL are analyzed for conditions where entrainment and/or horizontal advection separately predominate. The series are decomposed into small- and large- eddies based on a frequency cutoffmore » and their contributions to turbulent fluxes are analyzed. Phase difference between vertical velocity and water vapor density associated with large eddies reduces latent heat fluxes, especially in conditions where advection prevails. Furthermore, enlarged phase difference of large eddies linked to entrainment or advection occurrence leads to increased residuals of the surface energy balance.« less

Non-closure of the surface energy balance explained by phase difference between vertical velocity and scalars of large atmospheric eddies

DOE PAGES

Gao, Zhongming; Liu, Heping; Katul, Gabriel G.; ...

2017-03-16

It is now accepted that large-scale turbulent eddies impact the widely reported non-closure of the surface energy balance when latent and sensible heat fluxes are measured using the eddy covariance method in the atmospheric surface layer (ASL). However, a mechanistic link between large eddies and non-closure of the surface energy balance remains a subject of inquiry. Here, measured 10 Hz time series of vertical velocity, air temperature, and water vapor density collected in the ASL are analyzed for conditions where entrainment and/or horizontal advection separately predominate. The series are decomposed into small- and large- eddies based on a frequency cutoffmore » and their contributions to turbulent fluxes are analyzed. Phase difference between vertical velocity and water vapor density associated with large eddies reduces latent heat fluxes, especially in conditions where advection prevails. Furthermore, enlarged phase difference of large eddies linked to entrainment or advection occurrence leads to increased residuals of the surface energy balance.« less

Split spline screw

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1993-01-01

A split spline screw type payload fastener assembly, including three identical male and female type split spline sections, is discussed. The male spline sections are formed on the head of a male type spline driver. Each of the split male type spline sections has an outwardly projecting load baring segment including a convex upper surface which is adapted to engage a complementary concave surface of a female spline receptor in the form of a hollow bolt head. Additionally, the male spline section also includes a horizontal spline releasing segment and a spline tightening segment below each load bearing segment. The spline tightening segment consists of a vertical web of constant thickness. The web has at least one flat vertical wall surface which is designed to contact a generally flat vertically extending wall surface tab of the bolt head. Mutual interlocking and unlocking of the male and female splines results upon clockwise and counter clockwise turning of the driver element.

Rewetting of hot vertical rod during jet impingement surface cooling

NASA Astrophysics Data System (ADS)

Agrawal, Chitranjan; Kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun

2016-06-01

A stainless steel (SS-316) vertical rod of 12 mm diameter at 800 ± 10 °C initial temperature was cooled by normal impinging round water jet. The surface rewetting phenomenon was investigated for a range of jet diameter 2.5-4.8 mm and jet Reynolds number 5000-24,000 using a straight tube type nozzle. The investigation were made from the stagnation point to maximum 40 mm downstream locations, simultaneously for both upside and downside directions. The cooling performance of the vertical rod was evaluated on the basis of rewetting parameters i.e. rewetting temperature, wetting delay, rewetting velocity and the maximum surface heat flux. Two separate Correlations have been proposed for the dimensionless rewetting velocity in terms of rewetting number and the maximum surface heat flux that predicts the experimental data within an error band of ±20 and ±15 % respectively.

High-Speed Semiconductor Vertical-Cavity Surface-Emitting Lasers for Optical Data-Transmission Systems (Review)

NASA Astrophysics Data System (ADS)

Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Sakharov, A. V.; Ustinov, V. M.

2018-01-01

The main problems of providing a high-speed operation semiconductor lasers with a vertical microcavity (so-called "vertical-cavity surface-emitting lasers") under amplitude modulation and ways to solve them have been considered. The influence of the internal properties of the radiating active region and the electrical parasitic elements of the equivalent circuit of lasers are discussed. An overview of approaches that lead to an increase of the cutoff parasitic frequency, an increase of the differential gain of the active region, the possibility of the management of mode emission composition and the lifetime of photons in the optical microcavities, and reduction of the influence of thermal effects have been presented. The achieved level of modulation bandwidth of ˜30 GHz is close to the maximum achievable for the classical scheme of the direct-current modulation, which makes it necessary to use a multilevel modulation format to further increase the information capacity of optical channels constructed on the basis of vertical-cavity surface-emitting lasers.

Syntectonic fluid flux during rift faulting: Record from the MIS core, Victoria Land Basin, Antarctica

NASA Astrophysics Data System (ADS)

Millan, C.; Wilson, T. J.; Paulsen, T. S.

2009-12-01

The McMurdo Ice Shelf project successfully recovered 1285 m of Neogene sedimentary core from the Victoria Land Basin, a large rift basin within the West Antarctic Rift System (WARS) of Antarctica. The core contains 1475 natural fractures that were logged as faults, veins and clastic dikes, associated with the southern extension of the Neogene-active? Terror Rift fault zone. Veins constitute about 625 of this population. Most veins are filled with calcite, although zeolites and minor chlorite are common towards the bottom of the core. In the lower ~300 m of the core, veins contain opening-mode fiber fills and are wavy to tightly folded due to vertical shortening. Folded, opening-mode folded veins are filled by calcite fibers that grew normal to vein walls, indicating the host sediment was cohesive enough to fracture but was not fully lithified and accommodated vein buckling during compaction. Fold hinges are fractured and wedging of vein segments is marked by overlapping tips separated by zones with strong chlorite and clay fabrics, suggesting shearing during further vertical contraction of the host rock. Calcite veins are commonly strongly twinned. Cathodoluminescence microscopy shows minor changes in color and intensity and minimal concentric or sectoral zoning, suggesting relatively rapid crystallization of fluids of similar chemistry. However, stable isotope analyses reveal large variations in values, with carbon values ranging from -21.91 to -7.15 (VPBD) and oxygen values ranging from -5.35 to -11.97 (VPBD). Further detailed investigation of the fracture fills using cathodoluminescence and electron microscopy combined with isotopic analysis of carbon and oxygen will document the generations of the filling material in more detail and will constrain the sources and evolution of the fluids. There has clearly been significant structural control on fluid pathways during lithification, compaction and diagenesis of strata deforming within the Terror Rift zone.

An ocean large-eddy simulation of Langmuir circulations and convection in the surface mixed layer

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

Skyllingstad, E.D.; Denbo, D.W.

Numerical experiments were performed using a three-dimensional large-eddy simulation model of the ocean surface mixed layer that includes the Craik-Leibovich vortex force to parameterize the interaction of surface waves with mean currents. Results from the experiments show that the vortex force generates Langmuir circulations that can dominate vertical mixing. The simulated vertical velocity fields show linear, small-scale, coherent structures near the surface that extend downwind across the model domain. In the interior of the mixed layer, scales of motion increase to eddy sizes that are roughly equivalent to the mixed-layer depth. Cases with the vortex force have stronger circulations nearmore » the surface in contrast to cases with only heat flux and wind stress, particularly when the heat flux is positive. Calculations of the velocity variance and turbulence dissipation rates for cases with and without the vortex force, surface cooling, and wind stress indicate that wave-current interactions are a dominant mixing process in the upper mixed layer. Heat flux calculations show that the entrainment rate at the mixed-layer base can be up to two times greater when the vortex force is included. In a case with reduced wind stress, turbulence dissipation rates remained high near the surface because of the vortex force interaction with preexisting inertial currents. In deep mixed layers ({approximately}250 m) the simulations show that Langmuir circulations can vertically transport water 145 m during conditions of surface heating. Observations of turbulence dissipation rates and the vertical temperature structure support the model results. 42 refs., 20 figs., 21 tabs.« less

Investigation of Critical Heat Flux in Reduced Gravity Using Photomicrographic Techniques

NASA Technical Reports Server (NTRS)

Mudawar, Issam; Zhang, Hui

2003-01-01

Experiments were performed to examine the effects of body force on flow boiling critical heat flux (CHF). FC-72 was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface just prior to CHF. High-speed video imaging techniques were used to identify dominant CHF mechanisms corresponding to different flow orientations and liquid velocities. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed significant sensitivity to orientation for flow velocities below 0.2 m/s, where extremely low CHF values where measured, especially with downward-facing heated wall and downflow orientations. High flow velocities dampened the effects of orientation considerably. The CHF data were used to assess the suitability of previous CHF models and correlations. It is shown the Interfacial Lift-off Model is very effective at predicting CHF for high velocities at all orientations. The flooding limit, on the other hand, is useful at estimating CHF at low velocities and for downflow orientations. A new method consisting of three dimensionless criteria is developed for determining the minimum flow velocity required to overcome body force effects on near-saturated flow boiling CHF. Vertical upflow boiling experiments were performed in pursuit of identifying the trigger mechanism for subcooled flow boiling CHF. While virtually all prior studies on flow boiling CHF concern the prediction or measurement of conditions that lead to CHF, this study was focused on events that take place during the CHF transient. High-speed video imaging and photomicrographic techniques were used to record the transient behavior of interfacial features from the last steady-state power level before CHF until the moment of power cut-off following CHF. The video records show the development of a wavy vapor layer which propagates along the heated wall, permitting cooling prior to CHF only in wetting fronts corresponding to the wave troughs. Image analysis software was developed to estimate void fraction from the individual video images. The void fraction records for subcooled flow boiling show the CHF transient is accompanied by gradual lift-off of wetting fronts culminating in some maximum vapor layer mean thickness, following which the vapor layer begins to thin down as the transition to film boiling ensues. This study proves the Interfacial Lift-off Model, which has been validated for near-saturated flow boiling CHF, is equally valid for subcooled conditions.

Two-Dimensional Magnetotelluric Modelling of Ore Deposits: Improvements in Model Constraints by Inclusion of Borehole Measurements

NASA Astrophysics Data System (ADS)

Kalscheuer, Thomas; Juhojuntti, Niklas; Vaittinen, Katri

2017-12-01

A combination of magnetotelluric (MT) measurements on the surface and in boreholes (without metal casing) can be expected to enhance resolution and reduce the ambiguity in models of electrical resistivity derived from MT surface measurements alone. In order to quantify potential improvement in inversion models and to aid design of electromagnetic (EM) borehole sensors, we considered two synthetic 2D models containing ore bodies down to 3000 m depth (the first with two dipping conductors in resistive crystalline host rock and the second with three mineralisation zones in a sedimentary succession exhibiting only moderate resistivity contrasts). We computed 2D inversion models from the forward responses based on combinations of surface impedance measurements and borehole measurements such as (1) skin-effect transfer functions relating horizontal magnetic fields at depth to those on the surface, (2) vertical magnetic transfer functions relating vertical magnetic fields at depth to horizontal magnetic fields on the surface and (3) vertical electric transfer functions relating vertical electric fields at depth to horizontal magnetic fields on the surface. Whereas skin-effect transfer functions are sensitive to the resistivity of the background medium and 2D anomalies, the vertical magnetic and electric field transfer functions have the disadvantage that they are comparatively insensitive to the resistivity of the layered background medium. This insensitivity introduces convergence problems in the inversion of data from structures with strong 2D resistivity contrasts. Hence, we adjusted the inversion approach to a three-step procedure, where (1) an initial inversion model is computed from surface impedance measurements, (2) this inversion model from surface impedances is used as the initial model for a joint inversion of surface impedances and skin-effect transfer functions and (3) the joint inversion model derived from the surface impedances and skin-effect transfer functions is used as the initial model for the inversion of the surface impedances, skin-effect transfer functions and vertical magnetic and electric transfer functions. For both synthetic examples, the inversion models resulting from surface and borehole measurements have higher similarity to the true models than models computed exclusively from surface measurements. However, the most prominent improvements were obtained for the first example, in which a deep small-sized ore body is more easily distinguished from a shallow main ore body penetrated by a borehole and the extent of the shadow zone (a conductive artefact) underneath the main conductor is strongly reduced. Formal model error and resolution analysis demonstrated that predominantly the skin-effect transfer functions improve model resolution at depth below the sensors and at distance of ˜ 300-1000 m laterally off a borehole, whereas the vertical electric and magnetic transfer functions improve resolution along the borehole and in its immediate vicinity. Furthermore, we studied the signal levels at depth and provided specifications of borehole magnetic and electric field sensors to be developed in a future project. Our results suggest that three-component SQUID and fluxgate magnetometers should be developed to facilitate borehole MT measurements at signal frequencies above and below 1 Hz, respectively.

Large-scale fabrication of vertically aligned ZnO nanowire arrays

DOEpatents

Wang, Zhong Lin; Hu, Youfan; Zhang, Yan; Xu, Chen; Zhu, Guang

2014-09-09

A generator includes a substrate, a first electrode layer, a dense plurality of vertically-aligned piezoelectric elongated nanostructures, an insulating layer and a second electrode layer. The substrate has a top surface and the first electrode layer is disposed on the top surface of the substrate. The dense plurality of vertically-aligned piezoelectric elongated nanostructures extends from the first electrode layer. Each of the nanostructures has a top end. The insulating layer is disposed on the top ends of the nanostructures. The second electrode layer is disposed on the non-conductive layer and is spaced apart from the nanostructures.

Tiny surface plasmon resonance sensor integrated on silicon waveguide based on vertical coupling into finite metal-insulator-metal plasmonic waveguide.

PubMed

Lee, Dong-Jin; Yim, Hae-Dong; Lee, Seung-Gol; O, Beom-Hoan

2011-10-10

We propose a tiny surface plasmon resonance (SPR) sensor integrated on a silicon waveguide based on vertical coupling into a finite thickness metal-insulator-metal (f-MIM) plasmonic waveguide structure acting as a Fabry-Perot resonator. The resonant characteristics of vertically coupled f-MIM plasmonic waveguides are theoretically investigated and optimized. Numerical results show that the SPR sensor with a footprint of ~0.0375 μm2 and a sensitivity of ~635 nm/RIU can be designed at a 1.55 μm transmission wavelength.

Surface roughening of undoped and in situ B-doped SiGe epitaxial layers deposited by using reduced pressure chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Youngmo; Park, Jiwoo; Sohn, Hyunchul

2018-01-01

Si1- x Ge x (:B) epitaxial layers were deposited by using reduced pressure chemical vapor deposition with SiH4, GeH4, and B2H6 source gases, and the dependences of the surface roughness of undoped Si1- x Ge x on the GeH4 flow rate and of Si1- x Ge x :B on the B2H6 flow rate were investigated. The root-mean-square (RMS) roughness value of the undoped Si1- x Ge x at constant thickness increased gradually with increasing Ge composition, resulting from an increase in the amplitude of the wavy surface before defect formation. At higher Ge compositions, the residual strain in Si1- x Ge x significantly decreased through the formation of defects along with an abrupt increase in the RMS roughness. The variation of the surface roughness of Si1- x Ge x :B depended on the boron (B) concentration. At low B concentrations, the RMS roughness of Si1- x Ge x remained constant regardless of Ge composition, which is similar to that of undoped Si1- x Ge x . However, at high B concentrations, the RMS roughness of Si1- x Ge x :B increased greatly due to B islanding. In addition, at very high B concentrations ( 9.9 at%), the RMS roughness of Si1- x Ge x :B decreased due to non-epitaxial growth.

Nanometer polymer surface features: the influence on surface energy, protein adsorption and endothelial cell adhesion

NASA Astrophysics Data System (ADS)

Carpenter, Joseph; Khang, Dongwoo; Webster, Thomas J.

2008-12-01

Current small diameter (<5 mm) synthetic vascular graft materials exhibit poor long-term patency due to thrombosis and intimal hyperplasia. Tissue engineered solutions have yielded functional vascular tissue, but some require an eight-week in vitro culture period prior to implantation—too long for immediate clinical bedside applications. Previous in vitro studies have shown that nanostructured poly(lactic-co-glycolic acid) (PLGA) surfaces elevated endothelial cell adhesion, proliferation, and extracellular matrix synthesis when compared to nanosmooth surfaces. Nonetheless, these studies failed to address the importance of lateral and vertical surface feature dimensionality coupled with surface free energy; nor did such studies elicit an optimum specific surface feature size for promoting endothelial cell adhesion. In this study, a series of highly ordered nanometer to submicron structured PLGA surfaces of identical chemistry were created using a technique employing polystyrene nanobeads and poly(dimethylsiloxane) (PDMS) molds. Results demonstrated increased endothelial cell adhesion on PLGA surfaces with vertical surface features of size less than 18.87 nm but greater than 0 nm due to increased surface energy and subsequently protein (fibronectin and collagen type IV) adsorption. Furthermore, this study provided evidence that the vertical dimension of nanometer surface features, rather than the lateral dimension, is largely responsible for these increases. In this manner, this study provides key design parameters that may promote vascular graft efficacy.

Laser Sintered Porous Ti-6Al-4V Implants Stimulate Vertical Bone Growth.

PubMed

Cheng, Alice; Cohen, David J; Kahn, Adrian; Clohessy, Ryan M; Sahingur, Kaan; Newton, Joseph B; Hyzy, Sharon L; Boyan, Barbara D; Schwartz, Zvi

2017-08-01

The objective of this study was to examine the ability of 3D implants with trabecular-bone-inspired porosity and micro-/nano-rough surfaces to enhance vertical bone ingrowth. Porous Ti-6Al-4V constructs were fabricated via laser-sintering and processed to obtain micro-/nano-rough surfaces. Male and female human osteoblasts were seeded on constructs to analyze cell morphology and response. Implants were then placed on rat calvaria for 10 weeks to assess vertical bone ingrowth, mechanical stability and osseointegration. All osteoblasts showed higher levels of osteocalcin, osteoprotegerin, vascular endothelial growth factor and bone morphogenetic protein 2 on porous constructs compared to solid laser-sintered controls. Porous implants placed in vivo resulted in an average of 3.1 ± 0.6 mm 3 vertical bone growth and osseointegration within implant pores and had significantly higher pull-out strength values than solid implants. New bone formation and pull-out strength was not improved with the addition of demineralized bone matrix putty. Scanning electron images and histological results corroborated vertical bone growth. This study indicates that Ti-6Al-4V implants fabricated by additive manufacturing to have porosity based on trabecular bone and post-build processing to have micro-/nano-surface roughness can support vertical bone growth in vivo, and suggests that these implants may be used clinically to increase osseointegration in challenging patient cases.

Impact of plunging breaking waves on a partially submerged cube

NASA Astrophysics Data System (ADS)

Wang, A.; Ikeda, C.; Duncan, J. H.

2013-11-01

The impact of a deep-water plunging breaking wave on a partially submerged cube is studied experimentally in a tank that is 14.8 m long and 1.2 m wide with a water depth of 0.91 m. The breakers are created from dispersively focused wave packets generated by a programmable wave maker. The water surface profile in the vertical center plane of the cube is measured using a cinematic laser-induced fluorescence technique with movie frame rates ranging from 300 to 4,500 Hz. The pressure distribution on the front face of the cube is measured with 24 fast-response sensors simultaneously with the wave profile measurements. The cube is positioned vertically at three heights relative to the mean water level and horizontally at a distance from the wave maker where a strong vertical water jet is formed. The portion of the water surface between the contact point on the front face of the cube and the wave crest is fitted with a circular arc and the radius and vertical position of the fitted circle is tracked during the impact. The vertical acceleration of the contact point reaches more than 50 times the acceleration of gravity and the pressure distribution just below the free surface shows a localized high-pressure region with a very high vertical pressure gradient. This work is supported by the Office of Naval Research under grant N000141110095.

Equations for estimating loblolly pine branch and foliage weight and surface area distributions

Treesearch

V. Clark Baldwin; Kelly D. Peterson; Harold E. Burkhatt; Ralph L. Amateis; Phillip M. Dougherty

1996-01-01

Equations to predict foliage weight and surface area, and their vertical and horizontal distributions, within the crowns of unthinned loblolly pine (Pinus tueduL.) trees are presented. A right-truncated Weibull function was used for describing vertical foliage distributions. This function ensures that all of the foliage located between the tree tip and the foliage base...

Vertical-cavity surface-emitting lasers - Design, growth, fabrication, characterization

NASA Astrophysics Data System (ADS)

Jewell, Jack L.; Lee, Y. H.; Harbison, J. P.; Scherer, A.; Florez, L. T.

1991-06-01

The authors have designed, fabricated, and tested vertical-cavity surface-emitting lasers (VCSEL) with diameters ranging from 0.5 microns to above 50 microns. Design issues, molecular beam epitaxial growth, fabrication, and lasing characteristics are discussed. The topics considered in fabrication of VCSELs are microlaser geometries; ion implementation and masks; ion beam etching; packaging and arrays; and ultrasmall devices.

Comparison of two vertical condensation obturation techniques: Touch 'n Heat modified and System B.

PubMed

Silver, G K; Love, R M; Purton, D G

1999-08-01

The aims of this study were firstly to compare the area of canal occupied by gutta-percha, sealer or voids using the System B heating device with that obtained by a modified vertical condensation technique using the Touch 'n Heat: and secondly to compare the temperature changes at the root canal wall and external root surface during obturation with the above techniques. Forty-five resin blocks, each with a standardized, simulated, prepared main root canal and five lateral canals, were assigned to three equal experimental groups. The canals were obturated using either the System B technique at two different temperature settings, or vertical condensation with a Touch 'n Heat instrument as the heat source. A heat transfer model was used to simultaneously record internal and external root surface temperature elevations during obturation by the three techniques. Data were analysed using unpaired Student's t-test and Mann-Whitney U-test. Both obturation techniques produced root fillings consisting of over 90% gutta-percha at most levels, although the percentages of sealer and voids 2-3 mm from the working length following System B obturation were higher than those found following modified vertical condensation. Modified vertical condensation resulted in more gutta-percha in lateral canals. Obturation was accomplished more quickly using the System B, and temperature elevations produced during obturation with the System B were significantly less (P < 0.001) than with vertical condensation. An elevation of external root surface temperature by more than 10 degrees C occurred during vertical condensation. The results suggest that the System B may produce an acceptable obturation and that the use of a Touch 'n Heat source during vertical condensation may result in damage to the periodontium.

Space Radar Image of Oil Slicks

NASA Technical Reports Server (NTRS)

1994-01-01

This is a radar image of an offshore drilling field about 150 km (93 miles) west of Bombay, India, in the Arabian Sea. The dark streaks are extensive oil slicks surrounding many of the drilling platforms, which appear as bright white spots. Radar images are useful for detecting and measuring the extent of oil seepages on the ocean surface, from both natural and industrial sources. The long, thin streaks extending from many of the platforms are spreading across the sea surface, pushed by local winds. The larger dark patches are dispersed slicks that were likely discharged earlier than the longer streaks, when the winds were probably from a different direction. The dispersed oil will eventually spread out over the more dense water and become a layer which is a single molecule thick. Many forms of oil, both from biological and from petroleum sources, smooth out the ocean surface, causing the area to appear dark in radar images. There are also two forms of ocean waves shown in this image. The dominant group of large waves (upper center) are called internal waves. These waves are formed below the ocean surface at the boundary between layers of warm and cold water and they appear in the radar image because of the way they change the ocean surface. Ocean swells, which are waves generated by winds, are shown throughout the image but are most distinct in the blue area adjacent to the internal waves. Identification of waves provide oceanographers with information about the smaller scale dynamic processes of the ocean. This image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 9, 1994. The colors are assigned to different frequencies and polarizations of the radar as follows: Red is L-band vertically transmitted, vertically received; green is the average of L-band vertically transmitted, vertically received and C-band vertically transmitted, vertically received; blue is C-band vertically transmitted, vertically received. The image is located at 19.25 degrees north latitude and 71.34 degrees east longitude and covers an area 20 km by 45 km (12.4 miles by 27.9 miles). SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to Planet Earth.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol

NASA Astrophysics Data System (ADS)

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-01

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0 nM and 50 mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids.

Unification of height systems in the frame of GGOS

NASA Astrophysics Data System (ADS)

Sánchez, Laura

2015-04-01

Most of the existing vertical reference systems do not fulfil the accuracy requirements of modern Geodesy. They refer to local sea surface levels, are stationary (do not consider variations in time), realize different physical height types (orthometric, normal, normal-orthometric, etc.), and their combination in a global frame presents uncertainties at the metre level. To provide a precise geodetic infrastructure for monitoring the Earth system, the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), promotes the standardization of the height systems worldwide. The main purpose is to establish a global gravity field-related vertical reference system that (1) supports a highly-precise (at cm-level) combination of physical and geometric heights worldwide, (2) allows the unification of all existing local height datums, and (3) guarantees vertical coordinates with global consistency (the same accuracy everywhere) and long-term stability (the same order of accuracy at any time). Under this umbrella, the present contribution concentrates on the definition and realization of a conventional global vertical reference system; the standardization of the geodetic data referring to the existing height systems; and the formulation of appropriate strategies for the precise transformation of the local height datums into the global vertical reference system. The proposed vertical reference system is based on two components: a geometric component consisting of ellipsoidal heights as coordinates and a level ellipsoid as the reference surface, and a physical component comprising geopotential numbers as coordinates and an equipotential surface defined by a conventional W0 value as the reference surface. The definition of the physical component is based on potential parameters in order to provide reference to any type of physical heights (normal, orthometric, etc.). The conversion of geopotential numbers into metric heights and the modelling of the reference surface (geoid or quasigeoid determination) are considered as steps of the realization. The vertical datum unification strategy is based on (1) the physical connection of height datums to determine their discrepancies, (2) joint analysis of satellite altimetry and tide gauge records to determine time variations of sea level at reference tide gauges, (3) combination of geometrical and physical heights in a well-distributed and high-precise reference frame to estimate the relationship between the individual vertical levels and the global one, and (4) analysis of GNSS time series at reference tide gauges to separate crustal movements from sea level changes. The final vertical transformation parameters are provided by the common adjustment of the observation equations derived from these methods.

Improved Modeling of Surface Layer Parameters in a AGCM Using Refined Vertical Resolution in the Surface Layer

NASA Astrophysics Data System (ADS)

Shin, H. H.; Zhao, M.; Ming, Y.; Chen, X.; Lin, S. J.

2017-12-01

Surface layer (SL) parameters in atmospheric models - such as 2-m air temperature (T2), 10-m wind speed (U10), and surface turbulent fluxes - are computed by applying the Monin-Obukhov Similarity Theory (MOST) to the lowest model level height (LMH) in the models. The underlying assumption is that LMH is within surface layer height (SLH), but most AGCMs hardly meet the condition in stable boundary layers (SBLs) over land. To assess the errors in modeled SL parameters caused by this, offline computations of the MOST are performed with different LMHs from 1 to 100 m, for an idealized SBL case with prescribed surface parameters (surface temperature, roughness length and Obukhov length), and vertical profiles of temperature and winds. The results show that when LMH is higher than SLH, T2 and U10 are underestimated by O(1 K) and O(1 m/s), respectively, and the biases increase as LMH increases. Based on this, the refined vertical resolution with an additional layer in the SL is applied to the GFDL AGCM, and it reduces the systematic cold biases in T2 and the systematic underestimation of U10.

Modification of surface properties of cellulosic substrates by quaternized silicone emulsions.

PubMed

Purohit, Parag S; Somasundaran, P

2014-07-15

The present work describes the effect of quaternization of silicones as well as the relevant treatment parameter pH on the frictional, morphological and relaxation properties of fabric substrates. Due to their unique surface properties, silicone polymers are extensively used to modify surface properties of various materials, although the effects of functionalization of silicones and relevant process conditions on modification of substrates are not well understood. Specifically we show a considerable reduction in fabric friction, roughness and waviness upon treatment with quaternized silicones. The treatment at acidic pH results in better deposition of silicone polymers onto the fabric as confirmed through streaming potential measurements which show charge reversal of the fabric. Interestingly, Raman spectroscopy studies show the band of C-O ring stretching mode at ∼1095 cm(-1) shift towards higher wavenumber indicating lowering of stress in fibers upon appropriate silicone treatment. Thus along with the morphological and frictional properties being altered, silicone treatment can lead to a reduction in fabric strain. It is concluded that the electrostatic interactions play an initial role in modification of the fiber substrate followed by multilayer deposition of polymer. This multi-technique approach to study fiber properties upon treatment by combining macro to molecular level methods has helped in understanding of new functional coating materials. Copyright © 2014 Elsevier Inc. All rights reserved.

Characterization and Spectral Monitoring of Coffee Lands in Brazil

NASA Astrophysics Data System (ADS)

Alves, H. M. R.; Volpato, M. M. L.; Vieira, T. G. C.; Maciel, D. A.; Gonçalves, T. G.; Dantas, M. F.

2016-06-01

In Brazil, coffee production has great economic and social importance. Despite this fact, there is still a shortage of information regarding its spatial distribution, crop management and environment. The aim of this study was to carry out spectral monitoring of coffee lands and to characterize their environments using geotechnologies. Coffee fields with contiguous areas over 0.01 km2 within a 488.5 km2 region in the south of Minas Gerais state were selected for the study. Spectral data from the sensors OLI/Landsat 8 and the Shuttle Radar Topography Mission from 2014 to 2015 were obtained, as well as information on production areas, surface temperature, vegetation indexes, altitude and slope, were gathered and analyzed. The results indicate that there is great variation in the NDVI and NDWI values, with means ranging from 0.21 to 0.91 (NDVI) and 0.108 to 0.543 (NDWI). The altitude ranged from 803 to 1150 m, and the surface temperature from 20.9°C to 27.6°C. The altitude and the surface temperature distribution patterns were correlated with the vegetation indexes. The slope classes were very homogeneous, predominantly with declivities between 8 to 20 %, characterized as wavy relief. This study made possible the characterization and monitoring of coffee lands and its results may be instrumental in decision-making processes related to coffee management.

77 FR 10560 - United States v. International Paper Company et al.; Proposed Final Judgment and Competitive...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-22

..., Antitrust Division, Antitrust Documents Group, 450 Fifth Street NW., Suite 1010, Washington, DC 20530... Packaging Group, which produces containerboard and corrugated products, accounting for $8.4 billion. 10... linerboards in a wavy, fluted pattern. Linerboard is made from virgin wood fiber, recycled fiber (usually...

7 CFR 29.3154 - Tips (T Group).

Code of Federal Regulations, 2013 CFR

2013-01-01

... stalk. (See Rule 12.) Grades Grade names and specifications T3F Good Tan Tips. Medium body, mature to..., mature, firm, wavy dull finish, weak color intensity, narrow, under 16″ in length, 80 percent uniform, and 20 percent injury tolerance. T5F Low Tan Tips. Medium body, mature, firm, wrinkly, dingy finish...

7 CFR 29.3154 - Tips (T Group).

Code of Federal Regulations, 2014 CFR

2014-01-01

... stalk. (See Rule 12.) Grades Grade names and specifications T3F Good Tan Tips. Medium body, mature to..., mature, firm, wavy dull finish, weak color intensity, narrow, under 16″ in length, 80 percent uniform, and 20 percent injury tolerance. T5F Low Tan Tips. Medium body, mature, firm, wrinkly, dingy finish...

7 CFR 29.3154 - Tips (T Group).

Code of Federal Regulations, 2012 CFR

2012-01-01

... stalk. (See Rule 12.) Grades Grade names and specifications T3F Good Tan Tips. Medium body, mature to..., mature, firm, wavy dull finish, weak color intensity, narrow, under 16″ in length, 80 percent uniform, and 20 percent injury tolerance. T5F Low Tan Tips. Medium body, mature, firm, wrinkly, dingy finish...

Cloudy Waves (False Color)

NASA Image and Video Library

2017-08-14

Clouds on Saturn take on the appearance of strokes from a cosmic brush thanks to the wavy way that fluids interact in Saturn's atmosphere. Neighboring bands of clouds move at different speeds and directions depending on their latitudes. This generates turbulence where bands meet and leads to the wavy structure along the interfaces. Saturn's upper atmosphere generates the faint haze seen along the limb of the planet in this image. This false color view is centered on 46 degrees north latitude on Saturn. The images were taken with the Cassini spacecraft narrow-angle camera on May 18, 2017 using a combination of spectral filters which preferentially admit wavelengths of near-infrared light. The image filter centered at 727 nanometers was used for red in this image; the filter centered at 750 nanometers was used for blue. (The green color channel was simulated using an average of the two filters.) The view was obtained at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn. Image scale is about 4 miles (7 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21341

Visualizing Perturbation Decay in Shocked Granular Materials

NASA Astrophysics Data System (ADS)

Cooper, Marcia; Vogler, Tracy

2017-06-01

A new experiment continuously visualizing shock wave perturbation decay through an increasing thickness of granular material has been tested with a gas gun. The experiment confines powders of either tungsten carbide or cerium oxide into a wedge geometry formed by tilting the downstream observation window, plated with a reflective aluminum film, at a shallow angle from the driver plate. The driver is machined with a sinusoidal wavy pattern for incident shock wave perturbation. After projectile impact, the perturbed shock wave passes through the granular material, first emerging at the wedge toe. Image sequences collected at 5 MHz of reflectivity loss at the plated window-granular material interface capture the spatial variation in wave propagation with increasing sample thickness. Extracting the evolving wavy pattern from the images determines the temporal perturbation amplitude. The data are compared to continuum and mesoscale simulations in normalized terms of perturbation amplitude and wavelength. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

A Vertically Resolved Planetary Boundary Layer

NASA Technical Reports Server (NTRS)

Helfand, H. M.

1984-01-01

Increase of the vertical resolution of the GLAS Fourth Order General Circulation Model (GCM) near the Earth's surface and installation of a new package of parameterization schemes for subgrid-scale physical processes were sought so that the GLAS Model GCM will predict the resolved vertical structure of the planetary boundary layer (PBL) for all grid points.

49 CFR 572.43 - Lumbar spine and pelvis.

Code of Federal Regulations, 2010 CFR

2010-10-01

... vertical plane which is tangent to the back of the dummy's buttocks. (3) Align the test probe so that at... vertical planes perpendicular to the midsagittal plane passing through the designated impact point. (4) Adjust the dummy so that its midsagittal plane is vertical and the rear surfaces of the thorax and...

Decoding the origins of vertical land motions observed today at coasts

NASA Astrophysics Data System (ADS)

Pfeffer, J.; Spada, G.; Mémin, A.; Boy, J.-P.; Allemand, P.

2017-07-01

In recent decades, geodetic techniques have allowed detecting vertical land motions and sea-level changes of a few millimetres per year, based on measurements taken at the coast (tide gauges), on board of satellite platforms (satellite altimetry) or both (Global Navigation Satellite System). Here, contemporary vertical land motions are analysed from January 1993 to July 2013 at 849 globally distributed coastal sites. The vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic Green's functions. Special attention is paid to the effects of glacial isostatic adjustment induced by past and present-day ice melting. Various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally. In well-instrumented regions, predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres. Residual vertical land motions show a strong local variability, especially in the vicinity of plate boundaries due to the earthquake cycle. Significant residual signals are also observed at scales of a few hundred kilometres over nine well-instrumented regions forming observation windows on unmodelled geophysical processes. This study highlights the potential of our multitechnique database to detect geodynamical processes, driven by anthropogenic influence, surface mass changes (surface loading and glacial isostatic adjustment) and tectonic activity (including the earthquake cycle, sediment and volcanic loading, as well as regional tectonic constraints). Future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models.

Characterizing seasonal and diel vertical movement and habitat use of lake whitefish (Coregonus clupeaformis) in Clear Lake, Maine

USGS Publications Warehouse

Zydlewski, Joseph D.; Gorsky, Dimitry; Balsey, David

2016-01-01

Seasonal and daily vertical activity of lake whitefish Coregonus clupeaformis was studied in Clear Lake, Maine (253 ha), using acoustic telemetry from November 2004 to June 2009. Twenty adult lake whitefish were tagged with acoustic tags that had either a depth sensor or both depth and temperature sensors to assess vertical habitat use at a seasonal and daily resolution. Vertical habitat selection varied seasonally and was strongly influenced by temperature. Between December and April, when the lake was covered with ice, surface temperature was below 2°C and tagged individuals occupied deep areas of the lake (∼15 m). After ice-out, fish ascended into shallow waters (∼5 m), responding to increased water temperature and possibly to greater foraging opportunity. When surface water temperatures exceeded 20°C, fish descended below the developing thermocline (∼9 m), where they remained until surface temperatures fell below 20°C; fish then ascended into shallower depths, presumably for feeding and spawning. Through the winter, fish remained in thermal habitats that were warmer than the surface temperatures; in the summer, they selected depths with thermal habitats below 15°C. Though the amplitude varied greatly across seasons, lake whitefish displayed a strong diurnal pattern of activity as measured by vertical velocities. Fish were twofold more active during spring, summer, and fall than during winter. Lake whitefish exhibited diel vertical migrations, rising in the water column during nighttime and occupying deeper waters during the day. This pattern was more pronounced in the spring and fall and far less prominent during winter and summer. The strong linkage between temperature and habitat use may limit the current range of lake whitefish and may be directly impacted by climatic change.

Probabilistic reconstruction of GPS vertical ground motion and comparison with GIA models

NASA Astrophysics Data System (ADS)

Husson, Laurent; Bodin, Thomas; Choblet, Gael; Kreemer, Corné

2017-04-01

The vertical position time-series of GPS stations have become long enough for many parts of the world to infer modern rates of vertical ground motion. We use the worldwide compilation of GPS trend velocities of the Nevada Geodetic Laboratory. Those rates are inferred by applying the MIDAS algorithm (Blewitt et al., 2016) to time-series obtained from publicly available data from permanent stations. Because MIDAS filters out seasonality and discontinuities, regardless of their causes, it gives robust long-term rates of vertical ground motion (except where there is significant postseismic deformation). As the stations are unevenly distributed, and because data errors are also highly variable, sometimes to an unknown degree, we use a Bayesian inference method to reconstruct 2D maps of vertical ground motion. Our models are based on a Voronoi tessellation and self-adapt to the spatially variable level of information provided by the data. Instead of providing a unique interpolated surface, each point of the reconstructed surface is defined through a probability density function. We apply our method to a series of vast regions covering entire continents. Not surprisingly, the reconstructed surface at a long wavelength is dominated by the GIA. This result can be exploited to evaluate whether forward models of GIA reproduce geodetic rates within the uncertainties derived from our interpolation, not only at high latitudes where postglacial rebound is fast, but also in more temperate latitudes where, for instance, such rates may compete with modern sea level rise. At shorter wavelengths, the reconstructed surface of vertical ground motion features a variety of identifiable patterns, whose geometries and rates can be mapped. Examples are transient dynamic topography over the convecting mantle, actively deforming domains (mountain belts and active margins), volcanic areas, or anthropogenic contributions.

Temporal–Spatial Surface Seasonal Mass Changes and Vertical Crustal Deformation in South China Block from GPS and GRACE Measurements

PubMed Central

He, Meilin; Shen, Wenbin; Chen, Ruizhi; Ding, Hao; Guo, Guangyi

2017-01-01

The solid Earth deforms elastically in response to variations of surface atmosphere, hydrology, and ice/glacier mass loads. Continuous geodetic observations by Global Positioning System (CGPS) stations and Gravity Recovery and Climate Experiment (GRACE) record such deformations to estimate seasonal and secular mass changes. In this paper, we present the seasonal variation of the surface mass changes and the crustal vertical deformation in the South China Block (SCB) identified by GPS and GRACE observations with records spanning from 1999 to 2016. We used 33 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs) in SCB. The average weighted root-mean-square (WRMS) reduction is 38% when we subtract GRACE-modeled vertical displacements from GPS time series. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution in and around the South China Block. The correlation between GRACE and GPS time series is analyzed which provides a reference for further improvement of the seasonal variation of CGPS time series. The results of the GRACE observations inversion are the surface deformations caused by the surface mass change load at a rate of about −0.4 to −0.8 mm/year, which is used to improve the long-term trend of non-tectonic loads of the GPS vertical velocity field to further explain the crustal tectonic movement in the SCB and surroundings. PMID:29301236

Comparison of a vertically-averaged and a vertically-resolved model for hyporheic flow beneath a pool-riffle bedform

NASA Astrophysics Data System (ADS)

Ibrahim, Ahmad; Steffler, Peter; She, Yuntong

2018-02-01

The interaction between surface water and groundwater through the hyporheic zone is recognized to be important as it impacts the water quantity and quality in both flow systems. Three-dimensional (3D) modeling is the most complete representation of a real-world hyporheic zone. However, 3D modeling requires extreme computational power and efforts; the sophistication is often significantly compromised by not being able to obtain the required input data accurately. Simplifications are therefore often needed. The objective of this study was to assess the accuracy of the vertically-averaged approximation compared to a more complete vertically-resolved model of the hyporheic zone. The groundwater flow was modeled by either a simple one-dimensional (1D) Dupuit approach or a two-dimensional (2D) horizontal/vertical model in boundary fitted coordinates, with the latter considered as a reference model. Both groundwater models were coupled with a 1D surface water model via the surface water depth. Applying the two models to an idealized pool-riffle sequence showed that the 1D Dupuit approximation gave comparable results in determining the characteristics of the hyporheic zone to the reference model when the stratum thickness is not very large compared to the surface water depth. Conditions under which the 1D model can provide reliable estimate of the seepage discharge, upwelling/downwelling discharges and locations, the hyporheic flow, and the residence time were determined.

Holographic sol-gel monoliths: optical properties and application for humidity sensing

NASA Astrophysics Data System (ADS)

Ilatovskii, Daniil A.; Milichko, Valentin; Vinogradov, Alexander V.; Vinogradov, Vladimir V.

2018-05-01

Sol-gel monoliths based on SiO2, TiO2 and ZrO2 with holographic colourful diffraction on their surfaces were obtained via a sol-gel synthesis and soft lithography combined method. The production was carried out without any additional equipment at near room temperature and atmospheric pressure. The accurately replicated wavy structure with nanoscale size of material particles yields holographic effect and its visibility strongly depends on refractive index (RI) of materials. Addition of multi-walled carbon nanotubes (MWCNTs) in systems increases their RI and lends absorbing properties due to extremely high light absorption constant. Further prospective and intriguing applications based on the most successful samples, MWCNTs-doped titania, were investigated as reversible optical humidity sensor. Owing to such property as reversible resuspension of TiO2 nanoparticles while interacting with water, it was proved that holographic xerogels can repeatedly act as humidity sensors. Materials which can be applied as humidity sensors in dependence on holographic response were discovered for the first time.

Effect of starting point formation on the crystallization of amorphous silicon films by flash lamp annealing

NASA Astrophysics Data System (ADS)

Sato, Daiki; Ohdaira, Keisuke

2018-04-01

We succeed in the crystallization of hydrogenated amorphous silicon (a-Si:H) films by flash lamp annealing (FLA) at a low fluence by intentionally creating starting points for the trigger of explosive crystallization (EC). We confirm that a partly thick a-Si part can induce the crystallization of a-Si films. A periodic wavy structure is observed on the surface of polycrystalline silicon (poly-Si) on and near the thick parts, which is a clear indication of the emergence of EC. Creating partly thick a-Si parts can thus be effective for the control of the starting point of crystallization by FLA and can realize the crystallization of a-Si with high reproducibility. We also compare the effects of creating thick parts at the center and along the edge of the substrates, and a thick part along the edge of the substrates leads to the initiation of crystallization at a lower fluence.

Self-assembly of metal nanowires induced by alternating current electric fields

NASA Astrophysics Data System (ADS)

García-Sánchez, Pablo; Arcenegui, Juan J.; Morgan, Hywel; Ramos, Antonio

2015-01-01

We describe the reversible assembly of an aqueous suspension of metal nanowires into two different 2-dimensional stable configurations. The assembly is induced by an AC electric field of magnitude around 10 kV/m. It is known that single metal nanowires orientate parallel to the electric field for all values of applied frequency, according to two different mechanisms depending on the frequency. These different mechanisms also govern the mutual interaction between nanowires, which leads to directed-assembly into distinctive structures, the shape of which depends on the frequency of the applied field. We show that for frequencies higher than the typical frequency for charging the electrical double layer at the metal-electrolyte interface, dipole-dipole interaction leads to the formation of chains of nanowires. For lower frequencies, the nanowires form wavy bands perpendicular to the electric field direction. This behavior appears to be driven by the electroosmotic flow induced on the metal surface of the nanowires. Remarkably, no similar structures have been reported in previous studies of nanowires.

A New Species of Sexually Dimorphic Brittle Star of the Genus Ophiodaphne (Echinodermata: Ophiuroidea).

PubMed

Tominaga, Hideyuki; Hirose, Mamiko; Igarashi, Hikaru; Kiyomoto, Masato; Komatsu, Miéko

2017-08-01

We describe a new species of sexually dimorphic brittle star, Ophiodaphne spinosa, from Japan associated with the irregular sea urchin, Clypeaster japonicus based on its external morphology, and phylogenetic analyses of mitochondrial COI (cytochrome c oxidase subunit I). Females of this new species of Ophiodaphne are characterized mainly by the presence of wavy grooves on the surface of the radial shields, needle-like thorns on the oral skeletal jaw structures, and a low length-to-width ratio of the jaw angle in comparison with those of type specimens of its Ophiodaphne congeners: O. scripta, O. materna, and O. formata. A tabular key to the species characteristics of Ophiodaphne is provided. Phylogenetic analyses indicate that the new species of Ophiodaphne, O. scripta, and O. formata are monophyletic. Our results indicate that the Japanese Ophiodaphne include both the new species and O. scripta, and that there are four Ophiodaphne species of sexually dimorphic brittle stars with androphorous habit.

The solar wind structure that caused a large-scale disturbance of the plasma tail of comet Austin

NASA Technical Reports Server (NTRS)

Kozuka, Yukio; Konno, Ichishiro; Saito, Takao; Numazawa, Shigemi

1992-01-01

The plasma tail of Comet Austin (1989c1) showed remarkable disturbances because of the solar maximum periods and its orbit. Figure 1 shows photographs of Comet Austin taken in Shibata, Japan, on 29 Apr. 1990 UT, during about 20 minutes with the exposure times of 90 to 120 s. There are two main features in the disturbance; one is many bowed structures, which seem to move tailwards; and the other is a large-scale wavy structure. The bowed structures can be interpreted as arcade structures brushing the surface of both sides of the cometary plasma surrounding the nucleus. We identified thirteen structures of the arcades from each of the five photographs and calculated the relation between the distance of each structure from the cometary nucleus, chi, and the velocity, upsilon. The result is shown. This indicates that the velocity of the structures increases with distance. This is consistent with the result obtained from the observation at the Kiso Observatory.

Dawn's Early Light

NASA Image and Video Library

2017-07-10

The light of a new day on Saturn illuminates the planet's wavy cloud patterns and the smooth arcs of the vast rings. The light has traveled around 80 minutes since it left the sun's surface by the time it reaches Saturn. The illumination it provides is feeble; Earth gets 100 times the intensity since it's roughly ten times closer to the sun. Yet compared to the deep blackness of space, everything at Saturn still shines bright in the sunlight, be it direct or reflected. This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Feb. 25, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers. The view was obtained at a distance of approximately 762,000 miles (1.23 million kilometers) from Saturn. Image scale is 45 miles (73 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21336

Rippling Instability of a Collapsing Bubble

NASA Technical Reports Server (NTRS)

daSilveira, Rava; Chaieb, Sahraoui; Mahadevan, L.

1999-01-01

The rippling instability of a liquid sheet was first observed by Debregeas, de Gennes, an Brochard-Wyart [Science 279, 1704 (1998)] on a hemispherical bubble resting on a free surface. Unlike a soap bubble, it collapses under its own weight while bursting, and folds into a wavy structure which breaks the original axisymmetry. In fact, this effect occurs for both purely elastic and purely viscous (liquid) sheets, and an analogy can be made between the two mechanisms. We present a theory for the onset of the instability in both cases, in which the growth of the corrugation out of an inextensible initial condition is governed by the competition between gravitational and bending (shearing) forces. The instability occurs for a range of densities, stiffnesses (viscosities), and sizes, a result which arises less from dynamics than from geometry, suggesting a wide validity. We further obtain a quantitative expression for the number of ripples. Finally, we present the results of experiments, which are consistent with our predictions.

Azimuthal filter to attenuate ground roll noise in the F-kx-ky domain for land 3D-3C seismic data with uneven acquisition geometry

NASA Astrophysics Data System (ADS)

Arevalo-Lopez, H. S.; Levin, S. A.

2016-12-01

The vertical component of seismic wave reflections is contaminated by surface noise such as ground roll and secondary scattering from near surface inhomogeneities. A common method for attenuating these, unfortunately often aliased, arrivals is via velocity filtering and/or multichannel stacking. 3D-3C acquisition technology provides two additional sources of information about the surface wave noise that we exploit here: (1) areal receiver coverage, and (2) a pair of horizontal components recorded at the same location as the vertical component. Areal coverage allows us to segregate arrivals at each individual receiver or group of receivers by direction. The horizontal components, having much less compressional reflection body wave energy than the vertical component, provide a template of where to focus our energies on attenuating the surface wave arrivals. (In the simplest setting, the vertical component is a scaled 90 degree phase rotated version of the radial horizontal arrival, a potential third possible lever we have not yet tried to integrate.) The key to our approach is to use the magnitude of the horizontal components to outline a data-adaptive "velocity" filter region in the w-Kx-Ky domain. The big advantage for us is that even in the presence of uneven receiver geometries, the filter automatically tracks through aliasing without manual sculpting and a priori velocity and dispersion estimation. The method was applied to an aliased synthetic dataset based on a five layer earth model which also included shallow scatterers to simulate near-surface inhomogeneities and successfully removed both the ground roll and scatterers from the vertical component (Figure 1).

Near-surface energy transfers from internal tide beams to smaller vertical scale motions

NASA Astrophysics Data System (ADS)

Chou, S.; Staquet, C.; Carter, G. S.; Luther, D. S.

2016-02-01

Mechanical energy capable of causing diapycnal mixing in the ocean is transferred to the internal wave field when barotropic tides pass over underwater topography and generate internal tides. The resulting internal tide energy is confined in vertically limited structures, or beams. As internal tide beams (ITBs) propagate through regions of non-uniform stratification in the upper ocean, wave energy can be scattered through multiple reflections and refractions, be vertically trapped, or transferred to non-tidal frequencies through different nonlinear processes. Various observations have shown that ITBs are no longer detectable in horizontal kinetic energy beyond the first surface reflection. Importantly, this implies that some of the internal tide energy no longer propagates in to the abyssal ocean and consequently will not be available to maintain the density stratification. Using the NHM, a nonlinear and nonhydrostatic model based on the MITgcm, simulations of an ITB propagating up to the sea surface are examined in order to quantify the transformation of ITB energy to other motions. We compare and contrast the transformations enabled by idealized, smoothly-varying stratification with transformations enabled by realistic stratification containing a broad-band vertical wavenumber spectrum of variations. Preliminary two-dimensional results show that scattering due to small-scale structure in realistic stratification profiles from Hawaii can lead to energy being vertically trapped near the surface. Idealized simulations of "locally" generated internal solitary waves are analyzed in terms of energy flux transfers from the ITB to solitary waves, higher harmonics, and mean flow. The amount of internal tide energy which propagates back down after near-surface reflection of the ITB in different environments is quantified.

Ultra-thin flexible GaAs photovoltaics in vertical forms printed on metal surfaces without interlayer adhesives

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

Kim, Juho; Song, Kwangsun; Kim, Namyun

2016-06-20

Wearable flexible electronics often require sustainable power sources that are also mechanically flexible to survive the extreme bending that accompanies their general use. In general, thinner microelectronic devices are under less strain when bent. This paper describes strategies to realize ultra-thin GaAs photovoltaics through the interlayer adhesiveless transfer-printing of vertical-type devices onto metal surfaces. The vertical-type GaAs photovoltaic devices recycle reflected photons by means of bottom electrodes. Systematic studies with four different types of solar microcells indicate that the vertical-type solar microcells, at only a quarter of the thickness of similarly designed lateral-type cells, generate a level of electric powermore » similar to that of thicker cells. The experimental results along with the theoretical analysis conducted here show that the ultra-thin vertical-type solar microcells are durable under extreme bending and thus suitable for use in the manufacturing of wearable flexible electronics.« less

A model for calculating the vertical distribution of the atmospheric electric potential in the exchange layer in a maritime clean atmosphere

NASA Astrophysics Data System (ADS)

Kulkarni, M. N.; Kamra, A. K.

2012-11-01

A theoretical model is developed for calculating the vertical distribution of atmospheric electric potential in exchange layer of maritime clean atmosphere. The transport of space charge in electrode layer acts as a convective generator in this model and plays a major role in determining potential distribution in vertical. Eddy diffusion is the main mechanism responsible for the distribution of space charge in vertical. Our results show that potential at a particular level increases with increase in the strength of eddy diffusion under similar conditions. A method is suggested to estimate columnar resistance, the ionospheric potential and the vertical atmospheric electric potential distribution in exchange layer from measurements of total air-earth current density and surface electric field made over oceans. The results are validated and found to be in very good agreement with the previous aircraft measurements. Different parameters involved in the proposed methodology can be determined either theoretically, as in the present work, or experimentally using the near surface atmospheric electrical measurements or using some other surface-based measurement technique such as LIDAR. A graphical relationship between the atmospheric eddy diffusion coefficient and height of exchange layer obtained from atmospheric electrical approach, is reported.

KSC-04PD-1030

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- In the Orbiter Processing Facility, workers remove the Rudder Speed Brake panel on the vertical tail of the orbiter Atlantis. The Rudder Speed Brake is being removed for inspection and maintenance prior to Return to Flight. The vertical tail consists of a structural fin surface made of aluminum, the Rudder Speed Brake surface, a tip and a lower trailing edge. The rudder splits into two halves to serve as a speed brake. The vertical tail and Rudder Speed Brake are covered with a reusable thermal protection system. The Rudder Speed Brake is used to guide and slow the Shuttle as it comes in for a landing.

Vertically-coupled Whispering Gallery Mode Resonator Optical Waveguide, and Methods

NASA Technical Reports Server (NTRS)

Matsko, Andrey B. (Inventor); Savchenkov, Anatolly A. (Inventor); Matleki, Lute (Inventor)

2007-01-01

A vertically-coupled whispering gallery mode (WGM) resonator optical waveguide, a method of reducing a group velocity of light, and a method of making a waveguide are provided. The vertically-coupled WGM waveguide comprises a cylindrical rod portion having a round cross-section and an outer surface. First and second ring-shaped resonators are formed on the outer surface of the cylindrical rod portion and are spaced from each other along a longitudinal direction of the cylindrical rod. The first and second ringshaped resonators are capable of being coupled to each other by way an evanescent field formed in an interior of the cylindrical rod portion.

Two-stage epitaxial growth of vertically-aligned SnO 2 nano-rods on(001) ceria

DOE PAGES

Solovyov, Vyacheslav F.; Wu, Li-jun; Rupich, Martin W.; ...

2014-09-20

Growth of high-aspect ratio oriented tin oxide, SnO 2, nano-rods is complicated by a limited choice of matching substrates. We show that a (001) cerium oxide, CeO 2, surface uniquely enables epitaxial growth of tin-oxide nano-rods via a two-stage process. First, (100) oriented nano-wires coat the ceria surface by lateral growth, forming a uniaxially-textured SnO 2 deposit. Second, vertical SnO 2nano-rods nucleate on the deposit by homoepitaxy. We demonstrate growth of vertically oriented 1-2 μm long nano-rods with an average diameter of ≈20 nm.

Tube support

DOEpatents

Mullinax, Jerry L.

1988-01-01

A tube support for supporting horizontal tubes from an inclined vertical support tube passing between the horizontal tubes. A support button is welded to the vertical support tube. Two clamping bars or plates, the lower edges of one bearing on the support button, are removably bolted to the inclined vertical tube. The clamping bars provide upper and lower surface support for the horizontal tubes.

Vertical Displacement of the Surface Area over the Leakage to the Transverse salt Mine in 1992-2012

NASA Astrophysics Data System (ADS)

Lipecki, Tomasz

2018-03-01

The leakage of water in the salt mine caused considerable deformation of the surface. This article shows the vertical displacement in the area of leakage to the mine excavation, measured by precision leveling, carried out from the first days of leakage in 1992 until 2012. The geological and hydrogeological conditions of the mine, as well as the associated water hazards were described, which in conjunction with the inconvenient location of the excavation site in the northern frontage of the Carpathians and also inadequately conducted mining operations, contributed to the risk of flooding mine. The analysis of the vertical movements of the surface - subsidence and uplift - were present as well as the process of formation of the depression trough in the form of maps and graphs. The analyzes were based on 49 measurement series, starting from the first days of the disaster within the next 20 years. The course of development of the depression trough and the condition of the surface after stopping the water from the rock mass has been shown, which caused the surface to uplift.

The effect of the arbitrary level assignment of satellite cloud motion wind vectors on wind analyses in the pre-thunderstorm environment

NASA Technical Reports Server (NTRS)

Peslen, C. A.; Koch, S. E.; Uccellini, L. W.

1985-01-01

The impact of satellite-derived cloud motion vectors on SESAME rawinsonde wind fields was studied in two separate cases. The effect of wind and moisture gradients on the arbitrary assignment of the satellite data is assessed to coordinate surfaces in a severe storm environment marked by strong vertical wind shear. Objective analyses of SESAME rawinsonde winds and combined winds are produced and differences between these two analyzed fields are used to make an assessment of coordinate level choice. It is shown that the standard method of arbitrarily assigning wind vectors to a low level coordinate surface yields systematic differences between the rawinsonde and combined wind analyses. Arbitrary assignment of cloud motions to the 0.9 sigma surface produces smaller differences than assignment to the 825 mb pressure surface. Systematic differences occur near moisture discontinuities and in regions of horizontal and vertical wind shears. The differences between the combined and SESAME wind fields are made smallest by vertically interpolating cloud motions to either a pressure or sigma surface.

Using Ground Measurements to Examine the Surface Layer Parameterization Scheme in NCEP GFS

NASA Astrophysics Data System (ADS)

Zheng, W.; Ek, M. B.; Mitchell, K.

2017-12-01

Understanding the behavior and the limitation of the surface layer parameneterization scheme is important for parameterization of surface-atmosphere exchange processes in atmospheric models, accurate prediction of near-surface temperature and identifying the role of different physical processes in contributing to errors. In this study, we examine the surface layer paramerization scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) using the ground flux measurements including the FLUXNET data. The model simulated surface fluxes, surface temperature and vertical profiles of temperature and wind speed are compared against the observations. The limits of applicability of the Monin-Obukhov similarity theory (MOST), which describes the vertical behavior of nondimensionalized mean flow and turbulence properties within the surface layer, are quantified in daytime and nighttime using the data. Results from unstable regimes and stable regimes are discussed.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol.

PubMed

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-05

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0nM and 50mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids. Copyright © 2018. Published by Elsevier B.V.

Parameterization of turbulence and the planetary boundary layer in the GLA Fourth Order GCM

NASA Technical Reports Server (NTRS)

Helfand, H. M.

1985-01-01

A new scheme has been developed to model the planetary boundary layer in the GLAS Fourth Order GCM through explicit resolution of its vertical structure into two or more vertical layers. This involves packing the lowest layers of the GCM close to the ground and developing new parameterization schemes that can express the turbulent vertical fluxes of heat, momentum and moisture at the earth's surface and between the layers that are contained with the PBL region. Offline experiments indicate that the combination of the modified level 2.5 second-order turbulent closure scheme and the 'extended surface layer' similarity scheme should work well to simulate the behavior of the turbulent PBL even at the coarsest vertical resolution with which such schemes will conceivably be used in the GLA Fourth Order GCM.

Local and Remote Influences on Vertical Wind Shear over the Northern Tropical Atlantic Region

NASA Astrophysics Data System (ADS)

Saravanan, R.; Zhu, X.

2009-12-01

Vertical wind shear is one of the most important parameters controlling the frequency and intensity of Atlantic hurricanes. It has been argued that in global warming scenarios, the mechanical effect of changing vertical wind shear may even trump the thermodynamic effect of increasing Atlantic sea surface temperatures, when it comes to projected trends in Atlantic hurricane activity. Despite its importance, little is known about the connection between vertical shear in the north Atlantic region and the global atmospheric circulation, apart from the well-known positive correlation with El Nino-Southern Oscillation (ENSO). In this study, we analyze the statistical relationship between vertical shear and features of the large-scale circulation such as the distribution of sea surface temperature and vertical motion. We examine whether this relationship is different on interannual timescales associated with ENSO as compared to the decadal timescales associated with the Atlantic Multidecadal Oscillation (AMO). We also investigate how well the global general circulation models manage to simulate the observed vertical shear in this region, and its relationship to the large-scale circulation. Our analyses reveal an interesting sensitivity to air-sea coupling in model simulations of vertical shear. Another interesting property of vertical shear, as defined in the context of hurricane studies, is that it is positive definite, rather like precipitation. This means that it has a very nongaussian probability distribution on short timescales. We analyze how this nongaussianity changes when averaged over longer timescales.

Reduction of skylight reflection effects in the above-water measurement of diffuse marine reflectance: comment.

PubMed

Krotkov, N A; Vasilkov, A P

2000-03-20

Use of a vertical polarizer has been suggested to reduce the effects of surface reflection in the above-water measurements of marine reflectance. We suggest using a similar technique for airborne or spaceborne sensors when atmospheric scattering adds its own polarization signature to the upwelling radiance. Our own theoretical sensitivity study supports the recommendation of Fougnie et al. [Appl. Opt. 38, 3844 (1999)] (40-50 degrees vertical angle and azimuth angle near 135 degrees, polarizer parallel to the viewing plane) for above-water measurements. However, the optimal viewing directions (and the optimal orientation of the polarizer) change with altitude above the sea surface, solar angle, and atmospheric vertical optical structure. A polarization efficiency function is introduced, which shows the maximal possible polarization discrimination of the background radiation for an arbitrary altitude above the sea surface, viewing direction, and solar angle. Our comment is meant to encourage broader application of airborne and spaceborne polarization sensors in remote sensing of water and sea surface properties.

Cylindrical surface profile and diameter measuring tool and method

NASA Technical Reports Server (NTRS)

Currie, James R. (Inventor); Kissel, Ralph R. (Inventor); Smith, Earnest C. (Inventor); Oliver, Charles E. (Inventor); Redmon, John W., Sr. (Inventor); Wallace, Charles C. (Inventor); Swanson, Charles P. (Inventor)

1987-01-01

A tool is shown having a cross beam assembly made of beams joined by a center box structure. The assembly is adapted to be mounted by brackets to the outer end of a cylindrical case. The center box structure has a vertical shaft rotatably mounted therein and extending beneath the assembly. Secured to the vertical shaft is a radius arm which is adapted to rotate with the shaft. On the longer end of the radius arm is a measuring tip which contacts the cylindrical surface to be measured and which provides an electric signal representing the radius of the cylindrical surface from the center of rotation of the radius arm. An electric servomotor rotates the vertical shaft and an electronic resolver provides an electric signal representing the angle of rotation of the shaft. The electric signals are provided to a computer station which has software for its computer to calculate and print out the continuous circumference profile of the cylindrical surface, and give its true diameter and the deviations from the ideal circle.