Influence of post-cam design of posterior stabilized knee prosthesis on tibiofemoral motion during high knee flexion.

PubMed

Lin, Kun-Jhih; Huang, Chang-Hung; Liu, Yu-Liang; Chen, Wen-Chuan; Chang, Tsung-Wei; Yang, Chan-Tsung; Lai, Yu-Shu; Cheng, Cheng-Kung

2011-10-01

The post-cam design of contemporary posterior stabilized knee prosthesis can be categorized into flat-on-flat or curve-on-curve contact surfaces. The curve-on-curve design has been demonstrated its advantage of reducing stress concentration when the knee sustained an anteroposterior force with tibial rotation. How the post-cam design affects knee kinematics is still unknown, particularly, to compare the difference between the two design features. Analyzing knee kinematics of posterior stabilized knee prosthesis with various post-cam designs should provide certain instructions to the modification of prosthesis design. A dynamic knee model was utilized to investigate tibiofemoral motion of various post-cam designs during high knee flexion. Two posterior stabilized knee models were constructed with flat-on-flat and curve-on-curve contact surfaces of post-cam. Dynamic data of axial tibial rotation and femoral translation were measured from full-extension to 135°. Internal tibial rotation increased with knee flexion in both designs. Before post-cam engagement, the magnitude of internal tibial rotation was close in the two designs. However, tibial rotation angle decreased beyond femoral cam engaged with tibial post. The rate of reduction of tibial rotation was relatively lower in the curve-on-curve design. From post-cam engagement to extreme flexion, the curve-on-curve design had greater internal tibial rotation. Motion constraint was generated by medial impingement of femoral cam on tibial post. It would interfere with the axial motion of the femur relative to the tibia, resulting in decrease of internal tibial rotation. Elimination of rotational constraint should be necessary for achieving better tibial rotation during high knee flexion. Copyright © 2011 Elsevier Ltd. All rights reserved.

Properties of Special Types of Radiators

NASA Technical Reports Server (NTRS)

Parsons, S R

1921-01-01

This report discusses the general performance characteristics of three special classes of radiators: those with flat plate water tubes, fin and tube types, and types that whistle in an air stream. Curves and tables show the performance of representative radiators of each class and compare the flat plate and whistling types. Empirical equations are given for estimating the performance of flat plate radiators of various dimensions. This report also contains a brief discussion, with curves, showing the effect of yawing on the properties of a radiator.

Mass Distributions Implying Flat Galactic Rotation Curves

ERIC Educational Resources Information Center

Keeports, David

2010-01-01

The rotational speeds of stars in the disc of a spiral galaxy are virtually independent of the distances of the stars from the centre of the galaxy. In common parlance, the stellar speed versus distance plot known as a galactic rotation curve is by observation typically nearly flat. This observation provides strong evidence that most galactic…

Thermoluminescence response of flat optical fiber subjected to 9 MeV electron irradiations

NASA Astrophysics Data System (ADS)

Hashim, S.; Omar, S. S. Che; Ibrahim, S. A.; Hassan, W. M. S. Wan; Ung, N. M.; Mahdiraji, G. A.; Bradley, D. A.; Alzimami, K.

2015-01-01

We describe the efforts of finding a new thermoluminescent (TL) media using pure silica flat optical fiber (FF). The present study investigates the dose response, sensitivity, minimum detectable dose and glow curve of FF subjected to 9 MeV electron irradiations with various dose ranges from 0 Gy to 2.5 Gy. The above-mentioned TL properties of the FF are compared with commercially available TLD-100 rods. The TL measurements of the TL media exhibit a linear dose response over the delivered dose using a linear accelerator. We found that the sensitivity of TLD-100 is markedly 6 times greater than that of FF optical fiber. The minimum detectable dose was found to be 0.09 mGy for TLD-100 and 8.22 mGy for FF. Our work may contribute towards the development of a new dosimeter for personal monitoring purposes.

Effects of time-temperature profiles on glow curves of germanium-doped optical fibre

NASA Astrophysics Data System (ADS)

Lam, S. E.; Alawiah, A.; Bradley, D. A.; Mohd Noor, N.

2017-08-01

The Germanium (Ge) doped silica optical fibres have demonstrated the great potential to be developed as a thermoluminescent (TL) dosimeter that can be used in various applications in radiotherapy, diagnostic radiology, UV dosimetry system and food irradiation industry. Different time-temperature profile (TTP) parameters of the TL reader have been employed by many researchers in various of TL studies. Nevertheless, none of those studies adequately addressed the effects of the reader's preheat temperature and heating rate on the kinetic parameters of the TL glow curve specifically, the Ge-doped silica optical fibres. This research addresses the issue of TTP parameters with special attention to the determination of the kinetic parameters of the glow curve. The glow curve responses were explored and the kinetic parameters were analyzed by the WinGCF software, to show the effect of the preheat temperature and heating rate of the reader on Ge-doped fibre irradiated with 18 Gy of 6 MV photons radiation. The effect of TTP parameters was discussed and compared against the commercial fibre and tailored made fibre of 6 mol% Ge-doped of flat and cylindrical shape. The deconvolution of glow peaks and the kinetic parameters were obtained by the WinGCF software. This enables to fit accurately (1.5%

Lagrangian analysis of the laminar flat plate boundary layer

NASA Astrophysics Data System (ADS)

Gabr, Mohammad

2016-10-01

The flow properties at the leading edge of a flat plate represent a singularity to the Blasius laminar boundary layer equations; by applying the Lagrangian approach, the leading edge velocity profiles of the laminar boundary layer over a flat plate are studied. Experimental observations as well as the theoretical analysis show an exact Gaussian distribution curve as the original starting profile of the laminar flow. Comparisons between the Blasius solution and the Gaussian curve solution are carried out providing a new insight into the physics of the laminar flow.

Quantitative analysis and temperature-induced variations of moiré pattern in fiber-coupled imaging sensors.

PubMed

Karbasi, Salman; Arianpour, Ashkan; Motamedi, Nojan; Mellette, William M; Ford, Joseph E

2015-06-10

Imaging fiber bundles can map the curved image surface formed by some high-performance lenses onto flat focal plane detectors. The relative alignment between the focal plane array pixels and the quasi-periodic fiber-bundle cores can impose an undesirable space variant moiré pattern, but this effect may be greatly reduced by flat-field calibration, provided that the local responsivity is known. Here we demonstrate a stable metric for spatial analysis of the moiré pattern strength, and use it to quantify the effect of relative sensor and fiber-bundle pitch, and that of the Bayer color filter. We measure the thermal dependence of the moiré pattern, and the achievable improvement by flat-field calibration at different operating temperatures. We show that a flat-field calibration image at a desired operating temperature can be generated using linear interpolation between white images at several fixed temperatures, comparing the final image quality with an experimentally acquired image at the same temperature.

Synaptotagmin-mediated bending of the target membrane is a critical step in Ca2+-regulated fusion

PubMed Central

Hui, Enfu; Johnson, Colin P.; Yao, Jun; Dunning, F. Mark; Chapman, Edwin R.

2009-01-01

Summary Decades ago it was proposed that exocytosis involves invagination of the target membrane, resulting in a highly localized site of contact between the bilayers destined to fuse. The vesicle protein synaptotagmin-I (syt) bends membranes in response to Ca2+, but whether this drives localized invagination of the target membrane to accelerate fusion has not been determined; previous studies relied on reconstituted vesicles that were already highly curved and used mutations in syt that were not selective for membrane-bending activity. Here, we directly address this question by utilizing vesicles with different degrees of curvature. A tubulation-defective syt mutant was able to promote fusion between highly curved SNARE-bearing liposomes, but exhibited a marked loss of activity when the membranes were relatively flat. Moreover, bending of flat membranes by adding an N-BAR domain rescued the function of the tubulation-deficient syt mutant. Hence, syt-mediated membrane bending is a critical step in membrane fusion. PMID:19703397

Turbulent boundary layer heat transfer experiments: Convex curvature effects, including introduction and recovery

NASA Technical Reports Server (NTRS)

Simon, T. W.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.

1980-01-01

Heat transfer rates were measured through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20-50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15-20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: (1) the effect of initial boundary layer thickness; (2) the effect of freestream velocity; (3) the effect of freestream acceleration; (4) the effect of unheated starting length; and (5) the effect of the maturity of the boundary layer. Regardless of the initial state, curvature eventually forced the boundary layer into an asymptotic curved condition. The slope, minus one, is believed to be significant.

Buckling coefficients for simply supported and camped flat, rectangular sandwich panels under edgewise compression

Treesearch

Edward W. Kuenzi; Charles B. Norris; Paul M. Jenkinson

1964-01-01

“This report presents curves of coefficients and formulas for use in calculating the buckling of flat panels of sandwich construction under edgewise compressive loads. The curves were derived for sandwich panels having one facing of either of two orthotropic materials, the other facing of an isotropic material; both facings of orthotropic material; both facings of...

The effect of oblique angle of sound incidence, realistic edge conditions, curvature and in-plane panel stresses on the noise reduction characteristics of general aviation type panels

NASA Technical Reports Server (NTRS)

Grosveld, F.; Lameris, J.; Dunn, D.

1979-01-01

Experiments and a theoretical analysis were conducted to predict the noise reduction of inclined and curved panels. These predictions are compared to the experimental results with reasonable agreement between theory and experiment for panels under an oblique angle of sound incidence. Theoretical as well as experimental results indicate a big increase in noise reduction when a flat test panel is curved. Further curving the panel slightly decreases the noise reduction. Riveted flat panels are shown to give a higher noise reduction in the stiffness-controlled frequency region, while bonded panels are superior in this region when the test panel is curved. Experimentally measured noise reduction characteristics of flat aluminum panels with uniaxial in-plane stresses are presented and discussed. These test results indicate an important improvement in the noise reduction of these panels in the frequency range below the fundamental panel/cavity frequency.

Process and apparatus for indirect-fired heating and drying

DOEpatents

Abbasi, Hamid Ali; Chudnovsky, Yaroslav

2005-04-12

A method for heating flat or curved surfaces comprising injecting fuel and oxidant along the length, width or longitudinal side of a combustion space formed between two flat or curved plates, transferring heat from the combustion products via convection and radiation to the surface being heated on to the material being dried/heated, and recirculating at least 20% of the combustion products to the root of the flame.

Effect of boundary conditions and panel geometry on the response of laminated panels subjected to transverse pressure loads

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

1993-01-01

The behavior of thin laminated flat and curved panels subjected to transverse pressure and inplane loads is considered. The effects of panel geometry, boundary conditions and laminate stacking sequence on the response of panels subjected to transverse pressure loads up to 12.4 N/sq cm is presented. The response of thin laminated panels is evaluated analytically and selected results are compared with test data. A parametric study of the deformation and strain responses of panels with radius of curvature ranging from 20 to 305 cm is presented. The combination of inplane tensile and pressure loads is also considered.

Thermoluminescence characteristics of flat optical fiber in radiation dosimetry under different electron irradiation conditions

NASA Astrophysics Data System (ADS)

Alawiah, A.; Intan, A. M.; Bauk, S.; Abdul-Rashid, H. A.; Yusoff, Z.; Mokhtar, M. R.; Wan Abdullah, W. S.; Mat Sharif, K. A.; Mahdiraji, G. A.; Mahamd Adikan, F. R.; Tamchek, N.; Noor, N. M.; Bradley, D. A.

2013-05-01

Thermoluminescence (TL) flat optical fibers (FF) have been proposed as radiation sensor in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm3 contains pure silica SiO2 was selected for this research. The FF was annealed at 400°C for 1 h before irradiated. Kinetic parameters and dosimetric glow curve of TL response were studied in FF with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV using linear accelerator (LINAC) in the dose range of 2.0-10.0 Gy. The TL response was read using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80°C, maximum readout temperature is 400°C and the heating rate of 30°Cs-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used of LiF:MgTi dosimeter in medical radiotherapy application.

Shape Sensing a Morphed Wing with an Optical Fiber Bragg Grating

NASA Technical Reports Server (NTRS)

Tai, Hsiang

2005-01-01

We suggest using distributed fiber Bragg sensors systems which were developed locally at Langley Research Center carefully placed on the wing surface to collect strain component information at each location. Then we used the fact that the rate change of slope in the definition of linear strain is very small and can be treated as a constant. Thereby the strain distribution information of a morphed surface can be reduced into a distribution of local slope information of a flat surface. In other words a morphed curve surface is replaced by the collection of individual flat surface of different slope. By assembling the height of individual flat surface, the morphed curved surface can be approximated. A more sophisticated graphic routine can be utilized to restore the curved morphed surface. With this information, the morphed wing can be further adjusted and controlled. A numerical demonstration is presented.

Numerical Investigation of the Residual Stress Distribution of Flat-Faced and Convexly Curved Tablets Using the Finite Element Method.

PubMed

Otoguro, Saori; Hayashi, Yoshihiro; Miura, Takahiro; Uehara, Naoto; Utsumi, Shunichi; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo

2015-01-01

The stress distribution of tablets after compression was simulated using a finite element method, where the powder was defined by the Drucker-Prager cap model. The effect of tablet shape, identified by the surface curvature, on the residual stress distribution was investigated. In flat-faced tablets, weak positive shear stress remained from the top and bottom die walls toward the center of the tablet. In the case of the convexly curved tablet, strong positive shear stress remained on the upper side and in the intermediate part between the die wall and the center of the tablet. In the case of x-axial stress, negative values were observed for all tablets, suggesting that the x-axial force always acts from the die wall toward the center of the tablet. In the flat tablet, negative x-axial stress remained from the upper edge to the center bottom. The x-axial stress distribution differed between the flat and convexly curved tablets. Weak stress remained in the y-axial direction of the flat tablet, whereas an upward force remained at the center of the convexly curved tablet. By employing multiple linear regression analysis, the mechanical properties of the tablets were predicted accurately as functions of their residual stress distribution. However, the multiple linear regression prediction of the dissolution parameters of acetaminophen, used here as a model drug, was limited, suggesting that the dissolution of active ingredients is not a simple process; further investigation is needed to enable accurate predictions of dissolution parameters.

Calculated and measured stresses in simple panels subject to intense random acoustic loading including the near noise field of a turbojet engine

NASA Technical Reports Server (NTRS)

Lassiter, Leslie W; Hess, Robert W

1958-01-01

Flat 2024-t3 aluminum panels measuring 11 inches by 13 inches were tested in the near noise fields of a 4-inch air jet and turbojet engine. The stresses which were developed in the panels are compared with those calculated by generalized harmonic analysis. The calculated and measured stresses were found to be in good agreement. In order to make the stress calculations, supplementary data relating to the transfer characteristics, damping, and static response of flat and curved panels under periodic loading are necessary and were determined experimentally. In addition, an appendix containing detailed data on the near pressure field of the turbojet engine is included.

Complete super-sample lensing covariance in the response approach

NASA Astrophysics Data System (ADS)

Barreira, Alexandre; Krause, Elisabeth; Schmidt, Fabian

2018-06-01

We derive the complete super-sample covariance (SSC) of the matter and weak lensing convergence power spectra using the power spectrum response formalism to accurately describe the coupling of super- to sub-survey modes. The SSC term is completely characterized by the survey window function, the nonlinear matter power spectrum and the full first-order nonlinear power spectrum response function, which describes the response to super-survey density and tidal field perturbations. Generalized separate universe simulations can efficiently measure these responses in the nonlinear regime of structure formation, which is necessary for lensing applications. We derive the lensing SSC formulae for two cases: one under the Limber and flat-sky approximations, and a more general one that goes beyond the Limber approximation in the super-survey mode and is valid for curved sky applications. Quantitatively, we find that for sky fractions fsky ≈ 0.3 and a single source redshift at zS=1, the use of the flat-sky and Limber approximation underestimates the total SSC contribution by ≈ 10%. The contribution from super-survey tidal fields to the lensing SSC, which has not been included in cosmological analyses so far, is shown to represent about 5% of the total lensing covariance on multipoles l1,l2 gtrsim 300. The SSC is the dominant off-diagonal contribution to the total lensing covariance, making it appropriate to include these tidal terms and beyond flat-sky/Limber corrections in cosmic shear analyses.

The Universal Transverse Mercator (UTM) grid

USGS Publications Warehouse

,

1997-01-01

The most convenient way to identify points on the curved surface of the Earth is with a system of reference lines called parallels of latitude and meridians of longitude. On some maps the meridians and parallels appear as straight lines. On most modern maps, however, the meridians and parallels may appear as curved lines. These differences are due to the mathematical treatment required to portray a curved surface on a flat surface so that important properties of the map (such as distance and areal accuracy) are shown with minimum distortion. The system used to portray a portion of the round Earth on a flat surface is called a map projection.

The Universal Transverse Mercator (UTM) grid

USGS Publications Warehouse

,

1999-01-01

The most convenient way to identify points on the curved surface of the Earth is with a system of reference lines called parallels of latitude and meridians of longitude. On some maps, the meridians and parallels appear as straight lines. On most modern maps, however, the meridians and parallels appear as curved lines. These differences sre due to the mathematical treatment required to portray a curved surface on a flat surface so that important properties of the map (such as distance and areal accuracy) are shown with minimum distortion. The system used to portray a portion of the round Earth on a flat surface is called a map projection.

Application of the Spectral Element Method to Acoustic Radiation

NASA Technical Reports Server (NTRS)

Doyle, James F.; Rizzi, Stephen A. (Technical Monitor)

2000-01-01

This report summarizes research to develop a capability for analysis of interior noise in enclosed structures when acoustically excited by an external random source. Of particular interest was the application to the study of noise and vibration transmission in thin-walled structures as typified by aircraft fuselages. Three related topics are focused upon. The first concerns the development of a curved frame spectral element, the second shows how the spectral element method for wave propagation in folded plate structures is extended to problems involving curved segmented plates. These are of significance because by combining these curved spectral elements with previously presented flat spectral elements, the dynamic response of geometrically complex structures can be determined. The third topic shows how spectral elements, which incorporate the effect of fluid loading on the structure, are developed for analyzing acoustic radiation from dynamically loaded extended plates.

Advanced composites structural concepts and materials technologies for primary aircraft structures: Structural response and failure analysis

NASA Technical Reports Server (NTRS)

Dorris, William J.; Hairr, John W.; Huang, Jui-Tien; Ingram, J. Edward; Shah, Bharat M.

1992-01-01

Non-linear analysis methods were adapted and incorporated in a finite element based DIAL code. These methods are necessary to evaluate the global response of a stiffened structure under combined in-plane and out-of-plane loading. These methods include the Arc Length method and target point analysis procedure. A new interface material model was implemented that can model elastic-plastic behavior of the bond adhesive. Direct application of this method is in skin/stiffener interface failure assessment. Addition of the AML (angle minus longitudinal or load) failure procedure and Hasin's failure criteria provides added capability in the failure predictions. Interactive Stiffened Panel Analysis modules were developed as interactive pre-and post-processors. Each module provides the means of performing self-initiated finite elements based analysis of primary structures such as a flat or curved stiffened panel; a corrugated flat sandwich panel; and a curved geodesic fuselage panel. This module brings finite element analysis into the design of composite structures without the requirement for the user to know much about the techniques and procedures needed to actually perform a finite element analysis from scratch. An interactive finite element code was developed to predict bolted joint strength considering material and geometrical non-linearity. The developed method conducts an ultimate strength failure analysis using a set of material degradation models.

Low-cost fabrication and direct bond installation of flat, single-curvature and compound-curvature ablative heat shield panels

NASA Technical Reports Server (NTRS)

Norwood, L. B.

1972-01-01

Procedures for low cost fabrication and direct bond installation of flat, single curved, and compound curvature ablative heat shields on a DC-3 aircraft are discussed. The panel sizes and attachment locations are identified. In addition to the bonding of the four contoured panels, two flat panels were bonded to the nearly flat, lower surface of the center wing section. The detailed requirements and objectives of the investigation are described.

Forgetting Curves: Implications for Connectionist Models

ERIC Educational Resources Information Center

Sikstrom, Sverker

2002-01-01

Forgetting in long-term memory, as measured in a recall or a recognition test, is faster for items encoded more recently than for items encoded earlier. Data on forgetting curves fit a power function well. In contrast, many connectionist models predict either exponential decay or completely flat forgetting curves. This paper suggests a…

Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited)

NASA Astrophysics Data System (ADS)

Loisel, G. P.; Wu, M.; Stolte, W.; Kruschwitz, C.; Lake, P.; Dunham, G. S.; Bailey, J. E.; Rochau, G. A.

2016-11-01

The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (xop) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration data confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.

Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited)

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

Loisel, G. P., E-mail: gploise@sandia.gov; Wu, M.; Lake, P.

2016-11-15

The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (XOP) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration datamore » confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.« less

Research on low-frequency band gap property of a hybrid phononic crystal

NASA Astrophysics Data System (ADS)

Dong, Yake; Yao, Hong; Du, Jun; Zhao, Jingbo; Chao, Ding; Wang, Benchi

2018-05-01

A hybrid phononic crystal has been investigated. The characteristic frequency of XY mode, transmission loss and displacement vector have been calculated by the finite element method. There are Bragg scattering band gap and local resonance band gap in the band structures. We studied the influence factors of band gap. There are many flat bands in the eigenfrequencies curve. There are many flat bands in the curve. The band gap covers a large range in low frequency. The band gaps cover more than 95% below 3000 Hz.

Non-lightlike ruled surfaces with constant curvatures in Minkowski 3-space

NASA Astrophysics Data System (ADS)

Ali, Ahmad Tawfik

We study the non-lightlike ruled surfaces in Minkowski 3-space with non-lightlike base curve c(s) =∫(αt + βn + γb)ds, where t, n, b are the tangent, principal normal and binormal vectors of an arbitrary timelike curve Γ(s). Some important results of flat, minimal, II-minimal and II-flat non-lightlike ruled surfaces are studied. Finally, the following interesting theorem is proved: the only non-zero constant mean curvature (CMC) non-lightlike ruled surface is developable timelike ruled surface generated by binormal vector.

Acoustic radiation damping of flat rectangular plates subjected to subsonic flows

NASA Technical Reports Server (NTRS)

Lyle, Karen Heitman

1993-01-01

The acoustic radiation damping for various isotropic and laminated composite plates and semi-infinite strips subjected to a uniform, subsonic and steady flow has been predicted. The predictions are based on the linear vibration of a flat plate. The fluid loading is characterized as the perturbation pressure derived from the linearized Bernoulli and continuity equations. Parameters varied in the analysis include Mach number, mode number and plate size, aspect ratio and mass. The predictions are compared with existing theoretical results and experimental data. The analytical results show that the fluid loading can significantly affect realistic plate responses. Generally, graphite/epoxy and carbon/carbon plates have higher acoustic radiation damping values than similar aluminum plates, except near plate divergence conditions resulting from aeroelastic instability. Universal curves are presented where the acoustic radiation damping normalized by the mass ratio is a linear function of the reduced frequency. A separate curve is required for each Mach number and plate aspect ratio. In addition, acoustic radiation damping values can be greater than or equal to the structural component of the modal critical damping ratio (assumed as 0.01) for the higher subsonic Mach numbers. New experimental data were acquired for comparison with the analytical results.

The dose-response of Harshaw TLD-700H.

PubMed

Velbeck, K J; Luo, L Z; Ramlo, M J; Rotunda, J E

2006-01-01

Harshaw TLD-700H (7LiF:Mg,Cu,P) was previously characterised for low- to high-dose ranges from 1 microGy to 20 Gy. This paper describes the studies and results of dose-response and linearity at much higher doses. TLD-700H is a near perfect dosimetric material with near tissue equivalence, flat energy response, and the ability to measure beta, gamma and X rays. These new results extend the applicability of Harshaw TLD-700H into more dosimetric measurement environments. The simple glow curve structure provides insignificant fade, eliminating special oven preparation methods experienced by other materials. The work presented in this paper quantifies the performance of Harshaw TLD-700H in extended ranges.

Turbulent boundary layer heat transfer experiments: Convex curvature effects including introduction and recovery

NASA Technical Reports Server (NTRS)

Simon, T. W.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.

1982-01-01

Measurements were made of the heat transfer rate through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20% to 50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15% to 20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: the effect of initial boundary layer thickness, the effect of freestream velocity, the effect of freestream acceleration, the effect of unheated starting length, and the effect of the maturity of the boundary layer. An existing curvature prediction model was tested against this broad heat transfer data base to determine where it could appropriately be used for heat transfer predictions.

The Happiest thought of Einstein's Life

NASA Astrophysics Data System (ADS)

Heller, Michael

Finally, let us have a closer look at the place of the equivalence principle in the logical scheme of Einstein's general relativity theory. First, Einstein new well, from Minkowski's geometric formulation of his own special relativity, that accelerated motions should be represented as curved lines in a flat space-time. Second, the Galileo principle asserts that all bodies are accelerated in the same way in a given gravitational field, and consequently their motions are represented in the flat space-time by curved lines, all exactly in the same way. Third, since all lines representing free motions are curved exactly in the same way in the flat space-time, one can say that the lines remain straight (as far as possible) but the space-time itself becomes curved. Fourth, and last, since acceleration is (locally) equivalent to a gravitational field (here we have the equivalence principle), one is entitled to assert that it is the gravitational field (and not acceleration) that is represented as the curvature of space-time. This looks almost like an Aristotelian syllogism. However, to put all the pieces of evidence into the logical chain took Einstein a few years of hard thinking. The result has been incorporated into the field equations which quantitatively show how the curvature of space-time and gravity are linked together.

Solid particle impingement erosion characteristics of cylindrical surfaces, pre-existing holes and slits

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1983-01-01

The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.

Can reduction of uncertainties in cervix cancer brachytherapy potentially improve clinical outcome?

PubMed

Nesvacil, Nicole; Tanderup, Kari; Lindegaard, Jacob C; Pötter, Richard; Kirisits, Christian

2016-09-01

The aim of this study was to quantify the impact of different types and magnitudes of dosimetric uncertainties in cervix cancer brachytherapy (BT) on tumour control probability (TCP) and normal tissue complication probability (NTCP) curves. A dose-response simulation study was based on systematic and random dose uncertainties and TCP/NTCP models for CTV and rectum. Large patient cohorts were simulated assuming different levels of dosimetric uncertainties. TCP and NTCP were computed, based on the planned doses, the simulated dose uncertainty, and an underlying TCP/NTCP model. Systematic uncertainties of 3-20% and random uncertainties with a 5-30% standard deviation per BT fraction were analysed. Systematic dose uncertainties of 5% lead to a 1% decrease/increase of TCP/NTCP, while random uncertainties of 10% had negligible impact on the dose-response curve at clinically relevant dose levels for target and OAR. Random OAR dose uncertainties of 30% resulted in an NTCP increase of 3-4% for planned doses of 70-80Gy EQD2. TCP is robust to dosimetric uncertainties when dose prescription is in the more flat region of the dose-response curve at doses >75Gy. For OARs, improved clinical outcome is expected by reduction of uncertainties via sophisticated dose delivery and treatment verification. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Photonic band structures of two-dimensional magnetized plasma photonic crystals

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

Qi, L.

By using modified plane wave method, photonic band structures of the transverse electric polarization for two types of two-dimensional magnetized plasma photonic crystals are obtained, and influences of the external magnetic field, plasma density, and dielectric materials on the dispersion curves are studied, respectively. Results show that two areas of flat bands appear in the dispersion curves due to the role of external magnetic field, and the higher frequencies of the up and down flat bands are corresponding to the right-circled and left-circled cutoff frequencies, respectively. Adjusting external magnetic field and plasma density can not only control positions of themore » flat bands, but also can control the location and width of the local gap; increasing relative dielectric constant of the dielectric materials makes omni-direction gaps appear.« less

Diffractive optical elements on non-flat substrates using electron beam lithography

NASA Technical Reports Server (NTRS)

Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Wilson, Daniel W. (Inventor)

2002-01-01

The present disclosure describes a technique for creating diffraction gratings on curved surfaces with electron beam lithography. The curved surface can act as an optical element to produce flat and aberration-free images in imaging spectrometers. In addition, the fabrication technique can modify the power structure of the grating orders so that there is more energy in the first order than for a typical grating. The inventors noticed that by using electron-beam lithography techniques, a variety of convex gratings that are well-suited to the requirements of imaging spectrometers can be manufactured.

A curved edge diffraction-utilized displacement sensor for spindle metrology

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

Lee, ChaBum, E-mail: clee@tntech.edu; Zhao, Rui; Jeon, Seongkyul

This paper presents a new dimensional metrological sensing principle for a curved surface based on curved edge diffraction. Spindle error measurement technology utilizes a cylindrical or spherical target artifact attached to the spindle with non-contact sensors, typically a capacitive sensor (CS) or an eddy current sensor, pointed at the artifact. However, these sensors are designed for flat surface measurement. Therefore, measuring a target with a curved surface causes error. This is due to electric fields behaving differently between a flat and curved surface than between two flat surfaces. In this study, a laser is positioned incident to the cylindrical surfacemore » of the spindle, and a photodetector collects the total field produced by the diffraction around the target surface. The proposed sensor was compared with a CS within a range of 500 μm. The discrepancy between the proposed sensor and CS was 0.017% of the full range. Its sensing performance showed a resolution of 14 nm and a drift of less than 10 nm for 7 min of operation. This sensor was also used to measure dynamic characteristics of the spindle system (natural frequency 181.8 Hz, damping ratio 0.042) and spindle runout (22.0 μm at 2000 rpm). The combined standard uncertainty was estimated as 85.9 nm under current experiment conditions. It is anticipated that this measurement technique allows for in situ health monitoring of a precision spindle system in an accurate, convenient, and low cost manner.« less

Diagnosing Early Ischemic Changes with the Latest-Generation Flat Detector CT: A Comparative Study with Multidetector CT.

PubMed

Maier, I L; Leyhe, J R; Tsogkas, I; Behme, D; Schregel, K; Knauth, M; Schnieder, M; Liman, J; Psychogios, M-N

2018-05-01

One-stop management of mechanical thrombectomy-eligible patients with large-vessel occlusion represents an innovative approach in acute stroke treatment. This approach reduces door-to-reperfusion times by omitting multidetector CT, using flat detector CT as pre-mechanical thrombectomy imaging. The purpose of this study was to compare the diagnostic performance of the latest-generation flat detector CT with multidetector CT. Prospectively derived data from patients with ischemic stroke with large-vessel occlusion and mechanical thrombectomy were analyzed in this monocentric study. All included patients underwent multidetector CT before referral to our comprehensive stroke center and flat detector CT in the angiography suite before mechanical thrombectomy. Diagnosis of early ischemic signs, quantified by the ASPECTS, was compared between modalities using cross tables, the Pearson correlation, and Bland-Altman plots. The predictive value of multidetector CT- and flat detector CT-derived ASPECTS for functional outcome was investigated using area under the receiver operating characteristic curve analysis. Of 25 patients, 24 (96%) had flat detector CT with sufficient diagnostic quality. Median multidetector CT and flat detector CT ASPECTSs were 7 (interquartile range, 5.5-9 and 4.25-8, respectively) with a mean period of 143.6 ± 49.5 minutes between both modalities. The overall sensitivity was 85.1% and specificity was 83.1% for flat detector CT ASPECTS compared with multidetector CT ASPECTS as the reference technique. Multidetector CT and flat detector CT ASPECTS were strongly correlated ( r = 0.849, P < .001) and moderately predicted functional outcome (area under the receiver operating characteristic curve, 0.738; P = .007 and .715; P = .069, respectively). Determination of ASPECTS on flat detector CT is feasible, showing no significant difference compared with multidetector CT ASPECTS and a similar predictive value for functional outcome. Our findings support the use of flat detector CT for emergency stroke imaging before mechanical thrombectomy to reduce door-to-groin time. © 2018 by American Journal of Neuroradiology.

Hydrodynamic coupling of particle inclusions embedded in curved lipid bilayer membranes

DOE PAGES

Sigurdsson, Jon Karl; Atzberger, Paul J.

2016-06-27

Here, we develop theory and computational methods to investigate particle inclusions embedded within curved lipid bilayer membranes. We consider the case of spherical lipid vesicles where inclusion particles are coupled through (i) intramembrane hydrodynamics, (ii) traction stresses with the external and trapped solvent fluid, and (iii) intermonolayer slip between the two leaflets of the bilayer. We investigate relative to flat membranes how the membrane curvature and topology augment hydrodynamic responses. We show how both the translational and rotational mobility of protein inclusions are effected by the membrane curvature, ratio of intramembrane viscosity to solvent viscosity, and intermonolayer slip. For generalmore » investigations of many-particle dynamics, we also discuss how our approaches can be used to treat the collective diffusion and hydrodynamic coupling within spherical bilayers.« less

Hydrodynamic coupling of particle inclusions embedded in curved lipid bilayer membranes

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

Sigurdsson, Jon Karl; Atzberger, Paul J.

Here, we develop theory and computational methods to investigate particle inclusions embedded within curved lipid bilayer membranes. We consider the case of spherical lipid vesicles where inclusion particles are coupled through (i) intramembrane hydrodynamics, (ii) traction stresses with the external and trapped solvent fluid, and (iii) intermonolayer slip between the two leaflets of the bilayer. We investigate relative to flat membranes how the membrane curvature and topology augment hydrodynamic responses. We show how both the translational and rotational mobility of protein inclusions are effected by the membrane curvature, ratio of intramembrane viscosity to solvent viscosity, and intermonolayer slip. For generalmore » investigations of many-particle dynamics, we also discuss how our approaches can be used to treat the collective diffusion and hydrodynamic coupling within spherical bilayers.« less

Design considerations and analysis planning of a phase 2a proof of concept study in rheumatoid arthritis in the presence of possible non-monotonicity.

PubMed

Liu, Feng; Walters, Stephen J; Julious, Steven A

2017-10-02

It is important to quantify the dose response for a drug in phase 2a clinical trials so the optimal doses can then be selected for subsequent late phase trials. In a phase 2a clinical trial of new lead drug being developed for the treatment of rheumatoid arthritis (RA), a U-shaped dose response curve was observed. In the light of this result further research was undertaken to design an efficient phase 2a proof of concept (PoC) trial for a follow-on compound using the lessons learnt from the lead compound. The planned analysis for the Phase 2a trial for GSK123456 was a Bayesian Emax model which assumes the dose-response relationship follows a monotonic sigmoid "S" shaped curve. This model was found to be suboptimal to model the U-shaped dose response observed in the data from this trial and alternatives approaches were needed to be considered for the next compound for which a Normal dynamic linear model (NDLM) is proposed. This paper compares the statistical properties of the Bayesian Emax model and NDLM model and both models are evaluated using simulation in the context of adaptive Phase 2a PoC design under a variety of assumed dose response curves: linear, Emax model, U-shaped model, and flat response. It is shown that the NDLM method is flexible and can handle a wide variety of dose-responses, including monotonic and non-monotonic relationships. In comparison to the NDLM model the Emax model excelled with higher probability of selecting ED90 and smaller average sample size, when the true dose response followed Emax like curve. In addition, the type I error, probability of incorrectly concluding a drug may work when it does not, is inflated with the Bayesian NDLM model in all scenarios which would represent a development risk to pharmaceutical company. The bias, which is the difference between the estimated effect from the Emax and NDLM models and the simulated value, is comparable if the true dose response follows a placebo like curve, an Emax like curve, or log linear shape curve under fixed dose allocation, no adaptive allocation, half adaptive and adaptive scenarios. The bias though is significantly increased for the Emax model if the true dose response follows a U-shaped curve. In most cases the Bayesian Emax model works effectively and efficiently, with low bias and good probability of success in case of monotonic dose response. However, if there is a belief that the dose response could be non-monotonic then the NDLM is the superior model to assess the dose response.

2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...

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

2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

Microwave Photonics

DTIC Science & Technology

2005-11-01

along X & Z The active area of the detector used is about 3 mm in diameter. Figure 54 shows two measured light power coupling curves plotted against...the scanned detector positions along the X & Z axes. At the top of the power curves , there are flat areas. It indicates that the detector collects...is about 400 m long for curve scanning along X direction and is about 500 m long for curve scanning along Z direction. This difference might be

Analytical Proof That There is no Effect of Confinement or Curvature on the Maxwell-Boltzmann Collision Frequency

NASA Astrophysics Data System (ADS)

Carnio, Brett N.; Elliott, Janet A. W.

2014-08-01

The number of Maxwell-Boltzmann particles that hit a flat wall in infinite space per unit area per unit time is a well-known result. As new applications are arising in micro and nanotechnologies there are a number of situations in which a rarefied gas interacts with either a flat or curved surface in a small confined geometry. Thus, it is necessary to prove that the Maxwell-Boltzmann collision frequency result holds even if a container's dimensions are on the order of nanometers and also that this result is valid for both a finite container with flat walls (a rectangular container) and a finite container with a curved wall (a cylindrical container). An analytical proof confirms that the Maxwell-Boltzmann collision frequencies for either a finite rectangular container or a finite cylindrical container are both equal to the well-known result obtained for a flat wall in infinite space. A major aspect of this paper is the introduction of a mathematical technique to solve the arising infinite sum of integrals whose integrands depend on the Maxwell-Boltzmann velocity distribution.

Piezoceramic Actuator Placement for Acoustic Control of Panels

NASA Technical Reports Server (NTRS)

Bevan, Jeffrey S.; Turner, Travis L. (Technical Monitor)

2001-01-01

Optimum placement of multiple traditional piezoceramic actuators is determined for active structural acoustic control of flat panels. The structural acoustic response is determined using acoustic radiation filters and structural surface vibration characteristics. Linear Quadratic Regulator (LQR) control is utilized to determine the optimum state feedback gain for active structural acoustic control. The optimum actuator location is determined by minimizing the structural acoustic radiated noise using a modified genetic algorithm. Experimental tests are conducted and compared to analytical results. Anisotropic piezoceramic actuators exhibits enhanced performance when compared to traditional isotropic piezoceramic actuators. As a result of the inherent isotropy, these advanced actuators develop strain along the principal material axis. The orientation of anisotropic actuators is investigated on the effect of structural vibration and acoustic control of curved and flat panels. A fully coupled shallow shell finite element formulation is developed to include anisotropic piezoceramic actuators for shell structures.

Piezoceramic Actuator Placement for Acoustic Control of Panels

NASA Technical Reports Server (NTRS)

Bevan, Jeffrey S.

2000-01-01

Optimum placement of multiple traditional piezoceramic actuators is determined for active structural acoustic control of flat panels. The structural acoustic response is determined using acoustic radiation filters and structural surface vibration characteristics. Linear Quadratic Regulator (LQR) control is utilized to determine the optimum state feedback gain for active structural acoustic control. The optimum actuator location is determined by minimizing the structural acoustic radiated noise using a modified genetic algorithm. Experimental tests are conducted and compared to analytical results. Anisotropic piezoceramic actuators exhibit enhanced performance when compared to traditional isotropic piezoceramic actuators. As a result of the inherent isotropy, these advanced actuators develop strain along the principal material axis. The orientation of anisotropic actuators is investigated on the effect of structural vibration and acoustic control of curved and flat panels. A fully coupled shallow shell finite element formulation is developed to include anisotropic piezoceramic actuators for shell structures.

SU-E-T-162: Characterization of a New Oblong Cone for Use with the Intraoperative Mobetron Unit

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

Cantley, J; Colussi, V

Purpose: To evaluate the dosimetric characteristics of a new flat 7 cm x 12 cm oblong cone for intraoperative radiation therapy (IORT) procedures. Methods: Percent depth dose (PDD) curves and profile measurements at dose depths of D100, D90, D80, D50, and D30 were measured using a parallel-plate ion chamber and a 3-D water tank Blue phantom II (iba) for the three energies (6, 9, and 12 MeV) available with the new generation Mobetron 2000. In addition, PDD curves and profiles were made with Gafchromic EBT3 films in solid water phantom. H&D curves were created for each energy for absolute calibration.more » The films were analyzed using the RIT image analysis software and then compared with the ion chamber results. Output values were obtained by normalizing the dose/MU at D100 at the clinical axis of the oblong cone by the dose/MU at D100 for the flat 10cm cylindrical standard cone using ion chamber measurements. Results: Ion chamber results show that the PDDs from the flat oblong cone, at the clinical axis, match with the PDDs for its “cylindrical brother” 7cm flat cone. These PDDs are comparable with those from the 10cm standard cone. The D100 coincides for all three energies. The cone output factors for the oblong cone are 1.07 for all energies. Ion chamber profiles measurements and film analysis show that the use of flat oblong cone with the 6 and 9 MeV energies Result in horns of approximately 12% and 8%, respectively. Conversely, 12 MeV profiles show loss of flatness near the field edge. Conclusion: The potential advantage of the oblong cones is the elimination of the well-known difficulties of electron field matching, both dosimetrically and in clinical setup.« less

Elastic stability of laminated, flat and curved, long rectangular plates subjected to combined inplane loads

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Tamekuni, M.; Baker, L. L.

1974-01-01

A method is presented to predict theoretical buckling loads of long, rectangular flat and curved laminated plates with arbitrary orientation of orthotropic axes each lamina. The plate is subjected to combined inplane normal and shear loads. Arbitrary boundary conditions may be stipulated along the longitudinal sides of the plate. In the absence of inplane shear loads and extensional-shear coupling, the analysis is also applicable to finite length plates. Numerical results are presented for curved laminated composite plates with boundary conditions and subjected to various loadings. These results indicate some of the complexities involved in the numerical solution of the analysis for general laminates. The results also show that the reduced bending stiffness approximation when applied to buckling problems could lead to considerable error in some cases and therefore must be used with caution.

SU-E-T-635: Quantitative Study On Beam Flatness Variation with Beam Energy Change

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

Li, J S; Eldib, A; Ma, C

2014-06-15

Purpose: Beam flatness check has been proposed for beam energy check for photon beams with flattering filters. In this work, beam flatness change with beam energy was investigated quantitatively using the Monte Carlo method and its significance was compared with depth dose curve change. Methods: Monte Carlo simulations for a linear accelerator with flattering filter were performed with different initial electron energies for photon beams of 6MV and 10MV. Dose calculations in a water phantom were then perform with the phase space files obtained from the simulations. The beam flatness was calculated based on the dose profile at 10 cmmore » depth for all the beams with different initial electron energies. The percentage depth dose (PDD) curves were also analyzed. The dose at 10cm depth (D10) and the ratio of the dose at 10cm and 20cm depth (D10/D20) and their change with the beam energy were calculated and compared with the beam flatness variation. Results: It was found that the beam flatness variation with beam energy change was more significant than the change of D10 and the ratio between D10 and D20 for both 6MV and 10MV beams. Half MeV difference on the initial electron beam energy brought in at least 20% variation on the beam flatness but only half percent change on the ratio of D10 and D20. The change of D10 or D20 alone is even less significant. Conclusion: The beam energy impact on PDD is less significant than that on the beam flatness. If the PDD is used for checking the beam energy, uncertainties of the measurement could possibly disguise its change. Beam flatness changes more significantly with beam energy and therefore it can be used for monitoring the energy change for photon beams with flattering filters. However, other factors which may affect the beam flatness should be watched as well.« less

Curved CCD detector devices and arrays for multispectral astrophysical applications and terrestrial stereo panoramic cameras

NASA Astrophysics Data System (ADS)

Swain, Pradyumna; Mark, David

2004-09-01

The emergence of curved CCD detectors as individual devices or as contoured mosaics assembled to match the curved focal planes of astronomical telescopes and terrestrial stereo panoramic cameras represents a major optical design advancement that greatly enhances the scientific potential of such instruments. In altering the primary detection surface within the telescope"s optical instrumentation system from flat to curved, and conforming the applied CCD"s shape precisely to the contour of the telescope"s curved focal plane, a major increase in the amount of transmittable light at various wavelengths through the system is achieved. This in turn enables multi-spectral ultra-sensitive imaging with much greater spatial resolution necessary for large and very large telescope applications, including those involving infrared image acquisition and spectroscopy, conducted over very wide fields of view. For earth-based and space-borne optical telescopes, the advent of curved CCD"s as the principle detectors provides a simplification of the telescope"s adjoining optics, reducing the number of optical elements and the occurrence of optical aberrations associated with large corrective optics used to conform to flat detectors. New astronomical experiments may be devised in the presence of curved CCD applications, in conjunction with large format cameras and curved mosaics, including three dimensional imaging spectroscopy conducted over multiple wavelengths simultaneously, wide field real-time stereoscopic tracking of remote objects within the solar system at high resolution, and deep field survey mapping of distant objects such as galaxies with much greater multi-band spatial precision over larger sky regions. Terrestrial stereo panoramic cameras equipped with arrays of curved CCD"s joined with associative wide field optics will require less optical glass and no mechanically moving parts to maintain continuous proper stereo convergence over wider perspective viewing fields than their flat CCD counterparts, lightening the cameras and enabling faster scanning and 3D integration of objects moving within a planetary terrain environment. Preliminary experiments conducted at the Sarnoff Corporation indicate the feasibility of curved CCD imagers with acceptable electro-optic integrity. Currently, we are in the process of evaluating the electro-optic performance of a curved wafer scale CCD imager. Detailed ray trace modeling and experimental electro-optical data performance obtained from the curved imager will be presented at the conference.

HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...

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

HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. SAME VIEW AT CA-157-2. LOOKING NNE. GIS: N-37' 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

A deformation analysis of flat flexible gear and its equation of original curved surfaces

NASA Technical Reports Server (NTRS)

Yunwen, S.

1985-01-01

The equation of the original curved surface of end harmonic gearing is determined by displacement analysis of flat flexible gear. The displacement analysis is also used to calculate the strength and rigidity of the gear. The latter is regarded as a circular plate with two concentrated loads, since its torsional rigidity is much larger than its bending rigidity. Small-deflection theory of thin plates is used to solve for the displacement of any point in the middle plane of the gear. New expressions are given for radial and tangential displacements of the middle plane under asymmetrical loading. A digital computer is used to obtain numerical values for the displacements.

Consistent cosmic bubble embeddings

NASA Astrophysics Data System (ADS)

Haque, S. Shajidul; Underwood, Bret

2017-05-01

The Raychaudhuri equation for null rays is a powerful tool for finding consistent embeddings of cosmological bubbles in a background spacetime in a way that is largely independent of the matter content. We find that spatially flat or positively curved thin wall bubbles surrounded by a cosmological background must have a Hubble expansion that is either contracting or expanding slower than the background, which is a more stringent constraint than those obtained by the usual Israel thin-wall formalism. Similarly, a cosmological bubble surrounded by Schwarzschild space, occasionally used as a simple "swiss cheese" model of inhomogenities in an expanding universe, must be contracting (for spatially flat and positively curved bubbles) and bounded in size by the apparent horizon.

Free vibration of rectangular plates with a small initial curvature

NASA Technical Reports Server (NTRS)

Adeniji-Fashola, A. A.; Oyediran, A. A.

1988-01-01

The method of matched asymptotic expansions is used to solve the transverse free vibration of a slightly curved, thin rectangular plate. Analytical results for natural frequencies and mode shapes are presented in the limit when the dimensionless bending rigidity, epsilon, is small compared with in-plane forces. Results for different boundary conditions are obtained when the initial deflection is: (1) a polynomial in both directions, and (2) the product of a polynomial and a trigonometric function, and arbitrary. For the arbitrary initial deflection case, the Fourier series technique is used to define the initial deflection. The results obtained show that the natural frequencies of vibration of slightly curved plates are coincident with those of perfectly flat, prestressed rectangular plates. However, the eigenmodes are very different from those of initially flat prestressed rectangular plates. The total deflection is found to be the sum of the initial deflection, the deflection resulting from the solution of the flat plate problem, and the deflection resulting from the static problem.

High-Speed Laser Image Analysis of Plume Angles for Pressurised Metered Dose Inhalers: The Effect of Nozzle Geometry.

PubMed

Chen, Yang; Young, Paul M; Murphy, Seamus; Fletcher, David F; Long, Edward; Lewis, David; Church, Tanya; Traini, Daniela

2017-04-01

The aim of this study is to investigate aerosol plume geometries of pressurised metered dose inhalers (pMDIs) using a high-speed laser image system with different actuator nozzle materials and designs. Actuators made from aluminium, PET and PTFE were manufactured with four different nozzle designs: cone, flat, curved cone and curved flat. Plume angles and spans generated using the designed actuator nozzles with four solution-based pMDI formulations were imaged using Oxford Lasers EnVision system and analysed using EnVision Patternate software. Reduced plume angles for all actuator materials and nozzle designs were observed with pMDI formulations containing drug with high co-solvent concentration (ethanol) due to the reduced vapour pressure. Significantly higher plume angles were observed with the PTFE flat nozzle across all formulations, which could be a result of the nozzle geometry and material's hydrophobicity. The plume geometry of pMDI aerosols can be influenced by the vapour pressure of the formulation, nozzle geometries and actuator material physiochemical properties.

Thermally induced lamellar reorganization and thickening in spherical poly (L-lactic acid) crystalsome

NASA Astrophysics Data System (ADS)

Staub, Mark; Qi, Hao; Li, Christopher

Understanding fundamental aspects of spherical crystals is important for a variety of applications such as encapsulation and drug delivery. The curved nature of these crystals gives rise to differences in key crystallographic concepts such as grain boundaries and defect formation when compared to flat crystals. This curved crystallography is difficult to study experimentally, especially at the nanoscale. Our group has recently shown how an oil in water miniemulsion can be used to direct the crystallization of poly (L-lactic acid) (PLLA) at a curved liquid/liquid interface. This produces nanosized, polymer single-crystal-like capsules termed crystalsomes with increased stability and mechanical properties compared with non-crystalline counterparts. This system will serve as our model for examining spherical crystallography. In this work, combined wide angle X-ray diffraction, Atomic force microscopy, and differential scanning calorimetry is employed to examine how the curved interface effects crystal thickening and reorganization compared to flat PLLA crystals. The influence of degree of curvature on these processes is also studied by examining crystalsomes with differing diameters.

Can Tooth Preparation Design Affect the Fit of CAD/CAM Restorations?

PubMed

Roperto, Renato Cassio; Oliveira, Marina Piolli; Porto, Thiago Soares; Ferreira, Lais Alaberti; Melo, Lucas Simino; Akkus, Anna

2017-03-01

The purpose of this study was to evaluate if the marginal fit of computer-aided design and computer-aided manufacturing (CAD/CAM) restorations manufactured with CAD/CAM systems can be affected by different tooth preparation designs. Twenty-six typodont (plastic) teeth were divided into two groups (n = 13) according to the occlusal curvature of the tooth preparation. These were the group 1 (control group) (flat occlusal design) and group 2 (curved occlusal design). Scanning of the preparations was performed, and crowns were milled using ceramic blocks. Blocks were cemented using epoxy glue on the pulpal floor only, and finger pressure was applied for 1 minute. On completion of the cementation step, poor fits between the restoration and abutment were measured by microphotography and the silicone replica technique using light-body silicon material on mesial, distal, buccal, and lingual surfaces. Two-way ANOVA analysis did not reveal a statistical difference between flat (83.61 ± 50.72) and curved (79.04 ± 30.97) preparation designs. Buccal, mesial, lingual, and distal sites on the curved design preparation showed less of a gap when compared with flat design. No difference was found on flat preparations among mesial, buccal, and distal sites (P < .05). The lingual aspect had no difference from the distal side but showed a statistically significant difference from mesial and buccal (P < .05). Difference in occlusal design did not significantly impact the marginal fit. Marginal fit was significantly affected by the location of the margin; lingual and distal locations exhibited greater margin gap values compared with buccal and mesial sites regardless of the preparation design.

Reverse shoulder glenoid baseplate fixation: a comparison of flat-back versus curved-back designs and oval versus circular designs with 2 different offset glenospheres.

PubMed

Roche, Christopher P; Stroud, Nicholas J; Flurin, Pierre-Henri; Wright, Thomas W; Zuckerman, Joseph D; DiPaola, Matthew J

2014-09-01

In this glenoid loosening study, we compared the fixation strength of multiple generic reverse shoulder glenoid baseplates that differed only in backside geometry and shape and size to optimize design from a fixation perspective. The fixation strength of 4 generic baseplates was quantified in a low-density polyurethane substrate to isolate the contribution of baseplate profile and size (25 mm circular vs 25 × 34 mm oval) and backside geometry (flat back vs curved back) on fixation using 2 center-of-rotation glenospheres (0 mm and 10 mm lateral). The cyclic test simulated 55° of abduction as a 750 N load was continuously applied to induce a variable shear and compressive load. Before and after cyclic loading, baseplate displacement was measured in the directions of the applied static shear and compressive loads. Each generic baseplate was cyclically tested 7 times with each offset glenosphere for a total of 56 samples. Circular baseplates were associated with significantly more shear displacement in both the superior-inferior (SI) and anterior-posterior (AP) directions after cyclic loading than oval baseplates. No such significant differences in fixation were observed between flat-back and curved-back baseplates. Circular baseplates were also associated with significantly more SI and AP shear displacement with 10 mm glenospheres than with 0 mm glenospheres. No significant difference in SI or AP motion was observed with oval baseplates between 0 mm and 10 mm glenospheres. Our results suggest that baseplate shape and size affects fixation strength more than backside geometry. The 25 × 34 mm oval baseplates showed better fixation characteristics than their 25 mm circular counterparts; no discernible difference in fixation was observed between flat-back and curved-back baseplates. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

Build-up and surface dose measurements on phantoms using micro-MOSFET in 6 and 10 MV x-ray beams and comparisons with Monte Carlo calculations.

PubMed

Xiang, Hong F; Song, Jun S; Chin, David W H; Cormack, Robert A; Tishler, Roy B; Makrigiorgos, G Mike; Court, Laurence E; Chin, Lee M

2007-04-01

This work is intended to investigate the application and accuracy of micro-MOSFET for superficial dose measurement under clinically used MV x-ray beams. Dose response of micro-MOSFET in the build-up region and on surface under MV x-ray beams were measured and compared to Monte Carlo calculations. First, percentage-depth-doses were measured with micro-MOSFET under 6 and 10 MV beams of normal incidence onto a flat solid water phantom. Micro-MOSFET data were compared with the measurements from a parallel plate ionization chamber and Monte Carlo dose calculation in the build-up region. Then, percentage-depth-doses were measured for oblique beams at 0 degrees-80 degrees onto the flat solid water phantom with micro-MOSFET placed at depths of 2 cm, 1 cm, and 2 mm below the surface. Measurements were compared to Monte Carlo calculations under these settings. Finally, measurements were performed with micro-MOSFET embedded in the first 1 mm layer of bolus placed on a flat phantom and a curved phantom of semi-cylindrical shape. Results were compared to superficial dose calculated from Monte Carlo for a 2 mm thin layer that extends from the surface to a depth of 2 mm. Results were (1) Comparison of measurements with MC calculation in the build-up region showed that micro-MOSFET has a water-equivalence thickness (WET) of 0.87 mm for 6 MV beam and 0.99 mm for 10 MV beam from the flat side, and a WET of 0.72 mm for 6 MV beam and 0.76 mm for 10 MV beam from the epoxy side. (2) For normal beam incidences, percentage depth dose agree within 3%-5% among micro-MOSFET measurements, parallel-plate ionization chamber measurements, and MC calculations. (3) For oblique incidence on the flat phantom with micro-MOSFET placed at depths of 2 cm, 1 cm, and 2 mm, measurements were consistent with MC calculations within a typical uncertainty of 3%-5%. (4) For oblique incidence on the flat phantom and a curved-surface phantom, measurements with micro-MOSFET placed at 1.0 mm agrees with the MC calculation within 6%, including uncertainties of micro-MOSFET measurements of 2%-3% (1 standard deviation), MOSFET angular dependence of 3.0%-3.5%, and 1%-2% systematical error due to phantom setup geometry asymmetry. Micro-MOSFET can be used for skin dose measurements in 6 and 10 MV beams with an estimated accuracy of +/- 6%.

Effect of Curvature on the Impact Damage Characteristics and Residual Strength of Composite Plates

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Starnes, James H., Jr.

1998-01-01

The results of a study of the response and failure characteristics of thin, cylindrically curved, composite plates subjected to low-speed impact damage are presented. The results indicate that the plate radius and the plate thickness are important structural parameters that influence the nonlinear response of a plate for a given amount of impact energy. Analytical and experimental contact-force results are compared for several plates and the results correlate well. The impact-energy levels required to cause damage initiation and barely visible impact damage are a function of the plate radius for a given plate thickness. The impact-energy levels required to initiate impact damage for plates with a certain range of radii are greater than plates with other radii. The contact-force results corresponding to these impact-energy levels follow a similar trend. Residual strength results for plates with barely visible impact damage suggest that the compression-after-impact residual strength is also a function of plate radius. The residual strength of impact-damaged flat plates appears to be lower than the residual strength of the corresponding cylindrically curved plates.

UV scale calibration transfer from an improved pyroelectric detector standard to field UV-A meters and 365 nm excitation sources

NASA Astrophysics Data System (ADS)

Eppeldauer, G. P.; Podobedov, V. B.; Cooksey, C. C.

2017-05-01

Calibration of the emitted radiation from UV sources peaking at 365 nm, is necessary to perform the ASTM required 1 mW/cm2 minimum irradiance in certain military material (ships, airplanes etc) tests. These UV "black lights" are applied for crack-recognition using fluorescent liquid penetrant inspection. At present, these nondestructive tests are performed using Hg-lamps. Lack of a proper standard and the different spectral responsivities of the available UV meters cause significant measurement errors even if the same UV-365 source is measured. A pyroelectric radiometer standard with spectrally flat (constant) response in the UV-VIS range has been developed to solve the problem. The response curve of this standard determined from spectral reflectance measurement, is converted into spectral irradiance responsivity with <0.5% (k=2) uncertainty as a result of using an absolute tie point from a Si-trap detector traceable to the primary standard cryogenic radiometer. The flat pyroelectric radiometer standard can be used to perform uniform integrated irradiance measurements from all kinds of UV sources (with different peaks and distributions) without using any source standard. Using this broadband calibration method, yearly spectral calibrations for the reference UV (LED) sources and irradiance meters is not needed. Field UV sources and meters can be calibrated against the pyroelectric radiometer standard for broadband (integrated) irradiance and integrated responsivity. Using the broadband measurement procedure, the UV measurements give uniform results with significantly decreased uncertainties.

Alternatives to flat panel displays in vehicle turrets

NASA Astrophysics Data System (ADS)

Nicholson, Gail

2011-06-01

Space is a premium in vehicle turrets. Reducing the footprint of displays inside turrets frees up space for the warfighter. Traditional military ruggedized flat panel displays cannot reside flush with the curved turret wall and consumes more space than their advertized size. The lack of turret space also makes balancing human factors difficult. To better meet the Warfighter needs, alternatives and incremental upgrades to the flat panel displays in turrets were compiled. Each alternative technology was assessed against the constraints of a turret. Benefits, issues, and predictions to implementation are summarized. Viable alternatives are being developed into suitable options.

VLT/X-shooter GRBs: Individual extinction curves of star-forming regions★

NASA Astrophysics Data System (ADS)

Zafar, T.; Watson, D.; Møller, P.; Selsing, J.; Fynbo, J. PU; Schady, P.; Wiersema, K.; Levan, A. J.; Heintz, K. E.; Postigo, A. de Ugarte; D'Elia, V.; Jakobsson, P.; Bolmer, J.; Japelj, J.; Covino, S.; Gomboc, A.; Cano, Z.

2018-05-01

The extinction profiles in Gamma-Ray Burst (GRB) afterglow spectral energy distributions (SEDs) are usually described by the Small Magellanic Cloud (SMC)-type extinction curve. In different empirical extinction laws, the total-to-selective extinction, RV, is an important quantity because of its relation to dust grain sizes and compositions. We here analyse a sample of 17 GRBs (0.34

Stent conformity in curved vascular models with simulated aneurysm necks using flat-panel CT: an in vitro study.

PubMed

Ebrahimi, N; Claus, B; Lee, C-Y; Biondi, A; Benndorf, G

2007-05-01

Radiographic visibility of self-expandable intracranial stents is insufficient for assessment of conformability and deployment characteristics. The purpose of this study was to evaluate stent mechanics in a curved vessel model by using Flat-Panel CT (FPCT). The following stents were used: Neuroform 2, Neuroform Treo, Enterprise, and LEO. All stents were bent in the same polytetrafluoroethylene tubes with various angles ranging from 150 degrees to 30 degrees . To visualize potential prolapse of the stent struts, 4-, 5-, and 8-mm openings were created. FPCTs were obtained using a C-arm with flat detector. FPCT scans provided excellent visualization of deployment characteristics and stent mechanics and was superior to digital subtraction angiography (DSA) and digital radiography (DR). The Neuroform2/Treo showed, with increasing angle and diameter of the opening, a continuous increase in cell size. These stents also showed an outward prolapse at the convexity and an inwards prolapse of struts at the concavity of the curvature. The Enterprise showed an increasing trend to flatten and to kink with curvatures that are more acute. The LEO showed fewer trends to kink but an inward crimping of its ends with more acute angles. Deployment characteristics and conformability to a curved vessel model vary considerably, depending on the angle and the stent design. Adverse mechanics such as increased cell opening, strut prolapse, flattening, and kinking occur during stent placement in a curved vessel model, and may gain clinical importance. FPCT is superior to DSA and DR in visualizing small metallic stents and enables accurate detection of adverse stent mechanics.

Progress report. Task 1 - quaternary tectonics, 1 October 1991--30 September 1992

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

NONE

1992-09-30

Progress is reported on a study concerned with the quaternary tectonics of Yucca Mountain, the proposed site for an underground disposal facility for high-level radioactive wastes. Refinement and revision of crater Flat Quaternary stratigraphy continued and consisted of several activities: revision of rock varnish cation leaching curve; sample comparison of RV manganese;,iron microlaminations;and correlation of Crater Flat allostratigraphic units with regional chronologies.

The role of nicotinic receptor beta-2 subunits in nicotine discrimination and conditioned taste aversion.

PubMed

Shoaib, M; Gommans, J; Morley, A; Stolerman, I P; Grailhe, R; Changeux, J-P

2002-03-01

The subtypes of nicotinic receptors at which the behavioural effects of nicotine originate are not fully understood. These experiments use mice lacking the beta2 subunit of nicotinic receptors to investigate its role in nicotine discrimination and conditioned taste aversion (CTA). Wild-type and mutant mice were trained either in a two-lever nicotine discrimination procedure using a tandem schedule of food reinforcement, or in a counterbalanced two-flavour CTA procedure. Rates of lever-pressing of wild-type and mutant mice did not differ. Wild-type mice acquired discrimination of nicotine (0.4 or 0.8 mg/kg) rapidly and exhibited steep dose-response curves. Mutant mice failed to acquire these nicotine discriminations and exhibited flat dose-response curves. Both wild-type and mutant mice acquired discrimination of nicotine (1.6 mg/kg) although discrimination performance was weak in the mutants. Nicotine initially reduced response rates in wild-type and mutant mice, and tolerance developed to this effect in each genotype. Both genotypes acquired discrimination of morphine (3 mg/kg) with similar degrees of accuracy, and dose-response curves for morphine discrimination in the two genotypes were indistinguishable. Nicotine produced dose-related CTA in both genotypes, but the magnitude of the effect was less in the mutants than in the wild-type controls. It is concluded that nicotinic receptors containing the beta2 subunit play a major role in the discriminative stimulus and taste aversion effects of nicotine that may reflect psychological aspects of tobacco dependence. Such receptors appear to have a less crucial role in the response-rate, reducing effects of nicotine and in nicotine tolerance.

Late Neogene slip transfer and extension within the curved Whisky Flat fault system central Walker Lane, west-central Nevada

NASA Astrophysics Data System (ADS)

Biholar, Alexander Kenneth Casian

In Whisky Flat of west-central Nevada, northwest-striking faults in the Walker Lane curve to east-northeast orientations at the northern limits of the Mina deflection. This curve in strike results in the formation of ˜685 m deep depression bounded by north-south convex to the east range-front faults that at the apex of fault curvature are bisected at a high angle by a structural stepover. We use the vertical offset of a late Miocene erosional surface mapped in the highlands and inferred from gravity depth inversion in the basin to measure the magnitude of displacement on faults. A N65°W extensional axis determined through fault-slip inversion is used to constrain the direction in displacement models. Through the use of a forward rectilinear displacement model, we document that the complex array of faults is capable of developing with broadly contemporaneous displacements on all structures since the opening of the basin during the Pliocene.

Template-assisted electrodeposition of Ni and Ni/Au nanowires on planar and curved substrates

NASA Astrophysics Data System (ADS)

Guiliani, Jason; Cadena, John; Monton, Carlos

2018-02-01

We present a variant of the template-assisted electrodeposition method that enables the synthesis of large arrays of nanowires (NWs) on flat and curved substrates. This method uses ultra-thin (50 nm-10 μm) anodic aluminum oxide membranes as a template. We have developed a procedure that uses a two-polymer protective layer to transfer these templates onto almost any surface. We have applied this technique to the fabrication of large arrays of Ni and segmented composition Ni/Au NWs on silicon wafers, Cu tapes, and thin (0.2 mm) Cu wires. In all cases, a complete coverage with NWs is achieved. The magnetic properties of these samples show an accentuated in-plane anisotropy which is affected by the form of the substrate (flat or curve) and the length of the NWs. Unlike current lithography techniques, the fabrication method proposed here allows the integration of complex nanostructures into devices, which can be fabricated on unconventional surfaces.

Universal phase diagrams with superconducting domes for electronic flat bands

NASA Astrophysics Data System (ADS)

Löthman, Tomas; Black-Schaffer, Annica M.

2017-08-01

Condensed matter systems with flat bands close to the Fermi level generally exhibit, due to their very large density of states, extraordinarily high critical ordering temperatures of symmetry-breaking orders, such as superconductivity and magnetism. Here we show that the critical temperatures follow one of two universal curves with doping away from a flat band depending on the ordering channel, which completely dictates both the general order competition and the phase diagram. Notably, we find that orders in the particle-particle channel (superconducting orders) survive decisively farther than orders in the particle-hole channel (magnetic or charge orders) because the channels have fundamentally different polarizabilities. Thus, even if a magnetic or charge order initially dominates, superconducting domes are still likely to exist on the flanks of flat bands. We apply these general results to both the topological surface flat bands of rhombohedral ABC-stacked graphite and to the Van Hove singularity of graphene.

Analysis of diffusion in curved surfaces and its application to tubular membranes

PubMed Central

Klaus, Colin James Stockdale; Raghunathan, Krishnan; DiBenedetto, Emmanuele; Kenworthy, Anne K.

2016-01-01

Diffusion of particles in curved surfaces is inherently complex compared with diffusion in a flat membrane, owing to the nonplanarity of the surface. The consequence of such nonplanar geometry on diffusion is poorly understood but is highly relevant in the case of cell membranes, which often adopt complex geometries. To address this question, we developed a new finite element approach to model diffusion on curved membrane surfaces based on solutions to Fick’s law of diffusion and used this to study the effects of geometry on the entry of surface-bound particles into tubules by diffusion. We show that variations in tubule radius and length can distinctly alter diffusion gradients in tubules over biologically relevant timescales. In addition, we show that tubular structures tend to retain concentration gradients for a longer time compared with a comparable flat surface. These findings indicate that sorting of particles along the surfaces of tubules can arise simply as a geometric consequence of the curvature without any specific contribution from the membrane environment. Our studies provide a framework for modeling diffusion in curved surfaces and suggest that biological regulation can emerge purely from membrane geometry. PMID:27733625

Postbuckling behavior of graphite-epoxy panels

NASA Technical Reports Server (NTRS)

Starnes, J. H., Jr.; Dickson, J. N.; Rouse, M.

1984-01-01

Structurally efficient fuselage panels are often designed to allow buckling to occur at applied loads below ultimate. Interest in applying graphite-epoxy materials to fuselage primary structure led to several studies of the post-buckling behavior of graphite-epoxy structural components. Studies of the postbuckling behavior of flat and curved, unstiffened and stiffened graphite-epoxy panels loaded in compression and shear were summarized. The response and failure characteristics of specimens studied experimentally were described, and analytical and experimental results were compared. The specimens tested in the studies described were fabricated from commercially available 0.005-inch-thick unidirectional graphite-fiber tapes preimpregnated with 350 F cure thermosetting epoxy resins.

BUCLAP2

NASA Technical Reports Server (NTRS)

Halstead, D. W.; Tripp, L. L.; Tamekuni, M.; Baker, L. L.; Viswanathan, A. V.

1976-01-01

Program is used to predict buckling of rectangular flat and curved laminated plates subjected to in-plane normal and shearing loads, with each lamina composed of orthotropic material with arbitrary orientation of orthotropic axes.

Latest Progress in High Power VECSELs

DTIC Science & Technology

2013-01-01

are more efficient, and can be tailored to an application. In this manuscript we lay out some advantages to VECSELs as compared to many in-plane...semiconductor lasers. We review common fabrication and packaging techniques in Section 2. In Section 3, we discuss both small- signal and large-signal... out LR coating MQW DBR VECSEL chip Heat Spreader output coupler HR flat mirror BF at Brewster’s angle HR flat mirror HR curved mirror signal beam out

On superintegrable monopole systems

NASA Astrophysics Data System (ADS)

Fazlul Hoque, Md; Marquette, Ian; Zhang, Yao-Zhong

2018-02-01

Superintegrable systems with monopole interactions in flat and curved spaces have attracted much attention. For example, models in spaces with a Taub-NUT metric are well-known to admit the Kepler-type symmetries and provide non-trivial generalizations of the usual Kepler problems. In this paper, we overview new families of superintegrable Kepler, MIC-harmonic oscillator and deformed Kepler systems interacting with Yang-Coulomb monopoles in the flat and curved Taub-NUT spaces. We present their higher-order, algebraically independent integrals of motion via the direct and constructive approaches which prove the superintegrability of the models. The integrals form symmetry polynomial algebras of the systems with structure constants involving Casimir operators of certain Lie algebras. Such algebraic approaches provide a deeper understanding to the degeneracies of the energy spectra and connection between wave functions and differential equations and geometry.

Light curves of flat-spectrum radio sources (Jenness+, 2010)

NASA Astrophysics Data System (ADS)

Jenness, T.; Robson, E. I.; Stevens, J. A.

2010-05-01

Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850um covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (SCUBA) camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control - Data Reduction (ORAC-DR) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources. (2 data files).

Fretting Fatigue with Cylindrical-On-Flat Contact: Crack Nucleation, Crack Path and Fatigue Life

PubMed Central

Noraphaiphipaksa, Nitikorn; Manonukul, Anchalee; Kanchanomai, Chaosuan

2017-01-01

Fretting fatigue experiments and finite element analysis were carried out to investigate the influence of cylindrical-on-flat contact on crack nucleation, crack path and fatigue life of medium-carbon steel. The location of crack nucleation was predicted using the maximum shear stress range criterion and the maximum relative slip amplitude criterion. The prediction using the maximum relative slip amplitude criterion gave the better agreement with the experimental result, and should be used for the prediction of the location of crack nucleation. Crack openings under compressive bulk stresses were found in the fretting fatigues with flat-on-flat contact and cylindrical-on-flat contacts, i.e., fretting-contact-induced crack openings. The crack opening stress of specimen with flat-on-flat contact was lower than those of specimens with cylindrical-on-flat contacts, while that of specimen with 60-mm radius contact pad was lower than that of specimen with 15-mm radius contact pad. The fretting fatigue lives were estimated by integrating the fatigue crack growth curve from an initial propagating crack length to a critical crack length. The predictions of fretting fatigue life with consideration of crack opening were in good agreement with the experimental results. PMID:28772522

Mega-earthquakes rupture flat megathrusts.

PubMed

Bletery, Quentin; Thomas, Amanda M; Rempel, Alan W; Karlstrom, Leif; Sladen, Anthony; De Barros, Louis

2016-11-25

The 2004 Sumatra-Andaman and 2011 Tohoku-Oki earthquakes highlighted gaps in our understanding of mega-earthquake rupture processes and the factors controlling their global distribution: A fast convergence rate and young buoyant lithosphere are not required to produce mega-earthquakes. We calculated the curvature along the major subduction zones of the world, showing that mega-earthquakes preferentially rupture flat (low-curvature) interfaces. A simplified analytic model demonstrates that heterogeneity in shear strength increases with curvature. Shear strength on flat megathrusts is more homogeneous, and hence more likely to be exceeded simultaneously over large areas, than on highly curved faults. Copyright © 2016, American Association for the Advancement of Science.

Axisymmetric indentation of curved elastic membranes by a convex rigid indenter

PubMed Central

Pearce, S.P.; King, J.R.; Holdsworth, M.J.

2011-01-01

Motivated by applications to seed germination, we consider the transverse deflection that results from the axisymmetric indentation of an elastic membrane by a rigid body. The elastic membrane is fixed around its boundary, with or without an initial pre-stretch, and may be initially curved prior to indentation. General indenter shapes are considered, and the load–indentation curves that result for a range of spheroidal tips are obtained for both flat and curved membranes. Wrinkling may occur when the membrane is initially curved, and a relaxed strain-energy function is used to calculate the deformed profile in this case. Applications to experiments designed to measure the mechanical properties of seed endosperms are discussed. PMID:22298913

A complete characterization of relativistic uniform acceleration

NASA Astrophysics Data System (ADS)

Scarr, Tzvi; Friedman, Yaakov

2017-05-01

We use the Frenet frame to define and completely characterize “uniform acceleration” in flat spacetime. We extend the definition to arbitrary curved spacetime and provide an example in Schwarzschild spacetime.

The Buckling of Curved Tension-field Girders

NASA Technical Reports Server (NTRS)

Limpert, G

1938-01-01

The present paper reports on experiments made to determine the buckling load under shear of circular curved tension-field webs. The buckling load of the webs may be expressed with reference to the buckling load of the stiffeners. It is found that within the explored range the buckling load is approximately twice as great as that of the identically stiffened flat wall of equal web depth.

Forced convective heat transfer in curved diffusers

NASA Technical Reports Server (NTRS)

Rojas, J.; Whitelaw, J. H.; Yianneskis, M.

1987-01-01

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.

Illusions and Cloaks for Surface Waves

PubMed Central

McManus, T. M.; Valiente-Kroon, J. A.; Horsley, S. A. R.; Hao, Y.

2014-01-01

Ever since the inception of Transformation Optics (TO), new and exciting ideas have been proposed in the field of electromagnetics and the theory has been modified to work in such fields as acoustics and thermodynamics. The most well-known application of this theory is to cloaking, but another equally intriguing application of TO is the idea of an illusion device. Here, we propose a general method to transform electromagnetic waves between two arbitrary surfaces. This allows a flat surface to reproduce the scattering behaviour of a curved surface and vice versa, thereby giving rise to perfect optical illusion and cloaking devices, respectively. The performance of the proposed devices is simulated using thin effective media with engineered material properties. The scattering of the curved surface is shown to be reproduced by its flat analogue (for illusions) and vice versa for cloaks. PMID:25145953

Recovering a MOND-like acceleration law in mimetic gravity

NASA Astrophysics Data System (ADS)

Vagnozzi, Sunny

2017-09-01

We reconsider the recently proposed mimetic gravity, focusing in particular on whether the theory is able to reproduce the inferred flat rotation curves of galaxies. We extend the theory by adding a non-minimal coupling between matter and mimetic field. Such coupling leads to the appearance of an extra force which renders the motion of test particles non-geodesic. By studying the weak field limit of the resulting equations of motion, we demonstrate that in the Newtonian limit the acceleration law induced by the non-minimal coupling reduces to a modified Newtonian dynamics (MOND)-like one. In this way, it is possible to reproduce the successes of MOND, namely the explanation for the flat galactic rotation curves and the Tully-Fisher relation, within the framework of mimetic gravity, without the need for particle dark matter. The scale-dependence of the recovered acceleration scale opens up the possibility of addressing the missing mass problem not only on galactic but also on cluster scales: we defer a full study of this issue, together with a complete analysis of fits to spiral galaxy rotation curves, to an upcoming companion paper.

An experimental investigation of heat transfer to reusable surface insulation tile array gaps in a turbulent boundary layer with pressure gradient. M.S. Thesis

NASA Technical Reports Server (NTRS)

Throckmorton, D. A.

1975-01-01

An experimental investigation was performed to determine the effect of pressure gradient on the heat transfer to space shuttle reusable surface insulation (RSI) tile array gaps under thick, turbulent boundary layer conditions. Heat transfer and pressure measurements were obtained on a curved array of full-scale simulated RSI tiles in a tunnel wall boundary layer at a nominal freestream Mach number of 10.3 and freestream unit Reynolds numbers of 1.6, 3.3, and and 6.1 million per meter. Transverse pressure gradients were induced over the model surface by rotating the curved array with respect to the flow. Definition of the tunnel wall boundary layer flow was obtained by measurement of boundary layer pitot pressure profiles, and flat plate wall pressure and heat transfer. Flat plate wall heat transfer data were correlated and a method was derived for prediction of smooth, curved array heat transfer in the highly three-dimensional tunnel wall boundary layer flow and simulation of full-scale space shuttle vehicle pressure gradient levels was assessed.

Experimental study to the influences of rotational speed and blade shape on water vortex turbine performance

NASA Astrophysics Data System (ADS)

Kueh, T. C.; Beh, S. L.; Ooi, Y. S.; Rilling, D. G.

2017-04-01

Water vortex turbine utilizes the natural behaviour of water to form free surface vortex for energy extraction. This allows simple construction and ease of management on the whole water vortex power plant system. To our findings, the literature study specifically on water vortex turbine is inadequate and low efficiency was reported. Influences of operating speed and blade shape on turbine performance are the two parameters investigated in this study. Euler Turbomachinery Equation and velocity triangle are used in the improvement analysis. Two turbines with flat blades and curved blades are tested and compared. Both turbines show similar rotational speed at no load condition. This suggested that the circulation force of the water vortex has more dominant effect on the turbine rotational speed, compared to the turbine’s geometry. Flat-blades turbine showed maximum efficiency of 21.63% at 3.27 rad/s whereas curved-blades turbine showed 22.24% at 3.56 rad/s. When operating load is applied, the backward-leaning curve helps the turbine blades to reduce the disturbance on the water vortex, and hence provide a better performance.

The perception of 3-D shape from shadows cast onto curved surfaces.

PubMed

Norman, J Farley; Lee, Young-lim; Phillips, Flip; Norman, Hideko F; Jennings, L RaShae; McBride, T Ryan

2009-05-01

In a natural environment, cast shadows abound. Objects cast shadows both upon themselves and upon background surfaces. Previous research on the perception of 3-D shape from cast shadows has only examined the informativeness of shadows cast upon flat background surfaces. In outdoor environments, however, background surfaces often possess significant curvature (large rocks, trees, hills, etc.), and this background curvature distorts the shape of cast shadows. The purpose of this study was to determine the extent to which observers can "discount" the distorting effects of curved background surfaces. In our experiments, observers viewed deforming or static shadows of naturally shaped objects, which were cast upon flat and curved background surfaces. The results showed that the discrimination of 3-D object shape from cast shadows was generally invariant over the distortions produced by hemispherical background surfaces. The observers often had difficulty, however, in identifying the shadows cast onto saddle-shaped background surfaces. The variations in curvature which occur in different directions on saddle-shaped background surfaces cause shadow distortions that lead to difficulties in object recognition and discrimination.

Curved Piezoelectric Actuators for Stretching Optical Fibers

NASA Technical Reports Server (NTRS)

Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

2008-01-01

Assemblies containing curved piezoceramic fiber composite actuators have been invented as means of stretching optical fibers by amounts that depend on applied drive voltages. Piezoceramic fiber composite actuators are conventionally manufactured as sheets or ribbons that are flat and flexible, but can be made curved to obtain load-carrying ability and displacement greater than those obtainable from the flat versions. In the primary embodiment of this invention, piezoceramic fibers are oriented parallel to the direction of longitudinal displacement of the actuators so that application of drive voltage causes the actuator to flatten, producing maximum motion. Actuator motion can be transmitted to the optical fiber by use of hinges and clamp blocks. In the original application of this invention, the optical fiber contains a Bragg grating and the purpose of the controlled stretching of the fiber is to tune the grating as part of a small, lightweight, mode-hop-free, rapidly tunable laser for demodulating strain in Bragg-grating strain-measurement optical fibers attached to structures. The invention could also be used to apply controllable tensile force or displacement to an object other than an optical fiber.

Surface charge method for molecular surfaces with curved areal elements I. Spherical triangles

NASA Astrophysics Data System (ADS)

Yu, Yi-Kuo

2018-03-01

Parametrizing a curved surface with flat triangles in electrostatics problems creates a diverging electric field. One way to avoid this is to have curved areal elements. However, charge density integration over curved patches appears difficult. This paper, dealing with spherical triangles, is the first in a series aiming to solve this problem. Here, we lay the ground work for employing curved patches for applying the surface charge method to electrostatics. We show analytically how one may control the accuracy by expanding in powers of the the arc length (multiplied by the curvature). To accommodate not extremely small curved areal elements, we have provided enough details to include higher order corrections that are needed for better accuracy when slightly larger surface elements are used.

Sacramento Metropolitan Area, California

DTIC Science & Technology

1992-02-01

restriction would apply to virtually all of West Sacramento. Future conditions in the bypass areas are expected to remain essentially the same. During...frequency, the stage-frequency curve in the study area essentially becomes flat because of the large storage volume behind upstream levee breaches. This curve...and 400-year flood plains are also essentially the same (15 to 16 feet) because of the following: 1) the flood volume for each event is sufficient to

Flight-path estimation in passive low-altitude flight by visual cues

NASA Technical Reports Server (NTRS)

Grunwald, Arthur J.; Kohn, S.

1993-01-01

A series of experiments was conducted, in which subjects had to estimate the flight path while passively being flown in straight or in curved motion over several types of nominally flat, textured terrain. Three computer-generated terrain types were investigated: (1) a random 'pole' field, (2) a flat field consisting of random rectangular patches, and (3) a field of random parallelepipeds. Experimental parameters were the velocity-to-height (V/h) ratio, the viewing distance, and the terrain type. Furthermore, the effect of obscuring parts of the visual field was investigated. Assumptions were made about the basic visual-field information by analyzing the pattern of line-of-sight (LOS) rate vectors in the visual field. The experimental results support these assumptions and show that, for both a straight as well as a curved flight path, the estimation accuracy and estimation times improve with the V/h ratio. Error scores for the curved flight path are found to be about 3 deg in visual angle higher than for the straight flight path, and the sensitivity to the V/h ratio is found to be considerably larger. For the straight motion, the flight path could be estimated successfully from local areas in the far field. Curved flight-path estimates have to rely on the entire LOS rate pattern.

The effect of actuator nozzle designs on the electrostatic charge generated in pressurised metered dose inhaler aerosols.

PubMed

Chen, Yang; Young, Paul M; Fletcher, David F; Chan, Hak Kim; Long, Edward; Lewis, David; Church, Tanya; Traini, Daniela

2015-04-01

To investigate the influence of different actuator nozzle designs on aerosol electrostatic charges and aerosol performances for pressurised metered dose inhalers (pMDIs). Four actuator nozzle designs (flat, curved flat, cone and curved cone) were manufactured using insulating thermoplastics (PET and PTFE) and conducting metal (aluminium) materials. Aerosol electrostatic profiles of solution pMDI formulations containing propellant HFA 134a with different ethanol concentration and/or model drug beclomethasone dipropionate (BDP) were studied using a modified electrical low-pressure impactor (ELPI) for all actuator designs and materials. The mass of the deposited drug was analysed using high performance liquid chromatography (HPLC). Both curved nozzle designs for insulating PET and PTFE actuators significantly influenced aerosol electrostatics and aerosol performance compared with conducting aluminium actuator, where reversed charge polarity and higher throat deposition were observed with pMDI formulation containing BDP. Results are likely due to the changes in plume geometry caused by the curved edge nozzle designs and the bipolar charging nature of insulating materials. This study demonstrated that actuator nozzle designs could significantly influence the electrostatic charges profiles and aerosol drug deposition pattern of pMDI aerosols, especially when using insulating thermoplastic materials where bipolar charging is more dominant.

Fluid-structure interaction and aerodynamics damping; Proceedings of the Tenth Biennial Conference on Mechanical Vibration and Noise, Cincinnati, OH, September 10-13, 1985

NASA Astrophysics Data System (ADS)

Dowell, E. H.; Au-Yang, M. K.

1985-09-01

The response of a two-layer elastic coating to pressure disturbances from a turbulent boundary layer is considered along with the application of the finite element method in the calculation of transmission loss of flat and curved panels, the application of various solution techniques to the calculation of transonic flutter boundaries, and noise transmission of double wall composite shells. Other topics explored are related to chaotic behavior of a simple single-degree-of-freedom system, the entrainment of self-sustained flow oscillations, the effects of strong shock loading on coupled bending-torssion flutter of tuned and mistuned cascades, and turbulent buffeting of a multispan tube bundle. Attention is given to the dynamics of heat exchangers U-bend tubes with flat bar supports, a review of flow induced vibration of two circular cylinders in crossflow, the avoidance of leakage flow-induced vibration by a tube-in-tube slip joint, random load from multiple sources and its assessment, and wake-induced vibration of a conductor in the wake of another via a 3-D finite element method.

A study of the structural-acoustic response and interior noise levels of fuselage structures

NASA Technical Reports Server (NTRS)

Koval, L. R.

1978-01-01

Models of both flat and curved fuselage panels were tested for their sound transmission characteristics. The effect of external air flow on transmission loss was simulated in a subsonic wind-tunnel. By numerically evaluating the known equations for field-incidence transmission loss of single-walled panels in a computer program, a comparison of the theory with the test results was made. As a further extension to aircraft fuselage simulation, equations for the field-incidence transmission loss of a double-walled panel were derived. Flow is shown to provide a small increase in transmission loss for a flat panel. Curvature is shown to increase transmission loss for low frequencies, while also providing a sharp decrease in transmission loss at the ring frequency of the cylindrical panel. The field-incidence transmission loss of a double-walled panel was found to be approximately twice that for a single-walled panel, with the addition of dips in the transmission loss at the air gap resonances and at the critical frequency of the internal panel.

Flat Lens Focusing Demonstrated With Left-Handed Metamaterial

NASA Technical Reports Server (NTRS)

Wilson, Jeffrey D.; Schwartz, Zachary D.; Chevalier, Christine T.; Downey, Alan N.; Vaden, Karl R.

2004-01-01

Left-handed metamaterials (LHM's) are a new media engineered to possess an effective negative index of refraction over a selected frequency range. This characteristic enables LHM's to exhibit physical properties never before observed. In particular, a negative index of refraction should cause electromagnetic radiation to refract or bend at a negative angle when entering an LHM, as shown in the figure above on the left. The figure on the right shows that this property could be used to bring radiation to a focus with a flat LHM lens. The advantage of a flat lens in comparison to a conventional curved lens is that the focal length could be varied simply by adjusting the distance between the lens and the electromagnetic wave source. In this in-house work, researchers at the NASA Glenn Research Center developed a computational model for LHM's with the three-dimensional electromagnetic commercial code Microwave Studio, constructed an LHM flat lens, and used it to experimentally demonstrate the reversed refraction and flat lens focusing of microwave radiation.

Acoustic Levitation System

NASA Technical Reports Server (NTRS)

Gammell, P. M.; Wang, T. G.; Croonquist, A.; Lee, M. C.

1985-01-01

Dense materials, such as steel balls, continuously levitated with energy provided by efficient high-powered siren in combination with shaped reflector. Reflector system, consisting of curved top reflector and flat lower reflector, eliminates instability in spatial positioning of sample.

High frequency modulation and injection locking of terahertz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Gu, L.; Wan, W. J.; Zhu, Y. H.; Fu, Z. L.; Li, H.; Cao, J. C.

2017-06-01

Due to intersubband transitions, the quantum cascade laser (QCL) is free of relaxations and able to work under fast modulations. In this work, the authors investigate the fast modulation properties of a continuous wave (cw) terahertz QCL emitting around 3 THz (˜100 μm). Both simulation and experimental results show that the 3 dB modulation bandwidth for the device can reach 11.5 GHz and the modulation response curve is relatively flat upto ˜16 GHz. The radio frequency (RF) injection measurements verify that around the laser threshold the inter-mode beat note interacts strongly with the RF signal and the laser can be modulated at the round trip frequency of 15.5 GHz.

Molecular Beam Epitaxy Growth of High Crystalline Quality LiNbO3

NASA Astrophysics Data System (ADS)

Tellekamp, M. Brooks; Shank, Joshua C.; Goorsky, Mark S.; Doolittle, W. Alan

2016-12-01

Lithium niobate is a multi-functional material with wide reaching applications in acoustics, optics, and electronics. Commercial applications for lithium niobate require high crystalline quality currently limited to bulk and ion sliced material. Thin film lithium niobate is an attractive option for a variety of integrated devices, but the research effort has been stagnant due to poor material quality. Both lattice matched and mismatched lithium niobate are grown by molecular beam epitaxy and studied to understand the role of substrate and temperature on nucleation conditions and material quality. Growth on sapphire produces partially coalesced columnar grains with atomically flat plateaus and no twin planes. A symmetric rocking curve shows a narrow linewidth with a full width at half-maximum (FWHM) of 8.6 arcsec (0.0024°), which is comparable to the 5.8 arcsec rocking curve FWHM of the substrate, while the film asymmetric rocking curve is 510 arcsec FWHM. These values indicate that the individual grains are relatively free of long-range disorder detectable by x-ray diffraction with minimal measurable tilt and twist and represents the highest structural quality epitaxial material grown on lattice mismatched sapphire without twin planes. Lithium niobate is also grown on lithium tantalate producing high quality coalesced material without twin planes and with a symmetric rocking curve of 193 arcsec, which is nearly equal to the substrate rocking curve of 194 arcsec. The surface morphology of lithium niobate on lithium tantalate is shown to be atomically flat by atomic force microscopy.

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

NASA Technical Reports Server (NTRS)

Kerr, R. A.

1983-01-01

In a three dimensional simulation higher order derivative correlations, including skewness and flatness factors, are calculated for velocity and passive scalar fields and are compared with structures in the flow. The equations are forced to maintain steady state turbulence and collect statistics. It is found that the scalar derivative flatness increases much faster with Reynolds number than the velocity derivative flatness, and the velocity and mixed derivative skewness do not increase with Reynolds number. Separate exponents are found for the various fourth order velocity derivative correlations, with the vorticity flatness exponent the largest. Three dimensional graphics show strong alignment between the vorticity, rate of strain, and scalar-gradient fields. The vorticity is concentrated in tubes with the scalar gradient and the largest principal rate of strain aligned perpendicular to the tubes. Velocity spectra, in Kolmogorov variables, collapse to a single curve and a short minus 5/3 spectral regime is observed.

Edgeless composite laminate specimen for static and fatigue testing

NASA Technical Reports Server (NTRS)

Liber, T.; Daniel, I. M.

1978-01-01

The influence of edge effects on the tensile properties of angle-ply laminate composites can be eliminated by using edgeless (round tubular) specimens. However, uniaxial tests with such specimens, static and fatigue, have been generally unsuccessful because of the differential Poisson effect between the test section and the grips. An edgeless cylindrical specimen, developed to circumvent these difficulties, is examined in the present paper. It is a flattened tube consisting of two flat sides connected by curved sections. It can be handled much like the standard flat coupon. The flat ends of the specimen are provided with crossplied fiberglass gripping tabs, the same as used for flat test coupons. As part of the tabbing, the hollow ends must be plugged with inserts to prevent crushing of the ends. A special insert design was developed to minimize detrimental Poisson effects ordinarily introduced by inserts.

Turbulent boundary layer on a convex, curved surface

NASA Technical Reports Server (NTRS)

Gillis, J. C.; Johnston, J. P.; Kays, W. M.; Moffat, R. J.

1980-01-01

The effects of strong convex curvature on boundary layer turbulence were investigated. The data gathered on the behavior of Reynolds stress suggested the formulation of a simple turbulence model. Three sets of data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning, and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero - thus avoiding any effects of streamwise acceleration on the wall layers. Results show that after a sudden introduction of curvature, the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. In contrast, when the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions.

Tensor Minkowski Functionals for random fields on the sphere

NASA Astrophysics Data System (ADS)

Chingangbam, Pravabati; Yogendran, K. P.; Joby, P. K.; Ganesan, Vidhya; Appleby, Stephen; Park, Changbom

2017-12-01

We generalize the translation invariant tensor-valued Minkowski Functionals which are defined on two-dimensional flat space to the unit sphere. We apply them to level sets of random fields. The contours enclosing boundaries of level sets of random fields give a spatial distribution of random smooth closed curves. We outline a method to compute the tensor-valued Minkowski Functionals numerically for any random field on the sphere. Then we obtain analytic expressions for the ensemble expectation values of the matrix elements for isotropic Gaussian and Rayleigh fields. The results hold on flat as well as any curved space with affine connection. We elucidate the way in which the matrix elements encode information about the Gaussian nature and statistical isotropy (or departure from isotropy) of the field. Finally, we apply the method to maps of the Galactic foreground emissions from the 2015 PLANCK data and demonstrate their high level of statistical anisotropy and departure from Gaussianity.

A randomized controlled trial of chair interventions on back and hip pain among sewing machine operators: the los angeles garment study.

PubMed

Wang, Pin-Chieh; Ritz, Beate R; Janowitz, Ira; Harrison, Robert J; Yu, Fei; Chan, Jacqueline; Rempel, David M

2008-03-01

Determine whether an adjustable chair with a curved or a flat seat pan improved monthly back and hip pain scores in sewing machine operators. This 4-month intervention study randomized 293 sewing machine operators with back and hip pain. The participants in the control group received a placebo intervention, and participants in the intervention groups received the placebo intervention and one of the two intervention chairs. Compared with the control group, mean pain improvement for the flat chair intervention was 0.43 points (95% CI = 0.34, 0.51) per month, and mean pain improvement for the curved chair intervention was 0.25 points (95% CI = 0.16, 0.34) per month. A height-adjustable task chair with a swivel function can reduce back and hip pain in sewing machine operators. The findings may be relevant to workers who perform visual- and hand-intensive manufacturing jobs.

Spatial reflection patterns of iridescent wings of male pierid butterflies: curved scales reflect at a wider angle than flat scales.

PubMed

Pirih, Primož; Wilts, Bodo D; Stavenga, Doekele G

2011-10-01

The males of many pierid butterflies have iridescent wings, which presumably function in intraspecific communication. The iridescence is due to nanostructured ridges of the cover scales. We have studied the iridescence in the males of a few members of Coliadinae, Gonepteryx aspasia, G. cleopatra, G. rhamni, and Colias croceus, and in two members of the Colotis group, Hebomoia glaucippe and Colotis regina. Imaging scatterometry demonstrated that the pigmentary colouration is diffuse whereas the structural colouration creates a directional, line-shaped far-field radiation pattern. Angle-dependent reflectance measurements demonstrated that the directional iridescence distinctly varies among closely related species. The species-dependent scale curvature determines the spatial properties of the wing iridescence. Narrow beam illumination of flat scales results in a narrow far-field iridescence pattern, but curved scales produce broadened patterns. The restricted spatial visibility of iridescence presumably plays a role in intraspecific signalling.

Topographically driven crustal flow and its implication to the development of pinned oroclines

NASA Technical Reports Server (NTRS)

Hsui, Albert T.; Wilkerson, M. Scott; Marshak, Stephen

1990-01-01

Pinned oroclines, a type of curved orogen which results from lateral pinning of a growing fold-thrust belt, tend to resemble parabolic Newtonian curvature modified by different degrees of flattening at the flow front. It is proposed that such curves can be generated by Newtonian crustal flow driven by topographic variations. In this model, regional topographic differences create a regional flow which produces a parabolic flow front on interaction with lateral bounding obstacles. Local topographic variations modify the parabolic curves and yield more flat-crested, non-Newtonian-type curvatures. A finite-difference thin-skin tectonic simulation demonstrates that both Newtonian and non-Newtonian curved orogens can be produced within a Newtonian crust.

Effect of gold photocathode contamination on a flat spectral response X-ray diode

NASA Astrophysics Data System (ADS)

Wang, Kun-lun; Zhang, Si-qun; Zhou, Shao-tong; Huang, Xian-bin; Ren, Xiao-dong; Dan, Jia-kun; Xu, Qiang

2018-03-01

A detector with an approximately flat spectral response is important for diagnosing intense thermal X-ray flux. A flat-spectral-response X-ray diode (FSR-XRD) utilizes a gold photocathode X-ray diode and a specially configured gold filter to give rise to a nearly flat spectral response in the photon energy range of 100-4000 eV. It has been observed that the spectral responses of several FSR-XRDs changed after a few shots of z-pinch experiments on the Primary Test Stand facility. This paper presents an analysis of the changes by fitting the spectral responses of the gold photocathodes using a model with a free parameter which characterizes the thickness of the contamination. The spectral responses of FSR-XRDs were calibrated with synchrotron radiation, and several cleaning methods were tested with the calibration. Considering the results of model and cleaning, it may be anticipated that contamination was the major reason of the response changing. Contamination worsened the flatness of the spectral response of the FSR-XRD and decreased the averaged response, hence it is important to avoid contamination. Current results indicate a requirement of further study of the contamination.

The GTC exoplanet transit spectroscopy survey. IV. Confirmation of the flat transmission spectrum of HAT-P-32b

NASA Astrophysics Data System (ADS)

Nortmann, L.; Pallé, E.; Murgas, F.; Dreizler, S.; Iro, N.; Cabrera-Lavers, A.

2016-10-01

We observed the hot Jupiter HAT-P-32b (also known as HAT-P-32Ab) to determine its optical transmission spectrum by measuring the wavelength-dependent, planet-to-star radius ratios in the region between 518-918 nm. We used the OSIRIS instrument at the Gran Telescopio CANARIAS (GTC) in long-slit spectroscopy mode, placing HAT-P-32 and a reference star in the same slit and obtaining a time series of spectra covering two transit events. Using the best quality data set, we were able to yield 20 narrowband transit light curves, with each passband spanning a 20 nm wide interval. After removal of all systematic noise signals and light curve modeling, the uncertainties for the resulting radius ratios lie between 337 and 972 ppm. The radius ratios show little variation with wavelength, suggesting a high altitude cloud layer masking any atmospheric features. Alternatively, a strong depletion in alkali metals or a much smaller than expected planetary atmospheric scale height could be responsible for the lack of atmospheric features. Our result of a flat transmission spectrum is consistent with a previous ground-based study of the optical spectrum of this planet. This agreement between independent results demonstrates that ground-based measurements of exoplanet atmospheres can give reliable and reproducible results despite the fact that the data often is heavily affected by systematic noise as long as the noise source is well understood and properly corrected. We also extract an optical spectrum of the M-dwarf companion HAT-P-32B. Using PHOENIX stellar atmosphere models we determine an effective temperature of Teff = 3187+60-71 K, which is slightly colder than previous studies relying only on broadband infrared data. The 20 narrowband and white light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A65

Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO(2)] and temperature conditions?

PubMed

Hall, Marianne; Medlyn, Belinda E; Abramowitz, Gab; Franklin, Oskar; Räntfors, Mats; Linder, Sune; Wallin, Göran

2013-11-01

Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated [CO2] and elevated air temperature, separately and in combination. The treatments imposed were elevated temperature, +2.8 °C in July/August and +5.6 °C in December above ambient, and [CO2] (ambient CO2 ∼370 μ mol mol(-1), elevated CO2 ∼700 μ mol mol(-1)). The relative importance of parameterization of Q, T and D responses for effects on the photosynthetic rate, expressed on a projected needle area, and the annual shoot carbon uptake was quantified using an empirical shoot photosynthesis model, which was developed and fitted to the measurements. The functional form of the response curves was established using an artificial neural network. The [CO2] treatment increased annual shoot carbon (C) uptake by 50%. Most important was effects on the light response curve, with a 67% increase in light-saturated photosynthetic rate, and a 52% increase in the initial slope of the light response curve. An interactive effect of light saturated photosynthetic rate was found with foliage N status, but no interactive effect for high temperature and high CO2. The air temperature treatment increased the annual shoot C uptake by 44%. The most important parameter was the seasonality, with an elongation of the growing season by almost 4 weeks. The temperature response curve was almost flat over much of the temperature range. A shift in temperature optimum had thus an insignificant effect on modelled annual shoot C uptake. The combined temperature and [CO2] treatment resulted in a 74% increase in annual shoot C uptake compared with ambient conditions, with no clear interactive effects on parameter values.

Criteria for representing circular arc and sine wave spar webs by non-curved elements

NASA Technical Reports Server (NTRS)

Jenkins, J. M.

1979-01-01

The basic problem of how to simply represent a curved web of a spar in a finite element structural model was addressed. The ratio of flat web to curved web axial deformations and longitudinal rotations were calculated using NASTRAN models. Multiplying factors were developed from these calculations for various web thicknesses. These multiplying factors can be applied directly to the area and moment of inertia inputs of the finite element model. This allows the thermal stress relieving configurations of sine wave and circular arc webs to be simply accounted for in finite element structural models.

Stress analysis in curved composites due to thermal loading

NASA Astrophysics Data System (ADS)

Polk, Jared Cornelius

Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge of such a problem. It was ascertained and proven that the general, non-modified (original) version of classical lamination theory cannot be used for an analytical solution for a simply curved beam or any other structure that would require rotations of laminates out their planes in space. Finite element analysis was used to ascertain stress variations in a simply curved beam. It was verified that these solutions reduce to the flat beam solutions as the radius of curvature of the beams tends to infinity. MATLAB was used to conduct the classical lamination theory numerical analysis. A MATLAB program was written to conduct the finite element analysis for the flat and curved beams, isotropic and composite. It does not require incompatibility techniques used in mechanics of isotropic materials for indeterminate structures that are equivalent to fixed-beam problems. Finally, it has the ability to enable the user to define and create unique elements not accessible in commercial software, and modify finite element procedures to take advantage of new paradigms.

Seeing a straight line on a curved surface: decoupling of patterns from surfaces by single IT neurons

PubMed Central

Ratan Murty, N. Apurva

2016-01-01

We have no difficulty seeing a straight line drawn on a paper even when the paper is bent, but this inference is in fact nontrivial. Doing so requires either matching local features or representing the pattern after factoring out the surface shape. Here we show that single neurons in the monkey inferior temporal (IT) cortex show invariant responses to patterns across rigid and nonrigid changes of surfaces. We recorded neuronal responses to stimuli in which the pattern and the surrounding surface were varied independently. In a subset of neurons, we found pattern-surface interactions that produced similar responses to stimuli across congruent pattern and surface transformations. These interactions produced systematic shifts in curvature tuning of patterns when overlaid on convex and flat surfaces. Our results show that surfaces are factored out of patterns by single neurons, thereby enabling complex perceptual inferences. NEW & NOTEWORTHY We have no difficulty seeing a straight line on a curved piece of paper, but in fact, doing so requires decoupling the shape of the surface from the pattern itself. Here we report a novel form of invariance in the visual cortex: single neurons in monkey inferior temporal cortex respond similarly to congruent transformations of patterns and surfaces, in effect decoupling patterns from the surface on which they are overlaid. PMID:27733595

Soft material adhesion characterization for in vivo locomotion of robotic capsule endoscopes: Experimental and modeling results.

PubMed

Kern, Madalyn D; Ortega Alcaide, Joan; Rentschler, Mark E

2014-11-01

The objective of this work is to validate an experimental method and nondimensional model for characterizing the normal adhesive response between a polyvinyl chloride based synthetic biological tissue substrate and a flat, cylindrical probe with a smooth polydimethylsiloxane (PDMS) surface. The adhesion response is a critical mobility design parameter of a Robotic Capsule Endoscope (RCE) using PDMS treads to provide mobility to travel through the gastrointestinal tract for diagnostic purposes. Three RCE design characteristics were chosen as input parameters for the normal adhesion testing: pre-load, dwell time and separation rate. These parameters relate to the RCE׳s cross sectional dimension, tread length, and tread speed, respectively. An inscribed central composite design (CCD) prescribed 34 different parameter configurations to be tested. The experimental adhesion response curves were nondimensionalized by the maximum stress and total displacement values for each test configuration and a mean nondimensional curve was defined with a maximum relative error of 5.6%. A mathematical model describing the adhesion behavior as a function of the maximum stress and total displacement was developed and verified. A nonlinear regression analysis was done on the maximum stress and total displacement parameters and equations were defined as a function of the RCE design parameters. The nondimensional adhesion model is able to predict the adhesion curve response of any test configuration with a mean R(2) value of 0.995. Eight additional CCD studies were performed to obtain a qualitative understanding of the impact of tread contact area and synthetic material substrate stiffness on the adhesion response. These results suggest that the nondimensionalization technique for analyzing the adhesion data is sufficient for all values of probe radius and substrate stiffness within the bounds tested. This method can now be used for RCE tread design optimization given a set of environmental conditions for device operation. Copyright © 2014 Elsevier Ltd. All rights reserved.

46 CFR 69.113 - Superstructure tonnage.

Code of Federal Regulations, 2011 CFR

2011-10-01

... is one-half the nearest breadth. If an end is in the form of an arc or curve having a decided flat...-third of the interval between the points at which the breadths are taken. The product is the square foot...

46 CFR 69.113 - Superstructure tonnage.

Code of Federal Regulations, 2010 CFR

2010-10-01

... is one-half the nearest breadth. If an end is in the form of an arc or curve having a decided flat...-third of the interval between the points at which the breadths are taken. The product is the square foot...

An evaluation of intertidal feeding habitats from a shorebird perspective: Towards relevant comparisons between temperate and tropical mudflats

NASA Astrophysics Data System (ADS)

Piersma, Theunis; de Goeij, Petra; Tulp, Ingrid

Macrozoobenthic communities of intertidal soft sediments are reviewed worldwide from the perspective of a mollusc-eating shorebird species. Based on 19 sites, total biomass figures varied between 5 and 80 g AFDM per m 2 (average 24 g AFDM per m 2); no latitudinal trends are apparent. The contribution made by bivalves and gastropods varies between 1% and 99%, north-temperate intertidal flats having relatively more molluscs than tropical flats. Intertidal flats in the tropics contain a greater variety of taxa, with brachiopods in Indonesia and echinoderms in northwest Australia contributing significantly to biomass only there. Limits to the occurrence of avian predators of intertidal benthos are set by the harvestable fraction of the biomass on offer and the costs of living at a particular site. No systematic differences in the harvestable fraction of the total mollusc-biomass for a worldwide occurring shorebird species specializing on molluscs (knots Calidris canutus) were apparent between temperate and tropical intertidal areas, in spite of large differences in maintenance metabolism incurred by these birds. The harvestable fractions of bivalves in the two West African areas (Banc d'Arguin, Mauritania and Guinea-Bissau) tended to be high (23-84% of total biomass in six species), they were relatively low (2-52% in five species) in the temperate Wadden Sea and the tropical northwest Australian site. Harvestable biomass determines the intake rate of shorebirds, as illustrated by functional-response curves of knots feeding on two bivalves species. We argue that the collection of information on size-depth relationships along with faunal and biomass surveys at a range of sites is bound to greatly increase our understanding of both the biology of tidal-flat invertebrates and the resource base underpinning the spectacular seasonal migrations of shorebirds.

Effects of the foil flatness on irradiation performance of U10Mo monolithic mini-plates

DOE PAGES

Ozaltun, Hakan; Medvedev, Pavel G.; Rabin, Barry H.

2015-09-03

Monolithic plate-type fuels comprise of a high density, low enrichment, U10Mo fuel foil encapsulated in a cladding material. This concept generates several fabrication challenges such as flatness, centering or thickness variation. There are concerns, if these parameters have implications on overall performance. To investigate these inquiries, the effects of the foil flatness were studied. For this, a representative plate was simulated for an ideal case. The simulations were repeated for additional cases with various foil curvatures to evaluate the effects on the irradiation performance. The results revealed that the stresses and strains induced by fabrication process are not affected bymore » the flatness of the foil. Furthermore, fabrication stresses in the foil are relieved relatively fast in the reactor. The effects of the foil flatness on peak irradiation stressstrains are minimal. There is a slight increase in temperature for the case with maximum curvature. The major impact is on the displacement characteristics. Furthermore, while the case with a flat foil produces a symmetrical swelling, if the foil is curved, more swelling occurs on the thin-cladding side and the plate bows during irradiation.« less

Modelling rating curves using remotely sensed LiDAR data

USGS Publications Warehouse

Nathanson, Marcus; Kean, Jason W.; Grabs, Thomas J.; Seibert, Jan; Laudon, Hjalmar; Lyon, Steve W.

2012-01-01

Accurate stream discharge measurements are important for many hydrological studies. In remote locations, however, it is often difficult to obtain stream flow information because of the difficulty in making the discharge measurements necessary to define stage-discharge relationships (rating curves). This study investigates the feasibility of defining rating curves by using a fluid mechanics-based model constrained with topographic data from an airborne LiDAR scanning. The study was carried out for an 8m-wide channel in the boreal landscape of northern Sweden. LiDAR data were used to define channel geometry above a low flow water surface along the 90-m surveyed reach. The channel topography below the water surface was estimated using the simple assumption of a flat streambed. The roughness for the modelled reach was back calculated from a single measurment of discharge. The topographic and roughness information was then used to model a rating curve. To isolate the potential influence of the flat bed assumption, a 'hybrid model' rating curve was developed on the basis of data combined from the LiDAR scan and a detailed ground survey. Whereas this hybrid model rating curve was in agreement with the direct measurements of discharge, the LiDAR model rating curve was equally in agreement with the medium and high flow measurements based on confidence intervals calculated from the direct measurements. The discrepancy between the LiDAR model rating curve and the low flow measurements was likely due to reduced roughness associated with unresolved submerged bed topography. Scanning during periods of low flow can help minimize this deficiency. These results suggest that combined ground surveys and LiDAR scans or multifrequency LiDAR scans that see 'below' the water surface (bathymetric LiDAR) could be useful in generating data needed to run such a fluid mechanics-based model. This opens a realm of possibility to remotely sense and monitor stream flows in channels in remote locations.

Two diverse models of embedding class one

NASA Astrophysics Data System (ADS)

Kuhfittig, Peter K. F.

2018-05-01

Embedding theorems have continued to be a topic of interest in the general theory of relativity since these help connect the classical theory to higher-dimensional manifolds. This paper deals with spacetimes of embedding class one, i.e., spacetimes that can be embedded in a five-dimensional flat spacetime. These ideas are applied to two diverse models, a complete solution for a charged wormhole admitting a one-parameter group of conformal motions and a new model to explain the flat rotation curves in spiral galaxies without the need for dark matter.

Analysis of a microstrip reflectarray antenna for microspacecraft applications

NASA Technical Reports Server (NTRS)

Huang, J.

1995-01-01

A microstrip reflectarray is a flat reflector antenna that can be mounted conformally onto a spacecraft's outside structure without consuming a significant amount of spacecraft volume and mass. For large apertures (2 m or larger), the antenna's reflecting surface, being flat, can be more easily and reliably deployed than a curved parabolic reflector. This article presents the study results on a microstrip reflect-array with circular polarization. Its efficiency and bandwidth characteristics are analyzed. Numerous advantages of this antenna system are discussed. Three new concepts using this microstrip reflectarray are also proposed.

The use of clamping grips and friction pads by tree frogs for climbing curved surfaces

PubMed Central

Ji, Aihong; Yuan, Shanshan; Hill, Iain; Wang, Huan; Barnes, W. Jon P.; Dai, Zhendong; Sitti, Metin

2017-01-01

Most studies on the adhesive mechanisms of climbing animals have addressed attachment against flat surfaces, yet many animals can climb highly curved surfaces, like twigs and small branches. Here we investigated whether tree frogs use a clamping grip by recording the ground reaction forces on a cylindrical object with either a smooth or anti-adhesive, rough surface. Furthermore, we measured the contact area of fore and hindlimbs against differently sized transparent cylinders and the forces of individual pads and subarticular tubercles in restrained animals. Our study revealed that frogs use friction and normal forces of roughly a similar magnitude for holding on to cylindrical objects. When challenged with climbing a non-adhesive surface, the compressive forces between opposite legs nearly doubled, indicating a stronger clamping grip. In contrast to climbing flat surfaces, frogs increased the contact area on all limbs by engaging not just adhesive pads but also subarticular tubercles on curved surfaces. Our force measurements showed that tubercles can withstand larger shear stresses than pads. SEM images of tubercles revealed a similar structure to that of toe pads including the presence of nanopillars, though channels surrounding epithelial cells were less pronounced. The tubercles' smaller size, proximal location on the toes and shallow cells make them probably less prone to buckling and thus ideal for gripping curved surfaces. PMID:28228509

Dirac equation in 2-dimensional curved spacetime, particle creation, and coupled waveguide arrays

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

Koke, Christian, E-mail: christian.koke@stud.uni-heidelberg.de; Noh, Changsuk, E-mail: changsuk@kias.re.kr; Angelakis, Dimitris G., E-mail: dimitris.angelakis@gmail.com

When quantum fields are coupled to gravitational fields, spontaneous particle creation may occur similarly to when they are coupled to external electromagnetic fields. A gravitational field can be incorporated as a background spacetime if the back-action of matter on the field can be neglected, resulting in modifications of the Dirac or Klein–Gordon equations for elementary fermions and bosons respectively. The semi-classical description predicts particle creation in many situations, including the expanding-universe scenario, near the event horizon of a black hole (the Hawking effect), and an accelerating observer in flat spacetime (the Unruh effect). In this work, we give a pedagogicalmore » introduction to the Dirac equation in a general 2D spacetime and show examples of spinor wave packet dynamics in flat and curved background spacetimes. In particular, we cover the phenomenon of particle creation in a time-dependent metric. Photonic analogs of these effects are then proposed, where classical light propagating in an array of coupled waveguides provides a visualisation of the Dirac spinor propagating in a curved 2D spacetime background. The extent to which such a single-particle description can be said to mimic particle creation is discussed.« less

Impact of new physics on the EW vacuum stability in a curved spacetime background

NASA Astrophysics Data System (ADS)

Bentivegna, E.; Branchina, V.; Contino, F.; Zappalà, D.

2017-12-01

It has been recently shown that, contrary to an intuitive decoupling argument, the presence of new physics at very large energy scales (say around the Planck scale) can have a strong impact on the electroweak vacuum lifetime. In particular, the vacuum could be totally destabilized. This study was performed in a flat spacetime background, and it is important to extend the analysis to curved spacetime since these are Planckian-physics effects. It is generally expected that under these extreme conditions gravity should totally quench the formation of true vacuum bubbles, thus washing out the destabilizing effect of new physics. In this work we extend the analysis to curved spacetime and show that, although gravity pushes toward stabilization, the destabilizing effect of new physics is still (by far) the dominating one. In order to get model independent results, high energy new physics is parametrized in two different independent ways: as higher order operators in the Higgs field, or introducing new particles with very large masses. The destabilizing effect is observed in both cases, hinting at a general mechanism that does not depend on the parametrization details for new physics, thus maintaining the results obtained from the analysis performed in flat spacetime.

Controllable Curved Mirrors Made from Single-Layer EAP Films

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart

2004-01-01

A document proposes that lightweight, deployable, large-aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suitable for such use include piezoelectric, electrostrictive, ferroelectric, and dielectric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single- layer film made of a currently available EAP, it would be possible to control the focal length of a 2-m-diameter mirror from infinity to 1.25 m.

Impact resistance performance of diamond film on a curved molybdenum substrate

NASA Astrophysics Data System (ADS)

Chen, Yang; Gou, Li

2017-08-01

Diamond films with different thicknesses were deposited on flat and curved molybdenum substrate by the microwave plasma chemical vapour deposition (MPCVD) method. Scanning electronic microscopy, atomic force microscopy and Raman spectroscopy were employed to characterise the morphology, the surface roughness and the composition of the films, respectively. A NanoTest system was used for hardness, elastic modulus and nanoimpact tests. The curved surface and ductility of the molybdenum substrate allow large deformation for the thinner films. The substrate has less effect on impact for the thicker film, the deformation of which is mainly determined by the film composition. Under a load of 50 mN and 75 cycles, less deformation occurred for the 22 μm thick film on the curved molybdenum substrate.

Survey and evaluation of current design of evacuated collectors. Final technical report

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

Graham, B. J.

The general development of these collectors, is described and a description of numerous evacuated collectors is given which vary from collectors that have been widely used in various applications to others which are still being developed in the laboratory. A table summarizing all of the available collectors, along with their characteristics, is presented. There are four evacuated collectors which have been tested, used in demonstration sites, and developed for the market. These collectors are described in detail, and they are compared in performance and cost with a well-engineered, double glazed, selectively coated, flat plate collector. A rather simple model systemmore » of about 2000 ft/sup 2/ of collector area for each of the four evacuated collectors and the flat plate collector is described, along with the support structure and the piping for each. Details of the cost are presented in order to compare collector costs with component costs. All of the available efficiency curves of collectors were plotted for comparison with the efficiency curve of a good, flat plate collector. To show the extent of use of evacuated collectors, a list according to manufacturers and to location of all of the sites at which these collectors are being used is presented.« less

Research of X-ray curved crystals analyzer

NASA Astrophysics Data System (ADS)

Xiao, Shali; Xong, Xian-cai; Qian, Jia-yu; Zhong, Xian-xin; Yan, Guo-hong; Liu, Zhong-li; Ding, Yong-kun

2005-08-01

X-ray spectrograph has long been used as a means of diagnosing conditions of laser-produced plasmas, as information concerning both the temperature and density can be extracted from the emitted radiation. For the measurement of X-ray lines in the energy range of 0.6-6 keV, A curved crystal X-ray spectrometer of reflection type elliptical geometry is required. In order to obtain both high resolution and collection efficiency the elliptical geometry is more advantageous than the flat configurations. Elliptical curved crystals spectrograph with a relatively wide spectral range are of particular use for deducing electron temperatures by measurement of the ratios of lines associated with different charge states. Curved crystals analyzer was designed and manufactured for use on an experiment to investigate the properties of laser produced plasmas. The spectrograph has 1350mm focal length and for these measurements, utilized PET, LIF, KAP and MICA crystal bent onto an elliptical substrate. This crystal analyzer covers the Bragg angel range from 30 to 67.5. The analyzer based on elliptically geometrical principle, which has self-focusing characteristics. The experiment was carried out on Shanghai Shengguang-II Facility and aimed to investigate the characteristics of a high density plasma. Experimental results using Curved crystal analyzer are described which show spectrum of Ti, Au laser-plasma. The focusing crystal analyzer clearly gave an increase in sensitivity over a flat crystal. Spectra showing the main resonance line were recorded with X-ray CCD and with laser energies 150J laser wavelength 350nm. The calculated wavelength resolution is about 500-1000.

Study of curved glass photovoltaic module and module electrical isolation design requirements

NASA Technical Reports Server (NTRS)

1980-01-01

The design of a 1.2 by 2.4 m curved glass superstrate and support clip assembly is presented, along with the results of finite element computer analysis and a glass industry survey conducted to assess the technical and economic feasibility of the concept. Installed costs for four curved glass module array configurations are estimated and compared with cost previously reported for comparable flat glass module configurations. Electrical properties of candidate module encapsulation systems are evaluated along with present industry practice for the design and testing of electrical insulation systems. Electric design requirements for module encapsulation systems are also discussed.

Study of curved glass photovoltaic module and module electrical isolation design requirements

NASA Astrophysics Data System (ADS)

1980-06-01

The design of a 1.2 by 2.4 m curved glass superstrate and support clip assembly is presented, along with the results of finite element computer analysis and a glass industry survey conducted to assess the technical and economic feasibility of the concept. Installed costs for four curved glass module array configurations are estimated and compared with cost previously reported for comparable flat glass module configurations. Electrical properties of candidate module encapsulation systems are evaluated along with present industry practice for the design and testing of electrical insulation systems. Electric design requirements for module encapsulation systems are also discussed.

Optical analysis of a curved-slats fixed-mirror solar concentrator by a forward ray-tracing procedure.

PubMed

Pujol Nadal, Ramon; Martínez Moll, Víctor

2013-10-20

Fixed-mirror solar concentrators (FMSCs) use a static reflector and a moving receiver. They are easily installable on building roofs. However, for high-concentration factors, several flat mirrors would be needed. If curved mirrors are used instead, high-concentration levels can be achieved, and such a solar concentrator is called a curved-slats fixed-mirror solar concentrator (CSFMSC), on which little information is available. Herein, a methodology is proposed to characterize the CSFMSC using 3D ray-tracing tools. The CSFMSC shows better optical characteristics than the FMSC, as it needs fewer reflector segments for achieving the same concentration and optical efficiency.

The role of apical contractility in determining cell morphology in multilayered epithelial sheets and tubes

NASA Astrophysics Data System (ADS)

Zhen Tan, Rui; Lai, Tanny; Chiam, K.-H.

2017-08-01

A multilayered epithelium is made up of individual cells that are stratified in an orderly fashion, layer by layer. In such tissues, individual cells can adopt a wide range of shapes ranging from columnar to squamous. From histological images, we observe that, in flat epithelia such as the skin, the cells in the top layer are squamous while those in the middle and bottom layers are columnar, whereas in tubular epithelia, the cells in all layers are columnar. We develop a computational model to understand how individual cell shape is governed by the mechanical forces within multilayered flat and curved epithelia. We derive the energy function for an epithelial sheet of cells considering intercellular adhesive and intracellular contractile forces. We determine computationally the cell morphologies that minimize the energy function for a wide range of cellular parameters. Depending on the dominant adhesive and contractile forces, we find four dominant cell morphologies for the multilayered-layered flat sheet and three dominant cell morphologies for the two-layered curved sheet. We study the transitions between the dominant cell morphologies for the two-layered flat sheet and find both continuous and discontinuous transitions and also the presence of multistable states. Matching our computational results with histological images, we conclude that apical contractile forces from the actomyosin belt in the epithelial cells is the dominant force determining cell shape in multilayered epithelia. Our computational model can guide tissue engineers in designing artificial multilayered epithelia, in terms of figuring out the cellular parameters needed to achieve realistic epithelial morphologies.

Anti-gravity and galaxy rotation curves

NASA Astrophysics Data System (ADS)

Sanders, R. H.

1984-07-01

A modification of Newtonian gravitational attraction which arises in the context of modern attempts to unify gravity with the other forces in nature can produce rotation curves for spiral galaxies which are nearly flat from 10 to 100 kpc, bind clusters of galaxies, and close the universe with the density of baryonic matter consistent with primordial nucleosynthesis. This is possible if a very low mass vector boson carries an effective anti-gravity force which on scales smaller than that of galaxies almost balances the normal attractive gravity force.

Gravity and crustal structure

NASA Technical Reports Server (NTRS)

Bowin, C. O.

1976-01-01

Lunar gravitational properties were analyzed along with the development of flat moon and curved moon computer models. Gravity anomalies and mascons were given particular attention. Geophysical and geological considerations were included, and comparisons were made between the gravitional fields of the Earth, Mars, and the Moon.

Design guide for predicting nonlinear random response (including snap-through) of buckled plates

NASA Technical Reports Server (NTRS)

Ng, Chung Fai

1989-01-01

This design guide describes a method for predicting the random response of flat and curved plates which is based on theoretical analyses and experimental results. The plate curvature can be due to postbuckling, in-plane mechanical or thermal stresses. Based on a single mode formula, root mean square values of the strain response to broadband excitation are evaluated for different static buckled configurations using the equivalent linearization technique. The effects on the overall strain response due to instability motion of snap-through are included. Panel parameters include clamped and simply-supported boundaries, aspect ratio, thickness and length. Analytical results are compared with experimental results from tests with 12 in. x 15 in. aluminum plates under thermal loading in a progressive wave facility. Comparisons are also made with results from tests with a 2 in. x 15 in. x 0.032 in. aluminum beam under base mechanical excitation. The comparisons help to assess the accuracy of the theory and the conditions under which deviations from the theory due to effects of imperfection and higher modes are significant.

Comparison of thermoluminescence response of different sized Ge-doped flat fibers as a dosimeter

NASA Astrophysics Data System (ADS)

Begum, Mahfuza; Mizanur Rahman, A. K. M.; Abdul-Rashid, H. A.; Yusoff, Z.; Mat-Sharif, K. A.; Zulkifli, M. I.; Muhamad-Yasin, S. Z.; Ung, N. M.; Kadir, A. B. A.; Amin, Y. M.; Bradley, D. A.

2015-11-01

Prime dosimetric properties, including dose-response, linearity with dose, energy response, fading and threshold doses were investigated for three different dimension Ge-doped flat fibers. The results of measurement were also compared with two of the more commonly used standard TLD media, TLD-100 (LiF:Mg,Ti-7.5%6LiF) and TLD-700 (7LiF:Mg,Ti-99.9%7LiF) chips. The flat cross-section samples (60×180) μm2, (100×350) μm2 and (200×750) μm2 were fabricated using the Modified Chemical Vapor Deposition (MCVD) process and pulled from the same "preform." In the study, all flat fiber samples provided good linear dose-response for the photon and electron beams generated using a medical linear accelerator (LINAC), for doses in the range 0.5-8 Gy. Among the samples, the smallest dimension flat fiber provided the best response, with a sensitivity of some 61% and 54%, respectively of that of the TLD-100 and TLD-700 chips. The energy responses of the samples were studied for various photon (6 MV, 10 MV) and electron (6 MeV, 9 MeV) beam energies. TL fading of around 20% was observed over a period of thirty (30) days. These favorable TL characteristics point towards promising development of Ge-doped flat fibers for use in radiotherapy dosimetry.

Clinical application of a multi-modal endoscope with fluorescent peptide in detection of colorectal neoplasia (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dai, Zhenzhen; Joshi, Bishnu P.; Gao, Zhenghong; Lee, Jeonghoon; Ghimire, Navin; Prabhu, Anoop; Wamsteker, Erik J.; Kwon, Richard S.; Elta, Grace H.; Appelman, Henry D.; Owens, Scott R.; Kuick, Rork; Turgeon, Kim K.; Wang, Thomas D.

2017-02-01

Early detection of precursor lesions for colorectal cancer can greatly improve survival. Pre-neoplasia can appear flat with conventional white light endoscopy. Sessile serrated adenomas (SSA) are precursor lesions found primarily in the proximal colon and frequently appear flat and indistinct. We performed a clinical study of n=37 patients using a multimodal endoscopy with a FITC-labeled peptide specific for SSA. Lesions were imaged with white light, reflectance and fluorescence. White light images were acquired before the peptide was applied and were used to help localize regions of abnormal tissues rightly. Co-registered fluorescence and reflectance images were combined to get ratio images thus the distance was corrected. We calculated the target/background ratio (T/B ratio) to quantify the images and found 2.3-fold greater fluorescence intensity for SSA compared with normal tissues. We found the T/B ratio for SSA to be significantly greater than that for normal colonic mucosa with 89.47% sensitivity and 91.67% specificity at the threshold of 1.22. An ROC curve for SSA and normal mucosa was also plotted with area under curve (AUC) of 0.93. The result also shows that SSA and adenoma are statistically significant and can be identified with 78.95% sensitivity and 90.48% specificity at the threshold of 1.66. An ROC curve was plotted with AUC of 0.88. Therefore, our result shows that the application of a multimodal endoscope with fluorescently labeled peptide can quantify images and works especially good for the detection of SSA which is a premalignant flat lesion conferring a high risk of subsequently leading to a colon cancer.

Graphene nanoribbons production from flat carbon nanotubes

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

Melo, W. S.; Guerini, S.; Diniz, E. M., E-mail: eduardo.diniz@ufma.br

2015-11-14

Graphene nanoribbons are of great interest for pure and applied sciences due to their unique properties which depend on the nanoribbon edges, as, for example, energy gap and antiferromagnetic coupling. Nevertheless, the synthesis of nanoribbons with well-defined edges remains a challenge. To collaborate with this subject, here we propose a new route for the production of graphene nanoribbons from flat carbon nanotubes filled with a one-dimensional chain of Fe atoms by first principles calculations based on density functional theory. Our results show that Fe-filled flat carbon nanotubes are energetically more stable than non flattened geometries. Also we find that bymore » hydrogenation or oxygenation of the most curved region of the Fe-filled flat armchair carbon nanotube, it occurred a spontaneous production of zigzag graphene nanoribbons which have metallic or semiconducting behavior depending on the edge and size of the graphene nanoribbon. Such findings can be used to create a new method of synthesis of regular-edge carbon nanoribbons.« less

A novel flat-response x-ray detector in the photon energy range of 0.1-4 keV

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

Li Zhichao; Guo Liang; Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900

2010-07-15

A novel flat-response x-ray detector has been developed for the measurement of radiation flux from a hohlraum. In order to obtain a flat response in the photon energy range of 0.1-4 keV, it is found that both the cathode and the filter of the detector can be made of gold. A further improvement on the compound filter can then largely relax the requirement of the calibration x-ray beam. The calibration of the detector, which is carried out on Beijing Synchrotron Radiation Facility at Institute of High Energy Physics, shows that the detector has a desired flat response in the photonmore » energy range of 0.1-4 keV, with a response flatness smaller than 13%. The detector has been successfully applied in the hohlraum experiment on Shenguang-III prototype laser facility. The radiation temperatures inferred from the detector agree well with those from the diagnostic instrument Dante installed at the same azimuth angle from the hohlraum axis, demonstrating the feasibility of the detector.« less

A novel flat-response x-ray detector in the photon energy range of 0.1-4 keV.

PubMed

Li, Zhichao; Jiang, Xiaohua; Liu, Shenye; Huang, Tianxuan; Zheng, Jian; Yang, Jiamin; Li, Sanwei; Guo, Liang; Zhao, Xuefeng; Du, Huabin; Song, Tianming; Yi, Rongqing; Liu, Yonggang; Jiang, Shaoen; Ding, Yongkun

2010-07-01

A novel flat-response x-ray detector has been developed for the measurement of radiation flux from a hohlraum. In order to obtain a flat response in the photon energy range of 0.1-4 keV, it is found that both the cathode and the filter of the detector can be made of gold. A further improvement on the compound filter can then largely relax the requirement of the calibration x-ray beam. The calibration of the detector, which is carried out on Beijing Synchrotron Radiation Facility at Institute of High Energy Physics, shows that the detector has a desired flat response in the photon energy range of 0.1-4 keV, with a response flatness smaller than 13%. The detector has been successfully applied in the hohlraum experiment on Shenguang-III prototype laser facility. The radiation temperatures inferred from the detector agree well with those from the diagnostic instrument Dante installed at the same azimuth angle from the hohlraum axis, demonstrating the feasibility of the detector.

Monte Carlo modeling of ion chamber performance using MCNP.

PubMed

Wallace, J D

2012-12-01

Ion Chambers have a generally flat energy response with some deviations at very low (<100 keV) and very high (>2 MeV) energies. Some improvements in the low energy response can be achieved through use of high atomic number gases, such as argon and xenon, and higher chamber pressures. This work looks at the energy response of high pressure xenon-filled ion chambers using the MCNP Monte Carlo package to develop geometric models of a commercially available high pressure ion chamber (HPIC). The use of the F6 tally as an estimator of the energy deposited in a region of interest per unit mass, and the underlying assumptions associated with its use are described. The effect of gas composition, chamber gas pressure, chamber wall thickness, and chamber holder wall thicknesses on energy response are investigated and reported. The predicted energy response curve for the HPIC was found to be similar to that reported by other investigators. These investigations indicate that improvements to flatten the overall energy response of the HPIC down to 70 keV could be achieved through use of 3 mm-thick stainless steel walls for the ion chamber.

An accurate solution of the gas lubricated, flat sector thrust bearing

NASA Technical Reports Server (NTRS)

Etsion, I.; Fleming, D. P.

1976-01-01

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

Analysis of the gas-lubricated flat-sector-pad thrust bearing

NASA Technical Reports Server (NTRS)

Etsion, I.

1976-01-01

A flat sector-shaped pad geometry for a gas-lubricated thrust bearing is analyzed considering both the pitch and roll of the pad. It is shown that maximum load capacity is achieved when the pad is tilted so as to create uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves, and a comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

Bars and spirals in tidal interactions with an ensemble of galaxy mass models

NASA Astrophysics Data System (ADS)

Pettitt, Alex R.; Wadsley, J. W.

2018-03-01

We present simulations of the gaseous and stellar material in several different galaxy mass models under the influence of different tidal fly-bys to assess the changes in their bar and spiral morphology. Five different mass models are chosen to represent the variety of rotation curves seen in nature. We find a multitude of different spiral and bar structures can be created, with their properties dependent on the strength of the interaction. We calculate pattern speeds, spiral wind-up rates, bar lengths, and angular momentum exchange to quantify the changes in disc morphology in each scenario. The wind-up rates of the tidal spirals follow the 2:1 resonance very closely for the flat and dark matter-dominated rotation curves, whereas the more baryon-dominated curves tend to wind-up faster, influenced by their inner bars. Clear spurs are seen in most of the tidal spirals, most noticeable in the flat rotation curve models. Bars formed both in isolation and interactions agree well with those seen in real galaxies, with a mixture of `fast' and `slow' rotators. We find no strong correlation between bar length or pattern speed and the interaction strength. Bar formation is, however, accelerated/induced in four out of five of our models. We close by briefly comparing the morphology of our models to real galaxies, easily finding analogues for nearly all simulations presenter here, showing passages of small companions can easily reproduce an ensemble of observed morphologies.

Analysis of diffusion in curved surfaces and its application to tubular membranes.

PubMed

Klaus, Colin James Stockdale; Raghunathan, Krishnan; DiBenedetto, Emmanuele; Kenworthy, Anne K

2016-12-01

Diffusion of particles in curved surfaces is inherently complex compared with diffusion in a flat membrane, owing to the nonplanarity of the surface. The consequence of such nonplanar geometry on diffusion is poorly understood but is highly relevant in the case of cell membranes, which often adopt complex geometries. To address this question, we developed a new finite element approach to model diffusion on curved membrane surfaces based on solutions to Fick's law of diffusion and used this to study the effects of geometry on the entry of surface-bound particles into tubules by diffusion. We show that variations in tubule radius and length can distinctly alter diffusion gradients in tubules over biologically relevant timescales. In addition, we show that tubular structures tend to retain concentration gradients for a longer time compared with a comparable flat surface. These findings indicate that sorting of particles along the surfaces of tubules can arise simply as a geometric consequence of the curvature without any specific contribution from the membrane environment. Our studies provide a framework for modeling diffusion in curved surfaces and suggest that biological regulation can emerge purely from membrane geometry. © 2016 Klaus, Raghunathan, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Realization of the Gallium Triple Point at NMIJ/AIST

NASA Astrophysics Data System (ADS)

Nakano, T.; Tamura, O.; Sakurai, H.

2008-02-01

The triple point of gallium has been realized by a calorimetric method using capsule-type standard platinum resistance thermometers (CSPRTs) and a small glass cell containing about 97 mmol (6.8 g) of gallium with a nominal purity of 99.99999%. The melting curve shows a very flat and relatively linear dependence on 1/ F in the region from 1/ F = 1 to 1/ F = 20 with a narrow width of the melting curve within 0.1 mK. Also, a large gallium triple-point cell was fabricated for the calibration of client-owned CSPRTs. The gallium triple-point cell consists of a PTFE crucible and a PTFE cap with a re-entrant well and a small vent. The PTFE cell contains 780 g of gallium from the same source as used for the small glass cell. The PTFE cell is completely covered by a stainless-steel jacket with a valve to enable evacuation of the cell. The melting curve of the large cell shows a flat plateau that remains within 0.03 mK over 10 days and that is reproducible within 0.05 mK over 8 months. The calibrated value of a CSPRT obtained using the large cell agrees with that obtained using the small glass cell within the uncertainties of the calibrations.

Analysis of Flatness Deviations for Austenitic Stainless Steel Workpieces after Efficient Surface Machining

NASA Astrophysics Data System (ADS)

Nadolny, K.; Kapłonek, W.

2014-08-01

The following work is an analysis of flatness deviations of a workpiece made of X2CrNiMo17-12-2 austenitic stainless steel. The workpiece surface was shaped using efficient machining techniques (milling, grinding, and smoothing). After the machining was completed, all surfaces underwent stylus measurements in order to obtain surface flatness and roughness parameters. For this purpose the stylus profilometer Hommel-Tester T8000 by Hommelwerke with HommelMap software was used. The research results are presented in the form of 2D surface maps, 3D surface topographies with extracted single profiles, Abbott-Firestone curves, and graphical studies of the Sk parameters. The results of these experimental tests proved the possibility of a correlation between flatness and roughness parameters, as well as enabled an analysis of changes in these parameters from shaping and rough grinding to finished machining. The main novelty of this paper is comprehensive analysis of measurement results obtained during a three-step machining process of austenitic stainless steel. Simultaneous analysis of individual machining steps (milling, grinding, and smoothing) enabled a complementary assessment of the process of shaping the workpiece surface macro- and micro-geometry, giving special consideration to minimize the flatness deviations

The binary millisecond pulsar PSR J1023+0038 during its accretion state - I. Optical variability

NASA Astrophysics Data System (ADS)

Shahbaz, T.; Linares, M.; Nevado, S. P.; Rodríguez-Gil, P.; Casares, J.; Dhillon, V. S.; Marsh, T. R.; Littlefair, S.; Leckngam, A.; Poshyachinda, S.

2015-11-01

We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray binary phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to the irradiated secondary star and accretion disc. We also observe superimposed rapid flaring on time-scales as short as ˜20 s with amplitudes of ˜0.1-0.5 mag and additional large flare events on time-scales of ˜5-60 min with amplitudes of ˜0.5-1.0 mag. The power density spectrum of the optical flare light curves is dominated by a red-noise component, typical of aperiodic activity in X-ray binaries. Simultaneous X-ray and UV observations by the Swift satellite reveal strong correlations that are consistent with X-ray reprocessing of the UV light, most likely in the outer regions of the accretion disc. On some nights we also observe sharp-edged, rectangular, flat-bottomed dips randomly distributed in orbital phase, with a median duration of ˜250 s and a median ingress/egress time of ˜20 s. These rectangular dips are similar to the mode-switching behaviour between disc `active' and `passive' luminosity states, observed in the X-ray light curves of other redback millisecond pulsars. This is the first time that the optical analogue of the X-ray mode-switching has been observed. The properties of the passive- and active-state light curves can be explained in terms of clumpy accretion from a trapped inner accretion disc near the corotation radius, resulting in rectangular, flat-bottomed optical and X-ray light curves.

Streamline curvature in supersonic shear layers

NASA Technical Reports Server (NTRS)

Kibens, V.

1992-01-01

Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of curvature are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. Curvature must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.

Can cluster environment modify the dynamical evolution of spiral galaxies?

NASA Technical Reports Server (NTRS)

Amram, P.; Balkowski, C.; Cayatte, V.; Marcelin, M.; Sullivan, W. T., III

1993-01-01

Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows the construction of high-quality rotation curves. Details concerning the acquisition and reduction procedures of the data are given in Amram. We present and discuss our preliminary analysis and compare them with RWF's results.

Development of a novel configuration for a MEMS transducer for low bias and high resolution imaging applications

NASA Astrophysics Data System (ADS)

Emadi, Tahereh Arezoo; Buchanan, Douglas A.

2014-03-01

A robust capacitive micromachined ultrasonic transducer has been developed. In this novel configuration, a stack of two deflectable membranes are suspended over a fixed bottom electrode. Similar to conventional capacitive ultrasonic transducers, a generated electrostatic force between the electrodes causes the membranes to deflect and vibrate. However, in this new configuration the transducer effective cavity height is reduced due to the deflection of two membranes. Therefore, the transducer spring constant is more susceptible to bias voltage, which in return reduces the required bias voltage. The transducers have been produced employing a MEMS sacrificial technique where two different membrane anchoring (curved- and flat- anchors) structures, with similar membrane radii were fabricated. Highly doped polysilicon was used as the membrane material. The resonant frequencies of the two transducers have been investigated. It was found that the transducers with curved membrane anchors exhibits a larger resonant frequency shift compared to the transducers with flat membranes for a given bias voltage. Comparison has been made between the spring constant of the flat membrane transducer and that of a conventional single membrane transducer. It is shown that the multiple moving membrane transducer exhibits a larger reduction in the spring constant compared to the conventional transducer, when driven with the same bias voltage. This results in a transducer with a higher power generation capability and sensitivity.

TESTING NONSTANDARD COSMOLOGICAL MODELS WITH SNLS3 SUPERNOVA DATA AND OTHER COSMOLOGICAL PROBES

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

Li Zhengxiang; Yu Hongwei; Wu Puxun, E-mail: hwyu@hunnu.edu.cn

2012-01-10

We investigate the implications for some nonstandard cosmological models using data from the first three years of the Supernova Legacy Survey (SNLS3), assuming a spatially flat universe. A comparison between the constraints from the SNLS3 and those from other SN Ia samples, such as the ESSENCE, Union2, SDSS-II, and Constitution samples, is given and the effects of different light-curve fitters are considered. We find that analyzing SNe Ia with SALT2 or SALT or SiFTO can give consistent results and the tensions between different data sets and different light-curve fitters are obvious for fewer-free-parameters models. At the same time, we alsomore » study the constraints from SNLS3 along with data from the cosmic microwave background and the baryonic acoustic oscillations (CMB/BAO), and the latest Hubble parameter versus redshift (H(z)). Using model selection criteria such as {chi}{sup 2}/dof, goodness of fit, Akaike information criterion, and Bayesian information criterion, we find that, among all the cosmological models considered here ({Lambda}CDM, constant w, varying w, Dvali-Gabadadze-Porrati (DGP), modified polytropic Cardassian, and the generalized Chaplygin gas), the flat DGP is favored by SNLS3 alone. However, when additional CMB/BAO or H(z) constraints are included, this is no longer the case, and the flat {Lambda}CDM becomes preferred.« less

A novel flexible capacitive touch pad based on graphene oxide film.

PubMed

Tian, He; Yang, Yi; Xie, Dan; Ren, Tian-Ling; Shu, Yi; Zhou, Chang-Jian; Sun, Hui; Liu, Xuan; Zhang, Cang-Hai

2013-02-07

Recently, graphene oxide (GO) supercapacitors with ultra-high energy densities have received significant attention. In addition to energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as vibration and sound energy harvesting. Here, we experimentally create a macroscopic flexible capacitive touch pad based on GO film. An obvious touch "ON" to "OFF" voltage ratio up to ∼60 has been observed. Moreover, we tested the capacitor structure on both flat and curved surfaces and it showed high response sensitivity under fast touch rates. Collectively, our results raise the exciting prospect that the realization of macroscopic flexible keyboards with large-area graphene based materials is technologically feasible, which may open up important applications in control and interface design for solar cells, speakers, supercapacitors, batteries and MEMS systems.

Optofluidic lens actuated by laser-induced solutocapillary forces

NASA Astrophysics Data System (ADS)

Malyuk, A. Yu.; Ivanova, N. A.

2017-06-01

We demonstrate an adaptive liquid lens controlled by laser-induced solutocapillary forces. The liquid droplet serving as a lens is formed in a thin layer of binary liquid mixture by surface tension driven flows caused by the thermal action of laser irradiation. The shape of droplet, its aperture and the focal length are reversibly changed without hysteresis by varying the intensity of the laser beam. The focal length variation range of the droplet-lens lies in between infinity (a flat layer) to 15 mm (a curved interface). The droplet-lens is capable to adjust the in-plane lateral position in response to a displacement of the laser beam. The proposed laser controlled droplet-lens will enable to develop smart liquid optical devices, which can imitate the accommodation reflex and pupillary light reflex of the eye.

Postbuckling and Growth of Delaminations in Composite Plates Subjected to Axial Compression

NASA Technical Reports Server (NTRS)

Reeder, James R.; Chunchu, Prasad B.; Song, Kyongchan; Ambur, Damodar R.

2002-01-01

The postbuckling response and growth of circular delaminations in flat and curved plates are investigated as part of a study to identify the criticality of delamination locations through the laminate thickness. The experimental results from tests on delaminated plates are compared with finite element analysis results generated using shell models. The analytical prediction of delamination growth is obtained by assessing the strain energy release rate results from the finite element model and comparing them to a mixed-mode fracture toughness failure criterion. The analytical results for onset of delamination growth compare well with experimental results generated using a 3-dimensional displacement visualization system. The record of delamination progression measured in this study has resulted in a fully 3-dimensional test case with which progressive failure models can be validated.

A novel flexible capacitive touch pad based on graphene oxide film

NASA Astrophysics Data System (ADS)

Tian, He; Yang, Yi; Xie, Dan; Ren, Tian-Ling; Shu, Yi; Zhou, Chang-Jian; Sun, Hui; Liu, Xuan; Zhang, Cang-Hai

2013-01-01

Recently, graphene oxide (GO) supercapacitors with ultra-high energy densities have received significant attention. In addition to energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as vibration and sound energy harvesting. Here, we experimentally create a macroscopic flexible capacitive touch pad based on GO film. An obvious touch ``ON'' to ``OFF'' voltage ratio up to ~60 has been observed. Moreover, we tested the capacitor structure on both flat and curved surfaces and it showed high response sensitivity under fast touch rates. Collectively, our results raise the exciting prospect that the realization of macroscopic flexible keyboards with large-area graphene based materials is technologically feasible, which may open up important applications in control and interface design for solar cells, speakers, supercapacitors, batteries and MEMS systems.

Influence of wire-coil inserts on the thermo-hydraulic performance of a flat-plate solar collector

NASA Astrophysics Data System (ADS)

Herrero Martín, R.; García, A.; Pérez-García, J.

2012-11-01

Enhancement techniques can be applied to flat-plate liquid solar collectors towards more compact and efficient designs. For the typical operating mass flow rates in flat-plate solar collectors, the most suitable technique is inserted devices. Based on previous studies from the authors, wire coils were selected for enhancing heat transfer. This type of inserted device provides better results in laminar, transitional and low turbulence fluid flow regimes. To test the enhanced solar collector and compare with a standard one, an experimental side-by-side solar collector test bed was designed and constructed. The testing set up was fully designed following the requirements of EN12975-2 and allow us to accomplish performance tests under the same operating conditions (mass flow rate, inlet fluid temperature and weather conditions). This work presents the thermal efficiency curves of a commercial and an enhanced solar collector, for the standardized mass flow rate per unit of absorber area of 0.02 kg/sm2 (in useful engineering units 144 kg/h for water as working fluid and 2 m2 flat-plate solar collector of absorber area). The enhanced collector was modified inserting spiral wire coils of dimensionless pitch p/D = 1 and wire-diameter e/D = 0.0717. The friction factor per tube has been computed from the overall pressure drop tests across the solar collectors. The thermal efficiency curves of both solar collectors, a standard and an enhanced collector, are presented. The enhanced solar collector increases the thermal efficiency by 15%. To account for the overall enhancement a modified performance evaluation criterion (R3m) is proposed. The maximum value encountered reaches 1.105 which represents an increase in useful power of 10.5% for the same pumping power consumption.

Constraints on Non-flat Cosmologies with Massive Neutrinos after Planck 2015

NASA Astrophysics Data System (ADS)

Chen, Yun; Ratra, Bharat; Biesiada, Marek; Li, Song; Zhu, Zong-Hong

2016-10-01

We investigate two dark energy cosmological models (I.e., the ΛCDM and ϕCDM models) with massive neutrinos assuming two different neutrino mass hierarchies in both the spatially flat and non-flat scenarios, where in the ϕCDM model the scalar field possesses an inverse power-law potential, V(ϕ) ∝ ϕ -α (α > 0). Cosmic microwave background data from Planck 2015, baryon acoustic oscillation data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the joint light-curve analysis compilation of SNe Ia apparent magnitude observations, and the Hubble Space Telescope H 0 prior, are jointly employed to constrain the model parameters. We first determine constraints assuming three species of degenerate massive neutrinos. In the spatially flat (non-flat) ΛCDM model, the sum of neutrino masses is bounded as Σm ν < 0.165(0.299) eV at 95% confidence level (CL). Correspondingly, in the flat (non-flat) ϕCDM model, we find Σm ν < 0.164(0.301) eV at 95% CL. The inclusion of spatial curvature as a free parameter results in a significant broadening of confidence regions for Σm ν and other parameters. In the scenario where the total neutrino mass is dominated by the heaviest neutrino mass eigenstate, we obtain similar conclusions to those obtained in the degenerate neutrino mass scenario. In addition, the results show that the bounds on Σm ν based on two different neutrino mass hierarchies have insignificant differences in the spatially flat case for both the ΛCDM and ϕCDM models; however, the corresponding differences are larger in the non-flat case.

Numerical simulation of electromagnetic waves in Schwarzschild space-time by finite difference time domain method and Green function method

NASA Astrophysics Data System (ADS)

Jia, Shouqing; La, Dongsheng; Ma, Xuelian

2018-04-01

The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.

Gaussian-Beam/Physical-Optics Design Of Beam Waveguide

NASA Technical Reports Server (NTRS)

Veruttipong, Watt; Chen, Jacqueline C.; Bathker, Dan A.

1993-01-01

In iterative method of designing wideband beam-waveguide feed for paraboloidal-reflector antenna, Gaussian-beam approximation alternated with more nearly exact physical-optics analysis of diffraction. Includes curved and straight reflectors guiding radiation from feed horn to subreflector. For iterative design calculations, curved mirrors mathematically modeled as thin lenses. Each distance Li is combined length of two straight-line segments intersecting at one of flat mirrors. Method useful for designing beam-waveguide reflectors or mirrors required to have diameters approximately less than 30 wavelengths at one or more intended operating frequencies.

Plasmonic cloak using graphene at infrared frequencies

NASA Astrophysics Data System (ADS)

Li, Yan Xiu; Kong, Fan Min; Li, Kang; Zhuang, Hua Wei

2015-11-01

A carpet cloak based on graphene is designed and realized by making an approximate hemisphere surface which behaves as a flat surface, and the performances of the cloak are simulated by finite element method. The cloak performs perfectly through tuning conductivity of the graphene. The incident wave can propagate on the curved surface without being disturbed, and an object under the curved surface will be cloaked. It is indicated that graphene can be a platform for "on-atom-thick" cloaks, and the proposed methods can be applied in the practical design.

Cosmological constraints from measurements of type Ia supernovae discovered during the first 1.5 yr of the Pan-STARRS1 survey

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

Rest, A.; Scolnic, D.; Riess, A.

2014-11-01

We present griz {sub P1} light curves of 146 spectroscopically confirmed Type Ia supernovae (SNe Ia; 0.03 < z < 0.65) discovered during the first 1.5 yr of the Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is determined by a combination of on-site measurements of the instrument response function and observations of spectrophotometric standard stars. We find that the systematic uncertainties in the photometric system are currently 1.2% without accounting for the uncertainty in the Hubble Space Telescope Calspec definition of the AB system. A Hubble diagram is constructed with a subset of 113 out of 146 SNemore » Ia that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113 PS1 SNe Ia + 222 light curves from 197 low-z SNe Ia), using only supernovae (SNe) and assuming a constant dark energy equation of state and flatness, yields w=−1.120{sub −0.206}{sup +0.360}(Stat){sub −0.291}{sup +0.269}(Sys). When combined with BAO+CMB(Planck)+H {sub 0}, the analysis yields Ω{sub M}=0.280{sub −0.012}{sup +0.013} and w=−1.166{sub −0.069}{sup +0.072} including all identified systematics. The value of w is inconsistent with the cosmological constant value of –1 at the 2.3σ level. Tension endures after removing either the baryon acoustic oscillation (BAO) or the H {sub 0} constraint, though it is strongest when including the H {sub 0} constraint. If we include WMAP9 cosmic microwave background (CMB) constraints instead of those from Planck, we find w=−1.124{sub −0.065}{sup +0.083}, which diminishes the discord to <2σ. We cannot conclude whether the tension with flat ΛCDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full Pan-STARRS1 SN sample with ∼three times as many SNe should provide more conclusive results.« less

Ringin' the water bell: dynamic modes of curved fluid sheets

NASA Astrophysics Data System (ADS)

Kolinski, John; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran

2015-11-01

A water bell is formed by fluid flowing in a thin, coherent sheet in the shape of a bell. Experimentally, a water bell is created via the impact of a cylindrical jet on a flat surface. Its shape is set by the splash angle (the separation angle) of the resulting cylindrically symmetric water sheet. The separation angle is altered by adjusting the height of a lip surrounding the impact point, as in a water sprinkler. We drive the lip's height sinusoidally, altering the separation angle, and ringin' the water bell. This forcing generates disturbances on the steady-state water bell that propagate forward and backward in the fluid's reference frame at well-defined velocities, and interact, resulting in the emergence of an interference pattern unique to each steady-state geometry. We analytically model these dynamics by linearizing the amplitude of the bell's response about the underlying curved geometry. This simple model predicts the nodal structure over a wide range of steady-state water bell configurations and driving frequencies. Due to the curved water bell geometry, the nodal structure is quite complex; nevertheless, the predicted nodal structure agrees extremely well with the experimental data. When we drive the bell beyond perturbative separation angles, the nodal locations surprisingly persist, despite the strikingly altered underlying water bell shape. At extreme driving amplitudes the water sheet assumes a rich variety of tortuous, non-convex shapes; nevertheless, the fluid sheet remains intact.

Particle Detectors in the Theory of Quantum Fields on Curved Spacetimes

NASA Astrophysics Data System (ADS)

Cant, John Fraser

This work discusses aspects of a fundamental problem in the theory of quantum fields on curved spacetimes--that of giving physical meaning to the particle representations of the theory. In particular, the response of model particle detectors is analysed in detail. Unruh (1976) first introduced the idea of a model particle detector in order to give an operational definition to particles. He found that even in flat spacetime, the excitation of a particle detector does not necessarily correspond to the presence of an energy carrier--an accelerating detector will excite in response to the zero-energy state of the Minkowski vacuum. The central question I consider in this work is --where does the energy for the excitation of the accelerating detector come from? The accepted response has been that the accelerating force provides the energy. Evaluating the energy carried by the (conformally-invariant massless scalar) field after the interaction with the detector, however, I find that the detector excitation is compensated by an equal but opposite emission of negative energy. This result suggests that there may be states of lesser energy than that of the Minkowski vacuum. To resolve this paradox, I argue that the emission of a detector following a more realistic trajectory than that of constant acceleration--one that starts and finishes in inertial motion--will in total be positive, although during periods of constant acceleration the detector will still emit negative energy. The Minkowski vacuum retains its status as the field state of lowest energy. The second question I consider is the response of Unruh's detector in curved spacetime--is it possible to use such a detector to measure the energy carried by the field? In the particular case of a detector following a Killing trajectory, I find that there is a response to the energy of the field, but that there is also an inherent 'noise'. In a two dimensional model spacetime, I show that this 'noise' depends on the detector's acceleration and on the curvature of the spacetime, thereby encompassing previous results of Unruh (1976) and of Gibbons & Hawking (1977).

Large-Area High-Performance Flexible Pressure Sensor with Carbon Nanotube Active Matrix for Electronic Skin.

PubMed

Nela, Luca; Tang, Jianshi; Cao, Qing; Tulevski, George; Han, Shu-Jen

2018-03-14

Artificial "electronic skin" is of great interest for mimicking the functionality of human skin, such as tactile pressure sensing. Several important performance metrics include mechanical flexibility, operation voltage, sensitivity, and accuracy, as well as response speed. In this Letter, we demonstrate a large-area high-performance flexible pressure sensor built on an active matrix of 16 × 16 carbon nanotube thin-film transistors (CNT TFTs). Made from highly purified solution tubes, the active matrix exhibits superior flexible TFT performance with high mobility and large current density, along with a high device yield of nearly 99% over 4 inch sample area. The fully integrated flexible pressure sensor operates within a small voltage range of 3 V and shows superb performance featuring high spatial resolution of 4 mm, faster response than human skin (<30 ms), and excellent accuracy in sensing complex objects on both flat and curved surfaces. This work may pave the road for future integration of high-performance electronic skin in smart robotics and prosthetic solutions.

Observations of flat-spectrum radio sources at λ850 μm from the James Clerk Maxwell Telescope - I. 1997 April to 2000 April

NASA Astrophysics Data System (ADS)

Robson, E. I.; Stevens, J. A.; Jenness, T.

2001-11-01

Calibrated data for 65 flat-spectrum extragalactic radio sources are presented at a wavelength of 850μm, covering a three-year period from 1997 April. The data, obtained from the James Clerk Maxwell Telescope using the SCUBA camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control-Data Reduction (orac-dr) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves.

Further study on the wheel-rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

NASA Astrophysics Data System (ADS)

Jing, Lin; Han, Liangliang

2017-12-01

A comprehensive dynamic finite-element simulation method was proposed to study the wheel-rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel-rail materials and thermal stress due to the wheel-rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel-rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel-rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.

Showcasing electrode-electrolyte interfacial potential as a vital parameter in the hydrogen generation by metal oxides electrodes

NASA Astrophysics Data System (ADS)

Niveditha, C. V.; Nizamudeen, A. C.; Ramanarayanan, Rajita; Jabeen Fatima, M. J.; Swaminathan, Sindhu

2018-03-01

This investigation presents a new insight by experimentally demonstrating electrode-electrolyte interface potential that is flat band potential as a determinant in photoelectrochemical splitting of water. Two different metal oxides namely n type, nitrogen doped titania and p type copper oxides have been synthesized for the study. The flat band potential values of these oxide systems were obtained from Mott-Schottky analysis. The obtained flat band potential is used as a marker to fix the working potential in water splitting experiment. To obtain optimum photocurrent a potential more positive than flatband is applied to n-type N-TiO2 and vice-versa for p-type Cu2O. The findings are well supported by I-t curves derived from chronoamperometric measurements. Finally the mechanisms behind interfacial potential dynamics have been discussed in this work.

Comparison under a simulated sun of two black-nickel-coated flat-plate solar collectors with a nonselective black-paint-coated collector

NASA Technical Reports Server (NTRS)

Simon, F. F.

1975-01-01

A performance evaluation was made of two, black nickel coated, flat plate solar collectors. Collector performance was determined under a simulated sun for a wide range of inlet temperatures, including the temperature required for solar powered absorption air conditioning. For a basis of comparison a performance test was made on a traditional, two glass, nonselective, black paint coated, flat plate collector. Performance curves and performance parameters are presented to point out the importance of the design variables which determine an efficient collector. A black nickel coated collector was found to be a good performer at the conditions expected for solar powered absorption air conditioning. This collector attained a thermal efficiency of 50 percent at an inlet temperature of 366 K (200 F) and an incident flux of 946 watts/sq m (300 Btu/hr-sq ft).

TECHNICAL NOTE: Actuation displacement performance change of pre-stressed piezoelectric actuators attached to a flat surface

NASA Astrophysics Data System (ADS)

Goo, Nam Seo; Phuoc Phan, Van; Park, Hoon Cheol

2009-03-01

Pre-stressed piezoelectric actuators such as RAINBOW, THUNDER™, and LIPCA have a curvature due to a mismatch of the coefficient of thermal expansion, which inevitably exists during the manufacturing process. This technical note provides an answer to the question of how their actuation displacement performance changes when the curved pre-stressed piezoelectric actuators are attached to a flat surface. Finite element analysis with the ANSYS™ program was used to calculate the stress distribution inside a LIPCA, one of the pre-stressed piezoelectric actuators, after the LIPCA was cured and attached to the flat surface. The change of actuation displacement performance can be explained in terms of the relation between the piezoelectric strain constants and internal stress. As a result of the curing and attachment to a flat surface, the two-dimensional stress state inside the piezoceramic layer leads to an expected increase of around 51% for the longitudinal piezoelectric strain constant. To confirm this result, we reconsider the experimental results of the actuation moment measurement of the LIPCA and bare lead zirconium titanate.

Effects of thread interruptions on tool pins in friction stir welding of AA6061

DOE PAGES

Reza-E-Rabby, Md.; Tang, Wei; Reynolds, Anthony P.

2017-06-21

In this paper, effects of pin thread and thread interruptions (flats) on weld quality and process response parameters during friction stir welding (FSW) of 6061 aluminium alloy were quantified. Otherwise, identical smooth and threaded pins with zero to four flats were adopted for FSW. Weldability and process response variables were examined. Results showed that threads with flats significantly improved weld quality and reduced in-plane forces. A three-flat threaded pin led to production of defect-free welds under all examined welding conditions. Spectral analyses of in-plane forces and weld cross-sectional analysis were performed to establish correlation among pin flats, force dynamics andmore » defect formation. Finally, the lowest in-plane force spectra amplitudes were consistently observed for defect-free welds.« less

Effects of thread interruptions on tool pins in friction stir welding of AA6061

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

Reza-E-Rabby, Md.; Tang, Wei; Reynolds, Anthony P.

In this paper, effects of pin thread and thread interruptions (flats) on weld quality and process response parameters during friction stir welding (FSW) of 6061 aluminium alloy were quantified. Otherwise, identical smooth and threaded pins with zero to four flats were adopted for FSW. Weldability and process response variables were examined. Results showed that threads with flats significantly improved weld quality and reduced in-plane forces. A three-flat threaded pin led to production of defect-free welds under all examined welding conditions. Spectral analyses of in-plane forces and weld cross-sectional analysis were performed to establish correlation among pin flats, force dynamics andmore » defect formation. Finally, the lowest in-plane force spectra amplitudes were consistently observed for defect-free welds.« less

LAMOST Spectrograph Response Curves: Stability and Application to Flux Calibration

NASA Astrophysics Data System (ADS)

Du, Bing; Luo, A.-Li; Kong, Xiao; Zhang, Jian-Nan; Guo, Yan-Xin; Cook, Neil James; Hou, Wen; Yang, Hai-Feng; Li, Yin-Bi; Song, Yi-Han; Chen, Jian-Jun; Zuo, Fang; Wu, Ke-Fei; Wang, Meng-Xin; Wu, Yue; Wang, You-Fen; Zhao, Yong-Heng

2016-12-01

The task of flux calibration for Large sky Area Multi-Object Spectroscopic Telescope (LAMOST) spectra is difficult due to many factors, such as the lack of standard stars, flat-fielding for large field of view, and variation of reddening between different stars, especially at low Galactic latitudes. Poor selection, bad spectral quality, or extinction uncertainty of standard stars not only might induce errors to the calculated spectral response curve (SRC) but also might lead to failures in producing final 1D spectra. In this paper, we inspected spectra with Galactic latitude | b| ≥slant 60^\\circ and reliable stellar parameters, determined through the LAMOST Stellar Parameter Pipeline (LASP), to study the stability of the spectrograph. To guarantee that the selected stars had been observed by each fiber, we selected 37,931 high-quality exposures of 29,000 stars from LAMOST DR2, and more than seven exposures for each fiber. We calculated the SRCs for each fiber for each exposure and calculated the statistics of SRCs for spectrographs with both the fiber variations and time variations. The result shows that the average response curve of each spectrograph (henceforth ASPSRC) is relatively stable, with statistical errors ≤10%. From the comparison between each ASPSRC and the SRCs for the same spectrograph obtained by the 2D pipeline, we find that the ASPSRCs are good enough to use for the calibration. The ASPSRCs have been applied to spectra that were abandoned by the LAMOST 2D pipeline due to the lack of standard stars, increasing the number of LAMOST spectra by 52,181 in DR2. Comparing those same targets with the Sloan Digital Sky Survey (SDSS), the relative flux differences between SDSS spectra and LAMOST spectra with the ASPSRC method are less than 10%, which underlines that the ASPSRC method is feasible for LAMOST flux calibration.

Responses of estuarine circulation and salinity to the loss of intertidal flats – A modeling study

DOE PAGES

Yang, Zhaoqing; Wang, Taiping

2015-08-25

Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existingmore » baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.« less

Towards the modeling of nanoindentation of virus shells: Do substrate adhesion and geometry matter?

NASA Astrophysics Data System (ADS)

Bousquet, Arthur; Dragnea, Bogdan; Tayachi, Manel; Temam, Roger

2016-12-01

Soft nanoparticles adsorbing at surfaces undergo deformation and buildup of elastic strain as a consequence of interfacial adhesion of similar magnitude with constitutive interactions. An example is the adsorption of virus particles at surfaces, a phenomenon of central importance for experiments in virus nanoindentation and for understanding of virus entry. The influence of adhesion forces and substrate corrugation on the mechanical response to indentation has not been studied. This is somewhat surprising considering that many single-stranded RNA icosahedral viruses are organized by soft intermolecular interactions while relatively strong adhesion forces are required for virus immobilization for nanoindentation. This article presents numerical simulations via finite elements discretization investigating the deformation of a thick shell in the context of slow evolution linear elasticity and in presence of adhesion interactions with the substrate. We study the influence of the adhesion forces in the deformation of the virus model under axial compression on a flat substrate by comparing the force-displacement curves for a shell having elastic constants relevant to virus capsids with and without adhesion forces derived from the Lennard-Jones potential. Finally, we study the influence of the geometry of the substrate in two-dimensions by comparing deformation of the virus model adsorbed at the cusp between two cylinders with that on a flat surface.

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

Chen, Yun; Ratra, Bharat; Biesiada, Marek

We investigate two dark energy cosmological models (i.e., the ΛCDM and ϕ CDM models) with massive neutrinos assuming two different neutrino mass hierarchies in both the spatially flat and non-flat scenarios, where in the ϕ CDM model the scalar field possesses an inverse power-law potential, V ( ϕ ) ∝ ϕ {sup −} {sup α} ( α > 0). Cosmic microwave background data from Planck 2015, baryon acoustic oscillation data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the joint light-curve analysis compilation of SNe Ia apparent magnitude observations, and the Hubble Space Telescope H {sub 0} prior, are jointly employedmore » to constrain the model parameters. We first determine constraints assuming three species of degenerate massive neutrinos. In the spatially flat (non-flat) ΛCDM model, the sum of neutrino masses is bounded as Σ m {sub ν} < 0.165(0.299) eV at 95% confidence level (CL). Correspondingly, in the flat (non-flat) ϕ CDM model, we find Σ m {sub ν} < 0.164(0.301) eV at 95% CL. The inclusion of spatial curvature as a free parameter results in a significant broadening of confidence regions for Σ m {sub ν} and other parameters. In the scenario where the total neutrino mass is dominated by the heaviest neutrino mass eigenstate, we obtain similar conclusions to those obtained in the degenerate neutrino mass scenario. In addition, the results show that the bounds on Σ m {sub ν} based on two different neutrino mass hierarchies have insignificant differences in the spatially flat case for both the ΛCDM and ϕ CDM models; however, the corresponding differences are larger in the non-flat case.« less

Nondestructive measurement of tomato postharvest quality using a multichannel hyperspectral imaging probe

USDA-ARS?s Scientific Manuscript database

A multichannel hyperspectral imaging probe with 30 optic fibers covering the wavelength range of 550-1,650 nm and the light source-detector distances of 1.5-36 mm was recently developed for optical property measurement and quality evaluation of food products with flat or curved surface. This paper r...

Plasmon Surface Polariton Dispersion by Direct Optical Observation.

ERIC Educational Resources Information Center

Swalen, J. D.; And Others

1980-01-01

Describes several simple experiments that can be used to observe directly the dispersion curve of plasmon surface polaritons (PSP) on flat metal surfaces. A method is described of observing the increonental change in the wave vector of the PSP due to coatings that differ in thickness by a few nanometers. (Author/CS)

Structural Analysis of Pyrolytic Graphite Optics for the HiPEP Ion Thruster

NASA Technical Reports Server (NTRS)

Meckel, Nicole; Polaha, Jonathan; Juhlin, Nils

2006-01-01

The long lifetime requirements of interplanetary exploration missions is driving the need to develop long-life components for the electric propulsion thrusters that are being targeted for these missions. One of the primary life-limiting components of ion thrusters are the optics, which are continuously eroded during the operation of the thruster. Pyrolytic graphite optics are being considered for the High Power Electric Propulsion (HiPEP) ion thruster because of their very high resistance to erosion. This paper describes the structural analysis of the HiPEP pyrolytic graphite. A description of the development of the grid model, as well as the development of the effective properties and stress concentrations in the apertured area of the grids is included. An evaluation of the use of curved grids shows that the increased stiffness (compared to flat grids) prevents intergrid impact during launch, however, the residual stresses introduced by curving the grids pushes the resulting peak stresses beyond the critical stress. As a result, flat grids are recommended as the design solution. Thermally induced grid displacements during normal thruster operation are also presented.

High quality ion acceleration through the interaction of two matched counterpropagating transversely polarized Gaussian lasers with a flat foil target

NASA Astrophysics Data System (ADS)

Zhou, Weijun; Hong, Xueren; Xie, Baisong; Yang, Yang; Wang, Li; Tian, Jianmin; Tang, Rongan; Duan, Wenshan

2018-02-01

In order to generate high quality ion beams through a relatively uniform radiation pressure acceleration (RPA) of a common flat foil, a new scheme is proposed to overcome the curve of the target while being radiated by a single transversely Gaussian laser. In this scheme, two matched counterpropagating transversely Gaussian laser pulses, a main pulse and an auxiliary pulse, impinge on the foil target at the meantime. It is found that in the two-dimensional (2D) particle-in-cell (PIC) simulation, by the restraint of the auxiliary laser, the curve of the foil can be effectively suppressed. As a result, a high quality monoenergetic ion beam is generated through an efficient RPA of the foil target. For example, two counterpropagating transversely circularly polarized Gaussian lasers with normalized amplitudes a1=120 and a2=30 , respectively, impinge on the foil target at the meantime, a 1.3 GeV monoenergetic proton beam with high collimation is obtained finally. Furthermore, the effects on the ions acceleration with different parameters of the auxiliary laser are also investigated.

Influence of the geometry on magnetic interactions in a retina fixator based on a magnetoactive elastomer seal

NASA Astrophysics Data System (ADS)

Nadzharyan, T. A.; Makarova, L. A.; Kazimirova, E. G.; Perov, N. S.; Kramarenko, E. Yu

2018-03-01

We study the effects the geometric configuration has on magnetic interactions between a magnetoactive elastomer (MAE) sample and various systems of permanent magnets for problems with both flat and curved geometry. MAEs consist of a silicone polymer matrix and iron filler microparticles embedded in it. Permanent magnets are cylindrical neodymium magnets arranged in a line on a flat or curved solid surfaces. We use computer simulations, namely the finite element method, in order to study the interaction force and magnetic pressure in a system with an MAE sample and permanent magnets. The model is based on classical Maxwell magnetostatics and two factors taking into account field dependence of MAE’s magnetic properties and inhomogeneities caused by local demagnetization. We calculate magnetic pressure dependences on various geometric parameters of the system, namely, the diameter and the height of permanent magnets, the distance between the magnets and dimensions of MAE samples. This research aims to create a set of guidelines for choosing the geometric configuration of a retina fixator based on MAE seals to be used in eye surgery for retinal detachment treatment.

Colloids with high-definition surface structures

PubMed Central

Chen, Hsien-Yeh; Rouillard, Jean-Marie; Gulari, Erdogan; Lahann, Joerg

2007-01-01

Compared with the well equipped arsenal of surface modification methods for flat surfaces, techniques that are applicable to curved, colloidal surfaces are still in their infancy. This technological gap exists because spin-coating techniques used in traditional photolithographic processes are not applicable to the curved surfaces of spherical objects. By replacing spin-coated photoresist with a vapor-deposited, photodefinable polymer coating, we have now fabricated microstructured colloids with a wide range of surface patterns, including asymmetric and chiral surface structures, that so far were typically reserved for flat substrates. This high-throughput method can yield surface-structured colloidal particles at a rate of ≈107 to 108 particles per operator per day. Equipped with spatially defined binding pockets, microstructured colloids can engage in programmable interactions, which can lead to directed self-assembly. The ability to create a wide range of colloids with both simple and complex surface patterns may contribute to the genesis of previously unknown colloidal structures and may have important technological implications in a range of different applications, including photonic and phononic materials or chemical sensors. PMID:17592149

Ideas of Flat and Curved Space in History of Physics

NASA Astrophysics Data System (ADS)

Berezin, Alexander A.

2006-04-01

Since ``everything which is not prohibited is compulsory'' (assigned to Gell-Mann) we can postulate infinite flat Cartesian N-dimensional (N: any integer) space-time (ST) as embedding for any curved ST. Ergodicity raises quest of whether total number of inflationary and/or Everett bubbles (mini-verses) is finite, countably infinite (aleph-zero) or uncountably infinite (aleph-one). Are these bubbles form Gaussian distribution or form some non-random subsetting? Perhaps, communication between mini-verses (idea of D.Deutsch) can be facilitated by a kind of minimax non-local dynamics akin to Fermat principle? (Minimax Principle in Bubble Cosmology). Even such classical effects as magnetism and polarization have some non-local features. Can we go below the Planck length to perhaps Compton wavelength of our ``Hubble's bubble'' (h/Mc = 10 to minus 95 m, if M = 10 to 54 kg)? When talking about time loops and ergodicity (eternal return paradigm) is there some hysterisis in the way quantum states are accessed in ``forward'' or ``reverse'' direction? (reverse direction implies backward causality of J.Wheeler and/or Aristotelian final causation).

Landscape ecological security response to land use change in the tidal flat reclamation zone, China.

PubMed

Zhang, Runsen; Pu, Lijie; Li, Jianguo; Zhang, Jing; Xu, Yan

2016-01-01

As coastal development becomes a national strategy in Eastern China, land use and landscape patterns have been affected by reclamation projects. In this study, taking Rudong County, China as a typical area, we analyzed land use change and its landscape ecological security responses in the tidal flat reclamation zone. The results show that land use change in the tidal flat reclamation zone is characterized by the replacement of natural tidal flat with agricultural and construction land, which has also led to a big change in landscape patterns. We built a landscape ecological security evaluation system, which consists of landscape interference degree and landscape fragile degree, and then calculated the landscape ecological security change in the tidal flat reclamation zone from 1990 to 2008 to depict the life cycle in tidal flat reclamation. Landscape ecological security exhibited a W-shaped periodicity, including the juvenile stage, growth stage, and maturation stage. Life-cycle analysis demonstrates that 37 years is required for the land use system to transform from a natural ecosystem to an artificial ecosystem in the tidal flat reclamation zone.

Self-Interacting Dark Matter Can Explain Diverse Galactic Rotation Curves

NASA Astrophysics Data System (ADS)

Kamada, Ayuki; Kaplinghat, Manoj; Pace, Andrew B.; Yu, Hai-Bo

2017-09-01

The rotation curves of spiral galaxies exhibit a diversity that has been difficult to understand in the cold dark matter (CDM) paradigm. We show that the self-interacting dark matter (SIDM) model provides excellent fits to the rotation curves of a sample of galaxies with asymptotic velocities in the 25 - 300 km /s range that exemplify the full range of diversity. We assume only the halo concentration-mass relation predicted by the CDM model and a fixed value of the self-interaction cross section. In dark-matter-dominated galaxies, thermalization due to self-interactions creates large cores and reduces dark matter densities. In contrast, thermalization leads to denser and smaller cores in more luminous galaxies and naturally explains the flatness of rotation curves of the highly luminous galaxies at small radii. Our results demonstrate that the impact of the baryons on the SIDM halo profile and the scatter from the assembly history of halos as encoded in the concentration-mass relation can explain the diverse rotation curves of spiral galaxies.

Self-Interacting Dark Matter Can Explain Diverse Galactic Rotation Curves.

PubMed

Kamada, Ayuki; Kaplinghat, Manoj; Pace, Andrew B; Yu, Hai-Bo

2017-09-15

The rotation curves of spiral galaxies exhibit a diversity that has been difficult to understand in the cold dark matter (CDM) paradigm. We show that the self-interacting dark matter (SIDM) model provides excellent fits to the rotation curves of a sample of galaxies with asymptotic velocities in the 25-300  km/s range that exemplify the full range of diversity. We assume only the halo concentration-mass relation predicted by the CDM model and a fixed value of the self-interaction cross section. In dark-matter-dominated galaxies, thermalization due to self-interactions creates large cores and reduces dark matter densities. In contrast, thermalization leads to denser and smaller cores in more luminous galaxies and naturally explains the flatness of rotation curves of the highly luminous galaxies at small radii. Our results demonstrate that the impact of the baryons on the SIDM halo profile and the scatter from the assembly history of halos as encoded in the concentration-mass relation can explain the diverse rotation curves of spiral galaxies.

Assessment of GeB doped SiO2 optical fiber for the application of remote radiation sensing system

NASA Astrophysics Data System (ADS)

Alawiah, A.; Fadhli, M. M.; Bauk, S.; Abdul-Rashid, H. A.; Maah, M. J.

2013-12-01

The research and development efforts on the silica (SiO2) optical fiber for application in radiation sensing and other dosimetry field have become quite active. The widely used LiF based dosimeter (TLD) has shown a relatively low reproducibility and there is a time delay in dose assessment which loses its capability as direct real-time dose assessment dosimeters unlike diodes. The macroscopic size of the optical fiber generally does not allow direct in vivo dose sensing in the inner organ for radiotherapy and medical imaging. A flat optical fiber (FF) with nominal dimensions of (0.08 x10 x 10) mm3 of pure silica SiO2 and GeO2 with Boron doped silica fiber SiO2 was selected for this research. The Germanium was used a dopant to enhance the flat optical fiber to reach much higher responsiveness and dose sensitivity in high energy and high dose irradiation. Together with this combination, both TLD dimension and dose assessment issues was hoped to be overcome. The research conducted by comparing the response of pure silica SiO2 flat optical fiber with a GeO2 with Boron doped silica SiO2 flat optical fiber. The FF sample was annealed at 400°C for one hour before irradiated. Kinetic parameters and dosimetric glow curve of TL response and sensitivity were studied with respect to the electron beam of high dose of micro beam irradiation of 1.0 kGy, 5.0 kGy, 10.0 kGy, 50.0 kGy, 100.0 kGy, 500.0 kGy, and 1.0 MGy using Singapore Synchrotron Light Source's (PCIT) beamline. The PCIT operates at 500mA current with real time current range from 90-100mA, dose rate of 3.03 MGy/hour and energy at 8.9KeV. The source to Source Surface Distance (SSD) was at 6.0 cm, with a field size of 20mm × 8mm diameter of a half circle. The TL response was measured using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader was obtained to a preheat temperature of 150 °C for 5 s, the output signal being acquired at a temperature ramprate of 35 °Cs-1, acquisition time of 10 s and a maximum temperature of 400 °C each of the FF samples. All reading was taken under N2 gas flow, suppressing oxidation and potential triboluminescence. The proposed FF shows the excellent TL response for high energy irradiation and good reproducibility and exhibits a very low rate of fading and low variation background signal. From these results, the proposed FF can be used as a radiation dosimeter in remote radiation sensing and favorably compares with the widely used of LiF based dosimeter on common medical radiotherapy application.

Plastometric tests for plasticine as physical modelling material

NASA Astrophysics Data System (ADS)

Wójcik, Łukasz; Lis, Konrad; Pater, Zbigniew

2016-12-01

This paper presents results of plastometric tests for plasticine, used as material for physical modelling of metal forming processes. The test was conducted by means of compressing by flat dies of cylindrical billets at various temperatures. The aim of the conducted research was comparison of yield stresses and course of material flow curves. Tests were made for plasticine in black and white colour. On the basis of the obtained experimental results, the influence of forming parameters change on flow curves course was determined. Sensitivity of yield stresses change in function of material deformation, caused by forging temperature change within the scope of 0&C ÷ 20&C and differentiation of strain rate for ˙ɛ = 0.563; ˙ɛ = 0.0563; ˙ɛ = 0.0056s-1,was evaluated. Experimental curves obtained in compression test were described by constitutive equations. On the basis of the obtained results the function which most favourably describes flow curves was chosen.

Identification of geometric faces in hand-sketched 3D objects containing curved lines

NASA Astrophysics Data System (ADS)

El-Sayed, Ahmed M.; Wahdan, A. A.; Youssif, Aliaa A. A.

2017-07-01

The reconstruction of 3D objects from 2D line drawings is regarded as one of the key topics in the field of computer vision. The ongoing research is mainly focusing on the reconstruction of 3D objects that are mapped only from 2D straight lines, and that are symmetric in nature. Commonly, this approach only produces basic and simple shapes that are mostly flat or rather polygonized in nature, which is normally attributed to inability to handle curves. To overcome the above-mentioned limitations, a technique capable of handling non-symmetric drawings that encompass curves is considered. This paper discusses a novel technique that can be used to reconstruct 3D objects containing curved lines. In addition, it highlights an application that has been developed in accordance with the suggested technique that can convert a freehand sketch to a 3D shape using a mobile phone.

ESTIMATION OF EFFECTIVE SHEAR STRESS WORKING ON FLAT SHEET MEMBRANE USING FLUIDIZED MEDIA IN MBRs

NASA Astrophysics Data System (ADS)

Zaw, Hlwan Moe; Li, Tairi; Nagaoka, Hiroshi; Mishima, Iori

This study was aimed at estimating effective shear stress working on flat sheet membrane by the addition of fluidized media in MBRs. In both of laboratory-scale aeration tanks with and without fluidized media, shear stress variations on membrane surface and water phase velocity variations were measured and MBR operation was conducted. For the evaluation of the effective shear stress working on membrane surface to mitigate membrane surface, simulation of trans-membrane pressure increase was conducted. It was shown that the time-averaged absolute value of shear stress was smaller in the reactor with fluidized media than without fluidized media. However, due to strong turbulence in the reactor with fluidized media caused by interaction between water-phase and media and also due to the direct interaction between membrane surface and fluidized media, standard deviation of shear stress on membrane surface was larger in the reactor with fluidized media than without media. Histograms of shear stress variation data were fitted well to normal distribution curves and mean plus three times of standard deviation was defined to be a maximum shear stress value. By applying the defined maximum shear stress to a membrane fouling model, trans-membrane pressure curve in the MBR experiment was simulated well by the fouling model indicting that the maximum shear stress, not time-averaged shear stress, can be regarded as an effective shear stress to prevent membrane fouling in submerged flat-sheet MBRs.

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x-ray beam

PubMed Central

Zhang, Rongxiao; Glaser, Adam K.; Gladstone, David J.; Fox, Colleen J.; Pogue, Brian W.

2013-01-01

Purpose: Čerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the Čerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical Čerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams. Methods: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. Čerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on Čerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50–200 × 200 mm2), incident angles (0°–70°) and imaging regions were all varied. Results: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their Čerenkov emission is proportional to dose. Directly simulated local intensity of Čerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Čerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom. Conclusions: This study indicates that Čerenkov emission imaging might provide a valuable way to superficial dosimetry imaging in real time for external beam radiotherapy with megavoltage x-ray beams. PMID:24089916

High frequency wide-band transformer uses coax to achieve high turn ratio and flat response

NASA Technical Reports Server (NTRS)

De Parry, T.

1966-01-01

Center-tap push-pull transformer with toroidal core helically wound with a single coaxial cable creates a high frequency wideband transformer. This transformer has a high-turn ratio, a high coupling coefficient, and a flat broadband response.

Heat transfer through turbulent boundary layers - The effects of introduction of and recovery from convex curvature

NASA Technical Reports Server (NTRS)

Simon, T. W.; Moffat, R. J.

1979-01-01

Measurements have been made of the heat transfer through a turbulent boundary layer on a convexly curved isothermal wall and on a flat plate following the curved section. Data were taken for one free-stream velocity and two different ratios of boundary layer thickness to radius of curvature delta/R = 0.051 and delta/R = 0.077. Only small differences were observed in the distribution of heat transfer rates for the two boundary layer thicknesses tested, although differences were noted in the temperature distributions within the boundary layer

A curved surface micro-moiré method and its application in evaluating curved surface residual stress

NASA Astrophysics Data System (ADS)

Zhang, Hongye; Wu, Chenlong; Liu, Zhanwei; Xie, Huimin

2014-09-01

The moiré method is typically applied to the measurement of deformations of a flat surface while, for a curved surface, this method is rarely used other than for projection moiré or moiré interferometry. Here, a novel colour charge-coupled device (CCD) micro-moiré method has been developed, based on which a curved surface micro-moiré (CSMM) method is proposed with a colour CCD and optical microscope (OM). In the CSMM method, no additional reference grating is needed as a Bayer colour filter array (CFA) installed on the OM in front of the colour CCD image sensor performs this role. Micro-moiré fringes with high contrast are directly observed with the OM through the Bayer CFA under the special condition of observing a curved specimen grating. The principle of the CSMM method based on a colour CCD micro-moiré method and its application range and error analysis are all described in detail. In an experiment, the curved surface residual stress near a welded seam on a stainless steel tube was investigated using the CSMM method.

A mechanism to explain the spectrum of Hessdalen Lights phenomenon

NASA Astrophysics Data System (ADS)

Paiva, G. S.; Taft, C. A.

2012-07-01

In this work, we present a model to explain the apparently contradictory spectrum observed in Hessdalen Lights (HL) phenomenon. According to our model, its nearly flat spectrum on the top with steep sides is due to the effect of optical thickness on the bremsstrahlung spectrum. At low frequencies self-absorption modifies the spectrum to follow the Rayleigh-Jeans part of the blackbody curve. This spectrum is typical of dense ionized gas. Additionally, spectrum produced in the thermal bremsstrahlung process is flat up to a cutoff frequency, ν cut, and falls off exponentially at higher frequencies. This sequence of events forms the typical spectrum of HL phenomenon when the atmosphere is clear, with no fog.

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

Carey, H.V.; Tien, X.Y.; Wallace, L.J.

Muscarinic receptors involved in the secretory response evoked by electrical stimulation of submucosal neutrons were investigated in muscle-stripped flat sheets of guinea pig ileum set up in flux chambers. Neural stimulation produced a biphasic increase in short-circuit current due to active chloride secretion. Atropine and 4-diphenylacetoxy-N-methylpiperadine methiodide (4-DAMP) (10/sup -7/ M) were more potent inhibitors of the cholinergic phase of the response than was pirenzepine. Dose-dependent increases in base-line short-circuit current were evoked by carbachol and bethanechol; 4-hydroxy-2-butynyl trimethylammonium chloride (McN A343) produced a much smaller effect. Tetrodotoxin abolished the effects of McN A343 but did not alter the responsesmore » of carbachol and bethanechol. McN A343 significantly reduced the cholinergic phase of the neurally evoked response and caused a rightward shift of the carbachol dose-response curve. All muscarinic compounds inhibited (/sup 3/H)quinuclidinyl benzilate binding to membranes from muscosal scrapings, with a rank order of potency of 4-DAMP > pirenzepine > McN A343 > carbachol > bethanechol. These results suggest that acetylcholine released from submucosal neurons mediates chloride secretion by interacting with muscarinic cholinergic receptors that display a high binding affinity for 4-DAMP. Activation of neural muscarinic receptors makes a relatively small contribution to the overall secretory response.« less

X-Ray and Energy-Loss Spectroscopy | Materials Science | NREL

Science.gov Websites

, we see sharp peaks corresponding to the characteristic X-rays emitted by the atoms of the different ionization edges at high-energy losses, whose onset position is characteristic of the different types of flat c-Si/a-Si interface (see next). A graph with red, green, and blue curves shows different

Buckling analysis for anisotropic laminated plates under combined inplane loads

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Tamekuni, M.; Baker, L. L.

1974-01-01

The buckling analysis presented considers rectangular flat or curved general laminates subjected to combined inplane normal and shear loads. Linear theory is used in the analysis. All prebuckling deformations and any initial imperfections are ignored. The analysis method can be readily extended to longitudinally stiffened structures subjected to combined inplane normal and shear loads.

Lithium Ion Vehicle Start Batteries - Power for the Future

DTIC Science & Technology

2011-08-09

results in less power being available as the battery state of charge (and voltage) is decreased. Lithium Nanophosphate ( LiFePO4 ) exhibits this to...a much lesser extent. As shown in figure 1, the voltage v. SOC curve for LiFePO4 is nearly flat throughout most of its state of charge.[1] This

Determining Directional Emittance With An Infrared Imager

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E., Jr.; Puram, Chith K.

1994-01-01

Directional emittances of flat specimen of smooth-surfaced, electrically nonconductive material at various temperatures computed from measurements taken by infrared radiometric imager operating in conjunction with simple ancillary equipment. Directional emittances useful in extracting detailed variations of surface temperatures from infrared images of curved, complexly shaped other specimens of same material. Advantages: simplification of measurement procedure and reduction of cost.

4D Sommerfeld quantization of the complex extended charge

NASA Astrophysics Data System (ADS)

Bulyzhenkov, Igor E.

2017-12-01

Gravitational fields and accelerations cannot change quantized magnetic flux in closed line contours due to flat 3D section of curved 4D space-time-matter. The relativistic Bohr-Sommerfeld quantization of the imaginary charge reveals an electric analog of the Compton length, which can introduce quantitatively the fine structure constant and the Plank length.

Experimental data and model for the turbulent boundary layer on a convex, curved surface

NASA Technical Reports Server (NTRS)

Gillis, J. C.; Johnson, J. P.; Moffat, R. J.; Kays, W. M.

1981-01-01

Experiments were performed to determine how boundary layer turbulence is affected by strong convex curvature. The data gathered on the behavior of the Reynolds stress suggested the formulation of a simple turbulence model. Data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero. Two experiments were performed at delta/R approximately 0.10, and one at weaker curvature with delta/R approximately 0.05. Results show that after a sudden introduction of curvature the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. When the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions. A simple turbulence model, which was based on the theory that the Prandtl mixing length in the outer layer should scale on the velocity gradient layer, was shown to account for the slow recovery.

Effects of the foil flatness on the stress-strain characteristics of U10Mo alloy based monolithic mini-plates

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

Hakan Ozaltun; Pavel Medvedev

The effects of the foil flatness on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation were studied. Monolithic plate-type fuels are a new fuel form being developed for research and test reactors to achieve higher uranium densities. This concept facilitates the use of low-enriched uranium fuel in the reactor. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. To evaluate the effects of the foil flatness on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate frommore » RERTR-12 experiments (Plate L1P756) was considered. Both fabrication and irradiation processes of the plate were simulated by using actual irradiation parameters. The simulations were repeated for various foil curvatures to observe the effects of the foil flatness on the peak stress and strain magnitudes of the fuel elements. Results of fabrication simulations revealed that the flatness of the foil does not have a considerable impact on the post fabrication stress-strain fields. Furthermore, the irradiation simulations indicated that any post-fabrication stresses in the foil would be relieved relatively fast in the reactor. While, the perfectly flat foil provided the slightly better mechanical performance, overall difference between the flat-foil case and curved-foil case was not significant. Even though the peak stresses are less affected, the foil curvature has several implications on the strain magnitudes in the cladding. It was observed that with an increasing foil curvature, there is a slight increase in the cladding strains.« less

Model Prediction Results for 2007 Ultrasonic Benchmark Problems

NASA Astrophysics Data System (ADS)

Kim, Hak-Joon; Song, Sung-Jin

2008-02-01

The World Federation of NDE Centers (WFNDEC) has addressed two types of problems for the 2007 ultrasonic benchmark problems: prediction of side-drilled hole responses with 45° and 60° refracted shear waves, and effects of surface curvatures on the ultrasonic responses of flat-bottomed hole. To solve this year's ultrasonic benchmark problems, we applied multi-Gaussian beam models for calculation of ultrasonic beam fields and the Kirchhoff approximation and the separation of variables method for calculation of far-field scattering amplitudes of flat-bottomed holes and side-drilled holes respectively In this paper, we present comparison results of model predictions to experiments for side-drilled holes and discuss effect of interface curvatures on ultrasonic responses by comparison of peak-to-peak amplitudes of flat-bottomed hole responses with different sizes and interface curvatures.

Constraining the Physical Properties of Meteor Stream Particles by Light Curve Shapes Using the Virtual Meteor Observatory

NASA Technical Reports Server (NTRS)

Koschny, D.; Gritsevich, M.; Barentsen, G.

2011-01-01

Different authors have produced models for the physical properties of meteoroids based on the shape of a meteor's light curve, typically from short observing campaigns. We here analyze the height profiles and light curves of approx.200 double-station meteors from the Leonids and Perseids using data from the Virtual Meteor Observatory, to demonstrate that with this web-based meteor database it is possible to analyze very large datasets from different authors in a consistent way. We compute the average heights for begin point, maximum luminosity, and end heights for Perseids and Leonids. We also compute the skew of the light curve, usually called the F-parameter. The results compare well with other author's data. We display the average light curve in a novel way to assess the light curve shape in addition to using the F-parameter. While the Perseids show a peaked light curve, the average Leonid light curve has a more flat peak. This indicates that the particle distribution of Leonid meteors can be described by a Gaussian distribution; the Perseids can be described with a power law. The skew for Leonids is smaller than for Perseids, indicating that the Leonids are more fragile than the Perseids.

Nonflat equilibrium liquid shapes on flat surfaces.

PubMed

Starov, Victor M

2004-01-15

The hydrostatic pressure in thin liquid layers differs from the pressure in the ambient air. This difference is caused by the actions of surface forces and capillary pressure. The manifestation of the surface force action is the disjoining pressure, which has a very special S-shaped form in the case of partial wetting (aqueous thin films and thin films of aqueous electrolyte and surfactant solutions, both free films and films on solid substrates). In thin flat liquid films the disjoining pressure acts alone and determines their thickness. However, if the film surface is curved then both the disjoining and the capillary pressures act simultaneously. In the case of partial wetting their simultaneous action results in the existence of nonflat equilibrium liquid shapes. It is shown that in the case of S-shaped disjoining pressure isotherm microdrops, microdepressions, and equilibrium periodic films exist on flat solid substrates. Criteria are found for both the existence and the stability of these nonflat equilibrium liquid shapes. It is shown that a transition from thick films to thinner films can go via intermediate nonflat states, microdepressions and periodic films, which both can be more stable than flat films within some range of hydrostatic pressure. Experimental investigations of shapes of the predicted nonflat layers can open new possibilities of determination of disjoining pressure in the range of thickness in which flat films are unstable.

Convection induced by thermal gradients on thin reaction fronts

NASA Astrophysics Data System (ADS)

Ruelas Paredes, David R. A.; Vasquez, Desiderio A.

2017-09-01

We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients. If the effects of these gradients oppose each other, we observe a range of wavelengths that make the flat front unstable. Numerical solutions of the nonlinear model show curved fronts of steady shape with convection propagating faster than flat fronts. Exothermic fronts increase the temperature of the fluid as they propagate through the domain. This increment in temperature decreases with increasing speed.

The Role of Interface Shape on the Impact Characteristics and Cranial Fracture Patterns Using the Immature Porcine Head Model,.

PubMed

Vaughan, Patrick E; Vogelsberg, Caitlin C M; Vollner, Jennifer M; Fenton, Todd W; Haut, Roger C

2016-09-01

The forensic literature suggests that when adolescents fall onto edged and pointed surfaces, depressed fractures can occur at low energy levels. This study documents impact biomechanics and fracture characteristics of infant porcine skulls dropped onto flat, curved, edged, and focal surfaces. Results showed that the energy needed for fracture initiation was nearly four times higher against a flat surface than against the other surfaces. While characteristic measures of fracture such as number and length of fractures did not vary with impact surface shape, the fracture patterns did depend on impact surface shape. While experimental impacts against the flat surface produced linear fractures initiating at sutural boundaries peripheral to the point of impact (POI), more focal impacts produced depressed fractures initiating at the POI. The study supported case-based forensic literature suggesting cranial fracture patterns depend on impact surface shape and that fracture initiation energy is lower for more focal impacts. © 2016 American Academy of Forensic Sciences.

A simple method for estimating frequency response corrections for eddy covariance systems

Treesearch

W. J. Massman

2000-01-01

A simple analytical formula is developed for estimating the frequency attenuation of eddy covariance fluxes due to sensor response, path-length averaging, sensor separation, signal processing, and flux averaging periods. Although it is an approximation based on flat terrain cospectra, this analytical formula should have broader applicability than just flat-terrain...

Development of a low cost high precision three-layer 3D artificial compound eye.

PubMed

Zhang, Hao; Li, Lei; McCray, David L; Scheiding, Sebastian; Naples, Neil J; Gebhardt, Andreas; Risse, Stefan; Eberhardt, Ramona; Tünnermann, Andreas; Yi, Allen Y

2013-09-23

Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 μm; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using microinjection molding process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87°. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously.

Genome-wide transcriptional responses of Alteromonas naphthalenivorans SN2 to contaminated seawater and marine tidal flat sediment.

PubMed

Jin, Hyun Mi; Jeong, Hye Im; Kim, Kyung Hyun; Hahn, Yoonsoo; Madsen, Eugene L; Jeon, Che Ok

2016-02-18

A genome-wide transcriptional analysis of Alteromonas naphthalenivorans SN2 was performed to investigate its ecophysiological behavior in contaminated tidal flats and seawater. The experimental design mimicked these habitats that either added naphthalene or pyruvate; tidal flat-naphthalene (TF-N), tidal flat-pyruvate (TF-P), seawater-naphthalene (SW-N), and seawater-pyruvate (SW-P). The transcriptional profiles clustered by habitat (TF-N/TF-P and SW-N/SW-P), rather than carbon source, suggesting that the former may exert a greater influence on genome-wide expression in strain SN2 than the latter. Metabolic mapping of cDNA reads from strain SN2 based on KEGG pathway showed that metabolic and regulatory genes associated with energy metabolism, translation, and cell motility were highly expressed in all four test conditions, probably highlighting the copiotrophic properties of strain SN2 as an opportunistic marine r-strategist. Differential gene expression analysis revealed that strain SN2 displayed specific cellular responses to environmental variables (tidal flat, seawater, naphthalene, and pyruvate) and exhibited certain ecological fitness traits -- its notable PAH degradation capability in seasonally cold tidal flat might be reflected in elevated expression of stress response and chaperone proteins, while fast growth in nitrogen-deficient and aerobic seawater probably correlated with high expression of glutamine synthetase, enzymes utilizing nitrite/nitrate, and those involved in the removal of reactive oxygen species.

Genome-wide transcriptional responses of Alteromonas naphthalenivorans SN2 to contaminated seawater and marine tidal flat sediment

PubMed Central

Jin, Hyun Mi; Jeong, Hye Im; Kim, Kyung Hyun; Hahn, Yoonsoo; Madsen, Eugene L.; Jeon, Che Ok

2016-01-01

A genome-wide transcriptional analysis of Alteromonas naphthalenivorans SN2 was performed to investigate its ecophysiological behavior in contaminated tidal flats and seawater. The experimental design mimicked these habitats that either added naphthalene or pyruvate; tidal flat-naphthalene (TF-N), tidal flat-pyruvate (TF-P), seawater-naphthalene (SW-N), and seawater-pyruvate (SW-P). The transcriptional profiles clustered by habitat (TF-N/TF-P and SW-N/SW-P), rather than carbon source, suggesting that the former may exert a greater influence on genome-wide expression in strain SN2 than the latter. Metabolic mapping of cDNA reads from strain SN2 based on KEGG pathway showed that metabolic and regulatory genes associated with energy metabolism, translation, and cell motility were highly expressed in all four test conditions, probably highlighting the copiotrophic properties of strain SN2 as an opportunistic marine r-strategist. Differential gene expression analysis revealed that strain SN2 displayed specific cellular responses to environmental variables (tidal flat, seawater, naphthalene, and pyruvate) and exhibited certain ecological fitness traits –– its notable PAH degradation capability in seasonally cold tidal flat might be reflected in elevated expression of stress response and chaperone proteins, while fast growth in nitrogen-deficient and aerobic seawater probably correlated with high expression of glutamine synthetase, enzymes utilizing nitrite/nitrate, and those involved in the removal of reactive oxygen species. PMID:26887987

AGN Space Telescope and Optical Reverberation Mapping Project V. Continuum Time Delays and Disk Inclinations

NASA Astrophysics Data System (ADS)

Starkey, David; Agn Storm Team

2015-01-01

Reverberation mapping is a proven method for obtaining black hole mass estimates and constraining the size of the BLR. We analyze multi-wavelength continuum light curves from the 7 month AGN STORM monitoring of NGC 5548 and use reverberation mapping to model the accretion disk time delays. The model fits the light curves at UV to IR wavelengths assuming reprocessing on a flat, steady-state blackbody accretion disk. We calculate the inclination-dependent transfer function and investigate to what extent our model can determine the disk inclination, black hole MMdot and power law index of the disc temperature-radius relation.

An experimental study of the nonlinear dynamic phenomenon known as wing rock

NASA Technical Reports Server (NTRS)

Arena, A. S., Jr.; Nelson, R. C.; Schiff, L. B.

1990-01-01

An experimental investigation into the physical phenomena associated with limit cycle wing rock on slender delta wings has been conducted. The model used was a slender flat plate delta wing with 80-deg leading edge sweep. The investigation concentrated on three main areas: motion characteristics obtained from time history plots, static and dynamic flow visualization of vortex position, and static and dynamic flow visualization of vortex breakdown. The flow visualization studies are correlated with model motion to determine the relationship between vortex position and vortex breakdown with the dynamic rolling moments. Dynamic roll moment coefficient curves reveal rate-dependent hysteresis, which drives the motion. Vortex position correlated with time and model motion show a time lag in the normal position of the upward moving wing vortex. This time lag may be the mechanism responsible for the hysteresis. Vortex breakdown is shown to have a damping effect on the motion.

Influence of Nose Shape and L/D Ratio on Projectile Penetration in Frozen Soil

DTIC Science & Technology

1980-04-01

unexpected when soil properties are considered. Decreasing temperature below -10%C by 100 or 150 has little effect on the constitutive properties of... Effect ....... ............ ............. 10 L/D Influence .......................... .10 Target Temperature Effects ...10. Effect of L/D ratio and mass on flat nose pro- jectile penetration (the solid lines are least square curve fits to the data

Geometrically Nonlinear Analysis of Shell Structures Using Flat DKT Shell Elements.

DTIC Science & Technology

1985-11-22

In general 1r is a curved surface and the exact expressions of f1 e I are not simpler than f e 1. In fact they are theorically identical when the...1982. [23] Zienkiewicz, 0. C., The Finite Element Method (3rd Edition), McGraw-Hill, 1977. [24] Bergan, P. G., Holand , I., Soreide, T. H., "Use of

Binding the Mammalian High Mobility Group Protein AT-hook 2 to AT-Rich Deoxyoligonucleotides: Enthalpy-Entropy Compensation

PubMed Central

Joynt, Suzanne; Morillo, Victor; Leng, Fenfei

2009-01-01

HMGA2 is a DNA minor-groove binding protein. We previously demonstrated that HMGA2 binds to AT-rich DNA with very high binding affinity where the binding of HMGA2 to poly(dA-dT)2 is enthalpy-driven and to poly(dA)poly(dT) is entropy-driven. This is a typical example of enthalpy-entropy compensation. To further study enthalpy-entropy compensation of HMGA2, we used isothermal-titration-calorimetry to examine the interactions of HMGA2 with two AT-rich DNA hairpins: 5′-CCAAAAAAAAAAAAAAAGCCCCCGCTTTTTTTTTTTTTTTGG-3′ (FL-AT-1) and 5′-CCATATATATATATATAGCCCCCGCTATATATATATATATGG-3′ (FL-AT-2). Surprisingly, we observed an atypical isothermal-titration-calorimetry-binding curve at low-salt aqueous solutions whereby the apparent binding-enthalpy decreased dramatically as the titration approached the end. This unusual behavior can be attributed to the DNA-annealing coupled to the ligand DNA-binding and is eliminated by increasing the salt concentration to ∼200 mM. At this condition, HMGA2 binding to FL-AT-1 is entropy-driven and to FL-AT-2 is enthalpy-driven. Interestingly, the DNA-binding free energies for HMGA2 binding to both hairpins are almost temperature independent; however, the enthalpy-entropy changes are dependent on temperature, which is another aspect of enthalpy-entropy compensation. The heat capacity change for HMGA2 binding to FL-AT-1 and FL-AT-2 are almost identical, indicating that the solvent displacement and charge-charge interaction in the coupled folding/binding processes for both binding reactions are similar. PMID:19450485

Cell Geometry Guides the Dynamic Targeting of Apoplastic GPI-Linked Lipid Transfer Protein to Cell Wall Elements and Cell Borders in Arabidopsis thaliana

PubMed Central

Wasteneys, Geoffrey

2013-01-01

During cellular morphogenesis, changes in cell shape and cell junction topology are fundamental to normal tissue and organ development. Here we show that apoplastic Glycophosphatidylinositol (GPI)-anchored Lipid Transfer Protein (LTPG) is excluded from cell junctions and flat wall regions, and passively accumulates around their borders in the epidermal cells of Arabidopsis thaliana. Beginning with intense accumulation beneath highly curved cell junction borders, this enrichment is gradually lost as cells become more bulbous during their differentiation. In fully mature epidermal cells, YFP-LTPG often shows a fibrous cellulose microfibril-like pattern within the bulging outer faces. Physical contact between a flat glass surface and bulbous cell surface induces rapid and reversible evacuation from contact sites and accumulation to the curved wall regions surrounding the contact borders. Thus, LTPG distribution is dynamic, responding to changes in cell shape and wall curvature during cell growth and differentiation. We hypothesize that this geometry-based mechanism guides wax-carrying LTPG to functional sites, where it may act to “seal” the vulnerable border surrounding cell-cell junctions and assist in cell wall fortification and cuticular wax deposition. PMID:24260561

Structures in general relativity

NASA Astrophysics Data System (ADS)

Tieu, Steven

Structures within general relativity are examined. The differences between man-made structures and those predicted by the Einstein differential equations are very subtle. Exotic structures such as the Godel Universe and the Gott cosmic string are examined with emphasis on closed time-like curves. Newtonian models are seen to also have an exotic aspect in that a vast halo consisting of unknown matter dominates the galaxy. We introduce a model for galaxies based on a general relativity framework with the goal of excluding such artifacts from the system while describing the flat-rotation curves. Structures within this model were speculated to be exotic but after close scrutiny, their nature is shown to be benign. Numerical approaches are applied to model four galaxies: The Milky Way, NGC 3031, NGC 3198 and NGC 7331. Density and mass are deduced from these models and compared to the Newtonian models. Within the visible/HI region, there is 30% reduction in total mass. Extending the model to 10 times beyond the HI region using various fall-off scenerios, it is shown that there is only modest increase of the accumulated mass. In comparison to the Newtonian approach to galactic dynamics, the massive halos are not required to account for the flat velocity profiles.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry

NASA Astrophysics Data System (ADS)

Ghomeishi, Mostafa; Mahdiraji, G. Amouzad; Adikan, F. R. Mahamd; Ung, N. M.; Bradley, D. A.

2015-08-01

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2nd order kinetics.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry.

PubMed

Ghomeishi, Mostafa; Mahdiraji, G Amouzad; Adikan, F R Mahamd; Ung, N M; Bradley, D A

2015-08-28

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2(nd) order kinetics.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry

PubMed Central

Ghomeishi, Mostafa; Mahdiraji, G. Amouzad; Adikan, F. R. Mahamd; Ung, N. M.; Bradley, D. A.

2015-01-01

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2nd order kinetics. PMID:26314683

Sulcal set optimization for cortical surface registration.

PubMed

Joshi, Anand A; Pantazis, Dimitrios; Li, Quanzheng; Damasio, Hanna; Shattuck, David W; Toga, Arthur W; Leahy, Richard M

2010-04-15

Flat mapping based cortical surface registration constrained by manually traced sulcal curves has been widely used for inter subject comparisons of neuroanatomical data. Even for an experienced neuroanatomist, manual sulcal tracing can be quite time consuming, with the cost increasing with the number of sulcal curves used for registration. We present a method for estimation of an optimal subset of size N(C) from N possible candidate sulcal curves that minimizes a mean squared error metric over all combinations of N(C) curves. The resulting procedure allows us to estimate a subset with a reduced number of curves to be traced as part of the registration procedure leading to optimal use of manual labeling effort for registration. To minimize the error metric we analyze the correlation structure of the errors in the sulcal curves by modeling them as a multivariate Gaussian distribution. For a given subset of sulci used as constraints in surface registration, the proposed model estimates registration error based on the correlation structure of the sulcal errors. The optimal subset of constraint curves consists of the N(C) sulci that jointly minimize the estimated error variance for the subset of unconstrained curves conditioned on the N(C) constraint curves. The optimal subsets of sulci are presented and the estimated and actual registration errors for these subsets are computed. Copyright 2009 Elsevier Inc. All rights reserved.

Design and analysis of grid stiffened fuselage panel with curved stiffeners

NASA Astrophysics Data System (ADS)

Hemanth, Bharath; Babu, N. C. Mahendra; Shivakumar, H. G.; Srikari, S.

2018-04-01

Designing and analyzing grid stiffened panel to understand the effect of stiffeners on stiffness of the panel is crucial in designing grid stiffened cylinder for fuselage application. Traditionally only straight stiffeners were used due to limited manufacturing capabilities and in recent years GSS with curved stiffeners have become a reality. The present work is on flat grid stiffened panel and the focus is to realize the change in stiffness by converting straight stiffeners in an isogrid panel to curved stiffeners. An isogrid stiffened panel is identified from literature for which experimental results were available and was considered for replacing straight stiffeners with curved stiffeners. Defining and designing the curve for curved stiffeners which can be used to replace straight stiffeners in isogrid pattern is crucial. FE model of the grid stiffened fuselage panel with isogrid pattern identified from the literature for which experimental data was available was developed and evaluated for stiffness. For the same panel, curved grid pattern to enhance stiffness of the panel was designed following existing design procedure. FE model of the grid stiffened fuselage panel with designed curved stiffeners was developed and evaluated for stiffness. It is established that the stiffness of panel can be increased by minimum of 2.82% to maximum of 11.93% by using curved stiffeners of particular curvature as a replacement for straight stiffeners in isogrid pattern with a slight mass penalty.

Micro-cone targets for producing high energy and low divergence particle beams

DOEpatents

Le Galloudec, Nathalie

2013-09-10

The present invention relates to micro-cone targets for producing high energy and low divergence particle beams. In one embodiment, the micro-cone target includes a substantially cone-shaped body including an outer surface, an inner surface, a generally flat and round, open-ended base, and a tip defining an apex. The cone-shaped body tapers along its length from the generally flat and round, open-ended base to the tip defining the apex. In addition, the outer surface and the inner surface connect the base to the tip, and the tip curves inwardly to define an outer surface that is concave, which is bounded by a rim formed at a juncture where the outer surface meets the tip.

The Tully-Fisher relation for flat galaxies

NASA Astrophysics Data System (ADS)

Makarov, D. I.; Zaitseva, N. A.; Bizyaev, D. V.

2018-06-01

We construct a multiparametric Tully-Fisher (TF) relation for a large sample of edge-on galaxies from the Revised Flat Galaxy Catalog using H I data from the EDD database and parameters from the EGIS catalog. We incorporate a variety of additional parameters including structural parameters of edge-on galaxies in different bandpasses. Besides the rotation curve maximum, only the H I-to-optical luminosity ratio and optical colours play a statistically significant role in the multiparametric TF relation. We are able to decrease the standard deviation of the multiparametric TF relation down to 0.32 mag, which is at the level of best modern samples of galaxies used for studies of the matter motion in the Universe via the TF-relation.

Correlation of heat transfer coefficient in quenching process using ABAQUS

NASA Astrophysics Data System (ADS)

Davare, Sandeep Kedarnath; Balachandran, G.; Singh, R. K. P.

2018-04-01

During the heat treatment by quenching in a liquid medium the convective heat transfer coefficient plays a crucial role in the extraction of heat. The heat extraction ultimately influences the cooling rate and hence the hardness and mechanical properties. A Finite Element analysis of quenching a simple flat copper sample with different orientation of sample and with different quenchant temperatures were carried out to check and verify the results obtained from the experiments. The heat transfer coefficient (HTC) was calculated from temperature history in a simple flat copper disc sample experimentally. This HTC data was further used as input to simulation software and the cooling curves were back calculated. The results obtained from software and using experimentation shows nearly consistent values.

Fabrication and Characterization of Flexible Electrowetting on Dielectrics (EWOD) Microlens

PubMed Central

Li, Chenhui; Jiang, Hongrui

2014-01-01

We present a flexible variable-focus converging microlens actuated by electrowetting on dielectric (EWOD). The microlens is made of two immiscible liquids and a soft polymer, polydimethylsiloxane (PDMS). Parylene intermediate layer is used to produce robust flexible electrode on PDMS. A low-temperature PDMS-compatible fabrication process has been developed to reduce the stress on the lens structure. The lens has been demonstrated to be able to conform to curved surfaces smoothly. The focal length of the microlens is 29–38 mm on a flat surface, and 31–41 mm on a curved surface, varying with the voltage applied. The resolving power of the microlens is 25.39 line pairs per mm by a 1951 United States Air Force (USAF) resolution chart and the lens aberrations are measured by a Shack-Hartmann wavefront sensor. The focal length behavior on a curved surface is discussed and for the current lens demonstrated the focal length is slightly longer on the curved surface as a result of the effect of the curved PDMS substrate. PMID:25360324

Dose-dependent intracellular reactive oxygen and nitrogen species (ROS/RNS) production from particulate matter exposure: comparison to oxidative potential and chemical composition

NASA Astrophysics Data System (ADS)

Tuet, Wing Y.; Fok, Shierly; Verma, Vishal; Tagle Rodriguez, Marlen S.; Grosberg, Anna; Champion, Julie A.; Ng, Nga L.

2016-11-01

Elevated particulate matter (PM) concentrations have been associated with cardiopulmonary risks. In this study, alveolar macrophages and ventricular myocytes were exposed to PM extracts from 104 ambient filters collected in multiple rural and urban sites in the greater Atlanta area. PM-induced reactive oxygen/nitrogen species (ROS/RNS) were measured to investigate the effect of chemical composition and determine whether chemical assays are representative of cellular responses. For summer samples, the area under the ROS/RNS dose-response curve per volume of air (AUCvolume) was significantly correlated with dithiothreitol (DTT) activity, water-soluble organic carbon (WSOC), brown carbon, titanium, and iron, while a relatively flat response was observed for winter samples. EC50 was also correlated with max response for all filters investigated, which suggests that certain PM constituents may be involved in cellular protective pathways. Although few metal correlations were observed, exposure to laboratory-prepared metal solutions induced ROS/RNS production, indicating that a lack of correlation does not necessarily translate to a lack of response. Collectively, these results suggest that complex interactions may occur between PM species. Furthermore, the strong correlation between organic species and ROS/RNS response highlights a need to understand the contribution of organic aerosols, especially photochemically driven secondary organic aerosols (SOA), to PM-induced health effects.

Materials Database Development for Ballistic Impact Modeling

NASA Technical Reports Server (NTRS)

Pereira, J. Michael

2007-01-01

A set of experimental data is being generated under the Fundamental Aeronautics Program Supersonics project to help create and validate accurate computational impact models of jet engine impact events. The data generated will include material property data generated at a range of different strain rates, from 1x10(exp -4)/sec to 5x10(exp 4)/sec, over a range of temperatures. In addition, carefully instrumented ballistic impact tests will be conducted on flat plates and curved structures to provide material and structural response information to help validate the computational models. The material property data and the ballistic impact data will be generated using materials from the same lot, as far as possible. It was found in preliminary testing that the surface finish of test specimens has an effect on measured high strain rate tension response of AL2024. Both the maximum stress and maximum elongation are greater on specimens with a smoother finish. This report gives an overview of the testing that is being conducted and presents results of preliminary testing of the surface finish study.

Circles-in-the-sky searches and observable cosmic topology in a flat universe

NASA Astrophysics Data System (ADS)

Mota, B.; Rebouças, M. J.; Tavakol, R.

2010-05-01

In a universe with a detectable nontrivial spatial topology, the last scattering surface contains pairs of matching circles with the same distribution of temperature fluctuations—the so-called circles-in-the-sky. Searches for nearly antipodal circles-in-the-sky in maps of cosmic microwave background radiation have so far been unsuccessful. This negative outcome, along with recent theoretical results concerning the detectability of nearly flat compact topologies, is sufficient to exclude a detectable nontrivial topology for most observers in very nearly flat positively and negatively curved universes, whose total matter-energy density satisfies 0<|Ωtot-1|≲10-5. Here, we investigate the consequences of these searches for observable nontrivial topologies if the Universe turns out to be exactly flat (Ωtot=1). We demonstrate that in this case, the conclusions deduced from such searches can be radically different. We show that, although there is no characteristic topological scale in the flat manifolds, for all multiply-connected orientable flat manifolds, it is possible to directly study the action of the holonomies in order to obtain a general upper bound on the angle that characterizes the deviation from antipodicity of pairs of matching circles associated with the shortest closed geodesic. This bound is valid for all observers and all possible values of the compactification length parameters. We also show that in a flat universe, there are observers for whom the circles-in-the-sky searches already undertaken are insufficient to exclude the possibility of a detectable nontrivial spatial topology. It is remarkable how such small variations in the spatial curvature of the Universe, which are effectively indistinguishable geometrically, can have such a drastic effect on the detectability of cosmic topology. Another important outcome of our results is that they offer a framework with which to make statistical inferences from future circles-in-the-sky searches on whether the Universe is exactly flat.

Vibration of a Singly-curved Thin Shell Reflector with a Unidirectional Tension Field

NASA Technical Reports Server (NTRS)

Williams, R. Brett; Klein, Kerry J.; Agnes, Gregory S.

2006-01-01

Increased science requirements for space-based instruments over the past few decades have lead to the increased popularity of deployable space structures constructed from thin, lightweight films. Such structures offer both low mass and the ability to be stowed inside conventional launch vehicles. The analysis in this work pertains to large, singly-curved lightweight deployable reflectors commonly used in radar antennas and space telescopes. These types of systems, which can vary a great deal in size, often have frequency requirement that must be met. This work discusses two missions that utilize this type of aperture technology, and then develops a Rayleigh-Ritz model that predicts the natural frequencies and mode shapes for a (nearly) flat and singly-curved reflector with unidirectional in-plane loading. The results are compared with NASTRAN analyses.

Geometric Modeling of Construction Communications with Specified Dynamic Properties

NASA Astrophysics Data System (ADS)

Korotkiy, V. A.; Usmanova, E. A.; Khmarova, L. I.

2017-11-01

Among many construction communications the pipelines designed for the organized supply or removal of liquid or loose working bodies are distinguished for their functional purpose. Such communications should have dynamic properties which allow one to reduce losses on friction and vortex formation. From the point of view of geometric modeling, the given dynamic properties of the projected communication mean the required degree of smoothness of its center line. To model the axial line (flat or spatial), it is proposed to use composite curve lines consisting of the curve arcs of the second order or from their quadratic images. The advantage of the proposed method is that the designer gets the model of a given curve not as a set of coordinates of its points but in the form of a matrix of coefficients of the canonical equations for each arc.

Assessments of Fracture Toughness of Monolithic Ceramics-SEPB Versus SEVNB Methods

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

2006-01-01

Fracture toughness of a total of 13 advanced monolithic ceramics including silicon nitrides, silicon carbide, aluminas, and glass ceramic was determined at ambient temperature by using both single edge precracked beam (SEPB) and single edge v-notched beam (SEVNB) methods. Relatively good agreement in fracture toughness between the two methods was observed for advanced ceramics with flat R-curves; whereas, poor agreement in fracture toughness was seen for materials with rising R-curves. The discrepancy in fracture toughness between the two methods was due to stable crack growth with crack closure forces acting in the wake region of cracks even in SEVNB test specimens. The effect of discrepancy in fracture toughness was analyzed in terms of microstructural feature (grain size and shape), toughening exponent in R-curve, and stable crack growth determined using back-face strain gaging.

Laterally bendable belt conveyor

DOEpatents

Peterson, William J.

1985-01-01

An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making lateral turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rollers which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

Finite indentation of highly curved elastic shells

NASA Astrophysics Data System (ADS)

Pearce, S. P.; King, J. R.; Steinbrecher, T.; Leubner-Metzger, G.; Everitt, N. M.; Holdsworth, M. J.

2018-01-01

Experimentally measuring the elastic properties of thin biological surfaces is non-trivial, particularly when they are curved. One technique that may be used is the indentation of a thin sheet of material by a rigid indenter, while measuring the applied force and displacement. This gives immediate information on the fracture strength of the material (from the force required to puncture), but it is also theoretically possible to determine the elastic properties by comparing the resulting force-displacement curves with a mathematical model. Existing mathematical studies generally assume that the elastic surface is initially flat, which is often not the case for biological membranes. We previously outlined a theory for the indentation of curved isotropic, incompressible, hyperelastic membranes (with no bending stiffness) which breaks down for highly curved surfaces, as the entire membrane becomes wrinkled. Here, we introduce the effect of bending stiffness, ensuring that energy is required to change the shell shape without stretching, and find that commonly neglected terms in the shell equilibrium equation must be included. The theory presented here allows for the estimation of shape- and size-independent elastic properties of highly curved surfaces via indentation experiments, and is particularly relevant for biological surfaces.

Evolution of Starspots on LO Pegasi

NASA Astrophysics Data System (ADS)

Harmon, Robert; Bloodgood, Felise; Martin, Alec; Pellegrin, Kyle

2018-01-01

LO Pegasi is a young solar analog, a K main-sequence star that rotates with a period of 10.1538 hr. The rapid rotation yields a strong stellar dynamo associated with large starspots on the surface, which are regions where the magnetic field inhibits the convective transport of energy from below, so that the spots are cooler and thus darker than the surrounding photosphere. The star thus exhibits rotational modulation of its light curve as the starspots are carried into and out of view of Earth. CCD images of LO Peg were acquired at Perkins Observatory in Delaware, OH through standard B, V, R, and I photometric filters from 2017 June 1 to July 20. After subtracting dark frames and flat fielding the images, differential aperture photometry was performed to yield light curves through each of the four filters. The resulting light curves that were then analyzed via the Light-curve Inversion program created by one of us (Harmon) to produce surface maps. Our observations indicated that LO Pegasi’s light curve changed in both amplitude and shape between 2017 June and July, while its maximum brightness did not change. We present maps corresponding to these two distinct light curves, along with maps for data acquired from 2006-2016.

Finite indentation of highly curved elastic shells

PubMed Central

2018-01-01

Experimentally measuring the elastic properties of thin biological surfaces is non-trivial, particularly when they are curved. One technique that may be used is the indentation of a thin sheet of material by a rigid indenter, while measuring the applied force and displacement. This gives immediate information on the fracture strength of the material (from the force required to puncture), but it is also theoretically possible to determine the elastic properties by comparing the resulting force–displacement curves with a mathematical model. Existing mathematical studies generally assume that the elastic surface is initially flat, which is often not the case for biological membranes. We previously outlined a theory for the indentation of curved isotropic, incompressible, hyperelastic membranes (with no bending stiffness) which breaks down for highly curved surfaces, as the entire membrane becomes wrinkled. Here, we introduce the effect of bending stiffness, ensuring that energy is required to change the shell shape without stretching, and find that commonly neglected terms in the shell equilibrium equation must be included. The theory presented here allows for the estimation of shape- and size-independent elastic properties of highly curved surfaces via indentation experiments, and is particularly relevant for biological surfaces. PMID:29434505

Comparison of Themodynamic and Transport Property Models for Computing Equilibrium High Enthalpy Flows

NASA Astrophysics Data System (ADS)

Ramasahayam, Veda Krishna Vyas; Diwakar, Anant; Bodi, Kowsik

2017-11-01

To study the flow of high temperature air in vibrational and chemical equilibrium, accurate models for thermodynamic state and transport phenomena are required. In the present work, the performance of a state equation model and two mixing rules for determining equilibrium air thermodynamic and transport properties are compared with that of curve fits. The thermodynamic state model considers 11 species which computes flow chemistry by an iterative process and the mixing rules considered for viscosity are Wilke and Armaly-Sutton. The curve fits of Srinivasan, which are based on Grabau type transition functions, are chosen for comparison. A two-dimensional Navier-Stokes solver is developed to simulate high enthalpy flows with numerical fluxes computed by AUSM+-up. The accuracy of state equation model and curve fits for thermodynamic properties is determined using hypersonic inviscid flow over a circular cylinder. The performance of mixing rules and curve fits for viscosity are compared using hypersonic laminar boundary layer prediction on a flat plate. It is observed that steady state solutions from state equation model and curve fits match with each other. Though curve fits are significantly faster the state equation model is more general and can be adapted to any flow composition.

Fabrication and Deformation of 3D Multilayered Kirigami Microstructures.

PubMed

Humood, Mohammad; Shi, Yan; Han, Mengdi; Lefebvre, Joseph; Yan, Zheng; Pharr, Matt; Zhang, Yihui; Huang, Yonggang; Rogers, John A; Polycarpou, Andreas A

2018-03-01

Mechanically guided 3D microassembly with controlled compressive buckling represents a promising emerging route to 3D mesostructures in a broad range of advanced materials, including single-crystalline silicon (Si), of direct relevance to microelectronic devices. During practical applications, the assembled 3D mesostructures and microdevices usually undergo external mechanical loading such as out-of-plane compression, which can induce damage in or failure of the structures/devices. Here, the mechanical responses of a few mechanically assembled 3D kirigami mesostructures under flat-punch compression are studied through combined experiment and finite element analyses. These 3D kirigami mesostructures consisting of a bilayer of Si and SU-8 epoxy are formed through integration of patterned 2D precursors with a prestretched elastomeric substrate at predefined bonding sites to allow controlled buckling that transforms them into desired 3D configurations. In situ scanning electron microscopy measurement enables detailed studies of the mechanical behavior of these structures. Analysis of the load-displacement curves allows the measurement of the effective stiffness and elastic recovery of various 3D structures. The compression experiments indicate distinct regimes in the compressive force/displacement curves and reveals different geometry-dependent deformation for the structures. Complementary computational modeling supports the experimental findings and further explains the geometry-dependent deformation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3-D Displays Perceptual Research and Applications to Military Systems

DTIC Science & Technology

1982-09-30

physical button on the corresponding face of the response cube as fast as possible, while minimizing errors. Each observer served for six sessions...orientation, and this resulted in the fast flat reaction time function. The Rotat±nal Strategy: As can be seen from Figure 3, the 24 stimulus cube...instead of the TOP key, these two responses should show the fast , flat response time functions associated with use of the spatial strategy, whereas the

System for photometric calibration of optoelectronic imaging devices especially streak cameras

DOEpatents

Boni, Robert; Jaanimagi, Paul

2003-11-04

A system for the photometric calibration of streak cameras and similar imaging devices provides a precise knowledge of the camera's flat-field response as well as a mapping of the geometric distortions. The system provides the flat-field response, representing the spatial variations in the sensitivity of the recorded output, with a signal-to-noise ratio (SNR) greater than can be achieved in a single submicrosecond streak record. The measurement of the flat-field response is carried out by illuminating the input slit of the streak camera with a signal that is uniform in space and constant in time. This signal is generated by passing a continuous wave source through an optical homogenizer made up of a light pipe or pipes in which the illumination typically makes several bounces before exiting as a spatially uniform source field. The rectangular cross-section of the homogenizer is matched to the usable photocathode area of the streak tube. The flat-field data set is obtained by using a slow streak ramp that may have a period from one millisecond (ms) to ten seconds (s), but may be nominally one second in duration. The system also provides a mapping of the geometric distortions, by spatially and temporarily modulating the output of the homogenizer and obtaining a data set using the slow streak ramps. All data sets are acquired using a CCD camera and stored on a computer, which is used to calculate all relevant corrections to the signal data sets. The signal and flat-field data sets are both corrected for geometric distortions prior to applying the flat-field correction. Absolute photometric calibration is obtained by measuring the output fluence of the homogenizer with a "standard-traceable" meter and relating that to the CCD pixel values for a self-corrected flat-field data set.

Optical to extreme ultraviolet reddening curves for normal AGN dust and for dust associated with high-velocity outflows

NASA Astrophysics Data System (ADS)

Singh, Japneet; Gaskell, Martin; Gill, Jake

2017-01-01

We use mid-IR (WIRE), optical (SDSS), and ultraviolet (GALEX) photometry of over 80,000 AGNs to derive mean attenuation curves from the optical to the rest frame extreme ultraviolet (EUV) for (i) “normal” AGN dust dominating the optical reddening of AGNs and (ii) “BAL dust” - the dust causing the additional extinction in AGNs observed to have broad absorption lines (BALs). Our method confirms that the attenuation curve of “normal” AGN dust is flat in the ultraviolet, as found by Gaskell et al. (2004). In striking contrast to this, the attenuation curve for BAL dust is well fit by a steeply-rising, SMC-like curve. We confirm the shape of the theoretical Weingartner & Draine (2001) SMC curve out to 700 Angstroms but the drop in attenuation to still shorter wavelengths (400 Angstroms) seems to be less than predicted. We find identical attenuation curves for high-ionization and low-ionization BALQSOs. We suggest that attenuation curves appearing to be steeper than the SMC are due to differences in underlying spectra and partial covering by BAL dust. This work was This work was performed under the auspices of the Science Internship Program (SIP) of the University of California at Santa Cruz performed under the auspices of the Science Internship Program (SIP) of the University of California at Santa Cruz.

Computation of Bound Orbits in the Plane of a Galaxy with a Flat Rotation Curve

ERIC Educational Resources Information Center

Bacon, M. E.; Sharrar, Amber

2010-01-01

A standard topic in an advanced undergraduate classical mechanics course is the determination of the orbits in a gravitational field. In the present paper we report on the calculation of bound orbits in the gravitational field of a spiral galaxy. Calculations such as these could serve to focus attention on an area of cutting edge astrophysics and…

Some simulation estimates of mean annual increment of Douglas-fir: results, limitations, and implications for management.

Treesearch

Robert O. Curtis

1994-01-01

Patterns of development of mean annual increment in relation to age predicted by the widely used DFSIM, SPS, TASS, and ORGANON simulators were examined. Although predictions differ considerably among simulators for portions of the range of sites, ages, and treatments, comparisons indicated that (1) culmination is relatively late, (2) the curve is relatively flat in the...

Marital conflict and parental responses to infant negative emotions: Relations with toddler emotional regulation.

PubMed

Frankel, Leslie A; Umemura, Tomo; Jacobvitz, Deborah; Hazen, Nancy

2015-08-01

According to family systems theory, children's emotional development is likely to be influenced by family interactions at multiple levels, including marital, mother-child, and father-child interactions, as well as by interrelations between these levels. The purpose of the present study was to examine parents' marital conflict and mothers' and fathers' distressed responses to their infant's negative emotions, assessed when their child was 8 and 24 months old, in addition to interactions between parents' marital conflict and their distressed responses, as predictors of their toddler's negative and flat/withdrawn affect at 24 months. Higher marital conflict during infancy and toddlerhood predicted both increased negative and increased flat/withdrawn affect during toddlerhood. In addition, toddlers' negative (but not flat) affect was related to mothers' distressed responses, but was only related to father's distressed responses when martial conflict was high. Implications of this study for parent education and family intervention were discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Effective Elastic Modulus as a Function of Angular Leaf Span for Curved Leaves of Pyrolytic Boron Nitride

NASA Technical Reports Server (NTRS)

Kaforey, M. L.; Deeb, C. W.; Matthiesen, D. H.

1999-01-01

A theoretical equation was derived to predict the spring constant (load/deflection) for a simply supported cylindrical section with a line force applied at the center. Curved leaves of PBN were mechanically deformed and the force versus deflection data was recorded and compared to the derived theoretical equation to yield an effective modulus for each leaf. The effective modulus was found to vary from the pure shear modulus for a flat plate to a mixed mode for a half cylinder as a function of the sine of one half the angular leaf span. The spring constants of individual PBN leaves were usually predicted to within 30%.

Monogamy of Einstein-Podolsky-Rosen Steering in the Background of an Asymptotically Flat Black Hole

NASA Astrophysics Data System (ADS)

Wang, Jieci; Jing, Jiliang; Fan, Heng

2018-03-01

We study the behavior of monogamy deficit and monogamy asymmetry for Einstein-Podolsky-Rosen steering of Gaussian states under the influence of the Hawking effect. We demonstrate that the monogamy of quantum steering shows an extreme scenario in the curved spacetime: the first part of a tripartite system cannot individually steer two other parties, but it can steer the collectivity of the remaining two parties. We also find that the monogamy deficit of Gaussian steering, a quantifier of genuine tripartite steering, are generated due to the influence of the Hawking thermal bath. Our results elucidate the structure of quantum steering in tripartite quantum systems in curved spacetime.

75 FR 24744 - Notice of Lodging of Consent Decree Under the Comprehensive Environmental Response, Compensation...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-05

... Decree in United States of America v. AGC Flat Glass North America, Inc., et al., Civil Action No. 1:10... County, West Virginia (the ``Site''). The Consent Decree obligates AGC Flat Glass North America, Inc. and... States of America v. AGC Flat Glass North America, Inc., et al., Civil Action No. 1:10-cv-00069-IMK, (N.D...

Entanglement hamiltonian and entanglement contour in inhomogeneous 1D critical systems

NASA Astrophysics Data System (ADS)

Tonni, Erik; Rodríguez-Laguna, Javier; Sierra, Germán

2018-04-01

Inhomogeneous quantum critical systems in one spatial dimension have been studied by using conformal field theory in static curved backgrounds. Two interesting examples are the free fermion gas in the harmonic trap and the inhomogeneous XX spin chain called rainbow chain. For conformal field theories defined on static curved spacetimes characterised by a metric which is Weyl equivalent to the flat metric, with the Weyl factor depending only on the spatial coordinate, we study the entanglement hamiltonian and the entanglement spectrum of an interval adjacent to the boundary of a segment where the same boundary condition is imposed at the endpoints. A contour function for the entanglement entropies corresponding to this configuration is also considered, being closely related to the entanglement hamiltonian. The analytic expressions obtained by considering the curved spacetime which characterises the rainbow model have been checked against numerical data for the rainbow chain, finding an excellent agreement.

Melting behavior of SnI4 reexamined

NASA Astrophysics Data System (ADS)

Fuchizaki, Kazuhiro

2013-12-01

The low-pressure crystalline phase of a molecular crystal, SnI4, has a rising melting curve that breaks abruptly at around 1.5 GPa, beyond which it becomes almost flat, with a slight maximum at about 3 GPa. Although the overall aspect of this melting curve can be captured by the Kumari-Dass-Kechin equation, the values for the parameters involved in the equation were definitely different from those predicted on the basis of the Clapeyron-Clausius relationship. On the other hand, the accuracy of our experimental data prevented us from judging whether the parameters are derivable from the Lindemann melting law, as shown independently by Kumari and Dass, and by Kechin. The Kraut-Kennedy and Magalinskii-Zubov relationships seem to be valid in the low-pressure region where the melting curve is rising. The breakdown of these relationships suggests a qualitative change in the intermolecular interaction upon compression, thereby making the melting behavior unusual.

X-ray phase contrast imaging of objects with subpixel-size inhomogeneities: a geometrical optics model.

PubMed

Gasilov, Sergei V; Coan, Paola

2012-09-01

Several x-ray phase contrast extraction algorithms use a set of images acquired along the rocking curve of a perfect flat analyzer crystal to study the internal structure of objects. By measuring the angular shift of the rocking curve peak, one can determine the local deflections of the x-ray beam propagated through a sample. Additionally, some objects determine a broadening of the crystal rocking curve, which can be explained in terms of multiple refraction of x rays by many subpixel-size inhomogeneities contained in the sample. This fact may allow us to differentiate between materials and features characterized by different refraction properties. In the present work we derive an expression for the beam broadening in the form of a linear integral of the quantity related to statistical properties of the dielectric susceptibility distribution function of the object.

Swelling-induced and controlled curving in layered gel beams

PubMed Central

Lucantonio, A.; Nardinocchi, P.; Pezzulla, M.

2014-01-01

We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method. PMID:25383031

Remote sensing and laboratory techniques for monitoring ocean dumping

NASA Technical Reports Server (NTRS)

Ohlhorst, C. W.; Johnson, R. W.; Meyer, E. R.

1977-01-01

Results of field experiments conducted in the Atlantic Coastal Zone indicate that plumes resulting from ocean dumping of acid waste and sewage sludge have distinguishable spectral characteristics when the radiance of the pollutant is normalized (ratioed to) background ocean water. Acid waste spectra peak between 550-650 nm while sewage sludge spectra have peak values at wavelengths of about 700 nm or greater. Results indicate that identification of acid waste and sewage sludge plumes may be independent of geographical location in the Atlantic Coastal Zone. Radiance ratio curves obtained in the laboratory qualitatively agree with those obtained from field experiments. Results from the July 25, 1977, Galveston Deep Ocean Dump Site experiment show the radiance ratio curve of the biodigested industrial waste to be fairly flat and similar to the radiance ratio curves of sewage sludge line dumps and sewage sludge spot dumps that have been in the water for several hours.

Buckling analysis of curved composite sandwich panels subjected to inplane loadings

NASA Technical Reports Server (NTRS)

Cruz, Juan R.

1993-01-01

Composite sandwich structures are being considered for primary structure in aircraft such as subsonic and high speed civil transports. The response of sandwich structures must be understood and predictable to use such structures effectively. Buckling is one of the most important response mechanisms of sandwich structures. A simple buckling analysis is derived for sandwich structures. This analysis is limited to flat, rectangular sandwich panels loaded by uniaxial compression (N(sub x)) and having simply supported edges. In most aerospace applications, however, the structure's geometry, boundary conditions, and loading are usually very complex. Thus, a general capability for analyzing the buckling behavior of sandwich structures is needed. The present paper describes and evaluates an improved buckling analysis for cylindrically curved composite sandwich panels. This analysis includes orthotropic facesheets and first-order transverse shearing effects. Both simple support and clamped boundary conditions are also included in the analysis. The panels can be subjected to linearly varying normal loads N(sub x) and N(sub y) in addition to a constant shear load N(sub xy). The analysis is based on the modified Donnell's equations for shallow shells. The governing equations are solved by direct application of Galerkin's method. The accuracy of the present analysis is verified by comparing results with those obtained from finite element analysis for a variety of geometries, loads, and boundary conditions. The limitations of the present analysis are investigated, in particular those related to the shallow shell assumptions in the governing equations. Finally, the computational efficiency of the present analysis is considered.

Telephone Flat Geothermal Development Project Environmental Impact Statement Environmental Impact Report. Final: Comments and Responses to Comments

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

None

This document is the Comments and Responses to Comments volume of the Final Environmental Impact Statement and Environmental Impact Report prepared for the proposed Telephone Flat Geothermal Development Project (Final EIS/EIR). This volume of the Final EIS/EIR provides copies of the written comments received on the Draft EIS/EIR and the leady agency responses to those comments in conformance with the requirements of the National Environmental Policy Act (NEPA) and the California Environmental Quality Act (CEQA).

Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

2002-01-01

The fatigue behavior (stress-life curve) of gamma titanium aluminide (Ti-48Al-2Cr-2Nb, atomic percent) was examined by conducting two tests: first, a fretting wear test with a fatigue specimen in contact with a typical nickel-based superalloy contact pad in air at temperatures of 296 and 823 K and second, a high-cycle fatigue test of the prefretted Ti-48Al-2Cr-2Nb fatigue specimen at 923 K. Reference high-cycle fatigue tests were also conducted with unfretted Ti-48Al-2Cr-2Nb specimens at 923 K. All Ti-48Al-2Cr-2Nb fatigue specimens were machined from cast slabs. The results indicate that the stress-life results for the fretted Ti-48Al-2Cr-2Nb specimens exhibited a behavior similar to those of the unfretted Ti-48Al-2Cr-2Nb specimens. The values of maximum stress and life for the fretted specimens were almost the same as those for the unfretted specimens. The resultant stress-life curve for the unfretted fatigue specimens was very flat. The flat appearance in the stress-life curve of the unfretted specimens is attributed to the presence of a high density of casting pores. The fatigue strengths of both the fretted and unfretted specimens can be significantly affected by the presence of this porosity, which can decrease the fatigue life of Ti-48Al-2Cr-2Nb. The presence of the porosity made discerning the effect of fretting damage on fatigue strength and life of the specimens difficult.

The different baryonic Tully-Fisher relations at low masses.

PubMed

Brook, Chris B; Santos-Santos, Isabel; Stinson, Greg

2016-06-11

We compare the Baryonic Tully-Fisher relation (BTFR) of simulations and observations of galaxies ranging from dwarfs to spirals, using various measures of rotational velocity V rot . We explore the BTFR when measuring V rot at the flat part of the rotation curve, V flat , at the extent of H i gas, V last , and using 20 per cent ( W 20 ) and 50 per cent ( W 50 ) of the width of H i line profiles. We also compare with the maximum circular velocity of the parent halo, [Formula: see text], within dark matter only simulations. The different BTFRs increasingly diverge as galaxy mass decreases. Using V last  one obtains a power law over four orders of magnitude in baryonic mass, with slope similar to the observed BTFR. Measuring V flat gives similar results as V last when galaxies with rising rotation curves are excluded. However, higher rotation velocities would be found for low-mass galaxies if the cold gas extended far enough for V rot to reach a maximum. W 20 gives a similar slope as V last but with slightly lower values of V rot for low-mass galaxies, although this may depend on the extent of the gas in your galaxy sample. W 50 bends away from these other relations towards low velocities at low masses. By contrast, [Formula: see text] bends towards high velocities for low-mass galaxies, as cold gas does not extend out to the radius at which haloes reach [Formula: see text]. Our study highlights the need for careful comparisons between observations and models: one needs to be consistent about the particular method of measuring V rot , and precise about the radius at which velocities are measured.

Multifactorial etiology of Torus mandibularis: study of twins.

PubMed

Auškalnis, Adomas; Rutkūnas, Vygandas; Bernhardt, Olaf; Šidlauskas, Mantas; Šalomskienė, Loreta; Basevičienė, Nomeda

2015-01-01

The aim of this study is to investigate the multifactorial etiology of mandibular tori analyzing the influence of genetics, occlusal overload, various clinical variables and their interactions. Overall, plaster casts of 162 twins (81 twin pairs) were analyzed for the presence or absence of mandibular tori. Atypical wear facets on canine tips or incisors were recorded to diagnose bruxism. Angle Class, any kind of anterior open bite and positive, negative or flat curve of Wilson were recorded. Zygosity determination was carried out using a DNA test. Mandibular tori were found in 56.8% of the cases. In 93.6% of all monozygotic twin pairs both individuals had or did not have mandibular tori (κ=0.96±0.04; p<0.001), compared to 79.4% concordance of mandibular tori in dizygotic co-twins (κ=0.7±0.12; p<0.001). Prevalence of mandibular tori was significantly higher in the group of bruxers (67.5%) compared to non-bruxers (31.3%) (p<0.001). Significant association between mandibular tori and negative or flat curve of Wilson in the maxillary second premolars and first molars was found (OR=2.55, 95% CI (1.19-5.46), p=0.016). In all monozygotic bruxers, 97.1% showed concordance of mandibular tori presence in both co-twins compared to 78.9% dizygotic bruxers, and this difference is statistically significant (p=0.007). Our results suggest that the mandibular tori are of a multifactorial origin. Mandibular tori seem to have genetic predisposition, and may be associated with teeth grinding as well as with negative or flat CW in region of maxillary second premolar and first molar.

Zaccaria Lilio and the shape of the earth: A brief response to Allegro's "Flat earth science".

PubMed

Nothaft, C Philipp E

2017-12-01

This is a response to James J. Allegro's article "The Bottom of the Universe: Flat Earth Science in the Age of Encounter," published in Volume 55, Number 1, of this journal. Against the solid consensus of modern scholars, Allegro contends that the decades around 1500 saw a resurgence of popular and learned doubts about the existence of a southern hemisphere and the concept of a spherical earth more generally. It can be shown that a substantial part of Allegro's argument rests on an erroneous reading of his main textual witness, Zaccaria Lilio's Contra Antipodes (1496), and on a failure adequately to place this source in the context of the cosmographical debate of the late fifteenth and early sixteenth centuries. Once this context is taken into account, the notion that Lilio was a flat-earther falls flat.

Design and experimental evidence of a flat graded-index photonic crystal lens

NASA Astrophysics Data System (ADS)

Gaufillet, F.; Akmansoy, É.

2013-08-01

We report on the design and the experimental evidence of a flat graded index photonic crystal lens. The gradient has been designed so that the flat slab focuses a plane wave and so that it converts the wave issued from a point source into a plane wave. This graded-index photonic crystal lens operates as a convex lens. The gradient of index results from varying the filling factor of the photonic crystal in the direction perpendicular to that of the propagation of the electromagnetic field. The shape of the gradient of index has been designed by engineering the iso-frequency curves of the photonic crystal. As only a few layers were necessary and as graded photonic crystals may be fabricated by a variety of processes, this shows the ability of graded photonic crystals to efficiently apply for various photonic devices, from microwave range to the optical domain. 42.70.Qs Photonic bandgap materials, 78.67.Pt Optical properties of photonic structures, 41.20.Jb Electromagnetic wave propagation; radiowave propagation 84.40.Ba Antennas.

Spray Cooling Trajectory Angle Impact Upon Heat Flux Using a Straight Finned Enhanced Surface

NASA Technical Reports Server (NTRS)

Silk, Eric A.; Kim, Jungho; Kiger, Ken

2005-01-01

Experiments were conducted to study the effects of spray trajectory angles upon heat flux for flat and enhanced surface spray cooling. The surface enhancement consisted of straight fins machined on the top surface of a copper heater block. Spray cooling curves were obtained with the straight fin surface aligned both parallel (axial) and perpendicular (transverse) to the spray axis. Measurements were also obtained on a flat surface heater block for comparison purposes. Each copper block had a cross-sectional area of 2.0 sq cm. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) conditions. Results show that the maximum CHF in all cases was attained for a trajectory angle of 30' from the surface normal. Furthermore, trajectory angles applied to straight finned surfaces can have a critical heat flux (CHF) enhancement as much as 75% (heat flux value of 140 W/sq cm) relative to the vertical spray orientation for the analogous flat surface case under nominally degassed conditions.

Stress concentration in periodically rough Hertzian contact: Hertz to soft-flat-punch transition

PubMed Central

Raphaël, E.; Léger, L.; Restagno, F.; Poulard, C.

2016-01-01

We report on the elastic contact between a spherical lens and a patterned substrate, composed of a hexagonal lattice of cylindrical pillars. The stress field and the size of the contact area are obtained by means of numerical methods: a superposition method of discrete pressure elements and an iterative bisection-like method. For small indentations, a transition from a Hertzian to a soft-flat-punch behaviour is observed when the surface fraction of the substrate that is covered by the pillars is increased. In particular, we present a master curve defined by two dimensionless parameters, which allows one to predict the stress at the centre of the contact region in terms of the surface fraction occupied by pillars. The transition between the limiting contact regimes, Hertzian and soft-flat-punch, is well described by a rational function. Additionally, a simple model to describe the Boussinesq–Cerruti-like contact between the lens and a single elastic pillar, which takes into account the pillar geometry and the elastic properties of the two bodies, is presented. PMID:27713659

Exploring the Brighter-fatter Effect with the Hyper Suprime-Cam

NASA Astrophysics Data System (ADS)

Coulton, William R.; Armstrong, Robert; Smith, Kendrick M.; Lupton, Robert H.; Spergel, David N.

2018-06-01

The brighter-fatter effect has been postulated to arise due to the build up of a transverse electric field, produced as photocharges accumulate in the pixels’ potential wells. We investigate the brighter-fatter effect in the Hyper Suprime-Cam by examining flat fields and moments of stars. We observe deviations from the expected linear relation in the photon transfer curve (PTC), luminosity-dependent correlations between pixels in flat-field images, and a luminosity-dependent point-spread function (PSF) in stellar observations. Under the key assumptions of translation invariance and Maxwell’s equations in the quasi-static limit, we give a first-principles proof that the effect can be parameterized by a translationally invariant scalar kernel. We describe how this kernel can be estimated from flat fields and discuss how this kernel has been used to remove the brighter-fatter distortions in Hyper Suprime-Cam images. We find that our correction restores the expected linear relation in the PTCs and significantly reduces, but does not completely remove, the luminosity dependence of the PSF over a wide range of magnitudes.

The crust and uppermost mantle structure in Southern Peru from ambient noise and earthquake surface wave analysis

NASA Astrophysics Data System (ADS)

Ma, Y.; Clayton, R. W.

2012-12-01

We determine the Vs structure to a depth of 140 km of Southern Peru, where the subducted Nazca slab changes from normal to flat subduction. The data are from a box-like array that is approximately 300 km on a side, and with 150 stations in total. The structure is inverted from surface wave dispersion curves measured between 5 s to 23 s period from ambient noise cross-correlations, and between 25 s to 69 s from earthquake two-plane-wave analysis. From the map views of different depths, we observe that: (1) The forearc region is characterized by shallow crustal thickness and higher crustal velocity compared with the backarc. (2) The upper-crust velocity in the backarc above normal subduction (3.0-3.2 km/s) is lower compared with that above flat subduction region (3.2-3.4 km/s). The low velocity coincides with the deep sediments above the Altiplano plateau. (3) The transition from the normal to flat subduction is characterized by a comparatively lower upper-mid crust velocity (3.2-3.4 km/s). The lower velocity zone also coincides with the highest topography (>4700 m) in the study area. (4) The mantle wedge velocity above the flat subduction (4.6-4.9 km/s) is higher than the surrounding mantle and the mantle above the normal subduction region (4.3-4.5 km/s). We deduce that the upper-mid crust above the transition of the slab geometry is probably more felsic, which can be due to the old volcanic activity during the normal-flat transition, and thus can more easily accommodate the crustal shortening. The lack of present volcanism above the flat subduction, however, could be explained by the high velocity anomaly related to the flat slab. It may indicate a cold environment, and thus the lack of mantle melting.

Thermoluminescence Response of Ge-Doped Cylindrical-, Flat- and Photonic Crystal Silica-Fibres to Electron and Photon Radiation

PubMed Central

Entezam, A.; Khandaker, M. U.; Amin, Y. M.; Ung, N. M.; Bradley, D. A.; Maah, J.; Safari, M. J.; Moradi, F.

2016-01-01

Study has been made of the thermoluminescence (TL) response of silica-based Ge-doped cylindrical, flat and photonic crystal fibres (referred to herein as PCF-collapsed) to electron (6, 12 and 20 MeV) and photon (6, 10 MV) irradiation and 1.25 MeV γ-rays, for doses from 0.1 Gy to 100 Gy. The electron and photon irradiations were delivered through use of a Varian Model 2100C linear accelerator located at the University of Malaya Medical Centre and γ-rays delivered from a 60Co irradiator located at the Secondary Standard Dosimetry Laboratory (SSDL), Malaysian Nuclear Agency. Tailor-made to be of various dimensions and dopant concentrations (6–10% Ge), the fibres were observed to provide TL yield linear with radiation dose, reproducibility being within 1–5%, with insensitivity to energy and angular variation. The sensitivity dependency of both detectors with respect to field size follows the dependency of the output factors. For flat fibres exposed to 6 MV X-rays, the 6% Ge-doped fibre provided the greatest TL yield while PCF-collapsed showed a response 2.4 times greater than that of the 6% Ge-doped flat fibres. The response of cylindrical fibres increased with core size. The fibres offer uniform response, high spatial resolution and sensitivity, providing the basis of promising TL systems for radiotherapy applications. PMID:27149115

Principal Curves on Riemannian Manifolds.

PubMed

Hauberg, Soren

2016-09-01

Euclidean statistics are often generalized to Riemannian manifolds by replacing straight-line interpolations with geodesic ones. While these Riemannian models are familiar-looking, they are restricted by the inflexibility of geodesics, and they rely on constructions which are optimal only in Euclidean domains. We consider extensions of Principal Component Analysis (PCA) to Riemannian manifolds. Classic Riemannian approaches seek a geodesic curve passing through the mean that optimizes a criteria of interest. The requirements that the solution both is geodesic and must pass through the mean tend to imply that the methods only work well when the manifold is mostly flat within the support of the generating distribution. We argue that instead of generalizing linear Euclidean models, it is more fruitful to generalize non-linear Euclidean models. Specifically, we extend the classic Principal Curves from Hastie & Stuetzle to data residing on a complete Riemannian manifold. We show that for elliptical distributions in the tangent of spaces of constant curvature, the standard principal geodesic is a principal curve. The proposed model is simple to compute and avoids many of the pitfalls of traditional geodesic approaches. We empirically demonstrate the effectiveness of the Riemannian principal curves on several manifolds and datasets.

Does increased topside conformity in modular total knee arthroplasty lead to increased backside wear?

PubMed

Schwarzkopf, Ran; Scott, Richard D; Carlson, Evan M; Currier, John H

2015-01-01

Modular metal-backed tibia components allow surgeons intraoperative flexibility. Although it is known that modular tibia components introduce the possibility for backside wear resulting from relative motion between the polyethylene insert and the tibial baseplate, it is not known to what degree variability in the conformity of the tibial polyethylene liner itself might contribute to backside wear. The purpose of this study was to determine whether a flat, cruciate-retaining tibial polyethylene bearing generates less backside wear than a more conforming (curved) tibial polyethylene bearing in an analysis of specimens explanted during revision surgery. The study included 70 total knee inserts explanted at revision surgery, all implanted and explanted by the same surgeon. Two different cruciate-retaining insert options in an otherwise similar knee system were used: one with a curved-on-flat (17) articular geometry and one with a highly conforming curved-on-curved design (53); both groups were sequential cohorts. The composite backside wear depth for the insert as well as the volume of backside wear was measured and compared between groups. The median linear backside-normalized wear for the posterior lipped inserts was 0.0063 mm/year (range, 0-0.085 mm/year), which was lower than for the curved inserts at 0.05 mm/year (range, 0.00003-0.14 mm/year) (p<0.001). The median calculated volumetric backside-normalized wear for the posterior lipped inserts was 14.2 mm3/year (range, 0-282.8 mm3/year) compared with 117 mm3/year (range, 2.1-312 mm3/year) for the curved inserts (p<0.001). In this retrieval study, more conforming tibial inserts demonstrated more backside-normalized wear than the flatter designs. This suggests that in this modular total knee arthroplasty design, higher articular conformity to address the issues of high bearing contact stress comes at a price: increased torque transmitted to the backside insert-to-tray interface. We suggest further work be undertaken to examine newer insert designs to evaluate if our conclusions hold true with the newer generation locking mechanism, tibial tray finish and polyethylene designs, as more highly conforming tibial inserts are introduced into the market. Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Newtonian Gravity Reformulated

NASA Astrophysics Data System (ADS)

Dehnen, H.

2018-01-01

With reference to MOND we propose a reformulation of Newton's theory of gravity in the sense of the static electrodynamics introducing a "material" quantity in analogy to the dielectric "constant". We propose that this quantity is induced by vacuum polarizations generated by the gravitational field itself. Herewith the flat rotation curves of the spiral galaxies can be explained as well as the observed high velocities near the center of the galaxy should be reconsidered.

Rotational Symmetry Breaking in Baby Skyrme Models

NASA Astrophysics Data System (ADS)

Karliner, Marek; Hen, Itay

We discuss one of the most interesting phenomena exhibited by baby skyrmions - breaking of rotational symmetry. The topics we will deal with here include the appearance of rotational symmetry breaking in the static solutions of baby Skyrme models, both in flat as well as in curved spaces, the zero-temperature crystalline structure of baby skyrmions, and finally, the appearance of spontaneous breaking of rotational symmetry in rotating baby skyrmions.

Brushless Cleaning of Solar Panels and Windows

NASA Technical Reports Server (NTRS)

Schneider, H. W.

1982-01-01

Machine proposed for cleaning solar panels and reflectors uses multiple vortexes of air, solvent, and water to remove dust and dirt. Uses no brushes that might abrade solar surfaces and thereby reduce efficiency. Machine can be readily automated and can be used on curved surfaces such as aparbolic reflectors as well as on flat ones. Cleaning fluids are recycled, so that large quantities of water and solvent are not needed.

Wind tunnel test results for the direction controlled antitank DCAT missile at Mach numbers from 0.64 to 2.50

NASA Technical Reports Server (NTRS)

Martin, T. A.; Spring, D. J.

1973-01-01

Wind tunnel test results are presented to show aerodynamic characteristics over the Mach number range of 0.64 to 2.50 of the DCAT missile. Data are presented showing the interference created by the rear mounted reaction control system. Two candidate fins were installed on the model during tests: a flat folding fin and a curved wrap around fin.

Finite element analysis of wrinkling membranes

NASA Technical Reports Server (NTRS)

Miller, R. K.; Hedgepeth, J. M.; Weingarten, V. I.; Das, P.; Kahyai, S.

1984-01-01

The development of a nonlinear numerical algorithm for the analysis of stresses and displacements in partly wrinkled flat membranes, and its implementation on the SAP VII finite-element code are described. A comparison of numerical results with exact solutions of two benchmark problems reveals excellent agreement, with good convergence of the required iterative procedure. An exact solution of a problem involving axisymmetric deformations of a partly wrinkled shallow curved membrane is also reported.

Discussion of band selection and methodologies for the estimation of precipitable water vapour from AVIRIS data

NASA Technical Reports Server (NTRS)

Schanzer, Dena; Staenz, Karl

1992-01-01

An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set acquired over Canal Flats, B.C., on 14 Aug. 1990, was used for the purpose of developing methodologies for surface reflectance retrieval using the 5S atmospheric code. A scene of Rogers Dry Lake, California (23 Jul. 1990), acquired within three weeks of the Canal Flats scene, was used as a potential reference for radiometric calibration purposes and for comparison with other studies using primarily LOWTRAN7. Previous attempts at surface reflectance retrieval indicated that reflectance values in the gaseous absorption bands had the poorest accuracy. Modifications to 5S to use 1 nm step size, in order to make fuller use of the 20 cm(sup -1) resolution of the gaseous absorption data, resulted in some improvement in the accuracy of the retrieved surface reflectance. Estimates of precipitable water vapor using non-linear least squares regression and simple ratioing techniques such as the CIBR (Continuum Interpolated Band Ratio) technique or the narrow/wide technique, which relate ratios of combinations of bands to precipitable water vapor through calibration curves, were found to vary widely. The estimates depended on the bands used for the estimation; none provided entirely satisfactory surface reflectance curves.

The distribution of mass for spiral galaxies in clusters and in the field

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

Forbes, D.A.; Whitmore, B.C.

1989-04-01

A comparison is made between the mass distributions of spiral galaxies in clusters and in the field using Burstein's mass-type methodology. Both the H-alpha emission-line rotation curves and more extended H I rotation curves are used. The fitting technique for determining mass types used by Burstein and coworkers has been replaced by an objective chi-sq method. Mass types are shown to be a function of both the Hubble type and luminosity, contrary to earlier results. The present data show a difference in the distribution of mass types for spiral galaxies in the field and in clusters, in the sense thatmore » mass type I galaxies, where the inner and outer velocity gradients are similar, are generally found in the field rather than in clusters. This can be understood in terms of the results of Whitmore, Forbes, and Rubin (1988), who find that the rotation curves of galaxies in the central region of clusters are generally failing, while the outer galaxies in a cluster and field galaxies tend to have flat or rising rotation curves. 15 refs.« less

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

NASA Astrophysics Data System (ADS)

Juvan, Ines G.; Lendl, M.; Cubillos, P. E.; Fossati, L.; Tregloan-Reed, J.; Lammer, H.; Guenther, E. W.; Hanslmeier, A.

2018-02-01

Several studies have shown that stellar activity features, such as occulted and non-occulted starspots, can affect the measurement of transit parameters biasing studies of transit timing variations and transmission spectra. We present PyTranSpot, which we designed to model multiband transit light curves showing starspot anomalies, inferring both transit and spot parameters. The code follows a pixellation approach to model the star with its corresponding limb darkening, spots, and transiting planet on a two dimensional Cartesian coordinate grid. We combine PyTranSpot with a Markov chain Monte Carlo framework to study and derive exoplanet transmission spectra, which provides statistically robust values for the physical properties and uncertainties of a transiting star-planet system. We validate PyTranSpot's performance by analyzing eleven synthetic light curves of four different star-planet systems and 20 transit light curves of the well-studied WASP-41b system. We also investigate the impact of starspots on transit parameters and derive wavelength dependent transit depth values for WASP-41b covering a range of 6200-9200 Å, indicating a flat transmission spectrum.

Rotation curve for the Milky Way galaxy in conformal gravity

NASA Astrophysics Data System (ADS)

O'Brien, James G.; Moss, Robert J.

2015-05-01

Galactic rotation curves have proven to be the testing ground for dark matter bounds in galaxies, and our own Milky Way is one of many large spiral galaxies that must follow the same models. Over the last decade, the rotation of the Milky Way galaxy has been studied and extended by many authors. Since the work of conformal gravity has now successfully fit the rotation curves of almost 140 galaxies, we present here the fit to our own Milky Way. However, the Milky Way is not just an ordinary galaxy to append to our list, but instead provides a robust test of a fundamental difference of conformal gravity rotation curves versus standard cold dark matter models. It was shown by Mannheim and O'Brien that in conformal gravity, the presence of a quadratic potential causes the rotation curve to eventually fall off after its flat portion. This effect can currently be seen in only a select few galaxies whose rotation curve is studied well beyond a few multiples of the optical galactic scale length. Due to the recent work of Sofue et al and Kundu et al, the rotation curve of the Milky Way has now been studied to a degree where we can test the predicted fall off in the conformal gravity rotation curve. We find that - like the other galaxies already studied in conformal gravity - we obtain amazing agreement with rotational data and the prediction includes the eventual fall off at large distances from the galactic center.

Untangling the web: Mechanisms underlying ER network formation

PubMed Central

Goyal, Uma; Blackstone, Craig

2013-01-01

The ER is a continuous membrane system consisting of the nuclear envelope, flat sheets often studded with ribosomes, and a polygonal network of highly-curved tubules extending throughout the cell. Although protein and lipid biosynthesis, protein modification, vesicular transport, Ca2+dynamics, and protein quality control have been investigated in great detail, mechanisms that generate the distinctive architecture of the ER have been uncovered only recently. Several protein families including the reticulons and REEPs/DP1/Yop1p harbor hydrophobic hairpin domains that shape high-curvature ER tubules and mediate intramembrane protein interactions. Members of the atlastin/RHD3/Sey1p family of dynamin-related GTPases interact with the ER-shaping proteins and mediate the formation of three-way junctions responsible for the polygonal structure of the tubular ER network, with Lunapark proteins acting antagonistically. Additional classes of tubular ER proteins including some REEPs and the M1 spastin ATPase interact with the microtubule cytoskeleton. Flat ER sheets possess a different complement of proteins such as p180, CLIMP-63 and kinectin implicated in shaping, cisternal stacking and cytoskeletal interactions. The ER is also in constant motion, and numerous signaling pathways as well as interactions among cytoskeletal elements, the plasma membrane, and organelles cooperate to position and shape the ER dynamically. Finally, many proteins involved in shaping the ER network are mutated in the most common forms of hereditary spastic paraplegia, indicating a particular importance for proper ER morphology and distribution in large, highly-polarized cells such as neurons. PMID:23602970

Gratings Fabricated on Flat Surfaces and Reproduced on Non-Flat Substrates

NASA Technical Reports Server (NTRS)

Content, David; Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christopher M.

2009-01-01

A method has been developed for fabricating gratings on flat substrates, and then reproducing the groove pattern on a curved (concave or convex) substrate and a corresponding grating device. First, surface relief diffraction grating grooves are formed on flat substrates. For example, they may be fabricated using photolithography and reactive ion etching, maskless lithography, holography, or mechanical ruling. Then, an imprint of the grating is made on a deformable substrate, such as plastic, polymer, or other materials using thermoforming, hot or cold embossing, or other methods. Interim stamps using electroforming, or other methods, may be produced for the imprinting process or if the same polarity of the grating image is required. The imprinted, deformable substrate is then attached to a curved, rigid substrate using epoxy or other suitable adhesives. The imprinted surface is facing away from the curved rigid substrate. As an alternative fabrication method, after grating is imprinted on the deformable substrate as described above, the grating may be coated with thin conformal conductive layer (for example, using vacuum deposition of gold). Then the membrane may be mounted over an opening in a pressured vessel in a manner of a membrane on a drum, grating side out. The pressure inside of the vessel may be changed with respect to the ambient pressure to produce concave or convex membrane surface. The shape of the opening may control the type of the surface curvature (for example, a circular opening would create spherical surface, oval opening would create toroidal surface, etc.). After that, well-known electroforming methods may be used to create a replica of the grating on the concave or convex membrane. For example, the pressure vessel assembly may be submerged into an electro-forming solution and negative electric potential applied to the metal coated membrane using an insulated wire. Positive electric potential may be then applied to a nickel or other metal plate submerged into the same solution. Metal ions would transfer from the plate through the solution into the membrane, producing high fidelity metal replica of the grating on the membrane. In one variation, an adhesive may be deposited on the deformable substrate, and then cured without touching the rigid, curved substrate. Edges of the deformable substrate may be attached to the rigid substrate to ensure uniform deformation of the deformable substrate. The assembly may be performed in vacuum, and then taken out to atmospheric pressure conditions to ensure that no air is trapped between the deformable and rigid substrates. Alternatively, a rigid surface with complementary curvature to the rigid substrate may be used to ensure uniform adhesion of the deformable substrate to the rigid substrate. Liquid may be applied to the surface of the deformable substrate to uniformly distribute pressure across its surface during the curing or hardening of the adhesive, or the film may be pressed into the surface using a deformable object or surface. After the attachment is complete, the grooves may be coated with reflective or dielectric layers to improve diffraction efficiency.

Evaluation of left-right difference of impulse in impact forces at stance phase: comparison of measurements on flat land and stairs

PubMed Central

Tasato, Hiroshi; Kida, Noriyuki

2018-01-01

[Purpose] The purpose of this study was to investigate the measurement method and parameters to simply evaluate the condition of the knee that are necessary for preventing locomotive syndrome as advocated by the Japan Orthopedic Association. [Subjects and Methods] The subjects installed acceleration sensors in lateral condyles of the tibia and measured acceleration and load under the conditions of walking on a flat ground and walking using stairs; the difference between the impulse of impact forces (acceleration × load) of the two knees was defined as a simple evaluation parameter. [Results] Simple evaluation parameters were not correlated with age during walking on a flat ground, but during walking using stairs, it was almost flat up to the age of 20–40 years, and after the age of 49 years, based on the quadratic curve approximation (R2=0.99), a correlation of simple evaluation parameters with age could be confirmed. [Conclusion] The simple evaluation parameter during walking using stairs was highly correlated with age, suggesting a contribution to preventing locomotive syndrome by improving reliability. In the future, we plan to improve reliability by increasing the data, and establish it as a simple evaluation parameter that can be used for preventing locomotive syndrome in elderly people and those with KL classification grades 0–1. PMID:29706699

U.S. Nuclear Weapons: Changes in Policy and Force Structure

DTIC Science & Technology

2006-08-10

the Mound Plant , near Dayton OH; the Pinellas Plant , in Clearwater, FL; and the Pantex Plant near Amarillo, TX. These facilities were also operated...major nuclear weapons production facilities. These included the Rocky Flats Plant , outside Denver, CO; the Kansas City Plant , near Kansas City, MO...response to safety concerns. The Rocky Flats Plant , which produced the nuclear triggers, or “pits,” for nuclear weapons closed in 1989, in response

Spontaneous wettability patterning via creasing instability

PubMed Central

Chen, Dayong; McKinley, Gareth H.; Cohen, Robert E.

2016-01-01

Surfaces with patterned wettability contrast are important in industrial applications such as heat transfer, water collection, and particle separation. Traditional methods of fabricating such surfaces rely on microfabrication technologies, which are only applicable to certain substrates and are difficult to scale up and implement on curved surfaces. By taking advantage of a mechanical instability on a polyurethane elastomer film, we show that wettability patterns on both flat and curved surfaces can be generated spontaneously via a simple dip coating process. Variations in dipping time, sample prestress, and chemical treatment enable independent control of domain size (from about 100 to 500 μm), morphology, and wettability contrast, respectively. We characterize the wettability contrast using local surface energy measurements via the sessile droplet technique and tensiometry. PMID:27382170

Electronic Properties of Curved and Defective 2-D BN Nanostructures

NASA Astrophysics Data System (ADS)

Beach, Kory; Terrones, Humberto; Raeliarijaona, Aldo; Siegel, Ross; Florio, Fred

Density functional theory (DFT) with local density approximation (LDA) pseudopotentials is used to calculate the band structure and density of states of various novel 2-D BN nanostructures. Three types of systems are studied: Schwarzites, a Haeckelite, and an h-BN monolayer. Schwarzites are negatively curved structures in which the curvature is due to the introduction of octagonal rings of alternating boron and nitrogen atoms. In particular, three families of Schwarzites are analyzed: P, G and IWP. The Haeckelites on the other hand, are flat layers composed of squares and octagons of BN. It is found that all these BN allotropes are metastable in which the band gap is direct and smaller than the most stable system, h-BN. National Science Foundation (EFRI-1433311).

Serum studies in man after administration of vitamin A acetate and vitamin A alcohol

PubMed Central

Fitzgerald, Oliver; Fennelly, James J.; Hingerty, Daniel J.

1962-01-01

Vitamin A acetate and vitamin A alcohol, triolein I131, oleic acid I131, and fat balance tests have been assessed in studies on cases of coeliac disease, pancreatic insufficiency, and some disorders of the small intestinal wall. In coeliac disease a very low serum carotene and flat vitamin A absorption curves have been noted. The contrast between vitamin A acetate and alcohol curves has been clearly shown in cases of pancreatic disorder showing maldigestion. The correlation between vitamin A and triolein I131 absorption (0·89) is closer than that between vitamin A and fat balance. In assessing intestinal absorption serum carotene figures are of value only if very low figures are found. PMID:13893355

VizieR Online Data Catalog: Optical/NIR light curves of SN 2009ib (Takats+, 2015)

NASA Astrophysics Data System (ADS)

Takats, K.; Pignata, G.; Pumo, M. L.; Paillas, E.; Zampieri, L.; Elias-Rosa, N.; Benetti, S.; Bufano, F.; Cappellaro, E.; Ergon, M.; Fraser, M.; Hamuy, M.; Inserra, C.; Kankare, E.; Smartt, S. J.; Stritzinger, M. D.; van Dyk, S. D.; Haislip, J. B.; Lacluyze, A. P.; Moore, J. P.; Reichart, D.

2017-11-01

Optical photometry was collected using multiple telescopes with UBVRI and u'g'r'i'z' filters, covering the phases between 13 and 262d after explosion. The basic reduction steps of the images (such as bias-subtraction, overscan-correction, flat-fielding) were carried out using the standard IRAF tasks. The photometric measurement of the SN was performed using the point-spread function (PSF) fitting technique via the SNOOPY package in IRAF. Near-infrared photometry was obtained using the Rapid Eye Mount (REM) telescope in JH bands. Dithered images of the SN field were taken in multiple sequences of five. The object images were dark- and flat-field corrected, combined to create sky images then the sky images were subtracted from the object images. The images were then registered and combined. (3 data files).

Improving a high-efficiency, gated spectrometer for x-ray Thomson scattering experiments at the National Ignition Facility.

PubMed

Döppner, T; Kraus, D; Neumayer, P; Bachmann, B; Emig, J; Falcone, R W; Fletcher, L B; Hardy, M; Kalantar, D H; Kritcher, A L; Landen, O L; Ma, T; Saunders, A M; Wood, R D

2016-11-01

We are developing x-ray Thomson scattering for applications in implosion experiments at the National Ignition Facility. In particular we have designed and fielded MACS, a high-efficiency, gated x-ray spectrometer at 7.5-10 keV [T. Döppner et al., Rev. Sci. Instrum. 85, 11D617 (2014)]. Here we report on two new Bragg crystals based on Highly Oriented Pyrolytic Graphite (HOPG), a flat crystal and a dual-section cylindrically curved crystal. We have performed in situ calibration measurements using a brass foil target, and we used the flat HOPG crystal to measure Mo K-shell emission at 18 keV in 2nd order diffraction. Such high photon energy line emission will be required to penetrate and probe ultra-high-density plasmas or plasmas of mid-Z elements.

Effects of mistuning and matrix structure on the topology of frequency response curves

NASA Technical Reports Server (NTRS)

Afolabi, Dare

1989-01-01

The stability of a frequency response curve under mild perturbations of the system's matrix is investigated. Using recent developments in the theory of singularities of differentiable maps, it is shown that the stability of a response curve depends on the structure of the system's matrix. In particular, the frequency response curves of a cylic system are shown to be unstable. Consequently, slight parameter variations engendered by mistuning will induce a significant difference in the topology of the forced response curves, if the mistuning transformation crosses the bifurcation set.

Comparison of structural response and fatigue endurance of aircraft flap-like box structures subjected to acoustic loading

NASA Astrophysics Data System (ADS)

Xiao, Y.; White, R. G.; Aglietti, G. S.

2005-05-01

The results of an extensive test program to characterize the behavior of typical aircraft structures under acoustic loading and to establish their fatigue endurance are presented. The structures tested were the three flap-like box-type of structures. Each structure consisted of one flat (bottom) and one curved (top) stiffener stiffened skin panel, front, and rear spars, and ribs that divided the structures into three bays. The three structures, constructed from three different materials (aircraft standard aluminum alloy, Carbon Fibre Reinforced Plastic, and a Glass Fibre Metal Laminate, i.e., GLARE) had the same size and configuration, with only minor differences due to the use of different materials. A first set of acoustic tests with excitations of intensity ranging from 140 to 160 dB were carried out to obtain detailed data on the dynamic response of the three structures. The FE analysis of the structures is also briefly described and the results compared with the experimental data. The fatigue endurance of the structures was then determined using random acoustic excitation with an overall sound pressure level of 161 dB, and details of crack propagation are reported. .

From the limits of the classical model of sensitometric curves to a realistic model based on the percolation theory for GafChromic EBT films.

PubMed

del Moral, F; Vázquez, J A; Ferrero, J J; Willisch, P; Ramírez, R D; Teijeiro, A; López Medina, A; Andrade, B; Vázquez, J; Salvador, F; Medal, D; Salgado, M; Muñoz, V

2009-09-01

Modern radiotherapy uses complex treatments that necessitate more complex quality assurance procedures. As a continuous medium, GafChromic EBT films offer suitable features for such verification. However, its sensitometric curve is not fully understood in terms of classical theoretical models. In fact, measured optical densities and those predicted by the classical models differ significantly. This difference increases systematically with wider dose ranges. Thus, achieving the accuracy required for intensity-modulated radiotherapy (IMRT) by classical methods is not possible, plecluding their use. As a result, experimental parametrizations, such as polynomial fits, are replacing phenomenological expressions in modern investigations. This article focuses on identifying new theoretical ways to describe sensitometric curves and on evaluating the quality of fit for experimental data based on four proposed models. A whole mathematical formalism starting with a geometrical version of the classical theory is used to develop new expressions for the sensitometric curves. General results from the percolation theory are also used. A flat-bed-scanner-based method was chosen for the film analysis. Different tests were performed, such as consistency of the numeric results for the proposed model and double examination using data from independent researchers. Results show that the percolation-theory-based model provides the best theoretical explanation for the sensitometric behavior of GafChromic films. The different sizes of active centers or monomer crystals of the film are the basis of this model, allowing acquisition of information about the internal structure of the films. Values for the mean size of the active centers were obtained in accordance with technical specifications. In this model, the dynamics of the interaction between the active centers of GafChromic film and radiation is also characterized by means of its interaction cross-section value. The percolation model fulfills the accuracy requirements for quality-control procedures when large ranges of doses are used and offers a physical explanation for the film response.

Fracture on Curved Surfaces

NASA Astrophysics Data System (ADS)

Mitchell, Noah; Koning, Vinzenz; Vitelli, Vincenzo; Irvine, William T. M.

2014-03-01

When an elastic film conforms to a surface with Gaussian curvature, stresses arise in the film. As a result, cracks--typically studied in flat materials--interact with curvature when propagating through the system. Using silicone elastomer sheets that conform to the surface of a Gaussian bump, we find experimental evidence for the deflection of a crack propagating through the material. We interpret our experiments with reference to analytical modeling and simulations of a simplified model system.

Stability of Nonlinear Swarms on Flat and Curved Surfaces

DTIC Science & Technology

numerical experiments have shown that the system either converges to a rotating circular limit cycle with a fixed center of mass, or the agents clump ...Swarming is a near-universal phenomenon in nature. Many mathematical models of swarms exist , both to model natural processes and to control robotic...agents. We study a swarm of agents with spring-like at-traction and nonlinear self-propulsion. Swarms of this type have been studied numerically, but

Universal aspects of adhesion and atomic force microscopy

NASA Technical Reports Server (NTRS)

Banerjea, Amitava; Smith, John R.; Ferrante, John

1990-01-01

Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

The first UV spectrum of a Uranian satellite - IUE observations of Oberon from 2650-3200 A

NASA Technical Reports Server (NTRS)

Stern, S. A.; Festou, M. C.; Van Santvoort, J.; Buratti, B. J.

1990-01-01

Using the International Ultraviolet Explorer (IUE) observatory, the first vacuum UV spectrum of Oberon was obtained. The data contain useful information in the spectral range 2650-3200 A. Oberon's UV geometric albedo is found to be flat and essentially featureless with an average value of p(UV) = 0.19 + or - 0.025, and making it possible to extend Oberon's phase curve into the opposite region.

Comparison of Fresnel lenses and parabolic mirrors as solar energy concentrators.

PubMed

Lorenzo, E; Luque, A

1982-05-15

This paper compares the gain that can be achieved with a one- or two-stage concentrator, when the first stage is a Fresnel lens or a parabolic mirror, as a function of the luminosity of the concentrator. The results show that the achievable gain using a parabolic mirror is greater than that obtained using a flat or roof lens but is lower than that obtained using a curved lens.

Orientation-dependent deformation mechanisms of bcc niobium nanoparticles

NASA Astrophysics Data System (ADS)

Bian, J. J.; Yang, L.; Niu, X. R.; Wang, G. F.

2018-07-01

Nanoparticles usually exhibit pronounced anisotropic properties, and a close insight into the atomic-scale deformation mechanisms is of great interest. In present study, atomic simulations are conducted to analyse the compression of bcc nanoparticles, and orientation-dependent features are addressed. It is revealed that surface morphology under indenter predominantly governs the initial elastic response. The loading curve follows the flat punch contact model in [1 1 0] compression, while it obeys the Hertzian contact model in [1 1 1] and [0 0 1] compressions. In plastic deformation regime, full dislocation gliding is dominated in [1 1 0] compression, while deformation twinning is prominent in [1 1 1] compression, and these two mechanisms coexist in [0 0 1] compression. Such deformation mechanisms are distinct from those in bulk crystals under nanoindentation and nanopillars under compression, and the major differences are also illuminated. Our results provide an atomic perspective on the mechanical behaviours of bcc nanoparticles and are helpful for the design of nanoparticle-based components and systems.

Determination of the Elastic Moduli of a Single Cell Cultured on a Rigid Support by Force Microscopy.

PubMed

Garcia, Pablo D; Garcia, Ricardo

2018-06-19

The elastic response of a living cell is affected by its physiological state. This property provides mechanical fingerprints of a cell's dysfunctionality. The softness (kilopascal range) and thickness (2-15 μm) of mammalian cells imply that the force exerted by the probe might be affected by the stiffness of the solid support. This observation makes infinite sample thickness models unsuitable to describe quantitatively the forces and deformations on a cell. Here, we report a general theory to determine the true Young's moduli of a single cell from a force-indentation curve. Analytical expressions are deduced for common geometries such as flat punches, paraboloids, cones, needles, and nanowires. For a given cell and indentation, the influence of the solid support on the measurements is reduced by using sharp and high aspect ratio tips. The theory is validated by finite element simulations. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data

NASA Astrophysics Data System (ADS)

Fisher, L. E.; Lynch, K. A.; Fernandes, P. A.; Bekkeng, T. A.; Moen, J.; Zettergren, M.; Miceli, R. J.; Powell, S.; Lessard, M. R.; Horak, P.

2016-04-01

The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry.

Are driving and overtaking on right curves more dangerous than on left curves?

PubMed

Othman, Sarbaz; Thomson, Robert; Lannér, Gunnar

2010-01-01

It is well known that crashes on horizontal curves are a cause for concern in all countries due to the frequency and severity of crashes at curves compared to road tangents. A recent study of crashes in western Sweden reported a higher rate of crashes in right curves than left curves. To further understand this result, this paper reports the results of novel analyses of the responses of vehicles and drivers during negotiating and overtaking maneuvers on curves for right hand traffic. The overall objectives of the study were to find road parameters for curves that affect vehicle dynamic responses, to analyze these responses during overtaking maneuvers on curves, and to link the results with driver behavior for different curve directions. The studied road features were speed, super-elevation, radius and friction including their interactions, while the analyzed vehicle dynamic factors were lateral acceleration and yaw angular velocity. A simulation program, PC-Crash, has been used to simulate road parameters and vehicle response interaction in curves. Overtaking maneuvers have been simulated for all road feature combinations in a total of 108 runs. Analysis of variances (ANOVA) was performed, using two sided randomized block design, to find differences in vehicle responses for the curve parameters. To study driver response, a field test using an instrumented vehicle and 32 participants was reviewed as it contained longitudinal speed and acceleration data for analysis. The simulation results showed that road features affect overtaking performance in right and left curves differently. Overtaking on right curves was sensitive to radius and the interaction of radius with road condition; while overtaking on left curves was more sensitive to super-elevation. Comparisons of lateral acceleration and yaw angular velocity during these maneuvers showed different vehicle response configurations depending on curve direction and maneuver path. The field test experiments also showed that drivers behave differently depending on the curve direction where both speed and acceleration were higher on right than left curves. The implication of this study is that curve direction should be taken into consideration to a greater extent when designing and redesigning curves. It appears that the driver and the vehicle are influenced by different infrastructure factors depending on the curve direction. In addition, the results suggest that the vehicle dynamics response alone cannot explain the higher crash risk in right curves. Further studies of the links between driver, vehicle, and highway characteristics are needed, such as naturalistic driving studies, to identify the key safety indicators for highway safety.

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

Yang, Zhaoqing; Wang, Taiping

Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existingmore » baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.« less

[Investigation of the accurate measurement of the basic imaging properties for the digital radiographic system based on flat panel detector].

PubMed

Katayama, R; Sakai, S; Sakaguchi, T; Maeda, T; Takada, K; Hayabuchi, N; Morishita, J

2008-07-20

PURPOSE/AIM OF THE EXHIBIT: The purpose of this exhibit is: 1. To explain "resampling", an image data processing, performed by the digital radiographic system based on flat panel detector (FPD). 2. To show the influence of "resampling" on the basic imaging properties. 3. To present accurate measurement methods of the basic imaging properties of the FPD system. 1. The relationship between the matrix sizes of the output image and the image data acquired on FPD that automatically changes depending on a selected image size (FOV). 2. The explanation of the image data processing of "resampling". 3. The evaluation results of the basic imaging properties of the FPD system using two types of DICOM image to which "resampling" was performed: characteristic curves, presampled MTFs, noise power spectra, detective quantum efficiencies. CONCLUSION/SUMMARY: The major points of the exhibit are as follows: 1. The influence of "resampling" should not be disregarded in the evaluation of the basic imaging properties of the flat panel detector system. 2. It is necessary for the basic imaging properties to be measured by using DICOM image to which no "resampling" is performed.

The impact of galactic disc environment on star-forming clouds

NASA Astrophysics Data System (ADS)

Nguyen, Ngan K.; Pettitt, Alex R.; Tasker, Elizabeth J.; Okamoto, Takashi

2018-03-01

We explore the effect of different galactic disc environments on the properties of star-forming clouds through variations in the background potential in a set of isolated galaxy simulations. Rising, falling, and flat rotation curves expected in halo-dominated, disc-dominated, and Milky Way-like galaxies were considered, with and without an additional two-arm spiral potential. The evolution of each disc displayed notable variations that are attributed to different regimes of stability, determined by shear and gravitational collapse. The properties of a typical cloud were largely unaffected by the changes in rotation curve, but the production of small and large cloud associations was strongly dependent on this environment. This suggests that while differing rotation curves can influence where clouds are initially formed, the average bulk properties are effectively independent of the global environment. The addition of a spiral perturbation made the greatest difference to cloud properties, successfully sweeping the gas into larger, seemingly unbound, extended structures and creating large arm-interarm contrasts.

Ancient fluvial processes in the equatorial highlands of Mars

NASA Technical Reports Server (NTRS)

Craddock, Robert A.; Maxwell, Ted A.

1991-01-01

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves.

ON THE ROTATION SPEED OF THE MILKY WAY DETERMINED FROM H i EMISSION

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

Reid, M. J.; Dame, T. M.

2016-12-01

The circular rotation speed of the Milky Way at the solar radius, Θ{sub 0}, has been estimated to be 220 km s{sup −1} by fitting the maximum velocity of H i emission as a function of Galactic longitude. This result is in tension with a recent estimate of Θ{sub 0} = 240 km s{sup −1}, based on Very Long Baseline Interferometry (VLBI) parallaxes and proper motions from the BeSSeL and VERA surveys for large numbers of high-mass star-forming regions across the Milky Way. We find that the rotation curve best fitted to the VLBI data is slightly curved, and that this curvaturemore » results in a biased estimate of Θ{sub 0} from the H i data when a flat rotation curve is assumed. This relieves the tension between the methods and favors Θ{sub 0} = 240 km s{sup −1}.« less

Diffuse interface modeling of three-phase contact line dynamics on curved boundaries: A lattice Boltzmann model for large density and viscosity ratios

NASA Astrophysics Data System (ADS)

Fakhari, Abbas; Bolster, Diogo

2017-04-01

We introduce a simple and efficient lattice Boltzmann method for immiscible multiphase flows, capable of handling large density and viscosity contrasts. The model is based on a diffuse-interface phase-field approach. Within this context we propose a new algorithm for specifying the three-phase contact angle on curved boundaries within the framework of structured Cartesian grids. The proposed method has superior computational accuracy compared with the common approach of approximating curved boundaries with stair cases. We test the model by applying it to four benchmark problems: (i) wetting and dewetting of a droplet on a flat surface and (ii) on a cylindrical surface, (iii) multiphase flow past a circular cylinder at an intermediate Reynolds number, and (iv) a droplet falling on hydrophilic and superhydrophobic circular cylinders under differing conditions. Where available, our results show good agreement with analytical solutions and/or existing experimental data, highlighting strengths of this new approach.

SDO FlatSat Facility

NASA Technical Reports Server (NTRS)

Amason, David L.

2008-01-01

The goal of the Solar Dynamics Observatory (SDO) is to understand and, ideally, predict the solar variations that influence life and society. It's instruments will measure the properties of the Sun and will take hifh definition images of the Sun every few seconds, all day every day. The FlatSat is a high fidelity electrical and functional representation of the SDO spacecraft bus. It is a high fidelity test bed for Integration & Test (I & T), flight software, and flight operations. For I & T purposes FlatSat will be a driver to development and dry run electrical integration procedures, STOL test procedures, page displays, and the command and telemetry database. FlatSat will also serve as a platform for flight software acceptance and systems testing for the flight software system component including the spacecraft main processors, power supply electronics, attitude control electronic, gimbal control electrons and the S-band communications card. FlatSat will also benefit the flight operations team through post-launch flight software code and table update development and verification and verification of new and updated flight operations products. This document highlights the benefits of FlatSat; describes the building of FlatSat; provides FlatSat facility requirements, access roles and responsibilities; and, and discusses FlatSat mechanical and electrical integration and functional testing.

SU-E-T-439: Fundamental Verification of Respiratory-Gated Spot Scanning Proton Beam Therapy

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

Hamano, H; Yamakawa, T; Hayashi, N

Purpose: The spot-scanning proton beam irradiation with respiratory gating technique provides quite well dose distribution and requires both dosimetric and geometric verification prior to clinical implementation. The purpose of this study is to evaluate the impact of gating irradiation as a fundamental verification. Methods: We evaluated field width, flatness, symmetry, and penumbra in the gated and non-gated proton beams. The respiration motion was distinguished into 3 patterns: 10, 20, and 30 mm. We compared these contents between the gated and non-gated beams. A 200 MeV proton beam from PROBEAT-III unit (Hitachi Co.Ltd) was used in this study. Respiratory gating irradiationmore » was performed by Quasar phantom (MODUS medical devices) with a combination of dedicated respiratory gating system (ANZAI Medical Corporation). For radiochromic film dosimetry, the calibration curve was created with Gafchromic EBT3 film (Ashland) on FilmQA Pro 2014 (Ashland) as film analysis software. Results: The film was calibrated at the middle of spread out Bragg peak in passive proton beam. The field width, flatness and penumbra in non-gated proton irradiation with respiratory motion were larger than those of reference beam without respiratory motion: the maximum errors of the field width, flatness and penumbra in respiratory motion of 30 mm were 1.75% and 40.3% and 39.7%, respectively. The errors of flatness and penumbra in gating beam (motion: 30 mm, gating rate: 25%) were 0.0% and 2.91%, respectively. The results of symmetry in all proton beams with gating technique were within 0.6%. Conclusion: The field width, flatness, symmetry and penumbra were improved with the gating technique in proton beam. The spot scanning proton beam with gating technique is feasible for the motioned target.« less

Ion beam lithography system

DOEpatents

Leung, Ka-Ngo

2005-08-02

A maskless plasma-formed ion beam lithography tool provides for patterning of sub-50 nm features on large area flat or curved substrate surfaces. The system is very compact and does not require an accelerator column and electrostatic beam scanning components. The patterns are formed by switching beamlets on or off from a two electrode blanking system with the substrate being scanned mechanically in one dimension. This arrangement can provide a maskless nano-beam lithography tool for economic and high throughput processing.

Improved Polyurethane Storage Tank Performance

DTIC Science & Technology

2014-06-30

condition occurred if water overflowed from the tank vent prior to reaching 45 gallons. A spline curve was drawn around the perimeter of each image so...estimated footprint and height envelope was added for spatial reference. A spline color code key was developed, so that the progression of the tanks...Table 4.5.3). A standard flat plate platen was used for the double butt seams and some closing seams by one fabricator. The other utilized a “Slinky

Proca fields interpretation of spin 1 equation in Robertson-Walker space-time

NASA Astrophysics Data System (ADS)

Zecca, Antonio

2006-05-01

The general scheme for massive spin 1 equation in curved space-time is specialized to describe the Proca fields. The expressions of the Proca tensor fields are detailed in the Robertson-Walker space-time by means of the solutions of the spin 1 equation in a given tetrad and by the components of the tetrad itself. Asymptotic behaviours of the fields are discussed in the flat, closed and open space-time cases.

Device for reducing vehicle aerodynamic resistance

DOEpatents

Graham, Sean C.

2005-02-15

A device for a vehicle with a pair of swinging rear doors, which converts flat sheets of pliable material hinged to the sides of the vehicle adjacent the rear thereof into effective curved airfoils that reduce the aerodynamic resistance of the vehicle, when the doors are closed by hand, utilizing a plurality of stiffeners disposed generally parallel to the doors and affixed to the sheets and a plurality of collapsible tension bearings struts attached to each stiffener and the adjacent door.

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

Liu, Adrian; Zhang, Yunfan; Parsons, Aaron R., E-mail: acliu@berkeley.edu

Intensity mapping is a promising technique for surveying the large-scale structure of our universe from z  = 0 to z  ∼ 150, using the brightness temperature field of spectral lines to directly observe previously unexplored portions of our cosmic timeline. Examples of targeted lines include the 21 cm hyperfine transition of neutral hydrogen, rotational lines of carbon monoxide, and fine-structure lines of singly ionized carbon. Recent efforts have focused on detections of the power spectrum of spatial fluctuations, but have been hindered by systematics such as foreground contamination. This has motivated the decomposition of data into Fourier modes perpendicular and parallel tomore » the line of sight, which has been shown to be a particularly powerful way to diagnose systematics. However, such a method is well-defined only in the limit of a narrow-field, flat-sky approximation. This limits the sensitivity of intensity mapping experiments, as it means that wide surveys must be separately analyzed as a patchwork of smaller fields. In this paper, we develop a framework for analyzing intensity mapping data in a spherical Fourier–Bessel basis, which incorporates curved sky effects without difficulty. We use our framework to generalize a number of techniques in intensity mapping data analysis from the flat sky to the curved sky. These include visibility-based estimators for the power spectrum, treatments of interloper lines, and the “foreground wedge” signature of spectrally smooth foregrounds.« less

Spherical Harmonic Analyses of Intensity Mapping Power Spectra

NASA Astrophysics Data System (ADS)

Liu, Adrian; Zhang, Yunfan; Parsons, Aaron R.

2016-12-01

Intensity mapping is a promising technique for surveying the large-scale structure of our universe from z = 0 to z ˜ 150, using the brightness temperature field of spectral lines to directly observe previously unexplored portions of our cosmic timeline. Examples of targeted lines include the 21 cm hyperfine transition of neutral hydrogen, rotational lines of carbon monoxide, and fine-structure lines of singly ionized carbon. Recent efforts have focused on detections of the power spectrum of spatial fluctuations, but have been hindered by systematics such as foreground contamination. This has motivated the decomposition of data into Fourier modes perpendicular and parallel to the line of sight, which has been shown to be a particularly powerful way to diagnose systematics. However, such a method is well-defined only in the limit of a narrow-field, flat-sky approximation. This limits the sensitivity of intensity mapping experiments, as it means that wide surveys must be separately analyzed as a patchwork of smaller fields. In this paper, we develop a framework for analyzing intensity mapping data in a spherical Fourier-Bessel basis, which incorporates curved sky effects without difficulty. We use our framework to generalize a number of techniques in intensity mapping data analysis from the flat sky to the curved sky. These include visibility-based estimators for the power spectrum, treatments of interloper lines, and the “foreground wedge” signature of spectrally smooth foregrounds.

Association of microRNAs with Types of Leaf Curvature in Brassica rapa.

PubMed

Ren, Wenqing; Wang, Han; Bai, Jinjuan; Wu, Feijie; He, Yuke

2018-01-01

Many vegetable crops of Brassica rapa are characterized by their typical types of leaf curvature. Leaf curvature in the right direction and to the proper degree is important for the yield and quality of green vegetable products, when cultivated under stress conditions. Recent research has unveiled some of the roles of miRNAs in Brassica crops such as how they regulate the timing of leafy head initiation and shape of the leafy head. However, the molecular mechanism underlying the variability in leaf curvature in B. rapa remains unclear. We tested the hypothesis that the leaf curvature of B. rapa is affected by miRNA levels. On the basis of leaf phenotyping, 56 B. rapa accessions were classified into five leaf curvature types, some of which were comparable to miRNA mutants of Arabidopsis thaliana in phenotype. Higher levels of miR166 and miR319a expression were associated with downward curvature and wavy margins, respectively. Overexpression of the Brp - MIR166g-1 gene caused rosette leaves to change from flat to downward curving and folding leaves to change from upward curving to flat, leading to the decrease in the number of incurved leaves and size of the leafy head. Our results reveal that miRNAs affect the types of leaf curvature in B. rapa . These findings provide insight into the relationship between miRNAs and variation in leaf curvature.

Association of microRNAs with Types of Leaf Curvature in Brassica rapa

PubMed Central

Ren, Wenqing; Wang, Han; Bai, Jinjuan; Wu, Feijie; He, Yuke

2018-01-01

Many vegetable crops of Brassica rapa are characterized by their typical types of leaf curvature. Leaf curvature in the right direction and to the proper degree is important for the yield and quality of green vegetable products, when cultivated under stress conditions. Recent research has unveiled some of the roles of miRNAs in Brassica crops such as how they regulate the timing of leafy head initiation and shape of the leafy head. However, the molecular mechanism underlying the variability in leaf curvature in B. rapa remains unclear. We tested the hypothesis that the leaf curvature of B. rapa is affected by miRNA levels. On the basis of leaf phenotyping, 56 B. rapa accessions were classified into five leaf curvature types, some of which were comparable to miRNA mutants of Arabidopsis thaliana in phenotype. Higher levels of miR166 and miR319a expression were associated with downward curvature and wavy margins, respectively. Overexpression of the Brp-MIR166g-1 gene caused rosette leaves to change from flat to downward curving and folding leaves to change from upward curving to flat, leading to the decrease in the number of incurved leaves and size of the leafy head. Our results reveal that miRNAs affect the types of leaf curvature in B. rapa. These findings provide insight into the relationship between miRNAs and variation in leaf curvature. PMID:29467771

Modeling and measurement of electrostatic micromirror array fabricated with single-layer polysilicon micromachining technology

NASA Astrophysics Data System (ADS)

Min, Young-Hoon; Kim, Yong-Kweon

1998-09-01

A silicon based micro mirror array is a highly efficient component for use in optical applications as adaptive optical systems and optical correlators. Many types of micro mirror or micro mirror array have been studied and proposed in order to obtain the optimal performance according to their own purposes. A micro mirror array designed, fabricated and tested in this paper consists of 5 X 5 single layer polysilicon-based, electrostatically driven actuators. The micro mirror array for the optical phase modulation is made by using only two masks and can be driven independently by 25 channel circuits. About 6 (pi) phase modulation is obtained in He-Ne laser ((lambda) equals 633 nm) with 67% fill-factor. In this paper, the deflection characteristics of the actuators in controllable range were studied. The experimental results show that the deflection characteristics is much dependent upon a residual stress in flexure, the initial curvature of mirror due to stress gradient and an electrostatic force acted on other element except for mirror itself. The modeling results agree well with the experimental results. Also, it is important to fabricate a flat mirror that is not initially curved because the curved mirror brings a bad performance in optical use. Therefore, a new method to obtain the flat mirror by using the gold metallization in spite of the residual stress unbalance is proposed in this paper.

Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

1999-01-01

A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

Small bending and stretching of sandwich-type shells

NASA Technical Reports Server (NTRS)

Reissner, Eric

1950-01-01

A theory has been developed for small bending and stretching of sandwich-type shells. This theory is an extension of the known theory of homogeneous thin elastic shells. It was found that two effects are important in the present problem, which are not normally of importance in the theory of curved shells: (1) the effect of transverse shear deformation and (2) the effect of transverse normal stress deformation. The first of these two effects has been known to be of importance in the theory of plates and beams. The second effect was found to occur in a manner which is typical for shells and has no counterpart in flat-plate theory. The general results of this report have been applied to the solution of problems concerning flat plates, circular rings, circular cylindrical shells, and spherical shells. In each case numerical examples have been given, illustrating the magnitude of the effects of transverse shear and normal stress deformation.

Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmitarrays

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

Arbabi, Amir; Horie, Yu; Ball, Alexander J.

2015-05-07

Flat optical devices thinner than a wavelength promise to replace conventional free-space components for wavefront and polarization control. Transmissive flat lenses are particularly interesting for applications in imaging and on-chip optoelectronic integration. Several designs based on plasmonic metasurfaces, high-contrast transmitarrays and gratings have been recently implemented but have not provided a performance comparable to conventional curved lenses. Here we report polarization-insensitive, micron-thick, high-contrast transmitarray micro-lenses with focal spots as small as 0.57 λ. The measured focusing efficiency is up to 82%. A rigorous method for ultrathin lens design, and the trade-off between high efficiency and small spot size (or largemore » numerical aperture) are discussed. The micro-lenses, composed of silicon nano-posts on glass, are fabricated in one lithographic step that could be performed with high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.« less

Probing dark energy in the scope of a Bianchi type I spacetime

NASA Astrophysics Data System (ADS)

Amirhashchi, Hassan

2018-03-01

It is well known that the flat Friedmann-Robertson-Walker metric is a special case of Bianchi type I spacetime. In this paper, we use 38 Hubble parameter, H (z ), measurements at intermediate redshifts 0.07 ≤z ≤2.36 and its joint combination with the latest "joint light curves" (JLA) sample, comprising 740 type Ia supernovae in the redshift range of z ɛ [0.01 ,1.30 ] to constrain the parameters of the Bianchi type I dark energy model. We also use the same datasets to constrain flat a Λ CDM model. In both cases, we specifically address the expansion rate H0 as well as the transition redshift zt determinations out of these measurements. In both models, we found that using joint combination of datasets gives rise to lower values for model parameters. Also to compare the considered cosmologies, we have made Akaike information criterion and Bayes factor (Ψ ) tests.

Beam-Steerable Flat-Panel Reflector Antenna

NASA Technical Reports Server (NTRS)

Lee, Choon Sae; Lee, Chanam; Miranda, Felix A.

2005-01-01

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-born applications is an umbrella-type reflector antenna that can be folded while being lifted to the Earth orbit. There have been a number of issues to be resolved for this type of antenna. The reflecting surface of a fine wire mesh has to be light in weight and flexible while opening up once in orbit. Also the mesh must be a good conductor at the operating frequency. In this paper, we propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. Moreover it is possible to steer the beam without moving the entire antenna system.

Improving a high-efficiency, gated spectrometer for x-ray Thomson scattering experiments at the National Ignition Facility

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

Döppner, T., E-mail: doeppner1@llnl.gov; Bachmann, B.; Emig, J.

We are developing x-ray Thomson scattering for applications in implosion experiments at the National Ignition Facility. In particular we have designed and fielded MACS, a high-efficiency, gated x-ray spectrometer at 7.5–10 keV [T. Döppner et al., Rev. Sci. Instrum. 85, 11D617 (2014)]. Here we report on two new Bragg crystals based on Highly Oriented Pyrolytic Graphite (HOPG), a flat crystal and a dual-section cylindrically curved crystal. We have performed in situ calibration measurements using a brass foil target, and we used the flat HOPG crystal to measure Mo K-shell emission at 18 keV in 2nd order diffraction. Such high photonmore » energy line emission will be required to penetrate and probe ultra-high-density plasmas or plasmas of mid-Z elements.« less

Improving a high-efficiency, gated spectrometer for x-ray Thomson scattering experiments at the National Ignition Facility

DOE PAGES

Döppner, T.; Kraus, D.; Neumayer, P.; ...

2016-08-03

We are developing x-ray Thomson scattering for applications in implosion experiments at the National Ignition Facility. In particular we have designed and fielded MACS, a high-efficiency, gated x-ray spectrometer at 7.5-10 keV [T. Döppner et al., Rev. Sci. Instrum. 85, 11D617 (2014)]. Here in this paper we report on two new Bragg crystals based on Highly Oriented Pyrolytic Graphite (HOPG), a flat crystal and a dual-section cylindrically curved crystal. We have performed in situ calibration measurements using a brass foil target, and we used the flat HOPG crystal to measure Mo K-shell emission at 18 keV in 2nd order diffraction.more » Such high photon energy line emission will be required to penetrate and probe ultra-high-density plasmas or plasmas of mid-Z elements.« less

Observations of flat-spectrum radio sources at λ850μm from the James Clerk Maxwell Telescope II. April 2000 to June 2005

NASA Astrophysics Data System (ADS)

Jenness, T.; Robson, E. I.; Stevens, J. A.

2010-01-01

Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850μm covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (SCUBA) camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control - Data Reduction (ORAC-DR) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources.

Compact seaweed growth of peritectic phase on confined, flat properitectic dendrites

NASA Astrophysics Data System (ADS)

Ludwig, A.; Mogeritsch, J.

2016-12-01

Peritectic alloys form a variety of different solidification morphologies at low growth rates. An alloy with a concentration that corresponds to the hyper-peritectic limit should show a cellular/dendritic solidification of the peritectic phase for growth velocities above the corresponding constitutional undercooling limit. However, due to nucleation retardation of the peritectic phase we observed growth of properitectic dendrites before cellular growth of the peritectic could established. The transition happened via an overgrowth of dendrites with a thin layer of peritectic phase. The observations were made using a transparent, metal-like solidifying peritectic system that was solidified directionally in thin samples. In the gap between the flat dendrites and the tubing walls, the peritectic phase grew with a compact seaweed morphology, whereas in the interdendritic spacing it formed small-curved bumps. At same distance behind the tip region, more and more polycrystalline-like objects appeared at the elongated traces of the compact seaweed morphology.

Nonmonotonic Dose-Response Curves and Endocrine-Disrupting Chemicals: Fact or Falderal?**

EPA Science Inventory

Nonmonotonic Dose-Response Curves and Endocrine-Disrupting Chemicals: Fact or Falderal? The shape of the dose response curve in the low dose region has been debated since the 1940s, originally focusing on linear no threshold (LNT) versus threshold responses for cancer and noncanc...

Investigations of structural defects, crystalline perfection, metallic impurity concentration and optical quality of flat-top KDP crystal

NASA Astrophysics Data System (ADS)

Sharma, S. K.; Verma, Sunil; Singh, Yeshpal; Bartwal, K. S.; Tiwari, M. K.; Lodha, G. S.; Bhagavannarayana, G.

2015-08-01

KDP crystal grown using flat-top technique has been characterized using X-ray and optical techniques with the aim of correlating the defects structure and impurity concentration in the crystal with its optical properties. Crystallographic defects were investigated using X-ray topography revealing linear and arc like chains of dislocations and to conclude that defects do not originate from the flat-top part of the crystal. Etching was performed to quantify dislocation defects density. The crystalline perfection of the crystal was found to be high as the FWHM of the rocking curves measured at several locations was consistently low 6-9 arc s. The concentration of Fe metallic impurity quantified using X-ray fluorescence technique was approximately 5 times lower in the flat-top part which falls in pyramidal growth sector as compared to the region near to the seed which lies in prismatic sector. The spectrophotometric characterization for plates cut normal to different crystallographic directions in the flat-top potassium dihydrogen phosphate (FT-KDP) crystal was performed to understand the influence of metallic impurity distribution and growth sectors on the optical transmittance. The transmittance of the FT-KDP crystal at 1064 nm and its higher harmonics (2nd, 3rd, 4th and 5th) was determined from the measured spectra and the lower transmission in the UV region was attributed to increased absorption by Fe metallic impurity at these wavelengths. The results are in agreement with the results obtained using X-ray fluorescence and X-ray topography. Birefringence and Mach-Zehnder interferometry show that except for the region near to the seed crystal the optical homogeneity of the entire crystal was good. The laser-induced damage threshold (LDT) values are in the range 2.4-3.9 GW/cm2. The LDT of the plate taken from the flat-top region is higher than that from the bottom of the crystal, indicating that the flat-top technique has good optical quality and is comparable to those reported using rapid growth technique. The results indicate that the structural defects, crystalline quality and impurity concentration have a correlation with the optical properties of the FT-KDP crystal.

A perfect Fresnel acoustic reflector implemented by a Fano-resonant metascreen

NASA Astrophysics Data System (ADS)

Amin, M.; Siddiqui, O.; Farhat, M.; Khelif, A.

2018-04-01

We propose a perfectly reflecting acoustic metasurface which is designed by replacing the curved segments of the traditional Fresnel reflector by flat Fano-resonant sub-wavelength unit cells. To preserve the original Fresnel focusing mechanism, the unit cell phase follows a specific phase profile which is obtained by applying the generalized Snell's law and Fermat's principle. The reflected curved phase fronts are thus created at the air-metasurface boundary by tailoring the metasurface dispersion as dictated by Huygens' principle. Since the unit cells are implemented by sub-wavelength double slit-shaped cavity resonators, the impinging sound waves are perfectly reflected producing acoustic focusing with negligible absorption. We use plane-wave solution and full-wave simulations to demonstrate the focusing effects. The simulation results closely follow the analytical predictions.

Effect of limb darkening on earth radiation incident on a spherical satellite

NASA Technical Reports Server (NTRS)

Katzoff, S.; Smith, G. L.

1974-01-01

The thermal radiation from the earth incident on a spherical satellite depends on the angular distribution of earth-emitted radiation. An analysis is presented of this dependency, and calculated results are given, based on a published limb-darkening curve for the earth. The curve was determined from Tiros data, and is a statistical average over the entire globe between 75 deg latitude. The computed effect of limb darkening was 1.8 percent at 900 km altitude, 2.5 percent at 500 km altitude, and 3.0 percent at 300 km altitude. Below 300 km, it increased rapidly with decreasing altitude. Discussion is included of various other problems inherent in the use of orbiting spheres and stabilized flat plates to measure the heat radiated from the earth.

Active noise control using a distributed mode flat panel loudspeaker.

PubMed

Zhu, H; Rajamani, R; Dudney, J; Stelson, K A

2003-07-01

A flat panel distributed mode loudspeaker (DML) has many advantages over traditional cone speakers in terms of its weight, size, and durability. However, its frequency response is uneven and complex, thus bringing its suitability for active noise control (ANC) under question. This paper presents experimental results demonstrating the effective use of panel DML speakers in an ANC application. Both feedback and feedforward control techniques are considered. Effective feedback control with a flat panel speaker could open up a whole range of new noise control applications and has many advantages over feedforward control. The paper develops a new control algorithm to attenuate tonal noise of a known frequency by feedback control. However, due to the uneven response of the speakers, feedback control is found to be only moderately effective even for this narrow-band application. Feedforward control proves to be most capable for the flat panel speaker. Using feedforward control, the sound pressure level can be significantly reduced in close proximity to an error microphone. The paper demonstrates an interesting application of the flat panel in which the panel is placed in the path of sound and effectively used to block sound transmission using feedforward control. This is a new approach to active noise control enabled by the use of flat panels and can be used to prevent sound from entering into an enclosure in the first place rather than the traditional approach of attempting to cancel sound after it enters the enclosure.

Nematodes from galls on Myrtaceae. IV. Fergusobia from flat leaf galls on Eucalyptus and Corymbia, with descriptions of two new species.

PubMed

Davies, Kerrie A; Giblin-Davis, Robin M; Ye, Weimin; Taylor, Gary S; Thomas, W Kelley

2013-11-26

Two new species of Fergusobia are described. Both were collected from flat leaf galls from South Australia, one on Eucalyptus microcarpa and the other on E. porosa. Fergusobia microcarpae n. sp. Davies is characterised by the combination of a C-shaped parthenogenetic female with a short, broadly rounded conoid tail, an arcuate to open C-shaped infective female with an hemispherical tail tip, and arcuate to J-shaped males with angular spicules and short peloderan bursa. Fergusobia porosae n. sp. Davies is similar in having an arcuate to C-shaped parthenogenetic female with a small conoid tail, an almost straight to arcuate infective female with an hemispherical tail tip, and males that are almost straight to barely J-shaped with angular spicules and short peloderan bursa. They differ in that the bodies of parthenogenetic and infective females of F. microcarpae n. sp. are more curved than in F. porosae n. sp. Other known similar forms of Fergusobia/Fergusonina galls are outlined and the larval shield morphologies of their associated mutualistic Fergusonina fly species are discussed where known. An inventory of all known Fergusobia/Fergusonina associations from flat leaf galls from Corymbia spp. and Eucalyptus spp. is presented. Relationships of Fergusobia nematodes were inferred from analysis of sequences of 28S rDNA D2/D3 domains and a portion of mitochondrial DNA cytochrome oxidase subunit I (mtCOI). Nematodes from flat leaf galls appeared in two clades. 

Modeling of frost crystal growth over a flat plate using artificial neural networks and fractal geometries

NASA Astrophysics Data System (ADS)

Tahavvor, Ali Reza

2017-03-01

In the present study artificial neural network and fractal geometry are used to predict frost thickness and density on a cold flat plate having constant surface temperature under forced convection for different ambient conditions. These methods are very applicable in this area because phase changes such as melting and solidification are simulated by conventional methods but frost formation is a most complicated phase change phenomenon consists of coupled heat and mass transfer. Therefore conventional mathematical techniques cannot capture the effects of all parameters on its growth and development because this process influenced by many factors and it is a time dependent process. Therefore, in this work soft computing method such as artificial neural network and fractal geometry are used to do this manner. The databases for modeling are generated from the experimental measurements. First, multilayer perceptron network is used and it is found that the back-propagation algorithm with Levenberg-Marquardt learning rule is the best choice to estimate frost growth properties due to accurate and faster training procedure. Second, fractal geometry based on the Von-Koch curve is used to model frost growth procedure especially in frost thickness and density. Comparison is performed between experimental measurements and soft computing methods. Results show that soft computing methods can be used more efficiently to determine frost properties over a flat plate. Based on the developed models, wide range of frost formation over flat plates can be determined for various conditions.

Near field wireless power transfer using curved relay resonators for extended transfer distance

NASA Astrophysics Data System (ADS)

Zhu, D.; Clare, L.; Stark, B. H.; Beeby, S. P.

2015-12-01

This paper investigates the performance of a near field wireless power transfer system that uses curved relay resonator to extend transfer distance. Near field wireless power transfer operates based on the near-field electromagnetic coupling of coils. Such a system can transfer energy over a relatively short distance which is of the same order of dimensions of the coupled coils. The energy transfer distance can be increased using flat relay resonators. Recent developments in printing electronics and e-textiles have seen increasing demand of embedding electronics into fabrics. Near field wireless power transfer is one of the most promising methods to power electronics on fabrics. The concept can be applied to body-worn textiles by, for example, integrating a transmitter coil into upholstery, and a flexible receiver coil into garments. Flexible textile coils take on the shape of the supporting materials such as garments, and therefore curved resonator and receiver coils are investigated in this work. Experimental results showed that using curved relay resonator can effectively extend the wireless power transfer distance. However, as the curvature of the coil increases, the performance of the wireless power transfer, especially the maximum received power, deteriorates.

All-angle negative refraction and active flat lensing of ultraviolet light.

PubMed

Xu, Ting; Agrawal, Amit; Abashin, Maxim; Chau, Kenneth J; Lezec, Henri J

2013-05-23

Decades ago, Veselago predicted that a material with simultaneously negative electric and magnetic polarization responses would yield a 'left-handed' medium in which light propagates with opposite phase and energy velocities--a condition described by a negative refractive index. He proposed that a flat slab of left-handed material possessing an isotropic refractive index of -1 could act like an imaging lens in free space. Left-handed materials do not occur naturally, and it has only recently become possible to achieve a left-handed response using metamaterials, that is, electromagnetic structures engineered on subwavelength scales to elicit tailored polarization responses. So far, left-handed responses have typically been implemented using resonant metamaterials composed of periodic arrays of unit cells containing inductive-capacitive resonators and conductive wires. Negative refractive indices that are isotropic in two or three dimensions at microwave frequencies have been achieved in resonant metamaterials with centimetre-scale features. Scaling the left-handed response to higher frequencies, such as infrared or visible, has been done by shrinking critical dimensions to submicrometre scales by means of top-down nanofabrication. This miniaturization has, however, so far been achieved at the cost of reduced unit-cell symmetry, yielding a refractive index that is negative along only one axis. Moreover, lithographic scaling limits have so far precluded the fabrication of resonant metamaterials with left-handed responses at frequencies beyond the visible. Here we report the experimental implementation of a bulk metamaterial with a left-handed response to ultraviolet light. The structure, based on stacked plasmonic waveguides, yields an omnidirectional left-handed response for transverse magnetic polarization characterized by a negative refractive index. By engineering the structure to have a refractive index close to -1 over a broad angular range, we achieve Veselago flat lensing, in free space, of arbitrarily shaped, two-dimensional objects beyond the near field. We further demonstrate active, all-optical modulation of the image transferred by the flat lens.

Bioactive films of zein/magnetite magnetically stimuli-responsive for controlled drug release

NASA Astrophysics Data System (ADS)

Marín, Tíffany; Montoya, Paula; Arnache, Oscar; Pinal, Rodolfo; Calderón, Jorge

2018-07-01

The Zein films in two configurations with magnetite nanoparticles (zein/NPs) and magnetite-acetaminophen (zein/NPs/Drug) were used as magnetically stimuli-responsive systems to propose a model of controlled release by dissolution and diffusion mechanism. Composite material films of zein/NPs and zein/NPs/Drug were made by dispersion of magnetite nanoparticles into zein solution then solvent casting of the solution on a flat Teflon substrate. The properties of composite films were analyzed by magnetization curves of (MvsH) and measurements of magnetic force microscopy (MFM). Drug release from the zein/NPs/Drug composite films was determined using a type II dissolution apparatus for a period of 2 h under applied magnetic field conditions. In addition, the diffusion mechanism was tested with zein/NPs films into diffusion cell containing acetaminophen solution for 24 h and using a permanent magnet as a remote trigger device. The results showed that the magnetite nanoparticles contained in the zein/NPs and zein/NPs/Drug composite films are stable, i.e., they do not undergo sufficiently high levels of oxidation as to alter their magnetic properties. Furthermore, the dissolution and diffusion results lead us to conclude that zein composite films effectively behave as stimuli-responsive systems triggered by an external magnetic field applied. The result is a model controlled release system whereby drug release can be controlled by adjusting the magnitude of the applied magnetic field.

Hydrophysical Evaluation of Wells TW-B, TW-7, UE-6d, U-2gg PSE 3A, U-10L 1, and UE-6e in Yucca Flat

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

Pohlmann, Karl; Healey, John; Lyles, Bred

This study evaluated six wells in Yucca Flat in support of the Underground Test Area (UGTA) Activity conducted by the U.S. Department of Energy (DOE) at the Nevada National Security Site (NNSS). Accessibility and groundwater sampling conditions were assessed and if conditions permitted, samples were collected for tritium analysis. Four of the wells, TW-B, UE-6d, UE-6e, and TW-7 were sampled in support of UGTA responses to recommendations made by the Yucca Flat/Climax Mine External Peer Review Committee (Navarro, 2016). In addition to its role in support of these responses, TW-7 was included because it is listed in the NNSS Integratedmore » Groundwater Sampling Plan (DOE, 2014) as a required sampling location, although it had not been sampled since 1994. U-2gg PSE 3A and U-10L 1 were evaluated to determine whether deteriorating well conditions can be addressed so that these wells can be used as additional sampling points in Yucca Flat.« less

Structural characterization and viscoelastic constitutive modeling of skin.

PubMed

Sherman, Vincent R; Tang, Yizhe; Zhao, Shiteng; Yang, Wen; Meyers, Marc A

2017-04-15

A fascinating material, skin has a tensile response which exhibits an extended toe region of minimal stress up to nominal strains that, in some species, exceed 1, followed by significant stiffening until a roughly linear region. The large toe region has been attributed to its unique structure, consisting of a network of curved collagen fibers. Investigation of the structure of rabbit skin reveals that it consists of layers of wavy fibers, each one with a characteristic orientation. Additionally, the existence of two preferred layer orientations is suggested based on the results of small angle X-ray scattering. These observations are used to construct a viscoelastic model consisting of collagen in two orientations, which leads to an in-plane anisotropic response. The structure-based model presented incorporates the elastic straightening and stretching of fibrils, their rotation towards the tensile axis, and the viscous effects which occur in the matrix of the skin due to interfibrillar and interlamellar sliding. The model is shown to effectively capture key features which dictate the mechanical response of skin. Examination by transmission and scanning electron microscopy of rabbit dermis enabled the identification of the key elements in its structure. The organization of collagen fibrils into flat fibers was identified and incorporated into a constitutive model that reproduces the mechanical response of skin. This enhanced quantitative predictive capability can be used in the design of synthetic skin and skin-like structures. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In-line flat-top comb filter based on a cascaded all-solid photonic bandgap fiber intermodal interferometer.

PubMed

Geng, Youfu; Li, Xuejin; Tan, Xiaoling; Deng, Yuanlong; Yu, Yongqin

2013-07-15

In this paper, an in-line comb filter with flat-top spectral response is proposed and constructed based on a cascaded all-solid photonic bandgap fiber modal interferometer. It consists of two short pieces of all-solid photonic bandgap fiber and two standard single-mode fibers as lead fibers with core-offset splices between them. The theoretical and experimental results demonstrated that by employing a cut and resplice process on the central position of all-solid photonic bandgap fiber, the interference spectra are well tailored and flat-top spectral profiles could be realized by the controllable offset amount of the resplice. The channel position also could be tuned by applying longitudinal torsion with up to 4 nm tuning range. Such a flat-top fiber comb filter is easy-to-fabricate and with a designable passband width and flat-top profile.

Peginterferon alfa-2b and weight-based or flat-dose ribavirin in chronic hepatitis C patients: a randomized trial.

PubMed

Jacobson, Ira M; Brown, Robert S; Freilich, Bradley; Afdhal, Nezam; Kwo, Paul Y; Santoro, John; Becker, Scott; Wakil, Adil E; Pound, David; Godofsky, Eliot; Strauss, Robert; Bernstein, David; Flamm, Steven; Pauly, Mary Pat; Mukhopadhyay, Pabak; Griffel, Louis H; Brass, Clifford A

2007-10-01

This prospective, multicenter, community-based and academic-based, open-label, investigator-initiated, U.S. study evaluated efficacy and safety of pegylated interferon (PEG-IFN) alfa-2b plus a flat or weight-based dose of ribavirin (RBV) in adults with chronic hepatitis C. Patients (n = 5027) were randomly assigned to receive PEG-IFN alfa-2b 1.5 microg/kg/week plus flat-dose (800 mg/day) or weight-based (800-1400 mg/day) RBV for 48 weeks (patients with genotype 1, 4, 5, or 6) and for 24 or 48 weeks (genotype 2/3 patients). Primary end point was sustained virologic response (undetectable [<125 IU/mL] serum hepatitis C virus RNA at 24-week follow-up). Sustained virologic response, but not end-of-treatment, rates were significantly higher with weight-based than with flat-dose RBV (44.2% versus 40.5%; P = 0.008). Sustained virologic response rates by intention-to-treat analysis were 34.0% and 28.9%, respectively, in genotype 1 patients (P = 0.005) and 31.2% and 26.7%, respectively, in genotype 1 patients with high baseline viral load (P = 0.056). In genotype 2/3 patients, rates were not significantly different (61.8% and 59.5%, respectively) regardless of treatment duration. Besides greater hemoglobin reductions with weight-based RBV, safety profiles were similar across RBV dosing groups, including the 1400-mg/day group. PEG-IFN alfa-2b plus weight-based RBV is more effective than flat-dose RBV, particularly in genotype 1 patients, providing equivalent efficacy across all weight groups. RBV 1400 mg/day is appropriate for patients 105 to 125 kg. For genotype 2/3 patients, 24 weeks of treatment with flat-dose RBV is adequate; no evidence of additional benefit of extending treatment to 48 weeks was demonstrated.

Fractured toughness of Si3N4 measured with short bar chevron-notched specimens

NASA Technical Reports Server (NTRS)

Salem, J. A.; Shannon, J. L., Jr.

1985-01-01

The short bar chevron-notched specimen is used to measure the plane strain fracture toughness of hot pressed Si3N4. Specimen proportions and chevron-notch angle are varied, thereby varying the amount of crack extension to maximum load (upon which K sub IC is based). The measured toughness (4.68 + or - 0.19 MNm to the 3/2 power) is independent of these variations, inferring that the material has a flat crack growth resistance curve.

Fracture toughness of Si3N4 measured with short bar chevron-notched specimens

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Shannon, John L., Jr.

1987-01-01

The short bar chevron-notched specimen is used to measure the plane strain fracture toughness of hot pressed Si3N4. Specimen proportions and chevron-notch angle are varied, thereby varying the amount of crack extension to maximum load (upon which K sub IC is based). The measured toughness (4.68 + or 0.19 MNm to the 3/2 power) is independent of these variations, inferring that the material has a flat crack growth resistance curve.

Magnetic and Optical Properties of Submicron-Size Hollow Spheres

PubMed Central

Ye, Quan-Lin; Yoshikawa, Hirofumi; Awaga, Kunio

2010-01-01

Magnetic hollow spheres with a controlled diameter and shell thickness have emerged as an important class of magnetic nanomaterials. The confined hollow geometry and pronouncedly curved surfaces induce unique physical properties different from those of flat thin films and solid counterparts. In this paper, we focus on recent progress on submicron-size spherical hollow magnets (e.g., cobalt- and iron-based materials), and discuss the effects of the hollow shape and the submicron size on magnetic and optical properties.

Mach-Zehnder Interferometer Refractive Index Sensor Based on a Plasmonic Channel Waveguide

PubMed Central

Lee, Da Eun; Lee, Young Jin; Shin, Eunso; Kwon, Soon-Hong

2017-01-01

A Mach-Zehnder interferometer based on a plasmonic channel waveguide is proposed for refractive index sensing. The structure, with a small physical footprint of 20 × 120 μm2, achieved a high figure of merit of 294. The cut-off frequency behaviour in the plasmonic channel waveguide resulted in a flat dispersion curve, which induces a 1.8 times larger change of the propagation constant for the given refractive index change compared with previously reported results. PMID:29120381

PANDA2: Program for Minimum Weight Design of Stiffened, Composite, Locally Buckled Panels

DTIC Science & Technology

1986-09-01

a flat panel or a panel that spans less than about 45 degrees of circumference. However, in PANDA2 complete cylindrical shells can be treated by the...compression and that corresponding to maximum in-plane shear. It is usually best to treat complete cylindrical shells in this way rather than try to set up a...to treat panels, not complete cylindrical shells. Therefore, it is best applied to panels. In PANDA2 the curved edges of a cylindrical panel lie in

Frustrated honeycomb-lattice bilayer quantum antiferromagnet in a magnetic field

NASA Astrophysics Data System (ADS)

Krokhmalskii, Taras; Baliha, Vasyl; Derzhko, Oleg; Schulenburg, Jörg; Richter, Johannes

2018-05-01

Frustrated bilayer quantum magnets have attracted attention as flat-band spin systems with unconventional thermodynamic properties. We study the low-temperature properties of a frustrated honeycomb-lattice bilayer spin-1/2 isotropic (XXX) Heisenberg antiferromagnet in a magnetic field by means of an effective low-energy theory using exact diagonalizations and quantum Monte Carlo simulations. Our main focus is on the magnetization curve and the temperature dependence of the specific heat indicating a finite-temperature phase transition in high magnetic fields.

Multiwall TPS: An emerging concept

NASA Technical Reports Server (NTRS)

Shideler, J. L.; Kelly, H. N.; Avery, D. E.; Blosser, M. L.; Adelman, H. M.

1981-01-01

The transformation of a titanium multiwall thermal protection system from a conceptual design to a working reality is described. The thermal and structural performance of the basic multiwall concept is analyzed. Radiant heat, wind tunnel, vibration, acoustic, and lightning strike tests are used to verify the performance of multiwall tiles under representative operating conditions. Flat, all titanium multiwall configurations limited to temperature below 810 K are discussed. Curved surface, higher temperature versions of the multiwall are considered. Preliminary mass estimates for advanced multiwall concepts are presented.

Classical dynamics on curved Snyder space

NASA Astrophysics Data System (ADS)

Ivetić, B.; Meljanac, S.; Mignemi, S.

2014-05-01

We study the classical dynamics of a particle in nonrelativistic Snyder-de Sitter space. We show that for spherically symmetric systems, parameterizing the solutions in terms of an auxiliary time variable, which is a function only of the physical time and of the energy and angular momentum of the particles, one can reduce the problem to the equivalent one in classical mechanics. We also discuss a relativistic extension of these results, and a generalization to the case in which the algebra is realized in flat space.

X-ray Diffraction Crystal Calibration and Characterization

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

Michael J. Haugh; Richard Stewart; Nathan Kugland

2009-06-05

National Security Technologies’ X-ray Laboratory is comprised of a multi-anode Manson type source and a Henke type source that incorporates a dual goniometer and XYZ translation stage. The first goniometer is used to isolate a particular spectral band. The Manson operates up to 10 kV and the Henke up to 20 kV. The Henke rotation stages and translation stages are automated. Procedures have been developed to characterize and calibrate various NIF diagnostics and their components. The diagnostics include X-ray cameras, gated imagers, streak cameras, and other X-ray imaging systems. Components that have been analyzed include filters, filter arrays, grazing incidencemore » mirrors, and various crystals, both flat and curved. Recent efforts on the Henke system are aimed at characterizing and calibrating imaging crystals and curved crystals used as the major component of an X-ray spectrometer. The presentation will concentrate on these results. The work has been done at energies ranging from 3 keV to 16 keV. The major goal was to evaluate the performance quality of the crystal for its intended application. For the imaging crystals we measured the laser beam reflection offset from the X-ray beam and the reflectivity curves. For the curved spectrometer crystal, which was a natural crystal, resolving power was critical. It was first necessary to find sources of crystals that had sufficiently narrow reflectivity curves. It was then necessary to determine which crystals retained their resolving power after being thinned and glued to a curved substrate.« less

Rethinking the role of edaphic condition in halophyte vegetation degradation on salt marshes due to coastal defense structure

NASA Astrophysics Data System (ADS)

Xie, Tian; Cui, Baoshan; Bai, Junhong; Li, Shanze; Zhang, Shuyan

2018-02-01

Determining how human disturbance affects plant community persistence and species conservation is one of the most pressing ecological challenges. The large-scale disturbance form defense structures usually have a long-term and potential effect on phytocommunity in coastal saltmarshes. Coastal defense structures usually remove the effect of tidal wave on tidal salt marshes. As a consequence, edaphic factors such as the salinity and moisture contents are disturbed by tidal action blocking. However, few previous studies have explicitly addressed the response of halophyte species persistence and dynamics to the changing edaphic conditions. The understanding of the response of species composition in seed banks and aboveground vegetation to the stress is important to identify ecological effect of coastal defense structures and provide usefully insight into restoration. Here, we conducted a field study to distinguish the density, species composition and relationships of seed bank with aboveground vegetation between tidal flat wetlands with and without coastal defense structures. We also addressed the role of edaphic condition in vegetation degradation caused by coastal defense structures in combination with field monitor and greenhouse experiments. Our results showed the density of the seed bank and aboveground vegetation in the tidal flat without coastal defense structures was significantly lower than the surrounded flat with coastal defense structures. A total of 14 species were founded in the surrounded flat seed bank and 11 species in the tidal flat, but three species were only recorded in aboveground vegetation of the tidal flat which was much lower than 24 aboveground species in the surrounded flat. The absent of species in aboveground vegetation contributed to low germination rate which depend on the edaphic condition. The germination of seeds in the seed bank were inhabited by high soil salinity in the tidal flat and low soil moisture in the surrounded flat. Our study supported the hypothesis that the change of edaphic condition caused by coastal defense structures was the main reason for the difference of the species composition similarity between aboveground vegetation and the soil seed bank between the tidal and surrounded flats. Therefore, mitigating the hydrological disturbance and maintaining the original state of edaphic factors would be useful implications for reducing the ecological effect of defense structure to vegetation communities in coastal salt marshes.

Physiology, pathogenicity and immunogenicity of live, attenuated Salmonella enterica serovar Enteritidis mutants in chicks.

PubMed

Si, Wei; Wang, Xiumei; Liu, Huifang; Yu, Shenye; Li, Zhaoli; Chen, Liping; Zhang, Wanjiang; Liu, Siguo

2015-01-01

To construct a novel live, attenuated Salmonella vaccine, the lon, cpxR and cpdB genes were deleted from a wild-type Salmonella enterica serovar Enteritidis-6 (SM-6) strain using the phage λ Red homologous recombination system, resulting in SM-△CpxR, SM-△C/Lon and SM-△C/L/CpdB. The growth curves of strain SM-△C/Lon grew more rapidly than the other strains and had OD 600 values higher than the other strains starting at the 4 h time point. The growth curves of strain SM-△C/L/CpdB were relatively flat. The colonization time of SM-△C/L/CpdB is about 8-10 days. Deleting the lon/cpxR/cpdB (SM-6) genes resulted in an approximate 10(3)-fold attenuation in virulence assessed by the analysis of the LD50 of specific pathogen-free (SPF) chicks. This result indicated that the deletion of the lon, cpxR and cpdB genes induced significant virulence attenuation. The protective effects of SM-△C/L/CpdB vaccination in SPF chicks against 5 × 10(9) colony forming units (CFU) of S. Enteritidis were resulted from the induction of an effective immune response. These findings demonstrate the potential of mutant SM-△C/L/CpdB to be used as an effective vaccine. Copyright © 2015 Elsevier Ltd. All rights reserved.

Solar shutter arrangement

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

Fulkerson, P.L.

1988-02-02

In a structure having a roof with a skylight including a glass panel which transmits solar energy, a shutter arrangement supported on the roof is described comprising an insulative flat one-piece solid shutter in the form of a panel selectively and linearly slidable on tracks which conceal the side edges thereof from a position blocking transmittal of solar energy through the glass panel of the skylight into an area within the structure to a position permitting transmittal of solar energy through the glass panel of the skylight into the area within the structure. The skylight presents a space between themore » glass panel and the selectively and linearly slidable insulative flat one-piece solid shutter, where the latter serves as the selective inner wall of the space contiguous with the area within the structure and the glass panel serves as the fixed outer wall of the space, where temperature responsive means is disposed within the space and in direct engagement with the inner surface of the glass panel, where the temperature responsive means is a black thermocouple operating a motor in a driving relationship with the insulative flat one-piece solid shutter. The insulative flat one-piece solid shutter is supported by a cable secured to a rotatable shaft controlled by the motor, where bi-directional movement of the rotatable shaft achieves raising and lowering of the insulative flat one-piece solid shutter to each of the solar energy blocking and transmittal positions, and where the insulative flat one-piece solid shutter includes a reflective surface facing the skylight and a decorative surface facing the area within the structure.« less

Multiple-wavelength Variability and Quasi-periodic Oscillation of PMN J0948+0022

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

Zhang, Jin; Zhang, Hai-Ming; Zhu, Yong-Kai

We present a comprehensive analysis of multiple-wavelength observational data of the first GeV-selected narrow-line Seyfert 1 galaxy PMN J0948+0022. We derive its light curves in the γ -ray and X-ray bands from the data observed with Fermi /LAT and Swift /XRT, and generate the optical and radio light curves by collecting the data from the literature. These light curves show significant flux variations. With the LAT data we show that this source is analogous to typical flat spectrum radio quasars in the L {sub γ} –Γ {sub γ} plane, where L {sub γ} and Γ {sub γ} are the luminositymore » and spectral index in the LAT energy band. The γ -ray flux is correlated with the V-band flux with a lag of ∼44 days, and a moderate quasi-periodic oscillation (QPO) with a periodicity of ∼490 days observed in the LAT light curve. A similar QPO signature is also found in the V-band light curve. The γ -ray flux is not correlated with the radio flux in 15 GHz, and no similar QPO signature is found at a confidence level of 95%. Possible mechanisms of the QPO are discussed. We propose that gravitational-wave observations in the future may clarify the current plausible models for the QPO.« less

X-ray characterization of curved crystals for hard x-ray astronomy

NASA Astrophysics Data System (ADS)

Buffagni, Elisa; Bonnini, Elisa; Ferrari, Claudio; Virgilli, Enrico; Frontera, Filippo

2015-05-01

Among the methods to focus photons the diffraction in crystals results as one of the most effective for high energy photons. An assembling of properly oriented crystals can form a lens able to focus x-rays at high energy via Laue diffraction in transmission geometry; this is a Laue lens. The x-ray diffraction theory provides that the maximum diffraction efficiency is achieved in ideal mosaic crystals, but real mosaic crystals show diffraction efficiencies several times lower than the ideal case due to technological problems. An alternative and convenient approach is the use of curved crystals. We have recently optimized an efficient method based on the surface damage of crystals to produce self-standing uniformly curved Si, GaAs and Ge tiles of thickness up to 2-3 mm and curvature radii R down to a few meters. We show that, for curved diffracting planes, such crystals have a diffraction efficiency nearly forty times higher than the diffraction efficiency of perfect similar flat crystals, thus very close to that of ideal mosaic crystals. Moreover, in an alternative configuration where the diffracting planes are perpendicular to the curved ones, a focusing effect occurs and will be shown. These results were obtained for several energies between 17 and 120 keV with lab sources or at high energy facilities such as LARIX at Ferrara (Italy), ESRF at Grenoble (France), and ANKA at Karlsruhe (Germany).

H0 from ten well-measured time delay lenses

NASA Astrophysics Data System (ADS)

Rathna Kumar, S.; Stalin, C. S.; Prabhu, T. P.

2015-08-01

In this work, we present a homogeneous curve-shifting analysis using the difference-smoothing technique of the publicly available light curves of 24 gravitationally lensed quasars, for which time delays have been reported in the literature. The uncertainty of each measured time delay was estimated using realistic simulated light curves. The recipe for generating such simulated light curves with known time delays in a plausible range around the measured time delay is introduced here. We identified 14 gravitationally lensed quasars that have light curves of sufficiently good quality to enable the measurement of at least one time delay between the images, adjacent to each other in terms of arrival-time order, to a precision of better than 20% (including systematic errors). We modeled the mass distribution of ten of those systems that have known lens redshifts, accurate astrometric data, and sufficiently simple mass distribution, using the publicly available PixeLens code to infer a value of H0 of 68.1 ± 5.9 km s-1 Mpc-1 (1σ uncertainty, 8.7% precision) for a spatially flat universe having Ωm = 0.3 and ΩΛ = 0.7. We note here that the lens modeling approach followed in this work is a relatively simple one and does not account for subtle systematics such as those resulting from line-of-sight effects and hence our H0 estimate should be considered as indicative.

Limitations to maximum running speed on flat curves.

PubMed

Chang, Young-Hui; Kram, Rodger

2007-03-01

Why is maximal running speed reduced on curved paths? The leading explanation proposes that an increase in lateral ground reaction force necessitates a decrease in peak vertical ground reaction force, assuming that maximum leg extension force is the limiting factor. Yet, no studies have directly measured these forces or tested this critical assumption. We measured maximum sprint velocities and ground reaction forces for five male humans sprinting along a straight track and compared them to sprints along circular tracks of 1, 2, 3, 4 and 6 m radii. Circular track sprint trials were performed either with or without a tether that applied centripetal force to the center of mass. Sprinters generated significantly smaller peak resultant ground reaction forces during normal curve sprinting compared to straight sprinting. This provides direct evidence against the idea that maximum leg extension force is always achieved and is the limiting factor. Use of the tether increased sprint speed, but not to expected values. During curve sprinting, the inside leg consistently generated smaller peak forces compared to the outside leg. Several competing biomechanical constraints placed on the stance leg during curve sprinting likely make the inside leg particularly ineffective at generating the ground reaction forces necessary to attain maximum velocities comparable to straight path sprinting. The ability of quadrupeds to redistribute function across multiple stance legs and decouple these multiple constraints may provide a distinct advantage for turning performance.

Quantum particles in general spacetimes: A tangent bundle formalism

NASA Astrophysics Data System (ADS)

Wohlfarth, Mattias N. R.

2018-06-01

Using tangent bundle geometry we construct an equivalent reformulation of classical field theory on flat spacetimes which simultaneously encodes the perspectives of multiple observers. Its generalization to curved spacetimes realizes a new type of nonminimal coupling of the fields and is shown to admit a canonical quantization procedure. For the resulting quantum theory we demonstrate the emergence of a particle interpretation, fully consistent with general relativistic geometry. The path dependency of parallel transport forces each observer to carry their own quantum state; we find that the communication of the corresponding quantum information may generate extra particles on curved spacetimes. A speculative link between quantum information and spacetime curvature is discussed which might lead to novel explanations for quantum decoherence and vanishing interference in double-slit or interaction-free measurement scenarios, in the mere presence of additional observers.

Mechanical properties of composite materials

NASA Technical Reports Server (NTRS)

Thornton, H. Richard; Cornwell, L. R.

1993-01-01

A composite material incorporates high strength, high modulus fibers in a matrix (polymer, metal, or ceramic). The fibers may be oriented in a manner to give varying in-plane properties (longitudinal, transverse-stress, strain, and modulus of elasticity). The lay-up of the composite laminates is such that a center line of symmetry and no bending moment exist through the thickness. The laminates are tabbed, with either aluminum or fiberglass, and are ready for tensile testing. The determination of the tensile properties of resin matrix composites, reinforced by continuous fibers, is outlined in ASTM standard D 3039, Tensile Properties of Oriented Fiber Composites. The tabbed flat tensile coupons are placed into the grips of a tensile machine and load-deformation curves plotted. The load-deformation data are translated into stress-strain curves for determination of mechanical properties (ultimate tensile strength and modulus of elasticity).

Automated method for determining Instron Residual Seal Force of glass vial/rubber closure systems.

PubMed

Ludwig, J D; Nolan, P D; Davis, C W

1993-01-01

Instron Residual Seal Force (IRSF) of glass vial/rubber closure systems was determined using an Instron 4501 Materials Testing System. Computer programs were written to process raw data and calculate IRSF values. Preliminary experiments indicated both the appearance of the stress-deformation curves and precision of the derived IRSF values were dependent on the internal dimensions and top surface geometry of the cap anvil. Therefore, a series of five cap anvils varying in shape and dimensions were machined to optimize performance and precision. Vials capped with West 4416/50 PURCOAT button closures or Helvoet compound 6207 lyophilization closures were tested with each cap anvil. Cap anvils with spherical top surfaces and narrow internal dimensions produced more precise results and more uniform stress-deformation curves than cap anvils with flat top surfaces and wider internal dimensions.

Fabrication of a chirped artificial compound eye for endoscopic imaging fiber bundle by dose-modulated laser lithography and subsequent thermal reflow

NASA Astrophysics Data System (ADS)

Deng, Shengfeng; Lyu, Jinke; Sun, Hongda; Cui, Xiaobin; Wang, Tun; Lu, Miao

2015-03-01

A chirped artificial compound eye on a curved surface was fabricated using an optical resin and then mounted on the end of an endoscopic imaging fiber bundle. The focal length of each lenslet on the curved surface was variable to realize a flat focal plane, which matched the planar end surface of the fiber bundle. The variation of the focal length was obtained by using a photoresist mold formed by dose-modulated laser lithography and subsequent thermal reflow. The imaging performance of the fiber bundle was characterized by coupling with a coaxial light microscope, and the result demonstrated a larger field of view and better imaging quality than that of an artificial compound eye with a uniform focal length. Accordingly, this technology has potential application in stereoscopic endoscopy.

Universal behavior of generalized causal set d’Alembertians in curved spacetime

NASA Astrophysics Data System (ADS)

Belenchia, Alessio

2016-07-01

Causal set non-local wave operators allow both for the definition of an action for causal set theory and the study of deviations from local physics that may have interesting phenomenological consequences. It was previously shown that, in all dimensions, the (unique) minimal discrete operators give averaged continuum non-local operators that reduce to \\square -R/2 in the local limit. Recently, dropping the constraint of minimality, it was shown that there exist an infinite number of discrete operators satisfying basic physical requirements and with the right local limit in flat spacetime. In this work, we consider this entire class of generalized causal set d’Alembertins in curved spacetimes and extend to them the result about the universality of the -R/2 factor. Finally, we comment on the relation of this result to the Einstein equivalence principle.

Lifetimes and energetics of the first electronically excited states of NaH2O from time-resolved photoelectron imaging

NASA Astrophysics Data System (ADS)

Gartmann, Thomas E.; Yoder, Bruce L.; Chasovskikh, Egor; Signorell, Ruth

2017-09-01

The energetics and lifetimes of the first electronically excited states (;3p-states;) of NaH2O and NaD2O have been measured by pump-probe (740/780 and 400 nm) photoelectron imaging. The photoelectron spectra of NaH2O show two bands at an electron kinetic energy of 0.14 and 0.38 eV, respectively. We assign the former to excitation via the two energetically close lying ;pπ-states; with flat potential curves in the intermolecular degrees of freedom, and the latter to the excitation via the ;pσ-state; characterized by significantly steeper potential curves. The relaxation of all ;p-states; follows a double exponential decay with a lifetime around 110 ps for the dominant fast component.

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

USE OF MECHANISTIC DATA TO HELP DEFINE DOSE-RESPONSE CURVES

EPA Science Inventory

Use of Mechanistic Data to Help Define Dose-Response Curves

The cancer risk assessment process described by the U.S. EPA necessitates a description of the dose-response curve for tumors in humans at low (environmental) exposures. This description can either be a default l...

A transient, flat spectrum radio pulsar near the Galactic Centre

NASA Astrophysics Data System (ADS)

Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

2017-06-01

Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

Removal of ring artifacts in microtomography by characterization of scintillator variations.

PubMed

Vågberg, William; Larsson, Jakob C; Hertz, Hans M

2017-09-18

Ring artifacts reduce image quality in tomography, and arise from faulty detector calibration. In microtomography, we have identified that ring artifacts can arise due to high-spatial frequency variations in the scintillator thickness. Such variations are normally removed by a flat-field correction. However, as the spectrum changes, e.g. due to beam hardening, the detector response varies non-uniformly introducing ring artifacts that persist after flat-field correction. In this paper, we present a method to correct for ring artifacts from variations in scintillator thickness by using a simple method to characterize the local scintillator response. The method addresses the actual physical cause of the ring artifacts, in contrary to many other ring artifact removal methods which rely only on image post-processing. By applying the technique to an experimental phantom tomography, we show that ring artifacts are strongly reduced compared to only making a flat-field correction.

Driver Vision Based Perception-Response Time Prediction and Assistance Model on Mountain Highway Curve.

PubMed

Li, Yi; Chen, Yuren

2016-12-30

To make driving assistance system more humanized, this study focused on the prediction and assistance of drivers' perception-response time on mountain highway curves. Field tests were conducted to collect real-time driving data and driver vision information. A driver-vision lane model quantified curve elements in drivers' vision. A multinomial log-linear model was established to predict perception-response time with traffic/road environment information, driver-vision lane model, and mechanical status (last second). A corresponding assistance model showed a positive impact on drivers' perception-response times on mountain highway curves. Model results revealed that the driver-vision lane model and visual elements did have important influence on drivers' perception-response time. Compared with roadside passive road safety infrastructure, proper visual geometry design, timely visual guidance, and visual information integrality of a curve are significant factors for drivers' perception-response time.

Biomimetic heterogeneous multiple ion channels: a honeycomb structure composite film generated by breath figures

NASA Astrophysics Data System (ADS)

Han, Keyu; Heng, Liping; Wen, Liping; Jiang, Lei

2016-06-01

We design a novel type of artificial multiple nanochannel system with remarkable ion rectification behavior via a facile breath figure (BF) method. Notably, even though the charge polarity in the channel wall reverses under different pH values, this nanofluidic device displays the same ionic rectification direction. Compared with traditional nanochannels, this composite multiple ion channel device can be more easily obtained and has directional ionic rectification advantages, which can be applied in many fields.We design a novel type of artificial multiple nanochannel system with remarkable ion rectification behavior via a facile breath figure (BF) method. Notably, even though the charge polarity in the channel wall reverses under different pH values, this nanofluidic device displays the same ionic rectification direction. Compared with traditional nanochannels, this composite multiple ion channel device can be more easily obtained and has directional ionic rectification advantages, which can be applied in many fields. Electronic supplementary information (ESI) available: Pore size distribution histograms of the AAO substrates; SEM images of the side view of pure AAO membranes and top view of the flat PI/AAO composite film; the current-time curves of the flat composite film; the current-voltage characteristics curves of pure AAO nanochannels with different mean pore diameters; CA of the two surfaces of the composite PI/AAO film, the structural formula of the polymer polyimide resin (PI), and solid surface zeta potential. See DOI: 10.1039/c6nr02506d

Measurement of super large radius optics in the detection of gravitational waves

NASA Astrophysics Data System (ADS)

Yang, Cheng; Han, Sen; Wu, Quanying; Liang, Binming; Hou, Changlun

2015-10-01

The existence of Gravitational Wave (GW) is one of the greatest predictions of Einstein's relative theory. It has played an important part in the radiation theory, black hole theory, space explore and so on. The GW detection has been an important aspect of modern physics. With the research proceeding further, there are still a lot of challenges existing in the interferometer which is the key instrument in GW detection especially the measurement of the super large radius optics. To solve this problem, one solution , Fizeau interference, for measuring the super large radius has been presented. We change the tradition that curved surface must be measured with a standard curved surface. We use a flat mirror as a reference flat and it can lower both the cost and the test requirement a lot. We select a concave mirror with the radius of 1600mm as a sample. After the precision measurement and analysis, the experimental results show that the relative error of radius is better than 3%, and it can fully meet the requirements of the measurement of super large radius optics. When calculating each pixel with standard cylinder, the edges are not sharp because of diffraction or some other reasons, we detect the edge and calculate the diameter of the cylinder automatically, and it can improve the precision a lot. In general, this method is simple, fast, non-traumatic, and highly precision, it can also provide us a new though in the measurement of super large radius optics.

Tape functionality: sonographic tape characteristics and outcome after TVT incontinence surgery.

PubMed

Kociszewski, Jacek; Rautenberg, Oliver; Perucchini, Daniele; Eberhard, Jakob; Geissbühler, Verena; Hilgers, Reinhard; Viereck, Volker

2008-01-01

To investigate tension-free vaginal tape (TVT) position and shape using ultrasound (US) and correlate the findings to outcome. The results of TVT surgery were investigated in 72 women with urodynamic stress urinary incontinence. The main outcome parameters were US tape position in relation to the urethra and dynamic changes in TVT shape at rest and during straining. Sixty-two patients (86%) were continent, 6 (8%) significantly improved, and the operation failed in four cases (6%). The median tape position was at 66% of the urethral length measured by US. The median tape-urethra-lumen distance was 3.8 mm at rest. Tape placement in the upper or lower quarter of the urethra was associated with a higher failure rate. Tapes positioned less than 3 mm from the urethra significantly increased postoperative complications (P < 0.0001). The tape was flat at rest and curved during straining in 44 (61%) patients; 98% (43/44) of these women were continent after surgery. An unchanged tape shape was associated with a poorer outcome (P = 0.00038). Patients with a flat tape at rest and during straining failed in 25% and patients with a permanent curved shape in 10%. TVT position relative to the patient's urethra seems to play a role in treatment outcome. Outcome was best in patients with dynamic change in tape shape during straining and location of the tape at the junction between the lower and middle urethra and at least 3 mm from the urethral lumen. (c) 2008 Wiley-Liss, Inc.

Influence of high resolution rainfall data on the hydrological response of urban flat catchments

NASA Astrophysics Data System (ADS)

Cristiano, Elena; ten Veldhuis, Marie-claire; van de Giesen, Nick

2016-04-01

In the last decades, cities have become more and more urbanized and population density in urban areas is increased. At the same time, due to the climate changes, rainfall events present higher intensity and shorter duration than in the past. The increase of imperviousness degree, due to urbanization, combined with short and intense rainfall events, determinates a fast hydrological response of the urban catchment and in some cases it can lead to flooding. Urban runoff processes are sensitive to rainfall spatial and temporal variability and, for this reason, high resolution rainfall data are required as input for the hydrological model. A better knowledge of the hydrological response of system can help to prevent damages caused by flooding. This study aims to evaluate the sensitivity of urban hydrological response to spatial and temporal rainfall variability in urban areas, focusing especially on understanding the hydrological behaviour in lowland areas. In flat systems, during intense rainfall events, the flow in the sewer network can be pressurized and it can change direction, depending on the setting of pumping stations and CSOs (combined sewer overflow). In many cases these systems are also looped and it means that the water can follow different paths, depending on the pipe filling process. For these reasons, hydrological response of flat and looped catchments is particularly complex and it can be difficult characterize and predict it. A new dual polarimetric X-band weather radar, able to measure rainfall with temporal resolution of 1 min and spatial resolution of 100mX100m, was recently installed in the city of Rotterdam (NL). With this instrument, high resolution rainfall data were measured and used, in this work, as input for the hydrodynamic model. High detailed, semi-distributed hydrodynamic models of some districts of Rotterdam were used to investigate the hydrological response of flat catchments to high resolution rainfall data. In particular, the hydrological response of some subcatchments of the district of Kralingen was studied. Rainfall data were combined with level and discharge measurements at the pumping station that connects the sewer system with the waste water treatment plane. Using this data it was possible to study the water balance and to have a better idea of the amount of water that leave the system during a specific rainfall events. Results show that the hydrological response of flat and looped catchments is sensitive to spatial and temporal rainfall variability and it can be strongly influenced by rainfall event characteristics, such as intensity, velocity and intermittency of the storm.

Finite length-scale anti-gravity and observations of mass discrepancies in galaxies

NASA Astrophysics Data System (ADS)

Sanders, R. H.

1986-01-01

The modification of Newtonian attraction suggested by Sanders (1984) contains a repulsive Yukawa component which is characterised by two physical parameters: a coupling constant, α, and a length scale, r0. Although this form of the gravitational potential can result in flat rotation curves for a galaxy (or a point mass) it is not obvious that any modification of gravity associated with a definite length scale can reproduce the observed rotation curves of galaxies covering a wide range of mass and size. Here it is shown that the rotation curves of galaxies ranging in size from 5 to 40 kpc can be reproduced by this modified potential. Moreover, the implied mass-to-light ratios for a larger sample of galaxies are reasonable (one to three) and show no systematic trend with the size of the galaxy. The observed infrared Tully-Fisher law is shown to be consistent with the prediction of this revised gravity. The modified potential permits the X-ray emitting halos observed around elliptical galaxies to be bound without the addition of dark matter.

Torsion in gauge theory

NASA Astrophysics Data System (ADS)

Nieh, H. T.

2018-02-01

The potential conflict between torsion and gauge symmetry in the Riemann-Cartan curved spacetime was noted by Kibble in his 1961 pioneering paper and has since been discussed by many authors. Kibble suggested that, to preserve gauge symmetry, one should forgo the covariant derivative in favor of the ordinary derivative in the definition of the field strength Fμ ν for massless gauge theories, while for massive vector fields, covariant derivatives should be adopted. This view was further emphasized by Hehl et al. in their influential 1976 review paper. We address the question of whether this deviation from normal procedure by forgoing covariant derivatives in curved spacetime with torsion could give rise to inconsistencies in the theory, such as the quantum renormalizability of a realistic interacting theory. We demonstrate in this paper the one-loop renormalizability of a realistic gauge theory of gauge bosons interacting with Dirac spinors, such as the SU(3) chromodynamics, for the case of a curved Riemann-Cartan spacetime with totally antisymmetric torsion. This affirmative confirmation is one step toward providing justification for the assertion that the flat-space definition of the gauge-field strength should be adopted as the proper definition.

Assessment of AVIRIS data from vegetated sites in the Owens Valley, California

NASA Technical Reports Server (NTRS)

Rock, B. N.; Elvidge, Christopher D.; Defeo, N. J.

1988-01-01

Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were acquired from the Bishop, CA area, located at the northern end of the Owens Valley, on July 30, 1987. Radiometrically-corrected AVIRIS data were flat-field corrected, and spectral curves produced and analyzed for pixels taken from both native and cultivated vegetation sites, using the JPS SPAM software program and PC-based spreadsheet programs. Analyses focussed on the chlorophyll well and red edge portions of the spectral curves. Results include the following: AVIRIS spectral data are acquired at sufficient spectral resolution to allow detection of blue shifts of both the chlorophyll well and red edge in moisture-stressed vegetation when compared with non-stressed vegetation; a normalization of selected parameters (chlorophyll well and near infrared shoulder) may be used to emphasize the shift in red edge position; and the presence of the red edge in AVIRIS spectral curves may be useful in detecting small amounts (20 to 30 pct cover) of semi-arid and arid vegetation ground cover. A discussion of possible causes of AVIRIS red edge shifts in respsonse to stress is presented.

Linearly resummed hydrodynamics in a weakly curved spacetime

NASA Astrophysics Data System (ADS)

Bu, Yanyan; Lublinsky, Michael

2015-04-01

We extend our study of all-order linearly resummed hydrodynamics in a flat space [1, 2] to fluids in weakly curved spaces. The underlying microscopic theory is a finite temperature super-Yang-Mills theory at strong coupling. The AdS/CFT correspondence relates black brane solutions of the Einstein gravity in asymptotically locally AdS5 geometry to relativistic conformal fluids in a weakly curved 4D background. To linear order in the amplitude of hydrodynamic variables and metric perturbations, the fluid's energy-momentum tensor is computed with derivatives of both the fluid velocity and background metric resummed to all orders. We extensively discuss the meaning of all order hydrodynamics by expressing it in terms of the memory function formalism, which is also suitable for practical simulations. In addition to two viscosity functions discussed at length in refs. [1, 2], we find four curvature induced structures coupled to the fluid via new transport coefficient functions. In ref. [3], the latter were referred to as gravitational susceptibilities of the fluid. We analytically compute these coefficients in the hydrodynamic limit, and then numerically up to large values of momenta.

Drop shape visualization and contact angle measurement on curved surfaces.

PubMed

Guilizzoni, Manfredo

2011-12-01

The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces. Copyright © 2011 Elsevier Inc. All rights reserved.

Development of a Novel Transparent Flexible Capacitive Micromachined Ultrasonic Transducer

PubMed Central

Pang, Da-Chen; Chang, Cheng-Min

2017-01-01

This paper presents the world’s first transparent flexible capacitive micromachined ultrasonic transducer (CMUT) that was fabricated through a roll-lamination technique. This polymer-based CMUT has advantages of transparency, flexibility, and non-contacting detection which provide unique functions in display panel applications. Comprising an indium tin oxide-polyethylene terephthalate (ITO-PET) substrate, SU-8 sidewall and vibrating membranes, and silver nanowire transparent electrode, the transducer has visible-light transmittance exceeding 80% and can operate on curved surfaces with a 40 mm radius of curvature. Unlike the traditional silicon-based high temperature process, the CMUT can be fabricated on a flexible substrate at a temperature below 100 °C to reduce residual stress introduced at high temperature. The CMUT on the curved surfaces can detect a flat target and finger at distances up to 50 mm and 40 mm, respectively. The transparent flexible CMUT provides a better human-machine interface than existing touch panels because it can be integrated with a display panel for non-contacting control in a health conscious environment and the flexible feature is critical for curved display and wearable electronics. PMID:28632157

A Simple Experiment Demonstrating the Relationship between Response Curves and Absorption Spectra.

ERIC Educational Resources Information Center

Li, Chia-yu

1984-01-01

Describes an experiment for recording two individual spectrophotometer response curves. The two curves are directly related to the power of transmitted beams that pass through a solvent and solution. An absorption spectrum of the solution can be constructed from the calculated rations of the curves as a function of wavelength. (JN)

Constraints on the Generalized Chaplygin Gas Model from Recent Supernova Data and Baryonic Acoustic Oscillations

NASA Astrophysics Data System (ADS)

Wu, Puxun; Yu, Hongwei

2007-04-01

Constraints from the Gold sample Type Ia supernova (SN Ia) data, the Supernova Legacy Survey (SNLS) SN Ia data, and the size of the baryonic acoustic oscillation (BAO) peak found in the Sloan Digital Sky Survey (SDSS) on the generalized Chaplygin gas (GCG) model, proposed as a candidate for the unified dark matter-dark energy scenario (UDME), are examined in the cases of both a spatially flat and a spatially curved universe. Our results reveal that the GCG model is consistent with a flat universe up to the 68% confidence level, and the model parameters are within the allowed parameter ranges of the GCG as a candidate for UDME. Meanwhile, we find that in the flat case, both the Gold sample + SDSS BAO data and the SNLS sample + SDSS BAO data break the degeneracy of As and α and allow for the scenario of a cosmological constant plus dark matter (α=0) at the 68% confidence level, although they rule out the standard Chaplygin gas model (α=1) at the 99% confidence level. However, for the case without a flat prior, the SNLS SN Ia + SDSS BAO data do not break the degeneracy between As and α, and they allow for ΛCDM (α=0) and the standard Chaplygin gas model (α=1) at a 68% confidence level, while the Gold SN Ia + SDSS BAO break the degeneracy of As and α and rule out ΛCDM at a 68% confidence level and the standard Chaplygin gas model at a 99% confidence level.

Technical Note: A Feasibility Study of Using the Flat Panel Detector on Linac for the kV X-ray Generator Test.

PubMed

Cai, Bin; Dolly, Steven; Kamal, Gregory; Yaddanapudi, Sridhar; Sun, Baozhou; Goddu, S Murty; Mutic, Sasa; Li, Hua

2018-04-28

To investigate the feasibility of using kV flat panel detector on linac for consistency evaluations of kV X-ray generator performance. An in-house designed aluminum (Al) array phantom with six 9×9 cm 2 square regions having various thickness was proposed and used in this study. Through XML script-driven image acquisition, kV images with various acquisition settings were obtained using the kV flat panel detector. Utilizing pre-established baseline curves, the consistency of X-ray tube output characteristics including tube voltage accuracy, exposure accuracy and exposure linearity were assessed through image quality assessment metrics including ROI mean intensity, ROI standard deviation (SD) and noise power spectrums (NPS). The robustness of this method was tested on two linacs for a three-month period. With the proposed method, tube voltage accuracy can be verified through conscience check with a 2% tolerance and 2 kVp intervals for forty different kVp settings. The exposure accuracy can be tested with a 4% consistency tolerance for three mAs settings over forty kVp settings. The exposure linearity tested with three mAs settings achieved a coefficient of variation (CV) of 0.1. We proposed a novel approach that uses the kV flat panel detector available on linac for X-ray generator test. This approach eliminates the inefficiencies and variability associated with using third party QA detectors while enabling an automated process. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Modeling and regression analysis of semiochemical dose-response curves of insect antennal reception and behavior

USDA-ARS?s Scientific Manuscript database

Dose-response curves with semiochemicals are reported in many articles in insect chemical ecology regarding neurophysiology and behavioral bioassays. Most such curves are shown in figures where the x-axis has order of magnitude increases in dosages versus responses on the y-axis represented by point...

Nonmonotonic dose response curves (NMDRCs) are common after Estrogen or Androgen signaling pathway disruption. Fact or Falderal?##

EPA Science Inventory

Nonmonotonic dose response curves (NMDRCs) are common after Estrogen or Androgen signaling pathway disruption. Fact or Falderal? Leon Earl Gray Jr, USEPA, ORD, NHEERL, TAD, RTB. RTP, NC, USA The shape of the dose response curve in the low dose region has been debated since th...

1. VIEW, LOOKING EAST, OF THE WEST ELEVATION OF BUILDING ...

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

1. VIEW, LOOKING EAST, OF THE WEST ELEVATION OF BUILDING 120. BUILDING 120 HOUSES THE PROTECTIVE FORCE PERSONNEL RESPONSIBLE FOR CONTROLLING ENTRANCE TO AND EGRESS FROM THE ROCKY FLATS PLANT WEST ENTRANCE. - Rocky Flats Plant, Guard Facility, South side of west access road, approximately 2,323 feet east of Colorado Highway 93 & West Road, Golden, Jefferson County, CO

Fingering instabilities in bacterial community phototaxis

NASA Astrophysics Data System (ADS)

Vps, Ritwika; Man Wah Chau, Rosanna; Casey Huang, Kerwyn; Gopinathan, Ajay

Synechocystis sp PCC 6803 is a phototactic cyanobacterium that moves directionally in response to a light source. During phototaxis, these bacterial communities show emergent spatial organisation resulting in the formation of finger-like projections at the propagating front. In this study, we propose an analytical model that elucidates the underlying physical mechanisms which give rise to these spatial patterns. We describe the migrating front during phototaxis as a one-dimensional curve by considering the effects of phototactic bias, diffusion and surface tension. By considering the propagating front as composed of perturbations to a flat solution and using linear stability analysis, we predict a critical bias above which the finger-like projections appear as instabilities. We also predict the wavelengths of the fastest growing mode and the critical mode above which the instabilities disappear. We validate our predictions through comparisons to experimental data obtained by analysing images of phototaxis in Synechocystis communities. Our model also predicts the observed loss of instabilities in taxd1 mutants (cells with inactive TaxD1, an important photoreceptor in finger formation), by considering diffusion in mutually perpendicular directions and a lower, negative bias.

X-ray monochromators for high-power synchrotron radiation sources

NASA Astrophysics Data System (ADS)

Hart, Michael

1990-11-01

Exact solutions to the problems of power flow from a line source of heat into a semicylinder and of uniform heat flow normal to a flat surface are discussed. These lead to bounds on feasible designs and the boundary layer problem can be placed in proper perspective. While finite element calculations are useful if the sample boundaries are predefined, they are much less help in establishing design principles. Previous work on hot beam X-ray crystal optics has emphasised the importance of coolant hydraulics and boundary layer heat transfer. Instead this paper emphasises the importance of the elastic response of crystals to thermal strainfields and the importance of maintaining the Darwin reflectivity. The conclusions of this design study are that the diffracting crystal region should be thin, but not very thin, similar in area to the hot beam footprint, part of a thin-walked buckling crystal box and remote from the support to which the crystal is rigidly clamped. Prototype 111 and 220 cooled silicon crystals tested at the National Synchrotron Light Source at Brookhaven have almost perfect rocking curves under a beam heat load of {1}/{3}kW.

Polyvinylidene fluoride (PVDF) vibration sensor for stethoscope and contact microphones

NASA Astrophysics Data System (ADS)

Toda, Minoru; Thompson, Mitchell

2005-09-01

This paper describes a new type of contact vibration sensor made by bonding piezoelectric PVDF film to a curved frame structure. The concave surface of the film is bonded to a rubber piece having a front contact face. Vibration is transmitted from this face through the rubber to the surface of the PVDF film. Pressure normal to the surface of the film is converted to circumferential strain, and an electric field is induced by the piezoelectric effect. The frequency response of the device was measured using an accelerometer mounted between the rubber face and a rigid vibration exciter plate. Sensitivity (voltage per unit displacement) was deduced from the device output and measured acceleration. The sensitivity was flat from 16 Hz to 3 kHz, peaking at 6 kHz due to a structural resonance. Calculations predicting performance against human tissue (stethoscope or contact microphone) show results similar to data measured against the metal vibrator. This implies that an accelerometer can be used for calibrating a stethoscope or contact microphone. The observed arterial pulse waveform showed more low-frequency content than a conventional electronic stethoscope.

Real-time multi-channel stimulus artifact suppression by local curve fitting.

PubMed

Wagenaar, Daniel A; Potter, Steve M

2002-10-30

We describe an algorithm for suppression of stimulation artifacts in extracellular micro-electrode array (MEA) recordings. A model of the artifact based on locally fitted cubic polynomials is subtracted from the recording, yielding a flat baseline amenable to spike detection by voltage thresholding. The algorithm, SALPA, reduces the period after stimulation during which action potentials cannot be detected by an order of magnitude, to less than 2 ms. Our implementation is fast enough to process 60-channel data sampled at 25 kHz in real-time on an inexpensive desktop PC. It performs well on a wide range of artifact shapes without re-tuning any parameters, because it accounts for amplifier saturation explicitly and uses a statistic to verify successful artifact suppression immediately after the amplifiers become operational. We demonstrate the algorithm's effectiveness on recordings from dense monolayer cultures of cortical neurons obtained from rat embryos. SALPA opens up a previously inaccessible window for studying transient neural oscillations and precisely timed dynamics in short-latency responses to electric stimulation. Copyright 2002 Elsevier Science B.V.

The symmetry and coupling properties of solutions in general anisotropic multilayer waveguides.

PubMed

Hernando Quintanilla, F; Lowe, M J S; Craster, R V

2017-01-01

Multilayered plate and shell structures play an important role in many engineering settings where, for instance, coated pipes are commonplace such as in the petrochemical, aerospace, and power generation industries. There are numerous demands, and indeed requirements, on nondestructive evaluation (NDE) to detect defects or to measure material properties using guided waves; to choose the most suitable inspection approach, it is essential to know the properties of the guided wave solutions for any given multilayered system and this requires dispersion curves computed reliably, robustly, and accurately. Here, the circumstances are elucidated, and possible layer combinations, under which guided wave solutions, in multilayered systems composed of generally anisotropic layers in flat and cylindrical geometries, have specific properties of coupling and parity; the partial wave decomposition of the wave field is utilised to unravel the behaviour. A classification into five families is introduced and the authors claim that this is the fundamental way to approach generally anisotropic waveguides. This coupling and parity provides information to be used in the design of more efficient and robust dispersion curve tracing algorithms. A critical benefit is that the analysis enables the separation of solutions into categories for which dispersion curves do not cross; this allows the curves to be calculated simply and without ambiguity.

Modeling of a Variable Focal Length Flat Lens Using Left Handed Metamaterials

NASA Technical Reports Server (NTRS)

Reinert, Jason

2004-01-01

Left Handed Metamaterials (LHM) were originally purposed by Victor Veselago in1968. These substances would allow a flat structure to focus electromagnetic (EM) waves because they have a negative index of refraction. A similar structure made from conventional materials, those with a positive index of refraction, would disperse the waves. But until recently, these structures have been purely theoretical because substances with both a negative permittivity and negative permeability, material properties necessary for a negative index of refraction, do not naturally exist, Recent developments have produced a structure composed of an array of thin wires and split ring resonators that shows a negative index of refraction. area smaller than a square wavelength. How small the area is can be determined by how perfectly the lens is polished and how pure the substance is that composes the lens. These lenses must also be curved for focusing to occur. The focal length is determined by the curvature of the lens and the material. On the other hand, a flat structure made from LHM would focus light because of the effect of a negative index of refraction in Snell s law. The focal length could also be varied by simply adjusting the distance of the lens from the source of radiation. This could create many devices that are adjustable to different situations in fields such as biomedical imaging and communication. the software package XFDTD which solves Maxwell s equations in the frequency domain as well as the time domain. The program used Drude models of materials to simulate the effect of negative permittivity and negative permeability. Because of this, a LHM can be simulated as a solid block of material instead of an array of wires and split ring resonators. After a flat lens is formed, I am to examine the focusing effect of the lens and determine if a higher resolution flat lens can be developed. Traditional lenses made from conventional materials cannot focus an EM wave onto an My goal was to model LHMs and create a flat lens from them. This was to be done using

Spin-imbalanced pairing and Fermi surface deformation in flat bands

NASA Astrophysics Data System (ADS)

Huhtinen, Kukka-Emilia; Tylutki, Marek; Kumar, Pramod; Vanhala, Tuomas I.; Peotta, Sebastiano; Törmä, Päivi

2018-06-01

We study the attractive Hubbard model with spin imbalance on two lattices featuring a flat band: the Lieb and kagome lattices. We present mean-field phase diagrams featuring exotic superfluid phases, similar to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, whose stability is confirmed by dynamical mean-field theory. The nature of the pairing is found to be richer than just the Fermi surface shift responsible for the usual FFLO state. The presence of a flat band allows for changes in the particle momentum distributions at null energy cost. This facilitates formation of nontrivial superfluid phases via multiband Cooper pair formation: the momentum distribution of the spin component in the flat band deforms to mimic the Fermi surface of the other spin component residing in a dispersive band. The Fermi surface of the unpaired particles that are typical for gapless superfluids becomes deformed as well. The results highlight the profound effect of flat dispersions on Fermi surface instabilities, and provide a potential route for observing spin-imbalanced superfluidity and superconductivity.

The shape of the glucose response curve during an oral glucose tolerance test heralds biomarkers of type 2 diabetes risk in obese youth

USDA-ARS?s Scientific Manuscript database

The shape of the glucose response curve during an oral glucose tolerance test (OGTT), monophasic versus biphasic, identifies physiologically distinct groups of individuals with differences in insulin secretion and sensitivity. We aimed to verify the value of the OGTT-glucose response curve against m...

A mathematical function for the description of nutrient-response curve

PubMed Central

Ahmadi, Hamed

2017-01-01

Several mathematical equations have been proposed to modeling nutrient-response curve for animal and human justified on the goodness of fit and/or on the biological mechanism. In this paper, a functional form of a generalized quantitative model based on Rayleigh distribution principle for description of nutrient-response phenomena is derived. The three parameters governing the curve a) has biological interpretation, b) may be used to calculate reliable estimates of nutrient response relationships, and c) provide the basis for deriving relationships between nutrient and physiological responses. The new function was successfully applied to fit the nutritional data obtained from 6 experiments including a wide range of nutrients and responses. An evaluation and comparison were also done based simulated data sets to check the suitability of new model and four-parameter logistic model for describing nutrient responses. This study indicates the usefulness and wide applicability of the new introduced, simple and flexible model when applied as a quantitative approach to characterizing nutrient-response curve. This new mathematical way to describe nutritional-response data, with some useful biological interpretations, has potential to be used as an alternative approach in modeling nutritional responses curve to estimate nutrient efficiency and requirements. PMID:29161271

Bose–Einstein condensates and scalar fields; exploring the similitudes

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

Castellanos, E.; Macías, A.; Núñez, D.

We analyze the the remarkable analogy between the classical Klein–Gordon equation for a test scalar field in a flat and also in a curved background, and the Gross–Pitaevskii equation for a Bose–Einstein condensate trapped by an external potential. We stress here that the solution associated with the Klein–Gordon equation (KG) in a flat space time has the same mathematical structure, under certain circumstances, to those obtained for the Gross–Pitaevskii equation, that is, a static soliton solution. Additionally, Thomas–Fermi approximation is applied to the 3–dimensional version of this equation, in order to calculate some thermodynamical properties of the system in curvedmore » a space–time back ground. Finally, we stress the fact that a gravitational background provides, in some cases, a kind of confining potential for the scalar field, allowing us to remarks even more the possible connection between scalar fields and the phenomenon of Bose–Einstein condensation.« less

Self-gravitating strings in 2+1 dimensions

NASA Astrophysics Data System (ADS)

Ben-Menahem, Shahar

1993-05-01

We present a family of classical spacetimes in 2+1 dimensions. Such a spacetime is produced by a Nambu-Goto self-gravitating string. Because of the special properties of three-dimensional gravity, the metric is completely described as a Minkowski space with two identified world sheets. In the flat limit, the standard string is recovered. The formalism is developed for an open string with massive end points, but applies to other boundary conditions as well. We consider another limit, where the string tension vanishes in geometrical units but the end masses produce finite deficit angles. In this limit, our open string reduces to the free-masses solution of Gott, which possesses closed timelike curves when the relative motion of the two masses is sufficiently rapid. It is shown that the induced world sheet Liouville mode obeys (-classically)- a sinh- or cosh-Gordon differential equation, which reduces to the Liouville equation in the flat limit. A quadratic-action formulation of this system is presented. The possibility and significance of quantizing the self-gravitating string is discussed.

Lattice gas simulations of dynamical geometry in two dimensions.

PubMed

Klales, Anna; Cianci, Donato; Needell, Zachary; Meyer, David A; Love, Peter J

2010-10-01

We present a hydrodynamic lattice gas model for two-dimensional flows on curved surfaces with dynamical geometry. This model is an extension to two dimensions of the dynamical geometry lattice gas model previously studied in one dimension. We expand upon a variation of the two-dimensional flat space Frisch-Hasslacher-Pomeau (FHP) model created by Frisch [Phys. Rev. Lett. 56, 1505 (1986)] and independently by Wolfram, and modified by Boghosian [Philos. Trans. R. Soc. London, Ser. A 360, 333 (2002)]. We define a hydrodynamic lattice gas model on an arbitrary triangulation whose flat space limit is the FHP model. Rules that change the geometry are constructed using the Pachner moves, which alter the triangulation but not the topology. We present results on the growth of the number of triangles as a function of time. Simulations show that the number of triangles grows with time as t(1/3), in agreement with a mean-field prediction. We also present preliminary results on the distribution of curvature for a typical triangulation in these simulations.

Writing Bragg Gratings in Multicore Fibers.

PubMed

Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

2016-04-20

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

Writing Bragg Gratings in Multicore Fibers

PubMed Central

Lindley, Emma Y.; Min, Seong-sik; Leon-Saval, Sergio G.; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C.; Bland-Hawthorn, Joss

2016-01-01

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

[Theoretical modeling and experimental research on direct compaction characteristics of multi-component pharmaceutical powders based on the Kawakita equation].

PubMed

Si, Guo-Ning; Chen, Lan; Li, Bao-Guo

2014-04-01

Base on the Kawakita powder compression equation, a general theoretical model for predicting the compression characteristics of multi-components pharmaceutical powders with different mass ratios was developed. The uniaxial flat-face compression tests of powder lactose, starch and microcrystalline cellulose were carried out, separately. Therefore, the Kawakita equation parameters of the powder materials were obtained. The uniaxial flat-face compression tests of the powder mixtures of lactose, starch, microcrystalline cellulose and sodium stearyl fumarate with five mass ratios were conducted, through which, the correlation between mixture density and loading pressure and the Kawakita equation curves were obtained. Finally, the theoretical prediction values were compared with experimental results. The analysis showed that the errors in predicting mixture densities were less than 5.0% and the errors of Kawakita vertical coordinate were within 4.6%, which indicated that the theoretical model could be used to predict the direct compaction characteristics of multi-component pharmaceutical powders.

Pollutant emissions from flat-flame burners at high pressures

NASA Technical Reports Server (NTRS)

Maahs, H. G.; Miller, I. M.

1980-01-01

Maximum flame temperatures and pollutant emission measurements for NOx, CO, and UHC (unburned hydrocarbons) are reported for premixed methane air flat flames at constant total mass flow rate over the pressure range from 1.9 to 30 atm and for equivalence ratios from 0.84 to 1.12. For any given pressure, maxima typically occur in both the temperature and NOx emissions curves slightly to the lean side of stoichiometric conditions. The UHC emissions show minima at roughly the same equivalence ratios. The CO emissions, however, increase continually with increasing equivalence ratio. Flame temperature and NOx emissions decrease with increasing pressure, while the opposite is true for the CO and UHC emissions. The NOx data correlate reasonably well as a function of flame temperature only. Four flameholders, differing only slightly, were used. In general, the temperature and emissions data from these four flameholders are similar, but some differences also exist. These differences appear to be related to minor variations in the condition of the flameholder surfaces.

Responses of water environment to tidal flat reduction in Xiangshan Bay: Part II locally re-suspended sediment dynamics

NASA Astrophysics Data System (ADS)

Li, Li; Guan, Weibing; He, Zhiguo; Yao, Yanming; Xia, Yuezhang

2017-11-01

Xiangshan Bay is a semi-enclosed bay in China, in which tidal flats have been substantially reclaimed to support the development of local economies and society over previous decades. The loss of tidal flats has led to changes of tides and locally suspended sediment in the bay. The effects of tidal flat reduction on locally suspended sediment dynamics was investigated using a numerical model forced by tidal data and calibrated by observed tidal elevation and currents. The model satisfactorily reproduces observed water levels, currents, and suspended sediment concentration in the estuary, and therefore is subsequently applied to analyze the impact of tidal flat reclamation on locally suspended sediment transport. After the loss of the tidal flats from 1963 to 2010, the suspended sediment concentrations (SSC) at the bottom boundary layer were reduced/increased in the outer bay/tidal flat areas due to weakened tidal currents. In the inner bay, the SSC values near the bottom level increased from 1963 to 2003 due to the narrowed bathymetry, and then decreased from 2003 to 2010 because of the reduced tidal prism. The model scenarios suggest that: (1) a reduction of tidal flat areas appears to be the main factor for enhancing the transport of sediments up-estuary, due to the increased Eulerian velocity and tidal pumping; (2) A reduction of tidal flat areas impacts on spatial and temporal SSC distribution: reducing the SSC values in the water areas due to the reduced current; and (3) a tidal flat reduction influences the net sediment fluxes: lessening the erosion and inducing higher/lower landward/seaward sediment transportation.

Boolean Operations with Prism Algebraic Patches

PubMed Central

Bajaj, Chandrajit; Paoluzzi, Alberto; Portuesi, Simone; Lei, Na; Zhao, Wenqi

2009-01-01

In this paper we discuss a symbolic-numeric algorithm for Boolean operations, closed in the algebra of curved polyhedra whose boundary is triangulated with algebraic patches (A-patches). This approach uses a linear polyhedron as a first approximation of both the arguments and the result. On each triangle of a boundary representation of such linear approximation, a piecewise cubic algebraic interpolant is built, using a C1-continuous prism algebraic patch (prism A-patch) that interpolates the three triangle vertices, with given normal vectors. The boundary representation only stores the vertices of the initial triangulation and their external vertex normals. In order to represent also flat and/or sharp local features, the corresponding normal-per-face and/or normal-per-edge may be also given, respectively. The topology is described by storing, for each curved triangle, the two triples of pointers to incident vertices and to adjacent triangles. For each triangle, a scaffolding prism is built, produced by its extreme vertices and normals, which provides a containment volume for the curved interpolating A-patch. When looking for the result of a regularized Boolean operation, the 0-set of a tri-variate polynomial within each such prism is generated, and intersected with the analogous 0-sets of the other curved polyhedron, when two prisms have non-empty intersection. The intersection curves of the boundaries are traced and used to decompose each boundary into the 3 standard classes of subpatches, denoted in, out and on. While tracing the intersection curves, the locally refined triangulation of intersecting patches is produced, and added to the boundary representation. PMID:21516262

Modelling, validation and analysis of a three-dimensional railway vehicle-track system model with linear and nonlinear track properties in the presence of wheel flats

NASA Astrophysics Data System (ADS)

Uzzal, R. U. A.; Ahmed, A. K. W.; Bhat, R. B.

2013-11-01

This paper presents dynamic contact loads at wheel-rail contact point in a three-dimensional railway vehicle-track model as well as dynamic response at vehicle-track component levels in the presence of wheel flats. The 17-degrees of freedom lumped mass vehicle is modelled as a full car body, two bogies and four wheelsets, whereas the railway track is modelled as two parallel Timoshenko beams periodically supported by lumped masses representing the sleepers. The rail beam is also supported by nonlinear spring and damper elements representing the railpad and ballast. In order to ensure the interactions between the railpads, a shear parameter beneath the rail beams has also been considered into the model. The wheel-rail contact is modelled using nonlinear Hertzian contact theory. In order to solve the coupled partial and ordinary differential equations of the vehicle-track system, modal analysis method is employed. Idealised Haversine wheel flats with the rounded corner are included in the wheel-rail contact model. The developed model is validated with the existing measured and analytical data available in the literature. The nonlinear model is then employed to investigate the wheel-rail impact forces that arise in the wheel-rail interface due to the presence of wheel flats. The validated model is further employed to investigate the dynamic responses of vehicle and track components in terms of displacement, velocity, and acceleration in the presence of single wheel flat.

Outdoor performance results for NBS Round Robin collector no. 1

NASA Technical Reports Server (NTRS)

Miller, D. R.

1976-01-01

The efficiency of a PPG flat-plate solar collector was evaluated utilizing an outdoor solar collector test facility at the NASA-Lewis Research Center, as part of the National Bureau of Standards 'round robin' collector test program. The correlation equation for collector thermal efficiency Eta curve fit of the data was: Eta = 0.666 - 1.003(Btu/hr-sq ft-F) Theta, where the parameter Theta is the difference between the average fluid temperature and the ambient temperature, all divided by the total flux impinging on the collector.

Gravitational particle creation in a stiff matter dominated universe

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

Lankinen, Juho; Vilja, Iiro, E-mail: jumila@utu.fi, E-mail: vilja@utu.fi

A scenario for gravitational particle creation in a stiff matter dominated flat Friedmann-Robertson-Walker universe is presented. The primary creation of scalar particles is calculated using quantum field theory in curved spacetime and it is found to be strongly dependent on the scalar mass and the expansion parameter of the universe. The particle creation is most effective for a very massive scalar field and large expansion parameter. We demonstrate the phenomenon by applying it to cosmological toy model scenario, where secondary particles are created by the scalar field decay.

Gravitational particle creation in a stiff matter dominated universe

NASA Astrophysics Data System (ADS)

Lankinen, Juho; Vilja, Iiro

2017-08-01

A scenario for gravitational particle creation in a stiff matter dominated flat Friedmann-Robertson-Walker universe is presented. The primary creation of scalar particles is calculated using quantum field theory in curved spacetime and it is found to be strongly dependent on the scalar mass and the expansion parameter of the universe. The particle creation is most effective for a very massive scalar field and large expansion parameter. We demonstrate the phenomenon by applying it to cosmological toy model scenario, where secondary particles are created by the scalar field decay.

Free-stream turbulence and concave curvature effects on heated, transitional boundary layers, volume 1

NASA Technical Reports Server (NTRS)

Kim, J.; Simon, T. W.

1991-01-01

An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-streem turbulence levels was performed. Where possible, sampling according to the intermittency function was made. Such sampling allowed segregation of the signal into two types of behavior: laminar-like and turbulent-like. The results from the investigation are discussed. Documentation is presented in two volumes. Volume one contains the text of the report including figures and supporting appendices. Volume two contains data reduction program listings and tabulated data.

Modeling of dynamic effects of a low power laser beam

NASA Technical Reports Server (NTRS)

Lawrence, George N.; Scholl, Marija S.; Khatib, AL

1988-01-01

Methods of modeling some of the dynamic effects involved in laser beam propagation through the atmosphere are addressed with emphasis on the development of simple but accurate models which are readily implemented in a physical optics code. A space relay system with a ground based laser facility is considered as an example. The modeling of such characteristic phenomena as laser output distribution, flat and curved mirrors, diffraction propagation, atmospheric effects (aberration and wind shear), adaptive mirrors, jitter, and time integration of power on target, is discussed.

Heisenberg equation for a nonrelativistic particle on a hypersurface: From the centripetal force to a curvature induced force

NASA Astrophysics Data System (ADS)

Lian, D. K.; Hu, L. D.; Liu, Q. H.

2017-12-01

In classical mechanics, a nonrelativistic particle constrained on an N - 1 curved hypersurface embedded in N flat space experiences the centripetal force only. In quantum mechanics, the situation is totally different for the presence of the geometric potential. We demonstrate that the motion of the quantum particle is "driven" by not only the centripetal force, but also a curvature induced force proportional to the Laplacian of the mean curvature, which is fundamental in the interface physics, causing curvature driven interface evolution.

Use of asymptotic methods in vibration analysis

NASA Technical Reports Server (NTRS)

Ashley, H.

1978-01-01

The derivation of dynamic differential equations, suitable for studying the vibrations of rotating, curved, slender structures was examined, and the Hamiltonian procedure was advocated for this purpose. Various reductions of the full system are displayed, which govern the vibrating troposkien when various order of magnitude restrictions are placed on important parameters. Possible advantages of the WKB asymptotic method for solving these classes of problems are discussed. A special case of this method is used illustratively to calculate eigenvalues and eigenfunctions for a flat turbine blade with small flexural stiffness.

Performance Characteristics of Flush and Shielded Auxiliary Exits at Mach Numbers of 1.5 to 2.0

NASA Technical Reports Server (NTRS)

Abdalla, Kaleel L.

1959-01-01

The performance characteristics of several flush and shielded auxiliary exits were investigated at Mach numbers of 1.5 to 2.0, and jet pressure ratios from jet off to 10. The results indicate that the shielded configurations produced better overall performance than the corresponding flush exits over the Mach-number and pressure-ratio ranges investigated. Furthermore, the full-length shielded exit was highest in performance of all the configurations. The flat-exit nozzle block provided considerably improved performance compared with the curved-exit nozzle block.

The Hubble Web: The Dark Matter Problem and Cosmic Strings

NASA Astrophysics Data System (ADS)

Alexander, Stephon

2009-07-01

I propose a reinterpretation of cosmic dark matter in which a rigid network of cosmic strings formed at the end of inflation. The cosmic strings fulfill three functions: At recombination they provide an accretion mechanism for virializing baryonic and warm dark matter into disks. These cosmic strings survive as configurations which thread spiral and elliptical galaxies leading to the observed flatness of rotation curves and the Tully-Fisher relation. We find a relationship between the rotational velocity of the galaxy and the string tension and discuss the testability of this model.

User's Manual for Data for Validating Models for PV Module Performance

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

Marion, W.; Anderberg, A.; Deline, C.

2014-04-01

This user's manual describes performance data measured for flat-plate photovoltaic (PV) modules installed in Cocoa, Florida, Eugene, Oregon, and Golden, Colorado. The data include PV module current-voltage curves and associated meteorological data for approximately one-year periods. These publicly available data are intended to facilitate the validation of existing models for predicting the performance of PV modules, and for the development of new and improved models. For comparing different modeling approaches, using these public data will provide transparency and more meaningful comparisons of the relative benefits.

Calibrating Images from the MINERVA Cameras

NASA Astrophysics Data System (ADS)

Mercedes Colón, Ana

2016-01-01

The MINiature Exoplanet Radial Velocity Array (MINERVA) consists of an array of robotic telescopes located on Mount Hopkins, Arizona with the purpose of performing transit photometry and spectroscopy to find Earth-like planets around Sun-like stars. In order to make photometric observations, it is necessary to perform calibrations on the CCD cameras of the telescopes to take into account possible instrument error on the data. In this project, we developed a pipeline that takes optical images, calibrates them using sky flats, darks, and biases to generate a transit light curve.

Analysis of truss, beam, frame, and membrane components. [composite structures

NASA Technical Reports Server (NTRS)

Knoell, A. C.; Robinson, E. Y.

1975-01-01

Truss components are considered, taking into account composite truss structures, truss analysis, column members, and truss joints. Beam components are discussed, giving attention to composite beams, laminated beams, and sandwich beams. Composite frame components and composite membrane components are examined. A description is given of examples of flat membrane components and examples of curved membrane elements. It is pointed out that composite structural design and analysis is a highly interactive, iterative procedure which does not lend itself readily to characterization by design or analysis function only.-

Imperfection and Thickness Measurement of Panels Using a Coordinate Measurement Machine

NASA Technical Reports Server (NTRS)

Thornburgh, Robert P.

2006-01-01

This paper summarizes the methodology used to measure imperfection and thickness variation for flat and curved panels using a Coordinate Measurement Machine (CMM) and the software program MeasPanel. The objective is to provide a reference document so that someone with a basic understanding of CMM operation can measure a panel with minimal training. Detailed information about both the measurement system setup and computer software is provided. Information is also provided about the format of the raw data, as well as how it is post-processed for use in finite-element analysis.

Soil strength response of select soil disturbance classes on a wet pine flat in South Carolina

Treesearch

Emily A. Carter; W. Michael Aust; James A. Burger

2007-01-01

Harvest operations conducted under conditions of high soil moisture on a et pine flat in South Carolina resulted in a high degree of soil surface disturbance. Less soil surface disturbance occurred when soil moisture content was lower. Soil strength varied by soil disturbance class in wet harvested locations and highly disturbed areas were associated with low soil...

Fire history and fire management implications in the Yukon Flats National Wildlife Refuge, interior Alaska

Treesearch

S. A. Drury; P. J. Grissom

2008-01-01

We conducted this investigation in response to criticisms that the current Alaska Interagency Fire Management Plans are allowing too much of the landscape in interior Alaska to burn annually. To address this issue, we analyzed fire history patterns within the Yukon Flats National Wildlife Refuge, interior Alaska. We dated 40 fires on 27 landscape points within the...

Visible light focusing flat lenses based on hybrid dielectric-metal metasurface reflector-arrays

PubMed Central

Fan, Qingbin; Huo, Pengcheng; Wang, Daopeng; Liang, Yuzhang; Yan, Feng; Xu, Ting

2017-01-01

Conventional metasurface reflector-arrays based on metallic resonant nanoantenna to control the wavefront of light for focusing always suffer from strong ohmic loss at optical frequencies. Here, we overcome this challenge by constructing a non-resonant, hybrid dielectric-metal configuration consisting of TiO2 nanofins associated with an Ag reflector substrate that provides a broadband response and high polarization conversion efficiency in the visible range. A reflective flat lens based on this configuration shows an excellent focusing performance with the spot size close to the diffraction limit. Furthermore, by employing the superimposed phase distribution design to manipulate the wavefront of the reflected light, various functionalities, such as multifocal and achromatic focusing, are demonstrated for the flat lenses. Such a reflective flat lens will find various applications in visible light imaging and sensing systems. PMID:28332611

Very Low Volume Sprint Interval Exercise Suppresses Subjective Appetite, Lowers Acylated Ghrelin, and Elevates GLP-1 in Overweight Individuals: A Pilot Study.

PubMed

Holliday, Adrian; Blannin, Andrew K

2017-04-05

High-intensity exercise has been shown to elicit a transient suppression of appetite and create a more anorexigenic profile of appetite-associated hormones. It is yet to be fully elucidated whether such a response is observed following very low-volume, intermittent exercise at supramaximal intensity in those who are overweight. Eight overweight individuals (BMI 27.7 ± 1.7 kg·m²) completed resting (REST) and exercise (EX) trials in a counterbalanced order. EX consisted of 4 × 30 s "flat-out" cycling on an ergometer (adapted Wingate test). Two hours post-exercise (or REST), participants were presented with an ad libitum meal. Subjective appetite measures and blood samples were obtained throughout. Subjective appetite, measured using VAS, was significantly lower immediately after exercise compared with REST (38.0 ± 28.5 mm vs. 75.1 ± 26.2 mm, p = 0.018, d = 1.09). This difference remained significant 30 min post-exercise. Acylated ghrelin concentration was suppressed in EX compared with REST immediately post-exercise (113.4 ± 43.0 pg·mL -1 vs. 189.2 ± 91.8 pg·mL -1 , p = 0.03, d = 1.07) and remained lower until the ad libitum test-meal. Area-under-the-curve for GLP-1 concentration was significantly greater for EX, versus REST. There was no difference in absolute ad libitum intake or relative energy intake. As little as 4 × 30 s of "flat-out" cycling was sufficient to elicit a transient suppression of appetite and an enduring suppression of plasma acylated ghrelin. Nonetheless, food intake 2-h post-exercise was unaffected.

Very Low Volume Sprint Interval Exercise Suppresses Subjective Appetite, Lowers Acylated Ghrelin, and Elevates GLP-1 in Overweight Individuals: A Pilot Study

PubMed Central

Holliday, Adrian; Blannin, Andrew K.

2017-01-01

High-intensity exercise has been shown to elicit a transient suppression of appetite and create a more anorexigenic profile of appetite-associated hormones. It is yet to be fully elucidated whether such a response is observed following very low-volume, intermittent exercise at supramaximal intensity in those who are overweight. Eight overweight individuals (BMI 27.7 ± 1.7 kg·m2) completed resting (REST) and exercise (EX) trials in a counterbalanced order. EX consisted of 4 × 30 s “flat-out” cycling on an ergometer (adapted Wingate test). Two hours post-exercise (or REST), participants were presented with an ad libitum meal. Subjective appetite measures and blood samples were obtained throughout. Subjective appetite, measured using VAS, was significantly lower immediately after exercise compared with REST (38.0 ± 28.5 mm vs. 75.1 ± 26.2 mm, p = 0.018, d = 1.09). This difference remained significant 30 min post-exercise. Acylated ghrelin concentration was suppressed in EX compared with REST immediately post-exercise (113.4 ± 43.0 pg·mL−1 vs. 189.2 ± 91.8 pg·mL−1, p = 0.03, d = 1.07) and remained lower until the ad libitum test-meal. Area-under-the-curve for GLP-1 concentration was significantly greater for EX, versus REST. There was no difference in absolute ad libitum intake or relative energy intake. As little as 4 × 30 s of “flat-out” cycling was sufficient to elicit a transient suppression of appetite and an enduring suppression of plasma acylated ghrelin. Nonetheless, food intake 2-h post-exercise was unaffected. PMID:28379172

Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole.

PubMed

Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

2018-03-30

We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s-wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

Curved reformat of the paediatric brain MRI into a 'flat-earth map' - standardised method for demonstrating cortical surface atrophy resulting from hypoxic-ischaemic encephalopathy.

PubMed

Simpson, Ewan; Andronikou, Savvas; Vedajallam, Schadie; Chacko, Anith; Thai, Ngoc Jade

2016-09-01

Hypoxic-ischaemic encephalopathy is optimally imaged with brain MRI in the neonatal period. However neuroimaging is often also performed later in childhood (e.g., when parents seek compensation in cases of alleged birth asphyxia). We describe a standardised technique for creating two curved reconstructions of the cortical surface to show the characteristic surface changes of hypoxic-ischaemic encephalopathy in children imaged after the neonatal period. The technique was applied for 10 cases of hypoxic-ischaemic encephalopathy and also for age-matched healthy children to assess the visibility of characteristic features of hypoxic-ischaemic encephalopathy. In the abnormal brains, fissural or sulcal widening was seen in all cases and ulegyria was identifiable in 7/10. These images could be used as a visual aid for communicating MRI findings to clinicians and other interested parties.

Tilt Grain Boundary Topology Induced by Substrate Topography.

PubMed

Yu, Henry; Gupta, Nitant; Hu, Zhili; Wang, Kai; Srijanto, Bernadeta R; Xiao, Kai; Geohegan, David B; Yakobson, Boris I

2017-09-26

Synthesis of two-dimensional (2D) crystals is a topic of great current interest, since their chemical makeup, electronic, mechanical, catalytic, and optical properties are so diverse. A universal challenge, however, is the generally random formation of defects caused by various growth factors on flat surfaces. Here we show through theoretical analysis and experimental demonstration that nonplanar, curved-topography substrates permit the intentional and controllable creation of topological defects within 2D materials. We augment a common phase-field method by adding a geometric phase to track the crystal misorientation on a curved surface and to detect the formation of grain boundaries, especially when a growing monocrystal "catches its own tail" on a nontrivial topographical feature. It is specifically illustrated by simulated growth of a trigonal symmetry crystal on a conical-planar substrate, to match the experimental synthesis of WS 2 on silicon template, with satisfactory and in some cases remarkable agreement of theory predictions and experimental evidence.

Biofuel consumption, biodiversity, and the environmental Kuznets curve: trivariate analysis in a panel of biofuel consuming countries.

PubMed

Zaman, Khalid

2017-11-01

This study examined the relationship between biofuel consumption, forest biodiversity, and a set of national scale indicators of per capita income, foreign direct investment (FDI) inflows, trade openness, and population density with a panel data of 12 biofuels consuming countries for a period of 2000 to 2013. The study used Global Environmental Facility (GEF) biodiversity benefits index and forest biodiversity index in an environmental Kuznets curve (EKC) framework. The results confirmed an inverted U-shaped relationship between GEF biodiversity index and per capita income, while there is flat/no relationship between carbon emissions and economic growth, and between forest biodiversity and economic growth models. FDI inflows and trade openness both reduce carbon emissions while population density and biofuel consumption increase carbon emissions and decrease GEF biodiversity index. Trade openness supports to increases GEF biodiversity index while it decreases forest biodiversity index and biofuel consumption in a region.

Fast adaptive flat-histogram ensemble to enhance the sampling in large systems

NASA Astrophysics Data System (ADS)

Xu, Shun; Zhou, Xin; Jiang, Yi; Wang, YanTing

2015-09-01

An efficient novel algorithm was developed to estimate the Density of States (DOS) for large systems by calculating the ensemble means of an extensive physical variable, such as the potential energy, U, in generalized canonical ensembles to interpolate the interior reverse temperature curve , where S( U) is the logarithm of the DOS. This curve is computed with different accuracies in different energy regions to capture the dependence of the reverse temperature on U without setting prior grid in the U space. By combining with a U-compression transformation, we decrease the computational complexity from O( N 3/2) in the normal Wang Landau type method to O( N 1/2) in the current algorithm, as the degrees of freedom of system N. The efficiency of the algorithm is demonstrated by applying to Lennard Jones fluids with various N, along with its ability to find different macroscopic states, including metastable states.

Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole

NASA Astrophysics Data System (ADS)

Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

2018-03-01

We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s -wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

Heterogeneity in the pharmacodynamics of two long-acting methylphenidate formulations for children with attention deficit/hyperactivity disorder. A growth mixture modelling analysis.

PubMed

Sonuga-Barke, Edmund J S; Van Lier, Pol; Swanson, James M; Coghill, David; Wigal, Sharon; Vandenberghe, Mieke; Hatch, Simon

2008-06-01

To use growth mixture modelling (GMM) to identify subgroups of children with attention deficit hyperactive disorder (ADHD) who have different pharmacodynamic profiles in response to extended release methylphenidate as assessed in a laboratory classroom setting. GMM analysis was performed on data from the COMACS study (Comparison of Methylphenidates in the Analog Classroom Setting): a large (n = 184) placebo-controlled cross-over study comparing three treatment conditions in the Laboratory School Protocol (with a 1.5-h cycle of attention and deportment assessments). Two orally administered, once-daily methylphenidate (MPH) bioequivalent formulations [Metadate CD/Equasym XL (MCD-EQXL) and Concerta XL (CON)] were compared with placebo (PLA). Three classes of children with distinct severity profiles in the PLA condition were identified. For both MCD-EQXL and CON, the more severe their PLA symptoms the better, the children's response. However, the formulations produced different growth curves by class, with CON having essentially a flat profile for all three classes (i.e. no effect of PLA severity) and MCD-EQXL showing a marked decline in symptoms immediately post-dosing in the two most severe classes compared with the least severe. Comparison of daily doses matched for immediate-release (IR) components accounted for this difference. The results suggest considerable heterogeneity in the pharmacodynamics of MPH response by children with ADHD. When treatment response for near-equal, bioequivalent daily doses the two formulations was compared, marked differences were seen for children in the most severe classes with a strong curvilinear trajectory for MCD-EQXL related to the greater IR component.

Scaling of heat transfer augmentation due to mechanical distortions in hypervelocity boundary layers

NASA Astrophysics Data System (ADS)

Flaherty, W.; Austin, J. M.

2013-10-01

We examine the response of hypervelocity boundary layers to global mechanical distortions due to concave surface curvature. Surface heat transfer and visual boundary layer thickness data are obtained for a suite of models with different concave surface geometries. Results are compared to predictions using existing approximate methods. Near the leading edge, good agreement is observed, but at larger pressure gradients, predictions diverge significantly from the experimental data. Up to a factor of five underprediction is reported in regions with greatest distortion. Curve fits to the experimental data are compared with surface equations. We demonstrate that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle for all model geometries, even at the conditions of greatest distortion. This scaling may be explained by the application of Lees similarity. As a means of introducing additional local distortions, vortex generators are used to impose streamwise structures into the boundary layer. The response of the large scale vortices to an adverse pressure gradient is investigated. Surface streak evolution is visualized over the different surface geometries using fast response pressure sensitive paint. For a flat plate baseline case, heat transfer augmentation at similar levels to turbulent flow is measured. For the concave geometries, increases in heat transfer by factors up to 2.6 are measured over the laminar values. The scaling of heat transfer with turning angle that is identified for the laminar boundary layer response is found to be robust even in the presence of the imposed vortex structures.

HbA1c and Risks of All-Cause and Cause-Specific Death in Subjects without Known Diabetes: A Dose-Response Meta-Analysis of Prospective Cohort Studies

PubMed Central

Zhong, Guo-Chao; Ye, Ming-Xin; Cheng, Jia-Hao; Zhao, Yong; Gong, Jian-Ping

2016-01-01

Whether HbA1c levels are associated with mortality in subjects without known diabetes remains controversial. Moreover, the shape of the dose–response relationship on this topic is unclear. Therefore, a dose–response meta-analysis was conducted. PubMed and EMBASE were searched. Summary hazard ratios (HRs) were calculated using a random-effects model. Twelve studies were included. The summary HR per 1% increase in HbA1c level was 1.03 [95% confidence interval (CI) = 1.01–1.04] for all-cause mortality, 1.05 [95% CI = 1.02–1.07) for cardiovascular disease (CVD) mortality, and 1.02 (95% CI = 0.99–1.07) for cancer mortality. After excluding subjects with undiagnosed diabetes, the aforementioned associations remained significant for CVD mortality only. After further excluding subjects with prediabetes, all aforementioned associations presented non-significance. Evidence of a non-linear association between HbA1c and mortality from all causes, CVD and cancer was found (all Pnon-linearity < 0.05). The dose–response curves were relatively flat for HbA1c less than around 5.7%, and rose steeply thereafter. In conclusion, higher HbA1c level is associated with increased mortality from all causes and CVD among subjects without known diabetes. However, this association is driven by those with undiagnosed diabetes or prediabetes. The results regarding cancer mortality should be treated with caution due to limited studies. PMID:27045572

EXPERIMENTAL AND NUMERICAL APPROACHES OF TOPOGRAPHIC SITE EFFECTS CLAIMED TO BE RESPONSIBLE FOR 1909 PROVENCE EARTHQUAKE DAMAGE DISTRIBUTION

NASA Astrophysics Data System (ADS)

Duval, A.; Bertrand, E.; Régnier, J.; Grasso, E.; Gance, J.; Glinsky, N.; Semblat, J.

2009-12-01

One of the strongest historical earthquakes in France metropolitan territory occurred in 1909, in Provence, south of France. In the eighties, a scenario study predicted that a similar earthquake may lead to more than the 46 deaths of 1909 and a tremendous economical cost caused by increasing urbanisation in this area. The 1909 maximal intensity was estimated at IX. But a lot of municipalities exhibited strong variations in damage distribution. For some of them, like Rognes and Vernègues, the historical perched village suffered more damage than constructions built on the flat part of the territories. While seismologists realised site effect importance in earthquakes, this 1909 damage distribution became the most famous french illustration of topographic site effect. But if ray theory explains that relief can indubitably focus waves and amplify seismic signal for specific wavelength according to the location on the slope, some doubts remain about the real impact of topographic effects in 1909 damage distribution. It may also be related to the fact that the different types of building were not uniformly spread on the territories and/or that the old structures were more vulnerable than new ones. Finally, was the seismic signal really different along the relief during 1909 earthquake ? Trying to solve this question, several field campaigns were conducted on the village of Rognes. The first one consisted in measuring microtremors on several points and computing H/V ratios (Nogoshi, 1970, Nakamura, 1989). The H/V curves on flat part of the territory do not exhibit any clear peak except for one site on the north where a high frequency peak should be relative to a superficial and thin soft layer. On the contrary, the H/V curves obtained on the top of the relief show a high peak around 1 Hertz. We then decided to install 9 seismic stations to record continuously seismicity at key-points of the relief. The seismicity rate is very low in this region, but the 2 years of operation allow to compare recordings of local, regional and teleseismic events both in time and spectral domains. The first analyse confirms the importance of signal amplification on the top of the relief. Now, numerical simulations are conducted to confirm this amplification and the concerned frequency range. It should precise the repartition of the amplification along a 2D profile. These simulations are conducted simultaneously with different techniques (Finite Elements, Fast Multipole method, Discontinuous Galerkin Finite Elements). These numerical results, confirmed by experimental results, should latter drive to canonical models of seismic response for different relief. They may be directly used to predict ground motion along hills, which is an essential task for seismic risk mitigation, particularly in south France.

A dynamic wheel-rail impact analysis of railway track under wheel flat by finite element analysis

NASA Astrophysics Data System (ADS)

Bian, Jian; Gu, Yuantong; Murray, Martin Howard

2013-06-01

Wheel-rail interaction is one of the most important research topics in railway engineering. It involves track impact response, track vibration and track safety. Track structure failures caused by wheel-rail impact forces can lead to significant economic loss for track owners through damage to rails and to the sleepers beneath. Wheel-rail impact forces occur because of imperfections in the wheels or rails such as wheel flats, irregular wheel profiles, rail corrugations and differences in the heights of rails connected at a welded joint. A wheel flat can cause a large dynamic impact force as well as a forced vibration with a high frequency, which can cause damage to the track structure. In the present work, a three-dimensional finite element (FE) model for the impact analysis induced by the wheel flat is developed by the use of the FE analysis (FEA) software package ANSYS and validated by another validated simulation. The effect of wheel flats on impact forces is thoroughly investigated. It is found that the presence of a wheel flat will significantly increase the dynamic impact force on both rail and sleeper. The impact force will monotonically increase with the size of wheel flats. The relationships between the impact force and the wheel flat size are explored from this FEA and they are important for track engineers to improve their understanding of the design and maintenance of the track system.

Collapsed heteroclinic snaking near a heteroclinic chain in dragged meniscus problems.

PubMed

Tseluiko, D; Galvagno, M; Thiele, U

2014-04-01

A liquid film is studied that is deposited onto a flat plate that is inclined at a constant angle to the horizontal and is extracted from a liquid bath at a constant speed. We analyse steady-state solutions of a long-wave evolution equation for the film thickness. Using centre manifold theory, we first obtain an asymptotic expansion of solutions in the bath region. The presence of an additional temperature gradient along the plate that induces a Marangoni shear stress significantly changes these expansions and leads to the presence of logarithmic terms that are absent otherwise. Next, we numerically obtain steady solutions and analyse their behaviour as the plate velocity is changed. We observe that the bifurcation curve exhibits collapsed (or exponential) heteroclinic snaking when the plate inclination angle is above a certain critical value. Otherwise, the bifurcation curve is monotonic. The steady profiles along these curves are characterised by a foot-like structure that is formed close to the meniscus and is preceded by a thin precursor film further up the plate. The length of the foot increases along the bifurcation curve. Finally, we prove with a Shilnikov-type method that the snaking behaviour of the bifurcation curves is caused by the existence of an infinite number of heteroclinic orbits close to a heteroclinic chain that connects in an appropriate three-dimensional phase space the fixed point corresponding to the precursor film with the fixed point corresponding to the foot and then with the fixed point corresponding to the bath.

QL-09TRAJECTORY OF QUALITY OF LIFE AT END OF LIFE IN MALIGNANT GLIOMA: SUPPORT FOR THE TERMINAL DROP THEORY

PubMed Central

Farace, Elana; Sheehan, Jonas

2014-01-01

Very little is known about quality of life (QOL) at end-of-life (EOL) in malignant brain tumor patients, which limits clinicians ability to best to help patients at this stage. The QOL trajectory at EOL has commonly been hypothesized to be "terminal decline," a linear relationship to time before death with a relatively gradual decline. Alternately, QOL at EOL could be hypothesized to be analogous to the "terminal drop" theory of cognitive aging, wherein the patient QOL has a curvilinear relationship to time before death; a relatively flat curve with a rapid decline a short time before death. 89 patients with malignant glioma were enrolled in this NCI funded study of QOL and neurocognition. Patients completed the EORTC-QLQ-C30 at three month intervals until death. Mean length of follow-up was 224 days (median 155 days). Mean age of patients was 52 years (range 18-80). The gender ratio was 49% men and 51% women. One patient was Latino (so 97% Non-Hispanic), 69 participants were Caucasian, one was African American, and one was Native American. The mean educational level was 13 years (range 8-20). Twenty-eight patients had glioblastoma (grade IV), nine had a grade III oligodendroglioma, and six had a grade III oligoastrocytoma. Data were plotted over time to determine if the shape of the curve resembles terminal decline or terminal drop. Interestingly, as can be seen from the graph, Global QOL slightly improved over time. Growth Curve Analysis confirms this finding. Results of this study may supporting the terminal drop theory but may also illustrate response shift, a conundrum for QOL researchers in which patients' perspective changes and thus they report improved QOL. Longer follow-up is necessary to delineate this pattern. A better understanding of QOL at EOL will improve medical and psychosocial palliative care.

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

González, M. A. Pagnan, E-mail: miguelangel.pagnan@hotmail.com; Mitsoura, E., E-mail: meleni@uaemex.mx; Oviedo, J.O. Hernández

Mycosis fungoides is a cutaneous lymphoma that accounts for 2–3% of all lymphomas. Several clinical studies have demonstrated the effectiveness of TSEBT (Total Skin Electron Beam Therapy) in patients with mycosis fungoides. It is important to develop this technique and make it available to a larger number of patients in Mexico. Because large fields for electron TSEBT are required in order to cover the entire body of the patient, beam characterization at conventional treatment distances is not sufficient and a calibration distance of 500cm or higher is required. Materials and methods: Calibration of radiochromic Gafchromic® EBT2 film (RCF) for electronsmore » was performed in a solid water phantom (Scanditronix Wellhöfer) at a depth of 1.4cm and a Source Axis Distance (SAD) of 100cm. A polynomial fit was applied to the calibration curve, in order to obtain the equation relating dose response with optical density. The spatial distribution is obtained in terms of percentage of the dose, placing 3×3cm samples of RCF on the acrylic screen, which is placed in front of the patient in order to obtain maximum absorbed dose on the skin, covering an area of 200×100cm{sup 2}. The Percentage Depth Dose (PDD) curve was obtained placing RCF samples at depths of 0, 1, 1.2, 1.4, 1.5, 2, 3, 4, 5, 6, 7, 8 and 9cm in the solid water phantom, irradiated with an ELEKTA SINERGY Linear Accelerator electron beam, with an energy of 6 MeV, at a Source Skin Distance (SSD) of 500cm, with 1000MU = 100Gy, with a cone of 40×40cm and gantry angle of 90°. The RCFs were scanned on a flatbed scanner (EPSON EXPRESSION 10000 XL) and the images were processed with the ImageJ program using a region of interest (ROI) of 1×1cm{sup 2}. Results: The relative spatial dose distribution and the percentage depth dose for a SSD of 500±0.5cm, over an area of 200×100cm{sup 2} was obtained, resulting to an effective maximum dose depth (Z{sub ref}) for electrons of 1.4±0.05cm. Using the same experimental data, horizontal and vertical beam profiles were also graphed, showing a horizontal symmetry of ±035%, horizontal flatness of ±3.62%, vertical symmetry of ±2.1% and vertical flatness of ±14.2%. Conclusions: The electron beam was characterized and the data obtained were useful to determine the spatial dose distribution to a SSD of 500±0.5cm, in an area of 200×100cm{sup 2}. Dose profiles were obtained both horizontally and vertically, thus allowing to assess electron beam symmetry and flatness. PDD analysis up to a depth of 9±0.05cm, has made possible to establish the depth of electron penetration, assuring an only skin irradiation treatment.« less

Cone photoreceptor sensitivities and unique hue chromatic responses: correlation and causation imply the physiological basis of unique hues.

PubMed

Pridmore, Ralph W

2013-01-01

This paper relates major functions at the start and end of the color vision process. The process starts with three cone photoreceptors transducing light into electrical responses. Cone sensitivities were once expected to be Red Green Blue color matching functions (to mix colors) but microspectrometry proved otherwise: they instead peak in yellowish, greenish, and blueish hues. These physiological functions are an enigma, unmatched with any set of psychophysical (behavioral) functions. The end-result of the visual process is color sensation, whose essential percepts are unique (or pure) hues red, yellow, green, blue. Unique hues cannot be described by other hues, but can describe all other hues, e.g., that hue is reddish-blue. They are carried by four opponent chromatic response curves but the literature does not specify whether each curve represents a range of hues or only one hue (a unique) over its wavelength range. Here the latter is demonstrated, confirming that opponent chromatic responses define, and may be termed, unique hue chromatic responses. These psychophysical functions also are an enigma, unmatched with any physiological functions or basis. Here both enigmas are solved by demonstrating the three cone sensitivity curves and the three spectral chromatic response curves are almost identical sets (Pearson correlation coefficients r from 0.95-1.0) in peak wavelengths, curve shapes, math functions, and curve crossover wavelengths, though previously unrecognized due to presentation of curves in different formats, e.g., log, linear. (Red chromatic response curve is largely nonspectral and thus derives from two cones.) Close correlation combined with deterministic causation implies cones are the physiological basis of unique hues. This match of three physiological and three psychophysical functions is unique in color vision.

Cone Photoreceptor Sensitivities and Unique Hue Chromatic Responses: Correlation and Causation Imply the Physiological Basis of Unique Hues

PubMed Central

Pridmore, Ralph W.

2013-01-01

This paper relates major functions at the start and end of the color vision process. The process starts with three cone photoreceptors transducing light into electrical responses. Cone sensitivities were once expected to be Red Green Blue color matching functions (to mix colors) but microspectrometry proved otherwise: they instead peak in yellowish, greenish, and blueish hues. These physiological functions are an enigma, unmatched with any set of psychophysical (behavioral) functions. The end-result of the visual process is color sensation, whose essential percepts are unique (or pure) hues red, yellow, green, blue. Unique hues cannot be described by other hues, but can describe all other hues, e.g., that hue is reddish-blue. They are carried by four opponent chromatic response curves but the literature does not specify whether each curve represents a range of hues or only one hue (a unique) over its wavelength range. Here the latter is demonstrated, confirming that opponent chromatic responses define, and may be termed, unique hue chromatic responses. These psychophysical functions also are an enigma, unmatched with any physiological functions or basis. Here both enigmas are solved by demonstrating the three cone sensitivity curves and the three spectral chromatic response curves are almost identical sets (Pearson correlation coefficients r from 0.95–1.0) in peak wavelengths, curve shapes, math functions, and curve crossover wavelengths, though previously unrecognized due to presentation of curves in different formats, e.g., log, linear. (Red chromatic response curve is largely nonspectral and thus derives from two cones.) Close correlation combined with deterministic causation implies cones are the physiological basis of unique hues. This match of three physiological and three psychophysical functions is unique in color vision. PMID:24204755

The shape of the glucose concentration curve during an oral glucose tolerance test predicts risk for type 1 diabetes.

PubMed

Ismail, Heba M; Xu, Ping; Libman, Ingrid M; Becker, Dorothy J; Marks, Jennifer B; Skyler, Jay S; Palmer, Jerry P; Sosenko, Jay M

2018-01-01

We aimed to examine: (1) whether specific glucose-response curve shapes during OGTTs are predictive of type 1 diabetes development; and (2) the extent to which the glucose-response curve is influenced by insulin secretion. Autoantibody-positive relatives of people with type 1 diabetes whose baseline OGTT met the definition of a monophasic or biphasic glucose-response curve were followed for the development of type 1 diabetes (n = 2627). A monophasic curve was defined as an increase in OGTT glucose between 30 and 90 min followed by a decline of ≥ 0.25 mmol/l between 90 and 120 min. A biphasic response curve was defined as a decrease in glucose after an initial increase, followed by a second increase of ≥ 0.25 mmol/l. Associations of type 1 diabetes risk with glucose curve shapes were examined using cumulative incidence curve comparisons and proportional hazards regression. C-peptide responses were compared with and without adjustments for potential confounders. The majority of participants had a monophasic curve at baseline (n = 1732 [66%] vs n = 895 [34%]). The biphasic group had a lower cumulative incidence of type 1 diabetes (p < 0.001), which persisted after adjustments for age, sex, BMI z score and number of autoantibodies (p < 0.001). Among the monophasic group, the risk of type 1 diabetes was greater for those with a glucose peak at 90 min than for those with a peak at 30 min; the difference persisted after adjustments (p < 0.001). Compared with the biphasic group, the monophasic group had a lower early C-peptide (30-0 min) response, a lower C-peptide index (30-0 min C-peptide/30-0 min glucose), as well as a greater 2 h C-peptide level (p < 0.001 for all). Those with biphasic glucose curves have a lower risk of progression to type 1 diabetes than those with monophasic curves, and the risk among the monophasic group is increased when the glucose peak occurs at 90 min than at 30 min. Differences in glucose curve shapes between the monophasic and biphasic groups appear to be related to C-peptide responses.

Probabilistic assessment method of the non-monotonic dose-responses-Part I: Methodological approach.

PubMed

Chevillotte, Grégoire; Bernard, Audrey; Varret, Clémence; Ballet, Pascal; Bodin, Laurent; Roudot, Alain-Claude

2017-08-01

More and more studies aim to characterize non-monotonic dose response curves (NMDRCs). The greatest difficulty is to assess the statistical plausibility of NMDRCs from previously conducted dose response studies. This difficulty is linked to the fact that these studies present (i) few doses tested, (ii) a low sample size per dose, and (iii) the absence of any raw data. In this study, we propose a new methodological approach to probabilistically characterize NMDRCs. The methodology is composed of three main steps: (i) sampling from summary data to cover all the possibilities that may be presented by the responses measured by dose and to obtain a new raw database, (ii) statistical analysis of each sampled dose-response curve to characterize the slopes and their signs, and (iii) characterization of these dose-response curves according to the variation of the sign in the slope. This method allows characterizing all types of dose-response curves and can be applied both to continuous data and to discrete data. The aim of this study is to present the general principle of this probabilistic method which allows to assess the non-monotonic dose responses curves, and to present some results. Copyright © 2017 Elsevier Ltd. All rights reserved.

Wave actions and topography determine the small-scale spatial distribution of newly settled Asari clams Ruditapes philippinarum on a tidal flat

NASA Astrophysics Data System (ADS)

Nambu, Ryogen; Saito, Hajime; Tanaka, Yoshio; Higano, Junya; Kuwahara, Hisami

2012-03-01

There are many studies on spatial distributions of Asari clam Ruditapes philippinarum adults on tidal flats but few have dealt with spatial distributions of newly settled Asari clam (<0.3 mm shell length, indicative of settlement patterns) in relation to physical/topographical conditions on tidal flats. We examined small-scale spatial distributions of newly settled individuals on the Matsunase tidal flat, central Japan, during the low spring tides on two days 29th-30th June 2007, together with the shear stress from waves and currents on the flat. The characteristics of spatial distribution of newly settled Asari clam markedly varied depending on both of hydrodynamic and topographical conditions on the tidal flat. Using generalized linear models (GLMs), factors responsible for affecting newly settled Asari clam density and its spatial distribution were distinguished between sampling days, with "crest" sites always having a negative influence each on the density and the distribution on both sampling days. The continuously recorded data for the wave-current flows at the "crest" site on the tidal flat showed that newly settled Asari clam, as well as bottom sediment particles, at the "crest" site to be easily displaced. Small-scale spatial distributions of newly settled Asari clam changed with more advanced benthic stages in relation to the wave shear stress.

Planted Loblolly and Slash Pine Reponse to Bedding and Flat Disking on a Poorly Drained Site - An Update

Treesearch

Michael D. Cain

1978-01-01

Early gains in lobloliy and slash pine height growth achieved by bedding an imperfectly drained Beauregard-Caddo silt loam diminished somewhat by age 15. After age 8 there were no increases in growth response to site treatment for either species. For loblolly, yields on flat-disked and bedded plots were about 6 cords (500 ft3) per acre greater...

Wormholes with fluid sources: A no-go theorem and new examples

NASA Astrophysics Data System (ADS)

Bronnikov, K. A.; Baleevskikh, K. A.; Skvortsova, M. V.

2017-12-01

For static, spherically symmetric space-times in general relativity (GR), a no-go theorem is proved: it excludes the existence of wormholes with flat and/or anti-de Sitter asymptotic regions on both sides of the throat if the source matter is isotropic, i.e., the radial and tangential pressures coincide. It explains why in all previous attempts to build such solutions it was necessary to introduce boundaries with thin shells that manifestly violate the isotropy of matter. Under a simple assumption on the behavior of the spherical radius r (x ), we obtain a number of examples of wormholes with isotropic matter and one or both de Sitter asymptotic regions, allowed by the no-go theorem. We also obtain twice asymptotically flat wormholes with anisotropic matter, both symmetric and asymmetric with respect to the throat, under the assumption that the scalar curvature is zero. These solutions may be on equal grounds interpreted as those of GR with a traceless stress-energy tensor and as vacuum solutions in a brane world. For such wormholes, the traversability conditions and gravitational lensing properties are briefly discussed. As a byproduct, we obtain twice asymptotically flat regular black hole solutions with up to four Killing horizons. As another byproduct, we point out intersection points in families of integral curves for the function A (x )=gt t, parametrized by its values on the throat.

Evaporation of liquid droplets on solid substrates. II. Periodic substrates with moving contact lines

NASA Astrophysics Data System (ADS)

Amini, Amirhossein; Homsy, G. M.

2017-04-01

Experiments on evaporating droplets on structured surfaces have shown that the contact line does not move with constant speed, but rather in a steplike "stick-slip" fashion. As a first step in understanding such behavior, we study the evaporation of a two-dimensional volatile liquid droplet on a nonplanar heated solid substrate with a moving contact line and fixed contact angle. The model for the flat case is adapted to include curved substrates, numerical solutions are achieved for various periodic and quasiperiodic substrate profiles, and the dynamics of the contact line and the apparent contact angle are studied. In contrast with our results for a flat substrate, for which the contact line recedes in a nearly constant speed, we observe that the contact line speed and position show significant time variation and that the contact line moves in an approximate steplike fashion on relatively steep substrates. For the simplest case of a periodic substrate, we find that the apparent contact angle is periodic in time. For doubly periodic substrates, we find that the apparent contact angle is periodic and that the problem exhibits a phase-locking behavior. For multimode quasiperiodic substrates, we find the contact line behavior to be temporally complex and not only limited to a stick-slip motion. In all cases, we find that the overall evaporation is increased relative to the flat substrate.

Electrical properties of MIS devices on CdZnTe/HgCdTe

NASA Astrophysics Data System (ADS)

Lee, Tae-Seok; Jeoung, Y. T.; Kim, Hyun Kyu; Kim, Jae Mook; Song, Jinhan; Ann, S. Y.; Lee, Ji Y.; Kim, Young Hun; Kim, Sun-Ung; Park, Mann-Jang; Lee, S. D.; Suh, Sang-Hee

1998-10-01

In this paper, we report the capacitance-voltage (C-V) properties of metal-insulator-semiconductor (MIS) devices on CdTe/HgCdTe by the metalorganic chemical vapor deposition (MOCVD) and CdZnTe/HgCdTe by thermal evaporation. In MOCVD, CdTe layers are directly grown on HgCdTe using the metal organic sources of DMCd and DiPTe. HgCdTe layers are converted to n-type and the carrier concentration, ND is low 1015 cm-3 after Hg-vacancy annealing at 260 degrees Celsius. In thermal evaporation, CdZnTe passivation layers were deposited on HgCdTe surfaces after the surfaces were etched with 0.5 - 2.0% bromine in methanol solution. To investigate the electrical properties of the MIS devices, the C-V measurement is conducted at 80 K and 1 MHz. C-V curve of MIS devices on CdTe/HgCdTe by MOCVD has shown nearly flat band condition and large hysteresis, which is inferred to result from many defects in CdTe layer induced during Hg-vacancy annealing process. A negative flat band voltage (VFB approximately equals -2 V) and a small hysteresis have been observed for MIS devices on CdZnTe/HgCdTe by thermal evaporation. It is inferred that the negative flat band voltage results from residual Te4+ on the surface after etching with bromine in methanol solution.

Dynamical generation of Floquet Majorana flat bands in s-wave superconductors

NASA Astrophysics Data System (ADS)

Poudel, A.; Ortiz, G.; Viola, L.

2015-04-01

We present quantum control techniques to engineer flat bands of symmetry-protected Majorana edge modes in s-wave superconductors. Specifically, we show how periodic control may be employed for designing time-independent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support a Majorana pair per edge. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a pre-existing chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing chirality-breaking terms in the static Hamiltonian. Our results demonstrate how the use of time-dependent control enlarges the range of possibilities for realizing gapless topological superconductivity, potentially enabling access to topological states of matter that have no known equilibrium counterpart.

Novel Electronic Structures of Ru-pnictides RuPn (Pn = P, As, Sb)

NASA Astrophysics Data System (ADS)

Goto, H.; Toriyama, T.; Konishi, T.; Ohta, Y.

Density-functional-theory-based electronic structure calculations are made to consider the novel electronic states of Ru-pnictides RuP and RuAs where the intriguing phase transitions and superconductivity under doping of Rh have been reported. We find that there appear nearly degenerate flat bands just at the Fermi level in the high-temperature metallic phase of RuP and RuAs; the flat-band states come mainly from the 4dxy orbitals of Ru ions and the Rh doping shifts the Fermi level just above the flat bands. The splitting of the flat bands caused by their electronic instability may then be responsible for the observed phase transition to the nonmagnetic insulating phase at low temperatures. We also find that the band structure calculated for RuSb resembles that of the doped RuP and RuAs, which is consistent with experiment where superconductivity occurs in RuSb without Rh doping.

Responses of water environment to tidal flat reduction in Xiangshan Bay: Part I hydrodynamics

NASA Astrophysics Data System (ADS)

Li, Li; Guan, Weibing; Hu, Jianyu; Cheng, Peng; Wang, Xiao Hua

2018-06-01

Xiangshan Bay consists of a deep tidal channel and three shallow inlets. A large-scale tidal flat has been utilized through coastal construction. To ascertain the accumulate influences of these engineering projects upon the tidal dynamics of the channel-inlets system, this study uses FVCOM to investigate the tides and flow asymmetries of the bay, and numerically simulate the long-term variations of tidal dynamics caused by the loss of tidal flats. It was found that the reduction of tidal flat areas from 1963 to 2010 slightly dampened M2 tidal amplitudes (0.1 m, ∼6%) and advanced its phases by reducing shoaling effects, while amplified M4 tidal amplitudes (0.09 m, ∼27%) and advanced its phases by reducing bottom friction, in the inner bay. Consequently, the ebb dominance was dampened indicated by reduced absolute value of elevation skewness (∼20%) in the bay. The tides and tidal asymmetry were impacted by the locations, areas and slopes of the tidal flats through changing tidal prism, shoaling effect and bottom friction, and consequently impacted tidal duration asymmetry in the bay. Tides and tidal asymmetry were more sensitive to the tidal flat at the head of the bay than the side bank. Reduced/increased tidal flat slopes around the Tie inlet dampened the ebb dominance. Tidal flat had a role in dissipating the M4 tide rather than generating it, while the advection only play a secondary role in generating the M4 tide. The full-length tidal flats reclamation would trigger the reverse of ebb to flood dominance in the bay. This study would be applicable for similar narrow bays worldwide.

Impact of weight-based ribavirin with peginterferon alfa-2b in African Americans with hepatitis C virus genotype 1.

PubMed

Jacobson, Ira M; Brown, Robert S; McCone, Jonathan; Black, Martin; Albert, Clive; Dragutsky, Michael S; Siddiqui, Firdous A; Hargrave, Thomas; Kwo, Paul Y; Lambiase, Louis; Galler, Greg W; Araya, Victor; Freilich, Bradley; Harvey, Joann; Griffel, Louis H; Brass, Clifford A

2007-10-01

WIN-R (Weight-based dosing of pegINterferon alfa-2b and Ribavirin) was a multicenter, randomized, open-label, investigator-initiated trial involving 236 community and academic sites in the United States, comparing response to pegylated interferon (PEG-IFN) alfa-2b plus a flat or weight-based dose of ribavirin (RBV) in treatment-naive patients with chronic hepatitis C and compensated liver disease. Patients were randomized to receive PEG-IFN alfa-2b at 1.5 microg/kg/week plus flat-dose (800 mg/day) or weight-based-dose RBV (800 mg/day for weight <65 kg, 1000 mg/day for 65-85 kg, 1200 mg/day for >85-105 kg, or 1400 mg/day for >105-<125 kg). Sustained virologic response (SVR; undetectable [<125 IU/mL] hepatitis C virus [HCV] RNA at end of follow-up) in patients > or =65 kg was the primary end point. Low SVR rates have been reported among African American individuals, in whom there is a preponderance of HCV genotype 1. This subanalysis of WIN-R was conducted to evaluate the efficacy of weight-based dosing among African American individuals with genotype 1 infection enrolled in the trial. Of 362 African American patients in the primary efficacy analysis, 188 received RBV flat dosing and 174 received weight-based dosing. SVR rates were higher (21% versus 10%; P = 0.0006) and relapse rates were lower (22% versus 30%) in the weight-based-dose group than in the flat-dose group. Safety and rates of drug discontinuation were similar between the 2 groups. Weight-based dosing of RBV is more effective than flat dosing in combination with PEG-IFN alfa-2b in African American individuals with HCV genotype 1. Even with weight-based dosing, response rates in African American individuals are lower than reported in other ethnic groups.

A Comparison of Image Quality and Radiation Exposure Between the Mini C-Arm and the Standard C-Arm.

PubMed

van Rappard, Juliaan R M; Hummel, Willy A; de Jong, Tijmen; Mouës, Chantal M

2018-04-01

The use of intraoperative fluoroscopy has become mandatory in osseous hand surgery. Due to its overall practicality, the mini C-arm has gained popularity among hand surgeons over the standard C-arm. This study compares image quality and radiation exposure for patient and staff between the mini C-arm and the standard C-arm, both with flat panel technology. An observer-based subjective image quality study was performed using a contrast detail (CD) phantom. Five independent observers were asked to determine the smallest circles discernable to them. The results were plotted in a graph, forming a CD curve. From each curve, an image quality figure (IQF) was derived. A lower IQF equates to a better image quality. The patients' entrance skin dose was measured, and to obtain more information about the staff exposure dose, a perspex hand phantom was used. The scatter radiation was measured at various distances and angles relative to a central point on the detector. The IQF was significantly lower for the mini C-arm resulting in a better image quality. The patients' entrance dose was 10 times higher for the mini C-arm as compared with the standard C-arm, and the scatter radiation threefold. Due to its improved image quality and overall practicality, the mini C-arm is recommended for hand surgical procedures. To ensure that the surgeons' radiation exposure is not exceeding the safety limits, monitoring radiation exposure using mini C-arms with flat panel technology during surgery should be done in a future clinical study.

Solid perception mechanism by a shading pattern: spatial frequency components in a corrugated wave pattern.

PubMed

Nameda, N

1988-01-01

Illumination allows solid object perception to be obtained and depicted by a shading pattern produced by lighting. The shading cue, as one of solid perception cues (Gibson 1979), was investigated in regard to a white corrugated wave shape, using computer graphic device: Tospix-2. The reason the corrugated wave was chosen, is that an alternately bright and dark pattern, produced by shading, can be conveniently analyzed into contained spatial frequencies. This paper reports spatial frequency properties contained in the shading pattern. The shading patterns, input into the computer graphic device, are analyzed by Fourier Transformation by the same device. After the filtration by various spatial frequency low and high pass filters, Inverse Fourier Transformation is carried out for the residual components. The result of the analysis indicates that the third through higher harmonics components are important in regard to presenting a solid reality feeling in solid perception. Sakata (1983) also reported that an edged pattern, superimposed onto a lower sinusoidal pattern, was important in solid perception. The third through higher harmonics components express the changing position of luminance on the pattern, and a slanted plane relating to the light direction. Detection of a solid shape, constructed with flat planes, is assumed to be on the bottom of the perfect curved solid perception mechanism. Apparent evidence for this assumption, in difficult visual conditions, is that a flat paneled solid is seen before the curved solid. This mechanism is explained by two spatial frequency neural network systems, assumed as having correspondence with higher spatial frequency detection and lower spatial frequency detection.

Fault detection method for railway wheel flat using an adaptive multiscale morphological filter

NASA Astrophysics Data System (ADS)

Li, Yifan; Zuo, Ming J.; Lin, Jianhui; Liu, Jianxin

2017-02-01

This study explores the capacity of the morphology analysis for railway wheel flat fault detection. A dynamic model of vehicle systems with 56 degrees of freedom was set up along with a wheel flat model to calculate the dynamic responses of axle box. The vehicle axle box vibration signal is complicated because it not only contains the information of wheel defect, but also includes track condition information. Thus, how to extract the influential features of wheels from strong background noise effectively is a typical key issue for railway wheel fault detection. In this paper, an algorithm for adaptive multiscale morphological filtering (AMMF) was proposed, and its effect was evaluated by a simulated signal. And then this algorithm was employed to study the axle box vibration caused by wheel flats, as well as the influence of track irregularity and vehicle running speed on diagnosis results. Finally, the effectiveness of the proposed method was verified by bench testing. Research results demonstrate that the AMMF extracts the influential characteristic of axle box vibration signals effectively and can diagnose wheel flat faults in real time.

Nonlinear site response in medium magnitude earthquakes near Parkfield, California

USGS Publications Warehouse

Rubinstein, Justin L.

2011-01-01

Careful analysis of strong-motion recordings of 13 medium magnitude earthquakes (3.7 ≤ M ≤ 6.5) in the Parkfield, California, area shows that very modest levels of shaking (approximately 3.5% of the acceleration of gravity) can produce observable changes in site response. Specifically, I observe a drop and subsequent recovery of the resonant frequency at sites that are part of the USGS Parkfield dense seismograph array (UPSAR) and Turkey Flat array. While further work is necessary to fully eliminate other models, given that these frequency shifts correlate with the strength of shaking at the Turkey Flat array and only appear for the strongest shaking levels at UPSAR, the most plausible explanation for them is that they are a result of nonlinear site response. Assuming this to be true, the observation of nonlinear site response in small (M M 6.5 San Simeon earthquake and the 2004 M 6 Parkfield earthquake).

U-SHAPED DOSE-RESPONSE CURVES: THEIR OCCURRENCE AND IMPLICATIONS FOR RISK ASSESSMENT

EPA Science Inventory

A class of curvilinear dose-response relationships in toxicological and epidemiological studies may be roughly described by "U-shaped curves. uch curves reflect an apparent reversal or inversion in the effect of an otherwise toxic agent at a low or intermediate region of the dose...

Real space mapping of oxygen vacancy diffusion and electrochemical transformations by hysteretic current reversal curve measurements

DOEpatents

Kalinin, Sergei V.; Balke, Nina; Borisevich, Albina Y.; Jesse, Stephen; Maksymovych, Petro; Kim, Yunseok; Strelcov, Evgheni

2014-06-10

An excitation voltage biases an ionic conducting material sample over a nanoscale grid. The bias sweeps a modulated voltage with increasing maximal amplitudes. A current response is measured at grid locations. Current response reversal curves are mapped over maximal amplitudes of the bias cycles. Reversal curves are averaged over the grid for each bias cycle and mapped over maximal bias amplitudes for each bias cycle. Average reversal curve areas are mapped over maximal amplitudes of the bias cycles. Thresholds are determined for onset and ending of electrochemical activity. A predetermined number of bias sweeps may vary in frequency where each sweep has a constant number of cycles and reversal response curves may indicate ionic diffusion kinetics.

Effect of a viscoelastic target on the impact response of a flat-nosed projectile

NASA Astrophysics Data System (ADS)

Liu, Hu; Yang, Jialing; Liu, Hua

2018-02-01

Taylor impact is a widely used strategy in which a flat-nosed projectile is fired onto a rigid anvil directly to determine the dynamic strength of rod specimens. Nowadays, the rigid anvil is often replaced by an output target bar to ensure the accuracy of measurement via recording strain signals in the output bar. For testing the dynamic strength of low-density materials, a low-impedance target bar, which exhibits viscoelastic characteristics is often employed. In this paper, an extended Taylor model is proposed to improve the idealization of treating the target bar as perfectly rigid material in the classic Taylor model, and the viscoelastic effect of the target bar is incorporated. The viscoelastic target bar is depicted by two elastic springs and one dashpot. Based on the plastic shock wave theory in the flat-nosed projectile associated with the viscoelastic wave analysis in the target bar, the viscoelastic effect of the target bar on the impact response of the flat-nosed projectile is investigated. The finite element simulation is also carried out to verify the theoretical model, and good agreement is found. The present theoretical model is also called the Taylor-cylinder Hopkinson impact, which provides a more accurate way to identify the dynamic material parameters. The dynamic responses of the present model are further compared with previous elastic and rigid target bar models. It is found that the viscoelastic effect of the target bar should be taken into consideration in the Taylor-cylinder Hopkinson impact test for low-impedance materials.

Comparative Study of the Binding of Concanavalin A to Self-Assembled Monolayers Containing a Thiolated α-Mannoside on Flat Gold and on Nanoporous Gold

PubMed Central

Pandey, Binod; Tan, Yih Horng; Fujikawa, Kohki; Demchenko, Alexei V.

2013-01-01

We have prepared SAMs containing 8-mercaptooctyl α-D-mannopyranoside, either as a single component or in mixed SAMs with n-octanethiol on flat gold surfaces and on nanoporous gold. Electrochemical impedance spectroscopy showed that the mixed SAMs on flat gold surfaces showed the highest Con A binding near 1:9 solution molar ratio of thiolatedα-mannoside to n-octanethiol whereas those on NPG showed the highest response at 1:19 solution molar ratio of thiolated α-mannoside to n-octanethiol. Atomic force microscopy was employed to image the monolayers, and also to image the bound Con A protein. PMID:23519474

Effects of recording time and residue on dose-response by LiMgPO4: Tb, B ceramic disc synthesized via improved sintering process

NASA Astrophysics Data System (ADS)

Kong, Xirui; Fu, Zhilong; Que, Huiying; Fan, Yanwei; Chen, Zhaoyang; He, Chengfa

2018-05-01

The LiMgPO4: Tb, B ceramic disc is successfully synthesized via improved sintering method which enables the disc sample to have two flat and smooth surfaces. It is worth mentioning that the OSL signal intensity of LiMgPO4: Tb, B disc attenuates much faster than that of commercial Al2O3: C. It costs only 1 s to reduce the intensity to 10%, but the Al2O3:C needs more than 40 s to finish it. Some essential OSL properties related to the dose detection method of this sample also have been systematically investigated. Although the dose-response cure would have better linearity with longer recording time, extended recording time (≥6 s) will not make any contribution to the linearity of the curve. If the bleaching time is more than 35 s, the residue created by previous detection (high dose of 10 Gy) would do almost no influence (with a positive deviation lower than 5.59%) on next lower-dose detection (0.1 Gy). The material would reach its service life when the total-ionizing dose runs up to 30 k Gy. Therefore, the LiMgPO4: Tb, B ceramic material is a potential candidate for real-time dose monitoring with optical fiber telemetering technology.

On the role of tip curvature on flapping plates.

PubMed

Martin, Nathan; Gharib, Morteza

2018-01-09

During the flapping motion of a fish's tail, the caudal fin exhibits antero-posterior bending and dorso-ventral bending, the latter of which is referred to as chord-wise bending herein. The impact of chord-wise tip curvature on the hydrodynamic forces for flapping plates is investigated to explore potential mechanisms to improve the maneuverability or the performance of autonomous underwater vehicles. First, actuated chord-wise tip curvature is explored. Comparison of rigid curved geometries to a rigid flat plate as a baseline suggests that an increased curvature decreases the generated forces. An actuated plate with a dynamic tip curvature is created to illustrate a modulation of this decrease in forces. Second, the impact of curvature is isolated using curved plates with an identical planform area. Comparison of rigid curved geometries as a baseline corroborates the result that an increased curvature decreases the generated forces, with the exception that presenting a concave geometry into the flow increases the thrust and the efficiency. A passively-actuated plate is designed to capitalize on this effect by presenting a concave geometry into the flow throughout the cycle. The dynamically and passively actuated plates show potential to improve the maneuverability and the efficiency of autonomous underwater vehicles, respectively.

Experimental and numerical study of drill bit drop tests on Kuru granite

NASA Astrophysics Data System (ADS)

Fourmeau, Marion; Kane, Alexandre; Hokka, Mikko

2017-01-01

This paper presents an experimental and numerical study of Kuru grey granite impacted with a seven-buttons drill bit mounted on an instrumented drop test machine. The force versus displacement curves during the impact, so-called bit-rock interaction (BRI) curves, were obtained using strain gauge measurements for two levels of impact energy. Moreover, the volume of removed rock after each drop test was evaluated by stereo-lithography (three-dimensional surface reconstruction). A modified version of the Holmquist-Johnson-Cook (MHJC) material model was calibrated using Kuru granite test results available from the literature. Numerical simulations of the single drop tests were carried out using the MHJC model available in the LS-DYNA explicit finite-element solver. The influence of the impact energy and additional confining pressure on the BRI curves and the volume of the removed rock is discussed. In addition, the influence of the rock surface shape before impact was evaluated using two different mesh geometries: a flat surface and a hyperbolic surface. The experimental and numerical results are compared and discussed in terms of drilling efficiency through the mechanical specific energy. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Measuring the x-ray resolving power of bent potassium acid phthalate diffraction crystals

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

Haugh, M. J., E-mail: haughmj@nv.doe.gov; Jacoby, K. D.; Wu, M.

2014-11-15

This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals thatmore » we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories in Albuquerque, New Mexico. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a double crystal diffractometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.« less

Measuring the X-ray Resolving Power of Bent Potassium Acid Phthalate Diffraction Crystals

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

Haugh, M. J.; Wu, M.; Jacoby, K. D.

2014-11-01

This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals thatmore » we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories (SNL) in Albuquerque, NM. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a dual goniometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.« less

OGLE-2014-BLG-0289: Precise Characterization of a Quintuple-peak Gravitational Microlensing Event

NASA Astrophysics Data System (ADS)

Udalski, A.; Han, C.; Bozza, V.; Gould, A.; Bond, I. A.; and; Mróz, P.; Skowron, J.; Wyrzykowski, Ł.; Szymański, M. K.; Soszyński, I.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Kozłowski, S.; The OGLE Collaboration; Abe, F.; Barry, R.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Evans, P.; Fukui, A.; Hirao, Y.; Itow, Y.; Kawasaki, K.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyazaki, S.; Munakata, H.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Ranc, C.; Rattenbury, N.; Saito, T.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yamada, T.; Yonehara, A.; The MOA Collaboration; Street, R. A.; Tsapras, Y.; Bachelet, E.; Bramich, D. M.; DÁgo, G.; Dominik, M.; Figuera Jaimes, R.; Horne, K.; Hundertmark, M.; Kains, N.; Menzies, J.; Schmidt, R.; Snodgrass, C.; Steele, I. A.; Wambsganss, J.; Robonet Collaboration; Pogge, R. W.; Jung, Y. K.; Shin, I.-G.; Yee, J. C.; Kim, W.-T.; The μFun Collaboration; Beichman, C.; Carey, S.; Calchi Novati, S.; Zhu, W.; The Spitzer Team

2018-01-01

We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits five very unusual peaks, four of which were produced by caustic crossings and the other by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax {π }{{E}}. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius {θ }{{E}}. From the combination of {π }{{E}} and {θ }{{E}}, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses {M}1=0.52+/- 0.04 {M}ȯ and {M}2=0.42+/- 0.03 {M}ȯ separated in projection by {a}\\perp =6.4+/- 0.5 {au}. The lens is located in the disk with a distance of {D}{{L}}=3.3+/- 0.3 {kpc}. The reason for the absence of a lensing signal in the Spitzer data is that the time of observation corresponds to the flat region of the light curve.

Use of loading-unloading compression curves in medical device design

NASA Astrophysics Data System (ADS)

Ciornei, M. C.; Alaci, S.; Ciornei, F. C.; Romanu, I. C.

2017-08-01

The paper presents a method and experimental results regarding mechanical testing of soft materials. In order to characterize the mechanical behaviour of technological materials used in prosthesis, a large number of material constants are required, as well as the comparison to the original. The present paper proposes as methodology the comparison between compression loading-unloading curves corresponding to a soft biological tissue and to a synthetic material. To this purpose, a device was designed based on the principle of the dynamic harness test. A moving load is considered and the force upon the indenter is controlled for loading-unloading phases. The load and specimen deformation are simultaneously recorded. A significant contribution of this paper is the interpolation of experimental data by power law functions, a difficult task because of the instability of the system of equations to be optimized. Finding the interpolation function was simplified, from solving a system of transcendental equations to solving a unique equation. The characteristic parameters of the experimentally curves must be compared to the ones corresponding to actual tissue. The tests were performed for two cases: first, using a spherical punch, and second, for a flat-ended cylindrical punch.

Measuring the x-ray resolving power of bent potassium acid phthalate diffraction crystalsa)

NASA Astrophysics Data System (ADS)

Haugh, M. J.; Wu, M.; Jacoby, K. D.; Loisel, G. P.

2014-11-01

This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals that we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories in Albuquerque, New Mexico. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a double crystal diffractometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.

Wide steering angle microscanner based on curved surface

NASA Astrophysics Data System (ADS)

Sabry, Yasser; Khalil, Diaa; Saadany, Bassam; Bourouina, Tarik

2013-03-01

Intensive industrial and academic research is oriented towards the design and fabrication of optical beam steering systems based on MEMS technology. In most of these systems, the scanning is achieved by rotating a flat micromirror around a central axis in which the main challenge is achieving a wide mirror rotation angle. In this work, a novel method of optical beam scanning based on reflection from a curved surface is presented. The scanning occurs when the optical axis of the curved surface is displaced with respect to the optical axis of the incident beam. To overcome the possible deformation of the spot with the scanning angle, the curved surface is designed with a specific aspherical profile. Moreover, the scanning exhibits a more linearized scanning angle-displacement relation than the conventional spherical profile. The presented scanner is fabricated using DRIE technology on an SOI wafer. The curved surface (reflector) is metalized and attached to a comb-drive actuator fabricated in the same lithography step. A single-mode fiber, behaving as a Gaussian beam source, is positioned on the substrate facing the mirror. The reflected optical beam angle and spotsize in the far field is recorded versus the relative shift between the fiber and the curved mirror. The spot size is plotted versus the scanning angle and a scanning spot size uniformity of about +/-10% is obtained for optical deflection angles up to 100 degrees. As the optical beam is propagating parallel to the wafer substrate, a completely integrated laser scanner can be achieved with filters and actuators self-aligned on the same chip that allows low cost and mass production of this important product.

Real-time defect detection on highly reflective curved surfaces

NASA Astrophysics Data System (ADS)

Rosati, G.; Boschetti, G.; Biondi, A.; Rossi, A.

2009-03-01

This paper presents an automated defect detection system for coated plastic components for the automotive industry. This research activity came up as an evolution of a previous study which employed a non-flat mirror to illuminate and inspect high reflective curved surfaces. According to this method, the rays emitted from a light source are conveyed on the surface under investigation by means of a suitably curved mirror. After the reflection on the surface, the light rays are collected by a CCD camera, in which the coating defects appear as shadows of various shapes and dimensions. In this paper we present an evolution of the above-mentioned method, introducing a simplified mirror set-up in order to reduce the costs and the complexity of the defect detection system. In fact, a set of plane mirrors is employed instead of the curved one. Moreover, the inspection of multiple bend radius parts is investigated. A prototype of the machine vision system has been developed in order to test this simplified method. This device is made up of a light projector, a set of plane mirrors for light rays reflection, a conveyor belt for handling components, a CCD camera and a desktop PC which performs image acquisition and processing. Like in the previous system, the defects are identified as shadows inside a high brightness image. At the end of the paper, first experimental results are presented.

Determine Neuronal Tuning Curves by Exploring Optimum Firing Rate Distribution for Information Efficiency

PubMed Central

Han, Fang; Wang, Zhijie; Fan, Hong

2017-01-01

This paper proposed a new method to determine the neuronal tuning curves for maximum information efficiency by computing the optimum firing rate distribution. Firstly, we proposed a general definition for the information efficiency, which is relevant to mutual information and neuronal energy consumption. The energy consumption is composed of two parts: neuronal basic energy consumption and neuronal spike emission energy consumption. A parameter to model the relative importance of energy consumption is introduced in the definition of the information efficiency. Then, we designed a combination of exponential functions to describe the optimum firing rate distribution based on the analysis of the dependency of the mutual information and the energy consumption on the shape of the functions of the firing rate distributions. Furthermore, we developed a rapid algorithm to search the parameter values of the optimum firing rate distribution function. Finally, we found with the rapid algorithm that a combination of two different exponential functions with two free parameters can describe the optimum firing rate distribution accurately. We also found that if the energy consumption is relatively unimportant (important) compared to the mutual information or the neuronal basic energy consumption is relatively large (small), the curve of the optimum firing rate distribution will be relatively flat (steep), and the corresponding optimum tuning curve exhibits a form of sigmoid if the stimuli distribution is normal. PMID:28270760

Statistically generated weighted curve fit of residual functions for modal analysis of structures

NASA Technical Reports Server (NTRS)

Bookout, P. S.

1995-01-01

A statistically generated weighting function for a second-order polynomial curve fit of residual functions has been developed. The residual flexibility test method, from which a residual function is generated, is a procedure for modal testing large structures in an external constraint-free environment to measure the effects of higher order modes and interface stiffness. This test method is applicable to structures with distinct degree-of-freedom interfaces to other system components. A theoretical residual function in the displacement/force domain has the characteristics of a relatively flat line in the lower frequencies and a slight upward curvature in the higher frequency range. In the test residual function, the above-mentioned characteristics can be seen in the data, but due to the present limitations in the modal parameter evaluation (natural frequencies and mode shapes) of test data, the residual function has regions of ragged data. A second order polynomial curve fit is required to obtain the residual flexibility term. A weighting function of the data is generated by examining the variances between neighboring data points. From a weighted second-order polynomial curve fit, an accurate residual flexibility value can be obtained. The residual flexibility value and free-free modes from testing are used to improve a mathematical model of the structure. The residual flexibility modal test method is applied to a straight beam with a trunnion appendage and a space shuttle payload pallet simulator.

Dynamic equilibrium behaviour observed on two contrasting tidal flats from daily monitoring of bed-level changes

NASA Astrophysics Data System (ADS)

Hu, Zhan; van der Wal, Daphne; Cai, Huayang; van Belzen, Jim; Bouma, Tjeerd J.

2018-06-01

Dynamic equilibrium theory (DET) has been applied to tidal flats to systematically explain intertidal morphological responses to various distributions of bed shear stress (BSS). However, it is difficult to verify this theory with field observations because of the discrepancy between the idealized conceptions of theory and the complex reality of intertidal dynamics. The core relation between intertidal morphodynamics and BSS distribution can be easily masked by noise in complex datasets, leading to conclusions of insufficient field evidence to support DET. In the current study, hydrodynamic and morphodynamic data were monitored daily for one year on two tidal flats with contrasting wave exposures. BSS distribution was obtained by validated numerical models. Tidal flat dynamic equilibrium behaviour and BSS were linked via Empirical Orthogonal Function (EOF) analysis. We show that the principal morphodynamic modes corresponded well with the respective modes of BSS found at both sites. Tide-induced BSS was the dominant force at both sites, regardless of the level of wave exposure. The overall erosional and steepening trend found at the two flats can be attributed to the prevailing action of tidal forcing and reduced sediment supply. Hence, EOF analysis confirmed that tidal flat morphodynamics are consistent with DET, providing both field and model evidence to support this theory.

U.S. Nuclear Weapons: Changes in Policy and Force Structure

DTIC Science & Technology

2008-01-23

Pinellas Plant , in Clearwater, FL; and the Pantex Plant near Amarillo, TX. These facilities were also operated by industrial contractors. Finally, the...These included the Rocky Flats Plant , outside Denver, CO; the Kansas City Plant , near Kansas City, MO; the Mound Plant , near Dayton OH; the...In 1988, DOE closed the nuclear reactors at Hanford and Savannah River, in response to safety concerns. The Rocky Flats Plant , which produced the

The effect of language experience on perceptual normalization of Mandarin tones and non-speech pitch contours.

PubMed

Luo, Xin; Ashmore, Krista B

2014-06-01

Context-dependent pitch perception helps listeners recognize tones produced by speakers with different fundamental frequencies (f0s). The role of language experience in tone normalization remains unclear. In this cross-language study of tone normalization, native Mandarin and English listeners were asked to recognize Mandarin Tone 1 (high-flat) and Tone 2 (mid-rising) with a preceding Mandarin sentence. To further test whether context-dependent pitch perception is speech-specific or domain-general, both language groups were asked to identify non-speech flat and rising pitch contours with a preceding non-speech flat pitch contour. Results showed that both Mandarin and English listeners made more rising responses with non-speech than with speech stimuli, due to differences in spectral complexity and listening task between the two stimulus types. English listeners made more rising responses than Mandarin listeners with both speech and non-speech stimuli. Contrastive context effects (more rising responses in the high-f0 context than in the low-f0 context) were found with both speech and non-speech stimuli for Mandarin listeners, but not for English listeners. English listeners' lack of tone experience may have caused more rising responses and limited use of context f0 cues. These results suggest that context-dependent pitch perception in tone normalization is domain-general, but influenced by long-term language experience.

The wavelet response as a multiscale characterization of scattering processes at granular interfaces.

PubMed

Le Gonidec, Yves; Gibert, Dominique

2006-11-01

We perform a multiscale analysis of the backscattering properties of a complex interface between water and a layer of randomly arranged glass beads with diameter D=1 mm. An acoustical experiment is done to record the wavelet response of the interface in a large frequency range from lambda/D=0.3 to lambda/D=15. The wavelet response is a physical analog of the mathematical wavelet transform which possesses nice properties to detect and characterize abrupt changes in signals. The experimental wavelet response allows to identify five frequency domains corresponding to different backscattering properties of the complex interface. This puts quantitative limits to the validity domains of the models used to represent the interface and which are flat elastic, flat visco-elastic, rough random half-space with multiple scattering, and rough elastic from long to short wavelengths respectively. A physical explanation based on Mie scattering theory is proposed to explain the origin of the five frequency domains identified in the wavelet response.

Focal plane alignment and detector characterization for the Subaru prime focus spectrograph

NASA Astrophysics Data System (ADS)

Hart, Murdock; Barkhouser, Robert H.; Carr, Michael; Golebiowski, Mirek; Gunn, James E.; Hope, Stephen C.; Smee, Stephen A.

2014-07-01

We describe the infrastructure being developed to align and characterize the detectors for the Subaru Measure- ment of Images and Redshifts (SuMIRe) Prime Focus Spectrograph (PFS). PFS will employ four three-channel spectrographs with an operating wavelength range of 3800 °A to 12600 °A. Each spectrograph will be comprised of two visible channels and one near infrared (NIR) channel, where each channel will use a separate Schmidt camera to image the captured spectra onto their respective detectors. In the visible channels, Hamamatsu 2k × 4k CCDs will be mounted in pairs to create a single 4k × 4k detector, while the NIR channel will use a single Teledyne 4k × 4k H4RG HgCdTe device. The fast f/1.1 optics of the Schmidt cameras will give a shallow depth of focus necessitating an optimization of the focal plane array flatness. The minimum departure from flatness of the focal plane array for the visible channels is set the by the CCD flatness, typically 10 μm peak-to-valley. We will adjust the coplanarity for a pair of CCDs such that the flatness of the array is consistent with the flatness of the detectors themselves. To achieve this we will use an optical non-contact measurement system to measure surface flatness and coplanarity at both ambient and operating temperatures, and use shims to adjust the coplanarity of the CCDs. We will characterize the performance of the detectors for PFS consistent with the scientific goals for the project. To this end we will measure the gain, linearity, full well, quantum efficiency (QE), charge diffusion, charge transfer inefficiency (CTI), and noise properties of these devices. We also desire to better understand the non-linearity of the photon transfer curve for the CCDs, and the charge persistence/reciprocity problems of the HgCdTe devices. To enable the metrology and characterization of these detectors we are building two test cryostats nearly identical in design. The first test cryostat will primarily be used for the coplanarity measurements and sub- pixel illumination testing, and the second will be dedicated to performance characterization requiring at field illumination. In this paper we will describe the design of the test cryostats. We will also describe the system we have built for measuring focal plane array flatness, and examine the precision and error with which it operates. Finally we will detail the methods by which we plan to characterize the performance of the detectors for PFS, and provide preliminary results.

A useful approximation for the flat surface impulse response

NASA Technical Reports Server (NTRS)

Brown, Gary S.

1989-01-01

The flat surface impulse response (FSIR) is a very useful quantity in computing the mean return power for near-nadir-oriented short-pulse radar altimeters. However, for very small antenna beamwidths and relatively large pointing angles, previous analytical descriptions become very difficult to compute accurately. An asymptotic approximation is developed to overcome these computational problems. Since accuracy is of key importance, a condition is developed under which this solution is within 2 percent of the exact answer. The asymptotic solution is shown to be in functional agreement with a conventional clutter power result and gives a 1.25-dB correction to this formula to account properly for the antenna-pattern variation over the illuminated area.

Migration of magnetotactic bacteria in porous media.

PubMed

Rismani Yazi, Saeed; Nosrati, Reza; Stevens, Corey A; Vogel, David; Escobedo, Carlos

2018-01-01

Magnetotactic bacteria (MTB) migrate in complex porous sediments where fluid flow is ubiquitous. Here, we demonstrate that magnetotaxis enables MTB to migrate effectively through porous micromodels. Directed MTB can circumvent curved obstacles by traveling along the boundaries and pass flat obstacles by repeatedly switching between forward and backward runs. Magnetotaxis enables directed motion of MTB through heterogeneous porous media, overcoming tortuous flow fields with local velocities as high as 250  μ m s -1 . Our findings bring new insights into the migration behaviour of MTB in their natural habitats and their potential in vivo applications as microbiorobots.

Gas permeation measurements on small polymer specimens

NASA Technical Reports Server (NTRS)

Burns, Karen S.; Vannorman, John D.

1988-01-01

Mass spectrometry was used to measure oxygen and nitrogen permeabilities while polarography was used to measure oxygen permeabilities for several contact lens materials. Applicable sample holders were designed and fabricated to accommodate curved and flat specimens. A prepared standard was used to calibrate the mass spectrometric analyses. The oxygen permeability values determined by mass spectrometry were significantly greater than those determined by polarography. This was attributed to the phase boundary phenomena and the limiting oxygen permeance of water inherent in the polarographic technique. Polarographic values determined were in good agreement with proprietary values obtained by polarography, with the exception of one material.

Thin film diamond temperature sensor array for harsh aerospace environment

NASA Technical Reports Server (NTRS)

Aslam, M.; Masood, A.; Fredricks, R. J.; Tamor, M. A.

1992-01-01

The feasibility of using polycrystalline CVD diamond films as temperature sensors in harsh aerospace environment associated with hypersonic flights was tested using patterned diamond resistors, fabricated on flat or curved oxidized Si surfaces, as temperature sensors at temperatures between 20 and 1000 C. In this temperature range, the measured resistance was found to vary over 3 orders of magnitude and the temperature coefficient of resistance to change from 0.017/K to 0.003/K. After an annealing treatment, the resistance change was reproducible within 1 percent on the entire temperature range for short measuring times.

Progress in Suppressing Scattered Light into the Optical Beam Path of the NAO Rozhen 2m Telescope

NASA Astrophysics Data System (ADS)

Ovcharov, E. P.; Petrov, N.; Markov, H.; Bonev, T.; Donchev, Z.

2010-09-01

In this poster paper we present a summary of the published analysis of the spatial dependence of the magnitudes derived from images obtained in the RC focal plane of the 2m RCC NAO Rozhen telescope. An alert for the possible reason was the unusually curved flat-field images taken as a part of the standard CCD calibration procedure. The reasons for the problem are described and a solution is presented, which consists modification of the mirror baffles and mounting of special diaphragm at the entrance of the filter wheel.

Lamb wave tomographic imaging system for aircraft structural health assessment

NASA Astrophysics Data System (ADS)

Schwarz, Willi G.; Read, Michael E.; Kremer, Matthew J.; Hinders, Mark K.; Smith, Barry T.

1999-01-01

A tomographic imaging system using ultrasonic Lamb waves for the nondestructive inspection of aircraft components such as wings and fuselage is being developed. The computer-based system provides large-area inspection capability by electronically scanning an array of transducers that can be easily attached to flat and curved surface without moving parts. Images of the inspected area are produced in near real time employing a tomographic reconstruction method adapted from seismological applications. Changes in material properties caused by structural flaws such as disbonds, corrosion, and fatigue cracks can be effectively detected and characterized utilizing this fast NDE technique.

Linking Parameters Estimated with the Generalized Graded Unfolding Model: A Comparison of the Accuracy of Characteristic Curve Methods

ERIC Educational Resources Information Center

Anderson Koenig, Judith; Roberts, James S.

2007-01-01

Methods for linking item response theory (IRT) parameters are developed for attitude questionnaire responses calibrated with the generalized graded unfolding model (GGUM). One class of IRT linking methods derives the linking coefficients by comparing characteristic curves, and three of these methods---test characteristic curve (TCC), item…

Substrate Topography Induces a Crossover from 2D to 3D Behavior in Fibroblast Migration

PubMed Central

Ghibaudo, Marion; Trichet, Léa; Le Digabel, Jimmy; Richert, Alain; Hersen, Pascal; Ladoux, Benoît

2009-01-01

Abstract In a three-dimensional environment, cells migrate through complex topographical features. Using microstructured substrates, we investigate the role of substrate topography in cell adhesion and migration. To do so, fibroblasts are plated on chemically identical substrates composed of microfabricated pillars. When the dimensions of the pillars (i.e., the diameter, length, and spacing) are varied, migrating cells encounter alternating flat and rough surfaces that depend on the spacing between the pillars. Consequently, we show that substrate topography affects cell shape and migration by modifying cell-to-substrate interactions. Cells on micropillar substrates exhibit more elongated and branched shapes with fewer actin stress fibers compared with cells on flat surfaces. By analyzing the migration paths in various environments, we observe different mechanisms of cell migration, including a persistent type of migration, that depend on the organization of the topographical features. These responses can be attributed to a spatial reorganization of the actin cytoskeleton due to physical constraints and a preferential formation of focal adhesions on the micropillars, with an increased lifetime compared to that observed on flat surfaces. By changing myosin II activity, we show that actomyosin contractility is essential in the cellular response to micron-scale topographic signals. Finally, the analysis of cell movements at the frontier between flat and micropillar substrates shows that cell transmigration through the micropillar substrates depends on the spacing between the pillars. PMID:19580774

Complex, non-monotonic dose-response curves with multiple maxima: Do we (ever) sample densely enough?

PubMed

Cvrčková, Fatima; Luštinec, Jiří; Žárský, Viktor

2015-01-01

We usually expect the dose-response curves of biological responses to quantifiable stimuli to be simple, either monotonic or exhibiting a single maximum or minimum. Deviations are often viewed as experimental noise. However, detailed measurements in plant primary tissue cultures (stem pith explants of kale and tobacco) exposed to varying doses of sucrose, cytokinins (BA or kinetin) or auxins (IAA or NAA) revealed that growth and several biochemical parameters exhibit multiple reproducible, statistically significant maxima over a wide range of exogenous substance concentrations. This results in complex, non-monotonic dose-response curves, reminiscent of previous reports of analogous observations in both metazoan and plant systems responding to diverse pharmacological treatments. These findings suggest the existence of a hitherto neglected class of biological phenomena resulting in dose-response curves exhibiting periodic patterns of maxima and minima, whose causes remain so far uncharacterized, partly due to insufficient sampling frequency used in many studies.

Neural Responses to Electrical Stimulation on Patterned Silk Films

PubMed Central

Hronik-Tupaj, Marie; Raja, Waseem Khan; Tang-Schomer, Min; Omenetto, Fiorenzo G.; Kaplan, David L.

2013-01-01

Peripheral nerve injury is a critical issue for trauma patients. Following injury, incomplete axon regeneration or misguided axon innervation into tissue will result in loss of sensory and motor functions. The objective of this study was to examine axon outgrowth and axon alignment in response to surface patterning and electrical stimulation. To accomplish our objective, metal electrodes with dimensions of 1.5 mm × 4 cm, were sputter coated onto micropatterned silk protein films, with surface grooves 3.5 μm wide × 500 nm deep. P19 neurons were seeded on the patterned electronic silk films and stimulated at 120 mV, 1 kHz, for 45 minutes each day for 7 days. Responses were compared to neurons on flat electronic silk films, patterned silk films without stimulation, and flat silk films without stimulation. Significant alignment was found on the patterned film groups compared to the flat film groups. Axon outgrowth was greater (p < 0.05) on electronic films on day 5 and day 7 compared to the unstimulated groups. In conclusion, electrical stimulation, at 120 mV, 1 kHz, for 45 minutes daily, in addition to surface patterning, of 3.5 μm wide × 500 nm deep grooves, offered control of nerve axon outgrowth and alignment. PMID:23401351

Low cost fabrication of ablative heat shields

NASA Technical Reports Server (NTRS)

Cecka, A. M.; Schofield, W. C.

1972-01-01

A material and process study was performed using subscale panels in an attempt to reduce the cost of fabricating ablative heat shield panels. Although no improvements were made in the material formulation, a significant improvement was obtained in the processing methods compared to those employed in the previous work. The principal feature of the new method is the press filling and curing of the ablation material in a single step with the bonding and curing of the face sheet. This method was chosen to replace the hand troweling and autoclave curing procedure used previously. Double-curvature panels of the same size as the flat panels were fabricated to investigate fabrication problems. It was determined that the same materials and processes used for flat panels can be used to produce the curved panels. A design with severe curvatures consisting of radii of 24 x 48 inches was employed for evaluation. Ten low-density and ten high-density panels were fabricated. With the exception of difficulties related to short run non-optimum tooling, excellent panel filling and density uniformity were obtained.

Growth patterns for shape-shifting elastic bilayers.

PubMed

van Rees, Wim M; Vouga, Etienne; Mahadevan, L

2017-10-31

Inspired by the differential-growth-driven morphogenesis of leaves, flowers, and other tissues, there is increasing interest in artificial analogs of these shape-shifting thin sheets made of active materials that respond to environmental stimuli such as heat, light, and humidity. But how can we determine the growth patterns to achieve a given shape from another shape? We solve this geometric inverse problem of determining the growth factors and directions (the metric tensors) for a given isotropic elastic bilayer to grow into a target shape by posing and solving an elastic energy minimization problem. A mathematical equivalence between bilayers and curved monolayers simplifies the inverse problem considerably by providing algebraic expressions for the growth metric tensors in terms of those of the final shape. This approach also allows us to prove that we can grow any target surface from any reference surface using orthotropically growing bilayers. We demonstrate this by numerically simulating the growth of a flat sheet into a face, a cylindrical sheet into a flower, and a flat sheet into a complex canyon-like structure.

Soft pneumatic grippers embedded with stretchable electroadhesion

NASA Astrophysics Data System (ADS)

Guo, J.; Elgeneidy, K.; Xiang, C.; Lohse, N.; Justham, L.; Rossiter, J.

2018-05-01

Current soft pneumatic grippers cannot robustly grasp flat materials and flexible objects on curved surfaces without distorting them. Current electroadhesive grippers, on the other hand, are difficult to actively deform to complex shapes to pick up free-form surfaces or objects. An easy-to-implement PneuEA gripper is proposed by the integration of an electroadhesive gripper and a two-fingered soft pneumatic gripper. The electroadhesive gripper was fabricated by segmenting a soft conductive silicon sheet into a two-part electrode design and embedding it in a soft dielectric elastomer. The two-fingered soft pneumatic gripper was manufactured using a standard soft lithography approach. This novel integration has combined the benefits of both the electroadhesive and soft pneumatic grippers. As a result, the proposed PneuEA gripper was not only able to pick-and-place flat and flexible materials such as a porous cloth but also delicate objects such as a light bulb. By combining two soft touch sensors with the electroadhesive, an intelligent and shape-adaptive PneuEA material handling system has been developed. This work is expected to widen the applications of both soft gripper and electroadhesion technologies.