WorldWideScience

Sample records for length aspect ratio

  1. Nano-scaled graphene platelets with a high length-to-width aspect ratio

    Science.gov (United States)

    Zhamu, Aruna; Guo, Jiusheng; Jang, Bor Z.

    2010-09-07

    This invention provides a nano-scaled graphene platelet (NGP) having a thickness no greater than 100 nm and a length-to-width ratio no less than 3 (preferably greater than 10). The NGP with a high length-to-width ratio can be prepared by using a method comprising (a) intercalating a carbon fiber or graphite fiber with an intercalate to form an intercalated fiber; (b) exfoliating the intercalated fiber to obtain an exfoliated fiber comprising graphene sheets or flakes; and (c) separating the graphene sheets or flakes to obtain nano-scaled graphene platelets. The invention also provides a nanocomposite material comprising an NGP with a high length-to-width ratio. Such a nanocomposite can become electrically conductive with a small weight fraction of NGPs. Conductive composites are particularly useful for shielding of sensitive electronic equipment against electromagnetic interference (EMI) or radio frequency interference (RFI), and for electrostatic charge dissipation.

  2. Effect of process parameters on flow length and flash formation in injection moulding of high aspect ratio polymeric micro features

    DEFF Research Database (Denmark)

    Eladl, Abdelkhalik; Mostafa, Rania; Islam, Aminul

    2018-01-01

    part with four micro fingers with different aspect ratios (from 21 up to 150) and was carried out according to the Design of Experiments (DOE) statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect......This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (µIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature...... for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 µm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential...

  3. Length-dependent charge generation from vertical arrays of high-aspect-ratio ZnO nanowires.

    Science.gov (United States)

    Rivera, Vivian Farías; Auras, Florian; Motto, Paolo; Stassi, Stefano; Canavese, Giancarlo; Celasco, Edvige; Bein, Thomas; Onida, Barbara; Cauda, Valentina

    2013-10-18

    Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Effect of Process Parameters on Flow Length and Flash Formation in Injection Moulding of High Aspect Ratio Polymeric Micro Features

    Directory of Open Access Journals (Sweden)

    Abdelkhalik Eladl

    2018-01-01

    Full Text Available This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature were investigated using Polypropylene (PP and Acrylonitrile Butadiene Styrene (ABS. Three key characteristics of the mouldings were evaluated with respect to process settings and the material employed: part mass, flow length and flash formation. The experimentation employs a test part with four micro fingers with different aspect ratios (from 21 up to 150 and was carried out according to the Design of Experiments (DOE statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 μm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential parameters for increasing the amount of flash formation, with relative effects consistent for both materials. Higher melt and mould temperatures settings were less influential parameters for increasing the flash amount when moulding with both materials. Of the two investigated materials, PP was the one exhibiting more flash formation as compared with ABS, when corresponding injection moulding parameters settings for both materials were considered.

  5. Large Aspect Ratio Tokamak Study

    International Nuclear Information System (INIS)

    Reid, R.L.; Holmes, J.A.; Houlberg, W.A.; Peng, Y.K.M.; Strickler, D.J.; Brown, T.G.; Wiseman, G.W.

    1980-06-01

    The Large Aspect Ratio Tokamak Study (LARTS) at Oak Ridge National Laboratory (ORNL) investigated the potential for producing a viable longburn tokamak reactor by enhancing the volt-second capability of the ohmic heating transformer through the use of high aspect ratio designs. The plasma physics, engineering, and economic implications of high aspect ratio tokamaks were assessed in the context of extended burn operation. Using a one-dimensional transport code plasma startup and burn parameters were addressed. The pulsed electrical power requirements for the poloidal field system, which have a major impact on reactor economics, were minimized by optimizing the startup and shutdown portions of the tokamak cycle. A representative large aspect ratio tokamak with an aspect ratio of 8 was found to achieve a burn time of 3.5 h at capital cost only approx. 25% greater than that of a moderate aspect ratio design tokamak

  6. Noise of Embedded High Aspect Ratio Nozzles

    Science.gov (United States)

    Bridges, James E.

    2011-01-01

    A family of high aspect ratio nozzles were designed to provide a parametric database of canonical embedded propulsion concepts. Nozzle throat geometries with aspect ratios of 2:1, 4:1, and 8:1 were chosen, all with convergent nozzle areas. The transition from the typical round duct to the rectangular nozzle was designed very carefully to produce a flow at the nozzle exit that was uniform and free from swirl. Once the basic rectangular nozzles were designed, external features common to embedded propulsion systems were added: extended lower lip (a.k.a. bevel, aft deck), differing sidewalls, and chevrons. For the latter detailed Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations were made to predict the thrust performance and to optimize parameters such as bevel length, and chevron penetration and azimuthal curvature. Seventeen of these nozzles were fabricated at a scale providing a 2.13 inch diameter equivalent area throat." ! The seventeen nozzles were tested for far-field noise and a few data were presented here on the effect of aspect ratio, bevel length, and chevron count and penetration. The sound field of the 2:1 aspect ratio rectangular jet was very nearly axisymmetric, but the 4:1 and 8:1 were not, the noise on their minor axes being louder than the major axes. Adding bevel length increased the noise of these nozzles, especially on their minor axes, both toward the long and short sides of the beveled nozzle. Chevrons were only added to the 2:1 rectangular jet. Adding 4 chevrons per wide side produced some decrease at aft angles, but increased the high frequency noise at right angles to the jet flow. This trend increased with increasing chevron penetration. Doubling the number of chevrons while maintaining their penetration decreased these effects. Empirical models of the parametric effect of these nozzles were constructed and quantify the trends stated above." Because it is the objective of the Supersonics Project that

  7. Effect of Cell Aspect Ratio on Swarming Bacteria

    Science.gov (United States)

    Ilkanaiv, Bella; Kearns, Daniel B.; Ariel, Gil; Be'er, Avraham

    2017-04-01

    Swarming bacteria collectively migrate on surfaces using flagella, forming dynamic whirls and jets that consist of millions of individuals. Because some swarming bacteria elongate prior to actual motion, cell aspect ratio may play a significant role in the collective dynamics. Extensive research on self-propelled rodlike particles confirms that elongation promotes alignment, strongly affecting the dynamics. Here, we study experimentally the collective dynamics of variants of swarming Bacillus subtilis that differ in length. We show that the swarming statistics depends on the aspect ratio in a critical, fundamental fashion not predicted by theory. The fastest motion was obtained for the wild-type and variants that are similar in length. However, shorter and longer cells exhibit anomalous, non-Gaussian statistics and nonexponential decay of the autocorrelation function, indicating lower collective motility. These results suggest that the robust mechanisms to maintain aspect ratios may be important for efficient swarming motility. Wild-type cells are optimal in this sense.

  8. Transport in a small aspect ratio torus

    International Nuclear Information System (INIS)

    White, R.B.; Gates, D.A.; Mynick, H.E.

    2005-01-01

    Transport theory in toroidal devices often assumes large aspect ratio and also assumes the poloidal field is small compared to the toroidal field. These assumptions result in transport which in the low collision rate limit is dominated by banana orbits, giving the largest collisionless excursion of a particle from an initial flux surface. However in a small aspect ratio device the gyro radius may be larger than the banana excursion, resulting in significant deviations from the standard neoclassical predictions. In this paper we report numerical simulation of diffusion in low and high beta low aspect ratio equilibria. We also sketch an analytic theory. The diffusion, which we refer to as omniclassical, is a combination of neoclassical and properly averaged classical effects, and can be two or three times the neoclassical value. Good agreement of the analytic theory with numerical simulations is obtained. (author)

  9. Omniclassical Diffusion in Low Aspect Ratio Tokamaks

    International Nuclear Information System (INIS)

    Mynick, H.E.; White, R.B.; Gates, D.A.

    2004-01-01

    Recently reported numerical results for axisymmetric devices with low aspect ratio A found radial transport enhanced over the expected neoclassical value by a factor of 2 to 3. In this paper, we provide an explanation for this enhancement. Transport theory in toroidal devices usually assumes large A, and that the ratio B p /B t of the poloidal to the toroidal magnetic field is small. These assumptions result in transport which, in the low collision limit, is dominated by banana orbits, giving the largest collisionless excursion of a particle from an initial flux surface. However in a small aspect ratio device one may have B p /B t ∼ 1, and the gyroradius may be larger than the banana excursion. Here, we develop an approximate analytic transport theory valid for devices with arbitrary A. For low A, we find that the enhanced transport, referred to as omniclassical, is a combination of neoclassical and properly generalized classical effects, which become dominant in the low-A, B p /B t ∼ 1 regime. Good agreement of the analytic theory with numerical simulations is obtained

  10. Length Frequency Distribution And Sex Ratio Of Macrobrachium ...

    African Journals Online (AJOL)

    Length frequency distribution and sex ratio of Macrobrachium macrobrachion sampled by cane traps in the Lagos –Lekki lagoon system were estimated from May 2002 to April 2004. The total number of size classes for the first and second year for both male and female ranged from 10 – 12. The length range was 3 to 14cm ...

  11. Masks for high aspect ratio x-ray lithography

    International Nuclear Information System (INIS)

    Malek, C.K.; Jackson, K.H.; Bonivert, W.D.; Hruby, J.

    1997-01-01

    Fabrication of very high aspect ratio microstructures, as well as ultra-high precision manufacturing is of increasing interest in a multitude of applications. Fields as diverse as micromechanics, robotics, integrated optics, and sensors benefit from this technology. The scale-length of this spatial regime is between what can be achieved using classical machine tool operations and that which is used in microelectronics. This requires new manufacturing techniques, such as the LIGA process, which combines x-ray lithography, electroforming, and plastic molding

  12. On the ratios of Arc lengths to chord lengths in real Banach spaces ...

    African Journals Online (AJOL)

    Two new moduli are introduced to study the ratios of arc lengths to chord lengths in Banach spaces. Basic properties of those two moduli and the relation between them are studied. The relation between those two moduli and some geometric properties, including uniform convexity, uniform nonsquareness, and uniform ...

  13. Reusable High Aspect Ratio 3-D Nickel Shadow Mask

    Science.gov (United States)

    Shandhi, M.M.H.; Leber, M.; Hogan, A.; Warren, D.J.; Bhandari, R.; Negi, S.

    2017-01-01

    Shadow Mask technology has been used over the years for resistless patterning and to pattern on unconventional surfaces, fragile substrate and biomaterial. In this work, we are presenting a novel method to fabricate high aspect ratio (15:1) three-dimensional (3D) Nickel (Ni) shadow mask with vertical pattern length and width of 1.2 mm and 40 μm respectively. The Ni shadow mask is 1.5 mm tall and 100 μm wide at the base. The aspect ratio of the shadow mask is 15. Ni shadow mask is mechanically robust and hence easy to handle. It is also reusable and used to pattern the sidewalls of unconventional and complex 3D geometries such as microneedles or neural electrodes (such as the Utah array). The standard Utah array has 100 active sites at the tip of the shaft. Using the proposed high aspect ratio Ni shadow mask, the Utah array can accommodate 300 active sites, 200 of which will be along and around the shaft. The robust Ni shadow mask is fabricated using laser patterning and electroplating techniques. The use of Ni 3D shadow mask will lower the fabrication cost, complexity and time for patterning out-of-plane structures. PMID:29056835

  14. Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

    African Journals Online (AJOL)

    2018-02-07

    Feb 7, 2018 ... Aim/Background: Associations between axial length (AL) to corneal radius of curvature (CR) ratio and refractive status in a healthy Nigerian adult population were studied. Materials and Methods: Healthy students and members of staff of Obafemi Awolowo Teaching Hospitals Complex, Ile-Ife, South West ...

  15. Length-weight relationship, breeding season, sex ratio, maturity and ...

    African Journals Online (AJOL)

    Length-weight relationship, breeding season, sex ratio, maturity and fecundity of the Nile catfish Synodontis schall (Bloch and Schneider, 1801) (Pisces: Mochokidae) in Lake Chamo, Ethiopia. ... The average number of eggs g-1 of ovary (preserved wet weight) ranged from 983 to 3,797 with a mean of 1,847 eggs g-1.

  16. Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

    African Journals Online (AJOL)

    Aim/Background: Associations between axial length (AL) to corneal radius of curvature (CR) ratio and refractive status in a healthy Nigerian adult population were studied. Materials and Methods: Healthy students and members of staff of Obafemi Awolowo Teaching Hospitals Complex, Ile‑Ife, South West Nigeria, free of ...

  17. Fabrication of high aspect ratio micro electrode by using EDM

    International Nuclear Information System (INIS)

    Elsiti, Nagwa Mejid; Noordin, M.Y.; Alkali, Adam Umar

    2016-01-01

    The electrical discharge machining (EDM) process inherits characteristics that make it a promising micro-machining technique. Micro electrical discharge machining (micro- EDM) is a derived form of EDM, which is commonly used to manufacture micro and miniature parts and components by using the conventional electrical discharge machining fundamentals. Moving block electro discharge grinding (Moving BEDG) is one of the processes that can be used to fabricate micro-electrode. In this study, a conventional die sinker EDM machine was used to fabricate the micro-electrode. Modifications are made to the moving BEDG, which include changing the direction of movements and control gap in one electrode. Consequently current was controlled due to the use of roughing, semi-finishing and finishing parameters. Finally, a high aspect ratio micro-electrode with a diameter of 110.49μm and length of 6000μm was fabricated. (paper)

  18. Aspect Ratio Effects in the Driven, Flux-Core Spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E B; Romero-Talam?s, C A; LoDestro, L L; Wood, R D; McLean, H S

    2009-03-02

    Resistive magneto-hydrodynamic simulations are used to evaluate the effects of the aspect ratio, A (length to radius ratio) in a spheromak driven by coaxial helicity injection. The simulations are benchmarked against the Sustained Spheromak Physics Experiment (SSPX) [R. D. Wood, et al., Nucl. Nucl. Fusion 45, 1582 (2005)]. Amplification of the bias ('gun') poloidal flux is fit well by a linear dependence (insensitive to A) on the ratio of gun current and bias flux above a threshold dependent on A. For low flux amplifications in the simulations the n = 1 mode is coherent and the mean-field geometry looks like a tilted spheromak. Because the mode has relatively large amplitude the field lines are open everywhere, allowing helicity penetration. Strongly-driven helicity injection at A {le} 1.4 in simulations generates reconnection events which open the magnetic field lines; this state is characteristic of SSPX. Near the spheromak tilt-mode limit, A {approx} 1.67 for a cylindrical flux conserver, the tilt approaches 90{sup o}; reconnection events are not generated up to the strongest drives simulated. The time-sequence of these events suggests that they are representative of a chaotic process. Implications for spheromak experiments are discussed.

  19. Seed-Mediated Growth of Gold Nanorods: Limits of Length to Diameter Ratio Control

    Directory of Open Access Journals (Sweden)

    Christopher J. Ward

    2014-01-01

    Full Text Available The effects of the seed reaction conditions on the two-step seed-mediated growth of gold nanorods and the effect of gold and reducing agent content in the growth solution were evaluated. Results indicate that the reaction conditions used to produce the seeds have a significant impact on the aspect ratio of the gold nanorods produced. Increasing the concentration of gold or the reaction temperature in the seed production step results in lower length to diameter (aspect ratio gold rods. In addition, the amount of prepared seed added to the growth solution impacts the rod aspect ratio, with increasing amounts of seed reducing the aspect ratio. The effects of reducing agent, ascorbic acid (AA, and gold content of the growth solution on the aspect ratio of the produced rods are strongly interrelated. There exists a minimum ascorbic acid to gold concentration below which rods will not form; however, increasing the ratio above this minimum results in shorter rods being formed. Characterization of nanorod growth is performed by UV-vis-NIR spectrophotometry and transmission electron microscopy (TEM.

  20. Power reduction and the radial limit of stall delay in revolving wings of different aspect ratio.

    Science.gov (United States)

    Kruyt, Jan W; van Heijst, GertJan F; Altshuler, Douglas L; Lentink, David

    2015-04-06

    Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle of attack without stalling. Instead, they generate an attached vortex along the leading edge of the wing that elevates lift. Previous studies have demonstrated that this vortex and high lift can be reproduced by revolving the animal wing at the same angle of attack. How do flapping and revolving animal wings delay stall and reduce power? It has been hypothesized that stall delay derives from having a short radial distance between the shoulder joint and wing tip, measured in chord lengths. This non-dimensional measure of wing length represents the relative magnitude of inertial forces versus rotational accelerations operating in the boundary layer of revolving and flapping wings. Here we show for a suite of aspect ratios, which represent both animal and aircraft wings, that the attachment of the leading edge vortex on a revolving wing is determined by wing aspect ratio, defined with respect to the centre of revolution. At high angle of attack, the vortex remains attached when the local radius is shorter than four chord lengths and separates outboard on higher aspect ratio wings. This radial stall limit explains why revolving high aspect ratio wings (of helicopters) require less power compared with low aspect ratio wings (of hummingbirds) at low angle of attack and vice versa at high angle of attack. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  1. Towards a Reproducible Synthesis of High Aspect Ratio Gold Nanorods

    Directory of Open Access Journals (Sweden)

    Susanne Koeppl

    2011-01-01

    Full Text Available The seed-mediated method in presence of high concentrations of CTAB is frequently implemented in the preparation of high aspect ratio gold nanorods (i.e., nanorods with aspect ratios of 5 or more; however, the reproducibility has still been limited. We rendered the synthesis procedure simpler, decreased the susceptibility to impurities, and improved the reproducibility of the product distribution. As a result of the high aspect ratios, longitudinal plasmon absorptions were shifted up to very high absorption maxima of 1955 nm in UV-vis-NIR spectra (since this band is completely covered in aqueous solution by the strong absorption of water, the gold species were embedded in poly(vinyl alcohol films for UV-vis-NIR measurements. Finally, the directed particle growth in (110 direction leads to the conclusion that the adsorption of CTAB molecules at specific crystal faces accounts for nanorod growth and not cylindrical CTAB micelles, in agreement with other observations.

  2. Design Concepts for Low Aspect Ratio High Pressure Turbines for High Bypass Ratio Turbofans, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposal is to identify cycle improvements and verify structural feasibility of shrouding a low aspect ratio High Pressure Turbine(HPT) rotor designed to use...

  3. Effects of flexibility and aspect ratio on the aerodynamic performance of flapping wings.

    Science.gov (United States)

    Fu, Junjiang; Liu, Xiaohui; Shyy, Wei; Qiu, Huihe

    2018-01-26

    In the current study, we experimentally investigated the flexibility effects on the aerodynamic performance of flapping wings and the correlation with aspect ratio at angle of attack α = 45o. The Reynolds number based on the chord length and the wing tip velocity is maintained at Re = 5.3x103. Our result for compliant wings with an aspect ratio of 4 shows that wing flexibility can offer improved aerodynamic performance compared to that of a rigid wing. Flexible wings are found to offer higher lift-to-drag ratios; in particular, there is significant reduction in drag with little compromise in lift. The mechanism of the flexibility effects on the aerodynamic performance is addressed by quantifying the aerodynamic lift and drag forces, the transverse displacement on the wings and the flow field around the wings. The regime of the effective stiffness that offers improved aerodynamic performance is quantified in a range of about 0.5~10 and it matches the stiffness of insect wings with similar aspect ratios. Furthermore, we find that the aspect ratio of the wing is the predominant parameter determining the flexibility effects of compliant wings. Compliant wings with an aspect ratio of two do not demonstrate improved performance compared to their rigid counterparts throughout the entire stiffness regime investigated. The correlation between wing flexibility effects and the aspect ratio is supported by the stiffness of real insect wings. © 2018 IOP Publishing Ltd.

  4. High aspect ratio titanium nitride trench structures as plasmonic biosensor

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Repän, Taavi; Takayama, Osamu

    2017-01-01

    High aspect ratio titanium nitride (TiN) grating structures are fabricated by the combination of deep reactive ion etching (DRIE) and atomic layer deposition (ALD) techniques. TiN is deposited at 500 ◦C on a silicon trench template. Silicon between vertical TiN layers is selectively etched...

  5. Scattering and extinction from high-aspect-ratio trenches

    DEFF Research Database (Denmark)

    Roberts, Alexander Sylvester; Søndergaard, Thomas; Chirumamilla, Manohar

    2015-01-01

    We construct a semi-analytical model describing the scattering, extinction and absorption properties of a high aspect-ratio trench in a metallic film. We find that these trenches act as highly efficient scatterers of free waves. In the perfect conductor limit, which for many metals is approached...

  6. Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

    African Journals Online (AJOL)

    2017-12-05

    Dec 5, 2017 ... variously described as determined by the ocular biometric variables. There have been many studies on the relationship between refractive error and ocular axial length (AL), anterior chamber depth, corneal radius of curvature (CR), keratometric readings as well as other ocular biometric variables such as ...

  7. Calculation of the Crack Length for a Pipe Specimen using the Modified Load Ratio Method

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jung Hun; Koo, Jae Mean; Seok, Chang Sung [Sungkyunkwan University, Suwon (Korea, Republic of); Huh, Yong; Park, Jae Sil [Samsung Electronics Co., Suwon (Korea, Republic of)

    2009-12-15

    The objective of this paper is to apply the load ratio method to the measurement of the crack length of the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the relationship between the normalized compliance and the normalized crack length for the pipe specimen. In order to measure the crack length, the direct current potential drop method and the modified load ratio method were applied to the pipe test. The applicability of the modified load ratio method was confirmed by comparing the calculated crack length with the measured crack length from the pipe experiment.

  8. Calculation of the Crack Length for a Pipe Specimen using the Modified Load Ratio Method

    International Nuclear Information System (INIS)

    Choi, Jung Hun; Koo, Jae Mean; Seok, Chang Sung; Huh, Yong; Park, Jae Sil

    2009-01-01

    The objective of this paper is to apply the load ratio method to the measurement of the crack length of the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the relationship between the normalized compliance and the normalized crack length for the pipe specimen. In order to measure the crack length, the direct current potential drop method and the modified load ratio method were applied to the pipe test. The applicability of the modified load ratio method was confirmed by comparing the calculated crack length with the measured crack length from the pipe experiment

  9. High aspect ratio channels in glass and porous silicon

    International Nuclear Information System (INIS)

    Liang, H.D.; Dang, Z.Y.; Wu, J.F.; Kan, J.A. van; Qureshi, S.; Ynsa, M.D.; Torres-Costa, V.; Maira, A.; Venkatesan, T.V.; Breese, M.B.H.

    2017-01-01

    We have developed a micromachining process to produce high-aspect-ratio channels and holes in glass and porous silicon. Our process utilizes MeV proton beam irradiation of silicon using direct writing with a focused beam, followed by electrochemical etching. To increase throughput we have also developed another process for large area ion irradiation based on a radiation-resistant gold surface mask, allowing many square inches to be patterned. We present a study of the achievable channel width, depth and period and sidewall verticality for a range of channels which can be over 100 μm deep or 100 nm wide with aspect ratios up to 80. This process overcomes the difficulty of machining glass on a micro- and nanometer scale which has limited many areas of applications in different fields such as microelectronics and microfluidics.

  10. High aspect ratio channels in glass and porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Liang, H.D. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Nanoscience and Nanotechnology Initiative (NNI), National University of Singapore, Singapore 117411 (Singapore); Dang, Z.Y. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Wu, J.F. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Kan, J.A. van; Qureshi, S. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Ynsa, M.D.; Torres-Costa, V. [Department of Applied Physics, Universidad Autónoma de Madrid, Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Centro de Micro-Análisis de Materiales (CMAM), Universidad Autónoma de Madrid, Campus de Cantoblanco Edif. 22, Faraday 3, E-28049 Madrid (Spain); Maira, A. [Department of Applied Physics, Universidad Autónoma de Madrid, Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Venkatesan, T.V. [Nanoscience and Nanotechnology Initiative (NNI), National University of Singapore, Singapore 117411 (Singapore); Breese, M.B.H., E-mail: phymbhb@nus.edu.sg [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2017-03-01

    We have developed a micromachining process to produce high-aspect-ratio channels and holes in glass and porous silicon. Our process utilizes MeV proton beam irradiation of silicon using direct writing with a focused beam, followed by electrochemical etching. To increase throughput we have also developed another process for large area ion irradiation based on a radiation-resistant gold surface mask, allowing many square inches to be patterned. We present a study of the achievable channel width, depth and period and sidewall verticality for a range of channels which can be over 100 μm deep or 100 nm wide with aspect ratios up to 80. This process overcomes the difficulty of machining glass on a micro- and nanometer scale which has limited many areas of applications in different fields such as microelectronics and microfluidics.

  11. Low Aspect-Ratio Wings for Wing-Ships

    DEFF Research Database (Denmark)

    Filippone, Antonino; Selig, M.

    1998-01-01

    Flying on ground poses technical and aerodynamical challenges. The requirements for compactness, efficiency, manouverability, off-design operation,open new areas of investigations in the fieldof aerodynamic analysis and design. A review ofthe characteristics of low-aspect ratio wings, in- and out...... of ground, is presented. It is shownthat the performance of such wings is generally inferior to that of slender wings, although in ground placement can yield substantial improvements in the aerodynamic efficiency....

  12. Oscillatory convection in low aspect ratio Czochralski melts

    Science.gov (United States)

    Anselmo, A.; Prasad, V.; Koziol, J.; Gupta, K. P.

    1993-11-01

    Modeling of the crucible in bulk crystal growth simulations as a right circular cylinder may be adequate for high aspect ratio melts but this may be unrealistic when the melt height is low. Low melt height is a unique feature of a solid feed continuous Czochralski growth process for silicon single crystals currently under investigation. At low melt heights, the crucible bottom curvature has a dampening effect on the buoyancy-induced oscillations, a source of inhomogeneities in the grown crystal. The numerical results demonstrate how the mode of convection changes from vertical wall-dominated recirculating flows to Benard convection as the aspect ratio is lowered. This phenomenon is strongly dependent on the boundary condition at the free surface of the melt, which has been generally considered to be either adiabatic or radiatively cooled. A comparison of the flow oscillations in crucibles with and without curved bottoms at aspect ratios in the range of 0.25 to 0.50, and at realistic Grashof numbers (10 7 < Gr < 10 8) illustrate that changing the shape of the crucible may be an effective means of suppressing oscillations and controlling the melt flow.

  13. Water entry of cylindrical bodies with various aspect ratios

    Science.gov (United States)

    Kim, Nayoung; Park, Hyungmin

    2017-11-01

    We experimentally investigate the water entry of cylindrical bodies with different aspect ratio (1.0-8.0), focusing on the deformation of free surface and resulting phenomena over and under the surface. The experiment is performed using a high-speed imaging (upto 10000 fps) and PIV. The head and tail of bodies are hemispherical and the nose part is additionally roughened with a sandpaper to see the effect of roughness as well. The release height is also adjusted to change the impact velocity at the free surface (Reynolds number is order of 105). For smooth surface (without cavity formation), a thin liquid film rises up the body after impacting, gathers at the pole and forms a jet over the free surfaces. The jet is created in the form of a thick and thin jet. The thin jet is produced by a water film riding up the surface of an object, and a thick jet is produced by rising water from underwater as the object sinks. However, as the aspect ratio increases, the liquid film does not fully ride up the body and cannot close, so there is an empty space below the free surface. With roughness (with cavity), the liquid film is detached from the body and splash/dome is formed above the free surface. The splash height and its collapsing time decrease with increasing the aspect ratio. Supported by Grants (MPSS-CG-2016-02, NRF-2017R1A4A1015523) of the Korea government.

  14. Calcaneotalar ratio: a new concept in the estimation of the length of the calcaneus.

    Science.gov (United States)

    David, Vikram; Stephens, Terry J; Kindl, Radek; Ang, Andy; Tay, Wei-Han; Asaid, Rafik; McCullough, Keith

    2015-01-01

    Maintaining the calcaneal length after calcaneal fractures is vital to restoring the normal biomechanics of the foot, because it acts as an important lever arm to the plantarflexors of the foot. However, estimation of the length of the calcaneus to be reconstructed in comminuted calcaneal fractures can be difficult. We propose a new method to reliably estimate the calcaneal length radiographically by defining the calcaneotalar length ratio. A total of 100 ankle radiographs with no fracture in the calcaneus or talus taken in skeletally mature patients were reviewed by 6 observers. The anteroposterior lengths of the calcaneus and talus were measured, and the calcaneotalar length ratio was determined. The ratio was then used to estimate the length of the calcaneus. Interobserver reliability was determined using Cronbach's α coefficient and Pearson's correlation coefficient. The mean length of the calcaneus was 75 ± 0.6 mm, and the mean length of the talus was 59 ± 0.5 mm. The calcaneotalar ratio was 1.3. Using this ratio and multiplying it by the talar length, the mean average estimated length of the calcaneus was within 0.7 mm of the known calcaneal length. Cronbach's α coefficient and Pearson's correlation coefficient showed excellent interobserver reliability. The proposed calcaneotalar ratio is a new and reliable method to radiographically estimate the normal length of the calcaneus when reconstructing the calcaneus. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  15. Hydrodynamic thrust generation and power consumption investigations for piezoelectric fins with different aspect ratios

    Science.gov (United States)

    Shahab, S.; Tan, D.; Erturk, A.

    2015-12-01

    Bio-inspired hydrodynamic thrust generation using piezoelectric transduction has recently been explored using Macro-Fiber Composite (MFC) actuators. The MFC technology strikes a balance between the actuation force and structural deformation levels for effective swimming performance, and additionally offers geometric scalability, silent operation, and ease of fabrication. Recently we have shown that mean thrust levels comparable to biological fish of similar size can be achieved using MFC fins. The present work investigates the effect of length-to-width (L/b) aspect ratio on the hydrodynamic thrust generation performance of MFC cantilever fins by accounting for the power consumption level. It is known that the hydrodynamic inertia and drag coefficients are controlled by the aspect ratio especially for L/b< 5. The three MFC bimorph fins explored in this work have the aspect ratios of 2.1, 3.9, and 5.4. A nonlinear electrohydroelastic model is employed to extract the inertia and drag coefficients from the vibration response to harmonic actuation for the first bending mode. Experiments are then conducted for various actuation voltage levels to quantify the mean thrust resultant and power consumption levels for different aspect ratios. Variation of the thrust coefficient of the MFC bimorph fins with changing aspect ratio is also semi-empirically modeled and presented.

  16. THE LARGE ASPECT RATIO LIMIT OF NEOCLASSICAL TRANSPORT THEORY

    Energy Technology Data Exchange (ETDEWEB)

    WONG,SK; CHAN,VS

    2002-11-01

    OAK B202 THE LARGE ASPECT RATIO LIMIT OF NEOCLASSICAL TRANSPORT THEORY. This article presents a comprehensive description of neoclassical transport theory in the banana regime for large aspect ratio flux surfaces of arbitrary shapes. The method of matched asymptotic expansions is used to obtain analytical solutions for plasma distribution functions and to compute transport coefficients. The method provides justification for retaining only the part of the Fokker-Planck operator that involves the second derivative with respect to the cosine of the pitch angle for the trapped and barely circulating particles. It leads to a simple equation for the freely circulating particles with boundary conditions that embody a discontinuity separating particles moving in opposite directions. Corrections to the transport coefficients are obtained by generalizing an existing boundary layer analysis. The system of moment and field equations is consistently taken in the cylinder limit, which facilitates discussion of the treatment of dynamical constraints. it is shown that the nonlocal nature of Ohm's law in neoclassical theory renders the mathematical problem of plasma transport with changing flux surfaces nonstandard.

  17. Modeling of finite aspect ratio effects on current drive

    International Nuclear Information System (INIS)

    Wright, J.C.; Phillips, C.K.

    1996-01-01

    Most 2D RF modeling codes use a parameterization of current drive efficiencies to calculate fast wave driven currents. This parameterization assumes a uniform diffusion coefficient and requires a priori knowledge of the wave polarizations. These difficulties may be avoided by a direct calculation of the quasilinear diffusion coefficient from the Kennel-Englemann form with the field polarizations calculated by a full wave code. This eliminates the need to use the approximation inherent in the parameterization. Current profiles are then calculated using the adjoint formulation. This approach has been implemented in the FISIC code. The accuracy of the parameterization of the current drive efficiency, η, is judged by a comparison with a direct calculation: where χ is the adjoint function, ε is the kinetic energy, and rvec Γ is the quasilinear flux. It is shown that for large aspect ratio devices (ε → 0), the parameterization is nearly identical to the direct calculation. As the aspect ratio approaches unity, visible differences between the two calculations appear

  18. Modeling of finite aspect ratio effects on current drive

    Energy Technology Data Exchange (ETDEWEB)

    Wright, J.C.; Phillips, C.K. [Princeton Plasma Physics Lab., NJ (United States)

    1996-12-31

    Most 2D RF modeling codes use a parameterization of current drive efficiencies to calculate fast wave driven currents. This parameterization assumes a uniform diffusion coefficient and requires a priori knowledge of the wave polarizations. These difficulties may be avoided by a direct calculation of the quasilinear diffusion coefficient from the Kennel-Englemann form with the field polarizations calculated by a full wave code. This eliminates the need to use the approximation inherent in the parameterization. Current profiles are then calculated using the adjoint formulation. This approach has been implemented in the FISIC code. The accuracy of the parameterization of the current drive efficiency, {eta}, is judged by a comparison with a direct calculation: where {chi} is the adjoint function, {epsilon} is the kinetic energy, and {rvec {Gamma}} is the quasilinear flux. It is shown that for large aspect ratio devices ({epsilon} {r_arrow} 0), the parameterization is nearly identical to the direct calculation. As the aspect ratio approaches unity, visible differences between the two calculations appear.

  19. Experimental study of ionic liquid-water flow in T-shaped microchannels with different aspect ratios

    Science.gov (United States)

    Yagodnitsyna, A. A.; Kovalev, A. V.; Bilsky, A. V.

    2017-09-01

    Flow regimes of immiscible ionic liquid - water flow in T-shaped microchannels with 160 um hydraulic diameter and 1:2 and 1:4 aspect ratios are experimentally studied in the present work. Plug length and velocity were measured using high-speed visualization of the flow. Flow pattern maps were drawn for two channels. Parallel flow was shown to prevail for 1:4 aspect ratio channel in comparison to 1:2.

  20. Vortices in rotating and stratified flows: aspect ratio and sustainability

    Directory of Open Access Journals (Sweden)

    Le Gal P.

    2013-04-01

    Full Text Available In linear stratifications, vortices have a typical flat shape that appears to be not only a compromise between the rotation and the stratification of the background flow through their Coriolis parameter f and buoyancy frequency hbox{$ar{N}$} N̅ , but also involves the buoyancy frequency Nc within the vortices and their Rossby number Ro. We derive an analytical solution for the self-similar ellipsoidal shape of the vortices and the law for their aspect ratio. From this law, we show that long-lived vortices must necessary be either weakly stratified anticyclones or superstratified cyclones (which is less likely to occur. These predictions are experimentally and numerically verified and agree with published measurements for Jovian vortices and ocean meddies. This approach can be applied to a gaussian stratification to give good insights of the shape of vortices in protoplanetary disks and their sustainability.

  1. Noise Measurements of High Aspect Ratio Distributed Exhaust Systems

    Science.gov (United States)

    Bridges, James E.

    2015-01-01

    This paper covers far-field acoustic measurements of a family of rectangular nozzles with aspect ratio 8, in the high subsonic flow regime. Several variations of nozzle geometry, commonly found in embedded exhaust systems, are explored, including bevels, slants, single broad chevrons and notches, and internal septae. Far-field acoustic results, presented previously for the simple rectangular nozzle, showed that increasing aspect ratio increases the high frequency noise, especially directed in the plane containing the minor axis of the nozzle. Detailed changes to the nozzle geometry generally made little difference in the noise, and the differences were greatest at low speed. Having an extended lip on one broad side (bevel) did produce up to 3 decibels more noise in all directions, while extending the lip on the narrow side (slant) produced up to 2 decibels more noise, primarily on the side with the extension. Adding a single, non-intrusive chevron, made no significant change to the noise, while inverting the chevron (notch) produced up to 2decibels increase in the noise. Having internal walls (septae) within the nozzle, such as would be required for structural support or when multiple fan ducts are aggregated, reduced the noise of the rectangular jet, but could produce a highly directional shedding tone from the septae trailing edges. Finally, a nozzle with both septae and a beveled nozzle, representative of the exhaust system envisioned for a distributed electric propulsion aircraft with a common rectangular duct, produced almost as much noise as the beveled nozzle, with the septae not contributing much reduction in noise.

  2. Toroidal reactor designs as a function of aspect ratio

    International Nuclear Information System (INIS)

    Wong, C.P.C.; Wesley, J.C.; Stambaugh, R.D.; Cheng, E.T.

    2001-01-01

    This paper presents a 'common basis' systems study of superconducting (SC) and normal-conducting (NC) DT-burning fusion power and materials testing reactor designs. Figures-of-merit for power and materials-testing reactors are respectively; projected cost-of-electricity (COE) and direct cost (DC). A common 0-D plasma modeling basis is used and the plasma geometry and engineering aspects of the SC and NC designs are treated in an equivalent manner that is consistent with the limitations of their respective magnet technologies and other design constraints. Aspect ratios A in the range 1.2≤A≤6 and plasma elongations in the range 1≤κ≤3 are explored and a MHD stability (beta limit) physics basis that accurately describes the increase of normalized beta β N and toroidal beta β T with a decreasing A and/or increasing κ is incorporated. With this MHD basis taken into account and with the usual reactor geometry, physics and engineering constraints and costing bases applied, the results of the study show that for power reactors the minimum COE is pointing towards lower A∼2 than generally found in previous studies. The minimum is broader with higher κ. For test reactors with similar fusion power output, the direct cost for NC options is significantly lower than for SC coil options. With the NC category, testing designs that combine intermediate A and higher elongation show promise as a D-T burn next step device that could provide scientific and testing data to support future SC and NC reactors. For example, a NC coil design with A∼2, κ=3 could produce 200 MW fusion power at 1.23MW/m 2 average neutron wall loading at a total direct cost of about $643 M. This NC design with a fissile blanket could also convert ∼1270kg of fission reactor waste per full power year. (author)

  3. High aspect ratio catalytic reactor and catalyst inserts therefor

    Science.gov (United States)

    Lin, Jiefeng; Kelly, Sean M.

    2018-04-10

    The present invention relates to high efficient tubular catalytic steam reforming reactor configured from about 0.2 inch to about 2 inch inside diameter high temperature metal alloy tube or pipe and loaded with a plurality of rolled catalyst inserts comprising metallic monoliths. The catalyst insert substrate is formed from a single metal foil without a central supporting structure in the form of a spiral monolith. The single metal foil is treated to have 3-dimensional surface features that provide mechanical support and establish open gas channels between each of the rolled layers. This unique geometry accelerates gas mixing and heat transfer and provides a high catalytic active surface area. The small diameter, high aspect ratio tubular catalytic steam reforming reactors loaded with rolled catalyst inserts can be arranged in a multi-pass non-vertical parallel configuration thermally coupled with a heat source to carry out steam reforming of hydrocarbon-containing feeds. The rolled catalyst inserts are self-supported on the reactor wall and enable efficient heat transfer from the reactor wall to the reactor interior, and lower pressure drop than known particulate catalysts. The heat source can be oxygen transport membrane reactors.

  4. Large-aspect-ratio limit of neoclassical transport theory.

    Science.gov (United States)

    Wong, S K; Chan, V S

    2003-06-01

    This paper presents a comprehensive description of neoclassical transport theory in the banana regime for large-aspect-ratio flux surfaces of arbitrary shapes. The method of matched-asymptotic expansions is used to obtain analytical solutions for plasma distribution functions and to compute transport coefficients. The method provides justification for retaining only the part of the Fokker-Planck operator that involves the second derivative with respect to the cosine of the pitch angle for the trapped and barely circulating particles. It leads to a simple equation for the freely circulating particles with boundary conditions that embody a discontinuity separating particles moving in opposite directions. Corrections to the transport coefficients are obtained by generalizing an existing boundary layer analysis. The system of moment and field equations is consistently taken in the cylinder limit, which facilitates the discussion of the treatment of dynamical constraints. It is shown that the nonlocal nature of Ohm's law in neoclassical theory renders the mathematical problem of plasma transport with changing flux surfaces nonstandard.

  5. An Empirical Jet-Surface Interaction Noise Model with Temperature and Nozzle Aspect Ratio Effects

    Science.gov (United States)

    Brown, Cliff

    2015-01-01

    An empirical model for jet-surface interaction (JSI) noise produced by a round jet near a flat plate is described and the resulting model evaluated. The model covers unheated and hot jet conditions (1 less than or equal to jet total temperature ratio less than or equal to 2.7) in the subsonic range (0.5 less than or equal to M(sub a) less than or equal to 0.9), surface lengths 0.6 less than or equal to (axial distance from jet exit to surface trailing edge (inches)/nozzle exit diameter) less than or equal to 10, and surface standoff distances (0 less than or equal to (radial distance from jet lipline to surface (inches)/axial distance from jet exit to surface trailing edge (inches)) less than or equal to 1) using only second-order polynomials to provide predictable behavior. The JSI noise model is combined with an existing jet mixing noise model to produce exhaust noise predictions. Fit quality metrics and comparisons to between the predicted and experimental data indicate that the model is suitable for many system level studies. A first-order correction to the JSI source model that accounts for the effect of nozzle aspect ratio is also explored. This correction is based on changes to the potential core length and frequency scaling associated with rectangular nozzles up to 8:1 aspect ratio. However, more work is needed to refine these findings into a formal model.

  6. Fabrication process for tall, sharp, hollow, high aspect ratio polymer microneedles on a platform

    International Nuclear Information System (INIS)

    Ceyssens, Frederik; Chaudhri, Buddhadev Paul; Van Hoof, Chris; Puers, Robert

    2013-01-01

    This paper reports on a new lithographic process for fabricating arrays of tall, high aspect ratio (defined as height/wall thickness), hollow, polymer microneedles on a platform. The microneedles feature a high sharpness (down to 3 µm tip radius) and aspect ratio (>65) which is a factor 2 and 4 better than the state of the art, respectively. The maximum achievable needle shaft length is over 1 mm. The improved performance was obtained by using an anisotropically patterned silicon substrate covered with an antireflective layer as mold for the needle tip and an optimized SU-8 lithographic process. Furthermore, a platform containing liquid feedthroughs holding an arbitrary number of needles out of plane can be manufactured with only one additional process step. The high aspect ratio microneedles undergo failure at the critical load of around 230 mN in the case of 1 mm long hollow needles with triangular cross section and a base of 175 µm. Penetration into human skin is demonstrated as well. (paper)

  7. Changes of Root Length and Root-to-Crown Ratio after Apical Surgery

    DEFF Research Database (Denmark)

    von Arx, Thomas; Jensen, Simon S; Bornstein, Michael M

    2015-01-01

    INTRODUCTION: Apical surgery is an important treatment option for teeth with post-treatment periodontitis. Although apical surgery involves root-end resection, no morphometric data are yet available about root-end resection and its impact on the root-to-crown ratio (RCR). The present study assessed...... the length of apicectomy and calculated the loss of root length and changes of RCR after apical surgery. METHODS: In a prospective clinical study, cone-beam computed tomography scans were taken preoperatively and postoperatively. From these images, the crown and root lengths of 61 roots (54 teeth in 47....... The following parameters were assessed for all treated teeth as well as for specific tooth groups: length of root-end resection and percentage change of root length, preoperative and postoperative RCRs, and percentage change of RCR after apical surgery. RESULTS: The mean length of root-end resection was 3...

  8. High yield polyol synthesis of round- and sharp-end silver nanowires with high aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Nekahi, A.; Marashi, S.P.H., E-mail: pmarashi@aut.ac.ir; Fatmesari, D. Haghshenas

    2016-12-01

    Long silver nanowires (average length of 28 μm, average aspect ratio of 130) with uniform diameter along their length were produced by polyol synthesis of AgNO{sub 3} in ethylene glycol in the presence of PVP as preferential growth agent. Nanowires were produced with no addition of chloride salts such as NaCl or CuCl{sub 2} (or other additives such as Na{sub 2}S) which are usually used for lowering reduction rate of Ag ions by additional etchant of O{sub 2}/Cl{sup −}. Lower reduction rate was obtained by increasing the injection time of PVP and AgNO{sub 3} solutions, which was the significant factor in the formation of nanowires. Therefore, there was enough time for reduced Ag atoms to be deposited preferentially in the direction of PVP chains, resulting in high yield (the fraction of nanowires in the products) of nanowires (more than 95%) with high aspect ratio. The produced nanowires had both round- and sharp-ends with pentagonal cross section. Higher energy level of Ag atoms in borders of MTPs, which increases the dissolution rate of precipitated atoms, in addition to partial melting of MTPs at high synthesis temperatures, leads to the curving of the surfaces of exposed (111) crystalline planes in some MTPs and the formation of round-end silver nanowires. - Highlights: • Long silver nanowires with high aspect ratio of 130 were produced. • More than 95% nanowires were produced in products. • The produced nanowires had round- and sharp-ends with pentagonal cross section. • Additives were needed neither for high yield synthesis nor for round-end nanowires. • Melting and etching of MTPs in high energy borders resulted to round-end nanowires.

  9. Plasma features and alpha particle transport in low-aspect ratio tokamak reactor

    International Nuclear Information System (INIS)

    Xu Qiang; Wang Shaojie

    1997-06-01

    The results of the experiment and theory from low-aspect ratio tokamak devices have proved that the MHD stability will be improved. Based on present plasma physics and extrapolation to reduced aspect ratio, the feature of physics of low-aspect ratio tokamak reactor is discussed primarily. Alpha particle confinement and loss in the self-justified low-aspect ratio tokamak reactor parameters and the effect of alpha particle confinement and loss for different aspect ratio are calculated. The results provide a reference for the feasible research of compact tokamak reactor. (9 refs., 2 figs., 3 tabs.)

  10. Determination of Optimum Compression Ratio: A Tribological Aspect

    Directory of Open Access Journals (Sweden)

    L. Yüksek

    2013-12-01

    Full Text Available Internal combustion engines are the primary energy conversion machines both in industry and transportation. Modern technologies are being implemented to engines to fulfill today's low fuel consumption demand. Friction energy consumed by the rubbing parts of the engines are becoming an important parameter for higher fuel efficiency. Rate of friction loss is primarily affected by sliding speed and the load acting upon rubbing surfaces. Compression ratio is the main parameter that increases the peak cylinder pressure and hence normal load on components. Aim of this study is to investigate the effect of compression ratio on total friction loss of a diesel engine. A variable compression ratio diesel engine was operated at four different compression ratios which were "12.96", "15:59", "18:03", "20:17". Brake power and speed was kept constant at predefined value while measuring the in- cylinder pressure. Friction mean effective pressure ( FMEP data were obtained from the in cylinder pressure curves for each compression ratio. Ratio of friction power to indicated power of the engine was increased from 22.83% to 37.06% with varying compression ratio from 12.96 to 20:17. Considering the thermal efficiency , FMEP and maximum in- cylinder pressure optimum compression ratio interval of the test engine was determined as 18.8 ÷ 19.6.

  11. Diagnostics of BubbleMode Vortex Breakdown in Swirling Flow in a Large-Aspect-Ratio Cylinder

    DEFF Research Database (Denmark)

    Kulikov, D. V.; Mikkelsen, Robert Flemming; Naumov, Igor

    2014-01-01

    We report for the first time on the possible formation of regions with counterflow (bubble-mode vortex breakdown or explosion) at the center of strongly swirling flow generated by a rotating endwall in a large-aspect-ratio cylindrical cavity filled with a liquid medium. Previously, the possibility...... of bubble-mode breakdown was studied in detail for cylindrical cavities of moderate aspect ratio (length to radius ratios up to H/R ∼ 3.5), while flows in large-aspect-ratio cylinders were only associated with regimes of self-organized helical vortex multiplets. In the present study, a regime...... with nonstationary bubble-mode vortex breakdown has been observed in a cylindrical cavity with H/R = 4.5....

  12. High aspect ratio piezoelectric strontium-bismuth-tantalate nanotubes

    International Nuclear Information System (INIS)

    Morrison, Finlay D; Ramsay, Laura; Scott, James F

    2003-01-01

    We report the deposition and characterization of transparent ferroelectric/piezoelectric nanotubes of wall thickness about 40 nm, tube diameters ranging from a few hundred nanometres to 4 μm, and length about 100 μm. Comparison with other nanotubes is made and applications in dynamic random access memory trenching and ink-jet printers are discussed. (letter to the editor)

  13. The Relationship of Body Length and Ratio Pappilla with Sex in Gobi Fish (Sicyopterus macrostetholepis

    Directory of Open Access Journals (Sweden)

    Rona Taula Sari

    2017-07-01

    Full Text Available Research about the relationship of body length and ratio papilla with sex in goby fish (S. macrostetholepis Blkr. has been done at Animal Structure and Developmental Laboratory, Biologi Department, Faculty of Matematics and Natural Sciences, Andalas University, Padang, which purposed to analyse the relationship of body length and ratio papilla with sex of goby fish (S. macrostetholepis Blkr.. The samples were taken in wild stream area at Batangkuranji river, Padang City. This research used descriptive method and data were analyzed by qualitatively and quantitatively. The results of investigation showed that in several goby fishes (S. macrostetholepis Blkr. with different sex had the same of body length and the same of ratio papilla. So, there was not relationship between of body length and ratio papilla with sex.  Goby fishes (S. macrostetholepis Blkr. it belongs to the hermaphrodite protogini, which the androgynous young females, while in adulthood, it would change sex to male. The results of this study are expected to add to the treasures of knowledge and information about reproductive gobies (S. macrostetholepis Blkr. in the preservation and development of fish farming.   

  14. Axial length/corneal radius of curvature ratio and refractive status in ...

    African Journals Online (AJOL)

    Aim/Background: Associations between axial length (AL) to corneal radius of curvature (CR) ratio and refractive status in a healthy Nigerian adult population were studied. Materials and Methods: Healthy students and members of staff of Obafemi Awolowo Teaching Hospitals Complex, Ile‑Ife, South West Nigeria, free of ...

  15. Polyol Synthesis of Silver Nanowires by Heterogeneous Nucleation and Mechanistic Aspects Influencing its Length and Diameter

    Science.gov (United States)

    Schuette, Waynie Mark

    Various additives are employed in the polyol synthesis of silver nanowires (Ag NWs), which are typically halide salts such as NaCl. A variety of mechanistic roles have been suggested for these additives. My research showed that the early addition of NaCl in the polyol synthesis of Ag NWs from AgNO3 in ethylene glycol results in the rapid formation of AgCl nanocubes, which induce the heterogeneous nucleation of metallic Ag upon their surfaces. Ag NWs subsequently grow from these nucleation sites. The conclusions are supported by studies using ex-situ generated AgCl nanocubes. Additionally, the final mean silver nanowire diameter is found to be independent of the size of the heterogeneous nucleant, showing that the diameter is not significantly influenced by the nucleation event. Kinetics studies determine that nanowire diameter, length, and aspect ratio grow in parallel to one another and with the extent of the Ag+ reduction reaction, demonstrating that growth is reduction-rate limited. The results are interpreted to support nanowire growth by a surface-catalyzed reduction process occurring on all nanowire surfaces, and to exclude nanoparticle aggregation or Ostwald ripening as primary components of the growth mechanism.

  16. Injection molding of high aspect ratio sub-100 nm nanostructures

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels B

    2013-01-01

    as described by height, width and uniformity of the nanoscopic features. Use of a mold temperature transiently above the polymer glass transition temperature (Tg) was the most important factor in increasing the replication fidelity. Surface coating of the nickel molds with a fluorocarbon-containing thin film...... with FDTS. Reduced adhesion forces are consistent with lowered friction that reduces the risk of fracturing the nanoscopic pillars during demolding. Optimized mold surface chemistry and associated injection molding conditions permitted the fabrication of square arrays of 40 nm wide and 107 nm high (aspect...

  17. Dependence of the ac loss on the aspect ratio in a cable in conduit conductor

    International Nuclear Information System (INIS)

    Cau, F; Bruzzone, P

    2010-01-01

    The coupling current loss in rectangular superconducting cables is strictly dependent on their aspect ratio, which has an impact on the area linked by the field variation and consequently on the currents induced between strands. The relation between the ac loss and aspect ratio is studied with reference to the testing of three short cable in conduit conductor (CICC) samples at the SULTAN test facility. The first conductor is a 25 kA NbTi cable for the JT60-SA tokamak; the second is a 20 kA Nb 3 Sn cable for the HZB hybrid magnet. The last CICC is a 68 kA Nb 3 Sn cable with layout similar to that of the ITER toroidal field (TF) conductor (called the 'European toroidal field (EUTF) alternate'). All the samples are assembled with two conductor sections differing only in their orientation with respect to the external variable field. In the first and third samples, the cable of one leg is rotated by 90 0 , while in the HZB sample it is rotated by 45 0 with respect to the other leg. The ac loss is measured at the SULTAN test facility using a gas flow calorimetric method. A sample length of 39 cm is exposed to a sinusoidal field with an amplitude of ± 0.3 or ± 0.2 T (depending on the superconductor) and frequency variable in the range 0.1-0.8 Hz. A background field of 2 T perpendicular both to the sinusoidal field and to the sample axis is also applied. The ac loss is assessed by measuring the variation of the He enthalpy, assuming the metal enthalpy to be negligible. The loss curve for both legs is discussed in terms of the respective aspect ratios and the results, including data from former test campaigns, are compared with the aim of finding an analytical relation between the loss and the conductor dimensions.

  18. Development of a virtual probe tip with an application to high aspect ratio microscale features

    International Nuclear Information System (INIS)

    Bauza, Marcin B.; Hocken, Robert J.; Smith, Stuart T.; Woody, Shane C.

    2005-01-01

    Nondestructive measurement of microscale features remains a challenging metrology problem. For example, to assess a high aspect ratio small hole it is currently common to cut a cross section and measure the features of interest using an atomic force microscope, scanning probe microscope, or scanning electron microscope. Typically, these metrology tools may be suitable for surface finish measurement but often lack the capability for dimensional metrology. The aim of this article is to discuss the development of a high aspect-ratio microscale probe for measurement of microscale features. A 700:1 high aspect ratio probe shank is fabricated with a 7 μm diameter, and attached at one end to an oscillator. The oscillator produces a standing wave in the oscillating probe shank as opposed to conventional probes that use a microscale sphere on the end of a comparatively rigid shank. As a result of the standing wave formed in steady state vibration, the free end of the shank generates an amplitude of oscillation greater than the probe shank diameter. Thus, the probe does not require a spherical ball to serve as the contact point and simply uses the contact diameter of the free end of the vibrating shank. This methodology is referred to as a virtual probe tip. The virtual probe tip in conjunction with a nanopositioning scanner is used to measure surface profile measurements over traverse lengths of 130 μm. In this article, results from profiles of a 500 nm step height and a ruby sphere of diameter 1 mm are presented. Experiments in this article indicate the ability to repeatedly resolve surface features of less than 5 nm while maintaining bandwidths greater than 1 kHz. Furthermore, adhesion problems often encountered with micrometer scaled probes were not observed during profile measurements with this virtual probe

  19. Effect of Aspect Ratio on the Light Output of Scintillators

    CERN Document Server

    Pauwels, Kristof; Gundacker, S.; Knapitsch, A.; Lecoq, P.

    2012-01-01

    The influence of the geometry of the scintillators is presented in this paper. We focus on the effect of narrowing down the section of crystals that have a given length. The light output of a set of crystals with very similar scintillating properties but different geometries measured with several coupling/wrapping configurations is provided. We observe that crystals shaped in thin rods have a lower light output as compared to bulk or sliced crystals. The effect of unpolishing the crystal faces is also investigated, and it is shown that highest light outputs are not necessarily obtained with crystals having all faces polished. Simulation results based on a realistic model of the crystal that implements light scattering on the crystal edges are in agreement with the experimental data. Fine-tuning of this model would allow us to further explore the details of light propagation in scintillators and would be highly valuable to fast timing detection and highly granular detectors.

  20. High aspect ratio template and method for producing same

    Science.gov (United States)

    Sakamoto, Jeff S. (Inventor); Weiss, James R. (Inventor); Fleurial, Jean-Pierre (Inventor); Kisor, Adam (Inventor); Tuszynski, Mark (Inventor); Stokols, Shula (Inventor); Holt, Todd Edward (Inventor); Welker, David James (Inventor); Breckon, Christopher David (Inventor)

    2010-01-01

    Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers.

  1. Physics Studies of a Proposed Small Aspect Ratio Torsatron-Tokamak Hybrid

    Science.gov (United States)

    Valanju, P. M.; Gentle, K. W.; McCool, S.; Miner, W. H., Jr.; Ross, D. W.; Wiley, J. C.; Wootton, A. J.

    1996-11-01

    Physics studies of a proposed small aspect ratio torsatron-tokamak hybrid (SMARTH) are presented. This small aspect ratio configuration attempts to remedy a major drawback of conventional stellarator reactors, viz. the large volume resulting from the large aspect ratio. Considering a small aspect ratio machine with 8 field periods (m=8) and with 8 or 16 modular coils, we investigate vacuum configurations and MHD equilibria to determine the optimum configuration which produces large rotational transform, large plasma volume, large beta, and small field ripple. Implications for particle confinement will also be discussed. Effects of radial electric fields on orbit losses and confinement will also be explored.

  2. THE RAYLEIGH-TAYLOR INSTABILITY IN SMALL ASPECT RATIO CONTAINERS

    Energy Technology Data Exchange (ETDEWEB)

    RIVERA, MICHAEL K. [Los Alamos National Laboratory; ECKE, ROBERT E. [Los Alamos National Laboratory

    2007-01-22

    We present experimental measurements of density and velocity obtained from the mixing zone of buoyancy driven turbulence initiated by the Rayleigh-Taylor instability in a small aspect ration chamber (a chamber who's vertical height is significantly larger than its lateral dimesion). The mixing front propogates at a slightly slower rate than the expected t{sup 2} behavior obtained from earlier experiments and numerics. Once the front has propogated significantly far away, we observe that the mixing zone develops to a statistically stationary state. In this stationary state, the spectral distributions of energy and density deviate from the familiar k{sup -5/3} ubiquitous to turbulence in three dimensions.

  3. Aspects in the Synthesis of a Variable Compression Ratio Mechanism

    Science.gov (United States)

    Mănescu, Bogdan; Dragomir, Ionuţ; Stănescu, Nicolae–Doru; Pandrea, Nicolae; Clenci, Adrian; Popa, Dinel

    2017-10-01

    The mechanism considered in this paper is a VCR one consisting in a crank, a shaft, an intermediate triangular element and a control lever and it was described in previous papers of the authors. The authors start from a classical crank-shaft mechanism for which the extreme positions are known. The first stage of the synthesis consists in determination of the constraint function which has to be fulfilled by the new mechanism so that the extreme position remain unchanged. The new step consists in imposing new conditions for the mechanism so that some new positions have to be obtained. The main hypothesis is that the positions of different characteristic points of the mechanism may be written as continuous functions of the certain input data. Due to aspect, the synthesis of the mechanism implies continuous variations of the output data and, consequently, there exists at least one solution for the synthesis process. In each case the authors determine the extreme positions of the piston. These extreme positions are also continuous functions of the input data. Two main approaches are discussed in the paper. One approach consists in the exact determination of the solution using a numerical procedure. The second one is an approximate one and consists in the determination of an approximate solution of the synthesis and verifying the deviation of this solution. For the new mechanism obtained by synthesis the authors determined the reduced velocities and accelerations of different characteristic elements. Some aspects of the wear are discussed with the aid of the reduced relative velocities.

  4. Metallization of high aspect ratio, out of plane structures

    DEFF Research Database (Denmark)

    Vazquez, Patricia; Dimaki, Maria; Svendsen, Winnie Edith

    2009-01-01

    This work is dedicated to developing a novel three dimensional structure for electrochemical measurements in neuronal studies. The final prototype will allow not only for the study and culture on chip of neuronal cells, but also of brain tissue. The use of out-of-plane electrodes instead of planar...... ones increases the sensitivity of the system and increases the signal-to-noise ratio in the recorded signals, due to the higher availability of surface area. The main bottleneck of the out-of-plane electrode fabrication lies in the metallization process for transforming them into active electrodes...

  5. A Thermoacoustic Model for High Aspect Ratio Nanostructures

    Directory of Open Access Journals (Sweden)

    Masoud S. Loeian

    2016-09-01

    Full Text Available In this paper, we have developed a new thermoacoustic model for predicting the resonance frequency and quality factors of one-dimensional (1D nanoresonators. Considering a nanoresonator as a fix-free Bernoulli-Euler cantilever, an analytical model has been developed to show the influence of material and geometrical properties of 1D nanoresonators on their mechanical response without any damping. Diameter and elastic modulus have a direct relationship and length has an inverse relationship on the strain energy and stress at the clamp end of the nanoresonator. A thermoacoustic multiphysics COMSOL model has been elaborated to simulate the frequency response of vibrating 1D nanoresonators in air. The results are an excellent match with experimental data from independently published literature reports, and the results of this model are consistent with the analytical model. Considering the air and thermal damping in the thermoacoustic model, the quality factor of a nanowire has been estimated and the results show that zinc oxide (ZnO and silver-gallium (Ag2Ga nanoresonators are potential candidates as nanoresonators, nanoactuators, and for scanning probe microscopy applications.

  6. CFD simulation of length to diameter ratio effects on the energy separation in a vortex tube

    Directory of Open Access Journals (Sweden)

    Bramo Reza Abdol

    2011-01-01

    Full Text Available The objective of the present computational fluid dynamics analysis is an attempt to investigate the effect of length to diameter ratio on the fluid flow characteristics and energy separation phenomenon inside the Ranque-Hilsch vortex tube. In this numerical study, performance of Ranque-Hilsch vortex tubes (RHVT, with length to diameter ratios (L/D of 8, 9.3, 10.5, 20.2, 30.7 and 35 with six straight nozzles was investigated. It includes generating better understanding of the effects of the stagnation point location on the performance of RHVT. It was found that the best performance was obtained when the ratio of vortex tube length to the diameter was 9.3 and also fort this case the stagnation point was found to be the farthest from the inlet. The results show that the closer distance to the hot end is produced the larger magnitude of the temperature difference. Computed results show good agreement with published experimental results.

  7. Morphometric Characteristics and Length-Weight Relationship of Russian Sturgeon Juveniles Fed with Different Ratio

    Directory of Open Access Journals (Sweden)

    Raluca Cristina ANDREI(GURIENCU

    2017-11-01

    Full Text Available The aim of this paper was to analyze some morphometric characteristics and the correlation between them for Russian sturgeon juveniles (Acipenser gueldenstaedtii reared in a recirculating aquaculture system fed at different fed with different ratio: 1% body weight (BW, 1.5% BW, 2% BW and ad libitum feeding (which was around 2.8% BW.Fish, with an average body mass around 248.194 ± 1.59 g. Following biometric measurements were made for each fish, including weight (W, total length (TL, standard length (SL, fork length (FL, maximum body depth (last depth of caudal peduncle, H; preanal distance (AD, predorsal distance (PD, length of head (C, preorbital distance (PO, length of pectoral fin (LPF, interorbital distance (ID, maximum width of head (MH, width of mouth (WM, width of the head at the level of the mouth (WHM. The obtained results showed significant differences between all morphometric measurements (p<0.05 for all the experimental variants, emphasizing that in the ad libitum feeding all morphometric measurements were significantly higher than in the other experimental variants. In order to highlight more eloquent these differences, were developed some linear regressions between the morphometric measurements and significant positive correlation (p<0.05 between dependent and independent variables were found.

  8. A hypothetical model for predicting the toxicity of high aspect ratio nanoparticles (HARN)

    Science.gov (United States)

    Tran, C. L.; Tantra, R.; Donaldson, K.; Stone, V.; Hankin, S. M.; Ross, B.; Aitken, R. J.; Jones, A. D.

    2011-12-01

    The ability to predict nanoparticle (dimensional structures which are less than 100 nm in size) toxicity through the use of a suitable model is an important goal if nanoparticles are to be regulated in terms of exposures and toxicological effects. Recently, a model to predict toxicity of nanoparticles with high aspect ratio has been put forward by a consortium of scientists. The High aspect ratio nanoparticles (HARN) model is a platform that relates the physical dimensions of HARN (specifically length and diameter ratio) and biopersistence to their toxicity in biological environments. Potentially, this model is of great public health and economic importance, as it can be used as a tool to not only predict toxicological activity but can be used to classify the toxicity of various fibrous nanoparticles, without the need to carry out time-consuming and expensive toxicology studies. However, this model of toxicity is currently hypothetical in nature and is based solely on drawing similarities in its dimensional geometry with that of asbestos and synthetic vitreous fibres. The aim of this review is two-fold: (a) to present findings from past literature, on the physicochemical property and pathogenicity bioassay testing of HARN (b) to identify some of the challenges and future research steps crucial before the HARN model can be accepted as a predictive model. By presenting what has been done, we are able to identify scientific challenges and research directions that are needed for the HARN model to gain public acceptance. Our recommendations for future research includes the need to: (a) accurately link physicochemical data with corresponding pathogenicity assay data, through the use of suitable reference standards and standardised protocols, (b) develop better tools/techniques for physicochemical characterisation, (c) to develop better ways of monitoring HARN in the workplace, (d) to reliably measure dose exposure levels, in order to support future epidemiological

  9. Dielectrophoretically structured piezoelectric composites with high aspect ratio piezoelectric particles inclusions

    NARCIS (Netherlands)

    Ende, D.A. van den; Kempen, S.E. van; Wu, X.; Groen, W.A.; Randall, C.A.; Zwaag, S. van der

    2012-01-01

    Piezoelectric composites were prepared by dielectrophoretic alignment of high aspect ratio piezoelectric particles in a thermosetting polymer matrix. A high level of alignment was achieved in the cured composite from a resin containing randomly oriented high aspect ratio particles. Upon application

  10. Shape matters: synthesis and biomedical applications of high aspect ratio magnetic nanomaterials

    OpenAIRE

    Fratila, Raluca M.; Rivera-Fernández, Sara; Fuente, Jesús M. de la

    2015-01-01

    High aspect ratio magnetic nanomaterials possess anisotropic properties that make them attractive for biological applications. Their elongated shape enables multivalent interactions with receptors through the introduction of multiple targeting units on their surface, thus enhancing cell internalization. Moreover, due to their magnetic anisotropy, high aspect ratio nanomaterials can outperform their spherical analogues as contrast agents for magnetic resonance imaging (MRI) applications. In th...

  11. Power reduction and the radial limit of stall delay in revolving wings of different aspect ratio

    NARCIS (Netherlands)

    Kruyt, J.W.; Heijst, Van G.F.; Altshuler, D.L.; Lentink, David

    2015-01-01

    Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle

  12. Hot punching of high-aspect-ratio 3D polymeric microstructures for drug delivery

    DEFF Research Database (Denmark)

    Petersen, Ritika Singh; Keller, Stephan Sylvest; Boisen, Anja

    2015-01-01

    Hot punching: a highly versatile method of fabricating high-aspect-ratio 3D microstructures for drug delivery with good replication fidelity and yield.......Hot punching: a highly versatile method of fabricating high-aspect-ratio 3D microstructures for drug delivery with good replication fidelity and yield....

  13. New Vehicle Detection Method with Aspect Ratio Estimation for Hypothesized Windows

    Directory of Open Access Journals (Sweden)

    Jisu Kim

    2015-12-01

    Full Text Available All kinds of vehicles have different ratios of width to height, which are called the aspect ratios. Most previous works, however, use a fixed aspect ratio for vehicle detection (VD. The use of a fixed vehicle aspect ratio for VD degrades the performance. Thus, the estimation of a vehicle aspect ratio is an important part of robust VD. Taking this idea into account, a new on-road vehicle detection system is proposed in this paper. The proposed method estimates the aspect ratio of the hypothesized windows to improve the VD performance. Our proposed method uses an Aggregate Channel Feature (ACF and a support vector machine (SVM to verify the hypothesized windows with the estimated aspect ratio. The contribution of this paper is threefold. First, the estimation of vehicle aspect ratio is inserted between the HG (hypothesis generation and the HV (hypothesis verification. Second, a simple HG method named a signed horizontal edge map is proposed to speed up VD. Third, a new measure is proposed to represent the overlapping ratio between the ground truth and the detection results. This new measure is used to show that the proposed method is better than previous works in terms of robust VD. Finally, the Pittsburgh dataset is used to verify the performance of the proposed method.

  14. Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas

    International Nuclear Information System (INIS)

    Menard, J.E.; Bell, M.G.; Bell, R.E.; Gates, D.A.; Kaye, S.M.; LeBlanc, B.P.; Maingi, R.; Sabbagh, S.A.; Soukhanovskii, V.; Stutman, D.

    2003-01-01

    Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 (2000) 557] have achieved normalized beta values twice the conventional tokamak limit at low internal inductance and with significant bootstrap current. These experimental results have motivated a computational re-examination of the plasma aspect ratio dependence of ideal no-wall magnetohydrodynamic stability limits. These calculations find that the profile-optimized no-wall stability limit in high bootstrap fraction regimes is well described by a nearly aspect ratio invariant normalized beta parameter utilizing the total magnetic field energy density inside the plasma. However, the scaling of normalized beta with internal inductance is found to be strongly aspect ratio dependent at sufficiently low aspect ratio. These calculations and detailed stability analyses of experimental equilibria indicate that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in NSTX in a high bootstrap fraction regime

  15. A Sense of Proportion: Aspect Ratio and the Framing of Television Space

    OpenAIRE

    Cardwell, Sarah E. F.

    2015-01-01

    Aspect ratio’ is frequently overlooked or naively characterised. Yet it plays a fundamental, determining role in forming and framing television’s spaces. A balanced reappraisal of television’s varied aspect ratios and their unique dramatic and aesthetic possibilities can enhance our close analyses and our understanding of television’s ‘art history’. This paper challenges myths, misunderstandings and preconceptions about TV’s aspect ratios and their spatial properties. Countering prevailing p...

  16. Cellulosic fibers with high aspect ratio from cornhusks via controlled swelling and alkaline penetration.

    Science.gov (United States)

    Ma, Zhuanzhuan; Pan, Gangwei; Xu, Helan; Huang, Yiling; Yang, Yiqi

    2015-06-25

    Cellulosic fibers with high aspect ratio have been firstly obtained from cornhusks via controlled swelling in organic solvent and simultaneous tetramethylammonium hydroxide (TMAOH) post treatment within restricted depth. Cornhusks, with around 42% cellulose content, are a copious and inexpensive source for natural fibers. However, cornhusk fibers at 20tex obtained via small-molecule alkaline extraction were too coarse for textile applications. Continuous NaOH treatment would result in fine fibers but with length of about 0.5-1.5mm, too short for textile use. In this research, post treatment using TMAOH and under controlled swelling significantly reduced fineness of cornhusk fibers from 21.3±2.88 to 5.72±0.21tex. Fiber length was reduced from 105.47±10.03 to47.2±27.4mm. The cornhusk fibers had more oriented microstructures and cellulose content increased to 84.47%. Besides, cornhusk fibers had similar tenacity, longer elongation, and lower modulus compared to cotton and linen, which endowed them with durability and flexibility. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Microwave dynamics of high aspect ratio superconducting nanowires studied using self-resonance

    Science.gov (United States)

    Santavicca, Daniel F.; Adams, Jesse K.; Grant, Lierd E.; McCaughan, Adam N.; Berggren, Karl K.

    2016-06-01

    We study the microwave impedance of extremely high aspect ratio (length/width ≈ 5000) superconducting niobium nitride nanowires. The nanowires are fabricated in a compact meander geometry that is in series with the center conductor of a 50 Ω coplanar waveguide transmission line. The transmission coefficient of the sample is measured up to 20 GHz. At high frequency, a peak in the transmission coefficient is seen. Numerical simulations show that this is a half-wave resonance along the length of the nanowire, where the nanowire acts as a high impedance, slow wave transmission line. This resonance sets the upper frequency limit for these nanowires as inductive elements. Fitting simulations to the measured resonance enables a precise determination of the nanowire's complex sheet impedance at the resonance frequency. The real part is a measure of dissipation, while the imaginary part is dominated by kinetic inductance. We characterize the dependence of the sheet resistance and sheet inductance on both temperature and current and compare the results to recent theoretical predictions for disordered superconductors. These results can aid in the understanding of high frequency devices based on superconducting nanowires. They may also lead to the development of novel superconducting devices such as ultra-compact resonators and slow-wave structures.

  18. The ratio of intracellular CRY proteins determines the clock period length

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang [College of Biological Sciences, China Agricultural University, Beijing 100083 (China); National Institute of Biological Sciences, Beijing 102206 (China); Xiong, Wei [National Institute of Biological Sciences, Beijing 102206 (China); School of Life Sciences, Peking University, Beijing 100871 (China); Zhang, Eric Erquan, E-mail: zhangerquan@nibs.ac.cn [National Institute of Biological Sciences, Beijing 102206 (China)

    2016-04-08

    Although a deficiency in CRY1 or CRY2 correlates with a shorter or longer circadian period, the regulation of CRY proteins in the circadian period has not been well studied. In this study, we found that both CRY1 and CRY2 were able to rescue oscillation in CRY null cells and that they displayed different periods. Furthermore, we demonstrated that protein nuclear import rates, not protein stability, regulate the period-length at the cellular level. Co-transfection of CRY1 and CRY2 in various ratios in the same cells gives rise to the predicted period length in a dose-dependent manner. Given the distinct characteristics of the C-terminal tails of the CRY1 and CRY2 proteins, our study addresses a long-standing hypothesis that the ratio of these two CRY molecules affects the clock period. - Highlights: • Rhythmic CRY2, like CRY1, in the correct CRY1 phase is sufficient to rescue clock oscillation in CRY null cells. • The short-period mammalian CRY2 protein is more stable than the CRY1 protein. • The N-terminal polypeptide of CRY2 contributes to its stability and Per2 repression, but it does not affect the period. • The C-terminal tails of CRYs regulate their protein stability and nuclear import, but the import rate governs the period. • The ratio, rather than the absolute amounts of CRY1 and CRY2 proteins, determines the period in mammalian cells.

  19. Relationship between width and length ratios of upper anterior teeth in young Chilean population.

    Directory of Open Access Journals (Sweden)

    Jorge Troncoso-Pazos

    2017-08-01

    Full Text Available Introduction: Knowledge about the size and proportion of upper anterior teeth allows dental rehabilitation taking into consideration the local parameters of a population. The aim of this research is to determine the width, length and the relationship between width and length of central incisor, lateral incisor and canine teeth in both sexes in young Chilean population. Methodology: A cross-sectional study was performed. Study subjects included 187 dentistry students from two Chilean cities (mean age 21.35±2.7 years, 52.9% men. The teeth width and height were measured and the width/height ratio was calculated. Differences in measurements according to sex was analyzed (p<0.05; STATA v.10.0. Results: The width and height of the teeth were statistically and proportionally larger in men (p<0.05. The width/height ratio of lateral and canine incisors was significantly higher in women (p<0.05. Conclusion: In a sample of young Chileans, upper anterior teeth were longer and wider in men. However, the width/height ratio of teeth was found to be significantly higher in women.

  20. Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground

    Science.gov (United States)

    Fink, Marvin P.; Lastinger, James L.

    1961-01-01

    A wind-tunnel investigation has been conducted to determine the effect of ground proximity on the aerodynamic characteristics of thick highly cambered rectangular wings with aspect ratios of 1. 2, 4, and 6. The results showed that, for these aspect ratios, as the ground war, approached all wings experienced increases in lift-curve slope and reductions in induced drag which resulted in increases in lift-drag ratio. Although an increase in lift-curve slope was obtained for all aspect ratios as the ground was approached, the lift coefficient at an angle of attack of 0 deg for any given aspect ratio remained nearly constant. The experimental results were in general agreement with Wieselsberger's ground-effect theory (NACA Technical Memorandum 77). As the wings approached the ground, there was an increase in static longitudinal stability at positive angles of attack. When operating in ground effect, all the wings had stability of height at positive angles of attack and instability of height at negative angles of attack. Wing-tip fairings on the wings with aspect ratios of 1 and 2 produced small increases in lift-drag ratio in ground effect. End plates extending only below the chord plane on the wing with an aspect ratio of 1 provided increases in lift coefficient and in lift-drag ratio in ground effect.

  1. Preparation and characterization of fluorescent microtubes with high length/diameter ratios

    International Nuclear Information System (INIS)

    Chu Maoquan; Huang Jiasheng

    2009-01-01

    Fluorescent microtubes were prepared by self-assembly of CdTe quantum dots (QDs) following calcination at 500 °C using silkworm silks as templates. The obtained microtubes exhibited high length/diameter ratios. The cross-sectional dimension of the microtubes was no more than 10 µm, but the length could be up to several millimeters. The microtube wall was mainly composed of CdO, Cd 3 TeO 6 , and CdCO 3 nanocrystals. Compared with the original red fluorescent CdTe QDs and the silk/QD core–shell structures, the microtubes exhibited a bright green-yellow fluorescence. The approach reported in this work opens the possibility of the large-scale preparation of fluorescent microtubes for both fundamental research and applications

  2. Ultrasonographic measurement of fetal foot length and femur/foot length ratio in second trimester of normal pregnancy tn Korean women

    International Nuclear Information System (INIS)

    Ji, Eun Kyung

    2001-01-01

    The aim of this study was to determine, using prenatal ultrasongraphy, normal fetal foot length and the femur length ratio during the second trimester of a normal pregnancy in Korean women. From May to July 1999, and in September of the same year, 1018 normal Korean singleton pregnancies showing no abnormality on prenatal sonograms were included in this study. The gestational age ranged from 19 to 30 weeks. Femur and foot length were measured by one radiologist. Regression analysis was performed for foot length and gestational age, and the mean value of the femur/foot length ratio and 95th percentile confidence interval of that mean value were calculated. The data obtained was compared with that obtained from caucasians. Foot length correlated with gestational age (r 2 =0.87, ρ value= 0.0001). The regression formula was as follows; Gestational age (days) = 70.98-2.15 X foot length (mm). Mean foot length at each gestational week was not different from the corresponding figure for Cancasians. The mean (±SD) value of the femur/foot length ratio was 0.96 (±0.05) and the 95 th percentile confidence interval of that mean value was 0.96± 0.000301, figures which are significantly lower than those for Caucasians. Fetal foot length during the second trimester of a normal pregnancy in Korean women is a reliable parameter for use in the assessment of gestational age. In our study the fetal foot length was not different from that of caucasians, while the femur/foot length ratio was lower than the value in that group. The nomogram depicted in of this study will serve as a useful adjunct in the screening of chromosomal abnormality or skeletal dysplasia among Koreans

  3. Studying aerosol light scattering based on aspect ratio distribution observed by fluorescence microscope.

    Science.gov (United States)

    Li, Li; Zheng, Xu; Li, Zhengqiang; Li, Zhanhua; Dubovik, Oleg; Chen, Xingfeng; Wendisch, Manfred

    2017-08-07

    Particle shape is crucial to the properties of light scattered by atmospheric aerosol particles. A method of fluorescence microscopy direct observation was introduced to determine the aspect ratio distribution of aerosol particles. The result is comparable with that of the electron microscopic analysis. The measured aspect ratio distribution has been successfully applied in modeling light scattering and further in simulation of polarization measurements of the sun/sky radiometer. These efforts are expected to improve shape retrieval from skylight polarization by using directly measured aspect ratio distribution.

  4. Tailored Au nanorods: optimizing functionality, controlling the aspect ratio and increasing biocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Cai Xiaoqing; Wang, Cheng-Liang; Chen, Hsiang-Hsin; Chien, Chia-Chi; Lai Shengfeng; Chen Yiyun; Hua, Tzu-En; Kempson, Ivan M; Hwu, Y [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Yang, C S [Center for Nanomedicine, National Health Research Institutes, Miaoli, Taiwan (China); Margaritondo, G, E-mail: phhwu@sinica.edu.tw [Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2010-08-20

    Monodisperse gold nanorods with high aspect ratio were synthesized by x-ray irradiation. Irradiation was first used to stimulate the creation of seeds. Afterward, nanorod growth was stimulated either by chemical reduction or again by x-ray irradiation. In the last case, the entire process took place without reducing agents. The shape of the final products could be controlled by modulating the intensity of the x-ray irradiation during the seed synthesis. In turn, the nanorod aspect ratio determines the absorption wavelength of the nanorods that can thus be optimized for different applications. Likewise, the aspect ratio influences the uptake of the nanorods by HeLa cells.

  5. Effect of nozzle length-to-diameter ratio on atomization of turbulent liquid jets

    Science.gov (United States)

    Osta, Anu Ranjan

    Breakup of liquid jets is of considerable interest motivated by its applicability in combustion and propulsion systems (CI and SI engines), and agricultural fertilizer/pesticide sprays, among others. Almost all of the practical liquid injectors introduce some degree of turbulence in the liquid jet leaving the injector passage and an intriguing question is the relative importance of the liquid turbulence, cavitation, and the aerodynamic forces in the breakup processes of fuel injectors. A better design of liquid fuel injector would reduce pollutants and increase the efficiency of liquid fuel combustion processes. An experimental study to investigate the effect of nozzle length to diameter ratio on the surface properties of turbulent liquid jets in gaseous crossflow and still air was carried out. Straight cavitation-free nozzles with length/diameter ratios of 10, 20 and 40 were used to generate turbulent liquid jets in gaseous crossflow. The present study was limited to small Ohnesorge number liquid jets (Oh 110). The diagnostics consisted of pulsed shadowgraphy, pulsed digital holographic microscopy and x-ray diagnostics. The x-ray tests were conducted at the Advanced Photon Source (APS) facility of Argonne National Laboratory. The test matrix was designed to maintain the same aerodynamic forces in order to isolate the effects of jet turbulence on the breakup process. The measurements included liquid jet surface properties, breakup location of the liquid column as a whole, the breakup regime transitions, bubble size inside the jet and seeding particle displacement inside the jet structures. The results include the jet surface characteristics, the liquid column breakup lengths, bubble growth, and phenomenological analysis to explain the observed results. It is observed that for a jet breakup in crossflow the injector passage length does play a role in determining the breakup length as well as influence the characteristics of the jet upwind surface. The present

  6. Synthesis of high aspect ratio ZnO nanowires with an inexpensive handcrafted electrochemical setup

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, Ali, E-mail: at1361@aut.ac.ir, E-mail: atahery@aeoi.org.ir [Nuclear Science and Technology Institute (Iran, Islamic Republic of); Saramad, Shahyar; Setayeshi, Saeed [Amirkabir University of Technology, Faculty of Energy Engineering and Physics (Iran, Islamic Republic of)

    2016-12-15

    In this work, high aspect ratio zinc oxide nanowires are synthesized using templated one-step electrodeposition technique. Electrodeposition of the nanowires is done using a handcrafted electronic system. Nuclear track-etched polycarbonate membrane is used as a template to form the high aspect ratio nanowires. The result of X-ray diffraction and scanning electron microscopy shows that nanowires with a good crystallinity and an aspect ratio of more than 30 can be achieved in a suitable condition. The height of electrodeposited nanowires reaches to about 11 μm. Based on the obtained results, high aspect ratio ZnO nanowires can be formed using inexpensive electrodeposition setup with an acceptable quality.

  7. Numerical analysis of two-fluid tearing mode instability in a finite aspect ratio cylinder

    Science.gov (United States)

    Ito, Atsushi; Ramos, Jesús J.

    2018-01-01

    The two-fluid resistive tearing mode instability in a periodic plasma cylinder of finite aspect ratio is investigated numerically for parameters such that the cylindrical aspect ratio and two-fluid effects are of order unity, hence the real and imaginary parts of the mode eigenfunctions and growth rate are comparable. Considering a force-free equilibrium, numerical solutions of the complete eigenmode equations for general aspect ratios and ion skin depths are compared and found to be in very good agreement with the corresponding analytic solutions derived by means of the boundary layer theory [A. Ito and J. J. Ramos, Phys. Plasmas 24, 072102 (2017)]. Scaling laws for the growth rate and the real frequency of the mode are derived from the analytic dispersion relation by using Taylor expansions and Padé approximations. The cylindrical finite aspect ratio effect is inferred from the scaling law for the real frequency of the mode.

  8. The Effect of Nano seed Concentration on the Aspect Ratio of Gold Nano rod

    International Nuclear Information System (INIS)

    Sri Nengsih; Akrajas Ali Umar; Muhammad Mat Salleh

    2011-01-01

    This paper reports the synthesis of gold nano rod with controlled aspect ratio prepared by varying the concentration of nano seed addition into the growth solution via the seed mediated growth method. In typical process, the gold nano rod with aspect ratio from ca. 2.2 to 4.2 can be successfully obtained. Owing to its simplicity, the present approach could be used to produce gold nano rod with special properties for SERS and catalyst application. (author)

  9. The black silicon method VI: high aspect ratio trench etching for MEMS applications

    NARCIS (Netherlands)

    Jansen, Henricus V.; de Boer, Meint J.; Elwenspoek, Michael Curt

    1996-01-01

    Etching high aspect ratio trenches (HART's) in silicon is becoming increasingly important for MEMS applications. Currently, the most important technique is dry reactive ion etching (RIE). This paper presents solutions for the most notorious problems during etching HART's: tilting and the aspect

  10. Fabrication of high aspect ratio nanocell lattices by ion beam irradiation

    International Nuclear Information System (INIS)

    Ishikawa, Osamu; Nitta, Noriko; Taniwaki, Masafumi

    2016-01-01

    Highlights: • Nanocell lattice with a high aspect ratio on InSb semiconductor surface was fabricated by ion beam irradiation. • The fabrication technique consisting of top-down and bottom-up processes was performed in FIB. • High aspect ratio of 2 was achieved in nanocell lattice with a 100 nm interval. • The intermediate-flux irradiation is favorable for fabrication of nanocell with a high aspect ratio. - Abstract: A high aspect ratio nanocell lattice was fabricated on the InSb semiconductor surface using the migration of point defects induced by ion beam irradiation. The fabrication technique consisting of the top-down (formation of voids and holes) and bottom-up (growth of voids and holes into nanocells) processes was performed using a focused ion beam (FIB) system. A cell aspect ratio of 2 (cell height/cell diameter) was achieved for the nanocell lattice with a 100 nm dot interval The intermediate-flux ion irradiation during the bottom-up process was found to be optimal for the fabrication of a high aspect ratio nanocell.

  11. Fabrication of high aspect ratio nanocell lattices by ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Osamu [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Nitta, Noriko, E-mail: nitta.noriko@kochi-tech.ac.jp [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Center for Nanotechnology, Research Institute, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Taniwaki, Masafumi [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan)

    2016-11-01

    Highlights: • Nanocell lattice with a high aspect ratio on InSb semiconductor surface was fabricated by ion beam irradiation. • The fabrication technique consisting of top-down and bottom-up processes was performed in FIB. • High aspect ratio of 2 was achieved in nanocell lattice with a 100 nm interval. • The intermediate-flux irradiation is favorable for fabrication of nanocell with a high aspect ratio. - Abstract: A high aspect ratio nanocell lattice was fabricated on the InSb semiconductor surface using the migration of point defects induced by ion beam irradiation. The fabrication technique consisting of the top-down (formation of voids and holes) and bottom-up (growth of voids and holes into nanocells) processes was performed using a focused ion beam (FIB) system. A cell aspect ratio of 2 (cell height/cell diameter) was achieved for the nanocell lattice with a 100 nm dot interval The intermediate-flux ion irradiation during the bottom-up process was found to be optimal for the fabrication of a high aspect ratio nanocell.

  12. Effect of tip vortices on membrane vibration of flexible wings with different aspect ratios

    Directory of Open Access Journals (Sweden)

    Genç Mustafa Serdar

    2016-01-01

    Full Text Available In this study, the effect of the aspect ratio on the aerodynamics characteristic of flexible membrane wings with different aspect ratios (AR = 1 and AR = 3 is experimentally investigated at Reynolds number of 25000. Time accurate measurements of membrane deformation using Digital Image Correlation system (DIC is carried out while normal forces of the wing will be measured by helping a load-cell system and flow on the wing was visualized by means of smoke wire technic. The characteristics of high aspect ratio wings are shown to be affected by leading edge separation bubbles at low Reynolds number. It is concluded that the camber of membrane wing excites the separated shear layer and this situation increases the lift coefficient relatively more as compared to rigid wings. In membrane wings with low aspect ratio, unsteadiness included tip vortices and vortex shedding, and the combination of tip vortices and vortex shedding causes complex unsteady deformations of these membrane wings. The characteristic of high aspect ratio wings was shown to be affected by leading edge separation bubbles at low Reynolds numbers whereas the deformations of flexible wing with low aspect ratio affected by tip vortices and leading edge separation bubbles.

  13. Controlled Aspect Ratios of Gold Nanorods in Reduction-Limited Conditions

    Directory of Open Access Journals (Sweden)

    Jong-Yeob Kim

    2011-01-01

    Full Text Available Aspect ratios of gold nanorods have been finely modified in reduction-limited conditions via two electrochemical ways: by changing the amount of a growth solution containing small gold clusters in the presence of already prepared gold nanorods as seeds or by changing electrolysis time in the presence or absence of a silver plate. While the atomic molar ratio of gold in the growth solution to gold in the seed solution is critical in the former method, the relative molar ratio of gold ions to silver ions in the electrolytic solution is important in the latter way for the control of the aspect ratios of gold nanorods. The aspect ratios of gold nanorods decrease with an increase of electrolysis time in the absence of a silver plate, but they increase with an increase of electrolysis time in the presence of a silver plate.

  14. High-Speed Additive Manufacturing Through High-Aspect-Ratio Nozzles

    Science.gov (United States)

    Shaw, Leon; Islam, Mashfiqul; Li, Jie; Li, Ling; Ayub, S. M. Imran

    2018-01-01

    The feasibility of layer-by-layer manufacturing through high-aspect-ratio (HAR) nozzles for microextrusion of paste to deposit planes has been investigated. Various conditions for paste extrusion, including nozzle moving speed, piston speed, extrusion rate, and distance between the nozzle tip and substrate, have been evaluated. By linking various microextrusion parameters together with the aid of a critical distance concept derived from microextrusion using circular nozzles and addressing the extrusion delay in response to the change of the piston speed and air pocket problems properly, we successfully microextruded single planes, multilayer objects, and larger planes made of multiple smaller planes side by side through HAR nozzles. It is further demonstrated that the X-Y dimensions of an extruded plane in the steady-state extrusion stage are determined by the nozzle travel distance and the length of the HAR nozzle opening if microextrusion is conducted with proper conditions. However, the height of the extruded plane is not only determined by the microextrusion conditions, but also affected by the drying shrinkage of the paste after microextrusion. This demonstration of the feasibility of using a HAR nozzle machine opens the door to manufacture of multimaterial, multilayer devices with high productivity in the near future.

  15. Finite element analysis of high aspect ratio wind tunnel wing model: A parametric study

    Science.gov (United States)

    Rosly, N. A.; Harmin, M. Y.

    2017-12-01

    Procedure for designing the wind tunnel model of a high aspect ratio (HAR) wing containing geometric nonlinearities is described in this paper. The design process begins with identification of basic features of the HAR wing as well as its design constraints. This enables the design space to be narrowed down and consequently, brings ease of convergence towards the design solution. Parametric studies in terms of the spar thickness, the span length and the store diameter are performed using finite element analysis for both undeformed and deformed cases, which respectively demonstrate the linear and nonlinear conditions. Two main criteria are accounted for in the selection of the wing design: the static deflections due to gravitational loading should be within the allowable margin of the size of the wind tunnel test section and the flutter speed of the wing should be much below the maximum speed of the wind tunnel. The findings show that the wing experiences a stiffness hardening effect under the nonlinear static solution and the presence of the store enables significant reduction in linear flutter speed.

  16. High-Speed Additive Manufacturing Through High-Aspect-Ratio Nozzles

    Science.gov (United States)

    Shaw, Leon; Islam, Mashfiqul; Li, Jie; Li, Ling; Ayub, S. M. Imran

    2018-03-01

    The feasibility of layer-by-layer manufacturing through high-aspect-ratio (HAR) nozzles for microextrusion of paste to deposit planes has been investigated. Various conditions for paste extrusion, including nozzle moving speed, piston speed, extrusion rate, and distance between the nozzle tip and substrate, have been evaluated. By linking various microextrusion parameters together with the aid of a critical distance concept derived from microextrusion using circular nozzles and addressing the extrusion delay in response to the change of the piston speed and air pocket problems properly, we successfully microextruded single planes, multilayer objects, and larger planes made of multiple smaller planes side by side through HAR nozzles. It is further demonstrated that the X- Y dimensions of an extruded plane in the steady-state extrusion stage are determined by the nozzle travel distance and the length of the HAR nozzle opening if microextrusion is conducted with proper conditions. However, the height of the extruded plane is not only determined by the microextrusion conditions, but also affected by the drying shrinkage of the paste after microextrusion. This demonstration of the feasibility of using a HAR nozzle machine opens the door to manufacture of multimaterial, multilayer devices with high productivity in the near future.

  17. Finger length ratio (2D:4D) in adults with gender identity disorder.

    Science.gov (United States)

    Kraemer, Bernd; Noll, Thomas; Delsignore, Aba; Milos, Gabriella; Schnyder, Ulrich; Hepp, Urs

    2009-06-01

    From early childhood, gender identity and the 2nd to 4th finger length ratio (2D:4D) are discriminative characteristics between sexes. Both the human brain and 2D:4D may be influenced by prenatal testosterone levels. This calls for an examination of 2D:4D in patients with gender identity disorder (GID) to study the possible influence of prenatal testosterone on gender identity. Until now, the only study carried out on this issue suggests lower prenatal testosterone levels in right-handed male-to-female GID patients (MtF). We compared 2D:4D of 56 GID patients (39 MtF; 17 female-to-male GID patients, FtM) with data from a control sample of 176 men and 190 women. Bivariate group comparisons showed that right hand 2D:4D in MtF was significantly higher (feminized) than in male controls, but similar to female controls. The comparison of 2D:4D ratios of biological women revealed significantly higher (feminized) values for right hands of right handed FtM. Analysis of variance confirmed significant effects for sex and for gender identity on 2D:4D ratios but not for sexual orientation or for the interaction among variables. Our results indirectly point to the possibility of a weak influence of reduced prenatal testosterone as an etiological factor in the multifactorially influenced development of MtF GID. The development of FtM GID seems even more unlikely to be notably influenced by prenatal testosterone.

  18. INCLUSION RATIO BASED ESTIMATOR FOR THE MEAN LENGTH OF THE BOOLEAN LINE SEGMENT MODEL WITH AN APPLICATION TO NANOCRYSTALLINE CELLULOSE

    Directory of Open Access Journals (Sweden)

    Mikko Niilo-Rämä

    2014-06-01

    Full Text Available A novel estimator for estimating the mean length of fibres is proposed for censored data observed in square shaped windows. Instead of observing the fibre lengths, we observe the ratio between the intensity estimates of minus-sampling and plus-sampling. It is well-known that both intensity estimators are biased. In the current work, we derive the ratio of these biases as a function of the mean length assuming a Boolean line segment model with exponentially distributed lengths and uniformly distributed directions. Having the observed ratio of the intensity estimators, the inverse of the derived function is suggested as a new estimator for the mean length. For this estimator, an approximation of its variance is derived. The accuracies of the approximations are evaluated by means of simulation experiments. The novel method is compared to other methods and applied to real-world industrial data from nanocellulose crystalline.

  19. Effects of Aspect Ratio on Water Immersion into Deep Silica Nanoholes.

    Science.gov (United States)

    Zheng, Jing; Zhang, Junqiao; Tan, Lu; Li, Debing; Huang, Liangliang; Wang, Qi; Liu, Yingchun

    2016-08-30

    Understanding the influence of aspect ratio on water immersion into silica nanoholes is of significant importance to the etching process of semiconductor fabrication and other water immersion-related physical and biological processes. In this work, the processes of water immersion into silica nanoholes with different height/width aspect ratios (ϕ = 0.87, 1.92, 2.97, 4.01, 5.06) and different numbers of water molecules (N = 9986, 19972, 29958, 39944) were studied by molecular dynamics simulations. A comprehensive analysis has been conducted about the detailed process of water immersion and the influence of aspect ratios on water immersion rates. Five distinguishable stages were identified for the immersion process with all studied models. The results reveal that water can easily immerse into the silica nanoholes with larger ϕ and smaller N. The calculation also suggests that aspect ratios have a greater effect on water immersion rates for larger N numbers. The mechanism of the water immersion process is discussed in this work. We also propose a mathematical model to correlate the complete water immersion process for different aspect ratios.

  20. Formation of high aspect ratio polyamide-6 nanofibers via electrically induced double layer during electrospinning

    International Nuclear Information System (INIS)

    Nirmala, R.; Nam, Ki Taek; Park, Soo-Jin; Shin, Yu-Shik; Navamathavan, R.; Kim, Hak Yong

    2010-01-01

    In the present study, the formation of high aspect ratio nanofibers in polyamide-6 was investigated as a function of applied voltage ranging from 15 to 25 kV using electrospinning technique. All other experimental parameters were kept constant. The electrospun polyamide-6 nanofibers were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF). FE-SEM images of polyamide-6 nanofibers showed that the diameter of the electrospun fiber was decreased with increasing applied voltage. At the critical applied voltage, the polymer solution was completely ionized to form the dense high aspect ratio nanofibers in between the main nanofibers. The diameter of the polyamide-6 nanofibers was observed to be in the range of 75-110 nm, whereas the high aspect ratio structures consisted of regularly distributed very fine nanofibers with diameters of about 9-28 nm. Trends in fiber diameter and diameter distribution were discussed for the high aspect ratio nanofibers. TEM results revealed that the formation of double layers in polyamide-6 nanofibers and then split-up into ultrafine fibers. The electrically induced double layer in combination with the polyelectrolytic nature of solution is proposed as the suitable mechanisms for the formation of high aspect ratio nanofibers in polyamide-6.

  1. Effect of channel aspect ratio on chemical recuperation process in advanced aeroengines

    International Nuclear Information System (INIS)

    Zhang, Silong; Cui, Naigang; Xiong, Yuefei; Feng, Yu; Qin, Jiang; Bao, Wen

    2017-01-01

    The working process of an advanced aeroengine such as scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative cycle. The design of cooling channel in terms of engine real working conditions is very important for the chemical recuperation process. To study the effects of channel aspect ratio (AR) on chemical recuperation process of advanced aeroengines, three dimensional model of pyrolysis coolant flow inside asymmetrical rectangular cooling channels with fins is introduced and validated through experiments. Cases when AR varies from 1 to 8 are carried out. In the pyrolysis zone of the cooling channel, decreasing the channel aspect ratio can reduce the temperature difference and non-uniformity of fuel conversion in the channel cross section, and it can also increase the final conversion and corresponding chemical heat absorption. A small channel aspect ratio is beneficial for the chemical recuperation process and can guarantee the engine cooling performance in the pyrolysis zone of the cooling channel. - Highlights: • Large non-uniformity of conversion is bad for the chemical recuperation. • Small channel aspect ratio is beneficial for improving the chemical recuperation effectiveness. • Small channel aspect ratio is also beneficial for reducing the engine wall temperature.

  2. Evaluation of a Candidate Trace Contaminant Control Subsystem Architecture: The High Velocity, Low Aspect Ratio (HVLA) Adsorption Process

    Science.gov (United States)

    Kayatin, Matthew J.; Perry, Jay L.

    2017-01-01

    Traditional gas-phase trace contaminant control adsorption process flow is constrained as required to maintain high contaminant single-pass adsorption efficiency. Specifically, the bed superficial velocity is controlled to limit the adsorption mass-transfer zone length relative to the physical adsorption bed; this is aided by traditional high-aspect ratio bed design. Through operation in this manner, most contaminants, including those with relatively high potential energy are readily adsorbed. A consequence of this operational approach, however, is a limited available operational flow margin. By considering a paradigm shift in adsorption architecture design and operations, in which flows of high superficial velocity are treated by low-aspect ratio sorbent beds, the range of well-adsorbed contaminants becomes limited, but the process flow is increased such that contaminant leaks or emerging contaminants of interest may be effectively controlled. To this end, the high velocity, low aspect ratio (HVLA) adsorption process architecture was demonstrated against a trace contaminant load representative of the International Space Station atmosphere. Two HVLA concept packaging designs (linear flow and radial flow) were tested. The performance of each design was evaluated and compared against computer simulation. Utilizing the HVLA process, long and sustained control of heavy organic contaminants was demonstrated.

  3. Large eddy simulation of turbulent flow for wall mounted cantilever cylinders of aspect ratio 6 and 10

    International Nuclear Information System (INIS)

    Afgan, Imran; Moulinec, Charles; Prosser, Robert; Laurence, Dominique

    2007-01-01

    The flow structure around wall mounted circular cylinders of finite heights is numerically investigated via large eddy simulation (LES). The cylinder aspect ratios (AR) are 6 and 10 and the Reynolds number (Re) based on cylinder diameter and free stream velocity is 20,000 for both cases. The cantilever cylinder mounted on a flat plate is chosen since it gives insight into two entirely different flow phenomena; the tip effects of the free end (which show strong three-dimensional wake structures) and the base or junction effects (due to interaction of flow between the cylinder and the flat plate). Regular vortex shedding is found in the wake of the higher aspect ratio case as was anticipated, along with a strong downwash originating from the flow over the free end of the cylinder, whereas irregular and intermittent vortex shedding occurs in the lower aspect ratio case. Pressure distributions are computed along the length of the cylinder and compared to experimental results. Lift and drag values are also computed, along with Strouhal numbers

  4. High aspect ratio silver grid transparent electrodes using UV embossing process

    Science.gov (United States)

    Kim, Dong Jin; Lim, Mikyung; Lee, Seung S.; Kim, Jin-Ha

    2017-10-01

    This study presents a UV embossing process to fabricate high aspect ratio silver grid transparent electrodes on a polymer film. Transparent electrodes with a high optical transmittance (93 %) and low sheet resistance (4.6 Ω/sq) were fabricated without any high temperature or vacuum processes. The strong adhesion force between the UV resin and the silver ink enables the fabrication of silver microstructures with an aspect ratio higher than 3. The high aspect ratio results in a low sheet resistance while maintaining a high optical transmittance. Multi-layer transparent electrodes were fabricated by repeating the proposed UV process. Additionally, a large-area of 8-inch touch panel was fabricated with the proposed UV process. The proposed UV process is a relatively simple and low cost process making it suitable for large-area production as well as mass production.

  5. High aspect ratio silver grid transparent electrodes using UV embossing process

    Directory of Open Access Journals (Sweden)

    Dong Jin Kim

    2017-10-01

    Full Text Available This study presents a UV embossing process to fabricate high aspect ratio silver grid transparent electrodes on a polymer film. Transparent electrodes with a high optical transmittance (93 % and low sheet resistance (4.6 Ω/sq were fabricated without any high temperature or vacuum processes. The strong adhesion force between the UV resin and the silver ink enables the fabrication of silver microstructures with an aspect ratio higher than 3. The high aspect ratio results in a low sheet resistance while maintaining a high optical transmittance. Multi-layer transparent electrodes were fabricated by repeating the proposed UV process. Additionally, a large-area of 8-inch touch panel was fabricated with the proposed UV process. The proposed UV process is a relatively simple and low cost process making it suitable for large-area production as well as mass production.

  6. High aspect ratio PDMS replication through proton beam fabricated Ni masters

    International Nuclear Information System (INIS)

    Kan, J.A. van; Wang, L.P.; Shao, P.G.; Bettiol, A.A.; Watt, F.

    2007-01-01

    In application areas where multiple samples are required (for example tissue engineering substrates), proton beam writing (PBW) is a suitable technique to fabricate high quality metal masters. These masters can then be used to replicate multiple copies in polymers, either through nanoimprinting or softlithography. Since poly(dimethyl siloxane) (PDMS) is a compatible material in tissue engineering we explore PDMS casting on Ni masters as an alternative way to replicate high aspect ratio micro structures. Ni masters with grooves spaced 2.5 μm apart, and 13 μm deep were successfully replicated in PDMS: These PDMS structures, which have aspect ratio of more than 5, are comparable to the best high aspect ratios reported in PDMS replication

  7. SML resist processing for high-aspect-ratio and high-sensitivity electron beam lithography

    Science.gov (United States)

    Mohammad, Mohammad Ali; Dew, Steven K.; Stepanova, Maria

    2013-03-01

    A detailed process characterization of SML electron beam resist for high-aspect-ratio nanopatterning at high sensitivity is presented. SML contrast curves were generated for methyl isobutyl ketone (MIBK), MIBK/isopropyl alcohol (IPA) (1:3), IPA/water (7:3), n-amyl acetate, xylene, and xylene/methanol (3:1) developers. Using IPA/water developer, the sensitivity of SML was improved considerably and found to be comparable to benchmark polymethylmethacrylate (PMMA) resist without affecting the aspect ratio performance. Employing 30-keV exposures and ultrasonic IPA/water development, an aspect ratio of 9:1 in 50-nm half-pitch dense grating patterns was achieved representing a greater than two times improvement over PMMA. Through demonstration of 25-nm lift-off features, the pattern transfer performance of SML is also addressed.

  8. Wave-driver options for low-aspect-ratio steady-state tokamak reactors

    International Nuclear Information System (INIS)

    Ehst, D.A.

    1981-02-01

    Low aspect ratio designs are proposed for steady-state tokamak reactors. Benefits stem from reduced major radius and lessened stresses in the toroidal field coils, resulting in possible cost savings in the tokamak construction. In addition, a low aspect ratio (A = 2.6) permits the application of a bundle divertor capable of diverting 3-T fields to a power reactor using STARFIRE technology. Such a low aspect ratio is possible with the elimination of poloidal field coils in the central hole of the tokamak, which implies a need for noninductive current drive. Several plasma waves are considered for this application, and it appears likely that a candidate can be found which reduces the electric power for current maintenance to an acceptable value

  9. Interaction factors for two elliptical embedded cracks with a wide range of aspect ratios

    Directory of Open Access Journals (Sweden)

    Kisaburo Azuma

    2017-02-01

    Full Text Available The value of stress intensity factor may be increased through the interaction of multiple cracks that are in close proximity to one another. We investigated the interaction factors of two equal elliptical cracks with a wide range of aspect ratios. Finite element analysis for a linear elastic solid was used to obtain the interaction factor for embedded cracks in an infinite model subjected to remote tension loading. Relationships between interaction factors and dimensionless distances between the cracks were discussed. The results demonstrated that the interaction factors depend on the crack aspect ratio, whose effect is related to the dimensionless distance. Thus, it is suggested that interaction factors can be reasonably characterized using different dimensionless distances depending on the aspect ratio. Finally, we provide a simple empirical formula for obtaining the interaction factors for embedded cracks.

  10. Leptothrix sp sheaths modified with iron oxide particles: Magnetically responsive, high aspect ratio functional material

    Czech Academy of Sciences Publication Activity Database

    Šafařík, Ivo; Angelova, R.; Baldíková, Eva; Pospišková, K.; Šafaříková, Miroslava

    2017-01-01

    Roč. 71, FEB (2017), s. 1342-1346 ISSN 0928-4931 R&D Projects: GA ČR(CZ) GA14-11516S; GA MŠk(CZ) LD14075 Institutional support: RVO:67179843 Keywords : removal * Leptothrix * Magnetic modification * Iron oxide * High aspect ratio material Subject RIV: EI - Biotechnology ; Bionics OBOR OECD: Environmental science s (social aspects to be 5.7) Impact factor: 4.164, year: 2016

  11. Non-destructive automatic determination of aspect ratio and cross-sectional properties of fibres

    DEFF Research Database (Denmark)

    Miettinen, Arttu; Ojala, Antti; Wikström, Lisa

    2015-01-01

    A novel method for computerised estimation of the aspect ratio distribution and various cross-sectional geometrical properties of fibres in short-fibre reinforced composites is proposed. The method, based on X-ray micro-computed tomography, is non-destructive and does not require user intervention....... Based on results on specially fabricated model material, the accuracy and precision of the method seems adequate. The method is applied in analysing a manufacturing process of wood fibre reinforced thermoplastic composite. The results indicate a significant decrease of the aspect ratio of fibres during...

  12. Proton beam writing and electroplating for the fabrication of high aspect ratio Au microstructures

    International Nuclear Information System (INIS)

    Yue Weisheng; Ren Yaping; Kan, Jeroen Anton van; Chiam, S.-Y.; Jian, Linke; Moser, Herbert O.; Osipowicz, Thomas; Watt, Frank

    2009-01-01

    We present an approach to fabricate tall high aspect ratio Au microstructures by means of proton beam direct writing. Combining proton beam direct writing and electroplating, we successfully produced gold structures with sub-micrometer lateral dimensions, structure heights in excess of 11 μm, and aspect ratios over 28. Sidewall quality of the Au structures was improved by lowering the process temperature to 20 deg. C when developing PMMA patterns with GG developer. The application of such structures as X-ray masks for deep X-ray lithography with synchrotron radiation was demonstrated.

  13. Dispersion and Polarization of Surface Waves Trapped in High Aspect Ratio Electrode Arrays

    DEFF Research Database (Denmark)

    Laude, Vincent; Dühring, Maria Bayard; Moubchir, Hanane

    2007-01-01

    .Phys., 90(5):2492, 2001; Appl. Phys. Lett., 89:083515, 2006.) an experimental and theoretical analysis of the transduction of SAW under a metallic array of electrodes with a large aspect ratio on a piezoelectric substrate, whereby allowing the electrode height to become larger than one wavelength...... additional results on the polarization and the dispersion of the surface waves trapped by high aspect ratio electrode arrays. A finite element model, including periodic boundary conditions along the propagation direction and a perfectly matched layer (PML) to absorb waves away from the surface...... wave vector values....

  14. Finger length ratio (2D:4D) and dimensions of sexual orientation.

    Science.gov (United States)

    Kraemer, Bernd; Noll, Thomas; Delsignore, Aba; Milos, Gabriella; Schnyder, Ulrich; Hepp, Urs

    2006-01-01

    It has been suggested that both adult sexual orientation and the 2nd to 4th finger length ratio (2D:4D) are influenced by prenatal testosterone levels. Bearing this in mind, 2D:4D has been tested as a proxy measure of the putative prenatal testosterone impact on adult human homosexuality, but the results are inconsistent. To date, most studies in this field of research comprise categorical group comparison of heterosexuals and homosexuals with respect to their 2D:4D. The purpose of our study was to evaluate 2D:4D and the dimensional perspective of sexual orientation in addition to categorical results. We examined a community-based sample of 409 subjects and calculated correlations of 2D:4D and sexual orientation as a continuum ranging from homosexual to heterosexual. We found a significant negative correlation of 2D:4D with homosexual orientation (fantasy, attraction, activity and general score) in women, but not in men. Our results indicate that with higher prenatal testosterone levels in women, the likelihood of homosexual orientation might increase. We hypothesize a continuous neurohormonal sexual differentiation of the brain, most notably for women, that overrides categories and results in varying dimensions of sexual orientation. This hypothesis contrasts with the predominant suggestion of fixed organizational effects of androgens in the brain and a categorical sexual orientation.

  15. Experiments on a low aspect ratio wing at low Reynolds numbers

    Science.gov (United States)

    Morse, Daniel R.

    At the start of the 21st century much of the focus of aircraft design has been turned to unmanned aerial vehicles (UAVs) which generally operate at much lower speeds in higher risk areas than manned aircraft. One subset of UAVs are Micro Air Vehicles (MAVs) which usually are no larger than 20cm and rely on non-traditional shapes to generate lift at very low velocities. This purpose of this work is to describe, in detail with experimental methods, the flow field around a low aspect ratio wing operating at low Reynolds numbers and at high angles of attack. Quantitative measurements are obtained by Three Component Time Resolved Particle Image Velocimetry (3C TR PIV) which describe the mean and turbulent flow field. This research focuses on the leading edge separation zone and the vortex shedding process which occurs at the leading edge. Streamwise wing tip vortices which dominate the lift characteristics are described with flow visualization and 3C TR PIV measurements. Turbulent Kinetic Energy (TKE) is described at the leading edge over several angles of attack. Turbulent Reynolds stresses in all three directions are described over the wing span and several Reynolds numbers. Two primary cyclic processes are observed within the flow field; one low frequency oscillation in the separated region and one high frequency event associated with leading edge vortex formation and convection. Two length scales are proposed and are shown to match well with each other, one based on leading edge vortex shedding frequency and convective velocity and the other based on mean vortex separation distance. A new method of rendering velocity frequency content over large data sets is proposed and used to illustrate the different frequencies observed at the leading edge.

  16. Numerical Simulations of Noise Generated by High Aspect Ratio Supersonic Rectangular Jets - Validation

    Science.gov (United States)

    Viswanath, Kamal; Johnson, Ryan; Kailasanath, Kailas; Malla, Bhupatindra; Gutmark, Ephraim

    2017-11-01

    The noise from high performance jet engines of both civilian and military aircraft is an area of active concern. Asymmetric exhaust nozzle configurations, in particular rectangular, potentially offer a passive way of modulating the farfield noise and are likely to become more important in the future. High aspect ratio nozzles offer the further benefit of easier airframe integration. In this study we validate the far field noise for ideally and over expanded supersonic jets issuing from a high aspect ratio rectangular nozzle geometry. Validation of the acoustic data is performed against experimentally recorded sound pressure level (SPL) spectra for a host of observer locations around the asymmetric nozzle. Data is presented for a slightly heated jet case for both nozzle pressure ratios. The contrast in the noise profile from low aspect ratio rectangular and circular nozzle jets are highlighted, especially the variation in the azimuthal direction that shows ``quiet'' and ``loud'' planes in the farfield in the peak noise direction. This variation is analyzed in the context of the effect of mixing at the sharp corners, the sense of the vortex pairs setup in the exit plane, and the evolution of the high aspect ratio exit cross-section as it propagates downstream including possible axis-switching. Supported by Office of Naval Research (ONR) through the Computational Physics Task Area under the NRL 6.1 Base Program.

  17. Nonlinear Large Deflection Theory with Modified Aeroelastic Lifting Line Aerodynamics for a High Aspect Ratio Flexible Wing

    Science.gov (United States)

    Nguyen, Nhan; Ting, Eric; Chaparro, Daniel

    2017-01-01

    This paper investigates the effect of nonlinear large deflection bending on the aerodynamic performance of a high aspect ratio flexible wing. A set of nonlinear static aeroelastic equations are derived for the large bending deflection of a high aspect ratio wing structure. An analysis is conducted to compare the nonlinear bending theory with the linear bending theory. The results show that the nonlinear bending theory is length-preserving whereas the linear bending theory causes a non-physical effect of lengthening the wing structure under the no axial load condition. A modified lifting line theory is developed to compute the lift and drag coefficients of a wing structure undergoing a large bending deflection. The lift and drag coefficients are more accurately estimated by the nonlinear bending theory due to its length-preserving property. The nonlinear bending theory yields lower lift and span efficiency than the linear bending theory. A coupled aerodynamic-nonlinear finite element model is developed to implement the nonlinear bending theory for a Common Research Model (CRM) flexible wing wind tunnel model to be tested in the University of Washington Aeronautical Laboratory (UWAL). The structural stiffness of the model is designed to give about 10% wing tip deflection which is large enough that could cause the nonlinear deflection effect to become significant. The computational results show that the nonlinear bending theory yields slightly less lift than the linear bending theory for this wind tunnel model. As a result, the linear bending theory is deemed adequate for the CRM wind tunnel model.

  18. Effect of asymmetrical street aspect ratios on microclimates in hot, humid regions

    Science.gov (United States)

    Qaid, Adeb; Ossen, Dilshan R.

    2015-06-01

    Asymmetrical street aspect ratios, i.e. different height-to-width (H1/W-H2/W) ratios, have not received much attention in the study of urban climates. Putrajaya Boulevard (northeast to southwest orientation) in Malaysia was selected to study the influence of six asymmetrical aspect ratio scenarios on the street microclimate using the Envi-met three-dimensional microclimate model (V3.1 Beta). Putrajaya Boulevard suffers from high surface and air temperature during the day due to the orientation, the low aspect ratio and the wide sky view factor. These issues are a common dilemma in many boulevards. Further, low and high symmetrical streets are incompatible with tropical regions as they offer conflicting properties during the day and at night. These scenarios are examined, therefore, to find asymmetrical streets which are able to reduce the impact of the day microclimate on boulevards, and as an alternative strategy fulfilling tropical day and night climatic conditions. Asymmetrical streets are better than low symmetrical streets in enhancing wind flow and blocking solar radiation, when tall buildings confront winds direction or solar altitudes. Therefore, mitigating heat islands or improving microclimates in asymmetrical streets based on tall buildings position which captures wind or caste shades. In northeast to southwest direction, aspect ratios of 0.8-2 reduce the morning microclimate and night heat islands yet the negative effects during the day are greater than the positive effects in the night. An aspect ratio of 2-0.8 reduces the temperature of surfaces by 10 to 14 °C and the air by 4.7 °C, recommended for enhancing boulevard microclimates and mitigating tropical heat islands.

  19. Finite element analysis of surface acoustic waves in high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Laude, Vincent; Khelif, Abdelkrim

    2008-01-01

    This paper elaborates on how the finite element method is employed to model surface acoustic waves generated by high aspect ratio electrodes and their interaction with optical waves in a waveguide. With a periodic model it is shown that these electrodes act as a mechanical resonator which slows d...

  20. Improving surface acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Laude, Vincent; Khelif, Abdelkrim

    2009-01-01

    The acousto-optical interaction of an optical wave confined inside a waveguide and a surface acoustic wave launched by an interdigital transducer (IDT) at the surface of a piezoelectric material is considered. The IDT with high aspect ratio electrodes supports several acoustic modes...

  1. Key Techniques on Preparing High Aspect Ratio Micro and Nano Structures

    DEFF Research Database (Denmark)

    Jian, Zhao; Lianhe, Dong; Xiaoli, Zhu

    2016-01-01

    effectively. The mechanism of action between NaCl and HSQ was analyzed. The collapse and adhesion of resist structure due to the effect of gas-liquid interfacial capillary surface tension were suppressed by the CO2 supercritical drying method. Large-area dense nano-structures with the aspect ratio of 12...

  2. A Novel Demountable TF Joint Design for Low Aspect Ratio Spherical Torus Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    R.D. Woolley

    2009-05-29

    A novel shaped design for the radial conductors and demountable electrical joints connecting inner and outer legs of copper TF system conductors in low aspect ratio tokamaks is described and analysis results are presented. Specially shaped designs can optimize profiles of electrical current density, magnetic force, heating, and mechanical stress.

  3. A Novel Demountable TF Joint Design for Low Aspect Ratio Spherical Torus Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Robert D. Woolley

    2009-06-11

    A novel shaped design for the radial conductors and demountable electrical joints connecting inner and outer legs of copper TF system conductors in low aspect ratio tokamaks is described and analysis results are presented. Specially shaped designs can optimize profiles of electrical current density, magnetic force, heating, and mechanical stress.

  4. ASPECT RATIO DEPENDENCE OF THE FREE-FALL TIME FOR NON-SPHERICAL SYMMETRIES

    International Nuclear Information System (INIS)

    Pon, Andy; Johnstone, Doug; Toalá, Jesús A.; Vázquez-Semadeni, Enrique; Gómez, Gilberto C.; Heitsch, Fabian

    2012-01-01

    We investigate the collapse of non-spherical substructures, such as sheets and filaments, which are ubiquitous in molecular clouds. Such non-spherical substructures collapse homologously in their interiors but are influenced by an edge effect that causes their edges to be preferentially accelerated. We analytically compute the homologous collapse timescales of the interiors of uniform-density, self-gravitating filaments and find that the homologous collapse timescale scales linearly with the aspect ratio. The characteristic timescale for an edge-driven collapse mode in a filament, however, is shown to have a square-root dependence on the aspect ratio. For both filaments and circular sheets, we find that selective edge acceleration becomes more important with increasing aspect ratio. In general, we find that lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. We show that estimates for star formation rates, based upon gas densities, can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.

  5. SIP Shear Walls: Cyclic Performance of High-Aspect-Ratio Segments and Perforated Walls

    Science.gov (United States)

    Vladimir Kochkin; Douglas R. Rammer; Kevin Kauffman; Thomas Wiliamson; Robert J. Ross

    2015-01-01

    Increasing stringency of energy codes and the growing market demand for more energy efficient buildings gives structural insulated panel (SIP) construction an opportunity to increase its use in commercial and residential buildings. However, shear wall aspect ratio limitations and lack of knowledge on how to design SIPs with window and door openings are barriers to the...

  6. Leptothrix sp sheaths modified with iron oxide particles: Magnetically responsive, high aspect ratio functional material

    Czech Academy of Sciences Publication Activity Database

    Šafařík, Ivo; Angelova, R.; Baldíková, E.; Pospíšková, K.; Šafaříková, Miroslava

    2017-01-01

    Roč. 71, February (2017), s. 1342-1346 ISSN 0928-4931 Institutional support: RVO:60077344 Keywords : Leptothrix * magnetic modification * iron oxide * high aspect ratio material Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Material s engineering Impact factor: 4.164, year: 2016

  7. THE EFFECTS OF ASPECT RATIO AND INITIAL IMPERFECTION SHAPE ON THE UNIAXIAL PLATE STRENGTH

    Directory of Open Access Journals (Sweden)

    Numan Behlül BEKTAŞ

    1999-01-01

    Full Text Available This study is concerned with the imperfection and aspect-ratio sensitivity of the uniaxial strength of rectangular steel plates. To investigate the imperfection and aspect ratio sensitivity of the uniaxial strength of rectangular plates, over 90 different plate problems have been modelled and solved by using the user-element in ANSYS 5.0 which is a commercial finite element package. The user-element which is offered by ANSYS 5.0 as an extension of the element library, is used to implement subroutines written for analysing large deflection elastic-perfectlyplastic material behaviour of plates by using finite element method. The results obtained for each plate problem have been presented in figures. The maximum average strength of plates have been obtained for the different aspect ratios, the initial geometric imperfection modes and the complex initial geometric imperfections, achieved by combination of these modes. The levels of initial geometric imperfections are assumed as found in the literature. The effects of complex initial geometric imperfections and aspect ratios on plate strength for various modes have been determined. The combination of initial imperfection modes creates new geometrical imperfections and magnitudes, generally higher than previous values. These factors are shown to effect the plate by reducing its strength. The results obtained can help to design the rectangular plates and plated structures under uniaxial compression.

  8. Ultra-high aspect ratio replaceable AFM tips using deformation-suppressed focused ion beam milling

    DEFF Research Database (Denmark)

    Savenko, Alexey; Yildiz, Izzet; Petersen, Dirch Hjorth

    2013-01-01

    in terms of defining the shape and size of the tip. Due to beam-induced deformation, it has so far not been possible to define HAR structures using lateral FIB milling. In this work we obtain aspect ratios of up to 45, with tip diameters down to 9 nm, by a deformation-suppressing writing strategy. Several...

  9. Hummingbird wing efficacy depends on aspect ratio and compares with helicopter rotors

    NARCIS (Netherlands)

    Kruyt, J.W.; Quicazan Rubio, E.M.; Heijst, van G.J.F.; Altshuler, D.L.; Lentink, D.

    2014-01-01

    Hummingbirds are the only birds that can sustain hovering. This unique flight behaviour comes, however, at high energetic cost. Based on helicopter and aeroplane design theory, we expect that hummingbird wing aspect ratio (AR), which ranges from about 3.0 to 4.5, determines aerodynamic efficacy.

  10. A Novel Demountable TF Joint Design for Low Aspect Ratio Spherical Torus Tokamaks

    International Nuclear Information System (INIS)

    Woolley, R.D.

    2009-01-01

    A novel shaped design for the radial conductors and demountable electrical joints connecting inner and outer legs of copper TF system conductors in low aspect ratio tokamaks is described and analysis results are presented. Specially shaped designs can optimize profiles of electrical current density, magnetic force, heating, and mechanical stress

  11. A Novel Demountable TF Joint Design for Low Aspect Ratio Spherical Torus Tokamaks

    International Nuclear Information System (INIS)

    Woolley, Robert D.

    2009-01-01

    A novel shaped design for the radial conductors and demountable electrical joints connecting inner and outer legs of copper TF system conductors in low aspect ratio tokamaks is described and analysis results are presented. Specially shaped designs can optimize profiles of electrical current density, magnetic force, heating, and mechanical stress.

  12. Lee-side flow structures of very low aspect ratio cruciform wing–body configurations

    CSIR Research Space (South Africa)

    Tuling, S

    2013-12-01

    Full Text Available OF SPACECRAFT AND ROCKETS Vol. 50, No. 6, November–December 2013 Lee-Side Flow Structures of Very Low Aspect Ratio Cruciform Wing–Body Configurations S. Tuling∗ Council for Scientific and Industrial Research, Pretoria 0001, South Africa L. Dala...

  13. Study of blade aspect ratio on a compressor front stage aerodynamic and mechanical design report

    Science.gov (United States)

    Burger, G. D.; Lee, D.; Snow, D. W.

    1979-01-01

    A single stage compressor was designed with the intent of demonstrating that, for a tip speed and hub-tip ratio typical of an advanced core compressor front stage, the use of low aspect ratio can permit high levels of blade loading to be achieved at an acceptable level of efficiency. The design pressure ratio is 1.8 at an adiabatic efficiency of 88.5 percent. Both rotor and stator have multiple-circular-arc airfoil sections. Variable IGV and stator vanes permit low speed matching adjustments. The design incorporates an inlet duct representative of an engine transition duct between fan and high pressure compressor.

  14. Applications of the scoliosis width-to-length ratio for guiding selection of the surgical approaches of degenerative lumbar scoliosis.

    Science.gov (United States)

    Jiang, Chuan-jie; Yang, Yong-jun; Zhou, Ji-ping; Yao, Shu-qiang; Yang, Kai; Wu, Rui; Tan, Yuan-chao

    2016-02-01

    There does not exist a comprehensive parameter for guiding selection of short or long segment fusion for degenerative lumbar scoliosis (DLS). The aim of our study was to investigate the applications of the width-to-length ratio in guiding selection of the surgical approaches for DLS. A retrospective analysis was performed of 142 patients with DLS who underwent operative treatments from July 2000 to January 2012. The scoliosis width-to-length ratios were measured and used as a grouping criterion of surgical approaches. The Oswestry disability index (ODI) was used to evaluate the clinical outcomes. Radiological parameters such as Cobb's angle of main curve, Cobb's angle of compensatory curve were all measured. For patients with width-to-length ratio less than 0.36, the short segment group had better short-term postoperative outcomes with regard to Cobb's angle of main curve, Cobb's angle of compensatory curve and ODI scores compared to the long segment group. However, for patients with width-to-length ratio greater than 0.36, the postoperative outcomes for the long segment group were better compared to the short segment group. The scoliosis width-to-length ratio can provide a comprehensive preoperative assessment of the severity of the DLS and guiding selection of a therapeutic treatment regimen. Further studies with a larger number of samples and longer term of follow up are warranted.

  15. On current drive by Ohkawa mechanism of electron cyclotron wave in large inverse aspect ratio tokamaks

    Science.gov (United States)

    Zheng, Pingwei; Gong, Xueyu; Lu, Xingqiang; He, Lihua; Cao, Jingjia; Huang, Qianhong; Deng, Sheng

    2018-03-01

    A localized and efficient current drive method in the outer-half region of the tokamak with a large inverse aspect ratio is proposed via the Ohkawa mechanism of electron cyclotron (EC) waves. Further off-axis Ohkawa current drive (OKCD) via EC waves was investigated in high electron beta β e HL-2M-like tokamaks with a large inverse aspect ratio, and in EAST-like tokamaks with a low inverse aspect ratio. OKCD can be driven efficiently, and the driven current profile is spatially localized in the radial region, ranging from 0.62 to 0.85, where the large fraction of trapped electrons provides an excellent advantage for OKCD. Furthermore, the current drive efficiency increases with an increase in minor radius, and then drops when the minor radius beyond a certain value. The effect of trapped electrons greatly enhances the current driving capability of the OKCD mechanism. The highest current drive efficiency can reach 0.183 by adjusting the steering mirror to change the toroidal and poloidal incident angle, and the total driven current by OKCD can reach 20–32 kA MW‑1 in HL-2M-like tokamaks. The current drive is less efficient for the EAST-like scenario due to the lower inverse aspect ratio. The results show that OKCD may be a valuable alternative current drive method in large inverse aspect ratio tokamaks, and the potential capabilities of OKCD can be used to suppress some important magnetohydrodynamics instabilities in the far off-axis region.

  16. A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials

    Directory of Open Access Journals (Sweden)

    Hurt Robert H

    2011-05-01

    Full Text Available Abstract Background The most common causes of granulomatous inflammation are persistent pathogens and poorly-degradable irritating materials. A characteristic pathological reaction to intratracheal instillation, pharyngeal aspiration, or inhalation of carbon nanotubes is formation of epithelioid granulomas accompanied by interstitial fibrosis in the lungs. In the mesothelium, a similar response is induced by high aspect ratio nanomaterials, including asbestos fibers, following intraperitoneal injection. This asbestos-like behaviour of some engineered nanomaterials is a concern for their potential adverse health effects in the lungs and mesothelium. We hypothesize that high aspect ratio nanomaterials will induce epithelioid granulomas in nonadherent macrophages in 3D cultures. Results Carbon black particles (Printex 90 and crocidolite asbestos fibers were used as well-characterized reference materials and compared with three commercial samples of multiwalled carbon nanotubes (MWCNTs. Doses were identified in 2D and 3D cultures in order to minimize acute toxicity and to reflect realistic occupational exposures in humans and in previous inhalation studies in rodents. Under serum-free conditions, exposure of nonadherent primary murine bone marrow-derived macrophages to 0.5 μg/ml (0.38 μg/cm2 of crocidolite asbestos fibers or MWCNTs, but not carbon black, induced macrophage differentiation into epithelioid cells and formation of stable aggregates with the characteristic morphology of granulomas. Formation of multinucleated giant cells was also induced by asbestos fibers or MWCNTs in this 3D in vitro model. After 7-14 days, macrophages exposed to high aspect ratio nanomaterials co-expressed proinflammatory (M1 as well as profibrotic (M2 phenotypic markers. Conclusions Induction of epithelioid granulomas appears to correlate with high aspect ratio and complex 3D structure of carbon nanotubes, not with their iron content or surface area. This model

  17. Different methods to alter surface morphology of high aspect ratio structures

    Energy Technology Data Exchange (ETDEWEB)

    Leber, M., E-mail: moritz.leber@utah.edu [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Shandhi, M.M.H. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Hogan, A. [Blackrock Microsystems, Salt Lake City, UT (United States); Solzbacher, F. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Bhandari, R.; Negi, S. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Blackrock Microsystems, Salt Lake City, UT (United States)

    2016-03-01

    Graphical abstract: Surface engineering of high aspect ratio silicon structures. - Highlights: • Multiple roughening techniques for high aspect ratio devices were investigated. • Modification of surface morphology of high aspect ratio silicon devices (1:15). • Decrease of 76% in impedance proves significant increase in surface area. - Abstract: In various applications such as neural prostheses or solar cells, there is a need to alter the surface morphology of high aspect ratio structures so that the real surface area is greater than geometrical area. The change in surface morphology enhances the devices functionality. One of the applications of altering the surface morphology is of neural implants such as the Utah electrode array (UEA) that communicate with single neurons by charge injection induced stimulation or by recording electrical neural signals. For high selectivity between single cells of the nervous system, the electrode surface area is required to be as small as possible, while the impedance is required to be as low as possible for good signal to noise ratios (SNR) during neural recording. For stimulation, high charge injection and charge transfer capacities of the electrodes are required, which increase with the electrode surface. Traditionally, researchers have worked with either increasing the roughness of the existing metallization (platinum grey, black) or other materials such as Iridium Oxide and PEDOT. All of these previously investigated methods lead to more complicated metal deposition processes that are difficult to control and often have a critical impact on the mechanical properties of the metal films. Therefore, a modification of the surface underneath the electrode's coating will increase its surface area while maintaining the standard and well controlled metal deposition process. In this work, the surfaces of the silicon micro-needles were engineered by creating a defined microstructure on the electrodes surface using several

  18. Analyses of length and age distributions using continuation-ratio logits

    DEFF Research Database (Denmark)

    Rindorf, Anna; Lewy, Peter

    2001-01-01

    allows statistical testing of the effects of both continuous and discrete variables. Further, by utilising the smoothness of length and age distributions as a function of length, the method provides more accurate estimates of these distributions than traditional methods. The observations are assumed...... to be multinomially distributed, but cases in which the variance exceeds that of this distribution may also be analysed. The implementation of the method in existing statistical analysis software is straightforward and is demonstrated using length and age distributions of the lesser sandeel, Ammodytes marinus Raitt...

  19. Wakes behind surface-mounted obstacles: Impact of aspect ratio, incident angle, and surface roughness

    Science.gov (United States)

    Tobin, Nicolas; Chamorro, Leonardo P.

    2018-03-01

    The so-called wake-moment coefficient C˜h and lateral wake deflection of three-dimensional windbreaks are explored in the near and far wake. Wind-tunnel experiments were performed to study the functional dependence of C˜h with windbreak aspect ratio, incidence angle, and the ratio of the windbreak height and surface roughness (h /z0 ). Supported with the data, we also propose basic models for the wake deflection of the windbreak in the near and far fields. The near-wake model is based on momentum conservation considering the drag on the windbreak, whereas the far-wake counterpart is based on existing models for wakes behind surface-mounted obstacles. Results show that C˜h does not change with windbreak aspect ratios of 10 or greater; however, it may be lower for an aspect ratio of 5. C˜h is found to change roughly with the cosine of the incidence angle, and to depend strongly on h /z0 . The data broadly support the proposed wake-deflection models, though better predictions could be made with improved knowledge of the windbreak drag coefficient.

  20. Walk Ratio (Step Length/Cadence) as a Summary Index of Neuromotor Control of Gait: Application to Multiple Sclerosis

    Science.gov (United States)

    Rota, Viviana; Perucca, Laura; Simone, Anna; Tesio, Luigi

    2011-01-01

    In healthy adults, the step length/cadence ratio [walk ratio (WR) in mm/(steps/min) and normalized for height] is known to be constant around 6.5 mm/(step/min). It is a speed-independent index of the overall neuromotor gait control, in as much as it reflects energy expenditure, balance, between-step variability, and attentional demand. The speed…

  1. Jet-Surface Interaction - High Aspect Ratio Nozzle Test: Test Summary

    Science.gov (United States)

    Brown, Clifford A.

    2016-01-01

    The Jet-Surface Interaction High Aspect Ratio Nozzle Test was conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center in the fall of 2015. There were four primary goals specified for this test: (1) extend the current noise database for rectangular nozzles to higher aspect ratios, (2) verify data previously acquired at small-scale with data from a larger model, (3) acquired jet-surface interaction noise data suitable for creating verifying empirical noise models and (4) investigate the effect of nozzle septa on the jet-mixing and jet-surface interaction noise. These slides give a summary of the test with representative results for each goal.

  2. The effect of particle aspect ratio on the electroelastic properties of piezoelectric nanocomposites

    International Nuclear Information System (INIS)

    Andrews, C; Lin, Y; Sodano, H A

    2010-01-01

    Piezoelectric materials offer exceptional sensing and actuation properties; however, they are prone to breakage and difficult to apply on curved surfaces in their monolithic form. One method of alleviating these issues is through the use of 0–3 nanocomposites, which are formed by embedding piezoelectric particles into a polymer matrix. Material of this class offers certain advantages over monolithic materials; however, it has seen little use due to its low coupling. Here we develop micromechanics and finite element models to study the electroelastic properties of an active nanocomposite, as a function of the aspect ratio and alignment of the piezoelectric filler. Our results show that the aspect ratio is critical for achieving high electromechanical coupling, and with an increase from 1 to 10 at 30% volume fraction of piezoelectric filler the coupling can increase to 60 times its initial value and achieve a bulk composite coupling as high as 90% for a pure PZT-7A piezoelectric constituent

  3. Azimuthal instabilities and mixing characteristics of a small aspect ratio slot jet

    International Nuclear Information System (INIS)

    Gutmark, E.; Schadow, K.C.

    1987-01-01

    Two types of small aspect ratio slot jets were investigated. An orifice slot jet with a 3:1 aspect ratio was shown to have features similar to an elliptical jet with a well-designed contraction. A large spreading rate and highly turbulent mixing can be obtained using this orifice nozzle, which is advantageous for many practical applications. By adding a conical contraction to the slot jet (tapered slot jet) the characteristics were totally altered. The intersection between the contraction and the slot surface produced three dimensional vortical structures. These structures acted with the high modes of azimuthal instabilities, typical to this noncircular configuration, to produce highly efficient mixing in both the outside and inside segments of the jet. 10 references

  4. Comments on the asymptotic treatment of tokamak MHD-stability at large aspect ratio

    International Nuclear Information System (INIS)

    Rebhan, E.

    1980-01-01

    In the asymptotic treatment of tokamak MHD stability at small inverse aspect ratio epsilon, the special case of poloidal wave number m=0 has been treated improperly in the literature for both axisymmetric and non-axisymmetric modes. In axisymmetric stability, a contribution to the perturbational vacuum field is either omitted or cancelled. In a variational stability analysis this field contribution provides σ 2 W with a correction term proportional to (1nepsilon) -1 , which may change the asymptotic range of stability and improve agreement with numerical finite-aspect-ratio results. In non-axisymmetric stability, for the perturbational vacuum field of the m=0 modes, usually the wrong of two possible solutions is chosen. It is shown why in many cases this wrong choice has no consequences on the correctness of the stability results, and circumstances are pointed out under which consequences may arise. (author)

  5. Hybrid UV Lithography for 3D High-Aspect-Ratio Microstructures

    International Nuclear Information System (INIS)

    Park, Sungmin; Nam, Gyungmok; Kim, Jonghun; Yoon, Sang-Hee

    2016-01-01

    Three-dimensional (3D) high-aspect-ratio (HAR) microstructures for biomedical applications (e.g., microneedle, microadhesive, etc.) are microfabricated using the hybrid ultraviolet (UV) lithography in which inclined, rotational, and reverse-side UV exposure processes are combined together. The inclined and rotational UV exposure processes are intended to fabricate tapered axisymmetric HAR microstructures; the reverse-side UV exposure process is designed to sharpen the end tip of the microstructures by suppressing the UV reflection on a bottom substrate which is inevitable in conventional UV lithography. Hybrid UV lithography involves fabricating 3D HAR microstructures with an epoxy-based negative photoresist, SU-8, using our customized UV exposure system. The effects of hybrid UV lithography parameters on the geometry of the 3D HAR microstructures (aspect ratio, radius of curvature of the end tip, etc.) are measured. The dependence of the end-tip shape on SU-8 soft-baking condition is also discussed

  6. High Yield Synthesis of Aspect Ratio Controlled Graphenic Materials from Anthracite Coal in Supercritical Fluids.

    Science.gov (United States)

    Sasikala, Suchithra Padmajan; Henry, Lucile; Yesilbag Tonga, Gulen; Huang, Kai; Das, Riddha; Giroire, Baptiste; Marre, Samuel; Rotello, Vincent M; Penicaud, Alain; Poulin, Philippe; Aymonier, Cyril

    2016-05-24

    This paper rationalizes the green and scalable synthesis of graphenic materials of different aspect ratios using anthracite coal as a single source material under different supercritical environments. Single layer, monodisperse graphene oxide quantum dots (GQDs) are obtained at high yield (55 wt %) from anthracite coal in supercritical water. The obtained GQDs are ∼3 nm in lateral size and display a high fluorescence quantum yield of 28%. They show high cell viability and are readily used for imaging cancer cells. In an analogous experiment, high aspect ratio graphenic materials with ribbon-like morphology (GRs) are synthesized from the same source material in supercritical ethanol at a yield of 6.4 wt %. A thin film of GRs with 68% transparency shows a surface resistance of 9.3 kΩ/sq. This is apparently the demonstration of anthracite coal as a source for electrically conductive graphenic materials.

  7. Transmutation of nuclear waste with a low-aspect-ratio Tokamak neutron source

    International Nuclear Information System (INIS)

    Hong, Bong Guen; Moon, Se Youn

    2014-01-01

    The transmutation characteristics of transuranics (TRUs) in a transmutation reactor based on a LAR (Low-aspect-ratio) tokamak as a neutron source are investigated. The optimum radial build of a transmutation reactor is found by using a coupled analysis of the tokamak systems and the neutron transport. The dependences of the transmutation characteristics on the aspect ratio A in the range of 1.5 to 2.5 and on the fusion power in the range of 150 to 500 MW are investigated. An equilibrium fuel cycle is developed for effective transmutation, and show that with one unit of the transmutation reactor based on the LAR tokamak producing fusion power in the range of a few hundred MWs, up to 3 PWRs (1.0 GWe capacity) can be supported with a burn-up fraction larger than 50%.

  8. Hybrid UV Lithography for 3D High-Aspect-Ratio Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sungmin; Nam, Gyungmok; Kim, Jonghun; Yoon, Sang-Hee [Inha Univ, Incheon (Korea, Republic of)

    2016-08-15

    Three-dimensional (3D) high-aspect-ratio (HAR) microstructures for biomedical applications (e.g., microneedle, microadhesive, etc.) are microfabricated using the hybrid ultraviolet (UV) lithography in which inclined, rotational, and reverse-side UV exposure processes are combined together. The inclined and rotational UV exposure processes are intended to fabricate tapered axisymmetric HAR microstructures; the reverse-side UV exposure process is designed to sharpen the end tip of the microstructures by suppressing the UV reflection on a bottom substrate which is inevitable in conventional UV lithography. Hybrid UV lithography involves fabricating 3D HAR microstructures with an epoxy-based negative photoresist, SU-8, using our customized UV exposure system. The effects of hybrid UV lithography parameters on the geometry of the 3D HAR microstructures (aspect ratio, radius of curvature of the end tip, etc.) are measured. The dependence of the end-tip shape on SU-8 soft-baking condition is also discussed.

  9. Fabrication of High Aspect Ratio SU-8 Structures for Integrated Spectrometers

    DEFF Research Database (Denmark)

    Anhøj, Thomas Aarøe

    2007-01-01

    This dissertation deals with the fabrication of integrated spectrometers for use in miniaturized chemical analysis systems, also called 'lab-on-a-chip'-systems. The spectrometers are based on concave re ection gratings, and are fabricated in the epoxy-based material SU-8 by means...... of photolithography. Successful fabrication of re ection gratings requires a high degree of precision in the photolithographic process. The fabrication process has thus been optimized by optimizing the photolithographic process for fabrication of high aspect ratio structures, i.e. structures with details...... of the photolithographic SU-8 fabrication process has caused the aspect ratio of the narrowest resolvable trench to rise from approximately 6 to 11.4. Simultaneously, the optimized process eliminates all problems regarding cracks in the fabricated structures. If the fabrication of the re ection grating is not perfect...

  10. Jet-Surface Interaction: High Aspect Ratio Nozzle Test, Nozzle Design and Preliminary Data

    Science.gov (United States)

    Brown, Clifford; Dippold, Vance

    2015-01-01

    The Jet-Surface Interaction High Aspect Ratio (JSI-HAR) nozzle test is part of an ongoing effort to measure and predict the noise created when an aircraft engine exhausts close to an airframe surface. The JSI-HAR test is focused on parameters derived from the Turbo-electric Distributed Propulsion (TeDP) concept aircraft which include a high-aspect ratio mailslot exhaust nozzle, internal septa, and an aft deck. The size and mass flow rate limits of the test rig also limited the test nozzle to a 16:1 aspect ratio, half the approximately 32:1 on the TeDP concept. Also, unlike the aircraft, the test nozzle must transition from a single round duct on the High Flow Jet Exit Rig, located in the AeroAcoustic Propulsion Laboratory at the NASA Glenn Research Center, to the rectangular shape at the nozzle exit. A parametric nozzle design method was developed to design three low noise round-to-rectangular transitions, with 8:1, 12:1, and 16: aspect ratios, that minimizes flow separations and shocks while providing a flat flow profile at the nozzle exit. These designs validated using the WIND-US CFD code. A preliminary analysis of the test data shows that the actual flow profile is close to that predicted and that the noise results appear consistent with data from previous, smaller scale, tests. The JSI-HAR test is ongoing through October 2015. The results shown in the presentation are intended to provide an overview of the test and a first look at the preliminary results.

  11. Concept definition of KT-2, a large-aspect-ratio diverter tokamak with FWCD

    International Nuclear Information System (INIS)

    Kim, Sung Kyoo; Chang, In Soon; Chung, Moon Kyoo; Hwang, Chul Kyoo; Lee, Kwang Won; In, Sang Ryul; Choi, Byung Ho; Hong, Bong Keun; Oh, Byung Hoon; Chung, Seung Ho; Yoon, Byung Joo; Yoon, Jae Sung; Song, Woo Sub; Chang, Choong Suk; Chang, Hong Yung; Choi, Duk In; Nam, Chang Heui; Chung, Kyoo Sun; Hong, Sang Heui; Kang, Heui Dong; Lee, Jae Koo

    1994-11-01

    A concept definition of the KT-2 tokamak is made. The research goal of the machine is to study the 'advanced tokamak' physics and engineering issues on the mid size large-aspect-ratio diverter tokamak with intense RF heating (>5 MW). Survey of the status of the research fields, the physics basis for the concept, operation scenarios, as well as machine design concept are presented. (Author) 86 refs., 17 figs., 22 tabs

  12. RCD Large Aspect-Ratio Tokamak Equilibrium with Magnetic Islands: a Perturbed Approach

    Science.gov (United States)

    F. L., Braga

    2013-03-01

    Solutions of Grad-Shafranov (GS) equation with Reversed Current Density (RCD) profiles present magnetic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical (large aspect-ratio) RCD equilibrium configuration perturbed by the magnetic field of a circular loop (simulating a divertor) is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.

  13. Optimal Design of Airfoil with High Aspect Ratio in Unmanned Aerial Vehicles

    OpenAIRE

    Kyoungwoo Park; Ji-Won Han; Hyo-Jae Lim; Byeong-Sam Kim; Juhee Lee

    2008-01-01

    Shape optimization of the airfoil with high aspect ratio of long endurance unmanned aerial vehicle (UAV) is performed by the multi-objective optimization technology coupled with computational fluid dynamics (CFD). For predicting the aerodynamic characteristics around the airfoil the high-fidelity Navier-Stokes solver is employed and SMOGA (Simple Multi-Objective Genetic Algorithm), which is developed by authors, is used for solving the multi-objective optimization problem...

  14. Concept definition of KT-2, a large-aspect-ratio diverter tokamak with FWCD

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Kyoo; Chang, In Soon; Chung, Moon Kyoo; Hwang, Chul Kyoo; Lee, Kwang Won; In, Sang Ryul; Choi, Byung Ho; Hong, Bong Keun; Oh, Byung Hoon; Chung, Seung Ho; Yoon, Byung Joo; Yoon, Jae Sung; Song, Woo Sub [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Chang, Choong Suk; Chang, Hong Yung; Choi, Duk In; Nam, Chang Heui [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of); Chung, Kyoo Sun [Hanyang Univ., Seoul (Korea, Republic of); Hong, Sang Heui [Seoul National Univ., Seoul (Korea, Republic of); Kang, Heui Dong [Kyungpook National Univ., Taegu (Korea, Republic of); Lee, Jae Koo [Pohang Inst. of Science and Technology, Kyungnam (Korea, Republic of)

    1994-11-01

    A concept definition of the KT-2 tokamak is made. The research goal of the machine is to study the `advanced tokamak` physics and engineering issues on the mid size large-aspect-ratio diverter tokamak with intense RF heating (>5 MW). Survey of the status of the research fields, the physics basis for the concept, operation scenarios, as well as machine design concept are presented. (Author) 86 refs., 17 figs., 22 tabs.

  15. Effect of aspect ratio on the uptake and toxicity of hydroxylated-multi walled carbon nanotubes in the nematode,

    Directory of Open Access Journals (Sweden)

    Hyun-Jeong Eom

    2015-03-01

    Full Text Available Objectives In this study, the effect of tube length and outer diameter (OD size of hydroxylated-multi walled carbon nanotubes (OH-MWCNTs on their uptake and toxicity was investigated in the nematode Caenorhabditis elegans using a functional mutant analysis. Methods The physicochemical properties of three different OH-MWCNTs were characterized. Uptake and toxicity were subsequently investigated on C. elegans exposed to MWCNTs with different ODs and tube lengths. Results The results of mutant analysis suggest that ingestion is the main route of MWCNTs uptake. We found that OH-MWCNTs with smaller ODs were more toxic than those with larger ODs, and OH-MWCNTs with shorter tube lengths were more toxic than longer counterparts to C. elegans. Conclusions Overall the results suggest the aspect ratio affects the toxicity of MWCNTs in C. elegans. Further thorough study on the relationship between physicochemical properties and toxicity needs to be conducted for more comprehensive understanding of the uptake and toxicity of MWCNTs.

  16. Flight Loads Prediction of High Aspect Ratio Wing Aircraft Using Multibody Dynamics

    Directory of Open Access Journals (Sweden)

    Michele Castellani

    2016-01-01

    Full Text Available A framework based on multibody dynamics has been developed for the static and dynamic aeroelastic analyses of flexible high aspect ratio wing aircraft subject to structural geometric nonlinearities. Multibody dynamics allows kinematic nonlinearities and nonlinear relationships in the forces definition and is an efficient and promising methodology to model high aspect ratio wings, which are known to be prone to structural nonlinear effects because of the high deflections in flight. The multibody dynamics framework developed employs quasi-steady aerodynamics strip theory and discretizes the wing as a series of rigid bodies interconnected by beam elements, representative of the stiffness distribution, which can undergo arbitrarily large displacements and rotations. The method is applied to a flexible high aspect ratio wing commercial aircraft and both trim and gust response analyses are performed in order to calculate flight loads. These results are then compared to those obtained with the standard linear aeroelastic approach provided by the Finite Element Solver Nastran. Nonlinear effects come into play mainly because of the need of taking into account the large deflections of the wing for flight loads computation and of considering the aerodynamic forces as follower forces.

  17. Invariant Imbedding T-Matrix Method for Axial Symmetric Hydrometeors with Extreme Aspect Ratios

    Science.gov (United States)

    Pelissier, C.; Clune, T.; Kuo, K. S.; Munchak, S. J.; Adams, I. S.

    2017-12-01

    The single-scattering properties (SSPs) of hydrometeors are the fundamental quantities for physics-based precipitation retrievals. Thus, efficient computation of their electromagnetic scattering is of great value. Whereas the semi-analytical T-Matrix methods are likely the most efficient for nonspherical hydrometeors with axial symmetry, they are not suitable for arbitrarily shaped hydrometeors absent of any significant symmetry, for which volume integral methods such as those based on Discrete Dipole Approximation (DDA) are required. Currently the two leading T-matrix methods are the Extended Boundary Condition Method (EBCM) and the Invariant Imbedding T-matrix Method incorporating Lorentz-Mie Separation of Variables (IITM+SOV). EBCM is known to outperform IITM+SOV for hydrometeors with modest aspect ratios. However, in cases when aspect ratios become extreme, such as needle-like particles with large height to diameter values, EBCM fails to converge. Such hydrometeors with extreme aspect ratios are known to be present in solid precipitation and their SSPs are required to model the radiative responses accurately. In these cases, IITM+SOV is shown to converge. An efficient, parallelized C++ implementation for both EBCM and IITM+SOV has been developed to conduct a performance comparison between EBCM, IITM+SOV, and DDSCAT (a popular implementation of DDA). We present the comparison results and discuss details. Our intent is to release the combined ECBM & IITM+SOV software to the community under an open source license.

  18. Low aspect ratio micropores for single-particle and single-cell analysis.

    Science.gov (United States)

    Goyal, Gaurav; Mulero, Rafael; Ali, Jamel; Darvish, Armin; Kim, Min Jun

    2015-05-01

    This paper describes microparticle and bacterial translocation studies using low aspect ratio solid-state micropores. Micropores, 5 μm in diameter, were fabricated in 200 nm thick free-standing silicon nitride membranes, resulting in pores with an extremely low aspect ratio, nominally 0.04. For microparticle translocation experiments, sulfonated polystyrene microparticles and magnetic microbeads in size range of 1-4 μm were used. Using the microparticle translocation characteristics, we find that particle translocations result in a change only in the pore's geometrical resistance while the access resistance remains constant. Furthermore, we demonstrate the ability of our micropore to probe high-resolution shape information of translocating analytes using concatenated magnetic microspheres. Distinct current drop peaks were observed for each microsphere of the multibead architecture. For bacterial translocation experiments, nonflagellated Escherichia coli (strain HCB 5) and wild type flagellated Salmonella typhimurium (strain SJW1103) were used. Distinct current signatures for the two bacteria were obtained and this difference in translocation behavior was attributed to different surface protein distributions on the bacteria. Our findings may help in developing low aspect ratio pores for high-resolution microparticle characterization and single-cell analysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. High aspect ratio nanoholes in glass generated by femtosecond laser pulses with picosecond intervals

    Science.gov (United States)

    Ahn, Sanghoon; Choi, Jiyeon; Noh, Jiwhan; Cho, Sung-Hak

    2018-02-01

    Because of its potential uses, high aspect ratio nanostructures have been interested for last few decades. In order to generate nanostructures, various techniques have been attempted. Femtosecond laser ablation is one of techniques for generating nanostructures inside a transparent material. For generating nanostructures by femtosecond laser ablation, previous studies have been attempted beam shaping such as Bessel beam and temporal tailored beam. Both methods suppress electron excitation at near surface and initiate interference of photons at certain depth. Recent researches indicate that shape of nanostructures is related with temporal change of electron density and number of self-trapped excitons. In this study, we try to use the temporal change of electron density induced by femtosecond laser pulse for generating high aspect ratio nanoholes. In order to reveal the effect of temporal change of electron density, secondary pulses are irradiated from 100 to 1000 ps after the irradiation of first pulse. Our result shows that diameter of nanoholes is increasing and depth of nanoholes is decreasing as pulse to pulse interval is getting longer. With manipulating of pulse to pulse interval, we could generate high aspect ratio nanoholes with diameter of 250-350 nm and depth of 4∼6 μm inside a glass.

  20. The effect of aspect ratio on the leading-edge vortex over an insect-like flapping wing.

    Science.gov (United States)

    Phillips, Nathan; Knowles, Kevin; Bomphrey, Richard J

    2015-10-09

    Insect wing shapes are diverse and a renowned source of inspiration for the new generation of autonomous flapping vehicles, yet the aerodynamic consequences of varying geometry is not well understood. One of the most defining and aerodynamically significant measures of wing shape is the aspect ratio, defined as the ratio of wing length (R) to mean wing chord (c). We investigated the impact of aspect ratio, AR, on the induced flow field around a flapping wing using a robotic device. Rigid rectangular wings ranging from AR = 1.5 to 7.5 were flapped with insect-like kinematics in air with a constant Reynolds number (Re) of 1400, and a dimensionless stroke amplitude of 6.5c (number of chords traversed by the wingtip). Pseudo-volumetric, ensemble-averaged, flow fields around the wings were captured using particle image velocimetry at 11 instances throughout simulated downstrokes. Results confirmed the presence of a high-lift, separated flow field with a leading-edge vortex (LEV), and revealed that the conical, primary LEV grows in size and strength with increasing AR. In each case, the LEV had an arch-shaped axis with its outboard end originating from a focus-sink singularity on the wing surface near the tip. LEV detachment was observed for AR > 1.5 around mid-stroke at ~70% span, and initiated sooner over higher aspect ratio wings. At AR > 3 the larger, stronger vortex persisted under the wing surface well into the next half-stroke leading to a reduction in lift. Circulatory lift attributable to the LEV increased with AR up to AR = 6. Higher aspect ratios generated proportionally less lift distally because of LEV breakdown, and also less lift closer to the wing root due to the previous LEV's continuing presence under the wing. In nature, insect wings go no higher than AR ~ 5, likely in part due to architectural and physiological constraints but also because of the reducing aerodynamic benefits of high AR wings.

  1. Estimating the hemodynamic influence of variable main body-to-iliac limb length ratios in aortic endografts.

    Science.gov (United States)

    Georgakarakos, Efstratios; Xenakis, Antonios; Georgiadis, George S

    2018-02-01

    We conducted a computational study to assess the hemodynamic impact of variant main body-to-iliac limb length (L1/L2) ratios on certain hemodynamic parameters acting on the endograft (EG) either on the normal bifurcated (Bif) or the cross-limb (Cx) fashion. A customary bifurcated 3D model was computationally created and meshed using the commercially available ANSYS ICEM (Ansys Inc., Canonsburg, PA, USA) software. The total length of the EG, was kept constant, while the L1/L2 ratio ranged from 0.3 to 1.5 in the Bif and Cx reconstructed EG models. The compliance of the graft was modeled using a Fluid Structure Interaction method. Important hemodynamic parameters such as pressure drop along EG, wall shear stress (WSS) and helicity were calculated. The greatest pressure decrease across EG was calculated in the peak systolic phase. With increasing L1/L2 it was found that the Pressure Drop was increasing for the Cx configuration, while decreasing for the Bif. The greatest helicity (4.1 m/s2) was seen in peak systole of Cx with ratio of 1.5 whereas its greatest value (2 m/s2) was met in peak systole in the Bif with the shortest L1/L2 ratio (0.3). Similarly, the maximum WSS value was highest (2.74Pa) in the peak systole for the 1.5 L1/L2 of the Cx configuration, while the maximum WSS value equaled 2 Pa for all length ratios of the Bif modification (with the WSS found for L1/L2=0.3 being marginally higher). There was greater discrepancy in the WSS values for all L1/L2 ratios of the Cx bifurcation compared to Bif. Different L1/L2 rations are shown to have an impact on the pressure distribution along the entire EG while the length ratio predisposing to highest helicity or WSS values is also determined by the iliac limbs pattern of the EG. Since current custom-made EG solutions can reproduce variability in main-body/iliac limbs length ratios, further computational as well as clinical research is warranted to delineate and predict the hemodynamic and clinical effect of variable

  2. EFFECT OF END ANCHORAGE LENGTH AND STIRRUP RATIO ON BOND AND SHEAR CAPACITY OF CONCRETE BEAMS WITH NONMETALLIC REINFORCEMENT

    Directory of Open Access Journals (Sweden)

    RENDY THAMRIN

    2016-06-01

    Full Text Available This paper presents a study on the effect of end anchorage length and stirrup ratio on bond and shear capacity of concrete beams reinforced with Carbon Fiber Reinforced Polymer (CFRP bars. This study was carried out using test data on nine simply supported reinforced concrete beams with stirrups. The beams were subjected to two point monotonic loads and the test variables were the length of end anchorage and the stirrup ratio. Theoretical equations for calculating bond strength and shear capacity obtained from literature were applied and then compared with experimental values. Beams with inadequate end anchorage length showed premature bond failure even when there was sufficient stirrup ratio. Beams with adequate end anchorage length failed in shear or flexure modes depending on the stirrup ratio. A numerical model for bond stress and slip in response to pullout forces was also used to determine analytically the bond stress distributions along end anchorage. The behavior of tensile force acting on the stirrups was also examined. Finally, a simple model for predicting tension force acting on the stirrups was proposed.

  3. Effects of Variable Aspect-Ratio Inclusions on the Electrical Impedance of an Alumina Zirconia Composite at Intermediate Temperatures

    Science.gov (United States)

    Goldsby, Jon C.

    2010-01-01

    A series of alumina-yttria-stabilized zirconia composites containing either a high aspect ratio (5 and 30 mol%) hexagonal platelet alumina or an alumina low aspect ratio (5 and 30 mol%) spherical particulate was used to determine the effect of the aspect ratio on the temperature-dependent impedance of the composite material. The highest impedance across the temperature range of 373 to 1073 K is attributed to the grain boundary of the hexagonal platelet second phase in this alumina zirconia composite.

  4. Systematic in vitro nanotoxicity study on anodic alumina nanotubes with engineered aspect ratio: understanding nanotoxicity by a nanomaterial model.

    Science.gov (United States)

    Wang, Ye; Kaur, Gagandeep; Zysk, Aneta; Liapis, Vasilios; Hay, Shelley; Santos, Abel; Losic, Dusan; Evdokiou, Andreas

    2015-04-01

    Here, we report a detailed and systematic approach for studying the in vitro nanotoxicity study of high aspect ratio (HAR) nanomaterials using anodic alumina nanotubes (AANTs) as a nanomaterial model. AANTs with bio-inert properties and tailored aspect ratios ranging from 7.8 to 63.3 were synthesized by an electrochemical pulse anodization process. Cytotoxicity studies were conducted with RAW 264.7 mouse macrophage cells and MDA-MB 231-TXSA human breast cancer cells through several toxicity parameters, including cell viability and morphology, pro-inflammatory response, mitochondrial depolarization, lysosomal membrane permeabilization (LMP), induction of autophagy and endoplasmic reticulum (ER) stress. The resulting toxicity patterns were cell-type dependent and strongly related with AANTs dose, length of time, and importantly the AR of AANTs. Long AANTs triggered enhanced cell death, morphological changes, tumor necrosis factor α (TNF-α) release, LMP and ER stress than short AANTs. The toxic AR window of AANTs was determined to be 7.8, which is shorter than that of other previously reported HAR nanomaterials. This toxic AR window provides a promising opportunity to control the nanotoxicity of HAR nanomaterials for their advanced drug delivery application. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. 2D:4D finger-length ratios in children and adults with gender identity disorder

    NARCIS (Netherlands)

    Wallien, M.S.C.; Zucker, K.J.; Steensma, T.D.; Cohen-Kettenis, P.T.

    2008-01-01

    Previous research suggests that prenatal testosterone affects the 2D:4D finger ratio in humans, and it has been speculated that prenatal testosterone also affects gender identity differentiation. If both things are true, then one would expect to find an association between the 2D:4D ratio and gender

  6. The Impact of Volute Aspect Ratio on the Performance of a Mixed Flow Turbine

    Directory of Open Access Journals (Sweden)

    Samuel P. Lee

    2017-11-01

    Full Text Available Current trends in the automotive industry towards engine downsizing mean turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, mixed flow turbines can offer non-zero blade angles, reducing leading edge (LE separation at low velocity ratios. The current paper investigates the performance of a mixed flow turbine with three different volute aspect ratio (AR designs (AR = 0.5, 1 and 2. With constant A/r (ratio of volute area to centroid radius, the AR = 0.5 volute design produced a 4.3% increase in cycle averaged mass flow parameter (MFP compared to the AR = 2 design. For the purpose of performance comparison, it was necessary to manipulate the volute A/r’s to ensure constant MFP for aerodynamic similarity. With the volute A/r’s manipulated to ensure constant MFP for aerodynamic similarity, the maximum variation of cycle averaged normalized efficiency measured between the designs was 1.47%. Purely in the rotor region, the variation in normalized cycle averaged efficiency was 1%. The smallest tested volute aspect ratio showed a significant increase in volute loss while the ARs of 1 and 2 showed similar levels of loss. The smallest AR volute showed significant secondary flow development in the volute. The resulting variation in LE incidence was found to vary as a result.

  7. Performance and emission characteristics of LPG powered four stroke SI engine under variable stroke length and compression ratio

    International Nuclear Information System (INIS)

    Ozcan, Hakan; Yamin, Jehad A.A.

    2008-01-01

    A computer simulation of a variable stroke length, LPG fuelled, four stroke, single cylinder, water cooled spark ignition engine was done. The engine capacity was varied by varying the stroke length of the engine, which also changed its compression ratio. The simulation model developed was verified with experimental results from the literature for both constant and variable stroke engines. The performance of the engine was simulated at each stroke length/compression ratio combination. The simulation results clearly indicate the advantages and utility of variable stroke engines in fuel economy and power issues. Using the variable stroke technique has significantly improved the engine's performance and emission characteristics within the range studied. The brake torque and power have registered an increase of about 7-54% at low speed and 7-57% at high speed relative to the original engine design and for all stroke lengths and engine speeds studied. The brake specific fuel consumption has registered variations from a reduction of about 6% to an increase of about 3% at low speed and from a reduction of about 6% to an increase of about 8% at high speed relative to the original engine design and for all stroke lengths and engine speeds studied. On the other hand, an increase of pollutants of about 0.65-2% occurred at low speed. Larger stroke lengths resulted in a reduction of the pollutants level of about 1.5% at higher speeds. At lower stroke lengths, on the other hand, an increase of about 2% occurred. Larger stroke lengths resulted in increased exhaust temperature and, hence, make the exhaust valve work under high temperature

  8. Impact of Aspect Ratio and Solar Heating on Street Conyn Air Temperature

    Directory of Open Access Journals (Sweden)

    Rizwan Ahmed Memon

    2011-01-01

    Full Text Available The results obtained from RNG (Re-Normalization Group version of k-? turbulence model are reported in this study. The model is adopted to elucidate the impact of different building aspect ratios (i.e., ratio of building-height-to-street-canyon-width and solar heating on temperatures in street canyon. The validation of Navier-Stokes and energy transport equations showed that the model prediction for air-temperature and ambient wind provides reasonable accuracy. The model was applied on AR (Aspect Ratios one to eight and surface temperature difference (??s-a of 2 -8. Notably, air-temperatures were higher in high AR street canyons in particular on the leeward side of the street canyon. Further investigation showed that the difference between the air-temperature of high and low AR street canyons ( AR was positive and high with higher ??s-a. Conversely, the AR become negative and low gradually with lower values of ??s-a. These results could be very beneficial for the city and regional planners, civil engineers and HVAC experts who design street canyons and strive for human thermal comfort with minimum possible energy requirements.

  9. Arbitrary scattering of an acoustical Bessel beam by a rigid spheroid with large aspect-ratio

    Science.gov (United States)

    Gong, Zhixiong; Li, Wei; Mitri, Farid G.; Chai, Yingbin; Zhao, Yao

    2016-11-01

    In this paper, the T-matrix (null-field) method is applied to investigate the acoustic scattering by a large-aspect-ratio rigid spheroid immersed in a non-viscous fluid under the illumination of an unbounded zeroth-order Bessel beam with arbitrary orientation. Based on the proposed method, a MATLAB software package is constructed accordingly, and then verified and validated to compute the acoustic scattering by a rigid oblate or prolate spheroid in the Bessel beam. Several numerical examples are carried out to investigate the novel phenomenon of acoustic scattering by spheroids in Bessel beams with arbitrary incidence, with particular emphasis on the aspect ratio (i.e. the ratio of the polar radius over the equatorial radius of the spheroid), the half-cone angle of Bessel beam, the dimensionless frequency, as well as the angle of incidence. The quasi-periodic oscillations are observed in the plots of the far-field backscattering form function modulus versus the dimensionless frequency, owing to the interference between the specular reflection and the Franz wave circumnavigating the spheroid in the surrounding fluid. Furthermore, the 3D far-field scattering directivity patterns at end-on incidence and 2D polar plots at arbitrary angles of incidence are exhibited, which could provide new insights into the physical mechanisms of Bessel beam scattering by flat or elongated spheroid. This research work may provide an impetus for the application of acoustic Bessel beam in engineering practices.

  10. Simulation and Measurement of Neuroelectrodes' Characteristics with Integrated High Aspect Ratio Nano Structures

    Directory of Open Access Journals (Sweden)

    Christoph Nick

    2015-07-01

    Full Text Available Improving the interface between electrodes and neurons has been the focus of research for the last decade. Neuroelectrodes should show small geometrical surface area and low impedance for measuring and high charge injection capacities for stimulation. Increasing the electrochemically active surface area by using nanoporous electrode material or by integrating nanostructures onto planar electrodes is a common approach to improve this interface. In this paper a simulation approach for neuro electrodes' characteristics with integrated high aspect ratio nano structures based on a point-contact-model is presented. The results are compared with experimental findings conducted with real nanostructured microelectrodes. In particular, effects of carbon nanotubes and gold nanowires integrated onto microelectrodes are described. Simulated and measured impedance properties are presented and its effects onto the transfer function between the neural membrane potential and the amplifier output signal are studied based on the point-contact-model. Simulations show, in good agreement with experimental results, that electrode impedances can be dramatically reduced by the integration of high aspect ratio nanostructures such as gold nanowires and carbon nanotubes. This lowers thermal noise and improves the signal-to-noise ratio for measuring electrodes. It also may increase the adhesion of cells to the substrate and thus increase measurable signal amplitudes.

  11. Impact of aspect ratio and solar heating on street canyon air temperature

    International Nuclear Information System (INIS)

    Memon, R.A.; Lal, K.

    2011-01-01

    The results obtained from RNG (Re-Normalization Group) version of k-and turbulence model are reported in this study. The model is adopted to elucidate the impact of different building aspect ratios (i.e., ratio of building-height-to-street-canyon-width) and solar heating on temperatures in street canyon. The validation of Navier-Stokes and energy an sport equations showed that the model prediction for air-temperature and ambient wind provides reasonable accuracy. The model was applied on AR (Aspect Ratios) one to eight and surface temperature difference (delta and theta/sub s-a/)) of 2 -8. Notably, air-temperatures were higher in high AR street canyons in particular on the leeward side of the street canyon. Further investigation showed that the difference between the air-temperature 'high and low AR street canyons (AR) was positive and high with higher delta and theta/sub s-a/) conversely, the AR become negative and low gradually with lower values of delta and theta(/sub s-a/). These results could be very beneficial for the city and regional planners, civil engineers Id HVAC experts who design street canyons and strive for human thermal comfort with minimum possible energy requirements. (author)

  12. Simulation and optimization of a micromachined gyroscope using high-aspect-ratio micromachining fabrication process

    Science.gov (United States)

    Ruan, Aiwu Y.; Tse, Man S.; Chong, Gang Y.

    2001-11-01

    Micromachined gyroscopes rely on tuned vibration mode frequencies to measure rotation rates and typically have complex modes of vibration for the mechanical microstructures. Although there are many reports on how to exactly tune the drive and sense modes of vibration to maximize sensitivity of micromachined gyroscope, there are only few reports on the detailed analysis of modes of vibration. Modes of vibration are strongly dependent on the design parameters of the mechanical structure of the gyroscope including the dimension of the proof mass, types and dimensions of the suspension, and residual mechanical stress of the high aspect-ratio polysilicon film used to form the microstructures of the micromachined gyroscope. In this paper, an electrostatic drive and capacitive sense in-plane decoupled gyroscope for measuring vertical angular velocity is proposed to study the effects of the geometrical variables on modes of vibration. Finite-element analysis (FEA) simulation was performed on simplifiedmodel of the in-plane decoupled micromachined gyroscope microstructure. For optimal result the drive-mode and sense-mode suspensions of the micromachined gyroscope should be fabricated from thick polysilicon microstructure to give large aspect ratio suspension systems for the in-plane decoupled micromachined gyroscope. Folded-beam suspension design is recommended for the drive-mode suspension in order to relieve the residual stress of the thick polysilicon film for high aspect-ratio micromachine dgyroscope. It is critical to control the process variations of the suspension beam dimension, especially the beam width variation in order to achieve the goal of accurately control resonant frequencies of micromachined gyrocope.

  13. Planar silicon fabrication process for high-aspect-ratio micromachined parts

    Energy Technology Data Exchange (ETDEWEB)

    Barron, C.C.; Fleming, J.G. [Sandia National Labs., Albuquerque, NM (United States). Microelectronics Development Lab.

    1997-09-01

    Surface-micromachined silicon inertial sensors are limited to relatively high-G applications in part because of the fundamental limitations on proof mass imposed by the manufacturing technology. At the same time, traditional micromolding technologies such as LIGA do not lend themselves to integration with electronics, a capability which is equally necessary for high-performance inertial sensors. The silicon micromolding processes described in this report promise to offer both larger proof masses and integrability with on-chip electronics. In Sandia`s silicon micromolding process, the proof mass is formed using a mold which is first recessed into the substrate using a deep silicon trench etch, then lined with a sacrificial or etch-stop layer, and filled with mechanical polysilicon. Since the mold is recessed into the substrate, the whole micromechanical structure can be formed, planarized, and integrated with standard silicon microelectronic circuits before the release etch. In addition, unlike surface-micromachined parts, the thickness of the molded parts is limited by the depth of the trench etch (typically 10--50 {micro}m) rather than the thickness of deposited polysilicon (typically 2 {micro}m). The fact that the high-aspect-ratio section of the device is embedded in the substrate enables the monolithic integration of high-aspect-ratio parts with surface-micromachined mechanical parts, and, in the future, also electronics. The authors anticipate that such an integrated mold/surface micromachining/electronics process will offer versatile high-aspect-ratio micromachined structures that can be batch-fabricated and monolithically integrated into complex microelectromechanical systems including high-performance inertial sensing systems.

  14. The effect of filler aspect ratio on the electromagnetic properties of carbon-nanofibers reinforced composites

    Energy Technology Data Exchange (ETDEWEB)

    De Vivo, B.; Lamberti, P.; Spinelli, G., E-mail: gspinelli@unisa.it; Tucci, V. [Department of Information Engineering, Electrical Engineering and Applied Mathematics—DIEM, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano SA (Italy); Guadagno, L.; Raimondo, M. [Department of Industrial Engineering—DIIn, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano SA (Italy)

    2015-08-14

    The effect of filler aspect ratio on the electromagnetic properties of epoxy-amine resin reinforced with carbon nanofibers is here investigated. A heat treatment at 2500 °C of carbon nanofibers seems to increase their aspect ratio with respect to as-received ones most likely due to a lowering of structural defects and the improvement of the graphene layers within the dixie cup conformation. These morphological differences revealed by Raman's spectroscopy and scanning electron microscopy analyses may be responsible for the different electrical properties of the resulting composites. The DC characterization of the nanofilled material highlights an higher electrical conductivity and a lower electrical percolation threshold for the heat-treated carbon nanofibers based composites. In fact, the electrical conductivity is about 0.107 S/m and 1.36 × 10{sup −3} S/m for the nanocomposites reinforced with heat-treated and as received fibers, respectively, at 1 wt. % of nanofiller loading, while the electrical percolation threshold falls in the range [0.05–0.32]wt. % for the first nanocomposites and above 0.64 wt. % for the latter. Moreover, also a different frequency response is observed since the critical frequency, which is indicative of the transition from a resistive to a capacitive-type behaviour, shifts forward of about one decade at the same filler loading. The experimental results are supported by theoretical and simulation studies focused on the role of the filler aspect ratio on the electrical properties of the nanocomposites.

  15. Optimization of HNA etching parameters to produce high aspect ratio solid silicon microneedles

    International Nuclear Information System (INIS)

    Hamzah, A A; Yeop Majlis, B; Yunas, J; Dee, C F; Abd Aziz, N; Bais, B

    2012-01-01

    High aspect ratio solid silicon microneedles with a concave conic shape were fabricated. Hydrofluoric acid–nitric acid–acetic acid (HNA) etching parameters were characterized and optimized to produce microneedles that have long and narrow bodies with smooth surfaces, suitable for transdermal drug delivery applications. The etching parameters were characterized by varying the HNA composition, the optical mask's window size, the etching temperature and bath agitation. An L9 orthogonal Taguchi experiment with three factors, each having three levels, was utilized to determine the optimal fabrication parameters. Isoetch contours for HNA composition with 0% and 10% acetic acid concentrations were presented and a high nitric acid region was identified to produce microneedles with smooth surfaces. It is observed that an increase in window size indiscriminately increases the etch rate in both the vertical and lateral directions, while an increase in etching temperature beyond 35 °C causes the etching to become rapid and uncontrollable. Bath agitation and sample placement could be manipulated to achieve a higher vertical etch rate compared to its lateral counterpart in order to construct high aspect ratio microneedles. The Taguchi experiment performed suggests that a HNA composition of 2:7:1 (HF:HNO 3 :CH 3 COOH), window size of 500 µm and agitation rate of 450 RPM are optimal. Solid silicon microneedles with an average height of 159.4 µm, an average base width of 110.9 µm, an aspect ratio of 1.44, and a tip angle and diameter of 19.2° and 0.38 µm respectively were successfully fabricated. (paper)

  16. Stability of the n=1 ideal internal kink for large aspect ratio Shafranov equilibria

    International Nuclear Information System (INIS)

    Bondeson, A.; Bussac, M.N.

    1991-09-01

    Stability limits for the ideal internal kink mode are calculated analytically for the Shafranov current profile using the large aspect ratio expansion. For equilibria with q(a)>2 and circular cross section, the maximum stable poloidal beta is below 0.1. In the absence of a conducting wall, an equilibrium with q(a)<2 is unstable at arbitrarily small positive poloidal beta or shear inside the q = 1 surface. The effects of non-circularity are discussed and quantitative results are given for elliptic cross sections. (author) 2 figs., 10 refs

  17. The Aspect Ratio Dependence of the Attractor Dimension in Taylor-Couette Flow

    Science.gov (United States)

    1988-01-01

    and G. Iooss,"Calcul des solutions bifurquees pour le probl~me de Couette-Taylor avec les deux cylindres en rotation", J. Mec. theor applique Numero ...Procaccia and Badii-Politi algorithms. The aspect ratio was varied between 19.9 and 34.48 and the inner cylinder Reynolds numbers ranged between R/Rej...11 and R/Rc = 15, where Rc is the critical Reynolds number for the primary instability.) The variation of the dimension with Reynolds number was

  18. High-aspect-ratio grooves fabricated in silicon by a single pass of femtosecond laser pulses

    International Nuclear Information System (INIS)

    Ma Yuncan; Shi Haitao; Si Jinhai; Ren Hai; Chen Tao; Chen Feng; Hou Xun

    2012-01-01

    High-aspect-ratio grooves have been fabricated in silicon by a single pass of femtosecond laser pulses in water and ambient air. Scanning electron microscopy and energy dispersive x-ray spectroscopy were employed to image for the morphology of the photoinduced grooves and analyze the chemical composition in the surrounding of the grooves. It was observed that the sidewall of the grooves fabricated in water was much smoother than that in ambient air, and there were homogeneous nano-scale protrusions on the sidewall of the grooves fabricated in water. Meanwhile, oxygen species, which was incorporated into the grooves fabricated in air, was not observed in those in water.

  19. Dense high-aspect ratio 3D carbon pillars on interdigitated microelectrode arrays

    DEFF Research Database (Denmark)

    Amato, Letizia; Heiskanen, Arto; Hansen, Rasmus

    2015-01-01

    In this work we present high-aspect ratio carbon pillars (1.4 μm in diameter and ∼11 μm in height) on top of interdigitated electrode arrays to be used for electrochemical applications. For this purpose, different types of 2D and 3D pyrolysed carbon structures were fabricated and characterised...... including surface- and microstructure, electrical and electrochemical properties. A pre-treatment of oxidised Si wafers is introduced to eliminate electrode delamination and ensure structure stability in water during long time-experiments. Additionally, a heat treatment method is reported for regeneration...... of pyrolysed carbon films with increased film resistance due to oxidation during storage....

  20. Hyperthermia in low aspect-ratio magnetic nanotubes for biomedical applications

    Science.gov (United States)

    Gutierrez-Guzman, D. F.; Lizardi, L. I.; Otálora, J. A.; Landeros, P.

    2017-03-01

    A simple model for the magnetization reversal process of low aspect-ratio ferromagnetic nanotubes (MNTs) is presented. Because of advantages over other geometries, these structures are interesting for biomedical applications, such as magnetic hyperthermia cancer therapy, where the heat released during magnetic reversal is used to destroy tumors. For example, the tubular geometry provides two independent functional surfaces that may be selectively manipulated and also gives a storage cavity. Owing to their large surface to weight ratio and low mass density, MNTs are not decanted by gravity. We calculated magnetic phase diagrams, energy barriers, nucleation fields, and the amount of dissipated heat and specific absorption rate for magnetite nanotubes. The geometrical parameters were varied, and simple formulae were used to optimize the tube response under alternating excitation, as required for magnetic hyperthermia applications.

  1. Practical Aspects of Log-ratio Coordinate Representations in Regression with Compositional Response

    Directory of Open Access Journals (Sweden)

    Fišerová Eva

    2016-10-01

    Full Text Available Regression analysis with compositional response, observations carrying relative information, is an appropriate tool for statistical modelling in many scientific areas (e.g. medicine, geochemistry, geology, economics. Even though this technique has been recently intensively studied, there are still some practical aspects that deserve to be further analysed. Here we discuss the issue related to the coordinate representation of compositional data. It is shown that linear relation between particular orthonormal coordinates and centred log-ratio coordinates can be utilized to simplify the computation concerning regression parameters estimation and hypothesis testing. To enhance interpretation of regression parameters, the orthogonal coordinates and their relation with orthonormal and centred log-ratio coordinates are presented. Further we discuss the quality of prediction in different coordinate system. It is shown that the mean squared error (MSE for orthonormal coordinates is less or equal to the MSE for log-transformed data. Finally, an illustrative real-world example from geology is presented.

  2. Practical Aspects of Log-ratio Coordinate Representations in Regression with Compositional Response

    Science.gov (United States)

    Fišerová, Eva; Donevska, Sandra; Hron, Karel; Bábek, Ondřej; Vaňkátová, Kristýna

    2016-10-01

    Regression analysis with compositional response, observations carrying relative information, is an appropriate tool for statistical modelling in many scientific areas (e.g. medicine, geochemistry, geology, economics). Even though this technique has been recently intensively studied, there are still some practical aspects that deserve to be further analysed. Here we discuss the issue related to the coordinate representation of compositional data. It is shown that linear relation between particular orthonormal coordinates and centred log-ratio coordinates can be utilized to simplify the computation concerning regression parameters estimation and hypothesis testing. To enhance interpretation of regression parameters, the orthogonal coordinates and their relation with orthonormal and centred log-ratio coordinates are presented. Further we discuss the quality of prediction in different coordinate system. It is shown that the mean squared error (MSE) for orthonormal coordinates is less or equal to the MSE for log-transformed data. Finally, an illustrative real-world example from geology is presented.

  3. Pilot Study of Inhaled Aerosols Targeted via Magnetic Alignment of High Aspect Ratio Particles in Rabbits

    Directory of Open Access Journals (Sweden)

    Gillian E. S. Redman

    2011-01-01

    Full Text Available Recently, inhaled pharmaceutical aerosols have seen increased investigation in the treatment of lung cancer, where the inability to deliver adequate therapeutic drug concentrations to tumour sites may be overcome with improved targeted delivery to the site of the tumour. In this study, the feasibility of magnetically targeted delivery of high aspect ratio particles loaded with iron oxide nanoparticles was studied in 19 New Zealand White rabbits. Half of the exposed rabbits had a magnetic field placed externally over their right lung. Iron sensitive magnetic resonance images of the lungs were acquired to determine the iron concentrations in the right and left lung of each animal. The right/left ratio increased in the middle and basal regions of the lung where, due to the morphology of the rabbit lung, this method of targeting is most effective. With further optimization, this technique could be an effective method for increasing the dose of drug delivered to a specific site within the lung.

  4. Evaluation of the In Vitro Effect of Gold Nanorod Aspect Ratio, Surface Charge and Chemistry on Cellular Association and Cytotoxicity

    Science.gov (United States)

    2016-03-28

    Nanorods. Analytical Chemistry , 79(2), 572-579. doi: 10.1021/ac061730d 22 LIST OF ACRONYMS ATCC American Type Culture Collection AR Aspect...EVALUATION OF THE IN VITRO EFFECTOF GOLD NANOROD ASPECT RATIO, SURFACE CHARGE AND CHEMISTRY ON CELLULAR ASSOCIATION AND CYTOTOXICITY...July 2012 – Jan 2016 4. TITLE AND SUBTITLE EVALUATION OF THE IN VITRO EFFECT OF GOLD NANOROD ASPECT RATIO, SURFACE CHARGE AND CHEMISTRY ON

  5. Fabrication of 3D high aspect ratio PDMS microfluidic networks with a hybrid stamp.

    Science.gov (United States)

    Kung, Yu-Chun; Huang, Kuo-Wei; Fan, Yu-Jui; Chiou, Pei-Yu

    2015-04-21

    We report a novel methodology for fabricating large-area, multilayer, thin-film, high aspect ratio, 3D microfluidic structures with through-layer vias and open channels that can be bonded between hard substrates. It is realized by utilizing a hybrid stamp with a thin plastic sheet embedded underneath a PDMS surface. This hybrid stamp solves an important edge protrusion issue during PDMS molding while maintaining necessary stamp elasticity to ensure the removal of PDMS residues at through-layer regions. Removing edge protrusion is a significant progress toward fabricating 3D structures since high aspect ratio PDMS structures with flat interfaces can be realized to facilitate multilayer stacking and bonding to hard substrates. Our method also allows for the fabrication of 3D deformable channels, which can lead to profound applications in electrokinetics, optofluidics, inertial microfluidics, and other fields where the shape of the channel cross section plays a key role in device physics. To demonstrate, as an example, we have fabricated a microfluidic channel by sandwiching two 20 μm wide, 80 μm tall PDMS membranes between two featureless ITO glass substrates. By applying electrical bias to the two ITO substrates and pressure to deform the thin membrane sidewalls, strong electric field enhancement can be generated in the center of a channel to enable 3D sheathless dielectrophoretic focusing of biological objects including mammalian cells and bacteria at a flow speed up to 14 cm s(-1).

  6. Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders.

    Science.gov (United States)

    Szmyt, Wojciech; Guerra, Carlos; Utke, Ivo

    2017-01-01

    In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes.

  7. Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders

    Directory of Open Access Journals (Sweden)

    Wojciech Szmyt

    2017-01-01

    Full Text Available In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i the gas diffusion coefficient inside such arrays, (ii the time between collisions of molecules with the nanocylinder walls (mean time of flight, (iii the surface impingement rate, and (iv the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes.

  8. Etching of Silicon in HBr Plasmas for High Aspect Ratio Features

    Science.gov (United States)

    Hwang, Helen H.; Meyyappan, M.; Mathad, G. S.; Ranade, R.

    2002-01-01

    Etching in semiconductor processing typically involves using halides because of the relatively fast rates. Bromine containing plasmas can generate high aspect ratio trenches, desirable for DRAM and MEMS applications, with relatively straight sidewalk We present scanning electron microscope images for silicon-etched trenches in a HBr plasma. Using a feature profile simulation, we show that the removal yield parameter, or number of neutrals removed per incident ion due to all processes (sputtering, spontaneous desorption, etc.), dictates the profile shape. We find that the profile becomes pinched off when the removal yield is a constant, with a maximum aspect ratio (AR) of about 5 to 1 (depth to height). When the removal yield decreases with increasing ion angle, the etch rate increases at the comers and the trench bottom broadens. The profiles have ARs of over 9:1 for yields that vary with ion angle. To match the experimentally observed etched time of 250 s for an AR of 9:1 with a trench width of 0.135 microns, we find that the neutral flux must be 3.336 x 10(exp 17)sq cm/s.

  9. Large-Area High Aspect Ratio Plasmonic Interference Lithography Utilizing a Single High-k Mode.

    Science.gov (United States)

    Chen, Xi; Yang, Fan; Zhang, Cheng; Zhou, Jing; Guo, L Jay

    2016-04-26

    Plasmonic lithography, which utilizes subwavelength confinement of surface plasmon polartion (SPP) waves, has the capability of breaking the diffraction limit and delivering high resolution. However, all previously reported results suffer from critical issues, such as shallow pattern depth and pattern nonuniformity even over small exposure areas, which limit the application of the technology. In this work, periodic patterns with high aspect ratios and a half-pitch of about 1/6 of the wavelength were achieved with pattern uniformity in square centimeter areas. This was accomplished by designing a special mask and photoresist (PR) system to select a single high spatial frequency mode and incorporating the PR into a waveguide configuration to ensure uniform light exposure over the entire depth of the photoresist layer. In addition to the experimental progress toward large-scale applications of plasmonic interference lithography, the general criteria of designing such an exposure system is also discussed, which can be used for nanoscale fabrication in this fashion for various applications with different requirements for wavelength, pitch, aspect ratio, and structure.

  10. Manufacture of high aspect ratio micro-pillar wall shear stress sensor arrays

    Science.gov (United States)

    Gnanamanickam, Ebenezer P.; Sullivan, John P.

    2012-12-01

    In the field of experimental fluid mechanics the measurement of unsteady, distributed wall shear stress has proved historically challenging. Recently, sensors based on an array of flexible micro-pillars have shown promise in carrying out such measurements. Similar sensors find use in other applications such as cellular mechanics. This work presents a manufacturing technique that can manufacture micro-pillar arrays of high aspect ratio. An electric discharge machine (EDM) is used to manufacture a micro-drilling tool. This micro-drilling tool is used to form holes in a wax sheet which acts as the mold for the micro-pillar array. Silicone rubber is cast in these molds to yield a micro-pillar array. Using this technique, micro-pillar arrays with a maximum aspect ratio of about 10 have been manufactured. Manufacturing issues encountered, steps to alleviate them and the potential of the process to manufacture similar micro-pillar arrays in a time-efficient manner are also discussed.

  11. A high-aspect-ratio design for the International Thermonuclear Engineering Reactor

    International Nuclear Information System (INIS)

    Wesley, J.C.

    1992-01-01

    Design features and performance parameters for HARD - the high-aspect-ratio (A = 4) International Thermonuclear Engineering Reactor (ITER) design variant developed by the U. S. ITER Team - are presented. The HARD design makes it possible for ITER to achieve both the ignition/extended-burn and the steady-state/technology-testing performance goals set forth in the ITER Terms of Reference. These performance capabilities are obtained in a device that is otherwise similar in concept, size and cost to the low-aspect-ratio (A = 2.8) ITER design defined during the ITER Conceptual Design Activity (CDA). HARD is based on the same physics and engineering guidelines as the CDA design and achieves the same ignition performance (ignition margin evaluated against ITER-89P confinement scaling) with inductively-driven plasmas as ITER CDA, but with much greater margin for inductive sustainment of the pulse duration. With non-inductive current drive, HARD operates at lower plasma current and higher plasma density and bootstrap current fraction than ITER CDA, is less constrained by beta limit and divertor considerations, and has increased peaking of the neutron wall load at the test module location. These factors give HARD a much better potential than ITER CDA to achieve the steady-state operation and 1 MWa/m 2 technology-testing fluence goals of the ITER objectives

  12. Differences in the Aspect Ratio of Gold Nanorods that Induce Defects in Cell Membrane Models.

    Science.gov (United States)

    Lins, Paula M P; Marangoni, Valéria S; Uehara, Thiers M; Miranda, Paulo B; Zucolotto, Valtencir; Cancino-Bernardi, Juliana

    2017-12-19

    Understanding the interactions between biomolecules and nanomaterials is of great importance for many areas of nanomedicine and bioapplications. Although studies in this area have been performed, the interactions between cell membranes and nanoparticles are not fully understood. Here, we investigate the interactions that occur between the Langmuir monolayers of dipalmitoylphosphatidyl glycerol (DPPG) and dipalmitoylphosphatidyl choline (DPPC) with gold nanorods (NR)-with three aspect ratios-and gold nanoparticles. Our results showed that the aspect ratio of the NRs influenced the interactions with both monolayers, which suggest that the physical morphology and electrostatic forces govern the interactions in the DPPG-NR system, whereas the van der Waals interactions are predominant in the DPPC-NR systems. Size influences the expansion isotherms in both systems, but the lipid tails remain conformationally ordered upon expansion, which suggests phase separation between the lipids and nanomaterials at the interface. The coexistence of lipid and NP regions affects the elasticity of the monolayer. When there is coexistence between two phases, the elasticity does not reflect the lipid packaging state but depends on the elasticity of the NP islands. Therefore, the results corroborate that nanomaterials influence the packing and the phase behavior of the mimetic cell membranes. For this reason, developing a methodology to understand the membrane-nanomaterial interactions is of great importance.

  13. Pattern dynamics of the Benard-Marangoni instability in a medium aspect ratio container

    Energy Technology Data Exchange (ETDEWEB)

    Cerisier, P [IUSTI - CNRS UMR 6595, Polytech' Marseille, Technopole de Chateau-Gombert, 5 rue Enrico Fermi, 13453, Marseille Cedex 13 (France); Rahal, S [Department of Mechanical Engineering, University of Batna, Rue Boukhlouf Mohamed el Hadi, 05000 Batna (Algeria); Azuma, H [Department of Aerospace Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Sakai, Osaka 599-8531 (Japan)

    2007-04-15

    This study is an experimental work devoted to Benard-Marangoni instability in a medium vessel. The free surface deformation is visualised by interferometry and the free surface temperature field by infrared thermography. These two techniques are complementary, since each method provides specific information, which may allow the detection of peculiar phenomena such as the spatial resonance, which is a situation in which the interfacial deformation does not conform to the flow pattern. The influences of the aspect ratio, Rayleigh, Biot and Prandtl numbers, are considered. More dynamics are induced by increasing the Biot number. Conversely, increasing the Prandtl number reduces the dynamics. The deformation magnitude and the wavenumber increase as functions of the gradient of temperature. Two behaviours of the deformation, as a function of Prandtl and Biot numbers, were observed, depending on the value of the applied gradient of temperature. The obtained results are discussed with previous experimental, theoretical and numerical studies. Results of other authors were confirmed concerning the evolution as functions of the gradient of temperature and the aspect ratio and new results were obtained concerning the behaviour of the pattern as functions of Pr and Biot numbers.

  14. Control of size and aspect ratio in hydroquinone-based synthesis of gold nanorods

    International Nuclear Information System (INIS)

    Morasso, Carlo; Picciolini, Silvia; Schiumarini, Domitilla; Mehn, Dora; Ojea-Jiménez, Isaac; Zanchetta, Giuliano; Vanna, Renzo; Bedoni, Marzia; Prosperi, Davide; Gramatica, Furio

    2015-01-01

    In this article, we describe how it is possible to tune the size and the aspect ratio of gold nanorods obtained using a highly efficient protocol based on the use of hydroquinone as a reducing agent by varying the amounts of CTAB and silver ions present in the “seed-growth” solution. Our approach not only allows us to prepare nanorods with a four times increased Au 3+ reduction yield, when compared with the commonly used protocol based on ascorbic acid, but also allows a remarkable reduction of 50–60 % of the amount of CTAB needed. In fact, according to our findings, the concentration of CTAB present in the seed-growth solution do not linearly influence the final aspect ratio of the obtained nanorods, and an optimal concentration range between 30 and 50 mM has been identified as the one that is able to generate particles with more elongated shapes. On the optimized protocol, the effect of the concentration of Ag + ions in the seed-growth solution and the stability of the obtained particles has also been investigated

  15. Control of size and aspect ratio in hydroquinone-based synthesis of gold nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Morasso, Carlo, E-mail: cmorasso@dongnocchi.it; Picciolini, Silvia; Schiumarini, Domitilla [Fondazione Don Carlo Gnocchi ONLUS, Laboratory of Nanomedicine and Clinical Biophotonics (LABION) (Italy); Mehn, Dora; Ojea-Jiménez, Isaac [European Commission Joint Research Centre, Institute for Health and Consumer Protection (IHCP) (Italy); Zanchetta, Giuliano [Universitá degli Studi di Milano, Dipartimento di Biotecnologie Mediche e Medicina Traslazionale (Italy); Vanna, Renzo; Bedoni, Marzia [Fondazione Don Carlo Gnocchi ONLUS, Laboratory of Nanomedicine and Clinical Biophotonics (LABION) (Italy); Prosperi, Davide [Università degli Studi di Milano Bicocca, NanoBioLab, Dipartimento di Biotecnologie e Bioscienze (Italy); Gramatica, Furio [Fondazione Don Carlo Gnocchi ONLUS, Laboratory of Nanomedicine and Clinical Biophotonics (LABION) (Italy)

    2015-08-15

    In this article, we describe how it is possible to tune the size and the aspect ratio of gold nanorods obtained using a highly efficient protocol based on the use of hydroquinone as a reducing agent by varying the amounts of CTAB and silver ions present in the “seed-growth” solution. Our approach not only allows us to prepare nanorods with a four times increased Au{sup 3+} reduction yield, when compared with the commonly used protocol based on ascorbic acid, but also allows a remarkable reduction of 50–60 % of the amount of CTAB needed. In fact, according to our findings, the concentration of CTAB present in the seed-growth solution do not linearly influence the final aspect ratio of the obtained nanorods, and an optimal concentration range between 30 and 50 mM has been identified as the one that is able to generate particles with more elongated shapes. On the optimized protocol, the effect of the concentration of Ag{sup +} ions in the seed-growth solution and the stability of the obtained particles has also been investigated.

  16. Investigation of the Effects of Length to Depth Ratio on Open Supersonic Cavities Using CFD and Proper Orthogonal Decomposition

    Directory of Open Access Journals (Sweden)

    Ibrahim Yilmaz

    2013-01-01

    Full Text Available Simulations of supersonic turbulent flow over an open rectangular cavity are performed to observe the effects of length to depth ratio (L/D of the cavity on the flow structure. Two-dimensional compressible time-dependent Reynolds-averaged Navier-Stokes equations with k-ω turbulence model are solved. A reduced order modeling approach, Proper Orthogonal Decomposition (POD method, is used to further analyze the flow. Results are obtained for cavities with several L/D ratios at a Mach number of 1.5. Mostly, sound pressure levels (SPL are used for comparison. After a reduced order modeling approach, the number of modes necessary to represent the systems is observed for each case. The necessary minimum number of modes to define the system increases as the flow becomes more complex with the increase in the L/D ratio. This study provides a basis for the control of flow over supersonic open cavities by providing a reduced order model for flow control, and it also gives an insight to cavity flow physics by comparing several simulation results with different length to depth ratios.

  17. Mechanisms involved in the hydrothermal growth of ultra-thin and high aspect ratio ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Demes, Thomas [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Ternon, Céline, E-mail: celine.ternon@grenoble-inp.fr [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, LTM, F-38000 Grenoble (France); Morisot, Fanny [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, Grenoble-INP" 2, IMEP-LaHC, F-38000 Grenoble (France); Riassetto, David [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Legallais, Maxime [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, Grenoble-INP" 2, IMEP-LaHC, F-38000 Grenoble (France); Roussel, Hervé; Langlet, Michel [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France)

    2017-07-15

    Highlights: • ZnO nanowires are grown on sol-gel ZnO seed layers by hydrothermal synthesis. • Ultra-thin and high aspect ratio nanowires are obtained without using additives. • Nanowire diameter is 20–25 nm regardless of growth time and seed morphology. • A nanowire growth model is developed on the basis of thermodynamic considerations. • The nanowires are intended for integration into electrically conductive nanonets. - Abstract: Hydrothermal synthesis of ZnO nanowires (NWs) with tailored dimensions, notably high aspect ratios (AR) and small diameters, is a major concern for a wide range of applications and still represents a challenging and recurring issue. In this work, an additive-free and reproducible hydrothermal procedure has been developed to grow ultra-thin and high AR ZnO NWs on sol-gel deposited ZnO seed layers. Controlling the substrate temperature and using a low reagent concentration (1 mM) has been found to be essential for obtaining such NWs. We show that the NW diameter remains constant at about 20–25 nm with growth time contrary to the NW length that can be selectively increased leading to NWs with ARs up to 400. On the basis of investigated experimental conditions along with thermodynamic and kinetic considerations, a ZnO NW growth mechanism has been developed which involves the formation and growth of nuclei followed by NW growth when the nuclei reach a critical size of about 20–25 nm. The low reagent concentration inhibits NW lateral growth leading to ultra-thin and high AR NWs. These NWs have been assembled into electrically conductive ZnO nanowire networks, which opens attractive perspectives toward the development of highly sensitive low-cost gas- or bio-sensors.

  18. High-aspect-ratio HfC nanobelts accompanied by HfC nanowires: Synthesis, characterization and field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Song, E-mail: tiansong22@126.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Zhang, Yulei; Ren, Jincui; Qiang, Xinfa; Zhang, Shouyang [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Hejun, E-mail: lihejun@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China)

    2017-04-30

    Highlights: • HfC naobelts accompanied by HfC nanowires were synthesized by a catalytic CVD method. • HfC nanobelts as a novel structure of HfC ceramic are reported for the first time. • HfC nanobelts have 100–200 μm in lengths and reach up to 10 μm in widths. • The synthesized product is promising field nanoemitters. - Abstract: As a key refractory carbide, hafnium carbide (HfC) is commonly used as structural materials while the field emission (FE) application of HfC in the field of vacuum microelectronics is almost the only one for functional material purposes. Based on its outstanding physical and chemical characteristics, HfC is identified as a potential candidate with satisfactory mechanical properties and long-term and/or high-temperature FE stability for future applications in high-performance field emitters. However, the development of HfC in various FE applications is hindered because it is not facile to fabricate large-scale low-dimensional HfC field nanoemitters. Herein, High-aspect-ratio HfC nanobelts accompanied by HfC nanowires were synthesized on a large scale by a traditional and simple catalytic chemical vapor deposition (CVD) method. Classical vapor–liquid–solid (VLS) theory was employed to explain the growth of the HfC nanowires and nanobelts along axial direction. The thin HfO{sub 2} shell and thin C layer surrounding the nanostructures might give rise to the diameter fluctuation of HfC nanowires and the width increase of HfC nanobelts in lateral direction. Field emission results show that the high-aspect-ratio HfC nanobelts accompanied by the nanowires are promising field nanoemitters, which exhibit excellent field emission properties with a fairly low turn-on field of ∼1.5 V μm{sup −1} and a low current fluctuation less than ∼10%. This suggests that HfC ceramics with high-aspect-ratio nanostructures are ideal cathode material for various field emission applications.

  19. Theoretical estimates of magnitudes of earthquakes induced by pore-pressure perturbations with large aspect ratios

    Science.gov (United States)

    Galis, Martin; Ampuero, Jean-Paul; Mai, P. Martin; Cappa, Frédéric

    2017-04-01

    Being able to reliably and accurately estimate the possible maximum magnitude of fluid-injection-induced earthquakes is of critical importance to quantify the associated seismic hazard and to define operational constraints for geo-reservoirs. In previous studies, we developed theoretical estimates of the magnitude of fluid-injection-induced earthquakes based fracture mechanics, assuming circular pressure perturbations. However, natural reservoirs are typically much wider than thicker. Therefore, here we discuss the application of our model to horizontally elongated pressurized regions with realistic aspect ratios. Assuming circular pressure perturbations, we derived a physical model estimating how large a rupture will grow on a given fault and for a given pore-pressure perturbation. We used two approaches. The first, semi-analytical approach is based on pore pressure evolution obtained by solving the diffusion equation for a cylindrical reservoir with no-flow boundaries. The second approach is an approximation to the first one, based on a point-load approximation of the pres-sure perturbation on the fault, allowing derivation of a complete analytical formula relating the magnitude of the largest arrested rupture, Mmax-arr, to injection and slip-weakening friction parameters. We found that the Mmax-arr scales with cumulative injected fluid volume as a power law with exponent of 3/2. In contrast, the Mmax relation by McGarr (2014) is a linear scaling (exponent of 1). While for the dataset used by McGarr (2014) the difference between our and McGarr's models is relatively small, inclusion of datasets with broad range of injected fluid volumes (from 10-10m3 to 1010m3) suggests better agreement with our model. However, inclusion of extended pressure perturbations into our two models, while maintaining the (semi-)analytical character, is not viable. Therefore, we perform numerical dynamic-rupture simulations to investigate rupture nucleation and arrest for pressure

  20. Effect of torsional stiffness and inertia on the dynamics of low aspect ratio flapping wings.

    Science.gov (United States)

    Xiao, Qing; Hu, Jianxin; Liu, Hao

    2014-03-01

    Micro air vehicle-motivated aerodynamics in biological flight has been an important subject in the past decade. Inspired by the novel flapping wing mechanisms in insects, birds and bats, we have carried out a numerical study systematically investigating a three-dimensional flapping rigid wing with passively actuated lateral and rotational motion. Distinguishing it from the limited existing studies, this work performs a systematic examination on the effects of wing aspect ratio (AR = 1.0 to infinity), inertia (density ratio σ = 4-32), torsional stiffness (frequency ratio F = 1.5-10 and infinity) and pivot point (from chord-center to leading edge) on the dynamics response of a low AR rectangular wing under an initial zero speed flow field condition. The simulation results show that the symmetry breakdown of the flapping wing results in a forward/backward motion with a rotational pitching. When the wing reaches its stable periodic state, the induced pitching frequency is identical to its forced flapping frequency. However, depending on various kinematic and dynamic system parameters, (i.e. flapping frequency, density ratio and pitching axis), the lateral induced velocity shows a number of different oscillating frequencies. Furthermore, compared with a one degree of freedom (DoF) wing in the lateral direction only, the propulsion performance of such a two DoF wing relies very much on the magnitude of torsional stiffness adding on the pivot point, as well as its pitching axis. In all cases examined here, thrust force and moment generated by a long span wing is larger than that of a short wing, which is remarkably linked to the strong reverse von Kármán vortex street formed in the wake of a wing.

  1. Natural convection in a horizontal fluid layer with a periodic array of internal square cylinders - Need for very large aspect ratio 2D domains

    International Nuclear Information System (INIS)

    Lee, Jae Ryong; Ha, Man Yeong; Balachandar, S.

    2007-01-01

    We consider the problem of natural convection in a horizontal layer of fluid, bounded between two infinite parallel plates. The present configuration includes a periodic array of square cylinders embedded within the layer, which introduces an externally imposed horizontal length scale. The central question we address here is the effect of the horizontal extent of the computational domain (and the number of square cylinders contained within the domain) on the flow dynamics and overall heat transfer. Computations that use small aspect ratio domains, which contain only one or two of the square cylinders, severely constrain the plume dynamics. Only large aspect ratio computational domains (AR ≥ 10) allow multiple plumes and their complex dynamics, and begin to approach the results of an infinite layer. Here at a modest Rayleigh number of 10 6 , where the flow is unsteady, we systematically vary the horizontal extent of the computational domain by progressively including more of the internal periodic square cylinders. The approach to approximating an infinite layer is observed to be quite slow and even with wide aspect ratio computational domains that include as many as 12 internal periodic square cylinders the asymptotic state is not closely approximated. The need for very large aspect ratio computational domain in such problems is clear

  2. Static Footprint Local Forces, Areas, and Aspect Ratios for Three Type 7 Aircraft Tires

    Science.gov (United States)

    Howell, William E.; Perez, Sharon E.; Vogler, William A.

    1991-01-01

    The National Tire Modeling Program (NTMP) is a joint NASA/industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. Footprint local forces, areas, and aspect ratios were measured. Local footprint forces in the vertical, lateral, and drag directions were measured with a special footprint force transducer. Measurements of the local forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tires. Three tires were tested: (1) one representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes, (2) a nose landing gear tire for the Space Shuttle Orbiter, and (3) a main landing gear tire for the Space Shuttle Orbiter. Data obtained for various inflation pressures and vertical loads are presented for two aircraft tires. The results are presented in graphical and tabulated forms.

  3. Performance and stability limits at near-unity aspect ratio in the Pegasus Toroidal Experiment

    International Nuclear Information System (INIS)

    Fonck, R.J.

    2002-01-01

    The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, I p ≤ 0.15MA, and B t p =aB t is similar to that observed for NBI-heated START discharges. Achievable plasma current apparently is subject to a 'soft' limit of I p =I t f ≤ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q 95 approaches 5, in agreement with numerical predictions. (author)

  4. Measurement and simulation of jet mass caused by a high-aspect ratio pertubation

    Energy Technology Data Exchange (ETDEWEB)

    Keiter, Paul A [Los Alamos National Laboratory; Cooley, James [Los Alamos National Laboratory; Kyrala, George [Los Alamos National Laboratory; Wilson, Doug [Los Alamos National Laboratory; Blue, Brent [LLNL/GA; Elliott, Jim [LLNL; Edwards, John [LLNL; Robey, Harry [LLNL; Spears, Brian [LLNL

    2009-01-01

    Inertial confinement fusion (ICF) capsule performance can be negatively impacted by the presence of hydrodynamic instabilities. To perform a gas fill on an ICF capsule current plans involve drilling a small hole and inserting a fill tube to inject the gas mixture into the capsule. This introduces a perturbation on the capsule, which can seed hydrodynamic instabilities. The small hole can cause jetting of the shell material into the gas, which might adversely affect the capsule performance. We have performed simulations and experiments to study the hydrodynamic evolution of jets from high-aspect ratio holes, such as the fill tube hole. Although simulations using cold materials over predict the amount of mass in the jet, when a reasonable amount of preheat (< 1 eV) is introduced, the simulations are in better agreement with the experiment.

  5. Bio-nanotextured high aspect ratio micropillar arrays for high surface area energy storage devices

    Science.gov (United States)

    Chu, S.; Gerasopoulos, K.; Ghodssi, R.

    2015-12-01

    This paper presents fabrication and characterization of bio-nanotextured hierarchical nickel oxide (NiO) supercapacitor electrodes. The hierarchical electrode structure is created through self-assembly of Tobacco mosaic viruses (TMVs) on high aspect-ratio micropillar arrays. Enhanced assembly of the bio-nanoparticles was achieved by increasing TMV solution accessibility into the deep microcavities of the pillar arrays. Electrochemical characterization of the hierarchical NiO supercapacitor electrodes revealed a 25-fold increase in charge capacity compared to a planar NiO, and demonstrated excellent cycle stability over 1500 charge/discharge cycles at 2 mA/cm2. This study leverages the unique bio-nanoscaffolds for small scale energy storage devices through further optimization of the hierarchical structures and wetting techniques for significant improvements in micro/nano scale energy storage devices.

  6. Scaling model for high-aspect-ratio microballoon direct-drive implosions at short laser wavelengths

    International Nuclear Information System (INIS)

    Schirmann, D.; Juraszek, D.; Lane, S.M.; Campbell, E.M.

    1992-01-01

    A scaling model for hot spherical ablative implosions in direct-drive mode is presented. The model results have been compared with experiments from LLE, ILE, and LLNL. Reduction of the neutron yield due to illumination nonuniformities is taken into account by the assumption that the neutron emission is cut off when the gas shock wave reflected off the center meets the incoming pusher, i.e., at a time when the probability of shell breakup is greatly enhanced. The main advantage of this semiempirical scaling model is that it elucidates the principal features of these simple implosions and permits one to estimate very quickly the performance of a high-aspect-ratio direct-drive target illuminated by short-wavelength laser light. (Author)

  7. Laminar flow in radial flow cell with small aspect ratios: Numerical and experimental study

    DEFF Research Database (Denmark)

    Detry, J. G.; Deroanne, C.; Sindic, M.

    2009-01-01

    Studies on the effect of wall shear stress on soil and biofilm attachment and removal from a surface are one of the many applications of radial axisymmetrical flow. The particular nature of this flow allows taking advantage of a wide range of wall shear Stress applied at the analyzed surface...... in a single experiment. This type of experiments provides a critical radius up to which soil removal occurs. Good models are, however, still needed to convert the experimental data into critical wall shear stress. Analytical models are already available for creeping flow but Computational Fluid Dynamics must...... be applied for experiments performed at higher Reynolds numbers. The present study is a numerical analysis of the radial axisymmetrical flow for aspect ratios of 0.125, 0.25, 0.5 and 1 with inlet pipe Reynolds numbers varying from 0 to 2000, aiming at computing the wall shear stress distribution at any...

  8. Facile Route to Vertically Aligned High-Aspect Ratio Block Copolymer Films via Dynamic Zone Annealing

    Science.gov (United States)

    Singh, Gurpreet; Kulkarni, Manish; Yager, Kevin; Smilgies, Detlef; Bucknall, David; Karim, Alamgir

    2012-02-01

    Directed assembly of block copolymers (BCP) can be used to fabricate a diversity of nanostructures useful for nanotech applications. The ability to vertically orient etchable high aspect ratio (˜30) ordered BCP domains on flexible substrates via continuous processing methods are particularly attractive for nanomanufacturing. We apply sharp dynamic cold zone annealing (CZA-S) to create etchable, and predominantly vertically oriented 30nm cylindrical domains in 1 μm thick poly(styrene-b-methylmethacrylate) films on low thermal conductivity rigid (quartz) and flexible (PDMS & Kapton) substrates. Under similar static conditions, temporally stable vertical cylinders form within a narrow zone above a critical temperature gradient. Primary ordering mechanism of CZA-S involves sweeping this vertically orienting zone created at maximum thermal gradient. An optimal speed is needed since the process competes with preferential surface wetting dynamics that favors parallel orientation. GISAXS of etched BCP films confirms internal morphology.

  9. High aspect ratio MEMS capacitor for high frequency impedance matching applications

    DEFF Research Database (Denmark)

    Yalcinkaya, Arda Deniz; Jensen, Søren; Hansen, Ole

    2003-01-01

    We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb......-drive structures with vertical sidewalls. The process sequence for fabrication of the devices uses only one lithographic masking step and can be completed in a short time. The fabricated device was characterized with respect to electrical quality factor, tuning range, self-resonance frequency and transient...... response and it was found that the device is a suitable passive component to be used in impedance matching applications, band-pass filtering or voltage controlled oscillators in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands....

  10. Static Response of Functionally Graded Material Plate under Transverse Load for Varying Aspect Ratio

    Directory of Open Access Journals (Sweden)

    Manish Bhandari

    2014-01-01

    Full Text Available Functionally gradient materials (FGM are one of the most widely used materials in various applications because of their adaptability to different situations by changing the material constituents as per the requirement. Nowadays it is very easy to tailor the properties to serve specific purposes in functionally gradient material. Most structural components used in the field of engineering can be classified as beams, plates, or shells for analysis purposes. In the present study the power law, sigmoid law and exponential distribution, is considered for the volume fraction distributions of the functionally graded plates. The work includes parametric studies performed by varying volume fraction distributions and aspect ratio. The FGM plate is subjected to transverse UDL (uniformly distributed load and point load and the response is analysed.

  11. Maintenance oriented tokamak reactor with low activation material and high aspect ratio configuration

    International Nuclear Information System (INIS)

    Nishio, S.; Ueda, S.; Aoki, I.

    1997-01-01

    Some of the difficulties of maintenance of a tokamak system are due to the radioactivity of its materials and the complexity of its configuration. To mitigate the difficulties, very low activation SiC/SiC composite material and a torus configuration with a high aspect ratio of eight are introduced. The torus system is divided radially into equal sectors, each of which forms an assembling unit. All piping and feeder systems are shifted to the spacious central torus region. The new concept is called DREAM tokamak reactor, which is an acronym for DRastically EAsy Maintenance. The maximum toroidal field strength of 20 T and the plasma major and minor radii of 16 m and 2 m lead to a high fusion power of 5.5 GW, under moderate physics constraints such as an MHD safety factor of three, a Troyon factor of three for the beta limit and an energy confinement time enhancement factor of two. (author)

  12. Relaxed and partially relaxed magnetic equilibria in tight-aspect-ratio tori

    International Nuclear Information System (INIS)

    Browning, P.K.; Clegg, J.R.; Duck, R.C.; Rusbridge, M.G.

    1993-01-01

    Force-free equilibrium magnetic fields in tight-aspect-ratio toroidal configurations are investigated. The study is mainly directed to modelling field configurations in the 'rodomak', a modification to the SPHEX gun-injected spheromak in which a current-carrying rod is inserted along the geometric axis. A family of analytical relaxed states (∇ x B = μB, μ constant) is presented for a torus of rectangular cross section, with boundary conditions allowing for flux embedded in the walls, representing the gun. Numerically calculated fields in SPHEX geometry, with μ profiles relevant to the driven phase of operation, are also given. The dependence of the field configurations and global quantities such as energy, helicity and toroidal current on the controlling parameters (gun flux, gun current and rod current) and geometry is discussed. (author)

  13. Gust response analysis and wind tunnel test for a high-aspect ratio wing

    Directory of Open Access Journals (Sweden)

    Liu Yi

    2016-02-01

    Full Text Available A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisciplinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter boundary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quantitative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flexible wings.

  14. PEDOT:PSS/GO nanocomposites: Determination of the aspect ratio by indirect measurements

    Energy Technology Data Exchange (ETDEWEB)

    Giuri, Antonella; Colella, Silvia; Listorti, Andrea; Rizzo, Aurora; Corcione, Carola Esposito [University of Salento, via per Monteroni, km 1,73100, Lecce (Italy)

    2016-05-18

    Polymer nanocomposites properties significantly depend on the average size of the fillers dispersed into the matrix and on the grade of the dispersion, the latter influenced by the process techniques. In this work, we determined the aspect ratio of graphene oxide (GO) dispersed into Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), starting from the indirect measurement of the rheological behavior of polymer/filler mixtures, as a function of the shear rate and the volumetric composition. PEDOT:PSS+GO nanocomposite films were also realized by spin coating on different substrates and characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD), in order to analyze the quality of the dispersion, even by direct measurements.

  15. Surface tension-induced high aspect-ratio PDMS micropillars with concave and convex lens tips

    KAUST Repository

    Li, Huawei

    2013-04-01

    This paper reports a novel method for the fabrication of 3-dimensional (3D) Polydimethylsiloxane (PDMS) micropillars with concave and convex lens tips in a one-step molding process, using a CO2 laser-machined Poly(methyl methacrylate) (PMMA) mold with through holes. The PDMS micropillars are 4 mm high and have an aspect ratio of 251. The micropillars are formed by capillary force drawing up PDMS into the through hole mold. The concave and convex lens tips of the PDMS cylindrical micropillars are induced by surface tension and are controllable by changing the surface wetting properties of the through holes in the PMMA mold. This technique eliminates the requirements of expensive and complicated facilities to prepare a 3D mold, and it provides a simple and rapid method to fabricate 3D PDMS micropillars with controllable dimensions and tip shapes. © 2013 IEEE.

  16. Numerical investigation of non-Newtonian fluids in annular ducts with finite aspect ratio using lattice Boltzmann method

    Science.gov (United States)

    Khali, S.; Nebbali, R.; Ameziani, D. E.; Bouhadef, K.

    2013-05-01

    In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (dilatant and pseudoplastic fluids) is investigated for cases of finite aspect ratios. The study is conducted numerically using the lattice Boltzmann method (LBM). In many industrial applications, the apparatuses and installations drift away from the idealized case of an annulus of infinite length, and thus the end caps effect can no longer be ignored. The inner cylinder is rotating while the outer one and the end walls are maintained at rest. The lattice two-dimensional nine-velocity (D2Q9) Boltzmann model developed from the Bhatnagar-Gross-Krook approximation is used to obtain the flow field for fluids obeying the power-law model. The combined effects of the Reynolds number, the radius ratio, and the power-law index n on the flow characteristics are analyzed for an annular space of finite aspect ratio. Two flow modes are obtained: a primary Couette flow (CF) mode and a secondary Taylor vortex flow (TVF) mode. The flow structures so obtained are different from one mode to another. The critical Reynolds number Rec for the passage from the primary to the secondary mode exhibits the lowest value for the pseudoplastic fluids and the highest value for the dilatant fluids. The findings are useful for studies of the swirling flow of non-Newtonians fluids in axisymmetric geometries using LBM. The flow changes from the CF to TVF and its structure switches from the two-cells to four-cells regime for both Newtonian and dilatant fluids. Contrariwise for pseudoplastic fluids, the flow exhibits 2-4-2 structure passing from two-cells to four cells and switches again to the two-cells configuration. Furthermore, the critical Reynolds number presents a monotonic increase with the power-law index n of the non-Newtonian fluid, and as the radius ratio grows, the transition flow regimes tend to appear for higher critical Reynolds numbers.

  17. Fabrication of high-aspect-ratio nano structures using a nano x-ray shadow mask

    International Nuclear Information System (INIS)

    Kim, Yong Chul; Lee, Seung S

    2008-01-01

    This paper describes a novel method for the fabrication of high-aspect-ratio nano structures (HAR-nano structures) using a nano x-ray shadow mask and deep x-ray lithography (DXRL). The nano x-ray shadow mask is fabricated by depositing an x-ray absorber layer (Au, 3 µm) onto the back side of a nano shadow mask. The nano shadow mask is produced with nano-sized apertures whose dimensions are reduced to several tens of nanometers by the accumulation of low-stress silicon nitride (Si x N y ) using the LPCVD process on the shadow mask. A shadow mask containing apertures with a size of 1 µm is fabricated on a bulk micromachined Si x N y membrane. The thickness of an absorber layer must be in the range of several tens of micrometers in order to obtain a contrast of more than 100 for the conventional DXRL process at the Pohang Light Source (PLS). However, a 3 µm thick absorber layer can provide a sufficient contrast if the modified DXRL of the central beam-stop method is used, which blocks high-energy x-rays. A nano shadow mask with 30 nm sized apertures is fabricated and a nano x-ray shadow mask with 250 nm sized apertures is fabricated by depositing a 3 µm thick absorber layer on a nano shadow mask with 500 nm sized apertures. HAR-nano structures (circles with a diameter of 420 nm and lines with a width of 274 nm) with aspect ratios of over 10:1 on a 3.2 µm SU-8 are successfully fabricated by using the nano x-ray shadow mask and the central beam-stop method

  18. Unified model for the electromechanical coupling factor of orthorhombic piezoelectric rectangular bar with arbitrary aspect ratio

    Directory of Open Access Journals (Sweden)

    R. Rouffaud

    2017-02-01

    Full Text Available Piezoelectric Single Crystals (PSC are increasingly used in the manufacture of ultrasonic transducers and in particular for linear arrays or single element transducers. Among these PSCs, according to their microstructure and poled direction, some exhibit a mm2 symmetry. The analytical expression of the electromechanical coupling coefficient for a vibration mode along the poling direction for piezoelectric rectangular bar resonator is established. It is based on the mode coupling theory and fundamental energy ratio definition of electromechanical coupling coefficients. This unified formula for mm2 symmetry class material is obtained as a function of an aspect ratio (G where the two extreme cases correspond to a thin plate (with a vibration mode characterized by the thickness coupling factor, kt and a thin bar (characterized by k33′. To optimize the k33′ value related to the thin bar design, a rotation of the crystallogaphic axis in the plane orthogonal to the poling direction is done to choose the highest value for PIN-PMN-PT single crystal. Finally, finite element calculations are performed to deduce resonance frequencies and coupling coefficients in a large range of G value to confirm developed analytical relations.

  19. High-Yield Synthesis of Uniform Ag Nanowires with High Aspect Ratios by Introducing the Long-Chain PVP in an Improved Polyol Process

    Directory of Open Access Journals (Sweden)

    Jie-Jun Zhu

    2011-01-01

    Full Text Available Polyvinyl pyrrolidone (PVP with different molecular weights was used as capping agent to synthesize silver nanowires through a polyol process. The results indicated that the yields and aspect ratios of silver nanowires were controlled by the chain length of PVP and increased with increasing the molecular weight (MW of PVP. When the long-chain PVP-K90 (MW = 800,000 was used, the product was uniform in size and was dominated by nanowires with high aspect ratios. The growth mechanism of the nanowires was studied. It is proposed that the chemical adsorption of Ag+ on the PVP chains at the initial stage promotes the growth of Ag nanowires.

  20. Stress analysis of an agitated particle bed with different particle aspect ratios by the discrete element method

    Directory of Open Access Journals (Sweden)

    Goh Wei Pin

    2017-01-01

    Full Text Available The size distribution, shape and aspect ratio of particles are the common factors that affect their packing in a particle bed. Agitated powder beds are commonly used in the process industry for various applications. The stresses arising as a result of shearing the bed could result in undesirable particle breakage with adverse impact on manufacturability. We report on our work on analysing the stress distribution within an agitated particle bed with several particle aspect ratios by the Discrete Element Method (DEM. Rounded cylinders with different aspect ratios are generated and incorporated into the DEM simulation. The void fraction of the packing of the static and agitated beds with different particle aspect ratios is analysed. Principal and deviatoric stresses are quantified in the regions of interest along the agitating impeller blade for different cases of particle aspect ratios. The relationship between the particle aspect ratio and the stress distribution of the bed over the regions of interest is then established and will be presented.

  1. Radiological examination in diagnosis of dolicho-sigmoid taking into consideration the colon and sigmoid length ratio in pediatric patients

    International Nuclear Information System (INIS)

    Bober, S.T.

    1993-01-01

    The aim of the study was usefulness evaluation of radiological examination in the diagnosis of dolicho sigmoid, especially establishing diagnosis criteria of pictures on contrast enema films which may be pathognomonic for dolicho sigmoid in children. An attempt has been made to establish objectively the length of sigmoid and colon to calculated the radio of their sizes in children with dolicho sigmoid syndrome and in control group. Contrast enemas were performed in 176 children. Among the examined children, in 26 cases dolicho sigmoid syndrome was found, including two cases of dolicho colon. Children with dolicho sigmoid syndrome showed various anomalies in elongated sigmoid location at its different levels. Generally, it was situated at the level of between L 1 and L 5 . The sigmoid formed often two or more abnormal loops with various bending and twisting or irregular protrusions. The coefficient or our invention concerned the ratio of colon length to the length of elongated sigmoid and on the basis of calculations made on children suffering from dolicho sigmoid syndrome the numerical values ranged from 0.7 to 1.5. The same calculations performed on the control for the proposed coefficient ranged from 2.2 to 4.2. (author). 65 refs, 15 figs, 11 tabs

  2. Non-universal and universal aspects of the large scattering length limit

    Science.gov (United States)

    Miller, Gerald A.

    2018-02-01

    The momentum density, n (k) of interacting many-body Fermionic systems is studied (for k >kF) using examples of several well-known two-body interaction models. It is shown that n (k) can be approximated by a zero-range model for momenta k less than about 0.1 /re, where re the effective range. If the scattering length is large and one includes the effects of a fixed value of re ≠ 0, n (k) is almost universal for momenta k up to about 2 /re. However, n (k) can not be approximated by a zero-range model for momenta k greater than about 1 / (a re2)1/3, where a is the scattering length, and if one wishes to maintain a sum rule that relates the energy of a two component Fermi-gas to an integral involving the density. We also show that the short separation distance, s, behavior of the pair density varies as s6.

  3. Model systems with extreme aspect ratio, tunable geometry, and surface functionality for a quantitative investigation of the Lotus effect.

    Science.gov (United States)

    Hassel, Achim Walter; Milenkovic, Srdjan; Schürmann, Ulrich; Greve, Henry; Zaporojtchenko, Vladimir; Adelung, Rainer; Faupel, Franz

    2007-02-13

    Superhydrophobicity and superhydrophilicity of surfaces are key properties for fabrication of self-cleaning surfaces (Lotus effect). It is well known that the mechanism behind this is based on the surface roughness and surface functionalization. To obtain an understanding of the details of the underlying mechanism, a metal system based on a eutectic is suggested. In this study, a wide range tunability of its needlelike narrow size distributed nanostructure is demonstrated. The length of the needles as well as their density can be varied independently. In addition, an important parameter for the wettability, the roughness, is related directly to the growth parameters, which lead to excellent controllable and reproducible eutectic structures. Simply by varying etching time very high aspect ratios can be achieved, allowing studying the interaction of the very long needles with liquids. Moreover, the surface functionality can be tuned by RF-magnetron sputtering of PTFE onto the metal needles. As those layers can be very thin, our system allows, in principle, studying the transition from a metal to a polymer surface using submonolayers. Furthermore, the first contact angle measurements on the nanostructured and functionalized eutectic structures are presented and discussed.

  4. Favorable Street Canyon Aspect Ratios for Pollutant Removal- a Large-Eddy Simulation Approach

    Science.gov (United States)

    Chung, T. N.; Liu, C.

    2010-12-01

    Given the limited land resource, urbanization is one of the solutions to the current rapid economic development and population growth. Narrow streets flanked by high-rise buildings, also known as street canyons, are commonly found in metropolises nowadays. In recent years, this issue has been aroused the public awareness that the air pollutants from domestic sources and vehicular emissions are unable to be removed but trapped inside the street canopy level threatening human health and our living environment. A thorough understanding of the pollutant removal mechanism is the key step to rectify the current poor urban air quality. This study is therefore conceived to examine how the pollutant removal is related to the street width and building height. Large-eddy simulation (LES) with the one-equation subgrid-scale (SGS) turbulence model is employed to investigate the characteristic ventilation and pollutant transport in idealized two-dimensional (2D) street canyons of different building-height-to-street-width (aspect) ratios (ARs) h/b. Model validation is performed by comparing the LES results with those of k-ɛ turbulence model and laboratory experiments. A consistent trend of the pollutant exchange rate (PCH) among the LES, k-ɛ turbulence model, and experimental results is obtained. While its drag is largest, the street canyon of AR = 0.5 is found to be most favorable in the pollutant removal perspective. This finding seems contradict with the presumption that the smaller the AR (wider the street), the more efficient the pollutants removal. In the isolated roughness regime the flows in (wider) street canyons, the entrainment from the prevailing flow aloft down into the ground level purging pollutant away. On the contrary in the skimming flow regime, in (narrower) street canyons, the recirculating flows inside the street canyon are isolated from the prevailing flow in which the (vertical) pollutant removal is governed by roof-level intermittency. Unexpectedly, in

  5. BisGMA/TEGDMA dental composite containing high aspect-ratio hydroxyapatite nanofibers

    Science.gov (United States)

    Chen, Liang; Yu, Qingsong; Wang, Yong; Li, Hao

    2011-01-01

    Objectives The objectives of this study are to investigate the properties of high aspect-ratio hydroxyapatite (HAP) nanofibers and the reinforcing effect of such fibers on bisphenol A glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) dental resins (without silica microparticle filler) and dental composites (with silica microparticle filler) with various mass fractions (loading rates). Methods HAP nanofibers were synthesized using a wet-chemical method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal gravimetric analysis (TGA). Biaxial flexural strength (BFS) of the HAP nanofibers reinforced dental resins without any microsized filler and dental composites with silica microparticle filler was tested and analysis of variance (ANOVA) was used for the statistically analysis of acquired data. The morphology of fracture surface of tested dental composite samples was examined by SEM. Results The HAP nanofibers with aspect-ratios of 600 to 800 can be successfully fabricated with a simple wet-chemical method in aqueous solution. Impregnation of small mass fractions of the HAP nanofibers (5 wt% or 10 wt%) into the BisGMA/TEGDMA dental resins or impregnation of small mass fractions of the HAP nanofibers (2 wt% or 3 wt%) into the dental composites can substantially improve the biaxial flexural strength of the resulting dental resins and composites. A percolation threshold of HAP nanofibers, beyond which more nanofibers will no longer further increase the mechanical properties of dental composites containing HAP nanofibers, was observed for the dental composites with or without silica microparticle filler. Our mechanical testing and fractographic analysis indicated that the relatively good dispersion of HAP nanofibers at low mass fraction is the key reason for the significantly improved biaxial flexural strength, while higher mass fraction of HAP nanofibers tends to lead to bundles that cannot effectively

  6. High aspect ratio iridescent three-dimensional metal–insulator–metal capacitors using atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Burke, Micheal, E-mail: micheal.burke@tyndall.ie; Blake, Alan; Djara, Vladimir; O' Connell, Dan; Povey, Ian M.; Cherkaoui, Karim; Monaghan, Scott; Scully, Jim; Murphy, Richard; Hurley, Paul K.; Pemble, Martyn E.; Quinn, Aidan J., E-mail: aidan.quinn@tyndall.ie [Tyndall National Institute, University College Cork, Cork (Ireland)

    2015-01-01

    The authors report on the structural and electrical properties of TiN/Al{sub 2}O{sub 3}/TiN metal–insulator–metal (MIM) capacitor structures in submicron three-dimensional (3D) trench geometries with an aspect ratio of ∼30. A simplified process route was employed where the three layers for the MIM stack were deposited using atomic layer deposition (ALD) in a single run at a process temperature of 250 °C. The TiN top and bottom electrodes were deposited via plasma-enhanced ALD using a tetrakis(dimethylamino)titanium precursor. 3D trench devices yielded capacitance densities of 36 fF/μm{sup 2} and quality factors >65 at low frequency (200 Hz), with low leakage current densities (<3 nA/cm{sup 2} at 1 V). These devices also show strong optical iridescence which, when combined with the covert embedded capacitance, show potential for system in package (SiP) anticounterfeiting applications.

  7. Discriminating single-bacterial shape using low-aspect-ratio pores.

    Science.gov (United States)

    Tsutsui, Makusu; Yoshida, Takeshi; Yokota, Kazumichi; Yasaki, Hirotoshi; Yasui, Takao; Arima, Akihide; Tonomura, Wataru; Nagashima, Kazuki; Yanagida, Takeshi; Kaji, Noritada; Taniguchi, Masateru; Washio, Takashi; Baba, Yoshinobu; Kawai, Tomoji

    2017-12-12

    Conventional concepts of resistive pulse analysis is to discriminate particles in liquid by the difference in their size through comparing the amount of ionic current blockage. In sharp contrast, we herein report a proof-of-concept demonstration of the shape sensing capability of solid-state pore sensors by leveraging the synergy between nanopore technology and machine learning. We found ionic current spikes of similar patterns for two bacteria reflecting the closely resembled morphology and size in an ultra-low thickness-to-diameter aspect-ratio pore. We examined the feasibility of a machine learning strategy to pattern-analyse the sub-nanoampere corrugations in each ionic current waveform and identify characteristic electrical signatures signifying nanoscopic differences in the microbial shape, thereby demonstrating discrimination of single-bacterial cells with accuracy up to 90%. This data-analytics-driven microporescopy capability opens new applications of resistive pulse analyses for screening viruses and bacteria by their unique morphologies at a single-particle level.

  8. Gas-Assisted Heating Technology for High Aspect Ratio Microstructure Injection Molding

    Directory of Open Access Journals (Sweden)

    Shia-Chung Chen

    2013-01-01

    Full Text Available A hot gas is used for heating the cavity surface of a mold. Different mold gap sizes were designed. The mold surface temperature was heated to above the glass transition temperature of the plastic material, and the mold then closed for melt filling. The cavity surface can be heated to 130°C to assist the melt filling of the microfeatures. Results show that hot gas heating can improve the filling process and achieve 91% of the high aspect ratio microgrooves (about 640.38 μm of the maximum of 700 μm. The mold gap size strongly affects the heating speed and heating uniformity. Without surface preheating, the center rib is the highest. When the heating target temperature is 90°C or 100°C, the three microribs have a good uniformity of height. However, when the target temperature exceeds 100°C, the left side rib is higher than the other ribs.

  9. Influence of the aspect ratio of magnetic metallic additives on the microwave absorbing performance

    Science.gov (United States)

    de Souza Pinto, Simone; Barros Machado, João Paulo; Gomes, Newton A. S.; Cerqueira Rezende, Mirabel

    2017-09-01

    This work aims to show the behavior of radar absorbing materials (RAM) based on magnetic metallic additives with different aspect ratios. For this, two materials, carbonyl iron, constituted of spherical iron particles, and carbon-steel filaments were used. These additives were characterized considering their morphological and structural features. X-ray diffraction analysis shows that the two additives have the same crystallographic structure, but their morphologies are quite different in micrometer scale. Epoxy resin/metallic additive composites using the neat additives and their mixtures were prepared. The electromagnetic characterization of the composites evaluated the permittivity, permeability and reflectivity behaviors in the frequency range of 8.2-12.4 GHz. The results show that the samples obtained with the mixture of the two additives resulted in composites with high complex parameters of permittivity and permeability. Better RAM performance is observed for samples based on metallic filaments and for more concentrated mixtures containing the two additives (values up to  -14 dB or ~96% of attenuation). The influence of specimen-thickness on the RAM performance is also observed.

  10. Aspect Ratio of Receiver Node Geometry based Indoor WLAN Propagation Model

    Science.gov (United States)

    Naik, Udaykumar; Bapat, Vishram N.

    2017-08-01

    This paper presents validation of indoor wireless local area network (WLAN) propagation model for varying rectangular receiver node geometry. The rectangular client node configuration is a standard node arrangement in computer laboratories of academic institutes and research organizations. The model assists to install network nodes for the better signal coverage. The proposed model is backed by wide ranging real time received signal strength measurements at 2.4 GHz. The shadow fading component of signal propagation under realistic indoor environment is modelled with the dependency on varying aspect ratio of the client node geometry. The developed new model is useful in predicting indoor path loss for IEEE 802.11b/g WLAN. The new model provides better performance in comparison to well known International Telecommunication Union and free space propagation models. It is shown that the proposed model is simple and can be a useful tool for indoor WLAN node deployment planning and quick method for the best utilisation of the office space.

  11. Atomic Layer Deposition for Coating of High Aspect Ratio TiO2 Nanotube Layers

    Science.gov (United States)

    2016-01-01

    We present an optimized approach for the deposition of Al2O3 (as a model secondary material) coating into high aspect ratio (≈180) anodic TiO2 nanotube layers using the atomic layer deposition (ALD) process. In order to study the influence of the diffusion of the Al2O3 precursors on the resulting coating thickness, ALD processes with different exposure times (i.e., 0.5, 2, 5, and 10 s) of the trimethylaluminum (TMA) precursor were performed. Uniform coating of the nanotube interiors was achieved with longer exposure times (5 and 10 s), as verified by detailed scanning electron microscopy analysis. Quartz crystal microbalance measurements were used to monitor the deposition process and its particular features due to the tube diameter gradient. Finally, theoretical calculations were performed to calculate the minimum precursor exposure time to attain uniform coating. Theoretical values on the diffusion regime matched with the experimental results and helped to obtain valuable information for further optimization of ALD coating processes. The presented approach provides a straightforward solution toward the development of many novel devices, based on a high surface area interface between TiO2 nanotubes and a secondary material (such as Al2O3). PMID:27643411

  12. Progress in the fabrication of high aspect ratio zone plates by soft x-ray lithography

    International Nuclear Information System (INIS)

    Divan, R.; Mancini, D. C.; Moldovan, N. A.; Lai, B.; Assoufid, L.; Leondard, Q.; Cerrina, F.

    2002-01-01

    Fabrication of Fresnel zone plates for the hard x-ray spectral region combines the challenge of high lateral resolution (∼100 nm) with a large thickness requirement for the phase-shifting material (0.5-3 (micro)m). For achieving a high resolution, the initial mask was fabricated by e-beam lithography and gold electroforming. To prevent the collapse of the structures between the developing and electroforming processes, drying was completely eliminated. Fabrication errors, such as nonuniform gold electroplating and collapse of structures, were systematically analyzed and largely eliminated. We optimized the exposure and developing processes for 950k and 2200k polymethylmethacrylate of different thicknesses and various adhesion promoters. We discuss the effects of these fabrication steps on the zone plate's resolution and aspect ratio. Fresnel zone plates with 110 nm outermost zone width, 150 (micro)m diameter, and 1.3 (micro)m gold thickness were fabricated. Preliminary evaluation of the FZPs was done by scanning electron microscopy and atomic force microscopy. The FZP focusing performance was characterized at the Advanced Photon Source at Argonne National Laboratory

  13. Anodic formation of low-aspect-ratio porous alumina films for metal-oxide sensor application

    International Nuclear Information System (INIS)

    Gorokh, G.; Mozalev, A.; Solovei, D.; Khatko, V.; Llobet, E.; Correig, X.

    2006-01-01

    Thin nanoporous anodic alumina films, of low aspect ratio (1:1), with two distinctive pore sizes and morphologies were prepared by two-step constant-current anodising of aluminium layers on SiO 2 /Si substrates in 0.4 mol dm -3 tartaric (TA) and malonic acid (MA) electrolytes and then modified by open-circuit dissolution. The anodic films were employed as a support material for sputtering-deposition of thin WO 3 layers in view of exploiting their gas sensing properties. The films and deposits were characterized by scanning electron microscopy, X-ray diffraction and electric resistance measurements at fixed temperatures in the range of 100-300 deg. C upon NH 3 and CO gas exposures. Test sensors prepared from the annealed and stabilized alumina-supported WO 3 active layers were insensitive to CO but showed considerably enhanced responses to NH 3 at 300 deg. C, the sensitivity depending upon the anodic film nature, the pore size and the surface morphology. The increased sensor sensitivity is due to the substantially enlarged film surface area of the TA-supported WO 3 films and the nanostructured, camomile-like morphology of the MA-supported WO 3 films. Sensing mechanisms in the alumina-supported WO 3 active layers are discussed

  14. Aeroelastic Optimization Design for High-Aspect-Ratio Wings with Large Deformation

    Directory of Open Access Journals (Sweden)

    Changchuan Xie

    2017-01-01

    Full Text Available This paper presents a framework of aeroelastic optimization design for high-aspect-ratio wing with large deformation. A highly flexible wing model for wind tunnel test is optimized subjected to multiple aeroelastic constraints. Static aeroelastic analysis is carried out for the beamlike wing model, using a geometrically nonlinear beam formulation coupled with the nonplanar vortex lattice method. The flutter solutions are obtained using the P-K method based on the static equilibrium configuration. The corresponding unsteady aerodynamic forces are calculated by nonplanar doublet-lattice method. This paper obtains linear and nonlinear aeroelastic optimum results, respectively, by the ISIGHT optimization platform. In this optimization problem, parameters of beam cross section are chosen as the design variables to satisfy the displacement, flutter, and strength requirements, while minimizing wing weight. The results indicate that it is necessary to consider geometrical nonlinearity in aeroelastic optimization design. In addition, optimization strategies are explored to simplify the complex optimization process and reduce the computing time. Different criterion values are selected and studied for judging the effects of the simplified method on the computing time and the accuracy of results. In this way, the computing time is reduced by more than 30% on the premise of ensuring the accuracy.

  15. Physics issues for a very-low-aspect-ratio Quasi-Poloidal Stellarator (QPS)

    International Nuclear Information System (INIS)

    Lyon, J.F.; Berry, L.A.; Hirshman, S.P.

    2003-01-01

    A quasi-poloidal stellarator with very low plasma aspect ratio (R/a ∼ 2.7, 1/2-1/4 that of existing stellarators) is a new confinement approach that could ultimately lead to a high-beta compact stellarator reactor. The Quasi-Poloidal Stellarator (QPS) experiment is being developed to test key features of this approach. The QPS will study neoclassical and anomalous transport, stability limits at beta up to 2.5%, the configuration dependence of the bootstrap current, and equilibrium robustness. The quasi-poloidal symmetry leads to neoclassical transport that is much smaller than the anomalous transport. The reduced effective field ripple may also produce reduced poloidal viscosity, enhancing the ambipolar E x B poloidal drift and allowing larger poloidal flows for reduction of anomalous transport. A region of second stability exists in the QPS experiment at higher beta. Very-high-beta configurations with a tokamak-like transform profile have also been obtained with a bootstrap current 1/3-1/5 that in an equivalent tokamak. These configurations are stable to low-n ideal MHD kink and vertical instabilities for beta up to 11%. Ballooning-stable configurations are found for beta in the range 2% to 23%. (author)

  16. Bosch-like method for creating high aspect ratio poly(methyl methacrylate) (PMMA) structures

    KAUST Repository

    Haiducu, Marius

    2012-02-02

    This paper presents a method for etching millimetre-deep trenches in commercial grade PMMA using deep-UV at 254 nm. The method is based on consecutive cycles of irradiation and development of the exposed areas, respectively. The exposure segment is performed using an inexpensive, in-house built irradiation box while the development part is accomplished using an isopropyl alcohol (IPA):H2O developer. The method was tested and characterized by etching various dimension square test structures in commercial grade, mirrored acrylic. The undercut of the sidewalls due to the uncollimated nature of the irradiation light was dramatically alleviated by using a honeycomb metallic grid in between the irradiation source and the acrylic substrate and by rotating the latter using a direct current (DC) motor-driven stage. By using an extremely affordable set-up and non-toxic, environmentally friendly materials and substances, this process represents an excellent alternative to microfabricating microfluidic devices in particular and high aspect ratio structures in general using PMMA as substrate. © 2012 SPIE.

  17. Cycle length and COD/N ratio determine properties of aerobic granules treating high-nitrogen wastewater.

    Science.gov (United States)

    Cydzik-Kwiatkowska, Agnieszka; Bernat, Katarzyna; Zielińska, Magdalena; Wojnowska-Baryła, Irena

    2014-07-01

    Aerobic granule characteristic in sequencing batch reactors treating high-nitrogen digester supernatant was investigated at cycle lengths (t) of 6, 8 and 12 h with the COD/N ratios in the influent of 4.5 and 2.3. The biomass production (Y obs) correlated with the extracellular polymeric substances (EPS) in grams per COD removed. Denitrification efficiency significantly decreased as the amount of EPS in biomass increased, suggesting that organic assimilation in EPS hampers nitrogen removal. Granule hydrophobicity was highest at t of 8 h; the t has to be long enough to remove pollutants, but not so long that excessive biomass starvation causes extracellular protein consumption that decreases hydrophobicity. At a given t, reducing the COD/N ratio improved hydrophobicity that stimulates cell aggregation. At t of 6 h and the COD/N ratio of 2.3, the dominance of 0.5-1.0 mm granules favored simultaneous nitrification and denitrification and resulted in the highest nitrogen removal.

  18. [Are there Sex Differences Regarding Ski Length to Height Ratio, Ski Length to Weight Ratio, Sidecut Radius and Ski Boot Sole Abrasion among ACL Injured Male and Female Skiers?

    Science.gov (United States)

    Posch, Markus; Ruedl, Gerhard; Tecklenburg, Katja; Helle, Kenneth; Schranz, Alois; Burtscher, Martin

    2017-06-01

    Introduction  Female skiers suffer from knee injuries twice as much as male skiers, and the risk of an injury to the anterior cruciate ligament (ACL) is three times greater among females compared to males. The sex-specific ACL injury risk depends on internal (e. g. age, skiing skills, fitness level) and external (e. g. slope and weather conditions, ski equipment) factors. However, it is not clear whether male and female recreational skiers with an ACL injury differ regarding the sidecut radius and ski boot sole abrasion. Method  This questionnaire-based study was conducted in the winter seasons 2014/15 and 2015/16. During those periods, data of ACL-injured skiers were collected at an Austrian ski clinic. The questionnaire included information about demographics, skiing skills, type of fall, binding release, and injury diagnosis. Furthermore, the ski length and sidecut radius were notated from the ski, and abrasion of ski boot sole was measured at the toe and heel piece of the ski boot using a caliper. Results  In total 164 ACL-injured skiers (67 % females) with a mean age of 41.7 ± 11.5 years were recorded. Males used significantly longer skies compared to females (168.3 ± 6.6 vs. 157.5 ± 5.9 cm, p ski length to height ratio (94.0 ± 3.4 vs. 94.1 ± 3.3 %) showed no significant difference between the two sexes. The ski length to weight ratio was significantly different between females and males (2.5 ± 0.3 vs. 2.0 ± 0.2 cm/kg). The sidecut radius (13.5 ± 1.4 vs. 15.6 ± 2.6 m, p ski boot soles, neither at the toe piece (5.4 ± 1.2 vs. 5.5 ± 1.1 mm) nor at the heel piece (6.0 ± 1.7 vs. 6.0 ± 1.6 mm) between females and males. For both sexes the most common type of fall was the forward fall with body rotation (approximately 59 %). Failure of binding release was significantly more often reported by females compared to males (86 vs. 44 %, p ski length to weight ratio, and the

  19. Role of the ratio of biopolyelectrolyte persistence length to nanoparticle size in the structural tuning of electrostatic complexes

    Science.gov (United States)

    Shi, Li; Carn, Florent; Boué, François; Buhler, Eric

    2016-09-01

    Aggregation of nanoparticles of given size R induced by addition of a polymer strongly depends on its degree of rigidity. This is shown here on a large variety of silica nanoparticle self-assemblies obtained by electrostatic complexation with carefully selected oppositely charged biopolyelectrolytes of different rigidity. The effective rigidity is quantified by the total persistence length LT representing the sum of the intrinsic (Lp) and electrostatic (Le) polyelectrolyte persistence length, which depends on the screening, i.e., on ionic strength due to counterions and external salt concentrations. We experimentally show that the ratio LT/R is the main tuning parameter that controls the fractal dimension Df of the nanoparticles' self-assemblies, which is determined using small-angle neutron scattering: (i) For LT/R nanoparticles in excess, hence ramified structures with Df˜2 . (ii) For 0.3 nanoparticles), in good agreement with computer simulations. (iii) For LT/R >1 ,Le is strongly increased due to the absence of salt and repulsions between nanoparticles cannot be compensated for by the polyelectrolyte wrapping, which allows a spacing between nanoparticles and the formation of one-dimensional pearl necklace complexes. (iv) Finally, electrostatic screening, i.e., ionic strength, turned out to be a reliable way of controlling Df and the phase diagram behavior. It finely tunes the short-range interparticle potential, resulting in larger fractal dimensions at higher ionic strength.

  20. Biological markers of asexuality: Handedness, birth order, and finger length ratios in self-identified asexual men and women.

    Science.gov (United States)

    Yule, Morag A; Brotto, Lori A; Gorzalka, Boris B

    2014-02-01

    Human asexuality is defined as a lack of sexual attraction to anyone or anything and it has been suggested that it may be best conceptualized as a sexual orientation. Non-right-handedness, fraternal birth order, and finger length ratio (2D:4D) are early neurodevelopmental markers associated with sexual orientation. We conducted an Internet study investigating the relationship between self-identification as asexual, handedness, number of older siblings, and self-measured finger-lengths in comparison to individuals of other sexual orientation groups. A total of 325 asexuals (60 men and 265 women; M age, 24.8 years), 690 heterosexuals (190 men and 500 women; M age, 23.5 years), and 268 non-heterosexuals (homosexual and bisexual; 64 men and 204 women; M age, 29.0 years) completed online questionnaires. Asexual men and women were 2.4 and 2.5 times, respectively, more likely to be non-right-handed than their heterosexual counterparts and there were significant differences between sexual orientation groups in number of older brothers and older sisters, and this depended on handedness. Asexual and non-heterosexual men were more likely to be later-born than heterosexual men, and asexual women were more likely to be earlier-born than non-heterosexual women. We found no significant differences between sexual orientation groups on measurements of 2D:4D ratio. This is one of the first studies to test and provide preliminary empirical support for an underlying neurodevelopmental basis to account for the lack of sexual attraction characteristic of asexuality.

  1. Critical Aspects of the Coastal Drought Index: Length of Salinity Data Record and Ecological Response Data

    Science.gov (United States)

    Conrads, P. A.; Tufford, D. L.; Darby, L. S.

    2015-12-01

    The phenomenon of coastal drought has a different dynamic from upland droughts that are typically characterized by agricultural, hydrologic, meteorological, and(or) socio-economic impacts. Because of the uniqueness of drought impacts on coastal ecosystems, a coastal drought index (CDI) that uses existing salinity datasets for sites in South Carolina, Georgia, and Florida was developed using an approach similar to the Standardized Precipitation Index (SPI). CDIs characterizing the 1- to 24-month salinity conditions were developed and the evaluation of the CDI indicates that the index can be used for different estuary types (for example, brackish, olioghaline, or mesohaline), for regional comparison between estuaries, and as an index for wet conditions (high freshwater inflow) in addition to drought conditions. Unlike the SPI where long-term precipitation datasets of 50 to 100 years are available for computing the index, there are a limited number of salinity data sets of greater than 10 or 15 years for computing the CDI. To evaluate the length of salinity record necessary to compute the CDI, a 29-year dataset was resampled into 5-, 10-, 15-, and 20-year interval datasets. Comparison of the CDI for the different periods of record show that the range of salinity conditions in the 10-, 15-, and 20-year datasets were similar and results were a close approximation to the CDI computed by using the full period of record. The CDI computed with the 5-year dataset had the largest differences with the CDI computed with the 29-year dataset but did provide useful information on coastal drought and freshwater conditions. An ongoing National Integrated Drought Information System (NIDIS) drought early warning project in the Carolinas is developing ecological linkages to the CDI and evaluating the effectiveness of the CDI as a prediction tool for adaptation planning for future droughts. However, identifying potential coastal drought response datasets is a challenge. Coastal drought

  2. The flow field in a high aspect ratio cooling duct with and without one heated wall

    Science.gov (United States)

    Rochlitz, Henrik; Scholz, Peter; Fuchs, Thomas

    2015-12-01

    The flow in a high aspect ratio generic cooling duct is described for different Reynolds numbers and for adiabatic as well as non-adiabatic conditions. The Reynolds number is varied in a range from 39,000 to 111,000. The generic cooling duct facility allows for applying a constant temperature on the duct's lower wall, and it ensures having well-defined boundary conditions. The high-quality, optical noninvasive measurement methods, namely Particle Image Velocimetry (2C2D-PIV, i.e., two velocity components in a plane), Stereo Particle Image Velocimetry (3C2D-PIV, i.e., three velocity components in a plane) and Volumetric Particle Tracking Velocimetry (3C3D-PTV, i.e., three velocity components in a volume), are used to characterize the flow in detail. Pressure transducers are installed for measuring the pressure losses. The repeatability and the validity of the data are discussed in detail. For that purpose, modifications in the test facility and in the experimental setup as well as comparisons between the different measurement methods are given. A focus lies on the average velocity distribution and on the turbulent statistics. The longitudinal velocity profile is analyzed in detail for Reynolds number variations. Secondary flows are identified with velocities of two orders of magnitude smaller than the longitudinal velocity. Reynolds stress distributions are given for several different cases. The Reynolds number dependency of overline{u'^2} and overline{v'^2} is shown, and a comparison between the adiabatic and the heated case is given. overline{u'^2} changes significantly when the lower wall heat flux is applied, whereas overline{v'^2} and overline{u'v'} almost stay constant.

  3. High aspect ratio silicon nanowires control fibroblast adhesion and cytoskeleton organization

    Science.gov (United States)

    Andolfi, Laura; Murello, Anna; Cassese, Damiano; Ban, Jelena; Dal Zilio, Simone; Lazzarino, Marco

    2017-04-01

    Cell-cell and cell-matrix interactions are essential to the survival and proliferation of most cells, and are responsible for triggering a wide range of biochemical pathways. More recently, the biomechanical role of those interactions was highlighted, showing, for instance, that adhesion forces are essential for cytoskeleton organization. Silicon nanowires (Si NWs) with their small size, high aspect ratio and anisotropic mechanical response represent a useful model to investigate the forces involved in the adhesion processes and their role in cellular development. In this work we explored and quantified, by single cell force spectroscopy (SCFS), the interaction of mouse embryonic fibroblasts with a flexible forest of Si NWs. We observed that the cell adhesion forces are comparable to those found on collagen and bare glass coverslip, analogously the membrane tether extraction forces are similar to that on collagen but stronger than that on bare flat glass. Cell survival did not depend significantly on the substrate, although a reduced proliferation after 36 h was observed. On the contrary both cell morphology and cytoskeleton organization revealed striking differences. The cell morphology on Si-NW was characterized by a large number of filopodia and a significant decrease of the cell mobility. The cytoskeleton organization was characterized by the absence of actin fibers, which were instead dominant on collagen and flat glass support. Such findings suggest that the mechanical properties of disordered Si NWs, and in particular their strong asymmetry, play a major role in the adhesion, morphology and cytoskeleton organization processes. Indeed, while adhesion measurements by SCFS provide out-of-plane forces values consistent with those measured on conventional substrates, weaker in-plane forces hinder proper cytoskeleton organization and migration processes.

  4. Geometrical Nonlinear Aeroelastic Stability Analysis of a Composite High-Aspect-Ratio Wing

    Directory of Open Access Journals (Sweden)

    Chang Chuan Xie

    2008-01-01

    Full Text Available A composite high-aspect-ratio wing of a high-altitude long-endurance (HALE aircraft was modeled with FEM by MSC/NASTRAN, and the nonlinear static equilibrium state is calculated under design load with follower force effect, but without load redistribution. Assuming the little vibration amplitude of the wing around the static equilibrium state, the system is linearized and the natural frequencies and mode shapes of the deformed structure are obtained. Planar doublet lattice method is used to calculate unsteady aerodynamics in frequency domain ignoring the bending effect of the deflected wing. And then, the aeroelastic stability analysis of the system under a given load condition is successively carried out. Comparing with the linear results, the nonlinear displacement of the wing tip is higher. The results indicate that the critical nonlinear flutter is of the flap/chordwise bending type because of the chordwise bending having quite a large torsion component, with low critical speed and slowly growing damping, which dose not appear in the linear analysis. Furthermore, it is shown that the variation of the nonlinear flutter speed depends on the scale of the load and on the chordwise bending frequency. The research work indicates that, for the very flexible HALE aircraft, the nonlinear aeroelastic stability is very important, and should be considered in the design progress. Using present FEM software as the structure solver (e.g. MSC/NASTRAN, and the unsteady aerodynamic code, the nonlinear aeroelastic stability margin of a complex system other than a simple beam model can be determined.

  5. Study on the change of aspect ratios of small surface cracks emanated from a toe of corner boxing; Mawashi yosetsudome tanbu kara hassei denpasuru bishi bisho hyomen kiretsu no aspect hi henka ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Toyosada, M.; Yamaguchi, K.; Takeda, K.; Watanabe, Y. [Kyushu University, Fukuoka (Japan). Faculty of Engineering

    1997-10-01

    The fatigue test of specimens with a stiffener was carried out to examine the change in aspect ratio (crack depth/length) of fatigue cracks in a stress concentration field and residual stress field. The aspect ratio of surface cracks just after generation can be represented with the single virtual surface crack with the same value as K value at the deepest point considering an interference effect from near cracks. No discontinuous change in K value is found at the deepest point even during growth and combination of cracks on a surface. The change in K value at the deepest point is thus the criterion to represent growth and combination of surface cracks considering the interference effect. The change in aspect ratio of the typical single virtual surface crack linearly decreases with an increase in crack depth. The shape of surface cracks generating and growing in a residual stress field is more flat than that in no residual stress field. In addition, in a residual stress field, surface cracks are longer at the same crack depth, and fatigue lives are shorter. 7 refs., 12 figs.

  6. Time to achieving therapeutic international normalized ratio increases hospital length of stay after heart valve replacement surgery.

    Science.gov (United States)

    Arendt, Christopher J; Hong, Joon Hwa; Daly, Richard C; Scott, Christopher; Mehta, Ramila A; Bailey, Kent; Pathak, Jyotishman; Pereira, Naveen L

    2017-05-01

    Achieving a therapeutic international normalized ratio (INR) before hospital discharge is an important inpatient goal for patients undergoing mechanical cardiac valve replacement (MCVR). The use of clinical algorithms has reduced the time to achieve therapeutic INR (TTI) with warfarin therapy. Whether TTI prolongs length of stay (LOS) is unknown. Patients who underwent MCVR over a consecutive 42-month period were included. Clinical data were obtained from the Society of Thoracic Surgeons Adult Cardiac Surgery database and electronic medical records. Therapeutic INR was defined as per standard guidelines. Warfarin dose was prescribed using an inpatient pharmacy-managed algorithm and computer-based dosing tool. International normalized ratio trajectory, procedural needs, and drug interactions were included in warfarin dose determination. There were 708 patients who underwent MCVR, of which 159 were excluded for reasons that would preclude or interrupt warfarin use. Among the remainder of 549 patients, the average LOS was 6.4days and mean TTI was 3.5days. Landmark analysis showed that subjects in hospital on day 4 (n=542) who achieved therapeutic INR were more likely to be discharged by day 6 compared with those who did not achieve therapeutic INR (75% vs 59%, P<.001). Multivariable proportional hazards regression with TTI as a time-dependent effect showed a strong association with discharge (P=.0096, hazard ratio1.3) after adjustment for other significant clinical covariates. Time to achieve therapeutic INR is an independent predictor of LOS in patients requiring anticoagulation with warfarin after MCVR surgery. Alternative dosing and anticoagulation strategies will need to be adopted to reduce LOS in these patients. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Alignment method combining interference lithography with anisotropic wet etch technique for fabrication of high aspect ratio silicon gratings.

    Science.gov (United States)

    Zheng, Yanchang; Qiu, Keqiang; Chen, Huoyao; Chen, Yong; Liu, Zhengkun; Liu, Ying; Xu, Xiangdong; Hong, Yilin

    2014-09-22

    A method was developed for aligning interference fringes generated in interference lithography to the vertical {111} planes of oriented silicon wafers. The alignment error is 0.036°. This high precision method makes it possible to combine interference lithography with anisotropic wet etch technique for the fabrication of high aspect ratio silicon gratings with extremely smooth sidewalls over a large sample area. With this alignment method, 320 nm and 2 μm period silicon gratings have been successfully fabricated. The highest aspect ratio is up to 100. The sample area is about 50 mm × 60 mm. The roughness (root mean square) of the sidewall is about 0.267 nm.

  8. Geometry dependence of magnetic and transport AC losses in Bi-2223/Ag tapes with different aspect ratios

    International Nuclear Information System (INIS)

    Fang, J; Luo, X M; Chen, D X; Alamgir, A K M; Collings, E W; Lee, E; Sumption, M D; Fang, J G; Yi, H P; Song, X H; Guo, S Q; Liu, M L; Xin, Y; Han, Z

    2004-01-01

    On five Bi-2223/Ag tapes with different aspect ratios from 5 to 26, AC losses have been measured at 77 K while a parallel AC magnetic field or a perpendicular AC magnetic field or a longitudinal AC transport current is applied. It has been found that at any frequency the perpendicular magnetic losses per cycle increase, but the parallel magnetic losses per cycle and the transport losses per cycle decrease as the aspect ratio increases. These experimental results are in accord with theoretical results. Meanwhile, we investigated the geometry dependence of the decay time constant of coupling current and that of full penetration field

  9. Geometry dependence of magnetic and transport AC losses in Bi-2223/Ag tapes with different aspect ratios

    Energy Technology Data Exchange (ETDEWEB)

    Fang, J [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Luo, X M [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Chen, D X [ICREA and Grup Electromagnetisme, Departament de Fisica, Universitat Autonoma Barcelona, 08193 Bellaterra (Spain); Alamgir, A K M [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Collings, E W [MSE, Ohio State University, Columbus, OH 43210 (United States); Lee, E [MSE, Ohio State University, Columbus, OH 43210 (United States); Sumption, M D [MSE, Ohio State University, Columbus, OH 43210 (United States); Fang, J G [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Yi, H P [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Song, X H [Innova Superconductor Technology Co., Ltd, 7 Rongchang Dongjie, Longsheng Industrial Park, Beijing Economic and Technological Development Area, 100176 (China); Guo, S Q [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Liu, M L [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China); Xin, Y [Innopower Superconductor Cable Co., Ltd, 7 Rongchang Dongjie, Longsheng Industrial Park, Beijing Economic and Technological Development Area, 100176 (China); Han, Z [Applied Superconductivity Research Center, Tsinghua University, Beijing 100084 (China)

    2004-10-01

    On five Bi-2223/Ag tapes with different aspect ratios from 5 to 26, AC losses have been measured at 77 K while a parallel AC magnetic field or a perpendicular AC magnetic field or a longitudinal AC transport current is applied. It has been found that at any frequency the perpendicular magnetic losses per cycle increase, but the parallel magnetic losses per cycle and the transport losses per cycle decrease as the aspect ratio increases. These experimental results are in accord with theoretical results. Meanwhile, we investigated the geometry dependence of the decay time constant of coupling current and that of full penetration field.

  10. Variable deflection response of sensitive CNT-on-fiber artificial hair sensors from CNT synthesis in high aspect ratio microcavities

    Science.gov (United States)

    Slinker, Keith; Maschmann, Matthew R.; Kondash, Corey; Severin, Benjamin; Phillips, David; Dickinson, Benjamin T.; Reich, Gregory; Baur, Jeff

    2015-03-01

    Crickets, locusts, bats, and many other animals detect changes in their environment with distributed arrays of flow-sensitive hairs. Here we discuss the fabrication and characterization of a relatively new class of pore-based, artificial hair sensors that take advantage of the mechanical properties of structural microfibers and the electromechanical properties of self-aligned carbon nanotube arrays to rapidly transduce changes in low speed air flow. The radially aligned nanotubes are able to be synthesized along the length of the fibers inside the high aspect ratio cavity between the fiber surface and the wall of a microcapillary pore. The growth self-positions the fibers within the capillary and forms a conductive path between detection electrodes. As the hair is deflected, nanotubes are compressed to produce a typical resistance change of 1-5% per m/s of air speed which we believe are the highest sensitivities reported for air velocities less than 10 m/s. The quasi-static response of the sensors to point loads is compared to that from the distributed loads of air flow. A plane wave tube is used to measure their dynamic response when perturbed at acoustic frequencies. Correlation of the nanotube height profile inside the capillary to a diffusion transport model suggests that the nanotube arrays can be controllably tapered along the fiber. Like their biological counterparts, many applications can be envisioned for artificial hair sensors by tailoring their individual response and incorporating them into arrays for detecting spatio-temporal flow patterns over rigid surfaces such as aircraft.

  11. Experimental Investigation of a High-Speed Hydrofoil with Parabolic Thickness Distribution and an Aspect Ratio of 3

    Science.gov (United States)

    Christopher, Kenneth W.

    1961-01-01

    An experimental investigation has been made to determine the hydro-dynamic characteristics of a 10-percent-thick hydrofoil with an aspect ratio of 3 designed to operate with acceptable efficiency at speeds in the neighborhood of 100 knots (169 fps). A cambered hydrofoil model with parabolic thickness distribution was investigated at a depth of chord over a range of angles of attack from -0.5 deg to 4.0 deg and at speeds from 120 to 210 fps. substantially wider range of operation at acceptable lift-drag ratios as well as higher maximum lift-drag-ratio values than did a hydrofoil of similar design with an aspect ratio of 1.

  12. Validation of digit-length ratio (2D:4D) assessments on the basis of DXA-derived hand scans

    International Nuclear Information System (INIS)

    Romann, Michael; Fuchslocher, Jörg

    2015-01-01

    The second-to-fourth digit-length ratio (2D:4D) may be a correlate of prenatal sex steroids, and it has been linked to sporting prowess. The aim of the study was to validate dual-energy X-ray-absorptiometry (DXA) as a technique to assess 2D:4D in soccer players under 15 years of age (U-15). Paired X-ray and DXA scans of the left hands of 63 male U-15 elite soccer players (age: 14.0 ± 0.3 years) were performed, and 2D:4D was then compared between the two techniques. The 2D:4D measurements were performed twice by two blinded raters. Intrarater and interrater reliability, as well as agreement between the X-ray and the DXA assessments, were tested. Intrarater reliabilities of both raters using X-ray with intraclass correlation coefficients (ICCs) of 0.97 and 0.90 were excellent. Using DXA, the ICCs were 0.90 and 0.91 thus also showing excellent reliability. Interrater reliabilities were excellent using both the X-ray (ICC of 0.94) and the DXA (ICC of 0.90), assessments respectively. Bland-Altman plots demonstrated that the 2D:4D ratios of the two raters did not differ significantly between the X-ray and the DXA assessments. The standard errors of estimate were 0.01 for both techniques. The 95% limits of agreement of ±0.018 (±2.0%) and ±0.023 (±2.6%), respectively, were within the acceptable tolerance of 5%, and showed very good agreement. DXA offered a replicable technique for assessing 2D:4D in youth soccer players. Therefore, the DXA technique seems to be an alternative method for evaluating 2D:4D in youth sports

  13. Large-eddy simulation of the high-Reynolds-number flow through a high-aspect-ratio cooling duct

    NARCIS (Netherlands)

    Kaller, Thomas; Pasquariello, Vito; Hickel, S.; Adams, Nikolaus A.

    2017-01-01

    We present well-resolved large-eddy-simulations (LES) of a straight, high-aspect-ratio cooling duct (HARCD) at a bulk Reynolds number of Re = 110 • 103 and an average Nusselt number of Nu = 371. The geometry and boundary conditions have been defined together with Rochlitz et al.

  14. Influence of the aspect ratio of bioactive nanofillers on rheological behavior of PMMA-based orthopedic materials.

    Science.gov (United States)

    Liu, Tse-Ying; Chen, San-Yuan; Liu, Dean-Mo

    2004-10-15

    In this investigation, calcium-deficient hydroxyapatite (CDHA) nanocrystals with needle-like geometry were synthesized and incorporated with Poly(methyl methacrylate), PMMA, to form CDHA-PMMA nanocomposites. Rheological behaviors of the PMMA-CDHA melting suspensions were systematically investigated in terms of solid loading and aspect ratio of the CDHA nanoparticles. The maximum solid loadings of nano-CDHA particles with aspect ratios of 7.2, 10.4, and 17 were determined to be 28, 31, and 57%, respectively. An increase in solid concentrations causes pronounced shear-thinning behavior. This result suggests that a strong interaction, including Van der Waals attraction and mechanical interlocking, between the nano-CDHA particles makes the nanocomposite mixture more non-Newtonian. Furthermore, it was found that packing efficiency and yield strength in the suspension were strongly influenced by the aspect ratio, especially above the critical value of 8.8. The obtained critical aspect ratio and solid content provide not only appropriate design in the PMMA-CDHA polymeric suspension for fabrication process but also optimal conditions for the fabrication of orthopedic devices via injection molding or extrusion.

  15. A nanoscale conical polymethyl methacrylate (PMMA) sub-wavelength structure with a high aspect ratio realized by a stamping method.

    Science.gov (United States)

    Kim, Dae-Seon; Kim, Dong-Hyun; Jang, Jae-Hyung

    2013-04-08

    A high aspect ratio conical sub-wavelength structure (SWS) was designed by using rigorous coupled-wave analysis (RCWA) method and was realized on polymethyl methacrylate (PMMA) film using a stamping technique. The silicon template containing a hexagonal array of conical holes with a period of 350 nm and an aspect ratio of 2.8 was fabricated by electron-beam (e-beam) lithography followed by a two-step etching process. The SWS with a high aspect ratio was easily transferred from the fabricated silicon template to PMMA film using the stamping method. The replicated PMMA SWS has an array of cones with nanoscale tips and an aspect ratio higher than 2.8. The average reflectance and transmittance of the PMMA film with the conical SWS in the wavelength ranging from 500 and 1500 nm was improved from 7.1 and 91.1% to 4.3 and 94.2%, respectively, as compared to flat PMMA film.

  16. Large-scale high aspect ratio Al-doped ZnO nanopillars arrays as anisotropic metamaterials

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Takayama, Osamu; Panah, Mohammad Esmail Aryaee

    2017-01-01

    High aspect ratio free-standing Al-doped ZnO (AZO) nanopillars and nanotubes were fabricated using a combination of advanced reactive ion etching and atomic layer deposition (ALD) techniques. Prior to the pillar and tube fabrication, AZO layers were grown on flat silicon and glass substrates with...

  17. Fabrication of ultra-high aspect ratio (>160:1) silicon nanostructures by using Au metal assisted chemical etching

    Science.gov (United States)

    Li, Hailiang; Ye, Tianchun; Shi, Lina; Xie, Changqing

    2017-12-01

    We present a facile and effective approach for fabricating high aspect ratio, dense and vertical silicon nanopillar arrays, using a combination of metal etching following electron-beam lithography and Au metal assisted chemical etching (MacEtch). Ti/Au nanostructures used as catalysts in MacEtch are formed by single layer resist-based electron-beam exposure followed by ion beam etching. The effects of MacEtch process parameters, including half period, etching time, the concentrations of H2O2 and HF, etching temperature and drying method are systematically investigated. Especially, we demonstrate an enhancement of etching quality by employing cold MacEtch process, and an enhancement in preventing the collapse of high aspect ratio nanostructures by employing low surface tension rinse liquid and natural evaporation in the drying stage. Using an optimized MacEtch process, vertical silicon nanopillar arrays with a period of 250 nm and aspect ratio up to 160:1 are realized. Our results should be instructive for exploring the achievable aspect ratio limit in silicon nanostructures and may find potential applications in photovoltaic devices, thermoelectric devices and x-ray diffractive optics.

  18. Highly Manufacturable Deep (Sub-Millimeter) Etching Enabled High Aspect Ratio Complex Geometry Lego-Like Silicon Electronics

    KAUST Repository

    Ghoneim, Mohamed T.

    2017-02-01

    A highly manufacturable deep reactive ion etching based process involving a hybrid soft/hard mask process technology shows high aspect ratio complex geometry Lego-like silicon electronics formation enabling free-form (physically flexible, stretchable, and reconfigurable) electronic systems.

  19. Atomic layer deposition for coating of high aspect ratio TiO.sub.2./sub. nanotube layers

    Czech Academy of Sciences Publication Activity Database

    Zazpe, R.; Knaut, M.; Sopha, H.; Hromádko, L.; Albert, M.; Přikryl, J.; Gärtnerová, Viera; Bartha, J.W.; Macák, J. M.

    2016-01-01

    Roč. 32, č. 41 (2016), s. 10551-10558 ISSN 0743-7463 Institutional support: RVO:68378271 Keywords : aluminum * aluminum coatings * aspect ratio * coatings * nanotubes Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.833, year: 2016

  20. Narrow conductive structures with high aspect ratios through single-pass inkjet printing and evaporation-induced dewetting

    NARCIS (Netherlands)

    Abbel, R.; Teunissen, P.; Michels, J.; Groen, W.A.

    2015-01-01

    Inkjet printed silver lines contract to widths below 20-μm during drying on an organic planarization coating. Aspect ratios previously unprecedented with single pass inkjet printing on isotropic homogeneous substrates are obtained. This effect is caused by the subsequent evaporation of solvents from

  1. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3Nanofibers.

    Science.gov (United States)

    Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R

    2017-03-23

    There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO 3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO 3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO 3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO 3 NFs achieved the maximal energy storage density of 15.48 J/cm 3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

  2. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

    Science.gov (United States)

    Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R.

    2017-03-01

    There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

  3. The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

    Directory of Open Access Journals (Sweden)

    Laura Brum Prata

    2003-12-01

    Full Text Available This work investigated the influence of the aggregate's aspect ratio on the fracture behavior of a low cement aluminum silicate refractory castable treated at two different temperatures (110 °C and 1000 °C. The aggregates were cylindrical pellets with an aspect ratio of 1, 2, 3 and 4, produced by extruding a mixture of clay and calcined alumina fired at 1600 °C for 4 h to yield mullite (3Al2O3.2SiO2. The behavior of the R-Curve and other relevant fracture parameters were evaluated based on the "Two Parameter Fracture Model" in a three-point flexure test of single-edge straight through notched specimens. The two temperature treatments produced different degrees of matrix-aggregate adhesion. The larger aspect ratio aggregates were found to promote toughening only in the dried condition, at 110 °C, while the specimens fired at 1000 °C for 4 h, regardless of their aggregate aspect ratio, displayed no significant toughening. The best results for fired samples, however, were obtained from specimens containing conventional angular aggregates.

  4. A model for roll stall and the inherent stability modes of low aspect ratio wings at low Reynolds numbers

    Science.gov (United States)

    Shields, Matt

    The development of Micro Aerial Vehicles has been hindered by the poor understanding of the aerodynamic loading and stability and control properties of the low Reynolds number regime in which the inherent low aspect ratio (LAR) wings operate. This thesis experimentally evaluates the static and damping aerodynamic stability derivatives to provide a complete aerodynamic model for canonical flat plate wings of aspect ratios near unity at Reynolds numbers under 1 x 105. This permits the complete functionality of the aerodynamic forces and moments to be expressed and the equations of motion to solved, thereby identifying the inherent stability properties of the wing. This provides a basis for characterizing the stability of full vehicles. The influence of the tip vortices during sideslip perturbations is found to induce a loading condition referred to as roll stall, a significant roll moment created by the spanwise induced velocity asymmetry related to the displacement of the vortex cores relative to the wing. Roll stall is manifested by a linearly increasing roll moment with low to moderate angles of attack and a subsequent stall event similar to a lift polar; this behavior is not experienced by conventional (high aspect ratio) wings. The resulting large magnitude of the roll stability derivative, Cl,beta and lack of roll damping, Cl ,rho, create significant modal responses of the lateral state variables; a linear model used to evaluate these modes is shown to accurately reflect the solution obtained by numerically integrating the nonlinear equations. An unstable Dutch roll mode dominates the behavior of the wing for small perturbations from equilibrium, and in the presence of angle of attack oscillations a previously unconsidered coupled mode, referred to as roll resonance, is seen develop and drive the bank angle? away from equilibrium. Roll resonance requires a linear time variant (LTV) model to capture the behavior of the bank angle, which is attributed to the

  5. Effect of Aspect Ratio, Channel Orientation, Rib Pitch-to-Height Ratio, and Number of Ribbed Walls on Pressure Drop Characteristics in a Rotating Channel with Detached Ribs

    Directory of Open Access Journals (Sweden)

    K. Arun

    2007-01-01

    Full Text Available The present work involves experimental investigation of the effects of aspect ratio, channel orientation angle, rib pitch-to-height ratio (P/e, and number of ribbed walls on friction factor in orthogonally rotating channel with detached ribs. The ribs are separated from the base wall to provide a small region of flow between the base wall and the ribs. Experiments have been conducted at Reynolds number ranging from 10000–17000 with rotation numbers varying from 0–0.38. Pitch-to-rib height ratios (P/e of 5 and 10 at constant rib height-to-hydraulic diameter ratio (e/D of 0.1 and a clearance ratio (C/e of 0.38 are considered. The rib angle of attack with respect to mainstream flow is 90∘. The channel orientation at which the ribbed wall becomes trailing surface (pressure side on which the Coriolis force acts is considered as the 0∘ orientation angle. For one-wall ribbed case, channel is oriented from 0∘ to 180∘ about its axis in steps of 30∘ to change the orientation angle. For two-wall ribbed case, the orientation angle is changed from 0∘ to 90∘ in steps of 30∘. Friction factors for the detached ribbed channels are compared with the corresponding attached ribbed channel. It is found that in one-wall detached ribbed channel, increase in the friction factor ratio with the orientation angle is lower for rectangular channel compared to that of square channel for both the pitch-to-rib height ratios of 5 and 10 at a given Reynolds number and rotation number. Friction factor ratios of two-wall detached ribbed rectangular channel are comparable with corresponding two-wall detached ribbed square channel both under stationary and rotating conditions.

  6. Low-energy electron transmission through high aspect ratio Al O nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Jureta, J.; Víkor, G.

    2009-01-01

    Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined with resp......Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined...

  7. Large-area, high-aspect-ratio SU-8 molds for the fabrication of PDMS microfluidic devices

    International Nuclear Information System (INIS)

    Natarajan, S; Chang-Yen, D A; Gale, B K

    2008-01-01

    A relatively low-cost fabrication method using soft lithography and molding for large-area, high-aspect-ratio microfluidic devices, which have traditionally been difficult to fabricate, has been developed and is presented in this work. The fabrication process includes novel but simple modifications of conventional microfabrication steps and can be performed in any standard microfabrication facility. Specifically, the fabrication and testing of a microfluidic device for continuous flow deposition of bio-molecules in an array format are presented. The array layout requires high-aspect-ratio elastomeric channels that are 350 µm tall, extend more than 10 cm across the substrate and are separated by as little as 20 µm. The mold from which these channels were fabricated consisted of high-quality, 335 µm tall SU-8 structures with a high-negative aspect ratio of 17 on a 150 mm silicon wafer and was produced using spin coating and UV-lithography. Several unique processing steps are introduced into the lithographic patterning to eliminate many of the problems experienced when fabricating tall, high-aspect-ratio SU-8 structures. In particular, techniques are used to ensure uniform molds, both in height and quality, that are fully developed even in the deep negative-aspect-ratio areas, have no leftover films at the top of the structures caused by overexposure and no bowing or angled sidewalls from diffraction of the applied UV light. Successful microfluidic device creation was demonstrated using these molds by casting, curing and bonding a polydimethylsiloxane (PDMS) elastomer. A unique microfluidic device, requiring these stringent geometries, for continuous flow printing of a linear array of 16 protein and antibody spots has been demonstrated and validated by using surface plasmon resonance imaging of printed arrays

  8. Large flexibility of high aspect ratio carbon nanostructures fabricated by electron-beam-induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Beard, J D; Gordeev, S N, E-mail: jdb28@bath.ac.uk [Department of Physics, University of Bath, Bath BA2 7AY (United Kingdom)

    2010-11-26

    The mechanical properties of free-standing electron beam deposited amorphous carbon structures have been studied using atomic force microscopy. The fabricated carbon blades are found to be extraordinarily flexible, capable of undergoing vertical deflection up to {approx} 75% of their total length without inelastic deformation. The elastic bending modulus of these structures was calculated to be 28 {+-} 10 GPa.

  9. Ratio

    Science.gov (United States)

    Webster, Nathan A. S.; Pownceby, Mark I.; Madsen, Ian C.; Studer, Andrew J.; Manuel, James R.; Kimpton, Justin A.

    2014-12-01

    Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key bonding materials in iron ore sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.

  10. The impact of changing solar screen rotation angle and its opening aspect ratios on Daylight Availability in residential desert buildings

    KAUST Repository

    Sherif, Ahmed H.

    2012-11-01

    In desert sunny clear-sky regions solar penetration can become excessive. This can cause non-uniform daylight distribution, glare and high solar heat gain, affecting both visual and thermal comfort. Shading devices, such as solar screens, were usually used to diffuse and prevent direct solar penetration into spaces. This paper investigates the impact of changing solar screen axial rotation angle and screen opening aspect ratio on daylighting performance in a typical residential living room space under the desert sunny clear-sky. The larger aim is to arrive at efficient solar screen designs that suit the different orientations.The study was divided into three consecutive phases. In phase one, the effect of the two parameters on Daylight Availability was tested. The solar screen was axially rotated by three different angles at 10° increments. Also, the aspect ratio of the screen opening in both horizontal and vertical directions was changed systematically. Simulation was conducted using the annual Daylight Dynamic Performance Metrics (DDPMs). In phase two, the Annual Daylight Glare Probability (DGP) metric was evaluated for the cases that were found adequate in phase one. In the third phase, the annual solar energy transmittance through the screen was calculated for the cases that achieved acceptable performance in the two previous phases in order to identify the more energy efficient screens.Solar screens with openings having horizontal aspect ratios were found to be the most effective, while those with vertical aspect ratios were achieved the lowest performance. In the North orientation, since almost all the cases that were tested in this research provided acceptable daylighting performance, the designer now have a variety of options to choose from. Preference should be given to screen openings of horizontal aspect ratios, especially the 12:1 and 18:1 (H:V) screens that achieved the best performance where 92% of the space was " daylit" in comparison with only 53

  11. A comparative study of different aspects of manipulating ratio spectra applied for ternary mixtures: derivative spectrophotometry versus wavelet transform.

    Science.gov (United States)

    Salem, Hesham; Lotfy, Hayam M; Hassan, Nagiba Y; El-Zeiny, Mohamed B; Saleh, Sarah S

    2015-01-25

    This work represents a comparative study of different aspects of manipulating ratio spectra, which are: double divisor ratio spectra derivative (DR-DD), area under curve of derivative ratio (DR-AUC) and its novel approach, namely area under the curve correction method (AUCCM) applied for overlapped spectra; successive derivative of ratio spectra (SDR) and continuous wavelet transform (CWT) methods. The proposed methods represent different aspects of manipulating ratio spectra of the ternary mixture of Ofloxacin (OFX), Prednisolone acetate (PA) and Tetryzoline HCl (TZH) combined in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the reported HPLC method, showing no significant difference with respect to accuracy and precision. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. High aspect ratio nano-fabrication of photonic crystal structures on glass wafers using chrome as hard mask.

    Science.gov (United States)

    Hossain, Md Nazmul; Justice, John; Lovera, Pierre; McCarthy, Brendan; O'Riordan, Alan; Corbett, Brian

    2014-09-05

    Wafer-scale nano-fabrication of silicon nitride (Si x N y ) photonic crystal (PhC) structures on glass (quartz) substrates is demonstrated using a thin (30 nm) chromium (Cr) layer as the hard mask for transferring the electron beam lithography (EBL) defined resist patterns. The use of the thin Cr layer not only solves the charging effect during the EBL on the insulating substrate, but also facilitates high aspect ratio PhCs by acting as a hard mask while deep etching into the Si x N y . A very high aspect ratio of 10:1 on a 60 nm wide grating structure has been achieved while preserving the quality of the flat top of the narrow lines. The presented nano-fabrication method provides PhC structures necessary for a high quality optical response. Finally, we fabricated a refractive index based PhC sensor which shows a sensitivity of 185 nm per RIU.

  13. Effects of aspect ratio and specimen size on uniaxial failure stress of iron green bodies at high strain rates

    Directory of Open Access Journals (Sweden)

    Kuroyanagi Yuki

    2015-01-01

    Full Text Available Powder metallurgy is used for the production of a number of mechanical parts and is an essential production method. These are great advantages such as product cost effectiveness and product uniqueness. In general, however parts created by powder metallurgy have low strength because of low density. In order to increase strength as well as density, new techniques such as high-velocity-compaction (HVC was developed and further investigation has been conducted on improvement of techniques and optimum condition using computer simulation. In this study, the effects of aspect ratio and specimen size of iron green bodies on failure strength of uniaxial compression and failure behavior were examined using a split Hopkinson pressure Bar. The diameters of specimens were 12.5 mm and 25 mm the aspect ratios (thickness/diameter were 0.8 and 1.2.

  14. The field emission properties of high aspect ratio diamond nanocone arrays fabricated by focused ion beam milling

    Directory of Open Access Journals (Sweden)

    Z.L. Wang, Q. Wang, H.J. Li, J.J. Li, P. Xu, Q. Luo, A.Z. Jin, H.F. Yang and C.Z. Gu

    2005-01-01

    Full Text Available High aspect ratio diamond nanocone arrays are formed on freestanding diamond film by means of focused ion beam (FIB milling technology and hot-filament chemical vapor deposition (HFCVD method. The structure and phase purity of an individual diamond nanocone are characterized by scanning electron microscopy (SEM and micro-Raman spectroscopy. The result indicates that the diamond cones with high aspect ratio and small tip apex radius can be obtained by optimizing the parameters of FIB milling and diamond growth. The diamond nanocone arrays were also used to study the electron field emission properties and electric field shielding effect, finding high emission current density, low threshold and weak shielding effect, all attributable to the high field enhancement factor and suitable cone density of the diamond nanocone emitter

  15. High aspect ratio micro tool manufacturing for polymer replication using mu EDM of silicon, selective etching and electroforming

    DEFF Research Database (Denmark)

    Tosello, Guido; Bissacco, Giuliano; Tang, Peter Torben

    2008-01-01

    Mass fabrication of polymer micro components with high aspect ratio micro-structures requires high performance micro tools allowing the use of low cost replication processes such as micro injection moulding. In this regard an innovative process chain, based on a combination of micro electrical di...... discharge machining (mu EDM) of a silicon substrate, electroforming and selective etching was used for the manufacturing of a micro tool. The micro tool was employed for polymer replication by means of the injection moulding process....

  16. Effects of aspect ratio and concentration on rheology of epoxy suspensions containing model plate-like nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    White, K. L.; Takahara, A. [International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Hawkins, S.; Sue, H.-J., E-mail: hjsue@tamu.edu [Department of Materials Science and Engineering, Texas A& M University, College Station, Texas 77843 (United States); Miyamoto, M. [Kaneka US Materials Research Center, Kaneka America Holdings, Inc., College Station, Texas 77843 (United States)

    2015-12-15

    Hexagonal 2-dimensional α-zirconium phosphate crystals were prepared with lateral diameters ranging from 110 nm to 1.5 μm to investigate the effect of particle size on suspension rheology. The nanoplatelets were exfoliated to individual sheets with monodisperse thickness and dispersed in a Newtonian epoxy fluid. The steady shear response of dilute and semi-dilute suspensions was measured and compared to expressions obtained from theory for infinitely dilute suspensions. For suspensions containing the smaller nanoplatelets, aspect ratio ∼160, the low shear rate viscosity and transition to shear thinning behavior were well described by theory for loadings up to 0.5 vol. %. The agreement was improved by assuming a moderate polydispersity in lateral diameter, ∼30%–50%, which is consistent with experimental observation. For the higher aspect ratio nanoplatelets, good agreement between theory and experiment was observed only at high shear rates. At lower shear rate, theory consistently over-predicted viscosity, which was attributed to a progressive shift to non-isotropic initial conditions with increasing particle size. The results suggest that at a fixed Peclet number, there is an increasing tendency for the nanoplatelets to form transient, local stacks as particle size increases. The largest particles, aspect ratio ∼2200, showed unusual shear thinning and thickening behaviors that were attributed to particle flexibility. The findings demonstrate the surprising utility of theory for infinitely dilute suspensions to interpret, and in some cases quantitatively describe, the non-Newtonian viscosity of real suspensions containing high aspect ratio plate-like particles. A simple framework is proposed to interpret deviations from ideal behavior based on the local and collective behavior of the suspended nanoplatelets.

  17. Fractionation and Characterization of High Aspect Ratio Gold Nanorods Using Asymmetric-Flow Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Thao M. Nguyen

    2015-07-01

    Full Text Available Gold nanorods (GNRs are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field flow fractionation (A4F and single particle inductively coupled mass spectrometry (spICP-MS provide unique advantages for fractionating and analyzing the typically complex mixtures produced by common synthetic procedures. A4F fractions collected at specific elution times were analyzed off-line by spICP-MS. The individual particle masses were obtained by conversion of the ICP-MS pulse intensity for each detected particle event, using a defined calibration procedure. Size distributions were then derived by transforming particle mass to length assuming a fixed diameter. The resulting particle lengths correlated closely with ex situ transmission electron microscopy. In contrast to our previously reported observations on the fractionation of low-aspect ratio (AR GNRs (AR < 4, under optimal A4F separation conditions the results for high-AR GNRs of fixed diameter (≈20 nm suggest normal, rather than steric, mode elution (i.e., shorter rods with lower AR generally elute first. The relatively narrow populations in late eluting fractions suggest the method can be used to collect and analyze specific length fractions; it is feasible that A4F could be appropriately modified for industrial scale purification of GNRs.

  18. The Effects of pH on the Growth and Aspect Ratio of Chicken Egg White Lysozyme Crystals Prepared in Different Buffers

    Science.gov (United States)

    Gibson, U. J.; Horrell, E. E.; Kou, Y.; Pusey, Marc

    2000-01-01

    We have measured the nucleation and aspect ratio of CEWL crystals grown by vapor diffusion in acetate, butyrate, carbonate, succinate, and phosphate buffers in a range of pH spanning the pK(sub a) of these buffers. The nucleation numbers drop off significantly in the vicinity of pK(sub a) for each of the buffers except the phosphate system, in which we used only the pH range around the second titration point(pK2). There is a concomitant increase in the sizes of the crystals. Some typical nucleation number results are shown. These data support and extend other observations. In addition, we have examined changes in aspect ratio which accompany the suppression of nucleation within each buffer system. The length of the face in the [001] direction was measured, and compared to the width of the (110) face in the [110] type directions. We find that while the aspect ratio of the crystals is affected by pH, it is dominated by a correlation with the size of the crystals. Small crystals are longer in the [0011 direction than crystals that are larger (higher pH within a buffer system). This relationship is found to hold independent of the choice of buffer. These results are consistent with those of Judge et al, who used a batch process which resulted in uniform sizing of crystals at each pH. In these experiments, we specifically avoid agitating the protein/salt buffer mixture when combining the two. This permits the formation of a range of sizes at a given pH. The results for a .05 M acetate 5% NaCl buffer are also shown. We will discuss these results in light of a growth model.

  19. Influence of aspect ratio and surface defect density on hydrothermally grown ZnO nanorods towards amperometric glucose biosensing applications

    Science.gov (United States)

    Shukla, Mayoorika; Pramila; Dixit, Tejendra; Prakash, Rajiv; Palani, I. A.; Singh, Vipul

    2017-11-01

    In this work, hydrothermally grown ZnO Nanorods Array (ZNA) has been synthesized over Platinum (Pt) coated glass substrate, for biosensing applications. In-situ addition of strong oxidizing agent viz KMnO4 during hydrothermal growth was found to have profound effect on the physical properties of ZNA. Glucose oxidase (GOx) was later immobilized over ZNA by means of physical adsorption process. Further influence of varying aspect ratio, enzyme loading and surface defects on amperometric glucose biosensor has been analyzed. Significant variation in biosensor performance was observed by varying the amount of KMnO4 addition during the growth. Moreover, investigations revealed that the suppression of surface defects and aspect ratio variation of the ZNA played key role towards the observed improvement in the biosensor performance, thereby significantly affecting the sensitivity and response time of the fabricated biosensor. Among different biosensors fabricated having varied aspect ratio and surface defect density of ZNA, the best electrode resulted into sensitivity and response time to be 18.7 mA cm-2 M-1 and bio-sensing applications.

  20. Fabrication of high aspect ratio nanopillars and micro/nano combined structures with hydrophobic surface characteristics by injection molding

    Science.gov (United States)

    Zhou, Mingyong; Xiong, Xiang; Jiang, Bingyan; Weng, Can

    2018-01-01

    Polymer products with micro/nano-structures have excellent mechanical and optical properties, chemical resistance, and other advantages. Injection molding is one of the most potential techniques to fabricate polymer products with micro/nano-structures artificially in large numbers. In this study, a surface approach to fabricate high aspect ratio nanopillars and micro/nano combined structures was presented. Mold insert with micropillar arrays and nanopillars on its surface was prepared by combing anodic aluminum oxide (AAO) template and etched plate. Anti-sticking modification was done on the template to realize a better demolding quality. The influences of mold temperature and polymer material on the final replication quality were investigated. The results showed that the final replication quality of high aspect ratio nanopillars was greatly improved as compared with the unprocessed template. Polymer with low elongation at break was not suitable to fabricate structures with high aspect ratio via injection molding. For polypropylene surface, the experimental results of static contact angles were almost consistent with Cassie-Baxter equation. When the mold temperature reached 178 °C, hair-like polycarbonate nanopillars were observed, resulting in an excellent hydrophobic characteristic.

  1. ZnO Nanorods with Tunable Aspect Ratios Deriving from Oriented-attachment for Enhanced Performance in Quantum-dot Sensitized Solar Cells

    International Nuclear Information System (INIS)

    Wu, Dapeng; Wang, Xiaolu; Cao, Kun; An, Yipeng; Song, Xiaohui; Liu, Ning; Xu, Fang; Gao, Zhiyong; Jiang, Kai

    2017-01-01

    ZnO nanorods consisted of oriented aligned elongated-nanoparticles along the [0001] direction were readily prepared with tunable aspect ratios by a facile solvothermal method. An oriented-attachment growth mechanism was proposed based on time-dependent trails and first principle density function theory calculation. Control experiments indicated that the reaction medium played important roles to influence the oriented-attachment process and the aspect ratio could be tuned from ∼4.6 to ∼16.0 by simply altering the precursor dosages. The as-prepared ZnO nanorods were applied as photoanode materials in quantum-dot sensitized solar cells. The large pore size in the film structure and rough surface of the nanorod could enhance the quantum dots loading amounts and light scattering effect. In addition, the orderly aligned primary ENPs minimized the grain boundaries for suppressed recombination and provided a direct pathway for increased electron diffusion length. Meanwhile, the enhanced film hydrophilicity facilitated the electrolyte penetration and the regeneration of oxidized sensitizers. Therefore, a high power conversion efficiency of ∼4.83% was demonstrated, indicating substantial improvement compared with that of traditional nanoparticle based device (∼3.54%).

  2. Flow patterns and heat transfer characteristics of flat plate pulsating heat pipes with various asymmetric and aspect ratios of the channels

    International Nuclear Information System (INIS)

    Jang, Dong Soo; Lee, Joo Seong; Ahn, Jae Hwan; Kim, Dongwoo; Kim, Yongchan

    2017-01-01

    Highlights: • Flat plate pulsating heat pipes with asymmetric and aspect ratios were tested. • Flow patterns were investigated according to channel geometry and flow condition. • Heat transfer characteristics were analyzed with various heat inputs. • Optimum asymmetric and aspect ratios were suggested for maximum thermal performance. - Abstract: The thermal performance of flat plate pulsating heat pipes (PHPs) in compact electronic devices can be improved by adopting asymmetric channels with increased pressure differences and an unbalanced driving force. The objective of this study is to investigate the heat transfer characteristics of flat plate PHPs with various asymmetric ratios and aspect ratios in the channels. The thermal performance and flow pattern of the flat plate PHPs were measured by varying the asymmetric ratio from 1.0 to 4.0, aspect ratio from 2.5 to 5.0, and heat input from 2 to 28 W. The effects of the asymmetric ratio and aspect ratio on the thermal resistance were analyzed with the measured evaporator temperature and flow patterns at various heat inputs. With heat inputs of 6 W and 12 W, the optimum asymmetric ratio and aspect ratio for the flat plate PHPs were determined to be 4.0 and 2.5, respectively. With the heat input of 18 W, the optimum asymmetric ratio and aspect ratio were determined to be 1.5 and 2.5, respectively.

  3. Front-surface fabrication of moderate aspect ratio micro-channels in fused silica by single picosecond Gaussian-Bessel laser pulse

    Science.gov (United States)

    Liu, Xin; Sanner, Nicolas; Sentis, Marc; Stoian, Razvan; Zhao, Wei; Cheng, Guanghua; Utéza, Olivier

    2018-02-01

    Single-shot Gaussian-Bessel laser beams of 1 ps pulse duration and of 0.9 μm core size and 60 μm depth of focus are used for drilling micro-channels on front side of fused silica in ambient condition. Channels ablated at different pulse energies are fully characterized by AFM and post-processing polishing procedures. We identify experimental energy conditions (typically 1.5 µJ) suitable to fabricate non-tapered channels with mean diameter of 1.2 µm and length of 40 μm while maintaining an utmost quality of the front opening of the channels. In addition, by further applying accurate post-polishing procedure, channels with high surface quality and moderate aspect ratio down to a few units are accessible, which would find interest in the surface micro-structuring of materials, with perspective of further scalability to meta-material specifications.

  4. High aspect ratio template and method for producing same for central and peripheral nerve repair

    Science.gov (United States)

    Sakamoto, Jeff S. (Inventor); Tuszynski, Mark Henry (Inventor); Gros, Thomas (Inventor); Chan, Christina (Inventor); Mehrotra, Sumit (Inventor)

    2011-01-01

    Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers. The scaffolds may be used in, among other applications, the repair of central and peripheral nerves. Scaffolds for the repair of peripheral nerves may include a reservoir for the sustained release of nerve growth factor. The scaffolds may also include a multifunctional polyelectrolyte layer for the sustained release of nerve growth factor and enhance biocompatibility.

  5. Numerical investigation of Rayleigh–Bénard convection in a cylinder of unit aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bo-Fu; Jiang, Jin [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Zhou, Lin [Institute of Structural Mechanics, Chinese Academy of Engineering Physics, Mianyang, 621900 (China); Sun, De-Jun, E-mail: jinjiang@whu.edu.cn [Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China)

    2016-02-15

    Thermal convection in a vertical cylindrical cavity with a heated bottom, cooled top and insulated sidewall is investigated numerically. The radius to height ratio (Γ = height/radius) is fixed to unity and the Prandtl number is varied from 0.04 to 1. Rayleigh numbers up to 16 000 are considered in this study. Ten different kinds of flow regime have been identified, including both steady and unsteady patterns. The transition from steady to oscillatory flow occurs at a much lower Rayleigh number for small Prandtl number flow than for large Prandtl number flow. A bifurcation analysis shows the coexistence of two flow patterns in a certain parameter regime. The effect of flow structure on heat transfer is studied for a Prandtl number of unity. (paper)

  6. Nationwide age references for sitting height, leg length, and sitting height/height ratio, and their diagnostic value for disproportionate growth disorders

    NARCIS (Netherlands)

    Fredriks, A.M.; Buuren, S. van; Heel, W.J.M. van; Dijkman-Neerincx, R.H.M.; Verloove-Vanhorick, S.P.; Wit, J.M.

    2005-01-01

    Aims: To obtain age references for sitting height (SH), leg length (LL), and SH/H ratio in the Netherlands; to evaluate how SH standard deviation score (SDS), LL SDS, SH/H SDS, and SH/LL SDS are related to height SDS; and to study the usefulness of height corrected SH/H cut-off lines to detect

  7. Study of an optimal configuration of a transmutation reactor based on a low-aspect-ratio tokamak

    International Nuclear Information System (INIS)

    Hong, Bong Guen; Kim, Hoseok

    2016-01-01

    Highlights: • Optimum configuration of a transmutation reactor based on a low aspect ratio tokamak was found. • Inboard and outboard radial build are determined by plasma physics, engineering and neutronics constraints. • Radial build and equilibrium fuel cycle play a major role in determining the transmutation characteristics. - Abstract: We determine the optimal configuration of a transmutation reactor based on a low-aspect-ratio tokamak. For self-consistent determination of the radial build of the reactor components, we couple a tokamak systems analysis with a radiation transport calculation. The inboard radial build of the reactor components is obtained from plasma physics and engineering constraints, while outboard radial builds are mainly determined by constraints on neutron multiplication, the tritium-breeding ratio, and the power density. We show that the breeding blanket model has an effect on the radial build of a transmutation blanket. A burn cycle has to be determined to keep the fast neutron fluence plasma-facing material below its radiation damage limit. We show that the radial build of the transmutation reactor components and the equilibrium fuel cycle play a major role in determining the transmutation characteristics.

  8. HIGH ASPECT RATIO ION EXCHANGE RESIN BED - HYDRAULIC RESULTS FOR SPERICAL RESIN BEADS

    International Nuclear Information System (INIS)

    Duignan, M; Charles Nash, C; Timothy Punch, T

    2007-01-01

    A principal role of the DOE Savannah River Site is to safely dispose of a large volume of liquid nuclear waste held in many storage tanks. An in-tank ion exchange unit is being considered for cesium removal to accelerate waste processing. This unit is planned to have a relatively high bed height to diameter ratio (10:1). Complicating the design is the need to cool the ion exchange media; therefore, the ion exchange column will have a central cooling core making the flow path annular. To separate cesium from waste the media being considered is made of resorcinol formaldehyde resin deposited on spherical plastic beads and is a substitute for a previously tested resin made of crystalline silicotitanate. This spherical media not only has an advantage of being mechanically robust, but, unlike its predecessor, it is also reusable, that is, loaded cesium can be removed through elution and regeneration. Resin regeneration leads to more efficient operation and less spent resin waste, but its hydraulic performance in the planned ion exchange column was unknown. Moreover, the recycling process of this spherical resorcinol formaldehyde causes its volume to significantly shrink and swell. To determine the spherical media's hydraulic demand a linearly scaled column was designed and tested. The waste simulant used was prototypic of the wastes' viscosity and density. This paper discusses the hydraulic performance of the media that will be used to assist in the design of a full-scale unit

  9. Effects of cane length and diameter and judgment type on the constant error ratio for estimated height in blindfolded, visually impaired, and sighted participants.

    Science.gov (United States)

    Huang, Kuo-Chen; Leung, Cherng-Yee; Wang, Hsiu-Feng

    2010-04-01

    The purpose of this study was to assess the ability of blindfolded, visually impaired, and sighted individuals to estimate object height as a function of cane length, cane diameter, and judgment type. 48 undergraduate students (ages 20 to 23 years) were recruited to participate in the study. Participants were divided into low-vision, severely myopic, and normal-vision groups. Five stimulus heights were explored with three cane lengths, varying cane diameters, and judgment types. The participants were asked to estimate the stimulus height with or without reference to a standard block. Results showed that the constant error ratio for estimated height improved with decreasing cane length and comparative judgment. The findings were unclear regarding the effect of cane length on haptic perception of height. Implications were discussed for designing environments, such as stair heights, chairs, the magnitude of apertures, etc., for visually impaired individuals.

  10. Extension of the beam theory for polymer bio-transducers with low aspect ratios and viscoelastic characteristics

    International Nuclear Information System (INIS)

    Du, Ping; Lin, I-Kuan; Zhang, Xin; Lu, Hongbing

    2010-01-01

    Polydimethylsiloxane (PDMS)-based micropillars (or microcantilevers) have been used as bio-transducers for measuring cellular forces on the order of pN to µN. The measurement accuracy of these sensitive devices depends on appropriate modeling to convert the micropillar deformations into the corresponding reaction forces. The traditional approach to calculating the reaction force is based on the Euler beam theory with consideration of a linear elastic slender beam for the micropillar. However, the low aspect ratio in geometry of PDMS micropillars does not satisfy the slender beam requirement. Consequently, the Timoshenko beam theory, appropriate for a beam with a low aspect ratio, should be used. In addition, the inherently time-dependent behavior in PDMS has to be considered for accurate force conversion. In this paper, the Timoshenko beam theory, along with the consideration of viscoelastic behavior of PDMS, was used to model the mechanical response of micropillars. The viscoelastic behavior of PDMS was characterized by stress relaxation nanoindentation using a circular flat punch. A correction procedure was developed to determine the load–displacement relationship with consideration of ramp loading. The relaxation function was extracted and described by a generalized Maxwell model. The bending of rectangular micropillars was performed by a wedge indenter tip. The viscoelastic Timoshenko beam formula was used to calculate the mechanical response of the micropillar, and the results were compared with measurement data. The calculated reaction forces agreed well with the experimental data at three different loading rates. A parametric study was conducted to evaluate the accuracy of the viscoelastic Timoshenko beam model by comparing the reaction forces calculated from the elastic Euler beam, elastic Timoshenko beam and viscoelastic Euler beam models at various aspect ratios and loading rates. The extension of modeling from the elastic Euler beam theory to the

  11. Microfluidic active mixers employing ultra-high aspect-ratio rare-earth magnetic nano-composite polymer artificial cilia

    International Nuclear Information System (INIS)

    Rahbar, Mona; Gray, Bonnie L; Shannon, Lesley

    2014-01-01

    We present a new micromixer based on highly magnetic, flexible, high aspect-ratio, artificial cilia that are fabricated as individual micromixer elements or in arrays for improved mixing performance. These new cilia enable high efficiency, fast mixing in a microchamber, and are controlled by small electromagnetic fields. The artificial cilia are fabricated using a new micromolding process for nano-composite polymers. Cilia fibers with aspect-ratios as high as 8:0.13 demonstrate the fabrication technique's capability in creating ultra-high aspect-ratio microstructures. Cilia, which are realized in polydimethylsiloxane doped with rare-earth magnetic powder, are magnetized to produce permanent magnetic structures with bidirectional deflection capabilities, making them highly suitable as mixers controlled by electromagnetic fields. Due to the high magnetization level of the polarized nano-composite polymer, we are able to use miniature electromagnets providing relatively small magnetic fields of 1.1 to 7 mT to actuate the cilia microstructures over a very wide motion range. Mixing performances of a single cilium, as well as different arrays of multiple cilia ranging from 2 to 8 per reaction chamber, are characterized and compared with passive diffusion mixing performance. The mixer cilia are actuated at different amplitudes and frequencies to optimize mixing performance. We demonstrate that more than 85% of the total volume of the reaction chamber is fully mixed after 3.5 min using a single cilium mixer at 7 mT compared with only 20% of the total volume mixed with passive diffusion. The time to achieve over 85% mixing is further reduced to 70 s using an array of eight cilia microstructures. The novel microfabrication technique and use of rare-earth permanently-magnetizable nano-composite polymers in mixer applications has not been reported elsewhere by other researchers. We further demonstrate improved mixing over other cilia micromixers as enabled by the high

  12. Buckling of ZnS-filled single-walled carbon nanotubes – The influence of aspect ratio

    KAUST Repository

    Monteiro, André O.

    2014-08-16

    The mechanical response of single-walled carbon nanotubes (SWCNT) filled with crystalline zinc sulphide (ZnS) nanowires under uniaxial compression is studied using classical molecular dynamics. These simulations were used to analyse the behaviour of SWCNT, with and without ZnS filling, in terms of critical force and critical strain. Force versus strain curves have been computed for hollow and filled systems, the latter clearly showing an improvement of the mechanical behaviour caused by the ZnS nanowire. The same simulations were repeated for a large range of dimensions in order to evaluate the influence of the aspect ratio on the mechanical response of the tubes.

  13. Three-Dimensional Simulation of Large-Aspect-Ratio Ellipse-Shaped Charged-Particle Beam Propagation

    CERN Document Server

    Bhatt, Ronak; Zhou, Jing

    2005-01-01

    The three-dimensional trajectory code, OMNITRAK, is used to simulate a space-charge-dominated beam of large-aspect-ratio elliptic cross-section propagating in a non-axisymmetric periodic permanent magnet focusing field. The simulation results confirm theoretical predictions in the paraxial limit. A realistic magnetic field profile is applied, and the beam sensitivity to magnet nonlinearities and misalignments is studied. The image-charge effect of conductor walls is examined for a variety of beam tunnel sizes and geometries.

  14. High-aspect ratio micro- and nanostructures enabled by photo-electrochemical etching for sensing and energy harvesting applications

    Science.gov (United States)

    Alhalaili, Badriyah; Dryden, Daniel M.; Vidu, Ruxandra; Ghandiparsi, Soroush; Cansizoglu, Hilal; Gao, Yang; Saif Islam, M.

    2018-03-01

    Photo-electrochemical (PEC) etching can produce high-aspect ratio features, such as pillars and holes, with high anisotropy and selectivity, while avoiding the surface and sidewall damage caused by traditional deep reactive ion etching (DRIE) or inductively coupled plasma (ICP) RIE. Plasma-based techniques lead to the formation of dangling bonds, surface traps, carrier leakage paths, and recombination centers. In pursuit of effective PEC etching, we demonstrate an optical system using long wavelength (λ = 975 nm) infra-red (IR) illumination from a high-power laser (1-10 W) to control the PEC etching process in n-type silicon. The silicon wafer surface was patterned with notches through a lithography process and KOH etching. Then, PEC etching was introduced by illuminating the backside of the silicon wafer to enhance depth, resulting in high-aspect ratio structures. The effect of the PEC etching process was optimized by varying light intensities and electrolyte concentrations. This work was focused on determining and optimizing this PEC etching technique on silicon, with the goal of expanding the method to a variety of materials including GaN and SiC that are used in designing optoelectronic and electronic devices, sensors and energy harvesting devices.

  15. Controllable fabrication of periodic arrays of high-aspect-ratio micro-nano hierarchical structures and their superhydrophobicity

    Science.gov (United States)

    Ma, Zhibo; Jiang, Chengyu; Li, Xiangming; Ye, Fang; Yuan, Weizheng

    2013-09-01

    This paper demonstrates a flexible and controllable fabrication of vertically aligned and high-aspect-ratio (HAR) micro-nano hierarchical structures using conventional micro-technologies. We first masked the nanopatterns on a photoresist mold by shifting the same photomask, which could be performed using conventional contact microlithography. Thereby replicating nanopatterns onto an aluminium mold and successfully fabricating silicon nanopillar arrays about 300 nm in diameter and 5 µm in height via the deep reactive etching (DRIE) process. We also fabricated micro-nano hierarchical structures with variable aspect ratios using the proposed nanopattern technology and DRIE process without using any special nanopatterning equipment or techniques. The proposed method not only simplified the fabrication process but also produced HAR (higher than 15) structures. We also investigate the replica molding steps from the fabricated silicon stamp to a UV-curable polymer replica using a PDMS mold and conventional nano-imprinting, where each nanopillar diameter was 320 nm with 95% fidelity. As a result, the hierarchical structure arrays show stable superhydrophobic surface properties with a contact angle of approximately 160°. Owing to the cost efficiency of mass production and the fidelity of the strategy, the methodology could provide a general approach for fabricating complex three-dimensional periodic hierarchical structures onto a single chip and can be applied to various fields of multifunctional applications.

  16. Effects of AC/DC magnetic fields, frequency, and nanoparticle aspect ratio on cellular transfection of gene vectors

    Science.gov (United States)

    Ford, Kris; Mair, Lamar; Fisher, Mike; Rowshon Alam, Md.; Juliano, Rudolph; Superfine, Richard

    2008-10-01

    In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane.

  17. Aspect ratio effects of an adiabatic rectangular obstacle on natural convection and entropy generation of a nanofluid in an enclosure

    International Nuclear Information System (INIS)

    Sheikhzadeh, G. A.; Nikfar, M.

    2013-01-01

    In the present study, aspect ratio (AR) effects of a centered adiabatic rectangular obstacle numerically investigated on natural convection and entropy generation in a differentially heated enclosure filled with either water or nanofluid (Cu-water). The governing equations are solved numerically with finite volume method using the SIMPLER algorithm. The study has been done for Rayleigh numbers between 10 3 and 10 6 , the aspect ratio of 1/3, 1/2, 1, 2 and 3 and for base fluid as well as nanofluid. It is found that, using the nanofluid leads to increase the flow strength, average Nusselt number and entropy generation and decrease the Bejan number especially at high Rayleigh numbers. At low Rayleigh numbers entropy generation is very low. By increasing Rayleigh number, entropy generation and Bejan number increases. It is observed that the viscose entropy generation is more considerable than the thermal entropy generation and has dominant role in total entropy generation. The maximum entropy generation occurs at AR = 1/3 and 3 and the minimum entropy generation occurs at AR = 1 and 1/2. It is observed that the effect of AR on Nusselt number, entropy generation and Bejan number depends on Rayleigh number.

  18. Influence of aspect ratio on the thermal performance of rectangular shaped micro channel heat sink using CFD code

    Directory of Open Access Journals (Sweden)

    D.R.S. Raghuraman

    2017-03-01

    Full Text Available A numerical study has been carried out to investigate the heat transfer enhancement and fluid flow characteristics for various aspect ratios of rectangular micro channel heat sinks (MCHS. The working fluid considered for the analysis is water. The fluid flow and heat transfer characteristics of a three-dimensional MCHS are obtained numerically by solving the appropriate governing equations. The flow domain is discretized as finite volume elements and solved using ANSYS CFX 14.5, commercially available CFD code. The numerically predicted results obtained through CFD code are validated with the experiments carried out and it is found that the maximum deviation between the two is less than 5%. Hence the CFD code is further extended to study the influence of geometrical parameters. The channel size optimization has been carried out numerically to obtain the effective heat removal from the MCHS. Average convective heat transfer coefficient, outlet temperature, friction and pressure drop, pumping power and thermal resistance have been plotted against Reynolds number. Non-dimensional parameter, Nusselt number has been plotted as a function of Reynolds number for three heat sinks with different aspect ratios. Friction factor and pressure drop across the channels are obtained and plotted across the channels.

  19. Association of newborn diseases with weight/length ratio and the adequacy of weight for gestational age

    Directory of Open Access Journals (Sweden)

    José Ricardo Dias Bertagnon

    2011-09-01

    Full Text Available Objective: To compare the frequencies of newborn diseases in thosenewborns classified according to a weight/length rate and thoseclassified by the adequacy weight for gestational age. Methods: Aretrospective cross-sectional study by record assessment was carriedout enclosing all the live newborns at Hospital Geral do Grajaú, fromSeptember to December, 2009 (n =577 classified according to therate weight/length and also to the adequacy weight for gestationalage. The 10 and 90 percentiles of the weight/length distribution, nowdesignated as “indices” were calculated leading to the followingclassification: low index, for newborns below 54.8 g/cm; high index,for those over 75.8 g/cm; and average index, for the remainingnewborns. According to the adequacy weight for gestational age thenewborns were designated as pre-term for gestational age; term smallfor gestational age; appropriate term and large term. In this samplethere were no small and large pre-term or post-term newborns. Majordiseases were related to the index and adequacy extracts by the χ2test for a contingency table. Results: A significant association wasfound among low index, pre-term for gestational age newborns andterm small for gestational age; between average index and appropriatefor gestational age term newborns; and high index with large termappropriate for gestational age newborns (p< 0.001. Hypoglycemia(3.4% was associated to both low and high indices, to appropriatefor gestational age preterm newborns and to small for gestational ageterm newborns. Sepsis (3.1% was associated to both low index andpre-term appropriate for gestational age newborns. The respiratorydistress syndrome (1.3% was associated to low index and pre-termappropriate for gestational age newborns. Other respiratory distresssyndromes (3.8% were associated to low and high indices but notto the adequacy for gestational age classification. Jaundice (14.9%was not associated to the studied classifications

  20. A validated numerical investigation of the effects of high blockage ratio and train and tunnel length upon underground railway aerodynamics

    OpenAIRE

    Cross, D.; Hughes, B.; Ingham, D.; Ma, L.

    2015-01-01

    In order to ensure the safety and comfort of passengers and staff, an underground railway requires an extensive ventilation and cooling system. One mechanism for underground railway ventilation is the movement of air induced by trains, termed the ‘piston effect’. This study investigated the effect of altering the blockage ratio of an underground train upon the ventilating air flows driven by a train. First a computational model was developed and validated with experimental data from literatur...

  1. Recent Development in the CESE Method for the Solution of the Navier-Stokes Equations Using Unstructured Triangular or Tetrahedral Meshes With High Aspect Ratio

    Science.gov (United States)

    Chang, Sin-Chung; Chang, Chau-Lyan; Yen, Joseph C.

    2013-01-01

    In the multidimensional CESE development, triangles and tetrahedra turn out to be the most natural building blocks for 2D and 3D spatial meshes. As such the CESE method is compatible with the simplest unstructured meshes and thus can be easily applied to solve problems with complex geometries. However, because the method uses space-time staggered stencils, solution decoupling may become a real nuisance in applications involving unstructured meshes. In this paper we will describe a simple and general remedy which, according to numerical experiments, has removed any possibility of solution decoupling. Moreover, in a real-world viscous flow simulation near a solid wall, one often encounters a case where a boundary with high curvature or sharp corner is surrounded by triangular/tetrahedral meshes of extremely high aspect ratio (up to 106). For such an extreme case, the spatial projection of a space-time compounded conservation element constructed using the original CESE design may become highly concave and thus its centroid (referred to as a spatial solution point) may lie far outside of the spatial projection. It could even be embedded beyond a solid wall boundary and causes serious numerical difficulties. In this paper we will also present a new procedure for constructing conservation elements and solution elements which effectively overcomes the difficulties associated with the original design. Another difficulty issue which was addressed more recently is the wellknown fact that accuracy of gradient computations involving triangular/tetrahedral grids deteriorates rapidly as the aspect ratio of grid cells increases. The root cause of this difficulty was clearly identified and several remedies to overcome it were found through a rigorous mathematical analysis. However, because of the length of the current paper and the complexity of mathematics involved, this new work will be presented in another paper.

  2. Effect of multi-walled carbon nanotubes aspect ratio and temperature on the dielectric behavior of alternating alkene-carbon monoxide polyketone nanocomposites

    Science.gov (United States)

    Abu-Surrah, Adnan S.; Abdul Jawad, Saadi; Al-Ramahi, Esraa; Hallak, Awni B.; Khattari, Z.

    2015-04-01

    New alternating poly(propylene-alt-carbon monoxide/ethylene-alt-carbon monoxide) (PECO)/multiwalled carbon nanotubes (MWCNTs) composites have been prepared. Dielectric permittivity, electric modulus and ac conductivity of the isolated materials were investigated as a function of fiber aspect ratio, frequency and temperature. For aspect ratio of 30 and 200, a transition from insulator to semiconductor was observed at frequency 1×104. However, for high aspect ratio sample (660), no transition was observed and the conductivity is frequency independent in the measured frequency range of 10-106 Hz. The conductivity increases from about 1×10-4 for the sample that contain fibers of aspect ratio 30 and reaches 5×10-2 (Ω m)-1 for aspect ratio was 660. This behavior can be modeled by a circuit that consists of a contact resistance in series with a parallel combination of resistance (R) and capacitance (C). The calculated activation energy for sample filled with fibers having aspect ratio 30 is about 0.26 eV and decreases to about 0.16 eV when the aspect ratio is 660.

  3. Aspects

    Directory of Open Access Journals (Sweden)

    Fatma A. Abdel Razek

    2014-01-01

    Full Text Available The reproductive cycle of the eared horse mussel, Modiolus auriculatus, was followed for one year from February, 2011 to January, 2012 based on 240 individuals collected from Hurghada, north coast of Red Sea, Egypt. The gonadal maturation of M. auriculatus was examined by means of macroscopic and histological preparations of the mantle. Annual cycle with periods of growth, maturity and discharge of gonadic products occurs simultaneously in both sexes. Ripe individuals were observed throughout the year. The largest number of spawning for the individuals occurred from March to June and July for the population. So, it was clear to identify one heavy spawning period for this species. Sexation of M. auriculatus did not differ significantly from 1:1. Sexes were distinguishable in all individuals at the ripe stage with a shell length greater than 3.00 cm. A direct positive correlation was observed between gonad index and water temperature.

  4. A simple microfluidic gradient generator with a soft-lithographically prototyped, high-aspect-ratio, ~2 µm wide microchannel.

    Science.gov (United States)

    Ogawa, Tomohisa; Matsunaga, Nirai; Inomata, Saori; Tanaka, Masato; Futai, Nobuyuki

    2013-01-01

    We have developed a cast microfluidic chip that contains a thin (~2 µm wide) microchannel that is smoothly connected to thick microfluidics. The thin line features having high aspect ratio for a low-cost photolithography in which an emulsion photomask was used (1:1 ~ 1:3) were fabricated by exposing SU-8 photoresist to diffused 185 nm UV light emitted by a low-cost ozone lamp from the backside of the substrate to ensure sufficient crosslinking of small regions of the SU-8 photoresist. An H-shaped microfluidic configuration was used, in which the thin channel maintained constant diffusion fronts beyond purely static diffusion. We also demonstrated the long-term effects of a gradient of nerve growth factor on axon elongation by primary neurons cultured in the micro channel.

  5. Results of design studies and wind tunnel tests of high-aspect-ratio supercritical wings for an energy efficient transport

    Science.gov (United States)

    Steckel, D. K.; Dahlin, J. A.; Henne, P. A.

    1980-01-01

    These basic characteristics of critical wings included wing area, aspect ratio, average thickness, and sweep as well as practical constraints on the planform and thickness near the wing root to allow for the landing gear. Within these constraints, a large matrix of wing designs was studied with spanwise variations in the types of airfoils and distribution of lift as well as some small planform changes. The criteria by which the five candidate wings were chosen for testing were the cruise and buffet characteristics in the transonic regime and the compatibility of the design with low speed (high-lift) requirements. Five wing-wide-body configurations were tested in the NASA Ames 11-foot transonic wind tunnel. Nacelles and pylons, flap support fairings, tail surfaces, and an outboard aileron were also tested on selected configurations.

  6. Localized mold heating with the aid of selective induction for injection molding of high aspect ratio micro-features

    International Nuclear Information System (INIS)

    Park, Keun; Lee, Sang-Ik

    2010-01-01

    High-frequency induction is an efficient, non-contact means of heating the surface of an injection mold through electromagnetic induction. Because the procedure allows for the rapid heating and cooling of mold surfaces, it has been recently applied to the injection molding of thin-walled parts or micro/nano-structures. The present study proposes a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. For localized induction heating, a composite injection mold of ferromagnetic material and paramagnetic material is used. The feasibility of the proposed heating method is investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and in terms of the structural safety of the composite mold. The moldability of high aspect ratio micro-features is then experimentally compared under a variety of induction heating conditions.

  7. Experimental study of convective exchange in a low aspect ratio perforation: Application to cooling of multiperforated wall

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Phu Hung [Dept. Machine Hydraulique et Aeronautique de l' Instituts Polytechnique de Ha Noi. No. 1 DAI Co Viet-Hai ba Trung, Hanoi (Viet Nam); Dorignac, Eva [Laboratoire d' Etudes Thermiques (UMR 6608), Universite de Poitiers, 86961 Futuroscope Chasseneuil (France)

    2008-10-15

    This work presents an experimental study pertaining to convective transfer in pipes with a square-edged inlet simulating the perforation of a multiperforated wall. The experiments were performed for a range of Reynolds numbers from 3000 to 35,000 and an aspect ratio from 2 to 8. The results achieved have allowed us to characterize the different flow areas within the pipe: takeoff, landing, and developed; they have also enabled us to highlight the influence of aerothermic (Re) and geometric (l/d, type of inlet and number of perforations) parameters. We are likewise proposing correlations allowing for determination of the convective exchange coefficient from preliminarily underscored characteristic points (maximum, minimum and established) in the perforation. (author)

  8. Electrolytic Manganese Dioxide Coatings on High Aspect Ratio Micro-Pillar Arrays for 3D Thin Film Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Yafa Zargouni

    2017-05-01

    Full Text Available In this work, we present the electrochemical deposition of manganese dioxide (MnO2 thin films on carbon-coated TiN/Si micro-pillars. The carbon buffer layer, grown by plasma enhanced chemical vapor deposition (PECVD, is used as a protective coating for the underlying TiN current collector from oxidation, during the film deposition, while improving the electrical conductivity of the stack. A conformal electrolytic MnO2 (EMD coating is successfully achieved on high aspect ratio C/TiN/Si pillar arrays by tailoring the deposition process. Lithiation/Delithiation cycling tests have been performed. Reversible insertion and extraction of Li+ through EMD structure are observed. The fabricated stack is thus considered as a good candidate not only for 3D micorbatteries but also for other energy storage applications.

  9. Process optimization of high aspect ratio sub-32nm HSQ/AR3 bi-layer resist pillar

    Science.gov (United States)

    Chen, Wei-Su; Tsai, Ming-Jinn

    2011-04-01

    RRAM is the candidate of next generation new non-volatile memory. The etched stacking film thickness of RRAM cell pillar is not easy to reduce below 50 nm during CD scaling down since part of RRAM cell pillar height is removed during CMP polishing of dielectric passivation to expose the pillar top surface for the following metallization process. Therefore resist pillar pattern with high aspect ratio (AR) is needed to act as etch mask for defining thick RRAM cell pillar structure. Bilayer resist (BLR) process is most suitable for forming high AR pattern. Dry develop process is the key step for generating sub-32 nm high AR BLR pillar pattern. In this study optimization of dry develop process is investigated for high AR pillar with hydrogen silsesquioxane (HSQ) as upper thin imaging layer for e-beam exposure and AR3-600 as the thick underlayer for etching resistant. Experimental results are summarized below. Highest AR of ~6 for HSQ/AR3 BLR semi-dense L/S=1/2 pillar with vertical profile is obtained under optimized dry develop condition with O2, N2, Ar flow rates, chamber pressure, top and bottom power of 8, 5, 0 sccm, 1 mTorr, 200 and 100 watts respectively. AR is lower for looser pattern density. CD variation between HSQ/AR3-600 BLR pillars with different pattern density is optimized to 5.6 nm. The pillar profile is vertical in vacuum for pattern of any density but distorts more severe for denser pattern during ventilation to atmosphere. The most critical process parameters for obtaining high aspect ratio BLR pillar are O2 flow rate and top power. Sidewall profile angle of pillar is mainly dependent on chamber pressure and bottom power.

  10. Exploring the limits of case-to-capsule ratio, pulse length, and picket energy for symmetric hohlraum drive on NIF

    Science.gov (United States)

    Callahan, Debra

    2017-10-01

    Over the past two years, we have been exploring low gasfill hohlraums (He fill at 0.3-0.6 mg/cc) as an alternate to the high gasfill hohlraums used in NIC and the High Foot campaigns (He fill at 1-1.6 mg/cc). These low fill hohlraums have significantly reduced laser-plasma instabilities and increased coupling to the target as compared to the high fill hohlraums and take us to a new region of parameter space where the hohlraum is limited by hydrodynamic motion of the hohlraum wall rather than by laser plasma interactions. The outer cone laser beams interacting with the hohlraum wall produce a ``bubble'' of low density, high Z material that moves toward the center of the hohlraum. This gold or depleted uranium bubble eventually intercepts the inner cone beams and prevents the inner cone beams from reaching the waist of the hohlraum-where they are needed to get a symmetric implosion. Thus, the speed of the bubble expansion sets the allowable pulse duration in a given size hohlraum. Data and simulations suggest that the bubble is launched by the early part of the laser pulse (``picket'') and the gold/gas interfaces moves nearly linearly in time toward the axis of the hohlraum. The velocity of the bubble is related to the square root of the energy in the picket of the pulse - thus the picket energy and pulse duration set the allowable hohlraum size and case-to-capsule ratio. In this talk, will discuss a data based model to describe the bubble motion and apply this model to a broad set of data from a variety of ablators (CH, HDC, Be), pulse durations (6-14 ns), case-to-capsule ratios (rhohl/rcap of 3-4.2), hohlraum sizes (5.4-6.7 mm diameter), and hohlraum gasfill densities (0.3-0.6 mg/cc). We will discuss how this model can help guide future designs and how improvements in the hohlraum (foam liners, hohlraum shape) can open up new parts of parameter space. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National

  11. Effect of High-Lift Devices on the Static-Lateral-Stability Derivatives of a 45 deg Sweptback Wing of Aspect Ratio 4.0 and Taper Ratio 0.6 in Combination With A Body

    National Research Council Canada - National Science Library

    Lichtenstein, Jacob

    1952-01-01

    An investigation has been made in the Langley stability tunnel to determine the effect of high-lift devices on the low-speed static-lateral-stability derivatives of a 45 deg sweptback wing of aspect ratio 4.0 and taper ratio 0.6...

  12. WEIGHT-LENGTH RATIO AND CONDITION FACTOR OF PESCADA BRANCA (Plagioscion squamosissimus, HECKEL 1840 COMMERCIALISED IN THE MUNICIPALITY OF SANTARÉM, PARÁ, BRAZIL

    Directory of Open Access Journals (Sweden)

    Ericleya Mota Marinho Lima

    2017-06-01

    Full Text Available Fishing is one of the most important economic activities in the Amazon region. In the Lower Amazon, the species Plagioscion squamosissimus commonly known as pescada branca is one of the main commercial species. The objective of this study was to determine the weight-length relationship and the condition factor of “pescada branca” landed at the Fish Market in Santarém-PA. Data was gathered from August 2014 to July 2015 in the Fish Market. The sample had 352 individuals of the species studied. The mean length and mean weight of the individuals analyzed corresponded to 26,83 ± 2.64 cm and 234,87 ± 77, 60 g, respectively. These values generated two equations, namely Wt = 0,0382*Lt2,648 and Wt= 0,1424 *Lt 2,235 for the length-weight relationship for females and males, respectively. The value of b of length-weight ratio was < 3, thus the growth of species can be considered negative allometric for both genders. The annual variation of the condition factor suggests that fat accumulation occurs in the period of drought / flood. This estimation is of great use for the management of the pescada branca stocks and can provide subsidies for decision-making administratos, in order to promote the conservation and rational use of the fishery resource. Keywords: fishing landings; biological estimates; fisheries management.

  13. Numerical Investigation of Wind Conditions for Roof-Mounted Wind Turbines: Effects of Wind Direction and Horizontal Aspect Ratio of a High-Rise Cuboid Building

    Directory of Open Access Journals (Sweden)

    Takaaki Kono

    2016-11-01

    Full Text Available From the viewpoint of installing small wind turbines (SWTs on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs. The LES results confirmed that as HAR decreases (i.e., as the building width decreases, the variation in wind velocity over the roof tends to decrease. This tendency is more prominent as the angle between the wind direction and the normal vector of the building’s leeward face with longer roof edge increases. Moreover, at windward corners of the roof, wind conditions are generally favorable at relatively low heights. In contrast, at the midpoint of the roof's windward edge, wind conditions are generally not favorable at relatively low heights. At leeward representative locations of the roof, the bottoms of the height range of favorable wind conditions are typically higher than those at the windward representative locations, but the favorable wind conditions are much better at the leeward representative locations. When there is no prevailing wind direction, the center of the roof is more favorable for installing SWTs than the corners or the edge midpoints of the roof.

  14. Leukocyte Telomere Length and Serum Levels of High-Molecular-Weight Adiponectin and Dehydroepiandrosterone-Sulfate Could Reflect Distinct Aspects of Longevity in Japanese Centenarians

    Directory of Open Access Journals (Sweden)

    Yuji Aoki MD, PhD

    2017-03-01

    Full Text Available Leukocyte telomere length and serum levels of high-molecular-weight adiponectin and dehydroepiandrosterone-sulfate (DHEA-S were assessed in association with nutrition and performance status (PS in Japanese centenarians. Twenty-three centenarians (five men, 18 women were classified according to their PS 1 (nearly fully ambulatory, n = 2, 2 (in bed less than 50% of daytime, n = 10, 3 (in bed greater than 50%, n = 6, and 4 (completely bedridden, n = 5. Leukocyte telomere length was determined by the hybridization protection assay, and the adiponectin and DHEA-S levels were measured by chemiluminescent enzyme immunoassay. Among variables of PS, body mass index (BMI, albumin, adiponectin, DHEA-S, and telomere length, there were significant correlations between PS and albumin ( r = −.694, p < .01, between telomere length and BMI ( r = .522, p < .05, between adiponectin and BMI ( r = −.574, p < .01, and between DHEA-S and albumin ( r = .530, p < .01. When excluding two cancer-bearing centenarians with short telomere, telomere length significantly correlated with PS ( r = −.632, p < .01. It was indicated that the short leukocyte telomere was associated with poor PS and cancer development and that the adiponectin or DHEA-S was associated with adiposity or nutritional status. Despite a small number of subjects, these biomarkers seemed to reflect distinct aspects of longevity in Japanese centenarians.

  15. pH-Dependent Toxicity of High Aspect Ratio ZnO Nanowires in Macrophages Due to Intracellular Dissolution

    KAUST Repository

    H. Müller, Karin

    2010-11-23

    High-aspect ratio ZnO nanowires have become one of the most promising products in the nanosciences within the past few years with a multitude of applications at the interface of optics and electronics. The interaction of zinc with cells and organisms is complex, with both deficiency and excess causing severe effects. The emerging significance of zinc for many cellular processes makes it imperative to investigate the biological safety of ZnO nanowires in order to guarantee their safe economic exploitation. In this study, ZnO nanowires were found to be toxic to human monocyte macrophages (HMMs) at similar concentrations as ZnCl2. Confocal microscopy on live cells confirmed a rise in intracellular Zn2+ concentrations prior to cell death. In vitro, ZnO nanowires dissolved very rapidly in a simulated body fluid of lysosomal pH, whereas they were comparatively stable at extracellular pH. Bright-field transmission electron microscopy (TEM) showed a rapid macrophage uptake of ZnO nanowire aggregates by phagocytosis. Nanowire dissolution occurred within membrane-bound compartments, triggered by the acidic pH of the lysosomes. ZnO nanowire dissolution was confirmed by scanning electron microscopy/energy-dispersive X-ray spectrometry. Deposition of electron-dense material throughout the ZnO nanowire structures observed by TEM could indicate adsorption of cellular components onto the wires or localized zinc-induced protein precipitation. Our study demonstrates that ZnO nanowire toxicity in HMMs is due to pH-triggered, intracellular release of ionic Zn2+ rather than the high-aspect nature of the wires. Cell death had features of necrosis as well as apoptosis, with mitochondria displaying severe structural changes. The implications of these findings for the application of ZnO nanowires are discussed. © 2010 American Chemical Society.

  16. Effect of number of lobes and length-diameter ratio on stability of tilted-lobe hydrodynamic journal bearings at zero load

    Science.gov (United States)

    Schuller, F. T.

    1975-01-01

    Hydrodynamic journal stability tests were conducted with tilted-lobe bearings. The bearings had three, five, and seven lobes and length to diameter (L/D) ratios from 0.2 to 1.0. They were tested in water and MIL-L-7808G oil at 294 K (70 F) at speeds to 5400 rpm with zero load. Stability was not appreciably affected by the number of lobes and decreased with a decrease in L/D ratio. However, a three-tilted-lobe bearing with an offset factor of 0.76 and an L/D of 0.5 was more stable than a three centrally lobed bearing with an offset factor of 0.50 and an L/D of 1.0.

  17. Microfabrication of high-aspect-ratio Bi-Te alloy microposts and applications in microsized cooling probes

    Science.gov (United States)

    Huang, Lei; Wang, Wanjun; Murphy, Michael C.

    1998-09-01

    High aspect-ratio microposts of bismuth-telluride alloy with a height of up to 750 micrometer and a diameter of 150 micrometer have been fabricated with the LIGA technique. This work is the part of an on-going research effort to develop a microprobe based on Peltier effect for highly localized temperature manipulation on the microscale. Bismuth-telluride alloys were electrodeposited galvanostatically on a titanium substrate using an acidic solution containing Bi3+ and HTeO2- ions in 1 mol dm-3 nitric acid (pH equals 0). The Bi-Te alloy microposts were found to be monophasic, exhibit a polycrystalline structure, demonstrate excellent adhesion on the substrate and with good mechanical strength. The chemical composition of the microposts was dependent on the electrolyte composition of deposition bath and the current density used in the electroplating; by controlling these two factors either p- or n-type Bi-Te alloy microposts may be produced. This research demonstrates that the microfabrication of Peltier effect probes is feasible.

  18. GaAs on Si epitaxy by aspect ratio trapping: Analysis and reduction of defects propagating along the trench direction

    Energy Technology Data Exchange (ETDEWEB)

    Orzali, Tommaso, E-mail: tommaso.orzali@sematech.org; Vert, Alexey; O' Brien, Brendan; Papa Rao, Satyavolu S. [SEMATECH, 257 Fuller Rd Suite 2200, Albany, New York 12203 (United States); Herman, Joshua L.; Vivekanand, Saikumar [College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, 251 Fuller Road, Albany, New York 12203 (United States); Hill, Richard J. W. [Now at Micron Technologies, 8000 S Federal Way, Boise, Idaho 83716 (United States); Karim, Zia [AIXTRON, Inc., 1139 Karlstad Dr., Sunnyvale, California 94089 (United States)

    2015-09-14

    The Aspect Ratio Trapping technique has been extensively evaluated for improving the quality of III-V heteroepitaxial films grown on Si, due to the potential for terminating defects at the sidewalls of SiO{sub 2} patterned trenches that enclose the growth region. However, defects propagating along the trench direction cannot be effectively confined with this technique. We studied the effect of the trench bottom geometry on the density of defects of GaAs fins, grown by metal-organic chemical vapor deposition on 300 mm Si (001) wafers inside narrow (<90 nm wide) trenches. Plan view and cross sectional Scanning Electron Microscopy and Transmission Electron Microscopy, together with High Resolution X-Ray Diffraction, were used to evaluate the crystal quality of GaAs. The prevalent defects that reach the top surface of GaAs fins are (111) twin planes propagating along the trench direction. The lowest density of twin planes, ∼8 × 10{sup 8 }cm{sup −2}, was achieved on “V” shaped bottom trenches, where GaAs nucleation occurs only on (111) Si planes, minimizing the interfacial energy and preventing the formation of antiphase boundaries.

  19. Study aspect ratio of microchannel on different polymer substrates with CO2 laser and hot bonding for microfluidic chip

    Science.gov (United States)

    Chen, Xueye; Hu, Zengliang

    2018-01-01

    The paper demonstrates four different polymer substrates including Polymethyl-methacrylate (PMMA), Polycarbonate (PC), Polystyene (PS) and Polyethylene Terephthalate (PET) for fabricating microfluidic chips using CO2 laser and hot bonding machine. The experimental methods are very simple and convenient. The work aims to obtain combination of optimal polymer for hot bonding through comparing the influence of different polymer cover plates on aspect ratio of different polymer microchannels at the same hot bonding parameters. There are three microchannels in each polymer substrate. And three microchannels are processed at three different laser parameters. The hot bonding parameters include bonding temperature of 95°C, pressure of 1Mpa for time of 9min. The results show PS cover plate with the basic plate of other substrates is the best due to stability of microfluidic chip and the ignored microchannel deformation. Next, a fluid mixing experiment in microfluidic chip with PMMA basic plate and PS cover plate is successfully performed. The microchannel in PMMA is processed with laser speed of 10mm/s, laser power of 12W, distance between the sheet surface and the lens of 7.5mm.

  20. A high aspect ratio SU-8 fabrication technique for hollow microneedles for transdermal drug delivery and blood extraction

    International Nuclear Information System (INIS)

    Chaudhri, Buddhadev Paul; Ceyssens, Frederik; Van Hoof, Chris; Puers, Robert; De Moor, Piet

    2010-01-01

    Protein drugs, e.g. hormonal drugs, cannot be delivered orally to a patient as they get digested in the gastro-intestinal (GI) tract. Thus, it is imperative that these kinds of drugs are delivered transdermally through the skin. To provide for real-time feedback as well as to test independently for various substances in the blood, we also need a blood sampling system. Microneedles can perform both these functions. Further, microneedles made of silicon or metal have the risk of breaking inside the skin thereby leading to complications. SU-8, being approved of as being biocompatible by the Food and Drug Agency (FDA) of the United States, is an attractive alternative because firstly it is a polymer material, thereby reducing the chances of breakages inside the skin, and secondly it is a negative photoresist, thereby leading to ease of fabrication. Thus, here we present very tall (around 1600 µm) SU-8 polymer-based hollow microneedles fabricated by a simple and repeatable process, which are a very good candidate for transdermal drug delivery as well as blood extraction. The paper elaborates on the details that allow the fabrication of such extreme aspect ratios (>100).

  1. Optimization of laser energy deposition for single-shot high aspect-ratio microstructuring of thick BK7 glass

    Energy Technology Data Exchange (ETDEWEB)

    Garzillo, Valerio; Grigutis, Robertas [Dipartimento di Scienza e Alta Tecnologia, University of Insubria, Via Valleggio 11, I-22100 Como (Italy); Jukna, Vytautas [Centre de Physique Theorique, CNRS, Ecole Polytechnique, Université Paris-Saclay, F-91128 Palaiseau (France); LOA, ENSTA-ParisTech, CNRS, Ecole Polytechnique, Université Paris Saclay, F-91762 Palaiseau (France); Couairon, Arnaud [Centre de Physique Theorique, CNRS, Ecole Polytechnique, Université Paris-Saclay, F-91128 Palaiseau (France); Di Trapani, Paolo [Dipartimento di Scienza e Alta Tecnologia, University of Insubria and CNISM UdR Como, Via Valleggio 11, I-22100 Como (Italy); Jedrkiewicz, Ottavia, E-mail: ottavia.jedrkiewicz@ifn.cnr.it [Istituto di Fotonica e Nanotecnologie, CNR and CNISM UdR Como, Via Valleggio 11, I-22100 Como (Italy)

    2016-07-07

    We investigate the generation of high aspect ratio microstructures across 0.7 mm thick glass by means of single shot Bessel beam laser direct writing. We study the effect on the photoinscription of the cone angle, as well as of the energy and duration of the ultrashort laser pulse. The aim of the study is to optimize the parameters for the writing of a regular microstructure due to index modification along the whole sample thickness. By using a spectrally resolved single pulse transmission diagnostics at the output surface of the glass, we correlate the single shot material modification with observations of the absorption in different portions of the retrieved spectra, and with the absence or presence of spectral modulation. Numerical simulations of the evolution of the Bessel pulse intensity and of the energy deposition inside the sample help us interpret the experimental results that suggest to use picosecond pulses for an efficient and more regular energy deposition. Picosecond pulses take advantage of nonlinear plasma absorption and avoid temporal dynamics effects which can compromise the stationarity of the Bessel beam propagation.

  2. Large-Eddy Simulation of Flow and Pollutant Dispersion in High-Aspect-Ratio Urban Street Canyons with Wall Model

    Science.gov (United States)

    Li, Xian-Xiang; Liu, Chun-Ho; Leung, Dennis Y. C.

    2008-11-01

    A large-eddy simulation (LES) with a one-equation subgrid-scale (SGS) model was developed to investigate the flow field and pollutant dispersion inside street canyons of high aspect ratio (AR). A 1/7th power-law wall model was implemented near rigid walls to mitigate the demanding near-wall resolution requirements in LES. This LES model had been extensively validated against experimental results for street canyons of AR = 1 and 2 before it was applied to the cases of AR = 3 and 5. A ground-level passive pollutant line source, located in the middle of the street, was used to simulate vehicular emissions. Three and five vertically aligned primary recirculations were developed in the street canyons of AR 3 and 5, respectively. The ground-level mean wind speed was less than 0.5% of the free stream value, which makes it difficult for the pollutant to be transported upward for removal. High pollutant concentration and variance were found near the buildings where the air flow is upwards. It was found that the velocity fluctuation, pollutant concentration and variance were all closely related to the interactions between the primary recirculations and/or the free surface layer. Several quantities, which are non-linear functions of AR, were introduced to quantify the air quality in street canyons of different configurations.

  3. Sensitivity of wave propagation in the LHRF to initial poloidal position in finite-aspect-ratio toroidal plasmas

    Science.gov (United States)

    Larson, J. J.; Pinsker, R. I.; Bonoli, P. T.; Porkolab, M.

    2017-10-01

    The important effect of varying the initial poloidal wave-launching location to the core accessibility of lower hybrid slow waves in a torus of finite aspect ratio has been understood for many years. Since the qualitative properties of the wave propagation of the other branch in this regime, known as the `whistler', `helicon' or simply the `fast wave', are similar in some ways to those of the slow wave, we expect a dependence on launch position for this wave also. We study this problem for both slow and fast waves, first with simplified analytic models and then using the ray-tracing code GENRAY for realistic plasma equilibria. We assess the prospects of inside, top, bottom or conventional outside launch of waves on each of the two branches. Although the slow wave has been the focus of research for LHRF heating and current drive in the past, the fast wave will play a major role in burning plasmas beyond ITER where Te(0) = 10-20 keV. The stronger electron Landau damping of the slow wave will restrict the power deposition to the outer third of the plasma, while the fast wave's weaker damping allows the wave to penetrate to the hot plasma core before depositing its power. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER54698 and DE-FG02-91-ER54109.

  4. High aspect ratio silicon nanomoulds for UV embossing fabricated by directional thermal oxidation using an oxidation mask

    International Nuclear Information System (INIS)

    Chen, L Q; Chan-Park, Mary B; Yan, Y H; Zhang Qing; Li, C M; Zhang Jun

    2007-01-01

    Nanomoulding is simple and economical but moulds with nanoscale features are usually prohibitively expensive to fabricate because nanolithographic techniques are mostly serial and time-consuming for large-area patterning. This paper describes a novel, simple and inexpensive parallel technique for fabricating nanoscale pattern moulds by silicon etching followed by thermal oxidation. The mask pattern can be made by direct photolithography or photolithography followed by metal overetching for submicron- and nanoscale features, respectively. To successfully make nanoscale channels having a post-oxidation cross-sectional shape similar to that of the original channel, an oxidation mask to promote unidirectional (specifically horizontal) oxide growth is found to be essential. A silicon nitride or metal mask layer prevents vertical oxidation of the Si directly beneath it. Without this mask, rectangular channels become smaller but are V-shaped after oxidation. By controlling the silicon etch depth and oxidation time, moulds with high aspect ratio channels having widths ranging from 500 to 50 nm and smaller can be obtained. The nanomould, when passivated with a Teflon-like layer, can be used for first-generation replication using ultraviolet (UV) nanoembossing and second-generation replication in other materials, such as polydimethylsiloxane (PDMS). The PDMS stamp, which was subsequently coated with Au, was used for transfer printing of Au electrodes with a 600 nm gap which will find applications in plastics nanoelectronics

  5. A reanalysis of five studies on sexual orientation and the relative length of the 2nd and 4th fingers (the 2D:4D ratio).

    Science.gov (United States)

    McFadden, Dennis; Loehlin, John C; Breedlove, S Marc; Lippa, Richard A; Manning, John T; Rahman, Qazi

    2005-06-01

    Five studies have examined the relationship between sexual orientation and the relative lengths of the 2nd and 4th fingers (the 2D:4D ratio). Although differences have commonly been found between heterosexuals and homosexuals, the direction of the difference has not been consistent across studies. The original data from all five studies were reanalyzed in a search for possible explanations of the discrepancies. Because ethnicity is known to affect the 2D:4D ratio, the reanalysis focused on participants who identified themselves as White or Caucasian, the ethnic group that was most numerous in all of the studies. Age differences did not account for the discrepancies. Differences in variability within different groups were minor. One interesting result to emerge from the reanalysis was that the 2D:4D ratios for the homosexual groups were relatively similar across studies. It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies. The constancy of the 2D:4D ratio for the White homosexuals did not appear to extend to homosexuals of three other ethnicities, and there were also subpopulation differences related to right or left hands.

  6. Biodosimetry estimation using the ratio of the longest:shortest length in the premature chromosome condensation (PCC) method applying autocapture and automatic image analysis.

    Science.gov (United States)

    González, Jorge E; Romero, Ivonne; Gregoire, Eric; Martin, Cécile; Lamadrid, Ana I; Voisin, Philippe; Barquinero, Joan-Francesc; García, Omar

    2014-09-01

    The combination of automatic image acquisition and automatic image analysis of premature chromosome condensation (PCC) spreads was tested as a rapid biodosimeter protocol. Human peripheral lymphocytes were irradiated with (60)Co gamma rays in a single dose of between 1 and 20 Gy, stimulated with phytohaemaglutinin and incubated for 48 h, division blocked with Colcemid, and PCC-induced by Calyculin A. Images of chromosome spreads were captured and analysed automatically by combining the Metafer 4 and CellProfiler platforms. Automatic measurement of chromosome lengths allows the calculation of the length ratio (LR) of the longest and the shortest piece that can be used for dose estimation since this ratio is correlated with ionizing radiation dose. The LR of the longest and the shortest chromosome pieces showed the best goodness-of-fit to a linear model in the dose interval tested. The application of the automatic analysis increases the potential use of the PCC method for triage in the event of massive radiation causalities. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  7. On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Shaha, Poly Rani; Poddar, Nayan Kumar; Mondal, Rabindra Nath, E-mail: rnmondal71@yahoo.com [Department of Mathematics, Jagannath University, Dhaka-1100 (Bangladesh); Rudro, Sajal Kanti [Department of Mathematics, Notredame Colleage, Motijheel, Dhaka (Bangladesh)

    2016-07-12

    The study of flows through coiled ducts and channels has attracted considerable attention not only because of their ample applications in Chemical, Mechanical, Civil, Nuclear and Biomechanical engineering but also because of their ample applications in other areas, such as blood flow in the veins and arteries of human and other animals. In this paper, a numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a loosely coiled rectangular duct of large aspect ratio. Numerical calculations are carried out by using a spectral method, and covering a wide range of the Dean number, Dn, for two types of curvatures of the duct. The main concern of the present study is to find out effects of curvature as well as formation of secondary vortices on unsteady solutions whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if Dn is increased. Time evolution calculations as well as their phase spaces are performed with a view to study the non-linear behavior of the unsteady solutions, and it is found that the steady-state flow turns into chaotic flow through various flow instabilities, if Dn is increased no matter what the curvature is. It is found that the unsteady flow is a steady-state solution for small Dn’s and oscillates periodically or non-periodically (chaotic) between two- and twelve-vortex solutions, if Dn is increased. It is also found that the chaotic solution is weak for small Dn’s but strong as Dn becomes large. Axial flow distribution is also investigated and shown in contour plots.

  8. Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio

    Science.gov (United States)

    Yano, T.; Nishino, K.; Kawamura, H.; Ueno, I.; Matsumoto, S.

    2015-02-01

    This paper reports the experimental results on the instability and associated roll structures (RSs) of Marangoni convection in liquid bridges formed under the microgravity environment on the International Space Station. The geometry of interest is high aspect ratio (AR = height/diameter ≥ 1.0) liquid bridges of high Prandtl number fluids (Pr = 67 and 207) suspended between coaxial disks heated differentially. The unsteady flow field and associated RSs were revealed with the three-dimensional particle tracking velocimetry. It is found that the flow field after the onset of instability exhibits oscillations with azimuthal mode number m = 1 and associated RSs traveling in the axial direction. The RSs travel in the same direction as the surface flow (co-flow direction) for 1.00 ≤ AR ≤ 1.25 while they travel in the opposite direction (counter-flow direction) for AR ≥ 1.50, thus showing the change of traveling directions with AR. This traveling direction for AR ≥ 1.50 is reversed to the co-flow direction when the temperature difference between the disks is increased to the condition far beyond the critical one. This change of traveling directions is accompanied by the increase of the oscillation frequency. The characteristics of the RSs for AR ≥ 1.50, such as the azimuthal mode of oscillation, the dimensionless oscillation frequency, and the traveling direction, are in reasonable agreement with those of the previous sounding rocket experiment for AR = 2.50 and those of the linear stability analysis of an infinite liquid bridge.

  9. Leading-edge flow reattachment and the lateral static stability of low-aspect-ratio rectangular wings

    Science.gov (United States)

    Linehan, Thomas; Mohseni, Kamran

    2017-11-01

    The relationship between lateral static stability derivative, Clβ,lift coefficient, CL, and angle of attack was investigated for rectangular wings of aspect ratio A R =0.75 ,1 ,1.5 , and 3 using Stereo-Digital Particle Image Velocimetry (S-DPIV) and direct force and moment measurements. When the product Cl βA R is plotted with respect to CL, the lateral stability curves of each wing collapse to a single line for CL0.7 , the linearity and scaling of Clβwith respect to CL is lost. S-DPIV is used to elucidate the flow physics in this nonlinear regime. At α =10∘ , the leading-edge separation region emerges on the leeward portion of the sideslipped wing by means of vortex shedding. For the A R ≤1.5 wings at α >15∘ , the tip vortex downwash is sufficient to restrict the shedding of leading-edge vorticity thereby sustaining the lift of the leading-edge separation region at high angles of attack. Concurrently, the windward tip vortex grows in size and strength with increasing angle of attack, displacing the leading-edge separation region further toward the leeward wing. This reorganization of lift-generating vorticity results in the initial nonlinearities between Cl β and CL at angles of attack for which CL is still increasing. At angles of attack near that of maximum lift for the A R ≤1 wings, the windward tip vortex lifts off the wing, decreasing the lateral static stability of the wing prior to lift stall. For the A R =3 wing at α >10∘ , nonlinear trends in Cl β versus CL occur due to the spanwise evolution of stalled flow.

  10. Finite-span rotating flat-plate wings at low reynolds number and the effects of aspect ratio

    Science.gov (United States)

    Carr, Zakery R.

    In the complex and dangerous environments of the modern warrior and emergency professional, the small size, maneuverability, and stealth of flapping-wing micro air vehicles (MAVs), scaled to the size of large insects or hummingbirds, has the potential to provide previously inaccessible levels of situational awareness, reconnaissance capability, and flexibility directly to the front lines. Although development of such an efficient, autonomous, and capable MAV is years away, there are immediate contributions that can be made to the fundamental science of the flapping-wing-type propulsion that makes MAVs so attractive. This investigation contributes to those fundamentals by considering the unsteady vortex dynamics problem of a rigid, rectangular flat plate at a fixed angle of attack rotating from rest---a simplified hovering half-stroke. Parameters are chosen to be biologically-relevant and relevant to MAVs operating at Reynolds numbers of O (103), and experiments are performed in a 50% by mass glycerin-water mixture. These experiments use novel application of methodologies verified by rigorous uncertainty analysis. The overall objective is to understand the vortex formation and forces as well as aspect ratio ( AR) effects. Of interest is the overall, time-varying, three-dimensional vortex structure obtained qualitatively from dye visualization and quantitatively from volumes reconstructed using planar stereoscopic digital particle image velocimetry (S-DPIV) measurements. The velocity information from S-DPIV also allows statements to be made on leading-edge vortex (LEV) stability, spanwise flow, LEV and tip-vortex (TV) circulation, and numerous circulation scalings. Force measurements are made and the lift coefficient is discussed in the context of the flow structure, the dimensional lift and the ability to relate velocity and force measurements going forward. AR effects is a topic of continued interest to those performing MAV-related research and also a primary

  11. Electrodeposition of Gold to Conformally Fill High Aspect Ratio Nanometric Silicon Grating Trenches: A Comparison of Pulsed and Direct Current Protocols

    Science.gov (United States)

    Znati, Sami A.; Chedid, Nicholas; Miao, Houxun; Chen, Lei; Bennett, Eric E.; Wen, Han

    2016-01-01

    Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of x-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with an aspect ratio greater than 35 over a grating area of several square centimeters is challenging and has not been described in the literature previously. A comparison of pulsed plating and constant current plating led to a gold electroplating protocol that reliably filled trenches for such structures. PMID:27042384

  12. From neural oscillations to reasoning ability: Simulating the effect of the theta-to-gamma cycle length ratio on individual scores in a figural analogy test.

    Science.gov (United States)

    Chuderski, Adam; Andrelczyk, Krzysztof

    2015-02-01

    Several existing computational models of working memory (WM) have predicted a positive relationship (later confirmed empirically) between WM capacity and the individual ratio of theta to gamma oscillatory band lengths. These models assume that each gamma cycle represents one WM object (e.g., a binding of its features), whereas the theta cycle integrates such objects into the maintained list. As WM capacity strongly predicts reasoning, it might be expected that this ratio also predicts performance in reasoning tasks. However, no computational model has yet explained how the differences in the theta-to-gamma ratio found among adult individuals might contribute to their scores on a reasoning test. Here, we propose a novel model of how WM capacity constraints figural analogical reasoning, aimed at explaining inter-individual differences in reasoning scores in terms of the characteristics of oscillatory patterns in the brain. In the model, the gamma cycle encodes the bindings between objects/features and the roles they play in the relations processed. Asynchrony between consecutive gamma cycles results from lateral inhibition between oscillating bindings. Computer simulations showed that achieving the highest WM capacity required reaching the optimal level of inhibition. When too strong, this inhibition eliminated some bindings from WM, whereas, when inhibition was too weak, the bindings became unstable and fell apart or became improperly grouped. The model aptly replicated several empirical effects and the distribution of individual scores, as well as the patterns of correlations found in the 100-people sample attempting the same reasoning task. Most importantly, the model's reasoning performance strongly depended on its theta-to-gamma ratio in same way as the performance of human participants depended on their WM capacity. The data suggest that proper regulation of oscillations in the theta and gamma bands may be crucial for both high WM capacity and effective complex

  13. Forces and Moments on Flat Plates of Small Aspect Ratio with Application to PV Wind Loads and Small Wind Turbine Blades

    Directory of Open Access Journals (Sweden)

    Xavier Ortiz

    2015-03-01

    Full Text Available To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 104 to 2 × 105. Measurements were made for angles of attack between 0° and 90° both in the free stream and in wall proximity with increased turbulence and mean shear. The ratio of drag to lift closely follows the inverse tangent of the angle of incidence for virtually all measurements. This implies that the forces of interest are due largely to the instantaneous pressure distribution around the plate and are not significantly influenced by shear stresses. The instantaneous forces appear most complex for the smaller aspect ratios but the intensity of the normal force fluctuations is between 10% and 20% in the free-steam but can exceed 30% near the wall. As the wind tunnel floor is approached, the lift and drag reduce with increasing aspect ratio, and there is a reduction in the high frequency components of the forces. It is shown that the centre of pressure is closer to the centre of the plates than the quarter-chord position for nearly all cases.

  14. Low-temperature plasma etching of high aspect-ratio densely packed 15 to sub-10 nm silicon features derived from PS-PDMS block copolymer patterns

    International Nuclear Information System (INIS)

    Liu, Zuwei; Sassolini, Simone; Olynick, Deirdre L; Gu, Xiaodan; Hwu, Justin

    2014-01-01

    The combination of block copolymer (BCP) lithography and plasma etching offers a gateway to densely packed sub-10 nm features for advanced nanotechnology. Despite the advances in BCP lithography, plasma pattern transfer remains a major challenge. We use controlled and low substrate temperatures during plasma etching of a chromium hard mask and then the underlying substrate as a route to high aspect ratio sub-10 nm silicon features derived from BCP lithography. Siloxane masks were fabricated using poly(styrene-b-siloxane) (PS-PDMS) BCP to create either line-type masks or, with the addition of low molecular weight PS-OH homopolymer, dot-type masks. Temperature control was essential for preventing mask migration and controlling the etched feature’s shape. Vertical silicon wire features (15 nm with feature-to-feature spacing of 26 nm) were etched with aspect ratios up to 17 : 1; higher aspect ratios were limited by the collapse of nanoscale silicon structures. Sub-10 nm fin structures were etched with aspect ratios greater than 10 : 1. Transmission electron microscopy images of the wires reveal a crystalline silicon core with an amorphous surface layer, just slightly thicker than a native oxide. (paper)

  15. Fabrication of high aspect ratio TiO2 and Al2O3 nanogratings by atomic layer deposition

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Takayama, Osamu; Michael-Lindhard, Jonas

    2016-01-01

    The authors report on the fabrication of TiO2 and Al2O3 nanostructured gratings with an aspect ratio of up to 50. The gratings were made by a combination of atomic layer deposition (ALD) and dry etch techniques. The workflow included fabrication of a Si template using deep reactive ion etching fo...

  16. The evaluation of vacuum venting and variotherm process for improving the replication by injection molding of high aspect ratio micro features for biomedical application

    Science.gov (United States)

    Sorgato, Marco; Lucchetta, Giovanni

    2015-05-01

    The aspect ratio achievable in replicating micro features is one of the most important process characteristics and it is a major manufacturing constraint in applying injection molding in a range of micro engineering applications. Vacuum venting has been reported to be an effective technique in replicating micro features by microinjection molding. High surface-to-volume ratio and reduced dimensions of micro parts promote the instantaneous drop of melt temperature and consequently lead to incomplete filling. This study aims to investigate the effects of variotherm process, cavity evacuation and their interaction on the production of a micro fluidic filter for biomedical applications. A low-viscosity polystyrene and a cyclic olefin copolymer were molded applying a combination of mold evacuation and a rapid mold temperature variation that keeps the cavity temperature above the glass transition temperature during the injection phase. The research revealed the importance of these molding technologies in enhancing part filling and the replication quality for high aspect ratio micro features.

  17. Direct Observation of Two Phase Flow Generated by an Alumina Seeded Grain in High Aspect Ratio Channels

    Science.gov (United States)

    2010-06-01

    and the characteristic length is 44.45 mm. Finally, the convection coefficient is calculated to be 298 W/m2*K. Incropera and Dewitt note that...Advanced Strength and Applied Elasticity (4th ed.). Upper Saddle, NJ: Prentice Hall PTR, 2003. [11] F. P. Incropera and D. P. DeWitt

  18. Does the index-to-ring finger length ratio (2D:4D) differ in amyotrophic lateral sclerosis (ALS)? Results from an international online case-control study.

    Science.gov (United States)

    Parkin Kullmann, Jane Alana; Pamphlett, Roger

    2017-08-07

    The ratio of the length of the index finger (2D) to the ring finger (4D) (2D:4D) has been reported to be lower (ie, 2DALS) than non-ALS controls. This has led to suggestions that exposure to increased prenatal testosterone, which also lowers this ratio, could be a risk factor for ALS. In an attempt to test this hypothesis, we examined 2D:4Ds from large numbers of patients with ALS and controls. An online multilingual questionnaire enabling respondents to measure their own index and ring finger lengths. Of the initial 949 respondents, 572 remained for analysis after elimination for inability to straighten fingers, not answering the question, statistical outliers and aged ALS (125 males, 77 females) and 370 non-ALS controls (112 males, 258 females). Unpaired t-tests with 95% CIs were used to assess differences in mean 2D:4Ds. Males had significantly lower mean 2D:4Ds than females, in both ALS and control groups, for both left and right hands. No significant differences were found in 2D:4Ds between ALS and control groups, in either males or females, for either left or right hands. Receiver operating characteristic curves showed no power for 2D:4Ds to predict ALS status in either males or females. 2D:4Ds did not differ between patients with ALS and controls in this study. This was despite the dataset being large enough to confirm the established finding of lower 2D:4Ds in males compared with females. These findings do not support the hypothesis that exposure to increased prenatal testosterone is a risk factor for ALS. A putative lower 2D:4D has been proposed to explain the link between ALS and exercise, but our results indicate that other exercise-related factors are more likely to explain this association. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  19. Effect of aspect ratio and number of meshes on convergence of steady-state flow calculation using Newton-Raphson iterative procedure

    International Nuclear Information System (INIS)

    Shimizu, Takeshi

    1997-01-01

    In this paper, we discuss the stability of the convergence of a nonlinear iteration procedure which may be affected by a large number of numerical factors in a complicated way. A numerical parallel channel flow problem is solved using the finite element method and the Newton-Raphson iteration procedure. The numerical factors, on which we focus attention in this study, are the aspect ratio of the channel and the number of divided meshes. We propose a nondimensional value, which is obtained from the Reynolds number, the aspect ratio and the number of meshes. The results of the numerical experiment show that the threshold of divergence in the iteration is indicated clearly by the present nondimensional value. (author)

  20. Effects of prenatal Leydig cell function on the ratio of the second to fourth digit lengths in school-aged children.

    Directory of Open Access Journals (Sweden)

    Takahiko Mitsui

    Full Text Available Prenatal sex hormones can induce abnormalities in the reproductive system and adversely impact on genital development. We investigated whether sex hormones in cord blood influenced the ratio of the second to fourth digit lengths (2D/4D in school-aged children. Of the 514 children who participated in a prospective cohort study on birth in Sapporo between 2002 and 2005, the following sex hormone levels were measured in 294 stored cord blood samples (135 boys and 159 girls; testosterone (T, estradiol (E, progesterone, LH, FSH, inhibin B, and insulin-like factor 3 (INSL3. A total of 350 children, who were of school age and could be contacted for this survey, were then requested via mail to send black-and-white photocopies of the palms of both the left and right hands. 2D/4D was calculated in 190 children (88 boys and 102 girls using photocopies and derived from participants with the characteristics of older mothers, a higher annual household income, higher educational level, and fewer smokers among family members. 2D/4D was significantly lower in males than in females (p<0.01. In the 294 stored cord blood samples, T, T/E, LH, FSH, Inhibin B, and INSL3 levels were significantly higher in samples collected from males than those from females. A multivariate regression model revealed that 2D/4D negatively correlated with INSL3 in males and was significantly higher in males with <0.32 ng/mL of INSL3 (p<0.01. No correlations were observed between other hormones and 2D/4D. In conclusion, 2D/4D in school-aged children, which was significantly lower in males than in females, was affected by prenatal Leydig cell function.

  1. Reproductive and behavioral aspects of red-winged tinamous (Rhynchotus rufescens in groups with different sex ratios

    Directory of Open Access Journals (Sweden)

    VU Cromberg

    2007-09-01

    Full Text Available The aim of this research study was to evaluate the reproductive performance of tinamous submitted to five different male:female ratios. The study was carried out with 72 birds in a randomized experimental design with 4 replications. Tinamous were housed in cages, using the ratios of one (1:1, two (2:1, three (3:1 and four (4:1 females per male, and also one male was housed with three females individually (3R:1, in a rotational system. Reproductive records of the breeding season from September 2004 to March 2005 were used. The reproductive traits studied were: number of eggs laid, fertility, and percentage of eggs damaged and cracked by pecking. Nonparametric analyses of these traits were performed using Kruskal-Wallis test. Two replications of treatments 1:1 and 4:1, and one of treatment 2:1 were video-taped for three days, 12 hours/day. The videotapes were sampled according to the scan method to fit an ethogram. Birds were also watched for one hour per day to study dominance and agonistic behavior. None of the reproductive traits was affected by mating sex ratio (p<0.05. Female dominance could be related to displacement behavior (r=1.00, and male sitting in immobility plus sitting in activity behaviors were related to lower number of damaged eggs (r=-0.90. Social dominance was indirectly determined by displacement behavior in the study situation. A large number of damaged eggs occurred in all treatments, thereby not allowing a clear conclusion on the best male:female ratio.

  2. Synthesis and field emission characteristics of carbon nanocoils with a high aspect ratio supported by copper micro-tips

    International Nuclear Information System (INIS)

    Sung, Woo Yong; Ok, Jong Girl; Kim, Wal Jun; Lee, Seung Min; Yeon, Soon Chang; Lee, Ho Young; Kim, Yong Hyup

    2007-01-01

    Carbon nanocoils (CNCs) were synthesized via thermal chemical vapour deposition (CVD) with C 2 H 2 and NH 3 gases at 600 deg. C. A Ni catalyst was placed upon the copper micro-tip structures that were fabricated on a silicon substrate. Our CNCs had a long rope shape with a length not exceeding 100 μm and a nanoscale diameter. The copper micro-tips were formed through high current pulse electroplating, which played a significant role in characterizing our CNCs. The CNCs grown on the copper micro-tips showed outstanding field emission performance and long-term stability. Their turn-on field, defined as that at a current density of 10 μA cm -2 , was 1.30 V μm -1 and the maximum current density reached 11.17 mA cm -2 at an electric field of 2.39 V μm -1

  3. The variation in the lengths of two co-occurring Daphnia species (Crustacea) in the Hubenov Reservoir in years when the chlorophyll-phosphorus ratio was low

    Czech Academy of Sciences Publication Activity Database

    Hrbáček, Jaroslav; Albertová, O.

    2011-01-01

    Roč. 75, 1-2 (2011), s. 23-35 ISSN 1211-376X Institutional research plan: CEZ:AV0Z60170517 Keywords : Daphnia * length distribution * temporal changes * congeneric competition * reservoir Subject RIV: DA - Hydrology ; Limnology

  4. A PIV Study of Baseline and Controlled Flow over the Highly Deflected Flap of a Generic Low Aspect Ratio Trapezoidal Wing

    Science.gov (United States)

    Tewes, Philipp; Genschow, Konstantin; Little, Jesse; Wygnanski, Israel

    2017-11-01

    A detailed flow survey using PIV was conducted over a highly-deflected flap (55°) of a low-aspect ratio trapezoidal wing. The wing section is a NACA 0012 with 45° sweep at both the leading and trailing edges, an aspect ratio of 1.5 and a taper ratio of 0.27. The main element is equipped with 7 equally spaced fluidic oscillators, covering the inner 60 % of the span, located near the flap hinge. Experiments were carried out at 0° and 8° incidence at a Reynolds number of 1.7 .106 for both baseline and active flow control (AFC) cases. Velocity ISO-surfaces, x-vorticity and streamlines are analyzed / discussed. A flap leading edge vortex governs the baseline flow field for 0°. This vortical structure interacts with the jets emitted by the actuators (Cμ = 1 %). Its development is hampered and the vortex is redirected toward the trailing edge resulting in a CL increase. At 8°, the dominant flap leading edge vortex could not be detected and is believed to have already merged with the tip vortex. AFC attached the flow over the flap and enhanced the lift by up to 20 % while maintaining longitudinal stability. The dominant flow features in the AFC cases are actuator-generated streamwise vortices which appear stronger at 8°. This work was supported by the Office of Naval Research under ONR Grant No. N00014-14-1-0387.

  5. Imaging properties of high aspect ratio absorption gratings for use in preclinical x-ray grating interferometry.

    Science.gov (United States)

    Trimborn, Barbara; Meyer, Pascal; Kunka, Danays; Zuber, Marcus; Albrecht, Frederic; Kreuer, Sascha; Volk, Thomas; Baumbach, Tilo; Koenig, Thomas

    2016-01-21

    X-ray grating interferometry is one among various methods that allow extracting the so-called phase and visibility contrasts in addition to the well-known transmission images. Crucial to achieving a high image quality are the absorption gratings employed. Here, we present an in-depth analysis of how the grating type and lamella heights influence the final images. Benchmarking gratings of two different designs, we show that a frequently used proxy for image quality, a grating's so-called visibility, is insufficient to predict contrast-to-noise ratios (CNRs). Presenting scans from an excised rat lung, we demonstrate that the CNRs obtained for transmission and visibility images anti-correlate. This is explained by the stronger attenuation implied by gratings that are engineered to provide high visibilities by means of an increased lamella height. We show that even the visibility contrast can suffer from this effect when the associated reduced photon flux on the detector is not outweighed by a corresponding gain in visibility. Resulting in an inevitable trade-off between the quality of the two contrasts, the question of how an optimal grating should be designed can hence only be answered in terms of Pareto optimality.

  6. Balancing the daylighting and energy performance of solar screens in residential desert buildings: Examination of screen axial rotation and opening aspect ratio

    KAUST Repository

    Sabry, Hanan

    2014-05-01

    Solar screens are typically used to control solar access into building spaces. They proved their usefulness in improving the daylighting and energy performance of buildings in the hot arid desert environments which are endowed with abundance of clear skies.The daylighting and energy performance of solar screens is affected by many parameters. These include screen perforation, depth, reflectivity and color, aspect ratio of openings, shape, tilt angle and rotation. Changing some of these parameters can improve the daylighting performance drastically. However, this can result in increased energy consumption. A balanced solution must be sought, where acceptable daylighting performance would be achieved at minimum energy consumption.This paper aims at defining solar screen designs that achieve visual comfort and at the same time minimum energy consumption in residential desert settings. The study focused on the effect of changing the solar screen axial rotation and the aspect ratio of its openings under the desert clear-sky. The individual and combined effects of changing these parameters were studied.Results of this study demonstrated that a non-rotated solar screen that has wide horizontal openings (aspect ratio of 18:1) proved to be successful in the north and south orientations. Its performance in the east/west orientations was also superior. In contrast, the screen that was rotated along its vertical axis while having small size openings (aspect ratio of 1:1) proved to be more successful in the east/west orientations. Its performance in the north orientation was also good. These solutions enhanced daylighting performance, while maintaining the energy consumption at a minimum.Moreover, it was observed that combining two screen parameters which proved useful in previous studies on daylighting or thermal performance does not add up to better solutions. The combined solutions that were tested in this study did not prove successful in satisfying daylighting and thermal

  7. Semi-guiding high-aspect-ratio core (SHARC) fiber providing single-mode operation and an ultra-large core area in a compact coilable package

    Science.gov (United States)

    Rockwell, David A.; Shkunov, Vladimir V.; Marciante, John R.

    2011-07-01

    A new class of optical fiber is presented that departs from the circular-core symmetry common to conventional fibers. By using a high-aspect-ratio (~30:1) rectangular core, the mode area can be significantly expanded well beyond 10,000 μm2. Moreover, by also specifying a very small refractive-index step at the narrow core edges, the core becomes ``semi-guiding,'' i.e. it guides in the narrow dimension and is effectively un-guiding in the wide mm-scale dimension. The mode dependence of the resulting Fresnel leakage loss in the wide dimension strongly favors the fundamental mode, promoting single-mode operation. Since the modal loss ratios are independent of mode area, this core structure offers nearly unlimited scalability. The implications of using such a fiber in fiber laser and amplifier systems are also discussed.

  8. Solution Process Synthesis of High Aspect Ratio ZnO Nanorods on Electrode Surface for Sensitive Electrochemical Detection of Uric Acid

    Science.gov (United States)

    Ahmad, Rafiq; Tripathy, Nirmalya; Ahn, Min-Sang; Hahn, Yoon-Bong

    2017-04-01

    This study demonstrates a highly stable, selective and sensitive uric acid (UA) biosensor based on high aspect ratio zinc oxide nanorods (ZNRs) vertical grown on electrode surface via a simple one-step low temperature solution route. Uricase enzyme was immobilized on the ZNRs followed by Nafion covering to fabricate UA sensing electrodes (Nafion/Uricase-ZNRs/Ag). The fabricated electrodes showed enhanced performance with attractive analytical response, such as a high sensitivity of 239.67 μA cm-2 mM-1 in wide-linear range (0.01-4.56 mM), rapid response time (~3 s), low detection limit (5 nM), and low value of apparent Michaelis-Menten constant (Kmapp, 0.025 mM). In addition, selectivity, reproducibility and long-term storage stability of biosensor was also demonstrated. These results can be attributed to the high aspect ratio of vertically grown ZNRs which provides high surface area leading to enhanced enzyme immobilization, high electrocatalytic activity, and direct electron transfer during electrochemical detection of UA. We expect that this biosensor platform will be advantageous to fabricate ultrasensitive, robust, low-cost sensing device for numerous analyte detection.

  9. Simple and cost-effective fabrication of solid biodegradable polymer microneedle arrays with adjustable aspect ratio for transdermal drug delivery using acupuncture microneedles

    International Nuclear Information System (INIS)

    Cha, Kyoung Je; Kim, Taewan; Park, Sung Jea; Kim, Dong Sung

    2014-01-01

    Polymer microneedle arrays (MNAs) have received much attention for their use in transdermal drug delivery and microneedle therapy systems due to the advantages they offer, such as low cost, good mechanical properties, and a versatile choice of materials. Here, we present a simple and cost-effective method for the fabrication of a biodegradable polymer MNA in which the aspect ratio of each microneedle is adjustable using commercially available acupuncture microneedles. In our process, a master template with acupuncture microneedles, whose shape will be the final MNA, was carefully prepared by fixing them onto a plastic substrate with selectively drilled holes which, in turn, determine the aspect ratios of the microneedles. A polylactic acid (PLA; a biodegradable polymer) MNA was fabricated by a micromolding process with a polydimethylsiloxane (PDMS) mold containing the cavity of the microneedles, which was obtained by the PDMS replica molding against the master template. The mechanical force and degradation behavior of the replicated PLA MNA were characterized with the help of a compression test and an accelerated degradation test, respectively. Finally, the transdermal drug delivery performance of the PLA MNA was successfully simulated by two different methods of penetration and staining, using the skin of a pig cadaver. These results indicated that the proposed method can be effectively used for the fabrication of polymer MNAs which can be used in various microneedle applications. (paper)

  10. Simple and cost-effective fabrication of solid biodegradable polymer microneedle arrays with adjustable aspect ratio for transdermal drug delivery using acupuncture microneedles

    Science.gov (United States)

    Cha, Kyoung Je; Kim, Taewan; Jea Park, Sung; Kim, Dong Sung

    2014-11-01

    Polymer microneedle arrays (MNAs) have received much attention for their use in transdermal drug delivery and microneedle therapy systems due to the advantages they offer, such as low cost, good mechanical properties, and a versatile choice of materials. Here, we present a simple and cost-effective method for the fabrication of a biodegradable polymer MNA in which the aspect ratio of each microneedle is adjustable using commercially available acupuncture microneedles. In our process, a master template with acupuncture microneedles, whose shape will be the final MNA, was carefully prepared by fixing them onto a plastic substrate with selectively drilled holes which, in turn, determine the aspect ratios of the microneedles. A polylactic acid (PLA; a biodegradable polymer) MNA was fabricated by a micromolding process with a polydimethylsiloxane (PDMS) mold containing the cavity of the microneedles, which was obtained by the PDMS replica molding against the master template. The mechanical force and degradation behavior of the replicated PLA MNA were characterized with the help of a compression test and an accelerated degradation test, respectively. Finally, the transdermal drug delivery performance of the PLA MNA was successfully simulated by two different methods of penetration and staining, using the skin of a pig cadaver. These results indicated that the proposed method can be effectively used for the fabrication of polymer MNAs which can be used in various microneedle applications.

  11. Organization and dynamics of the large-scale motions of turbulent Rayleigh-Bénard Convection in a cylindrical domain with a moderate aspect ratio

    Science.gov (United States)

    Peet, Yulia; Sakievich, Philip; Adrian, Ronald

    2017-11-01

    At high Rayleigh numbers in moderate aspect-ratio cylindrical domains turbulent Rayleigh-Béenard convection (RBC) exhibits coherent large-scale motions that organize themselves into a collection of three-dimensional ``roll cells''. The current study presents a relatively long, on the order of 3000 free fall time units (or 100 eddy turnovers), Direct Numerical Simulation of the RBC in a cylindrical domain with a 6.3 aspect ratio and the Rayleigh number of 9.6x107. The study shows that the spatial organization of the roll cells in the investigated domain can be well described by the azimuthal Fourier modes. A hub-and-spoke mode-3 pattern first emerges and dominates the flow for the first 20 eddy turnovers, which then transitions into a mode-2 pattern that persists for the remainder of the simulations. A spatial inhomogeneity of the observed mode-3 and mode-2 structures is investigated. A conclusion follows that the cylindrical geometry constraint applies a ``squeezing'' effect to the large-scale structures, which forces them to align with a strong azimuthal periodicity. NSF CBET 1335731, NSF CBET 1707075.

  12. Controlling effective aspect ratio and packing of clay with pH for improved gas barrier in nanobrick wall thin films.

    Science.gov (United States)

    Hagen, David A; Saucier, Lauren; Grunlan, Jaime C

    2014-12-24

    Polymer-clay thin films constructed via layer-by-layer (LbL) assembly, with a nanobrick wall structure (i.e., clay nanoplatelets as bricks surrounded by a polyelectrolyte mortar), are known to exhibit a high oxygen barrier. Further barrier improvement can be achieved by lowering the pH of the clay suspension in the polyethylenimine (PEI) and montmorillonite (MMT) system. In this case, the charge of the deposited PEI layer is increased in the clay suspension environment, which causes more clay to be deposited. At pH 4, MMT platelets deposit with near perfect ordering, observed with transmission electron microscopy, enabling a 5× improvement in the gas barrier for a 10 PEI/MMT bilayer thin film (85 nm) relative to the same film made with pH 10 MMT. This improved gas barrier approaches that achieved with much higher aspect ratio vermiculite clay. In essence, lower pH is generating a higher effective aspect ratio for MMT due to greater induced surface charge in the PEI layers, which causes heavier clay deposition. These flexible, transparent nanocoatings have a wide range of possible applications, from food and electronics packaging to pressurized bladders.

  13. Influence of the ratio of gate length to drain-to-source distance on the electron mobility in AlGaN/AlN/GaN heterostructure field-effect transistors.

    Science.gov (United States)

    Lv, Yuanjie; Lin, Zhaojun; Meng, Lingguo; Luan, Chongbiao; Cao, Zhifang; Yu, Yingxia; Feng, Zhihong; Wang, Zhanguo

    2012-08-03

    Using measured capacitance-voltage curves with different gate lengths and current-voltage characteristics at low drain-to-source voltage for the AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) of different drain-to-source distances, we found that the dominant scattering mechanism in AlGaN/AlN/GaN HFETs is determined by the ratio of gate length to drain-to-source distance. For devices with small ratio (here, less than 1/2), polarization Coulomb field scattering dominates electron mobility. However, for devices with large ratio (here, more than 1/2), longitudinal optical (LO) phonon scattering and interface roughness scattering are dominant. The reason is closely related to polarization Coulomb field scattering.

  14. 3-D Numerical Simulation and Analysis of Complex Fiber Geometry RaFC Materials with High Volume Fraction and High Aspect Ratio based on ABAQUS PYTHON

    Science.gov (United States)

    Jin, BoCheng

    2011-12-01

    Organic and inorganic fiber reinforced composites with innumerable fiber orientation distributions and fiber geometries are abundantly available in several natural and synthetic structures. Inorganic glass fiber composites have been introduced to numerous applications due to their economical fabrication and tailored structural properties. Numerical characterization of such composite material systems is necessitated due to their intrinsic statistical nature, which renders extensive experimentation prohibitively time consuming and costly. To predict various mechanical behavior and characterizations of Uni-Directional Fiber Composites (UDFC) and Random Fiber Composites (RaFC), we numerically developed Representative Volume Elements (RVE) with high accuracy and efficiency and with complex fiber geometric representations encountered in uni-directional and random fiber networks. In this thesis, the numerical simulations of unidirectional RaFC fiber strand RVE models (VF>70%) are first presented by programming in ABAQUS PYTHON. Secondly, when the cross sectional aspect ratios (AR) of the second phase fiber inclusions are not necessarily one, various types of RVE models with different cross sectional shape fibers are simulated and discussed. A modified random sequential absorption algorithm is applied to enhance the volume fraction number (VF) of the RVE, which the mechanical properties represents the composite material. Thirdly, based on a Spatial Segment Shortest Distance (SSSD) algorithm, a 3-Dimentional RaFC material RVE model is simulated in ABAQUS PYTHON with randomly oriented and distributed straight fibers of high fiber aspect ratio (AR=100:1) and volume fraction (VF=31.8%). Fourthly, the piecewise multi-segments fiber geometry is obtained in MATLAB environment by a modified SSSD algorithm. Finally, numerical methods including the polynomial curve fitting and piecewise quadratic and cubic B-spline interpolation are applied to optimize the RaFC fiber geometries

  15. Rapid mold temperature variation for assisting the micro injection of high aspect ratio micro-feature parts using induction heating technology

    Science.gov (United States)

    Chen, Shia-Chung; Jong, Wen-Ren; Chang, Yaw-Jen; Chang, Jen-An; Cin, Jin-Chuan

    2006-09-01

    Hot embossing and injection molding are popular methods to duplicate micro features formed during polymer micro-fabrication of MEMS devices. However, both methods face challenges in filling the polymer melt completely into a micro-featured geometry of a high aspect ratio. In this study, electromagnetic induction heating combined with water cooling is used to achieve rapid mold surface temperature control during the micro-feature injection molding process. A CAE simulation was also developed through integration of both thermal and electromagnetic analysis modules of ANSYS, and its capability and accuracy were verified experimentally. Efficiency evaluations of induction heating and the uniformity of mold temperature control were conducted on a micro-featured mold. This mold was designed with a micro channel array of 30-50 µm in width and 120 and 600 µm in depth, corresponding to aspect ratios ranging from about 2.4 to 12. The accuracies of the micro channels in molded PMMA parts can be used to evaluate the effect of mold temperature on replication accuracy. It was found that rapid mold surface heating with temperature rising from 60 °C to between 100 °C and 140 °C by induction heating requires 2-3.5 s, while the mold temperature returns to 60 °C in about 70-110 s. The simulated mold surface temperature results are consistent with measured results. Achieving the same temperature variation by switching circulation coolants of different temperatures requires at least 7 min. The simulation also reveals that the electromagnetic wave can penetrate into the bottom of the micro channel and results in only about a 2 °C difference in temperature uniformity. For mold temperatures of 100 °C, 120 °C and 140 °C, the molded channel depths were 94.9 µm, 105.4 µm and 116.0 µm, respectively, when the ideal channel depth was 120 µm. When the channel depth is 600 µm, the mold temperature must exceed 120 °C, so that reasonable accuracy in micro-feature replication can be

  16. 'Length'at Length

    Indian Academy of Sciences (India)

    Admin

    He was interested to know how `large' is the set of numbers x for which the series is convergent. Here large refers to its length. But his set is not in the class ♢. Here is another problem discussed by Borel. Consider .... have an infinite collection of pairs of new shoes and want to choose one shoe from each pair. We have an ...

  17. Free-Stream Characteristics of A Family of Low-Aspect-Ratio, All-Movable Control Surfaces for Application to Ship Design

    Science.gov (United States)

    1958-12-01

    57.3a and (aCL/da)CL = O is computed from Equation [ la ]. A plot of the lift-curve slope is presented in Reference 3 as a function of several geometric...24 2 2 3 0 4 Angle ~ ~ ~ L ofji AAak i ere Figur 43- - -enod Nube o- 2.25d -AA 106 16 1.0 0.4 100- Seto17A 0506 Aspect Ratio I 80 16 Tip Shape Square...NACA 0015 068 Asec RaiI ~ so 1.6Sweep Angle 11Q~ 260- 1.500 .40 24- (P 1 056 0.44 Angl of Atac, dgre C; iur A5 r - -yn id Nube C -.A M4 10A 523 10

  18. Plastic Models Designed to Produce Large Height-to-Length Ratio Steady-State Planar and Axisymmetric (Radial) Viscous Liquid Laminar Flow Gravity Currents

    Science.gov (United States)

    Blanck, Harvey F.

    2012-01-01

    Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…

  19. Collective dynamics of large aspect ratio dusty plasma in an inhomogeneous plasma background: Formation of the co-rotating vortex series

    Science.gov (United States)

    Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

    2018-02-01

    In this paper, the collective dynamics of large aspect ratio dusty plasma is studied over a wide range of discharge parameters. An inductively coupled diffused plasma, which creates an electrostatic trap to confine the negatively charged grains, is used to form a large volume (or large aspect ratio) dusty plasma at low pressure. For introducing the dust grains into the potential well, a unique technique using secondary DC glow discharge plasma is employed. The dust dynamics is recorded in a two-dimension (2D) plane at a given axial location. The dust fluid exhibits wave-like behavior at low pressure (p 3 W). The mixed motion, waves and vortices, is observed at an intermediate gas pressure (p ˜ 0.08 mbar) and low power (P 0.1 mbar), the clockwise and anti-clockwise co-rotating vortex series are observed on edges of the dust cloud, whereas the particles in the central region show random motion. These vortices are only observed above the threshold width of the dust cloud. The occurrence of the co-rotating vortices is understood on the basis of the charge gradient of dust particles, which is orthogonal to the gravity. The charge gradient is a consequence of the plasma inhomogeneity from the central region to the outer edge of the dust fluid. Since a vortex has the characteristic size in the dissipative medium; therefore, a series of the co-rotating vortex on both sides of dusty plasma is observed. The experimental results on the vortex formation and its multiplicity are compared to an available theoretical model and are found to be in close agreement.

  20. Study of 3D-growth conditions for selective area MOVPE of high aspect ratio GaN fins with non-polar vertical sidewalls

    Science.gov (United States)

    Hartmann, Jana; Steib, Frederik; Zhou, Hao; Ledig, Johannes; Nicolai, Lars; Fündling, Sönke; Schimpke, Tilman; Avramescu, Adrian; Varghese, Tansen; Trampert, Achim; Straßburg, Martin; Lugauer, Hans-Jürgen; Wehmann, Hergo-Heinrich; Waag, Andreas

    2017-10-01

    GaN fins are 3D architectures elongated in one direction parallel to the substrate surface. They have the geometry of walls with a large height to width ratio as well as small footprints. When appropriate symmetry directions of the GaN buffer are used, the sidewalls are formed by non-polar {1 1 -2 0} planes, making the fins particularly suitable for many device applications like LEDs, FETs, lasers, sensors or waveguides. The influence of growth parameters like temperature, pressure, V/III ratio and total precursor flow on the fin structures is analyzed. Based on these results, a 2-temperature-step-growth was developed, leading to fins with smooth side and top facets, fast vertical growth rates and good homogeneity along their length as well as over different mask patterns. For the core-shell growth of fin LED heterostructures, the 2-temperature-step-growth shows much smoother sidewalls and less crystal defects in the InGaN QW and p-GaN shell compared to structures with cores grown in just one step. Electroluminescence spectra of the 2-temperature-step-grown fin LED are demonstrated.

  1. Double-diffusive natural convection in inclined porous cavities with various aspect ratios and temperature-dependent heat source or sink

    Science.gov (United States)

    Chamkha, Ali J.; Al-Mudhaf, Ali

    2008-04-01

    Laminar double-diffusive natural convective flow of a binary fluid mixture in inclined square and rectangular cavities filled with a uniform porous medium in the presence of temperature-difference dependent heat generation (source) or absorption (sink) is considered. Transverse gradients of heat and mass are applied on two opposing walls of the cavity while the other two walls are kept adiabatic and impermeable to mass transfer. The problem is put in terms of the stream function-vorticity formulation. A numerical solution based on the finite-difference methodology is obtained for relatively high Lewis numbers. Representative results illustrating the effects of the inclination angle of the cavity, buoyancy ratio, Darcy number, heat generation or absorption coefficient and the cavity aspect ratio on the contour maps of the streamline, temperature, and concentration as well as the profiles of velocity, temperature and concentration at mid-section of the cavity are reported. In addition, numerical results for the average Nusselt and Sherwood numbers are presented for various parametric conditions and discussed.

  2. Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study

    Directory of Open Access Journals (Sweden)

    Herrera Antonio

    2010-06-01

    Full Text Available Abstract Background Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied. Methods The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed. Results The mean loads to failure for each group were 295,44 N (Group 1; 9 × 23 screw, 564,05 N (Group 2; 9 × 28, 614,95 N (Group 3; 9 × 35, 651,14 N (Group 4; 10 × 28 and 664,99 (Group 5; 10 × 35. No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P Conclusions Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm do not achieve optimal fixation and should be implanted only with special requirements.

  3. Time-resolved stereo PIV measurements of the horseshoe vortex system at multiple locations in a low-aspect-ratio pin-fin array

    Science.gov (United States)

    Anderson, Corey D.; Lynch, Stephen P.

    2016-01-01

    Pin-fin arrays are a type of cooling feature found in heat exchangers, with elements (generally cylindrical or square) that span between two endwalls. Flow around the pin-fins generates highly turbulent mixing that increases convective heat transfer from the pins to the cooling flow. At the junction of a pin-fin and the endwall, a complex flow known as the horseshoe vortex (HSV) system is present. Although the HSV is a well-studied phenomenon, its behavior is not understood in the highly turbulent flow of a pin-fin array. Furthermore, the presence of close confining endwalls for low-aspect-ratio (short) pin-fins may have an impact on HSV dynamics. The present study utilized time-resolved stereo particle image velocimetry to examine the fluid dynamics of the HSV system in rows 1, 3, and 5 of a low-aspect-ratio pin-fin array, for a range of Reynolds numbers. In the first row, instantaneous flowfields indicated a clearly defined HSV at the leading edge, with dynamics similar to previous studies of bluff-body junction flows. The time-averaged HSV system moved closer to the pin with increasing Reynolds number, with more concentrated vorticity and turbulent kinetic energy (TKE). For downstream rows, there was a significant increase in the amount of mid-channel vorticity, with levels on the same order as the value in the core of the HSV. The time-averaged HSV system in downstream rows showed minimal variation with respect to either Reynolds number or row location. Regions of maximum streamwise and wall-normal turbulent fluctuations around the HSV were a result of its quasiperiodic oscillation between so-called backflow and zero-flow modes, which were present even in downstream rows despite the extremely high mid-channel turbulence. In the downstream rows, normalized TKE across the entire field of view decreased with increased Reynolds number, likely due to dissipation rates proportionally outpacing increases in mean channel velocity and Reynolds number. The flowfield

  4. Shales in the Qiongzhusi and Wufeng-Longmaxi Formations: a rock-physics model and analysis of the effective pore aspect ratio

    Science.gov (United States)

    Yang, Zhi-Qiang; He, Tao; Zou, Chang-Chun

    2017-09-01

    The shales of the Qiongzhusi Formation and Wufeng-Longmaxi Formations at Sichuan Basin and surrounding areas are presently the most important stratigraphic horizons for shale gas exploration and development in China. However, the regional characteristics of the seismic elastic properties need to be better determined. The ultrasonic velocities of shale samples were measured under dry conditions and the relations between elastic properties and petrology were systemically analyzed. The results suggest that 1) the effective porosity is positively correlated with clay content but negatively correlated with brittle minerals, 2) the dry shale matrix consists of clays, quartz, feldspars, and carbonates, and 3) organic matter and pyrite are in the pore spaces, weakly coupled with the shale matrix. Thus, by assuming that all connected pores are only present in the clay minerals and using the Gassmann substitution method to calculate the elastic effect of organic matter and pyrite in the pores, a relatively simple rock-physics model was constructed by combining the self-consistent approximation (SCA), the differential effective medium (DEM), and Gassmann's equation. In addition, the effective pore aspect ratio was adopted from the sample averages or estimated from the carbonate content. The proposed model was used to predict the P-wave velocities and generally matched the ultrasonic measurements very well.

  5. Large scale structures of a turbulent Rayleigh-Bénard convection in a liquid metal layer confined by a moderate aspect ratio box

    Science.gov (United States)

    Akashi, Megumi; Tasaka, Yuji; Yanagisawa, Takatoshi; Murai, Yuichi; Vogt, Tobias; Eckert, Sven

    2017-11-01

    We report laboratory experiments of Rayleigh-Bénard convection with a liquid metal, Prandtl number Pr = 0.03, in a rectangular cell at a moderate aspect ratio of 5. The Rayleigh number, Ra, was varied in a range from 7.9-103 to 3.5-105 in which the regime of thermal turbulence regime is to be expected. Multiple horizontal velocity profiles were measured in the fluid layer by ultrasonic velocity profiling. The reconstruction of the flow pattern elucidated the occurrence of large scale structures with periodic oscillations. An increasing Ra number causes a transition from a quasi-two-dimensional roll-like structure to a three-dimensional cell-like structure. The transition of the flow structure passes several unstable intermediate regimes accompanied by a stepwise increase of the horizontal scale. For explaining the increase in the horizontal scale, we suggest a model relying on observed Ra dependences of the oscillation frequency and the typical flow velocity of the large scales. Moreover, we have found that the morphology of the roll-like structure can be understood by evaluating the effective viscosity and diffusivity on the basis of turbulent fluctuations.

  6. Mosquitofish (Gambusia affinis preference and behavioral response to animated images of conspecifics altered in their color, aspect ratio, and swimming depth.

    Directory of Open Access Journals (Sweden)

    Giovanni Polverino

    Full Text Available Mosquitofish (Gambusia affinis is an example of a freshwater fish species whose remarkable diffusion outside its native range has led to it being placed on the list of the world's hundred worst invasive alien species (International Union for Conservation of Nature. Here, we investigate mosquitofish shoaling tendency using a dichotomous choice test in which computer-animated images of their conspecifics are altered in color, aspect ratio, and swimming level in the water column. Pairs of virtual stimuli are systematically presented to focal subjects to evaluate their attractiveness and the effect on fish behavior. Mosquitofish respond differentially to some of these stimuli showing preference for conspecifics with enhanced yellow pigmentation while exhibiting highly varying locomotory patterns. Our results suggest that computer-animated images can be used to understand the factors that regulate the social dynamics of shoals of Gambusia affinis. Such knowledge may inform the design of control plans and open new avenues in conservation and protection of endangered animal species.

  7. The longevity and aspect ratio of dust devils: Effects on detection efficiencies and comparison of landed and orbital imaging at Mars

    Science.gov (United States)

    Lorenz, Ralph

    2013-09-01

    We summarize data from Earth and Mars on the duration of dust devils as a function of their diameter: a strong positive correlation is seen (duration in minutes appears to vary as ∼0.66d0.66, where d is the diameter in meters). This duration information allows orbital measurements at Mars (where only one observation per day is typical) to be compared with landed or terrestrial surveys with continuous monitoring. Counts from orbit appear higher than those from the surface, possibly due to higher detection efficiency from near-vertical orbital imaging where the dust loading integrated along the line-of-sight may be higher than for near-horizontal field/landed imaging due to the slender aspect ratio (∼5) of dust devils, indicated by both Earth and Mars data. The diameter dependence of duration results in an enhancement in the effective detection area for large devils for small-area surveys which do not discriminate between devils that form within their defined nominal survey areas, and those that are advected into it by winds.

  8. Effect of Partial Shrouds on the Performance and Flow Field of a Low-Aspect-Ratio Axial-Flow Fan Rotor

    Directory of Open Access Journals (Sweden)

    N. Sitaram

    2011-01-01

    Full Text Available The flow field at the rotor exit of a low aspect ratio axial flow fan for different tip geometries and for different flow coefficients is measured in the present study. The following configurations are tested: (1 rotor without partial shroud, designated as rotor (wos, (2 rotor with partial shroud, designated as rotor (ws, and (3 rotor with perforated (perforations in the shape of discrete circular holes partial shroud, designated as rotor (wps. From steady state measurements, the performance of rotor (wps is found to be the best. Both the rotors with partial shrouds have stalled at a higher flow coefficient compared to that of rotor (wos. From periodic flow measurements, it is concluded that the low velocity region near the tip section is considerably reduced with the use of partial shrouds with perforations. The extent of this low velocity region for both rotor (wos and rotor (wps increases with decreasing flow coefficient due to increased stage loading. This core of low momentum fluid has moved inwards of the annulus and towards the pressure side as the flow coefficient decreases. The extent of the low momentum fluid is smaller for rotor (wps than that of rotor (wos at all flow coefficients.

  9. Catalytic Synthesis of Substrate-Free, Aligned and Tailored High Aspect Ratio Multiwall Carbon Nanotubes in an Ultrasonic Atomization Head CVD Reactor

    Directory of Open Access Journals (Sweden)

    Fahad Ali Rabbani

    2016-01-01

    Full Text Available Chemical vapor deposition (CVD method has proven its benchmark, over other methods, for the production of different types of carbon nanotubes (CNT on commercial and lab scale. In this study, an injection vertical CVD reactor fitted with an ultrasonic atomization head was used in a pilot-plant scale (height 274 cm, radius 25 cm for semicontinuous production of multiwall carbon nanotubes (MWCNTs. p-Xylene was used as a hydrocarbon precursor in which ferrocene was dissolved and provided the cracking catalyst. Atomization of the feed solution resulted in full and even dispersion of the catalytic solution. This dispersion led to the production of high aspect ratio MWCNTs (ranging from 8,000 to 12,000 at 850°C. Different experimental parameters affecting the quality and quantity of the produced CNTs were investigated. These included temperature, reaction time, and flow rate of the reaction and carrier gases. Different properties of the produced CNTs were characterized using SEM and TEM, while TGA was used to evaluate their purity. Specific surface area of selected samples was calculated by BET.

  10. An efficient top-down approach for the fabrication of large-aspect-ratio g-C3N4 nanosheets with enhanced photocatalytic activities.

    Science.gov (United States)

    Tong, Jincheng; Zhang, Li; Li, Fei; Li, Mingming; Cao, Shaokui

    2015-09-28

    Graphitic carbon nitride (g-C3N4) nanosheets with large aspect ratios were fabricated from bulk g-C3N4 through an efficient top-down approach of moderate disintegration-exfoliation using diluted H2SO4 as an "efficient knife". By prior disintegration in a diluted H2SO4 solution, the exfoliation of bulk g-C3N4 was effectively accelerated. The as-prepared g-C3N4 nanosheets possess a two-dimensional (2D) thin-layer structure with seven-atom thickness, a large lateral size of about 1 μm, and a high specific surface area of 80 m(2) g(-1). Compared with the bulk precursor, the g-C3N4 nanosheets showed much higher efficiency of photogenerated charge transfer and separation, and consequently exhibited enhanced photocatalytic activity toward hydrogen evolution and pollutant decomposition under both full-sunlight and visible-light irradiation.

  11. Chitosan-Assisted Assembly of Sub-10 nm Nanocrystals into Mesoporous TiO2 Fibers with High-Aspect-Ratio for Improved Lithium-Ion Storage

    International Nuclear Information System (INIS)

    Zong, Yunpeng; Liu, Yong; Zhao, Wenxia; Zhang, Hao; Li, Baojun; Zhou, Xiang; Shen, Hui

    2015-01-01

    Highlights: • Long mesoporous TiO 2 fibers are synthesized by a base-free hydrothermal route. • The mesopores are constructed with interconnected sub-10 nm nanocrystals. • Good cycling stability is obtained. - Abstract: Herein, we report a simple base-free hydrothermal route for the synthesis of mesoporous TiO 2 fibers by using chitosan as direct agent. This hierarchical structure combines advantages of mesopores constructed by interconnected sub-10 nm nanocrystals on nanoscale and 1D structure with large aspect ratio on micron-scale, which is desired structural characteristic needed for the high-performance anode materials. Benefiting from such unique structural features, it demonstrates superior high charge/discharge capability, good cycling stability and rate capability when used as lithium-ion batteries electrode. For example, it can deliver a capacity of 174 mA h g −1 at 0.5C and 137 mA h g −1 at 5C after 100 cycles.

  12. Improved energy storage, magnetic and electrical properties of aligned, mesoporous and high aspect ratio nanofibers of spinel-NiMn2O4

    Science.gov (United States)

    Bhagwan, Jai; Rani, Stuti; Sivasankaran, V.; Yadav, K. L.; Sharma, Yogesh

    2017-12-01

    Spinel-NiMn2O4 (NMO) nanofibers of high aspect ratio, high surface area (50 m2 g-1) and homogeneous pore size distribution are fabricated by electrospinning process and characterized by XRD, FTIR, XPS, BET, FESEM, TEM techniques. Further, multifunctional properties (energy storage properties, magnetic and electrical properties) of NMO nanofibers are also examined. High specific capacitance (Cs) of 410 (±5) F g-1 at 1 A g-1, good rate capability and high cycling stability (up to 5000 cycles) are demonstrated by NMO nanofibers. Furthermore, NMO-based solid-state symmetric supercapacitor (SSSC) shows a high Cs of 170 (±5) F g-1 at 0.5 A g-1 in potential range of 0.0V-2.0 V and exhibits excellent energy density of ∼95 W h kg-1 and power density of 1030 W Kg-1. The above storage properties i.e. high energy density and output voltage of 2.0 V are further supplemented by lighting up a red colored LED (1.8 V @ current 20 mA) at least for 5 min. The ionic diffusion coefficient of NMO based electrode is found to be ∼4.84 × 10-11 cm2 s-1. Magnetic and dielectric properties of NMO nanofibers are also examined and results are discussed.

  13. Genetic variation in pea (Pisum sativum L.) demonstrates the importance of root but not shoot C/N ratios in the control of plant morphology and reveals a unique relationship between shoot length and nodulation intensity.

    Science.gov (United States)

    Ludidi, Ndiko N; Pellny, Till K; Kiddle, Guy; Dutilleul, Christelle; Groten, Karin; VAN Heerden, Philippus D R; Dutt, Som; Powers, Stephen J; Römer, Peter; Foyer, Christine H

    2007-10-01

    Nodule numbers are regulated through systemic auto-regulatory signals produced by shoots and roots. The relative effects of shoot and root genotype on nodule numbers together with relationships to organ biomass, carbon (C) and nitrogen (N) status, and related parameters were measured in pea (Pisum sativum) exploiting natural genetic variation in maturity and apparent nodulation intensity. Reciprocal grafting experiments between the early (Athos), intermediate (Phönix) and late (S00182) maturity phenotypes were performed and Pearson's correlation coefficients for the parameters were calculated. No significant correlations were found between shoot C/N ratios and plant morphology parameters, but the root C/N ratio showed a strong correlation with root fresh and dry weights as well as with shoot fresh weight with less significant interactions with leaf number. Hence, the root C/N ratio rather than shoot C/N had a predominant influence on plant morphology when pea plants are grown under conditions of symbiotic nitrogen supply. The only phenotypic characteristic that showed a statistically significant correlation with nodulation intensity was shoot length, which accounted for 68.5% of the variation. A strong linear relationship was demonstrated between shoot length and nodule numbers. Hence, pea nodule numbers are controlled by factors related to shoot extension, but not by shoot or root biomass accumulation, total C or total N. The relationship between shoot length and nodule numbers persisted under field conditions. These results suggest that stem height could be used as a breeding marker for the selection of pea cultivars with high nodule numbers and high seed N contents.

  14. Morphometric aspects of Scyllarides latus

    Directory of Open Access Journals (Sweden)

    T. ROMEO

    2004-06-01

    Full Text Available The slipper lobster, Scyllarides latus (Latreille, 1803, is the only representative species of the genusScyllarides in the Mediterranean Sea. In this study, we examined some biological aspects of this species sampled in the Straits of Messina. The specimens were sexed, measured and weighed. The relationships between body measurements (length and width of the carapace, antennal length and length-weight relationship were calculated. Furthermore, the correlation matrix (Pearson’s coefficient was calculated. Two hundred specimens were collected, ranging in size from 81 to 305 mm in total length, and between 21 and 1490 g in weight. A rare juvenile of 39 mm CL was recorded. A sex ratio of 1:1 was found. The carapace length – weight relationship was almost isometric. The wide size range sampled and the presence of a juvenile, indicate an interesting habitat for studying the presence and growth of Scyllarides latus in the Straits of Messina.

  15. Aspect ratio control of Au nanorods via covariation of the total amount of HAuCl{sub 4} and ascorbic acid

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiao [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 122 Luoshi Road, Hongshan District, Wuhan 430070, Hubei (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Feng, Jinyang [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 122 Luoshi Road, Hongshan District, Wuhan 430070, Hubei (China); Zhao, Xiujian, E-mail: opluse@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 122 Luoshi Road, Hongshan District, Wuhan 430070, Hubei (China)

    2015-07-15

    Highlights: • The AR value decreased as the total amount of [HAuCl{sub 4}] and [AA] increasing. • The UV–vis absorption spectra showed the peak wavelength of TSPR at around 530 nm. • The wavelength of LSPR had a red-shifted effect. - Abstract: Controlling the aspect ratio (AR) of gold nanorods (GNRs) via covariation of the total concentrations of HAuCl{sub 4} ([HAuCl{sub 4}]) and ascorbic acid ([AA]) has been studied. Characteristics of GNRs were examined by transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) absorption spectrophotometry. TEM results showed that single crystalline GNRs grew along an elongated growth direction of [100]. TEM results also revealed that the quantity of plate shaped and nearly spherical nanoparticles increased as the total amount of [HAuCl{sub 4}] and [AA] decreased. The AR value measured from TEM images decreased from 4.74 to 2.41 as the total amount of [HAuCl{sub 4}] and [AA] was increased from 0.305 to 2.44 mM. The UV–vis absorption spectra of all samples showed that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 530 nm for all samples. The wavelength of longitudinal surface plasmon resonance (LSPR) peak increased from 640 to 894 nm as the total amount of [HAuCl{sub 4}] and [AA] decreased from 2.44 to 0.305 mM. The wavelength of LSPR peak shows a red-shifted effect except when the total amount of [HAuCl{sub 4}] and [AA] was 0.122 mM.

  16. Facile preparation of carbon nanotubes–graphene hybrids and the effect of aspect ratio of carbon nanotubes on electrical and thermal properties of silicone rubber based composites

    Science.gov (United States)

    Zhao, Shizhen; Bai, Lu; Zheng, Junping

    2018-01-01

    Thermal exfoliation, as an effective and easily scalable method, was widely used to produce graphene (GE). In order to prevent the severe stacking of GE sheets after thermal exfoliation process, a facile technique was used to solve this problem through the barrier effect of carbon nanotubes (CNTs). Two kinds of CNTs with different aspect ratios (AR) were taken to prepare CNTs–GE hybrids using this technique, and then the effect of AR of CNTs (namely CNTs-L for low AR and CNTs-H for high AR) in the hybrids on the performance of silicone rubber (SR) composites was investigated. The results indicate that the presence of CNTs can effectively impede the stacking of GE sheets and the hybrids are dispersed uniformly in the SR matrix. With the addition of CNTs–GE hybrids, the resulted SR composites exhibit greatly improved electrical and thermal properties, especially for the composites filled with CNTs-H–GE hybrid. At the hybrids content of 3.0 wt%, the volume resistivity of CNTs-H–GE/SR composite is 5 × 104 Ω cm (about 10 orders of magnitude decrease compared with pure SR). And the thermal conductivity increases by 78% compared to the pure SR. But as for the CNTs-L–GE/SR composite, the corresponding values are 3 × 106 Ω cm and 59%, respectively. In terms of thermal stability, the CNTs-H–GE/SR composite containing 1.0 wt% hybrid exhibits the maximum improvement of initial degradation temperature (419 °C) compared with the CNTs-L–GE/SR composite (393 °C) and pure SR (365 °C).

  17. An Improved Model for the Steric-Entropic Effect on the Retention of Rod-like Particles in Field-Flow Fractionation: Discussion of Aspect Ratio-Based Separation

    Directory of Open Access Journals (Sweden)

    Joontaek Park

    2015-07-01

    Full Text Available We developed an improved model for predicting the steric-entropic effect on the separation behaviors of rod-like particles in flow field-flow fractionation. Our new model incorporates the “pole-vault” rotation of a rod-like particle near a wall under shear flow into the original model developed by Beckett and Giddings which considered only Brownian rotation. We investigated the effect of the aspect ratio on the retention ratios and the cross-sectional concentration distribution in the separation of rods in field-flow fractionation (FFF. Our analyses involved comparing the results predicted using the original model and those from the new model under various rod geometries and flow conditions. We found that the new model can show the aspect ratio-enhanced elution trend in certain flow conditions for the assumption of non-constant cloud thickness (ratio between the cross flow rate and the rod diffusivity. We also deducted that the flow conditions allowing for the aspect ratio-enhanced elution are related to the interplay among the axial flow rate, cloud thickness, and rod geometry. The new model can be viewed as a prototype to qualitatively show the aspect ratio-enhanced trend since its quantitative agreement with the experimental data must be improved for our future work.

  18. Nearly constant ratio between the proton inertial scale and the spectrum break length scale in the plasma beta range from 0.2 to 1.4 in the solar wind turbulence

    Science.gov (United States)

    Wang, X.; Tu, C. Y.; He, J.; Wang, L.

    2017-12-01

    The spectrum break at the ion scale of the solar wind magnetic fluctuations are considered to give important clue on the turbulence dissipation mechanism. Among several possible mechanisms, the most notable ones are the two mechanisms that related respectively with proton thermal gyro-radius and proton inertial length. However, no definite conclusion has been given for which one is more reasonable because the two parameters have similar values in the normal plasma beta range. Here we do a statistical study for the first time to see if the two mechanism predictions have different dependence on the solar wind velocity and on the plasma beta in the normal plasma beta range in the solar wind at 1 AU. From magnetic measurements by Wind, Ulysses and Messenger, we select 60 data sets with duration longer than 8 hours. We found that the ratio between the proton inertial scale and the spectrum break scale do not change considerably with both varying the solar wind speed from 300km/s to 800km/s and varying the plasma beta from 0.2 to 1.4. The average value of the ratio times 2pi is 0.46 ± 0.08. However, the ratio between the proton gyro-radius and the break scale changes clearly. This new result shows that the proton inertial scale could be a single factor that determines the break length scale and hence gives a strong evidence to support the dissipation mechanism related to it in the normal plasma beta range. The value of the constant ratio may relate with the dissipation mechanism, but it needs further theoretical study to give detailed explanation.

  19. Enhancing the Wettability of High Aspect-Ratio Through-Silicon Vias Lined with LPCVD Silicon Nitride or PE-ALD Titanium Nitride for Void-Free Bottom-Up Copper Electroplating

    NARCIS (Netherlands)

    Saadaoui, M.; van Zeijl, H.; Wien, W. H. A.; Pham, H. T. M.; Kwakernaak, C.; Knoops, H. C. M.; Kessels, W. M. M.; R. van de Sanden,; Voogt, F. C.; Roozeboom, F.; Sarro, P. M.

    2011-01-01

    One of the critical steps toward producing void-free and uniform bottom-up copper electroplating in high aspect-ratio (AR) through-silicon vias (TSVs) is the ability of the copper electrolyte to spontaneously flow through the entire depth of the via. This can be accomplished by reducing the

  20. Enhancing the wettability of high aspect-ratio through-silicon vias lined with LPCVD silicon nitride or PE-ALD titanium nitride for void-free bottom-up copper electroplating

    NARCIS (Netherlands)

    Saadaoui, M.; Zeijl, H. van; Wien, W.H.A.; Pham, H.T.M.; Kwakernaak, C.; Knoops, H.C.M.; Erwin Kessels, W.M.M.; Sanden, R.M.C.M. van de; Voogt, F.C.; Roozeboom, F.; Sarro, P.M.

    2011-01-01

    One of the critical steps toward producing void-free and uniform bottom-up copper electroplating in high aspect-ratio (AR) through-silicon vias (TSVs) is the ability of the copper electrolyte to spontaneously flow through the entire depth of the via. This can be accomplished by reducing the

  1. Fundamental length and relativistic length

    International Nuclear Information System (INIS)

    Strel'tsov, V.N.

    1988-01-01

    It si noted that the introduction of fundamental length contradicts the conventional representations concerning the contraction of the longitudinal size of fast-moving objects. The use of the concept of relativistic length and the following ''elongation formula'' permits one to solve this problem

  2. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  3. Relativistic Length Agony Continued

    Science.gov (United States)

    Redzic, D. V.

    2014-06-01

    We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

  4. Nanowire assembly, e.g. for optical probes, comprises optically trapping high aspect ratio semiconductor nanowire with infrared single-beam optical trap and attaching nanowire to organic or inorganic structure

    OpenAIRE

    Pauzauskie, P.; Radenovic, A.; Trepagnier, E.; Liphardt, J.; Yang, P.

    2007-01-01

    NOVELTY - A nanowire assembly method comprises optically trapping a semiconductor nanowire with an infrared single-beam optical trap and attaching the nanowire to an organic or inorganic structure by laser fusing. The nanowire is further trapped in a fluid environment. The optical trap has a beam wavelength of 1064 nm. The nanowire has an aspect ratio greater than 100 and a diameter less than 100 (preferably less than 80) nm. The nanowire and the organic or inorganic structure form a heterost...

  5. Fundamental length

    International Nuclear Information System (INIS)

    Pradhan, T.

    1975-01-01

    The concept of fundamental length was first put forward by Heisenberg from purely dimensional reasons. From a study of the observed masses of the elementary particles known at that time, it is sumrised that this length should be of the order of magnitude 1 approximately 10 -13 cm. It was Heisenberg's belief that introduction of such a fundamental length would eliminate the divergence difficulties from relativistic quantum field theory by cutting off the high energy regions of the 'proper fields'. Since the divergence difficulties arise primarily due to infinite number of degrees of freedom, one simple remedy would be the introduction of a principle that limits these degrees of freedom by removing the effectiveness of the waves with a frequency exceeding a certain limit without destroying the relativistic invariance of the theory. The principle can be stated as follows: It is in principle impossible to invent an experiment of any kind that will permit a distintion between the positions of two particles at rest, the distance between which is below a certain limit. A more elegant way of introducing fundamental length into quantum theory is through commutation relations between two position operators. In quantum field theory such as quantum electrodynamics, it can be introduced through the commutation relation between two interpolating photon fields (vector potentials). (K.B.)

  6. ASPECTS CONCERNING THE DETERMINATION OF BANKRUPTCY RISK BY SOLVENCY AND LIQUIDITY RATIOS IN THE COMPANIES LISTED ON THE BUCHAREST STOCK EXCHANGE

    Directory of Open Access Journals (Sweden)

    Teodor Hada

    2014-07-01

    Full Text Available This paper presents issues related to determining the bankruptcy risk for 64 companies listed on the Bucharest Stock Exchange.The purpose of this paper is to determine the percentage of companies falling within the normal range. In the introduction, we set the goal, the research methodology, and the novelty value of this work. Hereinafter, we presented different views of risk concepts, bankruptcy, solvency and liquidity. After that, based on theoretical presentations, a case study was conducted to determine the solvency and liquidity ratios. In the end, on the basis of the above considerations, the conclusions were established and some proposals were listed.

  7. Reaction kinetics aspect of U3O8 kernel with gas H2 on the characteristics of activation energy, reaction rate constant and O/U ratio of UO2 kernel

    International Nuclear Information System (INIS)

    Damunir

    2007-01-01

    The reaction kinetics aspect of U 3 O 8 kernel with gas H 2 on the characteristics of activation energy, reaction rate constant and O/U ratio of UO 2 kernel had been studied. U 3 O 8 kernel was reacted with gas H 2 in a reduction furnace at varied reaction time and temperature. The reaction temperature was varied at 600, 700, 750 and 850 °C with a pressure of 50 mmHg for 3 hours in gas N 2 atmosphere. The reation time was varied at 1, 2, 3 and 4 hours at a temperature of 750 °C using similar conditions. The reaction product was UO 2 kernel. The reaction kinetic aspect between U 3 O 8 and gas H 2 comprised the minimum activation energy (ΔE), the reaction rate constant and the O/U ratio of UO 2 kernel. The minimum activation energy was determined from a straight line slope of equation ln [{D b . R o {(1 - (1 - X b ) ⅓ } / (b.t.Cg)] = -3.9406 x 10 3 / T + 4.044. By multiplying with the straight line slope -3.9406 x 10 3 , the ideal gas constant (R) 1.985 cal/mol and the molarity difference of reaction coefficient 2, a minimum activation energy of 15.644 kcal/mol was obtained. The reaction rate constant was determined from first-order chemical reaction control and Arrhenius equation. The O/U ratio of UO 2 kernel was obtained using gravimetric method. The analysis result of reaction rate constant with chemical reaction control equation yielded reaction rate constants of 0.745 - 1.671 s -1 and the Arrhenius equation at temperatures of 650 - 850 °C yielded reaction rate constants of 0.637 - 2.914 s -1 . The O/U ratios of UO 2 kernel at the respective reaction rate constants were 2.013 - 2.014 and the O/U ratios at reaction time 1 - 4 hours were 2.04 - 2.011. The experiment results indicated that the minimum activation energy influenced the rate constant of first-order reaction and the O/U ratio of UO 2 kernel. The optimum condition was obtained at reaction rate constant of 1.43 s -1 , O/U ratio of UO 2 kernel of 2.01 at temperature of 750 °C and reaction time of 3

  8. Reproductive aspects of a cichlid fish Tilapia zillii (Gervais) (Pisces ...

    African Journals Online (AJOL)

    A total of 1486 specimen of the fish Tilapia zillii was collected by gillnetting and analysed for aspect of its reproductive biology in Opa reservoir, between October 1991 and February 1994. Sex ratio was approximately 1:1 (male: female). Fish total length at maturity was 15.1cm (males) and 13.2cm (females). The fecundity ...

  9. Relativistic length agony continued

    Directory of Open Access Journals (Sweden)

    Redžić D.V.

    2014-01-01

    Full Text Available We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redžić 2008b, we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the ‘pole in a barn’ paradox. [Projekat Ministarstva nauke Republike Srbije, br. 171028

  10. Injection Molding of High Aspect Ratio Nanostructures

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels Bent

    We present a process for injection molding of 40 nm wide and >100 nm high pillars (pitch: 200 nm). We explored the effects of mold coatings and injection molding conditions on the replication quality of nanostructures in cyclic olefin copolymer. We found that optimization of molding parameters...

  11. Scavenging ratios

    International Nuclear Information System (INIS)

    Krey, P.W.; Toonkel, L.E.

    1977-01-01

    Total 90 Sr fallout is adjusted for dry deposition, and scavenging ratios are calculated at Seattle, New York, and Fayetteville, Ark. Stable-lead scavenging ratios are also presented for New York. These ratios show large scatter, but average values are generally inversely proportional to precipitation. Stable-lead ratios decrease more rapidly with precipitation than do those of 90 Sr, a decrease reflecting a lesser availability of lead to the scavenging processes

  12. Golden Ratio

    Indian Academy of Sciences (India)

    Our attraction to another body increases if the body is symmetricaland in proportion. If a face or a structure is in proportion,we are more likely to notice it and find it beautiful.The universal ratio of beauty is the 'Golden Ratio', found inmany structures. This ratio comes from Fibonacci numbers.In this article, we explore this ...

  13. The probabilistic distribution of metal whisker lengths

    Energy Technology Data Exchange (ETDEWEB)

    Niraula, D., E-mail: Dipesh.Niraula@rockets.utoledo.edu; Karpov, V. G., E-mail: victor.karpov@utoledo.edu [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States)

    2015-11-28

    Significant reliability concerns in multiple industries are related to metal whiskers, which are random high aspect ratio filaments growing on metal surfaces and causing shorts in electronic packages. We derive a closed form expression for the probabilistic distribution of metal whisker lengths. Our consideration is based on the electrostatic theory of metal whiskers, according to which whisker growth is interrupted when its tip enters a random local “dead region” of a weak electric field. Here, we use the approximation neglecting the possibility of thermally activated escapes from the “dead regions,” which is later justified. We predict a one-parameter distribution with a peak at a length that depends on the metal surface charge density and surface tension. In the intermediate range, it fits well the log-normal distribution used in the experimental studies, although it decays more rapidly in the range of very long whiskers. In addition, our theory quantitatively explains how the typical whisker concentration is much lower than that of surface grains. Finally, it predicts the stop-and-go phenomenon for some of the whiskers growth.

  14. Golden Ratio

    Indian Academy of Sciences (India)

    of mathematical biology. Our attraction to another body increases if the body is sym- metrical and in proportion. If a face or a structure is in pro- ... his practice of oral and maxillofacial surgery, and he developed a mask using the concept of golden ratio. The mask is called the. Marquardt beauty mask (Figure 1) [1]. Keywords.

  15. Statistical aspects of fish stock assessment

    DEFF Research Database (Denmark)

    Berg, Casper Willestofte

    statistical aspects of fish stocks assessment, which includes topics such as time series analysis, generalized additive models (GAMs), and non-linear state-space/mixed models capable of handling missing data and a high number of latent states and parameters. The aim is to improve the existing methods...... for stock assessment by application of state-of-the-art statistical methodology. The main contributions are presented in the form of six research papers. The major part of the thesis deals with age-structured assessment models, which is the most common approach. Conversion from length to age distributions...... in the catches is a necessary step in age-based stock assessment models. For this purpose, GAMs and continuation ratio logits are combined to model the probability of age as a smooth function of length and spatial coordinates, which constitutes an improvement over traditional methods based on area...

  16. Age, sex ratio, length-weight relationships and reproductive biology ...

    African Journals Online (AJOL)

    Exper Computer

    2012-02-21

    Feb 21, 2012 ... Sun et al., 2002, De Martini et al., 2007). In the. Mediterranean Sea, MLS has been restricted at 90 cm in. Spain and 120 cm in Morocco (ICCAT, 2011a). However, minimum catch-at-size data have been reported as 51 cm for the Aegean Sea (De Metrio, 1995); 53 cm for the northern Ionian Sea (De Metrio, ...

  17. The primary feather lengths of early birds with respect to avian wing shape evolution.

    Science.gov (United States)

    Wang, X; Nudds, R L; Dyke, G J

    2011-06-01

    We examine the relationships between primary feather length (f(prim)) and total arm length (ta) (sum of humerus, ulna and manus lengths) in Mesozoic fossil birds to address one aspect of avian wing shape evolution. Analyses show that there are significant differences in the composition of the wing between the known lineages of basal birds and that mean f(prim) (relative to ta length) is significantly shorter in Archaeopteryx and enantiornithines than it is in Confuciusornithidae and in living birds. Based on outgroup comparisons with nonavian theropods that preserve forelimb primary feathers, we show that the possession of a relatively shorter f(prim) (relative to ta length) must be the primitive condition for Aves. There is also a clear phylogenetic trend in relative primary feather length throughout bird evolution: our analyses demonstrate that the f(prim)/ta ratio increases among successive lineages of Mesozoic birds towards the crown of the tree ('modern birds'; Neornithes). Variance in this ratio also coincides with the enormous evolutionary radiation at the base of Neornithes. Because the f(prim)/ta ratio is linked to flight mode and performance in living birds, further comparisons of wing proportions among Mesozoic avians will prove informative and certainly imply that the aerial locomotion of the Early Cretaceous Confuciusornis was very different to other extinct and living birds. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

  18. Telomere length analysis.

    Science.gov (United States)

    Canela, Andrés; Klatt, Peter; Blasco, María A

    2007-01-01

    Most somatic cells of long-lived species undergo telomere shortening throughout life. Critically short telomeres trigger loss of cell viability in tissues, which has been related to alteration of tissue function and loss of regenerative capabilities in aging and aging-related diseases. Hence, telomere length is an important biomarker for aging and can be used in the prognosis of aging diseases. These facts highlight the importance of developing methods for telomere length determination that can be employed to evaluate telomere length during the human aging process. Telomere length quantification methods have improved greatly in accuracy and sensitivity since the development of the conventional telomeric Southern blot. Here, we describe the different methodologies recently developed for telomere length quantification, as well as their potential applications for human aging studies.

  19. Characterizing the reinforcement mechanisms in multiwall nanotube/polycarbonate composites across different length and time scales

    Science.gov (United States)

    Duncan, Renee Kelly

    The enthusiasm and interest in the potential properties of nanotube (NT)/polymer composites are based on several factors, including the potential for unsurpassed enhancements in mechanical properties together with electrical, thermal and optical properties. Using multiwall nanotubes (MWNTs) grown to a long aspect ratio, the study found that fragmentation tests can be completed in a similar manner to traditional fiber composites. It was found that the fragmentation length does not depend on the angle of the nanotube to the loading direction hence the ISS does not change with the orientation angle of the nanotube in the composite. A critical aspect ratio of 100 and 300 for untreated nanotubes (ARNT) and treated nanotubes (EPNT), respectively was also measured. For nanotubes that are well dispersed in the polycarbonate, it was observed at a critical angle of 60° that there was a change in failure mechanism from pullout to fracture of the nanotubes due to bending shear. Because the tensile strength of a MWNT is unknown a cumulative distribution was used to characterize the relative interfacial shear strength as a function of nanotube chemical modification. The second goal of this thesis is to use Dynamic Mechanical Thermal Analysis (DMTA) with controlled aspect ratios of multiwall nanotubes (MWNT) to isolate and quantify the effects of the interfacial region on modulus enhancements in nanotube-reinforced composites. One major finding of this study was that the shortest aspect ratio showed a significantly broadened relaxation spectrum than the longer aspect ratio nanotubes, despite the longer aspect ratio nanotubes being more percolated at the given weight percent. There is also a direct correlation between the free space parameter of the short aspect ratio nantoubes network and broadening of the relaxation spectrum, concluded to be a result of increased interaction of the interfacial polymer. The study found agreement with the premise that at a constant filler weight

  20. Telomere length and depression

    DEFF Research Database (Denmark)

    Wium-Andersen, Marie Kim; Ørsted, David Dynnes; Rode, Line

    2017-01-01

    BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...... as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication....... RESULTS: Attendance at hospital for depression was associated with short telomere length cross-sectionally, but not prospectively. Further, purchase of antidepressant medication was not associated with short telomere length cross-sectionally or prospectively. Mean follow-up was 7.6 years (range 0...

  1. Myofilament length dependent activation

    Energy Technology Data Exchange (ETDEWEB)

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  2. Upper Extremity Length Equalization

    OpenAIRE

    DeCoster, Thomas A.; Ritterbusch, John; Crawford, Mark

    1992-01-01

    Significant upper extremity length inequality is uncommon but can cause major functional problems. The ability to position and use the hand may be impaired by shortness of any of the long bones of the upper extremity. In many respects upper and lower extremity length problems are similar. They most commonly occur after injury to a growing bone and the treatment modalities utilized in the lower extremity may be applied to the upper extremity. These treatment options include epiphysiodesis, sho...

  3. Interdisciplinary aspects of turbulence

    CERN Document Server

    Kupka, Friedrich

    2008-01-01

    What do combustion engines, fusion reactors, weather forecast, ocean flows, our sun, and stellar explosions in outer space have in common? Of course, the physics and the length and time scales are vastly different in all cases, but it is also well known that in all of them, on some relevant length scales, the material flows that govern the dynamical and/or secular evolution of the systems are chaotic and often unpredictable: they are said to be turbulent. The interdisciplinary aspects of turbulence are brought together in this volume containing chapters written by experts from very different fields, including geophysics, astrophysics, and engineering. It covers several subjects on which considerable progress was made during the last decades, from questions concerning the very nature of turbulence to some practical applications. These subjects include: a basic introduction into turbulence, statistical mechanics and nonlinear dynamics, turbulent convection in stars, atmospheric turbulence in the context of nume...

  4. Telomere Length and Mortality

    DEFF Research Database (Denmark)

    Kimura, Masayuki; Hjelmborg, Jacob V B; Gardner, Jeffrey P

    2008-01-01

    Leukocyte telomere length, representing the mean length of all telomeres in leukocytes, is ostensibly a bioindicator of human aging. The authors hypothesized that shorter telomeres might forecast imminent mortality in elderly people better than leukocyte telomere length. They performed mortality...... telomeres predicted the death of the first co-twin better than the mTRFL did (mTRFL: 0.56, 95% confidence interval (CI): 0.49, 0.63; mTRFL(50): 0.59, 95% CI: 0.52, 0.66; mTRFL(25): 0.59, 95% CI: 0.52, 0.66; MTRFL: 0.60, 95% CI: 0.53, 0.67). The telomere-mortality association was stronger in years 3-4 than...

  5. A method for estimating the fibre length in fibre-PLA composites.

    Science.gov (United States)

    Chinga-Carrasco, G; Solheim, O; Lenes, M; Larsen, A

    2013-04-01

    Wood pulp fibres are an important component of environmentally sound and renewable fibre-reinforced composite materials. The high aspect ratio of pulp fibres is an essential property with respect to the mechanical properties a given composite material can achieve. The length of pulp fibres is affected by composite processing operations. This thus emphasizes the importance of assessing the pulp fibre length and how this may be affected by a given process for manufacturing composites. In this work a new method for measuring the length distribution of fibres and fibre fragments has been developed. The method is based on; (i) dissolving the composites, (ii) preparing the fibres for image acquisition and (iii) image analysis of the resulting fibre structures. The image analysis part is relatively simple to implement and is based on images acquired with a desktop scanner and a new ImageJ plugin. The quantification of fibre length has demonstrated the fibre shortening effect because of an extrusion process and subsequent injection moulding. Fibres with original lengths of >1 mm where shortened to fibre fragments with length of <200 μm. The shortening seems to be affected by the number of times the fibres have passed through the extruder, the amount of chain extender and the fraction of fibres in the polymer matrix. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

  6. Rod hydrodynamics and length distributions of single-wall carbon nanotubes using analytical ultracentrifugation.

    Science.gov (United States)

    Batista, Carlos A Silvera; Zheng, Ming; Khripin, Constantine Y; Tu, Xiaomin; Fagan, Jeffrey A

    2014-05-06

    Because of their repetitive chemical structure, extreme rigidity, and the separability of populations with varying aspect ratio, SWCNTs are excellent candidates for use as model rodlike colloids. In this contribution, the sedimentation velocities of length and density sorted single-wall carbon nanotubes (SWCNTs) are compared to predictions from rod hydrodynamic theories of increasing complexity over a range of aspect ratios from 400. Independently measuring all contributions to the sedimentation velocity besides the shape factor, excellent agreement is found between the experimental findings and theoretical predictions for numerically calculated hydrodynamic radius values and for multiterm analytical expansion approximations; values for the hydrodynamic radii in these cases are additionally found to be consistent with the apparent hydrated particle radius determined independently by buoyancy measurements. Lastly, we utilize this equivalency to calculate the apparent distribution of nanotube lengths in each population from their sedimentation coefficient distribution without adjustable parameters, achieving excellent agreement with distributions from atomic force microscopy. The method developed herein provides an alternative for the ensemble measurement of SWCNT length distributions and others rodlike particles.

  7. Full Length Research Article

    African Journals Online (AJOL)

    Administrator

    Out of the 320 male sheep examined, 87(27.2%) were infected, while 9(19.1%) of the 47 females examined were infected (Table 2). Infection varied from one abattoir to another. Age related distribution of P. cervi is shown in Table 3. Out of 356 adult sheep (>2yrs) examined, 35. Full Length Research Article. 12 ...

  8. Magnetic alloy nanowire arrays with different lengths: Insights into the crossover angle of magnetization reversal process

    Energy Technology Data Exchange (ETDEWEB)

    Samanifar, S.; Alikhani, M. [Department of Physics, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Almasi Kashi, M., E-mail: almac@kashanu.ac.ir [Department of Physics, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Ramazani, A. [Department of Physics, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Montazer, A.H. [Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of)

    2017-05-15

    Nanoscale magnetic alloy wires are being actively investigated, providing fundamental insights into tuning properties in magnetic data storage and processing technologies. However, previous studies give trivial information about the crossover angle of magnetization reversal process in alloy nanowires (NWs). Here, magnetic alloy NW arrays with different compositions, composed of Fe, Co and Ni have been electrochemically deposited into hard-anodic aluminum oxide templates with a pore diameter of approximately 150 nm. Under optimized conditions of alumina barrier layer and deposition bath concentrations, the resulting alloy NWs with aspect ratio and saturation magnetization (M{sub s}) up to 550 and 1900 emu cm{sup −3}, respectively, are systematically investigated in terms of composition, crystalline structure and magnetic properties. Using angular dependence of coercivity extracted from hysteresis loops, the reversal processes are evaluated, indicating non-monotonic behavior. The crossover angle (θ{sub c}) is found to depend on NW length and M{sub s}. At a constant M{sub s}, increasing NW length decreases θ{sub c}, thereby decreasing the involvement of vortex mode during the magnetization reversal process. On the other hand, decreasing M{sub s} decreases θ{sub c} in large aspect ratio (>300) alloy NWs. Phenomenologically, it is newly found that increasing Ni content in the composition decreases θ{sub c}. The angular first-order reversal curve (AFORC) measurements including the irreversibility of magnetization are also investigated to gain a more detailed insight into θ{sub c}. - Highlights: • Magnetic alloy NWs with aspect ratios up to 550 were fabricated into hard-AAO templates. • Morphology, composition, crystal structure and magnetic properties were investigated. • Angular dependence of coercivity was used to describe the magnetization reversal process. • The crossover angle of magnetization reversal was found to depend on NW length and M{sub s}.

  9. Gap length distributions by PEPR

    International Nuclear Information System (INIS)

    Warszawer, T.N.

    1980-01-01

    Conditions guaranteeing exponential gap length distributions are formulated and discussed. Exponential gap length distributions of bubble chamber tracks first obtained on a CRT device are presented. Distributions of resulting average gap lengths and their velocity dependence are discussed. (orig.)

  10. Length of excitable knots

    Science.gov (United States)

    Maucher, Fabian; Sutcliffe, Paul

    2017-07-01

    In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots. We also show that there is not a unique attractor within a given knot topology.

  11. Pion nucleus scattering lengths

    International Nuclear Information System (INIS)

    Huang, W.T.; Levinson, C.A.; Banerjee, M.K.

    1971-09-01

    Soft pion theory and the Fubini-Furlan mass dispersion relations have been used to analyze the pion nucleon scattering lengths and obtain a value for the sigma commutator term. With this value and using the same principles, scattering lengths have been predicted for nuclei with mass number ranging from 6 to 23. Agreement with experiment is very good. For those who believe in the Gell-Mann-Levy sigma model, the evaluation of the commutator yields the value 0.26(m/sub σ//m/sub π/) 2 for the sigma nucleon coupling constant. The large dispersive corrections for the isosymmetric case implies that the basic idea behind many of the soft pion calculations, namely, slow variation of matrix elements from the soft pion limit to the physical pion mass, is not correct. 11 refs., 1 fig., 3 tabs

  12. Purcell effect for finite-length metal-coated and metal nanowires

    DEFF Research Database (Denmark)

    Filonenko, Konstantin V.; Willatzen, Morten; Bordo, Vladimir G.

    2014-01-01

    We investigate the modification (enhancement and suppression) of the spontaneous emission rate of a dipole emitter in two configurations: inside a finite-length semiconductor nanowire surrounded by bulk metal and in the vicinity of a finite metal nanowire. Our analysis is based on a first......-principle approach, which is reduced to a seminumeric one in the limit of large nanowire aspect ratios. The numerical calculations are carried out for an emitter in a GaAs nanowire embedded in Ag or Au and for that nearby an Ag or Au nanowire in vacuum or dielectric. We consider in detail the Purcell and β factors...

  13. Length-weight and length-length relationships of freshwater wild ...

    African Journals Online (AJOL)

    Length-weight and length-length relationships of freshwater wild catfish Mystus bleekeri from Nala Daik, Sialkot, Pakistan. ... Linear regression analysis was used, first to compute the degree of relationship between length and weight and then among total (TL), standard (SL) and fork lengths (FL). LWR exhibited a highly ...

  14. Equations to convert compacted crown ratio to uncompacted crown ratio for trees in the Interior West

    Science.gov (United States)

    Chris Toney; Matthew C. Reeves

    2009-01-01

    Crown ratio is the proportion of total tree length supporting live foliage. Inventory programs of the US Forest Service generally define crown ratio in terms of compacted or uncompacted measurements. Measurement of compacted crown ratio (CCR) involves envisioning the transfer of lower branches of trees with asymmetric crowns to fill holes in the upper portion of the...

  15. Improving acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    In recent years experiments have shown that optical waves in waveguides can be modulated by mechanical stresses from surface acoustic waves (SAW), which have most of their energy density concentrated at the surface. In these experiments the SAWs are generated in piezoelectric materials...

  16. VIBRATION ANALYSIS OF LOW-ASPECT RATIO ROTATING ...

    African Journals Online (AJOL)

    hub radius x, y, z moving coordinate system n angular velocity. OJ natural frequency. P density of plate material. ( Y transpose of a vector. ( )' differentiation with respect to spatial coordinate. (.) differentiation with respect to time. INTRODUCTION. In day-to-day industrial engineering activities, it is a common experience to.

  17. Fabrication of high-aspect ratio SU-8 micropillar arrays

    DEFF Research Database (Denmark)

    Amato, Letizia; Keller, Stephan S.; Heiskanen, Arto

    2012-01-01

    to the resolution limit of photolithography. This paper describes process optimization for the fabrication of dense SU-8 micropillar arrays (2.5μm spacing) with nominal height ⩾20μm and nominal diameter ⩽2.5μm (AR ⩾8). Two approaches, differing in temperature, ramping rate and duration of the baking steps were...... compared as part of the photolithographic processing, in order to evaluate the effect of baking on the pattern resolution. Additionally, during the post-processing, supercritical point drying and hard baking were introduced yielding pillars with diameter 1.8μm, AR=11 and an improved temporal stability....

  18. Active Aeroelastic Tailoring of High-Aspect-Ratio Composite Wings

    Science.gov (United States)

    2005-09-01

    Dynamics, and Control of a Complete Aircraft," Ph.D. Thesis, Aerospace Engineering, Georgia Institute of Technology, May 1999. [15] Cheng , T...f 9zdV = mrr., +Ixz V Pa = PA + XUx + yUy + zUz (32) Ayz = A, = JpyzdV = mryr, +1I, = RhA V, 6 American Institute of Aeronautics and Astronautics

  19. In-flight Sorting of BNNTs by Aspect Ratio

    Data.gov (United States)

    National Aeronautics and Space Administration — The key technical challenges are: (a) mechanical sorting is ineffective for nanoscale product, (b) BNNTs are non-conductive and the agglomeration tendency is strong,...

  20. Magnetization reversal in textured Fe nanoparticles having different aspect ratios

    International Nuclear Information System (INIS)

    Garcia Sanchez, F.; Chubykalo-Fesenko, O.; Crespo, P.; Hernando, A.; Gonzalez, J.M.

    2005-01-01

    The use of micromagnetic models on the simulation of the magnetization reversal allows approaching the 'ad hoc' design of materials for particular applications. As an example of this and trying to identify a particulate system with reduced interparticle dipolar interactions, we report on the results of a study of the hysteretic properties of textured Fe particles having thicknesses of the order of the units of nanometre and in-plane dimensions from 400x30 to 400x250 nm. Our results show that for sufficiently wide particles the moment configurations at the remanence correspond to an outer shell where the moments are essentially oriented along the direction parallel to the particle surface (therefore minimizing the surface poles) and an inner core (having larger volume than the shell) in which the moments point along one of the two easiest crystallographic directions. The reversal field of the outer shell is larger than that of the core and consequently the latter coincides with the global particle coercivity

  1. Short cervical length dilemma.

    Science.gov (United States)

    Suhag, Anju; Berghella, Vincenzo

    2015-06-01

    Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality. With research efforts, the rate of PTB decreased to 11.4% in 2013. Transvaginal ultrasound (TVU) cervical length (CL) screening predicts PTB. In asymptomatic singletons without prior spontaneous PTB (sPTB), TVU CL screening should be done. If the cervix is 20 mm or less, vaginal progesterone is indicated. In asymptomatic singletons with prior sPTB, serial CL screening is indicated. In multiple gestations, routine cervical screening is not indicated. In symptomatic women with preterm labor, TVU CL screening and fetal fibronectin testing is recommended. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. discouraged by queue length

    Directory of Open Access Journals (Sweden)

    P. R. Parthasarathy

    2001-01-01

    Full Text Available The transient solution is obtained analytically using continued fractions for a state-dependent birth-death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well-known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed.

  3. Primary length standard adjustment

    Science.gov (United States)

    Ševčík, Robert; Guttenová, Jana

    2007-04-01

    This paper deals with problems and techniques connected with primary length standard adjusting, which includes disassembling of the device and by use of the secondary laser with collimated beam and diffraction laws successively reassembling of the laser. In the reassembling process the device was enhanced with substituting the thermal grease cooling of cold finger by copper socket cooler. This improved external cooling system enables more effective cooling of molecular iodine in the cell, which allows better pressure stability of iodine vapor and easier readjustment of the system.

  4. The Divine Ratio and Golden Rectangles.

    Science.gov (United States)

    Cooper, Martin

    1982-01-01

    The material examines aspects of Fibonacci and Lucas sequences, the generation of the Divine Ratio, and the nature of this ratio in golden rectangles, triangles, and figures made up of golden triangles. It is noted Lucas sequence is formed like Fibonacci but has one and three as the first elements. (Author/MP)

  5. The effects of axial length on the fracture and fragmentation of expanding rings

    Directory of Open Access Journals (Sweden)

    Razorenov S.V.

    2012-08-01

    Full Text Available Rings of Ti-6Al-4V with aspect ratios (wall thickness:axial length of 1 : 1, 1 : 2 and 1 : 4 have been expanded to failure at radial strain rates εr ∼ 1 × 104 s−1 using 4340 (EN24T steel and Cu-ETP cylindrical drivers containing a column of RDX. Expansion velocity was measured using VISAR enabling calculation of the stress-strain history of the ring alongside fragment recovery with up to 98% original ring mass recovered. Using the recovered samples average fragment length and mass and final strain have been measured along with analysis of the fracture sites to determine the active failure mechanisms. Perfect rings (aspect ratio 1 : 1 were found to undergo necking before failure, whereas the longer rings failed though ductile tensile cracking at 45∘ to the radius. This data is then compared with finite element analysis results.

  6. Correlation lengths of electrostatic turbulence

    International Nuclear Information System (INIS)

    Guiziou, L.; Garbet, X.

    1995-01-01

    This document deals with correlation length of electrostatic turbulence. First, the model of drift waves turbulence is presented. Then, the radial correlation length is determined analytically with toroidal coupling and non linear coupling. (TEC). 5 refs

  7. Correlation lengths of electrostatic turbulence

    International Nuclear Information System (INIS)

    Guiziou, L.; Garbet, X.

    1995-01-01

    In this paper, the radial correlation length of an electrostatic drift wave turbulence is analytically determined in various regimes. The analysis relies on the calculation of a range of mode non linear interaction, which is an instantaneous correlation length. The link with the usual correlation length has not been investigated yet. (TEC). 5 refs

  8. Design Concepts for Low Aspect Ratio High Pressure Turbines for High Bypass Ratio Turbofans, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The performance gains and weight reductions from using Ceramic Matrix Composite(CMC) turbine blades in both the High Pressure Turbine(HPT) and Low Pressure...

  9. Length distribution of single-walled carbon nanotubes in aqueous suspension measured by electrospray differential mobility analysis.

    Science.gov (United States)

    Pease, Leonard F; Tsai, De-Hao; Fagan, Jeffery A; Bauer, Barry J; Zangmeister, Rebecca A; Tarlov, Michael J; Zachariah, Michael R

    2009-12-01

    The first characterization of the length distribution of single-walled carbon nanotubes (SWCNT) dispersed in a liquid by electrospray differential mobility analysis (ES-DMA) is presented. Although an understanding of geometric properties of SWCNTs, including length, diameter, aspect ratio, and chirality, is essential for commercial applications, rapid characterization of nanotube length distributions remains challenging. Here the use of ES-DMA to obtain length distributions of DNA-wrapped SWCNTs dispersed in aqueous solutions is demonstrated. Lengths measured by ES-DMA compare favorably with those obtained from multiangle light scattering, dynamic light scattering, field flow fractionation with UV/vis detection, and atomic force microscopy, validating ES-DMA as a technique to measure SWCNTs of <250 nm in length. The nanotubes are previously purified and dispersed by wrapping with oligomeric DNA in aqueous solution and centrifuging to remove bundles and amorphous carbon. These dispersions are particularly attractive due to their amenability to bulk processing, ease of storage, high concentration, compatibility with biological and high-throughput manufacturing environments, and for their potential applications ranging from electronics and hydrogen-storage vessels to anticancer agents.

  10. Leukocyte telomere length variation due to DNA extraction method.

    Science.gov (United States)

    Denham, Joshua; Marques, Francine Z; Charchar, Fadi J

    2014-12-04

    Telomere length is indicative of biological age. Shorter telomeres have been associated with several disease and health states. There are inconsistencies throughout the literature amongst relative telomere length measured by quantitative PCR (qPCR) and different extraction methods or kits used. We quantified whole-blood leukocyte telomere length using the telomere to single copy gene (T/S) ratio by qPCR in 20 young (18-25 yrs) men after extracting DNA using three common extraction methods: Lahiri and Nurnberger (high salt) method, PureLink Genomic DNA Mini kit (Life Technologies) and QiaAmp DNA Mini kit (Qiagen). Telomere length differences of DNA extracted from the three extraction methods was assessed by one-way analysis of variance (ANOVA). DNA purity differed between extraction methods used (P=0.01). Telomere length was impacted by the DNA extraction method used (P=0.01). Telomeres extracted using the Lahiri and Nurnberger method (mean T/S ratio: 2.43, range: 1.57-3.02) and PureLink Genomic DNA Mini Kit (mean T/S ratio: 2.57, range: 2.24-2.80) did not differ (P=0.13). Likewise, QiaAmp and Purelink-extracted telomeres were not statistically different (P=0.14). The Lahiri-extracted telomeres, however, were significantly shorter than those extracted using the QiaAmp DNA Mini Kit (mean T/S ratio: 2.71, range: 2.32-3.02; P=0.003). DNA purity was associated with telomere length. There are discrepancies between the length of leukocyte telomeres extracted from the same individuals according to the DNA extraction method used. DNA purity could be responsible for the discrepancy in telomere length but this will require validation studies. We recommend using the same DNA extraction kit when quantifying leukocyte telomere length by qPCR or when comparing different cohorts to avoid erroneous associations between telomere length and traits of interest.

  11. Neonatal Length Growth and Height at Two Years.

    Science.gov (United States)

    Goisbault, Manon; Simon, Laure; Hanf, Mathieu; Darmaun, Dominique; Rozé, Jean-Christophe; Flamant, Cyril

    2016-01-01

    Birth length is correlated to height at 2 years and is a predictor of adult height. However, little is known about the relationship between length growth during neonatal hospitalization and height at 2 years. The objective was to determine the relationship between length growth during neonatal hospitalization and height at 2 years in preterm infants. A total of 1,760 preterm infants of less than 35 weeks of gestational age were included. Neonatal length growth was defined by the difference between length Z-scores at discharge and at birth according to Olsen curves. We calculated the odds ratios (OR) before and after adjustment for the risk of being in the 1st quintile of the height Z-score at 2 years. Height at 2 years was positively associated with birth length (p years was significantly associated with birth length (adjusted OR = 0.43, 95% CI: 0.38-0.49, for one Z-score) and with neonatal length growth (adjusted OR = 0.66, 95% CI: 0.56-0.76, for one Z-score) before and after adjustment for perinatal variables. In addition to birth length, neonatal length growth was associated with height at 2 years. These findings point to the need for a close follow-up of the length of preterm infants during hospitalization, so as to start an early management of those patients. © 2016 S. Karger AG, Basel.

  12. Financial Key Ratios

    OpenAIRE

    Tănase Alin-Eliodor

    2014-01-01

    This article focuses on computing techniques starting from trial balance data regarding financial key ratios. There are presented activity, liquidity, solvency and profitability financial key ratios. It is presented a computing methodology in three steps based on a trial balance.

  13. The Sharpe ratio of estimated efficient portfolios

    OpenAIRE

    Kourtis, Apostolos

    2016-01-01

    Investors often adopt mean-variance efficient portfolios for achieving superior risk-adjusted returns. However, such portfolios are sensitive to estimation errors, which affect portfolio performance. To understand the impact of estimation errors, I develop simple and intuitive formulas of the squared Sharpe ratio that investors should expect from estimated efficient portfolios. The new formulas show that the expected squared Sharpe ratio is a function of the length of the available data, the ...

  14. Link lengths and their growth powers

    International Nuclear Information System (INIS)

    Huh, Youngsik; No, Sungjong; Oh, Seungsang; Rawdon, Eric J

    2015-01-01

    For a certain infinite family F of knots or links, we study the growth power ratios of their stick number, lattice stick number, minimum lattice length and minimum ropelength compared with their minimum crossing number c(K) for every K∈F. It is known that the stick number and lattice stick number grow between the (1/2) and linear power of the crossing number, and minimum lattice length and minimum ropelength grow with at least the (3/4) power of crossing number (which is called the four-thirds power law). Furthermore, the minimal lattice length and minimum ropelength grow at most as O (c(K)[ln(c(K))] 5 ), but it is unknown whether any family exhibits superlinear growth. For any real number r between (1/2) and 1, we give an infinite family of non-splittable prime links in which the stick number and lattice stick number grow exactly as the rth power of crossing number. Furthermore for any real number r between (3/4) and 1, we give another infinite family of non-splittable prime links in which the minimum lattice length and minimum ropelength grow exactly as the rth power of crossing number. (paper)

  15. 7 Length-weight relationship

    African Journals Online (AJOL)

    Administrator

    Length-weight measurements were taken from well-preserved fish specimens from which stomachs were extracted for the analysis of the food contents, using frequency of occurrence, numerical and gravimetric methods, as well as index of relative importance. The length-frequency analysis showed a size distribution with a ...

  16. Comparison of fiber length analyzers

    Science.gov (United States)

    Don Guay; Nancy Ross Sutherland; Walter Rantanen; Nicole Malandri; Aimee Stephens; Kathleen Mattingly; Matt Schneider

    2005-01-01

    In recent years, several fiber new fiber length analyzers have been developed and brought to market. The new instruments provide faster measurements and the capability of both laboratory and on-line analysis. Do the various fiber analyzers provide the same length, coarseness, width, and fines measurements for a given fiber sample? This paper provides a comparison of...

  17. Digit ratio (2D:4D) and wearing of wedding rings.

    Science.gov (United States)

    Voracek, Martin

    2008-06-01

    Digit ratio (2D:4D), a putative marker for prenatal androgen levels, and absolute finger length, a marker for pubertal androgen action, were not associated with wearing of wedding rings in a sample of 150 male and 199 female married individuals. This failure to replicate associations previously reported by Manning was true for both men and women, self-reported and spousal ring-wearing behavior, and one's own and spousal 2D:4D or absolute finger lengths. Supplemental findings included sex differences and age effects in the prevalence of wearing wedding rings (more frequent in women and the younger than in men and the older) and a sex bias when ring-wearing behavior within couples was discordant (men more frequently did not wear their wedding ring when their wives did than vice versa). Discussed are implications of the current findings and directions for future research into possible associations of 2D:4D with other aspects of body ornamentation.

  18. Effects of Lower Limb Length and Body Proportions on the Energy Cost of Overground Walking in Older Persons

    Directory of Open Access Journals (Sweden)

    Federica Vannetti

    2014-01-01

    Full Text Available Background. Although walking has been extensively investigated in its biomechanical and physiological aspects, little is known on whether lower limb length and body proportions affect the energy cost of overground walking in older persons. Methods. We enrolled 50 men and 12 women aged 65 years and over, mean 69.1 ± SD 5.4, who at the end of their cardiac rehabilitation program performed the six-minute walk test while wearing a portable device for direct calorimetry and who walked a distance comparable to that of nondisabled community-dwelling older persons. Results. In the multivariable regression model (F = 12.75, P<0.001, adjusted R2=0.278 the energy cost of overground walking, expressed as the net energy expenditure, in kg−1 sec−1, needed to provide own body mass with 1 joule kinetic energy, was inversely related to lower limb length and directly related to lower limb length to height ratio (β±SEβ = -3.72*10-3±0.74*10-3, P<0.001, and 6.61*10-3±2.14*10-3, P=0.003, resp.. Ancillary analyses also showed that, altogether, 1 cm increase in lower limb length reduced the energy cost of overground walking by 2.57% (95%CI 2.35–2.79. Conclusions. Lower limb length and body proportions actually affect the energy cost of overground walking in older persons.

  19. Aspects and Polymorphism in AspectJ

    DEFF Research Database (Denmark)

    Lorenz, David Harel; Ernst, Erik

    2003-01-01

    There are two important points of view on inclusion or subtype polymorphism in object-oriented programs, namely polymorphic access and dynamic dispatch. These features are essential for object-oriented programming, and it is worthwhile to consider whether they are supported in aspect......-oriented programming (AOP). In AOP, pieces of crosscutting behavior are extracted from the base code and localized in aspects, losing as a result their polymorphic capabilities while introducing new and unexplored issues. In this paper, we explore what kinds of polymorphism AOP languages should support, using Aspect......J as the basis for the presentation. The results are not exclusive to AspectJ---aspectual polymorphism may make aspects in any comparable AOSD language more expressive and reusable across programs, while preserving safety....

  20. Scattering length density profile of Ni film under controlled corrosion ...

    Indian Academy of Sciences (India)

    the fundamental aspects of the mechanisms operating in the early stages of pitting. (leading to passivity breakdown ... The sample thickness was monitored by quartz crystal system during growth. The electrochemical ... system, N is the number density at a depth z and b is the coherent nuclear scat- tering length. From the ...

  1. Itinerary planning: Modelling cruise lines’ lengths of stay in ports

    NARCIS (Netherlands)

    Chen, Jamie M.; Nijkamp, Peter

    Cruise tourism is a fast-growing segment of the tourism industry that generates substantial benefits to port cities. This study explores strategic aspects of cruise lines’ itinerary planning, and models the determinants of their lengths of stay in ports, based on extensive observations of network

  2. Specific root length as an indicator of environmental change

    NARCIS (Netherlands)

    Ostonen, I.; Püttsepp, Ü.; Biel, C.; Alberton, O.; Bakker, M.R.; Löhmus, K.; Majdi, H.; Metcalfe, J.D.; Olsthoorn, A.F.M.; Pronk, A.A.; Vanguelova, E.; Weih, M.; Brunner, I.

    2007-01-01

    Specific root length (SRL, m g-1) is probably the most frequently measured morphological parameter of fine roots. It is believed to characterize economic aspects of the root system and to be indicative of environmental changes. The main objectives of this paper were to review and summarize the

  3. Leukocyte telomere length in major depression: correlations with chronicity, inflammation and oxidative stress--preliminary findings.

    Directory of Open Access Journals (Sweden)

    Owen M Wolkowitz

    2011-03-01

    Full Text Available Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of "accelerated aging" in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD, whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation.Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio and inflammation (IL-6. Analyses were controlled for age and sex.The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05. Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration was 281 base pairs shorter than that in controls (p<0.05, corresponding to approximately seven years of "accelerated cell aging." Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01 and in the controls (p<0.05 and with inflammation in the depressed subjects (p<0.05.These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening

  4. Diagnostic value of newborn foot length to predict gestational age

    Directory of Open Access Journals (Sweden)

    Mutia Farah Fawziah

    2017-08-01

    Full Text Available Background  Identification of gestational age, especially within 48 hours of birth, is crucial for newborns, as the earlier preterm status is detected, the earlier the child can receive optimal management. Newborn foot length is an anthropometric measurement which is easy to perform, inexpensive, and potentially efficient for predicting gestational age. Objective  To analyze the diagnostic value of newborn foot length in predicting gestational age. Methods  This diagnostic study was performed between October 2016 and February 2017 in the High Care Unit of Neonates at Dr. Moewardi General Hospital, Surakarta. A total of 152 newborns were consecutively selected and underwent right foot length measurements before 96 hours of age. The correlation between newborn foot length to classify as full term and gestational age was analyzed with Spearman’s correlation test because of non-normal data distribution. The cut-off point of newborn foot length was calculated by receiver operating characteristic (ROC curve and diagnostic values of newborn foot length were analyzed by 2 x 2 table with SPSS 21.0 software. Results There were no significant differences between male and female newborns in terms of gestational age, birth weight, choronological age, and newborn foot length (P>0.05. Newborn foot length and gestational age had a significant correlation (r=0.53; P=0.000. The optimal cut-off newborn foot length to predict full term status was 7.1 cm. Newborn foot length below 7.1 cm had sensitivity 75%, specificity 98%, positive predictive value 94.3%, negative predictive value 90.6%, positive likelihood ratio 40.5, negative likelihood ratio 0.25, and post-test probability 94.29%, to predict preterm status in newborns. Conclusion  Newborn foot length can be used to predict gestational age, especially for the purpose of differentiating between preterm and full term newborns.

  5. Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition

    Science.gov (United States)

    Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

    2013-08-01

    To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 μs at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 μm by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays.

  6. Impact of Cyclic Prefix length on OFDM system Capacity

    DEFF Research Database (Denmark)

    Rom, Christian; Sørensen, Troels Bundgaard; Mogensen, Preben Elgaard

    2005-01-01

    This paper is a study on the impact of the Cyclic Prefix (CP) length on the downlink Capacity in a base-band synchronized SISO-OFDM context. To measure this impact, the capacity, measured in bits per second per hertz, is chosen as quality parameter. The study shows how the lengthening of the CP......) the useful OFDM symbol duration, 2) the Signal to Noise Ratio (SNR) at the receiver and 3) the channel Power Delay Profile (PDP). Depending on the values of these parameters different optimum CP lengths are obtained. For a system using only one value of CP length we suggest an optimum value to be 4us...... for an OFDM symbol length of 40us and 6us for an OFDM symbol length of 80us....

  7. Experimental Study of Fiber Length and Orientation in Injection Molded Natural Fiber/Starch Acetate Composites

    DEFF Research Database (Denmark)

    Peltola, Heidi; Madsen, Bo; Joffe, Roberts

    2011-01-01

    Composite compounds based on triethyl citrate plasticized starch acetate and hemp and flax fibers were prepared by melt processing. Plasticizer contents from 20 to 35 wt% and fiber contents of 10 and 40 wt% were used. The compounded composites were injection molded to tensile test specimens...... was noticed. A reduction of fiber length along the increasing fiber content and the decreasing plasticizer content was also detected. This reduction originated from the increasing shear forces during compounding, which again depended on the increased viscosity of the material. Hemp fibers were shown to remain...... longer and fibrillate more than flax fibers, leading to higher aspect ratio. Thus, the reinforcement efficiency of hemp fibers by the processing was improved, in contrast with flax fibers. In addition, the analysis of fiber dispersion and orientation showed a good dispersion of fibers in the matrix...

  8. Discovering Early Aspects

    NARCIS (Netherlands)

    Baniassad, E.; Clements, P.; Araujo, J.; Moreira, A; Rashid, A.; Tekinerdogan, B.

    2006-01-01

    Traditionally, aspect-oriented software development (AOSD) has focused on the software life cycle's implementation phase: aspects are identified and captured mainly in code. But aspects are evident earlier in the life cycle, such as during requirements gathering and architecture development.

  9. SURVIVAL ANALYSIS AND LENGTH-BIASED SAMPLING

    Directory of Open Access Journals (Sweden)

    Masoud Asgharian

    2010-12-01

    Full Text Available When survival data are colleted as part of a prevalent cohort study, the recruited cases have already experienced their initiating event. These prevalent cases are then followed for a fixed period of time at the end of which the subjects will either have failed or have been censored. When interests lies in estimating the survival distribution, from onset, of subjects with the disease, one must take into account that the survival times of the cases in a prevalent cohort study are left truncated. When it is possible to assume that there has not been any epidemic of the disease over the past period of time that covers the onset times of the subjects, one may assume that the underlying incidence process that generates the initiating event times is a stationary Poisson process. Under such assumption, the survival times of the recruited subjects are called “lengthbiased”. I discuss the challenges one is faced with in analyzing these type of data. To address the theoretical aspects of the work, I present asymptotic results for the NPMLE of the length-biased as well as the unbiased survival distribution. I also discuss estimating the unbiased survival function using only the follow-up time. This addresses the case that the onset times are either unknown or known with uncertainty. Some of our most recent work and open questions will be presented. These include some aspects of analysis of covariates, strong approximation, functional LIL and density estimation under length-biased sampling with right censoring. The results will be illustrated with survival data from patients with dementia, collected as part of the Canadian Study of Health and Aging (CSHA.

  10. Difference and ratio plots

    DEFF Research Database (Denmark)

    Svendsen, Anders Jørgen; Holmskov, U; Bro, Peter

    1995-01-01

    hitherto unnoted differences between controls and patients with either rheumatoid arthritis or systemic lupus erythematosus. For this we use simple, but unconventional, graphic representations of the data, based on difference plots and ratio plots. Differences between patients with Burkitt's lymphoma...... and systemic lupus erythematosus from another previously published study (Macanovic, M. and Lachmann, P.J. (1979) Clin. Exp. Immunol. 38, 274) are also represented using ratio plots. Our observations indicate that analysis by regression analysis may often be misleading....

  11. CEBAF Upgrade Bunch Length Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mahmoud [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  12. Continuously variable focal length lens

    Science.gov (United States)

    Adams, Bernhard W; Chollet, Matthieu C

    2013-12-17

    A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

  13. The silver nanowires synthesized using different molecule weight of polyvinyl pyrrolidone for controlling diameter and length by one-pot polyol method

    Energy Technology Data Exchange (ETDEWEB)

    Junaidi, E-mail: junaidi.1982@fmipa.unila.ac.id [Departement of Physics, Universitas Gadjah Mada, Yogyakarta, 55281 (Indonesia); Departement of Physics, Lampung University, Bandar Lampung (Indonesia); Triyana, K., E-mail: triyana@ugm.ac.id; Suharyadi, E.; Harsojo [Departement of Physics, Universitas Gadjah Mada, Yogyakarta, 55281 (Indonesia); Nanomaterials Research Group, Universitas Gadjah Mada, Yogyakarta, 55281 (Indonesia); Hui, H.; Wu, L. Y. L., E-mail: ylwu@simtech.a-star.edu.sg [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore)

    2016-06-17

    In this paper, we report our investigation on the effect of the molecular weight and molar ratio of polyvinyl pyrrolidone (PVP) and silver nitrate (AgNO{sub 3}) for controlling diameter and length of the silver nanowires synthesized with a high-aspect-ratio. The silver nanowires synthesized by one-pot polyol method at a constant temperature oil bath of 130°C. Different molecule weights of PVP, i.e. 55 K, 360 K, and 1300 K were used combined with different molar ratios of [PVP:Ag]. The UV–vis spectrophotometry and Field-emission scanning electron microscopy (FE-SEM) were employed to characterize the silver nanowires. The results show that the molecular weight and molar ratio of [PVP:Ag] are very important for controlling growth and properties of the silver nanowires. The diameter and length of silver nanowires are obtained 80 to 140 nm and 30 to 70 µm, respectively. The higher molecular weight of PVP, the greater diameter and length of silver nanowires.

  14. The silver nanowires synthesized using different molecule weight of polyvinyl pyrrolidone for controlling diameter and length by one-pot polyol method

    International Nuclear Information System (INIS)

    Junaidi; Triyana, K.; Suharyadi, E.; Harsojo; Hui, H.; Wu, L. Y. L.

    2016-01-01

    In this paper, we report our investigation on the effect of the molecular weight and molar ratio of polyvinyl pyrrolidone (PVP) and silver nitrate (AgNO 3 ) for controlling diameter and length of the silver nanowires synthesized with a high-aspect-ratio. The silver nanowires synthesized by one-pot polyol method at a constant temperature oil bath of 130°C. Different molecule weights of PVP, i.e. 55 K, 360 K, and 1300 K were used combined with different molar ratios of [PVP:Ag]. The UV–vis spectrophotometry and Field-emission scanning electron microscopy (FE-SEM) were employed to characterize the silver nanowires. The results show that the molecular weight and molar ratio of [PVP:Ag] are very important for controlling growth and properties of the silver nanowires. The diameter and length of silver nanowires are obtained 80 to 140 nm and 30 to 70 µm, respectively. The higher molecular weight of PVP, the greater diameter and length of silver nanowires.

  15. Oocyte Structure, Fecundity and Sex Ratio of Heterobranchus ...

    African Journals Online (AJOL)

    The reproductive parameters – oocyte structure, fecundity and sex ratio of the catfish, Heterobranchus longifilis, Valenciennes 1840 were investigated ... The number of oocytes in both ovaries ranged from 6001 to 51,216 eggs per female Fecundity was linearly related to total length, standard length, body weight, and ovary ...

  16. Overview of bunch length measurements

    International Nuclear Information System (INIS)

    Lumpkin, A. H.

    1999-01-01

    An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed

  17. Kondo length in bosonic lattices

    Science.gov (United States)

    Giuliano, Domenico; Sodano, Pasquale; Trombettoni, Andrea

    2017-09-01

    Motivated by the fact that the low-energy properties of the Kondo model can be effectively simulated in spin chains, we study the realization of the effect with bond impurities in ultracold bosonic lattices at half filling. After presenting a discussion of the effective theory and of the mapping of the bosonic chain onto a lattice spin Hamiltonian, we provide estimates for the Kondo length as a function of the parameters of the bosonic model. We point out that the Kondo length can be extracted from the integrated real-space correlation functions, which are experimentally accessible quantities in experiments with cold atoms.

  18. Properties of discontinuous S2-glass fiber-particulate-reinforced resin composites with two different fiber length distributions.

    Science.gov (United States)

    Huang, Qiting; Garoushi, Sufyan; Lin, Zhengmei; He, Jingwei; Qin, Wei; Liu, Fang; Vallittu, Pekka Kalevi; Lassila, Lippo Veli Juhana

    2017-10-01

    To investigate the reinforcing efficiency and light curing properties of discontinuous S2-glass fiber-particulate reinforced resin composite and to examine length distribution of discontinuous S2-glass fibers after a mixing process into resin composite. Experimental S2-glass fiber-particulate reinforced resin composites were prepared by mixing 10wt% of discontinuous S2-glass fibers, which had been manually cut into two different lengths (1.5 and 3.0mm), with various weight ratios of dimethacrylate based resin matrix and silaned BaAlSiO 2 filler particulates. The resin composite made with 25wt% of UDMA/SR833s resin system and 75wt% of silaned BaAlSiO 2 filler particulates was used as control composite which had similar composition as the commonly used resin composites. Flexural strength (FS), flexural modulus (FM) and work of fracture (WOF) were measured. Fractured specimens were observed by scanning electron microscopy. Double bond conversion (DC) and fiber length distribution were also studied. Reinforcement of resin composites with discontinuous S2-glass fibers can significantly increase the FS, FM and WOF of resin composites over the control. The fibers from the mixed resin composites showed great variation in final fiber length. The mean aspect ratio of experimental composites containing 62.5wt% of particulate fillers and 10wt% of 1.5 or 3.0mm cutting S2-glass fibers was 70 and 132, respectively. No difference was found in DC between resin composites containing S2-glass fibers with two different cutting lengths. Discontinuous S2-glass fibers can effectively reinforce the particulate-filled resin composite and thus may be potential to manufacture resin composites for high-stress bearing application. Copyright © 2017. Published by Elsevier Ltd.

  19. Study on the crystallization of multiarm stars with a poly(ethyleneimine) core and poly(ϵ-caprolactone) arms of different length

    International Nuclear Information System (INIS)

    Díaz, Angélica; Bacaicoa, Anna; Casas, Maria Teresa; Franco, Lourdes; Serra, Angels; Puiggalí, Jordi

    2015-01-01

    Highlights: • Isothermal crystallization kinetics of multiarm stars. • Influence of the length of poly(ϵ-caprolactone) arms on crystallization kinetics. • Influence of the length of poly(ϵ-caprolactone) arms on secondary nucleation constant. • Crystallization of mixtures of stars having different arm lengths. - Abstract: Crystallization of multiarm star systems constituted by a core of poly(ethyleneimine) (PEI) and arms of poly(ϵ-caprolactone) (PCL) was studied by transmission electron microscopy, calorimetry and optical microscopy techniques. Three systems differing on the degree of polymerization of PCL were studied as well as binary mixtures constituted by systems differing on the length of PCL arms. Samples were able to crystallize from both diluted solutions and the melt state giving rise to well-formed lamellae and spherulites, respectively. Lamellae of samples with large PCL arms were highly regular and corresponded to elongated hexagonal crystals with an aspect ratio that decreased with the length of PCL arms. A significant decrease on equilibrium melting temperatures, degree of crystallinity and glass transition temperature was detected for samples having short PCL arms. Crystallization kinetics were also highly influenced by the length of PCL arms, being both nucleation density and secondary nucleation constant increased as the length of PCL arms decreased. Crystallization of star mixtures having different PCL lengths was determined by the larger arms since they initiated the process and subsequently shorter arms were progressively incorporated. A thermal nucleation was characteristic of multiarm star mixtures due to the different crystallization temperature ranges of samples with large and short PCL arms, whereas samples with a homogeneous arm length rendered an athermal nucleation

  20. Cyclic codes of length 2

    Indian Academy of Sciences (India)

    Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45

    [X]/〈X2m. − 1〉 are given. Cyclic codes of length 2m over the finite field Fq, of odd characteristic, are defined in terms of their generator polynomials. The exact minimum distance and the dimension of the codes are obtained. Keywords.

  1. Diet, nutrition and telomere length.

    Science.gov (United States)

    Paul, Ligi

    2011-10-01

    The ends of human chromosomes are protected by DNA-protein complexes termed telomeres, which prevent the chromosomes from fusing with each other and from being recognized as a double-strand break by DNA repair proteins. Due to the incomplete replication of linear chromosomes by DNA polymerase, telomeric DNA shortens with repeated cell divisions until the telomeres reach a critical length, at which point the cells enter senescence. Telomere length is an indicator of biological aging, and dysfunction of telomeres is linked to age-related pathologies like cardiovascular disease, Parkinson disease, Alzheimer disease and cancer. Telomere length has been shown to be positively associated with nutritional status in human and animal studies. Various nutrients influence telomere length potentially through mechanisms that reflect their role in cellular functions including inflammation, oxidative stress, DNA integrity, DNA methylation and activity of telomerase, the enzyme that adds the telomeric repeats to the ends of the newly synthesized DNA. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Fractional baud-length coding

    Directory of Open Access Journals (Sweden)

    J. Vierinen

    2011-06-01

    Full Text Available We present a novel approach for modulating radar transmissions in order to improve target range and Doppler estimation accuracy. This is achieved by using non-uniform baud lengths. With this method it is possible to increase sub-baud range-resolution of phase coded radar measurements while maintaining a narrow transmission bandwidth. We first derive target backscatter amplitude estimation error covariance matrix for arbitrary targets when estimating backscatter in amplitude domain. We define target optimality and discuss different search strategies that can be used to find well performing transmission envelopes. We give several simulated examples of the method showing that fractional baud-length coding results in smaller estimation errors than conventional uniform baud length transmission codes when estimating the target backscatter amplitude at sub-baud range resolution. We also demonstrate the method in practice by analyzing the range resolved power of a low-altitude meteor trail echo that was measured using a fractional baud-length experiment with the EISCAT UHF system.

  3. Femur length and biparietal diameter

    African Journals Online (AJOL)

    2014-12-02

    Dec 2, 2014 ... Shipp TD, Bromley B, Mascola M, Benacerraf B. Variation in fetal femur length with respect to maternal race. J Ultrasound Med 2001;20:141‑4. 25. Deter RL, Harrist RB, Birnholz JC, Hadlock FP. Quantitative Obstetrical. Ultrasonography. New York: Wiley; 1986. 26. Yeh MN, Bracero L, Reilly KB, Murtha L, ...

  4. Concept study: Use of grout vaults for disposal of long-length contaminated equipment

    International Nuclear Information System (INIS)

    Clem, D.K.

    1994-01-01

    Study considers the potential for use of grout vaults for disposal of untreated long length equipment removed from waste tanks. Looks at ways to access vaults, material handling, regulatory aspects, and advantages and disadvantages of vault disposal

  5. Potential support ratios

    DEFF Research Database (Denmark)

    Kjærgaard, Søren; Canudas-Romo, Vladimir

    2017-01-01

    , the prospective potential support ratio usually focuses on the current mortality schedule, or period life expectancy. Instead, in this paper we look at the actual mortality experienced by cohorts in a population, using cohort life tables. We analyse differences between the two perspectives using mortality models......, historical data, and forecasted data. Cohort life expectancy takes future mortality improvements into account, unlike period life expectancy, leading to a higher prospective potential support ratio. Our results indicate that using cohort instead of period life expectancy returns around 0.5 extra younger...

  6. Spatial correlation length of normalized cone data in sand

    DEFF Research Database (Denmark)

    Firouzianbandpey, Sarah; Griffiths, D. V.; Ibsen, Lars Bo

    2014-01-01

    it is rarely estimated during routine site investigations. Results from two different sites in the north of Denmark are reported in this paper, indicating quite strong anisotropy due to the depositional process, with significantly shorter spatial correlation lengths in the vertical direction. It is observed...... that the normalized cone resistance is a better estimator of spatial trends than the normalized friction ratio....

  7. Length-weight relationship and condition factor of Tilapia guineensis ...

    African Journals Online (AJOL)

    Also, T. guineensis exhibited sexual dimorphism with sex ratio of 1.2:1.0 which was significantly biased in favour of the females. The length-weight relationship showed negative allometric growth, with b= 2.01. Moreover, T. guineensis had a very high condition factor which ranged between 2.03-2.32 in both male and female ...

  8. The rectilinear Steiner ratio

    Directory of Open Access Journals (Sweden)

    PO de Wet

    2005-06-01

    Full Text Available The rectilinear Steiner ratio was shown to be 3/2 by Hwang [Hwang FK, 1976, On Steiner minimal trees with rectilinear distance, SIAM Journal on Applied Mathematics, 30, pp. 104– 114.]. We use continuity and introduce restricted point sets to obtain an alternative, short and self-contained proof of this result.

  9. The Reference Return Ratio

    DEFF Research Database (Denmark)

    Nicolaisen, Jeppe; Faber Frandsen, Tove

    2008-01-01

    The paper introduces a new journal impact measure called The Reference Return Ratio (3R). Unlike the traditional Journal Impact Factor (JIF), which is based on calculations of publications and citations, the new measure is based on calculations of bibliographic investments (references) and returns...

  10. AspectKE*

    DEFF Research Database (Denmark)

    Yang, Fan; Masuhara, Hidehiko; Aotani, Tomoyuki

    2010-01-01

    mechanism for pointcuts, so that pointcuts can uniformly specify join points based on both static and dynamic information about the program. Our implementation strategy performs fundamental static analysis at load-time, so as to retain runtime overheads minimal. We implemented a compiler for Aspect......Enforcing security policies to distributed systems is difficult, in particular, when a system contains untrusted components. We designed AspectKE*, a distributed AOP language based on a tuple space, to tackle this issue. In AspectKE*, aspects can enforce access control policies that depend...... on future behavior of running processes. One of the key language features is the predicates and functions that extract results of static program analysis, which are useful for defining security aspects that have to know about future behavior of a program. AspectKE* also provides a novel variable binding...

  11. Nuclear fuel, mass balances, conversion ratio, doubling time, and uncertainty

    International Nuclear Information System (INIS)

    Vondy, D.R.

    1976-11-01

    Information on the performance aspects of nuclear power plants is presented concerning conversion ratio, criticality, primitive economic analysis, stable breeder-converter industry, doubling time, breeder industry economic benefit, defining nuclear fuel, recommendations, and uncertainty

  12. Influence of recording length on reporting status

    DEFF Research Database (Denmark)

    Biltoft-Jensen, Anja Pia; Matthiessen, Jeppe; Fagt, Sisse

    2009-01-01

    : To investigate the impact of recording length on reporting status, expressed as the ratio between energy intake and calculated basal metabolic rate (EI/BMR), the percentage of consumers of selected food items and the number reported food items per meal and eating occasions per day. Methods: Data from two...... in a validation study and the Danish National Survey of Dietary Habits and Physical Activity 2000-2002, respectively. Both studies had a cross-sectional design. Volunteers and participants completed a pre-coded food diary every day for 7 consecutive days. BMR was predicted from equations. Results......: In the validation study, EI/BMR was significantly lower on 1st, 2nd and 3rd consecutive recording days compared to 4-7 recording days (P

  13. Influence of recording length on reporting status

    DEFF Research Database (Denmark)

    Biltoft-Jensen, Anja Pia; Matthiessen, Jeppe; Fagt, Sisse

    2009-01-01

    : To investigate the impact of recording length on reporting status, expressed as the ratio between energy intake and calculated basal metabolic rate (EI/BMR), the percentage of consumers of selected food items and the number reported food items per meal and eating occasions per day. Methods: Data from two...... increased with the number of recording days and was minimum 10 % higher for 7 days compared to 4 days. The number of eating occasions per day and the number of reported food items per meal did not differ between 4 and 7 recording days. Conclusion: Reducing the recording period from 7 to 4 consecutive days...... did not change EI/BMR at group level. Still a study effect seemed to occur in the two population samples resulting in lower estimates of EI/BMR day 1-2. The proportion of consumers was higher with a 7-day recording. These results support a reporting period from 4-7 days....

  14. Optimization image of magnetic resonance imaging (MRI) T2 fast spin echo (FSE) with variation echo train length (ETL) on the rupture tendon achilles case

    Science.gov (United States)

    Muzamil, Akhmad; Haries Firmansyah, Achmad

    2017-05-01

    The research was done the optimization image of Magnetic Resonance Imaging (MRI) T2 Fast Spin Echo (FSE) with variation Echo Train Length (ETL) on the Rupture Tendon Achilles case. This study aims to find the variations Echo Train Length (ETL) from the results of ankle’s MRI image and find out how the value of Echo Train Length (ETL) works on the MRI ankle to produce optimal image. In this research, the used ETL variations were 12 and 20 with the interval 2 on weighting T2 FSE sagittal. The study obtained the influence of Echo Train Length (ETL) on the quality of ankle MRI image sagittal using T2 FSE weighting and analyzed in 25 images of five patients. The data analysis has done quantitatively with the Region of Interest (ROI) directly on computer MRI image planes which conducted statistical tests Signal to Noise Ratio (SNR) and Contras to Noise Ratio (CNR). The Signal to Noise Ratio (SNR) was the highest finding on fat tissue, while the Contras to Noise Ratio (CNR) on the Tendon-Fat tissue with ETL 12 found in two patients. The statistics test showed the significant SNR value of the 0.007 (pTendon tissue, 0.364 (p>0.05) of the Fat, 0.912 (p>0.05) of the Fibula, and 0.436 (p>0.05) of the Heel Bone. For the contrast to noise ratio (CNR) of the Tendon-FAT tissue was about 0.041 (p>0.05). The results of the study showed that ETL variation with T2 FSE sagittal weighting had difference at Tendon tissue and Tendon-Fat tissue for MRI imaging quality. SNR and CNR were an important aspect on imaging optimization process to give the diagnose information.

  15. Length of a Hanging Cable

    Directory of Open Access Journals (Sweden)

    Eric Costello

    2011-01-01

    Full Text Available The shape of a cable hanging under its own weight and uniform horizontal tension between two power poles is a catenary. The catenary is a curve which has an equation defined by a hyperbolic cosine function and a scaling factor. The scaling factor for power cables hanging under their own weight is equal to the horizontal tension on the cable divided by the weight of the cable. Both of these values are unknown for this problem. Newton's method was used to approximate the scaling factor and the arc length function to determine the length of the cable. A script was written using the Python programming language in order to quickly perform several iterations of Newton's method to get a good approximation for the scaling factor.

  16. Keeping disease at arm's length

    DEFF Research Database (Denmark)

    Lassen, Aske Juul

    2015-01-01

    and physical activities at the activity centre. In this way, keeping disease at arm’s length is analysed as an ambiguous health strategy. The article shows the importance of looking into how active ageing is practised, as active ageing seems to work well in the everyday life of the older people by not giving......Many older people live with a range of chronic diseases. However, these diseases do not necessarily impede an active lifestyle. In this article the author analyses the relation between the active ageing discourse and the way older people at two Danish activity centres handle disease. How does...... active ageing change everyday life with chronic disease, and how do older people combine an active life with a range of chronic diseases? The participants in the study use activities to keep their diseases at arm’s length, and this distancing of disease at the same time enables them to engage in social...

  17. Electron plasma oscillations at arbitrary Debye lengths

    International Nuclear Information System (INIS)

    Lehnert, B.

    1990-12-01

    A solution is presented for electron plasma oscillation in a thermalized homogeneous plasma, at arbitrary ratios between the Debye length λ D and the perturbation wave length λ. The limit λ D D >> λ corresponds to the free-streaming limit of strong kinetic phase-mixing due to large particle excursions. A strong large Debye distance (LDD) effect already appears when λ D > approx λ. The initial amplitude of the fluid-like contribution to the macroscopic density perturbation then becomes small as compared to the contribution from the free-streaming part. As a consequence, only a small fraction of the density perturbation remains after a limited number of kinetic damping times of the free-streaming part. The analysis further shows that a representation in terms of normal model of the form exp(-iωt) leads to amplitude factors of these modes which are related to each other and which depend on the combined free-streaming and fluid behaviour of the plasma. Consequently, these modes are coupled and cannot be treated as being independent of each other. (au)

  18. Relationship Between Short Umbilical Cord Length and Adverse Pregnancy Outcomes.

    Science.gov (United States)

    Yamamoto, Yuriko; Aoki, Shigeru; Oba, Mari S; Seki, Kazuo; Hirahara, Fumiki

    2016-01-01

    To investigate how umbilical cord length relates to pregnancy outcomes, we retrospectively analyzed data from 89,042 deliveries recorded in the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System. We included term deliveries in which vaginal birth was attempted. Umbilical cord length was categorized into four groups: less than the first percentile, from the first percentile to less than the 10th percentile, from the 10th percentile to less than 25th percentile, and from the 25th percentile to less than the 75th percentile, which constituted the control group. Cord lengths of 33, 43, 48, 63 cm corresponded to the first, 10th, 25th, and 75th percentile values of the cord length distribution, respectively. Statistically significant differences were observed in the rate of unplanned cesarean delivery for all three short cord groups compared to control. There was a higher odds ratio for unplanned cesarean delivery as the umbilical cord became shorter.

  19. Smart Photonic Carbon Brush: FBG Length as Sensing Parameter

    Science.gov (United States)

    Morozov, O. G.; Nureev, I. I.; Kuznetsov, A. A.; Artemiev, V. I.

    2018-04-01

    This article deals with problem of carbon brush’s length measurements. There are many applications where regular inspection is not feasible because of a number of factors including, for example, time, labor, cost and disruptions due to down time. Thus, there is a need for a system that can monitor the brush’s length to calculate it’s wear rate, while the component is in operation or without removing of the component from its operational position. We propose a novel method for characterization of carbon brush’s length. This method based on the usage of advantages of the multiplicative response of FBGs and FBG arrays: spectral parameters depend on several aspects, such as grating’s period, refractive index, it’s physical length and so on. We are the first, in our point of view, who proposed to use third parameter for sensing application and prospectively all three parameters for complex measurement: the change of FBG’s length is used to measure length of the brush and it’s wear rate, grating’s central wavelength shift for temperature (due to refractive index change) and mechanical stress (due to grating’s period variations) measurements. The results of modelling and experiments are presented.

  20. Aspect-Oriented Programming

    NARCIS (Netherlands)

    Bergmans, Lodewijk; Videira Lopes, Cristina; Moreira, Ana; Demeyer, Serge

    1999-01-01

    Aspect-oriented programming is a promising idea that can improve the quality of software by reduce the problem of code tangling and improving the separation of concerns. At ECOOP'97, the first AOP workshop brought together a number of researchers interested in aspect-orientation. At ECOOP'98, during

  1. Lexical and Grammatical Aspect

    NARCIS (Netherlands)

    van Hout, Angeliek; Lidz, Jeffrey; Snyder, William; Pater, Joe

    The temporality of a given situation ‘out there in the world’ can be described in many ways. Tense and aspect offer the essential parameters. Lexical aspect characterizes event descriptions; a situation with a sleeping child can be referred to as a state of affairs (be asleep) or as a happening

  2. Hydrodynamic characteristics for flow around wavy wings with different wave lengths

    Directory of Open Access Journals (Sweden)

    Mi Jeong Kim

    2012-12-01

    Full Text Available The present study numerically investigates the effect of the wavy leading edge on hydrodynamic characteristics for the flow of rectangular wings with the low aspect ratio of 1.5. Five different wave lengths at fixed wavy amplitude have been considered. Numerical simulations are performed at a wide range of the angle of attack (0° ≤α ≤ 40° at one Reynolds number of 106. The wavy wings considered in this study did not experience enough lift drop to be defined as the stall, comparing with the smooth wing. However, in the pre-stall region, the wavy wings reveal the considerable loss of the lift, compared to the smooth wing. In the post-stall, the lift coefficients of the smooth wing and the wavy wings are not much different. The pressure coefficient, limiting streamlines and the iso-surface of the spanwise vorticity are also highlighted to examine the effect of the wave length on the flow structures.

  3. Focal Length Affects Depicted Shape and Perception of Facial Images.

    Directory of Open Access Journals (Sweden)

    Vít Třebický

    Full Text Available Static photographs are currently the most often employed stimuli in research on social perception. The method of photograph acquisition might affect the depicted subject's facial appearance and thus also the impression of such stimuli. An important factor influencing the resulting photograph is focal length, as different focal lengths produce various levels of image distortion. Here we tested whether different focal lengths (50, 85, 105 mm affect depicted shape and perception of female and male faces. We collected three portrait photographs of 45 (22 females, 23 males participants under standardized conditions and camera setting varying only in the focal length. Subsequently, the three photographs from each individual were shown on screen in a randomized order using a 3-alternative forced-choice paradigm. The images were judged for attractiveness, dominance, and femininity/masculinity by 369 raters (193 females, 176 males. Facial width-to-height ratio (fWHR was measured from each photograph and overall facial shape was analysed employing geometric morphometric methods (GMM. Our results showed that photographs taken with 50 mm focal length were rated as significantly less feminine/masculine, attractive, and dominant compared to the images taken with longer focal lengths. Further, shorter focal lengths produced faces with smaller fWHR. Subsequent GMM revealed focal length significantly affected overall facial shape of the photographed subjects. Thus methodology of photograph acquisition, focal length in this case, can significantly affect results of studies using photographic stimuli perhaps due to different levels of perspective distortion that influence shapes and proportions of morphological traits.

  4. Directional gear ratio transmissions

    Science.gov (United States)

    Lafever, A. E. (Inventor)

    1984-01-01

    Epicyclic gear transmissions which transmit output at a gear ratio dependent only upon the input's direction are considered. A transmission housing envelops two epicyclic gear assemblies, and has shafts extending from it. One shaft is attached to a sun gear within the first epicyclic gear assembly. Planet gears are held symmetrically about the sun gear by a planet gear carrier and are in mesh with both the sun gear and a ring gear. Two unidirectional clutches restrict rotation of the first planet gear carrier and ring gear to one direction. A connecting shaft drives a second sun gear at the same speed and direction as the first planet gear carrier while a connecting portion drives a second planet gear carrier at the same speed and direction as the first ring gear. The transmission's output is then transmitted by the second ring gear to the second shaft. Input is transmitted at a higher gear ratio and lower speed for all inputs in the first direction than in the opposite direction.

  5. Tau hadronic branching ratios

    CERN Document Server

    Buskulic, Damir; De Bonis, I; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Odier, P; Pietrzyk, B; Ariztizabal, F; Chmeissani, M; Crespo, J M; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Gaitan, V; Martínez, M; Orteu, S; Pacheco, A; Padilla, C; Palla, Fabrizio; Pascual, A; Perlas, J A; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Farilla, A; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Natali, S; Nuzzo, S; Ranieri, A; Raso, G; Romano, F; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Bonvicini, G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Engelhardt, A; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Jacobsen, R; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Markou, C; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Oest, T; Palazzi, P; Pater, J R; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wiedenmann, W; Wildish, T; Witzeling, W; Wotschack, J; Ajaltouni, Ziad J; Bardadin-Otwinowska, Maria; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rossignol, J M; Saadi, F; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Kyriakis, A; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Passalacqua, L; Rougé, A; Rumpf, M; Tanaka, R; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Delfino, M C; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Pepé-Altarelli, M; Dorris, S J; Halley, A W; ten Have, I; Knowles, I G; Lynch, J G; Morton, W T; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Smith, M G; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Braun, O; Geweniger, C; Graefe, G; Hanke, P; Hepp, V; Kluge, E E; Putzer, A; Rensch, B; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Beuselinck, R; Binnie, David M; Cameron, W; Colling, D J; Dornan, Peter J; Konstantinidis, N P; Moneta, L; Moutoussi, A; Nash, J; San Martin, G; Sedgbeer, J K; Stacey, A M; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Bowdery, C K; Brodbeck, T J; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Whelan, E P; Williams, M I; Galla, A; Greene, A M; Kleinknecht, K; Quast, G; Raab, J; Renk, B; Sander, H G; Wanke, R; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Thulasidas, M; Nicod, D; Payre, P; Rousseau, D; Talby, M; Abt, I; Assmann, R W; Bauer, C; Blum, Walter; Brown, D; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Jakobs, K; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wolf, G; Alemany, R; Boucrot, J; Callot, O; Cordier, A; Courault, F; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Musolino, G; Nikolic, I A; Park, H J; Park, I C; Schune, M H; Simion, S; Veillet, J J; Videau, I; Abbaneo, D; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Rizzo, G; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Triggiani, G; Vannini, C; Verdini, P G; Walsh, J; Betteridge, A P; Blair, G A; Bryant, L M; Cerutti, F; Gao, Y; Green, M G; Johnson, D L; Medcalf, T; Mir, L M; Perrodo, P; Strong, J A; Bertin, V; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Edwards, M; Maley, P; Norton, P R; Thompson, J C; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Beddall, A; Booth, C N; Boswell, R; Cartwright, S L; Combley, F; Dawson, I; Köksal, A; Letho, M; Newton, W M; Rankin, C; Thompson, L F; Böhrer, A; Brandt, S; Cowan, G D; Feigl, E; Grupen, Claus; Lutters, G; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Ragusa, F; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Bellantoni, L; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Harton, J L; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Schmitt, M; Scott, I J; Sharma, V; Turk, J; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G

    1996-01-01

    From 64492 selected \\tau-pair events, produced at the Z^0 resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special emphasis is given to the reconstruction of photons and \\pi^0's, and the removal of fake photons. A detailed study of the systematics entering the \\pi^0 reconstruction is also given. A complete and consistent set of tau hadronic branching ratios is presented for 18 exclusive modes. Most measurements are more precise than the present world average. The new level of precision reached allows a stringent test of \\tau-\\mu universality in hadronic decays, g_\\tau/g_\\mu \\ = \\ 1.0013 \\ \\pm \\ 0.0095, and the first measurement of the vector and axial-vector contributions to the non-strange hadronic \\tau decay width: R_{\\tau ,V} \\ = \\ 1.788 \\ \\pm \\ 0.025 and R_{\\tau ,A} \\ = \\ 1.694 \\ \\pm \\ 0.027. The ratio (R_{\\tau ,V} - R_{\\tau ,A}) / (R_{\\tau ,V} + R_{\\tau ,A}), equal to (2.7 \\pm 1.3) \\ \\%, is a measure of the importance of Q...

  6. Molecular aspects of toxicology

    National Research Council Canada - National Science Library

    Hathway, D. E

    1984-01-01

    The subject matter of this book is organized into chapters that deal wwith separate subjects and, whilst this treatment reveals the structure of molecular aspects of toxicology, it inevitably incurs...

  7. General safety aspects

    International Nuclear Information System (INIS)

    1998-01-01

    In this part next aspects are described: (1) Priority to safety; (2) Financial and human resources;; (3) Human factor; (4) Operator's quality assurance system; (5) Safety assessment and Verification; (6) Radiation protection and (7) Emergency preparedness

  8. Foundational aspects of security

    DEFF Research Database (Denmark)

    Chatzikokolakis, Konstantinos; Mödersheim, Sebastian Alexander; Palamidessi, Catuscia

    2014-01-01

    This Special Issue of the Journal of Computer Security focuses on foundational aspects of security, which in recent years have helped change much of the way we think about and approach system security.......This Special Issue of the Journal of Computer Security focuses on foundational aspects of security, which in recent years have helped change much of the way we think about and approach system security....

  9. Length-scale and strain rate-dependent mechanism of defect formation and fracture in carbon nanotubes under tensile loading

    Science.gov (United States)

    Javvaji, Brahmanandam; Raha, S.; Mahapatra, D. Roy

    2017-02-01

    Electromagnetic and thermo-mechanical forces play a major role in nanotube-based materials and devices. Under high-energy electron transport or high current densities, carbon nanotubes fail via sequential fracture. The failure sequence is governed by certain length scale and flow of current. We report a unified phenomenological model derived from molecular dynamic simulation data, which successfully captures the important physics of the complex failure process. Length-scale and strain rate-dependent defect nucleation, growth, and fracture in single-walled carbon nanotubes with diameters in the range of 0.47 to 2.03 nm and length which is about 6.17 to 26.45 nm are simulated. Nanotubes with long length and small diameter show brittle fracture, while those with short length and large diameter show transition from ductile to brittle fracture. In short nanotubes with small diameters, we observe several structural transitions like Stone-Wales defect initiation, its propagation to larger void nucleation, formation of multiple chains of atoms, conversion to monatomic chain of atoms, and finally complete fracture of the carbon nanotube. Hybridization state of carbon-carbon bonds near the end cap evolves, leading to the formation of monatomic chain in short nanotubes with small diameter. Transition from ductile to brittle fracture is also observed when strain rate exceeds a critical value. A generalized analytical model of failure is established, which correlates the defect energy during the formation of atomic chain with aspect ratio of the nanotube and strain rate. Variation in the mechanical properties such as elastic modulus, tensile strength, and fracture strain with the size and strain rate shows important implications in mitigating force fields and ways to enhance the life of electronic devices and nanomaterial conversion via fracture in manufacturing.

  10. Length-scale and strain rate-dependent mechanism of defect formation and fracture in carbon nanotubes under tensile loading

    Energy Technology Data Exchange (ETDEWEB)

    Javvaji, Brahmanandam [Indian Institute of Science, Department of Aerospace Engineering (India); Raha, S. [Indian Institute of Science, Department of Computational and Data Sciences (India); Mahapatra, D. Roy, E-mail: droymahapatra@aero.iisc.ernet.in [Indian Institute of Science, Department of Aerospace Engineering (India)

    2017-02-15

    Electromagnetic and thermo-mechanical forces play a major role in nanotube-based materials and devices. Under high-energy electron transport or high current densities, carbon nanotubes fail via sequential fracture. The failure sequence is governed by certain length scale and flow of current. We report a unified phenomenological model derived from molecular dynamic simulation data, which successfully captures the important physics of the complex failure process. Length-scale and strain rate-dependent defect nucleation, growth, and fracture in single-walled carbon nanotubes with diameters in the range of 0.47 to 2.03 nm and length which is about 6.17 to 26.45 nm are simulated. Nanotubes with long length and small diameter show brittle fracture, while those with short length and large diameter show transition from ductile to brittle fracture. In short nanotubes with small diameters, we observe several structural transitions like Stone-Wales defect initiation, its propagation to larger void nucleation, formation of multiple chains of atoms, conversion to monatomic chain of atoms, and finally complete fracture of the carbon nanotube. Hybridization state of carbon-carbon bonds near the end cap evolves, leading to the formation of monatomic chain in short nanotubes with small diameter. Transition from ductile to brittle fracture is also observed when strain rate exceeds a critical value. A generalized analytical model of failure is established, which correlates the defect energy during the formation of atomic chain with aspect ratio of the nanotube and strain rate. Variation in the mechanical properties such as elastic modulus, tensile strength, and fracture strain with the size and strain rate shows important implications in mitigating force fields and ways to enhance the life of electronic devices and nanomaterial conversion via fracture in manufacturing.

  11. Peak power ratio generator

    Science.gov (United States)

    Moyer, R.D.

    A peak power ratio generator is described for measuring, in combination with a conventional power meter, the peak power level of extremely narrow pulses in the gigahertz radio frequency bands. The present invention in a preferred embodiment utilizes a tunnel diode and a back diode combination in a detector circuit as the only high speed elements. The high speed tunnel diode provides a bistable signal and serves as a memory device of the input pulses for the remaining, slower components. A hybrid digital and analog loop maintains the peak power level of a reference channel at a known amount. Thus, by measuring the average power levels of the reference signal and the source signal, the peak power level of the source signal can be determined.

  12. Transformer ratio studies for single bunch plasma wakefield acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Massimo, F., E-mail: francesco.massimo@uniroma1.it [Dipartimento SBAI, “Sapienza” University of Rome, Rome (Italy); Marocchino, A. [Dipartimento SBAI, “Sapienza” University of Rome, Rome (Italy); Chiadroni, E.; Ferrario, M. [INFN-LNF, Frascati (Italy); Mostacci, A. [Dipartimento SBAI, “Sapienza” University of Rome, Rome (Italy); INFN-LNF, Frascati (Italy); Musumeci, P. [University of California, Department of Physics and Astronomy, Los Angeles (United States); Palumbo, L. [Dipartimento SBAI, “Sapienza” University of Rome, Rome (Italy); INFN-LNF, Frascati (Italy)

    2014-03-11

    In Plasma Wakefield Acceleration (PWFA) plasma oscillations are driven by ultra relativistic electron beams. The ratio of the maximum accelerating field behind the driving beam (bunch) and the maximum decelerating field inside the driving beam (bunch) is defined as Transformer Ratio, a key parameter that determines the energy gain in particle acceleration. We investigate the transformer ratio for different shapes of a single driving bunch. One dimensional, fluid, relativistic, cold plasma equations have been numerically solved. A complete map of the transformer ratio is obtained by varying: bunch shape, bunch length and density ratio. It is found that the transformer ratio critically depends on the bunch shape and on the density ratio. Moreover both in the linear as well as in the non-linear regime the theoretical limit of 2 for the transformer ratio of a single symmetric bunch can be exceeded using asymmetric bunches in the linear regime as well as symmetric bunches in nonlinear regime.

  13. Aspect in Greek Future Forms

    DEFF Research Database (Denmark)

    Lucas, Sandra

    2014-01-01

    Medieval Greek had three future periphrases making use of a finite verb and an infinitive: μέλλω + INF, ἔχω + INF, θέλω + INF. Given the parallel nature of the periphrases as well as the fact that the infinitive existed in both a perfective and an imperfective version, it might be expected...... of the Modern Greek verbal system: μέλλω + INF has a much higher ratio of imperfective infinitives than the two other periphrases especially in AD I, ἔχω + INF starts out using only the perfective infinitive when referring to the future, and θέλω + INF distinguishes for aspect before it gains future meaning...

  14. A study of damage zones or characteristic lengths as related to the fracture behavior of graphite/epoxy laminates

    Science.gov (United States)

    Yeow, Y. T.; Brinson, H. F.

    1977-01-01

    Uniaxial tensile tests conducted on a variety of graphite/epoxy laminates, containing narrow rectangular slits, square or circular holes with various aspect ratios are discussed. The techniques used to study stable crack or damage zone growth--namely, birefringence coatings, COD gages, and microscopic observations are discussed. Initial and final fracture modes are discussed as well as the effect of notch size and shape, and laminate type on the fracture process. Characteristic lengths are calculated and compared to each other using the point, average and inherent flaw theories. Fracture toughnesses are calculated by the same theories and compared to a boundary integral equation technique. Finite width K-calibration factors are also discussed.

  15. The Effect of Height, Wing Length, and Wing Symmetry on Tabebuia rosea Seed Dispersal

    Directory of Open Access Journals (Sweden)

    Yasmeen Moussa

    2014-12-01

    Full Text Available The relationship between the vertical drop height and the horizontal distance traveled (dispersal ratio was investigated for a sample of fifty Tabebuia rosea seeds by dropping the seeds from five heights ranging from 1.00 to 2.00 meters. The dispersal ratio was found to be a constant 0.16 m/m for these heights. The effects of total seed length and asymmetry of seed wings on dispersal ratio were also measured using separate samples of fifty Tabebuia rosea seeds. It was found that neither seed length nor asymmetry had a significant effect on the dispersal ratio.

  16. Energy Profit Ratio Compared

    International Nuclear Information System (INIS)

    Amano, Osamu

    2007-01-01

    We need more oil energy to take out oil under the ground. Limit resources make us consider other candidates of energy source instead of oil. Electricity shall be the main role more and more like electric vehicles and air conditioners so we should consider electricity generation ways. When we consider what kind of electric power generation is the best or suitable, we should not only power generation plant but whole process from mining to power generation. It is good way to use EPR, Energy Profit Ratio, to analysis which type is more efficient and which part is to do research and development when you see the input breakdown analysis. Electricity by the light water nuclear power plant, the hydrogen power plant and the geothermal power plant are better candidates from EPR analysis. Forecasting the world primly energy supply in 2050, it is said that the demand will be double of the demand in 2000 and the supply will not be able to satisfy the demand in 2050. We should save 30% of the demand and increase nuclear power plants 3.5 times more and recyclable energy like hydropower plants 3 times more. When the nuclear power plants are 3.5 times more then uranium peak will come and we will need breed uranium. I will analysis the EPR of FBR. Conclusion: A) the EPR of NPS in Japan is 17.4 and it is the best of all. B) Many countries will introduce new nuclear power plants rapidly may be 3.5 times in 2050. C) Uranium peak will happen around 2050. (author)

  17. Leukocyte Telomere Length and Cognitive Function in Older Adults

    Directory of Open Access Journals (Sweden)

    Emily Frith

    2018-04-01

    Full Text Available We evaluated the specific association between leukocyte telomere length and cognitive function among a national sample of the broader U.S. older adult population. Data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES were used to identify 1,722 adults, between 60-85 years, with complete data on selected study variables. DNA was extracted from whole blood via the LTL assay, which is administered using quantitative polymerase chain reaction to measure telomere length relative to standard reference DNA (T/S ratio. Average telomere length was recorded, with two to three assays performed to control for individual variability. The DSST (Digit Symbol Substitution Test was used to assess participant executive cognitive functioning tasks of pairing and free recall. Individuals were excluded if they had been diagnosed with coronary artery disease, congestive heart failure, heart attack or stroke at the baseline assessment. Leukocyte telomere length was associated with higher cognitive performance, independent of gender, race-ethnicity, physical activity status, body mass index and other covariates. In this sample, there was a strong association between LTL and cognition; for every 1 T/S ratio increase in LTL, there was a corresponding 9.9 unit increase in the DSST (β = 9.9; 95% CI: 5.6-14.2; P [JCBPR 2018; 7(1.000: 14-18

  18. Organisational aspects of care.

    Science.gov (United States)

    Bloomfield, Jacqueline; Pegram, Anne

    2015-03-04

    Organisational aspects of care, the second essential skills cluster, identifies the need for registered nurses to systematically assess, plan and provide holistic patient care in accordance with individual needs. Safeguarding, supporting and protecting adults and children in vulnerable situations; leading, co-ordinating and managing care; functioning as an effective and confident member of the multidisciplinary team; and managing risk while maintaining a safe environment for patients and colleagues, are vital aspects of this cluster. This article discusses the roles and responsibilities of the newly registered graduate nurse. Throughout their education, nursing students work towards attaining this knowledge and these skills in preparation for their future roles as nurses.

  19. Study of the Inception Length of Flow over Stepped Spillway Models ...

    African Journals Online (AJOL)

    The results showed that the inception (development) length increases as the unit discharge increases and it decreases with an increase in both stepped roughness height and chute angle. The ratio of the development length, in this study, to that of Bauer's was found to be 4:5. Finally, SMM-5 produced the least velocity of ...

  20. String matching with variable length gaps

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Vildhøj, Hjalte Wedel

    2012-01-01

    We consider string matching with variable length gaps. Given a string T and a pattern P consisting of strings separated by variable length gaps (arbitrary strings of length in a specified range), the problem is to find all ending positions of substrings in T that match P. This problem is a basic...