WorldWideScience

Sample records for aspect ratio

  1. Optimal aspect ratio of endocytosed spherocylindrical nanoparticle

    Science.gov (United States)

    Chen, Ying-Bing; Liu, Yan-Hui; Zeng, Yan; Mao, Wei; Hu, Lin; Mao, Zong-Liang; Xu, Hou-Qiang

    2015-02-01

    Recent simulations have demonstrated that bioparticle size and shape modulate the process of endocytosis, and studies have provided more quantitative information that the endocytosis efficiency of spherocylindrical bioparticles is decided by its aspect ratio. At the same time, the dimensions of the receptor-ligand complex have strong effects on the size-dependent exclusion of proteins within the cellular environment. However, these earlier theoretical works including simulations did not consider the effects of ligand-receptor complex dimension on the endocytosis process. Thus, it is necessary to resolve the effects of ligand-receptor complex dimension and determine the optimal aspect ratio of spherocylindrical bioparticles in the process of endocytosis. Accordingly, we proposed a continuum elastic model, of which the results indicate that the aspect ratio depends on the ligand-receptor complex dimension and the radius of the spherocylindrical bioparticle. This model provides a phase diagram of the aspect ratio of endocytosed spherocylindrical bioparticles, the larger aspect ratio of which appears in the phase diagram with increasing ligand density, and highlights the bioparticle design.

  2. 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

  3. High Aspect Ratio Semiconductor Heterojunction Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Redwing, Joan [Pennsylvania State Univ., University Park, PA (United States). Dept. of Material Science and Engineering; Mallouk, Tom [Pennsylvania State Univ., University Park, PA (United States). Dept. of Chemistry; Mayer, Theresa [Pennsylvania State Univ., University Park, PA (United States). Dept. of Electrical Engineering; Dickey, Elizabeth [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Wronski, Chris [Pennsylvania State Univ., University Park, PA (United States). Dept. of Electrical Engineering

    2013-05-17

    The project focused on the development of high aspect ratio silicon heterojunction (HARSH) solar cells. The solar cells developed in this study consisted of high density vertical arrays of radial junction silicon microwires/pillars formed on Si substrates. Prior studies have demonstrated that vertical Si wire/pillar arrays enable reduced reflectivity and improved light trapping characteristics compared to planar solar cells. In addition, the radial junction structure offers the possibility of increased carrier collection in solar cells fabricated using material with short carrier diffusion lengths. However, the high junction and surface area of radial junction Si wire/pillar array devices can be problematic and lead to increased diode leakage and enhanced surface recombination. This study investigated the use of amorphous hydrogenated Si in the form of a heterojunction-intrinsic-thin layer (HIT) structure as a junction formation method for these devices. The HIT layer structure has widely been employed to reduce surface recombination in planar crystalline Si solar cells. Consequently, it was anticipated that it would also provide significant benefits to the performance of radial junction Si wire/pillar array devices. The overall goals of the project were to demonstrate a HARSH cell with a HIT-type structure in the radial junction Si wire/pillar array configuration and to develop potentially low cost pathways to fabricate these devices. Our studies demonstrated that the HIT structure lead to significant improvements in the open circuit voltage (Voc>0.5) of radial junction Si pillar array devices compared to devices fabricated using junctions formed by thermal diffusion or low pressure chemical vapor deposition (LPCVD). In addition, our work experimentally demonstrated that the radial junction structure lead to improvements in efficiency compared to comparable planar devices for devices fabricated using heavily doped Si that had reduced carrier diffusion

  4. Achieving high aspect ratio wrinkles by modifying material network stress.

    Science.gov (United States)

    Chen, Yu-Cheng; Wang, Yan; McCarthy, Thomas J; Crosby, Alfred J

    2017-06-07

    Wrinkle aspect ratio, or the amplitude divided by the wavelength, is hindered by strain localization transitions when an increasing global compressive stress is applied to synthetic material systems. However, many examples from living organisms show extremely high aspect ratios, such as gut villi and flower petals. We use three experimental approaches to demonstrate that these high aspect ratio structures can be achieved by modifying the network stress in the wrinkle substrate. We modify the wrinkle stress and effectively delay the strain localization transition, such as folding, to larger aspect ratios by using a zero-stress initial wavy substrate, creating a secondary network with post-curing, or using chemical stress relaxation materials. A wrinkle aspect ratio as high as 0.85, almost three times higher than common values of synthetic wrinkles, is achieved, and a quantitative framework is presented to provide understanding the different strategies and predictions for future investigations.

  5. Deep Reactive Ion Etching for High Aspect Ratio Microelectromechanical Components

    DEFF Research Database (Denmark)

    Jensen, Søren; Yalcinkaya, Arda Deniz; Jacobsen, S.

    2004-01-01

    A deep reactive ion etch (DRIE) process for fabrication of high aspect ratio trenches has been developed. Trenches with aspect ratios exceeding 20 and vertical sidewalls with low roughness have been demonstrated. The process has successfully been used in the fabrication of silicon-on-insulator (SOI......) released comb drive based resonators and tunable capacitors for MEMS applications. Brief characterizations of the devices are presented....

  6. 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.

  7. Effects of finite aspect ratio on wind turbine airfoil measurements

    DEFF Research Database (Denmark)

    Kiefer, Janik; Miller, Mark A.; Hultmark, Marcus

    2016-01-01

    Wind turbines partly operate in stalled conditions within their operational cycle. To simulate these conditions, it is also necessary to obtain 2-D airfoil data in terms of lift and drag coefficients at high angles of attack. Such data has been obtained previously, but often at low aspect ratios...

  8. 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...

  9. 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...

  10. 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...

  11. 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.

  12. Method for fabricating high aspect ratio structures in perovskite material

    Science.gov (United States)

    Karapetrov, Goran T.; Kwok, Wai-Kwong; Crabtree, George W.; Iavarone, Maria

    2003-10-28

    A method of fabricating high aspect ratio ceramic structures in which a selected portion of perovskite or perovskite-like crystalline material is exposed to a high energy ion beam for a time sufficient to cause the crystalline material contacted by the ion beam to have substantially parallel columnar defects. Then selected portions of the material having substantially parallel columnar defects are etched leaving material with and without substantially parallel columnar defects in a predetermined shape having high aspect ratios of not less than 2 to 1. Etching is accomplished by optical or PMMA lithography. There is also disclosed a structure of a ceramic which is superconducting at a temperature in the range of from about 10.degree. K. to about 90.degree. K. with substantially parallel columnar defects in which the smallest lateral dimension of the structure is less than about 5 microns, and the thickness of the structure is greater than 2 times the smallest lateral dimension of the structure.

  13. 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....

  14. Instability of low viscosity elliptic jets with varying aspect ratio

    Science.gov (United States)

    Kulkarni, Varun

    2011-11-01

    In this work an analytical description of capillary instability of liquid elliptic jets with varying aspect ratio is presented. Linear stability analysis in the long wave approximation with negligible gravitational effects is employed. Elliptic cylindrical coordinate system is used and perturbation velocity potential substituted in the Laplace equation to yield Mathieu and Modified Mathieu differential equations. The dispersion relation for elliptical orifices of any aspect ratio is derived and validated for axisymmetric disturbances with m = 0, in the limit of aspect ratio, μ = 1 , i.e. the case of a circular jet. As Mathieu functions and Modified Mathieu function solutions converge to Bessel's functions in this limit the Rayleigh-Plateau instability criterion is met. Also, stability of solutions corresponding to asymmetric disturbances for the kink mode, m = 1 and flute modes corresponding to m >= 2 is discussed. Experimental data from earlier works is used to compare observations made for elliptical orifices with μ ≠ 1 . This novel approach aims at generalizing the results pertaining to cylindrical jets with circular cross section leading to better understanding of breakup in liquid jets of various geometries.

  15. 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

    2017-04-01

    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.

  16. High-aspect ratio magnetic nanocomposite polymer cilium

    Science.gov (United States)

    Rahbar, M.; Tseng, H. Y.; Gray, B. L.

    2014-03-01

    This paper presents a new fabrication technique to achieve ultra high-aspect ratio artificial cilia micro-patterned from flexible highly magnetic rare earth nanoparticle-doped polymers. We have developed a simple, inexpensive and scalable fabrication method to create cilia structures that can be actuated by miniature electromagnets, that are suitable to be used for lab-on-a chip (LOC) and micro-total-analysis-system (μ-TAS) applications such as mixers and flow-control elements. The magnetic cilia are fabricated and magnetically polarized directly in microfluidic channels or reaction chambers, allowing for easy integration with complex microfluidic systems. These cilia structures can be combined on a single chip with other microfluidic components employing the same permanently magnetic nano-composite polymer (MNCP), such as valves or pumps. Rare earth permanent magnetic powder, (Nd0.7Ce0.3)10.5Fe83.9B5.6, is used to dope polydimethylsiloxane (PDMS), resulting in a highly flexible M-NCP of much higher magnetization and remanence [1] than ferromagnetic polymers typically employed in magnetic microfluidics. Sacrificial poly(ethylene-glycol) (PEG) is used to mold the highly magnetic polymer into ultra high-aspect ratio artificial cilia. Cilia structures with aspect ratio exceeding 8:0.13 can be easily fabricated using this technique and are actuated using miniature electromagnets to achieve a high range of motion/vibration.

  17. Aspect ratio dependent cytotoxicity and antimicrobial properties of nanoclay.

    Science.gov (United States)

    Rawat, Kamla; Agarwal, Shweta; Tyagi, Aakriti; Verma, Anita K; Bohidar, H B

    2014-10-01

    Nanoclays may enter human body through various routes such as through the respiratory and gastrointestinal tract, skin, blood, etc. There is dearth of such studies evaluating the interaction of clay nanoparticles with human cells. In particular, the interaction of proteins and nucleic acids with nanoparticles of different aspect ratio remains a domain that is very poorly probed and understood. In the present study, we address the issue of cytotoxicity and antimicrobial attributes of two distinct nanoclay platelets namely, laponite (diameter = 25 nm and thickness = 1 nm) and montmorillonite (MMT, diameter = 300 nm and thickness = 1 nm), having different aspect ratio (25:1 vs 300:1). Cytotoxicity was assessed in both prokatyotes: Escherichia coli, eukaryotes-human embryonic kidney (HEK), and cervical cancer SiHa cell lines, and a comparative size-based analysis of the toxicity were made at different exposure time points by MTT assay. The antimicrobial activity of the nanoclays was evaluated by disc diffusion method (Kirbey-Bauer protocol). Laponite exhibited maximum efficacy as an antimicrobial agent against E. coli. Comparatively smaller size laponite could preferentially enter the cells, leading to relatively wider or larger zone of inhibition. On contradictory; laponite showed 74.67 % survival while MMT showed 89.02 % survival in eukaryotic cells at 0.00001 % (w/v) concentration. In summary, both MMT and laponite indicated cytotoxicity at 0.05 % concentration within 24 h of exposure on HEK and cervical cancer (SiHa) cell lines. The toxicity was possibly dependent on size, aspect ratio, and concentration.

  18. Alternative lithographic methods for variable aspect ratio vias

    Science.gov (United States)

    Schepis, Anthony R.

    The foundation of semiconductor industry has historically been driven by scaling. Device size reduction is enabled by increased pattern density, enhancing functionality and effectively reducing cost per chip. Aggressive reductions in memory cell size have resulted in systems with diminishing area between parallel bit/word lines. This affords an even greater challenge in the patterning of contact level features that are inherently difficult to resolve because of their relatively small area, a product of their two domain critical dimension image. To accommodate these trends there has been a shift toward the implementation of elliptical contact features. This empowers designers to maximize the use of free space between bit/word lines and gate stacks while preserving contact area; effectively reducing the minor via axis dimension while maintaining a patternable threshold in increasingly dense circuitry. It is therefore critical to provide methods that enhance the resolving capacity of varying aspect ratio vias for implementation in electronic design systems. This work separately investigates two unique, non-traditional lithographic techniques in the integration of an optical vortex mask as well as a polymer assembly system as means to augment ellipticity while facilitating contact feature scaling. This document affords a fundamental overview of imaging theory, details previous literature as to the technological trends enabling the resolving of contact features and demonstrates simulated & empirical evidence that the described methods have great potential to extend the resolution of variable aspect ratio vias using lithographic technologies.

  19. Specimen aspect ratio and light transmission in photoactive dental resins.

    Science.gov (United States)

    Hadis, Mohammed A; Shortall, Adrian C; Palin, William M

    2012-11-01

    To test the influence of specimen dimensions on light transmission and shrinkage strain properties of curing dental resins. Photocurable resin specimens (Bis-GMA/TEGDMA) with aspect ratios (AR) of 2 (4mm×2mm); 4 (4mm×1mm and 8mm×2mm); 8 (8mm×1mm); 12 (AR: 12mm×1mm); and 24 (12mm×0.5mm) were light cured. Light transmission and shrinkage-strain data were recorded throughout, and upper and lower surface hardness measurements were performed following cure. Light transmission was significantly affected by the specimen aspect ratio even at similar thicknesses (presin without photoinitiator, the lowest AR specimens showed a relative increase in transmission above 100% throughout curing, which was caused by specimen constraint. The extent of lower surface cure (as assessed by increasing hardness) was principally affected by cavity height and decreased for thicker specimens (presin-based restorations through depth. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. HAREM: high aspect ratio etching and metallization for microsystems fabrication

    Science.gov (United States)

    Sarajlic, Edin; Yamahata, Christophe; Cordero, Mauricio; Collard, Dominique; Fujita, Hiroyuki

    2008-07-01

    We report a simple bulk micromachining method for the fabrication of high aspect ratio monocrystalline silicon MEMS (microelectromechanical systems) in a standard silicon wafer. We call this two-mask microfabrication process high aspect ratio etching and metallization or HAREM: it combines double-side etching and metallization to create suspended micromechanical structures with electrically 'insulating walls' on their backside. The insulating walls ensure a proper electrical insulation between the different actuation and sensing elements situated on either fixed or movable parts of the device. To demonstrate the high potential of this simple microfabrication method, we have designed and characterized electrostatically actuated microtweezers that integrate a differential capacitive sensor. The prototype showed an electrical insulation better than 1 GΩ between the different elements of the device. Furthermore, using a lock-in amplifier circuit, we could measure the position of the moving probe with few nanometers resolution for a displacement range of about 3 µm. This work was presented in part at the 21st IEEE MEMS Conference (Tucson, AZ, USA, 13-17 January, 2008) (doi:10.1109/MEMSYS.2008.4443656).

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

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels B

    2013-01-01

    We have explored the use of mold coatings and optimized processing conditions to injection mold high aspect ratio nanostructures (height-to-width >1) in cyclic olefin copolymer (COC). Optimizing the molding parameters on uncoated nickel molds resulted in slight improvements in replication quality...... 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...... (FDTS) greatly enhanced the quality of replicated features, in particular at transient mold temperatures above Tg. Injection molding using the latter mold temperature regime resulted in a bimodal distribution of pillar heights, corresponding to either full or very poor replication of the individual...

  2. 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.

  3. Slope control on the aspect ratio of river basins

    Science.gov (United States)

    Castelltort, S.; Simpson, G.; Darrioulat, A.

    2009-04-01

    River networks and their drainage basins have attracted a large attention due to their remarkable statistical properties (1-5). For example, although fluvial networks patterns seem to be influenced by diverse geological and climatic processes, the river basins that enclose them appear to mirror each other faithfully. Basin area A and length L of rivers from around the world consistently scale following L=cAexp(h) (2) with h often close to 0.5 (and c a constant) suggesting that river basins are self-similar (1, 6). Likewise, the main river basins that drain linear mountain ranges consistently manifest similar length-width aspect ratios between 1 and 5 (7). These observations question how the interplay between climate and tectonics is reflected in landscapes, and they highlight the challenge of inverting modern landscape records to reveal previous climates and tectonics. The invariance of river basins aspect-ratio is puzzling when compared against observations at smaller spatial scales (Hack, US Geol. Surv. Prof. Pap. 294-B, (1957). 3.R. E. Horton, Geol. Soc. Am. Bull. 56, 275 (1945). 4.J. W. Kirchner, Geology 21, 591 (1993). 5.I. Rodriguez-Iturbe, A. Rinaldo, Fractal river basins: chance and self-organization. (1997). 6.D. R. Montgomery, W. E. Dietrich, Science 255, 826 (1992). 7.N. Hovius, Basin Res. 8, 29 (1996). 8.R. S. Parker, Hydrology Papers, Colorado State University 90, 58 (1977). 9.J. D. Pelletier, Geomorphology 53, 183 (2003). 10.Schumm, The Fluvial System. (John Wiley & Sons, New York, 1977), pp. 338. 11.G. D. H. Simpson, F. Schlunegger, J. Geophys. Res 108, 2300 (2003). 12.N. Schorghofer, D. H. Rothman, Geophys. Res. Lett. 29, 1633 (2002).

  4. 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.

  5. Design Optimization of a High Aspect Ratio Rigid/Inflatable Wing

    OpenAIRE

    Butt, Lauren Marie

    2011-01-01

    High aspect-ratio, long-endurance aircraft require different design modeling from those with traditional moderate aspect ratios. High aspect-ratio, long endurance aircraft are generally more flexible structures than the traditional wing; therefore, they require modeling methods capable of handling a flexible structure even at the preliminary design stage. This work describes a design optimization method for combining rigid and inflatable wing design. The design will take advantage of the ...

  6. 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.

  7. 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.

  8. 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...

  9. Relation between self-organized criticality and grain aspect ratio in granular piles

    NARCIS (Netherlands)

    Denisov, D.V.; Villanueva, Y. Y.; Lorincz-Nagy, K.; May, S.; Wijngaarden, R.J.

    2012-01-01

    We investigate experimentally whether self-organized criticality (SOC) occurs in granular piles composed of different grains, namely, rice, lentils, quinoa, and mung beans. These four grains were selected to have different aspect ratios, from oblong to oblate. As a function of aspect ratio, we

  10. Seasonal dependence of the urban heat island on the street canyon aspect ratio

    NARCIS (Netherlands)

    Theeuwes, N.E.; Steeneveld, G.J.; Ronda, R.J.; Heusinkveld, B.G.; Hove, van L.W.A.; Holtslag, A.A.M.

    2014-01-01

    In this paper we study the relation between the urban heat island (UHI) in the urban canyon and street geometry, in particular the aspect ratio. Model results and observations show that two counteracting processes govern the relation between the nocturnal UHI and the building aspect ratio: i.e.

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

    NARCIS (Netherlands)

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

    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

  12. 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

  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. 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...

  15. Three-dimensional numerical simulation of Marangoni instabilities in liquid bridges: influence of geometrical aspect ratio

    Science.gov (United States)

    Lappa, M.; Savino, R.; Monti, R.

    2001-05-01

    Oscillatory Marangoni convection in silicone oil-liquid bridges with different geometrical aspect ratios is investigated by three-dimensional and time-dependent numerical simulations, based on control volume methods in staggered cylindrical non-uniform grids. The three-dimensional oscillatory flow regimes are studied and compared with previous experimental and theoretical results. The results show that the critical wavenumber (m), related to the azimuthal spatio-temporal flow structure, is a monotonically decreasing function of the geometrical aspect ratio of the liquid bridge (defined as the ratio of length to diameter). For this function, a general correlation formula is found, which is in agreement with the previous experimental findings. The critical Marangoni number and the oscillation frequency are decreasing functions of the aspect ratio; however, the critical Marangoni number, based on the axial length of the bridge, does not change much with the aspect ratio. For each aspect ratio investigated, the onset of the instability from the axisymmetric steady state to the three-dimensional oscillatory one is characterized by the appearance of a standing wave regime that exhibits, after a certain time, a second transition to a travelling wave regime. The standing wave regime is more stable for lower aspect ratios since it lasts for a long time. This behaviour is explained on the basis of the propagation velocity of the disturbances in the liquid phase. For this velocity, a general correlation law is found as a function of the aspect ratio and of the Marangoni number. Copyright

  16. Augmented heat transfer in rectangular channels of narrow aspect ratios with rib turbulators

    Science.gov (United States)

    Han, J. C.; Ou, S.; Park, J. S.; Lei, C. K.

    1989-01-01

    The effects of the rib angle-of-attack on the distributions of the local heat transfer coefficient and on the friction factors in short rectangular channels of narrow aspect ratios with a pair of opposite rib-roughened walls are determined for Reynolds numbers from 10,000 to 60,000. The channel width-to-height ratios are 2/4 and 1/4; the corresponding rib angles-of-attack are 90, 60, 45, and 30 deg, respectively. The results indicate that the narrow-aspect-ratio channels give better heat transfer performance than the wide-aspect-ratio channels for a constant pumping power. Semiempirical friction and heat transfer correlations are obtained. The results can be used in the design of turbine cooling channels of narrow aspect ratios.

  17. 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.

  18. 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.

  19. 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

    Fabrication of ultra-high aspect ratio exchangeable and customizable tips for atomic force microscopy (AFM) using lateral focused ion beam (FIB) milling is presented. While on-axis FIB milling does allow high aspect ratio (HAR) AFM tips to be defined, lateral milling gives far better flexibility...... 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...

  20. 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.

  1. Nacre-mimetics with synthetic nanoclays up to ultrahigh aspect ratios

    National Research Council Canada - National Science Library

    Das, Paramita; Malho, Jani-Markus; Rahimi, Khosrow; Schacher, Felix H; Wang, Baochun; Demco, Dan Eugen; Walther, Andreas

    2015-01-01

    .... Here we demonstrate large progress of mechanical and functional properties of self-assembled polymer/nanoclay nacre-mimetics by using synthetic nanoclays with aspect ratios covering three orders in magnitude (25-3,500...

  2. 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.

  3. Template-mediated Synthesis of Hollow Microporous Organic Nanorods with Tunable Aspect Ratio

    Science.gov (United States)

    Li, Qingyin; Jin, Shangbin; Tan, Bien

    2016-01-01

    Hollow microporous organic nanorods (HMORs) with hypercrosslinked polymer (HCPs) shells were synthesized through emulsion polymerization followed by hypercrosslinking. The HMORs have tunable aspect ratios, high BET surface areas and monodispersed morphologies, showing good performance in gas adsorpion. PMID:27506370

  4. Approximate quasi-isodynamicity at a finite aspect ratio in a stellarator vacuum magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailov, M. I. [National Research Centre Kurchatov Institute (Russian Federation); Nührenberg, J., E-mail: Juergen.Nuehrenberg@ipp.mpg.de; Zille, R. [Max-Planck-Institut für Plasmaphysik (Germany)

    2015-12-15

    A stellarator vacuum field is found in which, at a finite aspect ratio (A ≈ 40), the contours of the second adiabatic invariant of nearly all particles reflected inside that surface are poloidally closed.

  5. Growth of large aspect ratio AuAg bimetallic nanowires on Si(110) substrate

    Science.gov (United States)

    Bhukta, Anjan; Guha, Puspendu; Satpati, Biswarup; Maiti, Paramita; Satyam, Parlapalli V.

    2017-06-01

    Large aspect ratio bimetallic nanowire structures comprise potential applications in areas such as higher catalytic activity and surface Raman enhancement spectroscopy (SERS) substrates. By using the highly anisotropic ultra-clean Si(110) surface and with initial growth of sub monolayer (ML) Ag on such surface, a high aspect ratio AuAg bimetallic nanostructures can be formed. We report on the formation of large aspect ratio (>7.2 ± 0.8) AuAg nanowires on ultra-clean Si(110) surfaces using 0.5 ML Ag followed by 3.0 ML Au using molecular beam epitaxy (MBE) at a growth temperature of 300 °C. Under similar growth conditions without pre-deposition of Ag and only with deposition of 3.0 ML of Au consequences smaller aspect ratio (2.1 ± 0.1) monometallic Au nanostructures. The enhancement in aspect ratio of the nanostructures is attributed to the formation of one dimensional Ag layer (prior to Au growth) and Au-Ag bimetallic intermixing at elevated temperature. Considering deposition of 3.0 ML Au, a regime of substrate temperature ≈ 270-330 °C is found to be optimum to growth some of high aspect ratio (>25.0) AuAg nanowires as well. Exterior of this regime, at lower temperature due to low mobility of the ad-atoms and at higher temperature due to probable inter-diffusion of Ag, such extremely high aspect ratio AuAg nanowires found to be infrequent to grow. For growth at substrate temperature 300 °C, mean aspect ratio of the AuAg nanostructures is gradually increased in accordance with Au thickness up to 3.0 ML due to preferential accumulation of ad-atoms (Au, Ag) along Si and thereafter reduces for adequate accumulation along Si .

  6. 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

  7. Growth of high aspect ratio ZnO nanorods by solution process: Effect of polyethyleneimine

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Han-Seok; Vaseem, Mohammad; Kim, Sang Gon; Im, Yeon-Ho [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Hahn, Yoon-Bong, E-mail: ybhahn@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2012-05-15

    High aspect ratio ZnO nanorods were grown vertically on ZnO seed layer deposited silicon, glass and polyimide substrates by a solution process at low-temperature using zinc nitrate hexahydrate and hexamethylenetetramine. We studied the effect of polyethlyeneimine (PEI) on the growth of ZnO nanorods. It was found that PEI has a prominent effect on controlling the aspect ratio of ZnO nanorods in solution. The morphological and photoluminescence properties of the ZnO nanorods were also examined with varying the growth temperature (60-90 Degree-Sign C). - Graphical abstract: With addition of polyehyleneimine (PEI) high aspect-ratio ZnO nanorods were grown. It is believed that during ZnO nanorods growth, protonized form of linear PEI molecules inhibits the lateral growth by being adsorbed on non-polar lateral planes. Thus the vertical growth is favored. Highlights: Black-Right-Pointing-Pointer A controlled growth of high aspect ratio ZnO nanorods on different substrates. Black-Right-Pointing-Pointer A prominent effect of polyethlyeneimine (PEI) on controlling the aspect ratio of ZnO nanorods in solution. Black-Right-Pointing-Pointer Precursor concentration and growth temperature effect for various aspect ratio ZnO nanorods.

  8. Aspect ratio dependence of heat transfer and large-scale flow in turbulent convection

    CERN Document Server

    Bailon-Cuba, Jorge; Schumacher, Joerg

    2010-01-01

    The heat transport and corresponding changes in the large-scale circulation (LSC) in turbulent Rayleigh-B\\'{e}nard convection are studied by means of three-dimensional direct numerical simulations as a function of the aspect ratio $\\Gamma$ of a closed cylindrical cell and the Rayleigh number $Ra$. For small and moderate aspect ratios, the global heat transfer law $Nu=A\\times Ra^{\\beta}$ shows a power law dependence of both fit coefficients $A$ and $\\beta$ on the aspect ratio. A minimum Nusselt number coincides with the point where the LSC undergoes a transition from a single-roll to a double-roll pattern. With increasing aspect ratio, we detect complex multi-roll LSC configurations. The aspect ratio dependence of the turbulent heat transfer for small and moderate $\\Gamma$ is in line with a varying amount of energy contained in the LSC, as quantified by the Proper Orthogonal Decomposition analysis. For $\\Gamma\\gtrsim 8$ the heat transfer becomes independent of the aspect ratio.

  9. 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.

  10. 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.

  11. Selecting the aspect ratio of a scatter plot based on its delaunay triangulation.

    Science.gov (United States)

    Fink, Martin; Haunert, Jan-Henrik; Spoerhase, Joachim; Wolff, Alexander

    2013-12-01

    Scatter plots are diagrams that visualize two-dimensional data as sets of points in the plane. They allow users to detect correlations and clusters in the data. Whether or not a user can accomplish these tasks highly depends on the aspect ratio selected for the plot, i.e., the ratio between the horizontal and the vertical extent of the diagram. We argue that an aspect ratio is good if the Delaunay triangulation of the scatter plot at this aspect ratio has some nice geometric property, e.g., a large minimum angle or a small total edge length. More precisely, we consider the following optimization problem. Given a set Q of points in the plane, find a scale factor s such that scaling the x-coordinates of the points in Q by s and the y-coordinates by 1=s yields a point set P(s) that optimizes a property of the Delaunay triangulation of P(s), over all choices of s. We present an algorithm that solves this problem efficiently and demonstrate its usefulness on real-world instances. Moreover, we discuss an empirical test in which we asked 64 participants to choose the aspect ratios of 18 scatter plots. We tested six different quality measures that our algorithm can optimize. In conclusion, minimizing the total edge length and minimizing what we call the 'uncompactness' of the triangles of the Delaunay triangulation yielded the aspect ratios that were most similar to those chosen by the participants in the test.

  12. Effects of aspect ratio of multi-walled carbon nanotubes on coal washery waste water treatment.

    Science.gov (United States)

    Aliyu, Ahmed; Kariim, Ishaq; Abdulkareem, Saka Ambali

    2017-11-01

    The dependency of adsorption behaviour on the aspect ratio of multi-walled carbon nanotubes (MWCNTs) has been explored. In this study, effect of growth temperature on yield and aspect ratio of MWCNTs by catalytic chemical vapour deposition (CCVD) method is reported. The result revealed that yield and aspect ratio of synthesised MWCNTs strongly depend on the growth temperature during CCVD operation. The resulting MWCNTs were characterized by High Resolution Transmission Electron Microscope (HRTEM), Dynamic Light Scattering (DLS) and X-ray diffraction (XRD) techniques to determine it diameter, hydrodynamic diameter and crystallinity respectively. Aspect ratio and length of the grown MWCNTs were determined from the HRTEM images with the hydrodynamic diameter using the modified Navier-Stokes and Stokes-Einstein equations. The effect of the prepared MWCNTs dosage were investigated on the Turbidity, Iron (Fe) and Lead (Pb) removal efficiency of coal washery effluent. The MWCNTs with higher length (58.17 μm) and diameter (71 nm) tend to show high turbidity and Fe removal, while MWCNTs with lower length (38.87 μm) and diameter (45 nm) tend to show high removal of Pb. Hence, the growth temperature during CCVD operation shows a great effluence on the aspect ratio of MWCNTs which determines it area of applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Microwave synthesis and photocatalytic activities of ZnO bipods with different aspect ratios

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Fazhe; Zhao, Zengdian [Analysis and Testing Center, Shandong University of Technology, Zibo 255100 (China); Qiao, Xueliang, E-mail: xuelqiao@163.com [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Tan, Fatang; Wang, Wei [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China)

    2016-02-15

    Highlights: • We synthesized linked ZnO nanorods by a facile microwave method. • The effect of reaction parameters on ZnO was investigated. • ZnO bipods with different aspect ratios were prepared. • The photocatalytic performance of ZnO bipods was evaluated. - Abstract: Linked ZnO nanorods have been successfully prepared via a facile microwave method without any post-synthesis treatment. The X-ray diffraction (XRD) patterns indicated the precursor had completely transformed into the pure ZnO crystal. The images of field emitting scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that linked ZnO nanorods consisted predominantly of ZnO bipods. The formation process of the ZnO bipods was clearly discussed. ZnO bipods with different aspect ratios have been obtained by tuning the concentrations of reagents and microwave power. Moreover, the photocatalytic performance of ZnO bipods with different aspect ratios for degradation of methylene blue was systematically evaluated. The results of photocatalytic experiments showed that the photocatalytic activity increased with the aspect ratios of ZnO bipods increased. The reason is that ZnO bipods with larger aspect ratio have higher surface area, which can absorb more MB molecules to react with ·OH radicals.

  14. Design of a vertical-axis wind turbine: how the aspect ratio affects the turbine’s performance

    National Research Council Canada - National Science Library

    Brusca, S; Lanzafame, R; Messina, M

    2014-01-01

    .... Since the aspect ratio variations of a vertical-axis wind turbine cause Reynolds number variations, any changes in the power coefficient can also be studied to derive how aspect ratio variations...

  15. Effect of tip vortices on flow over NACA4412 aerofoil with different aspect ratios

    Directory of Open Access Journals (Sweden)

    Genç Mustafa Serdar

    2016-01-01

    Full Text Available Effect of tip vortices on flow and laminar separation bubble over NACA4412 aerofoil at low Reynolds numbers and different angles of attack was investigated in detail by performing force and flow visualization via smoke wire technique. Experiments have been done at Reynolds number of 50000 and the wing model of aspect-ratio was 1 and 3, respectively. From the experimental results, the flow visualization results showed that tip vortices effect on the laminar separation bubble and the bubble reduces over the wing with low aspect ratio as the angle of attack increased. Moreover, it was noticed that stall angles decreased as aspect-ratio increased at the same Reynolds number.

  16. Inversion of spheroid particle size distribution in wider size range and aspect ratio range

    Directory of Open Access Journals (Sweden)

    Tang Hong

    2013-01-01

    Full Text Available The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.

  17. 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.

  18. Aspect Ratio Model for Radiation-Tolerant Dummy Gate-Assisted n-MOSFET Layout.

    Science.gov (United States)

    Lee, Min Su; Lee, Hee Chul

    2014-01-01

    In order to acquire radiation-tolerant characteristics in integrated circuits, a dummy gate-assisted n-type metal oxide semiconductor field effect transistor (DGA n-MOSFET) layout was adopted. The DGA n-MOSFET has a different channel shape compared with the standard n-MOSFET. The standard n-MOSFET has a rectangular channel shape, whereas the DGA n-MOSFET has an extended rectangular shape at the edge of the source and drain, which affects its aspect ratio. In order to increase its practical use, a new aspect ratio model is proposed for the DGA n-MOSFET and this model is evaluated through three-dimensional simulations and measurements of the fabricated devices. The proposed aspect ratio model for the DGA n-MOSFET exhibits good agreement with the simulation and measurement results.

  19. 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.

  20. 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.

  1. 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...

  2. Simple Systematic Synthesis of Periodic Mesoporous Organosilica Nanoparticles with Adjustable Aspect Ratios

    Directory of Open Access Journals (Sweden)

    Mohanty Paritosh

    2009-01-01

    Full Text Available Abstract One-dimensional periodic mesoporous organosilica (PMO nanoparticles with tunable aspect ratios are obtained from a chain-type molecular precursor octaethoxy-1,3,5-trisilapentane. The aspect ratio can be tuned from 2:1 to >20:1 simply by variation in the precursor concentration in acidic aqueous solutions containing constant amounts of triblock copolymer Pluronic P123. The mesochannels are highly ordered and are oriented parallel to the longitudinal axis of the PMO particles. No significant Si–C bond cleavage occurs during the synthesis according to29Si MAS NMR. The materials exhibit surface areas between 181 and 936 m2 g−1.

  3. Forced convection of low temperature nitrogen gas in rectangular channels with small aspect ratio

    Science.gov (United States)

    Mo, H. L.; Zhou, Y. X.; Zhu, T. Y.; Guo, T. W.

    2004-05-01

    Forced convection of low temperature (80-150 K) nitrogen gas flowing through rectangular channels with hydraulic diameters of 0.513-1.814 mm and aspect ratios of 0.013-0.048 has been investigated experimentally. Close attention was focused on the effects of channel depth and heat addition on the heat transfer and flow characteristics, the transition from laminar to turbulent flow and the existence of an optimum channel depth. A dimensionless heating number was adopted to characterize the heating effect. The experimental correlation developed for the Nusselt number shows that the heat addition is the most important effect, followed by the channel aspect ratio, Reynolds number and Prandtl number.

  4. Dissolvable base scaffolds allow tissue penetration of high-aspect-ratio flexible microneedles.

    Science.gov (United States)

    Yagi, Satoshi; Yamagiwa, Shota; Kubota, Yoshihiro; Sawahata, Hirohito; Numano, Rika; Imashioya, Tatsuya; Oi, Hideo; Ishida, Makoto; Kawano, Takeshi

    2015-09-16

    Microscale needle technology is important in electrophysiological studies, drug/chemical delivery systems, optogenetic applications, and so on. In this study, dissolvable needle-base scaffold realizes penetration of high-aspect-ratio flexible microneedles (e.g., 500 μm length) into biological tissues. This methodology, which is applicable to numerous high-aspect-ratio flexible microneedles, should reduce the invasiveness and provide safer tissue penetrations than conventional approaches. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Boundary layer suction through rectangular orifices: effects of aspect ratio and orientation

    Science.gov (United States)

    Van Buren, T.; Smits, A. J.; Amitay, M.

    2017-07-01

    The flow field generated by suction through a rectangular orifice within a laminar boundary layer is investigated using stereoscopic particle image velocimetry. For orifice aspect ratios of 6, 12, and 18, the impact of suction on the surrounding flow field appears to be self-similar, scaling with aspect ratio and suction velocity. Changing the orifice pitch angle had almost no impact on the surrounding boundary layer, but, as expected, changing the skew angle significantly altered the extent of the suction impact on the flow field.

  6. 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...

  7. 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 A numerical and experimental investigation was performed to study the dominant flow structures in the lee side of a cruciform wing–body configuration at supersonic speeds in the + orientation. The wings or strakes are of very low aspect ratio...

  8. Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios

    NARCIS (Netherlands)

    Ende, D.A. van den; Maier, R.A.; Neer, P.L.M.J. van; Zwaag, S. van der; Randall, C.A.; Groen, W.A.

    2013-01-01

    In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT - polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the

  9. A review on non-linear aeroelasticity of high aspect-ratio wings

    Science.gov (United States)

    Afonso, Frederico; Vale, José; Oliveira, Éder; Lau, Fernando; Suleman, Afzal

    2017-02-01

    Current economic constraints and environmental regulations call for design of more efficient aircraft configurations. An observed trend in aircraft design to reduce the lift induced drag and improve fuel consumption and emissions is to increase the wing aspect-ratio. However, a slender wing is more flexible and subject to higher deflections under the same operating conditions. This effect may lead to changes in dynamic behaviour and in aeroelastic response, potentially resulting in instabilities. Therefore, it is important to take into account geometric non-linearities in the design of high aspect-ratio wings, as well as having accurate computational codes that couple the aerodynamic and structural models in the presence of non-linearities. Here, a review on the state-of-the-art on non-linear aeroelasticity of high aspect-ratio wings is presented. The methodologies employed to analyse high aspect-ratio wings are presented and their applications discussed. Important observations from the state-of-the-art studies are drawn and the current challenges in the field are identified.

  10. Vibration analysis of low-aspect ratio rotating blade modeled as a ...

    African Journals Online (AJOL)

    Vibration analysis of a low-aspect ratio blade modeled as a plate is presented which uses MATLAB coded computer program. The analysis presented employs an accurate strain-displacement relationship based on the thin plate theory, known as the Kirchhoff - Lava hypothesis. The equation of motion of the blade is derived ...

  11. Crystallographic Silicon-Etching for Ultra-High Aspect-Ratio FinFET

    NARCIS (Netherlands)

    Jovanovic, V.; Suligoj, T.; Nanver, L.K.

    2008-01-01

    The fabrication process for the FinFET with ultra-high fin-height to fin-width aspect-ratio is presented. The processing is based on the crystallographic etching of (110) bulk silicon-wafers by TMAH to expose the vertical (111) planes. The nitride-spacers are used as the hard-mask for the

  12. Preload-responsive adhesion: effects of aspect ratio, tip shape and alignment

    NARCIS (Netherlands)

    Paretkar, D.; Kamperman, M.M.G.; Martina, D.; Zhao, J.; Creton, C.; Lindner, A.; Jagota, A.; McMeeking, R.; Arzt, E.

    2013-01-01

    We tested the adhesive response of polymer surfaces structured with arrays of cylindrical fibrils having diameters of 10–20 µm and aspect ratios 1–2.4. Fibrils had two different tip shapes of end-flaps and round edges. A preload-induced mechanical buckling instability of the fibrils was used to

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

    Energy Technology Data Exchange (ETDEWEB)

    Pon, Andy; Johnstone, Doug [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6 (Canada); Toala, Jesus A. [Instituto de Astrofisica de Andalucia, CSIC, Glorieta de la Astronomia s/n, E-18008, Granada (Spain); Vazquez-Semadeni, Enrique; Gomez, Gilberto C. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia Apartado Postal 3-72, 58090 Morelia, Michoacan (Mexico); Heitsch, Fabian, E-mail: arpon@uvic.ca, E-mail: Douglas.Johnstone@nrc-cnrc.gc.ca, E-mail: toala@iaa.es, E-mail: e.vazquez@crya.unam.mx, E-mail: g.gomez@crya.unam.mx, E-mail: fheitsch@unc.edu [Department of Physics and Astronomy, University of North Carolina Chapel Hill, CB 3255, Phillips Hall, Chapel Hill, NC 27599 (United States)

    2012-09-10

    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.

  14. 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...

  15. 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.

  16. The elastic relaxation energy and equilibrium aspect ratio of self-organized pyramidal quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Wangmin [College of Mechanical and Electrical Engineering, Zhejiang University of Technology, Hangzhou 310032 (China)], E-mail: wangminzhou@sohu.com; Cai Chengyu [College of Mechanical and Electrical Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Yin Shuyuan [College of Science, Zhejiang University of Technology, Hangzhou 310032 (China); Wang Chongyu [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2008-12-30

    The formation of dislocation-free three-dimensional island by heteroepitaxial growth of lattice-mismatched materials is used to produce quantum dots. The equilibrium shape of these islands results from the competition between surface and elastic energies. The system Ge/Si has been studied in detail. The elastic relaxation energy of the islands has been calculated within a continuum elasticity theory using finite element method, and the fitted function of relaxation factor with respect to aspect ratio, and functional relation between the aspect ratio and the volume of the deposited material when the epitaxial system is at equilibrium state has been obtained. The results obtained show that equilibrium aspect ration is increased with increasing QDs volume.

  17. 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

  18. Blade tip, finite aspect ratio, and dynamic stall effects on the Darrieus rotor

    Science.gov (United States)

    Paraschivoiu, I.; Desy, P.; Masson, C.

    1988-02-01

    The objective of the work described in this paper was to apply the Boeing-Vertol dynamic stall model in an asymmetric manner to account for the asymmetry of the flow between the left and right sides of the rotor. This phenomenon has been observed by the flow visualization of a two-straight-bladed Darrieus rotor in the IMST water tunnel. Also introduced into the aerodynamic model are the effects of the blade tip and finite aspect ratio on the aerodynamic performance of the Darrieus wind turbine. These improvements are compatible with the double-multiple-streamtube model and have been included in the CARDAAV computer code for predicting the aerodynamic performance. Very good agreement has been observed between the test data (Sandia 17 m) and theoretical predictions; a significant improvement over the previous dynamic stall model was obtained for the rotor power at low tip speed ratios, while the inclusion of the finite aspect ratio effects enhances the prediction of the rotor power for high tip speed ratios. The tip losses and finite aspect ratio effects were also calculated for a small-scale vertical-axis wind turbine, with a two-straight-bladed (NACA 0015) rotor.

  19. J* optimization of small aspect ratio stellarator/tokamak hybrid devices

    Energy Technology Data Exchange (ETDEWEB)

    Spong, D.A.; Hirshman, S.P.; Whitson, J.C. [and others

    1997-12-31

    A new class of low aspect ratio toroidal hybrid stellarators is found using more general plasma confinement optimization criterion than quasi-symmetrization. The plasma current profile and shape of the outer magnetic flux surface are used as control variables to achieve near constancy of the longitudinal invariant J* on internal flux surfaces (quasi-omnigeneity), in addition to a number of other desirable physics target properties. We find that a range of compact (small aspect ratio A), high {beta} (ratio of thermal energy to magnetic field energy), low plasma current devices exist which have significantly improved confinement both for thermal as well as energetic (collisionless) particle components. With reasonable increases in magnetic field and geometric size, such devices can also be scaled to confine 3.5 MeV alpha particle orbits.

  20. Flutter analysis of hybrid metal-composite low aspect ratio trapezoidal wings in supersonic flow

    Directory of Open Access Journals (Sweden)

    Shokrollahi Saeed

    2017-02-01

    Full Text Available An effective 3D supersonic Mach box approach in combination with non-classical hybrid metal-composite plate theory has been used to investigate flutter boundaries of trapezoidal low aspect ratio wings. The wing structure is composed of two main components including aluminum material (in-board section and laminated composite material (out-board section. A global Ritz method is used with simple polynomials being employed as the trial functions. The most important objective of the present research is to study the effect of composite to metal proportion of hybrid wing structure on flutter boundaries in low supersonic regime. In addition, the effect of some important geometrical parameters such as sweep angle, taper ratio and aspect ratio on flutter boundaries were studied. The results obtained by present approach for special cases like pure metallic wings and results for high supersonic regime based on piston theory show a good agreement with those obtained by other investigators.

  1. 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

  2. Auxiliary drying to prevent pattern collapse in high aspect ratio nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu Gang; Zhou Jie; Xiong Ying; Zhang Xiaobo; Tian Yangchao, E-mail: liugang@ustc.edu.cn [National Synchrotron Radiation Laboratory (NSRL), University of Science and Technology of China, Hefei, Anhui 230029 (China)

    2011-07-29

    Many defects are generated in densely packed high aspect ratio structures during nanofabrication. Pattern collapse is one of the serious problems that may arise, mainly due to the capillary force during drying after the rinsing process. In this paper, a method of auxiliary drying is presented to prevent pattern collapse in high aspect ratio nanostructures by adding an auxiliary substrate as a reinforcing rib to restrict deformation and to balance the capillary force. The principle of the method is presented based on the analysis of pattern collapse. A finite element method is then applied to analyze the deformation of the resist beams caused by the surface tension using the ANSYS software, and the effect of the nanostructure's length to width ratio simulated and analyzed. Finally, the possible range of applications based on the proposed method is discussed. Our results show that the aspect ratio may be increased 2.6 times without pattern collapse; furthermore, this method can be widely used in the removal of solvents in micro- and nanofabrication.

  3. Quantitative analysis of exfoliation and aspect ratio of calcium niobate platelets.

    Science.gov (United States)

    Gao, Hongsheng; Shori, Shailesh; Chen, Xiaoming; zur Loye, Hans-Conrad; Ploehn, Harry J

    2013-02-15

    This work employs tapping-mode AFM and dynamic light scattering (DLS) to investigate the effects of suspension composition (alkylammonium cation type, concentration) on the degree of exfoliation of a layered perovskite, calcium niobate (HCa(2)Nb(3)O(10), denoted as CNP). It is well known that in aqueous suspensions, tetrabutylammonium (TBA) cations intercalate CNP's layered structure, producing exfoliated platelets. This work shows that tetramethylammonium and tetraethylammonium cations do not produce significant levels of CNP exfoliation. However, TBA leads to complete exfoliation of CNP (>95%) in suspensions prepared with TBA:CNP ratios greater than 1:1. TGA and XRD data indicate that TBA uptake is limited by steric packing constraints. After depositing TBA-CNP platelets on mica surfaces for AFM imaging, quantitative image analysis provides the degree of exfoliation and distributions of platelet thickness, lateral size, and aspect ratio. The aspect ratio of TBA-CNP platelets has a lognormal distribution. Sedimentation of TBA-CNP suspensions under unit gravity removes unexfoliated particles from suspension, and centrifugation leads to differential sedimentation. The lateral size and aspect ratio of residual suspended TBA-CNP platelets decrease with increasing centrifugation speed. For all fractions of TBA-CNP platelets, the number-average lateral size from AFM agrees remarkably well with the effective spherical particle diameter measured by DLS. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Aspect-ratio dependence of transient Taylor vortices close to threshold

    Energy Technology Data Exchange (ETDEWEB)

    Manneville, Paul [Laboratoire d' Hydrodynamique, Ecole Polytechnique, Palaiseau (France); Czarny, Olivier [M2P2, UMR 6181 CNRS, Universites d' Aix-Marseille, I.M.T. La Jetee, Technopole de Chateau-Gombert, Marseilles Cedex 20 (France)

    2009-03-15

    We perform a detailed numerical study of transient Taylor vortices arising from the instability of cylindrical Couette flow with the exterior cylinder at rest for radius ratio {eta}=0.5 and variable aspect ratio {gamma}. The result of Abshagen et al. (J Fluid Mech 476:335-343, 2003) that onset transients apparently evolve on a much smaller time-scale than decay transients is recovered. It is shown to be an artefact of time scale estimations based on the Stuart-Landau amplitude equation which assumes frozen space dependence while full space-time dependence embedded in the Ginzburg-Landau formalism needs to be taken into account to understand transients already at moderate aspect ratio. Sub-critical pattern induction is shown to explain the apparently anomalous behaviour of the system at onset while decay follows the Stuart-Landau prediction more closely. The dependence of time scales on boundary effects is studied for a wide range of aspect ratios, including non-integer ones, showing general agreement with the Ginzburg-Landau picture able to account for solutions modulated by Ekman pumping at the disks bounding the cylinders. (orig.)

  5. Enhanced nucleation rate of polylactide in composites assisted by surface acid oxidized carbon nanotubes of different aspect ratios.

    Science.gov (United States)

    Xu, Zhaohua; Niu, Yanhua; Wang, Zhigang; Li, Heng; Yang, Liang; Qiu, Jie; Wang, Howard

    2011-09-01

    Biodegradable polylactide (PLA) composites added with acid oxidized multiwalled carbon nanotubes (A-MWCNTs) of two different aspect ratios (length to diameter) were prepared by coagulation. The aspect ratios and surface structures of A-MWCNTs were characterized by TGA, Raman, and SEM measurements. The percolation thresholds for gelation in the PLA composites with A-MWCNTs of large and small aspect ratios are 2.5 and 4.0 wt %, respectively, which were determined by a rheological method, and in turn, the rheological result confirms the aspect ratio differences for the added two types of A-MWCNTs in the composites. Isothermal crystallization kinetics of neat PLA and its composites were further investigated by using polarized optical microscope (POM) and differential scanning calorimetry (DSC) to clarify the effects of A-MWCNTs of different aspect ratios and concentrations. The different aspect ratio A-MWCNTs with the same carboxyl group mass percent show substantial effects on PLA crystallization kinetics. Those with smaller aspect ratios enhance nucleation rate for PLA spherulites much more than those with larger aspect ratios. This phenomenon can be attributed to fewer sidewall carboxyl groups on the surfaces of A-MWCNTs with smaller aspect ratios, which provides more nucleation sites for PLA crystallization than those with larger aspect ratios at the same concentration, resulting in faster PLA nucleation rates for the former one.

  6. Thermal stability of mesoporous silica-coated gold nanorods with different aspect ratios

    Energy Technology Data Exchange (ETDEWEB)

    Gergely-Fülöp, Eszter, E-mail: fulop.eszter@ttk.mta.hu; Zámbó, Dániel, E-mail: zambo.daniel@ttk.mta.hu; Deák, András, E-mail: deak.andras@ttk.mta.hu

    2014-12-15

    The effect of different temperatures (up to 900 °C) on the morphology of mesoporous silica-coated gold nanorods was systematically investigated. Gold nanorods with different aspect ratios (AR ranging from 2.5 to 4.3) were coated with a 15 nm thick mesoporous silica shell. Silicon supported monolayers of the particles were annealed in the temperature range of 300–900 °C. The resulting changes in particle morphology were investigated using scanning electron microscopy and visible wavelength extinction spectroscopy. The silica coating generally improved the stability of the nanorods from ca. 250 °C by several hundreds degree Celsius. For nanorods with AR < 3 the shape and the aspect ratio change is only moderate up to 700 °C. At 900 °C these nanorods became spherical. For nanorods with AR>3, lower stability was found as the aspect ratio decrease was more significant and they transformed into spherical particles already at 700 °C. It was confirmed by investigating empty silica shells that the observed conformal change of the shell material when annealing core/shell particles is dictated by the deformation of the core particle. This also implies that a significant mechanical stress is exerted on the shell upon core deformation. In accordance with this, for the highest aspect ratio (AR ∼ 4) nanorod the shell breaks up at 900 °C and the gold cores were partially released and coalesced into large spherical particles. - Highlights: • Deformation of mesoporous silica-coated gold nanorods upon annealing up to 900 °C. • The silica shell protects the gold cores from turning into spheres up to 500 °C. • Decreasing thermal stability with increasing aspect ratio. • Deformation of the silica shell dictated by the shape change of the gold core. • Core induced break-up of the shell for high aspect ratio nanorods.

  7. Fabrication of high aspect ratio X-ray grating using silicon dry etching method

    Science.gov (United States)

    Noda, Daiji; Tokuoka, Atsushi; Hattori, Tadashi

    2012-07-01

    We have fabricated the high aspect ratio X-ray gratings for X-ray phase imaging. Silicon dry etching technology makes it possible to fabricate rectangular structures by repeating two steps of etching process and protection process. Then, we introduce the ability of Si dry etching technology in order to fabricate un-tapered, high precision Si microstructures containing rectangular patterns for X-ray grating. Au electroforming was realized from the bottom of the Si microstructure groove using sidewall protection method. In these technologies, we succeeded in fabricating about 40 μm thick, void-free Au structures in a space as narrow as 2.6 μm in large effective area of 60 mm squares on 4 inch Si wafer. Therefore, it is expected to be used in the production of a narrow pitch and higher aspect ratio microstructures such as X-ray gratings.

  8. Fabrication of high-aspect-ratio microgrooves using an electrochemical discharge micromilling process

    Science.gov (United States)

    Han, Min-Seop; Chae, Ki Woon; Min, Byung-Kwon

    2017-05-01

    In this study, we created high-aspect-ratio microgrooves in hard, brittle materials using an electrochemical discharge machining (ECDM) process by introducing microtextured machining tool. To enhance the electrical discharge activity, the morphology of the tool side surface was treated via micro-electrical discharge machining to produce fine microprotrusive patterns. The resulting microtextured surface morphology enhanced the electric field and played a key role in improving the step milling depth in the ECDM process. Using the FEM analysis, the evaluation of the field enhancement factor is also addressed. Our experimental investigation revealed microgrooves having an aspect ratio of 1:4, with high geometric accuracy and crack-free surfaces, using one-step ECDM.

  9. Effect of aerofoil aspect ratio on the slope of the lift curve

    Science.gov (United States)

    Diehl, Walter S

    1922-01-01

    On of the most important characteristics of an airfoil is the rate of change of lift with angle of attack, (sup dC)L/d alpha. This factor determines the effectiveness of a tail plane in securing static longitudinal stability. The application of the Gottingen formulas given here for calculating the variation of (sup Dc)L/d alpha with aspect ratio should be of interest to many aeronautical engineers. For the convenience of the engineer, a set of curves calculated by the method set forth here are given in graphical form. Also, the observed values of (sup dC)L/d alpha for the same airfoil at various aspect ratios follow the calculated curves closely.

  10. Convergence acceleration of implicit schemes in the presence of high aspect ratio grid cells

    Science.gov (United States)

    Buelow, B. E. O.; Venkateswaran, S.; Merkle, C. L.

    1993-07-01

    The performance of Navier-Stokes codes are influenced by several phenomena. For example, the robustness of the code may be compromised by the lack of grid resolution, by a need for more precise initial conditions or because all or part of the flowfield lies outside the flow regime in which the algorithm converges efficiently. A primary example of the latter effect is the presence of extended low Mach number and/or low Reynolds number regions which cause convergence deterioration of time marching algorithms. Recent research into this problem by several workers including the present authors has largely negated this difficulty through the introduction of time-derivative preconditioning. In the present paper, we employ the preconditioned algorithm to address convergence difficulties arising from sensitivity to grid stretching and high aspect ratio grid cells. Strong grid stretching is particularly characteristic of turbulent flow calculations where the grid must be refined very tightly in the dimension normal to the wall, without a similar refinement in the tangential direction. High aspect ratio grid cells also arise in problems that involve high aspect ratio domains such as combustor coolant channels. In both situations, the high aspect ratio cells can lead to extreme deterioration in convergence. It is the purpose of the present paper to address the reasons for this adverse response to grid stretching and to suggest methods for enhancing convergence under such circumstances. Numerical algorithms typically possess a maximum allowable or optimum value for the time step size, expressed in non-dimensional terms as a CFL number or vonNeumann number (VNN). In the presence of high aspect ratio cells, the smallest dimension of the grid cell controls the time step size causing it to be extremely small, which in turn results in the deterioration of convergence behavior. For explicit schemes, this time step limitation cannot be exceeded without violating stability restrictions

  11. 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.

  12. An implicit wetting and drying approach for non-hydrostatic flows in high aspect ratio domains

    CERN Document Server

    Candy, Adam S

    2013-01-01

    A wetting and drying approach for free surface flows governed by the three-dimensional, non-hydrostatic Navier-Stokes equations in high aspect ratio domains is developed. This has application in the modelling of inundation processes in geophysical domains, where dynamics takes place over a large horizontal extent relative to vertical resolution, such as in the evolution of a tsunami, or an urban fluvial flooding scenario. The approach is novel in that it solves for three dimensional dynamics in these very high aspect ratio domains, to include non-hydrostatic effects and accurately model dispersive processes. These become important in shallow regions with steep gradients, a particularly acute problem where man-made structures exist such as buildings or flood defences in an urban environment. It is implicit in time to allow efficient time integration over a range of mesh element sizes. Specific regularisation methods are introduced to improve conditioning of the full three-dimensional pressure Poisson problem i...

  13. Fabrication of a Polymer High-Aspect-Ratio Pillar Array Using UV Imprinting

    Directory of Open Access Journals (Sweden)

    Jun Mizuno

    2013-04-01

    Full Text Available This paper presents UV imprinting methods for fabricating a high-aspect-ratio pillar array. A polydimethylsiloxane (PDMS mold was selected as the UV imprinting mold. The pillar pattern was formed on a 50 × 50 mm2 area on a polyethylene terephthalate (PET film without remarkable deformation. The aspect ratios of the pillar and space were about four and ten, respectively. The mold was placed into contact with a UV-curable resin under a reduced pressure, and the resin was cured by UV light irradiation after exposure to atmospheric pressure. The PDMS mold showed good mold releasability and high flexibility. By moderately pressing the mold before UV-curing, the thickness of the residual layer of the imprinted resin was reduced and the pattern was precisely imprinted. Both batch pressing and roll pressing are available.

  14. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting [Ventura, CA

    2011-04-26

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  15. 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

    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......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...... investigations. The experimental positions of these recirculation zones corresponded well to the numerical predictions. Based on this work, a map of the flow for the different aspect ratios was developed, which can be particularly interesting for the design of experimental devices involving axisymmetrical flow....

  16. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting

    2013-08-13

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  17. 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...... of pyrolysed carbon films with increased film resistance due to oxidation during storage....

  18. Alternative method for variable aspect ratio vias using a vortex mask

    Science.gov (United States)

    Schepis, Anthony R.; Levinson, Zac; Burbine, Andrew; Smith, Bruce W.

    2014-03-01

    Historically IC (integrated circuit) device scaling has bridged the gap between technology nodes. Device size reduction is enabled by increased pattern density, enhancing functionality and effectively reducing cost per chip. Exemplifying this trend are aggressive reductions in memory cell sizes that have resulted in systems with diminishing area between bit/word lines. This affords an even greater challenge in the patterning of contact level features that are inherently difficult to resolve because of their relatively small area and complex aerial image. To accommodate these trends, semiconductor device design has shifted toward the implementation of elliptical contact features. This empowers designers to maximize the use of free device space, preserving contact area and effectively reducing the via dimension just along a single axis. It is therefore critical to provide methods that enhance the resolving capacity of varying aspect ratio vias for implementation in electronic design systems. Vortex masks, characterized by their helically induced propagation of light and consequent dark core, afford great potential for the patterning of such features when coupled with a high resolution negative tone resist system. This study investigates the integration of a vortex mask in a 193nm immersion (193i) lithography system and qualifies its ability to augment aspect ratio through feature density using aerial image vector simulation. It was found that vortex fabricated vias provide a distinct resolution advantage over traditionally patterned contact features employing a 6% attenuated phase shift mask (APM). 1:1 features were resolvable at 110nm pitch with a 38nm critical dimension (CD) and 110nm depth of focus (DOF) at 10% exposure latitude (EL). Furthermore, iterative source-mask optimization was executed as means to augment aspect ratio. By employing mask asymmetries and directionally biased sources aspect ratios ranging between 1:1 and 2:1 were achievable, however, this

  19. Strong geographical variation in wing aspect ratio of a damselfly, Calopteryx maculata (Odonata: Zygoptera

    Directory of Open Access Journals (Sweden)

    Christopher Hassall

    2015-08-01

    Full Text Available Geographical patterns in body size have been described across a wide range of species, leading to the development of a series of fundamental biological rules. However, shape variables are less well-described despite having substantial consequences for organism performance. Wing aspect ratio (AR has been proposed as a key shape parameter that determines function in flying animals, with high AR corresponding to longer, thinner wings that promote high manoeuvrability, low speed flight, and low AR corresponding to shorter, broader wings that promote high efficiency long distance flight. From this principle it might be predicted that populations living in cooler areas would exhibit low AR wings to compensate for reduced muscle efficiency at lower temperatures. I test this hypothesis using the riverine damselfly, Calopteryx maculata, sampled from 34 sites across its range margin in North America. Nine hundred and seven male specimens were captured from across the 34 sites (mean = 26.7 ± 2.9 SE per site, dissected and measured to quantify the area and length of all four wings. Geometric morphometrics were employed to investigate geographical variation in wing shape. The majority of variation in wing shape involved changes in wing aspect ratio, confirmed independently by geometric morphometrics and wing measurements. There was a strong negative relationship between wing aspect ratio and the maximum temperature of the warmest month which varies from west-east in North America, creating a positive relationship with longitude. This pattern suggests that higher aspect ratio may be associated with areas in which greater flight efficiency is required: regions of lower temperatures during the flight season. I discuss my findings in light of research of the functional ecology of wing shape across vertebrate and invertebrate taxa.

  20. Nanoscale-Tipped High-Aspect-Ratio Vertical Microneedle Electrodes for Intracellular Recordings.

    Science.gov (United States)

    Kubota, Yoshihiro; Oi, Hideo; Sawahata, Hirohito; Goryu, Akihiro; Ando, Yoriko; Numano, Rika; Ishida, Makoto; Kawano, Takeshi

    2016-06-01

    Intracellular recording nanoscale electrode devices provide the advantages of a high spatial resolution and high sensitivity. However, the length of nanowire/nanotube-based nanoelectrodes is currently limited to fabrication issues for high-aspect-ratio nanoelectrodes. The concept reported here can address the technological limitations by fabricating >100 μm long nanoscale-tipped electrodes, which show intracellular recording capability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

  2. Additive-free hydrothermal synthesis of high aspect ratio ZnO particles from aqueous solution

    OpenAIRE

    Elen, Ken; van Bael, Marlies; Van den Rul, Heidi; D'Haen, Jan; MULLENS, Jules

    2006-01-01

    In this work, a new hydrothermal process is described, in which, for the first time, an aquatic Zn2+ precursor is used for the synthesis of high aspect ratio ZnO particles, without the presence of any organic additive. Characterization of the particles is carried out by XRD, TEM, and SAED. Also the influence of different reaction times and of another reaction medium on the morphology and the dimensions of the rods is investigated.

  3. Design and Analyses of High Aspect Ratio Nozzles for Distributed Propulsion Acoustic Measurements

    Science.gov (United States)

    Dippold, Vance F., III

    2016-01-01

    A series of three convergent, round-to-rectangular high aspect ratio (HAR) nozzles were designed for acoustic testing at the NASA Glenn Research Center Nozzle Acoustic Test Rig (NATR). The HAR nozzles had exit area aspect ratios of 8:1, 12:1, and 16:1. The nozzles were designed to mimic a distributed propulsion system array with a slot nozzle. The nozzle designs were screened using Reynolds-Averaged Navier-Stokes (RANS) simulations. In addition to meeting the geometric constraints required for testing in the NATR, the HAR nozzles were designed to be free of flow features that would produce unwanted noise (e.g., flow separations) and to have uniform flow at the nozzle exit. Multiple methods were used to generate HAR nozzle designs. The final HAR nozzle designs were generated in segments using a computer code that parameterized each segment. RANS screening simulations showed that intermediate nozzle designs suffered flow separation, a normal shockwave at the nozzle exit (caused by an aerodynamic throat produced by boundary layer growth), and non-uniform flow at the nozzle exit. The RANS simulations showed that the final HAR nozzle designs were free of flow separations, but were not entirely successful at producing a fully uniform flow at the nozzle exit. The final designs suffered a pair of counter-rotating vortices along the outboard walls of the nozzle. The 16:1 aspect ratio HAR nozzle had the least uniform flow at the exit plane; the 8:1 aspect ratio HAR nozzles had a fairly uniform flow at the nozzle exit plane.

  4. 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.

  5. 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.

  6. Invariant Imbedded T-Matrix Method for Axial Symmetric Hydrometeors with Extreme Aspect Ratios

    Science.gov (United States)

    Pelissier, Craig; Kuo, Kwo-Sen; Clune, Thomas; Adams, Ian; Munchak, Stephen

    2017-01-01

    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.

  7. The effect of different aspect ratio and bottom heat flux towards contaminant removal using numerical analysis

    Science.gov (United States)

    Saadun, M. N. A.; Nor Azwadi, C. S.; Malek, Z. A. A.; Manaf, M. Z. A.; Zakaria, M. S.; Hafidzal, M. H. M.

    2013-12-01

    Cubic Interpolated Pseudo-particle (CIP) numerical simulation scheme has been anticipated to predict the interaction involving fluids and solid particles in an open channel with rectangular shaped cavity flow. The rectangular shaped cavity is looking by different aspect ratio in modelling the real pipeline joints that are in a range of sizes. Various inlet velocities are also being applied in predicting various fluid flow characteristics. In this paper, the constant heat flux is introduced at the bottom wall, showing the buoyancy effects towards the contaminant's removal rate. In order to characterize the fluid flow, the numerical scheme alone is initially tested and validated in a lid driven cavity with a single particle. The study of buoyancy effects and different aspect ratio of rectangular geometry were carried out using a MATLAB govern by Navier-Stokes equation. CIP is used as a model for a numerical scheme solver for fluid solid particles interaction. The result shows that the higher aspect ratio coupled with heated bottom wall give higher percentage of contaminant's removal rate. Comparing with the benchmark results has demonstrated the applicability of the method to reproduce fluid structure which is complex in the system. Despite a slight deviation of the formations of vortices from some of the literature results, the general pattern is considered to be in close agreement with those published in the literature.

  8. 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.

  9. Is aspect ratio sufficient to classify intra-aneurysmal hemodynamics- a parametric approach

    Science.gov (United States)

    Durka, Michael; Robertson, Anne

    2013-11-01

    Intracranial aneurysms are a vascular pathology in which a localized bulge is formed in the arterial wall, most often in a saccular shape. It is believed that the blood flow field within the aneurysm plays a critical role in the degradation of the wall. Aneurysm rupture has a high mortality risk. Since only a small fracture of aneurysms rupture, and common treatments have their own risks, it is desirable to identify a useful means of assessing rupture risk. Therefore, numerous groups have endeavored to identify a correlation between rupture risk and sac geometry or flow dynamics. However, no clinically useful parameters have been identified to date. Prior work has suggested that the aspect ratio (sac height/neck) could be useful for risk stratification due to its influence on the sac hemodynamics. In this work, we make of a previously developed parametric model of the aneurysm geometry to evaluate the influence of aspect ratio (sac height/sac neck) on flow dynamics, using computational fluid dynamics. In particular, we assess the influence of aspect ratio on the number of vortices in the aneurysm sac over a wide range of sac geometries. The conclusions obtained for the parametric model are then assessed in 20 clinical cases.

  10. 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.

  11. Nacre-mimetics with synthetic nanoclays up to ultrahigh aspect ratios

    Science.gov (United States)

    Das, Paramita; Malho, Jani-Markus; Rahimi, Khosrow; Schacher, Felix H.; Wang, Baochun; Demco, Dan Eugen; Walther, Andreas

    2015-01-01

    Nacre-mimetics hold great promise as mechanical high-performance and functional materials. Here we demonstrate large progress of mechanical and functional properties of self-assembled polymer/nanoclay nacre-mimetics by using synthetic nanoclays with aspect ratios covering three orders in magnitude (25-3,500). We establish comprehensive relationships among structure formation, nanostructuration, deformation mechanisms and mechanical properties as a function of nanoclay aspect ratio, and by tuning the viscoelastic properties of the soft phase via hydration. Highly ordered, large-scale nacre-mimetics are obtained even for low aspect ratio nanoplatelets and show pronounced inelastic deformation with very high toughness, while those formed by ultralarge nanoplatelets exhibit superb stiffness and strength, previously only reachable for highly crosslinked materials. Regarding functionalities, we report formerly impossible glass-like transparency, and excellent gas barrier considerably exceeding earlier nacre-mimetics based on natural nanoclay. Our study enables rational design of future high-performance nacre-mimetic materials and opens avenues for ecofriendly, transparent, self-standing and strong advanced barrier materials.

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

    Science.gov (United States)

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

    2013-07-01

    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.

  13. Jet Surface Interaction Scrubbing Noise from High Aspect-Ratio Rectangular Jets

    Science.gov (United States)

    Khavaran, Abbas; Bozak, Richard F.

    2015-01-01

    Concepts envisioned for the future of civil air transport consist of unconventional propulsion systems in the close proximity of the airframe. Distributed propulsion system with exhaust configurations that resemble a high aspect ratio rectangular jet are among geometries of interest. Nearby solid surfaces could provide noise shielding for the purpose of reduced community noise. Interaction of high-speed jet exhaust with structure could also generate new sources of sound as a result of flow scrubbing past the structure, and or scattered noise from sharp edges. The present study provides a theoretical framework to predict the scrubbing noise component from a high aspect ratio rectangular exhaust in proximity of a solid surface. The analysis uses the Greens function (GF) to the variable density Pridmore-Brown equation in a transversely sheared mean flow. Sources of sound are defined as the auto-covariance function of second-rank velocity fluctuations in the jet plume, and are modeled using a RANS-based acoustic analogy approach. Acoustic predictions are presented in an 8:1 aspect ratio rectangular exhaust at three subsonic Mach numbers. The effect of nearby surface on the scrubbing noise component is shown on both reflected and shielded sides of the plate.

  14. Extending the concept of weighted CT dose index to elliptical phantoms of various aspect ratios.

    Science.gov (United States)

    Markovich, Andrey; Morgan, Ashraf G; Dong, Frank F; Primak, Andrew N; Li, Xiang

    2017-07-01

    The purpose of this study was to extend the concept of weighted CT dose index ([Formula: see text]) to the elliptical phantoms. Based on the published body dimension data, eight body aspect ratios were chosen between 1 (perfectly circular) and 1.72 (extremely elliptical). For each aspect ratio, two elliptical cylinders were created digitally to represent adult and pediatric bodies. Their cross-sectional areas were identical to the standard 32- and 16-cm CTDI phantoms. For each phantom, [Formula: see text] at center and periphery were simulated for tube voltages between 70 and 140 kVp using a validated Monte Carlo program. The simulations also provided the average dose over the cross-sectional area, [Formula: see text]. Values of [Formula: see text] and [Formula: see text] allowed linear systems of equations to be established, from which central and peripheral weighting coefficients were solved. Regardless of phantom shape, only two weighting coefficients were needed: [Formula: see text] for the central [Formula: see text] and [Formula: see text] for the average of the four peripheral [Formula: see text]'s. Over the full range of aspect ratios, [Formula: see text] increased linearly from 0.37 to 0.46, whereas [Formula: see text] decreased linearly from 0.63 to 0.54, allowing the concept of [Formula: see text] to be readily extended to the elliptical phantoms. When cross-sectional area (hence volume) was kept constant, all phantoms had the same [Formula: see text] regardless of shape.

  15. 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.

  16. Microfabricated silicon high aspect ratio flexures for in-plane motion

    Science.gov (United States)

    Keller, Christopher Guild

    The major contribution of this thesis is the invention and development of high aspect ratio molded low pressure chemical vapor deposited (LPCVD) polysilicon, a new process known as hexsil. Historically there has been a need for methods to fabricate high aspect ratio (height/width) elastic flexures for controlled in-plane motion in silicon micromachining. This thesis uses three methods for fabricating high aspect ratio micromachined silicon flexures: (1) molded LPCVD polysilicon, (2) timed 2-sided bulk etching of (100) wafers, and (3) reactive ion etching. Flexures with aspect ratios of up to 20:1 have been made with the polysilicon molding process. Hexsil is a basic technology for the fabrication of micrometer to millimeter scale structures with reusable molds plasma etched in silicon wafers. This has been demonstrated with LPCVD polysilicon devices with lateral dimensions up to 9 mm by 3mm and vertical dimensions up to 200 mum with beam widths ranging from 2 mum to 24 mum. Molded milliscale structures have been used as the mechanical foundation for subsequent surface micromachined layers with micrometer scale features. The high aspect ratio honeycomb is a geometry that can be deposited as an economical thin film that allows large z dimensions while requiring only a few micrometers of conformal sidewall film deposition. Up to three different beam compositions have been integrated into the same device by using mold trenches of three different widths: electroless nickel filled beams for metallic conductivity, in-situ phosphorous doped polysilicon beams for resistive thermal expansion elements, and undoped polysilicon for the insulating body of the micromachine. Beams that deflect vertically after HF release were made by depositing two or more layers that have different values of residual stress. Polysilicon tubing was made using a 2-wafer mold. The design and fabrication of a microtweezer is described, and its use in micro pick and place operations is demonstrated

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    Science.gov (United States)

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

    2012-09-01

    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:HNO3:CH3COOH), 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.

  3. High-throughput microcapillary pump with efficient integrated low aspect ratio micropillars

    OpenAIRE

    Madadi, Hojjat; Casals Terré, Jasmina; Castilla López, Roberto; Sureda Anfres, Miquel

    2013-01-01

    Prediction and reduction of pressure drop and resistance flow in micropillar arrays are important for the design of microfluidic circuits used in different lab-on-a-chip and biomedical applications. In this work, a diamond microchannel-integrated micropillar pump (dMIMP) with a resistance flow 35.5 % lower than a circular-based micropillar pump (cMIMP) has been developed via the optimization of the fluid dynamic behavior of different pillar shapes in a low aspect ratio (H/D ranged from 0.06 t...

  4. Nanometer scale high-aspect-ratio trench etching at controllable angles using ballistic reactive ion etching

    Energy Technology Data Exchange (ETDEWEB)

    Cybart, Shane; Roediger, Peter; Ulin-Avila, Erick; Wu, Stephen; Wong, Travis; Dynes, Robert

    2012-11-30

    We demonstrate a low pressure reactive ion etching process capable of patterning nanometer scale angled sidewalls and three dimensional structures in photoresist. At low pressure the plasma has a large dark space region where the etchant ions have very large highly-directional mean free paths. Mounting the sample entirely within this dark space allows for etching at angles relative to the cathode with minimal undercutting, resulting in high-aspect ratio nanometer scale angled features. By reversing the initial angle and performing a second etch we create three-dimensional mask profiles.

  5. 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

  6. Crystallographic Silicon-Etching for Ultra-High Aspect-Ratio FinFET

    OpenAIRE

    Jovanovic, V.; Suligoj, T.; Nanver, L.K.

    2008-01-01

    The fabrication process for the FinFET with ultra-high fin-height to fin-width aspect-ratio is presented. The processing is based on the crystallographic etching of (110) bulk silicon-wafers by TMAH to expose the vertical (111) planes. The nitride-spacers are used as the hard-mask for the fin-etching and the fins are isolated by the planarization and etch-back of the thick isolation oxide. The demonstration devices exhibit nearly ideal S of 62-64 mV/dec and DIBL of 10 mV/V or lower, for the g...

  7. Fabrication of high-aspect-ratio hard x-ray zone plates with HSQ plating molds

    Science.gov (United States)

    Lu, Ming; Ocola, Leonidas E.; Divan, Ralu; Mancini, Derrick C.

    2008-08-01

    Fresnel zone plates are important x-ray diffractive optics which offer a focusing resolution approaching the theoretical limit. In hard x-ray region, the refractive indices of all the materials are close to unity, which requests thick zone plate to achieve a reasonable efficiency. It makes high-resolution zone plate extremely difficult to fabricate due to its high aspect ratio. We report a LIGA-like fabrication process employing e-beam resist HSQ as the plating mold material, which is relative simply compared with traditional processes. 1-μm-thick gold zone plates with 80-nm-wide outermost zone have been fabricated with this process.

  8. Fluid-Structure Interaction of Oscillating Low Aspect Ratio Wings at Low Reynolds Numbers

    Science.gov (United States)

    2010-03-01

    the University of Bath. The forced plunging motion of a rectangular wing (semi aspect ratio sAR=2) with NACA0012 cross-section was provided by a...oscillation frequency A previous study [6] on the aerodynamic performance of an oscillating two-dimensional NACA0012 profile, elicited the existence of...Figure 9 with the vortex shedding frequencies reported by Huang and Lin [8] using the same NACA0012 profile at Re=1.1×10 4 , albeit with a larger

  9. 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...... down the SAWvelocity because of mechanical energy storage. A finite model is furthermore employed to study the acousto-optical interaction and shows that it is possible to get a bigger change in effective refractive index with these surface acoustic waves compared to using conventional interdigital...

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

    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......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...

  15. 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.

  16. 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.

  17. Computational design of low aspect ratio wing-winglet configurations for transonic wind-tunnel tests

    Science.gov (United States)

    Kuhlman, John M.; Brown, Christopher K.

    1989-01-01

    Computational designs were performed for three different low aspect ratio wing planforms fitted with nonplanar winglets; one of the three configurations was selected to be constructed as a wind tunnel model for testing in the NASA LaRC 8-foot transonic pressure tunnel. A design point of M = 0.8, C(sub L) is approximate or = to 0.3 was selected, for wings of aspect ratio equal to 2.2, and leading edge sweep angles of 45 deg and 50 deg. Winglet length is 15 percent of the wing semispan, with a cant angle of 15 deg, and a leading edge sweep of 50 deg. Winglet total area equals 2.25 percent of the wing reference area. The design process and the predicted transonic performance are summarized for each configuration. In addition, a companion low-speed design study was conducted, using one of the transonic design wing-winglet planforms but with different camber and thickness distributions. A low-speed wind tunnel model was constructed to match this low-speed design geometry, and force coefficient data were obtained for the model at speeds of 100 to 150 ft/sec. Measured drag coefficient reductions were of the same order of magnitude as those predicted by numerical subsonic performance predictions.

  18. Comparison of Aspect Ratio Effects on Neoclassical Tearing Modes Between DIII-D and NSTX

    Science.gov (United States)

    La Haye, R. J.; Buttery, R. J.; Gerhardt, S. P.; Sabbagh, S. A.; Brennan, D. P.

    2010-11-01

    Experimental data is analyzed in which m/n=2/1 neoclassical tearing modes self-stabilized; this ``marginal point'' is valuable for evaluating the relative importance of the terms in the balanced Modified Rutherford equation. DIII-D and NSTX have similar cross-sectional area and shape except for the large difference in aspect ratio. The aspect ratio effects for NTMs explicitly occur in the MRE in the destabilizing helically perturbed bootstrap current term, in the small island stabilizing effects, and in the stabilizing curvature term. The marginal island width on NSTX at q95˜8 is about three times the ion banana width. This agrees with the q95˜4 data on DIII-D but is a larger multiple than for DIII-D at q95˜7. The balance in the MRE indicates that while the stabilizing effect of the curvature term in DIII-D is negligible, it is important in NSTX. The temporal behavior of the mode suggests NSTX operates closer to marginal classical tearing stability, but benefits from the stabilizing effect of curvature.

  19. Ultra-high aspect ratio high-resolution nanofabrication for hard X-ray diffractive optics

    Science.gov (United States)

    Chang, Chieh; Sakdinawat, Anne

    2014-06-01

    Although diffractive optics have played a major role in nanoscale soft X-ray imaging, high-resolution and high-efficiency diffractive optics have largely been unavailable for hard X-rays where many scientific, technological and biomedical applications exist. This is owing to the long-standing challenge of fabricating ultra-high aspect ratio high-resolution dense nanostructures. Here we report significant progress in ultra-high aspect ratio nanofabrication of high-resolution, dense silicon nanostructures using vertical directionality controlled metal-assisted chemical etching. The resulting structures have very smooth sidewalls and can be used to pattern arbitrary features, not limited to linear or circular. We focus on the application of X-ray zone plate fabrication for high-efficiency, high-resolution diffractive optics, and demonstrate the process with linear, circular, and spiral zone plates. X-ray measurements demonstrate high efficiency in the critical outer layers. This method has broad applications including patterning for thermoelectric materials, battery anodes and sensors among others.

  20. 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.

  1. Parametrization of the Gay-Berne potential for conjugated oligomer with a high aspect ratio.

    Science.gov (United States)

    Lee, Cheng K; Hua, Chi C; Chen, Show A

    2010-08-14

    The Gay-Berne (GB) potential has been a popular semiempirical model for describing the short-range intermolecular forces for a wide variety of aspherical molecules, including liquid crystals and anisotropic colloids, with generally small molecular dimensions and low aspect ratios (<5). This study evaluates the parametrization of the GB potential for a high-aspect-ratio (=10) oligomer belonging to a model conjugated polymer. We elaborate that the semiflexibility associated with a large oligomer species demands a variant umbrella-sampling scheme in establishing the potentials of mean force (PMFs) for four pair ellipsoid arrangements typically utilized to parametrize the GB potential. The model ellipsoid so constructed is shown to capture the PMFs of essential intermediate arrangements as well, and, according to the results of simplex optimizations, recommendations are given for the minimum set of parameters to be included in the optimization of a large oligomer or particulate species. To further attest the parametrized GB potential, the coarse-grained (CG) Monte Carlo simulations employing the GB potential and the back-mapped, full-atom atomistic molecular dynamics (AMD) simulations were performed for a dense oligomer system at two representative system temperatures. The results indicated that the CG simulations can capture, with exceptional computational efficiency, the AMD predictions with good thermal transferability. In future perspectives, we remark on potential applications to construct efficient, parameter-free CG models for capturing fundamental material properties of large oligomer/particulate species as well as long-chain conjugated polymers.

  2. 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.

  3. A modified atmospheric non-hydrostatic model on low aspect ratio grids: part II

    Directory of Open Access Journals (Sweden)

    Wen-Yih Sun

    2013-06-01

    Full Text Available Sun et al. (2012 proposed a modified non-hydrostatic model (MNH, in which the left-hand side of the continuity equation is multiplied by a parameter δ (4≤δ≤16 in the article to suppress high-frequency acoustic waves. They showed that the MNH allows a longer time step than the original non-hydrostatic model (NH. The MNH is also more accurate and efficient than the horizontal explicit and vertical implicit scheme (HE–VI when the aspect ratio (Δx/Δz is small. In addition to multiplying a parameter δ, here we propose to add a smoothing on the right-hand side of the continuity equation in the MNH to damp shortest sound waves. Linear stability analysis and non-linear model simulations show that the MNH with smoothing (henceforth abbreviated as MNHS can use twice the time interval of the MNH while maintaining the same accuracy. The MNHS is also more accurate and efficient than HE–VI when the aspect ratio is small.

  4. A modified atmospheric non-hydrostatic model on low aspect ratio grids

    Directory of Open Access Journals (Sweden)

    Wen-Yih Sun

    2012-04-01

    Full Text Available It is popular to use a horizontal explicit and a vertical implicit (HE-VI scheme in the compressible non-hydrostatic (NH model. However, when the aspect ratio becomes small, a small time-interval is required in HE-VI, because the Courant-Fredrich-Lewy (CFL criterion is determined by the horizontal grid spacing. Furthermore, simulations from HE-VI can depart from the forward–backward (FB scheme in NH even when the time interval is less than the CFL criterion allowed. Hence, a modified non-hydrostatic (MNH model is proposed, in which the left-hand side of the continuity equation is multiplied by a parameter δ (4≤δ≤16, in this study. When the linearized MNH is solved by FB (can be other schemes, the eigenvalue shows that MNH can suppress the frequency of acoustic waves very effectively but does not have a significant impact on the gravity waves. Hence, MNH enables to use a longer time step than that allowed in the original NH. When the aspect ratio is small, MNH solved by FB can be more accurate and efficient than the NH solved by HE-VI. Therefore, MNH can be very useful to study cloud, Large Eddy Simulation (LES, turbulence, flow over complex terrains, etc., which require fine resolution in both horizontal and vertical directions.

  5. Aqueous solution route to high-aspect-ratio zinc oxide nanostructures on indium tin oxide substrates.

    Science.gov (United States)

    Ku, Chen-Hao; Wu, Jih-Jen

    2006-07-06

    High-aspect-ratio ZnO nanowires and nanotubes are formed on indium tin oxide (ITO) substrates using a three-step route at low temperatures. The three steps, including successive ionic layer absorption and reaction (SILAR) deposition of the ZnO seed layer, hydrothermal annealing of the seed layer, and chemical bath deposition (CBD) of the one-dimensional (1D) ZnO nanostructures, are all conducted in aqueous solutions at temperatures below 120 degrees C. Both the hydrothermal annealing of the SILAR seed layer and the low-concentration precursor solution employed in the CBD process are crucial in order to synthesize the uniform and high-aspect-ratio ZnO nanostructures on the ITO substrate. TEM analyses reveal that both the nanowire and the nanotube possess the single-crystal structure and are grown along [001] direction. Room-temperature cathodoluminescence spectrum of the 1D ZnO nanostructures shows a sharp ultraviolet emission at 375 nm and a broad green-band emission.

  6. Superconformal Bottom-Up Gold Deposition in High Aspect Ratio Through Silicon Vias.

    Science.gov (United States)

    Josell, D; Moffat, T P

    2017-01-01

    This work presents superconformal, bottom-up Au filling of high aspect ratio through silicon vias (TSVs) along with a predictive framework based on the coupling of suppression breakdown and surface topography. The work extends a previous study of superconformal Au deposition in lower aspect ratio TSVs. Deposition was performed in a Na3AuSO3 electrolyte containing a branched polyethyleneimine (PEI) deposition-rate suppressing additive. Voltammetric measurements using a rotating disk electrode (RDE) were used to assess the impact of the PEI suppressor concentration and transport on the rate of metal deposition, enabling the interplay between metal deposition and suppressor adsorption to be quantified. The positive feedback associated with suppression breakdown gives rise to an S-shaped negative differential resistance (S-NDR). The derived kinetics for suppressor adsorption and consumption were used in a mass conservation model to account for bottom-up filling of patterned features. Predictions, including the impact of deposition potential and additive concentration on feature filling, are shown to match experimental results for filling of TSVs. This further generalizes the utility of the additive derived S-NDR model as a predictive formalism for identifying additives capable of generating localized, void-free filling of TSVs by electrodeposition.

  7. Fabrication of High-Aspect-Ratio 3D Hydrogel Microstructures Using Optically Induced Electrokinetics

    Directory of Open Access Journals (Sweden)

    Yi Li

    2016-04-01

    Full Text Available We present a rapid hydrogel polymerization and prototyping microfabrication technique using an optically induced electrokinetics (OEK chip, which is based on a non-UV hydrogel curing principle. Using this technique, micro-scale high-aspect-ratio three-dimensional polymer features with different geometric sizes can be fabricated within 1–10 min by projecting pre-defined visible light image patterns onto the OEK chip. This method eliminates the need for traditional photolithography masks used for patterning and fabricating polymer microstructures and simplifies the fabrication processes. This technique uses cross-link hydrogels, such as poly(ethylene glycol (PEG-diacrylate (PEGDA, as fabrication materials. We demonstrated that hydrogel micropillar arrays rapidly fabricated using this technique can be used as molds to create micron-scale cavities in PDMS (polydimethylsiloxane substrates. Furthermore, hollow, circular tubes with controllable wall thicknesses and high-aspect ratios can also be fabricated. These results show the potential of this technique to become a rapid prototyping technology for producing microfluidic devices. In addition, we show that rapid prototyping of three-dimensional suspended polymer structures is possible without any sacrificial etching process.

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

    Science.gov (United States)

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

    2015-08-01

    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 Au3+ 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.

  9. High aspect ratio sharp nanotip for nanocantilever integration at CMOS compatible temperature

    Science.gov (United States)

    Wang, P.; Michael, A.; Kwok, CY

    2017-08-01

    In this paper, we demonstrate a novel low temperature nanofabrication approach that enables the formation of ultra-sharp high aspect ratio (HAR) and high density nanotip structures and their integration onto nanoscale cantilever beams. The nanotip structure consists of a nanoscale thermally evaporated Cr Spindt tip on top of an amorphous silicon rod. An apex radius of the tip, as small as 2.5 nm, has been achieved, and is significantly smaller than any other Spindt tips reported so far. 100 nm wide tips with aspect ratio of more than 50 and tip density of more than 5 × 109 tips cm-2 have been fabricated. The HAR tips have been integrated onto an array of 460 nm wide cantilever beams with high precision and yield. In comparison with other approaches, this approach allows the integration of HAR sharp nanotips with nano-mechanical structures in a parallel and CMOS compatible fashion for the first time to our knowledge. Potential applications include on-chip high-speed atomic force microscopy and field emission devices.

  10. 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.

  11. 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.

  12. The Universal Aspect Ratio of Vortices in Rotating Stratifi?ed Flows: Experiments and Observations

    CERN Document Server

    Aubert, Oriane; Gal, Patrice Le; Marcus, Philip S

    2012-01-01

    We validate a new law for the aspect ratio $\\alpha = H/L$ of vortices in a rotating, stratified flow, where $H$ and $L$ are the vertical half-height and horizontal length scale of the vortices. The aspect ratio depends not only on the Coriolis parameter f and buoyancy (or Brunt-Vaisala) frequency $\\bar{N}$ of the background flow, but also on the buoyancy frequency $N_c$ within the vortex and on the Rossby number $Ro$ of the vortex such that $\\alpha = f \\sqrt{[Ro (1 + Ro)/(N_c^2- \\bar{N}^2)]}$. This law for $\\alpha$ is obeyed precisely by the exact equilibrium solution of the inviscid Boussinesq equations that we show to be a useful model of our laboratory vortices. The law is valid for both cyclones and anticyclones. Our anticyclones are generated by injecting fluid into a rotating tank filled with linearly-stratified salt water. The vortices are far from the top and bottom boundaries of the tank, so there is no Ekman circulation. In one set of experiments, the vortices viscously decay, but as they do, they c...

  13. Nacre-mimetic bulk lamellar composites reinforced with high aspect ratio glass flakes.

    Science.gov (United States)

    Guner, Selen N Gurbuz; Dericioglu, Arcan F

    2016-12-05

    Nacre-mimetic epoxy matrix composites reinforced with readily available micron-sized high aspect ratio C-glass flakes were fabricated by a relatively simple, single-step, scalable, time, cost and man-power effective processing strategy: hot-press assisted slip casting (HASC). HASC enables the fabrication of preferentially oriented two-dimensional inorganic reinforcement-polymer matrix bulk lamellar composites with a micro-scale structure resembling the brick-and-mortar architecture of nacre. By applying the micro-scale design guideline found in nacre and optimizing the relative volume fractions of the reinforcement and the matrix as well as by anchoring the brick-and-mortar architecture, and tailoring the interface between reinforcements and the matrix via silane coupling agents, strong, stiff and tough bio-inspired nacre-mimetic bulk composites were fabricated. As a result of high shear stress transfer lengths and effective stress transfer at the interface achieved through surface functionalization of the reinforcements, fabricated bulk composites exhibited enhanced mechanical performance as compared to neat epoxy. Furthermore, governed flake pull-out mode along with a highly torturous crack path, which resulted from extensive deflection and meandering of the advancing crack around well-aligned high aspect ratio C-glass flakes, have led to high work-of-fracture values similar to nacre.

  14. 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

  15. 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

  16. The Effect of Building Aspect Ratio on Energy Efficiency: A Case Study for Multi-Unit Residential Buildings in Canada

    Directory of Open Access Journals (Sweden)

    Philip McKeen

    2014-07-01

    Full Text Available This paper examines the energy consumption of varying aspect ratio in multi-unit residential buildings in Canadian cities. The aspect ratio of a building is one of the most important determinants of energy efficiency. It defines the building surface area by which heat is transferred between the interior and exterior environment. It also defines the amount of building area that is subject to solar gain. The extent to which this can be beneficial or detrimental depends on the aspect ratio and climate. This paper evaluates the relationship between the geometry of buildings and location to identify a design vernacular for energy-efficient designs across Canada.

  17. A small perturbation based optimization approach for the frequency placement of high aspect ratio wings

    Science.gov (United States)

    Goltsch, Mandy

    Design denotes the transformation of an identified need to its physical embodiment in a traditionally iterative approach of trial and error. Conceptual design plays a prominent role but an almost infinite number of possible solutions at the outset of design necessitates fast evaluations. The corresponding practice of empirical equations and low fidelity analyses becomes obsolete in the light of novel concepts. Ever increasing system complexity and resource scarcity mandate new approaches to adequately capture system characteristics. Contemporary concerns in atmospheric science and homeland security created an operational need for unconventional configurations. Unmanned long endurance flight at high altitudes offers a unique showcase for the exploration of new design spaces and the incidental deficit of conceptual modeling and simulation capabilities. Structural and aerodynamic performance requirements necessitate light weight materials and high aspect ratio wings resulting in distinct structural and aeroelastic response characteristics that stand in close correlation with natural vibration modes. The present research effort evolves around the development of an efficient and accurate optimization algorithm for high aspect ratio wings subject to natural frequency constraints. Foundational corner stones are beam dimensional reduction and modal perturbation redesign. Local and global analyses inherent to the former suggest corresponding levels of local and global optimization. The present approach departs from this suggestion. It introduces local level surrogate models to capacitate a methodology that consists of multi level analyses feeding into a single level optimization. The innovative heart of the new algorithm originates in small perturbation theory. A sequence of small perturbation solutions allows the optimizer to make incremental movements within the design space. It enables a directed search that is free of costly gradients. System matrices are decomposed

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

    DEFF Research Database (Denmark)

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

    2009-01-01

    that are strongly confined to the surface, causing a significant increase in the strain underneath the surface. A finite element method is employed to model the surface acoustic waves generated by a finite length IDT with 12 electrode pairs and subsequently to study their interaction with an optical wave......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...... propagating in a waveguide buried in the lithium niobate substrate supporting the electrodes. The interaction can be increased up to 600 times using these new types of surface acoustic waves as compared to using a conventional IDT with thin electrodes. This result could find applications in improved acousto...

  19. Large-area thermoelectric high-aspect-ratio nanostructures by atomic layer deposition

    Science.gov (United States)

    Ruoho, Mikko; Juntunen, Taneli; Tittonen, Ilkka

    2016-09-01

    We report on the thermoelectric properties of large-area high-aspect-ratio nanostructures. We fabricate the structures by atomic layer deposition of conformal ZnO thin films on track-etched polycarbonate substrate. The resulting structure consists of ZnO tubules which continue through the full thickness of the substrate. The electrical and thermal properties of the structures are studied both in-plane and out-of-plane. They exhibit very low out-of-plane thermal conductivity down to 0.15 W m-1 K-1 while the in-plane sheet resistance of the films was found to be half that of the same film on glass substrate, allowing material-independent doubling of output power of any planar thin-film thermoelectric generator. The wall thickness of the fabricated nanotubes was varied within a range of up to 100 nm. The samples show polycrystalline nature with (002) preferred crystal orientation.

  20. On the Lateral Static Stability of Low-Aspect-Ratio Rectangular Wings

    Science.gov (United States)

    Linehan, Thomas; Mohseni, Kamran

    2017-11-01

    Low-aspect-ratio rectangular wings experience a reduction in lateral static stability at angles of attack distinct from that of lift stall. Stereoscopic digital particle image velocimetry is used to elucidate the flow physics behind this trend. Rectangular wings of AR = 0.75, 1, 1.5, 3 were tested at side-slip angles β = -10° and 0° with angle of attack varied in the range α =10° -40° . In side-slip, the leading-edge separation region emerges on the leeward wing where leading-edge flow reattachment is highly intermittent due to vortex shedding. The tip vortex downwash of the AR flow underneath it. The downwash of the AR = 3 wing is insufficient to reattach the leading-edge flow at high incidence. The flow stalls on the leeward wing with stalled flow expanding upstream toward the windward wing with increasing angle of attack.

  1. 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.

  2. The Capabilities of Electrodischarge Microdrilling of High Aspect Ratio Holes in Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Skoczypiec Sebastian

    2015-09-01

    Full Text Available In the first part of the article the review of ceramic materials drilling possibilities was presented. Among the described methods special attention is paid to electrodischarge drilling. This process have especially been predicted for machining difficult-to-cut electrically conductive materials. The second part consist of the results analysis of electrodischarge microdrilling of siliconized silicon carbide. The experiment involves the impact of current amplitude, discharge voltage and pulse time on the hole depth, side gap, linear tool wear and mean drilling speed. The results shows that electrodischarge drilling is a good alternative when machining inhomogeneous ceramic materials and gives possibility to drill high aspect ratio holes with relatively high efficiency (the drilling speed >2 mm/min.

  3. Physical modelling of temperature fluctuations in a high aspect ratio model of the Czochralski crystal growth

    Science.gov (United States)

    Pal, J.; Cramer, A.; Grants, I.; Eckert, S.; Gerbeth, G.

    2015-12-01

    A low temperature liquid metal model of the Czochralski (CZ) crystal growth process is considered experimentally for a high aspect ratio. Temperature fluctuations close to the edge of the model crystal are studied under the action of a rotating magnetic field (RMF) and/or rotation of the model crystal. A rotation of thermal structures is observed which loses its periodicity at sufficiently high strengths of the RMF. This finding is in qualitative agreement with previous findings in Rayleigh-Bénard (RB) cells. Opposing to that more generic case, the remaining amplitude of the temperature fluctuations stays significantly higher. I.e., the suppression of the fluctuations, which are detrimental to the growth of a mono-crystal, is weaker in the model under investigation.

  4. Secondary electron emission yield from high aspect ratio carbon velvet surfaces

    Science.gov (United States)

    Jin, Chenggang; Ottaviano, Angelica; Raitses, Yevgeny

    2017-11-01

    The plasma electrons bombarding a plasma-facing wall surface can induce secondary electron emission (SEE) from the wall. A strong SEE can enhance the power losses by reducing the wall sheath potential and thereby increasing the electron flux from the plasma to the wall. The use of the materials with surface roughness and the engineered materials with surface architecture is known to reduce the effective SEE by trapping the secondary electrons. In this work, we demonstrate a 65% reduction of SEE yield using a velvet material consisting of high aspect ratio carbon fibers. The measurements of SEE yield for different velvet samples using the electron beam in vacuum demonstrate the dependence of the SEE yield on the fiber length and the packing density, which is strongly affected by the alignment of long velvet fibers with respect to the electron beam impinging on the velvet sample. The results of SEE measurements support the previous observations of the reduced SEE measured in Hall thrusters.

  5. 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.

  6. Inverse metal-assisted chemical etching produces smooth high aspect ratio InP nanostructures.

    Science.gov (United States)

    Kim, Seung Hyun; Mohseni, Parsian K; Song, Yi; Ishihara, Tatsumi; Li, Xiuling

    2015-01-14

    Creating high aspect ratio (AR) nanostructures by top-down fabrication without surface damage remains challenging for III-V semiconductors. Here, we demonstrate uniform, array-based InP nanostructures with lateral dimensions as small as sub-20 nm and AR > 35 using inverse metal-assisted chemical etching (I-MacEtch) in hydrogen peroxide (H2O2) and sulfuric acid (H2SO4), a purely solution-based yet anisotropic etching method. The mechanism of I-MacEtch, in contrast to regular MacEtch, is explored through surface characterization. Unique to I-MacEtch, the sidewall etching profile is remarkably smooth, independent of metal pattern edge roughness. The capability of this simple method to create various InP nanostructures, including high AR fins, can potentially enable the aggressive scaling of InP based transistors and optoelectronic devices with better performance and at lower cost than conventional etching methods.

  7. A high aspect ratio silicon-fin FinFET fabricated upon SOI wafer

    Science.gov (United States)

    Liaw, Yue-Gie; Liao, Wen-Shiang; Wang, Mu-Chun; Lin, Cheng-Li; Zhou, Bin; Gu, Haoshuang; Li, Deshi; Zou, Xuecheng

    2016-12-01

    Three dimensional (3-D) FinFET devices with an ultra-high Si-fin aspect ratio (Height/Width = 82.9 nm/8.6 nm) have been developed after integrating a 14 Å nitrided gate oxide upon the silicon on insulator (SOI) wafers through an advanced CMOS logic platform. The drive current (ION), off current (IOFF), subthreshold swing (SS), drain-induced barrier lowering (DIBL) and transistor gate delay of 30 nm gate length (Lg) of FinFETs illustrate the promising device performance. The TCAD simulations demonstrate that both threshold voltage (Vth) and off current can be adjusted appropriately through the full silicidation (FUSI) of CoSi2 gate engineering. Moreover, the drive currents of n- and p-channel FinFETs are able to be further enhanced once applying the raised Source/Drain (S/D) approach technology for reducing the S/D resistance drastically.

  8. Single-shot ultrafast laser processing of high-aspect-ratio nanochannels using elliptical Bessel beams.

    Science.gov (United States)

    Meyer, R; Jacquot, M; Giust, R; Safioui, J; Rapp, L; Furfaro, L; Lacourt, P-A; Dudley, J M; Courvoisier, F

    2017-11-01

    Ultrafast lasers have revolutionized material processing, opening a wealth of new applications in many areas of science. A recent technology that allows the cleaving of transparent materials via non-ablative processes is based on focusing and translating a high-intensity laser beam within a material to induce a well-defined internal stress plane. This then enables material separation without debris generation. Here, we use a non-diffracting beam engineered to have a transverse elliptical spatial profile to generate high-aspect-ratio elliptical channels in glass of a dimension 350  nm×710  nm and subsequent cleaved surface uniformity at the sub-micron level.

  9. A new multifunctional platform based on high aspect ratio interdigitated NEMS structures.

    Science.gov (United States)

    Ghatnekar-Nilsson, S; Karlsson, I; Kvennefors, A; Luo, G; Zela, V; Arlelid, M; Parker, T; Montelius, L; Litwin, A

    2009-04-29

    A multifunctional NEMS platform based on a mass-producible, surface relief grating has been developed and fabricated directly in polymer materials. The pattern consists of high aspect ratio interdigitated nanometer-sized pairs of walls and can be produced in a low-complexity one-step patterning process with nanoimprint lithography. In this paper, we demonstrate the usefulness of the platform primarily by showing an application as a high-sensitivity mass sensor in air. The sensors, which are based on the high frequency resonant response of around 200 MHz, show a mass responsivity of the order of 0.1 Hz/zg per wall at room temperature and in ambient air. Their ability to selectively adsorb airborne target molecules, such as thiols, is also demonstrated. We also show that the same device can function as a varactor for electronic circuits based on its large tunable capacitive range.

  10. 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.

  11. 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....

  12. 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.

  13. Effect of filament aspect ratio on the dielectric response of multiwalled carbon nanotube composites

    Science.gov (United States)

    Kerr, C. J.; Huang, Y. Y.; Marshall, J. E.; Terentjev, E. M.

    2011-05-01

    Subpercolated composites consisting of highly polar fillers in an insulating matrix have long been predicted to exhibit a large dielectric constant. In this study, we examine the feasibility of experimentally reproducing such an effect based on a multiwalled carbon nanotubes (MWNTs)-polydimethylsiloxane (PDMS) composite system. MWNTs of different diameters were subjected to high-power ultrasound. The sonication-induced scission of nanotubes shows saturation at a final length dependent on the tube diameter, in agreement with a theoretical model. Sonication allows us to produce MWNTs with a prescribed mean aspect ratio between 10 and 55. Composites were formed from these MWNTs with PDMS elastomer at a fixed 1 wt% doping level, using a common solution-processing method. Results from AC impedance spectroscopy indicate that the tube length minimally affects the dielectric response of these composites when the doping level is below the percolation threshold.

  14. Convection-Enhanced Transport into Open Cavities : Effect of Cavity Aspect Ratio.

    Science.gov (United States)

    Horner, Marc; Metcalfe, Guy; Ottino, J M

    2015-09-01

    Recirculating fluid regions occur in the human body both naturally and pathologically. Diffusion is commonly considered the predominant mechanism for mass transport into a recirculating flow region. While this may be true for steady flows, one must also consider the possibility of convective fluid exchange when the outer (free stream) flow is transient. In the case of an open cavity, convective exchange occurs via the formation of lobes at the downstream attachment point of the separating streamline. Previous studies revealed the effect of forcing amplitude and frequency on material transport rates into a square cavity (Horner in J Fluid Mech 452:199-229, 2002). This paper summarizes the effect of cavity aspect ratio on exchange rates. The transport process is characterized using both computational fluid dynamics modeling and dye-advection experiments. Lagrangian analysis of the computed flow field reveals the existence of turnstile lobe transport for this class of flows. Experiments show that material exchange rates do not vary linearly as a function of the cavity aspect ratio (A = W/H). Rather, optima are predicted for A ≈ 2 and A ≈ 2.73, with a minimum occurring at A ≈ 2.5. The minimum occurs at the point where the cavity flow structure bifurcates from a single recirculating flow cell into two corner eddies. These results have significant implications for mass transport environments where the geometry of the flow domain evolves with time, such as coronary stents and growing aneurysms. Indeed, device designers may be able to take advantage of the turnstile-lobe transport mechanism to tailor deposition rates near newly implanted medical devices.

  15. Momentum transfer using variable gaseous plasma ion beams and creation of high aspect ratio microstructures

    Science.gov (United States)

    Maurya, Sanjeev Kumar; Paul, Samit; Shah, Jay Kumar; Chatterjee, Sanghamitro; Bhattacharjee, Sudeep

    2017-03-01

    Intense gaseous ion beams are created from compact microwave plasmas confined in a multicusp magnetic field. The wave frequency (ω) is comparable to the electron plasma frequency (ωpe) and ≫ the ion plasma frequency (ωpi); therefore, the heavier plasma (ions) are least disturbed by the high frequency electromagnetic waves. By changing the experimental gas, ion beams of different species are obtained, which expands the applicability of the ion beams. For the same applied accelerating potential, the controllability of the beam current owing to different velocities for different ionic species adds to the enhanced functionality. The ion beams are utilized to create a variety of microstructures by direct writing on metallic substrates, and microstructures of a high aspect ratio (ar = line width/depth) in the range of 100-1000 are created by varying the ion species and writing speed. For fixed species (Ga) and low current (1 pA) focused ion beam systems, typically ar ˜ 2.0 to 9.3 may be realized in a single beam scan. A parameter called current normalized force, defined as the momentum transfer per unit time, normalized with the beam current helps in understanding the different momentum transferred to the target sample upon impact by the ion beams of variable species. A mathematical formulation is developed to demonstrate this aspect.

  16. A systematic approach to fabricate high aspect ratio silicon micro-needles for transdermal drug delivery

    Science.gov (United States)

    Ng, H. B.; Shearwood, C.

    2007-12-01

    The successful development of micro-needles can help transport drugs and vaccines both effectively and painlessly across the skin. However, not all micro-needles are strong enough to withstand the insertion forces and viscoelasticity of the skin. The work here focuses on the micro-fabrication of high aspect ratio needles with careful control of needle-profile using dry etching technologies. Silicon micro-needles, 150μm in length with base-diameters ranging from 90 to 240μm have been investigated in this study. A novel, multiple-sacrificial approach has been demonstrated as suited to the fabrication of long micro-needle bodies with positive profiles. The parameters that control the isotropic etching are adjusted to control the ratio of the needle-base diameter to needle length. By careful control of geometry, the needle profile can be engineered to give a suitable tip size for penetration, as well as a broad needle base to facilitate the creation of either single or multiple-through holes. This approach allows the mechanical properties of the otherwise brittle needles to be optimized. Finite element analysis indicates that the micro-needles will fracture prematurely due to buckling, with forces ranging from 10 to 30mN.

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

    Science.gov (United States)

    Rouffaud, R.; Levassort, F.; Hladky-Hennion, A.-C.

    2017-02-01

    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.

  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. 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. 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. Simulation and experimental study of aspect ratio limitation in Fresnel zone plates for hard-x-ray optics.

    Science.gov (United States)

    Liu, Jianpeng; Shao, Jinhai; Zhang, Sichao; Ma, Yaqi; Taksatorn, Nit; Mao, Chengwen; Chen, Yifang; Deng, Biao; Xiao, Tiqiao

    2015-11-10

    For acquiring high-contrast and high-brightness images in hard-x-ray optics, Fresnel zone plates with high aspect ratios (zone height/zone width) have been constantly pursued. However, knowledge of aspect ratio limits remains limited. This work explores the achievable aspect ratio limit in polymethyl methacrylate (PMMA) by electron-beam lithography (EBL) under 100 keV, and investigates the lithographic factors for this limitation. Both Monte Carlo simulation and EBL on thick PMMA are applied to investigate the profile evolution with exposure doses over 100 nm wide dense zones. A high-resolution scanning electron microscope at low acceleration mode for charging free is applied to characterize the resultant zone profiles. It was discovered for what we believe is the first time that the primary electron-beam spreading in PMMA and the proximity effect due to extra exposure from neighboring areas could be the major causes of limiting the aspect ratio. Using the optimized lithography condition, a 100 nm zone plate with aspect ratio of 15/1 was fabricated and its focusing property was characterized at the Shanghai Synchrotron Radiation Facility. The aspect ratio limit found in this work should be extremely useful for guiding further technical development in nanofabrication of high-quality Fresnel zone plates.

  2. Emission behavior of sudan red 7B on dogbone-shaped gold nanorods: Aspect ratio dependence of the metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Dewan S.; Sharma, Debdulal; Ghosh, Sujit Kumar, E-mail: sujitkchem@gmail.com

    2014-01-31

    Highlights: • CTAB-stabilized gold dogbones of variable aspect ratio have been synthesized. • Sudan red 7B has been used as fluoroprobe to elucidate aspect ratio dependence of the dogbones. • The relative intensity decreases exponentially with increasing aspect ratio. • The mechanism of quenching has been ascribed to the electron and energy transfer processes. - Abstract: Cetyltrimethylammonium bromide-stabilized ‘dogbone-shaped’ gold nanorods of aspect ratio varying from 1 to 6 have been synthesized by seed-mediated growth method in aqueous medium. Then, sudan red 7B, an alien molecular probe has been used as local probe to elucidate aspect ratio dependence of the nanorods on the photophysical properties of the dye molecules. It is seen that the relative intensity decreases exponentially with increasing aspect ratio and has been attributed to decrease in overall surface area for a particular concentration of the nanorods. The mechanism of fluorescence quenching has been ascribed to the electron and energy transfer processes in the gold-fluorophore hybrid nanostructures.

  3. 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

  4. Jet Surface Interaction Noise in a High Aspect Ratio Rectangular Exhaust

    Science.gov (United States)

    Khavaran, Abbas

    2017-01-01

    A physics-based prediction model is employed to simulate jet surface interaction (JSI) noise in a transversely sheared jet exhaust. The methodology finds application in jets with a high aspect ratio (AR) rectangular exhaust in the proximity of a flat surface. Two component spectra are simulated: (i) mixing/scrubbing noise; (ii) trailing edge noise--and are superimposed to obtain the far field exhaust noise on either side of a nearby surface. This document describes the necessary input parameters (including mean flow and turbulence information for the nozzle exhaust of interest) that should be prepared in order to initiate the simulation for each noise component. Sample input/output files in connection with an 8:1 aspect ratio rectangular exhaust at Mach 0.98 near a rigid surface are described. Jet noise spectra are examined below at operating conditions listed in Table IV. Individual noise components, designated as Scrubbing Noise and Trailing Edge Noise, are presented and their sum Total Noise (Analysis) is compared with Measurement (Refs. 8 and 9) at selective number of observer polar angles at azimuth f = 90deg. Results are presented on an arc R = 17.80-ft (i.e., R = 100Deq) on both sides of a nearby surface. Although the predicted TE noise component is symmetric with respect to the edge due to symmetry in the propagator, measurements for the majority of cases are not quite symmetric and exhibit a slightly larger peak on the reflected side of the surface. Turbulent mixing/scrubbing noise component has a greater presence on the reflected side, as expected. Figure 13 to Figure 18 show that the peak in the predicted TE component could differ from measurements by as much as 4 dB due to lack of symmetry in measured data, however, the general trend is in agreement with data across the three Mach numbers. The overall sound pressure level (OASPL) associated with the TE noise component follows a U5 velocity scaling in the current modeling (Ref. 4). Directivity

  5. 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.

  6. 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.

  7. Dimensional measurement of micro parts with high aspect ratio in HIT-UOI

    Science.gov (United States)

    Dang, Hong; Cui, Jiwen; Feng, Kunpeng; Li, Junying; Zhao, Shiyuan; Zhang, Haoran; Tan, Jiubin

    2016-11-01

    Micro parts with high aspect ratios have been widely used in different fields including aerospace and defense industries, while the dimensional measurement of these micro parts becomes a challenge in the field of precision measurement and instrument. To deal with this contradiction, several probes for the micro parts precision measurement have been proposed by researchers in Center of Ultra-precision Optoelectronic Instrument (UOI), Harbin Institute of Technology (HIT). In this paper, optical fiber probes with structures of spherical coupling(SC) with double optical fibers, micro focal-length collimation (MFL-collimation) and fiber Bragg grating (FBG) are described in detail. After introducing the sensing principles, both advantages and disadvantages of these probes are analyzed respectively. In order to improve the performances of these probes, several approaches are proposed. A two-dimensional orthogonal path arrangement is propounded to enhance the dimensional measurement ability of MFL-collimation probes, while a high resolution and response speed interrogation method based on differential method is used to improve the accuracy and dynamic characteristics of the FBG probes. The experiments for these special structural fiber probes are given with a focus on the characteristics of these probes, and engineering applications will also be presented to prove the availability of them. In order to improve the accuracy and the instantaneity of the engineering applications, several techniques are used in probe integration. The effectiveness of these fiber probes were therefore verified through both the analysis and experiments.

  8. 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.

  9. High aspect ratio gratings for X-ray phase contrast imaging

    Science.gov (United States)

    Mohr, Jürgen; Grund, Thomas; Kunka, Danays; Kenntner, Johannes; Leuthold, Juerg; Meiser, Jan; Schulz, Joachim; Walter, Marco

    2012-07-01

    Differential phase contrast X-ray imaging (DPCI) has gained a lot of interest in the past years. It is based on X-ray grating interferometry and the image quality is strongly dependant on the grating quality. Periodic line and space structures with periods in the micron range are required for the source and absorption grating. In case of energies > 30 keV their height should be larger than 100 μm resulting in aspect ratios of more than 100. Deep X-ray lithography and gold electroforming (LIGA technology) is used to fabricate these challenging structures. After resist, design and process optimization gratings with 2.4 μm period have been electroformed up to 120 μm, Visibilities of up to 70% for 29 keV and up to 20% for 52 keV have been achieved for monochromatic synchrotron light. Structures with larger periods could be manufactured up to 200 μm; further increase of the height and the gratings quality is possible yielding to high performance gratings also for high energies.

  10. Numerical investigation of flow on NACA4412 aerofoil with different aspect ratios

    Directory of Open Access Journals (Sweden)

    Demir Hacımurat

    2016-01-01

    Full Text Available In this study, the flow over NACA4412 was investigated both numerically and experimentally at a different Reynolds numbers. The experiments were carried out in a low speed wind tunnel with various angles of attack and different Reynolds numbers (25000 and 50000. Airfoil was manufactured using 3D printer with a various aspect ratios (AR = 1 and AR = 3. Smoke-wire and oil flow visualization methods were used to visualize the surface flow patterns. NACA4412 aerofoil was designed by using SOLIDWORKS. The structural grid of numerical model was constructed by ANSYS ICEM CFD meshing software. Furthermore, ANSYS FLUENT™ software was used to perform numerical calculations. The numerical results were compared with experimental results. Bubble formation was shown in CFD streamlines and smoke-wire experiments at z / c = 0.4. Furthermore, bubble shrunk at z / c = 0.2 by reason of the effects of tip vortices in both numerical and experimental studies. Consequently, it was seen that there was a good agreement between numerical and experimental results.

  11. Computational study of a conical wing having unit aspect ratio at supersonic speeds

    Science.gov (United States)

    Mcgrath, Brian E.

    1993-01-01

    A study was conducted to identify and assess a computational method as a preliminary analysis and design tool for advanced military aircraft designs. The method of choice for this study was the Euler Marching Technique for Accurate Computation (EMTAC). Computational and experimental results were compared for a thick unit aspect ratio delta wing at Mach 2.8 and 4.0. This geometry along with the associated flow physics is representative of advanced aircraft designs. The comparisons of the lift and drag coefficients show that the computations agree with experimentally obtained data at Mach 2.8 and 4.0. Further, comparison between EMTAC and experiment shows that the computations accurately predict the overall shape and levels of the surface pressure distributions at Mach 2.8 and 4.0. Qualitative assessment of the computed flow-field properties shows that EMTAC captures the basic flow-field characteristics representative of advanced aircraft designs. The study further suggests that EMTAC can be successfully used in the preliminary analysis and design of advanced military aircraft.

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

    Energy Technology Data Exchange (ETDEWEB)

    Santavicca, Daniel F., E-mail: daniel.santavicca@unf.edu; Adams, Jesse K.; Grant, Lierd E. [Department of Physics, University of North Florida, Jacksonville, Florida 32224 (United States); McCaughan, Adam N.; Berggren, Karl K. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-06-21

    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.

  13. Inkjet Printing of High Aspect Ratio Superparamagnetic SU-8 Microstructures with Preferential Magnetic Directions

    Directory of Open Access Journals (Sweden)

    Loïc Jacot-Descombes

    2014-08-01

    Full Text Available Structuring SU-8 based superparamagnetic polymer composite (SPMPC containing Fe3O4 nanoparticles by photolithography is limited in thickness due to light absorption by the nanoparticles. Hence, obtaining thicker structures requires alternative processing techniques. This paper presents a method based on inkjet printing and thermal curing for the fabrication of much thicker hemispherical microstructures of SPMPC. The microstructures are fabricated by inkjet printing the nanoparticle-doped SU-8 onto flat substrates functionalized to reduce the surface energy and thus the wetting. The thickness and the aspect ratio of the printed structures are further increased by printing the composite onto substrates with confinement pedestals. Fully crosslinked microstructures with a thickness up to 88.8 μm and edge angle of 112° ± 4° are obtained. Manipulation of the microstructures by an external field is enabled by creating lines of densely aggregated nanoparticles inside the composite. To this end, the printed microstructures are placed within an external magnetic field directly before crosslinking inducing the aggregation of dense Fe3O4 nanoparticle lines with in-plane and out-of-plane directions.

  14. Bubble aspect ratio in dense bubbly flows: experimental studies in low Morton-number systems

    Science.gov (United States)

    Besagni, G.; Inzoli, F.; Ziegenhein, T.; Hessenkemper, H.; Lucas, D.

    2017-11-01

    Almost every modelling approach of bubbly flows includes assumptions concerning the bubble shape. Such assumptions are usually made based on single bubble experiments in quiescent flows, which is far away from the flow field observed in large-scale multiphase facilities. Considering low Morton-numbers and the highly deformable interface at medium and large Eötvös-numbers, the evaluation of the bubble shape in such systems under real flow conditions is highly desirable. In this study, we experimentally evaluate the bubble shape (in terms of aspect ratio), at low Morton-numbers, in different bubble column setups and a pipe flow setup under different operating conditions. The bubble shape in the bubble column experiments were obtained with cameras at Politecnico di Milano and Helmholtz-Zentrum Dresden Rossendorf (HZDR) whereas the shapes in the pipe flows were measured by the ultrafast electron beam X-ray tomography system (ROFEX) at HZDR. In the bubble column experiments almost the same shape is observed; conversely, the shape in the pipe flows distinctly depends on the flow conditions. In conclusion, in bubble columns the assumption of a constant shape regardless of the flow conditions is valid whereas in pipe flows the turbulence and shear rates can be strong enough to deform distinctly the bubbles.

  15. Leading-edge vortex burst on a low-aspect-ratio rotating flat plate

    Science.gov (United States)

    Medina, Albert; Jones, Anya R.

    2016-08-01

    This study experimentally investigates the phenomenon of leading-edge-vortex burst on rotating flat plate wings. An aspect-ratio-2 wing was driven in pure rotation at a Reynolds number of Re=2500 . Of primary interest is the evolution of the leading-edge vortex along the wing span over a single-revolution wing stroke. Direct force measurements of the lift produced by the wing revealed a single global lift maximum relatively early in the wing stroke. Stereoscopic particle image velocimetry was applied to several chordwise planes to quantify the structure and strength of the leading-edge vortex and its effect on lift production. This analysis revealed opposite-sign vorticity entrainment into the core of the leading-edge vortex, originating from a layer of secondary vorticity along the wing surface. Coincident with the lift peak, there emerged both a concentration of opposite vorticity in the leading-edge-vortex core, as well as axial flow stagnation within the leading-edge-vortex core. Planar control volume analysis was performed at the midspan to quantify the contributions of vorticity transport mechanisms to the leading-edge-vortex circulation. The rate of circulation annihilation by opposite-signed vorticity entrainment was found to be minimal during peak lift production, where convection balanced the flux of vorticity resulting in stagnation and eventually reversal of axial flow. Finally, vortex burst was found to be correlated with swirl number, where bursting occurs at a swirl threshold of Sw<0.6 .

  16. Experimental investigation of a large aspect ratio flat plate encountering a steam-wise gust

    Science.gov (United States)

    Mulleners, Karen; Mancini, Peter; Jones, Anya

    2015-11-01

    While humans are capable of mimicking, and even outperform, the kinematic capabilities of natural flyers, birds and insects are still way ahead of us when it comes to anticipating and dealing with turbulent and gusty flow conditions. To tailor and improve flight control capabilities of low Reynolds number flyers in real weather, we need to bridge this gap of knowledge. As a first step, we experimentally studied the aerodynamic influence of a simplified stream-wise gust on a large aspect ratio flat plate. The experiments were conduction in the 7 × 1 . 5 × 1 m3 towing tank at UMD which was equipped with a 4-axis computer-controlled motion system. The effect of a stream-wise gust was simulated by accelerating or decelerating the wing to a new constant velocity after an initial constant surge. A high-speed camera and light sheet optics were attached to the tow carriage allowing for time-resolved particle image velocimetry along the entire motion in addition to direct force measurements. A proper orthogonal decomposition of the flow field was carried out to study the time scales related to changes induced by the sudden acceleration or deceleration in addition to analyzing the size, position and trajectory of prominent vortices and associated forces during the gust encounter.

  17. High-speed microprobe for roughness measurements in high-aspect-ratio microstructures

    Science.gov (United States)

    Doering, Lutz; Brand, Uwe; Bütefisch, Sebastian; Ahbe, Thomas; Weimann, Thomas; Peiner, Erwin; Frank, Thomas

    2017-03-01

    Cantilever-type silicon microprobes with an integrated tip and a piezoresistive signal read out have successfully proven to bridge the gap between scanning force microscopy and stylus profilometry. Roughness measurements in high-aspect-ratio microstructures (HARMS) with depths down to 5 mm and widths down to 50 µm have been demonstrated. To improve the scanning speed up to 15 mm s-1, the wear of the tip has to be reduced. The atomic layer deposition (ALD) technique with alumina (Al2O3) has been tested for this purpose. Repeated wear measurements with coated and uncoated microprobe cantilevers have been carried out on a roughness standard at a speed of 15 mm s-1. The tip shape and the wear have been measured using a new probing tip reference standard containing rectangular silicon grooves with widths from 0.3 µm to 3 µm. The penetration depth of the microprobe allows one to measure the wear of the tip as well as the tip width and the opening angle of the tip. The roughness parameters obtained on the roughness standard during wear experiments agree well with the reference values measured with a calibrated stylus instrument, nevertheless a small amount of wear still is observable. Further research is necessary in order to obtain wear resistant microprobe tips for non-destructive inspection of microstructures in industry and microform measurements, for example in injection nozzles.

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

    Science.gov (United States)

    Kruyt, Jan W; Quicazán-Rubio, Elsa M; van Heijst, GertJan F; Altshuler, Douglas L; Lentink, David

    2014-10-06

    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. Previous quasi-steady experiments with a wing spinner set-up provide no support for this prediction. To test this more carefully, we compare the quasi-steady hover performance of 26 wings, from 12 hummingbird taxa. We spun the wings at angular velocities and angles of attack that are representative for every species and measured lift and torque more precisely. The power (aerodynamic torque × angular velocity) required to lift weight depends on aerodynamic efficacy, which is measured by the power factor. Our comparative analysis shows that AR has a modest influence on lift and drag forces, as reported earlier, but interspecific differences in power factor are large. During the downstroke, the power required to hover decreases for larger AR wings at the angles of attack at which hummingbirds flap their wings (p < 0.05). Quantitative flow visualization demonstrates that variation in hover power among hummingbird wings is driven by similar stable leading edge vortices that delay stall during the down- and upstroke. A side-by-side aerodynamic performance comparison of hummingbird wings and an advanced micro helicopter rotor shows that they are remarkably similar. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  19. Core/Shell and High Aspect Ratio Magnetic Oxide Nanoparticles for Antenna Applications

    Science.gov (United States)

    Ekiert, Thomas F., Jr.; O'Malley, Matthew; Yocum, Brandon; Lippold, Jennifer; Lyle, Mallory; Griner, Angela; Flynn, Cory; Nickel, Anna; Alexander, Max D., Jr.

    2012-02-01

    Improved antenna gain, reduced antenna aperture size, and improved bandwidth are of interest to an increasingly mobile world. To obtain these improvements our efforts are directed at developing new magnetic oxide nanoparticle/polymer composites with modifiable permeability and permittivity and low electrical losses. Our approach consists of producing core/shell and shape controlled magnetic nanoparticles. Methods of synthesis utilize microwave and traditional heating to perform hydrothermal and solvothermal reactions. Decomposition of metal acetylacetonates is performed using various alcohols resulting in spherical nanoparticles with diameters of 8-16 nm and 3-7 nm for Fe3O4 and CoFe2O4, respectively. Microwave methods result in similar particles, but are produced in an hour or less as compared to 48 hrs via the traditional solvothermal method. Successive growths are used to produce larger monolithic particles as well as core/shell systems where exchange coupling between the core and shell is observed. Hexaferrite particles have been produced via hydrothermal synthesis, while high aspect ratio Fe3O4 nanoparticles ( 10-100 nm) produced via hydrothermal synthesis result in nanoneedles with high μr.

  20. Outstanding adsorption performance of high aspect ratio and super-hydrophobic carbon nanotubes for oil removal.

    Science.gov (United States)

    Kayvani Fard, Ahmad; Mckay, Gordon; Manawi, Yehia; Malaibari, Zuhair; Hussien, Muataz A

    2016-12-01

    Oil removal from water is a highly important area due to the large production rate of emulsified oil in water, which is considered one of the major pollutants, having a negative effect on human health, environment and wildlife. In this study, we have reported the application of high quality carbon nanotube bundles produced by an injected vertical chemical vapor deposition (IV-CVD) reactor for oil removal. High quality, bundles, super hydrophobic, and high aspect ratio carbon nanotubes were produced. The average diameters of the produced CNTs ranged from 20 to 50 nm while their lengths ranged from 300 to 500 μm. Two types of CNTs namely, P-CNTs and C-CNTs, (Produced CNTs from the IV-CVD reactor and commercial CNTs) were used for oil removal from water. For the first time, thermogravimetric analysis (TGA) was conducted to measure maximum oil uptake using CNT and it was found that P-CNT can take oil up to 17 times their weight. The effect of adsorbent dosage, contact time, and agitation speed were examined on the oil spill clean-up efficiency using batch sorption experiments. Higher efficiency with almost 97% removal was achieved using P-CNTs compared to 87% removal using C-CNTs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Jet-Surface Interaction Noise from High-Aspect Ratio Nozzles: Test Summary

    Science.gov (United States)

    Brown, Clifford; Podboy, Gary

    2017-01-01

    Noise and flow data have been acquired for a 16:1 aspect ratio rectangular nozzle exhausting near a simple surface at the NASA Glenn Research Center as part of an ongoing effort to understand, model, and predict the noise produced by current and future concept aircraft employing a tightly integrated engine airframe designs. The particular concept under consideration in this experiment is a blended-wing-body airframe powered by a series of electric fans exhausting through slot nozzle over an aft deck. The exhaust Mach number and surface length were parametrically varied during the test. Far-field noise data were acquired for all nozzle surface geometries and exhaust flow conditions. Phased-array noise source localization data and in-flow pressure data were also acquired for a subset of the isolated (no surface) and surface configurations; these measurements provide data that have proven useful for modeling the jet-surface interaction noise source and the surface effect on the jet-mixing noise in round jets. A summary of the nozzle surface geometry, flow conditions tested, and data collected are presented.

  2. Effects of nanofiller morphology and aspect ratio on the rheo-mechanical properties of polyimide nanocomposites

    Directory of Open Access Journals (Sweden)

    2008-07-01

    Full Text Available New polyimide nanocomposites containing organically modified montmorillonite (MMT, synthetic silicate (chrysotile nanotubes (SNT, and zirconium dioxide (ZrO2 were prepared to investigate the influence of the nanoparticle morphology on the nanocomposite rheology and mechanical properties under selected conditions that the materials are likely to encounter during use. The efficiency of homogeneous dispersion of the nanoparticles in the polyimide matrix was studied by measuring the rheology of model oligoimides (OI dispersions containing the desired amounts of the nanoparticles. The OI/nanoparticles dispersions showed significant increase in complex viscosity with increasing concentration of the nanoparticles that depended strongly on the nanoparticle morphology and aspect ratio. Polyimide nanocomposite films (PI-PM prepared from the poly(amic acid of poly(pyromellitic dianhydride-co-4,4′-oxydianiline (PM filled with the desired concentration of the nanoparticles showed an increase in tensile modulus with increasing nanoparticle concentration in the order MMT>SNT>ZrO2. In contrast to the PI-PM/MMT films, the PI-PM films filled with 10 vol% of SNT and ZrO2 showed higher sample failure strains, suggesting that the SNT and ZrO2 may be more effective in improving the ductility of the polyimide nanocomposites for applications where the relatively brittle polyimide/MMT nanocomposites films are not useable.

  3. 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.

  4. 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.

  5. High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams.

    Science.gov (United States)

    Rapp, L; Meyer, R; Giust, R; Furfaro, L; Jacquot, M; Lacourt, P A; Dudley, J M; Courvoisier, F

    2016-09-27

    Femtosecond pulses provide an extreme degree of confinement of light matter-interactions in high-bandgap materials because of the nonlinear nature of ionization. It was recognized very early on that a highly focused single pulse of only nanojoule energy could generate spherical voids in fused silica and sapphire crystal as the nanometric scale plasma generated has energy sufficient to compress the material around it and to generate new material phases. But the volumes of the nanometric void and of the compressed material are extremely small. Here we use single femtosecond pulses shaped into high-angle Bessel beams at microjoule energy, allowing for the creation of very high 100:1 aspect ratio voids in sapphire crystal, which is one of the hardest materials, twice as dense as glass. The void volume is 2 orders of magnitude higher than those created with Gaussian beams. Femtosecond and picosecond illumination regimes yield qualitatively different damage morphologies. These results open novel perspectives for laser processing and new materials synthesis by laser-induced compression.

  6. 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.

  7. 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.

  8. Comparing wake structures behind a finite aspect ratio and an infinite span normal thin flat plate

    Science.gov (United States)

    Hemmati, Arman; Wood, David H.; Martinuzzi, Robert J.

    2014-11-01

    The wake of an infinite span (2D) thin flat plate and that of a finite aspect ratio, AR = 3.2, plate, both normal to a uniform stream, are compared using DNS at Re = 1200. For the 2D plate, three wake flow regimes are observed. Intervals of typical anti-symmetric Karman shedding (Regime M) are interrupted by intervals where the shear layer folding process first delayed (Regime L) and then accelerated, Regime H. The distinct flow patterns in these regimes have significant impact on lift and drag values, wake structure and instantaneous pressure loads. In contrast, only Regime M is observed for the AR = 3.2 plate. The presence of two lateral shear layers appears to maintain the Karman shedding. Compared to the infinite plate: the mean recirculation region shrinks by 45 % to 1.57H; the magnitude of the Reynolds Stresses drops significantly; Turbulent kinetic energy levels along the wake centerline and peak production and dissipation rates are significantly lower. Further, the three normal Reynolds stresses are comparable in magnitude. To better understand the impact of additional shear layers on the wake stability and resultant wake structures, the 3D structures will be reconstructed using DNS results. Pressure and stress distribution along the plate surfaces will also be examined. This work is supported by AITF and NSERC fellowship grants.

  9. 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.

  10. On the generation of Alfven wave current drive in low aspect ratio Tokamaks with neoclassical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bruma, C.; Cuperman, S.; Komoshvili, K. [School of Physics and Astronomy, Tel Aviv University, Tel Aviv (Israel)

    1998-08-01

    Several low aspect ratio (spherical) Tokamaks (ST's) are now in operation or under construction. These devices would permit cost-effective and attractive embodiment of future fusion reactors: they would provide high {beta}, good confinement and steady state operation at modest field values. Now, a steady state reactor has to be sustained by non-inductively driven currents. Recently, the generation of non-inductive current drive by Alfven waves (AWCD) has been investigated theoretically within the framework of ideal (E{sub p}arallel=0) MHD and non-ideal, resistive (E{sub p}arallel{ne}0) MHD; however, in all these cases, the tokamak device consisted of a cylindrical plasma with simulated toroidal effects. Rather encouraging results have been obtained. In this work we further investigate AWCD in ST's as follows: (i) we use consistent equilibrium profiles with neoclassical conductivity corresponding to an ohmic START discharge; (ii) incorporate effects due to neoclassical conductivity in the elements of the resistive MHD dielectric tensor, in the solution of the full (E{sub p}arallel{ne}0) wave equation as well as in the calculation of AWCD; and (iii) carry out a systematic search for antenna parameters optimizing the AWCD. (author)

  11. Ultra-high aspect ratio copper nanowires as transparent conductive electrodes for dye sensitized solar cells

    Science.gov (United States)

    Zhu, Zhaozhao; Mankowski, Trent; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2016-09-01

    We report the synthesis of ultra-high aspect ratio copper nanowires (CuNW) and fabrication of CuNW-based transparent conductive electrodes (TCE) with high optical transmittance (>80%) and excellent sheet resistance (Rs AZO) thin-film coatings, or platinum thin film coatings, or nickel thin-film coatings. Our hybrid transparent electrodes can replace indium tin oxide (ITO) films in dye-sensitized solar cells (DSSCs) as either anodes or cathodes. We highlight the challenges of integrating bare CuNWs into DSSCs, and demonstrate that hybridization renders the solar cell integrations feasible. The CuNW/AZO-based DSSCs have reasonably good open-circuit voltage (Voc = 720 mV) and short-circuit current-density (Jsc = 0.96 mA/cm2), which are comparable to what is obtained with an ITO-based DSSC fabricated with a similar process. Our CuNW-Ni based DSSCs exhibit a good open-circuit voltage (Voc = 782 mV) and a decent short-circuit current (Jsc = 3.96 mA/cm2), with roughly 1.5% optical-to-electrical conversion efficiency.

  12. Comparing nonlinear MHD simulations of low-aspect-ratio RFPs to RELAX experiments

    Science.gov (United States)

    McCollam, K. J.; den Hartog, D. J.; Jacobson, C. M.; Sovinec, C. R.; Masamune, S.; Sanpei, A.

    2016-10-01

    Standard reversed-field pinch (RFP) plasmas provide a nonlinear dynamical system as a validation domain for numerical MHD simulation codes, with applications in general toroidal confinement scenarios including tokamaks. Using the NIMROD code, we simulate the nonlinear evolution of RFP plasmas similar to those in the RELAX experiment. The experiment's modest Lundquist numbers S (as low as a few times 104) make closely matching MHD simulations tractable given present computing resources. Its low aspect ratio ( 2) motivates a comparison study using cylindrical and toroidal geometries in NIMROD. We present initial results from nonlinear single-fluid runs at S =104 for both geometries and a range of equilibrium parameters, which preliminarily show that the magnetic fluctuations are roughly similar between the two geometries and between simulation and experiment, though there appear to be some qualitative differences in their temporal evolution. Runs at higher S are planned. This work is supported by the U.S. DOE and by the Japan Society for the Promotion of Science.

  13. Effects of the target aspect ratio and intrinsic reactivity onto diffusive search in bounded domains

    Science.gov (United States)

    Grebenkov, Denis S.; Metzler, Ralf; Oshanin, Gleb

    2017-10-01

    We study the mean first passage time (MFPT) to a reaction event on a specific site in a cylindrical geometry—characteristic, for instance, for bacterial cells, with a concentric inner cylinder representing the nuclear region of the bacterial cell. A similar problem emerges in the description of a diffusive search by a transcription factor protein for a specific binding region on a single strand of DNA. We develop a unified theoretical approach to study the underlying boundary value problem which is based on a self-consistent approximation of the mixed boundary condition. Our approach permits us to derive explicit, novel, closed-form expressions for the MFPT valid for a generic setting with an arbitrary relation between the system parameters. We analyse this general result in the asymptotic limits appropriate for the above-mentioned biophysical problems. Our investigation reveals the crucial role of the target aspect ratio and of the intrinsic reactivity of the binding region, which were disregarded in previous studies. Theoretical predictions are confirmed by numerical simulations.

  14. Two-degree-of-freedom vortex-induced vibration of circular cylinders with very low aspect ratio and small mass ratio

    Science.gov (United States)

    Gonçalves, R. T.; Rosetti, G. F.; Franzini, G. R.; Meneghini, J. R.; Fujarra, A. L. C.

    2013-05-01

    The investigation of vortex-induced vibration on very short cylinders with two degrees of freedom has drawn the attention of a large number of researchers. Some investigations on such a problem are carried out in order to have a better understanding of the physics involved in vortex-induced motions of floating bodies such as offshore platforms. In this paper, experiments were carried out in a recirculating water channel over the range of Reynolds number 6000attention because of its smaller amplitude compared to the cases with the same aspect ratio and a larger mass ratio. This counter-intuitive behavior seems to be related to the energy transferring process from the steady stream to the oscillatory hydroelastic system. Finally, it is noteworthy that the characteristic of the “Strouhal-like” number decreases when the aspect ratio decreases, as also observed in previous works available in the literature, most of them for stationary cylinders.

  15. Investigation at low speeds of the effect of aspect ratio and sweep on rolling stability derivatives of untapered wings

    Science.gov (United States)

    Goodman, Alex; Fisher, Lewis R.

    1949-01-01

    A low scale wind tunnel investigation was conducted in rolling flow to determine the effects of aspect ratio and sweep (when varied independently) on the rolling stability derivatives for a series of untapered wings. Test results indicate that when the aspect ratio was held constant, an increase in the sweepback angle caused a significant reduction in the damping in roll at low lift coefficients for only the higher aspect ratios that were tested. This result was in agreement with available swept wing theory which indicated no effect of sweep for aspect ratios near zero. The result of the linear theory that the damping in roll is independent of lift coefficient and that the yawing moment and lateral force due to rolling are directly proportional to the lift coefficient was found to be valid for only a very limited lift coefficient range when the wings were highly swept. For such wings, the damping was found to increase in magnitude and the yawing moment due to rolling, to change from negative to positive at moderate lift coefficients. The effect of wing tip suction, not acounted for by present theory, was found to be very important with regard to the yawing moment due to rolling, particularly for low aspect ratio swept wings. An empirical means of correcting present theory for the effect of tip suction is suggested.

  16. Single-pulse femtosecond laser Bessel beams drilling of high-aspect-ratio microholes based on electron dynamics control

    Science.gov (United States)

    Zhao, Weiwei; Li, Xiaowei; Xia, Bo; Yan, Xueliang; Han, Weina; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    Microholes drilling has attracted extensive research efforts for its broad applications in photonics, microfluidics, optical fibers and many other fields. A femtosecond (fs) laser is a promising tool for high-precision materials processing with reduced recast/microcracks and minimized heat affected zones. But there remain many challenges in hole drilling using conventional fs laser with Gaussian beams, such as low aspect ratio and taper effects. We report small-diameter and high-aspect-ratio microholes with taper free drilling in PMMA (polymethyl methacrylate) using single-pulse fs laser Bessel beams. Axicon is used to transform Gaussian beams into Bessel beams, which then irradiate in the sample by a telescope consisting of plano-convex lens and microscope objective. Using this technique, we enhance the aspect ratio of microholes by 55 times as compared with Gaussian beams. We attribute this high aspect ratio and high quality microholes formation to the unique spatial intensity distribution and propagation stability of Bessel beams, which can effectively adjust the transient localized electron density distribution leading to a long and uniform localized-interacted zone. By using the optimized pulse energy and focal depth position, the microholes diameter ranges between 1.4-2.1 μm and the aspect ratio can exceed 460. This efficient technique is of great potentials for fabrication of microphotonics devices and microfluidics.

  17. Unsteady flow structure and loading of a pitching low-aspect-ratio wing

    Science.gov (United States)

    Visbal, Miguel R.

    2017-02-01

    This study addresses the flow structure and unsteady loading arising over a pitching low-aspect-ratio rectangular wing under low-Reynolds-number conditions of interest in small unmanned aerial vehicle operation and gust interactions. Simulations are performed employing a high-fidelity computational approach capable of accurately capturing the complex unsteady transitional flows. The wing is pitched about its quarter-chord axis to a maximum incidence of 45∘ over time intervals ranging from four to 16 convective time scales. The Reynolds number based on the wing chord varied from 103 to 4 ×104 . For the highest pitch rate, good agreement between the computed three-dimensional (3D) flow structure and recent experimental measurements is demonstrated. The 3D dynamic stall process is characterized by the formation of an initially spanwise-oriented leading-edge vortex which evolves into an arch-type structure with legs anchored to the wing surface. The normal vorticity in the arch vortex legs establishes a low-pressure region and swirling pattern on the wing surface. A distinct characteristic of the arch vortex is its upstream propagation and persistence over the wing, postulated to be the result of the self-induced velocity of the vortex and its image underneath the plate. Increasing either pitch rate or Reynolds number promotes a more coherent arch vortex and circulation pattern, and delays the onset of stall to a higher angle of attack. Even for the lowest pitch rate considered, a significant increase in maximum lift is achieved relative to the static situation.

  18. Geodesic acoustic modes and zonal flows in rotating large-aspect-ratio tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ilgisonis, V I; Lakhin, V P; Smolyakov, A I; Sorokina, E A [Department of Physics and Engineering Physics, RRC ' Kurchatov Institute' , 123182 Moscow (Russian Federation)

    2011-06-15

    The effect of equilibrium plasma rotation (toroidal and poloidal) on low-frequency, electrostatic modes-the geodesic acoustic modes (GAMs) and the zonal flows (ZFs)-in large aspect ratio tokamaks is studied within the framework of ideal MHD. It is shown that the plasma rotation results in a frequency up-shift of the ordinary GAM. The new branch of continuum modes induced by the poloidal rotation is found. This mode originates from the opposite sign Doppler shift of frequency due to poloidal rotation for m = {+-}1 poloidal side-band harmonics of the perturbed mass density, pressure and parallel velocity. In the case of slow poloidal rotation ({Omega}{sub P} << c{sub s}/qR{sub 0}) its frequency is close to the sound frequency c{sub s}/qR{sub 0} ({Omega}{sub P} is the poloidal angular velocity, c{sub s} is the speed of sound, q is the safety factor and R{sub 0} is the major radius of tokamak). The mode can be called the rotation-induced acoustic mode. This mode disappears in the case of purely toroidal plasma rotation. The frequency of the new mode in the case of relatively slow poloidal rotation ({Omega}{sub P} {<=} c{sub s}/qR{sub 0}) is lower than the frequency of the ordinary GAM modified by plasma rotation. In the case of larger poloidal angular velocities {Omega}{sub P} ({Omega}{sub P} {>=} 2c{sub s}/qR{sub 0}) the mode becomes unstable and is identified as the unstable ZF. With a further increase in the poloidal angular velocity at constant toroidal angular velocity the instability is suppressed, and the mode turns again into a marginally stable, oscillating mode.

  19. 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.

  20. 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.

  1. Global two-fluid simulations of geodesic acoustic modes in strongly shaped tight aspect ratio tokamak plasmas

    Science.gov (United States)

    Robinson, J. R.; Hnat, B.; Thyagaraja, A.; McClements, K. G.; Knight, P. J.; Kirk, A.; MAST Team

    2013-05-01

    Following recent observations suggesting the presence of the geodesic acoustic mode (GAM) in ohmically heated discharges in the Mega Amp Spherical Tokamak (MAST) [J. R. Robinson et al., Plasma Phys. Controlled Fusion 54, 105007 (2012)], the behaviour of the GAM is studied numerically using the two fluid, global code CENTORI [P. J. Knight et al. Comput. Phys. Commun. 183, 2346 (2012)]. We examine mode localisation and effects of magnetic geometry, given by aspect ratio, elongation, and safety factor, on the observed frequency of the mode. An excellent agreement between simulations and experimental data is found for simulation plasma parameters matched to those of MAST. Increasing aspect ratio yields good agreement between the GAM frequency found in the simulations and an analytical result obtained for elongated large aspect ratio plasmas.

  2. Global two-fluid simulations of geodesic acoustic modes in strongly shaped tight aspect ratio tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, J. R.; Hnat, B. [Physics Department, University of Warwick, Coventry, CV4 7AL (United Kingdom); Thyagaraja, A. [H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); McClements, K. G.; Knight, P. J.; Kirk, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Collaboration: MAST Team

    2013-05-15

    Following recent observations suggesting the presence of the geodesic acoustic mode (GAM) in ohmically heated discharges in the Mega Amp Spherical Tokamak (MAST) [J. R. Robinson et al., Plasma Phys. Controlled Fusion 54, 105007 (2012)], the behaviour of the GAM is studied numerically using the two fluid, global code CENTORI [P. J. Knight et al. Comput. Phys. Commun. 183, 2346 (2012)]. We examine mode localisation and effects of magnetic geometry, given by aspect ratio, elongation, and safety factor, on the observed frequency of the mode. An excellent agreement between simulations and experimental data is found for simulation plasma parameters matched to those of MAST. Increasing aspect ratio yields good agreement between the GAM frequency found in the simulations and an analytical result obtained for elongated large aspect ratio plasmas.

  3. Influence of orientation, glazing proportion and zone aspect ratio on the thermal performance of buildings during the winter period.

    Science.gov (United States)

    Zenginis, Dimitrios G; Kontoleon, Karolos J

    2017-07-25

    The objective of this study is to assess the effect of orientation, glazing proportion and aspect ratio of building zones on heat fluxes through their surfaces, under specific environmental conditions. The investigation is carried out for thermally-insulated building zones with a varying facade orientation corresponding to each cardinal point, during the winter period in the northern Greek region. For this purpose, three glazing-to-facade ratios (GR) are taken into account; along with the glazing ratio the influence of the glazing U value is also considered. Regarding the impact of the fenestration layout geometry, five different building aspect ratio profiles are examined. Thermal fluxes are assessed for two different indoor temperature settings, while the operation of the heating unit is assumed to be continuous. The transient thermal analysis with its mathematical formulation and solution are based on the thermal-network modelling approach, while the solar heat gain through glazing relies on the sunlit-pattern approach; in this way, the stricken by the solar rays glazing area is projected onto any interior surfaces to form the so called "sunlit" areas. As the orientation, glazing proportion and aspect ratio of the building zone vary, so do the sizes and shapes of the illuminated "sunlit" areas. Accordingly, the delivered into the zone direct solar energy and its diffused and ground reflected components can be determined. The adopted methodology provides a more accurate determination of solar heat gain with respect to glazing proportion and orientation as well as zone aspect ratio. With regard to surface orientation, glazing proportion and aspect ratio, computer results demonstrate the improvement of the thermal performance for a building zone with a south oriented glazing surface, as well as the deterioration for the other surface orientations; relative increases/decreases in the energy fluxes of a rectangular shaped building zone compared to a square

  4. 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 <5 s respectively. The observed results revealed that apart from high aspect ratio nanostructures and the extent of enzyme loading, surface defect density also hold a key towards ZnO nanostructures based bio-sensing applications.

  5. Femtosecond laser high-efficiency drilling of high-aspect-ratio microholes based on free-electron-density adjustments.

    Science.gov (United States)

    Jiang, Lan; Fang, Juqiang; Cao, Qiang; Zhang, Kaihu; Wang, Peng; Yu, Yanwu; Huang, Qiang; Lu, Yongfeng

    2014-11-01

    We studied the micromachining of high-aspect-ratio holes in poly(methylmethacrylate) using a visible double-pulse femtosecond laser based on free-electron-density adjustments. Hole depth and aspect ratio increased simultaneously upon decreasing the wavelength in the visible-light zone. When the pulse energy reached a high level, the free-electron density was adjusted by using a double-pulse laser, which induced fewer free electrons, a lower reflectivity plasma plume, and more pulse energy deposition in the solid bottom. Thus, the aspect ratio of the hole was improved considerably. At a moderate pulse energy level, a 1.3-1.4 times enhancement of both the ablation depth and the aspect ratio was observed when the double-pulse delay was set between 100 and 300 fs, probably due to an enhanced photon-electron coupling effect through adjusting the free-electron density. At a lower pulse energy level, this effect also induced the generation of a submicrometer string. In addition, the ablation rate was improved significantly by using visible double pulses.

  6. 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.

  7. 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

  8. 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

    2017-03-23

    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, 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/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.

  9. Facile Synthesis of Silver Nanowires with Different Aspect Ratios and Used as High-Performance Flexible Transparent Electrodes

    Science.gov (United States)

    Xue, Qingwen; Yao, Weijing; Liu, Jun; Tian, Qingyong; Liu, Li; Li, Mengxiao; Lu, Qiang; Peng, Rui; Wu, Wei

    2017-08-01

    Silver nanowires (Ag NWs) are the promising materials to fabricate flexible transparent electrodes, aiming to replace indium tin oxide (ITO) in the next generation of flexible electronics. Herein, a feasible polyvinylpyrrolidone (PVP)-mediated polyol synthesis of Ag NWs with different aspect ratios is demonstrated and high-quality Ag NWs transparent electrodes (NTEs) are fabricated without high-temperature thermal sintering. When employing the mixture of PVP with different average molecular weight as the capping agent, the diameters of Ag NWs can be tailored and Ag NWs with different aspect ratios varying from ca. 30 to ca. 1000 are obtained. Using these as-synthesized Ag NWs, the uniform Ag NWs films are fabricated by repeated spin coating. When the aspect ratios exceed 500, the optoelectronic performance of Ag NWs films improve remarkably and match up to those of ITO films. Moreover, an optimal Ag NTEs with low sheet resistance of 11.4 Ω/sq and a high parallel transmittance of 91.6% at 550 nm are achieved when the aspect ratios reach almost 1000. In addition, the sheet resistance of Ag NWs films does not show great variation after 400 cycles of bending test, suggesting an excellent flexibility. The proposed approach to fabricate highly flexible and high-performance Ag NTEs would be useful to the development of flexible devices.

  10. High Aspect Ratio Nanoimprint Mold-Cavity Filling and Stress Simulation Based on Finite-Element Analysis

    Directory of Open Access Journals (Sweden)

    Hongwen Sun

    2017-08-01

    Full Text Available High aspect ratio three-dimensional micro- and nanopatterns have important applications in diverse fields. However, fabricating these structures by a nanoimprinting method invites problems like collapse, dislocation, and defects. Finite-element analysis (FEA is a good approach to help understand the filling process and stress distribution. The FEA method was employed to simulate the nanoimprinting process using positive and negative molds with aspect ratios of 1:1, 3:1, 5:1, and 7:1. During the filling process, the resist adjacent to boundaries has the maximum displacement. The corners of contact areas between the protruding part of the mold and the resist has the maximum Von Mises stress. For both positive and negative molds, the maximum stress in the mold increases with aspect ratio. However, filling up negative molds is more difficult than positive ones. With the same aspect ratio, the maximum stress in a negative mold is approximately twice as large as that in a positive one.

  11. 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

  12. 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.

  13. Socio-cultural aspects of the high masculinity ratio in India.

    Science.gov (United States)

    Singh, J P

    2010-01-01

    The paper aims to explicate those factors accountable for the continuing imbalance in the sex ratio and its further masculinization over the whole of the 20th century. Here it is contended that the traditional practice of female infanticide and the current practice of female foeticide in the contemporary period, especially in the north-west and Hindi-speaking states, have significantly contributed to the high masculinity ratio in India. In addition, increasingly higher survival ratios of male children, particularly from the 1951 census onward, have been the prime reason for a declining proportion of females in the Indian population. As the Indian value system has been imbued with a relatively higher preference for sons, improvements in health facilities have benefited males more than females, giving rise to a highly imbalanced sex ratio in the country. This scenario, however, has steadily tended to alter in favour of greater balance in sex ratio.

  14. 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

  15. Considerations on using SU-8 as a construction material for high aspect ratio structures

    NARCIS (Netherlands)

    Melai, J.; Salm, Cora; Smits, Sander M.; Blanco Carballo, V.M.; Schmitz, Jurriaan; Hageluken, Ben

    2007-01-01

    This paper discusses two material aspects of SU-8 that have up till now been insufficiently documented. We present initial results on the outgassing behavior and a study on the dielectric properties of SU-8 at high bias voltage. The dielectric strength is determined to be at least 2 MV/cm. These

  16. A triaxial tensile deformation-induced nanoporous structure of aluminium: estimation of surface area, solid volume, and dimensionless aspect ratio.

    Science.gov (United States)

    Kumar, Sunil; Das, Suchandan K

    2017-08-09

    Nanoporous aluminium has great importance for large scale production of automobile and aerospace spare parts due to its lightweight and non-corrosive nature. It is also suitable for various packaging applications of edible things, electronic components, and medicines. We have used triaxial tensile deformation methodology to create a nanoporous structure of aluminium using molecular dynamics simulation. The surface area and solid volume have been calculated to characterize the 3-D nanoporous structure of aluminium. We have quantitatively characterized the growth and coalescences of the nanoporous structure via estimation of the number of nanopores, nanopore diameters, and dimensionless aspect-ratios (surface area to volume ratio). A high aspect ratio indicates a large number of tiny nanopores in the 3-D nanoporous structure of aluminium. We have found that crystalline aluminium (under ambient condition) significantly depicts a smaller aspect ratio as compared to amorphous aluminium during triaxial tensile deformation. We believe that the results of this study will provide new understanding to the researchers for the design and characterization of nanoporous metals.

  17. Cause and Cure - Deterioration in Accuracy of CFD Simulations With Use of High-Aspect-Ratio Triangular Tetrahedral Grids

    Science.gov (United States)

    Chang, Sin-Chung; Chang, Chau-Lyan; Venkatachari, Balaji Shankar

    2017-01-01

    Traditionally high-aspect ratio triangular/tetrahedral meshes are avoided by CFD re-searchers in the vicinity of a solid wall, as it is known to reduce the accuracy of gradient computations in those regions and also cause numerical instability. Although for certain complex geometries, the use of high-aspect ratio triangular/tetrahedral elements in the vicinity of a solid wall can be replaced by quadrilateral/prismatic elements, ability to use triangular/tetrahedral elements in such regions without any degradation in accuracy can be beneficial from a mesh generation point of view. The benefits also carry over to numerical frameworks such as the space-time conservation element and solution element (CESE), where triangular/tetrahedral elements are the mandatory building blocks. With the requirement of the CESE method in mind, a rigorous mathematical framework that clearly identities the reason behind the difficulties in use of such high-aspect ratio triangular/tetrahedral elements is presented here. As will be shown, it turns out that the degree of accuracy deterioration of gradient computation involving a triangular element is hinged on the value of its shape factor Gamma def = sq sin Alpha1 + sq sin Alpha2 + sq sin Alpha3, where Alpha1; Alpha2 and Alpha3 are the internal angles of the element. In fact, it is shown that the degree of accuracy deterioration increases monotonically as the value of Gamma decreases monotonically from its maximal value 9/4 (attained by an equilateral triangle only) to a value much less than 1 (associated with a highly obtuse triangle). By taking advantage of the fact that a high-aspect ratio triangle is not necessarily highly obtuse, and in fact it can have a shape factor whose value is close to the maximal value 9/4, a potential solution to avoid accuracy deterioration of gradient computation associated with a high-aspect ratio triangular grid is given. Also a brief discussion on the extension of the current mathematical framework to the

  18. 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.

  19. 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.

  20. 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.

  1. Single phase flow characteristics of FC-72 and ethanol in high aspect ratio rectangular mini- and micro-channels

    Science.gov (United States)

    Wang, Yuan; Wang, Zhen-guo

    2016-11-01

    Single phase flow friction factor of FC-72 and ethanol in mini-and micro-channels are experimentally investigated in the present study. High aspect ratio3 rectangular channels are selected, the hydraulic diameters of which are 571 µm, 762 µm and 1454 µm, and the aspect ratios are 20, 20 and 10 respectively. Degassed ethanol and FC-72 are used as working fluids. All the friction factors acquired in the 571 µm and 762 µm channels agree with the conventional friction theory within  ±20%-±25%. In the 1454 µm channel, however, deviations from the conventional theory occur and a modified empirical correlation of friction factor as a function of Reynolds number is proposed. Early transition from laminar to transitional flow is captured. Besides, effects of liquid physical properties are discussed. Lower viscosity and higher liquid density are responsible for the higher friction factor of FC-72. The influence of liquid properties weakens as the Reynolds number increases.

  2. 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.

  3. 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

  4. Effects of drilling parameters and aspect ratios on delamination and surface roughness of lignocellulosic HFRP composite laminates

    OpenAIRE

    Ismail, Sikiru; Dhakal, Hom Nath; Dimla, Eric; Beaugrand, Johnny; Popov, Ivan Eugeniev

    2015-01-01

    Hemp fibre-reinforced polycaprolactone (HFRP) composite has inherent good mechanical properties and benefits which include remarkably high specific strength and modulus, low density and renewability. No doubt, these properties have attracted wider applications of HFRP composite in engineering applications. This paper presents an investigation on the influence of drilling parameters and fibre aspect ratios, AR (0, 19, 26, 30 and 38) on delamination damage factor and surface roughness of HFRP c...

  5. 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.

  6. 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...... 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....

  7. 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.

  8. Seed-mediated synthesis of gold nanorods: control of the aspect ratio by variation of the reducing agent

    Energy Technology Data Exchange (ETDEWEB)

    Koeppl, Susanne; Ghielmetti, Nico [ETH Zurich, Laboratory for Nanometallurgy, Department of Materials (Switzerland); Caseri, Walter, E-mail: wcaseri@mat.ethz.ch [ETH Zurich, Polymer Technology, Department of Materials (Switzerland); Spolenak, Ralph [ETH Zurich, Laboratory for Nanometallurgy, Department of Materials (Switzerland)

    2013-03-15

    Seed-mediated growth methods involving reduction of tetrachloroaurate(III) with ascorbic acid are common for the synthesis of gold nanorods. This study shows, however, that simply by appropriate choice of the reducing agent a drastic influence on the aspect ratio can be attained. Weaker reducing agents, such as dihydroxybenzene isomers (hydroquinone, catechol or resorcinol) or glucose can increase the aspect ratio of the nanorods by an order of magnitude, up to values as high as 100 (nanowires). The increase in aspect ratio is mainly a consequence of an increase in length of the particles (up to 1-3 {mu}m). This effect is probably associated with a decrease in the reduction rate of gold(III) species by dihydroxybenzenes or glucose compared to ascorbic acid. The reduction potential of the reducing agents strongly depends on the pH value, and related effects on the dimensions of the nanoparticles are also reflected in this study. The nanorods exhibited penta-twinned nature without noteworthy defects (e.g. stacking faults and dislocations).

  9. Microdevice arrays of high aspect ratio poly(dimethylsiloxane) pillars for the investigation of multicellular tumour spheroid mechanical properties.

    Science.gov (United States)

    Aoun, Laurène; Weiss, Pierre; Laborde, Adrian; Ducommun, Bernard; Lobjois, Valérie; Vieu, Christophe

    2014-07-07

    We report the design, fabrication and evaluation of an array of microdevices composed of high aspect ratio PDMS pillars, dedicated to the study of tumour spheroid mechanical properties. The principle of the microdevice is to confine a spheroid within a circle of micropillars acting as peripheral flexible force sensors. We present a technological process for fabricating high aspect ratio micropillars (300 μm high) with tunable feature dimensions (diameter and spacing) enabling production of flexible PDMS pillars with a height comparable to spheroid sizes. This represents an upscale of 10 along the vertical direction in comparison to more conventional PDMS pillar force sensors devoted to single cell studies, while maintaining their force sensitivity in the same order of magnitude. We present a method for keeping these very high aspect ratio PDMS pillars stable and straight in liquid solution. We demonstrate that microfabricated devices are biocompatible and adapted to long-term spheroid growth. Finally, we show that the spheroid interaction with the micropillars' surface is dependent on PDMS cellular adhesiveness. Time-lapse recordings of growth-induced micropillars' bending coupled with a software program to automatically detect and analyse micropillar displacements are presented. The use of these microdevices as force microsensors opens new prospects in the fields of tissue mechanics and pharmacological drug screening.

  10. Effects of building aspect ratio, diurnal heating scenario, and wind speed on reactive pollutant dispersion in urban street canyons.

    Science.gov (United States)

    Tong, Nelson Y O; Leung, Dennis Y C

    2012-01-01

    A photochemistry coupled computational fluid dynamics (CFD) based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario (solar radiation affections in nighttime, daytime, and sun-rise/set), wind speed, building aspect ratio (building-height-to-street-width), and dispersion of reactive gases, specifically nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and O3. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of O3 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.

  11. A self-seeding synthesis of Ag microrods of tuned aspect ratio: ascorbic acid plays a key role.

    Science.gov (United States)

    Visaveliya, Nikunjkumar; Köhler, J Michael

    2013-08-30

    Control of the shape and size of nanoparticles is crucial for using them as labels or as building blocks in nanotechnology. In fact, silver has so far been considered as having the widest variety of different morphologies at the nano-scale and micro-scale levels. To make progress in these criteria, in our paper we have synthesized highly reproducible silver (Ag) microrods of controlled aspect ratios through a rapid self-seeding method. The Ag nano seeds are formed via the reduction of Ag ions in hot ethylene glycol by ascorbic acid, and the subsequent growth of microrods is controlled by further deposition of Ag atoms in the presence of poly(vinylpyrrolidone). Moreover, ascorbic acid is exclusively responsible for the rod morphology, as we describe here in detail. A very low concentration of ascorbic acid forms very few Ag microrods along with a majority of Ag colloidal particles, while random overgrowth on the surfaces is observed for higher concentrations. The critical reaction condition has been found in that the aspect ratio of the Ag microrods can be systematically tuned between 4 and 90. Also, the method in which ascorbic acid is added to the reaction medium plays a key role in controlling the aspect ratio of the Ag microrods. The non-monotonic dependence of the length and the diameter of the Ag microrods has been described by an empirical equation. The function can be interpreted by means of concentration-dependent competition between the adsorption of ligands and metal deposition.

  12. 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.

  13. Channel aspect ratio effect for serpentine proton exchange membrane fuel cell: Role of sub-rib convection

    Science.gov (United States)

    Wang, Xiao-Dong; Duan, Yuan-Yuan; Yan, Wei-Mon; Lee, Duu-Jong; Su, Ay; Chi, Pei-Hung

    A complete three-dimensional, two-phase, non-isothermal model for proton exchange membrane (PEM) fuel cells was used to investigate the effect of the sub-rib convection on the performances for the single and triple serpentine flow fields at various channel aspect ratios and different thermal constraints. The occurrence of sub-rib convection, which is affected by the serpentine flow field, significantly influences the cell performance if the oxygen supply or membrane moisture content was limited. For single serpentine flow field in which sub-rib convection presents under all ribs, changing channel aspect ratio has minimal effects on cell performance since the oxygen supply is sufficient. For triple serpentine flow field or for serpentine cell with poor external heat loss, owing to limited sub-rib convection or to low membrane moisture content, decrease in channel aspect ratio significantly enhances cell performance. Blocking up the sub-rib convection markedly reduces cell performance. Flow field design for PEM fuel cell should take into consideration the effects of sub-rib convection flow on cell performance.

  14. Versatile pattern generation of periodic, high aspect ratio Si nanostructure arrays with sub-50-nm resolution on a wafer scale.

    Science.gov (United States)

    Ho, Jian-Wei; Wee, Qixun; Dumond, Jarrett; Tay, Andrew; Chua, Soo-Jin

    2013-12-01

    We report on a method of fabricating variable patterns of periodic, high aspect ratio silicon nanostructures with sub-50-nm resolution on a wafer scale. The approach marries step-and-repeat nanoimprint lithography (NIL) and metal-catalyzed electroless etching (MCEE), enabling near perfectly ordered Si nanostructure arrays of user-defined patterns to be controllably and rapidly generated on a wafer scale. Periodic features possessing circular, hexagonal, and rectangular cross-sections with lateral dimensions down to sub-50 nm, in hexagonal or square array configurations and high array packing densities up to 5.13 × 107 structures/mm2 not achievable by conventional UV photolithography are fabricated using this top-down approach. By suitably tuning the duration of catalytic etching, variable aspect ratio Si nanostructures can be formed. As the etched Si pattern depends largely on the NIL mould which is patterned by electron beam lithography (EBL), the technique can be used to form patterns not possible with self-assembly methods, nanosphere, and interference lithography for replication on a wafer scale. Good chemical resistance of the nanoimprinted mask and adhesion to the Si substrate facilitate good pattern transfer and preserve the smooth top surface morphology of the Si nanostructures as shown in TEM. This approach is suitable for generating Si nanostructures of controlled dimensions and patterns, with high aspect ratio on a wafer level suitable for semiconductor device production.

  15. Effects of aspect ratio on the mode couplings of thin-film bulk acoustic wave resonators

    Science.gov (United States)

    Li, Nian; Qian, Zhenghua; Yang, Jiashi

    2017-05-01

    We studied mode couplings in thin film bulk acoustic wave resonators of a piezoelectric film on a dielectric layer operating with the fundamental thickness-extensional mode. A system of plate equations derived in our previous paper was used which includes the couplings to the unwanted in-plane extension, flexure, fundamental and second-order thickness shear modes. It was shown that the couplings depend strongly on the plate length/thickness ratio. For a relatively clean operating mode with weak couplings to unwanted modes, a series of discrete values of the plate length/thickness ratio should be avoided and these values were determined in the present paper. The results can be of great significance to the design and optimization of film bulk acoustic wave resonators.

  16. Maskless Shaping of Gold Stud Bumps as High Aspect Ratio Microstructures

    Science.gov (United States)

    2010-01-01

    electrodes/reactors for coulome- try and anodic stripping voltammetry in LOC devices [3,13]. Previ- ously we have employed electroplating through resist... factors affecting pattern transfer such as the ratio of im- print area to total surface area on the template and resolution. The 50 lm deep molds were...pertinent factors such as temperature, time and initial stud bump size or available gold volume (3.19 1013 m3) were kept constant. All metrology

  17. Numerical Study of the Rib Arrangements for Enhancing Heat Transfer in a Two-pass Channel of Large Aspect Ratio

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sol; Choi, Seok Min; Sohn, Ho-Seong; Cho, Hyung Hee [Yonsei Univ., Seoul (Korea, Republic of)

    2017-03-15

    The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was 60°, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio (e/D{sub n}) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

  18. 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)

  19. Ultra-high aspect ratio poly-Si FinFET using an improved spacer formation technique

    Science.gov (United States)

    Liu, Libin; Liang, Renrong; Wang, Jing; Xu, Jun

    2017-04-01

    An improved spacer formation technique was proposed and developed to fabricate poly-Si fin field-effect transistors (FinFETs) with an ultra-high aspect ratio. The as-demonstrated FinFETs have a fin channel with a width and height of 22 nm and 230 nm, respectively, corresponding to an aspect ratio of 10.5. The electrical and temperature properties of the FinFETs are described in detail in this paper. The poly-Si FinFETs exhibit a steep subthreshold swing (196 mV/dec), a low leakage current (∼10-14 A), a high on/off current ratio (2.2 × 107 at VDS = 0.1 V), and a low drain-induced barrier lowering effect (0.28 V). The excellent switching characteristics are attributed to the ultrathin channel body and the multi-gate structure combined with high-k Al2O3 dielectric. Furthermore, the electron field-effective mobility increases as the temperature increases. An analytical fitting model was derived and was utilized to account for this phenomenon. The fitting results indicate that the positive temperature coefficient originates from the grain boundary-controlled mechanism in the low gate voltage regime.

  20. Polydimethyl siloxane wet etching for three dimensional fabrication of microneedle array and high-aspect-ratio micropillars.

    Science.gov (United States)

    Deng, Yu-Luen; Juang, Yi-Je

    2014-03-01

    Among various transdermal drug delivery (TDD) approaches, utilizing the microneedles (MNs) not only can penetrate the skin but also deliver the drug with reduced tissue damage, reduced pain, and no bleeding. However, the MNs with larger height are required to overcome the skin barrier for effective TDD. Unlike 2D patterning, etching polydimethyl siloxane (PDMS) micropillars for fabrication of 3D microstructures is presented. The PDMS micropillars were first constructed by casting PDMS on the computer numerical control-machined cylindrical microwells, which then went through etching process to obtain the MNs for subsequent fabrication of polymer MNs or high aspect ratio micropillars.

  1. 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.

  2. Experimental investigation of the effect of curvature on heat transfer in a curved rectangular channel of high aspect ratio

    Science.gov (United States)

    Hawk, John R., III

    1987-03-01

    An experimental investigation was conducted to study convective heat transfer in straight and curved rectangular channels of high aspect ratio that approximate plates of infinite extent. Experiments were performed at steady state in the turbulent flow regime with one wall held at a constant heat flux and the opposite wall essentially adiabatic. The effect of curvature induced secondary flow on heat transfer on the concave and convex walls was observed by comparing Nusselt numbers for four different configurations at several different Reynolds numbers. Significant heat transfer enhancement was observed on the concave wall. Correlations for Nusselt number as a function of Reynolds number were calculated for the cases studied.

  3. Fabrication of Ni stamp with high aspect ratio, two-leveled, cylindrical microstructures using dry etching and electroplating

    DEFF Research Database (Denmark)

    Petersen, Ritika Singh; Keller, Stephan Sylvest; Hansen, Ole

    2015-01-01

    obtained by defining a reservoir and a separating trench with different depths of 85 and 125 μm, respectively, in a single embossing step. The fabrication of the required two leveled stamp is done using a modified DEEMO (dry etching, electroplating and molding) process. Dry etching using the Bosch process......We describe a process for the fabrication of a Ni stamp that is applied to the microstructuring of polymers by hot embossing. The target devices are microcontainers that have a potential application in oral drug delivery. Each container is a 3D, cylindrical, high aspect ratio microstructure...

  4. Freestanding membrane composed of micro-ring array with ultrahigh sidewall aspect ratio for application in lightweight cathode arrays

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lanlan [State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Liu, Hongzhong, E-mail: hzliu@mail.xjtu.edu.cn [State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Jiang, Weitao, E-mail: wtjiang@mail.xjtu.edu.cn [State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Gao, Wei [Key Laboratory of Mechanics on Western Disasters and Environment, Lanzhou University, Lanzhou 730000 (China); Chen, Bangdao [State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Li, Xin [Department of Microelectronics, Xi’an Jiaotong University, Xi’an 710049 (China); Ding, Yucheng [State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); An, Ningli [Department of Packaging Engineering, Xi’an University of Technology, Xi’an 710048 (China)

    2014-12-15

    Graphical abstract: A freestanding multilayer ultrathin nano-membrane (FUN-membrane) with a micro-ring array (MRA), in which the dimension of each micro-ring is 3 μm in diameter, 2 μm in height and sub-100 nm in sidewall thickness is successfully fabricated, as shown in the SEM image of figure (a). Due to the MRA with ultrahigh aspect ratio of dielectric-metal sidewall, the FUN-membrane can be transferred to either rigid or flexible substrate to be used as the cathode for lightweight display panel, as shown in the schematic of figure (b). - Highlights: • Exploring a new fabrication method for the freestanding ultrathin nano-membrane (FUN-membrane). • FUN-membrane is composed of micro-ring array with ultrahigh aspect ratio of the insulator-metal sidewall. • The sharp metal edge of each micro-ring is preferred to be served as the micro-emitter. - Abstract: A freestanding multilayer ultrathin nano-membrane (FUN-membrane) with a micro-ring array (MRA) is successfully fabricated through the controllable film deposition. Each micro-ring of FUN-membrane is 3 μm in diameter, 2 μm in height and sub-100 nm in sidewall thickness, demonstrating an ultrahigh sidewall aspect ratio of 20:1. In our strategy, a silica layer (200 nm in thickness), a chromium transition layer (5 nm-thick) and a gold layer (40 nm-thick), were in sequence deposited on patterned photoresist. After removal of the photoresist by lift-off process, a FUN-membrane with MRA was peeled off from the substrate, where the gold layer acted as a protecting layer to prevent the MRA from fracture. The FUN-membrane was then transferred to a flexible polycarbonate (PC) sheet coated with indium tin oxide (ITO) layer, which was then used as a flexible and lightweight cathode. Remarkably, the field emission effect of the fabricated FUN-membrane cathode performs a high field-enhancement factor of 1.2 × 10{sup 4} and a low turn-on voltage of 2 V/μm, indicating the advantages of the sharp metal edge of MRA. Due

  5. 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.

  6. Low-temperature Fabrication Process for Integrated High-Aspect Ratio Metal Oxide Nanostructure Semiconductor Gas Sensors

    Science.gov (United States)

    Clavijo, William P.

    This work presents a new low-temperature fabrication process of metal oxide nanostructures that allows high-aspect ratio zinc oxide (ZnO) and titanium dioxide (TiO2) nanowires and nanotubes to be readily integrated with microelectronic devices for sensor applications. This process relies on a new method of forming a close-packed array of self-assembled high-aspect-ratio nanopores in an anodized aluminum oxide (AAO) template in a thin (2.5 microm) aluminum film deposited on a silicon and lithium niobate substrate (LiNbO3). This technique is in sharp contrast to traditional free-standing thick film methods and the use of an integrated thin aluminum film greatly enhances the utility of such methods. We have demonstrated the method by integrating ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes onto the metal gate of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and the delay line of a surface acoustic wave (SAW) device to form an integrated ChemFET (Chemical Field-Effect Transistor) and a orthogonal frequency coded (OFC) SAW gas sensor. The resulting metal oxide nanostructures of 1-1.7 microm in height and 40-100 nm in diameter offer an increase of up to 220X the surface area over a standard flat metal oxide film for sensing applications.

  7. 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.

  8. Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

    Directory of Open Access Journals (Sweden)

    H. Munoz

    2017-08-01

    Full Text Available The complete stress–strain characteristics of sandstone specimens were investigated in a series of quasi-static monotonic uniaxial compression tests. Strain patterns development during pre- and post-peak behaviours in specimens with different aspect ratios was also examined. Peak stress, post-peak portion of stress–strain, brittleness, characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect ratio. Strain patterns of the rocks were obtained by applying three-dimensional (3D digital image correlation (DIC technique. Unlike conventional strain measurement using strain gauges attached to specimen, 3D DIC allowed not only measuring large strains, but more importantly, mapping the development of field strain throughout the compression test, i.e. in pre- and post-peak regimes. Field strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak regime. However, in post-peak regime, strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised zone. The extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength degradation. Strain localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

  9. A sub-atmospheric chemical vapor deposition process for deposition of oxide liner in high aspect ratio through silicon vias.

    Science.gov (United States)

    Lisker, Marco; Marschmeyer, Steffen; Kaynak, Mehmet; Tekin, Ibrahim

    2011-09-01

    The formation of a Through Silicon Via (TSV) includes a deep Si trench etching and the formation of an insulating layer along the high-aspect-ratio trench and the filling of a conductive material into the via hole. The isolation of the filling conductor from the silicon substrate becomes more important for higher frequencies due to the high coupling of the signal to the silicon. The importance of the oxide thickness on the via wall isolation can be verified using electromagnetic field simulators. To satisfy the needs on the Silicon dioxide deposition, a sub-atmospheric chemical vapor deposition (SA-CVD) process has been developed to deposit an isolation oxide to the walls of deep silicon trenches. The technique provides excellent step coverage of the 100 microm depth silicon trenches with the high aspect ratio of 20 and more. The developed technique allows covering the deep silicon trenches by oxide and makes the high isolation of TSVs from silicon substrate feasible which is the key factor for the performance of TSVs for mm-wave 3D packaging.

  10. 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.

  11. Electromechanical properties of multi-walled carbon nanotube/gelatin hydrogel composites: effects of aspect ratios, electric field, and temperature.

    Science.gov (United States)

    Tungkavet, Thawatchai; Seetapan, Nispa; Pattavarakorn, Datchanee; Sirivat, Anuvat

    2015-01-01

    The effects of multi-walled carbon nanotube (MWNT) aspect ratio, electric field strength and temperature on the electromechanical properties of MWNT/gelatin hydrogel composites were investigated. The highest aspect ratio of MWNT provides the composites with the highest dynamic moduli under electric field. The MWNT/gelatin hydrogel composites of 0.01, 0.1, 0.5, and 1 vol.% and the pure gelatin hydrogel possess the storage modulus sensitivity values of 0.69, 1.23, 0.94, 0.81 and 0.47, respectively, at 800 V/mm. The results can be interpreted in terms of the enhanced polarizability between the carboxyl groups of gelatin under the presence of MWNT. The effect of temperature on the electromechanical properties of MWNT/gelatin hydrogel composites investigated between 30 °C and 90 °C shows three distinct regimes of temperature-dependent storage modulus behavior. In the deflection testing, the effects of electric field on the deflection distance and the dielectrophoresis force of the MWNT/gelatin hydrogel composites were also investigated. MWNT/gelatin hydrogel composites suspended in the silicone oil between electrodes, respond rapidly with a deflection toward the anode site, indicating the attractive force between anode and the polarized carboxyl group as the gelatin structure possesses negative charges. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. 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.

  13. 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.

  14. Fabrication and characterization of analyzer gratings with high aspect ratios for phase contrast imaging using a Talbot interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Kenntner, Johannes; Altapova, Venera; Grund, Thomas; Pantenburg, Franz Josef; Meiser, Jan; Baumbach, Tilo; Mohr, Juergen [Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), 76021 Karlsruhe (Germany); Karlsruhe Institute of Technology (KIT), Laboratory for Application of Synchrotron Radiation, 76128 Karlsruhe (Germany); Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), 76021 Karlsruhe (Germany); Karlsruhe Institute of Technology (KIT), Laboratory for Application of Synchrotron Radiation, 76128 Karlsruhe (Germany); Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), 76021 Karlsruhe (Germany)

    2012-05-17

    In recent years, X-ray imaging based on the differential phase contrast gained more and more attention to be used in X-ray imaging. Among other techniques like crystal-based diffraction and propagation methods, the grating based Talbot interferometry offers an approach measuring phase modulations of X-rays while passing low absorbing objects. The Talbot interferometer yields for highly efficient X-ray imaging signals for hard X-rays with energies above 10 keV. One factor with high impact on the imaging performance of such grating interferometers is the gratings quality. We introduce a fabrication process allowing both, the fabrication of phase modulating and analyzer gratings with high aspect ratios, up to 100. Structural deviations from the optimal geometry of the gratings are investigated and their influence on the obtained image quality is discussed.

  15. Effect of aspect ratio on microstructure and magnetic properties of spinel CoFe2O4 nanowire arrays

    Science.gov (United States)

    Wu, Zhangben; Niu, Peili; Yang, Bai; Yu, Ronghai

    2011-10-01

    Cobalt ferrite (CoFe2O4) nanowire arrays with different diameters were prepared in porous anodic aluminum oxide (AAO) template by a sol-gel template method with the assistance of organic solvent and surfactant. The morphology was studied by scanning electron and transmission electron microscopy. A polycrystalline phase of spinel type structure was ascertained by X-ray diffraction (XRD) patterns. A magnetic test was performed using a physical property measurement system (PPMS), showing the uniaxial anisotropy with easy axis along the nanowire with an aspect ratio larger than 1000. A coercivity reduction from about 1500 Oe to about 800 Oe has been observed, while the diameter increases from 20 nm to 50 nm in this experiment. The cause of this has been discussed.

  16. CMOS patterning over high-aspect ratio topographies for N10/N7 using spin-on carbon hardmasks

    Science.gov (United States)

    Hopf, Toby; Ercken, Monique; Mannaert, Geert; Kunnen, Eddy; Tao, Zheng; Vandenbroeck, Nadia; Sebaai, Farid; Kikuchi, Yoshiaki; Mertens, Hans; Kubicek, Stefan; Demuynck, Steven; Horiguchi, Naoto

    2017-03-01

    In this paper proof-of-principle demonstrations of spin-on carbon (SOC)/spin-on glass (SOG)-based lithography processes which could replace standard patterning stacks within the FEOL for upcoming advanced nodes like N10/N7 are presented. At these dimensions the standard lithography approaches that have been utilized within the previous nodes will begin to run into fundamental limitations as a result of the extremely high aspect ratios of the device topography, requiring both new materials as well as new patterning flows in order to allow for continued device scaling. Here, novel SOC/SOG-based patterning flows have been demonstrated which could be applied to implement Source Drain Extension implantations and epitaxial growth processes for CMOS FinFET device architectures even down at N10/N7 dimensions.

  17. 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.

  18. Cultivation of the photosynthesis microorganism in a Taylor-Couette Vortex Flow with a small aspect ratio

    Science.gov (United States)

    Kawai, H.; Yasui, S.; Takahashi, H.; Kikura, H.; Aritomi, M.

    2009-02-01

    This study focuses on the dynamics of the Taylor-Couette Vortex Flow (TVF) in a photo-bioreactor in which CO2 is changed to O2 with high efficiency by the photosynthesis ability of micro algae. Stirring by means of a screw propeller is generally used for a simple agitation. However, the problem is that there exists a very high shearing flow region just near the propeller, which causes the destruction of the alga cell by the shearing force. In contrast, the TVF mixing is expected to reduce such a local and random shearing force because of their column of steady and orderly vortices. In this study, the relationship between the microorganism growth rate and the flow structures in dilute suspensions of a TVF is investigated and the flow characteristics are measured by using an ultrasonic velocity profiler with a small aspect ratio of 3.

  19. Hydrothermal synthesis of hexagonal WO3 nanowires with high aspect ratio and their electrochemical properties for lithium-ion batteries

    Science.gov (United States)

    Phuruangrat, Anukorn; Yayapao, Oranuch; Thongtem, Titipun; Thongtem, Somchai

    2017-12-01

    One dimensional WO3 nanowires with high aspect ratio of >200 were synthesized by hydrothermal method. The effects of reaction temperature and time on phase and morphologies were studied and discussed. In this research, a suitable hydrothermal condition is at 200°C for 48 h. XRD, SEM, and TEM results show that the product is hexagonal WO3 phase with diameter of 25 nm and several ten micrometers long with growth in the c direction. The electrochemical properties were tested for rechargeable lithium batteries. The WO3 NWs electrode exhibits a stability trend over the 30 cycle testing. Some long-term activation process is attributed to the WO3 NWs electrode during charge/discharge reaction.

  20. Internal Laser Writing of High-Aspect-Ratio Microfluidic Structures in Silicate Glasses for Lab-on-a-Chip Applications

    Directory of Open Access Journals (Sweden)

    Ya Cheng

    2017-02-01

    Full Text Available Femtosecond laser direct writing is unique in allowing for fabrication of 3D micro- and nanofluidic structures, thereby enabling rapid and efficient manipulation of fluidic dynamics in 3D space to realize innovative functionalities. Here, I discuss the challenges in producing fully functional and highly integrated 3D micro- and nanofluidic systems with potential applications ranging from chemical and biological analyses to investigations of nanofluidic behaviors. In particular, I review the achievements we have made in the past decade, which have led to 3D microchannels with controllable cross-sectional profiles and large aspect ratios, 3D nanofluidic channels with widths of several tens of nanometers, and smooth inner walls with roughness on the order of ~1 nm. Integration of the microfluidics with other functional microcomponents including microoptics and microelectrodes will also be discussed, followed by conclusions and the future perspective.

  1. 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.

  2. A vortex model for forces and moments on low-aspect-ratio wings in side-slip with experimental validation

    Science.gov (United States)

    DeVoria, Adam C.; Mohseni, Kamran

    2017-02-01

    This paper studies low-aspect-ratio (.org/1999/xlink" xlink:href="rspa20160760ie1"/>) rectangular wings at high incidence and in side-slip. The main objective is to incorporate the effects of high angle of attack and side-slip into a simplified vortex model for the forces and moments. Experiments are also performed and are used to validate assumptions made in the model. The model asymptotes to the potential flow result of classical aerodynamics for an infinite aspect ratio. The .org/1999/xlink" xlink:href="rspa20160760ie2"/> → 0 limit of a rectangular wing is considered with slender body theory, where the side-edge vortices merge into a vortex doublet. Hence, the velocity fields transition from being dominated by a spanwise vorticity monopole (.org/1999/xlink" xlink:href="rspa20160760ie3"/> ≫ 1) to a streamwise vorticity dipole (.org/1999/xlink" xlink:href="rspa20160760ie4"/> ˜ 1). We theoretically derive a spanwise loading distribution that is parabolic instead of elliptic, and this physically represents the additional circulation around the wing that is associated with reattached flow. This is a fundamental feature of wings with a broad-facing leading edge. The experimental measurements of the spanwise circulation closely approximate a parabolic distribution. The vortex model yields very agreeable comparison with direct measurement of the lift and drag, and the roll moment prediction is acceptable for .org/1999/xlink" xlink:href="rspa20160760ie5"/> ≤ 1 prior to the roll stall angle and up to side-slip angles of 20°.

  3. Periodic TiO₂ Nanostructures with Improved Aspect and Line/Space Ratio Realized by Colloidal Photolithography Technique.

    Science.gov (United States)

    Berthod, Loïc; Shavdina, Olga; Verrier, Isabelle; Kämpfe, Thomas; Dellea, Olivier; Vocanson, Francis; Bichotte, Maxime; Jamon, Damien; Jourlin, Yves

    2017-10-12

    This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures-in this case, hexagonally arranged nanopillars-printed in a layer of directly photopatternable sol-gel TiO₂. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a reflective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar's cross section. The theoretical analysis is carried out by rigorous modelling of the photonics nanojet underneath the microspheres and by optimizing the experimental conditions. Aspect ratios (structure height/lateral structure size) greater than 2 are predicted and demonstrated experimentally for structure dimensions in the sub micrometer range, as well as line/space ratios (lateral pillar size/distance between pillars) greater than 1. These nanostructures could lead for example to materials exhibiting efficient light trapping in the visible and near-infrared range, as well as improved hydrophobic or photocatalytic properties for numerous applications in environmental and photovoltaic systems.

  4. Periodic TiO2 Nanostructures with Improved Aspect and Line/Space Ratio Realized by Colloidal Photolithography Technique

    Directory of Open Access Journals (Sweden)

    Loïc Berthod

    2017-10-01

    Full Text Available This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography with the goal of better controlling the geometry of the fabricated nano-scale structures—in this case, hexagonally arranged nanopillars—printed in a layer of directly photopatternable sol-gel TiO2. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a reflective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar’s cross section. The theoretical analysis is carried out by rigorous modelling of the photonics nanojet underneath the microspheres and by optimizing the experimental conditions. Aspect ratios (structure height/lateral structure size greater than 2 are predicted and demonstrated experimentally for structure dimensions in the sub micrometer range, as well as line/space ratios (lateral pillar size/distance between pillars greater than 1. These nanostructures could lead for example to materials exhibiting efficient light trapping in the visible and near-infrared range, as well as improved hydrophobic or photocatalytic properties for numerous applications in environmental and photovoltaic systems.

  5. Periodic TiO2 Nanostructures with Improved Aspect and Line/Space Ratio Realized by Colloidal Photolithography Technique

    Science.gov (United States)

    Berthod, Loïc; Shavdina, Olga; Verrier, Isabelle; Dellea, Olivier; Vocanson, Francis; Bichotte, Maxime; Jamon, Damien; Jourlin, Yves

    2017-01-01

    This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures—in this case, hexagonally arranged nanopillars—printed in a layer of directly photopatternable sol-gel TiO2. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a reflective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar’s cross section. The theoretical analysis is carried out by rigorous modelling of the photonics nanojet underneath the microspheres and by optimizing the experimental conditions. Aspect ratios (structure height/lateral structure size) greater than 2 are predicted and demonstrated experimentally for structure dimensions in the sub micrometer range, as well as line/space ratios (lateral pillar size/distance between pillars) greater than 1. These nanostructures could lead for example to materials exhibiting efficient light trapping in the visible and near-infrared range, as well as improved hydrophobic or photocatalytic properties for numerous applications in environmental and photovoltaic systems. PMID:29023374

  6. Gram-scale synthesis of silica nanotubes with controlled aspect ratios by templating of nickel-hydrazine complex nanorods.

    Science.gov (United States)

    Gao, Chuanbo; Lu, Zhenda; Yin, Yadong

    2011-10-04

    We have developed a robust method for the synthesis of silica nanotubes with controlled aspect ratios on a large scale by templating against rod-like nanocrystals. Crystalline nanorods of a nickel-hydrazine complex are first formed in reverse micelles by surfactant capping on side facets, and subsequent silica coating and selective etching give rise to silica nanotubes of high uniformity and yield. The length of the silica nanotubes is tunable in the range 37-340 nm and can reach as long as micrometers. Control of the length is conveniently achieved by tuning the hydrazine/nickel ratio, which affects the growth kinetics of the nanocrystal templates. The inner diameter of the silica nanotubes can be adjusted in the range 10-20 nm by choosing different surfactants. This method is unique in utilizing reverse micelles as discrete nanoscale reactors for the growth of nanocrystals, allowing for precise control of the features of the nanotubes and opening up new opportunities in the synthesis of novel anisotropic nanomaterials, construction of nanodevices, and potential drug delivery applications. © 2011 American Chemical Society

  7. 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.

  8. pH-dependent toxicity of high aspect ratio ZnO nanowires in macrophages due to intracellular dissolution.

    Science.gov (United States)

    Müller, Karin H; Kulkarni, Jaideep; Motskin, Michael; Goode, Angela; Winship, Peter; Skepper, Jeremy N; Ryan, Mary P; Porter, Alexandra E

    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 ZnCl(2). Confocal microscopy on live cells confirmed a rise in intracellular Zn(2+) 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 Zn(2+) 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.

  9. Analytical calculation of the lower bound on timing resolution for PET scintillation detectors comprising high-aspect-ratio crystal elements

    Science.gov (United States)

    Cates, Joshua W.; Vinke, Ruud; Levin, Craig S.

    2015-07-01

    Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér-Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two 3× 3× 20 mm3 LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be 162+/- 1 ps FWHM, approaching the analytically calculated lower bound within 6.5%.

  10. Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

    Directory of Open Access Journals (Sweden)

    G. Magudeeswaran

    2014-09-01

    Full Text Available The activated TIG (ATIG welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention. The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency. The major influencing ATIG welding parameters, such as electrode gap, travel speed, current and voltage, that aid in controlling the aspect ratio of DSS joints, must be optimized to obtain desirable aspect ratio for DSS joints. Hence in this study, the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array (OA experimental design and other statistical tools such as Analysis of Variance (ANOVA and Pooled ANOVA techniques. The optimum process parameters are found to be 1 mm electrode gap, 130 mm/min travel speed, 140 A current and 12 V voltage. The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

  11. 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.

  12. Application of Self-Assembled Monolayers to the Electroless Metallization of High Aspect Ratio Vias for Microelectronics

    Science.gov (United States)

    Bernasconi, R.; Molazemhosseini, A.; Cervati, M.; Armini, S.; Magagnin, L.

    2016-10-01

    All-wet electroless metallization of through-silicon vias (TSVs) with a width of 5 μm and a 1:10 aspect ratio was carried out. Immersion in a n-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPTMS) self-assembled monolayer (SAM) was used to enhance the adhesion between the metal film and substrate. Contact angle variation and atomic force microscopy were used to verify the formation of a SAM layer. A PdCl2 solution was later used to activate the silanized substrates, exploiting the affinity of the -NH3 functional group of AEAPTMS to palladium. A nickel-phosphorus-boron electroless bath was employed to deposit the first barrier layer onto silicon. The NiPB growth rate was evaluated on flat silicon wafers, while the structure of the coating obtained was investigated via glow discharge optical emission spectroscopy. Cross-sectional scanning electron microscope observations were carried out on metallized TSVs to characterize the NiPB seed, the Cu seed layer deposited with a second electroless step, and the Cu superfilling obtained with a commercial solution. Complete filling of TSV was achieved.

  13. A minimally invasive micro sampler for quantitative sampling with an ultrahigh-aspect-ratio microneedle and a PDMS actuator.

    Science.gov (United States)

    Liu, Long; Wang, Yan; Yao, Jinyuan; Yang, Cuijun; Ding, Guifu

    2016-08-01

    This study describes a novel micro sampler consisting of an ultrahigh-aspect-ratio microneedle and a PDMS actuator. The microneedle was fabricated by a new method which introduced reshaped photoresist technology to form a flow channel inside. The microneedle includes two parts: shaft and pedestal. In this study, the shaft length is 1500 μm with a 45° taper angle on the tip and pedestal is 1000 μm. Besides, the shaft and pedestal are connected by an arc connection structure with a length of 600 μm. The microneedles have sufficient mechanical strength to insert into skin with a wide safety margin which was proved by mechanics tests. Moreover, a PDMS actuator with a chamber inside was designed and fabricated in this study. The chamber, acting as a reservoir in sampling process as well as providing power, was optimized by finite element analysis (FEA) to decrease dead volume and improve sampling precision. The micro sampler just needs finger press to activate the sampling process as well as used for quantitative micro injection to some extent. And a volume of 31.5 ± 0.8 μl blood was successfully sampled from the ear artery of a rabbit. This micro sampler is suitable for micro sampling for diagnose or therapy in biomedical field.

  14. Microdroplet-based On-Demand Drawing of High Aspect-Ratio Elastomeric Micropillar and Its Contact Sensing Application.

    Science.gov (United States)

    Li, Qiang; Dhakal, Rabin; Kim, Jaeyoun

    2017-12-05

    High aspect-ratio elastomeric micropillars play important roles as the platform for microscale sensing and actuation. Many soft-lithographic techniques have been developed for their facile realization but most of the techniques are limited to build the micropillars only on totally flat, widely accessible substrate areas with the micropillar's structural characteristics completely predetermined, leaving little room for in situ control. Here we demonstrate a new technique which overcomes these limitations by directly drawing micropillars from pipette-dispensed PDMS microdroplets using vacuum-chucked microspheres. The combined utilization of PDMS microdroplets and microspheres not only enables the realization of microsphere-tipped PDMS micropillars on non-flat, highly space-constrained substrate areas at in situ controllable heights but also allows arraying of micropillars with dissimilar heights at a close proximity. To validate the new technique's utility and versatility, we realize PDMS micropillars on various unconventional substrate areas in various configurations. We also convert one of them, the optical fiber/micropillar hybrid, into a soft optical contact sensor. Both the fabrication technique and the resulting sensing scheme will be useful for future biomedical microsystems.

  15. A CMOS-compatible high aspect ratio silicon-on-glass in-plane micro-accelerometer

    Science.gov (United States)

    Chae, Junseok; Kulah, Haluk; Najafi, Khalil

    2005-02-01

    This paper presents a post-CMOS-compatible micro-machined silicon-on-glass (SOG) in-plane capacitive accelerometer. The accelerometer is a high aspect ratio structure with a 120 µm thick single-crystal silicon proof-mass and 3.4 µm sense gap, bonded to a glass substrate. It is fabricated using a simple 3-mask, 5-step process, and is fully CMOS compatible. A CMOS switched-capacitor readout circuit and an oversampled Σ-Δ modulator are used to read out capacitance changes from the accelerometer. The CMOS chip is 2.6 × 2.4 mm2 in size, utilizes chopper stabilization and correlated double sampling techniques, has a 106 dB open-loop dynamic range, a low input offset of 370 µV, and can resolve better than 20 aF. The accelerometer system has a measured sensitivity of 40 mV g-1 and input referred noise density of 79 µg Hz-1/2. Using the SOG configuration, a post-CMOS monolithic integration technique is developed. The integration technique utilizes dielectric bridges, silicon islands and the SOG configuration to obtain a simple, robust and post-CMOS-compatible process. Utilizing this technique, an integrated SOG accelerometer has been fabricated using the University of Michigan 3 µm CMOS process.

  16. Directed self-assembly of lamellae-forming block copolymer with density multiplication for high aspect ratio structures

    Science.gov (United States)

    Chen, Xuanxuan; Rincon Delgadillo, Paulina; Jiang, Zhang; Wang, Jin; Strzalka, Joseph; Nealey, Paul; IMEC Collaboration; Advanced Photon Source, Argonne National Labratory Collaboration

    2014-03-01

    Directed self-assembly (DSA) of block copolymers provides the means to control structure over micro- and macroscopic dimensions. We investigate the potential for DSA to control nanostructure through sub-micron film thickness and realize near perfect structure in the plane of the film over macroscopic areas. Lamellae-forming poly (styrene) - block - poly (methyl methacrylate) (L0 = 28.5nm) was directed to assemble on chemical patterns with a pitch (LS) of 84nm. The three-dimensional structure of the films was characterized by SEM and GISAXS as a function of the geometry and chemistry of the chemical pattern, film thickness, and thermal annealing time. At optimal conditions, perpendicular through film structures was achieved with aspect ratio of 12 over 5 x 8 mm2 areas in 3 hours at 250 C. At non-optimal boundary conditions, time for assembly increases, and the maximum film thickness decreases, suggesting an assembly mechanism involving nucleation of structure at the pattern and free surface and differing governance of the pattern-directed structure in both the thermodynamics and kinetics of the system. GISAXS experiments reveals that a significant number of defect structures persist within the films even after the surface structures are perfectly aligned.

  17. Tailoring femtosecond 1.5-μm Bessel beams for manufacturing high-aspect-ratio through-silicon vias.

    Science.gov (United States)

    He, Fei; Yu, Junjie; Tan, Yuanxin; Chu, Wei; Zhou, Changhe; Cheng, Ya; Sugioka, Koji

    2017-01-18

    Three-dimensional integrated circuits (3D ICs) are an attractive replacement for conventional 2D ICs as high-performance, low-power-consumption, and small-footprint microelectronic devices. However, one of the major remaining challenges is the manufacture of high-aspect-ratio through-silicon vias (TSVs), which is a crucial technology for the assembly of 3D Si ICs. Here, we present the fabrication of high-quality TSVs using a femtosecond (fs) 1.5-μm Bessel beam. To eliminate the severe ablation caused by the sidelobes of a conventional Bessel beam, a fs Bessel beam is tailored using a specially designed binary phase plate. We demonstrate that the tailored fs Bessel beam can be used to fabricate a 2D array of approximately ∅10-μm TSVs on a 100-μm-thick Si substrate without any sidelobe damage, suggesting potential application in the 3D assembly of 3D Si ICs.

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

    Science.gov (United States)

    Demes, Thomas; Ternon, Céline; Morisot, Fanny; Riassetto, David; Legallais, Maxime; Roussel, Hervé; Langlet, Michel

    2017-07-01

    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.

  19. 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.

  20. Gust load alleviation wind tunnel tests of a large-aspect-ratio flexible wing with piezoelectric control

    Directory of Open Access Journals (Sweden)

    Ying Bi

    2017-02-01

    Full Text Available An active control technique utilizing piezoelectric actuators to alleviate gust-response loads of a large-aspect-ratio flexible wing is investigated. Piezoelectric materials have been extensively used for active vibration control of engineering structures. In this paper, piezoelectric materials further attempt to suppress the vibration of the aeroelastic wing caused by gust. The motion equation of the flexible wing with piezoelectric patches is obtained by Hamilton’s principle with the modal approach, and then numerical gust responses are analyzed, based on which a gust load alleviation (GLA control system is proposed. The gust load alleviation system employs classic proportional-integral-derivative (PID controllers which treat piezoelectric patches as control actuators and acceleration as the feedback signal. By a numerical method, the control mechanism that piezoelectric actuators can be used to alleviate gust-response loads is also analyzed qualitatively. Furthermore, through low-speed wind tunnel tests, the effectiveness of the gust load alleviation active control technology is validated. The test results agree well with the numerical results. Test results show that at a certain frequency range, the control scheme can effectively alleviate the z and x wingtip accelerations and the root bending moment of the wing to a certain extent. The control system gives satisfying gust load alleviation efficacy with the reduction rate being generally over 20%.

  1. A high aspect ratio SU-8 fabrication technique for hollow microneedles for transdermal drug delivery and blood extraction

    Science.gov (United States)

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

    2010-06-01

    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).

  2. 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.

  3. Design and Analysis of Novel Micromachined Thermocouples with Vertical Free-Standing High-Aspect-Ratio Geometry

    Science.gov (United States)

    Wick, M.; Hedler, H.; Seidel, H.

    2015-06-01

    This paper describes the design and analysis of free-standing three-dimensional (3D) thermocouples (TCs) for uncooled high-resolution infrared imaging. In contrast to the conventional horizontal thermocouple design, our 3D TCs consist of vertically oriented coaxial thermoelectric legs covered by an infrared absorber plate. The high aspect ratio of the 3D TCs of up to 100:1 leads to increased thermal resistance and, thus, higher electrical responsivity. Furthermore, reduced lateral dimensions of the device are achieved by coaxial mounting. This allows a closely packed arrangement of 3D TCs, which results in a high-resolution microarray sensor setup. These features represent the 3D TC's innovative uniqueness and open up new possibilities for further minimized uncooled thermal sensors and low-cost high-resolution imagers. We developed a fabrication process for 3D TCs with doped polysilicon as thermoelectric legs and a geometry with diameter of m and length of m. Performance analysis has been carried out using the lumped-heat-capacity method, resulting in an electrical responsivity and specific detectivity of a 3D TC of 383 V/W and cm /W, respectively.

  4. 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.

  5. 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.

  6. 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.

  7. Aspect-ratio-dependent phase transitions and concentration fluctuations in aqueous colloidal dispersions of charged platelike particles.

    Science.gov (United States)

    Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Fujita, Takako; Nakato, Teruyuki; Koizumi, Satoshi; Ohta, Noboru; Yagi, Naoto; Hashimoto, Takeji

    2012-01-01

    Phase transitions of aqueous colloidal dispersions of charged platelike particles of niobate nanosheets were investigated as a function of the aspect ratio (r(asp)) and particle volume concentration (φ(p)) by means of small-angle neutron scattering and small-angle x-ray scattering. The results elucidated the following three pieces of evidence: (1) the macroscopic phase separation of the dispersions into an isotropic phase and a liquid crystalline (LC) phase under the conditions of (a) varying r(asp) (1.3×10(-4) ≤ r(asp) ≤ 2.5×10(-3)) at a constant φ(p) = 0.01 and (b) varying φ(p) (0.01 ≤ φ(p) ≤ 0.025) at a constant r(asp) = 2.5×10(-3), a mechanism of which is proposed in the text, where r(asp) ≡ d/ ̅L, with d and ̅L being thickness and the average lateral size of the plates, respectively; (2) the r(asp)-induced phase transition of the LC phase from a nematic phase to a highly periodic layered phase, the line shapes of the scattering peaks of which were examined by Caillé's analysis, upon increasing r(asp) under the condition (a); (3) the LC phase having remarkable concentration fluctuations of the particles which are totally unexpected for the conventional lyotropic molecular LC but which are anticipated to be general for the platelike colloidal particles. © 2012 American Physical Society

  8. Nanofabrication of super-high-aspect-ratio structures in hydrogen silsesquioxane from direct-write e-beam lithography and hot development.

    Energy Technology Data Exchange (ETDEWEB)

    Ocola, L. E.; Tirumala, V. R.; Center for Nanoscale Materials; NIST

    2008-11-01

    Super-high-aspect-ratio structures (>10) in hydrogen silsesquioxane resist using direct write electron beam lithography at 100 kV and hot development and rinse are reported. Posts of 100 nm in width and 1.2 {micro}m tall have been successfully fabricated without the need of supercritical drying. Hot rinse solution with isopropyl alcohol has been used to reduce surface tension effects during drying. Dose absorption effects have been observed and modeled using known Monte Carlo models. These results indicate that for e-beam exposures of thick negative resists (>1 {micro}m), the bottom of the structures will have less cross-link density and therefore will be less stiff than the top. These results will have impact in the design of high-aspect-ratio structures that can be used in microelectromechanical system devices and high-aspect-ratio Fresnel zone plates.

  9. 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

  10. 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.

  11. Breaking the limits of line width and aspect ratio for inkjet printed conductive lines by controlling post-deposition ink contraction

    NARCIS (Netherlands)

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

    2014-01-01

    Electrically conductive structures comprising both narrow line widths and high aspect ratios are indispensable components of many electronic devices. Producing them reliably on an industrial scale by inkjet printing of metal-based inks is a serious challenge. Firstly, due to spreading of the ink on

  12. Characteristics of wall jets produced by the impingement on a ground plane of rectangular jets of aspect ratio one through eight

    Science.gov (United States)

    Kotansky, D. R.; Glaze, L. W.

    1981-01-01

    The azimuthal distributions of wall jet radial momentum flux have been experimentally determined for the impingement of turbulent jets emanating from rectangular nozzles with exit area aspect ratios between one and eight. Data are presented for parametric variations in nozzle exit height, nozzle pressure ratio and jet impingement angle caused by rotation of the nozzle about the nozzle exit major and minor axes. The momentum flux distributions were found to be highly directional and sensitive to variations in the above parameters. The effect of nozzle spacing on the fountain normal force measured between a pair of aspect-ratio-two nozzles is also presented. Examples are given in which stagnation line calculations for two rectangular exit area nozzle configurations are compared with experimental results.

  13. Fabrication of a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers

    Science.gov (United States)

    Zeng, Yongbin; Wang, Yufeng; Qu, Ningsong; Zhu, Di

    2013-09-01

    This paper describes a method for preparing a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers and a straight reciprocating motion applied at the anode via the liquid membrane electrochemical machining (ECM). Simulation results indicate that the application of a cathode coated with stretched-out insulating layers is beneficial for the localization of ECM. Moreover, a mathematical model was derived to estimate the final average diameter of the fabricated tools. Experiments were conducted to verify the versatility and feasibility of the proposed method and its mathematical model. It was observed that the calculated and the experimental results are in good agreement with each other. A sub-micron tool with an average diameter 140.8 nm and an aspect ratio up to 50 was fabricated using the proposed method.

  14. Investigation of impingement region and wall jets formed by the interaction of high aspect ratio lift jets and a ground plane

    Science.gov (United States)

    Kotansky, D. R.; Glaze, L. W.

    1978-01-01

    Flow characteristics of impinging jets emanating from rectangular exit area converging nozzles of exit area aspect ratio four, six, and eight were investigated. Azimuthal distributions of wall jet radial momentum flux in the ground plane were strongly directional and sensitive to rectangular nozzle exit area aspect ratio, jet impingement angle, and height above ground, H/D. Effects of jet exit velocity profile nonuniformities were also investigated. Data from the single nozzle rectangular jet impringement investigations were incorporated into an existing VTOL aircraft ground flow field computer program. It is suggested that this program together with the Douglas Neumann program modified for V/STOL applications may be used for the analysis and prediction of flow fields and resulting forces and moments on multijet V/STOL aircraft hovering in ground effect.

  15. Electrically conducting, ultra-sharp, high aspect-ratio probes for AFM fabricated by electron-beam-induced deposition of platinum.

    Science.gov (United States)

    Brown, Jason; Kocher, Paul; Ramanujan, Chandra S; Sharp, David N; Torimitsu, Keiichi; Ryan, John F

    2013-10-01

    We report on the fabrication of electrically conducting, ultra-sharp, high-aspect ratio probes for atomic force microscopy by electron-beam-induced deposition of platinum. Probes of 4.0 ±1.0 nm radius-of-curvature are routinely produced with high repeatability and near-100% yield. Contact-mode topographical imaging of the granular nature of a sputtered gold surface is used to assess the imaging performance of the probes, and the derived power spectral density plots are used to quantify the enhanced sensitivity as a function of spatial frequency. The ability of the probes to reproduce high aspect-ratio features is illustrated by imaging a close-packed array of nanospheres. The electrical resistance of the probes is measured to be of order 100 kΩ. © 2013 Elsevier B.V. All rights reserved.

  16. 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.

  17. 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.

  18. Engineered high aspect ratio vertical nanotubes as a model system for the investigation of catalytic methanol synthesis over Cu/ZnO.

    Science.gov (United States)

    Güder, Firat; Frei, Elias; Kücükbayrak, Umut M; Menzel, Andreas; Thomann, Ralf; Luptak, Roman; Hollaender, Bernd; Krossing, Ingo; Zacharias, Margit

    2014-02-12

    Catalytically synthesized methanol from H2 and CO2 using porous Cu/ZnO aggregates is a promising, carbon neutral, and renewable alternative to replace fossil fuel based transport fuels. However, the absence of surface-engineered model systems to understand and improve the industrial Cu/ZnO catalyst poses a big technological gap in efforts to increase industrial methanol conversion efficiency. In this work, we report a novel process for the fabrication of patterned, vertically aligned high aspect ratio 1D nanostructures on Si that can be used as an engineered model catalyst. The proposed strategy employs near-field phase shift lithography (NF-PSL), deep reactive ion etching (DRIE), and atomic layer deposition (ALD) to pattern, etch, and coat Si wafers to produce high aspect ratio 1D nanostructures. Using this method, we produced a model system consisting of high aspect ratio Cu-decorated ZnO nanotubes (NTs) to investigate the morphological effects of ZnO catalyst support in comparison to the planar Cu/ZnO catalyst in terms of the catalytic reactions. The engineered catalysts performed 70 times better in activating CO2 than the industrial catalyst. In light of the obtained results, several important points are highlighted, and recommendations are made to achieve higher catalytic performance.

  19. Effect of Aspect Ratio and Boundary Conditions in Modeling Shape Memory Alloy Nanostructures with 3D Coupled Dynamic Phase-Field Theories

    Directory of Open Access Journals (Sweden)

    R. Dhote

    2016-01-01

    Full Text Available The behavior of shape memory alloy (SMA nanostructures is influenced by strain rate and temperature evolution during dynamic loading. The coupling between temperature, strain, and strain rate is essential to capture inherent thermomechanical behavior in SMAs. In this paper, we propose a new 3D phase-field model that accounts for two-way coupling between mechanical and thermal physics. We use the strain-based Ginzburg-Landau potential for cubic-to-tetragonal phase transformations. The variational formulation of the developed model is implemented in the isogeometric analysis framework to overcome numerical challenges. We have observed a complete disappearance of the out-of-plane martensitic variant in a very high aspect ratio SMA domain as well as the presence of three variants in equal portions in a low aspect ratio SMA domain. The dependence of different boundary conditions on the microstructure morphology has been examined energetically. The tensile tests on rectangular prism nanowires, using the displacement based loading, demonstrate the shape memory effect and pseudoelastic behavior. We have also observed that higher strain rates, as well as the lower aspect ratio domains, resulting in high yield stress and phase transformations occur at higher stress during dynamic axial loading.

  20. Electrically conducting, ultra-sharp, high aspect-ratio probes for AFM fabricated by electron-beam-induced deposition of platinum

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Jason, E-mail: jason.brown@physics.ox.ac.uk [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Kocher, Paul; Ramanujan, Chandra S; Sharp, David N [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Torimitsu, Keiichi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, 243-0198 (Japan); Ryan, John F [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom)

    2013-10-15

    We report on the fabrication of electrically conducting, ultra-sharp, high-aspect ratio probes for atomic force microscopy by electron-beam-induced deposition of platinum. Probes of 4.0 ±1.0 nm radius-of-curvature are routinely produced with high repeatability and near-100% yield. Contact-mode topographical imaging of the granular nature of a sputtered gold surface is used to assess the imaging performance of the probes, and the derived power spectral density plots are used to quantify the enhanced sensitivity as a function of spatial frequency. The ability of the probes to reproduce high aspect-ratio features is illustrated by imaging a close-packed array of nanospheres. The electrical resistance of the probes is measured to be of order 100 kΩ. - Highlights: • Electrically conducting, ultra-sharp, high aspect-ratio probes for AFM with radius-of-curvature 4.0±±1.0 nm. • AFM probe fabrication by electron-beam-induced deposition of platinum. • Enhanced spatial resolution demonstrated through AFM of sputtered gold grains. • AFM imaging of deep clefts and recesses on a close-packed array of nanospheres.

  1. A study of the scattering properties of an ensemble of rectangular prisms of different composition, size distribution and aspect ratios: a possible application to cometary dust grains?

    Energy Technology Data Exchange (ETDEWEB)

    Vilaplana, Rosario [Dpto. de Fisica Aplicada, EPSA, Universidad Politecnica de Valencia, Pz. Ferrandiz y Carbonell, 2, E-03801. Alcoy. (Spain); Moreno, Fernando [Instituto de Astrofisica de Andalucia, CSIC, C/ Camino bajo de Huetor, 24, E-18008, Granada (Spain); Molina, Antonio [Instituto de Astrofisica de Andalucia, CSIC, C/ Camino bajo de Huetor, 24, E-18008, Granada (Spain); Dpto. de Fisica Aplicada, Universidad de Granada, C/ Fuente nueva, s/n, E-18010, Granada (Spain)

    2005-01-01

    We have approached the scattering properties of cometary dust using size and shape distributions of non-spherical randomly oriented compact particles having non-homogeneous composition. In our model we have used inhomogeneous rectangular prisms in which the aspect ratio between the main axes and the index of the power law size distribution are varied. Two different compositions have been considered. The first one is silicate with carbon inclusions mixed with dirty ice, while the second one is silicate with carbon inclusions. We have obtained that both the width and the depth of the negative polarization branch have a clear dependence on the aspect ratio of the rectangular prisms and the composition. The best fits to the linear polarization curve of cometary grains have been obtained by a non constant distribution of rectangular prisms of the second composition where the elongate-shaped prisms prevail. Moreover, although the irregularity is not accurately represented by this type of distribution, curiously, its usage has shown that the scattering matrix element F{sub 34}/F{sub 11} is very sensitive to the aspect ratio of the particles constituting the synthetic sample.

  2. 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.

  3. Performance of a high-work, low-aspect-ratio turbine stator tested with a realistic inlet radial temperature gradient

    Science.gov (United States)

    Stabe, Roy G.; Schwab, John R.

    1991-01-01

    A 0.767-scale model of a turbine stator designed for the core of a high-bypass-ratio aircraft engine was tested with uniform inlet conditions and with an inlet radial temperature profile simulating engine conditions. The principal measurements were radial and circumferential surveys of stator-exit total temperature, total pressure, and flow angle. The stator-exit flow field was also computed by using a three-dimensional Navier-Stokes solver. Other than temperature, there were no apparent differences in performance due to the inlet conditions. The computed results compared quite well with the experimental results.

  4. Evaluation of a strain-gage load calibration on a low-aspect-ratio wing structure at elevated temperature

    Science.gov (United States)

    Reardon, Lawrence F.

    1989-01-01

    The environmental aspect of elevated temperature and its relationship to the science of strain gage calibrations of aircraft structures are addressed. A section of a wing designed for a high-speed aircraft structure was used to study this problem. This structure was instrumented with strain gages calibrated at both elevated and room temperatures. Load equations derived from a high-temperature load calibration were compared with equations derived from an identical load calibration at room temperature. The implications of the high temperature load calibration were studied from the viewpoint of applicability and necessity. Load equations derived from the room temperature load calibration resulted in generally lower equation standard errors than equations derived from the elevated temperature load calibration. A distributed load was applied to the structure at elevated temperature and strain gage outputs were measured. This applied load was then calculated using equations derived from both the room temperature and elevated temperature calibration data. It was found that no significant differences between the two equation systems existed in terms of computing this applied distributed load, as long as the thermal shifts resulting from thermal stresses could be identified. This identification requires a heating of the structure. Therefore, it is concluded that for this structure, a high temperature load calibration is not required. However, a heating of the structure is required to determine thermal shifts.

  5. Fabrication of high aspect ratio submicron gratings on ˜100nm titanium membranes using electron beam lithography

    Science.gov (United States)

    Tiwari, Pragya; Mondal, Puspen; Srivastava, A. K.; Naik, P. A.

    2017-05-01

    We have developed a new technique for fabrication of 1:1 submicron gratings by means of single step electron beam lithography coupled with thin film deposition. The edge profile and the width ratio (line-to-groove) are easily controlled. Metal like gold or copper transmission gratings can be produced by an additional lift-off process. A 30kV electron beam was used to generate 500nm lines on standalone ˜2.3μm thick PMMA/Titanium. The dimensions of fabricated features together with their surface morphology and profiles were investigated by optical microscope and SEM. Low current slow writing coupled with special development is optimized to write structures smaller than the thickness of the resist membrane.

  6. Performance of a high-work low aspect ratio turbine tested with a realistic inlet radial temperature profile

    Science.gov (United States)

    Stabe, R. G.; Whitney, W. J.; Moffitt, T. P.

    1984-01-01

    Experimental results are presented for a 0.767 scale model of the first stage of a two-stage turbine designed for a high by-pass ratio engine. The turbine was tested with both uniform inlet conditions and with an inlet radial temperature profile simulating engine conditions. The inlet temperature profile was essentially mixed-out in the rotor. There was also substantial underturning of the exit flow at the mean diameter. Both of these effects were attributed to strong secondary flows in the rotor blading. There were no significant differences in the stage performance with either inlet condition when differences in tip clearance were considered. Performance was very close to design intent in both cases. Previously announced in STAR as N84-24589

  7. Excitation wavelength dependence of the photoluminescence quantum yield and decay behavior of CdSe/CdS quantum dot/quantum rods with different aspect ratios.

    Science.gov (United States)

    Geißler, D; Würth, C; Wolter, C; Weller, H; Resch-Genger, U

    2017-05-17

    The excitation wavelength (λexc) dependence of the photoluminescence (PL) quantum yield (ΦPL) and decay behavior (τPL) of a series of CdSe/CdS quantum dot/quantum rods (QDQRs), consisting of the same spherical CdSe core and rod-shaped CdS shells, with aspect ratios ranging from 2 to 20 was characterized. λexc between 400-565 nm were chosen to cover the first excitonic absorption band of the CdSe core material, the onset of absorption of the CdS shell, and the region of predominant shell absorption. A strong λexc dependence of relative and absolutely measured ΦPL and τPL was found particularly for the longer QDQRs with higher aspect ratios. This is attributed to combined contributions from a length-dependent shell-to-core exciton localization efficiency, an increasing number of defect states within the shell for the longest QDQRs, and probably also the presence of absorbing, yet non-emitting shell material. Although the ΦPL values of the QDQRs decrease at shorter wavelength, the extremely high extinction coefficients introduced by the shell outweigh this effect, leading to significantly higher brightness values at wavelengths below the absorption onset of the CdS shell compared with direct excitation of the CdSe cores. Moreover, our results present also an interesting example for the comparability of absolutely measured ΦPL using an integrating sphere setup and ΦPL values measured relative to common ΦPL standards, and underline the need for a correction for particle scattering for QDQRs with high aspect ratios.

  8. 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

  9. Highly transparent poly(glycidyl methacrylate-co-acryloisobutyl POSS) for 100 μm-thick submicron patterns with an aspect ratio over 100.

    Science.gov (United States)

    Kim, Kwanghyun; Yu, Sunyoung; Kim, Sung-Wook; Kim, Taegeon; Kim, Sang-Min; Kang, Se-Young; Han, Seung Min; Jang, Ji-Hyun

    2017-07-18

    This is the first report on the fabrication of defect-free submicron structures with more than 100 μm thickness and an aspect ratio over 100. Highly transparent poly(glycidyl methacrylate-co-acryloisobutyl POSS) (PGP) was synthesized via radical polymerization. The mechanical properties of the PGP submicron structure displayed a Young's modulus of 6.09 GPa and a hardness of 0.16 GPa, 4.2 and 8 times, respectively, than those of SU8 nanopatterns. These enhancements enable the utilization of ultrathick 2D-/3D-submicron structures as an ideal platform for microelectromechanical systems, big data storage systems, energy devices, etc.

  10. Experimental aerodynamic and static elastic deformation characterization of low aspect ratio flexible fixed wings applied to micro aerial vehicles

    Science.gov (United States)

    Albertani, Roberto

    The concept of micro aerial vehicles (MAVs) is for a small, inexpensive and sometimes expendable platform, flying by remote pilot, in the field or autonomously. Because of the requirement to be flown either by almost inexperienced pilots or by autonomous control, they need to have very reliable and benevolent flying characteristics drive the design guidelines. A class of vehicles designed by the University of Florida adopts a flexible-wing concept, featuring a carbon fiber skeleton and a thin extensible latex membrane skin. Another typical feature of MAVs is a wingspan to propeller diameter ratio of two or less, generating a substantial influence on the vehicle aerodynamics. The main objectives of this research are to elucidate and document the static elastic flow-structure interactions in terms of measurements of the aerodynamic coefficients and wings' deformation as well as to substantiate the proposed inferences regarding the influence of the wings' structural flexibility on their performance; furthermore the research will provide experimental data to support the validation of CFD and FEA numerical models. A unique facility was developed at the University of Florida to implement a combination of a low speed wind tunnel and a visual image correlation system. The models tested in the wind tunnel were fabricated at the University MAV lab and consisted of a series of ten models with an identical geometry but differing in levels of structural flexibility and deformation characteristics. Results in terms of full-field displacements and aerodynamic coefficients from wind tunnel tests for various wind velocities and angles of attack are presented to demonstrate the deformation of the wing under steady aerodynamic load. The steady state effects of the propeller slipstream on the flexible wing's shape and its performance are also investigated. Analytical models of the aerodynamic and propulsion characteristics are proposed based on a multi dimensional linear regression

  11. Protein-enabled layer-by-layer syntheses of aligned, porous-wall, high-aspect-ratio TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Berrigan, John D.; Cai, Ye; Sandhage, Kenneth H. [School of Materials Science and Engineering, Air Force Center of Excellence on Bio-Nano-Enabled Inorganic/Organic Nanocomposites and Improved Cognition (BIONIC), Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0400 (United States); Kang, Tae-Sik; Deneault, James R.; Durstock, Michael F. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, 45433-7702 (United States)

    2011-05-10

    An aqueous, protein-enabled (biomimetic), layer-by-layer titania deposition process is developed, for the first time, to convert aligned-nanochannel templates into high-aspect-ratio, aligned nanotube arrays with thin (34 nm) walls composed of co-continuous networks of pores and titania nanocrystals (15 nm ave. size). Alumina templates with aligned open nanochannels are exposed in an alternating fashion to aqueous protamine-bearing and titania precursor-bearing (Ti(IV) bis-ammonium-lactato-dihydroxide, TiBALDH) solutions. The ability of protamine to bind to alumina and titania, and to induce the formation of a Ti-O-bearing coating upon exposure to the TiBALDH precursor, enables the layer-by-layer deposition of a conformal protamine/Ti-O-bearing coating on the nanochannel surfaces within the porous alumina template. Subsequent protamine pyrolysis yields coatings composed of co-continuous networks of pores and titania nanoparticles. Selective dissolution of the underlying alumina template through the porous coating then yields freestanding, aligned, porous-wall titania nanotube arrays. The interconnected pores within the nanotube walls allow enhanced loading of functional molecules (such as a Ru-based N719 dye), whereas the interconnected titania nanoparticles enable the high-aspect-ratio, aligned nanotube arrays to be used as electrodes (as demonstrated for dye-sensitized solar cells with power conversion efficiencies of 5.2 {+-} 0.4%). (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  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. 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.

  14. Extremely high aspect ratio GaAs and GaAs/AlGaAs nanowaveguides fabricated using chlorine ICP etching with N{sub 2}-promoted passivation

    Energy Technology Data Exchange (ETDEWEB)

    Volatier, Maite; Ares, Richard; Aimez, Vincent [Centre de Recherche en Nanofabrication et en Nanocaracterisation (CRN2), Universite de Sherbrooke, Sherbrooke, QC, J1K 2R1 (Canada); Duchesne, David; Morandotti, Roberto, E-mail: Vincent.Aimez@USherbrooke.ca [Institut National de la Recherche Scientifique (INRS), Universite du Quebec, Varennes, QC, J3X 1S2 (Canada)

    2010-04-02

    Semiconductor nanowaveguides are the key structure for light-guiding nanophotonics applications. Efficient guiding and confinement of single-mode light in these waveguides require high aspect ratio geometries. In these conditions, sidewall verticality becomes crucial. We fabricated such structures using a top-down process combining electron beam lithography and inductively coupled plasma (ICP) etching of hard masks and GaAs/AlGaAs semiconductors with Al concentrations varying from 0 to 100%. The GaAs/AlGaAs plasma etching was a single-step process using a Cl{sub 2}/BCl{sub 3}/Ar gas mixture with various fractions of N{sub 2}. Scanning electron microscope (SEM) observations showed that the presence of nitrogen generated the deposition of a passivation layer, which had a significant effect on sidewall slope. Near-ideal vertical sidewalls were obtained over a very narrow range of N{sub 2}, allowing the production of extremely high aspect ratios (>32) for 80 nm wide nanowaveguides.

  15. 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.

  16. The aspect ratio effect of drug nanocrystals on cellular internalization efficiency, uptake mechanisms, and in vitro and in vivo anticancer efficiencies.

    Science.gov (United States)

    Tian, Baishun; Zhang, Xiujuan; Yu, Caitong; Zhou, Mengjiao; Zhang, Xiaohong

    2015-02-28

    In this paper, we investigated the aspect ratio (AR) effect of anticancer drug nanocrystals (NCs) on their cellular internalization efficiency, uptake mechanisms, biodistributions as well as in vitro and in vivo antitumor efficiencies. Both confocal imaging and flow cytometry show that shorter NCs with AR = 1.3 have a much faster cellular uptake rate and a much higher anticancer efficacy than longer NCs. All NCs with different ARs were found to enter the cells via an energy-dependent clathrin-mediated pathway. In vivo experiments indicate that NCs with higher ARs have a shorter half-life and are more easily captured by the liver, while the corresponding tumor uptake decreased. We also observed that NCs with the smallest AR have the highest therapeutic efficacy with appreciably less weight loss. These results would assist in the future design of drug NCs and may lead to the development of new drug nanostructures for biomedical applications.

  17. Turbulent natural convection in a differentially heated cavity of aspect ratio 5 filled with non-participating and participating grey media

    Energy Technology Data Exchange (ETDEWEB)

    Capdevila, R; Trias, F X; Perez-Segarra, C D [Centre Tecnologic de Transferencia de Calor (CTTC), Lab.Termotecnia i Energetica, Universitat Politecnica de Catalunya (UPC), C/Colom, 11, E08222 Terrassa, Barcelona (Spain); Lehmkuhl, O; Colomer, G, E-mail: cttc@cttc.upc.edu, E-mail: termofluids@termofluids.com [Termofluids, S. L., Magi Colet 8, E08204 Sabadell, Barcelona (Spain)

    2011-12-22

    In the present work, turbulent natural convection in a tall differentially heated cavity of aspect ratio 5:1, filled with air (Pr = 0.7) under a Rayleigh number based on the height of 4.5 {center_dot} 10{sup 10}, is studied numerically. Two different situations have been analysed. In the first one, the cavity is filled with a transparent medium. In the second one, the cavity contains a grey participating gas. The turbulent flow is described by means of Large Eddy Simulation (LES) using symmetry-preserving discretizations. Simulations are compared with experimental data available in the literature and with Direct Numerical Simulations (DNS). Surface and gas radiation have been simulated using the Discrete Ordinates Method (DOM). The influence of radiation on fluid flow behaviour has also been analysed.

  18. Fabrication of high aspect ratio TiO{sub 2} and Al{sub 2}O{sub 3} nanogratings by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shkondin, Evgeniy, E-mail: eves@fotonik.dtu.dk [Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark and Danish National Center for Micro- and Nanofabrication (DANCHIP), DK-2800 Kongens Lyngby (Denmark); Takayama, Osamu; Lavrinenko, Andrei V. [Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Lindhard, Jonas Michael; Larsen, Pernille Voss; Mar, Mikkel Dysseholm; Jensen, Flemming [Danish National Center for Micro- and Nanofabrication (DANCHIP), DK-2800 Kongens Lyngby (Denmark)

    2016-05-15

    The authors report on the fabrication of TiO{sub 2} and Al{sub 2}O{sub 3} 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 followed by ALD of TiO{sub 2} or Al{sub 2}O{sub 3}. Then, the template was etched away using SF{sub 6} in an inductively coupled plasma tool, which resulted in the formation of isolated ALD coatings, thereby achieving high aspect ratio grating structures. SF{sub 6} plasma removes silicon selectively without any observable influence on TiO{sub 2} or Al{sub 2}O{sub 3}, thus revealing high selectivity throughout the fabrication. Scanning electron microscopy was used to analyze every fabrication step. Due to nonreleased stress in the ALD coatings, the top parts of the gratings were observed to bend inward as the Si template was removed, thus resulting in a gradual change in the pitch value of the structures. The pitch on top of the gratings is 400 nm, and it gradually reduces to 200 nm at the bottom. The form of the bending can be reshaped by Ar{sup +} ion beam etching. The chemical purity of the ALD grown materials was analyzed by x-ray photoelectron spectroscopy. The approach presented opens the possibility to fabricate high quality optical metamaterials and functional nanostructures.

  19. Ultra-high aspect ratio Si nanowires fabricated with plasma etching: plasma processing, mechanical stability analysis against adhesion and capillary forces and oleophobicity

    Science.gov (United States)

    Zeniou, A.; Ellinas, K.; Olziersky, A.; Gogolides, E.

    2014-01-01

    Room-temperature deep Si etching using time-multiplexed deep reactive ion etching (DRIE) processes is investigated to fabricate ultra-high aspect ratio Si nanowires (SiNWs) perpendicular to the silicon substrate. Nanopatterning is achieved using either top-down techniques (e.g. electron beam lithography) or colloidal polystyrene (PS) sphere self-assembly. The latter is a faster and more economical method if imperfections in diameter and position can be tolerated. We demonstrate wire radii from below 100 nm to several micrometers, and aspect ratios (ARs) above 100:1 with etching rates above 1 μm min-1 using classical mass flow controllers with pulsing rise times of seconds. The mechanical stability of these nanowires is studied theoretically and experimentally against adhesion and capillary forces. It is shown that above ARs of the order of 50:1 for spacing 1 μm, SiNWs tend to bend due to adhesion forces between them. Such large adhesion forces are due to the high surface energy of silicon. Wetting the SiNWs with water and drying also gives rise to capillary forces. We find that capillary forces may be less important for SiNW collapse/bending compared to adhesion forces of dry SiNWs, contrary to what is observed for polymeric nanowires/nanopillars which have a much lower surface energy compared to silicon. Finally we show that SiNW arrays have oleophobic and superoleophobic properties, i.e. they exhibit excellent anti-wetting properties for a wide range of liquids and oils due to the re-entrant profile produced by the DRIE process and the well-designed spacing.

  20. Cause and Cure-Deterioration in Accuracy of CFD Simulations with Use of High-Aspect-Ratio Triangular/Tetrahedral Grids

    Science.gov (United States)

    Chang, Sin-Chung; Chang, Chau-Lyan; Venkatachari, Balaji

    2017-01-01

    In the multi-dimensional space-time conservation element and solution element16 (CESE) method, triangles and tetrahedral mesh elements turn out to be the most natural building blocks for 2D and 3D spatial grids, respectively. As such, the CESE method is naturally compatible with the simplest 2D and 3D unstructured grids and thus can be easily applied to solve problems with complex geometries. However, because (a) accurate solution of a high-Reynolds number flow field near a solid wall requires that the grid intervals along the direction normal to the wall be much finer than those in a direction parallel to the wall and, as such, the use of grid cells with extremely high aspect ratio (103 to 106) may become mandatory, and (b) unlike quadrilateral hexahedral grids, it is well-known that accuracy of gradient computations involving triangular tetrahedral grids tends to deteriorate rapidly as cell aspect ratio increases. As a result, the use of triangular tetrahedral grid cells near a solid wall has long been deemed impractical by CFD researchers. In view of (a) the critical role played by triangular tetrahedral grids in the CESE development, and (b) the importance of accurate resolution of high-Reynolds number flow field near a solid wall, as will be presented in the main paper, a comprehensive and rigorous mathematical framework that clearly identifies the reasons behind the accuracy deterioration as described above has been developed for the 2D case involving triangular cells. By avoiding the pitfalls identified by the 2D framework, and its 3D extension, it has been shown numerically.

  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. 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

  3. Colloidal aggregation and structural assembly of aspect ratio variant goethite (α-FeOOH) with nC60 fullerene in environmental media.

    Science.gov (United States)

    Ghosh, Saikat; Pradhan, Nihar R; Mashayekhi, Hamid; Zhang, Qiu; Pan, Bo; Xing, Baoshan

    2016-12-01

    may unlikely abate fullerene transport as envisaged in case of HAsp α-FeOOH. Thus, aspect ratio variation and associated material properties of naturally abundant α-FeOOH may significantly impact fullerene transport through environmental media. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Double-diffusive natural convection and entropy generation in an enclosure of aspect ratio 4 with partial vertical heating and salting sources

    Directory of Open Access Journals (Sweden)

    Fakher Oueslati

    2013-12-01

    Full Text Available Double-diffusive natural convection with entropy generation in a two-dimensional enclosure with partial vertical heating and salting sources for an aspect ratio Ar = 4 is investigated in the current study. A numerical methodology based on the finite volume method and a full multigrid technique is employed. The effects of various parameters; the Rayleigh number (103 ⩽ Ra ⩽ 2 x 105, the buoyancy ratio (−8 ⩽ N ⩽ 8, the source location (0 ⩽ η ⩽ 3, the Lewis number (10 ⩽ Le ⩽ 100, and, the source length (0.25 ⩽ d ⩽ 2 on the flow patterns are analyzed. Correlations of average Nusselt and Sherwood numbers are established as a function of two parameters (Ra, d and (Le, d, respectively. The numerical outcome of the present study shows that, by increasing the Lewis number in the range 10–100, the heat and mass transfer rates are significantly enhanced. In terms of irreversibility phenomena at the steady case, comparison of total entropy profiles with respect to N shows that irreversibility criterion is dominated by entropy generation due to fluid friction. Especial attention is attributed to the periodic flow behavior that appears for N in the range (0.87–0.99 outside of which it remains steady. According to the entropy generation phenomena, total entropy generation Stot and Bejan number Be were observed to oscillate with the same frequency but in opposing phases and with different amplitudes.

  5. High-beta analytic equilibria in circular, elliptical, and D-shaped large aspect ratio axisymmetric configurations with poloidal and toroidal flows

    Science.gov (United States)

    López, O. E.; Guazzotto, L.

    2017-03-01

    The Grad-Shafranov-Bernoulli system of equations is a single fluid magnetohydrodynamical description of axisymmetric equilibria with mass flows. Using a variational perturbative approach [E. Hameiri, Phys. Plasmas 20, 024504 (2013)], analytic approximations for high-beta equilibria in circular, elliptical, and D-shaped cross sections in the high aspect ratio approximation are found, which include finite toroidal and poloidal flows. Assuming a polynomial dependence of the free functions on the poloidal flux, the equilibrium problem is reduced to an inhomogeneous Helmholtz partial differential equation (PDE) subject to homogeneous Dirichlet conditions. An application of the Green's function method leads to a closed form for the circular solution and to a series solution in terms of Mathieu functions for the elliptical case, which is valid for arbitrary elongations. To extend the elliptical solution to a D-shaped domain, a boundary perturbation in terms of the triangularity is used. A comparison with the code FLOW [L. Guazzotto et al., Phys. Plasmas 11(2), 604-614 (2004)] is presented for relevant scenarios.

  6. Incipient- and Developed-Spin and Recovery Characteristics of a Modern High-Speed Fighter Design with Low Aspect Ratio as Determined from Dynamic-Model Tests

    Science.gov (United States)

    Lee, Henry A.; Libbey, Charles E.

    1961-01-01

    Incipient- and developed-spin and recovery characteristics of a modern high-speed fighter design with low aspect ratio have been investigated by means of dynamic model tests. A 1/7-scale radio-controlled model was tested by means of drop tests from a helicopter. Several 1/25-scale models with various configuration changes were tested in the Langley 20-foot free-spinning tunnel. Model results indicated that generally it would be difficult to obtain a developed spin with a corresponding airplane and that either the airplane would recover of its own accord from any poststall motion or the poststall motion could be readily terminated by proper control technique. On occasion, however, the results indicated that if a post-stall motion were allowed to continue, a fully developed spin might be obtainable from which recovery could range from rapid to no recovery at all, even when optimum control technique was used. Satisfactory recoveries could be obtained with a proper-size tail parachute or strake, application of pitching-, rolling-, or yawing-moment rockets, or sufficient differential deflection of the horizontal tail.

  7. Influence of High Aspect Ratio Vessel Cell Culture on TNF-Alpha, Insulin Secretion and Glucose Homeostasis in Pancreatic Islets of Langerhans from Wistar Furth Rats

    Science.gov (United States)

    Tobin, Brian W.a; Leeper-Woodford, Sandra K.

    1999-01-01

    The present studies were carried out to determine the influence of a ground based microgravity paradigm, utilizing the High Aspect Ratio Vessel (HARV) cell culture upon lipopolysaccharide (LPS) stimulated tumor necrosis factor alpha (TNF-alpha) production of pancreatic islets of Langerhans. An additional aim was to elucidate alterations in insulin secretion and glucose utilization using the HARV low shear, gravity averaged vector, cell culture technique. Islets were isolated (1726 +/- 117, 150 micron islet equivalent units) from Wistar Furth rats and assigned to four treatment groups: 1) HARV, 2) HARV plus LPS, 3) static culture, 4) static culture plus LPS. Following 48 hours of culture, insulin concentration was increased in both HARV and static cultures (pcultures were assayed for TNF-alpha (L929 cytotoxicity assay) and was measured at selected time points for 48 hours. TNF-alpha was significantly increased in LPS-induced HARV and static cultures, yet the increase was more pronounced in the static culture group (pculture (pcultures, suggesting a decreased reliance upon glucose as a metabolic substrate in the islets cultured in HARVS. In conclusion, the present studies demonstrate alterations in LPS induced TNF-alpha production of pancreatic islets of Langerhans, favoring a lesser TNF production in the microgravity HARV paradigm. Additionally, alterations in fuel homeostasis may be promulgated by HARV culture. The clinical and physiological significance of these observations remains to be determined.

  8. 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.

  9. A high aspect ratio Si-fin FinFET fabricated with 193nm scanner photolithography and thermal oxide hard mask etching techniques

    Science.gov (United States)

    Liao, Wen-Shiang

    2006-03-01

    A vertical double gate (FinFET) devices with a high Si-fin aspect ratio of height/width (H/W) = 87nm/11nm have been successfully fabricated on SOI wafers. Firstly, a 50nm-thick capping oxide layer was thermally grown upon the SOI crystalline silicon layer. Secondly, both 105nm-thick BARC and 265nm-thick photoresist were coated and a 193nm scanner lithography tool was used for the Si-fin layout patterning under high ASML exposure energy. Then, a deep sub-micron plasma etcher was used for an aggressive photoresist and BARC trimming down processing and the Si-fin capping oxide layer was subsequently plasma etched in another etching chamber without breaking the plasma etcher's loadlock vacuum. Continuously, the photoresist and BARC were removed with a plasma ashing and a RCA cleaning. Also, the patterned Si-fin capping oxide can be further trimmed down with an additional DHF cleaning and the remained ~22nm-thick capping oxide was still thick enough to act as a robust hard mask for the subsequent Si-fin plasma etching. Finally, an ultra thin Si-fin width 11nm and Si-fin height of 87nm can be successfully fabricated through the last silcon plasma etching.

  10. Influence of High Aspect Ratio Vessel Cell Culture on TNF-Alpha, Insulin Secretion and Glucose Homeostasis in Pancreatic Islets of Langerhans from Wistar Furth Rats

    Science.gov (United States)

    Tobin, Brian W.a; Leeper-Woodford, Sandra K.

    1999-01-01

    The present studies were carried out to determine the influence of a ground based microgravity paradigm, utilizing the High Aspect Ratio Vessel (HARV) cell culture upon lipopolysaccharide (LPS) stimulated tumor necrosis factor alpha (TNF-alpha) production of pancreatic islets of Langerhans. An additional aim was to elucidate alterations in insulin secretion and glucose utilization using the HARV low shear, gravity averaged vector, cell culture technique. Islets were isolated (1726 +/- 117, 150 micron islet equivalent units) from Wistar Furth rats and assigned to four treatment groups: 1) HARV, 2) HARV plus LPS, 3) static culture, 4) static culture plus LPS. Following 48 hours of culture, insulin concentration was increased in both HARV and static cultures (ppathophysiology of Type I and Type 11 diabetes. Glucose concentration in islet medium was lesser throughout the experiment in static cultures, suggesting a decreased reliance upon glucose as a metabolic substrate in the islets cultured in HARVS. In conclusion, the present studies demonstrate alterations in LPS induced TNF-alpha production of pancreatic islets of Langerhans, favoring a lesser TNF production in the microgravity HARV paradigm. Additionally, alterations in fuel homeostasis may be promulgated by HARV culture. The clinical and physiological significance of these observations remains to be determined.

  11. 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.

  12. Ultrathin BaTiO3 nanowires with high aspect ratio: a simple one-step hydrothermal synthesis and their strong microwave absorption.

    Science.gov (United States)

    Yang, Jin; Zhang, Jie; Liang, Chongyun; Wang, Min; Zhao, Pengfei; Liu, Mengmei; Liu, Jiwei; Che, Renchao

    2013-08-14

    In this paper, we report the facile synthesis of ultrathin barium titanate (BaTiO3) nanowires with gram-level yield via a simple one-step hydrothermal treatment. Our BaTiO3 nanowires have unique features: single crystalline, uniform size distribution and ultra high aspect ratio. The synergistic effects including both Ostwald ripening and cation exchange reaction are responsible for the growth of the ultrathin BaTiO3 nanowires. The microwave absorption capability of the ultrathin BaTiO3 nanowires is improved compared to that of BaTiO3 nanotorus,1 with a maximum reflection loss as high as -24.6 dB at 9.04 GHz and an absorption bandwidth of 2.4 GHz (synthesis yield, which might be developed to prepare other ferroelectric nanostructures. The strong microwave absorption property of the ultrathin BaTiO3 nanowires indicates that these nanowires could be used as promising materials for microwave-absorption and stealth camouflage techniques.

  13. 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.

  14. 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.

  15. 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.

  16. High Aspect Ratio Carbon Nanotube Membranes Decorated with Pt Nanoparticle Urchins for Micro Underwater Vehicle Propulsion via H2O2 Decomposition.

    Science.gov (United States)

    Marr, Kevin M; Chen, Bolin; Mootz, Eric J; Geder, Jason; Pruessner, Marius; Melde, Brian J; Vanfleet, Richard R; Medintz, Igor L; Iverson, Brian D; Claussen, Jonathan C

    2015-08-25

    The utility of unmanned micro underwater vehicles (MUVs) is paramount for exploring confined spaces, but their spatial agility is often impaired when maneuvers require burst-propulsion. Herein we develop high-aspect ratio (150:1), multiwalled carbon nanotube microarray membranes (CNT-MMs) for propulsive, MUV thrust generation by the decomposition of hydrogen peroxide (H2O2). The CNT-MMs are grown via chemical vapor deposition with diamond shaped pores (nominal diagonal dimensions of 4.5 × 9.0 μm) and subsequently decorated with urchin-like, platinum (Pt) nanoparticles via a facile, electroless, chemical deposition process. The Pt-CNT-MMs display robust, high catalytic ability with an effective activation energy of 26.96 kJ mol(-1) capable of producing a thrust of 0.209 ± 0.049 N from 50% [w/w] H2O2 decomposition within a compact reaction chamber of eight Pt-CNT-MMs in series.

  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. 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).

  19. 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.

  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. 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...

  2. 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.

  3. The effect of the size of the system, aspect ratio and impurities concentration on the dynamic of emergent magnetic monopoles in artificial spin ice systems

    Energy Technology Data Exchange (ETDEWEB)

    León, Alejandro, E-mail: alejandro.leon@udp.cl

    2013-08-15

    In this work we study the dynamical properties of a finite array of nanomagnets in artificial kagome spin ice at room temperature. The dynamic response of the array of nanomagnets is studied by implementing a “frustrated celular autómata” (FCA), based in the charge model and dipolar model. The FCA simulations allow us to study in real-time and deterministic way, the dynamic of the system, with minimal computational resource. The update function is defined according to the coordination number of vertices in the system. Our results show that for a set geometric parameters of the array of nanomagnets, the system exhibits high density of Dirac strings and high density emergent magnetic monopoles. A study of the effect of disorder in the arrangement of nanomagnets is incorporated in this work. - Highlights: • The dynamics of magnetic monopoles in spin ice systems strongly dependent on the size of the system. • Number of emerging magnetic monopoles, in the phase of magnetic reversal, depend of the aspect. • Different systems can be created based on this idea, for information technology.

  4. Effects of Sweep and Thickness on the Static Longitudinal Aerodynamic Characteristics of a Series of Thin, Low-aspect-ratio, Highly Tapered Wings at Transonic Speeds : Transonic-bump Method

    Science.gov (United States)

    Fournier, Paul G; Few, Albert G , Jr

    1954-01-01

    An investigation by the transonic-bump technique of the static longitudinal aerodynamic characteristics of a series of thin, low-aspect-ratio, highly tapered wings has been made in the Langley high-speed 7- by 10-foot tunnel. The Mach number range extended from about 0.60 to 1.18, with corresponding Reynolds numbers ranging from about 0.75 x 10(6) to 0.95 x 10(6). The angle of attack range was from -10 degrees to approximately 32 degrees.The effects on drag and lift-drag ratio of a variation in sweep angle from -14.03 degrees to 45 degrees with respect to the quarter-chord line for wings of 3-percent-chord thickness was found to be small in comparison to the effects of a variation in thickness from 2 percent chord to 4.5 percent chord for wings with 14.03 degree sweepback. For the range of variables considered, variations in plan form were considerably more important with regard to longitudinal stability characteristics than the variations in thickness. For the series of basic wings having an aspect ratio of 4, the most hearly linear pitching-moment characteristics were obtained with 26.57 degree of sweepback of the quarter-chord line. However, for the modified series of wings (obtained by clipping the tips of the original wings parallel to the plane of symmetry to give an aspect ratio of 3 and a taper ratio of 0.143), the most nearly linear pitching-moment characteristics were obtained with 36.87 degrees of sweepback. By decreasing the thickness-to-chord ratios from 0.03 to 0.02, a large increase in lift-curve slope was obtained for both the basic and modified wings. All of the wings of both series had fairly large inward shifts of the lateral center-of-pressure location (indicative of tip stalling) with increasing lift coefficient, except those wings having minimum sweepback angles.

  5. 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...... using native nickel molds only lead to slight improvements in replication quality. In contrast, a fluorocarbon based antistiction coating (FDTS) was found to improve the replication quality significantly....

  6. Robust high aspect ratio semiconductor device

    NARCIS (Netherlands)

    Roozeboom, F.; Goossens, M.; Besling, W.F.A.; Verhaegh, N.

    2014-01-01

    The invention relates to an semi-conductor device comprising a first surface and neighboring first and second electric elements arranged on the first surface, in which each of the first and second elements extends from the first surface in a first direction, the first element having a cross section

  7. Wind-tunnel investigation of aerodynamic loading on a 0.237-scale model of a remotely piloted research vehicle with a thick, high-aspect-ratio supercritical wing

    Science.gov (United States)

    Byrdsong, T. A.; Brooks, C. W., Jr.

    1983-01-01

    Wind-tunnel measurements were made of the wing-surface static-pressure distributions on a 0.237 scale model of a remotely piloted research vehicle equipped with a thick, high-aspect-ratio supercritical wing. Data are presented for two model configurations (with and without a ventral pod) at Mach numbers from 0.70 to 0.92 at angles of attack from -4 deg to 8 deg. Large variations of wing-surface local pressure distributions were developed; however, the characteristic supercritical-wing pressure distribution occurred near the design condition of 0.80 Mach number and 2 deg angle of attack. The significant variations of the local pressure distributions indicated pronounced shock-wave movements that were highly sensitive to angle of attack and Mach number. The effect of the vertical pod varied with test conditions; however at the higher Mach numbers, the effects on wing flow characteristics were significant at semispan stations as far outboard as 0.815. There were large variations of the wing loading in the range of test conditions, both model configurations exhibited a well-defined peak value of normal-force coefficient at the cruise angle of attack (2 deg) and Mach number (0.80).

  8. Synergistic effects of the aspect ratio of TiO2 nanowires and multi-walled carbon nanotube embedment for enhancing photovoltaic performance of dye-sensitized solar cells.

    Science.gov (United States)

    Ahn, Ji Young; Kim, Ji Hoon; Moon, Kook Joo; Park, So Dam; Kim, Soo Hyung

    2013-08-07

    The existence of numerous interfacial boundaries among TiO2 nanoparticles (NPs) accumulated in the photoelectrode layer of dye-sensitized solar cells (DSSCs) hinders the effective transport of photogenerated electrons to an electrode. Therefore, as a replacement for TiO2 NPs, one-dimensional TiO2 nanowires (NWs) can be suggested to provide pathways for fast electron transport by significantly reducing the number of interfacial boundaries. In order to provide direct evidence for the better performance of such longer TiO2 NWs than shorter TiO2 NWs, we examine the effect of the controlled aspect ratio of the TiO2 NWs randomly accumulated in the photoelectrode layer on the photovoltaic performance of DSSCs. It is clearly found that longer TiO2 NWs significantly improve the electron transport by reducing the TiO2/dye/electrolyte interfacial contact resistance. Furthermore, the embedment of multi-walled carbon nanotubes (MWCNTs) as an effective charge transfer medium in longer TiO2 NWs is proposed in this study to promote more synergistic effects, which lead to significant improvements in the photovoltaic properties of DSSCs.

  9. On the influence of magnetic field processing on the texture, phase assemblage and properties of low aspect ratio Bi2 Sr2 CaCu2 Ox /AgMg wire

    Directory of Open Access Journals (Sweden)

    Xiaotao Liu and Justin Schwartz

    2009-01-01

    Full Text Available Bi2 Sr2 CaCu2 Ox /AgMg conductors are potentially important for many applications up to 20 K, including magnets for cryogen-free magnetic resonance imaging and high field nuclear magnetic resonance research. One promising approach to increased critical current density is partial-melt processing in the presence of a magnetic field which has been shown to enhance c-axis texturing of wide, thin tape conductors. Here, we report on low aspect ratio rectangular conductors processed in an 8 T magnetic field. The magnetic field is applied during different stages of the heat treatment process. The conductors are electrically characterized using four-point critical current measurements as a function of magnetic field and magnetic field orientation relative to the conductor. The superconductive transition and magnetization hysteresis are measured using a SQUID magnetometer. The microstructures are characterized using scanning electron microscopy and energy dispersive spectroscopy and analyzed using digital image processing. It is found that the presence of a magnetic field during split melt processing enhances the electrical transport and magnetic behavior, but that the anisotropy is not consistently affected. The magnetic field also affects development of interfilamentary Bi2212 bridges, and that this depends on the initial shape of the Bi2212 filament. At least two behaviors are identified; one impacts the oxide phase assemblage and the other impacts textured growth.

  10. Golden Ratio

    Indian Academy of Sciences (India)

    Our attraction to another body increases if the body is sym- metrical and in proportion. If a face or a structure is in pro- portion, we are more likely to notice it and find it beautiful. The universal ratio of beauty is the 'Golden Ratio', found in many structures. This ratio comes from Fibonacci numbers. In this article, we explore this ...

  11. 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 ...

  12. Nominal aspect

    DEFF Research Database (Denmark)

    Rijkhoff, Jan

    1991-01-01

    In a general way the notion 'aspect' can be defined as the way in which a property or relation is represented in some dimension. Two kinds of aspect can be distinguished: verbal and nominal aspect. The study of verbal aspect has a long tradition, but nominal aspect has only been introduced recently......, at least in the sense in which it is used here (Rijkhoff 1989b, 1990a, 1990b). After a brief look at the more familiar verbal aspects, each of the nominal aspects is discussed in some detail. Then the relevance of nominal aspect will be considered in connection with (i) certain 'number markers' (which...... will be analysed as nominal aspect markers below), (ii) noun-incorporation, and (iii) predicate nouns....

  13. Midinfrared Surface Waves on a High Aspect Ratio Nanotrench Platform

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Bodganov, Andrey

    2017-01-01

    Optical surface waves, highly localized modes bound to the surface of media, enable manipulation of light at nanoscale, thus impacting a wide range of areas in nanoscience. By applying metamaterials, artificially designed optical materials, as contacting media at the interface, we can significant...

  14. Improving acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    these new types of SAWs compared to using the waves generated by the conventional interdigital transducer with thin electrodes. Thus, this indicates a way to improve acousto-optical interaction for integrated modulators, which have important applications such as optical phase shifters.......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....... With a periodic model it is first shown that these tall electrodes introduce several new confined SAW modes with slow phase velocities because of mechanical energy storage in the electrodes. The periodic model is then extended to a finite model by using perfectly matched layers at the substrate borders...

  15. Does mismatch of the femoral component aspect ratio

    Directory of Open Access Journals (Sweden)

    JIA Yu-tao

    2012-06-01

    Full Text Available 【Abstract】Objective: To study whether the range of knee flexion (ROF is affected by geometrical mismatch of the femoral component and the resultant change in the pos-terior condylar offset (PCO after high-flexion posterior-sta-bilized total knee arthroplasty (TKA. Methods: One hundred osteoarthritic patients (50 males and 50 females underwent femoral osteotomy by the ante-rior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was mea-sured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship be-tween changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed. Results: Compared with the preoperative value, the PCO was reduced by (3.45±3.28 mm after TKA, with a sig-nificantly larger reduction observed in female patients than male patients (P<0.05. When examining the subject popu-lation as a whole, there was a significant positive correla-tion between PCO and ROF improvement during TKA (P< 0.05, but this improvement was not maintained 2 years after TKA (P>0.05. However, when male and female patients were analyzed separately, there was a significant positive corre-lation between PCO change and ROF improvement for both sexes at both time points (all P<0.05. Conclusions: Restoration of PCO plays an important role in the optimization of knee flexion even after posterior-stabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior re-ferencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion. Key words: Arthroplasty, replacement, knee; Pros-thesis design; Range of motion, articular; Femur

  16. VIBRATION ANALYSIS OF LOW-ASPECT RATIO ROTATING ...

    African Journals Online (AJOL)

    vibrations. And the program developed may be used to include other design characteristics by way of refining the blade modeling. REFERENCES. [1] Campbell,W., "Tangential Vibration of Steam. Turbine Buckets." Trans. of ASME, pp. 643 -. 671, 1924. [2] Lo, H.; RenbargerJ.L.; "Bending Vibration of a Rotating Beams." Proc ...

  17. 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.

  18. 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.

  19. Downsizing of single crystalline high aspect ratio tungsten nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Milenkovic, Srdjan [IMDEA Materials Institute, Eric Kandel 2, 28906, Getafe (Spain); Drensler, Stefanie [Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Altenberger Str. 69, 4040, Linz (Austria); Hassel, Achim Walter [Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Altenberger Str. 69, 4040, Linz (Austria); Christian Doppler Laboratory for Combinatorial Oxide Chemistry, Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Str. 69, 4040, Linz (Austria)

    2015-06-15

    Directional solidification of eutectic NiAl-W alloys offers an intuitive method to produce tungsten nanowires. Through the use of two different methods, the well-established Bridgman method and a newer type floating zone method, the direct influence of process parameters, like the withdrawal rate and the temperature gradient, onto the sample microstructure were studied. The sharp temperature gradient, built up using a four mirror system focusing the light emitted by halogen lamps inside the optical floating zone furnace allows producing nanowires with a diameter as small as 75 nm. Differences in the solid/liquid interface morphology depending on the solidification method used are discussed. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. 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....

  1. Unsteady Flow Structure on Low Aspect Ratio Wings

    Science.gov (United States)

    2011-01-06

    mounted vertically on a plate above the tunnel test section. Each motor actuates a vertical “plunge rod”, which connects via a bushing to a coupler ...patterns, a prism system was attached to the exterior of the test section of the water channel, also shown in Figure F1b. The designated prisms were...necessarily yield optimal images due to radial distortion. Prasad and Jensen (1995) showed that the liquid prism is very efficient at reducing

  2. The sex ratio at birth.

    Science.gov (United States)

    Rubin, E

    1967-10-01

    Several aspects of the disparity in birth ratio of males over females are discussed including variations among different races, variations by order of birth, by age of the parent, and in multiple births. Avenues of statistical exploration are suggested in an attempt to indicate certain peculiarities in nature. The Negro population in the United States has a sex ratio of 102 males to 100 females as opposed to 105:100 for whites, a highly significant difference. Inferences from these statistics are suggested for study of the sex ratios of mixed unions. The group classified as Mulatto show a lower sex ratio and further analysis of this was suggested including examination of slave records. For the white population sex ratio declines from 106.2 to 102.9 between 1st order and 7th order births. This is highly significant. However, nonwhite determinations were more irregular. Data limitations on sex ratio by age of parent prevented conclusive results. Multiple births among whites show a decline from 105.3 for single live births to 103.2 for twins and 86.1 for all other plural deliveries. Among nonwhites these ratios are 102.3, 99.7, and 102.6 respectively. Further information should be developed using the multiple facts relating to the sex ratio at birth.

  3. Aspects and Polymorphism in AspectJ

    DEFF Research Database (Denmark)

    Lorenz, David Harel; Ernst, Erik

    2003-01-01

    -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 AspectJ...... 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....

  4. 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.

  5. Aspects, Dependencies, and Interactions

    NARCIS (Netherlands)

    Chitchyan, R; Fabry, J.; Bergmans, Lodewijk; Südholt, M.; Consel, C.

    2007-01-01

    For Aspect-Oriented Software Development (AOSD) the topic of Aspects, Dependencies and Interactions is of high importance across the whole range of development activities – from requirements engineering through to language design. Aspect interactions must be adequately addressed all across the

  6. 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.

  7. AspectKE*

    DEFF Research Database (Denmark)

    Yang, Fan; Masuhara, Hidehiko; Aotani, Tomoyuki

    2010-01-01

    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...

  8. On savings ratio.

    OpenAIRE

    Xiaochuan, Z.

    2011-01-01

    This paper explores the factors that affect saving and consumption behaviours, in a context where some believe that the high savings ratio of the East Asia and oil-producing countries is one major cause for the global imbalances and the crisis. The paper elaborates on the factors behind the high savings ratios in East Asia and oil producing countries and low savings ratios in the United States. It argues that the high savings in East Asia can mainly be explained by cultural and structural fac...

  9. 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....

  10. Declarative Aspect Composition

    NARCIS (Netherlands)

    Nagy, I.; Bergmans, Lodewijk; Aksit, Mehmet

    2004-01-01

    Aspect-oriented languages provide means to attach certain program units (e.g. advice, filters) to a given set of join points. It is possible that not just a single , but several units need to execute at the same join point. Aspects that specify the insertion of these units are said to "share" the

  11. Aspects, Dependencies and Interactions

    NARCIS (Netherlands)

    Sanen, F.; Chitchyan, R; Bergmans, Lodewijk; Fabry, J.; Sudholt, M.; Mehner, K.; Cebulla, M.

    2008-01-01

    The topics on aspects, dependencies and interactions are among the key remaining challenges to be tackled by the Aspect-Oriented Software Development (AOSD) community to enable a wide adoption of AOSD technology. This second workshop, organized and supported by the AOSD-Europe project, aimed to

  12. 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

  13. 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.

  14. Gender Ratio in Dyslexia.

    Science.gov (United States)

    Miles, T. R.; Haslum, M. N.; Wheeler, T. J.

    1998-01-01

    A study involving 11,804 British children (age 10) found that when specified criteria for dyslexia were used, 269 children qualified as dyslexic. These included 223 boys and 46 girls, for a ratio of 4.51 to 1. Difficulties in interpreting these data are discussed and a defense of the criteria is provided. (Author/CR)

  15. 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...

  16. 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....

  17. 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...

  18. Potential support ratios

    DEFF Research Database (Denmark)

    Kjærgaard, Søren; Canudas-Romo, Vladimir

    2017-01-01

    The ‘prospective potential support ratio’ has been proposed by researchers as a measure that accurately quantifies the burden of ageing, by identifying the fraction of a population that has passed a certain measure of longevity, for example, 17 years of life expectancy. Nevertheless, the prospect......The ‘prospective potential support ratio’ has been proposed by researchers as a measure that accurately quantifies the burden of ageing, by identifying the fraction of a population that has passed a certain measure of longevity, for example, 17 years of life expectancy. Nevertheless......, 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...

  19. Ultra by-pass ratio engine

    Energy Technology Data Exchange (ETDEWEB)

    Endo, Masanori; Sugiyama, Shichihisa

    1986-12-10

    A engine where ratio of fan's or propeller's air flow rate to air flow rate through engine combustion chamber is more than 15 is generally named the ultra bypass ratio engine (UBE). This engine employs the exhaust gas from the engine separately to the fan or propeller and jet nozzle exhaust to obtain higher total thrust efficiency. The increase rate of thrust by using UBE is equal to the improvement rate of fuel comsumption. Much efforts are continuously made to develop UBE toward the 21 century by many companies and it is necessary to develop the core engine of high specific output and high heat efficiency, and variable pitch / high aspect ratio fan or propeller and to reseach the integrated system technology. (5 refs, 9 figs)

  20. 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...

  1. Optimising AspectJ

    DEFF Research Database (Denmark)

    Avgustinov, Pavel; Christensen, Aske Simon; Hendren, Laurie

    2005-01-01

    AspectJ, an aspect-oriented extension of Java, is becoming increasingly popular. However, not much work has been directed at optimising compilers for AspectJ. Optimising AOP languages provides many new and interesting challenges for compiler writers, and this paper identifies and addresses three...... such challenges. First, compiling around advice efficiently is particularly challenging. We provide a new code generation strategy for around advice, which (unlike previous implementations) both avoids the use of excessive inlining and the use of closures. We show it leads to more compact code, and can also....... We present new techniques to minimise or eliminate the overhead of cflow using both intra- and inter-procedural analyses. Third, we have addressed the general problem of how to structure an optimising compiler so that traditional analyses can be easily adapted to the AOP setting. We have implemented...

  2. Requirements Engineering and Aspects

    Science.gov (United States)

    Yu, Yijun; Niu, Nan; González-Baixauli, Bruno; Mylopoulos, John; Easterbrook, Steve; Do Prado Leite, Julio Cesar Sampaio

    A fundamental problem with requirements engineering (RE) is to validate that a design does satisfy stakeholder requirements. Some requirements can be fulfilled locally by designed modules, where others must be accommodated globally by multiple modules together. These global requirements often crosscut with other local requirements and as such lead to scattered concerns. We explore the possibility of borrowing concepts from aspect-oriented programming (AOP) to tackle these problems in early requirements. In order to validate the design against such early aspects, we propose a framework to trace them into coding and testing aspects. We demonstrate the approach using an open-source e-commerce platform. In the conclusion of this work, we reflect on the lessons learnt from the case study on how to fit RE and AOP research together.

  3. Diagnostic aspects of gonorrhoea

    NARCIS (Netherlands)

    E. Stolz (Ernst)

    1974-01-01

    textabstractIn 1971 an investigation into the epidemiological, clinical, bacteriological and therapeutic aspects of gonorrhoea was started in collaboration with the Bacteriological Laboratory of the University Hospital/Medical Faculty Rotterdam. Jn the framework of this investigation, the data were

  4. [Psychosocial aspects of halitosis

    NARCIS (Netherlands)

    Jongh, A. de; Baat, C. de; Horstman, M.

    2012-01-01

    Using a representative sample from the Dutch population, some psychosocial aspects of halitosis were examined. The results of the survey showed that almost 90% of the Dutch population aged 16 years and older were regularly faced with halitosis. Forty percent reported to be exposed to someone with

  5. Sociological Aspects of Deafness.

    Science.gov (United States)

    World Federation of the Deaf, Rome (Italy).

    Nine conference papers treat the sociological aspects of deafness. Included are "Individuals Being Deaf and Blind and Living with a Well Hearing Society" by A. Marx (German Federal Republic), "A Deaf Man's Experiences in a Hearing World" by A. B. Simon(U.S.A.), "Problem of Text Books and School Appliances for Vocational…

  6. Theoretical Aspects of Translation.

    Science.gov (United States)

    House, Juliane M.

    This study attempts to bring some clarification into the concept of translation, especially into the theoretical problems presented by the difficulties of translation. The following aspects of the question are treated: (1) translation in the past and present, including the controversy over translation as an art or a science, the relevance of…

  7. Behavioural aspects of terrorism.

    Science.gov (United States)

    Leistedt, Samuel J

    2013-05-10

    Behavioural and social sciences are useful in collecting and analysing intelligence data, understanding terrorism, and developing strategies to combat terrorism. This article aims to examine the psychopathological concepts of terrorism and discusses the developing roles for behavioural scientists. A systematic review was conducted of studies investigating behavioural aspects of terrorism. These studies were identified by a systematic search of databases, textbooks, and a supplementary manual search of references. Several fundamental concepts were identified that continue to influence the motives and the majority of the behaviours of those who support or engage in this kind of specific violence. Regardless of the psychological aspects and new roles for psychiatrists, the behavioural sciences will continue to be called upon to assist in developing better methods to gather and analyse intelligence, to understand terrorism, and perhaps to stem the radicalisation process. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  8. Delusion disorder: Neuropsychological aspects

    Directory of Open Access Journals (Sweden)

    Leposavić Ivana

    2004-01-01

    Full Text Available Previous studies concerned with neuropsychological aspect of delusions, were mainly focused on specific forms of this disorder. Comparatively small number of investigations were concerned with cognitive deficiencies accompanying the delusions. The substance of this study includes the detection of neuropsychological disfunctions in patients with persistent delusion disorder, and in tracing of these cognitive distortions to appropriate brain regions. Besides, characteristics of attribution style in these patients are analysed, from the aspect of their connections with unadjusted localized input for their reasoning system. The investigation is designed as a comparative study. The sample includes: a group of patients with persistent delusion disorder; a group of patients with paranoid schizophrenia; a group of healthy individuals. The participants have been tested by a neuropsychological battery that represents the following cognitive functions: attention, memory, vizuospatial and vizuoconstruction organization, executive ability, verbal divergent thinking. Projective Rorschach's method was used for estimation of attribution style.

  9. ROBOTIC SURGERY: BIOETHICAL ASPECTS

    Science.gov (United States)

    SIQUEIRA-BATISTA, Rodrigo; SOUZA, Camila Ribeiro; MAIA, Polyana Mendes; SIQUEIRA, Sávio Lana

    2016-01-01

    ABSTRACT Introduction: The use of robots in surgery has been increasingly common today, allowing the emergence of numerous bioethical issues in this area. Objective: To present review of the ethical aspects of robot use in surgery. Method: Search in Pubmed, SciELO and Lilacs crossing the headings "bioethics", "surgery", "ethics", "laparoscopy" and "robotic". Results: Of the citations obtained, were selected 17 articles, which were used for the preparation of the article. It contains brief presentation on robotics, its inclusion in health and bioethical aspects, and the use of robots in surgery. Conclusion: Robotic surgery is a reality today in many hospitals, which makes essential bioethical reflection on the relationship between health professionals, automata and patients. PMID:28076489

  10. Aspects of Social Phobia

    OpenAIRE

    Marteinsdóttir, Ína

    2003-01-01

    Social phobia is a disabling, lifelong disorder characterised by fear in social settings. The aim of the present study was to gain more knowledge about diagnostic, neurobiologic and epidemiologic aspects of social phobia. Thirty-two individuals were assessed by the Structured Clinical Interview for DSM-IV Axis I and II psychiatric disorders, the Karolinska Scales of Personality and the Temperament and Character Inventory. Social phobia was accompanied by concurrent axis I disorders in about 2...

  11. Rectenna session: Micro aspects

    Science.gov (United States)

    Gutmann, R. J.

    1980-01-01

    Two micro aspects of rectenna design are discussed: evaluation of the degradation in net rectenna RF to DC conversion efficiency due to power density variations across the rectenna (power combining analysis) and design of Yagi-Uda receiving elements to reduce rectenna cost by decreasing the number of conversion circuits (directional receiving elements). The first of these involves resolving a fundamental question of efficiency potential with a rectenna, while the second involves a design modification with a large potential cost saving.

  12. Aspects of B physics

    Energy Technology Data Exchange (ETDEWEB)

    Gaillard, M.K.

    1987-10-14

    Various aspects of weak decays are commented on. Probing of the standard model and of phenomena beyond the standard model are discussed, followed by a theoretical view of B mesons and some experimental observations on B mesons. The point is made that any data on B decay would be interesting in that it would provide powerful new constraints in analyses of the standard model and extensions thereof. (LEW)

  13. Criminal Aspects of Pornography

    OpenAIRE

    Svoboda, Filip

    2015-01-01

    Criminal Aspects of Pornography Summary The main purpose of this thesis is to introduce the phenomenon of pornography in terms of criminal law, to point out flaws in the current relevant criminal legislation in the Czech Republic and to propose a possible solution in a form of potential legislative changes. The thesis is composed of five chapters. The first chapter deals with definition issue of vague legal term of "pornography" and other related terms ("child pornography", "hardcore pornogra...

  14. Psychosocial Aspects of Obesity.

    Science.gov (United States)

    Beck, Amy R

    2016-01-01

    This article is the sixth in a series of the comorbidities of childhood obesity and reviews psychosocial aspects with a focus on weight-based victimization and discrimination stemming from weight bias and stigma. Outcomes from these bullying and discriminatory experiences are pervasive and impact youth across all settings, including school. Lastly, this article provides recommendations on how to reduce bias and stigma to better serve these students in the school environment. © 2015 The Author(s).

  15. ROBOTIC SURGERY: BIOETHICAL ASPECTS

    OpenAIRE

    SIQUEIRA-BATISTA, Rodrigo; SOUZA, Camila Ribeiro; MAIA, Polyana Mendes; SIQUEIRA, Sávio Lana

    2016-01-01

    ABSTRACT Introduction: The use of robots in surgery has been increasingly common today, allowing the emergence of numerous bioethical issues in this area. Objective: To present review of the ethical aspects of robot use in surgery. Method: Search in Pubmed, SciELO and Lilacs crossing the headings "bioethics", "surgery", "ethics", "laparoscopy" and "robotic". Results: Of the citations obtained, were selected 17 articles, which were used for the preparation of the article. It contains br...

  16. Electrochemical kinetics theoretical aspects

    CERN Document Server

    Vetter, Klaus J

    1967-01-01

    Electrochemical Kinetics: Theoretical Aspects focuses on the processes, methodologies, reactions, and transformations in electrochemical kinetics. The book first offers information on electrochemical thermodynamics and the theory of overvoltage. Topics include equilibrium potentials, concepts and definitions, electrical double layer and electrocapillarity, and charge-transfer, diffusion, and reaction overvoltage. Crystallization overvoltage, total overvoltage, and resistance polarization are also discussed. The text then examines the methods of determining electrochemical reaction mechanisms

  17. THE WINERY ECOLOGICAL ASPECTS

    OpenAIRE

    Крусір, Г. В.

    2015-01-01

    The issues of wineries solid waste analysis as the environmental aspects of the wineries, as well as reducing the burden on the environment through the use of wineries solid wastes as secondary raw material for the new product obtaining are considered. The results of the wineries solid waste analysis as a valuable raw material for feed additive obtaining are given. It is proved that the dominant substance of marc and crests chemical composition are carbohydrates, namely cellulose.

  18. Energy Balance Bowen Ratio (EBBR) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Cook, D. R. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-01

    The Energy Balance Bowen Ratio (EBBR) system produces 30-minute estimates of the vertical fluxes of sensible and latent heat at the local surface. Flux estimates are calculated from observations of net radiation, soil surface heat flux, and the vertical gradients of temperature and relative humidity (RH). Meteorological data collected by the EBBR are used to calculate bulk aerodynamic fluxes, which are used in the Bulk Aerodynamic Technique (BA) EBBR value-added product (VAP) to replace sunrise and sunset spikes in the flux data. A unique aspect of the system is the automatic exchange mechanism (AEM), which helps to reduce errors from instrument offset drift.

  19. Energy Balance Bowen Ratio Station (EBBR) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Cook, DR

    2011-02-23

    The energy balance Bowen ratio (EBBR) system produces 30-minute estimates of the vertical fluxes of sensible and latent heat at the local surface. Flux estimates are calculated from observations of net radiation, soil surface heat flux, and the vertical gradients of temperature and relative humidity (RH). Meteorological data collected by the EBBR are used to calculate bulk aerodynamic fluxes, which are used in the Bulk Aerodynamic Technique (BA) EBBR value-added product (VAP) to replace sunrise and sunset spikes in the flux data. A unique aspect of the system is the automatic exchange mechanism (AEM), which helps to reduce errors from instrument offset drift.

  20. Some aspects of reproductive biology of the Crucian carp Carassius ...

    African Journals Online (AJOL)

    Some aspects of reproductive biology of Carassius carassius (L.) such as sex ratio, breeding season, size at first maturity and fecundity were studied from 539 fish samples collected from October 2003 to September 2004 in Lake Ziway, Ethiopia. The overall sex ratio (male: female) was 1.1.7 and deviated significantly from ...

  1. On the Smarandache LCM ratio

    National Research Council Canada - National Science Library

    A A K Majumdar

    2016-01-01

    Two types of the Smarandache LCM ratio functions have been introduced by Murthy [1]. Recently, the second type of the Smarandache LCM ratio function has been considered by Khainar, Vyawahare and Salunke...

  2. AspectJ in action practical aspect-oriented programming

    CERN Document Server

    Laddad, Ramnivas

    2003-01-01

    A guide to aspect-oriented programming and the AspectJ language, this book provides code examples that enable quick implementation of functionality in a system. Thorough introductions to AOP and AspectJ will help developers learn or advance their knowledge of AspectJ. Examples of everyday situations in which AspectJ solutions can be applied, such as logging, policy enforcement, resource pooling, business logic, thread-safety, authentication and authorization, and transaction management are provided. In addition, design patterns and idioms are covered, as is business rule implementation. The latest technologies, such as JEES, JAAS, and log4j, are explained and connected with AspectJ.

  3. Fractal aspects of hadrons

    Directory of Open Access Journals (Sweden)

    Deppman Airton

    2017-01-01

    Full Text Available The non extensive aspects of pT distributions obtained in high energy collisions are discussed in relation to possible fractal structure in hadrons, in the sense of the thermofractal structure recently introduced. The evidences of self-similarity in both theoretical and experimental works in High Energy and in Hadron Physics are discussed, to show that the idea of fractal structure of hadrons and fireballs have being under discussion for decades. The non extensive self-consistent thermodynamics and the thermofractal structure allow one to connect non extensivity to intermittence and possibly to parton distribution functions in a single theoretical framework.

  4. [Cutaneous hemangioma: clinical aspects].

    Science.gov (United States)

    Casanova, D; Norat, F; Bardot, J; Magalon, G

    2006-01-01

    Infantile cutaneous hemangioma is a benign vascular tumour present at 10% of the infants. It forms part of the group of the vascular tumours in the classification of International Society for Vascular Anomalies (ISSVA). Clinical diagnosis is easy in its triphasic typical form with a phase of sometimes brutal postnatal growth, a phase of stabilization and a phase of slow secondary regression. Classically, it is presented in the form of a mass or stains cutaneous red, of a subcutaneous mass or, generally, of a mixed form associating the two aspects.

  5. Aspects of Insider Threats

    DEFF Research Database (Denmark)

    Probst, Christian W.; Hunker, Jeffrey; Gollmann, Dieter

    2010-01-01

    The insider threat has received considerable attention, and is often cited as the most serious security problem. It is also considered the most difficult problem to deal with, because an “insider” has information and capabilities not known to external attackers. The difficulty in handling...... the insider threat is unsurprising under those circumstances; if one cannot define a problem precisely, how can one approach a solution, let alone know when the problem is solved? This chapter presents some aspects of insider threats, collected at an inter-disciplinary workshop in 2008....

  6. Knockout reactions: experimental aspects

    Energy Technology Data Exchange (ETDEWEB)

    Cortina Gil, D. [Santiago de Compostela Univ. (Spain)

    2007-07-01

    The availability of radioactive beams has given rise to intense activity in the field of direct reactions. The removal of one(two)-nucleon (referred to as nucleon knockout in this text) from a fast exotic projectile has been extensively investigated. This lecture provides a general overview of the experimental results achieved using this technique. The sensitivity of the method to different experimental aspects is illustrated with a few examples. Special attention is given to the application of nucleon-knockout reactions as a general purpose spectroscopic tool. (author)

  7. Analytic aspects of convexity

    CERN Document Server

    Colesanti, Andrea; Gronchi, Paolo

    2018-01-01

    This book presents the proceedings of the international conference Analytic Aspects in Convexity, which was held in Rome in October 2016. It offers a collection of selected articles, written by some of the world’s leading experts in the field of Convex Geometry, on recent developments in this area: theory of valuations; geometric inequalities; affine geometry; and curvature measures. The book will be of interest to a broad readership, from those involved in Convex Geometry, to those focusing on Functional Analysis, Harmonic Analysis, Differential Geometry, or PDEs. The book is a addressed to PhD students and researchers, interested in Convex Geometry and its links to analysis.

  8. Cognitive Aspects of Depression

    Science.gov (United States)

    Joormann, Jutta; Gotlib, Ian H.

    2012-01-01

    Depression is a prevalent and impairing psychiatric disorder that affects how we feel and how we think about ourselves and the world around us. Cognitive theories of depression have long posited that various thought processes are involved in the development, maintenance, and recurrence of depressive episodes. Contemporary research has utilized experimental procedures to examine cognitive processes in depressed individuals as well as the nature of the relation of these processes to the emotion dysregulation that is central to the disorder. For example, investigators have assessed the ways in which depression alters aspects of information processing, including attention and perception, interpretation, and memory processes; this research has generated relatively consistent findings. In addition, researchers have attempted to identify and elucidate the cognitive mechanisms that may link these biases in information processing to emotion dysregulation in depression. These mechanisms include inhibitory processes and deficits in working memory, ruminative responses to negative mood states, and the inability to use positive and rewarding stimuli to regulate negative mood. Results of these investigations converge on the formulation that depression is associated with increased elaboration of negative information, difficulties in cognitive control when processing this information, and difficulties disengaging from this information. Research examining cognitive aspects of depression not only enhances our understanding of this common and costly disorder, but also has implications for the treatment of depression and for future investigations of the biological foundations of this disorder. PMID:23240069

  9. Regulatory aspects on nanomedicines.

    Science.gov (United States)

    Sainz, Vanessa; Conniot, João; Matos, Ana I; Peres, Carina; Zupancic, Eva; Moura, Liane; Silva, Liana C; Florindo, Helena F; Gaspar, Rogério S

    2015-12-18

    Nanomedicines have been in the forefront of pharmaceutical research in the last decades, creating new challenges for research community, industry, and regulators. There is a strong demand for the fast development of scientific and technological tools to address unmet medical needs, thus improving human health care and life quality. Tremendous advances in the biomaterials and nanotechnology fields have prompted their use as promising tools to overcome important drawbacks, mostly associated to the non-specific effects of conventional therapeutic approaches. However, the wide range of application of nanomedicines demands a profound knowledge and characterization of these complex products. Their properties need to be extensively understood to avoid unpredicted effects on patients, such as potential immune reactivity. Research policy and alliances have been bringing together scientists, regulators, industry, and, more frequently in recent years, patient representatives and patient advocacy institutions. In order to successfully enhance the development of new technologies, improved strategies for research-based corporate organizations, more integrated research tools dealing with appropriate translational requirements aiming at clinical development, and proactive regulatory policies are essential in the near future. This review focuses on the most important aspects currently recognized as key factors for the regulation of nanomedicines, discussing the efforts under development by industry and regulatory agencies to promote their translation into the market. Regulatory Science aspects driving a faster and safer development of nanomedicines will be a central issue for the next years. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Palliative sedation: ethical aspects.

    Science.gov (United States)

    Miccinesi, Guido; Caraceni, Augusto; Maltoni, Marco

    2017-07-12

    Palliative sedation (PS), the medical act of decreasing a patient's awareness to relieve otherwise intractable suffering, is considered by some commentators to be controversial because of its consequences on residual survival and/or quality of life, and to be inappropriate for treating pure existential suffering. We will argue that PS must be always proportional, i.e. controlling refractory symptoms while keeping the loss of personal values (communication, affective relationships, care relationship) as low as possible, and that imminence of death is necessary too, from an ethical point of view, if a deep and continuous sedation (DCS) is proposed. Moreover, in case of pure existential suffering DCS should only be considered after repeated trials of respite sedation. The use of progressive consent and advance care planning to share the decision with the patient and to involve the family in the decision process as much as the patient desires is another ethical aspect to be pursued. Producing, implementing and sustaining guidelines at the higher scientific and professional level promise to help in improving both clinical and ethical aspects of the practice of PS.

  11. Neurological aspects of grief.

    Science.gov (United States)

    Silva, Adriana C; de Oliveira Ribeiro, Natalia P; de Mello Schier, Alexandre R; Arias-Carrión, Oscar; Paes, Flavia; Nardi, Antonio E; Machado, Sergio; Pessoa, Tamires M

    2014-01-01

    Despite grief being a universal experience and the increased scientific attention paid to grief and bereavement in recent years, studies that seek to better understand the role of the neurological aspects of grief are still scarce. We found 5 studies that discussed the relationship between the neurological aspects of grief due to the death of a loved one. All studies showed an activation of common areas, i.e., the anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), prefrontal cortex (PFC), insula and amygdala. These findings could indicate that there is a group of areas working together and responding to generate the symptomatology of grief. Because grief is a universal experience, it is essential that the necessary and effective support can be provided to those who experience the loss of someone considered important in their lives, and this requires understanding grief's manifestation, its differential diagnosis in reference to other clinical conditions, mainly psychiatric ones, and adequate forms of intervention and treatment when necessary. Proper understanding and support can help prevent the emergence of more serious health problems.

  12. Aspects of the Tutte polynomial

    DEFF Research Database (Denmark)

    Ok, Seongmin

    ), T(G;0,2)}. The three numbers, T(G;1,1), T(G;2,0) and T(G;0,2) are respectively the numbers of spanning trees, acyclic orientations and totally cyclic orientations of G. First, I extend Negami's splitting formula to the multivariate Tutte polynomial. Using the splitting formula, Thomassen and I found......-connected then T(G;1,1) ≤ T(G;0,2). Strengthening Thomassen's idea that acyclic orientations dominate spanning trees in sparse graphs, I conjecture that the ratio T(G;2,0)/T(G;1,1) increases as G gets sparser. To support this conjecture, I prove a variant of the conjecture for series-parallel graphs. The Merino......This thesis studies various aspects of the Tutte polynomial, especially focusing on the Merino-Welsh conjecture. We write T(G;x,y) for the Tutte polynomial of a graph G with variables x and y. In 1999, Merino and Welsh conjectured that if G is a loopless 2-connected graph, then T(G;1,1) ≤ max{T(G;2,0...

  13. 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...

  14. Formal aspects of resilience

    Directory of Open Access Journals (Sweden)

    Diana-Maria Drigă

    2015-12-01

    Full Text Available The concept of resilience has represented during the recent years a leading concern both in Romania, within the European Union and worldwide. Specialists in economics, management, finance, legal sciences, political sciences, sociology, psychology, grant a particular interest to this concept. Multidisciplinary research of resilience has materialized throughout the time in multiple conceptualizations and theorizing, but without being a consensus between specialists in terms of content, specificity and scope. Through this paper it is intended to clarify the concept of resilience, achieving an exploration of the evolution of this concept in ecological, social and economic environment. At the same time, the paper presents aspects of feedback mechanisms and proposes a formalization of resilience using the logic and mathematical analysis.

  15. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D.C.

    2013-12-16

    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  16. Aspects, Wrappers and Events

    Science.gov (United States)

    Filman, Robert E.

    2003-01-01

    This viewgraph presentation provides information on Object Infrastructure Framework (OIF), an Aspect-Oriented Programming (AOP) system. The presentation begins with an introduction to the difficulties and requirements of distributed computing, including functional and non-functional requirements (ilities). The architecture of Distributed Object Technology includes stubs, proxies for implementation objects, and skeletons, proxies for client applications. The key OIF ideas (injecting behavior, annotated communications, thread contexts, and pragma) are discussed. OIF is an AOP mechanism; AOP is centered on: 1) Separate expression of crosscutting concerns; 2) Mechanisms to weave the separate expressions into a unified system. AOP is software engineering technology for separately expressing systematic properties while nevertheless producing running systems that embody these properties.

  17. CUSTOMER LOYALTY THEORETICAL ASPECTS

    Directory of Open Access Journals (Sweden)

    Margarita IŠORAITĖ

    2016-08-01

    Full Text Available Customer loyalty - is a voluntary user solution for a long time to build relationships with the company. Loyalty is the user's desire for a long time to continue their relationship with a particular company, because loyal customers are those who purchase goods/services of the company from time to time. Loyalty can be treated as a customer desire, willingness to be a regular customer for a long time, buying and using the goods of the chosen companies by recommending them to friends and colleagues. Loyalty can be seen as a multi-dimension, covering behavioral and positional components, where positional aspect reflects customers' approach to business, while the behavioral dimension reveals a frequent and regular shopping, purchase quantity, size, range, availability, etc.

  18. Psychiatric aspects of burn

    Directory of Open Access Journals (Sweden)

    Dalal P

    2010-10-01

    Full Text Available Burn injuries and their subsequent treatment cause one of the most excruciating forms of pain imaginable. The psychological aspects of burn injury have been researched in different parts of the world, producing different outcomes. Studies have shown that greater levels of acute pain are associated with negative long-term psychological effects such as acute stress disorder, depression, suicidal ideation, and post-traumatic stress disorder for as long as 2 years after the initial burn injury. The concept of allostatic load is presented as a potential explanation for the relationship between acute pain and subsequent psychological outcomes. A biopsychosocial model is also presented as a means of obtaining better inpatient pain management and helping to mediate this relationship.

  19. ROBOTIC SURGERY: BIOETHICAL ASPECTS.

    Science.gov (United States)

    Siqueira-Batista, Rodrigo; Souza, Camila Ribeiro; Maia, Polyana Mendes; Siqueira, Sávio Lana

    2016-01-01

    The use of robots in surgery has been increasingly common today, allowing the emergence of numerous bioethical issues in this area. To present review of the ethical aspects of robot use in surgery. Search in Pubmed, SciELO and Lilacs crossing the headings "bioethics", "surgery", "ethics", "laparoscopy" and "robotic". Of the citations obtained, were selected 17 articles, which were used for the preparation of the article. It contains brief presentation on robotics, its inclusion in health and bioethical aspects, and the use of robots in surgery. Robotic surgery is a reality today in many hospitals, which makes essential bioethical reflection on the relationship between health professionals, automata and patients. A utilização de robôs em procedimentos cirúrgicos tem sido cada vez mais frequente na atualidade, o que permite a emergência de inúmeras questões bioéticas nesse âmbito. Apresentar revisão sobre os aspectos éticos dos usos de robôs em cirurgia. Realizou-se revisão nas bases de dados Pubmed, SciELO e Lilacs cruzando-se os descritores "bioética", "cirurgia", "ética", "laparoscopia" e "robótica". Do total de citações obtidas, selecionou-se 17 artigos, os quais foram utilizados para a elaboração do artigo. Ele contém breve apresentação sobre a robótica, sua inserção na saúde e os aspectos bioéticos da utilização dos robôs em procedimentos cirúrgicos. A cirurgia robótica é uma realidade, hoje, em muitas unidades hospitalares, o que torna essencial a reflexão bioética sobre as relações entre profissionais da saúde, autômatos e pacientes.

  20. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

    Science.gov (United States)

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; (Sam) Ma, Zhanshan

    2016-12-01

    There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s local mate competition (LMC) and Clark’s local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research.

  1. Psychological aspects of pain.

    Science.gov (United States)

    Gorczyca, Rafał; Filip, Rafał; Walczak, Ewa

    2013-01-01

    Pain is defined "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage". Pain is a sensation of the body, and is always an unpleasant emotional experience. The role of psychology is auxiliary and supplemental to medicine. This is an aid addressed to the patient, physician and patient's caregivers: professional caregivers, family members and significant others. At each stage of the diagnostic and therapeutic process, psychology offers help, both from the cognitive and practical aspects. The objective of the article is to present important psychological aspects of studies concerning pain, and the psychological methods and techniques of pain treatment. Pain is the leading reason for patients seeking medical care and is one of the most disabling, burdensome, and costly conditions. Pain accompanies many diseases, each one of which generates unique/separate diagnostic, therapeutic and research problems. DEPRESSION AND RELATED PSYCHICAL DISORDERS: There is a significant relationship between depression and pain symptoms, as well as between pain and suicidal thoughts. Patients with a long history of pain disorders also have increased depression and anxiety symptoms, as well as suicidal thoughts. Patients with more severe depression and anxiety symptoms also have an increase in pain problems. The intensity of pain correlates with the intensity of psychopathological symptoms - both with mood lowering and with anxiety symptoms and worry. Active pain coping strategies strive to function in spite of pain, or to distract oneself from pain, are associated with adaptive functioning. Passive strategies involve withdrawal or relinquishing control to an external force or agent and are related to greater pain and depression. Pain catastrophizing is a negatively distorted perception of pain as awful, horrible and unbearable. Catastrophizing is strongly associated with depression and pain. Studies in which

  2. Surface area-volume ratios in insects.

    Science.gov (United States)

    Kühsel, Sara; Brückner, Adrian; Schmelzle, Sebastian; Heethoff, Michael; Blüthgen, Nico

    2017-10-01

    Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume (SA/V) ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders (Diptera, Hymenoptera, Lepidoptera, and Coleoptera). Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 °C to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling (residuals of the SA/V ∼ mass2/3 relationship). Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/V ratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity. © 2016 Institute of Zoology, Chinese Academy of Sciences.

  3. [Psychosocial aspects of halitosis].

    Science.gov (United States)

    de Jongh, A; de Baat, C; Horstman, M

    2012-09-01

    Using a representative sample from the Dutch population, some psychosocial aspects of halitosis were examined. The results of the survey showed that almost 90% of the Dutch population aged 16 years and older were regularly faced with halitosis. Forty percent reported to be exposed to someone with halitosis at least once a week, men significantly more frequently than women. Although less strongly than body odour, halitosis was reported as being one of the most severe 'let-downs' in social interactions. The greater the social distance between subjects, the less likely is the chance that a person's attention will be drawn to halitosis experienced. When it comes to an unknown person, the chance was no more than 7%, suggesting that it is problematic to draw a person's attention to the presence of halitosis. Considering the potential social consequences of halitosis is it important that dentists and dental hygienists draw patients' attention to the presence of halitosis, when this is the case, thereby encouraging them to seek adequate treatment.

  4. Strategic Aspects of Communication

    Science.gov (United States)

    Hagen, Edward; Hammerstein, Peter; Hess, Nicole

    Rarely do human behavioral scientists and scholars study language, music, and other forms of communication as strategies—a means to some end. Some even deny that communication is the primary function of these phenomena. Here we draw upon selections of our earlier work to briefly define the strategy concept and sketch how decision theory, developed to explain the behavior of rational actors, is applied to evolved agents. Communication can then be interpreted as a strategy that advances the "fitness interests" of such agents. When this perspective is applied to agents with conflicts of interest, deception emerges as an important aspect of communication. We briefly review costly signaling, one solution to the problem of honest communication among agents with conflicts of interest. We also explore the subversion of cooperative signals by parasites and by plants defending themselves against herbivores, and we touch on biases in human gossip. Experiments with artificial embodied and communicating agents confirm that when there are conflicts of interest among agents, deception readily evolves. Finally, we consider signaling among super-organisms and the possible implications for understanding human music and language.

  5. Electrical aspects of rainout

    Energy Technology Data Exchange (ETDEWEB)

    Rosenkilde, C.E.

    1981-11-23

    Rainout commonly denotes the aggregate of phenomena associated with precipitation scavenging of radioactivity from a cloud of nuclear debris that is within a natural rain cloud. (In contrast, the term, washout, is applicable when the nuclear cloud is below the rain cloud and the term, fallout, commonly denotes the direct gravitational settling of contaminated solid material from a nuclear cloud.) Nuclear debris aerosols may be scavenged within natural clouds by a variety of different physical processes which may involve diffusion, convection, impaction, nucleation, phoresis, turbulence, and/or electricity among others. Processes which involve electrical aspects are scrutinized for their susceptibility to the intimate presence of the radioactive-cloud environment. This particular choice of electrical processes is not accidental. Nearly all of the listed processes were examined earlier by Williams. His rough estimates suggested that electrical effects, and to a lesser extent turbulence, could enhance the scavenging of those submicron aerosols which reside in the size-range that bridges the minimum in the scavenging rate coefficient which is commonly called the Greenfield gap. This minimum in the scavenging-rate coefficient is created by the simultaneous reduction of scavenging via diffusion and the reduction of scavenging via inertial impaction. However, Williams omitted the specific influence of a radioactive environment. This report aims to remedy this omission.

  6. HISTORICAL ASPECTS OF PHALLOPLASTY

    Directory of Open Access Journals (Sweden)

    P. S. Kyzlasov

    2017-01-01

    Full Text Available Reconstruction of the penis in transgender operations, amputation of the penis, congenital deformities and anomalies of the penis was and remains today an important issue in plastic surgery of the urogenital region. The only method to restore the penis is phalloplasty. In general, over the past decades, generations of clinicians have different ways and flaps for total fallouretheral reconstruction. Thus was formulated the characteristics of an ideal flap for the formation of neophallos, which should be safe, sensitive, without hair, and with long leg. However, despite the fact that the characteristics of a perfect flap, nowadays there is no “gold standard” in the formation of neophallos, as phalloplasty is a fairly complicated surgery, and the choice of method depends on many factors. The choice of methodology is determined by the plastics surgeon and to each patient is individual, depends on the etiology of the disease and the possibility of choosing the form of the donor’s transplant. This article presents a literature review devoted to the historical aspects of phalloplasty. In the article, in chronological order reflected the evolution of the different forming methods neofallos, phallourethrоplasty, describes their advantages and disadvantages.

  7. Applied aspects of chronoergohygiene.

    Science.gov (United States)

    Gaffuri, E; Costa, G

    1986-01-01

    Chronoergohygiene defines a field of study set on optimizing the work timing compared to the desiderata of human physiology in order to improve the working conditions. Production systems follow their own laws with a timing resulting from economic, technological and natural factors; this timing could contrast with che chronological variables of the person 'involved'. Important aspects to be considered in this regard concern: a energy expense and nutrition, in relation to the mechanization and automation of the working tasks, sociocultural models, individual behaviors in eating habits; b. work performance, with particular reference to the modifications during the life-span and the rhythmic variations in the circadian period; c. toxicologic risks, considering problems of chronokinetics of the toxic agent and of 'chronoesthesia' of the body functions and apparatuses; d. work and social organization, with special reference to shift work, work pace and commuting. The research for a dynamic evaluation of the human-machine interaction in time and into forms of chronological compatibility between man and work organization should optimize industrial hygiene.

  8. Psychiatric Aspects of Infertility

    Directory of Open Access Journals (Sweden)

    Hacer Sezgin

    2014-06-01

    Full Text Available Infertility can be defined as a crisis with cultural, religious, and class related aspects, which coexists with medical, psychiatric, psychological, and social problems. Relation between psychiatric and psychological factors stem from a mutual interaction of both. Family is an important institution in maintaining human existence and raising individuals in line with society's expectations. Fertility and reproduction are seen as universal functions unique to women with raising children as the expected result of the family institution. Incidence of infertility has increased recently and can become a life crisis for a couple. Even though not being able to have a child affects both sexes emotionally, women feel greater amounts of stress, pressure, anxiety, and depression.Consequences of infertility arise from short and long-term devastating effects on both individual's physical and mental health, and marital system. Many studies focus on infertility related psychological and psychiatric disorders (depression, anxiety, grief, marital conflict, gender differences, relation between the causes of infertility and psychopathology, the effects of psychiatric evaluation and intervention -when necessaryon the course of infertility treatment, pregnancy rates, and childbirth. The most important underlying causes of high levels of stress and anxiety that infertile women experience are the loss of maternity, reproduction, sense of self, and genetic continuity. In this review article is to investigate the relationship between medically unexplained symptoms and psychiatric symptoms. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2014; 6(2.000: 165-185

  9. Gestational surrogacy: Psychosocial aspects

    Directory of Open Access Journals (Sweden)

    Nicolás Ruiz-Robledillo

    2016-12-01

    Full Text Available Innovation in assisted reproductive technologies together with increased infertility and new family structures are increasing the use of gestational surrogacy as a means to have children. Before, during and after the process, it is necessary to study the psychosocial characteristics of triad members: the gestational surrogate, intended parents, and offspring. Research has indicated positive adaptation to the process and benefits for all members of the triad. Altruism is the main motivation of surrogates. Notably, psychological well-being has been found to be higher in individuals who have become parents through surrogacy than in those who have used egg donation or have followed a natural process of conception. Moreover, no differences in psychosocial characteristics have been observed in the offspring, compared with children born through natural conception or egg donation. Results highlight the positive aspects of surrogacy. Future research should investigate psychosocial factors that modulate the process, acting as risk and protective factors for well-being of the triad members, and identify the optimal profiles of surrogates for the process to be a success.

  10. Cultural aspects of suicide.

    Science.gov (United States)

    Maharajh, Hari D; Abdool, Petal S

    2005-09-08

    Undefined cultural factors cannot be dismissed and significantly contribute to the worldwide incidence of death by suicide. Culture is an all embracing term and defines the relationship of an individual to his environment. This study seeks to investigate the effect of culture on suicide both regionally and internationally. Culture-bound syndrome with suicidal behaviours specific to a particular culture or geographical region are discussed. Opinions are divided as to the status of religious martyrs. The law itself is silent on many aspects of suicidal behaviour and despite decriminalization of suicide as self-murder, the latter remains on the statutes of many developing countries. The Caribbean region is of concern due to its steady rise in mean suicide rate, especially in Trinidad and Tobago where socio-cultural factors are instrumental in influencing suicidal behaviour. These include transgenerational cultural conflicts, psycho-social problems, media exposure, unemployment, social distress, religion and family structure. The methods used are attributed to accessibility and lethality. Ingestion of poisonous substances is most popular followed by hanging. The gender differences seen with regard to suicidality can also be attributed to gender related psychopathology and psychosocial differences in help-seeking behaviour. These are influenced by the cultural environment to which the individual is exposed. Culture provides coping strategies to individuals; as civilization advances many of these coping mechanisms are lost unclothing the genetic predisposition of vulnerable groups. In the management of suicidal behaviour, a system of therapeutic re-culturation is needed with an emphasis on relevant culture- based therapies.

  11. Incentive Ratios of Fisher Markets

    DEFF Research Database (Denmark)

    Chen, Ning; Deng, Xuaitue; Zhang, Hongyang

    2012-01-01

    by misreporting their private information, we show that the percentage of improvement by a unilateral strategic play, called incentive ratio, is rather limited—it is less than 2 for linear markets and at most $e^{1/e}\\thickapprox 1.445$ for Cobb-Douglas markets. We further prove that both ratios are tight....

  12. Holes at High Blowing Ratios

    Directory of Open Access Journals (Sweden)

    Phillip M. Ligrani

    1996-01-01

    Full Text Available Experimental results are presented which describe the development and structure of flow downstream of a single row of holes with compound angle orientations producing film cooling at high blowing ratios. This film cooling configuration is important because similar arrangements are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 6d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 1.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise-averaged iso-energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift-off from the test surface just downstream of the holes.

  13. INTERPERSONAL COMMUNICATION: PSYCHOLINGUISTIC ASPECT

    Directory of Open Access Journals (Sweden)

    Mitrofanova, I.I.

    2016-09-01

    Full Text Available The article considers language as the organization of the speech of any person in any situation, without which it is impossible to characterize the internal structure of the speech stream. Language is exactly a system of guidelines necessary for the activity in the social world. Communication is primarily nothing but as a way of making one or another correction in the image of the interlocutor’s world. In order for a language to serve as a means of communication, it must have a single or a similar understanding of reality behind it. Conversely, the unity of understanding the reality and the unity of coherence presuppose the possibility of adequate communication. A mandatory component of communication is the communicative act, that is, the act of sharing information between people. The speech, i.e. the natural sound language is an important means of conveying information that defines this aspect of the communication process as verbal communication. The idea of dialogue as the space, in which the exchange of information takes place, is defined as initial. Essentially, it is the dialogue that in this case acts as the backbone principle in dealing with problems of language. It is here that the essence of social and psychological transition to the analysis of communication is most visibly concentrated. An individual essentially "lives" in the world of Another person’s worlds, and studying the words of this person, he or she studies the "world" of Another person. Thus, the dialogue is not merely the interaction (verbal with another person, but, ultimately, the interaction with the world of culture.

  14. Cultural Aspects of Suicide

    Directory of Open Access Journals (Sweden)

    Hari D. Maharajh

    2005-01-01

    Full Text Available Undefined cultural factors cannot be dismissed and significantly contribute to the worldwide incidence of death by suicide. Culture is an all embracing term and defines the relationship of an individual to his environment. This study seeks to investigate the effect of culture on suicide both regionally and internationally. Culture-bound syndrome with suicidal behaviours specific to a particular culture or geographical region are discussed. Opinions are divided as to the status of religious martyrs. The law itself is silent on many aspects of suicidal behaviour and despite decriminalization of suicide as self-murder, the latter remains on the statutes of many developing countries. The Caribbean region is of concern due to its steady rise in mean suicide rate, especially in Trinidad and Tobago where socio-cultural factors are instrumental in influencing suicidal behaviour. These include transgenerational cultural conflicts, psycho-social problems, media exposure, unemployment, social distress, religion and family structure. The methods used are attributed to accessibility and lethality. Ingestion of poisonous substances is most popular followed by hanging. The gender differences seen with regard to suicidality can also be attributed to gender related psychopathology and psychosocial differences in help-seeking behaviour. These are influenced by the cultural environment to which the individual is exposed. Culture provides coping strategies to individuals; as civilization advances many of these coping mechanisms are lost unclothing the genetic predisposition of vulnerable groups. In the management of suicidal behaviour, a system of therapeutic re-culturation is needed with an emphasis on relevant culture- based therapies.

  15. Emotional aspects of infertility.

    Science.gov (United States)

    Seibel, M M; Taymor, M L

    1982-02-01

    The psychologic aspects of infertility in men and women are reviewed, neuroendocrinologic factors thought to affect reproduction physiologically are described, and awareness of the stresses that infertility places on a couple's relationship is encouraged. Studies have found infertile women to be more neurotic, dependent, and anxious than fertile women, experiencing conflict over their femininity and fear associated with reproduction. In contrast to these reports, a double blind study could not determine the difference in the psychologic makeup of women who were infertile because of demonstrated somatic causes and those women in whom no somatic cause could be found and who were considered infertile on an emotional etiologic basis. Other studies have similarly come to negative conclusions regarding the relationship between psychologic factors and infertility. The 1st set of studies failed to consider the stress that infertility itself places on the couple. Emotional factors may negatively affect fertility in the male. Up to 10% of infertile males have had improvement in their semen analysis after cessation of all treatment for a prolonged period of time. The concept that emotional stress might lead to oligospermia was further supported in a report describing testicular biopsies obtained from men awaiting sentencing after raping and impregnating women. A more obvious effect of the emotional stress infertility places on the male is the occurrence of impotence. It has been estimated that up to 10% of infertilty may be partially or completely explained on the basis of male sexual dysfunction. The gradual unraveling of the complexities of neuroendocrinology have permitted increased understanding of the role that stress might play in infertility. Catecholamines, prolactin, adrenal steroids, endorphins, and serotonin all affect ovulation and in turn are all affected by stress. Such stress might result from infertility or habitual abortion. Infertility is frequently

  16. [Medical aspects of fasting].

    Science.gov (United States)

    Gavrankapetanović, F

    1997-01-01

    Fasting (arabic-savm) was proclaimed through islam, and thus it is an obligation for Holly Prophet Muhammad s.a.v.s.-Peace be to Him-in the second year after Hijra (in 624 after Milad-born of Isa a.s.). There is a month of fasting-Ramadan-each lunar (hijra) year. So, it was 1415th fasting this year. Former Prophets have brought obligative messages on fasting to their people; so there are also certain forms of fasting with other religions i.e. with Catholics, Jews, Orthodox. These kinds of fasting above differ from muslim fasting, but they also appear obligative. All revelations have brought fasting as obligative. From medical point of view, fasting has two basical components: psychical and physical. Psychical sphere correlate closely with its fundamental ideological message. Allah dz.s. says in Quran: "... Fasting is obligative for you, as it was obligative to your precedents, as to avoid sins; during very few days (II, II, 183 & 184)." Will strength, control of passions, effort and self-discipline makes a pure faithfull person, who purify its mind and body through fasting. Thinking about The Creator is more intensive, character is more solid; and spirit and will get stronger. We will mention the hadith saying: "Essaihune humus saimun!" That means: "Travellers at the Earth are fasters (of my ummet)." The commentary of this hadith, in the Collection of 1001 hadiths (Bin bir hadis), number 485, says: "There are no travelling dervishs or monks in islam; thus there is no such a kind of relligousity in islam. In stead, it is changed by fasting and constant attending of mosque. That was proclaimed as obligation, although there were few cases of travelling in the name of relligousity, like travelling dervishs and sheichs." In this paper, the author discusses medical aspects of fasting and its positive characteristics in the respect of healthy life style and prevention of many sicks. The author mentions positive influence of fasting to certain system and organs of human

  17. [Ethical aspects of forensic psychiatry].

    Science.gov (United States)

    Muysers, Jutta

    2014-07-01

    Ethical aspects of forensic psychiatry disclose a tension between complementary and conflicting issues. The field of tension extends from offenders and their criminal offence to experts, therapists and conditions of inpatient treatment. In addition, there are legal and political aspects as well as aspects concerning the public, the victims and their next of kins and finally the media. © Georg Thieme Verlag KG Stuttgart · New York.

  18. Pressure Ratio to Thermal Environments

    Science.gov (United States)

    Lopez, Pedro; Wang, Winston

    2012-01-01

    A pressure ratio to thermal environments (PRatTlE.pl) program is a Perl language code that estimates heating at requested body point locations by scaling the heating at a reference location times a pressure ratio factor. The pressure ratio factor is the ratio of the local pressure at the reference point and the requested point from CFD (computational fluid dynamics) solutions. This innovation provides pressure ratio-based thermal environments in an automated and traceable method. Previously, the pressure ratio methodology was implemented via a Microsoft Excel spreadsheet and macro scripts. PRatTlE is able to calculate heating environments for 150 body points in less than two minutes. PRatTlE is coded in Perl programming language, is command-line-driven, and has been successfully executed on both the HP and Linux platforms. It supports multiple concurrent runs. PRatTlE contains error trapping and input file format verification, which allows clear visibility into the input data structure and intermediate calculations.

  19. Nucleation of melting and solidification in confined high aspect ratio thin films

    Science.gov (United States)

    Mastandrea, J. P.; Ager, J. W.; Chrzan, D. C.

    2017-09-01

    Classical nucleation theory is used to consider the solidification of a melt confined between two planar surfaces. The critical nucleus shapes and the associated nucleation energy barriers are computed as a function of the thickness of the film and the film's relevant bulk and interface energies. The analysis is then repeated for the melting transition, and expressions for the depression and elevation of the melting temperature, relative to the thermodynamic bulk melting temperature of the film material, are found. A nucleus morphology diagram is constructed. This diagram presents the lowest energy morphology of the nuclei, as well as melting points, as a function of the system parameters. Using the nucleus morphology diagram, experimental and system parameters that allow for the desired nucleation behavior can be identified. Furthermore, the nucleus morphology diagram illustrates a region of parameter space where the film is predicted to solidify above its thermodynamic bulk melting temperature, a behavior termed presolidification. The theory is used to predict the temperature at which the nucleation of the solid phase and liquid phase is expected for Ge between two glass substrates. Furthermore, a possible route for controlling the orientation of the film is identified. By controlling the growth temperature, certain orientations may not be able to nucleate, thereby reducing the possible number of orientations within a film.

  20. Magnetic field alignment of randomly oriented, high aspect ratio silicon microwires into vertically oriented arrays.

    Science.gov (United States)

    Beardslee, Joseph A; Sadtler, Bryce; Lewis, Nathan S

    2012-11-27

    External magnetic fields have been used to vertically align ensembles of silicon microwires coated with ferromagnetic nickel films. X-ray diffraction and image analysis techniques were used to quantify the degree of vertical orientation of the microwires. The degree of vertical alignment and the minimum field strength required for alignment were evaluated as a function of the wire length, coating thickness, magnetic history, and substrate surface properties. Nearly 100% of 100 μm long, 2 μm diameter, Si microwires that had been coated with 300 nm of Ni could be vertically aligned by a 300 G magnetic field. For wires ranging from 40 to 60 μm in length, as the length of the wire increased, a higher degree of alignment was observed at lower field strengths, consistent with an increase in the available magnetic torque. Microwires that had been exposed to a magnetic sweep up to 300 G remained magnetized and, therefore, aligned more readily during subsequent magnetic field alignment sweeps. Alignment of the Ni-coated Si microwires occurred at lower field strengths on hydrophilic Si substrates than on hydrophobic Si substrates. The magnetic field alignment approach provides a pathway for the directed assembly of solution-grown semiconductor wires into vertical arrays, with potential applications in solar cells as well as in other electronic devices that utilize nano- and microscale components as active elements.

  1. An Automated High Aspect Ratio Mesher for Computational Fluid Dynamics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Computational fluid dynamics (CFD) simulations are routinely used while designing, analyzing, and optimizing air- and spacecraft. An important component of CFD...

  2. H-mode plasmas at very low aspect ratio on the Pegasus Toroidal Experiment

    Science.gov (United States)

    Thome, K. E.; Bongard, M. W.; Barr, J. L.; Bodner, G. M.; Burke, M. G.; Fonck, R. J.; Kriete, D. M.; Perry, J. M.; Reusch, J. A.; Schlossberg, D. J.

    2017-02-01

    H-mode is obtained at A˜ 1.2 in the Pegasus Toroidal Experiment via Ohmic heating, high-field-side fueling, and low edge recycling in both limited and diverted magnetic topologies. These H-mode plasmas show the formation of edge current and pressure pedestals and a doubling of the energy confinement time to {{H}98y,2}˜ 1 . The L-H power threshold {{P}\\text{LH}} increases with density, and there is no {{P}\\text{LH}} minimum observed in the attainable density space. The power threshold is equivalent in limited and diverted plasmas, consistent with the FM3 model. However, the measured {{P}\\text{LH}} is ˜ 15 × higher than that predicted by conventional International Tokamak Physics Activity (ITPA) scalings, and {{P}\\text{LH}}/{{P}\\text{ITPA08}} increases as A\\to 1 . Small ELMs are present at low input power {{P}\\text{IN}}˜ {{P}\\text{LH}} , with toroidal mode number n≤slant 4 . At {{P}\\text{IN}}\\gg {{P}\\text{LH}} , they transition to large ELMs with intermediate 5. The dominant-n component of a large ELM grows exponentially, while other components evolve nonlinearly and can damp prior to the crash. Direct measurements of the current profile in the pedestal region show that both ELM types exhibit a generation of a current-hole, followed by a pedestal recovery. Large ELMs are shown to further expel a current-carrying filament. Small ELM suppression via injection of low levels of helical current into the edge plasma region is also indicated.

  3. High aspect ratio metal microcasting by hot embossing for X-ray optics fabrication

    OpenAIRE

    Romano, Lucia; Vila-Comamala, Joan; Kagias, Matias; Vogelsang, Konrad; Schift, Helmut; Stampanoni, Marco; Jefimovs, Konstantins

    2017-01-01

    Metal microstructured optical elements for grating-based X-ray phase-contrast interferometry were fabricated by using an innovative approach of microcasting: hot embossing technology with low melting temperature (280{\\deg}C) metal alloy foils and silicon etched templates. A gold-tin alloy (80w%Au / 20w%Sn) was used to cast micro-gratings with pitch sizes in the range of 2 to 20 micrometers and depth of the structures up to 80 micrometers. The metal filling of the silicon template strongly dep...

  4. Deep proton writing of high aspect ratio SU-8 micro-pillars on glass

    Energy Technology Data Exchange (ETDEWEB)

    Ebraert, Evert, E-mail: eebraert@b-phot.org; Rwamucyo, Ben; Thienpont, Hugo; Van Erps, Jürgen

    2016-12-15

    Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer micro-structures. We use SU-8, a negative resist, spincoated in a layer up to 720 μm-thick in a single step on borosilicate glass, for irradiation with a collimated 12 MeV energy proton beam. Micro-pillars with a slightly conical profile are irradiated in the SU-8 layer. We determine the optimal proton fluence to be 1.02 × 10{sup 4} μm{sup −2}, with which we are able to repeatably achieve micro-pillars with a top-diameter of 138 ± 1 μm and a bottom-diameter of 151 ± 3 μm. The smallest fabricated pillars have a top-diameter of 57 ± 5 μm. We achieved a root-mean-square sidewall surface roughness between 19 nm and 35 nm for the fabricated micro-pillars, measured over an area of 5 × 63.7 μm. We briefly discuss initial testing of two potential applications of the fabricated micro-pillars. Using ∼100 μm-diameter pillars as waveguides for gigascale integration optical interconnect applications, has shown a 4.7 dB improvement in optical multimode fiber-to-fiber coupling as compared to the case where an air–gap is present between the fibers at the telecom wavelength of 1550 nm. The ∼140 μm-diameter pillars were used for mold fabrication with silicone casting. The resulting mold can be used for hydrogel casting, to obtain hydrogel replicas mimicking human tissue for in vitro bio-chemical applications.

  5. 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

    Interdigital transducers (IDT) is a classical technique for surface acoustic wave transduction. Usual IDT's make use of electrodes with limited heights, so that surface mode properties do not differ significantly from those of a free or a fully metalized surface. We have proposed previously (J Appl......, was implemented. The modal shapes of all resonances can thus be identified precisely, giving access to the polarization of the surface waves. In addition, the vertical vibrations of the IDT surface were monitored using a heterodyne optical probe and confirm computations. The dispersion of the surface modes...

  6. Bioeffects of Gold Nanorods as a Function of Aspect Ratio and Surface Chemistry

    Science.gov (United States)

    2012-11-01

    Tannins and Human Health: A Review . Critical Reviews in Food Science and Nutrition 38: 421-464. 70 DISTRIBUTION A. Approved for public release... REVIEWED AND IS APPROVED FOR PUBLICATION IN ACCORDANCE WITH ASSIGNED DISTRIBUTION STATEMENT. Saber ussam, Work Umt Manager Molecular Bioeffects Branch...collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources

  7. High aspect-ratio MEMS devices for the next generation of THz/MHz passive components

    NARCIS (Netherlands)

    Fiorentino, G.

    2015-01-01

    The realization of efficient passive devices directly on chip represents one of the most intriguing challenges in IC fabrication processes. The performance of such devices are intrinsically determined by physical parameters that cannot be easily scaled, making the on-chip integration of such

  8. 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...... appears to influence significantly only the intensity of the elastic transmission. The present results suggest a more complex nature of low-energy electron transport through insulating nanocapillaries than proposed for positive ions....... with respect to the capillary axis. On the other hand, the intensity of elastically transmitted electrons significantly varies with the alteration of electron energy and tilt angle. In addition, we measured an energy distribution of electrons transmitted both in the straightforward direction and at large tilt...

  9. Mechanical Design of High Lift Systems for High Aspect Ratio Swept Wings

    Science.gov (United States)

    Rudolph, Peter K. C.

    1998-01-01

    The NASA Ames Research Center is working to develop a methodology for the optimization and design of the high lift system for future subsonic airliners with the involvement of two partners. Aerodynamic analysis methods for two dimensional and three dimensional wing performance with flaps and slats deployed are being developed through a grant with the aeronautical department of the University of California Davis, and a flap and slat mechanism design procedure is being developed through a contract with PKCR, Inc., of Seattle, WA. This report documents the work that has been completed in the contract with PKCR on mechanism design. Flap mechanism designs have been completed for seven (7) different mechanisms with a total of twelve (12) different layouts all for a common single slotted flap configuration. The seven mechanisms are as follows: Simple Hinge, Upside Down/Upright Four Bar Linkage (two layouts), Upside Down Four Bar Linkages (three versions), Airbus A330/340 Link/Track Mechanism, Airbus A320 Link/Track Mechanism (two layouts), Boeing Link/Track Mechanism (two layouts), and Boeing 767 Hinged Beam Four Bar Linkage. In addition, a single layout has been made to investigate the growth potential from a single slotted flap to a vane/main double slotted flap using the Boeing Link/Track Mechanism. All layouts show Fowler motion and gap progression of the flap from stowed to a fully deployed position, and evaluations based on spanwise continuity, fairing size and number, complexity, reliability and maintainability and weight as well as Fowler motion and gap progression are presented. For slat design, the options have been limited to mechanisms for a shallow leading edge slat. Three (3) different layouts are presented for maximum slat angles of 20 deg, 15 deg and 1O deg all mechanized with a rack and pinion drive similar to that on the Boeing 757 airplane. Based on the work of Ljungstroem in Sweden, this type of slat design appears to shift the lift curve so that higher lift is achieved with the deployed slat with no increase in angle of attack. The layouts demonstrate that these slat systems can be designed with no need for slave links, and an experimental test program is outlined to experimentally validate the lift characteristics of the shallow slat.

  10. Superconformal Bottom-Up Cobalt Deposition in High Aspect Ratio Through Silicon Vias.

    Science.gov (United States)

    Josell, D; Silva, M; Moffat, T P

    2016-01-01

    This work demonstrates void-free cobalt filling of 56 μm tall, annular Through Silicon Vias (TSVs) using a mechanism that couples suppression breakdown and surface topography to achieve controlled bottom-up deposition. The chemistry, a Watts electrolyte containing a dilute suppressing additive, and processes are described. This work extends understanding and application of the additive-derived S-shaped Negative Differential Resistance (S-NDR) mechanism, including previous demonstrations of superconformal filling of TSVs with nickel, copper, zinc and gold.

  11. Ordered and Ultra-High Aspect Ratio Nanocapillary Arrays as a Model System

    Science.gov (United States)

    2015-10-13

    double layer capacitance, as well as improving the figure of merit in nanostructured thermoelectrics. Specifically of interest in this discussion is the...spectroscopy (EIS) of the electrolyte and within oxide barrier layer will be discussed; particularly the constant phase element dispersion behavior...Thin Film Battery 3.5V/25mF Supercapacitor 63V/220uF Electrolytic Capacitor Activated Carbon Microsupercapacitor rGO -CNT Microsupercapacitor Onion-like

  12. Single shot ultrafast laser processing of high-aspect ratio nanochannels using elliptical Bessel beams

    OpenAIRE

    Meyer, R.; Jacquot, M.; Giust, R.; Safioui, J.; Rapp, L.; Furfaro, L.; Lacourt, P. -A.; Dudley, J. M.; Courvoisier, F.

    2017-01-01

    Ultrafast lasers have revolutionized material processing, opening a wealth of new applications in many areas of science. A recent technology that allows the cleaving of transparent materials via non-ablative processes is based on focusing and translating a high-intensity laser beam within a material to induce a well-defined internal stress plane. This then enables material separation without debris generation. Here, we use a non-diffracting beam engineered to have a transverse elliptical spat...

  13. Computational local stiffness analysis of biological cell: High aspect ratio single wall carbon nanotube tip

    Energy Technology Data Exchange (ETDEWEB)

    TermehYousefi, Amin, E-mail: at.tyousefi@gmail.com [Department of Human Intelligence Systems, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology (Kyutech) (Japan); Bagheri, Samira; Shahnazar, Sheida [Nanotechnology & Catalysis Research Centre (NANOCAT), IPS Building, University Malaya, 50603 Kuala Lumpur (Malaysia); Rahman, Md. Habibur [Department of Computer Science and Engineering, University of Asia Pacific, Green Road, Dhaka-1215 (Bangladesh); Kadri, Nahrizul Adib [Department of Biomedical Engineering, Faculty of Engineering, University Malaya, 50603 Kuala Lumpur (Malaysia)

    2016-02-01

    Carbon nanotubes (CNTs) are potentially ideal tips for atomic force microscopy (AFM) due to the robust mechanical properties, nanoscale diameter and also their ability to be functionalized by chemical and biological components at the tip ends. This contribution develops the idea of using CNTs as an AFM tip in computational analysis of the biological cells. The proposed software was ABAQUS 6.13 CAE/CEL provided by Dassault Systems, which is a powerful finite element (FE) tool to perform the numerical analysis and visualize the interactions between proposed tip and membrane of the cell. Finite element analysis employed for each section and displacement of the nodes located in the contact area was monitored by using an output database (ODB). Mooney–Rivlin hyperelastic model of the cell allows the simulation to obtain a new method for estimating the stiffness and spring constant of the cell. Stress and strain curve indicates the yield stress point which defines as a vertical stress and plan stress. Spring constant of the cell and the local stiffness was measured as well as the applied force of CNT-AFM tip on the contact area of the cell. This reliable integration of CNT-AFM tip process provides a new class of high performance nanoprobes for single biological cell analysis. - Graphical abstract: This contribution develops the idea of using CNTs as an AFM tip in computational analysis of the biological cells. The proposed software was ABAQUS 6.13 CAE/CEL provided by Dassault Systems. Finite element analysis employed for each section and displacement of the nodes located in the contact area was monitored by using an output database (ODB). Mooney–Rivlin hyperelastic model of the cell allows the simulation to obtain a new method for estimating the stiffness and spring constant of the cell. Stress and strain curve indicates the yield stress point which defines as a vertical stress and plan stress. Spring constant of the cell and the local stiffness was measured as well as the applied force of CNT-AFM tip on the contact area of the cell. This reliable integration of CNT-AFM tip process provides a new class of high performance nanoprobes for single biological cell analysis. With greater understanding of the way in which mechanical properties of SWCNT-AFM, it may easily possible to continuously tune the selectivity and sensitivity of nanotubes in biological applications.

  14. Light extinction and scattering from individual and arrayed high-aspect-ratio trenches in metal

    DEFF Research Database (Denmark)

    Roberts, Alexander; Søndergaard, Thomas; Chirumamilla, Manohar

    2016-01-01

    for a two-dimensional scatterer. We construct a simple resonator model which predicts the wavelength-dependent extinction, scattering, and absorption cross section of the trench and compare the model findings with full numerical simulations. Both extinction and scattering cross sections are mainly...

  15. Influence of aspect ratio and anisotropy distribution in ordered CoNi nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, W.O., E-mail: wrosa@cbpf.br [Depto. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007-Oviedo (Spain); Centro Brasileiro de Pesquisas Fisicas, R. Dr. Xavier Sigaud, 150 - 22290-180, Rio de Janeiro (Brazil); Vivas, L.G. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco 28049-Madrid (Spain); Pirota, K.R. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970-Campinas (Brazil); Asenjo, A.; Vazquez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco 28049-Madrid (Spain)

    2012-11-15

    The size effects on magnetic properties of nanowires arrays were studied varying the nanowires diameter and maintaining the same periodicity among them, for two different nominal compositions of Co and Ni in the alloy form. The competition among magnetocrystalline and shape anisotropies changes drastically from smallest to biggest diameters altering the easy axis direction. In the case of 75% of Co in alloy, experimental values of the effective anisotropy constant (K{sub eff}) vary from positive to negative depending on the diameter, which means a reversal of the easy axis direction. For 50% of Co the shape anisotropy dominates over the magnetocrystalline for all studied diameters. - Highlights: Black-Right-Pointing-Pointer Highly ordered CoNi nanowire alloys have been produced by electrodeposition. Black-Right-Pointing-Pointer Electrolyte temperature ensures the deposition of CoNi alloys instead of Co and Ni segregated. Black-Right-Pointing-Pointer A competition between shape and magnetocrystalline anisotropies determines the direction of the easy magnetization axis. Black-Right-Pointing-Pointer Analysis of the effective anisotropy gives us information respect to the easy axis modification.

  16. Experimental investigation of low aspect ratio, large amplitude, aeroelastic energy harvesting systems

    Science.gov (United States)

    Kirschmeier, Benjamin; Summerour, Jacob; Bryant, Matthew

    2017-04-01

    Interest in clean, stable, and renewable energy harvesting devices has increased dramatically with the volatility of petroleum markets. Specifically, research in aero/hydro kinetic devices has created numerous new horizontal and vertical axis wind turbines, and oscillating wing turbines. Oscillating wing turbines (OWTs) differ from their wind turbine cousins by having a rectangular swept area compared to a circular swept area. The OWT systems also possess a lower tip speed that reduces the overall noise produced by the system. OWTs have undergone significant computational analysis to uncover the underlying flow physics that can drive the system to high efficiencies for single wing oscillations. When two of these devices are placed in tandem configuration, i.e. one placed downstream of the other, they either can constructively or destructively interact. When constructive interactions occurred, they enhance the system efficiency to greater than that of two devices on their own. A new experimental design investigates the dependency of interaction modes on the pitch stiffness of the downstream wing. The experimental results demonstrated that interaction modes are functions of convective time scale and downstream wing pitch stiffness. Heterogeneous combinations of pitch stiffness exhibited constructive and destructive lock-in phenomena whereas the homogeneous combination exhibited only destructive interactions.

  17. An Automated High Aspect Ratio Mesher for Computational Fluid Dynamics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The work will focus on the 3D implementation of the Phase 1 CHARM mesher, with solution-adaptive iteration for CFD and non-CFD applications. The proposed 3D method...

  18. Ultra-high aspect ratio titania nanoflakes for dye-sensitized solar cells

    Science.gov (United States)

    Lee, Yang-Yao; El-Shall, Hassan

    2017-12-01

    Micron sized titania flakes with thickness about 40 nm were used in the titania pastes to assemble dye-sensitized solar cells (DSSCs). Using the same deposition method, better particle dispersion of titania flakes resulted in well bonded and integral films comparing to cracking of Degussa P25 nanoparticle films during the evaporation and sintering processes. There are two features of titania flakes which leads to improved conversion efficiency of DSSC: (1) Higher and stronger adsorption of N-719 dyes due to high specific surface area (2) Stronger light scattering of visible light spectrum because of micron scale wide in two dimensions of the flakes. The thickness of the conducting TiO2 was critical to the IV characteristics of DSSC such as the short-circuit current density (Isc) and open-circuit voltage (Voc). Under the same thickness basis, calcined titania flakes provided 5 times higher efficiency than the photoelectrodes consisted of Degussa P25 nanoparticles (7.4% vs. 1.2%).

  19. Enhanced Differentiation of Human Embryonic Stem Cells Toward Definitive Endoderm on Ultrahigh Aspect Ratio Nanopillars

    DEFF Research Database (Denmark)

    Rasmussen, Camilla Holzmann; Reynolds, Paul M.; Petersen, Dorthe Roenn

    2016-01-01

    highlighted that the properties of the physical environment, such as substrate stiffness, affect cellular behavior. Here, mass-produced, injection molded polycarbonate nanopillars are presented, where the surface mechanical properties, i.e., stiffness, can be controlled by the geometric design...... population compared to planar control. By contrast, further differentiation toward the pancreatic endoderm is less successful on “soft” pillars when compared to “stiff ” pillars or control, indicating differential cues during the different stages of differentiation. To accompany the mechanical properties...

  20. Aerodynamic aspects of a high bypass ratio engine installation on a fuselage afterbody

    Energy Technology Data Exchange (ETDEWEB)

    Voogt, N.; van Hengst, J.; Kolk, J.Th.V.D.

    1981-01-01

    The paper describes the design process used in shaping rear fuselage mounted large diameter engine nacelles, pylons and fuselage for a transport type aircraft. The objective was to suppress the local velocity levels and pressure gradients to avoid aerodynamic interference drag of the nacelle-pylon-fuselage combination in high speed cruise flight. In the design process the shapes of fuselage afterbody, nacelle and stubwing were successively modified in a design-by-analysis process involving a number of iterations with a three-dimensional singularity method for high subsonic flow. Windtunnel tests confirmed the adequacy of the singularity method to analyze complex interference problems. 4 refs.

  1. Vortex Bursting Over a Unit Area Aspect Ratio Delta Wing Using Vortex Paneling Methods

    Science.gov (United States)

    1990-12-01

    Fiaures * Figure Page 1. Two-Dimensional Vortex Panel ... ....... 9 1 2. Vortex Panel Modeling of a NACA0012 Airfoil .......................... 14 3 3...Therefore, each node has a single vortex strength I (G).I I 7 109 5 4 I Figure 2. Vortex Panel Modeling of a NACA0012 Airfoil I 14I The no penetration...34 ." Figure 4. Enhanced Two-Dimensional Wake Splitting 2.4 Results The airfoil investigated was a NACA0012 airfoil. The following equation was used to

  2. High aspect-ratio MEMS devices for the next generation of THz/MHz passive components

    OpenAIRE

    Fiorentino, G.

    2015-01-01

    The realization of efficient passive devices directly on chip represents one of the most intriguing challenges in IC fabrication processes. The performance of such devices are intrinsically determined by physical parameters that cannot be easily scaled, making the on-chip integration of such components a complex task to solve. To pursue the envisioned scaling towards the realization of more compact and fast electronic devices, it is then clear that new, engineered materials and innovative dev...

  3. Hot embossing of photonic crystal polymer structures with a high aspect ratio

    DEFF Research Database (Denmark)

    Schelb, Mauno; Vannahme, Christoph; Kolew, Alexander

    2011-01-01

    Hot embossing is a promising approach for mass production of photonic crystal structures. This paper describes the fabrication of a replication tool for two-dimensional photonic crystal patterns and its replication in substrates of poly(methylmethacrylate) (PMMA) and cyclic olefin copolymer (COC...

  4. Evaluation of the Orwin 1988 Square Aspect Ratio, 20-Inch Diagonal Monochrome Monitor

    National Research Council Canada - National Science Library

    2000-01-01

    .... This COTS monitor is an excellent display for NIMA Imagery Exploitation Workstations. Accordingly, NIDL certifies the Orwin Associates 1988 Monochrome CRT Monitor as being suitable for IEC workstations requiring a monochrome monitor...

  5. Practical aspects of cervical cancer

    NARCIS (Netherlands)

    Tillaart, Sabrina Ada Hendrika Maria van den

    2013-01-01

    The thesis describes studies on practical aspects of cervical cancer, concering surgical considerations, and aspects of tumour behaviour and tumour spread. The thesis comprises studies on: the comparison of nerve-sparing and non-nerve-sparing radical hysterectomy for cervical cancer; a new surgical

  6. Tense and Aspect in English

    DEFF Research Database (Denmark)

    Davidsen-Nielsen, Niels

    2013-01-01

    In the 1990's the author cooperated with Carl Bache on a grammar of English. It turned out that the views they had previously arrived at individually on tense and aspect could be combined by operating with a fused system involving four ordered choices resulting in sixteen tense-aspect forms...

  7. Inbreeding and parasite sex ratios.

    Science.gov (United States)

    Nee, Sean; West, Stuart A; Read, Andrew F

    2002-04-07

    The breeding system of parasitic protozoa affects the evolution of drug resistance and virulence, and is relevant to disease diagnosis and the development of chemo- and immunotherapy. A major group of protozoan parasites, the phylum Apicomplexa, that includes the aetiological agents of malaria, toxoplasmosis and coccidiosis, all have dimorphic sexual stages. The sex ratio (proportion of males produced by parasites) is predicted to depend upon the inbreeding rate, and it has been suggested that sex-ratio data offer a relatively cheap and easy method for indirectly estimating inbreeding rates. Here, we exploit a new theoretical machinery to show that there are generally valid relationships between f, Wright's coefficient of inbreeding, and sex ratio, z(*), the generality being with respect to population structure. To focus the discussion, we concentrate on malaria and show that the previously derived result, f = 1 - 2z(*), does not depend on the artificial assumptions about population structure that were previously made. Not only does this justify the use of sex ratio as an indirect measure of f, but also we argue that it may actually be preferable to measure f by measuring sex ratios, rather than by measuring departures from Hardy-Weinberg genotypic proportions both in malaria and parasites more generally.

  8. Aspect-Oriented Design with Reusable Aspect Models

    Science.gov (United States)

    Kienzle, Jörg; Al Abed, Wisam; Fleurey, Franck; Jézéquel, Jean-Marc; Klein, Jacques

    The idea behind Aspect-Oriented Modeling (AOM) is to apply aspect-oriented techniques to (software) models with the aim of modularizing crosscutting concerns. This can be done within different modeling notations, at different levels of abstraction, and at different moments during the software development process. This paper demonstrates the applicability of AOM during the software design phase by presenting parts of an aspect-oriented design of a crisis management system. The design solution proposed in this paper is based on the Reusable Aspect Models (RAM) approach, which allows a modeler to express the structure and behavior of a complex system using class, state and sequence diagrams encapsulated in several aspect models. The paper describes how the model of the "create mission" functionality of the server backend can be decomposed into 23 inter-dependent aspect models. The presentation of the design is followed by a discussion on the lessons learned from the case study. Next, RAM is compared to 8 other AOM approaches according to 6 criteria: language, concern composition, asymmetric and symmetric composition, maturity, and tool support. To conclude the paper, a discussion section points out the features of RAM that specifically support reuse.

  9. Topological Aspects of Information Retrieval.

    Science.gov (United States)

    Egghe, Leo; Rousseau, Ronald

    1998-01-01

    Discusses topological aspects of theoretical information retrieval, including retrieval topology; similarity topology; pseudo-metric topology; document spaces as topological spaces; Boolean information retrieval as a subsystem of any topological system; and proofs of theorems. (LRW)

  10. Administrative Aspects of Human Experimentation.

    Science.gov (United States)

    Irvine, George W.

    1992-01-01

    The following administrative aspects of scientific experimentation with human subjects are discussed: the definition of human experimentation; the distinction between experimentation and treatment; investigator responsibility; documentation; the elements and principles of informed consent; and the administrator's role in establishing and…

  11. Verb aspect, alternations and quantification

    Directory of Open Access Journals (Sweden)

    Svetla Koeva

    2015-11-01

    Full Text Available Verb aspect, alternations and quantification In this paper we are briefly discuss the nature of Bulgarian verb aspect and argue that the verb aspect pairs are different lexical units with different (although related meaning, different argument structure (reflecting categories, explicitness and referential status of arguments and different sets of semantic and syntactic alternations. The verb prefixes resulting in perfective verbs derivation in some cases can be interpreted as lexical quantifiers as well. Thus the Bulgarian verb aspect is related (in different way both with the potential for the generation of alternations and with the prefixal lexical quantification. It is shown that the scope of the lexical quantification by means of verbal prefixes is the quantified verb phrase and the scope remains constant in all derived alternations. The paper concerns the basic issues of these complex problems, while the detailed description of the conditions satisfying particular alternation or particular lexical quantification are subject of a more detailed study.

  12. Verbal aspects in West Greenlandic

    DEFF Research Database (Denmark)

    Trondhjem, Naja Blytmann

    2017-01-01

    In this article, lexical aspectual types in West Greenlandic are investigated in the five aspectual types, states, achievements, semelfactives, activities and accomplishments. It is shown that derivational verbalizing affixes include aspectual type congruent with the lexical aspect and how...

  13. Motivational aspects of sport volunteers

    OpenAIRE

    Mičinec, Adam

    2017-01-01

    Title: The motivational aspects of sport volunteerism. Objectives: The main aim of this bachelor work is to find out motivational aspects of sport volunteers, who have taken part in sport event. Methods: In this thesis was used quality method to get informations - specifically it was a structure interview with associated questions. Results: It was find out that it is appropriate to get those volunteers with inner motivation. These volunteers do not need to be so much motivated by external mot...

  14. Inbreeding and parasite sex ratios

    OpenAIRE

    Nee, Sean; West, Stuart A; Read, Andrew F.

    2002-01-01

    The breeding system of parasitic protozoa affects the evolution of drug resistance and virulence, and is relevant to disease diagnosis and the development of chemo- and immunotherapy. A major group of protozoan parasites, the phylum Apicomplexa, that includes the aetiological agents of malaria, toxoplasmosis and coccidiosis, all have dimorphic sexual stages. The sex ratio (proportion of males produced by parasites) is predicted to depend upon the inbreeding rate, and it has been suggested tha...

  15. Measuring Economies of Size with Expense Ratios

    OpenAIRE

    Langemeier, Michael R.

    2013-01-01

    This paper examines the relationship between three expense ratios: total expense ratio; adjusted total expense ratio; and economic total expense ratio; and discusses economies of size for a sample of Kansas farms. The total expense ratio and the adjusted total expense ratios, though commonly used to examine financial efficiency, are not as good of indicators of economies of size as the economic total expense ratio which includes opportunity costs on unpaid operator and family labor, and farm ...

  16. Odds ratios deconstructed: A new way to understand and explain odds ratios as conditional risk ratios.

    Science.gov (United States)

    Hoppe, Fred M; Hoppe, Daniel J; Walter, Stephen D

    2017-02-01

    The aim of this analysis was to provide an alternative derivation of the odds ratio (OR) to provide an intuitive meaning, freeing it from any mention of odds, which may make it a more useful concept for clinicians to use when describing treatment effect. By examining the four possible combinations of treatment/control and corresponding outcomes, we considered the conditional risk ratio (RR, also known as relative risk) of an event with the treatment compared with an event with the control for pairs of patients for whom treatment and control would yield different results. Both matched and unmatched studies are considered. We found that the OR could be derived as the RR of an outcome with treatment compared with an outcome with control conditional on the treatment and control resulting in different outcomes, thus providing a measure of the net benefit of treatment. It has been claimed that the OR comparing the effect of treatment vs. control does not have the same clinical interpretability as RR because it involves ratios of odds and so is difficult to explain in terms of patient numbers. This new derivation provides an interpretation of the OR as an RR but conditional on treatment and control resulting in different outcomes. This may help explain the reason ORs cause interpretation difficulties in practice. Moreover, the OR may be a more clinically useful parameter to patients because it deals with only those situations where the outcome differs between the two groups. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. GOLD and the fixed ratio

    Directory of Open Access Journals (Sweden)

    Vestbo J

    2012-09-01

    Full Text Available Jørgen VestboUniversity of Manchester, Manchester, UKI read with interest the paper entitled "Diagnosis of airway obstruction in the elderly: contribution of the SARA study" by Sorino et al in a recent issue of this journal.1 Being involved in the Global Initiative for Obstructive Lung Diseases (GOLD, it is nice to see the interest sparked by the GOLD strategy document. However, in the paper by Sorino et al, there are a few misunderstandings around GOLD and the fixed ratio (forced expiratory volume in 1 second/forced volume vital capacity < 0.70 that need clarification.View original paper by Sorino and colleagues.

  18. Ratio Bias and Policy Preferences

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Tue

    2016-01-01

    Numbers permeate modern political communication. While current scholarship on framing effects has focused on the persuasive effects of words and arguments, this article shows that framing of numbers can also substantially affect policy preferences. Such effects are caused by ratio bias, which...... regarding salient political issues such as education and taxes. Furthermore, the effects of numerical framing are found across most groups of the population, largely regardless of their political predisposition and their general ability to understand and use numerical information. These findings have...

  19. Dynamic aspects of musical imagery.

    Science.gov (United States)

    Halpern, Andrea R

    2012-04-01

    Auditory imagery can represent many aspects of music, such as the starting pitches of a tune or the instrument that typically plays it. In this paper, I concentrate on more dynamic, or time-sensitive aspects of musical imagery, as demonstrated in two recently published studies. The first was a behavioral study that examined the ability to make emotional judgments about both heard and imagined music in real time. The second was a neuroimaging study on the neural correlates of anticipating an upcoming tune, after hearing a cue tune. That study found activation of several sequence-learning brain areas, some of which varied with the vividness of the anticipated musical memory. Both studies speak to the ways in which musical imagery allows us to judge temporally changing aspects of the represented musical experience. These judgments can be quite precise, despite the complexity of generating the rich internal representations of imagery. © 2012 New York Academy of Sciences.

  20. Mathematical aspects of natural dynamos

    CERN Document Server

    Dormy, Emmanuel

    2007-01-01

    Although the origin of Earth's and other celestial bodies' magnetic fields remains unknown, we do know that the motion of electrically conducting fluids generates and maintains these fields, forming the basis of magnetohydrodynamics (MHD) and, to a larger extent, dynamo theory. Answering the need for a comprehensive, interdisciplinary introduction to this area, ""Mathematical Aspects of Natural Dynamos"" provides a foundation in dynamo theory before moving on to modeling aspects of natural dynamos.Bringing together eminent international contributors, the book first introduces governing equatio