WorldWideScience

Sample records for aspect ratio tokamaks

  1. Large Aspect Ratio Tokamak Study

    International Nuclear Information System (INIS)

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

  2. Second regime tokamak operation at large aspect ratio

    International Nuclear Information System (INIS)

    The equilibrium, stability, and transport properties of large aspect ratio tokamaks operating at the second stability regime are described theoretically using numerical and analytical techniques. It has been shown that, at large aspect ratio, significant current profile control is possible with relatively modest amounts of neutral beam current drive, and the power needed to access and maintain the second regime operation is calculated to be about 3 MW using the results of an integrated 1.5D transport and stability code. An example second regime experiment has been described and the results are presented of extensive calculations illustrating several possible operating scenarios, external and internal model stability boundaries, and the experimental features needed to evaluate and test the high beta tokamak theories. The theory which describes the stabilizing effect of energetic particles during high beta operation was extended to finite aspect ratio. A key technical problem for application of this technique appears to be caused by ripple transport. Plasma rotation effects are found to be generally destabilizing and several other schemes for improved access to the second stability regime are discussed including ponderomotive stabilization of the plasma edge region and active feedback control

  3. Current drive and profile control in low aspect ratio tokamaks

    International Nuclear Information System (INIS)

    The key to the theoretically predicted high performance of a low aspect ratio tokamak (LAT) is its ability to operate at very large plasma current*Ip. The plasma current at low aspect ratios follows the approximate formula: Ip ∼ (5a2Bt/Rqψ) [(1 + κ2)/2] [A/(A - 1)] where A quadruple-bond R/a which was derived from equilibrium studies. For constant qψ and Bt, Ip can increase by an order of magnitude over the case of tokamaks with A approx-gt 2.5. The large current results in a significantly enhanced βt (quadruple-bond βNIp/aBt) possibly of order unity. It also compensates for the reduction in A to maintain the same confinement performance assuming the confinement time τ follows the generic form ∼ HIpP-1/2R3/2κ1/2. The initiation and maintenance of such a large current is therefore a key issue for LATs

  4. Configuration studies for a small-aspect-ratio tokamak stellarator hybrid

    International Nuclear Information System (INIS)

    The use of modulated toroidal coils offers a new path to the tokamak-stellarator hybrids. Low-aspect-ratio configurations can be found with robust vacuum flux surfaces and rotational transform close to the transform of a reverse-shear tokamak. These configurations have clear advantages in minimizing disruptions and their effect and in reducing tokamak current drive needs. They also allow the study of low-aspect-ratio effects on stellarator confinement in small devices

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

    International Nuclear Information System (INIS)

    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

  6. 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.

  7. Cyclotron wave adsorption in large aspect ratio elongated tokamaks

    International Nuclear Information System (INIS)

    Transverse dielectric susceptibility elements are derived for radio frequency waves in a large aspect ratio toroidal plasma with elliptic magnetic surfaces by solving the Vlasov equation for untrapped, t-trapped and d-trapped particles. These dielectric characteristics are suitable for estimating the wave absorption by the fundamental cyclotron resonance damping in the frequency range of ion-cyclotron and electron cyclotron resonances.

  8. All Metal Iron Core For A Low Aspect Ratio Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    D.A. Gates, C. Jun, I. Zatz, A. Zolfaghari

    2010-06-02

    A novel concept for incorporating a iron core transformer within a axisymmetric toroidal plasma containment device with a high neutron flux is described. This design enables conceptual design of low aspect ratio devices which employ standard transformer-driven plasma startup by using all-metal high resistance separators between the toroidal field windings. This design avoids the inherent problems of a multiturn air core transformer which will inevitably suffer from strong neutron bombardment and hence lose the integrity of its insulation, both through long term material degradation and short term neutron- induced conductivity.. A full 3-dimensional model of the concept has been developed within the MAXWELL program and the resultant loop voltage calculated. The utility of the result is found to be dependent on the resistivity of the high resistance separators. Useful loop voltage time histories have been obtained using achievable resistivities.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Bong Guen; Moon, Se Youn [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-10-15

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

  10. Transmutation of nuclear waste with a low-aspect-ratio tokamak neutron source

    Science.gov (United States)

    Hong, Bong Guen; Moon, Se Youn

    2014-10-01

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

  11. Neoclassical toroidal plasma viscosity with effects of finite banana width for finite aspect ratio tokamaks

    Science.gov (United States)

    Shaing, K. C.; Sabbagh, S. A.

    2016-07-01

    Theory for neoclassical toroidal plasma viscosity has been developed to model transport phenomena, especially, toroidal plasma rotation for tokamaks with broken symmetry. Theoretical predictions are in agreement with the results of the numerical codes in the large aspect ratio limit. The theory has since been extended to include effects of finite aspect ratio and finite plasma β. Here, β is the ratio of the plasma thermal pressure to the magnetic field pressure. However, there are cases where the radial wavelength of the self-consistent perturbed magnetic field strength B on the perturbed magnetic surface is comparable to the width of the trapped particles, i.e., bananas. To accommodate those cases, the theory for neoclassical toroidal plasma viscosity is further extended here to include the effects of the finite banana width. The extended theory is developed using the orbit averaged drift kinetic equation in the low collisionality regimes. The results of the theory can now be used to model plasma transport, including toroidal plasma rotation, in real finite aspect ratio, and finite plasma β tokamaks with the radial wavelength of the perturbed symmetry breaking magnetic field strength comparable to or longer than the banana width.

  12. High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.

    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; Schlossberg, D J

    2016-04-29

    Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  13. Stable bootstrap-current driven equilibria for low aspect ratio tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.L.; Lin-Liu, Y.R.; Turnbull, A.D.; Chan, V.S. [General Atomics, San Diego, CA (United States); Pearlstein, L.D. [Lawrence Livermore National Lab., CA (United States); Sauter, O.; Villard, L. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)

    1996-09-01

    Low aspect ratio tokamaks can potentially provide a high ratio of plasma pressure to magnetic pressure {beta} and high plasma current I at a modest size, ultimately leading to a high power density compact fusion power plant. For the concept to be economically feasible, bootstrap current must be a major component of the plasma. A high value of the Troyon factor {beta}{sub N} and strong shaping are required to allow simultaneous operation at high {beta} and high bootstrap current fraction. Ideal magnetohydrodynamic stability of a range of equilibria at aspect 1.4 is systematically explored by varying the pressure profile and shape. The pressure and current profiles are constrained in such a way as to assure complete bootstrap current alignment. Both {beta}{sub N} and {beta} are defined in terms of the vacuum toroidal field. Equilibria with {beta} {sub N}{>=}8 and {beta} {approx_equal}35% to 55% exist which are stable to n = {infinity} ballooning modes, and stable to n = 0,1,2,3 kink modes with a conducting wall. The dependence of {beta} and {beta}{sub N} with respect to aspect ratio is also considered. (author) 9 figs., 14 refs.

  14. Advanced Fuels Reactor using Aneutronic Rodless Ultra Low Aspect Ratio Tokamak Hydrogenic Plasmas

    Science.gov (United States)

    Ribeiro, Celso

    2015-11-01

    The use of advanced fuels for fusion reactor is conventionally envisaged for field reversed configuration (FRC) devices. It is proposed here a preliminary study about the use of these fuels but on an aneutronic Rodless Ultra Low Aspect Ratio (RULART) hydrogenic plasmas. The idea is to inject micro-size boron pellets vertically at the inboard side (HFS, where TF is very high and the tokamak electron temperature is relatively low because of profile), synchronised with a proton NBI pointed to this region. Therefore, p-B reactions should occur and alpha particles produced. These pellets will act as an edge-like disturbance only (cp. killer pellet, although the vertical HFS should make this less critical, since the unablated part should appear in the bottom of the device). The boron cloud will appear at midplance, possibly as a MARFE-look like. Scaling of the p-B reactions by varying the NBI energy should be compared with the predictions of nuclear physics. This could be an alternative to the FRC approach, without the difficulties of the optimization of the FRC low confinement time. Instead, a robust good tokamak confinement with high local HFS TF (enhanced due to the ultra low aspect ratio and low pitch angle) is used. The plasma central post makes the RULART concept attractive because of the proximity of NBI path and also because a fraction of born alphas will cross the plasma post and dragged into it in the direction of the central plasma post current, escaping vertically into a hole in the bias plate and reaching the direct electricity converter, such as in the FRC concept.

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

    Institute of Scientific and Technical Information of China (English)

    F.L.Braga

    2013-01-01

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

  16. All-metal transformer core for a low aspect ratio tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Gates, D.A., E-mail: dgates@pppl.gov [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, NJ 08543 (United States); Jun, C.; Zatz, I.; Zolfaghari, A. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, NJ 08543 (United States)

    2011-01-15

    A novel concept for incorporating an iron core transformer within a axisymmetric toroidal plasma containment device with a high neutron flux is described. This design enables conceptual design of low aspect ratio devices which employ standard transformer-driven plasma startup by using all-metal high resistance inserts between the toroidal field windings. This design avoids the inherent problems of a multi-turn air core transformer which will inevitably suffer from strong neutron bombardment and hence lose the integrity of its insulation, both through long term material degradation and short term neutron induced conductivity. A full 3-dimensional model of the concept has been developed within the MAXWELL program and the resultant loop voltage calculated. The utility of the result is found to be dependent on the resistivity of the high resistance inserts. Useful loop voltage time histories have been obtained using expected resistivities.

  17. Aspects of Tokamak toroidal magnet protection

    International Nuclear Information System (INIS)

    Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The ofly potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting torgidal magnets. It is found that the two general classificatigls of protectign methods are thermal and electrical. Computer programs were developed which aldow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed

  18. Physics aspects of the compact ignition tokamak

    International Nuclear Information System (INIS)

    The Compact Ignition Tokamak (CIT) is a proposed modest-size ignition experiment designed to study the physics of alpha particle heating. The basic concept is to achieve ignition in a modest-size minimum cost experiment by using a high plasma density to achieve nτE ≅ 2 x 1020 s/m3 required for ignition. The high density requires a high toroidal field (10 T). The high toroidal field allows a large plasma current (10 MA) which provides a high level of ohmic heating, improves the energy confinement, and allows a relatively high beta (≅ 6%). The present CIT design also has a high degree of elongation (κ ≅ 1.8) to aid in producing the large plasma current. A double null poloidal divertor and pellet injection are part of the design to provide impurity and particle control, improve the confinement, and provide flexibility for improving the plasma profiles. Auxiliary heating is expected to be necessary to achieve ignition, and 10-20 MW of ICRF is to be provided. (orig.)

  19. Aspects of Tokamak toroidal magnet protection

    Energy Technology Data Exchange (ETDEWEB)

    Green, R.W.; Kazimi, M.S.

    1979-07-01

    Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The only potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting toroidal magnets. It is found that the two general classifications of protection methods are thermal and electrical. Computer programs were developed which allow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed.

  20. Physics aspects of the Compact Ignition Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Post, D.; Bateman, G.; Houlberg, W.; Bromberg, L.; Cohn, D.; Colestock, P.; Hughes, M.; Ignat, D.; Izzo, R.; Jardin, S.

    1986-11-01

    The Compact Ignition Tokamak (CIT) is a proposed modest-size ignition experiment designed to study the physics of alpha-particle heating. The basic concept is to achieve ignition in a modest-size minimum cost experiment by using a high plasma density to achieve the condition of ntau/sub E/ approx. 2 x 10/sup 20/ sec m/sup -3/ required for ignition. The high density requires a high toroidal field (10 T). The high toroidal field allows a large plasma current (10 MA) which improves the energy confinement, and provides a high level of ohmic heating. The present CIT design also has a gigh degree of elongation (k approx. 1.8) to aid in producing the large plasma current. A double null poloidal divertor and a pellet injector are part of the design to provide impurity and particle control, improve the confinement, and provide flexibility for impurity and particle control, improve the confinement, and provide flexibility for improving the plasma profiles. Since auxiliary heating is expected to be necessary to achieve ignition, 10 to 20 MW of Ion Cyclotron Radio Frequency (ICRF) is to be provided.

  1. Effect of particle aspect ratio in magnetorheology

    Science.gov (United States)

    Morillas, Jose R.; Carreón-González, Elizabeth; de Vicente, Juan

    2015-12-01

    We investigate the influence of the aspect ratio of the dispersed particles in magnetorheology. Two systems are studied: conventional magnetorheological fluids prepared by dispersion of nickel nanowires, and inverse ferrofluids prepared by dispersion of glass fibers in a ferrofluid. In both cases the apparent yield stress is found to increase with aspect ratio in contradiction to available models in the literature. Experimental observations demonstrate that the particle volume fraction within the aggregates initially increases with increasing the aspect ratio of the dispersed particles. When the aspect ratio is further raised, a gel-like percolating structure forms inhibiting the formation of elongated clusters in the field direction.

  2. Study of aspect ratio effects on kinetic MHD instabilities in NSTX and DIII-D

    International Nuclear Information System (INIS)

    We report general observations of kinetic instabilities on the low aspect-ratio National Spherical Torus Experiment (NSTX) and describe explicit aspect ratio scaling studies of kinetic instabilities using both the NSTX and the DIII-D tokamak. The NSTX and the DIII-D tokamak are nearly ideal for such experiments, having a factor of two difference in major radius but otherwise similar parameters. We also introduce new theoretical work on the physics of kinetic ballooning modes (KBM), toroidal Alfven eigenmodes (TAE), and compressional Alfven eigenmodes (CAE) with applications to NSTX. (author)

  3. 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.

  4. Engineering development aspects of the HL-2A tokamak

    International Nuclear Information System (INIS)

    The HL-2A tokamak (design values: major radius 1.65 m, minor radius 0.4 m, plasma current 0.48 MA and toroidal field 2.8 T) is the first tokamak with an operating divertor in China. It is characterized by a large closed divertor chamber. This unique feature will make significant contributions to enhance our understanding of complex divertor plasma physics and to help validating divertor physics modelings. The engineering design, development, testing and commissioning of the HL-2A tokamak are described in this paper. Preliminary results show that the HL-2A tokamak has been successfully operated in the divertor configuration. The major parameters: plasma current Ip=168 kA, toroidal field BT=1.4 T, plasma line average density ne=1.7 x 1019 m-3, limiting vacuum pv=4.6 x 10-6 Pa, were achieved at the end of 2003. (authors)

  5. Transcription and the aspect ratio of DNA

    DEFF Research Database (Denmark)

    Olsen, Kasper Wibeck; Bohr, Jakob

    2013-01-01

    analysis of transcription. It is shown that under certain reasonable assumptions transcription is only possible if the aspect ratio is in the regime corresponding to further twisting. We find this constraint to be in agreement with long-established crystallographic studies of DNA....

  6. Short Wavelength Ion Temperature Gradient Driven Instability in Noncircular Flux Surface Plasmas with Finite Aspect Ratio

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; GAO Zhe

    2006-01-01

    @@ By employing the local equilibrium of shaped tokamak plasmas, a gyrokinetic model with integral eigenmode equations is developed to investigate effects of the finite aspect ratio and noncircular flux surface on short wavelength ion temperature gradient (SWITG) driven modes. It is found that when nonadiabatic electron and trapped particle effects are not considered, the SWITG mode can be stabilized by finite aspect ratio A, elongation κ and triangularity δ, and can be destabilized by the Shafranov shift gradient (e)R0/(e)r.

  7. Study of aspect ratio effects on MHD instabilities

    International Nuclear Information System (INIS)

    Full text: Aspect ratio affects kinetic instabilities in many ways. In this paper we describe explicit aspect ratio scaling studies of kinetic instabilities using the NSTX and DIII- D devices and introduce new theoretical work on the general kinetic physics of KBM, TAE, CAE with applications on NSTX. The National Spherical Torus Experiment (NSTX) and the DIII-D tokamak are nearly ideal for an Alfven mode similarity experiment, with similar neutral beams, fast-ion to Alfven speed, fast-ion pressure, and shape of the plasma, but the major radius differs by a factor of two. A similarity study of the toroidal Alfven mode (TAE) shows that the most unstable toroidal mode number scales as expected, supporting an expectation of a 'sea' of unstable modes in a reactor. Alfvenic instabilities with frequencies that chirp rapidly are common in NSTX but rare in DIII-D. Efforts to understand this difference in terms of the hole-clump theory of Berk and Breizman are reported. Compressional Alfven modes (CAE) on NSTX have the frequency scaling, polarization, dependence on the fast-ion distribution function, and low frequency limit qualitatively consistent with CAE theory. Experiments are planned to compare the stability limits on DIII-D with the NSTX stability limits, with the aim of determining if CAE will be excited by alphas in a reactor. The ballooning instability results from the release of free energy of non- uniform pressure that has a gradient in the same direction as the magnetic field curvature. We show that the combined kinetic effect of trapped electron dynamics and ion Larmor radii produces a large parallel electric field and hence a parallel current that greatly enhances the stabilizing effect of field line tension. We are grateful to the NSTX and DIII-D teams. (author)

  8. Aspects of long pulse commercial tokamak reactor design

    International Nuclear Information System (INIS)

    Illustrative design parameters have been developed for an Ultra-Long Pulse Tokamak Reactor (ULTR) with a pulse length of 24 hours. The principles developed for the 24 hour pulse length ULTR design have also been used in a scoping study for machines with shorter pulses. Parameters for a machine with a 4 hour pulse length are given. The ULTR design has an ohmic transformer which is optimized to satisfy the conflicting requirements of maximized OH drive and for reaction of the inward forces of the TF coil. The toroidal field magnet is completely modularized, with each coil in its own cryostat and shearing panels at room temperature. Analysis of effects of thermal fatigue on a representative first wall design has been performed. Windows of allowed operation have been found, limited by primary stress, swelling and fatigue. The analysis has been carried out for first walls made of stainless steel or vanadium

  9. Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Meglicki, Z

    1995-09-19

    We describe in detail the implementation of a weighted differences code, which is used to simulate a tokamak using the Maschke-Perrin solution as an initial condition. The document covers the mainlines of the program and the most important problem-specific functions used in the initialization, static tests, and dynamic evolution of the system. The mathematics of the Maschke-Perrin solution is discussed in parallel with its realisation within the code. The results of static and dynamic tests are presented in sections discussing their implementation.The code can also be obtained by ftp -anonymous from cisr.anu.edu.au Directory /pub/papers/meglicki/src/tokamak. This code is copyrighted. (author). 13 refs.

  10. Edge localized mode physics and operational aspects in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Becoulet, M [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Huysmans, G [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Sarazin, Y [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Garbet, X [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Ghendrih, Ph [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Rimini, F [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Joffrin, E [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Litaudon, X [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Monier-Garbet, P [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Ane, J-M [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Thomas, P [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Grosman, A [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Parail, V [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Wilson, H [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Lomas, P [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Vries, P de[Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Zastrow, K-D [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Matthews, G F [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Lonnroth, J [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Gerasimov, S [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom)] [and others

    2003-12-01

    Recent progress in experimental and theoretical studies of edge localized mode (ELM) physics is reviewed for the reactor relevant plasma regimes, namely the high confinement regimes, that is, H-modes and advanced scenarios. Theoretical approaches to ELM physics, from a linear ideal magnetohydrodynamic (MHD) stability analysis to non-linear transport models with ELMs are discussed with respect to experimental observations, in particular the fast collapse of pedestal pressure profiles, magnetic measurements and scrape-off layer transport during ELMs. High confinement regimes with different types of ELMs are addressed in this paper in the context of development of operational scenarios for ITER. The key parameters that have been identified at present to reduce the energy losses in Type I ELMs are operation at high density, high edge magnetic shear and high triangularity. However, according to the present experimental scaling for the energy losses in Type I ELMs, the extrapolation of such regimes for ITER leads to unacceptably large heat loads on the divertor target plates exceeding the material limits. High confinement H-mode scenarios at high triangularity and high density with small ELMs (Type II), mixed regimes (Type II and Type I) and combined advanced regimes at high beta{sub p} are discussed for present-day tokamaks. The optimum combination of high confinement and small MHD activity at the edge in Type II ELM scenarios is of interest to ITER. However, to date, these regimes have been achieved in a rather narrow operational window and far from ITER parameters in terms of collisionality, edge safety factor and beta{sub p}. The compatibility of the alternative internal transport barrier (ITB) scenario with edge pedestal formation and ELMs is also addressed. Edge physics issues related to the possible combination of small benign ELMs (Type III, Type II ELMs, quiescent double barrier) and high performance ITBs are discussed for present-day experiments (JET, JT-60U

  11. Aspect ratio dependence in magnetorotational instability shearing box simulations

    CERN Document Server

    Bodo, G; Cattaneo, F; Rossi, P; Ferrari, A

    2008-01-01

    Aims: We study the changes in the properties of turbulence driven by the magnetorotational instability in a shearing box, as the computational domain size in the radial direction is varied relative to the height Methods: We perform 3D simulations in the shearing box approximation, with a net magnetic flux, and we consider computational domains with different aspect ratios Results: We find that in boxes of aspect ratio unity the transport of angular momentum is strongly intermittent and dominated by channel solutions in agreement with previous work. In contrast, in boxes with larger aspect ratio, the channel solutions and the associated intermittent behavior disappear. Conclusions: There is strong evidence that, as the aspect ratio becomes larger, the characteristics of the solution become aspect ratio independent. We conclude that shearing box calculations with aspect ratio unity or near unity may introduce spurious effects.

  12. Retrieval of aerosol aspect ratio from optical measurements in Vienna

    Science.gov (United States)

    Kocifaj, M.; Horvath, H.; Gangl, M.

    The phase function and extinction coefficient measured simultaneously are interpreted in terms of surface distribution function and mean effective aspect ratio of aerosol particles. All optical data were collected in the atmosphere of Vienna during field campaign in June 2005. It is shown that behavior of aspect ratio of Viennese aerosols has relation to relative humidity in such a way, that nearly spherical particles (with aspect ratio ɛ≈1) might became aspherical with ɛ≈1.3-1.6 under low relative humidity conditions. Typically, >80% of all Viennese aerosols have the aspect ratio Vienna.

  13. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    International Nuclear Information System (INIS)

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label

  14. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E. [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece)

    2014-06-15

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label.

  15. Magneto-Hydrodynamic High-n Ballooning Mode Instability of an Analytic Axi-Symmetric Toroidal Equilibrium with Arbitrary Aspect Ratio

    Institute of Scientific and Technical Information of China (English)

    SHI Bing-Ren; LI Ji-Quan

    2007-01-01

    An exact ballooning mode eigen-equation is derived to study stability of axi-symmetric toroidal plasma with arbitrary aspect ratio, including the tokamak, the finite aspect ratio and the spherical torus plasmas. For comparison with the widely used ( s - α) model, an analytic exact equilibrium configuration with circular magnetic surfaces is analysed in detail. It is indicated that the (s - α) model needs to be improved for more realistic configurations.

  16. Perspectives on low-aspect-ratio torsatron/heliotron

    International Nuclear Information System (INIS)

    The advantages of the low-aspect-ratio torsatron/heliotron configuration is discussed from the point of view of plasma confinement. Recent numerical results on the configuration study and the experimental data base are reviewed. (author)

  17. Low-aspect-ratio toroidal equilibria of electron clouds

    International Nuclear Information System (INIS)

    Toroidal electron clouds with a low aspect ratio (as small as 1.3) and lasting for thousands of poloidal rotation periods have been formed in the laboratory. Characteristic toroidal effects like a large inward shift of the minor axis of equipotential contours, elliptical and triangular deformations, etc., have been observed experimentally for the first time. The results of new analytic and numerical investigations of low-aspect-ratio electron cloud equilibria, which reproduce many of the observed features, are also presented

  18. Effect of mineral dust aerosol aspect ratio on polarized reflectance

    International Nuclear Information System (INIS)

    The effects of dust particle aspect ratios on single- and multiple-scattering processes are studied using the spheroidal model in order to obtain a better understanding of the radiance and polarization signals at the top of the atmosphere (TOA) under various dust-aerosol-loading conditions. Specifically, the impact of the particle aspect ratio on the polarization state of the TOA radiation field is demonstrated by comparing the normalized polarized radiances observed by the POLDER (POLarization and Directionality of the Earth's Reflectances) instrument on board the PARASOL (Polarisation et Anisotropie des Reflectances au sommet de l'Atmosphère, couples avec un Satellite d'Observation emportant un Lidar) satellite with the corresponding theoretical counterparts. Furthermore, presented are the aspect ratio values inferred from multi-angular polarized radiance measurements of Saharan and Asian dust by the POLDER/PARASOL. - Highlights: • The radiative effect of dust aerosol aspect ratio is investigated. • A computational efficient vector radiative transfer model is developed. • Spaceborne Polarimetric measurements are used to retrieve aerosol properties. • A case study of Saharan dust shows a mean aspect ratio of 2.5. • Asian dust exhibits two aspect ratio values, 2.5 and 1.25

  19. SMARTOR: a small-aspect-ratio torus for demonstrating thermonuclear ignition

    International Nuclear Information System (INIS)

    A tokamak with 2.6-m major radius and aspect ratio of 1.9 is proposed for demonstrating thermonuclear ignition in deuterium-tritium. The 6-MA plasma current is established in part by coinjection only of 40 MW of 80-keV neutral beams (inducing approximately 2 MA at low density) and in part by the flux swing of the equilibrium-field system (inducing approximately 4 M as the plasma pressure is increased)--there is no central current transformer and no poloidal-field coils inboard of the plasma. The core of the device consists simply of a 1.9-m-diameter steel-reinforced conducting trunk formed by coalescence of the inner legs of the toroidal-field coils. Alternate designs are presented, each with an aspect ratio of 1.9, with R/sub 0/ = 2.6 m and a plasma density sufficiently large to provide a comfortable safety margin for achieving ignition conditions. The first design features higher beta (anti β = 0.10, b/a approx. 1.6) with low tensile stress at the copper trunk (1000 kg/cm2), while the second features lower beta (anti β = 0.06, b/a approximately 1.2) with high tensile stress (1800 kg/cm2). Extension of this small-major-radius, small-aspect-ratio configuration to an economically practical fusion reactor is also examined

  20. Misperception of aspect ratio in binocularly viewed surfaces.

    Science.gov (United States)

    Hibbard, Paul B; Goutcher, Ross; O'Kane, Lisa M; Scarfe, Peter

    2012-10-01

    The horizontal-vertical illusion, in which the vertical dimension is overestimated relative to the horizontal direction, has been explained in terms of the statistical relationship between the lengths of lines in the world, and the lengths of their projections onto the retina (Howe & Purves, 2002). The current study shows that this illusion affects the apparent aspect ratio of shapes, and investigates how it interacts with binocular cues to surface slant. One way in which statistical information could give rise to the horizontal-vertical illusion would be through prior assumptions about the distribution of slant. This prior would then be expected to interact with retinal cues to slant. We determined the aspect ratio of stereoscopically viewed ellipses that appeared circular. We show that observers' judgements of aspect ratio were affected by surface slant, but that the largest image vertical:horizontal aspect ratio that was considered to be a surface with a circular profile was always found for surfaces close to fronto-parallel. This is not consistent with a Bayesian model in which the horizontal-vertical illusion arises from a non-uniform prior probability distribution for slant. Rather, we suggest that assumptions about the slant of surfaces affect apparent aspect ratio in a manner that is more heuristic, and partially dissociated from apparent slant. PMID:22925917

  1. Aspect ratio effect on shock-accelerated elliptic gas cylinders

    Science.gov (United States)

    Zou, Liyong; Liao, Shenfei; Liu, Cangli; Wang, Yanping; Zhai, Zhigang

    2016-03-01

    The evolution of an elliptic heavy-gas (SF6) cylinder accelerated by a planar weak shock wave is investigated experimentally using particle image velocimetry (PIV) diagnostics, and the emphasis is on the aspect ratio effect on shock-elliptic cylinder interaction. Experiments are conducted at five different aspect ratios (the ratio of length in streamwise and spanwise directions) varied from 0.25 to 4.0. PIV raw images and quantitative flow field data are obtained at t = 0.6 ms after the shock impact. As the aspect ratio increases, the interface morphology develops faster owing to more vorticity produced along the interface and smaller vortex spacing between the two vortex cores. For each case in this study, the maximal fluctuating velocity locates at the middle point of the two counter-vortices. The histograms of fluctuating velocity reveal that a distinct double-peak structure appears in the largest aspect ratio case in comparison with a single-peak structure in the smallest aspect ratio case. The vortex velocities predicted by the theoretical model [G. Rudinger and L. M. Somers, "Behaviour of small regions of different gases carried in accelerated gas flows," J. Fluid Mech. 7, 161-176 (1960)] agree well with the experimental ones. With the increase of aspect ratio, the maximal value of vorticity increases as well as the circulation, and more low-magnitude quantities are generated, which indicates the formation of multi-scale flow structure in the late mixing process. It is found that the experimental circulation of the vortex motion is reasonably estimated by the ideal point vortex-pair model.

  2. Method of fabricating a high aspect ratio microstructure

    Science.gov (United States)

    Warren, John B.

    2003-05-06

    The present invention is for a method of fabricating a high aspect ratio, freestanding microstructure. The fabrication method modifies the exposure process for SU-8, an negative-acting, ultraviolet-sensitive photoresist used for microfabrication whereby a UV-absorbent glass substrate, chosen for complete absorption of UV radiation at 380 nanometers or less, is coated with a negative photoresist, exposed and developed according to standard practice. This UV absorbent glass enables the fabrication of cylindrical cavities in a negative photoresist microstructures that have aspect ratios of 8:1.

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

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels B

    2013-01-01

    with FDTS. Reduced adhesion forces are consistent with lowered friction that reduces the risk of fracturing the nanoscopic pillars during demolding. Optimized mold surface chemistry and associated injection molding conditions permitted the fabrication of square arrays of 40 nm wide and 107 nm high (aspect...... ratio >2.5) pillars on a 200 nm pitch....

  4. Transitions in Dynamo Modes Controlled by the Domain Aspect Ratio

    Science.gov (United States)

    Goudard, L.; Dormy, E.

    2007-12-01

    Magnetic fields of internal origin are observed on many planets in the solar system. The Sun itself acts as a dynamo. While these natural objects are very different in their composition, when it comes to dynamo modeling the governing equations are remarkably similar. One of the controlling parameters to distinguish between these objects is the aspect ratio of the convecting domain. Comparing the Sun to the Earth raises the issue of the nature of reversals. A challenging issue is to determine why the geomagnetic field reverses polarity on an irregular basis, whereas the Sun --which is a much larger object, governed by stronger nonlinearities-- reverses its magnetic polarity on a quasi-periodic timescale of 11 yrs. We use a three-dimensional Boussinesq model (the Parody code) to investigate the transition between these two types of behavior. We show that the aspect ratio of the convecting domain controls the nature of the dynamo field. We report a butterfly-like diagram at large aspect ratio, with magnetic activity near 30° of latitudes, which migrates with time toward the equator. We trace the existence of the dynamo wave solution at various aspect ratio and suggest possible consequences for the geomagnetic secular variation.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    We construct a semi-analytical model describing the scattering, extinction and absorption properties of a high aspect-ratio trench in a metallic film. We find that these trenches act as highly efficient scatterers of free waves. In the perfect conductor limit, which for many metals is approached...... in the long-wavelength regime, the scattering cross section has the maximum value for a dipolar scatterer, which depends exclusively on the wavelength. Numerical simulations are performed to validate model findings and evaluate under which circumstances the model is accurate. We fabricate tapered high aspect......-ratio trenches of various depths into a gold monocrystal, which we characterize by reflection spectroscopy and dark field imaging, confirming their resonantbehavior. Furthermore, we estimate the field enhancement by means of two-photonluminescence....

  6. High-aspect-ratio fine-line metallization

    Science.gov (United States)

    Chang, Chienliu; Chang, Peizen; Yen, Kaihsiang; Lu, Sheyshi

    1998-08-01

    This study is aimed at making metallic fine lines characterized with high aspect ratio. There are two methods we have developed. One is the trilevel lift-off method with submicron lithography, and the other is the lift-off method by using the commercial negative photoresist SU-8 made by IBM. First, the trilevel lift-off method is described. A pre- imidized, soluble polyimide layer of OCG Probimide 293 A is spun on a wafer with thickness 4 micrometer. A 120 nm thick layer of silicon oxynitride was formed on the polyimide by PECVD. A layer photoresist layer was applied and patterned. This photoresist layer is used as the etching mask of silicon oxynitride by RIE with the gas CF4 plasma. Similarly, the silicon oxynitride is used as the etching mask of the thick polyimide layers by RIE with the gas O2 plasma. After metallization the pre-imidized polyimide is dissolved in methylene chloride lifting off the oxynitride and metal layers. Following this way, the submicron lithography, such as silylation technology, is suitable to make the aspect ratio up to 10 and the metal line will still have 3 micrometer height. The other is the lift-off method by using negative photoresist SU-8. This SU-8 is originally used as high aspect ratio molding. The linewidth of SU-8 is reduced to 2 micrometer linewidth with 12 micrometer height, and used as the remover to lift off after metallization. This SU-8 makes the fine-line metallization of 2 micrometer linewidth to achieve the aspect- ratio up to 5.

  7. 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....

  8. Theoretical Additional Span Loading Characteristics of Wings with Arbitrary Sweep, Aspect Ratio, and Taper Ratio

    Science.gov (United States)

    Deyoung, John

    1947-01-01

    The Weissinger method for determining additional span loading has been used to find the lift-curve slope, spanwise center of pressure, aerodynamic center location, and span loading coefficients of untwisted and uncambered wings having a wide range of plan forms characterized by various combinations of sweep, aspect ratio, and taper ratio. The results are presented as variations of the aerodynamic characteristics with sweep angle for various values of aspect ratio and taper ratio. Methods are also included for determining induced drag and the approximate effects of compressibility. Despite the limitations of a lifting line method such as Weissinger's, the good agreement found between experimentally and theoretically determined characteristics warrants confidence in the method. In particular, it is believed that trends observed in results of the Weissinger method should be reliable. One of the most significant results showed that for each angle of sweep there is a taper ratio for which aspect ratio has little effect on the span loading and for which the loading is practically elliptical. This elliptic loading is approached at a taper ratio of 1.39 for 30 degree of sweepforward, 0.45 for zero degree of sweepback. (author)

  9. 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.

  10. Effects of rectangular microchannel aspect ratio on laminar friction constant

    Science.gov (United States)

    Papautsky, Ian; Gale, Bruce K.; Mohanty, Swomitra K.; Ameel, Timothy A.; Frazier, A. Bruno

    1999-08-01

    In this paper, the effects of rectangular microchannel aspect ratio on laminar friction constant are described. The behavior of fluids was studied using surface micromachined rectangular metallic pipette arrays. Each array consisted of 5 or 7 pipettes with widths varying from 150 micrometers to 600 micrometers and heights ranging from 22.71 micrometers to 26.35 micrometers . A downstream port for static pressure measurement was used to eliminate entrance effects. A controllable syringe pump was used to provide flow while a differential pressure transducer was used to record the pressure drop. The experimental data obtained for water for flows at Reynolds numbers below 10 showed an approximate 20% increase in the friction constant for a specified driving potential when compared to macroscale predictions from the classical Navier-Stokes theory. When the experimental data are studied as a function of aspect ratio, a 20% increase in the friction constant is evident at low aspect ratios. A similar increase is shown by the currently available experimental data for low Reynolds number (flows of water.

  11. Rapid homogeneous endothelialization of high aspect ratio microvascular networks.

    Science.gov (United States)

    Naik, Nisarga; Hanjaya-Putra, Donny; Haller, Carolyn A; Allen, Mark G; Chaikof, Elliot L

    2015-08-01

    Microvascularization of an engineered tissue construct is necessary to ensure the nourishment and viability of the hosted cells. Microvascular constructs can be created by seeding the luminal surfaces of microfluidic channel arrays with endothelial cells. However, in a conventional flow-based system, the uniformity of endothelialization of such an engineered microvascular network is constrained by mass transfer of the cells through high length-to-diameter (L/D) aspect ratio microchannels. Moreover, given the inherent limitations of the initial seeding process to generate a uniform cell coating, the large surface-area-to-volume ratio of microfluidic systems demands long culture periods for the formation of confluent cellular microconduits. In this report, we describe the design of polydimethylsiloxane (PDMS) and poly(glycerol sebacate) (PGS) microvascular constructs with reentrant microchannels that facilitates rapid, spatially homogeneous endothelial cell seeding of a high L/D (2 cm/35 μm; > 550:1) aspect ratio microchannels. MEMS technology was employed for the fabrication of a monolithic, elastomeric, reentrant microvascular construct. Isotropic etching and PDMS micromolding yielded a near-cylindrical microvascular channel array. A 'stretch - seed - seal' operation was implemented for uniform incorporation of endothelial cells along the entire microvascular area of the construct yielding endothelialized microvascular networks in less than 24 h. The feasibility of this endothelialization strategy and the uniformity of cellularization were established using confocal microscope imaging.

  12. High aspect ratio 3D nanopatterning using Proton Beam Writing

    Science.gov (United States)

    van Kan, Jeroen A.

    2009-03-01

    Proton beam writing (PBW) is a new direct write lithography using MeV protons, and is unique because of its ability to fabricate 3D structures of high aspect ratio structures directly in resist material like PMMA, SU-8 and HSQ. The introduction by CIBA, Singapore of a dedicated PBW facility, capable of writing at the micro- and nano- scale has facilitated high aspect ratio nanostructuring. PBW has demontrated high aspect ratio walls in HSQ down to the 20nm level. In recent experiments details down to sub 20 nm have been achieved in PMMA. Monte-Carlo calculations have shown that structuring down to the nanometer level is feasible. All this is possible because of the virtual absence of proximity effects (unwanted resist exposure by stray secondary electrons). The design and performance of this unique nanoprobe facility will be discussed. Two potential fields of application (eg nanofluidics and nanowire integration) of PBW will be discussed. Currently nanofluidics devices have typically only one critical dimension below 100 nm. Here we will introduce PBW as a powerful technique to fabricate molds for replication of PDMS nanofluidic circuits down to the sub 100 nm level in two dimensions. Initial chips with dimension down to 150 nm have successfully been used to study DNA folding in quasi-1d nanochannels in tandem with fluorescence imaging. Since the size of these PDMS nanochannels is not limited by the PDMS or PBW further miniaturization down to the sub 100 nm level is a realistic goal and initial results will be discussed. Nanowires are a potential building block for nano-electronic devices, and one critical problem is the integration of nanowires to form contacts. Porous alumina templates and high energy ion-tracks have been used for the production of nanowire templates in a random orientation. Since PBW is the only true 3D direct write nanolithographic technique it can be used to fabricate nanowire templates in a controlled manner.

  13. Masks for high aspect ratio x-ray lithography

    International Nuclear Information System (INIS)

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

  14. High aspect ratio transmission line circuits micromachined in silicon

    Science.gov (United States)

    Todd, Shane Truman

    The performance of complimentary metal-oxide-semiconductor (CMOS) monolithic microwave integrated circuits (MMICs) fabricated on silicon has improved dramatically. The scaling down of silicon transistors has increased the maximum frequency of transistors to the point where silicon MMICs have become a viable alternative to compound semiconductor MMICs in certain applications. A fundamental problem still exists in silicon MMICs however in that transmission lines fabricated on silicon can suffer from high loss due to the finite conductivity of the silicon substrate. A novel approach for creating low-loss transmission lines on silicon is presented in this work. Low-loss transmission lines are created on low resistivity silicon by using a micromachining method that combines silicon deep reactive ion etching (DRIE), thermal oxidation, electroplating, and planarization. Two types of high aspect ratio transmission lines are created with this method including high aspect ratio coplanar waveguide (hicoplanar) and semi-rectangular coaxial (semicoaxial). Transmission lines with impedances ranging from 20--80 O have been fabricated with minimum measured loss lower than 1 dB/cm at 67 GHz. Low-loss dielectrics are created for the high aspect ratio transmission lines using the mesa merging method. The mesa merging method works by creating silicon mesa arrays using DRIE and then converting and merging the mesa arrays into a solid oxide dielectric using thermal oxidation. The transmission lines are designed so that the fields penetrate the low-loss oxide dielectric and are isolated from the lossy silicon substrate. The mesa merging method has successfully created large volume oxide with depth up to 65 microm and width up to 240 microm in short oxidation times. Other advantages of the high aspect ratio transmission lines are demonstrated including low-loss over a wide impedance range, high isolation, and high coupling for coupled-line circuits. Transmission line models have been

  15. Large eddy simulation of a high aspect ratio combustor

    Science.gov (United States)

    Kirtas, Mehmet

    The present research investigates the details of mixture preparation and combustion in a two-stroke, small-scale research engine with a numerical methodology based on large eddy simulation (LES) technique. A major motivation to study such small-scale engines is their potential use in applications requiring portable power sources with high power density. The investigated research engine has a rectangular planform with a thickness very close to quenching limits of typical hydrocarbon fuels. As such, the combustor has a high aspect ratio (defined as the ratio of surface area to volume) that makes it different than the conventional engines which typically have small aspect ratios to avoid intense heat losses from the combustor in the bulk flame propagation period. In most other aspects, this engine involves all the main characteristics of traditional reciprocating engines. A previous experimental work has identified some major design problems and demonstrated the feasibility of cyclic combustion in the high aspect ratio combustor. Because of the difficulty of carrying out experimental studies in such small devices, resolving all flow structures and completely characterizing the flame propagation have been an enormously challenging task. The numerical methodology developed in this work attempts to complement these previous studies by providing a complete evolution of flow variables. Results of the present study demonstrated strengths of the proposed methodology in revealing physical processes occuring in a typical operation of the high aspect ratio combustor. For example, in the scavenging phase, the dominant flow structure is a tumble vortex that forms due to the high velocity reactant jet (premixed) interacting with the walls of the combustor. Since the scavenging phase is a long process (about three quarters of the whole cycle), the impact of the vortex is substantial on mixture preparation for the next combustion phase. LES gives the complete evolution of this flow

  16. Aspect ratio effects in turbulent duct flows studied with DNS

    Science.gov (United States)

    Vinuesa, R.; Noorani, A.; Lozano-Durán, A.; Schlatter, P.; Fischer, P.; Nagib, H.

    2012-11-01

    Three-dimensional effects present in turbulent duct flows, i.e., side-wall boundary layers and secondary motions, are studied by means of direct numerical simulations (DNS). The spectral element code Nek5000, developed by Fischer et. al. (2008), is used to compute turbulent duct flows with aspect ratios 1 and 3 in streamwise-periodic boxes of length 25 h (long enough to capture the longest streamwise structures). The total number of grid points is 28 and 62 million respectively, and the inflow conditions were adjusted iteratively in order to keep the same bulk Reynolds number at the centerplane (Reb , c = 2800) in both cases. Spanwise variations in wall shear, mean-flow profiles and turbulence statistics were analyzed with aspect ratio, and also compared with the 2D channel. The simulations were started from a laminar duct profile, and transition to turbulence was triggered by means of trip-forcing in the wall-normal direction, applied at the two horizontal walls. In addition, we developed a convergence criterion aimed at assessing the necessary averaging time TA for converged statistics. We find that econdary motions present in duct flows require longer averaging times and the total shear-stress profile is not necessarily linear.

  17. 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).

  18. Tilt stability of arbitrary aspect ratio ion rings

    International Nuclear Information System (INIS)

    A study is made of the low-frequency tilt stability of finite aspect ratio field-reversed ion rings. A new analytic-numerical method is described which overcomes the large-aspect-ratio assumption of previous analytical treatments. The method involves the numerical evaluation of the Vlasov time history integrals for the ring particles using orbits determined numerically in numerically calculated self-consistent equilibria. The method is applied to the tilt stability of fat, noncircular cross-section rings. The condition for tilt instability is found to be of the form ω/sub z/>kΩ, where the parameter k varies from 0.7 to 1.0 for the cases studied, and where ω/sub z/ is the mean axial betatron frequency and Ω is the mean toroidal circulation frequency. For weak rings (field-reversal factor delta = B/sub self//B/sub e/x< or =1), k approaches unity, whereas for strong rings (deltaroughly-equal2), kroughly-equal0.7. As a given ring is elongated axially it is found that ω/sub z/ decreases, while Ω changes relatively little. A saturation mechanism is proposed whereby tilt unstable rings reach a stable equilibrium through axial lengthening

  19. Residual strain effects on large aspect ratio micro-diaphragms

    Energy Technology Data Exchange (ETDEWEB)

    Hijab, R.S.; Muller, R.S. (California Univ., Berkeley, CA (USA))

    1988-09-30

    Highly compliant, large aspect ratio diaphragms for use in low-pressure, capacitive-readout sensors, have been investigated. In such structures, unrelaxed strain in the diaphragms can radically alter mechanical behavior. Although strain can be reduced by thermal annealing, it usually reaches a remnant irreducible minimum. The purpose of this paper is to describe techniques that result in low-strain materials and that reduce the effects of residual strain in micro-diaphragms. Square polysilicon grilles and perforated diaphragms made from both single and double polysilicon layers and from single-crystal silicon, with aspect ratios (side/thickness) of up to 1000 and very low compressive strain ({approx}6 {times} 10{sup {minus}5}), have been fabricated. Strain reduction is achieved by combining thermal annealing with one of two mechanical design techniques. The first technique makes use of a series of cantilever beams to support the diaphragms. In a second procedure, corrugated surfaces in thinned membranes of single-crystal silicon are formed. The corrugations result from the use of boron doping and anisotropic silicon etching. In both of these techniques to produce low-strain diaphragms, an etched cavity is purposely formed in the substrate crystal below them. Only one-sided processing of wafers is employed, thus aiding reproducibility and providing ease of compatibility with an MOS process. A fast-etching sacrificial-support layer (phosphorus-doped CVD oxide) is used. 4 refs., 10 figs.

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

    Directory of Open Access Journals (Sweden)

    Le Gal P.

    2013-04-01

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

  1. AERODYNAMIC OPTIMIZATION DESIGN OF LOW ASPECT RATIO TRANSONIC TURBINE STAGE

    Institute of Scientific and Technical Information of China (English)

    SONG Liming; LI Jun; FENG Zhenping

    2006-01-01

    The advanced optimization method named as adaptive range differential evolution (ARDE)is developed. The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution. Combined with parallel ARDE, surface modeling method and Navier-Stokes solution, a new automatic aerodynamic optimization method is presented. A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total. The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs. The isentropic efficiency of the optimum design is 1.6% higher than that of the reference design. The aerodynamic performance of the optimal design is much better than that of the reference design.

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

    Science.gov (United States)

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

    2016-02-01

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

  3. Photoimageable Polyimide: A Dielectric Material For High Aspect Ratio Structures

    Science.gov (United States)

    Cech, Jay M.; Oprysko, Modest M.; Young, Peter L.; Li, Kin

    1986-07-01

    Polyimide has been identified as a useful material for microelectronic packaging because of its low dielectric constant and high temperature stability. Difficulties involved with reactive ion etching (RIE), a conventional technique for patterning thick polyimide films (thickness greater than 5 microns) with vertical walls, can be overcome by using photimageable polyimide precursors. The processing steps are similar to those used with negative photoresists. EM Chemical's HTR-3 photosensitive polyimide has been spun on up to a thickness of 12 microns. Exposure with a dose of 780 mJcm-2 of ultraviolet light, followed by spin development produces clean patterns as small as 5 microns corresponding to an aspect ratio of 2.4. When the patterned precursor is heated, an imidization reaction occurs converting the patterned film to polyimide. Baking to ca. 400 degrees C results in substantial loss in the thickness and in line width. However, shrinkage occurs reproducibly so useful rules for mask design can be formulated. Near vertical wall structures can be fabricated by taking advantage of the optical and shrinkage properties of the polyimide precursor. After development, an undercut wall profile can be produced since the bottom of the film receives less exposure and is hence more soluble in the developer. During heating, lateral shrinkage pulls the top of the film inward producing a vertical wall since the bottom is fixed to the substrate by adhesion. As a result, fully cured polyimide structures with straight walls and aspect ratios greater than one can be obtained. Dielectric properties of the fully imidized films were investigated with capacitor test structures. A relative dielectric constant of 3.3 and a loss tangent of .002 were measured at 20 kHz. It was also found that the dielectric constant increases as a linear function of relative humidity.

  4. Model for aspect ratio dependent etch modulated processing

    International Nuclear Information System (INIS)

    A time-multiplexed, anisotropic, inductively coupled plasma Si deep reactive ion etch process is characterized in terms of the Si macroload, cross-wafer spatial variation, local pattern density, and feature size. The process regime is established as neutral flux limited, in which material transport occurs in the molecular flow to transition flow regimes. For this process regime, a semiempirical, unified analytic model and a numeric model are developed using the Dushman and Clausing vacuum conductance correction factors, respectively, in the Coburn and Winters model of aspect ratio dependent etching. The experimental reaction probability for etching of Si by F was found to be 0.24 for Dushman's factor and 0.22 for Clausing's factor. Each model is validated to ±10% against experimental depth data for microdonut and trench test structures and match each other to within 10% for depths of up to 160 μm. The observed depth range is 64 μm at a depth of 160 μm.

  5. Bootstrap Current in Spherical Tokamaks

    Institute of Scientific and Technical Information of China (English)

    王中天; 王龙

    2003-01-01

    Variational principle for the neoclassical theory has been developed by including amomentum restoring term in the electron-electron collisional operator, which gives an additionalfree parameter maximizing the heat production rate. All transport coefficients are obtained in-cluding the bootstrap current. The essential feature of the study is that the aspect ratio affects thefunction of the electron-electron collision operator through a geometrical factor. When the aspectratio approaches to unity, the fraction of circulating particles goes to zero and the contribution toparticle flux from the electron-electron collision vanishes. The resulting diffusion coefficient is inrough agreement with Hazeltine. When the aspect ratio approaches to infinity, the results are inagreement with Rosenbluth. The formalism gives the two extreme cases a connection. The theoryis particularly important for the calculation of bootstrap current in spherical tokamaks and thepresent tokamaks, in which the square root of the inverse aspect ratio, in general, is not small.

  6. Small scale electron density fluctuations in a tokamak: statistical aspects and links with magnetohydrodynamic activity

    International Nuclear Information System (INIS)

    The installation and operation of coherent microwave diffusion diagnostics in the TFR tokamak are outlined. The original setup was modified to make diagnostic information accessible to the computer. Microfluctuations were studied using a statistical method. Toroidal propagation of drift waves was assessed using a method of correlation between two diffusion diagnostics. Then, using only one of the diagnostics, statistical analysis tools were employed to evaluate the rate of nonlinear quadratic coupling between three modes. Experimental links between electron density fluctuations and MHD phenomena are demonstrated

  7. 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.

  8. Experimental study of the topological aspect of the ergodic divertor in Tore-supra tokamak

    International Nuclear Information System (INIS)

    The control of power deposition onto plasma facing components in tokamaks is a determining factor for future thermonuclear fusion reactors. Plasma surface interaction can be performed using limiters or divertors. The ergodic divertor installed on Tore Supra is an atypical example of a magnetic divertor. It consists in applying a magnetic perturbation which establishes a particular topology of the plasma in contact with the wall (edge plasma). We carried out dedicated experiments in order to study parallel heat flux which strike the divertor neutralizers. This quantitative and qualitative analysis of heat flux as a function of experimental conditions allows to determine the profiles of power deposition along the neutralizers. The influence of plasma electron density, additional heating, impurities and injected gas was established. An experimental study of the sheath heat transmission factor γ was carried out by correlating measurements made with Langmuir probes and infrared imaging. This study gave rise to a major conclusion: for ohmic discharges with deuterium injection and most of the time with helium, it was experimentally confirmed that γ=7 in agreement with classical sheath theory. However, an increase of this factor with additional power has been shown. Detached plasma, which is an attractive regime in order to reduce the power deposition, requires an optimized control. A new measurement of the detachment onset has been developed. It is based on the variation of heat flux onto the plates derived from infrared measurements. A detachment cartography with the determination of a new 2D 'IR' Degree of Detachment was carried out allowing to locate the zone where the detachment starts. We can apply this concept both to other tokamaks such as JET and ITER. A comparison between the axisymmetric divertor and the ergodic divertor is also presented concerning the power deposition in the two configurations. Low heat flux with the ergodic divertor is a major advantage

  9. Developing an edge-plasma diagnostic tool for the Globus-M tokamak based on measuring ratios of HeI lines

    Science.gov (United States)

    Timokhin, V. M.; Rykachevskii, A. I.; Miroshnikov, I. V.; Sergeev, V. Yu.; Kochergin, M. M.; Koval', A. N.; Mukhin, E. E.; Tolstyakov, S. Yu.; Voronin, A. V.

    2016-08-01

    A diagnostic technique that is based on measuring the ratios of neutral-helium line strengths has been developed for peripheral distributions of electron temperature and density of tokamak plasma. The main components of the technique are a four-channel filter-lens imaging polychromator (FLIP-4) and a Phantom Miro M110 high-speed camera for recording the images. The polychromator has been assembled, adjusted, and tested on an optical test bench. The optical system was installed on the spherical Globus-M tokamak. Some preliminary experiments were carried out. Images of the plasma-gun jet were obtained at neutralhelium lines.

  10. Neoclassical transport in high [beta] tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Cowley, S.C.

    1992-12-01

    Neoclassical, transport in high [beta] large aspect ratio tokamaks is calculated. The variational method introduced by Rosenbluth, et al., is used to calculate the full Onsager matrix in the banana regime. These results are part of a continuing study of the high [beta] large aspect ratio equilibria introduced in Cowley, et al. All the neoclassical coefficients are reduced from their nominal low [beta] values by a factor ([var epsilon]/q[sup 2][beta])[sup [1/2

  11. A compact Tokamak transmutation reactor

    Institute of Scientific and Technical Information of China (English)

    QiuLi-Jian; XiaoBing-Jia

    1997-01-01

    The low aspect ration tokamak is proposed for the driver of a transmutation reactor.The main parameters of the reactor core,neutronic analysis of the blanket are given>the neutron wall loading can be lowered from the magnitude order of 1 MW/m2 to 0.5MW/m2 which is much easier to reach in the near future,and the transmutation efficiency (fission/absorption ratio)is raised further.The blanket power density is about 200MW/m3 which is not difficult to deal with.The key components such as diverter and center conductor post are also designed and compared with conventional TOkamak,Finally,by comparison with the other drivers such as FBR,PWR and accelerator,it can be anticipated that the low aspect ratio transmutation reactor would be one way of fusion energy applications in the near future.

  12. Hydrodynamic chromatography and field flow fractionation in finite aspect ratio channels.

    Science.gov (United States)

    Shendruk, T N; Slater, G W

    2014-04-25

    Hydrodynamic chromatography (HC) and field-flow fractionation (FFF) separation methods are often performed in 3D rectangular channels, though ideal retention theory assumes 2D systems. Devices are commonly designed with large aspect ratios; however, it can be unavoidable or desirable to design rectangular channels with small or even near-unity aspect ratios. To assess the significance of finite-aspect ratio effects and interpret experimental retention results, an ideal, analytical retention theory is needed. We derive a series solution for the ideal retention ratio of HC and FFF rectangular channels. Rather than limiting devices' ability to resolve samples, our theory predicts that retention curves for normal-mode FFF are well approximated by the infinite plate solution and that the performance of HC is actually improved. These findings suggest that FFF devices need not be designed with large aspect ratios and that rectangular HC channels are optimal when the aspect ratio is unity.

  13. Hydrodynamic chromatography and field flow fractionation in finite aspect ratio channels.

    Science.gov (United States)

    Shendruk, T N; Slater, G W

    2014-04-25

    Hydrodynamic chromatography (HC) and field-flow fractionation (FFF) separation methods are often performed in 3D rectangular channels, though ideal retention theory assumes 2D systems. Devices are commonly designed with large aspect ratios; however, it can be unavoidable or desirable to design rectangular channels with small or even near-unity aspect ratios. To assess the significance of finite-aspect ratio effects and interpret experimental retention results, an ideal, analytical retention theory is needed. We derive a series solution for the ideal retention ratio of HC and FFF rectangular channels. Rather than limiting devices' ability to resolve samples, our theory predicts that retention curves for normal-mode FFF are well approximated by the infinite plate solution and that the performance of HC is actually improved. These findings suggest that FFF devices need not be designed with large aspect ratios and that rectangular HC channels are optimal when the aspect ratio is unity. PMID:24674643

  14. Digital controlled pulsed electric system of the ETE tokamak. First report; Sistema eletrico pulsado com controle digital do Tokamak ETE (experimento Tokamak esferico). Primeiro relatorio

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Luis Felipe de F.P.W.; Del Bosco, Edson

    1997-12-31

    This reports presents a summary on the thermonuclear fusion and application for energy supply purposes. The tokamak device operation and the magnetic field production systems are described. The ETE tokamak is a small aspect ratio device designed for plasma physics and thermonuclear fusion studies, which presently is under construction at the Laboratorio Associado de Plasma (LAP), Instituto Nacional de Pesquisas Espaciais (INPE) - S.J. dos Campos - S. Paulo. (author) 55 refs., 40 figs.

  15. 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......, since the coverage of the side walls of almost vertical pillars is not trivial by standard processes in a clean room facility. This paper will discuss the different steps taken towards this goal and present the results that we have obtained so far....

  16. Prime modes of fluid circulation in large-aspect-ratio turbulent Rayleigh-Bénard convection

    NARCIS (Netherlands)

    Verdoold, J.; Tummers, M.J.; Hanjalić, K.

    2009-01-01

    Based on a detailed experimental investigation in an aspect-ratio-4 rectangular cell in the range 3.7×107≤Ra≤3.7×109, we present evidence of possible scenarios of the long-term dynamics of large-scale circulations (LSC) in bounded large-aspect-ratio turbulent Rayleigh-Bénard convection. Karhunen-Loè

  17. 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. trap

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

    NARCIS (Netherlands)

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

    2012-01-01

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

  19. 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 o

  20. 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.

  1. The effect of aspect ratio on the performance of an energy harvesting hydrofoil

    Science.gov (United States)

    Kim, Daegyoum; Strom, Benjamin; Su, Yunxing; Mandre, Shreyas; Breuer, Kenneth

    2014-11-01

    We investigated the effect of aspect ratio on energy harvesting performance and flow structure of an oscillating hydrofoil. Power measurement and particle image velocimetry were performed in a water flume with a hydrofoil undergoing periodic heaving and pitching motions. Aspect ratio was varied from 2.5 to 4.5, and end plates were also mounted at the hydrofoil tips in order to suppress three-dimensional effects near the tips. For each aspect ratio, energy conversion efficiency was maximum at the same kinematics determined by reduced frequency and pitch amplitude. The efficiency is increased with the aspect ratio, and it is noticeably enhanced with the installation of the end plates. Leading-edge vortex formation and wake dynamics were compared at several spanwise sections among different aspect ratios. Their correlation with the efficiency was also examined. This research was supported by DOE ARPA-E.

  2. 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...

  3. Flow visualization study in high aspect ratio cooling channels for rocket engines

    Science.gov (United States)

    Meyer, Michael L.; Giuliani, James E.

    1993-11-01

    The structural integrity of high pressure liquid propellant rocket engine thrust chambers is typically maintained through regenerative cooling. The coolant flows through passages formed either by constructing the chamber liner from tubes or by milling channels in a solid liner. Recently, Carlile and Quentmeyer showed life extending advantages (by lowering hot gas wall temperatures) of milling channels with larger height to width aspect ratios (AR is greater than 4) than the traditional, approximately square cross section, passages. Further, the total coolant pressure drop in the thrust chamber could also be reduced, resulting in lower turbomachinery power requirements. High aspect ratio cooling channels could offer many benefits to designers developing new high performance engines, such as the European Vulcain engine (which uses an aspect ratio up to 9). With platelet manufacturing technology, channel aspect ratios up to 15 could be formed offering potentially greater benefits. Some issues still exist with the high aspect ratio coolant channels. In a coolant passage of circular or square cross section, strong secondary vortices develop as the fluid passes through the curved throat region. These vortices mix the fluid and bring lower temperature coolant to the hot wall. Typically, the circulation enhances the heat transfer at the hot gas wall by about 40 percent over a straight channel. The effect that increasing channel aspect ratio has on the curvature heat transfer enhancement has not been sufficiently studied. If the increase in aspect ratio degrades the secondary flow, the fluid mixing will be reduced. Analysis has shown that reduced coolant mixing will result in significantly higher wall temperatures, due to thermal stratification in the coolant, thus decreasing the benefits of the high aspect ratio geometry. A better understanding of the fundamental flow phenomena in high aspect ratio channels with curvature is needed to fully evaluate the benefits of this

  4. X-ray diagnostic line ratios for helium-like S XV applicable to tokamak plasmas

    International Nuclear Information System (INIS)

    Recent calculations of electron impact excitation rates for He-like S XV are used to derive the theoretical electron temperature and density sensitive emission line ratios G(=(f+i)/r) and R(=f/i), where f, i and r are the forbidden 1s21S-1s2s 3S, intercombination 1s21S-1s2p 3P1,2 and resonance 1s21S-1s2p 1P transitions, respectively. Our results for R are found to be significantly different from previous calculations, due primarily to the adoption of improved electron impact excitation rates in the present paper. We estimate that the present diagnostics should be accurate to approximately ±15%. (orig.)

  5. The Experiments of the small Spherical Tokamak Gutta

    International Nuclear Information System (INIS)

    GUTTA is a small spherical tokamak (R = 16cm, a = 8cm, Ip = 150kA) operating at the St. Petersburg State University since 2004 in the scope of the IAEA CRP ''Joint Research using Small Tokamaks''. Main scientific activities on GUTTA include development of new and improvement of existing mathematical models of plasma control, relevant for application on large tokamaks and ITER and verification of them on GUTTA; studies on the ECRH/EBW assisted breakdown and non-solenoid plasma formation in low aspect ratio tokamak; development of diagnostics; training and education of students.In this paper design properties of Gutta will be presented. Regimes of operation of the tokamak and plasma shape parameters are described and first results of the plasma formation and start-up studied will be discussed

  6. Numerical studies of the reversed-field pinch at high aspect ratio

    Science.gov (United States)

    Sätherblom, H.-E.; Drake, J. R.

    1998-10-01

    The reversed field pinch (RFP) configuration at an aspect ratio of 8.8 is studied numerically by means of the three-dimensional magnetohydrodynamic code DEBS [D. D. Schnack et al., J. Comput. Phys. 70, 330 (1987)]. This aspect ratio is equal to that of the Extrap T1 experiment [S. Mazur et al., Nucl. Fusion 34, 427 (1994)]. A numerical study of a RFP with this level of aspect ratio requires extensive computer achievements and has hitherto not been performed. The results are compared with previous studies [Y. L. Ho et al., Phys. Plasmas 2, 3407 (1995)] of lower aspect ratio RFP configurations. In particular, an evaluation of the extrapolation to the aspect ratio of 8.8 made in this previous study shows that the extrapolation of the spectral spread, as well as most of the other findings, are confirmed. An important exception, however, is the magnetic diffusion coefficient, which is found to decrease with aspect ratio. Furthermore, an aspect ratio dependence of the magnetic energy and of the helicity of the RFP is found.

  7. High aspect ratio composite structures with 48.5% thermal neutron detection efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Q.; Voss, L. F.; Conway, A. M.; Nikolic, R. J. [Center for Micro and Nano Technology, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Dar, M. A.; Cheung, C. L. [Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)

    2013-02-11

    The pillar structured thermal neutron detector is based on the combination of high aspect ratio silicon p-i-n pillars surrounded by the neutron converter material {sup 10}B. By etching high aspect ratio pillar structures into silicon, the result is a device that efficiently absorbs the thermal neutron flux by accommodating a large volume fraction of {sup 10}B within the silicon pillar array. Here, we report a thermal neutron detection efficiency of 48.5% using a 50 {mu}m pillar array with an aspect ratio of 25:1.

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

    Science.gov (United States)

    Genç, Mustafa Serdar; Özkan, Gökhan; Hakan Açikel, Halil; Sadık Kiriş, Mehmet; Yildiz, Rahime

    2016-03-01

    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.

  9. A systems assessment of the five Starlite tokamak power plants

    Energy Technology Data Exchange (ETDEWEB)

    Bathke, C.G.

    1996-07-01

    The ARIES team has assessed the power-plant attractiveness of the following five tokamak physics regimes: (1) steady state, first stability regime; (2) pulsed, first stability regime; (3) steady state, second stability regime; (4) steady state, reversed shear; and (5) steady state, low aspect ratio. Cost-based systems analysis of these five tokamak physics regimes suggests that an electric power plant based upon a reversed-shear tokamak is significantly more economical than one based on any of the other four physics regimes. Details of this comparative systems analysis are described herein.

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

    Science.gov (United States)

    Li, Qingyin; Jin, Shangbin; Tan, Bien

    2016-08-01

    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.

  11. Aspect ratio dependent fluorescence quenching of eosin Y by gold nanorods.

    Science.gov (United States)

    Weng, Guojun; Li, Jianjun; Zhang, Li; Zhao, Junwu

    2014-06-01

    Gold nanorods of different aspect ratios had been synthesized using seed mediated growth method. The formed gold nanorods had been characterized by the absorption and transmission electron microscopy (TEM) measurements. The obtained gold nanorods were used to study the quenched effect on fluorescence of Eosin Y. Experimental results revealed that Eosin Y molecules adsorbed on the metallic surfaces, suffering strong quenching of their fluorescence and the quenching efficiency was different for different aspect ratio. Using dielectric coated gold nanorods model, the probable mechanism of aspect ratio dependent quenching efficiency was obtained by numerical calculation based on fluorescence resonance energy transfer and quasi-static theory. The calculation results showed that the non-monotonic changing of fluorescence quenching was attributed to competing effects of aspect ratio and the dielectric constant of coated shell on surface plasmon resonance.

  12. Resistive wall stabilization by toroidal rotation: effects of partial wall configurations and aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Ward, D.J. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)

    1996-09-01

    The results of this work demonstrate that with a pair of close-fitting conducting plates, which leave a large gap at the outboard midplane, a high-{beta} equilibrium at conventional aspect ratio can be stabilized at a rotation speed reduced by a factor of over 3.5 compared to a fully surrounding, continuous and complete wall at the same separation. Results were also presented which show that low-aspect-ratio equilibria can be stabilized at significantly lower rotation speeds than at conventional aspect ratio. These two effects can perhaps be combined to enhance even further the effect of resistive wall stabilization at low aspect ratio. (author) 3 figs., 1 tab., 7 refs.

  13. Tractor tire aspect ratio effects on soil bulk density and cone index

    Science.gov (United States)

    A 580/70R38 tractor drive tire with an aspect ratio of 0.756 and a 650/75R32 tire with an aspect ratio of 0.804 were operated at two dynamic loads and two inflation pressures on a sandy loam and a clay loam with loose soil above a hardpan. Soil bulk density and cone index were measured just above t...

  14. Dynamic Light Scattering of Short Au Rods with Low Aspect Ratios

    OpenAIRE

    Rodriguez-Fernández, J.; Perez-Juste, J.; L.M. Liz-Marzán; Lang, P. R.

    2007-01-01

    The translational and rotational diffusion of a series of gold nanorods with low aspect ratios was investigated by dynamic light scattering (DLS). It is shown that the translational and rotational diffusion coefficients can be determined because the particle shape causes an anisotropy of the polarizability. This gives rise to two clearly distinguishable relaxation modes in the time correlation function of the scattered light. The particle length and aspect ratio were determined independently ...

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

    International Nuclear Information System (INIS)

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

  16. Primary oscillatory instability in low-aspect-ratio rotating disk - cylinder system (rotor - stator cavity)

    OpenAIRE

    Gelfgat, A. Yu

    2014-01-01

    Three-dimensional instability of axisymmetric flow in a rotating disk - cylinder configuration is studied numerically for the case of low cylinders with the height/radius aspect ratio varying between 1 and 0.1. A complete stability diagram for the transition from steady axisymmetric to oscillatory three-dimensional flow regime is reported. A good agreement with experimental results is obtained. It is shown that critical azimuthal wavenumber grows with the decrease of the aspect ratio, reachin...

  17. Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser

    OpenAIRE

    Chervinskii, S.; Drevinskas, R.; D. V. Karpov; Beresna, M; Lipovskii, A. A.; Svirko, Yu. P.; Kazansky, P. G.

    2015-01-01

    We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as ...

  18. A Stationary Vortex Phenomenon above a Low-Aspect-Ratio Wing

    Institute of Scientific and Technical Information of China (English)

    TANG Jian; ZHU Ke-Qin; TAN Guang-Kun

    2004-01-01

    @@ A stationary vortex phenomenon above a nondelta low-aspect-ratio wing was obtained in three-dimensional unsteady numerical simulation. Flow visualization is conducted in water channel using hydrogen bubbles. The results verify that there is a vortex trapped above the low-aspect-ratio wing and the stationary vortex consisted of two semi-balls and anti-rotation vortices which are different from the leading edge vortices on the delta wing.

  19. 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.

  20. Variable aspect ratio method in the Xu–White model for shear-wave velocity estimation

    International Nuclear Information System (INIS)

    Shear-wave velocity logs are useful for various seismic interpretation applications, including bright spot analyses, amplitude-versus-offset analyses and multicomponent seismic interpretations. This paper presents a method for predicting the shear-wave velocity of argillaceous sandstone from conventional log data and experimental data, based on Gassmann's equations and the Xu–White model. This variable aspect ratio method takes into account all the influences of the matrix nature, shale content, porosity size and pore geometry, and the properties of pore fluid of argillaceous sandstone, replacing the fixed aspect ratio assumption in the conventional Xu–White model. To achieve this, we first use the Xu–White model to derive the bulk and shear modulus of dry rock in a sand–clay mixture. Secondly, we use Gassmann's equations to calculate the fluid-saturated elastic properties, including compressional and shear-wave velocities. Finally, we use the variable aspect ratio method to estimate the shear-wave velocity. The numerical results indicate that the variable aspect ratio method provides an important improvement in the application of the Xu–White model for sand–clay mixtures and allows for a variable aspect ratio log to be introduced into the Xu–White model instead of the constant aspect ratio assumption. This method shows a significant improvement in predicting velocities over the conventional Xu–White model. (paper)

  1. Vortex formation and drag on low aspect ratio, normal flat plates

    Science.gov (United States)

    Ringuette, Matthew James

    Experiments were done to investigate the role of vortex formation in the drag force generation of low aspect ratio, normal flat plates starting from rest. This very simplified case is a first, fundamental step toward understanding the more complicated flow of hovering flight, which relies primarily on drag for propulsion. The relative importance of the plate's free end, or tip, with varying aspect ratio was also studied. Identifying the relationship among aspect ratio, vortex formation, and drag force can provide insight into the wing aspect ratios and kinematics found nature, with the eventual goal of designing man-made flapping wing micro air vehicles. The experiments were carried out using flat plate models in a towing tank at a moderate Reynolds number of 3000. Two aspect ratios, 6 and 2, were considered, the latter in order to have a highly tip-dominated case. A force balance measured the time-varying drag, and multiple, perpendicular sections of the flow velocity were measured quantitatively using digital particle image velocimetry. Vorticity fields were calculated from the velocity data, and features in the drag force for different aspect ratios were related to the vortex dynamics. Finally, since the flow is highly three-dimensional, dye flow visualization was done to characterize its structure and to augment the two-dimensional digital particle image velocimetry data.

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

    Science.gov (United States)

    Genç, Mustafa Serdar; Hakan Açikel, Halil; Demir, Hacımurat; Özden, Mustafa; Çağdaş, Mücahit; Isabekov, Iliasbek

    2016-03-01

    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.

  3. 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.

  4. 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.

  5. The Spherical Tokamak MEDUSA for Mexico

    Science.gov (United States)

    Ribeiro, C.; Salvador, M.; Gonzalez, J.; Munoz, O.; Tapia, A.; Arredondo, V.; Chavez, R.; Nieto, A.; Gonzalez, J.; Garza, A.; Estrada, I.; Jasso, E.; Acosta, C.; Briones, C.; Cavazos, G.; Martinez, J.; Morones, J.; Almaguer, J.; Fonck, R.

    2011-10-01

    The former spherical tokamak MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R Mexican Fusion Network. Strong liaison within national and international plasma physics communities is expected. New activities on plasma & engineering modeling are expected to be developed in parallel by using the existing facilities such as a multi-platform computer (Silicon Graphics Altix XE250, 128G RAM, 3.7TB HD, 2.7GHz, quad-core processor), ancillary graph system (NVIDIA Quadro FE 2000/1GB GDDR-5 PCI X16 128, 3.2GHz), and COMSOL Multiphysics-Solid Works programs.

  6. Stability of Tokamaks with respect to slip motions

    International Nuclear Information System (INIS)

    Using the energy principle in Tokamaks we investigate a class of perturbations which, if unstable, cannot be stabilized by the toroidal main field. On the assumptions of usual Tokamak ordering and in the limit of infinite aspect ratio, these perturbations are shown to be minimizing among all axisymmetric perturbations. In the case of finite aspect ratio, a detailed stability analysis is carried out using a constant pressure surface current model with elliptic, triangular or rectangular plasma cross-section. Definite stabilization by toroidal effects and by beta poloidal is demonstrated. (orig.)

  7. 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.

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

    Science.gov (United States)

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

    2015-04-01

    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 of attack without stalling. Instead, they generate an attached vortex along the leading edge of the wing that elevates lift. Previous studies have demonstrated that this vortex and high lift can be reproduced by revolving the animal wing at the same angle of attack. How do flapping and revolving animal wings delay stall and reduce power? It has been hypothesized that stall delay derives from having a short radial distance between the shoulder joint and wing tip, measured in chord lengths. This non-dimensional measure of wing length represents the relative magnitude of inertial forces versus rotational accelerations operating in the boundary layer of revolving and flapping wings. Here we show for a suite of aspect ratios, which represent both animal and aircraft wings, that the attachment of the leading edge vortex on a revolving wing is determined by wing aspect ratio, defined with respect to the centre of revolution. At high angle of attack, the vortex remains attached when the local radius is shorter than four chord lengths and separates outboard on higher aspect ratio wings. This radial stall limit explains why revolving high aspect ratio wings (of helicopters) require less power compared with low aspect ratio wings (of hummingbirds) at low angle of attack and vice versa at high angle of attack. PMID:25788539

  9. Thermo-mechanical properties of high aspect ratio silica nanofiber filled epoxy composites

    Science.gov (United States)

    Ren, Liyun

    The optimization of thermo-mechanical properties of polymer composites at low filler loadings is of great interest in both engineering and scientific fields. There have been several studies on high aspect ratio fillers as novel reinforcement phase for polymeric materials. However, facile synthesis method of high aspect ratio nanofillers is limited. In this study, a scalable synthesis method of high aspect ratio silica nanofibers is going to be presented. I will also demonstrate that the inclusion of high aspect ratio silica nanofibers in epoxy results in a significant improvement of epoxy thermo-mechanical properties at low filler loadings. With silica nanofiber concentration of 2.8% by volume, the Young's modulus, ultimate tensile strength and fracture toughness of epoxy increased ~23, ~28 and ~50%, respectively, compared to unfilled epoxy. At silica nanofiber volume concentration of 8.77%, the thermal expansion coefficient decreased by ˜40% and the thermal conductivity was improved by ˜95% at room temperature. In the current study, the influence of nano-sized silica filler aspect ratio on mechanical and thermal behavior of epoxy nanocomposites were studied by comparing silica nanofibers to spherical silica nanoparticles (with aspect ratio of one) at various filler loadings. The significant reinforcement of composite stiffness is attributed to the variation of the local stress state in epoxy due to the high aspect ratio of the silica nanofiber and the introduction of a tremendous amount of interfacial area between the nanofillers and the epoxy matrix. The fracture mechanisms of silica nanofiber filled epoxy were also investigated. The existence of high aspect ratio silica nanofiber promotes fracture energy dissipation by crack deflection, crack pinning as well as debonding with fiber pull-out leading to enhanced fracture toughness. High aspect ratio fillers also provide significant reduction of photon scattering due to formation of a continuous fiber network

  10. Size Dependent Cellular Uptake of Rod-like Bionanoparticles with Different Aspect Ratios

    Science.gov (United States)

    Liu, Xiangxiang; Wu, Fengchi; Tian, Ye; Wu, Man; Zhou, Quan; Jiang, Shidong; Niu, Zhongwei

    2016-01-01

    Understanding the cellular internalization mechanism of nanoparticles is essential to study their biological fate. Especially, due to the anisotropic properties, rod-like nanoparticles have attracted growing interest for the enhanced internalization efficiency with respect to spherical nanoparticles. Here, to elucidate the effect of aspect ratio of rod-like nanoparticles on cellular uptake, tobacco mosaic virus (TMV), a typical rod-like bionanoparticle, is developed as a model. Nanorods with different aspect ratios can be obtained by ultrasound treatment and sucrose density gradient centrifugation. By incubating with epithelial and endothelial cells, we found that the rod-like bionanoparticles with various aspect ratios had different internalization pathways in different cell lines: microtubules transport in HeLa and clathrin-mediated uptake in HUVEC for TMV4 and TMV8; caveolae-mediated pathway and microtubules transport in HeLa and HUVEC for TMV17. Differently from most nanoparticles, for all the three TMV nano-rods with different aspect ratios, macropinocytosis takes no effect on the internalization in both cell types. This work provides a fundamental understanding of the influence of aspect ratio on cellular uptake decoupled from charge and material composition. PMID:27080246

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

    Science.gov (United States)

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

    2016-08-30

    Understanding the influence of aspect ratio on water immersion into silica nanoholes is of significant importance to the etching process of semiconductor fabrication and other water immersion-related physical and biological processes. In this work, the processes of water immersion into silica nanoholes with different height/width aspect ratios (ϕ = 0.87, 1.92, 2.97, 4.01, 5.06) and different numbers of water molecules (N = 9986, 19972, 29958, 39944) were studied by molecular dynamics simulations. A comprehensive analysis has been conducted about the detailed process of water immersion and the influence of aspect ratios on water immersion rates. Five distinguishable stages were identified for the immersion process with all studied models. The results reveal that water can easily immerse into the silica nanoholes with larger ϕ and smaller N. The calculation also suggests that aspect ratios have a greater effect on water immersion rates for larger N numbers. The mechanism of the water immersion process is discussed in this work. We also propose a mathematical model to correlate the complete water immersion process for different aspect ratios. PMID:27506253

  12. Precise modulation of gold nanorods aspect ratio based on localized surface plasmon resonance

    Science.gov (United States)

    Wen, Xiaoyan; Shuai, Huang; Min, Li

    2016-10-01

    Gold nanorods (GNRs) aspect ratio is significant to GNRs-based biomedical sensors. In this paper precise modulation of GNRs aspect ratio was realized by H2O2 oxidation based on localized surface plasmon resonance (LSPR) of GNRs. The oxidation process was studied in detail. A linear relationship was revealed between H2O2 oxidation time and the longitudinal LSPR wavelength of GNR, the latter depending on GNRs aspect ratio. Using the relationship GNRs aspect ratios could be modulated by H2O2 oxidation time. Oxidation time deduced aspect ratio was verified by transmission electron microscope (TEM) characterization and the average error is 2.92%. Influences of temperature and pH value on the modulation process were investigated. Increase in temperature (from 30 °C to 60 °C) or solution acidity (pH value from 2.6 to 1.2) facilitated the oxidation process. The proposed method is characterized by its simplicity and efficiency, and would find extensive application prospects in GNRs-based biomedical sensing fields.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-12-01

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

  15. Mosquitofish (Gambusia affinis) responds differentially to a robotic fish of varying swimming depth and aspect ratio.

    Science.gov (United States)

    Polverino, Giovanni; Porfiri, Maurizio

    2013-08-01

    In this study, we explore the feasibility of using bioinspired robotics to influence the behaviour of mosquitofish (Gambusia affinis), a social freshwater fish species that is extensively studied for the ecological issues associated with its diffusion in non-native environments. Specifically, in a dichotomous choice test, we investigate the behavioural response of small shoals of mosquitofish to a robotic fish inspired by mosquitofish in its colouration, shape, aspect ratio, and locomotion. Our results indicate that the swimming depth and the aspect ratio of the robotic fish are both determinants of mosquitofish preference. In particular, we find that mosquitofish are never attracted by a robotic fish whose colouration and shape are inspired by live subjects and that the degree of repulsion varies as a function of the swimming depth and the aspect ratio. PMID:23684918

  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. Primary oscillatory instability in low-aspect-ratio rotating disk - cylinder system (rotor - stator cavity)

    CERN Document Server

    Gelfgat, A Yu

    2014-01-01

    Three-dimensional instability of axisymmetric flow in a rotating disk - cylinder configuration is studied numerically for the case of low cylinders with the height/radius aspect ratio varying between 1 and 0.1. A complete stability diagram for the transition from steady axisymmetric to oscillatory three-dimensional flow regime is reported. A good agreement with experimental results is obtained. It is shown that critical azimuthal wavenumber grows with the decrease of the aspect ratio, reaching the value of 19 at the aspect ratio 0.1. It is argued that the observed instability cannot be described as resulting from a B\\"odewadt flow or from a boundary layer only. Other reasons that can destabilize the flow are discussed.

  18. Development of high-aspect-ratio microchannel heat exchanger based on multi-tool milling process

    Institute of Scientific and Technical Information of China (English)

    潘敏强; 李金恒; 汤勇

    2008-01-01

    A high-aspect-ratio microchannel heat exchanger based on multi-tool milling process was developed. Several slotting cutters were stacked together for simultaneously machining several high-aspect-ratio microchannels with manifold structures. On the basis of multi-tool milling process, the structural design of the manifold side height, microchannel length, width, number, and interval were analyzed. The heat transfer performances of high-aspect-ratio microchannel heat exchangers with two different manifolds were investigated by experiments, and the influencing factors were analyzed. The results indicate that the magnitude of heat transfer area per unit volume dominates the heat transfer performances of plate-type micro heat exchanger, while the velocity distribution between microchannels has little effects on the heat transfer performances.

  19. 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. PMID:27350975

  20. 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.

  1. Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles

    Science.gov (United States)

    Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

    2016-05-01

    In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%.In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01896c

  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. Effect of aspect ratio on the energy extraction efficiency of three-dimensional flapping foils

    Science.gov (United States)

    Deng, Jian; Caulfield, C. P.; Shao, Xueming

    2014-04-01

    Numerical simulations are used to investigate the effect of variation of the aspect ratio and the structure of pitching motions on the energy extraction efficiency and wake topology of flapping foils. The central aim is to predict the energy extraction performance and efficiency of a flapping-foil-based energy harvesting system (EHS) in realistic working conditions with finite aspect ratios. A sinusoidal heaving motion is imposed upon the foil, as well as both a sinusoidal pitching motion and a variety of trapezoidal-like periodic pitching motions. The simulations employ a finite-volume method with body-fitted moving grids, allowing the capture of flow structure near the foil surface. A detailed analysis of the hydrodynamic performance shows two peaks per periodic cycle in the lift force time histories or equivalently, the energy extraction time histories. The first primary peak corresponds to an effective angle of attack around 15.4°, indicating good attachment of the flow on the foil surface without significant flow separation. The secondary peak corresponds to a leading edge vortex (LEV) travelling on the foil surface. The shape of the LEV is altered markedly as the aspect ratio varies, and consequently the secondary peak in the lift force time history is strongly affected by the effects of three-dimensionality for foils with smaller aspect ratios. By examining the relationship between energy extraction efficiency and aspect ratio, a critical aspect ratio of AR = 4 is identified for sinusoidal pitching motions, below which the three-dimensional low-aspect-ratio characteristics dominate the flow evolution. Therefore, the compromise between higher energy extraction efficiency and lower costs of manufacturing and installation suggests that an aspect ratio around AR = 4 is the most appropriate choice for a real EHS. Furthermore, although trapezoidal-like pitching motions are known to improve the efficiency in flows restricted to two dimensions, particularly for non

  4. Bound of aspect ratio of base-isolated buildings considering nonlinear tensile behavior of rubber bearing

    OpenAIRE

    Hino, J.; Yoshitomi, S.; Tsuji, M.; Takewaki, Izuru

    2008-01-01

    The purpose of this paper is to propose a simple analysis method of axial deformation of base-isolation rubber bearings in a building subjected to earthquake loading and present its applicability to the analysis of the bound of the aspect ratio of base-isolated buildings. The base shear coefficient is introduced as a key parameter for the bound analysis. The bound of the aspect ratio of base-isolated buildings is analyzed based on the relationship of the following four quantities; (i) ultimat...

  5. Effect of aspect ratio and surface defects on the photocatalytic activity of ZnO nanorods

    Science.gov (United States)

    Zhang, Xinyu; Qin, Jiaqian; Xue, Yanan; Yu, Pengfei; Zhang, Bing; Wang, Limin; Liu, Riping

    2014-04-01

    ZnO, aside from TiO2, has been considered as a promising material for purification and disinfection of water and air, and remediation of hazardous waste, owing to its high activity, environment-friendly feature and lower cost. However, their poor visible light utilization greatly limited their practical applications. Herein, we demonstrate the fabrication of different aspect ratios of the ZnO nanorods with surface defects by mechanical-assisted thermal decomposition method. The experiments revealed that ZnO nanorods with higher aspect ratio and surface defects show significantly higher photocatalytic performances.

  6. Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser

    Science.gov (United States)

    Chervinskii, S.; Drevinskas, R.; Karpov, D. V.; Beresna, M.; Lipovskii, A. A.; Svirko, Yu. P.; Kazansky, P. G.

    2015-09-01

    We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6 J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites.

  7. Disorder induced Coulomb gaps in graphene constrictions with different aspect ratios

    OpenAIRE

    Terres, B.; Dauber, J.; Volk, C.; Trellenkamp, S.; Wichmann, U.; Stampfer, C.

    2010-01-01

    We present electron transport measurements on lithographically defined and etched graphene nanoconstrictions with different aspect ratios including different lengths (l) and widths (w). A roughly length-independent disorder induced effective energy gap can be observed around the charge neutrality point. This energy gap scales inversely with the width even in regimes where the length of the constriction is smaller than its width (l

  8. 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-...

  9. The Flow Field Downstream of a Dynamic Low Aspect Ratio Circular Cylinder: A Parametric Study

    Science.gov (United States)

    Gildersleeve, Samantha; Dan, Clingman; Amitay, Michael

    2015-11-01

    Flow past a static, low aspect ratio cylinder (pin) has shown the formation of vortical structures, namely the horseshoe and arch-type vortex. These vortical structures may have substantial effects in controlling flow separation over airfoils. In the present experiments, the flow field associated with a low aspect ratio cylinder as it interacts with a laminar boundary layer under static and dynamic conditions was investigated through a parametric study over a flat plate. As a result of the pin being actuated in the wall-normal direction, the structures formed in the wake of the pin were seen to be a strong function of actuation amplitude, driving frequency, and aspect ratio of the cylinder. The study was conducted at a Reynolds number of 1875, based on the local boundary layer thickness, with a free stream velocity of 10 m/s. SPIV data were collected for two aspect ratios of 0.75 and 1.125, actuation amplitudes of 6.7% and 16.7%, and driving frequencies of 175 Hz and 350 Hz. Results indicate that the presence and interactions between vortical structures are altered in comparison to the static case and suggest increased large-scale mixing when the pin is driven at the shedding frequency (350 Hz). Supported by the Boeing Company.

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

    DEFF Research Database (Denmark)

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

    2009-01-01

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

  11. 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 compo

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

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  13. 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

    ). A nickel tool for the replication of structures with lateral dimensions of 110 nm and heights of approximately 370 nm is fabricated via electroplating of a nanostructured sample resulting in an aspect ratio of approximately 3.5. The structures are subsequently hot embossed into PMMA and COC substrates....

  14. 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. Pre

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

    Science.gov (United States)

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

    1979-01-01

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

  16. Selective aspect ratio of CNTs based on annealing temperature by TCVD method

    Science.gov (United States)

    Yousefi, Amin Termeh; Mahmood, Mohamad Rusop; Ikeda, Shoichiro

    2016-07-01

    Various aspect ratios of CNTs reported based on alteration of annealing temperature using thermal-chemical vapor deposition (TCVD) method. Also the growth dependent and independent parameters of the carbon nanotube (CNTs) array were studied as a function of synthesis method. The FESEM images indicate that the nanotubes are approximately perpendicular to the surface of the silicon substrate and form carbon nanotubes in different aspect ratios according to the applied annealing temperature. Furthermore, due to the optimized results it can be observed that, the mechanism of the CNTs growth is still present in the annealing step as well as deposition process and the most CNTs with crystalline aspect, produced in the annealing temperature, which was optimized at 700 - 900 ˚C. This result demonstrates that the growth rate, mass production, diameter, density, and crystallinity of CNT can be controlled by the annealing temperature.

  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. Localized magnetization reversal processes in cobalt nanorods with different aspect ratios

    Institute of Scientific and Technical Information of China (English)

    Marc Pousthomis[1; Evangelia Anagnostopoulou[1; Ioannis Panagiotopoulos[2,3; Rym Boubekri[1; Weiqing Fang[2; Frederic Ott[2; Kahina Ait Atmane[4; Jean-Yves Piquemal[4; Lise-Marie Lacroix[1; Guillaume Viau[1

    2015-01-01

    We present results of the synthesis of cobalt nanorods using the polyol process and the mechanism of magnetization reversal. We show that the nucleation step is significantly dependent on the nature of the ruthenium chloride used as the nucleating agent. This allows varying the diameter and aspect ratio of the cobalt nanorods independently. Co nanorods with aspect ratio, mean diameter, and mean length in the ranges ARm =3-16, Din= 7-25 nm, and Lm=30-300 nm, respectively, were produced using this method. X-ray diffraction and electron microscopy showed that a strong discrepancy between the structural coherence and morphological aspect ratio can exist because of stacking faults. The coercivity of assemblies of different nanorods was systematically measured, and the highest values were obtained for the smallest diameter and the largest structural coherence length. Micromagnetic simulations were performed to account for the dependence of the coercive field on the diameter. An important observation is that simple coherent magnetization rotation models do not apply to these magnetic nano-objects. Even for very small diameters (Dm = 5-10 nm) well below the theoretical coherent diameter Dcoh(CO)= 24 nm, we observed inhomogeneous reversal modes dominated by nucleation at the rod edges or at structural defects such as stacking faults. We conclude that, in order to produce high-coercivity materials based on nanowires, moderate aspect ratios of 5-10 are sufficient for providing a structural coherence similar to the morphological aspect ratio. Thus, the first priority should be to avoid the formation of stacking faults within the Co nanowires.

  19. 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.)

  20. 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

    . 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......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...... the processing steps. Finally, the feasibility of the method is assessed by estimating parameters of a micromechanical model for flax fibre composites and comparing the results with those from tensile tests. © 2015 Elsevier Ltd. All rights reserved....

  1. Rapid fabrication of high aspect ratio silicon nanopillars for chemical analysis

    Science.gov (United States)

    Sainiemi, Lauri; Keskinen, Helmi; Aromaa, Mikko; Luosujärvi, Laura; Grigoras, Kestas; Kotiaho, Tapio; Mäkelä, Jyrki M.; Franssila, Sami

    2007-12-01

    In this study, a method for fabrication of high aspect ratio silicon nanopillars is presented. The method combines liquid flame spray production of silica nanoparticle agglomerates with cryogenic deep reactive ion etching. First, the nanoparticle agglomerates, having a diameter of about 100 nm, are deposited on a silicon wafer. Then, during the subsequent cryogenic deep reactive ion etching process, the particle agglomerates act as etch masks and silicon nanopillars are formed. Aspect ratios of up to 20:1 are demonstrated. The masking process is rapid, cheap and has the potential to be scaled up for large areas. Three other structured silicon surfaces were fabricated for comparison. All four surfaces were utilized as desorption/ionization on silicon (DIOS) sample plates. The mass spectrometry results indicate that nanopillar surfaces masked with the liquid flame spray technique are well suited as DIOS sample plates.

  2. Dense high aspect ratio hydrogen silsesquioxane nanostructures by 100 keV electron beam lithography

    Energy Technology Data Exchange (ETDEWEB)

    Vila-Comamala, Joan; Gorelick, Sergey; Guzenko, Vitaliy A; David, Christian [Paul Scherrer Institut, Villigen CH-5232 (Switzerland); Faerm, Elina; Ritala, Mikko, E-mail: joan.vila@psi.ch [Department of Chemistry, University of Helsinki, Helsinki FI-00014 (Finland)

    2010-07-16

    We investigated the fabrication of dense, high aspect ratio hydrogen silsesquioxane (HSQ) nanostructures by 100 keV electron beam lithography. The samples were developed using a high contrast developer and supercritically dried in carbon dioxide. Dense gratings with line widths down to 25 nm were patterned in 500 nm-thick resist layers and semi-dense gratings with line widths down to 10 nm (40 nm pitch) were patterned in 250 nm-thick resist layers. The dense HSQ nanostructures were used as molds for gold electrodeposition, and the semi-dense HSQ gratings were iridium-coated by atomic layer deposition. We used these methods to produce Fresnel zone plates with extreme aspect ratio for scanning transmission x-ray microscopy that showed excellent performance at 1.0 keV photon energy.

  3. Dense high aspect ratio hydrogen silsesquioxane nanostructures by 100 keV electron beam lithography

    Science.gov (United States)

    Vila-Comamala, Joan; Gorelick, Sergey; Guzenko, Vitaliy A.; Färm, Elina; Ritala, Mikko; David, Christian

    2010-07-01

    We investigated the fabrication of dense, high aspect ratio hydrogen silsesquioxane (HSQ) nanostructures by 100 keV electron beam lithography. The samples were developed using a high contrast developer and supercritically dried in carbon dioxide. Dense gratings with line widths down to 25 nm were patterned in 500 nm-thick resist layers and semi-dense gratings with line widths down to 10 nm (40 nm pitch) were patterned in 250 nm-thick resist layers. The dense HSQ nanostructures were used as molds for gold electrodeposition, and the semi-dense HSQ gratings were iridium-coated by atomic layer deposition. We used these methods to produce Fresnel zone plates with extreme aspect ratio for scanning transmission x-ray microscopy that showed excellent performance at 1.0 keV photon energy.

  4. 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.

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

    Science.gov (United States)

    Li, Ting

    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.

  6. High aspect ratio tungsten grating on ultrathin Si membranes for extreme UV lithography

    Science.gov (United States)

    Peng, Xinsheng; Ying, Yulong

    2016-09-01

    Extreme ultraviolet lithography is one of the modern lithography tools for high-volume manufacturing with 22 nm resolution and beyond. But critical challenges exist to the design and fabrication of large-scale and highly efficient diffraction transmission gratings, significantly reducing the feature sizes down to 22 nm and beyond. To achieve such a grating, the surface flatness, the line edge roughness, the transmission efficiency and aspect ratio should be improved significantly. Delachat et al (2015 Nanotechnology 26 108262) develop a full process to fabricate a tungsten diffraction grating on an ultrathin silicon membrane with higher aspect ratio up to 8.75 that met all the aforementioned requirements for extreme ultraviolet lithography. This process is fully compatible with standard industrial extreme ultraviolet lithography.

  7. 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...

  8. Multiscale Domain Decomposition Methods for Elliptic Problems with High Aspect Ratios

    Institute of Scientific and Technical Information of China (English)

    Jфrg Aarnes; Thomas Y. Hou

    2002-01-01

    In this paper we study some nonoverlapping domain decomposition methods for solving a class of elliptic problems arising from composite materials and flows in porous media which contain many spatial scales. Our preconditioner differs from traditional domain decomposition preconditioners by using a coarse solver which is adaptive to small scale heterogeneous features. While the convergence rate of traditional domain decomposition algorithms using coarse solvers based on linear or polynomial interpolations may deteriorate in the presence of rapid small scale oscillations or high aspect ratios, our preconditioner is applicable to multiplescale problems without restrictive assumptions and seems to have a convergence rate nearly independent of the aspect ratio within the substructures. A rigorous convergence analysis based on the Schwarz framework is carried out, and we demonstrate the efficiency and robustness of the proposed preconditioner through numerical experiments which include problems with multiple-scale coefficients, as well problems with continuous scales.

  9. Mesh Regeneration Method for Jig-Shape Optimization Design of the High-Aspect-Ratio Wing

    OpenAIRE

    Huo, S. H.; Wang, F S; Z. Yuan; Yue, Z. F.

    2013-01-01

    A mesh regeneration method was put forward, and its application on the jig-shape optimization design of a high-aspect-ratio wing was carried out in the present study. In the mesh regeneration method, some control lines were selected based on configuration characters of the wing structure firstly. And then a new aerodynamic model was built according to the new control lines distribution which always keeps the same outline. Finally, mesh generation and quality optimization were carried out. Thr...

  10. Size Dependent Cellular Uptake of Rod-like Bionanoparticles with Different Aspect Ratios

    OpenAIRE

    Xiangxiang Liu; Fengchi Wu; Ye Tian; Man Wu; Quan Zhou; Shidong Jiang; Zhongwei Niu

    2016-01-01

    Understanding the cellular internalization mechanism of nanoparticles is essential to study their biological fate. Especially, due to the anisotropic properties, rod-like nanoparticles have attracted growing interest for the enhanced internalization efficiency with respect to spherical nanoparticles. Here, to elucidate the effect of aspect ratio of rod-like nanoparticles on cellular uptake, tobacco mosaic virus (TMV), a typical rod-like bionanoparticle, is developed as a model. Nanorods with ...

  11. 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

  12. An in vitro testing strategy towards mimicking the inhalation of high aspect ratio nanoparticles

    OpenAIRE

    Endes, Carola; Schmid, Otmar; Kinnear, Calum; Mueller, Silvana; Camarero-Espinosa, Sandra; Vanhecke, Dimitri; Foster, E Johan; Petri-Fink, Alke; Rothen-Rutishauser, Barbara; Weder, Christoph; Martin J. D. Clift

    2014-01-01

    Background The challenge remains to reliably mimic human exposure to high aspect ratio nanoparticles (HARN) via inhalation. Sophisticated, multi-cellular in vitro models are a particular advantageous solution to this issue, especially when considering the need to provide realistic and efficient alternatives to invasive animal experimentation for HARN hazard assessment. By incorporating a systematic test-bed of material characterisation techniques, a specific air-liquid cell exposure system wi...

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

    Science.gov (United States)

    Hassall, Christopher

    2015-01-01

    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. PMID:26336648

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

    OpenAIRE

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

    2009-01-01

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

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

    OpenAIRE

    Chang Chuan Xie; Jia Zhen Leng; Chao Yang

    2008-01-01

    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 ...

  16. Magnetic reversal modes in multisegmented nanowire arrays with long aspect ratio

    OpenAIRE

    Rando, E. A.; Allende, S.

    2015-01-01

    A detailed numerical analysis of the magnetization reversal processes in multisegmented nanowire arrays was developed. The nanowires have a long aspect ratio and are formed by magnetic and non-magnetic sections alternately arranged in such a way that the array resembles magnetic layers separated by non-magnetic layers. Attention has been focused on the influence of magnetostatic interaction in the magnetic pattern formation of these magnetic nanostructures. Results from a magnetic correlation...

  17. Digital controlled pulsed electric system of the ETE tokamak. First report

    International Nuclear Information System (INIS)

    This reports presents a summary on the thermonuclear fusion and application for energy supply purposes. The tokamak device operation and the magnetic field production systems are described. The ETE tokamak is a small aspect ratio device designed for plasma physics and thermonuclear fusion studies, which presently is under construction at the Laboratorio Associado de Plasma (LAP), Instituto Nacional de Pesquisas Espaciais (INPE) - S.J. dos Campos - S. Paulo. (author)

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

    OpenAIRE

    Philip McKeen; Fung, Alan S.

    2014-01-01

    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 ...

  19. 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.

  20. Economic trends of tokamak power plants independent of physics scaling models

    International Nuclear Information System (INIS)

    This study examines the effects of plasma radius, field on axis, plasma impurity level, and aspect ratio on power level and unit capital cost, $/kW/sub e/, of tokamak power plants sized independent of plasma physics scaling models. It is noted that tokamaks sized in this manner are thermally unstable based on trapped particle scaling relationships. It is observed that there is an economic advantage for larger power level tokamaks achieved by physics independent sizing; however, the incentive for increased power levels is less than that for fission reactors. It is further observed that the economic advantage of these larger power level tokamaks is decreased when plasma thermal stability measures are incorporated, such as by increasing the plasma impurity concentration. This trend of economy with size obtained by physics independent sizing is opposite to that observed when the tokamak designs are constrained to obey the trapped particle and empirical scaling relationships

  1. 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.

  2. Wet Etched High Aspect Ratio Microstructures on Quartz for MEMS Applications

    Science.gov (United States)

    Liang, Jinxing; Kohsaka, Fusao; Matsuo, Takahiro; Ueda, Toshitsugu

    Z cut α-quartz wafers were etched in saturated ammonium bifluoride solution at 87 degrees C. The side wall profiles were observed using the scanning electron microscopy (SEM) and plotted dependent on the polar direction. This research focused on investigating high aspect ratio trench and through-hole, which were dependent on the polar direction to the crystal axis. Aspect ratio in dependence on polar direction was also plotted and microchannels with aspect ratio > 3 could be achieved at the polar angle between 30° to 60°. The possibility of application for microcapillary was discussed, and the trench at 45° was considered best. Double-sided etching technique was used for manufacturing through-hole structures. Through-hole at 0° was demonstrated effective for fabrication of capacitive MEMS tilt sensor. Through-holes at 15° and 105° were proposed for fabrication of 90°-arranged two axis capactive tilt sensor, taking advantage of the twofold symmetry property around X axis and threefold symmetry property around Z axis.

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    Denisov, D. V.; Villanueva, Y. Y.; Lőrincz, K. A.; May, S.; Wijngaarden, R. J.

    2012-05-01

    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 determined the growth (β) and roughness (α) exponents, the avalanche fractal dimension (D), the avalanche size distribution exponent (τ), the critical angle (γ), and its fluctuation. At superficial inspection, three types of grains seem to have power-law-distributed avalanches with a well-defined τ. However, only rice is truly SOC if we take three criteria into account: a power-law-shaped avalanche size distribution, finite size scaling, and a universal scaling relation relating characteristic exponents. We study SOC as a spatiotemporal fractal; in particular, we study the spatial structure of criticality from local observation of the slope angle. From the fluctuation of the slope angle we conclude that greater fluctuation (and thus bigger avalanches) happen in piles consisting of grains with larger aspect ratio.

  5. Effects of fiber aspect ratio evaluated by elastic analysis in discontinuous composites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hong Gun [Jeonju University, Juenju (Korea, Republic of)

    2008-03-15

    An elastic stress analysis to investigate the effects of fiber aspect ratio in short fiber reinforced discontinuous composite materials has been done for different fiber volume fractions. In order to examine the elastic internal behavior, an evaluation of the load bearing capacity of discontinuous reinforcements is needed in advance. Accordingly, analytical derivation of composite mechanics has been carried out to predict fiber stresses and fiber/matrix interfacial shear stresses in discontinuous composites. The model is based on the theoretical development of conventional shear lag theory developed by Cox. However, the major shortcoming of the Cox model is due to the calculation without normal stress transfer from the end of fibers. In order to overcome the shortcoming, both of the normal and shear stress transfer mechanisms between the fiber and the matrix are accounted for with the stress concentration effects as well as material and geometrical properties. Results of predicted stresses concerning the various fiber aspect ratios are described by using the present model that is the closed form solution and compared with the Cox model and Taya model. It is found that the effect of fiber aspect ratio is significant to composite strengthening through load transfer from the matrix to the fiber, whereas the effect of fiber volume fraction is not so sensitive, relatively. It is also found that the present model has the capability to correctly predict the values of fiber stresses and fiber/matrix interfacial shear stresses

  6. Project and analysis of the toroidal magnetic field production circuits and the plasma formation of the ETE (Spherical Tokamak Experiment) tokamak; Projeto e analise dos circuitos de producao de campo magnetico toroidal e de formacao do plasma do Tokamak ETE (Experimento Tokamak Esferico)

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Luis Filipe F.P.W.; Bosco, Edson del

    1994-12-31

    This report presents the project and analysis of the circuit for production of the toroidal magnetic field in the Tokamak ETE (Spherical Tokamak Experiment). The ETE is a Tokamak with a small-aspect-ratio parameter to be used for studying the plasma physics for the research on thermonuclear fusion. This machine is being constructed at the Laboratorio Associado de Plasma (LAP) of the Instituto Nacional de Pesquisas Espaciais (INPE) in Sao Jose dos Campos, SP, Brazil. (author). 20 refs., 39 figs., 4 tabs.

  7. Experimental study of the topological aspect of the ergodic divertor in Tore-supra tokamak; Etude experimentale des aspects topologiques du divertor ergodique de Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Costanzo, L

    2001-10-01

    The control of power deposition onto plasma facing components in tokamaks is a determining factor for future thermonuclear fusion reactors. Plasma surface interaction can be performed using limiters or divertors. The ergodic divertor installed on Tore Supra is an atypical example of a magnetic divertor. It consists in applying a magnetic perturbation which establishes a particular topology of the plasma in contact with the wall (edge plasma). We carried out dedicated experiments in order to study parallel heat flux which strike the divertor neutralizers. This quantitative and qualitative analysis of heat flux as a function of experimental conditions allows to determine the profiles of power deposition along the neutralizers. The influence of plasma electron density, additional heating, impurities and injected gas was established. An experimental study of the sheath heat transmission factor {gamma} was carried out by correlating measurements made with Langmuir probes and infrared imaging. This study gave rise to a major conclusion: for ohmic discharges with deuterium injection and most of the time with helium, it was experimentally confirmed that {gamma}=7 in agreement with classical sheath theory. However, an increase of this factor with additional power has been shown. Detached plasma, which is an attractive regime in order to reduce the power deposition, requires an optimized control. A new measurement of the detachment onset has been developed. It is based on the variation of heat flux onto the plates derived from infrared measurements. A detachment cartography with the determination of a new 2D 'IR' Degree of Detachment was carried out allowing to locate the zone where the detachment starts. We can apply this concept both to other tokamaks such as JET and ITER. A comparison between the axisymmetric divertor and the ergodic divertor is also presented concerning the power deposition in the two configurations. Low heat flux with the ergodic divertor is a

  8. 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.

  9. 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.

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

    International Nuclear Information System (INIS)

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

  11. 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.

  12. Deposition of a-C:H films on inner surface of high-aspect-ratio microchannel

    Science.gov (United States)

    Hirata, Yuki; Choi, Junho

    2016-08-01

    Hydrogenated amorphous carbon (a-C:H) films were prepared on inner surface of 100-μm-width microchannel by using a bipolar-type plasma based ion implantation and deposition. The microchannel was fabricated using a silicon plate, and two kinds of microchannels were prepared, namely, with a bottom layer (open at one end) and without a bottom layer (open at both ends). The distribution of thickness and hardness of films was evaluated by SEM and nanoindentation measurements, respectively, and the microstructures of films were evaluated by Raman spectroscopy. Furthermore, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision and Direct Simulation Monte Carlo to investigate the coating mechanism for the microchannel. It was found that the film thickness decreased as the depth of the coating position increased in the microchannels where it is open at one end. The uniformity of the film thickness improved by increasing the negative pulse voltage because ions can arrive at the deeper part of the microchannel. In addition, the hardness increased as the depth of the coating position increased. This is because the radicals do not arrive at the deeper part of the microchannel, and the incident proportion of ions relative to that of radicals increases, resulting in a high hardness due to the amorphization of the film. The opening area of the microchannel where the aspect ratio is very small, radicals dominate the incident flux, whereas ions prevail over radicals above an aspect ratio of about 7.5. On the other hand, in the microchannels that are open at both ends, there were great improvements in uniformity of the film thickness, hardness, and the film structure. The a-C:H films were successfully deposited on the entire inner surface of a microchannel with an aspect ratio of 20.

  13. Morphology and aspect ratio of bismuth nanoparticles embedded in a zinc matrix

    Energy Technology Data Exchange (ETDEWEB)

    Song, Tae Eun; Wilde, Gerhard; Peterlechner, Martin [Institute für Materialphysik, Wilhelm-Klemm-Straße 10, D-48149 Münster (Germany)

    2014-12-15

    Nanoscale Bi particles embedded in a Zn matrix were obtained by casting and melt-spinning, resulting in quenching rate-dependent sizes and shapes. With decreasing Bi particle size, an increasing aspect ratio was observed. Due to high resolution transmission electron microscopy performed for different orientations of the nanoparticles and the matrix, the three-dimensional shape and the respective crystallographic orientations of the Bi nanoparticles as well as the orientation relationship with the matrix have been evaluated. It is suggested that the size-dependence of the nanoparticle morphologies has a strong impact on their thermal stabilities thus affecting the size dependence of the melting temperature.

  14. Morphology and aspect ratio of bismuth nanoparticles embedded in a zinc matrix

    Science.gov (United States)

    Song, Tae Eun; Wilde, Gerhard; Peterlechner, Martin

    2014-12-01

    Nanoscale Bi particles embedded in a Zn matrix were obtained by casting and melt-spinning, resulting in quenching rate-dependent sizes and shapes. With decreasing Bi particle size, an increasing aspect ratio was observed. Due to high resolution transmission electron microscopy performed for different orientations of the nanoparticles and the matrix, the three-dimensional shape and the respective crystallographic orientations of the Bi nanoparticles as well as the orientation relationship with the matrix have been evaluated. It is suggested that the size-dependence of the nanoparticle morphologies has a strong impact on their thermal stabilities thus affecting the size dependence of the melting temperature.

  15. Differential inertial focusing of particles in curved low-aspect-ratio microchannels

    Energy Technology Data Exchange (ETDEWEB)

    Russom, Aman; Gupta, Amit K; Nagrath, Sunitha; Di Carlo, Dino; Edd, Jon F; Toner, Mehmet [BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Shriners Hospital for Children, and Harvard Medical School, Boston, MA 02114 (United States)], E-mail: aman@kth.se

    2009-07-15

    Microfluidic-based manipulation of particles is of great interest due to the insight it provides into the physics of hydrodynamic forces. Here, we study a particle-size-dependent phenomenon based on differential inertial focusing that utilizes the flow characteristics of curved, low aspect ratio (channel width >> height), microfluidic channels. We report the emergence of two focusing points along the height of the channel (z-plane), where different sized particles are focused and ordered in evenly spaced trains at correspondingly different lateral positions within the channel cross-section. We applied the system for continuous ordering and separation of suspension particles.

  16. 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...... additional results on the polarization and the dispersion of the surface waves trapped by high aspect ratio electrode arrays. A finite element model, including periodic boundary conditions along the propagation direction and a perfectly matched layer (PML) to absorb waves away from the surface...

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

    DEFF Research Database (Denmark)

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

    2013-01-01

    in terms of defining the shape and size of the tip. Due to beam-induced deformation, it has so far not been possible to define HAR structures using lateral FIB milling. In this work we obtain aspect ratios of up to 45, with tip diameters down to 9 nm, by a deformation-suppressing writing strategy. Several...... FIB milling strategies for obtaining sharper tips are discussed. Finally, assembly of the HAR tips on a custom-designed probe as well as the first AFM scanning is shown....

  18. Calibration artefact for the microscale with high aspect ratio: The fiber gauge

    DEFF Research Database (Denmark)

    Marinello, Francesco; Savio, Enrico; Carmignato, Simone;

    2008-01-01

    The paper presents a new concept of micro-artefact, the fiber gauge, consisting of a set of optical fibers sticking out from a flat surface. The fibers are arranged as a regular array of different height cylinders, with aspect ratios up to 20:1. The artefact is produced taking advantage of optical...... fibers manufacturing technology, featuring relatively high geometrical accuracy, combined with very good mechanical properties. The fiber gauge can be applied to calibration of most contact or non-contact instruments for characterization of surface topographies and 3Dmicro-geometries, such as micro- or...

  19. Modelling and manufacture of regular microstructures with high aspect ratio in acrylic plastic

    International Nuclear Information System (INIS)

    The possibility of manufacture of microstructures with high aspect ratio in industrial acrylic plastic by the method of deep X-ray lithography is investigated. A characteristic dependence of the rate of dissolution of the polymer on the dose of the radiation absorbed is obtained. Processing regimes for the formation of deep structures were selected. A model for computation of the profile of development of structures in view of large exhibition depth was suggested. 25x25 μm through channels were obtained in sheet acrylic plastic 1000 μm thick

  20. 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

    Differentiation of human embryonic stem cells is widely studied as a potential unlimited source for cell replacement therapy to treat degenerative diseases such as diabetes. The directed differentiation of human embryonic stem cells relies mainly on soluble factors. Although, some studies have...... of the ultrahigh aspect ratio nanopillars (stiffness can be reduced by 25.000X). It is found that tall nanopillars, yielding softer surfaces, significantly enhance the induction of defi nitive endoderm cells from pluripotent human embryonic stem cells, resulting in more consistent differentiation of a pure...

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

    DEFF Research Database (Denmark)

    Amato, Letizia; Heiskanen, Arto; Hansen, Rasmus;

    2015-01-01

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

  2. Time-Scales for Non-Inductive Current Buildup in Low-Aspect-Ratio Toroidal Geometry

    International Nuclear Information System (INIS)

    The fundamental differences between inductive and non-inductive current buildup are clarified and the associated time-scales and other implications are discussed. A simulation is presented whereby the plasma current in a low-aspect-ratio torus is increased primarily by the self-generated bootstrap current with only 10% coming from external current drive. The maximum obtainable plasma current by this process is shown to scale with the toroidal field strength. The basic physics setting the time-scales can be obtained from a 1D analysis. Comparisons are made between the timescales found here and those reported in the experimental literature

  3. 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.

  4. 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.

  5. 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.

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

    International Nuclear Information System (INIS)

    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.

  7. Large area UV casting using diverse polyacrylates of microchannels separated by high aspect ratio microwalls.

    Science.gov (United States)

    Zhou, W X; Chan-Park, Mary B

    2005-05-01

    Large area molding of long and deep microchannels separated by high aspect ratio microwalls is important for high sensitivity and high throughput microfluidic devices. Ultraviolet (UV) casting is a feasible, economical and convenient method of replication of such microstructures in plastics. It is shown that a wide variety of polyacrylates with diverse properties such as those made from epoxy (EP), polyurethane (UR), polyester (ES), poly (ethylene glycol) (EG) and poly(propylene glycol) (PG) can be used for the high aspect ratio (7-9) UV casting of such linear microstructures over a 100 mm diameter, enlarging the range of applications of the replicated microstructures. Some challenges arise. With the EG formulation, wavy microstructures were observed; this can be overcome by stress relaxation. With non-polar PG formulation, poor adhesion between the polyester substrate and resin can lead to delamination of the casting from the substrate during demolding; this can be overcome by pre-coating a partially cured same resin on the polyester substrate. An optimum UV irradiation time was important for cure at the deepest end of the microstructure without excessive crosslinking leading to much increased demolding forces. The viscosity and wetting capability of the formulations were found to affect replication fidelity. PMID:15856087

  8. Braiding of submarine channels controlled by aspect ratio similar to rivers

    Science.gov (United States)

    Foreman, Brady Z.; Lai, Steven Y. J.; Komatsu, Yuhei; Paola, Chris

    2015-09-01

    The great majority of submarine channels formed by turbidity and density currents are meandering in planform; they consist of a single, sinuous channel that transports a turbid, dense flow of sediment from submarine canyons to ocean floor environments. Braided turbidite systems consisting of multiple, interconnected channel threads are conspicuously rare. Furthermore, such systems may not represent the spontaneous planform instability of true braiding, but instead result from erosive processes or bathymetric variability. In marked contrast to submarine environments, both meandering and braided planforms are common in fluvial systems. Here we present experiments of subaqueous channel formation conducted at two laboratory facilities. We find that density currents readily produce a braided planform for flow aspect ratios of depth to width that are similar to those that produce river braiding. Moreover, we find that stability model theory for river planform morphology successfully describes submarine channels in both experiments and the field. On the basis of these observations, we propose that the rarity of braided submarine channels is explained by the generally greater flow depths in submarine systems, which necessitate commensurately greater widths to achieve the required aspect ratio, along with feedbacks among flow thickness, suspended sediment concentration and channel relief that induce greater levee deposition rates and limit channel widening.

  9. Bifurcation induced by the aspect ratio in a turbulent Von-K\\'arm\\'an swirling flow

    CERN Document Server

    Liot, Olivier

    2016-01-01

    We evaluate the effect of two experimental parameters on the slow dynamics of a Von-K\\'arm\\'an swirling flow driven by two propellers in a closed cylinder. The first parameter is the inertia mo- mentum of the propellers, and the second parameter is the aspect ratio, i.e. the distance between the propellers $H$ divided by the diameter $D$. We use a cell with a fixed diameter $D$ but where the distance between the propellers can be turned continuously and where the inertia from the pro- pellers can also be changed using different gears. No change on the dynamics is observed when the momentum of inertia is modified. Some dramatic changes of the shear layer position are observed modifying the aspect ratio $\\Gamma=H/D$. A bifurcation of the shear layer position appears. Whereas for low $\\Gamma$ the shear layer position has a smooth evolution when turning the asymmetry between the rotation frequency of the propellers, for high $\\Gamma$ the transition becomes abrupt and a symmetry breaking appears. Secondly we obser...

  10. 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.

  11. Effect of tilting on turbulent convection: Cylindrical samples with aspect ratio $\\Gamma=0.50$

    CERN Document Server

    Weiss, Stephan

    2015-01-01

    We report measurements of properties of turbulent thermal convection of a fluid with a Prandtl number $\\Pra=4.38$ in a cylindrical cell with an aspect ratio $\\Gamma=0.50$. The rotational symmetry was broken by a small tilt of the sample axis relative to gravity. Measurements of the heat transport (as expressed by the Nusselt number \\Nu), as well as of large-scale-circulation (LSC) properties by means of temperature measurements along the sidewall, are presented. In contradistinction to similar experiments using containers of aspect ratio $\\Gamma=1.00$ \\cite[]{ABN06} and $\\Gamma=0.50$ \\cite[]{CRCC04,SXX05,RGKS10}, we see a very small increase of the heat transport for tilt angles up to about 0.1 rad. Based on measurements of properties of the LSC we explain this increase by a stabilization of the single-roll state (SRS) of the LSC and a de-stabilization of the double-roll state (DRS) (it is known from previous work that the SRS has a slightly larger heat transport than the DRS). Further, we present quantitativ...

  12. Effect of free surface on near-wake flow of elliptic cylinders with different aspect ratios

    Science.gov (United States)

    Lee, Sang Joon; Daichin, -

    2003-04-01

    The flow fields behind elliptic cylinders with different aspect ratios adjacent to a free surface were investigated experimentally in a circulating water channel. The elliptic cylinders tested in this study have same cross section area. For each elliptic cylinder, the experiments were carried out under different conditions by varying the submergence depth of the cylinder beneath the free surface. The flow fields were measured using a single-frame double-exposure PIV system. For each experimental condition, 350 instantaneous velocity fields were captured and ensemble-averaged to obtain the mean flow field information and spatial distribution of turbulent statistics. The near-wakes can be basically classified into three typical patterns, which are formation of Coanda effect, generation of substantial jet-like flow, and attachment of jet flow to the free surface. The general flow structures behind the elliptic cylinder are similar to previous results for a circular submerged near to a free surface. However, the wake width and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder are smaller than those for the circular cylinder. These trends are enhance with increasing of the cylinder aspect ratios.

  13. Thermal behavior in the cracking reaction zone of scramjet cooling channels at different channel aspect ratios

    Science.gov (United States)

    Zhang, Silong; Feng, Yu; Jiang, Yuguang; Qin, Jiang; Bao, Wen; Han, Jiecai; Haidn, Oskar J.

    2016-10-01

    To study the thermal behavior in the cracking reaction zone of regeneratively cooled scramjet cooling channels at different aspect ratios, 3-D model of fuel flow in terms of the fuel's real properties and cracking reaction is built and validated through experiments. The whole cooling channel is divided into non-cracking and cracking reaction zones. Only the cracking reaction zone is studied in this article. The simulation results indicate that the fuel conversion presents a similar distribution with temperature because the fuel conversion in scramjet cooling channels is co-decided by the temperature and velocity but the temperature plays the dominate role. For the cases given in this paper, increasing the channel aspect ratio will increase the pressure drop and it is not beneficial for reducing the wall temperature because of the much severer thermal stratification, larger conversion non-uniformity, the corresponding M-shape velocity profile which will cause local heat transfer deterioration and the decreased chemical heat absorption. And the decreased chemical heat absorption caused by stronger temperature and conversion non-uniformities is bad for the utilization of chemical heat sink, chemical recuperation process and the ignition performance.

  14. Fabrication of ultra-high aspect ratio silicon nanopores by electrochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Torsten; Zhang, Miao; Linnros, Jan, E-mail: linnros@kth.se [Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Isafjordsgatan 22, SE-164 40 Kista (Sweden); Yu, Shun [Department of Fibre and Polymer Technology, Polymeric Materials and Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden)

    2014-09-22

    We report on the formation of ultra-high aspect ratio nanopores in silicon bulk material using photo-assisted electrochemical etching. Here, n-type silicon is used as anode in contact with hydrofluoric acid. Based on the local dissolution of surface atoms in pre-defined etching pits, pore growth and pore diameter are, respectively, driven and controlled by the supply of minority charge carriers generated by backside illumination. Thus, arrays with sub-100 nm wide pores were fabricated. Similar to macropore etching, it was found that the pore diameter is proportional to the etching current, i.e., smaller etching currents result in smaller pore diameters. To find the limits under which nanopores with controllable diameter still can be obtained, etching was performed at very low current densities (several μA cm{sup −2}). By local etching, straight nanopores with aspect ratios above 1000 (∼19 μm deep and ∼15 nm pore tip diameter) were achieved. However, inherent to the formation of such narrow pores is a radius of curvature of a few nanometers at the pore tip, which favors electrical breakdown resulting in rough pore wall morphologies. Lowering the applied bias is adequate to reduce spiking pores but in most cases also causes etch stop. Our findings on bulk silicon provide a realistic chance towards sub-10 nm pore arrays on silicon membranes, which are of great interest for molecular filtering and possibly DNA sequencing.

  15. Fabrication of high aspect ratio microtube arrays for 2D photonic crystals

    International Nuclear Information System (INIS)

    This paper describes the fabrication of 2D photonic crystals made of high aspect ratio Si microtube arrays. The tube fabrication is based on the creation of macropore arrays in n-doped Si substrates via photoassisted electrochemical etching. These macropores are successively filled using thermal oxidation and chemical vapor depostion. The substrate material is partially removed by a KOH immersion, and the filled macropores are exposed, forming arrays of microtubes with very high aspect ratios of up to 1:60. Point and line defects are introduced into some of the tube arrays by selectively omitting macropores during the fabrication. The mechanical properties of the tubes were investigated by measuring their stiffness and elastic modulus using an atomic force microscope based setup. Additionally, the resonant modes of the microtubes were simulated with FEM methods. Optical simulations reveal that these tube arrays form 2D photonic crystals, which can contain bandgaps for TM polarized light. It is also shown that the optical properties of the photonic crystals depend strongly on the tube filling factor. Adjusting the filling factor of the tubes allows tuning of the photonic properties of the tube arrays. (papers)

  16. Numerical simulation of the tip vortex off a low-aspect-ratio wing at transonic speed

    Science.gov (United States)

    Mansour, N. N.

    1984-01-01

    The viscous transonic flow around a low aspect ratio wing was computed by an implicit, three dimensional, thin-layer Navier-Stokes solver. The grid around the geometry of interest is obtained numerically as a solution to a Dirichlet problem for the cube. A low aspect ratio wing with large sweep, twist, taper, and camber is the chosen geometry. The topology chosen to wrap the mesh around the wing with good tip resolution is a C-O type mesh. The flow around the wing was computed for a free stream Mach number of 0.82 at an angle of attack of 5 deg. At this Mach number, an oblique shock forms on the upper surface of the wing, and a tip vortex and three dimensional flow separation off the wind surface are observed. Particle path lines indicate that the three dimensional flow separation on the wing surface is part of the roots of the tip vortex formation. The lifting of the tip vortex before the wing trailing edge is observed by following the trajectory of particles release around the wing tip.

  17. Microscopic silicon-based lateral high-aspect-ratio structures for thin film conformality analysis

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Arpiainen, Sanna; Puurunen, Riikka L., E-mail: riikka.puurunen@vtt.fi [VTT Technical Research Centre of Finland, Tietotie 3, 02044 Espoo (Finland)

    2015-01-15

    Film conformality is one of the major drivers for the interest in atomic layer deposition (ALD) processes. This work presents new silicon-based microscopic lateral high-aspect-ratio (LHAR) test structures for the analysis of the conformality of thin films deposited by ALD and by other chemical vapor deposition means. The microscopic LHAR structures consist of a lateral cavity inside silicon with a roof supported by pillars. The cavity length (e.g., 20–5000 μm) and cavity height (e.g., 200–1000 nm) can be varied, giving aspect ratios of, e.g., 20:1 to 25 000:1. Film conformality can be analyzed with the microscopic LHAR by several means, as demonstrated for the ALD Al{sub 2}O{sub 3} and TiO{sub 2} processes from Me{sub 3}Al/H{sub 2}O and TiCl{sub 4}/H{sub 2}O. The microscopic LHAR test structures introduced in this work expose a new parameter space for thin film conformality investigations expected to prove useful in the development, tuning and modeling of ALD and other chemical vapor deposition processes.

  18. Planarization of High Aspect Ratio P-I-N Diode Pillar Arrays for Blanket Electrical Contacts

    Energy Technology Data Exchange (ETDEWEB)

    Voss, L F; Shao, Q; Reinhardt, C E; Graff, R T; Conway, A M; Nikolic, R J; Deo, N; Cheung, C L

    2009-03-05

    Two planarization techniques for high aspect ratio three dimensional pillar structured P-I-N diodes have been developed in order to enable a continuous coating of metal on the top of the structures. The first technique allows for coating of structures with topography through the use of a planarizing photoresist followed by RIE etch back to expose the tops of the pillar structure. The second technique also utilizes photoresist, but instead allows for planarization of a structure in which the pillars are filled and coated with a conformal coating by matching the etch rate of the photoresist to the underlying layers. These techniques enable deposition using either sputtering or electron beam evaporation of metal films to allow for electrical contact to the tops of the underlying pillar structure. These processes have potential applications for many devices comprised of 3-D high aspect ratio structures. Two separate processes have been developed in order to ensure a uniform surface for deposition of an electrode on the {sup 10}Boron filled P-I-N pillar structured diodes. Each uses S1518 photoresist in order to achieve a relatively uniform surface despite the non-uniformity of the underlying detector. Both processes allow for metallization of the final structure and provide good electrical continuity over a 3D pillar structure.

  19. 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.

    2010-08-01

    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.

  20. Synthesis and characterization of layered double hydroxides with a high aspect ratio

    International Nuclear Information System (INIS)

    A new route for synthesis of Mg/Al layered double hydroxide (Mg6Al2(OH)16(CO3).4H2O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1-6 μm and the thickness at ca. 35-60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO3- and CO32- keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio

  1. High aspect ratio PS-b-PMMA block copolymer masks for lithographic applications.

    Science.gov (United States)

    Ferrarese Lupi, F; Giammaria, T J; Volpe, F G; Lotto, F; Seguini, G; Pivac, B; Laus, M; Perego, M

    2014-12-10

    The control of the self-assembly (SA) process and nanostructure orientation in diblock copolymer (DBC) thick films is a crucial technological issue. Perpendicular orientation of the nanostructures in symmetric and asymmetric poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer films obtained by means of simple thermal treatments was demonstrated to occur in well-defined thickness windows featuring modest maximum values, thus resulting in low aspect ratio (h/d < 2) of the final lithographic mask. In this manuscript, the thickness window corresponding to the perpendicular orientation of the cylindrical structures in asymmetric DBC is investigated at high temperatures (190 °C ≤ T ≤ 310 °C) using a rapid thermal processing machine. A systematic study of the annealing conditions (temperature and time) of asymmetric PS-b-PMMA (Mn = 67.1, polydispersity index = 1.09) films, with thicknesses ranging from 10 to 400 nm, allowed ordered patterns, with a maximum value of orientational correlation length of 350 nm, to be obtained for film thicknesses up to 200 nm. The complete propagation of the cylindrical structures through the whole film thickness in a high aspect ratio PS template (h/d ≈ 7) is probed by lift-off process. Si nanopillars are obtained having the same lateral ordering and characteristic dimensions of the DBC lithographic mask as further confirmed by grazing-incidence small-angle X-ray scattering experiments. PMID:25387131

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

    Science.gov (United States)

    Leber, M.; Shandhi, M. M. H.; Hogan, A.; Solzbacher, F.; Bhandari, R.; Negi, S.

    2016-03-01

    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 methods such as laser ablation, focused ion beam, sputter etching, reactive ion etching (RIE) and deep reactive ion etching (DRIE). The surface modification processes were optimized for the high aspect ratio silicon structures of the UEA. The increase in real surface area while maintaining the geometrical surface area was verified using scanning electron

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

    International Nuclear Information System (INIS)

    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

  4. Formation and sustainment of a very low aspect ratio tokamak using coaxial helicity injection (the Helicity Injected Torus [HIT] experiment)

    International Nuclear Information System (INIS)

    In the paper we will detail the progress of the HIT experiment construction, including the following components: preliminary data and interpretation; diagnostic systems; vacuum vessel and pumping system; helicity source and power supplies; toroidal field coil and power supply; data acquisition system; collaboration with general atomics, with a brief summary given on each

  5. Formation and sustainment of a very low aspect ratio tokamak using coaxial helicity injection (the Helicity Injected Torus (HIT) experiment)

    Energy Technology Data Exchange (ETDEWEB)

    Jarboe, T.R.; Nelson, B.A.

    1992-01-01

    In the paper we will detail the progress of the HIT experiment construction, including the following components: preliminary data and interpretation; diagnostic systems; vacuum vessel and pumping system; helicity source and power supplies; toroidal field coil and power supply; data acquisition system; collaboration with general atomics, with a brief summary given on each.

  6. The effect of wing stroke and aspect ratio on the force generation a compliant membrane flapping wing

    Science.gov (United States)

    Schunk, Cosima; Swartz, Sharon M.; Breuer, Kenneth S.

    2015-11-01

    Aspect ratio is one parameter used in efforts to predict a bat species' flight performance based on wing shape. Bats with high aspect ratio wings are expected to have superior lift-to-drag ratios and therefore to fly faster or be able to sustain longer flights. In contrast, bats with lower aspect ratio wings are usually thought to exhibit higher maneuverability. These assumptions are often based on fixed-wing aerodynamic theory, and do not take the wide variation in flapping kinematics observed in bats into account. To examine the influence of different stroke patterns, we measure lift and drag of highly compliant membrane wings with different bat-relevant aspect ratios. A two degree of freedom shoulder joint allows for independent control of flapping amplitude and wing sweep. We test five models with the same variations of stroke patterns, flapping frequencies, and wind speeds.

  7. Research using small tokamaks

    International Nuclear Information System (INIS)

    This document consists of a collection of papers presented at the IAEA Technical Committee Meeting on Research Using Small Tokamaks. It contains 22 papers on a wide variety of research aspects, including diagnostics, design, transport, equilibrium, stability, and confinement. Some of these papers are devoted to other concepts (stellarators, compact tori). Refs, figs and tabs

  8. Research using small tokamaks

    International Nuclear Information System (INIS)

    discharges, production and self-organization of a turbulent plasma column in a spheromak (''SK-CG-1''), and (iv) a planned large-aspect ratio, high-beta tokamak (HBT-EP) experiment. Refs, figs and tabs

  9. 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

  10. Engineering Design Study of Quasi-Axisymmetric Stellarator with Low Aspect Ratio

    International Nuclear Information System (INIS)

    The engineering design of the quasi-axisymmetric stellarator CHS-qa is described, having a toroidal period number of 2, major radius of 1.5 m, and plasma aspect ratio of 3.2. Although the entire structure of the machine is highly nonaxisymmetric and deformative, the following major engineering concerns for the modular coils and the vacuum vessel have been resolved: (a) modular coil design (curvature and twist of conductors), (b) supporting structures for modular coils, (c) errors due to electromagnetic forces and misalignment in manufacturing processes (analysis shows that the magnetic surface is robust against such disturbances), (d) construction procedure for vacuum vessel and modular coils, and (e) ports for heating and diagnostics

  11. A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts

    Science.gov (United States)

    Alaferdov, A. V.; Savu, R.; Rackauskas, T. A.; Rackauskas, S.; Canesqui, M. A.; de Lara, D. S.; Setti, G. O.; Joanni, E.; de Trindade, G. M.; Lima, U. B.; de Souza, A. S.; Moshkalev, S. A.

    2016-09-01

    A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness ˜103) graphite nanobelt thin films deposited by a modified Langmuir-Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain-release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing.

  12. Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

    International Nuclear Information System (INIS)

    We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growth in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting

  13. 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.

  14. Effect of large aspect ratio of biomass particles on carbon burnout in a utility boiler

    Energy Technology Data Exchange (ETDEWEB)

    D. Gera; M.P. Mathur; M.C. Freeman; Allen Robinson [Fluent, Inc./NETL, Morgantown, WV (United States)

    2002-12-01

    This paper reports on the development and validation of comprehensive combustion sub models that include the effect of large aspect ratio of biomass (switchgrass) particles on carbon burnout and temperature distribution inside the particles. Temperature and carbon burnout data are compared from two different models that are formulated by assuming (i) the particles are cylindrical and conduct heat internally, and (ii) the particles are spherical without internal heat conduction, i.e., no temperature gradient exists inside the particle. It was inferred that the latter model significantly underpredicted the temperature of the particle and, consequently, the burnout. Additionally, some results from cofiring biomass (10% heat input) with pulverized coal (90% heat input) are compared with the pulverized coal (100% heat input) simulations and coal experiments in a tangentially fired 150 MW{sub e} utility boiler. 26 refs., 7 figs., 4 tabs.

  15. Millijoule femtosecond micro-Bessel beams for ultra-high aspect ratio machining.

    Science.gov (United States)

    Mitra, Sambit; Chanal, Margaux; Clady, Raphaël; Mouskeftaras, Alexandros; Grojo, David

    2015-08-20

    We report on a functional experimental design for Bessel beam generation capable of handling high-energy ultrashort pulses (up to 1.2 mJ per pulse of 50 fs duration). This allows us to deliver intensities exceeding the breakdown threshold for air or any dielectric along controlled micro-filaments with lengths exceeding 4 mm. It represents an unprecedented upscaling in comparison to recent femtosecond Bessel beam micromachining experiments. We produce void microchannels through glass substrates to demonstrate that aspect ratios exceeding 1200∶1 can be achieved by using single high-intensity pulses. This demonstration must lead to new methodologies for deep-drilling and high-speed cutting applications. PMID:26368773

  16. Millijoule femtosecond micro-Bessel beams for ultra-high aspect ratio machining.

    Science.gov (United States)

    Mitra, Sambit; Chanal, Margaux; Clady, Raphaël; Mouskeftaras, Alexandros; Grojo, David

    2015-08-20

    We report on a functional experimental design for Bessel beam generation capable of handling high-energy ultrashort pulses (up to 1.2 mJ per pulse of 50 fs duration). This allows us to deliver intensities exceeding the breakdown threshold for air or any dielectric along controlled micro-filaments with lengths exceeding 4 mm. It represents an unprecedented upscaling in comparison to recent femtosecond Bessel beam micromachining experiments. We produce void microchannels through glass substrates to demonstrate that aspect ratios exceeding 1200∶1 can be achieved by using single high-intensity pulses. This demonstration must lead to new methodologies for deep-drilling and high-speed cutting applications.

  17. Extreme hydrophobicity and omniphilicity of high-aspect-ratio silicon structures

    Science.gov (United States)

    Kwak, Moon Kyu; Park, Cheol Woo; Hwang, Kwang-Il; Park, Choon Man; Jeong, Hoon Eui; Choi, Jun Ho

    2015-03-01

    We present an application of high-aspect-ratio (high-AR) silicon structures (black silicon) with high water repellency and good wettability by oils and solvents. The fabrication of black silicon consists of a deep reactive-ion etching process for extremely-high-AR silicon structures and surface treatment with C4F8 gas. Such high-AR structures were found to be highly resistant against wetting by water, but they also have good wetting characteristics with respect to certain liquids such as ethanol, hexane and mineral oil. To determine the relationship between the AR of nanostructures and wetting selectivity, four different black silicon samples with different pattern heights were used. The static contact angles of various liquid were measured for the analysis of wetting properties of the four black silicon samples. To explore feasible applications, ethanol-water separation was performed as a miniaturized experimental simulation of environmental remediation.

  18. 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...... distance from the center. The simulations provided a thorough description of the complex flow pattern encountered close to the inlet section, which were validated for the laminar regime by dye injection. A total of up to four recirculation zones were identified in both numerical and experimental......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...

  19. A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts

    Science.gov (United States)

    Alaferdov, A. V.; Savu, R.; Rackauskas, T. A.; Rackauskas, S.; Canesqui, M. A.; de Lara, D. S.; Setti, G. O.; Joanni, E.; de Trindade, G. M.; Lima, U. B.; de Souza, A. S.; Moshkalev, S. A.

    2016-09-01

    A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness ∼103) graphite nanobelt thin films deposited by a modified Langmuir–Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain–release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing.

  20. Dihedral influence on lateral-directional dynamic stability on large aspect ratio tailless flying wing aircraft

    Institute of Scientific and Technical Information of China (English)

    Song Lei; Yang Hua; Zhang Yang; Zhang Haoyu; Huang Jun

    2014-01-01

    The influence of dihedral layout on lateral-directional dynamic stability of the tailless flying wing aircraft is discussed in this paper. A tailless flying wing aircraft with a large aspect ratio is selected as the object of study, and the dihedral angle along the spanwise sections is divided into three segments. The influence of dihedral layouts is studied. Based on the stability derivatives cal-culated by the vortex lattice method code, the linearized small-disturbance equations of the lateral modes are used to determine the mode dynamic characteristics. By comparing 7056 configurations with different dihedral angle layouts, two groups of stability optimized dihedral layout concepts are created. Flight quality close to Level 2 requirements is achieved in these optimized concepts without any electric stability augmentation system.

  1. 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.

  2. Controlled synthesis of uniform silver nanowires with high aspect ratios in aqueous solutions of gemini surfactant

    Institute of Scientific and Technical Information of China (English)

    XU Jian; LIU Weijun; LIU Honglai; HU Ying

    2007-01-01

    A simple solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 15-25 nm,and lengths usually in the range of tens of micrometers.In the presence of gemini surfactant 1,3-bis(cetyldimethylammonium)propane dibromide(16-3-16),the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios up to about 2,000.X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),energy-dispersive X-ray(EDX),X-ray powder diffraction (XRD),electron diffraction(ED),and UV-vis absorption spectroscopy,were used to characterize the as-prepared silver nanowires,indicating the formation of a highly pure phase,good crystallinity,as well as a uniform diameter.

  3. Dynamics of polymer nanoparticles through a single artificial nanopore with a high-aspect-ratio.

    Science.gov (United States)

    Cabello-Aguilar, Simon; Chaaya, Adib Abou; Bechelany, Mikhael; Pochat-Bohatier, Céline; Balanzat, Emmanuel; Janot, Jean-Marc; Miele, Philippe; Balme, Sébastien

    2014-11-14

    The development of nanometric Coulter counters for nanoparticle detection is an attractive and promising field of research. In this work, we have studied the influence of the nanopore surface state on charged polymer nanoparticle translocations. To make this, the translocation of carboxylate modified polystyrene microspheres (diameter 40, 70 and 100 nm) has been investigated through two kinds of high aspect ratio nanopores (negative and uncharged). The latter were tailored by a single track-etched and atomic layer deposition technique. It was shown that the mobility and the energy barrier are strongly dependent on nanopore surface charge. Typically if the latter exhibits negative surface charge, the microsphere mobility increases and the global energy barrier of entrance inside the nanopore decreases with its diameter, converse to the uncharged nanopore.

  4. 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.

  5. Fabrication of High Aspect Ratio Micro-Penning-Malmberg Gold Plated Silicon Trap Arrays

    CERN Document Server

    Narimannezhad, Alireza; Weber, Marc H; Lynn, Kelvin G

    2013-01-01

    Acquiring a portable high density charged particles trap might consist of an array of micro-Penning-Malmberg traps (microtraps) with substantially lower end barriers potential than conventional Penning-Malmberg traps [1]. We report on the progress of the fabrication of these microtraps designed for antimatter storage such as positrons. The fabrication of large length to radius aspect ratio (1000:1) microtrap arrays involved advanced techniques including photolithography, deep reactive ion etching (DRIE) of silicon wafers to achieve through-vias, gold sputtering of the wafers on the surfaces and inside the vias, and thermal compression bonding of the wafers. This paper describes the encountered issues during fabrication and addresses geometry errors and asymmetries. In order to minimize the patch effects on the lifetime of the trapped positrons, the bonded stacks were gold electroplated to achieve a uniform gold surface. We show by simulation and analytical calculation that how positrons confinement time depen...

  6. Measurement and simulation of jet mass caused by a high-aspect ratio hole perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Keiter, Paul A [Los Alamos National Laboratory; Cooley, James H [Los Alamos National Laboratory; Wilson, D C [Los Alamos National Laboratory; Kyrala, George A [Los Alamos National Laboratory; Blue, Brent E [LLNL; Edwards, J [LLNL; Elliott, James B [LLNL; Robey, H F [LLNL; Spears, B [Los Alamos National Laboratory

    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 overpredict 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.

  7. 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.

  8. 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.

  9. Design and Simulation of BTT Missile with High-Aspect-Ratio Wing Robust H∞ Autopilot

    Institute of Scientific and Technical Information of China (English)

    CUI Sheng-wang; LIU Li; MA Chun-yan

    2007-01-01

    For the strong coupling among the channels of bank-to-turn (BTT) missile with high-aspect-ratio wing,an autopilot is designed with a two loop control structure robust autopilot design methods.By the inner loop design,the question of pole-zero cancellation is solved,and the stabilization of structured uncertainty is achieved.Through the outer loop of H∞ controller design,the flying performance and robustness can be guaranteed.The nonlinear simulation results show that the autopilot designed has perfect time domain response,and can suppress bad influence of the inertial and kinematics couplings.It can make the missile fly stably in the large flying areas.The control is very effective.

  10. 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.

  11. Ni-Al2O3 and Ni-Al composite high-aspect-ratio microstructures

    Science.gov (United States)

    Wang, Tao; Sorrell, Melford; Kelly, Kevin W.; Ma, Evan

    1998-09-01

    High-aspect-ratio microstructures (HARMs) have a variety of potential applications in heat transfer, fluid mechanics, catalysts and other microelectromechanical systems (MEMS). The aim of this work is to demonstrate the feasibility to fabricate high performance particulate metal-matrix composite and intermetallic micromechanical structures using the LIGA process. Well-defined functionally graded Ni-Al2O3 and Ni-Al high-aspect-ratio microposts were electroformed into lithographically patterned PMMA holes from a nickel sulfamate bath containing submicron alumina and a diluted Watts bath containing microsized aluminum particles, respectively. SEM image analysis showed that the volume fraction of the alumina reached up to around 30% in the Ni-Al2O3 deposit. The Vickers microhardness of these composites is in the range of 418 through 545, which is higher than those of nickel microstructures from a similar particle-free bath and other Ni-based electrodeposits. In the work on Ni-Al electroplating, a newly developed diluted Watts bath was used to codeposit micron-sized aluminum particles. The intermetallic compound Ni3Al was formed by the reaction of nickel matrices and aluminum particles through subsequent annealing at 630 degrees Celsius. WDS and XRD analyses confirmed that the annealed coating is a two-phase (Ni-Ni3Al) composite. The maximum aluminum volume fraction reached 19% at a cathode current density of 12 mA cm-2, and the Vickers microhardness of the as-deposited coatings is in the range 392 - 515 depending on the amount of aluminum incorporated.

  12. High-Aspect Ratio Bio-Metallic Nanocomposites for Cellular Interactions

    Science.gov (United States)

    Deodhar, Sneha; Huckaby, Justin; Delahoussaye, Miles; DeCoster, Mark A.

    2014-08-01

    We synthesized high aspect ratio composites with biological and metal components. Scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed linear morphology and smooth surface texture. SEM, TEM and light microscopy showed that composites have scalable dimensions from nano- to micro-, with diameters as low as 60 nm, lengths exceeding 150 pm, and average aspect ratio of 100. The structures are stable, remaining intact for over one year in dried form and in liquid, and did not aggregate, in contrast to metal nanoparticles such as iron and copper. Many metal nanoparticles are toxic to cells, limiting their use for biological applications. The bio-metallic composites characterized here showed lower toxicity compared to their precursor metal nanoparticles in brain tumor cell cultures. Due to these more biocompatible properties, we tested the ability of the composites to interact with cells. Zeta potential analysis indicated that composites carry a net negative charge (-24.3 ± 2.2 mV), while the starting metal nanoparticles measured (43.3 ± 2.4 mV). We labeled the composites with poly-l-lysine fluorescein isothiocyanate (PLL-FITC), which shifted the potential to 3.5 ± 2.9 mV. It was observed by fluorescence microscopy that composites smaller than cells were internalized by some cells and larger composites remained outside. Cells became fluorescent over time due to leakage of PLL-FITC from the composites which lost fluorescence over time. Higher biocompatibility, low aggregation, and ability to control size distribution of the linear composites may make them ideal vehicles to deliver drugs or other materials to cells, and may be used as a scaffolding material for cells.

  13. Clothing polymer fibers with well-aligned and high-aspect ratio carbon nanotubes

    Science.gov (United States)

    Sun, Gengzhi; Zheng, Lianxi; An, Jia; Pan, Yongzheng; Zhou, Jinyuan; Zhan, Zhaoyao; Pang, John H. L.; Chua, Chee Kai; Leong, Kah Fai; Li, Lin

    2013-03-01

    It is believed that the crucial step towards preparation of electrical conductive polymer-carbon nanotube (CNT) composites is dispersing CNTs with a high length-to-diameter aspect ratio in a well-aligned manner. However, this process is extremely challenging when dealing with long and entangled CNTs. Here in this study, a new approach is demonstrated to fabricate conductive polymer-CNT composite fibers without involving any dispersion process. Well-aligned CNT films were firstly drawn from CNT arrays, and then directly coated on polycaprolactone fibers to form polymer-CNT composite fibers. The conductivity of these composite fibers can be as high as 285 S m-1 with only 2.5 wt% CNT loading, and reach 1549 S m-1 when CNT loading is 13.4 wt%. As-prepared composite fibers also exhibit 82% retention of conductivity at a strain of 7%, and have improved mechanical properties.It is believed that the crucial step towards preparation of electrical conductive polymer-carbon nanotube (CNT) composites is dispersing CNTs with a high length-to-diameter aspect ratio in a well-aligned manner. However, this process is extremely challenging when dealing with long and entangled CNTs. Here in this study, a new approach is demonstrated to fabricate conductive polymer-CNT composite fibers without involving any dispersion process. Well-aligned CNT films were firstly drawn from CNT arrays, and then directly coated on polycaprolactone fibers to form polymer-CNT composite fibers. The conductivity of these composite fibers can be as high as 285 S m-1 with only 2.5 wt% CNT loading, and reach 1549 S m-1 when CNT loading is 13.4 wt%. As-prepared composite fibers also exhibit 82% retention of conductivity at a strain of 7%, and have improved mechanical properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr34208e

  14. The Spherical Tokamak MEDUSA for Costa Rica

    Science.gov (United States)

    Ribeiro, Celso; Vargas, Ivan; Guadamuz, Saul; Mora, Jaime; Ansejo, Jose; Zamora, Esteban; Herrera, Julio; Chaves, Esteban; Romero, Carlos

    2012-10-01

    The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R>=3.6, under design[2]) and also the ongoing activities in low temperature plasmas. Courses in plasma physics at undergraduate and post-graduate joint programme levels are regularly conducted. The scientific programme is intend to clarify several issues in relevant physics for conventional and mainly STs, including transport, heating and current drive via Alfv'en wave, and natural divertor STs with ergodic magnetic limiter[3,4]. [1] G.D.Garstka, PhD thesis, University of Wisconsin at Madison, 1997 [2] L.Barillas et al., Proc. 19^th Int. Conf. Nucl. Eng., Japan, 2011 [3] C.Ribeiro et al., IEEJ Trans. Electrical and Electronic Eng., 2012(accepted) [4] C.Ribeiro et al., Proc. 39^th EPS Conf. Contr. Fusion and Plasma Phys., Sweden, 2012

  15. Effect of Taper Ratio on the Low-speed Rolling Stability Derivatives of Swept and Unswept Wings of Aspect Ratio 2.61

    Science.gov (United States)

    Brewer, Jack D; Fisher, Lewis R

    1951-01-01

    Results of tests conducted in the 6-foot-diameter rolling-flow test section of the Langley stability tunnel to determine the effects of varying taper ratio on the rolling and static stability characteristics of a swept wing are presented; results are also given for the effects of varying taper ratio on an unswept wing and for the effects of sweep on a tapered wing. All the models were of aspect ratio 2.61 and had NACA 0012 sections normal to the quarter-chord line. Taper ratios of 1.00, 0.50, and 0.25 and sweep angles of 0 degrees and 45 degrees were investigated.

  16. Studi Eksperimental Pemanas Air Tenaga Surya Pelat Absorber Type Sinusoidal dengan Variasi Terhadap Derajat Kevacuman dan Aspect Ratio

    Directory of Open Access Journals (Sweden)

    Izha Mahendra

    2014-03-01

    Full Text Available Sistem kolektor surya yang dirancang adalah kolektor dengan variasi tingkat kevakuman dan aspect ratio dengan tebal pelat (δ 1 mm . Untuk tingkat pemvakuman -20 cm.Hg, -40 cm.Hg, dan -60 cm.Hg serta menggunakan aspect ratio 1, 1.33, dan 2. Pengambilan data dilaksanakan dengan memvariasi debit fluida kerja dengan mengatur bukaan katup, yaitu dari 100 cc/menit sampai 300 cc/menits kenaikan 100 cc/menit. Dengan pemvariasian tingkat kevacuman di antara pelat absorber dan kaca penutup, diharapkan dapat memperkecil koefisien kehilangan, temperatur absorber naik, dan temperatur kaca penutup turun. Sehingga dapat meningkatkan efisiensi kolektor. Sehingga kita dapat menyimpulkan bahwa pada tingkat kevacuman -60 cmHg efisiensi yang didapat lebih besar dibandingkan dengan tingkat kevakuman -20 cmHg dan -40 cmHg. Sedangkan untuk aspect ratio 2 memiliki efisiensi terbesar dibandingkan aspect ratio 1 dan 1,33

  17. The effects of volume percent and aspect ratio of carbon fiber on fracture toughness of reinforced aluminum matrix composites

    International Nuclear Information System (INIS)

    Carbon fiber reinforced aluminum matrix composites are used as advanced materials in aerospace and electronic industries. In order to investigate role of aspect ratio of carbon fiber on fracture toughness of aluminum matrix composite, the composite was produced using stir casting. Al-8.5%Si-5%Mg selected as a matrix. The samples were prepared with three volume fractions (1, 2 and 3) and three aspect ratios (300, 500 and 800). Three-point bending test was performed on the specimens to evaluate the fracture toughness of the materials. The results showed that the fracture toughness of composites depends on both fiber volume fraction and aspect ratio. Scanning electron microscopy (SEM) was employed to elucidate the fracture behavior and crack deflection of composites. The study also, showed that the toughening mechanism depends strongly on fiber volume fraction, aspect ratio and the degree of wetting between fiber and matrix

  18. A CONCEPT FOR NEXT STEP ADVANCED TOKAMAK FUSION DEVICE

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A concept is introduced for initiating the design study of a special class of tokamak,which has a magnetic confinement configuration intermediate between contemporary advanced tokamak and the recently established spherical torus (ST,also well known by the name "spherical tokamak").The leading design parameter in the present proposal is a dimensionless geometrical parameter, the machine aspect ratio A=R0/a0=2.0,where the parameters a0 and R0 denote,respectively,the plasma (equatorial) minor radius and the plasma major radius.The aim of this choice is to technologically and experimentally go beyond the aspect ratio frontier (R0/a0≈2.5) of present day tokamaks and enter a broad unexplored domain existing on the (a0,R0) parameter space in current international tokamak database,between the data region already moderately well covered by the advanced conventional tokamaks and the data region planned to be covered by STs.Plasma minor radius a0 has been chosen to be the second basic design parameter, and consequently,the plasma major radius R0 is regarded as a dependent design parameter.In the present concept,a nominal plasma minor radius a0=1.2m is adopted to be the principal design value,and smaller values of a0 can be used for auxiliary design purposes,to establish extensive database linkage with existing tokamaks.Plasma minor radius can also be adjusted by mechanical and/or electromagnetic means to smaller values during experiments,for making suitable data linkages to existing machines with higher aspect ratios and smaller plasma minor radii.The basic design parameters proposed enable the adaptation of several confinement techniques recently developed by STs,and thereby a specially arranged central-bore region inside the envisioned tokamak torus,with retrieved space in the direction of plasma minor radius,will be available for technological adjustments and maneuverings to facilitate implementation of engineering instrumentation and real time high

  19. EFFECTS OF MOIST FROUDE NUMBER AND OROGRAPHIC ASPECT RATIO ON A CONDITIONALLY UNSTABLE FLOW OVER A MESOSCALE MOUNTAIN

    OpenAIRE

    Chen, Shu-Hua; Lin, Yuh-Lang; Zhao, Zhan; Dawn Reeves, Heather

    2005-01-01

    Abstract: A series of idealized simulations for an unsaturated, conditionally unstable flow over a two-dimensional mountain ridge were performed to investigate how the unsaturated moist Froude number (Fw) and the aspect ratio of mountain height to half-width (h/a), affect the propagation, cloud type and rainfall amount of orographically induced precipitation systems. The moist Froude number (Fw) was varied by increasing or decreasing the basic state wind speed (U) while the aspect ratio was v...

  20. Electronic transport through side-contacted graphene nanoribbons: effects of overlap, aspect ratio and orientation.

    Science.gov (United States)

    Krompiewski, S

    2011-11-01

    We numerically calculate the conductance and shot noise Fano factor of graphene nanoribbons (GNRs) side-contacted to metallic leads. A tight-binding model and Landauer's formalism are used in combination with a modified recursion method for Green's functions. The interfaces are modeled as a contact region between an infinite metallic electrode and a segment of the GNR put on top of it. The key question to answer in this study is how the size and orientation of the GNR and the GNR/electrode interface area influence the transport properties. It turns out that in general the transport characteristics depend strongly on overlap, meant as the ratio between the electrode-supported GNR length and the unsupported one. Moreover, a speed of convergence (with the overlap length) depends on both the transport direction and the aspect ratio of the GNR. It is shown that a short overlap interface is often, but not always, advantageous in nanoelectronics. These findings reconcile some seemingly conflicting opinions reported in the literature. PMID:21975438

  1. Electronic transport through side-contacted graphene nanoribbons: effects of overlap, aspect ratio and orientation

    Energy Technology Data Exchange (ETDEWEB)

    Krompiewski, S [Institute of Molecular Physics, Polish Academy of Sciences, ul. M Smoluchowskiego 17, 60179 Poznan (Poland)

    2011-11-04

    We numerically calculate the conductance and shot noise Fano factor of graphene nanoribbons (GNRs) side-contacted to metallic leads. A tight-binding model and Landauer's formalism are used in combination with a modified recursion method for Green's functions. The interfaces are modeled as a contact region between an infinite metallic electrode and a segment of the GNR put on top of it. The key question to answer in this study is how the size and orientation of the GNR and the GNR/electrode interface area influence the transport properties. It turns out that in general the transport characteristics depend strongly on overlap, meant as the ratio between the electrode-supported GNR length and the unsupported one. Moreover, a speed of convergence (with the overlap length) depends on both the transport direction and the aspect ratio of the GNR. It is shown that a short overlap interface is often, but not always, advantageous in nanoelectronics. These findings reconcile some seemingly conflicting opinions reported in the literature.

  2. Vortices behavior depending on the aspect ratio of an insect-like flapping wing in hover

    Science.gov (United States)

    Han, Jong-Seob; Chang, Jo Won; Cho, Hwan-Kee

    2015-09-01

    Force measurements and digital particle image velocimetry (DPIV) were carried out to reveal the effects of the aspect ratio (AR) of an insect-like flapping wing. A total of seven aspect ratios around that of an insect wing including 1.5, 2, 3, 4, 5, 6, and 8 were taken into account for the same hovering configurations. Time-course forces showed that both lift and drag in the translational phase were maximized in the case of AR = 3, which is the closest ratio to that of a living insect. The chordwise cross-sectional DPIV conclusively showed that the leading-edge vortex (LEV) on the wing of AR = 1.5 remained nearly unchanged in all cross sections. In other AR cases, however, the trailing-edge vortices (TEV) were clearly found with LEVs that lifted off the wing surfaces at the outboard cross sections. In each of these cases, the TEV interrupted the downwash, and the overall flows behind the wing became wakes similar to those found over a blunt body. The near-wake flow structures revealed that the tip vortex gradually entered the inner area from the wing tip as the AR increased. Circulations and downwash distributions showed a stretched LEV and asymmetrically developed tip and root vortices as the AR moved away from AR = 3. These results do not only indicate that the AR effects of a flapping wing are characteristics that are definitely distinctive from those of a typical aircraft, but also briefly imply that maintaining an LEV attachment by employing strong rotational accelerations is not the highest priority when attempting to achieve lift enhancements. Among the tested cases, the wing of AR = 3 had a balanced downwash flux as well as the best aerodynamic performance characteristics, including the maximum lift, reasonable efficiency, and a moderate pitching moment. This indirectly explains why the wings of living flyers adept at hovering have this AR, and it also suggests the appropriate AR for a flapping-type micro-air vehicle.

  3. 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.

  4. OCLATOR (One Coil Low Aspect Toroidal Reactor)

    International Nuclear Information System (INIS)

    A new approach to construct a tokamak-type reactor(s) is presented. Basically the return conductors of toroidal field coils are eliminated and the toroidal field coil is replaced by one single large coil, around which there will be placed several tokamaks or other toroidal devices. The elimination of return conductors should, in addition to other advantages, improve the accessibility and maintainability of the tokamaks and offer a possible alternative to the search for special materials to withstand large neutron wall loading, as the frequency of changeover would be increased due to minimum downtime. It also makes it possible to have a low aspect ratio tokamak which should improve the β limit, so that a low toroidal magnetic field strength might be acceptable, meaning that the NbTi superconducting wire could be used. This system is named OCLATOR

  5. Measurement and comparison with theory of the temperature dependence of satellite-to-resonance line ratios of heliumlike nickel from the JET tokamak

    International Nuclear Information System (INIS)

    The line ratios of the intercombination line x (1s2p 3P2→1s21S0), the dielectronic and inner-shell satellite line t [1s2p(3P)2s 2P1/2→1s22s2S1/2], and the n≥3 dielectronic satellite lines (1s2pnl→1s2nl) to the resonance line w (1s2p 1P1→1s21S0) in the spectrum of heliumlike nickel are measured with a high-resolution x-ray crystal spectrometer on the JET tokamak. The central electron temperatures for which the spectra are taken range from about one-third to twice the threshold energy for the line excitation. The measurements are compared with predictions from a model taking into account the spatial emission profiles of the different ionization stages of nickel calculated from the radial profiles of JET plasma parameters. The rate coefficients for the formation of excited states are taken from a single, self-consistent source of calculations of dielectronic and radiative recombination and electron-impact excitation. The rate coefficients for the calculation of the ionization balance are critically reviewed. Good agreement is found for the ratios t/w and (n≥3)/w, but for x/w significant disagreement is found. Possible causes for this disagreement are discussed. In particular, charge-exchange processes, which are omitted from the model, are found not to be plausible contributors. It is concluded that the present coronal equilibrium model correctly describes the ionization balance, the radiative and dielectronic recombination, and the electron-impact excitation of electric dipole transitions, but that there is a problem with the excitation of nondipole transitions

  6. Solenoid-free plasma start-up in spherical tokamaks

    Science.gov (United States)

    Raman, R.; Shevchenko, V. F.

    2014-10-01

    The central solenoid is an intrinsic part of all present-day tokamaks and most spherical tokamaks. The spherical torus (ST) confinement concept is projected to operate at high toroidal beta and at a high fraction of the non-inductive bootstrap current as required for an efficient reactor system. The use of a conventional solenoid in a ST-based fusion nuclear facility is generally believed to not be a possibility. Solenoid-free plasma start-up is therefore an area of extensive worldwide research activity. Solenoid-free plasma start-up is also relevant to steady-state tokamak operation, as the central transformer coil of a conventional aspect ratio tokamak reactor would be located in a high radiation environment but would be needed only during the initial discharge initiation and current ramp-up phases. Solenoid-free operation also provides greater flexibility in the selection of the aspect ratio and simplifies the reactor design. Plasma start-up methods based on induction from external poloidal field coils, helicity injection and radio frequency current drive have all made substantial progress towards meeting this important need for the ST. Some of these systems will now undergo the final stages of test in a new generation of large STs, which are scheduled to begin operations during the next two years. This paper reviews research to date on methods for inducing the initial start-up current in STs without reliance on the conventional central solenoid.

  7. Engineering design study of quasi-axisymmetric stellarator with low aspect-ratio

    International Nuclear Information System (INIS)

    The quasi-axisymmetric stellarator CHS-qa has been designed from physics point of view on the basis of the so-called optimization of helical magnetic field configurations. Once its engineering design was introduced briefly as a part of physics design, here the details are described. The toroidal period number N of 2 has been selected because it gives a small aspect ratio resulting in a large plasma volume favorable for physics experiments. CHS-qa has the following machine parameters: major radius R of 1.5 m, plasma minor radius a of 0.47 m (Ap(=R/a)=3.2), maximum toroidal magnetic field strength of 1.5 T, flat-top time of 1 sec at full field. Because of quasi-axisymmetry of the magnetic field structure with N=2 the whole structure of the machine is of highly non-axisymmetry and of deformation, which causes asymmetric centripetal forces on modular coils and complicated distributions of the electromagnetic force. Major engineering points on the modular coils and on the vacuum vessel are as follows: 1) modular coil design (curvature and twist of conductors), 2) supporting structures of modular coils, 3) manufacturing process of vacuum vessel and modular coils, 4) design of ports for heating and diagnostics. The following results have been obtained. 1) Shapes of modular coils are designed under the tolerable curvature and twist. 2) To cope with centripetal forces and overturning forces supporting structures for coils are designed by using elliptical plates on the inboard side and rods between modular coils. Stress analysis is also done under the condition where the ratio of modular coil currents is changed for controlling bumpiness of the magnetic field. 3) The vacuum vessel is inside the modular coils. How to make the whole assembly has been carefully examined. 4) Tangential injection of NB is available. (orig.)

  8. Long-range forces affecting equilibrium inertial focusing behavior in straight high aspect ratio microfluidic channels

    Science.gov (United States)

    Reece, Amy E.; Oakey, John

    2016-04-01

    The controlled and directed focusing of particles within flowing fluids is a problem of fundamental and technological significance. Microfluidic inertial focusing provides passive and precise lateral and longitudinal alignment of small particles without the need for external actuation or sheath fluid. The benefits of inertial focusing have quickly enabled the development of miniaturized flow cytometers, size-selective sorting devices, and other high-throughput particle screening tools. Straight channel inertial focusing device design requires knowledge of fluid properties and particle-channel size ratio. Equilibrium behavior of inertially focused particles has been extensively characterized and the constitutive phenomena described by scaling relationships for straight channels of square and rectangular cross section. In concentrated particle suspensions, however, long-range hydrodynamic repulsions give rise to complex particle ordering that, while interesting and potentially useful, can also dramatically diminish the technique's effectiveness for high-throughput particle handling applications. We have empirically investigated particle focusing behavior within channels of increasing aspect ratio and have identified three scaling regimes that produce varying degrees of geometrical ordering between focused particles. To explore the limits of inertial particle focusing and identify the origins of these long-range interparticle forces, we have explored equilibrium focusing behavior as a function of channel geometry and particle concentration. Experimental results for highly concentrated particle solutions identify equilibrium thresholds for focusing that scale weakly with concentration and strongly with channel geometry. Balancing geometry mediated inertial forces with estimates for interparticle repulsive forces now provide a complete picture of pattern formation among concentrated inertially focused particles and enhance our understanding of the fundamental limits of

  9. Electronic shell structure and carrier dynamics of high aspect ratio InP single quantum dots

    Science.gov (United States)

    Beirne, Gareth J.; Reischle, Matthias; Roßbach, Robert; Schulz, Wolfgang-Michael; Jetter, Michael; Seebeck, Jan; Gartner, Paul; Gies, Christopher; Jahnke, Frank; Michler, Peter

    2007-05-01

    Systematic excitation-power-density dependent and time-resolved single-dot photoluminescence studies have been performed on type-I InP/Ga0.51In0.49P quantum dots. These dots are rather flat and therefore exhibit larger than normal single-dot ground-state transition energies ranging from 1.791 to 1.873eV . As a result of their low height, the dots have a very high aspect ratio (ratio of width to height) of approximately 27:1 . In general, even at high excitation power densities, the dots with ground-state transition energies above 1.82eV exhibit only s -shell emission, while the larger dots exhibiting ground-state emission below 1.82eV tend to exhibit emission from several (in some cases up to eight) shells. Calculations indicate that this change is due to the smaller dots having only one confined election level while the larger dots have two or more. Time-resolved investigations indicate the presence of fast carrier relaxation and recombination processes for both dot types, however, only the larger dots display clear interlevel relaxation effects as expected. The temporal behavior has been qualitatively simulated using a rate equation model. Also, in a more detailed analysis, the fast carrier relaxation is described on the basis of a quantum kinetic treatment of the carrier-phonon interaction. Finally, the dots display a clear single-photon emission signature in photon statistics measurements.

  10. Future directions in fusion research: Super high field tokamaks

    International Nuclear Information System (INIS)

    Recent experimental results and advances in magnet engineering suggest that super high field, high aspect ratio tokamak devices could be a very efficient way to achieve burning plasma conditions and could open up a new area of research. Copper magnet devices with fields of 13 to 25 T at the plasma are considered. The super high field approach could also provide advantages for ETR and demonstration/commercial reactor concepts (magnetic fields at the plasma in the 8 to 13 T range)

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

    Science.gov (United States)

    Naik, Udaykumar; Bapat, Vishram N.

    2016-09-01

    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.

  12. 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 .

  13. Tunable Ultra-high Aspect Ratio Nanorod Architectures grown on Porous Substrate via Electromigration

    Science.gov (United States)

    Mansourian, Ali; Paknejad, Seyed Amir; Wen, Qiannan; Vizcay-Barrena, Gema; Fleck, Roland A.; Zayats, Anatoly V.; Mannan, Samjid H.

    2016-02-01

    The interplay between porosity and electromigration can be used to manipulate atoms resulting in mass fabrication of nanoscale structures. Electromigration usually results in the accumulation of atoms accompanied by protrusions at the anode and atomic depletion causing voids at the cathode. Here we show that in porous media the pattern of atomic deposition and depletion is altered such that atomic accumulation occurs over the whole surface and not just at the anode. The effect is explained by the interaction between atomic drift due to electric current and local temperature gradients resulting from intense Joule heating at constrictions between grains. Utilizing this effect, a porous silver substrate is used to mass produce free-standing silver nanorods with very high aspect ratios of more than 200 using current densities of the order of 108 A/m2. This simple method results in reproducible formation of shaped nanorods, with independent control over their density and length. Consequently, complex patterns of high quality single crystal nanorods can be formed in-situ with significant advantages over competing methods of nanorod formation for plasmonics, energy storage and sensing applications.

  14. High-aspect-ratio photoresist processing for fabrication of high resolution and thick micro-windings

    Science.gov (United States)

    Anthony, Ricky; Laforge, Elias; Casey, Declan P.; Rohan, James F.; O'Mathuna, Cian

    2016-10-01

    DC winding losses remain a major roadblock in realizing high efficiency micro-magnetic components (inductors/transformers). This paper reports an optimized photoresist process using negative tone and acrylic based THB-151N (from JSR Micro), to achieve one of the highest aspect ratio (17:1) and resolution (~5 µm) resist patterns for fabrication of thick (~80 µm) micro-winding using UV lithography. The process was optimized to achieve photoresist widths from 5 µm to 20 µm with resist thickness of ~85 µm in a single spin step. Unlike SU-8, this resist can be readily removed and shows a near-vertical (~91°) electroplated Cu side-wall profile. Moreover, the high resolution compared to available resist processes enables a further reduction in the footprint area and can potentially increase the number of winding thereby increasing the inductance density for micro-magnetic components. Resistance measurements of electroplated copper winding of air-core micro-inductors within the standard 0402 size (0.45 mm2 footprint area) suggested a 42% decrease in resistance (273 mΩ-159 mΩ) with the increase in electroplated Cu thickness (from 50 µm to 80 µm). Reduction of the spacings (from 10 µm to 5 µm) enabled further miniaturisation of the device footprint area (from 0.60 mm2 to 0.45 mm2) without significant increase in resistance.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    Liu Yi; Xie Changchuan; Yang Chao; Cheng Jialin

    2016-01-01

    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 multidisci-plinary 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 bound-ary. 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 quanti-tative 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 flex-ible wings.

  17. Development and investigation of a small, high aspect ratio, two-stroke engine

    Science.gov (United States)

    Disseau, Mael Leo David Soliman

    An engine for a novel compact palm sized electric power generator was developed. Due to fabrication and space limitations a flat, rectangular, piston with spring return two-cycle engine was selected. This novel geometry raised many issues that had to be solved. These included: sealing, scavenging, and high aspect ratio (i.e., flame quenching and high heat losses) effects. Engines as thin as 3.175 mm were developed that produced 11.6 W of mechanical power. A somewhat thicker engine (6.35 mm) produced 15W of electrical power when attached to a voice coil generator. To better understand the combustion process in these types of engines, constant volume combustion in thin, flat rectangular combustors was studied. A model was also developed to help determine the parameters that control the behavior in these combustors, some of which could not be measured directly. A range of thicknesses over which combustion propagates was identified and the variation of system efficiency and heat transfer losses as well as overall combustor behavior with thickness were also determined. In addition, a threshold thickness at which the combustor switches from heat generation dominated mode to a heat loss dominated regime was identified. Finally, bulk flow, turbulence and leaks were identified as the parameters that need to be added to the model to enable it to predict the operation of the engine.

  18. Proposal for a risk banding framework for inhaled low aspect ratio nanoparticles based on physicochemical properties.

    Science.gov (United States)

    Oosterwijk, Mattheus T T; Feber, Maaike Le; Burello, Enrico

    2016-08-01

    We present a conceptual framework that can be used to assign risk bands to inhaled low aspect ratio nanoparticles starting from exposure bands assigned to a specific exposure situation. The framework mimics a basic physiological scheme that captures the essential mechanisms of fate and toxicity of inhaled nanoparticles and is composed of several models and rules that estimate the result of the following processes: the deposition of particles in the respiratory tract, their (de-)agglomeration, lung burden and clearance, their diffusion through the lung mucus layer, translocation and cellular uptake and local and systemic toxicity. Each model is based on a set of particle's physicochemical properties, including the size and size distribution(s), the zeta potential (or net charge at a specific pH), the surface hydrophobicity or hydrophilicity, the conduction band energy (for metals, metal oxides, quantum dots, etc.) and the solubility at a specific pH. The framework takes the exposure bands as input and predicts, using the above-mentioned models, an internal dose band (module 1). Module 2 assigns a relative hazard ranking depending on the region of particle deposition in the respiratory tract, the likelihood of uptake and whether the toxicological effects are assumed to be local and/or systemic. By combining the results of Module 1 and 2, the framework provides a relative risk ranking. PMID:26763369

  19. High aspect ratio lead zirconate titanate tube structures: I. Template assisted fabrication - vacuum infiltration method

    Directory of Open Access Journals (Sweden)

    Vladimír Kovaľ

    2012-03-01

    Full Text Available Polycrystalline Pb(Zr0.52Ti0.48O3 (PZT microtubes are fabricated by a vacuum infiltration method. The method is based on repeated infiltration of precursor solution into macroporous silicon (Si templates at a sub-atmospheric pressure. The pyrolyzed PZT tubes of a 2-µm outer diameter, extending to over 30 µm in length were released from the template using a selective isotropic-pulsed XeF2 reactive ion etching of silicon. Free-standing microtubes, partially anchored at the bottom of the Si template, were then crystallized in pure oxygen atmosphere at 750 °C for 2 min using a rapid thermal annealer. The perovskite phase of the final PZT tubes was confirmed by X-ray diffraction (XRD analysis. The XRD spectrum also revealed a small amount of the pyrochlore phase in the structure and signs of possible fluoride contamination caused most likely by the XeF2 etching process. The surface morphology was examined using scanning electron microscopy. It was demonstrated that the whole surface of the pore walls was conformally coated during the repeated infiltration of templates, resulting in straight tubes with closed tips formed on the opposite ends as replicas of the pore bottoms. These high aspect ratio ferroelectric structures are suggested as building units for developing miniaturized electronic devices, such as memory storage (DRAM trenched capacitors, piezoelectric scanners and actuators, and are of fundamental value for the theory of ferroelectricity in systems with low dimensionality.

  20. Adaptive AFM scan speed control for high aspect ratio fast structure tracking

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Ahmad; Schuh, Andreas; Rangelow, Ivo W. [Department of Microelectronic and Nanoelectronic Systems, Faculty of Electrical Engineering and Information Technology Ilmenau University of Technology, Gustav-Kirchhoffstr. 1, 98684 Ilmenau (Germany)

    2014-10-15

    Improved imaging rates in Atomic Force Microscopes (AFM) are of high interest for disciplines such as life sciences and failure analysis of semiconductor wafers, where the sample topology shows high aspect ratios. Also, fast imaging is necessary to cover a large surface under investigation in reasonable times. Since AFMs are composed of mechanical components, they are associated with comparably low resonance frequencies that undermine the effort to increase the acquisition rates. In particular, high and steep structures are difficult to follow, which causes the cantilever to temporarily loose contact to or crash into the sample. Here, we report on a novel approach that does not affect the scanner dynamics, but adapts the lateral scanning speed of the scanner. The controller monitors the control error signal and, only when necessary, decreases the scan speed to allow the z-piezo more time to react to changes in the sample's topography. In this case, the overall imaging rate can be significantly increased, because a general scan speed trade-off decision is not needed and smooth areas are scanned fast. In contrast to methods trying to increase the z-piezo bandwidth, our method is a comparably simple approach that can be easily adapted to standard systems.

  1. Relationship between the consolidation parameter, porosity and aspect ratio in microporous carbonate rocks

    Science.gov (United States)

    de Ceia, Marco A. R.; Misságia, Roseane M.; Neto, Irineu Lima; Archilha, Nathaly

    2015-11-01

    The estimation of dry bulk modulus is required for the successful application of the Biot-Gassmann theory to forecast fluid changes within a reservoir. The Pride model is one of the several models described in the literature for predicting the dry elastic moduli of rocks. However, the accuracy of the Pride model depends on the estimation of the consolidation parameter. In this paper, the consolidation parameter was estimated using the pore stiffness, mineral bulk modulus and porosity. That approach allowed calculating the dry bulk modulus of a set of microporous carbonate rocks according to the Pride model and compare those estimates to the results obtained using the elastic velocities. The change in the consolidation parameter over a range of pressures suggests that the relationship between this parameter and the unconfined porosity increases at high effective pressure. Statistical analyses of the distribution of those consolidation parameter values were performed to verify how the effective pressure influences the mean value and variance. Mean pore aspect ratios were estimated using Kuster-Toksoz methodology to establish a relationship with the consolidation parameter and the unconfined porosity. Such relationship also accounts for pressure-dependence within the studied pressure range. Although only 20 samples were analyzed, those studies can contribute to advise the estimation of the consolidation parameter in this type of carbonate rocks.

  2. 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.

  3. 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.

  4. Shafranov shift in low-aspect-ratio heliotron/torsatron CHS

    International Nuclear Information System (INIS)

    The MHD equilibrium properties of neutral-beam-heated plasmas have been experimentally investigated in the Compact Helical System (CHS), a low-aspect-ratio (Ap ∼ 5) heliotron/torsatron. This configuration is characterized by a strong breaking of helical symmetry. The radial profiles measured by various diagnostics have shown significant Shafranov shift due to plasma pressure. The deviation of the magnetic axis from its vacuum position has reached 50% of the minor radius. When the three-dimensional equilibrium code VMEC is used to reconstruct the equilibrium from the experimental data, the result is in good agreement with the experimentally observed Shafranov shift as well as the diamagnetic pressure in plasmas with ≤ 1.2% and β0 ≤ 3.3%. This β value corresponds to half of the conventional equilibrium β limit defined by the Shafranov shift reaching a value of half the minor radius. Although tangential neutral beam injection has caused pressure anisotropies p parallel/p perpendicular ≤ 3, the description of the equilibrium assuming isotropic pressure is consistent with the experiment. (author)

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

    Science.gov (United States)

    Demir, Hacımurat; Özden, Mustafa; Genç, Mustafa Serdar; Çağdaş, Mücahit

    2016-03-01

    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.

  6. Vortex-induced drag and the role of aspect ratio in undulatory swimmers

    Science.gov (United States)

    Godoy-Diana, Ramiro; Raspa, Veronica; Ramananarivo, Sophie; Thiria, Benjamin

    2014-11-01

    During cruising, the thrust produced by a self-propelled swimmer is balanced by a global drag force. For a given object shape, this drag can involve skin friction or form drag, both being well-documented mechanisms. However, for swimmers whose shape is changing in time, the question of drag is not yet clearly established. We address this problem by investigating experimentally the swimming dynamics of undulating thin flexible foils. Measurements of the propulsive performance together with full recording of the elastic wave kinematics are used to discuss the general problem of drag in undulatory swimming. We show that a major part of the total drag comes from the trailing longitudinal vortices that roll-up on the lateral edges of the foils. This result gives a comparative advantage to swimming foils of larger span thus bringing new insight to the role of aspect ratio for undulatory swimmers. Ref: Physics of Fluids, Vol. 26, 041701 (2014). We gratefully acknowledge support by EADS Foundation through project ``Fluids and elasticity in biomimetic propulsion.''

  7. Mixing Characteristics and Bubble Behavior in an Airlift Internal Loop Reactor with Low Aspect Ratio

    Institute of Scientific and Technical Information of China (English)

    张伟鹏; 雍玉梅; 张广积; 杨超; 毛在砂

    2014-01-01

    The present study summarizes the results of macro-and micro-mixing characteristics in an airlift inter-nal loop reactor with low aspect ratio (H/D≤5) using the electrolytic tracer response technique and the method of parallel competing reactions respectively. The micro-mixing has never been investigated in airlift loop reactors. The dual-tip electrical conductivity probe technique is used for measurement of local bubble behavior in the reactor. The effects of several operating parameters and geometric variables are investigated. It is found that the increase in su-perficial gas velocity corresponds to the increase in energy input, liquid circulation velocity and shear rate, decreas-ing the macro-mixing time and segregation index. Moreover, it is shown that top clearance and draft diameter affect flow resistance. However, the bubble redistribution with a screen mesh on the perforated plate distributor for macro-mixing is insignificant. The top region with a high energy dissipation rate is a suitable location for feeding reactants. The analysis of present experimental data provides a valuable insight into the interaction between gas and liquid phases for mixing and improves the understanding of intrinsic roles of hydrodynamics upon the reactor de-sign and operating parameter selection.

  8. Viscous Faraday waves in 2D large aspect ratio annular containers

    Science.gov (United States)

    Vega, José M.; Mancebo, Francisco J.

    2002-11-01

    A weakly nonlinear analysis of viscous Faraday waves in a two-dimensional, large aspect ratio annulus is presented that accounts for the coupled, slow dynamics of both the surface wave envelope and the associated long wave flows. The analysis can be considered as the natural extension of well known linear results by Kumar & Tuckerman (1994). Two cases are considered, depending on the comparative values of the fluid depth and the wavelength of the excited surface waves. At small depth, a long wave, viscous mean flow must be considered that is slaved to the free surface deformation. The relevant amplitude equations coincide with those first derived by Coullet & Iooss (1990) in the analysis of spatially periodic patterns, and further analyzed by Matthews & Cox (2000). At larger depth, the system exhibits (a) an inviscid, long wave, oscillatory flow that is slaved to the surface wave envelope and (b) a long wave, viscous mean flow that exhibits its own dynamics. In both cases, the asymptotic equations have been derived from an exact formulation. Some analytically obtained results will be presented on the local and global stability of the simplest spatially uniform standing waves of the system.

  9. Photoablation characteristics of novel polyimides synthesized for high-aspect-ratio excimer laser LIGA process

    Science.gov (United States)

    Yang, Chii-Rong; Hsieh, Yu-Sheng; Hwang, Guang-Yeu; Lee, Yu-Der

    2004-04-01

    The photoablation properties of two soluble polyimides DMDB/6FDA and OT/6FDA with thicknesses of over 300 µm, synthesized by the polycondensation of a hexafluoropropyl group contained in a dianhydride with two kinds of diamines, are investigated using a 248 nm krypton fluoride (KrF) laser. The incorporation of the hexafluoropropyl group into the chemical structure gives these two polyimides higher etching rates than Kapton (a commercial polyimide film which is difficult to dissolve). The etching rates of synthesized polyimides are about 0.1-0.5 µm/pulse over a fluence range of 0.25-2.25 J cm-2. The photothermal mechanism for DMDB/6FDA contributes about 19% of etching depth at a laser fluence of 0.82 J cm-2. Moreover, the number of laser pulses seriously affects the taper angle of microstructures, especially at low fluence. Near-vertical side-wall structures can be built at high fluence (~2 J cm-2). Fresnel patterns with a thickness of 300 µm and a linewidth of 10 µm were fabricated, with an attainable aspect ratio of around 30. After photoablation, the complementary metallic microstructures were also fabricated by a sequential electroplating procedure. Then, those two new polyimides could be dissolved easily in most common solvents (such as THF, DMSO, NMP and DMF). These results indicate that these two soluble polyimides are highly suitable for use in the KrF laser LIGA process.

  10. 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.

  11. 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. PMID:27454037

  12. 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.

  13. Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, D. Q.; Petković, I., E-mail: ivana.petkovic@yale.edu; Lollo, A. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Castellanos-Beltran, M. A. [National Institute for Standards and Technology, Boulder, Colorado 80305 (United States); Harris, J. G. E. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2014-10-15

    We have fabricated large arrays of mesoscopic metal rings on ultrasensitive cantilevers. The arrays are defined by electron beam lithography and contain up to 10{sup 5} rings. The rings have a circumference of 1 μm, and are made of ultrapure (6N) Au that is deposited onto a silicon-on-insulator wafer without an adhesion layer. Subsequent processing of the SOI wafer results in each array being supported at the end of a free-standing cantilever. To accommodate the large arrays while maintaining a low spring constant, the cantilevers are nearly 1 mm in both lateral dimensions and 100 nm thick. The extreme aspect ratio of the cantilevers, the large array size, and the absence of a sticking layer are intended to enable measurements of the rings' average persistent current in the presence of relatively small magnetic fields. We describe the motivation for these measurements, the fabrication of the devices, and the characterization of the cantilevers' mechanical properties. We also discuss the devices' expected performance in measurements of .

  14. Preparation and Properties of Nanocomposites from Pristine and Modified SWCNTs of Comparable Average Aspect Ratios

    Science.gov (United States)

    Smith, Joseph G.; Delozier, Donavon M.; Watson, Kent A.; Connell, John W.; Bekyarova, E.; Haddon, R.; Yu, A.

    2008-01-01

    Low color, flexible, space-durable polyimide films with inherent and robust electrical conductivity to dissipate electrostatic charge (ESC) have been under investigation as part of a materials development activity for future NASA space missions. The use of single-walled carbon nanotubes (SWCNTs) is one means to achieving this goal. Even though the concentration of SWCNTs needed to achieve ESC dissipation is typically low, it is dependent upon purity, size, dispersion, and functionalization. In this study, SWCNTs prepared by the electric arc discharge method were used to synthesize nanocomposites using the LaRC(TradeMark) CP2 backbone as the matrix. Pristine and functionalized SWCNTs were mixed with an alkoxysilane terminated amide acid of LaRC(TradeMark) CP2 and the soluble imide form of the polymer and the resultant nanocomposites evaluated for mechanical, thermal, and electrical properties. Due to the preparative conditions for the pristine and functionalized SWCNTs, the average aspect ratio for both was comparable. This permitted the assessment of SWCNT functionalization with respect to various interactions (e.g. van der Waals, hydrogen bonding, covalent bond formation, etc.) with the matrix and the macroscopic effects upon nanocomposite properties. The results of this study are described herein.

  15. Simulation studies of the behavior of positrons in a microtrap with long aspect ratio

    CERN Document Server

    Narimannezhad, Alireza; Weber, Marc H; Xu, Jia; Lynn, Kelvin G

    2013-01-01

    The charged particles storage capacity of microtraps (micro-Penning-Malmberg traps) with large length to radius aspect ratios and radii of the order of tens of microns was explored. Simulation studies of the motions of charged particles were conducted with particle-in-cell plasma code WARP and the Charged Particle Optics (CPO) program. This paper presents how to reduce simulation noise by optimizing modeling parameters to achieve an equilibrium distribution. The new design of the trap consisted of an array of microtraps with confinement voltages of only 10 V. It was computationally shown that each microtrap with 50 micron radius stored positrons with density higher than a conventional Penning-Malmberg trap (10^11 cm-3). The results of the simulation of a plasma initialized with a uniform density and Boltzmann energy distributions showed that the plasma tends to transform to a soft edge distribution in radial direction as it approaches the equilibrium. The shorter the plasma we had, the faster the equilibrium ...

  16. Development of a low-aspect ratio fin for flight research experiments

    Science.gov (United States)

    Richwine, David M.; Delfrate, John H.

    1994-01-01

    A second-generation flight test fixture, developed at NASA Dryden Flight Research Center, offers a generic testbed for aerodynamic and fluid mechanics research. The new fixture, a low-aspect ratio vertical fin shape mounted on the centerline of an F-15B aircraft lower fuselage, is designed for flight research at Mach numbers up to 2.0. The new fixture is a composite structure with a modular configuration and removable components for functional flexibility. This report describes the multidisciplinary design and analysis approach used to develop the fixture. The approach integrates conservative assumptions with simple analysis techniques to minimize the time and cost associated with its development. Presented are the principal disciplines required for this effort, which include aerodynamics, structures, stability, and operational considerations. In addition, preliminary results from the first phase of flight testing are presented. Acceptable directional stability and flow quality are documented and show agreement with predictions. Future envelope expansion activities will minimize current limitations so that the fixture can be used for a wide variety of high-speed aerodynamic and fluid mechanics research experiments.

  17. The Universal Aspect Ratio of Vortices in Rotating Stratified Flows: Theory and Simulation

    CERN Document Server

    Hassanzadeh, Pedram; Gal, Patrice Le

    2012-01-01

    We derive a relationship for the vortex aspect ratio $\\alpha$ (vertical half-thickness over horizontal length scale) for steady and slowly evolving vortices in rotating stratified fluids, as a function of the Brunt-Vaisala frequencies within the vortex $N_c$ and in the background fluid outside the vortex $\\bar{N}$, the Coriolis parameter $f$, and the Rossby number $Ro$ of the vortex: $\\alpha^2 = Ro(1+Ro) f^2/(N_c^2-\\bar{N}^2)$. This relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and the background density gradient need not be uniform. Our relation for $\\alpha$ has many consequences for equilibrium vortices in rotating stratified flows. For example, cyclones must have $N_c^2 > \\bar{N}^2$; weak anticyclones (with $|Ro| \\bar{N}^2$. We verify our relation for $\\alpha$ with numerical simulations of the three-dimensional Boussinesq equations for a wide variety of vortices, including: vortices that are i...

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

    Science.gov (United States)

    2016-01-01

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

  19. Spherical tokamak research for fusion reactor

    International Nuclear Information System (INIS)

    Between ITER and the commercial fusion reactor, there are many technological problems to be solved such as cost, neutron and steady-state operation. In the conceptual design of VECTOR and Slim CS reactors it was shown that the key is 'low aspect ratio'. The spherical tokamak (ST) has been expected as the base for fusion reactors. In US, ST is considered as a non-superconducting reactor for use in the neutron irradiation facility. Conceptual design of the superconducting ST reactor is conducted in Japan and Korea independently. In the present article, the prospect of the ST reactor design is discussed. (author)

  20. Enhanced plasticity of bulk metallic glass in different aspect ratios via laser shock peening with multiple impacts

    Science.gov (United States)

    Fu, Jie; Zhu, Yunhu; Zheng, Chao; Liu, Ren; Ji, Zhong

    2016-09-01

    In this study laser shock peening (LSP) with multiple laser impacts was used to improve the mechanical properties especially the plasticity of Zr35Ti30Cu8.25Be26.75 bulk metallic glass (BMG) pillars in two aspect ratios (1:1 and 2:1). It was found that, with increasing laser impacts up to 5, the compression plastic strain of BMG pillar with aspect ratio of 1:1 increased from 0 to 1.48% and the compression strength increased significantly from 1569 MPa to 1721 MPa. With further laser impacts beyond 5, the changes in the plasticity and the compression strength were observed to be insignificant. Considering the effect of sample geometry at the same laser impacts, it could be concluded that the BMG pillars with smaller aspect ratio of 1:1 had better mechanical properties than that of the lager BMG pillars with aspect ratio of 2:1. Besides, the elastic strain limit of BMG pillars with LSP was not only independent of the laser impacts, but also irrelevant to the aspect ratio. At last, we discussed the reason for the increase of plasticity in view of the creation of excess free volume during LSP.

  1. EFFECT OF SPECIMEN ASPECT RATIO ON FATIGUE LIFE OF CLOSED CELL Al-Si-Ca ALLOY FOAM

    Institute of Scientific and Technical Information of China (English)

    Amkee Kim; Ilhyun Kim

    2008-01-01

    Quasi-static and compressive fatigue tests on the closed cell Al-Si-Ca alloy foam specimens with three different aspect ratios were performed.It turned out that the onset of cyclic shortening of foam with a lower aspect ratio took place earlier and the fatigue strength was lower compared with the specimen with a higher aspect ratio,although aU the dimensions of specimen satisfied the seven times the cell size criterion,while the quasi-static stress-strain curves were almost same having same Young's modulus,yield stress and plateau stress.Therefore,the seven times the cell size criterion for the quasi-static compression behavior was not applicable to the fatigue analysis of Al-Si-Ca alloy foam.

  2. Mechanical properties of natural rubber nanocomposites reinforced with high aspect ratio cellulose nanocrystals isolated from soy hulls.

    Science.gov (United States)

    Flauzino Neto, Wilson Pires; Mariano, Marcos; da Silva, Ingrid Souza Vieira; Silvério, Hudson Alves; Putaux, Jean-Luc; Otaguro, Harumi; Pasquini, Daniel; Dufresne, Alain

    2016-11-20

    Cellulose nanocrystals (CNCs) were isolated from soy hulls by acid sulfuric hydrolysis. The resulting CNCs were characterized using TEM, AFM, WAXS, elemental analysis and TGA. The CNCs have a high crystallinity, specific surface area and aspect ratio. The aspect ratio (around 100) is the largest ever reported in the literature for a plant cellulose source. These CNCs were used as a reinforcing phase to prepare nanocomposite films by casting/evaporation using natural rubber as matrix. The mechanical properties were studied in both the linear and non-linear ranges. The reinforcing effect was higher than the one observed for CNCs extracted from other sources. It may be assigned not only to the high aspect ratio of these CNCs but also to the stiffness of the percolating nanoparticle network formed within the polymer matrix. Moreover, the sedimentation of CNCs during the evaporation step was found to play a crucial role on the mechanical properties. PMID:27561481

  3. 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.

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

    Science.gov (United States)

    Rochlitz, Henrik; Scholz, Peter; Fuchs, Thomas

    2015-12-01

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

  5. Simulation Research on Stress Intensity Factors of Different Crack Aspect Ratios on Hollow Axles

    Institute of Scientific and Technical Information of China (English)

    ZHOU Suxia; XIE Jilong

    2009-01-01

    Because of the wicked service environment of the high speed train, it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch. Under the fatigue loading a crack can initiate from the notch and propagate to failure. It is noted that the stress intensity factor is the control parameter of the crack propagating, for the purpose of getting the more exact propagation characteristics, the stress intensity factor is studied mainly. The service loads of hollow axles are defined, and the stress distribution of hollow axles is obtained according to the load spectrum. The semi-ellipse crack configuration is defined with three parameters:the aspect ratio, the relative depth and the relative location along the crack front. Quarter point 20-node isoparametric degenerate singular elements are used for the region near the crack tip. The finite element model of crack extension of hollow axle is created, and the crack front is dispersed which can realize orthogonal extension. Based on this the stress intensity factors of crack front were calculated, and the distribution rules of the stress intensity factors of different initial crack shapes are obtained. The conclusions are compared with that of the analytic method and they agree with each other very well, and the calculating results show that there is a close relationship between the stress intensity factor and the initial crack shape. For a round crack the stress intensity factor at the surface point increases faster than the one at the center point with the crack propagation. However, for a narrow crack, the results are in contrast with that of a round one. So, all the cracks with different shapes propagate toward to a similar shape, and they grow at this shape to end. The study may contribute to the crack propagate characteristics research.

  6. SST and ADITYA tokamak research in India

    International Nuclear Information System (INIS)

    Steady state operation of tokamaks plays an important role in high temperature magnetically confined plasma research. Steady state Superconducting Tokamak (SST) programme in India deals with the development of various technologies in this direction. SST-1 machine has been engineered and is being fabricated at the Institute for Plasma Research. The objectives of the machine are to study physics of plasma processes under steady state condition and develop the technologies related to steady state operation. Various sub-systems are being prototyped and developed. SST-1 is a large aspect ratio machine with a major radius of 1.1 m and a plasma minor radius of 0.2 m with elongation of 1.7 to 1.9 and triangularity of 0.5 to 0.7. It has been designed for 1000 sec operation at 3 T toroidal magnetic eld. Neutral beam Injection and Radio frequency heating systems are being developed to heat the plasma. Lower hybrid Current Drive system would sustain 200 kA of plasma current during 1000 sec operation. ADITYA tokamak has been upgraded with new diagnostics and RF heating systems. Thomson Scattering and ECE diagnostics have been operated. 200 kW Ion Cyclotron Resonance Heating (ICRH) and 200 kW Electron Cyclotron Resonance Heating (ECRH) systems have been successfully commissioned. RF assisted initial breakdown experiments have been initiated with these systems. (author)

  7. Low Reynolds number flow in rectangular cooling channels provided with low aspect ratio pin fins

    Energy Technology Data Exchange (ETDEWEB)

    Armellini, Alessandro; Casarsa, Luca [Dipartimento di Energetica e Macchine, Universita di Udine, Via delle Scienze 208, 33100 Udine (Italy); Giannattasio, Pietro, E-mail: pietro.giannattasio@uniud.i [Dipartimento di Energetica e Macchine, Universita di Udine, Via delle Scienze 208, 33100 Udine (Italy)

    2010-08-15

    The flow structures around single heat transfer promoters of different shapes (square, circular, triangular and rhomboidal) have been investigated experimentally by means of a 2-D Particle Image Velocimetry (PIV) technique. The geometrical configuration and flow conditions considered are typical of real liquid cooling channels. They include low aspect ratio pin fins confined at both ends by the walls of a rectangular channel, water flow at low Reynolds numbers (Re = 800, 1800, 2800), high core flow turbulence and undeveloped boundary layers at the position of the obstacle. In front of the pin fins the high turbulence level is found to promote a strong instability of the horseshoe vortex system that forms at the wall/obstacle junction. In particular, frequent events of break-away of the primary vortices and inrush of core fluid, which are known to enhance the wall heat transfer, are observed in the cases of square and circular pins already from Re = 1800. The near wake downstream of the obstacles appears to be influenced by streamwise oriented vortical structures produced at the wall/obstacle junction. They give rise to spanwise velocity components (up-wash flow) that lead to a three-dimensional mass recirculation behind the pins. The combination of up-wash flows, low Reynolds number and high core flow turbulence gives rise to a competition between the classical alternate vortex shedding and an irregular shedding mode characterized by the decoupling of the shear layers and the absence of well organized primary structures. At Re = 800, the irregular shedding prevails and the mean wake topology is almost insensitive to the obstacle shape. As the Reynolds number is increased, the junction flow structures reduce in size and strength, their effect on the wake flow weakens and the recirculation structures behind the obstacles differentiate significantly according to the pin shape. Besides investigating complex flow structures in geometrical and flow configurations of

  8. SUEX process optimization for ultra-thick high-aspect ratio LIGA imaging

    Science.gov (United States)

    Johnson, Donald W.; Goettert, Jost; Singh, Varshni; Yemane, Dawit

    2011-04-01

    oven, taken out and cooled to RT then relaxed up to 3 days before development to reduce stress. Development was done in PGMEA for up to 3 hours for the 1000μm thick samples followed by a short IPA rinse and drying in air. Very high aspect ratios of 100 or more have been routinely patterned with nearly perfectly straight sidewalls (~1-1.5μm deviation for a 1mm tall structure) and excellent image fidelity.

  9. Tunable Microwave Absorption Frequency by Aspect Ratio of Hollow Polydopamine@α-MnO2 Microspindles Studied by Electron Holography.

    Science.gov (United States)

    She, Wen; Bi, Han; Wen, Zhiwei; Liu, Qinghe; Zhao, Xuebing; Zhang, Jie; Che, Renchao

    2016-04-20

    A tunable response frequency is highly desirable for practical applications of microwave absorption materials but remains a great challenge. Here, hollow lightweight polydopamine@α-MnO2 microspindles were facilely synthesized with the tunable absorption frequency governed by the aspect ratio. The size of the hard template is a key factor to achieve the unique shape; the polymer layer with uniform thickness plays an important role in obtaining spindles with homogeneous size. With the aspect ratio increasing, the maximum reflection loss, as well as the absorption bandwidth (<-10 dB), increases and then decreases; meanwhile, the microwave absorption band shifts to the low frequency. The optimized aspect ratio of the cavity about the hollow polydopamine@α-MnO2 microspindles is ∼2.8. With 3 mm thickness at 9.7 GHz, the strongest reflection reaches -21.8 dB, and the width of the absorbing band (<-10 dB) is as wide as 3.3 GHz. Via electron holography, it is confirmed that strong charge accumulates around the interface between the polydopamine and α-MnO2 layers, which mainly contributes to the dielectric polarization absorption. This study proposes a reliable strategy to tune the absorption frequency via different aspect ratio polymer@α-MnO2 microspindles. PMID:27027922

  10. Direct e-beam writing of dense and high aspect ratio nanostructures in thick layers of PMMA for electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Gorelick, Sergey; Guzenko, Vitaliy A; Vila-Comamala, Joan; David, Christian, E-mail: sergey.gorelick@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

    2010-07-23

    Due to the ability of 100 keV electrons to penetrate deep into resist with little scattering, we were able to directly write various dense and high aspect ratio nanostructures in 540 nm and 1.1 {mu}m thick layers of poly(methyl methacrylate) (PMMA) resist. The PMMA molds produced by electron beam lithography were developed using a high contrast developer. The molds were used to transfer the pattern into metallic nanostructures by filling the developed trenches with Au by electroplating. By exposing lines narrower than the target width, we observed improved process latitude and line width control. The obtained aspect ratios of the dense structures are nearly 20 in 1.1 {mu}m PMMA layers and > 16 for structures electroplated into this PMMA mold. The fabrication method was successfully applied to produce Au diffractive x-ray Fresnel zone plates of exceptionally good quality with 50 and 70 nm outermost zones using 540 nm and 1.1 {mu}m thick PMMA molds. In addition, we also produced regular arrays of high aspect ratio and dense Au nanorods with periods down to 100 nm and high aspect ratio split-ring resonators.

  11. Direct e-beam writing of dense and high aspect ratio nanostructures in thick layers of PMMA for electroplating

    Science.gov (United States)

    Gorelick, Sergey; Guzenko, Vitaliy A.; Vila-Comamala, Joan; David, Christian

    2010-07-01

    Due to the ability of 100 keV electrons to penetrate deep into resist with little scattering, we were able to directly write various dense and high aspect ratio nanostructures in 540 nm and 1.1 µm thick layers of poly(methyl methacrylate) (PMMA) resist. The PMMA molds produced by electron beam lithography were developed using a high contrast developer. The molds were used to transfer the pattern into metallic nanostructures by filling the developed trenches with Au by electroplating. By exposing lines narrower than the target width, we observed improved process latitude and line width control. The obtained aspect ratios of the dense structures are nearly 20 in 1.1 µm PMMA layers and > 16 for structures electroplated into this PMMA mold. The fabrication method was successfully applied to produce Au diffractive x-ray Fresnel zone plates of exceptionally good quality with 50 and 70 nm outermost zones using 540 nm and 1.1 µm thick PMMA molds. In addition, we also produced regular arrays of high aspect ratio and dense Au nanorods with periods down to 100 nm and high aspect ratio split-ring resonators.

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

    Directory of Open Access Journals (Sweden)

    Laura Brum Prata

    2003-12-01

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

  13. Fabrication of high aspect ratio TiO2 and Al2O3 nanogratings by atomic layer deposition

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Takayama, Osamu; Michael-Lindhard, Jonas;

    2016-01-01

    The authors report on the fabrication of TiO2 and Al2O3 nanostructured gratings with an aspect ratio of up to 50. The gratings were made by a combination of atomic layer deposition (ALD) and dry etch techniques. The workflow included fabrication of a Si template using deep reactive ion etching...

  14. 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

  15. 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.

  16. Finite-span rotating wings: three-dimensional vortex formation and variations with aspect ratio

    Science.gov (United States)

    Carr, Z. R.; Chen, C.; Ringuette, M. J.

    2013-02-01

    We investigate experimentally the effect of aspect ratio ( [InlineMediaObject not available: see fulltext.] ) on the time-varying, three-dimensional flow structure of flat-plate wings rotating from rest at 45° angle of attack. Plates of [InlineMediaObject not available: see fulltext.] = 2 and 4 are tested in a 50 % by mass glycerin-water mixture, with a total rotation of ϕ = 120° and a matched tip Reynolds number of 5,000. The time-varying, three-component volumetric velocity field is reconstructed using phase-locked, phase-averaged stereoscopic digital particle image velocimetry in multiple, closely-spaced chordwise planes. The vortex structure is analyzed using the {Q}-criterion, helicity density, and spanwise quantities. For both [InlineMediaObject not available: see fulltext.] s, the flow initially consists of a connected and coherent leading-edge vortex (LEV), tip vortex (TV), and trailing-edge vortex (TEV) loop; the LEV increases in size with span and tilts aft. Smaller, discrete vortices are present in the separated shear layers at the trailing and tip edges, which wrap around the primary TEV and TV. After about ϕ = 20°, the outboard-span LEV lifts off the plate and becomes arch-like. A second, smaller LEV and the formation of corner vortex structures follow. For [InlineMediaObject not available: see fulltext.] = 4, the outboard LEV moves farther aft, multiple LEVs form ahead of it, and after about ϕ = 50° a breakdown of the lifted-off LEV and the TV occurs. However, for [InlineMediaObject not available: see fulltext.] = 2, the outboard LEV lift-off is not progressive, and the overall LEV-TV flow remains more coherent and closer to the plate, with evidence of breakdown late in the motion. Inboard of about 50 % span, the [InlineMediaObject not available: see fulltext.] = 4 LEV is stable for the motion duration. Up to approximately 60 % span, the [InlineMediaObject not available: see fulltext.] = 2 LEV is distinct from the TV and is similarly stable

  17. 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

  18. Nanoimprinting ultrasmall and high-aspect-ratio structures by using rubber-toughened UV cured epoxy resist

    International Nuclear Information System (INIS)

    A simple and robust scheme is proposed for the fabrication of nanoscale (20 nm line width) and high-aspect-ratio (9:1) structures by using modulus-tunable UV curable epoxy resists. Additionally, the ability to control the Young’s modulus of the imprinted material from hard to rigiflex using these epoxy resists is demonstrated. The physical properties of the new epoxy resists were controlled by adjusting the ratio of bisphenol F-type epoxy resin and acrylonitrile–butadiene rubber-based epoxy resin in the formulation of the resist. The mechanical properties of the resist were tuned to obtain various aspect ratios as well as mold flexibility for conformal contact over non-planar surfaces and large areas. In order to reduce the line width of the imprinted patterns, a process to conformally coat the mold structure by atomic layer deposition of alumina was also developed. Narrow lines with high-aspect-ratio features and with very low defect density were achieved via the new approach and the high mechanical strength of the new resist formulation. (paper)

  19. Nanoimprinting ultrasmall and high-aspect-ratio structures by using rubber-toughened UV cured epoxy resist

    Science.gov (United States)

    Shin, Young Jae; Wu, Yi-Kuei; Guo, L. Jay

    2013-06-01

    A simple and robust scheme is proposed for the fabrication of nanoscale (20 nm line width) and high-aspect-ratio (9:1) structures by using modulus-tunable UV curable epoxy resists. Additionally, the ability to control the Young’s modulus of the imprinted material from hard to rigiflex using these epoxy resists is demonstrated. The physical properties of the new epoxy resists were controlled by adjusting the ratio of bisphenol F-type epoxy resin and acrylonitrile-butadiene rubber-based epoxy resin in the formulation of the resist. The mechanical properties of the resist were tuned to obtain various aspect ratios as well as mold flexibility for conformal contact over non-planar surfaces and large areas. In order to reduce the line width of the imprinted patterns, a process to conformally coat the mold structure by atomic layer deposition of alumina was also developed. Narrow lines with high-aspect-ratio features and with very low defect density were achieved via the new approach and the high mechanical strength of the new resist formulation.

  20. 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.

  1. The role of plasma rotation on MHD instabilities in tokamaks

    Science.gov (United States)

    Varadarajan, V.; Miley, G. H.

    An improved analysis of the linear stage of the internal kink mode has been developed to include plasma rotation and finite aspect ratio effects. The linear instability growth rates are increased by the plasma rotation. A pseudo-variational, bilinear formalism is used to discretize the linear instability equations; Fourier decomposition is used in the periodic coordinate, and a mixed-finite element procedure is adopted in the radial direction. The numerical studies with the resulting PEST-like code can be used to predict the complex plasma eigenfrequencies. The finite aspect ratio results are similar to the large aspect ratio results for flow instability. The complex instability frequencies found in the 'fishbone' and TAE modes would be strong determined by the large plasma rotation velocities observed in present-day tokamak devices. These effects could be studied by using the computationally convenient bilinear form derived from the Frieman-Rotenberg equation.

  2. 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

  3. Numerical Study of the Effect of the Sample Aspect Ratio on the Ductility of Bulk Metallic Glasses (BMGs) Under Compression

    Science.gov (United States)

    Jiang, Yunpeng

    2016-05-01

    In this article, a systematic numerical study was conducted to study the detailed shear banding evolution in bulk metallic glasses (BMGs) with various sample aspect ratios under uniaxial compression, and whereby the effect of the sample aspect ratio on the compressive ductility was elucidated. A finite strain viscoelastic model was employed to describe the shear banding nucleation, growth, and coalescence in BMG samples with the help of Anand and Su's theory, which was incorporated into the ABAQUS finite element method code as a user material subroutine VUMAT. The present numerical method was first verified by comparing with the corresponding experimental results, and then parameter analysis was performed to discuss the impact of microstructure parameters on the predicted results. The present modeling will shed some light on enhancing the toughness of BMG structures in the engineering applications.

  4. 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.

  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. Wind tunnel tests of high-lift systems for advanced transports using high-aspect-ratio supercritical wings

    Science.gov (United States)

    Allen, J. B.; Oliver, W. R.; Spacht, L. A.

    1982-01-01

    The wind tunnel testing of an advanced technology high lift system for a wide body and a narrow body transport incorporating high aspect ratio supercritical wings is described. This testing has added to the very limited low speed high Reynolds number data base for this class or aircraft. The experimental results include the effects on low speed aerodynamic characteristics of various leading and trailing edge devices, nacelles and pylons, ailerons, and spoilers, and the effects of Mach and Reynolds numbers.

  8. Prediction of CO Concentration and Maximum Smoke Temperature beneath Ceiling in Tunnel Fire with Different Aspect Ratio

    Directory of Open Access Journals (Sweden)

    S. Gannouni

    2016-01-01

    Full Text Available In a tunnel fire, the production of smoke and toxic gases remains the principal prejudicial factors to users. The heat is not considered as a major direct danger to users since temperatures up to man level do not reach tenable situations that after a relatively long time except near the fire source. However, the temperatures under ceiling can exceed the thresholds conditions and can thus cause structural collapse of infrastructure. This paper presents a numerical analysis of smoke hazard in tunnel fires with different aspect ratio by large eddy simulation. Results show that the CO concentration increases as the aspect ratio decreases and decreases with the longitudinal ventilation velocity. CFD predicted maximum smoke temperatures are compared to the calculated values using the model of Li et al. and then compared with those given by the empirical equation proposed by kurioka et al. A reasonable good agreement has been obtained. The backlayering length decreases as the ventilation velocity increases and this decrease fell into good exponential decay. The dimensionless interface height and the region of bad visibility increases with the aspect ratio of the tunnel cross-sectional geometry.

  9. Single macroscopic pillars as model system for bioinspired adhesives: influence of tip dimension, aspect ratio, and tilt angle.

    Science.gov (United States)

    Micciché, Maurizio; Arzt, Eduard; Kroner, Elmar

    2014-05-28

    The goal of our study is to better understand the design parameters of bioinspired dry adhesives inspired by geckos. For this, we fabricated single macroscopic pillars of 400 μm diameter with different aspect ratios and different tip shapes (i.e., flat tips, spherical tips with different radii, and mushroom tips with different diameters). Tilt-angle-dependent adhesion measurements showed that although the tip shape of the pillars strongly influences the pull-off force, the pull-off strength is similar for flat and mushroom-shaped tips. We found no tilt-angle dependency of adhesion for spherical tip structures and, except for high tilt angle and low preload experiments, no tilt-angle effect for mushroom-tip pillars. For flat-tip pillars, we found a strong influence of tilt angle on adhesion, which decreased linearly with increasing aspect ratio. The experiments show that for the tested aspect ratios between 1 and 5, a linear decrease of tilt-angle dependency is found. The results of our studies will help to design bioinspired adhesives for application on smooth and rough surfaces.

  10. Fabrication of high aspect ratio tungsten nanostructures on ultrathin c-Si membranes for extreme UV applications

    Science.gov (United States)

    Delachat, F.; Le Drogoff, B.; Constancias, C.; Delprat, S.; Gautier, E.; Chaker, M.; Margot, J.

    2016-01-01

    In this work, we demonstrate a full process for fabricating high aspect ratio diffraction optics for extreme ultraviolet lithography. The transmissive optics consists in nanometer scale tungsten patterns standing on flat, ultrathin (100 nm) and highly transparent (>85% at 13.5 nm) silicon membranes (diameter of 1 mm). These tungsten patterns were achieved using an innovative pseudo-Bosch etching process based on an inductively coupled plasma ignited in a mixture of SF6 and C4F8. Circular ultra-thin Si membranes were fabricated through a state-of-the-art method using direct-bonding with thermal difference. The silicon membranes were sputter-coated with a few hundred nanometers (100-300 nm) of stress-controlled tungsten and a very thin layer of chromium. Nanoscale features were written in a thin resist layer by electron beam lithography and transferred onto tungsten by plasma etching of both the chromium hard mask and the tungsten layer. This etching process results in highly anisotropic tungsten features at room temperature. The homogeneity and the aspect ratio of the advanced pattern transfer on the membranes were characterized with scanning electron microscopy after focus ion beam milling. An aspect ratio of about 6 for 35 nm size pattern is successfully obtained on a 1 mm diameter 100 nm thick Si membrane. The whole fabrication process is fully compatible with standard industrial semiconductor technology.

  11. 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).

  12. Neoclassical transport in high {beta} tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Cowley, S.C.

    1992-12-01

    Neoclassical, transport in high {beta} large aspect ratio tokamaks is calculated. The variational method introduced by Rosenbluth, et al., is used to calculate the full Onsager matrix in the banana regime. These results are part of a continuing study of the high {beta} large aspect ratio equilibria introduced in Cowley, et al. All the neoclassical coefficients are reduced from their nominal low {beta} values by a factor ({var_epsilon}/q{sup 2}{beta}){sup {1/2}} II. This factor is the ratio of plasma volume in the boundary layer to the volume in the core. The fraction of trapped particles on a given flux surface (f{sub t}) is also reduced by this factor so that {approximately} {sub ({var_epsilon}}/q{sup 2}{beta}){sup {1/2}}. Special attention is given to the current equation, since this is thought to be relevant at low 3 and therefore may also be relevant at high {beta}. The bootstrap current term is found to exceed the actual current by a factor of the square root of the aspect ratio.

  13. Modular coils and finite-β operation of a quasi-axially symmetric tokamak

    International Nuclear Information System (INIS)

    Quasi-axially symmetric tokamaks (QA tokamaks) are an extension of the conventional tokamak concept. In these devices the magnetic field strength is independent of the generalized toroidal magnetic co-ordinate even though the cross-sectional shape changes. An optimized plasma equilibrium belonging to the class of QA tokamaks has been proposed by Nuehrenberg. It features the small aspect ratio of a tokamak while allowing part of the rotational transform to be generated by the external field. In this article, two particular aspects of the viability of QA tokamaks are explored, namely the feasibility of modular coils and the possibility of maintaining quasi-axial symmetry in the free-boundary equilibria obtained with the coils found. A set of easily feasible modular coils for the configuration is presented. It was designed using the extended version of the NESCOIL code (MERKEL, P., Nucl. Fusion 27 (1987) 867). Using this coil system, free-boundary calculations of the plasma equilibrium were carried out using the NEMEC code (HIRSHMAN, S.P., VAN RIJ, W.I., MERKEL, P., Comput. Phys. Commun. 43 (1986) 143). It is observed that the effects of finite β and net toroidal plasma current can be compensated for with good precision by applying a vertical magnetic field and by separately adjusting the currents of the modular coils. A set of fully three dimensional (3-D) auxiliary coils is proposed to exert control on the rotational transform in the plasma. Deterioration of the quasi-axial symmetry induced by the auxiliary coils can be avoided by adequate adjustment of the currents in the primary coils. Finally, the neoclassical transport properties of the configuration are examined. It is observed that optimization with respect to confinement of the alpha particles can be maintained at operation with finite toroidal current if the aforementioned corrective measures are used. In this case, the neoclassical behaviour is shown to be very similar to that of a conventional tokamak

  14. KTM Tokamak is prototype of X XI century reactor. Future International laboratory of thermonuclear materials testing and power engineering

    International Nuclear Information System (INIS)

    In 29-31 May of 2000 the presentation of the joint Kazakhstan-Russian draft of Kazakhstan material-testing tokamak (KTM) was carried out. KTM tokamak is implementing by decision of the President and Government of Republic of Kazakhstan for supporting of the Kazakhstan participation in development of draft within framework of ITER fusion reactor construction. Scientific head of the project is Russian academician - Velikhov V. and Russian Research Center 'Kurchatovskij Institute' , General designers - Scientific Research Institute for Electrophysical Equipment after D. V. Efremov (Russian Federation) and Kazakh Research Inst. for Energy Industry (KazNIIEhnergoprom). Scientific part of the project is working out in National Nuclear Center of Republic of Kazakhstan and Scientific Research Institute of Experimental and Theoretical Physics. KTM tokamak is experimental fusion device for materials testing study, as well as for designing of methods for protection of the reactor first wall, in-chamber elements and divertor planes, high frequency heat of antennas in energetic load regimes close to both the ITER and the future fusion energy reactors. KTM by it design presents spheric tokamak, which successfully combining advantages of the spheromaks (compactness) and the tokamaks (high plasma density). Now in the world there are similar operating spheric tokamaks: NSTX (USA), MAST (Great Britain), GLOBUS-M (Russian Federation). Principal peculiarity of KTM tokamak is existence of moving divertor device, which with help of manipulator allows to changing of examining samples without high vacuum disruption. Values of the thermal loads and fluences in the KTM are equal or higher than loads in operating tokamaks and correspond with ITER reactor loads. KTM tokamak will be the only mega-ampere device in the world with the aspect ratio A=2

  15. Analytical solutions for Tokamak equilibria with reversed toroidal current

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Caroline G. L.; Roberto, M.; Braga, F. L. [Departamento de Fisica, Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, Sao Paulo 12228-900 (Brazil); Caldas, I. L. [Instituto de Fisica, Universidade de Sao Paulo, 05315-970 Sao Paulo, SP (Brazil)

    2011-08-15

    In tokamaks, an advanced plasma confinement regime has been investigated with a central hollow electric current with negative density which gives rise to non-nested magnetic surfaces. We present analytical solutions for the magnetohydrodynamic equilibria of this regime in terms of non-orthogonal toroidal polar coordinates. These solutions are obtained for large aspect ratio tokamaks and they are valid for any kind of reversed hollow current density profiles. The zero order solution of the poloidal magnetic flux function describes nested toroidal magnetic surfaces with a magnetic axis displaced due to the toroidal geometry. The first order correction introduces a poloidal field asymmetry and, consequently, magnetic islands arise around the zero order surface with null poloidal magnetic flux gradient. An analytic expression for the magnetic island width is deduced in terms of the equilibrium parameters. We give examples of the equilibrium plasma profiles and islands obtained for a class of current density profile.

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

    Science.gov (United States)

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

    2013-10-18

    Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device. PMID:24027171

  17. Near-wake flow structure of elliptic cylinders close to a free surface: effect of cylinder aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Daichin, Sang Joon Lee [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, 790-784, Nam-gu, Pohang (Korea)

    2004-05-01

    The flow fields behind elliptic cylinders adjacent to a free surface were investigated experimentally in a circulating water channel. A range of cylinder aspect ratios (AR=2, 3, 4) were considered, while the cross-sectional area of the elliptical cylinder was kept constant. The main objective of this study was to investigate the effect of cylinder aspect ratio and a free surface on the flow structure in the near-wake behind elliptic cylinders. For each elliptic cylinder, the flow structure was analyzed for various values of the submergence depth of the cylinder beneath the free surface. The flow fields were measured using a single-frame double-exposure PIV (Particle Image Velocimetry) system. For each experimental condition, 350 instantaneous velocity fields were obtained and ensemble-averaged to obtain the mean velocity field and spatial distribution of the mean vorticity statistics. The results show that near-wake can be classified into three typical flow patterns: formation of a Coanda flow, generation of substantial jet-like flow, and attachment of this jet flow to the free surface. The general flow structure observed behind the elliptic cylinders resembles the structure previously reported for a circular cylinder submerged near a free surface. However, the wake width and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder differ from those observed for a circular cylinder. These trends are enhanced as cylinder aspect ratio is increased. In addition, the free surface distortion is also discussed in the paper. (orig.)

  18. Near-wake flow structure of elliptic cylinders close to a free surface: effect of cylinder aspect ratio

    Science.gov (United States)

    Daichin, K. V.; Lee, Sang Joon

    The flow fields behind elliptic cylinders adjacent to a free surface were investigated experimentally in a circulating water channel. A range of cylinder aspect ratios (AR=2, 3, 4) were considered, while the cross-sectional area of the elliptical cylinder was kept constant. The main objective of this study was to investigate the effect of cylinder aspect ratio and a free surface on the flow structure in the near-wake behind elliptic cylinders. For each elliptic cylinder, the flow structure was analyzed for various values of the submergence depth of the cylinder beneath the free surface. The flow fields were measured using a single-frame double-exposure PIV (Particle Image Velocimetry) system. For each experimental condition, 350 instantaneous velocity fields were obtained and ensemble-averaged to obtain the mean velocity field and spatial distribution of the mean vorticity statistics. The results show that near-wake can be classified into three typical flow patterns: formation of a Coanda flow, generation of substantial jet-like flow, and attachment of this jet flow to the free surface. The general flow structure observed behind the elliptic cylinders resembles the structure previously reported for a circular cylinder submerged near a free surface. However, the wake width and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder differ from those observed for a circular cylinder. These trends are enhanced as cylinder aspect ratio is increased. In addition, the free surface distortion is also discussed in the paper.

  19. UV activation of polymeric high aspect ratio microstructures: ramifications in antibody surface loading for circulating tumor cell selection.

    Science.gov (United States)

    Jackson, Joshua M; Witek, Małgorzata A; Hupert, Mateusz L; Brady, Charles; Pullagurla, Swathi; Kamande, Joyce; Aufforth, Rachel D; Tignanelli, Christopher J; Torphy, Robert J; Yeh, Jen Jen; Soper, Steven A

    2014-01-01

    The need to activate thermoplastic surfaces using robust and efficient methods has been driven by the fact that replication techniques can be used to produce microfluidic devices in a high production mode and at low cost, making polymer microfluidics invaluable for in vitro diagnostics, such as circulating tumor cell (CTC) analysis, where device disposability is critical to mitigate artifacts associated with sample carryover. Modifying the surface chemistry of thermoplastic devices through activation techniques can be used to increase the wettability of the surface or to produce functional scaffolds to allow for the covalent attachment of biologics, such as antibodies for CTC recognition. Extensive surface characterization tools were used to investigate UV activation of various surfaces to produce uniform and high surface coverage of functional groups, such as carboxylic acids in microchannels of different aspect ratios. We found that the efficiency of the UV activation process is highly dependent on the microchannel aspect ratio and the identity of the thermoplastic substrate. Colorimetric assays and fluorescence imaging of UV-activated microchannels following EDC/NHS coupling of Cy3-labeled oligonucleotides indicated that UV-activation of a PMMA microchannel with an aspect ratio of ~3 was significantly less efficient toward the bottom of the channel compared to the upper sections. This effect was a consequence of the bulk polymer's damping of the modifying UV radiation due to absorption artifacts. In contrast, this effect was less pronounced for COC. Moreover, we observed that after thermal fusion bonding of the device's cover plate to the substrate, many of the generated functional groups buried into the bulk rendering them inaccessible. The propensity of this surface reorganization was found to be higher for PMMA compared to COC. As an example of the effects of material and microchannel aspect ratios on device functionality, thermoplastic devices for the

  20. Subsonic and transonic pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces

    Science.gov (United States)

    Sandford, M. C.; Ricketts, R. H.; Watson, J. J.

    1981-01-01

    A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form.

  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. 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

  3. The Effect of Aspect Ratio and Angle of Attack on the Transition Regions of the Inverted Flag Instability

    Science.gov (United States)

    Cosse, Julia; Sader, John; Fan, Boyu; Kim, Daegyoum; Gharib, Mory

    2014-11-01

    The inverted flag instability occurs when a pliable plate is held parallel to a free-stream, with the leading edge free to move and the trailing edge clamped. Large-amplitude flapping is observed across a slim band of non-dimensional wind speeds. This specific boundaries of this flapping band vary greatly, depending on both the aspect ratio and the angle of attack of the plate with respect to the incoming flow. In addition, both periodic and aperiodic flapping modes exist. The frequency of the plate motion was analyzed and was found to be consistent with vortex-induced vibration. This research is supported by the Gordon and Betty Moore Foundation.

  4. Aspect-Ratio Dependent Electron Transport and Recombination in Dye-Sensitized Solar Cells fabricated with one-dimensional ZnO nanostructures

    International Nuclear Information System (INIS)

    Highlights: • Investigated the aspect ratio dependence on electron transport proerties of ZnO. • Longer ZnO nanords showed better solar cell performance. • Low aspect ratio ZnO exhibit better light scattering effect. - Abstract: Though one-dimensional (1-D) ZnO nanrods are promising transport electron transport material in the photoanode of Dye Sensitized Solar Cells (DSSC), 1-D ZnO nanorod based DSSCs exhibit poor energy conversion efficiencies. In this study, DSSCs were fabricated with 1-D ZnO nanorods having different aspect ratio and the dependence of solar cell performance on aspect ratio of ZnO nanorods was investigated. Photoanodes fabricated with different 1-D ZnO nanorods having aspect ratios of 4.4, 5.4, 5.8, 6.8 and 7.6 showed increasing solar cell performance with the increase of aspect ratio where 2.1 and 4.7% light conversion efficiencies were observed respectively for the lowest and highest aspect ratio of 1-D ZnO nanostructures. We study the electrical and operational differences between DSSC made with ZnO nanostructures with different aspect ratio. Electrochemical impedance spectroscopy (EIS) is used to quantify the aspect ratio depended electron transport properties, charge recombination, life-time and charge diffusion lengths of excited electrons in 1D ZnO nanorods and electron transport properties are correlated to the observed cell performance. In addition, effect of aspect ratio of ZnO nanorods on dye loading amount and light scattering properties were also investigated

  5. Implications of rf current drive theory for next step steady-state tokamak design

    International Nuclear Information System (INIS)

    Two missions have been identified for a next-step tokamak experiment in the United States. The more ambitious Mission II device would be a superconducting tokamak, capable of doing long-pulse ignition demonstrations, and hopefully capable of also being able to achieve steady-state burn. A few interesting lines of approach have been identified, using a combination of logical design criteria and parametric system scans [SC85]. These include: (1) TIBER: A point-design suggested by Lawrence Livermore, that proposes a machine with the capability of demonstrating ignition, high beta (10%) and high Q (=10), using high frequency, fast-wave current drive. The TIBER topology uses moderate aspect ratio and high triangularity to achieve high beta. (2) JET Scale-up. (3) Magic5: It is argued here that an aspect ratio of 5 is a magic number for a good steady-state current drive experiment. A moderately-sized machine that achieves ignition and is capable of high Q, using either fast wave or slow wave current drive is described. (4) ET-II: The concept of a highly elongated tokamak (ET) was first proposed as a low-cost approach to Mission I, because of the possibility of achieving ohmic ignition with low-stress copper magnets. We propose that its best application is really for commercial tokamaks, using fast-wave current drive, and suggest a Mission II experiment that would be prototypical of such a reactor

  6. Fabrication of a high aspect ratio thick silicon wafer mold and electroplating using flipchip bonding for MEMS applications

    Science.gov (United States)

    Kim, Bong-Hwan; Kim, Jong-Bok

    2009-06-01

    We have developed a microfabrication process for high aspect ratio thick silicon wafer molds and electroplating using flipchip bonding with THB 151N negative photoresist (JSR micro). This fabrication technique includes large area and high thickness silicon wafer mold electroplating. The process consists of silicon deep reactive ion etching (RIE) of the silicon wafer mold, photoresist bonding between the silicon mold and the substrate, nickel electroplating and a silicon removal process. High thickness silicon wafer molds were made by deep RIE and flipchip bonding. In addition, nickel electroplating was developed. Dry film resist (ORDYL MP112, TOK) and thick negative-tone photoresist (THB 151N, JSR micro) were used as bonding materials. In order to measure the bonding strength, the surface energy was calculated using a blade test. The surface energy of the bonding wafers was found to be 0.36-25.49 J m-2 at 60-180 °C for the dry film resist and 0.4-1.9 J m-2 for THB 151N in the same temperature range. Even though ORDYL MP112 has a better value of surface energy than THB 151N, it has a critical disadvantage when it comes to removing residue after electroplating. The proposed process can be applied to high aspect ratio MEMS structures, such as air gap inductors or vertical MEMS probe tips.

  7. Fabrication of a high aspect ratio thick silicon wafer mold and electroplating using flipchip bonding for MEMS applications

    International Nuclear Information System (INIS)

    We have developed a microfabrication process for high aspect ratio thick silicon wafer molds and electroplating using flipchip bonding with THB 151N negative photoresist (JSR micro). This fabrication technique includes large area and high thickness silicon wafer mold electroplating. The process consists of silicon deep reactive ion etching (RIE) of the silicon wafer mold, photoresist bonding between the silicon mold and the substrate, nickel electroplating and a silicon removal process. High thickness silicon wafer molds were made by deep RIE and flipchip bonding. In addition, nickel electroplating was developed. Dry film resist (ORDYL MP112, TOK) and thick negative-tone photoresist (THB 151N, JSR micro) were used as bonding materials. In order to measure the bonding strength, the surface energy was calculated using a blade test. The surface energy of the bonding wafers was found to be 0.36–25.49 J m−2 at 60–180 °C for the dry film resist and 0.4–1.9 J m−2 for THB 151N in the same temperature range. Even though ORDYL MP112 has a better value of surface energy than THB 151N, it has a critical disadvantage when it comes to removing residue after electroplating. The proposed process can be applied to high aspect ratio MEMS structures, such as air gap inductors or vertical MEMS probe tips

  8. Three-dimensional wake topology and propulsive performance of low-aspect-ratio pitching-rolling plates

    Science.gov (United States)

    Li, Chengyu; Dong, Haibo

    2016-07-01

    The wake topology and propulsive performance of low-aspect-ratio plates undergoing a pitching-rolling motion in a uniform stream were numerically investigated by an in-house immersed-boundary-method-based incompressible Navier-Stokes equation solver. A detailed analysis of the vortical structures indicated that the pitching-rolling plate produced double-loop vortices with alternating signs from its trailing edge every half period. These vortices then shed and further evolved into interconnected "double-C"-shaped vortex rings, which eventually formed a bifurcating wake pattern in the downstream. As the wake convected downstream, there was a slight deflection in the spanwise direction to the plate tip, and the contained vortex ring size gradually increased. In addition, the analysis of the propulsive performance indicated that the shedding process of the double-loop vortices led to two peaks in the lift and thrust force production per half cycle. The observation of the double peaks in the force production is in agreement with previous flapping wing studies. Simulations were also used to examine the variations in the wake structures and propulsive performance of the plates over a range of major parameters. The aforementioned vortex structures were found to be quite robust over a range of Strouhal numbers, Reynolds numbers, and plate aspect ratios.

  9. Fast fabrication of a high-aspect-ratio, self-ordered nanoporous alumina membrane by using high-field anodization

    International Nuclear Information System (INIS)

    A series of processes for the fast fabrication of nanoporous anodic alumina membranes with high-aspect-ratio, self-ordered pore arrays was developed based on a high-field 2-step anodization in a 0.3 M oxalic electrolyte. The dielectric breakdown commonly driven by the high electric field was circumvented by using a linear sweep of the initial voltage from 0 to 140 V, followed by a constant voltage of 140 V for the first step and by using a controlled growth rate that was adjusted by varying the electrolyte concentration while applying an instantaneous constant voltage of 140 V for the second step. A thick nanoporous film of about 120 um was grown within 2 hours with an average interpore distance of 310 nm and an average pore size of 50 nm, where the aspect ratio of the pores was over 2000. In order to overcome the problems associated with a thick barrier layer formed during the high-field anodization, we applied a pulsed electrochemical detachment technique to remove the base Al metal. A through-hole membrane with a pore size of about 210 nm was fabricated after widening the pores through a chemical etching of the pore walls. These novel processes ensure reliable fabrication of a high-field nanoporous anodic alumina membrane and provide a new template for nano-scale research.

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

    Science.gov (United States)

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

    2008-10-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-04-01

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

  13. Application of toroidal multipoles to facilitate tokamak reactor studies

    International Nuclear Information System (INIS)

    A method of calculating the vacuum magnetic flux for plasma equilibrium over a range of aspect ratio A and major radius R is presented. Toroidal multipoles are used to fit the vacuum flux for a set of reference equilibria and the fitted moments are then used to parametrize the flux over the design space in A and R. An example is given in which the equilibrium flux for a D-shaped tokamak plasma is predicted and compared with the actual equilibrium code vacuum flux

  14. Simulations of edge and scrape off layer turbulence in mega ampere spherical tokamak plasmas

    DEFF Research Database (Denmark)

    Militello, F; Fundamenski, W; Naulin, Volker;

    2012-01-01

    The L-mode interchange turbulence in the edge and scrape-off-layer (SOL) of the tight aspect ratio tokamak MAST is investigated numerically. The dynamics of the boundary plasma are studied using the 2D drift-fluid code ESEL, which has previously shown good agreement with large aspect ratio machines...... of the edge/SOL density and temperature. In addition, we also discuss how the system changes when the length of the divertor leg is modified. This allows one to better understand the regime of operation of the Super-X divertor which will be implemented on MAST-Upgrade. The results obtained qualitatively agree...

  15. Equilibrium reconstruction in the START tokamak

    Science.gov (United States)

    Appel, L. C.; Bevir, M. K.; Walsh, M. J.

    2001-02-01

    The computation of magnetic equilibria in the START spherical tokamak is more difficult than those in more conventional large aspect ratio tokamaks. This difficulty arises partly as a result of the use of induction compression to generate high current plasma, as this precludes the positioning of magnetic diagnostics close to the outboard side of the plasma. In addition, the effect of a conducting wall with a high, but finite, conductivity must be included. A method is presented for obtaining plasma equilibrium reconstructions based on the EFIT code. New constraints are used to relate isoflux surface locations deduced from radial profile measurements of electron temperature. A model of flux diffusion through the vessel wall is developed. It is shown that neglecting flux diffusion in the vessel wall can lead to a significant underestimate in the calculation of the plasma βt. Using a relatively sparse set of magnetic signals, βt can be obtained to within a fractional error of +/-10%. Using constraints to relate isoflux surface locations, the principle involved in determining the internal q profile is demonstrated.

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

    Science.gov (United States)

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

    2013-05-01

    In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (dilatant and pseudoplastic fluids) is investigated for cases of finite aspect ratios. The study is conducted numerically using the lattice Boltzmann method (LBM). In many industrial applications, the apparatuses and installations drift away from the idealized case of an annulus of infinite length, and thus the end caps effect can no longer be ignored. The inner cylinder is rotating while the outer one and the end walls are maintained at rest. The lattice two-dimensional nine-velocity (D2Q9) Boltzmann model developed from the Bhatnagar-Gross-Krook approximation is used to obtain the flow field for fluids obeying the power-law model. The combined effects of the Reynolds number, the radius ratio, and the power-law index n on the flow characteristics are analyzed for an annular space of finite aspect ratio. Two flow modes are obtained: a primary Couette flow (CF) mode and a secondary Taylor vortex flow (TVF) mode. The flow structures so obtained are different from one mode to another. The critical Reynolds number Re(c) 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. PMID:23767615

  17. 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.

  18. Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses

    DEFF Research Database (Denmark)

    Stöhr, Frederik; Michael-Lindhard, Jonas; Hübner, Jörg;

    2015-01-01

    This article describes the realization of complex high-aspect ratio silicon structures with feature dimensions from 100 lm to 100nm by deep reactive ion etching using the Bosch process. As the exact shape of the sidewall profiles can be crucial for the proper functioning of a device, the authors...... investigated how sacrificial structures in the form of guarding walls and pillars may be utilized to facilitate accurate control of the etch profile. Unlike other sacrificial structuring approaches, no silicon-on-insulator substrates or multiple lithography steps are required. In addition, the safe removal of...... the sacrificial structures was accomplished by thermal oxidation and subsequent selective wet etching. The effects of the dimensions and relative placement of sacrificial walls and pillars on the etching result were determined through systematic experiments. The authors applied this process for exact...

  19. High fidelity replication of surface texture and geometric form of a high aspect ratio aerodynamic test component

    Science.gov (United States)

    Walton, Karl; Fleming, Leigh; Goodhand, Martin; Racasan, Radu; Zeng, Wenhan

    2016-06-01

    This paper details, assesses and validates a technique for the replication of a titanium wind tunnel test aerofoil in polyurethane resin. Existing resin replication techniques are adapted to overcome the technical difficulties associated with casting a high aspect ratio component. The technique is shown to have high replication fidelity over all important length-scales. The blade chord was accurate to 0.02%, and the maximum blade thickness was accurate to 2.5%. Important spatial and amplitude areal surface texture parameter were accurate to within 2%. Compared to an existing similar system using correlation areal parameters the current technique is shown to have lower fidelity and this difference is discussed. The current technique was developed for the measurement of boundary layer flow ‘laminar to turbulent’ transition for gas turbine compressor blade profiles and this application is illustrated.

  20. Breakdown of the large-scale wind in aspect ratio \\Gamma=1/2 rotating Rayleigh-B\\'enard flow

    CERN Document Server

    Stevens, Richard J A M; Lohse, Detlef

    2011-01-01

    Rotating Rayleigh-B\\'enard (RB) convection experiments and simulations performed have revealed that rotation increases the heat transport by changing the flow structure from a regime dominated by a large-scale circulation (LSC) at no or weak rotation, to a regime dominated by vertically-aligned vortices at strong rotation. For an aspect ratio of the sample of \\Gamma=1 the transition between the two regimes is indicated by a strong decrease in the relative LSC strength. Recently, Weiss and Ahlers, J. Fluid Mech., in press (2011), showed that in contrast in a \\Gamma=1/2 sample the relative LSC strength does not seem to decrease when the heat transport enhancement sets in. Here we show that this is due to the formation of a two-vortex state, in which one vortex extends vertically from the bottom into the sample interior and brings up warm fluid, while another vortex brings down cold fluid from the top.

  1. Superior Na-ion storage properties of high aspect ratio SnSe nanoplates prepared by a spray pyrolysis process

    Science.gov (United States)

    Park, Gi Dae; Lee, Jong-Heun; Kang, Yun Chan

    2016-06-01

    SnSe nanoplates with thin and uniform morphology are prepared by one-pot spray pyrolysis, and are examined as anode materials for Na-ion batteries. During the spray pyrolysis process, metallic Se and Sn are prepared from SeO2 and SnO2, respectively, under a reducing atmosphere. Metallic Sn and metalloid Se, with melting points of 232 and 221 °C, respectively, form a melted Sn-Se mixture, which reacts exothermally to form SnSe nanocrystals. Several of these nanocrystals are grown simultaneously forming a micron-sized powder. Complete elimination of the excess amount of metalloid Se, by forming H2Se gas, results in aggregation-free SnSe nanoplates. The aspect ratio of these nanoplates is as high as 11.3. The discharge capacities for the SnSe nanoplates, prepared from spray solutions containing 100, 400, and 800% of the stoichiometric SeO2 content needed to form SnSe, are 407, 558, and 211 mA h g-1, respectively, after 50 cycles at a constant current density of 0.3 A g-1 their capacity retentions calculated from the second cycle onwards are 77, 100, and 60%, respectively. The phase pure SnSe nanoplates with a high aspect ratio show good cycling and rate performances for Na-ion storage.SnSe nanoplates with thin and uniform morphology are prepared by one-pot spray pyrolysis, and are examined as anode materials for Na-ion batteries. During the spray pyrolysis process, metallic Se and Sn are prepared from SeO2 and SnO2, respectively, under a reducing atmosphere. Metallic Sn and metalloid Se, with melting points of 232 and 221 °C, respectively, form a melted Sn-Se mixture, which reacts exothermally to form SnSe nanocrystals. Several of these nanocrystals are grown simultaneously forming a micron-sized powder. Complete elimination of the excess amount of metalloid Se, by forming H2Se gas, results in aggregation-free SnSe nanoplates. The aspect ratio of these nanoplates is as high as 11.3. The discharge capacities for the SnSe nanoplates, prepared from spray solutions

  2. 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.

  3. Estimation of Particle Size Distribution and Aspect Ratio of Non-Spherical Particles From Chord Length Distribution

    CERN Document Server

    Agimelen, Okpeafoh S; Vasile, Massimiliano; Nordon, Alison; Haley, Ian; Mulholland, Anthony J

    2014-01-01

    Information about size and shape of particles produced in various manufacturing processes is very important for process and product development because design of downstream processes as well as final product properties strongly depend on these geometrical particle attributes. However, recovery of particle size and shape information in situ during crystallisation processes has been a major challenge. The focused beam reflectance measurement (FBRM) provides the chord length distribution (CLD) of a population of particles in a suspension flowing close to the sensor window. Recovery of size and shape information from the CLD requires a model relating particle size and shape to its CLD as well as solving the corresponding inverse problem. This paper presents a comprehensive algorithm which produces estimates of particle size distribution and particle aspect ratio from measured CLD data. While the algorithm searches for a global best solution to the inverse problem without requiring further a priori information on ...

  4. Propagation delay and power dissipation for different aspect ratio of single-walled carbon nanotube bundled TSV

    Science.gov (United States)

    Goyal, Tanu; Majumder, Manoj Kumar; Kaushik, Brajesh Kumar

    2015-06-01

    Through-silicon vias (TSVs) have provided an attractive solution for three-dimensional (3D) integrated devices and circuit technologies with reduced parasitic losses and power dissipation, higher input-output (I/O) density and improved system performance. This paper investigates the propagation delay and average power dissipation of single-walled carbon nanotube bundled TSVs having different via radius and height. Depending on the physical configuration, a comprehensive and accurate analytical model of CNT bundled TSV is employed to represent the via (vertical interconnect access) line of a driver-TSV-load (DTL) system. The via radius and height are used to estimate the bundle aspect ratio (AR) and the cross-sectional area. For a fixed via height, the delay and the power dissipation are reduced up to 96.2% using a SWCNT bundled TSV with AR = 300 : 1 in comparison to AR = 6 : 1.

  5. On the role of a tape's aspect ratio in the hysteresis losses of round superconducting cables

    Energy Technology Data Exchange (ETDEWEB)

    Stenvall, A [Electromagnetics, Tampere University of Technology, PO Box 692, FIN-33101 Tampere (Finland); Grilli, F; Vojenciak, M, E-mail: antti.stenvall@tut.fi [Karlsruhe Institute of Technology, Institute for Technical Physics, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2011-08-15

    Individual superconductors are made small to allow flexible manufacturing and low AC losses. When high currents are needed, several conductors are cabled together. These cables can be used to wind magnets or to transmit huge currents in electric power lines with very low losses. In DC use, the superconductor in these cables is lossless, but when the current or external magnetic field varies, AC losses arise in the cables. If a round cable is made of several flat tapes, the aspect ratio of the tape ({alpha} = width/thickness) plays an important role in the AC losses. Tapes with high {alpha} should be put as close to each other as possible in order to form a superconducting cylinder to reduce the hysteresis losses. However, if {alpha} is around 10, it is no longer evident what kind of configuration results in the lowest losses. When {alpha} approaches 1, the minimum losses are reached when the tapes do not interact at all. YBCO coated conductors have high {alpha}, but Bi-based conductors and MgB{sub 2} should not be forgotten. These can offer completely different values of {alpha} and thus show different behaviours under AC conditions. In this paper we study how the hysteresis losses of round cables are influenced by the tapes' aspect ratios. We investigate whether it is beneficial to pack the conductors tightly together or to let them operate individually, or whether an intermediate state is preferred. According to the results, there is a break-even {alpha} where the tight packing surpasses the individual operation, but the intermediate positioning can result in even lower losses in some cases.

  6. Atmospheric pressure ionization waves propagating through a flexible high aspect ratio capillary channel and impinging upon a target

    International Nuclear Information System (INIS)

    Atmospheric pressure ionization waves (IWs) propagating in flexible capillary tubes are a unique way of transporting a plasma and its active species to remote sites for applications such as biomedical procedures, particularly in endoscopic procedures. The propagation mechanisms for such IWs in tubes having aspect ratios of hundreds to thousands are not clear. In this paper, results are discussed from a numerical investigation of the fundamental properties of ionization waves generated by nanosecond voltage pulses inside a 15 cm long, 600 µm wide (aspect ratio 250), flexible dielectric channel. The channel, filled with a Ne/Xe = 99.9/0.1 gas mixture at 1 atm, empties into a small chamber separated from a target substrate by 1 cm. The IWs propagate through the entire length of the channel while maintaining similar strength and magnitude. Upon exiting the channel into the chamber, the IW induces a second streamer discharge at the channel–chamber junction. This streamer then propagates across the chamber and impinges upon the target. The average speeds of the capillary-bounded IW are about 5 × 107 cm s−1 and 1 × 108 cm s−1 for positive and negative polarities, respectively. The propagation speed is sensitive to the curvature of the channel. In both cases, the peak in ionization tends to be located along the channel walls and alternates from side-to-side depending on the direction of the local instantaneous electric field and curvature of the channel. The ionization region following the IW extends up to several centimeters inside the channel, as opposed to being highly localized at the ionization front in unconstrained, atmospheric pressure IWs. The maximum speed of the IW in the chamber is about twice that in the channel. (paper)

  7. Study on morphology of high-aspect-ratio grooves fabricated by using femtosecond laser irradiation and wet etching

    International Nuclear Information System (INIS)

    Highlights: • We studied morphologies of silicon grooves fabricated by laser irradiation and wet etching. • We found nano-ripple structures formed on the groove sidewall. • Formations of nano-ripples were due to the formation of standing wave and nanoplanes. • Remaining debris on the groove bottom was removed by KOH etching. - Abstract: Morphologies of high-aspect-ratio silicon grooves fabricated by using femtosecond laser irradiation and selective chemical etching of hydrofluoric acid (HF) were studied. Oxygen was deeply doped into silicon under femtosecond laser irradiation in air, and then the oxygen-doped regions were removed by HF etching to form high-aspect-ratio grooves. After HF etching, periodic nano-ripples which were induced in silicon by femtosecond laser were observed on the groove sidewalls. The ripple orientation was perpendicular or parallel to the laser propagation direction (z direction), which depended on the relative direction between the laser polarization direction and the scanning direction. The formation of nano-ripples with orientations perpendicular to z direction could be attributed to the standing wave generated by the interference of the incident light and the reflected light in z direction. The formation of nano-ripples with orientations parallel to z direction could be attributed to the formation of self-organized periodic nanoplanes (bulk nanogratings) induced by femtosecond laser inside silicon. Materials in the tail portion of laser-induced oxygen doping (LIOD) regions were difficult to be etched by HF solution due to low oxygen concentration. The specimen was etched further in KOH solution to remove remaining materials in LIOD regions and all-silicon grooves were fabricated

  8. Effects of the aspect ratio on the dye adsorption of ZnO nanorods grown by using a sonochemical method for dye-sensitized solar cells

    Science.gov (United States)

    Choi, Seok Cheol; Yun, Won Suk; Sohn, Sang Ho; Oh, Sang Jin

    2012-11-01

    Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the effects of their aspect ratios on the dye adsorption in DSSCs were studied. The control of the aspect ratio of well-aligned ZnO nanorods was performed by tuning the mole concentration of zinc acetate dehydrate in the range of 0.04-0.06M. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Visible absorbance by using the Beer-Lambert law. The efficiency of DSSCs with ZnO nanorods was measured to investigate the effects of the aspect ratio of the ZnO nanorods on the dye adsorption properties. A change in the aspect ratio of the ZnO nanorods was founded to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

  9. Influence of the aspect ratio and boundary conditions on universal finite-size scaling functions in the athermal metastable two-dimensional random field Ising model.

    Science.gov (United States)

    Navas-Portella, Víctor; Vives, Eduard

    2016-02-01

    This work studies universal finite size scaling functions for the number of one-dimensional spanning avalanches in a two-dimensional (2D) disordered system with boundary conditions of different nature and different aspect ratios. To this end, we will consider the 2D random field Ising model at T=0 driven by the external field H with athermal dynamics implemented with periodic and forced boundary conditions. We have chosen a convenient scaling variable z that accounts for the deformation of the distance to the critical point caused by the aspect ratio. In addition, assuming that the dependence of the finite size scaling functions on the aspect ratio can be accounted for by an additional multiplicative factor, we have been able to collapse data for different system sizes, different aspect ratios, and different types of the boundary conditions into a single scaling function Q̂. PMID:26986310

  10. Comparison of bootstrap current and plasma conductivity models applied in a self-consistent equilibrium calculation for Tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Maria Celia Ramos; Ludwig, Gerson Otto [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: mcr@plasma.inpe.br

    2004-07-01

    Different bootstrap current formulations are implemented in a self-consistent equilibrium calculation obtained from a direct variational technique in fixed boundary tokamak plasmas. The total plasma current profile is supposed to have contributions of the diamagnetic, Pfirsch-Schlueter, and the neoclassical Ohmic and bootstrap currents. The Ohmic component is calculated in terms of the neoclassical conductivity, compared here among different expressions, and the loop voltage determined consistently in order to give the prescribed value of the total plasma current. A comparison among several bootstrap current models for different viscosity coefficient calculations and distinct forms for the Coulomb collision operator is performed for a variety of plasma parameters of the small aspect ratio tokamak ETE (Experimento Tokamak Esferico) at the Associated Plasma Laboratory of INPE, in Brazil. We have performed this comparison for the ETE tokamak so that the differences among all the models reported here, mainly regarding plasma collisionality, can be better illustrated. The dependence of the bootstrap current ratio upon some plasma parameters in the frame of the self-consistent calculation is also analysed. We emphasize in this paper what we call the Hirshman-Sigmar/Shaing model, valid for all collisionality regimes and aspect ratios, and a fitted formulation proposed by Sauter, which has the same range of validity but is faster to compute than the previous one. The advantages or possible limitations of all these different formulations for the bootstrap current estimate are analysed throughout this work. (author)

  11. Non-Axisymmetric Shaping of Tokamaks Preserving Quasi-Axisymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Long-Poe Ku and Allen H. Boozer

    2009-06-05

    If quasi-axisymmetry is preserved, non-axisymmetric shaping can be used to design tokamaks that do not require current drive, are resilient to disruptions, and have robust plasma stability without feedback. Suggestions for addressing the critical issues of tokamaks can only be validated when presented with sufficient specificity that validating experiments can be designed. The purpose of this paper is provide that specificity for non-axisymmetric shaping. To our knowledge, no other suggestions for the solution of a number of tokamak issues, such as disruptions, have reached this level of specificity. Sequences of three-field-period quasi-axisymmetric plasmas are studied. These sequences address the questions: (1) What can be achieved at various levels of non-axisymmetric shaping? (2) What simplifications to the coils can be achieved by going to a larger aspect ratio? (3) What range of shaping can be achieved in a single experimental facility? The sequences of plasmas found in this study provide a set of interesting and potentially important configurations.

  12. Effect of the Shafranov shift and the gradient of $\\beta$ on intrinsic momentum transport in up-down asymmetric tokamaks

    CERN Document Server

    Ball, Justin; Lee, Jungpyo; Cerfon, Antoine J

    2016-01-01

    Tokamaks with up-down asymmetric poloidal cross-sections spontaneously rotate due to turbulent transport of momentum. In this work, we investigate the effect of the Shafranov shift on this intrinsic rotation, primarily by analyzing tokamaks with tilted elliptical flux surfaces. By expanding the Grad-Shafranov equation in the large aspect ratio limit we calculate the magnitude and direction of the Shafranov shift in tilted elliptical tokamaks. The results show that, while the Shafranov shift becomes up-down asymmetric and depends strongly on the tilt angle of the flux surfaces, it is insensitive to the shape of the current and pressure profiles (when specific experimental parameters are kept fixed). Next, local nonlinear gyrokinetic simulations of these MHD equilibria are performed with GS2, which reveal that the Shafranov shift can significantly enhance the momentum transport. However, to be consistent, the effect of $\\beta'$ (i.e. the radial gradient of $\\beta$) on the magnetic equilibrium was also included....

  13. Status of tokamak research

    International Nuclear Information System (INIS)

    An overall review of the tokamak program is given with particular emphasis upon developments over the past five years in the theoretical and experimental elements of the program. A summary of the key operating parameters for the principal tokamaks throughout the world is given. Also discussed are key issues in plasma confinement, plasma heating, and tokamak design

  14. 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.

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

    Institute of Scientific and Technical Information of China (English)

    G. MAGUDEESWARAN; Sreehari R. NAIR; L. SUNDAR; N. HARIKANNAN

    2014-01-01

    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.

  16. 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.

  17. Tokamak Systems Code

    International Nuclear Information System (INIS)

    The FEDC Tokamak Systems Code calculates tokamak performance, cost, and configuration as a function of plasma engineering parameters. This version of the code models experimental tokamaks. It does not currently consider tokamak configurations that generate electrical power or incorporate breeding blankets. The code has a modular (or subroutine) structure to allow independent modeling for each major tokamak component or system. A primary benefit of modularization is that a component module may be updated without disturbing the remainder of the systems code as long as the imput to or output from the module remains unchanged

  18. 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.

    2016-07-01

    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.

  19. 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).

  20. 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. PMID:27372944

  1. Feasibility study on 3-D shape analysis of high-aspect-ratio features using through-focus scanning optical microscopy

    Science.gov (United States)

    Attota, Ravi Kiran; Weck, Peter; Kramar, John A.; Bunday, Benjamin; Vartanian, Victor

    2016-01-01

    In-line metrologies currently used in the semiconductor industry are being challenged by the aggressive pace of device scaling and the adoption of novel device architectures. Metrology and process control of three-dimensional (3-D) high-aspect-ratio (HAR) features are becoming increasingly important and also challenging. In this paper we present a feasibility study of through-focus scanning optical microscopy (TSOM) for 3-D shape analysis of HAR features. TSOM makes use of 3-D optical data collected using a conventional optical microscope for 3-D shape analysis. Simulation results of trenches and holes down to the 11 nm node are presented. The ability of TSOM to analyze an array of HAR features or a single isolated HAR feature is also presented. This allows for the use of targets with area over 100 times smaller than that of conventional gratings, saving valuable real estate on the wafers. Indications are that the sensitivity of TSOM may match or exceed the International Technology Roadmap for Semiconductors (ITRS) measurement requirements for the next several years. Both simulations and preliminary experimental results are presented. The simplicity, lowcost, high throughput, and nanometer scale 3-D shape sensitivity of TSOM make it an attractive inspection and process monitoring solution for nanomanufacturing. PMID:27464112

  2. Optimization of laser energy deposition for single-shot high aspect-ratio microstructuring of thick BK7 glass

    Science.gov (United States)

    Garzillo, Valerio; Jukna, Vytautas; Couairon, Arnaud; Grigutis, Robertas; Di Trapani, Paolo; Jedrkiewicz, Ottavia

    2016-07-01

    We investigate the generation of high aspect ratio microstructures across 0.7 mm thick glass by means of single shot Bessel beam laser direct writing. We study the effect on the photoinscription of the cone angle, as well as of the energy and duration of the ultrashort laser pulse. The aim of the study is to optimize the parameters for the writing of a regular microstructure due to index modification along the whole sample thickness. By using a spectrally resolved single pulse transmission diagnostics at the output surface of the glass, we correlate the single shot material modification with observations of the absorption in different portions of the retrieved spectra, and with the absence or presence of spectral modulation. Numerical simulations of the evolution of the Bessel pulse intensity and of the energy deposition inside the sample help us interpret the experimental results that suggest to use picosecond pulses for an efficient and more regular energy deposition. Picosecond pulses take advantage of nonlinear plasma absorption and avoid temporal dynamics effects which can compromise the stationarity of the Bessel beam propagation.

  3. Formation of High Aspect Ratio TiO2 Nano tube Arrays by Anodization of Ti Foil in Organic Solution

    International Nuclear Information System (INIS)

    Titanium oxide (TiO2) nano tubes were successfully formed by anodization of pure titanium foil in a standard two-electrode bath consisting of ethylene glycol solution containing 5 wt % NH4F. The pH of the solution was ∼7 and the anodization voltage was 60 V. It was observed that such anodization condition results in ordered arrays of TiO2 nano tubes with smooth surface and a very high aspect ratio. It was observed that a minimum of 1 wt % water addition was required to form well ordered TiO2 nano tubes with length of approximately 18.5 μm. As-anodized sample, the self-organized TiO2 nano tubes have amorphous structure and annealing at 500 degree Celsius of the nano tubes promote formation of anatase and rutile phase. Photo catalytic activity of well ordered TiO2 nano tubes with two different lengths was evaluated by measuring the degradation of methyl orange (MO). The elaboration of this observation is described in detail in this paper. (author)

  4. Ionic transport through sub-10 nm diameter hydrophobic high-aspect ratio nanopores: experiment, theory and simulation.

    Science.gov (United States)

    Balme, Sébastien; Picaud, Fabien; Manghi, Manoel; Palmeri, John; Bechelany, Mikhael; Cabello-Aguilar, Simon; Abou-Chaaya, Adib; Miele, Philippe; Balanzat, Emmanuel; Janot, Jean Marc

    2015-06-03

    Fundamental understanding of ionic transport at the nanoscale is essential for developing biosensors based on nanopore technology and new generation high-performance nanofiltration membranes for separation and purification applications. We study here ionic transport through single putatively neutral hydrophobic nanopores with high aspect ratio (of length L = 6 μm with diameters ranging from 1 to 10 nm) and with a well controlled cylindrical geometry. We develop a detailed hybrid mesoscopic theoretical approach for the electrolyte conductivity inside nanopores, which considers explicitly ion advection by electro-osmotic flow and possible flow slip at the pore surface. By fitting the experimental conductance data we show that for nanopore diameters greater than 4 nm a constant weak surface charge density of about 10(-2) C m(-2) needs to be incorporated in the model to account for conductance plateaus of a few pico-siemens at low salt concentrations. For tighter nanopores, our analysis leads to a higher surface charge density, which can be attributed to a modification of ion solvation structure close to the pore surface, as observed in the molecular dynamics simulations we performed.

  5. Feasibility study on 3-D shape analysis of high-aspect-ratio features using through-focus scanning optical microscopy.

    Science.gov (United States)

    Attota, Ravi Kiran; Weck, Peter; Kramar, John A; Bunday, Benjamin; Vartanian, Victor

    2016-07-25

    In-line metrologies currently used in the semiconductor industry are being challenged by the aggressive pace of device scaling and the adoption of novel device architectures. Metrology and process control of three-dimensional (3-D) high-aspect-ratio (HAR) features are becoming increasingly important and also challenging. In this paper we present a feasibility study of through-focus scanning optical microscopy (TSOM) for 3-D shape analysis of HAR features. TSOM makes use of 3-D optical data collected using a conventional optical microscope for 3-D shape analysis. Simulation results of trenches and holes down to the 11 nm node are presented. The ability of TSOM to analyze an array of HAR features or a single isolated HAR feature is also presented. This allows for the use of targets with area over 100 times smaller than that of conventional gratings, saving valuable real estate on the wafers. Indications are that the sensitivity of TSOM may match or exceed the International Technology Roadmap for Semiconductors (ITRS) measurement requirements for the next several years. Both simulations and preliminary experimental results are presented. The simplicity, lowcost, high throughput, and nanometer scale 3-D shape sensitivity of TSOM make it an attractive inspection and process monitoring solution for nanomanufacturing. PMID:27464112

  6. 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.

  7. Facile synthesis of ultrafine TiO{sub 2} nanowires with large aspect ratio and its photoactivity

    Energy Technology Data Exchange (ETDEWEB)

    Anjusree, G.S.; Asha, A.M.; Subramanian, K.R.V.; Sivekumar, N.; Nair, A. Sreekumaran; Nair, Shantikumar V.; Balakrishnan, Avinash [Amrita Center for Nanoscience, Kochi (India). Nano Solar Div.

    2013-06-15

    In the present study, ultrafine TiO{sub 2} nanowires ({proportional_to} 80nm in diameter) exhibiting large aspect ratio in the order of 10{sup 3} were synthesized hydrothermally. Phase and morphological analysis of the nanowires was carried out using X-ray diffractometry, X-ray photoelectron spectroscopy and scanning electron microscopy. High resolution transmission electron microscopy revealed the wire exhibiting growth in (101). A Tauc plot derived from UV analysis showed the average band gap values for nanowires to be less than for nanoparticles of similar diameter. It was observed that nanowires exhibited a high degree of photoactivity in an eosin-based dye system which was found to be 20-30% more than that of nanoparticles. This high photoactivity in nanowires was attributed to the longer charge retention which was observed during lifetime measurements, resulting in easy radical formation and dye degradation. Lifetime measurements on the nanowires showed the recombination time to be 54 ns as compared to 43 ns for nanoparticles. (orig.)

  8. FFT-impedance spectroscopy analysis of the growth of magnetic metal nanowires in ultra-high aspect ratio InP membranes

    Science.gov (United States)

    Gerngross, M.-D.; Carstensen, J.; Föll, H.; Adelung, R.

    2016-01-01

    This paper reports on the characterization of the electrochemical growth process of magnetic nanowires in ultra-high-aspect ratio InP membranes via in situ fast Fourier transform impedance spectroscopy in a typical frequency range from 75 Hz to 18.5 kHz. The measured impedance data from the Ni, Co, and FeCo can be very well fitted using the same electric equivalent circuit consisting of a series resistance in serial connection to an RC-element and a Maxwell element. The impedance data clearly indicate the similarities in the growth behavior of Ni, Co and FeCo nanowires in ultra-high aspect ratio InP membranes—the beneficial impact of boric acid on the metal deposition in ultra-high aspect ratio membranes and the diffusion limitation of boric acid, as well as differences such as passivation or side reactions.

  9. Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

    Institute of Scientific and Technical Information of China (English)

    Jia Wei; Liu Huoxing

    2013-01-01

    In modem gas turbines,rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine.However,the purge flow supplied to the cavity through the rim seal interacts with the main flow,producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation,development and evolution of downstream secondary flow.In this paper,a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss.Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation.Then,a deep insight into the loss mechanism of interaction between purge flow and main flow is gained.The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity,but also alters the cascade exit flow angle distribution along the spanwise.Moreover,aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced.Therefore,the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design.What is more,it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.

  10. Aspect ratio control of Au nanorods via covariation of the total amount of HAuCl4 and ascorbic acid

    International Nuclear Information System (INIS)

    Highlights: • The AR value decreased as the total amount of [HAuCl4] 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 HAuCl4 ([HAuCl4]) 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 [HAuCl4] and [AA] decreased. The AR value measured from TEM images decreased from 4.74 to 2.41 as the total amount of [HAuCl4] 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 [HAuCl4] 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 [HAuCl4] and [AA] was 0.122 mM

  11. On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

    Science.gov (United States)

    Shaha, Poly Rani; Rudro, Sajal Kanti; Poddar, Nayan Kumar; Mondal, Rabindra Nath

    2016-07-01

    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.

  12. Unified Ideal Stability Limits for Advanced Tokamak and Spherical Torus Plasmas

    International Nuclear Information System (INIS)

    Ideal magnetohydrodynamic stability limits of shaped tokamak plasmas with high bootstrap fraction are systematically determined as a function of plasma aspect ratio. For plasmas with and without wall stabilization of external kink modes, the computed limits are well described by distinct and nearly invariant values of a normalized beta parameter utilizing the total magnetic field energy density inside the plasma. Stability limit data from the low aspect ratio National Spherical Torus Experiment is compared to these theoretical limits and indicates that ideal nonrotating plasma no-wall beta limits have been exceeded in regimes with sufficiently high cylindrical safety factor. These results could impact the choice of aspect ratio in future fusion power plants

  13. Aspect Ratio Plays a Role in the Hazard Potential of CeO2 Nanoparticles in Mouse Lung and Zebrafish Gastrointestinal Tract

    OpenAIRE

    Lin, Sijie; Wang, Xiang; Ji, Zhaoxia; Chang, Chong Hyun; Dong, Yuan; Meng, Huan; Liao, Yu-Pei; Wang, Meiying; Song, Tze-Bin; Kohan, Sirus; Xia, Tian; Zink, Jeffrey I.; Lin, Shuo; Nel, André E.

    2014-01-01

    We have previously demonstrated that there is a relationship between the aspect ratio (AR) of CeO2 nanoparticles and in vitro hazard potential. CeO2 nanorods with AR ≥ 22 induced lysosomal damage and progressive effects on IL-1β production and cytotoxicity in the human myeloid cell line, THP-1. In order to determine whether this toxicological paradigm for long aspect ratio (LAR) CeO2 is also relevant in vivo, we performed comparative studies in the mouse lung and gastrointestinal tract (GIT) ...

  14. Fabrication and characterization of high aspect ratio perpendicular patterned information storage media in an Al2O3/GaAs substrate

    OpenAIRE

    Wong, Joyce; Scherer, Axel; Todorovic, Mladen; Schultz, Sheldon

    1999-01-01

    In a new approach, we have fabricated 6:1 aspect ratio magnetic nanocolumns, 60–250 nm in diameter, embedded in a hard aluminum-oxide/gallium-arsenide (Al2O3/GaAs) substrate. The fabrication technique uses the highly selective etching properties of GaAs and AlAs, and highly efficient masking properties of Al2O3 to create small diameter, high aspect ratio holes. Nickel (Ni) is subsequently electroplated into the holes, followed by polishing, which creates a smooth and hard surface appropriate ...

  15. 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.

  16. Proto-CIRCUS Tilted-Coil Tokamak-Torsatron Hybrid: Design and Construction

    CERN Document Server

    Clark, A W; Hammond, K C; Kornbluth, Y; Spong, D A; Sweeney, R; Volpe, F A

    2014-01-01

    We present the field-line modeling, design and construction of a prototype circular-coil tokamak-torsatron hybrid called Proto-CIRCUS. The device has a major radius R = 16 cm and minor radius a < 5 cm. The six "toroidal field" coils are planar as in a tokamak, but they are tilted. This, combined with induced or driven plasma current, is expected to generate rotational transform, as seen in field-line tracing and equilibrium calculations. The device is expected to operate at lower plasma current than a tokamak of comparable size and magnetic field, which might have interesting implications for disruptions and steady-state operation. Additionally, the toroidal magnetic ripple is less pronounced than in an equivalent tokamak in which the coils are not tilted. The tilted coils are interlocked, resulting in a relatively low aspect ratio, and can be moved, both radially and in tilt angle, between discharges. This capability will be exploited for detailed comparisons between calculations and field-line mapping me...

  17. Tokamak engineering mechanics

    CERN Document Server

    Song, Yuntao; Du, Shijun

    2013-01-01

    Tokamak Engineering Mechanics offers concise and thorough coverage of engineering mechanics theory and application for tokamaks, and the material is reinforced by numerous examples. Chapter topics include general principles, static mechanics, dynamic mechanics, thermal fluid mechanics and multiphysics structural mechanics of tokamak structure analysis. The theoretical principle of the design and the methods of the analysis for various components and load conditions are presented, while the latest engineering technologies are also introduced. The book will provide readers involved in the study

  18. Tokamak concept innovations

    International Nuclear Information System (INIS)

    This document contains the results of the IAEA Specialists' Meeting on Tokamak Concept Innovations held 13-17 January 1986 in Vienna. Although it is the most advanced fusion reactor concept the tokamak is not without its problems. Most of these problems should be solved within the ongoing R and D studies for the next generation of tokamaks. Emphasis for this meeting was placed on innovations that would lead to substantial improvements in a tokamak reactor, even if they involved a radical departure from present thinking

  19. A facile phosphine-free colloidal synthesis of Cu2SnS3 and Cu2ZnSnS4 nanorods with a controllable aspect ratio.

    Science.gov (United States)

    Wang, Jian-Jun; Liu, Pai; Ryan, Kevin M

    2015-09-18

    Cu2SnS3 (CTS) nanorods were synthesized with a controllable aspect ratio via a facile phosphine-free colloidal synthesis. This synthesis can be readily extended to obtain Cu2ZnSnS4 (CZTS) nanorods with tunable Zn content. PMID:26235602

  20. Influence of Aspect Ratio on the Onset of Thermocapillary Oscillatory Convection in a Floating Half Zone of Large Prandtl Number Fluid

    Institute of Scientific and Technical Information of China (English)

    唐泽眉; 胡文瑞

    2003-01-01

    The onset of oscillatory thermocapillary convection in a floating half zone of l0cst silicon oil (Prandtl number 105.6) is studied by the three-dimensional and unsteady numerical simulation in microgravity environment (g =10--4gearth). The results show that the steady and axi-symmetric convection, for a fixed liquid bridge volume ratio Ve/Vo = 1, transits directly to the oscillatory convection if geometrical aspect ratio A is larger than the critical value Ac = 1.25, but transits to the oscillatory convection via the steady and non-axisymmetric flow if A is smaller than the critical value Ac. The result means that there are two bifurcation transitions in a liquid bridge of the large Prandtl number fluid with a smaller aspect ratio A.

  1. Drifts of electron orbits induced by toroidal electric field in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Abdullaev, S. S. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, D-52425 Jülich (Germany)

    2015-03-15

    The drifts of electron orbits induced by the toroidal electric field in tokamaks are analyzed. Based on the relativistic Hamiltonian equations for guiding centre motion, the formula for the drift velocity v{sub dr} is derived. It describes the outward drift of passing particles as well as the inward drift (the Ware pinch) of trapped particles. Unlike the approximate formula for v{sub dr} given in Guan et al. [Phys. Plasmas 17, 092502 (2010)] for circular electron orbits, it describes qualitatively new features of the outward drift of electron orbits. Particularly, the new formula describes the evolution of the orbit's shape, the formation of X-point and the associated separatrix. It is shown that the outward drift velocity is proportional to the inverse aspect ratio of tokamaks.

  2. Neoclassical Drift of Circulating Orbits Due toToroidal Electric Field in Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Qin; Guan, Xiaoyin; Fisch, Nathaniel J.

    2011-07-19

    In tokamaks, Ware pinch is a well known neoclassical effect for trapped particles in response to a toroidal electric field. It is generally believed that there exists no similar neoclassical effect for circulating particles without collisions. However, this belief is erroneous, and misses an important effect. We show both analytically and numerically that under the influence of a toroidal electric field parallel to the current, the circulating orbits drift outward toward the outer wall with a characteristic velocity O ({var_epsilon}{sup -1}) larger than the E x B velocity, where {var_epsilon} is the inverse aspect-ratio of a tokamak. During a RF overdrive, the toroidal electric field is anti-parallel to the current. As a consequence, all charged particles, including backward runaway electrons, will drift inward towards the inner wall.

  3. On a possibility of construction of a tokamak-reactor using warm windings

    International Nuclear Information System (INIS)

    Preliminary consideration of possible use of ''warm'' windings in tokamak-reactors based on extrapolation of present scalings to the range of ''steep'' fores with aspect ratio of about 2 discloses ways for reduction of ohmic losses in windings of the toroidal field approximately to 200-300 MW. This value is 1.3-1.7 times lower than for a tokamak with superconducting windings that is attained by β increase up to 5-8 %, optimization of coils of the toroidal field and decrease of thickness of radiation protection of magnets. Alongside with other merits use of ''warm'' windings permits to increase the magnetic field on the tore axis with corresponding improvement of plasma and energy parameters

  4. D-T burning plasma characteristics in an A=2 tokamak reactor

    Institute of Scientific and Technical Information of China (English)

    石秉仁

    2005-01-01

    The deuterium-tritium (D-T) burning plasma characteristic in an aspect ratio A=2 tokamak reactor is studied based on a simple equilibrium configuration, the Soloviev-type configuration. Operation limits for the Troyon beta value and for the Greenwald density value as well as for the ITER H-mode confinement scaling are used as the benchmark.It is found that in addition to suitable elongation, large triangularity has advantage for arriving at high beta value and obtaining high fusion power output. Compared to the present ITER design, the A=2 system can have very good merit for the avoidance of disruptions by setting rather high edge q value while keeping relatively large total toroidal current.The main disadvantage of decreasing the aspect ratio is due to the loss of more useful space in the inward region that leads to the decrease of toroidal magnetic field in the plasma region, then worsening the fusion merit. Our analysis and calculation also present a trade-off in this respect. Due to simple equilibrium configuration assumed, some other important issues such as the bootstrap current alignment cannot be optimized. However, the present analysis can offer an insight into the advantages of the medium aspect ratio reactor system that is a blank in present-day tokamak study.

  5. Single-photon-multi-layer-interference lithography for high-aspect-ratio and three-dimensional SU-8 micro-/nanostructures

    Science.gov (United States)

    Ghosh, Siddharth; Ananthasuresh, G. K.

    2016-01-01

    We report microstructures of SU-8 photo-sensitive polymer with high-aspect-ratio, which is defined as the ratio of height to in-plane feature size. The highest aspect ratio achieved in this work exceeds 250. A multi-layer and single-photon lithography approach is used in this work to expose SU-8 photoresist of thickness up to 100 μm. Here, multi-layer and time-lapsed writing is the key concept that enables nanometer localised controlled photo-induced polymerisation. We use a converging monochromatic laser beam of 405 nm wavelength with a controllable aperture. The reflection of the converging optics from the silicon substrate underneath is responsible for a trapezoidal edge profile of SU-8 microstructure. The reflection induced interfered point-spread-function and multi-layer-single-photon exposure helps to achieve sub-wavelength feature sizes. We obtained a 75 nm tip diameter on a pyramid shaped microstructure. The converging beam profile determines the number of multiple optical focal planes along the depth of field. These focal planes are scanned and exposed non-concurrently with varying energy dosage. It is notable that an un-automated height axis control is sufficient for this method. All of these contribute to realising super-high-aspect-ratio and 3D micro-/nanostructures using SU-8. Finally, we also address the critical problems of photoresist-based micro-/nanofabrication and their solutions.

  6. 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.

  7. Numerical design of X-ray tabletop Talbot interferometer using polycapillary optics as two-dimensional gratings with high aspect ratio

    Science.gov (United States)

    Sun, Weiyuan; Liu, Zhiguo; Sun, Tianxi; Sun, Xuepeng; Li, Fangzuo; Jiang, Bowen; Ding, Xunliang

    2015-12-01

    The polycapillary optics was proposed to be used as two-dimensional X-ray gratings with high aspect ratios for high energy X-rays. The X-ray Talbot interferometer was designed numerically using the polycapillary X-ray gratings and a conventional X-ray source. The simulation showed that it was available to get a high-aspect-ratio pattern of the polycapillary X-ray gratings for higher energies than 60 keV. Moreover, this design of polycapillary gratings decreased the requirement for high power of the X-ray source. The polycapillary X-ray gratings had potential applications in X-ray imaging technology for medical fields, industrial nondestructive tests, public security, physical science, chemical analysis, life science, nanoscience biology and energy science.

  8. Aspect ratio-related three-photon absorption and mechanism of α-FeOOH nanorods in the near-infrared

    Science.gov (United States)

    Zhu, Baohua; Wang, Fangfang; Wang, Chong; Cao, Yawan; Guo, Lijun; Zhang, Jiayu; Gu, Yuzong

    2016-07-01

    Tuning a semiconductor nanomaterial with large three-photon absorption (3PA) cross section in the near infrared and investigating the relationship between the nanostructure and nonlinear optical properties is a challenging topic, which is of significance in potential applications. Here, we report the aspect ratio-related 3PA response of α-FeOOH nanorods (NRs) in the near infrared. Large 3PA cross section at room temperature is achieved as high as ~10‑77 cm6 s2 photon‑2 when the distribution of photo-induced and intrinsic surface polarization charges of excitons to both ends of NRs is tuned through the aspect ratio, yielding total enhancement more than three times larger than that of NRs with 12.1 nm diameter.

  9. 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.

  10. Transonic steady- and unsteady-pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces

    Science.gov (United States)

    Sandford, M. C.; Ricketts, R. H.; Cazier, F. W., Jr.

    1980-01-01

    A supercritical wing with an aspect ratio of 10.76 and with two trailing-edge oscillating control surfaces is described. The semispan wing is instrumented with 252 static orifices and 164 in situ dynamic-pressure gages for studying the effects of control-surface position and motion on steady- and unsteady-pressures at transonic speeds. Results from initial tests conducted in the Langley Transonic Dynamics Tunnel at two Reynolds numbers are presented in tabular form.

  11. 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.

  12. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties

    Science.gov (United States)

    2014-01-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires. PMID:25050088

  13. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties

    Science.gov (United States)

    Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

    2014-06-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor ( RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

  14. Tokamak ARC damage

    International Nuclear Information System (INIS)

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage

  15. Survey of Tokamak experiments

    International Nuclear Information System (INIS)

    The survey covers the following topics:- Introduction and history of tokamak research; review of tokamak apparatus, existing and planned; remarks on measurement techniques and their limitations; main results in terms of electron and ion temperatures, plasma density, containment times, etc. Empirical scaling; range of operating densities; impurities, origin, behaviour and control (including divertors); data on fluctuations and instabilities in tokamak plasmas; data on disruptive instabilities; experiments on shaped cross-sections; present experimental evidence on β limits; auxiliary heating; experimental and theoretical problems for the future. (author)

  16. Plasma Turbulence in the Scrape-off Layer of the ISTTOK Tokamak

    CERN Document Server

    Jorge, Rogerio; Halpern, Federico D; Loureiro, Nuno F; Silva, Carlos

    2016-01-01

    The properties of plasma turbulence in a poloidally limited scrape-off layer (SOL) are addressed, with focus on ISTTOK, a large aspect ratio tokamak with a circular cross section. Theoretical investigations based on the drift-reduced Braginskii equations are carried out through linear calculations and non-linear simulations, in two- and three-dimensional geometries. The linear instabilities driving turbulence and the mechanisms that set the amplitude of turbulence as well as the SOL width are identified. A clear asymmetry is shown to exist between the low-field and the high-field sides of the machine. A comparison between experimental measurements and simulation results is presented.

  17. 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.

  18. Research using small tokamaks

    International Nuclear Information System (INIS)

    These proceedings of the IAEA-sponsored meeting held in Nice, France 10-11 October, 1988, contain the manuscripts of the 21 reports dealing with research using small tokamaks. The purpose of this meeting was to highlight some of the achievements of small tokamaks and alternative magnetic confinement concepts and assess the suitability of starting new programs, particularly in developing countries. Papers presented were either review papers, or were detailed descriptions of particular experiments or concepts. Refs, figs and tabs

  19. A conceptual design of superconducting spherical tokamak reactor

    International Nuclear Information System (INIS)

    This paper presents a fusion reactor concept named 'JUST (Japanese Universities' Super Tokamak reactor)'. From the plasma confinement system to the power generation system is evaluated in this work. JUST design has features as follows: the superconducting magnet, the steady state operation with high bootstrap current fraction, the easy replacement of neutron damaged first wall, the high heat flux in the divertor, and the low cost (or high β). By winding the OH solenoid over the center stack of toroidal field coil, we have the low aspect ratio and the 80cm thick neutron shield to protect the superconducting center stack. JUST is designed by using the 0-D transport code under the assumption that the energy confinement time is 1.8 times of the IPB98(y,2) scaling. Main parameters are as follows: the major radius of 4.5m, the aspect ratio of 1.8, the elongation ratio of 2.5, the toroidal field of 2.36T, the plasma current of 18MA, the toroidal beta of 22%, the central electron and ion temperature of 15keV and the fusion thermal power of 2.4GW. By using the mercury heat exchanger and the steam turbine, the heat efficiency is 33% and the electric power is 0.74GW. (author)

  20. Double-sided F and Cl adsorptions on graphene at various atomic ratios: Geometric, orientation and electronic structure aspects

    Science.gov (United States)

    Widjaja, Hantarto; Jiang, Zhong-Tao; Altarawneh, Mohammednoor; Yin, Chun-Yang; Goh, Bee-Min; Mondinos, Nicholas; Amri, Amun; Dlugogorski, Bogdan Z.

    2016-06-01

    Elemental adsorption on graphene offers an effective procedure in fine-tuning electronic and mechanical properties of graphene. The effects of dopants depend on adsorption site, the degree of coverage as well as on the configuration of the deployed supercell. In this contribution, the density functional theory (DFT) calculations were performed to investigate the electronic structures of F and Cl adsorption (double-sided, top site) on graphene in terms of adsorption orientation, atomic ratios, i.e., from C:F/Cl = 18:2 to C:F/Cl = 2:2. Despite being members of the halogens group, F- and Cl-adsorbed on graphene show contrasting trends. F is adsorbed to graphene more strongly than Cl. F favours full and 25% adsorption coverage, while Cl favours 25% coverage. Both F and Cl cases open band gap (at Fermi energy) at certain atomic concentration coverage, but none creates magnetization.

  1. 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.

  2. Stability and Control Characteristics of a Complete Airplane Model Having a Wing with Quarter-chord Line Swept Back 40 Degrees, Aspect Ratio 2.50, and Taper Ratio 0.42

    Science.gov (United States)

    Schulderfrei, Marvin; Comisarow, Paul; Goodson, Kenneth W

    1951-01-01

    An investigation has been made of a complete airplane model having a wing with the quarter-chord line swept back 40 degrees, aspect ratio 2.50, and taper ratio 0.42 to determine its low-speed stability and control characteristics. The longitudinal stability investigation included stabilizer and tail-off tests with different wing dihedral angles (Gamma = 0 degrees and Gamma = -10 degrees) over an angle-of-attack range for the cruising and landing configurations and tests. with a high horizontal-tail location (Gamma = -10 degrees) for the cruising configuration. Tests were made of the wing alone and to determine the effect of wing end plates in pitch. Lateral stability characteristics were determined for the airplane with different geometric wing dihedrals, with end plates, and with several dorsal modifications. Tests were made with ailerons and spoilers to determine control characteristics.

  3. Projections for a steady-state tokamak reactor based on the international thermonuclear experimental reactor

    Energy Technology Data Exchange (ETDEWEB)

    Devoto, R.S.; Barr, W.L.; Bulmer, R.H.; Campbell, R.B.; Fenstermacher, M.E.; Lee, J.D.; Logan, B.G.; Miller, J.R.; Reginato, L.L. (Lawrence Livermore National Lab., Livermore, CA (US)); Krakowski, R.A.; Miller, R.L. (Los Alamos National Lab., Los Alamos, NM (US))

    1991-03-01

    This paper examines the extensions of the physics and engineering guidelines for the International Thermonuclear Experimental Reactor (ITER) device needed for acceptable operating points for a steady-state tokamak power reactor. Noninductive current drive is provided in steady state by high-energy neutral beam injection in the plasma core, lower hybrid slow waves in the outer regions of the plasma, and bootstrap current. Three different levels of extension of the ITER physics/engineering guidelines, with differing assumptions on the possible plasma beta, elongation, and aspect ratio, are considered for power reactor applications. Plasma gain Q = fusion power/input power in excess of 20 and average neutron wall fluxes from 2.3 to 3.6 MW/m{sup 2} are predicted in devices with major radii varying from 7.0 to 6.0 m and aspect ratios from 2.9 to 4.3.

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

    Science.gov (United States)

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

    2000-01-01

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

  5. Imaging properties of high aspect ratio absorption gratings for use in preclinical x-ray grating interferometry

    Science.gov (United States)

    Trimborn, Barbara; Meyer, Pascal; Kunka, Danays; Zuber, Marcus; Albrecht, Frederic; Kreuer, Sascha; Volk, Thomas; Baumbach, Tilo; Koenig, Thomas

    2016-01-01

    X-ray grating interferometry is one among various methods that allow extracting the so-called phase and visibility contrasts in addition to the well-known transmission images. Crucial to achieving a high image quality are the absorption gratings employed. Here, we present an in-depth analysis of how the grating type and lamella heights influence the final images. Benchmarking gratings of two different designs, we show that a frequently used proxy for image quality, a grating’s so-called visibility, is insufficient to predict contrast-to-noise ratios (CNRs). Presenting scans from an excised rat lung, we demonstrate that the CNRs obtained for transmission and visibility images anti-correlate. This is explained by the stronger attenuation implied by gratings that are engineered to provide high visibilities by means of an increased lamella height. We show that even the visibility contrast can suffer from this effect when the associated reduced photon flux on the detector is not outweighed by a corresponding gain in visibility. Resulting in an inevitable trade-off between the quality of the two contrasts, the question of how an optimal grating should be designed can hence only be answered in terms of Pareto optimality.

  6. Development of numerical methods to calculate the propagation and the absorption of the hybrid wave in tokamaks; Developpement des methodes numeriques pour la resolution de la propagation et de l`absorption de l`onde hybride dans les tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Sebelin, E

    1997-12-15

    Full-wave calculations based on trial functions are carried out for solving the lower hybrid current drive problem in tokamaks. A variational method is developed and provides an efficient system to describe in a global manner both the propagation and the absorption of the electromagnetic waves in plasmas. The calculation is fully carried out in the case of circular and concentric flux surfaces. The existence and uniqueness of the solution of the wave propagation equation is mathematically proved. The first realistic simulations are performed for the high aspect ratio tokamak TRIAM-1M. It is checked that the main features of the lower-hybrid wave dynamics are well described numerically. (A.C.) 81 refs.

  7. Joint research using small tokamaks

    International Nuclear Information System (INIS)

    Small tokamaks have an important role in fusion research. More than 40 small tokamaks are operational. Research on small tokamaks has created a scientific basis for the scaling-up to larger tokamaks. Well-known scientific and engineering schools, which are now determining the main directions of fusion science and technology, have been established through research on small tokamaks. Combined efforts within a network of small and medium size tokamaks will further enhance the contribution of small tokamaks. A new concept of interactive coordinated research using small tokamaks in the mainstream fusion science areas, in testing of new diagnostics, materials and technologies as well as in education, training and broadening of the geography of fusion research in the scope of the IAEA Coordinated Research Project, is presented

  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. Advanced tokamak reactors based on the spherical torus (ATR/ST). Preliminary design considerations

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.L.; Krakowski, R.A.; Bathke, C.G.; Copenhaver, C.; Schnurr, N.M.; Engelhardt, A.G.; Seed, T.J.; Zubrin, R.M.

    1986-06-01

    Preliminary design results relating to an advanced magnetic fusion reactor concept based on the high-beta, low-aspect-ratio, spherical-torus tokamak are summarized. The concept includes resistive (demountable) toroidal-field coils, magnetic-divertor impurity control, oscillating-field current drive, and a flowing liquid-metal breeding blanket. Results of parametric tradeoff studies, plasma engineering modeling, fusion-power-core mechanical design, neutronics analyses, and blanket thermalhydraulics studies are described. The approach, models, and interim results described here provide a basis for a more detailed design. Key issues quantified for the spherical-torus reactor center on the need for an efficient drive for this high-current (approx.40 MA) device as well as the economic desirability to increase the net electrical power from the nominal 500-MWe(net) value adopted for the baseline system. Although a direct extension of present tokamak scaling, the stablity and transport of this high-beta (approx.0.3) plasma is a key unknown that is resoluble only by experiment. The spherical torus generally provides a route to improved tokamak reactors as measured by considerably simplified coil technology in a configuration that allows a realistic magnetic divertor design, both leading to increased mass power density and reduced cost.

  10. Advanced tokamak reactors based on the spherical torus (ATR/ST). Preliminary design considerations

    International Nuclear Information System (INIS)

    Preliminary design results relating to an advanced magnetic fusion reactor concept based on the high-beta, low-aspect-ratio, spherical-torus tokamak are summarized. The concept includes resistive (demountable) toroidal-field coils, magnetic-divertor impurity control, oscillating-field current drive, and a flowing liquid-metal breeding blanket. Results of parametric tradeoff studies, plasma engineering modeling, fusion-power-core mechanical design, neutronics analyses, and blanket thermalhydraulics studies are described. The approach, models, and interim results described here provide a basis for a more detailed design. Key issues quantified for the spherical-torus reactor center on the need for an efficient drive for this high-current (approx.40 MA) device as well as the economic desirability to increase the net electrical power from the nominal 500-MWe(net) value adopted for the baseline system. Although a direct extension of present tokamak scaling, the stablity and transport of this high-beta (approx.0.3) plasma is a key unknown that is resoluble only by experiment. The spherical torus generally provides a route to improved tokamak reactors as measured by considerably simplified coil technology in a configuration that allows a realistic magnetic divertor design, both leading to increased mass power density and reduced cost

  11. Spontaneous generation of rotation in tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Parra Diaz, Felix [Oxford University

    2013-12-24

    Three different aspects of intrinsic rotation have been treated. i) A new, first principles model for intrinsic rotation [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has been implemented in the gyrokinetic code GS2. The results obtained with the code are consistent with several experimental observations, namely the rotation peaking observed after an L-H transition, the rotation reversal observed in Ohmic plasmas, and the change in rotation that follows Lower Hybrid wave injection. ii) The model in [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has several simplifying assumptions that seem to be satisfied in most tokamaks. To check the importance of these hypotheses, first principles equations that do not rely on these simplifying assumptions have been derived, and a version of these new equations has been implemented in GS2 as well. iii) A tokamak cross-section that drives large intrinsic rotation has been proposed for future large tokamaks. In large tokamaks, intrinsic rotation is expected to be very small unless some up-down asymmetry is introduced. The research conducted under this contract indicates that tilted ellipticity is the most efficient way to drive intrinsic rotation.

  12. Two-fluid and magnetohydrodynamic modelling of magnetic reconnection in the MAST spherical tokamak and the solar corona

    CERN Document Server

    Browning, P K; Evans, M; Lucini, F Arese; Lukin, V S; McClements, K G; Stanier, A

    2015-01-01

    Twisted magnetic flux ropes are ubiquitous in space and laboratory plasmas, and the merging of such flux ropes through magnetic reconnection is an important mechanism for restructuring magnetic fields and releasing free magnetic energy. The merging-compression scenario is one possible start up scheme for spherical tokamaks, which has been used on the Mega Amp Spherical Tokamak MAST. Two current-carrying plasma rings, or flux ropes, approach each other through the mutual attraction of their like currents, and merge, through magnetic reconnection, into a single plasma torus, with substantial plasma heating. 2D resistive MHD and Hall MHD simulations of this process are reported, and new results for the temperature distribution of ions and electrons are presented. A model of the based on relaxation theory is also described, which is now extended to tight aspect ratio geometry. This model allows prediction of the final merged state and the heating. The implications of the relaxation model for heating of the solar ...

  13. A Consideration on Increasing Current Density in Normal Conducting Toroidal Field Coil for Spherical Tokamak Power Plant

    Institute of Scientific and Technical Information of China (English)

    Song Yuntao; Satoshi NISHIO

    2005-01-01

    The center post is the most critical component as an inboard part of the toroidal field coil for the low aspect ratio tokamak. During the discharge it endures not only a tremendous ohmic heating owing to its carrying a rather high current but also a large nuclear heating and irradiation owing to the plasma operation. All the severe operating conditions, including the structure stress intensity and the stability of the structure, largely limit the maximum allowable current density. But in order to contain a very high dense plasma, it is hoped that the fusion power plant system can operate with a much high maximum magnetic field BT ≥12 T~15 T in the center post. A new method is presented in this paper to improve the maximum magnetic field up to 17 T and to investigate the possibility of the normal conducting center post to be used in the future fusion tokamak power plant.

  14. Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate

    Energy Technology Data Exchange (ETDEWEB)

    Ali-Toudert, Fazia; Mayer, Helmut [Meteorological Institute, University of Freiburg,Werderring 10, D-79085 Freiburg (Germany)

    2006-02-01

    This paper discusses the contribution of street design, i.e. aspect ratio (or height-to-width ratio, H/W) and solar orientation, towards the development of a comfortable micro climate at street level for pedestrians. The investigation is carried out by using the three-dimensional numerical model ENVI-met, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for a typical summer day in Ghardaia, Algeria (32.40{sup o}N, 3.80{sup o}E, 469ma.s.l.), a region characterized by a hot and dry climate. Symmetrical urban canyons, with various height-to-width ratios (i.e. H/W=0.5, 1, 2 and 4) and different solar orientations (i.e. E-W, N-S, NE-SW and NW-SE), have been studied. Special emphasis is placed on a human bio-meteorological assessment of these microclimates by using the physiologically equivalent temperature (PET). The results show contrasting patterns of thermal comfort between shallow and deep urban streets as well as between the various orientations studied. A comparison of all case studies reveals that the time and period of day during which extreme heat stress occurs, as well as the spatial distribution of PETs at street level, depend strongly on aspect ratio and street orientation. This is crucial since it will directly influence the design choices in relation to street usage, e.g. streets planned exclusively for pedestrian use or including motor traffic, and also the time of frequentation of urban spaces. Both investigated urban factors can mitigate extreme heat stress if appropriately combined. The solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs for solar energy. (author)

  15. Evaluation of the Pioneer PDP-502MX 4 x 3 Aspect Ratio, 50 Inch Diagonal Color Plasma Display Panel

    Science.gov (United States)

    2000-12-01

    NIDL evaluated the thin, large screen, flat panel Pioneer 50 inch plasma display panel (PDP) to determine its usefulness to the display of images that are of interest to imagery analysts and GI specialists, As NIDL's ratings show, the Pioneer PDP-502MX is not going to be useful as the primary imagery analysis display on an IEC workstation, It fails many of the IEC requirements so we rate it "F" for IEC workstation monoscopic and stereo applications, Rather, its usefulness comes from its large, 50 inch diagonal size and its high pixel count for a PDP, up to 1280 x 768 pixels in the 16:9 and 1024 x 768 pixels in the 4:3 format, that could make it appropriate for group conference discussions, The Pioneer PDP-502MX has a relatively good gray scale capability; it can display 245 of 256 differences in input levels for a 7,94 bit depth, Its linearity surpasses that we have measured for CRT monitors, and comes about because of its precisely formed pixel structure, This pixel structure, like in LCD monitors, can have several non- operating pixels, It has a very high (exceeds 60% over the entire screen) and a very uniform 1-pixel-on/1-pixel-off contrast modulation for both the horizontal and vertical directions, The PDP can have a maximum luminance up to 40 fL for a small patch of white, and a minimum luminance of 0.2 fL For full screen white, its luminance is 18 fL, limited by internal circuitry to minimize panel heat generation and its luminance is more uniform than a CRT monitor, The reflectivity and the viewing angle are about the same as for a CRT monitor, It has a capability to do stereo imaging at 43 Hz per eye, which is on the borderline of visible flicker, and its dynamic range in stereo is good, The extinction ratio is poor, and is probably limited by the long persistence of the green phosphor, Most who have seen the Pioneer PDP-502MX would love to have one, at least for football games, The price is about 18,000.

  16. Simple and cost-effective fabrication of solid biodegradable polymer microneedle arrays with adjustable aspect ratio for transdermal drug delivery using acupuncture microneedles

    International Nuclear Information System (INIS)

    Polymer microneedle arrays (MNAs) have received much attention for their use in transdermal drug delivery and microneedle therapy systems due to the advantages they offer, such as low cost, good mechanical properties, and a versatile choice of materials. Here, we present a simple and cost-effective method for the fabrication of a biodegradable polymer MNA in which the aspect ratio of each microneedle is adjustable using commercially available acupuncture microneedles. In our process, a master template with acupuncture microneedles, whose shape will be the final MNA, was carefully prepared by fixing them onto a plastic substrate with selectively drilled holes which, in turn, determine the aspect ratios of the microneedles. A polylactic acid (PLA; a biodegradable polymer) MNA was fabricated by a micromolding process with a polydimethylsiloxane (PDMS) mold containing the cavity of the microneedles, which was obtained by the PDMS replica molding against the master template. The mechanical force and degradation behavior of the replicated PLA MNA were characterized with the help of a compression test and an accelerated degradation test, respectively. Finally, the transdermal drug delivery performance of the PLA MNA was successfully simulated by two different methods of penetration and staining, using the skin of a pig cadaver. These results indicated that the proposed method can be effectively used for the fabrication of polymer MNAs which can be used in various microneedle applications. (paper)

  17. Elimination of nanovoids induced during electroforming of metallic nanostamps with high-aspect-ratio nanostructures by the pulse reverse current electroforming process

    International Nuclear Information System (INIS)

    We studied a technique for fabricating metallic nanostamps with void-free, high-aspect-ratio nanostructures, using a pulse reverse current (PRC) electroforming process. During conventional electroforming of high-aspect-ratio nanostructures, a high current distribution is concentrated at the top and bottom corners, resulting in relatively fast growth of the nickel electroformed layer. This phenomenon leads to the formation of nanovoids in a metallic nanostamp, causing degradation of the stamp performance. To prevent the formation of nanovoids, we controlled the current waveform during the electroforming process. In this way, the process suppressed the formation of nanovoids, while effectively achieving a uniform current distribution. As practical examples, two types of metallic nanostamps were fabricated via direct current and PRC electroforming processes, one with a pitch of 0.8 µm and a height of 1.8 µm, and another with a pitch of 350 nm and a height of 525 nm. The internal nanovoids developed during the electroforming process were measured and analyzed. (paper)

  18. 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.

  19. 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)

  20. Texas Experimental Tokamak

    International Nuclear Information System (INIS)

    This progress report covers the period from November 1, 1990 to April 30, 1993. During that period, TEXT was operated as a circular tokamak with a material limiter. It was devoted to the study of basic plasma physics, in particular to study of fluctuations, turbulence, and transport. The purpose is to operate and maintain TEXT Upgrade as a complete facility for applied tokamak physics, specifically to conduct a research program under the following main headings: (1) to elucidate the mechanisms of working gas, impurity, and thermal transport in tokamaks, in particular to understand the role of turbulence; (2) to study physics of the edge plasma, in particular the turbulence; (3) to study the physics or resonant magnetic fields (ergodic magnetic divertors, intra island pumping); and (4) to study the physics of electron cyclotron heating (ECRH). Results of studies in each of these areas are reported

  1. Microwave Tokamak Experiment

    International Nuclear Information System (INIS)

    The Microwave Tokamak Experiment, now under construction at the Laboratory, will use microwave heating from a free-electron laser. The intense microwave pulses will be injected into the tokamak to realize several goals, including a demonstration of the effects of localized heat deposition within magnetically confined plasma, a better understanding of energy confinement in tokamaks, and use of the new free-electron laser technology for plasma heating. The experiment, soon to be operational, provides an opportunity to study dense plasmas heated by powers unprecedented in the electron-cyclotron frequency range required by the especially high magnetic fields used with the MTX and needed for reactors. 1 references, 5 figures, 3 tables

  2. Saddle point condition for D minus sup 3 He tokamak fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mitarai, O. (Kumamoto Inst. of Technology, Dept. of Electrical Engineering, Ikeda 4-22-1, Kumamoto 860 (JP)); Hirose, A.; Skarsgard, H.M. (Univ. of Saskatchewan, Dept. of Physics Sasakatoon, Saskatchewan, S7N 0W0 (CA))

    1991-03-01

    In this paper the concept of a generalized ignition contour map, showing {bar P}{sub ht}T{sup 2}{sub E}, NT{sub E}, and T, is used to study the ignition criterion for a D{minus}{sup 3}He fusion reactor with plasma temperature and density profiles. Direct heating scenarios to the D {minus} {sup 3}He ignition regime without the help of deuterium-tritium burning are considered. The machine size and enhancement factor for the confinement time required to reach D {minus} {sup 3}He ignition can be simple determined by comparing the height of the operation path with Goldston L-mode scaling and the height of the generalized saddle point. A confinement enhancement factor of 2 to 3 is required in the case of a large plasma current (30 to 80 MA) in a small-aspect-ratio tokamak. On the other hand, for a small plasma current ({approx lt} 10 MA), large-aspect-ratio tokamak, an enhancement factor of 5 to 6 is necessary to reach ignition. Fuel dilution effects by fusion products and impurities, the confinement degradation effect due to 14-MeV protons, and the operation paths are also considered. To lower the height of the saddle point, and hence the auxiliary heating power, we optimize the fuel composition and examine operation in the hot ion mode.

  3. Axisymmetric electrostatic magnetohydrodynamic oscillations in tokamaks with general cross-sections and toroidal flow

    Science.gov (United States)

    Chu, M. S.; Guo, Wenfeng

    2016-06-01

    displacements. Based on the general notion that the geodesic component of the GAM is more effective in tearing up the eddies in the electrostatic turbulence, it is important to preferentially excite the GAMs that are non-sound-wave like to maximize the efficiency on turbulence suppression through external means. Finally, approximate formulae for the frequencies of the EMF, ZF, SW, and the GAM for a large aspect ratio circular tokamak rotating at low Mach numbers are also provided.

  4. A Novel Method to Prepare High-aspect Ratio Gold Nanorods%一种制备高长径比金纳米棒的新方法

    Institute of Scientific and Technical Information of China (English)

    高倩; 钱勇; 夏炎; 蒋彩云; 钱卫平

    2011-01-01

    A novel approach to high-aspect ratio gold nanorods has been presented.The gold nanorods as long as(200±18.62) nm with aspect ratio of above 10 were prepared with optimizing the concentration of surfactant cetyltrimethylammonium bromide(CTAB) by seed-mediated growth method at 25 ℃.Mechanism for gold nanorods formation is discussed.It is shown that the aspect ratio and longitudinal surface plasmon resonance(SPR) can be correlated with the concentration of CTAB.Moreover,by simply enhancing the ion strength of the reaction solution,the as-prepared gold nanorods can be purified for the different electrostatic aggregation effects between gold nanorods and spherical nanoparticles.Shape change of gold nanorods is confirmed by transmission electron microscopy images(TEM) and scan electron microscopy(SEM).%报道了一种制备高长径比金纳米棒的新方法.在25℃条件下,采用种子介导生长法,通过优化表面活性剂十六烷基三甲基溴化铵(CTAB)的浓度,制备了长度(200±18.62)nm,长径比大于10的金纳米棒,并讨论了金纳米棒的形成机制.结果表明,金纳米棒的长径比和纵向吸收波长与CTAB的浓度有关.此外,通过提高反应液的离子强度,利用制备的金纳米棒与球形颗粒不同的静电作用将金纳米棒分离纯化.运用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对金纳米棒的表面形貌进行表征.

  5. 3-D Numerical Simulation and Analysis of Complex Fiber Geometry RaFC Materials with High Volume Fraction and High Aspect Ratio based on ABAQUS PYTHON

    Science.gov (United States)

    Jin, BoCheng

    2011-12-01

    Organic and inorganic fiber reinforced composites with innumerable fiber orientation distributions and fiber geometries are abundantly available in several natural and synthetic structures. Inorganic glass fiber composites have been introduced to numerous applications due to their economical fabrication and tailored structural properties. Numerical characterization of such composite material systems is necessitated due to their intrinsic statistical nature, which renders extensive experimentation prohibitively time consuming and costly. To predict various mechanical behavior and characterizations of Uni-Directional Fiber Composites (UDFC) and Random Fiber Composites (RaFC), we numerically developed Representative Volume Elements (RVE) with high accuracy and efficiency and with complex fiber geometric representations encountered in uni-directional and random fiber networks. In this thesis, the numerical simulations of unidirectional RaFC fiber strand RVE models (VF>70%) are first presented by programming in ABAQUS PYTHON. Secondly, when the cross sectional aspect ratios (AR) of the second phase fiber inclusions are not necessarily one, various types of RVE models with different cross sectional shape fibers are simulated and discussed. A modified random sequential absorption algorithm is applied to enhance the volume fraction number (VF) of the RVE, which the mechanical properties represents the composite material. Thirdly, based on a Spatial Segment Shortest Distance (SSSD) algorithm, a 3-Dimentional RaFC material RVE model is simulated in ABAQUS PYTHON with randomly oriented and distributed straight fibers of high fiber aspect ratio (AR=100:1) and volume fraction (VF=31.8%). Fourthly, the piecewise multi-segments fiber geometry is obtained in MATLAB environment by a modified SSSD algorithm. Finally, numerical methods including the polynomial curve fitting and piecewise quadratic and cubic B-spline interpolation are applied to optimize the RaFC fiber geometries

  6. Reconnection in tokamaks

    International Nuclear Information System (INIS)

    Calculations with several different computer codes based on the resistive MHD equations have shown that (m = 1, n = 1) tearing modes in tokamak plasmas grow by magnetic reconnection. The observable behavior predicted by the codes has been confirmed in detail from the waveforms of signals from x-ray detectors and recently by x-ray tomographic imaging

  7. Sawtooth phenomena in tokamaks

    International Nuclear Information System (INIS)

    A review of experimental and theoretical investigaions of sawtooth phenomena in tokamaks is presented. Different types of sawtooth oscillations, scaling laws and methods of interanl disruption stabilization are described. Theoretical models of the sawtooth instability are discussed. 122 refs.; 4 tabs

  8. Advanced tokamak concepts

    NARCIS (Netherlands)

    Oomens, A. A. M.

    1998-01-01

    From a discussion of fusion reactor designs based on today's well-established experience gained in the operation of large tokamaks, it is concluded that such reactors are economically not attractive. The physics involved in the various options for concept improvement is described and the main e

  9. Advanced tokamak concepts

    NARCIS (Netherlands)

    Oomens, A. A. M.

    1996-01-01

    From a discussion of fusion reactor designs based on today's well-established experience gained in the operation of large tokamaks, it is concluded that such reactors are economically not attractive. The physics involved in the various options for concept improvement is described and the main e

  10. Research using small tokamaks

    International Nuclear Information System (INIS)

    The technical reports contained in this collection of papers on research using small tokamaks fall into four main categories, i.e., (i) experimental work (heating, stability, plasma radial profiles, fluctuations and transport, confinement, ultra-low-q tokamaks, wall physics, a.o.), (ii) diagnostics (beam probes, laser scattering, X-ray tomography, laser interferometry, electron-cyclotron absorption and emission systems), (iii) theory (strong turbulence, effects of heating on stability, plasma beta limits, wave absorption, macrostability, low-q tokamak configurations and bootstrap currents, turbulent heating, stability of vortex flows, nonlinear islands growth, plasma-drift-induced anomalous transport, ergodic divertor design, a.o.), and (iv) new technical facilities (varistors applied to establish constant current and loop voltage in HT-6M), lower-hybrid-current-drive systems for HT-6B and HT-6M, radio-frequency systems for HT-6M ICR heating experimentation, and applications of fiber optics for visible and vacuum ultraviolet radiation detection as applied to tokamaks and reversed-field pinches. A total number of 51 papers are included in the collection. Refs, figs and tabs

  11. Ultrasmall Ge islands with low diameter-to-height aspect ratio on Si(1 0 0)-(2 x 1) surfaces

    International Nuclear Information System (INIS)

    Scanning tunneling microscopy (STM) and high resolution cross-sectional transmission electron microscopy (XTEM) studies have been used to investigate the formation of Ge nanocrystals grown on Si(1 0 0)-(2 x 1) surfaces by molecular beam epitaxy (MBE). We observe relatively high density of Ge islands where small 'pyramids', small 'domes' and facetted 'domes' of various sizes co-exist in the film. As revealed from XTEM images, a large fraction of islands, especially dome-shaped Ge islands have been found to have an aspect ratio of ∼1 (diameter):1 (height). Observation of truncated-sphere-shaped Ge islands with a narrow neck contact with the wetting layer is reported.

  12. Ultrasmall Ge islands with low diameter-to-height aspect ratio on Si(1 0 0)-(2 x 1) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, K. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Roy, Anupam [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Department of Materials Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032 (India); Ghatak, Jay; Satyam, P.V. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Dev, B.N., E-mail: msbnd@iacs.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Department of Materials Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032 (India)

    2009-10-30

    Scanning tunneling microscopy (STM) and high resolution cross-sectional transmission electron microscopy (XTEM) studies have been used to investigate the formation of Ge nanocrystals grown on Si(1 0 0)-(2 x 1) surfaces by molecular beam epitaxy (MBE). We observe relatively high density of Ge islands where small 'pyramids', small 'domes' and facetted 'domes' of various sizes co-exist in the film. As revealed from XTEM images, a large fraction of islands, especially dome-shaped Ge islands have been found to have an aspect ratio of {approx}1 (diameter):1 (height). Observation of truncated-sphere-shaped Ge islands with a narrow neck contact with the wetting layer is reported.

  13. Reinforcement of a poly(dimethyl siloxane) mold with high aspect ratio microstructures via a gas–liquid phase sol–gel process

    International Nuclear Information System (INIS)

    A gas–liquid phase sol–gel process was proposed to reinforce a poly(dimethyl siloxane) (PDMS) mold with high aspect ratio microstructures (HARMs) for micromolding. Unlike the conventional sol–gel process or in situ precipitation of silicate nanoparticles (SiO2) inside the PDMS network, the vapor of water and aminomethyl propanol-95 permeated through the PDMS which was pre-soaked with tetraethoxy silane (TEOS), leading to the occurrence of hydrolysis and condensation and reinforcement of the PDMS. The reinforced PDMS mold with HARMs was used for micromolding, and high replication accuracy was achieved. The proposed technique not only prevents the surface of microstructures on the mold from potential agglomeration of particles but also allows for the repetitive usage of the silicon mother mold without damage

  14. 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.

  15. Tokamak plasma interaction with limiters

    International Nuclear Information System (INIS)

    The importance of plasma purity is first discussed in terms of the general requirements of controlled thermonuclear fusion. The tokamak approach to fusion and its inherent problem of plasma contamination are introduced. A main source of impurities is due to the bombardment of the limiter by energetic particles and thus the three main aspects of the plasma-limiter interaction are reviewed, boundary plasma conditions, fuelling/recycling and impurity production. The experiments, carried out on the DITE tokamak at Culham Laboratory, UK, investigated these three topics and the results are compared with predicted behaviour; new physical phenomena are presented in all three areas. Simple one-dimensional fluid equations are found to adequately describe the SOL plasma, except in regard to the pre-sheath electric field and ambipolarity; that is, the electric field adjacent to the limiter surface appears to be weak and the associated plasma flow can be non-ambipolar. Recycling of fuel particles from the limiter is observed to be near unity at all times. The break-up behaviour of recycled and gas puffed D2 molecules is dependent on the electron temperature, as expected. Impurity production at the limiter is chemical erosion of graphite being negligible. Deposition of limiter and wall-produced impurities is found on the limiter. The spatial distributions of impurities released from the limiter are observed and are in good agreement with a sputtered atom transport code. Finally, preliminary experiments on the transport of impurity ions along field lines away from the limiter have been performed and compared with simple analytic theory. The results suggest that the pre-sheath electric field in the SOL is much weaker than the simple fluid model would predict

  16. Modelling of electron transport and of sawtooth activity in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Angioni, C

    2001-10-01

    Transport phenomena in tokamak plasmas strongly limit the particle and energy confinement and represent a crucial obstacle to controlled thermonuclear fusion. Within the vast framework of transport studies, three topics have been tackled in the present thesis: first, the computation of neoclassical transport coefficients for general axisymmetric equilibria and arbitrary collisionality regime; second, the analysis of the electron temperature behaviour and transport modelling of plasma discharges in the Tokamak a configuration Variable (TCV); third, the modelling and simulation of the sawtooth activity with different plasma heating conditions. The work dedicated to neoclassical theory has been undertaken in order to first analytically identify a set of equations suited for implementation in existing Fokker-Planck codes. Modifications of these codes enabled us to compute the neoclassical transport coefficients considering different realistic magnetic equilibrium configurations and covering a large range of variation of three key parameters: aspect ratio, collisionality, and effective charge number. A comparison of the numerical results with an analytical limit has permitted the identification of two expressions for the trapped particle fraction, capable of encapsulating the geometrical effects and thus enabling each transport coefficient to be fitted with a single analytical function. This has allowed us to provide simple analytical formulae for all the neoclassical transport coefficients valid for arbitrary aspect ratio and collisionality in general realistic geometry. This work is particularly useful for a correct evaluation of the neoclassical contribution in tokamak scenarios with large bootstrap cur- rent fraction, or improved confinement regimes with low anomalous transport and for the determination of the plasma current density profile, since the plasma conductivity is usually assumed neoclassical. These results have been included in the plasma transport code

  17. Engineering overview of the National Spherical Tokamak Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chrzanowski, J.H.; Fan, H.M.; Heitzenroeder, P.J.; Ono, M.; Robinson, J. [Princeton Plasma Physics Lab., NJ (United States)

    1995-12-31

    The National Spherical Tokamak Experiment (NSTX) is an ultra low aspect ratio device designed for a plasma current of 1 MA. It features auxiliary heating and current drive and a close-fitting conducting shell to maximize plasma pressure. NSTX is designed for a 5 sec. experimental pulse to demonstrate quasi-steady state non-inductively driven advanced tokamak operation. The device will be sited in the former Princeton Large Torus (PLT) test cell and will utilize the PLT radiation shielding, base structure, and cell utilities. NSTX will utilize the S-1 Spheromak vacuum vessel, poloidal field coils, and capacitor banks (for helicity injection). The poloidal Beta Experiment-Modified (PBX-M) power supplies will be shared to power the PF and TF coil systems. Existing RF hardware and infrastructure will be used for heating systems. TFTR data acquisition and diagnostics resources are planned to be used. In total, NSTX will utilize site credits with a value of {approximately}$50 M, reducing base construction cost of the device to $18.6 M. Twelve water-cooled copper demountable toroidal field (TF) coils provide the 5.4 kg (pulsed) and 3.5 kg (long pulse > 5 sec) toroidal field at the plasma center. Poloidal fields are generated by windings contained in the center column and four pairs water-cooled copper coils supported directly on the vacuum vessel. One of the most critical components of the device is the center stack, which consists of the inner legs of the TF coils overwrapped with ohmic heating and poloidal field windings. The ohmic heating coil windings are designed to optimize the V-s and together with the PF coils, produce a flux swing of 1 V-s.

  18. Next tokamak facility

    International Nuclear Information System (INIS)

    Design studies on a superconducting, long-pulse, current-driven, ignited tokamak, called the Toroidal Fusion Core Demonstration (TFCD), are being conducted by the Fusion Engineering Design Center (FEDC) and Princeton Plasma Physics Laboratory (PPPL) with additional broad community involvement. Options include the use of all-superconducting toroidal field (TF) coils, a superconducting-copper hybrid arrangement of TF coils, or all-copper TF coils. Only the first two options have been considered to date. The general feasibility of these approaches has been established with the goal of high performance (ignition, approx. 390 MW; wall loading approx. 2.2 MW/m2) at minimum capital cost. The preconceptual effort will be completed in early FY 1984 and a selection made from the indicated options. The TFCD is judged to represent a reasonable necessary step between the Tokamak Fusion Test Reactor (TFTR) and the Engineering Test Reactor

  19. Tritium catalyzed deuterium tokamaks

    International Nuclear Information System (INIS)

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the 3He from the D(D,n)3He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general)

  20. Tokamak fusion reactor exhaust

    International Nuclear Information System (INIS)

    This report presents a compilation of papers dealing with reactor exhaust which were produced as part of the TIGER Tokamak Installation for Generating Electricity study at Culham. The papers are entitled: (1) Exhaust impurity control and refuelling. (2) Consideration of the physical problems of a self-consistent exhaust and divertor system for a long burn Tokamak. (3) Possible bundle divertors for INTOR and TIGER. (4) Consideration of various magnetic divertor configurations for INTOR and TIGER. (5) A appraisal of divertor experiments. (6) Hybrid divertors on INTOR. (7) Refuelling and the scrape-off layer of INTOR. (8) Simple modelling of the scrape-off layer. (9) Power flow in the scrape-off layer. (10) A model of particle transport within the scrape-off plasma and divertor. (11) Controlled recirculation of exhaust gas from the divertor into the scrape-off plasma. (U.K.)

  1. Tokamak pump limiters

    International Nuclear Information System (INIS)

    Recent experiments with a scoop limiter without active internal pumping have been carried out in the PDX tokamak with up to 6MW of auxiliary neutral beam heating. Experiments have also been done with a rotating head pump limiter in the PLT tokamak in conjunction with RF plasma heating. Extensive experiments have been done in the ISX-B tokamak and first experiments have been completed with the ALT-I limiter in TEXTOR. The pump limiter modules in these latter two machines have internal getter pumping. Experiments in ISX-B are with ohmic and auxiliary neutral beam heating. The results in ISX-B and TEXTOR show that active density control and particle removal is achieved with pump limiters. In ISX-B, the boundary layer (or scape-off layer) plasma partially screens the core plasma from gas injection. In both ISX-B and TEXTOR, the pressure internal to the module scales linearly with plasma density but in ISX-B, with neutral beam injection, a nonlinear increase is observed at the highest densities studied. Plasma plugging is the suspected cause. Results from PDX suggest that a region may exist in which core plasma energy confinement improves using a pump limiter during neutral beam injection. Asymmetric radial profiles and an increased edge electron temperature are observed in discharges with improved confinement. The injection of small amounts of neon into ISX-B has more clearly shown an improved electron core energy confinement during neutral beam injection. While carried out with a regular limiter, this Z-mode of operation is ideal for use with pump limiters and should be a way to achieve energy confinement times similar to values for H-mode tokamak plasmas. The implication of all these results for the design of a reactor pump limiter is described

  2. [High beta tokamak research

    International Nuclear Information System (INIS)

    Our activities on High Beta Tokamak Research during the past 20 months of the present grant period can be divided into six areas: reconstruction and modeling of high beta equilibria in HBT; measurement and analysis of MHD instabilities observed in HBT; measurements of impurity transport; diagnostic development on HBT; numerical parameterization of the second stability regime; and conceptual design and assembly of HBT-EP. Each of these is described in some detail in the sections of this progress report

  3. Evaluation of toroidal torque by non-resonant magnetic perturbations in tokamaks for resonant transport regimes using a Hamiltonian approach

    CERN Document Server

    Albert, Christopher G; Kapper, Gernot; Kasilov, Sergei V; Kernbichler, Winfried; Martitsch, Andreas F

    2016-01-01

    Toroidal torque generated by neoclassical viscosity caused by external non-resonant, non-axisymmetric perturbations has a significant influence on toroidal plasma rotation in tokamaks. In this article, a derivation for the expressions of toroidal torque and radial transport in resonant regimes is provided within quasilinear theory in canonical action-angle variables. The proposed approach treats all low-collisional quasilinear resonant NTV regimes including superbanana plateau and drift-orbit resonances in a unified way and allows for magnetic drift in all regimes. It is valid for perturbations on toroidally symmetric flux surfaces of the unperturbed equilibrium without specific assumptions on geometry or aspect ratio. The resulting expressions are shown to match existing analytical results in the large aspect ratio limit. Numerical results from the newly developed code NEO-RT are compared to calculations by the quasilinear version of the code NEO-2 at low collisionalities. The importance of the magnetic shea...

  4. Synchronized vortex shedding and sound radiation from two side-by-side rectangular cylinders of different cross-sectional aspect ratios

    International Nuclear Information System (INIS)

    Synchronized vortex shedding from two side-by-side cylinders and the associated sound radiation were examined experimentally at Reynolds numbers of the order of 104 in low-Mach-number flows. In addition to a pair of square cylinders, a pair of rectangular cylinders, one with a square cross section (d × d) and the other with a rectangular cross section (d × c) having a cross-sectional aspect ratio (c/d) of 1.2–1.5, was considered. The center-to-center distance between the two cylinders L/d was 3.6, 4.5, and 6.0; these settings were within the non-biased flow regime for side-by-side square cylinders. In case of a square cylinder pair, anti-phase synchronized vortex shedding occurring for L/d = 3.6 and 4.5 generated a quadrupole-like sound source which radiated in-phase, planar-symmetric sound in the far field. Synchronized vortex shedding from the two rectangular cylinders with different c/d also occurred with almost the same frequency as the characteristic frequency of the square-cylinder wake in the case of the small center-to-center distance, L/d = 3.6, for all the cylinder pairs examined. The synchronized sound field was anti-phase and asymmetric in amplitude, unlike the case of a square cylinder pair. For larger spacing L/d = 4.5, synchronized vortex shedding and anti-phase sound still occurred, but only for close cross-sectional aspect ratios (c/d = 1.0 and 1.2), and highly modulated sound was radiated with two different frequencies due to non-synchronized vortex shedding from the two cylinders for larger differences in c/d. It was also found that when synchronized vortex shedding occurred, near-wake velocity fluctuations exhibited high spanwise-coherency, with a very sharp spectral peak compared with the single-cylinder case

  5. Two-fluid simulations of driven reconnection in the mega-ampere spherical tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Stanier, A.; Browning, P.; Gordovskyy, M. [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom); McClements, K. G.; Gryaznevich, M. P. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Lukin, V. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2013-12-15

    In the merging-compression method of plasma start-up, two flux-ropes with parallel toroidal current are formed around in-vessel poloidal field coils, before merging to form a spherical tokamak plasma. This start-up method, used in the Mega-Ampere Spherical Tokamak (MAST), is studied as a high Lundquist number and low plasma-beta magnetic reconnection experiment. In this paper, 2D fluid simulations are presented of this merging process in order to understand the underlying physics, and better interpret the experimental data. These simulations examine the individual and combined effects of tight-aspect ratio geometry and two-fluid physics on the merging. The ideal self-driven flux-rope dynamics are coupled to the diffusion layer physics, resulting in a large range of phenomena. For resistive MHD simulations, the flux-ropes enter the sloshing regime for normalised resistivity η≲10{sup −5}. In Hall-MHD, three regimes are found for the qualitative behaviour of the current sheet, depending on the ratio of the current sheet width to the ion-sound radius. These are a stable collisional regime, an open X-point regime, and an intermediate regime that is highly unstable to tearing-type instabilities. In toroidal axisymmetric geometry, the final state after merging is a MAST-like spherical tokamak with nested flux-surfaces. It is also shown that the evolution of simulated 1D radial density profiles closely resembles the Thomson scattering electron density measurements in MAST. An intuitive explanation for the origin of the measured density structures is proposed, based upon the results of the toroidal Hall-MHD simulations.

  6. Time-resolved spectroscopy in the Rijnhuizen Tokamak Project tokamak

    NARCIS (Netherlands)

    Box, F. M. A.; Howard, J.; VandeKolk, E.; Meijer, F. G.

    1997-01-01

    At the Rijnhuizen Tokamak Project tokamak spectrometers are used to diagnose the velocity distribution and abundances of impurity ions. Quantities can be measured as a function of time, and the temporal resolution depends on the line emissivity and can be as good as 0.2 ms for the strongest lines. S

  7. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    International Nuclear Information System (INIS)

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov's results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov's result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits

  8. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov's results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov's result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  9. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov`s results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov`s result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  10. 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.

  11. Material versatility using replica molding for large-scale fabrication of high aspect-ratio, high density arrays of nano-pillars

    International Nuclear Information System (INIS)

    Arrays of high aspect-ratio (AR) nano-pillars have attracted a lot of interest for various applications, such as for use in solar cells, surface acoustic sensors, tissue engineering, bio-inspired adhesives and anti-reflective surfaces. Each application may require a different structural material, which can vary in the required chemical composition and mechanical properties. In this paper, a low cost fabrication procedure is proposed for large scale, high AR and high density arrays of nano-pillars. The proposed method enables the replication of a master with high fidelity, using the subsequent replica molds multiple times, and preparing arrays of nano-pillars in a variety of different materials. As an example applied to bio-inspired dry adhesion, polymeric arrays of nano-pillars are prepared in this work. Thermoset and thermoplastic nano-pillar arrays are examined using an atomic force microscope to assess their adhesion strength and its uniformity. Results indicate the proposed method is robust and can be used to reliably prepare nano-structures with a high AR. (paper)

  12. Mosquitofish (Gambusia affinis preference and behavioral response to animated images of conspecifics altered in their color, aspect ratio, and swimming depth.

    Directory of Open Access Journals (Sweden)

    Giovanni Polverino

    Full Text Available Mosquitofish (Gambusia affinis is an example of a freshwater fish species whose remarkable diffusion outside its native range has led to it being placed on the list of the world's hundred worst invasive alien species (International Union for Conservation of Nature. Here, we investigate mosquitofish shoaling tendency using a dichotomous choice test in which computer-animated images of their conspecifics are altered in color, aspect ratio, and swimming level in the water column. Pairs of virtual stimuli are systematically presented to focal subjects to evaluate their attractiveness and the effect on fish behavior. Mosquitofish respond differentially to some of these stimuli showing preference for conspecifics with enhanced yellow pigmentation while exhibiting highly varying locomotory patterns. Our results suggest that computer-animated images can be used to understand the factors that regulate the social dynamics of shoals of Gambusia affinis. Such knowledge may inform the design of control plans and open new avenues in conservation and protection of endangered animal species.

  13. Inverted Ge islands in {111} faceted Si pits-a novel approach towards SiGe islands with higher aspect ratio

    International Nuclear Information System (INIS)

    A detailed study of the so far unexplored Ge island nucleation on Si (001) substrates patterned with {111} faceted pyramidal pits is reported. The pits are defined by an anisotropic wet-chemical etch through a SiNx hard mask. Due to the self-limiting of the wet etch, an extremely uniform pit pattern is achieved. On these substrates, Ge layers were grown by solid source molecular beam epitaxy at various growth temperatures TGe. For TGe=550 0C, Ge fills the pits in the form of inverted {111} pyramids with a rounded apex and a (001)-oriented top surface. These islands have aspect ratios much larger than upright pyramids and domes that are usually obtained on substrates with cylindrical pits fabricated by lithographic techniques and reactive ion etching. Based on the experimentally determined shape, three-dimensional (3D) energy level calculations in an envelop function approach have been performed for the inverted pyramids. They show that, due to the orientation of the pyramid square base along (110) directions, the overlap between the hole ground states and electron states confined to the Si conduction band valleys perpendicular to the growth direction is much larger than for upright SiGe domes and {105} pyramids. For elevated growth temperatures around 700 0C, already a Ge coverage of five monolayers induces a strong Si transfer into the {111} pits, effectively converting them towards {1 1 10} faceted ones.

  14. 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.

  15. 高厚径比HDI板电镀能力研究%Plating ability Of HDI with high aspect ratio item

    Institute of Scientific and Technical Information of China (English)

    班向东

    2013-01-01

    With the development of information technology, more layers, thickness, aperture smaller, thicker wiring denser PCB needs PCB manufacturers put forward higher requirements. High aspect ratio and BMV plating are two different processing direction of PCB plating, and the two requirements of both the product processing is the dififculty of electroplating. So to ifnd a balance between the two is very important. Through the experiment, we found the electroplating parameters, achieved the balance of the blind holes.%随着信息技术的不断发展,层数更多、板厚更厚、孔径更小、布线更密的PCB需求给PCB生产厂家提出的更高的要求。高纵横比与盲孔电镀是PCB电镀的两个不同的加工方向,而这两种要求并存的产品加工是电镀的难点,因此找到两者之间的平衡点至关重要。本文通过实验,找到两者兼顾的电镀参数,达到通盲孔兼顾的效果。

  16. Circularity, Solidity, Axes of a Best Fit Ellipse, Aspect Ratio, and Roundness of the Foramen Ovale: A Morphometric Analysis With Neurosurgical Considerations.

    Science.gov (United States)

    Zdilla, Matthew J; Hatfield, Scott A; McLean, Kennedy A; Cyrus, Leah M; Laslo, Jillian M; Lambert, H Wayne

    2016-01-01

    The structure of the foramen ovale of the sphenoid bone is clinically important, particularly with regard to surgical procedures that cannulate the foramen such as percutaneous trigeminal rhizotomy for the treatment of trigeminal neuralgia, percutaneous biopsy of parasellar lesions, and electroencephalographic analysis of the temporal lobe among patients undergoing selective amygdalohippocampectomy. Differences in the morphology of the foramen ovale (FO) have been reported to contribute to difficulties in the cannulation of the FO. Reports regarding the structure of the FO, however, use subjective and ambiguous descriptions of morphology, including "oval," "truly oval," "elongated oval," "elongated," "semicircular," "almond," "round," "rounded," "slit," "irregular," "D shape," and "pear." Therefore, it is necessary to describe the structure of the FO with reproducible objective morphometric data. This study analyzed 169 foramina to determine normative morphometric shape descriptions of the following: area, perimeter, circularity, solidity, axes of a best fit ellipse, aspect ratio, and roundness. The shape descriptors reported herein may aid in identification and description of structural variation in FO including bony projections encroaching upon the foramina and may improve surgical approaches to transovale cannulation. PMID:26703050

  17. Dynamics of Random Sequential Adsorption (RSA) of linear chains consisting of n circular discs - Role of aspect ratio and departure from convexity

    Science.gov (United States)

    Shelke, Pradip B.; Limaye, A. V.

    2015-07-01

    We study Random Sequential Adsorption (RSA) of linear chains consisting of n circular discs on a two-dimensional continuum substrate. The study has been carried out for n = 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 50, 70, 100 and 300. For all values of n, instantaneous coverage, Θ(t), in late time regime, is found to approach to jammed state coverage, Θ(∞), in a power law fashion, Θ(∞) - Θ(t) ~ t- p. It is observed that, with the increase in n, the exponent p goes on decreasing from the value 0.33 for n = 2 to the value 0.20 for n = 20 and then again starts rising to reach the value of 0.33 for large n. It is also found that for n ≤ 20, the exponent p has near perfect correlation with the coefficient of departure from convexity. On the other hand the jammed state coverage Θ(∞) is found to depend both on the coefficient of departure from convexity as well as on the aspect ratio of the chain.

  18. 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. PMID:26106943

  19. 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.

  20. Material versatility using replica molding for large-scale fabrication of high aspect-ratio, high density arrays of nano-pillars

    Science.gov (United States)

    Li, Y.; Ng, H. W.; Gates, B. D.; Menon, C.

    2014-07-01

    Arrays of high aspect-ratio (AR) nano-pillars have attracted a lot of interest for various applications, such as for use in solar cells, surface acoustic sensors, tissue engineering, bio-inspired adhesives and anti-reflective surfaces. Each application may require a different structural material, which can vary in the required chemical composition and mechanical properties. In this paper, a low cost fabrication procedure is proposed for large scale, high AR and high density arrays of nano-pillars. The proposed method enables the replication of a master with high fidelity, using the subsequent replica molds multiple times, and preparing arrays of nano-pillars in a variety of different materials. As an example applied to bio-inspired dry adhesion, polymeric arrays of nano-pillars are prepared in this work. Thermoset and thermoplastic nano-pillar arrays are examined using an atomic force microscope to assess their adhesion strength and its uniformity. Results indicate the proposed method is robust and can be used to reliably prepare nano-structures with a high AR.

  1. Magnetic confinement experiment -- 1: Tokamaks

    International Nuclear Information System (INIS)

    This report reviews presentations made at the 15th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion on experimental tokamak physics, particularly on advances in core plasma physics, divertor and edge physics, heating and current drive, and tokamak concept optimization

  2. Magnetic confinement experiment -- 1: Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Goldston, R.J.

    1994-12-31

    This report reviews presentations made at the 15th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion on experimental tokamak physics, particularly on advances in core plasma physics, divertor and edge physics, heating and current drive, and tokamak concept optimization.

  3. The tokamak as a neutron source

    International Nuclear Information System (INIS)

    This paper describes the tokamak in its role as a neutron source, with emphasis on experimental results for D-D neutron production. The sections summarize tokamak operation, sources of fusion and non-fusion neutrons, principal neutron detection methods and their calibration, neutron energy spectra and fluxes outside the tokamak plasma chamber, history of neutron production in tokamaks, neutron emission and fusion power gain from JET and TFTR (the largest present-day tokamaks), and D-T neutron production from burnup of D-D tritons. This paper also discusses the prospects for future tokamak neutron production and potential applications of tokamak neutron sources. 100 refs., 16 figs., 4 tabs

  4. Tokamak burn control

    International Nuclear Information System (INIS)

    Research of the fusion plasma thermal instability and its control is reviewed. General models of the thermonuclear plasma are developed. Techniques of stability analysis commonly employed in burn control research are discussed. Methods for controlling the plasma against the thermal instability are reviewed. Emphasis is placed on applications to tokamak confinement concepts. Additional research which extends the results of previous research is suggested. Issues specific to the development of control strategies for mid-term engineering test reactors are identified and addressed. 100 refs., 24 figs., 10 tabs

  5. Demonstration tokamak power plant

    Energy Technology Data Exchange (ETDEWEB)

    Abdou, M.; Baker, C.; Brooks, J.; Ehst, D.; Mattas, R.; Smith, D.L.; DeFreece, D.; Morgan, G.D.; Trachsel, C.

    1983-01-01

    A conceptual design for a tokamak demonstration power plant (DEMO) was developed. A large part of the study focused on examining the key issues and identifying the R and D needs for: (1) current drive for steady-state operation, (2) impurity control and exhaust, (3) tritium breeding blanket, and (4) reactor configuration and maintenance. Impurity control and exhaust will not be covered in this paper but is discussed in another paper in these proceedings, entitled Key Issues of FED/INTOR Impurity Control System.

  6. Design and fabrication of a high-aspect-ratio parylene-based comb-drive actuator for large displacements at a low driving force

    International Nuclear Information System (INIS)

    This paper presents a comb-drive actuator integrated with parylene-based flexible beams for large displacements at a low driving force. Single-crystal silicon and polysilicon are the traditional materials used for comb-drive actuators in the microeletromechanical systems industry. However, the larger Young's modulus limits the displacement at a low applied voltage. This study uses the parylene beams with the characteristic of a low modulus of the elastic comb-drive actuator as a compliant suspension to create a larger displacement (>50 µm) with smaller driving forces than that of silicon. High-aspect-ratio parylene beams can be fabricated through the deposition and removal of parylene in multiple stages on a silicon micro-trench. The proposed process uses a silicon-on-insulator wafer as the substrate to fabricate suspended silicon and parylene beams as rigid and compliant structures, respectively. The test devices of parylene- and silicon-based comb-drive actuators were fabricated with 100 pairs of comb fingers with gaps of 5 µm, and compliant beams of 15 µm in width, 2000 µm in span and 50 µm in thickness. When a driving voltage of 40 V dc was applied, the parylene-based comb-drive actuator generated a displacement of up to 55 µm, whereas the silicon-based comb-drive actuator generated a displacement of 2 µm. The parylene-based comb-drive actuator can generate about 27 times of displacement than that of silicon. This design is suitable for application in devices with large in-plane displacement and low switching speed. (paper)

  7. 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.

  8. ITER tokamak device

    Science.gov (United States)

    Doggett, J.; Salpietro, E.; Shatalov, G.

    1991-07-01

    The results of the Conceptual Design Activities for the International Thermonuclear Experimental Reactor (ITER) are summarized. These activities, carried out between April 1988 and December 1990, produced a consistent set of technical characteristics and preliminary plans for co-ordinated research and development support of ITER, a conceptual design, a description of design requirements and a preliminary construction schedule and cost estimate. After a description of the design basis, an overview is given of the tokamak device, its auxiliary systems, facility and maintenance. The interrelation and integration of the various subsystems that form the ITER tokamak concept are discussed. The 16 ITER equatorial port allocations, used for nuclear testing, diagnostics, fueling, maintenance, and heating and current drive, are given, as well as a layout of the reactor building. Finally, brief descriptions are given of the major ITER sub-systems, i.e., (1) magnet systems (toroidal and poloidal field coils and cryogenic systems), (2) containment structures (vacuum and cryostat vessels, machine gravity supports, attaching locks, passive loops and active coils), (3) first wall, (4) divertor plate (design and materials, performance and lifetime, a.o.), (5) blanket/shield system, (6) maintenance equipment, (7) current drive and heating, (8) fuel cycle system, and (9) diagnostics.

  9. Edge turbulence in tokamaks

    Science.gov (United States)

    Nedospasov, A. V.

    1992-12-01

    Edge turbulence is of decisive importance for the distribution of particle and energy fluxes to the walls of tokamaks. Despite the availability of extensive experimental data on the turbulence properties, its nature still remains a subject for discussion. This paper contains a review of the most recent theoretical and experimental studies in the field, including mainly the studies to which Wootton (A.J. Wooton, J. Nucl. Mater. 176 & 177 (1990) 77) referred to most in his review at PSI-9 and those published later. The available theoretical models of edge turbulence with volume dissipation due to collisions fail to fully interpret the entire combination of experimental facts. In the scrape-off layer of a tokamak the dissipation prevails due to the flow of current through potential shifts near the surface of limiters of divertor plates. The different origins of turbulence at the edge and in the core plasma due to such dissipation are discussed in this paper. Recent data on the electron temperature fluctuations enabled one to evaluate the electric probe measurements of turbulent flows of particles and heat critically. The latest data on the suppression of turbulence in the case of L-H transitions are given. In doing so, the possibility of exciting current instabilities in biasing experiments (rather than only to the suppression of existing turbulence) is given some attention. Possible objectives of further studies are also discussed.

  10. Dust Measurements in Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Rudakov, D; Yu, J; Boedo, J; Hollmann, E; Krasheninnikov, S; Moyer, R; Muller, S; Yu, A; Rosenberg, M; Smirnov, R; West, W; Boivin, R; Bray, B; Brooks, N; Hyatt, A; Wong, C; Fenstermacher, M; Groth, M; Lasnier, C; McLean, A; Stangeby, P; Ratynskaia, S; Roquemore, A; Skinner, C; Solomon, W M

    2008-04-23

    Dust production and accumulation impose safety and operational concerns for ITER. Diagnostics to monitor dust levels in the plasma as well as in-vessel dust inventory are currently being tested in a few tokamaks. Dust accumulation in ITER is likely to occur in hidden areas, e.g. between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering resolves size of particles between 0.16-1.6 {micro}m in diameter; the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast-framing cameras, detecting dust particles of a few microns in diameter and larger. Dust velocities and trajectories can be determined in 2D with a single camera or 3D using multiple cameras, but determination of particle size is problematic. In order to calibrate diagnostics and benchmark dust dynamics modeling, pre-characterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase of carbon atomic, C2 dimer, and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics.

  11. Axisymmetric control in tokamaks

    International Nuclear Information System (INIS)

    Vertically elongated tokamak plasmas are intrinsically susceptible to vertical axisymmetric instabilities as a result of the quadrupole field which must be applied to produce the elongation. The present work analyzes the axisymmetric control necessary to stabilize elongated equilibria, with special application to the Alcator C-MOD tokamak. A rigid current-conserving filamentary plasma model is applied to Alcator C-MOD stability analysis, and limitations of the model are addressed. A more physically accurate nonrigid plasma model is developed using a perturbed equilibrium approach to estimate linearized plasma response to conductor current variations. This model includes novel flux conservation and vacuum vessel stabilization effects. It is found that the nonrigid model predicts significantly higher growth rates than predicted by the rigid model applied to the same equilibria. The nonrigid model is then applied to active control system design. Multivariable pole placement techniques are used to determine performance optimized control laws. Formalisms are developed for implementing and improving nominal feedback laws using the C-MOD digital-analog hybrid control system architecture. A proportional-derivative output observer which does not require solution of the nonlinear Ricatti equation is developed to help accomplish this implementation. The nonrigid flux conserving perturbed equilibrium plasma model indicates that equilibria with separatrix elongation of at least sep = 1.85 can be stabilized robustly with the present control architecture and conductor/sensor configuration

  12. Deposit of thin films for Tokamaks conditioning

    International Nuclear Information System (INIS)

    discharge plasma, created in a calibrated mixture of methane-hydrogen during the hydrogenated amorphous carbon film deposit on the vessel wall of Novillo tokamak, were determined by mass spectrometry. By way of measuring the emission lines of the carbon and oxygen impurities in intense discharges, the time required by the plasma to interact with the wall was estimated. In addition to it, the temporal conduct of the emission line intensity of these impurities was observed by means of an intensified CCD detector. Once an ∼ 10 % of helium was introduced in the operating gas of the tokamak discharges, a 25-42 eV time variation of the electron temperature was measured using the intensity ratio technique. (Author)

  13. Time-resolved spectroscopy in the Rijnhuizen Tokamak Project tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Box, F.M.A.; Kolk, E. van de [Associatie Euratom-FOM, Nieuwegein (Netherlands). FOM-Instituut voor Plasmafysica; Howard, J. [Plasma Research Laboratory, Research School of Physical Science and Engineering, Australian National University, Canberra 0200 (Australia); Meijer, F.G. [Physics Faculty, University of Amsterdam, Amsterdam (Netherlands)

    1997-03-01

    At the Rijnhuizen Tokamak Project tokamak spectrometers are used to diagnose the velocity distribution and abundances of impurity ions. Quantities can be measured as a function of time, and the temporal resolution depends on the line emissivity and can be as good as 0.2 ms for the strongest lines. Several spectrometers, equipped with a charge-coupled device array, are being used with spectral ranges in the visible, the vacuum UV and the extreme UV. (orig.)

  14. Tokamak power systems studies, FY 1986: A second stability power reactor

    International Nuclear Information System (INIS)

    This report presents the results of the work at Argonne National Laboratory (ANL) during FY-1986 on the Tokamak Power Systems Study (TPSS). The purpose of the TPSS is to explore and develop ideas that would lead to improvements in the tokamak as a power reactor concept. The work at ANL concentrated on plasma engineering, impurity control, and the blanket/first wall/shield system. The work in FY-1986 extended these studies and focused them on a reference design point. The key features of the design point include: second stability regime with higher β and larger aspect ratio, steady-state operation with fast wave current drive, impurity control via a self-pumped slot limiter, a self-cooled liquid lithium, vanadium alloy blanket with simplified poloidal flow, and reduced reactor building volume with vertical lift maintenance. Sufficient work was carried out to report a preliminary cost estimate. In addition, reactor implications of steady-state operation in the first stability regime were also studied. 174 refs., 124 figs., 65 tabs

  15. Toroidal momentum transport in a tokamak caused by symmetry breaking parallel derivatives

    CERN Document Server

    Sung, Tobias; Casson, Francis; Fable, Emilino; Grosshauser, Stefan R; Hornsby, William; Migliano, Piereluigi; Peeters, Arthur G

    2013-01-01

    A new mechanism for toroidal momentum transport in a tokamak is investigated using the gyro-kinetic model. First, an analytic model is developed through the use of the ballooning transform. The terms that generate the momentum transport are then connected with the poloidal derivative of the ballooning envelope, which are one order smaller in the normalised Larmor radius, compared with the derivative of the eikonal. The mechanism, therefore, does not introduce an inhomogeneity in the radial direction, in contrast with the effect of profile shearing. Numerical simulations of the linear ion temperature gradient mode with adiabatic electrons, retaining the finite rho* effects in the ExB velocity, the drift, and the gyro-average, are presented. The momentum flux is found to be linear in the normalised Larmor radius (\\rho*) but is, nevertheless, generating a sizeable counter-current rotation. The total momentum flux scales linear with the aspect ratio of the considered magnetic surface, and increases with increasin...

  16. A Proposed Experiment to Study Relaxation Formation of a Spherical Tokamak with a Plasma Center Column

    CERN Document Server

    Hsu, S C

    2006-01-01

    A spherical tokamak (ST) with a plasma center column (PCC) can be formed via driven magnetic relaxation of a screw pinch plasma. An ST-PCC could in principle eliminate many problems associated with a material center column, a key weakness of the ST reactor concept. This work summarizes the design space for an ST-PCC in terms of flux amplification, aspect ratio, and elongation, based on the zero-beta Taylor-relaxed analysis of Tang & Boozer [Phys. Plasmas 13, 042514 (2006)]. The paper will discuss (1) equilibrium and stability properties of the ST-PCC, (2) issues for an engineering design, and (3) key differences between the proposed ST-PCC and the ongoing Proto-Sphera effort in Italy.

  17. Shearless bifurcation on symplectic maps of magnetic field lines in tokamaks with reversed current

    Science.gov (United States)

    Bartoloni, B.; Schelin, A. B.; Caldas, I. L.

    2016-07-01

    We introduce two-dimensional symplectic maps to describe the Poincaré maps of magnetic field lines in large aspect ratio tokamak equilibria with reversed non-monotonic plasma current density profiles. For these maps, we investigate the effect of the symmetry breaking due to the toroidal correction with a peculiar invariant, namely, a magnetic surface with a null rotation number, enclosing a vanishing current. We find that this rotationless invariant surface is surrounded by many small island chains. Furthermore, near such invariant, the symmetry breaking gives rise to two magnetic shearless invariants surrounded by twin island chains. We also find chaotic lines adjacent to all the observed islands created by the considered structurally unstable equilibria.

  18. Potential commercial reactor based on a small tokamak hybrid design

    International Nuclear Information System (INIS)

    An ignition tokamak reactor design has been obtained which represents a starting point for the conceptual design of a 1000 MW/sub e/ commercial system. The design includes Nb3Sn superconducting coils (TF, OH, and SF), water-cooled fissile blanket (e.g., uranium oxide), positive-ion based neutral beams with no direct energy recovery, and an ignited plasma with a = 0.9 m and an aspect ratio A = 4.0. The TF coil bore has a vertical bore of 7 m and a horizontal bore of 5 m both of which are a factor of two larger than the corresponding bore dimensions of the LCP (Large Coil Project) TF coil. The plasma is characterized as follows: stability factor q = 2.5, Z/sub eff/ approx. 1, poloidal beta β/sub p/ less than or equal to A, a elongation delta in the range between 1.6 and 1.7. A number of potential operating conditions for the plasma and device have been identified for which the plasma beta β lies within the range from 6.5% to 7.3%, and the plasma temperature has an average value between 11 keV and 12.5 keV. The design was obtained using the computer code COAST and represents a self-consistent sizing and costing result

  19. Initial Plasma Startup Test on SUNIST Spherical Tokamak

    Institute of Scientific and Technical Information of China (English)

    Wang Ying(王莹); Zeng Li(曾立); He Yexi(何也熙); SUMST Team

    2003-01-01

    The goal of the Sino-United Spherical Tokamak (SUNIST) at Tsinghua University is to extend the understanding of toroidal plasma physics at a low aspect ratio (R/a ≈ 1.3) and to demonstrate a maintainable target plasma by non-inductive startup. The SUNIST device is designed to operate with up to 13 kA of ohmic heating field current, and to 0.15 T of toroidal field at 10 kA of discharge current. All of the poloidal fields can provide 30 mVs of Volt-seconds transformer. Experimental results of plasma startup show that SUNIST has remarkable characteristics of high ramp rate (dIp/dt ≈ 50 MA/s ), high normalized current IN of about 2.8 (IN = Ip/aBT),and high-efficiency (Ip/IROD ≈ 0.4) production of plasma current while operating at a low toroidal field. Major disruption phenomena have not been observed from magnetic diagnostics of all testing shots. Initial discharges with 52 kA of plasma current (exceeding the designed value of 50 kA),2 ms of pulse length and 50 MA/s of ramp rate have been achieved easily with pre-ionized filament.

  20. Comparative study of Cl2, Cl2/O2, and Cl2/N2 inductively coupled plasma processes for etching of high-aspect-ratio photonic-crystal holes in InP

    NARCIS (Netherlands)

    Carlström, C.F.; Van der Heijden, R.; Andriesse, M.S.P.; Karouta, F.; Van der Heijden, R.W.; Van der Drift, E.W.J.M.; Salemink, H.W.M.

    2008-01-01

    An extensive investigation has been performed on inductively coupled plasma etching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Cl2 with the addition of N2 or O2 for sidewall passivation. The i

  1. Spheromak injection into a tokamak

    OpenAIRE

    Brown, M R; Bellan, P. M.

    1990-01-01

    Recent results from the Caltech spheromak injection experiment [to appear in Phys. Rev. Lett.] are reported. First, current drive by spheromak injection into the ENCORE tokamak as a result of the process of magnetic helicity injection is observed. An initial 30% increase in plasma current is observed followed by a drop by a factor of 3 because of sudden plasma cooling. Second, spheromak injection results in an increase of tokamak central density by a factor of 6. The high-current/high-density...

  2. Confinement and diffusion in tokamaks

    International Nuclear Information System (INIS)

    The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cTe/eB(δni/ni)rms which is also derived by a simple theory, the cross-field diffusion time, tp=a2/D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation

  3. Spherical tokamak development in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] (and others)

    2003-07-01

    The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

  4. Spherical tokamak development in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma; Barbosa, L.F.W. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil). Faculdade de Engenharia, Arquitetura e Urbanismo; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Div. de Mecanica Espacial e Controle; The high-power microwave sources group

    2003-12-01

    This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

  5. The ARIES tokamak reactor study

    Energy Technology Data Exchange (ETDEWEB)

    1989-10-01

    The ARIES study is a community effort to develop several visions of tokamaks as fusion power reactors. The aims are to determine the potential economics, safety, and environmental features of a range of possible tokamak reactors, and to identify physics and technology areas with the highest leverage for achieving the best tokamak reactor. Three ARIES visions are planned, each having a different degree of extrapolation from the present data base in physics and technology. The ARIES-I design assumes a minimum extrapolation from current tokamak physics (e.g., 1st stability) and incorporates technological advances that can be available in the next 20 to 30 years. ARIES-II is a DT-burning tokamak which would operate at a higher beta in the 2nd MHD stability regime. It employs both potential advances in the physics and expected advances in technology and engineering. ARIES-II will examine the potential of the tokamak and the D{sup 3}He fuel cycle. This report is a collection of 14 papers on the results of the ARIES study which were presented at the IEEE 13th Symposium on Fusion Engineering (October 2-6, 1989, Knoxville, TN). This collection describes the ARIES research effort, with emphasis on the ARIES-I design, summarizing the major results, the key technical issues, and the central conclusions.

  6. The ARIES tokamak reactor study

    International Nuclear Information System (INIS)

    The ARIES study is a community effort to develop several visions of tokamaks as fusion power reactors. The aims are to determine the potential economics, safety, and environmental features of a range of possible tokamak reactors, and to identify physics and technology areas with the highest leverage for achieving the best tokamak reactor. Three ARIES visions are planned, each having a different degree of extrapolation from the present data base in physics and technology. The ARIES-I design assumes a minimum extrapolation from current tokamak physics (e.g., 1st stability) and incorporates technological advances that can be available in the next 20 to 30 years. ARIES-II is a DT-burning tokamak which would operate at a higher beta in the 2nd MHD stability regime. It employs both potential advances in the physics and expected advances in technology and engineering. ARIES-II will examine the potential of the tokamak and the D3He fuel cycle. This report is a collection of 14 papers on the results of the ARIES study which were presented at the IEEE 13th Symposium on Fusion Engineering (October 2-6, 1989, Knoxville, TN). This collection describes the ARIES research effort, with emphasis on the ARIES-I design, summarizing the major results, the key technical issues, and the central conclusions

  7. Magnetohydrodynamic stability of internal kink modes in tokamaks: application of an equilibrium code using bicubic finite elements

    International Nuclear Information System (INIS)

    Magnetohydrodynamic (MHD) stability limits for the n=1 internal kink mode in a tokamak are investigated. As the internal kink mode is a weak instability, accurate equilibrium solutions are required to determine its stability boundaries. For this purpose, a numerical equilibrium code CHEASE using Hermite bicubic elements has been developed. The code computes equilibria and provides a mapping to flux coordinates for MHD stability calculations. Several tests are also presented for the eigenvalues of the stability calculations when the equilibrium mesh is varied. Using CHEASE and the toroidal resistive MHD stability code MARS, effects of current profile, plasma cross-section and resistivity on the stability of the internal kink mode are investigated for tokamak equilibria. The results show that the internal kink mode is more unstable than previously thought. The numerical ideal stability results for a circular plasma cross section are compared with the results obtained by an analytic large aspect ratio expansion. It is found that the internal kink is significantly destabilized by the ellipticity of the plasma cross section combined with low shear. A large aspect ratio expansion of the Mercier and the resistive interchange criteria retaining effects of ellipticity and triangularity is given, showing analytically the destabilization by ellipticity. For resistive internal kink modes, the stabilizing effect of small aspect ratio is confirmed, but as for the ideal case, the stability is very sensitive with respect to shaping of the plasma cross section. For finite pressure and small resistivity, only a very restricted set of equilibria is stable to the internal kink mode. (author) figs., tabs., 72 refs

  8. Formation and sustainment of a very low aspect ratio tokamak using coaxial helicity injection (the Helicity Injected Torus [HIT] experiment). Progress report No. 2, February 1, 1991--January 31, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Jarboe, T.R.; Nelson, B.A.

    1992-06-01

    In the paper we will detail the progress of the HIT experiment construction, including the following components: preliminary data and interpretation; diagnostic systems; vacuum vessel and pumping system; helicity source and power supplies; toroidal field coil and power supply; data acquisition system; collaboration with general atomics, with a brief summary given on each.

  9. Measurement of the internal magnetic field structure of tokamak plasmas

    International Nuclear Information System (INIS)

    The first part of this article deals with the physical fundaments and technical aspects of this polarimetric measuring method, with its diagnostic capability, but also with its limitations. The second part summarizes the essential experimental results and their feedback on the theoretical description of Tokamak plasmas, which caused a revision of the accepted ideas of the magnetic field structure and its magnetohydrodynamic stability, in particular in the area of the hot plasma core. (orig.)

  10. Bibliography of fusion product physics in tokamaks

    International Nuclear Information System (INIS)

    Almost 700 citations have been compiled as the first step in reviewing the recent research on tokamak fusion product effects in tokamaks. The publications are listed alphabetically by the last name of the first author and by subject category

  11. Neutronics design of the next tokamak. (Swimming pool type)

    International Nuclear Information System (INIS)

    A swimming pool type tokamak reactor (SPTR) has been proposed in the Japan Atomic Energy Research Institute as a candidate for the next generation tokamak reactor after the JT-60. The concept of the SPTR evolved from an incentive to relieve the difficulties of repair and maintenance procedures of a tokamak reactor. After about two years of the reactor design studies, several advantages of the SPTR over the conventional tokamak reactors such as the ease of penetration shielding, reduction in solid radwaste have been shown. On the other hand, some drawbacks and uncertainties of the SPTR have also been pointed out but so far no serious defect negating the concept has been found. This paper describes the neutronics aspect of the SPTR based mostly on the result of one dimensional calculations. At first, the radiation shielding capability of water is compared with those of other candidate materials used in the blanket and shield of fusion reactors. Based on the result of the comparison and other requirements such as tritium breeding, thermal mechanical design, repair and maintenance procedures, the material arrangements of the blanket and shield are determined. The result of the blanket neutronics calculations, the radiation shielding calculations for the superconducting magnets, shutdown dose calculations are given together with major penetration shielding considerations. (author)

  12. Fusion potential for spherical and compact tokamaks

    International Nuclear Information System (INIS)

    The tokamak is the most successful fusion experiment today. Despite this, the conventional tokamak has a long way to go before being realized into an economically viable power plant. In this master thesis work, two alternative tokamak configurations to the conventional tokamak has been studied, both of which could be realized to a lower cost. The fusion potential of the spherical and the compact tokamak have been examined with a comparison of the conventional tokamak in mind. The difficulties arising in the two configurations have been treated from a physical point of view concerning the fusion plasma and from a technological standpoint evolving around design, materials and engineering. Both advantages and drawbacks of either configuration have been treated relative to the conventional tokamak. The spherical tokamak shows promising plasma characteristics, notably a high β-value but have troubles with high heat loads and marginal tritium breeding. The compact tokamak operates at a high plasma density and a high magnetic field enabling it to be built considerably smaller than any other tokamak. The most notable down-side being high heat loads and neutron transport problems. With the help of theoretical reactor studies, extrapolating from where we stand today, it is conceivable that the spherical tokamak is closer of being realized of the two. But, as this study shows, the compact tokamak power plant concept offers the most appealing prospect

  13. Fusion potential for spherical and compact tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Sandzelius, Mikael

    2003-02-01

    The tokamak is the most successful fusion experiment today. Despite this, the conventional tokamak has a long way to go before being realized into an economically viable power plant. In this master thesis work, two alternative tokamak configurations to the conventional tokamak has been studied, both of which could be realized to a lower cost. The fusion potential of the spherical and the compact tokamak have been examined with a comparison of the conventional tokamak in mind. The difficulties arising in the two configurations have been treated from a physical point of view concerning the fusion plasma and from a technological standpoint evolving around design, materials and engineering. Both advantages and drawbacks of either configuration have been treated relative to the conventional tokamak. The spherical tokamak shows promising plasma characteristics, notably a high {beta}-value but have troubles with high heat loads and marginal tritium breeding. The compact tokamak operates at a high plasma density and a high magnetic field enabling it to be built considerably smaller than any other tokamak. The most notable down-side being high heat loads and neutron transport problems. With the help of theoretical reactor studies, extrapolating from where we stand today, it is conceivable that the spherical tokamak is closer of being realized of the two. But, as this study shows, the compact tokamak power plant concept offers the most appealing prospect.

  14. Moving Divertor Plates in a Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    S.J. Zweben, H. Zhang

    2009-02-12

    Moving divertor plates could help solve some of the problems of the tokamak divertor through mechanical ingenuity rather than plasma physics. These plates would be passively heated on each pass through the tokamak and cooled and reprocessed outside the tokamak. There are many design options using varying plate shapes, orientations, motions, coatings, and compositions.

  15. Electromagnetic microinstabilities in tokamak plasmas using a global spectral approach

    Energy Technology Data Exchange (ETDEWEB)

    Falchetto, G. L

    2002-03-01

    Electromagnetic microinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. The code is the electromagnetic extension of an existing electrostatic global gyrokinetic spectral toroidal code, called GLOGYSTO. Ion dynamics is described by the gyrokinetic equation, so that ion finite Larmor radius effects are taken into account to all orders. Non adiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A low frequency electromagnetic perturbation is applied to a low -but finite- {beta}plasma (where the parameter {beta} identifies the ratio of plasma pressure to magnetic pressure); thus, the parallel perturbations of the magnetic field are neglected. The system is closed by the quasi-neutrality equation and the parallel component of Ampere's law. The formulation is applied to a large aspect ratio toroidal configuration, with circular shifted surfaces. Such a simple configuration enables one to derive analytically the gyrocenter trajectories. The system is solved in Fourier space, taking advantage of a decomposition adapted to the toroidal geometry. The major contributions of this thesis are as follows. The electromagnetic effects on toroidal Ion Temperature Gradient driven (ITG) modes are studied. The stabilization of these modes with increasing {beta}, as predicted in previous work, is confirmed. The inclusion of trapped electron dynamics enables the study of its coupling to the ITG modes and of Trapped Electron Modes (TEM) .The effects of finite {beta} are considered together with those of different magnetic shear profiles and of the Shafranov shift. The threshold for the destabilization of an electromagnetic mode is identified. Moreover, the global formulation yields for the first time the radial structure of this so-called Alfvenic Ion Temperature Gradient (AITG) mode. The stability of the

  16. Ideal Stability of the Tokamak H--mode Edge Region

    Science.gov (United States)

    Wilson, H. R.

    1998-11-01

    Tokamak performance is often controlled by stability of the edge plasma. Consistent with ``stiff'' transport models, the confinement in tokamak discharges is strongly correlated with the magnitude of the edge pressure pedestal which is limited by MHD stability. Furthermore, the high performance ELM-free H--modes are terminated by low toroidal mode number n, MHD modes driven by high edge pressure gradient, and edge current. We have evaluated low n modes using the δ W code GATO, and both high edge pressure gradient and high edge current density are found to destabilize the n=1, 2, and 3 ideal modes. We have included the self-consistent bootstrap current in the equilibria generation, and have completed a thorough survey of the effects of plasma shape and edge pressure profiles on the edge ballooning stability. The bootstrap current density helps to provide access to the second regime of stability, which is easier for: higher elongation, intermediate triangularity, larger aspect ratio, narrower pedestal width, and higher q_95. The intermediate n stability is being evaluated using a high-mode-number peeling/ ballooning mode model,(J.W. Connor, R.J. Hastie, H.R. Wilson, and R.L. Miller, Phys. Plasmas 5), 2687 (1998). where a critical role is played by the edge current density. This edge model describes the interaction of peeling mode (current driven) and ballooning mode (pressure driven) effects at high, but finite, mode number; a modified ballooning mode formalism is shown to be valid at the plasma edge. Based upon this edge model, a 2D eigenvalue code has been written to determine the stability of these modes for arbitrary shape cross sections, and edge pressure and current profiles including bootstrap current effects. This model suggests a power threshold for L--H transitions and provides a plausible explanation for an ELM cycle. Results will be presented for the pressure gradient and edge current density stability boundaries for a range of shapes and pedestal widths

  17. Tokamak experimental power reactor

    International Nuclear Information System (INIS)

    A tokamak experimental power reactor has been designed that is capable of producing net electric power over a wide range of possible operating conditions. A net production of 81 MW of electricity is expected from the design reference conditions that assume a value of 0.07 for beta-toroidal, a maximum toroidal magnetic field of 9 T and a thermal conversion efficiency of 30%. Impurity control is achieved through the use of a low-Z first wall coating. This approach allows a burn time of 60 seconds without the incorporation of a divertor. The system is cooled by a dual pressurized water/steam system that could potentially provide thermal efficiencies as high as 39%. The first surface facing the plasma is a low-Z coated water cooled panel that is attached to a 20 cm thick blanket module. The vacuum boundary is removed a total of 22 cm from the plasma, thereby minimizing the amount of radiation damage in this vital component. Consideration is given in the design to the possible use of the EPR as a materials test reactor. It is estimated that the total system could be built for less than 550 million dollars

  18. Boronization of Russian tokamaks from carborane precursors

    International Nuclear Information System (INIS)

    A new and cheap boronization technique using the nontoxic and nonexplosive solid substance carborane has been developed and successfully applied to the Russian tokamaks T-11M, T-3M, T-10 and TUMAN-3. The glow discharge in a mixture of He and carborane vapor produced the amorphous B/C coating with the B/C ratio varied from 2.0-3.7. The deposition rate was about 150 nm/h. The primary effect of boronization was a significant reduction of the impurity influx and the plasma impurity contamination, a sharp decrease of the plasma radiated power, and a decrease of the effective charge. Boronization strongly suppressed the impurity influx caused by additional plasma heating. ECR- and ICR-heating as well as ECR current drive were more effective in boronized vessels. Boronization resulted in a significant extension of the Ne- and q-region of stable tokamak operation. The density limit rose strongly. In Ohmic H-mode energy confinement time increased significantly (by a factor of 2) after boronization. It rose linearly with plasma current Ip and was 10 times higher than Neo-Alcator time at maximum current. ((orig.))

  19. Comparative study of Cl2, Cl2/O2, and Cl2/N2 inductively coupled plasma processes for etching of high-aspect-ratio photonic-crystal holes in InP

    OpenAIRE

    Carlström, C.F.; Heijden, R. van der; Andriesse, M.S.P.; Karouta, F.; van der Heijden, R. W.; Van der Drift, E.W.J.M.; H. W. M. Salemink

    2008-01-01

    An extensive investigation has been performed on inductively coupled plasma etching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Cl2 with the addition of N2 or O2 for sidewall passivation. The influence of different process parameters such as gas flows, temperature, pressure, ion energy, and inductively coupled plasma power on the hole geometry is presented. It is concluded that photonic ...

  20. Plasma boundary phenomena in tokamaks

    International Nuclear Information System (INIS)

    The focus of this review is on processes occurring at the edge, and on the connection between boundary plasma - the scrape-off layer (SOL) and the radiating layer - and central plasma processes. Techniques used for edge diagnosis are reviewed and basic experimental information (ne and Te) is summarized. Simple models of the SOL are summarized, and the most important effects of the boundary plasma - the influence on the fuel particles, impurities, and energy - on tokamak operation dealt with. Methods of manipulating and controlling edge conditions in tokamaks and the experimental data base for the edge during auxiliary heating of tokamaks are reviewed. Fluctuations and asymmetries at the edge are also covered. (9 tabs., 134 figs., 879 refs.)